The Research On Resource Allocation For NOMA-enhanced Cellular And D2D Heterogeneous Networks

When confronting the diversified service requirements and technical challenges in the fifth-generation mobile communication system such as high traffic density and massive connections,conventional cellular network architectures had some severe problems such as low spectral efficiency and base station overloaded.Since D2 D technology allows neighboring devices to communicate directly without the assistance of the base-station,introducing it into the existing cellular network architecture can bring many advantages such as offloading the traffic on base stations and reducing end-to-end delay.Apart from D2 D technique,another emerging technique—non-orthogonal multiple access(NOMA)—is regarded as one of the promising candidates in future 5G networks for its potential to provide ultra high connections and significantly improve the spectral efficiency.Invoking it into cellular and D2 D heterogeneous networks is a promising development trend for future wireless networks,and has attracted widespread attention from researchers domestically and abroad.Although the introduction of new technologies can bring about performance improvements in many aspects,it posts new challenges to interference management.Reasonable resource allocation strategies can effectively alleviate co-channel interference.Aiming at the NOMA-enhanced cellular and D2 D heterogeneous network scenarios,this thesis has carried out the following works on the research of channel resource allocation:1)This thesis analyzes the D2 D communication mode and link establishment process,studies the basic principles of NOMA technology,and establishes the interference models for NOMA-enhanced cellular and D2 D heterogeneous networks.2)This thesis investigates the existing resource scheduling algorithms,summarizes the advantages and disadvantages of various methods,and highlights the principle of algorithms based on graph coloring and matching theory,which is a theoretical foundation for the design of subsequent algorithms.3)Aiming at the problem that traditional undirected graphs cannot model cumulative interference and asymmetric interference of dense heterogeneous networks simultaneously,this thesis introduces a directed hypergraph model,which is more accurate than traditional graph models and can simulate a more realistic interference environment.Based on this model,this thesis proposes a greedy coloring algorithm based on directed hypergraph to solve the problem of channel resource allocation in a single-cell heterogeneous network.Comparing this algorithm with exhaustive search algorithm,traditional graph coloring algorithm and genetic algorithm,the proposed algorithm shows its advantages in system capacity expanding and spectrum efficiency improving.Besides,the NOMA-enhanced D2 D communication scheme is capable of achieving promising gains in terms of the number of accessed users and resource utilization,compared to a traditional OMA-based D2 D communication scheme.4)In order to further simulate real-life scenarios,the joint D2 D group association and channel assignment in multi-cell heterogeneous networks have been studied.By modeling D2 D groups,base-stations,and available cellular channels as students,tutors and projects,the original problem is transformed into a student-project allocation problem with peer effects.A matching algorithm based on two-sided exchange-stable is proposed to solve this problem.Compare this algorithm with one-to-one matching algorithm and student-project allocation algorithm excluding peer effect.The results show that the proposed algorithm can obtain larger system capacity on the premise of guaranteeing the service quality of cellular users and accessible D2 D users.