Study on circularly arranged non-uniform constellations in dual-polarized MIMO-OFDM transmission

We have been conducting research on a transmission system using ultra-multilevel orthogonal frequency division multiplexing (OFDM) technology and dual-polarized multiple-input multiple-output (MIMO) technology for the next generation of terrestrial broadcasting. Regarding the carrier modulation scheme, we studied a non-uniform constellation (NUC) which improves transmission characteristics by optimizing the distance between the signal points. In this study, we considered a circularly arranged NUC configured by 2^m signal points in which m is an odd number. We performed simulations confirming that a NUC has advantages compared with a conventional uniform constellation (UC). Furthermore, we verified that the improvement in transmission performance varies depending on the number of signal points in the carrier modulation and the code rate of forward error correction (FEC). We also used a NUC in a dual-polarized MIMO-OFDM scheme. The results show the improvement of the NUCs tends to decrease in multipath environments.