Evaluating viterbi decoded reed-solomon block codes on a complex spreaded DS/SSMA CDMA system

Abstract

In recent years, the Viterbi Algorithm (VA) has been shown to be an efficient trellis decoder for binary and non-binary linear blocks. In this simulation study the performance of VA decoded non-binary Reed-Solomon (RS) block codes, employed in a wideband Code Division Multiple Access (CDMA) system, operating in multipath fading channel conditions, is considered. The RAKE receiver-based Direct Sequence Spread Spectrum Multiple Access (DS/SSMA) Quadrature Phase Shift Keying (QPSK) system employed in this study uses Complex Spreading Sequence (CSS), such as Zadoff-Chu (ZC), Double Sideband (DSB) Constant Envelope Linearly Interpolated Root-of-Unity (CE-LI-RU) filtered General Chirp-like (GCL), Analytical Bandlimited Complex (ABC) and Quadriphase (QPH) sequences. This paper firstly describes the notion of VA decoding of linear block codes. Background information is then given on the filtered and unfiltered CSS families employed in the simulation study. Next, the complex Direct Sequence Spread Spectrum Multiple Access (DS/SSMA) Quadrature Phase Shift Keying (QPSK) transmitter and RAKE receiver simulator structures, as well as a novel complex multipath fading channel simulator structure are presented. This is then followed by a description of this study's versatile multi-user multipath fading performance evaluation platform, which is constructed using the complex RAKE receiver-based DS/SSMA QPSK communication system and complex multipath fading channel simulator structures. Lastly, simulated Bit Error Rate (BER) performances are presented for uncoded wideband systems and wideband systems employing VA decoded non-binary RS block codes in realistic multi-user multipath fading channel conditions. The effect of Multi-User Interference (MUI), as well as that of Channel State Information (CSI) on the decoding performance of the VA are also considered.