Abstract:
A method and apparatus for forwarding non-consecutive data blocks in enhanced uplink (EU) transmissions. A wireless transmit/receive unit (WTRU) and one or more Node-Bs include one or more automatic repeat request (ARQ)/hybrid-ARQ (H-ARQ) processes for supporting an enhanced dedicated channel (E-DCH). Data blocks transmitted by the WTRU are re-ordered in a re-ordering entity located in the Node-B(s) or a radio network controller (RNC). Once a missing data block is identified, a data forwarding timer in the Node-B(s) or RNC is initiated and subsequent WTRU transmissions are monitored to determine whether the missing data block has been discarded by the WTRU. Upon recognition of the discard of the missing data block, the non-consecutive data blocks are forwarded to higher layers.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/095,912 filed Mar. 31, 2005, which claims the benefit of U.S. Provisional Application No. 60/566,588 filed Apr. 29, 2004, which are incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention is related to a wireless communication system including a 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 system for forwarding non-consecutive data blocks in enhanced uplink (EU) transmissions. 
       BACKGROUND 
       [0003]    Methods for improving uplink (UL) coverage, throughput and transmission latency are being investigated in Release 6 (R6) of the 3rd generation partnership project (3GPP). In order to successfully implement these methods, scheduling and assigning of UL physical resources have been moved from the RNC to the Node-B such that the Node-B can make decisions and manage UL radio resources on a short-term basis more efficiently than the RNC, even if the RNC retains overall control over the Node-B. 
         [0004]    One or more independent UL transmissions are processed on an enhanced dedicated channel (E-DCH) between a WTRU and a universal mobile telecommunication system (UMTS) terrestrial radio access network (UTRAN) within a common time interval. One example of this would be a medium access control (MAC) layer hybrid-automatic repeat request (H-ARQ) or a simple MAC layer ARQ operation where each individual transmission may require a different number of retransmissions to be successfully received by the UTRAN. This operation may result in a loss of transmission sequence at the MAC layer. 
         [0005]    In-sequence data delivery is required by the radio link control (RLC) layer for proper operation. A re-ordering function is needed to organize the received data blocks according to the sequence generated by the WTRU RLC entity. In the prior art, a data-forwarding timer, (called a T1 timer in high speed downlink packet access (HSDPA)), has been utilized for delivery of non-consecutive data blocks to higher layers. The timer is initialized when data blocks which have been correctly received cannot be delivered to the higher layers due to non-sequential reception. When the timer expires, all data blocks in the re-ordering buffer up to the next non-sequentially received data block are forwarded to higher layers. 
         [0006]    It is difficult to properly set duration for the data forwarding timer since, even in normal operation, cell congestion occasionally generates relatively long periods between transmissions. In addition, since out-of-sequence delivery to RLC acknowledged mode (AM) may result in unnecessary retransmissions, the worst case delay must be considered in setting the data forwarding timer for proper operation. Since transmission errors are unavoidable, this timer mechanism results in increased and potentially unacceptable latency in performing RLC retransmission procedures. 
         [0007]    In order to maintain quality of service (QoS), transmissions should not be unnecessarily delayed in providing sequential delivery. The timer mechanism is not efficient to provide proper QoS. If the duration of the timer is too short, out of sequence transmissions may be incorrectly perceived when only a particular transmission has been delayed, resulting in unnecessary requests for RLC retransmissions or potential release of the channel. If the duration of the timer is too long, detection and recovery of failed transmissions is delayed, resulting in greater difficulty in achieving low transmission latency QoS requirements. Determining the duration of the out of sequence forwarding timer is further complicated by relatively large variances in retransmission scheduling. 
       SUMMARY 
       [0008]    The present invention is related to a method and apparatus for forwarding non-consecutive data blocks in EU transmissions. A WTRU and one or more Node-Bs include one or more ARQ/H-ARQ processes for supporting EU transmissions. Data blocks transmitted by the WTRU are re-ordered in a re-ordering entity located in the Node-B(s) or an RNC. Once a missing data block is identified, a data forwarding timer in the Node-B(s) or RNC is initiated and subsequent WTRU transmissions are monitored to determine whether the missing data block has been discarded by the WTRU. Upon recognition of the discard of the missing data block, the non-consecutive data blocks are forwarded to higher layers. 
