Guard sequence optimization for block transmission over linear dispersive channels

We show that the optimum length-ν guard sequence for block transmission over a linear, noisy, and dispersive channel with memory ν is a linear combination of the N information symbols of the block. The channel block throughput is maximized through a joint numerical optimization of Nν linear combination coefficients determining the guard sequence and the N-dimensional auto-correlation matrix of the information symbols, subject to a total average energy constraint on the information and guard symbols. A closed-form solution for the optimum guard sequence is derived for the special case of high SNR. The achievable channel block throughput with the optimum guard sequence is compared with that achievable with two common guard sequence types, namely zero stuffing and cyclic prefix