HK1186038A - A method and apparatus for reducing battery consumption of a wireless transmit/receive unit - Google Patents

Abstract

A method and apparatus for reducing battery consumption of a wireless transmit/receive unit (WTRU). Wherein, the method comprising: the WTRU entering a discontinuous reception (DRX) mode such that the WTRU periodically wakes up according from 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 in a broadcast message based on the activity of the WTRU such that the DRX interval is increased as inactivity of the WTRU increases.

Description

Method and apparatus for reducing battery consumption of wireless transmit/receive unit

The present application is a divisional application of chinese patent application entitled "method and apparatus for maintaining uplink synchronization and reducing battery power consumption" filed on 3/22/2007 with application number 200780015082.5.

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to a method and apparatus for maintaining uplink synchronization and reducing battery power consumption of a wireless transmit/receive unit (WTRU).

Background

In conventional third generation partnership project (3 GPP) systems, there are four non-idle Radio Resource Control (RRC) states, roughly corresponding to four WTRU activities: a Dedicated Channel (DCH) Cell (Cell _ DCH) state, a Forward Access Channel (FACH) Cell (Cell _ FACH) state, a Paging Channel (PCH) Cell (Cell _ PCH) state, and a Universal Terrestrial Radio Access Network (UTRAN) registration area (URA) PCH (URA _ PCH) state. In the Cell _ DCH state, the WTRU has a dedicated physical channel for data transmission. In the Cell _ FACH state, no dedicated channel is allocated to the WTRU, but the WTRU may use the Random Access Channel (RACH) and FACH channels to communicate and receive signaling and user plane data. It is not efficient to transmit a large amount of user plane data in the Cell _ FACH state. The Cell _ PCH state reduces battery consumption by listening for PCH only in Discontinuous Reception (DRX) mode. The location of the WTRU in the Cell _ PCH state is known at the Cell level, as in the Cell _ DCH and Cell _ FACH states. A WTRU in the Cell _ PCH state temporarily enters the Cell _ FACH state when it is reassigned to a new Cell, thereby conveying its new location information. The URA _ PCH state is similar to the Cell _ PCH state except that in the URA _ PCH state the network is only notified when the WTRU moves to a new URA. When a WTRU changes cells, the WTRU typically stays in the same state. Currently, the handover in the Cell _ DCH state is network directed.

The WTRU in an active state has non-access stratum (NAS) connectivity so that the WTRU may communicate with a node in the core network. The WTRU in the active state also has Access Stratum (AS) connectivity such that radio bearer configuration has been completed for the WTRU (e.g., WTRU capability exchange, ciphering, etc.).

A WTRU in an idle state consumes less power and resources than a WTRU in a low power active state. An important feature of a WTRU in an idle state is that the WTRU does not have to participate in active mode handover. In other words, when a WTRU in an idle state moves from one cell to another, the WTRU does not configure a radio bearer with the new cell if the WTRU remains in the idle state.

One goal of next generation wireless communication systems is to maintain "always on" connectivity. However, battery power consumption is an issue for battery powered WTRUs. While "always on" connectivity is a desirable feature, it will reduce battery life.

Currently in 3GPP, a WTRU maintains uplink synchronization whenever it has a dedicated channel to a base station. The WTRU always maintains uplink synchronization in Cell _ DCH. The WTRU also resynchronizes its uplink whenever it has a new dedicated channel setting apart from the previous setting. Maintaining uplink synchronization (conventionally transmitted over the RACH) is one of the sources that consume the battery power of the WTRU.

It is therefore desirable to provide a scheme to efficiently maintain uplink synchronization and reduce battery consumption when the WTRU is in an active state.

Disclosure of Invention

The present invention relates to a method and apparatus for maintaining uplink synchronization and reducing battery power consumption of a WTRU. The node-B sends a polling message to the WTRU. The WTRU transmits an uplink synchronization burst in response to the polling message without contention. The node-B estimates an uplink timing shift based on the uplink synchronization burst and sends an uplink timing alignment command to the WTRU without contention. The WTRU then calibrates the uplink timing based on the uplink timing calibration command. Alternatively, the node-B may send a scheduling message to the WTRU for uplink synchronization. The WTRU may send an uplink 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. When a WTRU moves to a new cell, the WTRU may enter an idle state instead of performing a handover to the new cell. The DRX interval for the WTRU may be set based on the activity of the WTRU.

