Design Of Building Environment Monitoring System Based On LoRa Wireless Sensor Network

With the development of the Internet of Things,it is of great significance to apply the IoT technology to the building to realize the intelligent building,improve the comfort of the building environment,and promote the effective energy conservation of the building.Monitoring the building environment is the premise of related equipment control in the building.A building environment monitoring system based on LoRa wireless sensor network is designed in this paper,which solves the problems of wide monitoring area,many obstacles,long system operation period,many sensor nodes and complicated acquisition information in building environment monitoring.Firstly,some wireless communication technologies such as the Wi-Fi,ZigBee,Bluetooth,2G/3G/4G,LoRa are compared and analyzed in this paper.Based on the advantages of LoRa technology such as wide coverage,low power consumption and easy deployment,the application of LoRa technology in building environment monitoring is proposed.Then,the overall scheme of the building environment monitoring system is designed.A number of environmental parameter information,including temperature,relative humidity,illuminance and dust concentrations are collected by sensor nodes.Multiple sensor nodes and central aggregation nodes form a star wireless sensor network.Measurement data transmitted to the central aggregation node through LoRa wireless communication technology by sensor nodes,and then the measurement data of each sensor node transmitted to the server through the GPRS module by the central aggregation node,and users can query monitoring data through various methods such as local host program,mobile terminal and Web terminal.Next,the hardware of the sensor node and the central aggregation node are designed with the modular design idea.The hardware circuit parts of the sensor node include a power management module,an interface circuit of each sensor,an OLED display module,a LoRa communication module,and a minimum system module of the microcontroller.The hardware circuit parts of the central aggregation node include a power management module,a LoRa communication module,a GPRS communication module,and a minimum system module of the microcontroller.And then,the characteristics of typical embedded operating systems are analyzed.Considering the system perception layer with the limited memory and computing capacity,and the needs for security,reliability,networking capability,the Contiki IoT operating system with low hardware requirements and abundant network protocol stacks is selected as the software environment of the system.The core of the Contiki and its Rime protocol stack are transplanted.Based on the Contiki system,embedded software for multitask scheduling is designed,including multiple sensor data acquisition processes and display communication process.Then,in order to realize the safe storage,effective processing of system monitoring data,the service platform of the building environment monitoring system is designed,including the local host program for local service,the Android application and the Web application system for remote service.Finally,the designed system is tested.The test results have shown that the building environment monitoring system based on LoRa wireless sensor network designed in this paper has certain feasibility.