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THOUGHT: The use of Pocket PC Phone Edition on Airplanes
Posted by Arne Hess - on Thursday, 22.08.02 - 21:04:00 CET under 09 - Thoughts - Viewed 7045x
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Several sites like Pocket PC Thoughts and discussed the FAA announcement from USAToday that you are allowed to use PDAs on aircrafts, however I think the FAA missed the point here:

Thought 1: I don't see that that the wireless part of a Pocket PC Phone Edition is/should be allowed to use. The reason is pretty simple; we are talking about a radio module which - and it doesn’t matter if it is used for voice or data - (could) interfere the on-board electronic.

Thought 2: GSM will not work above the clouds. GSM and its antennas is designed to cover the ground. I’ve never seen a BTS which covers the air. You can see this even on skyscrapers in Manhattan. While you have a perfect coverage on ground you are out of coverage on the top levels, if no repeaters are installed. I saw this phenomena even in Hong Kong which is (I think so far) the best covered city in the world. Maybe near windows you will catch the one or the other signal but if you walk into the building you are out of any coverage which doesn’t happens on the ground floors.
So how we could believe that the area in 10.000 meters height is covered?

Thought 3: GSM has speed limits, not only for transferring data but also for transferring the waves. If I remember right, the speed limit for a GSM 900 MHz network is something around 400 km/h while it is something around 250 km/h for GSM 1800 MHz networks and even less for GSM 1900 MHz networks.
As far as I remember from my many flights a Boeing or Airbus fly faster than 400 km/h but for sure faster than 250 km/h only. So even if there would be coverage the handover between the BTS’ wouldn’t work anymore.

When I flew two weeks ago to Paris for a meeting, I’ve used my xda on the way to Paris as well as back to Munich (you might remember my thoughts about Vodafone GPRS roaming in Paris ;-) the flight attendees to Paris was relaxed when I was typing on my Pocket PC. However on the flight back to Munich a flight attendee asked me (more or less rude) to switch of my cell phone and she was right. She was a German woman who saw the TV commercials from o2 that the xda is (also) a mobile phone. And therefore she thought that I’m using my mobile phone during the flight. Also my explanation that the phone part is switched off and I’m using the PDA part only wasn’t clear for her but no attack here from my side because how should she knew what I was doing.

Also I have to confess that one time I forgot to switch off my mobile phone on a domestic flight in Germany. My mobile phones are always configured for manual network search and as you might know, Germany is a pretty good covered county.

So when I’ve arrived that time, the mobile phone asked me to select a new network which means it lost the connection to the original network. This is an indicator for me that there was no coverage available in the sky.

So I would like to ask to switch off your GSM enabled Pocket PC before you entering an aircraft because:

1st: It could interfere the electronic.

2nd: There is no coverage anyhow.

3rd: You would fly faster than the handover/signal works.

4th: I might be in the same aircraft and I would like to arrive safely!

So even if GSM wouldn't interfere the aircraft electronics your GSM device will not work above the clouds. GSM/GPRS is a different technology than Blackberry or Palm VII but a good approach could be "Connexion by Boeing" which I've wrote about some month ago.

Cheers ~ Arne


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Posted by Anirvan on 22.08.02 - 00:00:00

Just a thought:

The last time I flew to London (from Greece) I forgot to switch off my phone which I left in my briefcase. I was pretty surprised after the flight when friends of mine told me that when they tried several times to reach me on the phone during the flight (they did not know that I was flying to London at that time) they heard an operator speaking in different languages saying that the phone was unreachable. So obvioulsy the phone registered itself to several different networks (in the countries I flew above) during the flight.

Posted by Niall on 23.08.02 - 00:00:00

While I agree with you that, if mobile phones of any kind are dangerous to the systems on aircraft, a converged PDA should have its phone side turned off on the plane, I don't agree about the height thing.

I can get good signals on top of 1500m high hills in the UK, because they have better line-of-sight to a mast than some of the local valleys. 10000m with good LOS should just give a poor signal. I think the technical difficulties are more likely to be a problem with transit speed between base stations. I remember seeing an article about airphones that made that exact comment (quoting an American engineer).

Cities tend to be bad places to test mobile phone conectivity because big buildings block the signal. Since switching from Vodafone to Orange, I've been wanting to know about the absorption properties of the different frequencies used. Standing at the back of my local supermarket, I could never get a signal on Vodafone, but Orange picks up fine. I used to put it down to a more local Orange mast, but I've noticed that Orange generally seems to have a better signal when inside buildings. Got any in-depth knowledge you can share?

Posted by Arne Hess on 23.08.02 - 00:00:00

@Niall: Hills are something different to skyscrapers. Also in the Alps I can use for sure my cell phone but the reason is pretty easy, the base station is on the same level like me. It’s also mounted on the mountains. So it still covers the ground. From its perspective the wave angle is down or equal but never up. That’s what I mean with the skyscraper example. The wave angle is always equal to down.
Also the point isn’t the range here. Motorola tested BTS’ some years ago which worked up to 35 km, this would be enough to cover the air for sure because you have a “perfect” line of sight but it was never tested to cover the sky but rural areas only.

