JP4777216B2 - Handover control device, base station, edge router, relay router, wireless terminal, mobile communication system, and handover control method - Google Patents

Description

  The present invention relates to a handover control device, a base station, an edge router, a relay router, a wireless terminal, a mobile communication system, and a handover control method.

  Conventionally, a method proposed in IETF (Internet Engineering Task Force) (see, for example, Govind Krishnamurthi Robert C. Chalmers Charles E. Perkins, “Buffer management for smooth handovers in mobileipv6.”, INTERNET DRAFT, July 2001 (Non-patent Document 1) In ()), handover control for buffering packet data is performed.

  In this handover control, in order to realize a handover control in which no packet data loss occurs, the packet data is buffered in the edge router provided in the base station before the movement during the handover of the wireless terminal. Then, the buffered packet data is forwarded to the destination edge router after the handover is completed.

  The configuration of a mobile communication system in which such handover control is performed is shown in FIG. 6 and will be described.

  The mobile communication system shown in FIG. 6 includes a wireless terminal 10 that is mobile communication means such as a mobile phone, a plurality of base stations 12, 14, and 16 that perform wireless communication with the wireless terminal 10, and these base stations 12 ˜16 and edge routers 18, 20, and 22 provided in COR, and COR (Cross Over Router) 24, 26, and 28 connected to these edge routers 18˜22. Here, the CORs 24 to 28 have a hierarchical structure with the COR 28 as a vertex, the COR 24 is under the edge routers 18 and 20, the COR 26 is under the edge router 22, and the COR 28 is an edge via the CORs 24 and 26. The routers 18 to 22 are under its control.

  With such a configuration, in the handover control when the wireless terminal 10 moves from the connection area to the edge router 20 to the connection area to the edge router 22, the buffering place is the edge router 20 before the movement. In this handover control, all packet data sent from a communication node (not shown) that is a transmission source during the handover of the wireless terminal 10 are temporarily transferred via the CORs 28 and 24 as indicated by the arrow Y1. It was transferred to the edge router 20 and buffered here.

After that, when the wireless terminal 10 completes the handover to be connected to the edge router 22, it instructs the edge router 20 before moving to forward the buffered packet data, and as indicated by the arrow Y2 The packet data is forwarded from the edge router 20 to the wireless terminal 10 connected to the moved edge router 22 via the plurality of CORs 24, 28 and 26. In this way, by performing buffering in the edge router 20 before movement, handover without loss has been realized.
Govind Krishnamurthi Robert C. ChalmersCharles E. Perkins, "Buffer management for smooth handovers in mobileipv6.", INTERNET DRAFT, July 2001

  However, in the conventional handover control method, since the packet data is buffered in the edge router 20 to which the wireless terminal 10 was connected before moving during the handover, the buffering is performed after the wireless terminal 10 is handed over. Until the transfer of the ringed data is completed, as indicated by an arrow Y2, the wireless terminal 10 connected from the edge router 20 before movement to the edge router 22 after movement through the plurality of CORs 24, 28, 26. Until the packet data is forwarded. In other words, there is a problem that network resources are wasted because packet data is transferred through a redundant route during handover control.

  Further, in this handover control, as shown in FIG. 6, the buffer Y2 has a path Y2 for transferring the buffered packet data from the edge router 20 to the edge router 22, and a code for transferring the packet data from the communication node to the edge router 22. Since there are two Y3 paths at the same time, there is a problem in that the packet data passing through both paths arrives in a mixed manner, resulting in a packet order difference at the time of handover.

  The present invention has been made in view of the above points, and by realizing packet data transfer to a wireless terminal after movement in handover control through an optimum path, the network resource is effectively used and the order of packets at the time of handover is different. It is an object of the present invention to provide a handover control device, a base station, an edge router, a relay router, a wireless terminal, a mobile communication system, and a handover control method that can prevent the occurrence of the above.

  In order to solve the above-described problem, a handover control apparatus according to the present invention is a handover control apparatus that controls a handover in which a wireless terminal straddles between edge routers provided for each base station that performs wireless communication with the wireless terminal. During the handover, the data from the communication partner is held in the relay router to which the edge router to which the wireless terminal was connected before moving and all edge routers that are candidates for the moving destination are connected under control. It is characterized by comprising control means for performing control.

  According to this configuration, since the data from the communication partner is held in the relay router, it is possible to remove redundant paths when transferring packet data. This makes it possible to effectively use network resources. it can. In the prior art, since data was held in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Data was transferred until the network resources were wasted. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  In the handover control apparatus of the present invention, the relay router that holds the data from the communication partner has the minimum number of hops from the wireless terminal among the plurality of relay routers connected in a hierarchical structure. It is preferable that a relay router is applied.

  According to this configuration, since a redundant path does not occur in the path for transferring the stored packet data after the handover, the network resources can be used more effectively.

  In the handover control apparatus of the present invention, the control means attaches an identifier for identifying a packet together with the destination address of the wireless terminal to the data held by the relay router, and transfers the data held to the address It is preferable to be characterized by this.

  According to this configuration, the retained data can be properly transferred to the wireless terminal after movement by handover.

