Large Audience Environments Any location with a large WiFi user population WBA projected a growth rate of 350% per year for such WiFi deployments Various successful deployment models such as Boingo-Google, Mobily-Aruba etc. already exist Source: WBA(Wireless Broadband Alliance) Source: Wireless Broadband Alliance (WBA)
What about User Experience ? As number of active clients increases, user experience diminishes significantly
Well Known Factors Contention and collision – Increases with growing competition Rate Diversity – Slower STA slows down all other STAs – Various fairness realizations like WFQ, TBR etc. Random Losses and TCP performance – TCP treats packet losses as congestion signals – Usage of TCP ECN and proxy servers isolate wired and wireless networks Traffic Asymmetry
Downlink Traffic dominates for 90% of data traces
Traffic Asymmetry Majority of data traffic is Web based Downlink Traffic dominates compared to uplink Majority of data packets are for HTTP based web activities
Traffic Asymmetry In scope of our problem it is: – Downlink/Uplink Asymmetry – Channel Access Asymmetry Implications: – Packets spend more time at AP’s TxQ – Frequent packet drops
Wireless Channel Uplink Traffic Downlink Traffic Channel access for uplink traffic is more
Test Bed 2600 Sqft Area with multiple APs, 45 STAs Netgear 802.11 b/g wireless cards with Atheros chipsets and MADWIFI drivers Latency emulation using DummyNet Modified SURGE for web traffic generation Requests inter-arrival closely follows the ones observed for SIGCOMM traces Uplink UDP traffic using Iperf to emulate Background Traffic
Performance Experiment involves sending 25 requests and observe response for 4 minutes duration Request Serving rate is 4 times better than NPC Experiment involves sending 25 requests and observe response for 4 minutes duration Request Serving rate is 4 times better than NPC
Robustness Performance in presence of Multiple Aps ?? WiFox w/o WiFox
Robustness w/o WiFox WiFox Unfair Distribution Fairness Realization ??
Conclusion WiFox Delivers: – Deployment Ready Solution – Enhanced user experience with 400-700% Downlink Goodput improvements 40-60% faster response time Open Problems: – Characterizing asymmetry problem for 802.11n – Support for real time applications like chats etc. – QoS
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