Methods and Apparatus for Making a Handoff Determination as a Function of Service Level Indicating Metrics

• US 20090156211A1
• Filed: 03/14/2008
• Published: 06/18/2009
• Est. Priority Date: 12/13/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Anigstein, Pablo Alejandro, Hussain, Yunus, Hande, Prashanth, Patil, Shailesh
• Granted Patent: US 8,285,283 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/36 by user or terminal equipment

Abstract

Method and apparatus for an access terminal which makes handoff decisions between a number of potential alternative attachment points based on service level indicating metrics are described. The access terminal computes a service level indicating metric differently for a current connection than for a potential alternative connection. A service level indicating metric is a function of loading information and received signal strength. A selection may be made by selecting between attachment points by selecting the attachment point having the highest service level indicating metric from among a plurality of attachment points, one per possible carrier where the attachment point which is considered for a given carrier is the one having the best connection for the given carrier. The access terminal handoff decision approach provides handoff decisions which are nearly as optimal as those which can be achieved using a centralized control node but without the requirement for centralized handoff decisions.

Claims

1. A method of making handoff determinations in an access terminal, the method comprising:

calculating a first service level indicating metric corresponding to a current connection corresponding to a first attachment point using a first function;

calculating a second service level indicating metric corresponding to an alternative connection corresponding to a second attachment point using a second function which is different from said first function; and

making a handoff decision based on said first and second service level indicating metrics.

2. The method of claim 1, wherein calculating said first and second service level indicating metrics is performed as a function of loading factor information corresponding to the first and second attachment points, respectively.

3. The method of claim 2, wherein said second function used to calculate said second service level indicating metric includes a factor corresponding to an additional load which will be placed on said second attachment point if a handoff to said second attachment point occurs.

4. The method of claim 3, further comprising:

receiving power reference signals from attachment points; and

identifying on a per carrier basis, the attachment points with which the best connection can be established using the corresponding carrier.

5. The method of claim 4, wherein the power reference signals corresponding to a carrier were transmitted at the same power level;

and wherein identifying the attachment point with which the best connection can be established includes selecting the attachment point from which the strongest power reference level signal corresponding to the carrier was received.

6. The method of claim 4, wherein the power reference signals corresponding to a carrier are transmitted at different known power levels;

and

wherein identifying the attachment point with which the best connection can be established includes selecting the attachment point as a function of the difference between known transmission power levels corresponding to different attachment points and the strength of the power reference level signals received from the attachment points.

7. The method of claim 4, wherein for each carrier on which a power reference level signal was received, a service level indicating metric is calculated for the corresponding attachment point identified as having the best connection.

8. The method of claim 7, wherein service level indicating metrics are not computed for attachment points which are not identified as having the best connection.

9. The method of 3, wherein said loading factor information indicates a number of users using the corresponding connection.

10. The method of 3, wherein said loading factor information includes a total link sharing weight of the attachment point.

11. The method of claim 10, wherein the first and second functions are a function of a link sharing weight corresponding to the device for which a handoff determination is being made.

12. An access terminal comprising:

a first service level indicating metric calculation module for calculating a first service level indicating metric corresponding to a current connection corresponding to a first attachment point using a first function;

a second service level indicating metric calculation module for calculating a second service level indicating metric corresponding to an alternative connection corresponding to a second attachment point using a second function which is different from said first function; and

a handoff decision module for making a handoff decision based on said first and second service level indicating metrics.

13. The access terminal of claim 12, wherein said first service level indicating metric calculation module calculates said first service level indicating metric as a function of loading factor information corresponding to the first attachment point, and

wherein said second service level indicating metric calculation module calculates said second service level indicating metric as a function of loading factor information corresponding to the second attachment point.

14. The access terminal of claim 13, wherein said second function used to calculate said second service level indicating metric includes a factor corresponding to an additional load which will be placed on said second attachment point if a handoff to said second attachment point occurs.

15. The access terminal of claim 14, further comprising:

a wireless receiver module for receiving power reference signals from attachment points; and

a best connection identification module for identifying on a per carrier basis, the attachment points with which the best connection can be established using the corresponding carrier.

16. The access terminal of claim 15, wherein the power reference signals corresponding to a carrier were transmitted at the same power level;

and

wherein the best connection identification module includes

a received power based selection sub-module for selecting the attachment point from which the strongest power reference level signal corresponding to the carrier was received.

