JP4698706B2 - Access node - Google Patents

Description

  The present invention relates to a wireless communication system, a gateway, a node, and an access node that transfer a packet to a mobile terminal via any of a plurality of access nodes.

  In a conventional wireless communication system, each time a mobile terminal moves between cells, the mobile terminal needs to perform location registration with the wireless communication system via a base station (access node) that manages a destination cell. It was. The reason is that the conventional wireless communication system is configured to manage the identification information of the mobile terminal and the current location of the mobile terminal as location information, and forward the packet to the mobile terminal based on the location information. This is because.

  Also, in a conventional wireless communication system, a technique is known in which one scheduled arrival time is given to one packet for packet priority control (for example, Patent Document 1).

In the future, the wireless communication system is expected to handle large-capacity traffic (for example, gigabit class) such as future communication such as biological information communication. Along with this, for the purpose of increasing the radio transmission capacity, it is assumed that the size of the cell managed by the base station is minimized for the purpose of increasing the density of the radio channel. In addition, with the diversification of mobile terminals, there is a need to consider providing services for mobile terminals that move at ultra high speeds.
JP 2000-78188 A

  However, in the conventional wireless communication system, when the cell size is minimized or when a service is provided to a mobile terminal that moves at high speed, the frequency of inter-cell movement by the mobile terminal increases. As a result, the frequency of location registration increases, and there is a problem that there is a concern about the processing load of the network and the deterioration of communication quality.

  In addition, the technique disclosed in Patent Document 1 described above does not consider routing (route control) when a mobile terminal moves.

  The present invention has been made in view of the above points, and provides a wireless communication system, a gateway, a node, and an access node that do not require location registration every time a mobile terminal moves between cells under certain conditions. For the purpose.

  A first feature of the present invention is a wireless communication system that transfers a packet to a mobile terminal via one of a plurality of access nodes, and includes a plurality of pieces of movement prediction information that associates time information with access node identification information. A movement prediction information storage unit to store; a first transfer time storage unit that manages a first transfer time of a packet to each access node; the plurality of movement prediction information, the first transfer time, and a current time; And a destination access node determination unit that determines a destination access node of the packet based on the above.

  A second feature of the present invention is a gateway used in a wireless communication system that transfers a packet to a mobile terminal via any one of a plurality of access nodes, and includes a plurality of times for associating time information with identification information of an access node. A destination access node determination unit that determines a destination access node of the received packet based on the movement prediction information, the first transfer time of the packet to the access node, and the current time, and corresponds to the destination access node The gist of the present invention is to include a granting unit for giving the first movement prediction information to the packet and a routing unit for routing the packet to which the first movement prediction information is given.

  According to this invention, since the destination access node determination unit determines the destination access node of the packet based on the plurality of pieces of movement prediction information, the first transfer time, and the current time, the mobile terminal performs inter-cell movement. Even in this case, the mobile terminal can transfer the packet to the mobile terminal without performing location registration again.

  In the second aspect of the present invention, the destination access node determination unit may determine a destination access node of the packet in consideration of a transit time when the mobile terminal passes through an area where the radio wave condition is statistically bad. it can.

  According to this invention, when the mobile terminal exists in a region where two cells that are statistically in poor radio wave conditions overlap (that is, when moving between cells), the destination access node determination unit By transferring the packet to the destination access node instead of the source access node, packet loss can be prevented.

  In the second aspect of the present invention, when a request for correcting the movement prediction information is received from the destination access node, identification information of an access node that has established a radio link with the mobile terminal and the radio link A detection unit that detects an establishment time; a movement prediction information correction unit that corrects the movement prediction information based on the detection result; and a notification unit that notifies the corrected movement prediction information to the destination access node. can do.

  According to this invention, when the access node that manages the cell that the mobile terminal has already passed receives a packet addressed to the mobile terminal, the cell in which the mobile terminal exists is based on the corrected movement prediction information. It is possible to retransmit the packet to the access node that manages the packet.

  In the second aspect of the present invention, the method includes a calculation unit that calculates a scheduled establishment time at which a radio link is established between the destination access node and the mobile terminal based on the detection result, and the notification unit includes The schedule establishment time can be notified to the destination access node instead of the movement prediction information.

  According to this invention, since the mobile terminal has not yet arrived, the arrival time of the mobile terminal can be notified to the access node that buffers the packet addressed to the mobile terminal.

  A third feature of the present invention is a node used in a wireless communication system that transfers a packet to a mobile terminal via any of a plurality of access nodes, and stores a second transfer time of the packet to the access node A second transfer time storage unit, a plurality of pieces of movement prediction information associated with the received packet associated with the time information and the identification information of the access node, the second transfer time, the current time, Based on the above, the destination access node determination unit for determining the destination access node of the packet and routing the packet to the determined destination access node.

  According to this invention, the destination access node determination unit delays transfer of the packet by routing the packet to an access node different from the access node indicated by the movement prediction information given to the received packet. It is possible to flexibly cope with the case where it is.

  A fourth feature of the present invention is an access node that forwards a packet to a mobile terminal, a radio link information storage unit that stores radio link information with the mobile terminal, and when the packet is received, In the first situation indicating that the radio link information is not yet established or in the third situation indicating that the connection has already been completed, a buffer for buffering the packet and the radio link information are connected In a second situation indicating that the packet is in the middle, the gist is to include a transfer unit that transfers the packet to the mobile terminal.

