Abstract

Emerging mesh networks build on IEEE 802.11 wireless local area networking technology to deliver Internet access to mobile users or to areas where traditional wired access technologies are unprofitable. Such deployments are highly bandwidth constrained; in dense urban environments many users are competing for the wireless medium and long-haul wireless backbone connections have significant contention. In addition, IEEE 802.11 networks suffer from a high packet overhead—much higher than Ethernet, for example. This overhead consumes a significant share of the theoretical capacity. As networks advance to higher bitrates the proportion of this overhead increases, because packet preambles are transmitted at the lowest bitrate. We address this challenge through an adaptive, connection-agnostic aggregation mechanism that can reduce this overhead by combining multiple smaller packets into larger ones. One method uses a small delay on packets to enable the distributed aggregators to collect smaller packets from different network connections for assembling a larger packet. The second method automatically increases aggregation activity with network congestion; thus, it does not impose delays on network traffic in situations of low media utilization and also reduces delays under periods of high load. A prototype on a wireless testbed and simulation results for larger community network deployments show significant improvements in actual network capacity, ranging from a 60-270 % improvement for traditional “adhoc” scenarios and to a 100-500 % improvement for wireless networks using unidirectional antennas.

Citations