Proactive Eavesdropping via Jamming for Multichannel Decode-and-Forward Relay System

This letter studies the proactive eavesdropping in a suspicious decode-and-forward relay system, where the suspicious communication is divided into transmitter-to-relay (ST-SR) phase and relay-to-destination (SR-SD) phase with partial channel selection over <inline-formula> <tex-math notation="LaTeX">$N \ge 2$ </tex-math></inline-formula> orthogonal channels, and the monitor (E) can only jam/overhear the E-SR/SR-E link over <inline-formula> <tex-math notation="LaTeX">$M \le N$ </tex-math></inline-formula> sub-channels for practicality. Under this framework, with strict proof we first theoretically present the impact of jamming power and number of jamming channels selected by E on its eavesdropping success probability (ESP), and then reveal a fundamental trade-off: given jamming power (number of jamming channels), jamming with more channels (power) reduces the suspicious rate for E to overhear more clearly, but degrades the preconditions for successful eavesdropping. Results verify our obtained conclusions and show that the proposed jamming-assisted eavesdropping scheme with simple search method achieves pretty good performance compared with some intuitive schemes.