Quality for All

International audienceIn contrast to the common wisdom stating that 802.11 wireless LANs are not suitable for time-sensitive traffic, we have observed that in some conditions packet traffic transmitted over 802.11b may benefit from low delays even in saturation. Our analysis and measurements show that low delays can be obtained irrespectively of the greedy behavior of other hosts and without any traffic control mechanisms: when some hosts try to gain as much as possible of the transmission capacity of the radio channel, it is still possible for other hosts to experience low delay provided their packet rates are below some threshold value. The only situation in which a time-sensitive traffic source fails to obtain low delay is when its packet rate is too high with respect to its share of the channel capacity. We provide an analytical formula for determining the limiting packet rate that can be used to guide rate adaptive applications such as audio or video codecs to keep their output rates under the limiting rate and benefit in this way from low delays without any coordinated traffic control mechanisms