JP2002033736A - Multiple address communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multiple address communication system that can conduct multi-cast communication without deteriorating communication performance of clients, other than those for multi-cast communication, when conducting the multi-cast communication. SOLUTION: In the case of conducting multi-cast communication, the presence/absence of multi-cast distribution request is respectively registered in internal tables 105, 107, 113 of a server 101 and WAPs(wireless access points) 102, 111 in cross-reference with client information of clients having already been registered. The server 101 and the WAPs 102, 111 respectively calculate a transmission time interval on the basis of the contents of the tables 105, 107, 113 and respectively transmit a data frame at this interval. Furthermore, buffers 108, 114 of the WAPs 102, 111 hold data frames from the server 101 and resend the data frames to a client requesting re-sending of the data frames.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast system, and more particularly to a server using a wireless LAN including a server, an access point provided for the server, and a client provided for the access point.
The present invention relates to a broadcast system in a client system.

[0002]

2. Description of the Related Art In a conventional server / client system using a wireless LAN, a server and a WAP (wireless access point) at the time of file transfer using multicast communication transmit a transmission frame to all target clients. are doing. In the conventional file transfer using multicast communication, communication between a WAP and a client has been performed almost simultaneously.

[0003]

However, in the above-described conventional server / client system using a wireless LAN, communication between all WAPs and target clients is almost impossible at the time of transferring various files using multicast communication. Simultaneously and under a high load, radio interference between WAPs occurs, so that there is a drawback that errors in transferred data frames frequently occur.

[0004] As a result, a client that cannot receive data requests the server to retransmit the data frame, and the server frequently retransmits the data frame to the client. There is a disadvantage that the network load between the server and the WAP becomes heavy.

Furthermore, when transferring various files using multicast communication, since all WAPs perform high-load communication, the communication band is occupied. Is disadvantageous in that the communication performance is significantly degraded.

A first object of the present invention is to provide a broadcast communication system capable of reducing occurrence of data frame errors during multicast communication.

[0007] A second object of the present invention is to reduce the burden on the server and
An object of the present invention is to provide a server-client system capable of reducing a network load between a server and a WAP, and a broadcast communication method thereof.

A third object of the present invention is to provide a broadcast communication system capable of performing communication without significantly deteriorating the communication performance of clients that are not subjected to multicast communication during multicast communication.

[0009]

A broadcast communication system according to the present invention uses a wireless LAN server including a server, an access point provided to the server, and a client provided to the access point. A broadcast communication method in a client system, wherein the server, when performing multicast communication, according to a ratio of the number of clients belonging to the server that has made a multicast distribution request to the number of all clients belonging to the server; A data frame is transmitted to the access point at a transmission time interval.

[0010] In the broadcast communication method, the access point may transmit at a transmission time corresponding to a ratio between the number of clients belonging to the access point that has made the multicast distribution request and the number of all clients belonging to the access point. The data frame is transmitted from the server to a client belonging to the access point that has issued the multicast distribution request at intervals.

Further, in the broadcast communication system, the access point includes a holding unit for holding the data frame from the server, and a client belonging to the access point that has issued the multicast distribution request is a client that belongs to the access point. If at least one of the data frames from could not be received, when making a first retransmission request to retransmit the corresponding data frame to itself, the client that made the first retransmission request to the client The data frame stored in the storage unit is retransmitted.

Still further, in the above-mentioned broadcast communication system,
The access point receives the first retransmission request,
When the data frame is not held in the holding means, the server makes a retransmission request to retransmit the data frame to itself, and upon receiving the request, the server sends the first data via the access point. And retransmitting the data frame to the client that has made the retransmission request.

The operation of the present invention is as follows. When performing multicast communication, the client uses W
A multicast distribution request is made to the server via the AP.
Upon receiving the distribution request, the server calculates a ratio between the number of all clients belonging to the server and the number of clients belonging to the server that has requested the distribution, and determines a transmission time interval of a data frame to be transmitted. In addition, since WAP monitors the exchange between the server and the client belonging to itself, the WAP can calculate the ratio between the number of all clients belonging to itself and the number of clients belonging to itself which has requested the distribution. The transmission time interval of the received data frame is determined.

