JP2011044894A - Power control device and communication network system with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power control device that enhances throughput in general in a communication network with a plurality of communication devices connected to the network serving as a core. <P>SOLUTION: The power control device 60 operates throughput as local throughput in a local network of each of access points 10 to 21 in consideration of effect of power transmission in the local network of the access point adjacent to each of the access points 10 to 21. The power control device 60 decides twelve pieces of the power transmission in the local network of each of the access points 10 to 21 so as to maximize the local throughput. Thereafter, the power control device 60 adjusts the twelve pieces of the power transmission so that a difference of the power transmission between the adjacent two local networks is equal to or less than a threshold δ<SB>P</SB>in the twelve local networks corresponding to the access points 10 to 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power control apparatus that controls power and a communication network system including the same.

  Wireless LANs (Local Area Networks) are widely used in hot spots such as schools and event venues. In order to ensure coverage, access points are densely arranged.

  However, since the number of non-overlapping channels is limited (eg, there are only three non-overlapping channels at 2.4 GHz), many access points share the same channel. As the number of neighboring access points sharing the same channel increases, the problem of co-channel interference becomes increasingly severe and the performance of the entire network may be degraded.

  On the other hand, if the installed access points are dense, each terminal is likely to find an access point in a close range. When the distance between the terminal and the access point is shortened and there is a high-quality link, there is no need to transmit at the maximum transmission power. Instead, if transmission power is reduced, co-channel interference can be greatly reduced and throughput in the entire network can be improved.

  However, transmission power control causes asymmetric links, unfair channel usage, hidden terminal problems, and the like. In addition, a terminal that appears outside the communication range reduced by the transmission power control may not be able to communicate with the access point.

  IEEE 802.11, which is often used for wireless LANs, always requires an acknowledgment (ACK) after data transmission, so if an asymmetric link is formed, the adverse effect becomes very large. In order to avoid this problem, a method has been proposed in which transmission power is reduced while avoiding asymmetric links by using common transmission power on all networks (Non-Patent Document 1).

  Also, all access points are synchronized, the channel is divided into slots along the time axis, all access points transmit at the same power in the same slot, and transmission power is controlled by changing the transmission power for each slot Has been proposed (Non-patent Document 2).

  Furthermore, a method has been proposed in which transmission power is controlled so as to ensure a transmission rate while taking into consideration the link quality between the access point and the terminal device (Non-patent Document 3).

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.

  However, the method disclosed in Non-Patent Document 1 is inefficient because, as a result of using the same power throughout the network, the transmission power of the entire network increases if the quality of one link is poor.

  Moreover, with the method disclosed in Non-Patent Document 2, it is practically difficult to adjust the transmission power for each slot. Then, it is necessary to perform scheduling when transmitting a packet, which may cause a transmission delay.

  Furthermore, in the method disclosed in Non-Patent Document 3, a transmission rate is ensured, but it is difficult to determine transmission power in consideration of cooperation between access points.

  Therefore, when the transmission power is determined using the methods disclosed in Non-Patent Document 1 to Non-Patent Document 3, there is a problem that the throughput of the entire network including a plurality of access points decreases.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to control power that can improve overall throughput in a communication network including a plurality of communication devices connected to a core network. Is to provide a device.

  Another object of the present invention is to provide a communication network system including a power control device capable of improving the overall throughput in a communication network including a plurality of communication devices connected to a core network. .

  According to the present invention, the power control device is a power control device that controls transmission power in a plurality of communication devices that are connected to a network and use the same channel, and includes a determination unit, an adjustment unit, and a communication unit. With. The determining means is based on a first link quality between adjacent communication devices of the plurality of communication devices and a second link quality between the terminal device and the communication device directly connected to each communication device. The local throughput in the first local network composed of the first communication device of the plurality of communication devices and the first terminal device accessing the first communication device is adjacent to the first local network. (N is a positive integer) Calculated as the throughput in the first local network when the influence of the transmission power in the second local networks is taken into consideration, and the first local so that the calculated local throughput is maximized The power determination process for determining the transmission power in the network is applied to all of the plurality of local networks corresponding to the plurality of communication devices. To run Te. The adjusting means adjusts the transmission power in the second local network so that the transmission power difference between the first local network and the n second local networks is equal to or less than the first threshold value. The process is executed for all of the plurality of local networks corresponding to the plurality of communication devices. The communication unit transmits the transmission power adjusted by the adjustment unit to the plurality of communication devices.

  Preferably, the determination unit performs a process of calculating a transmission time per bit in each second local network based on the n second link qualities in the n second local networks. M which is executed for all of the two local networks and the received signal strength when receiving a packet from the second local network exceeds the carrier sense threshold in the first local network (m is an integer satisfying 1 ≦ m ≦ n) ) Second local networks are extracted from the n second local networks, and the reciprocal of the sum of the m transmission times in the extracted m second local networks is maximized. The transmission power in the second local network is changed to the transmission power in the first local network. To be determined.

  Preferably, the determining unit classifies the plurality of communication devices into a connection relationship set that is a set of communication devices that use the same channel and have the adjacency relationship based on an adjacency list that indicates an adjacency relationship between the communication devices. Then, the power determination process is executed for each classified connection relation set. The adjustment means executes power adjustment processing for each classified connection relation set.

