tailieunhanh - Mạng và viễn thông P15

Mobile Telephone Networks Being away from a telephone, a telex or a facsimile machine has become unacceptable for many individuals, not only because they cannot be contacted, but because they may be deprived also of the opportunity to refer to others for advice or information. For these individuals, the advent of mobile communications promises a era, one in which there will never be excuse for being new an ‘out-of-touch’. | Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic 75 Mobile Telephone Networks Being away from a telephone a telex or a facsimile machine has become unacceptable for many individuals not only because they cannot be contacted but also because they may be deprived of the opportunity to refer to others for advice or information. For these individuals the advent of mobile communications promises a new era one in which there will never be an excuse for being out-of-touch . This chapter discusses modern mobile radio communication technologies covering the principles of radio telephone service trunk mobile radio TMR cordless telephones the global system for mobilecommunication GSM as well as describing telephone communication with ships aircraft and trains and the emerging satellite mobile networks . Iridium and Globalstar . Mobile datacommunication networks are covered in Chapter 24. RADIO TELEPHONE SERVICE The first radio telephone services were manually operated in the high frequency radio band. These supported international telephone services as well as communication with ships and aircraft. Immediately after World War 2 a new breed of VHF very high frequency radio transmitters and receivers transceivers were developed. First used for applications such as the police the fire service and in taxis later development lead to their use as full radio telephones connected to the public switched telephone network PSTN for the receipt and generation of ordinary telephone calls. The technology used a radio mast located on a hill and equipped with a powerful multi-channel radio transceiver. The mobile stations were weighty but were nonetheless popular for commercial car telephone service which grew rapidly in popularity in the mid-1970s. For calls made to or from the radiotelephone user the public telephone network is connected via mobile .