CDMA vs. GSM: What’s the Difference?

If you’re shopping for a mobile phone, you’re in for a lot of acronyms. Here’s what you need to know about two basic, yet important, terms


Two basic technologies in mobile phones, CDMA and GSM represent a gap you can’t cross. They’re the reason you can’t use many AT&T phones on Verizon’s network and vice versa. But what does CDMA vs. GSM really mean for you?

CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for the two major radio systems used in cell phones. Both acronyms tend to group together a bunch of technologies run by the same entities. In this story, I’ll try to explain who uses which technology and what the real differences are.

Which Carriers Are CDMA? Which Are GSM?

In the US, Sprint, Verizon and US Cellular use CDMA. AT&T and T-Mobile use GSM.

Most of the rest of the world uses GSM. The global spread of GSM came about because in 1987, Europe mandated the technology by law, and because GSM comes from an industry consortium. What we call CDMA, by and large, is owned by chipmaker Qualcomm. This made it less expensive for third parties to build GSM equipment.

There are several variants and options carriers can choose, like toppings on their technological ice cream. In this story we’ll focus on US networks.

What CDMA vs. GSM Means to You

For call quality, the technology you use is much less important than the way your carrier has built its network. There are good and bad CDMA and GSM networks, but there are key differences between the technologies. Here’s what you, as a consumer, need to know.

It’s much easier to swap phones on GSM networks, because GSM carriers put customer information on a removable SIM card. Take the card out, put it in a different phone, and the new phone now has your number. What’s more, to be considered GSM, a carrier must accept any GSM-compliant phone. So the GSM carriers don’t have total control of the phone you’re using.

That’s not the case with CDMA. In the US, CDMA carriers use network-based white lists to verify their subscribers. That means you can only switch phones with your carrier’s permission, and a carrier doesn’t have to accept any particular phone onto its network. It could, but typically, US carriers choose not to.

Many Sprint and Verizon phones now have SIM cards, but that isn’t because of CDMA. The SIM cards are there for Sprint’s and Verizon’s 4G LTE networks, because the LTE standard also uses SIM cards. The phones may also have SIM slots to support foreign GSM networks as “world phones.”

3G CDMA networks (known as “EV-DO” or “Evolution Data Optimized”) also, generally, can’t make voice calls and transmit data at the same time. Once more, that’s an available option (known as “SV-DO” for “Simultaneous Voice and Data Optimization”), but one that US carriers haven’t adopted for their networks and phones.

On the other hand, all 3G GSM networks have simultaneous voice and data, because it’s a required part of the spec. (3G GSM is also actually a type of CDMA. I’ll explain that later.)

So why did so many US carriers go with CDMA? Timing. When Verizon’s predecessors and Sprint switched from analog to digital in 1995 and 1996, CDMA was the newest, hottest, fastest technology. It offered more capacity, better call quality and more potential than the GSM of the day. GSM caught up, but by then those carriers’ paths were set.

It’s possible to switch from CDMA to GSM. Bell and Telus in Canada have done it, to get access to the wider variety of off-the-shelf GSM phones. But Verizon and Sprint are big enough that they can get custom phones built for them, so they don’t see the need to waste money switching 3G technologies when they could be building out their 4G networks.

The Technology Behind CDMA vs. GSM

CDMA and GSM are both multiple access technologies. They’re ways for people to cram multiple phone calls or Internet connections into one radio channel.

GSM came first. It’s a “time division” system. Calls take turns. Your voice is transformed into digital data, which is given a channel and a time slot, so three calls on one channel look like this: 123123123123. On the other end, the receiver listens only to the assigned time slot and pieces the call back together.

The pulsing of the time division signal created the notorious “GSM buzz,” a buzzing sound whenever you put a GSM phone near a speaker. That’s mostly gone now, because 3G GSM (as I explain later) isn’t a time division technology.

CDMA required a bit more processing power. It’s a “code division” system. Every call’s data is encoded with a unique key, then the calls are all transmitted at once; if you have calls 1, 2, and 3 in a channel, the channel would just say 66666666. The receivers each have the unique key to “divide” the combined signal into its individual calls.

Code division turned out to be a more powerful and flexible technology, so “3G GSM” is actually a CDMA technology, called WCDMA (wideband CDMA) or UMTS (Universal Mobile Telephone System). WCDMA requires wider channels than older CDMA systems, as the name implies, but it has more data capacity.

Since its inception, GSM has evolved faster than CDMA. As I mentioned above, WCDMA is considered the 3G version of GSM technology. To further speed things up, the 3GPP (the GSM governing body) released extensions called HSPA, which have sped GSM networks up to as fast as 42Mbps, at least in theory.

Our CDMA networks, meanwhile, are stuck at 3.6Mbps. While faster CDMA technologies exist, US carriers chose not to install them and instead turned to 4G LTE to be more compatible with global standards.

LTE Closes the Gap

LTE, or “Long Term Evolution,” is the globally accepted 4G wireless standard. All of the US carriers use it. For more, see 3G vs. 4G: What’s the Difference? So you’d think, hey, that should make everyone compatible, right? Wrong.

While most phones in 2017 use LTE for data, Sprint phones still use CDMA for all voice calls, and Verizon still has a network-based whitelist for phones that will work on its network. You can try to wiggle around the whitelist, as ZTE did with its Axon 7 phone, but the process is very unreliable.

In June, Verizon introduced its first two LTE-only phones, the LG Exalt LTE and HTC U11. This is part of a move to an all-LTE system; Verizon says it wants to shut down CDMA by the end of 2019. Without CDMA, it’s going to become easier for AT&T, T-Mobile, and Verizon devices to be compatible in the future, but that still leaves Sprint out.

Also, the four carriers are using LTE in different frequency bands, with some of their phones specced to exclude the other carriers’ bands, making it harder to switch carriers. Sprint, once again, is the odd one out here, because it runs an unusual variant of LTE (TD-LTE) on an unusual frequency band (Band 41.)

A few phones support all four carriers by combining CDMA, GSM and LTE. The iPhone 6 and later; the Motorola Moto G4 and later; the Samsung Galaxy S7 and later; the Nexus 6 and later; the Google Pixel phones and the Moto E4 all work across all four carriers. Other manufacturers of unlocked devices generally don’t include CDMA radios because they don’t see a big market in unlocked phones being used on Sprint and Verizon.

So what does all of this mean for you? If you want to switch phones often, use your phone in Europe, or use imported phones, just go with AT&T, T-Mobile, or virtual carriers on those networks. Otherwise, pick your carrier based on coverage and call quality in your area and assume you’ll probably need a new phone if you switch carriers. Our Readers’ Choice and Fastest Mobile Networks awards are a great place to start.

What’s the difference between these cellular standards?

Posted on January 30, 2018 9:04 am

If you’re in the market for a new smartphone or carrier — or you’re simply interested in cell phone networks — you’ve likely encountered the acronyms CDMA and GSM before. But what are they, and how do they affect your phone?

The two cellular standards function in different regions and allow for global communication between individuals, and each converts incoming and outgoing data into radio waves differently. Neither should be a huge factor when buying a cell phone (unlike 4G and LTE), but it’s definitely worth knowing your stuff, since not all cell phones are guaranteed to work on both standard. It depends on where you are, what you’re looking for, and who you’re with.

CDMA explained

CDMA — or Code Division Multiple Access — is often found in the U.S and Russia, though GSM is also present in those countries. The Allied Forces developed the technology during World War II, primarily as a method to prevent Nazi forces from jamming radio signals. Unlike GSM, CDMA grants users full access to the entire spectrum of bands, thus allowing more users to connect at any given time. It also encodes each user’s individual conversation via a pseudo-randomized digital sequence, meaning the voice data remains protected and filtered so that only those participating in the phone call receive the data.

Phones on CDMA networks do not use SIM cards. Instead, each phone is built specifically to work on that carrier’s network. What does this mean for consumers? For starters, it means that phones are tied to a carrier and their bands, so if you decide to change providers, you’ll have to buy a new phone.

Is one better than the other?

Not necessarily. Both are the global standards for cell communication. The major factor affecting call quality is the network itself, not the method it uses to transmit information. Of course, there are some things to keep in mind when it comes time to choose between CDMA and GSM phones. For starters, CDMA phones without SIM slots are tied to their carriers, and cannot be transferred to other networks. A Verizon phone could not be transferred to Sprint’s network, for instance, or vice versa. But sometimes it’s not as cut and dried as all that — although some Verizon devices do use CDMA, they also have an unlocked SIM slot, so could be unlocked for use on other networks. Sprint is less forthcoming with unlocked SIM slots when its devices do contain one, but you can usually find ways get your carrier to unlock your phone when you’re done with them.

In contrast, GSM phones are fairly easy to unlock and transfer to other networks. Additionally, third-party manufacturers often sell phones designed for GSM networks, since they don’t require access to a specific carrier’s bands. GSM phones will even work in countries with compatible GSM networks.

CDMA networks allow for a greater number of users, meaning their capacity for communication is greater than that of GSM networks. Moreover, CDMA is the infrastructure on which all 3G networks are based — for both GSM and CDMA carriers. However, there’s now a third type of network that is quickly becoming the frontrunner in terms of quality, with many major cell phone companies quickly adopting it. Dubbed LTE for Long-Term Evolution, the technology represents an evolved form of GSM, and uses a similar technology as GSM networks. The new standard boasts enhanced voice quality and functions as the base of high-speed, 4G data networks. In this case, LTE does have an edge over the competition in terms of overall speed and quality.

If you’re a U.S. customer and wondering what companies use which type of network, the split is right down the middle: AT&T and T-Mobile are GSM carriers, while Verizon and Sprint are CDMA. In truth, picking a new phone or carrier solely based on what standard it adheres to doesn’t necessarily matter because the services, features, phones, and service quality a network offers aren’t solely dependent on their network infrastructure. So unless you have a particular need for choosing one over the other, go with the carrier that best fits your tastes, needs, and budget.

When consumers think about mobile network providers, their primary concern is with regards to coverage, quality, support, pricing, and other factors but when you pick a network carrier, you also make the choice between a GSM network or a CDMA network, at least in the US.

You have probably come across these terms in the past, when picking a mobile phone, or when first joining, or switching, network carriers, but what do they mean, and what is the difference between the two? We find out, as we take a closer look at GSM vs CDMA, and what it signifies for us as a consumer.

What is GSM?

GSM stands for Global System for Mobile Communication, and is now considered the standard for communication globally, particularly in Asia and Europe, with its availability in over 210 countries worldwide. It functions on four distinct frequency bands, 900 MHz and 1800 MHz is Europe and Asia, and 850 MHz and 1900 MHz in North and South America. The GSM Association is an international organization founded in 1987, that is intended to develop and oversee the expansion of the GSM wireless standard.

GSM uses a variant of TDMA (time division multiple access) that divides the frequency bands into multiple channels. With GSM, our voice is transformed into digital data, which is given a channel and a time slot. On the other end, the receiver listens only to the assigned time slot, with the call pieced together. Obviously, this happens in a negligible amount of time, and the receiver doesn’t notice the “break,” or time division, that occurs.

What is CDMA?

CDMA, or code division multiple access, was a standard designed and patented by Qualcomm, but subsequently used as the basis for the CDMA2000 and WCDMA standards for 3G. However, because of its proprietary nature, CDMA hasn’t seen the global adoption that GSM has, with less than 18% of the networks around the world using CDMA, and is primarily found in the US, with Verizon Wireless and Sprint both using CDMA networks, as well as in South Korea and Russia. You can find the full list of CDMA networks here.

