The reed solomon code may be used alone and as such

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Unformatted text preview: , and as such it provides an excellent forward error correction capability in a burst-noise channel. However, should the Reed-Solomon code alone not provide sufficient coding gain, it may be concatenated with the convolutional code defined in section 3. Used this way, the Reed-Solomon code is the outer code, while the convolutional code is the inner code. 4.2 4.2.1 GENERAL DATA RANDOMIZATION The pseudo-randomizer defined in section 9 shall be used unless the system designer verifies that the concerns identified in the note below are resolved by other means. NOTE – The recommended Reed-Solomon codes, by themselves, cannot guarantee sufficient bit transitions to keep receiver symbol synchronizers in lock. Because of the quasi-cyclic nature of these codes, undetected decoding errors may result from incorrect codeblock synchronization. The pseudo-randomizer is also used to aid signal acquisition and to mitigate spectral lines in the transmitted signal. 4.2.2 FRAME VALIDATION The Frame Error Control Field (FECF) specified in references [1] and [2] is optional. The system designer may choose to use it for additional codeblock validation, particularly with the E=8 code. NOTE – The Reed-Solomon code with E=16 has an extremely low undetected error rate, and that with E=8 has an undetected error rate low enough for some applications. Therefore the R-S decoder may be used alone to validate the codeblock, and consequently the contained TM Transfer Frame (reference [1]) or AOS Transfer Frame (reference [2]). 4.3 4.3.1 SPECIFICATION PARAMETERS The parameters of the selected Reed-Solomon (R-S) code are as follows: CCSDS 131.0-B-2 Page 4-1 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING a) J shall be 8 bits per R-S symbol. b) E shall be 16 or 8 R-S symbols. NOTE – E is the Reed-Solomon error correction capability, in symbols, within a R-S codeword. 4.3.2 GENERAL CHARACTERISTICS The code shall conform to the following general characteristics: a) J, E, and I (the depth of interleaving) are independent parameters. b) n = 2J–1 = 255 symbols per R-S codewor...
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