HK1133521A - Sending and reducing uplink feedback signaling for transmission of mbms data - Google Patents

Description

Sending and reducing uplink feedback signaling for MBMS data transmission

Technical Field

The present invention relates to wireless communication systems. And more particularly to a method, apparatus and system for reducing uplink feedback signaling for Multimedia Broadcast Multicast Service (MBMS) data transmission.

Background

In order to maintain technical competitiveness for a long period of time, the third generation partnership project (3GPP) and 3GPP2 are both considering Long Term Evolution (LTE), where evolution of the radio interface and network architecture is necessary.

Multimedia Broadcast Multicast Service (MBMS) is a feature that has been introduced into the 3GPP release six specifications that allows multimedia information (e.g., audio, video) transmission to be performed via point-to-point (PTP) or point-to-multipoint (PTM) operations. MBMS is supported in the terrestrial mobile telecommunications system (UMTS) release 6. In order to further improve MBMS as an efficient mechanism to reliably distribute multimedia content to users over evolved universal radio access (E-UTRA) networks, enhanced MBMS is being considered and studied in the 3gpp LTE standardization work.

In the prior art of UMTS release six, there is no wireless transmit/receive unit (WTRU) feedback for MBMS to a network base station (referred to as a node B in 3 GPP). WTRU feedback is proposed in 3GPP LTE to improve MBMS operation in E-UTRA systems. Thus, WTRU feedback transmission has become a very important design issue in E-UTRA systems.

In MBMS, the broadcast service is always operated in PTM mode, whereas the multicast service may be operated in PTP mode or PTM mode. For multicast services, the Radio Access Network (RAN) may select either the PTP mode or the PTM mode using an MBMS counting procedure and based on the number of wireless transmit/receive units (WTRUs) participating in the multicast service within a cell.

In the PTP mode, a Dedicated Channel (DCH) is used to transmit MBMS data to the end users. In PTM mode, data is transmitted on an MBMS Traffic Channel (MTCH) which is mapped to a Forward Access Channel (FACH) and in turn to a secondary common control physical channel (S-CCPCH). PTM allows for more efficient use of radio resources when numerous WTRUs subscribe to the same service.

Currently, High Speed Downlink Packet Access (HSDPA) has been introduced in the fifth release of 3GPP specifications. One enhancement introduced therein for MBMS is the transmission of MBMS data (i.e., MTCH logical channels) via HSDPA. In order to improve spectral efficiency, techniques such as Adaptive Modulation and Coding (AMC), hybrid automatic repeat request (H-ARQ) for fast feedback and fast node B scheduling are used in HSDPA to improve spectral efficiency.

AMC adapts the transmission data rate on the high speed downlink shared channel (HS-DSCH) according to the channel conditions perceived by the receiving WTRU. The node B may use the following information to determine the optimal rate and scheduling for individual transmissions:

1) channel Quality Information (CQI) reported from the WTRU that indicates the channel quality perceived by the WTRU;

2) transmit Power Control (TPC) commands for the associated dedicated channel; and

3) acknowledgement (ACK)/Negative Acknowledgement (NACK) feedback for previous transmissions.

Typically, for WTRUs that perceive adverse channel conditions (e.g., at the cell edge), their transmissions use lower data rates. For WTRUs that perceive favorable channel conditions, their transmissions use higher data rates.

For PTM operation, WTRUs subscribed to the multicast service receive MBMS data via the same radio resources. For MBMS over HSDPA, the WTRU decodes the same high speed physical downlink shared channel (HS-PDSCH) in a specified Transmission Time Interval (TTI), i.e., the same HS-DSCH transport block.

One challenge for the node B is the selection of modulation and coding schemes for the multicast transport block so that all WTRUs can reliably decode data without wasting cell capacity. In one aspect, the node B may always use a lower data rate for transmitting, thereby ensuring that all WTRUs, including WTRUs with unfavorable channel conditions, in the cell may reliably decode the data. On the other hand, the node B may perform transmission with a higher data rate in order not to waste HSDPA resources. In this case, WTRUs that are aware of the unfavorable channel conditions may be cumbersome in multicast transport block decoding.

One method for determining the optimal transmission rate for MBMS data is to report the CQI (i.e., the CQI via the high speed dedicated physical control channel (HS-DPCCH)) in the Uplink (UL) by configuring the WTRU. The node B may set its transmission rate based on the worst CQI report to ensure that all WTRUs may reliably decode the data. However, as the number of WTRUs subscribing to the multicast service increases, the transmission of CQI feedback information causes a significant increase in the noise in the uplink, thereby reducing the capacity available for other uplink transmissions. Current 3GPP release six specifications also do not provide support for optimal transmission rate selection and multicast transport block scheduling on the HS-DSCH.

Disclosure of Invention

A method, apparatus and system for WTRU uplink feedback signaling for MBMS transmission in a wireless communication system such as an E-UTRA system, HSDPA system or any Internet Protocol (IP) based system. Preferably, the feedback is transmitted directly by the synchronous or non-synchronous Random Access Channel (RACH), so that the node B does not schedule the uplink shared channel for the WTRU. In one embodiment, in response to a request for an uplink shared channel assignment sent by the WTRU on a synchronous or non-synchronous RACH, the WTRU sends feedback using the uplink shared data/control channel assigned to it.

In another embodiment, the uplink feedback signaling for MBMS data transmission over E-UTRA or HSDPA channels is reduced. A triggering criterion for reporting a Channel Quality Indicator (CQI) is set and the WTRU sends the CQI to the node-B only if the triggering criterion is met. The triggering criterion may be the current operating CQI value at the node B, so that the WTRU may transmit CQI when the channel conditions are not as good as the current operating CQI value. The triggering criterion may be generated based on statistics of erroneous high speed downlink shared channel (HS-DSCH) transport block receptions. The triggering criterion may also be a predetermined period of time, whereby the WTRU transmits CQI to the node B if the WTRU does not send CQI for a predetermined period of time. In addition, a random backoff procedure may be implemented before transmitting the CQI.

Another method for reducing feedback includes: the node B sends the multicast data a predetermined number of times so that the WTRU does not have to send a multicast data acknowledgement to the node B. Instead, the WTRU sends at least one of an average number of transmissions and an error rate required to successfully decode the data.

Other objects and advantages will be apparent to those skilled in the art from the following description of the preferred embodiments of the invention.

Drawings

Fig. 1 is a flow chart of a method for uplink feedback signaling related to MBMS transmissions.

Fig. 2 is a flow diagram of a method for uplink feedback signaling in connection with an MBMS transmission sent concurrently with uplink data or control information.

Figure 3 is a flow diagram of a method of providing uplink channel pre-allocation for a WTRU for feedback signaling related to MBMS transmissions.

Figure 4 is a block diagram of a WTRU configured for uplink feedback related to MBMS transmissions.

Fig. 5 is a flow diagram of a method for reducing CQI feedback related to MBMS transmissions.

Fig. 6 is a flow diagram of a method for reducing ACK/NACK feedback related to MBMS transmissions.

Detailed Description

The term "WTRU" as referred to below includes, but is not limited to, a User Equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. The term "node B" as referred to hereinafter includes, but is not limited to, a base station, a station controller, an access point, or any other type of interfacing device capable of operating in a wireless environment.

Described herein is an apparatus and method for providing a Radio Access Network (RAN) with information needed to determine an optimal transmission rate and scheduling for multimedia broadcast/multicast service (MBMS) data without causing excessive noise increase in the uplink. Also, an apparatus and method for reducing signaling overhead due to Channel Quality Indicator (CQI) feedback and acknowledgement/negative acknowledgement (ACK/NACK) for hybrid automatic repeat request (H-ARQ) operations are set forth herein.

WTRU feedback transmission for MBMS services may be implemented in a mixed unicast (uni-cast) and MBMS cell. Furthermore, for dedicated MBMS cells, the transmission is only applicable if there is no uplink channel.

For convenience of MBMS operation, WTRU feedback may be used for MBMS services and includes, but is not limited to, NACKs, Channel Quality Indicators (CQIs), and responses to network counting/polling. In WTRU NACK feedback for supporting MBMS point-to-point (PTP) retransmissions, the WTRU ID is explicitly or implicitly included in the NACK message. The WTRU ID need not be transmitted in the WTRU NACK feedback for MBMS-supported point-to-multipoint (PTM) retransmission. The WTRU ID is not necessarily included for WTRU CQI feedback for MCS adaptation supporting PTM. If the network performs simultaneous counting/polling processes for several MBMS services at the same time, the MBMS service ID should be included in the response to the network counting/polling.

In one embodiment, the allocated uplink channel information for WTRU feedback transmission is preferably transmitted on a Broadcast Channel (BCH). Alternatively, if the WTRU is configured for MBMS, the WTRU's transmission feedback is transmitted on the MBMS Control Channel (MCCH).

Figure 1 shows a flow diagram of a method of WTRU feedback transmission for MBMS. In step 101, the WTRU determines whether it is synchronized with the node B. If there is no synchronization, the non-synchronized RACH is used for MBMS feedback according to the following procedure. For example, in LTE, the procedure may be used when the WTRU is in LTE _ Idle state (i.e., no RRC connection) or when the WTRU is in LTE _ Active state (i.e., RRC connection is present). Next, if the system configuration does not require an uplink shared channel in step 102, the WTRU sends a message on the RACH in step 103 indicating the reason for random access for "feedback for MBMS", which is preferably sent inside the RACH preamble. A small number of preambles will be reserved for the reason "feedback for MBMS". In response to this indication, the node B does not allocate an uplink shared channel for MBMS feedback to the WTRU (step 104), and the WTRU sends MBMS feedback directly on the non-synchronized RACH (step 105), preferably in the RACH preamble.

Returning to step 102, if the system configuration requires an uplink shared channel assignment, the WTRU sends a request for the assignment in a non-synchronized RACH preamble as an indication (step 106). If a RACH cause is required, the amount of feedback can be conveyed using the current design of non-synchronized random access channels and there is no need to change the basic non-synchronized random access channel structure in order to convey feedback for MBMS.

Alternatively, the channel structure is modified for a non-synchronized random access channel conveying feedback for MBMS, including the following examples. The preamble of the non-synchronized random access channel can be extended longer in order to convey more implicit information. Further, more sequence indices may be used for preamble sequences (e.g., Zadoff-Chu or GCL sequences) of non-synchronized random access channels in order to convey more implicit information. The non-synchronized random access channel may explicitly convey MBMS feedback information. Furthermore, the random access burst may be extended longer in order to add a message/control field.

If a RACH cause indication is required (step 107), the WTRU sends an indication of "feedback for MBMS" and this indication is preferably sent in a non-synchronized RACH preamble (step 108). For the feedback information, a certain number of preambles may be reserved and a "feedback for MBMS" indication. The advantage of the reason for the need for RACH indication is that the node B would not otherwise recognize that the RACH burst is for MBMS feedback, and it would treat the information transmitted on the RACH as regular RACH access information. One solution is to perform blind detection by configuring the node B, but this trades off performance degradation against complexity improvement.

