In this paper, we present initial results on how the NS-3 LTE LENA stack is used to build a LTE testbed in an indoor lab network. We have extended the NS-3 MAC/PHY layer architecture to interface with a LabVIEW implementation of the LTE Physical layer and also extended NS-3 core modules to enable real-time performance. We present how this testbed can be used for prototyping a novel Software Defined Networking (SDN) scheme for interference management within dense heterogeneous deployments of cellular wireless networks. We provide an example case study for a Distributed Mobility Management (DMM) implementation using this testbed, where we demonstrate mobility of a emulated User Equipment device between LTE and WiFi networks. We plan to use this testbed for validation and demonstration of various SDN-based algorithms proposed within the framework of the EU FP7 CROWD (Connectivity management for eneRgy Optimised Wireless Dense networks) Project. We believe the proposed testbed is especially valuable for studying the cross-layer performance of cellular PHY/MAC algorithms in a realistic environment and shows how NS-3 can be used as a unified prototyping and simulation framework for wireless networks. Copyright is held by the owner/author(s).