JP6000646B2 - Wireless communication apparatus, wireless communication terminal, control method, communication method, and program - Google Patents

Description

  The present invention relates to a technique for transmitting data in parallel from one communication device to a plurality of communication terminals using one frequency band.

  IEEE 802.11ac is being formulated as a next-generation wireless LAN standard. In IEEE802.11ac, MU-MIMO (multi-user MIMO) will be adopted in addition to SU-MIMO (single user MIMO) conventionally used in IEEE802.11n in order to greatly increase the communication speed. It is. In MU-MIMO, since a wireless access point (AP) can transmit different data in parallel in one frequency band to a plurality of wireless stations (STAs), an improvement in transmission efficiency can be expected.

  In Patent Document 1, as a technique for transmitting data by MU-MIMO, a multi-RTS (mRTS) which is a technique for transmitting a plurality of RTS frames, which is an application technique of a conventional transmission request (Request To Send: RTS) frame. ) Is described. FIG. 4 is a frame timing diagram showing the state of MU-MIMO communication using mRTS frames. When there is data to be transmitted to each STA by the AP, the AP notifies each STA that is the destination of the data that there is a transmission request in the mRTS frame. Then, each STA that has received the notification notifies the AP that transmission is permitted by sending a transmission permission (Clear To Send: CTS) frame to the AP in order. Then, the data is multiplexed and transmitted to each STA, and when the STA receives the data, a Block ACK (BA) frame is sequentially transmitted to the AP as a confirmation frame indicating that the reception is successful.

US Patent Application Publication No. 2010/0309871

  However, when there is a difference in the transmission timing of each STA, frames transmitted by the respective STAs may collide. For example, STA-1 and STA-2 are in positions where they cannot sense each other. If STA-2 transmits CTS while STA-1 is transmitting CTS, the two CTSs collide. In this case, the AP cannot correctly receive the CTS frame, and the AP does not transmit data to the STA-1 and STA-2 that have not received the CTS. For this reason, there has been a problem that data that should have been transmitted simultaneously in parallel cannot be transmitted, and bandwidth utilization efficiency is reduced. In addition, the BA may collide in the same manner, and the AP retransmits data to the STA that could not receive the BA, so that there is still a problem that the band use efficiency deteriorates.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for preventing deterioration in band utilization efficiency when data is transmitted in parallel using one frequency band.

In order to achieve the above object, a communication device according to the present invention has a timing of receiving or transmitting a predetermined signal received from a first plurality of other communication devices, each of the first plurality of other communication devices. Among the first plurality of other communication devices, the timing of receiving or transmitting the predetermined signal is within the predetermined period. A management unit that manages a second plurality of other communication devices excluding a device determined to be not as a group that transmits data in parallel; and the second plurality of communication devices that belong to the group managed by the management unit Transmitting means for transmitting data for each of the second plurality of other communication devices in parallel to each of the other communication devices.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent the deterioration of the band utilization efficiency at the time of transmitting data in parallel using one frequency band.

The figure which shows the structural example of a radio | wireless communications system. The block diagram which shows the function structural example of an access point (AP). The flowchart which shows the detection process of the reception timing of CTS and BA. The conceptual diagram which shows the example of the transmission / reception timing of a frame. The conceptual diagram which shows the example of the transmission / reception timing of a frame, and grouping control. The conceptual diagram which shows the example of the transmission / reception timing of a frame, and grouping control. The conceptual diagram which shows the example of the transmission / reception timing of a frame, and grouping control. The flowchart which shows the detection process of receiving timings other than CTS and BA. The conceptual diagram of grouping control based on frames other than CTS and BA. The conceptual diagram which shows the example of the transmission / reception timing of a radio | wireless frame. The figure which shows the timing difference of the reception timing of each STA, and the timing which should be received originally. The flowchart which shows the operation | movement of grouping control based on a timing difference. The conceptual diagram which shows the transmission / reception timing of a radio | wireless frame at the time of performing grouping control based on a timing difference. The block diagram which shows the function structural example of a wireless LAN terminal (STA). The flowchart which shows the operation | movement of the reception timing detection process in STA, and the switching process of a communication system. The conceptual diagram which shows the radio | wireless frame transmitted / received when performing autonomous grouping control by STA.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< Embodiment 1 >>
(Configuration of wireless communication system)
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. As shown in FIG. 1, for example, the wireless communication system of this embodiment includes a single access point (AP) 101 serving as a wireless communication base station, and a plurality of wireless LANs serving as wireless communication terminals connected to the base station. Terminal (STA) 102-104. The AP 101 and the STAs 102 to 104 can communicate with each other using multi-user MIMO (MU-MIMO) or single-user MIMO (SU-MIMO). In the present embodiment, as shown in FIG. 1, the areas where the STA 102, the STA 103, and the STA 104 can communicate are 105 to 107, respectively, and an environment where a hidden terminal problem may occur is assumed. Therefore, in this wireless communication system, the AP 101 and the STAs 102 to 104 can perform normal communication by using a multi-transmission request (mRTS) / transmission permission (CTS) sequence.

