Design of QPSK Sequences for M-Ary Spread Spectrum OFDM Systems

Abstract

As an efficient tradeoff method between data rate and communication quality, M-ary spread spectrum (MSS) orthogonal frequency division multiplexing (OFDM) system may provide a flexible choice for different communication requirements. However, conventional BPSK sequences with single channel mode limits high-speed transmission to a great extent. In order to obtain higher data rate, a design method of QPSK sequences for MSS-OFDM systems is proposed in this paper. The provided QPSK sequences are constructed on the basis of complementary orthogonal sequence set which is simultaneously mapped to both of in-phase channel and quadrature channel. As a result, the increase of twice data rate may be achieved at the cost of peak-to-average power ratio growth from 3dB to 6dB.