Active Research Areas
His PhD thesis was entitled "Energy- and Information-Managed Wireless Sensor Networks: Modelling and Simulation", which he successfully defended in December 2008. His current and future research interests are in the areas of wireless sensing and sensor networks for medical applications, and he founded and chairs an ECS interest group on wireless sensing (WiSE) as part of the "sensor networks" research theme of the School's Pervasive Systems Centre. Dr Merrett is the author of a number of international journal and conference publications in the area of wireless sensor networks, and is currently contributing to a chapter on "Wireless Devices and Sensor Networks" in a book entitled "Energy Harvesting for Autonomous Systems".
Please note this page is under construction, and large sections of it may be inaccurate or incomplete.
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Wireless Sensors for Pervasive Healthcare
I am currently researching a number of different applications and technologies for wireless sensing in pervaisve healthcare. This section is currently under construction, but further information will appear here in due course.
Intelligent Crutch on BBC South Today
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Related Publications
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Energy- and Sensing-Aware Architectures for Embedded Sensor Nodes
This research has proposed a hardware/software architecture that provides equal weighting to all node functions; for example, communications, energy management, intelligent sensing, locationing and actuation. This promotes modular design, code reuse, and protocol standardisation in the development of all node functions.
Project Website: http://wise.ecs.soton.ac.uk/project.php?id=547
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Related Publications
Number of items: 4. Merrett, G. V. (2009) Energy- and Information- Managed Wireless Sensor Networks: Modelling and Simulation. PhD thesis, University of Southampton.
Merrett, G. V., Weddell, A. S., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2008) A Structured Hardware/Software Architecture for Embedded Sensor Nodes. In: 17th International Conference on Computer Communications and Networks, 03-07 August 2008, St Thomas, Virgin Islands (USA).
Weddell, A. S., Merrett, G. V., Harris, N. R. and Al-Hashimi, B. M. (2008) Energy Harvesting and Management for Wireless Autonomous Sensors. Measurement + Control, 41 (4). pp. 104-108. ISSN 0020-2940
Merrett, G. V., Weddell, A. S., Harris, N. R., White, N. M. and Al-Hashimi, B. M. (2006) The Unified Framework for Sensor Networks: A Systems Approach. Technical Report UF1, School of Electronics & Computer Science, University of Southampton. (Unpublished)
This list was generated on Fri Jul 30 01:07:39 2010 BST.
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Modelling and Simulating Wireless Sensor Networks
Network simulators are used to compare different network protocols and algorithms. In general (though it may require a modification or add-on), the simulator allows a number of sensor nodes to be distributed, which can communicate with each other using a communications protocol. The most widely used simulator for WSNs is the Unix based 'ns-2', a discrete event simulator targeted at networking research including wired and wireless networks. Other network simulators exist including OPNET's 'Modeler' and add-on module 'Wireless', the public source OMNET++ environment, and the TinyOS network simulator - TOSSIM.
Physical and Environmental Modelling
The decision was made to implement a custom simulator as it would allow results to be obtained early on in the project without overcoming the steep learning curve associated with available network simulators. Additionally, the simulator could be tailored specifically to the designed algorithm.
Simulating Wireless Sensor Networks
The simulator, named WSNsim (Wireless Sensor Network simulator), was developed in Microsoft Visual Studio .net. WSNsim creates a virtual environment over which sensor nodes and dynamic events (properties that can be monitored by a sensor node) are scattered. When the simulation is executed, nodes in the network detect events in their local area and, if required, propagate messages throughout the network using multi-hop routing. The operation of WSNsim is coordinated around the concept of the timestep - the smallest period of discrete time known by the nodes in the network. Every timestep, the sensor nodes inspect the environment around them to locate events, and receive an energy increase through harvesting (if applicable). Vibration harvesting (or any other form of energy harvesting) can be modelled in WSNsim using a mathematical representation, tabulated data, or a combination of both. The WSN can be configured to have either a fixed base station (all nodes attempt to send data to a single processing node), or a distributed network (nodes send data to other nodes in the network). WSNsim can simulate a wide variety of different configurations and applications, and provides a platform upon which objective observations can be made, without claiming to accurately model wireless channels or sensor nodes.
Project Website: http://wise.ecs.soton.ac.uk/project.php?id=545
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Related Publications
Number of items: 5. Merrett, G., White, N., Harris, N. and Al-Hashimi, B. (2009) Energy-Aware Simulation for Wireless Sensor Networks. In: Sixth Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON 2009), 22-26 June 2009, Rome, Italy.
Merrett, G. V. (2009) Energy- and Information- Managed Wireless Sensor Networks: Modelling and Simulation. PhD thesis, University of Southampton.
Weddell, A. S., Merrett, G. V., Harris, N. R. and White, N. M. (2009) Energy Devices for Sensor Networks: Properties for Simulation and Deployment. In: Wireless Communications, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology (Wireless VITAE); Special Session: Energy-Harvesting Wireless Sensor Networks, 17-20 May 2009, Aalborg, Denmark. pp. 26-30.
Merrett, G. V., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2008) Energy Managed Reporting for Wireless Sensor Networks. Sensors and Actuators A: Physical, 142 (1). pp. 379-389.
Merrett, G. V., Weddell, A. S., Lewis, A. P., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2008) An Empirical Energy Model for Supercapacitor Powered Wireless Sensor Nodes. In: 17th International IEEE Conference on Computer Communications and Networks, 03-07 August 2008, St Thomas, Virgin Islands (USA).
This list was generated on Thu Jul 29 14:55:23 2010 BST.
