A General Expression of Rake Receiver Performance in DS-CDMA Downlink

This paper deals with the orthogonality factor, 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. The theoretical expression is given for the time delay between paths inferior to the chip period. This paper shows the impact of the pulse shaping filter on the orthogonality factor. If the pulse shaping is not taken into account, in some cases the orthogonality factor will be overvalued by 3 dB. A right choice of the pulse shaping filter form can reduce the orthogonality factor. Another important conclusion is that the orthogonality factor can perfectly model the raw performance if the phase reference quality is good. However in the case of coded performance, the precision of the model is lesser. The different statistics of the interferences degrade the precision of the model for coded performance. Finally, the paper shows that the behaviour at the cell border with a dedicated phase reference is by far the most favourable to macrodiversity.