Abstract
In this paper, we studied the secure transmission of a hybrid automatic repeat request with chase combining (HARQ-CC) system, under the existence of multiple eavesdroppers and limited latency. First, we analyzed some critical performance metrics, including connection outage probability (COP), secrecy outage probability (SOP) and effective secrecy throughput (EST). Then, to maximize the EST, three optimization problems of rate adaption were discussed: (i) optimizing the code rate with a given secrecy redundancy rate by a parameterized closed-form solution; (ii) optimizing the secrecy redundancy rate with a given code rate by a fixed-point method; (iii) optimizing both code rate and secrecy redundancy rate by an iterative optimization algorithm. We also considered COP and SOP constraints among the problems while corresponding solutions were deduced. Finally, numerical and simulated results verified our conclusions that the approximated SOP matches well with Monte–Carlo simulation for a strict reliable constraint, and that the optimized transmitting rate enhances EST efficiently with multiple eavesdroppers and retransmissions. Moreover, the influence of the number of eavesdroppers on secrecy performance was analyzed. Briefly, secrecy performance inevitably deteriorates with increasing number of eavesdroppers due to raised information leakage.
Highlights
In modern wireless communication systems, physical layer security (PLS) is regarded as a critical aspect in providing confidential message transmission according to the characteristics of wireless channels
In order to improve the performance of secure transmission when multiple eavesdroppers exist and latency is limited, we optimized the code rate R B and secrecy redundancy rate R E to maximize the effective secrecy throughput (EST) of hybrid automatic repeat request with chase combining (HARQ-CC)
secrecy outage probability (SOP) monotonically decreases with increasing R E, which means that security will be enhanced by more secrecy redundancy
Summary
In modern wireless communication systems, physical layer security (PLS) is regarded as a critical aspect in providing confidential message transmission according to the characteristics of wireless channels. In our previous work, we extended the effective secrecy throughput (EST) of a single transmission [25] into a HARQ-CC system with a passive eavesdropper, and optimized secrecy redundancy rate for improved security [26]. Another common scenario, which includes multiple eavesdroppers, rate adaption and limited latency, has not yet been analyzed. When the code rate is given, the optimization problem of secrecy redundancy rate with EST criteria was analyzed We solved this problem by applying a fixed-point method, with and without the SOP constraint.
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