Antonio G. Ruzzelli

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.

Radio Sleep Mode Optimization in Wireless Sensor Networks

Energy efficiency is a central challenge in sensor networks, and the radio is a major contributor to overall energy node consumption. Current energy-efficient MAC protocols for sensor networks use a fixed low-power radio mode for putting the radio to sleep. Fixed low-power modes involve an inherent trade-off: deep sleep modes have low current draw and high energy cost and latency for switching the radio to active mode, while light sleep modes have quick and inexpensive switching to active mode with a higher current draw. This paper proposes adaptive radio low-power sleep modes based on current traffic conditions in the network. It first introduces a comprehensive node energy model, which includes energy components for radio switching, transmission, reception, listening, and sleeping, as well as the often disregarded microcontroller energy component for determining the optimal sleep mode and MAC protocol to use for given traffic scenarios. The model is then used for evaluating the energy-related performance of our recently proposed RFID impulse protocol enhanced with adaptive low-power modes, and comparing it against BMAC and IEEE 802.15.4, for both MicaZ and TelosB platforms under varying data rates. The comparative analysis confirms that RFID impulse with adaptive low-power modes provides up to 20 times lower energy consumption than IEEE 802.15.4 in low traffic scenario. The evaluation also yields the optimal settings of low-power modes on the basis of data rates for each node platform, and provides guidelines and a simple algorithm for the selection of appropriate MAC protocol, low-power mode, and node platform for a given set of traffic requirements of a sensor network application.

A flexible building management framework based on wireless sensor and actuator networks

Future buildings will be constantly monitored and managed through intelligent systems that allow having information about the building health, keeping a good comfort level for the building inhabitants and optimizing the energy spent. Despite many WSN programming frameworks have been to date developed and, in some cases, applied to support monitoring of buildings, none of them possesses all the specific features needed to develop WSN-based building applications. In this article a multi-platform domain specific framework based on Wireless Sensor and Actuator Networks (WSANs) for enabling efficient and effective management of buildings is presented. The proposed Building Management Framework (BMF) provides powerful abstractions that capture the morphology of buildings to allow for the rapid development and flexible management of pervasive building monitoring applications. The functionalities of the framework are shown in an emblematic case study concerning the SmartEnergyLab that is an effective operating scenario related to the monitoring of the usage of workstations in laboratories and offices. Finally, a performance evaluation of a WSAN running the BMF in terms of network usage and system lifetime is shown.

Evaluation of energy-efficiency in lighting systems using sensor networks

In modern energy aware buildings, lighting control systems are put in place so to maximise the energy-efficiency of the lighting system without effecting the comfort of the occupant. In many cases this involves utilising a set of presence sensors, with actuators, to determine when to turn on/off or dim lighting, when it is deemed necessary. Such systems are installed using standard tuning values statically fixed by the system installer. This can cause inefficiencies and energy wastage as the control system is never optimised to its surrounding environment. In this paper, we investigate a Wireless Sensor Network (WSN) as a viable tool that can help in analysing and evaluating the energy-efficiency of an existing lighting control system in a low-cost and portable solution. We introduce LightWiSe (LIGHTting evaluation through WIreless SEnsors), a wireless tool which aims to evaluate lighting control systems in existing office buildings. LightWiSe determines points in the control system that exhibit energy wastage and to highlight areas that can be optimised to gain a greater efficiency in the system. It will also evaluate the effective energy saving to be obtained by replacing the control system with a more judicious energy saving solution. During a test performed in an office space, with a number of different lighting control systems we could highlight a number of areas to reduce waste and save energy. Our findings show that each system tested can be optimised to achieve greater efficiency. LightWiSe can highlight savings in the region of 50% to 70% that are achievable through optimising the current control system or installing an alternative.

MERLIN: Cross-layer integration of MAC and routing for low duty-cycle sensor networks

Sensor network MAC protocols typically sacrifice packet latency to achieve energy efficiency. Such delays may well increase due to routing protocol operation. For this reason it is imperative that we attempt to quantify the end-to-end delay and energy consumption when jointly using low duty cycle MAC and routing protocols. In this paper, we present a comprehensive evaluation of MERLIN (MAC and efficient routing integrated with support for localization), a cross-layer protocol that integrates both MAC and routing features. 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 asynchronous burst ACK and negative burst ACK messages. 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 (an improved version of the DSR algorithm). The results illustrate that the joint usage of both SMAC and ESR, in low duty cycle scenarios, causes extremely high end-to-end delays and prevents acceptable data delivery rate. MERLIN, as an integrated approach, notably reduces latency, resulting in nodes that can deliver data in a very low duty cycle, yielding a significant extension to network lifetime.

Adaptive Radio Modes in Sensor Networks: How Deep to Sleep?

