JP2007028232A - Wireless lan system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless LAN system optimum to the distribution of a load taking into account a limit on the number of simultaneous speeches. <P>SOLUTION: A wireless voice terminal informs a central control unit about a speech channel request at call origination, call termination or handover, receives a speech channel assignment being its response to the request, starts a call control sequence at the call origination and the call termination, restarts a speech at the handover, searches a wireless base station when speech channel assignment is rejected from the central control unit, and informs the central control apparatus about a speech channel request again via the newly-connected wireless base station. At the end of the speech, the wireless voice terminal informs the central control apparatus about the opening of the speech channel after the end of the call control sequence for the end of the speech. The central control unit informs the wireless voice terminal about the speech channel assignment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless LAN system, and more particularly to a wireless LAN system having a configuration in which a plurality of wireless base stations are connected to the same network.

  Recently, wireless LAN systems have been widely applied. This wireless LAN system is also used in offices, homes, and so-called hot spots because of the convenience that a wired cable is not required when communicating via a network, for example. This wireless LAN system generally includes terminals such as personal computers and PDAs, and an access point (hereinafter referred to as “wireless network”) that performs wireless communication with these terminals and transfers data exchanged with a network (for example, a wired network). (Sometimes referred to as AP).

Further, when there is a plurality of terminals that cannot be accommodated by one AP, load distribution is performed by distributing the terminals using the plurality of APs.
In this type of wireless LAN system, communication performed between the terminal and the AP is performed using radio waves of weak power, for example, using radio waves of a frequency of 2.4 GHz band or 5 GHz band. A terminal in this wireless LAN system uses reception level information of a probe response transmitted by the AP as a response to a notification signal called a beacon periodically transmitted by the AP or a base station search signal called a probe request transmitted by the terminal, An AP having the maximum average reception level is selected and connected, and a service is received through the AP.

  However, in the above-described wireless LAN system including a plurality of APs, when traffic is concentrated in a limited area such as a hot spot or a conference room, the traffic may be biased between APs. . In this case, there is a problem that a terminal connected to an AP where traffic is concentrated has a low transmission speed, so that stable performance cannot be guaranteed.

  There is known a “method for selecting an access point based on access point status information” to solve this type of problem (see, for example, Patent Document 1). In this method, the AP transmits a beacon and a probe response with the number of connected terminals and traffic volume information being processed, and the terminal transmits not only the reception level information of the beacon and the probe response but also the number of connected terminals included therein. The wireless LAN system can also select and connect to an optimum AP with reference to traffic volume information being processed, and receive a service via the AP.

  However, even if the invention described in Patent Document 1 is applied to a wireless LAN, information on the number of connected terminals and traffic volume added to beacons and probe responses and an algorithm for selecting an optimum AP on the terminal side are not standardized. Also, since the specifications are not unified among manufacturers, the load balancing function cannot be used between APs and communication terminals of different manufacturers. In order to solve such a problem, a “wireless LAN access point load distribution method” is known (see, for example, Patent Document 2).

  According to this load balancing method, an AP whose number of connected terminals has increased or decreased notifies other APs belonging to a preset group of the number of connected terminals that have increased or decreased, so that each AP has information on the number of connected terminals of all APs belonging to the group. Owns. Therefore, when there is an AP with a small number of connected terminals, the AP operates so as to reject the connection even if a connection request is received from the terminal. The load distribution method described in Patent Document 2 does not require a special mechanism for load distribution on the terminal side. In other words, the terminal only has to select the AP having the maximum average reception level using the reception level information of the beacon and the probe response and try to connect.

Incidentally, if there is an AP having a lower load than the selected AP, the connection is rejected, and the connection with the next highest reception level is attempted. That is, if an AP that implements the technology described in Patent Document 2 is used, the load distribution function can be used without depending on the manufacturer of the communication terminal.
Alternatively, a “radio base station apparatus having a dynamic load distribution function” that solves the above-described problems is known (see, for example, Patent Document 3). Each AP in this radio base station apparatus monitors the total amount of transmission traffic for all connected terminals, and determines that the load is concentrated when the total amount of this traffic exceeds a predetermined threshold, Notify AP of load distribution request. The AP that has received the load distribution request calculates the distance between the two from the position information of the self AP and the source AP of the load distribution request stored in advance. If the distance between APs is less than or equal to a predetermined threshold and the total amount of transmission traffic is the smallest among the APs where the distance between APs is less than or equal to the predetermined threshold, Specify the disconnect terminal and notify the disconnect request instruction.