(Configuration of AP)
FIG. 2 is a block diagram illustrating a functional configuration example of the AP 101 according to the present embodiment. The AP 101 includes, for example, a wireless transmission / reception unit 201, a wireless communication control unit 202, a timing detection unit 203, a group management unit 204, and a storage unit 205.

  The wireless transmission / reception unit 201 transmits / receives wireless data using a wireless LAN communication method compliant with 802.11. As shown in FIG. 2, the wireless transmission / reception unit 201 can perform communication in SU-MIMO or MU-MIMO using a plurality of antennas. Here, SU-MIMO refers to MIMO communication between a single AP and a single STA, and is a communication technique that can be used when a plurality of antennas are used not only in the AP but also in the STA. . MU-MIMO is, for example, MIMO communication performed between a single AP and a plurality of STAs. In this case, the AP has a plurality of antennas, but the STA has at least one antenna. It only has to be.

  In the following, the case of using SU-MIMO and MU-MIMO will be described. However, these may be replaced by any method capable of transmitting and receiving a plurality of streams in parallel in one frequency band. Good. For example, when a CDMA (Code Division Multiple Access) system is used, even if each AP and STA have only one antenna, a code is assigned to a plurality of wireless communication terminals, so that it can be simultaneously performed in one frequency band. Thus, signals can be transmitted to a plurality of wireless communication terminals. Also, by assigning a multicode to one wireless communication terminal, a plurality of streams can be transmitted simultaneously in one frequency band, and an effect substantially equivalent to SU-MIMO can be obtained.

  The wireless communication control unit 202 is a functional block that controls messages transmitted and received by the wireless transmission / reception unit 201, and performs instructions for establishing and disconnecting wireless links, and transmission control of multiplexed data. The timing detection unit 203 is a block that detects transmission or reception timing of a frame transmitted by each STA, and detects a difference between an assumed frame reception (transmission) timing and an actual frame reception (transmission) timing. . Hereinafter, processing based on reception timing will be described. However, since the area of the wireless LAN is sufficiently small and the transmission timing and the reception timing can be regarded as almost simultaneous, the reception timing in the following discussion can be replaced with the transmission timing, and the technique according to this embodiment can be applied. Of course it is possible. Details of the processing of the timing detection unit 203 will be described later.

  When performing MU-MIMO, the group management unit 204 manages STAs that simultaneously transmit data using one frequency band as a group, and changes and updates the STAs included in the group. The group management unit 204 executes processing when it is determined that control for changing or updating a group (hereinafter referred to as grouping control) is necessary according to the detection result of the timing detection unit 203. The storage unit 205 stores a difference in timing of reception frames of the STAs detected by the timing detection unit 203 and STAs that are targets of grouping control.

  All the functional blocks have a mutual relationship in terms of software or hardware. The above functional blocks are examples, and a plurality of functional blocks may be configured as one functional block, or any one of the functional blocks may be divided into a plurality of functional blocks.

(Timing detection process)
FIG. 3 shows a detection process of the frame reception timing of each STA when a predetermined frame is transmitted based on the BA, that is, each STA, is scheduled for data transmission of CTS or MU-MIMO for mRTS. It is a flowchart. Here, the processing when the AP 101 receives the CTS for the mRTS from the STA 102, the STA 103, and the STA 104 will be described assuming the transmission / reception timings shown in FIGS.

