Fundamentals of Communication Systems, ELEC 360 Chapter 1 Introduction PDF

United Arab Emirates University Department of Electrical and Communication Engineering FUNDAMENTALS OF COMMUNICATION SYSTEMS, ELEC 360 Chapter 1: Introduction Lecturer Mohammed Abdel-Hafez Email : [email protected] Phone : (971) 3 7135143 Course Site: http://www.elearning.uaeu.ac.ae 1/6/2024 : M...

United Arab Emirates University Department of Electrical and Communication Engineering FUNDAMENTALS OF COMMUNICATION SYSTEMS, ELEC 360 Chapter 1: Introduction Lecturer Mohammed Abdel-Hafez Email : [email protected] Phone : (971) 3 7135143 Course Site: http://www.elearning.uaeu.ac.ae 1/6/2024 : M. A. Hafez 1 Course Information  Catalog Description: Background and overview of communication systems. Analysis and transmission of signals. Analog modulation techniques: amplitude modulation/demodulation, DSB, DSB-SC, SSB, and Phase and frequency Modulation/Demodulation. Analog communication Systems: Superheterodyne receiver, Multiplexing systems, Phase-locked loops, and Television and broadcast systems. Performance of Analog system in the presence of noise: Noise in AM receivers, noise in FM receivers. Sampling theory and Pulse Modulation: PAM, PPM, and PWM.      Instructor: Dr. Mohammed Abdel-Hafez, Office Tel: 03-7135143 Course Webpage: http://www.elearning.uaeu.ac.ae Prerequisite: ELEC 360-Signals and Systems. Office hours: F1 building, Monday, 11:00-12:00, C6 Building, Tuesday, 11:00-12:00 1/6/2024 M. A. Hafez 2 Textbook and References  Textbook: ◼  Modern Digital and Analog Communication Systems, 4th or 5th edition, B.P. Lathi, Oxford University Press, 2010/2022. References: ◼ ◼ 1/6/2024 Simon Haykin and Michael Moher, Communications Systems, 5th Edition, Wiley, 2010. Martin S Roden, Analog and Digital Communication Systems, 5th Edition, Discovery Press, 2003. M. A. Hafez 3 Course Outcomes 1. 2. 3. 4. 5. 6. Identify typical communication channels, channel attenuation and distortion effects, and noise on transmitted signals using Fourier transform and/or Fourier series. This includes identifying white noise, the signal-to-noise ratio’s effect, and its improvement on a communication system. [PLO2] Analyze ideal and practical filters, distortion (linear and nonlinear), spectral density, and correlation. [PLO2] Determine the mathematical expressions for amplitude, double sideband, single sideband, and vestigial sideband modulated signals. [PLO2] Determine the mathematical expressions for phase and frequency-modulated signals. [PLO2] Analyze the spectrum of phase and frequency-modulated signals and derive mathematical expressions for the transmission bandwidth. [PLO2] Identify different circuits and block diagrams for AM and FM modulation and demodulation. [PLO1] 1/6/2024 M. A. Hafez 4 Course Outline  Course Outline 1. 2. 3. 4. 5. 1/6/2024 Introduction to Communication Systems. Signal and Spectra analysis (Review). Transmission of signals. Amplitude modulation (AM). Angle modulation (FM/PM). M. A. Hafez 5 Grading and Exams ◼ Grading policy:      ◼ Exams’ Dates: TBA     1/6/2024 Tests (Two Tests) Midterm Final Exam Quizzes (Qnty 5) Project or Matlab Assignments 20% 20% 40% 10% 10% Test 1: Midterm: Test 2: Final Exam: M. A. Hafez 6 Chapter 1- INTRODUCTION  Chapter Outline: ◼ ◼ ◼ ◼ ◼ ◼ 1/6/2024 What is a Communication system? Brief History of Telecommunication. How do communication systems work? Block Diagram of a Communication System. Frequency allocation and propagation characteristics. Information and capacity measure. M. A. Hafez 7 What is a communication system?.    Communication describes the general information exchange (Systems, People, Media etc.) but, Telecommunication describes the communication with electronic systems. “telecommunication” from the Greek ◼ ◼  Tele-: far away, far off, at a distance Com-: with, together Modern telecommunication systems : ◼ ◼ ◼ 1/6/2024 television, radio, telephone, data Primitive (though effective) telecommunications systems smoke signals, drums, etc… What sorts of things are communicated? speech, pictures, video, data M. A. Hafez 8 What is a communication system?.   