METHOD AND APPARATUS FOR MAINTAINING UPLINK SYNCHRONIZATION AND REDUCING BATTERY POWER CONSUMPTION

• US 20070230394A1
• Filed: 03/22/2007
• Published: 10/04/2007
• Est. Priority Date: 03/24/2006
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Sammour, Mohammed, Chandra, Arty, Chen, John, Wang, Jin, Zhang, Guodong, Terry, Stephen
• Granted Patent: US 9,167,546 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A Node-B sends a polling message to a wireless transmit/receive unit (WTRU). The WTRU sends an uplink synchronization burst in response to the polling message without contention. The Node-B estimates an uplink timing shift based on the synchronization burst and sends an uplink timing adjustment command to the WTRU. The WTRU then adjusts uplink timing based on the uplink timing adjustment command. Alternatively, the Node-B may send a scheduling message for uplink synchronization to the WTRU. The WTRU may send a synchronization burst based on the scheduling message. Alternatively, the WTRU may perform contention-based uplink synchronization after receiving a synchronization request from the Node-B. The WTRU may enter an idle state instead of performing a handover to a new cell when the WTRU moves to the new cell. A discontinuous reception (DRX) interval for the WTRU may be set based on activity of the WTRU.

Claims

1. In a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, a method for maintaining uplink synchronization while the WTRU is in an active state, the method comprising:

the Node-B sending a polling message to the WTRU;

the WTRU sending an uplink synchronization burst to the Node-B based on the polling message;

the Node-B estimating an uplink timing shift based on the uplink synchronization burst;

the Node-B sending an uplink timing adjustment command to the WTRU; and

the WTRU adjusting uplink timing based on the uplink timing adjustment command.

2. The method of claim 1 wherein the polling message includes a specific time for the WTRU to send the synchronization burst.

3. The method of claim 1 wherein the polling message includes uplink interference information so that the WTRU estimates a transmit power for the synchronization burst.

4. The method of claim 1 wherein the polling message includes uplink transmit power information for the synchronization burst.

5. The method of claim 1 wherein the polling message is transmitted via a downlink common control channel granting an access to an uplink shared channel for the synchronization burst.

6. The method of claim 1 further comprising:

the WTRU entering into a discontinuous reception (DRX) mode.

7. The method of claim 1 wherein the polling message is addressed to multiple WTRUs to poll multiple synchronization bursts from multiple WTRUs.

8. The method of claim 7 wherein a polling rate is different for at least one of the WTRUs.

9. The method of claim 8 wherein the polling rate is determined based on at least one of an estimated clock drift and mobility of each WTRU.

10. The method of claim 8 wherein the polling rate is adaptively changed by one of the WTRU and the Node-B.

11. The method of claim 10 wherein the Node-B changes the polling rate based on uplink synchronization results.

12. The method of claim 1 wherein the polling message provides an uplink channel allocation.

13. The method of claim 12 wherein the uplink channel allocation is periodic.

14. The method of claim 12 wherein the uplink channel allocation indicates duration of an allocated uplink channel.

15. The method of claim 1 wherein the Node-B provides information about the polling message to the WTRU by broadcasting.

16. The method of claim 1 wherein the Node-B provides information about the polling message to the WTRU during registration.

17. The method of claim 1 wherein a polling rate is set differently based on a radio resource control (RRC) state of the WTRU.

18. The method of claim 1 wherein a polling rate is increased over time as inactivity of the WTRU increases.

19. The method of claim 18 wherein the polling rate is increased exponentially.

20. The method of claim 1 further comprising:

the WTRU sending scheduling information including an amount of data to be transmitted to the Node-B after receiving the polling message.

21. The method of claim 1 further comprising:

the WTRU sending a message indicating that the WTRU wants to obtain uplink resources for data transmission after receiving the polling message.

22. The method of claim 1 further comprising:

the WTRU sending a channel quality indicator (CQI) after receiving the polling message.

23. The method of claim 1 wherein the uplink synchronization burst does not include a WTRU identity (ID) and a cell ID.

24. The method of claim 1 wherein the Node-B includes a short identifier in the polling message and the WTRU includes the short identifier in the uplink synchronization burst.

25. The method of claim 1 wherein the polling message includes a request for the WTRU to send the synchronization burst.

26. The method of claim 25 wherein the WTRU sends the uplink synchronization burst using a slotted Aloha-based mechanism

27. The method of claim 26 wherein the WTRU sends the uplink synchronization burst via a random access channel (RACH).

30. The method of claim 1 wherein the Node-B sends an indication of whether it is mandatory or optional for the WTRU to send the uplink synchronization burst.

