JP2007243693A - Radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system 10 capable of reducing missing of communication data when a wireless LAN terminal 14 performs handover to an access point 20 belonging to a different segment. <P>SOLUTION: The communication system 10 accumulates communication data addressed to the wireless LAN terminal 14 until a new IP address is assigned to the wireless LAN terminal 14 and communication can be re-started when the access point 20 receives an assignment request from the wireless LAN terminal 14 and a call of the wireless LAN terminal 14 is maintained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication system including a relay station that relays wireless communication by a wireless communication terminal.

  In a wireless communication system composed of a plurality of segments, when a wireless communication terminal performs a handover across segments, the IP address used in the segment before the handover is sent to the wireless communication terminal in the handover destination segment. A different IP address is assigned. When such a handover across segments is executed during communication, communication data is lost along with the change of the IP address of the wireless communication terminal, and communication is disconnected in some cases.

  In order to prevent this, in Patent Document 1, when a wireless communication terminal executes handover, communication data addressed to itself is stored until handover is completed and communication can be resumed. A technique for instructing a relay station in a network via a radio base station in a segment is disclosed. Thereby, even when a handover across segments is executed during communication, it is possible to prevent communication data from being lost.

JP 2004-153542 A

  The technique of Patent Document 1 assumes that the radio wave environment is such that sufficient communication can be performed in the segment before the handover, and the radio base station in the segment before the handover generates a sufficiently strong radio wave. No consideration is given to the handover after the reception becomes impossible. Therefore, when a wireless communication terminal decides to perform handover to a different segment due to momentary interruption of radio waves or moving out of the coverage area of the wireless base station, it retains communication data addressed to itself at the handover destination. In some cases, the radio base station cannot be instructed, and communication data is often lost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the loss of communication data when a wireless communication terminal performs handover to a relay station belonging to a different segment during communication. is there.

  In order to solve the above-described problem, the wireless communication system according to the present invention is configured such that when a relay station receives an attribution request from a wireless communication terminal, the call of the wireless communication terminal is maintained. The communication data addressed to the wireless communication terminal is stored in the system until a new IP address is assigned to the terminal and communication can be resumed.

  For example, the present invention is connected to a communication network and connected to the communication network with a plurality of relay stations that relay communication data transmitted and received by the wireless communication terminal using the wireless communication via the communication network. A communication management server that manages communication performed by the wireless communication terminal via the relay station, and when the relay station receives the attribution request from the wireless communication terminal, the identification information of the wireless communication terminal that has transmitted the attribution request The IP address acquisition process executed via the own relay station is monitored by the belonging start notification transmitting means for transmitting the belonging start notification including the message to the communication management server and the belonging wireless communication terminal. When an IP address is distributed to a wireless communication terminal, an address including the distributed IP address and identification information of the belonging wireless communication terminal is sent. IP address distribution monitoring means for transmitting to the communication management server, the communication management server, the IP address distributed to the wireless communication terminal and the IP address of another communication device that is a communication partner of the wireless communication terminal, A communication state storage means for storing in association with the identification information of the wireless communication terminal; a communication control means for controlling communication by the wireless communication terminal; and a communication controlled by the communication control means for monitoring the communication state storage means. When a call is established between the wireless communication terminal corresponding to the IP address stored in the mobile station and the other communication device, the IP address of the other communication device is associated with the identification information of the wireless communication terminal. When the communication state management unit stored in the communication state storage unit and the storage instruction including the IP address of another communication device are received, the IP address included in the storage instruction When communication data from other communication devices is stored and a transfer instruction including the IP address of the wireless communication terminal is received, the stored communication data is transferred to the wireless communication terminal corresponding to the IP address included in the transfer instruction. When the attribution start notification is received from the data storage means and the relay station, the communication status storage means is referred to and the IP address of the other communication device communicates with the identification information included in the attribution start notification. If stored in the status storage means, the storage instruction including the IP address of the other communication device is transmitted to the data storage means, and the communication control means is instructed to transmit the communication data to the other communication device. Included in the received address notification by referring to the communication status storage means when the attribution start notification receiving means to be transmitted to the communication management server and the address notification from the relay station are received. When the identification information is not stored in the communication status storage means, the IP address included in the address notification is stored in the communication status storage means in association with the identification information included in the address notification, and the received address notification If the identification information included in the communication status storage means is stored in the communication status storage means, the IP address stored in the communication status storage means in association with the identification information is updated with the IP address included in the address notification. At the same time, it is determined whether the IP address of the other communication device is stored in the communication state storage means in association with the identification information, and the communication is performed with the IP address of the other communication device associated with the identification information. When stored in the status storage means, a transfer instruction including the IP address included in the received address notification is transmitted to the data storage means. And an address notification receiving unit that instructs the communication control unit to cause other communication devices to transmit communication data to the wireless communication terminal corresponding to the IP address included in the received address notification. A communication system is provided.