CDMA networks layer digitalized calls over one another, assigning unique codes to differentiate between them. Every call data is encoded with a different key, and the calls are then transmitted at the same time. The receivers each have the unique key as well, to split the combined signal into its individual calls.

Both are multiple access standards, which means that multiple calls can go through a single tower, but as you can see, the major difference between the two has to do with the way your data is converted into the radio waves that your phone broadcasts and receives. There are of course, more practical considerations that matter more for us as a consumer, which you can find listed below –

  • SIM cards: Before the advent of 4G LTE, the obvious difference between GSM and CDMA devices were with regards to the SIM card. GSM handsets came with a SIM card slot, while CDMA phones did not. In other words, CDMA is a handset based standard, with a phone number linked to a particular device. If you wanted to upgrade to another phone, you would have to get in touch with the network carrier, de-activate the old device and activate the new one. On the other hand, with GSM devices, the phone number is linked to the SIM card, so when switching devices, all you have to do is pop the SIM card into a new phone and you are good to go. (This is obviously without taking into consideration GSM devices being locked to network carriers, as seen in the US).
  • Network coverage: Network coverage doesn’t depend on whether it is  GSM or CDMA network, but rather on the infrastructure the carrier has in place. GSM networks are far more popular globally, but in the US, Verizon Wireless, a CDMA network, boasts the highest number of subscribers in the country.
  • International roaming: In your home market, it doesn’t matter what kind of network it is, with the focus instead on the available coverage. However, when it comes to international roaming, GSM has the upper hand, with their being a lot more GSM networks around the world, along with roaming deals between these providers. With a GSM phone, you also have the advantage of picking up a local SIM card wherever you are, assuming that you have an unlocked device. You may not get full access to data connectivity, depending on the device and network compatibility though.

With the advent of 4G and the adoption of LTE and LTE-Advanced as the standard by the majority of network carriers worldwide, the debate of GSM vs CDMA matters less everyday. You may have noticed the latest smartphones intended for CDMA networks also come with SIM card slots, to take advantage of the network’s 4G LTE capabilities.

While GSM and CDMA devices cannot be interchanged even now, and will never be cross-compatible, that won’t make a difference as we continue to make a push towards 4G LTE. Unless international roaming is a factor, as far as your voice call and 3G data needs are concerned, both GSM and CDMA networks are equally good, with factors like availability, coverage, customer service, and price, more at play here.

It’s also worth noting that many CDMA phones – like those offered from Verizon – also have support for GSM technology when roaming, so international travelers don’t really even have to worry much about this anymore.

CDMA and GSM networks are two types of cellular phone networks and generally, if you have a device made for one, it can’t be used on the other.

In the US, Sprint®* and Verizon run on CDMA networks while AT&T and T-Mobile run on GSM networks. Ting runs on both.

If you are porting a number into Ting, we would suggest checking here to see if it can port over.

What’s Different


There are slight differences in coverage depending on which network you choose to use. Our CDMA network has a larger footprint in rural areas so if this is a factor for you CDMA may be the network for you. In larger cities, both networks are pretty close to equal. The best way to know for sure, though, is to check our coverage maps.

GSM coverage map

CDMA coverage map

If you don’t know which network your device is compatible with, please our BYOD (Bring Your Own Device) checker.

BYOD checker

No matter which network you choose though, you’ll have access to voice text, and data (including LTE where available) while using native coverage, but only voice and text when roaming.


International roaming is available for GSM but not for CDMA devices. However, if you have a CDMA device, there are still options.

Device Selection

Just about any unlocked GSM device can be used on our GSM network with varying levels of compatibility, but for a device to work optimally on our CDMA network, it’s currently best that it’s a Sprint-branded device, with a few exceptions, particularly certain iPhone models. If you have great coverage on both of our networks and want some help figuring out what kind of devices can come to Ting, click the links below:

CDMA Bring Your Own Device Information

GSM Bring Your Own Device Information

Of course, you can also just head over to and purchase a device directly from us. You’re guaranteed that it will be completely compatible with at least one of our networks, if not both.

What’s the Same

Your Ting Account

On Ting, CDMA and GSM devices coexist under a single account and share a single pool of minutes, messages and megabytes. At the end of the billing cycle, they appear on a single monthly bill.

Plus, wherever we have both native Ting CDMA and GSM network coverage (and phone numbers available), you can move your number from a CDMA device to a compatible GSM SIM/device or vice versa.

Your Rates

On all domestic services, Ting service costs the same whether you’re using the CDMA or the GSM network. You pay the same $6 plus taxes for each active line/device on your account, regardless of whether it’s a CDMA or a GSM line.

Wi-Fi Calling

We are able to offer Wi-Fi calling on both the CDMA and GSM networks on supported devices. This would include iPhone 5c and higher on both networks and select Android devices.

Pros of the CDMA Network

Device compatibility is easier to figure out – With very few exceptions, as long as your CDMA device can make the leap to Ting, then you can expect it to have all of its functionality (voice, text, 2G, 3G, 4G and LTE data, tethering etc). GSM devices are a little trickier and you will need to be aware of what kind of data is supported for your device. A device may be compatible with Ting on the GSM network but not with full functionality. Our compatibility checker will let you know what kind of functionality to expect and you’ll need to decide if that works for you.

More coverage – Currently Ting on the CDMA network covers more area, especially in rural areas, so the chances are higher that you’ll be able to get coverage on the CDMA network than on the GSM network.

The bottom line:  If you want easy compatibility and you don’t live near a major city, then CDMA is probably the way to go.

Pros of the GSM Network

Better resale value – The resale value of GSM devices is generally higher because more people will pay for a phone that they have more chance of being able to unlock and take to another carrier.

Easier switching between carriers – Most GSM devices can be moved from one carrier to another, assuming they are unlocked and support the required bands. While that capability has been opened up for CDMA devices, it’s more difficult to do.

Easier switching between devices – In many cases moving from one device to another simply means moving a SIM card from one device to another. If the two devices take different size SIM cards, you can use the adapter that comes with the Ting GSM X1 SIM, purchase an adapter elsewhere or simply order a new SIM card; we can then move your number to the new SIM card.

International roaming options – While we have always recommended using your unlocked device with a local SIM card when you travel, if international roaming is important to you, then GSM will be the better choice for you with Ting. International roaming is supported for GSM devices but not CDMA devices on Ting.

The bottom line:  Assuming there’s solid GSM network coverage in your area if you want to switch phones often, or even use imported phones (though with limited compatibility), and you want more freedom to move between carriers, then Ting on the GSM network may be the choice for you.

CDMA, which stands for Code Division Multiple Access, is a competing cell phone service technology to GSM, the world’s most widely used cell phone standard.

You’ve probably heard of these acronyms when being told that you can’t use a certain phone on your mobile network because they’re using different technologies that are not compatible with each other. For example, you may have an AT&T phone that can’t be used on Verizon’s network for this very reason.

The CDMA standard was originally designed by Qualcomm in the U.S. and is primarily used in the U.S. and portions of Asia by other carriers.

Which Networks Are CDMA?

Of the five most popular mobile networks, here is a breakdown of which are CDMA and GSM:


  • Sprint
  • Verizon Wireless
  • Virgin Mobile


  • T-Mobile
  • AT&T

More Information on CDMA

CDMA uses a “spread-spectrum” technique whereby electromagnetic energy is spread to allow for a signal with a wider bandwidth. This allows multiple people on multiple cell phones to be “multiplexed” over the same channel to share a bandwidth of frequencies.

With CDMA technology, data and voice packets are separated using codes and then transmitted using a wide frequency range. Since more space is often allocated for data with CDMA, this standard became attractive for 3G high-speed mobile internet use.


Most users probably don’t need to worry about which cell phone network they choose in terms of which technology is better.

However, there are some key differences that we’ll look at here.


While CDMA and GSM compete head on in terms of higher bandwidth speed, GSM has more complete global coverage due to roaming and international roaming contracts.

GSM technology tends to cover rural areas in the U.S. more completely than CDMA.

Over time, CDMA won out over less advanced TDMA (Time Division Multiple Access) technology, which was incorporated into more advanced GSM.

Device Compatibility and SIM Cards

It’s really easy to swap phones on a GSM network versus CDMA. This is because GSM phones use removable SIM cards to store information about the user on the GSM network, while CDMA phones do not. Instead, CDMA networks use information on the carrier’s server side to verify the same type of data that GSM phones have stored in their SIM cards.

This means that the SIM cards on GSM networks are interchangeable. For instance, if you’re on the AT&T network, and therefore have an AT&T SIM card in your phone, you can remove it and put it into a different GSM phone, like a T-Mobile phone, to transfer all your subscription information over, including your phone number.

What this effectively does is lets you use a T-Mobile phone on the AT&T network.

Such an easy transition is simply not possible with most CDMA phones, even if they do have removable SIM cards. Instead, you typically need your carrier’s permission to perform such a swap.

Since GSM and CDMA are incompatible with one another, you can’t use a Sprint phone on a T-Mobile network, or a Verizon Wireless phone with AT&T.

The same goes for any other mix of device and carrier that you can make out of the CDMA and GSM list from above.

Tip: CDMA phones that use SIM cards do so either because the LTE standard requires it or because the phone has a SIM slot to accept foreign GSM networks. Those carriers, however, still use CDMA technology to store subscriber information.

Simultaneous Voice and Data Usage

Most CDMA networks do not allow voice and data transmissions at the same time. This is why you may get bombarded with emails and other internet notifications when you end a call from a CDMA network like Verizon. The data is basically on pause while you’re on a phone call.

However, you’ll notice that such a scenario works just fine when you’re on a phone call within range of a wifi network because wifi, by definition, isn’t using the carrier’s network.

Cellphone Glossary: What Is GSM vs. EDGE vs. CDMA vs. TDMA?

While selecting the right cell phone service plan at your carrier of choice is a supremely important decision, so is choosing the right cell phone service carrier in the first place. The type of technology the carrier uses makes a difference when you are buying a cell phone.

This article unravels the differences between the GSMEDGECDMA and TDMA cell phone technology standards.


For years, the two major types of mobile phone technologies—CDMA and GSM—have been incompatible competitors. This incompatibility is the reason many AT&T phones won’t work with Verizon service and vice versa.

  • GSM network providers put customer information on a removable SIM card. This makes it easy to switch phones; you just take the SIM card out of your old phone and insert it into your new one. GSM technology is widespread in Europe. Combine that fact with a phone with a removable SIM, and you have a phone you can use on overseas visits with just a SIM change.
  • CDMA phones may or may not have SIM cards, but the user information is stored with the service provider, which must give its permission for you to switch phones. CDMA phones must be programmed with every carrier you use. Whenever you switch carriers, the phone must be reprogrammed for that carrier—even if it is an unlocked phone.

Network Technology Effect on Quality

The quality of the phone service has nothing to do with the technology the provider uses. Quality depends on the network itself and how the provider structures it. There are both good and not-so-good networks with GSM and CDMA technology. You are more likely to run into quality concerns with smaller networks than with the big ones.

What About Unlocked Phones?

Beginning in 2015, all U.S. carriers must unlock their customer’s phones after they fulfill their contract. Even if you decide to have your phone unlocked or to buy a new unlocked phone, it is either a GSM or CDMA phone at heart, and you can only use it with compatible service providers. However, having an unlocked phone gives you are a wider range of service providers to pick from. You aren’t limited to just one.

of 04

What Is GSM?

