Regulation of mobile phones on GA flights

[jeling]

Hi,

I fly in Austalia and there is no restriction on the use of mobile phones AFAIK. I am just wondering if there are restrictions in any other parts of the world.

Cheers,

James

[hhobbit]

Well it seems they dont mind the odd text or two:

BBC NEWS | UK | Northern Ireland | Texting saved stricken aeroplane (http://news.bbc.co.uk/2/hi/uk_news/northern_ireland/7548555.stm)

[BEagle]

Funny you should ask that! I've been trying to get the CAA to advise me one way or another, but all they could come up with was:

Unfortunately, while I agree that some detailed guidance on the subject would be useful to the GA community, I have no knowledge about regulations outside those published by ourselves and of which you are doubtless aware. We cannot suggest that a particular course of action would be legal, or even acceptable, without detailed knowledge of every possible applicable regulation, and, as you know, our resources are limited.

Which is ***k all use to anyone, to be honest.

[Fuji Abound]

Beagle

In the nicest way - we did warn you.

[IO540]

What kind of guidance would one expect, and why?

One isn't going to ever get prosecuted for it, so why get guidance.

This isn't like whether one can fly a G-reg on a Mongolian IMC Rating in vis of 1499m, in Class A, under Special VFR :) OK, one isn't going to get prosecuted for that one, either ;)

[Gertrude the Wombat]

I don't give a **** what the regulations are, and I don't need to know:

(1) Airside at airfields which make it a condition of contract that phones be switched off, I switch my phone off.

(2) In the air, as I've seen interference with the COM radio myself and read reports of interference with the NAV radio, I switch my phone off. I would do so regardless of any regulation that did or didn't require me to.

(3) However in an emergency in the air if I needed to talk to someone and had no working radio I'd switch the phone on and use it. I would do so regardless of any regulation saying it wasn't allowed.

If you don't need to know a regulation then it doesn't matter what it is ... except, of course, when it comes to passing an Air Law exam. Some of the questions are just plain daft - who cares whether some visibility limit is 1500m or 1800m, the real answer to the question is not "B" or "D" but "I'm not going to go flying on a day with weather remotely that bad, so it really doesn't matter".

[Agaricus bisporus]

Beags, in the UK it is illegal to use a phone while airborne. It is not a CAA or even an aviation reg, rather one from the old GPO Wireless Telegraphy Act I imagine that restricts the height that the antenna of a transmitting device may be above ground, and is something like 5m max. Not much. A pal of mine got busted for this in the days of CB radio when he put his antenna in a tree to get more range. Done on 2 counts, illegal transmitter and illegal antenna placement.
It certainly used to be the case that when airborne the phone latches onto several relay stations and this gets noticed by the service providers. A pax of mine who regularly used his in the air had threatening letters about it (they thought he was using an illegal booster amplifier). Maybe modern digital phones don't but who knows?

But why? Who is so (self) important that they can't wait until they're on the ground?

I imagine the radio ham community would be the place to ask about this regulation.

[Fuji Abound]

Agaricus

Not wish to be a pain but rather to keep the record straight, I can find almost nothing that is accurate in your post.

I suggest having a look on the thread on this topic recently (use the search function). It has all been discussed very recently.

As to switching it off there is very little evidence it causes any interference at all, Boeing tried very hard to establish whether a problem existed and failed to identify a single case. Clearly there could be the odd exception and I always turn mine off if in IMC otherwise I cant say I really pay it any attention any more.

I suspect the interference argument may largely be one of those urban myths.

[Whopity]

Mobile phones are subject to a licence purchased by the phone company from the State where operation takes place. In many countries the terms of that licence does not permit operation from aircraft!I have no knowledge about regulations outside those published by ourselves and of which you are doubtless aware.Ignorance of the Law and all that!

[IO540]

Airside at airfields which make it a condition of contract that phones be switched off, I switch my phone off.

