application for remote monitoring smart grids Proposal of an experimental data and image transmission system and itspossible Technology Journal of Applied Researchand

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Availableonlineatwww.sciencedirect.com

Journal of Applied Research and Technology

www.jart.ccadet.unam.mx JournalofAppliedResearchandTechnology15(2017)303–310

Original

Proposal of an experimental data and image transmission system and its possible application for remote monitoring smart grids

Ibrahim Develi

^a,∗

, Yasin Kabalci

^b

aDepartmentofElectrical&ElectronicsEngineering,FacultyofEngineering,ErciyesUniversity,38039,Kayseri,Turkey

bDepartmentofElectronicsandAutomation,NigdeVocationalCollegeofTechnicalSciences,NigdeUniversity,51200,Nigde,Turkey Received14July2015;accepted27March2017

Availableonline27May2017

Abstract

Thispaperinvestigatesthebiterrorrate(BER)andthepeaksignal-to-noiseratio(PSNR)performancesofquasi-cycliclow-densityparity-check (QC-LDPC)codedorthogonalfrequency-divisionmultiplexing(OFDM)systemsoveranactualpowerlinecommunication(PLC)channelthatare acquiredbyperformingverylong-termexperimentalmeasurementsfromthegrid.Theexaminedsystemistestedbychangingsystemparameters suchascodelength,iterationnumber,codingrateandmessagetypeindetail.TheresultsofthisstudyshowthattheQC-LDPCcodedOFDM systemcanbeapossiblesolutionforcommunicationandremotemonitoringpurposesinsmartgrids.

Keywords: Smartgrids;Remotemonitoring;Powerlinecommunication(PLC);Quasi-cycliclow-densityparity-check(QC-LDPC)codes;Orthogonalfrequency- divisionmultiplexing(OFDM)

1. Introduction

The rapidly decreasing reserves of fossil fuels and envi- ronmentalconsiderationsarecurrentlycompellingresearchers to discover efficient alternative energy sources. The renew- able energy source (RES) is a widespread concept covering windenergy,solarenergy,biomass,geothermal,andtidalwave energieswhich are believed tohave the ability to tackleour dependency on fossil fuels. Extensive studies about electri- cal energy generation by using RESs have been performed by numerous research laboratories and scientists (Fu et al., 2014;Jain&Agarwal,2008;Kabalci,Kabalci,&Develi,2012;

Liserre,Sauter,&Hung,2010;Nehriretal.,2011;Spagnuolo etal.,2010;Yu,Zhang,Xiao,&Choudhury,2011).Atpresent, RESsareassumedasalternativeenergysourcestofuels,andthey canbeeasilyintegratedintocurrentlyusedgridinfrastructures.

SinceanenergyplantthatisbasedonRESneedstopermanently supplytheelectricalloadsaswellastheconventionalgrid,stan-

∗Correspondingauthor.

E-mailaddress:[email protected](I.Develi).

PeerReviewundertheresponsibilityofUniversidadNacionalAutónomade México.

dalone renewableenergy plants are assisted withbattery and energystoragesystems.

Distributedenergy sources(DES) aresuggestedas asolu- tion to energy demands by interconnecting several different energy sourcestogether. A robust microgrid structure that is constitutedfromvariousenergysourcesshouldbeabletobeeas- ilyconnectedtoanddisconnectedfromtheconventionalgrid;

thisrequirementmeanstheintegrationcapabilityofanyaddi- tionalsourceconnectiontotheexistingdistributedgeneration systemwithoutrequiringanysystemconfiguration(Spagnuolo et al., 2010; Yu et al., 2011). The monitoring and metering requirementsof microgridnetworksshouldbe metas wellas conducted inconventional grids.Although several measuring methods have been proposed such as wired or wireless, all the solutions are related to the smart grid concept that has been extensively researched (Gungor et al., 2011; Matanza, Alexandres,&Rodríguez-Morcillo,2014;Sung&Hsu,2013;

