JP2012209836A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of controlling transmission power in an environment where both a wireless device which can control transmission power and a wireless device which cannot control transmission power coexist.SOLUTION: A communication system comprises access points 11-20. The access points 11, 12, 15-20 are access points which control transmission power and access points 13, 14 are access points which do not control transmission power. The access points 11, 12, 15-20 transmit and receive data packets using the transmission power lower than the maximum transmission power Pmax in a doTPC time period of one slot. The access points 13, 14 transmit and receive data packets at the maximum transmission power Pmax in a noTPC time period of one slot.

Description

  The present invention relates to a communication system.

  Wireless LAN (Local Area Network) is widely used in hot spots such as schools and event venues. In order to ensure coverage, wireless LAN access points (APs) are densely installed.

  However, since the number of channels that do not overlap is limited (there are only three channels that do not overlap at 2.4 GHz), many APs share the same channel. As the number of neighboring APs sharing the same channel increases, the co-channel interference problem becomes increasingly severe and the performance of the entire network can be degraded.

  As a method for solving such a problem, transmission power control can be cited. However, transmission power control may cause asymmetric links, unfair channel usage, hidden terminal problems, and the like.

  In Non-Patent Document 1, by using common transmission power on all networks, transmission power is reduced while avoiding asymmetric links.

  In Non-Patent Document 2, all APs are synchronized and the channel is divided into slots along the time axis. Then, all APs transmit with the same power in the same slot, and the transmission power is changed for each slot, thereby improving the efficiency of transmission power control.

  In Non-Patent Document 3, transmission power control is performed so as to ensure a transmission rate while considering the link quality between the AP and the terminal.

  In Non-Patent Document 4, the transmission power of each cell is calculated in consideration of interference between adjacent cells, and the transmission power is adjusted so that the transmission power between adjacent APs on the network changes smoothly according to the AP density. To do.

V. Kawadia, P. R. Kumar, “Principles and protocols for power control in wireless ad hoc networks,” IEEE JSAC, Volume 23, Issue 1, Jan. 2005, Page (s): 76-88. Vishnu Navda, Ravi Kokku, Samrat Ganguly, Samir Das, “Slotted Symmetric Power Control in Wireless LANs,” Stony Brook University, Technical report, 2006. Aditya Akella, Glenn Judd, Srinivasan Seshan, Peter Steenkiste, “Self Management in Chaotic Wireless Deployments,” MobiCom’05, 2005. Suhua Tang, Hiroyuki Yomo, Akio Hasegawa, Mehdad N. Shirazi, Tetsuro Ueda, Ryu Miura, and Sadao Obana, “Improving performance of wireless networks with coordinated transmit power control,” IEICE Technical Report, Vol. 110, No. 19, RCS2010 -11, pp. 61-66, Apr., 2010.

  If the transmission power of all wireless devices can be controlled, the methods disclosed in Non-Patent Documents 1, 2, and 4 can solve the problem of asymmetric links.

  However, in practice, a radio apparatus that can control transmission power and a radio apparatus that cannot control transmission power coexist, and it is difficult to take advantage of controlling transmission power with conventional techniques. is there.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to control transmission power in an environment in which a wireless device that can control transmission power and a wireless device that cannot control transmission power coexist. It is an object of the present invention to provide a communication system that improves the throughput of a wireless device that can control transmission power by controlling the wireless device that can control transmission power without degrading performance without changing the setting of the wireless device that cannot.

  According to the embodiment of the present invention, the communication system includes first to third access points. The first access point transmits data packets by controlling transmission power. The second access point transmits the data packet with the maximum transmission power without controlling the transmission power using the same channel as the channel used in the first access point. The third access point controls transmission power using the same channel as the channel used in the first access point to transmit data packets, and controls the second access point. The third access point includes a first time zone in which the first and third access points transmit data packets in one slot, and a second time zone in which the second access point transmits data packets. A process of broadcasting the divided first and second time zones is executed for each slot, and a data packet is transmitted with a transmission power smaller than the maximum transmission power in the first time zone. Further, the first access point transmits a data packet with a transmission power smaller than the maximum transmission power in the first time zone. Further, the second access point stops transmitting the data packet in the first time zone and transmits the data packet with the maximum transmission power in the second time zone.

  In the communication system according to the embodiment of the present invention, the first and third access points that control transmission power perform radio communication in a different time zone from the second access point that does not control transmission power. As a result, the wireless communication by the first and third access points does not interfere with the wireless communication by the second access point. Even when the first and third access points control transmission power and transmit / receive data packets, an asymmetric link does not occur and throughput is improved. Further, the performance of the second access point does not deteriorate.

  Therefore, throughput can be improved by controlling transmission power in an environment in which a wireless device that can control transmission power and a wireless device that cannot control transmission power coexist.

It is the schematic which shows the structure of the communication system by embodiment of this invention. It is a block diagram of the terminal device 1 shown in FIG. It is a block diagram of the access point shown in FIG. It is a block diagram of the electric power control apparatus shown in FIG. It is a conceptual diagram of an access point of direct adjacent and an access point of indirect adjacent. It is a figure which shows a neighbor list. It is a figure which shows the specific example of CSG. It is a figure which shows the specific example of adjustment of transmission power. It is a figure for demonstrating the method to determine a control access point. It is a figure which shows the calculation example of the access point (AP of no TPC) which does not control the transmission power adjacent to the access point (AP of doTPC) which controls transmission power. It is a flowchart for demonstrating the method to determine a control access point. It is a block diagram of a SAM frame. It is a figure which shows the transmission power control operation | movement in Example 1 between an access point and a terminal device. It is a conceptual diagram of the communication method in embodiment of this invention. 10 is a flowchart for explaining a channel usage rate determination method according to the second embodiment. It is a figure which shows the information which a power control apparatus transmits to an access point. It is a figure which shows the transmission power control operation | movement in Example 2 between an access point and a terminal device.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram showing a configuration of a communication system according to an embodiment of the present invention. Referring to FIG. 1, a communication system 100 according to an embodiment of the present invention includes terminal devices 1 to 9, access points 10 to 21, a network 40, a monitoring server 50, and a power control device 60.

  In the embodiment of the present invention, each of access points 10 to 21 and terminal devices 1 to 9 transmits a control frame (including an ACK for the control frame) with the maximum transmission power.

  The terminal devices 1 to 9 are arranged in the wireless communication space. Each of the terminal devices 1 to 9 includes, for example, a WiFi wireless interface, and connects to any of the access points 10 to 21 in the infrastructure mode by the wireless interface provided.

  In this case, each of the terminal devices 1 to 9 accesses, for example, an access point that maximizes a potential throughput, which is a throughput when an unused channel is used only for wireless communication between itself and the access point. Select as a point.

  And the terminal device which can control transmission power among the terminal devices 1-9 performs radio | wireless communication using the transmission power received from the connected access point.

  In addition, each of the terminal devices 1 to 9 periodically receives a beacon frame from the access points 10 to 21. Then, the terminal device capable of controlling the transmission power creates an adjacent access point list indicating an access point adjacent to itself based on the received beacon frame, and monitors the generated adjacent access point list via the network 40. Send to server 50.

  Each of the access points 10 to 21 includes a WiFi wireless interface. Of the access points 10 to 21, the access points 10 to 12 and 15 to 21 are access points that transmit data packets (including ACKs for them) by controlling transmission power, and the access points 13 and 14 are , An access point that transmits a data packet (including an ACK for it) without controlling the transmission power (ie, using the maximum transmission power).

  As described above, in the communication system 100, the access points 10 to 12 and 15 to 21 that transmit data packets by controlling transmission power, and the access points 13 and 14 that transmit data packets without controlling transmission power, Coexist. Note that the terminal device transmits a data packet with the same power as that of the connection destination access point.

  Each of the access points 10 to 12 and 15 to 21 receives transmission power from the power control device 60, performs wireless communication with the terminal device through the WiFi wireless interface using the received transmission power, and via the network 40. It communicates with the monitoring server 50 and the power control device 60.

  In addition, each of the access points 13 and 14 performs wireless communication with the terminal device using a WiFi wireless interface using the maximum transmission power. Each of the access points 13 and 14 does not transmit various kinds of information to the monitoring server 50 and the power control apparatus 60 via the network 40, and does not receive various kinds of information from the power control apparatus 60 via the network 40.

Further, each of the access points 10 to 21 periodically transmits a beacon frame by wireless communication. In this case, the access point 10～12,15～21 includes a canTPCflag indicating whether it can control the transmission power, and doTPCflag representing whether to control the transmission power, the transmission power value ^{P N} to be used, A TPCIE including the slot length and the channel usage rate is added to the beacon frame Beacon and transmitted. On the other hand, the access points 13 and 14 transmit the normal beacon frame Beacon without adding the TPCIE to the beacon frame Beacon.

  Each of the access points 10 to 12 and 15 to 21 periodically detects an access point adjacent to itself by receiving a beacon frame Beacon transmitted from another access point, and an adjacent access point list to be described later Create

  Further, each of the access points 10 to 12 and 15 to 21 periodically detects the terminal device connected to itself in the infrastructure mode, and creates a terminal list to be described later.

  Further, each of the access points 10 to 12 and 15 to 21 determines whether to set the doTPC flag to “ON” or “OFF”. More specifically, each of the access points 10 to 12 and 15 to 21 has a terminal device that cannot control transmission power connected to itself (canTPCflag is not included in the association request, or canTPCflag is OFF) And doTPCflag is set to “OFF”, and when only a terminal device capable of controlling transmission power is connected to itself, doTPCflag is set to “ON”.

  Then, each of the access points 10 to 12 and 15 to 21 has its own MAC (Media Access Control) address, the ID of the channel used within its own communication range, and the adjacent access point list (MAC address + doTPCflag + beacon reception RSSI). The terminal list (MAC address + beacon reception RSSI) and doTPCflag are periodically transmitted to the monitoring server 50.

  The network 40 is composed of the Internet, for example.

  The monitoring server 50 is connected to the network 40. And the monitoring server 50 receives the adjacent access point list from the terminal device which can control transmission power among the terminal devices 1-9 regularly via the network 40, and also has access points 10-12 and 15-21. MAC address of each access point 10-12, 15-21 from each, ID of the channel used in the communication range of each access point 10-12, 15-21, adjacent access point list (MAC address + doTPCflag + beacon reception RSSI) The terminal list (MAC address + beacon reception RSSI) and doTPCflag are periodically received via the network 40, and the received MAC addresses of the access points 10-12 and 15-21 and the access points 10-12, 15 ~ 21 communication range Channel ID that are used in the inner, adjacent access point list (MAC address + DoTPCflag + beacon reception RSSI), manages a terminal list (MAC address + beacon reception RSSI) and DoTPCflag.