28. (canceled)

29. The method of claim 28 further comprising:

the Node-B designating at least one of a frame, a sub-frame and a timeslot to send the uplink synchronization burst.

31. In a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, a method for establishing uplink synchronization while the WTRU is in an active state, the method comprising:

the Node-B sending a scheduling message for uplink synchronization to the WTRU;

the WTRU sending an uplink synchronization burst to the Node-B based on the scheduling message;

the Node-B estimating an uplink timing shift based on the uplink synchronization burst;

the Node-B sending an uplink timing adjustment command to the WTRU; and

the WTRU adjusting uplink timing based on the uplink timing adjustment command.

32. The method of claim 31 wherein the schedule indicates predetermined times for uplink synchronization.

33. The method of claim 31 wherein the schedule indicates a resource for transmitting the uplink synchronization burst.

34. The method of claim 31 wherein the Node-B signals a resource for transmitting the uplink synchronization burst to the WTRU prior to the scheduled synchronization time.

35. The method of claim 31 the WTRU includes a next synchronization time in a current synchronization burst.

36. The method of claim 35 wherein the Node-B modifies the next synchronization time via a downlink signaling channel.

37. The method of claim 31 wherein the uplink synchronization burst does not include a WTRU identity (ID) and a cell ID.

38. The method of claim 31 wherein the Node-B includes a short identifier in the scheduling message and the WTRU includes the short identifier in the uplink synchronization burst.

39. The method of claim 31 wherein the Node-B sends an indication of whether it is mandatory or optional for the WTRU to send the uplink synchronization burst.

40. A method for reducing battery consumption of a wireless transmit/receive unit (WTRU) in a cellular wireless communication system, the method comprising:

the WTRU determining that the WTRU should move to a new cell; and

the WTRU entering an idle state instead of performing a handover to the new cell.

41. A method for reducing battery consumption of a wireless transmit/receive unit (WTRU) in a cellular wireless communication system, the method comprising:

the WTRU entering a discontinuous reception (DRX) mode such that the WTRU periodically wakes up according to a DRX interval to check a paging message and reenters an idle state if there is no paging message directed to the WTRU;

monitoring activity of the WTRU; and

setting the DRX interval based on the activity of the WTRU such that the DRX interval is increased as inactivity of the WTRU increases.

42. The method of claim 41 wherein the DRX interval is increased exponentially.

43. The method of claim 41 further comprising:

the WTRU informing whether the WTRU is powered by a battery or a constant power supply to set the DRX interval accordingly.

44. The method of claim 41 further comprising:

the WTRU informing its current battery capacity so that the DRX interval is set based on the current battery capacity.

45. In a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the Node-B for maintaining uplink synchronization, the Node-B comprising:

an uplink synchronization controller for generating at least one of a polling message, a scheduling message and a synchronization request message for the WTRU and estimating an uplink timing shift based on an uplink synchronization burst transmitted by the WTRU in response to one of the polling message, the scheduling message and the synchronization request message; and

a transceiver for sending an uplink timing adjustment command to the WTRU, whereby the WTRU adjusts uplink timing based on the uplink timing adjustment command.

46. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message includes a specific time for the WTRU to send the synchronization burst.

47. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message includes uplink interference information so that the WTRU estimates a transmit power for the synchronization burst.

48. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message includes uplink transmit power information for the synchronization burst.

49. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message is transmitted via a downlink common control channel granting an access to an uplink shared channel for the synchronization burst.

50. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message is addressed to multiple WTRUs to poll multiple synchronization bursts.

51. The Node-B of claim 50 wherein the uplink synchronization controller sets a polling rate differently for at least one of the WTRUs.

52. The Node-B of claim 51 wherein the uplink synchronization controller determines the polling rate based on at least one of an estimated clock drift and mobility of each WTRU.

53. The Node-B of claim 51 wherein the uplink synchronization controller adaptively changes the polling rate.

54. The Node-B of claim 53 wherein the uplink synchronization controller changes the polling rate based on uplink synchronization results.

55. The Node-B of claim 45 wherein at least one of the polling message, the scheduling message and the synchronization request message provides an uplink channel allocation.

56. The Node-B of claim 55 wherein the uplink channel allocation is periodic.

57. The Node-B of claim 55 wherein the uplink channel allocation indicates duration of an allocated uplink channel.

58. The Node-B of claim 45 wherein the Node-B provides information about the polling message to the WTRU by broadcasting.