  In order to solve the above-described problem, a base station of the present invention includes a holding unit that holds position information of an adjacent base station and a relay router to which the adjacent base station is connected in a base station that detects a handover of a wireless terminal. Determining means for determining a relay router to which the base station to which the wireless terminal is connected before moving and all the base stations that are candidates for the moving destination are connected under the position information held above; And an instruction means for instructing the determined relay router to retain data from a communication partner.

  According to this configuration, since an instruction to hold data from a communication partner is given to an appropriate relay router, data to be transmitted to a wireless terminal during handover is held so that no data reception loss occurs. Can do.

  Further, in the base station of the present invention, when the determining means determines the relay router, all candidate base stations that may move among the relay routers that are connected in a hierarchical structure. It is preferable that a relay router that minimizes the number of hops from the wireless terminal among the relay routers under the control of is determined.

  According to this configuration, it is possible to instruct the relay router that does not generate a redundant route in the path for transferring the held packet data after the handover to hold the data from the communication partner.

  Further, in the base station of the present invention, the instruction means instructs the relay router determined by the determination means to transfer the retained data to the moved wireless terminal after the wireless terminal moves by handover. It can also be characterized by doing.

  According to this configuration, after the handover, it is possible to instruct the relay router that does not generate a redundant route in the path for transferring the held packet data to transfer the data from the held communication partner.

  In order to solve the above-described problems, an edge router according to the present invention is provided in a base station that detects a handover of a wireless terminal, and in an edge router to which the wireless terminal is connected by wireless communication, Based on the holding means for holding the position information of the relay router to which the edge router is connected, and the position information held above, all the edge routers to which the wireless terminal was connected before moving and candidates for the moving destination It is characterized by comprising determining means for determining a relay router to be connected to the edge router, and instruction means for instructing the determined relay router to hold data from a communication partner.

  According to this configuration, since the data from the communication partner is held in the relay router, it is possible to remove redundant paths when transferring packet data. This makes it possible to effectively use network resources. it can. In the prior art, since data was held in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Data was transferred until the network resources were wasted. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  In the edge router of the present invention, when the determining means determines the relay router, the number of hops from the wireless terminal among the relay routers connected in a hierarchical structure is minimized. It is preferable that the relay router is determined.

  According to this configuration, the wireless terminal is a relay router to which the base station to which the wireless terminal was connected before moving and all the base stations that are candidates for the moving destination are connected under the control, and is a hop from the wireless terminal. It is possible to instruct the relay router having the smallest number to hold data from the communication partner.

  In the edge router of the present invention, the instruction means instructs the relay router determined by the determination means to transfer the retained data to the moved wireless terminal after the wireless terminal moves due to handover. It is preferable that it is performed.

  According to this configuration, the base station to which the wireless terminal was connected before moving and all base stations that are candidates for the destination transfer data from the communication partner held in the relay router connected under the control. Can be instructed to do.

  In order to solve the above-described problem, the relay router of the present invention holds data from a communication partner in response to a data holding instruction by any of the base stations or the instruction means of any of the edge routers, and performs handover. Change the packet transfer destination to the destination address of the wireless terminal according to the data transfer instruction of the subsequent wireless terminal, attach an identifier for identifying the packet, and transfer the packet to the current address of the wireless terminal It is characterized by doing.

  According to this configuration, it is possible to retain data transmitted to a wireless terminal during handover of the wireless terminal and appropriately transfer the retained data after the wireless terminal has moved the retained data. Further, according to this configuration, since the identifier is generated by the relay router, the packet data transmitted from the communication partner that is the transmission source is not rewritten, so that the wireless communication terminal after moving without being involved in the security problem Can be sent to the machine.

  Further, in the relay router of the present invention, storage means for storing an address for identifying the wireless terminal at the relay router in the handover, and an instruction to transmit the packet data held in the relay router to the destination wireless terminal When the packet data transferred from the relay router is received and the same address as the address stored in the storage means exists in the received data, the same address is added. It is preferable that the apparatus includes an acquisition unit that acquires the acquired data.

  According to this configuration, since the packet data can be transmitted with the address of the new wireless terminal after the wireless terminal moves in the relay router, the data sent to the wireless terminal before the movement is transmitted. The wireless terminal can be acquired appropriately.

  In order to solve the above problems, the wireless terminal of the present invention performs wireless communication with each base station, and performs a handover control over the edge routers provided for each base station, and controls the handover During the handover, the edge router to which the wireless terminal was connected before moving and all the edge routers that are candidates for the moving destination are relayed to the relay router from the communication partner. Control means for performing control to hold data is provided.

  According to this configuration, since the data from the communication partner is held in the relay router, it is possible to remove redundant paths when transferring packet data. This makes it possible to effectively use network resources. it can. In the prior art, since data was held in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Data was transferred until the network resources were wasted. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  In the wireless terminal of the present invention, the number of hops from the wireless terminal is the smallest among the relay routers connected in a hierarchical structure as the relay router that holds the data from the communication partner. It is preferable that the relay router is selected and applied.

  According to this configuration, since a redundant path does not occur in the path for transferring the stored packet data after the handover, the network resources can be used more effectively.

