What is the Difference Between GSM and CDMA

The cellular mobile service is being used everywhere, every day in the world by millions of people. Definitely, We have to agree that- the cellular is one of the fastest-growing and most demanding telecommunication services. Through the evaluations of cellular telecommunications, various systems have been developed and they have many problems directly related to compatibility, especially with the development of digital radio technology. In this article we will have a discussion on what is GSM and CDMA?, and The Difference Between GSM and CDMA communication technologies.

GSM (Global System for Mobile Communication)

What is GSM? – GSM stands for Global System for Mobiles. This is a worldwide standard for digital cellular telephony. Basically, GSM was created by the Europeans, GSM is a published standard by ETSI in 1982, and has now enjoyed widespread implementation in Europe, Asia, and increasingly America.

Time Division Multiple Access (TDMA)
Time Division Multiple Access (TDMA)
  • A GSM phone is a digital cellular technology used for transmitting mobile voice and data services.
  • GSM makes use of the narrowband Time Division Multiple Access (TDMA) technique for transmitting signals.
  • This circuit-switched system divides each 200 kHz channel into eight 25 kHz time-slots.
  • The GSM operates on the mobile communication bands 900 MHz and 1800 MHz in most parts of the world. In the US, GSM operates in the bands 850 MHz and 1900 MHz.
  • The GSM network is divided into three major systems: the switching system (SS), the base station system (BSS), and the operation and support system (OSS).
  • The switching system (SS) is responsible for performing call processing and subscriber-related functions.
  • All radio-related functions are performed in the BSS, it consists of base station controllers (BSCs) and the base transceiver stations (BTSs).
  • The operation and support system is to provide a network overview and support the maintenance activities of different operations and maintenance organizations.

Code Division Multiple Access (CDMA)

  • Code Division Multiple Access (CDMA) is a type of multiplexing that enables various signals to occupy a single transmission channel. It enhances the use of available bandwidth.
  • CDMA technology is known as a spread-spectrum technique that allows many users to occupy the same time and frequency allocations in a given space and band. Individual conversations are encoded with the help of a pseudo-random digital sequence.
Code Division Multiple Access (CDMA)
Code Division Multiple Access (CDMA)
  • The technology is commonly used in ultra-high-frequency (UHF) cellular telephone systems, bands ranging between the 800-MHz and 1.9-GHz.
  • Code Division Multiple Access technologies are different from Time and Frequency Division Multiple Access systems. In this system, a user has access to the whole bandwidth for the entire duration.
  • The basic principle is that different CDMA codes are used to distinguish between different users.
  • Techniques generally used are direct sequence spread spectrum modulation (DS-CDMA), frequency hopping, or mixed CDMA detection (JDCDMA).
  • Here, a signal is generated which extends over a wide bandwidth. A code called spreading code is used to perform this action.
  • Using a group of codes, which are orthogonal to each other, it is possible to select a signal with a given code in the presence of many other signals with different orthogonal codes.

Difference Between GSM and CDMA


  • The CDMA is based on spread spectrum technology which makes the optimal use of available bandwidth. It allows each user to transfer over the entire frequency spectrum all the time.
  • The GSM operates on the wedge spectrum called a carrier. This carrier is divided into a number of time slots and each user is assigned a different time slot so that until the ongoing call is finished, no other subscriber can have access to this.
  • GSM uses both TDMA and FDMA for the user and cell separation. TDMA offers multi-user access by chopping up the channel into different time slices and FDMA provides multiuser access by separating the used frequencies.


  • In CDMA technology, More security is provided as compared with the GSM technology because encryption is inbuilt in the CDMA.
  • A unique code is provided to each and every user and all the conversations between two users are encoded ensuring a greater level of security for CDMA users.
  • The signal cannot be traced easily in CDMA as compared to the signals of GSM, which are concentrated in the narrow bandwidth.
  • Therefore, CDMA phone calls are more secure than GSM calls. In terms of encryption, GSM technology has to be upgraded so as to make it operate more securely.

SIM Cards

  • A SIM (Subscriber Identity Module) is a specialized card that is required in a GSM phone. These are carrier-specific and can be replaced from one phone to another with the saved data protected.
  • The CDMA devices do not use SIM cards, but rather rely on ESNs (Electronic Serial Numbers).
  • To activate a phone, the user has to call their carrier or can use the online system to perform an ‘ESN’ change. As no SIM cards are used here so swapping of devices becomes difficult here as the user has to follow the above procedure.


  • GSM is more flexible than CDMA. The SIM card can be placed on any GSM supporting hardware and can have access to the service. The CDMA works only if ESN is registered in its database.
  • In case the current CDMA phone stops work, a new phone has to be bought, but this not the case with the GSM phones.

Spectrum Frequencies

  • The CDMA network operates in the frequency spectrum of CDMA 850 MHz and 1900 MHz.
  • The GSM network operates in the frequency spectrum of GSM 850 MHz and 1900 MHz.

Radiation Exposure

  • The GSM phones emit continuous wave pulses, so there is a large need to reduce the exposures to electromagnetic fields focused on cell phones with “continuous wave pulses”.
  • The CDMA cell phones do not produce these pulses. GSM phones emit about 28 times more radiation on average as compared to CDMA phones. Moreover, GSM phones are more biologically reactive as compared to CDMA.

Global Reach

  • GSM is in use over 80% of the world’s mobile networks in over 210 countries as compared to CDMA. CDMA is almost exclusively used in the United States and some parts of Canada and Japan.
  • Data Transfer Speed: – Both the technologies can be used with 3G standard phones, but 3G GSM speeds can be faster than 3G CDMA speeds.

This article is all about the difference between GSM and CDMA technology. Furthermore, for any help on GSM and CDMA technology-based projects or doubts regarding this article, you can contact us by commenting in the comment section given below.