Mobile Broadband in Aircraft
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Mobile Broadband in Aircraft
I've tried to use my mobile phone in my aircraft in the past to get updated METARs while in flight, over GPRS. It has rarely worked for me.
Has anyone tried using these new mobile broadband modems in their aircraft for enroute connections? Do they work any better?
dp
Has anyone tried using these new mobile broadband modems in their aircraft for enroute connections? Do they work any better?
dp
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900 MHz and 1800 MHz are used for GPRS in the UK. The higher the frequency the more directional they become when propagated, which is why most cell sites have three or six antennae, to give 360 degree terrestrial coverage. To give you coverage in the air they'd need another two or three, pointing skywards, but since not many people fly, there's no money in doing so!
There are other reasons as well
There are other reasons as well
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It depends. I've used mine on a few occasions and mostly it worked (although, IIRC, only once in the UK). From various discussions on here and own experience, it would seem that you tend to get better reception in rather sparsely populated areas (fewer masts, but stronger signal?). Also, in mountainous countries, the masts often sit rather high up, which helps.
YMMV
YMMV
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The Mobile broadband that has just came out from most networks is currently using the 3G HSDPA connection which doesn't currently cover the full of the UK. I doubt very much that the connection would be able to reach the air to be honest.
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One of the guys in our E&I team worked for Cellnet/O2, i am only quoting his words! "When you are at altitude, you will hit too many cells and the central system will block your phone out as a spurious response". Basically it seems to make sense? I have been able to phone a friend(Not on Chris Tarrants Show
) and my wife, but this was done below 1500'agl.
) and my wife, but this was done below 1500'agl.
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but this was done below 1500'agl
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dp, that was with my mobile phone. I might just give it a go with the modem I have next time.
pistongone this is, I believe, the reason why it seems to work better at altitude when in a sparsely populated (by both people and phone masts) area.
pistongone this is, I believe, the reason why it seems to work better at altitude when in a sparsely populated (by both people and phone masts) area.
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The reason there are three, and sometimes more, antennae on a mast is because each antenna is transmitting on a different frequency. This individual cell frequency then has a bandwidth limitation of about 5 or 6 users because the bandwidth in each antenna frequency band is limited to 8 time slots, or 8 channels, and generally only 5 or so of these time slots are used to support upto 5 or 6 simultaneous calls. As pilots we know that simultaneously transmitting on the same frequency causes problems. With the GSM system each cell user transmits on the same frequency, but in a sequence of carefully timed bursts or time slots. The remainder of time slot channels are used for sending control information. Mobile companies have a limited amount of bandwidth in the 900, 1800 and 1900 MHz regions, so they have to re-use the frequencies to get the call capacity. They then have to be very clever about how the frequencies are re-used to avoid interference from adjacent cells. This is why sometimes the antenna are even angled downwards, so as to limit their coverage and prevent them interfering elsewhere. Pointing them upwards to give coverage to aircraft would cause the signals to propagate much further, and cause severe interference. Beside this factor, I'm sure the number of people flying around the skies making use of this coverage would hardly make the effort financially viable.
You can get coverage in the air, but as someone has already said, it's generally at relatively low levels. Whilst flying there can be further issues with interference, and call handover (where the mobile is transferred to an adjacent cell as it moves where the signal strength becomes preferential) due to the additional number of cells a mobile would "see" at a higher altitude.
I can't remember what the velocity limit for handover is off the top of my head, but it was originally designed to handle the high speed TGV trains, so somewhere in excess of 200km/h. However this does depend on the size of the adjacent cell which you are moving to. GSM is termed as a break before make system, where the mobile breaks communication with it's current cell before camping onto the next. Cells can measure from a mater of tens of meters to several kilometres. So the user might pass through the cell before the mobile can establish onto it, causing the call to drop.
As Bose-X pointed out in more sparsely populated areas the coverage may be better. This is due to dipole type antenna being used. These have a doughnut shape propagation pattern which gives coverage to a large area. These were once common over the UK in the early days to give greater coverage, but have been phased out as the coverage area has been in-filled with smaller cells to give greater capacity.
