ANALOGUE AND DIGITAL COMMUNICATION Lecture#01

ANALOG AND DIGITAL COMMUNICATIONLecture#01-03

SanaHassan1Analog and Digital Communication Systems Spring 20151Important Notes which should be remembered throughout the semesterDiscipline: I expect you to remain disciplined in the class throughout semester. Using cell phone during lecture is highly prohibited . Strong disciplinary action will be taken in case of any violation.Attendance: Try to be on time. No one will be allowed to enter the class room after 5 min of commencement of the lecture. Please dont come to me for attendance compensation, whatsoever the reason is. Assignments: Copying assignments of others will have very serious impact on your grade. So avoid it.

2Analog and Digital Communication Systems Fall 20152Important Notes-contd..Analog and Digital Communication Systems Fall 20153I encourage you to ask the questions. Raise your hands before asking any question and speak after permission. Questions should be relevant to the topic of discussion, not from the topics which have been discussed in previous lectures or to be discussed in future.Hold your questions till end of lecture.Course ObjectiveTo acquire a mathematical understanding of Analog and Digital Communication Systems.Be able to design a practical communication system at the block diagram level under certain constraints and requirements.4Analog and Digital Communication Systems Fall 20154Books:Text book-1: Modern analog and digital communication, 4th edition, B.P.Lathi ,

5Analog and Digital Communication Systems Fall 20155Books:Text book-2: Digital Communications: Fundamentals and Applications, Bernard Sklar, Prentice Hall, 2nd ed, 2001.

6Analog and Digital Communication Systems Fall 20156Books:Reference Books:Digital Communications, Fourth Edition, J.G. Proakis,McGraw Hill, 2000.

7Analog and Digital Communication Systems Fall 20157Pre-requisite:EE-319 Probability and Random Processes.EE-223 Signals and Systems.Calculus

8Analog and Digital Communication Systems Fall 20158Course Outline: Introduction. Fourier Representation of Signals and Systems. Amplitude Modulation.Angle Modulation.Pulse Modulation: Transition from Analog to Digital Communications.Signals and Noise (Random processes)Baseband Data Transmission and detection. Digital Band-Pass Modulation Techniques and detection.9Analog and Digital Communication Systems Fall 20159Grading Policy (tentative):Analog and Digital Communication Systems Fall 201510Assigments and Quizes: 15%Sessional-I: 15%Sessional-II: 15%Class Participation: 5%Final Exam: 50% 10Analog and Digital Communication Systems Fall 201511Let us Start!!What is Communication??

Communication by electrical signals. Other ways? Torches. What about winks!!

Communication technology is alleviating the economic crisis. How? Teleconferencing.11Analog and Digital Communication Systems Fall 201512Examples of Communication Systems

12Analog and Digital Communication Systems Spring 201513Communication SystemsInput Transducer: Non Electrical signal converted into Electrical Waveform (Baseband)Transmitter: Modifies baseband signal for efficient transmissionChannel: medium-coaxial cable, optical fiber, wirelessReceiver: undoing signal modifications made at the transmitter and the channelsOutput Transducer: Converts Electrical Signal to its original form-the message

1314Signal Distortion

attenuation

noise

distortion14Analog and Digital Communication Systems Fall 201515Signal DistortionChannel acts as a filterDistortion because of various phase shifts- linear distortionDistortion that varies with the signal amplitudes is non- linear,caused through attenuationBoth can be partly corrected by an equalizer15Analog and Digital Communication Systems Fall 201516NoiseNoise is one of the basic factors that sets limit on the communication. It is a random signalExternal Noise-Signal traveling on near by channels Internal Noise-thermal motion of the electronsThe former can be reduced or eliminated but the later can only be reduced and never eliminated16Analog and Digital Communication Systems Fall 201517Signal-to-Noise RatioRatio of Signal power to noise powerThe SNR is continuously decreasing along the length of channel. Why? Accumulation of noiseAmplification of received signal to make up for the attenuation is of no avail because noise will be amplified in the same proportion17Analog and Digital Communication Systems Fall 201518Bandwidth

Analog and Digital Communication Systems Fall 201519The bandwidth of a signal is the difference between thehighest and the lowest frequencies contained in that signal.

