Method and apparatus for encoding and decoding a high speed shared control channel

#The present invention is related to wireless communication.

#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 Xccs and modulation scheme information Xms are multiplexed to generate a sequence of bits X1. Rate 1/3 convolutional coding is applied to the sequence of bits X1 to generate a sequence of bits Z1. The sequence of bits Z1 is punctured for rate matching to generate a sequence of bits R1. The rate matched bits R1 are masked in a WTRU-specific way using the WTRU ID to produce a sequence of bits S1. 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 1/2 convolutional coding.

#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;

#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.