{"id":413,"date":"2020-04-06T09:05:47","date_gmt":"2020-04-06T07:05:47","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=413"},"modified":"2020-04-06T17:06:56","modified_gmt":"2020-04-06T15:06:56","slug":"6-4-prenos-elektromagnetickym-vlnenim","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/06\/6-4-prenos-elektromagnetickym-vlnenim\/","title":{"rendered":"6.4.\u2002Prenos elektromagnetick\u00fdm vlnen\u00edm"},"content":{"rendered":"

V s\u00fa\u010dasnosti je elektromagnetick\u00e9 vlnenie v podstate jedin\u00fdm komunika\u010dn\u00fdm kan\u00e1lom na prenos inform\u00e1ci\u00ed. Elektromagnetick\u00e9 vlnenie m\u00f4\u017ee pren\u00e1\u0161a\u0165 prostredn\u00edctvom vodi\u010da\/dr\u00f4tu alebo vzduchom. V pr\u00edpade vodi\u010da m\u00f4\u017eeme vyu\u017ei\u0165 bu\u010f meden\u00fd, alebo optick\u00fd dr\u00f4t (aj svetlo je elektromagnetick\u00e9 vlnenie).<\/p>\n

6.4.1\u2002 Veden\u00fd prenos (vodi\u010dom)<\/h3>\n

V s\u00fa\u010dasnosti sa naj\u010dastej\u0161ie na prep\u00e1janie koncov\u00fdch po\u010d\u00edta\u010dov\u00fdch siet\u00ed pou\u017e\u00edva\u00a0kr\u00faten\u00e1 dvojlinka<\/strong><\/a>. Oproti telef\u00f3nnym dr\u00f4tom m\u00e1 skr\u00fatenos\u0165 t\u00fa v\u00fdhodu, \u017ee minimalizuje efekt ant\u00e9ny (vysielanie a prij\u00edmanie sign\u00e1lov z\/do okolia) a teda aj vplyv mo\u017en\u00fdch interferenci\u00ed. V r\u00e1mci jednej skr\u00fatenej dvojice dr\u00f4tov pren\u00e1\u0161aj\u00fa oba dr\u00f4ty rovnak\u00fd sign\u00e1l, a\u017e na polaritu (v jednom vodi\u010di sa pren\u00e1\u0161a akoby zrkadlov\u00fd obraz sign\u00e1lu v druhom vodi\u010di). S\u010d\u00edtan\u00edm hodn\u00f4t t\u00fdchto sign\u00e1lov sa tieto hodnoty navz\u00e1jom eliminuj\u00fa, \u010do sa d\u00e1 vyu\u017ei\u0165 na detekciu pr\u00edpadnej interferencie. Naj\u010dastej\u0161ie sa v kr\u00faten\u00fdch dvojdr\u00f4toch, ktor\u00e9 vyu\u017e\u00edvame v Ethernete s koncovkou\u00a0RJ45<\/a>, pou\u017e\u00edvaj\u00fa 4 skr\u00faten\u00e9 dvojice dr\u00f4tov. V Ethernete s r\u00fdchlos\u0165ou 100 Mbit\/s jedna dvojica sl\u00fa\u017ei na prenos jedn\u00fdm smerom, druh\u00e1 na prenos druh\u00fdm smerom a ostatn\u00e9 na prenos elektrickej energie, pr\u00edpadne maj\u00fa in\u00e9 vyu\u017eite.<\/p>\n

Kr\u00faten\u00e9 dvojdr\u00f4ty sa pod\u013ea toho, ak\u00e9 \u0161irok\u00e9 p\u00e1smo dok\u00e1\u017eu prenies\u0165, zara\u010fuj\u00fa do kateg\u00f3ri\u00ed. \u010c\u00edm vy\u0161\u0161ia kateg\u00f3ria, t\u00fdm v\u00e4\u010d\u0161ia \u0161\u00edrka prenosov\u00e9ho p\u00e1sma a t\u00fdm aj vy\u0161\u0161ie mo\u017en\u00e9 prenosov\u00e9 r\u00fdchlosti. Naj\u010dastej\u0161ie sa v s\u00fa\u010dasnosti pou\u017e\u00edvaj\u00fa kateg\u00f3ria 5 pre 100 Mb\/s, kateg\u00f3ria 5e pre 1 Gb\/s na men\u0161ie vzdialenosti a kateg\u00f3ria 6 pre 1 Gb\/s. Daj\u00fa sa u\u017e k\u00fapi\u0165 aj kateg\u00f3rie 6a a 7 deklaruj\u00face prenosov\u00e9 r\u00fdchlosti do 10 Gb\/s. Tieto kateg\u00f3rie s\u00fa dan\u00e9 kon\u0161trukciou vodi\u010da, ktor\u00e1 pri vy\u0161\u0161\u00edch kateg\u00f3ri\u00e1ch u\u017e obsahuje r\u00f4zne formy tienenia \u2013 vodivej f\u00f3lie okolo v\u0161etk\u00fdch 4 dvoj\u00edc dr\u00f4tov spolu (chr\u00e1nen\u00fd dr\u00f4t \u2013 ScTP \u2013 screened twisted pair), alebo aj okolo ka\u017edej dvojice dr\u00f4tov zvl\u00e1\u0161\u0165 (tienen\u00fd dr\u00f4t \u2013 STP \u2013 shielded twisted pair). Tieto kr\u00faten\u00e9 dvojdr\u00f4ty sa daj\u00fa pou\u017ei\u0165 do vzdialenosti cca 100 metrov.<\/p>\n

