Unlocked Cell Phones and Tablets, Using Them Overseas, 3G and 4G and LTE Explained (As Well As I Can Understand)

I have become semi-obssessed with things like cell phones and tablets, and using them overseas.  Part of this is because I travel a fair amount.  The other part of this is because I am a tech nerd (must be my Asian roots).  I was in Australia a couple of years ago, and it was a pleasure bringing an unlocked Pantech smartphone there, going into a mall, getting an Optus SIM card, putting it in, and within 30 minutes, having an operational local phone with a data plan for the month or two that I was there.  Having a local cell phone and being able to use the internet is a huge problem-solver when you are traveling.

I've spent hours trying to figure out what the best tablet or phone might be for my next trip and phone/tablet purchase.  I've therefore been forced to try to figure out and keep track of exactly what GSM, Edge, 3G, 4G, and LTE means.  I am writing down what I know in the hopes it will help other folks when they are deciding to buy an cell phone for use overseas.

First of all, if you want to buy a cell phone or tablet that will work both in the US and overseas, then you need to buy an UNLOCKED phone or tablet.  This means that you can take it to other countries such as Australia, and it will often work in those countries if you buy a cheap SIM card for a local carrier. This is HUGE if you travel internationally a lot. This is also a big deal if you want to switch from, say, AT&T to T-Mobile in the US.

I ONLY buy UNLOCKED tablets and phones. I have, for instance, an iPad 3 with a Verizon modem that I bought so I can use it in Australia. Turns out the the iPad 3 can use AT&T's frequency bands here in the US too, since the Verizon iPad 3 is unlocked (if you buy an AT&T iPad 3, it is locked to AT&T).

Second, the better the phone, the more frequency bands it can tune in to.   Here's what I know about frequency bands, and I welcome comments to clarify what I put down here.

In the US, the four major cellular phone carriers are Verizon, Sprint, AT&T, and T-Mobile.   Verizon and Sprint use older CDMA technology and newer LTE technology.  The older CDMA phones are always locked to Verizon or Sprint, so they can't be used overseas with another carrier, and they can't be unlocked to be used with AT&T or T-Mobile.

From an Ebay discussion: Any buyer who has ever wondered why they can't simply use a phone that was created for AT&T on a Verizon network and vice versa should know that the differences between CDMA and GSM technologies are the sole determining factor behind this. In effect, the two technologies represent different kinds of radio systems.

AT&T and T-Mobile in the US are GSM-based cell phone networks.   GSM, or Global System for Mobile, is the primary type of technology used for cell phones in the rest of the world. 

From the same Ebay discussion:

using a GSM-compliant phone also makes it much easier for a user to switch providers or networks, as all that they must do in order to make a switch is purchase a new SIM card for their device. The interchangeability of GSM cell phones, as well as the ability to easily switch between networks, makes them a much more appealing option for international travelers who plan to switch between different networks when on trips to countries that primarily use GSM technology.

This is especially important for those who take frequent trips to Europe. Europe adopted GSM technology in the 1980s and has been on this standard ever since. As the technology is required of network providers by law, users will not find access to CDMA networks in any countries within Europe. 

Verizon CDMA phones are often sold for dirt-cheap, because they can ONLY be used on the Verizon network.  As an example, the Moto G smartphone for Verizon is a great phone.  It sells for only $100 at Walmart (the Verizon version).  The Moto G phone with GSM bands sells for $199 everywhere else.  This is because Moto G phones (being Google-branded phones) are always unlocked, so you can use them on any carrier that uses GSM bands (such as AT&T and T-Mobile in the US). 

Older phones are often advertised as "quad-band GSM unlocked. " This is good.  This means that a buyer can use the phone on GSM networks in the US as well as overseas.  In the US,  GSM operates on the primary mobile communication bands 850 MHz and 1,900 MHz.  From what I understand, GSM/EDGE are considered 2G networks, suitable primarily for voice calls.  If you buy a quad-band, unlocked GSM phone, it will normally have the bands 850/900/1800/1900 MHz and will be able to work on any US GSM carrier -- eg AT&T and T-Mobile. 

