Improved Robust Techniques for Multiuser Detection in Non-Gaussian Channels

Abstract

In many physical channels where multiuser detection techniques are to be applied, the ambient channel noise is known through experimental measurements to be decidedly non-Gaussian, due largely to impulsive phenomena. This is due to the impulsive nature of man-made electromagnetic interference and a great deal of natural noise. This paper presents a robust multiuser detector for combating multiple access interference and impulsive noise in code division multiple access (CDMA) communication systems. A new M-estimator is proposed for "robustifying" the detector. The approach is corroborated with simulation results to evaluate the performance of the proposed robust multiuser detector compared with that of the linear decorrelating detector, and the Huber and the Hampel M-estimator based detectors. Simulation results show that the proposed detector with significant performance gain outperforms the linear decorrelating detector, and the Huber and the Hampel M-estimator based detectors. This paper also presents an improved robust blind multiuser detection technique based on a subspace approach, which requires only the signature waveform and the timing of the desired user to demodulate that user's signal. Finally, we show that the robust multiuser detection technique and its blind adaptive version can be applied to both synchronous and asynchronous CDMA channels.

Robust Multiuser Detection in Synchronous DS-CDMA System with MRC Receive Diversity over Nakagami-<i>m</i> Fading Channel

“…In this section, the influence functions of M-estimators proposed in the literature [12,14] are listed (see Fig. 1).…”

“…The Huber's M-estimator is determined by the Huber penalty function kν depends on the robustness measures derived from the influence function of [14], where k is a constant. …”

“…By assuming = l l α W , the probability of error, (14), for user #1 can be expressed, using the relation between ( ) ⋅ Q and complementary error function ( ) ⋅ erfc , as [9] 1 1 1 1 1 11 11…”

Adaptive Blind Multiuser Detection Under Impulsive Noise Using Principal Components

“…However, the batch algorithm [2] requires singular value decomposition (SVD), which is inconvenient for adaptive implementation. Further, it requires accurate rank estimation of the correlation matrix, which is not easy in an inherently noisy environment [4]- [9].…”

Improved Robust Multiuser Detection in Flat Fading Asynchronous non-Gaussian Channels

“…Recently, the problem of robust multiuser detection in nonGaussian channels has been addressed in the literature [1] & [2], which were developed based on the Huber and Hampel estimators. The Huber's estimator [3] can limit the effect of gross errors; however, the effect may still have to be large enough to reach an unacceptable level.…”