Hossein Fotouhi

MRPL : Boosting mobility in the Internet of Things

The 6loWPAN (the light version of IPv6) and RPL (routing protocol for low-power and lossy links) protocols have become de facto standards for the Internet of Things (IoT). In this paper, we show that the two native algorithms that handle changes in network topology —the Trickle and Neighbor Discovery algorithms– behave in a reactive fashion and thus are not prepared for the dynamics inherent to nodes mobility. Many emerging and upcoming IoT application scenarios are expected to impose real-time and reliable mobile data collection, which are not compatible with the long message latency, high packet loss and high overhead exhibited by the native RPL/6loWPAN protocols. To solve this problem, we integrate a proactive hand-off mechanism (dubbed smart-HOP) within RPL, which is very simple, effective and backward compatible with the standard protocol. We show that this add-on halves the packet loss and reduces the hand-off delay dramatically to one tenth of a second, upon nodes’ mobility, with a sub-percent overhead. The smart-HOP algorithm has been implemented and integrated in the

Smart-HOP: a reliable handoff mechanism for mobile wireless sensor networks

Handoff processes, the events where mobile nodes select the best access point available to transfer data, have been well studied in cellular and WiFi networks. However, wireless sensor networks (WSN) pose a new set of challenges due to their simple low-power radio transceivers and constrained resources. This paper proposes smart-HOP, a handoff mechanism tailored for mobile WSN applications. This work provides two important contributions. First, it demonstrates the intrinsic relationship between handoffs and the transitional region. The evaluation shows that handoffs perform the best when operating in the transitional region, as opposed to operating in the more reliable connected region. Second, the results reveal that a proper fine tuning of the parameters, in the transitional region, can reduce handoff delays by two orders of magnitude, from seconds to tens of milliseconds.

Reliable and Fast Hand-Offs in Low-Power Wireless Networks

Hand-off (or hand-over), the process where mobile nodes select the best access point available to transfer data, has been well studied in wireless networks. The performance of a hand-off process depends on the specific characteristics of the wireless links. In the case of low-power wireless networks, hand-off decisions must be carefully taken by considering the unique properties of inexpensive low-power radios. This paper addresses the design, implementation and evaluation of smart-HOP, a hand-off mechanism tailored for low-power wireless networks. This work has three main contributions. First, it formulates the hard hand-off process for low-power networks (such as typical wireless sensor networks - WSNs) with a probabilistic model, to investigate the impact of the most relevant channel parameters through an analytical approach. Second, it confirms the probabilistic model through simulation and further elaborates on the impact of several hand-off parameters. Third, it fine-tunes the most relevant hand-off parameters via an extended set of experiments, in a realistic experimental scenario. The evaluation shows that smart-HOP performs well in the transitional region while achieving more than 98 percent relative delivery ratio and hand-off delays in the order of a few tens of a milliseconds.

Radio Link Quality Estimation in Low-Power Wireless Networks

This book provides a comprehensive survey on related work for radio link quality estimation, which covers the characteristics of low-power links, the fundamental concepts of link quality estimation in wireless sensor networks, a taxonomy of existing link quality estimators and their performance analysis. It then shows how link quality estimation can be used for designing protocols and mechanisms such as routing and hand-off. The final part is dedicated to radio interference estimation, generation and mitigation.

An Overview on the Internet of Things for Health Monitoring Systems

The aging population and the increasing healthcare cost in hospitals are spurring the advent of remote health monitoring systems. Advances in physiological sensing devices and the emergence of reliable low-power wireless network technologies have enabled the design of remote health monitoring systems. The next generation Internet, commonly referred to as Internet of Things (IoT), depicts a world populated by devices that are able to sense, process and react via the Internet. Thus, we envision health monitoring systems that support Internet connection and use this connectivity to enable better and more reliable services. This paper presents an overview on existing health monitoring systems, considering the IoT vision. We focus on recent trends and the development of health monitoring systems in terms of: (1) health parameters and frameworks, (2) wireless communication, and (3) security issues. We also identify the main limitations, requirements and advantages within these systems.

