In Rel-15, for NR Bands n7, n38, n41, n77, n78, and n79 the UE shall be equipped with 4Rx ports as a baseline. In some conditions, e.g., in RRC idle/inactive mode, or in low data rate services for UE with high SINR (e.g., UEs at cell center), fallback to 2Rx antenna operation is also allowed to save UE power. In [2], simulation results show that power saving gain of adaptation to number of antenna is up to 30%, with tolerable packet delay loss. The related observations are as follows: