JP2017175205A - Radio communication system and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a band width and a channel of a radio base station while using a centralized control station in such a manner that throughput of an entire radio communication system is improved and that local throughput reduction can be avoided in an environment that radio base stations are concentrated.SOLUTION: A radio communication system comprises: multiple radio base stations; and a centralized control station for controlling a parameter to be used for communication control of each of the radio base stations in accordance with peripheral environment information and capability information of the multiple radio base stations or terminals. Each of the radio base stations includes radio environment information notification means for acquiring the peripheral radio environment information and capability information of the station and assigned terminals and notifying the centralized control station of the acquired information. The centralized control station includes parameter calculation means for calculating a band width and a channel of each of the radio base stations to be allocated in accordance with the radio environment information and the capability information reported from each of the radio base stations while using a utility function for evaluating throughput of each of the radio base stations.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a radio communication system and a radio communication method for controlling parameters used for communication control of each radio base station using a centralized control station connected to a plurality of radio base stations.

  In recent years, with the spread of portable and high-performance wireless terminals such as laptop computers and smartphones, wireless LANs based on the IEEE 802.11 standard have been widely used not only in businesses and public spaces, but also in general homes. The IEEE802.11 standard wireless LAN includes an IEEE802.11b / g / n standard wireless LAN using the 2.4 GHz band and an IEEE802.11a / n / ac standard wireless LAN using the 5 GHz band.

  In the wireless LAN of IEEE802.11b standard or IEEE802.11g standard, 13 channels are prepared at intervals of 5 MHz between 2400 MHz and 2483.5 MHz. However, when a plurality of channels are used at the same location, if the channels are used so that the spectra do not overlap in order to avoid interference, a maximum of 3 channels, and in some cases, 4 channels can be used simultaneously.

  In the wireless LAN of IEEE802.11a standard, in Japan, a total of 19 channels of 8 channels and 11 channels that do not overlap each other are defined between 5170 MHz and 5330 MHz and between 5490 MHz and 5710 MHz. In the IEEE802.11a standard, the bandwidth per channel is fixed at 20 MHz.

  The maximum transmission speed of the wireless LAN is 11 Mbps for the IEEE802.11b standard, and 54 Mbps for the IEEE802.11a standard or the IEEE802.11g standard. However, the transmission rate here is the transmission rate on the physical layer. Actually, since the transmission efficiency in the MAC (Medium Access Control) layer is about 50 to 70%, the upper limit of the actual throughput is about 5 Mbps in the IEEE802.11b standard, and 30 Mbps in the IEEE802.11a standard and the IEEE802.11g standard. Degree. In addition, the transmission rate further decreases as the number of communication stations that attempt to transmit information increases.

  On the other hand, in wired LANs, the introduction of Ethernet (registered trademark) 100Base-T interface and the spread of FTTH (Fiber to the home) using optical fiber in each home has led to the provision of high-speed lines of 100 Mbps to 1 Gbps. It is widespread, and further increase in transmission speed is required even in wireless LAN.

  Therefore, in the IEEE802.11n standard, which was standardized in 2009, the channel bandwidth, which had been fixed at 20 MHz, has been expanded to a maximum of 40 MHz, and the multiple input multiple output (MIMO) technology The introduction was decided. When transmission / reception is performed by applying all functions defined in the IEEE802.11n standard, a maximum communication speed of 600 Mbps can be realized in the physical layer.

  Furthermore, in the IEEE802.11ac standard, which was standardized in 2013, the channel bandwidth was expanded to 80 MHz or up to 160 MHz, and multi-user MIMO (MU) using Space Division Multiple Access (SDMA) was applied. -MIMO) The introduction of a transmission method has been decided (for example, see Non-Patent Document 1). If transmission and reception are performed by applying all the functions specified in the IEEE802.11ac standard, a maximum communication speed of about 6.9 Gbps can be realized in the physical layer.

  The IEEE802.11 standard wireless LAN operates in the 2.4 GHz band or the 5 GHz band in the license-free frequency band. Therefore, the IEEE802.11 standard wireless base station forms a wireless LAN cell (BSS: Basic Service Set). In addition, it is necessary to determine a frequency channel to be operated among frequency channels that can be handled by the own radio base station.

  Furthermore, in the wireless base station of the IEEE802.11n standard or the IEEE802.11ac standard, it is necessary to determine the operating bandwidth. For example, in the case of the IEEE802.11n standard, the maximum bandwidth is 40 MHz, but it may be more efficient to operate at 20 MHz instead of 40 MHz depending on the surrounding wireless environment conditions. Similarly, in the case of the IEEE802.11ac standard, continuous 80 MHz, continuous 160 MHz, or discontinuous 80 + 80 MHz, that is, up to 160 MHz can be supported, but it is more efficient to operate at 40 MHz or 20 MHz depending on the surrounding wireless environment conditions. There are cases.

  The channel used in the own cell, bandwidth and other parameter settings, and other parameters that can be supported by the own radio base station are the Beacon frame that is periodically transmitted and the Probe for the Probe Request frame that is received from the radio terminal. The cell is operated by transmitting a frame on a frequency channel described in a response frame or the like and determined to be used, and notifying the subordinate radio terminal and other peripheral communication stations.

