Research On Cooperative Jamming Technology In Wireless Communication

During the development process of wireless communication technology,the security of data transmission has occupied an increasingly important position.Whether in people's daily life,such as using mobile phones for communication,or in military communications with eavesdropping and anti-eavesdropping,security has played a very important role.The traditional way to ensure security relies on cryptographic protection mechanisms to encrypt data using an encryption algorithm on top layer of the network protocol stack.However,encryption algorithms often mean complicated key distribution,management,and update,which brings a lot of overhead;With the development of hardware technology,the computing power of eavesdropping devices has become stronger and stronger,which brings limitations to the encryption algorithm.Physical layer security technology has emerged as an alternative and complement to traditional cryptography technology.The physical layer security technology utilizes the randomness of the wireless channel,designs the precoding schemes,the power allocation schemes,and so on,so that the eavesdropper can not receive useful information,which ensures the security of the wireless communication.Cooperative jamming technology is one of the key technologies in the physical layer security technology.It uses the cooperative relay to transmit artificial interference signals to interfere the eavesdropper,thereby reduces the link quality of the eavesdropping channel.This paper focuses on the cooperative jamming technology in the following two situations: The first situation is the physical layer security technology in uncoordinated manner.The main idea is to use the uncoordinated relay to send interference signals to interfere with the eavesdropper,to reduce the quality of the eavesdropper link and achieve the effect of secure communication.The " uncoordinated " here is that the channel state information(CSI)is not shared between the relays,and the interference signals are designed independently.Here we mainly introduce two situations: relay has multiple antennas and the relay has a single antenna.When the relay has multiple antennas,the noise nulling scheme with lower complexity and the optimal noise scheme with higher complexity are introduced.The theoretical analysis and simulation verification show that for the security performance,the nulling scheme is a good approximation of the optimal noise scheme;when the relay has a single antenna,an optimization problem is proposed with the goal of maximizing the secrecy rate,and the solution is solved by using the one-dimensional search with convex optimization method.Finally,a noise-based nulling scheme with optimal relay selection is proposed.Compared with the traditional nulling scheme,the difference between relays is utilized to select a relay which can maximize the security rate.The simulation results show that the proposed scheme can significantly improve the security performance of the system.The Second situation is the physical layer security technology with imperfect channel state information.For the common case,a robust transmission scheme combining the information signal and the noise signal is introduced,which can effectively compensate for the performance loss caused by the imperfect channel information.For the multi-user large-scale MIMO case,the lower bound of traversal security capacity is analyzed.The channel prediction scheme based on Wiener filter is introduced.The theoretical analysis and simulation verification show that the channel prediction scheme can alleviate the loss of confidential performance caused by imperfect channel information.