Wireless Cache Design For Physical Layer Security

With the rapid development of modern intelligent devices and wireless networks,the arrival of the information age and the era of big data have led to the exponential growth of communication services,which has created an urgent need for large storage capacity and high transmission performance of the network.In order to solve the problems of limited capacity and transmission load,caching technology is becoming an important tool to alleviate the capacity shortage of modern wireless networks and increase the data transmission rate.Although caching technology can significantly reduce the transmission link backhaul cost and improve the user's perceived experience,there are still many important issues to be solved in theory and application for caching technology,for example: 1)How to ensure the effectiveness of the caching policy and the security of the cached contents when eavesdroppers appear in the cache network;2)How to deal with the problem of multiple eavesdroppers in a random cache network;3)How to achieve a secure caching strategy in the presence of multiple eavesdroppers;4)How to achieve a secure cache strategy in multi-user,multi-relay and multi-eavesdropper scenarios.In view of this,this paper will conduct a deep research on the above key issues,and briefly describe the innovative research results as follows:Firstly,for the issue of eavesdroppers in the cache network,we combine the caching technology with the physical-layer security technology to ensure the effectiveness of caching policy and the security of cached contents by studying the security performance of the cached content at the physical layer.The details about the achieving methods are as follows: firstly,contents are divided into three different groups in terms of their popularity;secondly,the cache devices are clustered by analyzing the transmission performance of the cache devices;thirdly,by combining the Most Popular Content(MPC)caching strategy,Largest Content Diversity(LCD)caching strategy and traditional caching strategy three caching strategies,a hybridcaching strategy is designed to store contents of different sets into different cache device memory;finally,the relevant theoretical research is extended to the specific network model,and which proves the correctness of the proposed research.Secondly,for the issue of multiple eavesdroppers in a random cache network,a deep analysis of how to achieve a secure caching strategy in the presence of multiple eavesdroppers is provided.Specifically,we model the position of the eavesdroppers by the uniform Poisson point process(PPP),and consider the worst eavesdropping scene that eavesdroppers receive and decode the contents through the maximum ratio combining.Then we derive the analytical result and the lower bound of the average successful transmission probability of the system,and optimize the caching strategy.The final results show that the proposed probabilistic caching strategy can guarantee the validity of the caching strategy and the security of the cached content even in the worst eavesdropping scenario.Finally,in order to solve the issue of how to design a secure caching strategy in a multi-user multi-relay multi-eavesdropper scenario,we first model the location of users,relays and eavesdroppers through a uniform PPP,and consider the impact of part users with caching on the overall cache strategy and overall performance of the system.Secondly,the cache performance of the cache device and the user is designed by analyzing the security performance of the four transmission modes.Thirdly,the average performance of the proposed caching strategy is measured by the security cache throughput,and the caching strategy is also optimized by the security cache throughput.The final results show that the proposed caching strategy can not only ensure the validness of the system caching strategy and the security of the cached contents,but also greatly improve the overall performance of the system.