JP6666817B2 - Wireless communication device and wireless communication method - Google Patents

Description

  An embodiment of the present invention relates to a wireless communication terminal and a wireless communication method.

  Consider that multi-user communication (multiplex communication) is performed between a base station and a plurality of wireless communication terminals (hereinafter, terminals). Uplink multi-user communication is described as UL-MU (UpLink Multi-User) communication, and downlink multi-user communication is described as DL-MU (DownLink Multi-User) communication.

  As multi-user communication, frequency multiplex communication in which different frequency components are allocated as communication resources for each terminal and transmission to a plurality of terminals or reception from a plurality of terminals is performed simultaneously is considered. Here, a resource unit including one or more subcarriers is defined as a frequency component, and the frequency component is assigned to a terminal as a communication resource of a minimum unit, so that transmission to a plurality of terminals or reception from a plurality of terminals is performed. Consider orthogonal frequency division multiple access (OFDMA), which is performed simultaneously. Simultaneous transmission from the base station to a plurality of terminals corresponds to downlink OFDMA (DL-OFDMA), and simultaneous transmission from a plurality of terminals to the base station corresponds to uplink OFDMA (UL-OFDMA). DL-OFDMA is an example of a DL-MU, and UL-OFDMA is an example of a UL-MU.

  When performing UL-OFDMA, a base station may consider transmitting a trigger frame that specifies a terminal to be subjected to UL-OFDMA and a resource unit allocated to the terminal in order to align uplink transmission timing. Can be In this method, the resource unit allocated to the specified terminal is not used effectively, such as when the specified terminal has transitioned to the sleep mode or the specified terminal does not have a request for uplink transmission, and communication resources are not used. There is a problem that efficiency is reduced.

  As another method, there is a method in which a trigger frame does not specify a terminal but specifies only a resource unit to be used. At this time, a terminal may be specified for some resource units and a terminal may not be specified for another resource unit. In any case, among terminals that have received the trigger frame, terminals to which none of the resource units have been allocated are randomly allocated from resource units with no terminal designation (which may be referred to as “STA unspecified RUs”). Select a unit to use. Such a trigger frame including the designation of the STA undesignated RU may be referred to as a random access trigger frame.

  The following methods are available for randomly selecting a resource unit. Every time a random access trigger frame is received, a value corresponding to the number of RUs not specified by the STA is counted down from a random number (backoff value) selected from the contention window (CW) for random access. When the backoff value after the countdown becomes 0 or less, the access right to the STA-unspecified RU is acquired, a resource unit is randomly selected from the STA-unspecified RU, and the selected resource unit transmits a frame. The CW for random access is different from the contention window used to determine the back-off time at the time of CSMA / CA carrier sensing.

  In the above-described method, when a plurality of terminals simultaneously obtain the access right, these terminals may select the same STA-unspecified RU and transmit the frame. In this case, at the access point, frames received from these terminals collide, and each frame cannot be decoded normally. Since these terminals do not receive the acknowledgment response from the access point, they determine that the frame transmitted by themselves is not normally received. In such a case, these terminals perform a similar process by selecting a random number from the newly set random access CW upon receiving the next random access trigger frame. It is not clear whether to re-select. If the CW for random access is selected under the same conditions as a terminal that succeeded in transmission (such as a terminal that did not select the same resource unit as another terminal), fairness is lacking. Also, it is not clear how to reselect a CW for a terminal whose frame has been normally received at the access point. As described above, this method lacks a protocol for repeatedly using a random access trigger frame.

  In particular, when a random access trigger frame is used to collect a UL-MU assignment request (uplink transmission request) from a terminal, a terminal that fails to transmit cannot receive the UL-MU allocation request because the request does not reach the access point. It will not be selected as a target terminal of the MU. On the other hand, a terminal that has successfully transmitted a UL-MU assignment request can be selected as a target terminal of the UL-MU in response to the request (a transmission opportunity in the UL-MU is obtained). Therefore, it is not fair to select the random access CW under the same conditions as those of a terminal that has successfully transmitted.

IEEE 802.11-15 / 1105 IEEE Std 802.11ac-2013 IEEE Std 802.11 (TM) -2012

  An embodiment of the present invention aims to impart a fair transmission opportunity to a plurality of wireless communication terminals.

  A wireless communication terminal according to one aspect of the present invention includes at least one antenna, a receiving unit coupled to the antenna, and receiving a frame, a transmitting unit coupled to the antenna, and transmitting a frame, the receiving unit, A communication processing unit coupled to the transmission unit; a network processing unit coupled to the communication processing unit for transmitting data to the communication processing unit and receiving data from another device; and coupling to the network processing unit. And a memory for caching the first data. The transmitting unit transmits a first frame including information designating a plurality of frequency components via the antenna, and the communication processing unit determines whether a second frame has been received for each of the plurality of frequency components. The transmitting unit determines the first information related to the first value range according to the number of the frequency components in which the second frame is received, the first information being used for determining whether or not a response to the first frame is possible. A third frame including the first data or the third frame is transmitted via the antenna, and the first frame or the third frame includes the first data or information based on the first data cached in the memory.

FIG. 2 is a functional block diagram of the wireless communication device according to the embodiment of the present invention. FIG. 4 is a diagram for explaining allocation of resource units. FIG. 3 is a diagram for explaining a form of a resource unit. FIG. 3 is a diagram showing a wireless communication group including a base station and a plurality of terminals. The figure which shows the example of a basic format of a MAC frame. The figure which shows the example of a format of an information element. FIG. 4 is a diagram showing an example of a basic operation sequence according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a format example of a physical packet. The figure which shows the example of a format of a trigger frame (including the case of the trigger frame for random access). The figure which shows the example of a structure of RU / AID field. FIG. 8 is a supplementary explanatory diagram of the operation sequence in FIG. 7. FIG. 3 is an explanatory diagram of a Multi-STA BA frame. FIG. 2 is a diagram illustrating a schematic format example of a physical packet used in DL-OFDMA transmission. FIG. 4 is a diagram showing an example of an operation sequence according to the embodiment of the present invention. FIG. 15 is a supplementary explanatory diagram of the operation sequence in FIG. 14. The figure which shows typically the mode of update of CWO (Content Window for UL-OFDMA). The figure which shows the example of an operation sequence at the time of transmitting a trigger frame instead of a delivery confirmation response frame. The figure which shows typically the operation | movement which concerns on the modification 1 of CWO update. The figure which shows typically the operation | movement which concerns on the modification 2 of CWO update. The figure which shows the example of a sequence of the operation | movement of the base station which concerns on the modification 4 of CWO update. The figure which shows the flowchart of an example of operation | movement of the terminal which concerns on embodiment of this invention. The figure which shows the flowchart of an example of operation | movement of the base station which concerns on embodiment of this invention. FIG. 9 is a functional block diagram of an access point or a terminal according to the second embodiment. The figure which shows the whole structural example of a terminal or a base station. FIG. 3 is a diagram illustrating a hardware configuration example of a wireless communication device mounted on a terminal or a base station. FIG. 1 is a perspective view of a wireless communication terminal according to an embodiment of the present invention. FIG. 1 is a diagram showing a memory card according to an embodiment of the present invention. The figure which shows an example of the frame exchange of a contention period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. IEEE Std 802.11 (TM) -2012 and IEEE which are known as wireless LAN standards
Std 802.11ac (TM) -2013, and IEEE 802.11-15 dated September 22, 2015, which is a specification framework document (Specification Framework Document) for IEEE Std 802.11ax, which is a next-generation wireless LAN standard. / 0132r9 is incorporated herein by reference in its entirety.

(First embodiment)
FIG. 1 shows a functional block diagram of the wireless communication device according to the first embodiment. This wireless communication device can be implemented in a wireless communication base station (hereinafter, a base station or an access point) or a wireless communication terminal (hereinafter, a terminal) that communicates with the base station. A base station has basically the same communication function as a terminal except that it mainly has a relay function, and thus is a form of a wireless communication terminal. The operations of the functional blocks are basically common to both, but there are some differences between the base station and the non-base station terminals. In the following description, the term “wireless communication terminal” or “terminal” may refer to a base station unless it is necessary to distinguish between them.

  The wireless communication system according to the present embodiment includes a base station on which the wireless communication device in FIG. 1 is mounted and a plurality of terminals. In this system, OFDMA (Orthogonal Frequency Division Multiple Access) can be used as multi-user communication (multiplex communication). Uplink OFDMA is described as UL-OFDMA. The downlink OFDMA is described as DL-OFDMA. In the system of the present embodiment, at least UL-OFDMA can be performed. Hereinafter, OFDMA will be described.

  In OFDMA, a resource unit including one or a plurality of subcarriers is allocated to a terminal, and transmission and reception are simultaneously performed between a base station and a plurality of terminals on a resource unit basis. The resource unit is a frequency component that is a minimum unit of a resource for communication.

  FIG. 2 shows resource units (RU # 1, RU # 2,... RU # K) secured in a continuous frequency domain of one channel (here, described as channel M). A plurality of subcarriers orthogonal to each other are arranged in the channel M, and a plurality of resource units including one or a plurality of subcarriers are defined in the channel M. One or more subcarriers (guard subcarriers) may be arranged between resource units, but guard subcarriers are not essential. Identification information for identifying the resource unit or the subcarrier may be set in each resource unit or each subcarrier in the channel. The bandwidth of one channel is, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, or the like, but is not limited thereto. A plurality of channels of 20 MHz may be combined into one channel. The number of subcarriers or the number of resource units in a channel may be different depending on the bandwidth. By using different resource units simultaneously by a plurality of terminals, OFDMA communication is realized.

  The bandwidth (or the number of subcarriers) of the resource unit may be common to each resource unit, or the bandwidth (or the number of subcarriers) may be different for each resource unit. FIG. 3 schematically shows an example of an arrangement pattern of resource units in one channel. The horizontal direction along the paper surface corresponds to the frequency domain direction. FIG. 3A shows an example in which a plurality of resource units (RU # 1, RU # 2,... RU # K) having the same bandwidth are arranged. FIG. 3B shows an example in which a plurality of resource units (RU # 11-1, RU # 11-2,..., RU # 11-L) having a larger bandwidth than FIG. . FIG. 3C shows an example in which resource units of three or more bandwidths are arranged. The resource units (RU # 12-1 and RU # 12-2) have the largest bandwidth, and the resource unit RU # 11- (L-1) has the same bandwidth and resource as the resource unit in FIG. The units (RU # K-1, RU # K) have the same bandwidth as the resource unit in FIG.

  As an example, when the entire 20 MHz channel width is used, 26 resource units can be set for 256 subcarriers (tones) arranged within the 20 MHz channel width. That is, nine resource units are set for a 20 MHz channel width, and the bandwidth of the resource unit is smaller than the 2.5 MHz width. In a 40 MHz channel width, for example, 18 resource units are set. For an 80 MHz channel width, for example, 37 resource units are set. To develop this, for example, with a 160 MHz channel width or an 80 + 80 MHz channel width, 74 resource units are set. Of course, the width of the resource unit is not limited to a specific value, and resource units of various sizes can be arranged.

  Note that the number of resource units used by each terminal is not limited to a specific value, and one or a plurality of resource units may be used. When the terminal uses a plurality of resource units, a plurality of frequency-continuous resource units may be bonded and used as one resource unit, or a plurality of resource units at distant locations may be used. Is also good. The resource unit # 11-1 in FIG. 3B may be considered as an example of a resource unit obtained by bonding the resource units # 1 and # 2 in FIG.

  Subcarriers in one resource unit may be continuous in the frequency domain, or a resource unit may be defined from a plurality of subcarriers arranged non-consecutively. The number of channels used in the OFDMA is not limited to one. In addition to the channel M, another channel (refer to channel N in FIG. 2) which is arranged at a position separated in the frequency domain is similar to the channel M. Resource units, and resource units in both channel M and channel N may be used. The allocation method of the resource units in the channel M and the channel N may be the same or different. The bandwidth of one channel is, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, or the like as described above, but is not limited thereto. It is also possible to use more than two channels. Note that the channel M and the channel N can be considered together as one channel.

  Note that a terminal that implements OFDMA has at least a channel having a basic channel width (a 20 MHz channel width if a terminal compatible with the IEEE 802.11a / b / g / n / ac standard is a legacy terminal) in a legacy terminal to be backward-compatible. It is assumed that a physical packet including a frame can be received and decoded (including demodulation and decoding of an error correction code). Carrier sensing is performed in units of the basic channel width.

The carrier sense is a physical carrier sense (Physical Carrier) related to busy / idle of CCA (Clear Channel Assessment).
Sense) and virtual carrier sense based on a medium reservation time described in a received frame. As in the latter case, a mechanism for virtually determining that a medium is busy, or a period in which a medium is virtually busy, is called a NAV (Network Allocation Vector). The carrier sense information based on CCA or NAV performed on a channel basis may be commonly applied to all resource units in the channel. For example, all resource units belonging to a channel whose carrier sense information indicates idle may be determined to be idle.

  In addition to the above-described resource unit-based OFDMA, OFDMA can also use channel-based OFDMA. The OFDMA in this case may be particularly referred to as MU-MC (Multi-User Multi-Channel). In MU-MC, an access point allocates a plurality of channels (one channel width is, for example, 20 MHz) to a plurality of terminals, and simultaneously transmits to a plurality of terminals or simultaneously receives from a plurality of terminals by using the plurality of channels simultaneously. Do. In the OFDMA described below, a resource unit-based OFDMA is assumed, but an embodiment of a channel-based OFDMA can be realized by performing necessary replacement such as replacing a resource unit described below with a channel.

  In the following description, a terminal capable of performing OFDMA may be referred to as an OFDMA-compatible terminal or the like. A terminal having no such capability may be referred to as a legacy terminal. If the capability of performing OFDMA communication can be switched between enabled (Enable) and disabled (Disable), a terminal for which the capability is enabled may be considered as an OFDMA-compatible terminal.

  As shown in FIG. 1, a wireless communication device mounted on a terminal (a terminal of a non-base station and a base station) includes an upper processing unit 90, a MAC processing unit 10, a PHY (Physical: physical) processing unit 50, a MAC / It includes a PHY management unit 60, an analog processing unit 70 (analog processing units 1 to N), and an antenna 80 (antennas 1 to N). N is an integer of 1 or more. In the figure, the N analog processing units and the N antennas are connected in pairs, but are not necessarily limited to this configuration. For example, the number of analog processing units may be one, and two or more antennas may be commonly connected to the analog processing units.

  The MAC processing unit 10, the MAC / PHY management unit 60, and the PHY processing unit 50 correspond to one form of a control unit or a baseband integrated circuit that performs processing related to communication with another terminal (including a base station). The analog processing unit 70 corresponds to, for example, a wireless communication unit that transmits and receives signals via the antenna 80 or an embodiment of an RF (Radio Frequency) integrated circuit. The integrated circuit for wireless communication according to the present embodiment includes at least the former of the baseband integrated circuit (control unit) and the RF integrated circuit. The function of the baseband integrated circuit may be performed by software (program) operated by a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware. The software may be stored in a storage medium such as a memory such as a ROM or a RAM, a hard disk, or an SSD and read and executed by a processor. The memory may be a volatile memory such as an SRAM or a DRAM, or a nonvolatile memory such as a NAND or an MRAM.

  The upper processing unit 90 performs a process for an upper layer on a MAC (Medium Access Control) layer. The upper processing unit 90 can exchange signals with the MAC processing unit 10. Typical upper layers include TCP / IP and UDP / IP, and an application layer thereabove, but this embodiment is not limited to this. The upper processing unit 90 may include a buffer for exchanging data between the MAC layer and the upper layer. A connection to a wired infrastructure via the host processing unit 90 may be made. The buffer may be a memory, an SSD, a hard disk, or the like. When the buffer is a memory, the memory may be a volatile memory such as an SRAM or a DRAM, or a nonvolatile memory such as a NAND or an MRAM.

  The MAC processing unit 10 performs processing for the MAC layer. As described above, the MAC processing unit 10 can exchange signals with the higher-level processing unit 90. Further, the MAC processing unit 10 can exchange signals with the PHY processing unit 50. The MAC processing unit 10 includes a MAC common processing unit 20, a transmission processing unit 30, and a reception processing unit 40.

  The MAC common processing unit 20 performs processing common to transmission and reception in the MAC layer. The MAC common processing unit 20 is connected to the upper processing unit 90, the transmission processing unit 30, the reception processing unit 40, and the MAC / PHY management unit 60, and exchanges signals with each other.

  The transmission processing unit 30 and the reception processing unit 40 are mutually connected. The transmission processing unit 30 and the reception processing unit 40 are connected to the MAC common processing unit 20 and the PHY processing unit 50, respectively. The transmission processing unit 30 performs transmission processing in the MAC layer. The reception processing unit 40 performs reception processing in the MAC layer.

  The PHY processing unit 50 performs a process for a physical layer (PHY layer). As described above, the PHY processing unit 50 can exchange signals with the MAC processing unit 10. The PHY processing unit 50 is connected to the antenna 80 via the analog processing unit 70.

  The MAC / PHY management unit 60 is connected to each of the upper processing unit 90, the MAC processing unit 10 (more specifically, the MAC common processing unit 20), and the PHY processing unit 50. The MAC / PHY management unit 60 manages a MAC operation and a PHY operation in the wireless communication device.

