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With the development of mobile communication technology, wireless cellular network coverage more widely,and the number of emergency calls initiated mobile communications in the share of all emergency calls will also rise in proportion. The existing cellular network can provide mobile communications for emergency call to auxiliary decision which is very small, the survey shows that about 25% of mobile users do not know the exact location when they initiate an emergency call , which brings the timely reasonable alarm to many restrictions .Accordingly, the mobile communication network can be able to provide accurate location information for mobile users to initiate an emergency call.
Cellular mobile communication has become an extraordinary success around the world , its development is so rapid that the business requirements far more than the original forecast.For the most part, the operator only restricts a fixed frequency, and almost hopeless increase the spectrum while the expansion original analog technology can not keep pace with demand . More recent technologies have more efficiently use the spectrum and provide users with improved safety and greater convenience.Nevertheless, the frequency band which are assigned to these new technologies are often overlapped with older technologies , which makes the transfer policy complicated.
Traditionally ,the 900MHz band was used in Europe while North America use 800MHz band, and
most Asian countries use both bands.The main criteria of the European 900MHz of analog frequency of allocation is a full access communication system, although some European countries using other standard GSM is a digital system 900MHz frequency band, which has been used in Europe as a common standard and many other countries in the world use, and provided a very useful device roaming.In addition, GMS standard has been used to 1800MHz (DCS 1800). Some countries are setting up an independent 1800 MHz network while others are trying to increase their use of this band GSM capacity. Because both bands using the protocol is uniform, and now people more commonly used the terms of GMS-900 and GSM-1800 rather than GSM and DCS1800.