GSM (Global System for Mobile communications) is the world’s most widely used cellphone technology, popular in both the U.S. and internationally.  Cellphone carriers T-Mobile and AT&T, along with many smaller cellular providers, use GSM for their networks.

GSM is the most popular cellular technology in the U.S., but it is even bigger in other countries. China, Russia, and India all have more GSM phone users than the U.S. It is common for GSM networks to have roaming arrangements with foreign countries, which means GSM phones are good choices for overseas travelers

GSM (pronounced gee-ess-em) is the most popular cell phone standard, and is used internationally, so you’ve probably heard about it in the context of GSM phones and GSM networks, especially when compared to CDMA.

GSM originally stood for Groupe Spécial Mobile but now means Global System for Mobile communications.

According to the GSM Association (GSMA), which represents the interests of the worldwide mobile communications industry, it’s approximated that 80% of the world uses GSM technology when placing wireless calls.

Which Networks Are GSM?

Here’s a quick breakdown of just a few mobile carriers and which use GSM or CDMA:


  • T-Mobile
  • AT&T
  • Indigo Wireless
  • Pine Cellular
  • TerreStar


  • Sprint
  • Verizon Wireless
  • Virgin Mobile


For practical and everyday purposes, GSM offers users wider international roaming capabilities than other US network technologies and can enable a cell phone to be a “world phone.” What’s more, things like easily swapping phones and using data while on a call is supported with GSM networks but not CDMA.

GSM carriers have roaming contracts with other GSM carriers and typically cover rural areas more completely than competing CDMA carriers, and often without roaming charges.

GSM also has the advantage of easily swappable SIM cards. GSM phones use the SIM card to store your (the subscriber’s) information like your phone number and other data that proves you are in fact a subscriber to that carrier.

This means you can put the SIM card into any GSM phone to instantly continue using it on the network with all your previous subscription information (like your number) to make phone calls, text, etc.

With CDMA phones, however, the SIM card does not store such information. Your identity is tied to the CDMA network and not the phone.

This means swapping CDMA SIM cards don’t “activate” the device in the same way. You instead need approval from the carrier before you can activate/swap devices.

For example, if you’re a T-Mobile user, you could use an AT&T phone on the T-Mobile network (or vice versa) so long as you put the T-Mobile phone’s SIM card into the AT&T device. This is super useful if your GSM phone is broken or you want to try out a friend’s phone.

Keep in mind, however, that this is only true for GSM phones on the GSM network. CDMA is not the same.

Something else to consider when comparing CDMA and GSM is that all GSM networks support making phone calls while using data. This means you can be out and about on a phone call but still use your navigation map or browse the internet. Such capability is not supported on most CDMA networks.

See our explanation of CDMA for some other details on the differences between these standards.

More Information on GSM

The origins of GSM can be traced back to 1982 when the Groupe Spécial Mobile (GSM) was created by the European Conference of Postal and Telecommunications Administrations (CEPT) for the purpose of designing a pan-European mobile technology. GSM didn’t begin being used commercially until 1991, where it was built using TDMAtechnology.

GSM provides standard features like phone call encryption, data networking, caller ID, call forwarding, call waiting, SMS, and conferencing.

This cell phone technology works in the 1900 MHz band in the US and the 900 MHz band in Europe and Asia. Data is compressed and digitized, and then sent through a channel with two other data streams, each using their own slot.

of 04

What Is EDGE?

EDGE (Enhanced Data Rates for GSM Evolution) is three times faster than GSM and is built upon GSM. It is designed to accommodate streaming media on mobile devices. AT&T and T-Mobile have EDGE networks.

Other names for EDGE technology include Enhanced GPRS (EGPRS), IMT Single Carrier (IMT-SC) and Enhanced Data Rates for Global Evolution

Any discussion of cellphone technology is filled with acronyms. You may have heard of GSM and CDMA, the two major—and not compatible—types of mobile phone technologies. EDGE (Enhanced Data rates for GSM Evolution) is a speed and latency advancement in GSM technology. GSM, which stands for Global System for Mobile communications, reigns as the world’s most widely used cellphone technology. It is used by AT&T and T-Mobile.

Its competitor, CDMA, is used by Sprint, Virgin Mobile, and Verizon Wireless.

The EDGE Advancement

EDGE is a faster version of GSM—a high-speed 3G technology that was built to the GSM standard.  EDGE networks were designed to deliver multimedia applications such as streaming television, audio, and video to mobile phones at speeds up to 384 Kbps. Although EDGE is three times as fast as GSM, its speed still pales in comparison to standard DSL and high-speed cable access.

The EDGE standard was first launched in the United States in 2003 by Cingular, which is now AT&T, on top of the GSM standard. AT&T, T-Mobile and Rogers Wireless in Canada all use EDGE networks.

Other names for EDGE technology include IMT Single Carrier (IMT-SC), Enhanced GPRS (EGPRS) and Enhanced Data  Rates for Global Evolution.

EDGE Usage and Evolution

The original iPhone, which launched in 2007, is a familiar example of an EDGE-compatible phone.

Since that time, an enhanced version of EDGE has been developed. Evolved EDGE is more than twice as fast as original EDGE technology.

of 04

What Is CDMA?

CDMA (Code Division Multiple Access) competes with GSM. Sprint, Virgin Mobile, and Verizon Wireless use the CDMA technology standard in the U.S, as do other smaller cellular providers.

When 3G CDMA networks, also known as “Evolution Data Optimized” or “EV-DO” networks, first rolled out, they couldn’t transmit data and make voice calls at the same time. In most cases, particularly with cellular providers with a 4G LTE network, that problem has been successfully addressed.

CDMA, which stands for Code Division Multiple Access, is a competing cell phone service technology to GSM, the world’s most widely used cell phone standard.

You’ve probably heard of these acronyms when being told that you can’t use a certain phone on your mobile network because they’re using different technologies that are not compatible with each other. For example, you may have an AT&T phone that can’t be used on Verizon’s network for this very reason.

Which Networks Are CDMA?

Of the five most popular mobile networks, here is a breakdown of which are CDMA and GSM:


  • Sprint
  • Verizon Wireless
  • Virgin Mobile


  • T-Mobile
  • AT&T

More Information on CDMA

CDMA uses a “spread-spectrum” technique whereby electromagnetic energy is spread to allow for a signal with a wider bandwidth. This allows multiple people on multiple cell phones to be “multiplexed” over the same channel to share a bandwidth of frequencies.

With CDMA technology, data and voice packets are separated using codes and then transmitted using a wide frequency range. Since more space is often allocated for data with CDMA, this standard became attractive for 3G high-speed mobile internet use.


Most users probably don’t need to worry about which cell phone network they choose in terms of which technology is better.

However, there are some key differences that we’ll look at here.


While CDMA and GSM compete head on in terms of higher bandwidth speed, GSM has more complete global coverage due to roaming and international roaming contracts.

GSM technology tends to cover rural areas in the U.S. more completely than CDMA.

Device Compatibility and SIM Cards

It’s really easy to swap phones on a GSM network versus CDMA. This is because GSM phones use removable SIM cards to store information about the user on the GSM network, while CDMA phones do not. Instead, CDMA networks use information on the carrier’s server side to verify the same type of data that GSM phones have stored in their SIM cards.

This means that the SIM cards on GSM networks are interchangeable. For instance, if you’re on the AT&T network, and therefore have an AT&T SIM card in your phone, you can remove it and put it into a different GSM phone, like a T-Mobile phone, to transfer all your subscription information over, including your phone number.

What this effectively does is lets you use a T-Mobile phone on the AT&T network.

Such an easy transition is simply not possible with most CDMA phones, even if they do have removable SIM cards. Instead, you typically need your carrier’s permission to perform such a swap.

Since GSM and CDMA are incompatible with one another, you can’t use a Sprint phone on a T-Mobile network, or a Verizon Wireless phone with AT&T.

Tip: CDMA phones that use SIM cards do so either because the LTE standard requires it or because the phone has a SIM slot to accept foreign GSM networks. Those carriers, however, still use CDMA technology to store subscriber information.

Simultaneous Voice and Data Usage

Most CDMA networks do not allow voice and data transmissions at the same time. This is why you may get bombarded with emails and other internet notifications when you end a call from a CDMA network like Verizon. The data is basically on pause while you’re on a phone call.

However, you’ll notice that such a scenario works just fine when you’re on a phone call within range of a wifi network because wifi, by definition, isn’t using the carrier’s network.

of 04

What Is TDMA?

TDMA (Time Division Multiple Access), which predates the more advanced GSM technology standard, has been incorporated into GSM. TDMA, which was a 2G system, is no longer in use by the major U.S. cell phone service carriers


TDMA technology, which stands for Time Division Multiple Access, is a cell phone standard that has been incorporated into the more advanced GSM standard, which is now the world’s most widely used cell phone technology.

TDMA is used in second-generation (2G) cell phone systems such as GSM. Most major third-generation (3G) cell phone systems are primarily based upon GSM rival CDMA. 3G allows for faster data speeds over 2G.

While TDMA and CDMA both achieve the same goal, they do so using different methods. TDMA technology works by dividing each digital cellular channel into three-time slots for the purpose of increasing the amount of data carried.

Multiple users, therefore, can share the same frequency channel without causing interference because the signal is divided into multiple time slots.

While each conversation is transmitted alternately over short lengths of time with TDMA technology, CDMA separates communications by code so multiple calls can also be routed into the same channel.

The major cell phone carriers in the U.S. no longer use TDMA. SprintVirgin Mobile, and Verizon Wireless use CDMA while T-Mobile and AT&T use GSM.



Also Known As:

Time Division Multiple Access


TDMA technology was incorporated into the more advanced GSM standard

America is divided! One faction is powerful and entrenched. The other is respected by the rest of the world, but can’t seem to seize power here. I’m talking, obviously, about our cellphones.

Buying a phone is a tough choice. No wait, scratch that: It’s a tough set of choices, a dozen decisions wrapped into one, made just once every two years. When you decide it’s time to buy, you’ve got to select between operating systems, hardware, and feature lists. Just as importantly, you’ve got to choose a network, with its distinct coverage areas, rate plans and customer service. But built into your choice of network, is yet another dilemma: network technology. GSM or CDMA? These inconspicuous acronyms, which an awful lot of people deem fit to ignore, define the most basic functions of your phone

What, Which, and Who

GSM and CDMA both serve as shorthand for different mobile phone technologies. GSM stands for Global System for Mobile Communications; it’s the world’s most prolific mobile standard (a standard being a set of rules and suggestions about how a mobile network should work). CDMA stands for Code Division Multiple Access—in the context of cellphones and mobile networks, people tend to use it interchangeably to refer to two different mobile standards: CDMAOne or CDMA 2000.

What’s the core difference? It all has to do with the way your data is converted into the radio waves that your cellphone broadcasts and receives. To keep from lulling you to sleep with the deep dive, I’ll just scratch the surface and say that GSM divides the frequency bands into multiple channels so that more than one user can place a call through a tower at the same time; CDMA networks layer digitized calls over one another, and unpack them on the back end with sequence codes.

CDMA was a late response to GSM, and in 1995 this more complex and modern channel access promised better security, fewer dropped calls, and more efficient infrastructure. But that was 1995, when car phones were still regularly spotted on city streets.