  The analog processing unit 70 includes an analog / digital and digital / analog (AD / DA) converter and an RF (Radio Frequency) circuit, converts a digital signal from the PHY processing unit 50 into an analog signal of a desired frequency, and The high-frequency analog signal transmitted from the antenna 80 and received from the antenna 80 is converted into a digital signal. Here, the AD / DA conversion is performed by the analog processing section 70, but a configuration in which the PHY processing section 50 has an AD / DA conversion function is also possible.

  In the wireless communication device according to the present embodiment, the mounting area of the antenna 80 can be reduced by including (integrating) the antenna 80 as a component in one chip. Further, in the wireless communication device according to the present embodiment, the transmission processing unit 30 and the reception processing unit 40 share N antennas 80 as shown in FIG. The transmission processing unit 30 and the reception processing unit 40 share the N antennas 80, so that the wireless communication device in FIG. 1 can be downsized. The wireless communication device according to the present embodiment may have a configuration different from that illustrated in FIG.

  When receiving a signal from a wireless medium, the analog processing unit 70 converts the analog signal received by the antenna 80 into a signal of a baseband (Baseband) that can be processed by the PHY processing unit 50, and further converts the signal into a digital signal. The PHY processing unit 50 receives a digital reception signal from the analog processing unit 70 and detects the reception level. The detected reception level is compared with a carrier sense level (threshold). If the received level is equal to or higher than the carrier sense level, the PHY processing unit 50 indicates that the medium (CCA: Clear Channel Assessment) is busy. To the MAC processing unit 10 (more precisely, the reception processing unit 40). If the reception level is lower than the carrier sense level, the PHY processing unit 50 outputs a signal indicating that the medium (CCA) is idle to the MAC processing unit 10 (more precisely, the reception processing unit 40). .

The PHY processing unit 50 performs a decoding process (including demodulation and decoding of an error correction code) and a process of removing a physical header (PHY header) including a preamble on the received signal, and extracts a payload. In the IEEE802.11 standard, this payload is transferred to the PHY side by a PSDU (physical layer convergence procedure).
(PLCP) service data unit. The PHY processing unit 50 passes the extracted payload to the reception processing unit 40, and the reception processing unit 40 handles this as a MAC frame. According to the IEEE 802.11 standard, this MAC frame is defined as medium access control (MAC) protocol data.
unit). In addition, the PHY processing unit 50 notifies the reception processing unit 40 when reception of the reception signal is started, and notifies the reception processing unit 40 when reception of the reception signal is completed. When the received signal is successfully decoded as a physical packet (PHY packet) (if no error is detected), the PHY processing unit 50 notifies the reception end of the received signal and that the medium is idle. Is passed to the reception processing unit 40. When detecting an error in the received signal, the PHY processing unit 50 notifies the reception processing unit 40 of the detection of the error with an appropriate error code corresponding to the type of the error. Further, when determining that the medium has become idle, the PHY processing unit 50 notifies the reception processing unit 40 of a signal indicating that the medium is idle.

  The MAC common processing unit 20 mediates the transmission of the transmission data from the upper processing unit 90 to the transmission processing unit 30 and the transmission of the reception data from the reception processing unit 40 to the upper processing unit 90. In the IEEE 802.11 standard, the data in the MAC data frame is called MSDU (medium access control (MAC) service data unit). Further, the MAC common processing unit 20 once receives an instruction from the MAC / PHY management unit 60, converts the instruction to the transmission processing unit 30 and the reception processing unit 40, and converts the instruction into a suitable one.

The MAC / PHY management unit 60 corresponds to, for example, an SME (Station Management Entity) in the IEEE 802.11 standard. In this case, the interface between the MAC / PHY management unit 60 and the MAC common processing unit 20 is MLME SAP (MAC subLayer Management) in the IEEE 802.11 standard.
An interface between the MAC / PHY management unit 60 and the PHY processing unit 50 corresponds to an Entity Service Access Point, and a PLME SAP (Physical Layer Management Agent) in an IEEE 802.11 wireless LAN (Local Area Network). Equivalent to.

  In FIG. 1, the MAC / PHY management unit 60 is illustrated as if the function unit for MAC management and the function unit for PHY management are integrated, but may be mounted separately. Good.

  The MAC / PHY management unit 60 holds a management information base (MIB). The MIB holds various information such as the capability of the terminal itself and whether various functions are valid or invalid. For example, whether or not the own terminal is compatible with OFDMA, and information on / off of a function of a capability of performing OFDMA in the case of OFDMA may be held. The memory for holding and managing the MIB may be included in the MAC / PHY management unit 60, or may be provided separately without being included in the MAC / PHY management unit 60. When a memory for holding and managing the MIB is provided separately from the MAC / PHY management unit 60, the MAC / PHY management unit 60 can refer to the other memory and rewrites rewritable parameters in the memory. It can be performed. The memory may be a volatile memory such as an SRAM or a DRAM, or a nonvolatile memory such as a NAND or an MRAM. Instead of a memory, a storage device such as an SSD or a hard disk may be used. In the base station, these pieces of information of other terminals as non-base stations can also be obtained by notification from the terminal. In this case, the MAC / PHY management unit 60 can refer to and rewrite information on other terminals. Alternatively, a memory for storing information on these other terminals may be held and managed separately from the MIB. In this case, the MAC / PHY management unit 60 or the MAC common processing unit 20 can refer to and rewrite the other memory. In addition, when implementing OFDMA (UL-OFDMA or DL-OFDMA), the MAC / PHY management unit 60 of the base station performs a resource unit for OFDMA on the basis of various information regarding the terminal as a non-base station or a request from the terminal. May also be provided with a selection function for selecting a terminal to which is assigned a. Further, the MAC / PHY management unit 60 or the MAC processing unit 10 may manage the transmission rate applied to the MAC frame and the physical header to be transmitted. The MAC / PHY management unit 60 of the base station may define and manage a support rate set that is a rate set supported by the base station. The support rate set may include a rate that the terminal connected to the base station must support and an optional rate.

  The MAC processing unit 10 handles three types of MAC frames, that is, a data frame, a control frame, and a management frame, and performs various processes defined in the MAC layer. Here, three types of MAC frames will be described.

  The management frame is used for managing a communication link with another terminal. As the management frame, for example, there is a beacon (Beacon) frame that broadcasts a group attribute and synchronization information in order to form a wireless communication group that is a Basic Service Set (BSS) in the IEEE 802.11 standard. There are also frames exchanged for authentication or for establishing a communication link. Here, a state in which one terminal has exchanged information necessary for performing wireless communication with another terminal has been described as a communication link being established. Necessary information exchange includes, for example, notification of a function (for example, support for the OFDMA scheme and various capabilities) supported by the terminal, negotiation on scheme setting, and the like. The management frame is generated by the transmission processing unit 30 based on an instruction received from the MAC / PHY management unit 60 via the MAC common processing unit 20.

In connection with the management frame, the transmission processing unit 30 has a notification unit that notifies other terminals of various information via the management frame. For example. The notifying means of the terminal as a non-base station transmits information on which of the OFDMA-compatible terminal, the IEEE802.11n-compatible terminal, and the IEEE802.11ac-compatible terminal into a management frame and transmits the information to the base station. The type of the own terminal may be notified. The management frame includes, for example, an Association used in an association process, which is one of the procedures for performing authentication between a terminal and a base station.
There is a Request frame or a Reassociation Request frame used in the rear association process. The notifying unit of the base station may notify the terminal of the non-base station of information on whether or not it can support OFDMA communication via a management frame. The management frame used for this includes, for example, a Beacon frame and a Probe Response frame which is a response to a Probe Request frame transmitted by a non-base station terminal. The base station may have a function of grouping a group of terminals connected to the base station. The above-mentioned notifying means of the base station may notify, via a management frame, a group ID which is a group identifier of a group to which each terminal belongs. As the management frame, for example, there is a Group ID Management frame.
For the group ID, for example, a group ID (6 bits) defined for downlink MU-MIMO (Multi-User Multi-Input Multi-Output) (DL-MU-MIMO) in IEEE Std 802.11ac-2013 is OFDMA. Or a group ID defined by another method.

  Here, the association ID (AID) will be described. The AID is an identifier (terminal identifier) of the terminal assigned by the base station in an association process for connecting the terminal to the base station and exchanging data frames with the BSS under the base station. Specifically, the association process transmits an Association Request frame from the terminal to the base station, transmits an Association Response frame from the base station to the terminal, and sets the terminal Status Code field in the Association Response frame to “0”, ie, success. Is a successful process. In both the Association Request frame and the Association Response frame, the communication capability (Capability) of the transmitting terminal is entered, whereby both the receiving terminals grasp the communication capability of the other party. If the terminal status code field in the association response frame is “0”, that is, success, the AID is extracted from the AID field (16 bits) in the frame and used as the AID of the destination terminal. That is, at this point, the AID has been assigned to the terminal from the base station, and the AID is valid as a terminal. In a state where the base station is connected to the terminal (Association), the AID of the terminal is valid. On the other hand, when the base station transmits a disassociation frame to the terminal and the terminal receives the disassociation frame, or when the terminal transmits the disassociation frame to the base station, the AID of the terminal becomes invalid (null). AID is, of course, invalid even for a terminal that has not gone through the association process with any base station. A state in which the AID is invalid can also be referred to as a state in which the AID is not specified.

  The reception processing unit 40 has a receiving unit that receives various information from another terminal via a management frame. As an example, the receiving unit of the base station may receive information on whether or not OFDMA is supported from a terminal as a non-base station. Also, when the terminal as the non-base station is a legacy terminal (such as a terminal conforming to the IEEE 802.11a / b / g / n / ac standard), information on a channel width (maximum available channel width) that can be supported is provided. You may receive it. The receiving means of the terminal may receive information on whether or not OFDMA is supported from the base station.

  The example of the information transmitted and received via the management frame described above is only an example, and various other information can be transmitted and received between terminals (including the base station) via the management frame. For example, an OFDMA-compatible terminal may use a resource unit, or a channel, or both of which the user desires to use in UL-OFDMA transmission, a carrier-sense non-interfering channel, or a non-interfering resource unit, or You may select from both. Then, information on the selected resource unit or channel or both of them may be notified to the base station. In this case, the base station may allocate resource units for UL-OFDMA communication to each OFDMA-compatible terminal based on the information. The channels used in the OFDMA communication may be all channels available as a wireless communication system, or may be a part (one or more) channels.

  The data frame is used to transmit data to another terminal in a state where a communication link has been established with another terminal. For example, data is generated in the terminal by a user's application operation, and the data is carried by a data frame. Specifically, the generated data is passed from the higher-level processing unit 90 to the transmission processing unit 30 via the MAC common processing unit 20, and the transmission processing unit 30 puts the data in the frame body field, and stores the data in the frame body field. A data frame is generated by adding a MAC header. Then, the PHY processing unit 50 adds a physical header to the data frame to generate a physical packet, and the physical packet is transmitted via the analog processing unit 70 and the antenna 80. When the PHY processing unit 50 receives a physical packet, the PHY processing unit 50 performs physical layer processing based on the physical header to extract a MAC frame (here, a data frame), and passes the data frame to the reception processing unit 40. Upon receiving the data frame (when it is determined that the received MAC frame is a data frame), the reception processing unit 40 extracts information of the frame body field as data, and extracts the extracted data via the MAC common processing unit 20. To the upper processing unit 90. As a result, operations on the application such as data writing and reproduction occur.

  The control frame is used for controlling transmission and reception (exchange) of the management frame and the data frame with another wireless communication device. As the control frame, for example, before starting exchange of a management frame and a data frame, an RTS (Request to Send) frame exchanged with another wireless communication device to reserve a wireless medium, a CTS (Clear to Send) Send) frame. Other control frames include a delivery confirmation response frame for confirming delivery of the received management frame and data frame. Examples of the delivery confirmation response frame include an ACK (Acknowledgment) frame, a BA (BlockACK) frame, and the like. Since the CTS frame is also transmitted as a response to the RTS frame, it can be said that the CTS frame is a frame indicating a delivery confirmation response. The CF-End frame is also one of the control frames. The CF-End frame is a frame that announces the end of a CFP (Content Free Period), that is, a frame that permits access to a wireless medium. These control frames are generated by the transmission processing unit 30. For a control frame (CTS frame, ACK frame, BA frame, etc.) transmitted as a response to the received MAC frame, the reception processing unit 40 determines the necessity of transmitting a response frame (control frame), Necessary information (type of control frame, information set in an RA (Receiver Address) field, etc.) is sent to the transmission processing unit 30 together with a transmission instruction. The transmission processing unit 30 generates an appropriate control frame based on information necessary for generating the frame and a transmission instruction.

  When transmitting the MAC frame based on CSMA / CA (Carrier Sense Multiple Access with Carrier Aviidance), the MAC processing unit 10 needs to acquire an access right (transmission right) on the wireless medium. The transmission processing unit 30 measures transmission timing based on the carrier sense information from the reception processing unit 40. The transmission processing unit 30 gives a transmission instruction to the PHY processing unit 50 according to the transmission timing, and further passes the MAC frame. In addition to the transmission instruction, the transmission processing unit 30 may also instruct the modulation scheme and the encoding scheme used for transmission. In addition to these, the transmission processing unit 30 may instruct transmission power. After acquiring the access right (transmission right), the MAC processing unit 10 obtains a transmission opportunity (TXOP) that can occupy the medium. However, the MAC processing unit 10 has a limitation such as a QoS (Quality of Service) attribute, but performs other wireless communication. MAC frames can be exchanged continuously with the device. The TXOP is acquired, for example, when the wireless communication device transmits a predetermined frame (for example, an RTS frame) based on CSMA / CA, and correctly receives a response frame (for example, a CTS frame) from another wireless communication device. When the predetermined frame is received by the other wireless communication device, the other wireless communication device transmits the response frame after a minimum frame interval (Short InterFrame Space; SIFS). As a method of acquiring a TXOP without using an RTS frame, for example, a data frame requesting transmission of an acknowledgment response frame by direct unicast (a frame having a concatenated frame or a concatenated May be transmitted, or a management frame may be transmitted, and a delivery acknowledgment frame (ACK frame or BlockACK frame) corresponding thereto may be correctly received. Alternatively, when a frame that does not request transmission of an acknowledgment frame to another wireless communication apparatus and whose duration is set to be equal to or longer than the time required for transmitting the frame in the Duration / ID field of the frame is transmitted. It may be interpreted that the TXOP of the period described in the Duration / ID field has been acquired from the stage of transmitting the frame.

  The reception processing unit 40 manages the carrier sense information described above. The carrier sense information is based on physical carrier sense (Physical Carrier Sense) information relating to busy / idle of the medium (CCA) input from the PHY processing unit 50 and the medium reservation time described in the received frame. It includes both virtual carrier sense (Virtual Carrier Sense) information. If either one of the carrier sense information indicates busy, the medium is considered to be busy, during which transmission is prohibited. In the IEEE 802.11 standard, the medium reservation time is described in a Duration / ID field in a MAC header. When the MAC processing unit 10 receives a MAC frame addressed to another wireless communication device (not addressed to itself), the medium is virtually busy from the end of the physical packet including the MAC frame to the medium reservation time. It is determined that there is. Such a mechanism for virtually determining that the medium is busy, or a period in which the medium is virtually busy, is called a NAV (Network Allocation Vector). It can be said that the medium reservation time indicates the length of the period for instructing suppression of access to the wireless medium, that is, the length of the period for delaying access to the wireless medium.

  Here, the data frame may be configured to connect a plurality of MAC frames or a payload portion of the plurality of MAC frames. The former is called A (Aggregated) -MPDU in the IEEE802.11 standard, and the latter is called A (Aggregated) -MSDU (MAC service data unit). In the case of the A-MPDU, a plurality of MPDUs are connected in the PSDU. Not only data frames but also management frames and control frames are connected. In the case of A-MSDU, a plurality of data payloads, that is, MSDUs, are concatenated in the frame body of one MPDU. In each of the A-MPDU and the A-MSDU, delimiter information (length information, etc.) is stored in a data frame so that the connection of a plurality of MPDUs and the connection of a plurality of MSDUs can be appropriately separated at a receiving terminal. Have been. Both A-MPDU and A-MSDU may be used in combination. Also, the A-MPDU may target only one MAC frame instead of a plurality of MAC frames, and in this case, the delimiter information is stored in the data frame. When an A-MPDU or the like is received, responses to a plurality of connected MAC frames are transmitted together. In this case, a BA (Block ACK) frame is used for the response instead of the ACK frame. In the following description and figures, the notation of MPDU may be used, but this also includes the case of A-MPDU or A-MSDU described above.

  According to the IEEE 802.11 standard, a non-base station terminal joins a BSS (referred to as an infrastructure BSS) composed mainly of a base station so that data frames can be exchanged within the BSS. A plurality of procedures are defined in stages. For example, there is a procedure called an association, in which a terminal of a non-base station transmits an association request frame to a base station to which the terminal requests connection. After transmitting the ACK frame for the association request frame, the base station transmits an association response (Association Response) frame, which is a response to the association request frame.

A terminal can store its capability (capability) in an association request frame and transmit it to notify the base station of the capability of the terminal. For example, the terminal may transmit a channel and / or a resource unit that can be supported by the terminal itself, or information for specifying a standard that the terminal supports, in the association request frame. This information may be set in a frame to be transmitted in a procedure called reassociation for reconnecting to another base station.
In this re-association procedure, a terminal transmits a re-association request (Reassociation Request) frame to another base station requesting re-connection. After transmitting the ACK frame for the reassociation request frame, the other base station transmits a reassociation response (Reassociation Response) frame that is a response to the reassociation request frame.

