PULLCAST: Peer-Assisted Video Multicasting for Wireless Mesh Networks

摘要

Multicast video streaming is experiencing a significant growth in wireless networks thanks to the resources provided by 4G/LTE and WiFi services. However, wireless communications are affected by attenuation, shadowing, fading, and unpredictable interference, that make multicast services extremely difficult (no ARQ). Nodes close to the streaming source (e.g., a node or an AP), however, always experience better signal quality than those farther away, so that some nodes can be expected to receive most of the stream, while others will not. In this paper we present PULLCAST, a cooperative protocol for multicast systems, where nodes receive video chunks via multicast from a streaming point, and cooperate at the application level, by building a local, h'ghtweight, P2P overlay that support unicast recovery of chunks not correctly received via multicast. PULLCAST sends 1-hop hello messages to build a local neighborhood where chunks can be retrieved sending unicast messages to "pull" a chunk from a neighbor that has it. We show that our solution improves the system performances both in scenarios where the mesh is highly structured, so that recovery of chunks is limited to the equivalent of an 802.11 BSS and in more complex scenarios where the mesh nodes offer connectivity to clients in a seamless network using a single radio channel.