APP and PHY in Harmony: A framework enabling flexible physical layer processing to address application requirements

Mobile data traffic, particularly mobile video, grows at an unprecedented pace. Despite recent advances at the physical layer, today´s wireless network infrastructure cannot keep up with this growth. This is partially due to the missing flexibility to adapt the physical layer continuously to best support both application level as well as network requirements. In this paper we show how to harness the flexibility of advanced physical layers in practice. We designed and implemented a research platform that provides a flexible application-centric physical layer for Android smartphones using software-defined radios (SDRs) as radio interfaces. Our solution allows applications to define flows and apply per-flow settings that are mapped into distinct physical layer settings. As a proof-of-concept and for testbed evaluation, we implemented our system together with a mobile video streaming application. The latter uses a Motion-JPEG based lightweight scalable video codec (SVC) to generate incremental data flows. We show that our system maximizes video quality at the receiver´s side, while keeping the energy consumption at the transmitter at a minimum. Our solution demonstrates that jointly optimizing network traffic and application quality is feasible in practice using a flexible physical layer processing approach.