KR101770598B1

KR101770598B1 - Method and apparatus for transmitting packet in wireless LAN

Info

Publication number: KR101770598B1
Application number: KR1020150063262A
Authority: KR
Inventors: 박재규; 김승연; 유인철; 오승석; 변성호; 윤강진; 최성현
Original assignee: 주식회사 엘지유플러스; 서울대학교산학협력단
Priority date: 2015-05-06
Filing date: 2015-05-06
Publication date: 2017-08-23
Also published as: KR20160131277A

Abstract

The present invention relates to a method of transmitting an A-MPDU in a wireless LAN environment and an apparatus therefor. A packet transmission apparatus supporting wireless LAN communication according to an embodiment of the present invention generates an A-MPDU frame using a data packet received from an upper layer and an A-MPDU frame for transmitting the A-MPDU frame to a lower layer MPDU frame for updating the length of the A-MPDU frame based on the radio channel change level and a radio channel change determination unit for determining a radio channel change level using a block response corresponding to the A-MPDU frame, And a length calculating unit. Accordingly, the present invention is advantageous in that it provides a packet transmission method for efficiently transmitting an A-MPDU packet in a wireless LAN environment and an apparatus therefor.

Description

[0001] The present invention relates to a method and apparatus for transmitting packets in a wireless LAN,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet transmission method in a wireless LAN, and more particularly, to a packet transmission method and apparatus in a wireless LAN in which a length of an A-MPDU can be adaptively controlled based on a change in a wireless channel environment .

As a standard for a wireless network, IEEE (Institute of Electrical and Electronics Engineers) 802.11 and the like can be mentioned.

For example, IEEE802. 11a / g adopts OFDM (Orthogonal Frequency Division Multiplexing) modulation, which is one of the multi-carrier systems, as a standard of wireless LAN. According to the OFDM modulation scheme, since the transmission data is divided and transmitted to a plurality of carriers set at mutually orthogonal frequencies, the bandwidth of each carrier becomes narrow, the frequency utilization efficiency is high, and the frequency selective fading is strong.

IEEE802. The standard of 11a / g supports a modulation scheme achieving a maximum transmission speed of 54Mbps. However, as the number of large multimedia services increases and the terminal performance increases, a standard supporting higher transmission speed is required. For example, IEEE802.11a / g is an extension standard of IEEE802.11a / g. 11n provides high-speed wireless LAN technology exceeding 100Mbps with effective throughput.

IEEE802. 11n employ an OFDM_MIMO scheme using OFDM for the primary modulation. MIMO (Multi-Input Multi-Output) communication is a technique for realizing high-speed wireless communication using a plurality of spatial streams multiplexed with a plurality of antenna elements on both the transmitter side and the receiver side.

A transmitter that supports MIMO distributes transmission data to a plurality of streams using a plurality of antennas and transmits the streams. The receiver space-separates the spatial multiplexed signals received by the plurality of antennas by performing signal processing using the channel characteristics, and extracts signals for each stream without crosstalk. According to the MIMO communication system, the transmission rate can be increased corresponding to the number of antennas used without increasing the frequency band.

Therefore, IEEE802. 11n, it is possible to support a transmission rate of up to 600 Mbps by speeding up the physical layer. However, this means that the maximum transmission rate at the moment of data transmission in the physical layer is 600Mbps, and the higher layer is required to be changed in order to improve the overall service speed.

Therefore, IEEE802. 11n, frame aggregation is standardized as a structure for improving the overall transmission rate by increasing the transmission time of packet data in the MAC layer. Here, frame aggregation means transmitting a large amount of data through one MAC frame by combining a plurality of packets received from an upper layer in an MAC layer. The frame aggregation can be broadly divided into an A-MSDU (Aggregated MAC Serving Data Unit) method and an A-MPDU (Aggregated MAC Protocol Data Unit) method. The A-MSDU scheme is a scheme of aggregating a plurality of MSDUs having the same priority and directed to the same DA (Destination Address) into one MSDU, and the A-MPDU is configured by aggregating one or more MPDUs. Each sub-frame in the A-MSDU is distinguished by a subframe header consisting of the MSDU length SA (Source Address) and DA. The configured A-MSDUs can be handled the same as regular MSDUs and can be fragmented, and the fragmented MSDUs are composed of MPDUs and transmitted.

