JP6083875B2 - Communication system and communication control method - Google Patents

Description

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

  In a wireless local area network (LAN), when a large number of channels (subcarriers) are used, a plurality of access points of the channel may need to share the same channel and communicate with the terminal device. Thus, when a plurality of adjacent access points share the same channel, co-channel interference (CCI: Co-Channel Interface) occurs, and communication quality such as throughput deteriorates. Thus, in order to suppress the degradation of transmission quality as much as possible in an environment where co-channel interference occurs, it is necessary to select a subcarrier having the smallest degree of co-channel interference.

  Therefore, CS-DCA (Channel Segregation-Dynamic Channel Assignment) has been proposed as a method in which an access point assigns a channel adaptively to the surrounding co-channel interference state (see, for example, Non-Patent Document 1). CS-DCA is a dynamic channel allocation method in which each access point independently determines a channel to be used based on channel segregation.

Under CS-DCA, each access point measures the instantaneous CCI power of each channel received from surrounding cells, and uses the measured instantaneous CCI power to calculate the average value of CCI power for each channel (average CCI). Power). The access point updates a priority table (CCI table) indicating the priority order for channel use according to the average CCI power of each channel. At the time of transmission, the access point uses the channel with the highest priority in the priority table, that is, the channel with the lowest average CCI power.
With such a channel allocation method based on CS-DCA, a channel (subcarrier) usage pattern that minimizes co-channel interference applied to surrounding cells in response to changes in the surrounding radio wave environment has a communication environment with a plurality of access points. Can form autonomously.

Also, in a terminal device that is far from the access point, communication quality deteriorates because sufficient power cannot be obtained for the received signal due to the effect of propagation loss. In addition, when an access point becomes unusable due to a natural disaster, equipment failure, or the like, a terminal device in an area covered by the unusable access point cannot communicate.
As a countermeasure against such a problem, communication by cooperative diversity in which access points are linked and transmitted / received at the same time is known (for example, see Non-Patent Document 2).

  Further, in allocating a channel used by each access point under cooperative diversity, a fully centralized control type dynamic channel allocation method can be applied (for example, see Non-Patent Document 3). As described above, the access point cooperation can be easily maintained by the complete centralized control type dynamic channel allocation technique.

Y. Matsumura, S. Kumagai, T. Obara, T. Yamamoto, and F. Adachi, “Channel Segregation Based Dynamic Channel Assignment for WLAN,” IEEE The 13th International Conference on Communication Systems (ICCS2012), Nov 2012. Shinya Kumagai, Atsushi Nagaoka, Yasunori Ohara, Tetsuya Yamamoto, Fumiyuki Adachi, “Cooperative Diversity Using STBC-OFDM”, IEICE Tech. RCS2012-112, pp. 97-102, August 2012. G. F. Marias, D. Skyrianoglou, and L. Merakos, “A centralized approach to dynamic channel assignment in wireless ATM LANs,” Proc. 18th Annual Joint Conference of the IEEE Computer and Communications Societies (Infocom’99), Mar. 1999.

  Under cooperative diversity, a plurality of access points need to communicate with a terminal device using the same channel in cooperation as described above. On the other hand, in the channel allocation method based on CS-DCA, each access point independently determines a channel that minimizes co-channel interference. For this reason, the channel to be used is different between adjacent access points. That is, under cooperative diversity, channel assignment by CS-DCA cannot be applied as it is.

If the fully centralized control-type dynamic channel allocation method according to Non-Patent Document 3 is applied to an access point that performs communication by cooperative diversity, it is possible to allocate channels under cooperative diversity.
However, in this case, since the channel to be allocated in conformity with the complicated cooperation of the access points is derived, the calculation processing amount of the control center becomes enormous.

  In view of the above circumstances, an object of the present invention is to provide a communication system and a communication control method capable of suppressing the amount of calculation processing related to channel assignment under communication by cooperative diversity.

One aspect of the present invention is a communication system including a plurality of access points, one or more terminal devices, and a control device, wherein the access points are configured to prioritize channels based on the situation of co-channel interference for each channel. A channel priority processing unit that updates the channel priority indicating the order and notifies the control device of the channel priority, and a notification based on information on a connection destination terminal device and an allocated channel that are notified from the control device. And a terminal-compatible communication control unit that transmits a beacon for communicating with the connection destination terminal device using the assigned channel, and the terminal device indicates a predetermined communication state index indicating a communication state with each of the access points A communication status indicator measuring unit for measuring the communication status indicator, and a candidate action determined based on the communication status indicator measured by the communication status indicator measuring unit. In accordance with the communication request processing unit that transmits a communication request including candidate access point information indicating a point to the control device, the allocated channel and the connection destination access point notified from the control device in response to the communication request, An access point corresponding communication control unit that performs communication with the connection destination access point using the allocated channel, and the control device is configured from among candidate access points indicated by candidate access point information included in the communication request. A master access point determination unit that determines a candidate access point with the maximum signal reception power as a master access point corresponding to the terminal device that is the transmission source of the communication request, and based on the channel priority notified from the access point , Empty channels possessed by the master access point Among the candidate access points indicated by the candidate access point information included in the communication request, a candidate access point with an empty allocation channel is selected as the source of the communication request. A connection destination access point determination unit that is determined as a connection destination access point corresponding to the terminal device, an allocation channel determined by the allocation channel determination unit as a response to the communication request, and a determination by the connection destination access point determination unit For each of the access point determined as the connection destination access point by the connection destination access point determination unit and the response processing unit that notifies the terminal device that is the transmission destination of the communication request Connection instruction information indicating the destination terminal device and the assigned channel A communication system comprising a connection instruction unit for transmitting

  One aspect of the present invention is the communication system described above, wherein the communication request processing unit is a terminal device that is a transmission source of the communication request derived based on the communication state index measured by the communication state index measurement unit The communication request further including communication state information indicating a communication state between the access point and the access point is transmitted to the control device, and the master access point determination unit has a good communication state indicated by the communication state information included in the communication request A master access point is determined in order from a terminal device that is not a communication request transmission source, and the allocation channel determination unit determines an allocation channel in the order of the master access point determined by the master access point determination unit.

