Efficient UE mobility in multi-RAT cellular networks using SDN

Though, Software Defined Networking (SDN) started with the wired networks, several architectural solutions have been proposed to incorporate SDN in the wireless domain, to improve the overall performance of the network. However, analyses of specific use cases or scenarios based on these architectural approaches have been largely unexplored. One of the architectural solutions proposed in the radio interface is to have a configurable data plane at the base station, e.g., OpenRadio, which can be programmed with different Radio Access Technologies (RATs) dynamically by the SDN controller. In this work, we further investigate the futuristic problem where schemes, like OpenRadio and SDN concepts, come into play to improve mobility of User Equipment (UE). It is a well-known fact that intra-RAT (e.g., LTE to LTE) mobility procedures have lower latency, and are far less complex than their inter-RAT (e.g., LTE to UMTS) counterparts. Hence, we can improve user experience by converting inter-RAT mobility procedures to intra-RAT counterparts. We already proposed this scenario in our previous work, and results showed substantial mobility improvements. However, this conversion requires SDN signaling to reconfigure the base station to the target RAT, followed by an intra-RAT mobility procedure for the UE. In this paper, we investigate the performance requirement of this combined SDN signaling and intra-RAT mobility procedures, in order to do better than the inter-RAT counterparts. Results using our analytical model show, a minimum of 20% reduction in time for combined SDN signaling and intra-RAT mobility can outperform existing inter-RAT mobility procedures. Simulation results validate the observations obtained from the analytical model. Comparison of results with OpenFlow scenario shows that achieving the required signaling performance is feasible.