WO2004070997A2

WO2004070997A2 - Mobile communication system with a proxy location registration option

Info

Publication number: WO2004070997A2
Application number: PCT/US2004/002955
Authority: WO
Inventors: Fumika Gotoh; Ryutaro Hamasaki; Masahiro Maeda
Original assignee: Motorola Inc.
Priority date: 2003-02-04
Filing date: 2004-02-03
Publication date: 2004-08-19
Also published as: JP4319842B2; JP2004241895A; WO2004070997A3

Abstract

To reduce the amount of signalling traffic used bv a plurality of mobile nodes (19) positioned in a vehicle (15), a mobile communication system (fig. 1 or 2) is provided with a vehicle proxy location register ( VPLR 17). The VPLR transmits (via 9 or 1 1) a router advertisement message containing information (PLR option), which indicates that proxy location registration can be performed. A mobile node (19) positioned in the vehicle (15) receives the router advertisement message and transmits a proxy location registration request which includes the information for requesting the VPLR to perform proxy location registration instead of directly refistering a location in the server to the vehicle proxy location register for the purpose of establishing communication between the mobile node and another communication node. This enables the mobile node positioned in the vehicle to communicate with another mobile node via the VPLR.

Description

MOBILE COMMUNICATION SYSTEM WITH A PROXY LOCATION REGISTRATION OPTION

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a mobile communication system for performing location registration in order to establish communication between a mobile node and another communication node, and more particularly to a technology for reducing the amount of communication by performing proxy location registration for a plurality of mobile nodes in a vehicle.

[0002] In a mobile communication system, a mobile node or a mobile terminal moves spatially. To establish communication with such a mobile node, therefore, it is necessary that a network for the mobile communication system constantly grasp the location of the mobile node. Consequently, it is necessary that each mobile node register its location in a network-connected server or the like.

[0003] The configuration of an HMIPv6 protocol based, mobile communication system will now be schematically described as a prior art mobile communication system with reference to FIG. 4. The mobile communication system shown in FIG. 4 comprises a home agent (HA) 1 and a plurality of mobility anchor points (MAPs) , which are linked to the home agent via a segment la. In FIG. 4, only one mobility anchor point 1 (MAP 1) 3a is show .

[0004] The segment la, which is linked to the home agent 1, is linked to another segment lb via a router 9, a network 7, and another router 11. A corresponding node (CN) 5 is linked to segment lb as a communication target . The network 7 can be considered as an arbitrary topology that comprises, for instance, routers and links. [0005] FIG. 4 assumes that a mobile node (MN) 19 is within an area that provides communication with a mobility anchor point 1 (MAPI) 3a. When the mobile node (MN) 19 moves to another area, the mobility anchor point (MAP) corresponding to that area communicates with the mobile node 19.

[0006] The mobile communication system shown in FIG.4, MAPI 3a broadcasts the information about MAPI 3a, including a router advertisement (RA) , to the corresponding area. The mobile node 19 receives the broadcast information to acquire the current location (LCoAl) of the mobile node and the address (RCoA) of MAPI.

[0007] The mobile node 19 then transmits a binding update (BU) , that is, a location registration message, to MAPI. MAPI returns a binding acknowledgement (BA) . This causes MAPI ' s cache, that is, a binding cache (location registration information memory) to store the current location information LCoAl in accordance with the home address of the mobile node 19.

[0008] Next, the mobile node 19 transmits a location registration message (BU) to the home agent (HA) 1. The home agent 1 performs a duplicate address detection (DAD) process to check for a duplicate address. If no abnormality is found, the home agent 1 returns a binding acknowledgement (BA) to the mobile node 19. The binding cache of the home agent 1 then stores the address of MAPI in accordance with the home address of the mobile node 19.

[0009] If, under the above circumstances, the corresponding node (CN) transmits a packet containing the address information about the mobile node 19 to communicate with the mobile node 19, the packet is forwarded to the home agent 1 via router 11, network 7, and router 9. In accordance with the transmitted packet data, the home agent 1 determines the location of the mobile node 19, and finds that the mobile node 19 is in a position to communicate with MAPI. The home agent 1 then transmits the packet data to the mobile node 19 via MAPI.

[0010] Accordingly, the mobile node 19 transmits the location registration message (BU) to the corresponding node

(CN) 5. The desired packet data is then transmitted from the corresponding node 5 to the mobile node 19 via MAPI . In this manner, the corresponding node 5 can communicate with the mobile node 19.

[0011] Because of a recent drastic increase in the number of mobile terminals, the location registration region has become increasingly smaller. The locations of users who use mobile nodes are frequently registered particularly in urban districts where the user density is very high.