  One aspect of the present invention is the communication system described above, wherein the master access point determination unit has the best communication state with the terminal device that is the transmission source of the communication request from among candidate access points having a free channel. A candidate access point is determined as a master access point.

  One aspect of the present invention is the communication system as described above, wherein the allocated channel determination unit has the highest channel priority notified by the master access point among the empty channels of the master access point. Is determined as the assigned channel.

One aspect of the present invention is a communication control method in a communication system including a plurality of access points, one or more terminal devices, and a control device, wherein the access points are based on a situation of co-channel interference for each channel. A channel priority processing step for updating the channel priority indicating the channel priority and notifying the control device of the channel priority, and information on the connection destination terminal device and the assigned channel notified from the control device. Based communication control step for transmitting a beacon for performing communication with the connection destination terminal device based on the notified allocation channel, and the terminal device indicates a predetermined communication state with each of the access points. A communication state index measuring step for measuring a communication state index of A communication request processing step for transmitting to the control device a communication request including candidate access point information indicating a candidate access point determined based on the communication status indicator, and the control device is notified in response to the communication request. An access point corresponding communication control step for performing communication with the connection destination access point using the allocation channel according to the allocated channel and the connection destination access point, and the control device includes a candidate included in the communication request A master access point determining step for determining a candidate access point having the maximum signal reception power among the candidate access points indicated by the access point information as a master access point corresponding to the terminal device that is the transmission source of the communication request; and Channel superior notified from point An allocation channel determination step for determining an allocation channel from among the empty channels of the master access point based on the order, and among the candidate access points indicated by the candidate access point information included in the communication request, the allocation channel is empty A connection destination access point determining step for determining the candidate access point as a connection destination access point corresponding to the terminal device that is the transmission source of the communication request, and the allocation determined by the allocation channel determining step as a response to the communication request A response processing step of notifying a channel and a connection destination access point determined by the connection destination access point determination step to a terminal device that is a transmission source of the communication request; and a connection destination access point by the connection destination access point determination step; And a connection instruction step of transmitting connection instruction information indicating a connection destination terminal apparatus and an assigned channel to each of the access points determined in this way.

  According to the present invention, it is possible to provide an effect that it is possible to provide a communication system and a communication control method capable of suppressing the amount of calculation processing related to channel assignment under communication by cooperative diversity.

It is a figure which shows the structural example of the communication system in this embodiment. It is a figure which shows the structural example of the access point in this embodiment. It is a figure which shows the structural example of the terminal device in this embodiment. It is a figure which shows the structural example of the control apparatus in this embodiment. It is a flowchart which shows the example of a process sequence which the access point in this embodiment performs for the update and notification of a channel priority. It is a flowchart which shows the example of a process sequence which the access point in this embodiment performs according to the connection instruction information transmitted from the control apparatus. It is a flowchart which shows the example of a process sequence which the terminal device in this embodiment performs in relation to channel allocation. It is a flowchart which shows the example of a process sequence for the control apparatus in this embodiment to acquire the channel priority for every access point. It is a flowchart which shows the example of a process sequence for the channel allocation which the control apparatus in this embodiment performs in response to the communication request from a terminal device.

<Configuration example of communication system>
FIG. 1 shows a configuration example of a communication system in the present embodiment. As shown in the figure, the communication system in the present embodiment includes a plurality of access points (AP) 100, a plurality of terminal devices (STA) 200, and a control device (CC: Control Center) existing in one communication control area 1. ) 300.
The access point 100 is a communication device that functions as a base station in a wireless local area network (LAN), for example, and performs wireless communication with the terminal device 200 in its own cell. The cell corresponds to the reach of the radio wave transmitted by the access point 100 and is a range in which the access point 100 can communicate with the terminal device 200.
The access point 100 can communicate with other access points 100 by radio.
The access point 100 is connected to another network, for example, by wire.

  The access point 100 according to the present embodiment performs communication with the terminal device 200 by a wireless access method using, for example, OFDMA (Orthogonal Frequency Division Multiple Access). In OFDMA, a plurality of channels (subcarriers) that are orthogonal to each other are provided, and the access point 100 performs communication by assigning different channels to each of the terminal devices 200.

The terminal device 200 performs wireless communication with the access point 100. The terminal device 200 can communicate with a server, a terminal, or the like connected to another network by communication via the access point 100.
The terminal device 200 is, for example, a mobile phone, a smartphone, a tablet terminal, a personal computer, or the like. As the terminal device 200 of this embodiment, a mobile body may be sufficient and it may be installed fixedly.

The control device 300 controls the access point 100 arranged in the communication control area 1. In the present embodiment, the control device 300 and the access point 100 in the communication control area 1 may be connected by wire. For example, at least a part of the access point 100 may be connected to the control device 300 by radio.
The communication control area 1 is a communication range covered by each cell of the access point 100 managed by the control device 300.

  In the communication system of this embodiment, communication by cooperative diversity is performed in which a plurality of peripheral access points 100 cooperate and transmit / receive simultaneously. By performing cooperative diversity, the communication range is expanded, and even the terminal device 200 located at a distance far from the access point 100 can perform communication.

  In addition, in the communication system according to the present embodiment, with the configuration described below, a channel used for communication between the access point 100 and the terminal device 200 is assigned while maintaining cooperative diversity.

[Example of access point configuration]
FIG. 2 shows a configuration example of the access point 100 in the present embodiment. The access point 100 shown in the figure includes an antenna 101, a communication unit 102, a co-channel interference state measurement unit 103, a channel priority order processing unit 104, a channel priority order table storage unit 105, and a terminal-compatible communication control unit 106.

The antenna 101 transmits and receives radio waves corresponding to the wireless LAN. Note that a plurality of antennas 101 may be provided corresponding to, for example, MIMO (Multiple-Input and Multiple-Output).
The communication unit 102 executes communication corresponding to the wireless LAN. The communication unit 102 transmits a transmission signal from the antenna 101 as a radio wave. The communication unit 102 inputs a received signal obtained according to the radio wave received by the antenna 101.

