Hariharan Rahul, Farinaz Edalat, Dina Katabi, Charles Sodini
ACM MOBICOM 2009, Beijing, China, September 2009
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 paper 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 3x throughput improvement in comparison to
frequency-oblivious systems that occupy the same spectrum.
[PDF (922KB)]
Bibtex Entry:
@inproceedings{rahul2009fara,
author = "Hariharan Rahul and Farinaz Edalat and Dina Katabi and Charles Sodini",
title = "{Frequency-Aware Rate Adaptation and MAC Protocols}",
booktitle = {ACM MOBICOM 2009},
year = {2009},
month = {September},
address = {Beijing, China}
}