An Extension to Quasi-orthogonal Sequences
An improved overloading scheme is presented for single user detection in the downlink of multiple access systems based on random OCDMA/OCDMA (O/O). By displacing in time the orthogonal signatures of the two user sets, that make up the overloaded system, the multiuser interference between the users of the two sets can be reduced by up to 50% (depending on the chip pulse bandwidth) as compared to Quasi-Orthogonal Sequences (QOS), that are presently part of the downlink standard of cdma2000. This reduction of the multiuser interference gives rise to an increase of the feasible Signal to Noise Ratio (SNR) for a particular channel load.
KeywordsMultiuser Detection User Signal CDMA System IEEE Communication Letter Symbol Interval
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