         [0009]    In an absolute priority scheme, a higher priority data block is always serviced before a lower priority data block, and a data block with the earliest transmission sequence number (TSN) is serviced first within the same priority data blocks. In such a mechanism, the Node-B may recognize that the WTRU has discarded the missing data block if all H-ARQ processes available and active for the WTRU at the Node-B have received successfully either: 1) a new transmission with the same priority and a higher TSN compared to the missing data block; or 2) a new transmission with a lower priority compared to the missing data block. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    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: 
           [0011]      FIG. 1A  is a block diagram of a wireless communication system including one or more Node-Bs with a data re-ordering entity in accordance with one embodiment of the present invention; 
           [0012]      FIG. 1B  is a block diagram of a wireless communication system including an RNC with a data re-ordering entity in accordance with another embodiment of the present invention; 
           [0013]      FIG. 2  is a flow diagram of a process for forwarding non-consecutive data blocks using either of the systems of  FIGS. 1A and 1B ; and 
           [0014]      FIG. 3  is a flow diagram of a process for forwarding non-consecutive data blocks using the system of  FIG. 1B . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    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. 
         [0016]    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. 
         [0017]      FIG. 1A  is a block diagram of a wireless communication system  100  including one or more Node-Bs with a data re-ordering entity  122  in accordance with one embodiment of the present invention. The system  100  includes a WTRU  102 , one or more Node-Bs  104  and an RNC  106 . The WTRU  102  transmits enhanced dedicated channel (E-DCH) data through an assigned E-DCH  142 . The Node-B(s)  104  transmits either an acknowledgement (ACK) message or a non-acknowledgement (NACK) message through the DL EU signaling channel  144 , depending on the success or failure of decoding the data at the Node-B(s)  104  using an H-ARQ or simple ARQ operation, as indicated by ARQ/H-ARQ process  112  and  128  in the WTRU  102  and Node-B(s)  104 , respectively. 
         [0018]    Referring to  FIG. 1A , new MAC entities  110 ,  120 ,  130  for EU transmissions, (i.e., MAC-e entities), are included in each of the WTRU  102 , the Node-B(s)  104  and the RNC  106 , respectively. The MAC-e entity  120  of the Node-B(s)  104  includes a re-ordering entity  122 , data re-ordering buffer  124 , a data forwarding timer  126  for in-sequence delivery of the data blocks, respectively. The data transmitted by the WTRU  102  over the E-DCH  142  is re-ordered by the re-ordering entity  122  before being forwarded to a higher layer. The re-ordering entity  122  receives data blocks, (MAC-e protocol data units (PDUs)), and delivers the MAC-e PDUs with consecutive TSNs to a higher layer. MAC-e PDUs that are not consecutive, (i.e., resulting in a missing data block), are not delivered to the higher layer until expiration of the data forwarding timer  126 . The re-ordering entity  122  uses the knowledge of the ARQ/H-ARQ process  128  to determine whether the missing data block has been discarded by the WTRU  102  and to forward non-consecutive data blocks to higher layers. 
         [0019]      FIG. 1B  is a block diagram of a wireless communication system  150  including an RNC with a data re-ordering entity  132  operating in accordance with another embodiment of the present invention. The system  150  also includes a WTRU  102 , one or more Node-Bs  104  and an RNC  106 , similar to the system  100  of  FIG. 1A . However, instead of the Node-B(s)  104  including a re-ordering entity  122 , the MAC-e entity  130  of the RNC  106  includes a re-ordering entity  132 , a re-ordering buffer  134  and a data forwarding timer  136  for in-sequence delivery of the data blocks, respectively. Data transmitted by the WTRU  102  over the E-DCH  142  is re-ordered by the re-ordering entity  132  before being forwarded to a higher layer. Via the Node-B(s)  104 , the re-ordering entity  132  receives data blocks, (MAC-e protocol data units (PDUs)), and delivers the MAC-e PDUs with consecutive TSNs to a higher layer. MAC-e PDUs that are not consecutive are not delivered to the higher layer until expiration of the data forwarding timer  136 . The re-ordering entity  13  uses the knowledge of the ARQ/H-ARQ process  128  in the Node-B(s)  104  to determine whether the missing data block has been discarded by the WTRU  102  and to forward non-consecutive data blocks to higher layers. 
         [0020]    The H-ARQ process assignment mechanism is preferably based on absolute priority of data blocks. After recognizing that a data block of a particular transmission sequence number (TSN) is missing in the re-ordering buffer in the UTRAN, (i.e., either a Node-B or an RNC), the re-ordering entity  122 ,  132  determines the missing data block is lost if subsequent to detection of the missing data block all ARQ/H-ARQ processes  128  available and active within the Node-B(s)  104  for that WTRU  102  have either: 1) a new transmission initiated for a transmission with the same priority class with a higher sequence number; or 2) a new transmission initiated for a transmission with a lower priority class. In such case, the re-ordering entity  122 ,  132  determines that the data block is lost at the MAC layer and forwards the non-consecutive data blocks to higher layers. 