  First, as shown in FIG. 4, a case will be described in which CTS from each STA is normally received with respect to the mRTS of the AP 101, and data is transmitted to each STA by MU-MIMO. In this example, as shown in FIG. 4, a CTS is transmitted from each STA based on SIFS, which is the shortest frame transmission interval defined by IEEE 802.11. After receiving the CTS for the mRTS from each STA, the AP 101 executes the process of FIG. 3 for each CTS frame.

  The timing detection unit 203 first determines whether the CTS frame has been received normally, that is, without occurrence of a CRC error or the like (S301). As shown in FIG. 4, when the CTS frame is normally received (Yes in S301), it is determined whether the reception timing of the frame is shifted from the predetermined timing by a predetermined time or more (S302). That is, for example, with reference to a predetermined timing, which is a timing obtained by adding the SIFS interval to the timing of completion of transmission or reception of the previous frame, it is determined whether a frame is received earlier or later than the reference by a predetermined time.

  The predetermined timing as a reference may be determined from the end timing of the mRTS frame, the CTS time length, and SIFS. That is, the predetermined timing of the STA 102 may be a timing obtained by adding SIFS to the timing after completion of mRTS transmission. The predetermined timing of the STA 103 may be a timing obtained by adding the CTS time length and SIFS to the predetermined timing of the STA 102, and the predetermined timing of the STA 104 may be a timing obtained by further adding the CTS time length and SIFS. As described above, in S302, it is determined whether or not the frame from each STA has been received within a predetermined period determined individually for each STA by a predetermined timing and a predetermined time.

  In the example of FIG. 4, any CTS frame can be received within a predetermined period (Yes in S302). For this reason, the timing detection unit 203 ends the processing assuming that each STA can transmit a frame at a normal timing. Note that, as in the example of FIG. 4, when there is no STA that is a grouping control target, the group management unit 204 does not perform processing.

  Next, as shown in FIG. 5, a case where the reception timings of the CTS 501 and the BA 502 transmitted from the STA 103 are not received within a predetermined period will be described. In the case of FIG. 5, since the CTS frame can be normally received (Yes in S301), the timing detection unit 203 advances the process to S302. However, in the example of FIG. 5, the reception timing of the CTS frame is outside the predetermined period (No in S302). Therefore, the timing detection unit 203 extracts the STA 103 that has not received a frame within a predetermined period as a grouping control target (S303).

  When a grouping control target STA is detected in the timing detection process, the group management unit 204 transmits a Group ID Management frame 503 to the detected STA, that is, the STA 103 in this example, as shown in FIG. The Group ID Management frame 503 is a signal that instructs the STA that is the destination of the frame to leave the MU-MIMO group. Accordingly, the operation of the STA 103 is switched from the MU-MIMO operation to the SU-MIMO operation, and the STA 103 communicates with the AP 101 by SU-MIMO thereafter.

  In this way, by causing STAs with different CTS or BA reception timings to leave MU-MIMO, collisions with CTSs and BAs transmitted by other STAs can be avoided in advance. In other words, in the example of FIG. 5, since the STA 103 cannot detect at least the CTS transmitted by the STA 102, when data is transmitted to the STA 103 and the STA 102 using MU-MIMO, there is a high probability that a frame collision will eventually occur. . Accordingly, by causing at least one of the STA 102 and the STA 103 to leave the group, a collision can be prevented in advance.

  Next, as illustrated in FIG. 6, a case where the reception timing of the CTS 601 transmitted from the STA 102 is after a predetermined period and collides with the CTS 602 transmitted by the STA 103 will be described. In this case, since the AP 101 has failed to receive the CTS 601 and the CTS 602, the AP 101 cancels the transmission of the data 603 and the data 604 that are scheduled to be transmitted to the STA 102 and the STA 103, respectively, by MU-MIMO. And since these data are not transmitted, STA102 and STA103 do not transmit BA605 and BA606, respectively.

