SYSTEMS AND METHODS FOR MULTIMODE WIRELESS COMMUNICATION HANDOFF

• US 20090279504A1
• Filed: 09/17/2008
• Published: 11/12/2009
• Est. Priority Date: 05/11/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naquib, Ayman Fawzy, Lee, Kuo-Chun, Chin, Tom
• Granted Patent: US 8,699,450 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/00837 Determination of triggering parameters for hand-off
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 36/1443 between licensed networks
• CPC Class Codes: H04W 36/247 by using coverage extension
• CPC Class Codes: H04W 36/302 due to low signal strength

Abstract

Methods and apparatus for autonomous handover between WiMAX (Worldwide Interoperability for Microwave Access) and CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×RTT (one times Radio Transmission Technology, or 1×) networks during normal operation of a dual-mode mobile station (MS) are provided. The methods and apparatus may improve service continuity during handover and need not require any changes to the WiMAX or CDMA standards.

Claims

1. A method for performing handover between network service via first and second radio access technologies (RATs), comprising:

while communicating via the first RAT, detecting a trigger to initiate a scan for network service via the second RAT, wherein the first and second RATs are different;

initiating the scan for the second RAT, in response to detecting the trigger; and

determining whether to handover to network service via the second RAT based on results of the scan.

2. The method of claim 1, wherein detecting the trigger comprises reacting to a periodic trigger.

3. The method of claim 1, wherein the first RAT is WiMAX (Worldwide Interoperability for Microwave Access) and the second RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×

RTT (one times Radio Transmission Technology).

4. The method of claim 3, wherein initiating the scan comprises transmitting a Scanning Interval Allocation Request (MOB_SCN-REQ) message.

5. The method of claim 3, wherein detecting the trigger comprises:

determining that a mean carrier-to-interference-plus-noise ratio (CINR) or a mean received signal strength indicator (RSSI) in the network service via the first RAT falls below a first threshold; and

determining there is no other channel communicating via the first RAT with a mean CINR or a mean RSSI above a second threshold.

6. The method of claim 3, wherein detecting the trigger comprises determining when a mean carrier-to-interference-plus-noise ratio (CINR) of all elements in a diversity set falls below a threshold.

7. The method of claim 6, wherein the threshold is equal to (1+γ

)*H_Delete, γ

is an adjustment factor ≧

0, and H_Delete is a WiMAX threshold used to determine when to drop an element from the diversity set.

8. The method of claim 3, wherein detecting the trigger comprises determining when a number of neighbors received in a Neighbor Advertisement Message (MOB_NBR-ADV) is less than β

multiplied by an average number of the neighbors in previous Neighbor Advertisement Messages, wherein β

is an adjustment factor ≧

0.

9. The method of claim 8, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor Advertisement Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th MOB_NBR-ADV message.

10. The method of claim 1, wherein the first RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) and the second RAT is WiMAX (Worldwide Interoperability for Microwave Access).

11. The method of claim 10, wherein initiating the scan comprises transmitting “

null cover”

as a Data Rate Control (DRC) cover.

12. The method of claim 10, wherein detecting the trigger comprises determining when all pilots in the CDMA active set have a pilot strength less than a threshold.

13. The method of claim 12, wherein the threshold is equal to (1+γ

)*T_DROP, γ

is an adjustment factor ≧

0, and T_DROP is a CDMA threshold used to determine when to drop a pilot from the CDMA active set.

14. The method of claim 10, wherein detecting the trigger comprises determining when a number of neighbors received in a Neighbor List Message is less than β

multiplied by an average number of the neighbors in previous Neighbor List Messages, wherein β

is an adjustment factor ≧

0.

15. The method of claim 14, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor List Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th Neighbor List Message.

16. The method of claim 14, wherein the Neighbor List Message is at least one of an Extended Neighbor List Message, a General Neighbor List Message, or a Universal Neighbor List Message.

