JP4800410B2 - Mobile station, base station, and radio communication system including these - Google Patents

Description

The present invention relates to a mobile station to enable seamless wireless communication using IP multicast, it relates to a radio communication system having a base station and these.

Conventionally, in the case of a wireless communication system composed of a plurality of mobile stations and a plurality of base stations as a wireless communication system, a connection-type data link layer represented by ARIB STD T70 (broadband mobile access system HiSWANa) is used. A wireless communication system has been developed.

FIG. 15 is a system configuration diagram of a wireless communication system having a connection type data link layer.
The wireless communication system shown in the figure includes a base station 1500, a mobile station 1501, and a physical link 1506. The physical link 1506 includes a broadcast link 1502, a unicast link 1503, a multicast link A (1504), and a multicast link B (1505).

FIG. 16 is a configuration diagram illustrating one configuration example of a mobile station in a conventional wireless communication system.
A mobile station 1501 of the wireless communication system shown in FIG. 1 includes a CPU 1601 that controls the whole, a wireless communication unit 1603 that is controlled by the CPU 1601, and a display unit 1602 that is connected to the CPU 1601.

  As shown in FIG. 15, the connection-type data link layer includes a physical link 1506 between a mobile station 1501 and a base station 1500, and a broadcast link 1502, unicast link 1503, It means a data link layer characterized in that a plurality of independent logical links can be established for each link type such as multicast link A (1504) and multicast link B (1505).

  The broadcast link 1502 is a one-way link from the base station 1500 to a plurality of mobile stations 1501, and data flowing using this link can be received by all the mobile stations 1501 accessing the base station 1500. The unicast link 1503 is a bidirectional link between one base station 1500 and one mobile station 1501, and only the base station and mobile station that have established this link can transmit and receive data. Furthermore, multicast link A (1504) and multicast link B (1505) are unidirectional links from base station 1500 to a plurality of mobile stations 1501, and data flowing using these links is received only by specific mobile stations. it can.

FIG. 17 is a system configuration diagram of IP multicast.
As a method for simultaneously distributing the same data to a plurality of terminals on an Internet protocol (IP) network, there is an Internet protocol (IP) multicast. In this IP multicast, when a terminal transmits an IP packet destined for an IP multicast address whose upper 4 bits are 1110 (hereinafter referred to as “IP multicast packet”), it passes through a plurality of routers. Is a protocol that allows all terminals receiving the IP multicast address to receive the packet simultaneously.

In addition, the management protocol based on Internet Group Management Protocol (RFC2236) is defined for this IP multicast by IETF (Internet Engineering Task Force).
Specifically, as shown in FIG. 17, the server 1700 first transmits an IP multicast packet in the IP network 1701. On the other hand, a terminal that wants to receive IP multicast (here, referred to as terminal 1703) transmits a request to join an IP multicast address to be received (IGMP Group Join message (see FIG. 7 described later)) to router 1702. . As a result, the router 1702 transfers the IP packet of the designated IP multicast address to the lower network, so that the terminal 1703 can receive the desired IP multicast packet. When stopping the reception of the IP multicast packet, the terminal 1703 transmits a request to leave the IP multicast address (IGMP Group Leave message, see FIG. 8) to the upper router 1702. As a result, the upper router 1702 inquires the subordinate terminals 1704 and 1705 as to whether or not it has joined the multicast group to be removed, and if there is no response, transfers the IP packet of the designated IP multicast address. Stop.

Further, MobileIP has been proposed as a method for providing continuous communication for a mobile node (MN) moving on a network having a different network address (hereinafter referred to as a subnet) on an IP network. This is because even if the MN moves between subnets and the IP address assigned by the router changes, the communication between the MN, HA (Home Agent) and CN (Corresponendent Node) is negotiated. It is characterized by being able to continue. There are MobileIPv4 made for IPv4 and MobileIPv6 made for IPv6, and the operation procedure is different, but MobileIPv6 will be described below.

FIG. 18 is a system configuration diagram of MobileIPv6.
In FIG. 18, it is assumed that the MN 1805 starts unicast communication with the CN 1800 via the router 1802. Here, when the MN 1805 moves while continuing the communication session and moves to the position of the MN ′ 1806, first, an IPv6 address is assigned from the router 1803, so that the MN 1805 has an IPv6 address prefix currently in use. Knows that they are different and detects that they have moved to a different network. Next, the MN 1805 notifies the HA 1804 and CN 1800 of the newly assigned IPv6 address. Recognizing that the address has changed, CN 1800 and HA 1804 continue to transmit packets for MN 1805 to MN ′ 1806. In subsequent communication, route optimization control based on the transmission source address of the transmission packet of MN ′ 1806 works, and direct communication between CN 1800 and MN ′ 1806 is performed. The above is the operation details of MobileIPv6. When the MN moves, the above processing is always executed.