Drawings

The invention will be understood in more detail from the following description of preferred embodiments, which are given by way of example and can be understood in conjunction with the accompanying drawings, in which:

fig. 1 is a signaling diagram of a process for maintaining uplink synchronization using a contention-free procedure according to an embodiment of the present invention;

FIG. 2 is a signaling diagram of a process for maintaining uplink synchronization using a contention-free procedure according to another embodiment of the present invention;

fig. 3 is a signaling diagram of an uplink synchronization process using a contention-based procedure according to the present invention; and

figure 4 is a block diagram of a node-B and WTRU configured in accordance with the present invention.

Detailed Description

When referred to hereafter, the term "WTRU" includes but is not limited to a User Equipment (UE), a mobile Station (STA), a fixed or mobile subscriber unit, a pager, a cellular telephone, a Personal Data Assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the term "node-B" includes but is not limited to a base station, a site controller, an Access Point (AP), or any other type of interfacing device capable of operating in a wireless environment.

The present invention is applicable to any wireless communication system including, but not limited to, Wideband Code Division Multiple Access (WCDMA) and Long Term Evolution (LTE) of 3GPP cellular networks beyond 3GPP release 7.

Fig. 1 is a signaling diagram of a process 100 for maintaining uplink synchronization using a contention-free procedure according to an embodiment of the present invention. For uplink synchronization, the node-B152 sends a poll message to the WTRU154 requesting transmission of an uplink synchronization burst (step 102). The WTRU154 may receive the polling message during registration or after registration by broadcast. The round robin message indicates a specific time (e.g., a system frame number or a Transmission Time Interval (TTI)) and/or resources for sending the uplink synchronization burst so that a specific WTRU may send the uplink synchronization burst without contending with other WTRUs. In response to the polling message, the WTRU154 transmits an uplink synchronization burst based on parameters (e.g., specific time, resources, etc.) included in the polling message (step 104). node-B152 receives the uplink synchronization burst and estimates an uplink timing shift based on the uplink synchronization burst (step 106). The node-B152 sends an uplink timing alignment command to the WTRU154 (step 108). The WTRU then calibrates uplink timing based on the uplink calibration command (step 110).

The polling message may include uplink interference information so that WTRU154 may use the information to determine the uplink transmit power for the uplink synchronization burst. Alternatively, the node-B152 may explicitly indicate the uplink transmit power for the uplink synchronization burst. node-B152 may send a polling message over the downlink common control channel to grant access to the uplink shared channel for the uplink synchronization burst.

Alternatively, to save additional power, the WTRU154 may enter DRX mode and wake up at predetermined intervals for paging or uplink shared channel allocation. If the WTRU154 enters DRX mode, the node-B152 does not need to send polling messages to the WTRU154 very often. The network configures the periodicity at which the node-B152 should send polling messages to the WTRU 154. The periodicity information may be sent to the WTRU154 via a broadcast message. In this manner, the WTRU154 may wake up only when a polling message is desired. After listening to the polling message and performing the necessary uplink transmission, the WTRU154 again enters DRX mode to save battery power.

The polling message may be addressed to several WTRUs containing parameters for several polled WTRUs to send their uplink synchronization bursts. The polling rate may be different for each WTRU. The polling rate may be determined based on the estimated clock drift and/or mobility of the WTRU. The polling rate may be adaptively changed by the WTRU154 (by requesting from the node-B152) or the node-B152. The polling rate may be different for each RRC (or Medium Access Control (MAC)) state of the WTRU 154. The polling rate may increase (e.g., exponentially) over time as periods of inactivity of the WTRU154 increase. The node-B152 may use the result of the uplink synchronization as a factor in adaptively changing the polling rate for the WTRU 154. The uplink channel allocation for the uplink synchronization burst provided by the polling message may be periodic or may optionally indicate the duration of the uplink channel.

