Notes 1 the purpose of this field is to provide a

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Unformatted text preview: sical Channel shall be determined based on the mission requirements for data quality and the selected options for the underlying Channel Coding Sublayer. This field may be mandatory depending on the selected options for the Channel Coding Sublayer. 4.1.6.2 Frame Error Control Field Encoding Procedure 4.1.6.2.1 The Encoding Procedure shall accept an (n–16)-bit Transfer Frame, excluding the Frame Error Control Field, and generate a systematic binary (n,n–16) block code by appending a 16-bit Frame Error Control Field as the final 16 bits of the codeblock, where n is the length of the Transfer Frame. 4.1.6.2.2 The equation for the contents of the Frame Error Control Field is: FECF = [(X16 ⋅ M(X)) + (X(n–16) ⋅ L(X))] modulo G(X) where – all arithmetic is modulo 2; – n is the number of bits in the encoded message; – M(X) is the (n–16)-bit message to be encoded expressed as a polynomial with binary coefficients; – L(X) is the presetting polynomial given by 15 L(X) = ∑ Xi ; i=0 G(X) is the generating polynomial given by G(X) = X16 + X12 + X5 + 1. NOTE – The X(n–16) ⋅ L(X) term has the effect of presetting the shift register to all ‘1’ state prior to encoding. CCSDS 132.0-B-1 Page 4-13 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL 4.1.6.3 Frame Error Control Field Decoding Procedure The error detection syndrome, S(X), is given by S(X) = [(X16 ⋅ C*(X)) + (Xn ⋅ L(X))] modulo G(X) where – C*(X) is the received block, including the Frame Error Control Field, in polynomial form; and – S(X) is the syndrome polynomial which will be zero if no error is detected and nonzero if an error is detected. 4.2 PROTOCOL PROCEDURES AT THE SENDING END 4.2.1 OVERVIEW This subsection describes procedures at the sending end associated with each of the functions shown in figure 4-5. Data flow from the top to the bottom of the figure. This figure identifies data-handling functions performed by the protocol entity at the sending end and shows logical relationships among these functions. Th...
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This document was uploaded on 03/06/2014.

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