JP6212443B2 - Wireless communication system and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication system and a wireless communication method.

  In a wireless LAN communication environment in which a large number of wireless LAN base stations exist on the same channel, there is a wireless communication system that superimposes and transmits different beacon frames for each subchannel in order to reduce the total transmission time of beacon frames (for example, Non-patent document 1).

  On the other hand, a wireless LAN base station compliant with the IEEE802.11 wireless LAN standard reports the control information to all wireless terminals that are connected or possibly connected in the communication area. A beacon (control signal) is periodically broadcast at a transmission rate (1 Mbps).

IEEE802.11, "Wireless LAN Medium Access Control (MAC) and Physical (PHY) Layer Specifications", February 2012

  In Non-Patent Document 1, a beacon frame is defined as a frame for periodically transferring information necessary for the wireless communication access point device to connect to itself, and specific frame information and transmission procedures are defined. Yes. In the wireless LAN system defined in Non-Patent Document 1, CSMA / CA (carrier sense multiple access / collision avoidance) is used as an access control method, and a certain level is set in the frequency channel to be transmitted. When the received power is detected, it is necessary to wait without newly starting transmission of a frame.

  Therefore, while the beacon frame is being transmitted, the wireless communication access point device and the wireless communication terminal that can receive the beacon frame cannot start transmission. Therefore, when a plurality of wireless communication access point devices are arranged in each communication cell and interfere with each other, a data frame or the like within a certain time for transmission of a beacon frame periodically generated at each wireless communication access point Opportunities for starting transmission of frames other than beacon frames are reduced. As described above, there is a problem in that throughput decreases as a result of a decrease in opportunities to transmit data frames within a certain period of time.

  The present invention has been made in view of such circumstances, and provides a wireless communication system and a wireless transmission method capable of improving the throughput by reducing the wireless communication time required for transmitting the beacon frame of the wireless communication base station apparatus. The purpose is to provide.

  The present invention is a wireless communication system that periodically broadcasts a beacon that notifies control information to wireless terminals that are currently connected and possibly connected in a communication area, and a plurality of wireless LAN base stations that can communicate with each other The device comprises a group, and comprises means for generating different beacon frames on each subchannel and transmitting beacon frames of a plurality of the wireless LAN base station devices at the same time.

The present invention, each wireless interference information between a plurality of the wireless LAN base station apparatus, the channel usage information, and to exchange all information of the beacon frame information, by using the interference information and channel use information, constitute the group The group is configured by determining wireless LAN base station devices participating in the group so that carrier sense results between the LAN base station devices are equal, and the beacon frame information is exchanged in advance within the group and at the same time One wireless LAN base station apparatus scheduled to be transmitted is determined at a beacon interval .

  The present invention is characterized in that one wireless LAN base station apparatus collectively transmits beacon frames of the wireless LAN base station apparatuses participating in the group.

  The present invention is characterized in that the wireless LAN base station apparatuses participating in the group simultaneously transmit beacon frames on different subchannels with synchronized transmission timing.

  The present invention is a wireless communication method performed by a wireless communication system that periodically broadcasts a beacon that notifies control information to wireless terminals that are currently connected and possibly connected, and can communicate with each other. The wireless LAN base station apparatuses form a group, generate different beacon frames on each subchannel, and simultaneously transmit a plurality of beacon frames of the wireless LAN base station apparatuses.

  According to the present invention, it is possible to reduce the radio communication time required for beacon frame transmission of all the radio communication base station devices constituting the group by aggregating beacon frame transmission, thereby improving throughput. The effect that it can be obtained.

