CDMA vs GSM: What’s the Difference?

March 27, 2018

CDMA and GSM are two acronyms that you will see regularly when reading about anything related to mobile telephony. This article explains what each of the two terms mean, how they are related, why they are different and why you should care.

CDMA or Code Division Multiple Access and GSM or Global System for mobiles are acronyms for the two main radio systems that are in mobile telephones. Each are a title for a collective group of technologies which are run by the same entities.

What is the technology behind GSM: in simple terms?

We start with GSM as this radio access technology was developed first in the evolution of mobile communications.

GSM is a time division system, whereby voice is broken down in to smaller parts and transformed in to digital data. This data is then allocated to a channel and a time slot, then when there are multiple calls happening on one line, the receiver is able to ‘listen’ to the specific channel and time slot, combine the data and replay the voice.

What is the technology behind CDMA: in simple terms?

CDMA is also a radio access technology, which allow us to fit multiple calls, connections and data streams on to one radio channel.

CDMA is a code division system, whereby each call’s data is encoded with a unique key, then the calls are all transmitted at once. The receivers then use a unique key to divide the combined signal back in to individual voice.

Of the two systems, code division became more powerful and is considered a much more flexible technology. However, since it began, GSM has evolved to be quicker than CDMA. CDMA networks are ‘stuck’ at 3.6Mbps whereas GSM networks can theoretically transmit at 42Mbps.

What CDMA vs. GSM Means to You

As a consumer the final call quality is not noticeably determined by the way your carrier has built their network, there may be some good and some bad CDMA and GSM networks, but there are several differences between the technologies that are key things to be aware of as a consumer.

If you want to swap your phone, then a GSM network is much better for you. That’s because GSM carriers put their customer information on a SIM card, which can be removed and inserted to another phone easily. Whereas, with CDMA, in some countries carriers used a network-based ‘white list’ to verify their subscribers. This means that you will require your carriers permission before you can go ahead and change phones.

3G CDMA networks generally are unable to make voice calls and transmit data at the same time, whereas 3g GSM have the ability to transmit these two data types simultaneously.

This handful of information will surely make you ask the question, why would carriers ever have gone with CDMA if GSM came first and seems to have a lot of better options for consumers. The answer is that, in the evolution of mobile networks, when carriers began to switch from analog to digital technologies, CDMA was the best available technology. However, GSM technologies soon caught up with GSM and then began to outperform them, but by that time a lot of carriers infrastructure was already set up and operational.

Although it is possible to switch from CDMA to GSM, many operators are choosing to develop and build out 4G and LTE services rather than investing money in areas that are now obsolete for many of their customers.

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