64 State Viterbi Encoder/Decoder

Digital Cable FEC Core


Reed-Solomon Decoder Core

FEC Core

ITU-T J.83-B / MCNS 64/256 QAM FEC Core


The FEC core is intended for use in digital cable demodulator systems, as well as for applications such as MCNS Compliant Cable Modems and Digital Broadcast Television. The FEC accepts 2's-compliment format data with 4 "soft" decision data bits for I and Q. The output of the FEC is an error corrected data stream, MPEG optional. Status and control signals are also available.


  • Automatic phase synchronization and monitoring.
  • Integrated 16 state Viterbi decoder.
  • Standards Compliance: MCNS DOCSIS, ITU-T J.83-B, IEEE 802.14.
  • Integrated 3-error correcting Reed-Solomon decoder.
  • Includes MPEG bit stream synchronization circuit.
  • BER monitoring, using path metric accumulator growth or Reed-Solomon statistics.
  • Supports all Interleaving modes, using either an internal or external RAM, or both.
  • Fully synchronous design.
  • Available as synthesizable Verilog-HDL source.
  • Includes test-vector files, as well as Verilog test benches.
  • Includes Matlab models for system integration and simulation.
  • Includes Synopsys synthesis scripts.
  • Customization available per request.
  • Proprietary FEC algorithms give highest possible performance.
  • Performance:
    • 256 QAM 10 -8 BER @ 27.3 dB SNR
    • 64 QAM 10 -8 BER @ 21.2 dB SNR
  • Requires 8 clocks per input symbol (approx. 50MHz).
  • FEC area requirements: approx. 95k gates with 10k bits of single port RAM.
  • RAM requirements for de-interleaver range from 448 x 7 bits up to 64k x 7 bits, depending upon which modes are supported.


Liz Bortolotto
Alantro Communications, Inc.

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