  In the example of FIG. 6, the timing detection unit 203 first determines that the CTS that should be transmitted from the first STA 102 has not been received (No in S301), and moves the process to S304. Then, the timing detection unit 203 determines whether the head portion of the CTS 601 transmitted from the STA 102 has been received (S304). In the case of the example of FIG. 6, since the head portion of the CTS 601 has been received (Yes in S304), the timing detection unit 203 subsequently continues the reception timing of the CTS 601 for a predetermined period individually determined for the STA 102. It is determined whether it was within (S305). Here, in the case of the example in FIG. 6, the CTS 601 is transmitted outside the predetermined period (No in S305). Therefore, the timing detection unit 203 extracts the STA 102 as a grouping control target (S303) and ends the process.

  In this case, the same processing is subsequently performed for the second STA 103. However, since the CTS 602 of the STA 103 has not normally received the head part of the frame (No in S304), the process ends without extracting the STA 103 as a grouping control target. Then, the group management unit 204 transmits a Group ID Management frame 607 to the STA 102 extracted as a grouping control target so as to switch from MU-MIMO to SU-MIMO. In this way, when frames from two STAs collide, any STA is excluded from data transmission by MU-MIMO. Thereby, collision of CTS and BA frames in MU-MIMO communication can be prevented, and deterioration of bandwidth utilization efficiency can be prevented.

  Finally, as shown in FIG. 7, a case where the CTS 702 is transmitted at a timing earlier than a predetermined period and collides with the CTS 701 transmitted by the STA 102 will be described. In this case, since the AP 101 has failed to receive the CTS 701 and the CTS 702, the AP 101 cancels transmission of the data 703 and the data 704 that were scheduled to be transmitted to the STA 102 and the STA 103, respectively, by MU-MIMO. And since these data are not transmitted, STA102 and STA103 do not transmit BA705 and BA706, respectively.

  In the example of FIG. 7, the timing detection unit 203 first determines that the CTS that should be transmitted from the first STA 102 has not been received (No in S301), and moves the process to S304. Then, the timing detection unit 203 determines whether the head part of the CTS 701 transmitted from the STA 102 has been received (S304). In the case of the example in FIG. 7, since the head portion of the CTS 701 has been received (Yes in S304), the timing detection unit 203 subsequently determines that the reception timing of the CTS 701 is within a predetermined period individually determined for the STA 102. It is determined whether there has been (S305).

  Here, in the case of the example in FIG. 7, the CTS 701 is transmitted within a predetermined period corresponding to the STA 102 (Yes in S305). Therefore, the timing detection unit 203 moves the process to S306, and determines whether the frame from the second STA 103 has been received (S306). In the example of FIG. 7, the CTS 702 from the second STA 103 has not been received (No in S306). For this reason, it is determined that the CTS 701 could not be received because the CTS 702 from the second STA 103 was transmitted at an early timing, and the second STA 103 is extracted as a grouping control target (S307). When the CTS 702 from the second STA 103 has been received (Yes in S306), it is determined that the reception of the CTS 701 from the first STA 102 has failed due to a factor other than a frame collision, and grouping control is performed. The process ends without extracting the target. 3 is similarly executed for the second STA 103. In this case, since the head portion of the frame has not been received normally (No in S304), the target of grouping control is not included in the processing. The process ends without extracting.

  Through the above processing, the group management unit 204 transmits a Group ID Management frame 707 to the STA 103 that is a grouping control target so as to switch from MU-MIMO to SU-MIMO. Thereby, in the subsequent MU-MIMO transmission, a collision between the frame of the STA 102 and the frame of the STA 103 can be prevented, and deterioration of the band use efficiency can be prevented.

  FIG. 8 shows a flowchart of processing for detecting reception timing for frames other than CTS and BA. Here, as illustrated in FIG. 9, an example in which the AP 101 transmits data to the STA 102 by SU-MIMO and detects the reception timing of the Ack corresponding to the data transmitted by the STA 102 will be described.

