Prospective study of the performances of Wi-Fi networks

The IEEE 802.11 standard is enjoying undeniable commercial success. It has become the de facto radio technology used in wireless LANs. Although 802.11 was developed for wireless networks with infrastructure, it can also be used to set up wireless networks with little or no infrastructure, thanks to its distributed medium access mode.

Ad hoc networks (also known as multi-hop wireless networks) belong to this category of wireless mobile networks. While multi-hop wireless networks have been extensively studied in the academic world, they are also the subject of real-world deployment. For example, various experimental platforms for such networks have been developed [TFA, NITOS], while some companies are now selling such communication systems [Luceor, P2MT]. To enable communication between remote mobiles in the network (i.e. not within communication range), a routing protocol is required. Research into ad hoc networks was given a major boost in the mid-1990s. The primary aim was to develop a routing protocol adapted to these potentially dynamic networks.

Most studies in ad hoc networks assumed that the underlying radio technology was 802.11 with its distributed access mode. However, in the early 2000s, initial studies showed that 802.11 performance in a multi-hop context was poor. Since then, various performance problems have come to light. The reasons for these problems are now better understood and explained.

The purpose of this article is to :

• present the performance of 802.11 and its distributed access mode under various wireless network configurations;

• explain the main causes of these problems.