A study on CRC-based blind rate detection in W-CDMA

In wideband direct sequence code division multiple access (W-CDMA) mobile radio, variable-rate data (VRD) services are supported to increase the link capacity. To recover VRD at a receiver, a cyclic redundancy check (CRC)-based blind rate detection scheme was proposed that does not require the transmission of any additional information. This paper proposes a modified CRC-based blind rate detection that improves the rate detection performance when different sizes of VRD blocks are transmitted frame by frame. If difference D in the number of bits between two possible VRD blocks becomes a very small value, the probability of false rate detection (PFRD) increases. The proposed method suppresses such an increase in the PFRD by time-reversing the VRD transmission order of the last R bits. Based on the performance evaluation of the proposed method by computer simulation, when R is set to L (CRC parity bit length), PFRD is reduced by 128 times for R = 8 and D = 2. Keywords-W-CDMA; variable-rate data; blind rate detection; cyclic redundancy check