  According to this invention, when the mobile terminal has not yet arrived or has already passed, that is, when the radio link is not established with the mobile terminal, the packet addressed to the mobile terminal By buffering, packet loss can be prevented.

  In the fourth feature of the present invention, the transit time at which the mobile terminal passes through an area where the radio wave condition is statistically bad is managed, and the packet can be buffered during the transit time.

  According to this invention, packet loss can be prevented by buffering packets addressed to the mobile terminal during the passage time when the mobile terminal passes through an area where the radio wave condition is statistically bad.

  In the fourth aspect of the present invention, when the packet is buffered because the radio link information is in the first situation, the buffering time of the packet or the buffering packet A monitoring unit that monitors the amount of data, and movement prediction information that associates time information with access node identification information when the buffering time has passed a predetermined time, or when the data amount exceeds a predetermined threshold. A modification request transmission unit that transmits a modification request, and a schedule establishment time reception unit that receives a schedule establishment time at which a radio link is established with the mobile terminal can be provided.

  According to this invention, the access node can prevent packet loss without using the buffer capacity wastefully by continuing the buffering of the packet until the received scheduled establishment time.

  In the fourth aspect of the present invention, when the packet is buffered because the radio link information is in the third situation, correction of movement prediction information associating time information with access node identification information A correction request transmitting unit for transmitting a request, a movement prediction information receiving unit for receiving the corrected movement prediction information, and adding the corrected movement prediction information to the packet, based on the corrected movement prediction information And a routing unit for routing the packet.

  According to this invention, even when the packet addressed to the mobile terminal is transferred to the access node that manages the cell that the mobile terminal has already passed, the routing unit is based on the corrected movement prediction information. Thus, by routing the buffered packet, the packet can be transferred to the mobile terminal without being discarded.

  As described above, according to the present invention, a wireless communication system, a gateway, a node, and an access node that do not require location registration each time the mobile terminal MN1 moves between cells (areas) under certain conditions are provided. can do.

(Configuration of wireless communication system according to first embodiment of the present invention)
The configuration of the wireless communication system according to the first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the wireless communication system according to the present embodiment forms a hierarchical structure of a gateway GW, a plurality of nodes # 1 to # 2, and a plurality of access nodes # 1 to # 6. .

  In the present embodiment, the wireless communication system transfers a packet transmitted by a communication partner CN connected to the IP network 2 to the mobile terminal MN1 via one of the plurality of access nodes # 1 to # 6. And

  Further, in the present embodiment, it is assumed that the mobile terminal MN1 is moving on the train 1 that moves almost in time and in a certain direction. In the present embodiment, it is assumed that one area (cell) # 1 to # 6 is formed between stations. In the present embodiment, the packet is transferred by the Internet protocol. In addition, it is assumed that the time information held by all the devices constituting the wireless communication system according to the present embodiment is exactly the same.

  The gateway GW is connected to the IP network 2 and transmits and receives packets to and from the IP network. As shown in FIG. 2, the gateway GW includes a movement prediction information database 11, a movement prediction information management unit 12, a required time measurement unit 13, a required time database 14, a reception unit 15, and a destination access node determination unit 16. And a header adding unit 17 and a routing unit 18.

  The movement prediction information database 11 is a movement prediction information storage unit that stores, for each mobile terminal MN, a plurality of movement prediction information that associates “time information” with “access node identification information”.

  FIG. 3A shows an example of the movement prediction information managed by the movement prediction information database 11 (for the mobile terminal MN1). In the example of FIG. 3A, the movement prediction information includes “time information” indicating a predetermined time and “access node identification” indicating an access node where the mobile terminal MN1 is scheduled to establish a radio link at the predetermined time. Information ”is associated with“ CoA address ”indicating a network address used when the mobile terminal MN1 is connected to the access node.

  According to the movement prediction information shown in FIG. 3A, for example, the mobile terminal MN1 is scheduled to connect to the access node AR1 at time T1, that is, exists in the area # 1 managed by the access node AR1. In this case, “CoA1” is scheduled to be used as the CoA address.

  The movement prediction information management unit 12 performs management processing on movement prediction information stored in the movement prediction information database 11.

  Specifically, the movement prediction information management unit 12 acquires, from the mobile terminal MN1, information indicating that the mobile terminal MN1 is moving on the train 1 that is moving approximately in time and in a certain direction. Next, the movement prediction information management unit 12 creates a movement schedule table of the train 1 from the operation table of the train 1 using the above acquisition as a trigger.

  And the movement prediction information management part 12 calculates the time when the said train 1 passes each area # 1 thru | or # 6 managed by each access node AR1 thru | or AR6 based on the movement schedule table | surface of the said train 1 mentioned above. Then, the movement prediction information in the movement prediction information database 11 described above is created.

  In addition, the movement prediction information management unit 12 creates a network address (CoA address) used by the mobile terminal MN1 under each of the areas # 1 to # 6 in advance as necessary, so that the mobile terminal MN1 and each access node AR1 to The network address may be distributed to the AR 6 in advance.