In general, the A-MSDU scheme can be efficient when the size of a packet to be transmitted is small and a large number of packets destined for the same destination are transmitted in a short time.

On the other hand, the A-MPDU scheme is located at the lower part of the MAC layer and aggregates one or more MPDUs to form one PPDU (Physical Layer Convergence Procedure Protocol Data Unit (PLCP)).

However, conventionally, due to a limited channel compensation procedure in an environment in which a radio channel changes rapidly, a synchronization loss is generated in the demodulation process of a receiving end so that a packet loss can be increased. As a result, the A-MPDUs can not be efficiently transmitted there was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a packet transmission method and apparatus in a wireless LAN.

It is another object of the present invention to provide a packet transmission method and apparatus in a wireless LAN that can adaptively control the length of an A-MPDU based on a change in a wireless channel environment.

It is still another object of the present invention to provide an A-MPDU transmission method and apparatus for adaptively controlling the length of an A-MPDU using probing when a change in a radio channel environment is not large.

It is still another object of the present invention to provide an A-MPDU transmission method and apparatus capable of adaptively controlling the length of an A-MPDU according to the cause of transmission failure.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

The present invention relates to a method of transmitting an A-MPDU in a wireless LAN environment and an apparatus therefor.

A packet transmission apparatus supporting wireless LAN communication according to an embodiment of the present invention generates an A-MPDU frame using a data packet received from an upper layer and an A-MPDU frame for transmitting the A-MPDU frame to a lower layer MPDU frame for updating the length of the A-MPDU frame based on the radio channel change level and a radio channel change determination unit for determining a radio channel change level using a block response corresponding to the A-MPDU frame, And a length calculating unit.

In addition, the packet transmission apparatus may further include a subframe loss rate statistics unit for calculating a loss rate of a subframe constituting the A-MPDU frame using the block response.

Here, the subframe may be divided into a plurality of zones according to a transmission order, and the radio channel change determination unit may determine the radio channel change degree based on a difference in the loss rate of the subframe by zone.

In addition, the zone includes a first half and a second half, and the radio channel change determiner can determine the degree of the radio channel change by comparing the difference between the second half of the subframe loss rate and the first half of the subframe loss rate with a predetermined reference value.

Also, the sub-frame loss rate statistics unit may further calculate an accumulated statistics on a sub-frame loss rate corresponding to a maximum number of sub-frames to be synthesized in the A-MPDU frame based on the block response, It is possible to calculate the length of the A-MPDU frame in which the yield is maximized based on the cumulative statistics.

Also, the A-MPDU frame length calculating unit may calculate an optimal A-MPDU frame transmission time using the transmission time of the overhead required for transmission of the A-MPDU frame and the calculated A-MPDU frame length.

Here, the transmission time of the overhead may include at least one of a transmission time of a preamble and a header, a transmission time of the block response, and an inter-frame-space (IFS) time.

Also, while the cumulative statistics are kept below a predetermined reference value, the length of the A-MPDU frame with the maximum yield can be calculated by increasing the probing MPDU inserted in the A-MPDU frame.

In addition, the number of probing MPDUs inserted into the A-MPDU frame may be arbitrarily determined by a predetermined index, a linear function, and the like.

In addition, if the radio channel compensation procedure is not normally performed through the length control of the A-MPDU frame according to the degree of the radio channel change, the RTS / CTS procedure can be performed.

A method of transmitting a packet in an apparatus supporting wireless LAN communication according to another embodiment of the present invention includes generating and transmitting an A-MPDU frame, receiving an A-MPDU response frame corresponding to the A-MPDU frame Determining a degree of a wireless channel change using a block response included in the A-MPDU response frame, and updating a length of the A-MPDU frame based on the determined degree of the radio channel change have.

The packet transmission method may further include calculating a loss rate of a subframe constituting the A-MPDU frame using the block response.

Here, the subframe is divided into a plurality of zones according to the transmission order, and the degree of the radio channel change can be determined based on the difference of the loss rates of the subframes for each zone.

Also, the area includes the first half and the second half, and the difference between the sub-frame loss rate of the second half and the sub-frame loss rate of the first half can be compared with a predetermined reference value to determine the degree of the wireless channel change.

The A-MPDU frame, which is based on the block response, is used to calculate cumulative statistics on the sub-frame loss rate corresponding to the maximum number of sub-frames to be combined in the A-MPDU frame, Can be calculated.