If the RACH cause indication is not required, then step 108 will be skipped. Whether or not the RACH cause indication is transmitted, the node B detects the RACH preamble and allocates an uplink shared channel (step 109). At step 110, the WTRU sends its MBMS feedback on the uplink shared data/control channel according to its grant assignment. The allocated uplink data/control channel should be long enough to allow the WTRU to transmit feedback on the MBMS within a predetermined period of time.

Returning to step 101, if the WTRU is synchronized with the node B, the WTRU uses the synchronous RACH according to the procedure used when the WTRU is in LTE _ Active state (with RRC connection) for the LTE case as an example.

If the system configuration does not require uplink shared channel allocation at step 122, the WTRU sends a message on the RACH indicating a "feedback for MBMS" random access reason, preferably sent within the RACH preamble, at step 123. For the reason of "feedback for MBMS", a small number of preambles may be reserved for it. In response to this indication, the node B does not allocate an uplink shared channel for MBMS feedback to the WTRU (step 124), and the WTRU sends MBMS feedback directly on the synchronous RACH (step 125), preferably in the RACH preamble.

According to this embodiment, when the WTRU transmits a scheduling request on the shared channel using a regular RACH preamble, if the size is sufficient, the WTRU uses the regular RACH preamble, or it uses an extended preamble to include an RACH cause indication or one or more explicit control bits. The synchronized RACH structure has a modified preamble sequence and control bit field mapping to indicate "feedback for MBMS". In addition, the new channel structure or reserved preamble also allows the node B to recognize that it is not a regular synchronous random access channel that simply transmits a scheduling request from the WTRU. Thus, the node B does not schedule the uplink shared channel for the WTRU.

If the amount of feedback can be transmitted using the current synchronous random access channel design (e.g., the currently specified 24-bit length), then the basic synchronous RACH structure does not need to be changed. Otherwise, a different channel structure is used for the synchronous random access channel carrying feedback for MBMS. Modifications to the RACH include, but are not limited to, the following examples:

the preamble of the synchronous random access channel can be extended longer in order to convey more implicit information;

more sequence indices can be used to synchronize the preamble sequence of the random access channel in order to convey more implicit information; and

the synchronous random access channel transmits more explicit information bits-the random access burst can be extended longer to transmit more bits for this purpose.

Returning to step 122, if the system configuration requires an uplink shared channel assignment, the WTRU sends a request for such assignment as an indication in the synchronous RACH preamble (step 126).

If a RACH cause indication is required (step 127), the WTRU sends an indication of "feedback for MBMS" preferably sent in a non-synchronized RACH preamble (step 128). For the feedback information and the RACH cause indication of "feedback for MBMS", a certain number of preambles may be reserved for it.

If the RACH cause indication is not required, then step 128 will be skipped. Whether or not the RACH cause indication is transmitted, the node B detects the RACH preamble and allocates an uplink shared channel (step 129). At step 130, the WTRU sends its MBMS feedback on the uplink shared data/control channel according to its grant assignment. The allocated uplink shared data/control channel should be large enough to allow the WTRU to send feedback for MBMS within a predetermined period of time.

Figure 2 is a flow diagram of a method for a WTRU to send feedback information for MBMS services that exists on a concurrent uplink shared channel. For LTE applications, this method is applicable when the WTRU is in LTE _ Active mode (with RRC connection) and has an uplink shared channel in the current TTI. In step 201, the WTRU establishes an RRC connection. In step 202, an uplink shared data channel is to be established. When the WTRU has MBMS feedback, the feedback is transmitted on the uplink shared data channel along with uplink data and data related control information, step 203. In step 204, the WTRU establishes an uplink non-data related shared control channel (e.g., CQICH, ACKCH) as a separate process or in combination with the previous steps. In step 205, the WTRU's MBMS feedback is transmitted on the uplink shared control channel along with uplink non-data related control information.

Fig. 3 is a flowchart of a method for node B to pre-allocate a channel region for MBMS feedback purposes. In one variant, the pre-allocation is configured for a single type of feedback, e.g. only for NACKs. In an alternative variant, multiple channel regions are pre-allocated, each with its own MBMS feedback type. For an LTE system, any OFDMA-based system, or any single carrier FDMA (SC-FDMA) type system, the time-frequency region (e.g., block or symbol) is pre-allocated by the node B (step 301). For WCDMA type systems, the node B would pre-allocate a common channelization code for the uplink MBMS feedback indication. In step 302, the node B sends a pre-allocation indication to the WTRU on a broadcast channel. In step 303, for each WTRU, if the MBMS feedback criterion is met, the WTRU transmits certain predefined bursts in either the pre-allocated time-frequency region or the common channelization code used for MBMS feedback. The feedback may include an indicator (e.g., a NACK message) or a small number of bits. The node B detects whether feedback is present by detecting whether the received signal power (or common channelization code) in the time-frequency region exceeds a predefined threshold. A processor within the node B may be configured to implement the node B method steps described above; a processor in the WTRU may be configured to perform the WTRU steps described above.

