Electronics and Communications Electronics and CommunicationsUNIVERSITYOFWOLLONGONGUNIVERSITY OFWOLLONGONGElectronics and CommunicationsElectronics and CommunicationsThree Components:1. Lectures Zhanchao Long2. TutorialsLzc12@. LaboratoryTel:87540850Participation in all three components is compulsory!ECTE212 .-T. Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITYOFWOLLONGONGCourse ObjectivesRecommended reference texts:Atthe end ofthe course you should know:•. Young,Electronic Communication Techniques, 3r ed.,Macmillan Int.–how to represent signals in time domain–how to represent signals in frequency domain?. Couch II, Digital and Analog Communication Systems, 6th ed., –what is modulation and demodulationPrentice-Hall–simple forms of modulation and demodulation (AM and FM)–simple electronic circuits to perform modulation and demodulationECTE212 .-T..ECTE212 Zhanchao Long39/10/2003 Zhanchao Long4 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITYOFWOLLONGONG WOLLONGONGTelecommunication SystemsIn this lecture we consider the following:Aim: to transmit information from one point to another (or point to multi-point)?What arethe main elements of a telecommunication system??Whatisthefunctionofthevariouselements?ChannelInformationTransmitterReceiverOutput?What is an analogue signal?source andtransducer andinput transducerinformation sink?What arethe basicmethods of signal representation in telecommunication systems?Examples: Radio, TV, Telephone, DataECTE212 .-Long.. .. 9/10/2003Zhanchao Long 6 Zhanchao Long5
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGDescription of Main ElementsDescription of Main Elements ctd?Information source and input transducer?The transmitter–information source: voice, image, text, etc–converts (or maps) the electrical signal into a suitable –a transducer is used to convert the source output into an section of the frequency spectrum for transmissionelectrical signal suitable for transmission?Output transducer and information sink–this process is referred to as modulation. The information –at the output a transducer signal is translated in frequency to complement the is used to convert the electrical signal to a form suitable for the userallocation of the channel–other functions may include amplification of modulated signal and radiation of signal via an antennaChannelInformationOutputsource andtransducer andTransmitterinput transducerinformation sinkECTE212 Zhanchao Long79/10/2003 Zhanchao Long 8 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGWhat is modulation?Why Modulation??Reasons for using modulation include:?Modulation is one of the crucial signal processing operations being commonly applied in communication –Conservation of spectrum: want to use as little of it as systems. possible»bandwidth is a scarce resource?It can be used to match a signal to the channel »the wider the bandwidth the more noisecharacteristics, to minimise the effect of channel –Translation of frequencies: use the allocated region of the impairments, and to provide capability to multiplex frequency spectrumseveral signals onto one physicalchannel.»makes it possible to accommodate transmission of multiple messages from many users over the same channel–Transmission efficiency: minimise the transmitter power to convey the information to the user–Design feasibility: simple and inexpensive .. Zhanchao Long 99/10/2003 Zhanchao Long10 Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGExamples of Use of ModulationChoice of Modulation Method?Speechhasa frequency .?The choice of modulation method is based on several factors:?Music contains frequency components of 0-20kHz.–amount of bandwidth available?However, frequencies at which radio stations broadcast are much higher! Eg:–types of noise and interference in the channel– MHz (ABC FM)–electronic devices available for signal amplification prior to transmission– MHz (JJJ FM)–cost of receivers and transmitters?Hence there must be a frequency conversion (or modulation) taking place. That allows more than 1 ?In this course, we will study two types of modulation: station to broadcast simultaneously (using different amplitudemodulation (AM) and frequencymodulationcarrier frequencies).(FM).ECTE212 Zhanchao Long119/10/2003 Zhanchao Long 12
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGDescription of Main Elements ctdNoise in Analogue Transmission?Channels are subject to noise, interference, fading and ?The channel:other degradation effects.–physical medium via which the signal output from the transmitter is sent (. transmitted) to the receiver?Noise is generated by numerous natural and man-made events and introduces errors or degrades signal quality.–channel may provide simplex,half-duplexorfull-duplextransmission?An important parameter in designing communication –examples of channels: free-space, copper twisted pair, systems is the so-called signal to noise ratio (SNR).coaxial cable, optical fibre?Noise will be considered in future communications subjects. In our current subject we ignore its .. Zhanchao Long9/10/2003 Zhanchao Long 1413 Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OFWOLLONGONGNoise in Analogue TransmissionDescription of Main ElementsA random, noise-like waveform?The receiver–extracts the message from the received signal. This is n(t)calleddemodulation.–also can perform some form of signal filtering and noise -1ReceiverECTE212 Zhanchao Long 159/10/2003 Zhanchao Long 16 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGSignals and WaveformsSignals and Waveforms ctd.?Two very important concepts used in analysis of ?A deterministic waveform, like a power supply 50 Hz communication systems are signals and wave is usually not a signal!u(t)?In literature, particularly related to the theory of signals 2402and systems, these two terms are very often used indistinguishably. ?Both waveforms and signals are functions of time, but signals are also functions of the information they have to [ms]1020?Practically, most often they are implemented as voltages, currents or field intensities.−2402?In this course, however, we refer toa signal as a waveform, which conveys an information intentionally associated with .. Zhanchao Long9/10/2003 Zhanchao Long 1817
Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGSignal Representation in Time DomainSignals and Waveforms ctd.?Sequences of pulses transmitted in a telecommunication ?What is an analoguesignal (or waveform)?network usually are signals.?A function of time that has a continuousrange of (t)s(d,t)1ttime-1ECTE212 Zhanchao Long 199/10/2003 Zhanchao Long 20 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OFWOLLONGONG WOLLONGONGSignal Representation in Time DomainSignal Representation in Time Domainw(t)t?In some applications, signals need to be represented at discrete values of time, only. ?Between these discrete-time instants the value of the w(t) is very often of no interest. ...?Usually, the intervals between signal samples are the , but they need not be. ...?A sample-data signal can later be quantized. Quantizingw(t)a sample value is rounding it to the nearest of a finite of allowable values. .-1.-2-3..-4ECTE212 .. Zhanchao Long219/10/2003 Zhanchao Long 22 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGSignal Representation in Time Domain 1: Sinusoidw(t)?Typically represented as voltage or current as a function of time.?We can use an oscilloscope to look at a signal as a timefunction of time.?In general, we denote a signal (or a waveform) by w(t).?Examples of signals:w(t)=Acos(2pift+θ)0–sinusoidal–square waveWhere –speechA-amplitudef-frequency of oscillations0θ-phaseECTE212 Zhanchao Long239/10/2003 Zhanchao Long 24
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OFWOLLONGONGExample 1: Sinusoid ctdEnergy and Power Waveforms ?One of the methods of classifying waveforms is based w(t)=Acos(2pift+θ)0on the total energyof the waveform or its average power.?Units for above parameters ?The instantaneous power p(t) of the waveform w(t),?A-amplitude -in Volts(V) or Amperes (A)normalised to a resistance of 1 ohm, is equal to 2?f-frequency of oscillations -in Hertz(Hz)0p(t)=w(t)?θ-phase -in radians(rad)?Hence, the normalised total energy of the waveform w(t) is given by?Sometimes we also use angular frequency ω= 2pif(in00rad/sec) which gives w(t) as:T2E=limw(t)dtjoules −TT→∞w(t)=Acos(ωt+θ)0ECTE212 .. Zhanchao Long259/10/2003 Zhanchao Long 26 Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGEnergy and Power Waveforms Energy and Power Waveforms?and its normalised average power is?It should be noted here that the energy and power classifications of waveforms are mutually exclusive since an energy waveform has its average power equal T12P=to zero, whereas a power waveform has infinite (t)dtwatts −TT→∞2T?In addition, most of the signals used in ?We refer to the waveform w(t) as an energy waveformtelecommunications are power and only if its total energy satisfies the condition0<E<∞?we refer to the waveform w(t) as a power waveformif and only if its average power satisfies the condition0<P<∞ECTE212 Zhanchao Long 279/10/2003 Zhanchao Long 28 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGSignal TranslationsSignal Translationsw(2t)w()w(t)w()1111ttttw(t)+12w(t)ww(-t)(t+1)1111ttttECTE212 .. Zhanchao Long 299/10/2003 Zhanchao Long 30
Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OFWOLLONGONGBreakConvolution?The output y(t) of a fixed, linear system characterised by the impulse response h(t) in response to an input x(t) is given by ∞y(t)=x(τ)h(t−τ)dτ −∞?The generally accepted notation for the convolution is ‘*’, . we can writey(t)=x(t)∗h(t)?The convolution of two signals x(t) and h(t) is a new function of time as the two convoluted signals are, and has several very useful Zhanchao Long 319/10/2003 Zhanchao Long 32 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGConvolutionProperties of Convolutionx(t)1y(t)?Commutativity:(t)∗h(t)=h(t)∗x(t)LinearSystem134246tt?Associativity:(t)1[x(t)∗h(t)]∗g(t)=x(t)∗[h(t)∗g(t)]-1?Distrubutivitywith addition:x(t)∗[h(t)+g(t)]=x(t)∗h(t)+x(t)∗g(t)12tECTE212 .. Zhanchao Long 339/10/2003 Zhanchao Long 34 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGProperties of ConvolutionProperties of Convolution?Shift property:?Area under the curve property: If the area under h(t)is equal to Aand the area under x(t) is equal to B,x(t−τ)∗h(t−τ)=x(t−τ)*h(t)=x(t)∗h(t−τ).:∞h(t)dt=A −∞∞?Time limits property:Ifh(t) is limited in time to (t,1x(t)dt=B t) and x(t) is limited in time to (t,t), then the −∞234then the area under x is equal to AB:(t)∗h(t)x(t)∗h(t)is limited in time to (t+t,t+t).∞1324x(t)∗h(t)dt=AB −∞ECTE212 Zhanchao Long359/10/2003 Zhanchao Long 36
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGCorrelationCorrelation?Correlation is another important operation on signals in time ?The argument τis often referred to as the delay, , or lag.?It is also often utilized in communication systems, and is very ?Cross-correlationR(τ) is a measure of similarity xysimilar to the two functions x(t) and y(t).Hence, it is ?For two signals x(t) and y(t), which in general can take often used in detection process of optimal detectors in complex values, the correlation is defined as:digital communication systems.∞?It is possible to show that operation of correlation is ∗R(τ)=x(t)y(t−τ)dtnot commutative, ., in general, we have:xy −∞∗wherey(t) denotes a complex conjugate of y(t).R(τ)≠R(τ)xyyx?If the signals x(t) and y(t) are identical, . x(t) = y(t),then the correlation R(τ) is referred to as autocorrelation, xxotherwise,R(τ) is called .. Zhanchao Long 379/10/2003 Zhanchao Long 38 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGCorrelationCorrelationR(xxτ) shifting one function to the right is equivalent to x(t)shifting another function to the left by an equal 1amount, R(τ) = R(-τ).xyyx-33t6-6τ?In addition, it is easy to notice that ∗R(τ)=x(τ)∗y(−τ)xyy(t)R(τ) simple relationship between correlation and convolution leads to implementation of correlation in a form of match filters.-11t4-4τECTE212 Zhanchao Long 399/10/2003 Zhanchao Long 40 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGCorrelation -ExampleCorrelation -Example?In order to find the function R(τ), let us first assume ?For a waveform x(t) equal to:xxthat the shift τ≥(−t),t≥0 x(t)x(t)= 1−exp(t),t<0x(t-τ) find its autocorrelation function R(τ).0τxxtx(t)-11?It is clearly visible there that the autocorrelation integral need to be split and calculated over the three 0tintervals (-∞, 0), (0, τ), and (τ,∞).-1ECTE212 .. Zhanchao Long419/10/2003 Zhanchao Long42