  The power control device 60 is connected to the network 40. Then, the power control device 60 transmits the MAC addresses of the access points 10 to 12 and 15 to 21 from the monitoring server 50 via the network 40 and the channels used within the communication range of the access points 10 to 12 and 15 to 21. ID, adjacent access point list (MAC address + doTPCflag + beacon reception RSSI), terminal list (MAC address + beacon reception RSSI), and doTPCflag are periodically acquired. Thereafter, the power control device 60 performs the same operation according to a method described later on the basis of the link quality between the access points included in the acquired adjacent access point list and the terminal list and the link quality between the access point and the terminal device. The transmission power used in the local network of each of the access points 10 to 12 and 15 to 21 sharing the channel is determined.

  Subsequently, the power control device 60 adjusts the transmission power used in the local networks of the access points 10 to 12 and 15 to 21 by a method described later.

  Further, the power control device 60 determines a control access point for controlling the access points 13 and 14 from the access points 10 to 12 and 15 to 21.

  Furthermore, the power control device 60 calculates a channel usage rate, which is a rate at which the access points 10 to 12 and 15 to 21 that control transmission power use the channel, by a method described later.

  Then, the power control device 60 is a slot length, adjusted transmission power used in the local network of each of the access points 10 to 12 and 15 to 21, and doChCtrl indicating whether or not the access point is a control access point. The access point set (monitorNoTpcApSet) and the channel usage rates of the access points 10 to 12 and 15 to 21 are transmitted to the access points 10 to 12 and 15 to 21.

  The access points 13 and 14 that do not control the transmission power include the following cases.

(1) When the access points 13 and 14 are access points whose transmission power cannot be controlled (2) Although the access points 13 and 14 are access points whose transmission power can be controlled, terminals connected to the access points 13 and 14 When the device is a terminal device that cannot control transmission power And, in the case of (1), the terminal device connected to the access points 13 and 14 is a terminal device that cannot control transmission power, and the access points 13 and 14 Both of the cases where the terminal device connected to the terminal device is a terminal device that can control transmission power but does not control transmission power are included.

  Accordingly, the access points 13 and 14 perform wireless communication with a terminal device that cannot control transmission power or a terminal device that can control transmission power but does not control transmission power.

  Moreover, in embodiment of this invention, it synchronizes between the access points 10-12 and 15-21 which control transmission power, and the terminal device which exists in the communication range of the access points 10-12 and 15-21. I take the.

  More specifically, when the access points 10 to 12 and 15 to 21 are connected to the same Ethernet (registered trademark), the access points 10 to 12 and 15 to 21 use the IEEE 1588 (Precision Time Protocol) for μsec. You can synchronize orders. A terminal device that can control transmission power can synchronize with the access point by receiving a beacon frame Beacon from the access point that controls the transmission power of the connection destination.

  Therefore, in the embodiment of the present invention, synchronization is established between the access points 10 to 12 and 15 to 21 that control the transmission power and the terminal devices existing within the communication range of the access points 10 to 12 and 15 to 21. I take the.

  The access point and the terminal device can perform transmission / reception using the WiFi MAC protocol, and can reserve a channel by a virtual carrier sense mechanism (Network Allocation Vector (NAV)). Specifically, the access point or terminal device sets the length of the channel to be reserved to the duration of the current transmission frame (see FIG. 12 described later), and transmits the frame. When the adjacent access point and the terminal device receive the frame, they use the received frame duration to know that a channel having a duration of duration from the reception time point is reserved by another wireless device, Suppress transmission from the terminal. The present invention does not change an existing wireless device whose transmission power cannot be controlled, and uses this NAV mechanism to control the transmission power by controlling the wireless device that controls the transmission power (doTPC) and control the transmission power. The channel is divided into no (no TPC) time zones, and transmission power control is performed in the do TPC time zones.

  FIG. 2 is a configuration diagram of the terminal device 1 shown in FIG. With reference to FIG. 2, the terminal device 1 includes an antenna 101, a wireless interface 102, a communication unit 103, and an application module 104.

  The wireless interface 102 performs wireless communication by a WiFi wireless communication method. The wireless interface 102 receives a beacon frame or data packet from an access point (any one of the access points 10 to 21), and detects the received signal strength when the beacon frame or data frame is received. Then, the wireless interface 102 outputs the detected received signal strength to the communication unit 103.

  Further, when the terminal device 1 can control the transmission power, the wireless interface 102 receives a beacon frame including the transmission power of the data packet, the slot length, and the channel usage rate from the access point (any of the access points 10 to 21). The transmission power, slot length, and channel usage rate are extracted from the received beacon frame and output to the communication means 103.

  The wireless interface 102 connects to an access point (any one of the access points 10 to 21) in the infrastructure mode, and transmits / receives a data packet to / from the access point (any one of the access points 10 to 21).

  That is, the wireless interface 102 transmits the data packet and transmission power received from the communication unit 103 to the access point (any one of the access points 10 to 21) via the antenna 101. The wireless interface 102 receives a data packet from the access point (any one of the access points 10 to 21) via the antenna 101, and outputs the received packet to the communication unit 103.

  The communication means 103 holds in advance the maximum transmission power in the communication system 100 (transmission power when each of the access points 10 to 21 transmits a beacon frame). When the terminal device 1 can control the transmission power, the communication unit 103 also holds the transmission power, the slot length, and the channel usage rate received from the wireless interface 102. Then, the communication means 103 calculates a doTPC time zone in which the transmission power is controlled and a no TPC time zone in which the transmission power is not controlled based on the channel usage rate and the slot length. The communication means 103 outputs the data packet and transmission power to the wireless interface 102 in the doTPC time zone. In addition, the communication unit 103 sets the NAV at its own terminal in the no TPC time zone and suppresses transmission from the own terminal. When the terminal device 1 cannot control the transmission power, the communication unit 103 outputs the data packet and the maximum transmission power Pamx to the wireless interface 102 if the NAV of the terminal device 1 is not set.

  The communication unit 103 receives the received signal strength from the wireless interface 102. And the communication means 103 calculates beacon reception RSSI when receiving a beacon frame by a method to be described later, based on the maximum transmission power and received signal strength.

Then, when the terminal device 1 can control the transmission power, the communication unit 103 includes the MAC address of the terminal device 1, the MAC address of the access point that is the beacon transmission source, the doTPC flag of the access point that is the beacon transmission source, the beacon reception RSSI, and The adjacent access point list APL _MN including the ID of the channel used by the wireless interface 102 is created, and the created adjacent access point list APL _MN is transmitted to the monitoring server 50 via the wireless interface 102.

  Further, the communication unit 103 receives a packet from the application module 104 and transmits the received packet using the wireless interface 102.

  Further, the communication unit 103 receives a packet from the wireless interface 102 and outputs the received packet to the application module 104.

  The application module 104 generates and outputs a packet to the communication unit 103 and receives the packet from the communication unit 103.

  Each of the terminal devices 2 to 9 shown in FIG. 1 has the same configuration as the terminal device 1 shown in FIG.

  FIG. 3 is a block diagram of the access point 10 shown in FIG. Referring to FIG. 3, access point 10 includes an antenna 111, a wireless interface 112, a communication unit 113, and a wired interface 114.

  The wireless interface 112 performs wireless communication by a WiFi wireless communication method. The wireless interface 112 receives the data packet from the communication unit 113 and transmits the received data packet via the antenna 111 with the transmission power received from the communication unit 113. The wireless interface 112 receives a data packet via the antenna 111 and outputs the received data packet to the communication unit 113.

  The communication unit 113 periodically generates a beacon frame and transmits the generated beacon frame to the terminal device (at least one of the terminal devices 1 to 9) via the wireless interface 112.

In this case, if the access point 10 can control the transmission power, the communication unit 113 can can transmit the transmission power, canTPCflag indicating that the transmission power can be controlled, doTPCflag indicating whether the transmission power is controlled, and the transmission power value P ^N to be used. , TPCIE including the slot length and the channel usage rate is added to the beacon frame Beacon and transmitted.

  The communication means 113 of the access point 10 capable of controlling the transmission power first transmits a beacon frame including doTPCflag = ON in which doTPCflag is set to ON. Then, when a terminal device that cannot control transmission power is connected by an association request that does not include canTPC, the communication unit 113 turns off the canTPC of the terminal device and sets doTPCflag = OFF in which the doTPCflag is set to OFF in the beacon frame. Include and send. Eventually, when all the terminal devices with canTPC set to OFF disappear from the communication range of the access point 10, the communication means 113 sets at least one terminal device with doTPCflag set to ON and canTPC set to OFF. Is set within the communication range of the access point 10, doTPCflag is set to OFF.

Furthermore, when the access point 10 can control transmission power, the communication means 113 creates a terminal list TL and an adjacent access point list APL _AP . The terminal list TL includes a MAC address of a terminal device that accesses the access point 10 and a beacon reception RSSI. The adjacent access point list APL _AP is composed of the MAC address of the access point adjacent to the access point 10, the doTPC flag, and the beacon reception RSSI.

Then, when the access point 10 can control the transmission power, the communication unit 113 includes the MAC address of the access point 10, the ID of the channel used by the wireless interface 112, the terminal list TL, the adjacent access point list APL _AP , doTPCflag is transmitted to the monitoring server 50 via the wired interface 114.

  Further, when the access point 10 can control the transmission power, the communication unit 113 transmits the transmission power used in the local network of the access point 10, the channel usage rate of the access point that controls the transmission power, the slot length, the control access point, And the access point to be controlled is received from the power control apparatus 60 via the wired interface 114.

  When the access point 10 can control the transmission power, the communication unit 113 sets the received transmission power in the wireless interface 112, and along with the received transmission power, slot length, channel usage rate, canTPCflag, and doTPCflag. The beacon frame is included in the TPCIE and transmitted to the terminal device (at least one of the terminal devices 1 to 9).

  Further, the communication means 113 uses the doTPC time zone (= slot length × channel usage rate) in which the access points 10 to 12 and 15 to 21 that control transmission power transmit data packets based on the channel usage rate and the slot length. Then, a no TPC time zone (= slot length × (1−channel usage rate)) in which the access points 13 and 14 that do not control transmission power transmit data packets is calculated for each slot. When the access point 10 is a control access point, the communication unit 113 generates a SAM (Slot Allocation Message), sets the length of the doTPC time zone to the duration of the SAM, and sets the SAM via the wireless interface 112. Broadcast.

  Further, the communication unit 113 receives the SAM via the wireless interface 112. An access point for which doTPC is ON does not set its own NAV when receiving this SAM. The other access point sets the NAV in its own terminal when it receives the SAM. Then, when the access point 10 is an access point that controls transmission power, the communication unit 113 transmits a data packet to the terminal device via the wireless interface 112 in the doTPC time zone. In addition, when the access point 10 is an access point that does not control transmission power, the communication unit 113 transmits a data packet to the terminal device via the wireless interface 112 in the no TPC time zone.

