Bit loading for OFDM with Quasi-constant transmission power

2006 ◽  
Author(s):  
Elad Izhak ◽  
Ofer Amrani
Keyword(s):  
Transmission Power ◽  
Bit Loading

scholarly journals Smart Helmet-Based Personnel Proximity Warning System for Improving Underground Mine Safety

2021 ◽  
Vol 11 (10) ◽  
pp. 4342
Author(s):  
Yeanjae Kim ◽  
Jieun Baek ◽  
Yosoon Choi
Keyword(s):  
Signal Detection ◽  
Performance Test ◽  
Warning System ◽  
Mine Safety ◽  
Transmission Power ◽  
Detection Distance ◽  
Task Load ◽  
Smart Glasses ◽  
Heavy Equipment ◽  
Equipment Operator

A smart helmet-based wearable personnel proximity warning system was developed to prevent collisions between equipment and pedestrians in mines. The smart helmet worn by pedestrians receives signals transmitted by Bluetooth beacons attached to heavy equipment, light vehicles, or dangerous zones, and provides visual LED warnings to the pedestrians and operators simultaneously. A performance test of the proposed system was conducted in an underground limestone mine. It was confirmed that as the transmission power of the Bluetooth beacon increased, the Bluetooth low energy (BLE) signal detection distance of the system also increased. The average BLE signal detection distance was at least 10 m, regardless of the facing angle between the smart helmet and Bluetooth beacon. The subjective workload for the smartphone-, smart glasses-, and smart helmet-based proximity warning system (PWS) was evaluated using the National Aeronautics and Space Administration task load index. All six workload parameters were the lowest when using the smart helmet-based PWS. The smart helmet-based PWS can provide visual proximity warning alerts to both the equipment operator and the pedestrian, and it can be expanded to provide worker health monitoring and hazard awareness functions by adding sensors to the Arduino board.

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