1 ijaest volume no 3 issue no 2 a survey of communication and sensing for energy management of...

8/7/2019 1 IJAEST Volume No 3 Issue No 2 a Survey of Communication and Sensing for Energy Management of Appliances 6

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A Survey of Communication and Sensing for EnergyManagement of Appliances

A Hardy, F Bouhafs, M MerabtiSchool of Computing and Mathematical Sciences

Liverpool John Moores UniversityLiverpool, United Kingdom

[email protected], [email protected], [email protected]

Abstract Concerns about climate change, dwindling legacy

energy sources and an aging and under-invested power grid has

lead to pressing energy management focus from governments,

energy producers, distributors and consumers. From the power

stations to the consumers, the appliances at its edge, this aging

power grid is large, complex and difficult to manage, but the

plethora of new appliances adding to consumption daily are stilllargely uncommunicative. Progress is beginning to be made with

a concept called Smart Grid. Smart Grid is described as the

future generation of the electricity network that functions more

cooperatively, responsively and organically. However

conversations around the outworking of this concept are still

ongoing. In this paper we survey communication and sensing for

managing the energy consumption of appliances. We begin by

looking at the wide range of elements across the power grid, their

roles in managing this energy consumption and the

communication required between them to fulfill these roles. We

go on to describe the necessary characteristics and qualities for

these communication and sensing technologies and with these

qualities in mind we assess a range of wired and wirelesscommunications, sensing and tagging.

Keywords-energy management; communication; sensing; smartgrid

I. INTRODUCTIONAmongst the conditions driving the need for energy

management, two are of primary impact.

The first is well known; global warming and CO2 emittingenergy sources have gained high focus in the last decade, mostare aware that government targets exist for CO2 reductions andincreases in renewable energy sources and visionaries portray afuture filled with wind turbines and solar panels.

The second is less well known; in this technological agemost of the electricity distribution infrastructure, the powergrid, was developed before microprocessors when currentquestions such as efficiency, customer choice and theenvironment were not concerns. The power grid is aging andunder-invested and has become large, complex and difficult tomanage.

The Smart Grid concept has played an important role inmoving towards better energy management. Smart Grid is thefuture generation of the electricity network that functions more

cooperatively, responsively and organically [1]. Smart Gridencompasses entities across the entire power network fromenergy producer to appliances in the home or office andadvocates real-time collaboration between these entities tomanage power intelligently. Early initiatives include DemandResponse and smart meters, but less attention is paid to the

appliances themselves. In 2009 the UK supplied a total of 357TWh. 8% was lost in transmission and distribution but afterdelivery the domestic sector was the largest consumer with thedomestic and service sector together totaling 70% of totalconsumption. Appliances are a very significant contributor inthese sectors and therefore deserve our considered attention.

Existing appliance energy management research projectsand technologies focus mainly on two approaches: applianceefficiency and user behavior change, while appliances cancontinue to squander energy unjustified. Without the rightcommunications technologies, appliances cannot obtain enoughinformation to consume responsibly. They need to be aware ofuser constraints; they need real-time load data from power

distribution systems and they need the right sensing andtagging technologies to make them aware of the context inwhich they consume and whether that consumption is valid.Appliances also need to publish their real-time state andconsumption so it can be better managed by users and by otherdevices. In the future energy grid, generation systems andstorage systems must use communications technologies toconnect with distribution systems and appliances to optimallyselect from available power sources. And to better manage peak load and respond to grid events appliances at the veryedge of the power grid must be able to connect with andrespond to these power distribution systems.

In this paper we discuss elements in the grid and their roles

in achieving energy management. Additionally we discuss thecommunication required between these elements to fulfill theseroles. Through this discussion we arrive at a set of idealqualities and functional characteristics and it is against thesethat we survey communication and sensing technologiessuitable for energy management.

II. ENERGY MANAGEMENT OF APPLIANCES IN CONTEXTIn order to assess the suitability of different communication

and sensing for energy management of appliances in theelectric power grid we must first appreciate the context in

A Hardy et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIESVol No. 3, Issue No. 2, 061 - 077

ISSN: 2230-7818 @ 2011 http://www.ijaest.iserp.org. All rights Reserved. Page 61


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which these technologies shall operate. The identification ofthe context implies; understanding the role, the functioning andthe location of the many elements required to be connected tomanage appliance energy consumption in the grid;understanding the nature of the communications requiredbetween these elements to fulfill their roles.

A. Necessary Elements for Energy ManagementAt the edge of the smart grid elements may include the

premises smart meter, various consuming smart appliances,distributed energy generation systems, energy storage systems,environmental sensing and tagging, energy managementsystems and In Home Displays (IHD). Elements across the gridinclude Electricity utility services, control centers, power griddistribution systems, appliance manufacturers and otherauthorized static or mobile devices. All these elements mustfulfill their particular role in order to fully manage the energyconsumption of appliances. Elements have differentrequirements and constraints and the nature of these elementswill inform the suitability of different communication andsensing. An overview of these elements and their connections

can be seen in Fig. 1.1) Smart Appliances

Typically the primary role of an appliance is to provide aservice or a collection of related services to its users or to otherappliances. The services could range from heating a room fullof people to recording a TV program while a property is empty.Appliances make a major and an increasing contribution to theload on the power grid and as such are a very important part ofany strategy for energy management. There are efforts toenable users to change their consumption behavior or toconfigure automated consumption thresholds, but this is notenough, appliances must be enabled to consume efficiently andintelligently in accordance with their wider context.

Appliances should respond to their environmental context,for example if there is no occupancy, it may be appropriate forAudio Visual equipment to remove power from display andaudio, while continuing to record an input channel or it maynot be appropriate to continue heating a cold room because allthe windows are open. To this end Appliances must beconnected with sensing elements and respond to theinformation they provide.

Appliances should also respond to their power grid context.They should publish their consumption and state informationfor the cooperative and responsive function of the smart grid.Fine grain appliance interaction will enable utilities to bettermanage supply in real-time and enable the implementation of

more intelligent and effective demand response services forconsumers. Appliances may be connected to a Home AreaNetwork (HAN), a network that allows remote connection andcontrol of appliances in the home using cordless or mobilephones, personal computers or dedicated appliance automationsystems.

Figure 1. Elements for Energy Management

2) Smart Meter and Energy System InterfaceSmart meters are one of the first smart grid remote

communication technologies. Early installations recordpremises energy consumption at regular intervals. In the future,smart meters will be able to notify this consumption to utilitiesautomatically across some kind of communications network.

Demand Response is another smart grid mechanism bywhich appliances act on direct grid state or utility pricingnotifications and cease or delay consumption or switch to low power modes of operation. Similarly Dynamic Responseenables the appliances to detect critical grid state and adjustwithout notification. Prices-to-Devices is an arrangement forutilities to communicate real-time pricing to individual devicesaccording to power grid conditions and for devices to respondaccordingly. Such arrangements require secure registration and

communication between appliances and utilities. This isachieved through a gateway often called the Energy SystemInterface (ESI). The ESI presents an interface to the energyproviders systems and services so they can be accessible fromPremises Energy Management Systems (PEMS) or otherdevices on the HAN. Smart meters are the likely implementersof ESI for demand-response and prices-to-devices mechanisms.

Other potential features incorporated into smart metersinclude visualizations for user consumption monitoring andanalysis and appliance remote control and automation eitherfrom in home or on-line.

3) Sensors and TagsSensors convert environmental stimulus into an electricalsignal that can be measured and stored. There are a variety of

sensor types, including: temperature, humidity, light, speed,acceleration, sound, magnetism. A sensor node is a device thatincorporates a number of sensors with computation and acommunication system. Typically sensors are deployed inhard-to-reach locations, hence they cannot be connected bywire and must therefore communicate wirelessly and operateon low power. The role of sensing in an energy managementsystem is to provide an environmental context in whichappliances can validate their mode of operation, for example




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adjusting the heating system according to a thermostat orturning off lights when there is no occupancy.

Tags are microchips that may be located in or carried byobjects, animals or people to allow remote identification ortracking. Radio Frequency Identification technology (RFID)comprises very small tags, composed of an IC and an antenna,and an RFID reader device. The reader transmits a radiofrequency and reads the back scattered signal reflected andmodulated by the tag to indicate its Id. Tagging can be used toextend the environmental context to indicate the presence ofspecified people or objects, for example preventing childrenfrom turning on high consuming devices or adjusting a fridgeor freezer according to its contents.

