Recovery from handoff error due to false detection of handoff completion signal at access terminal

• US 9,094,173 B2
• Filed: 06/24/2008
• Issued: 07/28/2015
• Est. Priority Date: 06/25/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Prakash, Rajat, Khandekar, Aamod, Gorokhov, Alexei, Borran (Jaber), Mohammad J.
• Primary Examiner(s): Ferris, Derrick
• Assistant Examiner(s): Esmaeilian, Majid
• Application Number:
  US12/144,969
• Publication Number:
  US 20090029706A1
• Time in Patent Office: 2,590 Days
• Field of Search: 455/436, 370/321, 370/331
• US Class Current: 1/1
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/1671 the supervisory signal being transmitted together with control information
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 36/0079 in case of hand-off failure or rejection

Abstract

Systems and methodologies are described that facilitate recovering from error due to false detection of completion signals at an access terminal. An access terminal specific request signal can be sent to a target base station to initiate handoff or semi-connected state exit. A completion signal can be transferred in response to the access terminal specific request signal. To mitigate errors stemming from false detection of the completion signal at the access terminal, forward link and reverse link confirmation signals can be transferred to confirm successful handoff or connected state re-entry completion. For example, the access terminal can determine handoff or re-entry to be successful when a forward link confirmation signal is detected prior to expiration of a timer. Moreover, the forward link and reverse link confirmation signals can each include more CRC bits as compared to a number of CRC bits included in the completion signal.

Claims

1. A method at an access terminal that facilitates mitigating error associated with false detection of completion signals in a wireless communication environment, comprising:

transmitting an access terminal specific request signal to a target base station;

detecting a completion signal in response to the access terminal specific request signal, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant;

starting a timer upon detecting the completion signal; and

confirming transmission of the completion signal from the target base station by determining whether a forward link confirmation signal is received from the target base station prior to an expiration of the timer.

2. The method of claim 1, wherein the access terminal specific request signal is a handoff request signal.

3. The method of claim 2, further comprising:

deciding to handoff from a source base station to the target base station; and

transmitting the handoff request signal while in a Try to Handoff state.

4. The method of claim 1, wherein the access terminal specific request signal is a reserved signal utilized to re-enter a connected state from a semi-connected state.

5. The method of claim 4, wherein the completion signal is the access grant.

6. The method of claim 1, wherein the access terminal specific request signal includes information pertaining to an identity of the access terminal.

7. The method of claim 1, further comprising transmitting the access terminal specific request signal with a non-zero buffer size even if a buffer associated with the access terminal is empty when request (REQ) based handoff is utilized.

8. The method of claim 1, further comprising transitioning to a confirmation state when the completion signal is detected.

9. The method of claim 1, further comprising returning to a Try to Handoff state upon determining that the timer expired prior to receipt of the forward link confirmation signal.

10. The method of claim 9, further comprising performing reconfirmation when the forward link confirmation signal is not received by transmitting access probes again if handoff was initiated by transmitting access probes or, if handoff was initiated by transmitting either a channel quality indicator (CQI) signal or a request (REQ) signal, continuing to transmit the CQI signal or the REQ signal until confirmation is attained.

11. The method of claim 1, wherein the timer expires at a threshold time duration.

12. The method of claim 1, wherein the forward link confirmation signal is one of a forward link packet or an acknowledgement to a reverse link packet.

13. The method of claim 1, further comprising transmitting a reverse link confirmation signal to the target base station to enable the target base station to recognize at least one of handoff to the target base station has been successful or reentry to connected state from a semi-connected state has been successful.

14. The method of claim 13, wherein the reverse link confirmation signal is one of a reverse link packet or an acknowledgement to a forward link packet.

15. The method of claim 13, wherein the forward link confirmation signal and the reverse link confirmation signal each include more cyclic redundancy check (CRC) bits than the completion signal.

16. An access terminal, comprising:

a memory that retains instructions related to sending an access terminal specific request signal to a target base station, receiving a completion signal in response to the access terminal specific request signal, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant, initiating a timer upon receiving the completion signal, and confirming transmission of the completion signal from the target base station by identifying whether a forward link confirmation signal is obtained from the target base station prior to an expiration of the timer; and

a processor, coupled to the memory, configured to execute the instructions retained in the memory.