  In the wireless terminal of the present invention, the control means attaches an identifier identifying the packet together with the destination address of the wireless terminal to the retained data of the relay router, and causes the retained data to be transferred to this address. It is preferable to characterize.

  According to this configuration, the retained data can be properly transferred to the wireless terminal after movement by handover.

  In order to solve the above problems, a mobile communication system according to the present invention is connected to a base station in a hierarchical structure above a base station in a mobile communication system in which a radio terminal straddles between base stations. A relay router that relays and holds data, and a base station to which the wireless terminal was connected before the movement during the handover and all base stations that are candidates for the movement are connected under the control An edge router provided for each base station that instructs the relay router to hold data from the other party of communication and also instructs the relay router to transfer the data held in the corresponding relay router to the wireless terminal after movement. It is characterized by comprising.

  According to this configuration, since the data from the communication partner is held in the relay router, it is possible to remove redundant paths when transferring packet data. This makes it possible to effectively use network resources. it can. In the prior art, since data was held in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Data was transferred until the network resources were wasted. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  In the mobile communication system of the present invention, it is preferable that the relay router attaches an identifier of packet data for identifying a data packet to the wireless terminal.

  According to this configuration, since the identifier is generated by the relay router, the packet data sent from the communication partner that is the transmission source is not rewritten, so that the wireless communication terminal after movement can be transmitted without being involved in security issues. It becomes possible to transmit.

  In the mobile communication system of the present invention, it is preferable that the wireless terminal negotiates a retention capacity of data from a communication partner with the relay router.

  According to this configuration, only the necessary data holding capacity can be secured in the relay router, which leads to effective use of the buffer.

  In the mobile communication system of the present invention, the wireless terminal notifies the relay router of information on data received by the wireless terminal before exceeding the data holding capacity determined by the negotiation. It is preferable to characterize.

  According to this configuration, the relay router can know which data is received by the wireless terminal that is the transfer destination of the retained data while retaining data from the communication partner.

  In the mobile communication system of the present invention, it is preferable that the relay router deletes data in order from the oldest when holding data exceeding the data holding capacity determined by the negotiation. .

  According to this configuration, in the relay router, when the retained data exceeds the retained capacity while retaining data from the communication partner, the data can be retained in the new order.

  In the mobile communication system of the present invention, the relay router deletes received data notified from the wireless terminal and updates an expiration date of a buffer area reserved for the wireless terminal. It is preferable to do.

  According to this configuration, when the data from the communication partner is held in the relay router, the data already received by the wireless terminal can be deleted, so that efficient data holding can be performed.

  In the mobile communication system of the present invention, it is preferable that the relay router deletes a buffer area that has expired.

  According to this configuration, the buffer area in the relay router can be effectively used.

  In the mobile communication system of the present invention, it is preferable that the radio terminal notifies the relay router of information on received data before the handover after the handover.

  According to this configuration, it is possible to know which data is received by the transfer destination wireless terminal before the handover at the relay router.

  Also, in the mobile communication system of the present invention, the relay router deletes data received before handover notified from the wireless terminal and transfers other data to the corresponding wireless terminal. Is preferable.

  According to this configuration, in the relay router, data that has been received before handover by the wireless terminal is deleted from the retained data, and other data is transferred to the wireless terminal, so only necessary data is transferred. Thus, efficient data transfer can be performed, and data duplication can be prevented.

  In order to solve the above-described problems, a handover control method of the present invention is a handover control method in which a wireless terminal controls handover across edge routers provided for each base station that performs wireless communication with the wireless terminal. In response to an instruction to hold data from a communication partner, the relay router to which the edge router to which the wireless terminal is connected before moving and all edge routers that are candidates for the moving destination are connected under control And a control step for performing control to hold data from the communication partner.

  According to this configuration, since the data from the communication partner is held in the relay router, it is possible to remove redundant paths when transferring packet data. This makes it possible to effectively use network resources. it can. In the prior art, since data was held in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Data was transferred until the network resources were wasted. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  Further, in the handover control method of the present invention, the relay routers that hold the data from the communication partner are all candidate bases that may move among the relay routers that are connected in a hierarchical structure. It is preferable that a relay router that minimizes the number of hops from the wireless terminal among the relay routers under the control of the station is applied.

  According to this method, since the data from the communication partner is held in the relay router closest to the moved wireless terminal, it can be transferred to the moved wireless terminal through the shortest route, thereby more network resources. Can be used effectively.

  Further, in the handover control method of the present invention, the control step adds the destination address of the wireless terminal to the data held by the relay router and transfers the data held to the address. Is preferred.

  According to this method, the retained data can be properly transferred to the wireless terminal after movement by handover.

  In the handover control method of the present invention, it is preferable that the control step attaches a data identifier when transferring the retained data.

  According to this method, since the identifier is generated by the relay router, the packet data sent from the communication partner that is the transmission source is not rewritten, and the wireless communication after movement is not involved in the security problem. It becomes possible to transmit to the terminal.

  In the handover control method of the present invention, it is preferable that the control step negotiates a data holding capacity from a communication partner in the relay router.

  According to this method, only the necessary data holding capacity can be secured in the relay router, which leads to effective use of the buffer.

