JP2007158538A - Packet transfer system, handover control apparatus and method, and software - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for simply reducing a packet loss and a transmission delay when a mobile station executes handover in a packet communication system employing a protocol in compliance with the Internet protocol. <P>SOLUTION: A handover control apparatus disclosed herein is provided to the mobile station or a base station and used in the packet communication system employing the protocol in compliance with the Internet protocol (IP). The apparatus includes: a means for determining a base station being a handover mobile destination; a means for discriminating a difference between a first IP network to which a mobile source base station and a second IP network to which a mobile destination base station belongs; and a means for selecting at least either of a layer 2 system and a layer 3 system. The layer 2 system is a system wherein a packet is stored and transferred in a layer 2 according to an instruction from the mobile station, and the layer 3 system is a system wherein a packet is stored and transferred in a layer 3 according to the instruction from the mobile station. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a packet transfer system, a handover control apparatus, a handover control method, and software for performing packet communication with a mobile station through a network conforming to the Internet Protocol (IP).

  In a packet communication system compliant with the Internet Protocol (IP), a mobile node (MN: Mobile Node) performs mobile communication throughout the service area by appropriately changing the base station (BS: Base Station) that is a connection point with the Internet. be able to. Therefore, the mobile node (MN) cannot in principle transmit and receive packets until the packet transfer path change processing is completed in addition to the base station change processing in the wireless section, and packets in between May be lost (packet loss). In order to improve packet loss, packet transmission delay, and the like, several techniques have been proposed so far.

  One such technique is to provide an anchor node (AN) with a buffering function in the IP mobility control system. When the mobile station hands off, the anchor node buffers the packet addressed to the mobile station, and transfers the buffered packet to the mobile station through the destination base station after the handoff processing is completed. Specifically, as shown in FIG. 1, it has been proposed that a mobility anchor point (MAP: Mobility Anchor Point) in a hierarchical mobile IPv6 (HMIP) system has such a buffering function. (For example, see Non-Patent Documents 1 and 2.)

  As shown on the left side of FIG. 1, a mobile station (MN) that performs handoff requests a mobility anchor point (MAP) to buffer packets through a base station (not shown) and an access router (AR) (1). . In response to the request, the mobility anchor point (MAP) subsequently buffers packets from the correspondent node (CN) (2). As shown in the right side of FIG. 1, the mobile station (MN) instructs the mobility anchor point (MAP) to cancel buffering, and updates the address correspondence related to the route change to the home agent (HA) (binding update is performed). (3). However, if there is no change in the MAP to which the mobile station belongs, the binding update is not necessary. Thereafter, the packet is transferred to the mobile station (MN) through a base station (not shown) as a handover destination (4). This method of causing the mobility anchor point (MAP) to perform buffering in the IP mobility control method is referred to as “HMIP-B method” for convenience.

Another technique for dealing with problems such as packet loss and packet transmission delay is to perform buffering and transfer of packets at the time of handover at the base station of the movement source (see, for example, Non-Patent Document 3). As shown in FIG. 2, the mobile station first reports the measurement result such as the received signal quality to the base station (1). The base station determines the necessity of handover based on the measurement result, and performs communication for parameter setting with the handover destination base station (movement destination base station) (2). Then, the source base station starts buffering the packet (3). When the mobile station enters a new cell, the mobile station requests the destination base station to transfer the packet (4), and this time the destination base station requests the source base station to transfer the packet ( 5). In response, the source base station transfers the buffered packet to the destination base station (6). Then, a message indicating the binding update is notified to the home agent (HA) (7). This method is already widely used in products on the market, and there are cases where a vendor uniquely implements a wireless LAN access point (AP). This method of buffering and transferring packets at the source base station is referred to as an “inter-base station transfer method” for convenience.
Takahashi, Kobayashi, Okajima, Umeda, "Communication Quality Evaluation of Hierarchical Mobile IPv6 with Buffering Extension", IPSJ Journal, Vol.46, No.2, pp.597-607, February 2005 J. Kempf, et al., “Problem Statement for IP Local Mobility”, draft-kempf-netlmm-nohost-ps-00.txt, June, 2005 Yamashita, Matsuki, Sugawara, Umeda, "Packet transfer between base stations during handover in packet communication systems", IEICE General Conference, B-5-142, March 2003

  FIG. 3A is a diagram for explaining a problem of the HMIP-B system. In the HMIP-B system, packet buffering and transfer at the time of handover are performed by MAP. Therefore, whenever a handover is performed, packets are buffered and transferred by the MAP. For this reason, there are many control signals (signals indicating a buffering request and its cancellation, etc.) accompanying the handover, and there is a problem that the processing load of the MAP is heavy. This problem becomes more serious as the number of mobile stations increases. Further, when the mobile station moves at high speed, the mobile station may enter the destination cell before buffering in the MAP starts. In this case, there is a concern that some packets before the start of buffering are lost (packet loss due to high-speed movement).