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGCorrelation -ExampleCorrelation -Example?Hence, we have:?The similar reasoning can be repeated for τ< 0, yieldingτR(τ)=(1+τ)e0τ∞xxtt−τ−tt−τ−t−(t−τ)R(τ)=(−e)(−e)dt+e(−e)dt+eedtxx −∞0τ?Combining these two results gives us:0τ∞−τ2t−ττ−2t−|τ|=eedt−edt+eedtR(τ)=(1−|τ|)exx −∞0τR(τ)xx11−τ−τ−τ1=e−τe+e22−τ=(1−τ)eforτ≥0-11τECTE212 Zhanchao Long439/10/2003 Zhanchao Long44 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OFWOLLONGONG WOLLONGONGCorrelationExamples of useful waveforms?The very basic waveform used in many areas of ?The autocorrelation R(τ) may be considered as a xxmeasure of similarityengineering is a unit step or switching function. It is between the signal x(t) and its shifted versusually denoted by u(t), and defined as:ion x(t-τ).?As result, it always reaches the maximum for τ= 0, 0,t≤0 when there is no shift between the (t)= 1,t>0?Therefore, in communication systems, autocorrelation is used to facilitate synchronization of a receiver with the transmitter. u(t)1?It is desired for the signals in such cases to have a single, distinctive maximum in their autocorrelation function. However, depending on the shape of x(t), the autocorrelationR(τ) might have several local maximaxx0tthat can make synchronization .. Zhanchao Long459/10/2003 Zhanchao Long 46 Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OFWOLLONGONGSignumfunctionRectangular pulse
t?The signumfunction sign(t) is equal to ‘-1’for negative ∏ T values of the argument, equal to zero when the 1argument is also equal to zero, and equal to ‘1’for positive values of the argument. sign(t)time1-T/2T/2−1,t<0 sign(t)=0,t=0 0t 1,|t|<T/2 1,t>0 Π(t/T)= 0,|t|>T/2-1 ECTE212 Zhanchao Long479/10/2003 Zhanchao Long 48
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGSquare WaveSquare Wavew(t)zw(t) general, a unipolarrectangular wave w(t) of an arbitrary zfundamental period Tcan be expressed as:0100
?The uniform unipolarrectangular wave w(t), can be 50∞t−kT 0zexpressed using Π(t) as a sum of time shifted replicas of w(t)=AΠz
T Π0(2t). k=−∞ ∞ w(t)=Π(2t−k)50
where Ais a height of the pulses for z= 25%), and a filling factor z<k=−∞100%.ECTE212 .. Zhanchao Long499/10/2003 Zhanchao Long 50 Electronics and Communications Electronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGThe sincpulseDirac Delta Function?Another very useful ?DiracDelta function δ(x)is defined as:waveform utilized in the +∞analysis of communication ∞, x=0systems is the sinc(t) pulsesinc(t)δand(x)=(x)dx=1δ 10, x≠0 −∞?For example, take Aδ(x-x)sin(pit)0sinc(t)=pitAδ(x-x)0A-115-5txx0?Ais referred to as the “weight” of the Zhanchao Long519/10/2003 Zhanchao Long 52 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGDirac Delta Function Function ctd.?An example of such ?The Diracdelta function denoted by δ(t) belongs to a functionsδ(t,τ) can be a class of functions referred to as generalised series of square pulses distributions, and was first introduced into quantum given by:mechanics by Dirac.δ(t,τ)?It is important to understand that no function in the 1τ2τ = ordinary sensecan satisfy the definingconditionsof ,|t|≤ 1t
τ2Diracdelta function.δ(t,τ)=Π= τττ τ → 0∞0,|t|>?Nevertheless, it can be considered as the limiting form 1τ = 1 2of a series of ordinary functions δ(t,τ) satisfying the τ = 2following conditions:?As it is visible, no matter how small τis, the area ∞0t≠0 beneathδ(t,τ) is always -1 1andtδ(t,τ)dt=1,τ>0limδ(t,τ)= equal to 1. τ→0∞t=0 −∞ECTE212 .. Zhanchao Long 539/10/2003 Zhanchao Long54
Electronics and Communications Electronics and CommunicationsUNIVERSITY OFWOLLONGONGUNIVERSITY OF WOLLONGONGDiracDelta Function Function ctd.?Some examples of the ?Properties of Dirac Delta function:functionsδ(t,τ) that can be –Scaling property2used to approximate δ(t)
1pit1 δ(t,τ)=exp− are:2δ(at)=δ(t) ττ |a|21ττ= δ(t,τ)=–Sifting property22pit+τ∞1x(t)δ(t−t)dt=x(t)00 δ(t,τ)=Π(tτ)1−∞ττ= 11–Sampling propertyδ(t,τ)=sinc(tτ)τ= 2τx(t)δ(t)=x(0)δ(t)2
-2-112t1pit δ(t,τ)=exp−2x(t)δ(t−t)=x(t)δ(t−t) 000ττ ECTE212 Zhanchao Long 55 9/10/2003 Zhanchao Long56 Electronics and Communications Electronics and CommunicationsUNIVERSITY OFUNIVERSITY OF WOLLONGONG WOLLONGONGDiracDelta Function & Comments?Properties of Dirac Delta function:–Replication property (convolution property)∞∞x(t)∗δ(t)=x(τ)δ(t−τ)dτ=x(t−τ)δ(τ)dτ=x(t) −∞−∞–which can be generalised to a form:x(t)∗δ(t−t)=x(t−t)00–relationship with the unit step functiontdδ(τ)dτ=1(t)or1(t)=δ(t) dt−∞ECTE212 .. Zhanchao Long9/10/2003 Zhanchao Long 58 57
Electronics and CommunicationsElectronics and Communications
& ' ! ($ ! " ##$ ! • ! lecture ) " $ " & * ! ( ! ( ) ' ! ? & ) ' ! +, / ! " +, / ! ( " ! & & ' ! ' ! ( & ! ($ Zhanchao Long ,τ/ 6$! 9 ( τ: ; 3 Lzc12@ ( # ' ! ( " ! & #! ( %87540850 & = ! ! #$ $! = & ' ! 3 ! " ! & !$ ! ! 6$! ( τ: ;3 %R(0)=R(0)= =R(0)=112mECTE212 .-Long. 12/10/2003 Zhanchao Long2Electronics and CommunicationsElectronics and Communications
& ' ! ($ & ' ! ($ b1(t)1? ! $ 3 ,;/ ( ( " ! & ? & & ' ! = * * = 3 * "$ ( & ' ! +, / ! " +, / ! " " " >= #* ! ( +, /3 +, / ($ * ' & abt &! ! ! > $ " b? & 6$! ( & !$ ! ( ! ' ! +, / 2(t) +*! " ! = ! > ! = 1! 9 & ( " ! & ' ! #3 ! " ' ! , / &!B ' ! ( " " >= ??+, /?? # >= ! ) '& " ! abt?A ) &!B % #> ! ( & bb3(t)∗($ x(t),x(t)=R(0)=x(t)x(t)dt1121,212 aabtb2bx(t)=R(0)=4(t)|x(t)|dtx,x a1( & ' ! " ( " & # B! D!3>F abtECTE212 .-Long. 12/10/2003 Zhanchao Long312/10/2003 Zhanchao Long4Electronics and CommunicationsElectronics and Communications
& ' ! ($ ! 9 "
$ ? ( & ( ($ G(, /J ! ! " #* ? ! $# & &! & + ! ( ( ( & ' ! ($ 3 &e & ' ! , / ! > ($ G(, /H : 3 3 I3 ∞J &! ! #$ $! = +* & B! D!3>F ! % & ' ! B & B! D!3 >F3 ∞s(t)=cf(t)b0,m≠n 2nn∗f(t)f(t)dt=f(t)δ= 2nmnmn=1,n af(t),m=nn ? & ( " ! ! ! 9 "
$ ?)& δ & K M " ! ($ " ( " ! % #3 ? & # #* #* &! & ! 9 " 0,m≠n
$ B ' , / ! →∞ δ=m ,n?< > ( & ! 3 ! ' $ * ( ( 1,m=n #* $ $! = ! = ' ' !** ! 3 > !$ & ! # ! )!= $ ! " # " $#> ( # ECTE212 .-Long. 12/10/2003 Zhanchao Long512/10/2003 Zhanchao Long6
Electronics and CommunicationsElectronics and Communications
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$ b? " ( " & B! $ ( (( & ?A M∗s(t)f(t)dt 3 $ #$ * = > & " ( >= & #* + k ac= N$'! ( & M &($ (, /3 ! " ' ! B kM2f(t)" #! ( k∞bb∗∗? & ! B ! ) M ) ( & ' ! s(t)f(t)dt=cf(t)f(t)dtk nnk ($ 3 M %A! # )!B , , /3 , /3 aan=1 +*,Nω //3 !" #! & ($ 3 ! & ($ 3 ?O !$ ( & & ' ! = ( & ($ G(, /J3 ! ! ($ 3 A!! ($ 3 ' " * = # ! 3 & # ( & & '& &! " " ! 6$! 9 + * ( : M ? ! ( & $ #* ( bb & ' ! ($ 22∗s(t)f(t)dt=cf(t)dt=cf(t)kkkkk aaECTE212 .-Long. 12/10/2003 Zhanchao Long712/10/2003 Zhanchao Long8Electronics and CommunicationsElectronics and Communications
A! # ($ A! # ($ ? & ! &! # ($ ! $ "! )!B , & ? ' & # ! = ' # " =3 & ! / &!B ' ## $ !> ( 6$ 3 & ! > +*! " " ! %( 6$ ! > +* " ! ' #$ * ( ! R(0)=cos(θ)cos(θ)cos(2pinft)cos(2pimft)dt($ "!# ! ( 6$ = (: P 1,21200;; T0? $ " ) $ & ($ ', / : , pi ( Q ;−cos(θ)sin(θ)cos(2pinft)sin(2pimft)dtθ/! " ', / : , pi#( Q θ/3)& ! " #! 1200 ; T0* B ' & B! $ ( & ! ($ ! 9 ,;/ +* " ! %−sin(θ)cos(θ)sin(2pinft)cos(2pimft)dt 3 1200 T0R(0)=cos(2pinft+θ)cos(2pimft+θ)dt+sin(θ)sin(θ)sin(2pinft)sin(2pimft)dt1,20102 1200 TT00=I−I−I+I1234ECTE212 .-Long. 12/10/2003 Zhanchao Long912/10/2003 Zhanchao Long10Electronics and CommunicationsElectronics and Communications
A! # ($ A! # ($ ? & ' ! ! > * " ! ! $# ( ) ?O !$ ! " #! * B ' 3 & ' ! !( !** = ' ! ' # " =%sin[2pi(n−m)ft]=sin[2pi(n−m)f(t+T])0001cos(αt)cos(βt)={cos[(α−β)t]+cos[(α+β)t]}sin[2pi(n+m)ft]=sin[2pi(n+m)f(t+T])0002?< ! $ 3 ) ' %?)& & = " I=01I=cos(θ)cos(θ)cos(2pinft)cos(2pimft)dt11200 T0? & !# * "$ ! > * ! " ( & ' ! 1 =cos(θ)cos(θ)cos[2pi(n−m)ft]dt+cos[2pi(n+m)ft]dt12 00
TT 3 3 ! " 3 $ ' 2 00 RS1 1=cos(θ)cos(θ)sin[2pi(n−m)ft]12 0T022pi(n−m)f 0R(0)=01,21 +sin[2pi(n+m)ft]0
T02pi(n+m)f0 ECTE212 .-Long. 12/10/2003 Zhanchao Long1112/10/2003 Zhanchao Long12
Electronics and CommunicationsElectronics and Communications
A! # ($ A! # ($ ? & # ( ! &! # ($ 3 , pi ( / ? # ! " ! ! > * ! " ( & ; , pi ( /3 " " * " 3 ! " " ! %($ ', / : , pi ( Q θ/ ! " ;R;R', / : , pi#( Q θ/ ! = * > *! ( ', /3 S;S T220g(t)=g(t)=cos(2pinft)dt=cos(2pimft)dt=', /3 ', /3 ! " ', /3 ( 3 #: 3 3 I 1200 RS TT200? ! ! = &! ! = ( & ($ T220g(t)=g(t)=sin(2pinft)dt=sin(2pimft)dt=', /3 ', /3 ', /3 ! " ', /3 & ' ! & ($ 3400 RS TT200', / : ;?
', / : 3 & # 3 & ) B 3 " (( %?A & & ' ! ( ! &! # ($ Φ; ! %g(t)=dt=T00 Φ={1,cos(2pinft),sin(2pinft),n=1,2, ∞}T000ECTE212 .-Long. 12/10/2003 Zhanchao Long1312/10/2003 Zhanchao Long14Electronics and CommunicationsElectronics and Communications
A! # ($ A! # ($ ?A 3 ( ! = ! ' ! +, / &!B ' ! ( # ! " ?< " & ' ! +, / ! > +*! " " B & B! " ( " B & B! D!3 >F $ & &! >U!: 3 D!3 >F ! ; &
$ (( ! ∞∞b1x(t)=a+acos(2pinft)+bsin(2pinft)0 n0 n0a=x(t)dt0n=1n=1 aT0b2a=x(t)cos(2pinft)dtn0 aT0b2b=x(t)sin(2pinft)dtn0 aT0ECTE212 .-Long. 12/10/2003 Zhanchao Long1512/10/2003 Zhanchao Long16Electronics and CommunicationsElectronics and Communications
#* + &! # ($ #* + &! # ($ ? & #* + &! # ($ ! ( & ( # γ, / : ? & # ( #* + &! # ($ 3 > ' 6$! +*,N pi ( /3 )& : ;3 ± 3 ± 3 I ( & !$ ! ! 9 3 6$! %;∗? ' & !# !** ! & ! ) & & ! &! # γ(t)=R(0)=γ(t)γ(t)dtnnnn T0($ 3 ) ! & ) &! & ($ γ, / ! & ' ! B & B! D!3 >F3 $ & &! >U!: =exp(j2pinft)exp(−j2pinft)dt00 T0;? & > !$ & ! ! 9 ( ! = =dt=T0 T ' B! $ ( #≠ ! ! 9 3 ! %0∗? & ( &
$ (( ( ! ( R(0)=γ(t)γ(t)dtn,mnm T0 # ! > ! = ' ! +, / " ( " B & B! D!3 >F ! ' B >=%=exp(j2pinft)exp(−j2pimft)dt00 T0b1c=x(t)exp(−j2pinft)dt,n=0,±1,±2, n0 =exp[j2pi(n−m)ft)dt=00aT T00ECTE212 .-Long. 12/10/2003 Zhanchao Long1712/10/2003 Zhanchao Long18
Electronics and CommunicationsElectronics and Communications
#* + &! # ($ !" #! & ($ ?A 3 & ' ! +, / ! > +*! " " B D!3 >F ! %? !** + #! " $ $ ($ 3 M ! '$ ! ! '$ ! *$ ! ! = +* # ! ∞"! !3 ' ! = #$ & # B $ x&! # ( & ' ! ($ (t)=cexp(j2pinft) n0n=−∞? ( & #* ( & ' ! ) B! $ " ($ ! ( "" !" #! & ($ 3 " ( " & B! D ; V3 ; VF ! %? & ( ( " ! ! #* +
$ 1,m=0 Rad(t)=m msign[sin(2pit)],m=1,2,3, ECTE212 .-Long. 12/10/2003 Zhanchao Long1912/10/2003 Zhanchao Long20Electronics and CommunicationsElectronics and Communications
!" #! & ($ ! & ($ Rad0(t) t? * > & ) &! ? ! & ($ ! ! #* ( & & ' ! !" #! & ($ ($ D SF &! ! !" #! & ($ Rad1(t) G !", /3 # : ;3 3 3 IJ #? & #* # & " " ( ! & ($ >= " $ ! $ ( = B A!"!#! " #! &! ! #* ( & ' ! & ' ! #! ( " > ' ! ' * ) ( ($ Rad2(t) ? & = ! " ( " ! ( ) ' )!=%Rad3(t) 11 HmHm =2 Hm=+1 1−12
Hm−Hm 22
Rad4(t) .-Long. 12/10/2003 Zhanchao Long2112/10/2003 Zhanchao Long22Electronics and CommunicationsElectronics and Communications
! & ($ ! & ($ Wal(0,t)01t#Wal(1,t)? & ) ( ! #! + A" ( & ($ ! ,;3 # / ! , 3 / & ( ) ' )!= 01t#Wal(2,t) 11111111 Wal(0,t)? ( ) " B " & B! D;3 F B! % 1−11−11−11−1Wal(7,t)01t 11−1−111−1−1 Wal(3,t)Wal(3,t)m 1 12 2−11−1−111−1−11Wal(4,t) 0H=, ,, , ,,10 81t mmmm1111−1−1−1−1Wal(1,t) 2 22 2Wal(4,t)
1−11−1−11−11Wal(6,t) 011−1−1−1−111Wal(2,t)1t? & & ! & ($ " ( " >= & & ) ( ! ##Wal(5,t) 1−1−11−111−1 Wal(5,t)#! + A
!M & B! $ ( W X & B! DMP 3 #01t,MQ /P F ( %Wal(6,t)In general, theithrow of the H(i,k+1)=1mm2matrix Adefines thekthWalsh 021tfunctionWal(k, t) where kis the Wal(7,t)number of sign changes in the 0? & ) !M & B! $ ( W X 1telements of that .-Long. 12/10/2003 Zhanchao Long2312/10/2003 Zhanchao Long24
Electronics and CommunicationsElectronics and Communications
&! &! ?A ) B 3 * > ? ( & ($ "!# ! =* (
$ $ " * B , & &! !#* ' ##$ ! ! " " ' ! ' ! * ' ! & #) &! ( & ' ! +*! ( ! ' ! +, / >= # ! ( ($ +, / >! " # " Osinc(t-nT) ∞& 93 ! " 1t−nT x(t)=asinc n1T≥2B n=−∞T? & & B! $ ( t−nT (( ! ( & ϕ(t)=sinc;n=0,±1,±2,
n! #* = & B! $ ( & -5T tT ' ! +, / ! 3 %? & ($ ϕ, /H : ;3 ± 3 I3 " $ ! a=x(nT),n=0,±1,±2, #* ( & ' ! ($ nECTE212 .-Long. 12/10/2003 Zhanchao Long2512/10/2003 Zhanchao Long26Electronics and CommunicationsElectronics and Communications
!# &# " & ' ! 9! ! ' &# !# &# " & ' ! 9! ! ' &#? ! & ($ > ' ' ! ( ($ Ψ: ? & ( *3 ) Gψ, /H : ;3 3 I3 J > #$ $! = & ' ! >$ ! = " * " γ(t)=ψ(t)00?A ($ ψ, / ∈Ψ ! > * " ! ! ! #> ! ( & ($ ψ, / ∈ΨH N≠ N? & 3 ( ! M: 3 3 I3 3 ! $# ' &! & ? #!= > !"B! !' $ ( " ! 6$ B! Γ ( & ' ! ($ γ, /H N : 3 I3 M ! ! !"= N#$ $! = & ' ! ($ Γ: Gγ, /H : ;3 3 I3 J ( $ "3 ) *$ %? & * ( ( " ' & Γ ( & ' ! >! ($ 6$ B! & Ψ M ) ! ! * ( k−1R(0)ψγkj & ' ! 9! γ(t)=ψ(t)−αγ(t)α=kk jjjR(0)? & #* & ' ! 9! ! '  M ) ! & !# j=1γγjj &# " & ' ! 9! * * " $ B = ECTE212 .-Long. 12/10/2003 Zhanchao Long2712/10/2003 Zhanchao Long28Electronics and CommunicationsElectronics and Communications
' ! * !
6$ = [ #! O !M? ( ) ! " ! ( 6$ ( 6$ = ! ' ( ! ' ! ? ( " & ( 6$ * ! ' ! ) " B ) ! ' ! B ! # & $ " > 6$ " $ ? !" ) #!M $ ( ! * $# * & ( 6$ = ( ! ' ! ECTE212 .-Long. 12/10/2003 Zhanchao Long2912/10/2003 Zhanchao Long30
Electronics and CommunicationsElectronics and Communications
$ ! ( #
$ ! ( # "?
