Harnessing Mobile Multiple Access Efficiency with Location Input

Benefiting from the abundant sensor hints of current mobile devices, their location information has become pervasively available and easy to access. As smartphones and tablets have become recently the main access devices of 802.11-based WLAN, location information provides large opportunity to improve the performance of underlying wireless communication. This paper presents CO-MAP (Co-Occurrence MAP) which leverages the position of devices to handle exposed and hidden terminal problems in mobile WLANs so as to improve the multiple access efficiency. With the location information, CO-MAP rapidly builds a co-occurrence map showing which two links can occur concurrently. Meanwhile, it selects the best settings of frame transmissions based on a novel analytical network model when hidden terminals are distinguished. CO-MAP improves the goodputs of both downlinks and uplinks in instant and distributed manner. Our implementation on a testbed of 6 laptops demonstrates that CO-MAP can accurately detect potential hidden and exposed interferers, and provide a large gain of goodput for both exposed terminal and hidden terminal scenarios. The simulation results of large scale networks on NS-2 also suggest that imperfect position hints can still bring substantial improvement on the multiple access efficiency.