 Detect Correct Peak Correction Peak location, (cut, scale, shape, amplitude, length cancel, ...) Peak Manager FIGURE 6-15 Example crest factor reduction (CFR) implementation. Typical filter implementations are Half-Band because of their lower implementation com- plexity. Note that the receiver operation includes a similar filtering stage to bring the over- sampled signal bandwidth down to baseband rate. Crest factor reduction CFR algorithms are a relatively simple mechanism to increase the PA efficiency (and hence achievable output power) of the system, even if (in low RF output power environments), DPD is not used to save system complexity. Many implementation options exist, we discuss a very basic one here (Fig. 6-15). Power measurement. Typically implemented as a Coordinate Rotation Digital Computer unit dedicated that converts the input signal (Z = A + jB) to polar. 232 Open Radio Access Network (O-RAN) Systems Architecture and Design The Peak Detector detects the occurrence of a peak PAPR situation. The Peak Detector can be as simple as detecting a hard boundary when the input signal X(n) becomes greater of equal to the defined peak level A. The Peak Manager defines the corrective action to be taken on the detected peak. For example, this unit could generate a "cancellation pulse" to be subtracted from the original signal. This pulse could rely on premade cancellation pulses that are selected from a memory. The Peak Corrector applies the counter action to reduce or remove the peak (in this example, perform the subtraction of the cancellation pulse from the baseband signal). A filter stage to smooth out the resulting signal and remove out-of-band artifacts. This filter can be implemented as an FIR filter in time domain or using FFT operations and a frequency domain implementation, depending on complexity tradeoffs. CFR implementations can work in streaming mode (typical for hardware or FPGA centric implementations) or batches of samples (typical for DSP software centric implementations) where batch processin