Experimental Evaluation of TCP Performance and Fairness in an 802.11e Test-bed

In this paper we present measurements made using an 802.11e wireless testbed. We demonstrate experimentally how the new 802.11e [1] QoS parameters behave in our testbed. We describe the testing methodology used to validate the operation of the 802.11e TXOP, AIFS and CWmin parameters and compare the experimental results to existing analytical models. We also discuss a number of practical issues encountered during our measurements. We then use the testbed to demonstrate some known problems with TCP’s performance caused by cross-layer interaction between the TCP congestion control algorithm and the MAC layer CSMA/CA contention mechanism. Finally, we study how these problems can be mitigated using the flexibility provided by the 802.11e parameters via the scheme suggested in [2]