Then, the server transmits data frames to the WAP at the above-mentioned transmission time interval, and the WAP holds some of these data frames in a buffer and transmits them to the client at the above-mentioned transmission time interval. Here, when the client fails to receive the data frame, the client requests the WAP to retransmit the data frame. WA
In response to the retransmission request, the P retransmits the relevant data frame to the client that has requested the retransmission if the relevant data frame is present in the buffer, and retransmits the relevant data frame to the client if the buffer does not have the relevant data frame. Request to. Upon receiving the retransmission request, the server retransmits the data frame to the client that has requested the retransmission via WAP.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a server-client system according to an embodiment of the present invention. The server / client system to which the present invention is applied includes, for example, a server 101 and a WAP 102 as shown in FIG.
, 111 and the client of the area 103 (200-2
03 and 300 to 302).

Each of the WAPs 102 and 111 is connected to the server 101 via a wired line 104. Also, the client (200
203) are connected to the WAP 102 by a wireless line, and the clients (300
To 302) are connected to the WAP 111 via a wireless line.

That is, the WAPs 102 and 111 are provided for the server 101, the client in the area 106 is provided for the WAP 102, and the client in the area 112 is provided for the WAP 111.
Further, the client belonging to the server 101 is stored in the area 10
3 and the client belonging to WAP 102 is the client of area 106 and WAP 1
11 belong to the area 112.

The server 101 transmits a data frame to the client in the area 103 using the wired line 104, and the IP (Internet Protocol) of all the clients in the area 103 belonging to the server 101.
Address and MAC (Media Access Con)
(Toll) address or client information having one of them, and a client registration table 105 for registering the client information in the area 103 in association with the presence / absence of a multicast distribution request.

Each of the WAPs 102 and 111 converts a data frame received from the server 101 via the wired line 104 into a wireless signal, and performs wireless communication with the clients in the areas 106 and 112. WAP10
2 has a client registration table 107 for registering the client information of all clients in the area 106 provided for itself in association with the presence / absence of a multicast distribution request of the client in the area 106. Further, the WAP 102 has a buffer 108 for holding some data frames transmitted from the server 101.

Similarly to the WAP 102, the WAP 111 registers the client information of all the clients in the area 112 provided for itself in association with the presence / absence of a multicast distribution request of the client in the area 112. Table 113 and server 10
And a buffer 114 for holding a number of data frames transmitted from one.

When performing the multicast communication, the server 101 transmits the names and version information of various files to the clients in the area 103 via the WAPs 102 and 111. The client in the area 103 receives the names and version information of these various files and returns to the server 101 whether or not there is a distribution request by multicast. The server 101 registers the returned information in the client registration table 105 in association with the already registered client information.

The WAPs 102 and 111 monitor the exchange between the server 101 and the clients in the areas 106 and 112, respectively, and associate the presence / absence of the distribution request of the clients in the areas 106 and 112 with the already registered client information. Client registration table 107
And 113 respectively.

The server 101 terminates the reception of the multicast distribution request after a lapse of a predetermined time or after registering in the client registration table 105 the presence or absence of the distribution request from the client in the area 103. After the reception is completed, the server 101 sets the client registration table 105
The number of clients (for example, 201, 202, 300, and 301) that made a distribution request, or the clients that did not make a distribution request (for example, 200, 203, and 30)
The number of 2) is calculated, and the number of distribution targets is determined.

After the above acceptance, the WAPs 102 and 1
Reference numeral 11 denotes a client (for example, W) that has made a distribution request based on the contents of the client registration tables 107 and 113.
201 and 202 for the AP 102 and 30 for the WAP 111
0, 301) or clients that did not (e.g., 200, 203, WAP1 in WAP102)
In step 11, 302) is calculated, and the number of distribution targets is determined.

The server 101 calculates the ratio between the number of distribution targets and the total number of clients in the area 103 determined from the number of client information registered in the client registration table 105. WAPs 102 and 11
1 also calculates the ratio between the respective distribution target numbers and the total number of clients in the areas 106 and 112 determined from the number of client information registered in the client registration tables 107 and 113, respectively.

