Research On Resource Allocation In Cognitive Relaying Network Based On Hybrid NOMA

With the development of wireless communication,the shortage of spectrum resources has become increasingly serious.Cognitive radio technology based on Non-Orthogonal Multiple Access(NOMA)is named Cognitive NOMA.Because of its high spectral efficiency and the advantages of allowing more users to access to the network,it has attracted wide attention and research from academia and industry.The collaborative relay technology is introduced into the cognitive NOMA network to form a cognitive collaborative NOMA network which not only has the advantages of cognitive NOMA,but also has the advantages of anti-fading capability and wide coverage.The existing research work on cognitive collaboration NOMA network has the following problems: First of all,although cooperative relay technology can enhance the system's antifading capability and expand the coverage of the primary network or cognitive network.However,the existing research does not consider that there is no direct transmission link between the primary user(PU)transceivers,and there is no direct transmission link between the secondary user(SU)transceiver.In this case,not only the sharing problem of the channel but also the sharing problem of the relay is involved.How to design the transmission strategy to ensure the performance of the primary network and improve the performance of the cognitive network is a problem which is worth of studying.In addition,when there are multiple subchannels and multiple users in the system,how to perform user scheduling and resource allocation to further improve the performance of the system is also a problem to be studied.In response to the above two questions,the research content of this paper is as follows.A hybrid NOMA transmission strategy is designed to ensure that the PUs' target rate is met,while providing cognitive users with access to the network.Further,the problem of resource allocation in hybrid relay network based on hybrid NOMA is studied.On the premise of ensuring that the target rate of the PUs is satisfied,the resource allocation and decoding mode are jointly optimized to maximize the number of SUs accessing the the network,and a heuristic algorithm is proposed to solve the optimization problem step by step.Heuristic algorithm is as follows: for the uplink,the power and subchannel allocation are performed when PUs have the exclusive subchannel by the greedy algorithm.Subsequently,the joint particle swarm optimization and greedy algorithm are used to solve the problem of resource allocation and decoding mode selection when SUs access to PUs' authorization band.For the downlink,firstly,the problem of resource allocation when PUs have the exclusive subchannel is modeled as mixed integer linear programming problem(MILP).Due to the high complexity of direct solution,the optimization problem is transformed into an assignment problem and Hungarian algorithm is used to find the best matching to obtain the result of resource allocation.On this basis,considering the resource allocation and decoding mode selection when SUs access to PUs' authorization band,the optimization problem is also MILP through analysis,modeling and transformation.The same algorithm is used to solve the problem.The simulation results show that the heuristic algorithm proposed in this paper greatly reduces the computational complexity while approximating the exhaustive search algorithm.In addition,the dynamic decoding mode allows more cognitive users to access to the network than the fixed decoding mode.