15 differences between GSM and CDMA

You may have heard the terms GSM and CDMA that are often discussed in mobile phone conversations, but what do they mean and what are the differences between GSM and CDMA?

GSM and CDMA are two radio technologies used by operators around the world. They are the most prominent technology in the 2G and 3G era. Different phones support one or both, but it’s important to know that they are different.

If you are wondering about the difference between GSM and CDMA and if GSM is better than CDMA or vice versa, you have come to the right place. So, without further ado, let’s talk about the differences between the two.

Read also: Types of Wireless Networks and Their Advantages and Disadvantages

What is GSM?

What is GSM

GSM stands for Global Mobile System. It is a cellular communication technology that allows the transmission of different voice and data signals on common communication channels, but at different time intervals.

GSM uses a SIM (Subscribers Identity Module) card as its main element. This is because each device on the network has its own specific SIM card. Thus, the different subscribers of GSM technology are distinguished by SIM. However, the user can switch from one SIM card to another at any time, giving them more flexibility.

Read also: SIM card: function, type and how it works

A network tower acts as a control center for mobile devices in that area. And the network stores the information of each device with a certain SIM card number.

In the case of GSM technology, the signal is transmitted at different time intervals so that the entire channel can be used to transmit the signal. This is why when a call is made to a certain number, then no other call can be connected to that particular number during a certain period. This is because the signal is transmitted in that time slot and thus keeps the time slot busy.

So, every subscriber in a GSM network has its own SIM card that has a certain identity, algorithm and authentication key associated with it.

What is CDMA?

What is CDMA

CDMA is an acronym for Code Division Multiple Access, originally known as IS-95. This is the technology that forms the basis of 3G mobile phones and was originally developed by Qualcomm. CDMA systems offer full use of bandwidth, providing a unique code for each signal to be transmitted across the entire bandwidth of the channel. Thus, the different CDMA signals transmitted on the channel are distinguished by different codes. Therefore, it uses direct modulation of the spread spectrum with mixed CDMA detection sequence.

In practice, in CDMA technology, each signal in the channel is assigned a separate broadcast code. This code helps to distinguish the different signals on the channel. A group of orthogonal codes is generally used to detect signals at the receiver.

CDMA base stations store different codes, so that when various signals are received from more than one base station, the base station distinguishes the signals by means of orthogonal propagation codes. The use of orthogonal codes minimizes the possibility of interference. Thus we can say that in the case of CDMA, each frequency is used by all users in the network, but each has a different code.

Unlike GSM, CDMA never uses a SIM card. However, CDMA authentication is based on a separate ESN present in each mobile device itself.

The difference between GSM and CDMA

Once you know the explanation of GSM and CDMA. Maybe you’re curious about the difference between the two now. Here are some differences between GSM and CDMA:

1 GSM stands for Global System for Mobile Communication. CDMA stands for Code Division Multiple Access.
2 GSM is based on a spectrum called the carrier. CDMA is based on broad spectrum technology.
3 This operator is divided into time intervals, and each user is assigned a different time interval. Thus, until the current call is completed, no other user can access the same slot. This technology allows any user to transmit all the time across the entire frequency spectrum.
4 Security is lower compared to CDMA technology. Security is better compared to GSM technology.
5 There is no built-in encryption. It has built-in encryption.
6 The signal can be detected because the GSM signal is concentrated in a narrow bandwidth. Signals cannot be easily detected in CDMA.
7 The GSM network operates on the 850MHz and 1900MHz frequency spectrum. The CDMA network operates on the 850MHz and 1900MHz frequency spectrum.
8 GSM is used by over 80% of the world’s cellular networks. CDMA is used exclusively in the United States, Canada, and Japan.
9 GSM uses EDGE data transfer technology. CDMA has faster data transfer because it uses EVDO data transfer technology.
10 It offers a maximum download speed of 384 Kbps. It offers a maximum download speed of 2 Mbps.
11 A SIM card is required for the GSM to work. CDMA phones do not use a SIM card for operation.
12 GSM is more flexible than CDMA because the SIM can be replaced with another GSM device. CDMA is not flexible.
13 GSM phones emit pulses from continuous waves. Thus, it is necessary to reduce the exposure to electromagnetic fields. CDMA phones do not have this feature.
14 GSM allows limited roaming CDMA allows worldwide roaming.
15 The average GSM phone emits 28 times more radiation than CDMA. Much lower radiation than GSM

GSM Vs. CDMA: Which is better?

