Research On Large Scale Access Method In Machine Type Communications

With the development of Internet of things,Machine Type Communications(MTC)has attracted the attention of scholars both at home and abroad.MTC contains a large number of MTC devices.If these large-scale MTC devices are directly connected to the existing wireless access network,it will lead to low access efficiency,high power consumption and packet loss.Aiming at solving the above problems,this thesis proposes two kinds of random access mechanisms in machine communication.Aiming at the problem of congestion and low efficiency in traditional timing advance(TA)comparison based random access mechanism when large-scale MTC devices are connected,this thesis presents a TA comparison based joint access control and resource allocation random access mechanism.This mechanism is on the basis of TA value comparison with ‘maximum access efficiency' as the goal,according to the change of the quantity of access MTC devices,dynamically allocating preamble resources and controlling the number of access MTC devices by using Access Class Barring(ACB).Simulation results show that compared with other mechanisms,the proposed mechanism can effectively alleviate congestion and maintain relatively high random access efficiency.Aiming at the problem of low access efficiency and large random access power consumption when large-scale MTC devices are connected,a random access mechanism based on spacial group for low power machine communication devices is proposed.Firstly,this mechanism increasing the number of preambles through spacial group,reduce the number of allocation of physical random access channel,alleviate the pressure of data transmission.Secondly,this mechanism based on the principle of ‘maximum access efficiency' and with the constraint of random access power consumption,dynamically allocates preamble resources and controls the number of access MTC devices by ACB.The simulation results show that compared with the existing mechanisms,this mechanism can get more preamble resources and increase the access efficiency,and consume less random access power,which is suitable for the random access of large-scale MTC devices with the demand of low power consumption.