Patent Abstract:
A method and apparatus for assigning automatic repeat request (ARQ)/hybrid-automatic repeat request (H-ARQ) processes in a wireless transmit/receive unit (WTRU) to support enhanced uplink (EU) data transmissions. After parameters associated with the ARQ/H-ARQ processes are configured, the WTRU assigns an ARQ/H-ARQ process for selected data. After transmitting the data, the WTRU determines whether feedback information for the data has been received. The WTRU releases the ARQ/H-ARQ process if an acknowledgement (ACK) message has been received, and retransmits the data if a non-acknowledgement (NACK) message or no feedback information has been received in a predetermined time period while incrementing a transmission counter in the WTRU. When an ARQ/H-ARQ transmission limit has been reached, the WTRU may discard the data or reinitiate the transmission. An ARQ/H-ARQ process assigned for transmission of lower priority data may be preempted for transmission of higher priority data when there is no available ARQ/H-ARQ process.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/568,931 filed May 7, 2004, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention is related to a wireless communication system including at least one wireless transmit/receive unit (WTRU), at least one Node-B and a radio network controller (RNC). More particularly, the present invention is related to a method and apparatus for assigning automatic repeat request (ARQ)/hybrid automatic repeat request (H-ARQ) processes in the WTRU for supporting enhanced uplink (EU) transmissions.  
       BACKGROUND  
       [0003]     Methods for improving uplink (UL) coverage, throughput and transmission latency are being investigated in the Third Generation Partnership Project (3GPP). In order to achieve these goals, scheduling and assigning of UL physical resources will be moved from the RNC to the Node-B.  
         [0004]     The Node-B can make decisions and manage UL radio resources on a short-term basis better than the RNC. However, the RNC still retains coarse overall control of the cell with EU services so that the RNC can perform functions such as call admission control and congestion control.  
         [0005]     A new medium access control (MAC) entity called MAC-e is created in a WTRU and the Node-B to handle the transmission and reception of enhanced dedicated channel (E-DCH) transmissions. There may be several independent uplink transmissions processed between the WTRU and UMTS terrestrial radio access network (UTRAN) within a common time interval. One example of this is MAC layer H-ARQ or MAC layer ARQ operation where each individual transmission may require a different number of transmissions to be successfully received by the UTRAN. Proper assignment of data blocks to ARQ/H-ARQ processes for transmission is necessary for operation of the EU services. This function includes rules for retransmitting failed transmissions, prioritization between different logical channels and provisioning of quality of service (QoS) related parameters.  
       SUMMARY  
       [0006]     The present invention is related to a method and apparatus for assigning an ARQ/H-ARQ process in a WTRU for supporting EU transmissions. After parameters associated with the ARQ/H-ARQ processes are configured, the WTRU assigns an ARQ/H-ARQ process for a selected data. After transmitting the data, the WTRU determines whether feedback information for the data has been received. The WTRU releases the ARQ/H-ARQ process if an acknowledgement (ACK) message has been received, and retransmits the data if a non-acknowledgement (NACK) message or no feedback information has been received in a predetermined time period while incrementing a transmission counter in the WTRU. When a transmission limit has been reached, the WTRU may discard the data or reinitiate the transmission. An ARQ/H-ARQ process assigned for transmission of lower priority data may be preempted for transmission of higher priority data when there is no available ARQ/H-ARQ process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawing wherein:  
         [0008]      FIG. 1  is a block diagram of a wireless communication system operating in accordance with the present invention;  
         [0009]      FIG. 2A  is a flow diagram of an EU transmission process implemented by the system of  FIG. 1  for assigning an ARQ or H-ARQ process in accordance with one embodiment of the present invention;  
         [0010]      FIG. 2B  is a flow diagram of an EU feedback reception process implemented by the system of  FIG. 1 ;  
         [0011]      FIG. 3A  is a flow diagram of an EU transmission process implemented by the system of  FIG. 1  for assigning an ARQ or H-ARQ process using preemption and re-initiation procedures in accordance with another embodiment of the present invention; and  
         [0012]      FIG. 3B  is a flow diagram of an EU feedback reception process implemented by the system of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     Hereafter, the terminology “WTRU” 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. When referred to hereafter, the terminology “Node-B” includes but is not limited to a base station, a site controller, an access point or any other type of interfacing device in a wireless environment.  
