Research On D2D-Based Cooperative Communication Strategy In Heterogeneous Wireless Networks

With the wireless communication network entering millions of households,the level of social informatization has been continuously improved.However,the increasing number of wireless communication services and users has exacerbated the scarcity of limited spectrum resources.In the framework of heterogeneous network,the introduction of cooperation mechanisms to promote the fusion and collaboration of diversified network technologies will effectively integrate network resources and provide users with much better service experience.Aiming at the problem that the macro base station with high load is incapable of responding to service requests of partial macro users timely,by deploying small cell base stations,this thesis enhances the network coverage capability of macro cell edge areas and then proposes a cooperative strategy that provide a way for macro users to transfer access path from macrocells to small cells in this heterogeneous network based on the cooperation of D2 D nodes with shorter service response time,which improve users' experience meanwhile relieve traffic congestion.The selfishness of the nodes in the network will hinder their enthusiasm for participating in the cooperation,which will damnify the network performance.In this thesis,a cooperative relay incentive mechanism is designed to be directed against the selfish behavior of D2 D nodes,and then the Stackelberg game is introduced to build the game model with one leader and many followers between the macro base station and D2 D nodes.Also,the cost function of base station and the utility function of D2 D nodes are established to measure benefit of the both respectively and then the existence of equilibrium points under this model is proved.Under the condition that multiple small cells coexist,the target small cell that macro user will access to is selected according to the principle of minimum cost.The simulation shows that the proposed strategy can effectively stimulate the D2 D nodes and provide a way for the macro base station to offload the burthen.In addition,the cooperative jamming technology is introduced for the security requirement of privacy service.Based on the cooperative relaying,this thesis proposes a security cooperative strategy uniting the cooperative jamming incentive mechanism and the small cell selection mechanism.Firstly,based on the contract theory,the optimal contract combination between the hierarchically-divided cooperative jamming nodes and the macro base station is solved.Based on this,the cooperative jamming power corresponding to the optimal cooperative jamming node in each small cell is obtained to be applied into the competition of macro user's access right among multiple small cells,and then the auction game is used as a tool to solve the optimal bid for each small cell.Finally the user selects the small cell with the largest utility value to access.Through simulation,it's indicated that the proposed security cooperative strategy can ensure the secure transmission of the user privacy service while guaranteeing the initiative of the nodes to act as cooperative jamming nodes and unload the load from the macro base station to the small cell,thereby balancing the overall load distribution of the network.