JP6417025B2 - Uplink subframe reduction in time division duplex (TDD) systems - Google Patents

Description

  The present invention relates generally to wireless communication systems, and more particularly to techniques for changing subframe length in a time division duplex (TDD) system.

  In a typical cellular radio system, an end user radio terminal, also known as a mobile station and / or user equipment unit (UE), communicates with one or more core networks via a radio access network (RAN). The radio access network (RAN) includes a geographical area divided into a plurality of cell areas, and each cell area is served by a base station, for example, a radio base station (RBS). In some networks, the radio base station may be referred to as “NodeB” or “eNodeB”, for example. A cell is a geographical area in which radio coverage is provided by a radio base station apparatus existing at the location of the base station. Each cell is identified by an identifier in the local radio area, which is broadcast in the cell. The base station communicates with user equipment units (UEs) that are within range of the base station via an air interface that operates on a radio frequency.

  In some radio access networks, a plurality of base stations may be connected to a radio network controller (RNC) or base station controller (BSC) by, for example, a terrestrial communication line or a microwave link. The radio network controller monitors and coordinates various activities of a plurality of base stations connected thereto. The radio network controller is typically connected to one or more core networks.

  Universal Mobile Telecommunication System (UMTS) is a third generation mobile communication system developed from Global System for Mobile Communications (GSM). UTRAN is a radio access network that uses wideband code division multiple access (W-CDMA) for communication between a UE and a base station called NodeB in the UTRAN standard.

  In a forum known as the 3rd Generation Partnership Project (3GPP), telecommunications suppliers are standards for 3rd generation networks in general, and in particular propose and agree on standards for UTRAN, considering technologies to improve radio data rates and radio capacities. Yes. 3GPP has begun to develop further radio access network technology based on UTRAN and GSM. Several releases have been issued for the specifications of the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and the standards continue to evolve. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) includes Long Term Evolution (LTE) and Service Architecture Evolution (SAE).

  Long Term Evolution (LTE) is a variant of 3GPP radio access technology where radio base station nodes are not connected to radio network controller (RNC) nodes but to core networks via access gateways (AGW) Is done. In general, in the LTE system, the functions of a radio network controller (RNC) node are distributed to radio base station nodes called ANodeB and AGW in the LTE specifications. As a result, the radio access network (RAN) of the LTE system has an architecture that includes radio base station nodes that do not directly belong to a radio network controller (RNC) node, which is sometimes referred to as a “flat” architecture.

  For example, transmission and reception from a node that is a wireless terminal such as a UE in a cellular system such as LTE can be multiplexed in the frequency domain, the time domain, or a combination thereof. In a frequency division duplex (FDD) system, as shown on the left side of FIG. 1, downlink transmission and uplink transmission are performed in different frequency bands that are well separated. In time division duplex (TDD), as shown on the right side of FIG. 1, downlink and uplink transmissions occur in different time slots that do not overlap. Thus, while TDD can operate in an unpaired frequency spectrum, FDD requires a paired frequency spectrum.

  Usually, transmission signals in a communication system are organized into some form of frame structure. For example, as shown in FIG. 2, LTE uses 10 subframes 0 to 9 having a length of 1 millisecond that are equal in size for each radio frame.

In the case of the FDD operation shown in the upper part of FIG. 2, there are two carrier frequencies: a carrier frequency (f _UL ) for uplink transmission and a carrier frequency (f _DL ) for downlink transmission. At least for wireless terminals in a cellular communication system, the FDD may be either full duplex or half duplex. In full-duplex mode, the terminal can transmit and receive simultaneously, but in half-duplex operation (see FIG. 1), the terminal cannot transmit and receive simultaneously (but the base station can transmit and receive simultaneously) That is, it can receive from one terminal and transmit to another at the same time). In LTE, a half-duplex wireless terminal monitors / receives in the downlink unless explicitly instructed to transmit on the uplink in a particular subframe.

In the case of TDD operation (shown in the lower part of FIG. 2), there is only a single carrier frequency F _{UL / DL,} and uplink transmission and downlink transmission are also time-separated in units of cells. Since the same carrier frequency is used for uplink transmission and downlink transmission, both the base station and the mobile terminal need to switch between transmission and reception. An important aspect of the TDD system is to provide a sufficiently long guard time in which neither downlink transmission nor uplink transmission occurs to avoid interference between uplink transmissions and downlink transmissions. . In the case of LTE, a special subframe (subframe 1 and possibly subframe 6) provides this guard time. The special subframe of TDD is divided into three parts: a downlink part (DwPTS), a guard period (GP), and an uplink part (UpPTS). The remaining subframes are assigned to either uplink transmission or downlink transmission.

  In time division duplex (TDD), the asymmetry of the amount of resources allocated to uplink and downlink transmissions can be different for different downlink / uplink configurations. In LTE, there are seven different configurations as shown in FIG. Each configuration has a different ratio of downlink subframes and uplink subframes in each radio frame of 10 milliseconds. For example, configuration 0 shown at the top of FIG. 3 includes two downlink subframes and three uplink subframes in each half-frame of 5 milliseconds, as indicated by the notation “DL: UL 2: 3”. Have. Configurations 0, 1 and 2 have the same arrangement in each half-frame of a radio frame, but the remaining arrangements do not have such an arrangement. For example, Configuration 5 has only one uplink subframe and nine downlink subframes, as indicated by the notation “DL: UL 9: 1”. Multiple configurations provide different ratios of uplink / downlink, so the system can select the optimal configuration for the expected traffic load.

  In order to avoid significant interference between downlink transmissions and uplink transmissions between different cells, adjacent cells need to have the same downlink / uplink configuration. When not having the same configuration, as shown in FIG. 4, when the uplink transmission to the base station 2 (BS2) in one cell interferes with the downlink transmission from the base station 1 (BS1) in the adjacent cell (Also, uplink transmissions to base station 1 (BS1) in one cell may interfere with downlink transmissions from base station 2 (BS2) in neighboring cells). In FIG. 4, the uplink transmission of the UE in the right cell identified as mobile station 1 (MS2) in the figure interferes with the downlink reception by the UE (MS1) in the left cell. As a result, downlink / uplink asymmetry does not vary from cell to cell. The downlink / uplink asymmetric configuration is signaled as part of the system information and is fixed for a long time.

