Interpolated Channel Estimation for Mobile OFDM Systems

In an OFDM system using pilot cells for channel estimation, time interpolation among pilot cells of different OFDM symbols is commonly used to improve the estimate. The estimated channel impulse response is also windowed to further reduce noise and disturbances. However, for a transmission over a time-varying channel, suboptimal time interpolation, implemented with a filter having only a few taps not matched to the maximum Doppler frequency, degrades channel estimation. As aliases can lead to an erroneous estimate of channel duration and consequent errors in windowing, the present invention implements a technique to detect aliases and correct the estimate of channel duration. Parameters of the detection techniques are optimized by an analysis that provides closed-form expressions of the false alarm and miss detection probabilities.