  The parameter setting values used in the own cell include, for example, parameter values related to access right acquisition and parameter values such as QoS (Quality of Services). Other parameters that can be supported by the own radio base station include the bandwidth used for frame transmission, the basic data rate used for control frame transmission, and the data rate set related to the modulation scheme and coding rate that data can be transmitted and received. included.

In the radio base station, there are the following four methods for selecting and setting the frequency channel, bandwidth and other parameters.
(1) Using the default parameter values set by the wireless base station manufacturer as they are
(2) Method to use manually set values by users operating radio base stations
(3) A method for autonomously selecting and setting parameter values based on the radio environment information detected by each radio base station at startup
(4) Method for setting parameter values determined by a central control station such as a wireless LAN controller

  Here, when the channel bandwidth is widened to 40 MHz, 80 MHz, and 160 MHz in the IEEE802.11ac standard, the number of channels that can be used simultaneously in the same place in the 5 GHz band is 19 channels with a channel bandwidth of 20 MHz and 19 channels. There are fewer 4 channels and 2 channels. That is, as the channel bandwidth increases, the number of usable channels decreases.

  Also, the number of channels that can be used simultaneously in the same location is 3, 2.4, 9 or 19 for 2.4 GHz wireless LAN depending on the channel bandwidth used for communication. Therefore, when actually introducing a wireless LAN, it is necessary to select a channel used by the wireless base station in its own BSS.

  At this time, in a dense environment of a wireless LAN where the number of BSSs is larger than the number of usable channels, a plurality of BSSs use the same channel (OBSS: Overlapping BSS). In this case, the throughput of the BSS and the entire system is reduced due to the influence of interference between BSSs using the same channel. Therefore, in the wireless LAN, autonomous distributed access control that uses CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) to transmit data only when a channel is free due to carrier sense is used.

  Specifically, a communication station that has generated a transmission request first performs carrier sense for a predetermined sensing period (DIFS: Distributed Inter-Frame Space) to monitor the state of the wireless medium, and during this time, transmission by other communication stations is performed. If no signal is present, a random backoff is performed. The communication station continues to perform carrier sense even during the random back-off period, and obtains a channel usage right (TXOP: Transmission Opportunity) when there is no transmission signal from another communication station during this period. A communication station (TXOP Holder) that has obtained the right to use the channel can transmit data to other communication stations in the same BSS and receive data from those communication stations. When such CSMA / CA control is performed, in a dense environment of a wireless LAN using the same channel, the frequency of the channel becoming busy due to carrier sense increases, so the transmission opportunity (opportunity to obtain channel usage rights) decreases. As a result, the throughput decreases. Therefore, it is important to monitor the surrounding environment and select an appropriate channel.

  The channel selection method in the radio base station is not determined by the IEEE802.11 standard, so each vendor adopts its own method, but the most common channel selection method is the channel with the least interference power. There is a method for selecting the items in an autonomous and distributed manner. The radio base station performs carrier sensing for all channels for a certain period, selects a channel with the smallest interference power, and transmits / receives data to / from a terminal device under the selected channel. The interference power is a level of a signal received from a neighboring BSS or another system, and can be measured by, for example, a received signal strength indicator (RSSI).

  The IEEE802.11 standard defines the channel change procedure when the radio conditions around the BSS change. Basically, the selected channel is reselected except for forced transition by radar detection. Not done. That is, in the current wireless LAN, the channel is not optimized according to changes in the wireless status.

IEEE 802.11ac Standard, December 2013.

  How to select and set the frequency channel, bandwidth and other parameters described above (1) to (4), especially for the inexpensive base station, use the default parameters set by the manufacturer of (1) as they are. Often to do. However, in an environment where multiple wireless base stations of the same manufacturer are installed nearby, all wireless base stations use the same frequency channel and transmission power value, so interference occurs between wireless base stations. As a result, there is a problem that communication quality deteriorates.

  In a relatively small network such as a general home, it is conceivable that a user operating the wireless LAN (2) sets appropriate parameters. However, although it is possible to set various parameters in an environment where there is no external interference source, it is appropriate for users or managers in environments where wireless LAN is used in urban areas, apartment buildings, etc., or in medium or large networks. Parameter setting is difficult.

  A radio base station capable of autonomous distributed operation can autonomously select parameter values based on radio environment information detected by each radio base station in (3) when it is activated. However, appropriate parameter values differ depending on the order in which the radio base stations are activated. In addition, each radio base station selects and sets the optimal parameter value in its own station, so it can be optimized locally, but the entire system cannot be optimized, and if the surrounding radio environment changes It becomes difficult. For example, when an environmental change occurs, such as a change in the number of active radio base stations, a change in radio terminal devices under each radio base station, or a change in the amount of data transmitted by radio devices in each cell, Since the use channel and the bandwidth are not optimized, there is a problem that a difference occurs between the throughputs of the respective cells or the throughput of the entire system is deteriorated.

  For this reason, for example, in the case of a small to large-scale wireless LAN system formed by several to several hundreds of wireless base stations such as a university, office, stadium, or station environment, the wireless LAN controller of (4) There is a need for a method for controlling a radio base station by determining parameter values of each radio base station by a centralized control station and reflecting the parameter values in the radio base station.

  The present invention uses a centralized control station to improve the bandwidth of a radio base station so that the overall throughput of the radio communication system can be improved and a decrease in local throughput can be avoided in an environment where radio base stations are crowded. It is an object of the present invention to provide a wireless communication system and a wireless communication method capable of setting channels.