The load distribution methods disclosed in these patent documents are performed based on the number of connected terminals for each AP or the total amount of transmission traffic.
Recently, in wireless LAN systems, not only data but also applications requiring real-time performance such as voice have been used. In order to ensure the quality of applications sensitive to such delays and delay fluctuations, a priority control mechanism in wireless LAN was standardized in IEEE802.11e in 2004, and is expected to spread in the future.
JP-A-2005-57728 JP 2004-140614 A JP 2004-320274 A

  However, the above-described conventional load balancing method is a method of distributing to other APs when the number of connected terminals for each AP or the total amount of transmission traffic exceeds a predetermined threshold, and the total amount of transmission traffic has a predetermined threshold. There is a problem that proper load distribution is not necessarily performed within the range not exceeding. In other words, based on the idea of sharing the communication bandwidth among a plurality of terminals, it is desirable to distribute the load regardless of the amount of traffic. However, the conventional load distribution method is not based on this kind of thinking and has a problem that optimum load distribution is not performed.

  Further, methods other than those disclosed in Patent Documents 1 to 3 described above, for example, a mechanism in which the terminal notifies the AP of its attributes, a mechanism in which the terminal notifies the AP of an SSID (service set identifier) is provided as standard. Therefore, if this is used to set the SSID to a different value for each communication attribute such as voice, video, and data, it is of course possible to realize load distribution even when a terminal of an arbitrary manufacturer is used. However, when the restriction for each communication attribute is performed not by the number of connections but by the total amount of transmission traffic, that is, the number of simultaneous calls, it is necessary to implement a mechanism for notifying the central control device of the start and end of the call in the terminal. However, since this type of mechanism is not provided as a standard specification of a wireless LAN, there is a problem that it can be used only by a terminal of a specific manufacturer that is implemented as an original specification.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wireless LAN system that is optimal for performing load distribution in consideration of the simultaneous call limit.

In order to achieve the above-described object, a wireless LAN system of the present invention is a wireless LAN system having a plurality of wireless base stations connected to a network and a plurality of wireless voice terminals accessing the wireless base station,
A centralized control device connected to the network and communicating with the plurality of radio base stations to control the operation of the radio base stations;
The wireless voice terminal notifies a call channel request to the central control device at the time of outgoing call, incoming call or handover, receives a call channel assignment from the central control device, starts a call control sequence at the time of outgoing and incoming calls, and at the time of handover When a call channel allocation is rejected by the central control device while the call is resumed, the radio base station is searched, and a call channel request is again made to the central control device via the newly connected radio base station. Notifying and at the time of the end of the call, while the call control sequence for the end of the call is completed, the communication channel release is notified to the centralized control device,
The central control device receives a notification of a call channel request including identification information of the connected radio base station from each of the radio voice terminals, and from the notification of the call channel request, the centralized control device receives the notification of the radio voice terminal in the radio base station. When there is another radio base station that manages information on the number of simultaneous calls and has a smaller number of simultaneous calls than the radio base station to which the radio voice terminal that has notified the call channel request is connected, the radio voice terminal The number of simultaneous calls of the radio base station connected to the wireless voice terminal that has notified the call channel request is the same as the number of simultaneous calls of other radio base stations located around the radio base station. When the number is approximately equal to the number, the wireless voice terminal is notified of call channel assignment.

  Preferably, the call channel assignment refusal message includes identification information of the other radio base station having a small number of simultaneous calls.

  According to the wireless LAN system according to claims 1 and 2 of the present invention, since the number of simultaneous calls of each wireless base station can be managed in the centralized control device, the optimum load can be flexibly and flexibly according to the uneven number of calls. In addition to realizing the distribution, an excellent effect of providing a load distribution function considering the number of simultaneous calls can be achieved.

