We consider an IEEE 802.11 based wireless LAN where an access point is used to connect a fixed number of users to the Web or to a shared file system. Users alternate between activity periods (corresponding to the download of a file) and idle periods (corresponding to think times). We first consider the interaction of TCP with the IEEE 802.11 MAC protocol, and get approximate expressions for the TCP throughput in the presence of n c competing persistent connections. This result is then used to develop a queueing model, which provides the mean session delay in the presence of short-lived flows. The analysis also accounts for the TCP delayed ACK option. Comparison with simulation outcomes is provided, validating the model and providing guidelines for network designers. A particular emphasis is devoted to the impact of the TCP's advertised window size; in particular, it is proved that setting it to a small value leads to insensitivity of mean file transfer times to the file size distribution.
In REF , a queueing model is proposed to compute the mean session delay of HTTP sessions in the presence of short-lived TCP flows and the impact of TCP maximum congestion window size on this delay is studied.
A queueing model for HTTP traffic over IEEE 802.11 WLANs
In To appear in Proc. of ITC Specialist Seminar on Performance Evaluation of Wireless and Mobile Systems
Computer Science