The Research On Random Access Technology For The Next Generation Mobile Communication Network

Since its birth in 1980 s,mobile communication networks have constantly integrated the various cutting-edge technologies of communication research to build an intelligent society with "Internet of Everything".The next generation of mobile communication network 5G will create a cross-industry integration of the ecological chain,including industrial manufacturing,intelligent family,the Internet of things,Augmented and virtual reality and other new application scenes.These new application sce narios that traditional mobile communication can't achieve will inevitably bring about a sharp increase in mobile and unlimited traffic.5G network should not only improves the speed and quality of communication between people,but also meets the requirements of low latency,low power consumption and high reliability.From 1G to 4G,user devices are connected to mobile communication network by RA(Random Access),as well as 5G.The higher QoS(Quality of Service)of the new mobile communication network generation puts forward the following requirements for the terminal access mechanism: on the one hand,it is necessary to improve the quality of the access capacity;on the other hand,to ensure that vast amounts of terminal rapid ly access to the system.Firstly,the LTE(Long Term Evolution)random access process and the related resource allocation are analyzed in detail.The random access schemes are divided into contention and non-contention,while the contention-based access is most used in the mobile communication networks.The LTE access is mainly focused on H2H(Human to Human),and the collision caused by the sudden arrival of large number of users causes large delay.In this paper,according to the scene of 5G mass access,the two-steps access based on grant free transmission is proposed.The details of the Data and preamble transmission processes in the two-steps access,as well as the corresponding channel and system information resources configuration are given.And the functions of backward compatibility and enhanced random access for the current contention random access are considered.Secondly,the performance of two-steps RA mechanisim based on grant free transmission is analyzed and simulated with Matlab.Compared with tranditional contention-based RA,the two-steps RA based on grant-free transmission can effectively reduce the latency and improve the probability of successful transmission,especially in the case of a large number of users access.Finally,the Data part of the two-steps RA is modeled and related mathematical derivation by using two dimensional Markov chain.Combining exponential backoff algorithm,the failure probability of the Data transmission was deduced.And the simulation analysis is presented.eNodeB can use this model to predict the transmission of different number of users,so as to better dynamically plan the grant-free resources according to the actual load.