Why did the us go with CDMA instead of gsm?

Discussion in 'iPhone' started by SilentLoner, Aug 7, 2008.

  1. SilentLoner macrumors 65816


    Dec 29, 2007
    does the signal travel further than gsm? Is their any advantages of gsm over CDMA because western Europe used to act smug when looking at American phones. Why was this?
  2. JWages macrumors regular

    Jul 31, 2008
    Illinois, USA
  3. TEG macrumors 604


    Jan 21, 2002
    Langley, Washington
    Who uses CDMA? Verizon Wireless, Alltel, Sprint, Telus, Bell Mobility. The US is half and half. I think a lot of it has to do with the deals the carriers were able to strike with cell phone makers and chipset manufactures.

    The iPhone uses GSM which aside from being a global standard is a lower power system than CDMA and is based on the older TDMA digital standard. To allow multiple access, certain time slices are used. Also, GSM antennas are much smaller than CDMA.

    CDMA uses a special coding system to encode all transmissions to prevent interfeerence. Also the antenna is much larger, something most people didn't know until the CDMA RAZR came out.

    However, the GSM 3G systems all use CDMA like technology, called WCDMA for 3G data, as it allows for higher speed than the TDMA like technology.

    I also think that when GSM and CDMA where starting, GSM only operated at one frequency range, and CDMA at another. At the time there were limited licenses in those ranges and the two technologies couldn't co-exist. So the company that had a majority of one range would use that technology and trade a company that has it where the didn't for the other range. When both GSM and CDMA were expanded to cover other frequencies, and were able to co-exist in the same spectrum, it became less of an issue, but companies are stubborn to change. But Verizon and Bell (and maybe even Telus) will be using LTE for their 4G systems, which is the GSM designated "next-gen" system after UMTS/HSPA.

  4. aphexii macrumors 6502

    Feb 22, 2006
    CDMA and GSM are competing standards. CDMA is thought to have better sound quality and I believe the communications can be encrypted for secure conversations. Also, I recall hearing awhile back that CDMA can get by with less towers and has a higher call capacity (something to do with how the data is sent).
  5. Small White Car macrumors G4

    Small White Car

    Aug 29, 2006
    Washington DC
    I don't think you guys are understanding the question.

    The answer (as near as I can tell) is that CDMA was available first. It sounds simple, but it's not like anyone officially "decided" it was what everyone was going to use or anything.

    Qualcomm started making phones and they started selling. That's about it, really. I don't think GSM was avaiable until after that.

    I'm not sure of this, bit that's my understanding of it.
  6. Stuart in Oz macrumors 6502

    Jan 16, 2008
    Sydney, Australia
    I think CDMA does have better range than GSM. Here in Australia we have very dense cities and then a massive rural area with very low population.

    Telstra (our dominant, privatised former telecom) ran CDMA in the bush for years whilst pushing GSM in the cities.

    Only last year they turned off the CDMA network and replaced it with a HSDPA 3G GSM network and there were lots of complaints from people in the bush (and their elected representatives) that the network reach of the new system was nowhere near as good as the old. Telstra had to build quite a lot of new base stations to match the old coverage before the government would give them permission to turn the CDMA off.
  7. GSMiller macrumors 68000


    Dec 2, 2006
    I prefer CDMA over GSM. Even in the more populated areas in the US the service just seems to be better.
  8. bradl macrumors 68040


    Jun 16, 2008
    When did Qualcomm start to sell phones? I know that before the doors blew open in the cell phone industry in the US (ca. 1998), things may have still been analog. By '98, digital phones were coming out, and Pacific Bell, AT&T, and Cingular were around, and were GSM (ATT was both GSM and TDMA). Sprint, Nextel, Verizon, Alltel, and a few others were all CDMA.

    I found this out the hard way when a friend of mine from Cairns tried to send me a SMS message, and I never got it. Found out then that the protocols didn't talk to eachother (unfortunately, I was on Sprint at the time).

  9. scaredpoet macrumors 604


    Apr 6, 2007
    Not correct. GSM was available a few years before CDMA.

    First off, the US didn't really decide anything. The FCC never mandated that any particular format run on certain frequencies. That choice was left to the carriers, with one exception: if a carrier had analog service, they had to keep it running until early 2008. This requirement is pivotal to some of the decisions made.

    And so, wireless companies in the US individually decided what they were going to do. And at the time, most cellular companies in the US were using AMPS, or analog phone service. A switch to GSM would have presented a serious technical challenge that they just weren't able to tackle with the technology available at the time (almost 10 years ago). You'd have to mix bandwidth-hungry analog systems with GSM, and that would involve different billing systems, different inventory control systems, different ways to manage ESNs versus IMEI/IMSI combos, etc. And, again, you couldn't just dump AMPS if you already had it.

    CDMA, on the other hand, was developed in part to be fully backward compatible with the existing AMPS system. It too used ESNs, and could be overlaid on top of an existing analog network without any trouble. This also allowed dual mode (analog/CDMA) phones to readily manufactured.

    So, at the time, it made sense for cell companies with an entrenched AMPS user base to go the CDMA route. Newer cell companies (VoiceStream, Western Wireless, and portions of what later became AT&T) were free to pick either GSM or CDMA.