  Preferably, when the number of communication devices included in one connection relation set exceeds the second threshold value, the determining unit divides the connection relation set into a plurality of connection relation sets, and the plurality of divided connection relations A power determination process is performed for each of the sets. The adjustment unit executes power adjustment processing for each of the plurality of divided connection relation sets.

  According to the invention, the communication network system includes a plurality of communication devices, a plurality of terminal devices, and a power control device. The plurality of communication devices are connected to a network. Each of the plurality of terminal devices performs wireless communication with one of the plurality of communication devices. The power control apparatus is connected to the network and controls transmission power in a plurality of communication apparatuses using the same channel. The power control apparatus includes a determination unit, an adjustment unit, and a communication unit. The determining means is based on a first link quality between adjacent communication devices of the plurality of communication devices and a second link quality between the terminal device and the communication device directly connected to each communication device. The local throughput in the first local network composed of the first communication device of the plurality of communication devices and the first terminal device accessing the first communication device is adjacent to the first local network. (N is a positive integer) Calculated as the throughput in the first local network when the influence of the transmission power in the second local networks is taken into consideration, and the first local so that the calculated local throughput is maximized The power determination process for determining the transmission power in the network is applied to all of the plurality of local networks corresponding to the plurality of communication devices. To run Te. The adjusting means adjusts the transmission power in the second local network so that the transmission power difference between the first local network and the n second local networks is equal to or less than the first threshold value. The process is executed for all of the plurality of local networks corresponding to the plurality of communication devices. The communication unit transmits the transmission power adjusted by the adjustment unit to the plurality of communication devices. Each of the plurality of communication devices transmits the first and second link qualities to the power control device, and performs wireless communication with the terminal device existing in its own local network with the transmission power received from the communication means of the power control device. Do. Each of the plurality of terminal devices performs wireless communication with the second communication device with the same transmission power as that of the second communication device to which the terminal device is directly connected.

  Preferably, each of the plurality of communication devices has a transmission power larger than the received transmission power when detecting a terminal device newly participating in the local network and outside the reduced communication range. Wireless communication is performed with a terminal device existing in its own local network.

  Preferably, the first communication device performs wireless communication with the first terminal device existing in the local network with a transmission power larger than the received transmission power and outside the reduced communication range. Do. When the second communication device adjacent to the first communication device detects that the first terminal device has newly joined the local network, the second communication device is outside the communication range in which the first terminal device is shortened. If it is located, wireless communication is performed with a terminal device existing in its own local network with a transmission power larger than the received transmission power.

  Preferably, the first terminal apparatus determines the transmission required power so that the link quality with the first communication apparatus becomes a desired link quality, and the determined transmission required power is the current transmission power of itself. If a packet is not transmitted to the first communication device for a certain period of time, the transmission power control request including the required transmission power is transmitted to the first communication device with the maximum transmission power. The first communication device receives the transmission power control request, and newly transmits a larger one of the required transmission power included in the received transmission power control request and the transmission power received from the power control device. The power is determined, and the determined new transmission power is transmitted to the first terminal device.

  In the present invention, the local throughput, which is the throughput in the first local network when the influence of the transmission power in the n second local networks adjacent to the first local network is considered, is calculated, and the calculation is performed. The transmission power in the first local network is determined so that the local throughput is maximized. This power determination process is executed for all of a plurality of local networks corresponding to a plurality of communication devices. The plurality of transmission powers of the plurality of local networks determined by the power determination process are adjusted so that the transmission power difference between two adjacent local networks is equal to or less than the first threshold value.

  As a result, the throughput is maximized in each of the plurality of local networks, and the difference in transmission power among the plurality of local networks is equal to or less than the first threshold value.

  Therefore, according to the present invention, it is possible to improve the overall throughput in a communication network including a plurality of communication devices connected to a core network.

It is the schematic which shows the structure of the communication network 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 adjacency and an access point of indirect adjacency. 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 the division | segmentation of CSG. It is a figure which shows the specific example of adjustment of transmission power. It is a figure for demonstrating the control method of the transmission power when a new terminal device enters. It is a figure for demonstrating the control method of the transmission power in case a terminal device hands over. It is a figure which shows the flow of the electric power control method by embodiment of this invention.

  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 network system according to an embodiment of the present invention. Referring to FIG. 1, a communication network 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 the access points 10 to 21 transmits a control frame (including an ACK for it) with the maximum transmission power, and a data frame (including an ACK for the same) described later. Transmit with power controlled by.

  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 uses, as an access point to be connected, an access point having the maximum potential throughput, which is a throughput when an unused channel is used only for wireless communication between itself and the access point. select.

  And each of the terminal devices 1-9 performs radio | wireless communication using the transmission power received from the connected access point.

  Each of the terminal devices 1 to 9 periodically receives a beacon frame from the access points 10 to 21 and creates an adjacent access point list indicating access points adjacent to the terminal device based on the received beacon frame. . Each of the terminal devices 1 to 9 transmits the created adjacent access point list to the monitoring server 50 via the network 40.