[0012] In MIPv6 and HMIPvδ, which are conventional standards of Internet Protocol (IP) , location registration is performed individually by mobile nodes. It is therefore necessary to transmit the location registration message (BU) to sequentially update the location registration in accordance with the move of the mobile node.

[0013] A situation where there are a large number of mobile nodes or mobile terminals in a small space within a vehicle such as a commuter train and that vehicle is moving will now be explained. In this situation, a large number of mobile nodes issue a location registration request to a home network. In this instance, the mobile node communications traffic itself may be extremely low.

[0014] In the above situation, the communications traffic for location registration requests to the home network drastically arises. As a result, the spectral resources turn out to be insufficient .

[0015] To solve the above problems, it is proposed that the locations of a plurality of mobile nodes in a vehicle be collectively registered within the vehicle.

[0016] However, the above proposal has not specifically stated the manner in which the locations of a plurality of mobile nodes are collectively registered.

[0017] The present invention proposes a method for furnishing a mobile communication system with a proxy location register and performing proxy location registration.

[0018] It is an object of the present invention to provide a mobile communication system that is capable of performing proxy location registration for a plurality of mobile nodes in a vehicle in order to reduce the amount of communication for location registration while maintaining the mobile communication system's simple configuration and the compatibility with existing systems.

SUMMARY OF THE INVENTION

[0019] According to one aspect of the present invention, a mobile communication system comprises at least one server for registering a location for allowing a mobile node to communicate with another communication node. The communication node and mobile node communicate with each other in accordance with the location information about the mobile node, which is registered in the server. The mobile communication system comprises a vehicle proxy location register (VPLR) that performs proxy location registration for a mobile node positioned in a vehicle. The vehicle proxy location register transmits a router advertisement message including information (PLR option) indicating that proxy location registration is achievable. A mobile node in the vehicle receives a router advertisement message from the vehicle proxy location register, and transmits a proxy location registration request, which includes the information for requesting the vehicle proxy location register to perform proxy location registration instead of directly registering a location in the server, to the vehicle proxy location register for the purpose of establishing communication between the mobile node and another communication node via the vehicle proxy location register.

[0020] The mobile communication system may be configured so that the mobile node first communicates with the other communication node via the vehicle proxy location register and the server, and then communicates with the other communication node via the vehicle proxy location register and without via the server .

[0021] It is preferred that the vehicle proxy location register transmit to the server a list of location registration information about a plurality of mobile nodes in the vehicle.

[0022] The mobile communication system may alternatively be configured so that the mobile node transmits the proxy location registration request to the vehicle proxy location register when a signal received from the vehicle proxy location register, which contains a router advertisement message, becomes stronger than the other signals received from the server after the mobile node is positioned in the vehicle.

[0023] The server is a home agent, which may be linked to the vehicle proxy location register and linked to another communication node via another link.

[0024] The mobile communication system may alternatively be configured so that the home agent is linked to a plurality of mobility anchor points, and that the vehicle proxy location register is linked to the home agent via the mobility anchor points .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating the configuration of a mobile communication system according to one embodiment of the present invention.

FIG. 2 is a schematic block diagram illustrating an operation performed by the communication system shown in FIG. 1 when a vehicle moves from its initial location.

FIG.3A schematically shows the format of a router advertisement from a vehicle proxy location register. FIG. 3B schematically shows the format of a location registration message from a mobile node.

FIG. 4 is a schematic block diagram illustrating the configuration of an HMIPvβ-based, prior art mobile communication system.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings . FIG. 1 schematically shows the configuration of a mobile communication system according to one embodiment of the present invention. In addition to the mobile communication system components shown in FIG. 4, the mobile communication system shown in FIG. 1 includes a vehicle proxy location register

(VPLR), which is provided in the vehicle 15. The other components are the same as for the system shown in FIG. 4. In FIG. 1, MAP2 3b, which is a second mobility anchor point, is shown in addition to the aforementioned MAPI 3a. [0026] In the mobile communication system shown in FIG. 1, the same operations are performed as described with reference to FIG. 4 before the mobile node (MN) 19 is positioned in the vehicle. The communication between the corresponding node 5 and mobile node 19 is effected, for instance, via MAPI.

[0027] In this instance, the vehicle proxy location register (VPLR) 17 is a router. For the communication from a higher level, it performs the same operations as the mobile node 19. More specifically, the VPLR 17 registers a location with MAPI in the same manner as described earlier with reference to the mobile node 19. Therefore, the binding cache of MAPI stores the VPLR's current location address (VCoAl) in accordance with the VPLR's home address.

[0028] Next, the VPLR 17 performs location registration with the home agent 1 in the same manner.