         [0014]     The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components.  
         [0015]     Hereafter, for simplicity, the present invention will be explained with reference to H-ARQ operation. However, it should be noted that the present invention is equally applicable to ARQ operation without affecting the functionality of the present invention.  
         [0016]      FIG. 1  is a block diagram of a wireless communication system  100  operating in accordance with the present invention. The system  100  includes at least one WTRU  102 , at least one Node-B  104  and an RNC  106 . The RNC  106  controls overall EU operation by configuring EU parameters for the Node-B  104  and the WTRU  102 , such as priority of each TrCH, MAC-d flow or logical channel mapped on an E-DCH, maximum number of transmissions for each TrCH or logical channel, maximum allowed EU transmit power or available channel resources per Node-B  104 . The WTRU  102  sends a channel allocation request via the UL EU channel  110  and receives channel allocation information via the DL EU signaling channel  112 . The WTRU  102  transmits E-DCH data via a UL EU channel  110  to the Node-B  104  in accordance with the channel allocation information. The Node-B  104  sends feedback information on the data block via the DL EU signaling channel  112  to the WTRU  102 .  
         [0017]     In accordance with the present invention, the assignment of an H-ARQ process for supporting a data transmission is controlled by the WTRU  102 . The Node-B  104  provides allocation of physical resources for which the WTRU  102  determines what data will be transmitted using which H-ARQ process. The WTRU  102  includes a pool of H-ARQ processes  114 , a controller  116  and a transmission counter  118 .  
         [0018]     The controller  116  controls the overall assignment of H-ARQ processes including selecting data for transmission based on priority, assigning one of the available H-ARQ processes  114  to the selected data and releasing H-ARQ processes  114  when the data transmission is successfully completed.  
         [0019]     The transmission counter  118  indicates the number of transmissions for a given H-ARQ process, which is equivalent to a receive sequence number (RSN). The transmission counter  118  may also be used to as a new data indicator (NDI).  
         [0020]     In one embodiment, a preemption procedure is used to manage E-DCH transmissions, whereby the assignment of the H-ARQ processes is based on absolute priority. The highest priority class traffic and the earliest transmission number within the same priority class takes precedence over other transmissions. The transmission of a data block is also subject to a maximum number of H-ARQ transmissions for each E-DCH TrCH, or each logical channel mapped to an E-DCH TrCH. An H-ARQ process servicing a lower priority data transmission may be superceded by a higher priority data transmission.  
         [0021]     In another embodiment, a re-initiation procedure is used to manage E-DCH transmissions, whereby if at least one of a transmission time limit and a maximum number of transmissions has been reached, the lower priority data transmission may be reassigned to an H-ARQ process.  
         [0022]      FIG. 2A  is a flow diagram of an EU transmission process  200  implemented by the system  100  of  FIG. 1  for assigning H-ARQ processes  114  in accordance with one embodiment of the present invention. When a radio access bearer (RAB) is configured to operate on an E-DCH, parameters related to assigning H-ARQ processes  114  in the WTRU  102  are configured by the RNC  106  to support EU data transmissions (step  202 ). The parameters include, but are not limited to, priority of each logical channel, MAC-d flow or TrCH mapped to an E-DCH, and maximum number of H-ARQ transmissions for each TrCH, MAC-d flow or logical channel mapped to an E-DCH.  