I didn't know that. Where is this written? Contract between exactly who? :ugh:

It would make it just slightly difficult to get SMS messages from homebriefing.com advising me of slots, etc. Or to phone the tower to ask if they have my flight plan (which I have filed from my internet-enabled laptop while sitting in the cockpit on the ground - this laptop uses a GSM radio just like a phone but a bit more powerful).

Loads of exec jets have a satellite phone installed.

Etc.

[Fuji Abound]

Mobile phones are subject to a licence purchased by the phone company from the State where operation takes place. In many countries the terms of that licence does not permit operation from aircraft!


Which if true would have nothing to do with me.

You lot seem to be making it up as you go. :)

[BEagle]

Which is why I asked our alleged regulator to get off its complacent backside and answer the damn question!

Anyway, I've asked again that they look into the question. Incidentally, it took one of those "You've had 10 working days now, might I expect an answer soon?" e-mails just to get the initial nonsensical reply.

[englishal]

My phone doesn't say "warning: Not to be used over 5m" ...?!

Anyway, who cares (other than air law - then say "not allowed"!)

[trex450]

Well done on your persistance with the CAA BEagle. I was on the internet the other day to get the football scores and everything seemed to be working fine apart from the signal strength between 4000-6000 ft then it improved again.:ok:

[Spitoon]

Which is why I asked our alleged regulator to get off its complacent backside and answer the damn question!If you are talking about the CAA, it seems to me that they've answered your question. They can advise you on interpretation of aviation-related legislation but why should they expend resources looking up regulations - on your behalf - set by other agencies? It's your responsibility as the operator (of both aircraft and phone) to ensure that you comply with all relevant regulations.

As Whopity points out - ignorance tends to be a fairly fallible defence in the eyes of the law.

[Fuji Abound]

No, I think Beagle has a point.

It is the CAAs responsibility to set out the aeronautical regulations concerning the use of mobile 'phones - which if Beagle has reproduced the whole of their reply, they have not done. It would seem by implication there is nothing so far as these regulations are concerned which would prohibit their use. If that is so, they should say so.

So far as other agencies are concerned it would be a simple matter to write to the mobile provider and Ofcom to establish their position if you were that interested.

I recall Boeing concluding in their study that it is unlikely a single CAT departs without at least one mobile 'phone be left switched on - if there is a law prohibiting the "use" of mobiles in flight it must be the most abused law on the statute - unless of course you know better! :}

I once asked a certain well known airport for permission to land.

Had I PPR'd - erhm, no, so please bu**er off they told me and 'phone in future.

I called and estimated the field in 10 minutes - the ATCo was delighted to take my "booking" although midly surprised I would be that quick - ah well I said, I havent got far to come.

[Spitoon]

Fuji, not that I work for the CAA but maybe I can help. There does not appear to be anything in the ANO or Rules of the Air specifically prohibiting the use of mobile phones in aircraft. AOC holders may need to put something in their Ops Manuals an the topic in order to get their certificate but I don't think there's anything similar or GA operations.

I don't know - any more than the CAA bod does - what restrictions the contract which someone else has with their telephone supplier...heck, I'm not even sure what my own one says! But if I cared enough, or thought it mattered in any particular situation, I would look it up. Just as anyone else should. And I wouldn't expect someone from the CAA to do for me - and I wouldn't want them to either...not at the rates they charge.

As you say, Ofcom or the phone service supplier are the best people to ask.

Going back to the ANO, there are many things that are either foolish or can go wrong when associated with aircraft. The rules don't cover everything. If you do something out and out stupid, the CAA has a general, 'catch-all' bit of legislation to prosecute people for endagering others. It's articles 73 and 74 for anyone who can't be bothered to do the research for themselves!

[Gertrude the Wombat]

Airside at airfields which make it a condition of contract that phones be switched off, I switch my phone off. I didn't know that. Where is this written? Contract between exactly who?
A notice on the gate leading airside? It's their train set, they can set the rules for people who want to play with it.

[mad_jock]

Gertrude once your in your aircraft the airport rules do not apply. As much as the airport manager would like to think.