Hereinafter, a wireless LAN system according to an embodiment of the present invention will be described with reference to the accompanying drawings. The attached drawings show an embodiment to which the wireless LAN system of the present invention is applied, and the present invention is not limited by these attached drawings.
FIG. 1 is a diagram showing an overall configuration of a wireless LAN system according to an embodiment of the present invention. In this figure, reference numeral 10 denotes a network to which a plurality of communication devices are connected, for example, a wired LAN such as Ethernet (registered trademark). Connected to the network 10 are a plurality of wireless terminals 12 to be described later and a plurality of wireless base stations 11 that mediate frame transfer between the networks 10. In FIG. 1, radio base stations 11-1 and 11-2 and a centralized control device 14 for load distribution are connected to a network 10. The wireless terminals 12-1 to 12-3 are connected to the wireless base stations 11-1 and 11-2 via a wireless LAN.

In FIG. 1, the radio base station 11-3 is connected to the radio base station 11-2 via a radio transmission path. The radio terminal 12-4 is a terminal connected to such a radio base station 11-3.
On the other hand, the network 10 is also connected to a private branch exchange 15 that accommodates a plurality of telephone lines and connects to the public network 18. That is, the wireless terminals 12-1 to 12-4 can communicate with the public network 18 not only between the wireless terminals but also with the private branch exchange 15. In this figure, the centralized control device 14 and the private branch exchange 15 are illustrated as separate devices, but they are realized as an integrated unit, that is, the function of the centralized control device 14 is incorporated into the private branch exchange 15. May be.

  FIG. 2 is a diagram showing an overall configuration of a wireless LAN system according to another embodiment of the present invention. The wireless LAN system shown in FIG. 2 differs from the wireless LAN system shown in FIG. 1 in that a call control server 17 and a router 16 are provided in place of the private branch exchange 15, and an Internet network 19 is connected in place of the public network 18. It is in the point. In FIG. 2, the central control device 14 and the call control server 17 are illustrated as separate devices. However, the central control device 14 and the call control server 17 can be realized in an integrated manner. Of course, it does not matter even if it is incorporated and configured.

  FIG. 22 is a block configuration of the central control apparatus 14 in the wireless LAN system of the present invention. The centralized control device 14 includes a wired communication interface unit 301 for performing communication with the wireless base station 11 via the network 10 and load distribution for analyzing and processing the load distribution control frame 320 from the wireless base station 11. In response to the load distribution control information 322 output from the control frame analysis unit 302 and the load distribution control frame analysis unit 302, load distribution for a load distribution control frame that requires updating and a response to a state management table for load distribution control Output from the load distribution control unit 303 when the load distribution control unit 303 that generates the response frame 321 and the load distribution control information 322 are information necessary for creating the wireless terminal connection number management table such as a connection request or a disconnection notification. Wireless terminal connection based on load distribution control information 323 for creating wireless terminal connection number management table Composed of the wireless terminal connections management table creating unit 304 and a wireless terminal connection number management table 305 to create a management table 305.

The centralized control device 14 in the case of performing load distribution in consideration of the reception level of the signal from the wireless terminal at each wireless base station further includes a base station reception level table creation unit 309, a base station reception level table 310, and candidate base stations A reception level range table 311 is included.
The inter-centralized control unit 14 when performing load distribution in consideration of the influence of interference from outside the system further includes an interference power management table creation unit 306, an interference power management table 307, and an interference power connection number conversion table 308.

  FIG. 3 is a block configuration diagram of the wireless base station 11 in the wireless LAN system according to the embodiment of the present invention. The wireless base station 11 includes an antenna 100 for transmitting and receiving wireless signals, a wireless communication interface unit 101 for transmitting and receiving wireless signals, a wired communication interface unit 102 for transmitting and receiving to and from the network 10, and a bridge for wireless communication and wired communication. A communication control unit 103 that performs operations, a radio management frame 104 that performs transmission / reception of radio management frames and a radio terminal connected to its own radio base station, and a load distribution control that communicates with the centralized control device 14 for load distribution The unit 105 is configured.