Since the WTRU154 in the active state is known to the node-B152 and the node-B152 can uniquely identify the WTRU154 by the number of times it is scheduled for the WTRU154, the WTRU154 may ignore the cell ID or WTRU ID (e.g., the controlling radio network temporary identity (C-RNTI)) in the uplink synchronization burst. This will reduce overhead.

Alternatively, the node-B152 may include a short (preferably random) identifier, tag, or sequence number in the polling message, and the WTRU154 may use the same short identifier, tag, or sequence number in the uplink synchronization burst. Overhead is reduced because such identifiers, tags or sequence numbers are smaller than other forms of identification (e.g., cell ID or C-RNTI).

Fig. 2 is a signaling diagram of a process 200 for maintaining uplink synchronization using a contention-free procedure according to another embodiment of the present invention. The node-B252 generates scheduling for uplink synchronization for the WTRU254 and sends a scheduling message for uplink synchronization to the WTRU254 (step 202). The scheduling message may include a schedule for several WTRUs. The uplink synchronization is performed a specified number of times using a predetermined resource specified in the scheduling message. The node-B252 may signal resources for uplink synchronization to the WTRU254 prior to scheduling synchronization time. The scheduling message may include uplink interference information or uplink transmission power information. The uplink transmit power information may be for a group of WTRUs in a similar situation. Alternatively, the uplink transmit power information may be for each WTRU or simply used as a reference. The scheduling message may be transmitted over a downlink common control channel and may be used to synchronize access to an uplink shared channel of the burst.

The WTRU254 sends an uplink synchronization burst based on the scheduling message (step 204). The WTRU254 may optionally indicate the next synchronization time in the uplink synchronization burst (i.e., the payload of the synchronization burst may include a field indicating the next synchronization time). The synchronization time may be viewed as a suggestion by the node-B252 that the node-B252 may modify the schedule or the suggestion by sending a signal via a downlink signaling channel (e.g., a shared control channel). The WTRU254 may also send a scheduling request to inform the amount of data waiting to be transmitted in the WTRU 254. The WTRU254 may also send measurement results, such as a Channel Quality Indicator (CQI).

The node-B252 estimates the uplink timing shift based on the uplink synchronization burst (step 206). The node-B252 sends an uplink timing alignment command to the WTRU 254. The WTRU254 then calibrates the uplink timing based on the uplink timing calibration command (step 210).

Since the WTRU254 in the active state is known to the node-B252 and the node-B252 can uniquely identify the WTRU254 by the number of times it is scheduled for the WTRU254, the WTRU254 may ignore the cell ID or WTRU ID (e.g., controlling radio network temporary identity (e.g., C-RNTI)) in the uplink synchronization burst. This will reduce overhead.

Alternatively, the node-B252 may include a short (preferably random) identifier, label, or sequence number in the polling message, and the WTRU254 may use the same short identifier, label, or sequence number in the uplink synchronization burst. Overhead is reduced because such identifiers, tags or sequence numbers are smaller than other forms of identification (e.g., cell ID or C-RNTI).

Fig. 3 is a signaling diagram of an uplink synchronization process 300 using a contention-based procedure according to the present invention. The node-B352 sends a synchronization request message to the WTRU354 to instruct or suggest the WTRU354 to perform an uplink synchronization procedure during which the WTRU354 is in an active state (step 302). The synchronization request message may be addressed to multiple WTRUs. The synchronization request message may include a particular time and/or resource at which the WTRU sent the synchronization burst. The synchronization request message may include uplink interference information or uplink transmission power information. The synchronization request message may be transmitted through a downlink common control channel to grant access to an uplink shared channel for the synchronization burst.

