Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/713,140 filed Aug. 31, 2005, which is incorporated by reference as if fully set forth. 

   FIELD OF INVENTION 
   The present invention is related to a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B. More particularly, the present invention is related to a wireless communication method and apparatus for decoding enhanced dedicated channel (E-DCH) absolute grant channel (E-AGCH) transmissions. 
   BACKGROUND 
   Enhanced uplink (EU) is one of the major features in third generation partnership project (3GPP) frequency division duplex (FDD) systems. EU offers a peak data rate of 5.76 Mbps. Several downlink physical channels are provided to support EU transmissions. One of the downlink channels is the E-AGCH. 
     FIG. 1  is a block diagram of a conventional wireless communication system  100  which supports EU. The system  100  includes a WTRU  102 , a Node-B  104  and a radio network controller (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 an 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)  110 , an E-AGCH  112 , an E-DCH relative grant channel (E-RGCH)  114  and an E-DCH hybrid automatic repeat request (H-ARQ) indicator channel (E-HICH)  116  are established for supporting E-DCH operations. 
   For E-DCH transmissions, the WTRU  102  sends scheduling requests, (also known as rate requests), for the logical channels which a radio resource control (RRC) determines that reporting is needed to be made to the Node-B  104  via the E-DCH  108 . The scheduling requests are transmitted in the form of scheduling information and happy bit. The happy bit is transmitted via the E-DPCCH  110  whenever the E-DPCCH  110  is transmitted. 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 data via the E-DCH  108 . In response to the E-DCH transmissions, the Node-B  104  sends an acknowledgement (ACK) or a non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH  116 . 
   The E-AGCH  112  is a very important channel for performing fast scheduling in the EU. The E-AGCH  112  carries the scheduling grant in the form of a maximum power ratio for the WTRU  102 . The maximum power ratio is given by the power ratio of the E-DCH dedicated physical data channel (E-DPDCH) over the dedicated physical control channel (DPCCH) (not shown in  FIG. 1 ). In addition, the E-AGCH  112  also carries an activation flag that is used to activate or deactivate H-ARQ processes, indicating activation or deactivation of either single or all H-ARQ processes. 
   The E-AGCH  112  is transmitted with an E-DCH radio network temporary identifier (E-RNTI). Under the current 3GPP standards, two E-RNTIs may be configured for the WTRU  102  at a time. One is a primary E-RNTI and the other is a secondary E-RNTI. Only one E-RNTI may be transmitted at a time. The WTRU  102  should monitor both E-RNTIs if configured. Decoding of the E-AGCH  112  has to be performed for both E-RNTIs if configured. The success or failure of the decoding of the E-AGCH  112  significantly affects the performance of the EU. Therefore, it is desirable to provide a reliable method for decoding the E-AGCH  112 . 
   SUMMARY 
   The present invention is related to a wireless communication method and apparatus for decoding E-AGCH transmissions. A WTRU receives E-AGCH data which includes a cyclic redundancy check (CRC) part and a data part. The CRC part is masked with a WTRU identity (ID) at a Node-B. The CRC part and the data part are demultiplexed and the CRC part is demasked with the WTRU ID. A CRC is then performed with the demasked CRC part. If the CRC passes, the data part is sent to an EU medium access control (MAC-e) entity. The WTRU ID may be a primary E-RNTI or a secondary E-RNTI. When the E-AGCH data is transmitted over a 10 ms frame, if the CRC fails, E-AGCH data via subsequent subframe may be soft combined with the previous E-AGCH data. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a block diagram of a conventional wireless communication system; 
       FIG. 2  is a block diagram of a decoding chain of a WTRU for decoding an E-AGCH after receive chip rate processing is performed in accordance with the present invention; 
       FIG. 3  is a block diagram of a WTRU ID-specific CRC unit in the decoding chain of  FIG. 2 ; 
       FIG. 4  is a flow diagram of a process for E-AGCH decoding in accordance with one embodiment of the present invention; and 
       FIG. 5  is a flow diagram of a process for E-AGCH decoding in accordance with another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   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 or any other type of interfacing device in a wireless environment. 
