X-Cast: Cross-Technology Broadcasts for Enhanced Spectrum Utilization in Low-Power Networks

Cross-technology interference is becoming a major challenge for reliable wireless communication. For instance, the 2.4 GHz ISM band accommodates various technologies such as Wi-Fi, Bluetooth Low Energy (BLE), and IEEE 802.15.4, often leading to significant coexistence issues. Devices such as Wi-Fi routers dominate the shared spectrum due to their greater power and bandwidth, negatively impacting reliability, increasing latency, and raising power consumption of low-power networks based on BLE or IEEE 802.15.4. Existing coexistence schemes primarily focus on efficiently utilizing overlapping radio channels by adjusting transmissions rather than preventing interference by smartly (re-)allocating radio channels. This paper introduces X-Cast, a novel approach for cooperatively reallocating radio channels among heterogeneous wireless networks to utilize the frequency spectrum more efficiently, reduce interference, and foster coexistence. X-Cast employs cross-technology broadcasts to share information about the radio channels a network uses with nearby appliances. Based on the underlying wireless technology, X-Cast autonomously determines appropriate actions, such as switching to a different channel or blocklisting a specific channel. We seamlessly integrate X-Cast into the Zepyhr operating system and evaluate its performance using off-the-shelf Wi-Fi, BLE, and ZigBee devices. Our experiments demonstrate the effectiveness of X-Cast, showing up to 18 % and 46 % improvements in linklayer packet reception for BLE and ZigBee devices, respectively. Moreover, X-Cast reduces the maximum communication latency by up to 3x for BLE devices and up to 10x for ZigBee devices while lowering their power consumption by as much as 25 %.