  FIG. 3B is a diagram for explaining problems of the inter-base station transfer method. In the inter-base station transfer method, the above problem is solved or alleviated. In this method, packets are transferred from the source base station to the destination base station, so that if they belong to the same IP link, the packet transfer can be executed quickly. However, when base stations before and after the movement of the mobile station belong to different IP links, there is a concern that the packet transfer route becomes complicated and the packet transfer time tends to be long. Further, when the packet transfer path becomes longer, the packet may be transmitted to the destination base station through the new path before the packet transfer from the source base station to the destination base station is completed. In such a case, the time between the packet transferred from the source base station and the packet transferred directly from the upper node to the destination base station without going through the source base station. There is a concern that it is difficult to secure the correct order.

  The present invention has been made to address at least one of the above-mentioned problems, and its problem is to easily reduce packet loss and transmission delay when a mobile station performs handover in a packet communication system compliant with the Internet protocol. It is to provide a packet transfer system, a handover control device, a handover control method, and software for reducing.

  In the present invention, a handover control device provided in a mobile station or a base station is used. This apparatus is used in a packet communication system compliant with the Internet Protocol (IP). The apparatus includes means for determining a handover destination base station, means for determining a difference between a first IP network to which the source base station belongs and a second IP network to which the destination base station belongs, And a means for selecting at least one of the layer 2 method and the layer 3 method. The layer 2 method is a method of storing and transferring packets in layer 2 in accordance with instructions from a mobile station. The layer 3 method is a method for storing and transferring packets in layer 3.

  According to the present invention, it is possible to easily reduce packet loss and transmission delay when a mobile station performs handover in a mobile IP network.

  In various aspects according to the present invention, generally (1) a handover destination of a mobile station is determined, (2) it is determined whether or not the destination base station is on the same IP link as the source base station, A method (layer 2 method or layer 3 method) for performing packet buffering and forwarding is appropriately selected according to the determination result. Proper use of layer 2 and / or layer 3 handover processing not only improves packet loss and transmission delay, but also reduces the probability of packet out-of-order, making it easier to implement more seamless handoffs Can do. When the IP link to which the source base station and the destination base station belong is the same, the layer 2 method is performed, and control signal processing and buffering at the MAP are not essential, so that the processing load on the MAP can be reduced. In the case of the layer 2 system, the probability of occurrence of packet loss is low even if high-speed movement is performed. On the other hand, when each base station belongs to a different IP link, the layer 3 method is performed, and it is not necessary to transfer a packet through a complicated propagation path from the source base station to the destination base station. Delay can be reduced. Also, since the MAP is the only node that forwards packets to the destination base station, the problem of packet order error is unlikely to occur (in the case of the layer 2 method, both the source base station and the MAP are temporary, although temporary) May transfer packets to the destination base station at the same time.)

  In the first embodiment of the present invention, both the processes (1) and (2) are performed at the mobile station. In the first mode, the mobile station determines a destination base station (Target Base Station) from the broadcast information of neighboring base stations. Further, the mobile station acquires prefix information of an access router higher than the base station from the broadcast information, and determines whether the base stations before and after the movement belong to the same IP link based on the prefix information. If they belong to different IP links, it is also determined what the mobility anchor point (MAP) is connected to both IP links. Depending on the determination result, it is determined whether packet buffering and forwarding are performed by the MAP (layer 3) or the base station (layer 2) connected to both IP links. In this embodiment, the mobile station performs both the determination of the destination base station and the determination of the packet buffering and transfer method. As a result, packet loss and transmission delay during handover can be easily reduced, and in addition, changes to the base station and higher-level devices and networks can be reduced when implementing the present invention.

  Typically, the base station performs layer 2 processing, and a higher-order node, router, mobility anchor point, or the like other than the base station performs layer 3 processing. However, names such as base stations, nodes, routers, mobility anchor points, etc. are not strictly distinguished as hardware, and in some cases, both layer 2 and layer 3 processing may be performed with the same hardware. .