Next, operations of the radio base station 11 and the central control apparatus 14 will be described in detail with reference to FIGS. 3 and 4.
The wireless reception frame 110 received via the wireless LAN includes both a communication frame and a wireless management frame. Here, the radio management frame is for establishing and maintaining a radio connection, and is transmitted between the radio terminal 12 and the radio base station 11. On the other hand, the communication frame is generated in the upper application layer and is transmitted between the wireless terminal 12 and the network 10. Both of these radio reception frames 110 are given to the communication control unit 103.

  Among these, the communication frame is given to the wired interface unit 102 as a wired transmission frame 113 and further transmitted to the network 10 when the destination terminal is not a wireless terminal connected to the own wireless base station. When the destination terminal is a wireless terminal connected to its own wireless base station, it is given to the wireless communication interface unit 101 as a wireless transmission frame 111 and transmitted from the antenna 100. The wired reception frame 112 received via the network 10 passes through the communication control unit 103, is given to the wireless communication interface unit 101 as a wireless transmission frame 111, and is transmitted from the antenna 100.

On the other hand, the wireless management frame in the wireless reception frame 110 received via the wireless LAN is given to the wireless management unit 104 via the communication control unit 103. Specifically, an internal block configuration of the wireless management unit 104 is shown in FIG.
The radio management frame 114 sent from the communication control unit 103 to the radio management unit 104 is given to the radio management frame analysis unit 132. The radio management frame analysis unit 132 analyzes the contents of the radio management frame, and provides radio management frame information 140 to the radio management control unit 133. When the wireless terminal information is changed by the received wireless management frame information 140, the wireless management control unit 133 updates the wireless terminal information 141 regarding the wireless terminal in the wireless terminal information storage unit 135.

An example of a terminal management table handled by the wireless terminal information storage unit 135 is shown in FIG. In this figure, the wireless terminal identifier is an identifier such as a MAC (media access control) address, and is a unique wireless terminal ID in the system. The wireless connection ID is an identifier uniquely assigned to the wireless terminal to which each wireless base station 11 is connected.
The terminal attribute is determined according to an application mainly used by the terminal. In the example of FIG. 5, the terminal attributes of the voice terminal and the data terminal are shown. Here, the voice terminal means that the main service to be provided is a call like a mobile phone. An example of the data terminal is a personal computer.

  The radio management control unit 133 creates a response frame for the received radio management frame as necessary. Examples of response frames include a wireless connection response to a wireless connection request and an authentication response to an authentication request. The radio management response frame 115 is transmitted from the antenna 100 to the radio transmission path via the communication control unit 103 and the radio communication interface unit 101.

  If the received wireless management frame is a connection or disconnection of a wireless terminal, the connection / disconnection monitoring unit 134 generates connection / disconnection information 118 based on the connection / disconnection monitoring information 142 to control load distribution. To part 105. Next, the load distribution control unit 105 generates a load distribution control transmission frame 123 for connection / disconnection notification, and notifies the centralized control device 14 via the wired communication interface unit 102 and the network 10.

  An example of a frame format of a unique command for communication between the load distribution control unit 105 and the centralized control device 14 is shown in FIG. The unique command shown in FIG. 6 is defined on the TCP / IP payload. An example of a connection request message and a disconnection request message is shown in FIG. The connection request and disconnection request messages include a wireless terminal identifier, a wireless base station identifier, and a wireless terminal attribute. The wireless terminal identifier is a unique identifier of the wireless terminal in the wireless LAN system. For example, the MAC address of the wireless terminal can be used.

  This wireless base station identifier is a unique identifier of the wireless base station in the wireless LAN system. For example, a BSS-ID (basic service set identity) of the wireless base station may be used. The wireless terminal attribute is a traffic category to which the main application of the wireless terminal belongs, and includes voice, video, best effort, and the like. For example, the wireless terminal attribute in the case of a portable telephone terminal is voice.

On the other hand, the centralized control device 14 manages the number of wireless terminals connected to each of the plurality of wireless base stations 11 for each wireless terminal attribute based on the received load distribution control frame for connection / disconnection notification.
Hereinafter, the operation of the central control apparatus 14 when receiving a load distribution control frame for connection / disconnection notification will be described again with reference to FIG.

