DIGEST: a decentralized divergecast scheduling algorithm for IEEE 802.15.4e TSCH in the internet of things

摘要

Internet of Things is emerging as a commercial phenomenon. It is conjectured that billions of appliances will be connected within the current Internet infrastructure by 2020. These networked appliances require low-power radio and reliability. Hence, IEEE brought up a very efficient, reliable and deterministic time-frequency enabled medium access control protocol, IEEE 802.15.4e time slotted channel hopping (TSCH), on top of low power IEEE 802.15.4 radio for the industrial market. IEEE 802.15.4e TSCH is able to run a communication schedule for MAC upon a communication schedule is built. However, the issue of how such scheduling will be made, updated, and maintained is beyond the scope of the IEEE 802.15.4e TSCH standard. The unit responsible for these tasks is also out of its scope. That means, required scheduling mechanism is absent in this standard. In order to complete this gap, several communication scheduling algorithms are introduced in the literature. In this study, we first introduce another decentralized divergecast communication scheduling algorithm, called as DIGEST, where divergecast implies that network traffic moves in any directions opposed to convergecast where network traffic moves from leave nodes to root. That DIGEST algorithm tries to schedule time slots by selecting a neighbor node at first. When choosing a neighbor node, it tries to make almost equal number of dedicated time slots to each neighbor. In this way, it can provide better schedules with neighbor nodes than other scheduling algorithms. We evaluate the effectiveness of DIGEST, Diva, and Berkeley's Aloha-based scheduling algorithms under static and mobile environments by running extensive simulations. Our simulation results indicate that the DIGEST algorithm is superior to the others in terms of the neighbor connectivity ratio.