The co-channel interference situation measuring unit 103 measures the co-channel interference situation for each channel.
In the case where a plurality of channels (subcarriers) are allocated to the terminal device 200 as in the present embodiment, the number of channels is finite. For this reason, for example, when a plurality of access points 100 are close to each other and cells of adjacent access points 100 are overlapped, co-channel interference may occur in a situation where there are many terminal devices 200. . The co-channel interference is radio wave interference that occurs in a shared channel when a plurality of access points 100 share the same channel.
Hereinafter, co-channel interference may also be referred to as CCI (Co-Channel Interface).
In this embodiment, “channel” and “subcarrier” are synonymous. More specifically, one channel corresponds to one of a plurality of subcarriers having different frequency bands in the communication band.

The co-channel interference situation measuring unit 103 measures the average CCI power as the co-channel interference situation for each channel. The co-channel interference situation measurement unit 103 measures the average CCI power as follows, for example.
The co-channel interference situation measurement unit 103 measures instantaneous CCI power for each channel. In measuring instantaneous CCI power, the co-channel interference state measurement unit 103 may use a signal for each channel transmitted and received by the communication unit 102. The co-channel interference situation measurement unit 103 performs instantaneous CCI power measurement at a predetermined time interval.
Note that the method for measuring the instantaneous CCI power by the co-channel interference situation measuring unit 103 in the present embodiment is not particularly limited, and any of various known methods may be employed, for example.
Then, the co-channel interference situation measurement unit 103 calculates the average CCI power by obtaining a moving average of instantaneous CCI power measured at regular intervals. Alternatively, the co-channel interference situation measurement unit 103 may calculate the average CCI power using the forgetting count.
The co-channel interference situation measurement unit 103 uses the average CCI power obtained as described above as a measurement result for the co-channel interference situation.

The channel priority processing unit 104 updates the channel priority indicating the channel priority based on the co-channel interference situation for each channel.
That is, the channel priority processing unit 104 updates the channel priority based on the average CCI power obtained as described above. Here, the channel priority is a priority for a channel to be used by the access point 100 when trying to reduce the average CCI power as much as possible.
As the channel priority, the average CCI power decreases as the rank increases. That is, the access point 100 may give the highest priority for the channel with the lowest average CCI power, and thereafter give a priority that decreases as the average CCI power increases.
The channel priority processing unit 104 updates the channel priority table stored in the channel priority table storage unit 105 when updating the channel priority. The channel priority table is a table having a structure in which one channel is associated with each priority.

  The channel priority processing unit 104 notifies the control device 300 of the channel priority. When notifying the controller 300 of the channel priority, the channel priority processor 104 transmits channel priority information indicating the channel priority indicated by the updated channel priority table via the communicable access point 100. 300 may be transmitted.

The terminal-compatible communication control unit 106 is a part that executes control related to wireless communication with the terminal device 200.
In channel assignment in the present embodiment, the connection destination terminal device and the assigned channel are notified from the control device 300 to the access point 100. The terminal-compatible communication control unit 106 transmits a beacon for communicating with the terminal device 200 as the connection destination terminal device using the notified allocation channel based on the notified connection destination terminal device and the allocation channel.

[Configuration example of terminal device]
FIG. 3 shows a configuration example of the terminal device 200 in the present embodiment. The terminal device 200 shown in the figure includes an antenna 201, a communication unit 202, a communication state index measurement unit 203, a candidate access point determination unit 204, a communication request processing unit 205, and an access point corresponding communication control unit 206.

The antenna 201 transmits and receives radio waves corresponding to the wireless LAN. Note that a plurality of antennas 201 may be provided corresponding to, for example, MIMO (Multiple-Input and Multiple-Output).
The communication unit 202 executes communication corresponding to the wireless LAN.

The communication state index measuring unit 203 measures a predetermined communication state index indicating a communication state with each of the access points 100.
The communication state index measurement unit 203 in the present embodiment measures received power (beacon received power) when a beacon transmitted from the access point 100 is received as a communication state index. Alternatively, the communication state index measurement unit 203 may measure the distance from the access point 100 as a communication state index based on, for example, the received electric field strength when a beacon transmitted from the access point 100 is received. In the following description, a case where the communication state index measurement unit 203 measures beacon received power as a communication state index will be described as an example.

Candidate access point determination section 204 determines a candidate access point based on beacon reception power that is a communication state index measured by communication state index measurement section 203.
A candidate access point is an access point that is a candidate for a connection destination access point of the terminal device 200.
Candidate access point determination unit 204, from among the access point 100 to determine the beacon received power, determines the N _t pieces of the access point 100, which is predetermined as a candidate access point. For example, the maximum number of access points 100 capable of cooperation in cooperation diversity is determined in advance. The number N _t of the candidate access point may be, for example, the maximum number of coordination that is accessible point 100.

The communication request processing unit 205 transmits a communication request for requesting communication with the access point 100 to the control device 300. The communication request processing unit 205 includes a terminal identifier, candidate access point information, and communication state information in the communication request.
The terminal identifier is an identifier that uniquely indicates the terminal device 200 as its own device. In the present embodiment, the terminal identifier is a number (terminal device number) assigned to each terminal device 200.
The candidate access point information indicates the access point number (identifier) of the candidate access point determined by the candidate access point determination unit 204.
The communication state information regarding the candidate access point is information indicating the communication state between the terminal device 200 that is the transmission source of the communication request and the access point 100. The communication state information is information derived based on the beacon received power (communication state index) of each candidate access point measured by the communication state index measurement unit 203. Specifically, the communication state information of the present embodiment is the maximum value (beacon reception power maximum value) of the beacon reception power of each candidate access point measured by the communication state index measurement unit 203.
Further, the communication request processing unit 205 receives a response (ACK or NACK) to the communication request transmitted from the control device 300.

