Register Login

CDMA vs. GSM Phone Networks: What's the Difference?

Updated Jan 23, 2020

Mobile phones and smartphones are used every day by millions of people all over the world. It is one of the most popular devices used across the globe. Two of the most popular cellular technologies are GSM and CDMA.


GSM stands for Global System for Mobile Communication, and CDMA stands for Code Division Multiple Access. GSM is considered the worldwide standard for cellular telephone communication. On the other hand, CDMA is regarded as the most secure telephonic network. Both the technologies differ by the process through which calls and data are sent over the respective systems.

Let us compare the two technologies to understand which one is better.


  • Spread spectrum technology is used in CDMA for properly utilizing the available bandwidth. It lets the users transmit signals over the complete frequency spectrum.
  • On the other hand, GSM works on a wedge spectrum that is known as a carrier. This is partitioned into several time slots where each slot is allocated to a user.
  • This is done so that no other subscriber can access the slot until the current call is completed.
  • GSM is much more in use than CDMA across the globe.

SIM cards

  • GSM phones require a SIM card that has the personal information of the user and can be used in another device without the data being lost.
  • There are no SIM cards in CDMA phones, but they use ESN (Electronic Serial Numbers). To activate such ESN enabled phones, you have to call the carrier or go online to do it.
  • ESN based phones are not so popular among users, as most of them prefer SIM-based phones. Therefore, GSM beats CDMA here as well.


  • CDMA is highly secure as it has inbuilt encryption facilities. Here you will get a unique code, and all your conversations will be encoded. This makes it difficult for outsiders to trace the signal and intercept the calls.
  • In GSM, temporary identification numbers are allocated to the user to secure the user’s numbers. Frequency hopping and encryption algorithms are used to protect the confidentiality of the conversations.
  • Here, CDMA beats GSM as its security algorithms are powerful.

Global Coverage

  • GSM is the most used mobile network in the world, having where more than 80% of users choose it over other networks. As international roaming is free in GSM, users prefer this over CDMA. It can be 3G devices but has faster data transfer speeds than CDMA.
  • Most of the users of CDMA are in Japan, Canada, and the USA. However, the facility does not work in Europe. In the rural areas of North America, CDMA is more popular than GSM.
  • Therefore, due to its worldwide coverage and popularity, GSM is better than CDMA.

Exposure to Radiation

  • GSM based phones emit 28 times more radiation as compared to CDMA phones. Continuous exposure to radiation can affect your health. So, CDMA phones are considered safer than GSM.

Let us dive into the details of the two technologies.

What is GSM?

GSM is a second-generation standard for mobile telephone networks that are used for exchanging voice and data signals. While sending signals, the Time Division Multiple Access techniques are used. It lays the foundation for 2G mobile phones.

When the services are provided, the area is divided into cells, where each cell has a network tower. All the mobile phones in that cell are serviced by the tower. GPRS (General Packet Radio Service) is used for transferring data to users.

GSM phones consist of a handset and a SIM (Subscriber Identity Module) card that is removable. This SIM card contains all your information if you are the user. Moreover, you can remove this SIM card and use it on another mobile device.

The underlying technology of GSM is TDMA and FDMA. In TDMA, the transmission channel is broken down into multiple time slices that allow many users to access it. In FDMA, the transmission channel is divided into frequencies for providing multi-user access.

Furthermore, it has led to the development of many wireless services such as EDGE (Enhanced Data Rates for GSM Evolution), GPRS, and UMTS (Universal Mobile Radio System). GSM users were the first to use the SMS (Short Messaging Service).

Advantages of GSM

The benefits of GSM are as follows:

  • It has massive coverage providing services to users in more than 200 countries due to its harmonized spectrum. This allows you to transfer between different networks quickly while keeping the same number.
  • As it is the most popular cellular technology used in the world, most mobile handsets operate under it. So, you have more flexibility and options while choosing your mobile phone.
  • You do not have to bear roaming charges for international calls. However, mobile service providers may charge fees for international calls.
  • Advanced versions of GSM having more number of antennas offer high download and upload speeds.
  • With GSM, you can easily integrate with other technologies such as CDMA and LTE.

What is CDMA?

CDMA is a technology similar to GSM and is the underlying standard for second and third-generation mobile networks. In CDMA devices, the SIM card is not removable. Your entire information will be stored in the device or handset.

Here, after the data is digitized, it is spread over the available bandwidth. The different calls are then overlapped on the transmission channel, and they are assigned a sequence code. The technique is called spread spectrum, where the data is sent in small pieces over the frequencies available for use.

During communication, a signal is created that spreads over a broad bandwidth. Spreading code is used for this signal creation. In CDMA, multiple users in a particular channel are distinguished by the code they use to send the signal.

Advantages of CDMA

The benefits of CDMA are:

  • It provides the cellular companies high capacity for catering to many customers as it shares the same wireless signal with all of the users. With higher capacity, you have lesser chances of having service failures and call disconnections.
  • A CDMA voice call is highly secure as it is a digital data stream and very difficult to intercept. This is because the signals are coded.
  • The fixed frequency spectrum is effectively utilized.
  • CDMA uses a power control system that reduces interference. It adjusts the power level, so the call is clear but without much interruption.
  • Many users can share the same bandwidth.
  • The data transmission rate is fast, as CDMA uses EVDO (Evolution-Data Optimized).

Key differences between CDMA and GSM

  • GSM is based on wedge spectrum technology, and CDMA is based on spread spectrum technology.
  • GSM uses EDGE as the technology for transferring data. On the other hand, CDMA uses EVDO for data transferring.
  • GSM devices make use of a SIM card. But CDMA devices do not use SIM cards and use ESN numbers instead.
  • As the GSM signals are concentrated in a narrow bandwidth, they can be detected easily. CDMA signals cannot be detected easily.
  • 80% of the networks in the world comprise of GSM. On the contrary, CDMA is exclusively used in Japan, Canada, and the USA.


If you look at the popularity and usage, GSM is way ahead of CDMA. As ESN numbers are not widely accepted, CDMA has fewer customers. The GSM devices are, therefore, more flexible than CDMA. However, in terms of security, CDMA has encryption algorithms that are more powerful than GSM. Furthermore, CDMA devices emit lesser radiation as compared to GSM, making these safer to use.

So, if you are looking for fantastic coverage and fast data transfers, GSM is the one for you. But if you are searching for a safer device having high security, choose CDMA. The choice ultimately boils down to your preferences.