Wen,Wang,Zhu,Li,&Zhou,2013;Yan,Qian,Sharif,&Tipper, 2013).The smart gridshould meetthe remote sensing,communication, controlling, monitoring andanalysis demands in a sustainable, secure and efficient way tomanage the entire infrastructure. Smartgrid applicationsare widelyused in the phasemeasurement,advancedmeteringandremotemonitoring

http://dx.doi.org/10.1016/j.jart.2017.03.001

1665-6423/©2017UniversidadNacionalAutónomadeMéxico,CentrodeCienciasAplicadasyDesarrolloTecnológico.Thisisanopenaccessarticleunderthe CCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

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ofsourceandloadamplitudes(Galli,Scaglione,&Wang,2010;

Gungoretal.,2011;Kabalcietal.,2012;Matanzaetal.,2014;

Sung&Hsu,2013;Yanetal.,2013;Yuetal.,2011).

Thetypeofcommunicationmediumpreferredinsmartgrids iswiredorwirelessbecauseofenvironmentalandsubstructural factors. Wireless communicationsystems are standardizedto wireless home area networks (HAN) and wireless wide area networks (WAN). Besides these standard networks, business areanetworks(BANs)andneighborhoodareanetworks(NANs) havealsobeenproposedbyseveralresearchersandalliances.

TheHANstandardsareimplementedandoperatedbyZigBee allianceandWi-Fialliancewhichincludetheglobalsystemfor mobilecommunications(GSM),ZigBee,Wi-Fi, andthe gen- eral packet radioservice (GPRS), while the WAN standards coverWiMaxthatisbasedonIEEE802.16standard(Gungor etal.,2011;Yanetal.,2013;Yuetal.,2011).Althoughwire- less communicationseemstobethemost convenientmethod totransferinformationandcontroldata,therequiredinfrastruc- ture greatly increases the installation costs. Furthermore, the destructiveeffectsofthecommunicationmediumdecreasethe sustainabilityandsecurityofdatatransferinwirelesscommu- nication.Analternativemethodtotransmitmeasureddataisto useelectricalpowerlinesasatransmissionmedium;thiscon- cept is defined as power line communication (PLC). PLC is consideredasapromisingtechnologyinsmartgridsbecauseof itseliminatingthe additionalcostsofwirelessandotherwire line communication methods (Galli et al., 2010), and owing toitshigh-speeddataratesof upto200 Megabitspersecond (Mbps).Moreover,PLCcanbeusedinindustrial,indoor,and outdoorapplicationsthankstoitsvariouscommunicationbands that are called broadband (BB) and narrowband (NB) (Galli etal., 2010;Gungor etal., 2011;Yan etal., 2013).NBPLC systemsoperatebelow500kHzbandaccordingtoCENELEC, FCCorARIBstandardsandgenerallyutilizesinglecarriersys- tems.Ontheotherhand,BBPLCsystemsrunbetweentheband rangeof 1–30MHzandexploit multicarriersystemssuch as orthogonalfrequency-divisionmultiplexing(OFDM),andespe- ciallycodedOFDM.Recentlyreportedstudiesintheliterature showedthat thelow-density parity-check(LDPC)codeisthe best solutionfor the channel coding processinPLC systems (Andreadou & Pavlidou, 2010; Andreadou, Assimakopoulos,

&Pavlidou,2007; Nakagawa,Umehara,Denno,&Morihiro, 2005;Spencer,2005;Wada,2004).Theauthorsin(Andreadou etal.,2007)aimedtocompareLDPCcode performancewith Reed-SolomonandConvolutionalcodesoverthePLCchannels andtheyshowed that LDPC codes perform betterthan other codes.In Nakagawa etal.(2005),the authors searched for a waytoimprovethedecodingprocessofLDPCcodesoverPLC channels withimpulsive noise.The performanceof highrate andshort-blockLDPC codesinlow bandwidthPLC systems isconsideredinSpencer(2005).TheauthorsinWada(2004) showedthattheperformanceofLDPCcodesisalsobetterthan thatofTurbocodesinPLCchannels.Theperformanceofirregu- larquasi-cyclic(QC)LDPCcodesoverastatisticalPLCchannel modelwithhighlyimpulsivenoiseisexaminedinAndreadou andPavlidou(2010).