FIG. 2 is a diagram showing an example of a method of calculating the transmission time interval of the server 101 shown in FIG. In FIG.
The total number of clients in the area 103 is, for example, 100,
The number of distribution targets is, for example, 80, and the predetermined minimum transmission time interval is, for example, 50 ms. By dividing the minimum transmission time interval by the ratio of the total number of clients to the number of distribution targets, the transmission time interval (about 60 ms) of the data frame transmitted from the server 101 is calculated.

FIG. 3 is a diagram showing an example of a method of calculating the transmission time interval of the WAP 102 shown in FIG. In FIG.
The total number of clients in the area 106 is, for example, 10, the number of distribution targets is, for example, 5, and the predetermined minimum transmission time interval is, for example, 80 ms. By dividing the minimum transmission time interval by the ratio of the total number of clients to the number of distribution targets, the transmission time interval (160 ms) of the data frame transmitted from WAP 102 is calculated. In addition, WA
The method of calculating the transmission time interval of P111 is the same as that of FIG.

The server 101 starts transmitting a data frame at a transmission time interval (about 60 ms) according to the above ratio.

FIG. 4 shows the server 101 and the WAP 1 shown in FIG.
02 is a diagram showing a configuration of a server / client system in which a client 201 in an area 106 is extracted, and portions equivalent to those in FIG. 1 are denoted by the same reference numerals. In FIG. 4, WAP 102 holds some data frames transmitted from server 101 in buffer 108, and transmits data frames at transmission time intervals (160 ms) according to the above ratio.

The client 201 receives the data frame transmitted from the WAP 102. If the data frame cannot be received, the client 201 requests the WAP 102 to retransmit the data frame that could not be received. When the WAP 102 receives the retransmission request from the client 201, and holds the corresponding data frame in the buffer 108,
The corresponding data frame is retransmitted to the client 201.

When the data frame is not held in the buffer 108 in response to the retransmission request, the WAP 102 issues a retransmission request to the server 101. Server 10
1 receives the retransmission request from the WAP 102 and sends the data frame to the client 2 via the WAP 102.
01.

FIG. 5 is a flowchart showing the operation of the server / client system according to the embodiment of the present invention when performing multicast communication. In FIG. 5, server 1
01 stores client information of all clients in the area 103 belonging to itself in the internal client registration table 1
05 (step S1). WAP102 and 1
11 are regions 106 and 11 provided corresponding to the respective regions.
The client information of all the clients 2 is registered in the internal client registration tables 107 and 113, respectively (step S2).

When the registration is completed, the server 101 sets the area 1
The name and version information of various files are transmitted to each client 03 (step S3). Area 103
When receiving this information (step S4), the client of the server 10 determines whether or not there is a multicast distribution request.
1 is returned (step S5). The client in the area 103 that has made the distribution request (step S6) waits for the multicast distribution (step S7), and the client in the area 103 that has not made the distribution request (step S6) stands by (step S20). The server 101
The presence / absence of a distribution request, which is the reply information of the client in the area 103, is registered in the client registration table 105 (step S8).

During this time, the WAPs 102 and 111 monitor the exchange between the server 101 and the client in the area 103, and determine whether there is a distribution request, which is the return information of the client in the area 106 or 112, in the client registration table 10.
7 and 113 (step S9). The server 101 terminates the reception of the distribution request after a lapse of a fixed time or after registering the presence or absence of the distribution request of all the clients in the area 103 (step S10).

The server 101 calculates a transmission time interval based on the contents of the client registration table 105 (step S11). Also, the WAPs 102 and 111 are based on the contents of the client registration tables 107 and 113,
Each transmission time interval is calculated (step S12). The server 101 starts transmitting the data frame at the calculated transmission time interval (step S13).