When the central control apparatus 14 receives the load distribution control frame, the wired communication interface unit 301 outputs a load distribution control reception frame 320 corresponding to the frame. The load distribution control reception frame 320 is given to the load distribution control frame analysis unit 302, and the load distribution control information 322 is output.
When the load distribution control unit 303 receives the load distribution control information 322 including the connection / disconnection notification, the load distribution control unit 303 outputs the management table creation load distribution control information 323 to the wireless terminal connection number management table creation unit 304. The wireless terminal connection number management table creation unit 304 creates the wireless terminal connection number management table 305 by obtaining the number of connections for each wireless base station and for each wireless terminal attribute based on the management table creation load distribution control information 323.

  An example of the wireless terminal connection number management table of such a centralized control device 14 is shown in FIG. As a specific method for creating the management table, when the central control device 14 receives a connection message, the corresponding connection number is increased by 1. When a disconnect message is received, the corresponding connection number is increased by 1. Only decrease. In the load distribution control transmission frame 123 for notification of connection / disconnection, the wireless terminal identifier is also notified together. Therefore, it may be managed together with not only the number of connections but also the wireless terminal identifier. In this case, when the connection message is received, it is confirmed whether or not the same wireless terminal identifier already exists on the management table, and if it exists, it can be deleted. This is effective in preventing double registration when a wireless terminal 12 that is out of service area is connected to another wireless base station 11.

  For the voice terminal illustrated in FIG. 8, the number of connections of the radio base station 11-2 is smaller than that of the radio base station 11-1, so that when there is a new connection message from the voice terminal, the radio base station It is desirable to preferentially connect to 11-2. Moreover, since the number of connections of the radio base station 11-1 is small for a best effort terminal such as a personal computer, it is desirable to connect to the radio base station 11-1.

  On the other hand, since the number of connections is the same between the two radio base stations 11-1 and 11-2, the video terminal may be connected to either radio base station. That is, connection permission is given to a connection message from a radio base station with the smallest number of connections, and connection is prohibited for connection messages from other radio base stations. When there are a plurality of wireless base stations with the smallest number of connections, connection permission is given to all of them.

A response frame having a connection permission or connection prohibition message is generated by the load distribution control unit 303 and transmitted to the network 10 by the wired communication interface unit 301.
The response frame transmitted from the central control device 14 is received by the radio base station 11 via the network 10.

Hereinafter, the operation of the radio base station 11 when receiving a response frame from the centralized control device 14 will be described again with reference to FIG.
The response signal from the centralized control device 14 is given to the load distribution control unit 105 as a load distribution control reception signal 124 through the wired communication interface unit 102. The load distribution control unit 105 analyzes this response and notifies the wireless management unit 104 of connection permission / prohibition information 119. Based on the connection permission / prohibition information 119, the wireless management control unit 133 in the wireless management unit 104 determines a response to the received wireless management frame, and sends a wireless management response frame 115 as a response signal to the communication control unit 103. give. This response signal is transmitted on the wireless transmission path via the wireless communication interface unit 101 and the antenna 100.

An example of a response message that is a response frame from the centralized control device 14 is shown in FIG. The response message is for the connection message, and there is no response message for the disconnect message.
In the above description, when the radio base station 11 receives a radio management frame for radio connection, the central control device 14 is requested to obtain a connection permission, and after obtaining the connection permission, the radio base station 11 operates to perform the radio connection. However, it is possible to adopt a method in which the centralized control device 14 notifies each wireless base station 11 of connection permission / connection prohibition for each wireless terminal attribute in advance based on the wireless terminal connection number management table.

  In this case, upon receiving the connection / disconnection information 118, the load distribution control unit 105 of the radio base station 11 generates a load distribution control transmission frame 123 for connection notification / disconnection notification, and the wired communication interface unit 102, The notification is sent to the central control device 14 via the network 10. The centralized control device 14 updates the wireless terminal connection number management table based on the information of the load distribution control frame for connection notification / disconnection notification, and based on the latest wireless terminal connection number management table, each wireless base station 11 Is notified of connection permission / connection prohibition for each wireless terminal attribute.

