It also would require differential detection which is

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Unformatted text preview: ave to be detected and resolved before decoding. CCSDS 131.0-B-2 Page 7-1 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING 7.2.2 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 LDPC codes, by themselves, cannot guarantee sufficient bit transitions to keep receiver symbol synchronizers in lock. Because of the quasicyclic nature of these codes, undetected decoding errors may result from incorrect codeword synchronization. The pseudo-randomizer is also used to aid signal acquisition and to mitigate spectral lines in the transmitted signal. 7.2.3 FRAME VALIDATION The LDPC decoder may be used alone to validate the codeword, and consequently the contained TM Transfer Frame (reference [1]) or AOS Transfer Frame (reference [2]). The Frame Error Control Field (FECF) specified in references [1] and [2] is optional, and the system designer may choose to use it for additional frame validation. NOTE – The undetected frame and bit error rates of these LDPC codes lie several orders of magnitude below the corresponding detected error rates for any given operating signal-to-noise ratio. 7.3 7.3.1 LOW-DENSITY PARITY-CHECK CODE WITH RATE 223/255 OVERVIEW The (8160,7136) recommended code is an expurgated, shortened, and extended version of a basic (8176,7156) LDPC code. The recommended code has rate 223/255, and matches the length and dimension of the (255,223) I=4 Reed-Solomon code. The basic code is transparent, although the modified version of this code is not, because of the sense of the fill bits. Construction of the initial code is described in 7.3.2, expurgation and encoding are described in 7.3.4, and the shortening and extension that yield the recommended code are described in 7.3.5. 7.3.2 BASIC (8176,7156) LDPC CODE USED IN CONSTRUCTION The parity check matrix for the (8176,7156) LDPC code shall be...
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