BLE Connectivity and its Multi-hop Extension for IoT Applications

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 박세웅.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.1 Introduction 1 1.1 Motivation 1 1.2 Related Work 4 1.2.1 Low power consumption of BLE 4 1.2.2 BLE multi-hop networking 5 1.3 Contributions and Outline 6 2 CABLE: Connection Interval Adaptation for BLE in Dynamic Wireless Environments 10 2.1 Introduction 10 2.2 Background and Problem Statement 14 2.2.1 Link layer operation 14 2.2.2 Connection loss due to supervision timeout 16 2.2.3 BLE protocol stack and connection interval set- ting 17 2.2.4 Problem of BLE with xed connection interval 19 2.3 Connection Interval Optimization 22 2.3.1 Problem formulation 22 2.3.2 Problem solution 26 2.4 CABLE System Design 29 2.4.1 PER estimator 30 2.4.2 TCI adjuster 33 2.5 Performance Evaluation 34 2.5.1 Simulation results 35 2.5.2 Experimental results 40 2.6 Summary 41 3 A Synergistic Architecture for RPL over BLE 43 3.1 Introduction 43 3.2 Background 47 3.2.1 RPL operation 47 3.2.2 BLE link layer operation 48 3.2.3 6LoWPAN for BLE 50 3.3 Design of RPL over BLE 52 3.3.1 Synergistic Network Architecture for RPL over BLE 52 3.3.2 DIO broadcast over advertising channels 54 3.3.3 Routing metric for RPL over BLE 57 3.3.4 RPL parent change with BLE connection man- agement 60 3.4 ALBER Implementation 61 3.5 Performance Evaluation 64 3.5.1 Testbed environments 64 3.5.2 Comparison of RPL over BLE vs. RPL over 802.15.4 65 3.5.3 Eect of varying connection interval 70 3.5.4 Eect of ECI-based routing metric 71 3.6 Summary 73 4 Wi-BLE: A Novel Layered Architecture of Wi-Fi & BLE Networks for Disaster Communications 74 4.1 Introduction 74 4.2 Background 78 4.2.1 Application requirements of ad-hoc networks for disaster communications 78 4.2.2 Candidate wireless interfaces for ad-hoc networks 79 4.2.3 Wi-BLE use scenario 79 4.3 Wi-BLE System Overview 80 4.3.1 Protocol Architecture 80 4.3.2 Operation Overview 81 4.4 MABLE: Mobile Ad-hoc for BLE 82 4.4.1 Routing protocol selection for MABLE 82 4.4.2 BLE Channel Usage for AODV over BLE 84 4.5 Wi-BLE: Wi-Fi Ad-hoc over BLE networks 88 4.5.1 Wi-BLE control packet delivery over BLE path 88 4.5.2 Routing protocol for Wi-BLE 89 4.5.3 Wi-Fi on/o control for energy saving 92 4.6 Implementation 92 4.7 Performance Evaluation 94 4.7.1 Testbed Environments 94 4.7.2 Hop distance &Throughput 95 4.7.3 Power Consumption 97 4.8 Summary 98 5 Conclusion 100 5.1 Research Contributions 100 5.2 Further Research Direction 102Docto