Also, the transmission time of the A-MPDU frame can be calculated using the transmission time of the overhead required for transmission of the A-MPDU frame and the calculated A-MPDU frame length.

In addition, the packet transmission method may further include a step of performing an RTS / CTS procedure when a radio channel compensation procedure is not normally performed through the length control of the A-MPDU frame according to the degree of the radio channel change.

According to another aspect of the present invention, there is provided a computer-readable recording medium having recorded thereon a program for executing any one of the packet transmission methods.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And can be understood and understood.

Effects of the method and apparatus according to the present invention will be described as follows.

First, the present invention has an advantage of providing a packet transmission method and apparatus capable of adaptively controlling the length of an A-MPDU in a wireless LAN environment.

Second, the present invention provides an A-MPDU transmission method and apparatus capable of maximizing a transmission efficiency according to a change of a wireless channel environment.

Third, the present invention has an advantage of providing an A-MPDU transmission method and apparatus for adaptively controlling the length of an A-MPDU using probing when the change of the radio channel environment is not large.

Fourth, the present invention provides an A-MPDU transmission method and apparatus capable of adaptively controlling the length of an A-MPDU according to the cause of transmission failure.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. It is to be understood, however, that the technical features of the present invention are not limited to the specific drawings, and the features disclosed in the drawings may be combined with each other to constitute a new embodiment.
1 is a configuration diagram of a wireless LAN system according to an embodiment of the present invention.
2 is a block diagram illustrating a structure of a PPDU defined in IEEE 802.11.
3 is a diagram for explaining the structure of an A-MPDU frame according to an embodiment of the present invention.
4 is a diagram for explaining a structure of an A-MPDU response frame according to an embodiment of the present invention.
5 is a view for explaining a method of controlling an A-MPDU frame length according to an embodiment of the present invention.
6 is a flowchart illustrating an adaptive A-MPDU frame transmission method in a transmitter according to an exemplary embodiment of the present invention.
7 is a flowchart illustrating a method of calculating a degree of change of a wireless channel according to an embodiment of the present invention.
8 is a block diagram illustrating a configuration of a packet transmission apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus and various methods to which embodiments of the present invention are applied will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. In addition, although all of the components may be implemented as one independent hardware, some or all of the components may be selectively combined to perform a part or all of the functions in one or a plurality of hardware. As shown in FIG. The codes and code segments constituting the computer program may be easily deduced by those skilled in the art. Such a computer program can be stored in a computer-readable storage medium, readable and executed by a computer, thereby realizing an embodiment of the present invention. As the storage medium of the computer program, a magnetic recording medium, an optical recording medium, or the like can be included.

It is also to be understood that the terms such as " comprises, "" comprising," or "having ", as used herein, mean that a component can be implanted unless specifically stated to the contrary. But should be construed as including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

1 is a configuration diagram of a wireless LAN system according to an embodiment of the present invention.

1, the wireless LAN system 1 may include an access point (AP) 10 and a plurality of mobile stations (first to Nth mobile stations) 20 connected to the AP 10 have. Here, the mobile station 20 may be not only a mobile device such as a smart phone, a laptop, or a tablet PC, but also a fixed device such as a desktop or an IP TV.

The AP 10 and the mobile station 10 perform wireless communication using the protocol stack defined in the IEEE 802.11 standard. Here, the protocol stack may include an application layer, a TCP / IP layer, a data link layer, a physical layer, and the like. At this time, each layer may be implemented using hardware and software combinations.

In addition, the data link layer can be divided into a logical link control (LLC) layer and a medium access control (MAC) layer located under the LLC.

2 is a block diagram illustrating a structure of a PPDU defined in IEEE 802.11.

A PLCP preamble 210 field, a PLCP header 220 field, and an MAC PDU 230 field may be included in the PPDU (Physical Layer Convergence Procedure)

The PLCP preamble 210 is used for frame timing acquisition, automatic gain control, frequency acquisition, channel estimation for decoding a subsequent signal, and the like Is used.

The PLCP header 220 field includes transmission rate identification information, data length identification information, service type identification information, parity bits or cyclic redundancy check (CRC) bits or forward error correction (FEC) bits, .

The MAC PDU 230 field has a variable length and is data received from an upper layer.

