Blind chip-rate multiuser equalisation

Abstract

This paper addresses blind multiuser detection in a DS-CDMA downlink channel.The synchronous users are separated by re-establishing orthogonality of their spreading sequences in a common chip-rate equaliser.The adaptation algorithm can be based either on a constant modulus (CMA) criterion of the various users, or on a decision directed (DD) scheme.In either case, a stochastic gradient descent algorithm will result, as derived, in a multiple error filtered-X LMS type approach, whereby the equaliser input to both the multichannel CMA or DD algorithm are replaced by spreading code filtered versions.Adaptation examples are given underlining some of the characteristics of the proposed algorithms.