The future wireless communications systems should be able to offer wide variety of applications, which have vastly different quality of service (QoS) requirements. The time-variable QoS may require the support of variable bit rates on the wireless links to the individual users. Multi-rate DS/CDMA is a promising basis on which to support the variable bit rates on the individual wireless links. C...

Today, in this information-hungry society, Internet traffic such as multimedia streaming applications is driving the demand for high speed data packet wireless services. Multiple access interference (MAI) limits the capacity of Direct Sequence Code Division Multiple Access (DS-CDMA) systems. Multiuser detection is an approach which uses filters for the optimization. However, the main drawback o...

We develop the minimum mean-squared-error (MMSE) multiuser generalized detector for nonorthogonal multipulse modulation in wireless sensor networks employed by remote sensing systems over the noncoherent additive white Gaussian noise channel. The generalized detector (GD) is constructed based on the generalized approach to signal processing in the presence of noise. We analyze the asymptotic pe...

A new linear multiuser detector that directly minimizes the bit-error rate (BER) subject to a set of reasonable constraints is proposed. It is shown that the constrained BER cost function has a unique global minimum. This allows us to develop an efficient barrier Newton method for finding the coefficients of the proposed detector using information about timing, amplitudes, channels, and the sig...

It is well-known that the optimum multiuser detector achieves the global maximum likelihood (GML) detection in the entire set of hypotheses and several other iterative detectors such as the SAGE detector achieve the local maximum likelihood (LML) detection in the smallest neighborhood. In this paper, we generalize the local maximum likelihood detection into any size of neighborhood. The charact...

In this paper we propose a new linear multiuser detector for synchronous CDMA systems. Speci.cally, the received signal is demodulated using an orthogonal multiuser (OMU) receiver that is matched to a set of orthogonal vectors that are closest in a least-squares sense to the signature vectors. We show that this approach is equivalent to optimally whitening the noise component in the output of t...

This paper introduces the notion of nonlinear MMSE multiuser detection and shows that MMSE signal estimates followed by single user detectors yield MAP (or minimum probability of error) decisions for CDMA signals. Iterative solutions are proposed for nonlinear MMSE estimation. If interferers’ codes are assumed to be known by the signal estimators for each user, the MMSE solution is shown to be ...