# Time Slotted Channel Hopping and ContikiMAC for IPv6 Multicast-Enabled Wireless Sensor Networks
## 4 Simulation Settings  
The simulations and placements of the nodes in the network were designed to analyze the performance of BMRF with TSCH and ContikiMAC, as well as to investigate under which circumstances multicast was an efficient solution for WSANs. A \(150\times 150\) m square field was used to place the nodes. Each node had a transmission range of 50 m, equal to the interference range. Three types of node placement were chosen:  
* Placement such that internal interference is kept at minimum. This was mainly used to be able to devise a simplified theoretical model for ContikiMAC and TSCH. It resulted in a RPL tree that would be favorable for ContikiMAC (Figure 4). * Placement with interference only between nodes of the same rank in the RPL tree (Figure 5). * Random placements that resulted in the RPL trees, as shown in Figure 6, to better mimic real situations and to discuss the influence of interference on the analyzed protocols. The number of nodes that form these topologies was increased to 31. In the two cases depicted in Figure 6, a node had at least five other nodes in the interference range. In each of the mentioned cases, node 1 was selected to be the root for the RPL tree. The rest of the nodes were placed in such a way that after running RPL, the RPL trees in Figure 4, Figure 5, and Figure 6 were obtained. In Figure 4, the nodes have only the preferred parent and their respective children in the radio range. In the linear topology (Figure 4a), each node has exactly one child per parent, and in the other two topologies, the nodes have two (Figure 4b) and three (Figure 4c) children per parent. Therefore, we obtained networks of a maximum depth of five hops, the linear topology (Figure 4a), three hops (Figure 4b), and two hops (Figure 4c). The hop count expresses the distance in hops between the source and the destination. For Figure 5, the positioning of the nodes was chosen such that RPL forms topologies with interference between same rank nodes. In Figure 5a, each node, apart from the leaf nodes, has three children per parent, and in Figure 5b, each node has four children per parent. The nodes with the same rank were placed close enough to each other to create interference between them. In Figure 5c, another realistic scenario is shown. Subsequently, two topologies with random placements of nodes and increased internal interference were used to test the protocols in realistic scenarios. These topologies are shown in Figure 6. Two positions were chosen for the root node: in the center of the topology (Figure 6a) and at the top of the topology (Figure 6b). To obtain the random topologies, we manually positioned the root node on a 150 \(\times\) 150 m square field at the desired positions (0 \(\times\) 0--center of the field; 75 \(\times\) 0--top of the field), and we used the Cooja simulator's random positions generator to randomly place the other 30 nodes. We made sure that all the nodes could communicate with the root. The script that automatically ran the simulations also checked whether all the nodes joined the RPL tree. If that was not the case, a warning message informed about the situation. We defined configurations featuring the following characteristics: BMRF in one of the specific modes (unicast or broadcast) and TSCH or ContikiMAC as RDC/MAC protocols. Each of these configurations was uploaded on every described topology, and we ran 10 simulations for each case. The source of the multicast messages was the root of the RPLtree. It transmitted 100 multicast packets with a 4 byte payload at a rate of 0.2 packets per second in each case. We chose these values to avoid queueing delays. Since TSCH is the default protocol in the Contiki-NG OS [19] and ContikiMAC is only implemented in Contiki OS, we used both operating systems. We chose version 4.x for Contiki-NG and version 3.x for Contiki-OS. All the other parameters not discussed in this paragraph had the default values from Contiki-NG or Contiki OS. The simulations were run using Cooja [20].