3 is a diagram for explaining the structure of an A-MPDU frame according to an embodiment of the present invention.

Referring to FIG. 3, a PPDU supporting an A-MPDU scheme, hereinafter simply referred to as an A-MPDU frame 300, includes a PLCP preamble 310 field, a PLCP header 320 field, An N A-MPDU subframe 330 field, a tail field 340 field, and a pad field 350.

The use and configuration of the PLCP preamble 310 and the PLCP header 320 will be replaced with the description of the PLCP preamble 210 and the PLCP header 220 in FIG.

Tail 340 may be a predetermined number of predefined symbols or bit sequences to indicate that A-MPDU subframe 330 is no longer present. In one example, the tail 340 may be defined as a value of all zeros having a length of 6 bits.

Pad 350 may be an additional bit for matching the length of the entire A-MPDU frame 300 to a particular byte. For example, the length of the A-MPDU frame 300 may be defined to be an integral multiple of 4 bytes.

In particular, the transmitting terminal according to the present invention can adaptively control the number of A-MPDU subframes 330 included in the A-MPDU 300 according to the change of the wireless channel environment and transmit the number.

4 is a diagram for explaining a structure of an A-MPDU response frame according to an embodiment of the present invention.

Referring to FIG. 4, the A-MPDU response frame 400 is a response signal to the A-MPDU frame 300 and includes a PLCP preamble 410 field, a PLCP header 420 field, Field. &Lt; / RTI >

The block response 430 includes information indicating whether the A-MPDU subframe 330 included in the A-MPDU frame 300 is normally received. The receiving end of the A-MPDU frame 300 may map an ACK signal or a NACK signal indicating whether the A-MPDU subframe is normally received to each bit of the block response field 430, and transmit the mapped ACK signal or the NACK signal to the transmitting end. For example, the ACK signal may be defined as 1 and the NACK signal as 0.

In addition, the length of the block response 430 field, i.e., the number of bits, may correspond to the number of A-MPDU subframes included in the received A-MPDU frame 300.

5 is a view for explaining a method of controlling an A-MPDU frame length according to an embodiment of the present invention.

Referring to FIG. 5, the transmitting terminal 510 may transmit a first A-MPDU frame 530 including 11 A-MPDU subframes to the receiving terminal 520.

The receiving end 520 decodes the A-MPDU frame 530 and generates an A-MPDU response frame (block 542) including a block response 541 indicating that the lower four A-MPDU subframes 531 are not normally received 540 to the transmitting end 510.

After that, the transmitting terminal 520 determines the length of the A-MPDU frame to be transmitted next, that is, the number of A-MPDU subframes, based on the received block response 541, -MPDU frame 550 and transmit it to the receiving end 520.

For example, as shown in FIG. 5, when it is determined that the lower 4 A-MPDU sub-frames 531 have failed to be transmitted through the block response 541, the transmitter 510 transmits 7 A-MPDU sub- And transmits the generated second A-MPDU frame 550 to the receiving end 520. [

6 is a flowchart illustrating an adaptive A-MPDU frame transmission method in a transmitter according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the transmitter transmits an A-MPDU frame and receives an A-MPDU response frame corresponding to the transmitted A-MPDU frame from the receiver (S601 to S603).

The transmitting end calculates the degree of change of the wireless channel based on the block response included in the received A-MPDU response frame (S605).

The transmitting terminal compares the degree of change of the calculated radio channel with a predetermined reference value (S607).

As a result of comparison, if the length of the A-MPDU frame needs to be changed, the transmitting end calculates the optimal A-MPDU frame length, and generates an A-MPDU frame according to the calculated A-MPDU frame length to transmit to the receiving end S609 to S611).

If it is determined in step 607 that it is not necessary to change the length of the A-MPDU frame, the transmitting end can generate the A-MPDU frame to be transmitted next with the length of the previously transmitted A-MPDU frame ( S613).

Thereafter, the transmitting end repeats steps 601 to 613 in transmitting the A-MPUD frame, and controls the length of the A-MPDU frame to be adaptively transmitted according to the change of the radio channel environment.

In the above description of FIG. 6, the transmitting terminal controls the length of the A-MPDU frame based on the degree of change of the radio channel environment. However, this is only one embodiment, It should be noted that the transmission time of the A-MPDU frame may be controlled according to the degree of change of the environment.

