MUD for overloaded CDMA system using Pseudo-user concept

Multiple access interference (MAI) is the major limiting factor for the channel capacity especially when it is desired to have large number of users (overloaded) in DS-CDMA system. We propose a scheme which removes MAI with very little computations. The scheme is based on two requirements, firstly, presence of a user called `Pseudo-user´ whose data is already known to the receiver and secondly, cross-correlation of the spreading code set for the users is the same throughout. To achieve the second requirement, we divide the users equally in groups, giving each group an identity through an orthogonal spreading code. Now the number of users is small in every group, thus making it possible to find a set of spreading codes with same cross-correlation. The bit error rate (BER) is almost independent of the number of users and MAI is removed elegantly with simple computations.