JP2005136502A - Mobile communication system, mobile terminal, node apparatus, and mobile communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system in which a delay time until reception of a multicast packet by a wireless base station at a moving destination is shortened. <P>SOLUTION: The mobile communication system includes: multicast routers 20a, 20b and 20c; data link layer switches 30a and 30b; wireless base stations 40a, 40b, 40c and 40d; and a mobile terminal 50, wherein the mobile terminal 50 is characterized in that it detects switching of the wireless base stations and transmits a path establishment request to a different multicast router when the mobile terminal 50 judges that a wireless base station adjacent to a wireless base station after the switching is connected to a different multicast router from one connected to the mobile terminal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mobile communication system, a mobile terminal, a node device, and a mobile communication method.

  In this specification, the device itself generates a packet and transmits that packet is transmitted. The packet generated by another device is duplicated if necessary, and is sent to the subordinate device (the transmission device is upstream and downstream). Sending is defined as delivery.

  In a network (IP network) using IP (Internet Protocol) in a broad sense including ICMP (Internet Control Message Protocol), IGMP (Internet Group Management Protocol), etc., the transmitting device is a file or moving image for a plurality of receiving devices. Multicast communication (IP multicast) for transmitting the data can be performed. A multicast group management procedure using IGMP is defined in RFC (Request For Comments) 1112 of IFTF (Internet Engineering Task Force) or the like.

  In such multicast communication, the receiving apparatus is connected to a transmitting apparatus that transmits multicast data via a multicast router. In this case, the receiving device and the multicast router are connected via a wired or wireless connection. Further, the receiving apparatus transmits an IGMP-join packet (route establishment request) or an IGMP-Report packet (route establishment request) (hereinafter simply referred to as a join packet) to the multicast router. The multicast router that has received this join packet (route establishment request) knows that it is necessary to distribute the multicast packet to the receiving device, and distributes the multicast packet supplied from the transmitting device.

  A multicast packet distribution route (multicast packet distribution route) in the IP network is established in the direction from the receiving device to the transmitting device. Specifically, when the receiving device transmits a join packet (route establishment request), the multicast router that has received the join packet (route establishment request) is requested by its join table (route establishment request) in its distribution table. The multicast group is added, and a request for establishing a multicast distribution route is transmitted upstream (from the receiving device side to the transmitting device side). The upstream multicast router that has received the multicast distribution route establishment request also updates the distribution table in the same manner, and further transmits a multicast distribution route establishment request (route establishment request) to the upstream multicast router.

  When a multicast distribution route establishment request (route establishment request) reaches a multicast router to which the transmission device is connected, a multicast distribution route from the transmission device to the reception device is established. When a receiving device transmits a join packet (route establishment request) to a multicast group, another receiving device has already received the multicast packet, and a certain multicast existing on the multicast distribution route between the transmitting and receiving devices. When a multicast distribution route has been established up to the router, the multicast distribution route from the transmitting device to the receiving device is established when the multicast distribution route establishment request (route establishment request) reaches the multicast router. .

  After establishing the multicast distribution route, the transmission device transmits the multicast packet to the multicast router to which it is connected. A multicast router replicates each received multicast packet and distributes each multicast distribution when there are multiple receiving devices under its control and multiple multicast distribution routes are required to transmit multicast packets to these multiple receiving devices. Send to route.

  In this way, a multicast router existing at a position where a plurality of multicast distribution routes exist, that is, at a position where the multicast distribution route branches, copies a multicast packet and transmits it only to the multicast distribution route that needs to be distributed. Therefore, it is possible to effectively use the bandwidth of the network without increasing traffic on the multicast distribution route more than necessary.

  The IP multicast described above is realized by copying and distributing a multicast router capable of performing IP layer processing, and a LAN (Local Area Network) for connecting the multicast router and the receiving device. Since the data link layer switch used in the network does not normally perform IP layer processing, multicast packets distributed from the multicast router are distributed to all routes regardless of whether or not there is a receiving device on the route. Bandwidth is wasted.

  In this way, as a method for preventing the bandwidth from being wastedly used in the LAN and distributing the multicast packet only to the path where the receiving device exists, the data link layer switch monitors the traffic passing through itself, By recording the port where the join packet (route establishment request) sent from the receiving device arrives, the route where the receiving device exists is recognized, and when the multicast packet is distributed from the multicast router, the receiving device exists. A method called IGMP-Snooping that distributes multicast packets only to the route is considered. This method is described, for example, in Non-Patent Document 1 below.

  By using this method, a multicast packet can be distributed only to a route where the receiving device exists even in the LAN, and the bandwidth can be used effectively.

  By the way, when the receiving device is connected to a relay device such as a data link layer switch via a wire, the receiving device may receive the multicast packet if the multicast packet is not transmitted to the path to which the receiving device is connected. Therefore, it is necessary for these relay apparatuses to duplicate and transmit multicast packets as many as the number of multicast distribution routes in which the receiving apparatuses are subordinate. On the other hand, when the relay device is a radio base station and a plurality of receiving devices receive multicast packets via the radio base station, the plurality of receiving devices simultaneously receive radio signals of multicast packets transmitted from the radio base station. can do. For this reason, the radio base station does not need to duplicate multicast packets as many as the number of receiving devices, and can distribute to a plurality of receiving devices using the same bandwidth as when transmitting packets to one receiving device. .

  When a receiving device that receives a multicast packet is connected to a data link layer switch via a radio base station, the receiving device may move between the radio base stations. When the receiving apparatus moves between radio base stations, the path where the radio base station before movement is connected to the data link layer switch is different from the path where the radio base station after movement is connected to the data link layer switch. Therefore, in order to receive a multicast packet via the destination radio base station, a multicast distribution route to the destination radio base station needs to be newly established in the data link layer switch. However, as described above, in the multicast distribution route, the receiving device transmits a join packet (route establishment request), and the data link layer switch is a route in which the receiving device exists from the port to which the join packet (route establishment request) has arrived. Established by recognizing. Normally, a receiver sends a join packet (route establishment request) when it joins a multicast group and when there is a receiver belonging to the corresponding multicast group among the subordinate receivers from the multicast router. Therefore, when an IGMP-Query packet (hereinafter simply referred to as a Query packet), which is a request for confirming the presence of the receiving apparatus, is received, it is transmitted only as a response. For this reason, after a move, a Query packet is transmitted from a multicast router existing upstream of the data link layer switch, and the receiving device receives the multicast packet until the receiving device transmits a join packet (path establishment request) in response. Can not do it. Since the default value of the query packet transmission interval is 120 seconds, when there is no receiving device of the same multicast group under the destination radio base station, the multicast packet is received for an average period of about 60 seconds. Will not be able to.

  Also, after the receiving device has moved, if there are no other receiving devices participating in the same multicast group under the source radio base station, distribution to the route to which the source radio base station is connected is stopped. However, since the multicast router transmits a query packet after the receiving apparatus moves, and there is no response of the join packet (route establishment request) from the route to which the source wireless base station is connected, the wireless base station Until the data link layer switch recognizes that there is no receiving device on the path to which the mobile station is connected, the distribution to the path to which the source radio base station is connected does not stop. Therefore, even after the receiving device moves, the multicast packet is distributed to the route to which the source wireless base station is connected, even though there is no receiving device receiving the multicast packet. Since it is also distributed from the station to the radio side, the bandwidth is wasted for a period of about 60 seconds on average.

  As a method for preventing the bandwidth from being wasted in this way and quickly deleting a multicast distribution route in which no receiving device exists, in IGMP, when a receiving device stops receiving a multicast packet, a multicast group There is a method of transmitting an IGMP-leave packet (withdrawal request) (hereinafter simply referred to as a “leave packet”) for requesting withdrawal from the multicast router. The multicast router that has received the leave packet (withdrawal request) transmits a query packet, checks whether the receiving device exists, and deletes the multicast distribution path if it does not exist. Distribution to a route that does not exist can be quickly stopped. However, in a wireless environment, the receiving apparatus needs to receive a multicast packet until immediately before moving, and therefore it is very difficult to transmit a Leave packet (withdrawal request) immediately before moving.

  In this way, in order to solve the problem that multicast packets are not distributed from the destination radio base station and multicast packet delivery to the route to which the source radio base station is connected cannot be stopped, A method is considered in which an MSA (Mobility Support Agent) is arranged for each station, and a multicast distribution route is established and deleted by this MSA. Specifically, the receiving apparatus is present in the path to which the source radio base station is connected after the movement, with respect to the MSA existing in the path to which the destination radio base station is connected before moving. A packet requesting establishment of a multicast distribution route at the destination and deletion of the multicast distribution route at the source is sent to the MSA. The MSA that has received this packet transmits a join packet (route establishment request) or a leave packet (withdrawal request) to the multicast router as a proxy for the receiving device. As a result, the multicast distribution path at the destination is established before the reception apparatus moves, and the multicast distribution path at the movement source is deleted after the movement. This method is described in Non-Patent Document 2 below, for example.

  Also, a method of transmitting a join packet (route establishment request) or a leave packet (withdrawal request) directly to the destination and source multicast routers without arranging the MSA is also considered. In this method, the connection strength of the radio link is used to predict the destination, and the join packet (route establishment request) is sent to the multicast router existing in the route to which the radio base station that is likely to move is moved. By transmitting a leave packet (withdrawal request) to a multicast router existing on the route to which the source wireless base station is connected, the multicast delivery route is established and deleted without placing an MSA. This method is described, for example, in Non-Patent Document 3 below.