Raw data from sensors and tags cannot be used directly tocontrol appliances. Some element of the system must providefunctionality to collated and interpreted this data to providerelevant environmental information. This information can then be communicated to appliances in order that they mightrespond with appropriate modes of operation.

It is also possible that this environmental information could

provide awareness to utilities and distribution systems of a riskof impending increased load or provide policy makers withenvironmental information along-side consumptioninformation enabling them to better direct energy savingresources. However, the sharing of environmental sensing doesraise privacy issues.

4) Premises Energy Management Systems (PEMS)PEMS is a software application for managing energy-

controllable smart appliances, such as Heating Ventilation andAir Conditioning (HVAC), lighting, white goods and variousconsumer electronics. PEMS may be a dedicated device or acollection of functions across appliance automation displays,laptops, Programmable Communicating Thermostats (PCT)

and so on.PEMS performs device and consumption monitoring,

allows configuration of energy thresholds, constraints and policies, and coordinates interconnection and meaningfulcommunication between elements such as sensors, smartappliances, smart meter, generation systems and storagesystems by executing the specified energy managementpolicies.

5) User Interface DevicesA User interface device or In Home Display (IHD) works

together with PEMS and ESI to present users with usefulinformation, such as detailed local consumption history, billingand energy management policies. Where utility data ispresented, secure mechanisms should exist to carefully manageany preparation and pre-processing possibly usingauthenticated common services or offloading this function ontoutilities.

The device also provides an interface to PEMS or ESI forthe configuration of local or utility controlled energymanagement programs.

6) Distributed Energy Generation SystemsHistorically, purchase of electric power has been relatively

involuntary. Choice has been minimal, payment often made

weeks after the supply and no empowerment to consider real-time energy sources during consumption.

Distributed generation employs technology for scatteredsmall-scale generation sources closer to the consumers, bothgeographically, and often in terms of control and ownership,providing generation participation and choice. Technology caninclude photo voltaic cells (PVC), wind turbines, damlesshydro, biomass and biofuel extracting energy from plants.Smart grid supports distributed generation through theprinciple of open communication standards for all elements onthe grid, allowing sources to cooperate with appliances, storagesystems, meters and gird distribution systems exchanging datasuch as appliance mode and consumption, grid loading,available local power, storage levels and so on.

When grid load is high and local appliance demand is low,locally generated power can be directed to local storage or to aMicrogrid, a close cooperating community of electricalgenerators and consumers. Alternatively power can be sold to autility. When local generation is high and utility prices are highit can support the local appliances and when local generation islow, appliances can adjust their mode of operation and useother power sources.

7) Storage SystemsThe greatest unpredictability in the power grid is in load.

Storage can be used during variable load to implement peakshaving bringing cost savings and grid stability. Additionallythe increase in renewable energy sources, such as wind andsolar and the introduction of distributed personal renewable power generation will see an increased unpredictability insupply. Storage can also be used to bring stability in times ofvariable supply.

Improvements are predicted in advanced battery and super-capacitor technologies with increases in energy density,

lifetime and efficiency. Moreover, It is expected that Plug-inElectric Vehicles (PEV) will also operate as efficient storageand supply devices. These efficiencies can begin to make itworthwhile for consumers to use local storage to buy energyand store it when the price is low and consume when the priceis high, while also making some contribution to peeksmoothing.

In order to select between storage and supply or sell modesaccording to load or price on the grid, storage systems requireintelligence and common communications with powerdistribution systems and utility control centres through an ESIat the smart meter as well as communication with PEMS inorder to balance supply and demand on the Home Area

Network (HAN).

8) Systems on the Power Distribution NetworkThe systems on the distribution network are responsible for

taking power from the high voltage transmissions lines andmore recently from distributed generation sources anddistributing it to a range of retail consumers. These systemsinclude distribution and collector substation systems,distribution transformers, distributed generation connectionequipment and network control centres.




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Substations are responsible for transforming voltage fromthe high voltage transmissions network to a number of outputlines on the distribution system and for providing switching toisolate faults, protect equipment, allow maintenance and switch between generation sources. Distribution transformers stepdown the voltage along the output lines until correct voltage isdelivered to household or commercial meters. Distributedgeneration sources can be connected behind the meter or

somewhere along the substation output line.Where retail consumers support it, distribution substations

or control centres can send Demand Response and LoadControl (DRLC) instructions to the Energy System Interface atthe retail smart meter to adjust individual appliance energymodes, thereby managing smoothing or unexpected load issueswith greater granularity. In a similar way substations mustmanage requests from commercial and personal generationdevices which would result in a reduced load and increasedvoltage, possibly communicating with registered storagedevices to offload excess capacity.

9) Control CentersDistribution Network Operators (DNO) implement control

centre systems for distribution network and the Energy ServiceProviders (ESP) or utility provides centres for retailmanagement. From behind the meter these systems can beaccessed through an ESI. Smart devices of the kind describedmay be enabled to connect and register in different ways. Somemay simply access data and services particular to a given retailmeter or premises; some may agree to a particular energymanagement plan and others may even authorize a centressystem to control of their modes of operation.

The role of control centres includes the intelligentmanagement of owned or authorized devices in the distributionnetwork in some of the ways described. Control centres alsomanage retail accounts, remote and secure meter reading and arange of remote and secure billing strategies including pre-payment, credit tokens and regular billing.

B. Necessary Communication for Energy ManagementIn order to fulfil their role in the management of appliance

energy consumption, the elements we have described mustintercommunicate with each other, sharing a range of dataincluding real-time appliance consumption data, appliancestate, direct appliance commands, tag and sensor data, userconstraints, pricing, current demand and emergency gridevents. The connected elements and the nature andrequirements of the data they communicate will inform thesuitability of different communication and sensing.

1) Communication between Sensor Nodes and AppliancesSmart Sensor nodes will register with PEMS and these

registered sensors will pull configuration and calibration datafrom PEMS. Once a sensor node is registered and calibratedPEMS periodically pulls sensor data from it, see Fig. 2. Ifsensor events are, by nature, occasional, such as occupancy,then an arrangement may be made for nodes to push sensorstate transition events to PEMS as they occur.

PEMS maintains environmental dependencies ofoperational and service modes for each type of registered smart

appliance. For example HVAC might depend on temperature,open windows and so on, while lighting might depend onillumination and occupancy. From time to time, uponprocessing sensor data, PEMS will initiate operational mode orservice mode adjustments in given types of smart appliance.

In this manner it is intended that appliances respond to non-transient changes in the environmental context for which they provide their service. For this reason the appropriate rate ofsensor communication and the size of the data are unlikely todemand high bandwidth. This condition is also likely to have afavourable impact upon functional lifetime of sensors.

Some of the data in this domain could be consideredsensitive, such as occupancy state and appliance control.Because sensor data is commonly communicated wirelessly onan open network, secure communication solutions need to beimplemented between appliance, sensor node and PEMS.

2) Communication with Accounting SystemsAdvanced Metering Infrastructure (AMI) supports the

secure communication of billing data from the utility customeraccounting system to the ESI which then redirects the data to

registered IHDs. Billing data for further processing on theHAN is communicated under strict guidelines to preventcustomer and utility information mismatch.

AMI also supports pre-payment facilities. There are anumber of different methods requiring differentcommunication messages. Where credit is managed by theutility customer accounting system secure, it sends creditmessages to the ESI at the AMI Smart Meter. Alternativemethods include customers adding credit tokens to the AMISmart Meter. The Smart Meter connects through an ESI with asecure clearing system to authorize the token and the ESInotifies this to utility customer accounting system. The utilitysystem would also be required to submit secure disconnection

or emergency provision messages.

Figure 2. Communication between Sensor Nodes and Appliances




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Figure 3. Communication with Distributed Generation Systems

3) Communication with Distributed Generation SystemsThe ESI will receive, from distribution network control,DG capability requests which it will direct to DG devices onthe HAN. These devices will respond with capability data andthe distribution network will proceed with a series of controland monitor messages. See Fig 3.

4) Communication with Control CentersSmart Appliances send registration message to a Utility or

Distribution Network Control Centre through an ESI and thecentre sends a registration confirmation. Registration may be ata number of different levels, including establishing access toauthorized data for a given premise or ESI, subscribing to agiven energy management policy or program or authorizing the

control centre to issue a range of direct operational modecommands.

Control Centres or Distribution equipment may send DRLCevents sent to an ESI at the smart meter. Messages for apremise are forwarded to a PEMS and message for registeredappliances are forwarded to those appliances andacknowledgments are returned through the ESI.

