Abstract:
This invention relates to a wireless LAN access point including a communication unit capable of communication by the first wireless communication method, a unit which detects that the traffic density in the communication band used by the first wireless communication method exceeds a predetermined traffic density, and a unit which limits the traffic density in the communication band of the first wireless communication method by a wireless LAN client when the traffic density is detected to exceed the predetermined traffic density.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-315911, filed Oct. 30, 2002, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a relay and communication system and, more particularly, to a relay and communication system capable of switching between two wireless communication methods. 
     2. Description of the Related Art 
     A technique of increasing the throughput has conventionally been developed (Jpn. Pat. Appln. KOKAI Publication No. 11-55286). According to this technique, the number of clients connectable to a wireless LAN access point is defined. If a wireless LAN access point is accessed by clients exceeding this determined number, connection requests from the wireless LAN access point are denied. 
     In this technique, an access is limited by only the number of clients accessible to a wireless LAN access point. An access is limited when clients each connected to an access point produce relatively light traffic, like a client which merely browses the Web or a client which uses only mail. 
     Such clients produce only light traffic, and even if more than a predetermined number of such clients are connected, the throughput does not decrease. However, accesses are limited even with a margin for the communication band, failing to effectively use the communication band. 
     BRIEF SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, there is provided a relay comprising a communication unit capable of communication by a first communication method, means for detecting that a traffic density in a communication band used by the first communication method exceeds a predetermined traffic density, and means for limiting the traffic density in the communication band of the first communication method by a client device when the traffic density is detected to exceed the predetermined traffic density. 
     According to the embodiment of the present invention, there is also provided a communication control method in a wireless relay capable of communication by a first wireless communication method, comprising detecting that a traffic density in a communication band used by the first wireless communication method exceeds a predetermined traffic density, and limiting the traffic density in the communication band of the first wireless communication method by a wireless terminal when the traffic density is detected to exceed the predetermined traffic density. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram showing a wireless LAN system according to the first embodiment of the present invention; 
         FIG. 2  is a functional block diagram showing an access point  1  according to the first embodiment of the present invention; 
         FIG. 3  is a flow chart for explaining the operation of the wireless LAN access point according to the first embodiment of the present invention; 
         FIG. 4  is a flow chart for explaining the operation of the wireless LAN access point according to the first embodiment of the present invention; 
         FIG. 5  is a flow chart for explaining the operation of a wireless LAN client; 
         FIG. 6  is a functional block diagram showing an access point in a wireless LAN system according to the second embodiment of the present invention; 
         FIG. 7  is a flow chart for explaining the operation of the wireless LAN system according to the second embodiment of the present invention; and 
         FIG. 8  is a flow chart showing the operation of a client in the wireless LAN system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     A wireless LAN system according to the first embodiment of the present invention will be described below with reference to several views of the accompanying drawing. 
       FIG. 1  is a block diagram showing the wireless LAN system according to the first embodiment of the present invention. 
     As shown in  FIG. 1 , the wireless LAN system according to the first embodiment of the present invention comprises an access point  1 , and clients  2   a  to  2   e  which wirelessly access the access point. 
     The access point  1  comprises a communication I/F  11 , relay unit  12 , controller  13 , memory  14 , and LAN I/F  15 . 
     The communication I/F  11  is an interface for communicating with the clients  2   a  to  2   e.    
     The relay unit  12  performs repeating processing between a wireless LAN comprised of the clients  2   a  and  2   e , and a wired LAN  21 , and routing processing in the wireless LAN. 
     The controller  13  controls the overall wireless LAN access point  1 , and executes the operation of the wireless LAN system according to the first embodiment of the present invention. This processing will be described later. 
     The memory  14  is used for processing by the relay unit  12  and controller  13 , and stores a table adopted in the first embodiment of the present invention. 
     The LAN I/F  15  is an interface for communication between the access point  1  and the wired LAN  21 . 
       FIG. 2  is a functional block diagram showing the access point  1  according to the first embodiment of the present invention. 
     As shown in  FIG. 2 , the access point  1  according to the first embodiment of the present invention comprises a communication unit  31 , traffic density detecting unit  32 , association request denying unit  33 , message sending unit  34 , and association unit  35 . 
     The communication unit  31  performs wireless communication between the access point and a client. The communication unit  31  comprises an IEEE 802.11a communication unit  31   a  and IEEE 802.11b communication unit  31   b  according to two communication methods. 
     The IEEE 802.11a communication unit  31   a  performs communication complying with the IEEE 802.11a communication method. 