The access point compatible communication control unit 206 performs communication with the access point 100 as the connection destination access point using the assignment channel according to the assignment channel and the connection destination access point notified from the control device 300 in response to the communication request. To do.
In the present embodiment, the control device 300 transmits an ACK (ACKnowledgement) in response to the communication request to the terminal device 200 including the allocated channel and the connection destination access point.
When there is no access point 100 that can communicate with the terminal device 200, the control device 300 transmits a NACK (Negative ACKnowledgement) as a response to the communication request. Thus, when NACK is transmitted, the access point corresponding | compatible communication control part 206 of the terminal device 200 stops communication with the access point 100. FIG.

[Configuration example of control device]
FIG. 4 shows a configuration example of the control device 300 in the present embodiment. The control device 300 shown in the figure includes a communication unit 301, a channel priority order acquisition unit 302, a master access point determination unit 303, an allocated channel determination unit 304, a connection destination access point determination unit 305, a response processing unit 306, and a connection instruction unit 307. Is provided.

  The communication unit 301 performs communication with each of the access points 100 in the communication control area 1. As described above, the communication between the communication unit 301 and the access point 100 may be performed via a wire. For example, the communication unit 301 and at least a part of the access point 100 may perform communication wirelessly. Also good.

  The channel priority acquisition unit 302 acquires the channel priority from the channel priority information transmitted from the access point 100.

The master access point determination unit 303 determines a candidate access point that satisfies a certain condition from among the candidate access points indicated by the candidate access point information included in the communication request as a master access point corresponding to the terminal device that has transmitted the communication request. To do.
The master access point is an access point 100 serving as a reference for determining an allocation channel among a plurality of access points 100 that should communicate with the terminal device 200 that has transmitted the communication request by cooperative diversity.

Specifically, the master access point determination unit 303 determines, as a master access point, a candidate access point having the best communication state with the terminal device 200 that is the transmission source of the communication request from among candidate access points having an empty channel. . In this embodiment, the master access point determination unit 303 determines a candidate access point having the maximum beacon reception power as a master access point among candidate access points having an empty channel.
As described above, in the present embodiment, a candidate access point having the best communication state with the terminal device 200 that is the transmission source of the communication request among candidate access points having an empty channel is determined as the master access point. By determining the master access point in this way, it is possible to improve the reliability in determining the allocation channel.

The allocation channel determination unit 304 determines an allocation channel to be allocated to the access point 100 that performs communication by cooperative diversity with the terminal device 200 that is the transmission source of the communication request.
In the access point 100, the channel priority processing unit 104 notifies the control device 300 of the channel priority as described above.
Allocation channel determination section 304 determines an allocation channel from among the free channels of the master access point based on the channel priority notified from the access point. Specifically, the assigned channel determination unit 304 determines, as an assigned channel, an available channel with the highest channel priority notified by the master access point from among available channels of the master access point.

The connection destination access point determination unit 305 determines a connection destination access point corresponding to the terminal device 200 that is the transmission source of the communication request. The connection destination access point is an access point 100 that the terminal device 200 should be a communication partner (connection destination) for performing the communication requested by the communication request transmitted by the terminal device 200. A plurality of access points 100 are determined as connection destination access points.
The plurality of access points determined as connection destination access points are access points 100 that perform simultaneous communication in cooperation with each other for cooperation diversity in communication with the terminal device 200 that is the transmission source of the communication request.

  The connection destination access point determination unit 305 determines, from among the candidate access points indicated by the candidate access point information included in the communication request, a candidate access point for which the allocated channel determined by the allocation channel determination unit 304 is empty as a connection destination access point. To do.

As a response to the communication request, the response processing unit 306 uses the allocation channel determined by the allocation channel determination unit 304 and the connection destination access point determined by the connection destination access point determination unit 305 as the terminal device that is the transmission source of the communication request 200 is notified.
As described above, when notifying the allocation channel and the connection destination access point, the response processing unit 306 includes information indicating the allocation channel and the connection destination access point in the ACK that is a response to the communication request, and transmits the information to the terminal device 200. Send. In this way, the terminal device 200 is notified of the allocation channel and the connection destination access point together with a response to the communication request.

The connection instruction unit 307 transmits connection instruction information indicating the connection destination terminal device and the assigned channel to each of the access points 100 determined as the connection destination access point by the connection destination access point determination unit 305.
The connection destination terminal device is a terminal device 200 to which the access point 100 determined as the connection destination access point should be a communication partner (connection destination) in communication by cooperative diversity. That is, the connection destination terminal device is the terminal device 200 that is the transmission source of the communication request.
Further, the allocation channel included in the connection instruction information is a channel to be used when the access point 100 determined as the connection destination access point performs communication by cooperation diversity with the terminal device 200 as the connection destination terminal device. Therefore, the allocation channel included in the connection instruction information may be the same as the allocation channel determined by the allocation channel determination unit 304.

[Example of access point processing procedure]
With reference to the flowchart of FIG. 5, an example of a processing procedure executed by the access point 100 of the present embodiment for channel priority update and notification will be described.
In FIG. 5, AP indicates the access point 100, STA indicates the terminal device 200, and CC (Control Center) indicates the control device 300. The same applies to FIGS. 6 to 9 described below.

In the access point 100, the co-channel interference state measurement unit 103 receives a beacon transmitted by another access point 100 in the vicinity (step S101).
The co-channel interference state measurement unit 103 measures the instantaneous CCI power of each channel using the beacon reception power measured for the beacon received in step S101 (step S102).

Next, the co-channel interference situation measurement unit 103 calculates the average CCI power of each channel using the instantaneous CCI power of each channel measured in step S102 (step S103).
The average CCI power can be obtained by the following Equation 1.

  The term on the left side in Equation 1 represents the average CCI power of the ch-th channel at time t for the m-th access point. On the right side, the term in which the letter I is not overlined represents the instantaneous CCI power. β is a forgetting count and can take a value in the range of 0 <β <1. That is, Equation 1 is an example of obtaining the average CCI power using the forgetting count.

Next, the channel priority processing unit 104 updates the channel priority shown in the channel priority table based on the average CCI power calculated in step S103 (step S104). The channel priority table value P _m for the m th access point can be expressed by Equation 2 below.

In Equation 2, P _k represents a channel number, and N _ch represents the total number of channels. The channel priority processing unit 104 may update the channel priority table represented as Equation 2 so as to satisfy the following Equation 3 using the average CCI power obtained by Equation 1.

