Performance of dual-polarized MIMO-high-order-modulation OFDM in deteriorated transmission channel

Japan Broadcasting Corporation (NHK) has been conducting research on high-order-modulation orthogonal frequency-division multiplexing (OFDM) schemes, such as 4096QaM, dual-polarized multiple-input multiple-output (MIMO), and low-density parity-check (LDPC) code schemes, for large-capacity transmissions of next-generation digital terrestrial broadcasting. In 2014, we conducted a field experiment on MIMO-OFDM transmission in Hitoyoshi-city, Kumamoto prefecture, Japan. In 2016, the technologies were tested in a field experiment in Rio de Janeiro (RJ), Brazil. In addition, we conducted a transmission simulation of MIMO-OFDM and a calculation of the MIMO channel capacity by using the deteriorated MIMO channel measurements from RJ. In our previous study, we reported that using weighted log likelihood ratios (LLRs) and an erasure process in each subcarrier improves the bit error rate (BER) performance in a single echo environment. The erasure process sets the LLR to 0 when the MIMO channel of a subcarrier deteriorates. In this study, we examined the BER performance in cases with or without the erasure process by using the deteriorated MIMO channel measurements from RJ. We found that the erasure process gives quasi-error free (QEF) results even when the MIMO demodulator uses a zero forcing (ZF) algorithm with a higher order modulation such as 4096QAM.