HMM-driven Smart White-space-aware Frame Control Protocol for coexistence of ZigBee and WiFi

ZigBee has been used more and more extensively in various applications such as wireless patient monitoring, herds monitoring, smart control in home networking and game remote controllers, etc. Most of these applications are performance-sensitive so the throughput and packet delivery ratio should be guaranteed for ZigBee system to work properly. However, since both WiFi and ZigBee are operated in unlicensed ISM spectrum, the interferences from WiFi hotspots make the coexistence of ZigBee and WiFi a big challenge. WiFi traffic contains quite a lot of white spaces between frame clusters in the time domain which could be taken advantage of to improve the performance of the systems with the coexistence of ZigBee and WiFi. Most existing mechanisms dealing with the coexistence of heterogeneous wireless systems neglects this important fact. In this paper, we propose a novel approach that ensures high performance of ZigBee in spite of the presence of strong interference from WiFi, and at the same time keep the WiFi performance almost unaffected. Our approach is to learn a Hidden Markov Model (HMM) based on traces of WiFi white-spaces in the current network. With such a HMM model we can accurately characterize the dynamic distribution of the durations of white spaces in different times. Based on the HMM model of white spaces and the analysis of system performance we develop a novel ZigBee frame control protocol called HMM-driven Smart White-space-aware Frame Control Protocol which can allow ZigBee networks to coexist with WiFi networks with desired link throughput and packet delivery ratio. Some initial experimental results have shown the effectiveness of our protocol.