What is GSM?
GSM or global mobile communication system is a mobile phone protocol that is standard in most parts of the world. Technology experts have created a protocol in the 80s and 90s to standardize a mobile phone service between countries in Europe. GSM phones use subscription identity cards (SIM), which is necessary for their function and allows the user to easily change phones. It is the main competitor of the Code Division Protocol more access (CDMA).
technology
Technically, the term GSM concerns second -generation (2G) voice networks, which work based on a combination of time distribution of multiple access (TDMA) and frequency distribution of multiple access (FDMA). TDMA takes the frequency channel that uses the phone and divides it into individual pieces of time that are assigned to each user. FDMA divides the frequency belt into sections and assigns one mobile phone tower. The towers usually spread far enough apart, so those that use the same fPropveniCiverlap of its area of coverage. In fact, this is called the Universal Mobile Telecommunication System (UMTS) and uses the standard air interface of the Air CDMA (W-CDMA) in most places. Although both Spectrum Spectrum, W-CDMA and Standard used by competing CDMA phones (usually CDMA2000) are not compatible.
GSM and CDMA
Although both refer to mobile phone networks, GSM and CDMA differ in the technology they use. The CDMA uses a system in which all signals are sent simultaneously, but each is spread over more frequencies. The servers assign each code to each transfer so that the signals do not interfere with each other and can be adapted between the sender and the receiver.
originally, both protocols varied in signal quality, consistency and voice distortion, among other things. However, both methods have been improved and there are few significant divisions between themPans in terms of call quality. GSM phones are a little more likely to drop calls when the user moves between cellular towers, but has better coverage of places with many mountains. This technology also allows voice and data transfer at the same time, which most CDMA phones cannot do.
In some parts of the world, both services are available, but one tends to be more common than the other. Most cell service providers use only one type of network because it is very expensive to maintain both types of services. GSM is an older service and is located in most places around the world, while CDMA is the most common in the US and Asia.
SIM card
GSM phones use a SIM card, a small card with a built -in integrated circuit that stores personal information, user of the user's number, account information and contacts. When the user switches the phones, the SIM card changes from one phone to another cell service and telephone number and activates a new phone. ListThe s, calendar and other personal data usually move easily between headphones.
data transfer information
The2G system is capable of transferring data up to 14.4 kilobites per second (KBPS). Originally, not all networks had this ability, but continued progress and improvements to increase speeds. 3G systems that are designed specifically for mobile internet and video can transmit data much faster; Depending on the interface, the theoretical download speeds range from 2 megabites per second (MBPS) to 56 Mbps.
Frequency
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 the 900 MHz And 1,800 MHz and 3G networks use the 2,100 MHz band. The United States works on frequencies in the range of 850 MHz and 1,900 MHz. Many other countries, including Australia and some places in South America, use the 850 MHz series. Most phones are designed for countries where they are usedMost often, but a four -band handset will process 850, 900, 1,800 and 1,900 MHz and usually work in most areas.
coverage
Since 2011, most countries from the Arctic area to Antarctica have been using the GSM protocol. It is especially common in Europe where it was created, and most of the Eastern hemisphere in general, including many developing countries. In the western hemisphere, the CDMA protocol is more frequent in the United States and several other countries. However, many countries, including Canada and Brazil, use GSM.
History
The European Institute of Telecommunications Standards (ETSI) created GSM to standardize mobile phone communication between European nations; Every country had its own protocol. Standardization of technology has created a large, growing user fund and the protocol has spread around the world. In 2002, approximately 70% of mobile phone clients around the world used GSM services, while about 12% used CDMA. In early 2010, the GSM Association said there were more n4 billion users and estimate that by 2015 it will be more than 6 billion.