Dynamic Time Allocation Based Physical Layer Security for Jammer-Aided Symbiotic Radio Networks

Symbiotic Radio Networks (SRNs) have emerged as an important communication protocol to solve the increasing energy demand and spectrum resource shortage. However, the low bit rates of the devices working in SRNs during backscatter communication, where the surrounding radio frequency resources are used by subsystems different from the main system, make SRNs very vulnerable to external attacks such as eavesdropping and jamming. To solve this problem, the Physical Layer Security (PLS) for SRNs with Signal Emitter (SE), user, jammer, receiver and eavesdropper (ED) is analyzed. While the SE conveys its information to the receiver, the user assists the SE in part of the time period and transmits its information to the receiver in the other part. While ED is overhearing SE and user's information over the wiretap channel, the jammer is trying to prevent ED with the signal it emits. This model, in which the secrecy rate is maximized over time parameters, is the first approach in which PLS analysis is carried out in the presence of a cooperative jammer when the perfect/imperfect Successive Interference Cancellation (SIC) technique is used at the receiver. Numerical results show that the existence of a symbiotic relationship between the user and the SE increases the secrecy rate of the system compared to the non-symbiotic situation. Moreover, adopting the perfect SIC technique at the receiver without energy constraint at the user resulted in a significant increase in PLS performance compared to the imperfect SIC under energy constraint.