Radio was first introduced in the United States in the 20th century, 40 years, is designed for mobile users to connect to the car's fixed network. In 1960, Bell System introduced the new system, called Improved Mobile Telephone Service "(the emperor), has brought many improvements, such as direct dial telephone and a higher bandwidth. IMTS first analog cellular systems, based on the developed to the 60 the beginning of the late seventies. System "mobile" because the coverage is divided into smaller areas or "cells", each has a low power transmitter and receiver.
This is the first generation (1 g) of the analog mobile communications system are two key improvements to see 70s of last century: the invention of the microprocessor and digital control of the connection between mobile phones and hundreds of people.
The second generation (2G) digital cellular system was first developed in the late '80s. Number of these systems is not only a confirmation link, and the voice signal. The new system provides high-quality, high-capacity, low-cost consumers.
Third-generation (3G) systems promise faster communications services, including voice, fax and the Internet, anywhere, anytime seamless global roaming. ITU IMT - 2000's global 3G standards has opened the way to innovative applications and services (such as multimedia entertainment, infotainment and location-based services, etc.). The first launch of 3G network in Japan in 2001.2.5G networks such as GPRS (Global Packet Radio Service), has been in parts of Europe.
Work has already started to develop the fourth generation (4G) technology in Japan.
It should be noted that the analog and digital systems, 1G and 2G, and still and there is many areas.
Mobile operators use radio spectrum to provide services. Spectrum is generally considered a scarce resource, has been identified as. In accordance with tradition, he agreed with a number of industries including broadcasting, mobile communications and military. World (WRC) of the 1993 appropriations to achieve the desired range of 2G mobile growth, based on the demand at that time. In 2000, the World Radiocommunication, WRC expanded significantly the scope of the resolution the possibility, for 3G, and by using the existing 2G spectrum blocks for 3G technology and 3G spectrum allocation of a maximum of 3 GHz.
Before the advent of mobile technology, ability to improve the distribution of frequencies, and because of channel. However, it reduced the total bandwidth available to each user, thus affecting the quality of service. Mobile technology, so that the Division's geographic area, rather than the frequency, resulting in more efficient use of spectrum. Such a geographical reuse of the radio is called "frequency reuse.
In mobile networks, the cells are usually organized in groups 7-1 cluster. There is a "1 percent" or "base" in the center of each cell, the transmitter / receiver antennas and switching equipment housing. The size of the grid depends on the density of users in the region: for example, in densely populated areas of network bandwidth can be increased by reducing the size of the cells or by adding a number of overlapping cells. This increases the number of channels will not increase the actual number of frequencies. All the base stations in each cell is connected to a central point, called the Mobile Switching Office (MSO), whether fixed-line telephone or microwave. MSO, often with the public telephone network (PSTN):
Mobile technology enables "hands off 'users from one cell to another as they go. This is the main feature, which allows mobile users. Continuation of the computer unit to track mobile users in the cell, when a user reaches a new phone, the computer automatically hands the phone, call to become a new channel in another cell.Norms of international roaming agreements the user to make and receive welcome home network coverage.Access Technologies (Frequency Division Multiple Access, Time Division Multiple Access, Code Division Multiple Access)
Site: frequency division multiple access (site) is the most common analog system. This technology, which is divided into frequency bands, and then assigned to the user. With the site, only one user at any time and spent a channel. Therefore, the channel closed, other people's dialogue, the first one until the last phone, or through a one-time for another channel. "Full duplex" FDMA transmission requires two channels, one for transmission and one for receiving.Site is used for the first generation analog system.
TDMA: Time Division Multiple Access (TDMA) improves spectrum capacity to split at each time interval. TDMA allows each user access to the entire radio frequency channel short-term call. In the other users sharing the same frequency channel at different times. Continuously from one base station to another user channels. TDMA is the dominant technology for second generation mobile cellular network.
CDMA: Code Division Multiple Access is based on spread-spectrum technology. Because it is applied to encrypted transmission, it is being used for military purposes. CDMA's ability to improve the spectrum of all channels for all users occupy the time. The transfer will be heard around the radio, any voice or data call is assigned a unique code to distinguish it from other requests by the same band. CDMA permission soft take off ", which means that the terminal can be with multiple base stations simultaneously. Dominated by the third generation of wireless mobile phone interface, or the IMT - 2000 is a wideband CDMA version of the three models (of IMT - Deputy the Secretary of the IMT - MC and the IMT - courses).
1G and 2G mobile standards
Each generation of mobile communications is based on leading technology that will significantly improve the possibility of the region. Prior to the arrival of the IMT - 2000 cellular network has been developed in accordance with the figures themselves, regional and national standards, the establishment of a decentralized market.
The first generation:
1) Advanced Mobile Phone System (AMPS) for the first time in the U.S.. It is similar to a system based on frequency division multiple access (Frequency Division Multiple Access) technology. Today is the most common analog system and the second largest in the world.
2) The Nordic mobile telephone (the NMT) development mainly in the Nordic countries. (450 million in 1998, some 40 countries, including the Nordic countries, Asia, Russia and other Eastern European countries)
3) Total Access Communications System (ARS) of the first use is in 1985 in Britain. It is based on AMPS technology.
There are many other proprietary systems, very few sell their own country.
The second generation:
1) The Global System for Mobile Communications (GSM) is the first commercial exploitation of the digital cellular communication system. Was first in the 20th century, 80 years later, the pan-European initiative Eureopean Commission, telecommunications operators and equipment manufacturers. European Telecommunications Standards Institute is responsible for the standardization of GSM. Mobile phone use TDMA (Time Division Multiple Access) technology. It is used in all European countries and adopeted other continents. This is the dominant mobile standard of today, the elderly (45%) users in the world in April 1999.
2) IS - 136 TDMA is a digital and analog AMPS technology improvements. This is known as D - AMPS binary, and then fist at the end of 1991, its main purpose is to protect a major investment, operating a bmade AMPS technology. Digital AMPS worry-free service launched in 70 countries around the world (in March 1999 a total of nearly 22 million TDMA phones in circulation, the dominant market, the United States and parts of Asia)
3) CDMA yes - 95 increases the likelihood that all radio stations, each with a unique code (CDMA, or Code Division Multiple Access). This series of digital transmission technology and the Republic of Korea is the largest CDMA IS - 95 of the market in the world.
4) Personal Digital Cellular (PDC) is the second largest digital mobile communications standard, although it is only used in Japan, where in 1994. Such as GSM, is based on TDMA technology access. In November 2001 a total of about 66.39 million PDC users in Japan.
5), Personal Handy Phone System (PHS) is a digital system used in Japan, first introduced in 1995, as a cheaper alternative to cellular systems. It is between mobile and wireless technologies. It allows the signal coverage area and restrict the use in moving vehicles. In November 2001, 5.68 million PHS users in Japan.
Other than acquiring a 1800 Number, companies also turn to mobile communication to serve their customers best.
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