## 3 Beacon-Based Hazard Alarm System Design
### Detailed Design of the Components
#### 3.3.1 Beacon-Based Distance Monitoring
Therefore, the planning of this type of sensor-based hazard alarm system would need to be complemented with a secondary hazard notification system, and it also should have a built-in self-monitoring mechanism so that the workers do not rely on the hazard alarm system when it is not functioning properly. Similar points have been put forward by other researchers. As a BLE-based safety monitoring system has several limitations, the integration of BLE with other sensor technologies, such as BIM, RFID, and GPS, can improve the effectiveness of safety monitoring systems in the construction sector [58]. ## 7 Conclusions

An experimental study was conducted to address the knowledge gaps regarding the impact of the beacon sensor locations on the effectiveness of beacon-based hazard alarm systems in construction sites. In the experiment, the locations where the experimenter received the first hazard alarm were recorded in repetitive trials while the beacon sensor was located in four different locations, such as (1) at the entrance of the room, (2) behind the front side wall, (3) on the internal wall facing the access point, and (4) on the internal wall not facing the access point, in a partially enclosed room in a concrete building. The results show that the hazard alarm function of the system could be severely affected by the beacon sensor's location in such a context and implies that the locations of the beacon sensors should be decided carefully based on the type of hazard to be warned of and the workers targeted to receive the alarms. Furthermore, the findings imply that the distance of the hazard alarm signal deliveries can be controlled by deciding the most appropriate location for the beacon sensors in construction work environments. For example, beacon sensors can be located behind walls to limit the area of interest for sending the alarms, and beacon sensors can be located near the access point to the workspace to send the hazard alarms to all workers in the wider area. These findings provide practical insights into how beacon sensors can be deployed for the best performance of hazard alarm systems. This research has several limitations that need to be considered in future research. As the RSSI value-based distance measure can be influenced by several environmental factors, such as the temperature, humidity, and obstacles that can block the sensor signals, the experiment would need to be repeated under different environmental conditions, such as different times of the year, different climates, and different structural materials, for a more comprehensive understanding of how beacon-based hazard alarm systems can work most effectively to send targeted hazard alarm notifications. Additionally, future research can investigate the sensor deployment problem in the context of multiple beacon sensors used simultaneously to localize construction workers for better accuracy of hazard alarm. Such location tracking-based hazard alarm systems can have advantages over single-sensor-based and proximity-based sensor systems in producing hazard alarm notifications with lower error rates, but sensor deployment plans cannot be as dynamic, flexible, or cost-effective as single-proximity sensor-based systems. Hence, the benefits and limitations of different sensor-based hazard alarm systems need to be investigated with further experimental research efforts, and more experimental studies would be required to compare the performance of different system designs while considering the practicality and user experience perspectives. Conceptualization, S.A., J.S. and T.W.K. ; methodology, S.A., J.S. and T.W.K. ; software, F.K. ; validation, F.K. and Y.H. ; formal analysis, F.K. ; investigation, F.K. ; resources, S.A. and Y.H. ; data curation, F.K. ; writing--original draft preparation, F.K. and S.A.; writing--review and editing, S.A., J.S. and T.W.K. ; visualization, F.



* [PERSON] et al. (2017) [PERSON]; [PERSON]; [PERSON]; [PERSON] Wearable Imu-Based Real-Time Motion Warning System for Construction Workers' Musculoskeletal Disorders Prevention.