METHOD AND APPARATUS FOR ADJUSTING A RESELECTION TIMER AND CELL RANKING CRITERIA, AND REPORTING DEGRADED SIGNAL MEASUREMENT OF A SERVING CELL

• US 20080220784A1
• Filed: 03/06/2008
• Published: 09/11/2008
• Est. Priority Date: 03/09/2007
• Status: Abandoned Application

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Sammour, Mohammed, Somasundaram, Shankar
• Application Number:
  US12/043,511
• Publication Number:
  US 20080220784A1
• Time in Patent Office: Days
• US Class Current: 455/437
• 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 36/302 due to low signal strength

Abstract

Various methods for adjusting a reselection timer and cell ranking criteria are disclosed. The ranking criteria of a serving or neighbor cell, or a reselection timer in a wireless transmit/receive unit (WTRU), is adjusted based on how a serving cell signal measurement, (e.g., signal strength, signal quality), compares to a plurality of thresholds over a time interval. In another method, cell ranking criteria is adjusted based on a hysteresis value and a scaling factor when a maximum number of reselections is exceeded and a high mobility factor is detected. Furthermore, a method of reporting cell signal measurements is disclosed, whereby a time-to-trigger time (TTT) interval is started when the neighbor cell signal measurement rises above a reporting range threshold. If the serving cell signal measurement falls below a serving cell threshold, the TTT interval is adjusted and thereby a measurement report is transmitted during the TTT interval.

Claims

1. A wireless communication method of adjusting the ranking criteria of a serving cell associated with a wireless transmit/receive unit (WTRU), the method comprising:

performing a signal measurement of a serving cell;

setting a serving cell hysteresis value to a first value if the signal measurement of the serving cell exceeds a first threshold;

setting the serving cell hysteresis value to a second value if the signal measurement of the serving cell is less that the first threshold and is greater than a second threshold for a first time interval;

setting the serving cell hysteresis value to a third value if the signal measurement of the serving cell is less than the second threshold for a second time interval; and

adjusting the ranking criteria of the serving cell based on the serving cell hysteresis value after being set to one of the first value, the second value and the third value.

2. The method of claim 1 wherein the serving cell signal measurement is reference symbol received quality (RSRQ) and the first and second thresholds are RSRQ thresholds.

3. The method of claim 1 wherein the serving cell signal measurement is received signal code power (RSCP) and the first and second thresholds are RSCP thresholds.

4. The method of claim 1 wherein the serving cell signal measurement is reference signal received power (RSRP) and the first and second thresholds are RSRP thresholds.

5. The method of claim 1 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

6. The method of claim 1 wherein the first value is greater than the second value, the second value is greater than the third value, and the first threshold is greater than the second threshold.

7. The method of claim 1 wherein the first, second and third values are signaled by a network.

8. The method of claim 1 wherein the first value and at least one scaling factor are signaled by a network, and the second and third values are derived from the first value using the at least one scaling factor.

9. The method of claim 1 further comprising:

adjusting a time value of a reselection timer located in the WTRU based on how the signal measurement compares to the first and second thresholds.

10. The method of claim 1 further comprising:

receiving a radio resource control (RRC) message indicating at least one of the first threshold and the second threshold.

11. The method of claim 1 further comprising:

receiving a radio resource control (RRC) message indicating at least one of the first value, the second value and the third value.

12. A wireless communication method of adjusting the ranking criteria of a neighbor cell associated with a wireless transmit/receive unit (WTRU), the method comprising:

performing a signal measurement of a serving cell;

setting a neighbor cell offset value to a first value if the signal measurement of the serving cell exceeds a first threshold;

setting the neighbor cell offset value to a second value if the signal measurement of the serving cell is less that the first threshold and is greater than a second threshold for a first time interval;

setting the neighbor cell offset value to a third value if the signal measurement of the serving cell is less than the second threshold for a second time interval; and

adjusting the ranking criteria of the neighbor cell based on the neighbor cell offset value after being set to one of the first value, the second value and the third value.

13. The method of claim 12 wherein the serving cell signal measurement is reference symbol received quality (RSRQ) and the first and second thresholds are RSRQ thresholds.

14. The method of claim 12 wherein the serving cell signal measurement is received signal code power (RSCP) and the first and second thresholds are RSCP thresholds.

15. The method of claim 12 wherein the serving cell signal measurement is reference signal received power (RSRP) and the first and second thresholds are RSRP thresholds.

16. The method of claim 12 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

17. The method of claim 12 wherein the first value is greater than the second value, the second value is greater than the third value, and the first threshold is greater than the second threshold.