7 is a flowchart illustrating a method of calculating a degree of change of a wireless channel according to an embodiment of the present invention.

Referring to FIG. 7, the transmitting terminal extracts a block response 430 from the received A-MPDU response frame in response to the A-MPDU frame transmitted in operation S701.

Subsequently, the transmitting end divides the block response 430 into two sections, a first half and a second half, and calculates a subframe loss rate of each zone according to the following equations (1) and (2) (S703 to S705).

(One)

(2)

In the above equation, when the number of A-MPUD subframes included in the A-MPDU frame is N, Si denotes the transmission result for the i-th A-MPDU subframe. For example, if the value of Si is 1, it means that the transmission of the A-MPUU subframe has succeeded. If the value of Si is 0, it means that the transmission of the A-MPDU subframe has failed. Also, Nf can be calculated as a value obtained by dividing N by 2 and then decreasing the value by half. In other words,

Lt; / RTI >

And subsequently, the transmitting end to the equation (3) calculating a difference value and SFER_1 SFER_2 (M _ampdu) steps, and the calculated M _ampdu comparison if greater than a predetermined threshold value (M _th) (S707).

M _amp = SFER_2 - SFER_1 (3)

As a result of comparison, if M _ampdu exceeds M _th , the transmitting end can start the procedure of calculating the optimum A-MPDU frame length (S 709).

Thereafter, the transmitting end generates the A-MPDU frame with the calculated A-MPDU frame length and transmits it to the receiving end (S711).

If it is determined in step 707 that the threshold value is not exceeded, the transmitting terminal may generate the A-MPDU frame with the length of the previously transmitted A-MPDU frame and transmit it to the receiving terminal in step S713.

In the above description of FIG. 7, the sub-frame loss rate is calculated for each A-MPDU response frame in which the transmitting terminal is received, but this is only an example, and the transmitting terminal according to another embodiment of the present invention The A-MPDU frame may be adaptively controlled by performing a cumulative statistical process on the transmission results of a plurality of A-MPDU frames transmitted for a predetermined time period, and then comparing the difference between the first half and the second half of the loss ratio of the subframe with a predetermined threshold .

The transmitting end performs cumulative statistics on the transmission result of the A-MPDU frame, and transmits the A-MPDU response frame to the transmitting end of the A-MPDU frame, The optimal A-MPDU length can be calculated by calculating the loss rate.

The transmitting end according to another embodiment of the present invention may calculate the accumulated statistics for the number of A-MPDU subframes included in the A-MPDU frame. In this case, the transmitting end identifies the number of A-MPDU subframes having the highest transmission efficiency and less degree of radio channel change based on the cumulative statistics, constructs an A-MPDU frame with the identified number of A-MPDU subframes, As shown in FIG.

Hereinafter, a method for adaptively determining a transmission time of an A-MPDU frame at a transmitting end will be described in detail.

The transmitter according to the present invention tracks the transmission result of the A-MPDU frame based on the Exponentially Weighted Moving Average (EWMA) in the environment where the physical layer data rate and the A-MPDU subframe size are fixed, May be calculated.

For example, assume that the number of maximum A-MPDU subframes aggregated in the A-MPDU frame is Nt, and the loss rate of the i-th A-MPDU subframe among the Nt subframes is P _i .

At this time, the transmission success rate ( P _i _, _new ) of the i- th subframe to be newly transmitted can be calculated by the following equation (4).

Using the statistics accumulated in Equation (4), the transmitting end calculates the number ( n _o ) of A-MPDU subframes in which the throughput in the current wireless channel environment is maximized, using the following equation (5) can do.

Here, L denotes the size of the A-MPUD subframe, and T _oh denotes the transmission time of the overhead fields fixedly included in the A-MPDU frame transmission. At this time, the overhead field includes a preamble field and a header field inserted in the physical layer, a PLCP preamble field inserted in the MAC layer, a PLCP header field, and a Block Response (BlockAck) At least one Inter-Frame Space (IFS) field, and so on. Also, R denotes a data transmission rate in the current physical layer of the transmitting end.

Subsequently, the transmitting end is the optimal A-MPDU frame transmission time (T _o) may be calculated through equation (6) below.

