Planes & Cell phones

Recentingly, in another thread, cell phones and planes came up. I
thought others might be interested in these links.

http://www.eweek.com/article2/0,1759,1568024,00.asp
http://wirelesscabin.com/
http://www.wired.com/wired/archive/1...art.html?pg=12

The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such calls
is tolerable, but a whole plane load moving through would disrupt the
ground-based users of the network. Remember, the farther you are from a
tower, the more power your cell phone uses to communicate with it's tower;
up to 5-watts. Worse, a plane full of 5-watt transmitters causes
terrestrial interference problems for the land cell users, in a large
radius around the plane.

This picocell concept (covered the above links) solves both problems by
moving the nearest cell tower to just a few feet away from the phone.
Therefore, the phone kicks into its lowest power tx setting,
and never talks to any other tower. Of course, I don't think you can
expect on in a small GA plane anytime soon.

I also found a quote that went like this:
"The restriction against cell phones is an FCC regulation and applies to
all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
switching cells during high speed flight causes all sorts of problems on
the cell network."

Can anyone confirm such an FCC regulation as it relates to airspeed? I
must admit, from I understand of the subject, it does make sense. Just
the same, confirmation would be great.

Lastly, can anyone confirm first hand accounts of cell phones actually
causing some type, instrumentation or radio interference?

At worst, hopefully this will be some food for thought.

Thanks! Cheers!

"Greg Copeland" wrote in message
news
Recentingly, in another thread, cell phones and planes came up. I
thought others might be interested in these links.

http://www.eweek.com/article2/0,1759,1568024,00.asp
http://wirelesscabin.com/
http://www.wired.com/wired/archive/1...art.html?pg=12

The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such
calls...

Here's a needed clarification. Are there still problems when the phone isn't
making a call, but just sitting there listening to the network? I know such
a phone is continuously acquiring the next tower down the road. Would it be
true that the problem with passive phones is the same as with active ones,
but to a lesser extent?

-- David Brooks

I think you have too much time on your hands...
cheers ... denny

"Greg Copeland" wrote in At worst, hopefully this
will be some food for thought.

Thanks! Cheers!

On Tue, 20 Apr 2004 12:21:33 -0700, David Brooks wrote:

"Greg Copeland" wrote in message
news
Recentingly, in another thread, cell phones and planes came up. I
thought others might be interested in these links.

http://www.eweek.com/article2/0,1759,1568024,00.asp
http://wirelesscabin.com/
http://www.wired.com/wired/archive/1...art.html?pg=12

The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such
calls...

Here's a needed clarification. Are there still problems when the phone isn't
making a call, but just sitting there listening to the network? I know such
a phone is continuously acquiring the next tower down the road. Would it be
true that the problem with passive phones is the same as with active ones,
but to a lesser extent?

-- David Brooks

Well, first let me say that I am NOT a subject matter expert on this, so
please, take my comments with a grain of salt.

When you speak of active versus passive, do you mean a phone being
actively used for calling versus a phone simply turned on? I'll assume
that's what you mean. A phone that is not actively particpating in a call is
still periodically attempting to locate it's best tower. It may be
sharing additional tidbits as well, I'm not sure. Nonetheless, if it's
transmitting, it's causing these problems. Like you, I suspect that it is
causing problems, just to a lessor extent.

If you have a phone, like mine, which periodically blinks, that blink
means it just transmitted. AFAIK, it's the fact that the phone is
transmitting, especially at 5-watts, that is causing some of the problems,
without regard for the content that is being transmitted. The fact that
you're traveling at a high rate of speed, probably causes more frequent
tower contacts (and tower hops) from your phone, however, that's purely
speculation on my part.

I think you have too much time on your hands...
cheers ... denny

Actually, I think it's a cool topic.

I'd be willing to fly slower than 200 knots if it meant I could legally use
my cell phone in the air!

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Greg Copeland" wrote in message
news snip
The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such calls
is tolerable, but a whole plane load moving through would disrupt the
ground-based users of the network. Remember, the farther you are from a
tower, the more power your cell phone uses to communicate with it's tower;
up to 5-watts. Worse, a plane full of 5-watt transmitters causes
terrestrial interference problems for the land cell users, in a large
radius around the plane.
snip

Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
in-car and bag phones going up to 3 watts. It can't output more than it's
maximum no matter how far you are away from the tower. The radius of
interference from 0.6 watt phones transmitting from inside an aluminum can
would be rather small. And it's a little hard to imagine a plane full of
people with bag phones.