  As the management frame, a beacon frame, a probe response (Probe Response) frame, or the like may be used in addition to the association request frame and the re-association request frame. The beacon frame is basically transmitted by the base station, and can store not only a parameter indicating the attribute of the BSS but also a parameter for notifying the capability of the base station itself. Thus, as a parameter for notifying the capability of the base station itself, the base station may add information on whether or not it can support OFDMA. Further, as another parameter, information of a supported rate (Supported Rate) of the base station may be notified. The support rate may include a rate mandatory for a terminal participating in the BSS formed by the base station and an optional rate. The probe response frame is a frame transmitted in response to receiving a probe request (Probe Request) frame from a terminal transmitting a beacon frame. Since the probe response frame basically notifies the same contents as the beacon frame, even if the probe response frame is used, the base station notifies the terminal that transmitted the probe request frame of the capability of the own station. be able to. By sending the notification to the OFDMA-compatible terminal, the terminal may perform an operation of, for example, enabling the OFDMA communication function of the terminal.

  In addition, the terminal may notify information of a rate executable by the terminal among the support rates of the base station, as the information to notify the base station of the capability of the terminal. However, as for the mandatory rate among the support rates, the terminal connected to the base station shall have the ability to execute the mandatory rate.

  It should be noted that among the information handled above, if there is information that determines the content of another information by notifying the certain information, the notification can be omitted. For example, consider a case in which a capability corresponding to a certain new standard or specification is defined, and if the capability is satisfied, the terminal is naturally an OFDMA-compatible terminal. In this case, the presence of the capability corresponding to the standard or the specification may be notified as the certain information, and the notification that the terminal is an OFDMA compatible terminal may not be explicitly notified as the other information.

  FIG. 4 shows a wireless communication system according to the present embodiment. This system includes a base station (AP: Access Point) 100 and a plurality of terminals (STAs: STAs) 1 to 8. A BSS (Basic Service Set) 1 is formed by the base station 100 and the subordinate terminals 1 to 8. This system is a wireless LAN system based on the IEEE802.11 standard using CSMA / CA (Carrier Sense Multiple Access with Carrier Aidance). Note that a legacy terminal (such as an IEEE 802.11a / b / g / n / ac standard compatible terminal) other than the terminal according to the present embodiment (OFDMA compatible terminal) may exist in the BSS1.

  FIG. 5A shows a basic format example of a MAC frame. The data frame, the management frame, and the control frame according to the present embodiment are based on such a frame format. This frame format includes a MAC header (MAC header), a frame body (Frame body), and FCS fields. 5B, the MAC header includes fields of Frame Control, Duration / ID, Address 1, Address 2, Address 3, Sequence Control, QoS Control, and HT (High Throughput) control.

  Not all of these fields need be present, and some fields may not be present. For example, the Address 3 field may not exist. In some cases, both or one of the QoS Control and HT Control fields may not be present. In some cases, the frame body field does not exist. There may be other fields not shown in FIG. For example, an Address 4 field may further be present. In the case of a trigger frame described later, the common information field and the terminal information field may be present in the frame body field or the MAC header.

  The Address 1 field contains a destination address (Receiver Address; RA), the Address 2 field contains a source address (Transmitter Address; TA), and the Address 3 field contains a BSS identifier according to the use of the frame. Enter BSSID (Basic Service Set IDentifier) or TA. The BSSID may be a wildcard BSSID (all bits are 1) for all BSSIDs.

  The Frame Control field includes two fields, such as a type (Type) and a subtype (Subtype). A data frame, a management frame, or a control frame is roughly classified in a Type field, and a detailed classification in a roughly classified frame is performed in a Subtype field. For example, control frames include frames such as a BA (Block Ack) frame, a BAR (Block Ack Request) frame, an RTS (Request to Send) frame, and a CTS (Clear to Send) frame, and these frames are identified by Subtype. Done in the field. Trigger frames to be described later may also be distinguished by combinations of types and subtypes. As an example, the trigger frame is classified as a control frame (type is “control”).

  The Duration / ID field describes the medium reservation time, and when a MAC frame addressed to another terminal is received, the medium is virtually busy from the end of the physical packet including the MAC frame to the medium reservation time. Is determined. Such a mechanism for virtually determining that the medium is busy, or a period in which the medium is virtually busy, is referred to as a NAV (Network Allocation Vector), as described above. The QoS field is used for performing QoS control for performing transmission in consideration of the priority of the frame. The HT Control field is a field introduced in IEEE 802.11n.

In the management frame, an information element (Information element; IE) to which a unique element ID (IDentifier) is assigned is set to Frame.
Set in the Body field. In the frame body field, one or more information elements can be set after a field specific to the type of the management frame. As shown in FIG. 6, the information element has each of an Element ID field, a Length field, and an information (Information) field. An information element is identified by an Element ID. The information field stores the content of the information to be notified, and the Length field stores the length information of the information field.

  In the FCS field, FCS (Frame Check Sequence) information is set as a checksum code used for detecting a frame error on the receiving side. Examples of the FCS information include a CRC (Cyclic Redundancy Code).

  FIG. 7 shows an operation sequence example of the base station (AP) 101 according to the present embodiment and a plurality of terminals including the terminals (STA) 1 to (STA) 8. Terminals 1 to 8 are OFDMA-compatible terminals. FIG. 7 shows a basic operation sequence according to the present embodiment, and the operation according to the features of the present embodiment will be described later with another operation sequence example (see FIG. 14).

  In this system, communication (single-user communication) is individually performed between the base station and some or all of the terminals 1 to 8 on a CSMA / CA basis. In single-user communication, for example, communication is performed between a base station and a terminal using one channel having a basic channel width (for example, 20 MHz). As an example of the single-user communication, when data for uplink transmission is held in a terminal, an access right to a wireless medium is acquired according to CSMA / CA. For this reason, the terminal performs carrier sense during a carrier sense time (standby time) between DIFS / AIFS [AC] and a randomly determined back-off time, and when the medium (CCA) is determined to be idle, Acquire the access right to transmit one frame. The terminal transmits a data frame including the data to be transmitted (more specifically, a physical packet including the data frame), and when the base station receives the data frame normally, after a SIFS time from the completion of the reception of the data frame, the transmission confirmation is performed. An ACK frame as a response frame (more specifically, a physical packet including the ACK frame) is returned. The terminal determines that the data frame has been successfully transmitted by receiving the ACK frame. The data frame transmitted to the base station may be an aggregation frame (A-MPDU or the like), and the delivery confirmation response frame to which the base station responds may be a BA frame (the same applies hereinafter). The DIFS / AIFS [AC] time means one of DIFS and AIFS [AC]. In the case of not supporting QoS, it indicates DIFS time, and in the case of supporting QoS, it indicates AIFS [AC] time determined according to an access category (AC: Access Category) (described later) of data to be transmitted. Note that the basic configuration of a physical packet is such that a physical header is added to a MAC frame stored in a data field, as shown in FIG. 8 described later.

  The base station determines the start of UL-OFDMA at an arbitrary timing. In this example, it is assumed that UL-OFDMA transmission is performed on the same channel as single-user communication (one channel having a basic channel width of 20 MHz). That is, it is assumed that UL-OFDMA transmission is performed using a plurality of resource units defined in a channel having a basic channel width of 20 MHz. However, it is also possible to perform UL-OFDMA transmission with another channel width such as 40 MHz or 80 MHz.

  When the base station determines to start UL-OFDMA, it transmits a UL-OFDMA trigger frame, more specifically, a random access trigger frame (more specifically, a physical packet including a random access trigger frame) 501.

  The random access trigger frame 501 allows use of an arbitrary terminal or a plurality of terminals for all or at least a part of a plurality of resource units available for UL-OFDMA. A specific terminal is not allocated to the resource unit (a terminal to be used is not limited to a specific terminal). Such a resource unit (RU) may be referred to as an “STA unspecified RU”. Note that a specific terminal may be assigned to a resource unit other than the STA-unspecified RU, and in that case, only that specific terminal uses that resource unit. That is, the STA-unspecified RU is a resource unit that allows the terminal to randomly select and use (uplink transmission). The trigger frame including the designation of the STA unspecified RU for at least some of the resource units is called a random access trigger frame. In the figure, the trigger frame for random access is expressed as “TF-R”.

  When transmitting the trigger frame 501 for random access, it is assumed that the base station has acquired the access right in accordance with CSMA / CA in advance. The trigger frame 501 for random access is transmitted on a channel having the same basic channel width as that of the single user communication. The physical packet including the random access trigger frame is obtained by adding a physical header to the head of the random access trigger frame. As an example, as shown in FIG. 8, the physical header is L-STF (Legacy-Short Training Field), L-LTF (Legacy-Long Training Field), L-SIG (Legacy Signal) defined in the IEEE 802.11 standard. Field). L-STF, L-LTF, and L-SIG are fields (legacy fields) that can be recognized by a terminal of a legacy standard such as IEEE 802.11a, for example, signal detection, frequency correction (channel estimation), and transmission speed, respectively. Is stored. Fields other than those described here (for example, fields that cannot be recognized by legacy-standard terminals and can be recognized by OFDMA-compatible terminals) may be included. The random access trigger frame 501 may be a frame that can be received and decoded by a legacy terminal in addition to an OFDMA-compatible terminal.

  FIG. 9 shows a format example of a trigger frame (including a case of a trigger frame for random access). It is based on the format of the general MAC frame shown in FIG. 5, and includes a Frame Control field, a Duration / ID field, an Address 1 field, an Address 2 field, a common information field (Common Info.) Field, and a plurality of terminal information (STA Info). .) Field and an FCS field. The Type and Subtype in the Frame Control field specify that the frame is a trigger frame. Type is “control” as an example, and Subtype may define a new value corresponding to the trigger frame. However, a trigger frame in which Type is set to "management" or "data" may be defined. Instead of defining a new value as Subtype, a field for notifying that the frame is a trigger frame may be expressed using a reserved field of the MAC header. In the Address 1 field, a broadcast address or a multicast address may be set as RA. The MAC address (BSSID) of the base station may be set as TA in the Address 2 field. However, the Address1 field and / or the Address2 field may be omitted. In the common information field, information to be commonly notified to a plurality of terminals is set. For example, information specifying the format of the terminal information field, information specifying the packet length to be transmitted in the response, information indicating the purpose of the trigger frame, and information specifying the type of the frame to be transmitted in the response may be set. Further, information on the number of terminal information fields may be set. Information to be individually notified to a plurality of terminals is set in the plurality of terminal information fields. FIG. 10 shows a detailed configuration example of the terminal information fields 1 to n. Each of the terminal information fields 1 to n includes an RU field and an AID field.

  Each of the terminal information fields 1 to n includes, for example, a pair (set) of an RU field (RU_1 to RU_n) and an AID field (AID_1 to AID_n). An identifier of an available resource unit is set in the RU field. In the AID field, an identifier (AID) of a terminal to which the resource unit is assigned or information indicating that use of a specific terminal is not specified is set. In the present embodiment, information indicating that use is not specified for a specific terminal is represented by “X” that is an unused AID value. X is an AID value not assigned to any terminal, and is a value defined in advance by a system or a standard or a value arbitrarily determined by a base station. The value of X may be notified in advance from the base station to each terminal in a management frame such as a beacon frame. The resource unit to which “X” is set is a resource unit that any terminal can use, that is, a resource unit for random access.

  A terminal for which the identifier of the terminal itself is set in any of the AID fields may or may not permit the use of the resource unit for random access in addition to the resource unit designated for use. It is not necessary. In the present embodiment, the terminal describes a mode in which the resource unit for random access is not used when there is a resource unit specified to be used, but the terminal is not limited to this.

  Note that a configuration is also possible in which the use of the resource unit for random access is limited to a specific terminal group or a group having a specific group ID. In the latter case, a group ID may be set in the AID field. In the former case, a plurality of AIDs may be set in association with the RU field. Methods other than those described here may be used.

  Note that n (the number of pairs of the RU field and the AID field) may be fixed or variable. If variable, the value of n may be set in the common information field, or a field notifying the end of the RU / AID field may be provided. The field for notifying the end may be a field in which a special value not set in the combination of the identifier of the resource unit and the AID is set. The terminal information field may include a field other than the RU field and the AID field. For example, a field for setting information for designating transmission power, MCS, and the like used by the terminal may exist.

  Hereinafter, an example will be described in which a plurality of terminal groups are made to randomly select a resource unit and perform frame transmission using a frame format having such an RU / AID field configuration.

  Trigger frames for random access (TF-R) 501 transmitted from the base station are received by terminals 1 to 8. In the present example, in the trigger frame 501 for random access, four resource units (RU # 1, RU # 2, RU # 3, and RU # 4) are specified, and "X" is set as the AID for each resource unit. Suppose That is, RU # 1 to RU # 4 are STA-unspecified RUs. However, more resource units may be specified in the random access trigger frame 501, or the AID of a specific terminal may be specified in some resource units.

  On the terminals 1 to 8 side, the random access trigger frame 501 is decoded, and among the four resource units RU # 1, RU # 2, RU # 3, and RU # 4, the use of the own terminal may be specified. In this case, since AID “X” is set in any of the resource units, it is determined that all of the resource units are resource units for random access (RUs not specified by the STA). . This determination is made by the MAC processing unit 10 (for example, the reception processing unit 30 or the MAC common processing unit 20) or the MAC / PHY management unit 60.

  The terminals 1 to 8 hold a backoff value (UL-OFDMA Backoff (OBO) Count) randomly selected from a range equal to or less than a contention window (UL-OFDMA: CWO) value for UL-OFDMA. I have. More specifically, a back-off value selected from a value range from 0 to the CWO value is held. CWO corresponds to information on a value range. In this example, the size of the value range is CWO-0 = CWO. However, the lower limit of the value range need not be 0. Here, the minimum value of CWO is described as CWOmin, and the maximum value of CWO is described as CWOmax. CWO is selected from the range of not less than CWOmin and not more than CWOmax. Here, it is assumed that “31” is selected as the CWO of the predetermined initial value. The CWO, back-off value (OBO value), CWOmin, and CWOmax may be managed by the MAC processing unit 10, the MAC / PHY management unit 60, or the like, and a memory accessible from the MAC processing unit 10, the MAC / PHY management unit 60, or the like. May be stored.

  The terminals 1 to 8 update the OBO by subtracting the number of STA-unspecified RUs specified in the random access trigger frame 501 from the back-off value of the terminal itself. When the updated OBO reaches a predetermined value, it is determined that there is a selection right, and an STA-unspecified RU is selected. Thereby, the access right to the selected STA unspecified RU is acquired. In the present embodiment, it is assumed that the predetermined value is 0. If the result of the subtraction is smaller than 0, the updated OBO is rounded up to 0. As described above, when the updated OBO value reaches 0, the right to select is obtained. In other words, when the trigger frame for random access is received, 1 is subtracted from the OBO value (OBO value -1), and the value is obtained by subtracting 1 from the number of STA-unspecified RUs of the trigger frame for random access ( If the number is equal to or less than the STA unspecified RU number-1), the right to select is obtained. In other words, if the OBO value at the time of receiving the random access trigger frame (the OBO value before the subtraction) is equal to or less than the number of STA-unspecified RUs of the random access trigger frame, the terminal acquires the right of selection. The determination of the OBO update and the acquisition of the selection right is performed by the MAC processing unit 10 (for example, the MAC common processing unit 20 or the reception processing unit 40) or the MAC / PHY management unit 60.

  Here, it is assumed that each of the terminals 1 to 8 has an uplink transmission request. The terminal having the transmission request holds the backoff value selected from the range equal to or less than the CWO value as described above. The first selection of the backoff value may be performed when a transmission request occurs before receiving the random access trigger frame 501, or may be performed upon receiving the random access trigger frame 501. If another random access trigger frame is received before the random access trigger frame 501 is received, the OBO value after the subtraction at that time is used as the value when the current random access trigger frame 501 is received. It may be used as it is as an OBO value (an OBO value before subtraction).

FIG. 11 is a supplementary diagram for explaining the sequence of FIG. 7, in which the horizontal direction corresponds to time and the vertical direction corresponds to frequency along the plane of the paper. The OBO values of the terminals 1 to 8 (STA1 to 8) are respectively STA1OBO = 10
STA 2 OBO = 3
STA 3 OBO = 5
STA 4 OBO = 4
STA 5 OBO = 1
STA 6 OBO = 8
STA 7 OBO = 8
STA 8 OBO = 10
In the trigger frame 501 for random access, the number of STA-unspecified RUs is 4, so 4 is subtracted from each, and the updated (subtracted) OBO value is as follows. Values smaller than 0 are fixed to 0.
STA 1 OBO = 10−4 = 6
STA2OBO = 3-4 = -1 (→ 0)
STA 3 OBO = 5-4 = 1
STA 4 OBO = 4-4 = 0
STA 5 OBO = 1-4 = -3 (→ 0)
STA 6 OBO = 8−4 = 4
STA 7 OBO = 8−4 = 4
STA 8 OBO = 10−4 = 6

  Since the terminals 2, 4, and 5 have reached the updated OBO value to the predetermined value (= 0), the terminals 2, 4, and 5 acquire the selection right. The terminals 2, 4, and 5 randomly select resource units from RUs # 1 to RU # 4, which are STA unspecified RUs specified in the random access trigger frame 501. Here, it is assumed that terminal 2 selects RU # 4, terminal 4 selects RU # 3, and terminal 5 selects RU # 1. Although it is assumed that one resource unit is selected, it is permissible to select two or more resource units. The terminals other than the terminals 2, 4, and 5 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted. The resource unit selection process may be performed by the MAC processing unit 10 (for example, the MAC common processing unit 20, the reception processing unit 40, the transmission processing unit 30, or the like) or the MAC / PHY management unit 60.

