Turbo codes for deep-space communications

Turbo codes were recently proposed by Berrou, Glavieux, and Thitimajshima [2], and it has been claimed these codes achieve near-Shannon-limit error correction performance with relatively simple component codes and large interleavers. A required Eb=No of 0.7 dB was reported for ab it error rate of 10 i 5 , using a rate 1/2 turbo code [2]. However, some important details that are necessary to reproduce these results were omitted. This article conflrms the accuracy of these claims, and presents a complete description of an encoder/decoder pair that could be suitable for deep-space applications, where lower rate codes can be used. We describe a new simple method for trellis termination, analyze the efiect of interleaver choice on the weight distribution of the code, and introduce the use of unequal rate component codes, which yields better performance.