IS-95 (CDMA) and GSM(TDMA)

America is unique in that it’s home to more CDMA users than GSM users, with the two largest CDMA carriers accounting for over 43% of the market. The two largest GSM carriers barely break 37%; worldwide, CDMA accounts for around 13% of phones, with GSM and its successor, UMTS making up of the remainder.

Which Acronym Are You?

If you just want to figure out which of these two sets of letters you’re working with, well, that’s easy:

• American CDMA carriers:
Verizon, Sprint and whoever uses their networks (Virgin, Boost, Alltel)

• American GSM carriers:
AT&T and T-Mobile, and whoever uses their networks (Suncom, Pure)

Of course, none of this tells us anything at all about what it means to use networks on either standard. Standards being basically a set of guidelines that participating companies abide by, most of the differences between CDMA and GSM are small details that you’ll never have to concern yourself with: frequency bands, audio codecs, the physical specifications of the network infrastructure, the way a user is linked to a phone, and so on.

But these rules are very important to the AT&Ts, Verizons, Apples, and Samsungs of the world: They outline pretty much every technical aspect of a cellular network, and, to a lesser extent, the phones that are used on it. In the same way that web standards ensure that webpages render properly in our browsers, the GSM and CDMA standards give carriers a set of instructions to (for the most part) follow, and cellphone makers a guide for making devices that’ll work on the world’s wireless networks.

The Differences

Most of us will never have to think about whether or not our phones are CDMA or GSM-based. These acronyms are meant to be transparent, just like so many other tech standards are. (Most HDTV owners don’t really care much if their images are delivered via Component or HDMI cable, nor do most music listeners mind if their music was encoded as a AAC file or an MP3—as long as the quality does not suffer.) But that’s not to say that they aren’t different.

Mildly Useful Network Trivia!

• US Frequency bands
GSM: 850MHz, 1900MHz
CDMA: 850MHz, 1700MHz, 1900MHz
• Audio Sampling/Bitrate
GSM: 8kHz @ 12.2kbps
CDMA: 8kHz @ 8.55kbps
• User ID systems

First, let’s get this out of the way: I’ve been using GSM and CDMA as blanket names for a set of standards that have changed over time. Most new phones on AT&T and T-Mobile actually adhere to both GSM and the newer UMTS (Universal Mobile Telecommunications System) standards. UMTS isn’t an official part of the GSM standard, but it is what GSM carriers use for 3G data transmission. Likewise, CDMA2000, based more directly on its predecessor includes a range of improvements over the original CDMAOne, key among them 3G data speeds. Though both GSM and CDMAOne standards are on their way out, I fully expect their names to live on as shorthands for what comes next. After all, they were the basis of the entire cellular industry as we knew it for decades.

Back in 1995, CDMA was an insurgent standard trying to supplant the dominant GSM, and the differences between the two technologies were more obvious. Old-school, 2G GSM phones worked better inside of buildings (neat trick: If you’re having trouble getting a signal indoors, switch off your 3G), but caused interference in unshielded speakers (side-effect of aforementioned ‘neat’ trick). At the same time, CDMA phones had a slightly more refined method for handing off calls from tower to tower, so they dropped fewer calls. This is still true. It’s also still true that 2G GSM networks can offer better coverage in mountainous terrain, since they utilize taller cell towers, though range of said towers is otherwise a bit shorter. Additionally, GSM (and UMTS) phones can send and receive data packets while making a call, which most CDMA networks still don’t support.

Such were the arguments for and against CDMA when it barged into the scene in 1995, at time when GSM was the only game in town and most people didn’t even own cellphones. So it follows that these original performance differences, which were striking at the time, now don’t matter matter quite so much anymore. If a Droid gets better reception at your house than an iPhone, it’s not because one is a CDMA2000 phone and the other is a GSM/UMTS phone. It’s most likely because Verizon has a tower closer to your pad, and the backhaul to support your calls.

The real differences—the ones that you should care about—are more obvious.

Both GSM and CDMA standards outline a way that phones are identified by carriers. In GSM phones, it’s a removable chip called a SIM card. In theory, you can pop a SIM card out of a GSM phone and stick it in any other GSM phone. (Although a lot of phones are “locked” to a specific carrier, which is majorly annoying.) The CDMA standard describes something similar, called the RUIM (removable user ID module), but that hasn’t really caught on. Instead, CDMA phones ship locked to one network, and can only be switched to another with the cooperation of both the old and new carriers.

This isn’t so important in a place like America, where phones are sold with contracts and discarded with after two years. But it’s a huge deal in the developing world, where phones are sold unlocked, independently of carriers, and need to work with any and all local networks. And even in the first world, sometimes it’s nice to be able to just switch numbers every once in a while. (A local pay-as-you-go SIM saved me a boatload of money on a recent trip overseas.)

And that leads us to the main reason you’ll need to consider when choosing between CDMA vs. GSM: travel. Basically, CDMA phones suck at this. A CDMA-only phone from Verizon or Sprint is only able to roam on other CDMA networks, which simply don’t exist in much of the world. Both carriers offer phones with built-in GSM support just for travelling, but this feature is missing from their most popular handsets.

Subtle as they may be, the outward differences between CDMA and GSM can tell you a lot about your phone, from where you can use it to how well it holds a call on the highway. I’m not saying that you should place more weight on a carrier’s choice of wireless tech standards than its phone choice, customer service or coverage in your area. I’m just saying that you shouldn’t ignore it.

1. Introduction

IS-95, or cdmaOne, and GSM (Global System for Mobile Communication) are two fundamental technologies enabling today’s cellular phone networks. IS-95 and GSM are 2G technologies implemented using CDMA (code division multiple access) and TDMA (time division multiple access) respectively. Approximately 80% of the mobile communications industry uses GSM technology, with IS-95 following at approximately 10-15%. As the market shifts to 3G technologies, GSM is moving towards the implementation of Wideband CDMA (W-CDMA), while the successor of IS-95 is CDMA 2000. The following document gives a technical overview of all these technologies.

Back to Top

2. Strengths and Weaknesses of IS-95(CDMA) and GSM (TDMA)

Both IS-95 and GSM are the most commonly used mobile communication technologies for cellular networks. Given the derivation from different multiple access schemes, both technologies persist with strengths and weaknesses. A summary of these qualities can be seen below in Figure 1. More detail about how CDMA and TDMA are structured and differ will be discussed in the following sections.

Figure 1: IS-95(CDMA) and GSM(TDMA) Summary

Back to Top

3. Technical Specifications

The technologies behind IS-95 and GSM are CDMA and TDMA, respectively. While both CDMA and TDMA use the same overall frequency range, they differ in how that range is divided up. TDMA uses time to divide the spectrum, allowing each communication the entire spectrum over a discrete time period. CDMA however allows every communication to have the entire spectrum all of the time. See Figure 2 below.


Figure 2. TDMA and CDMA Spectrum Division

Back to Top


There are three OSI layers involved with GSM: the physical Layer, the data layer, and signaling protocol layer. The physical layer is implemented with TDMA, using Gaussian Frequency Shift Keying (GFSK) as the modulation scheme. The common frequency range of GSM is in the 850-900 MHz range with channel spacing of 200 kHz. Peak data rates are around 14.4 kbps.

For TDMA, the signal is divided by time using the fundamental unit of a burst period. This burst period lasts approximately 15/26 ms and is grouped together by 8 bursts into a frame.  A single traffic channel is defined by grouping 26 frames together; giving a total timeframe of 120 ms. These traffic channels are used to transfer speech and data.

Additional control channels also exist for the following purposes:

    • Broadcast Control Channel (BCCH) serves for BS identification, broadcasts, and frequency allocations.
    • Frequency Correction Channel (FCCH) and Synchronization Channel (SCH) – used for synchronization, and physical layer definition (time slots, burst time…)
    • Random Access Channel (RACH) used by mobile to request access to the network.
    • Paging Channel (PCH) used for locating the mobile user
    • Access Grant Channel (AGCH) used to obtain a dedicated channel.

The data layer consists of the same protocol used in Integrated Services Digital Network or ISDN. The signaling protocol layer is further subdivided into three categories:

    • Radio Resource Management
    • Mobility Management
    • Connection Management

Back to Top

5. IS-95 (CDMA)

IS-95 consists of a physical layer implemented by CDMA. The modulation scheme commonly used is quadrature-phase shift keying (QPSK). The common frequency bands in the US and Korea are 825-849 MHz with channel spacing of 1.23 MHz. The data transfer rate is 9.6-115 kbps depending on which revision of the technology is being used.

Instead of segregating the spectrum by time, CDMA uses a unique spreading code technique to differentiate the channels. The signal is transmitted below noise level and is received through a correlator for dispreading of the wanted signal. This wanted signal is then processed through a narrow bandpass filter to reject unwanted signals. The codes, one/zero sequences, used to differentiate signals are designed and generated at a much higher rate than the baseband information.  This rate is referred to as a chip rate rather than a bit rate. The relationship between chip rate and bit rate can be seen in Figure 3. The Spread Factor used in CDMA is defined as equation 1.

Figure 3

Equation 1

Back to Top

6. Applications and future Generations (3G)

Applications for IS-95 (CDMA) and GSM (TDMA) include popular cellular phone services. GSM controls a majority of the worldwide services; however CDMA is popular in certain regions such as the US.

Future 3G versions of the technology include IS-2000 which uses CDMA2000 as its physical layer. This incorporates much higher transfer rates than the previous 2G versions. GSM 3G/EDGE technology is being implemented using CDMA, and a special form of W-CDMA. These new physical layers will be competitive with each other and lesser known 3G solutions in regards to data transfer rates and spectral efficiency.

IS-2000 (CDMA 2000)

There are several varieties of CDMA 2000 ranging from hybrid 2.5G technologies to full on 3G solutions. These variations include but are not limited to 1xRTT and EVDO. It is defined to operate at 450, 700, 800, 900, 1700, 1800, 1900, and 2100 MHz.

The 1xRTT variant of CDMA 2000 is defined to operate within the same radio bandwidth of the 2G IS-95. It improves upon the traditional IS-95 technology by adding 64 additional traffic channels. These new channels are orthogonal to the original 64 channels, doubling the capacity of the technology. A variation of 1xRTT is 3xRTT which triples the channel width from 1.25 MHz to 3.75 MHz in addition to the 64 new channels.

EVDO, or Evolution-Data Optimized, is an enhanced version of CDMA 2000 designed to provide higher data transfer rates. The EVDO channel is exactly the same spectral width as traditional IS-95 or IS-2000 channels. The difference lies in the time-based multiplexing of the tower to mobile device link. This forward link is split up into 1.667 ms long divisions, allowing each mobile device full access to the spectrum over the given time with independent modulation. These modulation schemes are determined by the quality of the mobile device’s current RF environment. The schemes can range from using QPSK, 8-PSK, and 16-QAM given multi-path and fade restrictions, where QPSK provides the lower end of data transfer speeds, and 16-QAM is used for the highest quality and speeds.


The third generation of GSM is also known as UMTS, or Universal Mobile Telecommunications System. Like IS-95 and its successor IS-2000, the underlying physical layer of UMTS is based on the concept of CDMA. More specifically, the most common form of CDMA used is W-CDMA or Wideband CDMA. W-CDMA makes use of channels with 5 MHz bandwidth and a chip rate of 3.84 Mcps. Data transfer rates of 2Mbps can be achieved, with further increases to 14.4 Mbps after the implementation of HSDPA.

