Orthogonality Factor for DS-CDMA

This paper deals with the orthogonality factor (alpha), a transfer coefficient which allows the transformation of a transmitted orthogonal signal into a received Gaussian noise to be made. Both produce the same degradation in terms of quality of service and have the same power. This paper shows the impact of the pulse shaping filter on alpha: A right choice of the pulse shaping chip waveform can reduce a. A new theoretical expression of a is established for the large response in time domain of the pulse shaping filter: A pronounced increase of a with pulse shaping filter length is clearly established. For frequency selective invariant channels, the simulation results are in perfect concordance with the theoretical results. However for frequency selective Rayleigh channels, the new expression of a must be modified to take into consideration the different statistic laws of the intra-cellular and inter-cellular interferences. So a coefficient (whitening coefficient) can be introduced with that in mind.

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