Abstract:
A method and apparatus for controlling enhanced dedicated channel (E-DCH) transmissions are disclosed. An enhanced uplink medium access control (MAC-e/es) entity processes a received scheduling grant to calculate a serving grant. The MAC-e/es entity determines whether both a hybrid automatic repeat request (H-ARQ) process for scheduled data and scheduled data are available. If an H-ARQ process for scheduled data and scheduled data are available, the MAC-e/es entity determines whether a serving grant exists. The MAC-e/es entity calculates a remaining power based on maximum allowed power and restricts an E-DCH transport format combination (E-TFC) based on the remaining power. The MAC-e/es entity selects an E-TFC using the serving grant and generates a MAC-e protocol data unit. The MAC-e/es entity may process the received scheduled grant is at each transmission time interval or may store the received scheduled grant in a grant list until there is E-DCH data to transmit.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. provisional application No. 60/704,273 filed Aug. 1, 2005, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention is related to wireless communication systems. More particularly, the present invention is related to a method and apparatus for controlling enhanced dedicated channel (E-DCH) transmissions.  
       BACKGROUND  
       [0003]     Methods for improving uplink (UL) coverage, throughput and transmission latency are currently being investigated in the third generation partnership project (3GPP). In order to achieve these goals with respect to an E-DCH, the control of UL resources, (i.e., physical channels), has been moved from the radio network controller (RNC) to the Node-B.  
         [0004]     In order to reduce complexity and power consumption, execution of wireless transmit/receive unit (WTRU) side enhanced uplink medium access control (MAC-e/es) functions, such as E-DCH transport format combination (E-TFC) selection and multiplexing, remaining transmit power calculation, and processing of absolute grants (AGs) and relative grants (RGs), needs to be properly controlled and coordinated.  
       SUMMARY  
       [0005]     The present invention is related to a method and apparatus for controlling E-DCH transmissions. A MAC-e/es entity of the WTRU receives a scheduling grant and processes the scheduling grant to calculate a serving grant. The MAC-e/es entity determines whether both a hybrid automatic repeat request (H-ARQ) process for scheduled data and the scheduled data are available. If an H-ARQ process for scheduled data and the scheduled data are both available, the MAC-e/es entity determines whether a serving grant exists. The MAC-e/es entity then calculates a remaining power based on the maximum allowed power and restricts an E-TFC based on the remaining power. The MAC-e/es entity selects an E-TFC using the serving grant and generates a MAC-e protocol data unit (PDU) for transmission. The MAC-e/es entity may process the received scheduled grant at each transmission time interval (TTI), or may store the received scheduled grant in a grant list until there is E-DCH data to transmit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a block diagram of a wireless communication system configured in accordance with the present invention.  
         [0007]      FIG. 2  is a block diagram of a protocol architecture of a WTRU in accordance with the present invention.  
         [0008]      FIG. 3  is a block diagram of a MAC-e/es entity of a WTRU in accordance with the present invention.  
         [0009]      FIG. 4  is a flow diagram of a process for controlling E-DCH transmissions in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]     When referred to 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 (AP) or any other type of interfacing device in a wireless environment.  
         [0011]     The present invention is applicable to any wireless communication systems including, but not limited to, universal mobile telecommunication systems (UMTS) frequency division duplex (FDD), UMTS time division duplex (TDD) and time division synchronous code division multiple access (TD-SCDMA) systems.  
         [0012]     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.  
         [0013]      FIG. 1  is a block diagram of a wireless communication system  100  configured in accordance with the present invention. The system  100  comprises a WTRU  102 , a Node-B  104  and an RNC  106 . The RNC  106  controls overall E-DCH operation by configuring E-DCH parameters for the Node-B  104  and the WTRU  102 , such as initial transmit power level, maximum allowed transmit power or available channel resources per Node-B. Between the WTRU  102  and the Node-B  104 , an E-DCH  108 , an E-DCH dedicated physical control channel (E-DPCCH), an absolute grant channel (E-AGCH)  112 , a relative grant channel (E-RGCH)  114  and an H-ARQ information channel (E-HICH)  116  are established for supporting E-DCH operations.  
         [0014]     For E-DCH transmissions, the WTRU  102  sends scheduling information, (also known as a rate request), to the Node-B  104  via the E-DPCCH  110 . The Node-B  104  sends a scheduling grant to the WTRU  102  via the E-AGCH  112  or the E-RGCH  114 . After E-DCH radio resources are allocated for the WTRU  102 , the WTRU  102  transmits UL data via the E-DCH  108 . In response to the E-DCH transmissions, the Node-B  104  sends an acknowledgement (ACK) or non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH  116 . The Node-B  104  may also respond with rate grants to the WTRU  102  in response to E-DCH data transmissions.  
         [0015]      FIG. 2  is a block diagram of a protocol architecture of the WTRU  102  in accordance with the present invention. The protocol architecture of the WTRU  102  includes higher layers  202 , a radio link control (RLC) layer  204 , a MAC layer  206  and a physical layer  208 . The MAC layer  206  includes a dedicated channel medium access control (MAC-d) entity  210  and a MAC-e/es entity  212 . The MAC-e/es entity  212  handles all functions related to the transmission and reception of an E-DCH including, but not limited to, H-ARQ transmissions and retransmissions, priority of data, MAC-d and MAC-es multiplexing, and E-TFC selection. The RLC layer  204  is provided for in-sequence delivery of data. A re-ordering function is provided in the RLC layer  204  to organize the received data blocks according to the sequence.  
         [0016]      FIG. 3  is a block diagram of the MAC-e/es entity  212  in accordance with the present invention. The MAC-e/es entity  212  includes an E-TFC selection entity  302 , a multiplexing and transmission sequence number (TSN) setting entity  304 , an H-ARQ entity  306 , a serving grant processing entity  308  and a memory  310 . The serving grant processing entity  308  receives an AG  312  and a RG(s)  314  from the physical layer  208  and processes the AG  312  and the RG(s)  314  to generate a serving grant or stores them in the memory  310 . There may be one or more RGs  314 . The E-TFC selection entity  302  selects an E-TFC based on the serving grant and performs an arbitration among different data flows mapped on the E-DCH.  
         [0017]     The multiplexing and TSN setting entity  304  concatenates multiple MAC-d PDUs into MAC-es PDUs, and multiplexes one or multiple MAC-es PDUs into a single MAC-e PDU to be transmitted in the next TTI as instructed by the E-TFC selection entity  302 . The multiplexing and TSN setting entity  304  also manages and sets a TSN per logical channel for each MAC-es PDU.  
         [0018]     The H-ARQ entity  306  controls a plurality of H-ARQ processes for storing MAC-e PDUs and retransmitting the MAC-e PDUs when a transmission failure is signaled via the E-HICH. An active H-ARQ process is used for transmission of scheduled data, while a non-active H-ARQ process is not used for transmission of scheduled data. At a given TTI, the H-ARQ entity  306  identifies an H-ARQ process for which a transmission should take place. At the time of a new transmission, the H-ARQ entity  306  provides an H-ARQ profile for all new transmissions and retransmissions of a MAC-e PDU. The H-ARQ profile includes information on the maximum number of transmissions and a power offset with which to configure the physical layer.  
         [0019]     The execution of the E-TFC selection by the E-TFC entity  302  depends on the availability of data mapped to the E-DCH with a grant (including an occurrence of a scheduling information rate request trigger) and the availability of an H-ARQ process. An H-ARQ process should be available before E-TFC selection is performed by the E-TFC selection entity  302 . The H-ARQ entity  306  identifies to the E-TFC selection entity  302  the availability of H-ARQ processes. H-ARQ processes may be available upon initial configuration, ACK reception, or exceeding the maximum number of retransmissions for any H-ARQ processes.  
         [0020]      FIG. 4  is a flow diagram of a process  400  for controlling E-DCH transmissions in accordance with the present invention. A physical layer receives a scheduling grant via an E-AGCH  112  and E-RGCHs  114  (step  402 ). After decoding of E-AGCH and E-RGCH, an AG  312  and RG(s)  314  are sent to the serving grant processing entity  308  in the MAC-e/es entity  212 . The serving grant processing entity  308  processes the AG  312  and RG(s)  314  to determine a serving grant. The scheduling grant may be an AG  312  from a serving E-DCH cell or an RG(s)  314  from either all cells in a serving E-DCH radio link set (RLS) or a non-serving radio link (RL). The scheduling grant is applied to a specific transmission time interval (TTI). This association is implicit based on the timing of the AG  312  and the RG(s)  314 .  
         [0021]     Upon reception of the scheduling grant, the serving grant processing entity  308  has two options when there is no data to transmit in the TTI associated to the scheduling grant. The serving grant processing entity  308  may process the received scheduling grant to determine a current serving grant each TTI (step  404 ). Alternatively, the serving grant processing entity  308  may store the received scheduling grant in a memory  310 , (i.e., a grant list), and process the stored scheduling grants when there are E-DCH data to transmit.  
