## 5 Experimental Results
### Performance Evaluation of Proposed Hardware D&F Co-Operative 5G Network  
This subsection shows experimental results for the D&F relay node co-operative 5G network in terms of the bit error rate and throughput of the 5G NR physical downlink shared channel transmission from base station. In the results, the proposed D&F protocol is compared with non-co-operative 5G network (direct link). Furthermore, we consider an experimental network encompassing one gnodeB equipped with \(\mathrm{N_{T}^{\mathrm{G}}}=\{1,2\}\) transmitter antennas, and transmitting the PDSCH over 64-QAM and 256-QAM modulation schemes. It should be highlighted that, in the figures, D&F relay node represents the received signal of the UE through the access link, and direct link symbolizes the waveform received at the UE directly from gnodeB. On the other hand, the D&F protocol is equipped with \(\mathrm{N_{R}^{R}}=\mathrm{N_{T}^{R}}=\{1,2\}\) receiver and transmitter antennas; furthermore, the user equipment is equipped with \(\mathrm{N_{R}^{D}}=\{1,2\}\). We have denoted \(\mathrm{N_{T}^{\mathrm{G}}}\times\mathrm{N_{R}^{R}}=\mathrm{N_{T}^{R}}\times \mathrm{N_{R}^{D}}\) as per the considered MIMO antenna technique in the proposed D&F relay node co-operative 5G network. The first results have been performed through the Arnitsu spectrum analyzer, in which the main aim is to demonstrate that the retransmitted signal by the D&F relay node can be demodulated by the commercial equipment and to verify the functioning correct of this stage on the proposed node. In addition, direct link has been measured for comparison. The PBCH demodulation and 5G summary of the signal transmitted by the gnodeB are shown in Figure 15, in which direct link has been taken into account. Moreover, Figure 16 shows the same results but considering the received signal from the access link (D&F protocol). Therefore, from the obtained results in Figures 15 and 16, it can be observed that there exists a full synchronization and demodulation in both links. Furthermore, it should be noted that the UE achieved better demodulation of the PBCH through the received signal from D&F relay node with 6.33% of RMS EVM. However, the PBCH demodulation is  
Figure 14: Median EVM at physical downlink shared channel for two modulation schemes, LOS and NLOS environment, and equalization step under real test. reached by means of direct link but with higher EVM, exactly 28.77%. Other channels and reference signals have been detected and their average EVM are shown in Figures 15 and 16, for example, PSS, SSS, and SS-SINR of the direct link with 35.20%, 32.39%, and 9.79 dB, respectively. Nevertheless, the obtained results of the EVM for access link are considerably low in comparison with direct link, 9.40% and 9.47%, respectively. Moreover, the SINR reached though the D&F protocol was 20.47 dB with a gain of 10.68 dB with respect to a direct connection between gnodeB to UE. The rest of the discussed results have been obtained through the implemented UE. Therefore, Figure 17 shows the corresponding BER performance comparison of the implemented D&F relay node co-operative 5G system and non-co-operative 5G network, taking into account the 64-QAM modulation scheme over the PDSCH. It can be seen that direct link with SISO achieved a discrete performance. However, the D&F protocol co-operative 5G network with SISO technique reached the best performance among the implemented system with SISO technology. From Figure 17, it can be verified that the direct link with SISO antenna technique reached the BER level of \(1.5\times 10^{-1}\) at around \(\mathrm{P_{\mathbf{BS}}}=15\) dBm. Nevertheless, when the MIMO antenna technology was introduced in the non-co-operative system, specifically 2 \(\times\) 2 MIMO, it can be seen that the direct link increased the BER performance, in comparison with the SISO technique.