Rate Adaptation for Conversational 3G Video

Wireless cellular environments, such as UMTS, are often affected by congestion and errors, which are inherent to wireless transmission channels due to fading, interference, resource scarcity, mobility, etc. For a conversational video application to be successful i.e., to provide good viewing quality to the receiver at all times, the sender must be able to quickly adapt its sending/encoding rate (and other related parameters) to that offered by the link. Moreover, for a rate adaptation scheme to be successful, the receiver must provide timely feedback in order to mitigate further losses due to congestion. In this paper, we investigate different rate adaptation mechanisms and redefine them for 3GPP networks, reusing existing RTCP extensions standardized in the IETF and in 3GPP where possible.