Improved channel duration estimate for mobile OFDM systems

Channel estimation for OFDM system using pilot carriers usually comprises time interpolation of the estimates across more OFDM symbols and then frequency interpolation. In order to improve estimate, the frequency response can be transformed into the time domain and windowed. To this end, an estimate of the channel duration is necessary and this process is particularly sensitive to the time interpolation process. In fact, for a transmission over a time-varying channel, if the time interpolation of the pilot estimates is not accurate, aliases arise in the estimated channel impulse response, thus affecting the channel duration estimate. We propose a technique to detect aliases and correct the estimation 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. Numerical results show the merits of the proposed techniques in a mobile transmission of the terrestrial digital video broadcasting standard (DVB-T).