Channel Estimation with Superimposed Pilot Sequence

For the purpose of various synchronization tasks (including carrier phase, time, frequency, and frame synchronization), one may add a known pilot sequence, typically a pseudo-noise sequence, to the unknown data sequence. This approach is known as a spread-spectrum pilot technique or as a superimposed pilot sequence technique. In previous work, we applied the superimposed pilot sequence technique for the purpose of channel estimation (CE) for single-carrier systems. We proposed and veriied a truly coherent receiver based on the Viterbi algorithm, which is optimal in the sense of per-survivor processing. We also suggested a generic low-cost receiver structure based on reduced-state sequence estimation. Here, we extend the receiver structure to cope with multi-carrier systems. Among the distinct advantages compared to conventional pilot-symbol-assisted CE are (i) a lack of bandwidth expansion and (ii) a signiicantly improved performance in fast fading environments.