Interoperability in heterogeneous Low-Power Wireless Networks for Health Monitoring Systems

Ensuring interoperability in the future Internet of Things applications can be a challenging task, especially in mission-critical applications such as Health Monitoring Systems. Existing low-power wireless network architectures are designed in isolated networks, and ensure a satisfying level of performance in homogeneous networks. However, with co-existence of different low-power networks, the interoperability related problems arise. To bridge this gap in this paper, we study various protocol stacks (i.e., Bluetooth, Bluetooth Low Energy, IEEE 802.15.4, ZigBee, 6LoWPAN and IEEE 802.15.6), and explain their specific features. Furthermore, we provide a generic protocol stack design that facilitates multiple radios with different protocol stacks, regardless of being IP-based or non-IP-based networks. We see this approach as a possibility to enhance network performance in terms of reliability, timeliness, and security, while providing higher levels of scalability and connectivity.

SDN-TAP: An SDN-based traffic aware protocol for wireless sensor networks

Congestion control is a challenging issue in wireless sensor networks with limited channel bandwidth. Thus, many protocols have been designed to provide a distributed traffic control during packet forwarding. However, all these approaches are applied to single-hop communication networks, ignoring the multi-hop restrictions. In this work, we take advantage of software defined networking paradigm by devising a controller node in such a way that it collects all the necessary information from wireless sensor network nodes. Thus, based on hop count and local traffic information, controller decides for possible flow path changes to evenly distribute the traffic. The evaluations revealed that the SDN-TAP outperforms conventional routing protocols by reducing packet loss rate up to 46%.

Data Flow and Collection for Remote Patients Monitoring: From Wireless Sensors through a Relational Database to a Web interface in Real Time

A reliable, secure, and real-time data collection from sensor devices to the end-user is an open research problem. Many research works have been focusing on the wireless communication level to obtain quality of service. This paper widens the problem, and provides a comprehensive system design, where it covers all the elements in a remote health monitoring application. The system collects measurements in a relational database, either through a C#.NET or a LabVIEW program. The end-user is able to observe either real-time data (i.e. with insignificant delay) or processed historical data on any web browser. We have shown that the inclusion of the relational database may impose a need for the data to be buffered before inserting into the database within a single transaction, but the buffering does not entail delays bigger than 50 ms.

An efficient placement of sinks and SDN controller nodes for optimizing the design cost of industrial IoT systems

Recently, a growing trend has emerged toward using Internet of Things (IoT) in the context of industrial systems, which is referred to as industrial IoT. To deal with the time‐critical requirements of industrial applications, it is necessary to consider reliability and timeliness during the design of an industrial IoT system. Through the separation of the control plane and the data plane, software‐defined networking provides control units (controllers) coexisting with sink nodes, efficiently coping with network dynamics during run‐time. It is of paramount importance to select a proper number of these devices (i.e., software‐defined networking controllers and sink nodes) and locate them wisely in a network to reduce deployment cost. In this paper, we optimize the type and location of sinks and controllers in the network, subject to reliability and timeliness as the prominent performance requirements in time‐critical IoT systems through ensuring that each sensor node is covered by a certain number of sinks and controllers. We propose PACSA‐MSCP, an algorithm hybridizing a parallel version of the max‐min ant system with simulated annealing for multiple‐sink/controller placement. We evaluate the proposed algorithm through extensive experiments. The performance is compared against several well‐known methods, and it is shown that our approach outperforms those methods by lowering the total deployment cost by up to 19%. Moreover, the deviation from the optimal solution achieved by CPLEX is shown to be less than 2.7%.

Communication and Security in Health Monitoring Systems -- A Review

The fast development of sensing devices and radios enables more powerful and flexible remote health monitoring systems. Considering the future vision of the Internet of Things (IoT), many requirements and challenges rise to the design and implementation of such systems. Bridging the gap between sensor nodes on the human body and the Internet becomes a challenging task in terms of reliable communications. Additionally, the systems will not only have to provide functionality, but also be highly secure. In this paper, we provide a survey on existing communication protocols and security issues related to pervasive health monitoring, describing their limitations, challenges, and possible solutions. We propose a generic protocol stack design as a first step toward handling interoperability in heterogeneous low-power wireless body area networks.