Alternative to NASA´s concatenated coding system for the Galileo mission

Because of delays in the Galileo mission an enhanced coding gain was required, compared to the gain achieved by the concatenated system recommended by CCSDS. NASA has met the requirement by exchanging the inner convolutional memory, rate 1/2 code with a memory 14, rate 1/4 code, whereby an enhanced coding gain of 1.6 dB can be obtained if infinite interleaving is assumed. To obtain this enhanced coding gain the complexity for the inner decoder is increased by at least 256 times. The author proposes an alternative system with a slightly larger enhanced coding gain obtained at interleaving degree 16, i.e. by a system which can be implemented in practice. The overall complexity is, however, at least 25 times smaller than the complexity for the system implemented by NASA