Regarding the signal strength of the Orange network: You are right, most GSM 1800 MHz seems to have a better coverage/stronger signal strength but this is realized through a higher penetration of BTS only.
In general the 900 MHz frequency covers a wider area and also “run” better through walls. So in general GSM 900 is the better technology for covering wider areas or realizing coverage within buildings.
The advantage of GSM 1800 is that 1800 MHz waves have a shorter coverage range. This means that you have to take more BTS to cover the same area than GSM 900 can do (up to 2.5 more BTS are required!). However, due to the higher frequency rate you get a higher voice quality which is the advantage of GSM 1800.

On the other hand higher frequencies mean higher sensitivity on hindrances. While GSM 900 still works perfect at strong fog, snow fall or rain it could be that this “hindrances” blocks the 1800/1900 MHz waves. This problem will increase – by the way – with 3G which use even a higher frequency than GSM 1800/1900.

Oh, BTW regarding covering wide areas. There is a GSM standard available which use 450 MHz (GSM 450). This was designed to cover wide areas with less BTS’ like the Sahara. However, GSM 450 was never introduced.

Posted by Anonymous on 23.08.02 - 00:00:00

Arne, wow!!! Thanks for your detailed explanation of GSM. Again a reason to come to, you are really a GSM insider with a deep knowledge of this technology!

Congratulations to such a good site; I'm visiting you daily!

Posted by Anonymous on 24.08.02 - 00:00:00

By luis Simão (Mozambique)

I have readed all about this and my concern is:
1-  if there are any interference to the airplanes must be only when landed, because you can imagine the transmittors placed around the airports to cover that areas and in each second how many celphones comunicate throw that transmitters, because there are to many electronic waves by the transmitters and not the cellphones.
2- There are not any signal for GSM in the air at 10.000 meters or 31.000 feet the cellphones are completly usless, no signal is available. Only, when switch on, they can produce same electronic waves but whitout any interference. If the airplane use bluethooth on the computer-on-board there are of course with any bluetooth device laptop or PDA, a possibility of comunication as Fujitso pocket LOOX.
3- I think will be possible comunicatte with your cellphone one day throu the airplane transmiter to any place on earth. Some companys use now (Singapure Airlaines) their phone on your seater on the airplane to phone anyware using a credit card.

So is a contaditory to FAA pass PDA yes not cellphones.

Posted by Arne Hess on 24.08.02 - 00:00:00

@Luis: Thanks for your contribution but let me add my thoughts here:

1: I don’t agree with you here. Just setup a voice call on your GSM device and hold it in front of your loudspeaker; you will hear the interferences! This will not happen with Bluetooth!
Also you hear no interferences with all the BTS’ around you – that’s something completely different!

2: A mobile phone tries to connect every 15 seconds if it is not logged into a GSM network and therefore it is searching/scanning every 15 seconds with the full power. This will/can interfere for sure!

3: Yes, you are right. There is a project here in Germany which will enables using the GSM phone by building in a repeater into the aircraft which will connects to the mobile phone one hand and the satellite on the other hand. However, also Airbus and Boeing are part of this project because they have to redesign the electronic within the aircraft. First results are expected within the next two years.

Posted by Anonymous on 29.08.02 - 00:00:00

There were reports on 9/11 of people in the plane calling their family on their cell phone while... so at least some cell phones must work fine on airplanes.

Posted by Pony99CA on 01.09.02 - 00:00:00


   I think the FAA understands that the phone part of the PDA must be switched off.  They mean using the PDA *part* is OK; the phone parts are still banned.

   Also, I'm surprised that GSM would have a "speed limit".  Cell phones work using radio waves, which travel at the speed of light.  The only speed limit I can think of is if you're moving so fast that you switch between cells before the last cell can lock on to you.  Not being an expert in telecommunications, though, that's just a guess.


Posted by Arne Hess on 01.09.02 - 00:00:00

@Steve: Well, regarding your first comment about the FAA: I just want to make it clear again that the phone should be switched of because some guys (on other sides) has a little bit different opinion about it and they used the FAA that it could be fine for them.
Regarding the “speed limit” concerns: It’s not because the waves and you are right – radio waves are using light speed. It’s about latency times and as you’ve said the handovers between the different cells. Please check also this very interesting article from the which gives some pretty interesting hints about distances.
Cheers ~ Arne

Posted by Matty on 30.09.02 - 00:00:00

i know for a fact that CDMA in the USA works over the clouds because i have flown from Washington State to Kansas and had coverage on my AOL Mobile Communicator (cdma Motient network) on several occasions over different cities - i would write e-mail over the clouds and it would automatically send it when i was over cities like Salt Lake City Utah and Denver Colorado.... it was on full signal over these cities.... what's the speed of that network? anyone know? Arne? My hero? Come on bro smile.

Posted by Anonymous on 03.10.02 - 00:00:00

Amongst the many thoughts brought on by the Sept 11th tragedy is this: some of those people were using cellphones as well as seatback phones to call loved ones, weren't they ?  So they must have worked, and also that number of people making the calls doesn't seem to have interfered with the systems, unless that's what caused the fourth one to crash away from its intended target, but I doubt that.

Posted by mschugh on 23.08.04 - 07:53:53

Well, I feel that the radio frequency which always while you on or off any gadget the disturbace occurs while onning the gadget the circuit always put full force to search the signals so that is the reason that the other singnals get disturbed e.g if you are receiving a call and any transister is on near you you can hear blur blur type of sound but only till you are connected as soon as you are connected the dieturbing sound vanishes.

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