Interference Cancellation: Better
Receivers for a New Wireless MAC
Daniel Halperin, Josie Ammer, Thomas
Anderson, and David Wetherall
(University of Washington)
Summary: One of the fundamental problems in shared channel simultaneous
has interference. The CSMA was designed for single contenteous
AP, but today
the deployments are dense and in 3-D.
The key idea is that exploit structure of interference to overcome its
effect; seperate it from noise; noise is random but interference has a
structure. The presenter showed how the different phase,
and amplitude to recover the packets that would otherwise be lost to
Q: What would happen when we use denser packing constellation, such as
A. Even in that case we should be able to of separate the
Q: Why do the real systems have a slack; why do the standards just
use the slack for better rates.
A: They cannot predict the scenarios that the standardized equipement
Q: How it is related to analog coding.
A: In analog coding case we need to know one or the other symbol,
which is not available in infrastructure-mode.
Q: When is it likely to happen, and when not; in particular, multiple
senders, multipath fading/interference, etc.
A: We need more work to evaluate those scenarios. But there
obvious cases where it will not work, e.g., when one of the receiver
is close to noise margin.
Q: Do you think that the AP will operate in this mode all the time?
A One possible way is that a AP just sits and listen and only recovers
there is a collision.
Q: How does is scale with the number of simultaneous speakers.
A: It blows up the search space, but one thing is that you can switch
to CSMA when there are more speakers.