TCM and turbo TCM for audio broadcasting

Trellis coded modulation (TCM) and serially concatenated trellis coded modulation (SCTCM) schemes are studied for hybrid in-band-on-channel (IBOC) systems that broadcast digital audio signals simultaneously with analog amplitude modulation (AM) programs in the AM bands. We compare the performance and complexity of SCTCM with those of TCM and the previously suggested multilevel concatenated Reed-Solomon (RS)/convolutional (CC) codes, and show that by using SCTCM, an efficient modulation scheme can be obtained for applications such as IBOC-AM broadcasting, with the price of increased block length and complexity. However, since decoding delay is not critical for digital audio broadcasting, SCTCM is a viable choice for these systems. We also show that the less complex TCM scheme performs better than the multilevel RS/CC concatenated schemes at the bit-error-rate of interest in these systems. Furthermore, symbol-by-symbol reliability can be derived from the TCM decoders so that sophisticated error mitigation or concealment algorithms for the audio decoders may be designed to optimize the decoded audio quality.