Tiago Camilo

An energy-efficient ant-based routing algorithm for wireless sensor networks

Wireless Sensor Networks are characterized by having specific requirements such as limited energy availability, low memory and reduced processing power. On the other hand, these networks have enormous potential applicability, e.g., habitat monitoring, medical care, military surveillance or traffic control. Many protocols have been developed for Wireless Sensor Networks that try to overcome the constraints that characterize this type of networks. Ant-based routing protocols can add a significant contribution to assist in the maximisation of the network lifetime, but this is only possible by means of an adaptable and balanced algorithm that takes into account the Wireless Sensor Networks main restrictions. This paper presents a new Wireless Sensor Network routing protocol, which is based on the Ant Colony Optimization metaheuristic. The protocol was studied by simulation for several Wireless Sensor Network scenarios and the results clearly show that it minimises communication load and maximises energy savings.

Diagnostic Tools for Wireless Sensor Networks: A Comparative Survey

The availability of tools to diagnose Wireless Sensor Network (WSN) failures is a key success factor for this type of networks as already demonstrated by several long-running deployments. By nature, WSNs are resource-constrained, fragile, complex to analyse, and failure-prone. Naturally, with the growing number of installations, it is becoming fundamental to efficiently diagnose failures as soon as possible, in order to deal with the underlying causes. In accordance with this, from 2005 onwards, the offer of diagnostic tools has been increasing, as the other base technologies (e.g. networking, operating system, localisation, synchronisation) become reasonably stable. The purpose of this survey is to provide an overview of existing post-deployment WSN diagnostic tools, by briefly presenting their functionality, architecture and constraints, in order to enable a basic understating of each tool. The survey also includes a multi-dimensional comparative analysis of the various tools, based on a proposed classification scheme and evaluation criteria, as well as an identification of the main open research issues. Although the number of diagnostic tools is high and considerable work has been done in this area, we conclude that there are still several challenges concerning post-deployment WSN diagnostic tools, regarding scope, flexibility, generality, mobility and security. Moreover, there is a need for mature, native diagnostic-oriented functionality in WSN platforms and operating systems.

Mobility management in IP-based Wireless Sensor Networks

Mobility is one of the most important issues in next generation networks. As wireless sensor networks are becoming the next elements of the future Internet, it is crucial to study new models that also support mobility of these nodes. This paper presents and studies three paradigms to support mobility in sensor nodes. This study is supported by prototyping. As a result a set of proposals are proposed and discussed. The work presented in this paper proposes the use of IP in wireless sensor networks as a unifying protocol and it is in compliance with the IETF 6LowPAN group.

IP in wireless sensor networks Issues and lessons learnt

This paper addresses the issue of IP in wireless sensor networks, comparing the use of IPv4 and IPv6. Although a considerable number of studies on wireless sensor networks exist, most of them are based on simulation only. This is not the case of the current paper. In order to validate and complement the simulation studies, this paper presents the construction, deployment and evaluation of a real testbed for the study of IP in Wireless Sensor Networks. The testbed is based on Contiki over embedded sensor boards nodes. The results show that the impact of IPv6 is negligible when compared with IPv4, and that IPv6 may even be beneficial due to its higher functionality and to the simpler composition of its headers.

Multicast in Wireless Sensor Networks The next step

Multicast potentially optimises bandwidth consumption and node resources, when several users simultaneously participate in a communication session. Nevertheless, contrary to the expectations, IP multicast has not experienced widespread deployment, with the exception of IPTV. On the other hand, emerging wireless sensor network (WSN) applications could greatly benefit from multicast and constitute another field where multicast can be an effective and efficient technique. The question is: do multicast advantages hold in WSN scenarios? This paper discusses and evaluates the use of multicast in wireless sensor networks. A WSN platform with IP support and multicast is being developed. Concurrently, simulation studies were performed in order to assess the usefulness of multicast in WSNs. The results clearly point to the benefits of the use of this technique in processing and energy-restricted environments such as this one

Hermes: A versatile platform for wireless embedded systems

This paper presents Hermes, a new modular platform that can be used in a variety of scenarios, including the role of body area network coordinator, enabling temperature, movement and heartbeat sensing, local and remote communication, and indoor and outdoor localization. Hermes is based on two main modules that can operate as a single system in a coordinated fashion or individually, depending on the application scenario. One of the modules uses a Telos-inspired architecture, with new processing, communication, sensing, storage and energy subsystems, and executing TinyOS. The other module is designed around a PIC 24F MCU, also supporting communication, sensing, storage, and executing a custom operating system. Both modules have expansion capabilities. The main innovative aspects of the implemented platform are its modularity and its capability to provide device abstraction, which considerably eases application development. The paper addresses the platform motivation, requirements, hardware architecture, implementation details, and performance evaluation.

iHorse — A WSN-based equine monitoring system

Horses played a key role in the history of mankind, having been instrumental in the rise and fall of great empires. In modern days, they are still very important assets, from economical, operational or even sentimental points of view. Their importance is, thus, the main motivation for developing the iHorse equine monitoring system presented in this paper. iHorse is a deployed, fully-operational, commercially-available, wireless-sensor-network-based system and application, developed and tested over a three-year period. The aim of this paper is to provide information on the main features of the system, including its architecture, implementation details and performance data. The paper also discusses the lessons learnt throughout the system development and deployment phases.

Assessing and Extending SSM for Highly Dynamic Mobility Environments

Although application-layer multicast has deserved some attention in the last few years due to the failure to deploy multicast at the network layer, recent work at this level has come up with a promising solution: source specific multicast (SSM). Nevertheless, in spite of the reduction in complexity inherent to SSM, there are still several problems to solve, especially when mobility is concerned. In this paper, an analysis of the limitations and drawbacks of SSM in mobile environments is presented, showing that existing proposals still suffer from the complexity and overhead syndromes characteristic of previous multicast proposals. In addition to this analysis, the paper presents a simple proposal for SSM-based multicast in wireless environments that uses the concept of multicast servers in order to limit the instability of multicast trees under highly dynamic conditions. The evaluation of this proposal was carried out by prototyping and simulation, showing that it has several advantages over the current internet draft proposal for mobile SSM, with no performance costs