HK1076552B - A method for use in a wireless transmit/ receive unit - Google Patents

Description

Method for use in a wireless transmit/receive unit

Technical Field

The present invention relates to the field of wireless communications, and more particularly, to optimizing power resources of wireless devices in a wireless communication system.

Background

The more frequently a battery operated device, such as a wireless transmit/receive unit (WTRU), looks for possible data to transmit to it, the more power the device consumes. In networks and devices that provide not only telephony but also data transmission, the manner in which the device looks for messages from the network varies depending on whether the device looks for an incoming call or an incoming data transmission.

With respect to the manner of calling by telephone, users are accustomed to a land network in which a ring tone is heard almost immediately after a specific telephone number is dialed. To meet this desire in a wireless environment, a WTRU must often scan the network to minimize the delay in establishing a connection when one is aware of a phone call, i.e., the WTRU must often scan the network for incoming calls to minimize the time between the network sending a call signal or message and the receiving WTRU actually checking for the call signal.

Such devices are well suited for use in telephone-based telephony, but are inefficient for data transmission. With respect to data transmission, there is no need for the strict requirements necessary to ensure a near real-time response to a call. Longer delays are generally tolerated when transmitting data to WTRUs such as pagers and the like. However, it is generally desirable that the device respond "in real time" to messages that show incoming data transmissions, so when handling data transmissions, the network must also be scanned quite frequently in some cases, but even in such cases the network must be scanned less frequently than when handling a telephone call mode.

The amount of delay that is acceptable depends on the form of data being transmitted and the user's preferences, for example, when data is updated infrequently (e.g., traffic or weather data), longer delays can be tolerated. In the case of a pager, a reasonable response time should be evaluated in response to a paged message with a time delay expected by the user. In the case of multiple network transmissions (e.g., stock quotes, sports scores, etc.), some users want the data to be updated occasionally so that they have a longer battery life, others are less interested in battery life and only want the data to be updated quickly. Examples of users who wish to be updated frequently are those who wish to have quick information updates and those whose WTRUs are connected to an external power supply. In the case of, for example, stock quotes, there are occasional viewers, and people who wish to get notification of immediate changes. Thus, if the user wishes to respond to the message quickly, the response time should be relatively fast, but still much longer than the response time required for the WTRU to know that there is a call placed.

Therefore, it is desirable to have a method and system to efficiently support data transmission and telephony.

Disclosure of Invention

A wireless network allows WTRUs to operate in a dormant (waiting) mode of operation according to a synchronization schedule, synchronization information being provided to the WTRUs to inform them when they may be in a dormant mode and when they must wake up and recover data.

The present invention provides a method for use in a wireless transmit/receive unit (WTRU), the method comprising:

receiving a frame including a synchronization schedule from a base station, wherein the frame includes a plurality of time slots, and the synchronization schedule indicates at least one time slot of the plurality of time slots including data scheduled by the WTRU;

receiving data during at least one of a plurality of time slots indicated as including data scheduled by the WTRU; and

operate in a dormant state during at least one of a plurality of time slots not indicated as including data scheduled by the WTRU.

The present invention also provides a method for use in a wireless transmit/receive unit (WTRU), the method comprising:

receiving a synchronization schedule from a base station, the data being received in frames, and each frame comprising a plurality of time slots, and for each frame the synchronization schedule indicating which of the plurality of time slots include data scheduled by the WTRU;

receiving data during each of a plurality of time slots in the synchronized schedule indicated as including data scheduled by the WTRU; and

entering a dormant state during each of a plurality of time slots in the synchronized schedule that are not indicated as including data scheduled by the WTRU.

Drawings

Fig. 1 is a diagram showing a wireless communication network.

Fig. 2 is a data diagram showing a frame structure for an embodiment of the present invention.

Detailed Description

In accordance with the present invention, synchronization information is provided to the wireless transmit/receive units (WTRUs) to inform them when they may be in a dormant mode (i.e., when they may be in a sleep state) and when they must wake up and resume data. For purposes of describing the present invention, a WTRU may have transmit-only, receive-only, or both transmit and receive capabilities, i.e., a WTRU may be any type of device capable of receiving and/or transmitting data in a wireless environment.

Referring now to fig. 1, a representation of a network is shown in which one or more base stations 21 communicate with a plurality of WTRUs, such as the WTRU22 mentioned, while describing the present invention. As explained, the WTRU22 may be any number of devices supported by the network, examples of which include User Equipment (UE), cell phones, pagers, blackberry (tm) devices, computers with modem connections, or any other device capable of operating in a wireless environment. The base stations 21 are controlled by a Radio Network Controller (RNC)25, which performs various network supervision and communication functions. The base station 21 comprises signal processing circuitry 31 and an RF stage 32, which includes transmission functions. Signals from the base station 21 are transmitted to WTRUs within its cell or transmission area (represented by antennas 33, 34). The WTRU22 has RF stages 37 and signal processing stages 38, a receive function being provided by the WTRU's RF stages 37 to receive signals transmitted by the base station 21. In the case of a dual path device, both RF stages 32 and 37 have transmit and receive functions, allowing WTRU22 to transmit data in the uplink and receive data in the downlink. Although transmission requires significantly more energy than reception, the problem of quiet operation mainly affects the downlink, and therefore the receiver function of the WTRU22 is very important.