         [0021]      FIG. 2  is a flow diagram of a process  200  for forwarding non-consecutive data blocks in accordance with one embodiment of the present invention. The process  200  may be implemented using either the configuration of system  100  of  FIG. 1A  or system  150  of  FIG. 1B . The Node-B(s)  104  maintains a finite number of ARQ/H-ARQ processes  128  for each WTRU  102 . The re-ordering entity  132  in the RNC  106  may not have knowledge about the H-ARQ operation in the WTRU  102  and the Node-B(s)  104 . Therefore, when the configuration of system  150  shown in  FIG. 1B  is used, the Node-B(s)  104  provide necessary information to the RNC  106  for enabling the re-ordering entity  132  to determine whether the WTRU  102  has discarded the missing data block. 
         [0022]    The Node-B(s)  104  or RNC  106  receives data blocks from the WTRU  102  and correctly decoded data blocks are rearranged in sequence in a re-ordering buffer  124  of the Node-B(s)  104  or the re-ordering buffer  134  of the RNC  106 . When the configuration of system  150  is used, the Node-B(s)  104  forwards the successfully decoded data block to the RNC  106  along with the H-ARQ process ID and/or the frame number when the transmission was received. The frame number may be either the frame when the NDI is received or the frame when the successful transmission occurred. 
         [0023]    The re-ordering entity  122  of the Node-B(s)  104  or the re-ordering entity  132  of the RNC  106  recognizes a missing data block utilizing a TSN (step  202 ). A unique TSN is assigned to each data block by the WTRU  102 . Upon recognition of the missing data block, the Node-B(s)  104  initializes the data forwarding timer  126  or the RNC initializes the data forwarding timer  136  (step  204 ). The re-ordering entity  122  or  132  determines whether the data forwarding timer  126  or  136 , respectively, has expired (step  206 ). If the timer  126  or  136  has expired, the re-ordering entity  122  or  132  forwards non-consecutive data blocks to higher layers (step  210 ), and a higher layer data recovery procedure is initiated. 
         [0024]    If the data forwarding timer  126  or  136  has not expired, the re-ordering entity  122  or  132  further determines whether the missing data block has been discarded by the WTRU  102  based on a known H-ARQ process assignment mechanism at the WTRU  102  (step  208 ). When the RNC  106  determines a discarded data block in step  208 , the H-ARQ process may be determined implicitly from the frame number the transmission was received in. Following an out-of-sequence reception based on rules for H-ARQ process assignment and the subsequent assignment of H-ARQ processes, the Node-B(s)  104  or the RNC  106  can determine when the WTRU  102  discarded the particular transmission. 
         [0025]    The H-ARQ process assignment mechanism at the WTRU  102  is preferably based on absolute priority of the data blocks, even though other mechanisms may be implemented. In an absolute priority scheme, a higher priority data block is always serviced before a lower priority data block, and a data block with the earliest TSN is serviced first within the same priority data blocks. In such a mechanism, the Node-B(s)  104  or the RNC  106  may recognize that the WTRU  102  has discarded the missing data block if all ARQ/H-ARQ processes  128  available and active for the WTRU  102  at the Node-B(s)  104  have received successfully either: 1) a new transmission with the same priority and a higher TSN compared to the missing data block; or 2) a new transmission with a lower priority compared to the missing data block. 
         [0026]    Alternatively, the Node-B(s)  104  or RNC  106  may recognize that the WTRU  102  has discarded the missing data block if the H-ARQ process which is associated with the lost data has successfully received either: 1) a new transmission with the same priority and a higher TSN compared to the missing data block; or 2) a new transmission with a lower priority compared to the missing data block. The H-ARQ process may be known by the time of transmission/reception. The time may be indicated as either a frame or subframe number. 
         [0027]    If either condition is met, the Node-B(s)  104  or RNC  106  determines at the MAC layer that the missing data block has been discarded by the WTRU  102 . Then, the re-ordering entity  122  or  132  forwards the non-consecutive data blocks to the higher layer without waiting for expiration of the data forwarding timer  126  or  136 . If neither condition is met, the Node-B(s)  104  or RNC  106  determines that the missing data block has not been discarded, the process  200  proceeds to step  212  to wait for the next TTI or data block, and the process  200  then returns to step  206 . 
