Abstract:
A method and apparatus for controlling transmissions of data via an enhanced dedicated channel (E-DCH) are disclosed. A list of available transport format combinations (TFCs) is generated based on a plurality of dedicated channel medium access control (MAC-d) flows. An enhanced uplink medium access control (MAC-e) protocol data unit (PDU) is generated using a TFC which is selected from the list of available TFCs. The MAC-e PDU is forwarded to a hybrid-automatic repeat request (H-ARQ) process unit for transmission. The list of available TFCs is continuously updated by eliminating and recovering TFCs based on remaining E-DCH power, an E-DCH transport format combination set (TFCS), a power offset of a highest priority MAC-d flow that has E-DCH data to transmit, and a gain factor for each TFC.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/673,076 filed Apr. 20, 2005, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to wireless communication systems. More particularly, the present invention is related to a method and apparatus for controlling transmissions via an enhanced dedicated channel (E-DCH).  
       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, enhanced uplink (EU) transmissions have been proposed in 3GPP, in which control, (i.e., scheduling and assigning), of UL resources, (i.e., physical channels), is moved from a radio network controller (RNC) to a Node-B.  
         [0004]      FIG. 1  shows a conventional wireless transmit/receive unit (WTRU), (e.g., mobile station), side medium access control (MAC) architecture  100 . The WTRU MAC architecture  100  includes an enhanced uplink medium access control (MAC-es/MAC-e) entity  105 , which comprises different independent sub-layer entities within the MAC. The MAC- es/-e functionality split is a result of how the MAC functionality is partitioned within the universal terrestrial radio access network (UTRAN). The WTRU MAC architecture  100  further includes a high speed MAC entity  110 , a common/shared MAC (MAC-c/sh)  115 , a dedicated channel medium access control (MAC-d)  120  and a MAC service access point (SAP)  125 . The MAC-c/sh  115  controls access to all common transport channels, except the HS-DSCH transport channel  145 . The MAC-d  120  controls access to all dedicated transport channels, to the MAC-c/sh  115  and the MAC-hs  110 . The MAC-hs  110  controls access to the HS-DSCH transport channel  145 .  
         [0005]     The MAC-es/MAC-e entity  105  controls access to an E-DCH  130 , whereby the MAC-d  120  may access the E-DCH  130  via a connection  135 , and the MAC control SAP  125  may access the E-DCH  130  via a connection  140 .  
         [0006]      FIG. 2  shows MAC interworking in the conventional WTRU of  FIG. 1 . As shown in  FIG. 2 , a radio link control (RLC) protocol data unit (PDU) enters the MAC-d on a logical channel. In the MAC-e header, a data description indicator (DDI) field, (6 bits), identifies the logical channel, MAC-d flow and MAC-d PDU size. A mapping table is signaled over radio resource control (RRC) signaling to allow the WTRU to set the DDI values. The N field, (fixed size of 6 bits), indicates the number of consecutive MAC-d PDUs corresponding to the same DDI value. A special value of the DDI field indicates that no more data is contained in the remaining part of the MAC-e PDU. The transmission sequence number (TSN) field (6 bits) provides the transmission sequence number on the E-DCH  130  shown in  FIG. 1 . The MAC-e PDU is forwarded to a hybrid-automatic repeat request (H-ARQ) entity, which then forwards the MAC-e PDU to layer  1  for transmission in one transmission time interval (TTI).  
         [0007]     An efficient MAC architecture for controlling the transmission of E-DCH data is desired.  
       SUMMARY  
       [0008]     The present invention is related to a method and apparatus for controlling transmissions via an E-DCH. A list of available transport format combinations (TFCs) is generated based on a plurality of MAC-d flows. A MAC-e PDU is generated using a TFC which is selected from the list of available TFCs. The MAC-e PDU is forwarded to an H-ARQ process unit for transmission. The list of available TFCs is continuously updated by eliminating and recovering TFCs based on remaining E-DCH power, an E-DCH transport format combination set (TFCS), a power offset of a highest priority MAC-d flow that has E-DCH data to transmit, and a gain factor for each TFC. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     A more detailed understanding of the invention may be had from the following description of a preferred example, given by way of example and to be understood in conjunction with the accompanying drawing wherein:  
         [0010]      FIG. 1  shows a conventional WTRU side MAC architecture;  
         [0011]      FIG. 2  shows prior art MAC inter-working in the conventional WTRU of  FIG. 1 ;  
         [0012]      FIG. 3  shows a WTRU MAC-e architecture configured in accordance with the present invention;  
         [0013]      FIG. 4  is a flow diagram of a process for TFC recovery and elimination in accordance with the present invention; and  
         [0014]      FIGS. 5A and 5B , taken together, depict a flow diagram of a process for multiplexing MAC-d flows into a MAC-e PDU in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [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]     Hereinafter, the terminology “MAC-e” will be used to reference both MAC-e and MAC-es collectively.  
