Evaluating and Modeling IEEE 802.15.4 TSCH Resilience against Wi-Fi Interference in New-Generation Highly-Dependable Wireless Sensor Networks

Thanks to its ability to effectively counteract disturbance and interference, including the traffic generated by co-located Wi-Fi networks, Time Slotted Channel Hopping (TSCH) is currently gaining momentum in many application fields characterized by demanding reliability and determinism requirements. In particular, the ability of TSCH to change transmission frequency on every attempt sensibly mitigates packet losses and latencies, improving the overall behavior in a tangible way. In this paper, the communication quality achieved by TSCH in a setup that includes real motes exposed to a realistic interfering traffic is evaluated experimentally. A theoretical model is also developed, based on quite simple assumptions about the effectiveness of time and frequency diversity, which satisfactorily matches the real behavior. The model permits to determine how much network parameters like, e.g., the retry limit, actually affect communication, and can be exploited to find proper settings for them. Finally, the ability of channel hopping to prevent narrowband interference from disrupting communication is assessed. As results show, this mechanism makes motes suffer from an equivalent interference that roughly corresponds to the mean interference evaluated over all physical channels.