IoT Based Smart Safety Wristband Using BLE Zone Sensing and LoRa Long-Range Alerting for High-Density Public Gatherings

Large religious and public gatherings, such as the Kumbh Mela, bring together millions of people in a small area for a short period. In these conditions mobile networks become congested, and an individual in distress often cannot be identified or reached in time. This paper presents the design of an IoT Based Smart Safety Wristband that combines two complementary low-power radio technologies. Bluetooth Low Energy (BLE) is used for short-range zone sensing and active geofencing: fixed beacons advertise their zone identity, and the wristband classifies the zone it is in. LoRa is used for long-range, infrastructure-independent delivery of compact alert packets to a gateway, from where a web dashboard shows the zone and status of every wristband. The wristband is built around an ESP32 microcontroller with an SOS button, an OLED display, a vibration motor, a buzzer and status LEDs, and is powered by a rechargeable Li-ion cell. We review thirteen published studies on LoRa range and reliability, BLE zone detection and crowd safety, and use their findings to justify key design choices: a very short payload, a sliding-window RSSI filter with hysteresis, and local alerting that works even when the backhaul is unavailable. The paper reports the system design, the alert protocol, an analytical time-on-air estimate and a structured evaluation plan. Field measurements are deliberately not reported, because the prototype tests are still in progress; the evaluation tables are provided so that measured values can be entered once available