18. The method of claim 12 wherein the first, second and third values are signaled by a network.

19. The method of claim 12 wherein the first value and at least one scaling factor are signaled by a network, and the second and third values are derived from the first value using the at least one scaling factor.

20. The method of claim 12 further comprising:

adjusting a time value of a reselection timer located in the WTRU based on how the signal measurement compares to the first and second thresholds.

21. The method of claim 12 further comprising:

receiving a radio resource control (RRC) message indicating at least one of the first threshold and the second threshold.

22. The method of claim 12 further comprising:

receiving a radio resource control (RRC) message indicating at least one of the first value, the second value and the third value.

23. A wireless transmit/receive unit (WTRU) comprising:

a receiver configured to perform a signal measurement of a serving cell; and

a processor configured to set a serving cell hysteresis value to a first value if the signal measurement of the serving cell exceeds a first threshold, set the serving cell hysteresis value to a second value if the signal measurement of the serving cell is less that the first threshold and is greater than a second threshold for a first time interval, set the serving cell hysteresis value to a third value if the signal measurement of the serving cell is less than the second threshold for a second time interval, and adjust the ranking criteria of the serving cell based on the serving cell hysteresis value after being set to one of the first value, the second value and the third value.

24. The WTRU of claim 23 wherein the serving cell signal measurement is reference symbol received quality (RSRQ) and the first and second thresholds are RSRQ thresholds.

25. The WTRU of claim 23 wherein the serving cell signal measurement is received signal code power (RSCP) and the first and second thresholds are RSCP thresholds.

26. The WTRU of claim 23 wherein the serving cell signal measurement is reference signal received power (RSRP) and the first and second thresholds are RSRP thresholds.

27. The WTRU of claim 23 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

28. The WTRU of claim 23 wherein the first value is greater than the second value, the second value is greater than the third value, and the first threshold is greater than the second threshold.

29. The WTRU of claim 23 wherein the first, second and third values are signaled by a network.

30. The WTRU of claim 23 wherein the first value and at least one scaling factor are signaled by a network, and the second and third values are derived from the first value using the at least one scaling factor.

31. The WTRU of claim 23 further comprising:

a reselection timer, wherein a time value of the reselection timer is adjusted based on how the signal measurement compares to the first and second thresholds.

32. The WTRU of claim 23 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first threshold and the second threshold.

33. The WTRU of claim 23 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first value, the second value and the third value.

34. A wireless transmit/receive unit (WTRU) comprising:

a receiver configured to perform a signal measurement of a serving cell; and

a processor configured to set a neighbor cell offset value to a first value if the signal measurement of the serving cell exceeds a first threshold, set the neighbor cell offset value to a second value if the signal measurement of the serving cell is less that the first threshold and is greater than a second threshold for a first time interval, set the neighbor cell offset value to a third value if the signal measurement of the serving cell is less than the second threshold for a second time interval, and adjust the ranking criteria of the neighbor cell based on the neighbor cell offset value after being set to one of the first value, the second value and the third value.

35. The WTRU of claim 34 wherein the serving cell signal measurement is reference symbol received quality (RSRQ) and the first and second thresholds are RSRQ thresholds.

36. The WTRU of claim 34 wherein the serving cell signal measurement is received signal code power (RSCP) and the first and second thresholds are RSCP thresholds.

37. The WTRU of claim 34 wherein the serving cell signal measurement is reference signal received power (RSRP) and the first and second thresholds are RSRP thresholds.

38. The WTRU of claim 34 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

39. The WTRU of claim 34 wherein the first value is greater than the second value, the second value is greater than the third value, and the first threshold is greater than the second threshold.

40. The WTRU of claim 34 wherein the first, second and third values are signaled by a network.

41. The WTRU of claim 34 wherein the first value and at least one scaling factor are signaled by a network, and the second and third values are derived from the first value using the at least one scaling factor.

42. The WTRU of claim 34 further comprising:

a reselection timer, wherein a time value of the reselection timer is adjusted based on how the signal measurement compares to the first and second thresholds.

43. The WTRU of claim 34 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first threshold and the second threshold.

44. The WTRU of claim 34 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first value, the second value and the third value.

45. A wireless transmit/receive unit (WTRU) comprising:

a reselection timer;

a receiver configured to perform a signal measurement of a serving cell; and

a processor configured to set the reselection timer to a first value if the signal measurement of the serving cell exceeds a first threshold, set the reselection timer to a second value if the signal measurement of the serving cell is less that the first threshold and is greater than a second threshold for a first time interval, and set the reselection timer to a third value if the signal measurement of the serving cell is less than the second threshold for a second time interval.

46. The WTRU of claim 45 wherein the serving cell signal measurement is reference symbol received quality (RSRQ) and the first and second thresholds are RSRQ thresholds.

