Research And Performance Analysis Of Physical Layer Security Of The Cooperative Relay Network

With the increasing of the communication quality requirements,raising the communication rate while ensuring system security has become an important research area of mobile communication technology. Cooperative relay technology has several advantages, such as enhancing the capacity of the system, expanding the coverage of the signal, and reducing the transmit power of source, which has become a hotspot of contemporary studies and one of the key technologies of wireless communications in the future. However, more open wireless network resources and more complex structures in cooperative relay wireless communication network systems bring more challenges to the communication security. Physical layer security technology utilizes the spatial characteristics of the wireless channel to protect the security of communications directly from the physical layer. There are problems when existing literature analyze the security performance of cooperative relay network: in a more realistic cooperative relay communication scenario, it is difficult for each node to obtain the perfect channel state information, which brings more troubles to the design of the security transmission scheme; meanwhile, existing literature has not taken security and reliability of the system into account at the same time, which makes the evaluation of system performance not comprehensive or rational.In this paper, we considered a more realistic communication scenario and designed an efficient transmission scheme with low complexity. Firstly, we proposed an untrusted relay system model using limited feedback technology while the transmitter only knows the partial channel state information of the legitimate channel. This model ensures the communication security by transmitting artificial noise at the destination node and executing self-interference cancellation while receiving information. Secondly, we studied the performance characteristics of the physical layer security in the untrusted amplify-and-forward relay system and derived the closed-form expressions of related security standard. Moreover, through theoretical research and Matlab simulation we analyzed the impact of limited feedback technology on the security and reliability of the system, and deduced the monotonicity of security outage probability and transmission outage probability about the feedback bits and the number of transmit antennas. As a conclusion, an adaptive selection scheme for the optimal number of feedback bits is proposed in order to simultaneously satisfy the requirements of both security and reliability.Our results proved: that, the amplify-and-forward untrusted relay system obtains a positive secrecy capacity through artificially transmitting noise interference information by the destination node under the condition of partial channel state information that is obtained from limited feedback; With the increase of the number of feedback bits, security outage probability increases monotonically with system security becoming worse, and transmission outage probability decreases monotonically with system reliability becoming better; By setting a reasonable threshold of SINR and selecting an appropriate number of feedback bits, the security of the system can be maximized and the reliability of the system can also be ensured. Key words: Physical layer security Limited feedback Untrusted relay...