Showing papers by "Raviv Raich published in 2000"

Bearing estimation for a distributed source: modeling, inherent accuracy limitations and algorithms

Abstract: The problem of using sensor array measurements to estimate the bearing of a radiating source surrounded by local scatterers is considered. The concept of "partial coherence" is introduced to account for temporal as well as spatial correlation effects often encountered in a Rayleigh fading-type propagation channel formed between a source and sensor array elements. A simple parametric model for temporal channel correlation is presented, yielding an overall spatio-temporal channel model that is more realistic than formerly proposed models (which assume either full or zero temporal channel correlation). Thus, previously proposed "distributed source" models for bearing estimation problems are generalized to a parametric spatio-temporal model for what is called "partially coherently distributed (PCD) sources". A study of the associated Cramer-Rao Bound (CRB) is undertaken for a simple but illustrative problem formulation. The inherent limitations in bearing estimation accuracy for this spatio-temporal problem are seen to lie between the cases of zero and full temporal correlation, becoming more severe as temporal channel correlation increases. In addition, the associated maximum likelihood estimators for source bearing are proposed, and their performance is compared with that predicted by the CRB.

Short-term mobile channel prediction using discrete scatterer propagation model and subspace signal processing algorithms

Abstract: The fading envelope encountered in narrowband mobile communications often dominates the impairments to communications usage of the channel. Signal processing techniques are extensively used to mitigate the limitations imposed by the fading, and many of the techniques require knowledge of the channel transfer function. The possibility of predicting the changing channel behaviour, in particular the position of the short-term fades, is therefore of interest for the subsequent communications signal processing. Different models of the multipath propagation encourage different algorithms for the model parameter estimation and channel behaviour prediction. These algorithms are reviewed and we present results from simulations showing the performance and limitations of prediction behaviour.