Channel estimation for systems with pll phase discontinuities

Abstract

Channel estimation performance depends on the amount of averaging performed by a channel impulse response coherent filter. For half-duplex UEs, which use a single phase locked loop (PLL) for both downlink transmissions and uplink transmissions, averaging may not be performed across downlink subframes before and after uplink subframes if the PLL's phase changes and locks to a random initial value when switching transmission directions. Techniques disclosed herein facilitate estimating the PLL's random initial phase and enable correcting the phase of symbols accordingly. By correcting the phase of the symbols, it is possible to average across symbols before and after a frequency re-tune and/or a transmission direction switch based on the phase correction. This may serve to improve the accuracy of channel estimation. Further techniques disclosed herein may improve the accuracy of Doppler estimations by enabling the inclusion of symbols before and after a frequency re-tuning when performing the Doppler estimation.