Subject: [NEXTEL-1] CRC model accuracy

From: Marcel <[email-masked]>
Date: Wed, 04 Dec 2002 13:58:16 -0500

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

I wish to report some results comparing drive test data and CRC-Predict model
point-by-point results at cellular frequencies in a 3rd-tier market area in
Iowa. The results are in terms of the std dev of comparison under certain
conditions:

"A" is the overall sigma of the entire drive data set as compared with CRC
predictions

"B" is the comparison sigma of a subset of the drive test data... constrained
so that the vehicle azimuth angle with respect to the cell site is constrained
to a small range essentially broadside to the vehicle (i.e., minimum
antenna-induced variations)

"C" is the sigma of the drive test data set

If we further assume that in "B" the drive data is perfectly accurate; then
"B" represents the sigma of prediction accuracy of the CRC model...in the test
venue, actually an upper bound on the spatial prediction accuracy of the
radiated field.

Assuming statistical independence in a lognormal process,

C^2 = A^2 - B^2.

Using this model, the following results were obtained:

Cell            A[dB]        CRC Sigma[dB]       DT Sigma[dB]

Fayette            5.98            3.80 rural                4.62
Independence   8.32            4.00 rural                7.63
                                         4.84 city
Manchester      7.62            3.89 rural                6.55
                                         4.77 city
Strawberry Pt   6.86            3.77 rural                5.73
Oelwein           6.87            4.03 rural                6.02

These results suggest
Averages         7.13            3.90 rural                6.02
                                        4.80 city

These results suggest that in such environments predicted results are more
accurate than drive test results. In the case of these tests, a
centrally-located omni rooftop antenna (with elevated feedpoint) was used on a
full-size sedan. To those who might interject that such engineering results
may be of minimal practical value and that all that matters is whether or not
phones work in cars...we would suggest that a particular unique test "setup"
compared to the situational ensemble of vehicle variety and available phones
in marginal coverage environments would pose similar statistics.

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