Now showing 1 - 10 of 26
  • Publication
    Diversity & interoperability : wireless technologies in ambient assisted living
    Ambient Assisted Living (AAL) demands the seamless integration of a range of technologies such that the particular needs of the elderly may be met. Given the heterogeneity of the elderly population, in their needs and circumstances amongst others, this is a significant challenge. In essence, it demands that a disparate suite of technologies be deployed, integrated, managed and interacted with in a seamless and intuitive fashion. In this paper, how this heterogeneity may be managed is discussed. In particular, the use of ontologies and middleware are proposed as potential solutions to this heterogeneity problem.
      645
  • Publication
    Debugging low-power and lossy wireless networks : a survey
    Recent economic and technical advances in wireless communication have allowed the deployment of low-power and lossy wireless networks—LowPANs, potentially comprised of a large number of nodes to serve new types of applications. However, the resource-constrained nature of microsensor platforms together with the unreliability and low-bandwidth of low-power and lossy wireless links have increased the risk and occurrence of network failures. Unlike with traditional wireless networks and controlled pre-deployment simulations and laboratory setups, likely events such as node crashes, inefficient networking and environmental interferences can potentially freeze a network post deployment. A survey of existing tools and related work in debugging LowPANs is presented, to provide a comprehensive state of the art of debugging tools and techniques. We divide debugging tools in two categories, pre-deployment tools and post-deployment tools, and evaluate their performance and limitations. From this study, we discuss the challenges in debugging LowPANs, providing the main issues and requirements that LowPANs’ specific constraints impose on debugging tools, to help developers choose the appropriate tool for specific needs.
    Scopus© Citations 19  1349
  • Publication
    Embedding intelligent decision making within complex dynamic environments
    Decision-making is a complex and demanding process often constrained in a number of possibly conflicting dimensions including quality, responsiveness and cost. This paper considers in situ decision making whereby decisions are effected based upon inferences made from both locally sensed data and data aggregated from a sensor network. Such sensing devices that comprise a sensor network are often computationally challenged and present an additional constraint upon the reasoning process. This paper describes a hybrid reasoning approach to deliver in situ decision making which combines stream based computing with multi-agent system techniques. This approach is illustrated and exercised through an environmental demonstrator project entitled SmartBay which seeks to deliver in situ real time environmental monitoring.
      1372Scopus© Citations 12
  • Publication
    MERLIN: A synergetic integration of MAC and Routing Protocol for Distributed Sensor Networks
    Notoriously, energy-efficient MAC protocols cause high latency of packets. Such delays may well increase when a routing protocol is applied. Therefore, quantifying the endto- end delay and energy consumption when low duty cycle MAC and routing protocols are jointly used, is of particular interest. In this paper, we present a comprehensive evaluation of the MERLIN (MAC and Efficient Routing integrated with support for localization) protocol. MERLIN integrates MAC and routing features into a single architecture. In contrast to many sensor network protocols, it employs a multicast upstream and multicast downstream approach to relaying packets to and from the gateway. Simultaneous reception and transmission errors are notified by using asynchronous burst ACK and negative burst ACK. A division of the network into timezones, together with an appropriate scheduling policy, enables the routing of packets to the closest gateway. An evaluation of MERLIN has been conducted through simulation, against both the SMAC and the ESR routing protocols,which is an improved version of the DSR algorithm. The results illustrate how both SMAC and ESR, jointly used in low duty cycle scenarios, can cause an impractical and very high end-to-end delays. MERLIN, as an integrated approach, notably reduces the latency, resulting in nodes that can operate in a very low duty cycle. Consequently, an extension of the operative lifetime of the sensor network is achieved.
    Scopus© Citations 12  492
  • Publication
    Protocol assessment issues in low duty cycle sensor networks : the switching energy
    Energy assessment of MAC protocols for wireless sensor networks is generally based on the times of transmit, receive and sleep modes. The switching energy between two consecutive states is generally considered negligible with respect to them. Although such an assumption is valid for traditional wireless ad hoc networks, is this assumption valid also for low duty cycle wireless sensor networks? The primary objective of this work is to shed some light on relationships between node switching energy and node duty cycle over the total energy consumption. In order to achieve the target, initially, we revisit the energy spent in each state and transitions of three widespread hardware platforms for wireless sensor networks by direct measurements on the EYES node. Successively, we apply the values obtained to the SMAC protocol by using the OmNet++ simulator. The main reason for using SMAC is that it is the protocol normally used as a benchmark against other architectures proposed.