  In the handover control method of the present invention, it is preferable that the control step deletes data in order from the oldest when performing data retention exceeding the data retention capacity determined by the negotiation. .

  According to this method, in the relay router, when the retained data exceeds the retained capacity while retaining data from the communication partner, the data can be retained in the new order.

  In the handover control method of the present invention, it is preferable that the control step deletes received data notified from the wireless terminal.

  According to this method, since the data received from the wireless terminal can be deleted when the data from the communication partner is held in the relay router, efficient data holding can be performed.

  Further, in the handover control method of the present invention, the control step deletes data received before the handover by the wireless terminal from the data held by the relay router after the wireless terminal has handed over. It is preferable that the data is transferred to the wireless terminal.

  According to this method, in the relay router, the data received before the handover by the wireless terminal is deleted from the retained data, and other data is transferred to the wireless terminal, so only the necessary data is transferred. Thus, efficient data transfer can be performed, and data duplication can be prevented.

  As described above, according to the present invention, when a handover is performed across base stations between wireless terminals, the wireless terminals are connected before moving among the edge routers provided for each base station. The edge router instructs the relay router to which the edge router and the edge routers of all the base stations that are candidates for the movement destination are connected to hold the data from the communication partner. An instruction is given to transfer the data held in the wireless terminal to the wireless terminal after movement after the handover, and the retained data is transferred to the wireless terminal. As a result, by realizing packet data transfer to the wireless terminal after movement in handover control through an optimum route, it is possible to effectively use network resources and prevent occurrence of packet order differences during handover.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a mobile communication system according to an embodiment of the present invention.

  The mobile communication system shown in FIG. 1 includes a wireless terminal 30 that is mobile communication means such as a mobile phone, a plurality of base stations 32, 34, and 36 that perform wireless communication with the wireless terminal 30, and these base stations 32. To 36 and edge routers 38, 40, and 42, and CORs 44, 46, and 48 connected to the edge routers 38 to 42, respectively.

  Here, the CORs 44 to 48 have a hierarchical structure with the COR 48 as a vertex, the COR 44 is under the edge routers 38 and 40, the COR 46 is under the edge router 42, and the COR 48 is an edge via the CORs 44 and 46. The routers 38 to 42 are under its control. Further, the edge routers 38, 40, and 42 hold information on peripheral edge routers where the wireless terminal 30 is expected to move next. For example, the edge router 40 holds information on adjacent edge routers 38 and 42 as information on peripheral edge routers to which the wireless terminal 30 is expected to move next.

  This mobile communication system is constructed in accordance with a technique such as Regiona1 Registrations, Hierarchical MobileIP, etc. proposed in IETF.

  With such a configuration, in the handover control when the wireless terminal 30 moves from the connection area to the edge router 40 to the connection area to the edge router 42, the wireless terminal 30 or the wireless terminal 30 is currently connected. This is started by the edge router 40 according to the radio wave condition of the wireless link. At this time, the wireless terminal 30 or the edge router 40 determines a COR 48 to be a relay router from the plurality of COR 44 to 48 based on the peripheral edge router information registered in the edge router 40.

  A method for determining the relay router will be described with reference to FIGS. First, as shown in FIG. 2, COR 58 is connected to each edge router 50, 52 provided in each base station, COR 60 is further connected to each edge router 54, 56, and COR 62 is above these COR 58, 60. When connected, for example, it is assumed that the wireless terminal 30 is connected to the edge router 56.

  At this time, if it is recognized from the peripheral edge router information held in the edge router 56 that the edge router that is a candidate for the movement destination of the wireless terminal 30 is one of the edge routers 54, the current connection state The COR 60 is connected to both the edge router 56 and the destination router edge router 54 at a higher level (the edge router 56 in the current connection state and the destination destination edge router 54 are connected under control). As determined. That is, the COR 60 that can transmit packet data from the communication node and relays the minimum number of hops from the corresponding wireless terminal 30 to both the edge router 56 in the currently connected state and the edge router 54 that is the movement destination candidate is relayed. Determined as a router. The number of hops indicates the distance from the wireless terminal to the relay router that holds data.

  Further, as shown in FIG. 3, COR 58 is connected to each edge router 50, 52 provided in each base station, COR 60 is further connected to each edge router 54, 56, and COR 62 is above the COR 58, 60. Further, the COR 78 is connected to each of the edge routers 70, 72, the COR 80 is connected to each of the edge routers 74, 76, the COR 82 is connected above the COR 78, 80, and the COR 84 is above the COR 62, 82. Assume that, for example, the wireless terminal 30 is connected to the edge router 54 when connected.

  At this time, it is assumed that the edge routers 52 and 56 are the edge routers that are candidates for the movement destination of the wireless terminal 30 from the peripheral edge router information held in the edge router 54. In this case, the COR 60 connected at the upper level to the edge router 54 in the currently connected state and the edge router 56 as the movement destination candidate, and the COR 58 connected at the higher level to another edge router 52 as the movement destination candidate. The COR 62 connected to both sides at the higher level is determined as a relay router.

