Real-Time Network Coding for Live Streaming in Hyper-Dense WiFi Spaces

Consumer demand for high-quality video over wireless networks is increasing at fast pace. The resulting technical challenges are particularly stringent in crowded spaces, where the density of users far exceeds the ability to deploy cellular base stations or WiFi infrastructure in a cost effective way. To address this problem, we present a reliable and scalable live streaming solution based on wireless multicast with real-time network coding. At the core of our approach is a timely delivery scheme that uses a minimum amount of feedback from the receivers to generate coded repair packets that are simultaneously useful to a large number of users. Our protocol, which we implemented and tested in a real-world wireless testbed, differs from traditional wireless unicast and multicast schemes in that (a) the feedback messages of the users are treated jointly and (b) the repair mechanism considers both the playout deadlines of individual packets and the list of packets already received by the clients. In comparison with a standard video approach that sends an MPEG-2 encoded stream over 802.11 unicast links, our solution offers real-time guarantees for all users commensurate with the link quality and an 11x improvement in terms of bandwidth usage. A commercial version of the proposed solution shows a strong increase in the number of clients that can access video streams simultaneously over a single WiFi hotspot.