In previous studies (Develi & Kabalci, 2014a; Kabalci, Develi,&Kabalci,2013),wehaveexaminedbiterrorrate(BER) performances of LDPC codedOFDM systems over Canete’s PLC channel model andaimedtoshow superiorityof LDPC codes amongothers inPLC channels.In Develiand Kabalci (2014b),effectofusingdifferentdecodingschemesontheLDPC codedOFDMsystemsoverindoorPLCchannelswasanalyzed.

In additiontotheseworks, animagetransmissionsystemfor smartgridswasalsoproposedin(Develi,Kabalci,&Basturk, 2014).Furthermore,aPLCchannelmodelproposalthatisbased onpracticalchannelmeasurementsacquiredfromelectricalnet- worksinTurkeywasreportedinDeveli,Kabalci,andBasturk (2015).

This paper presents investigation of the QC-LDPC coded OFDM systemperformances overapracticalPLC channelin contrasttopreviousstudiesreportedintheliterature.Toobtain arealisticPLCchannelmedium,long-termmeasurementswere carriedoutinNigdeVocationalCollegeofTechnicalSciences, Turkey.Thesimulationresultswereobtainedbyvaryingthecode rate,blocklengthanditerationnumbersoftheQC-LDPCcodes overthegeneratedPLCchannel.Furthermore,thesimulations were notonlycompleted bytransmittingrandomly generated data,butwerealsocarriedoutforthetransmissionofdifferent imagessuchaslenna,cameramanandbaboonwhicharewidely used forperformanceevaluationandcomparisoninthelitera- ture. Asa result,it wasconfirmed that the QC-LDPCcoded OFDM system,inwhichperformancewasanalyzed inareal PLCchannel,canbeutilizedinsmartgridsforcommunication andremotemonitoringpurposesinareliableway.

The rest of this paper is organized as follows: Section 2 describes the QC-LDPCcodes,the OFDM systemprinciples and systemmodel.The PLC channel measurementsystemis explainedinSection3.Finally,thesimulationresultsandcon- clusionsaregiveninSections4and5,respectively.

2. Systemmodel

2.1. LDPCandQC-LDPCcodes

LDPCcodesarerobusterrorcorrectingcodesandareaspe- cialtypeoflinearblockcode(Gallager,1963).Asparsematrix, calledparity-checkmatrixH,isexploitedtodefinethesecodes.

Whenan (n,k) LDPCcodeisconsidered, kdenotesinforma- tion bits and n represents coded bits with an r=k/n code rate.In addition,thedimensionsoftheparity-checkmatrixH areshownby (n−k) ×n.LDPCcodeshavesomeadvantages, suchasasimplecodingprocess,parallelanditerativedecoding operationsandgoodperformancewhentheyarecomparedwith Reed-Solomon,ConvolutionalorTurbocodes.Becauseoftheir high performanceandlowdecodingcomplexity comparedto otherchannelcodingschemes,LDPCcodeshavebeenexploited inmostmoderncommunicationsystemssuchasDVB-S2/-T2/- C2,802.11n(Wi-Fi),802.16e(WiMAX),IEEE802.3an(10Gbit Ethernet)andG.hn/G.9960.

QC-LDPCcodes,whichareaspecialtypeof LDPCcode, offerasimpleencodingprocessandbettererrorcorrectingper- formance.Thesecodesutilizetheshiftingmethodtodecrease

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encoding complexity. In addition, they can be easily imple- mentedbecauseoftheircycliccharacteristic(Myung,Yang,&

Kim,2005).Aparity-checkmatrixthatcomprisessub-matrices calledzeroor circulantpermutationmatricesdefinesabinary QC-LDPCcode.ApermutationmatrixPⁱofsizeL×Lisgiven with(1).

