Research On Relay Selection And Resource Allocation Method Of Cooperative NOMA System

Non-orthogonal multiple access technology based on fifth-generation mobile communication,as a new generation of communication technology with high speed,low latency and wide coverage,will be widely used in the industrial Internet of Things and smart industries.Non-orthogonal multiple access technology uses high frequency signals,which will result in poor service quality for users in high-density areas and edge areas.Existing cooperative transmission technologies effectively use relay cooperation for secondary transmission and it can improve users in the area service quality.This thesis combines the above two technologies,and establishs a cooperative NOMA system model.The research will be conducted from the perspective of relay path selection and power distribution,and corresponding improvements are proposedThe main work of this thesis is as follows1.Research on relay path selection of cooperative NOMA system.Aiming at the problem that the existing NOMA cooperative transmission model cannot guarantee the reliability of the system,a cooperative NOMA system model is established.Under the channel conditions between the relay nodes are comprehensively considered,a relay selection strategy based on a single source optimal path is proposed.It can get a better relay transmission path.The strategy takes the base station as the source node and the user as the node,then configures the channel parameters by using the channel conditions between users,finally selects the path with the best channel conditions.The base station collects all reachable channels and corresponding channel parameters from the destination node.By comparing the channel parameters,the base station can quickly select the optimal transmission channel.Based on user outage probability and system complexity,simulation results show that the proposed stratage has better performance than traditional NOMA cooperative transmission2.Research on power allocation optimization of cooperative NOMA system.Considering that traditional power allocation algorithms are not flexible,heuristic algorithms are introduced to optimize power allocation.The research will be conducted from he perspective of 2 users and multi-users power allocation.In 2 users power allocation,combining genetic algorithm and fractional order power allocation algorithm,improved genetic algorithm is proposed.Based on the maximum system throughput and minimum transmit power,the simulation results show that the proposed algorithm has better performance than other algorithms.In multi-users power allocation,combining tabu search algorithm and simulated annealing algorithm,improved simulated annealing algorithm is proposed Based on the simulation of maximum energy efficiency ratio,the simulation results show that the proposed algorithm can achieve better performance than other algorithms.