Low-Latency Broadcasting of Live Video Using Wi-Fi
The project addresses the problem of near real-time delivery of high-quality live video streams to multiple users via Wi-Fi. The users may be equipped with off-shelf portable devices such as tablets. Multiple streams are transmitted from one or multiple Wi-Fi access points (e.g. Wi-Fi enabled cameras) simultaneously. Each user may chose to view one stream in full resolution or multiple streams in reduced resolution. The number of users may be such that unicasting the streams to each of them exceeds the available network capacity. Therefore, the streams must be delivered via broadcast transmissions. Broadcasts in Wi-Fi are not acknowledged by the receivers and, therefore, retransmissions are disabled, which significantly increases the packet loss rate (PLR). While various retransmission schemes for broadcasting can be envisioned (e.g. driven by the user with the highest PLR) they would increase the transmission latency. Therefore, solutions based on FEC are preferred since they introduce minimum latency. Lower PHY modes (e.g. up to 6 Mb/s) provide stronger FEC protection, but reduce the network capacity, especially when multiple transmitters are competing for the channel using CSMA/CA. The project aims to build a reliable, low-latency video broadcasting solution for Wi-Fi by combining resilient video/image coding, FEC, and collision-free scheduling of transmitters.