  The notification frame transmitted from the central control device 14 is given to the load distribution control unit 105 via the network 10 and the wired communication interface unit 102. Based on this notification, the load distribution control unit 105 notifies the wireless management unit 104 of connection enable information 119 that is connection permission / connection prohibition information for each wireless terminal attribute. The wireless management control unit 133 in the wireless management unit 104 stores this connection enable information 119 and, when receiving the wireless management frame 114 for wireless connection, permits wireless connection based on this information. Alternatively, prohibition is determined, and a radio management frame corresponding to this is generated and given to the communication control unit 103. The radio management frame is transmitted on the radio transmission path via the radio communication interface unit 101 and the antenna 100. An example of the connection enable information notification message is shown in FIG. The enable information consists of enable bits (1 bit) corresponding to each wireless terminal attribute. When the wireless connection is prohibited, the wireless connection can be rejected by not transmitting a response signal to the wireless base station search request.

  Next, the block configuration of the wireless terminal 12 in the wireless LAN system of the present invention will be described using FIG. The wireless terminal 12 includes an antenna 200 for transmitting and receiving wireless signals, a wireless communication interface unit 201 for transmitting and receiving wireless signals, and communication control for distributing wireless management frames and communication frames to the wireless management unit 204 and the upper application unit 206. The unit 203 includes a radio management unit 204 that transmits and receives radio management frames.

  The wireless reception frame 210 received via the wireless LAN includes both a communication frame and a wireless management frame. The wireless reception frame 210 passes through the communication control unit 203 and is then transferred to the upper application unit 206 as the application frame 211. On the other hand, the wireless management frame in the wireless reception frame 210 received via the wireless LAN is given to the wireless management unit 204 via the communication control unit 203. FIG. 19 shows an internal block configuration of the radio management unit 204.

  The radio management frame 212 sent from the communication control unit 203 to the radio management unit 204 is given to the radio management frame analysis unit 232. Here, the contents of the radio management frame are analyzed, and radio management frame information 240 is given to the radio management control unit 233. The wireless terminal information storage unit 235 stores a wireless terminal identifier, a wireless terminal attribute, a wireless connection ID, a terminal state, and the like.

In the wireless terminal 12, the wireless management control unit 233 generates a wireless management frame when establishing a wireless connection with the wireless base station 11. At this time, wireless terminal information 241 which is information on the wireless terminal identifier and wireless terminal attribute in the wireless terminal information storage unit 235 is registered in the wireless base station 11. This information is stored in the terminal management table of the wireless terminal information storage unit 135 of the wireless base station 11.
Incidentally, at the time of wireless connection, registration of a wireless terminal identifier with a wireless base station using a wireless management frame is generally performed within the range of wireless LAN standard specifications. On the other hand, the concept of wireless terminal attribute is not a standard specification of wireless LAN, and it is not defined that it is registered in a wireless base station when wirelessly connected.

  By the way, according to the standard specification of the wireless LAN, it is defined that the network identifier is registered at the time of wireless connection. Originally, a wireless terminal must register a network identifier of a network desired to be wirelessly connected at the time of wireless connection. However, the wireless LAN standard specification allows a wireless base station to use a plurality of network identifiers. Therefore, for example, a different network identifier is used for each wireless terminal attribute, and if a wireless terminal performs registration using a network identifier corresponding to the terminal attribute, it is within the standard specification of the wireless LAN, that is, commercially available. Even when a wireless terminal is used, wireless terminal attribute information can be registered in the wireless base station.

  Next, the operation of the wireless connection of the wireless terminal 12 in the wireless LAN system of the present invention will be described using FIG. 20 and FIG. In FIG. 20, the radio terminal 12 first broadcasts a radio base station search signal for radio connection. The radio base station search signal is received by the radio base station 11-1, the radio base station 11-2, and the radio base station 11-3, and the base station search response signal is transmitted to the radio terminal 12, respectively. In the example of FIG. 20, the reception level of the base station search response signal at the wireless terminal 12 is the maximum at the wireless base station 11-1, the next is the response from the wireless base station 11-2, and the reception level is the lowest. Is a response from the radio base station 11-3. For this reason, the wireless terminal 12 transmits a wireless management frame for a wireless connection request to the wireless base station 11-1 having the highest reception level of the base station search response signal. This radio management frame includes information on the radio terminal identifier and radio terminal attributes of the radio terminal 12. The radio base station 11-1 that has received this radio management frame transmits a load distribution control transmission frame 123 for a connection request to the central control apparatus 14. The load distribution control transmission frame 123 for the connection request includes information on the wireless terminal identifier and the wireless terminal attribute of the wireless terminal 12 requesting the wireless connection.

