High efficiency spreading spectrum modulation using double orthogonal complex sequences

This paper presents a novel scheme of high efficiency spreading spectrum modulation using double orthogonal complex sequences (DoCS). In this scheme, input data bit stream is split into many groups with length M. Each group is then mapped into a word of width M and then utilized to select one sequence from 2M-2 DoCS sequences each with length L. After that, the selected sequence is modulated on carrier in quadrature phase shift keying (QPSK) mode. In addition, a new method named forward phase correction (FPC) is put forward for carrier recovery. Theoretical analysis and bit error ratio(BER) experiment results indicate that the proposed scheme has better performance than the conventional direct sequence spread spectrum(DSSS) scheme both in bandwidth efficiency and processing gain of the receiver.