Research On Access Control For Massive Machine Type Communication

Massive Machine Type Communication(mMTC)is one of the three types of services supported by 5G networks.In 6G,there will be ultralarge-scale machines connection in the Air-space-ground integration network.However,when plenty of devices access the base station at the same time,this will inevitably lead to serious network congestion due to the limited number of preamble resources and Physical Random Access Channel(PRACH)capacity in a single cell system.Network congestion and overload will inevitably increase latency,lead to packet loss,and even service interruptions in machine communication.To address these challenges,this paper studies the congestion problem and information collision caused by large-scale machine access,so as to maximize the use of preamble resources,and proposes a reasonable access flow control scheme to reduce the collision of channel resources and increase the number of User Equipment access.Optimizing the current random access procedure to achieve stable,reliable,and low-latency access.The main contributions of this paper are as follows:(1)Dynamic preamble access mechanism based on the combination of Slotted ALOHA and Dynamic-Access Class Barring(D-ACB)mechanism.Aiming at the congestion problem caused by the instantaneous influx of large-scale machine in 5G networks.The D-ACB factor algorithm is proposed to control the flow before access,and on this basis,the Slotted ALOHA mechanism is combined to achieve the purpose of fast retry.In response to the problem of low utilization rate of the preamble resources in the current access mechanism,an optimal dynamic preamble algorithm is proposed to improve the utilization rate of preamble.Simulation experiment shows that compared with the current access scheme with a fixed allocation preamble,the proposed dynamic preamble scheme shortens the total service time of the system by 150ms and increases the utilization rate of the preamble by 3.7%.The average access latency of a single device is reduced by 5.6%,which is close to the theoretical optimal 98%.Therefore,the dynamic preamble scheme proposed in this chapter shows better results in the above three performance indicators.(2)Priority-based access mechanism of dual preamble.For the access technology of 5G networks,when considering the requirements of different service quality of equipments,the 4-Step RA has always been adhered to,resulting in the problems of large signal overhead and long access time.In the existing 2-Step RA mechanism,the free grant transmission of devices leads to inaccurate estimation of the time advance amount of the base station,resulting in the problem of unstable access of time-sensitive devices.proposed low priority devices to adopt a single preamble,and high priority devices transmission solutions with dual preamble.The designed random access algorithm is verified,and the results show that compared with the traditional high-priority transmission of single preamble,the proposed high-priority dual preamble access mechanism of 2-Step RA reduces the overall average delay by 7.33ms,the average success rate increases by 16.7%,and the total device access success rate is increased by 2.8%.Therefore,the effectiveness of the proposed dual preamble random access algorithm is proved.