$ ! ( # ,(/ ( ' ! ), / ?< * $# > ! " >= !M ' &
$ " ( " ! % ! ( #,
/ ( & ' ! +∞?
$ ! ( # ! #! & #! ! −j2pift" # ( 6$ = #* ( ! ' ! W(f)=w(t)edt −∞? ! #!** ' ( # # " #! ( 6$ = ? % " #! %–*! !# ( ( " ! frequencyDA 9 : P F
–> & '! B ! " * B ( 6$ = #* ! w(t)→W(f) > ! " ,! two-sided spectrum ( ), / > ! "/– ' ! 3 ,(/ ! complex($ ECTE212 .-Long. 12/10/2003 Zhanchao Long3112/10/2003 Zhanchao Long32Electronics and CommunicationsElectronics and Communications
' ! * !
6$ = [ #! ' ! * !
6$ = [ #! ? ' ! 3 ,(/ ! > ! #* + ($ ( ? ' ! 3 ! > 6$ #* ! " ( 6$ = ) ! * ! ! $ ! !
$ ! ( # ( ! ' ! jθ(f)W(f)=Xor as(f)+jY(f)W(f)=|W(f)|e? ! $ & ) ( $
$ ! ( # !> ?? ,(/? ! " & #!' $" * $#, N$ ? $ & !> !
$ ! ( # *! % * $#/ $ " " # & #!' $" ( #* ( ! ' ! ! ! ($ ( ( 6$ = ?θ, / ! " & *&! * $# w(t)↔W(f)? * $# ! ! = ! $ " > ! ! !** + #! ( #!' $" * $# ? ,(/? ECTE212 .-Long. 12/10/2003 Zhanchao Long3312/10/2003 Zhanchao Long34Electronics and CommunicationsElectronics and Communications
+!#* ( !
$ ! ( # !> +!#* % * $# ( ! ! ' ! ?< ! , " / ' ! ' B ! %w(t)=A?O= $ '
$ ! ( # !> ) > !
$ ! ( # ! %W(f)=δ(f)?δ,(/ ( " ! & [ ! " ! ($ ,) "$ " ! ) M/ ECTE212 .-Long. 12/10/2003 Zhanchao Long3512/10/2003 Zhanchao Long36
Electronics and CommunicationsElectronics and Communications
+!#* % * $# ( ! $ "! ' ! ! + ?
! V " ' ! " !) #!' $" * $#%?< $ "! ' ! ' B ! %? &!B %w(t)=5w(t)w(t)=Acos(2pift+θ)0?O= $ '
$ ! ( # !> ) > ! t
$ ! ( # ! %?
$ ! ( # %1jθ−jθW(f)=5δ(f)W(f)=A[eδ(f−f)+eδ(f+f)]00|W(f)|2fECTE212 .-Long. 12/10/2003 Zhanchao Long3712/10/2003 Zhanchao Long38Electronics and CommunicationsElectronics and Communications
+!#* % * $# ( ! $ "! ' ! ) " ! 6$! !B "? ! " & #!' $" * $# A w(t)) ' %1W(f)=A[δ(f−f)+δ(f+f)]002Atime|W(f)|-T-T/4T/4T0000A/2?< 6$! )!B ! > $ " >= #> ' f!** * ! $ " \ -ff00? % ? & " >= &
$ +*! –) ' ! * $#– = ) ( 6$ ! * % (! " (; ;ECTE212 .-Long. 12/10/2003 Zhanchao Long3912/10/2003 Zhanchao Long40Electronics and CommunicationsElectronics and Communications
] "$ ' ! 6$! !B ( # $ " 6$! !B ( # $ " "w(t) > B! %?< 6$! )!B ! > * "$ " ! ! #* ( A $ " ? & # & '& &! # $" " & &! * & time 6$! )!B .-T-T/4T/4T0000W(f)?O! " & !> B > B! )&! ) $ " = $ +* & * $# ( ! 6$! )!B M M ^ V( R( ((R(V(;;;;;;frequencyECTE212 .-Long. 12/10/2003 Zhanchao Long4112/10/2003 Zhanchao Long42
Electronics and CommunicationsElectronics and Communications
& # ( > ! '
$ ! ( # + % * $# ( ! 6$! !B ( ] " !B ( # ? ! &! ! 6$! )!B ' B ! %?
! * " ($ ), / ) & * " %;n=∞n=∞w(t)=h(t−nT) 0w(t)=h(t−nT) 0n=−∞?)& n=−∞ &
$ ! ( # ,(/ ' B ! %h(t)=AΠ(t/(T/2))0n=∞? )! ( " &
$ ! ( # ( ), / O$ >= W(f)=fH(nf)δ(f−nf)0 00 $ ' &
$ ! ( # !> ) ! = ( " n=−∞ &
$ ! ( # ( ! ' ! '$ ! *$ ,! " ! )!B /\\)& A,(/ &
$ ! ( # ( &, / ! " (: ; P ( " ! & ($ "!# ! ( 6$ = ; ECTE212 .-Long. 12/10/2003 Zhanchao Long4312/10/2003 Zhanchao Long44Electronics and CommunicationsElectronics and Communications
* $# ( ! 6$! !B * $# ( ! 6$! !B "? ) !** = & !> B & # & ( ) ' 6$! ? * % " (= & * " ( & )!B ! " & ;)!B % & ($ "!# ! ( 6$ = (;? : _ ;), /?(: P_ A9 ;V? * % " (= & * ! ' *$ &, / , /&, / _ _V , / ECTE212 .-Long. 12/10/2003 Zhanchao Long4512/10/2003 Zhanchao Long46Electronics and CommunicationsElectronics and Communications
* $# ( ! 6$! !B " * $# ( ! 6$! !B "? * R%
" &
$ ! ( # A,(/ ( & ? * V% $> $ A, (/ to & ( #$ ! ( ,(/; * ! ' *$ &, /n=∞sin(pifT)sin(4pif)W(f)=fH(nf)δ(f−nf)000H (f)=AT=20pifT4pifn=−∞n=∞? * S% > ! A, (/;1sin(pin/2)=20δ(f−n/8) 8pin/2n=−∞n=∞sin(4pinf)sin(pin/2)020sin(pin/2)H(nf)=20=20=δ(f−n/8)0 4pinfpin/28pin/20n=−∞ECTE212 .-Long. 12/10/2003 Zhanchao Long4712/10/2003 Zhanchao Long48
Electronics and CommunicationsElectronics and Communications
* $# ( ! 6$! !B " * $# ( ! 6$! !B "? * ` "% !>$ ! & $ ? * `% B! $! ,(/ &! ,(/ ! > 9 = ( B! $ ( (! nfW(f)|W(f)|)& & ( : ( (! ) ! ) ,(/! %;0020/8=5/25/2Wn = 0(f)=fH(0f)δ(f−0f)000±1±f=±1/8±5/pi5/pi0+fH(1f)δ(f±1f)n = ± 1000±2±2f=±2/8000+fH(2f)δ(f±2f)n = ± 2000±3±3f=±3/8±5/(3pi)5/(3pi)0+ ECTE212 .-Long. 12/10/2003 Zhanchao Long4912/10/2003 Zhanchao Long50Electronics and CommunicationsElectronics and Communications
* $# ( ! 6$! !B B * $# ( ! 6$! !B " * $# ( ! $ "? * b% ] & $ ' #!' $" * $#? #*! & * ! ( ! 6$! )!B ! " ! |W(f)| $ " –O & * ! ( VP : <P – * $# ( ! 6$! )!B &! # , ! VP : <P 6$! )!B ! #> ! ( $ " / VP,R /VP,V / V( R( ((R(V(;;;;;;frequencyECTE212 .-Long. 12/10/2003 Zhanchao Long5112/10/2003 Zhanchao Long52Electronics and CommunicationsElectronics and Communications
($ ] * (
$ ! ( # #
$ ! ( # ] * ? " # ' ' ! * ! ) ( ! &!B #!M $ (
$ ! ( # * * ? # ( & $" %– ! =– # " !=–( 6$ = ! ! ECTE212 .-Long. 12/10/2003 Zhanchao Long5312/10/2003 Zhanchao Long54
Electronics and CommunicationsElectronics and Communications
! = ! + ?
$ ! ( # ( & $# ( ) # ($ ?[ !) & #!' $" * $# ( & ( ) ' ' ! % 6$! & $# ( &
$ ! ( # ( & " B "$! ($ 33w(t)=2cos(2pi3×10t)−3cos(2pi5×10t)?
+!#* 3 !M ? ,(/?w(t)=Acos(2pift)+Bcos(2pift)12?
$ ! ( # ' B ! % V V1 W(f)=Aδ(f−f)+δ(f+f)[11]21+Bδ(f−f)+δ(f+f)[22]RRRR V× ; R× ;R× ;V× ;( DA9F2ECTE212 .-Long. 12/10/2003 Zhanchao Long5512/10/2003 Zhanchao Long56Electronics and CommunicationsElectronics and Communications
# [ != ] * = # [ != ] * = +!#* ? !M ! ' ! ), /! " " != # >= ?< $ " ), / : , pi( /";), /), /), /"t # "? ,#!' $" / * $# %? & &
$ ! ( # ( & " != " ' ! ), / "' B ,>= $ ' & !> (
$ ! ( # * * / ? ,(/?! −j2pifTdW(f)e P P )& ,(/ &
$ ! ( # ( ), / ? # " != ' ! ' ! !(( = *&! * $# ! " #!' $" * $#\ ((;;(ECTE212 .-Long. 12/10/2003 Zhanchao Long5712/10/2003 Zhanchao Long58Electronics and CommunicationsElectronics and Communications
# [ != ] * = +!#* , "/
6$ = ! ! ] * =? &! & * $# ( ! $ " " != " # ^ ? !M ! ' ! ), /! " #$ * = >= ! $ " ) & ' ), / : , pi( Q piP /;( 6$ = ( ' % w(t)w(t)cos(2pif+θ)ct? & &
$ ! ( # ( & $ ! ' ! time' B ,>= $ ' & !> (
$ ! ( # * * / ! ? #!' $" * $# !'! %1jθ−jθeW(f−f)+eW(f+f)cc[]? ,(/?2 P P )& ,(/ &
$ ! ( # ( ), / A 3 #!' $" %1|W(f−f)|+|W(f+f)|[cc] ((;;(2ECTE212 .-Long. 12/10/2003 Zhanchao Long5912/10/2003 Zhanchao Long60
Electronics and CommunicationsElectronics and Communications
6$ = ! ! ] * = +!#*
6$ = ! ! ] * = "? & #!' $" * $# ( ! $ " ), / : , pi( /;? & ( 6$ = ! ! * * = %? ,(/?($ "!# ! # "$ ! & = P P ? ) = & * * = $ $"= ( <f ! "
f # "$ ! & 6$ ( ((;;? & ! ! " % =, / : , pi( / , pi( / ;?
,(/? PS PS PS PS( ( ( (Q (( ((Q( ; ; ; ;ECTE212 .-Long. 12/10/2003 Zhanchao Long6112/10/2003 Zhanchao Long62Electronics and Communications
j$ k ## ECTE212 .-Long. 12/10/2003 Zhanchao Long63
Electronics and CommunicationsElectronics and Communications
&! ' (!) * " ! % ! " ##$ ! •+! # & ! ##$ ! , # ?/ )! & $ & # "$ ! Zhanchao Long? 3 ! 6 ! # " #! lzc12@? 3 ! 6 ! & 9$ ," #! %87540850:$ 3
$ ! & # ! " 6 6 ; ECTE212 .-Long. Zhanchao Long2Electronics and CommunicationsElectronics and Communications
3 " " ! " ? $< " " 6 ! & ( $ ?+, $ 3 !
$ ! & # ' < ! ! " $< " " ? 3 " " ! " " $< " " 6 ! 6 $#: ' < ! < ( 6 ) ! " 3! ) & 9$ , #6 ; ?
! , 6 ) & 9$ , ( ! 6 " 3 3! ) ? =!#6 & # "$ ! & 9$ , 6 ( ! #! ( #! ! ) '6 ?
