# Performance Analysis of Two-Hop mmWave Relay Nodes over the 5G NR Uplink Signal
## 4 Simulation Results and Discussion
### Bit Error Rate Performance  
In this simulation, the objective function studied in this subsection is the bit error rate (BER) between the source (NR-UE) and destination (gNodeB) through the uplink mmWave relay node. Therefore, we compared the overall performance of the implemented relaying algorithms. Figure 11 shows the BER performance comparison of the uplink mmWave \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameters** & **Gali\({}_{84}\)** & **HMC292 ALC3B** & **HMC499 LC4** & **HMC944 APMSE** & **HMC519 LC4** \\ \hline Frequency Range (GHz) & 0 to 6 & 14 to 30 & 24 to 28 & 20 to 28 & 18 to 28 \\ \(\rm{G_{lin}}\) (dB) & 19.2 & –9 & 16 & 16 & 14.4 \\ Local Oscillator Freq. (GHz) & - & 25 & - & - & - \\ Input Return Loss (dB) & 18 & 13.2 & 8 & 12 & 15 \\ Output Return Loss (dB) & 8.9 & 12.5 & 12 & 22 & 20 \\ OIP3 (dBm) & 38 & 20 & 34 & 36 & 23 \\ \(\rm{P_{1 dB,out}}\) (dBm) & 21.2 & 9 & 23 & 27 & 11 \\ \(\rm{P_{sat,out}}\) (dBm) & 22.1 & 13 & 23.5 & 28 & 14 \\ Noise Figure (dB) & 4.4 & 10 & 5 & 4 & 3.5 \\ \(\rm{GS_{sat}}\) (dB) & 3.5 & 2.2 & 4 & 5 & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of the elements of mmWave transmitter and receiver chains. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Backhaul Link** & **Access Link** \\ \hline Signal Bandwidth & 25 MHz & 25 MHz \\ Carrier Frequency & 3.5 GHz & 26.1 GHz \\ Tx/Rx schemes & SISO, \(2\times 2\times 2\) and \(2\times 4\times 4\) & SISO, \(2\times 2\times 2\) and \(2\times 4\times 4\) \\ Subcarrier Spacing & 30 kHz \\ Modulations & 64-QAM and 256-QAM & 64-QAM and 256-QAM \\ Channel Models & CDL-D & CDL-D \\ Light-Vision & LOS & LOS \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Main parameters of simulation. MIMO co-operative network of the NR RNs versus SNR, where the 64-QAM modulation scheme has been considered. Through the comparison of simulation curves, it can be clearly seen that the BER performance of the proposed uplink mmWave SISO A&F protocol is discrete; however, the SISO D&F strategies with PCE and LS algorithms are better than the SISO A&F. Additionally, the uplink mmWave SISO NR-D&F strategy together with PCE exhibited the best performance among the proposed uplink mmWave SISO NR-RNs. In particular, it can be verified that the SISO D&F with PCE reached the BER level of 1.6 \(\times\) 10\({}^{-2}\) at around SNR = 20 dB. In addition, Figure 11 also shows that although the BER performance of the proposed SISO D&F protocol with LS algorithm is less than the SISO D&F with PCE, in this sense, the BER level is 1.9 \(\times\) 10\({}^{-2}\) at 20 dB. In order to better the performance in the communication between the NR-UE and gNodeB, the MIMO technique has been implemented in the link-level co-operative simulator, with exactly (2 \(\times\) 2) or (2 \(\times\) 4) mmWave MIMO channels and (2 \(\times\) 2) or (4 \(\times\) 4) sub-6 GHz MIMO channels in the access link and backhaul link, respectively, were considered. Since our proposed MIMO algorithm, it can be seen that the mmWave co-operative system considerably improved the BER performance, in comparison with the uplink mmWave SISO NR relay node co-operative network. It is interesting to observe that the uplink mmWave (2 \(\times\) 2 \(\times\) 2) NR-A&F protocol exhibits the same BER level of the SISO D&F with the PCE algorithm at around SNR = 18 dB; therefore, a performance gain of 2 dB is reached. As shown in Figure 11, the BER performance of the (2 \(\times\) 4 \(\times\) 4) MIMO NR-A&F strategy decreases tremendously, which, compared with the (2 \(\times\) 2 \(\times\) 2) MIMO NR-A&F protocol, is an enhancement of 7.5 dB. In addition, the uplink mmWave MIMO D&F strategies have generated an improved performance.