Energy-efficient Secure Relay Selection In Cooperative Relay Network

Over the last decade, cellular network market is growing at an alarming rate. Large demands for wireless equipments and services have been resulting in a substantial increase in the energy consumption of wireless communication technology and CO2 emissions. Meanwhile, it is necessary to control the energy consumption and reduce carbon emissions due to limited battery capacity. On the other hand, wireless communication is extremely vulnerable to eavesdropping attack due to the broadcast nature of wireless medium. Traditional methods to improve the security of wireless commutations are to encrypt the information in the network layer, but it is difficult to ensure security of system by using traditional methods due to the rapid increase in computer power of smart devices. Therefore, physical layer security which can take advantage of the wireless channel features to improve the security of the digital communication systems has attracted a widespread attention. Therefore, energy efficiency and physical layer security both are important issues for future communication networks.This paper proposes energy-efficient relay selection techniques for secure cooperative networks under constraints of communication reliability and physical layer security. We derive the relay selection rules for minimizing the total system power in amplify-and-forward(AF) and decode-and-forward(DF) protocols, respectively. We define the reliability and security outage probability(RSOP) as a measure of the system performance, and derive its closed-form expressions for numerical evaluations of the proposed technique for both AF and DF protocols. We also provide Monte Carlo simulation results to validate the energy efficiency and RSOP performances for the technique.The results show that:(1) The proposed energy-efficient secure AF and DF relay selection schemes can achieve substantial gains in both power consumption of total system and RSOP performance compared with the direct transmission scheme.(2) The threshold-based constraints have proved much stricter than the conventional secrecy capacity for physical layer security. So that proposed energy-efficient secure AF and DF relay selection schemes can ensure the security of the information transmission.(3) For the proposed energy-efficient secure DF relay selection scheme, as long as the source transmit power satisfies the reliability constrain on the link between the source and any specific relay, it has the same expressions as that of the proposed energy-efficient secure AF relay selection scheme for the optimal relay selection and generalized optimal relay selection.(4) It is worth mentioning that the system performance in both energy efficiency and system security can be improved substantially by increasing the number of relays, which is essentially based on the topology of the relay network relative to the eavesdropper.