  Terminals 2, 4, and 5 use RU # 4, RU # 3, and RU # 1 respectively after a predetermined time (T1) after the completion of the reception of the trigger frame 501 for random access, and use the frames 512, 514, and 515, respectively. Send The frame to be transmitted may be of a predetermined type, or may be a frame arbitrarily determined by each terminal. An example of a frame of a predetermined type may be a UL-OFDMA allocation request frame (a frame that notifies that there is a request to receive data unit allocation for its own terminal and transmit data using a trigger frame). In this case, by using a fixed-length frame, the frame length transmitted by each terminal (more specifically, the packet length of a physical packet including a frame) can be unified. Further, the terminal information field or the common information field of the random access trigger frame 501 specifies parameter information such as the packet length and MCS of each terminal, and the terminal generates a frame according to the parameter information, and generates the frame (more detailed information). May transmit a physical packet including a frame. If the packet length is less than the specified value, the packet length may be adjusted by adding padding data. Since RU # 2 was not selected by any terminal, transmission is not performed by RU # 2. If there is a resource unit other than RU # 1 to RU # 4 and the resource unit is specified to another terminal in the random access trigger frame 501, the terminal uses a frame in the specified resource unit. May be transmitted. In this case, the terminal and the terminals 2, 4, and 5 perform uplink transmission (UL-OFDMA transmission) at the same time. Note that the frames transmitted by the terminals 2, 4, and 5 may be aggregation frames (A-MPDU) in which a plurality of data frames and the like are aggregated.

  As the time T1, for example, a predefined IFS time [μs] can be used. The predefined IFS time may be a SIFS time (= 16 μs), which is a time interval between frames defined in the MAC protocol specification of the IEEE 802.11 wireless LAN, or may be a longer time or a shorter time. The value of the time T1 may be stored in the common information field or the MAC header of the trigger frame, and the terminal may read and use the value. Alternatively, the time T1 may be notified in advance by another method such as a beacon frame or another management frame.

  The base station receives and decodes frames 515, 514, and 512 transmitted from terminals 5, 4, and 2 at RU # 1, RU # 3, and RU # 4, and checks the decoded frame with an FCS check (such as a CRC check). To determine whether the frame has been successfully received. The base station generates and transmits an acknowledgment response frame 502 (downlink response) according to the inspection result of each frame (successful reception). Here, a single acknowledgment response frame 502 indicating all acknowledgments of the terminals 2, 4, and 5 is transmitted. The format of such an acknowledgment frame may be a newly defined format, or a Multi-STA BA frame using a BA (Block Ack) frame may be used. Here, it is assumed that a Multi-STA BA frame is transmitted.

Here, the Multi-STA BA frame will be described. The Multi-STA BA frame is obtained by diverting a Block Ack frame (BA frame) in order to confirm delivery to a plurality of terminals in one frame. The frame type may be control similarly to a normal BA frame, and the frame subtype may be BlockAck. FIG. 12A shows a format example of the Multi-STA BA frame. FIG. 12B shows an example of a format of a BA Control field in a BA frame, and FIG. 12C shows an example of a format of a BA Information field in a BA frame. When reusing the BA frame, the BA frame format extended for notifying the delivery acknowledgment regarding a plurality of terminals is indicated by BA
It may be indicated in the Control field. For example, in the IEEE 802.11 standard, the case where the Multi-TID subfield is 1 and the Compressed Bitmap subfield is 0 is the current reservation (Reserved). This may be used to indicate that it is an extended BA frame format for notifying delivery acknowledgments for a plurality of terminals. Alternatively, in FIG. 12B, the area of bits B3 to B8 is a reserved subfield, but a part or all of this area is in a BA frame format extended for notifying delivery acknowledgments for a plurality of terminals. May be defined to indicate something. Alternatively, such notification need not be explicitly performed.

The RA field in the BA frame may be, for example, a broadcast address or a multicast address. The number of users (the number of terminals) reporting in the BA Information field may be set in the Multi-User subfield of the BA Control field. The BA Information field includes, for each user (terminal), an association ID subfield, a Block Ack Starting Sequence Control (Block Ack Starting Sequence Control) subfield, and a Block Ack bitmap (Block).
(Ack Bitmap) subfield.

  An AID is set in the association ID subfield for user identification. More specifically, as shown in FIG. 12C, as an example, a part of a Per TID Info field is used as a subfield for an association ID. At present, 12 bits (B0 to B11) are reserved areas. The first 11 bits (B0-B10) are used as a subfield for association ID. The Block Ack start sequence control subfield and the Block Ack bitmap subfield may be omitted when the frame transmitted by the terminal is a single data frame (when it is not an aggregation frame). When the frame transmitted by the terminal is an aggregation frame, the sequence number of the first MSDU (medium access control (MAC) service data unit) of the delivery acknowledgment indicated by the BlockAck frame is stored in the Block Ack start sequence control subfield. I do. In the Block Ack bitmap subfield, a bitmap (Block Ack bitmap) including bits indicating whether or not each of the sequence numbers after the Block Ack start sequence number has been successfully received may be inserted.

The terminal that has received the Multi-STA BA frame 502 confirms the Type and the Subtype in the frame control field. When these are detected as control and BlockAck, the RA field is checked next, and since this value is a broadcast address or the like, each data frame in the frame transmitted by the terminal itself (in the case of an aggregation frame) is checked. The information of the delivery acknowledgment (success / non-success) is specified from the Block Ack Bitmap field, and whether the transmission of each data frame is successful is determined. For example, the TID Info subfield storing the AID of the own terminal is set to BA
The value (start sequence number) specified from the Information field and set in the Block Ack Starting Sequence Control subfield following the specified TID Info subfield is specified, and whether or not each sequence number after the start sequence number has been successfully transmitted is specified. From the Block Ack bitmap. The bit length of the AID may be shorter than the length of the TID Info subfield, and the AID may be, for example, as described above, a partial area of the TID Info subfield (for example, the first 11 bits (2 octets (16 bits) of the 2 octets (16 bits))). B0-B10)).

When a plurality of terminals transmit a single frame instead of an aggregation frame by UL-OFDMA (this case is assumed in the sequence of FIG. 7), for example, the following may be performed. As shown in FIG. 12C, one bit in the TID Info subfield of each BA information field (for example, of the 2 octets (16 bits), the 12th bit from the beginning (B11 if the beginning is B0)) Is used as a bit indicating an ACK or BA (ACK / BA bit), and a value indicating the ACK is set in the bit. When a value indicating ACK is set, the Block Ack Starting Sequence Control subfield and the Block Ack Bitmap subfield are omitted.
Thereby, ACKs of a plurality of terminals can be notified by one BA frame. Since it is not necessary to notify the ACK of the terminal whose test result has failed, it is not necessary to notify the terminal in the Multi-STA BA frame. The terminal on the receiving side can determine that transmission has failed because there is no ACK of the terminal itself. In this way, even when a plurality of terminals transmit either an aggregation frame or a single frame, it is possible to perform delivery confirmation for the plurality of terminals with a single delivery confirmation response frame using a BA frame.

  When transmitting the Multi-STA BA frame 502, the access point transmits the Multi-STA BA frame 502 in the same frequency band as the random access trigger frame 501 or the UL-OFDMA, or in the band of the basic channel width of 20 MHz, for example. You may.

  As a method other than transmitting the Multi-STA BA frame, an acknowledgment response frame (ACK frame or BA frame, etc.) may be transmitted individually for each terminal. At this time, the acknowledgment frame may be transmitted to a plurality of terminals simultaneously using DL-OFDMA.

FIG. 13 shows a configuration example of a physical packet when transmitting acknowledgment frames to a plurality of terminals by DL-OFDMA. For example, the L-STF, L-LTF, and L-SIG fields are transmitted with a channel width of 20 MHz as an example, and the same value (the same symbol) is set in any of the acknowledgment frames for each terminal. The SIG1 field sets common information for a plurality of terminals, and specifies, for example, a resource unit used for reception for each terminal. For example, information in which a terminal identifier is associated with a resource unit number (identifier) is set. The terminal identifier may be an association ID (AID) or a part of the AID (Partial
AID) or another identifier such as a MAC address. The SIG1 field is also transmitted, for example, with a channel width of 20 MHz. Each of the terminals can decode the SIG1 field. The SIG2 field is set individually for each resource unit, and as an example, information such as MCS necessary for decoding the corresponding data field may be set. Therefore, each terminal that has received the signal from the access point can recognize the resource unit to be decoded by decoding the SIG1 field. Each terminal receives the acknowledgment frame by decoding the signal of the designated resource unit. Note that the format example in FIG. 13 is an example, and one or more other fields may be arranged before and after the SIG2 field or before and after the SIG1 field. The other field may be a 20 MHz bandwidth or a resource unit width. Some or all of the other fields may be composed of known symbols, similarly to L-STF and L-LTF.

As a method other than transmitting transmission acknowledgment frames to multiple terminals by DL-OFDMA, transmission acknowledgment frames may be transmitted to multiple terminals by downlink MU-MIMO.
DL-MU-MIMO forms a spatially orthogonal beam for a plurality of terminals and transmits the beam to a plurality of terminals by using a technique called beamforming. DL-MU-MIMO is defined in the IEEE 802.11ac standard, and may be executed according to the standard.

  After transmitting the Multi-STA BA frame 502, the base station transmits a random access trigger frame 503 at a predetermined timing or an arbitrary timing. The configuration of the random access trigger frame 503 is similar to that of the random access trigger frame 501, in which RU # 1 to RU # 4 are specified as STA unspecified RUs. Arbitrary communication may be performed between the transmission of the Multi-STA BA frame 502 and the transmission of the trigger frame 503 for random access. For example, UL-OFDMA communication using a normal trigger frame (a trigger frame that does not include designation of an STA undesignated RU) may be performed.

The terminals 1 to 8 hold the OBO value (backoff value) updated when the previous random access trigger frame 501 was received. However, since the terminals 2, 4, and 5 have transmitted (random access) to the random access trigger frame 501, the OBO value is again taken from the range of 0 or more and CWO or less. Here, it is assumed that the CWO value is the same value 31 as the previous time. Then, it is assumed that the terminals 2, 4, and 5 respectively select 23, 7, and 18 from [0, 31]. Therefore, the OBO values of terminals 1 to 8 (STAs 1 to 8) are as follows.
STA 1 OBO = 6
STA 2 OBO = 23
STA 3 OBO = 1
STA 4 OBO = 7
STA 5 OBO = 18
STA 6 OBO = 4
STA 7 OBO = 4
STA 8 OBO = 6
Since the number of STA-unspecified RUs in the random access trigger frame 503 is 4, 4 is subtracted from the OBO value of each terminal, and the updated (subtracted) OBO is as follows. Values smaller than 0 are fixed to 0.
STA 1 OBO = 6-4 = 2
STA2OBO = 23-4 = 19
STA 3 OBO = 1-4 = -3 (→ 0)
STA 4 OBO = 7−4 = 3
STA5OBO = 18-4 = 14
STA 6 OBO = 4-4 = 0
STA 7 OBO = 4-4 = 0
STA 8 OBO = 6-4 = 2

  Since the updated OBO value has reached the predetermined value (= 0) for the terminals 3, 6, and 7, the terminals 3, 6, and 7 acquire the selection right. The terminals 3, 6, and 7 randomly select resource units from RUs # 1 to RU # 4, which are STA-unspecified RUs specified in the random access trigger frame 503. Here, it is assumed that terminal 3 has selected RU # 2, terminal 6 has selected RU # 4, and terminal 7 has selected RU # 1. Although it is assumed that one resource unit is selected, it is permissible to select two or more resource units. The terminals other than the terminals 3, 6, and 7 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted.

  Terminals 3, 6, and 7 transmit frames 523, 526, and 527 using RU # 2, RU # 4, and RU # 1, respectively, at a predetermined time after the completion of reception of trigger frame 503 for random access. The frame to be transmitted may be of a predetermined type, or may be a frame arbitrarily determined by each terminal. Since RU # 3 was not selected by any terminal, no transmission is performed by RU # 3. If a resource unit other than RU # 1 to RU # 4 is specified to another terminal in the trigger frame for random access 503, the terminal may transmit the frame using the specified resource unit. In this case, the terminal and the terminals 3, 6, and 7 perform uplink transmission (UL-OFDMA transmission) simultaneously. Note that the frames transmitted by the terminals 3, 6, and 7 may be aggregation frames (A-MPDU) in which a plurality of data frames and the like are aggregated.

  The base station receives and decodes frames 527, 523, and 526 transmitted from terminals 7, 3, and 6 with RU # 1, RU # 2, and RU # 4, and checks the decoded frames with an FCS check (such as a CRC check). To determine whether the frame has been successfully received. The base station generates and transmits (downlink response) an acknowledgment frame in accordance with the inspection result of each frame (successful reception). As described above, here, the Multi-STA BA frame 504 is transmitted as a single acknowledgment frame indicating all acknowledgments of the terminals 3, 6, and 7. The operation of the terminal that has received the Multi-STA BA frame 504 is the same as the case of the Multi-STA BA frame 502.

  Based on the above description, an operation sequence according to the features of the present embodiment will be described. FIG. 14 shows an example of this sequence. Elements that are the same as or correspond to those in FIG. 7 are denoted by the same reference numerals. FIG. 15 is a supplementary diagram for explaining the sequence of FIG. In the sequence example of FIG. 7, when a plurality of terminals that have acquired the right to select an STA-undesignated RU randomly select a resource unit, the resource unit selected by each terminal differs. Therefore, the frame transmitted from each terminal was normally received by the base station. On the other hand, in the sequence example of FIG. 14, it is assumed that a plurality of terminals have selected the same resource unit, and thus the base station cannot normally receive frames transmitted from the plurality of terminals. In such a case, one of the features of the present embodiment is to adjust the CWO value so that the priority of acquiring the selection right of the terminal that has failed in transmission is increased (the CWO value is 31 in the sequence of FIG. 7). Was fixed to As an example, in this sequence, the terminal that has failed in transmission sets the CWO value to be smaller than the previous CWO value. Such control ensures fairness between terminals. Hereinafter, the sequence of FIG. 14 will be described in detail. The description will focus on the differences from FIG. 7, and the description overlapping with FIG. 7 will be omitted.

  When the base station determines to start UL-OFDMA, the base station transmits a trigger frame for random access (TF-R) 501. In the random access trigger frame 501, four resource units (RU # 1, RU # 2, RU # 3, and RU # 4) are specified, and any of the resource units is designated as an STA unspecified RU, and the AID field includes an AID " X "is set.

  The terminals 1 to 8 decode the random access trigger frame 501, and it may be determined that use of the own terminal is specified among the four resource units RU # 1, RU # 2, RU # 3, and RU # 4. It is determined whether there is any resource unit. Here, since AID “X” is set in any resource unit, it is determined that all resource units are resource units for random access.

  The terminals 1 to 8 hold a back-off value (OBO value) randomly selected from the range of 0 or more and the CWO value or less. CWO is selected from the range of CWOmin and CWOmax. Here, it is assumed that all terminals have selected the initial value CWOini (= 31). The terminals 1 to 8 update the OBO value by subtracting the number of STA-unspecified RUs in the random access trigger frame 501 from the back-off value of the terminal itself. When the updated OBO value reaches a predetermined value (0 in this case), the right to select the STA unspecified RU is acquired.

Here, the OBO values of terminals 1 to 8 (STAs 1 to 8) are respectively STA 1 OBO = 10
STA 2 OBO = 3
STA 3 OBO = 5
STA 4 OBO = 4
STA 5 OBO = 1
STA 6 OBO = 8
STA 7 OBO = 2
STA 8 OBO = 10
In the random access trigger frame 501, since the number of STA-unspecified RUs is 4, subtract 4 from each, and the updated OBO value is as follows. Values smaller than 0 are fixed to 0.
STA 1 OBO = 10−4 = 6
STA2OBO = 3-4 = -1 (→ 0)
STA 3 OBO = 5-4 = 1
STA 4 OBO = 4-4 = 0
STA 5 OBO = 1-4 = -3 (→ 0)
STA 6 OBO = 8−4 = 4
STA 7 OBO = 2-4 = -2 (→ 0)
STA 8 OBO = 10−4 = 6

  Terminals 2, 4, 5, and 7 have the updated OBO at the predetermined value (0), so that terminals 2, 4, 5, and 7 acquire the selection right. The terminals 2, 4, 5, and 7 randomly select resource units from RUs # 1 to RU # 4, which are STA unspecified RUs specified in the random access trigger frame 501. Here, it is assumed that the terminal 2 selects RU # 4, the terminals 4 and 7 select RU # 3, and the terminal 5 selects RU # 1. Terminal 4 and terminal 7 have selected the same resource unit. The terminals other than the terminals 2, 4, 5, and 7 cannot acquire the selection right because the updated OBO value is greater than 0, and wait for the next random access trigger frame to be transmitted.

  Terminals 2, 4, 5, and 7 use RU # 4, RU # 3, RU # 1, and RU # 3 to determine frames 512, 514, and RU # after a predetermined time from the completion of reception of the random access trigger frame 501. 515 and 517 are transmitted. The terminal 4 and the terminal 7 transmit a frame using the same resource unit (see the hatched portion in FIG. 15).