This is one of the most frequently asked questions by mobile users, but answering this question is not as simple as you might think.

GSM and CDMA are different ways to achieve the same goal. The fact that such a popular network is built on every network proves that the quality of the network, not the standard, is what matters. For example, 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, none of them are better in terms of quality, but there are a few things here to consider. GSM phones can be unlocked and transferred between operators, but CDMA phones are often locked to a single operator and cannot be transferred.

Also, depending on where you bought your phone, it may come in GSM or CDMA models, or both. It all depends on which operator is available in your area. A GSM provider may have better coverage in some areas, while a CDMA provider may have better coverage in others.

How do I check the compatibility of GSM and CDMA networks?

You need to be careful when checking your phone’s network compatibility. Phones sold in markets that meet both standards often come in a GSM or CDMA version, but most are compatible with both.

If you purchased a CDMA phone from a third-party merchant, you will need to contact your carrier to activate it. If you are buying a GSM phone, you will need to purchase a SIM card to insert into the phone, which will activate the network capabilities of the phone.

CDMA phone owners don’t have to worry about SIM cards, but this makes CDMA phones have compatibility limitations that are hard to overcome, while GSM owners simply take out their SIMs and use them. replace with other operators.

Most CDMA networks do not allow the use of a phone originally purchased from another operator, even if the phone is technically compatible. This is an important limitation to keep in mind when using a CDMA network. If you decide to switch networks later, you may need to purchase a new phone, even if the network you are switching to also uses CDMA. This is one of the reasons why you should get an unlocked phone.

Even if GSM is more open, phone-supported frequency bands may restrict access. Some frequency bands are from 380 MHz to 1900 MHz, and the bands used may vary from market to market. Therefore, you should check your bandwidth usage again with your local operator and make sure that the phone you are buying is compatible with the same.

As such, GSM is concentrated around a core of the four bands, namely 850, 900, 1800 and 1900. Phones that support all four bands work in most countries, which is why GSM phones compatible with all four bands are often called the “world.” telephones.” .

GSM Vs. CDMA Vs. Oth

Although based on GSM principles, LTE is a separate standard that works separately from existing GSM and CDMA networks, it is the true fourth generation of cellular data that we commonly call 4G.

South Korea initially led the discovery of 4G LTE, but many countries, including Indonesia, have followed suit since then. This standard uses a SIM card to change networks by changing SIMs if the phone is compatible with the new network.

In the early days of 4G LTE, it was only used for data, but not for voice. Unfortunately, this means that the owner of the CDMA / LTE phone is still locked to the network.

However, this has changed with the launch of Voice over LTE (VoLTE), which allows users to make calls over a 4G LTE network. The downside is that not all carriers around the world support VoLTE. In this case, as long as 4G LTE coverage is available, calls will still be handled by CDMA or GSM technology.

In Indonesia alone, many carriers support VoLTE technology, so as long as your phone is compatible, you’ll be able to make clear calls compared to regular 2G / 3G network calls.

4G LTE has become the global standard for 4G and is available in various parts of the world, including Indonesia. Although more comprehensive coverage is excellent, there are also issues with the 4G LTE spectrum. Remember how GSM / CDMA works on many different bands? The same goes for LTE. You need to check that your phone is compatible with the frequency band supported by your carrier. You will not be able to use your LTE phone on other networks with the same standard, but with different frequency bands. Thus, the more bands the phone supports, the better.


So that’s the difference between GSM and CDMA. In short, both GSM and CDMA are technically better. They end up offering the same service, and the quality of the network depends on the operator, not the cellular standard used. GSM phones can be unlocked and replaced by the operator, while CDMA phones can be locked by the operator. It is usually cheaper to buy an unlocked GSM phone than a contract CDMA phone.

Remember to carefully check which bands your phone supports. Some work on GSM or CDMA, but most support both standards and offer several different frequencies globally. But by switching to the global LTE standard, you don’t have to worry too much about CDMA and GSM. Currently, they are only relevant for poor LTE coverage.

GSM and CDMA will remain irrelevant as carriers around the world switch to newer cellular network technologies, such as 5G and eventually 6G.

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