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Optimal training design and placement for channel estimation in cooperative networks

In this paper, optimal training design and placement are studied for channel estimation in a frequency selective, single relay, amplify and forward cooperative system. Using a two-phase transmission protocol, the power distribution between the phases, among the pilot tones as well as the positioning of pilot tones within the transmitted OFDM symbols are examined. The LMMSE and two variants of the LS estimator are analyzed and the optimal training design and placement strategies are derived. Closed-form expressions are derived for the minimum achievable MSE in each case, which are precisely verified through simulations.