Abstract:
A relay apparatus ( 100 ) acting as an access point of wireless LAN watches a packet showing a request of starting communication among the packets to be relayed between terminal apparatuses ( 101,102 ) and records the identification information of the terminal apparatus included in the packet. When the number of the terminal apparatuses whose identification information is recorded exceeds a preset upper limit value, the relay apparatus disconnects a communication relating to the latest identification information by transmitting a disconnection command or discarding the packet. With this arrangement, deterioration of streaming communication controlled by an access point (AP) of wireless LAN can be prevented.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a communication system making use of wireless LAN, and more particularly to a communication system by an access point (hereinafter, referred to as AP) in streaming communication. 
     2. Description of the Related Art 
     Heretofore, there is known streaming communication for carrying out audio communication and motion picture communication at a real time as a communication mode making use of a wireless LAN system. In general, in the streaming communication, communication can be carried out smoothly when the number of communications at an AP is relatively small. However, as the number of communications increases, since the communication band of the AP is oppressed, a packet is liable to be delayed or discarded. Thus, a disadvantage such as disconnection of communication and the like occurs on a terminal side, which makes it difficult to carry out communication comfortably. 
     To overcome the problem, conventional technologies propose to physically disperse a system load by installing a plurality of APs. As a kind of the technologies, there is a technology for prompting wireless connection to AP in a lower load state by that an AP in a higher load state forcibly disconnects the wireless connection of some terminal apparatuses. A technology relating to the above technology is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-124939 to be described below. 
     Further, there is also a technology for maintaining a load uniform in such a manner that a plurality of APs exchange load state information, and an AP having a high load reduces the strength of radio wave and an AP having a low load increases the strength of radio wave. A technology relating to the above technology is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2004-140614 and 2004-320274 described below. 
     Incidentally, to comfortably carry out streaming communication, the number of communications of APs must be taken into consideration. When, for example, IEEE802.11b is used as a standard of wireless LAN in a network to which VoIP (voice over Internet Protocol) is applied, the number of connections to one AP must be made to 10 or less to carry out audio communication comfortably. 
     Although the conventional method described above is effective to disperse the load of an AP, it pays no attention to keep the number of communications of the AP. Accordingly, even if the load is dispersed, there is a possibility that communication quality is deteriorated by that the number of communications of one set of an AP exceeds an upper limit. 
     SUMMARY OF THE INVENTION 
     An object of the present invention, which was made in view of the above problems, is to provide a method of preventing quality deterioration of streaming communication controlled by an AP. 
     A communication control method of the present invention comprising: recording identification information of a terminal apparatus at a relay apparatus acting as an access point of wireless LAN; wherein the identification information to be recorded is included in a packet showing a request of starting a communication among packets to be relayed by the relay apparatus; and disconnecting a communication relating to the latest identification information when the number of terminal apparatuses whose identification information is recorded exceeds a preset upper limit value. 
     A relay apparatus of the present invention comprising: a CPU carrying out a control program corresponding to process of a terminal apparatus acting as an access point, and a memory storing information used to carry out the control program; wherein the CPU records identification information of a terminal apparatus included in a packet showing a request of starting a communication among packets to be relayed, and disconnects a communication relating to the latest identification information when the number of the terminal apparatuses whose identification information is recorded exceeds a preset upper limit value. 
     According to the present invention, since the relay apparatus of wireless LAN carries out a control so as to disconnect a communication that exceeds the upper limit value as to the number of communicating apparatuses, the number of communicating apparatuses that is preferable to a streaming communication can be maintained. With this operation, deterioration of quality of the streaming communication can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a system arrangement of an embodiment according to the present invention; 
         FIG. 2  is a block diagram showing an arrangement of an AP of the embodiment; 
         FIG. 3  is a flowchart showing an operation procedure of a first embodiment; 
         FIG. 4  is a flowchart showing an operation procedure of a low load state according to a second embodiment; 
         FIG. 5  is a flowchart showing an operation procedure of a high load state according to the second embodiment; 
         FIG. 6  is a flowchart showing an operation procedure of timer process according to the second embodiment; 
         FIG. 7  is a flowchart showing an operation procedure of a low load state according to a third embodiment; 
         FIG. 8  is a flowchart showing an operation procedure according to the third embodiment; 
         FIG. 9  is a flowchart showing an operation procedure according to the third embodiment; 
         FIG. 10  is a flowchart showing an operation procedure according to the third embodiment; 
         FIG. 11  is a flowchart showing an operation procedure of a high load state according to a fourth embodiment; 
         FIG. 12  is a flowchart showing an operation procedure of timer process according to a fifth embodiment; 
         FIG. 13  is a flowchart showing an operation procedure of the timer process according to the fifth embodiment; and 
         FIG. 14  is a flowchart showing an operation procedure of a sixth embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  show hardware arrangements of a system  10  and an AP  100  of an embodiment according to the present invention. The arrangements shown in these figures are common to the embodiments described later. Further, although SIP (Session Initiation Protocol) is used as a protocol of a call control of VoIP communication in the respective embodiments described below, any other protocol may be used to embody the present invention, in addition to SIP. 