Communication systems are designed to transmit information. Communication systems Design concerns: ◼ ◼ ◼ ◼ Selection of the information–bearing waveform; Bandwidth and power of the waveform; Effect of system noise on the received information; Cost of the system. These factors will be discussed later in this course Communication systems spend the three sources for transferring information TIME 1/6/2024 FREQUENCY BAND M. A. Hafez MONEY 9 Goal of a Telecommunication System To design a telecommunication system so that the information is transmitted with as little deterioration as possible while satisfying design constraints: ◼ ◼ allowable transmittable energy allowable signal bandwidth Common signal deterioration measures: ◼ ◼ Analog System: Signal to Noise Ratio (SNR) at receiver output Digital System: Bit Error Rate (BER) (also called probability of error) 1/6/2024 M. A. Hafez 10 Brief History of Telecommunications 2020 5G networks 1/6/2024 M. A. Hafez 11 Some Examples of Communication Systems 1/6/2024 M. A. Hafez 12 Some Examples of Communication Systems 1/6/2024 M. A. Hafez 13 Digital and Analog Sources and Systems Basic Definitions:  Analog Information Source: An analog information source produces messages which are defined on a continuum. (E.g. :Microphone)  Digital Information Source: A digital information source produces a finite set of possible messages. (E.g. :Typewriter, PC keyboard) x(t) x(t) t t Analog 1/6/2024 Digital M. A. Hafez 14 Digital and Analog Sources and Systems A digital communication system transfers information from a digital source to the intended receiver. An analog communication system transfers information from an analog source to the intended receiver. A digital waveform is defined as a function of time that can have a discrete set of amplitude values. An Analog waveform is a function that has a continuous range of values. 1/6/2024 M. A. Hafez 15 Digital and Analog Sources and Systems  Specify whether a system is digital or analog by reference to the possible amplitudes of voltage (and/or current) waveforms. ◼ ◼  Analog Information Source produces values defined on a continuum e.g. human voice Digital Information Source produces a finite set of possible symbols e.g. computer keyboard Advantages and Disadvantages of Digital Communications: ◼ ◼ Advantages  privacy via data encryption  greater dynamic range possible  common channel for different data sources  better immunity to noise Disadvantages   1/6/2024 greater bandwidth requirements synchronization required M. A. Hafez 16 Deterministic and Random Waveforms A Deterministic waveform can be modeled as a completely specified function of time. s(t) 150 Amplitude w(t ) = A cos(0t + 0 ) 100 50 0 -50 -100 A Random Waveform (or stochastic waveform) cannot be modeled as a completely specified function of time and must be modeled probabilistically. -150 0 0.02 Time 0.04 0.06 n(t) 4 3 Amplitude 2 1 0 -1 -2 -3 -4 -0.01 0 0.01 Time 0.02 0.03 In this course we will focus mainly on deterministic waveforms. 1/6/2024 M. A. Hafez 17 Block Diagram of A Communication System Transmitter m(t): s(t): n(t): r(t): : 1/6/2024 Channel Receiver information message signal (prior to conditioning for transmission) produced by a source e.g. human voice. (baseband signal) signal conditioned for transmission. (bandpass signal) channel noise + interference. received signal. (bandpass signal) reconstructed received message (not necessarily the same as m(t) due to corruption in the channel). (baseband signal) M. A. Hafez 18 Block Diagram of A Communication System TRANSMITTER:    Signal compression e.g. Huffman or Arithmetic Coding (source coding) Add parity bits to aid in correcting bit errors due to channel noise (channel coding) Carrier modulation transfers the signal to a frequency band appropriate for the channel, e.g. optic fiber cable Baseband signal converted to light frequencies. Receiver Transmitter 1/6/2024 M. A. Hafez 19 Block Diagram of A Communication System Modulation Techniques:  AM (Amplitude Modulation).  FM (Frequency Modulation).  PM (Phase Modulation). 1/6/2024 M. A. Hafez 20 Block Diagram of A Communication System TRANSMITTER:   1/6/2024 The signal-processing block is used for more efficient transmission.  Examples:  In an analog system, the signal processor may be an analog low-pass filter to restrict the bandwidth of m(t).  In a hybrid system, the signal processor may be an analog-to-digital converter (ADC) to produce digital signals that represent samples of the analog input signal. The transmitter carrier circuit converts the processed Baseband signal into a frequency band (Bandpass signal) that is appropriate for the transmission medium of the channel (Modulation). M. A. Hafez 21 Block Diagram of A Communication System TRANSMITTER: ◼ Carries out signal conditioning i.e. transforms the signal to a more appropriate form for the channel. Message Signal m(t) ==> Conditioning in System ==> s(t) Transmitting Signal ◼ Examples:  Low Pass Filtering (LPF) to restrict signal bandwidth avoids wasting signal power on frequencies which will be filtered out by the channel anyway.  