Pⁱ=

⎡

⎢⎢

⎣

0 1 0 ··· 0 0 0 1 ··· 0 ... ... ... . .. ...

0 0 0 ··· 1 1 0 0 ··· 0

⎤

⎥⎥

⎦

(1)

Itisimportanttonotethatthecirculantpermutationmatrix PⁱshiftstheidentitymatrixIitimestotherightaslongasthe 0≤i<Lconditionistrue.Finally,theparity-checkmatrixH ofsizemL×nLisgivenas(Myungetal.,2005)

H=

⎡

⎢⎢

⎢⎣

Pâ¹¹ Pâ¹² ··· Pâ¹ⁿ Pâ²¹ Pâ²² ··· Pâ²ⁿ ... ... ... ... Pâ^m1 Pâ^m2 ··· Pâ^mn

⎤

⎥⎥

⎥⎦

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whereaij ∈ {0,1,...,L−1,∞},1≤i<mand1≤j<n.

Ontheotherhand,the decodingprocessof theQC-LDPC codescanbeperformedbyusingsoft-andhard-decisiondecoder schemessimilartoLDPCcodes(Chen,Dholakia,Eleftheriou, Fossorier, & Hu, 2005; Gallager, 1963; Jiang, Peng, Song, Pan, & Yang, 2009; Phakphisut, Supnithi, Sopon, & Myint, 2011;Zhong,Xu,Xie,&Zhang,2007).Althoughharddecision decoders havethe advantage of low complexity, theyalways exhibitlowerperformancethanthatofsoftdecisiondecoders.

Themost commonlyused soft-decision decoder isthe Belief Propagation(BP)decoder(Chenetal.,2005)thatperformsthe decodingprocessinaniterativeway;itisalsoutilizedinthis studyforthedecodingprocess.

2.2. QC-LDPCcodedOFDMsystemdesignformonitoring energysystems

Orthogonal frequency-division multiplexing (OFDM) (Chang,1966) is a transmissionmethod which, as the name implies,utilizes morethanoneorthogonalcarrier.AnOFDM systemconsists of both modulation and multiplexing infras- tructures (Chang, 1966; Hwang, Yang, Wu, Li, & Li, 2009;

Wu&Zou,1995;Zou&Wu,1995).Themostadvantageous propertiesoftheOFDMarebandwidthefficiencyanditsrobust structure against channel fading. Inter Symbol Interference (ISI) has attracted the attention of researchers and caused it tobe widely researched. The systemcan divide a frequency selectivechannelintoseveralsub-channelswithparallelfading properties that require proportionately simple processes for channel equalization. Several standards such as asymmetric digital subscriber lines (ADSL), very high-bit-rate digital subscriberlines(VDSL),digitaltelevision,radiobroadcasting

and wireless local areanetworks (WLAN) systems currently useOFDMsystems.

Ablockdiagramoftheproposedsystemformonitoringsmart gridsthroughpowerlinecommunicationisgiveninFig.1.As canbeseenfromthefigure,thecommunicationinfrastructure ofthemonitoringsystemisbasedonQC-LDPCcodedOFDM modems.Toshowtheefficiencyofthemonitoringsystem,the performanceof theQC-LDPCcodedOFDMmodemistested byusingdigitaldataandlenna,cameramanandbaboonimages with256×256pixels.Asmentionedbefore,theseimagesare selectedsincetheyarewidelyusedforthecomparisonofsys- tem performanceinthe literature.Thetransmissionof image processingbyusingtheQC-LDPCcodedOFDMsystemovera PLCchannelcanbesummarizedbrieflyasfollows.