  Note that when the access point 10 is an access point that does not control transmission power, the communication unit 113 does not receive transmission power from the power control device 60 via the wired interface 114, so the maximum transmission power in the communication system 100 is wirelessly transmitted. Set to interface 112.

  The wired interface 114 receives the packet from the communication unit 113 and transmits the received packet to the monitoring server 50 via the network 40.

  The wired interface 114 receives the transmission power, slot length, channel usage rate, control access point, and access point to be controlled from the power control device 60 via the network 40, and the received transmission power, slot length, The channel usage rate, the control access point, and the access point to be controlled are output to the communication means 113.

  Each of the access points 11 to 21 shown in FIG. 1 has the same configuration as that of the access point 10 shown in FIG.

  FIG. 4 is a configuration diagram of the power control device 60 shown in FIG. Referring to FIG. 4, power control device 60 includes a wired interface 61, a communication unit 62, a determination unit 63, and an adjustment unit 64.

  The wired interface 61 receives a packet via the network 40 and outputs the received packet to the communication unit 62.

  The wired interface 61 receives a packet from the communication unit 62 and transmits the received packet.

The communication unit 62 periodically acquires the terminal list TL and the adjacent access point lists APL _MN and APL _AP from the monitoring server 50 via the wired interface 61. Then, the communication unit 62 outputs the acquired terminal list TL and adjacent access point lists APL _MN and APL _AP to the determination unit 63 and the adjustment unit 64.

  The communication unit 62 receives the slot length, channel usage rate, control access point, and access point to be controlled from the determination unit 63, receives the adjusted transmission power from the adjustment unit 64, and receives the received slot length and channel. The usage rate, the control access point, the access point to be controlled, and the transmission power are transmitted to the access points 10 to 12 and 15 to 21 via the wired interface 61.

The determination unit 63 receives the terminal list TL and the adjacent access point lists APL _MN and APL _AP from the communication unit 62, and based on the received terminal list TL and the adjacent access point lists APL _MN and APL _AP , by a method described later, The transmission power used in the local network of each access point 10-12, 15-21 is determined. Then, the determination unit 63 outputs the ten transmission powers of the determined access points 10 to 12 and 15 to 21 to the adjustment unit 64.

  The determining unit 63 determines the channel usage rate of the access points 10 to 12 and 15 to 21 for controlling the transmission power by a method described later, a control access point for controlling an access point that does not control the transmission power, and a control. The access point to be controlled by the access point is determined by a method described later and output to the communication means 62.

  Then, the communication means 62 transmits the slot length, channel usage rate, transmission power, control access point, and control target access point to the access points 10 to 12 and 15 to 21 via the wired interface 61.

The adjusting unit 64 receives the terminal list TL and the adjacent access point lists APL _MN and APL _AP from the communication unit 62, and receives ten transmission powers of the access points 10 to 12 and 15 to 21 from the determining unit 63.

Then, the adjustment unit 64 uses the terminal list TL, the adjacent access point lists APL _MN , APL _AP, and the 10 transmission powers of the access points 10 to 12 and 15 to 21 according to the method described later by the method described later. , 15 to 21 are adjusted, and the adjusted ten transmission powers are output to the communication means 62. The communication unit 62 transmits the adjusted ten transmission powers to the access points 10 to 12 and 15 to 21 via the wired interface 61.

  Definitions of terms in the embodiment of the present invention will be described.

[Calculation of path loss and beacon reception RSSI]
Of the terminal devices 1 to 9, a terminal device that can control transmission power calculates a path loss (PL: Path Loss) according to the following procedure when receiving a frame from an access point (any one of the access points 10 to 21). .

  Further, each of the access points 10 to 12 and 15 to 21 calculates a PL according to the following procedure when receiving a frame from another access point or a terminal device (any one of the terminal devices 1 to 9). Note that the transmission power and RSSI are calculated in dBm units, and PL is calculated in dB units.

  (1) Among the terminal devices 1 to 9, each of the terminal devices or access points 10 to 12 and 15 to 21 that can control transmission power is a control frame such as a beacon frame or an ACK in response thereto, PL is calculated by PL = beacon transmission power−reception RSSI. The received RSSI is the received signal strength when a control frame or ACK is received. The beacon transmission power is a maximum transmission power set in advance in the communication network system 100.

  (2) Among the terminal devices 1 to 9, each of the terminal devices or access points 10 to 12 and 15 to 21 that can control transmission power is PL = data transmission when the received frame is a data frame or an ACK in response thereto. PL is calculated by power-reception RSSI. The received RSSI is the received signal strength when a data frame or ACK is received.

  (3) Of the terminal devices 1 to 9, each of the terminal devices or access points 10 to 12 and 15 to 21 that can control transmission power calculates an average value of PL by the following equation in order to eliminate the influence of fading and the like. To do.

newPL average value = oldPL average value × α + newPL value × (1−α) (1)
In the formula (1), α is, for example, 0.9. Moreover, the average value of PL calculated using the formula (1) is the second and subsequent average values.

  And each of the terminal device which can control transmission power among the terminal devices 1-9 or each of the access points 10-12, 15-21 calculates beacon reception RSSI by beacon reception RSSI = beacon transmission power-PL average value.

[Adjacent access point type]
The adjacent access point includes an access point that is directly adjacent (Direct neighbor) and an access point that is indirect adjacent (Indirect neighbor).

  Direct neighbor access points are two access points that operate on the same channel and can directly receive beacon frames from each other.

  In addition, indirect neighbor access points are two access points that operate on the same channel and are connected by a common terminal device.

  FIG. 5 is a conceptual diagram of a directly adjacent access point and an indirect adjacent access point.

Referring to (a) of FIG. 5, the monitoring server 50 determines whether the neighboring access point list APL _AP 1 = [MACadd11 / doTPCflag11 / beacon reception RSSI1] and channel ID = CH1 collected from the access point 10 and the access point 11 Based on the collected adjacent access point list APL _AP 2 = [MACadd10 / doTPCflag10 / beacon reception RSSI2] and channel ID = CH1, the access points 10 and 11 operate on the same channel CH1 and the beacon frames of each other are transmitted. It is detected that the access point can be directly received, and the access points 10 and 11 are set as directly adjacent access points.

  With reference to (b) of FIG. 5, it is assumed that the terminal device 1 is connected to the access point 10. The terminal device 1 knows the doTPCflag 10 of the access point 10 by receiving the beacon frame from the access point 10, detects the access point 10 as an adjacent access point, and calculates the beacon reception RSSI 3 by the method described above.

  Further, the terminal device 1 knows the doTPCflag 11 of the access point 11 by receiving the beacon frame from the access point 11, detects the access point 11 as an adjacent access point, and calculates the beacon reception RSSI 4 by the method described above.

Then, the terminal device 1 periodically generates an adjacent access point list APL _MN 1 = [MACadd10, MACadd11 / doTPCflag10, doTPCflag11 / channel ID = CH1 / beacon reception RSSI3, beacon reception RSSI4] and transmits it to the monitoring server 50. .

On the other hand, the access point 10 has its own MAC address MACadd10, its own channel ID = CH1, its own terminal list TL1 = [MACadd1 / beacon reception RSSI5], and its own neighboring access point list APL _AP 3 = [------ -/-] Is transmitted to the monitoring server 50.

Further, the access point 11 has its own MAC address MACadd11, its own channel ID = CH1, its own terminal list TL2 = [-/ ----], and its own adjacent access point list APL _AP 4 = [--- / −− // −−] is transmitted to the monitoring server 50.

In this case, the access point 10, 11 can not directly receive the beacon frame to each other, the neighboring access point list _APL AP 3, the neighboring access not contain data to _{APL AP} 4 point list _{APL AP} 3, _APL AP 4 Monitoring Send to server 50.

Then, the monitoring server 50 receives from the access point 10 the adjacent access point list APL _MN 1 = [MACadd10, MACadd11 / doTPCflag10, doTPCflag11 / channel ID = CH1 / beacon reception RSSI3, beacon reception RSSI4] received from the terminal device 1. MAC address MACadd10, channel ID = CH1, terminal list TL1 = [MACadd1 / beacon reception RSSI5] and adjacent access point list APL _AP 3 = [-/-/ ----] and received from access point 11 MAC address MACadd11 the channel ID = CH1, terminal list TL2 = [--- / ---] and its neighbor access point list _APL AP 4 = [--- / - / --- based on the, the access point 10 and 11 operate on the same channel, and detects that are connected via the terminal device 1. The monitoring server 50 sets the access points 10 and 11 as indirectly adjacent access points.

[CSG (Connected sub graph)]
The CSG is a graph showing a connection relationship between access points determined as adjacent access points according to the above-described definition.

  The CSG may consist of only directly adjacent access points, or may consist of directly adjacent access points and indirectly adjacent access points.

  Each of the access points 10 to 12 and 15 to 21 creates and manages a terminal list TL by an association request from a terminal device (any one of the terminal devices 1 to 9). Each of the access points 10 to 12 and 15 to 21 calculates a beacon reception RSSI by the method described above by receiving a frame from the terminal device (any one of the terminal devices 1 to 9).

Moreover, each access point 10-12, 15-21 detects an adjacent access point by receiving a beacon frame from another access point, and calculates beacon reception RSSI by the method mentioned above. When a beacon that does not include TPCIE is received, doTPCflag of the access point of the transmission source is set to OFF. Each of the access points 10 to 12 and 15 to 21 has its own terminal list TL (= the MAC address and beacon reception RSSI of the terminal device connected to itself) and the adjacent access point list APL _AP (= access adjacent to itself). The point MAC address, doTPCflag and beacon reception RSSI) are periodically transmitted to the monitoring server 50.

On the other hand, a terminal device that can control transmission power among the terminal devices 1 to 9 detects an adjacent access point by receiving a beacon frame from an access point (any one of the access points 10 to 21). When a beacon that does not include TPCIE is received, doTPCflag of the access point of the transmission source is set to OFF. Of the terminal devices 1 to 9, the terminal device that can control the transmission power uses its own adjacent access point list APL _MN (= the MAC address of the access point adjacent to itself, doTPC flag, channel ID, and beacon reception RSSI). It periodically transmits to the monitoring server 50.

The power control apparatus 60 includes the adjacent access point list APL _AP (= the MAC address of the access point adjacent to each access point 10 to 21, doTPCflag, and beacon reception RSSI) and each terminal of the access points 10 to 12 and 15 to 21. The adjacent access point list APL _{MN of the} devices 1 to 9 (= the MAC address, channel ID, doTPC flag, and beacon reception RSSI of the access point adjacent to each of the terminal devices 1 to 9) is periodically acquired from the monitoring server 50.

