Rain Outage Performance of Tandem and Path Diversity 18-GHz Short Hop Radio Systems By 1 L OSBORNE. (asanesit eso Ane 1, 10) ir performance with roped tx vain wage tine of dat path dari end nom path tity ender) azrangesens for IRAs ort bop rain Sotews fe conpted at otepaed, The ea ave on foo extespo- Iaions a) Re Serial’ theetoas average ofthe measured pray Uhlebutions jor vain aeration at 18 CH on a Bf-bm hap in Nes. ervey. The eGets of merge haps and jin fading buen hope the isenty apse, depend of th rain altoton drain on hop Tough, ad amortas ety i> the tal of the rds are inet. Pie rele se dh {the prerauca of tances eats cola to Tani ates increas othe ate fang iors, (8 a dorence {nthe numberof sepatere per nt Tew reyuned for ahor ond long tandem mnt te seal (i) the performance of he dienty ye i tdronaly dependent fie wnt of Joie fading been pel path, foul is) th pesformance of toe tale sats te strongly dependent om {he Cf te elevation dts. Nevtor of the Cetera factor it frm front rain alunwation menewemonts, Ou if he joint alnnation probable are sufiiedy high, then diver shows no astage over Towtam for ether of the axeured estropaatons. The wnesratty 1 the tai of te allman dition ane th srt the tandem spor, Devfrnener ta emphasise th ned far rte albmuaon measures ad to aba of abn 10" ‘Fue problems af utsing the trequeoree above 10 GF for radio relay commmunicainn have been discussed by L, C. Tillotson; the Inaiar technical problens ie attention by rnin Basel en eculte de- fed “iunt a ein gauge secwerk ix MeMonishie, Ragland, ish (ry mans ersrmm aueeaL JoUMNAy JANUARY EOL showed that the joint distribution of sain zetee for <¥o laterally fmparated pothe it igpifcartiy Jew than the distributions for Tie Individual path, D. C. Hage auggrsed che use of dua) path diversily fa mieane for reducing the magoiade of tke problem. Lewever, in deciding the value of path divenity, meny other fascons rl le fonsiderad such as variation of fade raeein wth hep length, merging of the diversity pals at witoing point, the nature of the atten tion aistutins, and the Argree of independence of tan lataraly seperated, pli Yoreas separation TL. 'T. Guster as previously celoulaced tho relibiity aul am sum legs of divesits and nondiversity systems at 11 tod 17 Gilt ‘besed on ettenuation divribusions derived irom six rain gauges on fivemile path in Now Jersey, and assumptions om joint dirution, merge path, and repeater pararictea. Ilo ennelited thas diversy syetems with shor hops and moderwe inde rage are ele“ long-aae! spetsms, but tat noadiverity eysieme ace avilable only zor short-haul ot low-reicility systoms. ‘Theeo ronlts have since boon ured in studies of log-baul mierowavo pole line systems." "This paper deseribes 1 new comparison of th rain outage perform see of 18-CHls dua! path civensity (diversity) eystancs and non-path Aiveiy (adem) epeteme tceksding the eects of merge paths fa the verity aysiem, fo fading helwaen diversity paths, denencence st ing tin alimanation uistsbution on bop engi, ead'uncesteiaty in ‘he tails of cha rain ettanuation dinsibution Chatacterines other than rain oxtage perortoanee, ach as path switching, delay equalization of Use versity pale, equips’ redundancy, nd inlerfersnoe may ‘weigh Tor oF against a peztianlareysiem, but thece “aeons are nat tered hore ‘The tandem and diversity eysteme are compsred on the basi of equal ushers of identical repeaters in a length whieh is equal to the Tenglh of a divarily ewilahiag won: Ube selion goneley i above in Fig. 1. Lergths @ tandene and diversity system with OM peveers ‘tal rain ontage Zane ave ealelated feo the rein alenvetioniiii= ihion se fusion of lance hop ‘eagth with setion length and the repeater fade margin an paraineter. Diversity path separation is so a paraencler in the dives este ad spacings of 10 and 20 kan fre wrod in te computations Sever lugs for outage tes other ‘hac DI perens are inversely prmportinal ta the outage tine, Ty approximate tie reduced repenter spacing neceesury ab the merge ports in the diveicy eystne, the Ieagtta ofthe Bret and lst hops fp each diverelty pth ere et equal ve (ho bap Tegts ithe compari= ton tandem system, "The rain ontage performace of a tandem eystem depends on the probability Galiborien of min ettemuation which ha fein of tho Ip lsgth; diveeng epee perfarmarce depends on te joint prob- soilty eisaibecione der larly eeparatod paral hops. The mens- tied 18-Glly atirmat'nn distbetisn “or « Blam bes in Helene, [Now Jere, cuporte hy R.A, Semple wl £9 tho base distriour tion, To extrapolte aad wa ined che efleste of yeeations in the ‘ail of obe