Multi-user Detection

In a CDMA system, many users simultaneously transmit across the entire frequency band and users’ data is separated on the basis of their signature waveforms. It is logical that the user signature waveforms be mutually orthogonal so as to avoid interference among different users. In this article, we briefly touch upon the reason for non-orthogonal signature waveforms being deployed in CDMA based cellular systems. The conventional matched filter detector is introduced and its drawbacks are discussed. We next discuss the optimum multi-user detector proposed by Verdú [1]. Lastly, we will briefly touch upon some sub-optimal approaches to multi-user detection that have been proposed in literature.