BLE Connectivity and its Multi-hop Extension for IoT Applications

Abstract

Bluetooth Low Energy (BLE) is one of the representative low-power communication protocols that are being used to provide wireless connectivity for resource constrained devices as part of Internet of Things (IoT). Despite its commercial adoption, BLE's current use is limited to short-range applications due to the lack of research about its coverage extension. In this dissertation, we investigate two issues that need to be addressed for BLE's network coverage extension and also consider a new application scenario using a BLE-based multi-hop network. First, we tackle the BLE connection maintenance and energy consumption problems by adaptively controlling one of BLE's link layer parameters (TCI ) under dynamic channel condition. We formulate an optimization problem to find an optimal TCI and design a connection interval adaptation mechanism for BLE to achieve high energy efficiency while maintaining robust connectivity. We evaluate our proposed solutions through testbed experiments and simulation which shows that it reduces energy consumption of BLE in dynamic channel environments. Secondly, we consider a protocol architecture that aims to run IPv6 routing protocol for low power and lossy networks (RPL) over BLE to construct BLE-based multi-hop networks. We design an adaptation layer between BLE and RPL which tightly couples RPL and BLE operation. We implement the adaptation layer in a Linux kernel to realize RPL over BLE. Through extensive experiments in an indoor testbed, we evaluate the performance of RPL over BLE and compare the performance results with that of RPL over IEEE 802.15.4 which shows signicant improvement. Lastly, we consider a new application scenario of BLE using the coverage extension of BLE based on multi-hop networking. We propose a novel layered architecture of Wi-Fi and BLE that constructs an energy efficient and high data rate supportable ad-hoc network for disaster communication. We implement the proposed architecture in Linux kernel and evaluate the performance through our indoor testbed. The result shows that our proposed solution reduces the average power consumption of nodes in the testbed compared to a conventional Wi-Fi ad-hoc network.