     The IEEE 802.11b communication unit  31   b  performs communication complying with the IEEE 802.11b communication method. 
     The traffic density detecting unit  32  detects traffic densities produced by the IEEE 802.11a communication unit  31   a  and IEEE 802.11b communication unit  31   b . More specifically, the traffic density detecting unit  32  detects that the communication band use amount of the IEEE 802.11a communication unit  31   a  exceeds a predetermined use amount. Also, the traffic density detecting unit  32  detects that the communication band use amount of the IEEE 802.11b communication unit  31   b  exceeds a predetermined use amount. The predetermined use amount is arbitrarily set to, e.g., a data rate of 20 MB/min. 
     The association request denying unit  33  denies an association request from a client when the traffic density detecting unit  32  detects that the traffic density exceeds a predetermined use amount. 
     More specifically, when the traffic density detecting unit  32  detects that the communication band use amount of the IEEE 802.11a communication unit  31   a  exceeds a predetermined use amount, the association request denying unit  33  denies an association request from a client in the IEEE 802.11a communication band. When the traffic density detecting unit  32  detects that the communication band use amount of the IEEE 802.11b communication unit  31   b  exceeds a predetermined use amount, the association request denying unit  33  denies an association request from a client in the IEEE 802.11b communication band. 
     The message sending unit  34  sends a message that communication should be done by another communication method when the association request denying unit  33  denies an association. More specifically, when an association request is denied in the IEEE 802.11a communication band, the message sending unit  34  sends a message in the IEEE 802.11a communication band to a client which has issued the association request. When an association request is denied in the IEEE 802.11b communication band, the message sending unit  34  sends a message in the IEEE 802.11b communication band to a client which has issued the association request. 
     In response to a message sent by the message sending unit  34 , the association unit  35  executes an association upon reception of an association request which is transmitted by a client according to a communication method different from the communication method of the first association request. 
     The operation of the wireless LAN access point according to the first embodiment of the present invention will be explained with reference to the flow charts of  FIGS. 3 and 4 . 
     Whether a client has issued an association request by the IEEE 802.11a method is decided (SI). If NO in Si, the flow shifts to processing in S 5  to be described later. 
     If YES in SI, whether the traffic density in the IEEE 802.11a band is equal to or larger than a predetermined traffic density is decided (S 2 ). 
     If NO in S 2 , an association starts by the IEEE 802.11a method (S 3 ). If YES in S 2 , it is determined that the traffic density in the IEEE 802.11a band is equal to or larger than a predetermined traffic density, i.e., heavy, and the association request issued by the IEEE 802.11a method is denied (S 4 ). 
     An error message that communication should be done by another communication method is sent in the IEEE 802.11a band to the wireless LAN client which has issued the association request (S 5 ). The contents of the error message prompt reconnection in the IEEE 802.11b communication band because the IEEE 802.11a communication band is crowded. 
     Whether an association request has been issued by the IEEE 802.11b method in response to the error message is decided (S 6 ). If YES in S 6 , whether the traffic density in the IEEE 802.11 band is equal to or larger than a predetermined traffic density is decided (S 7 ). If YES in S 7 , the association request issued by the IEEE 802.11b method is denied (S 9 ). If NO in S 6 , the flow returns to processing in S 1 . 
     After the association request is denied in S 9 , an error message is sent from the wireless LAN access point to the wireless LAN client which has issued the association request (S 10 ). The flow then returns to processing in S 1 . 
     This operation is performed at the wireless LAN access point. When the traffic density exceeds a predetermined traffic density in a given band, an association request in this band is denied, and an association is done in another band. In this manner, the communication band can be controlled. 
     The operation of the wireless LAN client will be explained with reference to the flow chart of  FIG. 5 . 
     Whether an error message has been received by the IEEE 802.11a method from the wireless LAN access point is decided (S 21 ). If YES in S 21 , IEEE 802.11a wireless connection is released, and an association request is transmitted to the wireless LAN access point by the IEEE 802.11b method (S 22 ). Thereafter, an association starts by the IEEE 802.11b method (S 23 ). 
     If NO in S 21 , whether an error message has been received by the IEEE 802.11b method from the wireless LAN access point is decided (S 24 ). 
     If YES in S 24 , IEEE 802.11b wireless connection is released, and an association request is transmitted to the wireless LAN access point by the IEEE 802.11a method (S 25 ). 
     After that, an association starts by the IEEE 802.11a method (S 26 ), and the flow returns to processing in S 21 . If NO in S 24 , the flow shifts to processing in S 21 . 
     The wireless LAN system according to the first embodiment of the present invention can control the wireless communication band by performing an association by another communication method when a wireless LAN client receives an error message from a wireless LAN access point. 
