The Big Difference in Cell Phone Technology: CDMA vs GSM

Posted on Posted in CDMA, GSM, Smart Phones

It’s hard enough to choose what cell phone carrier you want when purchasing a new cell phone.

When you decide to look for a new phone, not only do you have to choose which operating system you want (Apple iOS, Android, or Windows), but you also have a network to choose from with distinct coverage areas, data & minute plans, with many other features; let’s not forget their customer service.

Before you decide on a network carrier, there is a very important decision you must make: whether you want to use a phone with CDMA technology or GSM technology. Many people ignore these acronyms when they see them on the specs of their new phones, but these seemingly innocuous options define some of the basic functions of your phone.

In the smartphone world, these are the two main technologies used to transmit information.

They are the reason you can’t use an AT&T phone on a Verizon network. Two very simple acronyms, CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles), are very similar, yet different radio systems used in cell phones.

Many of us are familiar with the technology the rest of the world has grown accustom to, the GSM network. The phones that use those little plastic chips we so commonly refer to as: a SIM card. According to the GSM Association, in 2014 it became the industry standard for mobile communications, with over 90% of cellular networks using this technology in over 219 countries!

So why use another form of technology? At one point, GSM was thought of to be slow, and the way of the past. This new technology, called CDMA, offered more capacity for information sharing, and better quality radio frequency than the GSM of the day.

Although GSM has caught up to CDMA, companies such as Verizon and Sprint were already set to create phones using this new technology, as it was also more cost effective.

Which Carriers are CDMA vs GSM?

In the US, cellular networks mentioned above such as Verizon, Sprint, US Cellular, and other affiliates use CDMA.

The main reason the rest of the world now uses GSM technology, is because this form of communication was mandated by law in 1987 within Europe, and is a type of business consortium.

Whereas, CDMA is owned by one primary company, the chip-maker known as QualComm, which makes a large amount of smartphones processing chips. Because of this, it was much cheaper for third parties to use GSM, rather than getting permission from this parent company to use their technology and pay to use their technology.

America is unique in that it is home to more CDMA users than GSM users, with the two largest CDMA carriers accounting for over 43% of the market (Verizon & Sprint respectively). The two largest GSM carriers barely break 37% (AT&T and T-Mobile respectively). Worldwide, CDMA accounts for only 13% of all cell phones made, with GSM and its successor, UMTS making up of the remainder.

If you are planning to travel the world, it may be a good idea to purchase a GSM accessible phone, as you can switch SIM cards and use your phone anywhere in the world without much hassle.

Technological Differences

So what are the differences between these two technologies?

Most of these differences are so trivial, we will never really concern ourselves with them, from frequency bands, audio codecs, physical specs of the network infrastructure, to the way a user is linked to a phone.

These standards are only important to the big company’s of the world such as Apple, AT&T, Verizon Samsung, and so forth. The industry standards layout the technical aspect of a cellular network, and to a lesser extent, the phones we use on it.

What I mean by this is that these standards for communication ensure carriers have working devices on the worlds’ wireless networks. Think of it as the same way a webpage has to be coded or written to be compatible with each different web browser.

As certain codes allow web browsers to be viewed properly on particular browsers, whether it is ChromeSafari, or Microsoft’s Edge, similarly, CDMA & GSM provide a layout to follow, and cellphone makers a guide for making devices which allow you to access your network properly connecting your calls or internet.

Be aware for quality, the technology is much less important than the network you are on. If your phone works outside your home, but not inside certain parts, it is most likely because you do not have a Cellular Tower nearby that provides a strong enough signal.

GSM and CDMA are both multiple access technologies Meaning, they are different ways for people to have multiple phone calls or internet data being transferred through one radio channel.

As I mentioned before, GSM was the original and now current leader in the mobile communication technology. It has a “time division” system, where the calls take turns. Your voice is literally transformed into digital data, which is given a specific channel and time slot to go through the network.

Often times with old phones, you would hear a loud buzzing noise when you put a GSM phone near a music speaker. Luckily that doesn’t happen anymore. That is the pulsing time division signal which pieces the call back into sound over the radio frequency.

Luckily our technology has advanced and all but gotten rid of this problem.

CDMA requires more processing power however, and each call has a unique key and all the calls are transmitted at once. This is what made CDMA faster when it first came out.

This code division ended up being a more powerful and flexible technology, and was utilized in the “3G GSM” technology. You may see the 3G often times in your upper right corner, as your phone is connected to this processing technology.

3G is essentially integrated CDMA technology, called WCDMA (wideband CDMA) or UMTS (Universal Mobile Telephone System). As the name suggests, WCDMA requires wider channels than older CDMA systems, but has more data capacity, which is why it processes our internet connection faster than the original 2G or Edge network.

GSM is rapidly outgrowing and advancing the CDMA technology, and has become a global standard for the majority of smartphones. While the WCDMA is considered the 3G version of GSM technology, GSM has further advanced their internet speeds by creating something referred to as the HSPA extension, speeding GSM networks up as fast as 42Mbps (Megabytes per second).

