MOBILE CONTROL DEVICE AND HANDOVER CONTROL METHOD

• US 20080254802A1
• Filed: 06/24/2008
• Published: 10/16/2008
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tajima, Yoshiharu, Ohta, Yoshiaki, Kawabata, Kazuo
• Granted Patent: US 8,532,659 B2
• Time in Patent Office: Days
• US Class Current: 455/440
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 36/026 Multicasting of data during hand-off
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/28 involving a plurality of connections, e.g. multi-call or multi-bearer connections
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 88/14 Backbone network devices
• CPC Class Codes: H04W 92/12 between access points and access point controllers

Abstract

The present invention is a handover control method in a mobile communication system that performs handover control by switching base stations that communicate with a mobile terminal as the mobile terminal moves. In this handover control method, a mobile control device selects one or more handover base station candidates based on the communication state, and based on the communication capabilities of the handover base station candidates, decides a transmission rate for multicasting communication data, and transmits communication data to each of the handover base station candidates at the decided transmission rate, and a handover base station candidate that is decided as a handover base station sends the saved multicast communication data to the mobile terminal.

Claims

1. A handover control method in a mobile communication system that performs handover control by changing base stations that communicate with a mobile terminal as the mobile terminal moves, and comprising:

a first step of selecting one or more handover base station candidates based on the communication state;

a second step of deciding a multicast transmission rate for multicasting communication data based on the communication capabilities of each of the handover base station candidates;

a third step of multicasting the communication data to each of the handover base station candidates at the decided multicast transmission rate; and

a fourth step of sending the communication data that has been multicast and saved from a handover base station candidate that has been decided as a handover base station to the mobile terminal.

2. The handover control method of claim 1, wherein

in the second step, the communication capability is the buffer capacity of each of the handover base station candidates, and the multicast transmission rate for transmitting communication data is decided separately for each of the handover base station candidates based on the respective buffer capacity, or the minimum transmission rate of the handover base station candidates is decided as a common multicast transmission rate.

3. The handover control method of claim 1, wherein

in the second step, the communication capability is availability state of radio communication resources of each of the handover base station candidates, and the multicast transmission rate for transmitting communication data is decided separately for each of the handover base station candidates based on the availability state of the respective radio communication resource availability.

4. The handover control method of claim 1, wherein

in the second step, the communication capability is level of QoS (quality of service) that is executable by each of the handover base station candidates, and the multicast transmission rate for transmitting communication data is decided separately for each of the handover base station candidates based on the respective level of the executable QoS.

5. The handover control method of claim 1, wherein

each of the steps is executed by a mobile control device that is on a higher order than the base stations, or by the base station that is currently communicating with the mobile terminal.

6. The handover control method of claim 1, wherein the second step comprising:

acquiring the communication capability of each of the handover base station candidates by making an inquiry to each handover base station candidate for the communication capability.

7. The handover control method of claim 1, wherein the third step comprising:

in the second step, data that corresponds to the difference between the speed that communication data is input from the network and the speed at which data is multicast is saved separately for each handover base station candidate.

8. The handover control method of claim 1, wherein the third step comprising:

attaching identifiers to multicast packets in order to distinguish packets that are multicast from normal packets.

9. The handover control method of claim 1, wherein the third step comprising:

detecting change in the communication capability of a handover base station candidate during multicasting; and

based on the communication capability after change, adaptively changing the multicast transmission rate to the handover base station candidate, or removing the handover base station candidate as a multicast destination and stopping the multicast to that handover base station candidate.

10. The handover control method of claim 9, wherein the third step further comprising:

when removing the handover base station candidate as a multicast destination, instructing this handover base station candidate to delete the packets to which a multicast identifier is attached.

11. The handover control method of claim 10, wherein

after receiving the instruction to delete packets, the handover base station candidate deletes packets to which multicast identifiers are attached.

12. A mobile control device in a mobile communication system that performs handover control by changing base stations that communicate with a mobile terminal as the mobile terminal moves, and comprising:

a handover base station candidate decision unit that selects one or more handover base station candidates based on the communication state;

a transmission rate decision unit that decides a transmission rate for multicasting communication data based on the communication capabilities of each of the handover base station candidates;

a multicast unit that transmits the communication data to each of the handover base station candidates at the decided multicast transmission rate; and

a handover base station decision unit that decides one of the plurality of handover base station candidates as a handover base station.

13. The mobile control device of claim 12, wherein

each of the handover base station candidates saves the multicast data, and the handover base station candidate that is decided as the handover base station sends the saved communication data to the mobile terminal.

14. The mobile control device of claim 12, wherein

the transmission rate decision unit regards buffer capacity of each handover base station candidate as the communication capability, and based on the buffer capacity, decides a transmission rate for multicasting communication data separately for each handover base station candidate, or decides the minimum transmission rate among the handover base station candidates as a common multicast transmission rate.

15. The mobile control device of claim 12, wherein

the transmission rate decision unit regards availability state of radio communication resources of each handover base station candidate as the communication capability, and based on the availability state of the radio communication resource, decides a transmission rate for multicasting communication data separately for each handover base station candidate.

16. The mobile control device of claim 12, wherein

the transmission rate decision unit regards level of QoS (quality of service) that is executable by each handover base station candidate as the communication capability, and based on the level of the executable QoS, decides a transmission rate for multicasting communication data separately for each handover base station candidate.

17. The mobile control device of claim 12, wherein

the transmission rate decision unit acquires the communication capability of each of the handover base station candidates by making an inquiry to each handover base station candidate for the communication capability.

18. The mobile control device of claim 12, wherein

the multicast unit comprises a transmission rate adjustment unit that multicasts communication data to each of the handover base station candidates at the decided transmission rate;

and

the transmission rate adjustment unit comprises a buffer that saves data of which quantity corresponds to the difference between the speed that communication data is input from the network and the speed at which data is multicast separately for each handover base station candidate.

19. The mobile control device of claim 12, wherein

the multicast unit attaches identifiers to multicast packets in order to distinguish packets that are multicast from normal packets.

20. The mobile control device of claim 12, wherein

when a change in the communication capability of a handover base station candidate is detected during multicasting, the transmission rate decision unit, based on the communication capability after change, adaptively changes the multicast transmission rate to the handover base station candidate, or removes the handover base station candidate as a multicast destination and stops the multicast to that handover base station candidate.