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Telecommunications: Past, Present and Future

Telecommunications: Past, Present and Future. Branimir Vojcic ECE Dept, GWU. Outline. Why is telecommunications important? History of telecommunications What is the state-of-the art? What can we expect in the future?. Telecommunications versus Society/Economy. Service Economy. Knowledge

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Telecommunications: Past, Present and Future

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  1. Telecommunications: Past, Present and Future Branimir Vojcic ECE Dept, GWU

  2. Outline • Why is telecommunications important? • History of telecommunications • What is the state-of-the art? • What can we expect in the future?

  3. Telecommunications versus Society/Economy Service Economy Knowledge Economy Manufacturing Economy

  4. Ancient Communications Systems • Pigeons • Messengers • Optical signals using mirrors and light sources • Smoke signals • …

  5. History of Modern Communications (1) • 1837: The telegraph was invented by Samuel Morse (telegraph = distance writing) which marks the beginning of electrical communications; Morse code consists of a dot, a dash, a letter space and a word space • 1864: James Clerk Maxwel formulated the electromagnetic theory of light and predicted the existence of radio waves

  6. History of Modern Communications (2) • 1875: Emile Baudot invented telegraphic code for teletypewritters; each code word consists of 5 mark/space symbols (1/0 in today’s terminology) • 1875: Alexander Graham Bell invented the telephone for real-time speech transmission (the first step-by-step switch was invented in 1897 by Strowger)

  7. History of Modern Communications (3) • 1887: Heinrich Hertz demonstated the existence of radio waves • 1894: Oliver Lodge demonstrated radio communication over short distance (150 yards) • 1901: Guglielmo Marconi received in Newfoundland a radio signal that originated in England (1700 miles)

  8. History of Modern Communications (4) • 1904: John Ambrose Fleming invented the vacuum-tube diode • 1906; Lee de Forest invented the vacuum-tube triode • 1918: Edwin Armstrong invented the superheterodyne radio receiver • 1928: First all-electronic television demonstrated by Philo Farnsworth (and then in 1929 by Vladimir Zworykin) and by 1939 BBC had commercial TV broadcasting

  9. History of Modern Communications (5) • 1937: Alec Reeves invented pulse-code modulation (PCM) for digital encoding of speech signals • 1943: D.O. North invented the matched filter for optimum detection of signals in additive white noise • 1946: The idea of Automatic Repeat-Request (ARQ) was published by van Duuren

  10. History of Modern Communications (6) • 1947: Kotel’nikov developed the geometric representation of signals • 1948: Claude Shannon published “A Mathematical Theory of Communication” • 1948: The transistor was invented in Bell Labs by Walter Brattain, John Bardeen and William Shockley • 1950: Golay and Hamming proposed first non-trivial error correcting codes

  11. History of Modern Communications (7) • 1957: Soviet Union launched Sputnik I for transmission of telemetry signals (satellite communications originally proposed by Arthur Clark in 1945 and John Pierce in 1955) • 1958: The first silicon IC was made by Robert Noyce • 1959: The Laser (Light Amplification by Stimulated Emission of Radiation) was invented

  12. History of Modern Communications (8) • 1960: The first commercial telephone system with digital switching • 1965: Robert Lucky invented adaptive equalization • 1966: Kao and Hockham of Stanford Telephone Laboratories (UK) proposed fiber-optic communications • 1967: Viterbi Algorithm for max. likelihood decoding of convolutional codes

  13. History of Modern Communications (9) • 1971: ARPANET was put into service • 1982: Ungerboeck invented trellis coded modulation • 1993: Turbo codes introduced by Berrou, Glavieux and Thitimajshima • What’s next?

  14. Communication Systems An Overview

  15. Communication Systems

  16. INPUT MESSAGE INPUT SIGNAL TRANSMITTED SIGNAL INPUT TRANSDUCER TRANSMITTER OUTPUT TRANSDUCER RECEIVER OUTPUT MESSAGE OUTPUT SIGNAL RECEIVED SIGNAL Model of Communication Systems COMMUNICATION USING ELECTRICAL AND OPTICAL SIGNALS IS: • Fast • Far reaching • Economical DISTORTION NOISE INTERFERENCE CHANNEL

  17. 1 0 1 1 0 1 t Carried Information The input messages can be: • SPEECH • MUSIC • PICTURES • VIDEO • COMPUTER DATA INPUT MESSAGES ARE TRANSDUCED TO ELECTRICAL OR OPTICAL SIGNALS IF NECESSARY

