Cell selection in mobile radio systems

• US 6,542,742 B2
• Filed: 03/31/1999
• Issued: 04/01/2003
• Est. Priority Date: 04/01/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Müller, Frank, Olofsson, Håkan Gunnar, Schramm, Peter
• Primary Examiner(s): APPIAH, CHARLES NANA
• Application Number:
  US09/282,205
• Publication Number:
  US 20010046879A1
• Time in Patent Office: 1,462 Days
• Field of Search: 455/436, 455/444, 455/450, 455/455, 455/449, 455/485, 455/525, 455/524, 455/552, 455/553, 455/448, 455/434, 455/426, 455/422, 370/329, 370/335, 370/337, 370/331, 370/332, 370/333
• US Class Current: 455/436
• 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 with different air interface schemes, each of said cells comprising at least one Base Station, wherein a Mobile Station communicates with said mobile communications system through an air interface link to one of said at least one Base Station, the method comprising the steps of:

determining communications capabilities of said Base Stations and of said Mobile Station based on a corresponding air interface scheme;

determining possible links between said Mobile Station and said Base Stations based on the communication capabilities;

estimating the quality of each of said possible links between said Mobile Station and said Base Stations;

estimating a Quality of Service value for each of said possible links between said Mobile Station and said Base Stations based on at least the measured link quality and the communication capabilities; and

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

2. The method of claim 1 wherein, each air interface scheme based on a different coding and modulation scheme.

3. The method of claim 1 wherein, said communications capabilities of said plurality of 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 wherein, said capabilities of said plurality of Base Stations and of said Mobile Station are measured in terms of the multislot availability on the links to said plurality of Base Stations.

5. The method of claim 1 wherein, said capabilities of said plurality of Base Stations and of said Mobile Station are measured in terms of the multicarrier availability on the links to said plurality of Base Stations.

6. The method of claim 1 wherein, said highest Quality of Service is equivalent to the highest data throughput on said link.

7. The method of claim 1 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 claim 1 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 claim 1 wherein, said highest Quality of Service is equivalent to the highest speech quality.

10. The method of claim 1 further comprising the step of:

testing for a given system criterion.

11. The method of claim 10 wherein, said system criterion is the test if load is below a given threshold.

12. The method of claim 10 wherein, said system criterion is a test to determine if the increase in interference level is below a given threshold.

13. The method of claim 10 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 claim 1 wherein, said Mobile Station is currently accessing said mobile system from a first Base Station and said cell selection is performed for implementing a handover for said Mobile Station to a second Base Station.

15. The method of claim 1 wherein, said Mobile Station is preparing to access said mobile system and said cell selection is performed for selecting the best cell through which to access said system.

16. The method of claim 1 wherein, said cell selection is performed while said Mobile Station is in idle mode.

17. The method of claim 1 wherein, said Mobile Station and said plurality of Base Stations all support an equal number of air interface schemes.

18. The method of claim 1 wherein, said Mobile Station and at least one of said plurality of Base Stations supports an equal number of air interface schemes, and at least one of the plurality of Base Station supports fewer air interface schemes than said Mobile Station.

19. The method of claim 1 wherein, said Mobile Station and at least one of said plurality of Base Stations supports an equal number of air interface schemes, and at least one of the plurality of Base Station supports more air interface schemes than said Mobile Station.

20. The method of claim 1 wherein, said Mobile Station, at least one of said plurality of Base Stations and a second of said plurality of 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 with different air interface schemes, each of said cells comprises at least one Base Station, wherein a Mobile Station for communicating with said mobile system though an air interface link to one of said at least one Base Stations, comprising:

means for determining communication capabilities of said Base Stations and of said Mobile Station based on a corresponding air interface scheme;

means for determining possible links between said Mobile Station and said Base Stations based on the communication capabilities;

means for estimating the quality of each of said possible links between said Mobile Station and said Base Stations;

means for estimating a Quality of Service value for each of possible links between said Mobile Station and said Base Stations based on at least the measured link quality and the communication capabilities; 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 comprising:

means for testing for a given system criterion.

23. A radiocommunication system comprising:

a mobile station;

a first base station;

a second base station; and

a control unit connected to said first and second base stations, wherein communication capabilities of said first and second base stations and of said mobile station are determined based on a corresponding air interface scheme, wherein possible links between the mobile station and the first and second base stations are determined based on the communication capabilities, wherein the quality of each of the possible links between the mobile station and the first and second base stations are estimated, wherein a Quality of Service value for each of the possible links between the mobile station and the first and second base stations is estimated based on at least the measured link quality and the communication capabilities, and wherein a cell in the radiocommunication system associated with either the first or the second base stations is selected based upon the estimated Quality of Service.

24. The radiocommunication system of claim 23, wherein the control unit is a base station controller.