COMMUNICATION SYSTEMS ENGINEERING

1. COMMUNICATION SYSTEMS ENGINEERING Wayne M. Lawton Department of Mathematics National University of Singapore 2 Science Drive 2 Singapore 117543 Email matwml@nus.edu.sg Tel (65) 874-2749

2. IMAGINE A WORLD without telephone, radio, television, and internet, such was the world one century (100 years) ago ! These vufoils will describe key historical developments, systems engineering methods, some communication systems, analysis and design principles.

3. KEY HISTORICAL DEVELOPMENTS _ + 1799 Alessandro Volta invented the electric battery 1837 Samuel Morse developed the electric telegraph receiver transmitter _ + 1844 Washington-Baltimore (first) telegraph line becomes operational TUTORIAL PROBLEM 1. What can the green device be ? Discuss the limitations, in terms of speed, distance and required power of the simple telegraph system above ? What improvements are possible ?

4. KEY HISTORICAL DEVELOPMENTS Morse also developed the variable length code in which each letter of the alphabet, numeral 0-9, and 13 punctuation and special characters is represented by a sequence of dots and dashes (codeword) TUTORIAL PROBLEM 2. How are the relative frequencies of letters in English related to their Morse codeword lengths?

5. KEY HISTORICAL DEVELOPMENTS 1876 Alexander Graham Bell patents telephone 1876 Alexander Graham Bell establishes the Bell Telephone Company quality & range improved with carbon microphone and induction coil 1897 Stowger invents automatic (electromechanical) switch 1904 Fleming invents vacuum diode 1906 Lee DeForest invents vacuum triode amplifier 1915 transcontinental (US) telephone transmission 1947 Walter Brattain, John Bardeen, and William Schockly invent transistor – this enables economically feasible digital switching 1960 digital telephone switch service provided in Illinois TUTORIAL PROBLEM 2 The US had the worlds highest labor scarcity & wages in later 19 century, how did this promote invention ?

6. KEY HISTORICAL DEVELOPMENTS 1820 Oersted shows that electric current produces a magnetic field 1831 Faraday shows that moving magnet produces an electric field 1864 Maxwell predicts existence of electromagnetic radiation 1887 Hertz experimentally verifies Maxwell’s theory 1894 Oliver Lodge invents the coherer, a sensitive device for detecting radio signals, and uses it to demonstrate wireless communication over a distance of 150 yards at Oxford, England. 1895 Guglielmo Marconi demos transmission of radio signals 2km 1897 Guglielmo Marconi patents a radio telegraph system and establishes the Wireless Telegraph and Signal Company 1901 Guglielmo Marconi demos 1700 mile transmission of a radio signal from Cornwall, England to Signal Hill, Newfoundland, Canada TUTORIAL PROBLEM 3 Discuss invention versus innovation ?

7. KEY HISTORICAL DEVELOPMENTS 1920 Amplitude Modulation (AM) radio broadcast by KDKA, Pittsburg WWI Edwin Armstrong invents superheterodyne AM radio receiver and later, Frequency Modulation (FM) 1929 V. K. Zworkyin builds and demos first TV system 1933 Armstrong demonstrates first FM communications system 1936 British Broadcasting Corporation (BBC) broadcast TV in London 1941 Federal Communications Commission (FCC) authorizes US TV Recent Developments: integrated circuits (1958 Jack Kilby and Robert Noyce), laser (1958 Townes and Schawlow), satellites (1962 Telstar I), (1965 Early Bird), fiber optics, cellular telephony, wireless computers Future Developments: direct brain wave, teleportation, warp speeds

8. SYSTEMS ENGINEERING METHODS Conceptual Thinking – Modelling – Simulation - Imagination Makes extensive use of Functional Block Diagrams parts or elements – represented by boxes inputs and/or outputs – represented by arrows output signal transmitter information source and input transducer output transducer channel receiver Functional Block Diagram of a Communication System

9. COMMUNICATION SYSTEM Information source : speech produced sound, imaging devices produce pictures, text scanner or text file produces plain text, The information produced is modelled probabilistically – why ? Transducers: input transducer converts the output of the source into an electrical signal that is suitable for transmission - microphones, video camera; output transducer converts electrical signal into acoustic signals, images etc suitable for the user Transmitter: converts electrical signal into a form suitable for transmission through the physical channel or transmission device, ie in radio and TV broadcast, the FCC specifies the frequency range for each transmitting station, many voices are sent over 1 wire similarly; the conversion process is done by modulation of a sinusoidal carrier, other functions include filtering, amplification, and antenna radiation Receiver: recover transmitted electrical signal

10. MODULATION Amplitude and phase of a modulated sinusoid signal TUTORIAL PROBLEM 4. Compute s(t) as the sum of two sinusoids if a(t) = sin(Bt) and p(t) = 0

11. SAMPLING PRINCIPLE 1924 Nyquist discovers sampling principle for bandlimited signals This principle allows the modulation of a sinusoidal carriers so that digital sequences can be converted to analogue signals.

12. MAXIMUM DATA RATE 1928 Hartley computes channel capacity for bandlimited signals corrupted by white Gaussian (thermal) noise

13. REFERENCES Hartley, R. V., “Transmission of information,” Bell System Technical Journal, vol. 7, p. 535, 1928 Lawton, W., “An efficient sampling technique for sums of bandpass functions,” TDA Progress Report 42-68, Jet Propulsion Laboratory, California Institute of Technology, January 1982. S. Millman, Ed. A History of Engineering and Science in the Bell System – Communication Sciences (1925-1980) (AT&T Bell Laboratories, 1984). Nyquist, H., “Certain factors effecting telegraph speed,” Bell System Technical Journal, vol. 3, p. 324, 1924. Proakis, J. G. and Salehi, M., Communications Systems Engineering, second edition, Prentice Hall, New Jersey, 2002.