Abstract
In this paper, we investigate secure communication for a dual-hop multiuser relay network, where a source communication with N ( N ≥ 1 ) destinations via an untrusted variable gains relay. To exploit multiuser diversity while protecting source’s confidential message, we first propose a joint destination-based jamming and opportunistic scheduling (DJOS) scheme. Then, we derive closed-form approximated and asymptotic expressions of the secrecy outage probability (SOP) for the considered system with DJOS. Furthermore, we determine an asymptotical optimal power allocation (OPA), which minimizes the asymptotic SOP, to further improve the secrecy performance. Our analytical results show that the achievable secrecy diversity order in terms of SOP with fixed power allocation is min ( 1 , N 2 ) , whereas, with OPA, the achievable secrecy diversity order can be improved up to min ( 1 , 2 N N + 2 ) . This interesting result reveals that OPA can improve the secrecy diversity order of the single-user network. This is intuitive since full diversity order of 1 cannot be achieved when N = 1 , thus leaving some space for OPA to improve the diversity order. Nevertheless, for N ≥ 2 , the effect of OPA is to increase the secrecy array gain rather than the secrecy diversity order since full diversity order 1 has been achieved by the OS scheme. Finally, simulation results are presented to validate our analysis.
Highlights
IntroductionThere are extensive works aimed at enhancing the secrecy performance of cooperative relaying networks by exploiting various physical layer security (PLS) approaches, such as diversity techniques and/or cooperative jamming
We describe the opportunistic scheduling scheme, which aims at exploiting the multiuser diversity inherent in the considered multiuser relay networks as well as guaranteeing the system to achieve the optimal secrecy performance
We can see that the multiuser diversity (MUD) gain is harvested in the form of decreased secrecy outage probability (SOP) and increased secrecy diversity order, as N increases from 1 to 2
Summary
There are extensive works aimed at enhancing the secrecy performance of cooperative relaying networks by exploiting various PLS approaches, such as diversity techniques and/or cooperative jamming. Diversity techniques, such as multiple-input multiple-output (MIMO) [1], cooperative diversity (i.e., cooperative relaying) [2], and multiuser diversity [3,4], aim at increasing the capacity of the main channel while degrading that of the wiretap channel. Cooperative jamming (CJ) [5,6,7,8,9,10], which exploits artificial noise to confuse external eavesdroppers, can reduce the leakage rate to the eavesdroppers to improve the system security. Power allocation technique was investigated in [12,13] to further improve the secrecy performance
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