Distributed Slot Scheduling for QoS Guarantee over TSCH-based IoT Networks via Adaptive Parameterization

Internet of Things (IoT), which connects a large number of devices with wireless connectivity, has come into the spotlight. As the scope of IoT applications becomes wider, we observe a surge of missioncritical IoT services, e.g., industrial automation systems and medical IoT systems, requiring to satisfy stringent latency, reliability, and/or energy efficiency guarantees. For this purpose, a new MAC, called Time Slotted Channel Hopping (TSCH), has been standardized in IEEE 802.15.4e. However, it is challenging to design a distributed scheduling protocol that achieves the required QoS and energy efficiency at the same time due to complicated tradeoff (providing enough number of slots for QoS vs. minimizing scheduled slots for energy efficiency). In this paper, we propose a novel framework for providing QoS, called SSAP, which is designed to maximize network lifetime in a distributed fashion while satisfying given reliability and latency requirements. To this end, we decompose our goal into two crucial design components: (i) scheduling of slot and channel, and (ii) control of medium access period, each of which is performed by low-complexity and distributed mechanisms. To the best of our knowledge, this paper is the first work to comprehensively handle multiple QoSes for TSCH-based IoT networks. We implement SSAP in Contiki OS and perform extensive simulations and real experiments under various scenarios. Our evaluation results demonstrate that SSAP satisfies highly reliable communication and latency requirements while having the network lifetime that is 1.6 times longer compared to existing protocols for TSCH.