CDMA networks on the other hand are a mere 3.6Mbps on their 3G network speeds. US Carriers chose not to install this new advancement, and turn to the 4G LTE. Meanwhile, the older CDMA 3G phones are stuck at 3.6Mbps data speed.

While faster CDMA technologies exist, U.S. carriers chose not to install them and have turned to 4G LTE to be more compatible with global standards, and the now US federally regulated laws under the FCC.

Please watch the video by PC Magazine, as it explains this technology in greater detail.

The Differences You Should Care About

Both technologies represent the standards which allows phone carriers to identify their phones for their network. In other words, CDMA and GSM tell your cell phone network provider if it will be able to receive calls, or internet.

The GSM technology has one key difference: a removable chip called a SIM card. This makes it much easier to switch carriers and still keep your phone you spent all that money on. So long as it is unlocked, as many of these phones are “locked” to a specific carrier, as I’ve discussed in my previous articles about what unlocking means, and how to unlock your phone.

This is handy when you are considering traveling the world, as most networks run through GSM technology. Sometimes, phone manufacturers produce something called an “international” version of your smartphone, where it is unlocked and there are no carrier restrictions placed upon the phone.

Put a SIM card from a different carrier in your phone, and in theory the phone will work for any cell carrier network. Take the old card out, and put in a new SIM card from a different carrier, and this old phone will have your new number!

That’s not the case with CDMA based phones. While the standard for CDMA uses something called RUIM (or Removable User ID Network), which is very similar to that of a SIM card. It is essentially an integrated SIM card with the capability of extending the GSM technology to the CDMA technology.

Instead of using this RUIM, most CDMA based phones allow the phone to be switched to a new carrier, only with the agreement or cooperation of both the old and new carrier, creating a more frustrating experience when trying to switch cell phone services.

Even though places such as the US have phones sold on a contract basis, usually lasting two years, some people do not discard their phone and want to keep it, switching to another cell network.

The rest of the world and developing nations have phones sold unlocked, independently of carriers, for the full price, and need to work with all local networks. This creates an issue for those CDMA carrier locked phones not using the RUIM. After all, most people like to have the option to just switch numbers and not worry about getting a new phone each time we do so.

In the US, companies such as Sprint and Verizon using this CDMA-only phones are only able to roam on other CDMA networks, which simply doesn’t exist in most of the rest of the world. While both of these carriers offer phones with built-in GSM support (or SIM card slots), this feature is missing from most of their popular handsets like Sprints’ iPhone as an example.

CDMA carriers use network-based “white lists” in order to verify or confirm their subscribers. That means someone on a CDMA-phone in the US, the network does not have to accept a new phone you may want to switch to on their network.

Although several newer Sprint and Verizon phones now have SIM cards, it isn’t because of CDMA. These SIM cards are only there to utilize these carriers 4G LTE networks, because the standard for LTE uses SIM cards. The phones may also have SIM slots to support foreign GSM networks as “world phones.” But those carriers still use CDMA to authenticate their phones on their own home networks.

The Future of Cell Phone Networks

In the future, this gap between CDMA and GSM will come to a halt, as the future of smartphone technology leans towards a new network technology known as the 4G LTE (or Long Term Evolution).

This is the new globally accepted 4G Wireless Standard. The problem is, companies are turning it on through different frequency bands, with different 3G backup systems, and in some cases such as the Sprint Spark network, using an LTE variant (TD_LTE) that doesn’t work on any other US carriers phone. Currently, there are very few phones that support all of the carriers’ LTE bands.

Verizon has began to comply with the FCC regulations which state that all phones must be compatible to switch with all carrier networks, switching their phones to LTE-only phones this year, but those require special software to make voice calls. That doesn’t make things any easier when you want to switch carriers with your phone.

Even without CDMA, the idea of the carrier controlling what you can do with your phone will continue on.

There are some phone manufacturers that are trying to make this easier on consumers, supporting all these standards for phones. The iPhone 6, the iPhone 6 Plus and the Google Nexus 6 to name a few are the easiest phones to switch on nearly all carriers in the US. Even though the iPhone 6 and 6 Plus units from T-Mobile, AT&T, and Verizon can be switched to work on all three of these carriers, Sprint makes things difficult with their unique LTE band mentioned above.

Due to Sprints’ strict unlocking policies, their iPhones cannot be unlocked, despite having all the bands. Sprint also has a policy where it only allows phones purchased directly from Google or Sprint to work on its network. So while the Nexus 6 will work on all four carriers, it has to be purchased through Sprint or Google.

For Android users, phones such as the Samsung Galaxy S5 and HTC One (M8) on the Verizon network will work on T-Mobile’s and AT&T’s networks, with limited coverage due to the CDMA GSM and LTE, not allowing them to be on the same frequencies.

Hence why the variant models of these phones from AT&T and T-Mobile won’t work on Verizon at all because they lack the CDMA radio to function on the Verizon network.

If you want to be able to switch carriers with ease, I suggest going with a phone company using GSM based phone technology. Otherwise, pick your carrier on the coverage quality in your area, and assume you will be buying a new phone when you switch carriers. Hopefully this helps you make an informed decision!

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