Enhanced Time-Slotted Channel Hopping in WSNs Using Non-intrusive Channel-Quality Estimation

Cross-technology interference on the license-free ISM bands has a major negative effect on the performance of Wireless Sensor Networks (WSNs). Channel hopping has been adopted in the Time-Slotted Channel Hopping (TSCH) mode of IEEE 802.15.4e to eliminate blocking of wireless links caused by external interference on some frequency channels. This paper proposes an Enhanced version of the TSCH protocol (ETSCH) which restricts the used channels for hopping to the channels that are measured to be of good quality. The quality of channels is extracted using a new Non-Intrusive Channel-quality Estimation (NICE) technique by performing energy detections in selected idle periods every timeslot. NICE enables ETSCH to follow dynamic interference well, while it does not reduce throughput of the network. It also does not change the protocol, and does not require non-standard hardware. ETSCH uses a small Enhanced Beacon hopping Sequence List (EBSL) to broadcast periodic Enhanced Beacons (EB) in the network to synchronize nodes at the start of timeslots. Experimental results show that ETSCH improves reliability of network communication, compared to basic TSCH and a more advanced mechanism ATSCH. It provides higher packet reception ratios and reduces the maximum length of burst packet losses.