简介:ThecharacteristicofEDFAinWDMsystemisanalyzed.ThesimulationsystembasedonthearchitectureoftheChinaInformationNetwork(CAINONET)isintroduced,andtheinfluenceofnoisefigure,gainunflatnessandoutputpowerofEDFAontheBERperformanceandscaleofnetworkisinvestigated.Moreover,theinfluenceofnoisefigureisstudiedwithdifferentcrosstalk.Meanwhile,itisindicatedthatitisimportanttoapplythe"nodeisolationprinciple"intheopticalnetwork.Theresearchresultscanprovidethevaluablereferenceforthepracticalconstructionofallopticalnetwork.
简介:ThislettergivesarandomconstructionforLowDensityParityCheck(LDPC)codes,whichusesaniterativealgorithmtoavoidshortcyclesintheTannergraph.TheconstructionmethodhasgreatflexiblechoiceinLDPCcode'sparametersincludingcodelength,coderate,theleastgirthofthegraph,theweightofcolumnandrowintheparitycheckmatrix.ThemethodcanbeappliedtotheirregularLDPCcodesandstrictregularLDPCcodes.Systemiccodeshavemanyapplicationsindigitalcommunication,sothisletterproposesaconstructionofthegeneratormatrixofsystemicLDPCcodesfromtheparitycheckmatrix.Simulationsshowthatthemethodperformswellwithiterativedecoding.
简介:Becauseofitspotentialapplicationsinagriculture,environmentmonitoringandsoon,wirelessundergroundsensornetwork(WUSN)hasbeenresearchedmoreandmoreextensivelyinrecentyears.ThemainandmostimportantdifferenceofWUSNtoterrestrialwirelesssensornetwork(WSN)isthechannelcharacteristics,whichdeterminesthedesignmethodologyofit.Inthispaper,thepropagationcharacterofelectromagnetic(EM)waveinthenearsurfaceWUSNisanalyzed,aswellasthepathlossmodelofitisgiven.Inaddition,theinfluenceofhuman'sankletothechannelcharacteristicsofnearsurfaceWUSNisinvestigatedbyelectromagnetictheoryanalysis,simulationandexperiment.AnovelpathlossmodelofnearsurfaceWUSNwhichtakestheinterferenceofhuman'sankleintoconsiderationisproposed.ItisverifiedthattheexistingofhumanabovetheWUSNsystemmaycauseadditionalattenuationtothesignalofnearsurfaceWUSNwhichpropagatesaslateralwavealongtheground.Moreover,therelationoftheattenuationandoperatingfrequencyisdeduced,whichgivesareferencetoextendthefrequencybandappliedinWUSN.