Then, the power control device 60 includes the adjacent access point list APL _{AP of} each access point 10-12, 15-21 (= the MAC address of the access point adjacent to each access point 10-12, 15-21, doTPCflag, and beacon Reception RSSI) and adjacent access point list APL _{MN of} each terminal apparatus 1-9 (= MAC address of access point adjacent to each terminal apparatus 1-9, doTPCflag, channel ID and beacon reception RSSI) To build and divide the CSG.

[Calculation of transmission power]
A method for calculating transmission power in 10 local networks formed by 10 access points 10 to 12 and 15 to 21 will be described.

The communication means 62 of the power control device 60 acquires the terminal list TL of the access points 10 to 12 and 15 to 21 and the adjacent access point list APL _AP for controlling the transmission power from the monitoring server 50 via the wired interface 61, The obtained terminal list TL and adjacent access point list APL _AP are output to the determination means 63.

The determination unit 63 of the power control device 60 holds in advance a table TBL indicating the relationship between the RSSI and the transmission rate. Then, the determination unit 63 of the power control device 60 refers to the table TBL to detect the minimum RSSI (= RSSI _minrate ) that can satisfy the minimum transmission rate.

And the determination means 63 of the power control apparatus 60 takes out the average value (= RSSI _beacon ) of beacon reception RSSI for every terminal device in the terminal list TL. After that, the determination unit 63 of the power control device 60 includes a beacon transmission power (= maximum transmission power) P _beacon that is held in advance, an average value of beacon reception RSSI (= RSSI _beacon ), and a minimum RSSI (= RSSI _minrate). ) _Is substituted into the following equation to calculate the minimum transmission power _Pminrate .

P _minrate = RSSI _minrate + P _beacon -RSSI _beacon (2)
An area composed of the communication range (= data packet communication range) of the access point j (j = 10 to 12, 15 to 21) is defined as a cell j. Then, the minimum transmission power of the cell j is determined by the minimum transmission power of the cell j = max _i {the minimum transmission power of all the terminal devices i (i = 1 to 9) included in the cell j (= P _minrate )}. The

  The transmission power p is in the range of p = the lowest transmission power of cell j to the maximum transmission power.

When the RSSI _ij (P _beacon ) when the terminal device i receives a beacon frame from the access point j is RSSI _ij (P _beacon ), the determining unit 63 of the power control device 60 transmits the terminal device i from the access point j with the transmission power p. The data reception RSSI (= RSSI _ij (p)) when receiving the received data is calculated by the following equation.

RSSI _ij (p) = p−P _beacon + RSSI _ij (P _beacon ) (3)
Then, the determination unit 63 of the power control device 60 refers to the table TBL to detect the transmission rate r _ij (p) corresponding to the data reception RSSI (= RSSI _ij (p)).

Subsequently, the determination unit 63 of the power control apparatus 60 calculates the transmission required time t _j (p) per bit in the cell j by the following equation.

t _j (p) = Σ _i (1 / r _ij (p)) / (number of terminal devices in cell j) (4)
The required transmission time t _j (p) is an average required transmission time.

The minimum transmission power around the cell j is determined by the minimum transmission power around the cell j = max {the minimum transmission power of the cell j and its neighboring cells (= P _minrate )}.

  Further, the transmission power p 'is in the range of p' = the minimum transmission power around the cell j to the maximum transmission power.

When the transmission power is p ′, the access point list of the same channel competition of the access point _j is N _j (p ′).

Since N _j (p ′) is initially empty, access point j is placed in N _j (p ′).

  An access point that is directly adjacent to the access point j (a beacon frame can be directly received) and that controls transmission power is an access point k (k = 10 to 12, 15 to 21, k ≠ j).

The determining unit 63 of the power control device 60 calculates RSSI (= RSSI _kj (p ′)) when a packet transmitted by the access point k with the transmission power p ′ reaches the access point j by the following equation.

RSSI _kj (p ′) = p′−P _beacon + RSSI _kj (P _beacon )) (5)
RSSI _kj (P _beacon ) is a beacon reception RSSI when the access point j receives a beacon frame from the access point k, and is included in the adjacent access point list APL _AP from the access point j. Therefore, the determination unit 63 of the power control device 60 can calculate RSSI (= RSSI _kj (p ′)) by the equation (5).

When the RSSI _kj (p ′) is larger than the carrier sense threshold of the access point j, the determining unit 63 of the power control device 60 puts the access point k (= local network) into N _j (p ′).

Determining means 63 of the power control unit 60 'and the calculation of its computed _{RSSI kj (p RSSI kj (p} )' adjacent the comparison of) the carrier sense threshold to the access point j, and controls the transmission power This is executed for all the access points k to be executed.

Then, the determination unit 63 of the power control device 60 calculates the local throughput γ _j (p ′) in the local network of the access point j by the following equation.

γ _j (p ′) = 1 / [Σ _{kεNj (P ′)} 1 / t _k (p ′)] (6)
Note that t _k (p ′) is a transmission required time per bit at the access point k calculated using the above-described equation (4).

Further, when the local network of the access point j is the first local network and all the local networks of the access point k are n (n is a positive integer) number of second local networks, N _j (p ′) The access points k included in the network constitute “m (m is an integer satisfying 1 ≦ m ≦ n) second local networks”.

Subsequently, the determination unit 63 of the power control device 60 determines the power p ′ that maximizes the local throughput γ _j (p ′) as the transmission power P ^C _j in the local network of the access point j.

  In the embodiment of the present invention, the local throughput means the throughput of the access point j in the local network when the influence of the transmission power in the local network of the access point k adjacent to the access point j is considered.

[Construction of CSG]
The communication means 62 of the power control device 60 transmits the [MAC address MACadd10 / doTPCflag10 / channel ID = CH1 / terminal list TL10 / adjacent access point list APL _AP 10] to [MAC address MACadd12 / doTPCflag12 / channel ID = CH1 / terminal list TL12 / adjacent access point list APL _AP 12], [MAC address MACadd15 / doTPCflag15 / channel ID = CH1 / terminal list TL15 / adjacent access point list APL _AP 15] to [MAC address MACadd21 / DoTPCflag21 / channel ID = CH1 / terminal list TL 21 / adjacent access points monitor list _APL AP 21] server Obtained from 0, the obtained [MAC address MACadd10 / doTPCflag10 / channel ID = CH1 / terminal list TL10 / neighboring access point list _APL AP 10] ~ [MAC address MACadd12 / doTPCflag12 / channel ID = CH1 / terminal list TL12 / neighbor access point list _APL AP 12], [MAC address MACadd15 / doTPCflag15 / channel ID = CH1 / terminal list TL15 / neighboring access point list _APL AP 15] ~ [MAC address MACadd21 / doTPCflag21 channel ID = CH1 / terminal list TL 21 / adjacent access Point list APL _AP 21] is output to decision means 63.

Then, the determination unit 63 of the power control apparatus 60 includes [MAC address MACadd10 / doTPCflag10 / channel ID = CH1 / terminal list TL10 / adjacent access point list APL _AP 10] to [MAC address MACadd12 / doTPCflag12 / channel ID = CH1 / terminal. list TL12 / neighboring access point list _APL AP 12], [MAC address MACadd15 / doTPCflag15 / channel ID = CH1 / terminal list TL15 / neighboring access point list _APL AP 15] ~ [MAC address MACadd21 / doTPCflag21 / channel ID = CH1 / terminal A CSG is constructed based on the list TL21 / neighboring access point list APL _AP 21].

  Hereinafter, a method for constructing the CSG will be specifically described. FIG. 6 is a diagram showing a neighbor list. FIG. 7 is a diagram showing a specific example of CSG.

The decision means 63 of the power control device 60 is based on the channel ID = CH1 of the access points 10 to 12 and 15 to 21 and the neighbor access point lists APL _AP 10 to APL _AP 12 and APL _AP 15 to APL _AP 21. NBL1 (see FIG. 6A) is created. The communication unit 63 of the power control device 60 does not directly receive the adjacent access point list of the access point 13 and the access point 14. The communication means 63 of the power control device 60 knows that the access point 13 is adjacent to the access point 12 from the adjacent access point list of the access point 12, and also knows its channel number and beacon reception RSSI. Similarly, the communication means 63 of the power control device 60 recognizes that the access point 14 is adjacent to the access point 12 and the access point 15 from the adjacent access point list of the access point 12 and the access point 15. The received RSSI is also known. In this case, the CSG ID is set to “0” for all of the access points 10 to 21. Then, the determination unit 63 of the power control device 60 detects that the access points 10 to 21 share the same channel CH1 based on the neighbor list NBL1.

  Then, the determination unit 63 of the power control device 60 creates one graph GRP (see FIG. 7A) for the access points 10 to 21 sharing the same channel CH1.

  Thereafter, the determination unit 63 of the power control device 60 divides the graph GRP into two CSG1 and CSG2 by the following procedure.

(C1) A new CSGm (m = 1, 2, 3,...) Is prepared.
(C2) Select an access point j (CSG = 0) that is not in the existing CSG and put it in the CSGm.
(C3) An access point adjacent to the access point j is also entered into the CSGm.
(C4) The access point k is selected from the access points (CSG = 0) not included in the CSGm, and the processes (C1) to (C3) are performed.
(C5) When all access points adjacent to the access point in the CSGm are included in the CSGm, this CSG is constructed.
(C6) If there remains an access point that is not included in the existing CSG, the above processes (C1) to (C5) are repeated.
The construction of the CSG will be specifically described according to the above (C1) to (C6).

  The determination unit 63 of the power control device 60 first places the access point 10 in the CSG 1. Next, the determination unit 63 of the power control device 60 puts the access point 11 adjacent to the access point 10 into the CSG 1. Similarly, the determination unit 63 of the power control apparatus 60 puts the access point 12 adjacent to the access point 11 into the CSG 1, puts the access points 13, 14 and 15 adjacent to the access point 12 into the CSG 1, and is adjacent to the access point 15. The access points 16 and 17 to be entered are put into CSG1. Thereby, since the access points adjacent to the access points 10 to 17 are included in the CSG 1, the construction of the CSG 1 is completed.

  Similarly, the determination unit 63 of the power control device 60 constructs the CSG 2 including the access points 18 to 21.

  As a result, the determination unit 63 of the power control device 60 creates a neighbor list NBL2 (see FIG. 6B) and creates CSG1 and CSG2 (see FIG. 7B).

  The determination unit 63 of the power control device 60 constructs a CSG by the method described above. Then, the adjustment unit 64 of the power control device 60 first excludes the AP of the no TPC that does not control the transmission power from the CSG for each access point included in one CSG for each constructed CSG. The transmission power is adjusted for the remaining access points by the following method.