     Referring to  FIG. 1 , the system  10  includes the AP  100  as a relay apparatus of wireless LAN, a terminal apparatus  101  connected to the AP  100  via wireless LAN, and a terminal apparatus  102  as a communication partner of the terminal apparatus  101 . The AP  100  and the terminal apparatus  102  are connected to a wired LAN  103 . Further, although  FIG. 1  shows only one set of the terminal apparatus  101  connected to the AP  100  via wireless LAN to simplify the figure, it is assumed that a plurality of terminal apparatus  101  actually exist. 
     Referring to  FIG. 2 , the AP  100  includes a ROM  201  for storing a control program of wireless LAN and a set value used to control, a CPU  202  for carrying out arithmetic operation based on the control program, a RAM  203  acting as a work area when the CPU  202  carries out the control program, a wireless LAN unit  204  for carrying out communication processing according to a rule based on IEEE802.11, and a wired LAN unit  205  for connection to the wired LAN  103 . 
     The ROM  201  stores the control program  201   a , a limit threshold value  201   b  as the set value, a reference bit train  201   c  showing a message of SIP and the description of a packet header, a disconnection command  201   d  using a code for disconnecting communication, and the like. An operation procedure of the AP  100  described later corresponds to an operation carried out by the control program  201   a  carried out by the CPU  202 . 
     The limit threshold value  201   b  is a maximum value prescribing the number of streaming communications that can be carried out by one set of the AP  100  at the same time. The reference bit train  201   c  is a bit train showing an “INVITE” message showing a session start request, a packet header by RTP (Real-time Transport Protocol) used in streaming communication, and the like. Although the limit threshold value  201   b , the reference bit train  201   c  of the message, and the disconnection command  201   d  may be previously stored to the ROM  201  as a program, they may be appropriately modified and added by an operator and the like. 
     The RAM  203  stores an address table  203   a  for recording the MAC address, the communication standard, and the like of the terminal apparatus  101  that carries out a streaming communication by wireless LAN connection and data of a number of communicating apparatuses  203   b  that can be obtained from the table at the time. 
     First Embodiment 
     Operation of a first embodiment will be explained by a flowchart shown in  FIG. 3 . An AP  100  monitors all the transmission packets and the reception packets relating to a terminal apparatus  101  connected via wireless LAN (step A 1 ). During the time, the AP  100  compares the described contents a transmitted/received packet with an “INVITE” message shown by a reference bit train  201   c  of the ROM  201  (step A 2 ). 
     As a result of comparison, when “INVITE” is described in the packet as a target to be monitored (step A 2 : Yes), the AP  100  confirms whether or not the same MAC address as the MAC address of the terminal apparatus  101  included in the packet is included in an address table  203   a  (step A 3 ). 
     When the MAC address of the target exists in the address table  203   a , processing of the packet is completed, and the AP  100  begins processing of a next packet (from step A 3  to step A 1 ). Further, when the MAC address of the target does not exist in the address table  203   a , the AP  100  stores the MAC address to the address table  203   a  (step A 4 ). 
     Next, the AP  100  determines whether or not the number of the MAC addresses recorded in the address table  203   a  at the time, that is, a number of communicating apparatuses  203   b  exceeds a preset limit threshold value  201   b  (step A 5 ). As a result, when the determination is No, the AP  100  goes to processing of a next packet. 
     Further, when the number of communicating apparatuses  203   b  exceeds the limit threshold value  201   b  at the time, the AP  100  transmits a disconnection command  201   d  such as “600 Busy Everywhere”, “486 Busy Here”, or the like for disconnecting communication to a terminal apparatus  101  or  102  acting as a transmission source of a packet (step A 6 ). 