The channel priority processing unit 104 transmits channel priority information indicating the channel priority updated in step S104 to the control device 300 (step S105).
The access point 100 executes the process shown in FIG.

Next, an example of a processing procedure executed by the access point 100 according to the connection instruction information transmitted from the control device 300 will be described with reference to the flowchart of FIG.
In the access point 100, the communication unit 102 receives the communication instruction information transmitted from the control device 300 (step S111).
The communication instruction information received in step S111 includes a connection destination terminal device number indicating a connection destination terminal device and an allocation channel number indicating a channel number as an allocation channel. The terminal-compatible communication control unit 106 acquires the connection destination terminal apparatus number and the assigned channel number from the received communication instruction information (Step S112).

  Here, when there is no free channel that can be used as the allocation channel, a value indicating that there is no allocation channel is stored in the allocation channel area in the communication instruction information. Therefore, the terminal-compatible communication control unit 106 determines whether or not there is one or more assigned channels as a result of obtaining the assigned channel number in step S112 (step S113).

  When it is determined that there is an allocation channel (step S113: YES), the terminal-compatible communication control unit 106 transmits a beacon by each of the allocation channels acquired from the communication instruction information (step S114).

  On the other hand, when it is determined that there is no assigned channel (step S113—NO), the terminal-compatible communication control unit 106 refers to the channel priority table currently stored in the channel priority table storage unit 105. And the terminal corresponding | compatible communication control part 106 transmits a beacon by the channel with the highest priority in a channel priority table (step S115).

If the terminal device 200 of the connection destination terminal device number included in the communication instruction information responds to the beacon transmission in step S114 or step S115, the terminal-compatible communication control unit 106 performs processing for establishing a connection. Run. If the connection is established, the terminal-compatible communication control unit 106 performs control so that communication by cooperative diversity in cooperation with another access point 100 is performed thereafter.
The access point 100 executes the processing shown in FIG. 5 every time communication instruction information is received from the control device 300.

[Terminal device processing procedure example]
Next, an example of a processing procedure executed by the terminal device 200 in association with channel assignment will be described with reference to the flowchart of FIG.
In the terminal device 200, the communication state index measuring unit 203 measures the beacon reception power for the beacon transmitted by each access point 100 as the communication state index (step S201). Here, the beacon reception power of the mth access point at time t measured by the uth terminal apparatus 200 is represented by P _{u, m} (t).

Next, candidate access point determination section 204 determines N _t access points 100 as candidate access points in the descending order of beacon reception power received in step S201 (step S202).

  Here, in step S202, the candidate access point determined by the u-th terminal apparatus 200 can be expressed by the following Equation 4.

In Equation 4, n _{u, k} represents the kth (0 ≦ k ≦ N _t −1) th candidate access point corresponding to the uth terminal device 200. Candidate access point determination section 204 can select N _t access points 100 as candidate access points so that the following Expression 5 holds for beacon reception power for each candidate access point.

Next, the communication request processing unit 205 determines whether or not to transmit a communication request (step S203).
The communication request processing unit 205 may determine whether to transmit a communication request based on, for example, the current operation state of the terminal device 200. The communication request processing unit 205 determines that a communication request should be transmitted if it is necessary to execute communication as the current operation state, and should not be transmitted if communication is not necessary as the current operation state. Is determined.

  When it is determined that the communication request should not be transmitted (step S203—NO), the communication request processing unit 205 ends the process illustrated in FIG. 6 without transmitting the communication request.

  On the other hand, when it is determined that a communication request should be transmitted (step S203—YES), the communication request processing unit 205 transmits a communication request to the control device 300 (step S204). When the communication request processing unit 205 transmits the communication request in step S203, the communication request includes each of its own terminal device number, candidate access point number (candidate access point information), and beacon received power maximum value (communication state information). Include information.

The own terminal device number included in the communication request is a terminal device number indicating the terminal device 200 as the own device.
The candidate access point number included in the communication request is an access point number for each access point determined as a candidate access point in step S202. Note that the candidate access point number included in the communication request is in a format represented by, for example, Expression 4, and is attached according to the magnitude of the beacon reception power. Therefore, depending on the candidate access point number as the candidate access point information, the magnitude relationship of the beacon reception power between the candidate access points is also expressed.
The maximum beacon reception power included in the communication request is the beacon reception power of the first access point having the maximum beacon reception power among the candidate access points. The maximum beacon reception power value is represented by the rightmost term in Equation 5 above.

The control device 300 that has received the communication request transmitted in step S204 transmits ACK or NACK as a response.
Therefore, the communication request processing unit 205 of the terminal device 200 determines whether the response received in response to the transmission of the communication request is ACK or NACK (step S205).

  When the received response is NACK (step S205—NACK), the access point corresponding communication control unit 206 stops communication using the access point 100 as a connection destination thereafter (step S206).

On the other hand, when the received response is ACK (step S205-ACK), the access point corresponding communication control unit 206 acquires the following information from the received ACK.
That is, the ACK includes a connection destination access point number indicating the number of the connection destination access point determined by the control device 300 in response to the communication request, and an allocation channel number indicating the channel number of the allocation channel allocated to the terminal device 200. It is included.
The connection destination access points determined in response to the communication request are, for example, a plurality of access points that are to communicate with the terminal device 200 that is the transmission source of the communication request by cooperative diversity.
Therefore, the access point compatible communication control unit 206 acquires a connection destination access point number and an assigned channel number from the received ACK (step S207).

The access point compatible communication control unit 206 selects the channel indicated by the assigned channel number acquired in step S207 as the use channel (step S208).
The access point compatible communication control unit 206 starts communication with the access point 100 indicated by the connection destination access point number acquired from the ACK, using the channel selected as the use channel in step S208 (step S209).

[Control device processing procedure example]
Next, an example of a processing procedure for the control device 300 to acquire the channel priority for each access point 100 will be described with reference to the flowchart of FIG.
The communication unit 301 in the control device 300 receives the channel priority information transmitted from the access point 100 in step S105 of FIG. 5 (step S301).

