L64724 LSI Logic Corporation, L64724 Datasheet - Page 173

• Manufacturer Part Number: L64724
• Description: Satellite Receiver
• Manufacturer: LSI Logic Corporation

7.1.2 Punctured Codes
The L64724 supports not only the basic rate equal to 1/2 decoding
operations, but also code rates equal to 2/3, 3/4, 5/6, 6/7 and 7/8. The
code rate and underlying depuncture scheme chosen dictates the proper
sequence of symbols on the DEM_I and DEM_Q inputs.
the puncture patterns for various code rates.
Table 7.1
Figure 7.2
process for a rate 1/2 encoder. For each data bit D n , the upstream
encoder generates two corresponding encoded data symbols, I. n and
Q. n. By deleting or puncturing some of the encoded data symbols, the
puncturing process allows a rate 1/2 encoder to generate codes of higher
rates. The L64724’s depuncturing module allows its rate 1/2 decoder to
decode data transmitted at higher code rates.
puncture patterns for different code rates.
Viterbi Decoder Module
1/2
2/3
3/4
5/6
6/7
7/8
Code Rate
shows a block diagram of the puncturing and depuncturing
Puncture Patterns for Various Code Rates
Puncture Pattern
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
1
1
1 0
1 1
1 0 1
1 1 0
1 0 1 0 1
1 1 0 1 0
1 0 0 1 0 1
1 1 1 0 1 0
1 0 0 0 1 0 1
1 1 1 1 0 1 0
Figure 7.3
Table 7.1
illustrates the
shows
7-3