  According to a first aspect of the present invention, a plurality of radio base stations that perform radio communication with subordinate radio terminals and communication control of each radio base station according to environmental information and capability information around the radio base stations or the radio terminals. A wireless communication system including a centralized control station that controls parameters to be used, wherein each wireless base station acquires peripheral wireless environment information and capability information of its own station and belonging terminal and notifies the centralized control station Environmental information notification means is provided, and the centralized control station evaluates the bandwidth and channel of each radio base station allocated according to the radio environment information and capability information notified from each radio base station, and the throughput of each radio base station Parameter calculation means for calculating using the utility function is provided.

  In the radio communication system of the first invention, the parameter calculation means includes means for creating a list of radio base stations sharing the channel according to the bandwidth and channel allocatable to each radio base station, and each radio base station In accordance with the bandwidth and channel that can be allocated to the wireless base station in the list, the utility function when the wireless base station in the list shares the channel is calculated. The means for calculating the channel as temporary allocation, and the bandwidth of each wireless base station by repeatedly calculating the temporary allocation bandwidth and channel of each wireless base station so that the utility function for each wireless base station is improved as a whole. And means for optimizing the channel.

  In the wireless communication system of the first invention, the utility function assigns a bandwidth and a channel to the wireless base station for a maximum throughput that can be obtained when only the wireless base station exists, and sets the surrounding wireless base station and channel. The ratio of the expected throughput that can be acquired when shared.

  In the radio communication system of the first invention, the utility function is a minimum value in the throughput for each radio terminal belonging to the radio base station when a bandwidth and a channel are allocated to the radio base station.

  In the radio communication system of the first invention, means for optimizing the bandwidth and channel of each radio base station is the sum or multiplication of utility functions respectively used for the temporary allocation of the bandwidth and channel of each radio base station. This is a configuration in which values are calculated and the bandwidth and channel allocated to each radio base station are optimized so that the total value or the multiplied value does not deteriorate.

  In addition, the means for creating the list is that the channels that can be allocated to each radio base station and the radio base stations in the vicinity of each radio base station are in use or are in a relationship that interferes even with part of the temporarily allocated channels. In this configuration, peripheral wireless base stations are added to the list.

  A second invention is a centralized control station connected to a plurality of radio base stations that perform radio communication with subordinate radio terminals, respectively, according to environment information and capability information around the plurality of radio base stations or radio terminals. A wireless communication method for controlling parameters used for communication control of a wireless base station, wherein each wireless base station acquires surrounding wireless environment information and capability information of the own station and belonging terminal and notifies the centralized control station The central control station has a utility function for evaluating the throughput of each radio base station, the bandwidth and channel of each radio base station to be allocated according to the radio environment information and capability information notified from each radio base station. A parameter calculating step to calculate using

  In the radio communication method of the second invention, the parameter calculating step includes a step of creating a list of radio base stations sharing the channel according to the bandwidth and channel that can be allocated to each radio base station, and each radio base station In accordance with the bandwidth and channel that can be allocated to the wireless base station in the list, the utility function when the wireless base station in the list shares the channel is calculated. The step of calculating the channel as temporary allocation and the bandwidth and channel calculation of the temporary allocation of each radio base station are repeated, and the bandwidth of each radio base station is improved so that the utility function for each radio base station is improved as a whole. And performing channel optimization.

  In the wireless communication method of the second invention, the utility function assigns a bandwidth and a channel to the wireless base station for a maximum throughput that can be obtained when only the wireless base station exists, and assigns a surrounding wireless base station and channel to each other. The ratio of the expected throughput that can be acquired when shared.

  In the radio communication method of the second invention, the utility function is a minimum value in the throughput for each radio terminal belonging to the radio base station when the bandwidth and channel are allocated to the radio base station.

  In the radio communication method of the second invention, the step of optimizing the bandwidth and channel of each radio base station is the sum or multiplication of utility functions respectively used for the temporary allocation of the bandwidth and channel of each radio base station. A value is calculated, and a bandwidth and a channel allocated to each radio base station are optimized so that the total value or the multiplication value does not deteriorate.

  In addition, the step of creating the list includes a channel that can be allocated to each radio base station and a channel that is in use or temporarily allocated by a radio base station in the vicinity of each radio base station. In this configuration, peripheral wireless base stations are added to the list.

  The present invention considers interference of neighboring radio base stations that share a channel according to the bandwidth and channel that can be allocated by each radio base station, and uses the utility function for evaluating the throughput of each radio base station. By assigning the bandwidth and channel of the base station, the throughput of the entire wireless communication system including the wireless base station can be improved. In particular, according to the present invention, it is possible to avoid a local decrease in throughput in an environment where radio base stations are densely packed.

It is a figure which shows the Example structure of the radio | wireless communications system of this invention. It is a figure which shows the structural example of the centralized control station 4 in the radio | wireless communications system of this invention. It is a figure which shows the structural example of AP1,2 in the radio | wireless communications system of this invention. It is a figure which shows the example of fixed bandwidth transmission in IEEE802.11 standard specification. It is a figure which shows the variable bandwidth transmission example in IEEE802.11 standard specification. It is a flowchart which shows the outline | summary of the process sequence of the parameter calculation part 45 of the centralized control station 4 by this invention. It is a flowchart which shows the process sequence example of step S102. It is a figure explaining the example of preparation of list L (a, b, c) of AP which shares a channel with AP-a. It is a flowchart which shows the example of a process sequence of step S103.