         [0023]     For each transmit time interval (TTI) at step  204 , the WTRU  102  then determines whether physical resources have been allocated for the WTRU  102  for supporting EU operation (step  206 ). If physical resources have not been allocated at step  206 , the process  200  returns to step  204  until the next TTI occurs. If physical resources have been allocated at step  206 , the WTRU  102  selects a data block for transmission (step  208 ). For new data transmissions, the highest priority data block is selected for each assigned H-ARQ process. In step  210 , the WTRU  102  then determines a transmission status of the selected data. The transmission status is set as either “new transmission” or “retransmission.” 
         [0024]     If, in step  210 , the WTRU  102  determines that the transmission status of the selected data is “retransmission”, the same H-ARQ process  114  that was used for the previous transmission remains assigned to the data block, the transmission counter  118  in the WTRU  102  is incremented, and an NDI of the transmission is set to “old data” to indicate that the assigned H-ARQ process  114  retransmits data identical to what was transmitted previously, in order to allow for combining at the Node-B  104  (step  212 ). The process  200  then returns to step  204  until the next TTI occurs.  
         [0025]     If, in step  210 , the WTRU  102  determines that the transmission status of the selected data block is “new transmission”, the WTRU  102  assigns an available H-ARQ process  114  to the selected data block and sets an NDI to indicate “new data” (step  214 ). The data block is then transmitted using the assigned H-ARQ process and the transmission counter  118  in the WTRU  102  is incremented (step  216 ). The process  200  then returns to step  204  until the next TTI occurs.  
         [0026]      FIG. 2B  is a flow diagram of an EU feedback reception process  250  implemented by the system  100  of  FIG. 1 . In step  252 , the WTRU  102  determines whether feedback information for a previously transmitted data block has been received. If the WTRU  102  received an ACK message, the corresponding H-ARQ process  114  is released and is available for supporting another data transmission (step  254 ). If the WTRU  102  received a NACK message of a feedback timeout occurs, the WTRU  102  determines whether the transmission counter  118  in the WTRU  102  has reached a predetermined maximum number of H-ARQ transmissions (step  256 ).  
         [0027]     If the number of H-ARQ transmissions indicated by the transmission counter  118  in the WTRU  102  has not reached a predetermined maximum number at step  256 , the transmission status of the data block is set as a “retransmission” (step  258 ).  
         [0028]     If the maximum number of H-ARQ transmissions is reached at step  256 , the WTRU discards the data at the MAC layer and releases the associated H-ARQ process (step  260 ).  
         [0029]      FIG. 3A  is a flow diagram of an EU transmission process  300  implemented by the system  100  of  FIG. 1  for assigning H-ARQ processes  114  using preemption and re-initiation procedures in accordance with another embodiment of the present invention. When a RAB is configured to operate on an E-DCH, parameters related to assigning H-ARQ processes  114  in the WTRU  102  are configured by the RNC  106  to support EU data transmissions (step  302 ).  
         [0030]     For each transmit time interval (TTI) at step  304 , the WTRU  102  then determines whether physical resources have been allocated for the WTRU  102  for supporting EU operation (step  306 ). A priority class is configured for each logical channel, MAC-d flow or TrCH mapped to an E-DCH, whereby the highest priority data block is always serviced first. If physical resources have not been allocated at step  306 , the process  300  returns to step  304  until the next TTI occurs. If physical resources have been allocated at step  306 , the WTRU  102  selects for transmission the data block having the highest priority from all possible data that can be transmitted in the current TTI, (i.e., new data, previous unsuccessful transmissions and interrupted transmissions), (step  308 ). If several data blocks having the same highest priority are available for transmission, the WTRU  102  may prioritize the data block having the earliest sequence number or the data block having the highest number of transmissions. This operation assists “first-in first-out” (FIFO) processing and minimizes the delay for any data transmission. In step  310 , the WTRU  102  then determines a transmission status of the selected data. The transmission status is set as either “new transmission,” “retransmission” or “interrupted transmission.” 
