Dependable interference-aware time-slotted channel hopping for wireless sensor networks
IEEE 802.15.4 Time-Slotted Channel Hopping (TSCH) aims to improve communication reliability in Wireless Sensor Networks (WSNs) by reducing the impact of the medium access contention, multipath fading, and blocking of wireless links. While TSCH outperforms single-channel communications, cross-technology interference on the license-free ISM bands may affect the performance of TSCH-based WSNs. For applications such as in-vehicle networks for which interference is dynamic over time, it leads to non-guaranteed reliability of the communications over time. This article proposes an Enhanced version of the TSCH protocol together with a Distributed Channel Sensing technique (ETSCH+DCS) that dynamically detects good quality channels to be used for communication. The quality of channels is extracted using a combination of a central and a distributed channel-quality estimation technique. The central technique uses Non-Intrusive Channel-quality Estimation (NICE) technique that proactively performs energy detections in the idle part of each timeslot at the coordinator of the network. NICE enables ETSCH to follow dynamic interference, while it does not reduce throughput of the network. The distributed channel quality estimation technique is executed by all the nodes in the network, based on their communication history, to detect interference sources that are hidden from the coordinator. We did two sets of lab experiments with controlled interferers and a number of simulations using real-world interference datasets to evaluate ETSCH. Experimental and simulation results show that ETSCH improves reliability of network communications, compared to basic TSCH and the state-of-the-art solution. In some experimental scenarios NICE itself has been able to increase the average packet reception ratio by 22% and shorten the length of burst packet losses by half, compared to the plain TSCH protocol. Further experiments show that DCS can reduce the effect of hidden interference (which is not detectable by NICE) on the packet reception ratio of the affected links by 50%.
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