Consultative
Committee for
Space Data Systems
DRAFT RECOMMENDATION FOR SPACE
DATA SYSTEM STANDARDS
TELEMETRY
CHANNEL CODING
CCSDS 101.0-BP-5.1
BLUE BOOKPINK SHEETS
June 2001April 2002
DRAFT CCSDS RECOMMENDATION FOR TELEMETRY CHANNEL CODING
CCSDS 101.0-BP-5.1
3-2
June 2001April 2002
(a)
J, E, and I (the depth of interleaving) are independent parameters.
(b)
n = 2J1 = 255 symbols per R-S codeword.
(c)
2E is the number of R-S symbols among n symbols of an R-S codeword
representing parity checks.
(d)
k = n2E is the number of R-S symbols among n R-S symbols of an R-S
codeword representing information.
(4)
Field generator polynomial:
F(x) = x8 + x7 + x2 + x + 1
over GF(2).
(5)
Code generator polynomial:
g(x) = ∏
j=128 E
127 + E
( x α11j )
= ∑
i=0
2E
Gixi
over GF(28), where F(α) = 0.
It should be recognized that α11 is a primitive element in GF(28) and that F(x) and
g(x) characterize a (255,223) Reed-Solomon code when E = 16 and a (255,239)
Reed-Solomon code when E = 8.
(6)
The selected code is a systematic code. This results in a systematic codeblock.
(7)
Symbol Interleaving:
The allowable values of interleaving depth are I=1, 2, 3, 4, and 5, and 8. I=1 is
equivalent to the absence of interleaving. The interleaving depth shall normally be
fixed on a physical channel for a mission. Symbol interleaving is accomplished in a
manner functionally described with the aid of Figure 3-1. (It should be noted that
this functional description does not necessarily correspond to the physical
implementation of an encoder.)
DRAFT CCSDS RECOMMENDATION FOR TELEMETRY CHANNEL CODING
CCSDS 101.0-BP-5.1
6-1
June 2001April 2002
6 PSEUDO-RANDOMIZER
6.1 INTRODUCTION
In order to maintain bit (or symbol) synchronization with the received telemetry signal, every
ground data capture system requires that the incoming signal have a minimum bit transition
density (see reference [3]).
If a sufficient bit transi