Energy-efficient performance is a central challenge in sensor network deployments, and the radio is a major contributor to overall energy node consumption. Current energy- efficient MAC protocols for sensor networks use a fixed low power radio mode for putting the radio to sleep. Fixed low power modes involve an inherent tradeoff: deep sleep modes have low current draw and high energy cost and latency for switching the radio to active mode, while light sleep modes have quick and inexpensive switching to active mode with a higher current draw. This paper proposes adaptive radio low power sleep modes based on current traffic conditions in the network, as an enhancement to our recent RFID impulse low power wake-up mechanism. The paper also introduces a comprehensive node energy model, that includes energy components for radio switching, transmission, reception, listening, and sleeping, as well as the often disregarded micro-controller energy component to evaluate energy performance for both MicaZ and TelosB platforms, which use different MCUs. We then use the model for comparing the energy-related performance of RFIDImpulse enhanced with adaptive low power modes with BMAC and IEEE 802.15.4 for the two node platforms under varying data rates. The comparative analysis confirms that RFIDImpulse with adaptive low power modes provides up to 20 times lower energy consumption than IEEE 802.15.4 in low traffic scenario. The evaluation also yields the optimal settings of low power modes on the basis of data rates for each node platform, and it provides guidelines for the selection of appropriate MAC protocol, low power mode, and node platform for a given set of traffic requirements of a sensor network application.

Energy-efficient multi-hop medical sensor networking

Wireless sensor networks represent a key technology enabler for enhanced health care and assisted living systems. Recent standardization eorts to ensure compatibility among sensor network systems sold by dierent vendors have produced the IEEE 802.15.4 standard, which specifies the MAC and physical layer behavior. This standard has certain draw-backs: it supports only single-hop communication; it does not mitigate the hidden terminal problem; and it does not coordinate node sleeping patterns. The IEEE 802.15.4 standard design philosophy assumes that higher layer mechanisms will take care of any added functionality. Building on IEEE 802.15.4, this paper proposes TImezone COordinated Sleep Scheduling (TICOSS), a mechanism inspired by MERLIN [2] that provides multi-hop support over 802.15.4 through the division of the network into timezones. TICOSS is cross-layer in nature, as it closely coordinates MAC and routing layer behavior. The main contributions of TICOSS are threefold: (1) it allows nodes to alternate periods of activity and periods of inactivity to save energy; (2) it mitigates packet collisions due to hidden terminals belonging to nearby star networks; (3) it provides shortest path routing for packets from a node to the closest gateway. Simulation experiments confirm that augmenting IEEE 802.15.4 networks with TICOSS doubles the operational lifetime for high trac scenarios. TICOSS has also been implemented on the Phillips AquisGrain modules for testing and eventual deployment in assisted living systems.

A Review of Wireless-Sensor-Network-Enabled Building Energy Management Systems

Reducing energy consumption within buildings has been an active area of research in the past decade; more recently, there has been an increased influx of activity, motivated by a variety of issues including legislative, tax-related, as well as an increased awareness of energy-related issues. Energy usage both in commercial and residential buildings represents a significant portion of overall energy consumption; however, much of this may be categorized as waste, that is, energy usage that does not fulfil a definite purpose. In the past decade, the viability of Wireless Sensor Network (WSN) technologies has been demonstrated, leading to increased possibilities for novel services for building energy management. This development has resulted in numerous approaches being proposed for harnessing WSNs for energy management and conservation. This article surveys the state-of-the-art in building energy management systems. A generic architecture is proposed after which a detailed taxonomy of existing documented systems is presented. Gaps in the literature are highlighted and directions for future research identified.

Octopus: monitoring, visualization, and control of sensor networks

Sensor network monitoring and control are currently addressed separately through specialized tools. However, the high degree of coupling of network state to the physical environment in which the network is deployed demands that users can monitor the network and respond to network state changes continuously. This paper presents the open-source Octopus visualization and control tool. Octopus is a protocol-independent tool that provides live information about the network topology and sensor data in order to enable live debugging of deployed sensor networks. It enables operators to reconfigure the network behavior, such as switching between time-driven, event-driven, and query-driven modes or between awake and sleep modes of one, many, or all nodes through its graphical interface. Octopus also supports changing duty cycles of nodes, data reporting period, or sensing thresholds in event-driven networks. Reconfiguration of nodes is achieved through short request messages that support typical reconfiguration options without the overhead of epidemically sending new program images over the air. Our empirical tests showcase Octopuss capacity to debug application behavior and to characterize heterogeneous network performance under multiple settings, as a step toward establishing a rules database that relates data delivery to network-level parameters, and toward enabling autonomous network reconfiguration. Copyright

Multi-Hop RFID Wake-Up Radio: Design, Evaluation and Energy Tradeoffs

Energy efficiency is a central challenge in battery- operated sensor networks. Current energy-efficient mechanisms employ either duty cycling, which reduces idle listening but does not eliminate it, or low power wake-up radio, which adds complexity and cost to the sensor platform. In this paper, we propose a novel mechanism called RFIDImpulse that uses RFID technology as an out-of-band wake-up channel for sensor networks. RFIDImpulse is an on-demand mechanism that enables nodes to sleep until they have to send or receive packets. It relies on IEEE 802.15.4 radio to emulate an RFID reader at a sender node, and on an off-the-shelf RFID tag attached to the external interrupt pin of each sensor node. The sender can simply activate the receivers tag before sending it data packets. This setup enables both radio and microcontroller to go into deep sleep mode until they need to be active. We develop an analytical model to evaluate the energy tradeoffs of RFIDImpulse, and then evaluate the mechanism against BMAC and IEEE 802.15.4 in high and low traffic scenarios. The results confirm that RFIDImpulse reduces the energy consumption relative to both protocols for low and medium traffic scenarios, and they reveal the thresholds for adaptive activation of RFIDImpulse based on traffic load.