     The MAC address of the transmission source added to the disconnection command  201   d  from the AP  100  may be the MAC address of a terminal apparatus acting as a packet destination in place of the MAC address of the AP  100 . With this arrangement, the terminal apparatus of the transmission source of the packet can receive the disconnection command as that from the terminal apparatus of a communication partner. 
     That is, as to the packet to which the “INVITE” is described and which is processed when the number of communicating apparatuses  203   b  exceeds the limit threshold value  201   b , when for example, the transmission source of the packet is the terminal apparatuses  102  and the destination thereof is the terminal apparatus  101 , the AP  100  sets the MAC address of the terminal apparatus  101  as the transmission source of the disconnection command. With this arrangement, the terminal apparatuses  102  as the transmission source of “INVITE” recognizes the disconnection command transmitted from the AP  100  as a notification from terminal apparatus  101  as a communication partner. 
     As a method of disconnecting communication, the packet as the target may be discarded in place of that the AP  100  transmits the disconnection command  201   d . This is because when the target packet is discarded by the AP  100 , the “INVITE” message does not reach the partner, and, as a result, communication is not established. 
     On the completion of transmission of the disconnection command  201   d , the AP  100  deletes the MAC address stored to the address table  203   a  at step A 4  as to the terminal apparatus  101  (step A 7 ). 
     In contrast, when the contents of the received packet does not correspond to the “lNVITE” (step A 2 : No), the AP  100  determines whether or not it corresponds to the disconnection command  201   d . As a result, when it corresponds to the disconnection command  201   d  (step A 8 : Yes), the AP  100  deletes the MAC address of the terminal apparatus  101  stored to the address table  203   a  (step A 9 ). Further, when it does not correspond to the disconnection command  201   d  (step A 8 : No), the AP  100  carries out predetermined processing assuming that it is a packet of audio, an image, or character data being delivered, and the AP  100  goes to processing of a next packet. 
     As described above, the AP  100  of the first embodiment previously stores the number of streaming communications to be controlled as the limit threshold value  201   b , and when the present number of communicating apparatuses  203   b  exceeds the limit threshold value  201   b , the communications thereof are disconnected. As a result, quality deterioration of the streaming communication can be prevented. 
     Second Embodiment 
     Operation of a second embodiment will be explained. In the following embodiment, as to a load state of the AP  100 , a state in which the number of communicating apparatuses  203   b  reaches the threshold value  201   b  described above is called “a high load state”, and a state in which the number of communicating apparatuses  203   b  has a room to the threshold value  201   b  is called “a low load state”. That is, when the AP  100  is in “the low load state”, the terminal apparatus  101  can comfortably carry out the streaming communication when the AP  100  is in “the low load state”. However, when the AP  100  is in “the high load state”, it is difficult for the AP  100  to comfortably carry out streaming communication. 
     Operation of the AP  100  in “the low load state” will be explained with reference to a flowchart of  FIG. 4 . The AP  100  monitors a packet relating to the terminal apparatus  101  connected via wireless LAN (step B 1 ) and determines whether or not the packet corresponds to a reference bit train  201   c  showing an RTP header (step B 2 ). Although the RTP header is used here as the reference bit train  201   c  for showing streaming communication, the reference bit train  201   c  is not limited to the RTP header as long as it is information by which it can be confirmed that the packet is that of streaming communication. 
     When a result of the determination is No (step B 2 : No), the AP  100  goes to processing of next packet. Further, when the packet is the packet of streaming communication (step B 2 : Yes), the AP  100  confirms whether or not the MAC address of the terminal apparatus  101  included in the packet exists in the address table  203   a.    
     As a result, when the MAC address of a target exists in the address table  203   a  (step B 3 : Yes), a timer process  501  described later is reset (step B 4 ), and the AP  100  goes to processing of a next packet. Further, when the MAC address of a target does not exist in the address table  203   a  (step B 3 : No), the AP  100  stores the MAC address of the terminal apparatus  101  included in the packet to the address table  203   a  (step B 5 ). 
     When the AP  100  stores the MAC address to the address table  203   a , it begins the timer process  501  in relation to the MAC address (step B 6 ). The timer process  501  is carried out for the AP  100  to periodically determine whether or not the streaming communication of the terminal apparatus  101  connected via wireless LAN is continued. 
