Multiplex and division techniques of non-spread and spread spectrum signals

Abstract

This paper proposes a technique where non-spread and spread spectrum (SS) signals are combined in the same frequency band. It shows that the multiplex technique proposed is an effective method for making good use of a limited frequency band. Furthermore a system using this multiplex technique can transmit data of different speeds and quality at the same time. The multiplex signal presented here is where non-spread quadrature phase shift keying (QPSK) and direct sequence spread spectrum DS-SS signals are combined, with reference symbols being inserted without multiplexing for easy estimation of the channel condition. A technique is then proposed to divide the multiplex signal in the receiver. Using this technique, bit error rate (BER) performances of non-spread QPSK and DS-SS are calculated under additive white Gaussian noise (AWGN) and Rayleigh fading channels. According to the results of the BER performance for non-spread QPSK and DS-SS, it is clear that the multiplex signal can be divided and data can be retrieved in the receiver.