disaibution che mecsured distibucion is wyproximated by two Tunetion, and 1, Lp measured @stribuson for the 64k hop tad is aporesinations ae ecw in Fig 2 aa eurvee 12, Al, and L.A hop lsat dependence is nevorced which eauees the aprosimae tio ta the teseured 30.9.GH (1 lon hop length) stitionro- Dorted iy Semplak! when it ie cowarted to an equivalent 185-GHs Alstebution, his drieed 1RA-GH eitribatin for a 1m hop and its spproximatione are shown a3 curves 22, A2, and B2 in Hig 2 Figine 8(a) shows the neue) depezdenes of attention on lep Tengit for oouetsat probabitcy ard Fig. 4(8) shows tho fem of diss tributions tained from the npproximting funesien 1 wih hop lergh fe a parameter foint fading of the dinectty opposite and sist dagonnlly oppnsive dope in the diversity eystem ie included nthe fllowing way. When two Tops ar statistclly independent, the eistrintion of the tens ‘Mon wich ie exerded jointly an both hops i Uh produ of the fn 62 ame nots avomane oc, vovatas, sanuaane afieSateshiy enn gua 8 a eee cetieie Saing fe Een nC ATES Ei sogautacrtbe cS vidual disutbneions: wen die lwo ho2s are comsieely dependant (eorshinal peokebiities axe ivy) the ‘oint distribution in equ co the inciviuel citibution, Joint citributioae lying betreen these tivo speeieleuses are ascuced to he given by the indiidua! eseriba- Gon sie to an exponent, c, which bas valucs © = 2 in the independent age and ¢ = 1 in the eomploiely deperden, ewe. Diversity eystem perfomance is eeloulated for distributions eoerespanding to equal to 20, 18, 1.6, 14, ond 1.0, Theos dietibucons ene abown in Fig 4 for the approsistion BL in Wig. 2. Tha results of the enalvaie can bo opting, ano the meamuzed joint sttmuation distbution is knew, by finding the corresponding exponent, 2 forthe measure’ daributon, ‘All hops other than the aiensy opposite hos and he rst diagonally “opposite hope in the diversity spacers sre amed t be sataniealy independent, However, oink futing of olher poire of hops further deeroasee the performance of the diversity efetem relative to the tandem eyetem‘Thorofore the provoding nevimptionsexeabish mini ‘nm conditions under which the diversity system muse have superior Sun oir rearonseanen 8 nF ten i's Toba Gy Picabihydecsaoios of tbe eee entail hon ogi ns Farnowir ta ayoesuastegfinetion Wan eq Beh BN eh 9 a ARecpinnnain.traste uae om pesfermauce if it is to seuaia advantageous under wore rondiions "The reals of thie analysis ave shows in Figs. 5 through 8. In Fix 5, 6 aad 8 the lengths of tandem and diversity systame sith O01 Perse total zain outage times are pleted as a funetion of tandem hop lengih with the Joint facing exponent, ¢, a8 a parameter of the fiver eyetem, Figice 7 shows the probability that the rin wari ation will seed the bop fae margin for dierent hop lengths aad fado margine bused approximation R. The revue show in geoeral that (the performance of (uuiem ayeieus relive to. dlversty tyrteme inerenees ae Ube spiicm kath inereases, meking tandem, setems more suiteble for lng ays; (8) the difrence ia the umber of reponters per unit lengt required for short ana long terdem syne is sll; (Si) the performinee ofthe diversity sytem Alepends strangely on che dosrec of independecee of cho two partlll pai the diversity system; ard (ib! the performace othe tage ymen depeuda strongly oa the il of tae attensacion distribution, ‘Netchor of he letter tro famtare has Ts mated for eaiaaetemes oy) ao TN nese an sem yc wine 05 mms, everem rrewrerue rove E i “coh iy : Peon aS en Gn ee nif oa rp en ge ely Es Spec emioate, etn, mires aes aos Ou suRHCHOKASE on Proketiliy at he min wens erga the op fae magn veflny feign Sys aaa © Soe tion: ‘The unositainy in the til of the dinihution and the ensi- Livy 0 the tne sytem perlarmcir Wo fe resulta i about 9 £0 eneest mecrainty ine ranuber ef repeaters roquired and emph oes the ed for telinle reasueements of tho rain attenuation Wise tribution ant co's peobwlty of shout UP AL presnt, Scmplak’e moat dishibution extends only to ubuut 2 » 10-5 Figure (a) showe the ayvien lengths obtained with repeaters bbaving 8 40-dl fade margin ov « Lon hop, and with a action lenata ff 48 kr» ane path eepasnon of 10 ker. For a tardam aop length of 2 km, the tantem system curve skows thet the length af 9 tandem fystein with a tol ruin euiaye tine of OOL pancent is 660 ke, The he lengin of a diversity sytem wile by Mea 4. teeny 04 J.D. pe de of ieeoentce, tm tharos of the dn es sh Migs 8 oromeh eg the ieee eam SE Lee ibe beste tbs alee eo dpogni Ul he 68 es om, ovarmN mesTOM Jor, JN “E ad ee tomer NET Non ado Vo Sl Tear fae ris oP) A ed to 0S