  Further, the movement prediction information management unit 12 acquires additional information such as a disturbance of the train 1 schedule, and based on the acquired additional information, the movement prediction table in the train 1 and the movement prediction information in the movement prediction information database 11. Is configured to change (correct). Here, the movement prediction information management unit 12 may be configured to acquire the above-described additional information from the management company of the train 1, the mobile terminal MN1, or the like.

  When the movement prediction information management unit 12 receives a movement prediction information correction request from the access node AR, the movement prediction information management unit 12 establishes a radio link with the mobile terminal MN1 specified by the received correction request. Identification information and the establishment time of the wireless link are detected.

  At this time, the movement prediction information management unit 12 performs a general call (paging) to the access nodes AR1 to AR6 connected to the gateway GW, thereby establishing a radio link with the above-described mobile terminal MN1. The access node may be configured to acquire the identification information of the access node and the establishment time of the wireless link from the access node that has established

  Further, the movement prediction information management unit 12 may be configured to acquire the additional information from the access node when acquiring the identification information of the access node and the establishment time of the radio link. .

  Further, the movement prediction information management unit 12 corrects the movement prediction information related to the mobile terminal MN1 in the movement prediction information database based on the detection result described above, and notifies the access node AR of the corrected movement prediction information. It may be configured.

  Further, when the movement prediction information management unit 12 receives a movement prediction information correction request from the access node AR, the movement prediction information management unit 12 establishes a radio link between the access node AR and the mobile terminal MN1 based on the corrected movement prediction information. The scheduled establishment time may be calculated, and the calculated scheduled establishment time may be notified to the access node AR. Here, the movement prediction information management unit 12 may use the scheduled arrival time at which the mobile terminal MN1 arrives in the area managed by the access node AR as the schedule establishment time.

  Furthermore, the movement prediction information management unit 12 may be configured to statistically manage the quality of radio links in the area managed by each access node AR in advance.

  The movement prediction information management unit 12 can manage the passage time when the mobile terminal MN1 passes through an area where the radio wave condition is statistically bad based on the quality of the radio link. For example, as illustrated in FIG. 4, the movement prediction information management unit 12 sets a region (hatched portion in FIG. 4) where the radio wave intensity may be significantly deteriorated statistically, such as a region where cells overlap. As a passage time when MN1 passes, a period γn between Tn and (Tn + γn), a period γn + 1 between Tn + 1 and (Tn + 1 + γn + 1), and the like can be managed.

  The required time measuring unit 13 measures the first transfer time of the packets to the access nodes AR1 to AR6, that is, the time required for the packet transmitted from the gateway GW to arrive at the access nodes AR1 to AR6. It is. The required time measuring unit 13 can measure the first transfer time periodically using a Ping command or the like.

  The required time database 14 is a first transfer time storage unit that manages the first transfer time described above. FIG. 3B shows an example of the first transfer time managed by the required time database 14. In the example of FIG. 3B, the required time database 14 stores a “section” indicating a predetermined section in association with a “required time” indicating a time required for a packet to be transferred in the predetermined section. Yes.

  In the example of FIG. 3B, the required time database 14 includes not only the required time (first transfer time) α in the section between the gateway GW and each of the access nodes AR1 to AR6, but also the access nodes AR1 to AR6. And the required time β in each of the sections between the mobile terminal MN1 existing in the areas # 1 to # 6 is stored.

  Here, the required time α is measured by the required time measuring unit 13, and the required time β is generated based on the statistical information. Therefore, the required time in the section between the gateway GW and the mobile terminal MN1 existing in each of the areas # 1 to # 6 can be calculated by adding the required time α and the required time β.

  According to the required time shown in FIG. 3B, for example, the time during which a packet is transferred through a section between the gateway GW and the access node AR2 is “α2”, and exists in the access node AR2 and the area # 2. The time during which the packet is transferred through the section with the mobile terminal MN1 is “β2”.

  The receiving unit 15 receives a packet from the communication partner CN via the IP network 2 and receives a movement prediction information correction request transmitted from the access nodes AR1 to AR6.

  The destination access node determination unit 16 determines a destination access node of a packet received via the reception unit 15 based on the plurality of pieces of movement prediction information, the first transfer time, and the current time.

  Specifically, the destination access node determination unit 16 determines the destination access node as follows. Here, the current time is “T”, and the movement prediction information (time information, access node identification information) is (T1, AR1), (T2, AR2),... (Tn, ARn). To do. Further, T <T1, and T1 <T2 <.

  Furthermore, first transfer times required for packets to be transferred from the gateway GW to the access nodes AR1 to ARn are α1, α2,.

  Also, the time required for the packet to be transferred from each access node AR1 to ARn to the mobile terminal MN1 is β1, β2,. Here, when the time required for the packet to be transferred to each of the access nodes AR1 to ARn cannot be acquired in real time, the statistical values of β1, β2,... Βn may be used.

  The destination access node determination unit 16 determines “Tn” that is larger than “T + (αn + βn) (n = 1, 2,... N)” and closest to “T + (αn + βn)”, and determines “Tn” Is determined as a destination access node.

Further, the destination access node determination unit 16 calculates an average value (α + β) Av of “+” indicating an approximate packet transfer time from the gateway GW to the mobile terminal according to (Equation 1), and performs the above-described destination access. In the node determination method, an average value (α + β) Av may be used instead of (αn + βn).

