L64704 LSI Logic Corporation, L64704 Datasheet - Page 148

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

Table 7.1
Puncture Patterns
for Various Code
Rates
Figure 7.3
Puncturing and
Depuncturing Block
Diagram
7-4
Input
Data
Rate = 1/2
Encoder
Encoded
Viterbi Encoder
Input
Data
Data
Puncture
Module
Figure 7.3
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 L64704’s depuncturing module allows its rate 1/2 decoder to
decode data transmitted at higher code rates.
puncture patterns for different code rates.
The FEC Decoder Pipeline
Encoded
Q.1
Data
D1
I.1
Q.2
I.2
D2
Modulator
shows a block diagram of the puncturing and depuncturing
Q.3
D3
I.3
Q.4
D4
I.4
Communications
Code Rate
1/2
2/3
3/4
5/6
7/8
Punctured
Channel
Data
Q.5
D5
I.5
Q.6
I.6
D6
Puncture Pattern
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
DEM_I:
DEM_Q:
Demodulator
Q.7
D7
I.7
Q.8
D8
I.8
Depunctured
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 0 1 0 1
1 1 1 1 0 1 0
Data
Depuncture
Figure 7.4
Module
FIFO/
L64704
illustrates the
Rate = 1/2
Decoder
Viterbi
Output Data
Decoded