A model i s described which may be used t o p r e d i c t land mobile radio system performance over irregular t e r r a i n . The model uses a semi-empirical formulation t o c a l c u l a t e p r o p a g a t i o n l o s s e s from a selected basestation location to surrounding mobile locations within a variable-size "box" not exceeding two degrees l a t i t u d e by two degrees longitude. Terrain data is obtained from a computer-accessible data base. The output i s a p l o t showing contours of constant propagat i o n loss, power d e n s i t y , o r a v a i l a b l e r e c e i v e d power.Model's PurDose Land mobile communication system designers and engineers often must decide whether ; o use design-aid models not well suited to the problem of predicting s i g n a l a t t e n u a t i o n o v e r i r r e g u l a r t e r r a i n o r t o perform many tedious and laborious hand c a l c u l a t i o n s which, coupled with certain "rules of thumb", provide an estimate of system performance.The model documented i n t h i s t a l k p r o v i d e s r e l i e f from such problems. By using a computer to determine a p a r t i c u l a r a r e a ' s t e r r a i n c h a r a c t e r i s t i c s and a l s o l e t t i n g t h e computer make t h e t e d i o u s and complex c a l c u l a t i o n s o f propagation losses for the given terrain, the model user can spend more time optimizing the land mobile system's performance by evaluating different base s t a t i o n l o c a t i o n s , a n t e n n a h e i g h t s , e t c . CaDabilitiesFor communication systems which o p e r a t e a t VHF and higher frequencies, t h e character of t h e t e r r a i n between t h e transmitting and receiving antennas, as well as the heights of the antennas above immediate t e r r a i n , will a f f e c t s i g n i f i c a n t l y t h e a t t e n u a t i o n o f t h e r a d i o s i g n a l s .The model reported considers these terrain influences, along with other commonly considered influences, by automatically accessing digitized topographic data files* t o d e v e l o p t h e p a t h d a t a needed t o compute the basic transmission l o s s . Computation of the basic transmission loss i s accomplished using a formulation for point-to-point paths. The s t a t i s t i c a l c h a r a c t e r o f t h e b a s i c transmission loss r e s u l t s from long-term fading (time a v a i l a b i l i t y ) , p a t h -t o -p a t h d i f f e r e n c e s ( l o c a t i o n v a r i a b i l i t y ) and prediction confidence considered in t h e model'. The type of model output data i s s e l e c t e d by t h e user. Options range from s i m p l e p a t h t e r r a i n i n f o r m a t i o n t o b a s i c t r a n s m i s s i o n l o s s e s t o u t i l i z at i o n s o f t h e basic transmission loss i n computing power density or received signal level between a base s t a t i o n and any mobile location within time availab i l i t y and l o c a t i o n v a r i a b i l i t y . P l o t t e d o u t p u t data are contoured over a geographical area n o t t o exceed two d ...
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