# Escalator: An Autonomous Scheduling Scheme for Convergecast in TSCH
## 6 Evaluation
### Experimental Setup  
We measure the performance of Escalator with 6 TiSCH-minimal [24] and Orchestra [8], 6 TiSCH minimal uses a slotframe containing a shared timeslot and idle timeslots. All nodes of 6 TiSCH-minimal perform contention-based communication using the shared timeslot. In the evaluation, 6 TiSCH minimal is expressed as _minimal_, and the size of the slotframe is 5.  
Orchestra uses three slotframes separated by the traffic type. The EB slotframe is used for the transmission of the beacon, and its size is 397. The broadcast slotframe is used for transmission of the RPL control messages, and its size is 31. The unicast slotframe is used for the transmission of application traffic and consists of a sender-based shared timeslot in the evaluation. Orchestra is expressed as \(OrchestraX\), and \(X\) is the size of the unicast slotframe.  
Escalator uses the baseline and convergecast slotframes. The size of the baseline slotframe is 31, equal to the size of the broadcast slotframe of Orchestra. The maximum hop counts of the network are 20. In evaluation, Escalator is expressed as \(EscalatorX\), and \(X\) is the size of the convergecast slotframe.  
We use a testbed and a simulation to measure the performance of Escalator and existing autonomous scheduling schemes. First, the testbed consists of 11 devices using the NXP JN5168 platform. The devices of the testbed are divided into a sink and 10 source nodes. Figure 9a shows the network topology used in the testbed. In the testbed, we use the following settings for each scheduling scheme. 6 TiSCH-minimal uses a slotframe size of 5 (_minimal_). Orchestra uses a unicast slotframe size of 29 (_Orchestra_29). Escalator uses a convergecast slotframe size of 73 (_Escalator73_). We use the packet transmission interval of 20 s and 5 s for each scheduling scheme. In the experimental, all nodes send 2000 packets at the same interval up to the sink.  
Second, we run the simulation using Cooja [31]. Cooja is a Contiki network simulator that provides hardware-level emulation based on Mspsim (Java-based instruction level simulator for the MSP430 microcontroller) [32]. In the simulation, the network topology uses 16 and 36 nodes arranged in a square grid as shown in Figure 9b,c. We run the simulation using the settings for each scheduling scheme described below. 6 TiSCH-minimal uses a slotframe size of 5 (_minimal_). Orchestra uses two settings; the size of the unicast slotframe for each setting is 37 and 53, respectively (_Orchestra_37, _Orchestra_53). Escalator uses two settings; the size of the convergecast slotframe for each setting is 73 and 107, respectively (_Escalator73, Escalator_107). The simulation also uses the packet transmission interval of 20 s and 5 s as in the case of the testbed.  
We use the following network settings for the testbed and the simulation. The channel hopping uses 16 channels. The timeslot duration of TSCH uses 20 ms so that the reception processing of the packet could be completed within one timeslot. The packet buffer size of the node in the testbed is 16. In the simulation, the packet buffer size of the node is 12. Each node can retransmit packets up to 8 times. The application traffic of the nodes uses UDP packets of a 24-byte payload.