Mobile communication system, mobile terminal, and mobile communication method

Abstract

It is an object of the present invention to provide a mobile communication system capable of shortening a delay time preceding the reception of a multicast packet at a radio base station which has been reached by a movement of a mobile terminal. The mobile communication system includes a multicast router, a data layer link switch, a radio base station, and a mobile terminal. In cases where the mobile terminal detects switching of the radio base station but does not detect switching of the multicast router, a path establishing request, a withdrawal request, and another path establishing request are sequentially output. When the switching of the radio base station and the switching of the multicast router is detected, a path establishing request is transmitted to the new multicast router, and a withdrawal request is transmitted to the previous multicast router thereafter.

Description

technical field [0001] The invention relates to a mobile communication system, a mobile terminal and a mobile communication method. Background technique [0002] In this specification, an act of generating and transmitting a packet by the device itself is defined as transmission, and an act of copying and transmitting a packet generated by another device to a subordinate device as necessary is defined as distribution. [0003] 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 sending device can send data of files and moving images to multiple receiving devices multicast (IP multicast communication). RFC (Request For Comments) 1112 of IFTF (Internet Engineering Task Force) and the like define a management sequence of a multicast group using IGMP. [0004] In such multicast communication (mnlticast communication), a receiving device is connected to a...

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Problems solved by technology

[0026] However, in the technology described in the above-mentioned Non-Patent Document 3, in an environment where a data link layer switch is connected under the multicast router and a wireless base station is connected under it, even if the wireless base station moves, only the data link When the connection port of the road layer switch changes, but the multicast router connected to the upstream does not change, the join packet (path establishment request) and leave packet (leave request) must be sent to each port of the data link layer switch, but the data The link layer switch is not necessarily assigned an address, and not every port is assigned a different address, so there is a problem that the port cannot be specified for join and leave

[0027] However, in the technology described in the above-mentioned non-patent document 4, since the address of the multicast router of the advertisement packet is used for the movement detection of the receiving device, a data link layer switch is connected under the multicast router, and a wireless router is connected under it. In the base station environment, even if the wireless base station moves between wireless base stations, if the upstream multicast router does not change, but only the connected wireless base station changes, the join packet (path establishment request) cannot be sent, and the wireless base station of the moving destination is in Cannot receive multicast packets immediately after moving

In addition, of course, the deletion of the multicast distribution route of the moving source cannot be performed.

[0028] In this way, the conventional method has the following problems. In an environment where a data link layer switch is connected to the subordinate of the multicast router, a wireless base station is connected to it, and there is a receiving device subordinate to it, if it is not performed before moving When the receiving device moves between wireless base stations in the prediction of the moving destination, etc., the multicast packet cannot be received until the Query packet is sent from the multicast router after the move

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