Design of power- and bandwidth-efficient turbo-coded modulation schemes using constellation shaping

The paper presents a novel and simple technique for improving the error performance of bandwidth-efficient bit-interleaved turbo-coded modulation (BITCM) schemes. This method consists of using a shaping block code placed between the modulation and turbo coding functions in order to achieve constellation shaping. By considering the example of a 3 bit/dim BITCM system based on 16-ary pulse-amplitude modulation, the achievable shaping gain is evaluated using the concept of mutual information, and, in a detailed manner, some important design issues such as the search for good shaping codes are addressed. It is finally shown that, for typical BITCM systems, this technique offers error performance improvements approximately equal to 0.6 dB while adding little complexity to the system.