Linear Interference Suppression for Spread Spectrum Systems with Switched Interleaving and Limited Feedback

In this paper we propose a novel transmission scheme based on switched interleaving and limited feedback for downlink DS-CDMA systems. The proposed switched interleaving DS-CDMA scheme (SI-CDMA) requires the cooperation among the transmitter, the receiver and a feedback channel sending the index of the interleaver to be used. The transmit chip-interleaver is chosen by the receiver from a codebook of interleaving matrices known to both the receiver and the transmitter and the codebook index is sent back from the feedback channel using a limited number of bits. In order to design the codebook, we consider patterns such as the block interleavers, and a selection function is designed to maximize the received signal to interference plus noise ratio (SINR). We present a block-based linear minimum mean squared error (MMSE) receiver for interference suppression. Simulation results show that our proposed algorithm achieves significantly better performance than the conventional CDMA systems and the existing chip-interleaving schemes.