  In the second mode of the present invention, both (1) and (2) are performed at the source base station. In the second mode, triggered by a handover request from a mobile station, a source base station (also referred to as a source base station) acquires information about neighboring base stations using a backbone network (eg, backbone), etc., and performs handover. Necessity and the destination base station are determined. Further, the source base station determines whether or not the destination base station belongs to the same IP link as itself based on prefix information of an access router higher than the neighboring base station. Depending on the determination result, it is determined whether packet buffering and forwarding are performed in layer 3 or layer 2. In this embodiment, the source base station performs both the determination of the destination base station and the determination of the packet buffering and transfer method. As a result, the present invention can be realized only by changing the operator side without changing the device configuration and processing contents of the mobile station. This may be particularly advantageous when the number of mobile stations is very large.

  In the third embodiment of the present invention, the process (1) is performed by the mobile station, and the process (2) is performed by the source base station. In the third mode, the mobile station determines the destination base station from the notification information of the neighboring base station, and notifies the source base station of the destination base station. The source base station obtains access router prefix information from the destination base station determined by the mobile station, and based on the information, whether the destination base station belongs to the same IP link as itself Determine. Depending on the determination result, it is determined whether packet buffering and forwarding are performed in layer 3 or layer 2. In this embodiment, the destination base station is determined by the mobile station, but the packet buffering and forwarding method is determined by the source base station. Thereby, the processing function regarding this invention can be distributed to both a base station and a mobile station.

  In the following, several embodiments relating to the present invention will be described by way of example. The embodiment will be described with reference to a functional block diagram as necessary. The functional units in the figure may be realized as hardware, software, or both. The software is stored in the storage device of the mobile station, base station or both.

  FIG. 4 shows a functional block diagram of a mobile station according to an embodiment of the present invention. The mobile station has a transceiver 41, a processing device 42, and a storage device 43. The processing device 42 includes a movement destination candidate base station information acquisition function unit 421, a movement destination base station determination function unit 422, a prefix information acquisition function unit 423, a movement pattern determination function unit 424, and a method selection function unit. 425, a method execution function unit 426, a destination base station determination request function unit 427, and a destination base station information notification function unit 428.

  The destination candidate base station information acquisition function unit 421 acquires broadcast information including base station configuration information and radio resource information from neighboring base stations. These neighboring base stations are candidates for handover destinations. The notification information is stored in the storage device 43.

  The destination base station determination function unit 422 measures the reception quality of signals from neighboring base stations, and determines a destination base station (target base station) when handing over.

  The prefix information acquisition function unit 423 acquires prefix information of an access router existing above the neighboring base station. Prefix information can be extracted from broadcast information broadcast from each base station.

  Based on the prefix information, the movement pattern determination function unit 424 determines whether the movement source base station and the movement destination base station are in the same IP link, and moves the movement pattern of the mobile station (the same IP link). Or handover over different IP links).

  Based on the determination result of the movement pattern, the method selection function unit 425 determines whether to perform buffering and forwarding of packets associated with handover at the mobility anchor point (at layer 3) or at the base station (at layer 2). decide.

  The method execution function unit 426 sets various parameters so that packets are buffered and transferred according to the determined method.

  The destination base station determination request function unit 427 requests the source base station to determine the destination base station for handover, but this function is not used in the first and third embodiments. Used in examples.

  The destination base station information notification function unit 428 notifies the source base station of information related to the destination base station determined by the mobile station.

  FIG. 5 shows a functional block diagram of a base station according to an embodiment of the present invention. The base station 50 includes a transceiver 51, a processing device 52, and a storage device 54. The processing apparatus includes a base station information notification function unit 521, a prefix information notification function unit 522, a movement destination base station determination request reception function unit 523, a movement destination candidate base station information acquisition function unit 524, and a movement destination base station determination. A function unit 525, a prefix information acquisition function unit 526, a movement pattern determination function unit 527, a method selection function unit 528, a method execution function unit 529, and a destination base station information acquisition function unit 530 are further included. The function units after the destination base station determination request reception function unit 523 are not so important in the first embodiment, and they are mainly used in the second embodiment.

  The base station information notification function unit 521 performs processing for notifying its subordinate mobile stations of its configuration information and radio resource information as broadcast information. Information necessary for the notification information is stored in the storage device 54.