In response, WTRU354 performs a conventional contention-based procedure for uplink synchronization. The WTRU354 sends (e.g., via the RACH) an uplink transmission (e.g., RACH preamble) to the node-B352 using a contention-based mechanism (e.g., a slotted Aloha mechanism) (step 304). Either unsynchronized or synchronized RACH may be used for this uplink transmission, as indicated by RRC signaling or by a synchronization request message from node-B352. The node-B352 receives the uplink transmission and estimates an uplink timing shift based on the uplink transmission (step 306). The node-B352 sends an uplink timing alignment command to the WTRU354 (step 308). The WTRU354 then calibrates the uplink timing based on the uplink timing calibration command (step 310).

The node-B352 may include a short (preferably random) identifier, tag, or sequence number in the uplink synchronization request message, and the WTRU354 may use the same short identifier, tag, or sequence number in the uplink synchronization burst.

The node-B352 may assign frames, subframes, or time slots in which uplink synchronization procedures (or random access procedures) are performed when the WTRU354 is in an active state. The assigned frame, subframe, or time slot is different from the frame, subframe, or time slot used to perform the uplink synchronization procedure (or random access procedure) during which the WTRU354 is in the idle state, (i.e., different from the RACH time slot). The assignment of frames, subframes or slots may be performed by previous signaling (i.e., broadcast messages) or by pre-configuration. The node-B352 may provide different levels of service or meet different performance needs or goals relative to WTRUs in an active state versus WTRUs in an idle state. When the WTRU354 is in the active state, more stringent maintenance of uplink synchronization is required to support active traffic. Therefore, the WTRU354 may need to send uplink synchronization transmissions more frequently than in an idle state that requires less stringent uplink synchronization due to no active traffic going on.

In all of the above embodiments, the node-B may include a flag in the round robin message, the scheduling message, or the synchronization request message to indicate whether the WTRU is mandatory or optional to perform the uplink synchronization procedure. When a node-B needs to send a packet to a WTRU (e.g., High Speed Downlink Packet Access (HSDPA)), it is useful to command the WTRU to perform uplink synchronization (i.e., to set the flag to "mandatory") because the WTRU needs to perform uplink synchronization to send hybrid automatic repeat request (H-ARQ) positive feedback. Preferably, the flag is contained in a polling message, a scheduling message, or a synchronization request message. If the flag indicates that uplink synchronization is optional, the WTRU may perform an uplink synchronization procedure.

Figure 4 is a block diagram of a node-B400 and a WTRU450 configured in accordance with the present invention. The node-B400 includes an uplink synchronization controller 402 and a transceiver 404. The WTRU450 includes a transceiver 452 and an uplink synchronization controller 454. The uplink synchronization controller 402 generates a polling message, a scheduling message, or a synchronization request message for the WTRU 450. The transceiver 404 transmits the polling message, the scheduling message, or the synchronization request message to the WTRU 450. The transceiver 452 of the WTRU450 receives the polling message, the scheduling message, or the synchronization request message and transmits an uplink synchronization burst to the node-B400 based on the polling message, the scheduling message, or the synchronization request message.

The uplink synchronization controller 402 estimates the uplink timing shift based on the uplink synchronization burst transmitted by the WTRU450 and generates an uplink timing calibration command. The transceiver 404 then sends the uplink timing calibration command to the WTRU 450. Next, the uplink synchronization controller 454 of the WTRU450 calibrates the uplink timing based on the uplink timing calibration command.

In accordance with another embodiment of the present invention, the WTRU may use cell reselection as a trigger to go from a low power active state to an idle state. When the WTRU determines through its cell search and cell reselection procedures that the WTRU should move to a new cell, the WTRU may enter an idle state without performing handover and radio bearer reconfiguration. In this manner, the WTRU may conserve power by avoiding control signaling associated with handover and radio bearer reconfiguration.

According to yet another embodiment of the present invention, the DRX interval (i.e., WTRU wake-up time interval for reception) may be adaptively configured according to the service level (i.e., the activity of the WTRU). The DRX interval increases as the period of inactivity of the WTRU increases within a predetermined maximum value. The DRX interval may increase exponentially. Preferably, the network determines the DRX interval and sends it to the WTRU.