  Each of the access points 10 to 21 includes a WiFi wireless interface. Each of the access points 10 to 21 receives transmission power from the power control device 60, performs wireless communication with the terminal devices 1 to 9 through the WiFi wireless interface, and uses the received transmission power via the network 40. To communicate with the monitoring server 50 and the power control device 60.

  In addition, each of the access points 10 to 21 periodically transmits a beacon frame by wireless communication. Each of the access points 10 to 21 periodically detects an access point adjacent to itself by receiving a beacon frame transmitted from another access point, and creates an adjacent access point list to be described later.

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

  Then, each of the access points 10 to 21 periodically transmits the adjacent access point list and the terminal list 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. Then, the monitoring server 50 periodically receives the adjacent access point list from each of the terminal devices 1 to 9 via the network 40, and also receives the adjacent access point list and the terminal list from each of the access points 10 to 21. And periodically manage the received adjacent access point list and terminal list.

  The power control device 60 is connected to the network 40. Then, the power control device 60 periodically acquires the adjacent access point list and the terminal list from the monitoring server 50 via the network 40. 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 21 sharing the channel is determined.

  Subsequently, the power control device 60 adjusts the transmission power used in the local network of each access point 10 to 21 by a method described later, and sends the adjusted transmission power to the access points 10 to 21 via the network 40. Send.

  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 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 is received. Then, the wireless interface 102 outputs the detected received signal strength to the communication unit 103.

  Further, the wireless interface 102 receives a beacon frame including data transmission power from an access point (any one of the access points 10 to 21), and extracts transmission power from the received beacon frame.

  The wireless interface 102 is connected to the access point (any one of the access points 10 to 21) in the infrastructure mode, and packets are transmitted to the access point (any one of the access points 10 to 21) with the extracted transmission power. Send and receive.

  That is, the wireless interface 102 transmits the packet 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 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 network system 100 (transmission power when each of the access points 10 to 21 transmits a beacon frame).

  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 the method mentioned later based on the maximum transmission power and the received signal strength.

Then, the communication means 103 creates a neighboring access point list APL _MN including the beacon reception RSSI, the MAC (Media Access Control) address of the terminal device 1 and the ID of the channel used by the wireless interface 102, and the created neighboring access point The 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 packet from the communication unit 113 and transmits the received packet via the antenna 111 with the transmission power received from the communication unit 113. The wireless interface 112 receives a packet via the antenna 111 and outputs the received 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.

  Further, the communication unit 113 receives transmission power used in the local network of the access point 10 from the power control apparatus 60 via the wired interface 114 and sets the received transmission power in the wireless interface 112. And the communication means 113 includes the transmission power received from the power control device 60 in the beacon frame and transmits it to the terminal device (at least one of the terminal devices 1 to 9).

Further, 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 and the beacon reception RSSI. The communication unit 113 transmits the MAC address of the access point 10, the ID of the channel used by the wireless interface 112, the terminal list TL, and the adjacent access point list APL _AP to the monitoring server 50 via the wired interface 114. To do.

  Further, the communication unit 113 receives a packet from the wireless interface 112 and transmits the received packet via the wired interface 114. The communication unit 113 receives a packet via the wired interface 114 and outputs the received packet to the wireless 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.

  Also, the wired interface 114 receives transmission power from the power control device 60 via the network 40 and outputs the received transmission power to the communication unit 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.

  In addition, the communication unit 62 receives the adjusted transmission power from the adjustment unit 64 and transmits the received transmission power to the access points 10 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 10-21 is determined. Then, the determination unit 63 outputs the 12 transmission powers of the determined access points 10 to 21 to the adjustment unit 64.

The adjustment 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 the 12 transmission powers of the access points 10 to 21 from the determination unit 63.

Then, the adjusting unit 64 uses the terminal list TL, the adjacent access point list APL _MN , the APL _AP, and the 12 transmission powers of the access points 10 to 21 to adjust the 12 points of the access points 10 to 21 by a method described later. The transmission power is adjusted, and the twelve transmission powers after the adjustment are output to the communication means 62.

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

[Calculation of path loss and beacon reception RSSI]
Each of the terminal devices 1 to 9 calculates a path loss (PL: Path Loss) according to the following procedure when receiving a frame from the access point (any one of the access points 10 to 21).

Further, each of the access points 10 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) Each of the terminal devices 1 to 9 or each of the access points 10 to 21 calculates a PL by PL = beacon transmission power−reception RSSI when the received frame is a control frame such as a beacon frame or an ACK in response thereto. To do. 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) When each of the terminal devices 1 to 9 or each of the access points 10 to 21 is a data frame or an ACK responding thereto, the PL is calculated by PL = data transmission power-reception RSSI. The received RSSI is the received signal strength when a data frame or ACK is received.

  (3) Each of the terminal devices 1 to 9 or each of the access points 10 to 21 calculates an average value of PL by the following equation in order to eliminate the influence of fading and the like.

