Bluetooth low energy multi-hop networks face timing and collision challenges
Deconstructing BLE Multi-hop: a Model-based Approach to Quantifying the Challenges
Networking and Internet Architecture
Summary
Bluetooth Low Energy (BLE) was made for simple one-on-one connections, but people want to use it for networks where messages hop through several devices. The authors studied how tiny differences in device clocks cause trouble in these multi-hop networks, making connections collide and desynchronize. They built a math model to measure how often these collisions happen and tested it with real hardware. Their findings show that clock differences cause repeated collisions, limiting how well BLE can form multi-hop networks unless changes are made to the system or hardware.
What this means in practice
- •For wireless network engineers: Design more reliable BLE multi-hop networks by accounting for clock drift and collision risks quantified by the authors’ model.
- •For hardware developers: Develop BLE devices with improved clock accuracy or hardware features to reduce collisions in multi-hop setups.
Authors
Bozheng Pang, José Alamos, Thomas C. Schmidt, Matthias Wählisch
Abstract
Bluetooth Low Energy (BLE) was originally designed for point-to-point communication, but BLE multi-hop networks have attracted academic and industrial interest. Multi-hop communication, however, introduces desynchronized nodes to the network due to the difference in individual clocks. In this paper, we study the impact of clock drift on a BLE multi-hop network. The aim is to find out if a BLE multi-hop network can be properly set up, why, and how. For this goal, we develop a mathematical model to quantify the collision probability among BLE connections managed by a single device. We provide a simplified version of the model for constrained deployment. The impact of clock drift and our mathematical model are validated through practical experiments. Afterward, we find that a BLE multi-hop network cannot eliminate the impact of clock drift in most cases. Moreover, from a long-term point of view, the collision between BLE connections occurs with a fixed frequency. We further analyze the limitation of using BLE to form multi-hop networks, and propose possible solutions, such as topology limitation, changes to BLE stack or hardware. This paper is a clear and quantitative problem statement on the limitations of using BLE in multi-hop networks.