Nowadays flights provide internet connections ! And phones are disallowed due to the security reasons like terrorist activities etc . Some flights with highest securities doesnt allow economy class passengers to use USB internet or Pocket internet !
Above Certain altitude phones connections get disabled !

generally cell phones are not allowed in flights due to fear of interference with the communication system of the flight.
its true that some private flights are allowing the usage of mobiles..its not that their usage always is hazardous but it could be dangerous...so they wont allow them in the flights.
You are not allowed to use internet in flight unless it’s through the system the airlines promote.
hope you get the point

Its not only fear of interference with communications, but also with on-board avionics. When you are in air, you will receive no/very poor signals, hence your phone will transmit at a higher power trying to reach a BTS.There are still plenty of aircraft using old equipment are not fully shielded (by design), or EM shielding of current equipment that degrade over time.

As gwendollen said, use internet that is promoted by the airlines themselves. I think in the future there will be picocells with smart antennas on aircraft that let you use phones. Such proximity to the transceiver will at least reduce TX power of your device.

but in this case i got one doubt..
how can the cell phones signals reach BTS even though they transit with higher transmission power...is there any logic behind this or simply due to higher power transmission itself??

I have one more doubt Can there be proper Hand off at the rate of speed of aeroplane

gwendollen

but in this case i got one doubt..
how can the cell phones signals reach BTS even though they transit with higher transmission power...is there any logic behind this or simply due to higher power transmission itself??

Sorry, can you clarify your doubt? Are you talking about in the case of being airborne or in general? When phones receive signal they will transmit higher power to compensate. Most of the time at least, unless the service provider changes power control parameters at the BTS.

Conqueror

I have one more doubt Can there be proper Hand off at the rate of speed of aeroplane

Interesting question. For standard cells, nope. You need to either modify of the handover procedures to be a lot faster, or set up some prediction of the movement of the user which cell they will enter next to eliminate some steps all together, or make the cell super huge. If not, your calls will just drop all the time. Besides, you wont be able to receive much signal while in a metal body of an aircraft.

Unless the BTS (picocell) is in the plane itself!

ash

Sorry, can you clarify your doubt? Are you talking about in the case of being airborne or in general? When phones receive signal they will transmit higher power to compensate. Most of the time at least, unless the service provider changes power control parameters at the BTS.



Interesting question. For standard cells, nope. You need to either modify of the handover procedures to be a lot faster, or set up some prediction of the movement of the user which cell they will enter next to eliminate some steps all together, or make the cell super huge. If not, your calls will just drop all the time. Besides, you wont be able to receive much signal while in a metal body of an aircraft.

Unless the BTS (picocell) is in the plane itself!

from BTS the cell receives signals..the coverage area depends upon the base station or the cell..this is lateral concept..what about altitude wise?i mean upto what height can a base station able to transmit and receive signlas?

gwendollen

from BTS the cell receives signals..the coverage area depends upon the base station or the cell..this is lateral concept..what about altitude wise?i mean upto what height can a base station able to transmit and receive signlas?

Oh right, well by planning, the main lobe of the radio antenna will usually be aimed slightly downwards depending where its installed and its intended coverage. The antenna design makes it so that the upper side lobes are suppressed, to over overshooting and wasting power shooting into the air.

The vertical beam width for the main lobe of GSM antennas are usually 15 degrees. So, assuming the tilt of the antenna at 0 degrees (hence perpendicular to ground. Most cases not done as to avoid interference), you'd still get strong signals 7.5 degrees up.

How far the RF signal can propagate depends on link budget. If you know both the TX(BTS)/rx(phone) power & gain specs, you can derive the distance of how far the signal can reach from the path loss equation.

ash

Oh right, well by planning, the main lobe of the radio antenna will usually be aimed slightly downwards depending where its installed and its intended coverage. The antenna design makes it so that the upper side lobes are suppressed, to over overshooting and wasting power shooting into the air.

The vertical beam width for the main lobe of GSM antennas are usually 15 degrees. So, assuming the tilt of the antenna at 0 degrees (hence perpendicular to ground. Most cases not done as to avoid interference), you'd still get strong signals 7.5 degrees up.

How far the RF signal can propagate depends on link budget. If you know both the TX(BTS)/rx(phone) power & gain specs, you can derive the distance of how far the signal can reach from the path loss equation.

if there are no signals that strong towards up then how come the mobiles are receiving the signals??

gwendollen

if there are no signals that strong towards up then how come the mobiles are receiving the signals??

There are still possibilities signals can reach an aircraft, but they are very weak. Even so, if mobiles can detect some sort of signal within their receive sensitivity levels, they will transmit. And as per power control parameters, if it does receive a poor signal, it will transmit at even higher power to compensate (but unlikely it will reach the BTS anyway). Telco vendors & phone manufacturers do not have airborne communications in their scenario when designing equipment. If this situation occurs, its by accident, not design.

Its hard to contain RF coverage. In urban areas, you have buildings reflecting signals left and right. In rural areas, water diffracting signals, hills bouncing it around, etc. In rural areas, antenna tilt is usually higher as well.

So the gist is:
1) When the aircraft is far up in the atmosphere, there are low chances of receiving signal. But it can happen, and when it does, phones can transmit power to try registering in the network.
2) When the aircraft is taking off, it is still within cell coverage. As it climbs, receive signal will decrease, and mobile transmit power will increase.