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pchap(at)primus.ca
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 Posted: Tue Jan 06, 2009 6:18 pm Post subject: Cell phones and flying |
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At 20:44 06-01-09, you wrote:
| Quote: | | I understand the reasoning here. What I don't understand is how this works in Europe and Canada, where it is legal to use cell phones in planes while the |
Here's something from the Canadian Owners and Pilots Association from a few years ago: [my emphasis]
| Quote: | The April 20th, 2000 amendment to the AIP added paragraph COM 5.14, encouraging cell phone use during radio communications failures in aircraft. This lead your COPA staff to do some digging to find out exactly what the rules are for using cell phones from aircraft in flight.
Industry Canada, who regulate the use of the radio spectrum in Canada, indicated that there is no law prohibiting the use of cell phones from aircraft in Canada. Their technical representative did indicate that most airlines ban cell phone use because of potential interference with the airliner’s avionics. [ed: There are also Transport Canada recommendations on that matter.] There is also the potential for problems within the cellular network, due the high altitude airborne cell phone hitting several different network cells at one time.
In checking with one of the country’s largest cell phone service providers, they indicated that they have no rules prohibiting cell phone use from airplanes. They also indicated that they have had no problems with multiple cell “hits” from a single airborne phone causing problems and were unaware that any airborne calls were being made. |
While it is encouraging, it doesn't rule out some adverse effect out of proportion to the number of airborne users, that the company wasn't aware of.
Peter Chapman
Toronto, ON [quote][b]
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psm(at)att.net
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| Posted: Tue Jan 06, 2009 7:19 pm Post subject: Cell phones and flying |
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Hi Ron,
Your conclusion is based on the very wrong assumption that the cell
phone systems used in these different places are the same. They are not.
Cell phone systems depend on a plan of allocating frequency (channel)
and geographic space. There are many different ways to share the
radio frequencies, and all of them are in use in the USA. In other
countries there are usually a subset of the whole group of possible choices.
Each different technology has different geographic limits designed
into the network. In the original cell phone "Analog" system the
frequency use and potential collision problem was similar to the
radio frequency issues in aircraft radio systems. When two
transmitters turned on the same frequency and same geographic area at
the same time there was a collision and nothing got
received. Because of line of sight transmission limitations, the
frequencies were reused in cell sites (loosely the same as towers)
that were far enough apart that there could be no collisions. An
airplane that can transmit to both of these physically separate sites
defeats this design. Just like with aircraft radios, you can get
away with this sometimes and get clobbered other times. It depends
on whether there is another transmitter going at the same time as yours.
Newer, digital, technologies have new ways to share radio frequency
space while avoiding or tolerating collisions. In TDMA (Time
Division Multiple Access), messages are compressed and burst
transmitted on assigned frequencies. The compression allows several
transmitters to take turns over time without any collisions. In CDMA
(Code Division Multiple Access) a "Frequency Agile" approach is used
where each transmitter changes the frequency used after each few
bits. In this system collisions happen randomly but only for a few
bits at a time and the original message is recovered because of an
error correction code built into each message.
Still, there is a real chance of problems when the transmitter is in
an airplane and the signal travels hundreds of miles instead of only
a few miles as it would on the ground.
So, in reality the impact of using a cell phone in an airplane varies
on the type of cell phone used, the network technology involved, and
the local design of the actual network. If you are in a sparsely
populated area like Canada the impact is less likely to be a
problem. In other places like Europe the systems are so limited that
you don't face inter-system technology problems. I would guess the
most complicated set of different systems and heavy population is
found in the USA - at least from the point of view of cell phone
users and network providers.
So there is more likelihood of a problem with cell phone use in an
airplane in the USA. There are just too many people and too many
cell phones too close together for this to not be an issue.
Paul
XL getting close
do not archive
(and yes, you guessed it, the last honest work I did before retiring
was designing cell phones.)
At 05:44 PM 1/6/2009, you wrote:
| Quote: | I understand the reasoning here. What I don't understand is how
this works in Europe and Canada, where it is legal to use cell
phones in planes while the FCC insists we can't in the US. Seems to
me either we have a very poor cellular infrastructure or the FCC is
blowing smoke. The alternative is that they just don't care in
Canada or Europe and I'm definitely not buying that argument.
Ron
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rsteele(at)rjsit.com
Guest
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| Posted: Tue Jan 06, 2009 7:38 pm Post subject: Cell phones and flying |
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Interesting discussion. We are probably getting off topic, but I feel
it's a matter of safety as well as convenience. I understand most of
the world, including Europe and Canada use GSM while we have GSM, TDMA
and CDMA. I thought that one of the benefits of CDMA and TDMA is that
roaming from tower to tower was supposed to be more reliable with
fewer drops (The networks just increases compression until a call is
ended). Maybe this works against you in this situation. At any rate
my GSM phone puts an annoying buzz on the intercom every time is says
hello to the network, so I keep off anyway.