On the other hand, instead of establishing a multicast distribution route before moving as in the methods described in these two non-patent documents, the receiving device detects the movement after moving and transmits a join packet (route establishment request). Thus, a method of establishing a multicast distribution route before a query packet is transmitted from a multicast router is considered. In this method, when an advertisement packet sent by a multicast router after movement is received, if it is an advertisement from a multicast router different from the source multicast router, it is detected that it has moved and a join packet (route establishment request) ) Is transmitted, the time until the multicast packet after movement is received is shortened. This method is described in Non-Patent Document 4 below, for example.
Morten Jagd Christensen (Thrane & Thrane) et al., "Considerations for IGMP and MLD snooping switches", IETF Internet-draft, draft-ietf-magpo-magp. txt, July 2003. Jiang Wu (Department of Teleinformatics, Royal Institute of Technology, Stockholm) al., "AN IP Mobility Support Architecture for the 4GW Wireless Infrastructure", Proceedings of the 1999 Personal Computing and Communication Workshop (PCC'99). Yukimi Moritani et al., “Seamless Hand-off Method for Multicast Receivers Based on Wireless Link Intensity3, NCE3, Proceedings of IEW. Takashi Hashimoto et al., “A Study on Multicast Communication over Mobile IP Network”, IPSJ Mobile Computing and Wireless Communication Research Report No. 16-6

  However, in the technique described in Non-Patent Document 2, in the environment where the data link layer switch is connected under the multicast router, the wireless base station is connected under the multicast router, and the receiving device is under the wireless router, In order to realize the method described in Patent Document 2, unless an MSA is arranged for each radio base station, multicast packets are not distributed to the route to which the destination radio base station is connected. There was a problem that multicast packets could not be received after movement. In addition, when an MSA is arranged for each radio base station, the multicast is distributed to the radio section in the destination network before moving, and even if it does not move, the band of the radio section is wasted. There was a problem that. Also, after moving from the source radio base station to the destination radio base station, a leave packet (withdrawal request) is transmitted to the MSA connected to the source radio base station, and the source radio base station is connected. Since multicast distribution to the selected route is stopped, after moving to the destination radio base station, changing the direction of movement and moving to the source radio base station again, the multicast packet in the source radio base station There is a problem in that the distribution is stopped and the multicast packet cannot be received immediately after the movement.

  Further, in the technique described in Non-Patent Document 3, even if the data link layer switch is connected under the multicast router and the radio base station is connected under the multicast router, the radio base station is moved between the radio base stations. When the connection port of the data link layer switch only changes and the multicast router connected upstream does not change, the join packet (route establishment request) or leave packet (withdrawal) is sent to each port of the data link layer switch. Request), but the data link layer switch is not necessarily assigned an address, and a different address is not assigned to each port. Establishment request) and leave packets (withdrawal requests) cannot be sent There is. In addition, since the receiving device must receive the advertisement of the destination radio base station, the receiving device can receive radio waves from two radio base stations, the currently connected radio base station and the destination radio base station. It was necessary to have.

  In the technique described in Non-Patent Document 4, since the multicast router address of the advertisement packet is used to detect the movement of the receiving device, a data link layer switch is connected under the multicast router, and the wireless link is under the subordinate. In an environment where base stations are connected, if the upstream multicast router does not change even when moving between wireless base stations, only the connected wireless base station changes, the join packet (route establishment request) Cannot be transmitted, and the destination wireless base station cannot receive a multicast packet immediately after moving. Further, there is no mention of deletion of the multicast distribution route in the source radio base station, and there is a problem in that the multicast packet distribution cannot be stopped in the source radio base station.

  As described above, in the conventional method, in the environment where the data link layer switch is connected under the multicast router, the radio base station is connected under the multicast router, and the receiving device exists under the data link layer switch, the MSA of each radio base station is connected. If a special node device is not installed, or the receiving device does not have a function to receive radio waves from a plurality of radio base stations, when the receiving device moves between the radio base stations, the multicast router is moved after the move. There is a problem that a multicast packet cannot be received until a Query packet is transmitted. In addition, unless a special node device such as an MSA is installed for each radio base station, there is a problem that distribution of multicast packets from the source radio base station cannot be stopped. In addition, when a special node device such as MSA is installed for each radio base station, multicast packets are distributed to the radio section before moving, and the band of the radio section is wasted. there were. Therefore, there is a need for a method for solving these problems without installing a special node device for each radio base station or having a function for receiving devices to receive radio waves from a plurality of radio base stations. Yes.

  Therefore, in the present invention, a special node device is installed for each radio base station in an environment where a data link layer switch is connected under the multicast router, a radio base station is connected under the multicast router, and a receiving device exists under the switch. Or when the receiver moves between radio base stations without having the function of receiving radio waves from a plurality of radio base stations in the receiver and without wasting bandwidth in the radio section. It is an object of the present invention to provide a mobile communication system, a mobile terminal, a node device, and a mobile communication method that can shorten a delay time until reception of a multicast packet in a destination radio base station.

  The mobile communication system according to the present invention receives (1) an information signal transmitted from a transmitting device and addressed to a predetermined multicast group, and received when there is a mobile terminal desiring to distribute the information signal addressed to the multicast group. A multicast router capable of replicating the received signal and distributing it to the subordinate network, and (2) a mobile terminal that receives the information signal distributed by the multicast router and wishes to distribute the information signal addressed to the multicast group A data link layer switch capable of distributing the received information signal only to a multicast distribution path in which there is a data link; and (3) an information signal connected to the data link layer switch and distributed from the data link layer switch A wireless base station capable of delivering to a wireless network; and (4) no A mobile communication system including a mobile terminal that receives an information signal distributed from a base station, wherein the mobile terminal detects (4-1) that the radio base station to which it is connected has been switched. The switch detection means, (4-2) the multicast router to which the radio base station adjacent to the radio base station to which it is connected, and which multicast router is the multicast router to which it is connected Connection station determination means for determining; (4-3) establishment request transmission means for transmitting a route establishment request for requesting establishment of a multicast distribution route; and (4-4) withdrawing from the multicast group to which it belongs. A withdrawal request transmission unit that transmits a requested withdrawal request, and (4-5) an establishment request transmission unit according to the detection of the station switching detection unit and the determination of the connection station determination unit Transmission control means for outputting a first instruction signal for instructing to transmit a route establishment request and a second instruction signal for instructing the withdrawal request transmitting means to transmit the withdrawal request, and (a ) The multicast router to which the mobile terminal is connected is the multicast router to which the station switching detection means detects the switching of the radio base station and the connecting station determination means is connected to the radio base station adjacent to the radio base station after the switching. If it is determined that it is different from the router, the transmission control means transmits a route establishment request to the multicast router connected to the radio base station adjacent to the switched radio base station. Is output.

  According to the mobile communication system of the present invention, after switching between radio base stations, when the multicast router to which the radio base station adjacent to the radio base station after the switch is connected is different from the currently connected multicast router, Since the transmission control means outputs the first instruction signal so as to transmit the route establishment request to the multicast router to which the adjacent radio base station is connected, the route is sent to the multicast router that is the destination candidate before the movement. An establishment request is transmitted, and a multicast distribution route is established. For this reason, when the mobile terminal moves under the multicast router to which the adjacent radio base station is connected, the delay time until the reception of multicast data can be shortened. On the other hand, at this stage, since the multicast distribution route is not established in the data link layer switch existing under the multicast router connected to the adjacent radio base station, multicast data is distributed under the data link layer switch. The wireless bandwidth is not wasted.

  Further, in the mobile communication system of the present invention, the station switching detection unit detects the switching of the radio base station, and the connection station determination unit determines whether the multicast router to which the radio base station after the switching is connected previously connected to the route establishment request. If it is determined that it no longer matches the multicast router that sent the packet, the multicast router that sent the route establishment request previously excludes the multicast router to which the radio base station adjacent to the switched radio base station is connected. It is also preferable to output the second instruction signal so as to transmit a withdrawal request to the multicast router. In this way, after the radio base station is switched, when the mobile station moves to a radio base station that is not adjacent to the radio base station under the multicast router that previously established the multicast distribution route, the transmission control means Since the second instruction signal is output so as to transmit the withdrawal request, the multicast distribution route in the multicast router that is unlikely to move to the subordinate radio base station can be appropriately deleted, and the wired band or the multicast router can be deleted. It is possible to reduce wasteful consumption of resources such as memory.

  In the mobile communication system of the present invention, the mobile terminal includes (4-6) a router detection unit that detects that the multicast router to which the mobile terminal is connected has switched, and (4-5 ′) the transmission control unit includes: A function of outputting first and second instruction signals in response to the detection of the router detection means; (c) the station switching detection means detects the switching of the radio base station, but the router switching detection means switches the multicast router When the transmission control means does not detect the first instruction signal, the second instruction signal, and the route establishment request in order to sequentially transmit the route establishment request, the withdrawal request, and the route establishment request to the currently connected multicast router, When the first instruction signal is sequentially output, (d) the station switching detection means detects the switching of the radio base station, and the router switching detection means detects the switching of the multicast router The transmission control means outputs the first instruction signal to send a route establishment request to the multicast router after switching, and then the multicast router connected before switching, and the establishment request transmitting means before switching. It is also preferable to output the second instruction signal so as to transmit the withdrawal request to the multicast router that has transmitted the route establishment request.