17. The access terminal of claim 15, wherein the power reference signals corresponding to a carrier are transmitted at different known power level;

and wherein the best connection identification module includes

a received power based selection sub-module for selecting the AP as a function of the difference between known transmission power levels corresponding to different attachment points and the strength of the power reference level signals received from the attachment points.

18. The access terminal of claim 15, wherein for each carrier on which a power reference level signal was received, at least one of said first service level indicating metric calculation module and said second service level indicating metric calculation module calculates a service level indicating metric for the corresponding attachment point identified as having the best connection.

19. The access terminal of claim 18, wherein said second service level indicating metric calculation module does not compute a service level indicating metric for attachment points which are not identified as having the best connection.

20. The access terminal of 14, wherein said loading factor information indicates a number of users using the corresponding connection, the access terminal further comprising:

a loading factor recovery module for recovering loading factor information from received broadcast signals.

21. The access terminal of 14, wherein said loading factor information includes a total link sharing weight of the attachment point, the access terminal further comprising:

a loading factor recovery module for recovering loading factor information from received broadcast signals.

22. The access terminal;

of claim 21, wherein the first and second functions are a function of a link sharing weight corresponding to the device for which a handoff determination is being made.

23. An access terminal comprising:

first service level indicating metric calculation means for calculating a first service level indicating metric corresponding to a current connection corresponding to a first attachment point using a first function;

second service level indicating metric calculation means for calculating a second service level indicating metric corresponding to an alternative connection corresponding to a second attachment point using a second function which is different from said first function; and

handoff decision means for making a handoff decision based on said first and second service level indicating metrics.

24. The access terminal of claim 23, wherein said first service level indicating metric calculation means calculates said first service level indicating metric as a function of loading factor information corresponding to the first attachment point, and

wherein said second service level indicating metric calculation means calculates said second service level indicating metric as a function of loading factor information corresponding to the second attachment point.

25. The access terminal of claim 24, wherein said second function used to calculate said second service level indicating metric includes a factor corresponding to an additional load which will be placed on said second attachment point if a handoff to said second attachment point occurs.

26. The access terminal of claim 25, further comprising:

wireless receiver means for receiving power reference signals from attachment points; and

best connection identification means for identifying on a per carrier basis, the attachment points with which the best connection can be established using the corresponding carrier.

27. A computer program product, comprising:

computer-readable medium comprising;

code for causing a computer to calculate a first service level indicating metric corresponding to a current connection corresponding to a first attachment point using a first function;

code for causing a computer to calculate a second service level indicating metric corresponding to an alternative connection corresponding to a second attachment point using a second function which is different from said first function; and

code for causing a computer to make a handoff decision based on said first and second service level indicating metrics.

28. The computer program product of claim 27, wherein calculating said first and second service level indicating metrics is performed as a function of loading factor information corresponding to the first and second attachment points, respectively.

29. The computer program product of claim 28, wherein said second function used to calculate said second service level indicating metric includes a factor corresponding to an additional load which will be placed on said second attachment point if a handoff to said second attachment point occurs.

30. The computer program product of claim 29, wherein said computer-readable medium further comprises:

code for causing a computer to receive power reference signals from attachment points; and

code for causing a computer to identify on a per carrier basis, the attachment points with which the best connection can be established using the corresponding carrier.

31. An apparatus comprising:

a processor configured to;

calculate a first service level indicating metric corresponding to a current connection corresponding to a first attachment point using a first function;

calculate a second service level indicating metric corresponding to an alternative connection corresponding to a second attachment point using a second function which is different from said first function; and

make a handoff decision based on said first and second service level indicating metrics.

32. The apparatus of claim 31, wherein calculating said first and second service level indicating metrics is performed as a function of loading factor information corresponding to the first and second attachment points, respectively.

33. The apparatus of claim 32, wherein said second function used to calculate said second service level indicating metric includes a factor corresponding to an additional load which will be placed on said second attachment point if a handoff to said second attachment point occurs.

34. The apparatus of claim 33, wherein said processor is further configured to:

receive power reference signals from attachment points; and

identify on a per carrier basis, the attachment points with which the best connection can be established using the corresponding carrier.