I also found a quote that went like this:
"The restriction against cell phones is an FCC regulation and applies to
all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
switching cells during high speed flight causes all sorts of problems on
the cell network."

The switching is done in a fraction of a second. The most that would happen
is a dropped call.

On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:

Greg Copeland" wrote in message
news snip
The general theory on modern cell phones in flight, goes like this:
The FCC also has a ban because when you're in flight, you're always at
least 6-8 miles away from the nearest cell tower. You end up communicating
with too many towers and bogging down the network. One or two such calls
is tolerable, but a whole plane load moving through would disrupt the
ground-based users of the network. Remember, the farther you are from a
tower, the more power your cell phone uses to communicate with it's tower;
up to 5-watts. Worse, a plane full of 5-watt transmitters causes
terrestrial interference problems for the land cell users, in a large
radius around the plane.
snip

Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
in-car and bag phones going up to 3 watts. It can't output more than it's
maximum no matter how far you are away from the tower. The radius of
interference from 0.6 watt phones transmitting from inside an aluminum can
would be rather small. And it's a little hard to imagine a plane full of
people with bag phones.


Hmm. Everything I've ever read says that maximum output is 5-watts. I'm
not saying that's right, but that has been a constant. I'm not sure how
far you could even transmit on 0.6 of watt.

I also found a quote that went like this:
"The restriction against cell phones is an FCC regulation and applies to
all aircraft that can fly over a certain speed (maybe 200 kts?). Quickly
switching cells during high speed flight causes all sorts of problems on
the cell network."

The switching is done in a fraction of a second. The most that would happen
is a dropped call.

People forget that cell switching is not magical. And it's certainly is
not zero cost. I must admit I do not fully understand everything that
goes on, but I am sure it's not as simple as you imply. Everytime a call
switches cells, it creates lots of work for the cell network to make sure
only a single tower handles that call. So, while it may take a fraction
of a second from a given phone and a given tower, there is lots going on
behind the scenes. Worse, instead of it going on with one, two or maybe
three towers, now it's causing a flurry of on twenty or more (highest
estimates I've read) towers. Let's also not forget that each tower can
only process and multiplex n-number of signals at a given time. DSPs,
just like your CPU, does have finite capacity. During cell switching, as
I understand it, this finite resource is being used on each tower in
contact with the phone. So, to say, "it causes all sorts of problems on
the cell network", does seem like a spot on statement to me.

On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:

Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
in-car and bag phones going up to 3 watts. It can't output more than it's
maximum no matter how far you are away from the tower. The radius of
interference from 0.6 watt phones transmitting from inside an aluminum can
would be rather small. And it's a little hard to imagine a plane full of
people with bag phones.

I thought I might just toss this out there. I quickly looked. I did not
have any trouble finding modern, handheld phones, with 2-watts output.
So, I think it's safe to say that we know for sure it's at least 2-watts.

Greg Copeland wrote:

On Tue, 20 Apr 2004 16:35:03 -0500, FUji wrote:

Huh? Maximum output of most handheld cell phones is 0.6 watts with the old
in-car and bag phones going up to 3 watts. It can't output more than it's
maximum no matter how far you are away from the tower. The radius of
interference from 0.6 watt phones transmitting from inside an aluminum can
would be rather small. And it's a little hard to imagine a plane full of
people with bag phones.

I thought I might just toss this out there. I quickly looked. I did not
have any trouble finding modern, handheld phones, with 2-watts output.
So, I think it's safe to say that we know for sure it's at least 2-watts.

Both of my run-of-the-mill Nokias have a maximum transmit power of 600
mW. They are two different digital/analog models.

"Greg Copeland" wrote in message
news
[...] I'm not sure how far you could even transmit on 0.6 of watt.

FRS (the 90's answer to walkie-talkies) is limited to 0.5 watts and is
considered usable up to about 2 miles (not counting obstructions). Range is
dependent not just on the transmitted power, but also how sensitive the
receiver is. Pitifully weak signals are received over distances of hundreds
of millions of miles on a regular basis (just ask NASA).

Pete