# Resource Management for Collaborative 5G-NR-V2X RSUs to Enhance V2I/N Link Reliability
## 4 User Association Scheme for Collaborative RSUs
### Calculating the SINR UE-Tye RSU and BS-Type RSU Channel Model  
Each RSU type configures in a cellular multi-tier network consisting of different transmission power and other parameters. The VUE checks the RSU with the highest received SINR at the V2X application server and selects the RSU to serve the VUE. Based on the cellular V2X network presented earlier, we check the shaded area for each RSU type. In addition, we analyze the simulation results using the mutual cooperation of each RSU type, minimizing the shaded area. We conduct the simulation through SLS analysis implemented in the 5G-NR-V2X environment. After configuring the V2X environment considering the network layout (urban case), we evaluate the VUE distribution and mobility model, RSU distribution, channel model, traffic model, vehicle terminal interruption probability, reception interference, and average throughput. The received SINR, according to the RSU type of each vehicle, represents the shaded area within the simulation environment; (6) calculates the SINR for the general received area.  
\[SINR_{m,BS}^{n}=\frac{G_{m,BS}^{n}P_{m,BS}^{n}}{\sum_{k\
eq n,k=1}C_{m,BS}^{k} P_{m,BS}^{k}+\eta_{m}} \tag{6}\]  
In (6), \(G_{m,BS}^{n}\)\(P_{m,BS}^{n}\) are calculated by multiplying \(G_{m,BS}^{n}\), a propagation gain between BS-type RSU n and VUE m, and transmission power \(P_{m,BS}^{n}\) transmitted from BS-type RSU n and VUE m. \(G_{m,BS}^{k}\) and \(P_{m,BS}^{k}\) represent the total interference received from BS-type RSUs in all adjacent cells except the supported RSUs k, where \(\eta\) is the thermal noise per RB. UE-type RSU also calculates the generated incoming SINR by (7).  
\[SINR_{m,UE}^{n}=\frac{G_{m,UE}^{n}P_{m,UE}^{n}}{\sum_{k\
eq n,k=1}C_{m,UE}^{k} P_{m,UE}^{k}+\eta_{m}} \tag{7}\]The UE type RSU is calculated by multiplying the propagation gain \(G_{m,UE}^{n}\) and transmission power \(P_{m,UE}^{n}\) between VUE m and UE type RSU n, as described above. In cases of interference, the SINR value is calculated by considering the interference from all UE type RSUs k in the simulation except for the UE-type RSU being serviced, and the interference between VUE m and these RSUs. The VUE-received SINR, obtained by applying the SINR calculated through each equation to the SLS, is shown in Figure 3. In the case of Figure 3a, a SINR map represents the SINR received when the VUE receives services from the BS-type RSU, and in the case of Figure 3b, the SINR received when the VUE receives services from the UE-type. We apply (8) to minimize the shaded area and select the supported RSU according to the SINR received from the RSU.  
\[\begin{split} SINR_{BStype}<SINR_{UEtype}\text{ \emph{for} \emph{Seruing} \emph{BS} type RSU}\\ SINR_{BStype}>SINR_{UEtype}\text{ \emph{for} \emph{Seruing} \emph{UE} type RSU}\\ \end{split} \tag{8}\]  
Figure 3c shows the result through the SINR map when using the proposed hybrid RSU method. As a result of the simulation, we confirm that the proposed hybrid RSU method reduces the shadow area by mitigating co-channel interference.