Date of Award
Master of Science in Electrical Engineering - (M.S.)
Electrical and Computer Engineering
The problem of demodulating a direct-sequence (DS) spread-spectrum signal in the presence of single-tone or narrow-band interference and multi-path is discussed. A likelihood-ratio test (LRT) receiver is presented which consists of a whitening filter and a RAKE correlator.
A modified LRT receiver structure is then considered where the whitening filter is replaced by an antenna array with corresponding tap coefficients. The array spatially removes the interference by estimating it's angle-of-arrival. Using the array has an advantage over the original LRT receiver when a narrow-band interference is present. Both receivers are identical in performance under the single-tone interference model.
A third receiver structure is considered in which two LRT receivers are placed in parallel and each receiver is assumed to receive the transmitted signal via independent paths. The correlator outputs are then summed and fed to a common slicer for decision making. The decisions, or estimated bits, are fed back to both receivers.
The recursive least-squares (RLS) algorithm was used to simulate the receivers. Bit error rates (BER) were plotted under the single-tone and narrow-band inter-ference models as well as other parameters.
Cutcher, Jeffrey L., "A modified LRT-based spread-spectrum receiver using spatial and temporal processing" (1995). Theses. 1180.