It is a figure which shows the example of arrangement | positioning of the wireless LAN access point apparatus assumed by embodiment of this invention. It is a block diagram which shows the structure of wireless LAN access point apparatus AP1 shown in FIG. It is a figure which shows the beacon frame transmission frequency reduction procedure by one wireless LAN access point apparatus frequency-multiplexing and transmitting a plurality of beacon frames. It is a figure which shows the beacon frame transmission frequency reduction procedure by a some wireless LAN access point apparatus transmitting a beacon frame simultaneously on a different frequency channel. It is a figure which shows the procedure which determines one wireless LAN access point apparatus to be transmitted in advance, and transmits a plurality of beacon frames. FIG. 4 is a diagram illustrating an example in which a wireless LAN access point device that is to transmit a beacon frame is determined in advance in a cooperation group among the operations illustrated in FIG. 3. It is a figure which shows the example which the wireless LAN access point apparatus which acquired the transmission right first after TBTT implements beacon frame transmission among the operations shown in FIG. It is a figure which shows the example which implements transmission timing synchronization of a beacon frame by utilization of a timing notification frame among the operations shown in FIG. FIG. 5 is a diagram illustrating an example in which beacon frame transmission timing synchronization is performed using a timing notification frame and a response frame corresponding to the frame among the operations illustrated in FIG. 4. FIG. 5 is a state transition diagram showing a state of a group configuration between the wireless LAN access point devices shown in FIGS. 3 and 4. 11 is a flowchart showing a group cooperation start procedure of the wireless LAN access point device shown in FIG. 10. It is a flowchart which shows the update procedure for updating the information concerning the beacon frame transmission which the cooperation group between the wireless LAN access point apparatuses shown in FIG. 10 handles for every fixed period. It is a flowchart which shows the procedure at the time of the wireless LAN access point apparatus which becomes a participating member withdraws from the cooperation group between the wireless LAN access point apparatuses shown in FIG. It is a sequence diagram which shows the frame exchange sequence of the group cooperation start procedure shown in FIG. It is a sequence diagram which shows the modification of the frame exchange sequence of the group cooperation start procedure shown in FIG. It is a sequence diagram which shows the modification of the frame exchange sequence of the group cooperation start procedure shown in FIG.

  Hereinafter, a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an arrangement example of wireless LAN access point devices assumed in an embodiment of the present invention. In this figure, reference numeral 1 denotes a wireless communication cell in which a wireless LAN access point device AP1 is installed. Reference numeral 2 denotes a wireless communication cell in which a wireless LAN access point device AP1 is installed. Reference numeral 3 denotes a wireless communication cell in which a wireless LAN access point device AP3 is installed. Reference numeral 4 denotes a wireless communication cell in which a wireless LAN access point device AP4 is installed.

  The wireless LAN access point devices AP1, AP2, AP3, AP4 can receive signals transmitted from other wireless LAN access point devices installed in a wireless communication cell range other than the wireless LAN access point devices AP1, AP2, AP3, AP4. Also, the frequency channels used when the wireless LAN access point devices AP1, AP2, AP3, AP4 each communicate with the wireless LAN terminal as the connection destination are completely the same. The wireless LAN access point devices AP1, AP2, AP3, and AP4 are all wireless communication devices that perform wireless transmission / reception in accordance with the IEEE 802.11 standard, and are required for wireless communication connection once every fixed period as a wireless communication base station device. A beacon frame for notifying information is transmitted.

  Next, the configuration of the wireless LAN access point device AP1 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of the wireless LAN access point device AP1 shown in FIG. Since the wireless LAN access point devices AP2, AP3, and AP4 have the same configuration as the wireless LAN access point device AP1 shown in FIG. 2, detailed description thereof is omitted here.

  The wireless LAN access point device AP1 includes a wireless communication unit 10, a transmission right acquisition unit 20, an information management unit 30, and a control unit 40. The wireless communication unit 10 transmits / receives a signal generated by an orthogonal frequency division multiplexing modulation method in order to transmit / receive a wireless frame via an antenna. The transmission right acquisition unit 20 acquires the transmission right. The information management unit 30 performs information management. The control unit 40 controls the overall processing operation of the wireless LAN access point device AP1.

  In addition, as shown in FIGS. 3 to 8, the wireless communication unit 10 transmits a plurality of different signals transmitted and received on subchannels configured with a narrower bandwidth than the usable frequency bandwidth on the usable frequency channel. It is possible to perform transmission / reception processing individually. A subchannel that is always included when a wireless LAN terminal in a BSS (basic service set) transmits a frame is called a primary channel. On the other hand, other subchannels included in the frequency channel are referred to as secondary channels.

