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Difference Between GSM and CDMA

What is GSM?

GSM is an abbreviation for Global System for Mobile. It is a type of mobile communication technology that allows the transmission of various data signals and voice in different time slots over one common communication channel. GSM makes use of the FDMA and TDMA technology for allowing the transmission.

The Europeans first introduced this digital cellular technology for voice and data signal transmission. It uses the SIM (Subscribers Identity Module) card in the form of its major element. Every device in its network has a separate SIM card. It means that one can distinguish various GSM technology subscribers by SIM. Any user is free to switch between different SIM cards. So, they offer more flexibility.

In the case of GSM, a tower in any network area acts as a controlling center for all the mobile devices in the radius. This network contains information regarding all the devices using specific SIM card numbers. The GSM technique transmits signals in varied time slots. Thus, the complete channel stays available for transmission of the signals. It is the reason why when you make a call to a specific number then you can’t connect any other call to that specific number at that particular instance. It’s because the current signal transmission makes the time slot busy.

Every subscriber in a GSM network holds its own SIM card with an authentication key, unique algorithm, and specific identity. Thus, billing and network accessing directly get linked to the card instead of the concerned handset.

What is CDMA?

CDMA is an abbreviation for Code Division Multiple Access. Qualcomm originally developed it- initially called IS-95. The CDMA system offers utilization of the complete bandwidth. It offers a unique code to every signal, then transmits them over a complete bandwidth of the channel. Therefore, various codes differentiate the various CDMA signals that transmit through the channel.

CDMA technique provides a separate spreading code to each signal. KIt helps in distinguishing the different signals in a channel. It then uses a group of orthogonal codes for detecting the signal at the receiver’s end. The base station of a CDMA station has various different codes. Thus, when it receives multiple signals from various base stations, all the base stations distinguish these signals by using the spreading codes (these are orthogonal). Since it uses orthogonal codes, it minimizes all the chances of interference. It means that, for CDMA, all the users in the network use the frequency- but they all hold a different code.

Difference Between GSM and CDMA

Parameter GSM CDMA
Full-Form GSM stands for Global System for Mobile communication. CDMA stands for Code Division Multiple Access.
Basic It is SIM-specific. It is handset-specific.
Availability GSM is highly available and globally used. Over 80% of the entire world’s mobile networks use it. CDMA is not very common, and it is available in comparatively fewer carriers and countries. These devices are exclusive to Canada, Japan, and the United States.
Technology Used It uses the Time division multiple access (TDMA) and Frequency division multiple access (FDMA). It uses the Code division multiple access (CDMA).
Voice and Data GSM supports the transmission of both voice and data at once. The CDMA technology does not support any such feature. It cannot transmit voice and data simultaneously.
Rate of Data Speed It is slower. GSM offers 42 Mbps (Megabytes per second) in 3G (HSPA). It is faster. CDMA offers 3.6 Mbps (Megabytes per second) in CDMA.
Maximum Downloading Speed GSM offers a maximum speed of 384 Kbps (Kilobytes per second). CDMA offers a maximum speed of 2 Mbps (Megabytes per second).
Storing of Customer Information GSM stores it in the SIM card. CDMA stores it in a phone or headset.
Roaming GSM offers worldwide roaming. CDMA offers limited roaming.
Network In every cell, the network tower serves as a mobile phone in that particular area. It has a physical channel along with dedicated codes for every device present in the network.
Spectrum The GSM technology follows a wedge spectrum (carrier). The CDMA technology follows a spread spectrum technology.
Data Transfer Technology The GSM technology makes use of EDGE. The CDMA technology uses the EVDO ready data transfer technology. Thus, the data transfer here is also very fast.
Division The carrier is divided into time slots. Each user gets a different time slot. Therefore, no one else can access the same calling slot until the ongoing call ends. CDMA allows transmission of each user all the time over the entire frequency spectrum.
Signal Detection One can detect the GSM signals because they stay concentrated in a narrow bandwidth. One cannot easily detect signals in CDMA.
Built-in Encryption GSM does not come with built-in encryption. CDMA comes with built-in encryption.
Security The GSM technology offers less security as compared to the CDMA technology. The CDMA technology offers more security as compared to the GSM technology.
SIM Card For the working of a GSM device, one would always require a SIM card. The CDMA phones don’t have any such requirements.
Flexibility The GSM technology is more flexible compared to CDMA. One can interchangeably use and replace a SIM on multiple devices. The CDMA technology is not so flexible.
Radiation On average, the GSM phones emit approx 28 times more radiation than the CDMA ones. The CDMA devices emit very low radiation.
Wave Pulse A GSM phone emits a more continuous wave pulse. So, you don’t need to reduce its exposure to electromagnetic fields. The CDMA devices have no such pulses.

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