Tiia Ojanperä

Cross-layer Optimized Video Streaming in Heterogeneous Wireless Networks

The volume of data transmitted across wireless and mobile networks continues to grow at a rapid rate. Videos already account for most of this data traffic, and their share is expected to grow even bigger in the near future. The thesis presents a novel video service architecture designed to optimise video streaming according to wireless network capacity in order to achieve improved quality and efficient network resource usage. The solution essentially enables Quality of Service (QoS) sensitive video streaming services to take full advantage of the access diversity of heterogeneous wireless networks and to adapt efficiently to available network capacity. This nevertheless requires support beyond the layered communication architecture of today’s Internet as proposed in the thesis.

The proposed architecture relies on end-to-end cross-layer signaling and control for video streaming optimization. The architecture supports extensive context information collection and transfer in heterogeneous networks; thus, enabling the efficient management of video stream adaptation and user terminal mobility in a diverse and dynamic network environment. The thesis also studies and proposes cross-layer enhancements for adaptive video streaming and mobility management functions enabled by the cross-layer architecture. These include cross-layer video adaptation, congestion-triggered handovers, and concurrent utilization of multiple access networks in the video stream transport. For the video adaptation and multipath transmission, the flexible adaptation and transmission capabilities of the novel scalable video coding technology are used. Regarding the mobility management, the proposed solutions essentially enhance the handover decision-making of the Mobile IP protocol to better support QoS-sensitive video streaming. Finally, the thesis takes a holistic view on the application adaptation and mobility management, and proposes a solution for coordinated control of these two operations in order to achieve end-to-end optimization.

The resulting mobile video streaming system architecture and the cross-layer control algorithms are evaluated using network simulations and real prototypes. Based on the results, the proposed mechanisms can be seen to be viable solutions for improving video streaming performance in heterogeneous wireless networks. They require changes in the communication end-points and the access network but support gradual deployment. This allows service providers and operators to select only a subset of the proposed mechanisms for implementation. The results also support the need for cross-layer signaling and control in facilitating efficient management and utilization of heterogeneous wireless networks.