Reinvestigation of 16-QAM BI-STCM-ID labellings: Point-wise distance spectrum approach

This paper contributes a new method to unveil properties of BI-STCM-ID (Bit-Interleaved Space-Time Coded Modulation with Iterative Decoding) labellings. It consists in computation of point-wise distance spectrum. Thanks to the proposed approach, it is shown that several labelling maps, found here by means of the genetic algorithm, are equivalent to each other and to the optimal ones, known from the literature. Although the optimal labellings of BI-STCM-ID appear to be completely random, the point-wise spectrum shows that they are quite even. Prior to demonstration of the proposed method in action, the most important facts about BI-STCM-ID are reviewed.