Handover control method and apparatus, and mobile communication system

• US 20020137515A1
• Filed: 03/25/2002
• Published: 09/26/2002
• Est. Priority Date: 03/26/2001
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Yabusaki, Masami, Igarashi, Ken, Hayashi, Yasuhisa
• Granted Patent: US 6,970,707 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/22 for handling the traffic

Abstract

The handover control method for use in a mobile communication system changes a handover method according to an overlapping zone residence time of a mobile station by ranking three handover methods for the mobile station including a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method in association with how long the overlapping zone residence time of the mobile station is, and by selecting one handover method that corresponds to the overlapping zone residence time of the mobile station. When either the gateway handover method or the base station controller path extension handover method is selected for use, the handover method selects a handover path of which load on the system is minimum among the handover paths that can be employed by the selected handover method.

Claims

1. A handover control method for use in a mobile communication system, the method comprising the step of:

changing a handover method according to an overlapping zone residence time of a mobile station.

2. The handover control method as claimed in claim 1, wherein,

the step of changing a handover method comprising the sub-steps of:

ranking the handover methods for the mobile station including a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method in association with how long the overlapping zone residence time of the mobile station is; and

selecting one of the handover methods for the mobile station among the three methods, which method corresponds to the overlapping zone residence time of the mobile station.

3. The handover control method as claimed in claim 2, the method further comprising the step of:

selecting a handover path of which load on the system is minimum among the handover paths that can be employed by the selected handover method, when either the gateway handover method or the base station controller path extension handover method is selected for use.

4. The handover control method as claimed in claim 3, wherein:

the overlapping zone residence time is estimated on the basis of a velocity of the mobile station and a configuration of cells.

5. The handover control method as claimed in claim 3, wherein:

the overlapping zone residence time is estimated on the basis of an attenuation factor of electric field intensity from a previous base station before a handover process to a handover-performing mobile station.

6. A mobile communication system comprising base stations that can communicate with mobile stations, a communication network including a plurality of nodes, and a handover control apparatus, wherein,

the mobile station comprises:

a part for indicating a movement characteristic of the mobile station and a handover request to the handover control apparatus,

the handover control apparatus comprises;

a part for holding movement characteristics of the mobile stations;

a part for determining a handover method on the basis of the movement characteristic of a mobile station upon receiving a handover request from the mobile station;

a part for determining a handover path of which load on the system is minimum among the handover paths that can be employed by the determined handover method; and

a part for controlling the nodes and the base stations such that the mobile station are connected with the base station and the nodes using the determined handover path.

7. The mobile communication system as claimed in claim 6, wherein,

the movement characteristic is a velocity of the mobile station,

the part for determining a handover method comprises:

a part for estimating an overlapping zone residence time of the mobile station on the basis of the velocity of the mobile station and a configuration of cells; and

a determination part for determining a handover method on the basis of the overlapping zone residence time of the mobile station,

the determination part for determining a handover method selects one handover method used for the mobile station among three handover methods, which method corresponds to the overlapping zone residence time of the mobile station, and

the three handover methods include a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method, and are ranked in association with how long the overlapping zone residence time of the mobile station is.

8. The mobile communication system as claimed in claim 6, wherein,

the movement characteristic of the mobile station is an attenuation factor of electric field intensity from a previous base station before a handover process to a handover-performing mobile station,

the part for determining a handover method comprises:

a part for estimating an overlapping zone residence time of the mobile station on the basis of the attenuation factor; and

a determination part for determining a handover method on the basis of the overlapping zone residence time of the mobile station,

the determination part for determining a handover method selects one handover method used for the mobile station among three handover methods, which method corresponds to the overlapping zone residence time of the mobile station, and

the three handover methods includes a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method, and are ranked in association with how long the overlapping zone residence time of the mobile station is.

9. A handover control apparatus provided in a communication network including a plurality of nodes and base stations that can communicate with mobile stations, the apparatus comprising:

a part for holding movement characteristics reported from the mobile stations;

a part for determining a handover method on the basis of the movement characteristic of a mobile station upon receiving a handover request from the mobile station;

a part for determining a handover path of which load on the network is minimum among the handover paths that can be employed by the determined handover method; and

a part for controlling the nodes and the base stations such that the mobile station is connected with the base station and the nodes using the determined handover path.

10. The handover control apparatus as claimed in claim 9, wherein,

the movement characteristic is a velocity of the mobile station,

the part for determining a handover method comprises:

a part for estimating an overlapping zone residence time of the mobile station on the basis of the velocity of the mobile station and a configuration of cells; and

a determination part for determining a handover method on the basis of the overlapping zone residence time of the mobile station,

the determination part for determining a handover method selects one handover method used for the mobile station among three handover methods, which method corresponds to the overlapping zone residence time of the mobile station, and

the three handover methods include a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method, and are ranked in association with how long the overlapping zone residence time of the mobile station is.

11. The handover control apparatus as claimed in claim 9, wherein,

the movement characteristic of the mobile station is an attenuation factor of electric field intensity from a previous base station before a handover process to a handover-performing mobile station,

the part for determining a handover method comprises:

a part for estimating an overlapping zone residence time of the mobile station on the basis of the attenuation factor; and

a determination part for determining a handover method on the basis of the overlapping zone residence time of the mobile station,

the determination part for determining a handover method selects one handover method used for the mobile station among three handover methods, which method corresponds to the overlapping zone residence time of the mobile station, and

the three handover methods include a gateway handover method, a base station controller path extension handover method, and a radio link path extension handover method, and are ranked in association with how long the overlapping zone residence time of the mobile station is.