Handover Method in Wireless Communication System, Mobile Station, and Wireless Communication System

• US 20090190555A1
• Filed: 01/15/2009
• Published: 07/30/2009
• Est. Priority Date: 01/30/2008
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Oguchi, Naoki
• Granted Patent: US 8,457,065 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals

Abstract

A handover method, in a wireless communication system having a mobile station and a plurality of base stations, for performing handover of the mobile station from a connected base station to a neighbor base station, the method having the steps of: deciding that neighbor base station information non-reception handover is establish; searching a connectable neighbor base station; acquiring identification information for the neighbor base station; transmitting a handover request including the acquired identification information; transmitting, in the connected base station received the handover request, to the mobile station, service level information included with in a handover response, and deciding a handover destination based on the service level information.

Claims

1. A handover method, in a wireless communication system having a mobile station and a plurality of base stations, for performing handover of the mobile station from a connected base station to a neighbor base station, the method comprising the steps of:

deciding that neighbor base station information non-reception handover is establish, in the mobile station, if the mobile station is without receiving neighbor base station information relating to the neighbor base stations from the connected base station and radio wave strength of radio waves from the connected base station is below a threshold value;

searching a connectable neighbor base station based on frequencies stored in a table in the mobile station, if, in the decision step, a decision is made that the neighbor base station information non-reception handover is established;

acquiring, in the mobile station, identification information for the neighbor base station from the connectable neighbor base station;

transmitting, in the mobile station, a handover request including the acquired identification information to the connected base station;

transmitting, in the connected base station received the handover request, to the mobile station, service level information included with in a handover response, the service level information indicating information as to what extent of service flow can be handed over from the connected base station to the neighbor base station; and

acquiring, in the mobile station, the service level information from the handover response, and deciding a handover destination based on the service level information.

2. The handover method according to claim 1, wherein the decision step decides that the neighbor base station information non-reception handover is established, if calculation is made that the mobile station moves out of the cell of the connected base station without receiving the neighbor base station information based on a size of the cell estimated from the strength of radio wave from the connected base station, a movement velocity of the mobile station, and a transmission interval of the neighbor base station information.

3. The handover method according to claim 1, further comprising a step of transmitting, in the mobile station, to the connected base station an interruption request requesting a temporarily interruption of transmission of frames to the mobile station, wherein

the interruption request transmitting step comprises a step of acquiring the identification information from the connectable neighbor base station when transmission of the frames by the serving base station is interrupted due to the interruption request.

4. The handover method according to claim 1, wherein the identification information acquiring step is executed by the mobile station while transmitting and receiving the frame to and from the connected base station, if in the decision step a decision is made that the neighbor base station information non-reception handover is established.

5. The handover method according to claim 3, wherein the interruption request is a scan request or a sleep request.

6. The handover method according to claim 1, wherein the identification information acquisition step acquires the identification information in receiving frame configuration information from the connectable neighbor base station and in extracting the identification information for the connectable neighbor base station included in the frame configuration information.

7. The handover method according to claim 1, wherein the decision step decides as a handover destination base station the neighbor base station which can take over the greatest amount of service flow with the connected base station using the service level information and the radio waves of which are strongest.

8. A mobile station for performing handover from a serving base station to a neighbor base station, comprising:

a neighbor base station information non-reception handover decision unit which decides that neighbor base station information non-reception handover is established, if neighbor base station information relating to the neighbor base stations is not received from the serving base station and the radio wave strength of radio waves from the serving base station is lower than a threshold value;

a scan processing unit which searches for the connectable neighbor base station based on frequencies stored in a table, if the neighbor base station information non-reception handover decision unit decides that the neighbor base station information non-reception handover is established;

an identification information acquisition unit which acquires identification information for the neighbor base station from the connectable neighbor base stations; and

,

a handover processing unit which transmits to the serving base station a handover request including the acquired identification information, receives from the serving base station a handover response including service level information indicating information as to what extent of service flow can be taken over by the neighbor base stations from the connected base station, and decides the handover destination based on the service level information.

9. A wireless communication system comprising:

a mobile station, and

a plurality of base station, wherein,

the mobile station comprises;

a neighbor base station information non-reception handover decision unit which decides that neighbor base station information non-reception handover is established, if neighbor base station information relating to the neighbor base stations is not received from the serving base station and the radio wave strength of radio waves from the serving base station is lower than a threshold value;

a scan processing unit which searches for the connectable neighbor base station based on frequencies stored in a table, if the neighbor base station information non-reception handover decision unit decides that the neighbor base station information non-reception handover is established;

an identification information acquisition unit which acquires identification information for the neighbor base stations from the connectable neighbor base stations; and

,

a handover processing unit which transmits to the serving base station a handover request including the acquired identification information, receives from the serving base station a handover response including service level information indicating information as to what extent of service flow can be taken over by the neighbor base station from the serving base station, and decides the handover destination based on the service level information, and the serving base station comprises;

a handover response transmission unit which transmits to the mobile station the handover response including the service level information.

10. A processing method in a mobile station for executing a handover processing from a base station to another base station before the mobile station, which wirelessly connects to the base station notifying information relating to a neighbor base station intermittently, receives the information relating to the neighbor base station from the base station, the method comprising the steps of:

receiving signals transmitted from the neighbor base station, and receiving identification information for the neighbor base station;

transmitting the identification information to the connected base station;

receiving from the connected base station the information relating to the neighbor base station corresponding to the identification information; and

deciding a handover destination based-on the information relating to the neighbor base station.

11. A mobile station for executing a handover processing from a base station to another base station before the mobile station, which wirelessly connects to the base station notifying information relating to a neighbor base station intermittently, receives the information relating to the neighbor base station from the base station, the mobile station comprising:

an identification information reception unit which receives signals transmitted from the neighbor base station, and receives identification information from the neighbor base station;

a transmission unit which transmits the identification information to a connection targeted base station;

a neighbor base station information reception unit which receives from the connection targeted base station the information relating to the neighbor base stations corresponding to the identification information; and

a decision unit which decides the handover destination based on information relating to the neighbor base station.

12. A wireless communication system for executing a handover processing in a mobile station from a base station to a another base station before the mobile station, which wirelessly connects to the base station notifying information relating to a neighbor base station intermittently, receives the information relating to the neighbor base station from the base station, wherein,

the mobile station comprises:

an identification information reception unit which receives signals transmitted from the neighbor base station, and receives identification information from the neighbor base station;

a transmission unit which transmits the identification information to a connection targeted base station;

a neighbor base station information reception unit which receives from the connection targeted base station the information relating to the neighbor base station corresponding to the identification information; and

a decision unit which decides the handover destination based on information relating to the neighbor base station, and the connection targeted base station comprises;

a neighbor base station information transmission unit which transmits the information related to the neighbor base station corresponding to the identification information, based on the identification information transmitted from the mobile station.