  In LTE, the downlink is based on orthogonal frequency division multiplexing (OFDM), while the uplink is based on discrete Fourier transform spread (DFT spread) OFDM, also known as single carrier frequency division multiple access (SC-FDMA). Details can be found in the 3GPP document “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation”, 3GPP TS 36.211, V11.3.0, available at www.3gpp.org. The transmission time interval (TTI) is equal to 1 millisecond subframe, which is composed of 14 OFDM symbol periods in the downlink and 14 SC-FDMA symbol periods in the uplink. Given a cyclic prefix. The portions of the OFDM symbols and SC-FDMA symbols transmitted in these symbol periods are used to carry user data on physical channels called physical downlink shared channel (PDSCH) and physical uplink shared channel (PUSCH). The In future wireless communication systems, the length of subframes may be significantly reduced to reduce user data delay. Furthermore, in future wireless systems, both downlink and uplink may be based on OFDM.

  An important priority for the development of current radio systems and future radio communication systems is to increase the bit rate and reduce the delay, especially in the case of small cells. An increase in the bit rate can be achieved by using a high carrier frequency that can utilize, for example, a broadband spectrum resource. Also, interest in TDD (Time Division Duplex) is increasing. If a dynamic TDD system is used, ie a system where the TDD configuration is not necessarily static between one frame and the next, the number of sections used for the downlink (eNodeB to UE) and the uplink (from the UE By adaptively changing the relationship with the number of sections used for eNodeB), the downlink bit rate or uplink bit rate can be increased instantaneously. Since the propagation delay is small in the small cell, a short guard period can be used when switching from the downlink to the uplink. Accordingly, an improved technique for switching between downlink and uplink in a dynamic TDD system while keeping interference between downlink and uplink transmissions to a minimum and keeping control signaling to a minimum Is needed.

  If the relationship between uplink and downlink is fixed in a time division multiplexing (TDD) system, radio resources cannot be used flexibly. However, when the dynamic TDD system is used, if it is necessary to notify all user equipments (UEs) of subframes used as downlink and uplink subframes, the amount of control signaling is greatly increased. there is a possibility. In particular, if the guard period for switching between uplink and downlink is created by omitting one or more OFDM symbols in the downlink subframe, the eNodeB may omit the last OFDM symbol in the subframe. It is necessary to send a control message notifying all UEs that it will be used. This requires a large signaling overhead.

  Another method requires the UE to blindly detect if one or more of the last OFDM symbols are omitted. However, another UE may transmit on the uplink during their last downlink OFDM symbol, and interference will occur if the UEs are not well separated from each other. As a result of this interference, the reliability of detection of whether the OFDM symbol is omitted from the downlink frame is degraded, and the performance is degraded.

  In various embodiments of the present invention, the guard period for switching between uplink and downlink subframes is created by shortening the uplink subframe. This is done by omitting one or more symbols at the beginning of the uplink subframe transmission interval, ie, not transmitting during one or more symbol intervals at the beginning of the subframe interval. When a UE must transmit a subframe that is one or more OFDM (or SC-FDMA) symbols shorter than a normal subframe, and one or more OFDM ( (Or SC-FDMA) Signaling indicating where transmission of the subframe starts after a symbol delay is included in the uplink grant message sent to the UE.

  Several embodiments are described below in the context of an LTE system in which the uplink supports transmission from the UE to the eNodeB, but the disclosed technology may be applied to other radio systems, not necessarily the LTE eNodeB. It should be understood that it does not depend on the specific hierarchical configuration with the UE.

  Accordingly, an example of a method according to the technique disclosed in the present specification is a transmission subframe having a predetermined length that occurs in a defined subframe period and includes, for example, a predetermined number of symbol periods. Suitable for realization in a first wireless node configured to transmit data. In the LTE system, the first radio node is a UE and the subframe is an uplink subframe. The method of this example includes a step of determining that the transmission subframe is shortened compared to a predetermined length, and, according to the determination, without transmitting between the head portion of the subframe interval for the transmission subframe. Shortening the transmission of the transmission subframe by transmitting during the remaining part of the subframe interval. In some embodiments, such as in an LTE system, the predetermined length is a predetermined number of symbol intervals, and shortening the transmission of a subframe is between one or more symbol intervals at the beginning of a transmission subframe. Is done by not sending to.

  In some embodiments, the first radio node receives the grant message including subframe shortening information from the second radio node indicating that the transmission subframe is to be shortened, thereby transmitting the first transmission subframe. Is determined to be shortened. The subframe shortening information may be composed of, for example, a single bit indicating that a transmission subframe is shortened by a predetermined number of symbols, or may include a plurality of bits indicating the number of symbols omitted from the transmission subframe. Good. In other embodiments or other examples, the first radio node is not explicitly signaled from the second radio node, eg, in a reception subframe that precedes the transmission subframe and overlaps the transmission subframe. It may be determined that a transmission subframe is shortened by determining that a scheduled broadcast subframe is received.

  Another example of the method is suitable for implementation in a wireless node that is configured to receive data in a received subframe that occurs in a defined subframe interval and has a predetermined length. In an LTE system, this node may be an LTE eNodeB, and the received subframe is again an uplink subframe. The example method includes transmitting a grant message including subframe shortening information to a second radio node, eg, an LTE UE. The subframe shortening information indicates that a subframe transmitted by the second radio node is shortened during the first subframe period. Thereafter, the wireless node receives the shortened subframe from the second wireless node during the first subframe period. In this case, the subframe to be shortened is shortened compared to a predetermined length. Again, this subframe shortening information is a single bit that indicates that the subframe transmitted during the first subframe interval is shortened by omitting a predetermined number of symbols from the beginning of the transmission subframe. Or a plurality of bits indicating a specific number of symbols to be omitted from the transmission subframe.

  Corresponding devices, ie, wireless nodes configured to perform one or more of the methods outlined above, are also described in more detail in the following description.

  As described above, since the UE cannot perform transmission and reception at the same time, the guard period must always be included in the TDD system. When providing a guard period using omitting one or more symbols from the beginning of the uplink subframe, only the UE transmitting on the uplink needs to recognize the switching from the downlink to the uplink. There is. The control message included in the uplink grant has very little additional control signaling overhead caused thereby and can be received by the UE in subframes other than the subframe to be shortened. Accordingly, the techniques and apparatus disclosed herein do not require blind detection of downlink to uplink switching and are robust systems for performing dynamic TTD switching with low signaling load Can be used to provide

  Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will appreciate further features and advantages upon reading the following detailed description and upon reference to the accompanying drawings.

