Performance of M‐ary/SSMA using soft decision Viterbi decoding

Abstract

SUMMARYIn this paper, we discuss the performance of Mary/SSMA and M-ary/SSMA systems using convolutional code and co-channel interference (CCI) cancellation techniques. First, we show a proposed system model and describe a soft decision method of M-ary/SS which can operate soft decision Viterbi decoding. Next, we evaluate the system performance in an AWGN environment and a Rayleigh fading environment by computer simulations. As a result, spectral efficiency of the system using convolutional code is improved in both environments, though its effects depend on the coding rate. Finally, we discuss the systems using CCI cancellation and convolutional code. As a result, when the spreading factor becomes large, its performance becomes inferior to that of the system which applies no convolutional code in an AWGN environment. However, under a Rayleigh fading environment, a considerable improvement of the performance can be obtained.

Code tracking loop for M-ary/SS systems using outputs addition of correlators

“…It is known that among spread spectrum systems, the M-ary/SS scheme, in which one of several sequences prepared on the transmission side is selected depending on several bits of data and is transmitted, has better frequency use efficiency than the conventional DS/SS scheme [2][3][4][5][6]. Several synchronization systems using locking PN sequences have been proposed for code tracking [7][8][9][10][11][12].…”