A front end for tree-pruned multiuser detection apparatus, the front end comprising: a parameter estimator coupled to a data stream comprising an aggregate of a plurality of signals, each signal being assigned a channel, a number of said plurality of signals exceeding a number of mathematical dimensions for linearly distinguishing said plurality of signals of a multiuser detection system, said parameter estimator providing estimation values of said data stream; and a filter bank having a plurality of filters coupled to said data stream and coupled to said parameter estimator, each of said signals being individually coupled to a respective one of said plurality of filters to produce a filtered output; characterised in that the front end is a whitened front end further comprising: a whitener designer coupled to said parameter estimator, for computing a whitener factorization suitable to partially decorrelate multi-access interference and partially whiten the noise that was colored by said plurality of filters; an overloaded whitener unit coupled to said filter bank and said whitener designer for applying said whitener factorization to said filtered output to produce a partially de-correlated and whitened output; and a symbol-hypothesis testing section coupled to said whitener designer and said whitened output for using a hypothesis pruning to perform a decision tree search. a parameter estimator coupled to a data stream comprising an aggregate of a plurality of signals, each signal being assigned a channel, a number of said plurality of signals exceeding a number of mathematical dimensions for linearly distinguishing said plurality of signals of a multiuser detection system, said parameter estimator providing estimation values of said data stream; and a filter bank having a plurality of filters coupled to said data stream and coupled to said parameter estimator, each of said signals being individually coupled to a respective one of said plurality of filters to produce a filtered output; characterised in that the front end is a whitened front end further comprising: a whitener designer coupled to said parameter estimator, for computing a whitener factorization suitable to partially decorrelate multi-access interference and partially whiten the noise that was colored by said plurality of filters; an overloaded whitener unit coupled to said filter bank and said whitener designer for applying said whitener factorization to said filtered output to produce a partially de-correlated and whitened output; and a symbol-hypothesis testing section coupled to said whitener designer and said whitened output for using a hypothesis pruning to perform a decision tree search. a whitener designer coupled to said parameter estimator, for computing a whitener factorization suitable to partially decorrelate multi-access interference and partially whiten the noise that was colored by said plurality of filters; an overloaded whitener unit coupled to said filter bank and said whitener designer for applying said whitener factorization to said filtered output to produce a partially de-correlated and whitened output; and a symbol-hypothesis testing section coupled to said whitener designer and said whitened output for using a hypothesis pruning to perform a decision tree search.