  The timing detection unit 203 first determines whether a frame from the STA 102 has been received (S801). If the frame has not been received (No in S801), the timing detection unit 203 ends the process and does not execute grouping control. On the other hand, if the frame can be received (Yes in S801), is the reception timing of the frame not more than a predetermined time from a predetermined timing that is, for example, a timing obtained by adding SIFS to the timing after completion of data transmission? Is determined (S802). That is, it is determined whether the reception timing of the frame is within a predetermined period. When the frame reception timing is within the predetermined period (Yes in S802), the timing detection unit 203 ends the process and the grouping control is not performed. On the other hand, when the reception timing is outside the predetermined period as in Ack901 in FIG. 9 (No in S802), the STA is extracted as a grouping control target (S803). In the example of FIG. 9, the STA 102 is a grouping control target.

  When the timing detection unit 203 extracts STAs that are grouping control targets, the group management unit 204 changes the STAs from MU-MIMO control to SU-MIMO control. In the example of FIG. 9, the AP 101 changes the operation of the STA 102 only to SU-MIMO by transmitting the Group ID Management frame 902.

  In the present embodiment, grouping control is performed for each STA so that the number of times the frame reception timing is outside the predetermined period is counted and the STA having a high frequency is removed from the MU-MIMO. Also good.

  With the above processing, even when the STA frames collide with each other as shown in FIGS. 6 and 7 and it is difficult to detect the reception timing, the reception timing of other frames can be detected. Therefore, at this timing, it is possible to change the MIMO control so as to avoid the collision of frames in advance, and it is possible to prevent the deterioration of the band use efficiency.

<< Embodiment 2 >>
In the present embodiment, grouping control is performed in accordance with the timing difference from the original timing of the frame reception timing. The configuration of the wireless communication system of this embodiment and the functional configuration of the access point are assumed to be as shown in FIGS. 1 and 2, respectively, as in the first embodiment. In the present embodiment, the processes of the timing detection unit 203 and the group management unit 204 are different from those in the first embodiment, so that this point will be described below.

  In this embodiment, when the timing detection unit 203 receives CTSs 1001 to 1003 from each STA corresponding to mRTS shown in FIG. 10, the timing of receiving each frame and the timing at which the frame should be originally received are determined. Calculate the timing difference. Here, for example, for the CTS 1001 from the STA 102, the timing at which the frame should be received may be determined as a timing obtained by adding SIFS to the mRTS transmission completion timing. In addition, the timing at which the original frame for the CTS 1002 from the STA 103 should be received may be the timing at which the CTS 1001 is received plus the CTS time length and SIFS. The timing at which the original frame for the CTS 1003 should be received may be the timing at which the CTS 1002 is received plus the CTS time length and SIFS.

  FIG. 11 shows an example of the result of calculating the timing difference. FIG. 11 shows that the reception timings of CTS 1001 and CTS 1003 are delayed by 4 μsec and 0.3 μsec from the timing at which they should be received. Further, it is shown that the reception timing of the CTS 1002 is 1 μsec earlier than the timing to be originally received.

  The group management unit 204 performs grouping control after the timing detection process ends. FIG. 12 shows a flowchart of the grouping control process of the group management unit 204 in this embodiment. First, the group management unit 204 determines the frame transmission order of the STAs in the group from the reception timing difference between the original frame reception timing and the actual reception timing calculated by the timing detection unit 203 (S1201). . At this time, the frame transmission order within the group is made earlier as the STA has an actual reception timing earlier than the original reception timing. On the other hand, as the STA whose actual reception timing is later than the timing that should be originally received, the frame transmission order in the group is set later. In the case of the example in FIG. 11, the frame transmission order within the group is determined in the order of STA 103, STA 104, and STA 102. When determining the frame transmission order within the group, the group management unit 204 notifies each STA that the order of the group has been changed (S1202).

  FIG. 13 is a diagram illustrating an example of frame transmission / reception timing when the group management unit 204 notifies the STA of the frame transmission order of the group and then transmits data to each STA by MU-MIMO. Group ID management frames 1301, 1302, and 1303 are frames transmitted in S1202 of FIG. 12 that notify the STA 102, STA 103, and STA 104 that the order within the group has been changed. Each STA transmits a response, that is, CTS or BA in the order of STA 103, STA 104, and STA 102 as shown in FIG. 13 in response to data transmission from the AP 101 by mRTS or MU-MIMO.