     In the timer process  501 , the AP  100  monitors the arriving intervals of relating packets by a timer as to the respective MAC addresses of the address table  203   a , and when the timer is time out, the AP  100  determine that the streaming communication by the terminal apparatus  101  is completed. In the timer process  501 , a preset value, for example, 10 seconds is stored to the ROM  201 . 
     Further, the AP  100  monitors whether or not the present number of communicating apparatuses  203   b  reaches the limit threshold value  201   b  in parallel with the timer process  501  (step B 7 ). As a result, when the number of communicating apparatuses  203   b  reaches the limit threshold value  201   b , the load state of the AP  100  transits from the “the low load state” to “the high load state”. 
     Operation of the AP  100  in “the high load state” will be explained with reference to a flowchart of  FIG. 5 . The AP  100  monitors the packet relating to the terminal apparatus  101  (step C 1 ) and determines whether or not the contents of the packet corresponds to “INVITE” of the reference bit train  201   c  (step C 2 ). Then, when the packet corresponds to “INVITE”, “600 Busy Everywhere” or “486 Busy Here” as the disconnection command  201   d  is transmitted to the transmission sources of the packet (step C 3 ). As described above, the AP  100  in “the high load state” carries out a control so as not to make new connection to the terminal apparatus  101  in “the high load state”. 
     Even while the AP  100  is in “the high load state”, it compares the present number of communicating apparatuses  203   b  with threshold value  201   b , and while the number of communicating apparatuses  203   b  exceeds the threshold value  201   b  (step C 4 : Yes), the AP  100  executes the control of “the high load state”. Further, when the number of communicating apparatuses  203   b  is made less than the threshold value  201   b  by the operation of the timer process  501  described below (step C 4 : No), the load state of the AP  100  transits from “the high load state” to “the low load state”. The control of the AP  100  in “the low load state” is the same as that described above with reference to  FIG. 4 . 
     The timer process  501  will be explained with reference to a flowchart of  FIG. 6 . The timer process  501  is carried out periodically regardless of the load state of the AP  100 . The operation cycle of the timer process  501  is set to a value of 1 second and the like and stored to the ROM  201 . 
     The AP  100  reads out the value of a corresponding timer as to the respective MAC addresses registered to the address table  203   a  (step D 1 ) and determines whether or not the timer is time out (step D 2 ). When the timer is time out, that is, when it is determined that the streaming communication of a target terminal apparatus  101  is completed, the MAC address of the terminal apparatus  101  is deleted from the address table  203   a , and the corresponding timer is stopped (step D 3 ). 
     As described above, the MAC address of the terminal apparatus  101  which has completed the streaming communication is deleted from the address table  203   a , and when the number of communicating apparatuses  203   b  is made less than the threshold value  201   b  thereby, the AP  100  transits from “the high load state” to “the low load state”. 
     According to the second embodiment described above, since the timer process  501  described above for automatically recognizing the completion of the streaming communication is carried out to the MAC addresses recorded to the address table  203   a , the number of connections of the AP  100 , which is restricted by the limit threshold value  201   b , can be effectively used. 
     Third Embodiment 
     Operation of a third embodiment will be explained. The third embodiment carries out a control in consideration of dispersion of an amount of communication per unit time and a communication speed of streaming communication. 
     A control of “the low load state” of the AP  100  will be explained with reference to a flowchart shown in  FIG. 7 . Note that since the control procedure of the AP  100  as to “the high load state” and the timer process  501  according to the third embodiment is the same as that described above with reference to  FIGS. 5 and 6 , the explanation of the control procedure is omitted. Further, A procedure at steps E 1  to E 4  shown in  FIG. 7  is the same as the procedure at steps B 1  to B 4  shown in  FIG. 4 , the explanation of the procedure is also omitted. 
     When the AP  100  recognizes that the MAC address included in a target packet is not recorded in the address table  203   a  (step E 3 : No), the standard of wireless LAN is determined based on the communication speed of the packet. The communication speed of the packet is measured using a conventionally known method. 
     Although it is determined here whether or not the standard of wireless LAN is IEEE802.11b (step E 5 ), it may be specified whether or not the standard is any of a plurality of standards. Further, packets may be simply classified by their communication speeds in place of classifying them by the standard of the wireless LAN. Note that, in the above determination, the information of the communication speeds corresponding to the respective standards of wireless LAN is previously stored to the ROM  201 . This is, for example, 11 Mbps to IEEE802.11b, 54 Mbps to IEEE802.11g and IEEE802.11a other than IEEE802.11b. 
