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Text messages vs. cell phone calls

  1. Dec 23, 2009 #1

    Math Is Hard

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    My mother has always insisted that I have a cell phone with text capability. She says that she's heard that sometimes when cell phone service is not available, people will still be able to send text messages. I believe she's thinking that after a natural disaster, like an earthquake, all the phone circuits will be busy with frantic phone calls, but I will still be able to get a text message to her.

    Is there any truth to that? As far as I know, the text data will be traveling across the same circuits as voice data.
     
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  3. Dec 23, 2009 #2
    As far as I can tell SMS is a fully integrated part of the GSM and 3G models. I would find it hard to believe they have separate systems to deploy each. I used to often receive txt messages a day or two late. Either way I would find it hard pressed to find a non txt capable cell phone these days.
     
  4. Dec 23, 2009 #3

    Math Is Hard

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    Thanks, Greg. I guess it is a non-issue now. She had gotten this idea about the texting a few years ago and I don't know where it came from.
     
  5. Dec 23, 2009 #4
    Seems people use txtng where their batteries or signal might be too weak.

    http://scitech.blogs.cnn.com/2009/09/08/trapped-girls-update-facebook-instead-of-calling-cops/
     
  6. Dec 23, 2009 #5

    DaveC426913

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    I have done this too. Sending out a call is hard on a low battery. But a text message can still be made. The composition can be made offline, instead of while the phone is blasting its signal, and the signal itself lasts only a second or two.
     
  7. Dec 23, 2009 #6

    cristo

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    Like Greg, I don't see how the two are separable. Over here (in the UK), at midnight on new year's eve, phones get jammed so it's pretty much impossible to make or receive a call. I've also send or had text messages sent to me at that time, which don't get through until several hours later. Obviously, this isn't proof, but I'd imagine if the two were different, then the texts would be delivered immediately.
     
  8. Dec 23, 2009 #7

    DaveC426913

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    Your hypothesis assumes that the premium is on network bandwidth. Others are proposing that the premium has nothing to do with the network but is instead on cellphone power.
     
  9. Dec 23, 2009 #8

    Mark44

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    There might be something to what your mother is saying. I work for a company that sells a product that works with text and audio/video in IP telephony. The text messages are conveyed through the signaling layer via Session Initiation Protocol (SIP), while the audio and/or video parts are conveyed through the media layer via Session Description Protocol (SDP). I'm not familiar enough with cell phones to say that this is how they work, but it's possible they use a similar scheme.
     
  10. Dec 23, 2009 #9

    cristo

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    I thought the premise in the OP was that the networks were busy with frantic phone calls in a disaster? :confused:
     
  11. Dec 23, 2009 #10

    Borek

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    On several occasions on New Years eve I was able to send SMS but not able to initiate the call - so in my experience that makes sense. Doesn't mean it makes sense in general.
     
  12. Dec 23, 2009 #11

    DaveC426913

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    Yes. I think we're agreed on that one.
     
  13. Dec 23, 2009 #12

    turbo

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    'Way out there, but having texting capabilities could be really handy in a hostage/domestic violence situation if the victim could send out an SOS quietly without being noticed. Calling 911 is not an option in some situations, and the victim could be dead before the cops show up if the perpetrator knows about the 911 call.
     
  14. Dec 23, 2009 #13

    berkeman

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    Yes, both voice and txt use the same digital circuits and infrastructure. The difference is that txt takes much less data bandwidth to get through, and can be re-tried multiple times if a receiving phone is getting spotty reception.

    It's also standard protocol here in earthquake country to shut down phone traffic after a major earthquake, to make the bandwidth exclusively available to emergency service providers for a time. I would guess that they will let standard txt messages start going through before standard voice calls clog up the network.

    During a recent Gulf Coast hurricane, a friend of mine was totally unable to reach her sister by phone (land line or cell). But her sister was able to get a txt message out (with about a 2-3 hour delay) that they were doing okay.
     
  15. Dec 23, 2009 #14

    Math Is Hard

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    Thanks for the replies!
     
  16. Dec 26, 2009 #15

    Evo

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    Your mother might have confused the walkie talkie service available on Nextel cell phones here in the US. Emergency responders use Nextel because even if the cell phone towers are down (Katrina) they can still call each other via walkie talkie over a distance of 3 miles without cell phone service.
     
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