A low complexity MSK-based M-ary cyclic shift keying transceiver for direct sequence spread spectrum system over multipath fading channels

A low complexity minimum-shift-keying (MSK) with M-ary cyclic shift keying (MCSK) transceiver is proposed for the spread spectrum system over the frequency-selective fading channels. In this paper, a high rate QPSK-MCSK scheme with low complexity, constant envelope, and continuous phase modulation properties is proposed to acquire better quality performance than conventional direct sequence spread spectrum (DSSS) system. The design of the transceiver involves the following procedure. First, the data stream is mapped into QPSK-MCSK symbol in terms of the time-shifted orthogonal Gold code sequences. Second, the cyclic prefix (CP) is inserted to combat the interblock interference (IBI), and the MSK scheme is modulated to preserve the low peak-average power ratio (PAPR) property. The receiver performs MSK demodulation, removing CP, MCSK despreading and de-mapping schemes to detect the modulation symbol. Simulation results show that the proposed QPSK-MCSK system performs lower BER than the conventional DSSS system for AWGN channel and provides the robust better performance than theoretical QPSK system under multipath channel.