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 devices 1-9 or each of the access points 10-21 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 collects the adjacent access point list APL _AP 1 = [MACadd11 / beacon reception RSSI1] and channel ID = CH1 collected from the access point 10, and collected from the access point 11. Based on the adjacent access point list APL _AP 2 = [MACadd10 / beacon reception RSSI2] and channel ID = CH1, the access points 10 and 11 operate on the same channel CH1 and can directly receive each other's beacon frames. It is detected that it is a point, and the access points 10 and 11 are set as directly adjacent access points.

  With reference to (b) of FIG. 5, the terminal device 1 detects the access point 10 as an adjacent access point by receiving a beacon frame from the access point 10, and calculates the beacon reception RSSI 3 by the method described above.

  Moreover, the terminal device 1 detects the access point 11 as an adjacent access point by receiving a beacon frame from the access point 11, 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 / 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 = [MACadd1 / beacon reception RSSI6], 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 the adjacent access point list APL _MN 1 = [MACadd10, MACadd11 / channel ID = CH1 / beacon reception RSSI3, beacon reception RSSI4] received from the terminal device 1, and the MAC address MACadd10 received from the access point 10. , Channel ID = CH1, terminal list TL1 = [MACadd1 / beacon reception RSSI5] and adjacent access point list APL _AP 3 = [... /...], MAC address MACadd11 received from access point 11, channel ID = CH1, based on the terminal list TL2 = [MACadd1 / beacon reception RSSI6] and its neighbor access point list _{APL AP 4 = [··· / ···} ] and an 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 21 creates and manages a terminal list TL by association from a terminal device (any one of the terminal devices 1 to 9). Each access point 10-21 calculates a beacon reception RSSI by the method mentioned above by receiving a frame from a terminal device (any one of the terminal devices 1-9).

Each access point 10 to 21 detects a neighboring access point by receiving a beacon frame from another access point, and calculates a beacon reception RSSI by the method described above. Each of the access points 10 to 21 has its own terminal list TL (= the MAC address of the terminal device connected to itself and the beacon reception RSSI) and the adjacent access point list APL _AP (= the MAC address of the access point adjacent to itself). And beacon reception RSSI) are periodically transmitted to the monitoring server 50.

On the other hand, each terminal device 1-9 detects an adjacent access point by receiving a beacon frame from an access point (any one of the access points 10-21). Each terminal device 1 to 9 periodically transmits its own adjacent access point list APL _MN (= MAC address, channel ID and beacon reception RSSI of the access point adjacent to itself) to the monitoring server 50.

The power control device 60 includes the adjacent access point list APL _AP (= the MAC address of the access point adjacent to each access point 10-21 and the beacon reception RSSI) and the adjacent access of each terminal device 1-9. The point list APL _MN (= MAC address, channel ID and beacon reception RSSI of an access point adjacent to each terminal device 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 (= the MAC address of the access point adjacent to each access point 10 to 21 and the beacon reception RSSI) of each access point 10 to 21 and each terminal device 1 to 9. Based on the adjacent access point list APL _MN (= the MAC address, channel ID, and beacon reception RSSI of the access point adjacent to each of the terminal devices 1 to 9), the CSG is constructed and divided by the method described later.

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

The communication means 62 of the power control apparatus 60 acquires the terminal list TL of the access points 10 to 21 and the adjacent access point list APL _AP from the monitoring server 50 via the wired interface 61, and acquires the acquired terminal list TL and adjacent access. The point list APL _AP is output to the determination means 63.

The determination unit 63 of the power control device 60 holds a table TBL of RSSI and transmission rate in advance. 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 communication range) of the access point j (j = 10 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.

_Assuming that the RSSI _{ij (Pbeacon)} when the terminal device i receives the beacon frame from the access point j is RSSI _{ij (Pbeacon)} , 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. Data reception RSSI (= RSSI _{ij (P)} ) when data is received is calculated by the following equation.

RSSI _{ij (P)} = p-P _beacon + RSSI _{ij (Pbeacon)} (3)
Then, the determination unit 63 of the power control device 60 refers to the table TBL and detects 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 (that can receive a beacon frame directly) is defined as an access point k (k = 10 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 (Pbeacon)} ) (5)
Note that RSSI _{kj (Pbeacon)} 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 apparatus 60 can calculate RSSI (= RSSI _{kj (p ′)} ) by the equation (5).

Then, the determination unit 63 of the power control device 60 puts the access point k (= local network) into N _j (p ′) when RSSI _{kj (p ′)} is larger than the carrier sense threshold of the access point j.

Determining means 63 of the power control unit 60, performed for all of the access points k adjacent _'and operations, the computed _{RSSI kj (p RSSI kj (p} )' a comparison _between) the carrier sense threshold to the access point j To do.

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 and division of CSG]
(I) Construction of CSG The communication means 62 of the power control apparatus 60 transmits the [MAC address MACadd10 / channel ID = CH1 / terminal list TL10 / adjacent access point list APL _AP 10] to [MAC address MACadd21 / Channel ID = CH1 / terminal list TL21 / adjacent access point list APL _AP 21] is acquired from the monitoring server 50, and the acquired [MAC address MACadd10 / channel ID = CH1 / terminal list TL10 / adjacent access point list APL _AP 10]. ~ [MAC address MACadd21 / channel ID = CH1 / terminal list TL21 / adjacent access point list APL _AP 21] is output to the determination means 63.

