Optimized Design Of Random Access Scheme For MMTC

With the continuous development of mobile communication technology,the 5th Generation Mobile Communication Technology(5G)has gradually entered the public's vision.Compared with the 4th Generation Mobile Communication Technology(4G),5G will not only further enhance the experience of all network users,but also meet the needs of application interconnection of all things in the future.As a typical scenario in the framework of Internet of Things(Io T),massive Machine-Type Communication(m MTC)has become more and more famous among researchers.Among the key technologies of m MTC,congestion in random access is one of the bottlenecks that limit the system performance.Therefore,it is of great practical significance to further optimize the design of random access scheme for m MTC.The random access scheme for m MTC is inherited from LTE-A(LTE-Advanced),which includes two handshakes consisting of four steps.In this paper,we first describe the basic contention-based random access process in LTE-A,and a brief introduction of the preamble sequences in random access is shown.Subsequently,the system model for the random access scheme in m MTC is given,and the key performance parameters of the random access scheme are described.Finally,a random access scheme based on access barring and another backoff mechanism based random access scheme is introduced.The main steps and performance of the two schemes are summarized.In order to improve the system throughput and success probability and reduce the average delay of the success UEs,we propose a random access scheme based on joint optimization of access barring parameter and backoff parameter.Through the joint optimization of the access barring parameter and the backoff parameter,this scheme can largely solve the congestion problem caused by the slow update speed of the access barring parameter,prevent the situation that access delay is not able to meet the quality of service,alleviate access pressure of m MTC,and achieve a balance of throughput and access delay.The simulation and theoretical results show that,compared with the access barring random access and backoff-based random access,this scheme can obtain the maximum system throughput under the average delay limit,thereby improving the utilization efficiency of the system time-frequency resources and data transmission efficiency of Machine-Type-Communication User-Equipments in m MTC.Considering the non-orthogonal random access mechanism that essentially improves the Physical Random Access Channel(PRACH)capacity,we further propose a non-orthogonal random access scheme based on joint optimization of access barring parameter and backoff parameter.The theoretical and simulation results show that,compared with the random access scheme based on joint optimization of the access barring parameter and the backoff parameter above,the non-orthogonal mechanism can improve the system throughput without increasing the access delay.It improves the performance of random access systems essentially.