TURBO CODES, LDPC AND FIRE CODES TO ACHIEVE BETTER DEEP-SPACE COMMUNICATIONS: PERFORMANCE AND IMPLEMENTATION

摘要

Channel coding is a set of basic processes that manage the raw information given by a source and do a manipulation of its physical features in order to make the signals more invulnerable against the noise of the channel, possible interferences, or other sources of distortion. The goal is to increase the probability of receiving an error-free information. Some of these manipulation techniques are very sophisticated, such as TCM (Trellis Code Modulation) going up to the very modern Turbo codes, LDPC codes and Fire codes. These last three techniques of channel coding are the ones to be treated in this paper, because of their robustness on a deep space communication scenario. Turbo codes have shown themselves as especially suitable for deep space communications. The most recent space missions, such as the NASA and ESA missions to Mars, have already incorporated these codes in order to make possible a more complex and accurate exchange of data between the earth control and the vessel itself, but these codes are still a research domain. Another set of codes which are suitable for space communications, and probably even more interesting, are the LDPC codes and Fire codes. LDPC codes are already in use on the DVB-S2 standard for digital television broadcasting via satellite, and currently massively used. Fire codes are used for mobile communications, such as GSM. This paper analyzes briefly each of these codes, and tries to show the benefits of using them. It is also attractive to make an abridged show of some specific implementations of these codes, and finally a brief discussion on possible future applications is done.