In accordance with the present invention, when the RF stage 37 is receiving signals from the base station 21, the WTRU22 uses its signal processing circuitry 38 for control, which allows the operation of the receive function of the WTRU22 to be active primarily during times when signals are expected to include data intended for a particular WTRU22 (inter for). During at least some of the time when the signal is not intended for a particular WTRU22, the WTRU becomes stationary, which means that most of the reception and signal processing by the WTRU22 is turned off.

Regardless of the manner in which data is transmitted from the network, the WTRUs are preferably synchronized so that they can wake up and go to sleep to maximize battery life and meet user preferences. Synchronization information provided to WTRUs is provided in accordance with the manner in which data is transmitted from the network, i.e., regardless of the manner in which data is transmitted from the network, synchronization information is provided to WTRUs so that they know when they must wake up and when they can go to sleep.

As is known to those skilled in the art, data may be provided to the WTRU from the network in various ways as needed, and in one embodiment, the data may be transmitted via scheduled transmissions, in which case the network transmits various forms of broadcast or multicast data with a known schedule that is closely synchronized to the time frame known to the transmitting WTRU and the receiving WTRU. The WTRUs may then synchronize their wake-ups to find an opportunity when data may be or will be transmitted. For this embodiment in third generation cellular networks, the scheduling information may be provided by shared control channel (e.g., broadcast shared control channel (BCCH)) signaling or Dedicated Control Channel (DCCH) signaling. In the case where BCCH signaling is used, the scheduling (i.e., synchronization) information may be signaled for all broadcast and multicast services. If DCCH signaling is used, only scheduling specific to the receiving WTRU service is signaled.

In another embodiment, data may be transmitted in a multi-network transmission, i.e., as mentioned, some users want information to be updated only occasionally in favor of longer battery life, while other users want data to be updated quickly and less so. Therefore, in this embodiment, data is transmitted at a rate that meets the user's preference for frequency of update over battery life (even without any data changes). By transmitting data quickly at a synchronous rate (i.e., at the highest available rate required by the user) and repeating the transmission even when there is no change in data, the receiving WTRU alone may wake up and search for data at different time intervals according to user preference. By providing an adjustable degree of setting, this meets the needs of (and between) two groups of users.

Because the amount of acceptable delay varies depending on the particular user application, any tradeoff between delay and power consumption may have different optima for different users, so the delay (i.e., delay time) may be optimized on a usage basis because low delay conflicts with low power consumption. This situation becomes particularly significant when the WTRU is not in active use time.

For this embodiment in third generation cellular networks, once the receiving WTRU is aware of the scheduled broadcast or multicast transmission, it may then obtain service (i.e., scheduled broadcast or multicast transmission) for transmission on the Forward Access Channel (FACH) or Downlink Shared Channel (DSCH) based on a demand basis. The network may transmit broadcast or multicast data in a radio link control transparent or unacknowledged mode, which allows the receiving WTRU to decide whether reception is automatically needed without interaction or causes errors to be perceived on the network.

An improvement over this embodiment is that the multiple network transmissions are only provided for transmission until some WTRUs acknowledge receipt at the range of the network. This improvement has the advantage that the transfer can be ended when it is no longer necessary and also provides some robustness to the transfer of information to properly start the device. This improvement has the disadvantage of requiring uplink transmissions from the WTRU and may not be suitable for a large number of WTRUs. With respect to the third generation cellular network implementation, there are alternative implementations of multiple network acknowledgements, e.g., the rlc acknowledgement mode provides an automatic reply request mechanism to ensure transmission when there is a single receiving WTRU, and the layer 3 acknowledgement may be provided by transparent data transfer either by radio resource control signaling within the access layer or by non-access layer signaling when there are multiple receiving WTRUs.

In another embodiment, the network only transmits messages waiting for transmission, i.e., instead of always transmitting messages, it is more efficient to only notify WTRUs that there are messages intended for them at certain times. Where the availability of third generation cellular network messages is identified by a shared control channel (e.g., BCCH), those WTRUs desiring the message then request transmission of the message from the network, the request for the message may be a special message or registration of a multicast service to receive one or more messages associated with the service, which may be appropriate when only a small number of WTRUs are expected to request the actual message, and when multiple WTRUs desire the actual capability to do so. This may occur, for example, in the case of limited information in the initial transmission of the message informing the WTRU of the existence. In third generation cellular networks, the receiving WTRU generates a request for service by way of access stratum or non-access stratum signaling, and the network then signals broadcast scheduling information or establishes a dedicated radio bearer for service transmission. That is, the most efficient way for a network to decide on transmission knowing the number of WTRUs that have requested a message or multi-message service, if there are many recipients, the scheduling of information that identifies the shared channel, such as FACH or DSCH, and the transmission time for reception of the service is signaled on the shared control channel. If there are a small number of WTRUs requesting a message or service, a dedicated channel is established to each requesting or registered WTRU associated with the message or service.

