S.72-227 Digital Communication Systems

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S.72-227 Digital Communication Systems

• Cyclic Codes

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S.72-227 Digital Communication Systems

• Lectures Prof. Timo O. Korhonen, tel. 09 451
  2351, Research Scientist Michael Hall, tel. 09
  451 2343
• Course assistants Research Scientist Seppo
  Saastamoinen (seppo.saastamoinen_at_hut.fi), tel. 09
  451 5417, Research Scientist Yangpo Gao
  (gyp_at_cc.hut.fi ), tel. [phone], Research
  Scientist Naser Tarhuni (ntarhuni_at_pop.hut.fi ),
  tel. [phone] (Lecture Diaries)
• Compulsory study modules Examination/Tutorials
  (gradingpass/rejected), Project work
• Voluntary study modules Lecture diary - Maximum
  increase of grade 1.0
• Follow homepage for further info!

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Practicalities

• References
• A. B. Carlson Communication Systems (4th ed.)
• J. G. Proakis, Digital Communications (4th ed.)
• L. Ahlin, J. Zander Principles of Wireless
  Communications
• Prerequisites S-72.245 Transmission Methods in
  Telecommunication Systems
• Homepage http//www.comlab.hut.fi/opetus/227/
• Timetables
• Lectures Fridays 12-14, hall S2
• Tutorials Tuesdays10-12, hall S5, start 3.2.2004

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S.72-227 Digital Communication Systems 04

• Encoding and decoding of cyclic codes
• Convolutional codes
• Decoding of convolutional codes
• Trellis coded modulation (TCM) and
  ARQ1-techniques
• Coding for security and secrecy
• Overview to fading multipath radio channels
• Bandpass digital transmission in multipath
  channels
• Channel equalization
• Diversity techniques
• Spread spectrum technology and OFDM2
• Multiuser reception
• Fiber-optic communication

1Automatic Repeat reQuest 2Ortogonal Frequency
Division Multiplexing
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Topics in channel coding

• Cyclic codes
• presenting codes code polynomials
• systematic and non-systematic codes
• generating codes generator polynomials, usage of
  shift registers
• decoding syndrome decoding
• Convolutional codes
• convolutional encoder
• code trees and state diagram
• generator sequences
• structural properties
• code weight, path gain, and generating function
• code gain
• Syndrome and maximum likelihood detection
• Mod-2 arithmetics

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Background

• Coding is used for
• error detection and/or error correction (channel
  coding)
• ciphering (security) and compression (source
  coding)
• In coding extra bits are added or removed in data
  transmission
• Channel coding can be realized by two approaches
• FEC (forward error coding)
• block coding, often realized by cyclic coding
• convolutional coding
• ARQ (automatic repeat request)
• stop-and-wait
• go-back-N
• selective repeat etc.
• Note ARQ applies FEC for error detection

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Using shift registers for multiplication

• Figure shows a shift register to realize
  multiplication by 1p2p3
• In practice, multiplication can be realized by
  two equivalent topologies

unit delay element
alternate notation of XOR-circuit
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