Performance evaluation of multi-cell direct-sequence microcellular systems : Spread spectrum techniques

The performance of an asynchronous multi-cell Direct-Sequence Spread Spectrum Multiple-Access (DS/SSMA) system is evaluated in lineal microcells with flat Rician fading and shadowing. Both the Bit Error Rate (BER) of the uplink (i.e., the user to the base station) and the downlink (i.e., the base station to the user) are evaluated. We develop a new analytical model to evaluate the uplink performance which accounts for the user's spatial distribution, the chip waveform, the power control, and macro-selection diversity. On the downlink, since no power control is used, the designed signal follows a composite log-normal noncentral chi-square distribution. We propose an approximation method to reduce the computational complexity while still providing satisfactory precision. The analysis results show that the macro-selection diversity can reduce the other-cell interference effectively even for a channel with heavy shadowing. The Rician factor, the standard deviation of the shadowing, and the chip waveform have significant influence on the performance