error detection and correction codes - philpem/libdmr GitHub Wiki

EDC/ECC methods used in DMR

Quadratic residue

Quadratic residue (16,7,6) encoding is used for the EMB field.

Golay

Golay (20,8) encoding is used for the Slot Type.

Hamming (7,4)

Hamming (7,4) encoding is used for the TACT bits.

Block Product Turbo Codes (BPTC)

DMR uses two block product turbo codes (BPTC):

  • BPTC (196,96)
    • Hamming (15,11,3) Row code with Hamming (13,9,3) Column code
  • Variable Length BPTC
    • Hamming (16,11,4) Row code with simple parity check Column code.
    • Input length must be a multiple of 11 bits.

Rate 3/4 Trellis code (for Rate 3/4 Data)

TBD

Rate 1 Coded (for Rate 1 Data)

TBD

CRCs and checksums

Several CRC and checksum algorithms are also used:

  • DMR 5-bit checksum (Embedded Signalling)
  • 7-bit CRC (Reverse Channel signalling)
  • 8-bit CRC (Short LC in CACH)
  • CRC CCITT
  • 32-bit CRC (Rate 1/3, 3/4, and 1 data; Response Data Block)
  • CRC-9 (Rate 1/2, 3/4, and 1 data)
⚠️ **GitHub.com Fallback** ⚠️