# Effect of AQM-Based RLC Buffer Management on the eNB Scheduling Algorithm in LTE Network +
## 6 Simulation Result and Performance Evaluation
Thus, the gain in the reduction rate of the packet loss rate of SmRED as compared to RED is higher. To validate the improved performance achieved by different scheduling algorithms along with SmRED-4, we compared the performance of different scheduling algorithms with SmRED-4 and RED in a single-cell without handover (HO) and in multiple cells with HO. We kept the number of UEs at 10 to simulate high traffic-load conditions. In order to experience different channel conditions, the UEs were placed randomly in the single-cell within a distance of 500 m to 5000 m from the eNB. All UEs downloaded GBR video traffic from a single server. For multi-cell, all UEs were initially located in the first cell, moving towards other cells at a specific speed of 20 m/s. We used a 3 GPP-specified A3-RSRP handover algorithm that utilizes Reference Signal Received Power (RSRP) measurements and event A3, as designed in [43]. Event A3 is defined as a reporting triggering event which is activated when the neighboring cell's measured RSRP is better than that of the serving cell by a certain offset. We compared the download performance in terms of end-to-end average throughput and end-to-end average delay. The results are shown in Figures 10 and 11 for both single-cell and multi-cell. In the multi-cell network scenario, we explored the effect of handover on the TCP performance. Due to the handover, TCP throughput suffers from the packet duplicates and extra latency caused by buffering in the eNB. Thus, in the multi-cell network, the reduction in the total TCP throughput as compared to the single-cell network can be attributed to TCP. When the traffic-load is high (UE = 10), different scheduling algorithms with SmRED-4 outperform RED. This is because SmRED-4 has a higher dropping probability than RED when the traffic-load is high, which helps to inform the source more in advance than RED about the possible congestion. Thus, the TCP source reduces the window size in advance to avoid resending lost packets, which helps to achieve lower end-to-end average delay (Figure 11) without sacrificing the throughput much. An interesting observation is that, in a single-cell topology without handover, MT achieves the highest throughput as expected but in multi-cell topology with handover, its performance degradation is the highest among all the schedulers. This is because MT assigns RB to those users which have good signal quality in order to utilize the the full bandwidth. However, as the UEs are moving and handover occurs, different UE's face different signal conditions and MT assigns RB to one UE for a short period of time and then to others. Thus, the overall throughput degraded much but the fairness is increased as expected and can be seen from Figure 12. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**RLC Buffer Size** & **100** & **125** & **150** & **175** & **200** \\ \hline Pkt Loss Rate (RED) in Percentage & 8.98 & 7.01 & 6.18 & 4.48 & 4.29 \\ Pkt Loss Rate (SmRED) in Percentage & 8.31 & 6.80 & 5.31 & 4.27 & 3.98 \\ Reduction Rate in Percentage & 7.50 & 3.05 & 14.05 & 4.68 & 7.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Packet Loss Rate in the High Traffic Load Scenario. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**RLC Buffer Size** & **100** & **125** & **150** & **175** & **200** \\ \hline Pkt Loss Rate (RED) in Percentage & 5.16 & 4.28 & 4.06 & 3.18 & 3.10 \\ Pkt Loss Rate (SmRED) in Percentage & 3.70 & 3.51 & 2.69 & 2.44 & 2.04 \\ Reduction Rate in Percentage & 28.29 & 17.99 & 33.74 & 23.27 & 34.19 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Packet Loss Rate in the Moderate Traffic Load Scenario. Figure 12 shows the fairness of different schedulers (Jains fairness Index [44]). From the performance of MT, TBFQ and TTA, we can see that they blindly enhance the overall cell throughput by utilizing the effective channel in terms of spectral efficiency, but these approaches provide unfair resource sharing among users.