You can quite happily sit having a fag out of the window and there is nothing that the airport can do about it. If they try and enter your aircraft you tell them to leave. If they don't they are looking at 6 years for not obeying the lawfull instruction of the Captain in the UK. Its ok for crew to have a fag at the bottom of airframe steps airside put one foot on the ground and they will have you.

As spitoon says there is nothing in the ANO.

and I see your in Cam I have had the very argument with the airport OPS guys about Mobile phones while having my head stuck up the under carriage bay while dealing with a tech problem on my aircraft (the twin TP that sits all day usually next to the fence) the question of how the hell can I speak to my engineers and answer thier questions from outside the fence was never resolved but they never came near me again. That rule is to stop knob ends wandering across taxiways not looking where they are going.

[IO540]

I once asked a certain well known airport for permission to land.

Had I PPR'd - erhm, no, so please bu**er off they told me and 'phone in future.

I called and estimated the field in 10 minutes - the ATCo was delighted to take my "booking" although midly surprised I would be that quick - ah well I said, I havent got far to come.

I wonder if I was aboard when this happened?? ;) That particular airfield became well known for its mad PPR policy, and (according to one of its management people I spoke to more recently) decided to change things, because they found they lost a lot of traffic due to this. That's the way to deal with these places: publicise them and avoid going there. Eventually they get the message.

A notice on the gate leading airside? It's their train set, they can set the rules for people who want to play with it.

They can set the rules but (as with the yellow jacket "£100 fine" or whatever scenario) they cannot prosecute in the criminal court. Basically, they can get nasty and crude but that's about it.

Not being able to use a phone airside is a bizzare rule which has to be breached as soon as something urgent happens.

I can fully understand a phone ban on the baggage handlers - they used them to warn the organised gangs opening the luggage and nicking stuff out of it that security men are on their way.

[jeling]

Certainly different in Australia. When I spoke to CASA they recommended using mobiles as a backup for radio failure and some flight plans are submitted with mobiles on them!

There are issues with the Telco side of it, but I believe it is in the old protocols that revolved around roaming between towers and the protocol would have issues if there were many towers in line of sight with similar strengths, which would occur if you were flying, but I believe that many of these issues have been fixed.

I want to know because we are developing an application to tack planes in realtime using the GPS in mobile phones.

Thanks

James

[englishal]

It is all a moot point really. I was on a delta flight recently and they are starting to introduce moile phone use in the air as well as wifi internet access.

What Orange says about me using my phone "up high", I don't really care to be honest. If their phone system can't take it, well they better design it so it ca take it :)

[BEagle]

englishal, use of mobile phones on board suitably equipped airliners is an entirely different issue and there are regulations which cover such use already in place under the Wireless Telegraphy (Mobile Communications Services on Aircraft)(Exemption) Regulations 2008. Basically if the aircraft is fitted with a picocell terminal, 1800MHz cellphones may access it and will require very low power to do so. That is no problem.

It's the unsubstantiated "You aren't allowed to use cellphones in aircraft" mantra which I find hard to accept. The CAA seems to have a " 'cos we say so" attitude, but cannot point to any direct regulation. Ofcom just refer to 'current prohibitions of use', but again cannot point to a single specific regulation.

I suspect that, as I suggested to the CAA, the only 'prohibition' is covered under the broad provisions of Article 55 (1) of the Air Navigation Order 2005 which requires that all 'radios' used in aircraft shall be licensed. The only exemption for cellphones being as stated in the Wireless Telegraphy (Mobile Communications Services on Aircraft)(Exemption) Regulations 2008, provided that the requirements of those regulations are met.

[Whopity]

Which if true would have nothing to do with me.Except that if you are using a phone then you are bound by the licence owned by the operator of that phone system. Failing to do so would be, in the UK, a breach of the wireless telegraphy act, the penalties of which are quite substantial. Ignorance of the law is no defence.

[Fuji Abound]

IO

Yes, I think so.:)

Whopity

You cant bind me to a contract between the operator and the Government which was the point I was making. In contract law both parties must consent. Whether the operator binds the user when he purchases the 'phone is an entirely seperate issue. Given that you can buy a 'phone in Tesco with a sim card I doubt you are party to any such contract implied or otherwise. You are therefore only bound to use the 'phone in a "lawfully" way as prescribed by Ofcom - who havent got a great deal to say at all about how mobile 'phone users shall use their 'phones - not surprisingly.

