Standards/BCH

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BCH codes have been invented by Bose, Chaudhuri and Hocquenghem. They are used in communication systems for error correction. Similarly to Hamming codes, they are able to detect a certain number of errors and to correct a smaller quantity of them.

These codes are often implemented in addition to convolutional codes.

Definitions

A BCH code is specified by:

  • n : total code length
  • k : information data length
  • m : parity bits number
  • G : the generator polynomial

The coded BCH data is often filled with '0' bits up to a length which is a multiple of 8, thus allowing to be transmitted as bytes.

Coder

The parity bits are created with the help of a Linear Feedback Shift Register (LFSR).

The following picture shows a BCH encoder with 7 code bits :

BCH encoder (63, 56)

Decoder

The following picture shows the decoder for the previous encoder :

BCH decoder schematic.svg
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