Computer Propagation Analysis Tools

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Martha Lyons
5 years ago
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1 Compue Popagaion Analysis Tools. Compue Popagaion Analysis Tools Inoducion By now you ae pobably geing he idea ha pedicing eceived signal sengh is a eally impoan as in he design of a wieless communicaion sysem. Empiical models lie lognomal shadowing ae simple o use and don equie oo much inpu, bu hey only cudely epesen he eal wold. Ideally we would be able o pecisely descibe he elecomagneic popeies of ou envionmen and hen exacly calculae how adio waves will popagae in i. Tha s a pey all ode. Howeve, in some cases we can mae a sa by using opogaphic infomaion. In he US, he US Geological Suvey (see mainains Digial Elevaion Model (DEM) daa fo he enie US. These give elevaion as a funcion longiude and laiude. Using hese daa we can esimae diffacion effecs due o he gound. Noe ha he USGS daa is fo he gound only, i does no include buildings and sucues. In uban seings hose ae majo componens of he popagaion envionmen. Thee ae, howeve, pivae companies ha develop and sell daabases of uban sucues. These daa, as well as he USGS daa, ae pimaily calculaed fom aiplane and saellie images using seeoscopy and ohe mehods. Figue.: USGS opogaphic daa fo he Pullman aea. The veical scale is gealy exaggeaed. Pullman is compised by fou hills op lef is Miliay Hill, igh is College Hill, lowe lef is Sunnyside Hill, lowe cene is Pionee Hill. So, we will assume ha we have opogaphic daa fo any egion whee we ae ineesed in building a cellula sysem. Ulimaely we wan o be able o pedic popagaion ove he hee- EE43: RF Engineeing fo Telecommunicaions Sco Hudson, Washingon Sae Univesiy 05/8/7

2 Compue Popagaion Analysis Tools. dimensional gound. Since we ve aleady eaed diffacion in a wo-dimensional envionmen, le s sa wih consideing popagaion in a D envionmen. A Two-Dimensional Popagaion Tool Le s say we have a sampled wo-dimensional opogaphic pofile of he fom ( i, i ); i 0, N. Le he ansmie be a i 0 and he eceive a i N. (Because of ecipociy, we could swich hem wihou changing he esul.) The values give he ange (disance) fom he ansmie and he values he gound heigh a hose anges. Fuhemoe, le he ansmie and eceive heighs above he gound be h and h. This is illusaed in Figue.. h 0 m m y n n h N m N n Figue.: Geomey of a wo-dimensional diffacion poblem. We will model he gound by linealy inepolaing beween he sample poins. We wan o now whehe o no hee is a line-of-sigh (LOS) pah beween TX and RX. If he LOS is bloced hen we wan o esimae he diffacion gain. One appoach is as follows. Imagine ha we had a suveyo s sigh a boh TX and RX. We could loo a each daa poin and ecod is viewing angle above (o below) level. These ae he angles and in Figue.. Tha poin wih he lages angle defines he hoion. If he line beween TX and RX falls above he hoion, hen hee is a clea LOS pah, ohewise hee is no and we will need o conside diffacion. If hee is a clea LOS pah, hen we will use a log-nomal shadowing model of he fom P P0 0nlog (.) 0 o esimae eceived signal sengh. We could use, say, he Haa model o esimae P0 and n. We can calculae he angles and using igonomey EE43: RF Engineeing fo Telecommunicaions Sco Hudson, Washingon Sae Univesiy 05/8/7

3 Compue Popagaion Analysis Tools.3 0 an an ( ( N h ) N h ) (.) Le s assume ha he LOS is bloced, as shown in Figue.. If he hoion angles fom TX and RX ae m and n, especively, hen (0.4) gives N u ( m )( n ) ( N h ) ( an N 0 h ) (.3) We can hen calculae he diffacion gain Gd fom (0.) and modify he eceived signal sengh of (.) accodingly. A Thee-Dimensional Popagaion Tool Hee we ll conside a vey simple popagaion-modeling ool wien fo EE43 ha uses USGS opogaphic daa ogehe wih log-nomal shadowing and diffacion models. Conside Figue.3. We have some elevaion daa ( x, y) whee x,y denoes posiion on he gound. If he ansmie and eceive locaions ae ( x, y ) and ( x, y ) hen he line connecing TX and RX defines a wo-dimensional opogaphy () of he ind illusaed in Figue.. We have x( ) x y( ) y ( x ( y ( ) ( x( ), y( )) ( x x ) x ) y ) ( y y ) (.4) We can hen apply he ype of analysis descibed above. By doing his fo all possible RX poins (x,y) we can build a map of pediced signal sengh vs. locaion. EE43: RF Engineeing fo Telecommunicaions Sco Hudson, Washingon Sae Univesiy 05/8/7

4 Compue Popagaion Analysis Tools.4 y TX (x,y) x RX Figue.3: The pah beween TX and RX defines a wodimensional pofile of he ind illusaed in Figue.. Spheical Tigonomey ( x, y, ) (sin cos,sin sin,cos ) sin sin sin sin cos cos cos sin cos cos sin cos cos d cos sin sin cos cos cos A nauical mile is defined o be he disance along he suface of he eah coesponding o an angle of minue of ac. Expeimen As pa of a Senio Pojec a WSU, a goup of sudens placed a 95MH ansmie on op of he EME building. They used he popagaion ool descibed above o pedic signal sengh in he Pullman aea and hen pefomed an exensive dive es, using a GPS eceive and a field EE43: RF Engineeing fo Telecommunicaions Sco Hudson, Washingon Sae Univesiy 05/8/7

Compue Popagaion Analysis Tools.5 sengh mee, o measue he acual signal. Thei esuls ae shown in Figue.4. The dive es daa coveed a faily lage aea abou by miles. Figue.4: Example use of he popagaion ool in he Pullman aea.

5 Compue Popagaion Analysis Tools.5 sengh mee, o measue he acual signal. Thei esuls ae shown in Figue.4. The dive es daa coveed a faily lage aea abou by miles. Figue.4: Example use of he popagaion ool in he Pullman aea. A 95MH ansmie was place on op of he EME building. Pediced signal sengh is shown a lef. Dive-es measuemens ae shown a igh. Numbe on axes indicae minues of longiude/laiude. Figues ae appoximaely nauical miles on a side. EE43: RF Engineeing fo Telecommunicaions Sco Hudson, Washingon Sae Univesiy 05/8/7

, on the power of the transmitter P t fed to it, and on the distance R between the antenna and the observation point as. r r t

, on the power of the transmitter P t fed to it, and on the distance R between the antenna and the observation point as. r r t Lecue 6: Fiis Tansmission Equaion and Rada Range Equaion (Fiis equaion. Maximum ange of a wieless link. Rada coss secion. Rada equaion. Maximum ange of a ada. 1. Fiis ansmission equaion Fiis ansmission