  Further, the destination access node determination unit 16 may be configured to determine the destination access node of the packet in consideration of the passage time when the mobile terminal MN1 passes through a region where the radio wave condition is statistically bad.

  Specifically, as illustrated in FIG. 4, even when the destination access node determination unit 16 determines “ARn” as the destination access node by the above-described method, the time when the packet arrives at “ARn” is determined. When it is determined that it is between “Tn + 1” and “Tn + 1 + γn + 1”, “ARn + 1” is determined as the destination access node.

  The header assigning unit 17 assigns a header having an address of the destination access node ARn determined by the destination access node determination unit 16 as an “end point address (destination address)” to the received packet, and also sends the header to the destination access node ARn. Corresponding first movement prediction information is added to the received packet.

  In the example of FIG. 5, the header assigning unit 17 receives the received packet (the original address) by using IP in IP encapsulation, with the encapsulation header having “start address = gateway GW address” and “end address = access node AR1”. Packet).

  Further, the header adding unit 17 extends time information (arrival time) and access node identification information (arrival at arrival time) for the received packet (original packet) by extending the relay point option header of the IP header. The movement prediction information for associating with the address of the access node to be assigned is assigned.

  In the example of FIG. 5, the header adding unit 17 includes first movement prediction information corresponding to the access node AR1, second movement prediction information corresponding to the access node AR2, and third movement corresponding to the access node AR3. A relay point option header including prediction information is attached to the original packet.

  Here, considering the packet overhead, it is desirable that the number of pieces of movement prediction information to be given is small.

  Moreover, the header provision part 17 is comprised so that movement prediction information may be provided so that it may not exceed MTU (Maximum Transfer Unit) on a radio | wireless link.

  Further, the header assigning unit 17 can make the relay point option header a fixed length in order to easily determine the number of attached movement prediction information.

  The routing unit 18 routes the packet to which the first movement prediction information is assigned. In the example of FIG. 5, the routing unit 18 routes and transfers the received packet to the node # 1 or # 2 based on the encapsulation header.

  In this embodiment, the movement prediction information database 11, the movement prediction information management unit 12, the required time measurement unit 13, and the required time database 14 are provided as functions in the gateway GW, but all or part of these functions. However, it may be provided as a separate device from the gateway GW.

  Nodes # 1 and # 2 receive packets transferred from the gateway GW and transfer them to other nodes and access nodes. Since the function of the node # 1 and the function of the node # 2 are basically the same, the function of the node # 1 will be described below.

  As shown in FIG. 6, the node # 1 includes a required time measuring unit 33, a required time database 34, a receiving unit 35, a destination access node determining unit 36, a header changing unit 37, and a routing unit 38. To do.

  The required time measuring unit 33 has the same function as the required time measuring unit 13 of the gateway GW, and is transmitted from the second transfer time of the packets to the access nodes AR1 to AR3, that is, transmitted from the node # 1. The time required for each packet to arrive at each of the access nodes AR1 to AR3 is measured. The required time measuring unit 33 can measure the second transfer time periodically using a Ping command or the like.

  The required time database 34 is a second transfer time storage unit that manages the second transfer time described above. In the example of FIG. 6, the required time database 34 stores a “section” indicating a predetermined section and a “required time” indicating a time required for a packet to be transferred in the predetermined section in association with each other.

  In the example of FIG. 6, the required time database 34 includes not only the required time (second transfer time) A in the section between the node # 1 and each of the access nodes AR1 to AR3 but also the access nodes AR1 to AR3 and the area. The required time B in each section with the mobile terminal MN1 existing in # 1 to # 3 is stored.

  Here, the required time A is measured by the required time measuring unit 33, and the required time B is generated based on the statistical information. The required time B may take the same value as the required time β managed by the required time database 13 of the gateway GW. Therefore, by adding the required time A and the required time B, the required time in the section between the node # 1 and the mobile terminal MN1 existing in each of the areas # 1 to # 3 can be calculated.

  According to the required time shown in FIG. 6, for example, the time during which a packet is transferred in the section between the node # 1 and the access node AR2 is “A2”, and the mobile terminal exists in the access node AR2 and the area # 2. The time during which the packet is transferred through the section with MN1 is “B2”.

  The receiving unit 35 receives packets from the gateway GW or other nodes.

  The destination access node determination unit 36 determines the destination access node of the packet received via the reception unit 35 based on the movement prediction information given to the received packet, the second transfer time, and the current time. Is.

  Specifically, the destination access node determination unit 36 determines the destination access node as follows. Here, the current time is “T ′”, and the movement prediction information (time information, access node identification information) given to the received packet is (T1, AR1), (T2, AR2),. It is assumed that (Ta, ARa). Also, T ′ <T1 and T1 <T2 <.

  Furthermore, the second transfer times required for the packet to be transferred from the node # 1 to each of the access nodes AR1 to ARa are A1, A2,... Aa, respectively.

  In addition, the time required for a packet to be transferred from each access node AR1 to ARa to the mobile terminal MN1 is B1, B2,. Here, when the time required for the packet to be transferred to each of the access nodes AR1 to ARa cannot be acquired in real time, the statistical values of B1, B2,... Ba may be used.

