Projection Based Decorrelatingdetector for Synchronous Cdmacommunication

Multiuser detection allows for the eecient use of bandwidth in Code Division Multiple Access (CDMA) channels through mitigation of near-far eeects and multiple-access noise limitations. The decorrelating detector is a linear multiuser detector that is asymptoti-cally optimal in terms of near far resistance. An adaptive decorrelator is constructed which adaptively augments an existing conventional decorrelator to demodulate a new active user in addition to existing users. This adaptive decorrelator rst decorrelates the original users, and then determines the spreading code of the new user with 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 via the probability of making an error in determining the new user's signature sequence. Upper and lower bounds for this probability are investigated. In addition, a mod-iied decorrelator is proposed and investigated to demod-ulate the original users' information streams during the training phase.