TCP-friendly wireless multimedia flow control using ECN marking

In a wireless network packet losses can be caused by not only nehvork congestion but also unreliaMe erropprone wireless links. Therebre, flow control schemes which use packet loss as a congestion measureemnot be directly applicable to a wireless network because there is no way to distinguish congestion losses from wireless losses In this paper, we extend so-called TCP-friendly flow control scheme, which was developed for the control of multimedia flows carried over UDP in the presence of TCP flows, to a wireless environment by using ECN (Explicit Congestion Notification) marking capability with RED (Random Early Detection) routers. By early detecting congestion, explicitly informing multimedia sources ofcongestion using ECN marking and calcvlating TCP-friendly ratebasedon ECN-markedpacket probability insteadofpacket loss probability, we were able to effectively separate the effect of wi re la losses from Bow conbol and thus prevent tbroughput degradaCon of multimedia flows traveling through wireless links. In addilia4 we refine well-known TCP throughput model developed for TCP-friendliness of multimedia flows such that the refined model provides more accurate estimate of TCP flows' throughput when both ECN marking and RED queue management are used. Through simulations we show that the proposed scheme indeed improver lhe quality of delivered video significantly while maintaining TCP-friendliness for the case of wireless MPEG-4 video.