     When a target packet does not correspond to IEEE802.11b as a result of the determination (step E 5 : No), the AP  100  goes to step F described later. Further, when the target packet corresponds to IEEE802.11b (step E 5 : Yes), the AP  100  determines whether or not the number of packets per unit time of the terminal apparatus  101  exceeds a predetermined numerical value (step E 6 ). 
     The number of packets per unit time is a value obtained by counting the number of packets transmitted and received by the AP  100  as to one set of the terminal apparatus  101 , for example, every one second. Reference to the value can be realized by, for example, counting the number of packets by different processing and storing the value to the RAM  203 . In the third embodiment, a set value as to the number of packets per unit time is set to “50 packets per second”. 
     When the number of packets exceeds “50 packets per second”, the AP  100  goes to step G described later. Further, when the number of packets does not exceed “50 packets per second”, the AP  100  further determines whether or not the data length per unit time of the terminal apparatus  101  exceeds a predetermined data length (step E 7 ). The data length per unit time is a value obtained by counting the packets transmitted and received by the AP  100  as to one set of the terminal apparatus  101 , for example, every one second and summing the data lengths of the packets. The value is, for example, counted by different processing and stored to the RAM  203  likewise the case of the number of packets described above. 
     In the third embodiment, a set value as to the data length per unit time is set to “64 Kbps” and previously stored to the ROM  201 . This is a setting based on that a value known as a maximum value of a data length in audio communication is set to 64 Kbps. Further, this value has an object of determining that a case in which the value is exceeded is a motion picture communication. 
     In the above determination, when the AP  100  determines that the data length exceeds “64 Kbps”, that is, the streaming communication carried out by a target terminal apparatus  101  is a motion picture communication (step E 7 : Yes), the AP  100  stores the MAC address of the terminal apparatus  101  to the address table  203   a  after a weight value “2” is related to the MAC address (step E 8 ). 
     Further, when the determination is No, that is, it is determined that the streaming communication carried out by the target terminal apparatus  101  is an audio communication (step E 7 : Yes), the AP  100  stores the MAC address to which a weight value “5” is related to the address table  203   a  (step E 9 ). The weight value is not limited to the above ones and is appropriately set according to an object of control and prepared in the ROM  201  and the like. 
     When the AP  100  stores the MAC address to the address table  203   a , it begins the above-mentioned timer process  501  shown in  FIG. 6  (step E 10 ). When the number of communicating apparatuses  203   b  at the time reaches the limit threshold value  201   b  (step E 11 : Yes), the load state of the AP  100  transits from “the low load state” to “the high load state”. 
     At the time, although the number of communicating apparatuses  203   b  to be compared with the threshold value  201   b  is the total of the weight values of the respective MAC addresses, it is processed as described below in arithmetic operation. For example, it is assumed that the threshold value  201   b  is “40” as well as all the streaming communications of the terminal apparatus  101  connected at the time are motion picture communications (step E 7 : Yes). In this case, since the weight value in the motion picture communication is “2” (step E 8 ), a substantial limit threshold value  201   b  in consideration of the weight value is “20” from “40÷2=20”. Accordingly, when the number of communicating apparatuses  203   b  at the time is “20” or more, the AP  100  is made to “the high load state”. 
     With reference to a flowchart of  FIG. 8 , operation at step F will be explained in detail. When the packet to be processed does not correspond to IEEE802.11b ( FIG. 7 : step E 5 : No), the AP  100  determines whether or not the number of packets per unit time relating to the terminal apparatus  101  exceeds “30 packets per second” (step F 1 ). When as a result of determination is No, the AP  100  goes to step H described later. 
     Further, when the number of packets relating to the terminal apparatus  101  exceed “30 packets per second”, the AP  100  further determines whether or not the data length per unit time exceeds “64 Kbps” (step F 2 ). As a result of determination, when the data length per unit time exceeds “64 Kbps”, that is, when the streaming communication of the target terminal apparatus  101  is the motion picture communication, the AP  100  stores the MAC address of the terminal apparatus  101  to the address table  203   a  after a weight value “1” is related to the MAC address (step F 3 ). Further, when the streaming communication is the audio communication which does not exceed “64 Kbps”, the AP  100  stores the MAC address to which a weight value “3” is related to the address table  203   a  (step F 4 ). 
     When the AP  100  stores the MAC address to the address table  203   a , it begins the timer process  501  ( FIG. 7 : step E 10 ). 
