Fast phase acquisition receiver for LEO communications in Rician channels

We propose an open-loop receiver that performs simultaneous channel state estimation and symbol detection in frequency-flat, fast-fading Rician channels affected by large Doppler frequency shifts. This structure includes a Kay (1989) frequency estimator, a bank of nonlinear filters (one for each symbol of the M-ary alphabet) and a symbol decision algorithm. The nonlinear filters estimate the channel state, the errors produced by the Kay estimator, and provide the innovations processes for the symbol detection. This estimation/detection structure exhibits fast phase/frequency acquisition capability which is essential in burst transmissions or with fading channels. The receiver is able to cope with large frequency deviations that are typical in LEO/MEO communication systems