  As a conventional technique corresponding to a mobile station, for example, Patent Document 1 proposes a seamless data reception method by paying attention to the fact that a destination address of a multicast address is used in common among many hosts. Yes. Specifically, as shown in FIG. 19, an IP multicast address is dynamically or statically assigned to the mobile station 1908, and the server 1900 transmits the data for the mobile station 1908 as an IP multicast packet (Patent Document 1). reference.). According to this method, the mobile station 1908 requests the source base station 1905 to transfer the IP multicast packet to the destination base station 1906 immediately before switching the connected base station. Even after moving to the new base station 1906, data can be received from the server 1900 continuously.

JP 2003-37626 A

Internet Group Management Protocol Version 2 (RFC2236)

  By the way, the above-described wireless communication system including a plurality of mobile stations having a connection type data link layer and a plurality of base stations has the following problems. A case will be considered below wherein the mobile station performs seamless data reception by IP multicast such as streaming video reception while moving between a plurality of base stations.

  In this case, if a mobile station such as a mobile phone or a personal digital assistant moves and communication with the currently connected base station is interrupted due to deterioration of the radio wave environment, the mobile station immediately Detecting and attempting reconnection processing to a new base station (hereinafter, this processing is referred to as handover processing). Specifically, referring to FIG. 19, when the mobile station 1908 loses connection with the base station 1905, the mobile station 1908 searches for a neighboring base station, and when a new base station 1906 is found, Association processing will be performed.

  However, in order to actually continue seamless data reception by IP multicast, the mobile station 1908 maintains the unicast link, broadcast link, and multicast link connected to the base station 1905 even in the new base station. It is necessary to reconnect each link to the base station 1906. However, the ARIB STD T70 has a problem that it does not define the continuation of the link after the handover.

  Furthermore, even if the unicast link, the broadcast link, and the multicast link are reconnected at the data link layer after the handover process, the router to which the base station 1906 is connected determines the IP multicast address to which the base station 1905 was connected. There is no guarantee that data is being transferred, and when the mobile station 1908 moves the connection to the base station 1906, there is a high possibility that the IP multicast data received up to that point cannot be received.

  On the other hand, in the above-mentioned MobileIP, when a MN receiving an IP multicast moves, an IP tunnel (described later) is established between the HA and the destination MN as a method of seamlessly receiving data, and the received IP A method for forwarding a multicast packet to the MN via the IP tunnel has been proposed. Here, the IP tunnel means that an IP header addressed to the node B is added to the head of the IP packet received by the node A between the node A and the node B, and at the head of the IP packet received by the node B. This is a technique for establishing a virtual bidirectional link between node A and node B that are not directly connected by adding an IP header addressed to node A.

  However, when considering application to a wireless communication system having a connection-type data link layer, there is a problem that it is necessary to reconnect the unicast link. In addition, IP multicast originally is an effective means for reducing traffic when there are many terminals that receive the same data at the same time. There was a problem of becoming.

  Note that the technology disclosed in Japanese Patent Laid-Open No. 2003-37626 is a wireless communication system in which the target wireless communication system has a connectionless data link layer represented by IEEE 802.11b, and this is expressed as ARIB STD T70. In the case of application to a wireless communication system having a simple connection type data link layer, since the maintenance of the multicast link is not guaranteed after the mobile station moves to another base station, seamless IP multicast reception is actually performed. There was a problem that it could not be done.

The present invention has been made in view of such problems in the conventional wireless communication system, and in a wireless communication system having a connection type data link layer, a mobile station is receiving an IP multicast packet. provided in each case of switching the connection to the different base stations, without the application add any changes, the mobile station capable of performing seamless data reception, the base station and a radio communication system having these For the purpose.

The present invention has been made to solve the above-described problems, and is connected to an IP network through a router connected to the base station in a wireless communication system capable of wireless communication between a mobile station and a base station In addition, a physical link provided for each base station has a connection type data link layer capable of independently establishing a multicast link of a unidirectional link identified by a connection identifier and a unicast link of a bidirectional link , From the first base station connected to the first router and having one or more multicast links established, to the second base station connected to the second router and not forwarding IP multicast packets, the IP A mobile station that performs handover while receiving a multicast packet ,
When handing over from the first base station to the second base station, the second base station is requested to connect and the unicast link is established with the second base station. Means for requesting the second router to forward the received IP multicast packet to the second base station via the unicast link; and And means for establishing between the base station and the base station .

