An iterative groupwise multiuser detector with soft output

We consider a multiuser system in which the interfering users have the same pulse shape and are received in a synchronous, flat fading channel at an antenna array. This paper introduces a new iterative group-wise multiuser detection technique (IMUD) that gives a tradeoff of complexity and performance between joint maximum likelihood (JML) detection and zero forcing (ZF) MUD. It is shown that in the overloaded case the new IMUD algorithm significantly outperforms MMSE V-BLAST. Even with an equal number of users and receive antennas, IMUD gives better performance within two iterations. An additional feature of IMUD is that it inherently produces soft-output decisions.