Resource Allocation And Cache Node Selection Algorithm In D2D Communication System

D2D communication technology in cellular network allows users with close physical distance to communicate directly without passing through the base station,greatly improving the energy efficiency and system capacity.However,the introduction of D2 D communication will also bring intricate technical problems to the cellular network,such as channel allocation and power control.In addition,D2 D communication technology can be combined with caching technology to help the base station to offload cellular traffic,and the consequent selection strategy of cache nodes is the key to reduce the cost of user request files in the system.This thesis studies the channel allocation and power control problem of D2 D user multiplexed cellular user resources in heterogeneous cellular networks,and proposes the corresponding resource allocation algorithm.It also studies the selection of cache nodes based on D2 D communication,and proposes the corresponding selection algorithm.The main contents are as follows:(1)In order to effectively improve the energy efficiency of D2 D users on the premise of ensuring the service quality of cellular users,a NOMA-based D2 D communication joint subchannel and power allocation algorithm is proposed.The algorithm can be divided into two steps: firstly,the KM algorithm is used to allocate channels for each D2 D group,and then the power allocation scheme in each D2 D group is derived by using optimal KKT constraint condition.The simulation results show that the proposed algorithm can improve the total energy efficiency of D2 D users.For example,when the number of D2 D groups is 15,the total energy efficiency of D2 D users is increased by 25%.(2)In order to improve the total capacity of the system,a D2 D power game algorithm based on clustering is proposed.The algorithm first uses fuzzy C-means(FCM)algorithm to cluster according to the geographic location of the D2 D user,so that users in the cluster can not share the channel to reduce the interference between D2 D pairs,and then use the KM algorithm to allocate cellular user uplink channel for D2 D users in the cluster,which means optimally match the D2 D user with the cellular user.Considering the system capacity,QoS demand of users and D2 D users' transmission power,a non-cooperative game model is constructed,a non-cooperative game model is constructed to optimize the D2 D users' transmit power and the existence of its Nash equilibrium is proved.Simulation results show that the proposed algorithm can effectively improve the system throughput while ensuring the communication quality of users.(3)For cache-assisted D2 D communication system,a cache node selection algorithm based on D2 D communication is proposed to minimize the total cost of the system on the premise of ensuring that all users' file requirements can be met.The algorithm first defines the social relationship between users from the perspective of files,and then comprehensively considers the calculation method of base station acquisition cost and D2 D communication cost to obtain the judgment factor,and selects the cache node through the judgment factor.Simulation results show that the algorithm can effectively reduce the total cost of the system.