Frequency offset estimation for wireless systems based on channel impulse response

摘要

In a receiver, a received sync-word is fed into two or more filters, where each filter further comprises a matching filter and a sidelobe reduction filter. Each matching filter is matched to a particular subset of k samples of the known sync-word, e.g., k=3, and generates an m-tap estimate, where m≧2. The output signal of each matching filter is applied to a respective sidelobe filter, which reduces sidelobes resulting from the imperfections of matching the received sync- word in the matching filters. As a result, from each received sync-word, each filter forms a channel impulse response estimate of the communications channel at more than one symbol time. Each channel impulse response estimate comprises the amplitude as well as the phase of the channel impulse response. Since the channel impulse response does not change drastically from one symbol time to one or a few symbol times later, the next channel impulse response estimate comprises the same amplitude information but a different phase information. This difference in phases between the two channel impulse response estimates, aside from noise and other anomalies, is mainly due to the frequency offset. As a result, an estimate of frequency offset is easily derived from this phase difference.