On link rate adaptation in 802.11n WLANs
Sriram Lakshmanan, Shruti Sanadhya, and Raghupathy Sivakumar
GNAN Research Group
School of Electrical and Computer Engineering
Georgia Institute of Technology
Abstract
The IEEE 802.11n standard is gaining popularity
to achieve high throughput in Wireless LANs. In this paper,
we explore link adaptation in practical 802.11n systems using
experiments with off-the-shelf hardware. Our experiments reveal
several non-trivial insights. Specifically, (1) trivial extensions
of algorithms developed for 802.11g provide minimal benefits
in 802.11n systems; (2) in contrast to theoretical expectation,
multiple antenna transmission does not always lead to higher
throughput in practice; (3) both stream and antenna selection
are essential to reap the full benefits of MIMO technologies.
We use insights developed from experiments to develop a new
metric for stream selection called the Median Multiplexing Factor
(MMF). The proposed metric can be used to develop intelligent
rate selection algorithms that can achieve high throughput with
purely software changes.