  That is, the COR 62 that can transmit packet data from the communication node to the edge router 54 in the currently connected state and all the destination destination edge routers 56 and 52 and has the minimum number of hops from the wireless terminal 30. Is determined as a relay router.

  A buffering instruction message is transmitted to the COR (relay router) 48 shown in FIG. 1 determined as described above from the wireless terminal 30 or the edge router 40 that is currently connected to the wireless terminal 30 as indicated by the arrow Y3. To do. Upon receiving this message, the COR 48 buffers packet data transmitted as indicated by an arrow Y4 from the communication node as a relay router. Thereafter, the wireless terminal 30 performs handover to one edge router 42 from among the edge routers 38 and 42 that are the movement destination candidates.

  The wireless terminal 30 that has performed handover to the new edge router 42 acquires an address to be used by the edge router 42, and in order to register the position of the new address, a location registration message is indicated by the COR ( The data is transmitted to a home network (not shown) and a communication partner via a relay router 48.

  In the case of performing this transmission, in the present invention, a method of separately transmitting a location registration message and a forwarding instruction message, or two methods of transmitting both in one message are conceivable. When the forwarding instruction message passes through the COR (relay router) 48, the COR (relay router) 48 that has received the forwarding instruction message encapsulates the packet data buffered by the address of the current wireless terminal 30. Then, as shown by the arrow Y6, the data is forwarded to the wireless terminal 30 via the edge router 42. When the location registration is completed, the packet data transmitted from the transmission source communication node to the wireless terminal 30 is transmitted to the destination address, and buffering at the COR (relay router) 48 is completed. To do.

  Here, the operation of forwarding the packet data buffered in the COR (relay router) 48 will be described with reference to FIG. The wireless terminal 30 whose address is A for identifying the wireless terminal at the relay router instructs the COR (relay router) 48 to buffer the packet data addressed to the address A before handover by a buffering instruction message. To do. By this instruction, packet data addressed to address A from the communication partner indicated by reference numeral 90 is buffered in the COR (relay router) 48.

  Further, when the address B is assigned after the handover, the wireless terminal 30 registers a message for registering the location of the address B (location registration message) to the communication partner and a message for instructing forwarding of packet data addressed to the address A ( Forwarding instruction message). These messages can be transmitted as one message.

  When the COR (relay router) 48 receives these messages, it encapsulates the buffered packet data addressed to address A with a destination address B as indicated by reference numeral 91 and transmits this to address B. . When receiving the packet data 91 addressed to B, the wireless terminal 30 performs decapsulation as indicated by reference numeral 92. At this time, since the destination address of the decapsulated packet data 92 is A, the wireless terminal 30 cannot receive the packet data 92 if originally intended. However, in the present invention, since the wireless terminal 30 stores the address A before the movement, the packet data 92 addressed to the address A can also be received, so that the COR (relay router) can be received during the handover. The packet data addressed to the address A buffered in 48 can be received.

  As described above, according to the mobile communication system of the embodiment, when the wireless terminal 30 crosses between the base stations 34 and 36, the edge routers 40 and 42 provided for the base stations 34 and 36 are connected. Among them, the edge router 40 to which the wireless terminal 30 was connected before moving is connected to the relay router 48 to which the edge router 40 and the edge routers 42 of all the base stations 36 that are candidates for the movement destination are connected. An instruction to hold the packet data from the communication partner is issued, and an instruction to transfer the packet data held in the corresponding relay router 48 to the wireless terminal 30 after the handover by the instruction is given, and the held packet data is transferred to the wireless terminal Transfer to machine 30.

  As a result, the packet data from the communication partner is held in the relay router 48 during the handover, so that it is possible to remove the redundant path when transferring the packet data. be able to. Also, there is no packet order difference at the time of handover. In the prior art, since the wireless terminal holds the packet data in the edge router to which the wireless terminal was connected before the movement during the handover, the wireless terminal after the movement on the redundant route via the plurality of routers from the edge router before the movement Packet data was transferred to the machine and wasted network resources. In addition, there is a path for transferring packet data buffered from the edge router before movement to the edge router after movement and a path for transferring packet data from the communication partner to the edge router after movement at the same time. Arrived in a mixed order, so the order was out of order.

  In addition, the relay router 48 that holds packet data from the communication partner subordinates all candidate base stations that may move among the relay routers 44 to 48 that are connected in a hierarchical structure. Among the relay routers, a relay router having the minimum number of hops from the wireless terminal 30 is applied. This is a relay router in which the base station to which the wireless terminal 30 was connected before moving and all the base stations that are candidates for the moving destination are connected under the control, and the number of hops from the wireless terminal is reduced. Since the packet data from the communication partner is held in the minimum relay router 48, it can be transferred to the wireless terminal 30 after movement through the shortest path, thereby more effectively utilizing network resources.

  Further, in this embodiment, each edge router holds the position information of the adjacent edge router and the relay router to which the adjacent edge router is connected, and based on the held position information, the wireless under handover The relay router to which the edge router to which the terminal 30 was connected before moving and all the edge routers that are candidates for the moving destination are connected is determined, and packet data from the communication partner is determined to the determined relay router. The instruction to hold is performed. As a result, when a handover is detected at the base station, the appropriate relay router is instructed to hold the packet data from the communication partner, so that the packet data to be transmitted to the wireless terminal in handover is held and the packet data is received. It is possible to prevent loss.

