How does CDMA work

Discussion in 'iPhone' started by SilentLoner, Apr 21, 2012.

  1. SilentLoner macrumors 65816

    SilentLoner

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    #1
    I find mobile technology facinating and I am intrigued by the CDMA tech used by verizon. How does it interact with the handset with no sim card. How is the handset identified on the network? How does it differ from gsm
     
  2. DroidRules macrumors 65816

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  3. kdarling macrumors demi-god

    kdarling

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    With a SIM, such as used on GSM phones, the customer identity is stored on the SIM. (A SIM is a little microcomputer, for example an ARM with MBs of memory. UMTS-3G versions even include hardware to speed up encryption/decryption.)

    Verizon 1X and EVDO phones don't have a SIM. With the CDMA2000 phones, the customer identity is associated with that phone's electronic serial number via the carrier's internal provisioning system. This is initially set up when you get a Verizon account.

    To use a different SIM based phone, the customer physically moves the SIM from one phone to another. To use a different Verizon phone, the customer can call a rep, use the web, or simply dial a special number on the new phone and tap in their phone number and secret PIN, in order to associate the different phone with their phone number. No need to open up the old phone, or even have the old one around.
     
  4. mrbutters macrumors regular

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    Most, if not all of the 4G LTE Verizon phones have SIM cards, my Razr Maxx has one.
     
  5. saberahul macrumors 68040

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    #5
    First comes the C, then D, M afterwards, and finally A. Simple.
     
  6. kdarling macrumors demi-god

    kdarling

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    Right, they have SIMs if they have a GSM radio for international usage, or if they have an LTE radio.

    They're not used for the basic CDMA2000 phone.
     
  7. scaredpoet, Apr 21, 2012
    Last edited: Apr 21, 2012

    scaredpoet macrumors 604

    scaredpoet

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    In North America, the decision was made by CDMA carriers to identify phones by a combination of their hardware serial number, and the subscriber's Mobile Device Number (MDN), which is programmed into the phone's memory at the time of activation.

    This was done mainly to keep compatibility with the analong cellular systems that were predominant at the time, and used this very simple method of authentication.

    It's also important to note that CDMA doesn't HAVE to not have a SIM. In other countries (Asia primarily), CDMA can work with an R-UIM or the newer CSIM-capable UICC, which are similar in function to a SIM card.
     
  8. kdarling macrumors demi-god

    kdarling

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    It's interesting that Apple has pushed for a virtual SIM based solution. I.e. no more physical SIM, or space, or slot needed.

    The GSM carriers pushed back, since it might be even easier to switch carriers if all you had to do was punch a few buttons to activate a phone with your number on a specific network.
     
  9. dontwalkhand macrumors 601

    dontwalkhand

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    #9
    The CDMA portion of Verizon's LTE phones actually activate with the SIM Card, as the SIM Card included in LTE phones is called a C-SIM, which is why you don't have to (and shouldn't ever) *228 an LTE device.
     
  10. cambookpro macrumors 603

    cambookpro

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    #10
    Sorry to be n00bish, but generally speaking, does CDMA > GSM or the other way around?
     
  11. kdarling macrumors demi-god

    kdarling

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    Thank you very much! I stand corrected!

    I've clearly been too deep into my latest work project.

    Apologies to mrbutters, too.
     
  12. SilentLoner thread starter macrumors 65816

    SilentLoner

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    #12
    Thanks for all the responses. I'm British so I am used to the gsm method but I do kind of like the CDMA way :)
     
  13. Spectrum Abuser macrumors 65816

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    Isn't it easier to switch GSM phones versus CDMA, though? With GSM so long as the SIM card is currently activated all you have to do is put it in whatever phone you want and you have service(In a perfect non-frequency different or radio complications world).
     
  14. kdarling macrumors demi-god

    kdarling

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    I think it's easy on both, but the non-SIM method allows switching phones even if you've lost the SIM. And no need to open the back up, take out the battery, etc like on many phones. It would also allow for slimmer and perhaps less expensive phones.

    However, the worry the carriers had about the virtual SIM was not about switching phones. It was that it could lead to the ability for customers to switch CARRIERs just by dialing a number on their phone, and instantly activating themselves on a competitor. (Imagine seeing a TV ad for a cheap cell plan, and you just pick up your phone and move carriers while never getting up from the couch.)
     
  15. old-wiz macrumors G3

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    #15
    I think most people would say GSM is better than CDMA. GSM is used worldwide, where only a few countries use CDMA. Verizon would love to switch to GSM, but they have too much infrastructure to do it quickly.

    GSM allows voice and data at the same time, CDMA does not.
     
  16. Invincibilizer macrumors 6502a

    Invincibilizer

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    GSM is preferred. Like what the other person has said, every carrier would move to GSM if they could.
     
  17. Nermal Moderator

    Nermal

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    In my experience, CDMA phones tend to have better voice quality than GSM, but that could be specific to Telecom/Vodafone here. They also don't make external speakers go "beep beep buzz" when you get a text message :p
     
  18. scaredpoet, Apr 21, 2012
    Last edited: Apr 21, 2012

    scaredpoet macrumors 604

    scaredpoet

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    Depends on what you want out of it.

