On the performance of metro-scale ad hoc networks

Ad hoc networks based on IEEE 802.11 (Wi-Fi) wireless links are viable for small regions with a few tens of mobile nodes, but such networks suffer from frequently broken routes and low network utilization. In this paper, we investigate the use of wireless networks large enough to span a campus or a town. To make these networks reliable, we propose mixed networks which are mostly ad hoc networks with a few infrastructure nodes, i-nodes. These i-nodes are interconnected with point-to-point, p2p, links in addition to Wi-Fi capability. We modify an existing ad hoc routing protocol to incorporate the relatively stable p2p links with the broadcast type Wi-Fi channels in finding routes. We have simulated several ad hoc and mixed networks using the Glomosim simulator. Our results show that adding a small number of i-nodes with p2p links can improve the performance dramatically with throughput increasing by a factor of 3 or more. Our results also indicate that using too many i-nodes beyond a certain limit does not improve the performance and that reducing radio transmission power can significantly reduce radio interference and improve throughput significantly.