    A couple of other things to note:

    -All things being equal, it's actually GSM that has a wider range than CDMA. CDMA requires a much denser tower structure to truly work effectively. In places where CDMA seems to work equal to or better than GSM, it's because the wirelees carrier has spent a LOT more money to build out cell sites to make up for the discrepancy. The advantage: you can fit more calls on a CDMA network than you can on a 2G GSM network.

    Incidentally, this is partly why AT&T 3G sucks so much in some places. Because it uses a CDMA-like structure, it requires more cell sites to cover the same area that the old GSM network did. This is part of why some people are getting fewer "bars" on 3G than on EDGE (though it's not the whole story). Unfortunately, some people are more willing to blame the phones than the network, and there is no persuading them.

    I have seen some poorly-covered 3G areas get better though, as AT&T figures out where they need to sprinkle more cell sites to get the 3G coverage back on par. So time will bear out improvements. It just requires time and patience.

    - Call quality is NOT a function of GSM or CDMA, but rather the codecs that are used. GSM operators have tried to close the capacity gap by reducing the bitrates available for encoding speech. At normal bitrates, it sounds better. And, GSM operators don't need to compress as much in 3G, so that's why IT sounds better than 2G GSM.
  10. qacjared macrumors regular

    Jan 28, 2008
    This whole topic is very moot.

    AT&T and T-Mobile here in the states use GSM.

    Alltel uses CDMA as does Verizon Wireless and sprint.

    Verizon Wireless bought Alltel.

    Vodafone (which owns 45% of Verizon Wireless) forced VZW to adopt GSMs 4G technology so that presumably you can roam internationally without VZW or Vodafone paying carrier fees to eachother.

    In 5 years because of this AT&T, Verizon Wireless, T-Mobile, and Alltel will all be GSM just like the rest of the world. Sprint will be left alone on GSM but know how they are bleeding money they will probably be sold to someone (presumibly someone on GSM like Rogers in canada) and we all will be in GSM Heaven except for our poor Canadian neighbors.

    I mean where else is CDMA used? México?
  11. Nermal Moderator


    Staff Member

    Dec 7, 2002
    New Zealand
    NZ too, although I think we're getting rid of it in 2012.
  12. Bearxor macrumors 6502a

    Jun 7, 2007
    This is an easy one.

    The US allowed an open market for competing cellular technologies. In Europe, various countries came together to ensure that cellular phones would work seamlessly across the continent, thus GSM was born. And since Europe is so close to various other continents, other countries close by picked it up to ensure that phones would seamlessly work when traveling to Europe and, of course, from there, other nearby carriers/countries were forced to pick it up to ensure that people that subscribed to their service could visit neighboring countries with no problem, and so on, and so on.

    The CDMA footprint in North America is pretty large.

    LTE is coming. In the US, AT&T, Verizon and T-Mobile will be using LTE. Sprint will be going with WiMax. The two largest carriers in the US will be using the same technology. Who knows, in two years, maybe those dreams of using your iPhone on Verizon's network will come true...
  13. scaredpoet macrumors 604


    Apr 6, 2007
    In 10 years, probably. But for now, it's a VERY big issue.

    They can do that today, with dual-mode phones. And, considering Vodafone is a minority stakeholder (at 45%), it's hard for them to really force Verizon to do anything.

    On the other hand, VZW did need to migrate to a 4G technology, and there is currently no definite 4G upgrade path for CDMA. Verizon didn't want to go with WiMax, so LTE it was.

    Heh. Don't think for one second that LTE is going to change everything overnight, or even in five years. The 3G networks that we have now (EVDO, UMTS/HSPA, etc), were in the planning stages in the late 90s, and the networks were swearing that they would have it all up and running by 2001. It's 2008, and even today, not a single carrier in the US has 100% full 3G coverage across their network. Not a one.

    So, don't think for a second that the current crop of Verizon, Sprint and AT&T will be truly obsolete anytime soon. The carriers will promise the sun and moon, but in reality, things just don't move that quickly. In 5 years, you MIGHT get minimal LTE coverage in say, the top 50-100 cities on a limited basis. But it'll be a decade before you get anything close to full deployment.

    While that would be a nice fairy tale ending to Sprint, in reality I don't think anyone wants to even touch them. Sprint already has three disparate, incomaptible networks that they've committed to running, and they're stubbornly refusing to give up any of them. It's a total mess. Why would a GSM carrier want to buy Sprint, and then have to contend with maintaining four incompatible networks? It would be corporate suicide.

    The likely buyout candidate right now is SK Telecom, which has no network holdings in the US. That means, nothing to lose. They could easily decide to lop off one or two major assets and focus on the core stuff.

    CDMA is currently active on 257 commercial networks, in 99 countries (mostly Asian and Latin American). There were 535,330,000 subscribers as of the first quarter of 2008.

    that's not quite as big as the estimated 3 billion GSM users in the world, on 750 networks in 212 countries. But it's still not insignificant.
  14. yg17 macrumors G5


    Aug 1, 2004
    St. Louis, MO
    GSM is most definitely encrypted. Believe me, the GSM standard would've been dead a long time ago if it wasn't secure and encrypted.

    Why the rolleyes? Everything he said is true....Voda does own a 45% stake in Verizon Wireless. VZW is moving to the GSM standard for 4G (Called LTE) and they would make a ton of money if Verizon doesn't have to actually pay Vodafone for roaming and vice versa, yet can still charge out the ass for it

Share This Page