Effects of Body Occlusion on Bluetooth Low Energy RSSI in Identifying Close Proximity of Pedestrians in Outdoor Environments

Internet-of- Things (IoT) employs a variety of sensing technologies to monitor environment, activities, processes, and surrounding. One such sensing technology includes Bluetooth Low Energy (BLE) which could be used to study pedestrian traffic. This can subsequently be used to understand utilisation of spaces and to ameliorate mobility and transportation. Such studies can contribute to urban (re-)development plans to sustainably smarten the built environment, but this is only possible by having a clear understanding of the nature of BLE signal propagation and correlating its Received Signal Strength Indicator (RSSI) values to environmental topology and pedestrian movements. Additionally, in comparison to other pedestrian behaviour monitoring technologies, BLE limits pedestrians identification and hence, can be aligned to preserve their privacy. In this paper, we highlight the effect that body occlusion has on BLE RSSI values. The objective is to identify indicators in the pattern of RSSI values that identifies the way BLE devices are carried by pedestrians moving in the environment. This study will allow planners who study pedestrian traffic to form a better understanding of BLE signal propagation and signal interaction in outdoor environments. The knowledge acquired through this study will feed in to the development of an outdoor pedestrian monitoring system that is capable of identifying pedestrian behavioural patterns while preserving their privacy.