Difference Between GSM and CDMA

GSM and CDMA are the two major classifications of the mobile communication system. The crucial difference between GSM and CDMA is that GSM uses SIM (subscriber identification module) card as the major component of the mobile station. Thus, is also known as a SIM type of system. As against CDMA despite using a SIM card, operates on ESNs (electronic serial numbers) which is a mobile station-specific identity. Hence is regarded as a phone-based standard system.

Generally, these are also distinguished by the way these two systems transmit the data within the network. So, there are various differentiating factors between GSM and CDMA, which we will discuss here.

Content: GSM Vs CDMA

  1. Comparison Chart
  2. Definition
  3. Key Differences
  4. Conclusion

Comparison Chart

Basis for ComparisonGSMCDMA
Full formGlobal System for Mobile Code Division Multiple Access
Operation mechanism usedTDMA or FDMACDMA
Transmission rateSlow Comparitively fast.
Technology used EDGEEVDO
SecurityIt offers less secured communication.Comparatively more secured communication is offered by it.
Signal detectionEasyQuite difficult
EncryptionSignal must be additionally encrypted as no built-in encryption exist.It offers automatic encryption to the signal. Thus no additional encryption is required.
Global useMore Comparitively less
FlexibilityIt offers more flexibility.Comparitively less flexibility is offered by CDMA system.
Radiation emissionMoreLess

Definition of GSM

GSM stands for Global system for mobile. It is a mobile communication technology that allows the transmission of various voice and data signals over a common communication channel but in different time slots. It uses TDMA and FDMA in order to allow the transmission. This digital cellular technology to transmit voice and data signals was introduced by Europeans.

GSM uses the Subscribers Identity Module (SIM) card as its major element. This is so because each device in the network holds its own specific SIM card. Thus the various subscribers of the GSM technology are distinguished by SIM. However, any time the user can switch from one SIM card to another thus it offers more flexibility.

A tower in a network acts as the controlling center for the mobile device of that area. And the network holds the information of every device with the help of a specific sim card number.

In the case of the GSM technique, the signals are transmitted in different time slots thus the complete channel can be used for signal transmission. This is the reason when a call is made to a specific number then no other call can be connected to that specific number in that particular duration. This is so because in that time slot a signal is getting transmitted and thus making the time slot busy.

So, each subscriber in the GSM network holds their own SIM card which has a specific identity, algorithm, and authentication key associated with it. Thus network accessing and billing are linked with the card itself rather than the handset.

Definition of CDMA

CDMA is an acronym used for code division multiple access initially known as IS-95. It was originally developed by Qualcomm. CDMA system offers complete bandwidth utilization, by offering a unique code to each signal which is to be transmitted over a complete channel bandwidth. Thus various CDMA signals transmitted through the channel are differentiated by different codes. Therefore, it utilizes the direct sequence spread spectrum modulation with mixed CDMA detection.

Basically, in the CDMA technique, each signal in the channel is provided a separate spreading code. This code helps to distinguish the various signals present in the channel. A group of orthogonal codes is generally used to detect the signal at the receiver.

The base station of the CDMA station holds different codes, thus when various signals are received from multiple base stations then the base station distinguishes the signals with the help of spreading codes that are orthogonal in nature. The use of orthogonal codes minimizes the chances of interference. Thus we can say, in the case of CDMA, each frequency is used by all the users in the network but each holds a different code.

Unlike GSM, CDMA never uses a SIM card. However, the authentication in the case of CDMA is done on the basis of separate ESNs present on each mobile device itself.

Key Differences Between GSM and CDMA

  1. GSM is a mobile communication technique that makes use of TDMA, whereas CDMA utilizes the spread spectrum technique. The use of time division multiple access in GSM permits the transmission of various signals on a common channel in different time slots.
    While in a code division multiple access various signals are assigned specific code thus signals are separated by unique codes.
  2. GSM uses EDGE technology. As against EVDO is utilized by CDMA.
  3. GSM is a type of less secured communication technique. However, the use of unique code for each signal in the network provides more secure communication in the case of CDMA.
  4. The use of SIM card in GSM provides greater flexibility to the user. But as CDMA is basically ESN specified thus are less flexible.
  5. The data and voice transmission rate in GSM is comparatively lesser than the CDMA system.
  6. GSM offers somewhat easy detection of signals. But in the case of CDMA, the detection of various signals present on a common channel is quite difficult.
  7. GSM phones release continuous-wave pulses while these are not released by the CDMA handsets. Thus greater radiation is released from a GSM handset than a CDMA one.


Though both GSM and CDMA has its own region of importance, around 80% of the world’s mobile network uses GSM. However, mostly the US, Japan, and Canada use CDMA.

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