  For example, as shown in FIGS. 3 to 8, when the wireless LAN access point device AP1 can use up to 80 MHz bandwidth, there are four sub-channels of 20 MHz bandwidth, one of which is a primary channel and the remaining three are Secondary channel. Here, channel 1 (ch. 1) is a primary channel, and channels 2, 3, 4 (ch. 2, 3, 4) are secondary channels. The wireless communication unit 10 can transmit and receive frames for these four subchannels. Alternatively, frame transmission / reception can be performed in units of frequency resource blocks used in the wireless LAN system. Similarly, the transmission right acquisition unit 20, the information management unit 30, and the control unit 40 control each of a plurality of subchannels included in the frequency channel to manage information.

  In the present embodiment, a group is formed in a plurality of wireless LAN access point devices capable of frame exchange, TBTT (Target beacon transmission time) is synchronized, and frame transmission timing synchronization is performed after an IEEE 802.11 default carrier sense period. The time for transmitting a beacon frame by a plurality of wireless LAN access point devices is shortened by simultaneously transmitting beacon frames on different subchannels or frequency block units.

  For example, in the example shown in FIG. 3, a group is formed by the wireless LAN access point devices AP1 to AP4 shown in FIG. 1, and synchronization from Timestamp to TBTT included in each beacon frame is performed. FIG. 3 is a diagram illustrating a procedure for reducing the number of times a beacon frame is transmitted when one wireless LAN access point device transmits a plurality of beacon frames by frequency multiplexing. Here, a TSF (timing synchronization function) that synchronizes the time of a timer managed between wireless LAN terminals using Timestamp is a function that synchronizes the time with respect to the wireless LAN terminals in one BSS. In this embodiment, it is also used for time synchronization of a plurality of wireless LAN access point devices.

  Also, beacon frame information elements of wireless LAN access point devices other than the self constituting the group are acquired in advance. The wireless LAN access point apparatus sets a beacon frame as a transmission frame when the next transmission right is acquired at the timing of TBTT, and starts transmission preparation. When the transmission right is acquired, at time t1, the wireless LAN access point apparatus transmits a beacon frame including its own information element (beacon 1 in the case of the wireless LAN access point apparatus AP1) on the primary channel to the wireless LAN of the cooperation group. Beacon frames including information elements of access point devices (beacons 2 to 4 in the case of wireless LAN access point device AP1) are arranged on the secondary channel so as not to overlap with each other so that the frame time length on each subchannel is the same. Send in advance after adjusting in advance.

  At time t2, similarly, the wireless LAN access point device transmits a beacon frame (beacon 2 in the case of the wireless LAN access point device AP2) including its information element on the primary channel to the wireless LAN access point device of the cooperation group. Beacon frames (in the case of wireless LAN access point device AP2, beacons 3, 4, 1) are arranged on the secondary channel so that they do not overlap each other, and the frame time length on each subchannel is the same in advance. Send to the same time after adjusting.

  In the example shown in FIG. 4, the wireless LAN access point devices AP1 to AP4 shown in FIG. 1 form a group, and the synchronization from the timestamp to the TBTT included in each beacon frame is performed. FIG. 4 is a diagram showing a procedure for reducing the number of beacon frame transmissions by a plurality of wireless LAN access point devices transmitting beacon frames simultaneously on different frequency channels. After the TBTT is synchronized within the group, each wireless LAN access point device that is a group member sets a beacon frame as a transmission frame when the next transmission right is acquired at the timing of TBTT, and starts transmission preparation. .

  After the carrier sense, when the transmission right is acquired at time t1, a frame for timing synchronization of beacon frame transmission is transmitted and received between the wireless LAN access point devices of the group members, and the wireless communication of the group members is performed at the designated timing. The LAN access point device starts beacon frame transmission on different subchannels simultaneously. At this time, the wireless LAN access point device AP1 transmits a beacon 1. Further, the wireless LAN access point device AP2 transmits a beacon 2. The wireless LAN access point device AP3 transmits a beacon 3. Further, the wireless LAN access point device AP4 transmits a beacon 4.

  A similar operation is performed again at the next TBTT timing, and beacon frame transmission is performed at time t2. At this time, the subchannels transmitted by each wireless LAN access point device may not be the same each time so that each wireless LAN access point device can transmit a beacon frame on the primary channel at regular intervals. In addition, by synchronizing the clock frequency, transmission power level, and transmission start time between the wireless LAN access point devices via a wired or wireless LAN system and a wireless network of another wireless system, a plurality of wireless LAN access point devices can A means for suppressing inter-terminal interference that occurs during simultaneous transmission may be added.

