Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application Nos. 60/863,428 filed Oct. 30, 2006 and 60/863,473 filed Oct. 30, 2006, which is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present invention is related to wireless communication. 
     BACKGROUND 
     In third generation partnership project (3GPP) high speed downlink packet access (HSPDA), control information that is necessary for decoding high speed downlink shared channel (HS-DSCH) is transmitted via a high speed shared control channel (HS-SCCH). Multiple HS-SCCHs may be transmitted to a set of wireless transmit/receive units (WTRUs) associated with a particular cell. The HS-SCCH carries two (2) parts of data: part 1 data and part 2 data. The part 1 data includes channelization code set information, modulation scheme information, etc. The part 2 data includes transport block size information, hybrid automatic repeat request (HARQ) process information, redundancy and constellation version information, WTRU identity (ID), etc. An HS-SCCH frame includes three time slots. The part 1 data is transmitted in the first time slot, and the part 2 data is transmitted in the second and third time slots. 
       FIG. 1  shows conventional HS-SCCH encoding. For encoding the part 1 data, the channelization code set information X ccs  and modulation scheme information X ms  are multiplexed to generate a sequence of bits X 1 . Rate ⅓ convolutional coding is applied to the sequence of bits X 1  to generate a sequence of bits Z 1 . The sequence of bits Z 1  is punctured for rate matching to generate a sequence of bits R 1 . The rate matched bits R 1  are masked in a WTRU-specific way using the WTRU ID to produce a sequence of bits S 1 . Masking in this context means that each bit is conditionally flipped depending on the mask bit value. For the WTRU specific masking, intermediate code word bits are generated by encoding the WTRU ID using the rate ½ convolutional coding. 
     For encoding the part 2 data, the transport block size information X tbs , HARQ process information X hap , redundancy version information X rv , and new data indicator X nd  are multiplexed to generate a sequence of bits X 2 . From the sequence of bits X 1  and X 2 , cyclic redundancy check (CRC) bits are calculated. The CRC bits are masked with the WTRU ID, (X ue ), and then appended to the sequence of bits X 2  to form a sequence of bits Y. Rate ⅓ convolutional coding is applied to the sequence of bits Y to generate a sequence of bits Z 2 . The sequence of bits Z 2  is punctured for rate matching to generate a sequence of bits R 2 . The sequences of bits S 1  and R 2  are combined and mapped to the physical channel for transmission. 
     The performance of the detection of the part 1 data is influenced by the Hamming distance between the masks used for multiple HS-SCCHs. The conventional method produces a set of masks with a minimum distance of eight (8). When these minimum distance codes are used, the HS-SCCH detection performance is not optimal. In addition, with implementation of multiple-input multiple-output (MIMO) for HSDPA, more data need to be carried by the HS-SCCH. Therefore, it is necessary to make more room for transmission of data related to MIMO implementation in the HS-SCCH. 
     SUMMARY 
     A method and apparatus for encoding and decoding HS-SCCH data are disclosed. For part 1 data encoding, a mask may be generated using a WTRU ID and a generator matrix with a maximum minimum Hamming distance. For part 2 data encoding, CRC bits are generated based on part 1 data and part 2 data. The number of CRC bits may be less than the WTRU ID. The CRC bits and/or the part 2 data are masked with a mask. The mask may be a WTRU ID or a punctured WTRU ID of length equal to the CRC bits. The mask may be generated using the WTRU ID and a generator matrix with a maximum minimum Hamming distance. The masking may be performed after encoding or rate matching. 
    
    
     
       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  shows conventional HS-SCCH encoding; 
         FIG. 2  is a block diagram of an example Node-B for encoding HS-SCCH data; 
         FIG. 3  is a block diagram of an example WTRU for decoding HS-SCCH data; and 
         FIG. 4  shows simulation results for the selection error probability of the part 1 data v. signal-to-noise ratio (SNR) comparing the performance of the two HS-SCCH masking methods (prior art and the present invention) where two HS-SCCH codes are transmitted with different mask distances dictated the corresponding methods. 
     