Cheers,
Ron
On Jan 6, 2009, at 10:19 PM, Paul Mulwitz wrote:
| Quote: |
Hi Ron,
Your conclusion is based on the very wrong assumption that the cell
phone systems used in these different places are the same. They are
not.
Cell phone systems depend on a plan of allocating frequency
(channel) and geographic space. There are many different ways to
share the radio frequencies, and all of them are in use in the USA.
In other countries there are usually a subset of the whole group of
possible choices.
Each different technology has different geographic limits designed
into the network. In the original cell phone "Analog" system the
frequency use and potential collision problem was similar to the
radio frequency issues in aircraft radio systems. When two
transmitters turned on the same frequency and same geographic area
at the same time there was a collision and nothing got received.
Because of line of sight transmission limitations, the frequencies
were reused in cell sites (loosely the same as towers) that were far
enough apart that there could be no collisions. An airplane that
can transmit to both of these physically separate sites defeats this
design. Just like with aircraft radios, you can get away with this
sometimes and get clobbered other times. It depends on whether
there is another transmitter going at the same time as yours.
Newer, digital, technologies have new ways to share radio frequency
space while avoiding or tolerating collisions. In TDMA (Time
Division Multiple Access), messages are compressed and burst
transmitted on assigned frequencies. The compression allows several
transmitters to take turns over time without any collisions. In
CDMA (Code Division Multiple Access) a "Frequency Agile" approach is
used where each transmitter changes the frequency used after each
few bits. In this system collisions happen randomly but only for a
few bits at a time and the original message is recovered because of
an error correction code built into each message.
Still, there is a real chance of problems when the transmitter is in
an airplane and the signal travels hundreds of miles instead of only
a few miles as it would on the ground.
So, in reality the impact of using a cell phone in an airplane
varies on the type of cell phone used, the network technology
involved, and the local design of the actual network. If you are in
a sparsely populated area like Canada the impact is less likely to
be a problem. In other places like Europe the systems are so
limited that you don't face inter-system technology problems. I
would guess the most complicated set of different systems and heavy
population is found in the USA - at least from the point of view of
cell phone users and network providers.
So there is more likelihood of a problem with cell phone use in an
airplane in the USA. There are just too many people and too many
cell phones too close together for this to not be an issue.
Paul
XL getting close
do not archive
(and yes, you guessed it, the last honest work I did before retiring
was designing cell phones.)
At 05:44 PM 1/6/2009, you wrote:
> I understand the reasoning here. What I don't understand is how
> this works in Europe and Canada, where it is legal to use cell
> phones in planes while the FCC insists we can't in the US. Seems
> to me either we have a very poor cellular infrastructure or the FCC
> is blowing smoke. The alternative is that they just don't care in
> Canada or Europe and I'm definitely not buying that argument.
>
> Ron
|
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psm(at)att.net
Guest
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| Posted: Tue Jan 06, 2009 8:09 pm Post subject: Cell phones and flying |
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Hi Ron,
I'm glad you find this interesting. I was afraid I might be getting
too technical for this crowd. Give me a few more tries at
remembering all this dusty stuff and I probably can come up with some
really weird notions.
GSM is actually a single implementation of TDMA. It is used in
Europe, Asia, and now in the USA as well. There are other TDMA
systems in use simultaneously in the USA. In particular, IS-54 is
the one used by the last phone I designed. It is technologically
very similar to GSM but totally incompatible when used on the same
frequency set.
The changing of a call from one tower to another is called a "Hand
off". Just as it is in IFR radio use. The process is completely
done by computers in the cell phone case. In the FAA case, the hand
off is done with world war 2 human based technology. I don't think
there is a significant difference in hand off technology between the
various cell phone systems. In all cases the losing cell site asks
neighboring sites to measure the signal strength it sees for the
target phone. The one with the best signal gets the hand off. It is
easy to imagine that a distant phone in an airplane could interfere
with this process for an unsuspecting ground based user and network.
Paul
XL getting close
do not archive
At 07:37 PM 1/6/2009, you wrote:
| Quote: | Interesting discussion. We are probably getting off topic, but I feel
it's a matter of safety as well as convenience. I understand most of
the world, including Europe and Canada use GSM while we have GSM, TDMA
and CDMA. I thought that one of the benefits of CDMA and TDMA is that
roaming from tower to tower was supposed to be more reliable with
fewer drops (The networks just increases compression until a call is
ended). Maybe this works against you in this situation. At any rate
my GSM phone puts an annoying buzz on the intercom every time is says
hello to the network, so I keep off anyway.