47. The WTRU of claim 45 wherein the serving cell signal measurement is received signal code power (RSCP) and the first and second thresholds are RSCP thresholds.

48. The WTRU of claim 45 wherein the serving cell signal measurement is reference signal received power (RSRP) and the first and second thresholds are RSRP thresholds.

49. The WTRU of claim 45 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

50. The WTRU of claim 45 wherein the first value is greater than the second value, the second value is greater than the third value, and the first threshold is greater than the second threshold.

51. The WTRU of claim 45 wherein the first, second and third values are signaled by a network.

52. The WTRU of claim 45 wherein the first value and at least one scaling factor are signaled by a network, and the second and third values are derived from the first value using the at least one scaling factor.

53. The WTRU of claim 45 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first threshold and the second threshold.

54. The WTRU of claim 45 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first value, the second value and the third value.

55. A wireless communication method of adjusting the ranking criteria of a serving cell associated with a wireless transmit/receive unit (WTRU), the method comprising:

setting a reselection timer in the WTRU to a first value;

setting a hysteresis value to a second value;

monitoring a number of cell reselections associated with the WTRU that occur during a predetermined time period;

monitoring mobility factors associated with the WTRU; and

if the number of cell reselections exceeds a third value, and a high mobility factor is detected, determining whether to perform a first adjustment of the reselection timer by multiplying the first value with a first scaling factor, perform a second adjustment by multiplying the second value of the hysteresis value with a second scaling factor, or perform both of the first and second adjustments, to reduce the ranking of the serving cell.

56. The method of claim 55 wherein the determination as to whether or not to perform both of the first and second adjustments is based on a radio condition.

57. The method of claim 55 wherein the first scaling factor is the same as the second scaling factor.

58. The method of claim 55 wherein the first scaling factor is different than the second scaling factor.

59. The method of claim 55 wherein the first value indicates a time for which a neighbor cell is expected to meet a cell reselection criteria for the WTRU.

60. The method of claim 55 further comprising:

receiving a radio resource control (RRC) message indicating at least one of the first scaling factor and the second scaling factor.

61. A wireless transmit/receive unit (WTRU) comprising:

a receiver configured to monitor mobility factors associated with the WTRU;

a reselection timer; and

a processor configured to monitor a number of cell reselections associated with the WTRU that occur during a predetermined time period, set the reselection timer to a first value, set a hysteresis value to a second value, and determine whether to perform a first adjustment of the reselection timer by multiplying the first value with a first scaling factor, perform a second adjustment by multiplying the second value of the hysteresis value with a second scaling factor, or perform both of the first and second adjustments, to reduce the ranking of the serving cell, if the number of cell reselections exceeds a third value, and a high mobility factor is detected.

62. The WTRU of claim 61 wherein a determination as to whether or not to perform both of the first and second adjustments is based on a radio condition.

63. The WTRU of claim 61 wherein the first scaling factor is the same as the second scaling factor.

64. The WTRU of claim 61 wherein the first scaling factor is different than the second scaling factor.

65. The WTRU of claim 61 wherein the first value indicates a time for which a neighbor cell is expected to meet a cell reselection criteria for the WTRU.

66. The WTRU of claim 61 wherein the receiver is further configured to receive a radio resource control (RRC) message indicating at least one of the first scaling factor and the second scaling factor.

67. A cell signal measurement reporting method performed by a wireless transmit/receive unit (WTRU), the method comprising:

performing a serving cell signal measurement;

performing a neighbor cell signal measurement;

starting a time-to-trigger time (TTT) interval when the neighbor cell signal measurement rises above a reporting range threshold; and

if the serving cell signal measurement falls below a serving cell threshold, adjusting the TTT interval and transmitting a measurement report before the expiration of the TTT interval reporting that the serving cell signal measurement has fallen below the serving cell threshold and providing information about the neighbor cell used to generate a handover command.

68. The method of claim 67 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

69. The method of claim 67 wherein the handover command is associated with at least one of an intra-frequency handover, an inter-frequency handover and an inter-radio access technology (inter-RAT) handover.

70. A cell signal measurement reporting method performed by a wireless transmit/receive unit (WTRU), the method comprising:

performing a serving cell signal measurement;

performing a neighbor cell signal measurement;

starting a time-to-trigger time (TTT) interval when the neighbor cell signal measurement rises above a reporting range threshold; and

if the serving cell signal measurement falls below a serving cell threshold and stays below the threshold during a predetermined time interval, adjusting the TTT interval and transmitting a measurement report during the TTT interval reporting that the serving cell signal measurement has fallen below the serving cell threshold and providing information about the neighbor cell used to generate a handover command.

