UCast: WiFi Multicasting

Multicast is a popular way to distribute live streams, such as seminars and lectures, inside campuses and companies. With the rapid rise in WiFi-connected clients, the delivery of such multicast streams over infrastructure 802.11 networks is becoming important. Unfortunately, multicast over such networks is often inefficient, suffering from low throughput and significantly reducing the capacity available for other traffic. UCast is a system that uses cooperative client flooding to improve the delivery of WiFi multicast streams. UCast clients subscribed to a given multicast group along with the WiFi access points form a cooperative mesh network over which the multicast data is distributed from APs to the clients. The key to making this idea work is to use an efficient and robust flooding of data over the cooperative mesh. Experimental results over an indoor WiFi test-bed show that UCast can achieve about 4-7 times improvement in throughput over a scheme that is similar to it except that only APs send data and over DirCast+, an existing WiFi multicast protocol. Tools used: Click Modular Router, python, MATLAB. OS used: Linux. Hardware: Wireless nodes with 500 MHz AMD Geode LX800 CPU and a radio based on the Atheros 5212 chip-set.