Distributed Cross Layer Congestion Control for Real-Time Video over WLAN

We propose a distributed cross-layer congestion control algorithm that provides enhanced QoS and reliable operation for real-time uplink video over WiFi applications. Such applications are characterized by many wireless devices transmitting video at various PHY rates over a relatively congested channel. Unfortunately, today´s off-the-shelf 802.11 equipment can be easily demonstrated to suffer catastrophic failure when subject to these conditions - let alone provide acceptable perceptual quality to the user. We show that in order to remedy these issues, it is preferred to use a cross-layer approach rather than a single-layer approach. The idea is to use a fast frame-by-frame control loop in the MAC layer while simultaneously exploiting the powerful control-loop gain attainable by performing source-rate adaptation in the APP layer. We support the proposed algorithm through both simulation and experimentation.