  The prefix information notification function unit 522 includes the prefix information of the access router existing above itself in the broadcast information. The prefix information can be acquired from a router advertisement (RA) received from a higher-order access router. As an example, the prefix information is expressed by the upper 64 bits in a 128-bit IPv6 address.

  The destination base station determination request receiving function unit 523 receives a message requesting to determine a handover destination base station from the mobile station, and gives a trigger for performing the destination determination process to the related function unit.

  The destination candidate base station information acquisition function unit 524 acquires information on neighboring base stations that are destination candidates through, for example, a backbone network (backbone).

  The movement destination base station determination function unit 525 determines the movement destination base station based on the request from the mobile station and information on the neighboring base stations.

  The prefix information acquisition function unit 526 acquires the prefix information of the access router existing above the neighboring base station from the information obtained from the neighboring base station.

  Based on the prefix information, the movement pattern determination function unit 527 determines whether the movement source base station and the movement destination base station are in the same IP link, and determines the movement pattern of the mobile station.

  Based on the movement pattern determination result, the method selection function unit 528 determines whether to perform buffering and forwarding of packets associated with handover at the mobility anchor point (at layer 3) or at itself (at layer 2). To do.

  The method execution function unit 529 sets various parameters so that packets are buffered and transferred in the determined method.

  The destination base station information acquisition function unit 530 communicates with the base station determined as the destination among the destination candidates to prepare for transferring the buffered packet to the destination base station ( Parameter setting).

  Hereinafter, an operation according to an embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows an operation example of the mobile station, FIG. 7 shows an operation example of the base station, and FIG. 8 shows an overall view for explaining the operation. As shown in FIG. 6, the mobile station in the present embodiment receives broadcast information from neighboring base stations in step S11. The broadcast information includes base station configuration information, radio resource status, and the like.

  In step S2, the mobile station determines whether or not a handover is necessary, and determines the destination base station when the handover is performed. For example, a base station with good transmission quality and sufficient radio resources may be determined as the destination.

  On the other hand, in step S12, the mobile station acquires the access router prefix information from the broadcast information.

  In step S3, it is determined based on the prefix information whether the source base station (currently connected base station) and the destination base station belong to the same IP link. If one base station can communicate with the other base station without going through the AR above the IP link (local IP network) to which it belongs, both IP links are equal. However, if one base station cannot communicate with the other base station without passing through the MAP on the upper side of the IP link to which the base station belongs, the two IP links are different. More specifically, the difference between the IP links can be determined using the prefix information of the access router above the base station. Specifically, the prefix information of the host device (access router) of the source base station and the prefix information of the host device of the destination base station are compared, and if they match, they belong to the same IP link. Otherwise, it belongs to a different IP link. In accordance with such a determination result, the mobile station determines whether to perform buffering and forwarding of packets associated with handover at the mobility anchor point (at layer 3) or at the source base station (at layer 2). To do.

  Note that the difference in IP links may be partially matched in addition to completely matching or completely different. For example, the source base station belongs only to IP link A, but the destination base station may belong to both IP link A and IP link B. In such an IP link difference determination, priority may be given to being the same or priority may be given to being different, and it is only necessary to make some arrangement in advance regarding the difference determination.

  In step S41, processing is performed in the case where buffering and forwarding of packets accompanying handover are performed at the mobility anchor point (at layer 3). In order for this to happen, the mobile station sends an execution request message to the source base station. The execution request message includes content for requesting buffering to the mobility anchor point. In the case of HMIP-B, a binding update message with a buffering request flag set is transmitted to the MAP.

  In step S42, processing is performed in the case where packet buffering and transfer accompanying handover are performed at the source base station (at layer 2). Also in this case, the mobile station transmits an execution request message to the source base station.

  In step S5, the selected method is actually executed, and a handover process with less packet loss and transmission delay is performed.

  In the example shown in FIG. 6, buffering and forwarding at layer 3 and buffering and forwarding at layer 2 are performed alternatively according to the determination result of step S <b> 3. However, this is only for the purpose of simplifying the description, and packet buffering and forwarding may be performed using not only one of the two methods but also both.

  Table 1 below shows an example of a combination of methods for buffering and forwarding packets.

選択例１では、移動先基地局が移動元基地局と同一のＩＰリンクに属していた場合にはレイヤ２のバッファリング及び転送方式が使用され、移動先基地局が異なるＩＰリンクに属していた場合にはレイヤ３のバッファリング及び転送方式が使用される。この選択例は最も原則的であり、図６で説明されたものに相当する。

In Selection Example 1, when the destination base station belongs to the same IP link as the source base station, the layer 2 buffering and transfer method is used, and the destination base station belongs to a different IP link. In some cases, layer 3 buffering and forwarding schemes are used. This selection example is the most fundamental and corresponds to that described in FIG.