    
    
     DETAILED DESCRIPTION 
     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, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user 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 capable of operating in a wireless environment. 
       FIG. 2  is a block diagram of an example Node-B  200  for encoding HS-SCCH data. The Node-B  200  comprises an encoder  201 , a rate matching unit  204 , a masking unit  206 , a multiplexer  210 , a CRC unit  212 , a masking unit  214 , an encoder  218 , a rate matching unit  220 , and a transceiver  224 . The HS-SCCH data comprises part 1 data and part 2 data. The part 1 data is sent to the encoder  202 . The encoder  202  performs channel coding on the part 1 data  201 . The channel coded part 1 data  203  is then punctured by the rate matching unit  204  for rate matching. The rate matched part 1 data  205  is then masked with a mask by the masking unit  206 . The mask may be generated based on the WTRU ID  208 . 
     Codes are usually selected for both their performance and for the simplicity of the decoders. Convolutional codes are a good example of codes that have both good performance and low decoder complexity. There is of course some tradeoff between performance and decoder complexity. However, the decoder complexity is not a factor when selecting a code to use for the masking because the corresponding decoder need not exist in the WTRU. All that is needed is the mask itself which can be created by the much simpler encoder. 
     The masking unit  206  generates the mask by block coding the WTRU ID  208  with a generator matrix which produces masks with a maximum minimum-Hamming-distance. The mask is generated by a vector-matrix product of the WTRU ID and the generator matrix. The resulting mask is a linear combination of the rows of the generator matrix. An example generator matrix for (40,16) code is given below. It should be noted that the generator matrix shown below is provided as an example, not as a limitation, and any other generator matrix may be used alternatively. In this example, the mask is the 40-bit mask, and the WTRU ID is 16-bits long. This example uses a block code with a specified generator matrix which produces masks with minimum distance of twelve (12). This provides much better performance when multiple HS-SCCH transmissions at the minimum distance are used. 
     
       
         
               
             
           
               
                   
               
             
             
               
                 [1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 1 0 0 1 0 0 1 1 1 0 0 1 0 0 1 1 1 0 ] 
               
               
                 [0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 1 0 1 0 1 0 0 0 1 1 1 0 0 1 0 0 1 ] 
               
               
                 [0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 1 0 1 0 1 0 0 0 1 1 1 0 0 1 0 1 ] 
               
               
                 [0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 1 0 1 0 1 0 0 0 1 1 1 0 0 1 1 ] 
               
               
                 [0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 1 1 1 0 1 0 1 1 1 0 0 1 1 0 1 0 1 1 0 ] 
               
               
                 [0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 1 1 1 0 1 1 0 0 0 1 0 0 0 0 1 0 1 ] 
               
               
                 [0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 1 1 1 0 1 1 0 0 0 1 0 0 0 0 1 1 ] 
               
               
                 [0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1 1 1 1 0 0 1 0 0 0 0 0 0 0 1 1 0 0 1 1 1 0 ] 
               
               
                 [0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 0 1 0 0 1 0 0 0 1 1 0 1 1 0 1 0 0 0 1 0 0 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 0 1 0 0 1 0 0 0 1 1 0 1 1 0 1 0 0 0 1 0 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 0 1 0 0 1 0 0 0 1 1 0 1 1 0 1 0 0 0 1 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 0 1 1 0 0 0 0 0 0 1 1 1 1 1 0 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 1 1 1 1 0 0 0 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 1 1 1 1 0 0 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 1 1 0 1 1 0 1 1 1 0 1 1 1 1 0 1 ] 
               
               
                 [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 1 1 0 1 1 0 1 1. 1 0 1 1 1 1 1 ] 
               
               
                   
               
             
          
         
       
     