Other messages include secure pricing data which may in asimilar way be sent to the meter for the premises pricing orthrough an ESI to a PEMS or to a registered applianceindicating energy price for a specific device, often calledprices-to-devices.

III. THE TECHNOLOGIESThe technologies will be assessed according to certain

functional characteristics and according to some relativequalities for energy management. Values for functionalcharacteristics are presented in tables in section 4. Table 1 liststhe relative qualities short names and descriptions. Entries infurther tables in section 4 reflect the technologies weak orstrong relative contributions to desired qualities. Contributionsare relative to all technologies discussed in the paper, not just

those in the table. An empty entry indicates a lack ofsignificant contribution.

Given the diversity of element types and locations, the gridwill not be served by a single communication medium.Amongst the medium characteristics to be considered are rangeand interference. Requirements will vary according to whichelements are being connected. For example, connectinglighting to occupancy sensing will have different requirementsfrom connecting an appliance to a property meter in a largecommercial building or connecting a meter with a substation.We must also consider the qualities of the elements themselves,such as functional lifetime, cost, form factor, and installationand configuration effort. For example, most appliances areconnected to the power infrastructure, but elements such assensing must be able to manage power efficiently.

TABLE I. DESIRED QUALITIES

Quality Description

Cost

Low collective cost/benefit for license,

certification, development, installation andoperation of equipment, for example adapters,routers, wiring and subsequent power andmaintenance costs.

Form factor

Small relative size of components such asadapters and especially tags and sensor nodeswhich often require embedded or unobtrusivelocating.

InstallationLow cost in money, time and inconvenience todeploy and configure equipment.

TransportGood potential to support widely commonnetwork and transport protocols such as TCP/IP.

AdoptionAttracting wide industry support and acceptancefor applicability in a manner that could lead tomass adoption.

Ubiquitous

Possessing technical characteristics which support

the potential for installation anywhere and foreverybody.

MaturityUsing a relatively long established publishedstandard, well adopted by industry and tested inthe market place.

StandardsUsing an open and free standard published andcertified internationally.

Stakeholders

Having potential to benefit a wide range ofstakeholders. Not benefiting the consumer to thedetriment of the utility or the productmanufacturer.

Media

Having an affinity between two or morecommunication media. For example, acommunications LED as main lightinginfrastructure may be considered a candidate as aVLC PLC adapter.

Applications

Having good potential to support relevantapplication level protocols in the domain ofenvironmental sensing, Advanced MeteringInfrastructure and other smart grid functions.

Security

Considering the medium and the highercommunication layers, having good potential to prevent interception of communication andunauthorized access to or control of networkelements.




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Given diversity across the power network from source toappliance and given the collaborative aims of the smart grid,interoperability is an important quality for our technologies. Itshould be considered whether our communication technologieshave the potential to support a common transport layer, whataffinity they might foster amongst mixed communicationmedia and whether inter-working can be achieved withemerging power grid elements such as smart meters.

Finally we have a number of non-functional qualities, suchas; the technologys potential for wide adoption and whether itsdesign supports ubiquitous deployment; the status of itsstandard, whether it is open and free and how widely it iscertified; and the technologys potential for benefit to a widerange of stakeholders, including consumers, utilities andappliance manufacturers.

We have divided the technologies into three categories;wired communication, wireless communication, and sensingand tagging. In the final section we give brief overviews of aselection of existing and proposed appliance energymanagement architectures and discuss the communication andsensing technologies they use.

A. Wired CommunicationIn this section we assess wired communication technology

suitable for energy management of appliances. Essentiallythere are two suitable mediums; dedicated local home andoffice data network wiring, typically Ethernet, and the powerlines that supply power from an electricity distributor to theappliances in homes and offices.

1) Power Line Communication (PLC)Historically, Power Line Communication (PLC), over-

viewed in [2, 3], has been a popular communication mediumfor appliance control. PLC technology uses power line

infrastructures for data and control and its primary advantageover other wired network medium is its pre-existence invirtually every part of every building. PLC can use sockets forpower and communication and provide a pre-existing line backto the Utility, though there can be performance issues over longdistances and over complex legacy power networks. A numberof open and proprietary standards exist for this medium.

While there is no doubt that new technology is beginning tomanage power line problems better, this is still a legacy hostileand unstable medium often requiring the intervention ofcompensating devices. Much of the technology is proprietaryand existing standards are limited. Devices are locationrestricted and the network is difficult to extend making this an

unlikely medium for realizing context awareness.2) X10

X10 [4, 5] is a long standing open standard for homeautomation device communication. Its primary medium fordata and control is the residential power line network making ita candidate for ubiquitous appliance communication. Data isencoded on a 120 kHz carrier which is transmitted in burstsone bit is sent at or within a specified proximity to each zerocrossing of the 50 or 60 Hz AC alternating current wave. Thismethod is standardized in IEC 61334 also used for electricitymeters, water meters and SCADA.

However, the X10 code protocol sends 1 bit at a time. Four bits (code value 1 - 16) are used to represent the property/building, four for the device and four for thecommand, making support for DRLC and retail servicesunlikely. Due to retransmissions and other issues the data ratesmay be only 20 bit/s, meaning X10 is only really suitable forturning devices on or off or sending very simple instructions.As a carrier for energy consumption data or as a backup

medium for environmental sensor data X10 would be seriouslylimited. X10 does define a radio frequency (RF) protocol, butthe primary purpose is to allow control from remote keypadand not to provide a second medium through which to accessappliances. The packet data sent from the keypad is much thesame as the PLC X10 code protocol sent from a PLC controldevice.

Additionally a range of other users devices attached to thePL network can contribute to issues with attenuation,impedance and noise and the protocol itself presents issues ofspeed and collision. X-10 networks commonly require phasecouplers, blocking filters and signal boosters for larger powerline networks, failing to meet goals of self-configuration and

one-off easy deployment. Given its maturity, X-10 is notsignificantly low cost and form factor is medium to large.

X-10 protocol provides limited security in the form ofsecure device addressing. This is manually configured on thedevice only during the installation state and is unlikely to besuitable for billing and other sensitive data. Moreover X-10 isnot design to work well with common transport protocols suchas TCP/IP. Together these qualities make X-10 an unlikelycandidate for wide scale adoption and unlikely to be seen assupporting the requirements of all energy managementstakeholders.

3) InsteonInsteon is designed and owned by Smart-home Technology.

The company has been in Home Automation for almost 20years and Insteon is a mature product at nearly 10 years. Thishybrid peer-to-peer mesh network uses proprietary INSTEONPower line protocol and INSTEON ISM band RF protocol andis intended chiefly for automated home control [6]. Devicesmay be single or dual medium. The network is self configuring,though mapping is required of buttons on controllers to devicefunctions.

The INSTEON Power line protocol can coexist with X10and developers can implement devices that support andinterface these protocols together. Insteon supports integrationof existing X-10 only networks and devices, but extends speedand number of devices. Insteon achieves a sustained raw data

2,880 bps operating the dual medium. The network employs a Non-routing topology where all nodes receive and repeatmessages. In order to take advantage of common transportprotocols such as TCP/IP Insteon devices must be fitted withpurpose built serial interfaces such as USB, RS232 or Ethernetand connected with other digital devices which support bridging to other Insteon incompatible networks such as aLocal Area Network (LAN) or the Internet.




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TABLE II. WIRED COMMUNICATION FUNCTIONAL CHARACTERISTICS

Recently North Americas biggest distributor for electricityutilities, HD Supply Utilities, will be offering to utilities packages of smart grid solutions using integrated smart grid

configurations of SmartLabs Incs certified Insteon devices.Offerings are expected to provide demand response, homedevices, AMI, management of meter data and security. Incontrast Insteon does less well in the area of environmentalsensing. Insteons devices are large form factor, expensive andare all battery powered, characteristics do not support the idealof ubiquitous environmental context awareness.

Finally, Insteons proprietary nature makes wide adoptionunlikely. Through paid membership of the Insteon Alliance onemay have the opportunity to influence Insteon design, but itsspecification is not approved by European or Internationalstandards bodies and is copyrighted by and only available fromSmart-home Technology. Dependency on such proprietary

technologies may constrain ubiquitous deployment.