Alternatively, the WTRU may inform the node-B whether the WTRU is currently battery powered or constant power powered, and set the DRX accordingly. The WTRU may inform the node-B of its current remaining battery capacity and other characteristics (e.g., power consumed in transmitting data), which may help the node-B calculate an estimated battery life. The node-B then sets an energy-saving policy (e.g., DRX interval) for the WTRU based on the information.

Examples

1. A method for maintaining uplink synchronization when a WTRU is in an active state in a wireless communication system including the WTRU and a node-B.

2. The method of embodiment 1 comprising the node-B sending a polling message to the WTRU.

3. The method of embodiment 2 comprising the WTRU sending an uplink synchronization burst to the node-B based on the polling message.

4. The method of embodiment 3 comprising the node-B estimating an uplink timing shift based on the uplink synchronization burst.

5. The method of embodiment 4 comprising the node-B sending an uplink timing calibration command to the WTRU.

6. The method of embodiment 5 comprising the WTRU calibrating uplink timing based on the uplink timing calibration command.

7. The method as in any one of embodiments 2-6 wherein the polling message comprises a specific time that the WTRU sent the synchronization burst.

8. The method as in any one of embodiments 2-7 wherein the polling message includes uplink interference information so that the WTRU estimates a transmit power for the synchronization burst.

9. The method as in any one of embodiments 2-8 wherein the polling message comprises uplink transmit power information for the synchronization burst.

10. The method as in any one of embodiments 2-9 wherein the polling message is transmitted over a downlink common control channel to grant access to an uplink shared channel for the synchronization burst.

11. The method as in any one of embodiments 2-10 further comprising the WTRU entering DRX mode.

12. The method as in any one of embodiments 2-11 wherein the polling message is addressed to a plurality of WTRUs to poll a plurality of synchronization bursts from the plurality of WTRUs.

13. The method as in any one of embodiments 2-12 wherein a polling rate is different from at least one of the plurality of WTRUs.

14. The method of embodiment 13 wherein the polling rate is determined based on at least one of the following estimated clock drift and mobility of each WTRU.

15. The method of embodiment 13 wherein the polling rate is adaptively changed by one of the WTRU and node-B.

16. The method as in any one of embodiments 15 wherein the node-B changes the polling rate based on an uplink synchronization result.

17. The method as in any one of embodiments 2-16 wherein the polling message provides an uplink channel allocation.

18. The method of embodiment 17 wherein the uplink channel allocation is periodic.

19. The method of embodiment 17 wherein the uplink channel allocation indicates a duration of an allocated uplink channel.

20. The method as in any one of embodiments 2-19 wherein the node-B provides information about the polling message to the WTRU by broadcast.

21. The method as in any one of embodiments 2-19 wherein the node-B provides information about the polling message to the WTRU during registration.

22. The method as in any embodiments 2-21 wherein the polling rate is set differently based on the RRC state of the WTRU.

23. The method as in any one of embodiments 2-22 wherein the polling rate increases over time.

24. The method of embodiment 23 wherein the polling rate increases exponentially.

25. The method as in any one of embodiments 2-24 comprising the WTRU sending scheduling information comprising an amount of data to be transmitted to the node-B after receiving the polling message.

26. The method as in any one of embodiments 2-25 further comprising the WTRU sending a message after receiving the polling message indicating that the WTRU wishes to acquire uplink resources for data transmission.

27. The method as in any one of embodiments 2-26 further comprising the WTRU sending a CQI after receiving the polling message.

28. The method as in any one of embodiments 3-27 wherein the uplink synchronization burst does not include a WTRU ID and a cell ID.

29. The method as in any one of embodiments 3-28 wherein the node-B includes a short identifier in the polling message and the WTRU includes the short identifier in the uplink synchronization burst.

30. The method as in any one of embodiments 2-29 wherein the polling message comprises a request for the WTRU to send the synchronization burst.

31. The method of embodiment 30 wherein the WTRU sends the uplink synchronization burst using a slotted Aloha-based mechanism.

32. The method as in any one of embodiments 30-31 wherein the WTRU sends the uplink synchronization burst over a RACH.

33. The method as in any one of embodiments 30-32 further comprising the node-B assigning at least one of a frame, a subframe, and a slot to send the uplink synchronization burst.

