# Resource Management for Collaborative 5G-NR-V2X RSUs to Enhance V2I/N Link Reliability
## 4 User Association Scheme for Collaborative RSUs
### Relailibilty Evaluation Based on BS-Type, UE-Type, and Hybrid RSU  
We conduct a performance evaluation to confirm the reduction of the shaded area through the hybrid RSU method on the following three surfaces. Outage probability is defined as the probability that the received SINR of a VUE is less than the SINR threshold value presented, and the SINR threshold is set as the SINR value of the VUE when 5% of all VUEs in the simulation experience an outage. In addition, we evaluate and calculate the outage probability in each case using (9). \[P_{out}=1-P_{b}(SINR\geq SINR_{Threshold}) \tag{9}\]  
In the case of Figure 4a, the cumulative distribution function (CDF) represents the received SINR values of VUEs that occur in the cases of UE-type RSU, BS-type RSU, and Hybrid RSU, and the SINR threshold value for checking the outage probability is set assuming that 5% of all VUEs experience an outage in the presented scenario. It can be observed that the received SINR values in the presented overall scenario are generally higher in the Hybrid RSU approach, and the SINR threshold values at which the outage probability can occur in each case are \(-\)4.85 dB for UE-type RSU, \(-\)2.64 dB for BS-type RSU, and \(-\)0.84 dB for Hybrid RSU, respectively. The presented Hybrid RSU has a higher SINR threshold value than UE/BS-type RSU, and overall, the received SINR is improved when the UE/BS-type RSUs cooperate. We confirm outage probability for each type by setting the SINR threshold value as the reference for the presented Hybrid RSU type to perform a more detailed evaluation and analysis. When we check outage probability at the presented  
Figure 3: (a) BS\(-\)type RSU; (b) UE\(-\)type RSU; (c) Hybrid RSU SINR map. SINR threshold value for UE/BS-type RSU, we find that 16% of all VUEs experienced an outage. When we apply the presented Hybrid RSU approach, the proportion of all VUEs experiencing an outage is reduced to 5% as the SINR of VUEs effectively increases, and the outage probability is reduced up to 11% compared to the UE/BS-type RSU approach. This indicates that the Hybrid RSU approach is helpful in the system. The decrease in the outage probability in the simulation can be represented as a reduction in the shadow area, and this approach is more efficient for resource allocation. Furthermore, the improvement in throughput occurs when the outage experienced by VUEs is reduced, which can be clearly observed in Figure 4c. Additionally, the evaluated VUE received interference refers to all interference received from adjacent cells, not the serving cell providing service to the VUE. The interference is calculated using Equation (10). \[\sum_{k\
eq n,k=1}G_{m,UE}^{k}P_{m,UE}^{k}+\eta_{m} \tag{10}\]  
In the case of interference, the UE-type RSU has a higher interference than the BS-type RSU, because of the denser distribution of UE-type RSUs than the BS type. Accordingly, the interference from other UE-type RSUs increases and the VUE receives a signal from a nearby UE-type RSU. Thus, we confirm a significant VUE interference due to the application of different parameters from the BS-type RSU. In the case of Figure 4b, it is an evaluation of  
Figure 4: (a) 5G\(-\)NR V2X BS/UE/Hybrid RSU outage probability; (b) 5G\(-\)NR V2X BS/UE/Hybrid RSU interference; (c) 5G\(-\)NR V2X BS/UE/Hybrid RSU throughput. the 50% interval of the cumulative distribution function (CDF) to confirm interference. It has a value of \(-77.37\) dB for BS-type RSU, \(-50.71\) dB for UE-type RSU, and \(-62.26\) dB for hybrid RSU. In the case of throughput, we evaluate the 50% CDF and calculate throughput using (11). \[Throughput=\frac{TB}{Accounted_{TTIs}\times TTI_{Time}} \tag{11}\]  
Throughput means the transport block (TB) size received per unit of time. The TB value represents the total number of bits received in the VUE, and TTI\({}_{\text{Time}}\) represents the size of the maximum transmission time interval(TTI), and Accounted\({}_{\text{TTIs}}\) represents the number of RBs assigned to the VUE receiver.