This paper analyzes the performance of direct-sequence periodic commutation spreading for severely dispersive single-user multipath channels. The system employs a set of K symbol-length spreading codes, with each member of the set used in turn. The analysis leads to the mixed cross-correlation function that is used to aid in development of a sequence selection algorithm. The algorithm is used to select sets of sequences from the large set of Kasami sequences to maximize performance. Analysis for specular multipath channels shows that the error probability performance of a system using periodic commutation spreading can exceed a system using traditional single-code spreading by 3 dB or more.
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