    Scopus© Citations 27  408
  • Publication
    Coordinated sleeping for beaconless 802.15.4-based multihop networks
    The last few years have seen a wide adoption of the IEEE 802.15.4 MAC/PHY standard for low-power communication between wireless sensor nodes. Within this work we study some fundamental drawbacks of the 802.15.4 specifications for multihop network deployments, which adversely affect the delivery rate and efficient node energy consumption. These issues are rectified by investigating a timezone-based scheduling, V-Route, that builds on 802.15.4 beaconless mode to enable both a synchronized sleep scheduling and a bidirectional communication between nodes in the sensor network and the PAN coordinator. The contributions of V-Route are threefold: (1) mitigate collisions, (2) enable packet routing and (3) provide energy saving in a multihop context, while maintaining the full compliancy with the 802.15.4 standard. We present a performance evaluation on energy consumption and latency with real experiments on Philips AquisGrain sensor nodes. Enhancing 802.15.4-based multi-hop networks with V-Route yields energy reduction ranging from 27.3% to 85.3%, according to the required end-to-end latency.
    Scopus© Citations 2  2106
  • Publication
    Dynamic reassignment of aggregation point for network load balancing
    Some wireless sensor network applications forward data to a central aggregation point (AP) that is responsible for processing, aggregating, and relaying information to the base station. For example one node in a body sensor network is responsible for aggregating data and then forwarding only useful information to an external ambient network. This procedure leads to asymmetry in the AP node energy consumption due to (1) higher forwarding activity for nodes in the vicinity of the AP and (2) higher AP activity relative to nodes. Existing approaches of load and energy consumption balancing employ either suboptimal periodical route changes or random AP rotations. In contrast, we propose a novel technique1 to enable a dynamic reassignment of the sensor AP according to a novel cost function that is based on relevant node energy metrics. We show that the technique lead to a network lifetime extension up to 50% for applications, such as medical, that require power-intensive tasks at the AP and for high traffic applications.
      108
  • Publication
    Autonomous management and control of sensor network-based applications
    A central challenge facing sensor network research and development is the difficulty in providing effective autonomous management capability. This is due to a large number of parameters to control, unexpected changes of the network topology and dynamic application requirements. Network management is also a challenging task for the remote user due to the large-scale of the network and scarce visibility of live network happenings. Preferably the network should have autonomous decision-making capabilities as network conditions and application requirements changes. To cope with such uncertainties, firstly we consider Octopus, a powerful software tool that provides live information about the network topology and sensor data. At present, the tool can provide monitoring and require a user to control the network state manually. This paper describes how Octopus is reengineered to accommodate a multi-agent system to provide autonomic managing capabilities. In particular, we detail two distinct architectures, the static and mobile agent architectures, which can be effectively applied to deliver autonomous system management. This paper sets the basis for a full autonomous network management via a multi agent system to work with Octopus.
      1154Scopus© Citations 2
  • Publication
    A Low-Latency Routing Protocol for Wireless Sensor Networks
    Recent advances in wireless sensors network (WSN) technology have made possible the manufacturing of tiny low-cost, low-power sensors with wireless multi-hop communication and sensing capabilities. Energy conservation for WSNs is a primary objective that needs to be addressed at all layers of the networking protocol stack. In many applications latency is another crucial factor to be addressed. However this must be done in the context of the energy constraints imposed by the network. In this paper we present an experimental evaluation of two node scheduling regimes within MERLIN (MAC energy efficient, routing and localization integrated), an energy-efficient low-latency integrated protocol for WSNs. In particular we contrast the X and V scheduling family schemes with respect to the following properties: network setup time, network lifetime and message latency. We conduct our experiments within the OmNet++ simulator.
      355Scopus© Citations 15
  • Publication
    Real-time recognition and profiling of appliances through a single electricity sensor
    Sensing, monitoring and actuating systems are expected to play a key role in reducing buildings overall energy consumption. Leveraging sensor systems to support energy efficiency in buildings poses novel research challenges in monitoring space usage, controlling devices, interfacing with smart energy meters and communicating with the energy grid. In the attempt of reducing electricity consumption in buildings, identifying individual sources of energy consumption is key to generate energy awareness and improve efficiency of available energy resources usage. Previous work studied several non-intrusive load monitoring techniques to classify appliances; however, the literature lacks of an comprehensive system that can be easily installed in existing buildings to empower users profiling, benchmarking and recognizing loads in real-time. This has been a major reason holding back the practice adoption of load monitoring techniques. In this paper we present RECAP: RECognition of electrical Appliances and Profiling in real-time. RECAP uses a single wireless energy monitoring sensor easily clipped to the main electrical unit. The energy monitoring unit transmits energy data wirelessly to a local machine for data processing and storage. The RECAP system consists of three parts: (1) Guiding the user for profiling electrical appliances within premises and generating a database of unique appliance signatures; (2) Using those signatures to train an artificial neural network that is then employed to recognize appliance activities (3) Providing a Load descriptor to allow peer appliance benchmarking. RECAP addresses the need of an integrated and intuitive tool to empower building owners with energy awareness. Enabling real-time appliance recognition is a stepping-stone towards reducing energy consumption and allowing a number of major applications including load-shifting techniques, energy expenditure breakdown per appliance, detection of power hungry and faulty appliances, and recognition of occupant activity. This paper describes the system design and performance evaluation in domestic environment.
    Scopus© Citations 223  2962