1. An Agile and Efficient MAC for Wireless Access over TV Whitespaces
Abstract:
The FCC mandate of allowing TV Whitespaces for unlicensed access has
the potential for dramatic improvements in wireless access data rates. We
argue that an ideal MAC should account for diverse user-location and
spectrum dependent channel rates to provide fair data rates and efficient
utilization. Furthermore, due to limited tunable bandwidth of a radio and
fragmented spectrum, the AP should support multiple radios. We make
the following contributions by designing a MAC for wireless LAN access
over TV Whitespace. (i) We propose an architecture and beaconing
mechanism to enable such a MAC. Our MAC is an evolution of 802.11
MAC. (ii) We propose an algorithm that chooses the Whitespaces for the
different radios of the AP and assigns clients to the radios. Our algorithm
has provable guarantee and is near-optimal in many scenarios. (iii)
Extensive simulation over OMNET platform demonstrates the benefit of
our design over a frequency and client-location agnostic Wi-Fi-like MAC.
The typical throughput gain is 30-76 percent, whereas, the reduction in
collisions is up to 80 percent. (iv) We implemented a proof-of-concept
prototype (by modifying madWiFi drivers) that demonstrates feasibility of
our design, robustness to temporal variation of available spectrum, and
system throughput.