APP and PHY in harmony: Demonstrating scalable video streaming supported by flexible physical layer control Wireless, high-bandwidth data transfer gains increasing significance with a wider adoption of high-quality video streaming on mobile devices. Technologies enabling such data transfer (e.g., 802.11 or LTE) can adapt dynamically to changing conditions, which allows data transfers in a reliable way. However, applications have little or no influence on how those underlying systems execute their adaptations. Yet, in applications such as video streaming, this could provide important clues on what requirements are relevant for data delivery. In this demonstration, we present a system that allows application-defined underlay control to use such potentials in a mobile scalable video based streamingscenario by combining Android smartphones with software-defined radios (SDRs) for advanced physical layer control.