•  
• As an example, the Moto G phone for AT&T has the following GSM bands and is described as:
•  Quad-band GSM/GPRS/EDGE; quad-band UMTS/HSPA support.
• We'll get to the second part in a bit.  The first part refers to: 

• 2G Network

  GSM 850 / 900 / 1800 / 1900

•  This means that this phone can work for voice calls on most GSM networks in the world.  
• 
  
• The second specification: quad-band UMTS/HSPA support, refers to:
•  HSDPA 850 / 900 / 1900 / 2100  for the Moto G worldwide phone
  HSDPA 850 / 1700 / 1900 / 2100 - for T-Mobile, AT&T
•  
• As I understand it, and I am sure that I am grossly oversimplifying this, HSDPA and UTMS refer to 3G networks.  3G networks succeed GSM/EDGE (which are 2G networks).  They offer faster data rates.  From phonearena: This makes them especially suitable for use in modern smartphones, which require constant high-speed internet connection for many of their applications.

3G networks are fast enough to view Netflix videos.  That's plenty fast for me.  In the US, AT&T 3G phones use the following frequencies:  "3G UMTS network 850/1900MHz bands."  T-Mobile has been using the 1700 band, which few other carriers in the world use.  Therefore if you buy a T-Mobile phone or tablet that has 3G capability, it will likely have the 1700 band.  However, T-Mobile is moving more of their data/capability to the 1900 band. 

• 
  

As you can see above, the Moto G worldwide phone has quad-band support, but leaves out the little-used (except in the US, for T-Mobile) 1700 band.  The Moto G phone for T-Mobile includes the 1700 band.

An excellent resource that explains these things can be found at:

http://www.gsmarena.com/network-bands.php3

So, a quick summary: if you want a cheaper, older, inexpensive smartphone or tablet that you can use in the US and in other countries, you will want to buy an UNLOCKED, quad-band GSM, and quad-band 3G phone.

The newer smartphones and tablets are using 4G network, the fourth generation of mobile phone communications standards.  From gsmarena:

4G is the fourth generation of mobile phone communications standards. It is a successor of the 3G and provides ultra-broadband internet access for mobile devices. The high data transfer rates make 4G networks suitable for use in USB wireless modems for laptops and even home internet access.

I believe that most uses of the term "4G" also means "LTE."  With 4G LTE, Verizon has gone back to using SIM cards, and it's possible to buy a smartphone or tablet that can use, for instance, either AT&T or Verizon SIM cards.  

Wikipedia has a good table showing the various bands: 

http://en.wikipedia.org/wiki/Cellular_frequencies

As you can see from the table, there are many 4G frequency bands, and they are associated with a band number to simplify things. 

Here's an example of how these 4G and LTE bands are specified and used:

A recent Ebay auction had an iPad mini  32GB WiFi +3G & 4G LTE White or Black UNLOCKED GSM 1st Generation UNLOCKED TO WORLD WIDE GSM advertised.  I researched the exact specifications of this iPad mini and here are the frequency bands that it could tune in to:
GSM/EDGE (850, 900, 1800, 1900 MHz)
UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz)
LTE (Bands 4 and 17) which are 1700 and 2100

This means that this iPad mini is quad-band GSM and 3G capable.  It is also 4G capable on bands 4 and 17 (1700 and 2100).  These are the bands for AT&T and T-Mobile, so this iPad mini first generation should work on AT&T and T-Mobile networks as long as it is not locked to a specific carrier (thus the wording "unlocked" in the Ebay title).  And here's a cool thing -- this iPad mini should be able to use a Verizon network SIM card also!  From the above table, Verizon also uses band 4.

(I could be wrong about T-Mobile.  In a note I have, I don't know where it came from, I see that T-Mobile uses the frequency bands: 4G LTE network AWS / 700 / 850 / 1900MHz bands. )

Here's another example. I just bought an Asus Nexus tablet for my wife (I may steal it from her when I take a trip overseas).  It was the T-Mobile 4G LTE version, but like all Google-sponsored cellular products, it is unlocked.