  In addition, as shown in FIG. 5, interference information, the number of connected terminals, channel usage information, and the like are collected between wireless LAN access point devices via a wired or wireless LAN system and a wireless network of another wireless system to form a cooperation group. You may determine the wireless LAN access point apparatus which participates in a cooperation group so that the carrier sense result between each wireless LAN access point apparatus to comprise becomes equivalent. FIG. 5 is a diagram illustrating a procedure for transmitting a plurality of beacon frames by determining one wireless LAN access point device to be transmitted in advance.

  Here, the interference information is the number of wireless LAN access point devices and wireless LAN terminals that can receive frames. The channel use information is a ratio of time determined to be busy as a result of own carrier sense within a single time. Information collection via the network is performed by the wireless LAN access point device or the computer server S connected to the network.

  The wireless LAN access point device AP1 collects interference information and channel usage information from the computer server S (A1 in FIG. 5). On the other hand, the computer server S transmits a recommended cooperation group configuration (designates the destination wireless LAN access point device as a coordinator) (FIG. 5B).

  Further, the wireless LAN access point device AP2 collects interference information / channel usage information with respect to the computer server S (FIG. 5A2). On the other hand, the computer server S transmits a recommended cooperation group configuration (not specifying the destination wireless LAN access point device as a coordinator) (FIG. 5C1).

  Also, the wireless LAN access point device AP3 collects interference information and channel usage information for the computer server S (A3 in FIG. 5). In response to this, the computer server S performs transmission of the recommended cooperation group configuration (not specifying the destination wireless LAN access point device as a coordinator) (FIG. 5C2).

  Further, the wireless LAN access point device AP4 collects interference information and channel usage information from the computer server S (A4 in FIG. 5). On the other hand, the computer server S performs transmission of the recommended cooperation group configuration (not specifying the destination wireless LAN access point device as a coordinator) (FIG. 5C3).

  FIG. 6 is a diagram illustrating an example in which a wireless LAN access point device that is to transmit a beacon frame is determined in advance in the cooperation group in the operation illustrated in FIG. In the example shown in FIG. 6, beacon frame information elements of each wireless LAN access point device are exchanged in advance within the cooperation group, and at the same time, one wireless LAN access point device scheduled to be transmitted is determined at each beacon interval. By determining one wireless LAN access point device to be transmitted in advance, collision of beacon frames transmitted by each wireless LAN access point device can be avoided.

  Note that the transmission schedule is determined so that the transmission frequency between the wireless LAN access point devices in the cooperation group is fair (for example, in rotation order). In each beacon interval, wireless LAN access point devices other than the wireless LAN access point devices scheduled to transmit among the wireless LAN access point devices participating in the cooperation group are scheduled to transmit beacon frames at the TBTT at which this beacon interval starts. Do not set as a frame.

  On the other hand, the wireless LAN access point device scheduled to transmit sets a beacon frame as a frame scheduled to be transmitted in TBTT. In the example shown in FIG. 6, the wireless LAN access point device (AP1) is scheduled to transmit in the beacon interval 1, and the wireless LAN access point device (AP2) is the wireless LAN access point device scheduled to transmit in the beacon interval 2.

  The wireless LAN access point device scheduled to transmit starts transmission of a beacon frame when acquiring a transmission right after carrier sense for a random time determined by the back-off process. One beacon frame is generated with a radio frame of each subchannel bandwidth of 20 MHz. The beacon frame uses all channels that can be used by the wireless LAN access point device, and simultaneously transmits beacon frames including information elements of different wireless LAN access point devices in each subchannel. At this time, by transmitting a beacon frame including its own information element on the primary channel, the wireless communication device which is connected to itself or wishes to connect and supports only the existing standards is also able to Information can be sent.

  FIG. 7 is a diagram illustrating an example in which the wireless LAN access point apparatus that first acquires the transmission right after TBTT performs beacon frame transmission among the operations illustrated in FIG. 3. In the example shown in FIG. 7, the beacon frame information elements of the wireless LAN access point devices are exchanged in advance in the cooperation group. At the same time, the TBTT and the beacon interval are synchronized.

