Performance issues with IEEE 802.11 in ad hoc networking

Although 802.11 is initially designed for infrastructure based networks, the Distributed Coordination Function (DCF) provided in 802.11 allows mobiles to access the radio medium without the need of a base station. Thus, studies in wireless multi-hops networks, also called ad hoc networks often rely on the use of the IEEE 802.11 standard for the physical and MAC layers. But, since a couple of years, the use of 802.11 in ad hoc networks has been called into question. Different scenarios show serious performance issues. The performances offered by 802.11 are often low and directly impact the performances of higher layers protocols. In this article, we provide a summarize of the different performance issues that have been extracted so far. We identify the main causes of performance losses and we classify the different basic encountered situations according to these causes. We then discuss the known impacts on complex ad hoc topologies and on higher layers protocols. We hope that this classification will help to design more appropriate MAC protocols for ad hoc networks