802.11 Buffers: When Bigger Is Not Better?

While there have been considerable advances in the modelling of 802.11’s MAC layer in recent years, 802.11 with finite buffer space is considered difficult to analyse. In this paper, we study the impact of finite buffers’ effect on the 802.11 performance, in view of the requirements of interactive applications sensitive to delay and packet loss. Using both state-of-the art and simplified queueing models, we identify a surprising result. Specifically, we find that increased buffering throughout an 802.11 network will not only incur delay, but may actually increase the packet loss experienced by stations. By means of numerical analysis and simulations we show that this non-monotonic behaviour arises because of the contention-based nature of the medium access protocol, whose performance is closely related to the traffic load and the buffer size. Finally, we discuss on protocol and buffer tuning towards eliminating such undesirable effect.