Maximum Entropy and Performance Analysis of Spread Spectrum Multiple Access Systems

F. Solms
Dept Applied Mathematics
Rand Afrikaans University
PO Box 524
Auckland Park
2092
South Africa

P.G.W. van Rooyen
Alcatel/Altec/Telkom
PO Box 286
Boksburg
1460
South Africa

J.S. Kunicki
Cybernetics Laboratory
Rand Afrikaans University
PO Box 524
Auckland Park
2092
South Africa

Abstract

We use the maximum entropy method to evaluate the performance of spread spectrum multiple access systems with and without Rayleigh and Doppler fading. We find that the maximum entropy results are superior to the results obtained with the widely used Gauss-Quadrature method. This improvement is particularly important when the moments of the error probability distribution are obtained experimentally --- typically only 4 moments are measured. The maximum entropy method also supplies a convenient tool to test the validity of the Gaussian noise approximation, i.e. that the multiple access interference (the signals created by other users) and the thermal noise add up to Gaussian noise. We find that the Gaussian approximation becomes more accurate as the number of users increases. Finally, the maximum entropy method gives good results for practically important cases where one wants to work with high signal to noise ratios and low error probabilities. It is in these cases that the traditional Gauss-Quadrature method fails.
MaxEnt 94 Abstracts / mas@mrao.cam.ac.uk