Bit Error Rate Performance of Wireless CDMA Communications Systems: with and without Filters

Code-division multiple- access (CDMA) implemented with direct-sequence spread spectrum (DS/SS) signaling is expected to play a key role in the wireless telecommunications services such as personal communications, mobile telephony, and wireless networks. To gain insight and understanding of DS/CDMA system performance without actually building it first requires both analysis and simulations. In this thesis, DS/CDMA system performance analysis and simulations are addressed. Calculating the bit error probability for DS/CDMA systems is analytically difficult and computationally intensive. A simple and accurate approximation technique is applied to the calculation of DS/CDMA bit error probability under the assumption of infinite RF bandwidth. The bit error probability, expressed as a real function of a random variable, is simplified by using a technique that expands the function in Taylor series. As well, an architecture for DS/CDMA system with filters is developed and its performance measures, signal to noise ratio (SNR) and bit error rate (BER), are analyzed. This analysis investigates the effect of filtering on the performance of DS/CDMA systems using correlator receiver. Computer simulations of the system are also performed in this thesis. Simulation results of BER show a reasonable agreement with the BER obtained from analysis. This agreement justifies the approximation used in the analysis. It is also concluded from the simulations that filters with a bandwidth equivalent to twice the data rate provide a good BER results for a DS/CDMA system. compared to the BER performance of DS/CDMA system without filters (in which an infinite bandwidth is assumed)