Serial concatenation of codes is based on the concept that the output bits of an encoder are used as input bits for another encoder. Turbo and LDPC codes in particular have been considered for concatenation in [7], where deep-space communications were targeted; Fig. 1 shows the proposed idea. The performance of these two types of codes are somewhat complementary; while turbo codes guarantee much better performance than LDPC codes at low SNR, they suffer from higher error floors [26]. Consequently, the LDPC encoder is placed before the