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Contents

   



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1 Encoding  




2 References  













2B1Q






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From Wikipedia, the free encyclopedia
  

Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL).[1] 2B1Q is a four-level pulse-amplitude modulation (PAM-4) scheme without redundancy, mapping two bits (2B) into one quaternary symbol (1Q). Symbol rate is half of data rate.

A competing encoding technique in the ISDN basic rate U interface, mainly used in Europe, is 4B3T.

Encoding[edit]

To minimize error propagation, bit pairs (dibits) are assigned to voltage levels according to a Gray code, as follows:

Dibit

Signal level

10

+450 mV

11

+150 mV

01

−150 mV

00

−450 mV

If the voltage is misread as an adjacent level, this causes only a 1-bit error in the decoded data. 2B1Q code is not DC-balanced.

References[edit]

  1. ^ Reeve, Whitham D. (1995). Subscriber Loop Signaling and Transmission Handbook. IEEE Telecommunications Handbook Series. IEEE Press. ISBN 0780304403.
Line coding (digital baseband transmission)

Main articles

  • Bipolar encoding
  • On-off keying
  • Mark and space

    • Basic line codes

  • Non-return-to-zero, level (NRZ/NRZ-L)
  • Non-return-to-zero, inverted (NRZ-I)
  • Non-return-to-zero, space (NRZ-S)
  • Manchester
  • Differential Manchester/biphase (Bi-φ)

    • Extended line codes

  • 4B3T
  • 4B5B
  • 2B1Q
  • Alternate mark inversion
  • Modified AMI code
  • Coded mark inversion
  • MLT-3 encoding
  • Hybrid ternary code
  • 6b/8b encoding
  • 8b/10b encoding
  • 64b/66b encoding
  • Eight-to-fourteen modulation
  • Delay/Miller encoding
  • TC-PAM

    • Optical line codes

  • Alternate-phase return-to-zero

  • Baud
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  • Digital signal
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  • Ethernet physical layer
  • Pulse modulation methods
  • Pulse-amplitude modulation (PAM)
  • Pulse-code modulation (PCM)
  • Serial communication
  • Category:Line codes


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