17. The access terminal of claim 16, wherein the access terminal specific request signal is a handoff request signal.

18. The access terminal of claim 16, wherein the access terminal specific request signal is a reserved signal utilized to re-enter a connected state from a semi-connected state.

19. The access terminal of claim 18, wherein the completion signal is the access grant.

20. The access terminal of claim 16, wherein the access terminal specific request signal includes information pertaining to an identity of the access terminal.

21. The access terminal of claim 16, wherein the memory further retains instructions related to sending the access terminal specific request signal with a non-zero buffer size even if a buffer associated with the access terminal is empty when a request (REQ) based handoff is employed.

22. The access terminal of claim 16, wherein the memory further retains instructions related to switching to a confirmation state when the completion signal is received.

23. The access terminal of claim 16, wherein the memory further retains instructions related to switching to a Try to Handoff state upon determining that the timer expired before obtaining the forward link confirmation signal.

24. The access terminal of claim 23, wherein the memory further retains instructions related to effectuating reconfirmation when the forward link confirmation signal is not received by sending access probes again if handoff was initiated by sending access probes or, if handoff was initiated by sending either a channel quality indicator (CQI) signal or a request (REQ) signal, continuing to send the CQI signal to the REQ signal until confirmation is attained.

25. The access terminal of claim 16, wherein the timer expires at a threshold time duration.

26. The access terminal of claim 16, wherein the forward link confirmation signal is one of a forward link packet or an acknowledgement to a reverse link packet.

27. The access terminal of claim 16, wherein the memory further retains instructions related to sending a reverse link confirmation signal to the target base station to enable the target base station to recognize at least one of handoff to the target base station has been successful or re-entry to connected state from semi-connected state has been successful.

28. The access terminal of claim 27, wherein the reverse link confirmation signal is one of a reverse link packet or an acknowledgement to a forward link packet.

29. The access terminal of claim 27, wherein the forward link confirmation signal and the reverse link confirmation signal each include more cyclic redundancy check (CRC) bits than the completion signal.

30. An access terminal that enables utilizing an error recovery scheme in a wireless communication environment, comprising:

means for transferring an access terminal specific request signal to a target base station;

means for initiating a timer when a completion signal is detected, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

means for confirming transmission of the completion signal from the target base station by determining whether a forward link confirmation signal is obtained before an expiration of the timer.

31. The access terminal of claim 30, further comprising means for transferring the access terminal specific request signal to the target base station to effectuate a handoff from a source base station to the target base station.

32. The access terminal of claim 31, wherein the access terminal specific request signal is a handoff request signal.

33. The access terminal of claim 32, wherein the handoff request signal has a non-zero buffer even if a buffer associated with the access terminal is empty when a request (REQ) based handoff is effectuated.

34. The access terminal of claim 30, further comprising means for transferring the access terminal specific request signal to the target base station to effectuate transitioning from a semi-connected state to a connected state.

35. The access terminal of claim 34, wherein the access terminal specific request signal is a reserved signal and the completion signal is the access grant.

36. The access terminal of claim 30, wherein the timer expires at a threshold time duration that is one of preset or dynamically determined.

37. The access terminal of claim 36, further comprising means for switching to a Try to Handoff state if the forward link confirmation signal is not obtained within the threshold time duration.

38. The access terminal of claim 30, further comprising means for performing reconfirmation when the forward link confirmation signal is not obtained.

39. The access terminal of claim 30, further comprising means for transferring a reverse link confirmation signal to the target base station to enable the target base station to recognize at least one of handoff to the target base station has been successful or re-entry to connected state from semi-connected state has been successful.

40. The access terminal of claim 39, wherein the forward link confirmation signal and the reverse link confirmation signal each include more cyclic redundancy check (CRC) bits than the completion signal.

41. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code for transferring an access terminal specific request signal by an access terminal to a target base station;

code for initiating a timer at the access terminal when a completion signal is detected, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

code for confirming transmission of the completion signal from the target base station at the access terminal by determining whether a forward link confirmation signal is obtained by the access terminal before an expiration of the timer.

42. The computer program product of claim 41, wherein the computer-readable medium further comprises code for transferring the access terminal specific request signal to the target base station to effectuate a handoff from a source base station to the target base station.