  According to the wireless communication system of the present invention, it is possible to reduce communication data loss when a wireless communication terminal performs handover to a relay station in a different segment during communication.

  Embodiments of the present invention will be described below.

  FIG. 1 is a system configuration diagram showing a configuration of a wireless LAN system 10 according to an embodiment of the present invention. The communication system 10 includes a communication management server 30 and a plurality of access points 20.

  The network 11a and the network 11b are connected via a router 12a and constitute different segments. A DHCP (Dynamic Host Configuration Protocol) server 13a and a DHCP server 13b are connected to the network 11a and the network 11b, respectively.

  The access point 20a is connected to the network 11a and relays communication of the wireless LAN terminal 14 in the cover area 16a. The access point 20b is connected to the network 11b and relays communication of the wireless LAN terminal 14 in the cover area 16b. The wireless LAN terminal 14 communicates with another communication device 15 via the access point 20 by performing communication based on the wireless LAN with the nearest access point 20.

  The communication management server 30 is connected to the network 11 in the communication system 10 (network 11b in the example shown in FIG. 1), and controls communication via the access point 20 by the wireless LAN terminal 14 in the communication system 10. In the present embodiment, the wireless LAN terminal 14 performs VoIP communication with other wireless LAN terminals 14 and communication devices 15 based on SIP. The communication management server 30 has a SIP server function, and controls VoIP communication by the wireless LAN terminal 14 in accordance with a procedure defined in SIP.

  1 shows an example in which the network 11 is realized by wired communication. However, the present invention is not limited to this, and the network 11 may be realized by wireless communication.

  FIG. 2 is a block diagram illustrating an example of a detailed functional configuration of the access point 20. The access point 20 includes a wired communication unit 21, an IP address monitoring unit 22, an attribution processing unit 23, and a wireless communication unit 24.

  The wireless communication unit 24 performs wireless communication with the wireless LAN terminal 14 based on the wireless LAN. The wireless communication unit 24 sends the communication data received from the wireless LAN terminal 14 to the wired communication unit 21 and sends the control data received from the wireless LAN terminal 14 to the attribution processing unit 23. Further, the wireless communication unit 24 sends the communication data received from the wired communication unit 21 to the wireless LAN terminal 14 and sends the control data received from the attribution processing unit 23 to the wireless LAN terminal 14.

  The wired communication unit 21 communicates with the DHCP server 13, the communication management server 30, the communication device 15, another access point 20, or the like via the network 11 based on, for example, Ethernet (registered trademark).

  When the attribution processing unit 23 receives an attribution request including a terminal ID for identifying the wireless LAN terminal 14 from the wireless LAN terminal 14 via the wireless communication unit 24, the attribution processing unit 23 sends an attribution start notification including the terminal ID to the wired LAN. The data is transmitted to the communication management server 30 via the communication unit 21. Then, the attribution processing unit 23 executes attribution processing with the wireless LAN terminal 14 in accordance with the attribution request. In the present embodiment, the terminal ID is a MAC (Media Access Control Address) address of the wireless LAN terminal 14 corresponding to the terminal ID.

  The IP address monitoring unit 22 monitors communication data between the DHCP server 13 and the wireless LAN terminal 14 via the wireless communication unit 24. When a new IP address is assigned to the wireless LAN terminal 14, the new IP address monitoring unit 22 An address notification including the IP address assigned to and the terminal ID of the wireless LAN terminal 14 to which the IP address is assigned is transmitted to the communication management server 30 via the wired communication unit 21.

  When the IP address monitoring unit 22 detects, for example, DHCPACK in communication data via the wireless communication unit 24, the IP address monitoring unit 22 includes the IP address included in the DHCPACK and the terminal ID of the wireless LAN terminal 14 that is the transmission destination of the DHCPACK. The address notification is transmitted to the communication management server 30 via the wired communication unit 21.

