DCO 332 Digital Communication

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DCO 332Digital Communication
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• Neetesh Purohit
• Lecturer, IIIT,
• Allahabad, UP, India
• http//profile.iiita.ac.in/np/
• (Other details, course material, assignments,
  midsem, endsem marks, notices etc are available)

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The syllabus

• Unit I
• Spectra of analog signals, Analog modulation
  techniques, sampling and reconstruction of analog
  signals, PCM, delta and adaptive delta
  modulation, ADPCM
• Unit II
• Line coding techniques (RZ, NRZ, AMI, and
  Manchester), Spectra of digital signals, Spectral
  shaping by precoding, digital multiplexing,
  Digital continuous wave modulation techniques
  ASK, FSK, PSK, staggered and non staggered QPSK,
  p/4-QPSK, MSK, GMSK, coherent and non coherent
  systems.

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• Unit III
• Information measure and source coding theorem,
  Krafts inequality, Shannon Fano coding, Huffman
  coding, Lempvel Ziv coding, run length predictive
  coding, JPEG, MPEG, mutual information, Binary
  symmetric channel, Channel capacity, Shannon
  Hartley law.
• Spread Spectrum, Jamming considerations, CDMA
  fundamentals.

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•  Unit IV
• Hamming distance, triple repetition codes,
  Systematic and non systematic hamming codes,
  Cyclic codes, Generation of convolution codes,
  code tree, code trellis, state diagram, free
  distance, D-domain analysis, coding gain,
  decoding methods, turbo codes, trellis coded
  modulation.

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Books

• Text Book
• Communication systems, IV edition
• A B Carlson McGraw Hill
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• Reference books
• 1. Digital Communication, IV edition
• J. Proakis McGraw Hill
• 2. Digital Communication, II edition
• B Sklar Prentice Hall

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Distribution of Internal Marks

• Proportionate marks for attendance (10)
• Quiz marks (1010)
• Unsolved problems at the end of all concerned
  chapters is an assignment. You should solve 10
  problems and submit within 2 days after
  completion of a particular unit. (15)
• The problem numbers will be (your roll number
  x) mod N x0,4,8,12,16 And N number of problems

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What is communication?

• Some information is available at a place and the
  way of transferring this information to a distant
  place is called communication.
• Information may be an idea in someones mind or
  it may be a news that something has been happened
  or will happen etc.

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Various types of Comm. systems

• Postal system
• Telephone, mobile
• Fax, etc
• What is the common requirement of these systems
  to function properly?

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• The available information must be transformed in
  a form which is compatible with characteristics
  of the communication system
• What does it mean?

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Electrical Communication system

• Information Information

I/P Transducer
O/P Transducer
Electrical signal
Receiver
Transmitter
channel
Twisted Copper wire coaxial cable optical
fiber space
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Tx and Rx sections

• Each channel has some characteristics features
  e.g. copper cables carry voltages/currents, EM
  wave travels thru space etc. besides some
  fundamental limitations.
• The job of transmitter is to provide
  compatibility at this stage.
• The job of receiver is to perform inverse
  operation of Tx.

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Fundamental limitations

• Noise
• - thermal agitation of electrons produces
  thermal noise, as explained in kinetic theory of
  gases.
• - S/N ration must be maintained

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• Bandwidth
• - stored energy in inductances and capacitances
  can not be changed instantaneously.
• - Copper channels have distributed capacitances
  and inductances
• -Telephone cables act as low pass filters and
  attenuate high frequency components. It results
  in distortion.

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Designing of Analog comm. system

• Estimation of BW of intended analog signals
• Select a channel such that
• BW of system gt BW of signal
• Design the Tx and Rx.
• Measure the performance in terms of fidelity

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Designing of Digital Comm. system

• Estimate the data rate of intended service.
• Determine BW using Nyquist theorem
• Ch BW gt (signaling rate)/2
• - for real time traffic (voice video) r
  determines the value of B
• - for non real time traffic (data) B
  determines r
• Measure the performance in terms of accuracy

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Techniques for improving the performance

• Modulation
• - systematic alteration of carrier wave in
  accordance with instantaneous value of the
  message signal.
• - Integral part of all transmitters
• - several advantages e.g. practicability of
  antenna, multiplexing, noise reduction etc

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• Coding

purpose
BW Control
Error Control
Efficient representation (source coding)
Decreasing BW (Binary to M-ary)
Error Detection and ARQ
Forward Error Correction
Increasing BW (M-ary to binary)