The channel priority acquisition unit 302 acquires the channel priority indicated by the channel priority information received in step S301 in association with the access point 100 that is the transmission source of the channel priority information (step S302). As a specific example, the channel priority order acquisition unit 302 acquires the channel priority order in the format represented by Equation 2 in step S302.
The control device 300 executes the processing shown in FIG.

  Next, a processing procedure example for channel assignment executed by the control device 300 in response to a communication request from the terminal device 200 will be described with reference to a flowchart of FIG.

In the control device 300, for example, the master access point determination unit 303 waits for reception of the communication request transmitted in step S204 in FIG. 7 (step S311-NO).
Then, the master access point determination unit 303 executes the following process in response to the communication request being received (step S311-YES). That is, the master access point determination unit 303 includes each information of a request source terminal device number, a candidate access point number (candidate access point information), and a beacon reception power maximum value (communication state information) included in the received communication request. Is acquired (step S312). The request source terminal device number is the own terminal device number included in the communication request transmitted in step S204 of FIG.

The request source terminal device number acquired by the master access point determination unit 303 in step S312 is represented as u _req . The candidate access point number acquired from the communication request of the terminal device 200 that is the u _req request source can be expressed as in Equation 6 below.

In Equation 6, k (0 ≦ k ≦ N _t −1) corresponds to each candidate access point number. And the relationship between the order of the candidate access point numbers acquired from the communication request and the beacon reception power measured for the beacon received corresponding to each candidate access point by the requesting terminal device 200 is expressed by the following Expression 7. It is expressed as follows.

  Further, the maximum beacon reception power value acquired from the communication request is represented by the rightmost term in Equation 7.

After the process of step S312, the master access point determination unit 303 determines whether or not the process of step S312 for communication requests from all the request source terminal devices 200 has been completed (step S313).
If the process has not yet been completed (step S313—NO), the master access point determination unit 303 returns the process to step S311. On the other hand, if processing for communication requests from all requesting terminal devices 200 has been completed (step S313-YES), the following processing is executed.

The master access point determination unit 303 rearranges the request source terminal device numbers corresponding to each request source terminal device 200 in ascending order of the maximum beacon received power acquired from the communication request in step S312 (step S314). .
Here, the number of request source terminal devices 200 is U _req, and a set of request source terminal device numbers is expressed by the following Expression 8.

  Further, the master access point determination unit 303 obtains a set of request source terminal device numbers obtained by rearranging the set of request source terminal device numbers represented by Equation 8 in ascending order of maximum beacon received power. This is represented by Equation 9.

  The magnitude relationship of the beacon reception power of the terminal device 200 corresponding to each request source terminal device number corresponding to Equation 9 is expressed by Equation 10 below.

Next, the control device 300 executes loop processing LP1. The loop process LP1 is repeatedly executed in the order of k = 0, 1,..., U _req −1 with _respect to the terminal device 200 that is the u ′ _k th request source. That is, in the loop process LP1, processing targets are selected in order from the requesting terminal device 200 having the smallest beacon received power maximum value.

In the loop process LP1, first, the loop process LP2 is executed.
The loop processing LP2 is executed in the order of l = 0, 1,..., N _t −1 for the l-th candidate access point corresponding to the u ′ _k- th requesting terminal device 200. Here, as shown in Expression 6 and Expression 7, the beacon reception power of the candidate access points decreases in the order of l = 0, 1,..., N _t −1. Therefore, the loop processing LP2 is executed with candidate access points as processing targets in descending order of beacon reception power.

In the loop processing LP2, the master access point determination unit 303 determines whether or not there is a free channel in the l-th (n _{u′k, l-} th) candidate access point corresponding to the u ′ _k- th request source terminal device 200. Is determined (step S315).

In the determination in step S315, for example, the master access point determination unit 303 _{inquires the nu′k, l-} th candidate access point for the state of an empty channel through communication via the communication unit 301, and sends a response to the inquiry. It only has to be received. In the received response, the presence / absence of an empty channel at the n _{u′k, lth} candidate access point is indicated, and if there is an empty channel, the channel number of the empty channel is indicated.
Alternatively, in the channel priority order information received by the processing of FIG. 8 above, for example, information indicating whether or not there is an empty state for each priority order may be included. In this case, the master access point determination unit 303 determines whether there is a free channel by using the free state information for each priority indicated in the channel priority information received from the n _{u′k, l} th candidate access point. It can be determined whether or not.

When there is no free channel (step S315—NO), the master access point determination unit 303 determines whether or not the variable l corresponding to the candidate access point number is equal to N _t −1 (step S316).
If the variable l is less than N _t −1 (step S316—NO), the master access point determination unit 303 increments the variable l and then returns to step S315. As a result, a determination is made as to whether or not there is an empty channel in the candidate access point of the next number.

If it is determined in step S316 that the variable l is equal to N _t −1 (step S316—YES), there is no empty channel in any of the candidate access points. In this case, the requesting terminal device 200 cannot perform communication in response to the communication request. Therefore, in this case, it sends a NACK against u _'k th requesting terminal apparatus 200 (step S317).
The NACK transmitted in this way is received corresponding to step S205 of FIG.
After the NACK is transmitted in step S317, if processing for the next requesting terminal device 200 remains, loop processing LP2 is executed for the requesting terminal device 200 of the next number. The

On the other hand, when it is determined that there is an empty channel (step S315—YES), the master access point determination unit 303 determines the n _{u′k, l} th candidate access point as the u ′ _k th request source terminal device 200. Is determined as a master access point corresponding to (step S318).
Regarding loop processing LP2, even if a candidate access point with an older number still remains after that, it is determined in step S315 that the _{nu′k, l-} th candidate access point has an empty channel. It may be completed with. That is, the loop process LP2 may be terminated when an access point as a master access point is specified.

As described above, the master access point determination unit 303 determines a candidate access point having the maximum beacon reception power as a master access point among candidate access points having an empty channel. That is, the master access point determination unit 303, from among the candidate access point having a free channel, the communication state between u _'k th requesting terminal apparatus 200 determines the best access point 100 as the master access point.

