Research On Equipment Access And Resource Allocation Algorithm In Massive Machine Type Communication

As the first version of the 5G international standard was officially frozen in September 2018,the door to 5G was officially opened.The widespread application of5 G technology has brought tremendous changes to all aspects of people's lives.Machine-type Communication(MTC)is one of the three typical scenarios of 5G cellular communication network and is supposed to support connection density of 1million devices per square kilometer.Random access initiated by such a large amount of devices may lead to congestion,conflicts and packet loss.How to design an effective device access scheme to avoid network congestion is a crucial issue.The 5G international standard defines as many as 256 slot formats.How to use novel slot formats to form a flexible frame structure to meet the needs of different types of services has become a topic worthy of study.The first part of this paper designs a dynamic Preamble selection and allocation algorithm based on Q learning.This article uses Early Data Transmission(EDT)mechanism to enhance the system's support for delay-sensitive devices.MTC devices were divided into two groups of delay-sensitive and delay-tolerant according to the maximum delay tolerance of the services.Some of the preamble resources were pre-reserved for delay-sensitive devices.Delay-sensitive device selected a preamble randomly from the pre-reserved set and performed EDT.Delay-tolerant device selected a preamble randomly from the rest of the preambles and performed normal4-step random access procedure.The number of elements in the pre-reserved set was dynamically adjusted using Q-learning algorithm according to the successful access proportion of the two types of devices.And then the base station would update and broadcast the service types which were permitted to use EDT.Simulation results show that the scheme proposed in this work improves the successful access proportion and meet the delay requirement of delay-sensitive devices.The second part of the work is to design an adaptive frame structure that comprehensively considers service traffic characteristics and service requirements.Firstly,suitable slot formats are adapted for various services in the mixed services scenario,and then use these slot formats form a frame structure adapted to the mixed scenario.Periodically adjust the number of uplink/downlink symbols in special time slots by detecting changes in downlink queue length and system throughput,so as to ensure system throughput.The simulation results show that the design and adjustment of the frame structure takes into account the traffic characteristics of various services and the changes in system throughput,so the system throughput can be guaranteed in a dynamic environment;on the other hand,due to the design of this article the frame structure period is short,thereby effectively reducing the time delay.