Research On LoRaWAN Adaptive Data Rate Algorithm Based On OPNET

LoRaWAN technology can achieve high-efficiency long-distance communication with low energy consumption in harsh environments and is increasingly being used in outdoor wireless sensor networks(WSN).Adaptive Data Rate(ADR)is the advantage of LoRaWAN,whi ch can allocate an appropriate data rate to terminal devices to improve channel utilization and reduce network energy consumption.However,the basic ADR algorithm is only suitable for static terminal equipment.Due to the location change of the mobile nod e,the selected data rate may not match the new environment,resulting in communication packet loss,and the complex and changeable external environment will also make the channel condition worse.Dynamic changes are generated,thereby affecting or even limiting the adjustment ability of the basic ADR algorithm.So,it is not applicable in remote areas such as complex and variable farmland environments and dense forests.In view of the shortcomings of LoRaWAN adaptive data rate regulation in complex environment,this paper explored and researched a series of problems from adaptive data rate regulation algorithm design,FLoRaWAN simulation framework establishment,and network performance analysis.The main work is accomplished in the following aspects.First,based on the existing ADR algorithm regulation mechanism and its shortcomings,considering the two major difficulties of ADR algorithm regulation in practical application scenarios,i.e.,channel quality assessment and rate selection,this paper proposed a novel and more effective ADR algorithm,called ND-ADR(New-Dynamic ADR)algorithm.The algorithm can dynamically allocate the number of packets received according to the actual condition of each terminal node as the calculation basis for rate adjustment,and use the received signal strength indicator(RSSI)and the average signal-to-noise ratio(SNR)of the terminal node as the allocation basis for rate adjustment,thus making the ND-ADR algorithm more adaptable in such environment.Second,considering that the actual propagation loss model constructed by the Friis transmission equation has problems such as larger error values and fewer application scenarios,the Okumura-Hata propagation loss model was constructed in this paper by combining the characteristics of LoRa modulation technology.Third,in order to better study and analyze the LoRaWAN network performance of ADR algorithm under different environmental disturbances,based on the LoRaWAN protocol stack architecture and network topology,this paper d eveloped a simulation framework FLoRaWAN(Frame for LoRaWAN)for LoRaWAN protocol in OPNET.In the FLoRaWAN simulation framework,the LoRaWAN node model was constructed,which covers the physical layer model and the three-layer process model to realize the ADR algorithm regulation process;the LoRaWAN channel transmission model was constructed based on the built Okumura-Hata propagation loss model with the introduction of adjustable factors to reflect the perturbation of channel transmission by the change of external communication environment.In addition,two network scenarios,static node and random mobile node,were constructed based on different terminal device application scenarios.Finally,in order to better analyze and judge the LoRaWAN network performance under ADR algorithm,three key network performance parameters,namely,network energy consumption,transmission delay and effective throughput,were selected in this paper,and the number of received packets selected by ND-ADR algorithm in different nodes were statistically analyzed to compare and analyze the network performance of three ADR algorithms in two LoRaWAN application scenarios based on different external interference conditions.A large number of simulations have shown that the number of packets to be received varies for different terminal devices when assigning data rates,and that the ND-ADR algorithm can reduce the network energy consumption by about 13% and the network transmission delay by about 18%,and improve the effective throughput by about 15% compared to the basic ADR algorithm,even based on mobile network scenarios in harsh environments.Therefore,the ND-ADR algorithm proposed in this paper is more suitable for wireless communication of removable nodes in variable and complex environments.Its advantages are better sensing of link environment,faster data rate adjustment,improved channel utilization,and further reduction of network energy consumption.