  The wireless LAN access point devices participating in the cooperation group at the timing of TBTT set the beacon frame as a wireless frame scheduled to be transmitted next time. The wireless LAN access point device starts a transmission right acquisition procedure, and as a result of carrier sense during the random time determined by the back-off process, the wireless LAN access point device that has acquired the transmission right starts beacon frame transmission.

  The beacon frame uses all channels that can be used by the wireless LAN access point device, and simultaneously transmits beacon frames including information elements of different wireless LAN access point devices in each subchannel. At this time, by transmitting a beacon frame including its own information element on the primary channel, the wireless communication device which is connected to itself or wishes to connect and supports only the existing standards is also able to Information can be sent. Further, when a wireless LAN access point device in one of the cooperation groups in which the self participates receives a beacon frame transmitted earlier than the self, the transmission of the beacon frame set to be currently transmitted is canceled.

  FIG. 8 is a diagram illustrating an example of performing beacon frame transmission timing synchronization by using a timing notification frame among the operations illustrated in FIG. 4. In the example shown in FIG. 8, after starting carrier sense at the timing of TBTT, the wireless LAN access point device scheduled to use the primary channel when transmitting a beacon frame or all wireless LAN access point devices in the group acquire the transmission right. The wireless LAN access point apparatus that has acquired the transmission right as a result of the carrier sense during the random time determined by the back-off process transmits a timing notification frame. The timing notification frame is generated by a radio frame having a bandwidth of 20 MHz, which is a sub-channel bandwidth, and the same radio frame as the frame is simultaneously transmitted on each sub-channel.

  Note that the timing notification frame includes at least the address of the wireless LAN access point apparatus that performed the transmission, the Timestamp, the duration until transmission of the beacon frame is completed, and the wireless LAN access point to which the beacon frame transmitted on each subchannel belongs. Information is included. The wireless LAN access point device that has transmitted the timing notification frame has successfully received the timing notification frame transmitted by any member of the group to which it belongs after a short inter frame space (SIFS) time after completion of transmission. The device transmits a beacon frame on the subchannel that each device intends to use after SIFS time after completion of reception.

  After a beacon frame prepared at the timing of TBTT is transmitted, even if a timing notification frame transmitted by any member of the group to which it belongs is received, a new beacon frame is transmitted until the next TBTT. Do not do. Further, when the timing notification frame transmitted by another wireless LAN access point apparatus belonging to the group is normally received, the self cancels the transmission of the timing notification frame scheduled to be transmitted by the next TBTT.

  FIG. 9 is a diagram illustrating an example in which beacon frame transmission timing synchronization is performed using a timing notification frame and a response frame corresponding to the frame in the operation illustrated in FIG. 4. In FIG. 9, after starting carrier sense at the timing of TBTT, carrier sense is performed for a random time determined by backoff processing, and the channel is unused, the primary channel is used when transmitting a beacon frame. The scheduled wireless LAN access point device or all wireless LAN access point devices in the group transmit the timing notification frame. The timing notification frame is generated by a radio frame having a bandwidth of 20 MHz, which is the bandwidth of the subchannel, and the same radio frame as this frame is simultaneously transmitted on each subchannel.

  Note that the timing notification frame includes at least the address of the wireless LAN access point apparatus that performed the transmission, the Timestamp, the duration until transmission of the beacon frame is completed, and the wireless LAN access point to which the beacon frame transmitted on each subchannel belongs. Information is included. The wireless LAN access point devices constituting the group include the wireless LAN access point device that has transmitted the timing notification frame and the other wireless LAN access point devices that are participating in the group, as described in (1) and (2) below. Response frame transmission is started on the subchannels each of which is scheduled to be used at the timing.

(1) The wireless LAN access point device that has transmitted the timing notification frame starts a timer after completion of transmission, and timing after SIFS time.
(2) The wireless LAN access point device that has normally received the timing notification frame transmitted by any member of the group to which it belongs starts the timer after completion of reception and the timing after SIFS time.

  By using a CTS (clear to send) frame defined by IEEE 802.11 as the response frame, all wireless LAN terminals located in a range in which the wireless frame can be received can be received. Alternatively, a new frame including information necessary for timing synchronization or the like can be transmitted as a response frame. It is assumed that the wireless LAN terminal that has received the response frame is using the media only for the period indicated by the duration information of the frame received in the previous period (virtual carrier sense), and sets this period as a transmission stop (NAV: network allocation vector) period. .