The TA, or Timing Advance, is used to ensure the mobile signal reaches the antenna in the correct timeslot as mobiles are usually different distances away. It also normally limits the diameter of the cell to 35km. This should have little bearing, but if the user was moving towards, or away from the antenna at very high speed then perhaps the mobile would not be commanded to change it's TA soon enough, and the signal would start to interfere with the users of the adjacent time slots.
As for the new 3G networks, that's a different nightmare.
Sorry for the laborius post, but I hope it helps.
You can get coverage in the air, but as someone has already said, it's generally at relatively low levels. Whilst flying there can be further issues with interference, and call handover (where the mobile is transferred to an adjacent cell as it moves where the signal strength becomes preferential) due to the additional number of cells a mobile would "see" at a higher altitude.
I can't remember what the velocity limit for handover is off the top of my head, but it was originally designed to handle the high speed TGV trains, so somewhere in excess of 200km/h. However this does depend on the size of the adjacent cell which you are moving to. GSM is termed as a break before make system, where the mobile breaks communication with it's current cell before camping onto the next. Cells can measure from a mater of tens of meters to several kilometres. So the user might pass through the cell before the mobile can establish onto it, causing the call to drop.
As Bose-X pointed out in more sparsely populated areas the coverage may be better. This is due to dipole type antenna being used. These have a doughnut shape propagation pattern which gives coverage to a large area. These were once common over the UK in the early days to give greater coverage, but have been phased out as the coverage area has been in-filled with smaller cells to give greater capacity.
The TA, or Timing Advance, is used to ensure the mobile signal reaches the antenna in the correct timeslot as mobiles are usually different distances away. It also normally limits the diameter of the cell to 35km. This should have little bearing, but if the user was moving towards, or away from the antenna at very high speed then perhaps the mobile would not be commanded to change it's TA soon enough, and the signal would start to interfere with the users of the adjacent time slots.
As for the new 3G networks, that's a different nightmare.
Sorry for the laborius post, but I hope it helps.
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GPRS and 3G tend to not work when airborne above about 2000ft.
SMS (text over GSM) is a lot better but even then it does need at least intermittent signal reception which is rare above 3000ft. That said, I recall having a 9600 baud dial up connection over GSM over France at FL080 once...
The way to do this is a satellite phone. Most can do data, and most of the packages available over here do the basic 2400 baud data, more "with compression"
That's good enough for a dial-up connection to an ISP, and getting TAFs/METARs when airborne. Would also work, painfully, for other kinds of weather. I will be investigating this soon. The rates have dropped considerably since the old days when iridium were charging £10/minute; now e.g. thuraya.com rates are comparable to a mobile-mobile phone call.
As for "broadband" that is a totally different animal and yes you can get it, at a helluva price and with special certified installations. I am not sure if there are any antennae suitable for light aircraft but certainly turboprops and jets are OK. I did however see one system the other day (beast part of 5 figures) whose antenna is no bigger than a normal GPS antenna. The pricing of this service is eye-watering, but it's common on yachts and I guess jets also.
SMS (text over GSM) is a lot better but even then it does need at least intermittent signal reception which is rare above 3000ft. That said, I recall having a 9600 baud dial up connection over GSM over France at FL080 once...
The way to do this is a satellite phone. Most can do data, and most of the packages available over here do the basic 2400 baud data, more "with compression"
That's good enough for a dial-up connection to an ISP, and getting TAFs/METARs when airborne. Would also work, painfully, for other kinds of weather. I will be investigating this soon. The rates have dropped considerably since the old days when iridium were charging £10/minute; now e.g. thuraya.com rates are comparable to a mobile-mobile phone call.As for "broadband" that is a totally different animal and yes you can get it, at a helluva price and with special certified installations. I am not sure if there are any antennae suitable for light aircraft but certainly turboprops and jets are OK. I did however see one system the other day (beast part of 5 figures) whose antenna is no bigger than a normal GPS antenna. The pricing of this service is eye-watering, but it's common on yachts and I guess jets also.
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IO, you are going to be severely disappointed with your sat phone experiment. I have tried it and it is virtually impossible to get a constant signal lock for the data connection. You need to have a constant clear view of the sky to get the thing to lock in the first place. Not to mention that the data transfer rates are shocking. You will not be able to run any modern graphical based application over the feed which might be a theoretical 2400 but experience has shown it to be much less due to retry errors. I used to use it to collect email when working on the boats in Egypt and a single small email would take 2-3 minutes to download. Also remember you are paying by the minute, a set of TAFS starts to get very expensive!
