Error Performance of Direct Sequence Spread Spectrum Systems on Nonselective Generalized rayleigh Fading Channel

摘要

The error performance of direct-sequence spread spectrum multiple-access communications systems on nonselective fading channels is investigated. The channels considered are those for which the fading intensity is slow, nonselective, and exhibit a generalized Rayleigh distribution. The generalized Rayleig distribution encompasses the important special cases of a Rician (specular plus Rayleigh) fading, Nakagami m-distributed fading, and Rayleigh fading. Results are obtained for the special cases of a single cochannel interferer without additive noise and multiple independent cochannel interferers with additive white Gaussian noise. The results are developed as a series expansion in the moments of the cross-correlation between the spreading codes (single interferer) or a series expansion in the powers of the second moment of the code cross-correlation (multiple interferers). To develop simple estimates of the probability of error, empirical estimates of the low-order cross-correlation moments of the spreading codes (taken to be Gold codes) are developed from a generalized gamma density approximation based on the cross-correlation moments for both Gold codes and random codes. Numerical results for the probability of error are obtained with these estimates and compared with the results based on exact moments developed from the code cross-correlation probability density. (Author)