Firstly,theLDPCencoderinvolvesproperlyadjustedimage dataastheinput.Hence,thepixelsofthepatternimagearecon- vertedto8-bitgrayscaledigitaldatabeforebeingappliedtothe encoder.Theinitialblockofthetransmitter,theLDPCencoder, executesthechannel-coding processfor messagebitsthat are transferredtothemodulationprocesstomaptheencodeddata stream.Afterwards,pilotsymbolsareintegratedintothemodu- lateddatainordertoobtainapreciseestimationonthereceiver side.Inthefollowingstep,theparalleldatathataregenerated bybeingconvertedfromserialdataaretransferredtotheinverse fastFouriertransform(IFFT)processwhereOFDMsignalsare generatedinthetimedomain.The ISIeffectiseliminatedby addingaguardintervaltotheOFDMsignalsbycyclicprefixes.

Theparalleldataareconvertedtoserialdatathatareprepared forapplicationtopracticalPLCchannelsattheback-endofthe cyclicprefixinsertionprocess.

The receiverpartof the entiresystemstartsafter thePLC channels.Thereceiveddataarefirstlyconvertedtoparalleltype andthenare appliedtothe fastFouriertransform (FFT)pro- cessingbyremovingtheguardinterval.TheoutputoftheFFT processisagainconvertedtoserialdataandthenchannelestima- tionandpilotsymbolremovingprocessesareappliedtotheserial data in the frequency domain.The demodulation and LDPC decodingprocessesconfigurethelaststepofthereceiverside.

Theoverallperformanceofthesystemisdetectedbycompar- ingthepeaksignal-to-noiseratio(PSNR)ofthetransmittedand receivedimage.ThePSNRmethodthatiswidelyusedtodetect imagequalityinvolvesthecalculationofthemeansquareerror (MSE)asseenin(3)

MSE= 1 x×y

x−1 x=0

y−1 y=0

S (x,y) −R (x,y)² (3)

wherex×y definestheimagesize,andSandRstandfor the transmitted and received image pixel values in binary form, respectively.Ontheotherhand,thePSNRvaluecanbedefined byusingtheMSEasgivenbelow

PSNR=10log₁₀

MAX² MSE

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AC

DC DC

DC AC

AC DC DC

Measurement and image acquisition

center

QC-LDPC coded OFDM

transmitter

QC-LDPC coded OFDM

receiver Energy and security

monitoring center Customers

Power delivery

Power line channel Power line channel

Fig.1.BlockdiagramoftheQC-LDPCcodedOFDMsystemsformonitoringenergysystemsthroughpowerlinecommunication.

Measurement storage and analysis system

Measurement device

Power lines Coupling device

and EMI filter

Fig.2.Practicalmeasurementsystemusedtoacquirecharacteristicsofpowerlines.

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–35

–40

–45

–50

–55

–60

–65

–70

–75

–80

–85

0.5 5 10 15 20

Frequency (f) [MHz]

H(f) [dB]

Daily variations of PLC channel Average variation of PLC channel

25 30

Fig.3.PLCchannelfrequencyresponsesmeasuredinNigdeVocationalCollege ofTechnicalSciences,Turkey.

whereMAXdepictsthemaximumpixelvalueoftheimage.Since eachofthepixelsisconvertedto8-bitdata,theMAXvalueis setto256inthisstudy.

3. PLCchannelmeasurementsystem

Thepowerlinecommunication(PLC)measurementstudies werecarriedoutbetween500kHzand30MHzbyinstallingthe measurementtestbedatNigdeVocationalCollegeofTechnical Sciences, Turkey.The practical measurementsystemused to acquirethe characteristics of the powerlines is illustrated in Fig.2.Ascanbeseenfromthefigure,securemeasurementis performedowingtothecouplingcircuitthateliminatespossible damagesbyelectricallyisolatingthemeasurementsystemfrom thegridandsevereloadsconnectedtoanddisconnectedfrom thegrid.Themeasurementmeterthatisconnectedovercoupling circuits provides reliability of measurement by obtaining the instantchangesinthepowerlinechannelintermsoffrequency domain.

