Link-condition based proxies for QoS management in wireless networks

In this paper, we analyze the performance of proxy functions for controlling the quality of service in wireless networks, where the proxy performs aggressive content reduction as a means to throttle traffic when the radio link is congested. The proxy may be located at different parts of the network, thus affecting the feedback delay from the base station to the proxy. A queueing model is constructed and solved to study the performance tradeoffs among system parameters and in particular, how the proxy performance is affected by the feedback control delay between base stations and the proxy. Using image compression as an example, we examine response time and fraction of compression as a function of the control delay. Our results reveal that the proxy function can effectively control response time in the case of link congestion, if the delay is reasonably small, e.g. when the proxy is located close to the radio link. We also find that to assess the effectiveness of the control mechanism, it is necessary to examine whether the proxy performs content reduction when and only when link congestion occurs. Towards this end, we study the system-state probabilities and the correlation between response time and compression.