Rejane Dalce

Improvement of range-free localization technology by a novel DV-hop protocol in wireless sensor networks

Localization is a fundamental issue for many applications in wireless sensor networks. Without the need of additional ranging devices, the range-free localization technology is a cost-effective solution for low-cost indoor and outdoor wireless sensor networks. Among range-free algorithms, DV-hop (Distance Vector-hop) has the advantage to localize the mobile nodes which has less than three neighbour anchors. Based on the original DV-hop algorithm, this paper presents two improved algorithms (Checkout DV-hop and Selective 3-Anchor DV-hop). Checkout DV-hop algorithm estimates the mobile node position by using the nearest anchor, while Selective 3-Anchor DV-hop algorithm chooses the best 3 anchors to improve localization accuracy. Then, in order to implement these DV-hop based algorithms in network scenarios, a novel DV-hop localization protocol is proposed. This new protocol is presented in detail in this paper, including the format of data payloads, the improved collision reduction method E-CSMA/CA, as well as parameters used in deciding the end of each DV-hop step. Finally, using our localization protocol, we investigate the performance of typical DV-hop based algorithms in terms of localization accuracy, mobility, synchronization and overhead. Simulation results prove that Selective 3-Anchor DV-hop algorithm offers the best performance compared to Checkout DV-hop and the original DV-hop algorithm.

SISP: A lightweight synchronization protocol for Wireless Sensor Networks

This paper presents a new synchronization protocol suitable for light nodes in a Wireless Sensor Network. This protocol, called SISP, is detailed with its algorithm and its sequence diagram. The simulation results obtained with a dedicated simulator are completed by the results of prototyping. The results show the effectiveness of SISP. Several prospects are discussed in conclusion.

Comparison of Indoor Localization Systems Based on Wireless Communications

Localization using a Wireless Sensor Network (WSN) has become a field of interest for researchers in the past years. This information is expected to aid in routing, systems maintenance and health monitoring. For example, many projects aiming to monitor the elderly at home include a personal area network (PAN) which can provide current location of the patient to the medical staff. This article presents an overview of the current trends in this domain. We introduce the mathematical tools used to determine position then we introduce a selection of range-free and range-based proposals. Finally, we provide a comparison of these techniques and suggest possible areas of improvement.

Indoor self-localization in a WSN, based on Time Of Flight: Propositions and demonstrator

IEEE 802.15.4 is a widely adopted foundation for the lower layers of wireless sensor networks. This standard has recently started to take localization into account. This has led to the addition of two new PHY layers, Ultra-Wide Band (UWB) and Chirp Spread Spectrum (CSS), but also the specification of a Time Of Flight-based ranging protocol named Symmetric Double-Sided Two-Way Ranging (SDS-TWR). This paper describes the results obtained from a CSS-based prototype using a variant of SDS-TWR. Our solution differs from others exploiting the same tools by not involving a localization server. The location estimation algorithm is executed by the mobile node, right after the ranging phase. The obtained localization error is generally under 200cm in 90% of the situations and the mean error is around 1m.

OpenWiNo: An open hardware and software framework for fast-prototyping in the IoT

The Internet of Things promises an always-connected future where the objects surrounding us will communicate in order to make our lives easier, more secure, etc. This evolution is a research opportunity as new solutions must be found to problems ranging from network interconnection to data mining. In the networking community, innovative solutions are being developed for the Device Layer of the Internet of Things, which includes the IoT wireless protocols. In order to study their performance, researchers turn more often to real world platforms, commonly designated by the term “testbeds”, on which they may implement and test the protocols and algorithms. This is even more important in the Industrial IoT field, where environments are perturbed by industrial systems like automated production systems. In this paper, after a brief presentation of the context of testbeds, we introduce WiNo and OpenWiNo, an open hardware and software framework for fast-prototyping in the field of the Internet of Things. Compared to existing platforms, the solution WiNo+OpenWiNo offers a wide array of Physical layers and easy integration of various sensors as it is developed as part of the Arduino ecosystem. It also allows research teams to easily and quickly deploy their own testbed into real environments.

