Measurement and modelling of TCP downstream throughput dependence on SNR in an IEEE802.11b WLAN system

摘要

The dependence of TCP downstream throughput (TCPdownT) on signal to noise ratio (SNR) has been studied in this paper. Measurements were taken for multiple users in small offices, open corridors and free space environments using an infrastructure based IEEE 802.11b WLAN while transmitting different quality of service (QoS) traffic. Models able to predict TCPdownT with respect to SNR observed were developed and validated for different signal categories. We observed RMS errors of 0.938012 Mbps, 1.047012 Mbps, 0.65833 Mbps and 0.452927 Mbps for the general (all SNR) model, strong signals model, grey signals model and Weak signals model respectively which were much lower than that of similar models with which they were compared. Comparing our results with previous work on TCP upstream throughput showed that it is more accurate to investigate upstream and downstream throughput separately. Using our models, IEEE 802.11b WLAN installers will be able to predict the TCPdownT by simply measuring and monitoring only the received SNR which is already part of the network installation process.