The WAPs 102 and 111 are
Respectively hold several data frames transmitted from the internal buffers 108 and 114 (step S
14) At the same time, the data frame is transmitted at the calculated transmission time interval (step S15). Regions 106 and 11
If the client No. 2 can receive the distributed data (step S16), it ends the communication and waits (step S16).
20) In the case where reception was not possible (step S16),
Each of the WAPs 102 and 111 is requested to retransmit a data frame that could not be received (step S17).

In response to the retransmission request, WAPs 102 and 11
1 retransmits the corresponding data frame, if any, in the buffers 108 and 114 (step S18) (step S15). When there is no corresponding data frame (step S18), the server 101 requests the server 101 to retransmit the data frame (step S19). Upon receiving the retransmission request, the server 101 retransmits the data frame (step S13).

As described above, in the above embodiment, the transmission time interval of the data frame is determined by the number of clients that have requested distribution, so that the bandwidth occupancy rate during multicast communication can be limited, and The communication can be performed without significantly deteriorating the communication performance when the client performs communication.

Further, in this embodiment, since a buffer for holding a data frame is provided in the WAP, processing can be performed between the WAP and the client in response to a client retransmission request, and The burden and the network load between the server and the WAP can be reduced.

[0040]

The first effect of the present invention is that the occurrence of data frame errors during multicast communication can be reduced. The reason is that multiple W
The AP determines transmission time intervals of data frames in accordance with the ratio of clients requesting multicast communication, and transmits data frames at the respective transmission time intervals, thereby reducing radio interference between WAPs. This is because you can do it.

A second advantage of the present invention is that the load on the server and the network load between the server and the WAP can be reduced. The reason is that by holding the data frame transmitted from the server in the WAP, the WAP can retransmit the data frame held by itself in response to a retransmission request from the client. This is because the request can be processed between the WAP and the client without sending the request to the server.

A third effect of the present invention is that, during multicast communication, communication can be performed without significantly deteriorating the communication performance of clients not subject to multicast communication. The reason is that each of the server and the WAP determines the transmission time interval of the data frame according to the ratio of the client requesting the multicast communication, and transmits the data frame at the transmission time interval. This is because the band can be limited and efficient communication can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a server / client system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a method of calculating a transmission time interval of a server 101 illustrated in FIG.

FIG. 3 is a diagram illustrating an example of a method of calculating a transmission time interval of WAP 102 illustrated in FIG.

4 is a diagram showing a configuration of a server-client system in which a server 101, a WAP 102, and a client 201 in an area 106 shown in FIG. 1 are extracted.

FIG. 5 is a flowchart showing an operation of the server / client system according to the embodiment of the present invention when performing multicast communication.

[Explanation of symbols]

 101 Server 102, 111 WAP 103, 106, 112 Client area 104 Wired line 105, 107, 113 Client registration table 108, 114 Buffer 200-203, 300-302 Client

Claims (4)

[Claims] 1. A broadcast communication system in a server-client system using a wireless LAN including a server, an access point provided to the server, and a client provided to the access point, When performing a multicast communication, the server transmits a data frame to the access point at a transmission time interval corresponding to a ratio between the number of clients belonging to the server that has made a multicast distribution request and the number of all clients belonging to the server. A broadcast method characterized by: 2. The method according to claim 1, wherein the access point transmits the multicast distribution request at a transmission time interval corresponding to a ratio between the number of clients belonging to the access point that has issued the multicast distribution request and the number of all clients belonging to the access point. The broadcast method according to claim 1, wherein the data frame from the server is transmitted to a client belonging to the access point that has performed the operation. 3. The access point includes a holding unit that holds the data frame from the server, and a client belonging to the access point that has issued the multicast distribution request transmits at least one of the data frames from the access point. If one cannot be received, when the first retransmission request is made to retransmit the corresponding data frame to itself, it is held in the holding unit by the client that made the first retransmission request. 3. The broadcast system according to claim 2, wherein said corresponding data frame is retransmitted. 4. The access point receives the first retransmission request, and when not holding the corresponding data frame in the holding unit, issues a retransmission request to the server to retransmit the corresponding data frame to itself. 4. The broadcast communication method according to claim 3, wherein the server transmits the data frame to the client that has made the first retransmission request via the access point.