Channel identification using known symbol guard intervals

Block transmission systems with guard intervals usually either use a cyclic prefix or introduce a sequence of zeros of length greater than or equal to an upper bound of the channel memory between blocks to prevent inter-block interference. Another possibility is to transmit known symbols in the guard interval. Although this has been considered before, the proposed channel identification algorithm was computationally intensive. We propose a simpler algorithm based on first order statistics. At the receiver, the channel is estimated by first computing the mean of the relevant parts of the received blocks. To enhance the performance at high signal-to-noise ratio, we combine the first order statistical algorithm with a simple iterative source-channel estimation algorithm. There is no extra loss of information rate as opposed to training sequence based methods for systems with guard intervals, no condition imposed on the channel and no scaling ambiguity as opposed to second (or higher) order statistical or finite alphabet-based methods. Just like zero guard intervals, known symbol guard intervals guarantee free inter-block interference and channel irrespective symbol detectability.