Becausetheinstantdataacquisitionsyieldsimilarresultsto thescenarioofanactualpowerlinechannel,themeasurement processesarecarriedoutforlonglastingperiods;forexample, aperiodindicates24h,andalong-termmeasurementtakestwo months.Theinstantmeasurementsaretransmittedtothecom- puterandaresavedasmasterfiles.Fig.3depictstheperformed measurementsandtheaveragefrequencyresponseofthechan- nel,H(f),versusfrequencyf.Whenthemeasurementsacquired fromthepracticalpowerlinesareanalyzed,thedailyvariations ofthePLCchannelareobservedwithincertainlimits.Theaver- agevalueofthePLCchannel,shownbytheredcurveinFig.3, iscalculatedandconsideredasaPLCchannelmediuminthis study.

Table1

CoderatesandlengthsofQC-LDPCcodesemployedinthesimulations.

Coderates Codelengths

Short-lengthcodes Long-lengthcodes

1/4 (900×225) (1800×450)

1/3 (900×300) (1800×600)

1/2 (900×450) (1800×900)

2/3 (900×600) (1800×1200)

5/6 (900×750) (1800×1500)

10⁰

10^–1

10^–2

10^–3

10^–4

10^–5

0 5

(900x225) QC-LDPC (900x300) QC-LDPC (900x450) QC-LDPC (900x600) QC-LDPC (900x750) QC-LDPC Uncoded case

E_b/N₀ [dB]

BER

10 15

Fig.4.BERperformancesofOFDMsystemsencodedwithshort-lengthQC- LDPCcodesoverarealisticPLCchannel.

4. Resultsanddiscussion

Inthissection,weinvestigatetheperformanceofQC-LDPC codedOFDMsystemsoveraPLCchannelobtainedwithprac- tical measurements interms of data andimagetransmission.

In order to perform a comprehensive analysis, ten different- lengthQC-LDPCcodeswithvariouscoderateswereexamined throughcomputersimulations.Table1givesthecoderatesand code lengthsutilized inthisstudy. Inaddition, aBPdecoder schemeispreferredonthereceiverofthemodeledcommunica- tionsystembecauseofitsgoodperformanceandthemaximum iterationnumberofthedecoderwassetto10and50forthedata andimagetransmissionprocess,respectively.Whiletheperfor- manceresultsfordatatransferarepresentedinFigs.4and5,the resultsforimagetransmissionoverapracticalPLCchannelare illustratedinFig.6.

Fig.4showstheBitErrorRate(BER)performancesofthe OFDMsystemversussignal-to-noiseratio(E_b/N0)when the systemisencodedbyusingshort-lengthQC-LDPCcodes.Itis clearlyseenfromFig.4thattheBERperformanceoftheOFDM systemishighlyincreasedwhenQC-LDPCcodesareemployed.

Whenhigh-densitycodesarecomparedwiththeuncodedcase, theimprovementofferedbythe (900,600) codeisnearly6.25dB whilethe (900,750) codeprovides4dBbetterperformancefor

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10⁰

10^–1

10^–2

10^–3

10^–4

10^–5

0 5

E_b/N₀ [dB]

(1800x450) QC-LDPC (1800x600) QC-LDPC (1800x900) QC-LDPC (1800x1200) QC-LDPC (1800x1500) QC-LDPC Uncoded case

BER

10 15

Fig.5.BERperformanceresultsofOFDMsystemsoverarealisticPLCchannel withlong-lengthQC-LDPCcodes.

aBERlevelof10⁻².Inaddition,theQC-LDPCcodewitha1/4 rate providesapproximately11.4dBimprovementattheBER levelof10⁻².

