On the Secure Performance of Intelligent Reflecting Surface-Assisted HARQ Systems

Abstract

This paper analyzes the physical layer security performance of hybrid automatic repeat request (HARQ) systems with the assistance of an intelligent reflecting surface (IRS) and aims to reveal the primary factors that enhance PLS. First, closed-form expressions for the connection outage probability (COP) and secrecy outage probability (SOP) in HARQ with chase combining (HARQ-CC) are acquired using the generalized-K (KG) distribution. Then, these two critical metrics are derived while adopting HARQ with incremental redundancy (HARQ-IR), resorting to the mixture gamma (MG) distribution and the Mellin transform. Diversity and coding gain are also addressed through an asymptotic analysis of the COP and SOP. Finally, an evaluation of the numerical results demonstrates that a greater gain in the main channel and the wiretap channel can be produced by increasing the number of meta-surfaces rather than increasing the maximum transmission number, except for the higher signal-to-noise (SNR) region of HARQ-IR where the latter is preferred. This finding provides a significant guidance for the joint configuration of IRS and HARQ to achieve secure communication.

Post-Cancellation-Based LLR Refining for MIMO Multiple ARQ Systems

“…This is because, for a large Q, ordering based on the current channel response becomes inaccurate for the retransmitted packets in CSHIC and the number of decoding iterations per outer iteration is insufficient to successfully decode the retransmitted packets by using the combined LLRs in CIHIC. Meanwhile, because the average PER is the multiplication of the average BLERs as shown in (10), the average BLER of a higher HARQ round has more effects on the average PER than the average BLER of a lower HARQ round [27]. Consequently, the average BLER characteristics in Figure 12 are similar to the average PER results in Figures 6 and 8 under the quasi-static fading channel.…”

“…The combined technique of forward error correction (FEC) and automatic repeat request (ARQ), hybrid ARQ (HARQ), is an essential technique in wireless communication systems [1][2][3][4][5][6][7][8][9][10][11]. When the wireless channel condition is poor, by jointly using FEC to improve the error correction capability without considering retransmissions, HARQ can reduce the number of retransmissions in comparison to ARQ.…”

“…[8] provided a contemporary survey of HARQ in wireless communications systems and standards. The joint use of variable-power allocation and HARQ for low-earth orbit satellite communication systems was investigated in [9], and the physical-layer security performance of HARQ systems with intelligent reflecting surface was studied in [10]. In [11], an adaptive HARQ scheme based on reinforcement learning for selecting the timing and frequency of retransmission was investigated.…”