Next, the allocated channel determination unit 304 selects a free channel having the highest channel priority among the free channels at the master access point determined in step S318 (step S319).
In selecting a free channel with the highest channel priority in step S319, the allocated channel determination unit 304 determines the channel priority for the master access point from the channel priorities acquired by the process in step S302 of FIG. Refer to the ranking.
That is, the assigned channel determination unit 304 may check the channel priority for each empty channel recognized corresponding to the previous step S315, and select the empty channel with the highest channel priority as a result of the comparison.

  Subsequent to step S319, loop processing LP3 is executed. The loop process LP3 is a process of determining a channel (allocation channel) to be allocated to the requesting terminal device 200 and the connection destination access point and an access point (connection destination access point) to be connected to the requesting terminal device 200. is there.

Similarly to the loop process LP2, the loop process LP3 is also executed in the loop process LP1, and corresponding to the terminal device 200 of the u ′ _kth request source, l = 0, 1,..., N _t −1. It is executed in order of candidate access points with numbers. In addition, the loop process LP3 is executed with each candidate access point having a number of l = 0, 1,..., N _t −1 being processed (that is, the master access point is also included in the process target). .

In the loop process LP3, the allocation channel determination unit 304 determines whether or not a channel having the same number as the empty channel selected in step S319 is vacant at the _{nu′k, lth} candidate access point (step S320). .
When the same channel as the selected vacant channel is not vacant in the n _{u′k, l-} th candidate access point (step S320—NO), the assigned channel determination unit 304 performs the step for the next number of candidate access points. The determination process of S320 is executed.

On the other hand, when the same channel as the selected vacant channel is vacant at the _{nu′k, l-} th candidate access point (step S320—YES), the allocated channel determination unit 304 executes the following processing.
That is, the assigned channel determining unit 304 determines the channel having the same number as the selected empty channel as the assigned channel of the n _{u′k, l-} th candidate access point (step S321).

Further, the connection destination access point determination unit 305 determines the n _{u′k, l} th candidate access point as the connection destination access point of the u ′ _k th requesting terminal device 200 (step S322).
If the candidate access point to be processed still remains after the process of step S322 is completed, the processes after step S320 are executed for the candidate access point of the next number.

Then, at the stage where the processing for each candidate access point numbered by l = 0, 1,..., N _t −1 is completed by the loop processing LP3, the following state is obtained.
That is, a vacant candidate access point is determined as a connection destination access point of the requesting terminal device 200 for the channel having the same number as the vacant channel selected in step S319. Also, an allocation channel to be used between the request source terminal device 200 and the connection destination access point is determined.

Accordingly, in response to the end of the loop processing LP3, the response processing unit 306 indicates the allocated channel number indicating the determined allocated channel and the connection destination access point to the _u′k- th requesting terminal device 200. The access point number of the connection destination is included in the ACK.
The response processing section 306, an ACK allocation channel number and the destination access point number is included as described above, to the u _'k th requesting terminal apparatus 200 (step S323).
Requesting terminal apparatus 200 of u _'k-th ACK is received, as indicated as step S207~S209 of FIG. 7, using the channel specified by the allocation channel number contained in the ACK, the connection destination access Communication is performed with the access point 100 indicated by the point number. As a result, a state is obtained in which the plurality of access points 100 indicated by the connection destination access point numbers communicate with the _u′k- th requesting terminal device 200 by cooperative diversity.

  If the requesting terminal device 200 of the next number still remains after the processing of step S323 is completed, the process returns to step S315 to allocate the requesting terminal device 200 of the next number as an object. A channel and a connection destination access point are determined.

Then, at the stage where the loop processing LP1 is executed with all the request source terminal devices 200 as processing targets, the allocation channel, the connection destination access point, Has been determined.
Therefore, the connection instruction unit 307 transmits connection instruction information to each of the access points determined as connection destination access points (step S324). The connection instruction unit 307 includes, in the connection instruction information to be transmitted, an allocation channel number determined corresponding to the transmission destination access point and a connection destination indicating the requesting terminal device 200 with which the transmission destination access point should communicate. Include terminal device number.

  As described above, the access point 100 that has received the connection instruction information transmits a beacon for communication with the terminal device 200 indicated by the connection destination terminal device number by the process shown in FIG.

As can be understood from the above description, in this embodiment, the channel priority information used independently by the access point 100 under the CS-DCA is transmitted to the control device 300. Yes.
In addition, the terminal device 200 according to the present embodiment transmits the candidate access point information determined based on the beacon reception power and the beacon reception power maximum value (communication state information) in the communication request.
Then, the control device 300 determines the access point 100 having the best communication state with the requesting terminal device 200 (the highest beacon reception power) from among the candidate access points having free channels as the master access point.
In addition, the control device 300 determines an empty channel having the highest channel priority in the determined master access point, that is, an empty channel in the master access point, as an assigned channel. In addition, the control device 300 determines a candidate access point that includes the master access point and whose assigned channel is an empty channel as a connection destination access point of the terminal device 200 that is the communication request transmission source.
Then, the control device 300 notifies the access point 100 and the terminal device 200 of the assigned channel determined as described above.

As described above, in the communication system according to the present embodiment, only the master access point is taken into consideration, and the combination of the terminal device 200 and the group of access points 100 communicating by channel assignment and cooperative diversity is determined. Thereby, in this embodiment, it is possible to reduce the amount of calculation processing for channel allocation.
Further, in the communication system of the present embodiment, as shown as step S319 in FIG. 9, the channel priority order at the master access point is reflected when the assigned channel is determined. That is, in the present embodiment, a channel allocation method based on CS-DCA Channel Segregation-Dynamic Channel Assignment can be applied to a communication system in which the access point 100 communicates with the terminal device 200 by cooperative diversity. Thereby, in the communication system of this embodiment, it becomes possible to allocate a channel so that co-channel interference may be suppressed.

