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Generation Rack-
Mount RDMS™
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Quasonix, Inc.
Figure 117: I and Q Data from Single Convolutional Encoder
The appropriate decoder for this method is selected by setting Convolutional Symbol to Enabled.
4.4.2.22.4 Reed-Solomon Decoder (K7 Option Required) (Legacy PSK modes only)
Reed-Solomon encoding is another form of legacy forward error correction. Like LDPC, it is a block code that adds
redundant information at the transmitting end of a telemetry link and then uses that redundancy to detect and correct
errors at the receiving end of the link. Unlike LDPC, however, encoding/decoding occurs on 8-bit symbols, and
errors are detected and corrected on a symbol-by-symbol basis, regardless of the number of bits in error within a
symbol. This characteristic makes Reed-Solomon encoding suitable for correcting burst errors. Details of Reed-
Solomon encoding are presented in CCSDS 131.0-B-2 Section 4. The specific variant of Reed-Solomon decoder
implemented is the (255, 223) code.
While Reed-Solomon encoding can be used by itself, it is a far less powerful code than LDPC. Its primary use is as a
second code to correct burst errors that arise in the Viterbi decoder. The concatenation of Reed-Solomon encoding
and convolutional encoding results in far better performance than either code by itself.
The Reed-Solomon control requires the K7 option, and the RDMS must be set to one of the following PSK modes:
BPSK, QPSK, AQPSK, AUQPSK, OQPSK, or UQPSK. The RDMS has only one Reed-Solomon decoder.
Therefore, in AQPSK and AUQPSK modes, only the ‘A’ data will be decoded when Reed
-Solomon decoding is
enabled; ‘B’ data will be output without decoding.
Reed-Solomon decoding and Viterbi decoding can be used together or separately.
The Reed-Solomon decoder is selected by setting R-S Decoder to Enabled, as shown in Figure 118.
Figure 118: FEC Menu, R-S Decoder
