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Thread: Why companies chose/choose CDMA over GSM

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    Question Why companies chose/choose CDMA over GSM

    Been wondering for a while and I did a search and couldnt find the answer so I thought Id start a new thread:

    Why do/did companies like Verizon, Sprint, Bell Canada, and Telus (to stick with the major North American carriers) choose to go with CDMA over GSM? Was it that it was cheaper to implement? Did they start implementing it before GSM was around and then didnt want to switch?
    Do they want to have more control over their customers and dont want them to be able to swap out sim cards and be forced to roam in foreign countries? Do they want the control of not allowing foreign bought phones onto their network? There must be a real reason!
    Your help is appreciated!!
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    Quote Originally Posted by ab0rt
    Did they start implementing it before GSM was around and then didnt want to switch?
    GSM was around way before CDMA.

    Basically, it's kind of the other way around. As I understand it, CDMA is superior to GSM in a lot of ways - better range, better capacity, soft handoffs, less interference with speakers and such. GSM's main advantage is that more countries use it, since they standardized on it before CDMA existed, and thus GSM is better for roaming in other countries. CDMA makes it easier to cover a greater area with fewer towers, which made it more attractive to rural carriers who have a lot of area to cover in places where the population is low and you don't want to put too many towers spaced closer together. It also made CDMA attractive to Verizon, which markets based on the strength of its network.

    Once the GSM networks are replaced by UMTS/HSDPA, which use WCDMA instead of the TDMA interface that GSM uses, this should hopefully be a moot point, if I understand correctly.
    Last edited by CharlesS; 06-25-2007 at 09:17 PM.

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    1 haven't seen any evidence that CDMA has better range than GSM. Here in Saskatchewan, where the terrain is pretty level and in the rural parts there are almost no people, Rogers' and SaskTel's towers are at similar intervals and seem to work about the same. CDMA definitely has less range than AMPS does (you can get crappy staticky but usable AMPS service where CDMA from the same tower won't work).

    CDMA sites also lose coverage range as they get trafficked up. GSM towers have fixed coverage area regardless of traffic. Of course, CDMA sites are offset in this regard by their higher call capacity.

    CDMA 800 certainly has higher range than GSM 1900 does... but GSM 850 has higher range than CDMA 1900 does. If you compare apples to apples (and despite the numbers, CDMA 800 and GSM 850 are at the same frequencies), the coverage area is pretty similar.

    The conversion of GSM systems to WCDMA won't do a thing to make life easier. 1x and EvDO CDMA are completely different from WCDMA, much the same as Old English and modern English are utterly incompatible despite both being English.
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    GSM phones: Too many to list.

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    Quote Originally Posted by PhotoJim
    1 haven't seen any evidence that CDMA has better range than GSM. Here in Saskatchewan, where the terrain is pretty level and in the rural parts there are almost no people, Rogers' and SaskTel's towers are at similar intervals and seem to work about the same. CDMA definitely has less range than AMPS does (you can get crappy staticky but usable AMPS service where CDMA from the same tower won't work).

    CDMA sites also lose coverage range as they get trafficked up. GSM towers have fixed coverage area regardless of traffic. Of course, CDMA sites are offset in this regard by their higher call capacity.

    CDMA 800 certainly has higher range than GSM 1900 does... but GSM 850 has higher range than CDMA 1900 does. If you compare apples to apples (and despite the numbers, CDMA 800 and GSM 850 are at the same frequencies), the coverage area is pretty similar.
    Well, in the States, GSM coverage tends to be noticeably worse in rural areas. That could be due to a number of factors, yes... but according to what I've read, CDMA is supposed to work at a greater distance. It had something to do with the time-based nature of TDMA - if it takes too long for the packets to travel back and forth, the phone can't keep up the connection. Also, features like CDMA's soft handoffs make it easier for a phone to work well without dropping a call when you've got a low signal, which is definitely nice out in the middle of nowhere.

    The conversion of GSM systems to WCDMA won't do a thing to make life easier. 1x and EvDO CDMA are completely different from WCDMA, much the same as Old English and modern English are utterly incompatible despite both being English.
    Well, it won't allow roaming on CDMA networks such as Verizon's or Alltel's, if that's what you're referring to. But it should bring us the other features and benefits of CDMA (at the expense of some battery life). So in the long run, if I've read everything properly, we should have better coverage once we're all converted over to WCDMA. And I'll never have to hear that interference that GSM makes when it gets too close to a speaker again either, which is a plus.

    Just waiting for Cingular, I mean AT&T, to release some UMTS phones that have the features I want...

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    The question should be, "Why did US carriers pick GSM and not CDMA." CDMA was the much more natural solution. CDMA was designed to dovetail into the existing AMPS cellular system. It could easily fall back to analog when it found itself in a non-CDMA coverage. It was in effect just a different air interface for AMPS. GSM was a completely different system. The issue is that in ~1994 CDMA was not ready for 1900 MHz and GSM was. GSM was already being used on 1800 MHz in Europe and it was just a minor tweek to get it working on 1900 MHz.
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    Why did it have to be 1900MHz, though? I imagine that if the US got and stuck with 850MHz GSM the 1900MHz spectrum would now be clear for Euro-WCDMA (instead of the 2100/1700 pairup).