Further, in the communication system of the present embodiment, the master access points are determined in the order of the terminal device 200 with the smallest beacon reception power maximum value, as shown as step S314 and loop processing LP1 in FIG. That is, the master access point determination unit 303 determines the master access points in order from the terminal device that is the transmission source of the communication request whose communication state indicated by the communication state information included in the communication request is not good.
In response to this, the allocation channel determination unit 304 determines the allocation channel in the order of the master access points determined by the master access point determination unit 303.
By allocating channels in such an order, in the present embodiment, channel allocation is preferentially performed from the terminal device 200 having a poor communication state indicated by the communication state information included in the communication request.
As a result, the terminal device 200 having an unsatisfactory communication state is advantageous as a channel assignment condition, and the communication states of the plurality of terminal devices 200 that are the request sources of the communication requests are leveled. As a result, it is possible to improve communication quality in the entire communication system.

  In addition, you may make it implement | achieve each function of the access point 100 in the embodiment mentioned above, the terminal device 200, and the control apparatus 300 with a computer. In that case, a program for realizing these functions may be recorded on a computer-readable recording medium, and the program recorded on the 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 a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Access point, 101 ... Antenna, 102 ... Communication part, 103 ... Co-channel interference condition measurement part, 104 ... Channel priority processing part, 105 ... Channel priority table storage part, 106 ... Terminal corresponding | compatible communication control part, 200 ... Terminal device, 201 ... antenna, 202 ... communication unit, 203 ... communication state index measurement unit, 204 ... candidate access point determination unit, 205 ... communication request processing unit, 206 ... access point compatible communication control unit, 300 ... control device, 301 ... Communication unit, 302 ... Channel priority order acquisition unit, 303 ... Master access point determination unit, 304 ... Allocated channel determination unit, 305 ... Connection destination access point determination unit, 306 ... Response processing unit, 307 ... Connection instruction unit

Claims (5)

A communication system comprising a plurality of access points, one or more terminal devices, and a control device,
The access point is
A channel priority processing unit that updates the channel priority indicating the channel priority based on the status of the same channel interference for each channel, and notifies the controller of the channel priority;
A terminal-compatible communication control unit that transmits a beacon for performing communication with the connection destination terminal device through the notified allocation channel based on information on the connection destination terminal device and the allocation channel notified from the control device. ,
The terminal device
A communication state index measuring unit that measures a predetermined communication state index indicating a communication state with each of the access points;
A communication request processing unit that transmits a communication request including candidate access point information indicating a candidate access point determined based on the communication state index measured by the communication state index measurement unit, to the control device;
An access point corresponding communication control unit that performs communication with the connection destination access point using the allocation channel according to the allocation channel and the connection destination access point notified from the control device in response to the communication request. ,
The controller is
Master access that determines a candidate access point having the maximum signal reception power as a master access point corresponding to the terminal device that is the transmission source of the communication request from among the candidate access points indicated by the candidate access point information included in the communication request A point determination unit;
An allocation channel determination unit that determines an allocation channel from among the free channels of the master access point based on the channel priority notified from the access point;
Of the candidate access points indicated by the candidate access point information included in the communication request, a connection destination that determines a candidate access point with an empty allocation channel as a connection destination access point corresponding to the terminal device that is the transmission source of the communication request An access point determination unit;
As a response to the communication request, a response for notifying the allocation channel determined by the allocation channel determination unit and the connection destination access point determined by the connection destination access point determination unit to the terminal device that is the transmission source of the communication request A processing unit;
A communication system comprising: a connection instruction unit that transmits connection instruction information indicating a connection destination terminal device and an allocated channel to each of the access points determined as connection destination access points by the connection destination access point determination unit. The communication request processing unit
The control request includes the communication request further including communication status information indicating a communication status between a terminal device that is a transmission source of the communication request and an access point derived based on the communication status index measured by the communication status index measuring unit. To
The master access point determination unit
The master access point is determined in order from the terminal device that is the transmission source of the communication request in which the communication state indicated by the communication state information included in the communication request is not good.
The allocation channel determination unit includes:
The communication system according to claim 1, wherein allocation channels are determined in order of master access points determined by the master access point determination unit. The master access point determination unit
The communication system according to claim 1 or 2, wherein a candidate access point having the best communication state with a terminal device that is a transmission source of the communication request is determined as a master access point from candidate access points having an empty channel. The allocation channel determination unit includes:
The communication system according to any one of claims 1 to 3, wherein an empty channel having the highest channel priority notified by the master access point is determined as an allocation channel among the empty channels of the master access point. A communication control method in a communication system comprising a plurality of access points, one or more terminal devices, and a control device,
The access point is
A channel priority processing step of updating the channel priority indicating the priority of the channel based on the status of the same channel interference for each channel, and notifying the controller of the channel priority;
A terminal-compatible communication control step of transmitting a beacon for communicating with the connection destination terminal device using the notified allocation channel based on information on the connection destination terminal device and the allocation channel notified from the control device. ,
The terminal device
A communication state index measuring step of measuring a predetermined communication state index indicating a communication state with each of the access points;
A communication request processing step of transmitting a communication request including candidate access point information indicating a candidate access point determined based on the communication state index measured by the communication state index measuring step to the control device;
An access point corresponding communication control step for performing communication with the connection destination access point using the allocation channel according to the allocation channel and the connection destination access point notified from the control device in response to the communication request. ,
The controller is
Master access that determines a candidate access point having the maximum signal reception power as a master access point corresponding to the terminal device that is the transmission source of the communication request from among the candidate access points indicated by the candidate access point information included in the communication request A point determination step;
An allocation channel determination step of determining an allocation channel from among the empty channels of the master access point based on the channel priority notified from the access point;
Of the candidate access points indicated by the candidate access point information included in the communication request, a connection destination that determines a candidate access point with an empty allocation channel as a connection destination access point corresponding to the terminal device that is the transmission source of the communication request An access point determination step;
As a response to the communication request, a response that notifies the terminal device that is the transmission source of the communication request of the allocation channel determined in the allocation channel determination step and the connection destination access point determined in the connection destination access point determination step Processing steps;
A communication control method comprising: a connection instruction step of transmitting connection instruction information indicating a connection destination terminal apparatus and an assigned channel to each of the access points determined as a connection destination access point by the connection destination access point determination step.

Images