         [0022]     The E-TFC selection entity  302  determines whether any H-ARQ processes for scheduled data, (i.e., an active H-ARQ process) and scheduled data are both available (step  406 ). If an H-ARQ process for scheduled data and scheduled data are both available, the process  400  proceeds to step  410  to determine whether a serving grant exists. Alternatively, if both the H-ARQ process for scheduled data and the scheduled data are both available, and if the second option is implemented, (i.e., the received scheduling grant is stored in the memory  310 ), the serving grant processing entity  308  processes the scheduling grant stored in the memory  310  to determine a serving grant at step  408  before proceeding to the step  410 .  
         [0023]     A serving grant indicates a maximum E-DPDCH to dedicated physical control channel (DPCCH) power ratio that the WTRU is allowed to allocate for the upcoming transmission for scheduled data. The serving grant is updated based on the AG and the RG.  
         [0024]     In processing the scheduling grant stored in the grant list, the serving grant processing entity  308  may process the last N AGs among the stored scheduling grants to generate the serving grant. The value of N is larger than one.  
         [0025]     Alternatively, the serving grant processing entity  308  may maintain only the most recent primary AG and subsequent RGs, including the latest secondary AG in the grant list. A primary AG is an AG received with a primary radio network temporary ID (RNTI) and a secondary AG is an AG received with a secondary RNTI. When a new primary AG is received previous AG and RGs except for the last secondary AG are removed from the grant list when the next transmission requiring a scheduling grant occurs. This reduces significant processing overhead following transmission idle periods.  
         [0026]     In addition, whenever a serving cell change occurs, the serving grant processing entity  308  discards all stored AGs and RGs in the grant list. This operation is equivalent to setting an AG to zero and discarding all RGs.  
         [0027]     At step  410  if it is determined that there is no serving grant, (i.e., a current serving grant is zero), the E-TFC selection entity  302  limits an E-TFC to a minimum set of E-TFCs (step  412 ) and calculates a remaining power based on the minimum set of E-TFCs (step  414 ). If it is determined that there is a serving grant at step  410 , the E-TFC selection entity  302  calculates a remaining power based on a maximum allowed power (step  414 ).  
         [0028]     After the remaining power is calculated, the E-TFC selection entity  302  restricts E-TFCs for this TTI based on the remaining power (step  416 ). The E-TFC selection entity  302  then selects an E-TFC and the multiplexing and TSN setting entity  304  generates a MAC-e PDU by multiplexing MAC-d flows and MAC-es PDUs (step  418 ). A happy bit which indicates whether the WTRU is satisfied with a current scheduling grant is then set for transmission in this TTI (step  420 ) and the MAC-e/es entity waits for the next TTI (step  422 ).  
         [0029]     If it is determined at step  406  that either an H-ARQ process for scheduled data, (i.e., an active H-ARQ process), is not available or scheduled data is not available, the E-TFC selection entity  302  then determines whether an H-ARQ process for non-scheduled data and the non-scheduled data are both available (step  424 ). If an H-ARQ process for non-scheduled data and the non-scheduled data are both available, the E-TFC selection entity  302  further determines whether there is any non-scheduled grant (step  426 ). The non-scheduled grant is set by an RNC in terms of maximum number of non-scheduled bits that can be included in a MAC-e PDU. The WTRU is allowed to transmit non-scheduled transmissions up to the sum of the non-scheduled grant if multiplexed in the same TTI. If there is a non-scheduled grant, the process proceeds to step  414  to calculate a remaining power and subsequent MAC-e functions, (i.e., steps  416 - 422 ), are performed as described hereinbefore.  
         [0030]     If it is determined at step  426  that there is no non-scheduled grant, it is determined whether there is any H-ARQ processes available (step  428 ). If there is an available H-ARQ process, it is determined if scheduling information needs to be reported, (i.e., whether a triggering event occurs) (step  430 ).  
         [0031]     Reporting of scheduling information is triggered by a plurality of different events, which are configurable. Generation of scheduling information is well known in the art and is not within the scope of the present invention. If it is determined at step  430  that there is scheduling information that needs to be transmitted, scheduling information bits are generated (step  432 ) and the process proceeds to step  414  to calculate a remaining power. Subsequent MAC-e functions, (i.e., steps  416 - 422 ), are then performed as described hereinbefore. If there is no scheduling information to be transmitted, no new transmission occurs in this TTI and the MAC-e entity waits for the next TTI (step  422 ).  
         [0032]     If it is determined at step  428  that there is no available H-ARQ process, (which means that the transmission in this TTI is a retransmission), a happy bit is set for the transmission in this TTI to indicate whether the WTRU is satisfied with the scheduling grant (step  434 ) and the MAC-e entity waits for the next TTI (step  422 ).  
         [0033]     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.