The impact of link layer assisted multimedia adaptation in wireless networks

Higher layer protocols in wireless networks need to dynamically adapt to observed network response. A common approach in multimedia is to employ end-to-end monitoring to estimate quantities of interest like delay, delay jitter and available bandwidth. We show by experimentation that end-to-end adaptation does not work in networks with wireless 802.11 links. Transport measurements are unreliable and converge very slowly. Therefore we develop a link layer assisted architecture for one and multi hop wireless networks. We first show that end-to-end mechanisms cannot scale to many connections and it is preferable to merely use low rate non adaptive streams. On the other hand our link-network feedback architecture is very successful and scalable to number of connections. It offers increased QoS when this is feasible, or otherwise at least the QoS of a low rate transmission.