     Second Embodiment 
     A wireless LAN system according to the second embodiment of the present invention will be described below. The hardware arrangement of the wireless LAN system according to the second embodiment of the present invention is the same as that shown in  FIG. 1 . 
     In the first embodiment, when the traffic density is equal to or larger than a predetermined traffic density, an association from a client is denied, and a message for an association by another communication method is sent to the client. 
     In the wireless LAN system according to the second embodiment of the present invention, a client which has already achieved an association is disassociated from the access point side. 
       FIG. 6  is a functional block diagram showing an access point in the wireless LAN system according to the second embodiment of the present invention. 
     As shown in  FIG. 6 , an access point  1  according to the second embodiment of the present invention comprises a communication unit  41 , traffic density detecting unit  42 , field intensity measuring unit  43 , communication time measuring unit  44 , table  45 , client selecting unit  46 , association unit  47 , message sending unit  48 , and wireless connection releasing unit  49 . 
     The communication unit  41  performs wireless communication between the access point and a client. The communication unit  41  comprises an IEEE 802.11a communication unit  41   a  and IEEE 802.11b communication unit  41   b  according to two communication methods. 
     The IEEE 802.11a communication unit  41   a  performs communication complying with the IEEE 802.11a communication method. 
     The IEEE 802.11b communication unit  41   b  performs communication complying with the IEEE 802.11b communication method. 
     The traffic density detecting unit  42  detects traffic densities produced by the IEEE 802.11a communication unit  41   a  and IEEE 802.11b communication unit  41   b . More specifically, the traffic density detecting unit  42  detects that the communication band use amount of the IEEE 802.11a communication unit  41   a  exceeds a predetermined use amount. Also, the traffic density detecting unit  42  detects that the communication band use amount of the IEEE 802.11b communication unit  41   b  exceeds a predetermined use amount. 
     The field intensity measuring unit  43  measures the field intensity of radio waves transmitted by a client. 
     The communication time measuring unit  44  measures communication times with a plurality of associated wireless LAN clients. 
     The table  45  stores the priority levels of a plurality of associated wireless LAN clients. For example, as shown in  FIG. 6 , client numbers “1” and “2” are set to priority “AA”; client number “3”, to priority “C”; and client number “4”, to priority “B”. 
       FIG. 6  shows the three, field intensity measuring unit  43 , communication time measuring unit  44 , and table  45 . However, the system suffices to comprise a function corresponding to a client selecting method in the client selecting unit  46 . 
     That is, the system suffices to comprise only the field intensity measuring unit  43  when the client selecting unit  46  selects a client on the basis of the field intensity, or the communication time measuring unit  44  when the client selecting unit  46  selects a client on the basis of the communication time. 
     The client selecting unit  46  selects a wireless LAN client to be disassociated from a plurality of associated wireless LAN clients in accordance with a predetermined selecting method. 
     For example, to select a wireless LAN client to be disassociated on the basis of the field intensity, the client selecting unit  46  selects a wireless LAN client having the lowest field intensity among the field intensities of a plurality of wireless LAN clients that are measured by the field intensity measuring unit  43 . 
     To select a wireless LAN client to be disassociated on the basis of the communication time, the client selecting unit  46  selects a wireless LAN client having the shortest communication time among the communication times of a plurality of wireless LAN clients that are measured by the communication time measuring unit  44 . 
     To select a wireless LAN client to be disassociated on the basis of priority, the client selecting unit  46  selects a wireless LAN client having the lowest priority by referring to the table  45  in which the client number and priority are associated. 
     When the client selecting unit  46  selects a client, the message sending unit  48  sends by the current communication method a message which prompts reconnection. The message which prompts reconnection can contain information representing a communication method for reconnection, and information representing an access point to be reconnected. 
     After the message sending unit  48  sends a message, the wireless connection releasing unit  49  cuts off communication with a client selected by the client selecting unit  46 . The operation of the wireless LAN system according to the second embodiment of the present invention will be explained with reference to the flow chart of  FIG. 7 . 
     Whether the traffic density in the IEEE 802.11a band is equal to or larger than a predetermined traffic density is decided (S 31 ). If YES in S 31 , a client to be disassociated is selected (S 32 ). 
     The client selecting method complies with any one of the following rules. 
     1. The field intensities of radio waves transmitted by a plurality of associated wireless LAN clients are measured. A wireless LAN client which has transmitted radio waves at the lowest field intensity among the measured field intensities is selected. 
