Improved multipath resolution using joint space-time maximum likelihood estimation

Multipath propagation is a phenomenon that occurs in many frequency bands. The multipath components can arrive with different angles of arrival and frequency shifts. We present the first results obtained through the use of the space-time 2D-DOSE algorithm. We show that it is capable of resolving the multipath components received at an antenna array in terms of their azimuth, elevation and frequency offset from the transmitted carrier frequency. This is demonstrated for two different multipath scenarios, one corresponding to ionospheric propagation at HF and the other to cellular mobile radio. To process the latter, a particularly fast FFT based version of the 2D-DOSE algorithm is employed. The basis of this joint estimation method is that both direction of arrival (DOA) and frequency are estimated together rather than making independent estimates of each. This approach has significant advantages.