2-D SPATIAL SMOOTHING FOR MULTIPATH COHERENT SIGNAL SEPARATION

The use of two-dimensional spatial smoothing (SS) to increase channel capacity of wireless communications system is discussed. The necessary and sufficient conditions on array configuration for applying SS to m ultiple signal classification (MUSIC), and adaptive beamforming algori thms are defined and proved. This array must have an orientational inv ariance structure with an ambiguity free center array, and the Dumber of subarrays must be larger than. or equal to the size of the largest group of coherent signals. We also studied the cause of ambiguities in a multipath environment. We found the necessary and sufficient condit ions for a three-sensor array manifold to be ambiguity free and identi fied several higher order ambiguity situations. If an array is also ce ntral symmetric, the forward/backward SS (FBSS) can be used to improve the resolution. Finally, we extended our results to the estimation of signal parameters via rotational invariance techniques (ESPRIT). All the predicted results are verified by simulations.