     Operation at step G will be explained in detail with reference to a flowchart of  FIG. 9 . When the number of packets of the terminal apparatus  101  exceeds “50 packets per second” ( FIG. 7 : step E 6 : Yes), the AP  100  further determines whether or not the data length per unit time of the terminal apparatus  101  exceeds “64 Kbps” (step G 1 ). 
     As a result of determination, when the communication of the target terminal apparatus  101  is the motion picture communication which exceeds “64 Kbps”, the AP  100  stores the MAC address of the terminal apparatus  101  to the address table  203   a  after a weight value “4” is related to the MAC address (step G 2 ). Further, when the communication is the audio communication which does not exceed “64 Kbps”, the AP  100  stores the MAC address to which a weight value “10” is related to the address table  203   a  (step G 3 ). 
     Operation at step H will be explained in detail with reference to a flowchart of  FIG. 10 . When the determination at step F 1  ( FIG. 8 ) described above is No, the AP  100  further determines whether or not the data length per unit time of the terminal apparatus  101  exceeds “64 Kbps” (step H 1 ). 
     As a result of determination, when the communication of the terminal apparatus  101  is the motion picture communication which exceeds “64 Kbps”, the AP  100  stores the MAC address of the terminal apparatus  101  to the address table  203   a  after a weight value “2” is related to the MAC address (step H 2 ). Further, when the communication is the audio communication which does not exceed “64 Kbps”, the AP  100  stores the MAC address to which a weight value “5” is related to the address table  203   a  (step H 3 ). 
     According to the third embodiment described above, when the MAC address is recorded to the address table  203   a , a weight value is set according to a communication mode of the terminal apparatus  101 . As a result, even if communications having a different amount of data mixedly exist as in audio distribution and image distribution or in lEEE802.11b and lEEE802.11g, determination to the threshold value  201   b  can be properly carried out. 
     Fourth Embodiment 
     Operation of a fourth embodiment will be explained. The fourth embodiment is a control for coping with the terminal apparatus  101  which intends to carry out roaming during streaming communication when the AP  100  is in “the high load state” in which the number of communicating apparatuses  203   b  at the time exceeds the threshold value  201   b.    
     The AP  100  in “the high load state” monitors a packet relating to the terminal apparatus  101  connected to wireless LAN (step J 1 ) and determines whether or not an “INVITE” message is described in the packet (step J 2 ). As a result, when the AP  100  detects the packet with “INVITE”, the AP  100  transmits from “600 Busy Everywhere” or “486 Busy Here” which is the disconnection command  201   d  to the transmission source of the packet (step J 3 ). 
     When a target packet is not the packet with “INVITE” (step J 2 : No), the AP  100  determines whether or not the header of the target packet corresponds to RTP (step J 4 ). As a result, when a result of determination is No, the AP  100  goes to processing of a next packet. Further, when the header of the packet corresponds to RTP, AP  100  determines whether or not the MAC address of the terminal apparatus  101  included in the packet exists in the address table  203   a  (step J 5 ). 
     As a result of determination, when the MAC address of the terminal apparatus  101  exists in the address table  203   a , the AP  100  resets the timer process  501  (step J 3 ) and goes to processing of a next packet. Further, when the result of determination is No, that is, when the packet belongs to the terminal apparatus  101  that intends to carry out roaming to the AP  100  as the packet moves during the streaming communication, the AP  100  transmits a packet of “ICMP Port Unreachable” to notify the transmission source included in the packet and to the MAC address of a destination of communication impossible (step J 7 ). 
     As described above, in the fourth embodiment, the AP  100  in “the high load state” carries out the control for rejecting the communication of the terminal apparatus  101  which intends to carry out roaming. With this control, there can be protected the communications of the other terminal apparatus  101  that are already connected to the AP  100  and carry out streaming communication. 
     Fifth Embodiment 
     Operation of a fifth embodiment will be explained. In the fifth embodiment, a band use ratio or a number of packets per unit time of the AP  100  is used as an index for determining a load state of the AP  100 . Since the band use ratio and the number of packets per unit time of the AP  100  can be easily obtained by an existing technology, the explanation thereof is omitted. 
     Note that the processing described below is carried out in combination with the second to fourth embodiments described above. That is, in the second to fourth embodiments that use the number of communicating apparatuses  203   b  as a determination standard of the load state, processing using other determination standard is carried out in parallel. 
