Partial correlations and cyclic prefixes in direct sequence spread spectrum

The RAKE receiver for direct sequence (DS) spread spectrum can separate energy received over multiple propagation paths with different time delays. Each finger in the RAKE sees signals with a specific time delay, but it also sees some unwanted residual crosstalk from signals over differently delayed paths. If bit transitions occur in delayed reflection, the crosstalk between two fingers in the RAKE detector is determined by two partial correlation functions, which exhibit substantially inferior properties than can be achieved for the full (or periodic) autocorrelation function. The aim of this paper is twofold: (1) to propose a new model to estimate the variance of partial correlations; (2) to show that cyclic prefixes improve the BER experienced when DS is transmitted over a dispersive multipath channel.