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    Quote Originally Posted by yangj08
    Why did it have to be 1900MHz, though? I imagine that if the US got and stuck with 850MHz GSM the 1900MHz spectrum would now be clear for Euro-WCDMA (instead of the 2100/1700 pairup).
    Because the world didn't come into existance yesterday and there's a lot of history. This subject has been debated so long that there's probably a MB of threads on the topic.

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    ... You said that GSM was chosen over CDMA by some providers because it was ready for 1900MHz. I'm asking why the FCC decided to try/use 1900MHz instead of sticking to 850/800MHz.

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    Quote Originally Posted by yangj08
    ... You said that GSM was chosen over CDMA by some providers because it was ready for 1900MHz. I'm asking why the FCC decided to try/use 1900MHz instead of sticking to 850/800MHz.
    Because there wasn't enough 850 MHz.

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    The N.American carriers chose CDMA because it was an upgrade and based on the same core network as their existing AMPS and TDMA systems, which meant less cost to develop it because it would just be an upgrade of their existing systems.

    On the other hand, GSM was created from scratch and was completely incompatible with present AMPS sytems. The Americans couldn't handle this but the Europeans could, since they had no AMPS systems in the first place, they had a lot of different 1G systems (like NMT, TACS etc.) and GSM was a completely new technology that would unify them all, and it was successfull in doing that.

    In N.America on the other hand, the carriers chose to build CDMA because it was designed to work side by side with existing AMPS and TDMA systems in the same spectrum and it could even fall back on analogue where digital coverage was not present. Considering that the US has a vast territory and cellphone carriers didn't get any money to extend digital coverage, CDMA looked as the best "digital upgrade" back then!
    It was designed in order to use the same signaling and authentication algorithms (CAVE) as the existing systems, it was flexible and could fit in the same spectrum according to each carrier's needs and it also provided for automatic fallback on analogue when this was (and still is) necessary!

    Also, in the US it was a home-grown technology and that's why it seems that CDMA fits so well to local American providers' needs and that's why they chose it!

    Hope I covered your question!
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    Quote Originally Posted by gmmour
    On the other hand, GSM was created from scratch and was completely incompatible with present AMPS sytems.
    ....
    Hope I covered your question!
    The only thing about GSM that wasn't created from scratch is that it used the same 900 MHz band that was in common use in Europe for systems like ETACS but not used in North America.

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    thanx guys n girls

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    The real question ought to be "Why did my dad sell his Quallcomm investment that would've been worth $20 million today?"

    But why did companies like Sprint develop a PCS GSM network around Washington DC and turn around a sell it later to Voicestream and start up a CDMA network?

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    Quote Originally Posted by char777
    But why did companies like Sprint develop a PCS GSM network around Washington DC and turn around a sell it later to Voicestream and start up a CDMA network?
    Sprint's GSM network in DC was among the first PCS systems in the US, along with Omnipoint in NYC. At the time they started up, about 1995, there was no equipment for CDMA on PCS. (I think CDMA was just starting to work at 850 MHz.) They needed a stable, proven technology and went with GSM, which had been working at 1800 MHz in Europe since about '92 (I think). Sprint later (about 1996) reevaluated the situation and came to the conclusion that CDMA would serve them better. For a few years they ran two systems but eventually converted their DC system over to CDMA.

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    I think certain carriers chose CDMA because:

    A) You likely can't use any phone, you have to buy it through them.
    B) Once you do buy the phone, you can only use their network with that phone.
    C) It increases hassle and more "cost of exit barriers," thus worsening the problem of vendor lock-in. See item B. This is especially true in the case of costly phones, such as Treos.
    D) It's very difficult to "unlock" a CDMA phone, and just as hard to let it use another CDMA provider (requires the cooperation of the other provider). See item C.
    E) They don't have to use the CDMA equivalent of the SIM card, called the RUIM. This limits consumer choice. See all previous items.

    I think it's all about control, especially since wireless, by it's very nature, cannot be a monopoly.

    At least landlines and other utilities are heavily regulated. Imagine if the power company could charge whatever.


    Everyone should use GSM because:

    A) It's what the rest of the world uses. It's useful if for whatever reason you need to visit other countries.
    B) GSM phones use SIM cards, thus segregating the network from the phone.
    C) You can use whatever GSM phone with whatever GSM network, provided the phone supports the frequencies. Quad-band phones aren't costly, so there's no reason not to get one. This is especially important if you want to use a phone that isn't easily available where you live, but is easily available in another country. See item B.
    D) While GSM phones sold through carriers are generally locked to specific SIM cards, it's easy to unlock them.


    I think most people who sign up for CDMA service just don't know any better. I was one of them once.

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