Handover to any cell of a target base station in a wireless communication system

• US 8,909,227 B2
• Filed: 10/02/2007
• Issued: 12/09/2014
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kitazoe, Masato, Flore, Oronzo
• Primary Examiner(s): Elhag, Magdi
• Application Number:
  US12/439,722
• Publication Number:
  US 20100178920A1
• Time in Patent Office: 2,625 Days
• Field of Search: 455/432.1, 455336-444, 370328-342
• US Class Current: 455/436
• CPC Class Codes: H04W 36/0079 in case of hand-off failure or rejection
• CPC Class Codes: H04W 92/20 between access points

Abstract

Techniques for performing handover of a user equipment (UE) in a cell-to-base station manner are described. The UE may receive a handover command to perform handover from a source base station to a target base station. The source base station may send context information for the UE to the target base station, and the context information may be available to all cells of the target base station. The UE may attempt handover from a serving cell of the source base station to a first cell of the target base station. The UE may attempt handover to a second cell of the target base station if the handover to the first cell fails. The UE may (i) receive the first and second cells from the source base station or (ii) receive only the first cell from the source base station and determine the second cell based on broadcast system information.

Claims

1. An apparatus for wireless communication, comprising:

at least one processor configured to;

initiate handover of a user equipment (UE) from a cell of a source base station to a first cell of a target base station, and

initiate handover to a second cell of the target base station if the handover to the first cell of the target base station fails, wherein the first cell and the second cell are both served by the target base station, wherein context information for the UE is transferred from the source base station to the target base station for the handover, and wherein the context information is available to both the first and second cells of the target base station; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1, wherein the at least one processor is configured to send a first random access preamble to the first cell of the target base station to initiate handover to the first cell, and to send a second random access preamble to the second cell of the target base station to initiate handover to the second cell.

3. The apparatus of claim 2, wherein the at least one processor is configured to determine that the handover to the first cell of the target base station failed if a random access response is not received from the first cell.

4. The apparatus of claim 1, wherein the at least one processor is configured to receive information regarding the first and second cells of the target base station from the source base station.

5. The apparatus of claim 1, wherein the at least one processor is configured to receive information regarding the first cell of the target base station from the source base station, and to determine the second cell of the target base station based on system information broadcast by the source base station.

6. The apparatus of claim 1, wherein the at least one processor is configured to receive a list of candidate cells of the target base station from the source base station, and to select the first and second cells from the list of candidate cells.

7. The apparatus of claim 1, wherein the at least one processor is configured to first select the first cell based on measurements for cells of the target base station, and to next select the second cell based on the measurements.

8. The apparatus of claim 1, wherein the at least one processor is configured to receive configuration information for the target base station from the source base station, and to use the configuration information to send signaling to initiate handover to each cell of the target base station.

9. The apparatus of claim 1, wherein the first and second cells of the target base station cover different geographic areas.

10. The apparatus of claim 1, wherein the first and second cells of the target base station operate on different frequencies and have overlapping coverage area.

11. The apparatus of claim 1, wherein the at least one processor is configured to transition to an idle state if the handover to the second cell of the target base station fails and no other cells of the target base station are available to initiate handover.

12. The apparatus of claim 1, wherein the at least one processor is configured to initiate handover to another cell of the source base station if the handover to the second cell of the target base station fails.

13. A method for wireless communication, comprising:

initiating handover of a user equipment (UE) from a cell of a source base station to a first cell of a target base station; and

initiating handover to a second cell of the target base station if the handover to the first cell of the target base station fails, wherein the first cell and the second cell are both served by the target base station, wherein context information for the UE is transferred from the source base station to the target base station for the handover, and wherein the context information is available to both the first and second cells of the target base station.

14. The method of claim 13, wherein the initiating handover to the first cell comprises sending a first random access preamble to the first cell of the target base station to initiate handover to the first cell, and wherein the initiating handover to the second cell comprises sending a second random access preamble to the second cell of the target base station to initiate handover to the second cell.

15. The method of claim 13, further comprising:

receiving information regarding the first and second cells of the target base station from the source base station.

16. The method of claim 13, further comprising:

receiving information regarding the first cell of the target base station from the source base station; and

determining the second cell of the target base station based on system information broadcast by the source base station.

17. An apparatus for wireless communication, comprising:

means for initiating handover of a user equipment (UE) from a cell of a source base station to a first cell of a target base station; and

means for initiating handover to a second cell of the target base station if the handover to the first cell of the target base station fails, wherein the first cell and the second cell are both served by the target base station, wherein context information for the UE is transferred from the source base station to the target base station for the handover, and wherein the context information is available to both the first and second cells of the target base station.

18. The apparatus of claim 17, wherein the means for initiating handover to the first cell comprises means for sending a first random access preamble to the first cell of the target base station to initiate handover to the first cell, and wherein the means for initiating handover to the second cell comprises means for sending a second random access preamble to the second cell of the target base station to initiate handover to the second cell.

19. The apparatus of claim 17, further comprising:

means for receiving information regarding the first and second cells of the target base station from the source base station.

20. The apparatus of claim 17, further comprising:

means for receiving information regarding the first cell of the target base station from the source base station; and

means for determining the second cell of the target base station based on system information broadcast by the source base station.

21. A non-transitory machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:

initiating handover of a user equipment (UE) from a cell of a source base station to a first cell of a target base station; and

initiating handover to a second cell of the target base station if the handover to the first cell of the target base station fails, wherein the first cell and the second cell are both served by the target base station, wherein context information for the UE is transferred from the source base station to the target base station for the handover, and wherein the context information is available to both the first and second cells of the target base station.