  Further, in this embodiment, when determining a relay router, among the relay routers that are connected in a hierarchical structure, each relay router that subordinates all candidate base stations that may move. Of these, a function of determining a relay router that minimizes the number of hops from the wireless terminal 30 is provided. As a result, it is possible to instruct the relay router closest to the moved wireless terminal 30 to hold the packet data from the communication partner.

  Further, in the present embodiment, after the wireless terminal 30 moves due to handover, the relay router holding the packet data has a function of instructing transfer of the retained packet data to the moved wireless terminal 30. This is a relay router in which the base station to which the wireless terminal 30 was connected before moving and all the base stations that are candidates for the moving destination are connected under the control, and the number of hops from the wireless terminal is reduced. It is possible to instruct to transfer packet data from the communication partner held in the relay router that is the smallest.

  The relay router holds packet data from the communication partner in response to an instruction to hold packet data from the edge router, and stores the packet data in the wireless terminal 30 according to an instruction to transfer packet data from the edge router. And a function of transferring the encapsulated data to the destination address. As a result, the packet data transmitted to the wireless terminal 30 can be retained, and the retained packet data can be appropriately transferred after the wireless terminal 30 has moved the retained packet data.

  The radio terminal 30 stores an address for identifying the radio terminal at the relay router in the handover, receives the encapsulated data transferred from the relay router, and stores the address stored in the received packet data. When the same address exists, packet data to which the same address is added is acquired. As a result, even if a new address is assigned to the wireless terminal 30 after movement, the address before movement can be recognized from the encapsulated data, and packet data to which the recognized address is added can be obtained. That is, it is possible to properly acquire the packet data sent to the wireless terminal before the movement even after the movement whose address has been changed.

  In addition to the above description, the buffering instruction message transmitted from the edge router or the wireless terminal to the relay router is, when the relay router is changed, when the wireless terminal needs to change the buffer amount of the relay router, This happens when the buffer is about to expire. However, when considering a large-scale network, a method of notifying a default buffer value to all wireless terminals together with RA (Router Advertisement) rather than exchanging messages with a relay router for each wireless terminal can be considered. The buffering instruction message is retransmitted at predetermined intervals until a response {BA (Buffer Acknowledgment)} when actually receiving packet data is received.

  After sending the BA, all packet data forwarded to the wireless terminal in the relay router is copied and stored in the buffer. Thereafter, the wireless terminal notifies the relay router of information {BC (Buffer Clear)} for clearing the already received packet data, thereby deleting the notified packet data from the buffer.

  Further, in the relay router, when the buffer prepared before BC reception becomes full, old packet data is deleted in order. The timing for raising BC is sent for the purpose of updating the validity period and preventing the assigned buffer area from becoming full within the validity period of the assigned buffer.

  In the present invention, the above method is realized as described later by inserting a sequence number or a time stamp into an unencapsulated header sent from the relay router to the wireless terminal.

  As described above, the encapsulation technology is used for data transfer between the relay router and the wireless terminal. However, since the header used for encapsulation is generated by the relay router, it is generated from the communication partner that is the transmission source. It becomes possible to configure freely without considering the security problem that occurs when the packet data to be sent is rewritten. For this reason, an optional header indicating the sequence number or time stamp of the arrived packet data is introduced into the header to be encapsulated. In this option, the order of arrival of packets addressed to the same wireless terminal at the relay router is entered. Since this value may increase infinitely, it is reused at regular intervals by taking the modulo of the maximum value that the prepared field can take.

  Note that the same option is essential for a buffering instruction message and a forwarding instruction message, which are messages requesting a response. Then, in order to clarify which message is the response to those responses, the identifier of the message that triggered the response message is specified.

  The aforementioned forwarding instruction message transmitted after the handover indicates the maximum sequence number or time stamp of the packet received before the handover. The relay router that has received the forwarding instruction message deletes up to the packet data described in the forwarding instruction message and forwards the subsequent packet data to the wireless terminal. It should be noted that all the messages described above can be combined with a data packet or a signaling packet used in Mobile IP.

  Regarding the sequence number, it is necessary to manage the sequence number for each flow. However, using a time stamp is effective in a large-scale network or the like because it does not require management for each flow as compared with the case of using a sequence number.

  As described above, the relay router has a function of attaching a data identifier when transferring retained data to a wireless terminal in accordance with a transfer instruction from an edge router, a base station, or a wireless terminal. As a result, since the identifier is generated by the relay router, it is possible to freely configure without considering the security problem that occurs when rewriting the packet data sent from the communication partner that is the transmission source.

  In addition, the wireless terminal has a function of negotiating a retention capacity of data from a communication partner in the relay router. More specifically, the wireless terminal transmits information regarding how much capacity is desired to be secured as a data retention capacity from the communication partner to the relay router. As a result, only necessary data holding capacity can be secured in the relay router, so that efficient data holding can be performed.

