Secrecy Performance Analysis of Multi-Tag Bistatic Backscatter Communication Systems With Outdated CSI and Link Correlation

LIU Yingting; TANG Yong; LI Xingwang

doi:10.11999/JEIT260823

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LIU Yingting, TANG Yong, LI Xingwang. Secrecy Performance Analysis of Multi-Tag Bistatic Backscatter Communication Systems With Outdated CSI and Link Correlation[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260823

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LIU Yingting, TANG Yong, LI Xingwang. Secrecy Performance Analysis of Multi-Tag Bistatic Backscatter Communication Systems With Outdated CSI and Link Correlation[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260823

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Secrecy Performance Analysis of Multi-Tag Bistatic Backscatter Communication Systems With Outdated CSI and Link Correlation

doi: 10.11999/JEIT260823 cstr: 32379.14.JEIT260823

1.
School of Electronic and Information Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
2.
School of Physics and Electronic Information Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Funds: The National Natural Science Foundation of China (No.62561037, No.62571182), Key Project of Gansu Provincial Natural Science Foundation (No. 26JRRA058), The Youth Doctoral Support Project of Gansu Provincial Department of Education (No. 2024QB-045), Henan Provincial Natural Science Foundation (No.252300421510)

Received Date: 2026-06-18
Accepted Date: 2026-07-29
Rev Recd Date: 2026-07-13

Available Online: 2026-08-08

Abstract

Abstract

Objective Due to feedback delay, the channel state information (CSI) used in the tag selection phase may become outdated during the actual data transmission phase, leading to a mismatch between the selected tag and the actual optimal tag. Meanwhile, most existing studies on outdated CSI are based on the independent and identically distributed (i.i.d.) channel assumption, which may fail to accurately reflect the heterogeneous characteristics of practical links caused by different propagation distances. In addition, when the eavesdropping node is close to the destination, the legitimate and eavesdropping links may experience correlated fading. Ignoring these factors may lead to theoretical results that deviate from the actual system performance. Accordingly, under independent and non-identically distributed (i.n.i.d.) channel conditions, this paper studies the secrecy performance of a multi-tag BBC system subjected to the joint impact of outdated CSI and the correlation between the legitimate link and the eavesdropping link. Methods In this paper, candidate tags are ranked by their backscatter-link channel gains, and the tag with the largest gain is selected for transmission. An outdated CSI model is introduced to characterize the mismatch between the CSI used for tag selection and the actual CSI during data transmission. Since tag selection depends only on the backscatter-link CSI, outdated CSI is modeled only for this link. Meanwhile, a correlated Rayleigh fading model is adopted to capture the statistical dependence between the legitimate and eavesdropping links. Under i.n.i.d. Rayleigh fading, order statistics are used to derive the PDF of the selected tag’s outdated backscatter-link channel gain in (30)–(36) and the joint PDF of the legitimate and eavesdropping channel gains in (10)–(13). Based on these results, closed-form and high-transmit-power asymptotic expressions for the secrecy outage probability are obtained, and the secrecy performance is analyzed in terms of the gain ratio between the legitimate and eavesdropping links. Results and Discussions Monte Carlo simulations validate the analytical and asymptotic results. The results show that outdated CSI significantly degrades secrecy performance, as feedback delay may cause the CSI used for tag selection to differ from the actual CSI during transmission, so the selected tag may no longer provide the largest backscatter-link gain. For a fixed gain ratio between the legitimate and eavesdropping links, a secrecy outage floor emerges at high transmit power (Fig. 2), indicating that increasing transmit power alone cannot eliminate the performance bottleneck. In contrast, increasing the gain ratio effectively mitigates this floor and enables a secrecy diversity order of 1 (Fig. 4). Meanwhile, under the considered system model, correlation between the legitimate and eavesdropping links also improves secrecy performance (Fig. 3) by reducing the likelihood that the legitimate link experiences deep fading while the eavesdropping link remains strong. Moreover, despite outdated CSI, the proposed gain-order-based tag selection scheme remains effective and consistently outperforms random tag selection (Fig. 3). Conclusions This paper develops a secrecy-performance analysis framework for multi-tag BBC systems with outdated CSI and correlated legitimate and eavesdropping links. Closed-form SOP and high-transmit-power asymptotic expressions characterize the effects of CSI outdated, link correlation, and the legitimate-to-eavesdropping gain ratio. The results identify outdated CSI as a major source of secrecy degradation, highlighting the need for low-latency feedback. Enhancing the legitimate-link gain advantage and employing backscatter-link gain-based tag selection effectively improve system secrecy performance.
- Correlated Fading,
- Outdated Channel State Information,
- Backscatter Communication(BackCom),
- Secrecy Outage Probability (SOP)

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References(23)

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