ABSTRACT
The challenge to find practical decoders for large codes was not encountered until turbo codes, introduced by Berrou et al. in 1993 [1]. The performance of these new codes is close to the Shannon limit with relatively simple component codes and large interleavers. Turbo codes are a new class of error correction codes introduced along with a practical decoding algorithm. Turbo codes are important because they enable reliable communications with power efficiencies close to the theoretical limit predicted by Claude Shannon. They are the most efficient codes for low-power applications such as deep-space and satellite communications, as well as for interference limited applications such as third generation cellular and personal communication services. Because turbo codes use convolutional codes as their constituent codes, a natural extension of the turbo concept, which improves bandwidth efficiency, is its application to systems using TCM. The main principle of turbo codes, given in [1], is conveyed to TCM and this new scheme is denoted as turbo trelliscoded modulation (TTCM). Hence, the important properties and advantages of both structures are retained. Just as binary turbo codes, TTCM uses a parallel concatenation of two binary recursive convolutional encoders, two recursive TCM encoders are concatenated, and interleaving and puncturing are adapted as in [2,3].
