Abstract not found

Multi-user detection allows for the efficient use of bandwidth in Code Division Multiple Access (CDMA) channels through mitigation of near-far effects and multiple-access noise limitations. The decorrelating detector, developed by Lupas, is a linear multi-user detector that is asymptotically optimal in terms of near far resistance when certain communication parameters are completely known to the detector. In this paper, a simple adaptive decorrelating detector is developed by placing constraints on the set of spreading codes to be used by the active users. This adaptive detector has two modules: it first decorrelates the existing users, and then determines the spreading code of a new user entering the network with or without the use of a training sequence. Maximum Likelihood detection is proposed for determining the new user's spreading code. The performance of this algorithm is studied by investigating the probability of making an error in determining the new user's spreading code as ...

The detection of a weak stochastic signal in multi-variate impulsive noise is investigated. The signal is that of a new user in a Code-Division Multiple-Access multi-user system. A particular type of transformation noise is considered: the transmitted signal vector is modified by a linear transformation prior to signal detection thereby yielding a signal process and noise process that are dependent from component to component of the received vector. The linear operator is designed to combat multiple-access interference. The effect of such a transformation is studied by deriving the efficacies and asymptotic relative efficiencies of several detectors. Both linear and non-linear cross-correlator detector structures are examined. The performance of the detectors is determined for two types of non-Gaussian noise: impulsive noise and residual multiple-access interference noise. The numerical results are consistent with previous findings and motivate the investigation of a hybrid detector wh...

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