VSC6134
Datasheet
Figure 2. Interleaving (Encoding)
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Outer Code
Inner Code
(read/write order)
Important The two rows of the G.709 are not interleaved over the BCH(3904,3832) outer code word.
This ensures that the framing bits are transmitted and received uninterleaved.
1.2.3
BCH Codes
1
The outer code is a BCH(3904,3832). The chosen BCH code is a narrow-sense (that is, first root is b )
primitive. This code is capable of correcting 6 bit-errors. The overhead of the outer code is 488/479.
The BCH(2040,1952, 8) inner code is capable of correcting 8-bit errors. The BCH(2040, 1952,8) code
is shortened by 8 bits from BCH(2047,1959,8). The inner code overhead of 2040/1952 = 255/244
(4.5% overhead).
The inner code concatenated with the BCH(3904,3832) outer code uses 8 bits for CRC calculation;
therefore, the overhead of the outer code is:
3904
3824 239
244
----------- = --------
The overhead of the concatenated code is:
255244
244239
255
239
----------------
= -------- = 1.066949
41 of 438
VMDS-10185 Revision 4.0
July 2006
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
