Sparsity-aware, Channel Order-Blind Pilot Placement with Channel Estimation in Orthogonal Frequency Division Multiplexing Systems.

Equispaced pilot arrangement is the most popular scheme for pilot-aided transmission in orthogonal frequency division multiplexing systems. In this study, the authors argue that a non-equispaced pilot pattern may outperform its equispaced counterpart, if they fully take into account the sparsity of the channel impulse response which is inherent in wireless channels. More specifically, a sparsity-aware pilot arrangement scheme based on the coherence criterion is investigated in this study. To address the resulting non-deterministic polynomial (NP)-hard combinatorial optimisation problem, they propose an efficient local search algorithm. For channel estimation, they convert it to a sparse recovery problem. To enhance the applicability of the authors scheme, that is, when there is no prior knowledge about the channel order, they propose to employ the Bayesian information criterion to estimate the channel order first and then recover the sparse channel vector via existing low-complexity methods, for example, orthogonal matching pursuit. By combining the above pilot arrangement scheme with channel estimation, their scheme exhibits substantially better performance in comparison with the conventional equispaced schemes with linear (or spline) interpolation, in terms of total number of pilot symbols and bit error rate.