  18. Physical Media EXAMPLES OF COMMUNICATION CHANNELS ARE: • WIRE Communication channels are physical media through which signals propogate. • COAXIAL CABLE • WAVEGUIDE • OPTICAL FIBER • RADIO LINK

  19. Communication Channel Communication channel introduces: DISTORTION NOISE INTERFERENCE

  20. AMPLITUDE MODULATED WAVE • FREQUENCY MODULATED WAVE Modulation • Modulation is the process that modifies the input signal into a form appropriate for transmission over a communication channel (transmitted signal) • Typically, the modulation involves varying some parameters of a carrier wave in accordance with the input signal: • CARRIER • INPUT SIGNAL

  21. +Δ -Δ Modulation Type • Receiver recovers the input signal from the received signal. • Modulation can be: • ANALOG (Parameter changes of the transmitted signal directly follow changes of the input signal) • DIGIGAL (Parameter changes of the transmitted signal represent discrete-time finite-precision measurements of the input signal) • Primary communication system design considerations: Transmitted power, Channel bandwidth and Fidelity of output message • Digital communication systems are more efficient and reliable ANALOG MODULATION DIGITAL MODULATION

  22. Optical Networks

  23. Why Optical Transmission? • Immune to electrical interference • No radiation • Low attenuation, long transmission distance • Less bulky than cables • Tremendous capacity • High data rates • Less maintenance cost coaxial transmission generally has a bandwidth limit of 500 MHz. Current fiber optic systems have not even begun to utilize the enormous potential bandwidth that is possible.

  24. Attenuation vs. Frequency

  25. Attenuation vs. Wavelength

  26. Attenuation and Dispersion

  27. Multiplexing

  28. TDM vs. WDM TDM WDM

  29. Relationship Between WDM & TDM

  30. Optical Devices

  31. Optical Networks Market ($Millions)

  32. Wireless Networks

  33. Wireless is Growing Rapidly Source: The Economist Sept. 18-24, 1999

  34. Traffic Increasingly Consists of Data Source:http://www.qualcomm.com

  35. Mobile/Cellular Communications Mobile Station Base Station

  36. F2 F7 F3 F2 F1 F7 F3 F6 F4 F1 F5 F6 F4 F5 Cellular Concept • Every cell corresponds to the service area of one Base Station • Each frequency can be reused in a sufficiently distant cell

  37. PDN BSC BTS MS MSC HLR, VLR AUC OMC ISDN BSC PSTN BTS Network Architecture Public Networks Network Switching Subsystem Base Station Subsystem

  38. Ad-Hoc Mobile Internet

  39. Satellite Communications Un-tethered, Global, Broadband, Mobile and Ubiquitous.

  40. Wireless Mobility Satellite Regional Area Emerging Connectivity Solutions: Cellular, Satellite, Microwave, and Packet Radio Wide Area Local Area SOURCE: CISCO

  41. Satellite Features • New Wideband Frequency Allocations • Global Access • Rapid Deployment • User Mobility • Multicasting, Broadcasting • Bypass and/or Serve Terrestrial Disaster • High Startup Costs, Lower Incremental Cost

  42. Existing Systems • Global and Regional Trunking • Direct TV Broadcast • VSAT Networks • Mobile Satellite Systems (MSS) • Paging • Aeronautical/ Maritime • Global Positioning (GPS and GLONASS)

  43. Iridium 66 Polar Orbits with spot beams

  44. Local Area Networks

  45. Local Area Networks (1) • A local Area Network provides the interconnection of a heterogeneous population of mainframes, work stations,personal computers, servers, intelligent terminals and peripherals. • Topologically, LAN’s connect the devices or stations in the form of a bus, a tree, a ring or a star configuration. • Wireline (Token Ring, Ethernet) • Wireless (802.11, Bluetooth, UWB,…)

  46. Wireless Local Area Networks Source: Proxim

  47. Portal Distribution System Local Area Networks 802.11 LAN 802.x LAN STA1 BSS1 Access Point Access Point ESS BSS2 STA2 STA3 802.11 LAN

  48. Bluetooth

  49. LAN Applications • Client-Server communications • Shared database access • Word processing, Electronic mail • Sharing of mass storage devices, printers and other peripherals, software and computational resources • Data exchange between computers and mass storage devices • CAD/CAM, Inventory control, Process control, Device control

  50. A Lesson From the Past “Well Informed people know it is impossible to transmit the voice over wires and that, were it possible to do so, the thing would be of no practical value” Excerpt from an 1865 BOSTON POST editorial

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