FIG. 1 is a diagram illustrating transmission of frequency division duplex, half duplex frequency division and time division duplex. FIG. 2 is a diagram illustrating an LTE uplink / downlink time / frequency configuration for frequency division duplex (FDD) and time division duplex (TDD). FIG. 3 is a diagram illustrating as an example seven different downlink / uplink configurations for time division duplex (TDD) in Long Term Evolution (LTE). FIG. 4 is a diagram illustrating an example of uplink / downlink (UL / DL) interference in time division duplex (TDD). FIG. 5 is a diagram illustrating a part of an example of an LTE network including a plurality of user equipments (UEs). FIG. 6 is a diagram illustrating downlink and uplink timing in the TDD system. FIG. 7 is a diagram illustrating an uplink-downlink configuration according to the 3GPP specification. FIG. 8 is a diagram showing details of frame configuration type 2 (in the case of a switching point cycle of 5 milliseconds) specified by 3GPP. FIG. 9 is a diagram illustrating shortening of an uplink OFDM symbol after a downlink subframe. FIG. 10 is a diagram illustrating that an uplink OFDM symbol is not omitted when there is no downlink subframe before the uplink subframe. FIG. 11 is a diagram illustrating that an uplink OFDM symbol for UE2 after an uplink subframe is not omitted. FIG. 12 is a diagram illustrating omitting uplink OFDM symbols in a first subframe of an uplink grant for multiple subframes. FIG. 13 is a diagram illustrating omitting an uplink OFDM symbol after a fixed downlink subframe. 14A is a diagram illustrating subframes having DM-RS, CSI-RS, and eSS, and FIG. 14B is a diagram illustrating subframes in which DM-RS, CSI-RS, and eSS are time-shifted. 14C is a diagram illustrating a subframe in which two OFDM symbols are omitted and DM-RS, CSI-RS, and eSS are time-shifted. FIG. 15A is a diagram illustrating subframes mapped according to time after first mapped according to frequency, and FIG. 15B is a diagram illustrating subframes mapped according to frequency after being mapped according to time first. FIG. 16 is a process flow diagram illustrating an example of a method according to the technique disclosed in this specification. FIG. 17 is a process flow diagram illustrating another example of the method. FIG. 18 is a block diagram illustrating components of an example of a user device. FIG. 19 is a block diagram illustrating an example of a base station.

  In the following description, specific details of specific embodiments of the invention are set forth for purposes of illustration and not limitation. Those skilled in the art will appreciate that other embodiments may be used without those specific details. Further, in some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not to obscure the description with unnecessary detail. One skilled in the art will appreciate that the functions described may be implemented in one node or multiple nodes. Some or all of the functions described may be implemented using hardware and circuitry such as analog and / or discrete logic gates, ASICs, PLAs, etc. that are interconnected to perform specialized functions. Similarly, some or all of the functions may be implemented using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. When describing nodes that communicate using an air interface, it will be understood that those nodes further comprise suitable wireless communication circuitry. Further, the present invention provides some form of computer readable memory including non-transitory embodiments such as solid state memory, magnetic disk or optical disk, including a suitable set of computer instructions that cause a processor to perform the techniques described herein. It is further conceivable that it is fully realized within.

  Hardware implementations of the present invention include, but are not limited to, digital signal processor (DSP) hardware, reduced instruction set processors, application specific integrated circuits (ASICs) and / or field programmable gate arrays (FPGAs). It may include, but is not limited to, hardware (eg, digital or analog) circuitry, as well as state machines (where appropriate) that can perform such functions.

  With respect to computer implementations, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms “computer”, “processor” and “controller” may be used interchangeably. If provided by a computer, processor or controller, the functionality may be provided by a single dedicated computer, processor or controller, may be provided by a single shared computer, processor or controller, and some may be shared Or it may be provided by a plurality of individual computers, processors or controllers which may be distributed. Further, the term “processor” or “controller” further refers to other hardware capable of performing such functions and / or executing software, such as the hardware examples described above.

  Referring now to the drawings, FIG. 5 shows an example of a mobile communication network for providing a wireless communication service to the mobile terminal 100. Three mobile terminals 100 called “user equipment” or “UE” in 3GPP terminology are shown in FIG. The mobile terminal 100 may include, for example, a mobile phone, a personal digital assistant, a smartphone, a laptop computer, a handheld computer, a machine type communication / machine to machine (MTC / M2M) device, or other device having a wireless communication function. As used herein, the term “mobile terminal” refers to a terminal that operates in a mobile communication network, and does not necessarily mean that the terminal itself is portable or mobile. Thus, as used herein, the term should be understood to be interchangeable with the term “wireless device” and installed in a fixed configuration, such as a particular machine-to-machine application. A terminal, a portable device, a device installed in an automobile, and the like may be shown.

  The mobile communication network includes a plurality of geographic cell areas or sectors 12. Each geographic cell area or sector 12 is served by a base station 20 called eNodeB in the context of an LTE radio access network, formally known as an evolved universal terrestrial radio access network (E-UTRAN). . One base station 20 may provide service in multiple geographic cell areas or sectors 12. The mobile terminal 100 receives signals from the base station 20 on one or more downlink (DL) channels and transmits signals to the base station 20 on one or more uplink (UL) channels.

  In the LTE network, the base station 20 is an eNodeB, and may be connected to one or more other eNodeBs via an X2 interface (not shown). The eNodeB is further connected to the MME 130 via the S1-MME interface and may be connected to one or more other network nodes such as a serving gateway (not shown).

  For purposes of illustration, embodiments of the present invention will be described in an EUTRAN system. However, those skilled in the art will appreciate that embodiments of the present invention may be more generally applicable to other wireless communication systems.

  As mentioned above, the same frequency is used for both downlink and uplink in TDD (Time Division Duplex) systems. In that case, assuming that full-duplex operation is not possible, both the UE and the eNodeB need to switch between transmission and reception. FIG. 6 shows the timing between the downlink and the uplink, which shows the subframe transmission time and the subframe reception time at both UE and eNodeB, which is OFDM (or It can be measured in units of (SC-FDMA) symbol index. Due to the propagation delay that can change as the UE moves within the coverage area of the eNodeB, downlink subframes transmitted by the eNodeB are delayed and received at the UE. The Fast Fourier Transform (FFT) window at the receiver of the UE is such that the cyclic prefix (CP) portion of the subframe can overlap the edge of the FFT window while the data portion of the subframe is completely included in the FFT window. To the received subframe. The uplink subframe transmitted by the UE can be transmitted only after completion of the switching time from the reception mode to the transmission mode of the UE, and is received at the eNodeB with a propagation delay. The timing of UE transmission is controlled by the eNodeB so that the data transport portions of consecutive uplink subframes from multiple UEs do not overlap each other and are included in the FFT window of the eNodeB receiver. . Also in this case, the subframe portion including the cyclic prefix (CP) may overlap the edge of the eNodeB FFT window.