4) LonworksLonworks was designed to address the needs of building

control applications and meter reading. Although developershave extended its application field, Lonworks still has issueswith flexibility and scale-ability [7], which make otherapplications difficult. The platform is based on protocolsdeveloped by The Echelon Corporation. The Lonworksnetwork employs a connectionless domain-wide broadcasttopology with loop-free learning routers and repeaters.Lonworks is an approved national standard in America,ANSI/CEA 709, in Europe, EN 14908 and in China GB/Z20177. While most of the Lonworks protocol is public and

open, layers 3 to 7 of the standards are closed and proprietary[7]. Additionally Lonworks wiring system is proprietary.Echelon have designed The Neuron Chip, which builds inmuch of the Lonworks protocols and addressing, providing foreconomical development and a benchmark for the standard.This brings down cost and benefits installation, but whileEchelon no longer make the use of their chip a requirement forcertification, in practice manufacturers find it difficult to workwithout the chip and this tie in may be a detriment to wideadoption.

The Layers MAC and above are based on the publishedstandard [8] ANSI-CEA-709.1. At the physical layer mediumsinclude twisted pair[9]and power line[10] making it a moderate

candidate for ubiquitous deployment. These standards arespecified as ANSI-CEA-709.3 and ANSI-CEA-709.2respectively. Recently ISO and IEC have also granted anumber of standard numbers. Although there are examples ofLonworks technology working with RF networks and withsensing, Lonworks is not a good supporter of mixed media,since it does not specify an RF standard of its own and canonly implement tailored solutions using intelligent gateways.

Support for a common transport protocol is found onlyindirectly in ISO/IEC 14908-4, IP compatibility (tunnelling)technology. Lonworks security provides authentication, butfails to provide for data encryption.

5)

Universal Power line Bus (UPB)UPB, described in [11], is a mature open low-rate PLCstandard developed by PCS Power line Systems forimplementation on general-purpose micro-controllers. Its useof Power line makes it a contender for ubiquitous deployment, but the lack of support for alternative mediums impactreliability and application. UPBs main competitor is X10 andwhile UPB is more reliable and faster, its cost is a prohibitingfactor and its relatively low rate still limit its application.Though UPB is generally reliable, there are reports [12] thatUPB has a vulnerability to being jammed by dimmerappliances. The technology requires manual installation andrequires configuration dedicated device and software makingwide adoption unlikely.

6) HomeplugThe Homeplug Power line Alliance [13] was setup to

standardize and encourage networks over power lines.Homeplug is a mature technology since 2001 and one of thefew to overcome many of the inherent difficulties with thismedium, providing easy installation, high speed and reliability.Another challenge for power line technologies has beenuniversal standardization and this challenge was met whenIEEE P1901, based on the Homeplug de-facto standard, wasratified in September 2010. However, despite its maturityHomeplug has not seen the cost reductions one might have

Name Data Rate Range Power

X10[17] 60bps (Bit Rate) or 1 command/s Not published 2w (adapter)

Homeplug 1.0[3] 85Mbps (Bit Rate) 200m 5w (adapter)

Homeplug AV[3] 150Mbps 200m 5w (adapter)

Lonworks Twisted

Pair[16]

78,125bps2200m maximum 3w (adapter)

Lonworks PLC[16] 4800bps Tx: 80dB +9 S/N < 20km Not published

Insteon PLC[6] 1698bps max 1 mile < 1w

UPB[17] 480bps (Bit Rate) or 5 commands/s Not published 2w (adapter)

Ethernet[14] 1Mbs - 10 GBps (Bit Rate) 100m


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expected. Homeplug was originally developed to extend oradapt an Ethernet network bus and its devices [3] making it perfect for communication over a common transport.Homeplug has since been extended to include Homeplug AVfor Audio Visual (AV), Homeplug Command & Control(C&C) for control of Heating Ventilation and AirConditioning (HVAC), lighting and security and HomeplugAccess BPL for Broadband Power line (BPL) and recently

Homeplug Green PHY (GP) . Homeplug C&C and GP areaimed at appliance control and Smart Grid and Smart Energyapplications. Work in the upper layers of these appliance andenergy standards is ongoing, however in addition HomeplugAlliance have joined with the Zigbee Alliance in thedevelopment of ZigBee Smart Energy Profile which willsupport Homeplug and 6LowPAN RF networks. WithHomeplugs use of power line, its stability and its universalstandard make the technology a strong candidate for ubiquitousdeployment, but devices are large form factor and integrationwith small and dispersed sensors has not been a commonfeature and there is not yet a clear catalyst for widespreadadoption.

7) KNXKNX [15] is a mature and open but proprietary Home andBuilding Control standard owned by an industry alliance, TheKNX Association. The standard may be obtained eitherthrough paid membership of the association or for a separatefee. KNX has gained a number of standards approvalsincluding International Standard ISO/IEC 14543-3.

KNX power line operates in the 90125 kHz band and at a bit rate of 1200 bps, while dedicated twisted pair wiringachieves 9600 bps and a maximum cable length of 1000m.KNX can also be tunnelled over an Ethernet LAN or theInternet using the KNXnet/IP specification. Ease of installationis a key feature with KNX providing a single tool which

supports all implementations and all user levels. KNX ismainly found for lighting and HVAC

TABLE III. RELATIVE WIRED CONTRIBUTION

KNX is most visible in its home country of Germany [16].KNX shows some interest in Energy Management and SmartGrid, but its involvement in practice has been limited comparedto Homeplug, Insteon and Lonworks. KNX RF has the potential to realize a WSN, but form factor is restrictive forubiquitous environmental sensing. The restricted openness ofthe specification and the high cost of membership andcertification have been the main prohibiting factors to wide

adoption. KNX support for multiple media is a strong asset, butis let down by a lack of security in KNX RF.

8) EthernetLess popular for appliance and energy management is

Ethernet. Installation effort and cost are high due to thefrequent requirement to introduce new wiring, particularly inhomes and though common in offices, this effort would ruleout ubiquitous deployment and discourage widespreadadoption for energy management applications. Having saidthis, a number of relevant appliance communication standardssupport Ethernet. KNX protocol for building control includesEthernet amongst its communication media and Homeplug wasdeveloped to extend or adapt an Ethernet network over power

line. Ethernet is also provides excellent support for commontransport such as TCP/IP.

In the main however, Ethernet is the standard of choice forwired local area networks though it will provide high qualitycommunication for building appliance monitoring and controlwhere wiring already exists. Ethernet is mature and globallystandardized by IEEE 802.3 [14] and defines the PHY andMAC layers of a wired Local Area Network. The MAC layerprotocol operates Carrier Sense Multiple Access with CollisionDetection and specifies half and full duplex operation. ThePHY layer is over coaxial, twisted pair or optic and operationcan be between 1Mbs and 10 GBps. Ethernet is a sharedmedium and relies heavily on upper layer protocols for

security, though the risk is lessened by switched Ethernet.Although gateways and adapters exist to extend Ethernet toother media such as Wi-Fi, ADSL, PLC and RF, thetechnology does not have an inherent affinity with other mediaand form factor is still not small enough for ubiquitousenvironmental sensing.

Quality X10 Insteon Lonworks UPB Homeplug Ethernet KNX

Cost +

Form factor

Installation + ++ + ++

Transport + ++ ++ +

Adoption

Ubiquitous + + + +

Maturity ++ + ++ ++ +++ ++

Standards + ++ +++ +

Stakeholders

Media + + ++

Applications ++ + ++

Security +




9/17

TABLE IV. WIRELESS COMMUNICATION FUNCTIONALCHARACTERISTICS

B. Wireless CommunicationIn this section we look at wireless communication suitable

for energy management of appliances. Wirelesscommunication has been with us now for over a hundred years.In the last decade however, wireless communicationtechnology has seen sudden growth and in the last five to sevenyears we have begun to see the kind of technology that mightsupport energy management through widespreadenvironmental sensing. This has come through the inceptionand advancement of low-power, low-cost Radio Frequency(RF) wireless communication with smaller form factor, greatersensing density and longer functional lifetime.

1) InfraredWith the introduction of teletext in the late 1970s there was

a drive to extend the function of remote controls in televisions

and we began to see the proliferation of infrared (IR) remotecontrol for a range of consumer electronics. The technology isnow mature and a number of essentially public standards haveemerged. For infrared remote controls standards evolvedinformally with two proprietary Philips protocols, RC-5 andRECS-80, becoming the two de-facto standards and nowadopted pretty much internationally. With infrared datacommunications the increasing number of incompatible parallel proprietary protocols threatened the future of thistechnology for appliance manufacturers and there wascollective demand for a common specification, which lead toformation of The Infrared Data Association (IrDA).