  The base station receives and decodes frame 515 transmitted from terminal 5 in RU # 1, frames 514 and 517 transmitted from terminals 4 and 7 in RU # 3, and frame 512 transmitted from terminal 2 in RU # 4. Then, by performing FCS inspection (CRC inspection or the like) on the decoded frame, it is determined whether the reception of the frame is successful. The frame 515 of the terminal 5 received by the RU # 1 and the frame 512 of the terminal 2 received by the RU # 4 are successfully received, and the frames 514 and 517 of the terminals 4 and 7 received by the RU # 3 fail. And

The base station, in response to the inspection result of each frame (success or unsuccessful reception), as a delivery confirmation response frame, a Multi-STA BA frame including that the frames 512 and 515 transmitted from the terminals 2 and 5 have been successfully received. 507 is transmitted. Since the reception of the frames 514 and 517 transmitted from the terminals 4 and 7 has failed, the ACK for the terminals 4 and 7 is not included in the Multi-STA BA frame 507. When an aggregation frame including a plurality of data frames is transmitted from the terminals 4 and 7, if reception of all of the aggregated data frames fails, the response to the terminals 4 and 7 is a Multi-STA.
It is not included in the BA frame 507. When a part of the data frame has been successfully received, a notification about the partially received data frame may be sent via the Block Ack start sequence control subfield and the Block Ack bitmap subfield.

  Among the terminals that have received the Multi-STA BA frame 507, the terminals 2, 4, 5, and 7 determine whether the ACK for the frames 512, 514, 515, and 517 transmitted by the own terminal is included in the Multi-STA BA frame 507. Confirm. The terminals 2 and 5 detect that the ACKs of the frames 512 and 515 transmitted by the own terminal are included, but the terminals 4 and 7 cannot confirm the ACKs of the frames 514 and 517 transmitted by the own terminals. Judge that transmission failed. Here, transmission failed means that, when a plurality of terminals did not normally receive a frame in the same resource unit at the base station that transmitted the frame (in this example), only one terminal in a certain resource unit was transmitted. This includes the case where a frame is transmitted, but the base station fails to receive the frame due to poor radio wave environment. If a downlink response frame such as a Multi-STA BA frame or the like is not received within a predetermined time (SIFS time or the like) from the completion of transmission of the frames 512, 514, 515, and 517, it may be determined that the transmission has failed. When the terminal transmits an aggregation frame obtained by aggregating a plurality of data frames and successfully transmits some of the data frames, for example, the terminal determines that transmission (random access) has succeeded, and If the transmission of the data frame has failed, it may be determined that the transmission (random access) has failed.

  After transmitting the Multi-STA BA frame 507, the base station transmits the random access trigger frame 503 at a predetermined timing or at an arbitrary timing. The configuration of the random access trigger frame 503 is similar to that of the random access trigger frame 501, in which RU # 1 to RU # 4 are specified as STA unspecified RUs. Note that any communication may be performed during a period after the Multi-STA BA frame 505 and before the transmission of the random access trigger frame 503. For example, the base station transmits a normal trigger frame (a trigger frame specifying a terminal for each source unit), and communication is performed in which each terminal performs uplink transmission (UL-OFDMA) using the specified resource unit. It doesn't matter.

  The terminals 1 to 8 hold the OBO value (backoff value) updated when the previous random access trigger frame 501 was received. However, since the terminals 2, 4, 5, and 7 have made random access to the trigger frame 501 for random access, the OBO value is selected again from the range of 0 to CWO. However, the terminals 2 and 5 succeeded in transmission, and the terminals 4 and 7 failed in transmission. Therefore, the present embodiment is characterized in that CWO selection is performed as follows.

  The terminals 4 and 7 that have failed in transmission select a CWO smaller than the previous time (CWO = 31) in the range of CWOmin and CWOmax. Every time transmission fails, CWO is gradually reduced to CWOmin. If the transmission is successful, the process returns to the initial CWOini (for example, 31).

  As an example, it is assumed that CWOmin = 1, CWOmax = 31, and that the initial CWOini is 31, which is CWOmax. Each time transmission fails, the CWO is gradually reduced from 31 to 1. Each time a failure occurs, a constant value may be cumulatively subtracted from 31 or a larger value may be cumulatively subtracted as the number of failures increases. As an example of the latter, 1 may be subtracted for the first failure, 2 may be subtracted for the second failure, and 3 may be subtracted for the third failure. In this case, if the starting CWO is 31, the CWO after the first failure is 30 (= 31-1), the second after the failure is 28 (= 30-2), and the third after the failure is 25 (= 30-2). = 28-3). The amount of adjustment of how much the CWO value is adjusted (decreased here) may be notified from the base station to the terminal. The notification direction may be the same as the various notification methods described later.

As another method, the formula for calculating the CWO using the exponent part P may be defined as, for example, “2 ＾ P−1”, and the value of P may be reduced as failures are repeated. As an example, if P = 5 in the case of CWOmax, then CWOmax = 2 ＾ 5-1 = 31. If P = 1 when CWOmin = 1, then CWOmin = 2 ＾ 1-1 = 1. At the start, it is assumed that CWO matches CWOmax. In this case, each time a failure is repeated, the CWO is updated as follows.
Start time 31 (= 2 ＾ 5-1)
-<Failure> → 15 (= 2 ＾ 4-1)
-<Failure> → 7 (= 2 ＾ 3-1)
-<Failure> → 3 (= 2 ＾ 2-1)
-<Failure> → 1 (= 2 ＾ 1-1)
FIG. 16 schematically shows this update. If the transmission is successful, the CWO returns to CWOmax = 31. The value of P may be reported from the base station to the terminal. The notification direction may be the same as the various notification methods described later. The value of P is also an example of the adjustment amount.

  In the case where the latter method is used, in this sequence, if the terminals 4 and 7 have failed for the first time, the CWO will be 15 (= 2 ＾ 4-1), for example. Since the terminals 2 and 5 have successfully transmitted, 31 (= 2 ＾ 5-1) which is still the initial CWOini (= CWOmax) is used as the CWO.

  The terminals 4 and 7 randomly select an OBO value (back-off value) from [0, 15], and assume that the terminal 4 and 7 have selected 7 and 4, respectively (see FIG. 15). The terminals 2 and 5 randomly select an OBO value (backoff value) from [0, 31], and assume that the terminal 2 has selected 23 and the terminal 5 has selected 18 (see FIG. 15). Other terminals use the OBO value currently held as it is.

Therefore, the OBO values of the terminals 1 to 8 (STAs 1 to 8) are as follows (as a result, the OBO values of the terminals are the same as in the sequence example of FIG. 7).
STA 1 OBO = 6
STA 2 OBO = 23
STA 3 OBO = 1
STA 4 OBO = 7
STA 5 OBO = 18
STA 6 OBO = 4
STA 7 OBO = 4
STA 8 OBO = 6

In the random access trigger frame 503, since the number of STA-unspecified RUs is 4, 4 is subtracted from the OBO value of each terminal, and the updated OBO value is as follows. Values smaller than 0 are fixed to 0 (as a result, the OBO value of each terminal is the same as in the sequence example of FIG. 7).
STA 1 OBO = 6-4 = 2
STA2OBO = 23-4 = 19
STA 3 OBO = 1-4 = -3 (→ 0)
STA 4 OBO = 7−4 = 3
STA5OBO = 18-4 = 14
STA 6 OBO = 4-4 = 0
STA 7 OBO = 4-4 = 0
STA 8 OBO = 6-4 = 2

  The terminals 3, 6, and 7 whose updated OBO value has reached the predetermined value (0) are the terminals 3, 6, and 7, and thus the terminals 3, 6, and 7 acquire the selection right. The terminals 3, 6, and 7 randomly select resource units from RUs # 1 to RU # 4, which are STA-unspecified RUs specified in the random access trigger frame 503. Here, it is assumed that terminal 3 has selected RU # 2, terminal 6 has selected RU # 4, and terminal 7 has selected RU # 1. The terminals other than the terminals 3, 6, and 7 cannot acquire the selection right because the updated OBO value is larger than 0, and wait for the next random access trigger frame to be transmitted.

  Terminals 3, 6, and 7 transmit frames 523, 526, and 527 using RU # 2, RU # 4, and RU # 1, respectively, at a predetermined time after the completion of reception of trigger frame 503 for random access. Since RU # 3 was not selected by any terminal, no transmission is performed by RU # 3. Note that the frames transmitted by the terminals 3, 6, and 7 may be aggregation frames (A-MPDU) in which a plurality of data frames and the like are aggregated.

  The base station receives and decodes frames 527, 523, and 526 transmitted from terminals 7, 3, and 6 with RU # 1, RU # 2, and RU # 4, and checks the decoded frames with an FCS check (such as a CRC check). To determine whether the frame has been successfully received. The base station generates and transmits (downlink response) an acknowledgment frame in accordance with the inspection result of each frame (successful reception). As described above, here, the Multi-STA BA frame 504 is transmitted as a single acknowledgment frame indicating all acknowledgments of the terminals 3, 6, and 7. The operation of the terminal that has received the Multi-STA BA frame 504 is the same as the case of the Multi-STA BA frame 502.

  The values of CWOmax and CWOmin may be reported from the base station to a terminal group belonging to the BSS by using a beacon frame or a trigger frame (including a trigger frame for random access). In the case of notification using a trigger frame, a field for setting CWOmax and CWOmin may be provided in the common information field or the terminal information field. The CWO initial value (CWOini) may be notified in the same manner, or may be determined in advance by a system or a standard.

  The difference between updating the CWO value according to the present embodiment and updating the contention window (CW) used in the CSMA / CA random back-off mechanism will be described. It is assumed that a certain terminal performs back-off (carrier sense) in CSMA / CA for a time based on CW and transmits the terminal as carrier sense idle. At this time, if the transmission to another terminal happens to be the same, the terminal determines that there is no ACK response based on ACK Timeout and exponentially increases the CW value. The initial value of the CW value is CWmin, and the CW value is increased up to CWmax as retransmission is performed. This is a measure for giving a further variation on the time axis in order to avoid simultaneous transmission by judging that the CW value used for the competing terminals did not sufficiently vary. On the other hand, in the mechanism of the trigger frame for random access according to the present embodiment, there are two types of terminals that can acquire the STA-unspecified RU and those that cannot acquire the STA-unspecified RU among a plurality of terminals that have acquired the selection right at the same time (CSMA). In the / CA random back-off mechanism, terminals that transmit at the same time basically fail to transmit all terminals (no ACK response). This is different from the random back-off mechanism on the time axis. At this time, fairness is lacking if the same condition is used for acquiring the STA-unspecified RU in the next random access trigger frame between the terminal that can acquire the STA-unspecified RU and the terminal that cannot acquire the STA-unspecified RU. Therefore, in the present embodiment, the priority of acquisition is higher than that of terminals that have succeeded in obtaining by lowering the CWO value of terminals that have failed to obtain each time failures occur, thereby increasing the fairness between terminals. Secure.

  In the above-described embodiment, the acknowledgment response frame (Multi-STA BA frame) is transmitted as a downlink response to a plurality of terminals that have successfully transmitted (randomly accessed), but instead of transmitting the acknowledgment response frame, A form in which the trigger frame is transmitted is also possible. FIG. 17 shows a sequence example in this case.

  The Multi-STA BA frames 507 and 504 in FIG. 14 are replaced with trigger frames 541 and 542. In the trigger frames 541 and 542 in this case, a terminal to be allocated for each resource unit is specified. The format of the trigger frame basically uses the format shown in FIG. 9, and the configuration of the common information field, the terminal information field, or both of them may be different from that of the random access trigger frame. The terminal specified by the trigger frames 541 and 542 transmits a frame such as a data frame by a predetermined time after the completion of reception of the trigger frames 541 and 542 using the resource unit allocated to the own terminal. . The frame to be transmitted may be an aggregation frame in which a plurality of data frames and the like are aggregated.

  When transmitting the trigger frames 541 and 542, the base station specifies a terminal that has successfully transmitted by random access to the random access trigger frames 501 and 503. Thus, the terminal that has succeeded in transmission can recognize that the random access to the random access trigger frames 501 and 503 has been successful by specifying its own terminal in the trigger frames 541 and 542. Further, among the terminals that have been randomly accessed, terminals that are not specified in the trigger frames 541 and 542 can be determined to have failed in their own transmission. The frame transmitted by random access may be a frame for notifying the assignment request in the trigger frames 541 and 542. Note that it is also possible to specify a terminal that is not performing random access or a terminal that has failed to transmit by using the trigger frames 541 and 542. The trigger frames 541 and 542 may further include information (packet length, transmission power, MCS, or the like) necessary for the terminal to transmit, in addition to the information specifying the resource unit and the terminal. The selection of the terminal specified by the trigger frame may be performed by the MAC processing unit 10 (for example, the MAC common processing unit 20, the reception processing unit 40, the transmission processing unit 30, or the like) or the MAC / PHY management unit 60.

(Modification 1 of CWO update)
In the above-described embodiment, the CWO value of the terminal is reduced each time transmission fails, but in the first modification, in addition to this, the CWO initial value (CWOini) is set to increase the CWO value each time the transmission succeeds. , CWOmin and CWOmax. The value of CWOinit may be reported from the base station to the terminal in a beacon frame, a trigger frame, or the like.

The operation of the first modification is schematically shown in FIG. First, the value of CWO is set to CWOinit. In this example, 2 ＾ 3-1 = 7, which is an intermediate value between CWOmin and CWOmax (an intermediate value of a power portion). If it succeeds, it raises by one step (addition of 1 to the exponent P), and if it fails, it returns to the previous step (subtraction of 1 by 1). Specific examples are shown below.
At the beginning 7
− <Successful transmission> → 15
− <Successful transmission> → 31
-<Transmission failure> → 7
-<Transmission failure> → 3

(Modification 2 of CWO update)
The initial CWOini is started from CWOmin. In the case of transmission failure, CWO is maintained, and in the case of transmission success, CWO is gradually increased to CWOmax. FIG. 19 schematically illustrates the operation according to the second modification.

At first, the value of CWO is set to CWOmin (2 ＾ 3-1 = 7 in this example). If succeeded, the next step is incremented by one (addition of exponent part P by 1) and the CWO value is maintained (the value of exponent part P is maintained). Specific examples are shown below.
At the beginning 7
− <Successful transmission> → 15
− <Successful transmission> → 31
− <Transmission failure> → 15
-<Transmission failure> → 7

  This method is similar to the CW / CW determination method in the CSMA / CA random back-off mechanism described above, but differs in the following points. In the second modification, the CWO value is increased each time the operation succeeds, whereas the CSMA / CA random back-off mechanism increases the CW each time the operation fails. Therefore, the operations of failure and success are reversed.

(Modification 3 of CWO update)
Modification 3 is used in combination with the above-described embodiment and the first and second modifications. In the third modification, when the same determination (success or failure) is made N consecutive times, the CWO value is changed. Otherwise, keep the same CWO. The value of N is notified from the base station to a terminal belonging to the BSS in a beacon frame, a trigger frame, or the like. For example, N may be 2 or 3 or more.

  For example, when the third modification is combined with a mode in which CWO is reduced when transmission fails, the CWO value is reduced when N consecutive failures occur. If the consecutive failures are interrupted (successful) by the (N-1) th time, the CWO value is not changed. When combined with a mode in which the CWO value is increased when the transmission is successful, the CWO value is increased when the transmission succeeds N times. If continuous success is interrupted (failed) by the N-1th time, the CWO value is not changed.

(Modification 4 of CWO update)
As an operation of the base station, a time until the next trigger frame for random access (TF-R) is transmitted in a beacon frame is reported as, for example, a target transmission time. In the next trigger frame for random access, it is notified whether or not the trigger frame for random access is continuously transmitted. For example, the more data field of the Frame Control field is Cascaded.
This bit is set to 1 when it is used as an indication bit to notify that a subsequent random access trigger frame exists (is scheduled). To notify that the subsequent random access trigger frame does not exist (is not scheduled), the bit is set to 0. A Cascaded Indication bit may be provided in the common information field, the terminal information field, the reserved area of the MAC header, or the like of the trigger frame for random access.

FIG. 20 shows a sequence example of the operation of the base station according to this modification. In the beacon frame 551, the time until the start of the next random access trigger frame 561 is set to target
Notify as transmission time. For example, an information element for notifying the target transmission time may be newly defined. In the random access trigger frame 561, the Cascaded Indication bit is set to 1 because the subsequent transmission of the random access trigger frame 562 is scheduled. In the random access trigger frame 562, the Cascaded Indication bit is set to 1 because the subsequent random access trigger frame 563 is scheduled. In the random access trigger frame 563, the Cascaded Indication bit is set to 0 because no subsequent random access trigger frame is scheduled. In FIG. 20, illustration of other frames transmitted by the base station (for example, illustration of a Multi-STA BA frame) is omitted.

  In such a sequence, if a Cascaded Indication bit receives a random access trigger frame with 1 (followed by the next random access trigger frame), the terminal sets the CWO value according to the previous embodiment or the modified example. Update as needed. If a random access trigger frame with a Cascaded Indication bit of 0 is received (the time until the next random access trigger frame is considered to be long), the CWO value is reset to the initial value (CWOini). return. In this sequence example, when there is a terminal in the power save mode, the terminal that has received the beacon frame 551 grasps the time until the next random access trigger frame 561 and transitions to the sleep mode during the time. May be. Alternatively, after receiving the trigger frame 563 for random access in which the Cascaded Indication bit is 0, random access may be performed if necessary, and then the mode may be shifted to the sleep mode. Note that the present modification can also support a normal terminal that is not in the power save mode. This modification can be used in combination with the above-described embodiment or another modification.

