Propagation of Radiowave for Lmds Systems

The design, planning and deployment of LMDS (Local Multipoint Distribution Service) systems require a good understanding of radio wave propagation. After a presentation of the different propagation mechanisms , we present the propagation channel characteristics: attenuation, variability and frequency selectivity due to multi-path; the selectivity being defined from wideband parameters such as delay spread, delay window, coherence bandwidth ...To each environment correspond particular typical models (theoretical, statistic or semi-empirical). Different models for narrow bandwidth prediction in different environments found in the literature will be summarised; effects of vegetation and rain will be taken into account. In broadband some frequency selectivity characteristics will be given from France Telecom measurements and experimental data found in the literature.