An NB-IoT Monitoring System for Digital Mobile Radio With Industrial IoT Performance and Reliability Evaluation

A digital mobile radio (DMR) system facilitates direct person-to-person communication and serves as a vital communication tool, particularly in buildings. In situations where the mobile network signal is weak or blocked within a building, DMR system ensures seamless communication. Reliability is paramount, especially in emergencies. Therefore, this study puts forward a monitoring system that uses data analysis and prediction to prevent DMR system failures and communication disruptions within a building. The monitoring hardware is strategically positioned at DMR stations, such as DMR base stations or bidirectional amplifiers (BDAs). This monitoring hardware contains two essential components: a sensing circuit and a narrowband Internet of Things (NB-IoTs) network analyzer. The sensing circuit includes five sensors—ac current sensor, device temperature sensor, particulate matter (PM) sensor, RF meter, and temperature and humidity sensor—which are used for data collection and performance analysis of the DMR system. The NB-IoT network analyzer is integrated to monitor network stability. Initially, it assesses the NB-IoT network stability by examining the receive signal indicators (RSSIs) across supported frequency bands. The data collected aids in selecting the optimal band for the monitoring system and determining the stability of the location. The analyzer continues to monitor the network stability even after the sensing circuit is installed. In the event of abnormal situations such as low ac current and RF power, the DMR monitoring system sends alerts to users, enabling immediate issue resolution and preventing severe problems like DMR system disconnection. Experiments were conducted to evaluate and validate the proposed monitoring system.