The present invention provides a wireless communication system capable of wireless communication between a mobile station and a base station, connected to an IP network via a router, and a connection identifier in a physical link provided between the mobile station and the mobile station. A base station having a connection-oriented data link layer capable of independently establishing a multicast link of a unidirectional link and a unicast link of a bidirectional link,
An IP address database storing the mobile station identification number assigned to the mobile station and the IP multicast address received by the mobile station in association with each other, and an IP multicast packet of the IP multicast address for the mobile station When the last mobile station that has received the IP multicast packet stops receiving the IP multicast packet based on the IP address database, the router connected to the local station And means for requesting to stop the transfer of the multicast packet.

  The present invention also includes the mobile station, a plurality of base stations, a router connected to each of the base stations, and a server connected to the plurality of routers via an Internet protocol network. A wireless communication system provided.

  According to the present invention, in a wireless communication system having a connection type data link layer, even when a mobile station receives an IP multicast packet, even if the connection is switched to a different base station, the application is not changed. There is an effect that seamless data reception can be continued.

  That is, the mobile station can continue to receive the IP multicast packet received when connected to the first base station even after moving to the second base station. Further, the mobile station requests the first router to stop distributing IP multicast packets immediately before moving, and unnecessary IP multicast packets flow to the first base station after moving. Nor.

  In addition, since the time required for reconnection of the multicast link is not zero, in this way, by ranking the multicast links that are to be reconnected during the handover process, the link where data has actually flowed until immediately before The connection is restored as soon as possible, and there is an advantage that the packet loss is low for the upper application being used.

Also, just before the mobile station transmits the IGMP Group Leave message for the base station, even go out communication range, the transfer of IP multicast packets the first base station automatically to the first router Since the stop is requested, useless data can be prevented from being transferred to the first base station indefinitely.

It is a block diagram which shows the system configuration | structure of the radio | wireless communication method which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one structural example of the mobile station of the radio | wireless communication method which concerns on the 1st Embodiment of this invention. It is a block diagram which shows one structural example of the base station of the radio | wireless communication method which concerns on the 1st Embodiment of this invention. 6 is a flowchart showing an operation of IP multicast reception processing in the mobile station of the wireless communication system according to the first embodiment of the present invention. 5 is a flowchart showing an operation during a handover process in the mobile station of the wireless communication system according to the first embodiment of the present invention. 2 shows an example of the data configuration of an IP address database provided in the mobile station of the wireless communication system according to the first embodiment of the present invention. It shows an example of an IGMP Group Join message provided in a mobile station of a wireless communication system. An example of the IGMP Group Leave message with which the mobile station of a radio | wireless communications system is provided is shown. It is a flowchart which shows the operation | movement at the time of the IP multicast setting process of the base station of the radio | wireless communications system which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of the handover process in the base station of the radio | wireless communications system which concerns on the 2nd Embodiment of this invention. It shows an example of the data structure of the IP address database of the base station of the radio communication system according to the second embodiment of the present invention. It shows an example of the data structure of the IP address database with which the mobile station of the radio | wireless communications system which concerns on the 3rd Embodiment of this invention is provided. It is a flowchart which shows the operation | movement at the time of the usage frequency totaling process in the mobile station of the radio | wireless communications system which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows IP multicast address extraction operation | movement at the time of the handover process in the mobile station of the radio | wireless communications system which concerns on the 3rd Embodiment of this invention. 1 is a system configuration diagram of a wireless communication system having a connection type data link layer. FIG. It is a block diagram which shows one structural example of the mobile station in the conventional radio | wireless communications system. 1 is a system configuration diagram of IP multicast. It is a system configuration | structure figure of MobileIPv6. 1 is a system configuration diagram of a wireless communication system disclosed in Patent Document 1. FIG.

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

[First Embodiment]
FIG. 1 is a configuration diagram showing a system configuration of a radio communication system according to the first embodiment of the present invention.
The wireless communication system according to the present embodiment shown in the figure includes a server 100, an IP network 101, a router 103, a router 104, a base station 105, a base station 106, and a communication range 109 of the base station 105. (Region), within the communication range 110 (region) of the base station 106, the mobile station 107 within the communication range 109, and the mobile station 108 after moving to the communication range 110 of the mobile station 107. ing.

