Research On Large-Capacity Access Congestion Control Mechanism For 5G Applications

With the rapid increase of intelligent terminal equipment,communication services and network traffic,5G came into being.The latest 5G white thesis states that wireless access will continue to evolve based on 4G Machine to Machine(M2M)features in order to meet the demand for mass connectivity in the Msachine Type Communication(MTC)scenario.This thesis analyzes the characteristics of MTC services and communication requirements.Based on the existing large-capacity access congestion mechanism,an access mechanism based on dynamic allocation of PRACH and a distributed queue access mechanism based on preamble packets are studied.Based on the Vienna LTE system-level simulation platform,a visual simulation platform is built.First,this article briefly describes the application scenarios,development trends,and key technologies of 5G.Then,the dissertation expounds the enhancement of wireless access in the massive MTC scenario,and gives the research significance and research status of the large-capacity access mechanism.Then the random access process is described,and its modeling,theoretical derivation,and simulation verification of theoretical indicators are performed.Secondly,this thesis makes deep research on ACB mechanism and adaptive access overload control mechanism,and analyzes their shortcomings.Based on this,an access congestion control mechanism based on dynamically allocated PRACH resources is proposed.Based on this,an access congestion control mechanism based on dynamically allocated PRACH resources is proposed.Simulation results show that the DPRACH studied in this thesis can guarantee higher access success rate and lower access delay of MTC equipment under the same load.On the premise that the low-priority access performance is not reduced,the high-priority access delay of DPRACH is always lower than 250 ms,and the high-priority access success rate of DPRACH is 20% higher than that of QoS-Dracon.Compared with adaptive access overload control mechanism,DPRACH solves the high-priority delay-sensitive problem very well.Then,this thesis studies the access congestion mechanism based on Distributed Queue(DQ).In order to solve the shortcomings of DQRA in delay and RA slot,this thesis proposes a preamble-based grouping distributed queue access mechanism.Simulation and comparison found that PGDQRA can also guarantee lower access delay and less consumption of RA slots when the load is heavy.When the number of devices reaches 50,000,PGDQRA achieves a 30% delay reduction and saves 28% of RA resources.In addition,simulations give curves for different packet sizes.Therefore,in actual use,we can choose different preamble grouping sizes according to the delay of the equipment,the requirements of RA resource consumption and the success rate.In the end,this thesis makes secondary development based on Vienna LTE system-level simulation platform and builds a visual simulation platform.The visual simulation platform is equipped with a random access module,so it lays the foundation for subsequent research on access congestion mechanisms based on system-level indicators.