FARA: Frequency-Aware Rate Adaptation and MAC Protocols
overview
There has been burgeoning interest in wireless technologies that
can use wider frequency spectrum. Technology advances, such as
802.11n and ultra-wideband (UWB), are pushing toward wider frequency
bands. The analog-to-digital TV transition has made 100-
250 MHz of digital whitespace bandwidth available for unlicensed
access. Also, recent work on WiFi networks has advocated discarding
the notion of channelization and allowing all nodes to access the
wide 802.11 spectrum in order to improve load balancing. This shift
towards wider bands presents an opportunity to exploit frequency
diversity. Specifically, frequencies that are far from each other in the
spectrum have significantly different SNRs, and good frequencies
differ across sender-receiver pairs.
This project presents FARA, a combined frequency-aware rate
adaptation and MAC protocol. FARA makes three departures from
conventional wireless network design: First, it presents a scheme
to robustly compute per-frequency SNRs using normal data transmissions.
Second, instead of using one bit rate per link, it enables
a sender to adapt the bitrate independently across frequencies
based on these per-frequency SNRs. Third, in contrast to traditional
frequency-oblivious MAC protocols, it introduces a MAC protocol
that allocates to a sender-receiver pair the frequencies that work best
for that pair. We have implemented FARA in FPGA on a wideband
802.11-compatible radio platform. Our experiments reveal that
FARA provides a 3.1× throughput improvement in comparison to
frequency-oblivious systems that occupy the same spectrum.
papers
Frequency-Aware Rate Adaptation and MAC Protocols,
Hariharan Rahul, Farinaz Edalat, Dina Katabi, and Charles Sodini,
ACM MOBICOM 2009. PDF
people
Hariharan Rahul
Massachusetts Institute of Technology
Farinaz Edalat
RKF Engineering Solutions, LLC
Dina Katabi
Massachusetts Institute of Technology
Charles Sodini
Massachusetts Institute of Technology