# ! 3 3 6 & ) ' ' ! " ? 3 ! / = 36 ) & 9$ , ?>#6 $" / "$ ! :>/;?> ! $ A ' & 6 " " 6 ! : & 6 ) & 9$ ,; ?/ "$ ! " =? " " 6 ! ! ! 6 "$ " <, !< ! , 9$ 6# : 3 6 $# ! ! , ; ECTE212 .-Long. Zhanchao Long3Zhanchao Long4Electronics and CommunicationsElectronics and Communications
? $< " " ) 3 " " 6 ! ? $< " " ! " 3 " " 6 !?? $< " " 6 $#? " ( & ' 3 9$! '!) ': ;%|W(f)|>G w(t)>G >G:F ;2>G:B ; B& F& &&F&B&DDDDDDfrequencyt|W(f)| >G ? 3 " " 6 $#>G ? ! < ! " $< " "#!3 $" 6 $# <, >G:F ;$ 3
$ ! & # >G:B ;&F&B&DDDfrequencyECTE212 .-Long. Zhanchao Long5Zhanchao Long6
Electronics and CommunicationsElectronics and Communications
9$ , 6 ! & 6 "
9$ , 6 ! & 6 " 3 ! 3 ! =!#6 % 3 ! 3$ ! I$ ? &! ' (!) * " ! 6 " 3 ! – ( #!3 $" 6 ! & t ∏ T ? (! (!66 & ! 3 ! 6 " H–! ! =!#6 A ' " ! 3 ! 3$ ! 6$ G G # ECTE212 .-Long. Zhanchao Long7Zhanchao Long8Electronics and CommunicationsElectronics and Communications
6 $# & > 3 ! 3$ ! I$ 6 $# & > 3 ! 3$ ! I$ "?+, $ 3
$ ! & # !< ' 3 %?J ( #!3 $" 6 $# K :&;K 3 ) ! %sin(pifT)sin(pifT)W(f)=TW(f)=TpifTpifT|W(f)| FG G G G G FG & 9$ , FG G G G G FG & 9$ ,ECTE212 .-Long. Zhanchao Long9Zhanchao Long10Electronics and CommunicationsElectronics and Communications
Square Wave . Single Rectangular Pulse> ( 6 " 3 ! % 6 ( 3 ! ': ;|W(f)|>G >G >G:F ;>G:B ; B& F& &&F&B&DDDDDDfrequency|W(f)|K :&;K FG G G G G FG & 9$ ,? % ( ! 3 ! 6 " ( #!3 $" 6 $# & $ $ : * ( ! & 6 " 3 ! ; ECTE212 .-Long. Zhanchao Long11Zhanchao Long12
Electronics and CommunicationsElectronics and Communications
" ! " 3 ! 6 $# " ! " 3 ! 6 $#K :&;K? 6 ! & ! & 3 ! : 3 6 (; ! & 3$ ! ! " " && $ " < ( # #! ( #! ! , ? & ' , #6 &, ( 6 ! & $ ( & 3 ! ( $ " ! " 3 ! 6 ! K :&;K?> ## " ! " 6 $# ( ! 3$ ! 6 $# '( ( ' ' $ ( $ &ECTE212 .-Long. Zhanchao Long13Zhanchao Long14Electronics and CommunicationsElectronics and Communications
+! <! "! " +! "6! 3 ! +! <! "! " +! "6! 3 ! "? & ! &, 3 ! ' ! 3 % <! <! "?> <! "6! 3 ! (! ( & ' 3 6 ! 6 6 %! " <! "6! :" 6 " 3 ( 6 ! 6 6 ; – M ! <! " ! " ! $ " & 9$ ,?> <! <! " 3 ! (! ( & ' 3 6 ! 6 6 %f=±fwheref>>0cc–M '( – M ( ) , & & N D–M '( ?& & " ! ( ! & 9$ , ? 3 ! ! ! " ' ( ! & #! $ $ $! , ! ? =!#6 & <! "6! 3 ! ! 3 ! ! # " <, <! <! " 3 ! : 3 ) ; !" ! K :&;KK :&;K&& && ECTE212 .-Long. Zhanchao Long15Zhanchao Long16Electronics and CommunicationsElectronics and Communications
+! <! "! " +! "6! 3 ! "+! <! "! " +! "6! 3 ! "?> , 6(, ! <! "6! 3 ! ': ; ! < 6 " ?> ( 9$ )! 6 ! & ( <! "6! <,% 3 ! %jωtcw(t)=Re{g(t)e}w(t)=R(t)cosωt+θ(t)[c]?'( '( OPQ " ( ! 6! & OPQA 3: ; & " ! ( #6 = ) 6 & ': ;A ! " j∠g(t)jθ(t)g(t)=|g(t)|e=R(t)e? ( ! #6 (! %ω=2pifccReg(t)=R(t)cos[θ(t)]{}Img(t)=R(t)sin[θ(t)]{}ECTE212 .-Long. Zhanchao Long17Zhanchao Long18
Electronics and CommunicationsElectronics and Communications
+! <! "! " +! "6! 3 ! "+! <! "! " +! "6! 3 ! "? ( <! "<! 3 ! ! ! < 6 " ! %? ( '!) & # 3: ;A =: ;A ,: ;A : ;A ! "θ : ; ! ! <! <! " '!) & # w(t)=x(t)cos(ωt)−y(t)sin(ωt)cc? ( '!) & # =: ;A ,: ;A : ;A ! "θ : ; ! ! '!) & # ?'( ? : ; ! '!, 3! ) x(t)=Reg(t){}?3: ; ! A 3 ! A < ! #6 = 3 ! y(t)=Img(t){}?J # ' *% =6 : ; ! " θ: ; <, # ! & =: ; ! " ,: ; ECTE212 .-Long. Zhanchao Long19Zhanchao Long20Electronics and CommunicationsElectronics and Communications
/ "$ ! ! " ? # "$ ! ! $##! , & 6 ) " ##$ ! , #?> ( !3 & ( $<R ' * ' ( ' 6 3 ! TransmitterReceiver– # " #! :S 6 U !66 ! (;#: ; : ;#: ;# !3 3 ! # "$ ! " 3 ! # !3 3 ! –& 9$ , " #! :S 6 $# ! ! , U !66 ! (;" # "$ ! ? " $ ( ' !66 ! ( # "$ ! !* 6 ! ( !* 6 ! ( ! * ( 6 < # &# "$ ! ! " " # "$ ! ?/ "$ ! %#!66 3 & #: ; : ;?? # "$ ! %#!66 3 & : ; #: ;ECTE212 .-Long. Zhanchao Long21Zhanchao Long22Electronics and CommunicationsElectronics and Communications
/ "$ ! 6 ! & / "$ ! " 3 ! ? ( # "$ ! " 3 ! R$ ! 6 ! !66 ! & ( ? ! (! # "$ ! #6 , " #!* <! "6! 6 ! ($ ( # "$ ! " 3 ! : ; && $ & !)! !< (! <! "' " ( ! < =6 " ! % ( ) ) & 9$ , ! ! : jωt#!66 3 & ! <! <! "c 3 ! #: ; ! e(t)=Re{g(t)e}<! "6! 3 ! : ;; ? ( #6 = ) 6 3: ; ! &$ & # "$ ! " ?V (, $ & 9$ , ! ! 3 ! #: ;A ##$ ! , # Hg(t)=g[m(t)]– ) , ! $ ( !# 6 $#– ! , $ !$ ( " 6 $# ?J 3WPX 6 & # #!66 3A '( ( " # ( – #! ! ! M # "$ ! ,6 ECTE212 .-Long. Zhanchao Long23Zhanchao Long24
Electronics and CommunicationsElectronics and Communications
9$ , ! ! =!#6 + !*? " ! $ "! 3 ! =: ; " & " ! %#KY:&;K#=: ;x(t)=Acos(2pift)#mmm>G >G ## &&&## cos(2pift)?/$ 6 , =: ; <, #c? (! ( $ 3 #!3 $" 6 $#HECTE212 .-Long. Zhanchao Long25Zhanchao Long26Electronics and CommunicationsElectronics and Communications
9$ , ! ! =!#6 "
9$ , ! ! =!#6 "?/ ( " % ( & 9$ , ! ! 6 6 , & ?/ ( " % <! 3 # , (
$ ! & # :
$ ! & # !< ; 11cos(A)cos(B)=cos(A−B)+cos(A+B)22? ( $ 3 3 ! A ( # " #! A 3 ) <,%? ( $ 3 3 ! A ( # " #! A 3 ) <,%y(t)=x(t)cos(2pift)my(t)=x(t)cos(2pift)cmc? ( & A #!3 $" 6 $# 9$! %=Acos(2pift)cos(2pift)mmc11=Acos[2pi(f−f)]+Acos[2pi(f+f)]mcmmcm1122|Y(f)|=|X(f−f)|+|X(f+f)|mcmc22? ' !66 ,
$ ! & # ,: ; ECTE212 .-Long. Zhanchao Long27Zhanchao Long28Electronics and CommunicationsElectronics and Communications
9$ , ! ! =!#6 "
9$ , ! ! =!#6 ? ( $ 3 #!3 $" 6 $# %? " ! 3 ! 3 ! =: ; " & " ! & ' #': ;K :&;K##K
:&;K>G\>G\>G\>G\#### &&&#!=#!= & & & &[ && &&[& # # # #?/$ 6 , =: ;<,cos(2pift) &&#c ? (! ( $ 3 #!3 $" 6 $#HECTE212 .-Long. Zhanchao Long29Zhanchao Long30
Electronics and CommunicationsElectronics and Communications
9$ , ! ! =!#6 " ## I ) $ ' =!#6 ? ( $ 3 #!3 $" 6 $# %? =!#6 ! " =!#6 & # "$ ! ?/ "$ ! : ( ! ; N & 9$ , ! ! K
:&;K?
9$ , ! ! ! < < ! " <, #$ 6 , 3 ' 3 ! >G >G ' 66 " <! " " <! "? $ (! 6 & # $ ( #$ 6 ! ! " ! # = . & & & &[&& &&&[&& #!= #!= #!= #!=ECTE212 .-Long. Zhanchao Long31Zhanchao Long32Electronics and CommunicationsElectronics and Communications
/$ 6 ! & ' 3 ! ! & ! & / "$ ! ,6 ? ! (! ! # "$ ! " 3 ! ! < =6 " ! %jωtce(t)=Re{g(t)e}x(t)x(t)y(t)?& ! , 3 ) # "$ ! ,6 ? ( ! ) ! # "$ ! ,6 A '( ( ! < " && ! " ( <! & ( #6 = ) 6 y(t)3: ; g(t)=g[m(t)]/ = ECTE212 .-Long. Zhanchao Long33Zhanchao Long34Electronics and CommunicationsElectronics and Communications
! & ! & / "$ ! ,6 >#6 $" / "$ ! Modulation? ) %Techniques–# !3 : # "$ ! 3; 3 ! ! "Analog Modulation–$ # "$ ! " ! 3 ! : ,6 ! , ! $ ";Schemes)! , ( !#6 $" & ( ! 3 ! AmplitudeAngle! "! ' ( ( # !3 3 ! ModulationModulationDSB AMDSB SCSSBFMPMDigital ModulationSchemesECTE212 .-Long. Zhanchao Long35Zhanchao Long36
Electronics and CommunicationsElectronics and Communications
>#6 $" / "$ ! : ";>#6 $" / "$ ! : ";# !3 3 ! %?/! ( #! ! , ' ! " < ( !< ) 6 ! % km(t)e(t)=A1+cos(2pift)c
c ! 3 ! %A c '( > !#6 $" & ( ! '!) $ ! >/ 3 ! %ECTE212 .-Long. Zhanchao Long37Zhanchao Long38Electronics and CommunicationsElectronics and Communications
>#6 $" / "$ ! & 6 ( 3 ! >#6 $" / "$ ! <, ! 3 ! message signal? & ' $ ! $ " ! ! # !3 3 ! ( $ " m(t)& ( 6$ 6 $ ( ! $ " & " ! ! tone 3 ! A %m(t)=Acos(2pift)mm?>/ # "$ ! <, ! 3 ! $ %AM signalkAme(t)e(t)=A[1+cos(2pift)]cos(2pift)cmcAcECTE212 .-Long. Zhanchao Long39Zhanchao Long40Electronics and CommunicationsElectronics and Communications
>#6 $" / "$ ! <, ! 3 ! /!3 $" 6 $# & >/ 3 ! '( / !3 3 ! ! 3 ! message signal m(t)= tone signal? ' ) ( 6 < # $ 3 ! 3 # " # ( " e(t)=[A+kAcos(2pift)]cos(2pift)cmmc=Acos(2pift)+kAcos(2pift)cos(2pift)ccmmc11=Acos(2pift)+kAcos[2pi(f−f)t]+kAcos[2pi(f+f)t]ccmcmmcm22AM signale(t) FECTE212 .-Long. Zhanchao Long41Zhanchao Long42
Electronics and CommunicationsElectronics and Communications
/!3 $" 6 $# & >/ 3 ! '( /!3 $" 6 $# & >/ 3 ! & ! / !3 3 ! ! 3 ! " ! :! " " ! "; / !3 3 ! #: ;K/:&;K/!3 $" 6 $# & ( >G >G ##? ) ( 6 < # ' $ ( & 9$ , ! ! 3 ! 6 6 , &
$ ! & # &&&##e(t)=A+km(t)cos(2pift)[]cc=Acos(2pift)+km(t)cos(2pift)ccc>G K :&;K>G /!3 $" ? ( & ( #!3 $" 6 $# & : ; 3 ) <,% 6 $# & ( k>G4 k>G\k>G4 k>G\####>/ 3 ! 1|E(f)|={|δ(f−f)|+|δ(f+f)|}cc&2 & & &[ && &&[& # # # #k+|M(f−f)|+|M(f+f)|cc && 2ECTE212 .-Long. Zhanchao Long43Zhanchao Long44Electronics and CommunicationsElectronics and Communications
/!3 $" 6 $# & >/ 3 ! & ! AM Generation ! : " ! "; / !3 3 ! : ";? '! < ! %e(t)=A+m(t)cos(2pift)[c]cK/:&;K &&&#!=#!=K :&;K? ! # ' 66 " <! " " <! "V J ' ! ' #6 # $ ( ! # = H & & & &[&& &&&[&& #!= #!= #!= #!=ECTE212 .-Long. Zhanchao Long45Zhanchao Long46Electronics and CommunicationsElectronics and Communications
#6 # ! & >#6 $" #6 # ! & >#6 $" / "$ ! : ";/ "$ ! : ";? (! ! ! " ) H? ## !66 ! ( $ ! ! " ) %xoutm(t)Non-linearxxindeviceoutNon-linearFilterΣdevicexinAcos(2pift)c?
" " nonl ! " ) : 3
; ' 3 %Local2oscillatorx=a+ax+axout01in2inECTE212 .-Long. Zhanchao Long47Zhanchao Long48
Electronics and CommunicationsElectronics and Communications
#6 # ! & >#6 $" #6 # ! & >#6 $" / "$ ! : ";/ "$ ! : ";?> $# 3 (! ( ! & 9$ , 3 & ! , 3 ! (! ( #!= #$# & 9$ , #6 & $ ? 3 ( 6$ G $ 6$ (! ! & ! " # "$ ! 3 3 ! A ' ! 3 $6 ( # ( " non ! " ) ' 3 ( & ' 3 $ < 3 ( <! "' " ( & & $ A ! " ( #6 # ! & >/ # "$ ! %'( ( ' ! & $ 2x(t)=a+a[m(t)+Acos(ωt)]+a[m(t)+Acos(ωt)]out01c2c?> $ A ' ! ' %=a+am(t)+aAcos(ωt)011c2 ' & 9$ ,aA22 # 222x(t)=a++am(t)+am(t)out012+am(t)+2aAm(t)cos(ωt)+aAcos(ωt)22c2c2? "+aAcos(ωt)+2aAm(t)cos(ωt)1c2c # ? ' ' ! $ ! #6 3 # " ,%2aA2J 3( & 9$ ,12+cos(2ωt)ccos(ωt)=[1+cos(2ωt)] #cc22ECTE212 .-Long. Zhanchao Long49Zhanchao Long50Electronics and Communications
V$ ] ## ECTE212 .-Long. Zhanchao Long51
Electronics and CommunicationsElectronics and Communications
&! ' (!) * " ! % +! # & ! ##$ ! , # ! " ##$ ! / ! 3 ! # ! "
" #!
$ "!# ! 3 & 6#3 $" Zhanchao Long9 "$ ! lzc@ % 87540850ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
& this $ ! $ 69 / ! % 6#3 $" # "$ ! ( & # & : +
e(t)=[A+m(t)]cos(2pift)cc69% '! ! ( !#3 $" 6 & ( # !/ #
# "$ ! " ; / ! #= > ! ! ( 3 ' & ( # !/ / ! ! ) ( 3 ' & ( ! / !
) 3 " # ! $ ( ! ) !#3 $" & ( # !/ ! "
3 "$ " ! / ! ' $ # "$ ! " ; #
3 ' & : + F 69 / ! 9 "$ ! " ; =! $# / ! # "$ ! / / ! > " & " ! % : $< " <! " $33 " ! =: + > / ! / Amm=AcECTE212 .-Long. 2 Electronics and CommunicationsElectronics and Communications
9 ! $ / 9 "$ ! " ; 69 / & ! & 9 "$ ! " ; 9 "$ ! " ; # $ $! , ;3 " ! ! #3 !/ = / # B D & D G 66 # "$ ! > + ! ( ! $ (! ( (!3 & ( $ = ( ) 3 > & ( 69 / ! 3 " ( # !/ / ! / ! ! ? ( 69 / ! / ) <,% H ? '(! ( && ( 69 / ! & )! , / ( #!/ $" & #Ie(t)=[A+m(t)]cos(2pift)cc! " ( # "$ ! " ; A$! %∆VA−Bmm==A+BA+BECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
69 / ! & ! $ ! $ & 6#3 $" 9 "$ ! =# B D>9 "$ ! " ;# !/ / ! $< $ / ( # "$ ! " ; ( & #$ ! & #= >B6 = pi& >##69 / ! ? , " % e(t)=[A+Acos(2pift)]cos(2pift)cmmc=A[1+mcos(2pift)]cos(2pift)cmc $ ( ( & ' / 3! !# %69 / ! &B D*JK? 6B ? &B *JK # = > ' ' '! < ) = >& )! $ )! $ & # # ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
6#3 $" 9 "$ ! =# B M>6#3 $" 9 "$ ! =# B > # !/ / ! # !/ / ! #= >B6 = pi& >###= >B6 = pi& >## 69 / ! 69 / ! = > = > # # ECTE212 .-Long. !Electronics and CommunicationsElectronics and Communications
9 "$ ! " ; # N I < )! # !/ / ! #= >B6 = pi& >## ( ) 3 & ( 69 / ! ( !# (!3 ! ( # !/ / ! ? & # ≤ & # N ( ) 3 ! 3, & ( # !/ (!3 69 / ! = > # H ( $ # !/ ( 69 / ! 'IECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
) 3 : " # ! / ! ! 69 / ! $ / ! # ; ( ) 3 " ! < $ " ) ( ! # # !/ / ! & # ( 69 / ! " (! & # "$ ! " ; # ≤ ( ) 3 ## , $ " 69 !" ) & ( 69 / ! ! 3, & ( # !/ & # ≤ ' ! ) $ # !/ <, 3 & # / #3 ! " ( !3 " ) ) 3 " ( 69 / ! ( ) ; ' " 3 ! & ! ) 3 " ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
) 3 : = "> ) 3 : = "> H J ' " ' ; ! ( ) 3 & ! 69 / ! I 6 $ , $ ! 3 !* !#3 $" " O ! # ) = >#= >#= ># "$ ! " / ! # !/ # !/ / ! / ! : # "$ ! <, ) 3 " ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
) 3 $
%
& ) 3 $
%
&) 3 ! & ! 3 !* !#3 $" " %)) )) )) ) ) #! $# " " "$ '( )N )=B > $ 3$ 3 "$ " B 3 ) 3 !* & ( 69 / ! ! / " # ( $ ( ) " # !/ $ ! ' 3! & H J ' )' $ " * * & ' 'I ECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
( & ! " ) 3 ( & ! " ) 3 : : ! & # & " / (! ( $ && & A$ , ,3 ! , ' ( & ! " ( " # & & ! ' 3! & / ) ! %#!; #$# ! '!< )! $ & $ && $ $ (! & ! / ! ( #!; #$# 1! '!< )! $ & / ) <,%f=cut−off2piRC ( # ! (! < ( (! ( 2(1/m)−1 $ && & A$ , & #$ ( (! ! $ &&C≤& A$ , &! " #$ ( ! / (! ( ( /( # !/ 2piRf& A$ , &=#!;>#m1f(max)<<<<fmc2piRCECTE212 .-Long. !Electronics and CommunicationsElectronics and Communications
: # "$ ! / 69 / ! ' ( # N ) 3 $
%
& ! $ ! 3 "$ " '( # N ! $ ) 3 " ) # !/ / ! & # N = '( # "$ ! &! ? ' ! ! $ ! 3 "$ " & ! , # !< ) G> J ' ) ? ! 3 "$ " # #3 ; (! ! ) 3 " +$ ( # !/ / ! ( 69 / ! O 9 ( " & " # "$ ! $ / ! 3 "$ " ! " ( " H$ % ! ' <$ " ! " # "$ ! '( ( 9 ( " & " # "$ ! $ / ! ) 3 " ' ) ! # !/ / ! & # ! 69 ! " ( " / ! ' ( # "$ ! / ! (! GIECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
P "$ : P "$ : 3 ! ' ( ) ## = >;= >,= > 9 ; / & ! 69 / ! ' ( / ! " ! ! ! 3 ! & ( ! '!) & # $ % = pi& > x(t)=e(t)cos(2pift)c'
=A+m(t)cos(2pift)cos(2pift) #
[]ccc=Acos(2pift)cos(2pift)+m(t)cos(2pift)cos(2pift)cccccAm(t)c=[1+cos(4pift)]+[1+cos(4pift)]cc22 % ( 3 "$ " $ ! ! 3, & ( ! 12cos(ωt)=[1+cos(2ωt)]cc2ECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
P "$ : *
$
+) %
& ( $ ! #!/ $" 3 $# & ;= >%SU=&>S6Q $ , , ## - 6QR6QR 6Q " - ,% &' ( ) ##6QR6QR = >;= > & & && & #!;#!; = pi& > 633 , / ' 3! & / ) ,= >'( #!/ $" 3 $# ( ! % / ! S
=&>S6Q '
#
6Q & & && & #!;#!; ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
633 ! & P(! * " 3 69P "$ : #3 # ! 6 #% '! 3 "$ ! / ! '( ( , ( " = ( ' (> ( 69 / ! " 3 ) " ! = ( > ! / ! ! ( ) ( / ! (! (!) ( !# & A$ , ! " 3(! 69 / ! ! ( ! / ! ( 69 / ! = #$ < = > , ( " ( 69 / ! > # H J ' ! ' 3 "$ $ ( ! ( / ! I ( ! , / ! " ! 6 ! 3(! * " 3 =P > / ! (! ( !# & A$ , ! = > <$ ! # #!/ $" ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
P(! * " 3 =P > !/ " ! = >)= >)= > ' ( ) ##)= >)= >)= > ./+ )= > 6 $# (! ( (! ! & $ / & A$ , & ? '( ( # ! (! '( )= > B ( & A$ , & )= > ./+f=fo ! ! $ $ 3$ & A$ , & & ( ( ( #3 %/ ) ! % 9 ; f=f+kv(t) !/ " ! = > oo2V ' P!
ECTE212 .-Long. !
Electronics and CommunicationsElectronics and Communications
P 3 ! P 3 ! = ">v(t)=Acos(2pift+θ) 6 $# (! %inininin & ( & $ / & A$ , & ( &B & ( %v(t)=Acos(2pift+θ)oooo J ( # ; $ 3$ )= > < # % AAin0v(t)=cos(θ−θ)2in02v(t)=Acos(2pift+θ)Acos(2pift+θ)1ininin000AA P
in0AA=cos(θ)in0e # ) =cos(2pift+θ+2pift+θ)inin0022 ( #AA +$ )= > $33 " < K ($ ? ' '! in0 +cos(2pift+θ−2pift−θ)inin00θBW X 2 6& ( P
3 ! ' (!) )= > % AAin0v(t)=cos(2pif+θ−2pif−θ)2inin002ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
P 3 ! = ">P $##! ,' ( ) ##)= >)= >)= > P 3 "$ ! / ! )= > '( ( (! ( !# & A$ , ! ( # / / ! )= > = &B &> )= > P(! " && θ< ' ( # / / ! )= > ! " )= > ! ./+ !/ )= > ( ( P ! #3 * 3 3(! " && θB θ θ A$! W = ! (! ' A$ )= > B ' & B &> J )= > , ( " )= > ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
P 633 ! P 633 ! : & 69 ##$ ! ' ( ) ##)= >)= >)= > ( 69 " )= >
9 "
A$ , , ( ./+ : 3 3! / ! ? : 33 " & $ / & A$ , & &= ! & A$ ,> 6 ! $ ? '( P * ' / )= > B J ( 3(! " && θ< ' )= > ! " )= > B W X <, ( & / )= > <, W X ' ! < ! ! ( ! / ! ! A$ " ECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
P 633 ! : & 69 $##! , & 69 &! = >#= >' ( ) ## 69 / ! / ) <,% $ 3 "$ " < # %e(t)=[A+m(t)]cos(2pift)cc'
#
! " #!/ $" 3 $# %'*0 % &S =&>S: ! #1% & *''W Y ' 33 1
" <! " " <! "
2
#
& & & &[&& &&&[&& #!; #!; #!; #!;# - '*0,% &ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
$##! , & 69 &! = "> $##! , & 69 &! = ">
# ( #!/ $" 3 $# & ( 69 : +
69 ' ! " # "$ ! ( / ! / ! ' ! (! = ) ( # !/ / ! ! ( ) > $ /%
' ! # ' " <! " = ' ! " $33 >?
) 3 " & # "$ ! " ; # ≤
' ! # ( ! / !
3 "$ " & ! )! $ & # ( ,3 & 69 # "$ ! ! " " $< " <! " &$ ! =: +
> ECTE212 .-Long. ECTE212 .-Long. !Electronics and CommunicationsElectronics and Communications
$##! , & 69 &! = ">P ' & ! : +
69 / ! ( ! 3 ' & ! 69 / ! % ! # ) P=P+P+PAMcLSBUSB'( = >#= >#= ># "$ ! " / ! # !/ # !/ P 3 ' ( ! ? / ! / ! P 3 ' ( ' " <! "? + P 3 ' ( $33 " <! " : # "$ ! % + 9 "$ ! % ) 3 " & # ≤ $ / ! " ) 3 "$ " & ! , #
! / # "$ ! / / ! ? ' (!) % / # ; 222mmmP=P+P+P=P[1+]AMcccc442ECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
P ' & ! : +
69 / ! " P ' & ! : +
69 / ! " ;!#3 %
6 K # ! $ "! # "$ ! / / ! !33 " ! 9 "$ ! && , ! # !" ! / ! 69 / ! ' ( * 3 '
( 3 !/ & ( ! 3 ' & ( # "$ ! "
" ( ! 3 ' * ' / (! ( # "$ ! / " ; / ! (! ) , & #! MD (! 3 !/ & ( ! 3 ' ( ! ? ! " '(! ( 3 ' ! ( " <! "I2m(t) $ η=×100%P2AMP==7805 W1+m(t)c2m1+2'( \]N " ( # !) !/ P−PAMCP=P=100%=%LSBUSB2PAMECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
P ' & ! : +
69 / ! " $##! , & : +
= "> 6 / # "$ ! / / !
: +
' %35
" ( ! / ! ( 69 / ! ?30
$ ( ! / ! ( 69 / ! & ) 3 " 3 & # " = ( " >?25
$ ! ! , / ! " ! / ! & 3 "$ " 20 3 & # " = ( " > 15 ( # "$ ! && , & ( : +
/ ! / ' 6 / & ! 3 & ( ! # " 3 ' 10 & ! # / ( ! / ! '( ( " ! , ! , & #! Index9 "$ ! " ;ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
: $< " +! " $33 " ! $##! , & : +
= "> H ! ' #3 ) ( # "$ ! && ,? ! " : + ' / %< !< ) ( # "$ ! / / ! Ie(t)=m(t)cos(2pift)c & 3 "$ " $ " ' " " $" ( ! / ! ( 69 / ! #!/ $" 3 $# % & ( ! / ! $" " ( # ( " & S =&>S# "$ ! ! ": $< " +! " $33 " ! =: + > 69 : + A$ )! : +
' ( ( # "$ ! 33 ' ' 33 " <! " " <! " " <! " " <! " " ; #→∞ & & & &[&& &&&[&& #!; #!; #!; #!;ECTE212 .-Long. 9 "$ ! && , ^G_Modulation Efficiency
Electronics and CommunicationsElectronics and Communications
;!#3 : +
) : + # : #! , ## - # - 3,% & 9 !/ #= > B = pi& > ' ( &B D*JK # "$ ! ! ## ! = > B = pi& > ' ( &B *JK : !' ( #!/ $" 3 ! &
# - 3
#% &!> : +
69 / ! ' ( # B `
<> : + 69 / ! $"450/ # - 3 ,6! $"45"/ # - 3ECTE212 .-Long. !Electronics and CommunicationsElectronics and Communications
;!#3 $ ;!#3 $ !> : +
69 ( 3 " / #!/ $" 3 $# S =&>S %e(t)=[A+Acos(2pift)]cos(2pift)cmmc=A[1+mcos(2pift)]cos(2pift)cmcS =&>S b D b D $ ! 6B ! " #B ` J ? 6B D # ( & D D D D33e(t)=[+cos(2pi×5×10t)]cos(2pi×100×10t) D WDWD D& ^*JK_ECTE212 .-Long. Electronics and CommunicationsElectronics and Communications
;!#3 $ ! & : + 69 '! < ! %
: + ' (!) %e(t)=Acos(2pift)cos(2pift)mmc33e(t)=m(t)cos(2pift)c=cos(2pi×5×10t)cos(2pi×100×10t) " (! ' $ ! # ; % ( 3 " / #!/ $" 3 $# % S =&>S D D D D D WDWD D =
# ; #3 # ! $ W >& ^*JK_ECTE212 .-Long.
Electronics and Communications
H$ f ## ECTE212 .-Long.
Electronics and CommunicationsElectronics and Communications
&# ' # ( ) !%•*"+ #! " !# , / " / & 3
! ""# *6%– ) + ! –+ !# ! Zhanchao Long–+ ( / & 3
*6 ' Long$ #9 ! 9 ! #++ ! :& 3 ; %87540850 ' ' ECTE212 .-Long. 2Electronics and CommunicationsElectronics and Communications
/ this # / & 3 *6? ( 9 %? / & 3 *6?& " !# / & 3 *6e(t)=m(t)cos(2pift)c? ' ! 9 ! #++ ! *6 : 3 *6;? ! , ( # " < %ECTE212 .-Long. 34Electronics and CommunicationsElectronics and Communications
/ & 3 *6 < "+ 3 ! 6 !# : ; ": ;? # 1= ( , ) ! ! " < "+ " ! *6" !# # ' " ! , ( / ! # +# ! ! "+ : ;* : pi/ ; Σ?>% ( / # , "+ = ? * : pi/ ; ? , @= ( # ! ! , = 9# @ / , " !# ' - : ; ' , ! & "+ ": ;*6" !# ? / = ) / , , = " ', 9 ) @ ! // # ! @ # ! ( / A# @ "+ , ) ! ' : , ? , ( " !# , ) , " "+ #! ) @ ! / (, , / # , ' , " # ' , " " !# ! < / , + !# ! & 3 B;
' ? , # # 9 ! " !# B? , ( , , # +# : ; / , 9 ! " !# / & 3 " !# ! ' ECTE212 .-Long. 56
Electronics and CommunicationsElectronics and Communications
# & " !# / & 3 *6? , " !# ! < / 9 , " !# 9 D ? + !# ! %? , = , ' : ; ! : ; % Low pass : ;<: ;@: ;filtere(t)=A[1+km(t)]cos(2pift)1cc : pi/ ; e(t)=A[1−km(t)]cos(2pift)2ccLocaloscillator?* ! , # +# ' : ; %? , A# ( " , ( 9 , s(t)=e(t)−e(t)=2Akm(t)cos(2pift)=Am(t)cos(2pift)12ccc ' / " , & 3 *6 ' ECTE212 .-Long. 78Electronics and CommunicationsElectronics and Communications
9 ' , ' Obtaining a Coherent Carrier Signal / " & 3 *6% A# ' +from DSB-SC AM? , & 3
*6 ( #! ! , : ;I": ; : / ; ( + ' , *6 ' :( , ! "+ FG / /; , ( ! # # ! @ H + !# , ' A# ! / + !# J K*": ;JLocal Oscillator* : / ;J ! A# (3 !+
A# @ " ! ) / & ) ! ÷ ? & 3 *6 ( ! #! , , *6 , ' , " ! // # + !# <: ;<: ;<: ; M , ' (, , ( ! / + !# ' ! # (, , 9 # ! / , +# + A# ' + +. # ( < " , + / , "+ ECTE212 .-Long. 910Electronics and CommunicationsElectronics and Communications
A# ( & ) 3 !+
<: ;<: ; 3 !+ : ;<: ; A# ( / ! ) ?* , " #'' = ( , ) %?3 !+ / ( , / A# @ A# / ?N ( , ) %22x(t)=[e(t)]=[m(t)cos(2pift)]11c2x(t)=m(t)cos(4pift)2c222=m(t)cos(2pift)c1? , # <: ; ' & 3 ' ( , 2 =m(t)[1+cos(4pift)]c" !# ' ' 9 ' ' ) ' 2 , / = , ( ) / , / A# @ / 1122=m(t)+m(t)cos(4pift) ( @ + ) ' "+ #! ' , c22O ECTE212 .-Long. 1112
Electronics and CommunicationsElectronics and Communications
A# @ & ) ! 9@ " ) # *J<: ;<: ;
A# @MP<: ;<: ; M& ) ! ÷ " ) *J?* , " #'' = / ? " " "+ #! ) / , +# ' ? , / %x(t)=Acos(4pift)30cx(t)=Acos(4pift)30c( , ) %x(t)=Acos(2pift)40cECTE212 .-Long. 1314Electronics and CommunicationsElectronics and Communications
H, D ! + H, D ! + ! Low pass): ; ? D ! , +# #++ ! / A# @ filter/( , +, / θ * : pi/ Fθ;? , ) ' ): ; ! ): ; , # +# / , J ): ;P9 9 ! ( + / %): ;MLocalLow pass : ;oscillatorfilter1 v(t)=AAcos(θ)m(t)10ce 2 -90º phase 1 v(t)=AAsin(θ)m(t)20ceshift 2 * : pi/ Fθ): ;;J Low pass filter? θ " = , "+ #! / ): ; "# , ' , , / ): ; ECTE212 .-Long. 1516Electronics and CommunicationsElectronics and Communications
H, D ! + ! H, D ! + ! ? , ) ' , ' ) 9@%?3 # ): ; + + ": ;= , ! " !# ! # +# / , + !# ! v(t)=Ksin(2θ)4e? , + !# ) ' ): ; A# %M? , Q A# %211
22v(t)=AAm(t)sin(2θ) 30ce11
222 K=AAm(t) 0c22 ? , ) ' ): ; / ! ( , H
, ) ' # // M? , ! ) ' #// D + , / A# @ ! , / ' D ! /( , " +, θ + !# , ! ) ' ECTE212 .-Long. 1718
Electronics and CommunicationsElectronics and Communications
& !) ' 3 D?3 , H ! , A# ' + , ) " R ! !) ' = SJU +, "9 '# @ ? , ) , + ' != + 9 , +, D ( @ , ! " !# ! # +# + + ": ; , , ": ; ? , + 9 " / #! ' = ": ; # ! # , " ": ; N ( ) = , " ', 9 + 9 " / ! ""# ECTE212 .-Long. 1920Electronics and CommunicationsElectronics and Communications
< "+ # ?