Figure 4 shows a WTRU 401 implementing the MBMS feedback method described above. The WTRU 401 includes a physical layer (PHY) entity 402 and a Radio Resource Control (RRC) entity 403, which are implemented as a single processor 404. Alternatively, a separate processor may be used to implement these entities. The PHY entity 402 is responsible for generating MBMS feedback messages (e.g., CQI or NACK). The RRC entity 403 monitors its connection state and, for LTE, determines whether the current mode is LTE _ Active or LTE _ Idle. In addition, the RRC entity 403 selects a synchronous or non-synchronous RACH for transmitting MBMS feedback according to its connection state.

Feedback traffic control on the uplink is a very desirable feature since the number of WTRUs subscribing to MBMS may be large. The preferred embodiment of the present invention includes a probability-based feedback reduction mechanism for MBMS, such as reducing the number of CQI and NACK messages sent by the WTRU. The network (i.e. node B or access gateway) will configure the response/feedback probability parameters for the specific type of MBMS feedback. For example, a network deciding an estimated probability of 0.3 for CQI MBMS feedback would prevent MBMS feedback overload and would keep the uplink traffic at an acceptable level. Therefore, the threshold parameter for CQI feedback is 0.3. The network informs the WTRU of the parameters via a control channel or a broadcast channel. When the WTRU wishes to send MBMS feedback, it selects a random number. If the random number is lower than the response/feedback probability parameter, the WTRU transmits feedback for the MBMS. Otherwise the WTRU will not transmit feedback. The network may configure different response/feedback probability parameters for different types of feedback. In addition, for the feedback using a larger number of bits on the uplink channel and the feedback using a smaller number of bits, the MBMS feedback traffic can be further reduced by configuring the former with a lower probability threshold parameter than the latter.

For HSDPA transmission, the node B will need CQI feedback from the WTRU to optimally select the transmission rate and schedule the multicast data on the HS-DSCH. The WTRU transmits CQI when the channel state is worse than or equal to the current operating CQI value employed on the node B. The current operating CQI value corresponds to the worst CQI in the contracted WTRU that is known at the node B. Once the WTRU has advertised a CQI to the node B that is inferior to the current operating CQI value, the node B updates the current operating CQI value. To minimize this type of MBMS feedback, a CQI report triggering criterion is established and CQI reports are sent only if the triggering criterion is met. This process is different from conventional HSDPA control signaling where CQI reports are generated continuously or periodically by the WTRU.

Fig. 5 is a flow chart of a method for reducing CQI feedback according to the present embodiment. For triggering criteria, such as the current operating CQI value, to be known to all subscribing WTRUs, CQI transmission may be triggered when needed. The triggering criteria may be explicitly advertised to the WTRU by the node B using a high speed shared control channel (HS-SCCH) (step 501). In addition, additional bits may be added in the conventional HS-SCCH slot format to indicate the triggering criteria. The additional bit may be added in each multicast service mapped to the HS-DSCH or may be combined for all multicast services. The trigger criteria may be transmitted via a HSDPA medium access control (MAC-hs) header modified to include the trigger criteria, or via an MBMS Control Channel (MCCH), or via a new physical layer signal or L2 control channel in the downlink that conveys control information related to the multicast/broadcast service in the cell.

Alternatively, the WTRU may infer the triggering criteria for the multicast service based on the transmission rate used by the node-B, as shown in step 502. A look-up table may be used to map the transmission rate to the trigger criteria. The advantage of this alternative is that only less signalling is required in the downlink, but it will force the node B to perform the transmission at a rate corresponding to the current trigger criterion. This would eliminate the flexibility of the node B to further optimize the transmission rate if a certain level of failure could also be met.

In step 503, a triggering criterion is monitored, such as whether the WTRU CQI is equal to or less than the current operating CQI value. Another possible triggering criterion for uplink CQI reporting is based on the reception of erroneous HS-DSCH transport blocks. For this criterion, the CQI transmission is triggered when N consecutive failed HS-DSCH transport blocks are received. Alternatively, the WTRU may transmit the CQI when receiving N transport blocks out of M previous transport blocks fails. The values of the parameters N and M may be configured by the RAN and may be signaled to the WTRU when the WTRU subscribes to a multicast service. Alternatively, the triggering criteria are timer based as shown below. The WTRU may transmit a CQI to the node B if the WTRU does not send the CQI in a predetermined period (e.g., in the last T seconds). The period of time (i.e., the value of the parameter T) may be configured by the RAN. The RAN may adjust the period (i.e., the value of T) during the multicast service. For example, as more users are added to the multicast service, the RAN may increase the value of T to further reduce uplink overhead.

Once the triggering criteria are met, the WTRU sends a CQI feedback report, step 504. The trigger criteria are periodically updated as needed (step 505). For example, if the current operating CQI is the triggering criterion, the node B updates the current operating CQI to correspond to the worst case value in the WTRU-transmitted CQI report.

To avoid sudden simultaneous transmissions by multiple WTRUs, a random backoff period or hysteresis may be applied to the triggering criteria. For WTRUs transmitting CQI in the uplink, the triggering criteria must persist for a random duration (e.g., evenly distributed between 1-10 TTIs in a TTI interval). The parameters associated with the random back-off time may be configured by the RAN. The RAN may also update the back-off time parameter. For example, the RAN may promote the random backoff interval as the number of WTRUs subscribing to the multicast service increases. Furthermore, the random backoff may be applied to any one of the aforementioned three embodiments.

To determine the initial current operating CQI value or MBMS transmission rate, the RAN may perform a cyclic polling of the WTRUs to comply with the CQI. The worst CQI reported in this process will become the initial current operating CQI value. The WTRU cyclic polling for inclusion of CQI may be a procedure used on its own under control of the RAN. The periodicity of the polling is a parameter determined by the RAN. The RAN may also perform random polling of a WTRU to update the current operating CQI value or to determine the MBMS transmission rate.