Then, the determination unit 63 of the power control apparatus 60 selects [MAC address MACadd10 / channel ID = CH1 / terminal list TL10 / adjacent access point list APL _AP 10] to [MAC address MACadd21 / channel ID = CH1 / terminal list TL21 / adjacent. A CSG is constructed based on the 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 determination unit 63 of the power control device 60 creates a neighbor list NBL1 (see FIG. 6A) based on the channel ID = CH1 of the access points 10 to 21 and the adjacent access point lists APL _AP 10 to APL _AP 21. To do. 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 device 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 connects to the access point 15 The access points 16 and 17 to be entered are put into the 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).

(Ii) Division of CSG The determination unit 63 of the power control apparatus 60 divides the CSG according to the following procedure.

  (D1) All CSGs on all channels constitute one CSG set. The determination unit 63 of the power control device 60 attaches a division flag flag_DV to each CSG in the CSG set if the number of access points included in the CSG exceeds a threshold (= 20, for example).

  (D2) The determination unit 63 of the power control device 60 selects one CSG from the CSGs with the splittable flag flag_DV.

    (D2-1) The determination unit 63 of the power control apparatus 60 sets all access points included in the selected CSG as a severable access point, and prevents access points adjacent to the sharable access point from overlapping as follows. Divide into subsets.

(D2-1-1) A new subset subset _p (p = 1, 2, 3,...) Is prepared.

(D2-1-2) An access point j not included in the existing subset is selected from access points adjacent to the splittable access point, and is entered into the subset subset _p .

(D2-1-3) For each access point that belongs to an access point adjacent to the divisible access point and does not belong to the existing subset, is it adjacent to the access point that belongs to the subset subset _p ? Check if. If it is adjacent, it is put into the subset subset _p . This process is repeated until there are no more access points in the subset subset _p .

      (D2-1-4) If there remains an access point that is not in the existing subset, the processes (D2-1-1) to (D2-1-3) are repeated.

      (D2-1-5) If an access point adjacent to a divisible access point can be divided into two or more subsets that do not overlap, it is determined as a division candidate.

    (D2-2) The determination unit 63 of the power control apparatus 60 confirms whether or not the CSG can be divided there for each division candidate by the following method.

      (D2-2-1) Extract division candidates from the CSG.

      (D2-2-2) When the original CSG is divided into two, the division candidate belongs to a CSG with many adjacent access points. Then, the two divided new CSGs are put into the CSG set. If the number of access points included in the new CSG exceeds a threshold value (= 20), a splittable flag_DV is attached to the CSG. If the original CSG is not divided into two CSGs for all division candidates, the CSG splittable flag_DV of this CSG is cleared.

  (D3) If the splittable flag_DV is not set for all the CSGs in the CSG set, the determination unit 63 of the power control device 60 ends the CSG division. On the other hand, the determination unit 63 of the power control apparatus 60 repeatedly executes the above (D2) if the splittable flag_DV is set for any CSG in the CSG set.

  FIG. 8 is a diagram illustrating a specific example of CSG division. With reference to FIG. 8, access points 10 to 21 constitute one CSG 3. Then, the determination unit 63 of the power control device 60 detects that the four access points 11, 12, 13, and 14 are adjacent to the access point 10.

  Thereafter, the determination unit 63 of the power control device 60 first places the access point 11 in the subset suset1. Next, the determination unit 63 of the power control device 60 confirms whether or not the access point 12 is adjacent to the access point 11 put in the subset suset1.

  Since the access point 12 is adjacent to the access point 11, the determination unit 63 of the power control device 60 puts the access point 12 in the subset suset 1.

  Subsequently, the determination unit 63 of the power control device 60 confirms whether or not the access point 13 is adjacent to the access points 11 and 12 included in the subset suset1.

  Since the access point 13 is not adjacent to any of the access points 11 and 12, the determination unit 634 of the power control device 60 puts the access point 13 into the subset subset2.

  Thereafter, since the access point 14 is adjacent to the access point 13, the determination unit 63 of the power control device 60 places the access point 14 in the subset subset 2.

  Since the adjacent access points 11 to 14 of the access point 10 are divided into two subsets subset 1 and subset 2 that do not overlap, the CSG 3 may be divided at the access point 10. Therefore, the determination unit 63 of the power control device 60 sets the access point 10 as a division candidate.

  Then, the determination unit 63 of the power control device 60 causes the division candidate (= access point 10) to belong to the access points 11, 12, 15 to 19 having many adjacent access points. Thereby, CSG3 is divided into two CSG4 and CSG5. Thereafter, the determination unit 63 of the power control device 60 clears the splittable flag_DV attached to the CSG 3. Thereby, the determination unit 63 of the power control device 60 ends the division of the CSG 3.

  The determination unit 634 of the power control device 60 constructs or divides the CSG by the method described above. Then, the determination unit 63 and the adjustment unit 64 of the power control device 60 calculate the transmission power between access points included in one CSG for each final CSG constructed or divided by the following method, and the calculation Prepare the transmitted power.