IrDA [18] was launched in 1993 with around 70

companies. The newly formed association made cost a highpriority, setting initial goals of device adaptation under $5, datarates up to 115 kbps, coverage by a 30 degree half angle coneand a range of at least 1 meter. The standards progressed fromversions 1.x through Advanced Infrared (AIR) along with thespecification, including 5 meter range at 4 Mbps and 10 meterrange at 256 kbps as well as a low-power, short-range categoryfor power consumption constrained devices such as one mightfind in a sensing and appliance energy managementarchitecture. IrDA has no designed support for energymanagement however.

While IrDA provides no security, the nature of IR allowscommunication to be blocked if necessary. With advances inLEDs and ICs, Components have reduced form factor and arefound in many devices including mobile phones and USBadapters. For most communication installation andconfiguration is automatic, however connection to a local areanetwork (LAN) and support for common transport is limitedsince IrDAs IrLAN does not offer the required TCP/IPconfiguration protocols such as DHCP and DNS.

IR remote control and IrDA already has wide adoption,however future adoption for energy management seemsunlikely. IR still has issues of range and line of sight and insome cases one-way communication and for these reasonsmanufacturers are making moves to drop IR in favor of RFtechnologies. Additionally there is nothing in IR technologythat would suggest ubiquitous deployment or provide aninherent affinity with other media.

IR has similar absorption and reflection characteristics tovisible light and behaves in a similar way with translucent andnon-translucent materials. For communication the wave lengthis generally in the near infrared band between 780 and 950nanometer. The authors in [19] suggest the medium has anumber of advantages, including virtually unlimited andunregulated bandwidth. Additionally interference orinterception can be limited to a single room or building; thisalso provides a high combined capacity and simplification ofinter-room communication for infrared local area networks.These characteristics could be an advantage for energymanagement architectures enabling management of sensingand appliances in selected rooms while recognizing a collectionof rooms as an entire building. Also, intensity Modulation andDirect Detection can prevent the multi-path fading often seenin radio signals where changes in signal strength and phase arecommon.

2) Wi-FiThe end of the nineties saw the emergence of the now

common place Wireless LAN (WLAN) (IEEE 802.11).802.11-1997 was the first published RF communication


IrDA - Advanced Infrared(AIR) 256kbps 4Mbps 5 10m Low

Wi-Fi (802.11) 54Mbps (802.11n


10/17

standard for WLAN. The standard defines the characteristics ofthe PHY layer including frequency and modulation method andthe MAC layer using CSMA/CA with Binary exponential backoff algorithm. Two Coordination functions are supported bythe standard; Distributed Coordination Function (DCF) withasynchronous communication and Point Coordination Function(PCF). PCF is setup in the access point and uses station pollingto provide synchronous communication for time critical data

such as video. The standard also supports a hybrid coordinationfunction (HCF). The standard is an extension to the EthernetMedia and often an access point to a variety of networks andmedia, providing wireless mobility and ease of installationwhile continuing to carry the common networking andtransport protocols TCP/IP. WLAN does not possessintrinsically ubiquitous characteristics, but the explosion oflaptops and WiFi enabled mobile devices has drivenwidespread adoption. Widespread adoption in the field ofenergy management however seems unlikely; the design doesnot have energy management in mind and for manyapplications, particularly environmental sensing, WLAN isconsider too power hungry and in some cases components arestill too large.

A large number of amendments exist to the legacy standardand the technology is now mature with low cost commoditystatus. These amendments were more recently rolled up into anew base standard, 802.11-2007 [41]. These amendmentsprovide for a range of frequencies including 2.4, 3.7 and 5 GHzand a range of modulation methods including DSSS, OFDMand FHSS. Power consumption of 802.11 exceeds that of802.15.1 (Bluetooth) and 802.15.4 including Zigbee and otherWireless Personal Area Networks (WPANs).

The early standard supported speeds of 1 Mbps at up to100m in a 20 MHz channel. The latest amendments to thestandard (n) [42] support a 20 MHz channel and a 40 MHz

channel with a data rate of up to 150 Mbps and up to twice therange of the legacy standard. Additionally optional featuressuch as A-MPDU and Greenfield preamble can save powerconsumption. Security is provided through Wi-Fi ProtectedAccess (WPA) based on Extensible Authentication Protocol(EAP) and Advanced Encryption Standard (AES) with theimproved WPA2 providing CCMP, a new AES-basedencryption. Wi-Fi is the certification for WLAN IEEE 802.11standard compliant devices.

3) Bluetooth ClassicThe Bluetooth Standard was formed by the Bluetooth

Special Interest Group, initially Nokia, Intel, IBM and Toshiba[43]. The original vision of global very high growth technology

has not been realized as far as predicted, but the scale of production has been sufficient for a significantly low cost.Amongst many others, Bluetooth is found in the mobile phone,PC USB dongle, remote printer, keyboard or mouse and in thewireless games controller. Government regulations for mobile phone use while driving, has been seen as the catalyst toBluetooth awareness and mass adoption in the form of wirelessheadsets. Form factor can be small, however the inherent power demand preclude the use of Bluetooth for small, lowpower, long lifetime ubiquitous sensing nodes.

The group increased in size and became the first task groupof the IEEE 802.15 WPAN working group and the standardwas submitted and ratified in 2002 as 802.15.1. The standardhas matured and is currently at 2.1 [44].

Bluetooth is a short range standard for industrial home andoffice use. Using 2.4GHz ISM band and a Gaussian FSKModulation the standard achieves a range of 10m and a datarate up to 1 to 3Mbps according to the standard version. Thisfrequency may have some conflict with WLAN 802.11 [45],but it may be possible to configure WLAN to operate on 5GHz.Reliability is managed through FEC and ARQ. There are threeclasses of radio using power ranging from 1 to 100mw.Bluetooth has a higher power cost to 802.15.4 and Zigbee,though a significantly higher data rate. Bluetooth does not havean inherent affinity with other mediums such as PLC.

The Bluetooth Transport Protocol Baseband layer definesthe Piconet topology. Piconet recognizes a slave role and amater role. Piconets are not formed through any central control, but are started by a master and can include slaves whichregister with the master. The master allocates addresses, uniquewithin the Piconet, for active slaves, which may not exceedseven. Nodes may have dual role and be master in one Piconetand slave in another forming a Scatternet. Piconetimplementations have the potential to be self-installing andself-organizing.

A number of middleware protocols exist. ServiceDiscovery Protocol was added to the basic standard in orderthat devices could find out what services or application profilesare supported by devices in preparation for using the servicewhere some other function supports it. Radio frequencycommunication RFCOMM Protocol exposes a serial interfaceto the transport layer, enabling certain legacy applications tocommunicate without modification. TCS Protocol enables ATcommands to be sent over RFCOMM enabling functions, such

as activating mobile dialing through a remotely connecteddevice. More recent protocols from version 2.1 include SecureSimple Pairing to secure private data or safely allow theconnecting device to take control of the connected device,using public key cryptography in a number of modes.Bluetooth has a range of adopted protocols including TCP/IPmaking it a strong candidate for integration into a commontransport. Bluetooth provides no direct support however forenergy management applications.

4) IEEE 802.15.4IEEE 802.15 Standards address Wireless Personal Area

Networks (WPAN). Task Group 4 of the standard is chargedwith investigating simple low power, low data rate WPAN

solutions for applications such as long lived small form factorubiquitous sensing, remote identification and home andindustrial automation. IEEE 802.15.4 defines the PHY andMAC layers and can be found at [20].

At the physical layer 802.15.4 specifies three different bands from amongst the available Industrial Scientific &Medical (ISM) frequencies for various locations, 868-868.6MHz (1 channel, 20 kb/s), 902-928 MHz (10 channels, 40 kb/s)and 2.40-2.48 GHz (16 channels, 250 kb/s) and more recently779-787 MHz (802.15.4c) and 950MHz -956MHz (802.15.4d).Different modulations are available for carrying data in the




11/17

different bands, DSSS and a choice of PSK types may be used.Interfacing with Wi-Fi or Ethernet is common, but there is littleaffinity with other media such as PLC, IR or VLC.

Network installation is relatively self-configuring. At theMAC layer devices can be full or reduced function, FFD orRFD. Each network segment has a single FFD co-coordinatornode responsible for management of the network segment (orPersonal Area Network, PAN). FFDs may communicate peerto peer, but RFD may only communicate with the coordinator.A network segment may operate beacon or non-beaconmanagement. If beaconing is enabled, the coordinator node willperiodically send out a beacon with detailed information aboutthe network segment and possibly guaranteed time-slots forcertain nodes. In the time between the beacons nodes in thenetwork may send data controlled by CSMA-CA. Non-beaconed networks simply send data using CSMA-CA without beaconing. Some security services are provided for upperlayers by the MAC, but extended security is implemented athigher layers.