  The server 100 is a multicast server connected to the IP network 101, and is a device that transmits IP multicast packets to various terminals connected to the IP network 101, such as PCs, PDAs, mobile phones, and the like. The mobile stations 107 and 108 of this embodiment are also one of various terminals.

  The IP network 101 is a network constructed by the Internet protocol. Each IP network 101 supports an IP multicast link. Therefore, when the server 100 transmits an IP multicast packet, the IP multicast packet can be transferred.

  The router 103 has a function of distributing the received packet to an appropriate IP network based on the destination address of the IP packet. In the present embodiment, the router 103 is connected to the base station 105 and its base from the IP network 101 side. When an IP packet addressed to the mobile station 107 connected to the station 105 is received, the IP packet is transferred to the base station 105. Conversely, when an IP packet for the IP network 101 is received from the base station 105 side. The packet is transferred to the IP network 101.

  In addition, when the router 103 receives an IGMP Group Join message (FIG. 7 described later) from a subordinate terminal, when the IP packet of the IP multicast address specified in the message flows to the IP network 101. Forwards the IP packet to the subordinate network. Furthermore, when an IGMP Group Leave message is received from a subordinate terminal, an inquiry is made as to whether or not there is a terminal receiving the IP multicast address specified in the message in the subordinate terminal. If the terminal does not exist, the transfer of the IP multicast packet to the base station 105 is stopped.

The router 104 provides the same function as that of the router 103 described above to the IP network 101 and the base station 106.
The mobile station 107 is a mobile terminal such as a PC, a portable information terminal, and a mobile phone. The base station 105 and the base station 106 are wirelessly connected to the mobile stations 107 and 108 that exist within their communicable ranges 109 and 110. Can communicate. Conventionally, as a wireless communication method, ARIB STD has been used.
Although T70 is normally used, in the radio communication system according to the present embodiment, ARIB
Not only STD T70 but a wireless communication system having a connection type data link layer can be used.

FIG. 2 is a block diagram showing one configuration example of the mobile station according to the first embodiment of the present invention.
The mobile station 107 shown in the figure is accessed from the CPU 202, the link control unit 203 controlled by the CPU 202, the display unit 204 connected to the CPU 202, the wireless communication unit 205 controlled by the CPU 202, and the link control unit 203. And an IP address database 206 to be configured.

The CPU 202 is a processor that centrally controls all processes in the mobile station 107.
The display unit 204 is a device that displays data received by the mobile station 107.
The wireless communication unit 205 is a circuit that performs wireless communication, and includes, for example, an RF circuit, a PHY circuit, a MAC circuit, and the like.

As described above, the wireless communication method that can be employed in the wireless communication unit 205 is normally ARIB STD.
Although it is T70, not only this ARIB STD T70 but a wireless communication system having a connection type data link layer can be used.

The link control unit 203 controls the wireless communication unit 205 via the CPU 202. In addition, association processing and disassociation processing are performed, and further link establishment of a broadcast link, a unicast link, and a multicast link is performed. In addition, the data amount and the last reception time for each link can be acquired. Further, the link control unit 203 can issue an IGMP message and request the router 104 to start and stop the transfer of the IP multicast packet via the wireless communication unit 205.
The IP address database 206 is a database that holds a list of currently connected IP multicast addresses.

FIG. 3 is a block diagram showing one configuration example of the base station according to the first embodiment of the present invention.
As shown in the figure, the base station 105 and the base station 106 include a CPU 301, a link control unit 302 controlled by the CPU 301, an IP address database 303 accessed from the link control unit 302, and a wired control controlled by the CPU 301. The communication unit 304 and the wireless communication unit 305 are provided.

The CPU 301 is a processor that centrally controls all processes in the base station.
The wireless communication unit 305 is a circuit on which, for example, an RF circuit, a PHY circuit, a MAC circuit, and the like are mounted, and the same communication method as that adopted for the mobile station 107 is employed.
The link control unit 302 controls the wireless communication unit 305 via the CPU 301. In addition, it is possible to manage the presence / absence of a connected mobile station, issue an IGMP message as necessary, and request the router 104 to start and stop transfer of an IP multicast packet via the wired communication unit 304 .
The IP address database 303 is a database that holds a correspondence list of currently received IP multicast addresses and received mobile stations.