  In this embodiment, as described above, the STA that received a frame earlier than the timing that should be originally received moves the frame transmission order in the group forward, and the STA that received the frame later moves the frame transmission order in the group later. As a result, even if there is an STA that transmits a frame at a timing that is too early, the STA that transmits the frame before that transmits the frame at an earlier timing, so that no frame collision occurs. Even if there is an STA that transmits a frame at a timing that is too late, a STA that transmits a frame after that transmits a frame at a later timing, so that no frame collision occurs. Thus, according to the present embodiment, even if there is a deviation in the transmission timing of STAs participating in MU-MIMO, the possibility of collision is reduced while all STAs are allowed to participate in MU-MIMO. By doing so, it is possible to prevent the deterioration of the band use efficiency.

  In the present embodiment, when a timing difference of a predetermined time or more occurs, it may be excluded from the MU-MIMO as in the first embodiment without being included in the sort target in S1201. In addition, the detection of the frame reception timing may be detected not only by CTS and BA for mRTS but also by other frames.

<< Embodiment 3 >>
In the present embodiment, a method will be described in which a STA detects the frame transmission timing of another STA and avoids frame collision. The configuration of the communication system according to this embodiment is assumed to be as shown in FIG. 1 as in the above-described embodiment. In the present embodiment, a case will be described in which the STA 103 can receive a frame transmitted from the STA 102 and the STA 104, but the STA 102 and STA 104 cannot receive a frame transmitted from the STA 103.

(Structure of STA)
FIG. 14 is a block diagram illustrating a functional configuration example of the STA 103. For example, as illustrated in FIG. 14, the STA 103 includes a wireless transmission / reception unit 1401, a wireless communication control unit 1402, a timing detection unit 1403, a group management unit 1404, and a storage unit 1405. The wireless transmission / reception unit 1401, the wireless communication control unit 1402, and the storage unit 1405 are the same as the wireless transmission / reception unit 201, the wireless communication control unit 202, and the storage unit 205 related to the AP 101 in FIG. Compared to the AP 101, in order to execute MU-MIMO, it is not necessary to provide a plurality of antennas, and the number of antennas may be one. However, the STA 103 may include a plurality of antennas in order to execute SU-MIMO.

  The timing detection unit 1403 detects the timing of the frames transmitted from the other STAs 102 and 104 in the STA 103. Then, when a frame from another STA is received, the timing detection unit 1403 detects a timing difference between the assumed reception timing and the actual frame reception timing. The group management unit 1404 leaves the STA 103 itself from the MU-MIMO group according to the timing difference detected by the timing detection unit 1403 and switches the communication method to SU-MIMO.

(Timing detection process)
Next, processing executed by the STA 103 will be described with reference to FIG. Prior to processing, the STA 103 detects the reception timing of the CTS transmitted by another STA in response to the AP 101 transmitting mRTS. Then, the STA 103 determines whether the reception timing of the CTS from the STA in which the transmission order of frames in the group is earlier, for example, the STA 102, is later than the predetermined timing by a predetermined time, that is, after the predetermined period ( S1501). For example, in the case of the CTS 1601 from the STA 102 in the example of FIG. 16, the predetermined timing is a timing obtained by adding SIFS to the mRTS reception completion timing.

  In FIG. 16, the CTS 1601 from the STA 102 is transmitted and received with a delay of a predetermined time or more from a predetermined timing obtained by adding SIFS to the mRTS reception completion timing. In this case, the STA 103 determines that the reception timing of the frame from the preceding STA 102 is later than the predetermined period (Yes in S1501), and advances the process to S1503. On the other hand, when the reception timing of the frame from the STA 102 is within the predetermined period or before the predetermined period (No in S1501), the STA 103 advances the process to S1502.

  In S1502, the STA 103 determines whether the reception timing of the CTS from the STA whose frame transmission order in the group is later, for example, the STA 104, is before a predetermined period (S1502). For example, in the case of FIG. 16, the STA 103 advances the processing to S1503 because the reception timing of the CTS 1602 from the STA 104 whose transmission order is later is before the predetermined period. On the other hand, when the reception timing of the frame from the STA 104 is within the predetermined period or after the predetermined period (No in S1502), the STA 103 completes the process without switching between MU-MIMO and SU-MIMO. .