IEEE 802.15.4 is a mature and adopted standard, but therange of IEEE 802.15.4 implementations and networkinglayers, including Zigbee, WirelessHART, Miwi, RF4CE,6LowPAN, coupled with a choice of other cheap and mature pre-existing low rate RF solutions mean that economies ofscale and ubiquitous ad hoc interoperability still elude thisstandard. Reducing the cost of entry by network layerimplementers, such as ZigBee, may help, but the markets forIEEE 802.15.4 and ISM are very varied and total far less thanBluetooth or Wi-Fi with very mixed returns for stakeholders.Mass adoption catalysts, such as government mobile phonelegislation for Bluetooth, seem unlikely, though ZigBeesRF4CE remote control replacement is a possibility. Somecommentators suggest the future of IEEE 802 lies in thesupporting networking layer 6LowPAN, interoperable with the

common transport IPv4.5) Zigbee

Zigbee is a self-organizing mesh open wireless networkingstandard ratified by the ZigBee Industry Alliance in 2004. Thestandard is optimized for medium range, 10 75m, low rate,low power and long functional life-time. Applications includesmall to medium form factor sensing and communication forindustrial, medical and home and building automation andenergy management, with The ZigBee Alliance specifying arange of their own application profiles, such as ZigBee HomeAutomation, ZigBee Smart Energy 1.0 and ZigBee HealthCare. Zigbee was developed by the members of the ZigbeeAlliance, and is specified in [21].

Zigbee specifies Application, Network and Securityprotocols and is built on the IEEE 802.15.4 RF standard for thePHY and MAC layers. The network layer defines the stack profile and the network rules, and implements discovery,addressing, routing and maintenance. The stack sets networkrules such as level of security, timeout, sizes, maximumrouters, children and depth of network. To this end Zigbeespecifies three Zigbee devices a layer above 802.15.4,controller, router and end device. Interfacing with Wi-Fi orEthernet is common, but there is little affinity with other mediasuch as PLC, IR or VLC.

Network installation is relatively self-configuring. Therecan be only one coordinator device per network. Thecoordinator initiates the network, selecting network Id, stack profile and RF channel. At the MAC layer it is the Zigbeecoordinator that acts as the 802.15.4 PAN coordinator. Routers join the coordinator and other routers joining those routers.Once the network is formed the coordinator also acts as routerand can perform other applications as required. End devices

join routers.Routers extend the network coverage, although a minimum

network may have no routers. Routers will try to find andconnect to the Zigbee coordinator or another router. The routermaintains its own set of end devices and neighbor routingtables providing routing and addressing locally and providingrouting for other multi-hop messages on the network. At theMAC layer the router provides the FFD 802.15.4 coordinatorfunction.

An end device will find and connect to a router or thecoordinator. It has no children and performs no routing. This isthe lowest powered node on the network and relies on its routerto wake it up when required. At the MAC layer the Zigbee enddevice provides the 802.15.4 RFD function.

Zigbee uses a tree structured address assignment calledCSkip, meaning Child Skip. Addresses are allocated based onposition in the tree. Using the maximum depth and maximumchildren and router children per depth a CSkip value iscalculated for each depth which allows for a sufficient pool ofaddresses at that depth and for source and destination addressesto be used to calculate a route.

ZigBee is a mature and adopted standard, but as discussedfor 802.15.4, mass adoption and economies of scale also eludethe ZigBee standard with similar markets and returns forstakeholders. Cost of entry set by the Alliance is certainly a

factor in the level of adoption. Zigbee networking standarddoes not support a common transport, but there are signs thatthe ZigBee Alliance may be moving away from this part of thestandard or at least breaking the sole dependency on IEEE802.15.4. Version 2.0 of ZigBee Alliance Smart EnergyProfile, whose requirements are specified in [22], is mediumindependent, using the IPv6 common network and transportlayer; implementations based on IEEE 802.15.4 will use theIETF 6LoWPAN adaptation layer.

6) RF4CERF4CE Consortium was founded by Panasonic

Corporation, Royal Philips Electronics, Samsung ElectronicsCo., Ltd. and Sony Corporation on June 12 2008 to look at

overcoming the limitations of Consumer Electronics IR remotecontrols by using RF technology.

Issues with legacy IR remote control include field of vision,line of sight, one way communication and interference fromother light sources such as large HD televisions. WhileRF4CEs [23]primary focus is an RF remote controlreplacement, it could equally support many other applications,such as communication with small form factor automatedcontrollers or sensors.

In March 2009 they teamed with Zigbee providing a ZigbeeAlliance published standard for RF remote control [24]. As




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with Zigbee, cost of license and certification still affectsdemand and widespread adoption and economies of scale arenot yet fully realized. Bluetooth Low Energy published inDecember 2009 includes Home Automation and RF remotecontrol among its applications and its interoperability with thewidely adopted Classic Bluetooth make it a strong contender.However, early indications are that IEEE 802.15.4 basedstandards have the edge on performance.

The Standard is based on the IEEE 802.15.4 PHY/MACstandard. On top of this is RF4CE simple networking and public application profiles, such as Consumer ElectronicsRemote Control (CERC), which interface to user applications.The public application profiles may include vendor specificextensions. The operational frequency is 2.4GHz. The networkis an asymmetric star topology made up of two types of nodes,controllers and targets, though controllers need not be remotecontrols and could even be appliances.

Installation effort is relatively low, targets have authority tocheck channel suitability and for any pre-existing personal areanetworks (PANs) and then start a new PAN. Multiplecontrollers can join networks by pairing with targets. Targetscan communicate with other targets and join PANs to form aRF4CE network, see Fig. 4. Communication is protected using128-bit cryptographic key pairs and services for confidentiality,authenticity and replay protection. Power management can beachieved by a range of configurations for enabling or disablingpower saving mode, including operating a receiver duty cyclewhere the sender targets the active period. Channel agilitymeans target devices can after creating their PAN switchchannels, if conditions dictate, and controllers will try otherchannels until communication is re-established.

Through RF4CE and its marriage with ConsumerElectronics companies, the critical mass required, for wide

adoption and almost ubiquitous deployment for homeautomation including energy management, could be finallyrealized [25].

Figure 4. Example ZigBee RF4CE network topology [23

Providing CERC and other profiles with two way RFcommunications opens the way to a range of new applicationsto attract consumers and manufacturers. Although RF4CE doesnot support energy management applications directly, there issupport for additional profiles over the same network layer andwith ZigBees Smart Energy profile there may be room fordual function. Communication across the Internet usingcommon transport would require some kind of gateway or

tunnelling function.

7) Bluetooth Low EnergyThe Bluetooth special interest group began looking into

expanding the technology into the low power market in2000[26]. In 2001 Nokia, a member of the group, wereexamining the limitations of current wireless technologies. Asa result of these examinations, the Nokia Research Centerdeveloped Wibree, an adaptation of the existing Bluetoothstandard which operated on low power, but minimize impacton the key Bluetooth characteristics.

Wibree was first published in 2004 as a Low End Extensionfor Bluetooth [27]. In 2007 The Bluetooth SIG and Nokiatogether adopted Wibree as a part of the Bluetooth Technology plan, calling it Ultra Low Power (ULP) Bluetooth. Thetechnology was finalized in December 2009 and added toBluetooth Core Specification version 4.0 as Bluetooth LowEnergy (BLE). Devices were expected to come on-linethrough 2010.

BLE uses a simplification of the Classic Bluetooth protocolwith relaxed RF requirements, shorter packets and greateroptimization of power when not transmitting. There are twodevice types, single-mode devices support BLE only andcannot communicate with a Classic Bluetooth device; whiledual-mode devices are Classic Bluetooth devices whichsimultaneously support BLE communication. The current trendis that dual-mode devices will replace all Classic Bluetoothdevices over the next few years. Dual-mode devices areexpected to bear much of the configuration load and provideInternet connectivity on behalf of low powered single-modedevices.

Bluetooth low energy uses the 2.4 GHz RF Band and anultra-low duty-cycle transceiver, using advanced sniff-sub-rating, which allows a host to be woken by a controller forsending and so allows at least a year between single button battery cell recharge. Data is transferred in short packets,connection setup and tear-down is fast giving low latency andspeeds of up to 1 Mbps at ranges of up to 100 meters. Accuracyand security are provided through strong 24 bit CRC and FullAES-128 encryption with CCM.