  The destination access node determination unit 36 is larger than “T ′ + (Aa + Ba) (a = 1, 2,... A)” among the movement prediction information given to the received packet, and most “T ′”. “Ta” close to “+ (Aa + Ba)” is determined, and the access node ARa corresponding to the determined “Ta” is determined as the destination access node.

  Similarly to the destination access node determination unit 16 of the gateway GW described above, the destination access node determination unit 36 considers the passage time when the mobile terminal MN1 passes through an area where the radio wave condition is statistically bad, and considers the packet destination. It may be configured to determine an access node.

  The header changing unit 37 changes the header of the packet received via the receiving unit 35 according to the determination by the destination access node determining unit 36.

  Specifically, the header changing unit 37 changes the “end point address (destination address)” of the encapsulation header to the address of the destination access node ARa determined by the destination access node determination unit 36, and also changes the relay option header. The movement prediction information corresponding to the destination access node is changed to “first movement prediction information”.

  At this time, the header changing unit 37 once unencapsulates the IP in IP encapsulation, and receives the encapsulated header with “start address = node # 1 address” and “end address = access node ARa” as the received packet (original Packet).

  Here, when the address of the destination access node determined by the destination access node determination unit 36 is set in the encapsulation header of the received packet, the header changing unit 37 sets the “end point address (destination) of the encapsulation header. Do not change the address).

  Further, the header changing unit 37 may be configured to delete the movement prediction information whose arrival time that is set is older than the current time.

  The routing unit 38 routes received packets based on the encapsulation header.

  The access nodes AR1 to AR6 establish radio links with the mobile terminals MN existing in the areas # 1 to # 6, respectively, and perform radio communication. For example, a base station or an accelerator router corresponds to the access nodes AR1 to AR6. Since the functions of the access nodes AR1 to AR6 are basically the same, the function of the access node AR1 will be described below.

  As shown in FIG. 7, the access node AR1 includes a reception unit 51, a radio link information management unit 52, a buffer 53, a transmission unit 54, a movement prediction information correction request unit 55, and a scheduled arrival time reception unit 56. And a header conversion unit 57.

  The receiving unit 51 receives the packet from the node # 1 and transfers the received packet to the transmitting unit 54.

  The radio link information management unit 52 stores radio link information with the mobile terminal MN. Specifically, as shown in FIG. 8, the radio link information management unit 52 stores “mobile terminal ID”, “connection status”, and “establishment time” in association with each other.

  “Connection status” is based on “unarrived (first status)” and “mobile terminal ID” indicating that a radio link with the mobile terminal MN identified by “mobile terminal ID” has not been established yet. Connection of the radio link with the mobile terminal MN identified by “connected (second situation), mobile terminal ID” indicating that the radio link with the identified mobile terminal MN is being connected Is one of “passing (third situation)” indicating that it has already been completed.

  In other words, when the “connection status” is “not arrived (first status)”, the mobile terminal MN1 has not yet arrived in the area # 1 managed by the access node AR1. Further, when the “connection status” is “connected (second status)”, the mobile terminal MN1 exists in the area # 1. Furthermore, when the “connection status” is “pass (third status)”, the mobile terminal MN1 has already passed through the area # 1.

  The “establishment time” indicates the time when the wireless link is established when the “connection status” is “connected (second status)”.

  The buffer 53 buffers the packet transferred from the receiving unit 51 in response to an instruction from the transmitting unit 54. The buffer 53 manages the buffering time of each packet and the data amount of the buffered packet.

  The transmission unit 54 refers to the radio link information management unit 52, buffers the packet according to the radio link information related to the destination mobile terminal MN of the packet received from the reception unit 51, or Decide whether to transfer.

  Specifically, in the transmission unit 54, the radio link information related to the destination mobile terminal MN of the packet received from the reception unit 51 is “not arrived (first situation)” or “passed (third situation)”. If so, the buffer 53 buffers the packet. On the other hand, when the above-described wireless link information is “connected (second situation)”, the transmission unit 54 transfers the packet to the destination mobile terminal MN.

  The transmission unit 54 also monitors the radio link information management unit 52, and the radio link information related to the destination mobile terminal of the packet buffered in the buffer 53 is “connected (second situation)”. If changed, the packet is forwarded to the destination mobile terminal MN.

  Here, when transferring the packet to the destination mobile terminal MN, the transmission unit 54 deletes the encapsulation header (see FIG. 5) attached to the packet.

  Further, the transmission unit 54 manages the passage time when the mobile terminal MN passes through an area where the radio wave condition is statistically bad, and the above-described wireless link information is “connected (second situation)”. Even in such a case, the packet may be buffered in the buffer 53 during the passage time.

  In addition, the transmission unit 54 prepares to transmit a packet addressed to the mobile terminal MN buffered in the buffer 53 at the arrival time of the mobile terminal MN notified from the estimated arrival time reception unit 56. That is, after the above-described arrival time, the transmission unit 54 can allocate an area in which a packet addressed to the mobile terminal MN is buffered as an area for buffering other packets.

  In addition, the transmission unit 54 routes and transfers the packet transmitted from the header conversion unit 57 based on the header of the packet.

  Further, when receiving a general call (paging) from the gateway GW, the transmission unit 54 refers to the radio link information management unit 52 and establishes a radio link with the mobile terminal MN specified by the general call. If the wireless link is established, the gateway GW is notified of the fact and the establishment time of the wireless link.

