Traveling abroad and staying connected is further complicated by different radio frequencies. So here’s the straight talk CDMA vs GSM. The first question you may be asking yourself is, what the heck is CDMA and GSM? More importantly, do you really need to know all this? Perhaps. Knowing the difference between the two technologies will allow you to make educated decisions on how to stay connected using wireless technology. It may even affect your choice of compatible smart phones.

Straight Talk CDMA vs GSM

CDMA and GSM are two radio frequencies used in mobile phone technology. Verizon, Sprint, and U.S. Cellular use CDMA. These two technologies are not compatible–you cannot swap between the two. How did this happen? The chipmaker, Qualcomm, owns CDMA so the radio frequency is built into the hardware of the cell phone. The two biggest players in mobile phone service, Verizon and Sprint, chose to go down the CDMA road back in the mid 1990’s when they had to chose between CDMA and GSM.

So why didn’t the big players, Verizon and Sprint, jump onto the GSM bandwagon? One reason is that back in the mid 1990’s when phones were switching from analog to digital, CDMA was the fastest technology and the most popular. Pair that with the fact Qualcomm owned CDMA and the technology was built into the phones, making it cheaper for the big boys, Verizon and Sprint, to acquire cheaper phones. Also, at that time, CDMA offered better call quality than GSM. In the meantime, GSM not only caught up but surpassed CDMA.

  • GSM is both voice and data technology whereas CDMA is only voice.
  • Sim cards are needed for data technology. Even the newer 3G CDMA can’t transmit data and make calls at the same time.
  • CDMA towers could accommodate more subscribers than GSM towers making it a cheaper route as well.

GSM Radio Frequency

So here’s the difference. While CDMA phones have all their carrier information built into the phone, GSM phones (used by AT&T and T-Mobile) carry all their carrier information on a sim card making them beautifully portable, right? Maybe.


GSM phones are more widely used in European countries while CDMA phones are more widely used in the USA. With CDMA phones, you can’t switch phones without your carrier’s permission.  However, AT&T and T-Mobile don’t make it easy for you either. Switching between these two companies may not work well because they use slightly different frequencies.

Can they both coexist nicely?

Sprint and Verizon have had to make the leap into sim card phones in order to provide data service on their 4G LTE networks which is sim card based. In my opinion, they may still have a stranglehold on the U.S. market. Personally, I’m not happy with the idea that a company can tell me when I can upgrade my phone or that I have to get permission to even switch phones! And CDMA carriers may not allow you to bring your own CDMA phone to their network. They could, but they typically don’t. And Sprint rejects any non-Sprint phones!

So what does all this mean for you?

If you are traveling abroad and have a phone without a sim card, getting it unlocked will not allow you to simply buy a sim card, put it into your phone and start talking. If you want to travel abroad and stay connected, you’ll need to buy a separate phone that is a GSM, quad-band, unlocked phone. Alternatively, if your carrier is AT&T or T-Mobile, you could get the phone unlocked and before you travel purchase a sim card for the country you are visiting. It would also be wise to consult your carrier on whether your unlocked phone will work abroad.


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