  In addition, the wireless terminal has a function of notifying the relay router of information on data received by the wireless terminal before exceeding the data holding capacity determined by the negotiation. As a result, the relay router can know which data is received by the wireless terminal to which the retained data is transferred while retaining data from the communication partner.

  In addition, the relay router has a function of deleting data in order from the oldest when holding data exceeding the data holding capacity determined by the negotiation. As a result, in the relay router, when the retained data exceeds the retention capacity while retaining data from the communication partner, the data can be retained in the new order.

  Further, the relay router has a function of deleting received data notified from the wireless terminal. As a result, when the data from the communication partner is held in the relay router, the data already received by the wireless terminal can be deleted, so that efficient data holding can be performed.

  In addition, the wireless terminal has a function of notifying the relay router of data information received before the handover after the handover. As a result, the relay router can know which data is received by the transfer destination wireless terminal before the handover.

  Further, the relay router has a function of deleting data received before handover notified from the wireless terminal and transferring other data to the corresponding wireless terminal. As a result, in the relay router, the data received before the handover by the wireless terminal is deleted from the retained data, and other data is transferred to the wireless terminal, so that only necessary data can be transferred. As a result, efficient data transfer can be performed, and duplication of data can be prevented.

  Further, in the above-described embodiment, when the handover is detected, all of the edge routers to which the wireless terminal 30 during handover is connected and the destination candidates are all based on the position information held in the edge router. The relay router to be connected to the edge router is determined, and the determined relay router is instructed to hold the packet data from the communication partner (buffering instruction). Prior to (that is, irrespective of handover detection), the determination of the relay router and the buffering instruction may be performed. In this case, the data transmitted to the wireless terminal 30 before the handover is performed is buffered in the relay router and transmitted to the wireless terminal 30 via the source edge router. In this case, the relay router transmits the data with the identifier to the wireless terminal 30 through the source edge router.

  In the above embodiment, as described with reference to FIG. 4, the relay router encapsulates the packet data addressed to the address A that is buffered with the transmission destination address B, and transmits the packet data to the address B. The wireless terminal 30 received and decapsulated the packet data 91 addressed to B. However, as shown in FIG. 5, this is because the relay router that has received the packet data 95 addressed to the address A including the address HA set at the time of registration of the wireless terminal 30 uses the address HA as a key to transmit the packet data. It may be rewritten with packet data addressed to address B and transmitted to the wireless terminal 30 after movement.

It is a block diagram which shows the structure of the mobile communication system which concerns on embodiment. It is a 1st block diagram for demonstrating the determination method of the relay router in the mobile communication system which concerns on embodiment. It is a 2nd block diagram for demonstrating the determination method of the relay router in the mobile communication system which concerns on embodiment. It is a block diagram for demonstrating the operation | movement which forwards the packet data buffered by the relay router in the mobile communication system which concerns on embodiment. It is a block diagram for demonstrating the operation | movement which forwards the packet data buffered by the relay router in the mobile communication system which concerns on embodiment. It is a block diagram which shows the structure of the conventional mobile communication system.

Explanation of symbols

  30 ... wireless terminal, 32, 34, 36 ... base station, 38, 40, 42 ... edge router, 44, 46, 48 ... COR (Cross Over Router)

Claims (26)

