Chip-interleaved WCDMA with parallel-interference-cancellation receiver in multipath Rayleigh fading channels

Multiple access interference (MAI) is a major limiting factor of DS-CDMA system capacity. Parallel interference cancellation (PIC) is an effective means to mitigate MAI. However, if the initial decisions on which the PIC is based have high error probabilities, then PIC cannot perform well. To improve the performance of PIC, we propose chip-interleaving to provide intra-bit diversity. Then the initial decisions can be more accurate so as to enhance the PIC´s performance. We design a chip-interleaving scheme based on some 3GPP WCDMA system features, such as the use of the Q-branch to transmit control bits and the I-branch to transmit data bits in a QPSK-like modulation scheme. Simulation results show that the proposed chip-interleaved WCDMA (CI-WCDMA) transmission can have significant performance advantage compared to simple WCDMA in transmission over fading multipath channels with MAI.