Section: New Results

IoT and Wireless Sensor Networks

More than 50 billions of devices will be connected in 2020. This huge infrastructure of devices, which is managed by highly developed technologies, is called Internet of Things (IoT). The latter provides advanced services, and brings economical and societal benefits. This is the reason why engineers and researchers of both industry and scientific communities are interested in this area. The Internet of Things enables the interconnection of smart physical and virtual objects, managed by highly developed technologies. WSN (Wireless Sensor Network), is an essential part of this paradigm. The WSN uses smart, autonomous and usually limited capacity devices in order to sense and monitor their environment.

Deployment of autonomous and mobile wireless sensor nodes

Participants : Ines Khoufi, Pascale Minet.

This work was done in collaboration with Nadia Boufares (ENSI, University of Manouba, Tunisia) and Leila Saidane (ENSI, University of Manouba, Tunisia).

Wireless Sensor Networks (WSNs) are used in a wide range of applications due to their monitoring and tracking abilities. Depending on the applications goals, sensor nodes are deployed either in a two-dimensional (2D) area or in a three-dimensional (3D) area. In addition, WSN deployment can be either in a distributed or a centralized manner. In 2017, we were interested in a fully distributed deployment of WSN in several 3D-flat-surface configurations using autonomous and mobile nodes. Our goal was to ensure full 3D flat surfaces coverage and maintain network connectivity for these surfaces. To reach our goal we proposed 3D-DVFA-FSC, a distributed deployment algorithm based on virtual forces strategy to move sensor nodes over different 3D-flat-surface shapes. Initially, nodes were randomly deployed. Full coverage was reached in the given configurations and maintained up to the end of simulation. We also evaluated the total distance traveled by nodes. Simulation results show that sensor nodes still move even when full 3D-surface coverage is reached. This is due to the node oscillations problem. This problem will be tackled in our future work. We will also focus on how to stop nodes when full coverage is reached and consider 3D surface complex shapes where the challenges of coverage and connectivity are more complicated. This work was presented at the IWCMC 2017 conference, see [15].

Collision avoidance on shared slots in wireless slotted networks

Participants : Ines Khoufi, Pascale Minet, Paul Muhlethaler.

We propose an analysis of slotted based protocols designed for devices of the Internet of Thing (IoT). In contrast to other TDMA-based protocols this scheme uses a random technique to access shared slots which presents similarities with CSMA protocols. In practice the transmissions are scheduled in a given back-off window of slots whose duration allows the transmission of a packet and its acknowledgment. Therefore this protocol can be analyzed according to the methodology introduced by Bianchi for the IEEE 802.11 protocol even if the protocol studied differs in many aspects. The model we use is also particular because we succeed in obtaining a Markov model even if the scheme used to send a packet (in a node) may depend on the transmission of the previous packet(s). We distinguish two protocols. In the first one, at the initial stage or after a successful transmission, the packets are transmitted without any back-off, whereas in the second protocol each transmission is always preceded by the count down of a random back-off. Extensive simulations show a very good match between the model and the simulation results, see [22]. For moderate medium load, the protocol performing a backoff before each transmission outperforms the TSCH protocol, when the number of neighboring nodes is greater than or equal to 8. For a smaller number of neighboring nodes, the TSCH protocol provides a higher throughput. For high medium load, the TSCH protocol provides the highest normalized throughput at the cost of some unfairness in the transmission opportunities.

Security in the OCARI wireless sensor network

Participant : Pascale Minet.

Wireless Sensor Networks and Industrial Internet of Things use smart, autonomous and usually limited capacity devices in order to sense and monitor industrial environments. The devices in a wireless sensor network are managed by a controller, also called CPAN, which should authenticate them before they join the network. OCARI is a promising wireless sensor network technology providing optimized protocols in order to reduce the energy consumption and support pedestrian mobility. However, it needs to be secured against the different threats, especially those that concern confidentiality, data integrity, and entities authentication. This challenge was addressed in a joint work with Mohammed Tahar Hammi (Telecom ParisTech), Erwan Livolant (AFNet, Boost technologies), Patrick Bellot (Telecom ParisTech), Ahmed Serhouchni (Telecom ParisTech) and Pascale Minet (Inria). The main results have been published in two papers.