  As a result, when the radio base station has been switched but the multicast router has not been switched, the transmission control means sends the first instruction signal, the second instruction signal, and the first instruction signal to the currently connected multicast router. Since the information is sequentially output, a route establishment request, a withdrawal request, and a route establishment request are sequentially transmitted from the mobile terminal to the current multicast router. In addition, when both the radio base station and the multicast router are switched, the transmission control means sends the first instruction signal to the currently connected multicast router as the target, the multicast router that was connected before the switching, and the before the switching. Since the second instruction signal is output for the multicast router that sent the route establishment request to the multicast router, the route establishment request is sent to the multicast router after switching, and the multicast distribution route is established to the multicast router that was established before switching A withdrawal request is sent. In either case, since the route establishment request is transmitted first, the delay time until reception of the information signal after the radio base station is switched can be shortened. If the multicast router does not switch, the route establishment request is sent again after the withdrawal request is sent, so the data link layer switch can be notified of which port it is under. it can. On the other hand, when a multicast router is switched, including the multicast router before switching, there is a mobile terminal as a receiving device subordinate to the multicast router with respect to the multicast router that established the multicast distribution route before switching It is possible to provide information that can be used to confirm

  In the mobile communication system of the present invention, when the data link layer switch receives the (2-1) route establishment request, the data link layer switch establishes a multicast distribution route for the route according to the received route establishment request. And (2-2) upon receiving an existence confirmation request transmitted from the multicast router to confirm whether or not there is a mobile terminal belonging to the multicast group in response to the withdrawal request, It is also preferable to provide distribution route reconfiguring means for redistributing the subordinate and reconfiguring the multicast distribution route in response to a route establishment request returned in response to the distribution. Since the multicast distribution route is established according to the route establishment request transmitted from the mobile terminal side, multicast distribution can be performed only on the route where the mobile terminal as the receiving device exists. Also, the existence confirmation request transmitted from the multicast router side is distributed to the mobile terminal side, and the multicast distribution route is reconfigured in response to the route establishment request returned as a result, so there is no mobile terminal as a receiving device. It is possible to avoid sending an information signal to the route.

  A mobile terminal according to the present invention is a mobile terminal that belongs to a multicast group and receives an information signal transmitted by multicast via a multicast router, a data link layer switch, and a radio base station. The station switching detection means for detecting that the station has been switched, the multicast router to which the radio base station adjacent to the radio base station to which the station is connected is connected, and which multicast router is the multicast router to which the station is connected Connection station determination means for determining whether or not, a request for establishment request transmission for requesting establishment of a multicast distribution route, and a withdrawal request for requesting withdrawal from the multicast group to which it belongs Of the withdrawal request transmission means, the detection of the station switching detection means, and the connection station determination means The first instruction signal for instructing the establishment request transmitting means to transmit the route establishment request and the second instruction signal for instructing the withdrawal request transmitting means to transmit the withdrawal request are output in accordance with certain conditions. A multicast router connected to a wireless base station adjacent to the wireless base station after the switching is moved by the station switching detection means, and the connected station determination means is moved. If it is determined that the terminal is different from the multicast router to which the terminal is connected, the transmission control means transmits a route establishment request to the multicast router to which the radio base station adjacent to the switched radio base station is connected. The first instruction signal is output as described above.

  According to the mobile terminal of the present invention, after the radio base station is switched, if the multicast router connected to the radio base station adjacent to the radio base station after the switch is different from the currently connected multicast router, the transmission is performed. Since the control means outputs the first instruction signal so as to send a route establishment request to the multicast router to which the adjacent radio base station is connected, the route is established to the multicast router that is the destination candidate before the movement. A request is sent and a multicast delivery route is established. For this reason, when the mobile terminal moves under the multicast router to which the adjacent radio base station is connected, the delay time until the reception of multicast data can be shortened. On the other hand, at this stage, since the multicast distribution route is not established in the data link layer switch existing under the multicast router connected to the adjacent radio base station, multicast data is distributed under the data link layer switch. The wireless bandwidth is not wasted.

  In the mobile terminal of the present invention, the station switching detection unit detects the switching of the radio base station, and the connecting station determination unit sends the route establishment request to the multicast router to which the radio base station after the switching is connected previously. If it is determined that it does not match the transmitted multicast router, the multicast router to which the wireless base station adjacent to the switched wireless base station is connected is excluded from the multicast router that previously transmitted the route establishment request. It is also preferable to output the second instruction signal so as to transmit a withdrawal request to the multicast router. In this way, after the radio base station is switched, when the mobile station moves to a radio base station that is not adjacent to the radio base station under the multicast router that previously established the multicast distribution route, the transmission control means Since the second instruction signal is output so as to transmit the withdrawal request, the multicast distribution route in the multicast router that is unlikely to move to the subordinate radio base station can be appropriately deleted, and the wired band or the multicast router can be deleted. It is possible to reduce wasteful consumption of resources such as memory.

  The mobile terminal of the present invention further comprises router detection means for detecting that the multicast router to which it is connected has switched, and the transmission control means sends the first and second instruction signals in response to detection by the router detection means. If the station switching detection means detects the switching of the radio base station but the router switching detection means does not detect the switching of the multicast router, the transmission control means In order to sequentially transmit a route establishment request, a withdrawal request, and a route establishment request to the router, the first instruction signal, the second instruction signal, and the first instruction signal are sequentially output, and the station switching detection unit switches the radio base station. And the router switching detection means detects that the multicast router has been switched, the transmission control means After the first instruction signal is output to send a route establishment request to the multicast router that was connected before switching, and the multicast router that the establishment request sending means sent the route establishment request before switching switched out It is also preferable to output the second instruction signal so as to transmit the request.

  As a result, when the radio base station has been switched but the multicast router has not been switched, the transmission control means sends the first instruction signal, the second instruction signal, and the first instruction signal to the currently connected multicast router. Since the information is sequentially output, a route establishment request, a withdrawal request, and a route establishment request are sequentially transmitted from the mobile terminal to the current multicast router. In addition, when both the radio base station and the multicast router are switched, the transmission control means sends the first instruction signal to the currently connected multicast router as the target, the multicast router that was connected before the switching, and the before the switching. Since the second instruction signal is output for the multicast router that sent the route establishment request to the multicast router, the route establishment request is sent to the multicast router after switching, and the multicast distribution route is established to the multicast router that was established before switching A withdrawal request is sent. In either case, since the route establishment request is transmitted first, the delay time until reception of the information signal after the radio base station is switched can be shortened. If the multicast router does not switch, the route establishment request is sent again after the withdrawal request is sent, so the data link layer switch can be notified of which port it is under. it can. On the other hand, when a multicast router is switched, including the multicast router before switching, there is a mobile terminal as a receiving device subordinate to the multicast router with respect to the multicast router that established the multicast distribution route before switching It is possible to provide information that can be used to confirm

  The node device of the present invention receives an information signal addressed to a predetermined multicast group transmitted from the transmission device, and duplicates the received signal when there is a mobile terminal that desires distribution of the information signal addressed to the multicast group. A multicast router that can be distributed to the subordinate network and a multicast distribution route that receives the information signal distributed by the multicast router and has a mobile terminal that wants to distribute the information signal addressed to the multicast group. Only the data link layer switch that can deliver the received information signal and the information link that is connected to the data link layer switch and can be delivered to the subordinate wireless network Wireless base station and information signal distributed from the wireless base station A first wireless base station connected to a first network in which the mobile terminal is connected to a mobile communication system including the first wireless base station and a second wireless adjacent to the first wireless base station. When the base station is connected to a second network different from the first network, the correspondence between the first radio base station and a node device different from itself connected to the second network is held for the mobile terminal It is characterized by comprising holding means and notification means for notifying the mobile terminal of the correspondence.

  According to the node apparatus of the present invention, it is possible to notify the mobile terminal of the correspondence between the radio base station and the node apparatus that manages the network, and the mobile terminal is adjacent to the radio base station to which the mobile terminal is connected. The network to which the station is connected can be recognized, the multicast distribution route in the movement candidate network can be established before moving, and the multicast distribution route in the network that is unlikely to move can be deleted It becomes like this.

  The mobile communication method of the present invention is a mobile communication method for a mobile terminal belonging to a multicast group to receive an information signal transmitted by multicast via a multicast router, a data link layer switch, and a radio base station. The station switching detection means of the terminal detects that the radio base station to which the mobile terminal itself is connected has switched, and the connection station determination means of the mobile terminal connects to the radio to which the mobile terminal itself is connected. Station switching in the connected station determination step for determining which multicast router is connected to the wireless router adjacent to the base station and the multicast router to which the mobile terminal is connected, and the station switching detection step. The detecting means detects the switching of the radio base station, and the connecting station determining means in the connecting station determining step When it is determined that the multicast router to which the radio base station adjacent to the switched radio base station is connected is different from the multicast router to which the mobile terminal is connected, the mobile station establishment request transmission means And a first update step of transmitting a route establishment request to a multicast router to which a wireless base station adjacent to the wireless base station is connected.

