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45182637-Lecture-Large-Scale

45182637-Lecture-Large-Scale - Mobile Radio Propagation...

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1 Mobile Radio Propagation Large- Scale Path Loss 1. Introduction to Radio Wave Propagation Electromagnetic wave propagation reflection diffraction scattering Urban areas No direct line-of-sight high-rise buildings causes severe diffraction loss multipath fading due to different paths of varying lengths Large-scale propagation models predict the mean signal strength for an arbitrary T-R separation distance. Small-scale (fading) models characterize the rapid fluctuations of the received signal strength over very short travel distance or short time duration.
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2 Small-scale fading: rapidly fluctuation sum of many contributions from different directions with different phases random phases cause the sum varying widely. (ex: Rayleigh fading distribution) Local average received power is predicted by large-scale model (measurement track of 5 to 40 ) λ λ 2. Free Space Propagation Model The free space propagation model is used to predict received signal strength when the transmitter and receiver have a clear line-of-sight path between them. satellite communication microwave line-of-sight radio link Friis free space equation : transmitted power : T-R separation distance (m) : received power : system loss : transmitter antenna gain : wave length in meters : receiver antenna gain L d G G P d P r t t r 2 2 2 ) 4 ( ) ( π λ = t P ) ( d P r t G r G d L λ
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