Considerations on CDMA-OFDM System Performances in Different Channel Environments for Different Modulation and Coding Scenarios

This paper presents a number of results obtained based on a CDMA-OFDM simulator developed in Matlab. The simulator has been extended to accommodate in a flexible manner to different modulation schemes, multiple access techniques, spreading codes types and lengths, convolutional codes rates, number of users and types of channels. The performances are evaluated and compared based on the Bit Error Rate (BER) as a function of the Signal to Noise Ratio (SNR) results achieved in different scenarios. In this paper are presented the results obtained by the developed simulator for two types of spreading codes-perfectly orthogonal Walsh type codes versus pseudo-orthogonal Gold type codes. The performances are evaluated in different channel environments the classical AWGN, pedestrian, vehicular and indoor ITU-R M.1225 models, for BPSK and QPSK modulations and 1/2 respectively 3/4 rate channel coding. Furthermore, since the results shown that the Gold spreading codes, QPSK modulation and 1/2 rate coding achieves the best performances in all type of channels analyzed, the authors investigate the effect of the code length and of the number of users on these results.