The 6TiSCH protocol stack is introduced by IETF as a standard for communication of low-power memory constrained wireless devices in the Internet-of-Things (IoT). For its Medium Access Control (MAC) layer, this protocol stack employs the Time Slotted Channel Hopping (TSCH) mechanism, which is as an operational modes of the IEEE 802.15.4 technology standard. This mechanism uses Time Division Multiple Access (TDMA) together with channel hopping, which make the communications collision-free, and alleviate the impact of cross-technology interference and multi-path fading. Thus the mechanism is a suitable option for low-power and reliable networking in IoT. In the TDMA-based protocols (e.g., TSCH), timeslot scheduling is done based on nodes’ neighborhood in such a way so that the nodes in each other’s communication range pick different time slots for their packet transmissions. Node mobility changes the neighborhood of the nodes in the network leading to collisions. The main challenge for node mobility support in TDMA-based MMC layers is adapting the timeslot schedules to avoid collisions. Timeslot scheduling in a TSCH network can either be centralized or distributed. The former scheduling method is not applicable for networks with node mobility due to its high overhead and complexity for adapting the schedules. Thus the distributed scheduling mechanisms, which only use local information, are the main option. However, the scheduler should be fortified with proper adaptive mechanisms to efficiently support node mobility. This thesis proposes solutions for supporting node mobility in networks running the 6TiSCH protocol stack. The applications in which there is a static network as well as some mobile nodes (e.g., health monitoring applications) are considered. The objective is to provide a communication mechanism in the TSCH layer for mobile nodes to reduce collisions due to mobility leading to better Quality-of-Services such as end-to-end latency and data delivery ratio. The main idea is to separate the static and mobile nodes, and dedicate particular timeslots in each time period of TSCH for packet transmissions by the mobile nodes. The proposed solutions are implemented on top of the Contiki operating system and their performance is evaluated by Cooja simulations of several network scenarios. The achieved results shows that the solutions considerably reduces the end-to-end latency and packet drop ratio for the scenarios with node mobility. Key Words : 1-Wireless Sensor Networks, 2-6TiSCH, 3-TSCH Protocol, 4-Channel Hopping, 5-Mobility.
