Bounding Latency in Bluetooth Low Energy Device Discovery

Bluetooth Low Energy (BLE) is designed for the purpose of reducing the energy consumption and extending the life cycle of Bluetooth devices. Its application scenario lies in a small-scale Internet of Things environment. These devices are usually small and exquisite and easy to carry. Since these devices are powered by the battery inside, it is an important issue for BLE to reduce power consumption and extend usage time without reducing performance. The data communication of BLE devices can only start after advertising, scanning, and connecting. Therefore, the configuration of advertising and scanning parameters of BLE devices is another important issue that affects performance. For advertising, there are advertising interval, advertising event, random delay, etc. For scanning, there are scan window, scan interval, etc. The combination of different parameters can lead to a large variation in the neighbor discovery process (NDP) time. In this paper, we investigate and analyze the relationship between parameters and the discovery latency. We show that unbounded latency could occur when the advertising interval is equal to an integer multiple of scan interval minus the average random delay. We further propose a method to bound the discovery latency by adjusting the parameters as appropriate during the discovery process.