Cross-Layer Optimization of Coded Wireless Network.

摘要

The network coding paradigm advocates that intermediate nodes should not only forward, but also process and combine packets, which has the potential to increase throughput and facilitate distributed operation of networks. This dissertation focuses on wireless networks, where network coding can be gracefully combined with and exploit the properties of the wireless networks. The goal is to design and evaluate algorithms and protocols, on top of given constructive network coding schemes, so as to fully exploit the network coding capabilities. The contributions of this dissertation are the joint optimization of (i) video streaming, (ii) rate control, and (iii) error correction, together with the underlying network coding mechanisms.;We first study video streaming over coded wireless networks. Our key insight is that, when the transmitted flows are video, network codes should be selected so as to maximize not only the network throughput but also the video quality. We propose video-aware opportunistic network coding schemes that take into account the importance and deadlines of video packets.;Second, we study rate control and scheduling. The key intuition is that network coding introduces network coded flows and new conflicts between nodes, which should be taken into account both in rate control and scheduling. We consider two types of traffic; video and TCP. In the case of video, its time-varying nature affects the underlying network coding opportunities. We observe that by delaying some scenes and by optimizing the rate allocation, we can create more network coding opportunities and thus improve video quality. In the case of TCP traffic, TCP flows do not fully exploit the network coding opportunities due to their bursty behavior and due to the fact that TCP is agnostic to network coding. In order to improve the performance of TCP flows over coded wireless networks, we propose a network-coding aware queue management scheme.;In the last part of this thesis, we combine inter- and intra-session network coding (I2NC). Our scheme, I2NC provides resilience to loss thanks to the error-correcting capabilities of intra-session network coding. Furthermore, it allows intermediate nodes to operate without the knowledge of the decoding buffers at their neighbors.