TheBERperformanceresultsoftheQC-LDPCcodedOFDM systemobtained by using long-lengthcodesare illustratedin Fig. 5. It is observedthat, when the uncodedsystem is con- sidered, about 15dB is needed for a BER value of 10⁻². However, the similarperformancewith2/3 and5/6rate QC- LDPC codesare presented atE_b/N0≈8.1dB andE_b/N0≈ 10.4dB,respectively.

In cases wherethe 1/3 and 1/2 rate QC-LDPC codes are utilizedinsteadofhigh-densitycodes,theachievedgainswith respecttotheuncodedcasebythesecodesare10.75dBand9dB ataBERlevelof10⁻²,respectively.Inaddition,whenthe1/4 ratecodeisused,about6dBisrequiredforaBERvalueof10⁻⁵. Finally,wecanseefromFigs.4and5thatlong-lengthQC-LDPC codesprovidenearly0.75dBbetterperformancethanthatofthe short-lengthcodesinhighrates.

Fig.6indicatestheimagetransmissionresultsfortheQC- LDPCcodedOFDMsystemwiththe (1800,600) codeoverthe PLCchannel.WhenthecodedsystemresultsshowninFig.6a-c arecomparedwiththeuncodedcasesdepictedinFig.6d-f,the

SNR= 4 dB PSNR= 23.03 dB

a b c

d e f

SNR= 30 dB PSNR= 43.21 dB SNR= 6 dB

PSNR= 39.95 dB

Fig.6.ComparisonofuncodedandQC-LDPCcodedOFDMsystemsfordifferentimagesinPLCchannels((a),(b)and(c)presentQC-LDPCcodeperformances;

(d),(e)and(f)showuncodedcases).

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PSNRvalueof24.75dBisobtainedata26dBSNRvalueinthe uncodedOFDMsystem, whilenearlythesamePSNRperfor- mancecanbeachievedatalowerSNRvaluesuchas4dBinthe codedsystemforthelennaimage.Intheeventofthecameraman imageresultsforthesameQC-LDPCcodepresentedinFig.6 areanalyzed,itisshownthatabout28dBSNRisneededfora mediumqualityimagetransmissionwitha31.86PSNRvaluein theuncodedsystem.However,betterperformanceisprovided atthe6dBSNRvalueinthecodedOFDMsystem.Whenthe transmissionresultsforthebaboonimagesusing1/3rate and long-lengthQC-LDPCcodesareconsidered,itisclearlyseen fromFig.6 thatvery highqualityimagetransmissioncanbe obtainedattheSNRvalueof8dBandanextremelyhighPSNR valueof61.07dBowingtothecodedOFDMsystem.

Asa final remark, all of the simulation results show that QC-LDPCcodesprovide significantimprovementintermsof dataandimagetransmission overthe practical PLC channel.

In addition, the results obtained confirm that the QC-LDPC codedOFDMsystemcanbeutilizedinsmartgridsforremote monitoringenergysystems.

5. Conclusion

ThispaperinvestigatedtheperformanceofQC-LDPCcoded OFDM systems for both data and image transmission using practical PLC channel conditions. The long-term PLC chan- nelmeasurementswerecarriedouttoobtainanactualchannel model.Inordertorealizeacomprehensiveanalysis,thesimu- lationstudiesexamined bothdifferentcode lengths andcode rates. All of the simulation results achieved over the actual PLC channel show that the QC-LDPC codes ensure consid- erableimprovement interms of dataand imagetransmission performance.Theresultsofthisstudyalsoemphasizethatthe QC-LDPCcodedOFDMsystemtestedinanactualPLCchan- nelcanbe reliablyutilizedinsmartgrids forcommunication andremotemonitoringpurposes.

Conﬂictsofinterest

Theauthorshavenoconflictsofinteresttodeclare.

Acknowledgements

ThisworkwassupportedbytheScientificandTechnological ResearchCouncilofTurkey(TUBITAK)undergrant113E425 andby the ResearchFund of Erciyes University under grant FBD-12-3986.

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