US 5,450,615 AGranted

Prediction of indoor electromagnetic wave propagation for wireless indoor systems

AssigneeAT&T Corp.

InventorsSteven J. Fortune, David M. Gay, Brian W. Kernighan, Orlando Landron, Reinaldo A. Valenzuela, Margaret H. Wright

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Abstract

Techniques are disclosed for predicting RF propagation within a structure such as a building. A reference transmitter location and a plurality of reference receiver locations are selected. For each reference receiver location, RF propagation pathways are determined with respect to the reference transmitter location. The RF propagation pathways include a direct path joining the reference transmitter location to a given reference receiver location across a straight-line path, as well as one or more reflection paths joining the reference transmitter location to a given reference receiver location via reflections from one or more reflective surfaces. One or more propagation pathways may pass through an RF obstacle, such as, for example, a lossy dielectric material. Each reflective surface and RF obstacle is associated with a reflection coefficient and a transmission coefficient. These coefficients are computed for each object and surface from a multilayer dielectric model, maintaining angle and polarization dependencies. For each propagation pathway, a propagation component consisting of the propagation loss relative to free-space propagation is calculated as the product of the magnitude squared of the reflection and transmission coefficients. The local mean of received RF power at each of the reference receiver locations is calculated as the scalar sum of the powers of all the propagation pathway components reaching the specified location.

A method for predicting RF propagation including the following steps:

(i) selecting a reference transmitter location and at least one reference receiver location;
(ii) determining a plurality of propagation pathways between said reference transmitter location and each of said reference receiver locations;
said propagation pathways including at least one direct path joining said reference transmitter location to one of said reference receiver locations along a straight-line path, and at least one reflection path joining said reference transmitter location to one of said reference receiver locations via at least one reflective surface;
(iii) associating each of said reflective surfaces with a reflection coefficient specifying the ratio of reflected to incident RF energy, and a transmission coefficient specifying the ratio of RF energy transmitted through the surface to incident RF energy;
(iv) for each propagation pathway, calculating a propagation component representing propagation loss relative to free-space propagation of RF energy from a reference transmitter at the reference transmitter location producing a reference RF power level, the propagation loss being equal to the product of the magnitude squared of the reflection and transmission coefficients;
and
(v) for each reference receiver location, calculating a local mean of received power equal to the scalar sum of the powers of all of the propagation pathway components corresponding to the reference receiver location;
(vi) calculating the propagation component of each reflection path including one reflective surface using a ray imaging procedure comprising the following steps:
(a) from the at least one reference receiver location, tracing the reflection path backwards, in a direction opposite to the direction of travel of the RF energy, to encounter a first reflective surface;
(b) determining a first reference receiver location image about the first reflective surface as the reference receiver location reflected about a plane including the first reflective surface;
and
(c) calculating the overall reflection path length as the distance between the reference transmitter point and the first reference receiver location image.

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Abstract

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