Presenter

Mr Matthias Carlier - ETRO, VUB [Email]

Abstract

The phenomena of connecting millions of different devices to the internet gave rise to the so-called Internet of Things (IoT). A subset of those IoT networks are wireless sensor and actuator networks (WSANs), in which constrained devices equipped with sensors and/or actuators connect to each other and to the internet. In a WSAN, the need arises to send the same message to a lot of different receivers for example for switching off all the lights in a building. For traditional IP-based networks, protocols for enabling point-to-multipoint communication, also called multicast protocols, exist.

We designed and implemented a new multicast protocol for WSANs, called Bidirectional Multicast RPL Forwarding (BMRF). BMRF combines the best features of the Routing Protocol for Low Power and Lossy Networks (RPL) multicast on the one hand and of the Stateless Multicast RPL Forwarding (SMRF) on the other hand. As most important new functionalities, BMRF includes bidirectionality, dynamic group registration and the ability to have multiple senders (multipoint-to-multipoint). An additional feature is the possibility for a node receiving an IP multicast packet to opt for Link Layer (LL) broadcast versus LL unicast to forward the packet to its interested children. Using LL broadcast to send an IP multicast packet is efficient when only one LL packet needs to be sent in order to reach all interested receivers. Unfortunately, in WSANs which deploy a radio duty cycling (RDC) protocol, the sender is forced to send the packet during a full Channel Check Interval (CCI). In contrast, when the radio would always be ON, only one packet would need to be sent. This work studies under which circumstances LL broadcast is still a viable option.

The performance of BMRF under different working conditions is thoroughly analyzed using a simplified theoretical model and simulation studies, using ContikiMAC as underlying RDC protocol. We observed that LL broadcast mode performs comparably with SMRF, since they use the same forwarding mechanism. However, LL unicast mode is generally better than LL broadcast mode, except when the CCR of ContikiMAC is higher than 8.

Finally, a highly efficient key management protocol for group-based communications in a distributed WSANs with a cloud-based network multicast manager (NMM), based on symmetric keys, is developed. The protocol establishes confidentiality, integrity and authentication for communication between an arbitrary group of motes in the network. In addition, the established group key remains a secret for the NMM. A unicast approach and a multicast approach are described to share the group keys with all members. Both approaches are also tested while using BMRF in different situations and on different topologies. In all simulations, the multicast approach resulted in a better or equal delay and less energy consumption.

Short CV

Master in de Industriele Wetenschappen, EhB, 2013