The polling signal may be advertised by the RAN/node B by adding polling signal bits (or WTRU identity if it is not present in the primary signal format) to:

1) the existing HS-SCCH slot format;

2) MAC-hs header format;

3) MCCH; or

4) A new L1 physical signal or L2 control channel in downlink that transmits control information related to a multicast service in a cell.

The CQI transmission of a WTRU may be performed by (exclusively or in combination) the following mechanisms:

1) using an existing HS-DPCCH uplink control channel;

2) on a Random Access Channel (RACH);

3) a new L1 physical signal or L2 control signal for conveying CQI is used. In the case of an L1 physical signal, where a predetermined bit sequence may be used to indicate that the CQI is increased or decreased in steps relative to the current operating CQI value of the node B. In either case, the CQI report may be either associated with (i.e., raised or lowered) the current operating CQI value or an absolute value.

Fig. 6 is a flow diagram of a method for reducing another form of feedback signal that a WTRU typically sends in H-ARQ operation, where the feedback is ACK or ACK feedback. The ACK/NACK packet will indicate to the node B whether the packet was successfully decoded.

In step 601, the node B transmits each MAC-hs Packet Data Unit (PDU) a predetermined number of times. The node-B does not need to decide when to send a new MAC-hs pdu based on the ACK/NACK feedback. However, it is still very desirable for node B to have a mechanism to be able to understand the general performance of the different links.

To provide the required feedback, the following steps define a new signaling format and procedure that is more efficient than the process of transmitting an ACK or NACK after each single transmission from the node B.

In step 602, the WTRU continuously monitors whether a triggering criterion is met, such that an ACK/NACK signal for MBMS feedback needs to be sent. Once the triggering criteria are met, the WTRU signals to the node-B a message containing link performance information, such as an indication of the average number of H-ARQ transmissions required to successfully decode the PDU or the error rate, in step 603. The link performance data is determined by the WTRU, which may be temporarily stored and accessed when needed (step 606). The transmission of the indication is triggered only if it differs from the previously transmitted indication, or if other triggering conditions are met. Alternatively, the indication may be transmitted at a relatively high interval (e.g., every 8 or 16 completed MAC-hs PDU transmissions). The number of bits required to convey this information may be two (or even a single bit). An exemplary mapping is shown in table 1.

TABLE 1

Bit sequence	Means of
		00	H-ARQ error rate between 0% -25%
01	H-ARQ error rate between 25% -50%
		10	H-ARQ error rate between 50% -75%
11	H-ARQ error rate between 75% -100%

It should be understood that the values shown above are merely exemplary, and that any other values are possible. In particular, a rule may be set wherein the triggering criteria implemented by the WTRU for feedback (step 602) delays any reporting if the H-ARQ error rate (or average number of necessary transmissions) is below a certain threshold (e.g., 25%). In this case it is not necessary to map the bit sequence to an H-ARQ error rate below 25% and the range of mapped values will be reduced (i.e. 25-100% instead of 0-100%). Preferably, the exact mapping between the bit sequence and the H-ARQ error rate (or average number of necessary transmissions) is predetermined by the specification, or alternatively it may be signalled by higher layers.

The bit sequence used for the indication may be appropriately coded to improve reception reliability and match the minimum bit rate of the physical channel over which the sequence is transmitted. Furthermore, if the expected feedback frequency is low enough, this information may also be included in higher layer messages.

The node B monitors MBMS feedback from all WTRUs (step 604). In response to this feedback, the node B can adjust the MCS and/or transmission rate as appropriate for the WTRU to listen to the MBMS channel as a whole in step 605. For example, upon receiving feedback from one or several WTRUs indicating a high H-ARQ error rate, the node-B may decide to use a less aggressive MCS scheme or to boost transmission power. In contrast, if a lower error rate is signaled to the node-B from most or all WTRUs, the node-B may use a more aggressive MCS scheme and/or reduce the transmission power. Thereby freeing resources to other applications. This mechanism can be used in combination with the CQI reporting mechanism defined in the previous embodiments or even be completely replaced.

Examples

1. In a wireless transmit/receive unit (WTRU) in communication with a wireless communication system, a method comprising:

transmitting a request for uplink shared channel allocation in a Random Access Channel (RACH) preamble;

receiving an uplink shared channel assignment;

a Multimedia Broadcast Multicast Service (MBMS) feedback transmission is sent on a shared uplink channel.

2. The method of embodiment 1 wherein the WTRU uses a synchronous RACH preamble.

3. The method of embodiment 2 wherein the WTRU is in LTE _ Active state.

4. The method of embodiment 1 wherein the WTRU uses a non-synchronized RACH preamble.

5. The method of embodiment 4 wherein the WTRU is in LTE _ Active state or LTE _ Idle state.

6. The method of any preceding embodiment further comprising the WTRU sending a message with an indication that the reason for random access to the RACH is feedback for MBMS.

7. In a wireless transmit/receive unit (WTRU) in communication with a wireless communication system, a method comprising:

transmitting an indication in a Random Access Channel (RACH) preamble indicating that a reason for random access to the RACH is feedback for MBMS;

a Multimedia Broadcast Multicast Service (MBMS) feedback transmission is sent on the RACH.