FIG. 4 is a flowchart showing an operation of IP multicast reception processing in the mobile station according to the first embodiment of the present invention.
Hereinafter, the operation at the time of IP multicast reception processing in mobile station 107 of the radio communication system according to the present embodiment will be described using the flowchart shown in FIG. 4 with reference to FIGS. As a situation in this case, the mobile station 107 is located within the communicable range of the base station 105 and starts receiving an IP multicast packet transmitted by the server 100 (see FIG. 1).

First, the link control unit 203 of the mobile station 107 requests the wireless communication unit 205 to establish a multicast link (S400), whereby the wireless communication unit 205 establishes a multicast link with the base station 105. Try.
Next, the link control unit 203 checks whether or not the establishment of the multicast link is completed (that is, the connection is successful) (S401), and if the connection is successful, the process proceeds to step S402 and the connection fails. If so, the process is immediately terminated.

  In step S <b> 402, the link control unit 203 transmits an IGMP Group Join message for receiving the IP multicast packet transmitted by the server 100 to the router 103. As shown in FIG. 7 to be described later, the IGMP Group Join message includes the IP multicast group address transmitted by the server 100.

  Next, the link control unit 203 adds the above-described IP multicast address to the IP address database 206 (S403). An example of the data structure of the IP address database is shown in FIG.

  Finally, the wireless communication unit 205 receives the IP multicast packet transmitted from the server 100 via the base station 105 (S404). Incidentally, the router 103 that has received the IGMP Group Join message starts to transfer to the base station 105 an IP packet whose destination is the IP multicast address included in the IGMP Group Join message. The IP multicast packet transmitted from the mobile station 107 reaches the mobile station 107 via the base station 105.

  Thus, the IP multicast reception process is completed, and the mobile station 107 can receive the IP multicast packet transmitted from the server 100. Therefore, the CPU 202 processes the received IP multicast packet and displays the processing result on the display unit 204. .

  Next, a process when the mobile station 107 moves from the communication range 109 of the base station 105 to the communication range 110 of the base station 106 while receiving the IP multicast packet from the server 100 (handover process) will be described. To do.

FIG. 5 is a flowchart showing an operation during handover processing in the mobile station according to the first embodiment of the present invention.
Hereinafter, the operation at the time of the handover process in the mobile station 107 of the radio communication system according to the present embodiment will be described using the flowchart shown in FIG. 5 with reference to FIGS.

  First, the link control unit 203 of the mobile station 107 acquires received power from the wireless communication unit 205 (S500). Next, the link control unit 203 determines whether or not the acquired received power is lower than −77 dBm. If the received power is lower than −77 dBm, the process proceeds to step S502, and if it is −77 dBm or more, the process is immediately terminated. To do.

  Step S502 shows a case where communication is difficult because the distance from the currently connected base station is far away or there is a radio wave shielding object between them. 203 searches for another base station via the wireless communication unit 205. This search method is, for example, scanning all the usable frequencies, but since it is defined by the wireless communication method used, it depends on the wireless communication method installed in the mobile station here. And

  Next, the search result is verified (S503). If a new base station 106 is found, the process proceeds to step S504. If a new base station 106 is not found, the process is immediately terminated.

  In step S504, first, the link control unit 203 transmits an IGMP Group Leave message to the router 103 via the currently connected base station 105. This message includes the IP multicast address received up to now as shown in FIG. The router 103 that has received this message stops forwarding the IP multicast packet flowing in the IP network 101 if there is no terminal receiving the same IP multicast packet under the router 103.

Next, the link control unit 203 requests the wireless communication unit 205 to perform disassociation with the currently connected base station 105 (S505), and then disconnects all connected links.
Subsequently, the link control unit 203 instructs the wireless communication unit 205 to make an association request to the newly discovered base station 106 (S506).
After completing the association, the link control unit 203 requests the wireless communication unit 205 to establish a broadcast link and a unicast link with the base station 106 (S507).

Next, the link control unit 203 retrieves the IP multicast address received immediately before from the IP address database 206 (S508).
Finally, the link control unit 203 starts IP multicast reception processing of this IP multicast address (S509).
Note that the IP multicast reception processing is as already described using the flowchart shown in FIG.

Through this series of processing, the mobile station 107 can continue to receive the IP multicast packet received when it is connected to the base station 105 even after moving to the base station 106. Further, the mobile station 107 requests the router 103 to stop distributing the IP multicast packet immediately before moving, and the mobile station 107 does not flow an unnecessary IP multicast packet to the base station 105 after moving. .
In addition, these processes are processes closed by the link control unit 203, the wireless communication unit 205, and the IP address database 206, and the application that actually processes the IP multicast packet and the display unit 204 have nothing to do with it. This is a process that can be executed without any changes.

