Low-rate turbo codes for deep-space communications

We develop b/n multiple turbo codes and an iterative turbo decoding scheme based on an approximation to the optimum bit decision rule (MAP). For random interleaver size of 16384 bits, a bit error probability of 10/sup -5/ at a required E/sub b//N/sub 0/ of about 0.8 dB from the binary-input channel capacity for rate b/n was obtained for various turbo codes. Examples are given for rate b/n=1/2, 1/3, 1/4 and 2/6 turbo codes using component codes with up to 16 states.