(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. 9 is a diagram illustrating a specific example of transmission power adjustment. In FIG. 9, the threshold [delta] _P is assumed to be 1 dBm.

Referring to FIG. 9, the transmission power ^{P N} of the access point 10 to 14, respectively, 15 dBm, 14 dBm, 13 dBm, 14 dBm, and is calculated as 9 dBm.

When the transmission power ^P _{N 6} of the access point 15 is calculated, the transmission power ^P _{N 6} under the influence of the access point 13 is calculated as 13 dBm.

As a result, the transmission power difference (= 4 dBm) between the access point 14 and the access point 15 exceeds the threshold value δ _P (= 1 dBm). The 14 flag flag_CF is cleared.

Thereafter, the transmission powers P ^N ₇ and P ^N _{8 of} the access points 16 and 17 are calculated as 13 dBm and 12 dBm, respectively.

Then, the adjustment means 64 of the power control device 60 determines that the difference between the transmission power P ^N ₅ (= 9 dBm) of the access point 14 and the transmission power P ^N ₆ (= 13 dBm) of the access point 15 is the threshold δ _P (= The transmission power P ^N ₅ of the access point 14 is adjusted from 9 dBm to 12 dBm so as not to exceed 1 dBm).

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 _{1 to} P ^N ₈ of the access points 10 to 17 included in one CSG are adjusted.

Then, the adjustment means 64 of the power control device 60 outputs the adjusted transmission powers P ^N _{1 to} P ^N ₈ to the communication means 62, and the communication means 62 outputs the transmission powers P ^N _{1 to} P ^N ₈ to the access point. To 10-17.

The access points 10 to 17 receive transmission powers P ^N _{1 to} P ^N ₈ from the power control device 60, respectively, and include the received transmission powers P ^N _{1 to} P ^N ₈ in a beacon frame within their own local network. It transmits to the existing terminal device (at least one of the terminal devices 1 to 9).

Then, the access point 10 to 17, respectively, for transmitting and receiving (at least one terminal device 1-9) and a data frame terminal device existing within its local network at a transmission power ^P _N 1 ^~P _{N 8.}

In the embodiment of the present invention, each of the terminal devices 1 to 9 and the access points 10 to 21 basically uses RTS (Request To Send) / CTS (Clear To Send) when transmitting a frame. First, the control frame (and the response (ACK) to it) is transmitted with the transmission power for the known beacon frame (= maximum transmission power), and the data frame (and the response (ACK) to it) is determined by the method described above. The transmission power ^PN is transmitted.

[Exception handling]
FIG. 10 is a diagram for explaining a transmission power control method when a new terminal device joins. Referring to FIG. 10, terminal devices 1, 4, 5, and 7 are connected to access point 10 in the infrastructure mode. The region REG1 is a range where a data frame from the access point 10 reaches, and the region REG2 is a range where a beacon frame from the access point 10 reaches.

The terminal devices 1, 4, 5, 7 and the access point 10 transmit / receive data frames to / from each other using the transmission power P ^N ₁₀ received from the power control device 60.

  In such a situation, a new terminal device 3 newly enters the area REG2 outside the area REG1. In this case, the terminal device 3 can receive a beacon frame from the access point 10 but cannot receive a data frame from the access point 10.

Therefore, the access point 10 performs wireless communication with the terminal device 3 by temporarily increasing the transmission power P ^N ₁₀ .

  FIG. 11 is a diagram for explaining a transmission power control method when a terminal apparatus is handed over.

Referring to FIG. 11, terminal device 7 is initially connected to access point 10, but is moving toward access point 11. Since the terminal device 7 gradually deteriorates the link quality between the terminal device 7 and the access point 10 before switching from the access point 10 to the access point 11, the transmission power P ^N ₁₀ is temporarily increased to Bail out.

When the terminal device 7 newly enters the local network of the access point 11, the access point 11 temporarily increases the transmission power P ^N ₁₁ and performs wireless communication with the terminal device 7.

  Thereby, even when the terminal device 7 is handed over from the local network of the access point 10 to the local network of the access point 11, communication can be continuously performed.

  In the embodiment of the present invention, the active terminal device is dealt with by the following method.

  Each of the access points 10 to 21 always observes a packet (a control message when newly entering or a data message when moving) from a terminal device (at least one of the terminal devices 1 to 9). Data reception RSSI is calculated by the method described above.

Moreover, each access point 10-21 uses transmission power so that link quality between the terminal devices (at least one of the terminal devices 1 to 9) can be satisfied using the above-described equation (2) or the following equation. p (= P _minrate or P _maxrate ) is calculated periodically (immediately before transmitting a beacon frame).

P _maxrate = RSSI _maxrate + P _beacon -RSSI _beacon (7)
In Expression (7), RSSI _maxrate is the minimum RSSI that satisfies the maximum transmission rate detected with reference to the RSSI and transmission rate table TBL. P _maxrate is the minimum transmission power.

When each of the access points 10 to 21 calculates the transmission power p, the transmission power selected by max (p, P ^N ) (the larger of p and P ^N ) is set as the new transmission power P ^N , and the new Transmission power ^PN is included in a beacon frame and transmitted to a terminal device existing in its own local network.