(ADJ1) sorts the transmission power ^{P C} of the access point in descending order, the initial transmit power ^{P N.}
(ADJ2) IDs of access points after sorting are set to 1, 2, 3,..., And P ^N ₁ ≧ P ^N ₂ ≧ P ^N ₃ ≧.
(ADJ3) A transmission power controlled flag_CF is set for each access point. In this case, first, flag_CF (M) (M = 1, 2, 3,...) = 0.
(ADJ4) calculates the transmission power ^P _{C M} of the access point M.
(ADJ4-1) If flag_CF is not “0”, the access point is skipped.
(ADJ4-2) P ^N _M = max {Maximum value of P ^N of access point adjacent to access point _M− δ _P , P ^C _M } is calculated, and flag flag_CF (M) is attached. Here, the [delta] _P, is the threshold of the difference in transmission power between the adjacent access points.
^(ADJ4-3) and the access point M by updating the ^P _{N M,} the difference in transmission power between the access point L adjacent to the access point _{^{M | P N M -P N L}} | exceeds the [delta] _P, access The flag flag_CF of point L is cleared.
(ADJ5) The processing of (ADJ4) is performed for the access point whose flag flag_CF is “0”, and the transmission power is adjusted again.

FIG. 8 is a diagram illustrating a specific example of transmission power adjustment. In FIG. 8, the threshold [delta] _P is assumed to be 1 dBm.

8, in CSG1, transmission power ^{P N} of the access point 10,17,16,12, respectively, 15 dBm, 14 dBm, 13 dBm, and is calculated as 9 dBm.

When the transmission power ^P _{N 11} of the access point 11 is calculated, the transmission power ^P _{N 11} under the influence of the access point 10 is calculated as 14 dBm.

As a result, the transmission power difference (= 5 dBm) between the access point 12 and the access point 11 exceeds the threshold value δ _P (= 1 dBm). The 12 flag flag_CF is cleared.

Thereafter, the transmission power ^P _{N 15} of the access point 15 is calculated as 12 dBm.

Then, the adjustment means 64 of the power control device 60 determines that the difference between the transmission power P ^N ₁₂ (= 9 dBm) of the access point 12 and the transmission power P ^N ₁₁ (= 14 dBm) of the access point 11 is the threshold δ _P (= The transmission power P ^N ₁₂ of the access point 12 is adjusted from 9 dBm to 13 dBm so as not to exceed 1 dBm).

In CSG2, the transmission powers P ^N _{18 to} P ^N ₂₁ of the access points 18 to ₂₁ are similarly adjusted.

Thus, in the embodiment of this invention, adjustment means 64 of the power control unit 60, the difference between the transmission power P ^N between two adjacent access point does not exceed the threshold δ _{P (=} 1dBm) As described above, the transmission powers P ^N _{10 to} P ^N ₁₂ and P ^N _{15 to} P ^N ₂₁ of the access points _{10 to 12} and _{15 to 21} that control the transmission power included in one CSG are adjusted.

Then, the adjustment unit 64 of the power control device 60 outputs the adjusted transmission powers P ^N _{10 to} P ^N ₁₂ and P ^N _{15 to} P ^N ₂₁ to the communication unit 62, and the communication unit 62 transmits the transmission power P ^N. _{10 to} P ^N ₁₂ and P ^N _{15 to} P ^N ₂₁ are transmitted together with other information to the access points 10 to ₁₂ and _{15 to 21} .

The access points _{10 to 12} and _{15 to 21} receive transmission powers P ^N _{10 to} P ^N ₁₂ and P ^N _{15 to} P ^N ₂₁ from the power control device 60, respectively, and the received transmission powers P ^N _{10 to} P ^N _{12 are received.} , P ^N _{15 to} P ^N ₂₁ are included in the beacon frame and transmitted to the terminal devices (at least one of the terminal devices 1 to 9) existing in the local network.

The access points _{10 to 12} and _{15 to 21} are terminal devices (terminal devices 1 to 9) that exist in their own local networks with transmission powers P ^N _{10 to} P ^N ₁₂ and P ^N _{15 to} P ^N ₂₁ , respectively. At least one) and a data frame. The terminal device transmits a data packet with the same transmission power as the connected accelerator point.

[Determination of channel usage]
The determination unit 63 of the power control device 60 classifies the access points 10 to 21 as CSG by the method described above. In this case, for example, the determination unit 63 classifies the access points 10 to 21 into CSG1 = access points 11 to 20 and CSG2 = access points 10 and 21.

  Then, the determining unit 63 controls the access power from the access points 11 to 20 classified as CSG 1 based on doTPC = ON transmitted from the access points 11 to 12 and 15 to 20. ˜20 and access points 13 and 14 that do not control transmission power are extracted.

  Thereafter, the determining unit 63 controls the transmission power so that the access points 11 to 12 and 15 to 20 that control the transmission power and the access points 13 and 14 that do not control the transmission power share the channel fairly. The channel usage rates of 11 to 12 and 15 to 20 are determined.

  More specifically, the determination unit 63 determines the channel usage rate by channel usage rate = (number of access points of doTPC included in one CSG) / (number of access points included in one CSG).

  In the above example, the number of access points 11 to 12 and 15 to 20 that control transmission power is 8, and the number of access points 11 to 20 included in CSG 1 is 10. The channel usage rate is determined to be 8/10.

  Further, the determination unit 63 similarly determines the channel usage rate as 2/2 = 1 for the CSG2.

  Thus, the determination unit 63 determines the channel usage rate for each CSG. All doTPC access points (access points that control transmission power) included in one CSG have the same channel usage rate.

  Access points 11-12, 15-20 that control transmission power so that access points 11-12, 15-20 that control transmission power and access points 13, 14 that do not control transmission power share a channel fairly. By determining the channel usage rate, the access points 11 to 20 can equally ensure opportunities for wireless communication.

  Further, since all doTPC access points (access points for controlling transmission power) included in one CSG use the same channel usage rate, access points 11 to 12, 15 to 20 (included in one CSG) The access point for controlling the transmission power) can ensure equal opportunities for wireless communication.

[Determining control access points and access points to be controlled]
FIG. 9 is a diagram for explaining a method of determining a control access point. Referring to FIG. 9, it is assumed that access points 11 to 20 are included in one CSG. Here, access points that control transmission power (APs of doTPC) are access points 11 to 12 and 15 to 20, and access points that do not control transmission power (APs of no TPC) are access points 13 and 14. .

  FIG. 10 is a diagram illustrating a calculation example of an access point (noTPC AP) that does not control transmission power adjacent to an access point (doTPC AP) that controls transmission power. FIG. 11 is a flowchart for explaining a method of determining a control access point.

  In the following, an access point that controls transmission power (AP of APPC) is referred to as “transmission power control AP”, and an access point that does not control transmission power (AP of no TPC) is referred to as “transmission power non-control AP”. .

  Referring to FIG. 11, when a series of operations is started, determination means 63 receives access points 11 to 20 included in one CSG (step S1).

  Then, the determination unit 63 calculates the set NoTpcApSet = AP13 and AP14 of the transmission power non-controlling AP (AP of no TPC) in the CSG (Step S2).

  Thereafter, the determination unit 63 calculates a set DoTpcApSet = AP11 to AP12 and AP15 to AP20 of the transmission power control AP (AP of doTPC) in the CSG (step S3).

  Subsequently, the determination unit 63 empties the set of checked access points, checkedNoTpcApSet (step S4).

  Then, the determining unit 63 sets, for each transmission power control AP (AP of doTPC), a set NoTpcApNeigh (see FIG. 10) of transmission power non-controlling AP (AP of no TPC) adjacent to the transmission power control AP (AP of doTPC). Calculate (step S5).

  Thereafter, the determination unit 63 sets the transmission power control AP (doTPCpSet) in descending order of the number of transmission power non-controlling APs (NoTpcApNeigh) adjacent to the transmission power control AP (doTPC AP). AP) are sorted (step S6). In the case shown in FIG. 10, since the number of NoTpcApNeigh of the access points AP11, AP17 to AP19 is 1, and the number of NoTpcApNeigh of the access points AP12, AP15, AP16, AP20 is 0, the determining unit 63 Access points AP11, AP17 to AP19 are sequentially selected from AP11, AP17 to AP19, and then access points AP12, AP15, AP16, and AP20 are sequentially selected from access points AP12, AP15, AP16, and AP20. That is, the determination unit 63 assigns an arbitrary order to the access points AP11, AP17 to AP19 and the access points AP12, AP15, AP16, AP20 having the same number of NoTpcApNeigh, thereby providing the access points AP11, AP12. , AP15 to AP20 are determined in the order of access points AP11, AP17, AP18, AP19, AP12, AP15, AP16, AP20 in order of determining whether or not they are control access points.

  Subsequently, the determination unit 63 sets i = 1, selects the first transmission power control AP (AP of doTPC) = AP11 (step S7), and sets the selected transmission power control AP (AP of doTPC) as the selected transmission power control AP. Of the set NoTpcApNeigh of adjacent transmission power non-controlling APs, the one not included in the check target access point set checkedNoTpcApSet is calculated as newNoTpcApSet (step S8).

  And the determination means 63 determines whether newNoTpcApSet is empty (step S9).

  When it is determined in step S9 that newNoTpcApSet is not empty, the determination unit 63 turns on doChCtrl of the transmission power control AP (AP of doTPC) (step S10). That is, the determination unit 63 sets the transmission power control AP (doTPC AP) as the control access point.

  Then, the determining unit 63 sets the set monitorNoTpcApSet of the access point to be controlled by the transmission power control AP (AP of doTPC) as newNoTpcApSet (step S11).

  Thereafter, the determination unit 63 puts newNoTpcApSet into the checkpointed NoTpcApSet of the access point to be checked (step S12).

  On the other hand, when it is determined in step S9 that newNoTpcApSet is empty, the determination unit 63 turns off doChCtrl of the transmission power control AP (AP of doTPC) (step S13).

  Thereafter, the determination unit 63 empties the set monitorNoTpcApSet of the access point to be controlled by the transmission power control AP (AP of doTPC) (step S14).

  Then, after step S12 or step S14, the determination unit 63 determines whether or not all the transmission power control APs (doTPC APs) in the set DoTpcApSet of the transmission power control APs (doTPC APSet) have been processed (steps). S15).

  When it is determined in step S15 that all transmission power control APs (doTPC APs) are not processed, the determination unit 63 sets i = i + 1, and the next transmission power control AP (doTPC AP) = AP17 is selected (step S16).

  Thereafter, the series of operations returns to step S8, and step S8 to step S16 described above are repeatedly executed until it is determined in step S15 that all transmission power control APs (doTPC APs) have been processed.

  If it is determined in step S15 that all transmission power control APs (doTPC APs) have been processed, the series of operations ends.

  In step S7, the first access point 11 (= AP11) is selected. Since checkedNoTpcApSet is empty (see step S4), transmission power non-control AP = AP13 adjacent to AP11 is not included in checkedNoTpcApSet. Therefore, in step S8, transmission power non-control AP = AP13 is calculated as newNoTpcApSet.

