Low-complexity coherent RAKE combining with a Kalman phase tracker

RAKE combining at high symbol rates f_sym is addressed. A scheme designed for such implicitly low normalized Doppler (f_dn =f_d/f_sym) multipath channels and for reception with a carrier frequency offset δ·f_sym is presented. The phases of the different paths are estimated using what we refer to as Kalman phase tracking (KPT). This closed loop estimator employs decision feedback to remove the data dependency in the received signal and a multi I/O Kalman filter to track the phases, In addition, the KPT performs carrier frequency estimation and compensation. The results from simulations of two different 3-branch, time-invariant AWGN channels and three values of δ show that near-optimal bit error rates can be achieved but that the receiver in its present form requires a post-detection differential decoder in order to become completely reliable