Pilot-assisted channel estimation has been studied only in common cooperative AF (Amplify-and-Forward) OFDM which has no feedback mechanism. In this paper, for cooperative AF-OFDM system, we propose a feedback technique in which the pilot allocation mechanism is adapted to the cooperative mobile channel. Then we show how uniform pilots may no longer be optimal compared with our pilots. After deducing the instantaneous system SNR is the function of the pilot allocation, we optimize the pilot

more »

... tions using optimization method at the destination node. We examine the feedback overhead that is associated with our method and make comparisons with the conventional uniform pilot allocation. To improve system capacity, we suggest reduce the feedback information using K-means clustering algorithm. Simulation results confirmed that the proposed optimization method has an ideal performance gains and the algorithm of feedback reduction can reduce the feedback information under the premise of ideal performance.