1/6/2024 Analog to Digital Conversion (ADC) produces a digital word which represents a sample of the analog message waveform M. A. Hafez 22 Block Diagram of A Communication System Channel: ◼ Channels represents the path in which signals travel from transmitter to receiver. Very general classification of channels are:  Wired: twistedpair, copper telephone lines, waveguides, coaxial cable fibreoptic, cable.  Wireless: air (atmosphere), vacuum (space), sea water. Receiver Transmitter 1/6/2024 M. A. Hafez 23 Block Diagram of A Communication System Channel: ◼ ◼ ◼ 1/6/2024 Channels always attenuate signals to some degree as well as add noise and, most often, interference. In general, the channel medium attenuates the signal so that the delivered information deteriorated from that of the source. The channel noise may arise from natural electrical disturbances or from artificial sources. M. A. Hafez 24 Block Diagram of A Communication System Channel: Examples of a communication channels include: A pair of wires. Coaxial cable. Fiber optics. Microwave radio link (air) 1/6/2024 M. A. Hafez 25 Block Diagram of A Communication System Channel: Channel Characteristics  Noise Sources ◼ ◼ Internal noise: noise generated by components within a communication system, such as resistors and solid-state active devices. Thermal noise, shot noise, and flicker noise External noise: noise generated from sources outside a communication system, including atmospheric, man-made, and extraterrestrial sources.    ◼ Other interferences   1/6/2024 Atmospheric noise: Impulsive noise, Below about 100MHz, Inversely proportional to frequency. Man-made noise: Ignition noise (impulsive noise), Switching noise (impulsive noise), Radio-frequency interference (RFI), Below about 100MHz, Inversely proportional to frequency Extraterrestrial noise: Solar & cosmic noise, A few megahertz to a few gigahertz Multiple transmission paths: Diffuse type: numerous reflected components, Specular type: one or two strong reflected rays. Signal degradation: Fading M. A. Hafez 26 Block Diagram of A Communication System Channel:  Types of Transmission Channels ◼ Electromagnetic-Wave Propagation Channels  Propagation modes: ▪ line-of-sight ▪ ground-wave ▪ ionospheric skip-wave ◼ Guided ElectromagneticWave Channels  ◼ Wire lines, Coaxial-cable lines, Millimeter-wave waveguide Optical Links  1/6/2024 Fiber optic cables and Infrared, laser, etc… M. A. Hafez 27 Block Diagram of A Communication System Channel: Attenuation: Is the reverse process of amplification. s(t) 1 0.5 Alpha = 0.5 0.5 0 -0.5 -1 0 0.5 1 Time 1.5 s(t) -0.5 -1 0 0.5 1 Time 1.5 Transmitted Signal s (t ) = sin(2 t ) 0 t  2 Channel X r(t) = a s(t) Amplitude 1 0 Alpha = 0.1 0 -0.5 0.5 1 Time 1 α Attenuation Factor α 2 0.5 -1 0 2 Amplitude Amplitude r(t) 1 Amplitude  1.5 2 Alpha = 0.01 0.5 0 -0.5 -1 0 0.5 1 Time 1.5 2 s (t ) =  sin(2 t ) Received Signal 0 t  2 1/6/2024 M. A. Hafez 28 Block Diagram of A Communication System Channel: Distortion: The process that changes the original shape of the Amplitude  1 0 transmitted signal. It can be 0 introduced within the transmitter, some cases it can be corrected using 0.04 Filter Output 0.2 0.4 0.6 Normalized frequency 0.8 1 1 0.5 0 0 1/6/2024 0.03 0.5 0 Distortion, however, disappears 0.02 Time 0 channel equalizers, gain and frequency control systems. 0.01 1 LPF H(f) the receiver and the channel. In when the signal is turned off. 0.5 0.01 0.02 Time 0.03 0.04 29 Distortion caused by improper filtering M. A. Hafez Block Diagram of A Communication System Channel:  Noise: It is characterized as random, unpredictable electrical signals caused by man-made and natural sources. Man-made-sources include power lines, machinery, ignition systems, other channel users, and so on; on the other hand, natural sources include atmospheric noise, thermal noise, shot noise, and so on. Noise 4 3 2 n(t) 1 0 -1 -2 -3 1/6/2024 -4 0 2 M. A. Hafez 4 time 6 8 10 30 Block Diagram of A Communication System Channel: 1.5 s(t) 1 0.5 0 Example of distortion and noise -0.5 0 0.01 0.02 Time 0.03 0.04 0.01 0.02 Time 0.03 0.04 1/6/2024 1 0 LPF H(f) -1 0 Filter Output This example shows a square-pulsetrain s(t) contaminated by noise n(t) and passed through a LPF that will Introduce distortion. r(t) 2 1 0.5 0 0 1.5 0.05 0.1 Normalized frequency 0.15 1 0.5 0 -0.5 0 0.01 0.02 Time 0.03 0.04 Random Distortion caused by improper filtering and noise M. A. Hafez 31 Block Diagram of A Communication System Receiver: The receiver takes the corrupted signal at the channel output and converts it to be a Baseband signal (Demodulation) that can be handled by the receiver’s Baseband processor. The Baseband processor cleans up this signal and delivers an estimate of the source information m(t) to the communication system output. In analog systems, the performance measure is usually taken to be the Signal-to-noise Ratio (SNR) at the receiver output. In digital systems, the measure of signal deterioration is usually taken to be the probability of bit error Pe – also called Bit Error Rate (BER) of the delivered data m(t). Receiver Transmitter 1/6/2024 M. A. Hafez 32 What makes a Communication System GOOD We can measure the “GOODNESS” of a communication system in many ways: ▪ How close is the estimate    ▪  Less B means more users can share the channel Exception: Spread Spectrum -- users use same B. How much information is transmitted?   