  In LTE Release 11, a fixed allocation of uplink and downlink subframes is used, which is “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation”, 3GPP, available at www.3gpp.org. Defined in TS 36.211, V11.3.0 A number of predefined assignments are specified as shown in FIG. In the figure, uplink-downlink configurations 0-6 are shown with a period of 5 ms or 10 ms each. In the table shown in FIG. 7, each of the subframe numbers 0 to 9 represents “D” subframe corresponding to the downlink subframe, “U” subframe corresponding to the uplink subframe, and “S” corresponding to the special subframe. Is shown as one of the sub-frames. The special subframe is inserted between successive downlink subframes and uplink subframes. Details of the special subframe are shown in FIG. The special subframe includes both an OFDM symbol for the downlink and an SC-FDMA symbol for the uplink, and a guard period between them. This guard period is used by the UE to transmit with timing advance so that uplink symbols are received within the eNodeB FFT window as shown in FIG. The guard period further provides time for the eNodeB and UE transceiver circuits to switch from downlink mode to uplink mode.

  In a dynamic TDD system, the relationship between the number of downlink subframes and the number of uplink subframes is not fixed according to the quasi-static configuration shown in FIG. 7 and depends on what is currently required. It can be configured flexibly. For example, the UE may treat all subframes as downlink subframes unless explicitly instructed to transmit in a given subframe. This approach to dynamic TDD was published on June 23, 2011, and is hereby incorporated by reference in its entirety, which is incorporated herein by reference. No. 0149813. If flexible subframes are used, the eNodeB may control signals indicating the time and method that the UE is scheduled for reception (ie, downlink assignment) and the time and method of transmitting on the uplink (ie, uplink grant). Is sent to the UE. In LTE, this control signaling can be carried by either a physical downlink control channel (PDCCH) or an enhanced physical downlink control channel (EPDCCH). The downlink assignment is transmitted in the same subframe in which user data is transmitted, while the uplink grant is transmitted a few subframes before the UE is scheduled to transmit in the uplink.

  If the relationship between uplink and downlink is fixed, radio resources cannot be used flexibly. However, when dynamic TDD is used, if all UEs need to recognize subframes used as downlink subframes and uplink subframes, the amount of control signaling may increase significantly. . Furthermore, in dynamic TDD, a guard period is required between consecutive downlink subframes and uplink subframes in order for the UE circuit to switch from the downlink mode to the uplink mode.

  The guard period can be created by omitting one or more OFDM symbols in the downlink. In a system that uses redundant coding, the receiving UE can treat those omitted OFDM symbols as “punctured” symbols, and normally the data carried by the symbols is a normal decoding technique. Can be reconfigured using Alternatively, the receiving-side UE can decode the data in the remaining part of the subframe and avoid symbol periods that do not carry data. In any case, if the guard period is created by omitting one or more OFDM symbols in the downlink, the eNodeB will send a control signal indicating that the last OFDM symbol of the subframe is omitted. Must be sent to the UE. Thus, according to this approach, signaling is included in the downlink grant, which indicates that the eNodeB is transmitting one or more OFDM (or SC-FDMA) symbol shorter subframes than the normal subframe. And where the transmission of the subframe ends one or more OFDM (or SC-FDMA) symbol periods earlier than in the case of a normal subframe. Note that this indication needs to be signaled to all UEs scheduled for that subframe, and therefore a large signaling overhead may be required.

  An alternative is that the UE can detect blindly whether one or more of the last OFDM symbols are omitted. However, interference occurs when another UE transmits on the uplink during their last downlink OFDM symbol when the UEs are not sufficiently separated from each other. As a result of this interference, the reliability of detection of whether or not the OFDM symbol is omitted decreases and the performance decreases.

  Another approach is for the UE to create a guard period by omitting one or more symbols from the beginning of the uplink subframe transmission. According to this approach, the base station requires that the UE transmit a subframe that is one or more OFDM (or SC-FDMA) symbols shorter than a normal subframe, and that the transmission of the subframe is: Signaling indicating where to start one or more OFDM (or SC-FDMA) symbol periods later than normal subframes is included in the UL grant.

  FIG. 9 shows subframe timing according to the latter approach, where a series of subframes are flexibly scheduled, one subframe is scheduled for use in the uplink (UL), 2 One other subframe is scheduled for use in the downlink (DL) and the remaining subframes are not scheduled. The uplink grant is transmitted on the downlink in subframe n (n = 5 in FIG. 9), indicating that the UE needs to transmit on the uplink in subframe n + g (g = 5 in FIG. 9). When the eNodeB transmits in the downlink in subframe n + g-1 (subframe 9), the UE starts from the beginning of the transmission of uplink subframe n + g (subframe 10 in FIG. 9) to create a short guard period. One or more OFDM (or SC-FDMA) symbols need to be omitted. Thus, a “subframe shortening message” is included in the uplink grant, which informs the UE that the UE needs to omit one or more symbols from the beginning of the uplink subframe transmission. As shown at the bottom of FIG. 9, the uplink subframe spans a subframe section including 14 symbol periods numbered 0-13. Each of these symbol periods typically carries OFDM (or SC-FDMA) symbols. However, the OFDM symbol can be omitted from one or more symbol periods at the beginning of the subframe period. In the example shown in FIG. 9, the guard period is created by omitting the first two OFDM symbols in the subframe section.