17. A receiver for wireless communication, comprising:

trigger-detection logic configured to detect a trigger to initiate a scan for network service via a second ratio access technology (RAT) while communicating via a first RAT, wherein the first and second RATs are different;

scan-initiation logic configured to initiate the scan for the second RAT, in response to detecting the trigger; and

handover-determination logic configured to determine whether to handover to network service via the second RAT based on results of the scan.

18. The receiver of claim 17, wherein the trigger-detection logic is configured to react to a periodic trigger.

19. The receiver of claim 17, wherein the first RAT is WiMAX (Worldwide Interoperability for Microwave Access) and the second RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×

RTT (one times Radio Transmission Technology).

20. The receiver of claim 19, wherein the trigger-detection logic is configured to determine whether a mean carrier-to-interference-plus-noise ratio (CINR) or a mean received signal strength indicator (RSSI) in the network service via the first RAT falls below a first threshold and to determine whether there is no other channel communicating via the first RAT with a mean CINR or a mean RSSI above a second threshold.

21. The receiver of claim 19, wherein the trigger-detection logic is configured to determine when a mean carrier-to-interference-plus-noise ratio (CINR) of all elements in a diversity set falls below a threshold.

22. The receiver of claim 21, wherein the threshold is equal to (1+γ

)*H_Delete, γ

is an adjustment factor ≧

0, and H_Delete is a WiMAX threshold used to determine when to drop an element from the diversity set.

23. The receiver of claim 19, wherein the trigger-detection logic is configured to determine when a number of neighbors received in a Neighbor Advertisement Message (MOB_NBR-ADV) is less than β

multiplied by an average number of the neighbors in previous Neighbor Advertisement Messages, wherein β

is an adjustment factor ≧

0.

24. The receiver of claim 23, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor Advertisement Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th MOB_NBR-ADV message.

25. The receiver of claim 17, wherein the first RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) and the second RAT is WiMAX (Worldwide Interoperability for Microwave Access).

26. The receiver of claim 25, wherein the trigger-detection logic is configured to determine when all pilots in the CDMA active set have a pilot strength less than a threshold.

27. The receiver of claim 26, wherein the threshold is equal to (1+γ

)*T_DROP, γ

is an adjustment factor ≧

0, and T_DROP is a CDMA threshold used to determine when to drop a pilot from the CDMA active set.

28. The receiver of claim 25, wherein the trigger-detection logic is configured to determine when a number of neighbors received in a Neighbor List Message is less than β

multiplied by an average number of the neighbors in previous Neighbor List Messages, wherein β

is an adjustment factor ≧

0.

29. The receiver of claim 28, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor List Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th Neighbor List Message.

30. The receiver of claim 28, wherein the Neighbor List Message is at least one of an Extended Neighbor List Message, a General Neighbor List Message, or a Universal Neighbor List Message.

31. An apparatus for performing handover between network service via first and second radio access technologies (RATs), comprising:

means for detecting a trigger to initiate a scan for network service via the second RAT while communicating via the first RAT, wherein the first and second RATs are different;

means for initiating the scan for the second RAT, in response to detecting the trigger; and

means for determining whether to handover to network service via the second RAT based on results of the scan.

32. The apparatus of claim 31, wherein the means for detecting the trigger is configured to react to a periodic trigger.

33. The apparatus of claim 31, wherein the first RAT is WiMAX (Worldwide Interoperability for Microwave Access) and the second RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×

RTT (one times Radio Transmission Technology).

34. The apparatus of claim 33, wherein the means for detecting the trigger is configured to determine whether a mean carrier-to-interference-plus-noise ratio (CINR) or a mean received signal strength indicator (RSSI) in the network service via the first RAT falls below a first threshold and to determine whether there is no other channel communicating via the first RAT with a mean CINR or a mean RSSI above a second threshold.

35. The apparatus of claim 33, wherein the means for detecting the trigger is configured to determine when a mean carrier-to-interference-plus-noise ratio (CINR) of all elements in a diversity set falls below a threshold.