  When the destination base station belongs to the same IP link as the source base station, the layer 2 buffering and transfer method is used, and when the destination base station belongs to a different IP link, the layer 3 This buffering and transfer method is common to the selection examples 1, 2, and 3. However, in selection example 2, when the destination base station belongs to a different IP link, not only layer 3 but also layer 2 buffering and transfer methods are used together. As described above, in the layer 3 method, since packet buffering is performed at the mobility anchor point (MAP), if the mobile station moves to the next cell before the buffering is started, some packet is transmitted. There is a risk of loss. By using the layer 2 method together as in selection example 2, the occurrence of such packet loss can be suppressed. Further, in the selection example 3, when the destination base station belongs to the same IP link as the source base station, not only the layer 2 but also the buffering and transfer method of the layer 3 are used together. As described above, with the layer 2 method alone, there is a possibility that the order of the packet transferred via the source base station and the packet transferred directly without going through the source base station may be disturbed. In the selection example 3, both methods are used together, and after the packet transfer from the source base station to the destination base station is completed, the buffering at the MAP is canceled and the packet is transferred along the new route. The function of ensuring the packet order can be strengthened. Although not explicitly shown in Table 1, from the viewpoint of supporting the handover fairly reliably, both the layer 2 method and the layer 3 method may always be performed regardless of the difference in the IP link. .

  FIG. 7 is a flowchart showing an operation example of the base station according to one embodiment of the present invention. In step S1, the base station includes configuration information, radio resource usage, and the like in the broadcast information. In step S2, the base station includes the prefix information of the upper access router in the broadcast information. In step S3, a broadcast message including broadcast information is broadcast to subordinate mobile stations. The order of steps S1 and S2 may be changed or may be performed simultaneously. The prefix information may be transmitted as it is, or information with a small number of bits equivalent to the prefix information may be transmitted.

  The operation will be further described with reference to FIG. Processing related to the handover of the two left and right mobile stations (MN-1, MN-2) will be described. First, the mobile station uses the broadcast information from each base station to determine the necessity of handover and the destination base station (target BS) (1-1, 2-1). The mobile station determines whether the source BS and the target BS belong to the same IP link based on the prefix information included in the broadcast information (1-2, 2-2).

  Taking the mobile station (MN-1) on the left as an example, AR1 (2000: 12: 21/64), AR2 (2000: 12: 22/64) are placed above the source BS and target BS of this mobile station. And three access routers indicated by AR3 (2000: 12: 23/64) exist in common in both base stations. Therefore, the source BS and the target BS belong to the same IP link. On the other hand, in the case of the right mobile station (MN-2), AR1 (2000: 12: 21/64), AR2 (2000: 12: 22/64), and AR3 (2000) are placed above the source BS. : 12: 23/64), there are three access routers, but AR4 (2000: 12: 31/64), AR5 (2000: 12: 32/64), and AR6 are above the target BS. There are three other access routers indicated by (2000: 12: 33/64). Therefore, the source BS and the target BS belong to different IP links.

  When the IP link to which the target BS belongs is determined, an appropriate buffering and transfer method is performed according to the determination result (1-3, 2-3). In the illustrated example, the layer 2 scheme is adopted for one mobile station (MN-1), buffering is performed at the source BS, and packets are transferred from the source BS to the target BS. For the other mobile station (MN-2), the layer 3 method is adopted, buffering is performed by the MAP, and the packet is transferred from the MAP to the target BS.