  Each wireless LAN access point device transmits a beacon frame on a subchannel that is scheduled to be used after SIFS time after completion of response frame transmission. After a beacon frame prepared at the timing of TBTT is transmitted, even if a timing notification frame transmitted by any member of the group to which it belongs is received, a new beacon frame is transmitted until the next TBTT. Do not do. If the timing notification frame transmitted from another wireless LAN access point apparatus belonging to the group is normally received, the transmission of the timing notification frame scheduled to be transmitted by the next TBTT is canceled.

  FIG. 10 is a state transition diagram showing the state of the group configuration between the wireless LAN access point devices shown in FIGS. In the initial state, a group between wireless LAN access point devices is not configured, and each wireless LAN access point device independently performs beacon transmission. Thereafter, a group cooperation participation start procedure is executed in response to detection of a wireless LAN access point apparatus capable of cooperation and transmission of a group cooperation participation request frame from the detected wireless LAN access point apparatus. After the collaborative group is configured by the above procedure, the specific or each wireless LAN access point device starts a timer.

  The timer is provided to execute the group configuration update procedure at regular intervals. When the timer indicates a predetermined time, the update procedure is started. Further, the wireless LAN access point device participating in the group desires to leave the group due to the suspension of the wireless LAN communication function or the change of the frequency channel to be used, or a group withdrawal request frame is transmitted from the wireless LAN access point device. If this happens, start the group withdrawal procedure. After the group withdrawal procedure is completed, if there are not a plurality of wireless LAN access point devices constituting the group, the operation returns to the beacon frame transmission operation alone.

  Next, a group cooperation start procedure of the wireless LAN access point device will be described. FIG. 11 is a flowchart showing a group cooperation start procedure of the wireless LAN access point device shown in FIG. When configuring a group between wireless LAN access point devices, determination of subchannels used by each wireless LAN access point device and frame exchange / withdrawal procedures for recording / participating procedures of the wireless LAN access point devices constituting the group It is possible to set a specific wireless LAN access point device that executes the frame exchange as a Coordinator. By setting the Coordinator, it is possible to centrally manage information related to beacon frame transmission handled by the cooperation group. When the coordinator starts group cooperation with two wireless LAN access point apparatuses, the wireless LAN access point apparatus that has transmitted the group cooperation participation frame first takes charge.

  First, the wireless LAN access point device (AP) performs channel switching when the area moves when it starts up (step S1). Then, the wireless LAN access point device performs a beacon scan and a beacon transmission (step S2). The beacon includes information on the presence / absence of the wireless LAN access point device cooperation function.

  Next, the wireless LAN access point device determines whether or not a collaborative wireless LAN access point device or group exists in the vicinity (step S3). If the result of this determination is that there is no wireless LAN access point device or group in the vicinity, the wireless LAN access point device transmits a beacon alone (step S4).

  On the other hand, when there are wireless LAN access point devices or groups around, the wireless LAN access point device transmits a cooperation participation request frame (step S5). If there is a Coordinator, the cooperation participation request frame is transmitted to the wireless LAN access point device that is the Coordinator, and if there is no Coordinator, any wireless LAN access point participating in the wireless LAN access point device cooperation group Send to the device.

  Next, the wireless LAN access point device determines whether or not cooperation is possible (step S6). As a result of this determination, if cooperation is possible, the wireless LAN access point device finalizes the schedule and exchanges information (step S7). Then, cooperative transmission is started (step S8). On the other hand, when the cooperation is not possible, the wireless LAN access point device performs beacon transmission alone (step S9).

  Next, an update procedure for updating information related to beacon frame transmission handled by a cooperation group between wireless LAN access point devices at regular intervals will be described. FIG. 12 is a flowchart showing an update procedure for updating information related to beacon frame transmission handled by the cooperation group between the wireless LAN access point devices shown in FIG. 10 at regular intervals.

  First, when the update timing comes (step S11), the wireless LAN access point device (AP) lists other wireless LAN access point devices whose frames cannot be confirmed for a certain period (step S12).

