Evaluation of selective RAKE receiver in direct sequence ultra wideband communications in the presence of interference

Performance of a selective RAKE (SRAKE) receiver is evaluated for direct sequence ultra wideband (DS-UWB) communications considering an independent Rayleigh channel having exponentially decaying power delay profile (PDP). BEP performance is shown. The results obtained are compared with similar results in a channel having flat PDP. Assumption of a flat PDP (as was previously made in DS-SS) is found to predict the optimum spreading bandwidth to be lower and suboptimum operating performance beyond optimum spreading bandwidth to be severely worse than what is achievable in a real channel with an SRAKE receiver having fixed number of combined paths. Optimum spreading bandwidth for SRAKE in a channel having exponentially decaying PDP is shown to be much larger than the one in a channel having flat PDP. This is specifically good news for UWB communication. Effects of partial band interference have also been considered. Interference is found to be less effective in case of exponentially decaying PDP.