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 multinode 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, each user node can obtain the channel state information (CSI) between itself and $D$, which is unavailable to the eavesdropper $E$. By exploiting such CSI and the transmit information symbols, weighting coefficient is designed 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.