Arvind <arvind.phd@gmail.com> hath wroth:
>I would appreciate it if someone could feedback on our new routing
>protocol idea. The basic idea is to develop metrics that can be used
>to route around congestion. Please let me know if you can have seen
>better ideas, prior work in this topic since we are examining the
>possibility of publishing it in a journal.
>
>The paper is available at http://www.ces.clemson.edu/~swamina/milcom06.pdf
Well, it's obvious you've done quite a bit of work on the problem.
It's also obvious that it hasn't survived a peer review. I did a
superficial read through and found a few things I didn't like:
1. The document is 11MBytes big. For 8 pages, that's a bit large.
The problem seems to be that you inserted several 2MByte images of
graphs at the bottom of the document, and then scaled them to size.
Bad idea. I suggest you reformat the document to a smaller size.
2. There are products on the market that do roughly what you propose.
Some do it with switched antennas:
<http://www.ruckuswireless.com/technology/beamflex.php>
or with steerable antennas as in beam forming MIMO:
<http://en.wikipedia.org/wiki/Beamforming>
or with multiple radios and antennas:
<http://www.xirrus.com>
The intent is largely the same as yours. By controlling the antenna
pattern, you can simultaneously improve the link performance and
eliminate any interference.
3. Your paper fails to distinguish between layer 2 switching and
layer 3 routing. I also cannot tell if you're modelling an 802.11
wireless network, or inventing some new protocol. I'll assume it's
802.11 which is *ALL* layer 2 switching. There's no routing anywhere
in sight in 802.11. You can read through the IEEE specs and never see
the word routing. Your article also makes no mention of layer 3
protocols. I suggest you do not use the term "routing" and replace it
with switching where appropriate.
4. The paper describes this traffic contention metric as:
"The traffic-contention metric for a path is the sum of link
contention metrics for the links in the path, and the link
contention metrics are determined in turn from metrics
associated with the node/sector pair that forms the link.
Considerable effort is then spent detailing how this traffic
contention metric is calculated. The problems are (as usual) at the
boundary conditions. With no traffic, you have the optimum link
quality thus giving priority to an unused path. With a link saturated
with traffic, you lose managment frames, which are presumably used to
communicate the link metrics to the next node, as well as data. Both
extremes are an invitation to "route thrashing" where a link is
subject to being periodically switched in an out as its traffic goes
from zero to saturated. You mention this possibility, but I can't
decode your method of preventing it.
5. You mention:
"For each transmission of a network-layer data packet,
a Ready-to-Send (RTS)/Clear-to-Send (CTS) packet exchange
is employed on the control channel."
It's "request to send" and there is no "control channel" in 802.11.
You list your own paper as the only relevent reference (16).
6. For your scheme to work, link metrics would need to be
communicated to each adjacent node. That works fine for a flat earth,
no obstruction, ideal topology. I have some experience trying to make
such geogrphic routing work with Metricom. Using link quality metrics
to optimize the path was a good start, but it does nothing if you have
to route around a hill or building. More simply, it doesn't turn
corners very gracefully. The bulk of your paper is on how this link
quality metric is calculated, but shows little as to how it's to be
used in a realistic wireless network.
7. I question the (Matlab?) as the graphs apparently do not show the
effects of collisions. If you employ CTS/RTS flow control to
eliminate collisions (and hidden nodes), then your thruput will suffer
more than your CA scheme can hope to compensate. Of course you can
slow down the link switching update rate but that will make it
worthless for dynamic situations such as roaming and highly reflective
environments.
Enough for now.... Best of luck on getting your paper published. I
also suggest you build a live model, using greatly simplified metric
(i.e. signal strength or SNR only) to see how it works. I suspect
you'll run into many of the problems Metricom discovered with
geographic routing and why the Houston NOC was constantly tinkering
with the route biases.
--
Jeff Liebermann
jeffl@cruzio.com
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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