34. The method as in any one of embodiments 2-33 wherein the node-B sends an indication as to whether the WTRU sending the uplink synchronization burst is mandatory or optional.

35. The method of embodiment 1 comprising the node-B sending a scheduling message for uplink synchronization to the WTRU.

36. The method of embodiment 35 comprising the WTRU sending an uplink synchronization burst to the node-B based on the scheduling message.

37. The method as in embodiment 36 comprising the node-B estimating an uplink timing shift based on the uplink synchronization burst.

38. The method of embodiment 37 comprising the node-B sending an uplink timing calibration command to the WTRU.

39. The method of embodiment 38 comprising the WTRU calibrating uplink timing based on the uplink timing calibration command.

40. The method as in any one of embodiments 35-39 wherein the schedule indicates a predetermined time for uplink synchronization.

41. The method as in any one of embodiments 35-40, wherein the scheduling indicates resources for transmitting the uplink synchronization burst.

42. The method as in any one of embodiments 35-41 wherein the node-B signals resources for transmitting the uplink synchronization burst to the WTRU prior to a scheduled synchronization time.

43. The method as in any one of embodiments 36-42 wherein the WTRU includes a next synchronization time in a current synchronization burst.

44. The method as in embodiment 43 wherein the node-B modifies the next synchronization time through a downlink signaling channel.

45. The method as in any one of embodiments 36-44 wherein the uplink synchronization burst does not include a WTRU ID and a cell ID.

46. The method as in any one of embodiments 36-45 wherein the node-B includes a short identifier in the scheduling message and the WTRU includes the short identifier in the uplink synchronization burst.

47. The method as in any one of embodiments 36-46 wherein the node-B sends an indication as to whether the WTRU sending the uplink synchronization burst is mandatory or optional.

48. A method for reducing battery consumption of a WTRU in a cellular wireless communication system.

49. The method of embodiment 48 comprising the WTRU determining that the WTRU should move to a new cell.

50. The method of embodiment 49 comprising the WTRU entering an idle state without performing a handover to the new cell.

51. The method of embodiment 48 comprising the WTRU entering DRX mode whereby the WTRU periodically wakes up according to a DRX interval to check for paging messages and then the WTRU again enters idle state if no paging message is directed to the WTRU.

52. The method of embodiment 51 comprising monitoring activity of the WTRU.

53. The method of embodiment 52 comprising setting the DRX interval based on the WTRU's activity such that the DXR interval increases as the inactivity of the WTRU increases.

54. The method of embodiment 53 wherein the DRX interval increases exponentially.

55. The method as in any one of embodiments 53-54 further comprising the WTRU notifying whether the WTRU is battery powered or constant power to set the DRX interval accordingly.

56. The method as in any one of embodiments 53-55 further comprising the WTRU notifying its current battery capacity to set the DRX interval based on the current battery capacity.

57. A node-B for maintaining uplink synchronization in a wireless communication system including a WTRU and the node-B.

58. The node-B of embodiment 57 comprising an uplink synchronization controller to generate at least one of a poll message, a scheduling message, and a synchronization request message for the WTRU and to estimate an uplink timing shift based on an uplink synchronization burst transmitted by the WTRU in response to the at least one of the poll message, the scheduling message, and the synchronization request message.

59. The node-B of embodiment 58 comprising a transceiver for sending an uplink timing calibration command to the WTRU, whereby the WTRU calibrates uplink timing based on the uplink timing calibration command.

60. The node-B of any of embodiments 58-59 wherein at least one of the polling message, scheduling message, and synchronization request message includes a specific time at which the WTRU sent the synchronization burst.

61. The node-B of any of embodiments 58-60 wherein at least one of the polling message, scheduling message, and synchronization request message includes uplink interference information such that the WTRU estimates a transmit power for the synchronization burst.

62. The node-B of any of embodiments 58-61 wherein at least one of the poll message, the scheduling message and the synchronization request message includes uplink transmit power information for the synchronization burst.

