# QoS-Aware Downlink Traffic Scheduling for Cellular Networks with Dual Connectivity
###### Abstract
As discussed above, downlink traffic scheduling in a cellular network with dual connectivity enhancement should consider (i) data dispatching between the MeNB and SeNBs and (ii) RB assignments in the MeNB and SeNBs. In this work, we design a QoS-aware scheduling solution that contains two parts. First, we propose a _QoS downlink data dispatching_ (_QDD_) method for the MeNB. In QDD, when the MeNB receives downlink data from the Internet, the MeNB considers eNBs' capabilities and flows' QoS parameters to decide whether to dispatch flows to the corresponding SeNBs. The dispatching decisions aim to guarantee that separated downlink data can be processed in time at the SeNB. In QDD,  
Figure 1: The protocol stack of a cellular network with dual connectivity enhancement. we model a linear programming formulation whose goal is to maximize network throughput, and dispatching decisions can be obtained by solving the proposed formulation. Second, we propose a _QoS eNB scheduling_ (_QED_) method for the MeNB and SeNBs. To reduce packet loss, the QED attempts to give more opportunities to those high-priority packets that are going to expire. However, before giving resources, the QED evaluates channel qualities and packets' remaining transmissions to ensure those high-priority traffics can be processed before deadlines. In this work, we verify our design using simulation programs. The experimental results show that compared to the existing methods, the proposed scheme can effectively increase system throughput and decrease packet drop ratios. The contributions of this paper are summarized below. * We propose QDD and QED methods to schedule downlink traffics for cellular networks with dual connectivity enhancement. The proposed schemes can satisfy QoS requirements while increasing system throughput and decreasing packet drop ratios. * In previous works, the MeNB dispatches downlink data to SeNBs without considering SeNBs' capabilities; as a result, the data dispatched to SeNBs may not be processed in time. The proposed QDD method makes dispatching decisions by referring to SeNBs' capabilities and statuses. This design ensures that data flow will not arbitrarily forward to SeNBs. * When allocating radio resources (i.e., RBs), most previous works favor high-priority data flows, and thus, resources may be wasted to disseminate packets that cannot be fully processed before timeout. The proposed QED method evaluates the status of buffered GBR packets before giving resources to high-priority data flows. This design can avoid wasting radio resources on packets that are going to expire soon. * Based on our surveys, this is the first work to jointly consider QoS requirements and system capabilities when making data dispatching and RB assignment decisions. Furthermore, the proposed solutions can be compatible with the 3 GPP standards. The remainder of this paper is organized as follows. Section 2 reviews previous studies on traffic scheduling in dual connectivity networks and MAC scheduling of the MeNB and SeNBs. Section 3 describes network models and system flows of this work. Then, Section 4 and Section 5 present the proposed QDD and QED methods, respectively. Next, Section 6 evaluates the network performance of the proposed scheme and compares its performance with previous schemes. Finally, Section 7 concludes this paper and outlines the future work.