  According to the mobile communication method of the present invention, after switching between radio base stations, when the multicast router to which the radio base station adjacent to the radio base station after the switch is connected is different from the currently connected multicast router, Since the establishment request transmission means transmits a route establishment request to the multicast router to which the adjacent wireless base station is connected, the route establishment request is transmitted to the multicast router that is the destination candidate before movement, and multicast distribution is performed. A route is established. For this reason, when the mobile terminal moves under the multicast router to which the adjacent radio base station is connected, the delay time until the reception of multicast data can be shortened. On the other hand, at this stage, since the multicast distribution route is not established in the data link layer switch existing under the multicast router connected to the adjacent radio base station, multicast data is distributed under the data link layer switch. The wireless bandwidth is not wasted.

  In the mobile communication method of the present invention, the station switching detection means detects the switching of the radio base station in the station switching detection step, and the multicast router to which the radio base station after the switching is connected in the connection station determination step If it is determined that it no longer matches the multicast router that transmitted the route establishment request, a wireless base station adjacent to the wireless base station after the switch is connected from the multicast router that previously transmitted the route establishment request. It is also preferable to include a second update step of sending a withdrawal request to the multicast router excluding the multicast router. In this way, when the wireless base station is switched to a wireless base station that is not adjacent to a wireless base station under a multicast router that has previously established a multicast distribution route after the wireless base station is switched, the withdrawal request transmission means is connected to the multicast router. Since the withdrawal request is sent to the multicast base station, the multicast distribution route in the multicast router that is unlikely to move to the subordinate radio base station can be appropriately deleted, and resources such as wired bandwidth and multicast router memory are also wasted. Can reduce unnecessary consumption.

  In the mobile communication method of the present invention, the router detection means of the mobile terminal switches the radio base station in the router detection step for detecting that the multicast router to which the mobile terminal is connected is switched, and the station switching detection step. If it is detected but multicast router switching is not detected in the router switching detection step, the mobile station establishment request sending means and the withdrawal request sending means send a route establishment request and withdrawal to the currently connected multicast router. If a wireless base station switch is detected in the third update step that sequentially transmits a request and a route establishment request and a station switch detection step, and a multicast router switch is detected in the router switch detection step, the route establishment of the mobile terminal is established. Multicast router after request sending means is switched Send a route establishment request to the multicast router that the withdrawal request transmission means of the mobile terminal was connected to before switching and the multicast router that sent the route establishment request by the establishment request sending means before switching. And a fourth update step to transmit.

  As a result, when the wireless base station has been switched but the multicast router has not been switched, a route establishment request, withdrawal request, route establishment from the mobile terminal to the current multicast router is targeted for the currently connected multicast router. Requests are sent sequentially. Also, when both the wireless base station and multicast router are switched, a route establishment request is sent to the multicast router after switching, and a withdrawal request is sent to the multicast router for which the multicast distribution route was established before switching . In either case, since the route establishment request is transmitted first, the delay time until reception of the information signal after the radio base station is switched can be shortened. If the multicast router does not switch, the route establishment request is sent again after the withdrawal request is sent, so the data link layer switch can be notified of which port it is under. it can. On the other hand, when a multicast router is switched, including the multicast router before switching, there is a mobile terminal as a receiving device subordinate to the multicast router with respect to the multicast router that established the multicast distribution route before switching It is possible to provide information that can be used to confirm

  According to the mobile communication system, mobile terminal, node device, and mobile communication method of the present invention, a function of installing a special node device for each radio base station or receiving radio waves from a plurality of radio base stations in a receiving device When the receiver moves between radio base stations without wastefully consuming the bandwidth of the radio section, the delay time until the multicast packet is received at the destination radio base station is shortened. It becomes possible to do.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown for illustration only. Subsequently, embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals, and redundant description is omitted.

  First Embodiment FIG. 1 is a conceptual diagram of a mobile communication system according to a first embodiment of the present invention. This mobile communication system has a transmission device 10 that transmits multicast packets by multicast communication, multicast routers 20a, 20b, and 20c that distribute multicast packets from the transmission device 10 and distributes packets distributed from the multicast routers. Data link layer switches 30a and 30b having an IGMP-Snooping function that replicates and distributes only to the port where the receiving device exists, and wireless base stations 40a and 40b that transmit packets distributed from the data link layer switch to the subordinate wireless network , 40c, 40d.

  A multicast router 20 a is connected to the transmission device 10. Multicast routers 20b and 20c are further connected under the multicast router 20a, and the multicast routers are formed in a tree shape. In the present embodiment, for the sake of simplicity, an example in which multicast routers are connected on a tree has been shown. However, it is possible to form a complex network that does not have a tree structure by using more multicast routers. Each of the multicast routers 20b and 20c manages a LAN. The data link layer switch 30a is connected to the multicast router 20a, and the data link layer switch 30b is connected to the multicast router 20b. ing. Further, radio base stations 40a and 40b are connected under the data link layer switch 30a, and radio base stations 40c and 40d are connected under the data link layer switch 30b. Circles drawn around each radio base station indicate areas where these radio base stations can communicate, and the mobile terminal 50 first connects to the radio base station 40a and receives multicast packets.

  Further, the multicast routers 20b and 20c also have a function as a management node device, and the correspondence between the radio base station existing at the end of the LAN managed by each router and the address of the management node device in the adjacent network. Tables 201 and 202 are held. The correspondence tables 201 and 202 are information set in advance by a LAN administrator or a mobile communication system provider, and the radio base station existing at the end of the LAN managed by the multicast router 20b is the radio base station 40b. The management node device of the adjacent network is the multicast router 20c, while the radio base station existing at the end of the LAN managed by the multicast router 20c is the radio base station 40c, and the management node device of the adjacent network is the multicast router 20c. Therefore, correspondence tables 201 and 202 as shown in FIG. 1 are held in the multicast routers 20b and 20c, respectively.

  The transmission device 10 is an information processing terminal such as a personal computer or a workstation. The transmitting device 10 transmits, for example, software, file data such as moving images, moving images acquired in real time, and the like as multicast packets to the multicast router 20a.

  The multicast router 20a duplicates the necessary number of multicast packets, and distributes the duplicated multicast packets to the subordinate multicast routers 20b and 20c. Further, the multicast routers 20b and 20c distribute the received multicast packet to the subordinate data link layer switch, if necessary. The data link layer switch duplicates the necessary number of multicast packets and distributes them to the subordinate radio base stations. The wireless base station distributes the received multicast packet to the subordinate wireless network. At this time, since the radio base station is subordinate to the radio section, even if there are a plurality of subordinate multicast receivers, the radio base station only transmits wirelessly once and distributes multicast packets to the subordinate multicast receivers. be able to.

  The mobile terminal 50 is a multicast receiving device. As shown in FIG. 33, the mobile terminal 50 includes, as functional components, a station switching detection unit 501 (station switching detection unit), a router switching detection unit 502 (router switching detection unit), and a connected station determination unit 503 (station). A determination unit), an establishment request transmission unit 504 (establishment request transmission unit), a withdrawal request transmission unit 505 (withdrawal request transmission unit), and a transmission control unit 506 (transmission control unit). The station switching detection unit 501 is a part that detects that the radio base station to which the mobile terminal 50 is connected has been switched. The router switching detection unit 502 is a part that detects that the multicast router connected to the mobile terminal 50 has been switched. The connection station determination unit 503 is a part that determines whether or not the radio base station to which the mobile terminal is currently connected is a radio base station present in the correspondence table. The establishment request transmission unit 504 is a part that transmits a route establishment request for requesting establishment of a distribution route for distributing multicast data to the data link layer switch and the multicast router. The withdrawal request transmission unit 505 is a part that transmits a withdrawal request for requesting withdrawal from the multicast group to which the mobile terminal 50 belongs. The transmission control unit 506 transmits a route establishment request to the establishment request transmission unit 504 according to the detection and determination result of the station switching detection unit 501, the router switching detection unit 502, and the connection station determination unit 503. The second instruction signal for instructing the withdrawal request transmission unit 505 to transmit the withdrawal request is output to the supporting first instruction signal. Details of each part will be described later.

  The establishment request transmission unit 504 of the mobile terminal 50 can receive a multicast packet addressed to a desired multicast group via the wireless base station 40a to which the establishment request transmission unit 504 is currently connected. A multicast distribution route establishment request (route establishment request) is transmitted to the router. In addition, the withdrawal request transmission unit 505 of the mobile terminal 50 similarly transmits a withdrawal request for a multicast group via the currently connected radio base station 40a when reception of the multicast packet becomes unnecessary.

  When the multicast routers 20b and 20c receive the withdrawal request, the multicast routers 20b and 20c send a confirmation request transmitting unit (confirmation request transmitting means, illustrated) for confirming whether there is a mobile terminal belonging to the multicast group. (Details will be described later).

  When the data link layer switches 30a and 30b receive a route establishment request transmitted from the mobile terminal 50 side, the data link layer switches 30a and 30b establish a multicast distribution route for the route corresponding to the received route establishment request (route (Establishing means, not shown), and upon receiving the presence confirmation request from the multicast routers 20b and 20c, the presence confirmation request is distributed to the subordinate network, and a route establishment request is returned according to the distribution. And a distribution route reconfiguring unit (distribution route reconfiguring means) for reconfiguring the multicast distribution route according to

  In such a mobile communication system, an operation of the mobile communication system and a mobile communication method realized using the mobile communication system will be described by taking as an example that the mobile terminal 50 receives a multicast packet addressed to a predetermined multicast group. The address of the multicast group (referred to as multicast group G) is specified as “239.1.2.3”, for example.

