# QoS-Aware Downlink Traffic Scheduling for Cellular Networks with Dual Connectivity
## 5 Proposed QoS eNB Scheduling (QED) Method
Finally, if the measured drop ratio \(\mathcal{L}(b_{i})\) is higher, the packet \(p\) is allowed to enter the GTT more easily. When a packet \(p\) is in the GTT set, the QED calculates a priority value \(\hat{Q}(p)\) for \(p\) using the following equation:  
\[\hat{Q}(p)=\frac{qci(b_{i})\times\mathcal{R}(p)}{cqi(u_{i})} \tag{3}\]  
In Equation (3), \(qci(b_{i})\) is the QoS QCI value of the corresponding bearer \(b_{i}\), and \(cqi(u_{i})\) is the CQI value reported by the destination UE \(u_{i}\). In our design, if the \(\hat{Q}(p)\) is smaller, the packet \(p\) can have a higher priority. Next, we discuss the design of Equation (3). According to the 3 GPP standard, when the QCI value is smaller, the priority of the corresponding data flow is higher, and thus, the corresponding packet \(p\) can have higher priority. Then, when the remaining transmission time \(\mathcal{R}(p)\) decreases, the packet \(p\) can have higher priority. Finally, if the reported CQI \(cqi(u_{i})\) is higher, this means that the corresponding UE \(u_{i}\)'s signal quality is better, and this packet can have a higher priority. After calculating the priority value for every packet in GTT, the QED sorts packets in GTT according to their priorities in nondecreasing order. In every TTI, when scheduling RBs, the packets in GTT will be assigned to RBs earlier. The QED then allocates the remaining RBs to existing data flows using the proportional fair (PF) scheduling method [28]. Furthermore, Algorithm 1 outlines the overall procedures of the QED algorithm. ```
1 Discard those packets that have expired;
2 foreach\(GBR\) flow \(f\) in the systemdo
3 foreachpacket \(p\) in GBR flow \(f\)do
4 ifRemaining transmission time of \(p\) is less than \(\hat{T}_{n}\) and \(\mathcal{E}(p)\geq\mathcal{R}(p)\)then
5\(p\) will be put to GTT set;
6 Sort packets in GTT set according to their priority;
7 whilethere are remaining RBsdo
8 Assign enough RBs to disseminate first packet in GTT set;
9 Remove the first packet in GTT set;
10 ifthere are remaining RBsthen
11 Assign RBs to remaining flows by proportional fair (PF) algorithm;

## 6 Simulation Results

In this work, we evaluate our designs using simulation programs implemented by C programming language. In our simulations, the network area is a circle with radius 2 km, and the MeNB is located in the center. There are \(l\) SeNBs in the network, and the distance between MeNB and SeNB is 1 km. In every TTI, the MeNB and SeNB can assign 100 and 30 RBs to UEs, respectively. All UEs in the network have dual connectivity capabilities. The initial locations of UEs are randomly distributed in the network area, and each UE will move to a random direction every 0.5 s with a default moving speed of 5 km/h. Based on the locations of the UEs, some UEs may only be connected to the MeNB. Each UE has three downlink traffics: voice, video, and constant bit rate (CBR) with rates of 8.4, 242, and 12 kbps, respectively. The voice traffic and video traffic are taken as GBR types in our simulations, and voice traffic has higher priorities than video traffic. Furthermore, our simulator adopts the urban macro-cell model as the propagation model, where the path loss is calculated by \(128.1+37.6\log{(L)}\), the thermal noise is set to \(-174\) dBm/Hz, and the fast fading model is Rayleigh. The maximum transmit power levels of the MeNB and SeNB are set to 46 and 23 dBm, respectively. We compare the proposed QDD data dispatching scheme with (i) the DTS scheme in [16] and (ii) the fixed dispatching scheme (denoted by FIX). The FIX scheme always dispatches 50% of downlink data to the SeNB. We compare QDD with DTS because DTS uses similar concepts to dispatch downlink data to SeNBs. Moreover, we compare the proposed QED scheduling scheme with the DFS scheme in [26] since the DFS has similar features with QED as mentioned in Section 2.2. The DFS jointly considers QoS and maximizing throughput while scheduling.