Research On Performance Evaluation And Optimization Of EDRX Mechanism In NB-IoT

The standardization of Narrowband Internet of Things(NB-IoT)paved the way for the use of low-power wide area networks(LPWA).NB-IoT can be used in a large number of IoT devices with low communication rates in licensed frequency bands.With the rapid increase in the number of NB-IoT devices worldwide,the energy consumption of NB-IoT technology has become critical.In response to this problem,NB-IoT has made the following improvements: NB-IoT adopts an extended discontinuous reception mechanism(eDRX)and a low power mode(PSM)in order to complete the design goal of low power consumption.The eDRX mechanism is developed from the Discontinuous Reception Mechanism(DRX)mechanism.On the basis of DRX,adaptive changes have been made according to the application scenarios of the NB-IoT technology.The eDRX mechanism uses a non-continuous monitoring channel mechanism to reduce energy consumption and achieve the purpose of energy saving.This thesis conducts an in-depth study on the performance and optimization of the eDRX mechanism in NB-IoT.The main research contents are as follows:Firstly,considering that the NB-IoT large-scale terminal device access scenario may cause more access conflicts,and the impact of the backoff mechanism in the random access process,the eDRX and PSM solutions adopted in 3GPP NB-IoT are modeled as A brandnew Markov model.Based on this model,a closed expression of terminal equipment energy consumption and delay is derived.In order to analyze the impact of random access backoff mechanism on the performance of NB-IoT in more depth,this thesis also derives the expression of the same performance index of the backoff time linear increase scheme and the fixed backoff time scheme.The simulation results show that the backoff time can greatly affect the performance of the NB-IoT system and the linear backoff time scheme is effective in optimizing energy consumption.It also proves that the eDRX mechanism and the PSM mechanism can effectively reduce the system energy consumption.Secondly,considering the influence of the inactivity timer in the eDRX mechanism on the energy consumption and system practicability of the NB-IoT system,this thesis proposes a multi-threshold adaptive configuration eDRX parameter algorithm—M-eDRX algorithm to optimize the performance of the NB-IoT system.The main idea of the algorithm is: when the device is in a poor channel environment,extend the working time of the inactivity timer in the eDRX mechanism to ensure its transmission efficiency;when the device is in a better channel environment,shorten the inactivity time of the eDRX mechanism.Both can reduce energy consumption while ensuring the practical performance of the NB-IoT system.Simulation results show that the M-eDRX algorithm is better than the standard eDRX algorithm.