63. The node-B of any of embodiments 58-62 wherein at least one of the polling message, scheduling message, and synchronization request message is transmitted over a downlink common control channel to grant access to an uplink shared channel for the synchronization burst.

64. The node-B of any of embodiments 58-63 wherein at least one of the polling message, scheduling message, and synchronization request message is addressed to a plurality of WTRUs to poll a plurality of synchronization bursts.

65. The node-B of embodiment 64 wherein the uplink synchronization controller sets the polling rate differently for at least one of the plurality of WTRUs.

66. The node-B of embodiment 65 wherein the uplink synchronization controller determines the polling rate based on at least one of an estimated clock drift and mobility of each WTRU.

67. The node-B of any of embodiments 65-66 wherein the uplink synchronization controller adaptively changes the polling rate.

68. The node-B of any of embodiments 65-67 wherein the uplink synchronization controller changes the polling rate based on an uplink synchronization result.

69. The node-B of any of embodiments 58-68 wherein at least one of the polling message, scheduling message and synchronization request message provides an uplink channel allocation.

70. The node-B of embodiment 69 wherein the uplink channel assignment is periodic.

71. The node-B of any of embodiments 69-70 wherein the uplink channel allocation indicates a duration of an allocated uplink channel.

72. The node-B as in any of embodiments 58-71 wherein the node-B provides information about the polling message to the WTRU by broadcast.

73. The node-B as in any of embodiments 58-71 wherein the node-B provides information about the polling message to the WTRU during registration.

74. The node-B of any of embodiments 58-73 wherein the uplink synchronization controller sets the polling rate differently for each RRC state of the WTRU.

75. The node-B of any of embodiments 58-74 wherein the uplink synchronization controller increases a polling rate over time as inactivity of the WTRU increases.

76. The node-B of embodiment 75 wherein the polling rate increases exponentially.

77. The node-B as in any of embodiments 58-76 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.

78. The node-B of any of embodiments 58-77 wherein the uplink synchronization controller assigns at least one of a frame, a subframe, and a time slot to send the uplink synchronization burst.

79. The node-B as in any of embodiments 58-78 wherein the uplink synchronization controller sends an indication that the WTRU sent the uplink synchronization burst as mandatory or optional.

80. A WTRU for maintaining uplink synchronization in a wireless communication system including the WTRU and a node-B.

81. The WTRU of embodiment 80 comprising a transceiver for transmitting an uplink synchronization burst based on one of a polling message, a scheduling message, and a synchronization request message received from the node-B.

82. The WTRU of embodiment 81 comprising an uplink synchronization controller to calibrate uplink timing based on an uplink timing calibration command received from the node-B, the node-B generating the uplink timing calibration command after estimating uplink timing shift based on the uplink synchronization burst.

83. The WTRU as in any one of embodiments 81-82 wherein at least one of the polling message, scheduling message and synchronization request message comprises a specific time at which the WTRU sends the synchronization burst.

84. The WTRU as in any one of embodiments 81-83 wherein at least one of the polling message, scheduling message and synchronization request message includes uplink interference information such that a transmit power for the synchronization burst is controlled based on the interference information.

85. The WTRU as in any one of embodiments 81-84 wherein at least one of the polling message, scheduling message and synchronization request message includes uplink transmit power information for the synchronization burst.

86. The WTRU as in any one of embodiments 81-85 wherein the WTRU enters DRX mode.

87. The WTRU as in any one of embodiments 81-86 wherein the transceiver receives the information regarding the polling message by broadcast.

88. The WTRU as in any one of embodiments 81-86 wherein the transceiver receives information about the polling message during registration.

89. The WTRU as in any one of embodiments 82-88 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.

90. The WTRU as in any one of embodiments 82-89 wherein the uplink synchronization controller sends a scheduling request indicating that the WTRU wishes to acquire uplink resources for data transmission after receiving the polling message.

91. The WTRU as in any one of embodiments 82-90 wherein the WTRU sends a CQI after receiving the polling message.

92. The WTRU as in any one of embodiments 82-91 wherein the uplink synchronization controller does not include a WTRU ID and a cell ID in the uplink synchronization burst.

