Irregular Signal Constellations , Mappings and Precoder

This paper investigates adaptive bit-interleaved coded modulation (BICM) with different iterative decoding schemes for bandwidth efficient transmission. We assume knowledge of the average channel quality at the transmitter. For a fixed modulation scheme, the bandwidth efficiency can be adapted to the channel quality by changing the channel code rate and the iterative decoding procedure can be optimized by using irregular codes. In this paper, we will fix the channel code and focus on the modulation in the BICM system. We propose irregular modulation schemes, where different signal constellations, mappings and precoder may be used within one code block. With these schemes, the bandwidth efficiency can be adapted to the channel quality in an accurate way and the iterative decoding procedure can be optimized for a fixed channel code. Thus, new additional possibilities to design a highly adaptive system are given.