         [0017]     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.  
         [0018]      FIG. 3  shows a WTRU MAC-e architecture  300  configured in accordance with the present invention. The WTRU MAC-e architecture  300  comprises an E-TFC selection and multiplexing unit  305 , an H-ARQ process unit  310  and a lower layer management unit  315 .  
         [0019]     The E-TFC selection and multiplexing unit  305  receives a scheduled grant signal  320 , which indicates the amount of transmit power that can be used by scheduled MAC-d flows  325 . The amount of transmit power indicated by the scheduled grant signal  320  can be identified either as a ratio to the DPCCH power or the maximum transmit power  330  provided by the lower layer management unit  315  that can be used for scheduled MAC-d flows  325 .  
         [0020]     The WTRU sends scheduled MAC-d flows  325  in accordance with a scheduling grant and may also send non-scheduled MAC-d flows  335  at any time up to a configured bit rate.  
         [0021]     The E-TFC selection and multiplexing unit  305  comprises a TFC recovery and elimination unit  355 , a multiplexer  360  and a TFC selection and padding unit  365 . The E-TFC selection and multiplexing unit  305  receives scheduled and non-scheduled MAC-d flows  325 ,  335  and generates a MAC-e PDU  348  after selecting a TFC for the MAC-e PDU  348 . The TFC recovery and elimination unit  355  receives remaining E-DCH power signal  340 , based in part on the maximum allowed power  330 . The multiplexer  360  receives rate request bits  345  from a rate request unit  370  which is generated based in part on a signal  350  output by the H-ARQ process unit  310  which indicates an H-ARQ failure from a serving cell.  
         [0022]     The TFC recovery and elimination unit  355  computes the allowed E-DCH TFCS subset. The TFCS subset is continuously updated by eliminating and recovering TFCs based on the remaining E-DCH power  340 , an E-DCH TFCS  342 , the power offset of the highest priority MAC-d flow that has E-DCH data to transmit, (based on MAC-d flow power offsets  344 ), a gain factor for each E-TFC, (inferred from the MAC-d flow power offsets  344 ), and an E-DCH minimum set rate (included in the E-DCH TFCS  342 ).  
         [0023]     Referring to  FIG. 4 , a process  400  for TFC recovery and elimination in accordance with the present invention is explained hereinafter. Upon E-DCH establishment, parameters related to TFC selection are initialized (step  402 ). For each configured MAC-d flow with a unique power offset, a required transmit power of each E-TFC is calculated based on current DPCCH transmit power, the number of bits in each E-TFC and a gain factor of the E-TFC. A list of TFCs sorted by the power requirements is then stored. Each entry in the list identifies the power requirement for the TFC with the power offset for the associated MAC-d flow. Alternatively, one complete list for all MAC-d flows with indices may be stored. RRC signaled parameters, such as the E-DCH transport channel (TrCH) minimum set data rate and other parameters are also set.  
         [0024]     For each TTI, the E-TFC recovery and elimination procedure may be initiated. When the E-TFC recovery and elimination procedure is initiated, the TFC recovery and elimination unit  355  receives and stores the remaining E-DCH power  340  (step  404 ). Based on buffer occupancy and priority of each logical channel and MAC-d flow mapped to the E-DCH, the MAC-d flow with the highest priority data is determined among all MAC-d flows mapped to the E-DCH that contains logical channel(s) with non-zero buffer occupancy (step  406 ). The power offset of this MAC-d flow is used in subsequent steps.  
         [0025]     For the power offset of the highest priority MAC-d flow, the associated list of TFCs sorted by the power requirements is determined (step  408 ). The list of the TFCs is then indexed with the remaining E-DCH power requirement (step  410 ). E-TFCs are eliminated if the transmit power required by the E-TFC exceeds the remaining power for the E-DCH (P E-TFC &gt;P remain ) and recovered if the transmit power required by the E-TFC is supported by the remaining power for the E-DCH (step  412 ). Preferably a minimum set of E-TFCs is defined such that the E-DCH TFCs within the minimum set are never blocked due to transmit power restriction. The E-TFC recovery and elimination unit  355  outputs a TFCS subset  358  to the multiplexer  360  (step  414 ).  
