# Performance Analysis of Two-Hop mmWave Relay Nodes over the 5G NR Uplink Signal
## 3 Link-Level Co-Operative Simulator
### Network Model: Topology and Communication Channel  
In this subsection, the description of the scenario and the channel models used in the link-level co-operative simulator will be introduced. The simulation scenario to the assessment of uplink mmWave MIMO NR-relay node co-operative network through the proposed link-level co-operative simulator is presented and described. A series of Monte-Carlo simulations in an urban environment, particularly in the indoor-to-outdoor scenario has been performed. Thus, the indoor-to-outdoor environment scenario with uplink mmWave MIMO new radio relay protocol, which has been considered in this paper, is presented in Figure 8. Hence, there is a line-of-sight channel in both links, between the NR-UE and NR-relay node and the NR-relay node and gNodeB, respectively. The 5G network in Figure 8 is composed of one NR-UE, which serves an uplink gNodeB by means of the mmWave new radio relay node (NR RN). As seen from the figure, A&F and D&F mmWave new radio RNs have been designed, where the protocols operate in out-band frequency. Therefore, the access link and backhaul link work, respectively, at 26 GHz, taking advantage of the unlicensed bands (FR2) and in sub-6 GHz bands in accordance with 5G standards (FR1), as has been described in the previous section. The relays used in the mmWave two-hop architecture are out-band and are intended to extend the 5G mobile coverage to an indoor environment. In the topology, the NR-relay node can use either the A&F and D&F relaying strategies. Finally, the direct link between the NR-UE inside the building and the gNodeB have not been simulated due to both nodes work in the different frequency bands and, additionally, the 5G base station coverage is unreachable by the NR-UE. In the developed link-level co-operative simulator, the performance of both proposed and implemented relays will be compared to observe the improvement achieved by our mmWave architecture. In Table 1, the corresponding distances to determine the path loss of the indoor-to-outdoor environment proposed and simulated in this paper are presented. Figure 8: Indoor-to-outdoor environment scenario with uplink mmWave MIMO new radio relay protocol. Then, the channel and path loss models used in the link-level co-operative simulator will be explained in detail. It should be highlighted that the employed channel model is emulated through Matlab(tm) ToolBox software, which considers standardization of the 3 GPP [21]. In this work, we have assumed that the access link is implemented as a Line-of-Sight (LOS) channel, and the channel model of the Clustered Delay Line (CDL)-D [22] were considered. It should be noted that, in [22], a large number of 5G NR propagation channels show support frequency bands over the range 0.5-100 GHz, which can simulate environments such as an urban microcell street canyon, urban macrocell, indoor office, rural macrocell, and mobility, also including, a geometry-based stochastic channel model. In this sense, the 3 GPP indoor office path loss model is used to emulate the mmWave LOS channel access link, being capable of simulating various typical indoor deployments. Accordingly, the mmWave indoor office path loss model can be written by  
\[\text{PL}_{\text{AL}}=32.4+17.3\log_{10}(\text{d}_{\text{AL}}^{1})+20\log_{10} (\text{f}_{\text{c}})+\sigma_{\text{AL}}\quad\quad 1\text{ m}\leq\text{d}_{\text{AL}}^{1}\leq 100 \text{ m}, \tag{11}\]  
where \(\text{d}_{\text{AL}}^{1}\) (m) represents the distance between NR-UE and NR-RN and \(\sigma_{\text{AL}}\) denotes the shadowing term with zero mean and standard deviation of 3 dB. Additionally, \(\text{f}_{\text{c}}\) is the carrier frequency in GHz. On the other hand, the CDL-D channel model is considered for the FR1 backhaul link, which is modeled according to the specification of the 3 GPP and emulated by the communication ToolBox of Matlab(tm) software.