  When subframe n + g-1 (subframe 9) does not include downlink transmission from eNodeB as shown in FIG. 10, or when subframe n + g + 1 is an uplink subframe from another UE as shown in FIG. The UE does not need to omit one or more symbols from the beginning of the uplink subframe in subframe n + g. Thus, FIG. 10 is similar to FIG. 9 except that the downlink subframe is not scheduled for the subframe period preceding the scheduled uplink subframe, which is This means that it is not necessary to create a guard period by omitting symbols from the beginning of the link subframe. FIG. 11 is also similar to FIG. 9 except that two consecutive uplink subframes, one for each of the two UEs, are scheduled immediately after the downlink subframe. Since the uplink subframe scheduled for UE2 follows the uplink subframe scheduled for UE1, not the downlink subframe, UE2 creates a guard period in the second uplink subframe There is no need to do. Accordingly, as shown at the bottom of FIG. 11, only the first subframe of the two uplink subframes includes a guard period created by omitting the leading symbol of the subframe section. These examples (ie, the scenarios shown in FIGS. 10 and 11) are also controlled by the uplink grant, i.e. omit the subframe shortening message completely or indicate that a given uplink subframe does not require shortening. Controlled by including subframe shortening messages. Note that if the eNodeB sends an uplink grant in subframe n, it may not be certain that subframe n + g-1 is used for downlink transmission. In general, if the eNodeB knows that the subframe n + g-1 is not used for downlink transmission, depending on the planned messaging implementation, the eNodeB indicates that no message is required. It is necessary to send a shortened message or omit the subframe shortened message from the uplink grant. If the eNodeB does not know whether downlink transmission is performed in subframe n + g-1, the eNodeB assumes that downlink transmission is performed in subframe n + g-1 and assumes an appropriate subframe shortening message. Must be sent out.

  In some embodiments, the subframe shortening message in the uplink grant includes only a single bit that signals whether to omit the first OFDM (or SC-FDMA) symbol of the uplink transmission. In these embodiments, the UE is pre-configured by hard programming to omit a predetermined number of symbols when a subframe shortening message is received, or pre-quasi-statically, eg, by RCC signaling. It may be configured. A more flexible format is also possible where the subframe shortening message explicitly indicates the number of OFDM (or SC-FDMA) symbols to be omitted. With this approach, if the round trip time is short, only one OFDM (or SC-FDMA) symbol needs to be omitted, and a UE with a long round trip time may need to omit multiple OFDM symbols. In some embodiments, the eNodeB may be configured to always use the same indication based on cell size. In other embodiments, the round trip time of each UE is estimated and continuously tracked at the eNodeB so that the subframe shortening message can be adapted to the round trip time of individual UEs.

  For example, assume that 2 bits are used for a subframe shortening message. In this example, the bit sequence “00” may be used to signal that the uplink OFDM (or SC-FDMA) symbol need not be omitted. The sequence “01” can be used to indicate that one OFDM (or SC-FDMA) symbol needs to be omitted, and the sequence “10” needs to omit two OFDM (or SC-FDMA) symbols. The sequence “11” indicates that three OFDM (or SC-FDMA) symbols are omitted. Alternatively, the number of punctured OFDM symbols indicated by the bit (s) of the subframe shortening message can be quasi-statically configured by higher layers.

  It will be appreciated that the uplink grant can include grants for multiple subframes. If these uplink subframes are contiguous, signaling for subframe shortening is only required for the first of the simultaneously scheduled subframes. This is shown in FIG. FIG. 12 shows a scenario where the uplink grant schedules the UE for four consecutive uplink subframes following the downlink subframe. As shown at the bottom of FIG. 12, only the first uplink subframe includes a guard period created by omitting one or more symbols from the beginning of the subframe.

  A dynamic TDD system may also be configured with several subframes that are fixed for the downlink and therefore not used for the uplink. These subframes may be needed for synchronization and broadcast control messages used for continuous synchronization, initial synchronization and call setup, for example. One or more of those fixed downlink subframes may be present in the UE's multi-subframe uplink grant. In this case, the UE cannot transmit during the fixed downlink subframe, but can continue transmission thereafter. The UE may continue to transmit all remaining subframes according to its uplink grant, or the entire uplink transmission effectively includes one subframe less than the number indicated by the uplink grant As such, one of the subframes in the grant may be considered “punctured” by the fixed downlink subframe. In any case, the UE needs to omit one or more OFDM (or SC-FDMA) symbols in the first subframe after the fixed downlink subframe as shown in FIG. In FIG. 13, the fixed downlink subframe is indicated by “D”. As in the previous figure, the uplink grant is transmitted in the downlink in subframe n (n = 5 in FIG. 13), and the UE starts in subframe n + g (g = 5 in FIG. 13) and uplinks Indicates that it needs to be sent. In this case, the multi-subframe grant overlaps with the fixed downlink subframe in subframe 12, which indicates that the uplink subframe transmitted after the downlink subframe needs to be shortened. However, since the UE already recognizes the fixed downlink subframe, the necessity to shorten this subframe does not need to be signaled to the UE. If flexible shortening of subframes is used, a default number of OFDM (or SC-FDMA) symbols that may be omitted may be used. Alternatively, subframe shortening according to the last received subframe shortening message in the uplink grant for a particular UE may be used. In either case, the UE creates a guard period at the beginning of the first uplink subframe following the fixed downlink subframe, as shown at the bottom of FIG.

  The eNodeB may use beamforming on either or both the downlink and uplink to increase the signal to interference noise ratio (SINR) for the UE. This beamforming can be done in baseband, in which case the change between different beamformers can be done on a sample basis. However, for other types of beamforming techniques such as analog beamforming implemented using microwave or RF phase adjusters, if a guard is required for the component to apply this beamforming change There is. The guard period can also be used to suspend transmission on the uplink during the calibration phase. In these cases, the eNodeB may instruct the UE to omit one or more of the first OFDM (or SC-FDMA) symbols in a given uplink subframe for this purpose. .

  FIG. 14A shows an example of a resource block of a subframe (a time-frequency resource composed of 12 consecutive OFDM subcarriers in a subframe section). In the figure, a plurality of subcarriers are shown vertically, and a subframe section extends horizontally. In the illustrated example, a subframe is composed of 14 OFDM symbols, and includes a plurality of demodulation reference signals (DM-RS), channel state information reference symbols (CSI-RS), and cell-specific reference signals (CRS). Contains a reference signal. For further details of these signals, see the 3GPP document “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation”, 3GPP TS 36.211, V11.3.0, available at www.3gpp.org. Similar mapping can be used in future wireless standards.

  FIG. 14B shows an example of another mapping, in which the mapping of reference symbols has been modified to facilitate the start of channel estimation before receiving all OFDM symbols of a subframe. . However, if the first OFDM symbol of a subframe is omitted, the reference symbol should not be omitted. If one or more OFDM symbols are omitted in those subframes, another mapping of reference symbols and user data modulation symbols as shown for example in FIG. 14C is conceivable.