Hereinafter, a method of adaptively controlling the length of an A-MPDU frame in a state in which the degree of change of a radio channel is not large, i.e., a state in which a radio channel compensation procedure is effectively maintained, according to an embodiment of the present invention Will be described in detail.

The transmitter can determine whether the channel compensation procedure in the current wireless channel environment is effectively maintained based on the accumulated statistical A-MPUD subframe loss rate. For example, the transmitter can determine that the radio channel compensation procedure is being performed effectively if the accumulated statistical A-MPDU subframe loss rate is maintained below a predetermined level for a unit time.

If it is determined that the radio channel compensation procedure is effectively maintained, the transmitting terminal may increase the transmission length (time) of the A-MPDU frame using the probing MPDU.

For example, the transmitting end may ascertain the number of maximum probing MPDUs in which the A-MPDU subframe loss rate is kept below a certain level while increasing the number of probing MPDU transmissions incrementally using a predetermined exponential function. Subsequently, the transmitting end can determine an optimal new A-MPDU frame transmission time using the confirmed maximum probing MPDU count information.

The transmitting end according to another embodiment of the present invention may arbitrarily determine the number of probing MPDUs inserted in the A-MPDU frame by a predetermined linear function.

For example, the optimal A-MPDU frame transmission time of the radio channel is kept in a state where compensation process is effective (T _o) can be calculated by the equation (7) below.

Here, L denotes the size of the A-MPDU sub-frame, and n _p is the number of probing MPDU. Therefore, the optimal A-MPDU transmission time ( T _o ) can be determined as the minimum of the transmission time required for transmission including the probing MPDU and the maximum allowable transmission time ( T _max ) of the A-MPDU frame defined in the standard have.

Also, the number n _p of probing MPDUs can be calculated by applying an Exponential Weighting Factor? As shown in Equation (8) below for fast radio channel adaptation.

(8)

Here, K means the number of consecutive probing times.

Hereinafter, an adaptive length adjustment method of an A-MPDU frame considering an interference according to another embodiment of the present invention will be described.

In the wireless LAN environment according to the present invention, when a plurality of transmitting terminals transmit at the same time, an interference phenomenon by a neighboring transmitting terminal may occur in a specific transmitting terminal. However, the transmitting end can misinterpret the continuous transmission failure due to the interference phenomenon as a transmission failure due to the radio channel state change. In this case, the transmitting end can control the A-MPDU frame transmission time using the adaptive A-MPDU frame transmission scheme based on the change of the radio channel state. As a result, the transmitting terminal can not find the optimal A-MPDU frame length by erroneously determining the cause of transmission failure of the A-MPDU.

Therefore, the transmitter according to an embodiment of the present invention can determine the cause of the transmission failure and control the transmission length of the A-MPDU frame adaptively based on the determination result, as shown in Table 1 below.

division If the wireless channel compensation procedure does not work effectively When the wireless channel compensation procedure works effectively Interference (simultaneous transmission collision) is expected - A-MPDU Frame length adjustment (reduction)
- Using RTS / CTS - A-MPDU frame length adjustment (increase)
- Using RTS / CTS Interference (simultaneous transmission collision) is not expected - A-MPDU Frame length adjustment (reduction)
- RTS / CTS not used - A-MPDU frame length adjustment (increase)
- RTS / CTS not used

If the cause of the transmission failure is expected to be due to interference - that is, a simultaneous transmission collision - the transmitting end can identify the cause of the transmission failure through the Request-To-Send (RTS) / Clear-To- have. Of course, in this case as well, the transmitting terminal can adaptively control the A-MPDU frame length by determining whether the wireless channel compensation procedure is effectively performed.

On the other hand, if it is expected that the cause of the transmission failure is not due to interference, the transmitting end may adaptively control the A-MPDU frame length according to whether the radio channel compensation procedure is effectively performed without using the RTS / CTS procedure have.

For example, the transmitting end may determine that the radio channel compensation procedure is not effectively performed when the calculated radio channel variation based on the block response exceeds a predetermined reference value.

8 is a block diagram illustrating a structure of a WLAN packet transmission apparatus according to an embodiment of the present invention.

8, the packet transmission apparatus 800 includes a wireless interface unit 810, an A-MPDU frame processing unit 820, a wireless channel conversion determination unit 830, a subframe loss rate statistics unit 840, an A-MPDU A frame length calculator 850, a controller 860, and the like.

