Now showing 1 - 5 of 5
  • Publication
    COPOLAN : non-invasive occupancy profiling for preliminary assessment of HVAC fixed timing strategies
    Nowadays, control of heating, cooling and ventilation equipment operation is mainly achieved via timers with fixed setback schedules, configured using experience and standard models of space occupancy. Applying generic timing strategies is however rarely optimal. Sensor-based systems offer a solution for dynamic control of equipment operation using real-time space occupancy input, but both deployment time and cost constraints hinder their integration if savings and return on investment are uncertain. This work introduces COPOLAN, a tool that correlates power consumption pat- terns and computers’ VLAN activity. Utilising computers’ VLAN activity auditing is key to obtain the power state of employees’ computer equipment over time, a prime indicator of employees’ presence within a building. At low cost and non-invasively, COPOLAN uncovers misalignment and pro- duces ground for (1) determining opportunities of improv- ing HVAC timing strategies and (2) helping decision making prior to integrating new equipment such as sensor-based systems. COPOLAN has been experimented on within a University department, where misalignment between power consumption and space occupancy patterns have highlighted 10 % energy saving opportunities.
    Scopus© Citations 12  837
  • Publication
    On the RFID Wake-up Impulse for Multi-hop Sensor Networks
    Communication protocols for wireless sensor networks reduce the energy consumption by duty cycling the node activity and adopting a periodic sleeping scheduling. This approach often results in idle listening and therefore energy dissipated for listening to a channel free from packet transmitted. Duty cycling trades-off energy consumption due to idle listening and high end-to-end delay. Proposed solutions mitigate this issue for example through extra low-power radio components (wake-up radio) that listen to the radio and wake-up the node if some channel activity is sensed. These extra components also consume some energy to listen to the channel. In contrast, we propose an on-demand wake-up capability, namely RFIDimpulse, which is achieved through using an off-the-shelf batteryless RFID tag attached to each sensor node that is also provided with RFID reader capability. Because modern RFID techniques can trigger all the neighbouring tags at once or pinpoint a particular tag, RFIDimpluse provides both unicast and multicast capability. RFIDimpulse allows eventdriven communication and eliminates node idle listening.
      359
  • Publication
    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.
      2537
  • Publication
    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 RFIDImpulse 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 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 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.
    Scopus© Citations 123  1217
  • 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