On the other hand, the centralized control device 14 determines whether to permit or prohibit the requested connection request based on the wireless terminal connection number management table. FIG. 20 shows a transmission sequence in which a connection permission response frame is transmitted from the central control apparatus 14 to the radio base station 11-1.
Upon receiving the connection permission response frame, the wireless base station 11-1 generates and transmits a wireless management frame for connection permission to the wireless terminal 12. When the wireless terminal 12 receives the wireless management frame for connection permission, the wireless connection between the wireless terminal 12 and the wireless base station 11-1 is established.

  FIG. 21 is the same as FIG. 20 until the radio base station 11-1 transmits a load distribution control transmission frame 123 for connection request to the centralized control device 14. However, FIG. 21 shows that the centralized control device 14 transmits a connection prohibition response frame to the wireless base station 11-1 based on the wireless terminal connection number management table. In this case, upon receiving the connection prohibition response frame, the radio base station 11-1 generates and transmits a radio management frame for refusing connection to the radio terminal 12. When the wireless terminal 12 receives the wireless management frame for connection refusal, the wireless base station 11-2 having the second highest reception level in the wireless base station search is selected, and the wireless base station search signal is transmitted again. On the other hand, the radio base station 11-2 transmits a base station search response signal to the radio terminal 12.

When receiving the base station search response signal from the radio base station 11-2, the radio terminal 12 transmits a radio management frame for a radio connection request to the radio base station 11-2. The wireless management frame also includes information on the wireless terminal identifier and wireless terminal attribute of the wireless terminal 12.
On the other hand, the radio base station 11-2 that has received the radio management frame transmits a load distribution control frame for a connection request to the central control device 14. The load distribution control frame for the connection request also includes information on the wireless terminal identifier and the wireless terminal attribute of the wireless terminal 12 requesting the wireless connection.

In the example of FIG. 21, the centralized control device 14 sends a connection permission response to the radio base station 11-2, and the radio base station 11-2 receives this, and the radio management of the connection permission to the radio terminal. A frame is being transmitted.
Thus, in the wireless LAN system of the present invention, the wireless voice terminal (wireless terminal) 12 notifies the central control device 14 of a call channel request at the time of outgoing call, incoming call or handover, and receives the call channel request means. 14 receives a call channel assignment and starts a call control sequence at the time of outgoing and incoming calls, and resumes a call at the time of handover. On the other hand, if the call control channel assignment is rejected by the centralized control device 14, the radio base station 11 is searched. The communication channel request is again notified to the central control apparatus 14 via the newly connected radio base station 11.

  At the end of the call, the wireless voice terminal is provided with communication control means for notifying the central control device that the call channel is released after completion of the call control sequence for the end of the call, while the central control device 14 is connected from each of the wireless voice terminals 12. The communication channel request notification including the identification information of the wireless base station 11 is received, information on the number of simultaneous calls of the wireless voice terminal 12 in the wireless base station 11 is managed, and the wireless voice terminal 12 that has notified the call channel request is When there is another wireless base station having a smaller number of simultaneous calls than the connected wireless base station 11, the wireless voice terminal 12 is notified of call channel allocation refusal.

  When the number of simultaneous calls of the radio base station 11 connected to the radio voice terminal 12 that has notified the call channel request is substantially equal to the number of simultaneous calls of other radio base stations located around the radio base station 11, It is equipped with a notification means for notifying the voice terminal 12 of call channel assignment, can manage the number of simultaneous calls of a plurality of radio base stations 11, and can realize optimal load distribution flexibly according to the uneven number of calls In addition, it is possible to provide a load balancing function considering the number of simultaneous calls.

