as used in worldwide interoperability for microwave access (WiMAX) and digital video broadcasting-second generation satellite (DVB-S2) that greatly reduce the number of errors the OC has to correct. The RS + convolutional FEC scheme used by CCSDS allows these codes to rival with the more powerful LDPC and turbo codes. In [22], the performance of the common turbo + RS FEC scheme is analyzed in relation to their interleaver. Good results are observed with complex interleavers and at very high signal-to-noise ratio (SNR). However, this is not the only possible criterion of choice. In [23], LDPC and recursive systematic convolutional codes are concatenated in parallel, with good performance and little additional complexity with respect to a standard LDPC code. Block turbo codes and LDPC codes have been concatenated in [24], where a FEC scheme for three-dimensional high-definition television (3D HDTV) is devised. The scheme outperforms the digital video broadcasting-second generation terrestrial (DVB-T2) standard serial concatenation of BCH and LDPC codes. Satellite communications are handled through the concatenation of Luby transform (LT) codes and nonbinary LDPC (NB-LDPC) codes in [25]. Thanks to the high error correction capabilities of NB-LDPC and the intrinsic flexibility of LT codes, the resulting system is very versatile. 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