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Developing a Physically Based Model for Multipath Fading. Dwight Hutchenson Clemson University Advisor: Dr. Daniel Noneaker. 2003 SURE Program. Basic Wireless Communication System. TX and RX In general, LOS and reflected signal components. Often no LOS component in mobile communications
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Developing a Physically Based Model for Multipath Fading Dwight Hutchenson Clemson University Advisor: Dr. Daniel Noneaker 2003 SURE Program
Basic Wireless Communication System • TX and RX • In general, LOS and reflected signal components • Often no LOS component in mobile communications • Transmitted Signal: s(t) • Received Signal: r(t) = A1s(t - d1/c) + A2s(t – d2/c) + . . .
Multipath Fading • Interference pattern results from radio waves reaching the receiver by two or more paths
Motivation • Statistical model of fading channel often used in communication system analysis • e.g. , Clarke-Jakes model • Our goal: develop deterministic fading-channel model based on geometry of reflectors • Focus on asymptotic behavior • TX dist >> reflector dist • Reflector dist >> RX variation
Signal at O through Pn: Signal at O through P0: (reference signal) (baseband-equivalent complex representation) Signal at the Origin due to Single Reflector
Signal at S through Pn : Signal at the Receiver due to Single Reflector
Signal at the Receiver due to Multiple Reflectors • Consider circular array of reflectors at distance r from O • Find the signal at S for N total reflectors:
Signal at the Receiver due to Multiple Reflectors (cont.) • Signal strength per reflected component must be normalized, to consider what happens as N approaches infinity • As N approaches infinity: • Bessel Function of the first kind of zero order:
Evaluating Signal Equation with the Bessel Function • Inserting Result into Signal Equation:
Density of Field Strengths • Empirical density of field strengths for fixed path through origin
Densities of Field Strengths (cont.) • Investigate possible relationship to density of sin function Density of sin(x)
Future Work • Spatial Correlation of Field Strengths • Corresponds to temporal correlation for receiver in motion • Non-circular reflector geometries