Furthermore, since the call channel assignment refusal message can include the identification information of other radio base stations 11 with a small number of simultaneous calls, the radio terminal can be connected to the radio base station to which it is connected even when call channel assignment is rejected. There is no need to search for the station 11 anew, a new wireless connection can be established in a short time, and there is little deterioration of the call quality.
The wireless LAN system of the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram showing an overall configuration of a wireless LAN system according to an embodiment of the present invention. The figure which shows the whole structure of the wireless LAN system which concerns on another embodiment of this invention. 1 is a block configuration diagram of a wireless base station in a wireless LAN system according to an embodiment of the present invention. The figure which shows the internal block structure of the radio | wireless management part shown in FIG. The figure which shows an example of the terminal management table in the radio | wireless terminal information storage part of the radio | wireless management part shown in FIG. The figure which shows an example of the frame format in communication between the load distribution control part of a wireless base station, and the centralized control apparatus. The figure which shows an example of the message of the connection and disconnection in communication between the load distribution control part of a wireless base station, and the centralized control apparatus. The figure which shows an example of the wireless terminal connection number management table in a centralized control apparatus. The figure which shows an example of the response message in communication between the load distribution control part of a wireless base station, and the centralized control apparatus. The figure which shows an example of the notification message of the connection enable information in communication between the load distribution control part of a wireless base station, and the centralized control apparatus. The figure which shows an example of the interference electric power notification message in communication between the load distribution control part of a wireless base station, and the centralized control apparatus. The figure which shows an example of the interference power management table in a centralized control apparatus. The figure which shows an example of the conversion table for converting interference power into the number of connections. The figure which shows an example of the wireless terminal connection number management table including the influence of the interference in a centralized control apparatus. The figure which shows an example of the base station search reception level notification message in communication between the load distribution control unit of the radio base station and the centralized control device. The figure which shows an example of the table of the base station reception level for every radio | wireless terminal in a centralized control apparatus. The figure which shows an example of the relationship between an average receiving level maximum value and an average receiving level tolerance | permissible_range. The block diagram which shows schematic structure of a radio | wireless terminal. The figure which shows the internal block structure of the radio | wireless management part in the radio | wireless terminal shown in FIG. The sequence diagram which shows wireless terminal registration operation (in the case of registration permission). The sequence diagram which shows wireless terminal registration operation (in the case of registration refusal). 1 is a block configuration diagram of a centralized control device in a wireless LAN system according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Network 11 Wireless base station 12 Wireless terminal 14 Centralized control apparatus 15 Private branch exchange 16 Router 17 Call control server 18 Public network

Claims (2)

A wireless LAN system having a plurality of wireless base stations connected to a network and a plurality of wireless voice terminals accessing the wireless base station,
A centralized control device connected to the network and communicating with the plurality of radio base stations to control the operation of the radio base stations;
The wireless voice terminal notifies a call channel request to the central control device at the time of outgoing call, incoming call or handover, receives a call channel assignment from the central control device, starts a call control sequence at the time of outgoing and incoming calls, and at the time of handover When a call channel allocation is rejected by the central control device while the call is resumed, the radio base station is searched, and a call channel request is again made to the central control device via the newly connected radio base station. Notifying and at the time of the end of the call, while the call control sequence for the end of the call is completed, the communication channel release is notified to the centralized control device,
The central control device receives a notification of a call channel request including identification information of the connected radio base station from each of the radio voice terminals, and from the notification of the call channel request, the centralized control device receives the notification of the radio voice terminal in the radio base station. When there is another radio base station that manages information on the number of simultaneous calls and has a smaller number of simultaneous calls than the radio base station to which the radio voice terminal that has notified the call channel request is connected, the radio voice terminal The number of simultaneous calls of the radio base station connected to the wireless voice terminal that has notified the call channel request is the same as the number of simultaneous calls of other radio base stations located around the radio base station. A wireless LAN system that notifies the wireless voice terminal of call channel assignment when the number is substantially equal to the number.   2. The wireless LAN system according to claim 1, wherein the call channel allocation rejection message includes identification information of another wireless base station having a small number of simultaneous calls.

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