Fixed and Floating-point implementation of DS-CDMA system using Complete Complementary codes under both frequencyselective and flat fading channel conditions

In this paper we present the results for both fixed and floating-point operation of a Single-Input-Single-Output (SISO) Direct Spreading Code-Division Multiple-Access (DS-CDMA) communication system. Conventional Walsh codes DS-CDMA systems suffer from high levels of both Multiple-Access-Interference (MAT) and Inter-Symbol-Interference (ISI) under multipath fading channel condition, due to the loss of Walsh codes mutual orthogonality, which exists under flat fading channel conditions. This high level of interference limits the maximum error-free data rates achieved. The proposed SISO CDMA system uses Complete Complementary (CC) codes that exhibit robust orthogonality in multipath fading channels, and is termed CC-CDMA. The simulation results reveal significant improvement in Bit-Error-Rate (BER) performance and feasible data rates when compared with a SISO-CDMA system using conventional Walsh spreading codes under frequency selective fading channels. Finally to reduce complexity and power consumption of the CC-CDMA system a fixed point Digital Signal Processing (DSP) implementation is presented and a comparison with the original floating point system is drawn.