Deterministic and low-latency communications for multi-application mesh networks in the sub-GHz band

The rapid expansion of the Low-power and Lossy Networks (LLNs) has revolutionized connectivity, driving the development of networks tailored for low-power, lossy environments. These networks support diverse applications, including smart cities, smart utilities, and industrial automation, where energy efficiency, low and bounded latency, and end-to-end network reliability are critical. Wireless Smart Ubiquitous Network (Wi-SUN) is one of the leading communication standards for such environments. It is based on a collection of open standards and differentiates itself from the other Internet of Things (IoT)-based technologies by being natively IPv6-based, meshed, and using sub-GHz bands. 

Wi-SUN relies on the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) routing protocol. This protocol organizes network nodes into a hierarchical structure using a Destination-Oriented Directed Acyclic Graph (DODAG). It enables efficient multipoint-to-point communications (from devices inside the LLN towards the DODAG root node) and point-to-multipoint communications (from the DODAG root node to a subset of devices inside the LLN). However, the increasing demand for point-to-point (peer-to-peer) communications between devices inside the LLN highlights inherent limitations in the standard RPL design.

RPL is ideal for communications between the nodes of a Field Area Network (FAN) and a central node (DODAG root) or towards the Internet. While many applications follow such a traffic pattern, others need mainly peer-to-peer communications.  For instance, smart streetlights need to send a message to their neighbors to turn on (or to increase their brightness) whenever they detect a pedestrian or a vehicle.  There is no need for such messages to reach the root; doing so would only increase the latency and the network traffic. The most efficient and fastest solution is for streetlights to exchange messages directly, as they are typically close enough to each other to communicate directly.

The dissertation aims to propose and implement new mechanisms to guarantee Quality of Service (QoS) in Wi-SUN networks, namely low latency, low jitter, and reliable message delivery. While several proposals for peer-to-peer communications in RPL networks exist, they do not offer any QoS guarantees. The work of the Reliable and Available Wireless (RAW) working group of the Internet Engineering Task Force could be a starting point. 

After proposing one or more solutions, the Ph.D. candidate will evaluate their performance through simulations and will implement at least one solution in the Silicon Labs stack.

IMT Atlantique, internationally recognised for the quality of its research, is a leading general engineering school under the aegis of the Ministry of Industry and Digital Technology, ranked in the three main international rankings (THE, SHANGHAI, QS).

Located on three campuses, Brest, Nantes and Rennes, IMT Atlantique aims to combine digital technology and energy to transform society and industry through training, research and innovation. It aims to be the leading French higher education and research institution in this field on an international scale. With 290 researchers and permanent lecturers, 1000 publications and 18 M€ of contracts, it supervises 2300 students each year and its training courses are based on cutting-edge research carried out within 6 joint research units: GEPEA, IRISA, LATIM, LABSTICC, LS2N and SUBATECH. 
The proposed thesis is part of the research activities of the OCIF team of the IRISA laboratory and the SRCD department. 

• Excellent programming skills in C and Python, & embedded software development.
• Good knowledge of operating systems and system programming (Linux).
• Good knowledge of Wireless networks (protocols and radio propagation) and energy efficiency.
• Proficiency in English. (Knowledge of French is helpful but not mandatory.)