Voice is not to bad, a bit variable.
I have offered to lend you my Motorala sat phone.
Voice is not to bad, a bit variable.
I have offered to lend you my Motorala sat phone.
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bose/x
Which network were you on, and was it contract or payg?
I suspect yours is an old phone. Which model is it? The technology moves fast in this business. Also most of the older phones have no doppler correction so don't work well in moving vehicles.
Globalstar is all but dead now.
Iridium offers pole to pole coverage but is expensive, with stupid PAYG pricing, so for a European application one would not use it; Thuraya is a lot better.
I have an offer of a new Thuraya phone from a dealer, so thank you but I will want to test a current product.
A TAF etc is under 1k of data which even at a fraction of 2400 baud is only seconds.
Which network were you on, and was it contract or payg?
I suspect yours is an old phone. Which model is it? The technology moves fast in this business. Also most of the older phones have no doppler correction so don't work well in moving vehicles.
Globalstar is all but dead now.
Iridium offers pole to pole coverage but is expensive, with stupid PAYG pricing, so for a European application one would not use it; Thuraya is a lot better.
I have an offer of a new Thuraya phone from a dealer, so thank you but I will want to test a current product.
A TAF etc is under 1k of data which even at a fraction of 2400 baud is only seconds.
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I don't know "best" Bose X but I do know that if I was flying to VNKT (have you seen the approach plate; I would love to do that - in VMC - one day) then I would certain get an Iridium phone. For Europe it's a waste of money. OTOH one has no choice if one wants a high speed airborne link.
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The most significant factor causing poor performance inside aircraft is the limited transmit power of the terminal.
This is usually around 1 Watt, depending on the device and technology. On the other hand the base stations transmit around 30 W for GSM
and up to a maximum around 20 Watts for UMTS. Add to that you are inside a semi-Faraday cage like fuselage, this further attenuates
the already weak uplink signal.
The theoretical maximum distance between a terminal and base station in a GSM system is 35 km but in reality this is often limited by poor uplink
performance, particularly on 1800 MHz (in the UK T-Mobile and Orange) hence the problems inside aircraft.
UMTS has a maximum distance of between 10 and 20 km.
A secondary factor is Doppler shift, which for GSM starts to cause synchronization problems around 300 km/h.
With UMTS as well as being uplink limited in this scenario (2100 MHz in Europe) there is the additional problem of interference.
All the base stations transmit on the same frequency, on the ground the networks are designed to have minimal cell overlaps and the correct neighbor cells are defined.
In an aircraft signals from many base stations will be received in effect “jamming“ the terminal.
Actually a few years ago while working for a UK network operator we received a complaint from a police service about poor UMTS performance in their helicopter!
As previous posters have stated GSM and UMTS networks are designed and optimised for use on the ground.
Hope this helps.
KDY
This is usually around 1 Watt, depending on the device and technology. On the other hand the base stations transmit around 30 W for GSM
and up to a maximum around 20 Watts for UMTS. Add to that you are inside a semi-Faraday cage like fuselage, this further attenuates
the already weak uplink signal.
The theoretical maximum distance between a terminal and base station in a GSM system is 35 km but in reality this is often limited by poor uplink
performance, particularly on 1800 MHz (in the UK T-Mobile and Orange) hence the problems inside aircraft.
UMTS has a maximum distance of between 10 and 20 km.
A secondary factor is Doppler shift, which for GSM starts to cause synchronization problems around 300 km/h.
With UMTS as well as being uplink limited in this scenario (2100 MHz in Europe) there is the additional problem of interference.
All the base stations transmit on the same frequency, on the ground the networks are designed to have minimal cell overlaps and the correct neighbor cells are defined.
In an aircraft signals from many base stations will be received in effect “jamming“ the terminal.
Actually a few years ago while working for a UK network operator we received a complaint from a police service about poor UMTS performance in their helicopter!
As previous posters have stated GSM and UMTS networks are designed and optimised for use on the ground.
Hope this helps.
KDY
