Optimum pilot placement for chunk-based OFDMA uplink: Single chunk scenario

In this paper, we investigate the optimum pilot placement for the chunk-based OFDMA uplink. The proposed scheme is optimized for the single-chunk scenario, i.e., the channel estimation is carried out for each individual chunk, and the channel estimator is based on the least-square linear interpolation. Unlike the state-of-the-art optimum pilot placements, the proposed scheme takes into account the impact of modeling mismatch in addition to the noise. It is established that the optimum pilot placement for the large-SNR range should minimize the impact of the modeling mismatch. The optimum pilot spacing along the frequency direction is 1/root 3 of the chunk bandwidth. The pilot spacing should be increased (up to the chunk width) with decreasing the signal-to-noise ratio. Computer simulations are provided, and show a good match with the analytical result.