93. The WTRU as in any one of embodiments 82-91 wherein the uplink synchronization controller includes a short identifier previously included in the polling message in the uplink synchronization burst.

94. The WTRU as in any one of embodiments 83-93 wherein the transceiver transmits the uplink synchronization burst using a slotted Aloha-based mechanism.

95. The WTRU as in any one of embodiments 83-94 wherein the transceiver transmits the uplink synchronization burst via a RACH.

96. The WTRU as in any one of embodiments 83-95 wherein the transceiver transmits the uplink synchronization burst in a frame, subframe or time slot assigned by the node-B.

97. The WTRU as in any one of embodiments 83-96 wherein the uplink synchronization controller includes a next synchronization time in the uplink synchronization burst.

98. A WTRU configured to reduce battery consumption in a cellular wireless communication system.

99. The WTRU of embodiment 98 comprising a cell search unit configured to determine that the WTRU should move to a new cell.

100. The WTRU of embodiment 99 comprising a controller for entering an idle state without performing a handover to the new cell upon determining that the WTRU should move to the new cell.

101. The WTRU of embodiment 98 comprising a monitor for monitoring activity of the WTRU.

102. The WTRU of embodiment 101 comprising a DRX controller to enter DRX mode according to a DRX interval determined by a network based on activity of the WTRU, such that the DRX interval increases as inactivity of the WTRU increases.

103. The WTRU of embodiment 102 wherein the DRX interval increases exponentially.

104. The WTRU as in any one of embodiments 102-103 wherein the WTRU provides information to the network whether the WTRU is battery powered or constant power powered and the network sets the DRX interval based on the information.

105. The WTRU as in any one of embodiments 102-104 wherein the WTRU informs the network of its current battery capacity such that the DRX interval is set based on the current battery capacity.

Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. The methods or flow charts provided in the present invention may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium, examples of which include Read Only Memory (ROM), Random Access Memory (RAM), registers, buffer memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and Digital Versatile Disks (DVDs).

For example, suitable processors include: a general-purpose processor, a special-purpose processor, a conventional processor, a Digital Signal Processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) circuit, any other Integrated Circuit (IC), and/or a state machine.

A processor in association with software may be used to implement a radio frequency transceiver for use in a Wireless Transmit Receive Unit (WTRU), User Equipment (UE), terminal, base station, Radio Network Controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a video circuit, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, bluetoothA module, a Frequency Modulation (FM) radio unit, a Liquid Crystal Display (LCD) display unit, an Organic Light Emitting Diode (OLED) display unit, a digital music player, a media player, a video game player module, an internet browser, and/or any Wireless Local Area Network (WLAN) module.

Claims (8)

1. 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 whereby the WTRU periodically wakes up according to a DRX interval to check for paging messages, and the WTRU again entering an idle state if no paging message is directed to the WTRU;

monitoring activity of the WTRU; and

setting the DRX interval in a broadcast message based on the WTRU's activity such that the DXR interval increases as inactivity of the WTRU increases.

2. The method of claim 1, wherein the DRX interval increases exponentially.

3. The method of claim 1, further comprising:

the WTRU informs the WTRU whether it is battery powered or constant power to set the DRX interval accordingly.

4. The method of claim 1, further comprising:

the WTRU notifies its current battery capacity to set the DRX interval based on the current battery capacity.

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

a monitor to monitor activity of the WTRU; and

a Discontinuous Reception (DRX) controller to enter a DRX mode according to a DRX interval determined by a network in a broadcast message based on activity of the WTRU, such that the DRX interval increases with increasing inactivity of the WTRU.

6. The WTRU of claim 5, wherein the DRX interval increases exponentially.

7. The WTRU of claim 5, wherein the WTRU provides information to the network whether the WTRU is powered by a battery or a constant power source, and the network sets the DRX interval based on the information.

8. The WTRU of claim 5, wherein the WTRU notifies the network of its current battery capacity to set the DRX interval based on the current battery capacity.