Making sense of all these acronyms

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,


Jerry Hildenbrand
Senior Editor — Google Ecosystem

Jerry is an amateur woodworker and struggling shade tree mechanic. There's nothing he can't take apart, but many things he can't reassemble. You'll find him writing and speaking his loud opinion on Android Central and occasionally on Twitter.