Polarization estimation of individual propagation paths using the SAGE algorithm

This contribution describes an extension of the ISI-SACR (initialization-and-search-improved space-alternating generalized expectation maximization) algorithm originally published in [B.H. Fleury, et al., 2001] and [2002] to include polarization estimation. The proposed scheme allows for joint estimation of the relative delay, the direction (i.e. azimuth and co-elevation) of departure, the direction of incidence, the Doppler frequency and the complex polarization matrix of propagation paths between the transmitter (Tx) site and the receiver (Rx) site in mobile radio environments. This contribution presents the initialization procedure of the extended ISI-SAGR algorithm and discusses necessary and sufficient conditions regarding the responses of multiple-element Tx and Rx arrays for the system consisting of these two arrays to be able to estimate all coefficients of the polarization matrix. Experimental investigations in a line-of-sight microcellular environment illustrate the application potential of the ISI-SACR algorithm for gaining insight into the polarization states of individual paths. This information is of paramount importance for the design of stochastic and prediction models ut the radio channel for communication systems equipped with multiple Tx and Rx dual-polarized antennae.