Evaluation of bluetooth low energy for drone-led opportunistic sensor data collection

Abstract

This document presents a study of Bluetooth Low Energy (BLE) in opportunistic data collection scenarios. An overview of BLE protocol stack is examined making emphasis in the Link Layer states and roles, PDU and connection and timing. An introduction to the BLE121LR module is reviewed with its general characteristics such as current consumption and range. A brief description of the software tools that Bluegiga provides to configure the module is shown. Four projects were build; one for the broadcaster role, two for the peripheral role and one for the central device. A theoretical study of the most important performance parameters for opportunistic data collection were performed. Firstly, the propose scenario is Conferred: a drone flying by once a day over a sensor connected to a BLE device. Using a parameter like the drone speed and height, an expression for the contact time is calculated. Then, the average current, the lifetime, the maximum transferred information and the energy to transmit one bit are calculated as well. An experimental evaluation was conducted using a power analyzer and the different parameters were validated. Also, throughput test were performed with the objective of maximizing the amount of information that can be transferred. The results show that BLE is suitable for opportunistic data collection scenarios and that the contact time is a critical factor in the lifetime of the BLE device when acting in the peripheral role; this, while for the broadcaster role is the advInterval. As more information is transferred between modules, the average current of Tcontact becomes critical and this value should be optimized, taking into an account the amount of information the application will need to transfer. The throughput test results obtained were higher than those achieved by the manufacturer with an operating range of 200 m.