# Performance Analysis of Two-Hop mmWave Relay Nodes over the 5G NR Uplink Signal
## 5 Conclusions  
In this paper, the uplink in a two-hop 5G new radio co-operative system in millimeter bands has been simulated and studied, based on practical assumptions in terms of system and network implementation. For the millimeter band operation of relay nodes, 26 GHz Tx/Rx chains have been designed and implemented. An indoor-to-outdoor scenario has been considered. Two relaying strategies have been studied: an RN amplify-and  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**RN Protocols** & **Products** & **Summations** & **Flops** \\ \hline A\&F & \(\rm N_{T}^{R}N_{R}^{R}T\) & \(\rm N_{T}^{R}T(N_{R}^{R}-1)\) & \(\rm 2N_{T}^{R}N_{R}^{R}T-N_{T}^{R}T\) \\  & \(\rm N_{T}^{S}N_{R}^{R}[\frac{73^{2}+97^{2}-47}{6}]\) & \(\rm N_{T}^{S}N_{R}^{R}[\frac{73^{2}+15T^{2}+27}{6}]forward relay node (A&F RN) and RN decode-and-forward relay node (D&F RN). For the decode-and-forward strategy, two schemes have been analyzed and implemented. The first one considers channel knowledge (PCE) to perform the decoding and encoding stages and the second one takes into account the practical channel estimation through the Least Square (LS) estimator. The 5G NR uplink signal fulfills the requirements standardized by the 3 GPP and SISO and MIMO schemes have also been considered. A hardware implementation of the co-operative network and relay nodes has been simulated at the link level using Matlab\({}^{\text{TM}}\) and Simulink\({}^{\text{TM}}\) commercial software.  
Key perfomance indicators (KPIs) of the uplink mmWave NR-RNs have been studied and analyzed. The numerous results obtained from the Monte-Carlo simulation of the system showed that a two-hop uplink mmWave NR-RN co-operative system can greatly improve the average performance of the communications between the User Equipment (UE) and gNodeB. The obtained results demonstrate that the key performance indicators obtained by uplink mmWave NR A&F protocol are lower than the those obtained via the uplink mmWave NR D&F strategy. Furthermore, it can be concluded that the NR D&F PCE algorithm presents a higher average performance than the NR D&F LS protocol. For example, the maximum throughput of the proposed NR D&F PCE algorithm with the SISO antenna technique and 64-QAM constellation is 15.83 Mbps at SNR = 20 dB; however, taking into account the NR D&F LS strategy, the reached average throughput is lower, by approximately 13.23 Mbps. It can be noted that the uplink mmWave NR-RN co-operative system with MIMO technology led to a considerable average performance in terms of the indoor-to-outdoor communication, which achieved higher KPIs in the 256-QAM signal. In addition, it was demonstrated that D&F relay node presents high computational complexity in comparison with A&F and the proposed co-operative simulator, which is a topic not deeply addressed in related research. Additionally, this paper introduces the first step for the implementation of the uplink mmWave MIMO NR-RN co-operative network through Matlab\({}^{\text{TM}}\) and Software Defined Radio (SDR), which will be followed up on by our research team.  
[PERSON] conceived the paper, designed the experiments, performed experiments, analyzed the data, and wrote the paper; [PERSON] and [PERSON] reviewed and edited the paper. Both authors have read and agreed to the published version of the manuscript.  
This work was supported by the Spanish Ministry of Science, Innovation and Universities within the project TEC2017-87061-C3-1-R (CIENCIA/AEI/FEDER, UE). The work of [PERSON] is supported by a pre-doctoral Contract PRE2018-085032 from the Ministry of Science and Innovation.  
Data Availability StatementData sharing not applicable.  
The authors declare no conflict of interest.