(Modification 5 of CWO update)
When the base station determines that many terminals have failed in transmission in response to the random access trigger frame (UL-OFDMA), the base station may forcibly instruct the CWO value to be returned to CWOmax or CWOinit. For example, a bit (field) for the notification is defined in the trigger frame for random access, and an instruction to return the CWO value to CWOmax or the initial value (CWOinit) is given by the bit. The bit may be provided in the common information field or the terminal information field, or a reserved area of an existing field may be used. The terminal that has received the instruction returns CWO to the initial value or CWOmax if the bit for notification is 1 in the next random access trigger frame even if transmission fails, You may add a bit that is predetermined or which one you choose.) The timing of returning the CWO value to CWOmax or CWOinit may be the next timing of updating the CWO value (timing of successful or unsuccessful transmission), or may be changed immediately, and the back-off value (OBO value) may be changed with the changed CWO value. ) May be taken again. As another example, an instruction to prohibit the terminal from lowering the CWO value may be considered. By adjusting the CWO value as in the present modification, the random access timing of the terminal can be varied. The CWO value may be an instruction to return the CWO value to a value other than CWOmax or CWOini, for example, an intermediate value between CWOmax and CWOmin. The instruction to change the CWO value to CWOmax, CWOini, or the like may be applied to the terminal that failed to transmit and the terminal that succeeded, or may be applied to at least one of them. In the latter case, a field for notifying a terminal that failed to transmit (notification field) and a notification field for a terminal that succeeds transmission may be defined, and an instruction to change the CWO value may be separately set.

  Here, the determination that the number of terminals that have failed in transmission at the base station is large may be made when the number of failed terminals or the number of resource units that failed in transmission is equal to or greater than a threshold. Alternatively, the ratio of the number of resource units that failed to receive to the number of STA undesignated RUs specified in the random access trigger frame (or the total number of resource units that succeeded and failed to receive) may be equal to or larger than a threshold, or Method may be used. This modification can be used in combination with the above-described embodiment or another modification.

(Modification 6 of CWO update)
If the terminal does not receive a downlink response (response of a delivery confirmation response frame such as a Multi-STA BA frame) from the base station after transmitting a response to the trigger frame for random access (random access), the terminal sets CWO to CWOmax or an initial value. (CWOinit). In such a case, it is determined that there are many terminals that have failed in transmission. Thus, by changing the CWO value in this way, it is possible to vary the timing of random access of terminals. Instead of setting the CWO value to CWOmax or the initial value (CWOinit), the previous CWO value may be maintained as it is. This modification can be used in combination with the above-described embodiment or another modification.

  Although a normal trigger frame (see 541 and 542 in FIG. 17) is transmitted as a downlink response, only the terminal already specified in the random access trigger frame is specified in the normal trigger frame. Also, the terminal may operate according to the case where there is no downlink response from the base station. Also, when the terminal specified in the random access trigger frame does not exist, or when there is no uplink transmission from the specified terminal, there is a case where there is no normal trigger frame transmission from the base station . At this time, the operation may be performed according to the case where there is no downlink response.

  Further, the terminal may operate as follows. If there is a downlink response (such as a Multi-STA BA frame) from the base station, the number of terminals that have successfully transmitted in the RU not specified by the STA is counted. In the case where the transmission of the own terminal has failed, if the number of successful terminals is equal to or greater than the threshold, or if the ratio of the number of successful terminals to the number of STA unspecified RUs is equal to or greater than the threshold, the CWO value may be reduced, for example. Good. Alternatively, a frame of a downlink response transmitted from the base station may be provided with a field of a notification bit instructing to lower the CWO value, and the base station may instruct the base station to lower the CWO value with the bit. In this case, the terminal lowers the CWO value according to the bit. The method for lowering the CWO may be in accordance with the above-described embodiment or the modification.

(Modification of operation when transmission fails)
The terminal uses the OBO value (OBO value before subtracting the number of STA unspecified RUs) used when the transmission in the STA unspecified RU has failed in the next random access trigger frame and uses it. Is also good.

On the other hand, the base station determines whether there are many terminals that have failed in transmission in response to the random access trigger frame (UL-OFDMA), and when it determines that there are many terminals, in the next random access trigger frame, The number of STA unspecified RUs may be increased.
This takes into account the possibility that a terminal that newly obtains a selection right may additionally occur. Alternatively, it is also possible to define a random access trigger frame that specifies only terminals that have failed in transmission as targets of random access, and transmit the frame. For example, even if a notification bit that designates only a terminal that failed to transmit as a target of random access is provided in the common information field, the terminal information field, or the MAC header, and a random access trigger frame with the notification bit turned on is transmitted. Good. The notification bit may use a reserved area in any field of the MAC header, or may reuse a used area for this purpose.

(Modification of operation at successful transmission)
The base station may limit the number of times of waiting or the waiting time for responding to the next or subsequent random access trigger frame (permitting random access) to a terminal that has successfully transmitted (randomly accessed).

  The information of this restriction is included in the downlink response after the base station receives the response (UL-OFDMA) to the trigger frame for random access, together with the information of the successfully received terminal, via the notification field for the successful terminal. You only need to be notified. When the downlink response is in the BA format (for example, when using a Multi-STA BA frame), the notification field may be configured by using the reserved area of the BA format frame or reusing the used area. When a trigger frame is used as a downlink response, the notification field may be provided in a common information field, a terminal information field, a MAC header, or the like. In the trigger frame, it is assumed that the terminal that succeeds in the transmission is specified as a target of UL-OFDMA.

  If the terminal detects that the transmission has been successful due to the ACK of the terminal itself or the designation of the terminal itself in the frame of the downlink response, the terminal determines the restriction of the number of times of waiting or the waiting time from the notification field of the frame of the downlink response. , And operates so as to refrain from transmission (random access) while the restriction is applied.

  If the constraint is the number of waits, the number of waits is decremented every time a trigger frame for random access is received. When the number of waits becomes zero, the operation related to random access (from the OBO value to the STA (Eg, a process of subtracting the number of unspecified RUs). If the restriction is a waiting time, the apparatus waits for a specified time, and then starts an operation related to random access from receiving a trigger frame for random access.

  While the above constraint is applied, the OBO value (OBO value before subtracting the number of STA unspecified RUs) at the time of the previous successful transmission is maintained, and the random access trigger after the constraint is removed Upon receiving the frame, the number of STA-unspecified RUs is subtracted from the maintained OBO value, and when the number reaches 0, a selection right is acquired and random access is performed. Instead of maintaining the OBO value, a new OBO value may be obtained from the current CWO.

(Modification of base station response method)
The base station measures the reception quality of the terminal that has successfully transmitted in response to the random access trigger frame for the resource unit that has transmitted. Examples of the reception quality include, but are not limited to, a received RSSI (Received Signal Strength Indicator) or a received EVM (Error Vector Magnitude). For example, an SN ratio (Signal to Noise Ratio) may be used. The base station determines whether the measured value is equal to or less than a certain value or equal to or more than a certain value according to the used index, and determines whether the reception quality satisfies a criterion required for a response (whether bad or not). .

  The base station determines that the radio wave environment of the terminal in the resource unit is poor for the terminal having poor reception quality and does not respond to the downlink (the ACK of the terminal is not included in the Multi-STA BA frame, or the trigger frame is not included). And do not specify the terminal). This causes the terminal to determine that transmission (random access) has failed. Note that the base station may make a downlink response to a terminal having poor reception quality, and at this time, information for specifying the reception quality may be added to a downlink response frame. The terminal may select another resource unit next time if it determines that the transmission has been successful but the reception quality at the base station is poor, based on the frame of the downlink response. The base station may notify the information specifying the reception quality using the reserved area of the frame in the BA format, or may reuse the area used in the frame for this purpose. May be.

  Here, the terminal selectively transmits to the base station whether it wants to respond regardless of the reception quality when the base station succeeds in reception or does not want to respond when the reception quality is poor. Notification may be provided. A request bit (request field) is provided in a MAC header or the like of a frame transmitted by the terminal. If the reception quality is poor, the bit is set to 1 if no response is desired. If a response is desired regardless of the reception quality, the bit is set. May be set to 0. The relationship between bits 1 and 0 may be reversed. The base station may switch the response operation in the case of successful reception according to the request bits included in the frame.

(Modified example of designation of random number range and selection of STA unspecified RU)
In the above-described embodiment or each modified example, as a result of subtracting the number of STA-unspecified RUs from the OBO value, the OBO value becomes 0 or less, and the terminal that has obtained the selection right can select any resource unit from the STA-unspecified RUs. Was selected. For example, a resource unit was selected at random. In this modification, the resource unit to be selected is determined according to the OBO value at the time of waiting for the trigger frame for random access. For example, when the random access trigger frame is received with the OBO value being 3, and the number of STA-unspecified RUs is 4, the OBO value becomes 3-4 = 1 (→ 0), and the right of selection is obtained. In this case, since the OBO value during standby is 3, a resource unit (for example, RU # 3) corresponding to "3" is selected. The association between the OBO value and the resource unit may be determined in advance. A plurality of resource units may be associated with one value. In this case, a random selection may be made from the plurality of associated resource units.

As another example, every time a trigger frame for random access is received, a CWO that is M times the number of STA-unspecified RUs (M is an integer of 1 or more) is set. That is, the CWO is set according to the number of RUs not specified by the STA. For example, if the number of STA-unspecified RUs is 4 and M is 2, CWO = 8. Then, a random number (OBO value) is selected from the range of 0 to (CWO-1).
If the selected random number is a value equal to or less than a value obtained by subtracting 1 from the number of STA-unspecified RUs (that is, “the number of STA-unspecified RUs−1”), a selection right is acquired and a resource unit is selected from the STA-unspecified RUs. . “STA-undesignated RU number−1” is an example, and may be the STA-undesignated RU number or another value. The selection of the resource unit may be performed in advance by associating the OBO value with the resource unit and in accordance with the association. However, it is also possible to select at random. After transmitting based on the resource unit selected by the terminal, the terminal may adjust the value of M from an initial value depending on whether the transmission was successful or successful. The minimum and maximum values of M may be defined and adjusted within that range. The method of adjusting M may be performed in the same manner as changing the CWO in the above-described embodiment or each of the modifications. Decreasing CWO corresponds to decreasing M, and increasing CWO corresponds to increasing M. Setting the CWO according to the number of STA-unspecified RUs described in this paragraph may be applied to other modified examples.

  Note that the value of M (at least one of the initial value, the minimum value, and the maximum value) may be notified to the terminal in a beacon frame or a trigger frame (including a trigger frame for random access). An information element for notifying the value of M may be set in the beacon frame, or the value of M may be set using a reserved area of an arbitrary field of the beacon frame. Also, a field for notifying the value of M may be provided in the common information field or the terminal information field of the trigger frame, or a reserved area of the MAC header is used, or a used area in the MAC header is reused. Then, the value of M may be notified.

(Other modifications)
In the above-described embodiment and each modified example, the terminal that failed in transmission adjusted the CWO value by autonomous determination, but the base station may instruct the terminal to adjust the CWO value. As an example, in addition to information for specifying a terminal for each resource unit, at least one of a notification field for a terminal that has failed to transmit and a notification field for a terminal that has successfully transmitted, in a trigger frame (see 541 and 542 in FIG. 14). , Information on the CWO adjustment method is set. In the adjustment method, an instruction is set to reduce, increase, return to the initial value, maximize, or minimize the CWO. When instructing to decrease or increase the CWO, the adjustment method may be determined in the same manner as the terminal operation described above. The notification field may be provided in the common information field or the terminal information field of the trigger frame. Alternatively, the notification field may be configured by using a reserved area of an arbitrary field of the MAC header, or by reusing a used area of the MAC header. For example, when the terminal detects that its own terminal is not specified in the trigger frame, the terminal updates the CWO value according to the adjustment method specified in the notification field for the failed terminal.

  FIG. 21 is a flowchart illustrating an example of the operation of the terminal according to the embodiment of the present invention. The terminal receives, from the base station, a trigger frame (random access trigger frame) specifying a plurality of STA-unspecified RUs (resource units for random access) (S101). In the frame, use of a specific terminal may be specified for some resource units. The terminal subtracts the number of STA unspecified RUs specified in the random access trigger frame from a backoff value (OBO value) selected from a range equal to or less than the CWO value, and the value after the subtraction is a predetermined value (for example, 0). ) Is checked (S102). If it has reached the predetermined value, it is determined that the right to select the STA undesignated RU has been obtained (YES), and if it has not reached the predetermined value, it is determined that the right of selection has not been obtained (NO). It is not necessary to actually perform the subtraction. As described above, for example, it is determined whether or not the selection right has been acquired based on the magnitude relationship between the OBO value at the time of receiving the trigger frame for random access and the number of STA unspecified RUs. Is also good. When the terminal has acquired the selection right, the terminal transmits the frame using an arbitrary resource unit selected from the STA unspecified RU (S104). The type of frame to be transmitted may be arbitrary, or may be of a predetermined type (for example, a frame for notifying the presence or absence of a request for uplink transmission). The operation described here is merely an example, and various operations are possible according to the above-described embodiment and each modification.

FIG. 22 shows a flowchart of an example of the operation of the base station according to the embodiment of the present invention.
The base station transmits a trigger frame (random access trigger frame) specifying a plurality of STA-unspecified RUs (random access resource units) (S201). The frame may specify the use of a specific terminal for some resource units. The base station determines whether a frame has been received within a certain period of time from the transmission using an STA-unspecified RU specified by the random access trigger frame (S202). More specifically, by decoding the radio signal received by each STA undesignated RU and checking the frame, it is determined whether the frame is normally received. The base station performs downlink transmission of a frame including information specifying a terminal that has successfully received the frame (S203). The frame may be a Multi-STA BA frame as described above, or may be a trigger frame in which a terminal is assigned to each resource unit to be used. In the case of a trigger frame, the designation of a terminal that has been successfully received shall be included. The downlink transmission frame may include information of a value range (CWO value) for controlling whether the terminal determines whether or not to respond to the random access trigger frame (random access). As an example, the number of terminals that succeeded in transmission (the number of resource units in which a frame was normally received) is grasped, and information (an initial value, a minimum value, or a minimum value) related to a CWO value determined according to the number of terminals (or the number of resource units) is determined. Information for specifying the maximum value). Information on the CWO value may be set separately in each notification field for a terminal that has succeeded in transmission and a terminal that has failed, or may define a notification field for only one of the terminals, and Information may be set. In addition, a frame to be transmitted by downlink may include information described in each of the above-described modifications.

  As described above, according to the embodiment of the present invention, the CWO of each terminal is individually adjusted in accordance with the failure or success of transmission of each terminal with respect to the trigger frame for random access, so that fair transmission between terminals (random access ) Can be offered.

  In the present embodiment, random access in the case of performing UL-OFDMA on a trigger frame for random access has been described. However, a communication method (UL-MU-MIMO) combining UL-OFDMA and uplink MU-MIMO (UL-MU-MIMO) is described. Random access in the case of performing UL-OFDMA & UL-MU-MIMO is also possible. UL-MU-MIMO is intended to increase the efficiency of uplink transmission by transmitting frames (spatial multiplex transmission) to a base station in the same frequency band at the same timing by a plurality of terminals. By including the preamble signals orthogonal to each other in the physical headers of frames transmitted from a plurality of terminals, the base station can estimate the uplink channel response with each terminal based on these preamble signals and separate these frames. . In UL-OFDMA & MU-MIMO, a plurality of terminals perform MU-MIMO transmission using the same resource unit for each resource unit. At this time, a plurality of terminals using the same resource unit transmit using different preamble signals. The present embodiment is applicable to such a system.

(Second embodiment)
FIG. 23 is a functional block diagram of a base station (access point) 400 according to the second embodiment. This access point includes a communication processing unit 401, a transmission unit 402, a reception unit 403, antennas 42A, 42B, 42C, 42D, a network processing unit 404, a wired I / F 405, and a memory 406. . The access point 400 is connected to the server 407 via a wired I / F 405. The communication processing unit 401 has the same function as the control unit 101 described in the first embodiment. The transmitting unit 402 and the receiving unit 403 have functions similar to those of the transmitting unit 102 and the receiving unit 102 described in the first embodiment. The network processing unit 404 has the same function as the higher-level processing unit described in the first embodiment. Here, the communication processing unit 401 may internally have a buffer for transferring data with the network processing unit 404. This buffer may be a volatile memory such as a DRAM or a nonvolatile memory such as a NAND or MRAM.

  The network processing unit 404 controls data exchange with the communication processing unit 401, data writing / reading with the memory 406, and communication with the server 407 via the wired I / F 405. The network processing unit 404 may perform communication processing above the MAC layer, such as TCP / IP and UDP / IP, and processing of the application layer. The operation of the network processing unit may be performed by processing of software (program) by a processor such as a CPU, may be performed by hardware, or may be performed by both software and hardware.

  As an example, the communication processing unit 401 corresponds to a baseband integrated circuit, and the transmitting unit 402 and the receiving unit 403 correspond to an RF integrated circuit that transmits and receives frames. The communication processing unit 401 and the network processing unit 404 may be configured by one integrated circuit (one chip). The part that performs processing in the digital domain and the part that performs processing in the analog domain of the transmitting unit 402 and the receiving unit 403 may be configured by different chips. Further, the communication processing unit 401 may execute a higher-layer communication process of the MAC layer such as TCP / IP or UDP / IP. Although the number of antennas is four here, it is sufficient that at least one antenna is provided.

  The memory 406 stores data received from the server 407, data received by the receiving unit 402, and the like. The memory 406 may be, for example, a volatile memory such as a DRAM or a nonvolatile memory such as a NAND or an MRAM. Further, it may be an SSD, HDD, SD card, eMMC, or the like. The memory 406 may be external to the base station 400.