  In any of the embodiments described above, the uplink subframe may be shortened by simply not transmitting the first one or two symbols of the subframe. If the system is designed for an environment where the distance between the eNodeB and the UE is long, that is, an environment where a long round trip time is expected, it may be possible to omit more symbols. However, in LTE Release 11, channel coding is designed so that some of the user data may not be decoded if the first symbol is omitted. More specifically, as specified in “Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding”, 3GPP TS 36.212, V11.3.0, available at www.3gpp.org, Segmented into code blocks. Each such code block is individually turbo encoded and interleaved, after which the codewords are concatenated, modulated, and mapped to OFDM (or SC-FDMA) symbols. In this mapping, as shown in FIG. 15A, the sequence of concatenated modulation symbols is first mapped to subframes in frequency (ie across multiple subcarriers) and then in time. FIG. 15A and FIG. 15B each show an example of a resource block composed of 12 consecutive OFDM subcarriers in a subframe section. In the figure, a plurality of subcarriers are shown vertically, and a subframe section extends horizontally. In the illustrated example, a subframe is composed of 14 OFDM symbols and includes a plurality of reference signals including a demodulated reference signal (DM-RS). Other reference symbols are omitted for clarity. In FIG. 15A, the sequence of modulation symbols is first mapped vertically (ie, over frequency) and then horizontally (ie, over time) as indicated by the arrows. As a result of this mapping, one or more codewords are completely punctured when puncturing the entire one or more OFDM (or SC-FDMA) symbols. One solution to this problem is to change the way in which concatenated modulation symbol sequences are mapped to OFDM symbols and SC-FDMA symbols. FIG. 15B shows one method, in which the mapping is first done in time, as indicated by the horizontal arrow. However, one drawback of first mapping in time is that frequency diversity is reduced. This can be mitigated when mapping in time and mapping in frequency are performed alternately.

  In the above, various techniques for transmitting and receiving shortened subframes have been described in the context of LTE systems. However, it should be understood that these techniques are more generally applicable to TDD radio links between radio nodes and do not rely on radio nodes having a UE and base station relationship found in LTE systems. Accordingly, FIG. 16 illustrates a first configuration configured to transmit data in a transmission subframe that occurs in a defined subframe interval and has a predetermined length (eg, a predetermined number of symbol intervals). A method suitable for implementation in a wireless node is shown. If this method is implemented in LTE context, the first radio node may be a UE communicating with an eNodeB.

  As shown in block 1610, the illustrated method can generate configuration information from a second radio node that specifies a predetermined number of symbols to be omitted from an uplink subframe when a shortened subframe is transmitted. You may start by receiving. In FIG. 16, this action is illustrated by a dashed frame, which indicates that this action is not present in all embodiments or all examples of the illustrated method.

  As shown at block 1620, the illustrated method includes determining that a transmission subframe is shortened compared to a predetermined length. In some embodiments or some examples, this may be done by receiving a grant message that includes subframe shortening information. However, in other embodiments or other examples, the first wireless node determines that a scheduled broadcast subframe is received in a reception subframe that precedes and overlaps a transmission subframe. Thus, it may be determined that the transmission subframe is shortened.

  As shown in block 1630, the illustrated method further includes shortening the transmission of the transmission subframe. This is done by transmitting during the remaining portion of the subframe interval without transmitting during the beginning portion of the subframe interval for the transmission subframe. In some embodiments, the predetermined duration of the subframe is a predetermined number of symbol periods, in which case shortening the transmission of the subframe may be a reduction of one or more symbol periods at the beginning of the transmission subframe. Including not sending in between. It should be noted that as the terminology is used in this specification, a subframe section is composed of a specific number (for example, 14) of symbol sections, and each symbol section normally carries a transmitted symbol. If the subframe is shortened, one or more of the subframe intervals do not carry transmission symbols.

  As described above, determining that the first transmission subframe is shortened is receiving a grant message including subframe shortening information indicating that the transmission subframe is shortened from the second radio node. May be included. In some embodiments, the subframe shortening information consists of a single bit that indicates that the transmission subframe is shortened by omitting a predetermined number of symbols from the beginning of the transmission subframe. In some of the above embodiments, the first wireless node receives configuration information specifying a predetermined number from the second wireless node before receiving the grant message, as shown in block 1610. . In other embodiments, the subframe shortening message received from the second radio node specifies the number of symbols to be omitted at the beginning of the transmission subframe.

  FIG. 17 shows a method implemented at the other end of the link from the wireless node corresponding to FIG. Accordingly, the method shown in FIG. 17 is configured to receive data in a received subframe that occurs in a defined subframe interval and has a predetermined length (eg, a predetermined number of symbol intervals). Suitable for realization in wireless nodes. For LTE context, this node may be an eNodeB.

  As shown in block 1710, the illustrated method transfers configuration information specifying a predetermined number of symbols to be omitted from an uplink subframe to a second radio node when a shortened subframe is transmitted. You may start by sending. In FIG. 17, this action is illustrated by a dashed box, which indicates that this action is not present in all embodiments or all examples of the illustrated method.

  As shown in block 1720, the illustrated method includes a grant message including subframe shortening information indicating that a subframe transmitted by the second wireless node is shortened during the first subframe interval. Following transmission to the second wireless node. In the case of the LTE context, this second radio node is, for example, a UE. As shown in block 1730, the method continues with receiving a first shortened subframe from a second wireless node during a first subframe interval. In this case, the first shortened subframe is shortened compared to a predetermined length.

  In some embodiments, the subframe shortening information sent to the second radio node specifies the number of symbols to be omitted at the beginning of the subframe transmitted during the first subframe interval. In another embodiment, the subframe shortening information simply indicates that a subframe transmitted during the first subframe interval is shortened by omitting a predetermined number of symbols from the beginning of the transmission subframe. It consists of one bit. In some of these embodiments, the wireless node configures the number of symbols to be omitted from the beginning of the subframe transmitted during the first subframe interval before transmitting the grant message. Is transmitted to the second wireless node.

  In some embodiments, the wireless node decodes data from the first shortened subframe by treating one or more omitted symbols at the beginning of the first subframe interval as punctured data. Turn into. In another embodiment, the wireless node demaps the data symbols from the first uplink subframe according to a demapping pattern that ignores the first omitted symbol period of the first subframe period, and demaps the data symbol. Decoded data is extracted from the first shortened subframe by decoding the mapped data symbols.

