Time-slicing high throughput wifi networks using centralized queueing and scheduling

We study fine grained (10s of ms) overlay time-slicing, and centralized queuing and scheduling, for the performance management of "high throughput" (HT) IEEE 802.11 standards, where cochannel interference reduces PHY rates and aggregation, causing poor performance. In overlay time-slicing, interference between AP-STA (Access Point and associated Station) links is eliminated by queuing downlink packets in a scheduler, between the wireline network and the APs, and releasing packets to a set of AP-STA links only in their time-slice. This can manage downlink and uplink FTP and HTTP transfers, and downlink packet voice traffic. We utilize a stochastic approximation based closed-loop mechanism that releases only as much data in a time-slice as can be "served," so that the AP-STA links mapped to that time-slice are inactive at the end of their time-slice, thus, eliminating cochannel interference. Fine-grained overlay time-slicing is demonstrated on an experimental network with two cochannel AP-STA pairs, a setting that we see in our campus WiFi network. In our approach, even for small time-slices (20ms to 50ms), for downlink and uplink TCP bulk transfers, in spite of the scheduler working with partial information, the time-slice boundaries are respected, and performance is close to network utility optimal. Fine-grained time-slicing reduces HTTP access delay, prevents TCP connections over the wide area network from reacting to the path interruptions, and also permits slicing of applications such as interactive packet voice.