E W101 Attenuation in dB per km added empirical data which makes it more useful. Hata gives some closed-form equations for median path loss in urban areas. (See page 364 of the 0.4 referenced handbook.) Plugging in some numbers, the median path loss for a 10-km path through a city at 1 GHz with a 33-meter-high transmit Somewhat antenna and a 3-meter-high receiving antenna Less for 0.3 predicts approximately 161 dB path loss. Hata Horizontal gives correction factors for large cities and subPolarization urban areas which make relatively small changes to this value. 0.2 The Okumura and Hata models give approxiIndependent mations, but accurate predictions must be made of from computer programs that use environment Polarization 0.1 models. Mr. McLarnon gives one suggestion for a starting point (described as "crude but useful." The suggestion is taken from J.D. Parsons' book, The Mobile Radio Propagation Channel (Wiley, 1992).) 1 0.2 0.5 2 This approach is to approximate loss in an urban 3 Frequency in GHz environment by assuming line-of-sight loss out to 1 km and two-ray propagation beyond 1 km. Figure 2: Attenuation through a dense forest depends on the distance through One comment in literature is that antennas Figure 2: Attenuation through a dense forest depends on the distance through the the forest and the frequency. forest and the frequency. above the roof top heights will provide signifinet received-signal strength will be the vector sum of all cantly lower loss paths. of these signals. My personal field experience supports the assertion that In the IEEE Mobile Communications Handbook, the Okumura when your receiver is within line of sight of a transmitter in an urban or suburban environment, propagation is reasonably Model for urban area radio propagation is described as the most close to the line of sight propagation model. I suspect this is widely used propagation model. However, the Hata Model has The Journal of Electronic Defense | July 2015 44 XMTR BUILDING BUILDING BUILDING BUILDING BUILDING BUILDING RCVR Figure 3: An urban or suburban environment has significant numbers of multi-path components to received signals.