Unformatted text preview: c) Turbo coding (section 5);
d) Low-Density Parity-Check (LDPC) coding (section 7).
One of the convolutional codes described in section 3 alone may be satisfactory depending
on performance requirements.
For Physical Channels, which are bandwidth-constrained and cannot tolerate the increase in
bandwidth required by the basic convolutional code specified in 3.3, the punctured
convolutional codes specified in 3.4 have the advantage of smaller bandwidth expansion.
Alternatively, the Reed-Solomon codes and the high rate LDPC code specified in sections 4
and 7 also have the advantage of smaller bandwidth expansion and have the capability to
indicate the presence of uncorrectable errors. Where a greater coding gain is needed than can
be provided by a convolutional code or Reed-Solomon code alone, a concatenation of a
convolutional code as the inner code with a Reed-Solomon code as the outer code may be
used for improved performance.
The Turbo codes specified in section 5 or the LDPC codes specified in section 7 may be used
to obtain even greater coding gain where the environment permits.
1 In this Recommended Standard, the characteristics of the codes are specified only to
the extent necessary to ensure interoperability and cross-support. The specification
does not attempt to quantify the relative coding gain or the merits of each approach
discussed, nor does it specify the design requirements for encoders or decoders. 2 The domains of applicability for the codes specified in this document are delineated
in Mission Profiles for TM Synchronization and Channel Coding (reference [E5]). 2.2.3 FRAME VALIDATION After decoding is performed, the upper layers at the receiving end also need to know whether
or not each decoded Transfer Frame can be used as a valid data unit; i.e., an indication of the
quality of the received frame is needed. This function is called Frame Validation. The ReedSolomon and LDPC decoders can determine, with a very high probability, whether or not they
can correctly decode a Transfer Frame. T...
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