Abstract
In order to comprehensively improve the sensitivity of fire warning and effectively shorten the warning time, this paper proposes and implements an indoor distributed fire alarm system based on low power wide area network. The system is mainly composed of three parts: a multisensor acquisition node based on LoRa technology, a distributed edge gateway, and a remote user monitoring system. The multisensor collection node obtains environmental parameters such as indoor temperature, smoke concentration, and air quality and then transmits the sensing data to edge gateway by LoRa after preprocessing. The edge gateway is based on an embedded Linux platform and is deployed in distributed state to collect and store data from multiple collection nodes. Besides, edge gateway forwards valid data to the remote user monitoring system by standard MQTT protocol. The user monitoring system displays current deployment area parameters to users in real time and provides early warning prompts based on relevant preset indicators to help the administrator make more accurate decisions on corresponding measures. The system has been deployed and tested in Nanjing Institute of Technology. By sensor calibration experiments, LoRa communication experiments, and system tests in different environments, the experimental results show that the average received signal strength in a small interference space is -104.12 dBm, and the average received signal strength in a noisy signal environment is -57.5 dBm. By setting the optimal transmitting power for each distance, the packet receiving rate can reach more than 95%, and the alarm accuracy can reach 100% under premise of ensuring the lowest power consumption. Finally, this paper conducts a comprehensive performance analysis on the wireless communication performance of environmental collection nodes, multisensor data fusion algorithm, distributed LoRa edge gateway deployment performance, and remote system early warning accuracy.
Highlights
Nowadays, fire is a common serious problem faced by countries all over the world
When the concentration of carbon monoxide in air reaches 50 ppm, it is the maximum content allowed for an adult to be in it
When it exceeds 200 ppm, the human body will have symptoms such as headaches and nausea. erefore, when the carbon monoxide concentration is set to 50 ppm, it is alarm threshold
Summary
Fire is a common serious problem faced by countries all over the world. While causing casualties, it will bring certain property losses and adverse sociopolitical effects. Many countries have conducted a lot of research on wireless communication technology applications to indoor fire protection Scholars such as Bo Chang studied the indoor fire monitoring system that used ZigBee wireless network to monitor the temperature, humidity, and smoke concentration of fire site in real time [3]. Liu Yunhong and other scholars studied the use of ZigBee to Wi-Fi communication gateway to collect the data collected by sensor nodes to gateway and upload it to servers to solve the indoor location problems of fire locations and evacuation plans [4] Scholars such as SwetaBasu adopted Wireless Sensor Network (WSN) to accumulate accurate environmental data by sensor nodes such as temperature, relative humidity, and different gas concentrations and send these data to base stations connected to the ground [5, 6].
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