[0029] The VPLR 17 then broadcasts a router advertisement (RA) . As shown in FIG. 3A, the router advertisement contains, for instance, 1-bit PLR option information in addition to various items of information. In other words, the VPLR 17 broadcasts the router advertisement (RA) , which contains the PLR option, to announce that the VPLR 17 is capable of performing proxy location registration.

[0030] It is now assumed that the mobile node 19 is positioned in the vehicle 15, which has not started moving. In this state, MPA1 broadcasts MAPI information as well as the router advertisement. The VPLR 17 periodically broadcasts the information about MAPI and VPLR as well as the router advertisement. The router advertisement contains the PLR option.

[0031] In this instance, the mobile node 19 merely possesses one interface. Therefore, the mobile node 19 cannot receive the router advertisement from the VPLR 17. Consequently, the mobile node 19 cannot change its corresponding MAP, which is MAPI, or its own address. In this state, therefore, packets are transmitted from the corresponding node 5 to the mobile node 19 via the home agent 1 (initially only) and MAPI.

[0032] Next, a situation where the vehicle such as a train in which a user possessing the mobile node 19 exists has started moving will now de described with reference to FIG.2 in addition to FIG. 1. For this situation, it is assumed that the vehicle 15 moves from an MAPI coverage area to an MAP2 coverage area.

[0033] The VPLR 17 has a plurality of interfaces for communicating with higher-level routers and is therefore capable of receiving a router advertisement (RA) from both MAPI and MAP2. Consequently, the VPLR 17 can retain two current locations (LCoA) , which are VCoAl and VCoA2. These current locations respectively correspond to the MAPI and MAP2 addresses .

[0034] As the vehicle moves, the router advertisement from MAP2 becomes stronger and the router advertisement from MAPI becomes weaker. Therefore, the VPLR 17 selects MAP2 as its MAP, and a handover takes place .

[0035] The VPLR 17 transmits its own location registration message (BU) to MAPI, MAP2 , and home agent (HA) 1. Next, the VPLR 17 broadcasts a router advertisement with a PLR option as shown in FIG. 3A.

[00363 The operation performed by the mobile node 19 positioned in the vehicle 15 will now be described. The vehicle 15 moves from the MAPI coverage area to the MAP2 coverage area. In this state, the router advertisement (RA) from MAPI, which is received by the mobile node 19, has become increasingly weak. Therefore, the mobile node 19 operates another router advertisement and detects a router advertisement from the VPLR 17 as a stronger signal.

[0037] The mobile node 19 detects the PLR option contained in the router advertisement of the VPLR 17 and realizes that the VPLR 17 can perform proxy location registration. The mobile node 19 then acquires the current location (LCoA2 : static address) of the mobile node 19 and transmits a location registration message (BU) to the VPLR 17. The binding cache of the VPLR 17 then stores the home address of the mobile node 19 and the current location (LCoA2) according to the home address .

[0038] As described earlier, the mobile node 19 understands that the PLR option is set by the router advertisement from the VPLR 17, that is, proxy location registration can be performed. Therefore, the mobile node 19 transmits a location registration message (BU) to the VPLR 17 in HMIPvδ instead of directly transmitting it to the home agent 1 and corresponding node (CN) 5.

[0039] Figs. 3A and 3B schematically illustrate the formats of the router advertisement from the VPLR 17 and the location registration message (BU) from the mobile node 19. The router advertisement, which is shown in FIG. 3A, contains the PLR option as described earlier. The PLR option is, for instance, 1-bit data. The employed configuration is such that proxy location registration can be performed when the data is "1", and that proxy location registration cannot be performed when the data is "0" .

[0040] The location registration message from the mobile node 19, that is, the binding update (BU) , which is shown in FIG. 3B, similarly contains PLR option data, which is, for instance, 1-bit data. If, for instance, the 1-bit data is "1", it may indicate that the mobile node 19 asks the VPLR 17 to perform proxy location registration. If, on the other hand, the 1-bit data is "0", it may indicate that the mobile node 19 does not ask the VPLR 17 to perform proxy location registration.

[0041] Upon receipt of the aforementioned location registration message (BU) from the mobile node 19, the VPLR 17 transmits the location registration message to the home agent 1. This ensures that the packet communication from the corresponding node (CN) to the mobile node 19 is conveyed from the corresponding node 5 to the home agent 1, VPLR 17, and mobile node 19.

[0042] Next, the VPLR 17 transmits the location registration message (BU) of the mobile node 19 to corresponding node (CN) 5. Subsequently, the packet communication between the mobile node 19 and corresponding node 5 is conveyed from the corresponding node 5 to the VPLR 17 and mobile node 19.