Here's the table of frequencies for this tablet, from http://en.wikipedia.org/wiki/Nexus_7_(2nd_generation)

The second column shows the frequencies for the model made for T-Mobile, AT&T, and Verizon.  It seems that I could put in a SIM card (micro-SIM) from any of these three networks in this tablet and it should work.  The fourth column shows the bands that the worldwide version of this tablet offers.

This great tablet is quad-band GSM unlocked, 3G quad-band unlocked.  It offers seven different LTE bands so you can use it with three US cellular carriers, and the world version offers seven LTE bands so you can use it with many carriers around the world.  It has LTE bands 7 and 20 whereas the US version has LTE bands 13 and 17. 

Here's the description of the 2nd generation Asus Nexus tablet from the Google Play site:
Optional 4G LTE
       
        North America:
        GSM: 850/900/1800/1900 MHz
        HSPA+: 850/900/1900/1700/2100 (AWS) MHz (Bands: 1/2/4/5/8)
        LTE: 700/750/850/1700/1800/1900/2100 MHZ (Bands: 1/2/3/4/5/13/17)
       
        Europe:
        GSM: 850/900/1800/1900 MHz
        HSPA+: 850/900/1900/1700/2100 (AWS) MHz (Bands: 1/2/4/5/8)
        LTE: 800/850/1700/1800/1900/2100/2600 MHz (Bands: 1/2/3/4/5/7/20)


Engadget wrote about this:
On that particular model, ASUS managed to squeeze six LTE frequencies (bands 1, 2, 4, 5, 13 and 17), pentaband HSPA+ and quadband GSM / EDGE into its North American version, which means it will be compatible with AT&T, Verizon and T-Mobile in the US, as well as a smattering of operators in other parts of the globe. This is actually a pretty huge feat, as we haven't seen a device that's compatible with both Verizon and AT&T LTE before. There's also a European option, which provides seven LTE bands (1/2/3/4/5/7/20), pentaband HSPA+ and quadband GSM / EDGE. Not too shabby.


Here's a summary:
If you want an older, inexpensive smartphone that will work both in the US and overseas, then you might want to look for a quad-band unlocked 3G and GSM smartphone or tablet.  The ones I recommend are the Samsung Galaxy Tab 3 7.0-inch worldwide unlocked 3G "phablet", which is a phone AND a tablet (basically a tablet with voice-calling capability).  I see these on Amazon for about $225.  Be sure to get the unlocked world version of this phablet.  I also recommend the $199 Moto G and $129 Moto E world edition phones from Google Play. 

I understand that the Moto G, as of today, will soon be coming out with G4 LTE capability.  That's pretty cool -- all earlier versions are 3G only.

Ipads 3rd generation and above, and iPad minis first generation and above, are unlocked and can work with both Verizon and AT&T in the US (and probably T-Mobile in some places).  They can work with some overseas carriers  on LTE Bands 4 and 17.  This is a bit limited.  If I were to travel soon, I'd borrow my wife's new Asus Nexus 2nd generation and take it overseas with me instead of my iPad 3rd generation, because it covers so many more LTE bands. 

If you buy an iPad, consider buying an iPad with a Verizon modem, which have up to now been unlocked -- rather than an AT&T iPad, which have been locked so you can ONLY use it with AT&T's network and plans.

The Google-sponsored phones and tablets, such as the Asus Nexus tablets and the Moto X, G and E smartphones, are all unlocked out of the box.  They seem to be excellently made phones in nice price ranges.

I have not consider iPhones in this blog posting because I personally can't see spending over $500 for a dang phone.  


Please do your own research before buying anything based on the information in this blog posting.  I cannot guarantee that anything here is correct, and I am the first to admit that my understanding of these matters is of the "inexperienced" level.  I welcome comments that clarify this post.