Research On D2D Access And Resource Allocation Algorithms In Heterogeneous Cellular Networks

With the development of Internet of Things technology,the era of Internet of Everything has arrived.Access to many terminals poses serious challenges for spectral resources.In the situation of increasingly tight spectrum resources,how to realize the faster transmission of mobile data,expand the scope of network coverage,and improve the utilization rate of frequency resources has become a hot issue for scholars to solve.Traditional cellular networks,because the flexibility of the network is not high,it is difficult to meet the future wireless applications in many terminal access and user needs.Introducing Device-to-Device(D2D)technology to heterogeneous cellular networks can effectively improve frequency utilization,reduce transmission delays,increase network coverage,and improve system performance.However,there are still some technical problems that need to be solved in realizing the fast access and reasonable resource allocation of D2 D users.In view of the above technical background,the thesis mainly studies how to realize the rapid access of D2 D user pairs and the technical problems of spectrum resource allocation in heterogeneous cellular networks.The main work and innovation are summarized as follows:1)The history of communication technology,the advantages of small base station technology and D2 D communication technology in heterogeneous cellular networks are introduced in this thesis,and the current research status at home and abroad is described.In terms of D2 D basic theory,it mainly includes the following parts of research: first,the discovery and session establishment process of D2 D devices are introduced in detail;then the types of D2 D communication are further elaborated;finally,the power control and resources in D2 D communication The distribution is analyzed emphatically,and the main algorithms currently researched at home and abroad are analyzed.2)Aiming at the problem of network selection in heterogeneous cellular networks,this thesis proposes a Fuzzy-TOPSIS access algorithm based on SDN system architecture.The algorithm collects current network information through the SDN controller to assist in network discovery and network pre-selection;the Fuzzy controller receives the pre-processed network information and generates the Qo S ranking under the current network;and uses the improved TOPSIS algorithm to generate the final network ranking to realize the fast access of D2 D user terminal.The simulation results show that compared with other algorithms,the Fuzzy-TOPSIS access algorithm based on the SDN system architecture reduces the delay by 10.9%,reduces the terminal energy consumption by 18.5% on average,and increases the average network throughput by 8.9%.The probability of connectivity increased by 8.3% on average.3)The thesis proposes a D2 D resource allocation algorithm based on the probability of system outage,aiming at the problem of energy consumption control and system interruption of the resource allocation algorithm after selecting a heterogeneous cellular network.This algorithm preliminarily determines the user transmission power through an improved exhaustive search algorithm.According to the two-dimensional multiplexing table of user Qo S information,it contains the Qo S of cellular users and D2 D users.The simulated annealing algorithm is introduced to optimize the multiplexing combination of D2 D users and cellular users and adjust the power dimension through the exhaustive power algorithm,and then focus on optimizing the system outage probability index.Through simulation verification,the proposed D2 D resource allocation algorithm based on system outage probability is compared with other algorithms.In the system channel allocation stage,the user's connection probability is increased by 10.2% on average,the calculation time is reduced by 10.1%on average,and the average power average decreased by 78.3% during the user power distribution phase.