  9A, 9B, and 9C show usage examples of prefix information of the access router. In the example shown in FIG. 9A, the prefix information of each of the three access routers is included in the broadcast information as it is. In the illustrated example, the broadcast information includes three prefix information of 2000: 12: 21/64, 2000: 12: 22/64, 2000: 12: 23/64. If each prefix information is expressed by 64 bits, three times (64 × 3) bits are occupied in the broadcast information. In the example shown in FIG. 9B, identification information is associated with each of the three prefix information, and the identification information is included in the broadcast information instead of the prefix information itself. In the example shown, 2000: 12: 21/64, 2000: 12: 22/64, 2000: 12: 23/64 are converted to ID: 1, ID: 2 and ID: 3, respectively. : 2, ID: 3 is included in the broadcast information. Assume that the correspondence relationship, conversion rule, or mapping relationship between prefix information and identification information is known by the mobile station. In this way, the number of bits occupied by prefix information in broadcast information can be saved. In the example shown in FIG. 9C, a portion (minimum common prefix information) common to prefix information of the upper access router is calculated by the base station as a link ID, and is included in the broadcast information. In the illustrated example, the link ID is 2000: 12 :: / 64, which is included in the broadcast information (for example, J. Choi, et al., “DNA Solution: Link I dentifier based approach”, draft-jinchoi-dna-protocol2-01.txt, June, 2005.) According to this example, the number of bits for prefix information can be reduced as compared with the case of FIG. 9A, and there is no need to notify or prepare the mapping relationship in advance as in the case of FIG. 9B. . The minimum common prefix information can be obtained by referring to the router advertisement (RA) (for example, T. Narten, et al., “Neighbour Discovery for IP version 6 (IPv6)”, Request For Comments 2461, December, 1998).

  In the first embodiment, both the determination of the destination base station and the determination of the packet buffering and transfer method are performed by the mobile station. In the second embodiment described below, both of them are performed at the source base station. Therefore, in this embodiment, the mobile station mainly uses the destination base station determination request function unit 427 of FIG. 4, and the source base station mainly uses the various function units 521 to 530 of FIG.

  Hereinafter, the operation according to the second embodiment will be described with reference to FIGS. FIG. 10 shows an operation example of the mobile station, FIG. 11 shows an operation example of the base station, and FIG. 12 shows an overall view for explaining the operation. As shown in FIG. 10, the mobile station performs handover when the reception quality of the signal from the source base station falls below a threshold, or when another base station that provides better reception quality is found. Is confirmed and notified to the source base station (handover is requested). The mobile station may include information on neighboring base stations measured by itself in the handoff request message and notify the source base station of the information.

  As shown in FIG. 11, the base station in this embodiment receives a handover request message from the mobile station in step S1. When the information on the neighboring base station measured by the mobile station is described in this message, the neighboring base station may be a candidate for the handover destination base station.

  In step S21, the base station acquires configuration information and radio resource information of neighboring base stations via a backbone network or the like.

  In step S3, the base station of the handover destination is determined based on the information obtained from the neighboring base stations. The source base station may notify the base station determined as the destination at this time.

  On the other hand, in step S22, the source base station acquires prefix information of the access router existing above the base station that is the destination candidate. This information can also be acquired through a backbone network or the like. For the prefix information, some methods described in relation to FIGS. 9A, 9B, and 9C and other methods may be used. Prefix information is typically obtained from router advertisements (RA) from higher routers.

  In step S3, it is determined based on the prefix information whether the source base station (self) and the destination base station belong to the same IP link. Specifically, the prefix information of its host device (access router) and the prefix information of the host device of the destination base station are compared, and if they match, they belong to the same IP link, otherwise they are different. It belongs to the IP link. Depending on the determination result, whether the source base station performs buffering and forwarding of packets associated with handover at the mobility anchor point (at layer 3) or at the source base station (at layer 2) To decide.

  In step S51, processing is performed in the case where buffering and forwarding of packets accompanying handover are performed at the mobility anchor point (at layer 3). The source base station requests buffering from the mobility anchor point. In the case of HMIP-B, a binding update message with a buffering request flag set is transmitted to the MAP.

  In step S52, processing is performed in the case where packet buffering and transfer accompanying handover are performed at the source base station (at layer 2). For example, the source base station transmits an execution start request message to the destination base station.

  In step S6, the selected method is actually executed, and a handover process with less packet loss and transmission delay is performed.

  The operation will be further described with reference to FIG. Processing related to the handover of the two left and right mobile stations (MN-1, MN-2) will be described. First, the mobile station transmits a handover request (HO request) to the source base station (source BS) (1-1, 2-1). The source BS acquires information on neighboring base stations (neighboring BS information) (1-2, 2-2). The neighbor BS information includes prefix information. The source BS determines a destination base station (target BS) based on neighboring BS information (1-3, 2-3). Based on the prefix information, it is determined whether the source BS and the target BS belong to the same IP link (1-4, 2-4). In the case of the mobile station (MN-1) on the left side in the figure, the source BS and the target BS belong to the same IP link. On the other hand, in the case of the right mobile station (MN-2), the source BS and the target BS belong to different IP links. If the IP link to which the target BS belongs is determined to be different, an appropriate buffering and transfer method is performed according to the determination result (1-5, 2-5). In the illustrated example, the layer 2 method is adopted for one mobile station (MN-1), the layer 3 method is adopted for the other mobile station (MN-2), and buffering is performed at the MAP. The packet is transferred from the MAP to the target BS.