  In some embodiments, the wireless node further transmits a scheduled broadcast subframe during the second subframe interval, and during the third subframe interval immediately after the second subframe interval. A second shortened subframe may be received. This is shown in blocks 1740 and 1750, which are “optional” in the sense that these operations may not be performed in all embodiments or all examples of the illustrated embodiments. In order to show, it is shown with a broken-line frame.

  Several of the methods described above and generally shown in FIGS. 16 and 17 may be implemented using radio circuitry and electronic data processing circuitry provided at the mobile terminal. FIG. 18 shows an example characteristic of a wireless node 1800 according to embodiments of the present invention, which is realized as a mobile terminal in this example. A mobile terminal 1800, which may be a UE configured to operate in an LTE system, includes a transceiver 1820 that communicates with one or more base stations, and a processing circuit 1810 that processes signals transmitted and received by the transceiver 1820. Is provided. The transceiver 1820 includes a transmitter 1825 coupled to one or more transmit antennas 1828 and a receiver 1830 coupled to one or more receive antennas 1833. The same antennas 1828 and 1833 may be used for both transmission and reception. The receiver 1830 and transmitter 1825 typically use known radio processing and signal processing components and radio processing and signal processing techniques according to a specific communication standard, such as the 3GPP standard for LTE. Various details and technical trade-offs related to the design and implementation of such circuits are known and are not necessary to fully understand the present invention, so no further details are given herein. .

  The processing circuitry 1810 includes one or more processors 1840 coupled to one or more memory elements 1850 that make up the data storage device 1855 and the program storage device 1860. In some embodiments, the processor 1840 identified as CPU 1840 in FIG. 18 may be a microprocessor, microcontroller, or digital signal processor. More generally, the processing circuitry 1810 may include a processor / firmware combination, dedicated digital hardware, or a combination thereof. The memory 1850 may include one or more types of memory such as read only memory (ROM), random access memory, cache memory, flash memory elements, optical storage devices, and the like. Again, various details and technical trade-offs associated with the design of the baseband processing circuit for the mobile device are known and are not necessary for a complete understanding of the invention, so further details are provided herein. Not shown in the book.

  Typical functions of the processing circuit 1810 include modulation and coding of the transmitted signal and demodulation and decoding of the received signal. In embodiments, the processing circuit 1810 performs one of the described techniques of transmitting a shortened subframe using, for example, appropriate program code stored in the program storage memory 1860. Configured.

  Accordingly, in various embodiments of the present invention, the processing circuitry is configured to perform one or more of the techniques described in detail above. Similarly, other embodiments include a mobile terminal (eg, LTE UE) that includes one or more such processing circuits. In some examples, these processing circuits may implement one or more of the techniques described herein using suitable program code stored in one or more suitable memory devices. Configured. Of course, it will be understood that not all of these technical steps are necessarily performed in a single microprocessor or module.

  The mobile terminal 1800 of FIG. 18 is configured to operate in a wireless communication network, and a plurality of functional modules, each of which may be implemented using analog and / or digital hardware, or suitable software and / or Or it may be understood as an example of a radio | wireless apparatus provided with the processing circuit comprised using firmware or those combination. For example, in some embodiments, a mobile terminal includes a transceiver circuit that includes a transmitter circuit that transmits data in a transmission subframe that occurs in a defined subframe period and has a predetermined number of symbol periods; A determination circuit that determines that a transmission subframe is shortened compared to a predetermined number of symbols, and, depending on the determination circuit, between one or more symbol times at the beginning of a subframe section for the transmission subframe A subframe shortening circuit that shortens transmission of the transmission subframe by transmitting during the remaining part of the subframe section without transmitting. It will be appreciated that the variations described above in connection with the method shown in FIG. 16 are equally applicable to the mobile terminal implementation described herein.

  FIG. 19 is a schematic diagram of an example of a wireless node 1900 implemented as a base station that can implement a method for implementing one or more of the techniques described above in this example. A computer program for controlling a base station to perform the method embodying the present invention is stored in a program storage 1930 comprising one or more memory devices. Data used while performing the method implementing the technology is stored in a data storage 1920 that also includes one or more memory devices. While performing the method of implementing the present technology, program steps are retrieved from the program storage 1930 and executed by the central processing unit (CPU) 1910, which retrieves data from the data storage 1920 as needed. The output information obtained as a result of performing the method embodying the present invention can be stored in the data storage 1930, or can be provided with an input / output (I / O) Can be sent to interface 1940. Similarly, input / output (I / O) interface 1940 may comprise a receiver that receives data from other nodes for use by CPU 1910, for example. The CPU 1910, data storage 1920, and program storage 1930 together constitute a processing circuit 1960. Base station 1900 further comprises a wireless communication circuit 1950 that includes a receiver circuit 1952 and a transmitter circuit 1955 adapted in accordance with known designs and techniques to communicate with one or more mobile terminals.

  According to a plurality of embodiments of the present invention, generally a base station apparatus 1900, and more specifically, a radio communication circuit 1950 is generated in a defined subframe period and has a predetermined number of symbol periods. It is configured to receive data in a frame. The processing circuit 1960 sends a grant message including subframe shortening information indicating that a subframe transmitted by the second radio node during the first subframe period is shortened via the transmitter circuit 1955. The receiver circuit 1952 and the transmitter circuit 1955 in the wireless communication circuit 1950 are configured to transmit to two wireless nodes. The processing circuit 1960 is further configured to receive the first shortened subframe from the second wireless node via the receiver circuit 1952 during the first subframe interval. In this case, the first shortened subframe is shortened by one or more symbol periods compared to a predetermined number of symbol periods.

  Accordingly, in various embodiments of the present invention, the processing circuitry is configured to perform one or more of the techniques described in detail above. Similarly, other embodiments include a base station that includes one or more such processing circuits. In some examples, the processing circuits may implement one or more of the techniques described herein using suitable program code stored in one or more suitable memory devices. Configured. Of course, it will be understood that not all of these technical steps are necessarily performed in a single microprocessor or module.