Referring now to fig. 2, a signal frame diagram including a sequence of transmissions transmitted by a base station to multiple WTRUs is shown. As mentioned, when a particular WTRU or a new WTRU associated with the message or service is awake and seeking data, the delivery of the transmission is synchronized such that messages directed to the particular WTRU or group of WTRUs associated with the message or service are delivered, and to accomplish this, in one embodiment, the transmission is divided into frames 54, wherein seventy-two (72) frames 54 constitute a superframe (superframe), as shown in fig. 2. For simplicity in describing the present invention, portions of two superframes 51, 52 are shown. However, it should be noted that the superframes 51, 52 are part of a repeating series of superframes, and it should also be noted that having a superframe of 72 frames is provided by way of example only, as other multiple frame sequences are also possible.

Frame 54 is divided into slots 56 as shown in expanded view 71E of frame 71. Transmission packets designated as zeros (0) through (14) are included in the time slot 56 of each frame (e.g., frame 71), and each time slot 56 may include one or more device-specific data. For example, slot 6 includes data for WTRU 101, while slot 12 includes data for WTRUs 102 and 103.

WTRUs 101-103 preferably synchronize their reception so that they can receive data at their respective assigned time intervals. The use of a fixed time period for data reception means that once the WTRU is provided with its synchronization messages (i.e., messages regarding a specific time sequence of the WTRU's intended signal), the WTRU may synchronize with the time sequence and maintain a sleep state (i.e., quiet) for a portion of the super frame. This procedure results in reduced power consumption because most or all of the RF receiving circuitry of the WTRU in the sleep state is off. The WTRU preferably has most of its signal processing circuitry turned off as well. In this embodiment, the reduction in power consumption corresponds approximately to the number of frames being ignored.

Once synchronized, the WTRUs 101-103 are only awake in their respective time slot, radio frame, or frames with a particular overlap period, referred to as the transmission time interval (TT 1). From the network perspective, for each superframe, the network waits for frame 71, slot 6, before transmitting data to WTRU 101.

It should be noted that WTRUs may wake up at other times (i.e., other than their assigned time slots) if desired, e.g., it may be necessary to wake up by some common signals. In addition, the network and the WTRUs may be adapted so that a special "wake up" signal is transmitted from the network to a particular WTRU or group of WTRUs, where the WTRUs must wake up and receive data outside of their designated time slots.

It should be noted that the division of transmissions into superframes, frames, and time slots may vary as desired. For example, in the discussion above, it was assumed that the WTRU woken up in at least each superframe and looked for data in at least one slot of at least one frame. However, as described, data transmission may be provided to the user as needed to meet the user's preferences for battery life and frequency of data updates. Therefore, the timing of the particular synchronization mechanism may be similarly varied. For example, it may result in synchronized scheduling between network data delivery and its receipt by the WTRU, where more than one superframe of time elapses (pass) between the WTRU waking up and the WTRU waking up period at its designated frame and slot finding message.

While this invention has been described in terms of preferred embodiments, other variations within the scope of this invention will be apparent to those skilled in the art.

Claims (10)

1. A method for use in a wireless transmit/receive unit (WTRU), the method comprising:

receiving a frame including a synchronization schedule from a base station, wherein the frame includes a plurality of time slots, and the synchronization schedule indicates at least one time slot of the plurality of time slots including data scheduled by the WTRU;

receiving data during at least one of a plurality of time slots indicated as including data scheduled by the WTRU; and

operate in a dormant state during at least one of a plurality of time slots not indicated as including data scheduled by the WTRU.

2. The method of claim 1, wherein at least one of the plurality of time slots includes data for a plurality of WTRUs.

3. The method of claim 2 wherein the frames are grouped into a series of frames and each WTRU is assigned at least one of a plurality of time slots within the series of frames.

4. The method of claim 2 wherein the frames are grouped into a series of frames and each WTRU is assigned some of a plurality of time slots within the series of frames.

5. The method of claim 4, wherein one of the plurality of time slots is allocated to a WTRU for each series of frames.

6. A method for use in a wireless transmit/receive unit (WTRU), the method comprising:

receiving a synchronization schedule from a base station, the data being received in frames, and each frame comprising a plurality of time slots, and for each frame the synchronization schedule indicating which of the plurality of time slots include data scheduled by the WTRU;

receiving data during each of a plurality of time slots in the synchronized schedule indicated as including data scheduled by the WTRU; and

entering a dormant state during each of a plurality of time slots in the synchronized schedule that are not indicated as including data scheduled by the WTRU.

7. The method of claim 6, wherein at least one of the plurality of time slots includes data for a plurality of WTRUs.

8. The method of claim 6 wherein the frames are grouped into a series of frames and each WTRU is assigned one of a plurality of time slots within the series of frames.

9. The method of claim 6, wherein the frames are grouped into a series of frames and a plurality of WTRUs are allocated some of a plurality of time slots within the series of frames.

10. The method of claim 9, wherein for each series of frames, one of the plurality of time slots is allocated to a WTRU.