Cellular technology can be broken down into two basic categories – GSM and CDMA. Both work well and provide the same function, but are different enough that they aren’t interchangeable. Lets have a look at each and try to clear everything up.


GSM (Groupe Spécial Mobile) is the most popular standard for mobile telephone systems in the world. If you hail from Europe, Africa or Asia, you’re probably using a GSM carrier. More on the Americas in a bit. GSM phones use sim cards to hold the network programming and user information. One cool thing is that you can easily swap phones by placing your sim card into a new phone and powering it up. Through the week you can use your business-oriented phone, and come Friday throw that sim into your multimedia phone for weekend fun. When you see advertisements for “phone unlocking” this is why. Unlocked GSM phones can be used across carriers. There are some drawbacks – GSM doesn’t have quite the range of CDMA, and is a little weaker in the “building penetration” department.


CDMA (Code Division Multiple Access) is short for CDMA2000 – a mobile technology standard that uses CDMA channel access for cellular communication. While most of the world uses GSM tech for mobile transmission, parts of the Americas, the Indian subcontinent, Eastern Europe, and East Africa have CDMA carriers as well. CDMA networks work well in three specific areas:

  • rural areas where towers will be few and far between
  • high-population-density areas where lots of users will be sharing the towers
  • deep inside buildings

You’re not able to swap out sim cards, as CDMA phones don’t use them. This is a heartbreaker for those of us that have no local GSM carriers, but happen to be phone junkies.

OK. We see there’s a difference and not every phone is going to work on every network. Maybe one day this will change, but don’t look for that any time soon. So this leads to the big question – where will my dream phone work? Well I took the time to compile a list of carriers by region, and then I came across the following link.

Worldwide CDMA networks

Yeah, wikipedia, I know. But surprisingly this list is pretty complete. It’s a list of the CDMA carriers worldwide. Have a look. If the folks who you pay your bill to every month are listed there, then you’re running on a CDMA network. If not, you’re almost certainly using a GSM network. Satellite CDMA networks are there own breed, and if you are using one you already know it ;)

Unlocked phones

Can’t talk about this sort of thing without mentioning unlocked phones. Simply put, an unlocked phone is a GSM phone that has been programmed to work with any sim card (to the limit of its radio frequency). We can use the phone everyone loves to hate for this example – the iPhone. When you wander into an AT&T or Vodaphone store and buy an iPhone, it’s locked to the carrier. You can’t just swap sims and have it work on other cell carriers without unlocking it. Android phones work the same way. When you contact an unlocking company, they send you some code(s) you enter into the phones programming interface to enable the feature of sim swapping. Hopefully, Android’s open spirit will move carriers away from selling locked down phonesand this whole mess becomes a thing of the past.

There is one region that needs talked about here. The Americas. Just like many other areas, we crazy New Worlders can’t leave well enough alone when it comes to cellular technology. The safest bet here is to ask for specifics - will phoneX work on carrierY? There are a few constants though –

  • Phones for use on AT&T will work on T-Mobile, but you get no 3G (and vice-versa)

  • HSDPA and HSDPA+ will only work on carriers that support it (T-Mobile, Bell, Telus)

  • Sprint and Verizon will only activate phones branded for use on their system, even though the internals are identical.

Confused yet? Well don’t look for unification any time soon. 4G is starting to roll out worldwide and it also uses more than one standard. Since the HTC EVO tried to steal the show at CITA let’s talk about 4G.


WiMax is the 4G technology that’s currently in use worldwide. ZDNet has a neat map showing where it’s currently in use:

WiMax map

Think of WiMax as high speed, long range WiFi. It’s the same principle on a bigger scale. While WiMax is mostly used for broadband network access, there are some phones using the technology in Russia. In North America, Sprint has decided that they will be using WiMax for their 4G rollout, and introduced the HTC EVO 4G as the first US 4G capable mobile phone. Go Android!


LTE is the technology that most of the cellular carriers have chosen to use for 4G. Currently it has a very limited footprint in Scandinavia, but plans for expansion this year are in effect. It’s generally believed that China Telecom/Unicom will adopt LTE for their 4G network, thus driving the rest of the world to follow suit. LTE is the logical progression of GSM network technology. While WiMax is an offshoot that works, LTE will very likely be the world standard in a few years. In North America, all major carriers (besides Sprint) have made known that they will be adopting LTE for 4G in the near future, and Samsung  has announced that they will be offering an LTE device through Metro PCS late this year. Other carriers plan to start their LTE rollout this year, with LTE phones becoming available sometime during mid 2011. Yes you read that right. Metro PCS. Gotta love the underdog.

Yes the whole subject is a mess. Other than the HTC Evo 4G and the Dell Aero we really don’t know which phones will work where. But at least this way, when you hear the news about the upcoming Android superphones, you have an idea if it will work with your carrier or not. One thing you can bet on, regardless of your carrier you’ll probably be seeing at least one of the new breed of Android handsets coming your way this year. That’s something we all can understand and enjoy.

Until next week,



Reader comments

Making sense of all these acronyms


good article I have sprint witch is cdma but I herd some rumors on the web that rhere 4g wimax could be switched over to LTE, so dose that mean that the evo 4g witch has a 4g wimax chip not work if sprint was to switch over to ltte or is it kinda universal ,

just because you can unlock a phone and use it on any carieer doesnt make it supior CDMA tech travels farther and goes throu buildings easily GSM doesnt didnt you read the article above? CDMA has 1 disadvantage it cant be unlocked if locked thats it

Well, that and its not as widely used as GSM, so it makes it difficult to travel internationally with your CDMA phone.

Would be nice if you also explained what UMTS, HSDPA, HSDPA+ and WCDMA mean...
A list of frequencies would be even better (so that when we see a phone supporting 2100, we know which of these it supports).

GSM has a few other advantages as well

International Roaming - GSM is much more widely supported and you can roam almost world wide (or unlock your phone and get a cheap local sim pay as you go)

Phone Support - Because most of the world is GSM you are likely to get more phone choices.

Speed - A GSM "3.5G" (HSDPA) network is only slightly slower than the new 4G from verizon (7.1 mbps vs 10 mbps) and HSDPA + is much faster than the current '4G' (21 mbps vs 10 mbps). Really Verizon shouldn't be calling their new network 4G.

Cdma phones can also get unlocked and at times connected to other carriers. Do a little reading at your older brother site treocentral.com and you might learn a bit.

Also the frequencies the phone can handle makes a big difference. And. Greatly effects coverage. That's why the att nexus one and T-Mobile nexus one don't do 3g on each other- wrong frequency. And why the same phone on Verizon might get better coverage on a building that a sprint version. Verizon has a mix of original 'cellualr' and newer "pcs' frequencies. Sprint is all pcs. Which doesn't penetrate as well.