  As a result, in step S9, it is determined that newNoTpcApSet is not empty, and in step S10, transmission power control AP = AP11 is set as the control access point.

  Thereafter, in step S11, the transmission power control AP = AP13, which is the control target of the transmission power control AP = AP11, is put into newNoTpcApSet. In step S12, newNoTpcApSet (= AP13) is entered in checkedNoTpcApSet.

  Next, transmission power control AP = AP17 is processed in the same manner as transmission power control AP = AP11 in steps S8 to S12, and transmission power non-control AP = AP14 is put into newNoTpcApSet (see step S11), and newNoTpcApSet ( = AP14) is put into checkedNoTpcApSet (see step S12).

  Thereafter, the transmission power control AP = AP 18 has the AP 14 as a transmission power non-control AP adjacent to itself (see FIG. 10), but the AP 14 is already included in the checkedNoTpcApSet. Accordingly, when step S8 is executed for transmission power control AP = AP18, there is no transmission power uncontrolled AP that is not included in checkedNoTpcApSet, and therefore there is no transmission power uncontrolled AP calculated as newNoTpcApSet in step S8. As a result, in step S9, it is determined that newNoTpcApSet is empty, transmission power control AP = AP18 is not set as a control access point (see step S13), and transmission power control AP = AP18 is not subject to transmission power control. The control AP is emptied (see step S14).

  Transmission power control AP = AP19 is also processed in the same manner as transmission power control AP = AP18.

  For transmission power control AP = AP12, AP15, AP16, AP20, there is no adjacent transmission power non-controlling AP (see FIG. 10), so transmission power control AP = AP12, AP15, AP16, AP20 is set as a control access point. Is not performed (see step S13).

  As shown in FIG. 9, the transmission power control AP = AP17, AP18, AP19 is adjacent to the transmission power non-control AP = AP14, but the transmission power control AP = AP17, AP18, AP19 is set as the control access point. It is only AP17.

  Therefore, the number of control access points can be minimized by determining the control access points according to the flowchart shown in FIG.

  The determining means 63 determines the access points 11 and 17 as control access points by executing the flowchart shown in FIG. 11 for the access points 11 to 20 shown in FIG. 9, and sets the access points 13 and 14 as the access points 11 and 14, respectively. 17 is determined as an access point to be controlled.

  The determining unit 63 executes the flowchart shown in FIG. 11 for each CSG, and determines a control access point and a transmission power non-controlling AP to be controlled for each CSG.

The decision means 63 includes the channel usage rate of the transmission power control AP, the control access points = AP11 and AP17, the transmission power non-controlling APs to be controlled = AP13 and AP14, and the transmission powers P ₁₁ ^N , P ₁₂ ^N , P ₁₅ ^{N to} P _{When 20} ^N is determined, the channel usage rate of the transmission power control AP, the control access points = AP11 and AP17, the transmission power uncontrolled APs to be controlled = AP13 (AP11), AP14 (AP17), and the transmission powers P ₁₁ ^N and P ₁₂ ^N and P ₁₅ ^{N to} P ₂₀ ^N are transmitted to the access points 11 to 12 and _{15 to 20} through the communication unit 62 and the wired interface 61.

[Example 1]
The access points 11 to 12 and 15 to 20 are the channel usage rate of the transmission power control AP, the control access point = AP11, AP17, the transmission power not controlled AP = AP13 (AP11), AP14 (AP17) and the transmission power P ₁₁ ^N , P ₁₂ ^N , and P ₁₅ ^{N to} P ₂₀ ^N are received from the power control device 60 via the network 40. And the access points 11-12 and 15-20 notify a terminal device of transmission power, slot length, and a channel usage rate via a beacon.

  At the start of the slot, the doTPC access point and the terminal device set the doTPC time slot and the no TPC time slot by the following formula: doTPC time slot = slot length × channel usage rate and no TPC time zone = slot length × (1-channel usage rate). calculate. The access points 11 and 17 that are control access points generate a SAM including the calculated doTPC time zone.

  FIG. 12 is a configuration diagram of a SAM frame. Referring to FIG. 12, the SAM frame is defined according to the standard frame format of WiFi, and includes Frame Ctrl, A1 to A3, Seq Ctrl, Frame Body, and FCS.

  Frame Ctrl, A1, A2, A3, Seq Ctrl, Frame Body, and FCS have lengths of 2 bytes, 2 bytes, 6 bytes, 6 bytes, 6 bytes, 2 bytes, 0-2312 bytes, and 4 bytes, respectively. Have.

  Frame Ctrl is a type field and stores “00”. Duration stores doTPC time slot = end time of doTPC time slot−SAM frame transmission start time−SAM frame transmission time.

  A1 stores BROADCAST indicating the broadcast address, A2 stores the MAC address of the control access point, and A3 stores BSSID that identifies the communication range of the control access point. Seq Ctrl stores the SAM sequence number. In Frame Body, type = SAM is stored. FCS is an error correction code.

  In Duration, only the doTPC time zone is stored. When the noTPC access point and the terminal device receive the SAM frame, they automatically set the NAV up to the end time of the doTPC time zone and do not communicate in the doTPC time zone. When the NAV timer expires, it is just the noTPC time zone. In the noTPC time zone, the doTPC access point and the terminal device suppress communication, and therefore communication is performed only between the noTPC access point and the terminal device. Thus, a SAM frame substantially includes both a doTPC time zone and a no TPC time.

  FIG. 13 is a diagram illustrating the transmission power control operation in the first embodiment between the access point and the terminal device.

  Referring to FIG. 13, access point 11 serving as a control access point generates SAM1 including doTPC time zone 1 in slot 1 and accesses the channel with the highest priority, and blows at the maximum transmission power Pmax. Cast. In this case, doTPC time zone 1 is stored in Duration of SAM1, BROADCAST is stored in A1, MAC address MacAdd11 of access point 11 is stored in A2, and communication of access point 11 is stored in A3. A BSSID for identifying the range is stored.

  The terminal devices existing within the communication range of the access points 12, 13, 15, 16 and the access points 11, 12, 13, 15, 16 receive the SAM1. Then, the access point 13 and the terminal device existing within the communication range of the access point 13 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 1. Other doTPC access points and terminal devices communicate with each other without setting NAV even when SAM1 is received.

  In addition, the access point 17 serving as the control access point generates a SAM 2 including the doTPC time zone 1 in slot 1 and accesses the channel with the highest priority, and broadcasts with the maximum transmission power Pmax. In this case, doTPC time zone 1 is stored in Duration of SAM2, AROBAST is stored in A1, MAC address MacAdd17 of access point 17 is stored in A2, and communication of access point 17 is stored in A3. A BSSID for identifying the range is stored.

  Terminal devices that are within the communication range of the access points 14, 18, 19, 20 and the access points 14, 17, 18, 19, 20 receive the SAM2. Then, the access point 14 and the terminal device existing within the communication range of the access point 14 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 1. Other doTPC access points and terminal devices communicate with each other without setting NAV even when SAM2 is received.

Then, the access points ₁₁ , ₁₂ , and _{15 to 20} that control the transmission power transmit data packets to the terminal device at the transmission powers P ₁₁ ^N , P ₁₂ ^N , and P ₁₅ ^{N to} P ₂₀ ^N , respectively, in the doTPC time zone 1. Send and receive between.

  When the doTPC time slot 1 ends, the access point and the terminal device that control transmission power suppress transmission until the end of slot 1. When the doTPC time zone 1 ends, the NAV timers of the access points 13 and 14 that do not control the transmission power expire, so the data packet with the maximum transmission power enters the noTPC time zone 1 and the cells of the access points 13 and 14 Is sent.

  However, since the access point 13 that does not control the transmission power cannot correctly receive the SAM1 due to a packet error and does not set the NAV, the access point 13 is transmitting a data packet in the doTPC time zone 1 where communication is originally prohibited. Therefore, the access point 11 that is the control access point has the highest priority at the timing when it is detected that the access point 13 has transmitted the data packet (detected based on whether the BSSID of the frame is the BSSID of the access point 13). The channel is accessed, and SAM3 is further broadcast with the maximum transmission power Pmax. The duration 3 stored in the SAM 3 is the remaining time zone of the duration 1. Note that when the access point 11 broadcasts the SAM3, the access point that controls transmission power sets a new doTPC time zone, which is a time zone in which wireless communication is performed, so the doTPC time zone is updated and broadcasted. It corresponds to doing. By updating the doTPC time zone, the wireless communication of the access point 13 in the doTPC time zone can be further suppressed, and the wireless communication in which the transmission power by the access points 12, 15 to 20 is controlled can be further secured. As a result, it is possible to further ensure transmission power control in an environment in which the access points 11, 12, 15 to 20 that control transmission power and the access points 13 and 14 that do not control transmission power coexist.

  When slot 1 ends, access point 11 as the control access point generates SAM 4 including doTPC time zone 2 in slot 2 to access the channel with the highest priority, and broadcasts with the maximum transmission power Pmax. To do. In this case, doTPC time zone 2 is stored in Duration of SAM4, BROADCAST is stored in A1, MAC address MacAdd11 of access point 11 is stored in A2, and communication of access point 11 is stored in A3. A BSSID for identifying the range is stored.

  The terminal devices existing within the communication range of the access points 12, 13, 15, 16 and the access points 11, 12, 13, 15, 16 receive the SAM4. Then, the access point 13 and the terminal device existing within the communication range of the access point 13 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 2. Other doTPC access points and terminal devices communicate with each other without setting a NAV even when receiving SAM4.

  In addition, the access point 17 serving as the control access point generates a SAM 5 including the doTPC time zone 2 in the slot 2, accesses the channel with the highest priority, and broadcasts with the maximum transmission power Pmax. In this case, doTPC time zone 2 is stored in Duration of SAM5, BROADCAST is stored in A1, MAC address MacAdd17 of access point 17 is stored in A2, and communication of access point 17 is stored in A3. A BSSID for identifying the range is stored.

  The terminal devices existing within the communication range of the access points 14, 18, 19, 20 and the access points 14, 17, 18, 19, 20 receive the SAM 5. Then, the access point 14 and the terminal device existing within the communication range of the access point 14 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 2. Other doTPC access points and terminal devices communicate with each other without setting a NAV even when receiving SAM5.

Then, the access points ₁₁ , ₁₂ , and _{16 to 20} that control the transmission power transmit data packets to the terminal device at the transmission powers P ₁₁ ^N , P ₁₂ ^N , and P ₁₆ ^{N to} P ₂₀ ^N , respectively, in the doTPC time zone 2. Send and receive between.

  In addition, the access points 13 and 14 that do not control the transmission power transmit and receive data packets to and from the terminal device with the maximum transmission power in the no TPC time zone 2.