  FIG. 3 is a block diagram illustrating an example of a detailed functional configuration of the communication management server 30. The communication management server 30 includes a communication state storage unit 31, a communication state management unit 32, an address notification reception unit 33, an attribution start notification reception unit 34, a call control unit 35, a data storage unit 36, and a wired communication unit 37.

  The wired communication unit 37 communicates with the communication device 15 and the access point 20 via the network 11 based on, for example, Ethernet. The address notification receiving unit 33, the belonging start notification receiving unit 34, the call control unit 35, and the data storage unit 36 transmit and receive data via the wired communication unit 37.

  For example, as illustrated in FIG. 4, the communication status storage unit 31 includes a terminal address 311 that is an IP address of the wireless LAN terminal 14 belonging to the access point 20, and an IP address of a communication partner device of the wireless LAN terminal 14. Is stored in association with the terminal ID 310 of the wireless LAN terminal 14. When the IP address is stored in the communication partner address 312 column, the wireless LAN terminal 14 having the corresponding terminal ID 310 establishes a call with the communication device having the IP address stored in the communication partner address 312 column. Indicates that

  When the attribution start notification receiving unit 34 receives the attribution start notification from the access point 20, the attribution start notification receiving unit 34 refers to the communication state storage unit 31 based on the terminal ID included in the attribution start notification, and the terminal ID is the communication state storage unit. It is determined whether or not it is stored in 31. When the terminal ID included in the attribution start notification is stored in the communication status storage unit 31, the attribution start notification reception unit 34 refers to the communication status storage unit 31 and associates the communication partner address with the terminal ID. It is determined whether the wireless LAN terminal 14 corresponding to the terminal ID has been established with another communication device.

  When the terminal ID included in the attribution start notification is not stored in the communication status storage unit 31 or when the communication partner address is associated with the terminal ID and is not stored in the communication status storage unit 31, the attribution start notification The receiving unit 34 does not perform any process related to the attribution start notification.

  When the terminal ID included in the attribution start notification is stored in the communication state storage unit 31 and the communication partner address is associated with the terminal ID, the attribution start notification receiving unit 34 transmits the communication data. A transmission destination change instruction that is an instruction to change the destination is transmitted to the call control unit 35, and the communication partner stored in the communication state storage unit 31 in association with the terminal ID included in the belonging start notification and the terminal ID A data storage instruction including an address is transmitted to the data storage unit 36.

  Here, the transmission destination change instruction includes a change device address that is an IP address of a device that changes the transmission destination of communication data, and a change destination address that is an IP address of a new transmission destination device of communication data. . The transmission destination change instruction transmitted by the attribution start notification receiving unit 34 includes the communication partner address stored in the communication state storage unit 31 in association with the terminal ID included in the attribution start notification as the changed device address. Thus, the IP address of the communication management server 30 is included as the change destination address.

  When the address notification receiving unit 33 receives an address notification from the access point 20, the address notification receiving unit 33 refers to the communication state storage unit 31 based on the terminal ID included in the address notification, and the IP address corresponding to the terminal ID is registered. If the IP address corresponding to the terminal ID has already been registered, the IP address included in the address notification is registered in the communication state storage unit 31 in association with the terminal ID. The IP address associated with the terminal ID and stored in the communication state storage unit 31 is updated with the IP address included in the address notification.

  Further, the address notification receiving unit 33 refers to the communication state storage unit 31 based on the terminal ID included in the address notification, and when the communication partner address is stored in association with the terminal ID, A stored data transfer instruction including the communication partner address and the terminal ID included in the address notification is transmitted to the data storage unit 36. Then, the address notification receiving unit 33 transmits a transmission destination change instruction to the call control unit 35.

  The transmission destination change instruction transmitted by the address notification receiving unit 33 includes the communication partner address stored in the communication state storage unit 31 in association with the terminal ID included in the address notification as the changed device address. The IP address included in the address notification is included as the change destination address.

  When the data storage unit 36 receives a data storage instruction from the attribution start notification receiving unit 34, the data storage unit 36 receives communication data received from a device corresponding to the IP address included in the data storage instruction, as a terminal included in the data storage instruction It accumulates in association with the ID and IP address. For example, as illustrated in FIG. 5, the data storage unit 36 uses a communication partner address 361 included in the data storage instruction and communication data 362 received from a device corresponding to the communication partner address 361 as a terminal ID 360 included in the data storage instruction. Are stored in association with each other.

