A new optimal MUD algorithm based on searching in the local space of sub-optimal MMSE solutions for DS-UWB communication systems

Abstract

In this paper, we have studied the multiuser detection (MUD) technology applied in multiaccess (MA) direct sequence ultrawideband (DS-UWB) systems. Some typical MUD algorithms were analyzed and a new approximate optimal MUD algorithm based on searching in the local space of suboptimal minimum mean-squared error (MMSE) solution was proposed. In this new algorithm, the suboptimal solution of MMSE is considered as the initial value for the local search, and then a local solution space of this suboptimal solution is constructed by Euclidean distance. Within this space, some likely solutions for the classical optimal MUD algorithm (OMUD) are searched and the optimal one of them is chosen as the solution of this new optimal MUD algorithm. Theoretical analysis and simulation results indicate that, the BER performance and the Near-far Effect resistant ability of this proposed algorithm are much better than those of MMSE and adaptive MMSE detections, which are very close to those of OMUD. Furthermore, its time complexity is much lower than OMUD's. Compared to adaptive MMSE, this algorithm has no difficulty in choosing the suitable parameters for adaptive MMSE. Besides these, we examine the application of this new algorithm to the problem of suppressing the digital narrowband interference (NBI). It is clearly seen that this approximate optimal algorithm has perfect performance under strong NBI circumstance and coincides with the classical OMUD algorithm bound in the same condition.