36. The apparatus of claim 35, wherein the threshold is equal to (1+γ

)*H_Delete, γ

is an adjustment factor ≧

0, and H_Delete is a WiMAX threshold used to determine when to drop an element from the diversity set.

37. The apparatus of claim 33, wherein the means for detecting the trigger is configured to determine when a number of neighbors received in a Neighbor Advertisement Message (MOB_NBR-ADV) is less than β

multiplied by an average number of the neighbors in previous Neighbor Advertisement Messages, wherein β

is an adjustment factor ≧

0.

38. The apparatus of claim 37, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor Advertisement Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th MOB_NBR-ADV message.

39. The apparatus of claim 31, wherein the first RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) and the second RAT is WiMAX (Worldwide Interoperability for Microwave Access).

40. The apparatus of claim 39, wherein the means for detecting the trigger is configured to determine when all pilots in the CDMA active set have a pilot strength less than a threshold.

41. The apparatus of claim 40, wherein the threshold is equal to (1+γ

)*T_DROP, γ

is an adjustment factor ≧

0, and T_DROP is a CDMA threshold used to determine when to drop a pilot from the CDMA active set.

42. The apparatus of claim 39, wherein the means for detecting the trigger is configured to determine when a number of neighbors received in a Neighbor List Message is less than β

multiplied by an average number of the neighbors in previous Neighbor List Messages, wherein β

is an adjustment factor ≧

0.

43. The apparatus of claim 42, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor List Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th Neighbor List Message.

44. The apparatus of claim 42, wherein the Neighbor List Message is at least one of an Extended Neighbor List Message, a General Neighbor List Message, or a Universal Neighbor List Message.

45. A mobile device, comprising:

a receiver front-end for communicating via a first radio access technology (RAT);

trigger-detection logic configured to detect a trigger to initiate a scan for network service via a second RAT while communicating via the first RAT, wherein the first and second RATs are different;

scan-initiation logic configured to initiate the scan for the second RAT, in response to detecting the trigger; and

handover-determination logic configured to determine whether to handover to network service via the second RAT based on results of the scan.

46. The mobile device of claim 45, wherein the trigger-detection logic is configured to react to a periodic trigger.

47. The mobile device of claim 45, wherein the first RAT is WiMAX (Worldwide Interoperability for Microwave Access) and the second RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×

RTT (one times Radio Transmission Technology).

48. The mobile device of claim 47, wherein the trigger-detection logic is configured to determine whether a mean carrier-to-interference-plus-noise ratio (CINR) or a mean received signal strength indicator (RSSI) in the network service via the first RAT falls below a first threshold and to determine whether there is no other channel communicating via the first RAT with a mean CINR or a mean RSSI above a second threshold.

49. The mobile device of claim 47, wherein the trigger-detection logic is configured to determine when a mean carrier-to-interference-plus-noise ratio (CINR) of all elements in a diversity set falls below a threshold.

50. The mobile device of claim 49, wherein the threshold is equal to (1+γ

)*H_Delete, γ

is an adjustment factor ≧

0, and H_Delete is a WiMAX threshold used to determine when to drop an element from the diversity set.

51. The mobile device of claim 47, wherein the trigger-detection logic is configured to determine when a number of neighbors received in a Neighbor Advertisement Message (MOB_NBR-ADV) is less than γ

multiplied by an average number of the neighbors in previous Neighbor Advertisement Messages, wherein γ

is an adjustment factor ≧

0.

52. The mobile device of claim 51, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor Advertisement Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th MOB_NBR-ADV message.

53. The mobile device of claim 45, wherein the first RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) and the second RAT is WiMAX (Worldwide Interoperability for Microwave Access).

54. The mobile device of claim 53, wherein the trigger-detection logic is configured to determine when all pilots in the CDMA active set have a pilot strength less than a threshold.

55. The mobile device of claim 54, wherein the threshold is equal to (1+γ

)*T_—

DROP, γ

is an adjustment factor ≧

0, and T_DROP is a CDMA threshold used to determine when to drop a pilot from the CDMA active set.