[IO540]

I want to know because we are developing an application to tack planes in realtime using the GPS in mobile phones.

I assume you mean "track" but that won't work because GSM reception falls off drastically above about 2000ft.

There are some notable but very rare exceptions. I can fly from UK to say Croatia at FL180 and upon landing find SMSs from every phone company along the 900nm track welcoming me to Country X and telling me the call rates :) But these messages are the result of a very brief connection, lasting perhaps only seconds, and one would never be able to transmit a deliberate SMS if one needed to do so.

I am 100% certain that the phone companies have sorted out the software so that the network does not get brought to its knees (as many allege) by multiple connections from a phone high up. Loads of airline passengers forget to switch off their phones, and the networks must be getting massive multiple connections from each airliner as it climbs or descends. Yet it does not cause problems. It must have been sorted out many years ago.

[mm_flynn]

I am 100% certain that the phone companies have sorted out the software so that the network does not get brought to its knees (as many allege) by multiple connections from a phone high up.
This is also probably why it is so difficult to maintain a connection above 2000ft. Once the system 'sees' you on several masts, it probably just ignores the poll requests and you loose connectivity.

[Gertrude the Wombat]

This is also probably why it is so difficult to maintain a connection above 2000ft. Once the system 'sees' you on several masts, it probably just ignores the poll requests and you loose connectivity.
I'm not aware of any system for detecting and suppressing an MS which is doing Location Updates faster than expected.

Other issues will be that the base station aerials are optimised for horizontal propagation, and I would suspect relativity might come into it - timing is important in the GSM air interface and if the MS is moving too fast it may not work too well.

[Speedbird48]

In the US it is possible to get a trangulation to a Cell 'phone from towers nearby to aid in rescue should there have been an accident. It has been seen to be very useful on many occaisions.

At uncontrolled fields it is ofter easier to use the cell 'phone for a clearance as the VHF links can be difficult.

But, Brits would have to get a decree from the Queen, and have a yellow reflective jacket in order to use it sensibly. Maybe the signal will reflect off of those jackets that you all love, and I forgot the 4 stripe Private Pilots!!!

Jacket, Tin Hat and I am leaving!!

Speedbird 48.

[mad_jock]

AXE10's and associated MSC and BSC can handle speeds of 400mph+ they have no problem with the high speed trains in france.

The distance you can pick up a signal from a cell is a configuration setting on the cell to do with packet timing. So the inner city ones are set for .5km but can handle more phones hanging off them than a country one which is set at 1.5 km.

There are a few set at silly distances like the mast a Glenshee which you can pick up at FL200 at Foyle because its setup for hillwalkers dialing 999.

The new digital exchanges will have no probs at all with a spam can at 2000ft doing 100knts. If they could be bothered doing a software change it would be a piece of piss to drop you off the network when everyou got over 100ft from the highest point in the cells sector.

They have things called wago units which hard simulate all this stuff.

[IO540]

I think the reality is:

- the tower aerials are set up to barely radiate above 2000ft

- there is no speed issue - one can drive a car faster than some GA planes fly, yet we never hear of problems with people making calls at 100mph (apart from the driver being a right pl0nker who should be banned)

- a few masts are set up to radiate high up (which explains some amazing connectivity situations e.g. me getting a solid internet connection at FL080 over SE France, a few years ago, for quite a few minutes, on plain 9.6k GSM (not GPRS/3G which for me has never worked airborne))

In the US it is possible to get a trangulation to a Cell 'phone from towers nearby to aid in rescue should there have been an accident. It has been seen to be very useful on many occaisions.

Well, I have news for you :) Here in the UK, the position of every phone (that is switched on, obviously) is logged every time it connects to a base station (about every 10 mins) or every time you make a call or send/receive an SMS, and these position reports are stored in a database, for ever. (All text messages are also similarly stored). This was secret for years until some US magazine printed it (5 years ago?) and it has been used to catch a lot of criminals. Still, not many people are aware of it, and the police regularly hope that some mug is thick enough to not know this. Overt GSM phone tracking is also available as a commercial service.