  Next, the wireless LAN access point apparatus determines whether a frame other than itself cannot be confirmed for a certain period (step S13). As a result of this determination, if a frame other than itself cannot be confirmed for a certain period, the wireless LAN access point device transmits a beacon alone (step S14).

  On the other hand, when a frame other than itself can be confirmed, the wireless LAN access point device performs schedule confirmation and information exchange only with the wireless LAN access point device capable of frame confirmation (step S15). In the information exchange, all information on the request side may be sent first when the wireless LAN access point apparatus cooperation participation request is transmitted.

  Next, a procedure when a wireless LAN access point device that is a participating member withdraws from a cooperation group between wireless LAN access point devices will be described. FIG. 13 is a flowchart illustrating a procedure when a wireless LAN access point device that is a participating member leaves the cooperation group between wireless LAN access point devices illustrated in FIG. 10. When the Coordinator is provided in the group and the Coordinator desires to leave, the Coordinator transmits a withdrawal request frame to any of the wireless LAN access point devices participating in the group and receives the frame. The wireless LAN access point device is newly in charge of Coordinator.

  First, when the withdrawal procedure is started (step S21), the wireless LAN access point device to withdraw transmits a withdrawal request (step S22). When there is a Coordinator, the withdrawal request is transmitted to the wireless LAN access point device that is the Coordinator. If the device itself is a Coordinator, it is transmitted to one of the participating wireless LAN access point devices, and this destination wireless LAN access point device becomes a new Coordinator. If there is no Coordinator, the message is transmitted to one of the wireless LAN access point devices participating in the wireless LAN access point device cooperation group.

  In response to this, the wireless LAN access point device that has cooperated with the wireless LAN access point device to be withdrawn, which is the destination of the request frame, determines the schedule again (step S23).

  Next, the wireless LAN access point device determines whether a plurality of participating wireless LAN access point devices still remain (step S24). If it remains as a result of this determination, the wireless LAN access point device transmits the reschedule content to the participating wireless LAN access point devices other than the withdrawal wireless LAN access point device (step S25). Then, the wireless LAN access point device starts cooperative transmission (step S26).

  On the other hand, when a plurality of participating wireless LAN access point devices do not remain, the participating wireless LAN access point device performs beacon transmission alone (step S27). At this time, the presence or absence of the wireless LAN access point device cooperation function is notified at the time of beacon transmission.

Table 1 shows information included in a frame exchanged between a wireless LAN access point device that wishes to participate in a cooperation group and a wireless LAN access point device that accepts participation in the group cooperation start procedure shown in FIG. An example is shown. Note that the wireless LAN access point device in charge of schedule adjustment in Table 1 is in charge of the wireless LAN access point device in charge of the coordinator in the case of a cooperation group having a coordinator.

  Next, the frame exchange sequence of the group cooperation start procedure will be described. FIG. 14 is a sequence diagram showing a frame exchange sequence of the group cooperation start procedure shown in FIG. First, the wireless LAN access point device that wishes to participate transmits a cooperation request to the wireless LAN access point device of the Coordinator (step S31). In response, the Coordinator's wireless LAN access point device returns a cooperation response to the wireless LAN access point device desired to participate (step S32). Then, the wireless LAN access point device that wishes to participate transmits participation information to the wireless LAN access point device of the Coordinator (step S33).

  Next, the coordinator's wireless LAN access point device transmits scheduling information to the wireless LAN access point device desired to participate and the wireless LAN access point device (or devices) that have already participated (steps). S34, S35).

  Next, the wireless LAN access point device that wishes to participate returns an ACK to the wireless LAN access point device of the Coordinator (step S36). Subsequently, the coordinator's wireless LAN access point device transmits a polling to the wireless LAN access point devices that have already participated (step S37) and has an ACK returned (step S38) (step S39). , S40).

  Next, a modification of the frame exchange sequence of the group cooperation start procedure will be described. FIG. 15 is a sequence diagram showing a modification of the frame exchange sequence of the group cooperation start procedure shown in FIG. First, the wireless LAN access point device that wishes to participate transmits a cooperation request and participation information to the wireless LAN access point device of the Coordinator (step S51). In response, the Coordinator wireless LAN access point device returns a cooperation response to the wireless LAN access point device that wishes to participate (step S52).