The core frequencies for UMTS include 1920-1980 and 2110-2170 MHz using Frequency Division Duplex and W-CDMA as well as 1900-1920 and 2010-2025 MHz using Time Division Duplex and TDMA or CDMA. Additional spectrum regions include 1980-2010 and 2170-2200 MHz which are used primarily for satellite uplink and downlink. Spreading codes used in W-CDMA are Orthogonal Variable Spreading Factor (OVSF) codes, which remain orthogonal in order to allow multiple users without mutual interference. A second stage of spreading is accomplished using a pseudo-random number (PN) code to help differentiate between the signals.

Back to Top

7. National Instruments Hardware for IS-95 (CDMA) and GSM (TDMA)

The current generation of NI RF hardware (566x, 567x) reaches up to 2.7 GHz with a 20 MHz of bandwidth.  In combination with the LabVIEW Modulation Toolkit you can generate and analyze the physical modulation schemes required to implement CDMA and TDMA.


Back to Top

8. CDMA and GSM (TDMA) Software Solutions



Anyone with cell phone service in the United States knows that there are four major wireless carriers. Usually, the typical concerns for consumers regarding that service are low prices, great coverage and quality and selection of smartphones. However, there is another aspect of mobile network providers: a choice between a GSM or CDMA network. If you have been with more than one carrier, you may have come across the issue of different network technologies preventing you from using your old phone. Many people don’t know the difference between the two. Here is all the information regarding GSM vs CDMA networks and what it means for consumers.

What is GSM?

GSM is the most common technology standard for mobile communications throughout the world. It stands for “Global System for Mobile Communication” and is especially prevalent in Europe and Asia and is available in more than 210 countries across the globe. In general, GSM technology runs on four frequency bands of 900 MHz and 1800 MHz in Europe and Asia and 850 MHz and 1900 MHz in North and South America. In 1987, an international organization called the GSM Association was founded for the purposes of developing and overseeing the expansion of the GSM wireless standard.

In addition, there is a specific variant that GSM technology used known as TDMA or time division multiple access. It helps to divide the GSM frequency bands into a variety of channels. GSM technology allows a mobile phone user’s voice to be transformed into digital data that is designated to a specific time slot and channel thanks to TDMA. At the other end of a phone call, the receiver can only listen to that time slot with the call being pieced together. In other words, there is a break within the time division that occurs, but it happens in such a minute amount of time that the receiver doesn’t even notice it. You can compare GSM cell phone plans using Wirefly’s comparison tool.

What is CDMA?

CDMA technology was developed and patented by Qualcomm, a famous chip maker. It stands for code division multiple access and is used for the standards of 3G that include CDMA2000 and WCDMA. It is proprietary in nature, which has resulted in the technology not being adopted globally in the manner in which GSM has seen. At this point in time, fewer than 18 percent of wireless networks around the world use CDMA technology. It is mostly found in the US within two of the four major wireless carriers, Sprint and Verizon Wireless. There are other countries that also use it, specifically Japan, South Korea and Russia.

The way CDMA networks perform is that calls digitalized over one another and a unique code is given to each for the purposes of differentiating them. Each set of data for every call is given a different key and calls are transmitted simultaneously. When someone makes a call using a CDMA phone on a CDMA network, the receiver will also get a unique key so that the combined signal can be split apart into an individual call. You can compare CDMA cell phone plans using Wirefly’s comparison tool.

Differences Between GSM and CDMA Technology

Both GSM and CDMA standards get multiple access, meaning that a large number of calls can go through a single cell phone tower. However, the one chief difference between the two standards involves the way the data is transformed through the radio waves a smartphone receives and broadcasts. Of course, there are a variety of reasons why you might want to opt for one technology standard over the other. Here are the most practical reasons why you would choose GSM over CDMA or vice versa:

SIM Cards

Previously, before 4G LTE connectivity was created, the one big difference between GSM and CDMA phones had everything to do with SIM cards. GSM phones always included a SIM card slot and CDMA cell phones lacked them. In general, this means that CDMA is a standard for handsets, along with a phone number assigned for a particular phone. If a user wished to upgrade to a new cell phone, it meant contacting the carrier through its customer service line and having their old phone deactivated. The new phone had to be activated through the wireless carrier. However, with GSM cell phones, the phone number is assigned to the SIM card instead of the phone. In other words, if you want to get a new device, the only thing necessary is to remove your SIM card from your old phone and put it into the new one. The only exception to this rule is if you decide to switch to a different carrier. For example, if you were an AT&T customer and had a phone locked to the carrier but left to join T-Mobile and your old phone is locked to AT&T, you would not be able to use it on your new carrier.

Network Coverage

The coverage offered by a wireless carrier doesn’t depend on the standard it uses but on the infrastructure it has built. GSM networks are more popular overall, but in the US, Verizon has the greatest number of subscribers.

International Roaming: GSM has the advantage when it comes to international roaming. Because it is the dominant standard globally, if you have a GSM phone that is unlocked, you can use it with any SIM card in any country that uses GSM technology. That means if you are a frequent traveler, being on a GSM network with an unlocked smartphone allows you to buy a SIM card wherever you are and pop it in to use your phone in that country.

The current standard of LTE and the emergence of LTE-Advanced means it definitely matters whether you use a GSM or CDMA network. Many of the latest CDMA phones are now equipped with SIM card slots so that they can get 4G LTE. Generally, both standards are excellent for voice calls, but when you choose a carrier, you have to consider other aspects as well.

Most cell phone owners around the world only have to worry about a single carrier technology. It’s called the Global System for Mobile Communications, or GSM for short. As its name implies, this standard was developed for, and has been adopted by, almost the entire globe as the way to communicate via cellular calls.

But not everyone has jumped on the GSM train. An alternative cellular standard known as Code Division Multiple Access, or CDMA, is used by many carriers around the world. It is most popular in the United States and Russia. However, it’s also used in some Asian and African countries, often alongside competing GSM carriers.

Here’s what cell phone users stuck on choosing between them should know before purchasing a phone.

GSM vs. CDMA: What’s Better?

This the first question many potential owners ask, and it makes sense, but in this case there’s no easy answer to that question.

GSM and CDMA are different ways to accomplish the same goal. The fact that extremely popular networks are built on each simply proves that it’s the quality of the network, not the standard, which is important. For instance, in the United States, two of the four major carriers (Verizon and Sprint) use CDMA while the other two (AT&T and T-Mobile) use GSM.

Technically, neither is the better in terms of quality, but there are some things here for your consideration. GSM phones are able to be unlocked and moved between carriers, but CDMA phones are often locked to a single carrier and unable to be transferred.

Additionally, most phones only come in GSM or CDMA models, so your choice of phone could determine which standard you end up using. It all depends on which carriers are available to you in your area. Some areas may be better covered by GSM-providers, while CDMA-providers will have better coverage in other areas. (Rubbish cell-coverage? Here’s some effective ways to boost your signal!)

Which Phones Support Which?

Many phones are compatible with either GSM or CDMA, but not both. For CDMA phones, you will need to buy a phone made for your specific carrier. The easiest way to do this is buy directly from your carrier. For example, if you want an iPhone on Verizon, you need to buy a Verizon-branded iPhone — not a Sprint- or AT&T-branded iPhone — because it has the specific bands and compatibility with Verizon. However, if you ever want to leave Verizon, you won’t be able to take your phone with you; it is locked to that carrier.

If you don’t want to be trapped with one carrier, however, you can also look for unlocked GSM phones from third-party retailers. These phones will work with any GSM carrier simply by popping in your SIM card. For example, Amazon sells tons of unlocked GSM phones, while Google sells their Nexus 5, Pixel, and a couple of Google Play Edition phones unlocked. Any retail or online store dealing in cellular phones should provide information regarding the networks a phone works with.

Check Compatibility

You must be careful when examining a phone’s network compatibility, though. Phones sold in markets that service both standards often come in a GSM version or a CDMA version, but only a few phones are compatible with both. If you buy a CDMA phone from a third-party retailer, you’ll need to call your carrier to have it activated. If you buy a GSM phone, you’ll need to purchase a SIM card to put into your phone that will activate your phone’s network capabilities.

Owners of CDMA phones don’t need to worry about SIM cards, but this is more a curse than a blessing. CDMA phones bake in compatibility restrictions that are difficult to get around, while GSM owners can simply take out their SIM and replace it with one from another carrier. Most CDMA networks do not allow the use of a phone originally purchased from another carrier even if the phone is otherwise technically compatible. This is an important restriction to remember when going with a CDMA network. If you decide to switch networks later you’ll likely need to buy a new phone even if the network you’re switching to also uses CDMA.

LTE is a new standard that’s come into vogue over the last few years. Though based on the principles of GSM, LTE is its own separate standard that operates apart from existing GSM and CDMA networks — it’s the real fourth generation of cellular data.

The highest adoption of LTE can be found in South Korea, where it commands the majority of the market. However, it is also popular in Japan, Australia, Sweden, and the United States. So far it’s used primarily for data, but standards have been drawn up for using LTE as a replacement to traditional cellular networks. Verizon Wireless in the US, for example, has announced its plan to roll out LTE-only phones in late 2014.

This standard uses a SIM card, so users can switch networks by replacing the SIM if the phone is compatible with the new network. With that said, at this time phones that use LTE generally use it only for data, but not for voice. This means CDMA/LTE phone owners are still locked into a network. That will change as carriers like Verizon move to LTE-only networks, but this process could take many years.

Global Adoption

While it has the potential to be a global standard, there are some obstacles in the way. Outside of South Korea there’s no market where LTE’s reach is more than a quarter of the services available. South Korea in general, and Verizon Wireless in the US, are exceptions to the rule; in most markets, even carriers that offer LTE only offer it in a slim selection of the total area they cover.

And then there’s the problem of spectrum. Remember how GSM/CDMA operates on many different bands? The same is true of LTE. You need to check that the compatibility of your phone matches the frequency band supported by your carrier. You won’t be able to use an LTE phone on other networks with the same standard, but a different frequency band. It’s unclear at this point if this standard will ever become “global” in the same way as GSM, which settled on a core of four frequencies across the world that are supported by most GSM phones.

And before you know it, the next global communication standard — 5G — will be upon us.

Wrapping It Up

Take a deep breath; it’s time to review this buffet of confusing information.

First, neither GSM or CDMA is technically better; they ultimately provide the same service and the quality of a network depends on the carrier, not the cellular standard used.

Second, GSM phones can be unlocked and switch carriers, whereas CDMA phones are locked to a carrier. It’s usually cheaper to buy unlocked GSM phones than on-contract CDMA phones.

Third, you need to check what bands your chosen phone supports carefully. Most either work on GSM or CDMA, and both standards offer multiple frequencies that differ across the globe.

Finally, LTE is being rolled out as a global standard. Unfortunately, it falls victim to even more frequency division than GSM and CDMA. The technology also suffers from limited adoption because it’s relatively new.

Hopefully this has cleared up any questions you had. Cellular services are undergoing constant evolution and the standards commonly supported by phones can change from year to year.

Are you gazumped by GSM? Confused by CDMA? Feel free to leave your questions and comments below, and we’ll try and answer your questions!

Nowadays, we seem to use our mobile phones for connecting to the Internet and other online services more than we use them for actually making phone calls.

Sadly, the quality of the Internet service you receive can vary significantly. For example, some countries have more advanced telecom networks than others. Remote areas of wilderness will not necessarily have the same quality of coverage as big cities.

