Digital CommunicationsDr. Ghazi Al Sukkaremail: ghazi.alsukkar@ju.edu.jowebpage: www2.ju.edu.jo/sites/acadimic/ghazi.alsukkar

COMMUNICATIONS2 (EE422)

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Course Information:Instructor: Dr. Ghazi Al Sukkar.

Email: ghazi.alsukkar@ju.edu.joOffice: E315Website: www2.ju.edu.jo/sites/acadimic/ghazi.alsukkar Office Hours: See website.

Prerequisites: EE421Textbook: Modern Digital and Analog communication Systems, fourth edition, by: B.P. Lathi and Zhi Ding, fourth edition, 2009. Readings:

Probability and Random Variables (Ch8 and Ch9) “first and second quizz”Dr. Hawa handouts:

Line coding (first exam). Digital Modulation Techniques (second exam).

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Course Syllabus: Introduction: history of telecommunicatios.Baseband Digital Systems:

Line coding Pulse shapping and ISI

Passband Digital Systems: Digital Modulation Techniques. Digital Modems.

Digital Systems Performance. Optimum receivers. Symbol error rates.

Spread Spectrum Techniques. FHSS DSSS

Orthogonal Frequency Division Multiplexing.For details see: http://www2.ju.edu.jo/sites/Academic/ghazi.alsukkar/Material/Forms/AllItems.aspx

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History of CommunicationsThe highlights of the inventions which have lead to communications as we know it today are listed below:1440: Printing press - Gutenberg1826: Ohm’s law - Ohm1837: Line telegraphy invention - Gauss, Weber1844: Line telegraphy patent - Morse1858: 1st transatlantic cable (fails after 26 days)1864: Electromagnetic radiation predicted – Maxwell1866: Successful transatlantic telegraph cable (Valentia to Newfoundland)

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Cont.1875: Telephone invented - Bell1877: Phonograph invented - Edison1887: Detection of radio waves - Hertz1894: Wireless communication over 150 yards - Lodge1895: Wireless telegraphy - Marconi1897: Automatic telephone exchange - Strowger1901: Transatlantic radio transmission – Marconi1904: Diode valve - Fleming1905: Wireless transmission of speech and music - Fesseden

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Cont.1906: Triode valve - de Forest1907: Regular radio broadcasts1915: Trans. USA telephone line - Bell System1918: Superheterodyne radio receiver - Armstrong1919: Commercial broadcast radio - KDKA Pittsburg1920: Sampling applied to communications - Carson1926: Television invented - Baird (UK), Jenkins (USA)1928: All electronic television - Farnsworth1928: Theory of transmission of telegraph - Nyquist

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Cont.1928: Information theory - Hartley1933: FM demonstrated - Armstrong1934: Radar - Kuhnold1937: PCM (pulse code modulation) proposed - Reeves1939: Commercial TV broadcasting - BBC1943: Microwave radar used1944: Statistical methods to describe noise and extract signals – Rice1945: Geostationary satellites proposed - Clarke

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Cont.1946: ARQ (automatic repeat request) proposed - Duuren1948: Mathematical theories of communication - Shannon1948: Invention of transistor - Shockley, Bardeen, Brattain1953: Transatlantic telephone cable1955: Invention of laser - Townes, Schawlow1961: Stereo FM transmission

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Cont.1962: Satellite communication - TELSTAR1963: Touch tone telephone - Bell System1963: Geostationary communications satellite - SYNCOM II1963: Error correction codes developed1964: First electronic telephone exchange1965: Commercial communications satellite - Early Bird1966: optical fibre proposed - Kao, Hockman1968: Cable TV

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Cont.1970: Medium scale data networks - ARPA/TYMNET1970: LAN, MAN, WAN1971: ISDN proposed - CCITT1972: First cellular mobile phone1974: The Internet - Cerf, Kahn1978: Cellular radio1978: Navstar GPS (global positioning system)1980: Fibre optic communications system developed -Bell System1980: OSI 7 layer reference model - ISO

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Cont.1981: HDTV (high-definition television) demonstrated1985: ISDN basic rate access introduced - UK1986: SDH introduced (SONET in USA)1991: GSM (global system for mobile Communications)- Europe1999: WAP (wireless application protocol)

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Communications SystemIn its simplest form a telecommunications system consists of a transmitter, a channel, a receiver and two transducers.

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TransducerConverts the input message into an electrical signal. Examples of transducers include:

Microphone – converts sound to electrical signal Camera – converts image to electrical signal

A transducer is also used to convert electrical signals to an output message (or approximation of the input message), e.g., sound, images etc.

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TransmitterConverts electrical signal to a form that is suitable for transmission through the transmission medium or channel.Generally matching of signal to channel is done by modulation.Modulation uses the information (message signal) to vary the amplitude, frequency or phase of a sinusoidal carrier, e.g. amplitude/frequency modulation AM/FM.The transmitter also filters and amplifies the signal.

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ReceiverRecovers the message contained in the received signal Demodulates the message signalFilters signal and suppresses noise

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Communication ModesThere are a few basic modes of communication: Unicast: where one user wishes to communicate with one other user. Communication is normally two-way.Broadcast: Where one sender communicates with all capable receivers who cannot respond. The communication is therefore normally one-way.Multicast: One sender communicates with a nominated set of receivers who cannot respond.

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Methods of Data TransmissionThere are a few basic methods of data transmission:Simplex: Data is transmitted in one direction only. The receiver cannot communicate with the sender.Duplex: Data transmission can take place in both directions simultaneously.Half-Duplex: Data transmission can take place in both directions but not at the same time.

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Time ConstraintsThere are generally two sets of time restraints; real-time or time-lapse:

Real-Time: Real-time communication is instant and data must be sent and received simultaneously. An example of this is the telephone network or two-way radio communications.

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Cont.If a conversation is to be maintained there must be immediate interaction between the talkers. Delays will make the conversation difficult or impossible.Time-Lapse: Data may be received at any time after having been sent. Examples include email, downloading a file from a central server or from the Internet. A delay of a few seconds or even minutes is acceptable. The time of receipt is not important.

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Transmission ModesAll transmission is analogue, in the sense that physical quantities (voltage, current, electromagnetic radiation) must vary in a smooth way. However, the representation of the underlying signals may be either analogue or digital.

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Cont.

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Cont.

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Block Diagram of a Communication System: