Adaptive Packetization for Conversational Video Service over IEEE 802.11 WLANs with Hidden Terminals

For IEEE 802.11-based wireless local area networks (WLANs), due to inherent random access mechanisms, it is very challenging to provision video services, which are subject to very stringent quality-of-service (QoS) constraints. Collision and fading are two main sources of packet loss in WLANs and as such, both are affected by the packetization at the medium access control (MAC) layer. While a larger packet is preferred to balance protocol header overhead, a shorter packet is less vulnerable to packet loss due to channel fading errors or staggered collisions in the presence of hidden terminals. In this paper, we exploit estimate of collision probabilities to adapt packetization for video frames. We first show analytically that the effective throughput is a unimodal function of packet size when considering both channel fading and staggered collisions. We then design an additive increase and multiplicative decrease (AIMD) packetization strategy which adjusts the MAC-layer packet size based on local estimate of staggered collision probability. It is demonstrated that the proposed approach can greatly improve the effective throughput of WLAN and reduce video frame transfer delay.