  Further, when the data storage unit 36 receives a stored data transfer instruction from the address notification receiving unit 33, the data storage unit 36 stores the communication stored in the data storage unit 36 in association with the terminal ID included in the stored data transfer instruction. Data is transmitted to the wireless LAN terminal 14 corresponding to the IP address included in the stored data transfer instruction.

  The call control unit 35 controls the VoIP communication of the wireless LAN terminal 14 in accordance with a procedure defined in SIP, and performs a process of establishing or disconnecting a VoIP communication call by the wireless LAN terminal 14. Further, when the call control unit 35 receives the transmission destination change instruction from the address notification reception unit 33 or the belonging start notification reception unit 34, the call control unit 35 sets the transmission destination of the communication data to the change destination address included in the transmission destination change instruction. Instruct the device corresponding to the changed device address included in the transmission destination change instruction to change to the corresponding device.

  Based on the received destination change instruction, the call control unit 35 uses, for example, a reINVITE request described in RFC 3725, and sets a line beginning with “c =” in SDP (Session Description Protocol) as the change destination address. The reINVITE request is transmitted to the device corresponding to the changed device address, thereby instructing the change of the transmission destination of the communication data.

  The communication state management unit 32 monitors call control performed by the call control unit 35 and, when a call is established, acquires the IP addresses of the two devices with which the call is established from the call control unit 35. Then, the communication state management unit 32 searches the terminal address 311 of the communication state storage unit 31 for an IP address that matches one of the two IP addresses acquired from the call control unit 35. When an IP address that matches the one IP address is detected from the terminal address 311, the communication state management unit 32 uses the other IP address as the communication partner address 312 of the wireless LAN terminal 14 corresponding to the detected IP address. Register the IP address.

  Then, the communication state management unit 32 searches the terminal address 311 for an IP address that matches the other IP address out of the two IP addresses acquired from the call control unit 35. When an IP address that matches the other IP address is detected from within the terminal address 311, the communication state management unit 32 sets the IP address of the communication partner device of the wireless LAN terminal 14 corresponding to the detected IP address. The one IP address is registered in the communication partner address 312.

  In addition, the communication state management unit 32 monitors call control performed by the call control unit 35, and acquires the IP addresses of the two devices from which the call is disconnected from the call control unit 35 when the call is disconnected. . Then, the communication state management unit 32 searches the communication partner address 312 of the communication state storage unit 31 for an IP address that matches one of the two IP addresses acquired from the call control unit 35. When an IP address that matches the one IP address is detected from within the communication partner address 312, the communication state management unit 32 deletes the detected IP address from the communication partner address 312.

  Then, the communication state management unit 32 searches the communication partner address 312 for an IP address that matches the other IP address of the two IP addresses acquired from the call control unit 35. When an IP address that matches the other IP address is detected from the communication partner address 312, the communication state management unit 32 deletes the detected IP address from the communication partner address 312.

  As a result, the communication status management unit 32 registers not only the call establishment status between the wireless LAN terminal 14 and the other communication device 15 but also the call establishment status between the wireless LAN terminals 14 in the communication status storage unit 31. can do.

  FIG. 6 is a flowchart showing an example of the operation of the access point 20 according to the present invention. For example, at a predetermined timing such as when the power is turned on, the access point 20 starts the operation shown in this flowchart.

  First, the attribution processing unit 23 determines whether an attribution request including a terminal ID is received from the wireless LAN terminal 14 (S100). When the attribution request is received (S100: Yes), the attribution processing unit 23 transmits an attribution start notification including the terminal ID to the communication management server 30 (S101). Then, the attribution processing unit 23 performs attribution processing (S102) and executes the processing shown in Step 100 again.

  In step 102, when attribution is not permitted during the attribution process, the attribution processing unit 23 transmits an attribution rejection response to the wireless LAN terminal 14 and cancels attribution start including the terminal ID of the wireless LAN terminal 14. By notifying the communication management server 30, the processing performed by the communication management server 30 may be canceled in response to the transmitted attribution start notification.

