5 ms·

* Cell phones flying by overhead while landing or taking off overload cellular base stations.* [citation needed] I've heard this, as one of many theories, dis

by brk 14y ago

* Cell phones flying by overhead while landing or taking off overload cellular base stations.* [citation needed] I've heard this, as one of many theories, discussed about the rationale for this rule. A plane typically has about 150 passengers and there is a narrow window of time during takeoff and landing when you can actually get cell coverage. I find it hard to believe that with the popularity of cell phones today that the towers would be overloaded by 150 phones (or, let's extrapolate to 1000 phones accounting for the takeoff/landing windows) moving rapidly across a couple of towers.

mikeash 14y ago
I believe this dates from the bad old days of analog phones and relatively dumb networks. I've read accounts (reliable? not sure, but believable) of people getting billed several times for a single call made from the air, because multiple cells picked it up and they didn't coordinate among each other. I don't believe this is a problem today. I fly small planes for fun and sometimes use my phone in the air to check weather. The biggest problem is that it doesn't work above about 5,000ft because the signal gets too weak. I never bother to turn my phone off, and neither do most of my pilot friends. I spent about fifteen minutes flying a plane with an instructor friend once while he chatted on the phone with his wife about when we was going to get home!
- freehunter 14y ago
  I do know of an AT&T tower in my state that is malfunctioning (by my standards) and refuses to release the connection once my phone had established the connection. When I'm driving down the freeway past the tower, my signal strength will get weaker and weaker and then I run into no service, even in great service areas. I have to pull the battery (my iPhone toting friends/family have to power down the phone) before it will recognize it's moved to another tower. Obviously it's a different circumstance, but it's another point of data where cell towers aren't always 100% functional when the target is moving.
  - mikeash 14y ago
    The supposed issue isn't movement, it's that cell towers assume a limited signal range due to terrain, which is no longer true once you're in an airplane and high enough to have a horizon of dozens of miles. Edit: by the way, have you reported the problem to AT&T? I have no idea how responsive they are, but it seems like it could be worthwhile, especially if it's as easy to reproduce the problem as you make it sound.
kalleboo 14y ago
The window isn't that narrow, I think it can still pose a problem. Last time I left my phone on by mistake in my bag, when I picked it up I had "Welcome to X country! Your roaming rates here are..." from 3 different countries, none of which were the starting or landing countries.
- brk 14y ago
  I fly about 50-70K miles in a given year. I never turn my phone fully off, I usually put it in "Airplane mode" after I'm out of the coverage area (to conserve the battery so it's not trying to hunt to unreachable towers). I usually find that the phone has lost a signal well before we've hit the 10,000 ft. altitude where electronic devices are "allowed". Roughly this seems to happen about 8-12 minutes into the flight. I would consider the first 1,500 feet of altitude to be a zone where appearance of cellphones would be considered "normal", so the window in which you're truly in the supposed problem zone is even smaller. I'm not sure that the evidence your phone connected to some random carriers is any evidence that phones in flight could be problematic for modern towers. RF systems are also very interesting... I'm not an RF engineer, but I know enough about it that the cell towers coverage pattern is not spherical with equal coverage in all directions. The antennas would be designed and placed to direct the signals mostly out and to lower elevations, not up. Again, this would limit the chances that phones zooming overheard are appearing to multiple towers simultaneously, or moving tower to tower faster than the billing and tracking systems could manage.

by brk 14y ago

mikeash 14y ago

I believe this dates from the bad old days of analog phones and relatively dumb networks. I've read accounts (reliable? not sure, but believable) of people getting billed several times for a single call made from the air, because multiple cells picked it up and they didn't coordinate among each other. I don't believe this is a problem today. I fly small planes for fun and sometimes use my phone in the air to check weather. The biggest problem is that it doesn't work above about 5,000ft because the signal gets too weak. I never bother to turn my phone off, and neither do most of my pilot friends. I spent about fifteen minutes flying a plane with an instructor friend once while he chatted on the phone with his wife about when we was going to get home!

freehunter 14y ago
I do know of an AT&T tower in my state that is malfunctioning (by my standards) and refuses to release the connection once my phone had established the connection. When I'm driving down the freeway past the tower, my signal strength will get weaker and weaker and then I run into no service, even in great service areas. I have to pull the battery (my iPhone toting friends/family have to power down the phone) before it will recognize it's moved to another tower. Obviously it's a different circumstance, but it's another point of data where cell towers aren't always 100% functional when the target is moving.
- mikeash 14y ago
  The supposed issue isn't movement, it's that cell towers assume a limited signal range due to terrain, which is no longer true once you're in an airplane and high enough to have a horizon of dozens of miles. Edit: by the way, have you reported the problem to AT&T? I have no idea how responsive they are, but it seems like it could be worthwhile, especially if it's as easy to reproduce the problem as you make it sound.

kalleboo 14y ago

The window isn't that narrow, I think it can still pose a problem. Last time I left my phone on by mistake in my bag, when I picked it up I had "Welcome to X country! Your roaming rates here are..." from 3 different countries, none of which were the starting or landing countries.

brk 14y ago
I fly about 50-70K miles in a given year. I never turn my phone fully off, I usually put it in "Airplane mode" after I'm out of the coverage area (to conserve the battery so it's not trying to hunt to unreachable towers). I usually find that the phone has lost a signal well before we've hit the 10,000 ft. altitude where electronic devices are "allowed". Roughly this seems to happen about 8-12 minutes into the flight. I would consider the first 1,500 feet of altitude to be a zone where appearance of cellphones would be considered "normal", so the window in which you're truly in the supposed problem zone is even smaller. I'm not sure that the evidence your phone connected to some random carriers is any evidence that phones in flight could be problematic for modern towers. RF systems are also very interesting... I'm not an RF engineer, but I know enough about it that the cell towers coverage pattern is not spherical with equal coverage in all directions. The antennas would be designed and placed to direct the signals mostly out and to lower elevations, not up. Again, this would limit the chances that phones zooming overheard are appearing to multiple towers simultaneously, or moving tower to tower faster than the billing and tracking systems could manage.