43. The computer program product of claim 41, wherein the computer-readable medium further comprises code for transferring the access terminal specific request signal to the target base station to effectuate transitioning from a semi-connected state to a connected state.

44. The computer program product of claim 41, wherein the computer-readable medium further comprises code for returning to a Try to Handoff state upon determining that the timer expired before obtaining the forward link confirmation signal.

45. The computer program product of claim 41, wherein the timer expires at a threshold time duration that is one of preset or dynamically determined.

46. The computer program product of claim 41, wherein the computer-readable medium further comprises code for transferring a reverse link confirmation signal to the target base station to enable the target base station to recognize at least one of handoff to the target base station has been successful or re-entry to a connected state from a semi-connected state has been successful.

47. The computer program product of claim 46, wherein the forward link confirmation signal and the reverse link confirmation signal each include more cyclic redundancy check (CRC) bits than the completion signal.

48. In a wireless communications system, an access terminal comprising:

a processor configured to;

transmit an access terminal specific request signal to a target base station;

detect a completion signal in response to the access terminal specific request signal, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant;

start a timer upon detecting the completion signal; and

confirm transmission of the completion signal from the target base station by determining whether a forward link confirmation signal is received from the target base station prior to an expiration of the timer.

49. A method at a base station that facilitates recovering from false completion signal detection in a wireless communication environment, comprising:

receiving an access terminal specific request signal from an access terminal;

transmitting a completion signal to the access terminal in response to the access terminal specific request signal, the completion signal indicates resources assigned to the access terminal, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

transmitting a forward link confirmation signal to the access terminal, wherein the forward link confirmation signal enables the access terminal to confirm receipt of the completion signal prior to expiration of a timer of the access terminal.

50. The method of claim 49, wherein the access terminal specific request signal is one of a handoff request signal or a reserved signal utilized by the access terminal to exit semi-connected state.

51. The method of claim 49, further comprising analyzing the access terminal specific request signal to determine at least one of an identity of the access terminal or a context associated with the access terminal.

52. The method of claim 49, further comprising allocating non-zero amounts of resources to the access terminal.

53. The method of claim 49, further comprising transitioning to a confirmation state upon transmitting the completion signal to the access terminal.

54. The method of claim 49, wherein the forward link confirmation signal is one of a forward link assignment block or an acknowledgement (ACK) to a reverse link packet.

55. The method of claim 49, further comprising transmitting the completion signal to the access terminal irrespective of buffer data being included in the access terminal specific request signal.

56. The method of claim 49, further comprising:

receiving a reverse link confirmation signal from the access terminal; and

recognizing at least one of handoff for the access terminal has completed or the access terminal has returned to connected state from semi-connected state upon receiving the reverse link confirmation signal.

57. The method of claim 49, further comprising:

receiving a backhaul message that indicates a disparate base station serves the access terminal; and

transitioning to a Non-Serving state from at least one of a Serving state or a Confirm Handoff state upon receiving the backhaul message.

58. A wireless communications base station, comprising:

a memory that retains instructions related to obtaining an access terminal specific request signal from an access terminal, sending a completion signal to the access terminal in response to the access terminal specific request signal, the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant, and sending a forward link confirmation signal to the access terminal, wherein the forward link confirmation signal enables the access terminal to confirm receipt of the completion signal prior to expiration of a timer of the access terminal; and

a processor, coupled to the memory, configured to execute the instructions retained in the memory.

59. The wireless communications base station of claim 58, wherein the access terminal specific request signal is one of a handoff request signal or a reserved signal utilized by the access terminal to exit semi-connected state.

60. The wireless communications base station of claim 58, wherein the memory further retains instructions related to analyzing the access terminal specific request signal to determine at least one of an identity of the access terminal or a context associated with the access terminal.

61. The wireless communications base station of claim 58, wherein the memory further retains instruction related to transitioning to a confirmation state upon transmitting the completion signal to the access terminal.

62. The wireless communications base station of claim 58, wherein the forward link confirmation signal is one of a forward link assignment block or an acknowledgement (ACK) to a reverse link packet.

63. The wireless communications base station of claim 58, wherein the memory further retains instructions related to sending the completion signal to the access terminal irrespective of buffer data being included in the access terminal specific request signal.