  In S1503, the group management unit 1404 executes a process for causing the STA 103 itself to leave the MU-MIMO group. That is, the group management unit 1404 leaves the MU-MIMO group by switching the communication method of the STA 103 from MU-MIMO to SU-MIMO. Specifically, the STA 103 transmits a DEAUTH (De-authentication frame) 1603 to the AP 101 and disconnects the connection to the AP 101 in MU-MIMO. After that, the STA 103 transmits an ASSOC (Association Request) 1604 to reconnect to the AP 101. At this time, the STA 103 notifies the AP by the ASSOC that only SU-MIMO is supported in order to prevent the STA 103 from rejoining the MU-MIMO group. Note that, in this embodiment, instead of switching to SU-MIMO, only leaving from a group having an STA whose frame transmission timing is shifted may be performed. In that case, communication by MU-MIMO in a group having no detached STA may be continued.

  In the present embodiment, as described above, the STA detects another STA whose frame transmission timing is shifted in the group to which the STA currently belongs, and autonomously leaves the group. As a result, it is possible to prevent a frame transmitted from another STA from colliding with a CTS or BA transmitted from the STA, and it is possible to prevent deterioration in bandwidth utilization efficiency.

  In each of the above-described embodiments, detection of the reception timing of each STA frame may be performed a plurality of times. Then, the average value may be calculated, and the grouping control may be performed when the average value of the frame reception timing deviation is equal to or longer than a predetermined time. As described above, “reception timing” in each of the above embodiments may be replaced with “transmission timing”. That is, grouping control may be performed according to transmission timing in each STA. As described above, the transmission timing may be considered to be the same as the reception timing, may be estimated by the AP, or explicitly includes the transmission time information in the frame, based on the information. You may get it.

<< Other Embodiments >>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (7)

A communication device,
Whether the timing of reception or transmission of the predetermined signal received from the first plurality of other communication apparatuses is within a predetermined period determined for each of the first plurality of other communication apparatuses. Determination means for determining;
Of the first plurality of other communication devices, a second plurality of other communication devices excluding a device for which the timing of receiving or transmitting the predetermined signal is determined not to be within the predetermined period, A management means for managing data as a group for transmitting data in parallel;
Transmitting means for transmitting data for each of the second plurality of other communication devices in parallel to each of the second plurality of other communication devices belonging to the group managed by the management means;
A communication apparatus comprising: The transmission means transmits data for each of the second plurality of other communication devices in parallel using multi-user MIMO (Multi Input-Multi Output).
The communication apparatus according to claim 1. The predetermined signal is a CTS (Clear To Send) signal.
The communication apparatus according to claim 1 or 2, wherein The first plurality of other communication devices includes a first other communication device and a second other communication device,
Transmission of the first predetermined signal and the first predetermined signal transmitted from the first other communication apparatus within a predetermined period determined for the first other communication apparatus is started. If the second predetermined signal transmitted from the second other communication device collides with the second predetermined signal, the determination means determines whether the timing of reception or transmission of the second predetermined signal is the second predetermined signal. It is determined that it is not within a predetermined period set for another communication device.
The communication device according to any one of claims 1 to 3, wherein Based on a difference between reception or transmission timing of a predetermined signal from the first plurality of other communication devices and start timing of a predetermined period determined for each of the first plurality of other communication devices. And determining means for determining the order in which the predetermined signals are transmitted,
The communication apparatus according to any one of claims 1 to 4, wherein the communication apparatus is characterized in that: A communication device control method comprising:
Whether the timing of reception or transmission of the predetermined signal received from the first plurality of other communication apparatuses is within a predetermined period determined for each of the first plurality of other communication apparatuses. A determination step for determining;
Of the first plurality of other communication devices, a second plurality of other communication devices excluding a device for which the timing of receiving or transmitting the predetermined signal is determined not to be within the predetermined period, A management process for managing data as a group that transmits in parallel;
A transmission step of transmitting data for each of the second plurality of other communication devices in parallel to each of the second plurality of other communication devices belonging to the group;
A control method characterized by comprising:   The program for operating a computer as a communication apparatus of any one of Claim 1 to 5.

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