Analytical Description of Self-Interference in Direct Sequence Spread Spectrum Communications

A new analytical statistical model has been developed in order to describe the self-interference that results due to multipath propagation in a BPSK spread spectrum system. Motivation for this work was the fact that the well-known Gaussian approximation that has been extensively used in the past in order to describe such terms is not satisfactory, especially when the probability of error is smaller than10−2 or 10−3. The existence of two paths inthe radio channel has been assumed. The amplitude of each path has been assumed as Rayleigh distributed while the arrival time of the second path with respect to the arrival time of the first one has been assumed to be uniformly distributed. The validity of the developed model has been examined by comparing analytical results with results obtained by simulation using Monte Carlo techniques. Results taken from the Gaussian approximation were also compared with the simulation results. It was shown that the developed model describes with great accuracy the pre-mentioned undesirable term. On the contrary, the Gaussian approximation exhibits significant differences when compared to the simulation results. This is also evident by the use of a comparison parameter which is several orders of magnitude smaller for the developed model than for the Gaussian approximation (the smaller this parameter is the better the fit between two groups of data).

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