[jeling]

We are in advanced Beta testing of a mobile phone application. We want to determine what the level is that we can work with to get a phone signal. Not too concerned if we loose phone signal as we have ways of dealing with it.

Also keen to see how well the GPS's in the phones hold lock.

James

[mad_jock]

jeling as I said previously it is comletely dependent on how the BSC is setup.
And I presume you know that differnet phone do GPS in different ways. For example the N95 needs a signal for it to work and N96 can do it in airplane mode. THe N96 was quite happy maintaining lock at FL200 and 250knts TAS. In fact it was alot happier there than wandering around london.



The time frame for how often the handset poles the BSC depends what make of handset it is. From memory Ericisson does it every 13mins and Nokia's every 45mins which is why nokia for years had a huge advantage over standby time compared to all the rest.

[Ultranomad]

The official Finnish VFR handbook prohibits the use of mobile phones in flight except in emergency situations, and encourages pilots to state their mobile phone number in flight plan remarks.

I'm not aware of any system for detecting and suppressing an MS which is doing Location Updates faster than expected.
In fact, if such a system were in use, it would give lots of false alarms - I have once observed my own phone randomly switch between 3 different base stations for no apparent reason while completely stationary. The stations identified themselves through cell broadcast, so I could see the station name change roughly once a minute.

The time frame for how often the handset poles the BSC depends what make of handset it is. From memory Ericisson does it every 13mins and Nokia's every 45mins which is why nokia for years had a huge advantage over standby time compared to all the rest.
In most phones, network search frequency can be set to 2-3 different levels using the phone setup menu. In some cases, e.g. when the phone spontaneously migrates between networks while in roaming, it makes sense to disable automatic search altogether (e.g. if you want to stay on the same network for cost reasons).

[bjornhall]

One thing you can never get around is that a phone that is visible from many cells uses up radio resources in all those cells. That can include blocking out particular frequencies from use (GSM), requiring other phones and the base station to increase their output power (which is a limited resource in the base station and reduces battery time in the phone), or preventing the use of the fastest modulation schemes such as 64-QAM. So while the network won't collapse, capacity will be reduced in each cell, to the extent that radio resources is what limits capacity (rather than backhaul network or RNC capacity etc).

Not much of a problem with an occasional phone left on in a plane, but not good if everyone were to use their phones in the air.

[Spitoon]

The official Finnish VFR handbook prohibits the use of mobile phones in flight except in emergency situations, and encourages pilots to state their mobile phone number in flight plan remarks.What an eminently sensible way of writing the rules.

[IO540]

One thing you can never get around is that a phone that is visible from many cells uses up radio resources in all those cells. That can include blocking out particular frequencies from use (GSM), requiring other phones and the base station to increase their output power (which is a limited resource in the base station and reduces battery time in the phone), or preventing the use of the fastest modulation schemes such as 64-QAM. So while the network won't collapse, capacity will be reduced in each cell, to the extent that radio resources is what limits capacity (rather than backhaul network or RNC capacity etc).

Not much of a problem with an occasional phone left on in a plane, but not good if everyone were to use their phones in the air.

I agree with the above, as a technical statement, but it seems to be totally evident that somehow the predicted problem doesn't exist.

How many airliners, full of people with their phones left ON, are in the arrival/departure phases at any instant, within say one country? Can we still use mobile phones? Of course we can. So, somehow, the problem has been solved. So why worry about it?

The extra load on the network costs nothing.

It's like asking what is the cost (to say British Telecom) of you making a specific phone call. In a packet switched network, it is only the cost of the ink used to print that call's details on an itemised bill :)

[PH-UKU]

Bursting for a pee at 3000' over the Solway Firth I texted ahead to Castle Kennedy for PPR (out of courtesy cos' it's unmanned).

"In you come and use the bushes on the south side" ... was the cheery response.