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Energy- and Information-Management Algorithms for Wireless Sensor Networks (IDEALS/RMR)
A Wireless Sensor Network (WSN) consists of a collection of small, locally powered, intelligent sensor nodes that communicate detected events over a wireless channel (typically through multi-hop routing). WSNs are continuing to receive an escalating research interest, due in part to the considerable range of applications that they are suited to. These applications include environmental monitoring, smart buildings, smart structures, object tracking, healthcare, security and defence.
One of the key challenges facing researchers is in overcoming the limited network lifetime inherent in the small locally powered sensor nodes. This project aims to investigate a network management algorithm (not a routing algorithm) to maximise network lifetime through exploiting energy harvesting and energy management, considering the importance of data, and by using only local (or selfish) decisions to minimise negotiation overheads. Additionally, the system will be simulated, analysed and implemented.
This project is developing IDEALS (Information manageD Energy aware ALgorithm for Sensor networks), which increases the network lifetime for important data, by controlling the degradation of the network. This extension in the network lifetime is obtained at the expense of less important data. IDEALS operates upon a system of priorities and thresholds, and through the exploitation of energy harvesting, energy management and data importance. Each sensor node in the network decides its own network involvement based on a trade-off between data importance, and its own energy availability.
The results obtained from WSNsim (see below) show that a significant increase in the network lifetime can be obtained.
Project Website: http://wise.ecs.soton.ac.uk/project.php?id=545
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Related Publications
Number of items: 6. Merrett, G. V. (2009) Energy- and Information- Managed Wireless Sensor Networks: Modelling and Simulation. PhD thesis, University of Southampton.
Merrett, G. V., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2008) Energy Managed Reporting for Wireless Sensor Networks. Sensors and Actuators A: Physical, 142 (1). pp. 379-389.
Merrett, G. V., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2006) Rule Managed Reporting in Energy Controlled Wireless Sensor Networks. In: Eurosensors XX, 17th-20th September 2006, Gothenburg, Sweden. pp. 402-403.
Merrett, G. V., Harris, N. R., Al-Hashimi, B. M. and White, N. M. (2006) Energy Controlled Reporting for Industrial Monitoring Wireless Sensor Networks. In: IEEE Sensors 2006, 22nd-25th October 2006, Daegu, Korea. pp. 892-895.
Merrett, G., Al-Hashimi, B. M., White, N. M. and Harris, N. R. (2005) Information Managed Wireless Sensor Networks with Energy Aware Nodes. In: 2005 NSTI Nanotechnology Conference and Trade Show (NanoTech 2005), 8-12 May 2005, Anaheim, California. pp. 367-370.
Merrett, G. V., Al-Hashimi, B. M., White, N. M. and Harris, N. R. (2005) Resource Aware Sensor Nodes in Wireless Sensor Networks. In: Sensors & their Applications XIII, 6-8 September 2005, Chatham Maritime, Kent. pp. 137-142.
This list was generated on Thu Jul 29 17:45:33 2010 BST.
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WSNs for Personnel Monitoring in Industrial Environments
The aim of this project is to implement a demonstration Wireless Sensor Network (WSN) to monitor people and activity in the new Mountbatten Cleanroom at the University of Southampton. The demonstration network aims to have 20 fixed nodes, and 10 portable/wearable nodes (for tracking cleanroom users), though it will be scalable to cover the entire cleanroom.
A fundamental purpose of the project is to provide a WSN showcase and development platform. However, additional aims of the project are for Information Provision (enabling cleanroom users, vistors and the public to see what is happening inside the cleanroom), and Administration (monitoring machine and personnel usage).
This project is currently in the design stage - more information will appear here as it becomes available.
Project Website: http://wise.ecs.soton.ac.uk/project.php?id=534
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Related Publications
Number of items: 1. Merrett, G. V., Weddell, A. S., Berti, L., Harris, N. R., White, N. M. and Al-Hashimi, B. M. (2008) A Wireless Sensor Network for Cleanroom Monitoring. In: Eurosensors 2008, 07-11 September 2008, Dresden, Germany. pp. 1553-1556.
This list was generated on Thu Jul 29 17:45:34 2010 BST.
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Inactive Research Areas
CMOS Leakage Power
This project investigated leakage power in deep submicron digital circuits. Basic combinational gates, including NOT, NAND, NOR and XOR, are fundamental building blocks in CMOS digital circuits. This project analysed and compared the power consumption due to transistor leakage of low-order and high-order basic logic gates.
NAND and NOR gates implemented using different design styles and circuit topologies - including complementary CMOS, partitioned logic and complementary pass-transistor logic - were compared. The XOR gate was implemented and analysed using a variety of additional circuit topologies, including double pass-transistor logic, differential cascade voltage switch logic and a gate designed specifically for low power. Building on the analysis of the basic gates, the leakage power consumption of the 1-bit full adder was analysed, and compared across a range of different circuit topologies.
The circuits were simulated with HSPICE using the Berkeley Predictive Technology Models (BTPM) for three deep submicron technologies (0.07um, 0.1um and 0.13um). The results obtained were used to consider leakage power reduction methods, and to make observations regarding leakage power sensitive design.
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Radio Frequency Identification (RFID)
During an industrial work placement, I wrote firmware for an embedded processor in a 13.56MHz RF-ID tagging system. This involved debugging and modifying previously untested hardware.
Following this, I designed and wrote a database structured software package for managing a commercial RF-ID tagging product. An addition to providing standard database functions (data entry, deletion, modification, filtering and sorting), this software implemented features including hardware communication, PDA synchronisation, security/encryption and report generation.
In addition, I developed software to control and interface a high speed PCI data logger, and produced smaller software solutions to assist the company in resource management.
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Related Publications
Number of items: 0.
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