s are considered impractical today due to high OTA losses, making the TE transmit power requirement too high. For the transmitter 12.5 Dual Uplink Performance Challenges for NSA Operation OFF power, the requirement of -35 dBm would need to be relaxed by 24 dB to become "test-able," bringing the "Off" Tx power at higher level than the minimum transmit power requirement. With the OFF power not being finalized, the dynamic On/Off tran- sient time is also problematic. Another major challenge in OTA conformance is the related test cases that must be tested under ETC conditions, where the temperature and battery voltage must be var- ied. For temperature control, it has been proposed to enclose the UE in "air bubbles" to meet the -10+55°C range. For the battery, the UE must be modified to accom- modate a dummy battery that is connected to an external power supply. With these constraints, any test that requires device rotation becomes impractical to measure at ETC. For example, there has been a recent agreement that TRP, EIS, and EIRP SC are not tested at ETC, but the question of peak searches is still being debated as it is consid- ered not practical to perform device rotation over an hemisphere or even a full sphere within an "air bubble" [14]. Considering that OTA testing is intrinsically more time con- suming than conducted testing, test cases that are selected for ETC should also consider the impact of the test time and therefore the product development cost. Other TE limitations such as lack of UL MIMO decoding capability limit uplink testing to be performed one polarization at a time. 12.5 Dual Uplink Performance Challenges for NSA Operation 12.5.1 From Single UL to Dual UL Operation With many bands and features common to LTE, the support of 5G for standalone oper- ation in FR1 constitutes an evolution from legacy solutions. As such, 5G radio solutions inherit from the successive challenges imposed as we moved from single-carrier opera- tion, to downlink carrier aggregation to dual uplink operation. Figure 12.16 s