PHYSICAL CHANNEL ESTIMATOR

摘要

A physical channel estimator (30) for a communication system using pilot symbols and an equalizer (16) uses a model of the system in which the impuls e response of the physical channel (24) is considered separately from the impulse responses of the pulse shaping filters (22, 28) in the transmitter a nd receiver of the communication system. The system is modeled as if the signal s were propagated first through both pulse shaping filters (22, 28) and then through the physical channel (24). To estimate the physical channel impulse response, known pilot symbols are transmitted and then sampled. The pilot symbol samples and the known impulse responses of the pulse shaping filters (22, 28) are then used to estimate the physical channel impulse response. In one embodiment, the physical channel impulse response is considered time- invariant over the estimation period and a sufficient number of pilot symbol samples are taken so that the system is overdetermined. A least squares meth od is then used to estimate the physical channel impulse response from the pilo t symbol samples and the known responses of the pulse shaping filters (22, 28) . Further refinements include conditioning the estimated physical channel impulse response to improve performance in low SNR conditions and estimating a DC offset incurred from demodulating the received signal.