Bluetooth Low Energy Performance Analysis and Optimization in Environments with Interference

As a representative of low-power and low-range wireless communication protocols, Bluetooth Low Energy has been used more and more in various devices and applications. It is a wireless protocol defined in the 2.4 GHz frequency band, which is a license-free frequency band shared by many communication protocols. As a result, Bluetooth Low Energy is affected by the interference in this frequency band. In general, the interference for Bluetooth Low Energy can be distinguished into two categories. The first one is interference from other wireless communication protocols, such as Wi-Fi and ZigBee. Due to the wide range of applications of Wi-Fi in the 2.4 GHz frequency band, it is considered the most occurring interference for Bluetooth Low Energy. The second one is the interference from Bluetooth Low Energy itself. Although all the Bluetooth Low Energy devices implement the same protocol, neighboring devices and their communications impact each other since they share the same frequency band.

As a result of interference, the performance of Bluetooth Low Energy communications drops. This thesis focuses on the performance of Bluetooth Low Energy communications under interference. In this thesis, the classification of wireless interference for Bluetooth Low Energy is followed, thus the research is divided into two directions, i.e., Bluetooth Low Energy communication performance under Wi-Fi interference, and Bluetooth Low Energy communication performance under interference from other Bluetooth Low Energy devices. Furthermore, reliability and throughput are the two main performance metrics researched in this thesis.

The primary objective of the first research direction is to enhance the performance of Bluetooth Low Energy in the presence of Wi-Fi interference. To achieve this, two improvements are proposed based on the performance degradation of Bluetooth Low Energy caused by Wi-Fi interference. These improvements focus on optimizing the channel selection algorithms of Bluetooth Low Energy. By gathering interference information in the 2.4 GHz frequency band and developing corresponding algorithms, the channel selection process becomes more efficient. This enables Bluetooth Low Energy to avoid using channels occupied by Wi-Fi interference during communication, resulting in improved performance. Comparing to existing research, the two improvements reach the state-of-the-art level according to the experimental results. The new algorithms and logic proposed in this research direction can be further considered to be integrated into the standard.

The goal of the second research direction is to explain and quantify the performance degradation of Bluetooth Low Energy when subjected to interference from other Bluetooth Low Energy devices. According to the results of experiment and simulation, two mathematical models are proposed to explain the degradation in reliability and throughput of Bluetooth Low Energy. These two models quantify the impact of various factors on the performance metrics, such as Bluetooth Low Energy communication parameters and interference strength from other Bluetooth Low Energy devices. Through these two models, the reliability and throughput of Bluetooth Low Energy can be predicted under the interference from neighboring devices. Furthermore, these two models are combined to illustrate the trade-off between reliability and throughput within Bluetooth Low Energy communication under interference. Compared with the state of the art, these two models are the first to quantify the Bluetooth Low Energy performance metrics. Besides, the trade-off within Bluetooth Low Energy communication is also the first time discovered. The models can help the developers and researchers to set up Bluetooth Low Energy communication more efficiently.