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Crookshanks

join:2008-02-04
Binghamton, NY

2 edits
reply to patcat88

Re: it really has nothing to do with the aircraft....

said by patcat88:

Take a ferry or drive a car over a long causeway/viaduct in a heavily populated metro area, with skyscrapers. Your phone will see 100s of towers.

Urban areas have very few macro cells that provide long range coverage. Micro and pico cells are far more common. The macro cells are used to service fast moving (e.g., phones in cars, on the train, etc.) or more distant mobiles, while the rest are directed to micro/pico cells that serve a much smaller footprint. In your scenario the phone would not hear more than a handful of towers, as it would quickly move out of range of the micro and pico cells.

said by patcat88:

A phone can not switch towers without the tower's/network's permission.

Cellular networks are divided into paging areas. Your mobile does not notify the network when it switches to a different base station within the same paging area, it only tells the network when it moves into a new paging area. The cellular network has no idea which specific base station an idle mobile is listening to, and it may well be listening to more than one at a time in a CDMA network. Asking for permission for every single base station hand off while idle would consume a lot of power.

The network can command a mobile to switch channels or base stations, but the mobile does not have to request permission to move between base stations while idle. An idle mobile doesn't even have its receiver turned on a majority of the time, it wakes up every so often to check for pages, then goes back to sleep. This is another power saving feature, and one of the reasons why LTE can be such a battery hog -- getting low latency requires keeping the receiver on more than older technologies.