Subject: [NEXTEL-1] CRC Prediction Model

From: Marcel <[email-masked]>
Date: Mon, 02 Dec 2002 16:04:28 -0500

------- Original Message --------
From: "Terry S, Cory, P.E." <[email-masked]>
Subject: CRC Prediction Model

We have been working with CRC-Predict source code since 1994; and, currently
hold one of two licenses that have resulted in viable RF planning tools...ours
is sublicensable.

We have confirmed the prediction accuracy of CRC-Predict in rural and suburban
city morphologies using 30-meter DEM and 30-meter NLCD clutter to be less than
a sigma of 5 dB...and, less than 4 dB in rural environments. The accuracy is
best visualized with a plot of the field strength along a point-to-point
profile...which shows the predicted terrain-induced variations...in many cases
essentially the spatial impulse response of the terrain/clutter.

In simplest terms, CRC-Predict is quai-exact in two dimensions as a
physical-optics-based wavefront model that performs a chained point-by-point
boundary value calculation
superposing direct and specular component in which the Huygens source field is
integrated from the top of the clutter to infinity. The novelty of the
software resides in the efficient
integration algorithms developed by Jim Whitteker.

Our recent studies have shown that in such environments the field may be more
accurately predicted than can be obtained via drive testing....due to
drive-test instrumentation calibration and azimuthal antenna variations at the
mobile. Typical drive test measurement error using a roof-top antenna is
within a 6 dB sigma.

Additionally, we have compared the accuracy of CRC-Predict with the NOLC
Advanced Parabolic Equation Model, using the classic measured R-Data...finding
the prediction accuracy of both these physical optics models to be comparable
at PCS frequencies...APM enjoyes an accuracy advantage at lower frequencies.

We have proven to our own satisfaction that composite CDMA cochannel
interference cannot be predicted with sufficient accuracy to enable design or
performance simulation using either empirical regression-line Hata/Okumura
models or quasi-predictive Lee models which employ terrain averaging and/or
far-field knife (or, rounded) edge diffraction appliques.

Wave Concepts Intl
Terry S. Cory, P.E.
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