56. The mobile device of claim 53, wherein the trigger-detection logic is configured to determine when a number of neighbors received in a Neighbor List Message is less than β

multiplied by an average number of the neighbors in previous Neighbor List Messages, wherein β

is an adjustment factor ≧

0.

57. The mobile device of claim 56, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor List Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th Neighbor List Message.

58. The mobile device of claim 56, wherein the Neighbor List Message is at least one of an Extended Neighbor List Message, a General Neighbor List Message, or a Universal Neighbor List Message.

59. A computer-program apparatus for performing handover between network service via first and second radio access technologies (RATs) comprising a computer readable medium having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:

instructions for, while communicating via the first RAT, detecting a trigger to initiate a scan for network service via the second RAT, wherein the first and second RATs are different;

instructions for initiating the scan for the second RAT, in response to detecting the trigger; and

instructions for determining whether to handover to network service via the second RAT based on results of the scan.

60. The computer-program apparatus of claim 59, wherein the instructions for detecting the trigger comprises instructions for reacting to a periodic trigger.

61. The computer-program apparatus of claim 59, wherein the first RAT is WiMAX (Worldwide Interoperability for Microwave Access) and the second RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) or 1×

RTT (one times Radio Transmission Technology).

62. The computer-program apparatus of claim 61, wherein the instructions for detecting the trigger comprises:

instructions for determining that a mean carrier-to-interference-plus-noise ratio (CINR) or a mean received signal strength indicator (RSSI) in the network service via the first RAT falls below a first threshold; and

instructions for determining there is no other channel communicating via the first RAT with a mean CINR or a mean RSSI above a second threshold.

63. The computer-program apparatus of claim 61, wherein the instructions for detecting the trigger comprises instructions for determining when a mean carrier-to-interference-plus-noise ratio (CINR) of all elements in a diversity set falls below a threshold.

64. The computer-program apparatus of claim 63, wherein the threshold is equal to (1+γ

)*H_Delete, γ

is an adjustment factor ≧

0, and H_Delete is a WiMAX threshold used to determine when to drop an element from the diversity set.

65. The computer-program apparatus of claim 61, wherein the instructions for detecting the trigger comprises instructions for determining when a number of neighbors received in a Neighbor Advertisement Message (MOB_NBR-ADV) is less than β

multiplied by an average number of the neighbors in previous Neighbor Advertisement Messages, wherein β

is an adjustment factor ≧

0.

66. The computer-program apparatus of claim 65, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor Advertisement Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th MOB_NBR-ADV message.

67. The computer-program apparatus of claim 59, wherein the first RAT is CDMA (Code Division Multiple Access) EVDO (Evolution-Data Optimized) and the second RAT is WiMAX (Worldwide Interoperability for Microwave Access).

68. The computer-program apparatus of claim 67, wherein the instructions for detecting the trigger comprises instructions for determining when all pilots in the CDMA active set have a pilot strength less than a threshold.

69. The computer-program apparatus of claim 68, wherein the threshold is equal to (1+γ

)*T_DROP, γ

is an adjustment factor ≧

0, and T_DROP is a CDMA threshold used to determine when to drop a pilot from the CDMA active set.

70. The computer-program apparatus of claim 67, wherein the instructions for detecting the trigger comprises instructions for determining when a number of neighbors received in a Neighbor List Message is less than β

multiplied by an average number of the neighbors in previous Neighbor List Messages, wherein β

is an adjustment factor ≧

0.

71. The computer-program apparatus of claim 70, wherein the average number of the neighbors, represented as A_N_NBR(n) for the n^th Neighbor List Message, is an exponential moving average equal to α

*N_NBR(n)+(1−

α

)*A_N_NBR(n−

1), where α

is a smoothing factor for the moving average and N_NBR(n) is the number of the neighbors for the n^th Neighbor List Message.

72. The computer-program apparatus of claim 70, wherein the Neighbor List Message is at least one of an Extended Neighbor List Message, a General Neighbor List Message, or a Universal Neighbor List Message.