FIG. 6 shows an example of the data structure of the IP address database provided in the mobile station according to the first embodiment of the present invention.
As shown in the figure, the data structure of the data recorded in the IP address database provided in the mobile station 107 (FIG. 1) is in a table format, and an entry for recording the IP multicast address is provided.

FIG. 7 shows an example of the IGMP Group Join message provided in the mobile station of the wireless communication system.
As shown in the figure, the IGMP Group Join message includes a multicast group address as main information. In addition, an identification code, a checksum, etc. can be included.
As described above, this message is transmitted from the link control unit 203 of the mobile station 107 to the router 103 in order for the mobile station 107 to receive the IP multicast packet transmitted by the server 100.

FIG. 8 shows an example of the IGMP Group Leave message provided in the mobile station of the wireless communication system.
As shown in the figure, the IGMP Group Join message includes a multicast group address as main information. In addition, an identification code, a checksum, etc. can be included.
As described above, this message is transmitted from the link control unit 203 of the mobile station 107 to the router 103 in order to stop the transfer of the IP multicast packet flowing in the IP network 101.

[Second Embodiment]
The system configuration of the radio communication system according to the second embodiment of the present invention is the same as the system configuration (FIG. 1) of the radio communication system according to the first embodiment of the present invention. Since only setting processing is added, IP multicast setting processing in the base station will be described below.

When the mobile station 107 starts the IP multicast reception process, the IP multicast setting process of the base station 105 starts. FIG. 9 is a flowchart showing an operation at the time of IP multicast setting processing of the base station of the wireless communication system according to the second embodiment of the present invention.
Hereinafter, the operation at the time of the IP multicast setting process of the base station 105 (FIG. 3) of the wireless communication system according to the present embodiment will be described using the flowchart shown in FIG. 9 with reference to FIGS.

First, the link control unit 302 receives a multicast link request from the mobile station 107 via the wireless communication unit 305 (S900).
Thereby, the link control unit 302 establishes a multicast link (S901).
Then, it waits until it receives an IGMP Group Join message from the mobile station (S902).

  When the message is received from the mobile station, first, the IP multicast address included in the message is extracted, and the identification number and IP multicast address of the mobile station 107 are extracted into the IP address database 303 (see FIG. 11 described later). Is written (S903), and the IP multicast setting process is terminated. Thereafter, the mobile station 107 moves from the communication range 109 of the base station 105 to the communication range 110 of the base station 106 while receiving the IP multicast packet from the server 100. At this time, the handover process of the mobile station 107 is executed as described in the first embodiment.

FIG. 10 is a flowchart showing an operation during a handover process in the base station of the wireless communication system according to the second embodiment of the present invention.
Hereinafter, the operation at the time of the handover process in the base station 105 of the radio communication system according to the present embodiment will be described using the flowchart shown in FIG. 10 with reference to FIGS.

  However, here, in the process of step S503 in the flowchart shown in FIG. 5, the mobile station 107 has already left the communication range 109 of the base station 105 before transmitting the IGMP Group Leave message to the base station 105. A handover process in this case will be described.

First, when connected from the mobile station 107, the base station 105 periodically transmits a survival confirmation message to the mobile station 107 (S1000).
Next, it is verified whether or not a survival confirmation response is transmitted from the mobile station 107 (S1001). If a survival confirmation response is not transmitted, the process proceeds to step S1002. If a survival confirmation response is transmitted, the process is immediately terminated. Normally, when the mobile station 107 receives the survival confirmation request, it transmits a survival confirmation response to the base station 105. Therefore, the base station 105 can confirm that the mobile station 107 still exists. When 107 moves outside the communication range 109, the survival confirmation response from the mobile station 107 cannot be received.

In step S1002, the base station 105 determines that the mobile station 107 is already out of the range of its communication range 109, executes disassociation processing (S1002), and clears all links.
Next, the link control unit 302 retrieves the IP multicast address received by the disassociated mobile station 107 from the IP address database 303 (S1003).

  Finally, the link control unit 302 transmits an IGMP Group Leave message to the router 103 (S1004). The IGMP Group Leave message includes the IP multicast address that has been received so far. The router 103 that has received this message stops forwarding the IP multicast packet flowing in the IP network 101 when there is no terminal receiving the same IP multicast packet under the router 103.