The wireless interface unit 810 converts the signal received through the receive antenna to a baseband, decodes the signal into a data frame, and transmits the data frame to an upper layer. Modulated and transmitted through a transmission antenna. Here, the upper layer may include an A-MPDU frame processing unit 820.

The A-MPDU frame processing unit 820 generates an A-MPDU frame using data units received from an upper layer (for example, a TCP / IP layer or an LLC (Link Layer Control) And interprets and processes the data frames received from the interface 810.

In particular, the A-MPDU frame processing unit 820 can generate the A-MPDU frame with the frame length or the frame transmission time calculated by the A-MPDU frame length calculating unit 850.

Also, the A-MPDU frame processing unit 820 may generate an A-MPDU frame based on the number of probing MPDUs calculated by the A-MPDU frame length calculating unit 850.

The wireless channel change calculator 830 measures the degree of wireless channel change based on the block response received from the receiver for the A-MPDU frame that has been transmitted, and determines whether the A-MPDU frame length is changed based on the measurement result can do.

Here, the radio channel change information is obtained by dividing the A-MPDU subframe included in the A-MPDU into a predetermined number of zones, for example, the first half and the second half according to the transmission order, Frame loss rate, and then comparing the calculated difference value with a predefined reference value.

If the wireless channel compensation procedure does not normally operate due to the radio channel change level exceeding the reference value, the controller 860 transmits a predetermined control signal for reducing the A-MPDU frame length to the A-MPDU frame length calculator 850, Lt; / RTI >

On the other hand, when the degree of the radio channel change is less than the reference value, that is, when the radio channel compensation procedure normally operates, the controller 860 transmits a predetermined control signal for increasing the A-MPDU frame length to the A- 850).

The subframe loss rate statistics unit 840 may perform a cumulative statistical processing on the loss rate of the subframe based on the block response received from the receiver.

The A-MPDU frame length calculator 850 can calculate the A-MPDU frame length or the A-MPDU frame transmission time at which the throughput is maximized based on the accumulated statistics on the subframe loss rate.

In addition, the A-MPDU frame length calculator 850 calculates the A-MPDU frame length 840 based on the A-MPDU frame length calculated by the A-MPDU frame length calculator 840, The MPDU may be incrementally increased to increase the A-MPDU frame length or the A-MPDU frame transmission time. In this case, the A-MPDU frame transmission time can be controlled so as not to exceed the maximum defined A-MPDU frame transmission time.

According to another embodiment of the present invention, the controller 860 may control the RTS / CTS procedure to be performed when interference is expected to occur. Generally, the IEEE 802.11 standard is provided with a Dynamic Channel Assignment (DCA) protocol.

The DCA protocol defines an RTS / CTS procedure, which is a separate control procedure for reserving a data channel (DC) for data packet transmission.

The transmitter / receiver maintains a CUL (Channel Usage List), which is information on the occupied channel, and a FCL (Free Channel List), which is information on the unoccupied channel.

When the transmitting terminal A transmits an RTS signal including the FCL information through a control channel (CC) to the receiving terminal B, the receiving terminal B receives a data channel to be reserved based on the FCL information received through its local FCL and RTS You can choose. Subsequently, the receiving end B can transmit the CTS signal including the information on the selected data channel to the transmitting end A via the control channel. Thereafter, the transmitting terminal A transmits a Reservation (RES) packet indicating that the corresponding data channel is reserved to the adjacent nodes through the control channel, and then starts transmitting the data packet for the receiving terminal B using the reserved data channel .

That is, the transmitting terminal according to the present invention can remove the interference element by initiating the RTS / CTS procedure when interference (simultaneous transmission collision) is expected to occur.

On the other hand, the transmitting terminal can save radio resources by not performing the RTS / CTS procedure if interference (simultaneous transmission collision) is not expected to occur.