FIG. 1 shows an embodiment of a radio communication system according to the present invention.
In FIG. 1, wireless base stations (AP) 1 and 2 perform wireless communication with their associated wireless terminals (STA, not shown). The APs 1 and 2 are connected to the central control station 4 through the network 3. The central control station 4 calculates setting parameter values used for communication control of the AP based on the environment information and capability information collected from the APs 1 and 2 and sets them in each AP.

FIG. 2 shows a configuration example of the central control station 4 in the wireless communication system of the present invention.
In FIG. 2, the central control station 4 includes a connection unit 41, a communication unit 42, a control unit 43, an information collection unit 44, and a parameter calculation unit 45.

  The communication unit 42 communicates with the APs 1 and 2 via the connection unit 41. The information collecting unit 44 collects and holds environment information (wireless environment information, traffic information, current setting information) and capability information from the controlled APs 1 and 2 existing in the wireless communication system. The parameter calculation unit 45 performs averaging processing and updating of each information collected by the information collection unit 44, and assigns the belonging STA according to the bandwidth and channel that can be allocated to the APs 1 and 2 based on each information. As the service quality, for example, utility functions used for evaluation of satisfaction such as throughput and overall system throughput are calculated, and a bandwidth and a channel at which the utility function is maximized or exceeds a predetermined threshold are determined. The control unit 43 performs overall control of the operation of the central control station 4 including collection of information of the APs 1 and 2 and calculation and setting of AP setting parameter values.

FIG. 3 shows a configuration example of the APs 1 and 2 in the wireless communication system of the present invention. AP1 and AP2 have the same configuration.
In FIG. 3, APs 1 and 2 are a connection unit 11, a communication unit 12, a control unit 13, an environment information holding unit 14, a parameter setting unit 15, an access right acquisition unit 16, a wireless communication unit 17, And an antenna unit 18.

  The communication unit 12 communicates with the central control station 4 on the network 3 through the connection unit 11. The environment information holding unit 14 holds environment information acquired by periodically scanning the periphery of the radio base station. The parameter setting unit 15 sets parameters notified from the central control station 4. The access right acquisition unit 16 acquires an access right by CSMA / CA. The wireless communication unit 17 uses the parameters set by the parameter setting unit 15, acquires the access right by CSMA / CA, and performs wireless communication with the belonging STA via the antenna unit 18. The wireless communication unit 17 scans each channel that can be used in wireless communication for a predetermined period, and outputs the obtained surrounding environment information to the environment information holding unit 14. The control unit 13 controls the overall operation of the AP.

Here, examples of (1) radio environment information, (2) traffic information, (3) current setting information, and (4) capability information are shown below.
(1) Radio environment information Peripheral radio environment information measured by the AP and STA, for example, the number of neighboring APs, each SSID, each BSSID (MAC address), the received RSSI value of each frame transmitted, and each used channel Each used bandwidth (20 MHz, 40 MHz, 80 MHz, 160 MHz, 80 + 80 MHz), each capability information, each AP belonging terminal number, each time occupation rate information, each traffic information, and the like. Further, it is wireless environment information related to the belonging terminal measured by the AP, and is wireless environment information related to the connection destination AP measured by the STA.

(2) Traffic information The amount of traffic addressed to the belonging terminal accommodated in the buffer by the AP, the amount of traffic addressed to the connected AP accommodated in the buffer by the STA, the traffic rate input to the AP / STA buffer, the AP / STA This is the traffic rate sent from the buffer.

(3) Current setting information The current operation standard of AP and STA (11a / b / g / n / ac type), channel, bandwidth (20 MHz, 40 MHz, 80 MHz, 160 MHz, 80 + 80 MHz), etc.

(4) Capability information Supported standards (11a / b / g / n / ac), supported frequency bands, supported bandwidths (20MHz, 40MHz, 80MHz, 160MHz, 80 + 80MHz).

FIG. 4 shows an example of fixed bandwidth transmission in the IEEE 802.11 standard. FIG. 5 shows an example of variable bandwidth transmission in the IEEE 802.11 standard.
4 and 5, AP1 using 36 channels as a primary channel with a bandwidth of 80 MHz and its subordinate STA5 exist, and AP2 used for 48 channels as a primary channel with a bandwidth of 20 MHz and STA6 under its control are located around AP1 and STA5. Assuming an environment where

  In the fixed bandwidth transmission shown in FIG. 4, data can be transmitted only when no signal is detected in the entire data transmission planned bandwidth (80 MHz for AP1 and 20 MHz for AP2). That is, the AP 1 determines whether or not to detect signals in all of the primary channel 36 ch, the secondary 20 channel 40 ch, and the secondary 40 channel 44 ch and 48 ch. Therefore, when AP2 and STA6 are communicating on 48ch, AP1 and STA5 cannot communicate, and it is necessary to wait until the communication between AP2 and STA6 is completed.

  On the other hand, in the variable bandwidth transmission shown in FIG. 5, data can be transmitted when a signal from another AP or STA is not detected on at least the primary channel. The bandwidth used at this time is reduced to a bandwidth where no signal is detected. For this reason, when AP2 and STA6 are communicating on 48ch, AP1 and STA5 transmit data by reducing the bandwidth to 40 MHz, and when AP2 and STA6 are not communicating, the bandwidth is reduced. Data is transmitted at 80MHz.