   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. The present invention may be implemented in the form of an application specific integrated circuit (ASIC) and/or digital signal processing (DSP), as software or hardware. 
     FIG. 2  is a block diagram of a decoding chain  200  of a WTRU for decoding an E-AGCH after receive chip rate processing is performed in accordance with the present invention. The decoding chain  200  includes a de-rate matching unit  202 , a Viterbi decoder  204  and a WTRU ID-specific CRC unit  206 . An input sequence  201  recovered by a receive chip rate processor (not shown) is sent to the de-rate matching unit  202 . The input sequence  201  is a sequence of soft bits in an E-AGCH subframe obtained after a receive chip rate processing is performed. The decoding chain  200  operates on a subframe basis, (i.e., 2 ms). 
   The de-rate matching unit  202  performs de-rate matching on the input sequence  201  to obtain a de-rate matched sequence  203 . The de-rate matching is an inverse process of the rate matching process which is performed in a Node-B. The de-rate matched sequence  203  is sent to the Viterbi decoder  204  for convolutional decoding, resulting in a bit sequence  205 . The bit sequence  205  is sent to the WTRU ID-specific CRC unit  206  for performing CRC(s). 
   The bit sequence  205  includes a data part, (i.e., the absolute grant information), and a CRC part. At the Node-B, a 16-bit CRC is attached to the data part and the CRC is masked with one of the two WTRU IDs, (i.e., a primary E-RNTI  208  or a secondary E-RNTI  209 ). The masking is performed by a modular-2 addition of the CRC part and the WTRU ID. The WTRU does not know which ID has been used to mask the CRC part. Therefore, the WTRU ID-specific CRC unit  206  performs a CRC with either the primary E-RNTI  208  or the secondary E-RNTI  209  for each received E-AGCH transmission. If the CRC passes, the data part is sent to a MAC-e entity (not shown), (or to a radio link set (RLS) macro combiner for macro combining). If the CRC fails, the data part may be discarded or stored in a memory to be combined with a subsequent transmission. 
     FIG. 3  is a block diagram of the WTRU ID-specific CRC unit  206  of the decoding chain  200  of  FIG. 2 . The WTRU ID-specific CRC unit  206  includes a demultiplexer  302 , a switch  304 , a demasking unit  306 , a CRC unit  308  and a controller  310 . The bit sequence  205  is sent to the demultiplexer  302 . As stated above, the bit sequence  205  includes a data part  303   a  and a CRC part  303   b . The data part  303   a  and the CRC part  303   b  is demultiplexed by the demultiplexer  302  so that the CRC part  303   b  is sent to the demasking unit  306  and the data part  303   a  is sent to the CRC unit  308  and the controller  310 . The demasking unit  306  performs demasking on the CRC part  303   b  with one of the WTRU ID, (i.e., the primary E-RNTI  208  or the secondary E-RNTI  209 ). The primary E-RNTI  208  or the secondary E-RNTI  209  is sent to the demasking unit  306  via the switch  304  under the control of the controller  310 . 
   The demasked CRC part  307  is sent to the CRC unit  308 . The CRC unit  308  performs a CRC with the data part  303   a  and the demasked CRC part  307  and sends a pass/fail signal  309  to the controller  310 . If the CRC passes, the controller  310  sends the data part  303   a  to the MAC-e entity (not shown), (or to an RLS macro combiner). If the CRC fails, the controller  310  sends a control signal  311  to the switch  304  to switch the WTRU ID so that the demasking unit  306  demasks the CRC part  303   a  with the other WTRU ID and a second CRC is performed by the CRC unit  308  with a demasked CRC part  307 , (demasked with the other WTRU ID), and the data part  303   a . If the second CRC also fails, the data part  303   a  may be discarded. 