  In FIG. 1, a multicast distribution route to the mobile terminal 50 has already been established. First, establishment of this distribution route will be described. In order to receive the multicast packet addressed to the multicast group G, the establishment request transmission unit 504 of the mobile terminal 50 transmits a multicast distribution route establishment request so as to reach the multicast router connected upstream thereof. The multicast distribution route establishment request addressed to the multicast group G also serves as a multicast packet distribution request addressed to the multicast group G and a request to join the multicast group G.

  The route establishment request for the multicast distribution route transmitted from the mobile terminal 50 reaches the port 102 of the data link layer switch 30a via the radio base station 40a. At this time, the route establishing unit (not shown) of the data link layer switch 30a recognizes that the receiving device of the multicast group G exists under the port 102 by looking at the contents of the route establishment request of the multicast delivery route, The fact that the multicast packet addressed to the multicast group G needs to be distributed to the port 102 is recorded in the multicast distribution management table, and the received multicast distribution route establishment request is transferred to the multicast router 20b through the port 101. When the multicast router 20b receives the request for establishment of the multicast distribution route, the multicast router 20b adds the fact that the requested multicast group is distributed to its own multicast distribution management table, and sends the multicast distribution route to the upstream multicast router 20a. Send a request to establish When a request for establishing a multicast distribution route reaches the multicast router 20a to which the transmission device is connected and the multicast router 20a adds that the requested multicast group is distributed to its own multicast distribution management table, the transmission device 10 receives the reception device. A multicast distribution route to 50 is established. In addition, although different from FIG. 1, if the receiving device of the same multicast group G other than the mobile terminal 50 exists under another multicast router and the multicast distribution route to the receiving device is already established, When a multicast distribution route establishment request reaches a router that already has a distribution route, the multicast distribution route is established.

  When the multicast distribution path from the transmission apparatus 10 to the mobile terminal 50 is established, the multicast packet transmitted from the transmission apparatus 10 is transmitted to the mobile terminal 50 via the multicast routers 20a and 20b, the data link layer switch 30a, and the radio base station 40a. Will be reached. The multicast router 20a and the data link layer switch 30a do not distribute a multicast packet to a route that does not have a multicast distribution route, so that the multicast packet is not consumed wastefully and only to a receiving device that needs the multicast packet. Can deliver.

  In addition, the withdrawal request transmission unit 505 of the mobile terminal 50 transmits a withdrawal request from the multicast group so as to reach the currently connected multicast router 20b when reception of the multicast packet becomes unnecessary. The data link layer switch 30a does not delete the multicast distribution path only by receiving the withdrawal request from the multicast group, and transfers it to the multicast router 20b. The confirmation request transmission unit (not shown) of the multicast router 20b that has received the withdrawal request from the multicast group transmits an existence confirmation request in order to confirm whether or not there are other multicast receiving devices under control. If there is no response to the existence confirmation request, the multicast router 20b deletes the multicast distribution route for the multicast group and transmits a multicast distribution route deletion request to the multicast router 20a. The distribution path reconfiguration unit (not shown) of the data link layer switch 30a looks at the content of the existence confirmation request transmitted from the multicast router 20b, records the maximum response time described therein, and performs multicast distribution. The existence confirmation request is distributed to the port where the route exists. The receiving device that has received the existence confirmation request always transmits a route establishment request within the maximum response time, so the multicast distribution route is deleted for the port that has not responded within the recorded maximum response time. By doing so, it is possible to quickly delete the multicast distribution route for the port where the receiving device exists while maintaining the multicast distribution route. Note that the data link layer switch may distribute only the presence confirmation request to all ports other than the reception port, not the port where the multicast distribution path exists.

  As shown in FIG. 1, when the mobile terminal 50 has joined the multicast group G and receives a multicast packet via the radio base station 40a, the mobile terminal 50 is as shown by a two-dot chain line in the figure. Consider moving the connected radio base station while switching from the radio base station 40a to the radio base station 40b, the radio base station 40c, and the radio base station 40d. The router switching detection unit 502 of the mobile terminal 50 holds IP address information of its own multicast router by receiving an advertisement or the like periodically transmitted by the multicast router. Further, the connection station determination unit 503 of the mobile terminal 50 acquires and holds the IP address information of the currently connected radio base station when establishing a connection with the radio base station. In FIG. 1, the multicast router and connected radio base station upstream of itself are identified by the IP address. However, if the IP address is not the IP address, it can be distinguished from other multicast routers and radio base stations. Any identification method may be used.

  As shown in FIG. 2, when the mobile terminal 50 switches the connected radio base station from the radio base station 40a to the radio base station 40b, the station switching detection unit 501 of the mobile terminal 50 has switched its connected base station. Is detected. The station switching detection unit 501 may be anything as long as it can detect that the radio base station connected to the mobile terminal has been switched, for example, a radio base station switch notification from a radio interface card. It may be. When the mobile terminal 50 detects that the connected radio base station has been switched to the radio base station 40b, the mobile terminal 50 transmits the multicast group G via the switched radio base station 40b as indicated by the dotted arrow in FIG. Send a route establishment request for. The route establishment unit (not shown) of the data link layer switch 30a that has received the route establishment request from the port 103 looks at the content of the route establishment request, so that there is also a receiving device of the multicast group G under the port 103. Recognizing this, the fact that the multicast packet addressed to the multicast group G needs to be distributed to the port 103 is recorded in the multicast distribution management table, and the received route establishment request is transferred to the multicast router 20b through the port 101. Note that since the multicast router 20b already has a distribution route addressed to the multicast group G, the route establishment request is not newly transmitted upstream. As a result, as shown in FIG. 3, since the multicast packet (information signal) addressed to the multicast group G is distributed from both the ports 102 and 103 of the data link layer switch 30a, the mobile terminal 50 A multicast packet addressed to the multicast group G can be received via the station 40b.

  Next, the router switching detection unit 502 of the mobile terminal 50 investigates whether the upstream multicast router has changed from the previous multicast router. As this investigation method, for example, an advertisement request packet is transmitted to the multicast router 20b as shown by a dotted arrow in FIG. 4, and the multicast packet 20b sends an advertisement packet as a response as shown by a dotted arrow in FIG. This can be done by transmitting and comparing the information of the advertisement packet with the multicast router information held by itself. At this time, the multicast router 20b transmits the advertisement packet including the correspondence table 201 held by itself.

  When the mobile terminal 50 switches the connected radio base station from the radio base station 40a to the radio base station 40b, the upstream multicast router remains the multicast router 20b. When the upstream multicast router does not change in this way, the mobile terminal 50 transmits a withdrawal request from the multicast group G to the upstream multicast router 20b as indicated by the dotted arrow in FIG.

  When the confirmation request transmitting unit (not shown) of the multicast router 20b receives the withdrawal request from the multicast group G, as described above, in order to confirm whether there is any other receiving device, the dotted line arrow in FIG. Send a presence confirmation request as shown.

  Since the mobile terminal 50 participates in the multicast group G, when receiving the existence confirmation request, the mobile terminal 50 sends a route establishment request to the port 103 of the data link layer switch 30a within the maximum response time as shown by the dotted line arrow in FIG. Send through. The route establishment request may be transmitted in response to the presence confirmation request from the multicast router. However, for simplicity, the route establishment request may be transmitted subsequent to the withdrawal request from the multicast group G described above.

  The distribution path reconfiguration unit (not shown) of the data link layer switch 30a records only the port 103 that responds within the maximum response time described in the existence confirmation request in the multicast distribution management table, and stores it in the previous distribution table. Since the described port 102 is not recorded, multicast packets addressed to the multicast group G are distributed only to the port 103 as shown in FIG.

  In this way, the mobile terminal 50 can receive the multicast packet immediately after moving, and since the multicast packet is not distributed to the route where the receiving device no longer exists due to movement, the receiving device exists. Multicast packets can be distributed only to the route, and the bandwidth can be used effectively. If there is another receiving apparatus under the radio base station 40a, the receiving apparatus transmits a route establishment request in response to the existence confirmation request from the multicast router 20b. Therefore, the multicast distribution route is not deleted by mistake.

  Next, the connection station determination unit 503 of the mobile terminal 50 determines whether or not its connection base station exists in the acquired correspondence table 201. In this case, it is recognized that the current connection base station 40b exists in the acquired correspondence table, and that the adjacent node device is the multicast router 20c. For this reason, the mobile terminal 50 transmits a route establishment request to the multicast router 20c in order to establish a multicast distribution route to the multicast router 20c in advance before movement, as indicated by a dotted arrow in FIG. At this time, since the route establishment request for the normal multicast distribution route can be transmitted only to the multicast router to which it is directly connected, for example, the route establishment request is encapsulated in a unicast packet addressed to the multicast router 20c and transmitted. In addition to the method of encapsulating and transmitting the route establishment request, for example, a special type of route establishment request different from the normal route establishment request may be transmitted directly to the multicast router 20c. Any device can be used as long as it can recognize that there is a receiving device requesting establishment. Further, since the mobile terminal 50 has transmitted a route establishment request to the multicast router 30c, the mobile terminal 50 adds the multicast router 30c to the route established list.