  Naturally, the variable bandwidth transmission is efficient, but if the bandwidth used is reduced immediately before transmitting the data signal, the frame length and NAV period described in the data need to be recalculated and the processing amount increases. For this reason, all APs and STAs currently on the market perform signal transmission in a fixed band, and the present invention also assumes fixed bandwidth transmission.

  FIG. 6 shows an outline of the processing procedure of the parameter calculation unit 45 of the centralized control station 4 according to the present invention. In FIG. 6, the parameter calculation unit 45 of the centralized control station 4 calculates the maximum throughput and the primary channel access probability that can be acquired in each AP to be controlled, assuming an environment where there is no interference such as no other AP in the vicinity. (S101).

Let t (s, a, b) be the total time that AP-a spends in transmitting and receiving M (s, a, b) bits in communication using STA-s and bandwidth b. The time t (s, a, b) includes all overhead in the data communication. The maximum throughput Max Thput (a) obtainable in an environment where only AP-a exists, that is, no interference source is
Max Thput (a) = (Σ _s M (s, a, b)) / (Σ _s t (s, a, b))
It can be expressed as. Here, Σ _s represents the integration from s = 1 to s = n (a) where the number of AP-a belonging STAs is n (a).

Next, the primary channel occupation time rate α (a) in AP-a is α (a) = min [θ (a) × n (a) / Max Thput (a), 1].
Calculate as Here, θ (a) is the amount of accommodated traffic per AP-a belonging STA, and θ (a) × n (a) is the total amount of generated traffic.

Next, the access probability λ (a, c) of the primary channel c in AP-a is
Calculated as λ (a, c) = α (a).

  Next, for each AP to be controlled, a bandwidth and a primary channel for which the utility function indicating the satisfaction degree of throughput from the assignable bandwidth and the primary channel is maximum or equal to or greater than a predetermined threshold value are temporarily allocated (S102). The processing procedure of step S102 will be separately described with reference to FIG. Next, the iterative calculation optimizes the bandwidth and primary channel for each AP so that the utility function for each AP to be controlled is improved in the entire system, and repeats when a predetermined convergence condition is satisfied. The calculation is terminated (S103). The processing procedure of step 103 will be described separately with reference to FIG. Finally, the bandwidth and the primary channel optimized for each AP are allocated and the process ends (S104).

(Processing procedure of step S102)
FIG. 7 shows an example of the processing procedure of step S102.
In FIG. 7, first, one AP to be controlled is selected (S201). Let the selected AP be AP-a. One bandwidth b is selected from the bandwidths that can be transmitted / received in AP-a based on the information on AP-a registered in the central control station in advance or the information collected from AP-a. The primary channel c is selected according to the width b (S202). For example, when AP-a is compatible with IEEE802.11ac and the usable bandwidth is 80 MHz, the bandwidth b allocated to AP-a is three, {20, 40, 80}. In the process of S202, one bandwidth b is selected from these. Then, the primary channel c assigned to the AP-a is selected according to the selected bandwidth b. However, if the rule that cannot use the secondary 20 channels of the neighboring AP is set as the selection rule of the primary channel c of the AP-a when the bandwidth b is 40 MHz or more, the secondary 20 channel is excluded. Select primary channel c.

  Next, when the bandwidth b and the primary channel c are allocated to the AP-a and the operation is started, a list L (a, b, c) of APs sharing the channel with the AP-a is created (S203). The list L (a, b, c) includes its own AP.

  The list of APs L (a, b, c) sharing the channel with AP-a is a list of APs using the primary channel c or its secondary channel according to the bandwidth b allocated to AP-a. That is, if the bandwidth b of the AP-a is 20 MHz, the AP using the primary channel c is targeted, and if the bandwidth b is 40 MHz, 80 MHz, 160 MHz, 80 + 80 MHz, the primary channel c and its secondary 20 channels, secondary This applies to APs that use 40 channels and secondary 80 channels. Furthermore, among APs sharing a channel with AP-a, APs having a signal level (RSSI) in AP-a of a predetermined threshold or more may be targeted.

Here, an example of creating a list L (a, b, c) of APs sharing a channel with AP-a will be shown with reference to FIG. There are AP-x, AP-y, and AP-z that can be detected in the vicinity of AP-a, and the bandwidth / primary channel of each is as follows.
AP-x: 40MHz / 44ch
AP-y: 20MHz / 60ch
AP-z: 80 + 80MHz / 128ch (52ch)

When the bandwidth b = 20 MHz and the primary channel c (36 to 64ch in this case) are allocated to the AP-a, the list L (a, b, AP) of the AP sharing the channel with the AP-a based on the following criteria: c) is as follows.
・ AP with bandwidth of 20MHz or more with cch as primary channel
・ AP with bandwidth of 40 MHz or more with cch secondary 20 channels as primary channel
AP with bandwidth of 80 MHz or more with cch secondary 40 channels as primary channel AP with bandwidth of 160 MHz with cch secondary 80 channels as primary channel
・ AP with bandwidth 80 + 80MHz including cch in secondary 80 channels

b = 20 MHz, c = 36 ch: L (a, b, c) = {a}
c = 40ch: L (a, b, c) = {a}
c = 44ch: L (a, b, c) = {a, x}
c = 48ch: L (a, b, c) = {a, x}
c = 52ch: L (a, b, c) = {a, z} (illustrated in FIG. 8)
c = 56ch: L (a, b, c) = {a, z}
c = 60ch: L (a, b, c) = {a, y, z}
c = 64ch: L (a, b, c) = {a, y, z}

