Phased array multipath detection: Power delay profile vs. information theoretic criteria

For a realistic outdoor propagation scenario, there are often many multipath components, perhaps more than an array can successfully resolve. An N element array is only capable of resolving N - 1 different signals. Information theoretic criteria are expected to become more accurate as the number of samples increases; however, in this case increasingly large sample windows saturate the array. This may be due to multipath components that arrive simultaneously, but from different directions. Beamforming the array to particular spatial clusters may allow finer PDP measurements as well as reducing the number of signals in that particular beamspace; further research is required. Waveforms that are close enough in time such that they are not separable in delay may be distinguishable in space, which would lead to disagreement between PDP detection and algorithms like MDL or AIC. Steering the array toward different incoming signals and performing subsequent delay spectrum measurements could indicate if this is occurring. Covariance matrices can also be calculated after despreading; however, the capture time was not long enough to record enough despread symbols. Further work with longer capture times (or shorter PN sequence lengths) may be warranted.