\u010eal\u0161\u00ed typ kovov\u00e9ho vodi\u010da je\u00a0koaxi\u00e1lny k\u00e1bel<\/strong><\/a>. Ten m\u00e1 tak\u00fa kon\u0161trukciu, \u017ee jeden vodi\u010d je vo vn\u00fatri a druh\u00fd je okolo neho oddelen\u00fd nevodivou vrstvou. Tento dr\u00f4t zvl\u00e1da vy\u0161\u0161ie frekvencie aj \u0161ir\u0161ie frekven\u010dn\u00e9 rozsahy. Pou\u017e\u00edval sa v minulosti v LAN sie\u0165ach. Dnes ho be\u017ene vyu\u017e\u00edvaj\u00fa spolo\u010dnosti poskytuj\u00face k\u00e1blov\u00fa telev\u00edziu. Dosah odosielania sign\u00e1lu t\u00fdmto dr\u00f4tom je a\u017e nieko\u013eko kilometrov.<\/p>\n

Optick\u00e9 vl\u00e1kno<\/strong><\/a>\u00a0pren\u00e1\u0161aj\u00fa u\u017e ve\u013ek\u00e9 elektromagnetick\u00e9 frekvencie r\u00e1dovo v THz, ako u\u017e n\u00e1zov napoved\u00e1, z vidite\u013en\u00e9ho spektra. \u0160\u00edrka p\u00e1sma, ktor\u00e9 sa d\u00e1 v optick\u00fdch dr\u00f4toch vyu\u017ei\u0165, je obrovsk\u00e1. Svetlo sa v optickom dr\u00f4te pren\u00e1\u0161a v tenu\u010dkom optickom vl\u00e1kne, ktor\u00e9 je obalen\u00e9 neprieh\u013eadn\u00fdm obalom, od ktor\u00e9ho sa odr\u00e1\u017ea. Tento odraz je \u00fapln\u00fd, pokia\u013e nedopad\u00e1 pod pr\u00edli\u0161 ostr\u00fdm uhlom (tieto dr\u00f4ty sa nem\u00f4\u017eu pr\u00edli\u0161 oh\u00fdba\u0165, aby sa \u00fapln\u00fd odraz zachoval).<\/p>\n

Optick\u00e9 dr\u00f4ty pozn\u00e1me mnohovidov\u00e9 a jednovidov\u00e9. V\u00a0mnohovidov\u00fdch dr\u00f4toch<\/strong>\u00a0m\u00e1 optick\u00e9 jadro priemer zhruba 50-62,5 \u00b5m a svetlo sa v \u0148om \u0161\u00edri vo viacer\u00fdch l\u00fa\u010doch, z ktor\u00fdch m\u00f4\u017ee d\u00f4js\u0165 k prij\u00edma\u010du ka\u017ed\u00fd v inom \u010dase a doch\u00e1dza tak k deform\u00e1cii sign\u00e1lu. Z toho d\u00f4vodu sa mnohovidov\u00e9 vl\u00e1kna nepou\u017e\u00edvaj\u00fa na ve\u013ek\u00e9 vzdialenosti. S\u00fa v\u0161ak lacnej\u0161ie a jednoduch\u0161ie sa s nimi manipuluje. Svetlo m\u00f4\u017ee generova\u0165 aj LED di\u00f3da.<\/p>\n

V jednovidov\u00fdch dr\u00f4toch m\u00e1 jadro priemer iba 4-10 \u00b5m a umo\u017e\u0148uje tak prenos iba jedn\u00e9ho l\u00fa\u010da a preto nedoch\u00e1dza k deform\u00e1cii sign\u00e1lu. Jednovidov\u00e9 vl\u00e1kna s\u00fa drah\u0161ie, n\u00e1ro\u010dnej\u0161ie na sp\u00e1janie a svetlo mus\u00ed by\u0165 generovan\u00e9 laserom. Daj\u00fa sa pou\u017ei\u0165 na ve\u013emi ve\u013ek\u00e9 vzdialenosti (nieko\u013eko stov\u00e1k km).<\/p>\n

