CELL SELECTION IN MOBILE RADIO SYSTEMS

• US 20010046879A1
• Filed: 03/31/1999
• Published: 11/29/2001
• Est. Priority Date: 04/01/1998
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: MULLER, FRANK, SCHRAMM, PETER, OLOFSSON, HAKAN GUNNAR
• Granted Patent: US 6,542,742 B2
• Time in Patent Office: Days
• US Class Current: 455/525
• CPC Class Codes: H04W 36/26 by agreed or negotiated communication parameters
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/304 due to measured or perceived resources with higher communication quality
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

The present invention relates generally to the problem of cell selection, for e.g. cell handover, in mobile telecommunication systems, and more particularly to the problem of selecting the optimum cell among cells with differing capabilities due to different air interface modes. Known algorithms for cell selection and handover are extended by applying additional criteria that take into account the capabilities, due to different modulation and coding schemes, of the mobile station and the base stations that are possible candidates. The quality of service (“QoS”) is predicted for the different cell candidates based on a combination of signal strength or C/I, different cell capabilities, multislot capability, etc. Then the cell is selected for which the predicted QoS is maximum. In another embodiment the invention is extended by taking into account further criteria which are suitable from a system point of view, e.g. to avoid a significant increase of average outage probability or interference level. The present invention increases the use of base stations supporting high data rates. The result is an increase in overall system throughput.

Claims

1. A method for cell selection in a cellular mobile communications system having a plurality of cells, each with at least one Base Station, and a Mobile Station for communicating with said mobile system, using an air interface scheme supported by the at least one Base Station and the Mobile Station, through an air interface link to one of said at least one Base Stations, comprising the steps of:

measuring the quality of the links between said Mobile Station and said Base Stations;

said method characterized by further comprising the following steps;

determining the communications capabilities of said Base Stations and of said Mobile Station;

estimating a Quality of Service value for each possible link between said Mobile Station and said Base Stations; and

selecting the cell with the Base Station having the highest estimated Quality of Service.

2. The method of

claim 1

further characterized wherein:

each air interface scheme being based on a different coding and modulation scheme;

3. The method of

claim 1

or

2

further characterized wherein:

said communications capabilities of said Base Stations and of said Mobile Station are measured in terms of the capabilities of said air interface schemes.

4. The method of

claim 1

or

2

further characterized wherein:

said capabilities of said Base Stations and of said Mobile Station are measured in terms of the multislot availability on the links to said Base Stations.

5. The method of

claim 1

or

2

further characterized wherein:

said capabilities of said Base Stations and of said Mobile Station are measured in terms of the multicarrier availability on the links to said Base Stations.

6. The method of claims 1-5 further characterized wherein:

said highest Quality of Service is equivalent to the highest data throughput on said link.

7. The method of claims 1-5 further characterized wherein:

said highest Quality of Service is equivalent to a combination of the lowest Bit Error Rate and a sufficient data rate.

8. The method of claims 1-5 further characterized wherein:

said highest Quality of Service is equivalent to a combination of the sufficient Bit Error Rate and the highest data rate.

9. The method of claims 1-5 further characterized wherein.

said highest Quality of Service is equivalent to the highest speech quality.

10. The method of the above claims wherein said method further comprises the step of:

testing for a given system criterion.

11. The method of

claim 10

, further characterized wherein:

said system criterion is the test if load is below a given threshold.

12. The method of

claim 10

further characterized wherein:

said system criterion is a test to see if the increase in interference level is below a given threshold.

13. The method of

claim 10

further characterized wherein:

said system criterion is the test if system criterion indicator based on a combination of load, interference level, and desired data rate is below a given threshold.

14. The method of the above claims further characterized wherein:

said Mobile Station is currently accessing said mobile system from a first Base Station and said cell selection is performed for the purpose of implementing a handover for said Mobile Station to a second Base Station.

15. The method of claims 1-13 further characterized wherein:

said Mobile Station is preparing to access said mobile system and said cell selection is performed for the purpose of selecting the best cell through which to access said system.

16. The method of claims 1-13 further characterized wherein:

said cell selection is performed while said Mobile Station is in idle mode.

17. The method of the above claims further characterized wherein:

said Mobile Station and said Base Stations all support an equal number of air interface schemes.

18. The method of claims 1-16 further characterized wherein:

said Mobile Station and at least one of said Base Stations supports an equal number of air interface schemes, and at least one Base Station supports fewer air interface schemes than said Mobile Station.

19. The method of claims 1-16 further characterized wherein:

said Mobile Station and at least one of said Base Stations supports an equal number of air interface schemes, and at least one Base Station supports more air interface schemes than said Mobile Station.

20. The method of claims 1-16 further characterized wherein:

said Mobile Station, at least one of said Base Stations and a second of said Base Stations each support a different number of air interface schemes.

21. A system for cell selection in a cellular mobile communications system having a plurality of cells, each with at least one Base Station, and a Mobile Station for communicating with said mobile system through an air interface link to one of said at least one Base Stations, comprising:

means for measuring the quality of the links between said MS and said Base Stations;

and further characterized by

said Mobile Station and said Base Stations supporting at least one air interface scheme;

means for determining the capabilities of said Base Stations and of said Mobile Station;

means for estimating a Quality of Service value for each possible link between said Mobile Station and said Base Stations; and

means for selecting the cell with the Base Station having the highest estimated Quality of Service.

22. The system for cell selection of

claim 21

further characterized by:

means for testing for a given system criterion.