Through this series of processing, the mobile station 107 transmits an IGMP group to the base station 105.
Even if the base station 105 automatically goes out of the communication range immediately before sending the Leave message, the base station 105 automatically requests the router 103 to stop forwarding the IP multicast packet, so that useless data is transferred to the base station 105 indefinitely. Can be prevented.

  However, when a plurality of mobile stations are connected to the base station 105, one of the mobile stations connected to the base station 105 (here, the mobile station 107) moves outside the communication range of the base station 105. In this case, the router 103 connected to the base station 105 is not requested to stop forwarding the multicast packet.

FIG. 11 shows an example of the data configuration of the IP address database of the base station of the radio communication system according to the second embodiment of the present invention.
As shown in the figure, the data structure of the data recorded in the IP address database 303 provided in the base stations 105 and 106 is in a table format, and an entry for recording a multicast address corresponding to the mobile station identification number is provided. Yes.

[Third Embodiment]
The system configuration of the wireless communication system according to the third embodiment of the present invention is the same as the system configuration (FIG. 1) of the wireless communication system according to the first embodiment of the present invention. The content of the IP address database 206 is different from the above form.

  Similarly to the operation of the wireless communication system according to the first embodiment described above, in the wireless communication system according to the present embodiment, each time the IP multicast reception process of the mobile station 107 is executed, the link control unit 203 Adds the received IP multicast address to the IP address database 206. However, in the wireless communication system according to the present embodiment, not only the above-described IP multicast address is recorded, but also the received data amount and the last reception time are recorded in the IP address database 206. In the present embodiment, the handover process is also different from that in the first embodiment.

FIG. 12 shows an example of the data structure of the IP address database provided in the mobile station of the wireless communication system according to the third embodiment of the present invention.
As shown in the figure, the data structure of the data recorded in the IP address database 206 is a table format, and the received data amount and the last reception time corresponding to all the IP multicast addresses received by the mobile station 107 are recorded. Entries are provided. Each time the IP multicast reception process is executed, the link control unit 203 adds the IP multicast address to this table and records the corresponding received data amount and the last reception time.

  In the case of the data example shown in the figure, the mobile station 107 is assigned to three IP multicast groups having an IP address 224.5.6.7, an IP address 224.5.6.10, and an IP address 224.10.10.10. Participating, and for IP address 224.5.6.7, 500 bytes of data have been received so far, and the last received was 15:00:05 on January 1, 2004. As for the address 224.5.6.10, the data amount of 1,000 bytes has been received so far, and the last received was 17:00 on January 1, 2004, and the IP address 224.10. 10.10.10 indicates that the data amount of 4,000,000 bytes has been received so far, and that the last received was 17:00 on January 1, 2004.

FIG. 13 is a flowchart showing an operation at the time of use frequency counting processing in the mobile station of the wireless communication system according to the third embodiment of the present invention.
Hereinafter, with reference to FIG. 1 to FIG. 3 and FIG. 12, the operation at the time of use frequency counting processing in the mobile station of the radio communication system according to the present embodiment will be described using the flowchart shown in FIG. 13.

First, the link control unit 203 of the mobile station 17 verifies whether or not data of an IP multicast address has been received (S1300). If the data has been received, the process proceeds to step S1301, and the data is received. If not, the process ends immediately.
In step S1301, the link control unit 203 adds the received data amount to the data amount corresponding to the IP multicast address recorded in the table (FIG. 12) of the IP address database 206.
Finally, the link control unit 203 updates the last reception time (S1302).

  Thereafter, the mobile station 107 moves from the communication range 109 of the base station 105 to the communication range 110 of the base station 106 while receiving the IP multicast packet. At this time, the handover process of the mobile station 107 is executed as described in the first embodiment.

  However, the handover process shown in FIG. 4 is a flowchart showing the handover process of the mobile station 107, but in the wireless communication system according to the present embodiment, the process of extracting the IP multicast address from the IP address database 206 (Processing corresponding to step S408 shown in FIG. 5) is different from the processing of the wireless communication system according to the first embodiment.

FIG. 14 is a flowchart showing an IP multicast address extraction operation at the time of handover processing in the mobile station of the wireless communication system according to the third embodiment of the present invention.
Hereinafter, an operation when performing processing for extracting an IP multicast address from the IP address database 206 will be described.

