Copyright © 2005 Elsevier B.V. All rights reserved.
Received 22 October 2004;
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Abstract
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 nc 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.
Keywords: IEEE802.11; TCP; HTTP; Performance analysis
Article Outline
- 1. Introduction
- 2. The network scenario
- 2.1. Protocol description
- 2.2. Delayed ACK techniques
- 2.3. System parameters
- 3. Persistent TCP connections: throughput analysis
- 3.1. Single station
- 3.2. Multiple stations
- 4. Short-lived TCP flows: mean delay analysis
- 4.1. An affine model for the single station case
- 4.2. Concurrent TCP sessions: a queueing model
- 4.3. On the use of delayed ACK for short TCP connections
- 5. Conclusions
- Appendix A. Impact of the maximum TCP congestion window size W*
- References
- Vitae







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