A robust mutual authentication is the challenge addressed in the paper presented at the ICMWT 2017 conference [28]. We proposed a lightweight, robust, and energy efficient WSN mutual authentication protocol. This protocol is especially designed to be implemented on devices with low storage and computing capacities. It has been implemented on OCARI. All nodes wanting to access the network should be authenticated at the MAC sub-layer of OCARI. This solution provides a protection against “replay attacks”, because the exchanged OTPs are based on random numbers, therefore, they are valid only for one transaction. Using the blacklisting mechanism we can secure our systems against “some DoS” attacks. Finally it is flexible and does not decrease the scalability of the system, and can be deployed in different WSNs technologies, while keeping the same level of robustness. In our future work we aim to ensure the confidentiality of the transmitted messages exchanged after the MAC sub-layer association and authentication procedure. And thus we will have a secure system which ensures the “Confidentiality”, “Integrity, and “Authentication” services.

In the paper presented at CSNet 2017 ([27] , we designed a security protocol that enables to secure most of the WSNs thanks to its lightness and energy efficiency. It ensures a mutual authentication of the communicating entities and a protection of both the integrity and the confidentiality of the exchanged data. The “personalization” mechanism solves the problem of the internal identity usurpation. The proposed key management allows a safe and secure keys exchange between the concerned entities. Furthermore, this protocol provides a very fast establishment of a secure channel based on a robust, fast, and lightweight symmetric encryption algorithm (AES GCM/CCM). Finally, this solution is resilient against the cryptanalysis and the replay attacks. In our future works, we aim to create a secure communicating system between different CPANs and to facilitate a secure migration of devices from a network managed by a CPAN to a network managed by another CPAN.

Security in Wireless Sensor Networks

Participants : Selma Boumerdassi, Paul Muhlethaler.

Sensor networks are often used to collect data from the environment where they are located. These data can then be transmitted regularly to a special node called a sink, which can be fixed or mobile. For critical data (like military or medical data), it is important that sinks and simple sensors can mutually authenticate so as to avoid data to be collected and/or accessed by fake nodes. For some applications, the collection frequency can be very high. As a result, the authentication mechanism used between a node and a sink must be fast and efficient both in terms of calculation time and energy consumption. This is especially important for nodes which computing capabilities and battery lifetime are very low. Moreover, an extra effort has been done to develop alternative solutions to secure, authenticate, and ensure the confidentiality of sensors, and the distribution of keys in the sensor network. Specific researches have also been conducted for large-scale sensors. At present, we work on an exchange protocol between sensors and sinks based on low-cost shifts and xor operations. After this publication, we have been working on the performance evaluation of the solution to determine the memory overhead together with both computing and communication latencies.

Massive MIMO Cooperative Communications for Wireless Sensor Networks

Participants : Nadjib Achir, Paul Muhlethaler.

This work is done in collaboration with Mérouane Debbah (Supelec, France).

The objective of this work is to propose a framework for massive MIMO cooperative communications for Wireless Sensor Networks. Our main objective is to analyze the performances of the deployment of a large number of sensors. This deployment should cope with a high demand for real time monitoring and should also take into account energy consumption. We have assumed a communication protocol with two phases: an initial training period followed by a second transmit period. The first period allows the sensors to estimate the channel state and the objective of the second period is to transmit the data sensed. We start analyzing the impact of the time devoted to each period. We study the throughput obtained with respect to the number of sensors when there is one sink. We also compute the optimal number of sinks with respect to the energy spent for different values of sensors. This work is a first step to establish a complete framework to study energy efficient Wireless Sensor Networks where the sensors collaborate to send information to a sink. Currently, we are exploring the multi-hop case.