  The wired I / F 405 transmits and receives data to and from the server 407. In the present embodiment, communication with the server 407 is performed by wire, but communication with the server 407 may be performed wirelessly. In this case, the wireless I / F may be used instead of the wired I / F 405.

  The server 407 is a communication device that receives a data transfer request for requesting data transmission and returns a response including the requested data. For example, an HTTP server (Web server), an FTP server, or the like is assumed. However, the present invention is not limited to this as long as it has a function of returning requested data. A communication device such as a PC or a smartphone operated by a user may be used. Further, the communication with the base station 400 may be performed wirelessly.

  When a STA belonging to the BSS of base station 400 issues a data transfer request to server 407, a packet related to the data transfer request is transmitted to base station 400. The base station 400 receives this packet via the antennas 42A to 42D, and executes processing of the physical layer by the receiving unit 403 and processing of the MAC layer by the communication processing unit 401.

  The network processing unit 404 analyzes the packet received from the communication processing unit 401. Specifically, a destination IP address, a destination port number, and the like are confirmed. If the data of the packet is a data transfer request such as an HTTP GET request, the network processing unit 404 stores the data requested by the data transfer request (for example, the data existing in the URL requested by the HTTP GET request) It is checked whether the data is cached (stored) in the memory 406. The memory 406 stores a table in which a URL (or a reduced expression thereof, for example, a hash value or an alternative identifier) is associated with data. Here, the fact that the data is cached in the memory 406 is expressed as the presence of cache data in the memory 406.

  If no cache data exists in the memory 406, the network processing unit 404 transmits a data transfer request to the server 407 via the wired I / F 405. That is, the network processing unit 404 transmits a data transfer request to the server 407 on behalf of the STA. Specifically, the network processing unit 404 generates an HTTP request, performs a protocol process such as adding a TCP / IP header, and passes the packet to the wired I / F 405. The wired I / F 405 transmits the received packet to the server 407.

  The wired I / F 405 receives from the server 407 a packet that is a response to the data transfer request. The network processing unit 404 recognizes from the IP header of the packet received via the wired I / F 405 that the packet is addressed to the STA, and passes the packet to the communication processing unit 401. The communication processing unit 401 performs processing of the MAC layer for the packet, and the transmitting unit 402 performs processing of the physical layer, and transmits a packet addressed to the STA from the antennas 42A to 42D. Here, the network processing unit 404 stores the data received from the server 407 as cache data in the memory 406 in association with the URL (or a reduced representation thereof).

  When cache data exists in the memory 406, the network processing unit 404 reads the data requested by the data transfer request from the memory 406, and transmits the data to the communication processing unit 401. Specifically, an HTTP header or the like is added to the data read from the memory 406, a protocol process such as addition of a TCP / IP header is performed, and the packet is transmitted to the communication processing unit 401. At this time, as an example, the source IP address of the packet is set to the same IP address as the server, and the source port number is set to the same port number as the server (the destination port number of the packet transmitted by the communication terminal). Therefore, from the STA's point of view, it looks as if they are communicating with the server 407. The communication processing unit 401 performs processing of the MAC layer for the packet, and the transmitting unit 402 performs processing of the physical layer, and transmits a packet addressed to the STA from the antennas 42A to 42D.

  By such an operation, frequently accessed data responds based on the cache data stored in the memory 406, and traffic between the server 407 and the base station 400 can be reduced. Note that the operation of the network processing unit 404 is not limited to the operation of the present embodiment. A general cache proxy that obtains data from the server 407 instead of the STA, caches the data in the memory 406, and responds to a data transfer request for the same data from the cache data in the memory 406. There is no problem with another operation.

  The base station (access point) of the present embodiment can be applied as the base station of the first embodiment. The transmission of the frame, data, or packet used in the above-described first embodiment may be executed using the cache data stored in the memory 406. Further, information obtained in a frame, data, or packet received by the base station of the first embodiment may be cached in the memory 406. In the first embodiment, the frame transmitted by the access point may include cached data or information based on the data. The information based on the data may be, for example, information on the presence / absence of data addressed to the terminal, information on the size of data, and information on the size of a packet required for data transmission. Further, information such as a modulation method necessary for data transmission may be used.

  In the present embodiment, a base station having a cache function has been described. However, a terminal (STA) having a cache function can be realized with the same block configuration as in FIG. The terminal here is a terminal of a non-base station (the base station is also a form of the wireless communication terminal as described above). In this case, the wired I / F 405 may be omitted. The transmission of frames, data or packets by the terminal according to the first embodiment described above may be executed using cache data stored in the memory 406. Further, information obtained in a frame, data, or packet received by the terminal of the first embodiment may be cached in the memory 406. In the first embodiment, the frame transmitted by the terminal may include cached data or information based on the data. The information based on the data may be, for example, information on the presence or absence of data to be transmitted, information on the size of data, and information on the size of a packet required for data transmission. Further, information such as a modulation method necessary for data transmission may be used.

(Third embodiment)
FIG. 24 shows an example of the overall configuration of a terminal (terminal of a non-base station) or a base station. This configuration example is an example, and the present embodiment is not limited to this. The terminal or the base station includes one or more antennas 1 to n (n is an integer of 1 or more), a wireless LAN module 148, and a host system 149. The wireless LAN module 148 corresponds to the wireless communication device according to the first embodiment. The wireless LAN module 148 has a host interface, and is connected to the host system 149 via the host interface. In addition to being connected to the host system 149 via a connection cable, it may be directly connected to the host system 149. Further, a configuration is also possible in which the wireless LAN module 148 is mounted on a board with solder or the like and connected to the host system 149 via wiring on the board. The host system 149 communicates with an external device using the wireless LAN module 148 and the antennas 1 to n according to an arbitrary communication protocol. The communication protocol may include TCP / IP and higher-layer protocols. Alternatively, TCP / IP may be mounted on the wireless LAN module 148, and the host system 149 may execute only higher-layer protocols. In this case, the configuration of the host system 149 can be simplified. This terminal is, for example, a mobile terminal, a TV, a digital camera, a wearable device, a tablet, a smartphone, a game device, a network storage device, a monitor, a digital audio player, a web camera, a video camera, a project, a navigation system, an external adapter, and an internal device. Adapters, set-top boxes, gateways, printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, automobiles, etc.
The wireless LAN module 148 (or wireless communication device) may have a function of another wireless communication standard such as LTE (Long Term Evolution) or LTE-Advanced (standards for mobile phones) in addition to IEEE802.11. .

  FIG. 25 illustrates a hardware configuration example of the wireless LAN module. This configuration can be applied to a case where the wireless communication device is mounted on both a non-base station terminal and a base station. That is, it can be applied as an example of a specific configuration of the wireless communication device shown in FIG. In this configuration example, there is only one antenna, but two or more antennas may be provided. In this case, a plurality of sets of a transmission system (216, 222 to 225), a reception system (217, 232 to 235), a PLL 242, a crystal oscillator (reference signal source) 243, and a switch 245 are arranged corresponding to each antenna. Each set may be connected to the control circuit 212, respectively. The PLL 242 and / or the crystal oscillator 243 correspond to the oscillator according to the present embodiment.

The wireless LAN module (wireless communication device) is a baseband IC (Integrated)
Circuit 211, an RF (Radio Frequency) IC 221, a balun 225, a switch 245, and an antenna 247.

  The baseband IC 211 includes a baseband circuit (control circuit) 212, a memory 213, a host interface 214, a CPU 215, a DAC (Digital to Analog Converter) 216, and an ADC (Analog to Digital Converter) 217.

  The baseband IC 211 and the RF IC 221 may be formed on the same substrate. Further, the baseband IC 211 and the RF IC 221 may be formed by one chip. DAC 216 and / or ADC 217 may be located on RF IC 221 or on another IC. In addition, both or one of the memory 213 and the CPU 215 may be arranged in an IC different from the baseband IC.

  The memory 213 stores data to be transferred to and from the host system. Further, the memory 213 stores information notified to the terminal or the base station, information notified from the terminal or the base station, or both. Further, the memory 213 may store a program necessary for the CPU 215 to execute, and may be used as a work area when the CPU 215 executes the program. The memory 213 may be a volatile memory such as an SRAM or a DRAM, or a nonvolatile memory such as a NAND or an MRAM.

  The host interface 214 is an interface for connecting to a host system. The interface may be anything such as UART, SPI, SDIO, USB, PCI Express, and the like.

  The CPU 215 is a processor that controls the baseband circuit 212 by executing a program. The baseband circuit 212 mainly performs processing of the MAC layer and processing of the physical layer. The baseband circuit 212, the CPU 215, or both of them correspond to a communication control device that controls communication or a control unit that controls communication.

  At least one of the baseband circuit 212 and the CPU 215 includes a clock generation unit that generates a clock, and the internal time may be managed by the clock generated by the clock generation unit.

  The baseband circuit 212 performs, for example, addition of a physical header, encoding, encryption, and modulation processing as processing of a physical layer on a frame to be transmitted. For example, two types of digital baseband signals (hereinafter, digital I signal and digital Q signal) are used. Signal).

  The DAC 216 performs DA conversion of a signal input from the baseband circuit 212. More specifically, DAC 216 converts a digital I signal to an analog I signal and a digital Q signal to an analog Q signal. It is to be noted that there is a case where a signal of one system is transmitted without performing quadrature modulation. When a plurality of antennas are provided and one system or a plurality of systems of transmission signals are distributed by the number of antennas and transmitted, DACs and the like may be provided in a number corresponding to the number of antennas.

The RF IC 221 is, for example, an RF analog IC, a high-frequency IC, or both. The RF IC 221 includes a filter 222, a mixer 223, a preamplifier (PA) 224, a PLL (Phase Locked Loop) 242, a low noise amplifier (LNA), a balun 235, a mixer 233, and a filter 232.
Some of these elements may be located on baseband IC 211 or another IC. The filters 222 and 232 may be band-pass filters or low-pass filters.

  The filter 222 extracts a signal of a desired band from each of the analog I signal and the analog Q signal input from the DAC 216. The PLL 242 uses an oscillation signal input from the crystal oscillator 243 and generates a signal of a fixed frequency synchronized with the phase of the input signal by dividing or multiplying the oscillation signal or both. Note that the PLL 242 includes a VCO (Voltage Controlled Oscillator), and performs a feedback control using the VCO based on an oscillation signal input from the crystal oscillator 243 to obtain a signal of the constant frequency. The generated constant frequency signal is input to mixers 223 and 233. The PLL 242 corresponds to an example of an oscillator that generates a signal of a constant frequency.

  The mixer 223 up-converts the analog I signal and the analog Q signal that have passed through the filter 222 to a radio frequency using a signal of a constant frequency supplied from the PLL 242. The preamplifier (PA) amplifies the radio frequency analog I signal and analog Q signal generated by the mixer 223 to desired output power. The balun 225 is a converter for converting a balanced signal (differential signal) into an unbalanced signal (single-ended signal). The balanced signal is handled by the RF IC 221, but the unbalanced signal is handled from the output of the RF IC 221 to the antenna 247. Therefore, these signals are converted by the balun 225.

  The switch 245 is connected to the balun 225 on the transmitting side when transmitting, and is connected to the balun 234 or the RF IC 221 on the receiving side when receiving. The control of the switch 245 may be performed by the baseband IC 211 or the RF IC 221. Alternatively, another circuit for controlling the switch 245 may be provided, and the switch 245 may be controlled from the circuit.

  The analog I signal and analog Q signal of the radio frequency amplified by the preamplifier 224 are balanced-unbalanced converted by the balun 225 and then radiated from the antenna 247 into space as radio waves.

  The antenna 247 may be a chip antenna, an antenna formed by wiring on a printed circuit board, or an antenna formed using a linear conductor element.

  The LNA 234 in the RF IC 221 amplifies a signal received from the antenna 247 via the switch 245 to a level that allows demodulation while keeping noise low. The balun 235 performs unbalanced-balanced conversion of the signal amplified by the low noise amplifier (LNA) 234. Mixer 233 down-converts the received signal converted into a balanced signal by balun 235 to baseband using a signal of a constant frequency input from PLL 242. More specifically, the mixer 233 has a unit that generates carrier waves that are 90 ° out of phase with each other based on the constant frequency signal input from the PLL 242, and converts the received signals converted by the balun 235 into 90 ° Quadrature demodulation is performed by the carrier wave having a phase shift to generate an I (In-phase) signal having the same phase as the received signal and a Q (Quad-phase) signal delayed by 90 ° from the received signal. The filter 232 extracts a signal of a desired frequency component from the I signal and the Q signal. The I signal and the Q signal extracted by the filter 232 are output from the RF IC 221 after the gain is adjusted.

  The ADC 217 in the baseband IC 211 converts the input signal from the RF IC 221 from analog to digital. More specifically, ADC 217 converts the I signal to a digital I signal and converts the Q signal to a digital Q signal. In some cases, only one system of signals is received without performing quadrature demodulation.

  When a plurality of antennas are provided, a number of ADCs corresponding to the number of antennas may be provided. The baseband circuit 212 performs a physical layer process such as a demodulation process, an error correction code process, and a physical header process based on the digital I signal and the digital Q signal to obtain a frame. The baseband circuit 212 performs MAC layer processing on the frame. Note that, when TCP / IP is implemented, the baseband circuit 212 may be configured to perform TCP / IP processing.

  The details of the processing of each unit described above are self-evident from the description of FIG.

(Fourth embodiment)
FIGS. 26A and 26B are perspective views of a wireless terminal according to the fourth embodiment. The wireless terminal in FIG. 26A is a notebook PC 301, and the wireless terminal in FIG. 26B is a mobile terminal 321. The notebook PC 301 and the mobile terminal 321 are equipped with wireless communication devices 305 and 315, respectively. As the wireless communication devices 305 and 315, a wireless communication device mounted on the wireless terminal described above, a wireless communication device mounted on the base station 11, or both of them can be used. Wireless terminals equipped with wireless communication devices are not limited to notebook PCs and mobile terminals. For example, TV, digital camera, wearable device, tablet, smartphone, game device, network storage device, monitor, digital audio player, web camera, video camera, project, navigation system, external adapter, internal adapter, set-top box, gateway, It can be installed in printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, automobiles, and the like.

  Also, the wireless communication device mounted on the wireless terminal or the base station 11, or both, can also be mounted on a memory card. FIG. 27 shows an example in which the wireless communication device is mounted on a memory card. The memory card 331 includes a wireless communication device 355 and a memory card main body 332. The memory card 331 uses the wireless communication device 335 for wireless communication with an external device (the wireless terminal and / or the base station 11 or both). In FIG. 27, other elements (for example, memory) in the memory card 331 are omitted.

(Fifth embodiment)
In the fifth embodiment, in addition to the configuration of the wireless communication device (the wireless communication device of the base station and / or the wireless communication device of the wireless terminal) according to the above-described embodiment, a bus, a processor unit, and an external interface It has a unit. The processor and the external interface are connected to an external memory (buffer) via a bus. Firmware operates in the processor unit. As described above, by including the firmware in the wireless communication device, the function of the wireless communication device can be easily changed by rewriting the firmware. The processor unit on which the firmware operates may be the control unit according to the present embodiment or a processor that performs processing of the control unit, or may be another processor that performs processing related to function expansion or change of the processing. Good. The processor unit on which the firmware operates may be provided in the base station, the wireless terminal, or both of them according to the present embodiment. Alternatively, the processor unit may be provided in an integrated circuit in a wireless communication device mounted on a base station or an integrated circuit in a wireless communication device mounted on a wireless terminal.

(Sixth embodiment)
The sixth embodiment includes a clock generation unit in addition to the configuration of the wireless communication device (the wireless communication device of the base station and / or the wireless communication device of the wireless terminal) according to the above-described embodiment. The clock generation unit generates a clock and outputs the clock to the outside of the wireless communication device from an output terminal. Thus, by outputting the clock generated inside the wireless communication device to the outside and operating the host with the clock output to the outside, the host and the wireless communication device can be operated in synchronization with each other. It becomes possible.

(Seventh embodiment)
In the seventh embodiment, in addition to the configuration of the wireless communication device (the wireless communication device of the base station or the wireless communication device of the wireless terminal) according to the above-described embodiment, a power supply unit, a power supply control unit, and a wireless power supply unit are provided. Including. The power control unit is connected to the power supply unit and the wireless power supply unit, and performs control for selecting power to be supplied to the wireless communication device. In this manner, by providing a power supply in the wireless communication device, a power-saving operation in which the power supply is controlled can be performed.

(Eighth embodiment)
The eighth embodiment includes a SIM card in addition to the configuration of the wireless communication device according to the above-described embodiment. The SIM card is connected to, for example, a control unit in a wireless communication device. As described above, by providing the SIM card in the wireless communication device, the authentication process can be easily performed.

(Ninth embodiment)
The ninth embodiment includes a moving image compression / decompression unit in addition to the configuration of the wireless communication device according to the above-described embodiment. The moving image compression / decompression unit is connected to the bus. As described above, by providing the moving image compression / decompression unit in the wireless communication device, transmission of the compressed moving image and expansion of the received compressed moving image can be easily performed.

(Tenth embodiment)
The tenth embodiment includes an LED unit in addition to the configuration of the wireless communication device (the wireless communication device of the base station and / or the wireless communication device of the wireless terminal) according to the above-described embodiments. The LED unit is connected to the transmitting unit, the receiving unit, the control unit, or a plurality of these units. As described above, by providing the wireless communication device with the LED unit, it is possible to easily notify the user of the operation state of the wireless communication device.

