Optimized Pilot Placement for Sparse Channel Estimation in OFDM Systems

Compressed sensing (CS) has recently been applied for pilot-aided sparse channel estimation. However, the design of the pilot placement has not been considered. In this letter, we propose a scheme using the modified discrete stochastic approximation to optimize the pilot placement in OFDM systems. The channel data is employed to offline search the near-optimal pilot placement before the transmission. Meanwhile we also get a criterion to select CS algorithms based on the mean squared error (MSE) minimization. Simulations using a sparse wireless channel model have validated the effectiveness of the proposed scheme, which is demonstrated to be much faster convergent and more efficient than the exhaustive search. It has been shown that substantial performance improvement can be achieved for OMP and YALL1 based channel estimation, where YALL1 is preferred.