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

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

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

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)

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)

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

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

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

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

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

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?

Communication Systems An Overview

Communication Systems

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

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

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

Communication channel introduces: DISTORTION NOISE INTERFERENCE Communication Channel

 CARRIER  INPUT SIGNAL  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:

 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 +Δ+Δ -Δ-Δ Modulation Type

Optical Networks

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.

Attenuation vs. Frequency

Attenuation vs. Wavelength

Attenuation and Dispersion

Multiplexing

TDM vs. WDM TDM WDM

Relationship Between WDM & TDM

Optical Devices

Optical Networks Market ($Millions)

Wireless Networks

Wireless is Growing Rapidly Source: The Economist Sept , 1999

Traffic Increasingly Consists of Data Source:

Mobile/Cellular Communications Mobile Station Base Station

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

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

Ad-Hoc Mobile Internet

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

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

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

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

Iridium 66 Polar Orbits with spot beams

Local Area Networks

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,…)

Wireless Local Area Networks Source: Proxim

Local Area Networks Distribution System Portal 802.x LAN Access Point LAN BSS LAN BSS 1 Access Point STA 1 STA 2 STA 3 ESS

Bluetooth

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

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