V s\u00fa\u010dasnosti dok\u00e1\u017eeme vyu\u017ei\u0165 iba ve\u013emi mal\u00fd zlomok prenosov\u00e9ho potenci\u00e1lu tohto prenosov\u00e9ho p\u00e1sma z d\u00f4vodu pomal\u00fdch koncov\u00fdch zariaden\u00ed, ktor\u00e9 konvertuj\u00fa sign\u00e1l pre kovov\u00e9 spoje. Konverzia je nutn\u00e1, ke\u010f\u017ee zatia\u013e neexistuj\u00fa \u010disto optick\u00e9 koncov\u00e9 zariadenia \u2013 po\u010d\u00edta\u010de, smerova\u010de, a podobne.<\/p>\n

6.4.2\u2002 Bezdr\u00f4tov\u00fd prenos<\/h3>\n

Vzduchom dok\u00e1\u017eeme pren\u00e1\u0161a\u0165 prakticky v\u0161etky frekvencie elektromagnetick\u00e9ho vlnenia. Na prenos d\u00e1t je mo\u017en\u00e9 vyu\u017ei\u0165 n\u00edzke frekvencie nieko\u013ek\u00fdch hertzov a\u017e po vidite\u013en\u00e9 svetlo dosahuj\u00face nieko\u013eko stov\u00e1k THz. Vy\u0161\u0161ie frekvencie by boli aj teoreticky vyu\u017eite\u013en\u00e9, ale s\u00fa \u0161kodliv\u00e9 (ultrafialov\u00e9, r\u00f6ntgenov\u00e9 a\u017e \u03b3 \u017eiarenie).<\/p>\n

Nako\u013eko sa \u017eiarenie \u0161\u00edri v\u0161etk\u00fdmi smermi, \u017eiarenia bl\u00edzkych frekvenci\u00ed spolu interferuj\u00fa a \u0161kodlivo m\u00f4\u017ee p\u00f4sobi\u0165 aj ve\u013emi siln\u00e9 \u017eiarenie ni\u017e\u0161\u00edch frekvenci\u00ed , je nutn\u00e9 regulova\u0165 vyu\u017e\u00edvanie frekvenci\u00ed. Na Slovensku je tak\u00fdmto regul\u00e1torom Telekomunika\u010dn\u00fd \u00farad SR, u ktor\u00e9ho je mo\u017en\u00e9 si za presne dan\u00fdch podmienok k\u00fapi\u0165 mo\u017enos\u0165 vysielania v niektorom frekven\u010dnom rozsahu. Niektor\u00e9 mal\u00e9 frekven\u010dn\u00e9 rozsahy s\u00fa takzvan\u00e9 bezlicen\u010dn\u00e9 p\u00e1sma, v ktor\u00fdch je mo\u017en\u00e9 vysiela\u0165 s vopred danou maxim\u00e1lnou intenzitou zadarmo. Pr\u00e1ve bezlicen\u010dn\u00e9 p\u00e1sma bl\u00edzke 2,4 GHz a 5GHz sa pou\u017e\u00edvaj\u00fa napr\u00edklad ako komunika\u010dn\u00fd kan\u00e1l v technol\u00f3gi\u00e1ch Wireless LAN (WiFi). Ke\u010f\u017ee v t\u00fdchto kan\u00e1loch vysielaj\u00fa viacer\u00e9 sie\u0165ov\u00e9 adapt\u00e9ry, je potrebn\u00e9 rie\u0161i\u0165 probl\u00e9my komunik\u00e1cie na zdie\u013eanom spoji, ktor\u00e9 rie\u0161i pr\u00edstupov\u00e1 met\u00f3da na spojovej vrstve (napr. CSMA\/CA).<\/p>\n","protected":false},"excerpt":{"rendered":"

V s\u00fa\u010dasnosti je elektromagnetick\u00e9 vlnenie v podstate jedin\u00fdm komunika\u010dn\u00fdm kan\u00e1lom na prenos inform\u00e1ci\u00ed. Elektromagnetick\u00e9 vlnenie m\u00f4\u017ee pren\u00e1\u0161a\u0165 prostredn\u00edctvom vodi\u010da\/dr\u00f4tu alebo vzduchom. V pr\u00edpade vodi\u010da m\u00f4\u017eeme…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"_links":{"self":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/413"}],"collection":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/comments?post=413"}],"version-history":[{"count":2,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/413\/revisions"}],"predecessor-version":[{"id":486,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/413\/revisions\/486"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=413"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=413"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=413"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}