The UE may perform the process of FIG. 12 multiple times. The UE may determine the total GD for different combinations of transmit and receive antennas. If the UE is FDD capable, then frequencies may be taken into account. For an FDD capable UE, it is usually the case that the UE Rx does not have to listen at its Tx frequency. Even if the UE includes a special RX for that frequency, it may not have the same group delay as the usual Rx chain. In this instance, as part of its capability reporting, the UE may report whether it has such a special Rx, and a corresponding accuracy of group-delay measurement based on the difference in center frequency. In an aspect, the special Rx may be a regular Rx with a different down-conversion frequency fc in the RF front-end, and the impact of fc on group delay may be calibrated, e.g., in off-line testing as part of factory calibration. Even for FDD group delay determination, it may be prudent to include resources for calibration gap with rank reduction, for example, to free up some transmit antennas which may then be used for reception instead, as described earlier. Other factors such as the modulation and coding scheme (MCS) may also be considered.