' 9 9 !|M(f)|? ) # , ( ! ! " ' #! + #" / , " !# ' ' ": ;= & 3 *6 ' = (, , " ' ' , ) ' " ' #! '# ( ) / " ' ) ,
'# ( , , + #" ' ) /# ! " + ! I J " ! "+ #! * I J
'# = , -fmaxfmafx = ! , / A# @ / , A# KJ " ' #! + #" / DNO D , , ( ! ! " ' #! + #" / , , + ! ' " !# ! ' ! ' / ) + & 3 ' / |E(f)| "+ / , ! 9 ! , / " + ! 9
'# 9 = / , " < "#" / A# @w(t)UpperLowerLower/ / , 9 9 !Upper" <sidebandsidebandsidebandsideband "+ A ' / @ ( , " , / A# @-f-f-f-f+f-T-T/4T/4Tcmaxcmaxf-fcmaxff+ffcccmax0000/. ECTE212 .-Long. 2122Electronics and CommunicationsElectronics and Communications
# # ? , / = # ( ! / / ! , ?3@ # ' ,
# / " 9 ( / ! " ' #! + #" / , 9 9 ! ' = ! , , / "# / ,
# / " / '# + / " , / A# @ +# N:/ ; ? # = ( , ) %?
, 9 9 !" ' ' = ( , ) %sin(pifT)• , /# ! " + ! I J " JH(f)=AT• , "+ #! * I pifT• , /# ! " / A# @/I JJ NOJ• , +# ( ! , I K " −3sin(5pif×10)−3=6×10−35pif×10ECTE212 .-Long. 2324
Electronics and CommunicationsElectronics and Communications
# # ? O ' , , / "# / ,
# ? , <+ 9 # ! # , / " / + ! +# = @ ! %( ', /& V +# , / A# @ ! " ? , ) # / , / < ( ', " ' #! ' ) ∞ , 9 W(f)=fH(nf)δ(f−nf)0 00n=−∞nnf [Hz]0W(nf)∞0sin()−=1006×10δ(f−nf) 0±±=−∞±2±2000∞±3±()=δ(f−nf)±4±4000 ±5±=−∞ECTE212 .-Long. 2526Electronics and CommunicationsElectronics and Communications
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Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OFWOLLONGONGContentsLecture 14•History?Examples of Wireless Communication Systems?RegulationsWireless Communication?Trends?Cellular SystemZhanchao Long?Differences between wireless and fixed telephone networks?Historical development ofWNs?Elements of 2GWNs?Traffic routing inWNs?Call and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHistoryHistory–1895 -Guglielmo Marconi–1935 -Edwin Armstrong ?1864 James Clerk Maxwell formulated equations describing discovered that increase in demonstrates and magnetic phenomenon at the macroscopic level, transmission distance could be –The 1940s -trials and hypothesizing the existence of electromagnetic wave obtained with larger antennas, introduction (1946) of mobile invented elevated antenna telephony..structures with ground –The 1950s and 1960s -connections at both transmitter development of cellular and receiver -transmission ?Maxwell summarized the state of the electromagnetic science radiotelephonydistance of earlier by Coulomb, Gauss, Ampere, Faraday, and –1897 -Marconi gains a patent his wireless telegraph (commonly accepted birth of mobile radio communications).?1885-1887 Olivier Heaviside made Maxwell’s equations more –12 Dec. 1901 first Trans-Atlantic to practicing scientists. He simplified mathematical –The 1930s -trials of mobile complexities, and introduced vector systems using AM by police in US, and other countries(car ignition being a major problem).ECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHistoryExample -GSM?Mobile Telephony–Pre 1970s -numerous private mobile radio networks -citizen MS→ BS: 890 – 915 MHZband (CB) radio, ham operator mobile radio, portable home Frequency BandBSradiote→ MS: 935 – 960 MHZlephones, etc. -no common standards, different frequency bands from 30 MHz to 3 spacing200 kHzDuplex spacing45 MHz–First standards (around the mid 1970s) -analog mobile No. of carriers125telephony -so called first-generation systems:System bandwidth2 x 25 MHz»Nordic Mobile Telephone (NMT) -Ericsson,»Advanced Mobile Phone Services (AMPS) -AT& accessTDMADuplexing methodFDD–Second-generation systems (the late 1980s):ModulationGMSK (BT = )»Groupe Spécial Mobile (GSM) -first fully digital, pan Frame bit rate271 kbit/sEuropean cellular telephony standard, -several derivatives,»American TDMA standards .: DAMPS (IS-54), IS-136,Frame ms»IS-95 (1992) -first CDMA standard -designed to coexist with
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGExample -IS-95Regulations?Global coordination of telecommunication networks and MS→ BS: 824 – 849 MHZservices (including mobile communications) is performed by the Frequency BandBS→ MS: 869 – 894 MHZInternational Telecommunication Union (ITU).Carrier spacing1250 kHz?The ITU’s activities include coordination, development, Duplex spacing45 MHzregulation and standardization of . of carriers20?In the Regulations, the ITU divides the world into 3 Regions:System bandwidth2 x 25 MHz–Region 1:Europe, Africa, all territories of former Soviet Union, Multiple accessCDMATurkey, Mongolia, and Arab states,Duplexing methodFDD–Region 2:North and South America,ModulationQPSK/BPSK SS–Region 3:Australia, Oceania, rest of Asia not included in the Region bit Mbit/sFrame length20 msECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGRadio WavesMicrowave – GHz30 – 300 Hz10000 – 1000 – GHz3 – 30 kHz100 – 10 kmMyriametric – GHz30 – 300 kHz10 – 1 kmKilometric wavesLF300 – 3000 kHz1000 – 100 mHectometric – GHz3 – 30 MHz100 – 10 mDecametric – 36 GHz30 – 300 MHz10 – 1 mMetric – GHz300 – 3000 MHz100 – 10 cmDecimetric wavesUHFKa17 – 31 GHz3 – 30 GHz10 – 1 cmCentimetric wavesSHFQ36 – 46 GHz30 – 300 GHz10 – 1 mmMillimetric wavesEHFV46 – 56 GHz300 – 3000 GHz1 – mmSub-millimetric wavesECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGRegulationsRegulations? Chinese spectrum allocation arrangements are embodied ?The Plan is reviewed on a regular basis, in response to the into theChineseRadio-frequency Spectrum World Radiocommunication Conferences.?The Plan is intended to:?Printed copies of the“Chinese RadiofrequencySpectrum–provide a basis for management oftheradio-frequencyPlanincludingGeneral Information” canbe gotten fromspectruminChinese,fromthe Uni. library.–inform radio-communication users about various types of ?A way of managing the radio frequency spectrum used for services thatcan be operated in each frequency band, commercial purposes is Spectrum Licensingintroducedinand conditions attached to their operation,Chinesebythe Radiocommunications.–reflectChinese obligations as amember of the ITU,–provide details of the international frequency allocations agreed by the ITU for the three world regions.?Licensees have the flexibility to plan and deploy devices within their spectrum space.?Licenses are issued for a fixed term -up to 15
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGRegulations900 MHz Band Plan Diagram?Within the bounds of spectrum space and the technical coordination framework, licensees are free to operate whatever type of communications service they choose, and can change that service in response to technical improvements or user demands.?Some types of devices must be registered with the CCAbefore they can be operated.?Spectrum licenses are tradable.?Spectrum license can be aggregated or sub-divided to form new licenses.?Licensees can negotiate with others to buy or sell spectrum space or authorize the others to use their spectrum and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFuture Trends3G Systems?3G systems should support a substantially wider and enhanced ?Global communications: Anytime, Anywhere, of services with respect to those supported by 2G systems.?Mobile phones for voice, fixed lines for data.?This enhancement includes interactive multimedia services.?Internet access (medium to high rates) using mobile terminals –WAP, GPRS capability.?The enhanced services involve additional requirements on the fixed network functions necessary to support mobility.?Broadband wireless access.?Intelligent and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTransition 2G →3GTransition 2G →3G?Meeting the 3G requirements should be achieved according to IMT2000an evolution Phase 2+EDGEWCDMAExisting New or spectrumreformed?The evolution to 3G should capitalize on the investments, both kb/sin place and planned, for 2G kb/
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGIn-Home Networks -VisionBreak?Seamless ad hoc networking?PCs communicate with all digital devices?Access networks shared by all digital devicesxDSLCordlesscommunicatorInternetGatewayDisplayEnterInternet and Home InDisplay tranetentertainmentDigitalPadgatewaycablenetworkEntertainmentgatewayDigitalsatellitenetworkECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGCellular SystemsCellular SystemsCAI?The cellular telephony systems are responsible for providing BS1Mobile coverage throughout a coverage PSTNCentre (MSC)?To perform this task, an integrated network of base stations (BSs) must be deployed to provide sufficient radio coverage CAIto all mobile users.?Each BS must be connected to a central hub, referred to as BS2Voice and a mobile switching centre (MSC).data links?The MSC provides connections among the base stations and between the base stationsBSn and the public switched telephone network (PSTN).Block diagram of a mobile cellular system:?The connections between BS and mobile subscribers are CAI -Common air interfaceestablished using the protocol called common air interface PSTN -public switched telephone network(CAI).BS -base and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGWireless telephone networksWireless telephone networksLocal landline telephone network:PABX -Private Automatic Branch Exchange?In the fixed telephone network, each subscriber loop is MUX -multiplexer, (concentrator)fixed, and a twisted pair connection is provided between a subscriber and the CO, or in some cases, several subscribers Trunkare connected to the concentrator, which is connected via a CentralPSTNtrunk connection to the (CO)?The network configurations in the PSTN are virtually static. Connections may only be changed when a subscriber changes the place of residence. Such changes require reprogramming MUXat the local CO.?Fixed networks are difficult to change, and require a substantialinvestment to accommodate any new
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFirst Generation NetworkWireless telephone networks?The only fixed connections are between BSs and the BSBSMSC, and between the MSC and the →Roamer?Wireless networks are highly dynamic, with the network SS 7configuration being rearranged every time a subscriber MSC 1MSC 2moves into the coverage area of a different MSCVisitor MSC?There are several limitations to WN, like bandwidth PSTNallocation, interference, multipath propagation, Doppler HLRspread, which will be discussed -Home Location Register?Both modernPSTNsand second generationWNs use VLR -Visitor Location RegisterVLRseparate signalling channels, according to common AuC -Authentication Centrechannel SignallingSystem SS MSC DatabaseHome MSC DatabaseECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHistorical development ofWNsHistorical development ofWNs?The global cellular network is required to keep track of all ?In first generation cellular networks, the system mobile users registered in all areas throughout the network. control for each area resides in the MSC, which This allows for forwarding incoming callsto roaming users at maintains all information about mobiles, and controls any mobile handoff.?Whenactivated mobile user’s phone,which isnotinvolved in a ?The MSC performs all of the network management call, monitors the strongest control channel in the , including call handling and processing, billing, and fraud detection.?When the user roams into a new area covered by different MSC, the wireless network must register the user in the new ?The MSC is connected with PSTN via trunk and cancel its registration with the previous MSC so ?MSCs are also connected together via dedicated that calls may be routed to the roamer as it moves through signalling channels for exchange of location, validation the coverage areas of different call signalling information.?Each mobilereports its Mobile Identification Number(MIN)and Electronic Serial Number (ESN ) during brief registration ?PSTN is a separate network from the SS 7 to MSC which validates and updates the customer list within the and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGBSSBSSBTSBase Transceiver Station (BTS)BTSBTSBTSVLRBSCTRAU?BTS takes care of the BTSBTSBSSradio-related tasks and MSCprovides the connectivity BTSBTSBSSbetween the network and BTSBTSBTSthe mobile terminals via areaBTSBTSBTSBTSHLREIRsaeThe architecture of raCa second generation SMMSC arearepublic land mobile other MSC areasECTE212 PSTN
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTranscodingrate and adaptation unit Base Station Controller (BSC)(TRAU)–One of the most important –The BTSsof an area (. aspects of a mobile network size of a small city) are is the effectiveness with connected to the BSC via BSSwhich it uses the avaiBSSlable an interface calledAbis-spectrum. This is reflected BTSBTSinterface. The BSC takes BTSBTSin the number of calls that BTSBTScare of all the central BTScan be made using a certain BTSBSCBSCTRAUTRAUfunctions and the control of subsystem, referred to –One of the methods as the base station employed in 2G systems BTSBTSBTSBTSsubsystem (BSS).(. GSM) to increase bandwidthutilisationis BTSBTSBTSBTS–The BSS comprises the itself and the –Data compression is in both mobile –BSC allows for closing terminal and the TRAU. traffic within the BSS –From architectural point of without involving the , the TRAU is a part of the and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMobile Services Switching Centre(MSC)Home Location Register (HLR)?A large number ofBSCsare connected to the MSC via the A-interface. The MSC is very ?The MSC is only onesubcentersimilar to a regular digital of 2G network. Anothertelephone exchange and is subcenteris the HLR. accessed by external networks EIRMSCexactly the same way.?The major tasks of the MSC ?HLR is a repository that stores MSC areaare routing of incoming and the data of a large number of outgoing calls and the subscribers. An HLR can be assignment of user channels on regarded as a large database HLRthe administers the data of literally all (hundreds of To other MSC areas?The computational load of the ?The architectural change has thousands) subscribers of the MSC is greatly reduced allowed the data interface to the case of 1G between the BSC and the MSC systems because of the introduction of theBSCs, and to be standardized, allowing ?Every 2G PLMN requires at due to the employing of a carriers to use different least one assisted for MSC and BSC componentsECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGEquipment Identity Register (EIR)Visitor Location Register (VLR)?The VLR was introduced to EIRVLRreduce the number of inquiries to HLR about its area?In the 2G systems, like GSM, ?Like the HLR, every VLR MSCidentity of subscribers and HLRcontains subscriber data, but their mobiles are separate. only about the subscribers STo other MSC areastolen equipment can be reused roaming in the area for which by simply using any valid the VLR is responsible.(Subscriber Identity Module) SIM. Barring subscriber by the ?The geographic area of the ?This can be used to bar operator doesbarthe mobile?When the subscriber moves out VLR consists of the total area fraudulent calls and even track the VLR area, the HLR covered by thoseBTSswhich down a thief byanalysingthe requests removal of the data are related to theMSCsfor related SIM data.?There is a provision in some 2G related to that subscriber from which the VLR provides its systems (. GSM) to equip ?This is possible, because every the PLMN with an additional GSM terminal equipment database, the EIR, in which contains a unique identifier, stolen equipment is international mobile equipment identity (IMEI).ECTE212
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGCommon Air InterfaceCommon Air Interface?Communication between the base station and the ?Control channels are: mobiles is defined by a standard common air interface–used for transmission and reception of data messages (CAI) that specifies four different to call initiation and service requests,?These are:–monitored by mobiles when they do not have call in progress,–Forward voice channel(FVC) used for voice transmission from the base station to mobile.–used during handoffs.–Reverse voice channel(RVC) used for voice transmission ?FCCs also serve as beacons which continually broadcast from mobile to the of the traffic requests for all mobiles in the –Forward control channel(FCC). system.–Reverse control channel(RCC).?Supervisory and data messages are sent in a number of ways to facilitate automatic channel changes and ?Control channels are often referred to as setup handoff instructions for the mobiles during and before channels since they are mainly involved in setting up a the and moving it to an unused pair of voice and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGCall setupMobile initiated call?Idle state:–After turning the mobile phone on, it first scans the group of FCCs to determine the one of the strongest –Then, MT monitors that control channel until the signal drops below a usable level.–At this point it again scans the control channels in search of the strongest base station signal.?The control channels are defined and standardized for PSTNa given system, making typically about 5% of the total number of channels available in the systemECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMobile initiated callMobile terminating call (GSM)CallinitiationrequestsubscriberMIN&numberofcalled?The GSM user can roam nationally and even .?The number dialed to reach a mobile subscriber is called Pageforcalledmobile,ilehasaVerificationthattheMobMobile Subscriber ISDN (MSISDN), which is defined by the instructingittomoveeCvalidMIN& numbering matches own MIN ?The first few digits of the MSISDN (after a country code) with received MIN, moves usually identify the subscriber’s HLR within the home the Vspecoified voice icetransmissionchannels?An incoming mobile terminating call is directed to the Gateway MSC (GMSC). The GMSC is a switch that is able to contact the subscriber’s HLR to obtain routing information and thus contains a table linking MSISDNs to their ionVorecepticecorresponding HLRs.?GMSC is very often implemented in one of the