When a bandwidth b = 40 MHz and a primary channel c (36 to 64ch in this case) are assigned to AP-a, a list L (a, b, AP) of APs sharing the channel with AP-a is based on the following criteria. c) is as follows.
・ AP with bandwidth of 20MHz or more with cch as primary channel
-AP with bandwidth 20 MHz or higher with cch secondary 20 channels as primary channel
AP with bandwidth of 80 MHz or more with cch secondary 40 channels as primary channel AP with bandwidth of 160 MHz with cch secondary 80 channels as primary channel
・ AP with bandwidth 80 + 80MHz including cch in secondary 80 channels

b = 40 MHz, c = 36 ch: L (a, b, c) = {a}
c = 40ch: L (a, b, c) = {a}
c = 44ch: L (a, b, c) = {a, x}
c = 48ch: L (a, b, c) = {a, x}
c = 52ch: L (a, b, c) = {a, z}
c = 56ch: L (a, b, c) = {a, z}
c = 60ch: L (a, b, c) = {a, y, z}
c = 64ch: L (a, b, c) = {a, z}
If there is the above selection rule for the primary channel c of AP-a, 48ch that is the secondary 20 channel of AP-x and 64ch that is the secondary 20 channel of AP-y are excluded. The same applies when the bandwidth b is 80 MHz or higher.

When a bandwidth b = 80 MHz and a primary channel c (36 to 64ch in this case) are assigned to AP-a, a list L (a, b, AP) of APs sharing the channel with AP-a is based on the following criteria. c) is as follows.
・ AP with bandwidth of 20MHz or more with cch as primary channel
-AP with bandwidth 20 MHz or higher with cch secondary 20 channels as primary channel
AP with bandwidth of 20 MHz or more with cch secondary 40 channels as primary channel AP with bandwidth of 160 MHz with cch secondary 80 channels as primary channel
・ AP with bandwidth 80 + 80MHz including cch in secondary 80 channels

b = 80 MHz, c = 36 ch: L (a, b, c) = {a, x}
c = 40ch: L (a, b, c) = {a, x}
c = 44ch: L (a, b, c) = {a, x}
c = 48ch: L (a, b, c) = {a, x}
c = 52ch: L (a, b, c) = {a, y, z} (illustrated in FIG. 8)
c = 56ch: L (a, b, c) = {a, y, z}
c = 60ch: L (a, b, c) = {a, y, z}
c = 64ch: L (a, b, c) = {a, y, z}

When a bandwidth b = 160 MHz and a primary channel c (36 to 64ch in this case) are allocated to AP-a, a list L (a, b, c) of APs sharing channels with AP-a based on the following criteria: ) Is as follows.
・ AP with bandwidth of 20MHz or more with cch as primary channel
-AP with bandwidth 20 MHz or higher with cch secondary 20 channels as primary channel
・ AP with bandwidth of 20 MHz or more with cch secondary 40 channels as primary channel ・ AP with bandwidth of 20 MHz or more with cch secondary 80 channels as primary channel
・ AP with bandwidth 80 + 80MHz including cch in secondary 80 channels

b = 160 MHz, c = 36 ch: L (a, b, c) = {a, x, y, z}
c = 40ch: L (a, b, c) = {a, x, y, z}
c = 44ch: L (a, b, c) = {a, x, y, z}
c = 48ch: L (a, b, c) = {a, x, y, z}
c = 52ch: L (a, b, c) = {a, x, y, z}
c = 56ch: L (a, b, c) = {a, x, y, z}
c = 60ch: L (a, b, c) = {a, x, y, z}
c = 64ch: L (a, b, c) = {a, x, y, z}

When the bandwidth b = 80 + 80 MHz and the primary channel c (36 to 64ch in this case) are allocated to the AP-a, the AP list L (a, b, sharing the channel with the AP-a is based on the following criteria. c) is as follows.
・ AP with bandwidth of 20MHz or more with cch as primary channel
-AP with bandwidth 20 MHz or higher with cch secondary 20 channels as primary channel
・ AP with bandwidth of 20 MHz or higher with cch secondary 40 channel as primary channel ・ All APs with cch secondary 80 channel as primary / secondary channel

b = 80 + 80 MHz, c = 36 ch (100 ch): L (a, b, c) = {a, x}
c = 40ch (100ch): L (a, b, c) = {a, x}
c = 44 ch (100 ch): L (a, b, c) = {a, x}
c = 48ch (100ch): L (a, b, c) = {a, x}
c = 52 ch (100 ch): L (a, b, c) = {a, y, z}
c = 56 ch (100 ch): L (a, b, c) = {a, y, z}
c = 60ch (100ch): L (a, b, c) = {a, y, z}
c = 64 ch (100 ch): L (a, b, c) = {a, y, z}

  Thus, when the bandwidth b and the primary channel c are allocated to the AP-a, the AP having the secondary 20 channel, the secondary 40 channel, and the secondary 80 channel as the primary channel also changes. It can be seen that the shared AP list L (a, b, c) is different. That is, since the throughput in AP-a is determined by the relationship between the bandwidth b, the primary channel c, and the AP sharing the channel, the utility function U for evaluating the throughput according to the bandwidth b and the primary channel c in AP-a is It is necessary to select the bandwidth b and the primary channel c according to the utility function U. Furthermore, it is effective to consider not only AP-a but also the throughput of the entire AP to be controlled.