   Since the WTRU does not know which WTRU ID was used for masking at the Node-B, the WTRU needs to check for either the primary E-RNTI  208  or the secondary E-RNTI  209 . Initially, the WTRU may start with the primary E-RNTI  208 . Alternatively, the WTRU may use the one with which the CRC passes in the last successful decoding of the E-AGCH  112 . 
     FIG. 4  is a flow diagram of a process  400  for decoding an E-AGCH  112  in accordance with one embodiment of the present invention. E-AGCH data is received (step  402 ). The received E-AGCH data is demultiplexed into a CRC part and a data part (step  404 ). The CRC part is demasked with a WTRU ID (step  406 ). A CRC is performed with the data part and the demasked CRC part (step  408 ). It is then determined whether the CRC passes (step  410 ). If the CRC passes, the data part is sent to the MAC-e entity (step  412 ). If the CRC fails, it is determined whether all WTRU IDs have been checked (step  414 ). If so, the process  400  ends. If not, the WTRU ID is switched to the other WTRU ID (step  416 ) and the process  400  returns to step  406 . 
   Under the current 3GPP standards, the absolute grant information is transmitted over either one E-AGCH subframe (2 ms) or one E-AGCH frame (10 ms) depending on the E-DCH transmission time interval (TTI). When the E-DCH TTI is equal to 10 ms, the absolute grant information for the WTRU is repeated in all the E-AGCH 2 ms subframes in the same 10 ms frame such that the same sequence of E-AGCH bits (60 bits per subframe) is repeated over all the 2 ms subframes in the same 10 ms frame. 
   If the WTRU successfully decodes (no CRC error) the data received in an E-AGCH subframe j, then the data part is delivered to the MAC-e entity and the process stops (in order for the WTRU to avoid unnecessary processing). However, if the WTRU fails to decode the E-AGCH data for both WTRU IDs, the WTRU then has the following two options. 
   In accordance with the first option, the WTRU may decode E-AGCH data in each 2 ms subframe independently. An erroneous E-AGCH data in subframe j is discarded and the WTRU freshly processes the E-AGCH data received in a subframe j+1 of the same 10 ms radio frame as described hereinbefore. 
   In accordance with the second option, the WTRU may soft combine the E-AGCH data received in the previous 2 ms subframes and in the current 2 ms subframe of the 10 ms same radio frame. Because the same sequence of absolute grant data is transmitted over all the 2 ms subframes of the same E-AGCH frame for the 10 ms E-DCH TTI, the WTRU may perform soft combining (bit-by-bit combining before decoding) of the sequence of the E-AGCH bits received in 2 ms subframe j+1 with the sequence(s) received in the previous E-AGCH 2 ms subframe(s) of the same 10 ms radio frame, where j=1, 2, 3, 4. Optionally, weighting factors may be applied to the individual 2 ms subframes. The weighting factor may be determined as a function of a signal-to-interference ratio (SIR) of the E-AGCH in the corresponding 2 ms subframe. 
     FIG. 5  is a flow diagram of a process  500  for E-AGCH decoding in accordance with another embodiment of the present invention. E-AGCH data is received (step  502 ). The received E-AGCH data is demultiplexed into a CRC part and a data part (step  504 ). The CRC part is demasked with a WTRU ID (step  506 ). A CRC is performed with the data part and the demasked CRC part (step  508 ). It is then determined whether the CRC passes or fails (step  510 ). If the CRC passes, the data part is sent to the MAC-e entity (step  512 ). The CRC process may be performed with two WTRU IDs so that if the CRC fails with one WTRU ID, the same process is repeated with the other WTRU ID, as explained hereinbefore. If the CRC fails with all WTRU IDs, subsequent E-AGCH data is received in a subsequent subframe (step  514 ). The subsequent E-AGCH data may be soft combined with the data received in the previous subframe (step  516 ). The process  500  then returns to step  504 . 
   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 Category: h