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMobile terminating call (GSM)Mobile terminating call (GSM)PSTNGMSCHLRPSTNMSC/VLR?Typically, the HLR stores only the SS7 address of the subscriber’s current VLR, and does not have the Mobile MSISDNStation Roaming Number (MSRN).MSISDN?The HLR has to query the subscriber’s current VLR, that temporarily allocate an MSRN from its pool for the call.?This MSRN is returned to the HLR and back to the -Gateway MSCMSISDN -Mobile Subscriber ISDNIMSI -International Mobile Subscriber -Mobile Station Roaming NumberECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMobile terminating call (GSM)Mobile terminating call (GSM)PSTNGMSCHLRPSTNMSC/VLR?The GMSC can now route the incoming call to the subscriber’s current the subscriber’s current MSC, the IMSI MSRNcorresponding to the MSRN is looked up, and the mobile is paged in its current location area.?In GSM cells are grouped into location areas. Mobile sends an updating messages when moving between location -Gateway MSCMSISDN -Mobile Subscriber ISDNIMSI -International Mobile Subscriber -Mobile Station Roaming NumberECTE212 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMobile terminating call (GSM)Questions & CommentsPSTNGMSCHLRPSTNMSC/VLRMSISDNIMSIMSISDNMSRNMSRNMSRNMSRNIMSIGMSC -Gateway MSCMSISDN -Mobile Subscriber ISDNIMSI -International Mobile Subscriber -Mobile Station Roaming NumberECTE212
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGContents•Introduction?Frequency reuse techniqueLecture 2: Cellular Concept?Channel assignment strategies?Handoff mechanisms?Interference and system capacityZhanchao LongLzc12@: -LongECTE465/ and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGIntroductionIntroduction?The frequency spectrum available for mobile communication ?A method to improve the spectral efficiency of the mobile purposes is is the cellular concept.?Demand for mobile communication services is always growing -?A cellular concept allows for replacing a single, high power much faster than the amount of frequency spectrum allocated transmitter covering a large area with many low power for these , each servicing only a small portion of the total service area.?First mobile systems were designed to achieve large coverage by using a single base station having a high powered transmitter and an antenna on a tall tower.?Each base station is allocated a portion of total number of channels available to the entire system.?No means of reusing frequencies through the system due to interference problems.?The Bell mobile system in New York City in the 1970s could support ?Neighbouring base stations are assigned different groups of only 12 simultaneous calls over a thousand square frequencies (channels), so the interference is -LongECTE465/ and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFrequency ReuseFrequency Reuse?The concept of frequency reuse significantly increases system capacity indicated by the total number of available duplex channels.?Frequency band allocated to the system is organized into a finite ?Cellular system can serve more customers compared with the case number of channels which can be reused in different geographic when the whole system area is covered by just a single base -so-called cells.?Reuse of frequency channels causes interference between those cells ?A hexagonal shape is normally proposed as a model to approximatethat use the same frequency channel -co-channel area of the actual base station.?A major task of cellular system design is to maximize capacity and to minimize the interference.?Capacity can be increased by using smaller cells and interference ABCDEdecreases by using larger cells, thus a compromise is required.?The whole coverage area of a cellular system can be usually represented by a homogeneous grid of some special applications, . design of a system in large city areas, a non-homogeneous grid is of the cellular concept by means of a seven-cell cluster. The seven groups of frequencies are labeled A through -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFrequency ReuseFrequency Reuse?If a total number of duplex channels available in the system is equal ?Because of the hexagonal geometry, the number of cells in a cluster to S, and each cell is allocated kchannels, then we have:can only take certain values, and is given by:22S = = I+ IJ + J?The group of cells utilizing the complete set of N channels is where shift parameters I and J are nonnegative to as a cluster, and the parameter N is called a cluster size.?Assuming M clusters in a system, the total number of duplex channels ABCDEwhich can be simultaneously used in the system is given by:L = MkN = ratio 1/N indicating what portion of a total number of channels in the cellular system is available to each cell is referred to as the frequency reuse = 2EFGABJ= -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFrequency ReuseChannel Assignment Strategies?Channel assignment strategies are employed to achieve the objectives ?Exampleof efficient utilization of the radio spectrum, as well as keeping the –Assuming a total of 60 MHz bandwidth is allocated to an co-channel interference within the allowed mobile cellular system which uses two 25 kHz simplex channels to provide full duplex communication, find the ?Channel assignment strategies can be classified as:number of channels available per cell, if the shift –fixed, orparameters I and J are equal to:–dynamic.»I = 1, J = 1;»I = 2, J = 1;?The choice of the particular strategy impacts the system »I = 2, J = , in particular during the handoffs.?Fixed strategies are simpler to implement, while dynamic strategies allow for better utilization of the radio -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGChannel Assignment StrategiesChannel Assignment Strategies?Fixed channel assignment strategy:?Dynamic channel assignment:–Channels are not allocated to cells permanently.–Each cell is allocated a predetermined set of voice channels.–When a call request is made, the serving BS requests a channel from MSC.–Any call attempt can be served within the cell only by the unused channels in that particular cell.–The MSC allocates then a channel to requesting cell, taking into account the likelihood of future blocking within the cell, reuse distance of the channel, and other –If all channels are occupied, the call is blocked (the subscriber cannot receive the service).channels currently in use as well as other cost functions.–Dynamic channel assignment increases the trunking –Modifications, . -borrowing strategy -a cecapability of the system, since all the available channels ll is allowed to borrow channels from a neighbouring cell if all of its own channels can be accessed from all of the already in use. The Mobile Switching Centre (MSC) supervises–It requires the MSC to collect real-time data on the this and ensures that it does not interrupt or interfere with any channel occupancy, traffic distribution, and radio signal of the calls in progress in the donor indications (RSSI) of all channels in a continuous manner. -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsHandoff Mechanisms?A handoff occurs when a mobile moves into a different cell whilea ?Threshold at which handoffs are made:call is in progress.–Optimal signal level at which to initiate the handoff needs to be ?During the handoff, the MSC automatically transfers the call to a specified by system channel belonging to the new BS.–The value of this level is derived from the value of minimum ?The handoff operation involves identifying a new BS, and allocation of usable signal strength, P, for acceptable voice quality (-the voice and control signals to channels associated with this new -usable90 dBm to -100 dBm).?Usually, handoff requests have priority over the new call initiations when allocating unused channels in a cell site.–A signal slightly stronger, P, is used as a threshold at which handoff?Handoffs must be as infrequent, and imperceptible to the user ashandoff is .–The margin, ∆= P-P, cannot be too small or too handoff min-usable?Handoffs are initiated on the basis of signal .?Unsuccessful handoffs cause calls to be dropped.»∆too small -the time for doing handoff might be insufficient,»∆too large -there may be unnecessary -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsLevel at poHandoff Mechanismsint AHandoff threshold?Improper handoff situation happens when during the Minimum acceptable signal levelhandoff (before it is completed) signal strength drops Level at point B -call terminatedbelow the minimum acceptable level. This can be due to:Time–Excessive delay by MSC in assigning the channel in the neighbouring cell, as a result of:»computational loading at MSC,»lack of an available channel in the nearby –The margin ∆is set too small for the handoff time in the handoff -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsHandoff MechanismsLevel at point ALevel at point BLevel at which handoff is made?Decisions to handoff need to include considerations whetherthe drop Minimum acceptable signal levelin the measured signal level is not due to temporary fading and that mobile is really moving away from the serving base station.?Base station monitors the signal strength for a certain period of time before a handoff is initialized. Time?The duration of measurements must be optimized to avoid unnecessary handoffs, while ensuring completion of the necessaryhandoffs before the call is length of time required to make a decision depends on the vehicle velocity.?Information about the vehicle speed can be computed from the Proper handoff situationstatistics of thereceivedslow-termfadingat thebase -LongECTE465/965 signal levelReceived signal level
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsHandoff Mechanisms?The time over which a call may be maintained within a cell ?First generation of cellular systems:without a handoff is referred to as the dwell time.–Signal strength measurements are made by the BS and supervised by the MSC.?The dwell time for a particular user depends on several factors, including: propagation conditions, interference, –Each base station constantly monitors the signal levels of all of distance between the subscriber and the BS, velocity of the its reverse voice channels to determine the distance of each mobile from the , relative movements of other objects within the cell, etc.–Another, spare receiver, referred to as a locator receiver, is used to monitor signal strength of mobiles in neighbouring cells.?All this results in the dwell time being a random variable, –The locator receiver is controlled by the MSC and is used to having a probability distribution depending on those on the basis of RSSI (Received Signal Strength ?The statistics of the dwell time are important in designing of Indicator)to determine those mobiles, which may be in a need of a handoff .–Based on RSSI from each station, the MSC decides, if and between which BSs the handoff is -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsBreak?Second generation cellular systems (TDMA):–Handoff decisions are mobile assisted (MAHO).–In MAHO, every mobile terminal measures the received power from surrounding BSs and reports the results to the servicing BS on a continuous basis.–A handoff is initiated when the power from the BS in a neighbouring cells starts to exceed the power received from the serving BS by a certain level and/or for a certain period of time.–The MAHO can be faster than in the first generation systems -the MSC is no longer involved in monitoring the signal strength.–The MAHO are specially suited for microcellular environment, where frequent handoffs are -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsHandoff Mechanisms?Comparison of handoffs in the first and second ?Second generation cellular systems (CDMA):generation systems:–In IS-95 CDMA cellular system a soft handoffcan be provided.–In this CDMA system all cells share the same SS channel, –1G systems so there is no need to assign different carrier frequency »time to make a handoff -up to 10 seconds,(different radio channel) during the handoff between BSs.»margin∆-6 to 12 dB.–When mobile terminal enters the handoff zone, the MSC may decide which version of the user’s signal is best at –2G systems (TDMA)any moment of time.»time to make a handoff -1 or 2 seconds,–It is done by a simultaneous analysis of signals from a »margin∆-between 0 dB and 6 user received at several neighbouring BSs.–This ability to select between the instantaneous received signals from several base stations is called a soft -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITYOFWOLLONGONGUNIVERSITY OF WOLLONGONGHandoff MechanismsHandoff Mechanisms?Managing handoff requests:?Microcells and ‘umbrella’ cell.–By using different antennas and different transmitted power –Handoff requests can be served in the same way as the levels it is possible to provide microcells and large, ‘umbrella’ cell originating calls -this approach results in the same at the same of terminating a call during the handoff as of –The ‘umbrella’ cell is used to minimize the number of handoffs blocking of incoming high speed users in a microcell environment (city centre).–Guard channel concept where a fraction of total available channels is reserved for servicing handoff requests -Large fewer channels are allocated to originating calls-can be ‘umbrella’ cell well incorporated into dynamic channel allocation for high traffic–Queuing of handoff requests -the tradeoff between the decreased probability of forced termination and total carried to implement because there is a finite time to successfully perform the not Small cells for guarantee the dropping probability to be reduced to speed -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity?The co-channel interference does not depend on transmission ?A large co-channel reuse ratio means that transmission power but on the ratio between distance D of a cell to the quality is high, since co-channel interference is kept low due centre of the nearest co-channel cell and the radius R of the to a reasonable spatial separation of co-channel .?Large capacity can be obtained when the cluster size, and ?This parameter is called the co-channel reuse ratio, and is correspondingly the co-channel reuse ratio is by:Q=D/R=3N?Usually, the co-channel interference can be quantified by computing the signal-to-interference ratio (SIR).-LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity?To calculate SIR, let γdenote the path loss exponent, and ?Considering only co-channel interfering cells from the first assumeγto be constant over the whole coverage area of the tier only, and assuming that all those BSs are at a distance D cellular the desired BS, the SIR can be approximated as:?In a mobile environment, γusually takes values between 2 and 4.γγγ?In addition, let all BSs transmit the same (D/R)(3N)?The SIR at mobile terminal can be estimated by:===Iiii−γ000SR=i−γ0ID ii=1where iis the number of co-channel interfering -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity?The worst-case if interference happens when the mobile is ?Examplelocated at the boundary of the cell.–Assuming that SIR required for the satisfactory voice ?The SIR for the worst-case scenario can be approximated performance on the froward channel of a cellular system, by:what is the frequency reuse factor and the corresponding cluster size for the maximum system capacity if the path loss exponent is:»(a)γ= 4,S1»(b)γ= 3,=−γ−γ−γ»(c)γ= (Q−1)+2Q+2(Q+1)Take to account that the system is fully developed, . there are 6 interfering co-channel cells in the first -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System CapacitySignal-to-Interference Ratio for Various Cluster SizesThe path loss exponent is take as equal to 4, and the number of ?Subjective tests undertaken for voice services have shown co-channel interfering cells in a fully developed system is 6, that S/I = 18 dB gives satisfactory quality.(i= 6).0?In a homogeneous hexagonal system, this SIR requires a S/I in DBcluster size of at least -?If the worst-case scenario is taken to an account, this would caserequire a 12 cell cluster a decrease in the system capacity (7/12) would not be to accommodate for the worst case situation which rarely -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity?Apart from frequency reuse, there are some other techniques –Disadvantages of sectoring:to improve system capacity. These include:»Increased number of antennas at each BS–sectoring -replacement of omnidirectional antennas at a BS by oseveral sector antennas; most commonly 3 or 6 sectors with 120»Decrease in trunking efficiency due to channel sectoring at oor 60directional antennas illuminating a certain sector. Due to the BS. The available channels in the cell must be subdivided less co-channel interferers in the first tier of a sectorized and dedicated to a specific antenna. Thus instead of a osystem (3 not 6 with 120antennas), this approachincreases the common pool of channels at the BS the channels are divided signal-to-interference ratio, and thus allows for a smaller cluster into smaller (. higher capacity).»Increase in the number of handoffs, because sectoring reduces the coverage area for a particular group of channels. Some modern BSs support sectoring by allowing 12handoffs between the sectors to be performed without 13control by the -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity?Microcell Zones:–A solution to the problem of increased handoffs when ?Cell splittingsectoring is employed, is a concept of microcell zones. –It is the a process of subdividing a congested cell into Microwavesmaller cells. or fibre link –Each smaller cell has its own BS, antenna heights are reduced, as well as the transmitted power.