  When the attribution request has not been received (S100: No), the IP address monitoring unit 22 determines whether or not DHCPACK has been transmitted to the belonging wireless LAN terminal 14 to thereby determine whether the belonging wireless LAN terminal 14 has been assigned. It is determined whether or not a new IP address has been assigned (S103). If a new IP address has not been assigned to the wireless LAN terminal 14 that belongs (S103: No), the attribution processing unit 23 executes the process shown in step 100 again.

  When a new IP address is assigned to the belonging wireless LAN terminal 14 (S103: Yes), the IP address monitoring unit 22 sends an address notification including the terminal ID and the IP address included in DHCPACK to the communication management server 30. Then, the attribution processing unit 23 executes the process shown in step 100 again.

  FIG. 7 is a flowchart illustrating an example of the operation of the communication management server 30. For example, at a predetermined timing such as when the power is turned on, the communication management server 30 starts the operation shown in this flowchart.

  First, the attribution start notification receiving unit 34 determines whether an attribution start notification is received from the access point 20 (S200). When the attribution start notification is received (S200: Yes), the attribution start notification receiving unit 34 refers to the communication state storage unit 31 based on the terminal ID included in the attribution start notification, and the terminal ID is the communication state storage unit. It is determined whether it is stored in 31 (S201). When the terminal ID included in the attribution start notification is not stored in the communication state storage unit 31 (S201: No), the attribution start notification receiving unit 34 executes the process shown in step 200 again.

  When the terminal ID included in the attribution start notification is stored in the communication status storage unit 31 (S201: Yes), the attribution start notification reception unit 34 refers to the communication status storage unit 31 and communicates with the terminal ID. It is determined whether or not the partner address is associated, that is, whether or not the call of the wireless LAN terminal 14 corresponding to the terminal ID has been established (S202). When the call of the wireless LAN terminal 14 corresponding to the terminal ID is not established (S202: No), the belonging start notification receiving unit 34 executes the process shown in Step 200 again.

  When the call of the wireless LAN terminal 14 corresponding to the terminal ID is established (S202: Yes), the belonging start notification receiving unit 34 is associated with the terminal ID included in the belonging start notification, and the communication state storing unit 31. Is transmitted to the call control unit 35 with the communication partner address stored in the communication device address as the change device address and the IP address of the communication management server 30 as the change destination address (S203), and the terminal included in the attribution start notification A data storage instruction including the communication partner address stored in the communication state storage unit 31 in association with the ID and the terminal ID is transmitted to the data storage unit 36.

  Next, in response to the data accumulation instruction received from the attribution start notification receiving unit 34, the data accumulation unit 36 uses the communication data received from the device corresponding to the IP address included in the data accumulation instruction as the data accumulation instruction. The process of storing in association with the included terminal ID and IP address is started (S204), and the belonging start notification receiving unit 34 executes the process shown in step 200 again.

  In step 204, the data storage unit 36 deletes the communication data if it does not receive the stored data transfer instruction corresponding to the communication data even after a predetermined time has elapsed since the start of the storage of the communication data. You may make it do. As a result, the data storage unit 36 deletes the communication data of the wireless LAN terminal 14 that has transmitted the attribution request to the access point 20 but is unable to continue communication because the attribution is rejected by the access point 20. can do.

  If no attribution start notification has been received in step 200 (S200: No), the address notification reception unit 33 determines whether an address notification has been received (S205). When the address notification is received (S205: Yes), the address notification receiving unit 33 refers to the communication state storage unit 31 based on the terminal ID included in the address notification, and the IP address corresponding to the terminal ID is in the communication state. It is determined whether it is registered in the storage unit 31 (S206). When the IP address corresponding to the terminal ID is not registered in the communication state storage unit 31 (S206: No), the address notification receiving unit 33 communicates the IP address included in the address notification in association with the terminal ID. Registration in the state storage unit 31 (S211), the attribution start notification reception unit 34 executes the process shown in step 200 again.

  On the other hand, when the IP address corresponding to the terminal ID is registered in the communication state storage unit 31 (S206: Yes), the address notification reception unit 33 stores the IP address corresponding to the terminal ID in the communication state storage unit 31. The updated IP address is updated with the IP address included in the address notification (S207). Then, the address notification receiving unit 33 refers to the communication state storage unit 31 to determine whether or not the communication partner address is associated with the terminal ID, that is, the call of the wireless LAN terminal 14 corresponding to the terminal ID. It is determined whether it has been established (S208). When the call of the wireless LAN terminal 14 corresponding to the terminal ID is not established (S208: No), the belonging start notification receiving unit 34 executes the process shown in Step 200 again.