  In the first embodiment, both the determination of the destination base station and the determination of the packet buffering and transfer method are performed by the mobile station. In the second embodiment, both of them are performed at the source base station. In the third embodiment described below, the destination base station is determined by the mobile station, and the packet buffering and the transfer method are determined by the source base station. Accordingly, the mobile station mainly uses the destination candidate base station information acquisition function unit 421, the destination base station determination function unit 422, and the destination base station information notification function unit 428 of FIG. The stations mainly include a base station information notification function unit 521, a destination base station information acquisition function unit 530, a prefix information acquisition function unit 526, a movement pattern determination function unit 527, a method selection function unit 528, and a method execution function unit 529 of FIG. Used for.

  Hereinafter, the operation according to the third embodiment will be described with reference to FIGS. FIG. 13 shows an operation example of the mobile station, FIG. 14 shows an operation example of the base station, and FIG. 15 shows an overall diagram for explaining the operation. As shown in FIG. 13, the mobile station receives broadcast information from neighboring base stations in step S1. The broadcast information includes base station configuration information, radio resource status, and the like.

  In step S2, the mobile station determines whether or not a handover is necessary, and determines the destination base station when the handover is performed.

  In step S3, the mobile station notifies the movement-source base station of the movement-destination base station and related information.

  FIG. 14 shows an operation example of the base station. In step S1, the source base station includes configuration information, radio resource usage, and the like in the broadcast information. In step S2, the source base station broadcasts a notification message including notification information to subordinate mobile stations. In step S3, the source base station acquires information on the destination base station determined by the mobile station from the mobile station. In step S4, the source base station acquires prefix information of the access routers higher than the source and destination base stations. For the prefix information, some methods described in relation to FIGS. 9A, 9B, and 9C and other methods may be used. Prefix information is typically obtained from router advertisements (RA) from higher routers. Steps S5, S61, S62, and S7 are the same as those in the already described flow of FIG. 11 (S4, S51, S52, and S6), and thus redundant description is omitted.

  The operation will be further described with reference to FIG. Processing related to the handover of the two left and right mobile stations (MN-1, MN-2) will be described. First, the mobile station determines a destination base station (target BS) based on the broadcast information (1-1, 2-1). The mobile station notifies the information on the determined target BS to the source base station (source BS) (1-2, 2-2). The source BS acquires prefix information of the access routers higher than itself and the target BS (1-3, 2-3). Based on the prefix information, the source BS determines whether the source BS and the target BS belong to the same IP link (1-4, 2-4). In the case of the mobile station (MN-1) on the left side in the figure, the source BS and the target BS belong to the same IP link. On the other hand, in the case of the right mobile station (MN-2), the source BS and the target BS belong to different IP links. If the IP link to which the target BS belongs is determined to be different, an appropriate buffering and transfer method is performed according to the determination result (1-5, 2-5). In the illustrated example, the layer 2 method is adopted for one mobile station (MN-1), and the layer 3 method is adopted for the other mobile station (MN-2).

It is FIG. (1) which shows the conventional system which performs buffering and transfer of a packet. FIG. 6 is a diagram (part 2) illustrating a conventional method for buffering and transferring a packet; It is a figure for demonstrating the problem of the conventional system of FIG. It is a figure for demonstrating the problem of the conventional system of FIG. It is a functional block diagram of the mobile station by one Example of this invention. FIG. 3 is a functional block diagram of a base station according to an embodiment of the present invention. 5 is a flowchart illustrating an example of operation of a mobile station according to an embodiment of the present invention. 5 is a flowchart illustrating an operation example of a base station according to an embodiment of the present invention. It is a general view for explaining the operation according to an embodiment of the present invention. It is a figure which shows the usage example of the prefix information of an access router. It is a figure which shows the usage example of the prefix information of an access router. It is a figure which shows the usage example of the prefix information of an access router. 5 is a flowchart illustrating an example of operation of a mobile station according to an embodiment of the present invention. 5 is a flowchart illustrating an operation example of a base station according to an embodiment of the present invention. It is a general view for explaining the operation according to an embodiment of the present invention. 5 is a flowchart illustrating an example of operation of a mobile station according to an embodiment of the present invention. 5 is a flowchart illustrating an operation example of a base station according to an embodiment of the present invention. It is a general view for explaining the operation according to an embodiment of the present invention.

