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Optimal training design for channel estimation in OFDM/OQAM cooperative systems

Channel estimation in OFDM/OQAM-based cooperative systems is considered in this paper. Cooperation is based on a single AF relay, and a well established two-phase protocol is adopted for its operation. The problem of optimally designing the preambles in the two phases is investigated for LS channel estimation, where optimality is in the sense of minimum MSE subject to a transmit energy constraint. Optimal conditions are derived for the energy allocations and positions of the pilot symbols. Equalization is also considered, where a relay-induced interference term is identified at the destination node. A simple cancellation procedure is proposed and evaluated. Simulation results are reported that corroborate the analysis and provide a comparison with the corresponding CP-OFDM system.