How Mobile Phones Work Behind the Scenes 220
adamengst writes "We seldom think about how our mobile phones actually work, but in this TidBITS article, Rich Mogull pulls back the covers and peels away the jargon to explain why text messages work when voice calls are dropped, why your battery lasts longer in some places than in others, why you're not allowed to use phones on airplanes, why you can be notified of a voicemail message when your phone never rang, and more."
Re:Already slashdotted! (Score:5, Insightful)
>>>Or why a text message can get through when a call can't?
This is no great mystery. A test message can just sit in a buffer until your phone is within broadcast distance, and then it's sent. But a call has to be done in realtime; if reception is poor the caller gets a busy signal (and then send a text instead).
Re:wrong audience, buddy (Score:5, Insightful)
why you're not allowed to use phones on airplanes
One crash in light aircraft ages ago suggested possible connection, unlikely.
How about "You're a loud-talking asshole and you're enclosed in a tight, cylindrical object for several hours with a couple of hundred other people who don't want to hear about your stupid business plan."
Re:Short summary isn't always good (Score:4, Insightful)
3. You're not allowed to use phones on airplanes because of paranoid ignoramuses and the insightful people who realize how bad it could get when people in a flying bomb know what's going on (and how annoying cell phones are).
Or, just possibly it's because:
1. GSM phones are known to emit strong pulses of RF that interfere with nearby electronics (audio amplifiers, televisions, speakerphones, etc).
2. Airplanes contain quite a few important electronic systems for navigation, communication, flight control, etc.
3. Considering the number of passengers who are carried by airplanes each year, even something with a one-in-a-million chance of causing a problem would be a very bad thing.
Re:Phones on airplanes (Score:2, Insightful)
Then why were people able to make cell phone calls on the 9/11 planes with no problem. The couple I've heard were long and clear.
Re:Short summary isn't always good (Score:2, Insightful)
Re:Already slashdotted! (Score:3, Insightful)
Except that a text messages takes FAR less than 1/21 of the data that a similarly priced voice call does.
Re:Phones on airplanes (Score:3, Insightful)
Sigh, mythbusting time...
1) The "metal tube" myth: Get in an elevator, and compare the performance of a 2G (GSM, CDMA) phone and a 3G (UMTS) phone -- you might be surprised. In the 2100MHz band at least, most 3G phones work just fine.
2) The "hundreds of MPH" myth: Nope. Phones are not banned on high speed trains in Europe or Asia, which also travel at hundreds of MPH. The story I heard was that it's not the speed of the handoffs that's the problem, it's the fact that a phone in an airplane at cruising altitude can see too many base stations at once, hence it becomes difficult to route the call properly.