[Chapter-delegates] WIFI and FM Radio

Joly MacFie joly at punkcast.com
Tue Nov 10 17:08:06 PST 2015


Reformatted for readability

​
http://www.npr.org/sections/alltechconsidered/2015/11/10/455386738/slow-wi-fi-fm-radio-might-help-with-that
​
If you live in an apartment building or another densely populated area and
your Wi-Fi is slow, your neighbors bingeing on Netflix may be to blame.

Your and your neighbors' Wi-Fi networks have a limited number of wireless
frequency channels to move your data. And when things get crowded and busy,
Wi-Fi networks can overlap and bump into each other and slow down your
Internet connection.

"I'm doing something, you're doing something, but none of us have a
reference point about when the other party will do something or not," says
Aleksandar Kuzmanovic, associate professor
<http://www.cs.northwestern.edu/~akuzma/> of electrical engineering and
computer science at Northwestern University, describing how Wi-Fi devices
might operate.

"There's no sense of timing, no sense of coordination. And hence, I listen
a little bit, I don't hear, I send something. This may create trouble to
you because you just sent something. And then we both back off. There could
be time wasted before somebody grabs the airtime," he says.

Looking for a way to organize this common discord, Kuzmanovic and his
colleagues Marcel Flores and Uri Klarman have found
<http://www.mccormick.northwestern.edu/news/articles/2015/11/using-fm-to-improve-wireless-networks.html>
an
interesting aide: FM radio.

It's not a simple app to install on your phone, but the researchers say
they've developed the first system for Wi-Fi devices to coordinate for
everyone's benefit without explicit communication or human involvement. And
it comes over FM — strong enough to reliably travel through walls and
ubiquitous enough that many devices are already geared to receive it.

Knowing that Wi-Fi devices already hear each other over Wi-Fi frequencies,
the scientists looked for a way to help the devices harmonize.

That's where FM radio comes in.

When you're listening to the radio, say, in your car, your display may show
the name of the artist and song playing on the station, or sometimes
traffic and weather alerts. That information arrives over a digital signal,
called the Radio Data System or RDS, which travels right beside the
broadcast signal.

RDS data, Kuzmanovic explains, have a signal structure that delivers bits
of information in a series that constantly repeats itself.

So if Wi-Fi networks can converge on the same RDS (by scanning the FM dial
for the lowest-frequency radio station with a strong enough signal), they
can use it to harmonize their time-telling.

"Devices are able to detect that there is this particular repeating
structure and hence they are all able to independently come to the
conclusion that hey, this must be the beginning of this particular RDS
signal sequence that's repeating in time," Kuzmanovic tells All Tech.

"And then once they come to that particular point ... they divide the time
into particular time slots and then they listen to how others are behaving
relative to these time slots and that further determines their own behavior
— when will they send data, when they will not send data," he says.

Put simply, the RDS signal acts as a clock for Wi-Fi devices to time the
quietest slot — and we're talking milliseconds — during which to send data.

The researchers dub this technique Wi-FM, describing it in a new paper
<http://networks.cs.northwestern.edu/publications/wifm/icnp2015-flores.pdf>
presented
Tuesday at the IEEE International Conference on Network Protocols
<http://icnp15.cs.ucr.edu/> in San Francisco.

The paper outlines one possible scheduling algorithm that would help Wi-Fi
devices coordinate by using an FM signal. But as with many things in the
industry, Kuzmanovic says others could come up with alternative approaches
to reach the same goals with some universal parameters.

And while individually people could start adapting software on their Wi-Fi
devices to adopt the Wi-FM technique, Kuzmanovic says the system would work
best industrywide. His hope is for Google or Apple to spread the idea
through its operating system, though he hasn't heard from the industry yet.

On Tue, Nov 10, 2015 at 7:36 PM, Glenn McKnight <mcknight.glenn at gmail.com>
wrote:

>
> http://www.npr.org/sections/alltechconsidered/2015/11/10/455386738/slow-wi-fi-fm-radio-might-help-with-that
>
> Slow Wi-Fi? FM Radio Might Help With That
>
-- 
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Joly MacFie  218 565 9365 Skype:punkcast
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