And even something as simple as being indoors can have a significant effect.

Your smartphone lets you know the strength of your mobile Internet coverage by using an alphanumeric code near the signal bar. If you’ve ever noticed something like E, 3G, or H on the notification bar, you’ll know what we are talking about.

But what do all those codes mean? Keep reading to find out so you’re never confused or caught off guard.


Let’s work through these from slowest to fastest.

2G was first launched way back in 1991 and was the technology that ultimately allowed data services such as SMS and MMS to become prolific on mobile phones later in the decade.

It also signified the first time that radio signals became digital rather than analog (1G), thus providing greater spectrum efficiency and helping mobile phones with market penetration.

It only has a maximum speed of 50 kilobits per second, and in large parts of Europe and North America, the 2G networks are now being turned off. Despite that, it is still the network of choice in vast swathes of the developing world.


G is short for General Packet Radio Service (or GPRS). It started to become widely used in 2000 and earned the unofficial nickname of 2.5G. It is considered to be the first major stepping stone on the way to developing the now ubiquitous 3G networks.

It was the first “always on” mobile internet network, but it can only transfer data up to amaximum speed of 114 kilobits per second, which makes it the slowest connection that you’re likely to come across these days.

That speed means that although the network can support instant messaging services such as WhatsApp, apps and webpages that are more complex will either timeout, malfunction, or in the best of cases, load extremely slowly. (Certainly more slowly than is practical, and it’d probably drive you nuts.)


The letter E represents the Enhanced Data rates for GSM Evolution (or EDGE) network. The network started to spread in popularity some time in 2003 by offering speeds that were almost three times faster than any of its predecessors.

It supports a maximum speed of 217 kilobits per second, so even though it’s significantly faster than G network speeds, you’ll still struggle to browse a modern website or watch YouTube videos in anything but the lowest resolutions.

That being said, there are now 604 EDGE networks in 213 countries, making it one of the most widely-used mobile Internet technologies in the world. It was the final widely-used network before 3G came into prominence, so it’s often referred to as 2.75G.


3G technology is actually a lot older than many people realize. The first commercial network was launched in Japan in October 2001, Norway followed suit in December 2001, and most of Europe and South East Asia was online by early 2002. The first 3G network in the United States was Verizon Wireless and went live in July 2002.

The 3G network is based on Universal Mobile Telecommunication Service (UMTS) standards rather than any of its three predecessors mentioned above (GSM, GPRS, and EDGE).


It was the first network that was fast enough to support mobile Internet browsing as we know it today, and thanks to its maximum speed of 384 kilobits per second, it’s more than adequate for streaming music and even some videos.

It is probably the most well-known of all the mobile Internet networks thanks to its widespread usage and the development of the smartphone. Today you’ll find 3G technology in everything from wireless voice telephones to mobile television.

An H symbol means that you have High Speed Packet Access (HSPA) connectivity. The HSPA standard is based on the same technology as 3G but replaces 3G’s UMTS standard, resulting in a maximum speed of 7.2 Megabits per second.

It can comfortably handle YouTube videos, Spotify streaming, Web browsing, and other app usage. It is not good enough, however, to support movie downloads or large torrent files — they would still take a very long time. Worldwide adoption began in 2010, and it’s now available in most developed countries.


H+ refers to Evolved High Speed Packet Access (HSPA+). There are five releases of this technology, each of which provides significantly greater download speeds than the previous version.

Release 6 brought a maximum speed of 14.4 Megabits per second, Release 7 upped that to 21.1 Megabits per second, Release 8 increased it further to 42.2 Megabits per second, Release 9 took it to 84.4 Megabits per second, before it topped out with Release 10 at a maximum speed of 168.8 Megabits per second.

As you can see, the technology evolved very quickly here, but it’s important to remember that one will rarely see these speeds during normal usage. This is the fastest form of connectivity that most people can get right now since global 4G networks are still limited in availability.


Do you see 4G in your notification bar? If so, give yourself a pat on the back, you are one of the lucky few who has access to the latest and greatest mobile network!

The first public 4G networks in the world came online in Stockholm and Oslo in 2009, and other countries slowly joined them in following years. In the U.K., the nationwide rollout occurred in 2014, while in the U.S., most of the largest cities now have the network.

Most of these networks use the Long Term Evolution (LTE) standard, though some — including Sprint in the U.S. — are using the less-common Worldwide Interoperability for Microwave Access (WiMAX) standard. In Europe and North America, most carriers will be dropping WiMAX by the end of 2017.

For the end user, the differences between the two are negligible. The biggest shortcoming of WiMAX is that not enough carriers adopted it to make it viable, thus making LTE the de facto standard. Why did carriers choose against WiMAX adoption?

  • WiMAX networks don’t support legacy systems like 2G and 3G, while LTE is compatible and enables co-existence and easier roaming.
  • LTE has a higher maximum speed, especially as the next-gen LTE-A starts to rollout.
  • LTE draws less battery power on a handset.

Speeds on 4G will soon be able to go as high as 1 Gigabit per second. And for the record, rumors suggest that when 5G eventually arrives, it will be able to support speeds up to 1 Terabit per second!

Still Confused? Check This Chart!

If you’re still confused, or if you feel overwhelmed by everything above, the chart below will tell you everything you need to know about the speeds and standards you can expect from each type of network.


Looking at the speeds on that chart, it really is incredible how far we’ve come in the last 15 years. It would have been impossible to imagine Gigabit speeds back in 2000 — but isn’t that the way with so much of the tech world these days?

Who knows where we might be in another 15 years. Assuming we are up to 7G or 8G by then, we’ll probably be enjoying several Terabits per second. No more pixelated YouTube videos!

What speeds are you currently getting in your hometown? Are you blessed with 4G or are you lumbering along on EDGE? Let us know your experiences in the comments section below.

The mobile industry is beginning to experiment with new 5G data technology, and the results are mind-blowing. Some early tests have achieved 1 Terabit per second (Tbps) speeds — enough to download 10 full-length feature films in under a second. Seriously.

Fifth generation mobile data networks will eventually replace our current 4G technology, which operates at a comparatively slower 15 Mbps. It’s expected to revolutionize mobile technology as well as the Internet of Things (IoT), and it’s just five years away.

Why 5G?

Mobile data use is expected to blow up over the next few years. From smartphones and tablets to connected cars and smart home devices, there will be more things connected to the Internet than ever before. Our current 4G networks won’t be able to support the Internet of Things at scale. 5G, on the other hand, could theoretically manage connections for 7 trillion devices — meaning everyone on Earth would have to have around 1,000 connected devices to overload the network.

Beyond that, 5G networks will be more energy efficient, saving up to 90% power consumption compared to current systems.

And yes, it will be fast. If speed is your concern, in just a few years you may be inclined choose a wireless 5G connection over a wired connection. We’re talking about something thousands of times faster than anything currently available wirelessly.

“We have developed 10 more breakthrough technologies and one of them means we can exceed 1Tbps wirelessly,” Professor Rahim Tafazolli, director of 5GICtold V3. “This is the same capacity as fiber optics but we are doing it wirelessly.”

To be fair, these speeds were achieved in a test environment over a distance of 100 meters — so it’s unclear precisely how much of that performance will scale. However, it’s safe to say that it will be much faster than anything we’ve used before.

The Technology

The next-generation networks will utilize multiple input multiple output (MiMo) technology, which utilizes a set of small antennae to manage each individual data stream. Each user is served by a separate antenna, which alleviates the problem of cluttering the available radio spectrum with many competing devices: each antenna will talk to only one device.

In the past, obstacles and distance have caused problems for wireless connectivity. But the FCC and major industry players have found hope in a high-energy spectrum colloquially known as “millimeter waves,” due to their high frequency. In the 24 gigahertz range, signals could be effectively bounced around obstacles.

Potential Hurdles

The industry has a few hurdles to overcome if it wants to make 5G tech a reality.

One such issue is the availability of spectrum. The amount of spectrum allocated to 5G will determine the speed of future networks based on the technology. For 5G networks to reach the speeds that proponents are promising, operators will need significantly more bandwidth. According to Computerworld, the World Radiocommunication Conference in Geneva this November will be the first step to solving that problem. Operators hope the conference, organized by the International Telecommunications Union, will set aside spectrum for 5G, enabling the next-generation service.

It’s also imperative that 5G networks be developed to be more inclusive than previous protocols. For example, 4G wasn’t developed to handle the types of traffic that it handles today. With the growing popularity of wearable techsmart home devices, and Internet-connected vehicles, the industry has had to adjust the technology to optimize it for a variety of new applications. With 5G, the goal is to be all-inclusive and ready for everything from day one.

“You don’t want to be too late to understand that some part of the network is breaking down when all the cars in Germany are depending on it,” said Eric Kuisch, technology director at Vodafone Germany. Professor Rahim Tafazolli, director of the 5G Innovation Centre at U of Surrey, concurs:

“An important aspect of 5G is how it will support applications in the future. We don’t know what applications will be in use by 2020, or 2030 or 2040 for that matter, but we know they will be highly sensitive to latency […] We need to bring end-to-end latency down to below one millisecond so that it can enable new technologies and applications that would just not be possible with 4G.”

With everything from gaming to connected cars depending on 5G, near-zero latency will be a must.  That kind of performance would even enable wireless virtual reality glasses that stream experiences directly from your PC, without nauseating latency.

Are You Ready?

The applications of 5G technology are endless. It’s going to shake up the telecom industry and enable all sorts of new innovation.  Are you excited about 5G networks? What applications do you see for such high-speed and low-latency connections? Let us know your thoughts in the comments below!

Never Buy a Phone From Your Carrier! Buy Unlocked Phones and Save Hundreds

Did you know it’s much cheaper to buy unlocked phones? Big cell companies sell contract phones at a tremendous markup, disguising their overpricing through subterfuge: The true price of the phone gets rolled into your monthly cellular bill.

Never buy a smartphone from a carrier — ever. Most consumers don’t know that they can purchase contract-free phones. Unlocked phones can work with MVNO plans, with plans costing half that charged by major carriers.

The six phones presented in this article provide excellent value. The prices start at $20 and run as high as $650. However, if you are looking to sign a contract with a carrier (and I strongly suggest that you do not), check out Riley Dennis’s list of the best Android smartphones — she’s absolutelycorrect. However, if you need reasons to dump your carrier and hook up with an MVNO, read about it here.

Two Kinds of Phones

As I’ve mentioned before, there exist two kinds of unlocked phones—those that work with GSM networks and those that work with CDMA. Other cellular technologies exist, but they’re not entirely mainstream and are largely based on the ubiquitous GSM standard. Also, a rare number of phones work on both GSM and CDMA networks, such as the Google Pixel.

CDMA: CDMA technology semi-locks phones into a single network, so while these phones can unlock, there are all kinds of hassles in transferring them between carriers. For GSM phones, however, phones can migrate to another network by simply changing the SIM card. Note, though, that many CDMA phones do not use SIM cards.

  • In the US: Verizon Wireless, Sprint Nextel, MetroPCS, and US Cellular.
  • In Japan: DoCoMo.

GSM: Internationally, GSM remains the dominant cell technology. CDMA does exist in almost all markets, although it’s generally associated with third tier carriers. It’s only in the US that it possesses the lion’s share of the market. Consequently, most dual-SIM international phones are GSM based.

