L64724 LSI Logic Corporation, L64724 Datasheet - Page 181

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

7.3.1.1 Forward Error Correction (FEC)
d
K
m
N
T
FEC requires an encoder that appends redundant check bytes to a
message before transmission. The check bytes, with an indeterminate
number of bits, are referred to as symbols. The message symbols
followed by redundant check symbols are called code words. The check
symbols are redundant in the sense that they are derived from the
message and are appended to the message. Check symbols are also
referred to as “redundant check bytes,” and sometimes as “correction
bytes.”
Figure 7.7
Reed-Solomon Decoder
illustrates a code word. Explanatory text follows the figure.
Detection Power
Detection power specifies the maximum number of
detectable errors. Detection power has a minimum value
of
Message Length
The message contains multiple bytes. The size of the
message varies, depending on the code word length and
the check bytes used, where K = N – R.
Symbol Size
A data transfer contains multiple symbols. The symbol
size, m, is 8 bits.
Codeword Length
The variable N is the sum of the number of message
bytes and the number of check bytes (K + R). The value
of N is 204 for DVB; 147 for DSS (includes the MPEG
sync bit).
Number of Error Corrections
This variable is the maximum number of error corrections
performed by the decoder. The value of T is 8.
R
--- -
2
and a maximum value of R.
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