An experimental performance study of an original ranging protocol based on an IEEE 802.15.4a UWB testbed

In this article, we study the behaviour of an Ultra-Wide Band (UWB) physical layer when executing our protocol Parallel Symmetric Double-Sided Two-Way Ranging. We compare it to the reference protocol introduced in IEEE 802.15.4a Symmetric Double-Sided Two-Way Ranging, in terms of precision of the obtained estimates and to other existing protocols such as SDS-TWR-MA and D-TWR in terms of overhead. These samples were obtained using a testbed made of IEEE 802.15.4a UWB nodes. From these first experiments, we derive a simple correction mechanism which reduces the localisation error compared to the case where no dynamic correction takes place. The location error reduction varies between 41 and 60% while the algorithm manages to estimate the position 99.9% of the time with the addition of the correction.

DecaDuino: An open framework for Wireless Time-of-Flight ranging systems

One of the objectives of applications based on Wireless Sensor Networks, and more generally the Device Layer of the Internet of Things, is to make human life better. In order to seamlessly become part of our daily lives, future networks may require nodes with the ability to self-localise: for instance, to map collected measurements to a precise location without human intervention. Localisation techniques have been studied for years, but a particular Physical Layer proposed in the IEEE 802.15.4-2011 standard, based on Ultra Wide Band (UWB), enables very precise ranging between neighbour nodes. By using the Time-of-Flight principle over UWB, a cm-level precision can be achieved. As UWB transceivers are hitting the market, evaluating this Physical Layer on a real testbed becomes possible. The aim of the paper is to present an Open Source Framework called DecaDuino, which enables fast prototyping of protocols based on this UWB Physical Layer. After a presentation of the related work and a classification of the localisation techniques used in the Wireless Network context, the DecaDuino Framework is presented, with several results from the implementation of classic protocols such as TWR and SDS-TWR, but also the original 2M-TWR, to illustrate the possibilities of the framework.

Reducing Localisation Overhead: A Ranging Protocol and an Enhanced Algorithm for UWB-Based WSNs

The ability for the nodes in a Wireless Sensor Network to determine their position is a desirable trait. Routing as well as other client applications can benefit from this information. In this paper, we introduce the results obtained from our UWB-based prototype. We implemented two adaptations of the Symmetric Double-Sided Two-Way Ranging (SDSTWR) protocol, namely Sequential Symmetric Double-Sided Two- Way Ranging (SSDS-TWR), and Parallel Double-Sided Two-Way Ranging (PDS-TWR), the latter being one of our contributions. PDS-TWR significantly reduces the overhead associated with ranging. We also introduce the enhanced version of our localisation algorithm, inter-Ring Localisation Algorithm (iRingLA), which is a good alternative for conventional trilateration. This new version improves the ability to compute the position when thin rings are used by focusing on the exact intersection: the number of test points remains small and the algorithm can be implemented on computationally constrained platforms. Using PDS-TWR and 2 anchors, we obtained a 2D localisation error of 79cm in an indoor environment.

Towards a new range-based localization method for WSNs: Challenges, Constraints and Correction

Applying Localization methods to a Wireless Sensor Network (WSN) is not simply a matter of proposing an algorithm. Several aspects must be taken into account as they influence the performance of both the localization service and the network. Network lifetime and medium availability are key resources that the localization service should not monopolize: the proposed protocol must be designed in order to minimize localization overhead or at least ensure fairness of access between localization and the other applications. On the other hand, hardware platform characteristics have a direct impact on the precision of the results. In this article, we first review these aspects then, as we present our framework for a distributed localization method, we introduce our proposition of an efficient correction method that can be implemented on nodes with limited resources. Results obtained using this correction are also briefly introduced.

A Study of the Ranging Error for Parallel Double Sided-Two Way Ranging Protocol

Indicating its own position is an important ability for a mobile wireless node. As a matter of fact, it is a key enabler for future applications in fields as diverse as routing, security, logistics, entertainment and so on. This position can be computed in many different ways. In a protocol-based approach to positionning, the foundation of this localisation service is the ranging protocol. In this paper, we focus on Time of Flight (ToF)-based localisation. We investigate the performance in terms of ranging precision of our proposed protocol, Parallel Double Sided-Two Way Ranging. We define the mathematical model which allows prediction of the error behaviour and derive a dynamic correction tool. We then implement our solution using the Decaduino platform and verify our models ability to identify the real distance. Using the correction method derived from the model in a real indoor environment, we were able to reduce the ranging error by at least 90%.