  The movement prediction information correction requesting unit 55 monitors the buffer 53, and when the buffering time of a specific packet whose “wireless link information” is “not yet arrived (first situation)” has passed a predetermined time, A request for correcting the movement prediction information given to the packet is transmitted to the gateway GW.

  Further, the movement prediction information correction requesting unit 55 monitors the buffer 53 and is buffered in the buffer 53 (packet whose “wireless link information” is “not arrived (first situation)”). When the data amount exceeds the predetermined threshold value, a movement prediction information correction request is transmitted to the gateway GW.

  Further, since the radio link information is “pass (third situation)”, the movement prediction information correction request unit 55 transmits a correction request for movement prediction information given to the buffered packet.

  Further, the movement prediction information correction request unit 55 receives the movement prediction information (modified movement prediction information) transmitted from the gateway GW in response to the above-described movement prediction information correction request and notifies the header conversion unit 57 of the movement prediction information. .

  The scheduled arrival time receiving unit 56 receives a scheduled establishment time at which a radio link is established with the destination mobile terminal MN of the packet buffered in the buffer 53 from the gateway GW.

  The header conversion unit 57 converts the header of the packet buffered in the buffer 53 in accordance with the movement prediction information (modified movement prediction information) notified from the movement prediction information correction requesting unit 55.

  For example, the header conversion unit 57 inserts the corrected movement prediction information into the relay option header of the corresponding packet. Then, the header conversion unit 57 transfers the packet with the corrected movement prediction information to the transmission unit 54.

(Operation of the wireless communication system according to the present embodiment)
The operation of the wireless communication system according to the present embodiment will be described with reference to FIGS. First, the operation of the gateway GW according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 9, in step 1001, the required time measuring unit 13 of the gateway GW updates the content of the required time database 14 at a predetermined cycle.

  In step 1002, when the receiving unit 15 of the gateway GW receives a packet addressed to the mobile terminal MN1 from the communication partner CN via the IP network 2, the operation proceeds to step 1003.

  The destination access node determination unit 16 determines the destination access node of the received packet by the method shown in steps 1003 to 1006. Here, “T” indicates the current time, and “ARn” is an access node corresponding to “Tn” in the movement prediction information database 11. Further, “αn” indicates a required time (first transfer time) required for packet transfer in a section between the gateway GW and the access node ARn, and “βn” indicates the access node ARn and the area #n. The time required for packet transfer in the section with the mobile terminal MN1 is shown. “Αn” and “βn” are stored in the required time database 14.

  In the method shown in steps 1003 to 1006, the destination access node determination unit 16 makes “Tn” larger than “T + (αn + βn) (n = 1, 2,... N)” and closest to “T + (αn + βn)”. And the access node ARn corresponding to the determined “Tn” is determined as the destination access node.

  In step 1007, the header assigning unit 17 performs first movement prediction information corresponding to the access node ARn, second movement prediction information corresponding to the access node ARn + 1, and third movement prediction information corresponding to the access node ARn + 2. Is added to the received packet.

  Specifically, the header assigning unit 17 encapsulates the received packet with the encapsulation header having the access node ARn as the destination address, and transmits the relay option header including the first to third movement prediction information to the packet. Insert into.

  In step 1008, the routing unit 18 routes the packet based on the encapsulation header.

  Secondly, the operation of the node # 1 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 10, in step 2001, the required time measuring unit 33 of the node # 1 updates the contents of the required time database 34 at a predetermined cycle.

  In step 2002, when the reception unit 35 of the node # 1 receives a packet addressed to the mobile terminal MN1 from the gateway GW, the operation proceeds to step 2003. Here, the destination address of the encapsulation header of the received packet is the address of the access node AR1.

  The destination access node determination unit 36 determines the destination access node of the received packet by the method shown in steps 2003 to 2007. Here, “T ′” indicates the current time, and “Ta” indicates the arrival time in the a-th movement prediction information inserted in the received packet. “Aa” indicates a required time (second transfer time) required for packet transfer in a section between the node # 1 and the access node ARa in the a-th movement prediction information, and “Ba” indicates The time required for packet transfer in the section between the access node ARa and the mobile terminal MN1 in the area #n is shown. “Aa” and “Ba” are stored in the required time database 34.

  In the method shown in steps 2003 to 2007, the destination access node determination unit 36 selects “T ′ + (Aa + Ba) (a = 1, 2,... A) from a plurality of pieces of movement prediction information given to the received packet. ) ”And closest to“ T ′ + (Aa + Ba) ”are determined, and an access node ARa corresponding to the determined“ Ta ”is determined as a destination access node.

  In step 2007, when the destination access node ARa determined by the destination access node determination unit 36 corresponds to the first movement prediction information, the header of the packet is not changed, Proceed to 2010.

  Even when the destination access node ARa cannot be determined by the destination access node determination unit 36, the header of the packet is not changed, and the operation proceeds to step 2010.

  On the other hand, if the destination access node ARa determined by the destination access node determination unit 36 corresponds to the second (or third) movement prediction information, the operation proceeds to step 2008.

  In step 2008, the header changing unit 37 encapsulates the received packet with the encapsulated header having the destination access node ARa as the destination address, and the first (and second) movement prediction information from the relay option header. delete.

