| LPWAN,represented by LoRaWAN,Sigfox and NB-IoT,is widely used in the Internet of Things.The main characteristic of LPWAN is to support the access of mass devices in the Internet of Things.LPWAN has the advantages of low power consumption,long distance and low operation and maintenance costs.In order to ensure the connection of mass devices,the access technology of LPWAN is particularly important.This paper studies two access strategies for LoRaWAN.Firstly,aiming at the problem of high access conflict probability in LoRaWAN,this paper proposes a dynamic backoff access mechanism,gives the mathematical model of the access process of LoRaWAN Class A terminal equipment and the mathematical model of the dynamic backoff access mechanism,and makes simulation comparison and analysis.The simulation results show that the dynamic backoff mechanism can effectively reduce the collision probability of terminal equiprment data in the channel,and then reduce the number of retransmissions of terminal equipment.Secondly,aiming at the problem of low efficiency and low utilization of SF(Spreading Factor)allocation in LoRaWAN,this paper proposes a SF balancing algorithm,which is based on the access process of LoRaWAN Class B,and proposes an access strategy based on broadcast signal.In this paper,the performance of spread spectrum factor balance algorithm is analyzed from three aspects:packet loss rate,energy efficiency and spread spectrum factor distribution.The simulation results show that the performance of the spread spectrum factor balancing algorithm designed in this paper is better,which is conducive to the improvement of LoRaWAN's data transmission success rate and access delay. |