  At the next power control timing, the transmission power between the access points 10 to 21 is adjusted by the method described above, and the difference in transmission power between adjacent access points becomes small.

  Furthermore, in the embodiment of the present invention, the inactive terminal apparatus is dealt with by the following method.

  Even if each terminal device 1-9 is connected to an access point (any one of the access points 10-21), it may move without communicating. In this case, each of the access points 10 to 21 does not grasp the change in the link quality to the terminal device, and therefore does not perform the corresponding transmission power control.

  As a result, when communication is resumed after the terminal devices 1 to 9 are separated from the access point, there is a possibility that the data frame does not reach the communication partner.

  Therefore, in order to solve such a problem, each of the terminal devices 1 to 9 always observes the beacon reception RSSI from the access point (any one of the access points 10 to 21), and uses the observed beacon reception RSSI. Based on this, the received RSSI of the data is calculated, and the required transmission power p that can satisfy the link quality is calculated using Equation (2) or Equation (7).

  When p is larger than the current transmission power and there is no transmission (data or ACK) to the access point within a certain time (this time is a parameter), each of the terminal devices 1 to 9 has its own transmission power. A transmission power control request frame including p is transmitted to the access point (any one of the access points 10 to 21) with the maximum transmission power.

The access point (any one of the access points 10 to 21) sets the transmission power (p or P ^N , whichever is larger) selected by max (p, P ^N ) as the new transmission power P ^N, and sets the new transmission power P ^N. The transmission power ^PN is included in the beacon frame and transmitted to the terminal device existing in its own local network.

  FIG. 12 shows a flow of the power control method according to the embodiment of the present invention. In addition, in FIG. 12, the flow in the case of controlling the transmission power in the local network of the access points 10 and 11 is demonstrated taking the terminal devices 1 and 2 and the access points 10 and 11 as an example. In FIG. 12, the terminal device 1 accesses the access point 10, and the terminal device 2 accesses the access point 11.

  Referring to FIG. 12, terminal apparatus 1 calculates path loss PL1 with the access point 10 by the method described above (step S1), and terminal apparatus 2 performs path loss with the access point 11 by the method described above. PL2 is calculated (step S2).

  Thereafter, the access point 10 transmits its own address AP10, channel ID = CH4, terminal list NL = [STA1] (STA1 represents the terminal device 1) and adjacent access point list NB = [AP11] to the monitoring server 50. (Step S3).

  Similarly, the access point 11 sends its own address AP11, channel ID = CH4, terminal list NL = [STA2] (STA2 represents the terminal apparatus 2) and adjacent access point list NB = [AP10] to the monitoring server 50. Transmit (step S4).

  Thereafter, the power control device 60 transmits an information request to the monitoring server 50 (step S5), and the monitoring server 50 transmits necessary information such as a channel ID, a terminal list, and an adjacent access point list to the power control device 60. (Step S6).

Then, the power control device 60 calculates the transmission power P ^C _j for each cell j by the method described above based on the necessary information (step S7).

Thereafter, the power control device 60 constructs and divides the CSG by the method described above (step S8). Subsequently, the power control apparatus 60 adjusts the transmission power P ^C _j to the transmission power P ^N _j for each CSG by the method described above (step S9).

Then, the power control device 60 transmits the adjusted transmission power P ^N ₁ in the local network of the access point 10 to the access point 10 (step S10). Further, the power control device 60 transmits the adjusted transmission power P ^N ₂ in the local network of the access point 11 to the access point 11 (step S11).

The access points 10 and 11 receive the transmission powers P ^N ₁ and P ^N ₂ from the power control device 60, respectively, and receive the received transmission powers P ^N ₁ and P ^N ₂ for a while according to the response to the handover or the like. (Step S12).

Then, the access point 10 transmits the adjusted transmission power P ^N ₁ to the terminal device 1 (step S13), and the access point 11 transmits the adjusted transmission power P ^N ₂ to the terminal device 2 (step S14). ).

  As a result, the operation for controlling the transmission power is completed.

According to the embodiment of the present invention, a local throughput which is a throughput in one local network when the influence of transmission power in n adjacent local networks adjacent to one local network is considered (n is a positive integer). Is calculated, and transmission power in one local network is determined so that the calculated local throughput is maximized. This power determination process is executed for all of the plurality of local networks corresponding to the plurality of access points 10 to 21. The plurality of transmission power of a plurality of local networks that are determined by the power determining process, a transmission power difference between the adjacent two local networks is adjusted to be less than the threshold [delta] _P.

As a result, in each of the plurality of local networks, together with the throughput is maximized, the difference in transmission power is below the threshold value [delta] _P across multiple local networks.

  Therefore, according to the present invention, the overall throughput in the communication network system 100 including the plurality of access points 10 to 21 connected to the core network can be improved.

  In the embodiment of the present invention, the access points 10 to 21 constitute “a plurality of communication devices”, and the terminal devices 1 to 9 constitute “a plurality of terminal devices”.

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

  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 power control apparatus capable of improving the overall throughput in a communication network including a plurality of communication apparatuses connected to a core network. The present invention is also applied to a communication network system including a power control device capable of improving the overall throughput in a communication network including a plurality of communication devices connected to a core network.

