High resolution of electromagnetic waves in time-varying radio channels

The applicability of the SAGE (space-alternating generalized expectation-maximization) algorithm to the estimation of time variant radio channels is demonstrated. This algorithm allows one to separate the complex multi-dimensional optimization problem required to compute the estimate of the parameters characterizing the impinging waves, i.e. their delay, incidence azimuth, Doppler frequency, and complex amplitude, into separate one dimensional optimization processes that can be performed sequentially. The performance of the scheme, i.e. its convergence behavior and its accuracy, is investigated in synthetic and real channels.