  When the call of the wireless LAN terminal 14 corresponding to the terminal ID is established (S208: Yes), the address notification receiving unit 33 includes the terminal ID included in the address notification and the wireless LAN terminal 14 corresponding to the terminal ID. Is transmitted to the data storage unit 36. In response to the received stored data transfer instruction, the data storage unit 36 corresponds to the communication data stored in association with the terminal ID included in the stored data transfer instruction in correspondence with the IP address included in the stored data transfer instruction. To the wireless LAN terminal 14 (S210), the belonging start notification receiving unit 34 executes the process shown in step 200 again.

  If the address notification is not received in step 205 (S205: No), the communication state management unit 32 determines whether or not a new call is established by the call control unit 35 (S212). When a new call is established (S212: Yes), the communication state management unit 32 registers the communication partner address in the communication state storage unit 31 (S213), and the attribution start notification reception unit 34 again shows in step 200. Execute the process.

  When a new call has not been established (S212: No), the communication state management unit 32 determines whether or not the call established by the call control unit 35 has been disconnected (S214). When the call is disconnected (S214: Yes), the communication state management unit 32 deletes the corresponding communication partner address from the communication state storage unit 31 (S215), and the attribution start notification reception unit 34 again shows in step 200. Execute the process.

  FIG. 8 is a sequence diagram illustrating an example of the operation of the communication system 10. In this sequence diagram, it is assumed that the wireless LAN terminal 14 is handed over between the access point 20a and the access point 20b arranged as shown in FIG. In this sequence diagram, it is assumed that the terminal ID and IP address of the wireless LAN terminal 14 are not registered in the communication state storage unit 31 as an initial state.

  First, the wireless LAN terminal 14 transmits an attribution request to the nearest access point 20a (S300). The access point 20a transmits an attribution start notification to the communication management server 30 (S301). In step 301, since the terminal ID and IP address of the wireless LAN terminal 14 are not registered in the communication state storage unit 31, the communication management server 30 does not perform any processing corresponding to step 301.

  Next, the wireless LAN terminal 14 and the access point 20a perform attribution processing (S302). Then, after belonging to the access point 20a, the wireless LAN terminal 14 requests the DHCP server 13 to distribute an IP address via the access point 20a (S303). In step 303, the wireless LAN terminal 14 broadcasts a DHCPDISCOVER message into the network 11 via the access point 20a, for example.

  Then, the wireless LAN terminal 14 receives the IP address distribution from the DHCP server 13 via the access point 20a (S304). In step 304, the DHCP server 13 transmits, for example, a DHCPACK including an IP address to be assigned to the wireless LAN terminal 14 to the wireless LAN terminal 14 via the access point 20a, so that the assigned IP address is transmitted to the wireless LAN terminal 14. Notice.

  Next, the access point 20a detects DHCPACK sent to the wireless LAN terminal 14, and transmits an address notification including the terminal ID and IP address included in the DHCPACK to the communication management server 30 (S305). The communication management server 30 registers the IP address included in the received address notification in the communication state storage unit 31 in association with the terminal ID included in the address notification (S306).

  Next, the communication management server 30 establishes a call between the wireless LAN terminal 14 and the communication device 15 of the communication partner of the wireless LAN terminal 14 according to the procedure specified in SIP (S307). The IP address is registered in the communication state storage unit 31 as a communication partner address corresponding to the wireless LAN terminal 14 (S308). The wireless LAN terminal 14 starts communication with the communication device 15 (S309).

  Next, the wireless LAN terminal 14 executes handover to the access point 20b by moving from the cover area 16a of the access point 20a to the cover area 16b of the access point 20b (S310). In step 310, the wireless LAN terminal 14 moves from within the cover area 16a of the access point 20a to outside the cover area 16a of the access point 20a and the cover area 16b of the access point 20b, and then to the cover area 16b of the access point 20b. Move and perform handover belonging to the access point 20b.

  The wireless LAN terminal 14 transmits an attribution request to the nearest access point 20b (S311). The access point 20b transmits an attribution start notification to the communication management server 30 (S312). Then, the wireless LAN terminal 14 and the access point 20b perform attribution processing (S313).