The access point 15 can transmit and receive data packets to and from the terminal device at the transmission power P ₁₅ ^N in the doTPC time slot 2 of the slot 2, but does not transmit or receive data packets in the example shown in FIG. Only.

  Further, the sum of the doTPC time zone 1 and the noTPC time zone 1 is equal to the length of the slot 1, and the sum of the doTPC time zone 2 and the no TPC time zone 2 is equal to the length of the slot 2, so that the access point 11 , 17 calculate the doTPC time zone 1 and the no TPC time zone 1, and calculating the doTPC time zone 2 and the no TPC time zone 2 is to divide the slot into the doTPC time zone and the no TPC time zone. Equivalent to.

  Furthermore, as described above, the access point that controls the transmission power can control the transmission power, and since the terminal device connected to itself is a terminal device that controls the transmission power, the access point 11, 12, 15 to 20 perform wireless communication with a terminal device that transmits data packets by controlling transmission power.

  Further, as described above, an access point that does not control transmission power is a terminal device that cannot control transmission power by itself, and a terminal device connected to itself can control transmission power but does not control transmission power. Since the terminal device connected to itself is a terminal device that cannot control transmission power, the access points 13 and 14 are terminal devices that cannot control transmission power. Alternatively, wireless communication is performed with a terminal device that can control transmission power but does not control transmission power.

  The access points 11, 12, and 15 to 20 do not control the transmission power because the access point that controls the transmission power performs wireless communication with the terminal device that controls the transmission power and transmits the data packet. The wireless communication is performed by removing the interference from the wireless communication by controlling the transmission power with the terminal device existing within the communication range of itself. Therefore, control of transmission power can be ensured in an environment where access points 11, 12, 15 to 20 that control transmission power and access points 13 and 14 that do not control transmission power coexist.

  In addition, the access points 13 and 14 can perform their own wireless communication with a terminal device that does not control transmission power or a terminal device that can control transmission power but does not control transmission power. Data packets are transmitted / received with the maximum transmission power to / from terminal devices existing within the communication range. Therefore, it is possible to prevent deterioration in the throughput of wireless communication by the access points 13 and 14 that do not control transmission power.

FIG. 14 is a conceptual diagram of a communication method according to the embodiment of the present invention. Referring to FIG. 14, access points ₁₁ , ₁₂ , and _{15 to} 20 that control transmission power transmit power P ₁₁ ^N , P ₁₂ ^N , and P _{15 that} are smaller than maximum transmission power Pmax, respectively, in the doTPC time zone. ^The access points 13 and 14 that transmit and receive data packets to and from the terminal device with ^{N 1} to P ₂₀ ^N and do not control the transmission power can transmit and receive data packets to and from the terminal device with the maximum transmission power Pmax in the no TPC time zone. Send and receive with.

  As a result, the wireless communication by the access points 11, 12, 15 to 20 that control the transmission power and the wireless communication by the access points 13 and 14 that do not control the transmission power do not interfere, and the access point that controls the transmission power. Even if 11, 12, 15 to 20 control the transmission power to a transmission power smaller than the maximum transmission power Pmax and transmit a data packet, an asymmetric link does not occur and the throughput can be increased.

  Therefore, throughput can be improved by controlling transmission power even in an environment where access points 11, 12, 15 to 20 that control transmission power and access points 13 and 14 that do not control transmission power coexist.

  Further, as described above, the access point 11 that is the control access point monitors whether or not the access point 13 that is the control target transmits a data packet in the doTPC time zone 1, and the access point 13 that is the control target. Is transmitting a data packet, the SAM 3 is newly broadcast to prohibit the communication of the access point 13.

  Therefore, it is possible to further suppress the radio communication by the access points 11, 12, 15 to 20 that control the transmission power from interfering with the radio communication by the access points 13 and 14 that do not control the transmission power. As a result, the transmission power can be more reliably controlled in an environment in which the wireless communication by the access points 11, 12, 15 to 20 that control the transmission power and the wireless communication by the access points 13 and 14 that do not control the transmission power coexist. .

[Example 2]
In the second embodiment, the channel usage rate is determined by excluding transmission power control APs (= access points that control transmission power) that are not adjacent to transmission power non-controlling APs (= access points that do not control transmission power) from the CSG. .

  More specifically, taking the access points 11 to 20 shown in FIG. 9 as an example, the access points 12, 15, 16, and 20 are not adjacent to the access points 13 and 14 that do not control transmission power. 63, after determining the channel usage rate of the access points 12, 15, 16, and 20 to be “1” and setting the doChCtrl of the access points 12, 15, 16, and 20 to OFF, the access points 12, 15, 16 and 20 are excluded from the CSG.

  Then, the determination unit 63 executes the CSG construction method described above, and divides the remaining access points 11, 13, 14, 17, 18, and 19 into a plurality of blocks.

  Then, the determination unit 63 determines a channel usage rate, a control access point, and a control target access point for each block.

  FIG. 15 is a flowchart for explaining a channel usage rate determination method according to the second embodiment.

  Referring to FIG. 15, when a series of operations is started, determination means 63 of power control device 60 accepts an access point included in one CSG (step S21).

  Then, the determination unit 63 sets i = 1 and selects the first access point APi in the CSG (step S22). After that, the determination unit 63 determines whether or not APi is an access point (doTPC AP) that controls transmission power and is not adjacent to an access point (noTPC AP) that does not control transmission power (step S23). ).

  When it is determined in step S23 that APi is not an access point that controls transmission power (AP of APPC) or is adjacent to an access point that does not control transmission power (AP of no TPC), the series of operations proceeds to step S29. Transition.

  On the other hand, when it is determined in step S23 that APi is an access point that controls transmission power (AP of APTP) and is not adjacent to an access point that does not control transmission power (AP of no TPC), determining means 63 Then, the channel usage rate of APi is set to “1” (step S24), and doChCtrl of APi is turned OFF (step S25).

  Thereafter, the determination unit 63 empties the set monitorNoTpcApSet of APi controlled access points (step S26), and excludes APi from the CSG (step S27).

  Then, the determination unit 63 determines whether all APs have been processed (step S28).

    When it is determined in step S28 that all APs have been processed, or in step S23, APi is not an access point that controls transmission power (AP of doTPC), or an access point that does not control transmission power (noTPC) When it is determined that it is adjacent to the AP, the determination unit 63 sets i = i + 1 and selects the next AP (step S29).

  Thereafter, the series of operations returns to step S23, and step S23 to step S29 described above are repeatedly executed until it is determined in step S28 that all APs have been processed.

  When it is determined in step S28 that all APs have been processed, the determination unit 63 divides the AP left in the CSG into a plurality of blocks using the above-described CSG construction method (step S30).

  Thereafter, the determination unit 63 sets j = 1 and selects the first block (step 31). Then, the determination unit 63 sets the ratio of the number of APs of the doTPC in the block BLKj and the total number of APs in the block BLKj as the channel usage rate of the AP of the doTPC in the block BLKj (Step S32).

  Subsequently, the determining unit 63 calculates the set monitorNoTpcApSet of the control access point and the control target access point in the block BLKj according to the flowchart shown in FIG. 11 (step S33).

  If it does so, the determination means 63 will determine whether all the blocks were processed (step S34).

  When it is determined in step S34 that all blocks have not been processed, the determination unit 63 sets j = j + 1 and selects the next block (step S35).

  Thereafter, the series of operations returns to step S32, and step S32 to step S35 described above are repeatedly executed until it is determined in step S34 that all blocks have been processed.

  When it is determined in step S34 that all blocks have been processed, the series of operations ends.

  Note that the flowchart shown in FIG. 15 is executed for each CSG.

  When the flowchart shown in FIG. 15 is executed for the access points 11 to 20 shown in FIG. 9, the channel usage rate is set to “1” for the access points 12, 15, 16, and 20, and doChCtrl is set to OFF. And excluded from the CSG. The access points 11, 13, 14, 17, 18, and 19 remaining in the CSG are divided into a block BLK1 including the access points 11 and 13 and a block BLK2 including the access points 14, 17, 18, and 19.

  Thereafter, since the block BLK1 is composed of an access point 11 that controls transmission power and an access point 13 that does not control transmission power, the channel usage rate in the block BLK1 is calculated as ½. Further, the control access point in the block BLK1 is determined as the access point 11, and the access point to be controlled is determined as the access point 13.

  In addition, since the block BLK2 includes access points 17, 18, and 19 that control transmission power and an access point 14 that does not control transmission power, the channel usage rate in the block BLK2 is calculated as 3/4. Further, the control access point in the block BLK2 is determined as the access point 17, and the access point to be controlled is determined as the access point 14.

  FIG. 16 is a diagram illustrating information that the power control device 60 transmits to the access point. Referring to FIG. 16, determining unit 63 acquires information IF by executing the flowchart shown in FIG.

  The information IF is obtained by associating doChCtrl indicating whether the access point is a control access point, monitorNoTpcApSet indicating the access point to be controlled, and the channel usage rate with each access point that controls transmission power.

  Then, the determination unit 63 transmits the information IF to the access points 11, 12, 15 to 20 via the communication unit 62 and the wired interface 61.

  The access points 11, 12, 15 to 20 receive the information IF. Then, the access point 11 detects that it is a control access point, that the access point to be controlled is the access point 13, and that the channel usage rate is ½.

  Further, the access point 17 detects that it is a control access point, that the access point to be controlled is the access point 14, and that the channel usage rate is 3/4.

  Further, the access points 12, 15, 16, and 20 detect that they are not control access points, that there is no access point to be controlled, and that the channel usage rate is 1.

  Further, the access points 18 and 19 detect that they are not the control access point, that there is no access point to be controlled, and that the channel usage rate is 3/4.

  FIG. 17 is a diagram illustrating a transmission power control operation in the second embodiment between the access point and the terminal device.

  In slot 3, the doTPC access point 11 and the terminal device connected thereto calculate doTPC time slot 3 = slot length × 1/2 using the channel usage rate = ½ and the slot length.

  Then, the access point 11 as the control access point generates a SAM 6 including the doTPC time zone 3, accesses the channel with the highest priority, and broadcasts it with the maximum transmission power Pmax. A1, A2, and A3 of SAM6 are as described in the first embodiment.

  Then, the terminal apparatus existing within the communication range of the access point 13 and the access points 11 and 13 receives the SAM 6. Then, the access point 13 and the terminal device existing within the communication range of the access point 13 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 3. Other doTPC access points and terminal devices communicate with each other without setting the NAV even when receiving the SAM6.