Cheers,
Ron
|
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JohnDRead(at)aol.com
Guest
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| Posted: Tue Jan 06, 2009 8:18 pm Post subject: Cell phones and flying |
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Lighten up Jay. The FAA reccemends carrying a cell phone as a backup communication method.
John Read
CH701 - Elbert CO - Jabiru 3300
Phone: 303-648-3261
Fax: 303-648-3262
Cell: 719-494-4567
In a message dated 1/6/2009 11:42:52 A.M. Mountain Standard Time, jmaynard(at)conmicro.com writes:
| Quote: | --> Zenith-List message posted by: Jay Maynard <jmaynard(at)conmicro.com>
On Tue, Jan 06, 2009 at 01:26:23PM -0500, Frank Roskind wrote:
| Quote: | The following link says a tower has a service area of about 10 square
miles. Using the area formula, r**2=10/pi. That implies a radius of
about 9420 feet. Thus your slant range to the tower would need to be
about 9420 feet. If there is a tower every mile that implies you could
fly to about 7800 feet above the tower height.
http://www.mobiledia.com/guides/page1.html
|
That is only valid for a ground level station, and includes effects such as
attenuation from trees and buildings and the curvature of the earth. A cell
site can see a phone from much farther away if it's airborne.
--
Jay Maynard, K5ZC, PP-ASEL, AGI http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (KFRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC he es y - MATRONICS WEB FORUMS =========================< - List Contribution Web Site ; =========================
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latest news - from fashion trends to celebrity break-ups and everything in between.
[quote][b]
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jmaynard
Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)
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| Posted: Tue Jan 06, 2009 8:26 pm Post subject: Cell phones and flying |
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On Tue, Jan 06, 2009 at 11:17:06PM -0500, JohnDRead(at)aol.com wrote:
| Quote: | Lighten up Jay. The FAA reccemends carrying a cell phone as a backup
communication method.
|
In an emergency? Sure, anything goes. Lost comm, especially when IFR, is an
emergency. Under normal circumstances? No way. Just because it might be
cool? Get real. Paul's postings this evening about the reasons why using a
cellphone in flight is a Bad Idea are right on (as one would expect from
someone who actually knows about the subject, deep down, from having
designed the things). My cellphone, and that of my passenger, gets turned
off before taxi, and stays off until after landing, not only because I want
no part of that annoying buzz, but because it's the right thing to do.
--
Jay Maynard, K5ZC, PP-ASEL, AGI http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (KFRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml
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Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC |
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notsew_evets(at)frontiern
Guest
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| Posted: Tue Jan 06, 2009 8:34 pm Post subject: Cell phones and flying |
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Trying to stay out of this but:::
One time I lost transmit but could receive ok on my radio.
ATC asked and requested me to call them on my cell phone. Class "D" and
thats what they wanted.
SW
---
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leo.gates
Joined: 29 Nov 2008
Posts: 35
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| Posted: Tue Jan 06, 2009 9:23 pm Post subject: Cell phones and flying |
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Darn I bought a cell phone adapter for my plane from ACS. I guess I can
use it on the ground.
Do not archive
--
Leo Gates
N601Z - CH601HDS TDO
Rotax 912UL
Frank Roskind wrote:
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Rhino
Joined: 01 Aug 2007
Posts: 56
Location: Xenia, Ohio
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| Posted: Tue Jan 20, 2009 12:56 pm Post subject: Re: Cell phones and flying |
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| rsteele(at)rjsit.com wrote: | | I understand the reasoning here. What I don't understand is how this works in Europe and Canada, where it is legal to use cell phones in planes while the FCC insists we can't in the US. Seems to me either we have a very poor cellular infrastructure or the FCC is blowing smoke. |
Smoke. Sort of.
First, the regulation cited above is in part 22 of CFR 47. That part deals with the 800 Mhz band only. There are no such prohibitions in the other bands and very few cell phones are still in the 800 Mhz band. The guy who wrote that particular regulation for the FCC is actually a GA pilot.
http://www.pilotsofamerica.com/forum/showthread.php?t=23309
Second, the 'problems' cited with cell towers from an aircraft aloft are based on high altitude airliners, and high speeds that could conceiveably make tower 'tracking' extremely difficult. Tooling around in your little Zenith isn't going to get you seen by very many additional towers. And God knows your speed won't be a problem.
Third, actual measured tests of cell phones in high altitude, high speed aircraft have demonstrated that none of those perceived problems actually exist. They also demonstrated that cell phones do not interfere with aircraft systems. Imagine that.
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Bob Simmons
CH 750
N750TN (reserved) |
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