B-hop: Time-Domain Adjustment of BLE Frequency Hopping Against Wi-Fi Beacon Interference

As Wi-Fi access points (APs) are deployed more densely, the cross-technology interference (CTI) from Wi-Fi is becoming a real threat to co-existing low-power Internet of Things protocols such as Bluetooth low energy (BLE). In this work, we pay attention to Wi-Fi beacons that take a substantial amount of airtime in the 2.4-GHz Industrial Scientific Medical (ISM) band. We develop B-hop, a standard-compliant framework that adjusts BLE frequency hopping to avoid expected Wi-Fi beacons in the time domain. B-hop operates on BLE central devices where Wi-Fi and BLE protocols are co-located, and it requires no modifications to Wi-Fi devices or BLE peripheral devices. B-hop predicts future beacon transmissions and reschedules the time domain of frequency hopping to avoid collisions. We implement a B-hop prototype using Zephyr, an open-source embedded operating system that allows us to modify necessary BLE link-layer operations. We evaluate the performance of B-hop through simulations and test-bed experiments and demonstrate that B-hop significantly outperforms legacy BLE frequency hopping schemes that only use frequency-domain adjustment.