  In the multicast router 20c that has received the route establishment request, since the distribution route addressed to the multicast group G has not yet been established, the fact that the requested multicast group G is distributed is added to its own multicast distribution management table. As shown by the dotted arrow, a route establishment request is transmitted to the upstream multicast router 20a. As a result, as shown in FIG. 12, packets addressed to the multicast group G are also distributed to the LAN under the multicast router 20c. Since the data link layer switch 30b has not received a route establishment request from a receiving device under its control, the data link layer switch 30b does not distribute packets addressed to the multicast group G to any port, and the multicast group G is not transmitted to the radio base stations 40c and 40d. Packets addressed to G are not distributed, and the bandwidth of the wireless section is not wasted. In this way, the mobile terminal 50 can establish a multicast distribution route to the multicast router 20c, which is the destination multicast router, before moving, without wasting the bandwidth of the wireless section. The delay time until the subsequent multicast packet reception can be shortened. In this case, the data link layer switch 30b stops the packet addressed to the multicast group G, but the mode of stopping the distribution of this packet is not limited to this. For example, since the upper multicast router 20c has not received a route establishment request from a receiving device under its control, the multicast router 20c may stop packets addressed to the multicast group G.

  When the mobile terminal 50 further moves and the mobile terminal 50 switches the connected radio base station from the radio base station 40b to the radio base station 40c, the station switching detection unit of the mobile terminal 50 is as shown by a dotted arrow in FIG. In order for the destination radio base station 40c to receive the multicast packet addressed to the multicast group G, a route establishment request is transmitted via the radio base station 40c. The data link layer switch 30b that has received the route establishment request from the port 112 recognizes that a receiving device that requests reception of the multicast group G appears under the port 112 by looking at the content of the route establishment request. The fact that the multicast packet addressed to the multicast group G needs to be distributed to the port 112 is recorded in the multicast distribution management table, and the received route establishment request is transferred to the multicast router 20c through the port 111. Since the multicast distribution path is already established and distributed in the multicast router 20c, the multicast distribution path to the mobile terminal 50 is established only by the processing of the data link layer switch, and the multicast group is set to the port 111 of the data link layer 30b switch. When the packet addressed to G arrives, the data link layer switch 30b delivers the packet to the port 112, so that the mobile terminal 50 can receive the packet addressed to the multicast group G as shown in FIG. .

  Next, the router switching detection unit 502 of the mobile terminal 50 transmits an advertisement request packet as shown by the dotted arrow in FIG. 15 in order to investigate whether the upstream multicast router has changed from the previous multicast router, As indicated by the dotted line arrow in FIG. 16, since the multicast router 20c transmits an advertisement including the correspondence table 202 as a response, it knows that the upstream multicast router has been switched from the multicast router 20b to the multicast router 20c. For this reason, as indicated by the dotted arrow in FIG. 17, the mobile terminal 50 transmits a withdrawal request from the multicast group to the multicast router 20b in order to delete the multicast distribution route existing under the mobile terminal 50. Also in this case, as in the case of the route establishment request described above, the withdrawal request from the normal multicast group can be transmitted only to the multicast router to which it is directly connected. For example, the withdrawal request from the multicast group is sent to the multicast router 20b. Encapsulated with unicast packet addressed and sent. In addition to the method of encapsulating and transmitting a withdrawal request packet from a multicast group, for example, a withdrawal request packet from a multicast group in a different format may be transmitted directly to the multicast router 20b. Can recognize that there is a receiving device that wants to leave the multicast group.

  Receiving the withdrawal request from the multicast group, the multicast router 20b transmits an existence confirmation request as shown by a one-dot chain line arrow in FIG. 18 in order to confirm whether there is any other receiving device.

  Next, the connection station determination unit 503 of the mobile terminal 50 determines whether or not its own connection base station exists in the acquired correspondence table 202. In this case, it is recognized that the current connection base station 40c exists in the acquired correspondence table, and that the adjacent node device is the multicast router 20b. For this reason, the mobile terminal 50 transmits a route establishment request to the multicast router 20b in order to establish a multicast distribution route to the multicast router 20b, as indicated by a dotted arrow in FIG.

  Since there is no multicast receiving device under the multicast router 20b, there is no response to the route establishment request for the existence confirmation request from the subordinate, and after the maximum response time elapses, the data link layer switch 30a has its own multicast Delete the delivery route. On the other hand, since the multicast router 20b receives the route establishment request from the mobile terminal 50, the multicast router 20b holds the distribution route addressed to the multicast group G. Therefore, thereafter, as shown in FIG. 20, the packet addressed to the multicast group G is delivered from the multicast router 20b, but is not delivered from the data link layer switch 30a.

  In the above, the mobile terminal 50 transmits a withdrawal request to the multicast router 20b, and then transmits a route establishment request, thereby deleting only the multicast distribution route of the data link layer switch 30a, and the multicast router 20b. The method of keeping the multicast distribution route is described. However, if the method can hold the multicast distribution route of the multicast router 20b while transmitting the existence confirmation request to the multicast router 20b, a withdrawal request and a route establishment request are sent. For example, a special packet requesting to maintain the multicast distribution route may be transmitted while transmitting the existence confirmation request to the multicast router 20b.

  In this way, even when both the connecting radio base station and the multicast router change, the mobile terminal 50 can receive the multicast packet immediately after moving, and there is no receiving device due to movement. Since the multicast packet is not distributed to the route, the multicast packet can be distributed only to the route where the receiving device exists, and the wireless band can be used effectively. In this case as well, when there is another receiving device under the radio base station 40b, the receiving device transmits a route establishment request in response to the presence confirmation request from the multicast router 20b, and therefore there is no receiving device. Despite this, the multicast delivery route is not accidentally deleted. Even if the mobile terminal 50 changes direction and moves again under the radio base station 40b, the multicast router 20b still holds the multicast distribution route, so that the mobile terminal 50 Multicast packets can be received.

  When the mobile terminal 50 further moves and the mobile terminal 50 switches the connected radio base station from the radio base station 40c to the radio base station 40d, the station switching detection unit of the mobile terminal 50 is as shown by the dotted line arrow in FIG. In order for the destination radio base station 40d to receive the multicast packet addressed to the multicast group G, a route establishment request is transmitted via the radio base station 40d. The route establishing unit (not shown) of the data link layer switch 30b recognizes that there is a receiving device of the multicast group G under the port 113 by looking at the contents of the route establishment request. Is recorded in the multicast distribution management table, and the received route establishment request is transferred to the multicast router 20c through the port 111. Note that since the multicast router 20c already has a distribution route addressed to the multicast group G, the route establishment request is not newly transmitted upstream. As a result, as shown in FIG. 22, since the multicast packet (information signal) addressed to the multicast group G is distributed from both the ports 112 and 113 of the data link layer switch 30b, the mobile terminal 50 A multicast packet addressed to the multicast group G can be received via the station 40d.

  Next, the router switching detection unit 502 of the mobile terminal 50 transmits an advertisement request packet as shown by a dotted arrow in FIG. 23 in order to investigate whether the upstream multicast router has changed from the previous multicast router, As indicated by a dotted arrow in FIG. 24, since the multicast router 20c transmits an advertisement including the correspondence table 202 as a response, the mobile terminal 50 recognizes that the upstream multicast router remains the multicast router 20c. For this reason, as in the case where the connected radio base station is switched from the radio base station 40a to the radio base station 40b, the mobile terminal 50 is connected to the upstream multicast router 20c as shown by the dotted arrow in FIG. A withdrawal request from the multicast group G is transmitted.

  When the confirmation request transmission unit (not shown) of the multicast router 20c receives the withdrawal request from the multicast group G, as in the case described above, it confirms whether there is any other receiving device. An existence confirmation request is transmitted as indicated by a chain line arrow.

  Since the mobile terminal 50 participates in the multicast group G, when receiving the presence confirmation request, the mobile terminal 50 sends a route establishment request to the port 113 of the data link layer switch 30b within the maximum response time as shown by the dotted arrow in FIG. Send through.

  The distribution path reconfiguration unit (not shown) of the data link layer switch 30b records only the port 113 that responds within the maximum response time described in the existence confirmation request in the multicast distribution management table, and stores it in the previous distribution table. Since the described port 112 is not recorded, thereafter, as shown in FIG. 28, the multicast packet addressed to the multicast group G distributed from the multicast router 20c is distributed only to the port 113 of the data link layer switch 30b. become.

  Next, the connection station determination unit 503 of the mobile terminal 50 determines whether or not its own connection base station exists in the acquired correspondence table 202. In this case, since the current connection base station 40d does not exist in the acquired correspondence table, the mobile terminal 50 makes a diagram to the multicast router 20b in order to delete the currently established multicast distribution route. As indicated by a dotted arrow in 29, a withdrawal request from the multicast group is transmitted.

  Receiving the withdrawal request from the multicast group, the multicast router 20b transmits an existence confirmation request as shown by a one-dot chain line arrow in FIG. 30 in order to confirm whether there is any other receiving device. Since there is no other multicast receiving device under the multicast router 20b, there is no response to the presence confirmation request, and after the maximum response time has elapsed, the multicast router 20b deletes the multicast distribution route held by itself.

  Thereafter, as indicated by a dotted arrow in FIG. 31, the multicast router 20b transmits a multicast distribution route deletion request to the multicast router 20a.

  Upon receiving the multicast distribution route deletion request from the multicast router 20b, the multicast router 20a deletes the multicast distribution route related to the route in which the multicast router 20b exists, and does not distribute the multicast packet. Finally, as shown in FIG. The multicast packet is distributed only to the route where the receiving device 50 exists.