Explanation of symbols

AR access router BU binding update CN communication partner node HA home agent MAP mobility anchor point MN mobile node BS base station 41 transceiver; 42 processing device; 43 storage device 421 destination candidate base station acquisition function unit 422 destination destination base station determination function Unit 423 prefix information acquisition function unit 424 movement pattern determination function unit 425 method selection function unit 426 method execution function unit 427 movement destination base station determination request function unit 428 movement destination base station information notification function unit 51 transceiver; 52 processing device; 54 Storage Device 521 Base Station Information Notification Function Unit 522 Prefix Information Notification Function Unit 523 Target Destination Base Station Determination Request Reception Function Unit 524 Target Destination Base Station Information Acquisition Function Unit 525 Target Destination Base Station Determination Function Unit 526 Prefix Broadcast acquisition module 528 mode selecting function unit 529 system executing function unit 530 the target base station information acquisition function unit

Claims (9)

A handover control device used in a packet communication system compliant with the Internet Protocol (IP) and provided in a mobile station or a base station,
Means for determining a handover destination base station;
Means for determining the difference between the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs;
Means for selecting at least one of the layer 2 method and the layer 3 method according to the determination result;
The layer 2 method is a method for storing and transferring packets in layer 2 in accordance with instructions from a mobile station, and the layer 3 method is a method for storing and transferring packets in layer 3 A handover control device. The handover control apparatus according to claim 1, wherein the determination unit determines whether the IP address prefix information related to the first IP network is different from the IP address prefix information related to the second IP network. The handover control apparatus according to claim 2, wherein the prefix information is notified to a mobile station or a base station as identification information encoded so as to be expressed by a smaller number of bits. The handover control apparatus according to claim 2, wherein information common to a plurality of prefix information is derived, and the derived information is notified to a mobile station or a base station. A packet communication system compliant with the Internet Protocol (IP) having a mobile station and a plurality of base stations, the mobile station comprising:
Means for determining a handover destination base station;
Means for determining the difference between the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs;
Means for selecting at least one of the layer 2 method and the layer 3 method according to the determination result;
The layer 2 method is a method in which the base station performs packet accumulation and transfer in layer 2 in accordance with instructions from a mobile station, and the layer 3 method is a method in which packet accumulation and transfer is performed in layer 3. A packet communication system characterized by being. A packet communication system compliant with the Internet Protocol (IP) having a mobile station and a plurality of base stations, wherein the mobile station has means for determining whether or not handover is necessary,
Means for determining a handover destination base station in response to a request from a mobile station;
Means for determining the difference between the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs;
Means for selecting at least one of the layer 2 method and the layer 3 method according to the determination result;
The layer 2 method is a method for storing and transferring packets in layer 2 in accordance with instructions from a mobile station, and the layer 3 method is a method for storing and transferring packets in layer 3 A packet communication system. A packet communication system compliant with the Internet Protocol (IP) having a mobile station and a plurality of base stations,
The mobile station has means for determining a handover destination base station;
The handover source base station determines the difference between the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs, and the layer 2 system and the layer according to the determination result Means for selecting at least one of the three methods,
Packet communication characterized in that the layer 2 method is a method of storing and forwarding packets in layer 2 in accordance with instructions from a mobile station, and the layer 3 method is a method of storing and forwarding packets in layer 3 system. A handover control method used in a mobile station or a base station of a packet communication system compliant with the Internet Protocol (IP),
Determining a handover destination base station; and
Determining whether the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs;
Selecting at least one of the layer 2 method and the layer 3 method according to the determination result;
The layer 2 method is a method for storing and transferring packets in layer 2 in accordance with instructions from a mobile station, and the layer 3 method is a method for storing and transferring packets in layer 3 A handover control method. Software used in a packet communication system compliant with the Internet Protocol (IP),
Determining a handover destination base station; and
Determining whether the first IP network to which the source base station belongs and the second IP network to which the destination base station belongs;
Selecting at least one of the layer 2 method and the layer 3 method according to the determination result;
The layer 2 method is a method for storing and forwarding packets in layer 2 in accordance with instructions from the mobile station, and the layer 3 method is for storing and forwarding packets in layer 3 Software characterized by the method.

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