Experimental investigations into TCP performance over wireless multihop networks

Abstract

The results of an extensive experimental study of the performance of the TCP protocol over wireless multi-hop ad hoc networks are presented. The investigations are performed in a real indoor environment over a network of laptops equipped with off-the-shelf IEEE 802.11b wireless cards. The cards were partially covered with copper tape to reduce their range, which enabled creation of manageable topologies. Several tools were written and assembled to make the entire process of experimentation including topology setup, traffic generation, trace collection, and archival and analysis of data repeatable, reliable and as automated as possible. The experimental observations are subjected to a thorough statistical analysis. The final result of the study is a recommendation of some TCP and IEEE 802.11 parameters that are best for TCP performance over wireless multi-hop networks. The most critical of these include setting a destination dependent clamp on the sender congestion window and disabling the RTC-CTS handshake. The methods and techniques used, as well as the support tools developed, and statistical analysis, may be of larger interest in wireless network experimentation.