64. The wireless communications base station of claim 58, wherein the memory further retains instruction related to recognizing at least one of handoff for the access terminal has completed or the access terminal has returned to a connected state from a semi-connected state upon detecting a reverse link confirmation signal.

65. The wireless communications base station of claim 58, wherein the memory further retains instruction related to transitioning to a Non-Serving state from at least one of a Serving state or a Confirm Handoff state upon receiving a backhaul message that indicates a disparate base station serves the access terminal.

66. A wireless communications base station that enables mitigating error associated with false completion signal detection in a wireless communication environment, comprising:

means for analyzing an obtained request signal specific to an access terminal;

means for sending a completion signal to the access terminal based upon the request Signal specific to the access terminal, wherein the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

means for transmitting a forward link confirmation signal to the access terminal that allows the access terminal to confirm receipt of the completion signal prior to expiration of a timer of the access terminal.

67. The wireless communications base station of claim 66, wherein the request signal to the access terminal is one of a handoff request signal or a reserved signal utilized by the access terminal to exit semi-connected state.

68. The wireless communications base station of claim 66, further comprising means for determining at least one of an identity of the access terminal or a context corresponding to the access terminal based upon analyzing the request signal specific to the access terminal.

69. The wireless communications base station of claim 66, further comprising means for transitioning to a confirmation state upon sending the completion signal to the access terminal.

70. The wireless communications base station of claim 66, wherein the forward link confirmation signal is one of a forward link assignment block or an acknowledgement (ACK) to a reverse link packet.

71. The wireless communications base station of claim 66, further comprising means for sending the completion signal to the access terminal irrespective of buffer data being included in the request signal specific to the access terminal.

72. The wireless communications base station of claim 66, further comprising means for recognizing at least one of handoff for the access terminal has completed or the access terminal has returned to connected state from semi-connected state upon detecting a reverse link confirmation signal from the access terminal.

73. The wireless communications base station of claim 66, further comprising means for switching to a Non-Serving state from at least one of a Serving state or a Confirm Handoff state upon receiving a backhaul message that indicates a disparate base station serves the access terminal.

74. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code for evaluating an obtained request signal specific to an access terminal by a target base station;

code for transferring a completion signal to the access terminal by the target base station based upon the request signal specific to the access terminal, the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

code for transferring a forward link confirmation signal by the target base station to the access terminal that allows the access terminal to confirm receipt of the completion signal prior to expiration of a timer of the access terminal.

75. The computer program product of claim 74, wherein the request signal specific to the access terminal is one of a handoff request signal employed by the access terminal to handoff from a source base station or a reserved signal utilized by the access terminal to exit a semi-connected state.

76. The computer program product of claim 74, wherein the computer-readable medium further comprises code for determining at least one of an identity of the access terminal or a context corresponding to the access terminal based upon analyzing the request signal specific to the access terminal.

77. The computer program product of claim 74, wherein the computer-readable medium further comprises code for transitioning to a confirmation state upon transferring the completion signal to the access terminal.

78. The computer program product of claim 74, wherein the forward link confirmation signal is one of a forward link assignment block or an acknowledgement (ACK) to a reverse link packet.

79. The computer program product of claim 74, wherein the computer-readable medium further comprises code for transferring the completion signal to the access terminal irrespective of buffer data being included in the request signal.

80. The computer program product of claim 74, wherein the computer-readable medium further comprises code for recognizing at least one of handoff for the access terminal has completed or the access terminal has returned to a connected state from a semi-connected state upon detecting a reverse link confirmation signal from the access terminal.

81. The computer program product of claim 74, wherein the computer-readable medium further comprises code for transitioning to a Non-Serving state from at least one of a Serving state or a Confirm Handoff state upon receiving a backhaul message that indicates a disparate base station serves the access terminal.

82. In a wireless communications system, a base station comprising:

a processor configured to;

receive an access terminal specific request signal from an access terminal;

transmit a completion signal to the access terminal in response to the access terminal specific request signal, the completion signal is one of a reverse link assignment block, a forward link assignment block, or an access grant; and

transmit a forward link confirmation signal to the access terminal, wherein the forward link confirmation signal enables the access terminal to confirm receipt of the completion signal prior to expiration of a timer of the access terminal.