71. The method of claim 70 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

72. The method of claim 70 wherein the handover command is associated with at least one of an intra-frequency handover, an inter-frequency handover and an inter-radio access technology (inter-RAT) handover.

73. A wireless transmit/receive unit (WTRU) comprising:

a receiver configured to perform a serving cell signal measurement and a neighbor cell signal measurement;

a time-to-trigger time (TTT) timer;

a processor configured to start a TTT interval established by the TTT timer when the neighbor cell signal measurement rises above a reporting range threshold and adjust the TTT interval; and

a transmitter configured to transmit a measurement report before the expiration of the TTT interval if the serving cell signal measurement falls below a serving cell threshold, the measurement report indicating that the serving cell signal measurement has fallen below the serving cell threshold and provide information about the neighbor cell used to generate a handover command.

74. The WTRU of claim 73 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

75. The method of claim 73 wherein the handover command is associated with at least one of an intra-frequency handover, an inter-frequency handover and an inter-radio access technology (inter-RAT) handover.

76. A wireless transmit/receive unit (WTRU) comprising:

a receiver configured to perform a serving cell signal measurement and a neighbor cell signal measurement;

a time-to-trigger time (TTT) timer; and

a processor configured to start a TTT interval established by the TTT timer when the neighbor cell signal measurement rises above a reporting range threshold and adjust the TTT interval; and

a transmitter configured to transmit a measurement report during the TTT interval if the serving cell signal measurement falls below a serving cell threshold and stays below the threshold during a predetermined time interval, the measurement report indicating that the serving cell signal measurement has fallen below the serving cell threshold and provide information about the neighbor cell used to generate a handover command.

77. The WTRU of claim 76 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

78. The method of claim 76 wherein the handover command is associated with at least one of an intra-frequency handover, an inter-frequency handover and an inter-radio access technology (inter-RAT) handover.

79. A wireless communication method of adjusting the ranking criteria of a serving cell associated with a wireless transmit/receive unit (WTRU), the method comprising:

establishing a plurality of thresholds;

performing a signal measurement of a serving cell;

setting a hysteresis value to a particular value that depends upon how the serving cell signal measurement compares to the plurality of thresholds; and

adjusting the ranking criteria of the serving cell based on the hysteresis value after being set to the particular value.

80. The method of claim 79 wherein the serving cell signal measurement is reference symbol received quality (RSRQ).

81. The method of claim 79 wherein the serving cell signal measurement is received signal code power (RSCP).

82. The method of claim 79 wherein the serving cell signal measurement is reference signal received power (RSRP).

83. The method of claim 79 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

84. A wireless communication method of adjusting a reselection timer in a wireless transmit/receive unit (WTRU), the method comprising:

establishing a plurality of thresholds;

performing a signal measurement of a serving cell; and

adjusting the reselection timer based on the how the serving cell signal measurement compares to the plurality of thresholds.

85. The method of claim 84 wherein the serving cell signal measurement is reference symbol received quality (RSRQ).

86. The method of claim 84 wherein the serving cell signal measurement is received signal code power (RSCP).

87. The method of claim 84 wherein the serving cell signal measurement is reference signal received power (RSRP).

88. The method of claim 84 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

89. A wireless communication method of adjusting the ranking criteria of a neighbor cell associated with a wireless transmit/receive unit (WTRU), the method comprising:

establishing a plurality of thresholds;

performing a signal measurement of a serving cell;

setting a neighbor cell offset value to a particular value that depends upon how the serving cell signal measurement compares to the plurality of thresholds; and

adjusting the ranking criteria of the neighbor cell based on the neighbor cell offset value after being set to the particular value.

90. The method of claim 89 wherein the serving cell signal measurement is reference symbol received quality (RSRQ).

91. The method of claim 89 wherein the serving cell signal measurement is received signal code power (RSCP).

92. The method of claim 89 wherein the serving cell signal measurement is reference signal received power (RSRP).

93. The method of claim 89 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.

94. A wireless communication method of adjusting a reselection timer in a wireless transmit/receive unit (WTRU), the method comprising:

establishing a plurality of thresholds;

performing a signal measurement of a serving cell; and

adjusting the reselection timer based on the how the serving cell signal measurement compares to the plurality of thresholds.

95. The method of claim 94 wherein the serving cell signal measurement is reference symbol received quality (RSRQ).

96. The method of claim 94 wherein the serving cell signal measurement is received signal code power (RSCP).

97. The method of claim 94 wherein the serving cell signal measurement is reference signal received power (RSRP).

98. The method of claim 94 wherein the serving cell signal measurement is used to calculate different levels of speed associated with the WTRU.