  The communication management server 30 receives the attribution start notification in step 312, the terminal ID and IP address of the wireless LAN terminal 14 are registered in the communication state storage unit 31, and the communication partner address corresponding to the wireless LAN terminal 14 Is registered in the communication state storage unit 31, it is detected that a call is established between the wireless LAN terminal 14 and the communication device 15.

  Then, the communication management server 30 transmits a transmission destination change instruction for changing the transmission destination of communication data from the wireless LAN terminal 14 to the communication management server 30 (S314). In response to the transmission destination change instruction, the communication device 15 changes the transmission destination of communication data from the wireless LAN terminal 14 to the communication management server 30 (S315). The communication management server 30 accumulates the communication data received from the communication device 15 (S316).

  Next, the wireless LAN terminal 14 requests the DHCP server 13 to distribute the IP address via the access point 20b (S317), and receives the IP address distribution from the DHCP server 13 (S318). The access point 20b detects DHCPACK sent to the wireless LAN terminal 14, and transmits an address notification including the terminal ID and IP address included in the DHCPACK to the communication management server 30 (S319).

  Next, the communication management server 30 updates the IP address stored in the communication state storage unit 31 in association with the terminal ID included in the address notification with the IP address included in the received address notification (S320). ). Then, the communication management server 30 transmits the communication data stored in association with the terminal ID included in the address notification to the wireless LAN terminal 14 (S321). Then, the communication management server 30 transmits a transmission destination change instruction for changing the transmission destination of communication data from the communication management server 30 to the wireless LAN terminal 14 to the communication device 15 (S322). Then, the wireless LAN terminal 14 and the communication device 15 resume communication (S323).

  As described above, the wireless LAN terminal 14 reliably transmits the communication data transmitted from the communication device 15 until the IP address is assigned and the communication can be resumed after the belonging process is started. Can be received. As a result, it is possible to reduce the instantaneous interruption of voice generated by the handover, and it is possible to continue communication more appropriately.

  Next, the communication management server 30 performs communication termination processing between the wireless LAN terminal 14 and the communication device 15 in response to a request from the wireless LAN terminal 14 or the communication device 15 (S324). The IP address of the partner device is deleted from the communication state storage unit 31 (S325).

  The embodiment of the present invention has been described above.

  As is clear from the above description, according to the communication system 10 of the present embodiment, it is possible to reduce the loss of communication data when the wireless communication terminal performs handover to the access point 20 of a different segment during communication. .

  In addition, this invention is not limited to said embodiment, Many deformation | transformation are possible within the range of the summary.

  For example, in the above-described embodiment, VoIP communication that is real-time communication has been described as an example. However, the present invention is not limited to this, and the present invention can be similarly applied to communication that does not have real-time characteristics. Thereby, the communication system 10 can suppress the loss of communication data due to handover, and can reduce the number of retransmission requests generated due to the loss of communication data. Accordingly, the communication system 10 can suppress an increase in network traffic.

  In the above embodiment, the access point 20 and the router 12 are described as separate devices. However, the present invention is not limited to this, and the access point 20 may have the function of the DHCP server 13. In this case, one access point 20 among the plurality of access points 20 provided in one network segment validates the DHCP function.

  In the above embodiment, the access point 20 detects a new IP address distributed to the wireless LAN terminal 14 to which it belongs, and transmits it to the communication management server 30 as an address notification. However, the present invention is not limited to this. I can't. For example, the DHCP server 13 stores a list of terminal IDs of the wireless LAN terminal 14 in advance, and when a new IP address is assigned to the wireless LAN terminal 14, the DHCP server 13 generates an address notification to generate a communication management server. You may make it transmit to 30. This eliminates the need for the access point 20 to monitor data in a layer above the session layer, and the access point 20 can be configured at a lower cost.

  In the above-described embodiment, SIP has been described as an example of the call control protocol. However, the present invention is not limited to this, and may be realized using another call control protocol.