Note19Analog and Digital Communication Systems Fall 201520Contd.The bandwidth of channel is range of frequencies that it can transmit with reasonable reliability.If a channel can transmit with reasonable reliability, a signal whose frequencies components occupy a range from 0 to 5000 Hz, channel bandwidth is 5000 or 5 KHz.20Analog and Digital Communication Systems Spring 201521Classification of SignalsContinuous-Time & Discrete-Time Signals

21Analog and Digital Communication Systems Spring 201522Analog & Digital Signals

22Analog and Digital Communication Systems Fall 201523Deterministic & Random SignalsA signal whose physical description is known completely, in either a mathematical form or a graphical form is deterministic signal. If a signal is known only in terms of probabilistic description, such as mean value, mean squared value and so on, rather than its complete mathematical or graphical description, is a random signal. Most of the message & noise signals encountered in practice are random signals. 23Analog and Digital Communication Systems Fall 201524Two parameters are considered to design a communication system to achieve certain data rate R.Channel Bandwidth Transmission Power24Analog and Digital Communication Systems Fall 201525Analog-to-Digital Conversion (ADC)

Analog and Digital Communication Systems Fall 201526Contd

Sampling

Quantization26Analog and Digital Communication Systems Fall 201527ADC Conversion

27Analog and Digital Communication Systems Fall 201528ADC Conversion

Analog and Digital Communication Systems Fall 201529ADC ConversionIn 16 ary case (PAM) 16 distinct waveforms are required (+/- A/2, +/- 3A/2,)Each of the two wave forms separated by A to guard against the noise and distortionIn pulse code modulation (PCM),also known as binary communication, two basic pulses +/- A/2 are used.So to transmit each sample, 4 binary pulses are transmitted. a sequence of four such pulses gives 16 patterns29ADC ConversionAnalog and Digital Communication Systems Fall 201530Bandwidth Comparison between PCM and PAMIn binary case, however, we need to transmit four pulses in each sampling interval Ts (the time required to transmit one sample) instead of just one pulse required in 16 ary case.Thus the required channel bandwidth in binary case (PCM) is four times as great that of 16 ary case (PAM). ADC ConversionAnalog and Digital Communication Systems Fall 201531Transmission Power Comparison between PCM and PAMIn 16 ary case, the peak amplitude of the transmitted pulses is 15A/2.In binary ary case, the peak amplitude of the transmitted pulses is A/2. Thus transmitted power is considerably reduced in PCM than that of 16 ary case (PAM)ADC ConversionAnalog and Digital Communication Systems Fall 201532Comparison between PCM and PAMIn 16 ary case (PAM), to achieve certain data rate R we need less channel bandwidth and more transmission power.In binary ary case(PCM), to achieve certain data rate R we need more channel bandwidth and less transmission power.Hence to achieve certain data R, if we decrease channel bandwidth, we have to increase transmission power and vice versa.Analog and Digital Communication Systems Fall 201533Two primary resources are the channel bandwidth and transmitted power.In a given scenario one resource may be more valuable to other and communication system should be designed accordingly.Satellite communication (Less power, more bandwidth)Telephone (more power, less bandwidth) Analog and Digital Communication Systems Fall 201534

Analog and Digital Communication Systems Fall 201535ExampleWe can calculate the theoretical highest bit rate of a regular telephone line. A telephone line normally has a bandwidth of 3KHz. The signal-to-noise ratio is usually 3162. For this channel the capacity is calculated asC = B log2 (1 + SNR) = 3000 log2 (1 + 3162) = 3000 log2 (3163)C = 3000 11.62 = 34,860 bpsAnalog and Digital Communication Systems Fall 201536Signals & Systems

Signals: A signal as the term implies, is a set of information or data. Signals are generally functions of the independent variable time.Systems: Signals may be processed further by systems, which may modify them or extract additional information for them.Signal Energy

Signal PowerAnalog and Digital Communication Systems Fall 201537

37Analog and Digital Communication Systems Fall 201538Question??Is there any signal for which neither the energy nor the power exists?

YESRamp SignalAnalog and Digital Communication Systems Fall 201539Example 2.1Determine the suitable measures of the signals in Fig 2.3

39Analog and Digital Communication Systems Spring 20154040

Unit Impulse Function

Multiplication of a Function by an ImpulseTall, narrow rect pulseSince impulse exists only at t=0 and the value phi (t) at t=0 is phi (0)4040Analog and Digital Communication Systems Spring 20154141

4141Analog and Digital Communication Systems Fall 201542Time Scaling

Fig 2.8 Time scaling a signal

42Analog and Digital Communication Systems Fall 201543Example

43Analog and Digital Communication Systems Fall 201544

Example 2.3 Figure 2.10a and b shows the signals g(t) and z(t), respectively, Sketch: (a) g(3t); (b) z(t/2).44Analog and Digital Communication Systems Fall 201545

Fig 2.11 Time inversion (reflection) of a signalTime Inversion (Time Reversal)

2.1645Analog and Digital Communication Systems Fall 201546

Example 2.446Analog and Digital Communication Systems Fall 201547Combinations of OperationsEasier to Determine the final signal in stagesCreate intermediary signals in which one operation is performedy(t) = g(-2t-1) V1(t) = g(t-1) Time shifting V2(t) = V1(2t) = g(2t-1) Time Scaling y(t) = V2(-t) = g(-2t-1) Time Inversion47Analog and Digital Communication Systems Fall 201548

48