  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 network system , 101 Antenna, 102, 112 Wireless interface, 104 Application module.

Claims (8)

A power control device for controlling transmission power in a plurality of communication devices connected to a network and using the same channel,
Based on a first link quality between adjacent communication devices of the plurality of communication devices, and a second link quality between the communication device and a terminal device directly connected to each communication device, A local throughput in a first local network composed of a first communication device of a plurality of communication devices and a first terminal device that accesses the first communication device is adjacent to the first local network. It is calculated as a throughput in the first local network when the influence of transmission power in n (n is a positive integer) number of second local networks is considered, and the first local network is calculated so that the calculated local throughput is maximized. A power determination process for determining transmission power in one local network is performed for a plurality of local networks corresponding to the plurality of communication devices. Determining means for executing all of the network,
Power adjustment processing for adjusting transmission power in the second local network so that a transmission power difference between the first local network and the n second local networks is equal to or less than a first threshold value. Adjusting means for executing all of a plurality of local networks corresponding to the plurality of communication devices;
A power control apparatus comprising: communication means for transmitting the transmission power adjusted by the adjustment means to the plurality of communication apparatuses.   The determining means performs a process of calculating a transmission required time per bit in each second local network based on the n second link qualities in the n second local networks. This is executed for all the second local networks, and m (m is 1 ≦ m ≦ n) where the received signal strength when receiving a packet from the second local network exceeds the carrier sense threshold in the first local network. Integer) second local networks are extracted from the n second local networks, and the reciprocal of the sum of the m transmission times in the extracted m second local networks is maximized. The transmission power in the second local network is Determining a transmit power in click, the power control device according to claim 1. The determining means classifies the plurality of communication devices into a connection relationship set that is a set of communication devices that use the same channel and have an adjacency relationship based on an adjacency list that indicates an adjacency relationship between the communication devices. And executing the power determination process for each classified connection relation set,
The power control apparatus according to claim 1, wherein the adjustment unit executes the power adjustment process for each of the classified connection relation sets. When the number of communication devices included in one connection relation set exceeds a second threshold, the determination unit divides the connection relation set into a plurality of connection relation sets, and the plurality of divided connection relation sets Performing the power determination process for each of the
The power control apparatus according to claim 3, wherein the adjustment unit executes the power adjustment process for each of the plurality of divided connection relation sets. A plurality of communication devices connected to the network;
A plurality of terminal devices each performing wireless communication with any of the plurality of communication devices;
A power control device for controlling transmission power in the plurality of communication devices connected to the network and using the same channel;
The power control device
Based on a first link quality between adjacent communication devices of the plurality of communication devices, and a second link quality between the communication device and a terminal device directly connected to each communication device, A local throughput in a first local network composed of a first communication device of a plurality of communication devices and a first terminal device that accesses the first communication device is adjacent to the first local network. It is calculated as a throughput in the first local network when the influence of transmission power in n (n is a positive integer) number of second local networks is considered, and the first local network is calculated so that the calculated local throughput is maximized. A power determination process for determining transmission power in one local network is performed for a plurality of local networks corresponding to the plurality of communication devices. Determining means for executing all of the network,
Power adjustment processing for adjusting transmission power in the second local network so that a transmission power difference between the first local network and the n second local networks is equal to or less than a first threshold value. Adjusting means for executing all of a plurality of local networks corresponding to the plurality of communication devices;
Communication means for transmitting the transmission power adjusted by the adjustment means to the plurality of communication devices,
Each of the plurality of communication devices transmits the first and second link qualities to the power control device, and is present in its own local network with transmission power received from the communication means of the power control device Wirelessly communicate with the device,
Each of the plurality of terminal devices is a communication network system that performs wireless communication with the second communication device with the same transmission power as the transmission power of the second communication device to which the terminal device is directly connected.   When each of the plurality of communication devices detects a terminal device newly participating in the local network and outside the contracted communication range, each of the plurality of communication devices is self-transmitting with a transmission power larger than the received transmission power. The communication network system according to claim 5, wherein wireless communication is performed with a terminal device existing in the local network. The first communication device performs wireless communication with the first terminal device existing in the local network and outside the reduced communication range with a transmission power larger than the received transmission power. Done
When the second communication device adjacent to the first communication device detects that the first terminal device has newly joined in its own local network, the communication range in which the first terminal device is shortened 6. The communication network system according to claim 5, wherein the communication network system performs wireless communication with a terminal device existing in its own local network with a transmission power larger than the received transmission power. The first terminal apparatus determines a transmission required power so that a link quality with the first communication apparatus becomes a desired link quality, and the determined transmission required power is greater than a current transmission power of the own terminal apparatus. And when a packet is not transmitted to the first communication device for a certain period of time, a transmission power control request including the required transmission power is transmitted to the first communication device with a maximum transmission power,
The first communication device receives the transmission power control request, and uses a larger one of the required transmission power included in the received transmission power control request and the transmission power received from the power control device. The communication network system according to claim 5, wherein the communication network system is determined as new transmission power, and the determined new transmission power is transmitted to the first terminal device.

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