     2. Communication times with a plurality of associated wireless LAN clients are measured. A wireless LAN client having the shortest communication time among the measured communication times is selected. 
     3. A table which stores the priority levels of a plurality of associated wireless LAN clients is referred to, and a wireless LAN client having the lowest priority is selected. 
     After that, an error message is sent to the selected client (S 33 ). The contents of the error message prompt reconnection in the IEEE 802.11b communication band because the IEEE 802.11a communication band is crowded. 
     Wireless communication with the selected client is cut off (S 34 ). Whether an association request has been issued by the IEEE 802.11b communication method in response to the error message is decided (S 35 ). 
     If NO in S 35 , the flow returns to processing in S 31 . If YES in S 35 , an association with the client starts by the IEEE 802.11b communication method (S 36 ), and the flow returns to step S 31 . 
     If NO in S 31 , whether the traffic density in the IEEE 802.11b band is equal to or larger than a predetermined traffic density is decided (S 37 ). If YES in S 37 , a client to be disassociated is selected (S 38 ). This client selecting method has been explained in S 32 . 
     An error message is sent to the selected client (S 39 ). The contents of the error message prompt reconnection in the IEEE 802.11a communication band because the IEEE 802.11b communication band is crowded. 
     Wireless communication with the selected client is cut off (S 40 ). Whether an association request has been issued by the IEEE 802.11a communication method in response to the error message is decided (S 41 ). 
     If NO in S 41 , the flow returns to processing in S 31 . If YES in S 41 , an association with the client starts by the IEEE 802.11a communication method (S 42 ), and the flow returns to step S 31 . 
     In the wireless LAN system according to the second embodiment of the present invention, when a given communication band is crowded, a message which prompts reconnection in another communication band is sent from an access point to a client, releasing connection with the associated client. The wireless LAN system can effectively utilize the communication band. 
     In the above-described embodiments, the access point decides a communication status, and the topology is changed by an action of the access point. Alternatively, the client may grasp the status and change the topology. 
     In wireless LAN communication, an access point operates not as a switching hub (which sends packets to only a port corresponding to an MAC address), but as a bridge or dumb hub (which sends all packets by broadcasting). Packets received by an access point and packets received by a client are the same. 
     However, this does not apply when the hidden station problem occurs. Hence, the client side can satisfactorily decide the traffic density, and preferably performs settings in accordance with its purpose. 
     For example, for a user who wants to only read mail but use IEEE 802.11a for printing or transfer of a large-capacity file, an IEEE 802.11b path may be decided to be more preferable than a crowded IEEE 802.11a path. 
     To the contrary, a client which transfers moving pictures that become useless without any IEEE 802.11a band is set not to shift to IEEE 802.11b. In this case, the client decides the traffic density, disassociates connection with IEEE 802.11a, and shifts to IEEE 802.11b. 
       FIG. 8  is a flow chart for explaining an operation of deciding the traffic density by a client and releasing wireless connection. 
     As shown in  FIG. 8 , whether the traffic density in the IEEE 802.11a band is a predetermined traffic density is decided (S 51 ). If YES in S 51 , IEEE 802.11a wireless connection with an access point is released (S 52 ), and the flow returns to processing in S 51 . 
     If NO in S 51 , whether the traffic density in the IEEE 802.11b band is equal to or larger than a predetermined traffic density is decided (S 53 ). 
     If NO in S 53 , the flow returns to processing in S 51 . If YES in S 53 , IEEE 802.11b wireless connection with an access point is released (S 54 ), and the flow returns to processing in S 51 . 
     In the above-described embodiments, two communication methods are switched on the basis of the traffic density in the wireless LAN access point and client. The number of communication methods is not limited to two, that is, three or more communication methods may be adopted. For three or more communication methods, a message which prompts reconnection by a communication method using the least crowded band may be inserted in an error message. With this setting, the client can access an access point by the optimal communication method. 
     In the above-described embodiments, one access point performs communication by two communication methods. The access point may have only a function of performing communication by one communication method. In this case, when the traffic density exceeds a predetermined traffic density, the access point sends to a client an error message that reconnection is done by another communication method. The client which has received the error message associates with another access point by the reconnection communication method. 
     The present invention is not limited to the above-described embodiments, and can be variously modified without departing from the spirit and scope of the invention in practical use. The respective embodiments can be combined as properly as possible. In this case, the effects of the combination can be obtained. The embodiments include inventions on various stages, and various inventions can be extracted by an appropriate combination of building components disclosed. For example, when an invention is extracted by omitting several building components from all those described in the embodiments, the omission is properly compensated for by a well-known technique in practicing the extracted invention. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.