  In step S204, when the bandwidth b and the primary channel c are allocated to the AP-a, the utility function U (a, b) for evaluating the throughput when the AP and the channel of the list L (a, b, c) are shared. , c).

  Here, an example of the utility function U is shown below. The expected throughput that can be obtained when the bandwidth b and the primary channel c are allocated to the AP-a and the channel is shared with the AP of the list L (a, b, c), or the ratio of the expected throughput to the traffic volume of the AP-a , Or the expected throughput of the belonging STA, or the minimum value of the expected throughput of the belonging STA when there are a plurality of belonging STAs, the access probability that can be obtained by the AP-a, or the throughput of the entire system.

An example of calculating the utility function U (a, b, c) is shown below.
U (a, b, c) = A / mim (B, C)
Here, A assigns bandwidth b and primary channel c to AP-a, and the expected throughput Exptd Thput (a, b, c) that can be acquired when sharing the channel with the AP of list L (a, b, c). c). B is the maximum throughput Max Thput (a) that can be acquired when only AP-a exists, and is calculated in S101 of FIG. C is the total amount of traffic (θ (a) × n (a)) generated between the AP-a and the assigned STA.

The expected throughput Exptd Thput (a, b, c) that can be acquired by the AP-a is calculated as follows according to the capability of the neighboring AP, the number of belonging terminals, and the amount of stored data including the AP-a. The transmission opportunity rate γ (a) for transmitting a frame per belonging STA in AP-a is:
γ (a) = 1 / n (a)
It becomes. However, this is a case where the number of belonging STAs n (a) is 1 or more. If n (a) = 0, γ (a) = 1.

Here, when the bandwidth b is 20 MHz, 40 MHz, 80 MHz, 160 MHz, 80 + 80 MHz, the communication times T ₁ , T ₂ , T ₃ , T ₄ , and T ₅ in the AP-a are calculated as follows. The
T ₁ = Σ _i [λ (i, c) γ ( i) Σ s t (s, i, 20) ]
T ₂ = Σ _i [λ (i, c) γ ( i) Σ s t (s, i, 40) ]
T ₃ = Σ _i [λ (i, c) γ ( i) Σ s t (s, i, 80) ]
T ₄ = Σ _i [λ (i, c) γ ( i) Σ s t (s, i, 160) ]
T ₅ = Σ _i [λ (i, c) γ ( i) Σ s t (s, i, 80 + 80) ]

Here, Σ _i represents an integration corresponding to APs in the list L (a, b, c) sharing the channel with AP-a. Σ _s represents an integration from s = 1 to s = n (i), where n (i) is the number of AP-i belonging STAs.

Therefore, the expected throughput Exptd Thput (a, b, c) and utility function U (a, b, c) that can be obtained when the bandwidth b and the primary channel c are allocated to AP-a are calculated as follows: Is done.
Exptd Thput (a, b, c)
= Min [(λ (a, c) × γ (a) × Σ s M (s, a, b) / (T 1 + T 2 + T 3 + T 4 + T 5), θ (a) × n (a) ] U (a, b, c) = Exptd Thput (a, b, c) / min [Max Thput (a), θ (a) × n (a)]

  Next, the processing of steps S202 to S204 is performed for all bandwidths b and primary channels c that can be allocated to AP-a (S205), and the utility function U has a predetermined condition (maximum or A bandwidth b and a primary channel c that satisfy a predetermined threshold or more are assumed to be temporarily allocated (S206).

  Next, the process returns to step S201 until the same process is completed for other APs to be controlled (S207), and a bandwidth and a primary channel for temporary allocation are determined for each AP to be controlled. When the above process is completed, the process proceeds to the process of step S103 shown in FIG. 6 for optimizing the bandwidth and primary channel for improving the performance of each AP to be controlled and the entire system.

(Processing procedure of S103)
FIG. 9 shows an example of the processing procedure of step S103.
In FIG. 9, after the processing of S102 in FIG. 6 (S201 to S207 in FIG. 7), the bandwidth b and the primary channel c that the utility function U satisfies the predetermined condition in each AP to be controlled are temporarily allocated, and then each AP The total value ΣU of the utility function U is calculated (S301).

  Next, one AP to be controlled is selected (S302), the processing of steps S202 to S205 in FIG. 7 is performed on AP-a, and the bandwidth b satisfying a predetermined condition for the utility function U in AP-a The primary channel c is provisionally allocated (S303).

Next, the total value ΣU ^* of the utility function U in each AP is calculated (S304). Next, the total value ΣU ^* of the utility function U in each AP is compared with the previous total value ΣU (S305), and if improved, the bandwidth b and the primary channel c of each temporary allocation AP are updated. (S306).

  The above processing is repeated until the total value ΣU of the utility function U in each AP is updated or until a predetermined convergence condition is satisfied (S307). The centralized control station 4 sets the bandwidth and primary channel in each AP to be controlled, which is determined by such repeated processing, in each AP.

