## 2 Related Work
However, unlike distributed scheduling, each node can autonomously choose its own schedule without any signaling for schedule creation or modification. Autonomous scheduling has the advantage of less overhead in the network for scheduling than centralized and distributed approaches. The publication of Orchestra [14] initiated the field of autonomous scheduling for TSCH. Orchestra is a recent scheduling solution for TSCH which brings important advantages such as the use of simple scheduling rules with a high delivery rate. Orchestra has several strengths that make it a promising scheduling solution for TSCH networks. Orchestra scheduling is neither centralized nor distributed and is calculated autonomously, where each network node locally maintains its own schedule based on information from the routing layer. The Orchestra schedule consists of three types of slotframes: The EB slotframe, which has a size of 397 timeslots, is dedicated to EB (TSCH Enhanced Beacon) transmissions, and is used for TSCH association and child-parent synchronization. The broadcast slotframe, which has a size of 31 timeslots, is intended for broadcasting control messages and for transmitting any packet when a unicast cell is not planned. Finally, the unicast slotframe is intended for the transmission of traffic between the RPL parent and all of its children. Escalator [15], another autonomous scheduling scheme which is based on Orchestra, generates a consecutive timeslot schedule along the packet forwarding path to minimize the packet transmission delay. This means that in one timeslot, a node receives a packet generated from a descendant node, and in the next timeslot, the node sends the received packet to its parent immediately. On the other hand, ALICE [16] allocates a unique cell for each traffic direction link instead of allocating a cell for each node. This strategy has helped reduce contention, collision, and latency issues. e-TSCH-Orch [17] also tried to reduce Orchestra latency by focusing on scheduling. It operates such that when a node sends a packet to a neighboring node, it indicates the number of packets in its transmit queue. Its neighboring node schedules this amount of consecutive Rx cells, and when the slotframe has enough free time slots, the node can use them to empty its queue. TESLA [18] is an adaptive approach that aims to minimize energy consumption without sacrificing reliable packet delivery by utilizing incoming traffic load to estimate channel contention level experienced by each neighbor. It periodically self-estimates the contention level of the neighbors based on the traffic load and adjusts its slotframe size. The limitation of setting slotframe size as a fixed global constant is addressed by periodically adjusting the slotframe. In TESLA, each node continuously sends its traffic load to its neighbor nodes exchanging control packets so that all nodes in the network can figure out their neighbors' traffic loads, and add or remove slots from the slotframe continuously. Parametrized Adaptive and Autonomous Scheduling (PAAS) [19] is another autonomous and distributed algorithm, and it works adaptively to traffic intensity, slotframe length, and reliability requirements. Nodes using PAAS exchange useful information for scheduling and allocates more cells if they are needed. Deciding which schedule is a good one actually depends on how high the traffic intensity is. In [20], the authors show that Orchestra has problems when operating under limited link capacity conditions, especially in regions close to the network's root node. To this end, the authors of [20] design and evaluate a special Orchestra scheduler rule for the root node. This rule adds a dedicated slotframe for communication between the root node and the nodes directly adjacent to the root node. The option to have multiple root nodes in a single TSCH network is also introduced. A network node is expected to install the root slotframe if it has any root nodes as direct neighbors.