(Eleventh embodiment)
The eleventh embodiment includes a vibrator unit in addition to the configuration of the wireless communication device (the wireless communication device of the base station and / or the wireless communication device of the wireless terminal) according to the above-described embodiment. The vibrator unit is connected to, for example, a control unit in a wireless communication device. As described above, by providing the vibrator unit in the wireless communication device, it is possible to easily notify the user of the operation state of the wireless communication device.

(Twelfth embodiment)
The twelfth embodiment includes a display in addition to the configuration of the wireless communication device (the wireless communication device of the base station and / or the wireless communication device of the wireless terminal) according to the above-described embodiments. The display may be connected to a control unit of the wireless communication device via a bus (not shown). With the configuration including the display as described above, by displaying the operation state of the wireless communication device on the display, it is possible to easily notify the user of the operation state of the wireless communication device.

(Thirteenth embodiment)
In this embodiment, [1] a frame type in a wireless communication system, [2] a method of disconnection between wireless communication devices, [3] an access method of a wireless LAN system, and [4] a frame interval of a wireless LAN will be described.
[1] Frame Type in Communication System Generally, as described above, frames handled in a wireless access protocol in a wireless communication system are roughly divided into three types: a data frame, a management frame, and a control frame. Divided into types. These types are usually indicated by a header section commonly provided between frames. As a display method of the frame type, three types may be distinguished by one field, or a combination of two fields may be distinguished. According to the IEEE802.11 standard, the frame type is identified by two fields, Type and Subtype, in the Frame Control field in the frame header of the MAC frame. A data frame, a management frame, or a control frame is roughly classified in a Type field, and a detailed classification in a roughly classified frame, for example, a Beacon frame in a management frame is identified in a Subtype field.

  The management frame is a frame used for managing a physical communication link with another wireless communication device. For example, there are a frame used for setting communication with another wireless communication device, a frame for releasing a communication link (that is, disconnecting a connection), and a frame related to a power saving operation in the wireless communication device. .

  The data frame is a frame for transmitting data generated inside the wireless communication device to another wireless communication device after a physical communication link has been established with another wireless communication device. The data is generated in a higher layer of the present embodiment, and is generated by, for example, a user operation.

  The control frame is a frame used for control when transmitting / receiving (exchanging) a data frame with another wireless communication device. When the wireless communication device receives a data frame or a management frame, a response frame transmitted to confirm delivery of the data frame or the management frame belongs to a control frame. The response frame is, for example, an ACK frame or a BlockACK frame. The RTS frame and the CTS frame are also control frames.

These three types of frames are transmitted through the antenna as physical packets through necessary processing in the physical layer. Note that the IEEE 802.11 standard (the aforementioned IEEE Std)
In the case of an extended standard such as 802.11ac-2013), there is an association process as one of the procedures for establishing a connection. An Association Request frame and an Association Response frame used in the association process are management frames, and the Association Request is used. Since the frame or the association response frame is a unicast management frame, it requests the receiving wireless communication terminal to transmit an ACK frame, which is a response frame. The ACK frame is a control frame as described above.

[2] Method of disconnecting connection between wireless communication devices There are an explicit method and an implicit method for disconnecting (release) the connection. As an explicit method, one of the wireless communication devices that has established a connection transmits a frame for disconnection. In the IEEE 802.11 standard, a Deauthentication frame corresponds to this, and is classified as a management frame. Normally, the wireless communication device that transmits the frame that disconnects the connection disconnects the connection when the frame is transmitted, and the wireless communication device that receives the frame that disconnects the connection disconnects the connection when the frame is received. judge. Thereafter, if the terminal is a non-base station wireless communication terminal, the terminal returns to the initial state in the communication phase, for example, the state of searching for a BSS to connect. If the connection between the wireless communication base station and a certain wireless communication terminal is disconnected, for example, if the wireless communication base station has a connection management table for managing the wireless communication terminal that joins its own BSS, the connection management The information related to the wireless communication terminal is deleted from the table. For example, when assigning an AID at the stage where the wireless communication base station permits connection to each wireless communication terminal that subscribes to its own BSS in the association process, if the AID is assigned, the holding information associated with the AID of the wireless communication terminal that disconnected the connection May be deleted and the AID may be released and assigned to another newly subscribed wireless communication terminal.

  On the other hand, as an implicit method, frame transmission (transmission of a data frame and a management frame, or transmission of a response frame to a frame transmitted by the own device) is detected from a wireless communication device of a connection partner that has established a connection for a certain period of time. If there is no connection, the connection state is determined to be disconnected. Such a technique exists because, in the situation where the disconnection is determined as described above, the communication distance with the wireless communication apparatus to which the wireless communication apparatus is connected is so large that the wireless signal cannot be received or decoded. This is because a state in which a wireless link cannot be secured is conceivable. That is, it is not possible to expect to receive a frame for disconnecting the connection.

  As a specific example of determining the disconnection by an implicit method, a timer is used. For example, when transmitting a data frame requesting an acknowledgment frame, a first timer (for example, a retransmission timer for a data frame) that limits the retransmission period of the frame is activated, and the first timer expires (that is, until the first timer expires). If no acknowledgment frame for the frame is received (until the desired retransmission period has elapsed), retransmission is performed. When receiving the acknowledgment frame for the frame, the first timer is stopped.

  On the other hand, if the first timer expires without receiving the acknowledgment frame, it is determined whether the wireless communication device of the connection partner is still present (within the communication range) (in other words, whether the wireless link has been secured). The control unit transmits a management frame for performing the retransmission, and at the same time, starts a second timer (for example, a retransmission timer for the management frame) for limiting a retransmission period of the frame. Similarly to the first timer, the second timer performs retransmission unless the acknowledgment frame for the frame is received until the second timer expires, and determines that the connection has been disconnected when the second timer expires. . When it is determined that the connection is disconnected, a frame for disconnecting the connection may be transmitted.

  Alternatively, when a frame is received from the wireless communication device of the connection partner, the third timer is started, and every time a frame is newly received from the wireless communication device of the connection partner, the third timer is stopped and restarted from the initial value. When the third timer expires, a management frame for confirming whether the wireless communication device of the connection partner is still present (within the communication range) (in other words, whether a wireless link has been secured) is transmitted as described above. At the same time, a second timer (for example, a retransmission timer for a management frame) for limiting the retransmission period of the frame is started. Also in this case, if the acknowledgment frame for the frame is not received until the second timer expires, retransmission is performed, and if the second timer expires, the connection is determined to be disconnected. Also in this case, when it is determined that the connection has been disconnected, a frame for disconnecting the connection may be transmitted. The latter management frame for confirming whether the wireless communication device of the connection partner still exists may be different from the management frame in the former case. In the latter case, the timer for restricting retransmission of the management frame is the same as the second timer here as the second timer, but a different timer may be used.

[3] Access method of wireless LAN system For example, there is a wireless LAN system that is assumed to communicate or compete with a plurality of wireless communication devices. In the IEEE802.11 wireless LAN, CSMA / CA (Carrier Sense Multiple Access with Carrier Aviidance) is the basis of the access method. In a system in which transmission from a certain wireless communication device is grasped and transmission is performed at a fixed time after the end of the transmission, transmission is simultaneously performed by a plurality of wireless communication devices grasping the transmission of the wireless communication device. The frame transmission fails due to collision of radio signals. By grasping the transmission of a certain wireless communication device and waiting for a random time from the end of the transmission, the transmissions of the plurality of wireless communication devices that grasped the transmission of the wireless communication device are stochastically dispersed. Therefore, if only one wireless communication device subtracts the earliest time from the random time, frame transmission by the wireless communication device succeeds, and it is possible to prevent frame collision. Since the acquisition of the transmission right becomes fair among a plurality of wireless communication devices based on a random value, the method employing Carrier Aviodance is said to be a method suitable for sharing a wireless medium among a plurality of wireless communication devices. be able to.

[4] Wireless LAN Frame Interval The IEEE 802.11 wireless LAN frame interval will be described. Frame interval used in IEEE802.11 wireless LAN, distributed coordination function interframe space (DIFS), arbitration interframe space (AIFS), point coordination function interframe space (PIFS), short interframe space (SIFS), extended interframe space (EIFS) , Reduced interframe space (RIFS), and the like.

  In the IEEE 802.11 wireless LAN, the definition of the frame interval is defined as a continuous period in which carrier sense idle should be confirmed and opened before transmission, and a period from a strict previous frame will not be discussed. Therefore, the description in the IEEE 802.11 wireless LAN system here follows the definition. In the IEEE 802.11 wireless LAN, the time to wait for random access based on CSMA / CA is the sum of the fixed time and the random time, and it can be said that such a definition is used to clarify the fixed time.

  DIFS and AIFS are frame intervals used when trying to start frame exchange during a contention period competing with another wireless communication device based on CSMA / CA. The DIFS is used when there is no distinction between priorities based on the traffic type, and the AIFS is used when a priority based on the traffic type (Traffic Identifier: TID) is provided.

  Since operations related to DIFS and AIFS are similar, the following description will be made mainly using AIFS. In the IEEE 802.11 wireless LAN, access control including start of frame exchange is performed in the MAC layer. Further, when QoS (Quality of Service) is supported when data is passed from the upper layer, a traffic type is notified together with the data, and the priority of the data at the time of access is classified based on the traffic type. The class at the time of this access is called an access category (AC). Therefore, an AIFS value is provided for each access category.

  PIFS is a frame interval for enabling access having priority over other competing wireless communication devices, and has a shorter period than any of the values of DIFS and AIFS. SIFS is a frame interval that can be used when transmitting a control frame for a response system or when frame exchange is continued in a burst after acquiring an access right once. EIFS is a frame interval activated when frame reception fails (the received frame is determined to be error).

  RIFS is a frame interval that can be used when a plurality of frames are continuously transmitted to the same wireless communication device in a burst after the access right is once obtained. Does not request a response frame.

  FIG. 28 shows an example of frame exchange during a contention period based on random access in an IEEE 802.11 wireless LAN.

  It is assumed that when a transmission request for a data frame (W_DATA1) occurs in a certain wireless communication apparatus, the medium is recognized as a busy medium as a result of carrier sense. In this case, an AIFS is provided for a fixed time from the time when the carrier sense becomes idle, and thereafter, when a random time (random backoff) is provided, the data frame W_DATA1 is transmitted to the communication partner. If it is recognized that the medium is not busy as a result of the carrier sense, that is, the medium is idle, a data frame W_DATA1 is transmitted to the communication partner after a fixed time AIFS is left after the start of the carrier sense. Send to

  The random time is obtained by multiplying a slot time by a pseudorandom integer derived from a uniform distribution during a contention window (CW) given as an integer from 0. Here, the value obtained by multiplying the slot time by the CW is called a CW time width. The initial value of CW is given by CWmin, and every time retransmission is performed, the value of CW is increased until it becomes CWmax. Both CWmin and CWmax have a value for each access category, similar to AIFS. In the wireless communication apparatus of the transmission destination of W_DATA1, if the data frame is successfully received and the data frame is a frame requesting transmission of a response frame, the occupation end of the physical packet including the data frame on the wireless medium is ended. A response frame (W_ACK1) is transmitted after SIFS time from the time point. Upon receiving W_ACK1, the wireless communication apparatus that has transmitted W_DATA1 transmits the next frame (for example, W_DATA2) after the SIFS time from the end of the occupation of the physical packet containing W_ACK1 on the wireless medium within the transmission burst time limit. can do.

  AIFS, DIFS, PIFS, and EIFS are functions of SIFS and slot time, and SIFS and slot time are defined for each physical layer. Also, parameters for which values are provided for each access category such as AIFS, CWmin, and CWmax can be set for each communication group (Basic Service Set (BSS) in IEEE 802.11 wireless LAN), but default values are defined. .

  For example, in the standardization of 802.11ac, the SIFS is 16 μs and the slot time is 9 μs, whereby the PIFS is 25 μs, the DIFS is 34 μs, and the frame interval of the access category of BACKGROUND (AC_BK) in AIFS is 79 μs. BEST EFFORT (AC_BE) frame interval has a default value of 43 μs, VIDEO (AC_VI) and VOICE (AC_VO) frame interval has a default value of 34 μs, and CWmin and CWmax have default values of 31 and 1023 for AC_BK and AC_BE, respectively. , 15 for AC_VI and 7 and 15 for AC_VO. The EIFS is basically the sum of the SIFS, the DIFS, and the time length of the response frame when transmitting at the lowest required physical rate. In a wireless communication device capable of efficiently taking an EIFS, the occupation time length of a physical packet carrying a response frame to a physical packet that has activated the EIFS is estimated, and the sum of SIFS, DIFS and the estimated time may be used. it can.

  Note that the frame described in each embodiment may refer to a packet called a packet in the IEEE 802.11 standard or a compliant standard such as Null Data Packet.

  The frames multiplex-transmitted by a plurality of terminals may be frames having different contents or frames having the same contents. As a general expression, when describing that a plurality of terminals transmit or receive the Xth frame, the contents of these Xth frames may be the same or different. X is an arbitrary value.

  The terms used in this embodiment should be interpreted broadly. For example, the term “processor” may include a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and the like. In some circumstances, "processor" may refer to an application specific integrated circuit, a field programmable gate array (FPGA), a programmable logic circuit (PLD), and the like. “Processor” may refer to a combination of processing devices, such as a plurality of microprocessors, a combination of a DSP and a microprocessor, or one or more microprocessors cooperating with a DSP core.

  As another example, the term "memory" may encompass any electronic component capable of storing electronic information. "Memory" means random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), non-volatile It may refer to random access memory (NVRAM), flash memory, magnetic or optical data storage, which are readable by a processor. If a processor reads and / or writes information to and from a memory, then the memory can be said to be in electrical communication with the processor. The memory may be integrated with the processor, and again, the memory may be said to be in electrical communication with the processor. Further, the circuit may be a plurality of circuits arranged on a single chip, or one or more circuits dispersedly arranged on a plurality of chips or a plurality of devices.

  In this specification, “at least one of a, b, and c” means not only a combination of a, b, c, ab, ac, bc, abc, but also aa , Abb, aabbcc, etc., are also expressions including a plurality of combinations of the same elements. In addition, the expression covers a configuration including elements other than a, b, and c, such as a combination of abcd.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements in an implementation stage without departing from the scope of the invention. Various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

Claims (12)

A transmitting unit that transmits a first frame that is a trigger frame including information specifying a plurality of frequency components for OFDMA (Orthogonal Frequency Division Multiple Access) random access to a plurality of terminals ;
A receiving unit that receives at least one second frame transmitted via at least one of the plurality of frequency components in response to the first frame ,
The transmitting unit transmits a third frame including at least one of first information and second information for updating a first value range,
The first value range is based on a first value randomly selected from the first value range and the number of the plurality of frequency components specified by the information of the first frame. Used to acquire the transmission right to respond to one frame,
The first information is used for updating the first value range in a first terminal that has failed to transmit the second frame, and the second information is used for a second terminal that has successfully transmitted the second frame. Used for updating the first value range at the terminal
Wireless communication device.   The transmitting unit transmits a fourth frame that is a trigger frame including information specifying a plurality of frequency components for the OFDMA random access,
  In the first terminal that has received the fourth frame, a second value randomly selected from the first value range updated based on the first information and the plurality of packets specified in the fourth frame And a transmission right for responding to the fourth frame is acquired based on the number of frequency components of
  In the second terminal that has received the fourth frame, a third value randomly selected from the first value range updated based on the second information and a plurality of the third values specified in the fourth frame A transmission right for responding to the fourth frame is acquired based on the number of frequency components
  The wireless communication device according to claim 1. The first information or the second information, the wireless communication apparatus according to claim 1 or 2 including an indication of setting the magnitude of the first value range to an initial value. The wireless communication device according to claim 3 , wherein the initial value is an intermediate value between a minimum value and a maximum value of the first value range. The first information or the second information, the wireless communication apparatus according to claim 1 or 2 including an indication of setting the magnitude of the first value range to a maximum value. The first information or the second information, the wireless communication apparatus according to claim 1 or 2 including information specifying at least one of the minimum and maximum values of the first value range. Wherein the first information and the second information, the wireless communication apparatus according to claim 1 or 2 including the information indicating the adjustment amount of the first value range. The third frame includes a first field for notification to the first terminal ,
The wireless communication device according to any one of claims 1 to 7 , wherein the first information is included in the first field in the third frame. The third frame includes a second field for notification to the second terminal ,
The wireless communication device according to any one of claims 1 to 8 , wherein the second information is included in the second field in the third frame. Wherein according to the number of the frequency components of successful reception of the second frame, the radio communication apparatus according to claim 2 to adjust the number of frequency components specified in the fourth frame.   With at least one antenna
  The wireless communication device according to claim 1. Transmitting a first frame, which is a trigger frame including information specifying a plurality of frequency components for OFDMA (Orthogonal Frequency Division Multiple Access) random access, to a plurality of terminals ,
Receiving at least one second frame transmitted over at least one of the plurality of frequency components in response to the first frame;
Transmitting a third frame including at least one of the first information and the second information for updating the first value range;
The first value range is based on a first value randomly selected from the first value range and the number of the plurality of frequency components specified by the information of the first frame. Used to acquire the transmission right to respond to one frame,
The first information is used for updating the first value range in a first terminal that has failed to transmit the second frame, and the second information is used for a second terminal that has successfully transmitted the second frame. Used for updating the first value range at the terminal
Wireless communication method.

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