  • In the US: T-Mobile and AT&T.
  • In India: Airtel, Reliance Communications, and Idea Cellular
  • In the United Kingdom: O2, EE, and Vodafone

The phones presented in this article are specifically labeled with the correct network that they function on. When purchasing a phone, always make sure you’re buying the right model for your network. If you’re switching to an MVNO, the MVNO will correspond with a particular network—for example, Airvoice Wireless (which rents spectrum from AT&T) only works with GSM phones. MVNOs cost very little per month. Oftentimes, you can save between $20 and $100 per month.


I use three factors in determining the phone’s final grade: First, the best features of the phone are weighed. Second, the worst features of the phone are weighed. Third, I divide the price of the device by the aggregated consumer feedback scores from Amazon, Newegg or other smartphone review websites (whichever was available). The final result shows how much you pay per star of rating. This measure isn’t intended as a serious metric, although it should indicate better overall value, rather than raw performance.

Technically the BLU Tank 2 T193 is a dumbphone with limited smart capabilities. You might call it a semi-smartphone. I consider it among the best phones for the elderly as it doesn’t require interacting with a touchscreen and the features are limited to the essentials. On top of that, its battery life is ridiculously long, so it makes the perfect gift for someone with failing memory.

Networks: GSM


  • Amazing battery life
  • Super low cost
  • Small size; easy to carry around
  • Physical buttons make it easy for the elderly to use


  • Limited feature set; lack of apps
  • Tiny screen

Per star rating: $21 / 3.8 stars = $6 per star

Since the article was published, Blu has released a new version of their phones, the BLU Tank 3.

BLU Advance 5.5 HD is the lowest priced Android 6.0 smartphone you can buy unlocked, anywhereBLU made a name for itself by reselling China-based Gionee smartphones in the United States. Their phones generally emphasize value over performance.

Networks: GSM


  • Lowest priced, unlocked Android phone with Marshmallow (Android 6.0)
  • Dual SIM for international travelers
  • Good performance, particularly for the money
  • Great value and lowest total price for a brand-new smartphone
  • microSD card support


  • Won’t ever receive a firmware update
  • Weak support from chipset vendor
  • Average battery life

Per star rating: $90/3.7 stars = $24 per star

Startup NextBit released the Robin to widespread cheers. It managed to squeeze modern smartphone guts into an inexpensive package totaling less than $165. It comes with all the bells and whistles that you need, including 802.11ac wireless connectivity, 32GB of storage, and the Snapdragon 808 processor. Overall, you get a lot for your money. Some shortcomings include a plastic frame prone to warping, and average battery life.

In all honesty, this is the phone that I would have purchased had Google not tricked me into buying the Pixel XL.

Networks: GSM


  • Elegant and sleek design
  • Modern smartphone guts
  • Excellent hardware (particularly for the money)
  • Best value out of all smartphones on today’s market


  • Snapdragon 808 processor runs a little warm
  • Battery life is average
  • No microSD card support

Per star rating: $174.94 / 2.8 stars = $62 per star


Motorola Moto Z Play

The Motorola Moto Z offers a high powered processor, modularity (what’s a modular smartphone?), and overall outstanding performance. Motorola’s Moto Mods program allows consumers to add a high powered camera, projector, or speaker to their device. The extensibility also adds additional battery life.

Networks: GSM


  • Excellent features, including gesture support and voice recognition
  • Uses one of the fastest processors on smartphones
  • Modular design enables long battery life via Moto Mods


Per star rating: $400 / 4.5 stars = $89 per star

Apple created the smartphone market. The iPhone 7 offers one of the fastest and most reliable handsets around. But beware: Apple produced two models of iPhone! One is for CDMA carriers(Verizon and Sprint) and one for GSM carriers. Fortunately, an unlocked iPhone includes both CDMA and GSM compatibility. iPhone 7s sold on contract through either T-Mobile or AT&T won’t be able to function on Sprint or Verizon networks.

Networks: GSM and CDMA (with restrictions, see above)


  • Latest, state-of-the-art product from Apple
  • Cutting edge features
  • iOS, if you are locked into the Apple app ecosystem
  • Water resistance


  • Expensive
  • Fewer features compared to Android
  • Unlocked model is substantially better than GSM-only model

Per star rating: $650/4.3 stars = $151 per star

Save Money By Switching To An MVNO: 4 Requirements You Must Know

In the United States and Canada, getting ripped off doesn’t take any effort, just a signature. When you sign a contract for cellular service, you also sign away your freedom. Carriers scam customers by offering cheap phones combined with bloated monthly payments. Saving money, conversely, takes a small amount of work.

What may shock readers: You don’t need to sign a contract to get cellular service. Companies, known as MVNOs, offer the same service as the big four network providers, without contracts at all. Switching over to an MVNO doesn’t require much effort, either. However, a few barriers to entry might prevent many from dumping the big carriers and switching over.

This article details four requirements for those seeking to switch to MVNOs: Unlocked phonescontractscovered regions and following directions.

MVNO Requirements

Like everything worth doing, it takes a little bit of effort to start saving. It works like this: MVNOs are cellular companies that rent broadcast spectrum in volume from the big four networks, and resell it to consumers at a substantial discount. Before getting started, you must meet four pre-requirements:

  1. Own an unlocked mobile phone;
  2. Not be on contract with a cellular carrier (Ting pays 25% of your Early Termination Fees);
  3. Live in a region covered by a cellular network;
  4. A willingness to follow directions without a lot of hand-holding.

Own an Unlocked Phone

If you buy or own an unlocked phone, keep in mind that it must broadcast on the same frequencies as the MVNO and it must not be carrier-locked.

Unlocked Phones

You can either unlock your current phone by completing your contract and contacting your carrier or by buying an unlocked device, such as the Nexus 5 (our review of the Nexus 5).

The two major differences between a locked and an unlocked phone are simple:

First, you pay the full price for an unlocked phone. For example, the Nexus 5 (the cheapest flagship phone you can buy) costs $349-399. For comparison, a locked phone comes directly from a carrier and will only work on a single network, at least until you fulfill the terms of your contract. Locked devices include “subsidies” meaning they’re cheap at the point of sale, but come with contracts and bloated monthly payments. You actually pay more in the long-run for subsidized, locked devices than you do for unlocked ones.

Second, locked devices can switch over to any network, provided it uses a compatible technology. Most unlocked phones work on GSM networks, although some (like the Nexus 5 and iPhone 4) can work on both CDMA (Sprint/Verizon) or GSM (AT&T/T-Mobile).

Broadcast Frequencies

Before signing up for an MVNO, you need to own a phone capable of operating on your MVNO’s network. A simple rule to remember about unlocked smartphones is that their data capabilities function best on the network they’ve originated from. For example, a Verizon phone works on Verizon-based MVNOs, such as PagePlus Wireless. However, T-Mobile and AT&T phones using the GSM standard are interoperable with one another’s networks.

Also, MVNOs broadcast on the same frequencies as the network they’re based on. For example, AirVoice Wireless broadcasts on AT&T’s GSM frequencies of 850/1900 (measured in MHz) and UMTS frequencies of 850/1900. Ptel broadcasts on T-Mobile’s GSM (850/1900) and UMTS (1700/1900). For this reason, if you have an older phone from a particular network, it’s easier to move that device onto an MVNO that rents spectrum from a network that your phone originated from.

LTE frequencies possess a bit more complexity. Some MVNOs don’t offer it while others do. Ultimately, whether or not you can get LTE depends on three factors: (1) whether it’s offered by your MVNO, (2) whether it’s offered by the network in your area and, (3) whether your phone supports the LTE frequency on that particular network.

You may find a list of MVNOs, with their corresponding network, on Wikipedia.

Not Be on Contract

Once you sign a contract with a carrier, they own you. The cheap price of a phone on contract disguises the outrageous monthly payments charged by carriers. The simple math, unfortunately, adds up to hundreds more a year, compared to what MVNOs charge.

Look at it this way: What costs more — a $350 phone and payments of $45 a month or a $200 phone and payments of $80-100 per month? If you’re on contract, don’t do anything that extends your contract, especially don’t buy a new phone. And if you’re off-contract, consider switching over as soon as possible.

Regions Covered by MVNOs

Each MVNOs comes associated with a major network. For example, Ting uses the Sprint network. On the other hand, perennial favorite Straight Talk uses all four networks. Each network remains separate from one another. To choose an MVNO, make sure your region has coverage.

First, pick an MVNOs that has a plan fitting your needs. There are many. Second, make sure the network covers the region where you live. Most MVNOs offer ZIP-code lookup tool, to verify that you will receive access.

Very Little Handholding

I’ll hold your hand, if it comes down to it, but if you run into problems, you will need to do your own configuration and troubleshooting setup. Two of the biggest problems that MVNO uses encounter are SIM card size mismatches and APN settings.

SIM Card Sizes

For those of you coming from T-Mobile or AT&T, you already know what a SIM card does. For Verizon or Sprint customers, you won’t be able to use your phone on any network other than one based on Verizon or Sprint. AT&T and T-Mobile phones can simply swap out SIM cards to change networks between T-Mobile or AT&T.

SIM cards are a GSM technology. They come in varying sizes: miniSIM, microSIM and nanoSIM. Some MVNOs only offer SIM cards in one size, the most popular being miniSIM. Unfortunately, newer phones often require the smaller sized microSIM and nanoSIM cards. Adapters can convert microSIM into miniSIM and miniSIM can be cut down to fit into a microSIM (or nanoSIM) form factor.

APN Settings

Non-functional data connections remains a common issue encountered with data-enabled smartphones. Fortunately, by reconfiguring your phone’s APN settings, you can establish proper data connectivity with the MVNO network. The process doesn’t take much effort, either.


Don’t sign contracts with cellular companies. They may offer marked down prices on phones, but you will pay for this in the long-run. Most users end up shelling out hundreds more than had they purchased an unlocked phone. Unfortunately, not everyone can make the switch. If you own a locked device, signed a contract, live in a region without cellular coverage or can’t follow simple directions, MVNOs aren’t for you. For everyone else, they will save substantial amounts of money.

Image Credits: Phone via MorgueFileHand Holding via MorgueFilePhone via MorgueFile

The struggle with SIM cards can be an annoyance when upgrading to a new cell phone or reverting to a backup. Haven’t we come far enough with technology that such a thing shouldn’t matter anymore? What is a SIM card and why is it so important? Is there a way to use a mobile phone without requiring one? Keep reading to find out.

What Are SIM Cards?

In the world of mobile phones, there are two primary phone types that are available to consumers: GSM (Global System for Mobile) and CDMA (Code Division Multiple Access). GSM phones are the ones that utilize SIM cards while CDMA phones do not.

SIM cards are the small cards which contains a chip that must be inserted into GSM phones before they will work. Without a SIM card, a GSM phone won’t be able to tap into any mobile network. The card is what holds all of the critical information.

For comparison sake, CDMA carriers keep a list of all phones that are allowed to use their network. Phones are tracked by their ESN (electronic serial number) so they do not require SIM cards. Once activated, a CDMA phone is tied directly to that particular carrier’s network.

In the United States, most mobile carriers provide CDMA phones. The two exceptions are AT&Tand T-Mobile, who both provide GSM phones. Internationally, GSM is the more popular technology by a landslide. Why? Mostly due to legislature and industry influence that nudged providers towards using GSM.

How Do SIM Cards Work?