59. The Node-B of claim 45 wherein the Node-B provides information about the polling message to the WTRU during registration.

60. The Node-B of claim 45 wherein the uplink synchronization controller sets a polling rate differently for each radio resource control (RRC) state of the WTRU.

61. The Node-B of claim 45 wherein the uplink synchronization controller increases a polling rate over time as inactivity of the WTRU increases.

62. The Node-B of claim 61 wherein the polling rate is increased exponentially.

63. The Node-B of claim 45 wherein the uplink synchronization controller includes a short identifier in the polling message and the WTRU includes the short identifier in the uplink synchronization burst.

64. The Node-B of claim 45 wherein the uplink synchronization controller designates at least one of a frame, a sub-frame and a timeslot to send the uplink synchronization burst.

65. The Node-B of claim 45 wherein the uplink synchronization controller sends an indication of whether it is mandatory or optional for the WTRU to send the uplink synchronization burst.

66. In a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the WTRU for maintaining uplink synchronization, the WTRU comprising:

a transceiver for sending an uplink synchronization burst based on one of a polling message, a scheduling message and a synchronization request message received from the Node-B; and

an uplink synchronization controller for adjusting uplink timing based on a uplink timing adjustment command received from the Node-B, the Node-B generating the uplink timing adjustment command after estimating an uplink timing shift based on the uplink synchronization burst.

67. The WTRU of claim 66 wherein at least one of the polling message, the scheduling message and the synchronization request message includes a specific time for the WTRU to send the synchronization burst.

68. The WTRU of claim 66 wherein at least one of the polling message, the scheduling message and the synchronization request message includes uplink interference information so that a transmit power for the synchronization burst is controlled based on the interference information.

69. The WTRU of claim 66 wherein at least one of the polling message, the scheduling message and the synchronization request message includes uplink transmit power information for the synchronization burst.

70. The WTRU of claim 66 wherein the WTRU enters into a discontinuous reception (DRX) mode.

71. The WTRU of claim 66 wherein the transceiver receives information about the polling message via broadcasting.

72. The WTRU of claim 66 wherein the transceiver receives information about the polling message during registration.

73. The WTRU of claim 66 wherein the uplink synchronization controller sends scheduling information including an amount of data to be transmitted to the Node-B after receiving the polling message.

74. The WTRU of claim 66 wherein the uplink synchronization controller sends a scheduling request indicating that the WTRU wants to obtain uplink resources for data transmission after receiving the polling message.

75. The WTRU of claim 66 wherein the WTRU sends a channel quality indicator (CQI) after receiving the polling message.

76. The WTRU of claim 66 wherein the uplink synchronization controller does not include a WTRU identity (ID) and a cell ID in the uplink synchronization burst.

77. The WTRU of claim 66 wherein the uplink synchronization controller includes in the uplink synchronization burst a short identifier that was included in the polling message.

78. The WTRU of claim 66 wherein the transceiver sends the uplink synchronization burst using a slotted Aloha-based mechanism

79. The WTRU of claim 78 wherein the transceiver sends the uplink synchronization burst via a random access channel (RACH).

80. The WTRU of claim 78 wherein the transceiver transmits the uplink synchronization burst via a frame, a sub-frame or a timeslot designated by the Node-B.

81. The WTRU of claim 66 wherein the uplink synchronization controller includes a next synchronization time in the uplink synchronization burst.

82. A wireless transmit/receive unit (WTRU) for reducing battery consumption in a cellular wireless communication system, the WTRU comprising:

a cell searching unit for determining that the WTRU should move to a new cell; and

a controller for entering an idle state instead of performing a handover to the new cell when it is determined that the WTRU should move to the new cell.

83. A wireless transmit/receive unit (WTRU) for reducing battery consumption in a cellular wireless communication system, the WTRU comprising:

a monitor for monitoring activity of the WTRU; and

a discontinuous reception (DRX) controller for entering a DRX mode in accordance with a DRX interval determined by a network based on the activity of the WTRU such that the DRX interval is increased as inactivity of the WTRU increases.

84. The WTRU of claim 83 wherein the DRX interval is increased exponentially.

85. The WTRU of claim 83 wherein the WTRU provides the network with information whether the WTRU is powered by a battery or a constant power supply and the network sets the DRX interval based on the information.

86. The WTRU of claim 83 wherein the WTRU informs the network about its current battery capacity so that the DRX interval is set based on the current battery capacity.