  In step 2010, the routing unit 38 routes the packet based on the encapsulation header.

  Thirdly, with reference to FIG. 11, the operation of the access node AR1 according to the present embodiment will be described.

  As illustrated in FIG. 11, in step 3001, the reception unit 51 of the access node AR <b> 1 receives the packet transmitted from the node # 1 and transfers the packet to the transmission unit 54.

  In step 3002, the transmission unit 54 refers to the radio link information management unit 52 and confirms the radio link information related to the destination mobile terminal MN1 of the packet.

  When the wireless link information is “connected (second situation)”, in step 3003, the transmission unit 54 deletes the encapsulation header (see FIG. 5) attached to the packet and is currently connected. The packet is transmitted to the mobile terminal MN1 via the wireless link.

  On the other hand, when the radio link information is “pass (third situation)”, the transmission unit 54 buffers the packet in the buffer 53 in step 3004.

  In step 3005, the movement prediction information correction requesting unit 55 transmits a movement prediction information correction request to the gateway GW.

  In step 3006, the movement prediction information correction requesting unit 55 receives the corrected movement prediction information from the gateway GW. In step 3007, the header conversion unit 57 is buffered based on the corrected movement prediction information. In step 3008, the transmission unit 54 routes and forwards the packet based on the converted header. Here, the packet is forwarded to another access node such as access node # 2, for example.

  If the radio link information is “not arrived (first situation)”, the transmission unit 54 buffers the packet in the buffer 53 in step 3009.

  When detecting that the radio link information has been changed to “connected (second situation)” in step 3010, the transmission unit 54 transmits the packet to the mobile terminal MN1 in step 3003.

  On the other hand, if the buffering time of the packet has passed a predetermined time without changing the wireless link information to “connected (second situation)” in step 3011 (or the wireless link information is “ In a case where the data amount of the packet addressed to the mobile terminal that has not arrived (first situation) exceeds a predetermined threshold value), in step 3012, the transmission unit 54 sends the destination mobile terminal of the packet to the gateway GW Requests correction of movement prediction information related to MN1.

  In step 3013, the estimated arrival time receiving unit 56 receives the estimated arrival time of the destination mobile terminal MN1 from the gateway GW. The transmitter 54 prepares to transmit the packet to the mobile terminal MN1 at the estimated arrival time (step 3003).

  Next, with reference to FIG. 12, the operation | movement which corrects movement prediction information in the radio | wireless communications system which concerns on this embodiment is shown.

  In step 4001, when the radio link information related to the destination mobile terminal MN1 of the packet received from the node # 1 is “pass (third situation)”, the transmission unit 54 of the access node AR1 buffers the packet. At the same time, the gateway GW is requested to correct the movement prediction information corresponding to the destination mobile terminal MN1 of the packet.

  In step 4002, the destination access node determination unit 16 of the gateway GW calculates again the movement prediction information to be inserted into the packet addressed to the destination mobile terminal MN1 in response to the received movement prediction information correction request. In the example of FIG. 12, it is assumed that the movement prediction information corresponding to the access node AR3 is calculated as the first movement prediction information and should be inserted into the packet.

  In step 4003, the movement prediction information management unit 12 of the gateway GW transmits movement prediction information corresponding to the access node AR3 to the access node AR1 as the corrected first movement prediction information.

  In step 4004, the header conversion unit 57 of the access node AR1 adds an encapsulation header with the address of the access node AR3 as the destination address (the address of the access node AR1 is the source address) for the buffered packet. In addition, the movement prediction information corresponding to the access node AR2 is given as the first movement prediction information.

  In step 4005, the transmission unit 54 of the access node AR1 routes and forwards the packet to the accelerator node AR3 based on the above-described encapsulation header.

  In step 4006, the transmission unit 54 of the access node AR3 confirms that the radio link information related to the destination mobile terminal MN1 of the packet received from the access node AR1 is “connected (second situation)”. The packet is transmitted to the destination mobile terminal MN1.

(Operations and effects of the wireless communication system according to this embodiment)
According to the wireless communication system according to the present embodiment, the destination access node determination unit 16 determines the destination access node AR of the packet based on the plurality of movement prediction information, the first transfer time, and the current time. Even when the mobile terminal MN1 moves between cells (areas), the mobile terminal MN1 can transfer the packet to the mobile terminal MN1 without performing location registration again.

  Further, according to the gateway GW according to the present embodiment, the mobile terminal MN1 is present in a region where two cells (areas #n and # n + 1) that are statistically in a poor radio wave condition are overlapped (that is, The destination access node determination unit 16 can prevent packet loss by transferring the packet to the destination access node ARn + 1 instead of the source access node ARn. .

  Also, according to the gateway GW according to the present embodiment, when the access node AR1 managing the cell (area # 1) that the mobile terminal MN1 has already passed through receives a packet addressed to the mobile terminal MN1, the correction is made. Based on the movement prediction information, the packet can be retransmitted to the access node AR3 that manages the cell (area # 3) in which the mobile terminal MN1 exists.

  Further, according to the gateway GW according to the present embodiment, since the mobile terminal MN1 has not yet arrived, the arrival of the mobile terminal MN1 with respect to the access node AR1 buffering a packet addressed to the mobile terminal MN1. The time can be notified.

