Efficient Random Access And Resource Allocation Schemes For M2M Communications

With the development of the 5th generation(5G)mobile communication system,Machine to Machine(M2M)Communications can realize mutual interconnection between multiple autonomous devices.M2 M is a networked application and service centered on intelligent interaction between machine terminals.With the popularization and rapid development of the Internet of Things,more and more devices have the ability to communicate and connect,and networking everything has gradually become a reality.At the same time,M2 M communications will inevitably introduce a large amount of user equipments and data.When a large number of machinetype communication devices(MTCD)request access to the network within a short time,the random access process will be inefficient due to frequent transmission collisions,network congestion and resource wastage.Therefore,how to improve the success access probability and resource efficiency of the random access process becomes an important issue.For deeply understanding the random access process,we first introduce the random access scheme in Long Term Evolution(LTE)system,and mainly focus on the contention-based random access scheme.Subsequently,the problems that may occur in the random access process for M2 M communications are described.Then,one main random access scheme for M2 M communication,non-orthogonal random access(NORA)scheme is introduced.To address signaling overhead and resource shortage problems of M2 M communications in cellular networks,in this thesis,we propose a joint NORA and data transmission(DT)scheme,i.e.NORA-DT scheme.Considering the fact that most MTCDs just transmit smallsize data,NORA-DT allows MTCDs to schedule the corresponding Physical Uplink Shared Channel(PUSCH)resources after transmitting preambles,and then directly transmit data packets along with the connection setup request message(Msg.3)to simplify the access process.Based on the proposed NORA-DT scheme,we propose a resource allocation scheme which can allocate uplink resources between PRACH and PUSCH reasonably.As a result,the resource allocation can maximize the utilization of throughput and uplink resources.Simulation results show that compared with orthogonal random access and transmission scheme(ORADTP),the proposed scheme can improve resource efficiency by about 30%.Considering the problem of the huge number of MTCDs and limited preambles in the random access procedure for M2 M communications,in this thesis,we propose a random access scheme based on NORA-DT named Spatial Group Based Non-Orthogonal Random Access and Data Transmission Scheme(SG-NORA-DT).By dividing the cell coverage into multiple groups with the distance optimization method,SG-NORA-DT can increase the number of available preambles by using a root index within each group separately.As a result,SG-NORA-DT could further effectively increase the number of MTCDs that can be accommodated in the cell which could reduce preamble collision probability and improve resource utilization in the system.