8. The method of claim 7 wherein the RACH used by the WTRU is a synchronous RACH.

9. The method of embodiment 7 wherein the RACH used by the WTRU is a non-synchronous RACH.

10. The method as in any embodiments 7-9, wherein the MBMS feedback transmission is sent in a message/control bit field of a random access burst.

11. The method as in any embodiments 7-9, wherein a small number of preambles are reserved for MBMS feedback transmission.

12. The method as in any embodiments 7-9, wherein MBMS feedback transmission is transmitted as implicit or explicit information.

13. In a wireless communication system having a wireless transmit/receive unit (WTRU), a method comprising:

establishing an uplink shared channel; and

feedback information for the MBMS service is simultaneously transmitted on an uplink shared channel along with other uplink information.

14. The method of embodiment 13 wherein the shared channel is a data channel and the other uplink information is uplink data and data-related control information.

15. The method of embodiment 13 wherein the shared channel is a control channel and the other uplink information is control information.

16. The method as in any embodiments 13-15, further comprising establishing an RRC connection and an uplink shared channel in a current Transmission Time Interval (TTI).

17. In a wireless communication system having a wireless transmit/receive unit (WTRU) and a node-B, a method comprising:

the node B pre-allocates a time-frequency region for MBMS feedback transmission on an uplink channel; and

the WTRU sends MBMS feedback as a predefined burst in a pre-allocated time-frequency region of an uplink channel.

18. The method of embodiment 17 wherein the MBMS feedback is a NACK message, a Channel Quality Indicator (CQI) or a response to network counting or polling.

19. The method of embodiment 17 or 18 wherein the node B detects the presence or absence of MBMS feedback by detecting whether the received signal power in a pre-allocated time-frequency region exceeds a predefined threshold.

20. In a wireless communication system having a wireless transmit/receive unit (WTRU) and a node-B, a method comprising:

the node B pre-allocates a common channelizing code for MBMS feedback transmission in an uplink channel;

the WTRU transmits the MBMS feedback as a predefined burst using a pre-allocated common channelization code for the uplink channel.

21. In a wireless communication system including a plurality of wireless transmit/receive units (WTRUs), a method for reducing uplink feedback signaling for multicast data transmission over a High Speed Downlink Packet Access (HSDPA) channel, the embodiment comprising:

receiving a trigger criterion for reporting a Channel Quality Indicator (CQI); and

if the trigger criteria are met, a CQI is sent to the node B.

22. The method of embodiment 21 wherein the triggering criterion is a current operating CQI value at the node B, whereby the WTRU transmits a CQI when the channel state of the WTRU is not better than the current operating CQI value.

23. The method of embodiment 22 wherein the current operating CQI value is received by the WTRU on a high speed shared control channel (HS-SCCH).

24. The method of embodiment 22 wherein the current operating CQI value is received by the WTRU on a HSDPA medium access control (MAC-hs) header.

25. The method of embodiment 22 wherein the current operating CQI value is received by the WTRU on a Multimedia Broadcast Multicast Service (MBMS) control channel (MCCH).

26. The method of embodiment 22 wherein the current operating CQI value is received by the WTRU using physical layer signaling.

27. The method of embodiment 21 wherein the triggering criterion is generated based on the reception of an erroneous high speed downlink shared channel (HS-DSCH) transport block.

28. The method of embodiment 21 wherein the transmission of the CQI is triggered upon receipt of N consecutive failed HS-DSCH transport blocks.

29. The method of embodiment 21 wherein the transmission of the CQI is triggered upon receipt of N failed HS-SCCH transport blocks of the M HS-SCCH transport blocks, and wherein the values N and M are configurable by the system.

30. The method of embodiment 21 wherein the triggering criterion is a predetermined period of time, whereby the WTRU transmits a CQI if the WTRU does not send a CQI for the predetermined period of time.

31. In a wireless communication system including a node B and a plurality of wireless transmit/receive units (WTRUs), a method for reducing uplink feedback signaling for multicast service data transmission over a High Speed Downlink Packet Access (HSDPA) channel, the method comprising:

the WTRU sends an indication of at least one of an average number of transmissions required to successfully decode the data and a bit error rate.

32. The method of embodiment 31 wherein the indication is transmitted at a relatively high interval.

33. The method of embodiment 31 wherein the indication is transmitted only if it is different from a previously transmitted indication.

34. The method of embodiment 31 wherein the indication is transmitted only if a triggering criterion is met.

35. The method of embodiment 31 wherein the WTRU does not transmit the indication if the bit error rate or the average number of necessary transmissions is below a certain threshold.

36. The method as in any embodiments 31-35, further comprising a node B adjusting a modulation and coding scheme, or a transmission power level, or a combination thereof, based on the indication.

37. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), comprising:

a processor configured to transmit a Random Access Channel (RACH) preamble containing a request for uplink shared channel allocation; receiving an uplink shared channel assignment; and sending a Multimedia Broadcast Multicast Service (MBMS) feedback transmission on the shared uplink channel.

38. The WTRU of embodiment 37 wherein the RACH is a synchronous RACH preamble.

39. The WTRU of embodiment 38 wherein the WTRU is in LTE _ Active state.

40. The WTRU of embodiment 37 wherein the WTRU uses a non-synchronized RACH preamble.

41. The WTRU of embodiment 40 wherein the WTRU is in LTE _ Active state or LTE _ Idle state.

42. The WTRU as in any one of embodiments 37-41, wherein the WTRU sends a message with an indication that a reason for random access to the RACH is feedback for MBMS.

43. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), comprising:

a processor configured to send an indication in a Random Access Channel (RACH) preamble indicating that a reason for random access to a RACH is feedback for MBMS; and sending a Multimedia Broadcast Multicast Service (MBMS) feedback transmission on the RACH.

44. The WTRU of embodiment 43 wherein the RACH used by the WTRU is a synchronous RACH.

45. The WTRU of embodiment 43 wherein the RACH used by the WTRU is a non-synchronous RACH.

46. The WTRU of embodiment 43 wherein the MBMS feedback transmission is sent within a message/control bits field in a random access burst.

47. The WTRU of embodiment 43 wherein a small number of preambles are reserved for MBMS feedback transmission.

48. The WTRU of embodiment 43 wherein the MBMS feedback transmission is transmitted as implicit or explicit information.

49. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), comprising:

a processor configured to establish an uplink shared channel; and simultaneously transmitting feedback information for the MBMS service and other uplink information on the uplink shared channel.

50. The WTRU of embodiment 49 wherein the shared channel is a data channel and the other uplink information is uplink data or data-related control information.

51. The WTRU of embodiment 49 wherein the shared channel is a control channel and the other uplink information is control information.

52. The WTRU of embodiment 49, further comprising a Radio Resource Control (RRC) entity configured to establish the RRC connection and the uplink shared channel in a current Transmission Time Interval (TTI).

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 execution by a general purpose computer or a processor.

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 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, terminal, base station, radio network controller, 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 (60)

1. In a wireless transmit/receive unit (WTRU) in communication with a wireless communication system, a method comprising:

transmitting a request for uplink shared channel allocation in a Random Access Channel (RACH) preamble;

receiving the uplink shared channel assignment;

a Multimedia Broadcast Multicast Service (MBMS) feedback transmission is sent on a shared uplink channel.

2. The method of claim 1 wherein the WTRU uses a synchronous RACH preamble.

3. The method of claim 2 wherein the WTRU is in an LTE _ Active state.

4. The method of claim 1 wherein the WTRU uses a non-synchronized RACH preamble.

5. The method of claim 4 wherein the WTRU is in an LTE _ Active state or an LTE _ Idle state.

6. The method as in claim 1 further comprising the WTRU sending a message with an indication that the reason for random access RACH is feedback for MBMS.

7. In a wireless transmit/receive unit (WTRU) in communication with a wireless communication system, a method comprising:

sending an indication in a Random Access Channel (RACH) preamble indicating that a reason for random access to the RACH is feedback for a Multimedia Broadcast Multicast Service (MBMS);

the MBMS feedback transmission is sent on the RACH.

8. The method of claim 7 wherein the RACH used by the WTRU is a synchronous RACH.

9. The method of claim 7 wherein the RACH used by the WTRU is a non-synchronous RACH.

10. The method of claim 7, wherein the MBMS feedback transmission is sent in a message/control bits field of a random access burst.

11. The method of claim 7, wherein a small number of preambles are reserved for the MBMS feedback transmission.

12. The method of claim 7, wherein the MBMS feedback transmission is transmitted as implicit or explicit information.

13. A method for wireless communication with a wireless transmit/receive unit (WTRU), the method comprising:

establishing an uplink shared channel; and

transmitting feedback information for the MBMS service and other uplink information simultaneously on the uplink shared channel.

14. The method of claim 13, wherein the shared channel is a data channel and the other uplink information is uplink data and data-related control information.

15. The method of claim 13, wherein the shared channel is a control channel and the other uplink information is control information.

16. The method of claim 13, further comprising establishing an RRC connection and an uplink shared channel in a current Transmission Time Interval (TTI).

17. A method of wireless communication using a node B, the method comprising:

the node B pre-allocates a time-frequency region for MBMS feedback transmission on an uplink channel; and

the node B receives MBMS feedback as a predefined burst in a pre-allocated time-frequency region of the uplink channel.

18. The method of claim 35, wherein the MBMS feedback is a NACK message, a Channel Quality Indicator (CQI), or a response to a network count or poll.

19. The method of claim 17 wherein the node B detects the presence of MBMS feedback by detecting whether the power of the received signal in the pre-allocated time-frequency region exceeds a predefined threshold.

20. A method of wireless communication using a node B, the method comprising:

the node B pre-allocates a common channelization code for MBMS feedback transmission in an uplink channel;

the node B receives MBMS feedback as a predefined burst using a pre-allocated common channelization code for the uplink channel.

21. In a wireless communication system including a node B and a plurality of wireless transmit/receive units (WTRUs), a method for reducing uplink feedback signaling for multicast service data transmission over a High Speed Downlink Packet Access (HSDPA) channel, the method comprising:

receiving a trigger criterion for reporting a Channel Quality Indicator (CQI); and

if the trigger criteria are met, a CQI is sent to the node B.

22. The method as in claim 21 wherein the triggering criterion is a current operating CQI value at a node B, whereby the WTRU transmits the CQI when the channel condition of the WTRU is not better than the current operating CQI value.

23. The method of claim 22 wherein the current operating CQI value is received by the WTRU on a high speed shared control channel (HS-SCCH).

24. The method of claim 22 wherein the current operating CQI value is received by the WTRU on a HSDPA medium access control (MAC-hs) header.

25. The method of claim 22 wherein the current operating CQI value is received by the WTRU on a Multimedia Broadcast Multicast Service (MBMS) control channel (MCCH).

26. The method of claim 22 wherein the current operating CQI value is received by the WTRU using physical layer signaling.