  Further, according to the node # 1 according to the present embodiment, the destination access node determination unit 36 sets the access node AR2 different from the access node AR1 indicated by the first movement prediction information given to the received packet. By routing the packet, it is possible to flexibly cope with a case where the transfer of the packet is delayed.

  Further, according to the access node AR1 according to the present embodiment, when the mobile terminal MN1 has not yet arrived or has already passed, that is, a radio link has been established with the mobile terminal MN1. In the absence, packet loss can be prevented by buffering packets addressed to the mobile terminal.

  Further, according to the access node AR1 according to the present embodiment, a packet loss is performed by buffering a packet addressed to the mobile terminal MN1 during a transit time when the mobile terminal MN1 passes through an area where the radio wave condition is statistically bad. Can be prevented.

  Also, according to the access node AR1 according to the present embodiment, packet loss can be prevented without wasting buffer capacity by continuing buffering of packets until the received scheduled establishment time.

  Further, according to the access node AR1 according to the present embodiment, when a packet addressed to the mobile terminal MN1 is transferred to the access node AR1 that manages a cell (area # 1) that the mobile terminal MN1 has already passed. Even if it exists, it becomes possible for the transmission part 54 to transfer to the said mobile terminal MN1 without discarding the said packet by routing the packet which is buffering based on the corrected movement prediction information. .

1 is an overall configuration diagram of a wireless communication system according to a first embodiment of the present invention. It is a functional block diagram of the gateway of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the movement prediction information database and required time database of the gateway of the radio | wireless communications system which concern on the 1st Embodiment of this invention. In the radio | wireless communications system which concerns on the 1st Embodiment of this invention, it is a figure for demonstrating the passage time when a mobile terminal passes the area | region where a radio wave condition is statistically bad. It is a figure which shows an example of the packet format used with the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a functional block diagram of the node of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a functional block diagram of the access node of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the content of the radio link information management part of the access node of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the gateway of the radio | wireless communications system which concerns on the 1st Embodiment of this invention. 5 is a flowchart showing an operation of a node of the wireless communication system according to the first embodiment of the present invention. 5 is a flowchart showing an operation of an access node of the wireless communication system according to the first embodiment of the present invention. It is a sequence diagram in case the movement prediction information is corrected in the radio | wireless communications system which concerns on the 1st Embodiment of this invention.

Explanation of symbols

AR ... access node GW ... gateway MN ... mobile terminal 1 ... train 2 ... IP network 11 ... movement prediction information database 12 ... movement prediction information management unit 13, 33 ... required time measuring unit 14, 34 ... required time database 15, 35, 51 ... receiving unit 16, 36 ... destination access node determining unit 17 ... header assigning unit 18, 38 ... routing unit 37, 57 ... header changing unit 52 ... radio link information managing unit 53 ... buffer 54 ... transmitting unit 55 ... movement prediction information Correction requesting unit 56 ... Expected arrival time receiving unit

Claims (3)

An access node that forwards packets to a mobile terminal,
A radio link information storage unit for storing radio link information with the mobile terminal;
When the packet is received, the wireless link information is in a first situation indicating that a wireless link with the mobile terminal has not yet been established, and the wireless link information has already been connected to the wireless link. A buffer for buffering the packet; and
When the wireless link information is a second situation indicating that the wireless link information is being connected, a transfer unit that transfers the packet to the mobile terminal;
When the packet is buffered because the radio link information is in the first situation, a monitoring unit that monitors the buffering time of the packet or the data amount of the buffered packet;
When the buffering time has passed a predetermined time, or when the data amount exceeds a predetermined threshold, time information indicating the time of passing through the area managed by the access node and access node identification information; A correction request transmission unit that transmits a correction request for movement prediction information to associate with the gateway ,
A schedule establishment time receiving unit for receiving a schedule establishment time at which a radio link is established with the mobile terminal from the gateway ;
The scheduled establishment time is determined based on a detection result of identification information of an access node that establishes a radio link with the mobile terminal specified in the modification request and the establishment time of the radio link. The movement prediction information is corrected, calculated based on the corrected movement prediction information,
The access node , wherein the transfer unit prepares to transmit the packet to the mobile terminal at the received scheduled establishment time . An access node that forwards packets to a mobile terminal,
A radio link information storage unit for storing radio link information with the mobile terminal;
When the packet is received, the wireless link information is in a first situation indicating that a wireless link with the mobile terminal has not yet been established, and the wireless link information has already been connected to the wireless link. A buffer for buffering the packet; and
When the wireless link information is a second situation indicating that the wireless link information is being connected, a transfer unit that transfers the packet to the mobile terminal;
When the packet is buffered because the radio link information is in the third situation, time information indicating the time of passing through the area managed by the access node and access node identification information A correction request transmission unit that transmits a correction request for the associated movement prediction information to the gateway ;
A movement prediction information receiving unit for receiving the corrected movement prediction information;
An access node, comprising: a routing unit that assigns the modified movement prediction information to the packet and routes the packet based on the modified movement prediction information. On the basis of the quality of the radio link, the cell is a overlapping and regions statistically poor radio wave condition region, manages the passage time of the mobile terminal passes through the region, between the passage time, the The access node according to claim 1 or 2 , wherein the packet is buffered.

Images