LoRaWAN Adaptive Data Rate Algorithm For Mobile Scenarios

LoRa is one of the most widely used low-power WAN technologies with the greatest research potential,LoRa enables long-distance communication with low energy consumption,LoRaWAN is the MAC layer protocol of LoRa.lo Ra WAN allows the network server to dynamically manage the data rate and transmission power of each device by introducing the Adaptive Data Rate(ADR)algorithm,which allows the network server to select different modulation parameters according to the link communication quality.LoRaWAN dynamically manages the data rate and transmission power of each device by introducing the Adaptive Data Rate(ADR)algorithm,which allows the network server to select different modulation parameters according to the link communication quality.However,the standard ADR algorithm is only suitable for static nodes where the wireless channel environment changes little and the link state is stable.When the nodes are mobile and the wireless channel changes rapidly,the standard ADR algorithm has poor real-time performance and lagging data rate adjustment,which cannot effectively sense the rapidly changing wireless channel and adjust the LoRaWAN modulation parameters in time.For the shortage of LoRaWAN adaptive data rate adjustment in mobile scenarios,this paper designs a flexible Mobile ADR algorithm,and the main content includes:(1)To address the problem of insufficient link state awareness in standard ADR algorithms,the Mobile ADR algorithm adds the carrier frequency offset and signal strength of LoRa signals as parameter indicators for the design of the ADR algorithm.Based on the three LoRa signal characteristics of Signal Noise Ratio(SNR),Received Signal Strength Indicator(RSSI),and frequency offset,it more effectively senses changes in channel conditions in mobile scenarios where the channel environment is variable,Improved awareness of link state.(2)Aiming at the lack of hysteresis in data rate adjustment of standard ADR algorithms,Mobile ADR algorithms are improved from two perspectives: improving the data rate of LoRa communication,and dynamically calculating the number of data packets selected.Firstly,the time on air(To A)of different modulation parameter combinations is used as a selection index for the adjustment scheme,expanding the bandwidth selection range and improving the data rate of the node;Secondly,according to the Doppler frequency offset formula,the maximum movement speed of different modulation parameter combinations under stable communication is calculated.Taking the movement speed as the adjustment basis,the number of data packets is dynamically adjusted to improve the response speed to changes in channel conditions.(3)According to the effect of motion status of the node on ADR,a multiple linear regression model of the motion speed,moving distance,and path loss of the moving node is established.At the same time,a positioning algorithm with less energy consumption and higher accuracy is designed.Based on the distance between the node and the gateway and the node movement speed,the network margin is dynamically determined,achieving a dynamic balance between data rate and packet extraction rate.This paper adopts the method of combining simulation and field test,the simulation results show that compared with the standard ADR and Blind ADR algorithms,the packet acquisition rate of Mobile ADR algorithm is improved by 27% on average,the packet collision rate is reduced by45% on average,and the network energy consumption is reduced by 8% on average.Then,this paper designs a hardware testbed,and is drop test experimental results show that the packet acquisition rate of Mobile ADR algorithm is improved by 14% on average,and the convergence time is shorter.Therefore,the Mobile ADR algorithm proposed in this paper improves the communication quality of LoRaWAN network in mobile scenarios,has strong adaptability and robustness,has good performance even in static scenarios,and is a suitable LoRaWAN communication mechanism in complex and variable environments.