[0043] The above description deals with a situation where there is only one mobile node 19 in the vehicle 15. In reality, however, a plurality of or a large number of mobile nodes (MN) can be positioned in the vehicle 15. Therefore, the VPLR 17 can simultaneously transmit the location registration messages for a plurality of mobile nodes to the home agent 1 or MAP2. More specifically, the VPLR 17 can simultaneously transmit the information about a plurality of mobile nodes, such as the home address and current location, in the form, for instance, of a table or list.

[00443 When the vehicle 15 continuously moves, the current location (LCoA) of the VPLR 17 continues to vary. For example, it changes from VCoA3 to VCoA3 , and so on to VCoAlO (not shown) .

[0045] However, the current location (LCoA) of the mobile node 19 continues to be LCoA2 as far as it is positioned within the same vehicle 15. [0046] As for signaling for communication control, the mobile node 19 simply has to transmit a location registration message (BU) to the VPLR 17 at the first time only. Even if the vehicle 15 moves later, the mobile node 19 does not have to transmit a location registration message again. As regards the transmission of a location registration message from the mobile node 19 to the home agent 1 or from the mobile node 19 to the corresponding node 5, the VPLR 17 transmits such a location registration message by proxy. Therefore, the mobile node 19 does not have to transmit such a location registration message to the home agent 1 and corresponding node 5 as far as the mobile node 19 is in the vehicle 15. In addition, the VPLR 17 can simultaneously transmit the location registration messages for many mobile nodes, for example, mobile nodes for 100 persons. As a result, when the vehicle 15 moves over a relatively long distance, the amount of packet traffic can be properly reduced.

[0047] If the mobile node 19 and its user both leave the vehicle 15, the HMIPv6-based operation described at the beginning is performed again.

[0048] As is obvious from the foregoing description, the location registration message communications traffic between a mobile node and home agent and between the mobile node and corresponding node can be substantially reduced when a vehicle carrying the mobile node moves over a long distance.

[0049] Further, the packets for the mobile node positioned in the vehicle are relayed by the VPLR. Therefore, the VPLR can be used to transmit various items of information in addition to the information from the corresponding node. For example, news, advertisements, local information, and other information can be effectively conveyed to a plurality of mobile nodes within the vehicle . [0050] It is also possible to automatically vary the operating mode of a mobile node under control of the VPLR. For example, the mobile node of a user in the vehicle can be placed in the vibration mode in which vibration occurs instead of ring tone generation.

[0051] Further, the VPLR can transmit appropriate location information about each mobile node to the home agent or the like. In other words, the VPLR can refrain from transmitting the current locations of individual nodes and convey information indicating that a mobile node is positioned in a train or other vehicle

[0052] For an old mobile node that is not capable of making a request for proxy location registration, the mobile communication system according to the present invention can perform the same operation as a conventional HMIPvδ-based operation. Further, the VPLR has two interfaces, which are convenient for mobile node packet transfer and soft handover. Furthermore, no changes are required for MAPs .

Claims

1. A mobile communication system having at least one server for registering a location for allowing a mobile node to communicate with another communication node, wherein said communication node and said mobile node communicate with each other in accordance with the location information about said mobile node, which is registered with the server, said mobile communication system comprising: a vehicle proxy location register (VPLR) mounted in a vehicle in which a plurality of mobile nodes can be positioned, to perform proxy location registration for a mobile node in said vehicle, wherein said vehicle proxy location register transmits a router advertisement message including information (PLR option) indicating that proxy location registration is achievable, and wherein a mobile node in said vehicle receives a router advertisement message from said vehicle proxy location register and transmits a proxy location registration request, which includes the information for requesting said vehicle proxy location register to perform proxy location registration instead of directly registering a location in said server, to said vehicle proxy location register for the purpose of establishing communication between said mobile node and another communication node via said vehicle proxy location register.

2. The mobile communication system according to claim 1, wherein said mobile node first communicates with said another communication node via said vehicle proxy location register and said server, and then communicates with said another communication node via said vehicle proxy location register and without via said server.

3. The mobile communication system according to claim 1, wherein said vehicle proxy location register transmits to said server a list of location registration information about a plurality of mobile nodes in said vehicle.

4. The mobile communication system according to claim 1, wherein said mobile node transmits said proxy location registration request to said vehicle proxy location register when a signal received from said vehicle proxy location register, which contains a router advertisement message, becomes stronger than the other signals received from the server after said mobile node is positioned in said vehicle.

5. The mobile communication system according to claim 1, wherein said server is a home agent, and wherein the home agent is linked to said vehicle proxy location register and linked to another communication node via another link.

6. The mobile communication system according to claim 5, wherein said home agent is linked to a plurality of mobility anchor points, and wherein said vehicle proxy location register is linked to said home agent via said mobility anchor points.