–Cell splitting increases the capacity of a cellular system by increasing the number of times the frequency channels Baseare –The new microcellsare added to the system in a way that preserves the frequency reuse plan.–Cell splitting allows a system to grow by replacing the Zone Selectorlarge cells with smaller cells, while not upsetting the channel allocation scheme required for maintaining the minimum co-channel reuse ratio of the microcell zones -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGInterference and System CapacityInterference and System Capacity–Each of the zone sites are connected to a single BS, and –The advantage of this approach comes from the fact that share the same radio transmitters require lower power, which leads to the increase in SIR without degradation totrunkingefficiency caused by sectoring.–As a mobile travels within the cell, it is served by the zone with the strongest signal.–The microcell zones allow for reduction in the cluster size from 7 to 3, while maintaining the 18 dB of SIR.–The antennas are placed at the outer edges of the cell.–It allows for times increase in the system capacity.–Any channel may be assigned to any zone by the base station.–Zone cell architectures are being used in many cellular and PCSs.–As a mobile travels between the zones of the same BS, it retains the channel, and the BS simply switches it between the -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGWireless LAN Infrastructure NetworkRoamingAccess Point BAccess Point BStation 6Station 1Station 2Station 5Station 6Station 1Station 2Station 5Access Point AAccess Point CAccess Point AAccess Point CStation 4Station 7Station 4Station 3Station 7Station 3?Each Station is Associated with a particular AP–Stations 1, 2, and 3 are associated with Access Point A?Mobile stations may move…–Stations 4 and 5 are associated with Access Point B–Stations 6 and 7 are associated with Access Point -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGRoamingRoamingAccess Point BAccess Point BStation 6Station 2Station 5Station 6Station 2Station 5Access Point AAccess Point CAccess Point AAccess Point CStation 1Station 4Station 7Station 3Station 4Station 7Station 3Station 1?Mobile stations may move…?Mobile stations may move…–beyond the coverage area of their Access Point–beyond the coverage area of their Access Point–but within range of another Access -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGRoamingRoaming ApproachAccess Po?Station decides that link to its current AP is poorint B?Station uses scanning function to find another APStation 6Station 2Station 5–or uses information from previous scans?Station sends ReassociationRequest to new APAccess Point AAccess Point C?If ReassociationResponse is successful –then station has roamed to the new APStation 4Station 7Station 3–else station scans for another AP?If AP accepts ReassociationRequestStation 1–AP indicates Reassociationto the Distribution System?Mobile stations may move…–Distribution System information is updated–beyond the coverage area of their Access Point–normally old AP is notified through Distribution System–but within range of another Access Point?Reassociationallows station to continue -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGScanningActive Scanning Example?Scanning required for many to Association:–finding and joining a network–finding a new AP while roamingStation sends Probe.–initializingan Independent BSS (ad hoc) network? MAC uses a common mechanism for all Point Cess Point A–single or multi channel–passive or active scanning?Passive Scanning–Find networks simply by listening for Beacons?Active Scanning–On each channel»Send a Probe, Wait for a Probe Response?Beacon or Probe Response contains information necessary to Initial connection to an Access Pointjoin new -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGActive Scanning ExampleActive Scanning ExampleSteps to Association:Steps to Association:Station sends sends Probe AAccess Point Cess PoinAPssend Probe AAccess Point Cess PointStation selects best connection to an Access PointInitial connection to an Access -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGActive Scanning ExampleActive Scanning ExampleSteps to Association:Steps to Association:Station sends sends Probe Probe AAccess Point Cess PAccAccess Point Cess Point AStation selects best selects best sends AssociationStation sends AssociationRequest to selected to selected sends connection to an Access PointInitial connection to an Access -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITYOFWOLLONGONGUNIVERSITY OF WOLLONGONGActive Scanning ExampleSummarySteps to Association:?IntroductionStation sends Probe Point Cess Point AStation selects best AP.?Frequency reuse techniqueStation sends Association–Hexagonal gridRequest to selected AP.–Cells and cell clusterAP sends AssociationResponse.–Frequency reuse factorInitial connection to an Access Point?Channel assignment strategies-ReAssociationfollows a similar process–Fixed and dynamic -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITYOFWOLLONGONGSummaryQuestions & Comments?Handoff mechanisms–General concept–Comparison between 1G and 2G systems–Soft handoff and hard handoff–Managing handoff requests?Interference and system capacity–SIR–Methods to increase SIR?Reassociation and scanning in -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGContentsLecture16•Digital Modulation Schemes–PSKZhanchao Long–QAM–MSKlzc12@–GMSKtel:-LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGIntroductionDigital Modulation Schemes?Factors influencing the choice of a modulation scheme:?A digital modulator is a device that maps digital information onto analog waveforms.–power efficiency (sometimes referred to as energy efficiency)η,often expressed as the ratio of the signal P?This is done to:energy per bit to noise power spectral density E/Nb0–minimize the effect of channelrequired at the receiver input for a certain probability of -6–minimize the energy per transmitted symbolerror (. 10),–minimize the bandwidth–bandwidth efficiency ηdescribing the ability of a Bmodulation scheme to accommodate data within the given –facilitate distinction between different ; if R is data rate, and B is the bandwidth occupied by the modulated signal, thenη=R/B bps/ -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OFWOLLONGONGDigital Modulation SchemesExamples of Modulation Schemes?Example of digital modulation schemes used in wireless communication systems:?Factors influencing the choice of a modulation scheme (ctd.):Digital Modulation–cost and complexity of mobile terminal,Schemes–performance of a modulation scheme under mobile channel impairments, like Rayleigh and Rician fading, multipath LinearCPMSpreadpropagation (resulting in time dispersion), given a Spectrumparticular implementation of the demodulator,–performance of a modulation scheme in an interference BPSKFSKFrequencyenvironment,Hopping–sensitivity to Doppler spread (due to movements of mobile terminaQPSKGMSKDirectls),Sequence–sensitivity to detection of timing jitter, caused by time-varying -LongECTE212 -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGBPSK (1)BPSK (2)?Binary Phase Shift Keying (BPSK)?The transmitted BPSK signal is either:–The phase of a constant amplitude carrier is switched 2Ebs(t)=cos(2pif+θ)0≤t<TBPSKccbTbetween two values according to the modulating data m1bfor binary +1,and mcorresponding to binary 1 and 0 or +1 and –To obtain the best error performance, the two phases are 2Eoorbseparated by (t)=cos(2pif+pi+θ)BPSKccTb–For the sinusoidal carrier of the amplitude A, the energy cper bit is given by:2Eb=−cos(2pif+θ)0≤t<TccbTb2E2bE= , which givesbcbA=cfor binary -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGBPSK (3)BPSK (4)2?The 90% of the BPSK signal energy is contained within a 1bandwidth of approximately -1-2-1001234562-201-300-40-1-20123456-50t/Tb-60Example plots for BPSKsignalling.-70-3-2-10123(f -f)TcbECTE212 -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGBPSK (5)QPSK (1)?Quaternary PSK (QPSK) sometimes referred to as ?To improve spectral performance of BPSK, it is convenient to introduce pulse shaping, and such a generalized BPSK signal QuadraturePSK, has twice the bandwidth efficiency of can be expressed as:BPSK, as 2 bits are transmitted in a single modulation symbol. 2Ebs(t)=±m(t)cos(ω+θ)BPSKccTb?To minimize the error probability, the phase of the carrier takes on 1 of 4 equally spaced values, such as 0, pi/2,pi,where the pulse m(t)is chosen to have a raised cosine 3pi/2, with each phase value corresponding to a unique pair of spectrum with the rollofffactor α= QPSK signal, for this set of phases, can be expressed (t)=2ETcos[ωt+(k−1)]≤t<Tk=1,2,3,-3-2-10123T=2Tsbt/TbECTE212 -LongECTE212 -LongECTE465/965 PSD [dB]
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGQPSK (2)QPSK (3)?The latest formula leads to the graphical representation of ?Using a simple trigonometric identity, we can write:QPSK signalss(t)=2ETcos[(k−1)]cos(ωt)QPSKsscQQ−2ETsin[(k−1)]sin(ωt)sscEs?Assuming two orthogonal basis functions:IIφ(t)=2Tcos(ωt),φ(t)=2Tsin(ωt)1sc2scare defined over the interval [0,T), then we can write ss(t) in a form:QPSKs(t)=Ecos[(k−1)]φ(t)−Esin[(k−1)]φ(t)QPSKs1s2QPSKconstellations:k=1left --the carrier phases are: 0, pi/2, pi, 3pi/2,,2,3,4right--the carrier phases are: pi/4, 3pi/4, 5pi/4, 7pi/ -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGBER for Coherent BPSK and QPSKFrom QPSK to QAM (1)?Quadrature Amplitude Modulation (QAM) is a generalization of QPSKsignalling.?Contrary to PSK, it allows for both phase and amplitude modulation.?Each modulated signal symbol is characterized by a pair of amplitude A, and phase θ, or more often as a pair kkof two amplitudes Iand -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFrom QPSK to QAM (2)From QPSK to QAM (3)?Graphical illustration of a QAM principle.?Using the previously two orthogonal basis functions, 0<t<T:sQφ(t)=2Tcos(ωt),φ(t)=2Tsin(ωt)1sc2scQkwe can represent any modulated signal symbol having an amplitudeA, and phase θ, as:kkAks(t)=Icos(ωt)−Qsin(ωt)QAMkckcIwhere:θkIkI=Acos(θ),andQ=Asin(θ)kkkkkkQ=Asin(θ)kkkI=Acos(θ)kkkECTE212 -LongECTE212 -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTypes of QAMExample?Example constellations for 8-QAM and and phase shift keying can be combined to transmit Iseveral bits per symbol ( in this case M= 4) . They all require linear amplification.?16QAM has the largest distance between points, but requires very linear amplification. 16PSK has less stringent linearity requirements, but has less spacing between constellation points, and is therefore more affected by noise.?M-aryschemes are more bandwidth efficient, but more susceptible to -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGOther Digital Phase Modulation SchemesBreak?In order to improve performance of digital modulation used in wireless communication systems, several modifications to BPSK and QPSK have been proposed, and successfully applied.?Some of these schemes are:–Differential BPSK --DBPSK–Offset QPSK --OQPSK–pi/4 QPSKECTE212 -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGDifferentialpi/4QPSKTypes of QPSKQBitPhasesequencedifference11pi/4I013pi/400-3pi/4o?Conventional QPSK has transitions through zero (ie. 180phase 10-pi/4transition) . Highly linear amplifier required.?In Offset QPSK, the transitions on the I and Q channels are ostaggered. Phase transitions are therefore limited to 90.?Inpi/4-QPSK the set of constellation points are toggled each symbol, so transitions through zero cannot occur. This scheme produces the lowest envelope variations.?All QPSK schemes require linear power -LongECTE212 -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGGeneral QAM ModulatorMSK (1)I(t)Pulse?Minimum Shift Keying (MSK) is a special type of Continuous GeneratorPhase-Frequency Shift Keying (CP-FSK), in which the peak frequency deviation is equal to the half of bit (ωt)cCarrier?MSK is equivalent to CP-FSK with a modulation index Generatorh= (2∆f)/Rs(t)DataS/P QAMFSKbΣConverterequal to . Here, 2∆f is the peak-to-peak frequency modulation index h= , corresponds to the minimum FSK-Asin(ωt)cfrequency spacing between upper and lower frequencies in PulseFSK, required for two FSK signals to be (t)GeneratorECTE212 -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGMSK (2)GMSK (1)?MSK is spectrally efficient modulation scheme, and therefore ?Gaussian Minimum Shift Keying (GMSK) is a derivative of it is attractive for wireless and mobile .?By passing the modulating NRZ data waveform through a ?In addition, MSK is:premodulation Gaussian pulse-shaping filter, the sidelobe –a constant envelope signalling,levels of the spectrum are significantly reduced, compared –characterized with good BER performance (because of the with ),–a self-synchronizing signal.?The premodulation Gaussian filtering introduces inter-symbol interference (ISI) but it is not severe for the 3-dB ?MSK can be regarded as a special form of OQPSK where the bandwidth-bit duration product (BT) of the filter not lower brectangularbasebandpulses are replaced with half-sinusoidal than .?GMSK with BT= is used in -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGGMSK (2)GMSK (3)?The GMSK filter has an impulse response given by:?In MSK , the BT is infinity and this allows the square bit 2 pipi2ln2transients to directly modulate 2 h(t)=exp−t,α=the ααB GMSK, low values of BT significant intersymbol = ( ISI) . In the , the portion of the energy αacts as ISI adjacent BT is less than , some of combating the ISI is -3-2-10123Normalized time t/TECTE212 -LongECTE212 -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGGMSK SpectraMultiple Access Techniques?Multiple access techniques are used to allow sharing of a finite amount of radio spectrum by many simultaneous users.?The major multiple access techniques:–Frequency Division Multiple Access (FDMA)–Time Division Multiple Access (TDMA)–Code Division Multiple Access (CDMA)?Other multiple access techniques:?GMSK has a main lobe times that of QPSK.–Packet Radio (PR)?GMSK generally achieves a bandwidth efficiency less than bits per second per Hz ( QPSK can be as high as bits per second per –Space Division Multiple Access (SDMA)Hz) .ECTE212 -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGFDMA -(1)FDMA -(2)ω1BPFDemodulatorm(t)1mModulator(t)1ω111ω2BPFDemodulatorm(t)2mModulatorRF(t)2ω2RF22ΣModulatorDEmodulatorωnBPFDemodulatorm(t)nm(t)ModulatornωnnnFDMA TransmitterFDMA ReceiverECTE212 -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTDMA -(1)FDMA -(3)m(t)1?The FDMA channel carries only one phone circuit at any (t)1?An idle FDMA channel cannot be used by another (t)?FDMA is usually implemented in narrowband (t)2?The symbol time is large compared to the average delay spread. Therefore, the amount of ISI is low, and little or no equalization is required.?Tight filtering is required which increases the cost of both mobile m(t)nm(t)terminal and a base of the nonlinearities, there is a problem of intermodulation interference, resulting in the adjacent-channel interference.?To limit the adjacent-channel interference to other systems, a guard band at the edges of allocated spectrum is andTiming andsynchronizationsynchronizationSimplified blockdiagram of a TDMA system ECTE212 -LongECTE212 -LongECTE465/965
Electronics and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTDMA -(2)TDMA -(3)?High synchronization overhead is required due to the burst transmission.?TDMA systems divide the radio channel into time slots, and each user is allocated a single a result, each user occupies a ?One can allocate different number of time slots to the differentcyclically repeating time , which allows for a bandwidth-on-demand services.?Efficiency of a TDMA system:?TDMA shares a single carrier frequency with several users. b ?Data transmission for users of TDMA system occurs in η=1−×100%TDMA ?Because of a discontinuous transmission, the handoff process is b t wheresimpler for a mobile unit, as it can listen to the base stations during idle time -is the total number of bits per frame,t?TDMA uses different time slots for transmission and the -is the number of overhead bits per frame, equal to:oh?Because of the transmission rates much higher than in FDMA, adaptive equalizers are usually = Nb+ Nb+Nb+ Nbohrrtptgrg?The guard time between the slots is the number of reference bursts per frame, Nis the number of rttraffic bursts per frame, bis the number of overhead bits per reference rburst, bis the number of preamble bits in each slot, bis the number of pgequivalent bits per guard time -LongECTE212 -LongECTE465/965 and CommunicationsElectronics and CommunicationsUNIVERSITY OF WOLLONGONGUNIVERSITY OF WOLLONGONGTDMA -(4)TDMA -(5) Frame Information MessageTrail Bitspreamble?Problem:–The GSM system uses 25 MHz for the forward link. The forward link is broken into 200 kHz radio channels. Slot 1Slot 2Slot 3Slot NtAssuming that each radio channel supports 8 speech channels in a TDMA way, and that there is no guard band, find the number of simultaneous users that can be active in the GSM bitsTDMA frame -LongECTE212 -LongECTE465/965 and CommunicationsUNIVERSITY OF WOLLONGONGQuestions & CommentsECTE212 -LongECTE465/965
