Rake receiver sensitivity to spreading sequence
A. Wautier, S. Ammari · 2002
We study the performance of direct sequence spread-spectrum (DSSS) systems using RAKE receivers. The RAKE receiver is used to take benefit of path diversity The performances obtained with this receiver are close to the optimum for very long sequences so that they can be modeled as random sequences. This approximation is not valid for small spreading factors as used in the TD-CDMA mode of the UMTS. The study is focused on the influence of the spreading sequence on the bit error rate performance of a single-user RAKE receiver. Analytical expressions of the bit error rate are derived for non-ideal sequences. This study shows that sequences of a family set do not have the same behavior on a particular channel profile. RAKE receiver sensitivity to the number of fingers can also be easily evaluated with the analytical approach. RAKE performance degradation due to channel estimation and to multiple users are also evaluated.