Q: What is the Hata/Davidson propagation model?
A: Hata/Davidson builds on previous propagation models:
The Okumura model was described in from "Field Strength and Its Variability in VHF and UHF Land-Mobile Radio Service," by Yoshihisa Okumura, et.al., Review of the Electrical Communications Laboratory, Vol. 16, No. 9-10, September-October 1968. The application of that model involves the use of numerous curves (based primarily on Okumuras empirical field strength data) to determine adjustment factors to be applied to field strength.
Hata ("Empirical formula for propagation loss in Land Mobile radio services," IEEE Transactions on Vehicular Technology, Vol. 29, No. 3, Aug 80) reduced many of Okumuras adjustment to equations, but the equations were limited to paths of less than 20km, as well as other limits on its application.
Hata/Davidson ("A Report on Technology Independent Methodology for the Modeling, Simulation and Empirical Verification of Wireless Communications System Performance in Noise and Interference Limited Systems Operating on Frequencies between 30 and 1500MHz", TIA TR8 Working Group, IEEE Vehicular Technology Society Propagation Committee, May 1997.
Hata and Hata/Davidson ignore some of the adjustment factors included in Okumura, such as the slope of the terrain, street orientation, and correction for location on hills. The main factors included in Hata/Davidson are the area type (Urban, Suburban, Quasi-open, Open) as well as corrections for the receiver antenna height. Hata/Davidson also includes frequency and distance corrections to extend the limitations on Hata, particularly the distance range to 300km.
It should also be noted that Hata/Davidson computes the basic median field strength (to which the various adjustments are applied) on the Height Above Average Terrain (HAAT) of the transmit antenna (typically based on the 3-16km segment of a path), rather than the topography of the entire path.
Under some conditions, the Hata/Davidson calculation can yield losses less than free-space loss. In these case, the free-space value is used.
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