Citation
Abstract
In the proposed NASA/ESA telemetry/coding standard, a (255, 223) Reed-Solomon code is concatenated with an inner (7, 1/2) convolutional code. Under some circumstances, it would be desirable to use a shorter outer code word length. For example, the format of the data coming from science instruments on board a spacecraft may lend itself naturally to a word length of 200 symbols rather than 223. To accommodate such code word lengths, the Reed-Solomon code can be shortened to an (N, N-32) code where N can be any integer between 33 and 255. Shortening the code, however, changes its performance. On one hand, the amount of redundancy per information symbol increases. This would, by itself, imply that performance would improve, However, because of this increased redundancy, the amount of energy per information symbol is decreased by code shortening. The overall effect is to degrade the performance of the code, This report develops the theory of Reed-Solomon code shortening in general and quantifies the degradation due to shortening in the context of concatenated coding. It is shown that in the NASA/ESA concatenated system, significant degradations (greater than 0.1 dB at a bit error rate of 10~°) occur only when N < 180.
Details
- Volume
- 42-75
- Published
- November 15, 1983
- Pages
- 14–20
- File Size
- 408.7 KB