Research On MTC Device Random Access Congestion Avoidance In Cellular Networks

With the rapid development of Internet of Things,Machine-type Communication as one of its key technologies has also received extensive attention from the international industry and academia.MTC refers to a technology that enables widespread connection between machines through the LTE network.With the widespread application of emerging MTC industries such as smart home,unmanned driving,and telemedicine,the number of MTC devices is bound to explosive increase,which brings great challenges to the traditional random access method.In this thesis,we focus on the random access process in MTC communication,and research the congestion caused by the large number of random access.First of all,in view of the characteristics of various types of MTC devices and the problem of low resource utilization caused by preamble collisions when a large number of devices are accessed,a random access scheme for multiple MTC devices based on enhanced PRACH technology is proposed.MTC devices are divided into high,medium,and low priorities according to different Qo S requirements.Through enhanced PRACH technology,preamble collision information is known in advance to avoid scheduling of PUSCH channel resources in the next step,and the ACB mechanism is used for different priority devices.Different ACB access probability factors are used to control the number of access devices for different priorities MTC devices.Finally,under the conditions of targeting the maximum service access capacity and high-priority Qo S requirements,we obtain the optimal resource allocation of uplink resource between PRACH channel and PUSCH channel.The simulation results show that the proposed scheme achieves the differentiated requirements of MTC devices.On the premise of ensuring access capacity,the specific delay and packet loss rate requirements of high-priority equipment are guaranteed.Secondly,considering the poor mobility of most MTC devices,the constant timing advance information of these devices is used to identify the congested devices and reduce the preamble conflict rate.Therefore,a static scenario-oriented random access scheme for MTC devices based on ACB is proposed.The scheme includes two parts: preamble resource allocation and adaptive ACB.All devices covered by the base station are divided into delay-sensitive devices and delay-tolerant devices according to different delay requirements.We give high priority to the delay-sensitive devices when allocationg preambles,then each category of devices uses an adaptive ACB mechanism,determining the optimal ACB access probability factors to maximize the access capacity by searching algorithm.Simulation results prove that,compared with other related schemes,this scheme reduces access delay and achieves a higher preamble access success rate.