  The base station 1900 of FIG. 19 is configured to operate in a wireless communication network, and a plurality of functional modules, each of which may be implemented using analog and / or digital hardware, or appropriate software and / or Or it may be understood as an example of a radio | wireless apparatus provided with the processing circuit comprised using firmware or those combination. For example, in some embodiments, a base station receives a transmitter circuit and a receiver circuit that receives data in a transmission subframe that occurs in a defined subframe period and has a predetermined number of symbol periods; A grant message including subframe shortening information indicating that a subframe transmitted during the first subframe period is shortened by the second radio node is transmitted to the second radio node via the transmitter circuit. And a grant communication circuit. The subframe processing circuitry in these embodiments is further configured to receive the first shortened subframe from the second radio node via the receiver circuit during the first subframe interval. In this case, the first shortened subframe is shortened by one or more symbol periods compared to a predetermined number of symbol periods. It will be appreciated that the variations described above in connection with the method shown in FIG. 17 are equally applicable to the base station implementation described herein.

  As described above, when the UE cannot transmit and receive at the same time, the guard period must always be included in the TDD system. When using puncturing on downlink signals, all UEs need to be aware of the guard period by explicitly signaling to all UEs or by detecting at the UE. As detailed herein, by puncturing only uplink transmissions, only UEs transmitting on the uplink need be aware of this switch from downlink to uplink. The control messages included in the uplink grants result in very little additional control signaling overhead and can be received by the UE in subframes other than the punctured subframe. Therefore, according to the disclosed technique, it is not necessary to detect switching from the downlink to the uplink, and a robust system with a small signaling load can be obtained.

  Exemplary embodiments of the present invention have been described above in detail with reference to the accompanying drawings of specific embodiments. It is naturally impossible to describe all possible combinations of components or techniques, so that various changes may be made to the above-described embodiments without departing from the scope of the invention. Those skilled in the art will understand. For example, while the above embodiment has been described with reference to part of a 3GPP network, an embodiment of the present invention is equally applicable to similar networks such as successors of 3GPP networks having similar functional components. Will be easily understood. Therefore, in particular, the term “3GPP” and related terms used now or in the future in the above description, the accompanying drawings and the appended claims should be interpreted accordingly.

  In particular, modifications and other embodiments of the disclosed invention will be devised by those skilled in the art having the benefit of the teachings presented in the foregoing description and the associated drawings. Thus, it should be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the present disclosure. Although specific terms are employed herein, they are comprehensive and are used for illustration only and not for purposes of limitation.

Claims (12)

A subframe that occurs in a defined subframe period, and is configured to receive and transmit data in a subframe of a time division duplex system in which a predetermined number of symbol periods are used in a normal subframe. A method in a first wireless node, comprising:
A grant message indicating that the first radio node is scheduled in a transmission subframe, information indicating that fewer symbol intervals are used in the transmission subframe than in the normal subframe; Receiving a grant message including from a second wireless node;
Depending on the information indicating that a small number of symbol periods are used, symbols in the remaining part of the subframe period without being transmitted in one or more symbol periods at the beginning of the subframe period for the transmission subframe Transmitting the transmission subframe according to the grant message by transmitting in a section;
A method comprising the steps of:   The method according to claim 1, wherein the information indicating that a small number of symbol intervals are used specifies the number of symbol intervals that are not used at the head of the subframe interval. A subframe that occurs in a defined subframe period, and is configured to transmit and receive data in a subframe of a time division duplex system in which a predetermined number of symbol periods are used in a normal subframe. A method in a second radio node, comprising:
A grant message indicating that a first radio node is scheduled for transmission in subframes during a subframe interval, wherein the subframe is transmitted by the first radio node during the subframe interval A grant message including information indicating that fewer symbol periods are used than in the normal subframe by not transmitting in one or more symbol periods at the head of the subframe period. Transmitting to the wireless node;
Receiving a first subframe from the first radio node during the subframe period according to the grant message;
A method comprising the steps of:   4. The method according to claim 3, wherein the information indicating that a small number of symbol intervals are used specifies the number of symbol intervals that are not used at the head of the subframe interval. A subframe that occurs in a defined subframe period, in which a predetermined number of symbol periods are used in a normal subframe so that data is received and transmitted in a subframe of a time division duplex system, respectively. A first wireless node comprising: a configured receiver circuit and a transmitter circuit; and a processing circuit configured to control the receiver circuit and the transmitter circuit, the processing circuit comprising:
A grant message indicating that the first radio node is scheduled in a transmission subframe, information indicating that fewer symbol intervals are used in the transmission subframe than in the normal subframe; Including a grant message from the second wireless node via the receiver circuit;
Depending on the information indicating that a small number of symbol periods are used, symbols in the remaining part of the subframe period without being transmitted in one or more symbol periods at the beginning of the subframe period for the transmission subframe A first radio node further configured to control the transmitter circuit to transmit the transmission subframe according to the grant message by transmitting in a leg.   The first radio node according to claim 5, wherein the information indicating that a small number of symbol intervals are used specifies the number of symbol intervals not used at the head of the subframe interval. A sub-frame that occurs in a defined sub-frame period, in which a predetermined number of symbol periods are used in a normal sub-frame, so that data is transmitted and received respectively in a sub-frame of a time division duplex system. A second wireless node comprising: a configured transmitter circuit and a receiver circuit; and a processing circuit configured to control the receiver circuit and the transmitter circuit, wherein the processing circuit comprises:
A grant message indicating that a first radio node is scheduled for transmission in subframes during a subframe interval, wherein the subframe is transmitted by the first radio node during the subframe interval In the transmitter circuit, a grant message including information indicating that fewer symbol periods are used than in the normal subframe by not transmitting in one or more symbol periods at the head of the subframe period. To the first wireless node via
The first radio node further configured to receive a first subframe from the first radio node via the receiver circuit during the subframe period according to the grant message .   The first radio node according to claim 7, wherein the symbol indicating that a small number of symbol intervals are used specifies the number of symbol intervals that are not used at the head of the subframe interval.   To receive and transmit data in a subframe of a time division duplex system, which is a subframe that occurs in a defined subframe period and in which a predetermined number of symbol periods are used in a normal subframe. 3. A computer program for a first radio node configured in the first radio node when executed by the first radio node, wherein each step of the method according to claim 1 or 2 is performed. A computer program comprising computer program code for executing   A second configured to transmit and receive data in a subframe of a time division duplex system that occurs in a defined subframe period and a predetermined number of symbol periods are used in a normal subframe. 5. A computer program code for a wireless node, wherein the computer program code causes the second wireless node to execute the steps of the method according to claim 3 or 4 when executed by the second wireless node. A computer program comprising:   A computer-readable medium in which the computer program according to claim 9 is stored.   A computer-readable medium in which the computer program according to claim 10 is stored.

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