Secrecy Rate Maximization for Symbiotic Radio Network with Relay-Obstacle

The idea that everything can communicate with each other with high bit rate and low latency is the main goal for next generation communication systems. In this context, allocating spectrum resources and providing energy to each device that can communicate is a big problem. In order to develop different techniques in this regard, symbiotic radio networks (SRNs) have been proposed in the literature. In SRN, devices transmit information to the same receiver by using the communication infrastructure together. However, this situation may create a security problem. In this paper, SRN with relay-obstacle is proposed to test physical layer security (PLS). This model is the first approach that maximizes the secrecy rate of SRN by using the ambient radio frequency resource in the presence of relay-obstacle. There are two different clusters in the system model and each cluster contains a device, a relay and an obstacle. An eavesdropper (ED) overhearing to the signals transmitted by the relays and is blocked by a cooperative jammer. The proposed system model is mathematically modeled and the secrecy rate expression is maximized over the time parameters. In the numerical analysis, the advantages of using the channel symbiotically compared to the nonsymbiotic scenario where the energy harvest-then-transmit (HTT) protocol is used in the literature are evaluated in terms of the reflection coefficient, noise power, signal transmission power and quality of service (QoS) of the devices and its superiority is revealed.