# QoS-Aware Downlink Traffic Scheduling for Cellular Networks with Dual Connectivity
## 5 Proposed QoS eNB Scheduling (QED) Method
We aim to observe the advantage of QED, which considers the status of GBR packets before giving resources to those packets that are going to expire. In our simulations, we show the results on different combinations of the above data dispatching and MAC scheduling schemes. Furthermore, we solve the proposed linear programming formulation of QDD using the lpsolve solver [29]. The QDD makes dispatching decisions (i.e., to solve the proposed linear formulation) every \(I_{t}=100\) ms. Furthermore, for QED, we set \(\hat{T}_{n}=10\) ms, i.e., a GBR packet can enter QTT when its remaining transmission time is less than 10 ms. Each simulation result is derived by averaging the results produced within a 60 s simulation time. Figure 4 shows the simulation results when the network has one MeNB and one SeNB, and we vary the number of UEs in the network. First, Figure 4a,b indicates the results of voice and video throughput, respectively. We can see that in Figure 4a,b, the proposed QDD+QED scheme can outperform the others. On average, the QDD+QED can be 9%, 14%, 36%, and 44% (resp., 5%, 15%, 28%, and 49%) better than DTS+QED, DTS+DFS, FIX+QED, and FIX+DFS in voice (resp. video) throughput, respectively. In DTS, the authors do not consider QoS parameters when making dispatching decision. As a result, DTS's GBR traffic throughput will be lower since more packets may be dropped in the SeNB. On the other hand, we can also see that GBR traffic throughput of DTS+QED can be better than that of DTS+DFS. This result indicates that the proposed QED scheme can indeed facilitate the scheduling of GBR traffics. The FIX+QED and FIX+DTS will have the worst GBR throughput. This implies that a well-designed dispatching scheme can facilitate the increase of GBR downlink data throughput. Furthermore, Figure 4c indicates the throughput of CBR traffics (i.e., non-GBR traffics). We can see that the CBR throughput of QDD+QED will be lower than that of DTS+DFS. This is because both DTS and DFS aim to maximize network throughput without considering the status of GBR traffics. Therefore, the combination of DTS+DFS may allocate more resources to non-GBR traffic. Finally, Figure 4d shows the overall system throughput. Since there are more video traffics in the simulated networks, the overall system throughput of the proposed scheme can be better than the others. On average, the QDD+QED can be 9%, 12%, 22%, and 32% better than DTS+QED, DTS+DFS, FIX+QED, and FIX+DFS in system throughput, respectively. Figure 4(a)b indicates the packet drop ratios of video and CBR traffics of Figure 4(b) and Figure 4(c), respectively. In the simulation, when the number of UEs is less than 90, the drop ratios of video traffic and CBR traffic will be less than 0.5%, and thus, we do not show the results when the number of UEs is less than 90. From Figure 4(a), QDD+QED will have the lowest packet drop ratios on video traffic, so the video throughput of QDD+QED can be higher (as discussed above). Again, from Figure 4(b), DTD+DFS will have the lowest packet drop ratios on CBR traffic; thus, the CBR throughput of DTD+DFS can be higher (as discussed above). From these two results, we can see that, by the QDD+QED scheme, video traffic drop ratios can always be lower than CBR traffic drop ratios. This result demonstrates that the proposed scheme can indeed help facilitate the transmissions of GBR traffic. Moreover, Figure 4(c) indicates the system packet drop ratio. From the result, we can observe that the proposed QDD+QED can achieve the lowest drop ratio for the entire network. From the result, on average, the QDD+QED can be 6%, 3%, 23%, and 25% better than DTS+QED, DTS+DFS, FIX+QED, and FIX+DFS in system packet drop ratios, respectively. Next, we fix the number of SeNBs and UEs to be 1 and 55, respectively, and we observe the results when varying the UEs' moving speeds. Figure 6 indicates the results. From Figure 5(a),b, we see that the proposed QDD+QED can outperform the others in GBR throughput.