Essence of 16-QAM labelling diversity

Labelling diversity has appeared to be an efficient method to improve the performance of bit-interleaved space-time coded modulation with iterative decoding. It consisists in applying two different labelling maps within two spacial streams of the transmitter, which improves the benefits derived from multi-antenna transmission. This reported work reveals a cardinal rule the two labellings must obey to become the optimal pair for labelling diversity purposes. It is concluded from results of a generalised binary switching optimisation algorithm, delivered herein, and from distance spectrum analysis.