  FIG. 34 is a flowchart showing the operation of the mobile terminal 50 in FIGS. When detecting that the radio base station has been switched, the mobile terminal 50 transmits a multicast distribution route establishment request via the switch-destination radio base station (step 101). Next, the mobile terminal 50 transmits an advertisement request to determine whether or not the connected multicast router has been switched (step 102). Since the multicast router transmits an advertisement including the correspondence table as a response, the advertisement is received (step 103). It is determined whether or not the connected multicast router has been switched based on the received advertisement (step 104). If the multicast router has not been switched, a request for withdrawal from the multicast group is transmitted to the current multicast router in order to delete the multicast distribution route to the wireless base station before movement (step 105). Thereafter, a route establishment request for the multicast distribution route is transmitted again (step 106). On the other hand, when the connected multicast router is switched, a request for withdrawal from the multicast group is transmitted to the previous multicast router in order to stop multicast distribution to the radio base station before movement (step 107). Next, with reference to the correspondence table, a request to leave the multicast group is transmitted to the multicast router that is not an adjacent node of the current radio base station by the established multicast router (step 108). Further, in order to establish a multicast distribution route to the movement candidate network in advance, a multicast route establishment request is transmitted to a multicast router that has not established a route in an adjacent node corresponding to the current wireless base station (step 109). ).

  By following this flowchart, the mobile terminal 50 can start receiving multicast packets immediately after moving, stop multicast distribution in the radio base station before moving, and appropriately delete unnecessary multicast distribution paths, Can be used effectively. In addition, since the multicast receiving device presence confirmation request is transmitted before the multicast router deletes the multicast distribution route, the multicast distribution route is not erroneously deleted.

  By the way, in the description so far, the mobile terminal 50 first transmits a multicast distribution route establishment request after detecting the switching of the radio base station, and then investigates whether or not the multicast router has changed. First, it is possible to investigate whether the multicast router has changed, and then send a request for establishing a multicast distribution route.

  In the description so far, it has been described that the management of the correspondence table is performed with the IP addresses of the radio base station and the management node device (multicast router). However, these correspondences do not necessarily have to be performed with the IP address. It may be performed with the MAC (Media Access Control) address of the radio base station and the IP address of the multicast router, so that the mobile terminal can identify the radio base station and transmit a packet to the management node device of the adjacent network. As long as it is satisfied that information is provided, it may be anything. In the above description, the case where there is only one radio base station in the correspondence table is described. However, when there are a plurality of adjacent networks, it is assumed that there are a plurality of radio base stations in the correspondence table. In addition, when one radio base station is adjacent to a plurality of networks, a plurality of adjacent node devices may be associated with one radio base station. In that case, a route establishment request and a withdrawal request are transmitted to a plurality of adjacent node devices when the connected radio base station is switched.

  In this application, the advertisement request packet and the advertisement packet are used to detect whether the upstream multicast router has changed and to determine the management node device of the adjacent radio base station by acquiring the correspondence table. It is not necessary to perform detection and determination of the management node device of the adjacent radio base station in one packet, and detection of whether the upstream multicast router has changed uses an advertisement to determine the management node device of the adjacent radio base station The correspondence table may be transmitted from the multicast router in a packet different from the advertisement. Further, even if the method is not based on the packet, any method can be used as long as the mobile terminal can detect whether the upstream multicast router has changed and can determine the management node device of the adjacent radio base station. Good.

  Second Embodiment FIG. 35 shows a conceptual diagram of a mobile communication system according to a second embodiment of the present invention. In this embodiment, proxy servers 60a and 60b for transmitting a withdrawal request from a multicast group on behalf of a mobile terminal are provided under the multicast routers 20b and 20c, and these proxy servers serve as LAN management node devices. The correspondence tables 601 and 602 are respectively managed. Upon receiving the route establishment request and withdrawal request from the multicast group from the mobile terminal 50, these proxy servers 60 transmit a withdrawal request from the multicast group to the multicast router to which the proxy server 60 is connected and from the mobile terminal 50. When an advertisement request is received, an advertisement including a correspondence table is transmitted.

  In the first embodiment, when the mobile terminal 50 transmits a route establishment request or a withdrawal request to a device other than the currently connected multicast router, the mobile terminal 50 directly transmits to the corresponding multicast router. When it is necessary to send a route establishment request or withdrawal request to a router other than the currently connected multicast router, the mobile terminal 50 sends a route establishment request or withdrawal request to the proxy server 60. The proxy server 60 that has received these request packets from the mobile terminal 50 transmits a route establishment request and a withdrawal request to the multicast router 20 of the network to which the proxy server 60 is connected.

  As described above, when a route establishment request or withdrawal request is transmitted to a network other than the currently connected network, the proxy server 60 is used to transmit the route establishment request or withdrawal request to the multicast router 20 so that the route establishment request or withdrawal request can be received. Thus, the packet reaches the multicast router from the downstream side of the multicast packet distribution, and the route establishment request and the withdrawal request can faithfully follow the principle of multicast communication that is performed from the requesting side. For this reason, this brings about an advantage that consistency with other protocols related to multicast communication is improved.

  (3rd embodiment) FIG. 36: shows the conceptual diagram of the mobile communication system by 3rd embodiment of this invention. In the above description, only one data link layer switch is connected to one multicast router. However, as shown in this figure, a plurality of data link layer switches may be connected in a tree shape. Each data link layer switch sees the route establishment request and the existence confirmation request as described above, and individually performs the process related to its own multicast distribution management table, so that only the packet where the receiving device exists is multicast packet. Can be delivered.

  As described above, according to the above-described embodiments, when the mobile terminal 50 detects that the connected radio base station has been switched, the mobile terminal 50 checks whether the connected multicast router has also switched, and the connected multicast router has changed. If not, send a route establishment request, a withdrawal request, and a route establishment request in order to the multicast router of the currently connected network. The withdrawal request is sent to the multicast router of the network before the movement to the multicast router.

  In addition, the mobile terminal 50 refers to the acquired correspondence table, and in the adjacent network considered as a destination candidate, in order to establish a multicast distribution route in advance, the currently connected wireless base station is included in the correspondence table. If there is, a route establishment request is transmitted to the corresponding adjacent node device. When it is no longer necessary to hold a previously established multicast distribution route, a withdrawal request is transmitted to the corresponding node device in order to delete the multicast distribution route. In this way, the delay time until the mobile terminal starts receiving multicast packets after moving can be shortened, and the multicast packets can be delivered to routes that do not have multicast receivers early. It is possible to stop and reduce unnecessary multicast packet distribution to prevent unnecessary use of bandwidth.

1 is a conceptual diagram of a mobile communication system according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram illustrating a next stage of FIG. 1. FIG. 3 is a conceptual diagram showing the next stage of FIG. 2. FIG. 4 is a conceptual diagram showing the next stage of FIG. 3. FIG. 5 is a conceptual diagram showing the next stage of FIG. 4. FIG. 6 is a conceptual diagram showing the next stage of FIG. 5. FIG. 7 is a conceptual diagram illustrating the next stage of FIG. 6. FIG. 8 is a conceptual diagram illustrating the next stage of FIG. 7. It is a conceptual diagram showing the next step of FIG. FIG. 10 is a conceptual diagram illustrating the next stage of FIG. 9. It is a conceptual diagram showing the next step of FIG. FIG. 12 is a conceptual diagram illustrating the next stage of FIG. 11. FIG. 13 is a conceptual diagram showing the next stage of FIG. 12. FIG. 14 is a conceptual diagram illustrating the next stage of FIG. 13. FIG. 15 is a conceptual diagram illustrating the next stage of FIG. 14. FIG. 16 is a conceptual diagram illustrating the next stage of FIG. 15. FIG. 17 is a conceptual diagram illustrating the next stage of FIG. 16. FIG. 18 is a conceptual diagram illustrating the next stage of FIG. 17. FIG. 19 is a conceptual diagram showing the next stage of FIG. 18. FIG. 20 is a conceptual diagram illustrating the next stage of FIG. 19. FIG. 21 is a conceptual diagram illustrating the next stage of FIG. 20. FIG. 22 is a conceptual diagram showing the next stage of FIG. 21. FIG. 23 is a conceptual diagram showing the next stage of FIG. 22. FIG. 24 is a conceptual diagram illustrating the next stage of FIG. 23. FIG. 25 is a conceptual diagram illustrating the next stage of FIG. 24. FIG. 26 is a conceptual diagram illustrating the next stage of FIG. 25. FIG. 27 is a conceptual diagram illustrating the next stage of FIG. 26. FIG. 28 is a conceptual diagram illustrating the next stage of FIG. 27. FIG. 29 is a conceptual diagram illustrating the next stage of FIG. 28. FIG. 30 is a conceptual diagram illustrating the next stage of FIG. 29. FIG. 31 is a conceptual diagram showing the next stage of FIG. 30. FIG. 32 is a conceptual diagram illustrating the next stage of FIG. 31. It is the figure which showed the structure of the mobile terminal which concerns on 1st embodiment of this invention. FIG. 33 is a flowchart showing an operation of the mobile terminal in FIGS. 1 to 32. FIG. It is a conceptual diagram of the mobile communication system which concerns on 2nd embodiment of this invention. It is a conceptual diagram of the mobile communication system which concerns on 3rd embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Transmission apparatus, 20a, 20b, 20c ... Multicast router, 30a, 30b, 30c, 30d, 30e ... Data link layer switch, 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h ... Radio base station, 50 ... mobile terminals, 60a, 60b ... proxy servers, 101, 102, 103, 104, 111, 112, 113, 114 ... ports of data link layer switches, 201, 202 ... correspondence tables held by multicast routers, 601, 602 ... Correspondence table held by the proxy server.