Boy oh boy was I relieved ? If it was illegal (except in an emergency) should I declare a 'pan' :)

PS Use of mobiles airside .. best leave it off or well out the way if you are refuelling with AVGAS....

PPS So, out of interest, if I'm standing on top of Ben Lomond at 3196ft watching the seaplanes scoot along below .... who is likely to be setting off more mobile cells ?

[bjornhall]

I agree with the above, as a technical statement, but it seems to be totally evident that somehow the predicted problem doesn't exist

How in all the world can you tell? As a user you will not be able to note this, except at most as a vague feeling that you are not getting the bandwidth or quality of service you would like but with no clue why that is. You couldn't tell a capacity decrease due to airborne phones from a capacity decrease due to the operator saving some money (big money!) by installing smaller base station configurations or by not using the latest radio access network software releases.

The operators are the only ones who can determine in practice whether or not this is a problem. They can see whether or not they get the capacity they are supposed to get given the configurations they have installed (number of radio units, number of carriers, diversity, MIMO, output power licenses and so on and so forth). It becomes a problem if it forces the operators to install more capacity, or if it prevents them from supplying the bandwidth and quality they would like.

Provided it is even measurable, which I somewhat doubt given the small number of phones we're talking about.

[BEagle]

Back to the question which the Belgranists of the CAA seem incapable of answering:

Q. On a private flight in a GA aircraft, mobile telephones:

1. Must always be switched off.
2. May be used at the Commander's discretion.
3. May only be used in emergency.
4. May be used without restriction.

(Time allowed: 5 years)

Extra paper available if required.

[IO540]

How in all the world can you tell?

The mobile phone scene, and the jet transport scene, have been more or less constant for years.

If accidental mobile phone activity at altitude was a technology/ asset/capacity utilisation issue for the networks, they have had ample time to assess the extent of it and do something about it - perhaps by software fixes which reduce the probability of such a phone getting a connection of any kind (which, looking at how relatively useless phones are even for sending text messages when airborne, wouldn't suprise me and that is exactly how I would have solved this - any phone seen to be connecting to multiple networks within say 1 second will be barred from all of them for say the next 100 seconds).

[liam548]

jeling as I said previously it is comletely dependent on how the BSC is setup.
And I presume you know that differnet phone do GPS in different ways. For example the N95 needs a signal for it to work and N96 can do it in airplane mode. THe N96 was quite happy maintaining lock at FL200 and 250knts TAS. In fact it was alot happier there than wandering around london.



The time frame for how often the handset poles the BSC depends what make of handset it is. From memory Ericisson does it every 13mins and Nokia's every 45mins which is why nokia for years had a huge advantage over standby time compared to all the rest.



Thats wrong, the N95 works with no problems in offline mode.

I have a N95 8GB and regularly use it to track my flights when I am PIC with no problems and its just sat on the seat in the back. I can then upload the tracks to the goFLYING website or google earth etc.

They do have a feature of assisted GPS which uses cell sites to get a rough idea of your location (which even without GPS is usually within half a mile, but this is not obviously on when you are in offline mode). The main reason I keep mine in offline mode while I am flying PIC it is to avoid the interference on the headset. Not because my phone being on will cause the whole mobile network to collapse and satellites to fall from the sky! ;)




In fact even on airliners it has no issues maintaining lock over 500mph, while in Offline mode. (Flight mode and no cell signal) Even OVI maps (nokia maps 3) can track my route real time. Interesting to have on since live mapping on screens on board is rare on flights these days especially the shorter flights.

To be honest I think most people would be surprised how well the GPS works on Nokia handsets especially the Nseries devices. They are getting even better too, the N86 8MP has a built in compass too which it uses to build a better picture of your navigation.

I only know of Jet2 that actually say they allow you to select flight or offline mode, while others dont. I honestly think that airlines need to re-think their policies. So long as you dont set up a 14metre HAM radio station while on board I cannot see phones causing issues in aircraft especially with offine mode selected. Wonder what the air steward would say to having this device swithed on:
BLACK-BOX Airband Monitor @ Flightstore Pilot Supplies (http://www.flightstore.co.uk/prod/WSTBLACK/DEPT-AIR/AIRR/)

The use of phones in GA aircraft is not covered anywhere in the PPL syllabus. Note the term for SE phones "Flight Mode".




