QoS-aware scheduling in LTE-A networks with SDN control Emmanouil Skondras 1 , Angelos Michalas 2 , Aggeliki Sgora 1 , Dimitrios D. Vergados 1 1 Department of Informatics, University of Piraeus, Piraeus, Greece, Email: {skondras, asgora, vergados}@unipi.gr 2 Department of Informatics Engineering, Technological Education Institute of Western Macedonia, Kastoria, Greece, Email: amichalas@kastoria.teiwm.gr Abstract—The 3GPP Long Term Evolution Advanced (LTE-A) standard specifies a set of pioneer features such as relay nodes and carrier aggregation. At the same time, the Software Defined Networks (SDN) have become an emerging technology which provides centralized control and programmability to modern networks. In the current communication environment, cloud computing could combine the advantages of both technologies in order to create a novel cloud assisted Software Defined LTE- A architecture with relay nodes. Moreover, due to the increased requirements of modern services, the optimal resource allocation is a necessity. In such a context, this paper describes a QoS aware cross carrier scheduler for downlink flows, aiming at the optimization of system resources allocation. The proposed scheduler is evaluated against the PF, MLWDF, EXP/PF, EXP RULE, LOG RULE, FLS and FLSA schedulers in a cloud assisted Software Defined LTE-A topology with relay nodes. Simulation results show that the proposed scheduler improves the real time services performance while at the same time maintains an acceptable performance for best effort flows. I. I NTRODUCTION The LTE network technology uses an all-IP, purely packet- switched architecture to provide high communication speeds and satisfy the increased QoS requirements of modern ser- vices. The first LTE release (rel. 8) [1] provides data rates up to 100 Mbps for downlink and up to 50Mbps for uplink. In such an architecture, information is transmitted in frames of 10ms of length and every frame is split into 10 sub-frames of 1 Time Transmission Interval (TTI) of length each. The minimum resource which can be allocated for transmission is called Resource Block (RB). The scheduler assigns RBs to users in each TTI and the number of available RBs per TTI depends on the system bandwidth. The LTE-A (rels. from 11 to 14) [2] significantly enhances the rel. 8 specifications and improves the access network capacity using evolved characteristics, such as Relay Nodes (RNs) and Carrier Aggregation (CA) providing increased cov- erage with rates up to 1Gbps for downlink and up to 500Mbps for uplink. Relaying is one of the vital elements of LTE-A to fulfill the users’ requirements on high data rate coverage. Wireless small-range cells improve connectivity of mobile users experiencing bad channel conditions within the coverage area of an LTE base station (eNodeB). Relays are connected to the backbone network by maintaining wireless connections with the base station. Furthermore, using CA mode in LTE- A, the system bandwidth is increased by aggregating up to 5 component carriers and thus having more available RBs for scheduling in each TTI. The first component carrier is referred as Primary Component Carrier (PCC) and the rest component carriers are referred as Secondary Component Carriers (SCCs). According to the Cross Carrier Scheduling (CCS) method- ology, the PCC includes both a control region and a data region, while each SCC includes only a data region. Regarding the non-Cross Carrier Scheduling (n-CCS) operating principle each PCC and SCC use their own control regions to allocate RBs. Both principles provide flexible component carrier band- widths from 1.4 up to 20MHz while 100 RBs are available for allocation per component carrier in the case of 20MHz bandwidth. However, the CCS methodology manipulates the individual component carriers as a single entity and acquires a total supervision of the channel conditions optimizing system capacity. On the other hand, Software Defined Networks (SDN) is an emerging technology that centralizes the network intelli- gence enhancing the flexibility of resource manipulation. More specifically, the network control functions are decoupled from the data forwarding procedures while the network architecture becomes easily programmable. Thus, resource optimization is achieved by dynamically adjusting the traffic forwarding to meet the changing needs that exist in the modern wireless communication environment. In this context, cloud computing could combine both LTE and SDN technologies advantages to create a novel cloud assisted Software Defined LTE-A network architecture with RNs. In this architecture, network control operations are centrally organized having a wide view of the entire system. This paper presents the FLS Advanced - Cross Carrier (FLSA-CC) downlink scheduler which is an enhanced version of the FLS Advanced (FLSA) presented in [3]. FLSA-CC operates in a relay assisted LTE-A network which supports CA. The proposed scheduler aims at a QoS aware resource allocation, satisfying the requirements of strict real times services while maintaining an acceptable level of performance for the best effort service. The performance of FLSA-CC is studied on a software defined cloud architecture where flow forwarding and resource scheduling decisions are performed centrally by a global controller implemented on the cloud. The