22. An apparatus for wireless communication, comprising:

at least one processor configured to;

send a request for handover of a user equipment (UE) from a source base station to a target base station,

send context information for the UE to the target base station, and

send a handover command to the UE to initiate handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station; and

a memory coupled to the at least one processor.

23. The apparatus of claim 22, wherein the at least one processor is configured to send information regarding the first and second cells of the target base station in the handover command to the UE.

24. The apparatus of claim 22, wherein the at least one processor is configured to send only information regarding the first cell of the target base station in the handover command to the UE, and to broadcast a neighbor cell list comprising cells of the target base station.

25. The apparatus of claim 22, wherein the at least one processor is configured to send configuration information for the target base station to the UE, the configuration information being used by the UE to send signaling to initiate handover to each cell of the target base station.

26. The apparatus of claim 22, wherein the at least one processor is configured to send a measurement control message comprising a list of cells of the target base station to the UE, to receive measurements made by the UE based on the measurement control message, and to select the target base station for handover of the UE based on the measurements.

27. A method for wireless communication, comprising:

sending a request for handover of a user equipment (UE) from a source base station to a target base station;

sending context information for the UE to the target base station; and

sending a handover command to the UE to initiate handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station.

28. The method of claim 27, further comprising:

sending information regarding the first and second cells of the target base station in the handover command to the UE.

29. The method of claim 27, further comprising:

sending only information regarding the first cell of the target base station in the handover command to the UE; and

broadcasting a neighbor cell list comprising cells of the target base station.

30. An apparatus for wireless communication, comprising:

at least one processor configured to;

receive a request for handover of a user equipment (UE) from a source base station to a target base station,

receive context information for the UE from the source base station,

exchange signaling with the UE for handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station, and

serve the UE based on the context information if the handover of the UE to the first or second cell is successful; and

a memory coupled to the at least one processor.

31. The apparatus of claim 30, wherein the at least one processor is configured to receive a first random access preamble from the UE at the first cell, to send a first random access response to the UE from the first cell, to receive a second random access preamble from the UE at the second cell, and to send a second random access response to the UE from the second cell.

32. The apparatus of claim 30, wherein the at least one processor is configured to decode in error a first random access preamble sent by the UE to the first cell, to decode correctly a second random access preamble sent by the UE to the second cell, and to send a random access response to the UE from the second cell.

33. A method for wireless communication, comprising:

receiving a request for handover of a user equipment (UE) from a source base station to a target base station;

receiving context information for the UE from the source base station;

exchanging signaling with the UE for handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station; and

serving the UE based on the context information if the handover of the UE to the first or second cell is successful.

34. The method of claim 33, wherein the exchanging signaling with the UE for handover comprises

receiving a first random access preamble from the UE at the first cell,

sending a first random access response to the UE from the first cell,

receiving a second random access preamble from the UE at the second cell, and

sending a second random access response to the UE from the second cell.

35. The method of claim 33, wherein the exchanging signaling with the UE for handover comprises

decoding in error a first random access preamble sent by the UE to the first cell,

decoding correctly a second random access preamble sent by the UE to the second cell, and

sending a random access response to the UE from the second cell.

36. An apparatus for wireless communication, comprising:

means for sending a request for handover of a user equipment (UE) from a source base station to a target base station;

means for sending context information for the UE to the target base station; and

means for sending a handover command to the UE to initiate handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station.

37. The apparatus of claim 36, further comprising:

means for sending information regarding the first and second cells of the target base station in the handover command to the UE.

38. The apparatus of claim 36, further comprising:

means for sending only information regarding the first cell of the target base station in the handover command to the UE; and

means for broadcasting a neighbor cell list comprising cells of the target base station.

39. A non-transitory machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:

sending a request for handover of a user equipment (UE) from a source base station to a target base station;

sending context information for the UE to the target base station; and

sending a handover command to the UE to initiate handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station.

40. An apparatus for wireless communication, comprising:

means for receiving a request for handover of a user equipment (UE) from a source base station to a target base station;

means for receiving context information for the UE from the source base station;

means for exchanging signaling with the UE for handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station; and

means for serving the UE based on the context information if the handover of the UE to the first or second cell is successful.

41. The apparatus of claim 40, wherein the means for exchanging signaling with the UE for handover comprises

means for receiving a first random access preamble from the UE at the first cell,

means for sending a first random access response to the UE from the first cell,

means for receiving a second random access preamble from the UE at the second cell, and

means for sending a second random access response to the UE from the second cell.

42. The apparatus of claim 40, wherein the means for exchanging signaling with the UE for handover comprises

means for decoding in error a first random access preamble sent by the UE to the first cell,

means for decoding correctly a second random access preamble sent by the UE to the second cell, and

means for sending a random access response to the UE from the second cell.

43. A non-transitory machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:

receiving a request for handover of a user equipment (UE) from a source base station to a target base station;

receiving context information for the UE from the source base station;

exchanging signaling with the UE for handover of the UE to the target base station, the UE first initiating handover to a first cell of the target base station and next initiating handover to a second cell of the target base station if the handover to the first cell fails, wherein the first cell and the second cell are both served by the target base station, and wherein the context information for the UE is available to both the first and second cells of the target base station; and

serving the UE based on the context information if the handover of the UE to the first or second cell is successful.