Thereafter, the access point 11 transmits / receives data packets to / from a terminal device existing in its own communication range using the transmission power P ₁₁ ^N smaller than the maximum transmission power Pmax in the doTPC time zone 3 of the slot 3. When the doTPC time zone 3 ends, the NAV timer at the access point 13 and the terminal device connected to the access point 13 expires, so the no TPC time zone 3 of the slot 3 enters, and the access point 13 receives the maximum transmission power Pmax. Is used to transmit / receive data packets to / from a terminal device existing within its own communication range. Further, the access points ₁₂ , ₁₅ , and ₁₆ use transmission powers P ₁₂ ^N , P ₁₅ ^N , and P ₁₆ ^N that are smaller than the maximum transmission power Pmax in the doTPC time zone 3 and the no TPC time zone 3 of the slot 3, respectively. The data packet is transmitted / received to / from a terminal device existing within the communication range of itself.

  On the other hand, in slot 3, doTPC access points 17 to 19 and the terminal devices connected thereto calculate doTPC time slot 4 = slot length × 3/4 using channel utilization rate = 3/4 and slot length. To do.

  Then, the access point 17 serving as the control access point generates a SAM 7 including the doTPC time zone 4, accesses the channel with the highest priority, and broadcasts it with the maximum transmission power Pmax. A1, A2, and A3 of SAM7 are as described in the first embodiment.

  If it does so, the terminal device which exists in the communication range of access point 14,18,19 and access point 14,17,18,19 will receive SAM7. Then, the access point 14 and the terminal device existing within the communication range of the access point 14 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 4. Other doTPC access points and terminal devices communicate with each other without setting a NAV even when receiving SAM7.

Thereafter, the access point 17 transmits / receives data packets to / from a terminal device existing within its own communication range using the transmission power P ₁₇ ^N smaller than the maximum transmission power Pmax in the doTPC time zone 4 of the slot 3. When the doTPC time zone 4 ends, the NAV timer at the access point 14 and the terminal device connected to the access point 14 expires. Therefore, the noTPC time zone 4 of the slot 3 enters, and the access point 14 receives the maximum transmission power Pmax. Is used to transmit / receive data packets to / from a terminal device existing within its own communication range. Furthermore, in the doTPC time zone 4 of the slot 3, the access points 18 and 19 are terminal devices that exist within their own communication ranges using transmission powers P ₁₈ ^N and P ₁₉ ^N that are smaller than the maximum transmission power Pmax, respectively. Send and receive data packets.

Since the access points ₁₂ , ₁₅ , ₁₆ , and ₂₀ have a channel usage rate = 1, in the slot 3, the transmission powers P ₁₂ ^N , P ₁₅ ^N , P ₁₆ ^N , and P ₂₀ ^N are smaller than the maximum transmission power Pmax. It uses it to send and receive data packets to and from terminal devices that are within its own communication range.

  When the slot 3 ends, the doTPC access point 11 and the terminal device connected to the access point 11 use the channel usage rate = 1/2 and the slot length in the slot 4, and doTPC time slot 5 = slot length × 1/2. Is calculated.

  Then, the access point 11 serving as the control access point generates a SAM 8 including the doTPC time zone 5, accesses the channel with the highest priority, and broadcasts it with the maximum transmission power Pmax. A1, A2, and A3 of SAM8 are as described in the first embodiment.

  Then, the terminal apparatus existing within the communication range of the access point 13 and the access points 11 and 13 receives the SAM 8. Then, the access point 13 and the terminal device existing within the communication range of the access point 13 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 5 and do not communicate until the doTPC time zone 5 ends. Other doTPC access points and terminal devices communicate with each other without setting a NAV even when receiving SAM8.

Thereafter, the access point 11 transmits / receives data packets to / from a terminal device existing in its own communication range using the transmission power P ₁₁ ^N smaller than the maximum transmission power Pmax in the doTPC time zone 5 of the slot 4. When the doTPC time zone 5 ends, the NAV timer at the access point 13 and the terminal device connected to it expires, so the no TPC time zone 5 of slot 4 is entered. The access point 13 transmits / receives a data packet to / from a terminal device existing within its own communication range using the maximum transmission power Pmax in the no TPC time zone 5 of the slot 4. Further, the access points ₁₂ , ₁₅ , and ₁₆ use transmission powers P ₁₂ ^N , P ₁₅ ^N , and P ₁₆ ^N that are smaller than the maximum transmission power Pmax in the doTPC time slot 5 and the no TPC time slot 5 of the slot 4, respectively. The data packet is transmitted / received to / from a terminal device existing within the communication range of itself.

  On the other hand, the access points 17 to 19 of the doTPC and the terminal devices connected to them use the channel usage rate = 3/4 and the slot length in the slot 4, and doTPC time slot 6 = slot length × 3/4. And noTPC time slot 6 = slot length × (1-3 / 4).

  Then, the access point 17 serving as the control access point generates a SAM 9 including the doTPC time zone 6 and the no TPC time zone 6, accesses the channel with the highest priority, and broadcasts it with the maximum transmission power Pmax. A1, A2, and A3 of SAM9 are as described in the first embodiment.

  If it does so, the terminal device which exists in the communication range of access point 14,18,19 and access point 14,17,18,19 will receive SAM9. Then, the access point 14 and the terminal device existing within the communication range of the access point 14 set the NAV indicating the time zone during which no wireless communication is performed to the doTPC time zone 6 and do not communicate until the doTPC time zone 6 ends. Other doTPC access points and terminal devices communicate with each other without setting NAV even when SAM9 is received.

Thereafter, the access point 17 transmits / receives data packets to / from a terminal device existing in its own communication range using the transmission power P ₁₇ ^N smaller than the maximum transmission power Pmax in the doTPC time zone 6 of the slot 4. Further, the access point 14 transmits / receives data packets to / from a terminal device existing within its own communication range using the maximum transmission power Pmax in the no TPC time zone 6 of the slot 4. Furthermore, in the doTPC time zone 6 of the slot 4, the access points 18 and 19 are terminal devices that exist within their communication ranges using transmission powers P ₁₈ ^N and P ₁₉ ^N that are smaller than the maximum transmission power Pmax, respectively. Send and receive data packets.

Since the access points ₁₂ , ₁₅ , ₁₆ , and ₂₀ have a channel usage rate = 1, in the slot 4, transmission powers P ₁₂ ^N , P ₁₅ ^N , P ₁₆ ^N , and P ₂₀ ^N that are smaller than the maximum transmission power Pmax are set. It uses it to send and receive data packets to and from terminal devices that are within its own communication range.

  Also in the second embodiment, the access points 11 and 17 that are control access points monitor whether or not the access points 13 and 14 are performing wireless communication in the doTPC time zone, respectively.

  As described above, in the second embodiment, the access points 12, 15, 16, and 20 that are not adjacent to the access points 13 and 14 to be controlled always perform wireless communication by controlling the transmission power. Further, the access points 11 and 17 to 19 perform wireless communication by controlling transmission power during the slot doTPC time zone. Furthermore, the access points 13 and 14 perform wireless communication without controlling the transmission power during the no TPC time slot of the slot.

  As a result, the wireless communication by the access points 13, 14 does not interfere with the wireless communication by the access points 11, 12, 15-20, so that the access points 11, 12, 15-20 perform the wireless communication by controlling the transmission power. However, asymmetric links do not occur and throughput can be improved.

  Therefore, throughput can be improved by controlling transmission power even in an environment where access points 11, 12, 15 to 20 that control transmission power and access points 13 and 14 that do not control transmission power coexist.

  Further, since the access points 12, 15, 16, and 20 that are not adjacent to the access points 13 and 14 to be controlled always perform wireless communication by controlling the transmission power, the wireless communication by the access points 12, 15, 16, and 20 is performed. Can be improved as compared with the case where the access points 12, 15, 16, and 20 perform wireless communication only in the doTPC time zone.

  Other explanations in the second embodiment are the same as those in the first embodiment.

  In the above, the power control device 60 determines the transmission power, slot length, channel usage rate, control access point, and control target access point used at the access points 11, 12, 15 to 20, and the access points 11, 12 , 15 to 20, in the embodiment of the present invention, the transmission power, the slot length, the channel usage rate, the control access point, and the access point to be controlled are not limited to this. It may be determined by a device other than the device 60 and may be finally input to the access points 11, 12, 15 to 20. Therefore, the communication system according to the embodiment of the present invention only needs to include access points 10 to 21.

  In the embodiment of the present invention, the CSG constitutes a “connection relation set”.

  In the embodiment of the present invention, the access points 12, 15, 16, and 18 to 20 constitute a "first access point", and the access points 13 and 14 define a "second access point". The access points 11 and 17 constitute a “third access point”.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a communication system.

  1-9 terminal device, 10-21 access point, 40 network, 50 monitoring server, 60 power control device, 61, 114 wired interface, 62, 103, 113 communication means, 63 determination means, 64 adjustment means, 100 communication system, 101 antenna, 102, 112 wireless interface, 104 application module.

Claims (7)

A first access point for controlling transmission power and transmitting data packets;
A second access point that transmits a data packet with the maximum transmission power without controlling the transmission power using the same channel as the channel used in the first access point;
A data packet is transmitted by controlling transmission power using the same channel as the channel used in the first access point, and a third access point for controlling the second access point,
The third access point has one slot in a first time zone in which the first and third access points transmit the data packet and a second time in which the second access point transmits the data packet. A process of dividing the divided into time zones and broadcasting the divided first and second time zones is executed for each slot, and data is transmitted with transmission power smaller than the maximum transmission power in the first time zone. Send a packet,
The first access point transmits a data packet with a transmission power smaller than the maximum transmission power in the first time period;
The communication system, wherein the second access point stops transmitting data packets in the first time zone and transmits data packets with the maximum transmission power in the second time zone.   The said 3rd access point updates the said 1st time slot | zone, and broadcasts, when the data packet transmitted from the said 2nd access point is received in the said 1st time slot | zone. Communication system.   The access point that is not adjacent to the second access point among the first access points transmits data packets with transmission power smaller than the maximum transmission power in the first and second time zones. Item 12. The communication system according to Item 1. The first time period is calculated by multiplying the channel length of the first and third access points by the slot length,
4. The communication system according to claim 1, wherein the second time period is calculated by multiplying a subtraction result obtained by subtracting the channel usage rate from 1 by the slot length. 5.   The communication system according to claim 4, wherein the channel usage rate is determined so that the first and third access points and the second access point use the channel fairly. The first to third access points are included in a connection relation set that is a set of access points having an adjacent relation capable of transmitting and receiving radio waves,
The communication system according to claim 4 or 5, wherein the channel usage rate of the first access point is determined to be the same as the channel usage rate of the third access point.   The transmission power in each of the first and third access points is the throughput in the communication range of each of the first and third access points, excluding the communication range of the second access point. The communication system according to claim 6, wherein calculation is performed in consideration of an influence of transmission power in an adjacent communication range adjacent to each communication range of the third access point, and the calculated throughput is calculated to be maximized. .

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