adio Access Network (O-RAN) Systems Architecture and Design Receiver Reference sensitivity level: Minimum mean power received at the antenna connector for which a throughput requirement (95%@QPSK, R = 1/3). Wide area: -95.7 - 101.7 dBm; medium range: -90.7...96.7 dBm; local area: -87.7 - 93.7 dBm depending on channel B/W. In-band selectivity and blocking: Defines capability to operate in interference condition where interference signal is ~ 10 dB below wanted signal. Out-of-band blocking: Defines capability to receive a wanted signal in presence of an unwanted interferer in outside bands. Receiver spurious emissions: Defines unwanted emissions from the receiver, either generated internally or from interaction with a colocated transmitter. Receiver intermodulation: Defines sensitivity from two interfering signals (say, fl, f2) where the interfering frequencies are set such that their third-order intermodulation products (2x f1 -f1; 2x f2-f1) are such that they fall into receiver passband. In-channel selectivity: Measures receiver capability to receive a wanted signal in its assigned frequency space (REs) with an interfering signal in the same channel but at different allocated frequency space (and at higher power spectral density). Calibration Analog subsystems never behave perfectly, and RF is an example of this. Hence, RF subsys- tems need to be calibrated to measure and enable compensation for inaccuracies. A few examples include: Rx/Tx IQ mismatch: IQ imbalance or IQ mismatch is an artifact of a zero-IF RF demodulator. The demodulator multiplies the RF signal with an in-phase (0 degree) and a quadrature (90-degree offset) signal to generate I and Q baseband signals, but the 0 and 90 degrees are not necessarily perfect given that they are generated through an analog delay. Compensation can be done in the analog domain (adjust the delay to generate the 90-degree offset signal) or in the digital time or frequency domains. Measurement is done typically at boot time and tracked slowly over time given its semistatic