GSM altitude signal

[dengorius]

Hello everybody,

I'm looking for the max altitude at which a GSM connection can be established. Does anybody know anything about that or is able to give me a link?

If that can make any difference I'm interested in Europe's parameters

Any clue on what kind of antenna should be used for an high altitude connection would be much appreciated.
I'm actually going to use this one http://www.sparkfun.com/commerce/product_info.php?products_id=290

TIA

[DJPhil]

It's going to depend on your local conditions, particularly the characteristics of the cell towers at hand. The towers can be implemented in a number of different ways, and the radiation pattern of the cell tower antenna will be optimized for ground coverage. The GSM specification itself is good to a maximum of about 20 miles (with the strongest tower implementations), and the handset power is limited to 2W in the 900MHz band and 1W in the 1.8GHz band. There is no GSM system imposed limitation on altitude, it'd just be a matter of getting and maintaining a good signal.

The sparkfun antenna you linked has an omnidirectional pattern, which may or may not work well for you. Omni antennas actually have a toroidal pattern that leaves a vertical dead zone, so be sure to take that into account. If you mount it to give coverage in a horizontal plane at ground level then as it gains altitude you'll be relying more and more on distant cell towers operating at shallow angles to keep a connection, though that's not necessarily a bad thing. Directional antennas can be anything from very sharply to very loosely directional, so it may be more useful to focus your antenna coverage more generally downward. It depends on your other limitations.
Come to think of it, what are you doing? 

There's likely to be some good info from the rocketry and ballooning hobbyists on the details of high altitude telemetry.

Hope that helps some. 

[dengorius]

I'm planning some sounding balloon experiments

Yes, thank you, that was helpful. I'm also looking for some practical values, but I'm aware that it will be rather complicated to find them

[wesso]

Hi All
Actually, I am planning to design and install a quadcaptor flight, and I am thinking to control the quadcaptor by using the mobile antenna network coverage as a signal to flight for long distance. Is there any problems with the connections if the quadcaptor flight at high altitude?
I will be very happy of any word or comment...

All the best

[Rerouter]

while i cannot say for up, i can for out, while coming out of the Sydney heads on a cruise, i was able to maintain not just mobile but data reception some 20Km out to sea at a height of 55m above sea level, (cruise ship)

[wesso]

very good..... but do you think the signal will be stable at a certain level of altitude if the quadcaptor flight at a steady level?

I will be very happy of any word or comment...

All the best

[Rerouter]

As radio waves can be attenuated by structures on the ground but not in the line of sight, i would say it would vary, (think its called area of influence)

[wesso]

definitely YES... but I think in the real experiment a lot of things will establish ... thanks a lot.

I will be very happy of any word or comment.


 

[peter.mitchell]

latency may be an issue, make sure the quad is super stable.

[Rerouter]

its likely that the stability control is on the quad locally, and he is simply wanting to waypoint over gsm,

[kolbep]

Most cell towers I have seen run sectored antennas, that have a radiation pattern like a teardrop on its side. The problem with that is that the signal is designed for about 30d above and below horizontal. If you are out of that zone, you might have problems.
But then maybe that 30d above horizontal means that you can get signal from a further away tower, where their 30d angle corresponds with your altitude. Hope that makes sense.

Maybe you can get an amplifier or repeater for your gsm frequency, keep the amp at ground level, omni antenna to establish connection with cell tower. Hook a yagi antenna or parabolic dish to the other side of the repeater, and get an assistant to aim it towards your cellphone in the sky.
P

[peter.mitchell]

its likely that the stability control is on the quad locally, and he is simply wanting to waypoint over gsm,

Indeed, but in that case, wouldnt generic UHF be better?

[Psi]

Could hack up a RF power amp onto a femotcell and feed that into a high gain antenna towards the sky.

Probably quite illegal though

[hagster]

Any problems will not be caused by weak signal strength. The problem is co-channel interference from cells on the same RF channel. There is a fair amount of reuse in GSM. This is not normally an issue as propagation at ground level is pretty poor.

The system layout is designed to cope with tower blocks and hills and stuff, so as long as your at a comparable height to these you might be OK.

Whatever way you're going to have to cope with periods of no signal.


As for flying a quadcopter you get into the whole legal aspects of operating beyond line of sight. In Europe you would never get clerance for such an activity.

For a balloon a point to point link is the way to go. Probably at UHF if you don't need massive data rates. You've basically got free space propagation so range and antenna gain calcs are easy.

[Psi]

Sparkfun used to have some nice 2W 9xx mhz modem modules that could go 50km easy with good antennas but they seem to have stopped selling them.
Probably legal reasons, i don't think they could be used legally anywhere without a ham licence.

If it's just for waypoint communication and monitoring sensors look for some 433mhz long range radio modules.
With a good antenna you can get some crazy range from those things.

People have gone 40km on Rangelink tx/rx sets and they're only 0.5W 433mhz
 

[KJDS]

while i cannot say for up, i can for out, while coming out of the Sydney heads on a cruise, i was able to maintain not just mobile but data reception some 20Km out to sea at a height of 55m above sea level, (cruise ship)

From what i remember, Australian GSM was configured to only use every other timeslot which more than doubles the range.

EU GSM range is fundamentally limited by the inter timeslot gap and propagation delays.

[G7PSK]

Not sure if has any bearing or if it's even true, but I read some time ago that the real reason you are or were not allowed to use a cell phone in a plane was that the phone would reach so many cells that it would confuse and crash the system. That would imply that the system would not only work at height but at distance as well, but as I said previously not sure if this is true or true now as I read this in an electronics mag. in the late 90's or early 2000's.

[KJDS]

Not sure if has any bearing or if it's even true, but I read some time ago that the real reason you are or were not allowed to use a cell phone in a plane was that the phone would reach so many cells that it would confuse and crash the system. That would imply that the system would not only work at height but at distance as well, but as I said previously not sure if this is true or true now as I read this in an electronics mag. in the late 90's or early 2000's.

Basestations have to cope with up to eight mobiles on each frequency at a time. The receive these in timeslots and the organization of the slots is part of the basestations' responsibilities. There is only a 31uS gap between the 4.5mS slots and the mobile can be asked to delay things its transmission a little to fit into that slot. If a mobile is asked to transmit by one basestation then the network is planned so that other stations on that frequency can't hear it. Once the mobile is elevated it gains extra range and can interfere with other stations. That doesn't mean that the burst will fit neatly into the other stations slot and all the other issues needed will be ok for communications.

[hiddensoul]

Here is a really good write up on the subject of phone reception on an aircraft. You wouldn't have to deal with Doppler effect with a balloon but it has other information that would be relevant..
http://www.datasync.com/~rsf1/cell-air.htm