The new technology shares much of Classic Bluetoothsradio characteristics and functionality and therefore mitigatescost and promotes manufacturer migration to dual-modedevices with the incentive that a whole range of newapplications are enabled by connecting new low energy devicesand accessories with an established Classic Bluetooth 1 billionunit base. This will promote wide adoption and allow single-mode small device manufacturers and handset manufacturers toshare a common authenticated network.




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TABLE V. RELATIVE WIRELESS CONTRIBUTION

Bluetooth low energy is tipped as a strong competitor totechnologies such as Zigbee. Applications that connect smallform factor sensing with personal mobile devices such as phones could see the technology gain critical mass drivingdown cost and promoting near ubiquitous deployment. Homeautomation, Health Care and consumer electronics remotecontrol are already some of the suggested applications forBluetooth low energy.

8) Visible Light CommunicationThe latest 802.15 (WPAN) task group is 802.15.7. This

group is writing a PHY and MAC standard for Visible LightCommunications (VLC). Visible light is defined by thewavelength range 400nm to 700nm. The medium has theAdvantage of low power, but with very high bandwidth overshort distances, sufficient for common transport protocols, forexample by connecting Ethernet installations over a series oflighting fixtures and allowing mobile devices to connectthrough building LED emitters. Potential deploymentcharacteristics of VLC include a ubiquitous lightinginfrastructure, with communication that is low noise, secureand low cost. Additionally with the possibility of anexponential proliferation of Radio Frequency (RF)communication, health and safety critical concerns, regulationand conflict is bound to have a raised profile. Where localizedcommunication is necessary, VLC is environmentally friendly,

safe and unregulated and will work alongside safety critical RFapplications without conflict. The vision is for installation to beas easy as screwing in a light bulb. The shadowing effect isgreatly reduced over IR and cost and power are comparable toRF.

In recent years the light-emitting diode has undergoneserious evolution, with increased intensity, efficiency, controland greatly reduced cost. The LED is now a genuine candidatefor a ubiquitous illumination technology [28] and therefore a potentially ubiquitous VLC communications infrastructurepowered through the existing power grid.

LED form factor is smaller [28] than existing lighting andthe communications technology is expected to integrate wellwith existing technology. Additionally there is a strong potential for affinity between VLC and power linecommunication [29] [30], indeed many architectures to achievethis are already proposed. Such an infrastructure could be astrong contender for the mission to unite appliances, sensors,meters and other smart grid elements to work together.However though there is already strong industry collaborationand a number of proposed applications, there is yet no clearcatalyst for widespread adoption.

9) OthersA number of self-published open standards exist, such as

Threshold initiated royalty free One-Net standard, found at [31][32], whose alliance partners include Texas Instruments andFreescale, and a number of proprietary technologies such as Z-Wave focusing on home automation, though reported to bedifficult to install and configure, Wavenis optimized for ultralow power and long range but low traffic and Addinet fromAlciom supporting low latency and ultra low power, butcurrently used by just one Alciom customer, Srett.

C. SensingIn this section we look at sensors and tags suitable for

energy management of appliances.

1) RFIDRFID tags are microchips that may be located in or carried

by objects, animals or people to allow remote identification ortracking and more recently also for sensing [33]. RadioFrequency Identification technology (RFID) comprises tags,composed of an IC and an antenna, and RFID readers. Thereader transmits a radio frequency and reads the back scatteredsignal reflected and modulated by the tag to indicate its Id.Passive tags are powered remotely by the readerstransmission, while active tags are battery assisted and havegreater range and capabilities. Read rate is affected by

Quality IR Wi-Fi BT 802.15.4 Zigbee RF4CE BLE VLC

Cost ++ ++ + + +

Form factor ++ + + + + + +

Installation + + + + + + ++

Transport ++ ++ ++ ++

Adoption + ++ +++

Ubiquitous + + +++

Maturity ++ ++ ++ + +

Standards + ++ ++ ++ + +

Stakeholders + + ++

Media ++ ++

Applications + +

Security ++ + + + + +




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frequency with higher frequency tags have higher read rates.Read rate as a proportion of successful reads is also affected bydistance, with active battery assisted tags supporting a higherproportion of the maximum read rate at greater distances. RFIDis common for product identification, and communication isthrough the Electronic Product Code (EPC). The protocol canselect from multiple tags using a tree walking technique andsupports sending data to tags using amplitude shift- keyed

(ASK) modulation. RFID is a very mature and low costtechnology and this together with its potential for very smallform factor make it a strong candidate for a ubiquitous sensingnetwork. As a networked solution however, RFID has higherinstallation effort due to its asymmetric topology, itsdependence on RFID reader devices and the limitedimplementation of two way communication, additionally RFIDis less secure due to its reduced support for computation. RFIDalready has a major stakeholder presence in asset tracking andrecent interest from global retailers may lead to universaladoption and commodity status. However, widespread adoptionin the energy management field is still uncertain due to theintegration difficulties and the lack of a common transport.

2) Sensor MotesSensors convert environmental stimulus into an electricalsignal that can be measured and stored. There are a variety ofsensor types, including: temperature, humidity, light, speed,acceleration, sound, magnetism. Progress in electronics andlow power communications has seen the inception andadvancement of the smart sensor.

In [34] the author describes smart sensors, or sensor motes,as a low power devices equipped with one or more sensors, aprocessor, memory, a power supply, a radio, and an actuator.These motes can include a number of different sensors and aregenerally battery powered, though some devices may include amechanism, such as photovoltaic cells, to harvest energy.

Sensor motes generally form wireless sensor networks (WSN)either as a large scattering of motes or as a smaller number ofstrategically placed motes. Motes can have different roles inthe WSN, such as general sensing, data relay or motemanagement, managing motes join or leave the network. Thenetwork also includes a base station or sink, often connected toa fixed powered network.

The memory and processing added to sensors supportstorage and operating systems, enable protocols and provideservices to enhance efficiency in sensor operation and routing.Operating systems include event driven implementations suchas TinyOS and Contiki.

TABLE VI. SENSING FUNCTIONAL CHARACTERISTICS

WSN use their own protocols from PHY to Transport layer,optimized for ad-hoc and low power. Many such protocols areimplemented in published standards such as IEEE 802.15.4,Zigbee, specified in [21], WirelessHART, ISA 100.11, IETF6lowPAN and the 2009 IEEE 802.15.1 Bluetooth Ver4.0 Low-Energy. Important services include synchronization savingenergy by reducing collisions or retransmission orimplementing duty-cycles, GPS, anchor base and proximity

based localization and methods and tools to balance the needfor coverage with the cost of coverage. Other services includesecurity and data compression and aggregation.

The cost of sensor motes is coming down; however numberof parallel standards and the range of open and proprietarysolutions mean that economies of scale and ubiquitous ad hocinteroperability still elude the sensor mote industry. Moreover,the markets are very varied and total far less than commonBluetooth or Wi-Fi devices with very mixed returns forstakeholders. These factors have precluded wide adoption andthe realization of a ubiquitous sensing infrastructure.

The size of sensor motes is reducing, but theirminiaturization has been overtaken by the introduction ofsensing to RFID which is far less constrained by the need for a power supply. On the other hand sensor motes provide farmore computation and are beginning to implement commontransport protocols and already support a range of applicationsand services that are far beyond the capabilities of RFID.Supported energy management applications for sensor nodeprotocols already exist.

The standards for sensor mote communication are reachingmaturity; there is good support for security and many networksare symmetric and self-configuring.

3) WISPIn an effort to address functional lifetime and form-factor in

sensors, sensing has been introduced to battery free UHF RFIDusing fixed function, non-programmable sensing, with single bit communication [35, 36]. More recently, the WirelessIdentification and Sensing Platform (WISP) project [36]proposed the more flexible RFID Sensor Network (RSN). This project adds remotely programmable computation andimplements communication through control of all 64 bits of theId tag using EPC primitives. WISP sacrifices some range inproviding computation, but opens up possibilities for on-boardfiltering, security and more. Open research issues include balancing computational load with harvested energy,development of new protocols and integration of RSN withWSN.


Sensor Motes < 1 Mbps - 100m Ultra Low - Low ( for example: TmoteSky/TelosB,3 mW / 3.24 mW active, 6 W / 15 W sleeping,6 sec wake-up time [38])

RFID (UHF): Passive:


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TABLE VII. RELATIVE SENSING CONTRIBUTION

Quality Sensor Motes RFID WISP

Cost +

Form factor ++ +++

Installation +

Transport ++

Adoption

Ubiquitous ++

Maturity + ++

Standards + +

Stakeholders ++

Media

Applications +

Security ++ +

WISP technology is of course very immature and new protocols or EPC adaptations are still awaited. However theprimary benefits of RSN will come from its very small formfactor, long life and ability to operate without an attached power source, allowing it to support applications that requiresemi-permanent and possibly ubiquitous deployment ininaccessible locations.