1/6/2024 Lower power = longer battery life, less interference How much bandwidth B is required to transmit s(t)?  ▪ Better estimate = higher quality transmission Signal to Noise Ratio (SNR) for analog m(t) Bit Error Rate (BER) for digital m(t) How much power is required to transmit s(t)?  ▪ to the original signal m(t) In analog systems information is related to B of m(t). In digital systems information is expressed in bits/sec. M. A. Hafez 33 Why Digital Communication? 1/6/2024 M. A. Hafez 34 Why Digital Communication? Advantages Relatively inexpensive digital circuits may be used; Privacy is preserved by using data encryption; Data from voice, video, and data sources may be merged and transmitted over a common digital transmission system; In long-distance systems, noise dose not accumulate from repeater to repeater. Data regeneration is possible Errors in detected data may be small, even when there is a large amount of noise on the received signal; Errors may often be corrected by the use of coding. Disadvantages 1/6/2024 Generally, more bandwidth is required than that for analog systems; Synchronization is required. M. A. Hafez 35 Encoding and Decoding for Digital Communication Coding involves adding extra (redundant) bits to data to reduce or correct errors at the output of the receiver. The disadvantage of these extra bits is to increase the data rate and the bandwidth of the encoded signal. 1/6/2024 M. A. Hafez 36 Frequency Bands 1/6/2024 Regulations specify, modulation type, bandwidth, power, type of information and etc. that a user can transmit over designed frequency bands. Frequency assignments and technical standards are set internationally by International Telecommunication Union (ITU). Each nation of ITU retains sovereignty over spectral usage and standards adopted in its territory. Each nation is expected to abide by the overall frequency plan adopted by ITU. M. A. Hafez 37 Speed, Wavelength, Frequency Light speed = Wavelength x Frequency = 3 x 108 m/s = 300,000 km/s 1/6/2024 M. A. Hafez 38 Frequency Bands 1/6/2024 M. A. Hafez 39 Frequency Bands 1/6/2024 M. A. Hafez 40 Frequency Bands 1/6/2024 M. A. Hafez 41 Frequency Bands 1/6/2024 M. A. Hafez 42 Propagation of Electromagnetic Waves 1/6/2024 The propagation characteristics of electromagnetic waves used in wireless channels are highly dependent on the frequency. Based on carrier frequency EM wave propagations can be classified as: GROUND-WAVE PROPAGATION SKY-WAVE PROPAGATION Line of Sight (LOS) PROPAGATION M. A. Hafez 43 Ionized Regions Above Earth. Ionization of air is caused by Ultra Violet (UV) rays from the sun. Ionized air shows different properties at different levels (Density and pressure). Speed of the wave differs with the changing properties. Dominant regions are named as D, E, F1 and F2. 1/6/2024 M. A. Hafez 44 GROUND-WAVE PROPAGATION Dominant mode of propagation for frequencies below 2 MHz. Diffraction of the wave causes the wave to propagate along the earth’s surface. This propagation mode is used in AM Radio Broadcasting. Diffraction of waves in the “D” layer helps propagation along the earth’s surface. 1/6/2024 M. A. Hafez 45 SKY-WAVE PROPAGATION Dominant mode of propagation for EM waves in the frequency range of 2 MHz to 30 MHz. Long coverage is obtained by reflection of wave at the ionosphere and at the Earth’s boundary. This mode is used in HF band International Broadcasting (Shortwave Radio). Sky-wave propagation is caused primarily by reflection from the F layer (90 to 250 miles in altitude). 1/6/2024 M. A. Hafez 46 SKY-WAVE PROPAGATION 1/6/2024 M. A. Hafez 47 LINE-OF SIGHT (LOS) PROPAGATION Dominant mode of propagation for EM waves above 30 MHz. This mode can be used in Satellite Communications and point-to-point microwave links. The disadvantage of LOS is that the signal path has to be above the horizon and the receiver antennas need to be placed on tall towers so that they can see each other. 1/6/2024 M. A. Hafez 48 LOS Calculations Let’s assume d = Distance to the horizon; h = Antenna height... r = Effective radius of earth Where h