256QAM DL / 64QAM UL enablement and conditions

256QAM Downlink Requirements

256QAM in downlink and 64QAM in uplink represent the highest modulation orders in 5G NR, providing significant throughput gains when channel conditions support them. 256QAM DL carries 8 bits per symbol compared to 64QAM's 6 bits — a 33% increase in spectral efficiency. However, 256QAM requires excellent conditions because constellation points are much closer together: SS-SINR must exceed 20 dB for clean symbol discrimination, the gNB transmitter EVM (Error Vector Magnitude) must be below 3.5% demanding strict linearity, and the UE must report 256QAM capability since not all devices have the…