1 is a system configuration diagram illustrating a configuration of a communication system 10 according to an embodiment of the present invention. 2 is a block diagram illustrating an example of a detailed functional configuration of an access point 20. FIG. 3 is a block diagram illustrating an example of a detailed functional configuration of a communication management server 30. FIG. It is explanatory drawing which shows an example of the data structure stored in the communication status storage part. 4 is an explanatory diagram illustrating an example of a data structure stored in a data storage unit 36. FIG. 4 is a flowchart showing an example of the operation of the access point 20. 5 is a flowchart showing an example of the operation of the communication management server 30. 3 is a sequence diagram illustrating an example of an operation of the communication system 10. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Communication system, 11 ... Network, 12 ... Router, 13 ... DHCP server, 14 ... Wireless LAN terminal, 15 ... Communication equipment, 16 ... Cover area, 20. ..Access point, 21 ... Wired communication unit, 22 ... IP address monitoring unit, 23 ... Attribution processing unit, 24 ... Wireless communication unit, 30 ... Communication management server, 31 ... Communication state storage unit, 310 ... terminal ID, 311 ... terminal address, 312 ... communication partner address, 32 ... communication state management unit, 33 ... address notification reception unit, 34 ... attribution Start notification receiving unit, 35 ... call control unit, 36 ... data storage unit, 360 ... terminal ID, 361 ... communication partner address, 362 ... communication data, 37 ... wired communication unit

Claims (4)

A plurality of relay stations connected to a communication network and relaying communication data transmitted and received by a wireless communication terminal using wireless communication via the communication network;
A communication management server that is connected to the communication network and manages communication performed by the wireless communication terminal via each relay station;
The relay station is
When an attribution request is received from the wireless communication terminal, attribution start notification transmission means for transmitting an attribution start notification including identification information of the wireless communication terminal that has transmitted the attribution request to the communication management server;
When the belonging wireless communication terminal monitors the IP address acquisition process executed through its own relay station and the IP address is distributed to the belonging wireless communication terminal, the distributed IP address and the IP address distribution monitoring means for transmitting an address notification including identification information of the belonging wireless communication terminal to the communication management server,
The communication management server
Communication state storage means for storing an IP address distributed to the wireless communication terminal and an IP address of another communication device that is a communication partner of the wireless communication terminal in association with identification information of the wireless communication terminal;
Communication control means for controlling communication by the wireless communication terminal;
When the communication controlled by the communication control unit is monitored and a call is established between the wireless communication terminal corresponding to the IP address stored in the communication state storage unit and the other communication device, A communication state management means for storing the IP address of the other communication device in the communication state storage means in association with the identification information of the wireless communication terminal;
When a storage instruction including the IP address of the other communication device is received, communication data from another communication device corresponding to the IP address included in the storage instruction is stored, and the IP address of the wireless communication terminal is included. Data storage means for transferring the stored communication data to a wireless communication terminal corresponding to the IP address included in the transfer instruction when receiving the transfer instruction;
When the belonging start notification is received from the relay station, the communication state storage means is referred to, and the IP address of the other communication device is associated with the identification information included in the belonging start notification. When stored in the storage means, the storage instruction including the IP address of the other communication device is transmitted to the data storage means, and the communication control means is instructed to communicate with the other communication device. Attribution start notification receiving means for transmitting data to the communication management server;
When receiving the address notification from the relay station, refer to the communication state storage means,
If the identification information included in the received address notification is not stored in the communication state storage means, the IP state included in the address notification is associated with the identification information included in the address notification and the communication state storage is performed. Stored in the means,
When the identification information included in the received address notification is stored in the communication state storage unit, the IP address stored in the communication state storage unit in association with the identification information is included in the address notification. And whether or not the IP address of the other communication device is stored in the communication state storage means in association with the identification information,
When the IP address of the other communication device is stored in the communication state storage unit in association with the identification information, a transfer instruction including the IP address included in the received address notification is sent to the data storage unit. And an address notification receiving unit that instructs the communication control unit to transmit the communication data to the wireless communication terminal corresponding to the IP address included in the received address notification. A wireless communication system. The wireless communication system according to claim 1,
The wireless communication system, wherein the identification information of the wireless communication terminal is a MAC (Media Access Control) address. The wireless communication system according to claim 1 or 2,
The wireless communication terminal performs VoIP (Voice over Internet Protocol) communication with the other communication device based on SIP (Session Initiation Protocol),
The wireless communication system, wherein the communication control unit controls VoIP communication between the wireless communication terminal and the other communication device based on SIP. The wireless communication system according to any one of claims 1 to 3,
A wireless communication system, wherein the wireless communication terminal and the relay station transmit and receive communication data by wireless communication based on a wireless LAN standard.

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