Abstract:

In amplify-and-forward (AF) orthogonal frequency division multiplexing (OFDM)-based coope-rative network, to acquire channel state information (CSI) of different links efficiently, channel estimation scheme based on combined superimposed training is proposed. In the new scheme, different pilots are superimposed onto the transmitted data at source nodes and relay nodes respectively while channel estimation of cascaded link (S→R→D)and single-hop link (R→D)are achieved at destination nodes using source pilots and relay pilots. In order to eliminate the severe interference for channel estimation induced by data sequence in the superimposed pilots scheme, a data-nulling superimposed pilots (DNSP) method with pre-processing at the transmitter is proposed for source pilots design. Moreover, a novel cooperative interference cancelation (CIC) method is employed for relay pilots design. The degradation on performance of R→D channel estimation induced by cooperative data is canceled with the detected symbols from S→D link while the information distortion is compensated and detecting performance is improved using iterative reconstruction. Simulation results are provided that the proposed scheme can eliminate the spending of bandwidth for pilots and approach the detecting performance of traditional frequency division multiplexing (FDM) schemes.