TAILIEUCHUNG - Điện thoại di động mạng lưới Radio P1

During the first half of this century, the transmission of human voice through the telephone was the dominant means of communication next to telegraphy. Radio-supported mobile communication has constantly grown in importance during the last few decades and particularly the last few years to technical advances in transmission and switching technology as well as in microelectronics. Table presents an overview of the chronological development of mobile radio systems. In contrast to wireline networks, mobile radio networks that comply with the wish for geographically unrestricted communication can be used anywhere where it is not economic or possible to install cabling | Mobile Radio Networks Networking and Protocols. Bernhard H. Walke Copyright 1999 John Wiley Sons Ltd ISBNs 0-471-97595-8 Hardback 0-470-84193-1 Electronic 1 Introduction During the first half of this century the transmission of human voice through the telephone was the dominant means of communication next to telegraphy. Radio-supported mobile communication has constantly grown in importance during the last few decades and particularly the last few years to technical advances in transmission and switching technology as well as in microelectronics. Table presents an overview of the chronological development of mobile radio systems. In contrast to wireline networks mobile radio networks that comply with the wish for geographically unrestricted communication can be used anywhere where it is not economic or possible to install cabling. Whereas the limiting factor with wireline networks is the network infrastructure that has to be created the capacity of radio networks is determined by the frequency spectrum available and the physical attributes of radio waves in the earth s atmosphere. The development of radio systems is influenced considerably by the scarcity of an important resource frequencies. For instance spectral efficiency can be improved through the digitalization of speech and the use of source and channel coding. Existing analogue radio systems are therefore being replaced more and more by digital mobile radio networks. Modern digital techniques used in modulation coding and equalization enable bandwidth-efficient transmission and offer better interference behaviour and lower susceptibility to noise than analogue-modulated signals. Digital voice and data can be processed and stored before being transmitted. This allows the use of multiplexing methods such as TDM Time-Division Multiplexing FDM Frequency-Division Multiplexing and CDM CodeDivision Multiplexing that enable services to be provided to many users. For example with TDM a large number of users in a

• Kĩ thuật Viễn thông
• Mạng lưới Radio
• mạng di động
• truyền thông điện báo
• kỹ thuật truyền tải
• mạng vô tuyến di động
• nguyên tắc truyền Radio