08-17-2017, 12:37 AM
introduction
Pick up any newspaper today, and it's safe to say that you will find an article somewhere related to mobile communications. If this is not the case in the technology he is almost certain to be in the business section and are associated with increases in prices of shares of operators and equipment makers, or acquire and absorb them. Such is the prevalence of mobile communication, which affects practically "lives with and became everyone the main political topic and makes a significant contribution to national gross domestic product (GDP).
The main factor of change in the field of mobile for the past 10 years has been massive, allowing the impact of digital technology, as in digital signal processing and services. equivalent to the driver now, and in the next five years, it is the prevalence of software in both networks and Terminal. the digital revolution is well underway, and we stand on the threshold of a revolution software. Accompanying these changes of social development with the expansion in the use of mobile phones. On the basis of speech is dominated by services, that we are experiencing a significant increase in applications related to SMS (Short Message Service) together with the beginning of Internet applications that use the WAP (wireless application protocol) and I-Mode.Mobile phone not only followed the clock, calculator and organizer of an important personal accessory, but include all of them. With new Internet Extensions, it will also lead to a convergence of PC, Hi-y and television and to ensure mobility on objects, previously only available in one network.
Development of analog systems of the first generation (1985 g.) to the second generation (2 g) digital GSM (1992) was the heart of the digital revolution. But much more than that, it was a huge success for Standardization coming from Europe and is slowly spreading around the world.
However, worldwide roaming continues to pose some problems with pockets of standards IS-95 United States (code division multiple access [CDMA] channels instead of plural access with time division of channels [TDMA] digital system) and IS-136 (TDMA variant) are rooted in some countries. Expansion of GSM (2 g) through GPRS (General Packet Radio Service) and EDGE (enhanced data rates for GSM evolution) (E-GPRS), as well as WAP and I-Mode (so-called 2.5 G) enables data transmission with higher rates, as well as before the introduction of 3 g.
Mobile radio access systems contain, together with the support of the underlying network. The Latter is characterized by the GSM MAP (mobile application protocol), which provides mobility management system functions.
GSM was designed for digital data or voice services to low-bandwidth, that could fit in the speech of the channel (for example, 9.6 kbit/s). This is a chain and not a package oriented network and therefore ineffective to transfer data. To address the rapid growth in popularity of Internet services, GPRS, GSM, is added to allow packets (Internet Protocol [IP]) connection at speeds of up to around 100kbit/s.
Third generation (3 g) system have been standardized in 1999, these include the IMT-2000 (International Mobile Telecommunications 2000) that has been standardized by the ITU-R and it includes UMTS (Universal Mobile Telecommunications System) European standard ETSI (European Telecommunications Standards Institute), the United States is a CDMA 2000 and the Japanese NTT DoCoMo W-CDMA (Wideband Code Division multiple access) system. Such systems are expanding services (raznotempovoj) high quality multimedia and converged fixed, cellular and satellite components. Radio-radio interface standards are based on the W-CDMA (UTRA FDD and TDD in the UMTS UTRA, with many CDMA carriers 2000 and one carrier UWC-136 on derivative American standards). basic network were not standardized, but the Group three ?? developed GSM (MAP), developed the ANSI-41 (from the American National Standards Institute) and IP-based ?? all the candidates. 3 g is also about a variety of terminal types, including many non-voice terminal, such as embedded into all kinds of consumer goods. Bluetooth (another standard in 3 g orbit, but probably related to him) is the middle that drew attention to such applications. Thus, services from a few bits per second up to 2 Mbit/s can be represented.
For broadband wireless communications, internal standards, such as 2 HIPERLAN (High Performance Local Area Network ?? ETSI "broadband radio access network [BRAN]) and IEE 802.lla appeared to support IP-based services and provide some QoS (quality of service) support. Such systems are based on orthogonal frequency division of channels (OFDM) rather than CDMA and is planned for 5 Ghz range.