tailieunhanh - Wireless địa phương vòng - lý thuyết và ứng dụng P6

Wireless communications systems offer a great deal of flexibility for mobile users and represent a key component in future global personal communications. Local loop systems are envisaged to allow the integration of many services into a high-speed digital system which allows communication inside buildings and access to the external world. Wireless systems potentially offer unprecedented flexibility for home or office data communications systems and reduced overheads costs for both installation and equipment | Wireless Local Loops Theory and Applications Peter Stavroulakis Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-49846-7 Hardback 0-470-84187-7 Electronic 6 Wide-band Wireless Outdoor to Indoor Local Loop Channel Models for Urban and Suburban Environments at 2 GHz Ian Oppermann and Jaakko Talvitie Introduction Wireless communications systems offer a great deal of flexibility for mobile users and represent a key component in future global personal communications. Local loop systems are envisaged to allow the integration of many services into a high-speed digital system which allows communication inside buildings and access to the external world. Wireless systems potentially offer unprecedented flexibility for home or office data communications systems and reduced overheads costs for both installation and equipment. For reasons associated with both cost and flexibility the idea of WLL or wireless to the home has generated significant interest with telecommunications service providers. Some systems have been proposed that it should be possible to offer low mobility users very high data rates and may even be intergrated into B-ISDN services 1 . In order to assist in the development of such systems knowledge of the characteristics of the WLL channel must be investigated. To date little has been published on wide-band WLL channel models at this frequency so little is known about the channel characteristics. Narrowband channels are far better understood 2 3 and narrowband WLL systems have proven the usefulness of the approach. Recent papers published which address the subject of wide-band WLL channel characteristics and has measurement details are given in 4 5 . Therefore to determine the characteristics of a wide-band channel model for the WLL in urban and suburban environments a series of measurements were carried out in offices and homes both at Sydney Australia and in Helsinki Finland. Seperate measurement procedures were followed in Sydney and Helsinki however .