27. The method of claim 21 wherein the triggering criterion is based on receiving an erroneous high speed downlink shared channel (HS-DSCH) transport block.

28. The method according to claim 21, wherein the transmission of CQI is triggered upon reception of N consecutive failed HS-DSCH transport blocks.

29. The method of claim 21 wherein the transmission of the CQI is triggered upon receiving N failed HS-SCCH transport blocks of the M HS-SCCH transport blocks, and wherein the values N and M are configured by the system.

30. The method of claim 21 wherein the triggering criterion is a predetermined period of time such that the WTRU transmits a CQI if the WTRU does not send a CQI within the predetermined period of time.

31. In a wireless communication system including a node B and a plurality of wireless transmit/receive units (WTRUs), a method for reducing uplink feedback signaling for multicast service data transmission over a High Speed Downlink Packet Access (HSDPA) channel, the method comprising:

the WTRU sends an indication of at least one of an average number of transmissions and a bit error rate required to successfully decode the data.

32. The method of claim 31, wherein the indication is transmitted on a relatively higher interval.

33. The method of claim 31, wherein the indication is transmitted only if the indication is different from a previously transmitted indication.

34. The method of claim 31, wherein the indication is transmitted only if a trigger condition is satisfied.

35. The method of claim 31 wherein the WTRU does not transmit the indication if the bit error rate or average number of necessary transmissions is below a certain threshold.

36. The method of claim 31, further comprising the node B adjusting a modulation and coding scheme, or a transmission power level, or a combination thereof, based on the indication.

37. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), the WTRU comprising:

a processor configured to transmit a Random Access Channel (RACH) preamble containing a request for uplink shared channel allocation; receiving the uplink shared channel assignment; and sending a Multimedia Broadcast Multicast Service (MBMS) feedback transmission on the shared uplink channel.

38. The WTRU of claim 37 wherein the RACH is a synchronous RACH preamble.

39. The WTRU of claim 38 wherein the WTRU is in an LTE _ Active state.

40. The WTRU of claim 37 wherein the WTRU uses a non-synchronized RACH preamble.

41. The WTRU of claim 40 wherein the WTRU is in an LTE _ Active state or an LTE _ Idle state.

42. The WTRU of claim 37 wherein the WTRU sends a message with an indication that the reason for random access RACH is feedback for MBMS.

43. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), the WTRU comprising:

a processor configured to send an indication in a Random Access Channel (RACH) preamble indicating that a cause of random access to a RACH is feedback for an MBMS; and sending a Multimedia Broadcast Multicast Service (MBMS) feedback transmission on the RACH.

44. The WTRU of claim 43 wherein the RACH used by the WTRU is a synchronous RACH.

45. The WTRU of claim 43 wherein the RACH used by the WTRU is a non-synchronous RACH.

46. The WTRU of claim 43 wherein the MBMS feedback transmission is sent in a message/control bit field in a random access burst.

47. The WTRU of claim 43 wherein a small number of preambles are reserved for the MBMS feedback transmission.

48. The WTRU of claim 43 wherein the MBMS feedback transmission is transmitted as implicit or explicit information.

49. A wireless transmit/receive unit (WTRU) in a wireless communication system supporting Multimedia Broadcast Multicast Service (MBMS), comprising:

a processor configured to establish an uplink shared channel; and simultaneously transmitting feedback information for the MBMS service and other uplink information on the uplink shared channel.

50. The WTRU of claim 49 wherein the shared channel is a data channel and the other uplink information is uplink data or data-related control information.

51. The WTRU of claim 49 wherein the shared channel is a control channel and the other uplink information is control information.

52. The WTRU of claim 49 further comprising a Radio Resource Control (RRC) entity configured to establish an RRC connection and an uplink shared channel in a current Transmission Time Interval (TTI).

53. A wireless communication system having a wireless transmit/receive unit (WTRU) and a node-B, the system comprising:

a node B configured to pre-allocate a time-frequency region for MBMS feedback transmission in an uplink channel; and

a WTRU configured to transmit MBMS feedback as a predefined burst in a pre-allocated time-frequency region of an uplink channel.

54. The system of claim 53, wherein the MBMS feedback is a NACK message, a Channel Quality Indicator (CQI), or a response to a network count or poll.

55. The system of claim 53 wherein the node B detects the presence of MBMS feedback by detecting whether the received signal power in the pre-allocated time-frequency region exceeds a predefined threshold.

56. A wireless communication system, the system comprising:

a node B configured to pre-allocate a common channelization code for MBMS feedback transmission in an uplink channel; and

a wireless transmit/receive unit (WTRU) configured to transmit the MBMS feedback as a predefined burst using a pre-allocated common channelization code for the uplink.

57. A node B adapted to perform MBMS transmissions; pre-allocating a time-frequency region for MBMS feedback transmission in an uplink channel; and receiving the MBMS feedback as a predefined burst in a pre-allocated time-frequency region of the uplink channel.

58. The node B of claim 60 wherein MBMS feedback is a NACK message, a Channel Quality Indicator (CQI), or a response to network counting or polling.

59. The node B of claim 57, wherein the node B detects the presence of MBMS feedback by detecting whether a received signal power in the pre-allocated time-frequency region exceeds a predefined threshold.

60. A node B adapted to perform MBMS transmission in a wireless communication; pre-allocating a common channelization code for MBMS feedback transmission in an uplink channel; and receiving the MBMS feedback as a predefined burst using a pre-allocated common channelization code for the uplink channel.