TECHNIQUE FOR CONTROLLING HANDOVERS WITHIN A MULTI-RADIO WIRELESS COMMUNICATION SYSTEM

• US 20090017823A1
• Filed: 05/30/2005
• Published: 01/15/2009
• Est. Priority Date: 05/30/2005
• Status: Active Grant

• Current Assignee: Optis Cellular Technology LLC (Brevet Capital)
• Original Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson), Ericsson GmbH (Telefonaktiebolaget LM Ericsson)
• Inventors: Sachs, Joachim, Simonsson, Arne, Magnusson, Per
• Granted Patent: US 8,213,382 B2
• Time in Patent Office: Days
• US Class Current: 455/437
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface

Abstract

A technique is provided for use by a Multi-Radio Management Resource (MRRM) component of a multi-radio wireless communication system for controlling the handover of a mobile terminal between different radio access technologies (RAT). In one example, all suitable RATs having coverage areas currently covering the location of a mobile terminal are identified. The performance gain that might be achieved via a handover to one of the other RATs is then determined by the MRRM based on various performance gain factors. Handover costs that will be incurred as a result of the handover are also explicitly calculated. Then, a cost-adjusted gain is determined by the MRRM based on the performance gain and the handover costs. A handover is only triggered by the MRRM if the cost-adjusted gain exceeds a minimum threshold. The speed and trajectory of the mobile terminal may also be considered.

Claims

1. A method for use by a multi-radio wireless communication system for controlling a handover of a mobile terminal between different radio access technologies, the method comprising the steps of:

controlling the handover based on handover cost-adjusted gain that depends on characteristics of the radio access technologies,

wherein the handover is triggered on the network side by a network unit implemented either within at least one of the radio access technologies or in a multi-radio network controller.

2. The method of claim 1, wherein the handover controlling step is performed for a plurality of mobile terminals in operation at a given time.

3. The method of claim 1 further comprising the steps of:

identifying radio access technologies having coverage areas currently covering a location of the mobile terminal;

determining a performance gain between a current radio access technology and other radio access technologies covering the location of the mobile terminal based on performance gain factors;

determining handover costs between the current radio access technology and other radio access technologies based on handover cost factors;

determining a handover cost-adjusted gain based on the performance gain and the handover costs;

identifying the radio access technology having the largest handover cost-adjusted gain; and

triggering handover of the mobile terminal to the radio access technology having the largest handover cost-adjusted gain.

4. The method of claim 3, wherein the step of triggering handover of the mobile terminal is only performed if the handover cost adjusted gain of the radio access technology to receive the handover exceeds a minimum threshold.

5. The method of claim 3, wherein the performance gain factors depend on at least one characteristic of the radio access technologies and characteristics of a particular service class.

6. The method of claim 5, wherein the performance gain factors are representative of one or more of the frequency band, data rate, security support, free capacity, cell load, signal strength, channel quality, service efficiency, and spectral efficiency of the radio access technologies.

7. The method of claim 3, wherein the handover cost factors are representative of one or more of data loss switching delay, signaling overhead, protocol interaction, link characteristics, switching algorithms, switching point locations of the radio access technologies and characteristics of a particular service class.

8. The method of claim 1, wherein the handover cost adjusted gain is further adjusted based on terminal mobility.

9. The method of claim 1, further comprising the steps of:

estimating time periods during which gains from a switch to another radio access technology could be achieved based on motion of the mobile terminal and/or estimating the frequency at which handovers are anticipated within another radio access technology based on the motion of the mobile terminal; and

determining a mobility-compensated handover cost-adjusted gain based on performance gain, handover costs, and at least one of the estimated time periods and the estimated frequencies.

10. The method of claim 8, wherein the adjustments based on the terminal mobility are based on average handover rates of the radio access technologies.

11. The method of claim 1, further comprising the steps of:

retrieving prestored average time periods during which gains from a switch to another radio access technology are achieved or retrieving prestored average handover rates at which handovers occur within another radio access technology, and

determining a mobility-compensated handover cost-adjusted gain based on performance gain, handover costs, and at least one of the average time period and the average handover rate.

12. The method of claim 9, wherein the steps of identifying the radio access technology having the largest handover cost-adjusted gain and triggering handover of the mobile terminal to the radio access technology having the largest handover cost-adjusted gain are performed using the mobility-compensated handover cost-adjusted gain.

13. The method of claim 1 wherein the radio access technologies exploit one or more of GSM, UMTS. S3G, WLAN, WiMAX, high speed download packet access (HSDPA) technologies, and IEEE-specified technologies including 802.11;

802.16;

802.20;

802.22; and

802.15 protocols.

14. The method of claim 1 wherein different operators operate the different radio access technologies and the handover cost-adjusted gain depends on the particular operator.

15-17. -17. (canceled)

18. A device for use by a multi-radio wireless communication system for controlling a handover of a mobile terminal between different radio access technologies, the device comprising:

means for controlling the handover based on a handover cost-adjusted gain that depends on characteristics of the radio access technologies, and

a handover triggering unit for triggering the handover on the network side, the triggering unit being implemented either within at least one of the radio access technologies or in a multi-radio network controller.

19. The device of claim 18, adapted to control handovers for a plurality of mobile terminals in operation at a given time.

20. The device of claim 18, wherein the device is implemented as a stand-alone component separated from the radio access technologies, as a component of the multi-radio network controller, or as a component within one of the radio access technologies.

21. The device of claim 18, wherein the device is incorporated within a base station controller or a radio network controller.

22. The device of claim 18, wherein sub-components of the device are distributed among various components of the multi-radio wireless communication system.

23. The device of claim 18 further comprising:

a coverage area determination unit for identifying radio access technologies having coverage areas currently covering a current location of the mobile terminal;

a performance gain determination unit for determining a performance gain between a current radio access technology controlling communications with the mobile terminal and other radio access technologies currently covering the mobile terminal based on performance gain factors;

a handover cost determination unit for determining handover costs between the current radio access technology and the other radio access technologies based on handover cost factors; and

a cost-adjusted gain determination unit for determining a cost adjusted gain based on the performance gain and the handover costs; and

the handover triggering unit operative to identify the radio access technology having the largest cost-adjusted gain and to selectively trigger handover of the mobile terminal to the radio access technology having the largest cost-adjusted gain.

24. The device of claim 23, wherein the handover triggering unit further comprises means for triggering handover of the mobile terminal only if the handover cost-adjusted gain of the radio access technology to receive the handover exceeds a minimum threshold.

25. The device of claim 18 further comprising:

a mobility compensation unit for compensating the handover cost-adjusted gain based on mobility.