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Digital Communications Evolution: Principles and Milestones

Explore the evolution, principles, and milestones of digital communications. Learn about Claude Shannon's work in 1948, X.25, IEEE 802.3, ARPANET, CDMA, GSM, VOIP, and SIP protocols. Delve into information theory, fundamental limits, and digital modulation in communication systems. Enhance your understanding with resources like Agilent's application note and slide presentation. Gain insights into circuit switching, packet switching, and digital communication paradigms. Get acquainted with communications systems, transceivers, error control, encryption, modulation, and demodulation processes. Discover the importance of MATLAB, Simulink, and various software tools for communication studies.

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Digital Communications Evolution: Principles and Milestones

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  1. Digital Communications0909.402.03/0909.504.01Fall 2002 Lecture 1September 9, 2002 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall02/digcomm/

  2. Plan • Introduction Digital Communications • Evolution • Rationale • Course Logistics • Review of ECOMMS • Signals • Systems • Digital Communications Transceiver (CODEC/MODEM) • Principles • Introduction to Lab

  3. Digital Communications • Some Milestones • Claude Shannon, 1948 • X.25 (Telephony) • IEEE 802.3 (Ethernet) • ARPANET, 1969 • IEEE 802.5 (FDDI) • ISO-OSI 7-layer Network Reference Model • CDMA • GSM • VOIP • SIP protocols.com

  4. Wireless Comm Evolution/Revolution: UMTS (3G) http://www.3g-generation.com/ http://www.nttdocomo.com/reports/010902_ir_presentation_january.pdf

  5. Evolution

  6. And there’s more…. Joseph M. Nowack, http://www.jacksons.net/~tac/

  7. Digital Communications: Rationale • Information Theory: • What is the fundamental limit on the compression and refinement of information generated by the source? • What is the fundamental limit on the transmission rate of information over a noisy channel? • How do we approach these limits?

  8. Digital Communications • Please read these!!!! • Digital Modulation in Communications Systems: An Introduction, Hewlett-Packard Application Note 1298 http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf Mirrored at: http://engineering.rowan.edu/~shreek/spring00/ecomms/notes/ 5965-7160E.pdf • Source Basics, Agilent Technologies Teachers Tools Slide Presentation http://www.educatorscorner.com/tools/lectures/slides/srcbas.html Mirrored at: http://engineering.rowan.edu/~shreek/spring00/ecomms/notes/ scrbas.ppt

  9. Message 1 Message 1 Multiplexer 2 Demultiplexer 1 2 3 1 S 2 3 S Message 2 Message 2 Message 3 Message 3 3 H H 1 Depacket-izing Message 1 2 H Message 1 3 H H 1 Depacket-izing Packetizing Message 2 Message 2 2 H 3 H Message 3 Depacket-izing H 1 Message 3 2 H Digital Communication Paradigms Circuit Switching Sync bits Packet Switching Header bits

  10. Course Logistics http://engineering.rowan.edu/~shreek/fall02/digcomm/

  11. ECOMMS http://engineering.rowan.edu/~shreek/spring02/ecomms/

  12. Info Sink Info Source Comm System What is a communications system? • Communications Systems: Systems designed to transmit and receive information

  13. Info Source m(t) message from source Receiver Rx Transmitter Tx Channel received message to sink s(t) transmitted signal r(t) received signal Block Diagram Info Sink

  14. Digital Communications Transceiver Anti- aliasing Filter Error Control Encoder Data Encryption Encoder Channel/ Line Encoder Source Encoder Sampling Quantization Modulator MUX ADC Analog i/p CODEC MODEM Multiple access channel Analog o/p Error Control Decoder Data Encryption Decoder Source Decoder Audio Amp Reconstruction/ DAC Equalization / Decision Circuits Demod-ulator DEMUX

  15. Digital Modulation Carrier signal: Ac cos (2pfct + f) Modulation: m(t) Modulated signal: Ac (t) cos (2pfc(t) t + f(t))  m(t); discrete Vary Vary Vary amplitude frequency phase Variations are discrete!!!!!

  16. Principle Digital message 1 1 1 0 1 0……… 0 0 Digital code Analog message modulate 1 0 1 0 Sinusoidal carrier AM FM PM AM & PM

  17. Signal Vector Representation s(t) = Ac(t) cos (2pfct + f(t)) fixed!!! Q S Magnitude Phase 0 degrees I I-Q Plane

  18. Phase Change Magnitude Change S2 Q Q S1 S1 S2 I I Magnitude & Phase Change Q S1 S2 I Signal Changes:Representation in the IQ Plane I-Q Diagrams or Constellations Frequency Change ???

  19. Quadrature Phase Shift Keying(QPSK) IQ Diagram s(t) = Ac cos(2pfct + f(t)) Q 3p/4 01 11 10 f(t) p/4 00 p/4 t I 10 -p/4 11 01 00 -3p/4

  20. M-ary Quadrature Amplitude Modulation(M-ary-QAM) Q I 16 QAM I-Q Constellation

  21. Laboratory Software • Matlab & Simulink • DSP Toolbox • DSP Blockset • Communications Toolbox • Communications Blockset

  22. Summary

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