Electromagnetic Wave Propagation Through Rain
Electromagnetic Wave Propagation Through Rain – Review
To start with, the title is really something of a misnomer. A superior title would be “Empirically Estimating Long Term Attenuation Statistics of Terrestrial Radio Links”. His results do not extend beyond radio frequencies and they are difficult to apply to anything other than global links. And he does not actually provide greatly insight into EM wave propagation so much as experimental parameters which are difficult to validate. Better for a tutorial on the issue of communication of radio waves and the atmosphere is: Doppler Radar and Weather Observations by Richard J. Doviak, Dusan S. Zrnic or any of a figure of books on radar meteorology. Apologies to the communications community but the radar guys have the most comprehensive action of the field, because it is the purpose of their study, rather than merely an impairment. Crane’s claim to fame is that you can use his book (and originally included Excel file) to make predictions about link availability for radio and radar installations. One shortcoming is trying to extend his result to other than surface to surface and surface to satellite links. It’s possible, but I don’t believe he’s greatly help. There is a similar ITU model and either is about as easy to use. I do not believe that one is decisively better than the other. Your option of model may depend further on you institutions prejudices and traditions or your customers’ “comfort level” with either model. One problem with this book, IMHO is that its “derivations” are overly empirical and difficult to extend. (I do not think I am being uncharitable in publicly expressing the opinion that they are mathematically unsound in places and the mathematically unsound derivations frequently depend on bodily assumptions which he never certainly justifies.) I’ve seen people make very casual analyses based on misapplication “Crane’s model.” And these results, inherited at third hand and hardly understood, become gospel. Admittedly this is not so much the fault of Crane but of his prospective disciples. Another problem is that his models are not easy to apply, as presented, one wants to depend on his spreadsheets. (This is Crane’s fault.) It is difficult to extend his spreadsheet to portable platforms, such as aircraft and ships. It would be nice to have the climate zone boundaries in tabular form so that one could model such platforms as they move around the earth. The ITU models are more or less the same, the parameters and zone boundaries are different. Use whichever you’re comfortable with. If you want to make ballpark assessments of link availability Crane’s spreadsheet should be fine. If you need to learn about electromagnetic wave propagation through rain, go elsewhere.