Research On Secure Communication And Power Allocation In Untrusted Relay Networks

With a growing demand for high spectrum utilization and low energy consumption of data transmission in wireless communication systems,cooperative communication technologies based on relay nodes have attracted rising attention.In the research of physical layer security for wireless communication,the main concern on relay transmission is the trustworthiness of relays.The physical layer security transmission strategy based on cooperative interference in untrusted relay networks is studied and the main work of this dissertation can be summarized as follows:For the one-way untrusted relay system based on energy harvesting,a cooperative interference secure transmission protocol is proposed where the amplify-and-forward protocol and the time-switched energy harvesting protocol are adopted in the relay.The necessity of introducing cooperative interference signals is demonstrated in the one-way untrusted network.The mathematical expressions of the secrecy rates and the outage probabilities of one-way untrusted relay networks are derived analytically.To maximize the secrecy rates of the one-way untrusted relay networks,a joint power allocation and time switching scheme is designed.The closed-loop optimal solution to cooperative interference power allocation is derived,and the optimal time switching factor is given with the interior-point method.Finally,the proposed cooperative interference strategy and the time switching scheme are simulated and analyzed.For the two-way untrusted relay communication system under imperfect channel state information,a two-way cooperative interference strategy with self-interference introduced into each source node is suggested.Firstly,the expression of the secrecy capacity for the system in the suggested strategy is derived.To maximize the secrecy capacity under given power constraints,the power allocation problem between the expected signal transmit power and the interference signal transmit power of the two source nodes is investigated.The iterative power allocation algorithms under total power constraints based on interior point method and genetic algorithm are provided.The closed-loop optimal solution to power allocation under independent power constraints is obtained.Meanwhile,to compare the security performance of the transmission strategies,the non-cooperative interference strategy and the one-way cooperative interference strategy are investigated.Simulation results indicate that the security performance of the system with two-way cooperative interference strategy is better than that of its comparison schemes.