Adaptive DF Relaying Transmission for Security

This paper comprehensively studies the secure decode-and-forward (DF) relaying transmission in slow fading channels. To maximize the secrecy throughput under a secrecy outage probability constraint, we propose three adaptive transmission schemes (ATSs) with different complexity and flexibility, and design system parameters according to the instantaneous channel state information of the legitimate receiver. Specifically, in ATS-SW, source and relay use the same codeword, and eavesdropper employs the maximal ratio combining (MRC) reception; whereas in ATS-DWSR and ATS-DBDR, the source and relay either use independent codewords with identical code rates, or different codebooks with different code rates so that the eavesdropper can only decode the two-hop signals individually instead of MRC method. For all the three ATSs, we provide explicit solutions on the optimal system parameters, including the resource allocation between the source and relay, and the code rates. We also present numerical results and comparisons on the secrecy throughput of these schemes.