Date Added: Nov 2010
In wireless Orthogonal Frequency Division Multiplexing (OFDM) systems, the time-varying channel is often estimated by algorithms based on pilot symbols. Such an estimator, however, requires statistical prior knowledge that is not easily obtained. Therefore, the pilot tones have to be close enough to fulfill the sampling theorem. In this case the statistical knowledge of the channel is not required to reconstruct correctly the Channel Impulse Response (CIR). This paper explores the optimal placement and number of pilot symbols, the authors investigate optimal training sequences in OFDM systems and the authors analyze the number of pilot symbols required to fulfill the sampling theorem.