  Next, the coordinator's wireless LAN access point device transmits scheduling information to the wireless LAN access point device desired to participate and the wireless LAN access point device (or devices) that have already participated (steps). S53, S54).

  Next, the wireless LAN access point device that wishes to participate returns an ACK to the wireless LAN access point device of the Coordinator (step S55). Subsequently, the coordinator's wireless LAN access point device transmits a polling to the wireless LAN access point device that has already participated (step S56), and has an ACK returned (step S57) (step S58). , S59).

  Next, a modification of the frame exchange sequence of the group cooperation start procedure will be described. FIG. 16 is a sequence diagram showing a modification of the frame exchange sequence of the group cooperation start procedure shown in FIG. First, the wireless LAN access point device that wishes to participate transmits a cooperation request and participation information to the wireless LAN access point device of the Coordinator (step S51). In response, the Coordinator's wireless LAN access point device sends a cooperative response and scheduling information to the wireless LAN access point device that it wants to join and the wireless LAN access point device that has already participated (there may be a plurality of wireless LAN access point devices). Is transmitted (steps S62 and S63).

  Next, the wireless LAN access point device that wishes to participate returns an ACK to the wireless LAN access point device of the Coordinator (step S64). Subsequently, the coordinator's wireless LAN access point device transmits a polling to the wireless LAN access point devices that have already participated (step S65) and returns an ACK (step S66) (step S67). , S68).

  As described above, in a wireless LAN communication environment in which a large number of wireless LAN base stations exist on the same channel, in the conventional technology, transmission opportunities for data frames are lost due to beacon frames transmitted by a large number of wireless LAN base stations. There was a problem that the throughput was lowered. The wireless communication system according to the present embodiment groups wireless LAN base stations that interfere with each other, and transmits beacon frames using different frequency channels at the same timing. With this configuration, it is possible to suppress a decrease in transmission opportunities such as data frames and suppress a decrease in throughput.

  The wireless LAN access point device in the embodiment described above may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  As mentioned above, although embodiment of this invention has been described with reference to drawings, the said embodiment is only the illustration of this invention, and it is clear that this invention is not limited to the said embodiment. is there. Therefore, additions, omissions, substitutions, and other modifications of the components may be made without departing from the technical idea and scope of the present invention.

  Multiple wireless communications that interfere with each other in order to reduce the wireless communication time consumed when transmitting beacon frames while all wireless communication access point devices transmit beacon frames periodically as before. It can also be applied to uses where it is indispensable to transmit beacon frames in cooperation with access point devices.

  1, 2, 3, 4,... Wireless communication cell, AP 1, AP 2, AP 3, AP 4... Wireless LAN access point device (wireless LAN base station device) 10. Transmission right acquisition unit, 30 ... information management unit, 40 ... control unit

Claims (3)

A wireless communication system that periodically broadcasts a beacon that notifies control information to wireless terminals that are connected and possibly connected in a communication area,
A plurality of wireless LAN base station devices communicable with each other constitute a group, comprising a transmission means for generating different beacon frames on each subchannel and simultaneously transmitting a plurality of beacon frames of the wireless LAN base station devices ,
One wireless LAN base station apparatus collectively transmits the beacon frames of the wireless LAN base station apparatuses participating in the group . Interference information between a plurality of the wireless LAN base station apparatus, the channel usage information, and to exchange all information of the beacon frame information, the interference information and using the channel usage information, each wireless LAN base station apparatus constituting the group The group is configured by determining wireless LAN base station devices participating in the group so that the carrier sense results between them are equal, and the beacon frame information is exchanged in advance within the group and transmitted at each beacon interval. The wireless communication system according to claim 1, wherein one scheduled wireless LAN base station apparatus is determined. A wireless communication method performed by a wireless communication system that periodically broadcasts a beacon that notifies control information to wireless terminals that are currently connected and possibly connected in a communication area,
Communicable plurality of wireless LAN base station apparatus to form a group together have a transmission step of transmitting the beacon frame of each to produce a different beacon frames on subchannel at the same time a plurality of the wireless LAN base station apparatus,
One wireless LAN base station apparatus collectively transmits the beacon frames of the wireless LAN base station apparatuses participating in the group .

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