Screenshots to show phone had no issues maintaining GPS lock on an airline:- Last shot is on way back, with head wind ;)

http://img202.imageshack.us/img202/4577/scr000037.jpg (http://img202.imageshack.us/i/scr000037.jpg/)http://img202.imageshack.us/img202/scr000037.jpg/1/w240.png (http://g.imageshack.us/img202/scr000037.jpg/1/)

http://img59.imageshack.us/img59/7793/scr000038.jpg (http://img59.imageshack.us/i/scr000038.jpg/)http://img59.imageshack.us/img59/scr000038.jpg/1/w240.png (http://g.imageshack.us/img59/scr000038.jpg/1/)

http://img524.imageshack.us/img524/879/scr000040m.jpg (http://img524.imageshack.us/i/scr000040m.jpg/)http://img524.imageshack.us/img524/scr000040m.jpg/1/w240.png (http://g.imageshack.us/img524/scr000040m.jpg/1/)

http://img75.imageshack.us/img75/343/17323784.jpg (http://img75.imageshack.us/i/17323784.jpg/)

[liam548]

We are in advanced Beta testing of a mobile phone application. We want to determine what the level is that we can work with to get a phone signal. Not too concerned if we loose phone signal as we have ways of dealing with it.

Also keen to see how well the GPS's in the phones hold lock.

James


James see my post above. Apologies if it has been posted but what is this application you are creating, I am interested in it. What platform will it be on?

[west lakes]

One thing you can never get around is that a phone that is visible from many cells uses up radio resources in all those cells. This keeps coming up time and time again and is incorrect (I'm fed up of posting tech details as to why)
The only similarity between a mobile phone & an aircraft transceiver is that they both use the radio spectrum - there is no other comparison!

In the mobile phone case the network (computers - heard of them) allocates resources and in modern networks allocates resources at a single cell site to individual phones. Yes the other cells can see the phone, but that is all.
As the signal strength at those sites varies the network will eventually transfer the individual phone to another site.

It is worth noting that:-
Adjacent cell sites use different frequencies
Phones are frequency agile & transmit/recieve on frequencies to match the site they are allocated to, the network tells the phone which frequency to use
If the phone can see another site using the same frequency, the network will still not allow traffic through mulitiple sites.

As regards use in aircraft, the instruction manual (in the safe use section) for the Nokia I just got states that use onboard an aircraft is illegal, of course you have all read your instrucion manuals!

[bjornhall]

This keeps coming up time and time again and is incorrect (I'm fed up of posting tech details as to why)
The only similarity between a mobile phone & an aircraft transceiver is that they both use the radio spectrum - there is no other comparison!

In the mobile phone case the network (computers - heard of them) allocates resources and in modern networks allocates resources at a single cell site to individual phones. Yes the other cells can see the phone, but that is all.
As the signal strength at those sites varies the network will eventually transfer the individual phone to another site.

It is worth noting that:-
Adjacent cell sites use different frequencies
Phones are frequency agile & transmit/recieve on frequencies to match the site they are allocated to, the network tells the phone which frequency to use
If the phone can see another site using the same frequency, the network will still not allow traffic through mulitiple sites.

You are still addressing the same old question of whether or not the network can stay up and keep functioning when a phone is visible from several cells simultaneously. There is no question that it can.

But I am talking about something else entirely; even though the network will not go down and connectivity is not lost, capacity in each cell can go down. To see why, one really has to consider the radio side of the problem, not just the back-end and networking aspects. The key point is that the better the quality of the radio channel, the less radio resources are needed to achieve a given performance (bit rate, capacity, etc).