    Feature-wise, hands down GSM beats out CDMA. GSM mimics an ISDN circuit pretty closely, and you can execute all sorts of standardized feature codes and queries from any GSM handset. There's also the fact that you can conference call up to 5 people with an iPhone on a GSM network (as opposed to just two on CDMA), and that the 3G evolution of GSM permits you to use data while on a voice call (whereas on 3G CDMA you can't).



    On the other hand, CDMA was built from the ground up to closely mimic the behavior and vertical feature codes of a North American POTS line. Back when analog was king in the US, CDMA was a much easier upgrade for cellular carriers as CDMA maintained backward compatibility quite well. SO at the time, CDMA was great. But that backward compatibility has become a liability, especially when the last analog networks were finally turned off, but the cell carriers using CDMA still had to grapple with all of the drawbacks (the exhaustion of ESNs, or instance, and the transition to MEID).


    There are still some technical advantages for carriers though. CDMA 3G requires less contiguous bandwidth (5MHz per carrier) to deploy than 3G UMTS/HSPA (15MHz per carrier). And, 3G was an easy upgrade for CDMA networks to deploy, since most of it was just a change in software and the replacement of some interface cards on older equipment. For GSM, 3G was a massive (and expensive) upgrade, requiring wholesale replacements in hardware.

    Bottom line: from a user perspective, GSM > CDMA, but from a carrier/network perspective, CDMA > GSM, sometimes.

    ----------

    While that's true, the flip side to that is the carrier's billing and activations systems are required to be in on the switch with the SIMless methods. That means you must either contact customer care or log into a website (which may or may not always work) to switch over your service from one phone to another.

    The last time I dealt with swapping phones on a CDMA network was 2007. I remember it being a cumbersome process, far from immediate, and not always reliable. Data provisioning post phone-swap tended to lag behind voice provisioning by quite a bit. And the web-based phone-swap interfaces only worked for some phone models but not others. Maybe things have improved since then, though it sure hadn't changed much in the 7+ years prior, that I had been on Sprint and Verizon.

    So it becomes a matter of preference... do you want to deal with customer care because you don't want to open up your phone or find a paper clip, or would rather just switch SIMs and be done with it because you don't want do deal with the phone company to swap out our handset?

    That's true if you have the MEID or ESN either written down or can retrieve it from the the smartphone's configuration screen. If not, you still have to remove the battery of a CDMA handset to access the sticker underneath with the ESN/MEID to get entered in for activation.
     
  19. wordoflife macrumors 604

    wordoflife

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    Thanks for mentioning this, it never occurred to me. In addition, SIMS can be only used with one number and can't be reused. So yeah, CDMA wins there.

    I still prefer GSM though due to nonsplitting up of text messages, dual data and voice, more people on conference call and faster internet....etc :D
     
  20. bandofbrothers macrumors 601

    bandofbrothers

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    Here in the Uk you know if you lose or have your phone stolen someone can simply rip out your sim card and replace it with their own.

    Even if you lock or block it they can be opened.

    Is the CDMA more secure as you can't take out a sim card ?
     
  21. Nermal Moderator

    Nermal

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    That'll be an operator-specific restriction; I've been able to put a new number on an old SIM.

    The phone can be blocked at the IMEI level, but that's operator-specific. Over here the two biggest companies share blacklists, but the smaller ones don't so you could take a stolen phone to one of the small operators and use it there.

    On the other hand, CDMA operators tend to only connect phones that they originally sold, so you can't for example use a Sprint US phone on Telecom NZ, and vice versa. Roaming is an exception; I can roam on Verizon and Sprint, and likewise Verizon users can roam on Telecom. But you can't connect the phone "locally"; you're stuck with roaming.
     
  22. bandofbrothers macrumors 601

    bandofbrothers

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    Yes the network can imei block the phone but there are software workarounds that we won't go into.

    One big issue is that the imei lock only holds in the country it was attached. Lots of phones are stolen to be shipped abroad so the imei lockout fails.
     
  23. twigman08 macrumors 6502

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    #23

    I don't know the exact technical details causing this, but my GSM (AT&T) iPhone 4 doesn't do that to the speakers when it is on 3G or WiFi. Though I turned 3G off the other day to do a quick little test using the Edge network. I received a text message and it caused my speakers to get the interference. Though of course 99% of people are always on 3G now and rarely have to use the Edge network really.
     
  24. SilentLoner thread starter macrumors 65816

    SilentLoner

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  25. scaredpoet macrumors 604

    scaredpoet

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    No, LTE is an extension of GSM/UMTS technically speaking.

    http://en.wikipedia.org/wiki/3GPP_Long_Term_Evolution

    When you get down to it though, a lot of the definitions are blurred, really. 3G HSPA, when you get down to it, is really a very heavily enhanced, sideband version of CDMA. It's just how the carriers have chosen to deploy their air interfaces and a lot of the call routing and network functions under the hood that make them so different.
     

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