         [0028]    New transmissions may be realized by the Node-B(s)  104  by receiving of a new data indicator (NDI). NDI is used to indicate whether a transmission is new data or old data (retransmission). For old data, some kind of combining can be done at the Node-B(s)  104 . An NDI may also be represented by an H-ARQ process transmission counter. When the H-ARQ process transmission is set to an initial value, this represents the NDI. New transmissions may also be determined by received transmission queue identities (IDs) and the TSN following decoding. 
         [0029]    The Node-B(s)  104  may support several re-ordering queues for each WTRU  102 , and the out of sequence detection and forwarding logic may operate independently for each re-ordering queue. 
         [0030]    In another embodiment, the H-ARQ process assignment mechanism at the WTRU  102  is associated with the lost data block. In an absolute priority scheme, a higher priority data block is always serviced before a lower priority data block, and a data block with the earliest TSN is serviced first within the same priority data blocks. In such a mechanism, the Node-B(s)  104  may recognize that the WTRU  102  has discarded the missing data block if all ARQ/H-ARQ processes  128  available and active for the WTRU  102  at the Node-B(s)  104  have received successfully either: 1) a new transmission with the same priority and a higher TSN compared to the missing data block; or 2) a new transmission with a lower priority compared to the missing data block. 
         [0031]    If either condition is met, the Node-B(s)  104  determines at the MAC layer that the missing data block has been discarded by the WTRU  102 , then the re-ordering entity  122  forwards the non-consecutive data blocks to the higher layer not waiting for expiration of the data forwarding timer  126 . If neither condition is met, the Node-B(s)  104  determines that the missing data block has not been discarded, the process  200  proceeds to step  212  to wait for the next TTI in the case of the Node-Bs  104  or, in the case of the RNC  106 , the next data block. The process  200  returns to step  206  after the next TTI occurs or the next data block is received. 
         [0032]    New transmissions may be realized by the Node-B(s)  104  by receiving of a new data indicator (NDI). The NDI may be used to allow for H-ARQ chase combining in the Node-B(s)  104 . New transmissions may also be determined by received transmission queue identities (IDs) and the TSN following decoding. 
         [0033]      FIG. 3  is a flow diagram of a process  300  for forwarding non-consecutive data blocks in accordance with a third embodiment of the present invention. In this embodiment, the RNC  106  notifies the Node-B(s)  104  that there is a missing data block and the Node-B(s)  104  detects whether the WTRU  102  has discarded the missing data block and reports it to the RNC  106 . 
         [0034]    A re-ordering entity  132  in the RNC  106  checks whether there is a missing data block in the re-ordering buffer  134  (step  302 ). If there is no missing data block, the process  300  proceeds to step  312  to wait for the next received data block. If there is a missing data block, the re-ordering entity  132  initializes a data forwarding timer  136  and sends a “start watch” command to the Node-B(s)  104  (step  304 ). The frame number originally reported by the Node-B(s)  104  when the out-of-sequence data block in the re-ordering buffer  134  is recognized and the priority and sequence number of the missing data block are also included in the “start watch” command. 
         [0035]    After receiving the start watch command from the RNC  106 , the Node-B(s)  104  checks its current database to check all data blocks subsequent to the frame number indicated by the RNC  106  and monitors subsequent transmissions in order to determine whether the WTRU  102  has discarded the missing data block based on the known H-ARQ process assignment mechanism at the WTRU  102  (step  306 ). As explained hereinabove, the ARQ/H-ARQ processes  112  are preferably assigned in accordance with an absolute priority scheme. In such case, the Node-B(s)  104  determines whether all ARQ/H-ARQ processes  128  available and active for the WTRU  102  within the Node-B(s)  104  have either 1) a new transmission with the same priority but with a higher TSN compared to the missing data block or 2) a new transmission data block with a lower priority compared to the missing data block. 
         [0036]    If either condition is met, the Node-B(s)  104  sends a transmission failure message to the re-ordering entity  132  in the RNC  106  via E-DCH frame protocol (step  308 ). In the transmission failure message, the priority, which indicates the re-ordering queue ID, and sequence number of the data block is also included. The Node-B(s)  104  then stops watching for such an event. If neither condition is met, the process  300  proceeds to step  312  to wait for the next received data block. 
         [0037]    Upon receiving the transmission failure message, the re-ordering function in the RNC  106  forwards the non-consecutive data blocks to higher layers before the timer expires (step  310 ). 
         [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. 
         [0039]    While the present invention has been described in terms of the preferred embodiment, other variations which are within the scope of the invention as outlined in the claims below will be apparent to those skilled in the art.