  Instead of the total value ΣU of the utility function U at each AP, a multiplication value of the utility function U at each AP may be used.

1, 2 Radio base station (AP)
3 Network 4 Centralized control station 5, 6 Wireless terminal (STA)
DESCRIPTION OF SYMBOLS 11 Connection part 12 Communication part 13 Control part 14 Environment information holding part 15 Parameter setting part 16 Access right acquisition part 17 Wireless communication part 18 Antenna part 41 Connection part 42 Communication part 43 Control part 44 Information collection part 45 Parameter calculation part

Claims (12)

A plurality of radio base stations that perform radio communication with subordinate radio terminals,
A wireless communication system comprising: a centralized control station that controls parameters used for communication control of each wireless base station according to environmental information and capability information around the plurality of wireless base stations or the wireless terminals,
Each of the radio base stations includes a radio environment information notification means for acquiring peripheral radio environment information and capability information of the own station and the belonging terminal, and notifying the central control station,
The centralized control station evaluates the throughput of each radio base station using the bandwidth and channel of each radio base station allocated according to the radio environment information and the capability information notified from each radio base station. A wireless communication system comprising a parameter calculation means for calculating using a function. The wireless communication system according to claim 1, wherein
The parameter calculation means includes
Means for creating a list of radio base stations sharing a channel according to the bandwidth and channel that can be allocated to each radio base station;
According to the bandwidth and channel that can be allocated to each radio base station, the utility function when the radio base stations in the list share the channel is calculated, and the utility function is maximized for each radio base station or Means for calculating a bandwidth and a channel that are equal to or greater than a predetermined threshold as a temporary allocation;
The calculation of the bandwidth and channel of each radio base station is repeated, and the bandwidth and channel of each radio base station are optimized so that the utility function for each radio base station is improved as a whole. And a wireless communication system. The wireless communication system according to claim 1 or 2,
The utility function can be acquired when a bandwidth and a channel are allocated to the radio base station and a channel is shared with a neighboring radio base station for the maximum throughput that can be acquired when only the radio base station exists. A wireless communication system characterized by a ratio of expected throughput. The wireless communication system according to claim 1 or 2,
The wireless communication system, wherein when the bandwidth and channel are allocated to the wireless base station, the utility function is a minimum value in throughput for each wireless terminal belonging to the wireless base station. The wireless communication system according to claim 2,
The means for optimizing the bandwidth and channel of each radio base station calculates the total value or multiplication value of the utility functions respectively used for the temporary allocation of the bandwidth and channel of each radio base station, A wireless communication system, wherein a bandwidth and a channel to be allocated to each of the wireless base stations are optimized so that a value or a multiplication value does not deteriorate. The wireless communication system according to claim 2,
The means for creating the list is a channel that can be allocated to each radio base station, and if there is a relationship that interferes even with a part of the channels that are in use or temporarily allocated in the radio base stations around each radio base station, A wireless communication system, characterized in that the wireless base station in the vicinity is added to the list. In a centralized control station connected to a plurality of radio base stations that perform radio communication with subordinate radio terminals, each of the radio base stations according to environmental information and capability information around the radio base stations or the radio terminals A wireless communication method for controlling parameters used for communication control,
Each of the radio base stations has a step of acquiring surrounding radio environment information and capability information of the own station and the belonging terminal, and notifying the central control station,
The centralized control station evaluates the throughput of each radio base station using the bandwidth and channel of each radio base station allocated according to the radio environment information and the capability information notified from each radio base station. A wireless communication method comprising a parameter calculation step of calculating using a function. The wireless communication method according to claim 7, wherein
The parameter calculation step includes:
Creating a list of radio base stations sharing a channel according to the bandwidth and channel that can be allocated to each radio base station;
According to the bandwidth and channel that can be allocated to each radio base station, the utility function when the radio base stations in the list share the channel is calculated, and the utility function is maximized for each radio base station or Calculating a bandwidth and a channel that are equal to or greater than a predetermined threshold as a temporary allocation;
The calculation of the bandwidth and channel of each radio base station is repeated, and the bandwidth and channel of each radio base station are optimized so that the utility function for each radio base station is improved as a whole. A wireless communication method comprising the steps of: In the wireless communication method according to claim 7 or 8,
The utility function can be acquired when a bandwidth and a channel are allocated to the radio base station and a channel is shared with a neighboring radio base station for the maximum throughput that can be acquired when only the radio base station exists. A wireless communication method characterized by setting a ratio of expected throughput. In the wireless communication method according to claim 7 or 8,
The wireless communication method according to claim 1, wherein when the bandwidth and channel are allocated to the wireless base station, the utility function is a minimum value in throughput for each wireless terminal belonging to the wireless base station. The wireless communication method according to claim 8, wherein
The step of optimizing the bandwidth and channel of each radio base station calculates the total value or multiplication value of the utility functions respectively used for the temporary allocation of the bandwidth and channel of each radio base station, A wireless communication method characterized by optimizing a bandwidth and a channel allocated to each of the radio base stations so that a value or a multiplication value does not deteriorate. The wireless communication method according to claim 8, wherein
The step of creating the list includes a channel that can be allocated to each radio base station and a relationship that interferes with a part of the channels that are in use or temporarily allocated by the radio base stations around each radio base station, A wireless communication method comprising adding the wireless base stations in the vicinity to the list.

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