Research On D2D Secure Communication In Network Environment Underlaying Cellular System

With the rapid increase of mobile data,the global data transmission volume has increased by1,000 times compared with the past.However,the traditional pure cellular communication network that centers on base station facilities has some problems such as low frequency spectrum utilization and heavy base station load and so on,which can no longer meet the current increasing service requirements.In this environment,the direct cellular communication(D2D,Device-to-Device)technology is introduced into the pure cellular network,becoming key technology of the 5G system(5G,Fifth-Generation).It does not require an intermediate entity and can realize peer-to-peer direct communication between users,enabling nearby social services,effectively improving network communication performance,and forming a heterogeneous networking form where D2 D and cellular communication are mixed.Therefore,this paper conducts related researches on the heterogeneous networking form where D2 D and cellular communication are mixed from two aspects.The main research contents are as follows:First,this paper studies the performance improvement of D2 D communication underlaying cellular system compared with the traditional pure cellular network based on the coupled queuing models of system.Specifically,cellular users,D2 D user pairs,and base station entities are mapped in the queuing models.Combining the M/G/1 queuing model,GI/G/1 queuing model and the coupling between the queues,the paper establishes queuing network of two communication systems respectively and uses the embedded Markov chain to analyze the feasibility of networks' stable distribution,which helps to theoretically obtain the mathematical model of the average queue length and average waiting time of each communication link.Finally,the system throughput and system time delay are used as the main indicators in order to evaluate the performance of networks through Matlab simulation.Comparing the performance of D2 D and cellular heterogeneous network and pure cellular network,the result verifies the advantage of heterogeneous network when it is used as communication system model.Secondly,this paper studies the communication security of D2 D communication underlaying cellular system based on the artificial noise assisted model.After verifying the performance advantage of D2 D communication underlaying cellular system,it is used as the basic communication system model.The paper uses multi-antenna method to add artificial noise at base station and the transmitting end of D2 D users at the same time and designs artificial noise signal and the precoding of the expected signal by using the characteristic of the channel null space and the optimization algorithm of the mixed penalty function.Finally,with the goal of maximizing confidential communication capacity of the system,an optimal power allocation scheme between D2 D transmitter and base station is proposed.Through Matlab simulation,the best power distribution coefficient under this scheme is obtained and its impact factors are analyzed,realizing the analysis and evaluation of system communication security capacity.In short,this paper first verifies that the introduction of D2 D communication in the network environment underlaying cellular system can effectively increase network performance and reduce transmission delay.And then based on this,to address the risk of communication leakage due to the openness of the D2 D communication transmission medium,the paper takes the heterogeneous network environment as system model and explores the solution to improve communication security from the perspective of the physical layer.