In another example, if the radio channel compensation procedure does not operate effectively, the transmitter can determine that interference has occurred despite the A-MPDU frame length adjustment according to the degree of the radio channel change, and accordingly, the RTS / CTS procedure May be initiated. Here, the effective operation of the radio channel compensation procedure can be determined based on the cumulative statistical information for the unit time with respect to the A-MPDU subframe loss rate.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

10: Access point (AP)
20: First to Nth mobile stations
300: A-MPDU frame
400: A-MPDU response frame
430: Block response
800: Packet transmission device
820: A-MPDU frame processor
830: Radio channel change determination unit
840: Subframe loss rate statistics section
850: A-MPDU frame length calculating section

Claims

A packet transmission apparatus supporting wireless LAN communication,
An A-MPDU frame processing unit for generating an A-MPDU frame using a data packet received from an upper layer and transmitting the A-MPDU frame to a lower layer;
A subframe loss rate statistic unit for calculating a loss rate of a subframe constituting the A-MPDU frame using a block response corresponding to the A-MPDU frame;
A radio channel change judging unit for judging a radio channel change degree based on a difference of a plurality of divided subframe loss rates according to a transmission order of the subframe; And
And an A-MPDU frame length calculating unit for updating a length of the A-MPDU frame based on the degree of the radio channel change,
The packet transmission apparatus comprising:

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The method according to claim 1,
Wherein the radio channel change determination unit compares a difference between a subframe loss rate of the second half and a subframe loss rate of the first half with a predetermined reference value to determine the degree of the radio channel change.

The method according to claim 1,
Wherein the A-MPDU frame length calculating unit further calculates an accumulated statistics on a subframe loss rate corresponding to a maximum number of subframes to be combined in the A-MPDU frame based on the block response, And calculates a length of the A-MPDU frame in which the yield is maximized based on the A-MPDU frame.

6. The method of claim 5,
Wherein the A-MPDU frame length calculating unit calculates an optimal A-MPDU frame transmission time using the transmission time of the overhead required for transmission of the A-MPDU frame and the calculated A-MPDU frame length.

The method according to claim 6,
The transmission time of the overhead is
A transmission time of the preamble and a header, a transmission time of the block response, and an IFS (Inter-Frame-Space) time.

6. The method of claim 5,
Wherein a length of the A-MPDU frame in which the yield is maximized is increased by increasing a probing MPDU inserted in the A-MPDU frame while the cumulative statistics are kept below a predetermined reference value.

9. The method of claim 8,
Wherein the number of the probing MPDUs inserted into the A-MPDU frame is arbitrarily determined by a predetermined exponent and a linear function.

The method according to claim 1,
Wherein the RTS / CTS procedure is performed when the radio channel compensation procedure is not normally performed through the length control of the A-MPDU frame according to the degree of the radio channel change.

A packet transmission method in a device supporting wireless LAN communication,
Generating and transmitting an A-MPDU frame;
Receiving an A-MPDU response frame corresponding to the A-MPDU frame;
Calculating a loss rate of a subframe constituting the A-MPDU frame using a block response included in the A-MPDU response frame;
Determining a degree of radio channel change based on a difference in a plurality of divided subframe loss rates according to a transmission order of the subframe; And
Updating the length of the A-MPDU frame based on the determined degree of the radio channel change
And transmitting the packet.

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12. The method of claim 11,
Wherein the area includes a first half and a second half, wherein the degree of the radio channel change is determined by comparing a difference between a subframe loss rate of the second half and a subframe loss rate of the first half to a predetermined reference value.

12. The method of claim 11,
Calculating a cumulative statistic of a subframe loss rate corresponding to a maximum number of subframes to be synthesized in the A-MPDU frame based on the block response, calculating a cumulative statistic of the A-MPDU frame having a maximum yield based on the cumulative statistics, To the packet.

16. The method of claim 15,
Wherein the transmission time of the A-MPDU frame is calculated using the transmission time of the overhead required for transmission of the A-MPDU frame and the calculated A-MPDU frame length.

17. The method of claim 16,
The transmission time of the overhead is
A transmission time of the preamble and a header, a transmission time of the block response, and an IFS (Inter-Frame-Space) time.

16. The method of claim 15,
Wherein a length of the A-MPDU frame in which the yield is maximized is increased by increasing a probing MPDU inserted in the A-MPDU frame while the cumulative statistics are kept below a predetermined reference value.

19. The method of claim 18,
Wherein the number of probing MPDUs inserted into the A-MPDU frame is arbitrarily determined by a predetermined exponent and a linear function.

12. The method of claim 11,
And performing an RTS / CTS procedure when the radio channel compensation procedure is not normally performed through the length control of the A-MPDU frame according to the degree of the radio channel change.

A computer-readable recording medium having recorded thereon a program for executing the method according to any one of claims 11 to 14.