Since starting this Android blog, I’ve run across a number of questions from individuals and often times I have to explain a number of different things regarding cell phone network technologies.  It usually starts with a question about which Android phone to get, and after I explain that most the time, in the US at least, the phone also dictates the network you can use if you want to take full advantage of the phone’s features.  To start with, Android phones are set into a special phone category of  “smart phone” and as such the service plans offered are unique to this category and cost more than the typical cell phone contract.  The user is bound to a data plan, as these phones are data heavy, and in reality you want the data.  That is the point of a smart phone, data.  But, the questions often end up going towards, “What is CDMA?  What is GSM?  Does GSM have 3g, or CDMA 3G?”  Well, let’s try and answer a few questions as simply as possible. 

I am writing this guide in the most simple terms.  True network geeks might find some of my comparisons and analogies a little crude, but this is meant for the average person to understand the technologies and be able to make a better choice for themselves.

In the US, there are two primary cell phone technologies.  Verizon Wireless and Sprint use a technology called CDMA.  I won’t even explain the acronym, that’s not important, just understand this is what those companies use and in order to use their services the cell phone must support CDMA.  Likewise, AT&T and T-Mobile use a technology called GSM.  Again, in order to use those companies service, the cell phone must support GSM.

Like I mentioned earlier, it’s not important you know exactly what CDMA and GSM are, just understand they don’t play together.  Both are very capable of transmitting data back and forth from one user to the next.

The next part of the cell phone service technology that many people are hearing about is 3G.  What is 3G?  3G is the term being used for the current highest speed data service available through the service providers and it is replacing 2G data.  It’s a faster data service than what is standard now.  It’s what you want to have.

All current major US cell service providers offer a minimum of 2G data service in their entire available coverage area.  Check the maps on each service provider’s website, or here. All current major US cell service providers offer some 3G service as well.  Verizon Wireless had 3G on 100% of it’s service map, meaning if you have Verizon signal, you have 3G data.  AT&T and T-Mobile have 3G data on the majority of their major markets, which include large cities and such.  Check their 3G maps to see if you are covered.

3G is not exclusive to CDMA or GSM.  3G is simply a term used to state high speed data.  So, a 3G CDMA phone has high speed data using CDMA.  A 3G GSM phone has high speed data using GSM.  3G CDMA is not 3G GSM, it’s still using the different technologies (CDMA versus GSM).  However, depending on who you talk to the speeds are the same.  3G CDMA speed is about the same speed as 3G GSM speed.

One last thing that makes everything even more complex.  Each service provider purchases airwaves from the USG to use for their service.  Typical frequencies you might read about are 850, 900, 1700, 1900, 2100 Mhz etc.  In the GSM world in the US, standard cell phone frequencies are the same, so that if I have a GSM phone, I can use it with AT&T or T-Mobile for my basic telephone needs, making and receiving phone calls.  I also can get 2G data on either network.  However, in the 3G world.  AT&T and T-Mobile use different frequencies, so that if a GSM phone has the hardware to work only with T-Mobile’s 3G network, then the user can only get 3G speeds with T-Mobile.  They can still use AT&T for phone calls and slower 2G data, just not the faster 3G data.  Likewise, if a GSM phone has the hardware to work only with AT&T’s 3G network, then no 3G data with T-Mobile.

So where does that leave us?  We have got two different base technologies for cell service, CDMA and GSM, different data speeds (2G and 3G) and finally 3G GSM frequencies in the US don’t match up.

The user is basically left with choosing a cell service provider and using the phones available, or likewise, choose the cell phone they want and use the provider that supports it.  Kind of crummy.  So, which do you choose?

I am not going to try and compare one network’s performance, in terms of speed and customer support etc, against another.  I will leave that to the user to determine, based off maps and coverages available in the user’s area.  I will explain a couple things though, just for informational purposes.

Verizon is the largest cell service provider in the US in terms of coverage.  The entire network is 3G.  This makes the largest network in the US CDMA.

GSM is used much more around the world than CDMA.  Those links point out about 3 billion on GSM verses 0.5 billion on CDMA.  As such, typically it’s easier to use your GSM phone in other countries than CDMA.

My personal tip is this, if you are a world traveler, think about GSM and/or check that the countries you travel to offer CDMA.  If you stick to the US mostly, check your service where you live and work.  Does it have 3G coverage?  Do you live in a rural area that might not have service from one company?  This is by no means the end all decision maker, nor did I set out trying to define everything.  I wanted to give some basic background information so the consumer looking to purchase their next Android understands some of the basics behind cell phone service technologies.

UPDATE:  As pointed out by McQ, I forgot to mention SIM cards.  For those that don’t know, a SIM card is a small platic card, about the size of a large thumbnail, with a microchip on it that identifies GSM phones.  It carries your phone number and network data on it to connect with the GSM networks.  AT&T and T-Mobile use them in the US, as do other GSM carriers around the world.  CDMA phones have nothing like that.  The phone information is stored internally on memory.  A SIM card can be easily removed by the user and another put in it’s place, which is very useful for international travel as the user can purchase a local SIM card, something like a pay-as-you-go variety, and have local phone service without paying high international rates.  This requires unlocking your phone, which I won’t get into, but most carriers will do this if you are in good standing with your account and you call requesting to have that done.

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2. T-Mobile Preps 3G for Nexus One
3. Nexus One Advertising and Sales

3G, AT&T, CDMA, GSM, Service Providers, Sprint, T-Mobile, Verizon Wireless