earticle

영어

In this paper, a multicast network in the presence of an untrusted relay is investigated. A three-phase AF-based cooperative jamming with power allocation is proposed to enhance the system secrecy rate. Based on time division based cooperative multicast (TDCM) protocol, the source uses part of its available power to broadcast pre-defined jamming signals in order to create interference at the untrusted relay, while the relay amplifies the linearly combined two received signals and then re-transmits it to the destination. Optimum power allocation policy involving the allocation between the information and jamming signals at the source and between two combined signal factors at the relay to maximize the achievable worse secrecy rate or sum-rate are derived and analyzed. Numerical results are provided to demonstrate our analytical results and reveal that compared with the two benchmarks schemes, the proposed scheme can obtain significantly higher positive secrecy rate for the same transmit power budget, especially in the case of maximizing secrecy sum-rate.