A3: Adaptive Autonomous Allocation of TSCH Slots

Abstract

Time Slotted Channel Hopping (TSCH), defined in the IEEE 802.15.4e standard requires complicated slot scheduling to enjoy its collision-free multihop communication capabilities fully. Recently, several autonomous scheduling algorithms that allocate slots without central control and additional control message exchange have been devised. However, autonomous algorithms are traffic oblivious, assigning the same number of slots regardless of traffic demands. Undifferentiated resource allotment is identified as the root cause that impairs the performance of TSCH networks. To address the issue, we propose A(3), an autonomous and adaptive slot allocation scheme that adjusts the number of slots per slot-frame according to varying traffic loads. A key component of A(3) is receiver-side load estimation in real-time without any explicit control message exchange. A(3) can be combined with any autonomous scheduling protocols, such as Orchestra and ALICE. With extensive evaluation on a large public testbed comprising 62 nodes, we verify that A(3) significantly enhances autonomous scheduling algorithms' performance. It improves throughput by more than twice, PDR (Packet Delivery Ratio) by more than six times, and reduces the latency by ten times.