WISP has been predicted as the new smart dust in [37], andmay, in time, contribute to the concept of a ubiquitous contextsensing environment. On the other hand WISP retains many ofthe RFID integration difficulties described above and may stilllack a common transport. Additionally its short operation rangeand its narrow field of application make it an unlikely

candidate for wide adoption or a primary solution to energymanagement.

D. Energy Management ProjectsIn this section we give brief overviews of a selection of

existing and proposed appliance energy managementarchitectures. In particular we note the communication andsensing technologies they use.

1) Network architecture for home energy managementsystem [39]

Historically the wired medium of Power lineCommunication (PLC) has been popular in home automation

and energy management. Though a number of existing PLCtechnologies existed at the time of their research, the authors ofthis architecture proposed their own dispersed-Tone PowerLine Communication because it does not hinder regularnarrow-band power line communication, but deals withnarrow-band noise that other Power Line Communication doesnot. The architecture also includes a controller (PC) formonitoring and controlling sensors and appliances and a homegateway making possible external monitoring and control. Akey component of their work is the Compact ApplianceControl Interface (CACI) and the provision of network

adapters with CACI to make CACI supporting appliances andsensors network ready without requiring network function.

2) A novel power line network architecture for managingthe energy resources of the residential environment [40]

The authors of this architecture also propose the use ofPower line Communication to monitor appliances energyconsumption, enforce limits of consumption and manage

appliances in standby. The architecture employs KNX asdiscussed above. Consumption may be constrained by user andoperator, and the electricity provider may obtain geographicalstatistics through the Residential Gateway (RG).

One of the key elements in this architecture is an EnergyManagement Device (EMD). The device provides a bridgebetween KNX on the IP residential gateway and KNX on thePLC Network of appliances. In addition the EMD provides auniform KNX API and management primitives for all theconnected appliance as well as monitoring energy and providing operation mode changes or auto switch off forstandby appliances.

3) Wireless Sensor Networks for Commercial LightingControl: Decision Making with Multi-agent Systems [41]

In response to the large proportion of US electricity usedfor lighting in commercial buildings, the authors propose anintelligent automated multi-agent commercial lighting system,implemented as a Wireless Sensor Network (WSN). Theauthors also propose the implementation of user lighting preference. RFID, a common battery-less building securityfeature, is discussed, but the authors choose miniature cardswith embedded sensor nodes to link with the sensor networkand to actuate the users lighting preferences. Privacy may be aconcern for users, but person identification could manageoperation modes for much more than lighting combiningenergy saving and personal preference.

4) Wireless networked lighting systems for optimizingenergy savings and user satisfaction[42]

In this project the authors use wireless sensor and actuatortechnologies to implement a lighting control system thatoptimizes energy management, user preferences and the needsof a modern lighting system. The technologies are networkedover the 802.15.4 communication standard using T-Mote Skysensor nodes. An optimization algorithm is designed tominimize energy use while reading lighting conditions andaccommodating notified user preferences. The hardwareinstallation is designed for minimal adaptation of existinglighting infrastructure.

5) Architectural design of home energy saving systembased on realtime energy-awareness[43]

The authors of this project propose a Home Energy SavingSystem (HESS). The key components of the system are theHESS Client and the HESS Server. The system provides no-new-wire client/server linkage through a Power LineCommunication (PLC) network or a Zigbee network. TheHESS client can be deployed as a wall power outlet adapter orbuilt-in to an appliance power module.

The system monitors and presents appliance powerconsumption, alarms users when thresholds are breached,




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monitors for thresholds or standby state in order to manageappliance operational or power state and also detects the usersintention to switch an appliance back on in order to reintroducepower.

6) A communication stack over PLC for multi physicallayer IPv6 Networking

The goal of this project is to provide a common stable

communication stack for operation across multiple media. Thesolution is implemented with an adapted version of 802.15.4and 6LowPAN for deployment across PLC and wireless. Atestbed is implemented and a range of interoperability testsperformed. While this project makes good use of a number ofour surveyed standards, its primary theme relates to our qualitycharacteristic for media; the realization that no singletechnology will meet requirements but that the key toprogressing will be in addressing cross-media communicationand common transport.

IV. CONCLUSIONSClimate change, dwindling legacy energy sources and

aging and under-invested power grids have forcedgovernments, energy producers, distributors and consumers,with some urgency, to focus significant resources on long termstrategies for energy management. The UK supplied 357.2TWh of electricity in 2009 and the domestic sector was thelargest consumer with the domestic and service sector togethertotaling 70% of total consumption [44]. With appliancescontributing significantly in these sectors, it is clear that theyshould be a very important part of this energy managementfocus.

In order to contribute to energy management appliancesneed to collaborate with users, the grid and their environment.Our ideal appliance communication and sensing technologies

should enable simple ubiquitous deployment of small low costself-configuring devices. These devices should automaticallyand securely connect and collaborate across multiple mediaover a common transport using a fully adopted and openenergy management application protocol. The network should benefit all stakeholders including users, appliancemanufacturers, utilities, personal and commercial energygenerators and energy policy makers. However, realizing thisideal is a different matter.

We are beginning to see some exciting developments incommunication and sensing; improved implementations ofPower line Communication (PLC) and the ratification ofHomeplug based IEEE P1901 in September 2010; Bluetooth

Low Energy, 6LowPAN and the inception of 802.15.7, VisibleLight Communication (VLC); Reductions in size, reductions in power and the provision of two way communication sensingand on-board computation using harvested energy [36].However, many of these achievements exist in isolation.

It is becoming clear that that an imperative to architectingthe solution will be in addressing cross-media communicationand common transport. Given the diverse nature and locationof elements across the grid and inside premises there will be aneed for a multi-technology solution, and yet there remains astrong requirement for collaboration. There exists some work

in this area already; IEC62480 is the ratification of the work ofthe Echonet project [45] to specify a design for a commonnetwork adapter; there is also work to integrate PLC and VLC[30] and work to integrate PLC and RF [46] over a commontransport.

Finally there is an overarching need to address the concernsof particular stakeholders. There is already an understandingand acceptance within the appliance industry that we areprogressing towards smart appliances and research shows thatthere is already some willingness amongst consumers to acceptsmart operation [47]. However, for appliance manufacturers itis essential that they protect their huge design and developmentinvestment their market and their consumers. To Progress theindustry from concept acceptance to realization it will beessential that their concerns are addressed. The primaryconcerns of appliance manufacturers are cost, added benefit toconsumers, simplicity, stability and privacy [48]. As thetechnologies and standards mature we may see mediaintegration, common transport, support for a ubiquitousinfrastructure, catalysts for wide adoption and wide support forthe energy management application domain; however nothing

will be realized if we fail to address the concerns of thesestakeholders.

REFERENCES

[1] The smart grid: an introduction, Report by Litos StrategicCommunication. An account of work on the Smart Grid sponsored byThe United States Department of Energy., 2010.

[2] M. S. Yousuf and M. El-Shafei, Power line communications: anoverview - part i ser. Innovations07: 4th International Conference onInnovations in Information Technology, IIT. Dubai, United Arabemirates: Inst. of Elec. and Elec. Eng. Computer Society, 2008, pp. 218222.

[3] M. S. Yousuf, S. Z. Rizvi, and M. El-Shafei, Power linecommunications: an overview - part ii ser. 2008 3rd InternationalConference on Information and Communication Technologies: FromTheory to Applications, ICTTA. Damascus, Syria: Inst. of Elec. and Elec.Eng. Computer Society, 2008.

[4] Standard and extended x10 code protocol, Revision 2.4, 1975.

[5] The x-10 powerhouse power line interface model pl513 and two-waypower line interface model tw523, Revision 2.4, 1975.

[6] Insteon, Insteon the details, 2005.

[7] B. L. Capehart, Web based energy information and control systems :case studies and applications 1st ed. Fairmont Press, 2005.

[8] Ansi-cea-709.1, Lonworks building control protocol specification forlayers MAC and above, 2005.

[9] E. Corporation, Free-topology twisted-pair channel specification ansi-cea-709.3, Lonworks building control protocol specification for FreeTopology TwistedPair Channel Specification (ANSICEA709.3),2006.

[10 Cea-709.2 - control network power line (pl) channel specification,Lonworks building control protocol specification for powerline PHYlayer Rev A, 2006.

[11] Upb techn

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