Eavesdropping-Resistant Space-Time Network Coding for Cooperative Communications

Due to the broadcast nature, wireless transmissions can be overheard by any receiver within the transmission range. A physical layer approach for secure wireless cooperative communications is proposed in this paper. Considering the asynchronous nature of cooperative communications, this paper proposes an eavesdropping-resistant space-time network coding (STNC) scheme for cooperative communications to prevent eavesdropping and overcome the problem of imperfect synchronization. In the proposed scheme, training symbols are transmitted by the destination D instead of the user nodes. Therefore, based on the assumption of channel reciprocity, each user node can obtain the channel state information (CSI) between itself and D, which is unavailable to the eavesdropper E. Weighting coefficient is designed by exploiting such CSI at each user node to prevent E from interception and ensure successful decoding at D. Based on the pairwise error probability (PEP) analysis, STNC is designed to achieve full diversity at D and improve the transmission efficiency of the asynchronous cooperative system. Simulation results are presented to verify the performance of the proposed eavesdropping-resistant STNC scheme.