First, the link control unit 203 extracts communication data with the latest final reception time from the communication data recorded in the IP address database 206 for prioritization (S1400). Here, it is assumed that communication data indicated by an IP address (multicast address) of 224.5.5.6.10 and an IP address of 224.1.10.10 is data that satisfies the above-described conditions. Incidentally, the reception times indicated by both communication data are both 17:00:30 and are the same time.
Next, the link control unit 203 extracts an IP address in which communication data having the largest data amount is recorded from the extracted communication data (S1401).

  As a result, the IP address 224.10.10.10 is selected. Accordingly, the link control unit 206 first performs IP multicast reception processing (processing corresponding to step S509 shown in FIG. 5) for the IP address 224.10.10.10. Thereafter, similar addresses are extracted and IP multicast reception processing is performed by excluding addresses that have already been subjected to IP multicast reception processing.

  Since the time required for reconnection of the multicast link is not zero, in this way, by ranking the multicast links to be reconnected during the handover process, the link where data has actually flowed until immediately before is faster. The connection is restored and the upper application that is used has the advantage that the packet loss is small.

  In this embodiment, the latest reception time is used to rearrange the latest ones, and the higher priority is given to the larger ones according to the amount of data. However, the ranking may be performed by any other combination.

  Further, in each of the embodiments of the present invention described above, the data content of the received IP multicast packet is not particularly described. However, in actuality, it is a packet of moving image data such as MPEG2, or MP3 (MPEG1 Audio Layer3). ) And the like, and the present invention is not limited to this. Other arbitrary data configurations are possible, and the data content may be arbitrary.

  As described above, according to the radio communication system according to the present invention, the mobile station 107 similarly receives the IP multicast packet received when connected to the base station 105 after moving to the base station 106. You can keep receiving. Since the mobile station 107 requests the router 103 to stop IP multicast distribution before moving, an unnecessary IP multicast packet is transmitted to the base station 105 after the mobile station 107 has moved. There is nothing. Furthermore, since all the processes are executed by being closed by the link control unit 203, the wireless communication unit 205, and the IP address database 206, the upper-level application that is actually processing the IP multicast packet and the display of the application There is an effect that there is no need to make any changes in the parts.

  Note that at least a part of the processing of each component of the mobile station and the base station according to the present invention is executed by computer control, and the above processing is shown in the flowcharts of FIGS. 4, 5, 7, 8, 13, and 14. The program to be executed by the computer according to the procedure described above may be distributed after being stored in a computer-readable recording medium such as a semiconductor memory, a CD-ROM, or a magnetic tape. A computer including at least a microcomputer, a personal computer, and a general-purpose computer may read the program from the recording medium and execute the program.

100 server 101 IP network 103, 104 router 105, 106 base station 107, 108 mobile station 109, 110 within communication range of base station 202 CPU (mobile station)
203 Link control unit (mobile station)
204 Display unit 205 Wireless communication unit (mobile station)
206 IP address database 301 CPU (base station)
302 Link control unit (base station)
304 Wired communication unit 305 Wireless communication unit (base station)

Claims (2)

In a wireless communication system capable of wireless communication between a mobile station and a base station, connected to an IP network via a router connected to the base station, and connected within a physical link provided for each base station A connection type data link layer capable of independently establishing a multicast link of one-way link identified by an identifier and a unicast link of a bidirectional link, and connecting to a first router to establish one or more multicast links; A mobile station which is handed over while receiving an IP multicast packet from a first base station connected to a second router to a second base station to which an IP multicast packet is not transferred,
When handing over from the first base station to the second base station, the second base station is requested to connect and the unicast link is established with the second base station. Means,
Means for requesting the second router to forward the received IP multicast packet to the second base station via the unicast link;
Means for establishing the multicast link with the second base station;
A mobile station characterized by comprising: A mobile station according to claim 1;
And a double the number of base stations,
A router connected corresponding to each of the plurality of base stations;
A server connected to the plurality of routers via an IP network;
With
The base station
In a wireless communication system capable of wireless communication between a mobile station and a base station, a piece identified by a connection identifier is connected to an IP network through a router, and a physical link provided between the mobile station and the mobile station A base station having a connection-oriented data link layer capable of independently establishing a multicast link of a directional link and a unicast link of a bidirectional link,
An IP address database for storing the mobile station identification number assigned to the mobile station and the IP multicast address received by the mobile station in association with each other;
While the IP multicast packet of the IP multicast address is being transmitted to the mobile station, the last mobile station that has received the IP multicast packet has stopped receiving the IP multicast packet based on the IP address database A means for requesting the router connected to the local station to stop forwarding the multicast packet;
Wireless communication system comprising the.

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