Abstract
Relay identification is necessary in many cooperative communication applications such as detecting the presence of malicious relays for communication security, selecting the intended relays for signal forwarding, and tracing a specific relay. However, this identification task becomes extremely challenging for amplify-and-forward (AF) relaying systems since AF relays usually have no capability of adopting traditional identification methods implemented above the physical layer. This paper proposes a physical-layer AF relay identification scheme based on the exploitation of the device-specific in-phase and quadrature-phase imbalance (IQI) feature. Given that IQI estimation is mandatory in most present receivers for compensation, it is cost-effective to make use of these estimation results for fingerprinting AF relays. A generalized likelihood ratio test-based fingerprint differentiation technique is adopted to detect the minor difference between two range-limited IQI fingerprints. Using this differentiation technique, a whitelist-based identification algorithm consisting of fingerprint registration, update, and identification is proposed. Furthermore, the optimal training signals that lead to the maximal detection probability are derived for the typical quadrature amplitude modulation and phase-shift keying modulation schemes. The simulation results validate our derivations and confirm that the proposed method can accurately identify AF relays.
Highlights
Relaying technique is a promising part of 5G and beyond cellular networks since it works toward broadening the communications coverage area, improving the communication reliability, and increasing the throughput of the network
A cross-layer decode-and-forward relay identification was investigated in [8], this method cannot be applied to amplify-and-forward (AF) relay identification since AF nodes only work in the physical layer without any content modifications to the forwarded signals
This paper proposes an accurate AF relay identification method using physical-layer in-phase and quadrature-phase imbalance (IQI)-based fingerprinting without the aid of any upper-layer identification technique
Summary
Relaying technique is a promising part of 5G and beyond cellular networks since it works toward broadening the communications coverage area, improving the communication reliability, and increasing the throughput of the network. A cross-layer decode-and-forward relay identification was investigated in [8], this method cannot be applied to amplify-and-forward (AF) relay identification since AF nodes only work in the physical layer without any content modifications to the forwarded signals. This implies that all existing upper-layer identification methods are not applicable to the case of AF relaying, resulting in the need to fingerprint AF relays in the physical layer. Hao et al EURASIP Journal on Wireless Communications and Networking imperfection estimations are usually mandatory for signal reception, and it is cost-effective to use these estimation results for wireless transmitter identification
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