         [0031]     If the data block has not been previously transmitted, or an H-ARQ transmission is restarted, the transmission status is set as a “new transmission” in step  310 . If the data block has been transmitted but was not successfully delivered, (and not interrupted by a higher priority data block), the transmission status of the data is set as a “retransmission” at step  310 . The WTRU  102  may optionally implement preemption of an H-ARQ process assigned to support higher priority data. An H-ARQ process already assigned for lower priority data which needs to be transmitted may be preempted with higher priority data when there is no other H-ARQ process available. If the H-ARQ process assigned to the data block is preempted, the lower priority data is blocked from transmission in the current TTI and the transmission status of the blocked data is set as an “interrupted transmission” at step  310 .  
         [0032]     If, in step  310 , the WTRU  102  determines that the transmission status of the selected data is “retransmission”, the same H-ARQ process  114  that was used for the previous transmission remains assigned to the data block, a transmission counter  118  is incremented and an NDI of the transmission is set to “old data” to indicate that the assigned H-ARQ process  114  retransmits data identical to what was transmitted previously, in order to allow for combining at the Node-B  104  (step  312 ). The process  300  then returns to step  304  until the next TTI occurs.  
         [0033]     If, in step  310 , the WTRU  102  determines that the transmission status of the selected data block is “new transmission”, the WTRU  102  determines whether there are any H-ARQ processes  114  available (step  314 ). If an H-ARQ process is available, (or a process supporting lower priority data is available), one of the available H-ARQ processes  114  is selected (step  316 ). If the transmission status of the selected data block is a “new transmission,” the WTRU  102  selects an available H-ARQ process  114  (step  316 ). The WTRU  102  assigns the selected H-ARQ process  114  to the selected data block and sets an NDI to indicate “new data” (step  318 ). The data block is then transmitted using the assigned H-ARQ process and the transmission counter  118  in the WTRU  102  is incremented (step  320 ). The process  300  then returns to step  304  until the next TTI occurs.  
         [0034]     If, in step  310 , the WTRU  102  determines that the transmission status of the selected data block is “interrupted transmission”, (which is the case for which preemption is permitted), the WTRU  102  determines whether there are any H-ARQ processes  114  available (step  322 ). If there are no H-ARQ processes  114  available at step  322 , transmission of a lower priority data block is interrupted and a transmission status of the interrupted lower priority data is set to “interrupted transmission” (step  324 ). The H-ARQ process  114  previously assigned for the lower priority data is assigned for the currently selected data block and an NDI is set to indicate new data (step  318 ). The data block is then transmitted using the assigned H-ARQ process and the transmission counter  118  in the WTRU  102  is incremented (step  320 ). The process  300  then returns to step  304  until the next TTI occurs.  
         [0035]      FIG. 3B  is a flow diagram of an EU feedback reception process  350  implemented by the system  100  of  FIG. 1 . In step  352 , the WTRU  102  determines whether feedback information for a previously transmitted data block has been received. If the WTRU  102  received an ACK message, the corresponding H-ARQ process  114  is released and is available for supporting another data transmission (step  354 ). If the WTRU  102  received a NACK message or a feedback timeout occurs, the WTRU  102  determines whether the number of H-ARQ transmissions indicated by the transmission counter  118  in the WTRU  102  has reached a predetermined maximum number of H-ARQ transmissions (step  356 ).  
         [0036]     If the maximum number of H-ARQ transmissions has not been reached at step  356 , the transmission status of the data block is set as a “retransmission” (step  358 ).  
         [0037]     If the maximum number of H-ARQ transmissions is reached at step  356 , the WTRU  102  has two options  360 ,  362 . In the first option  360 , the WTRU  102  discards the data block at the MAC layer and releases the assigned H-ARQ process  114 . In the second option  362 , the WTRU  102  may set the transmission status of the data block as a “restarted transmission” and starts a new transmission for the data block. The transmission counter  118  is then set to zero and the NDI is set to “new data” (step  364 ).  
         [0038]     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.

Technology Classification (CPC): 7