In a handover control apparatus that performs handover control over which a wireless terminal straddles between edge routers provided for each base station that performs wireless communication with a wireless terminal,
Control that holds data from a communication partner in a relay router connected under the edge router to which the wireless terminal was connected before moving and all edge routers that are candidates for the moving destination during the handover a control means for performing,
The relay router that holds the data from the communication partner is a relay router that has the minimum number of hops from the wireless terminal among the plurality of relay routers connected in a hierarchical structure. A handover control apparatus characterized by the above .   2. The handover according to claim 1, wherein the control unit attaches an identifier for identifying a packet together with a moving destination address of the wireless terminal to the held data of the relay router, and transfers the held data to the address. Control device. In a base station that detects a handover of a wireless terminal,
Holding means for holding position information of an adjacent base station and a relay router to which the adjacent base station is connected;
Based on the stored location information, a determining unit that determines a relay router to which the base station to which the wireless terminal is connected before moving and all the base stations that are candidates for the moving destination are connected under control,
An instruction means for instructing the determined relay router to hold data from a communication partner ; and
The determining means, when determining the relay router, wirelessly among the relay routers that subordinate all candidate base stations that may move among the relay routers connected in a hierarchical structure. A base station that determines a relay router that minimizes the number of hops from a terminal . 4. The instruction unit according to claim 3 , wherein after the wireless terminal moves due to handover, the instruction unit instructs the relay router determined by the determination unit to transfer the retained data to the wireless terminal after movement. base stations of. In an edge router that is provided in a base station that detects handover of a wireless terminal, and the wireless terminal is connected by wireless communication,
Holding means for holding the position information of the adjacent edge router and the relay router to which the adjacent edge router is connected;
Based on the stored location information, a determination unit that determines relay routers to which the edge router to which the wireless terminal is connected before moving and all edge routers that are candidates for the moving destination are connected under control;
An instruction means for instructing the determined relay router to hold data from a communication partner ; and
The determining means, when determining the relay router, determines a relay router having a minimum number of hops from the wireless terminal among a plurality of relay routers connected in a hierarchical structure. Edge router. 6. The instruction unit according to claim 5 , wherein after the wireless terminal moves by handover, the instruction unit instructs the relay router determined by the determining unit to transfer the retained data to the wireless terminal after movement. Edge router. The base station according to claim 3 or 4 or the edge router according to any of claims 5 or 6 holds data from a communication partner in response to a data holding instruction by the instruction means, and the instruction The data from the communication partner is held in accordance with the data transfer instruction by the means, and the address of the current wireless terminal is attached, the identifier for identifying the packet is attached, and the packet data is set to the address of the current wireless terminal. A relay router that transfers the packet data to the address of the current wireless terminal in accordance with the transfer instruction after the wireless terminal moves. In the wireless terminal connected to communicate with the relay router according to claim 7,
Storage means for storing an address identifying the radio terminal in the relay router in a handover,
To forward the packet data after a handover in the relay router, the address of the previous mobile radio terminal, to change the address of the current wireless terminal, the packet data to the relay router to the address of the current wireless terminal A wireless terminal comprising an instruction means for issuing an instruction to transmit. A wireless terminal that performs wireless communication with each base station and performs handover control during handover across edge routers provided for each base station,
During the handover, the relay router to which the edge router to which the wireless terminal was connected before moving and all the edge routers that are candidates for the moving destination are subordinately connected holds data from the communication partner. comprising a control means for,
Select and apply a relay router that minimizes the number of hops from the wireless terminal among relay routers connected in a hierarchical structure as a relay router that holds data from the communication partner. A featured wireless terminal. The wireless communication apparatus according to claim 9 , wherein the control means attaches an identifier for identifying a packet together with a movement destination address of the wireless terminal to the retained data of the relay router and transfers the retained data to the address. Terminal machine. In a mobile communication system where handover is performed between base stations between wireless terminals,
A relay router connected to the base station in a hierarchical structure, relaying data to the base station and holding data;
An instruction to hold data from a communication partner is sent to a relay router to which the base station to which the wireless terminal is connected before the movement and all the base stations that are candidates for the movement destination are connected under the handover. And an edge router provided for each base station that gives an instruction to transfer the data held in the relay router according to this instruction to the wireless terminal after movement,
Equipped with,
The relay router that holds the data from the communication partner is a relay router that has the minimum number of hops from the wireless terminal among the plurality of relay routers connected in a hierarchical structure. A mobile communication system. In response to an instruction to hold the packet data of the edge router, the relay router transfers the packet data with a data identifier attached to the wireless terminal while holding the packet data in the relay router, and after the handover 12. The mobile communication system according to claim 11 , wherein packet data is transferred to an address of the current wireless terminal in response to a packet data transfer instruction of the wireless terminal. The mobile communication system according to claim 11 or 12 , wherein the wireless terminal negotiates a retention capacity of data from a communication partner with the relay router. The mobile communication according to claim 13 , wherein the wireless terminal notifies the relay router of information on data received by the wireless terminal before exceeding a data holding capacity determined by the negotiation. system. 14. The mobile communication system according to claim 13 , wherein the relay router deletes data in order from the oldest when holding data exceeding the data holding capacity determined by the negotiation. 15. The relay router according to claim 14 , wherein the relay router deletes the received data notified from the wireless terminal and updates an expiration date of a buffer area reserved for the wireless terminal. Mobile communication system. 15. The mobile communication system according to claim 14 , wherein the relay router deletes a buffer area that has expired. The mobile communication system according to any one of claims 12 to 17 , wherein the radio terminal notifies the relay router of data information received before the handover after the handover. 19. The mobile communication system according to claim 18 , wherein the relay router deletes data received before the handover notified from the wireless terminal and transfers other data to the corresponding wireless terminal. In a handover control method for controlling handover in which a wireless terminal straddles between edge routers provided for each base station that performs wireless communication with a wireless terminal,
In response to an instruction to hold data from a communication partner, the edge router to which the wireless terminal was connected before moving and all the edge routers that are candidates for the moving destination are relay routers connected to the subordinate A control step for performing control to hold data from the communication partner ,
The relay router that holds data from the communication partner is characterized in that a relay router that has the minimum number of hops from the wireless terminal among the relay routers connected in a hierarchical structure is applied. hand-over control method. 21. The handover control method according to claim 20 , wherein the control step attaches the current address of the wireless terminal to the data held by the relay router and transfers the data held to the address. The handover control method according to claim 21 , wherein the control step attaches an identifier of data when transferring the retained data. 23. The handover control method according to claim 21 or 22 , wherein the control step negotiates a storage capacity of data from a communication partner in the relay router. 24. The handover control method according to claim 23 , wherein, in the control step, data is deleted in chronological order when data retention is performed exceeding the data retention capacity determined by the negotiation. 24. The handover control method according to claim 23 , wherein the control step deletes received data notified from the wireless terminal. In the control step, after the wireless terminal is handed over, the data received before the handover by the wireless terminal is deleted from the data held by the relay router, and other data is transferred to the wireless terminal. The handover control method according to any one of claims 21 to 25 .

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