## 3 Implementation and Measurement
### Experimental Setup Testbed
Therefore, for our particular results in the transmission path, the EVM is preserved from a linear target dataset, using the complex baseband input signal \(x(n)\) that considers an interference-free situation and calculated at the receiver signal to obtain a representation of the impact of hardware impairments. As shown in the Figures 6 and 7, we evaluate two target performance tests: (_i_) the best EVM used \(I_{bst}(n)\) to preserve metrics, which is saved as an actual transmitter signal, then we compare (_ii_)  
after clipping conditioning. If we consider the first test with negligible hardware impairments, thus, the EVM should only be determined by the receiver noise. In Figure 7, the system performance evaluated is shown with its EVM associated at transmitter and receiver, and the EVM is sampled and compared against the OFDM symbols. As it is well known, the calculated EVM is sensitive to any noise and signal distortions that are reflected in its amplitude and phase components, thus a further correction can be applied using DPD. As a rule, when calculating the EVM, systematic errors (i.e., the shift of the constant component of current or voltage, phase, I/Q or amplitude imbalance, etc.) are not taken into account and require preliminary correction. However, such correction is not full. On the other hand, a very important role has the distance between sources of signals in angle coordinates. The EVM is calculated from its percentage as the square root of the power ratio between mean error vector to the mean reference vector power for a given number of samples \(N=2^{12}\) as follows:  
\[\text{EVM}(\%)=\sqrt{\frac{\frac{\frac{1}{N}\sum\limits_{n=1}^{N}\left|I_{bst} (n)-I_{meas}(n)\right|^{2}+\sum\limits_{n=1}^{N}\left|Q_{bst}(n)-Q_{meas}(n) \right|^{2}}}{\sum\limits_{n=1}^{N}\left|I_{bst}(n)+Q_{bst}(n)\right|^{2}}} \times 100 \tag{10}\]  
Figure 6: Constellations diagram for the actual transmitter LTE 10–MHz 64–QAM signal and CFR scale factor, (**a**) actual 64–QAM 10–MHz signal, and (**b**) receiver signal. It consists of two transmitter cards that enable the upconversion and filtering through the AD9361 transceiver before passing it to the ADC in the receiver processing. To estimate PAPR and the signaling condition, it is crucial to evaluate the TX-RX overall performance, in [25] it is defined as a weighted cubic-spline approach as a proper alternative and multivariable analytical modeling to reinforce the spectral efficiency. The purpose of using this development board is to integrate RF applications with systems capable of being programmed with variable bandwidths for LTE applications. To evaluate the PAPR obtained, the CCDF is used to represent the probability that the envelope signal exceeds a defined threshold in the implementation stage. In this evaluation, a PAPR target reduction of at least 3 dB is defined, the CFR process-clipping based is introduced in the implementation stage for LTE signals evaluation, under OFDM multiplexing, in this case the PAPR is calculated with the real-valued samples data as:  
\[\text{PAPR}(n)=\frac{\left|x(n)\right|^{2}}{\frac{1}{N}\sum_{n}^{N-1}\left|x(n )\right|^{2}} \tag{11}\]  
CCDF is related to the PAPR calculation based on the relation:  
\[\text{CCDF}(\%)=P_{t}(\text{PAPR}>P_{ref}), \tag{12}\]  
where \(P_{t}\) provides information on the amount of time the signal spends at or above a specific power level, and \(P_{ref}\) is denoted as the PAPR target. The setup system is calibrated so that a synchronized signal is applied properly to the amplifier input. Note that we set a calibration power for power peak and average levels at the amplifier output after each iteration in order to obtain several CFR factors. Figure 5B shows the transceiver that operates in the band; the ARRadio card integrates an AD9361 RF transceiver to operate in an range of 2.4-2.5 GHz. Once the sample rate and RF bandwidth have been established, the signal to be implemented in MATLAB is designed as shown in Figure 5E, performing with the 64-QAM modulation.