         [0026]     The multiplexer  360  concatenates multiple MAC-d PDUs into MAC-es PDUs, and to multiplex one or multiple MAC-es PDUs into a single MAC-e PDU  348 . The multiplexer  360  also manages and sets the transmission sequence number (TSN) per logical channel for each MAC-es PDU. The multiplexer  360  takes into account the transmit power indicated by the scheduled grant signal  320  for the E-DCH, (i.e., a ratio to DPCCH power), rate grants  352  for non-scheduled MAC-d flows, maximum TFC allowed by the E-DCH remaining power, allowed MAC-d flow combinations  354 , relative priority of each logical channel and a header of rate request bits  345 , (if the rate request is transmitted in this TTI).  
         [0027]      FIGS. 5A and 5B , taken together, depict a flow diagram of a process  500  for multiplexing MAC-d flows into a MAC-e PDU  348  in accordance with the present invention. The multiplexer  360  calculates the maximum supported payload, (i.e., maximum MAC-e PDU size included in the list of supported E-TFCs (TFCS subset)), that can be sent by the WTRU during the upcoming TTI based on the power offset and the remaining power (step  502 ). Rate request bits are reserved if there is a rate request in the upcoming TTI. The available payload is set to the maximum supported payload (step  504 ). Based on the transmit power indicated by the scheduled grant signal  320 , the multiplexer  360  calculates the maximum scheduled payload that can be transmitted at the selected power offset for this transmission (step  506 ). The available scheduled payload is set to the maximum scheduled payload (step  508 ). For each MAC-d flow with a non-scheduled grant, the available non-scheduled payload is set to the value of the non-scheduled grant (step  510 ).  
         [0028]     The following steps are performed for each logical channel in the order of priorities. The highest priority is selected (step  512 ). It is determined whether there is at least one logical channel having data with the allowed MAC-d flow combination in the selected priority (step  514 ). If not, the process proceeds to step  536  to determine whether the selected priority is the lowest priority. If it is not the lowest priority, the next priority is selected (step  538 ) and the process  500  returns back to step  514 . If the priority is the lowest, the process ends.  
         [0029]     If it is determined at step  514  that there is a logical channel having data, any logical channel is selected randomly if more than one (step  516 ) and it is further determined whether there is an available payload (step  518 ). If there is no available payload, the process  500  ends. If there is available payload, it is further determined whether the logical channel belongs to a MAC-d flow with non-scheduled grants or scheduled grants (step  520 ).  
         [0030]     If the logical channel belongs to the MAC-d flow with non-scheduled grants, it is further determined whether there is an available non-scheduled payload for this MAC-d flow (step  522 ). If so, the MAC-e PDU  348  is filled up to the minimum of the available payload, the available non-scheduled payload and available data of the logical channel (step  524 ). The available payload and the available non-scheduled payload are decreased by the filled data bits and related header bits accordingly (step  526 ) and the process  500  proceeds to step  534 .  
         [0031]     If the logical channel belongs to the MAC-d flow with scheduled grants, it is determined whether there is an available scheduled payload (step  528 ). If so, the MAC-e PDU  348  is filled up to the minimum of the available payload, the available scheduled payload and available data of the logical channel (step  530 ). The available payload and the available scheduled payload are decreased by the filled data bits and related header bits accordingly (step  532 ) and the process  500  proceeds to step  534 .  
         [0032]     At step  534 , it is determined whether there is another logical channel of this priority having data with allowed MAC-d flow combinations. If there is no other logical channel, the process  500  proceeds to step  536  to select a next priority. If there is another logical channel with the same priority, the process  500  returns to step  516 .  
         [0033]     The TFC selection and padding unit  365  selects an appropriate E-TFC and applies padding for the MAC-e PDU  348  to fit the selected E-TFC. The TFC selection and padding unit  365  determines the MAC-e PDU size and selects the smallest TFC out of the list of supported TFCs for this power offset, which is larger than the MAC-e PDU size after multiplexing. The TFC selection and padding unit  365  then adds padding to the MAC-e PDU  348  to fit the selected TFC. The E-TFC selection and multiplexing unit  305  outputs a MAC-e PDU  376 , a TFC  378 , power offset  380 , the maximum number of retransmissions  382 , a rate request indication  384  and a happy bit  386  to the H-ARQ process unit  310 .  
         [0034]     The H-ARQ process unit  310  is responsible for managing each H-ARQ process. The H-ARQ process unit  310  provides synchronous operation for transmissions and retransmission, H-ARQ feedback processing on H-ARQ information channel (HICH), (i.e., ACK/NACK), and tracking the maximum number of retransmissions per H-ARQ process. The H-ARQ process unit  310  may output a signal  350  when an H-ARQ failure from a serving cell occurs. When an H-ARQ process is available, an H-ARQ process availability indication  388  is sent to the E-TFC selection and multiplexing unit  305 .  
         [0035]     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.