     A method of using the band use ratio of the AP  100  will be explained with reference to a flowchart of  FIG. 12 . The AP  100  discriminates the load state by timer process  601  shown in  FIG. 12 . A timer actuation time in the timer process  601  and a set value as to the band use ratio are previously set to the ROM  201 . 
     When a timer of the timer process  601  is actuated (step K 1 ) and time out (step K 2 : Yes), the AP  100  determines whether or not the band use ratio exceeds the set value at the time. It is assumed here that “50%” is set as the set value of the band use ratio. 
     As a result of determination, when the band use ratio of the AP  100  at the time is less than “50%”, it is assumed that the load state is “the low load state” (step K 3 : No), whereas when the band use ratio is “50%” or more, it is assume that the load state is “the high load state” (step K 3 : Yes). 
     Next, a method of using the number of packets per unit time of the AP  100  will be explained in detail with reference to a flowchart of  FIG. 13 . The AP  100  discriminates the load state by a timer process  701  shown in  FIG. 13 . A timer actuation time in the timer process  701  and a set value as to the number of packets are previously set to the ROM  201 . 
     The AP  100  actuates a timer of the timer process  601  (step L 1 ), and when the timer is time out (step L 2 : Yes), the AP  100  determines whether or not a terminal corresponding to IEEE802.11b is included in the terminal apparatus  101  connected to wireless LAN (step L 3 ). In the determination, the AP  100  refers to the information of the communication standard recorded in the address table  203   a.    
     A reason why determination as to the communication standard is carried out resides in that, in general, the communication speed of IEEE802.11b is different from those of IEEE802.11g and the like. Accordingly, a different determination standard is employed as to the number of packets per unit time in a case in which IEEE802.11b is included in a present communication and in a case in which IEEE802.11b is not included therein. 
     When the terminal corresponding to IEEE802.11b is included in the currently connected terminal apparatus  101 , the AP  100  determines whether or not a present number of packets per unit time is “2000 pieces per second” or more. As a result of determination, when the present number of packets per unit time is less than “2000 pieces per second” (step L 4 : No), the AP  100  determines that the load state is “the low load state”, whereas when the present number of packets per unit time is “2000 pieces per second” or more (step L 4 : Yes), the AP  100  determines that the load state is “the high load state”. 
     In contrast, when the terminal corresponding to IEEE802.11b is not included in the currently connected terminal apparatus  101  (step L 3 : No), the AP  100  determines whether or not the present number of packets per unit time is “5000 pieces per second” or more. When a result is No (step L 5 : No), the AP  100  determines that the load state is “the low load state”, whereas when the present number of packets per unit time is “5000 pieces per second” or more (step L 5 : Yes), the AP  100  determines that the load state is “the high load state”. 
     The AP  100  can multilaterally determine whether or not the load state is “the high load state” in which a new communication must be disconnected by carrying out the processing of the fifth embodiment described above in parallel with the processings of the embodiments described above. 
     Sixth Embodiment 
     Operation of a sixth embodiment will be explained. The sixth embodiment controls communication based on a strength of magnetic field of the terminal device  101  connected to the AP  100 . The control may be carried out by being combined with the respective embodiments described above. 
     Operation of the sixth embodiment will be explained with reference to a flowchart shown in  FIG. 14 . The AP  100  monitors the packet of the terminal apparatus  101  connected to wireless LAN (step N 1 ) and determines whether or not “INVITE” is described to the packet (step N 2 ). 
     As a result, when the AP  100  detects “INVITE” from the packet, it confirms the strength of the magnetic field of the terminal apparatus  101 . The magnetic field is confirmed making use of a conventionally known technology. As a result, when the strength of magnetic field of the terminal apparatus  101  is “−70 dBm” or less previously set to the ROM  201  (step N 3 : Yes), “600 Busy Everywhere” or “486 Busy Here” that is the disconnection command is transmitted to the transfer source of the packet (step N 4 ). 
     As described above, when the magnetic field of the terminal apparatus  101  to be connected to wireless LAN is greatly small, the AP  100  of the six embodiment carries out a control so as not to connect the terminal apparatus  101  determining that it is difficult for the terminal apparatus  101  to carry out streaming communication. With this operation, reduction of performance of the AP  100  can be prevented. 
     Although the exemplary embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and alternatives can be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Further, it is the inventor&#39;s intent to retrain all equivalents of the claimed invention even if the claims are amended during prosecution.