Experimental evaluation and characterization of the magnets wireless backbone

Abstract

High-speed wireless backbones have the potential to replace or complement wired connections. This paper provides a comprehensive network and transport layer performance evaluation of the Magnets WiFi backbone. The backbone, deployed in a metropolitan area of Berlin, consists of six 108 Mbps capable links using directional antennas and spans over 2.3 km. Built with off-the-shelf hardware, it features mixed 802.11a/g technology, link distances between 330 m and 930 m and support for two enhanced MAC/PHY layer modes at the access points (AP) to improve their performance. These unique characteristics provide a challenging environment to investigate the impact of a wide range of parameters. In particular, using CBR and VBR traffic profiles, we assess the influence of distance, 802.11 technology and AP modes on throughput, delay, packet loss and jitter between pairs of adjacent nodes. For example, our measurements show that the average UDP throughput of the 802.11g links varies between 15.9 and 18.7 Mbps, whereas the 802.11a link achieves 27.8 Mbps. Finally, the average UDP throughput can even be increased to 55.2 Mbps by concomitantly enabling the two enhanced AP modes.