     Conventionally, the mask is generated by encoding the WTRU ID  208  using the rate ½ convolutional coding. The minimum Hamming distance of the conventional masks is eight (8). The improved Hamming distance of the masks generated by the present invention results in a performance improvement of the part 1 HS-SCCH decoder at the WTRU.  FIG. 4  shows simulation results for the selection error probability of the part 1 data v. SNR comparing the performance of the two HS-SCCH masking methods (prior art and the present invention) where two HS-SCCH codes are transmitted with different mask distances dictated the corresponding methods.  FIG. 4  shows performance improvement when using the mask with the Hamming distance of twelve (12) compared to the mask with the Hamming distance of eight (8). 
     Referring again to  FIG. 2 , the part 1 data  201  and the part 2 data  211  are sent to the CRC unit  212  to calculate CRC bits. The CRC bits are attached to the part 2 data  211 . The number of CRC bits may be less than the length of the WTRU ID so that more data, (e.g., data for MIMO), may be included as the part 2 data. The combined part 2 data and the CRC bits  213  are sent to the masking unit  214 . The masking unit  214  performs masking to the CRC bits or CRC bits plus some or all of the part 2 data with a mask, which will be explained in detail below. The masked part 2 data and CRC bits  217  are encoded by the encoder  218 . The encoded part 2 data and CRC bits  219  are punctured by the rate matching unit  220 . The rate matched part 2 data and CRC bits  221  and the rate matched part 1 data  209  are multiplexed by the multiplexer  210  and sent to the transceiver  224  for transmission. 
     In accordance with one embodiment, the masking unit  214  may generate a mask having a size equal to or smaller than the size of the CRC bits plus the part 2 data. A portion of the mask is extracted and applied to the CRC bits and the remaining portion of the mask is applied to all or part of the part 2 data. The mask may be generated using the WTRU ID  216  and a generator matrix as disclosed above with respect to part 1 data masking to maximize the minimum Hamming distance of the masks. 
     In accordance with another embodiment, the WTRU ID may be used as a mask. The length of the WTRU ID may be longer than the CRC bits. Therefore, a part of the WTRU ID is used to mask the CRC bits and the remaining of the WTRU ID is used to mask the part 2 data. In accordance with yet another embodiment, the WTRU ID is punctured to be the same length as the CRC bits and the punctured WTRU ID is used to mask the CRC bits. 
     In accordance with still another embodiment, the masking unit  214  may be moved between the encoder and the rate matching unit. The masking unit  214  generates a mask of length equal to the rate matched part 2 data and CRC bits  221 . The masking unit  214  then applies the mask to the encoded part 2 data and CRC bits  219 . Alternatively, the masking unit  214  may be moved between the rate matching unit  220  and the multiplexer  210 , and applies the mask to the rate matched part 2 data and CRC bits  221 . The mask may be 80-bits long. The mask may be generated using the WTRU ID  216  and a generator matrix as disclosed above with respect to part 1 data masking to maximize the minimum Hamming distance of the masks. 
       FIG. 3  is a block diagram of an example WTRU  300  for decoding HS-SCCH data. The WTRU  300  includes a transceiver  302 , a de-multiplexer  304 , a de-masking unit  306 , a de-rate matching unit  310 , a decoder  312 , a de-rate matching unit  314 , a decoder  316 , a de-masking unit  318 , and a CRC unit  322 . The transceiver  302  receives a HS-SCCH transmission  301  including a first part on a first time slot of an HS-SCCH frame corresponding to the part 1 data and a second part on the second and third time slots of the HS-SCCH frame corresponding to the part 2 data. The first part  305   a  and the second part  305   b  are de-multiplexed by the de-multiplexer  304 . 
     The first part  305   a  is de-masked by the de-masking unit  306 . The de-masking unit  306  generates the same mask used at the Node-B in the same way using the WTRU ID  308 . The mask may be generated with the WTRU ID  308  and the generator matrix as disclosed above. The de-rate matching unit  310  reverts the puncturing performed at the Node-B on the de-masked first part  309 . The de-rate matched first part  311  is then decoded by the decoder  312  to output part 1 data  313 . The part 1 data is also sent to the CRC unit  322 . 
     The second part  305   b  is de-rate matched by the de-rate matching unit  314  to revert the puncturing performed at the Node-B. The de-rate matched second part  315  is then decoded by the decoder  316  to output part 2 data (may or may not be masked at the NodeB) and masked CRC bits  317 . The masked CRC bits and optionally the masked part 2 data  317  are de-masked by the de-masking unit  318 . The de-masking unit  318  uses the same mask used at the Node-B for the de-masking. The mask may be the WTRU ID  320 , punctured WTRU ID, or a mask generated by using the WTRU ID  320  and a generator matrix. The de-masking unit  318  outputs de-masked part 2 data and CRC bits  321  to the CRC unit  322 . The CRC unit  322  then performs a CRC check with the part 1 data  313 , the part 2 data, and CRC bits. 
     The de-masking unit  318  may be moved between the decoder  316  and the de-rate matching unit  314 , or between the de-rate matching unit  314  and the de-multiplexer  304  depending on the masking scheme performed at the Node-B. In this case, the mask may be 80-bits long, and the mask may be generated using the WTRU ID  216  and a generator matrix as stated above to maximize the minimum Hamming distance of the masks. 
     Although the features and elements of the present invention are described in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
     Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. 
     A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) module.

Technology Category: 5