## 4 Simulation Scenario with Ultra-Dense Urban Environment
### Performance Evaluation  
A load of a cell indicates the utilization of the resources of the cell expressed as a percentage ratio of currently used Physical Resource Blocks \(PRB\)s to the total number of \(PRB\)s in that cell:  
\[Load(\%)=\frac{PRB_{Usel}}{PRB_{Total}}\times 100 \tag{7}\]  
Handover Performance:  
* Attach failure rate is the metric that measures the percentage ratio of attach attempts to a cell that fails to the total attach attempts. A high attach failure rate can indicate issues related to cell discovery, signal degradation during the attach attempt, congestion, etc. \[Attach\ Failure(\%)=\frac{Failed_{attachAttemps}}{Total_{attachAttemps}} \times 100\] (8)
* Handover failure rate (HOF) is the metric that expresses specifically the percentage ratio of handover attempts that fail to the total number of HO requests received by a cell. This could be due to several reasons such as target cell rejection, issues with the HO signaling process, or sudden signal degradation during ongoing handover, etc. \[Handover\ Failure(\%)=\frac{Failed_{HandoverRequests}}{Total_{HandoverRequests }}\times 100\] (9)
* Radio link failure rate (RLF) is the metric that expresses the percentage ratio of the unexpected termination of an established data session due to signal quality-related issues or resource availability-related issues. \[Radio\ Link\ Failure(\%)=\frac{Failed_{RadioLink}}{Total_{SuccessfulAttachAttempts}} \times 100\] (10)
* Handover ping-pong rate (HOPP) is the metric that measures the percentage ratio of a UE that switches back and forth between two cells within a short period due to the close difference in signal strength between cells. \[Handover\ PingPong(\%)=\frac{PingPong_{HandoverRequests}}{Total_{Successful }{\color[rgb]{0,0,0}\definecolor[named]{pgfstrokecolor}{rgb}{0,0,0} \pgfsys@color@gray@stroke{0}\pgfsys@color@gray@fill{0}\text{{{{{{{{{{{{{{{{{{{{{{{{                                               } \mid}}}} } } {} {} {}} {\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{ \text{\text{\  
2. Algorithm 1-min Interval: represents the DDLB algorithm with an execution interval of 1 min. The algorithm performs its functionality every minute within the simulation. 3. Algorithm 3-min Interval: represents the DDLB algorithm that performs its functionality with a less frequent execution interval of 3 min. By utilizing the same network configurations and user distribution across all three environments within a simulation, the impact of the DDLB algorithm and its execution frequency on network performance are effectively isolated. These controlled settings allow for a robust evaluation. The results presented in Figure 7 represent the percentage of mean and standard deviation values of system performance metrics obtained from the tested cells initially determined. The system performance metrics comprise various aspects such as HOF, HOPP, overloaded state, attach failure, and RLF calculated across 56 simulations. Each metric is independently measured for each cell at each simulation step. Then, the average and standard deviation are obtained for all cells. Each scenario was simulated for over 550k steps, where each step represents a millisecond. The mean metric of HOF exhibits the highest rate at an average of 27.17% for the environment without the DDLB algorithm across all simulations as shown in Figure 8. This signifies a relatively high number of failed handover attempts. Utilizing the DDLB  
Figure 7: Metrics of mean and standard deviation of system performance. The OL state is a critical factor that can affect the performance of the network. The mean metric of the OL state also shows an effective reduction compared with the mean value achieved by the environment when the DDLB algorithm was not utilized. The improvement with the DDLB algorithm with an execution interval of 1 and 3 min achieved 36.24% and 33.29%, respectively, as shown in Figure 10.  
The DDLB algorithm also demonstrated a positive impact on the mean metrics of attach failure and radio link failure (RLF).