The radio channel is generally fading- and/or interference limited. Interference can loosely be said to manifest itself as 'noise'. Phones and base stations that have some degree of overlap between the radio resources they use will appear as noise sources to each other. For WCDMA there is always such overlap since all spreading codes are not quite orthogonal; for GSM there can be such overlap between phones in neighboring cells (more on that later). To the extent the channel is interference limited, adding more interference has to be offset by using up more radio resources.

As an example, somewhat still in the future, one can look at the constellation diagrams for 16-QAM vs. 64-QAM (should be on Wikipedia somewhere). Even intuitively one can surmise that 64-QAM will be more sensitive to the channel quality than 16-QAM, since the dots are more densely packed in the diagram. If one does the math one comes to the same conclusion. If the added interference would be enough to force the controller to switch from 64-QAM to 16-QAM for a particular link, instantaneous bit rate drops by roughly 33 %. Now the base station has to spend proportionally more time talking to a particular cell phone to provide the same data rate, or the user will see a drop in data rate. The same principle applies to the other radio resources that are required for a particular radio access technology.

You talk about how resources are allocated to individual phones. When doing the cell planning, which determines what resources the different cells have available to allocate to phones in thair area, one takes into account the distance that a particular phone will be 'loud' enough to interfere measurably with other phones and base stations. Radio resources are re-used in cells that are far enough apart for interference to be sufficiently low. But an airborne phone will be visible from far longer distances than was considered during cell planning, and will therefore cause much more interference than predicted.

If there are still free resources available, such as free frequencies in GSM, the cells can null out the interferer and keep functioning at full capacity. But a sensibly dimensioned network will be working near full capacity part of the time. If the operator wanted to save some money on the configurations it could be working near full capacity all the time, sharing the available capacity between the users. Any interference that reduces capacity in those cases will immediately reduce the bandwidth, quality etc for the user. For instance, in a GSM network running at high capacity there may not be any free frequencies available when an airborne phone is visible in many cells simultaneously. Some phones can therefore be forced to use the same frequency as the distant airborne phones, and use other means to deal with the interference created (increase their transmit power etc).

Again, none of this is likely to be a problem with the occasional airborne phone. The effects will hardly be measurable. But if cell phones were routinely used in the air, the factors I am talking about would definitely manifest themselves, make no mistake about that. The operators would have to build bigger radio base station configurations to achieve the same capacity, costing them money (and guess who would have to pay for that; not their share holders!). Or, perhaps more likely, the users would see their network performance drop. They might not even notice that drop, or realize why it happens, but they would get less performance than if the airborne phones were not there.

The mobile phone scene, and the jet transport scene, have been more or less constant for years.

It might appear so if you are not working in either business! ;) We are delivering networks that are capable of over 40 Mbit/s already, with over 80 Mbit/s just around the corner, and that is still WCDMA. Over 20 Mbit/s is already in use. We are already delivering the first 100+ Mbit/s LTE networks (field trials up and running, individual sites up in the live nets). We didn't sell those things 10 years ago.

If accidental mobile phone activity at altitude was a technology/ asset/capacity utilisation issue for the networks, they have had ample time to assess the extent of it and do something about it - perhaps by software fixes which reduce the probability of such a phone getting a connection of any kind (which, looking at how relatively useless phones are even for sending text messages when airborne, wouldn't suprise me and that is exactly how I would have solved this - any phone seen to be connecting to multiple networks within say 1 second will be barred from all of them for say the next 100 seconds).

Now you're just speculating... I don't have to speculate, I design these things for a living... Yes, the way the systems are designed limit the impact of airborne phones interfering with multiple cells. Phones are supposed to be visible in multiple cells; that is how we deal with hand-overs. But the problem is not that phones connect to multiple nodes; the problem is that they create interference in more cells than was predicted during cell planning.

[west lakes]

bjornhall
Ah that makes more sense - thanks

[jeling]

Hi Liam,

The application is GPS Logbooks - Home | Black Box Flight Recording, using only your Android cell phone (http://www.gpslogbooks.com). It is now working on Windows Mobile, iPhone and Android.

We have it now returning points every second and being updated on the website in realtime.

Feel free to download the application (it is free) and send through any feedback.

Cheers,

James