Claims (11)

When there is a mobile terminal that receives an information signal addressed to a predetermined multicast group transmitted from a transmission apparatus and desires to distribute an information signal addressed to the multicast group, the received signal is copied and directed to a subordinate network. A multicast router that can be
A data link layer that receives an information signal distributed by the multicast router and can distribute the received information signal only to a multicast distribution path in which a mobile terminal desiring to distribute the information signal addressed to the multicast group exists A switch,
A radio base station connected to the data link layer switch and capable of delivering an information signal delivered from the data link layer switch toward a subordinate radio network;
A mobile communication system including a mobile terminal that receives an information signal distributed from the radio base station,
The mobile terminal
Station switching detection means for detecting that the wireless base station to which it is connected has switched,
A multicast router to which a radio base station adjacent to the radio base station to which it is connected is connected, and a connection station determination means that determines which multicast router is the multicast router to which it is connected;
An establishment request transmitting means for transmitting a route establishment request for requesting establishment of a multicast distribution route;
A withdrawal request transmitting means for transmitting a withdrawal request for requesting withdrawal from the multicast group to which the device belongs;
In response to the detection of the station switching detection means and the determination of the connection station determination means, the first instruction signal that instructs the establishment request transmission means to transmit the route establishment request and the withdrawal request transmission means A transmission control means for outputting a second instruction signal for instructing the transmission of the withdrawal request,
The mobile terminal is connected to a multicast router in which the station switching detection unit detects switching of a radio base station and the connection station determination unit is connected to a radio base station adjacent to the switched radio base station. The transmission control means transmits the route establishment request to the multicast router to which the radio base station adjacent to the switched radio base station is connected. Outputting the first instruction signal;
A mobile communication system. A multicast router to which the station switching detection unit detects switching of a radio base station and the connection station determination unit is connected to a radio base station adjacent to the switched radio base station has previously issued the route establishment request. If it is determined that it does not match the transmitted multicast router, the multicast router to which the wireless base station adjacent to the switched wireless base station is connected is excluded from the multicast router that previously transmitted the route establishment request. The mobile communication system according to claim 1, wherein the second instruction signal is outputted so as to transmit the withdrawal request to a multicast router. The mobile terminal includes router detection means for detecting that a multicast router to which the mobile terminal is connected has switched,
The transmission control means has a function of outputting the first and second instruction signals in response to detection by the router detection means,
When the station switching detection means detects the switching of the radio base station, but the router switching detection means does not detect the switching of the multicast router, the transmission control means In order to sequentially transmit the route establishment request, the withdrawal request, and the route establishment request, the first instruction signal, the second instruction signal, and the first instruction signal are sequentially output,
When the station switching detection unit detects switching of a radio base station and the router switching detection unit detects switching of the multicast router, the transmission control unit establishes the route to the multicast router after switching. After leaving the first instruction signal to send a request, the withdrawal to the multicast router connected before switching, and the multicast router to which the establishment request sending means sent the route establishment request before switching The mobile communication system according to claim 1 or 2, wherein the second instruction signal is output so as to transmit a request. The data link layer switch
Route establishment means for establishing a multicast distribution route for a route according to the received route establishment request when the route establishment request is received;
In response to the withdrawal request, when receiving a presence confirmation request sent by the multicast router to confirm whether there is a mobile terminal belonging to the multicast group, the presence confirmation request is distributed to the subordinate And a delivery route reconfiguring means for reconfiguring a multicast delivery route in response to a route establishment request returned in response to the delivery. 5. The mobile communication system according to claim 1, further comprising: . A mobile terminal that belongs to a multicast group and receives an information signal transmitted by multicast via a multicast router, a data link layer switch, and a radio base station,
Station switching detection means for detecting that the wireless base station to which it is connected has switched,
A multicast router to which a radio base station adjacent to the radio base station to which it is connected is connected, and a connection station determination unit that determines which multicast router is the multicast router to which it is connected;
An establishment request transmitting means for transmitting a route establishment request for requesting establishment of a multicast distribution route;
A withdrawal request transmitting means for transmitting a withdrawal request for requesting withdrawal from the multicast group to which the device belongs;
In response to the detection of the station switching detection means and the determination of the connection station determination means, the first instruction signal that instructs the establishment request transmission means to transmit the route establishment request and the withdrawal request transmission means A transmission control means for outputting a second instruction signal for instructing the transmission of the withdrawal request,
The mobile terminal is connected to the multicast router in which the station switching detection unit detects the switching of the radio base station and the connection station determination unit is connected to the radio base station adjacent to the radio base station after the switching. The transmission control means transmits the route establishment request to the multicast router to which the radio base station adjacent to the switched radio base station is connected. Outputting the first instruction signal;
A mobile terminal characterized by that. A multicast router to which the station switching detection unit detects switching of a radio base station and the connection station determination unit is connected to a radio base station adjacent to the switched radio base station has previously issued the route establishment request. If it is determined that it does not match the transmitted multicast router, the multicast router to which the wireless base station adjacent to the switched wireless base station is connected is excluded from the multicast router that previously transmitted the route establishment request. The mobile terminal according to claim 5, wherein the second instruction signal is output so as to transmit the withdrawal request to a multicast router. It has a router detection means that detects when the multicast router to which it is connected has switched,
The transmission control means has a function of outputting the first and second instruction signals in response to detection by the router detection means,
When the station switching detection means detects the switching of the radio base station, but the router switching detection means does not detect the switching of the multicast router, the transmission control means In order to sequentially transmit the route establishment request, the withdrawal request, and the route establishment request, the first instruction signal, the second instruction signal, and the first instruction signal are sequentially output,
When the station switching detection unit detects switching of a radio base station and the router switching detection unit detects switching of the multicast router, the transmission control unit establishes the route to the multicast router after switching. After leaving the first instruction signal to send a request, the withdrawal to the multicast router that was connected before switching, and the multicast router that the establishment request sending means sent the route establishment request before switching The mobile terminal according to claim 5 or 6, wherein the second instruction signal is output so as to transmit a request. When there is a mobile terminal that receives an information signal addressed to a predetermined multicast group transmitted from a transmission apparatus and desires to distribute an information signal addressed to the multicast group, the received signal is copied and directed to a subordinate network. A multicast router that can be
A data link layer that receives an information signal distributed by the multicast router and can distribute the received information signal only to a multicast distribution path where a mobile terminal desiring to distribute the information signal addressed to the multicast group exists A switch,
A radio base station connected to the data link layer switch and capable of delivering an information signal delivered from the data link layer switch toward a subordinate radio network;
A mobile terminal that receives an information signal distributed from the radio base station, and a node device connected to a mobile communication system including:
Move when a first radio base station connected to the first network in which it is located and a second radio base station adjacent to the first radio base station are connected to a second network different from the first network Holding means for holding the correspondence between the first radio base station and a node device different from itself connected to the second network for the terminal;
Notification means for notifying the mobile terminal of the correspondence,
A node device characterized by that. A mobile communication method for a mobile terminal belonging to a multicast group to receive an information signal transmitted by multicast via a multicast router, a data link layer switch, and a radio base station,
The station switching detection step of the mobile terminal detects that the radio base station to which the mobile terminal itself is connected has switched,
The mobile station connecting station determination means is a multicast router to which a wireless base station adjacent to the wireless base station to which the mobile terminal itself is connected, and which multicast router is the multicast router to which the mobile terminal is connected. A connection station determination step for determining whether there is,
In the station switching detection step, the station switching detection unit detects switching of a radio base station, and in the connection station determination step, the connection station determination unit connects a radio base station adjacent to the switched radio base station. If the multicast router is different from the multicast router to which the mobile terminal is connected, the establishment request transmission means of the mobile terminal is connected to the radio base station adjacent to the switched radio base station A first update step of sending a route establishment request to the multicast router;
A mobile communication method comprising: In the station switching detection step, the station switching detection means detects switching of the radio base station, and in the connection station determination step, the multicast router to which the radio base station after the switching is connected previously transmitted the route establishment request. If it is determined that the multicast router is no longer matched with the multicast router, the multicast router excluding the multicast router to which the radio base station adjacent to the switched radio base station is connected from the multicast router that previously transmitted the route establishment request The mobile communication method according to claim 9, further comprising a second update step of transmitting a withdrawal request to the router. A router detection step in which the router detection means of the mobile terminal detects that the multicast router to which the mobile terminal is connected has switched;
If the switching of the radio base station is detected in the station switching detection step but the switching of the multicast router is not detected in the router switching detection step, the establishment request transmission means and the withdrawal request transmission of the mobile terminal are detected. A third update step of sequentially transmitting the route establishment request, the withdrawal request, and the route establishment request to the multicast router to which the means is currently connected;
When the switching of the radio base station is detected in the station switching detection step, and the switching of the multicast router is detected in the router switching detection step, the route establishment request transmission means of the mobile terminal determines To the multicast router to which the withdrawal request transmission means of the mobile terminal is connected before switching, and to the multicast router that has transmitted the path establishment request by the establishment request transmitting means before switching. The mobile communication method according to claim 9, further comprising a fourth update step of transmitting the withdrawal request to the mobile phone.

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