al algorithms required to improve the performance of this chain, including Crest Factor Reduction (CFR) and Digital Pre Distortion (DPD) algorithm selection and implementation. 128 Open Radio Access Network (O-RAN) Systems Architecture and Design Instantaneous bandwidth and occupied bandwidth After RF operating frequency and output power, Instantaneous BandWidth (IBW) is probably one of the most important RU parameters. It defines the frequency boundaries of the allo- cated bands-from the lowest to the highest frequency occupied. Occupied BandWidth (OBW) defines the sum of allocated/occupied bandwidths in the frequency occupied (Fig. 3-15). In case of contiguous spectrum, IBW and OBW are the same, but in case of mul- ticarrier deployment, IBW and OBW are different-consider a deployment example in the United States CBRS bands where (worst case), IBW can be 145 MHz (3.55-3.7 GHz) but OBW can be 20 MHz (one 10 MHz carrier in 3.55-3.65 GHz and one 10 MHz carrier in 3.69-3.7 GHz). OBW is relevant for low-PHY components such as beamforming and FFT complexity whereas IBW is relevant for Digital Front End (DFE) functions that are implemen- ted across the whole IBW. This includes the data converters and related components. Receiver chain analysis Some back-of-the-envelope calculations can help us understand the performance of the receiver chain, to understand the receiver sensitivity and dynamic range metrics. This also helps explain the bypass option for the secondary Low Noise Amplifier (LNA) and the requirement to be able to configure the demodulator gain and/or baseband Variable Gain Amplifier (VGA) gain. Consider a general Radio Frequency (RF) transmitter & receiver diagram with a baseband I/Q interface, as shown below (Fig. 3-16): Without dictating physical chip boundaries, we can analyze the sensitivity and dynamic range by assessing the component performance of the various components in the (bottom) receive chain. Table 3-6 shows some examples with typical values. In this example, we assume that the Analog-to-Digi