What Is GSM (Global System for Mobile Communications)

GSM, or Global System for Mobile Communications, is a mobile phone protocol that is common in most parts of the world. Technology experts created the protocol in the 1980s and 90s to standardize mobile phone service between countries in Europe. GSM phones use Subscriber Identity Module (SIM) cards, which are crucial to their function and enable the user to change phones easily. It is a chief competitor to Code Division Multiple Access (CDMA) protocol.


Technically, the term GSM refers to second-generation (2G) voice networks operating based on a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA). TDMA takes frequency channel using the phone and divides it into some bits of time allocated to each user. FDMA divides the frequency band into sections and assigns one to each mobile phone tower. The towers are usually spread far enough apart so that those using the same frequency do not overlap their areas of coverage.

The term “GSM” is also used to refer to third generation (3G) technology put in place by the same company and using the same underlying network. This is actually called Universal Mobile Telecommunications System (UMTS), and uses the Wideband CDMA (W-CDMA) air interface standard in most places. Although both are scattered spectrum technology, the W-CDMA and standard used by competing CDMA phones (usually CDMA2000) are not compatible.


Although both refer to cellular networks, GSM and CDMA differ in technology they use. CDMA uses a system where all signals are transmitted simultaneously, but each is spread across multiple frequencies. Servers assign an individual code for each transmission so that the signals do not interfere with each other and can be matched between the sender and receiver.

Originally, the two protocols differed in signal quality, consistency, and voice distortion, among other features. Both methods have been improved, however, and there are few significant differences between the two in terms of call quality. GSM phones are a bit more likely to drop calls as a user moves between base stations, but they have better coverage in high mountain locations. This technology also allows voice and data transmission at the same time that most CDMA phones cannot.

In some parts of the world, both services are available, but tend to be more common than the other. Most cellular service providers only use one type of network because it is very expensive to maintain both types of services. GSM is the older service, and is found in most parts of the world, while CDMA is most common in the US and Asia.

SIM card 

GSM phones use a SIM card, which is a small card with a built-in integrated circuit that stores personal information, the user’s phone number, account information and contacts. When a user switches phones, the SIM card exchanges from one phone to the other transfers the cell service and phone number, and activates the new phone. The contact list, calendar and other personal data are usually easily moved between phones.

Data transfer Information 

The 2G system is capable of data transfer rates of up to 14.4 kilobits per second (kbps). Originally, not all networks had this capability, but continued advances and improvements in the system have raised speeds. 3G systems designed specifically for mobile internet and video can transfer data much faster; Depending on the interface, theoretical download speeds range from 2 megabits per second (Mbps) to 56 Mbps.


The frequency band used by these phones depends on several factors, including location and technological changes. For example, in Europe, 2G GSM networks operate in areas of 900MHz and 1,800MHz and 3G networks use the 2100MHz band. The United States operates on frequencies ranging from 850MHz to 1.900MHz. Many other countries, including Australia and some places in South America, use 850 MHz. Most phones are designed for those countries where they are most commonly used, but a quad-band phone will handle 850, 900, 1800, and 1.900MHz, and usually work in most areas.


As of 2011, most countries from the Arctic to Antarctica use the GSM protocol. It is especially common in Europe, where it originated, and most of the Eastern hemisphere in general, including many developing countries. In the Western Hemisphere, the CDMA protocol is more common in the United States and some other countries. But many countries, including Canada and Brazil, use GSM.


The European Telecommunications Standards Institute (ETSI) created GSM to standardize cellular communications among European nations; Before this, each country had its own protocol. Standardization of technology created a large, growing pool of users, and the protocol spread throughout the world. In 2002, about 70% of cell phone customers worldwide used GSM services, while about 12% used CDMA. At the beginning of 2010, the GSM Association stated that it was over 4 billion users, and they expect it to be over 6 billion by 2015.

  • SIM card used in GSM phones.
  • A phone using a GSM network.
  • Brazil is a western hemisphere country using GSM technology.
  • The SIM card is placed in a GSM mobile phone.
  • Base stations provide coverage for cellular phone services using GSM or CDMA protocols.


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