Computationally efficient blind MMSE receivers for long code WCMDA using time-varying systems theory

Abstract UMTS systems will employ long-code wideband CDMA modulation schemes. Receivers for this system are for computational reasons usually based on simple matched-filter techniques, and hence suffer from multiaccess interference. Decorrelating RAKE and MMSE receivers do not have this problem but, until now, were considered as too complex, due to the inversion of a large code matrix. As is shown in this paper, the code matrix can be interpreted as a time-varying system. Efficient implementations are then possible by carrying out the inversion using time-varying state space theory, yielding a complexity comparable to that of the conventional RAKE receiver.

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