Performance Analysis Of IEEE802.11 WLAN

Widespread deployment of infrastructure WLANs has made Wi-Fi an integral part of today's Internet access technology. Past research has focused on one layer protocol enhancement, analysis and simulation-based performance evaluation without sufficient consideration for the evaluation from crossing layer view, also without sufficient consideration to see the WLANs wireless network as one, and evaluate the performance from cross-layer collaboration, also did not have WLAN performance study based on experiment of practical scale. In order to provide experimental data to the actual network deployment and application, find the actual performance of cross layer impact, we take a fresh look at IEEE 802.11 WLANs and using experiment, simulation, and analysis demonstrate its performance and vast potentials. We also show that TCP-over-WLAN achieves high throughput even in the saturation regime in the dense environment, facilitated by the self-regulating of DCF and TCP feedback control.The focus of this paper is on WLAN performance in hot spots, which is the dominant mode of WLAN usage today, in which we concern the performance degradation from contention-based multiple access the most. In several respects, there are ambiguities about the performance of WLANs, for example, some research show that the 802.11 WLAN performance significantly declines when the offered load is increased because DCF system throughput significantly declines. But we show that the analysis did not consider the effect of physical layer channel diversity that mitigates throughput degradation. And some view show that forward TCP data traffic can collide with reverse acknowledgment traffic, significantly increasing the frame error rate and declining the WLAN performance. But in the practical scale experiment and system simulation, we show that this potential TCP Data/Ack collision problem does not materialize due to the self-regulating actions of DCF and TCP feedback control.This paper, with the help of practical scale experiment, clarify some of the ambiguities surrounding WLAN performance, incorporation of the impact of cross layer cooperation. We prove that TCP-over-WLAN performance, with the cross layer cooperation, achieve high throughput, even under saturated conditions where the number of wireless station is very large. We also show that TCP-over-WLAN prowess is facilitated by the self-regulating actions of DCF and TCP feedback control, which jointly drive the shared resources at an effective load of two to three wireless stations. As a consequence, the TCP Data/Ack collision does not manifest as a real performance concern. TCP-over-WLAN also mitigates persistent unfairness due to physical layer channel diversity and throughput degradation stemming form dynamic rate shifting.We also confirmed our conclusion using mathematics model of ARF-DCF model, TCP-over-DCF model and system simulation. We simulated the TCP-over-WLAN system, and analyzed the key performance parameters, including the collision rate, throughput of uplink and downlink, delay, packet dropping rate, fairness, jitter and so on, and analyzed the simulation results and experiment results to get the accurate conclusion.