What sort of information does a SIM card hold? The most important bits of data include the IMSI (International Mobile Subscriber Identity) and the authentication key that validates the IMSI. This authentication key is provided by the carrier. If you’re interested in the nitty-gritty, SIM authentication goes like this:

  • On startup, the phone obtains the IMSI from the SIM card and relays it to the network. Think of this as the “request for access.”
  • The network takes the IMSI and looks in its internal database for that IMSI’s known authentication key.
  • The network generates a random number, A, and signs it with the authentication key to create a new number, B. This is the response it would expect if the SIM card is legitimate.
  • The phone receives A from the network and forwards it to the SIM card, which signs it with its own authentication key to create a new number, C. This number is relayed back to the network.
  • If the network’s number A matches the SIM card’s number C, then the SIM card is declared legitimate and access is granted.

Long story short: this data not only determines which network to connect to but also acts as the “login credentials” which allow a phone to use said network.

For this reason, SIM cards are actually quite convenient when it comes to switching phones. Since your subscriber data is on the card itself, you can plug the SIM into a different phone and all will be well. On the other hand, switching phones with a CDMA carrier is more difficult since the phone itself is the entity that’s registered with the network.

Each SIM card has a unique identifier called the ICCID (Integrated Circuit Card Identifier), which is stored in the card and engraved upon it. The ICCID contains 3 numbers: an identifying number for the SIM card issuer, an identifying number for the individual account, and a parity digit that’s calculated from the other two numbers for extra security.

SIM cards are also capable of storing other information, such as contact list data and SMS messages. Most SIM cards have a capacity between 32 to 128 KB. Transferring this data mainly involves removing the SIM card from one phone and inserting it into another, though this has become less important with the advent of backup apps. However, SIM card storage is now dwarfed by internal phone storage capabilities, so SIM cards really have no use other than to grant access to specific networks now.

What About Locked SIMs?Technically, the GSM phone is the entity that’s locked. Not the SIM card.

In practice, GSM carriers can implement software on phones such that a particular phone will only accept a designated SIM card from a particular network. If the phone and SIM card do not match up, the phone won’t operate. This is what it means when a phone is “locked.”

Unlocking a phone, then, is the process of removing this limitation such that a phone can accept SIM cards from other networks. If you ever plan on selling your phone, this is an important consideration since the buyer won’t be able to use it unless it’s been unlocked. Similarly, if you’ve bought (or been gifted) a locked phone, it will most likely need to be unlocked before you can use it.

There’s also one other important point to consider: pre-paid SIM cards. These pay-as-you-go SIM cards do not require a subscription or a contract and tend to be cheaper, especially if you purchase them from a MVNO. These can be immensely useful if you travel internationally and want to avoid expensive roaming charges.


In the end, SIM cards are both a blessing and a curse. They grant freedom to customers to move from phone to phone as long as those phones are compliant with GSM standards, but can prove annoying if the card itself is somehow lost or damaged since they hold so much crucial data.

Image Credit: Professor teaching via ShutterstockSIM Card via ShutterstockMobile Network via ShutterstockSIM Locked via Shutterstock

Is It Legal Or Illegal To Unlock My Smartphone In The US?

Unlocking cell phones in the United States is no longer a criminal offense, after President Obama signed into law the Unlocking Consumer Choice and Wireless Competition Act.

The bill — which enjoyed bipartisan support in both the Senate and the House Of Representatives — will give consumers more choice with respect to how they use their cell phones, and with what providers they use.

Unlocking phones was made illegal in early 2013, when an exemption that had been issued to a clause in the Digital Millennium Copyright Act (DMCA) lapsed. Tools used to remove the carrier locks on devices without the permission of the phone networks were also considered to be illegal under similar legislation.

The exemption will only be valid through 2015, meaning that another exemption will have to be issued when it expires. Until then, consumers are free to move their phones on to other networks without risking jail time or a steep fine.

But are you curious about the laws surrounding phone unlocking in the United States? Read on.

How Does The DMCA Relate To Phone Unlocking?

The DMCA is a significant piece of legislation that was first introduced in 1998 and brought the US into harmony with two treaties from the World Intellectual Property Organization (WIPO).

It was designed to protect rights holders and content creators, and when it was signed into law by President Clinton, the Internet was very much in its infancy. Broadband didn’t really exist — at least for consumers — and in terms of usage was nowhere near to reaching the massive level of ubiquity it enjoys now.

The DMCA remains a phenomenally controversial piece of legislation, largely due to greatly stiffening the penalties for copyright infringement. But in many respects it was also remarkably forward thinking.

The ‘Safe Harbor’ provisions of the DMCA allowed site operators to avoid responsibility for the copyright infringement of their users, provided that they removed infringing material within a reasonable period after being alerted to the existence of it.

This exemption allows sites that host user-submitted content — like Facebook, Vimeo, and Youtube — to operate without being sued into oblivion by rights holders.

So, what’s a piece of legislation designed to protect rights holders got to do with cell phones? Well, despite the DMCA being relatively forward thinking for the year 1998, there were also some major issues with how the act was written. These relate to the anti-circumvention provisions in the second portion of Title One of the act.

The issues with this section were two-fold. Firstly, the act prohibits circumventing digital locks that can control access to copyrighted works. Sadly, the way in which this section was written was far too broad-reaching, and meant that using tools to circumvent the carrier locks on cell phones was illegal.

Another significant issue was that the DMCA had no fair-use exemptions included, which meant that it was impossible to use a personal-use justification for unlocking phones.

And that was the case for a while, until 2006 came around.

Under LOC And Key

In 2006, the Library Of Congress (LOC) issued an exemption to the DMCA that made cellphone unlocking legal. This helpful exemption stuck around until 2012, when the LOC decided not to renew it, making cellphone unlocking illegal once again. The exemption officially expired in January of 2013.

The LOC justified letting the exemption expire by saying that consumers had the option of buying plenty of mobile phones without any carrier locks. By this, they referred to phones like the Nexus 4 and the iPhone, which could be bought without having to enter into a contract.

Opponents of this decision argued that not all phones could be bought without a contract, and that this would allow wireless carriers to unfairly refuse to unlock devices.

As It Is Today

And now, the current legislation that was just signed into law changes all of this. It’s now legal to unlock your phone on your own without getting on the wrong side of Uncle Sam. At least until 2015, when we’ll have to go through this all over again. Fun, right?



It’s probably not fair to go too hard on the US carrier market. For the most part, if your contract has ended in the US, you should be able to unlock your phone.

  • T-Mobile is happy to unlock any devices, provided that the account associated with the device is in good standing, the phone is a T-Mobile device that hasn’t been reported as lost, stolen or blocked, and all payments have been completed and satisfied in full.
  • Verizon will unlock any phone, provided that it has been active for 60 days and the account associated with the device is in good standing. This policy applies to 3G phones, as 4G devices are not locked.
  • Sprint will unlock any device, provided that the contract associated with the device has lapsed, and the account is in good standing.
  • AT&T will unlock any phone, provided that the contract has lapsed with the device, has had service for at least 60 days, and the account associated with the contract is not delinquent.

Thanks, Obama

Thinking of unlocking your phone? You can breathe a little easier now that the rules have been changed. At least until 2015.

Got any thoughts on this topic? Let me know. The comment box is below.

Photo Credit: President Bill Clinton (Alan Light)Freedom (Johan Jarsson)Unlocked Cell Phone Shack (Consumerist)ATT Store (Mike Mozart)mobile phone (Irita Kirsbluma)


The Digital Millenium Copyright Act (DMCA) is a major slice of law put in place by the United States government in order to crack down on the piracy of common media, software and other intellectual property.

Chilling Effects is an information portal and compendium of cease-and-desist or DMCA “takedown” notices, submitted by the individuals who sent or received them. The site makes for an interesting read and contains thousands of angry letters from copyright holders, ordering material to be removed.

Would you know what to do if you received a takedown notice? Are you aware of how DMCA cease-and-desist orders can be counter-productive for copyright holders? Read on to find out more.

The Chilling Effects Website

At the forefront of the Chilling Effects movement are the Electronic Frontier Foundation, the self proclaimed defenders of freedom in the digital world. Along with the EFF are several prominent universities and law schools, including Harvard, Stanford and the George Washington School of Law.

Not only is Chilling Effects home to a searchable database of takedown notices, but also contains advice and information regarding specific copyright infractions and advice on what to do if you receive a cease-and-desist order yourself.

Above all, the website recommends that you send in a copy of the takedown notice, so that it can be added to the database, analysed and publicly displayed. There are also simplified, easy to understand explanations of individual areas, such as copyrightfan fiction and defamation.

Sending & Receiving Takedown Notices

The website is geared towards those who have received and those who have sent cease-and-desist orders, and has submission areas for both receiving and issuing a notice. If you have sent a takedown notice then you’ll be asked for your details, the recipient’s details and a copy of the notice itself.

On the other hand if you have received a notice yourself then the submission process is a little more complicated. First you must find a category for the complaint, of which there are many spanning topics like defamation, parody websites and patent infringement.

Next fill in your personal information and the senders details, and copy and paste the notice you received into the C&D Notice Body box. Hit Enter to send your report, and wait. Chilling Effects, its academic foundations and the law students who attend these institutions will then attempt to provide legal feedback regarding the notice you received.

Whilst there is no guarantee that your case in particular will receive a personal reply, your report may improve Chilling Effects in the long run:

When you send us a cease and desist notice, we will categorize it and add it to the “chilling effects” database. The law school clinics will then review the general issues raised and add to the developing set of FAQs on the subject(s). Each letter or incident added to the database also helps describe the scope of the “chilling” problem: How much legitimate activity is being stopped by meritless threats, and who is sending ungrounded claims?

Missing The Point?

If you do receive a notice it is often best not to challenge it at all. Once you have removed the content your website is no longer liable, and you should be in the clear. Fighting the case will often require legal representation, which is often far more costly for the individual than the multi-national claimant.

There has been widespread criticism of the DMCA, many claiming that takedown notices are overpowered and make it too easy for copyright owners to remove content that may or may not be infringing.

In March 2009 Google published statistics which confirmed that over half of all takedown notices received (57%) were sent by businesses targeting rivals. It also emerged that 37% of cease-and-desist orders were not valid copyright claims at all.

In a move that’s typically Google, the company have been sending the valid DMCA takedown notices they have received to Chilling Effects for inclusion in the database. As Google is a search giant, these notices often relate to search results and website listings within the Google database.


One such issuer of DMCA notices has been Microsoft, who regularly seem to get in touch with Google over copyright infringements, especially when it comes to the Windows operating system. When these full reports are published on Chilling Effects they include offending search terms andlinks to websites that house this content.

I’m not advocating piracy, but many of the copyright claims against Google relate to pirated software, and these reports are public once Chilling Effects get hold of them. These reports all contain the locations of suspected pirated materials, delivered by the claimants themselves.

This presents somewhat of a catch 22 situation. Many feel it is important to have a public recordof these notices (sharing filed reports does not contravene the DMCA), but each successful takedown notice points to another bit of questionable copyright.


Chilling Effects is a fantastic resource, especially if you run a public website (such as forums or image boards) and are concerned about your responsibility over content. If you do ever receive a copyright infringement notice then submitting it to the website can not only help you, but also others who are browsing the site for guidance.Did You Know: 5 Illegal Website Ideas For The United States Did You Know: 5 Illegal Website Ideas For The United StatesREAD MORE

Have you encountered any DMCA brick walls? Takedown notices? Ever filed a complaint? Concerned about intellectual property rights? The MakeUseOf court is in session, take your place in the witness box below.