2 saluran transmisi

8/3/2019 2 saluran transmisi

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Elfitrin Syahrul

Universitas Gunadarma

DASARTELEKOMUNIKASI


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Transmission media

I. Guided media / wireline

metalik atau optis

karakteristik yangjelas sangat berbeda

II. Unguided media / wireless


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I. Guided media

1. Transmisi metal (metallic transmission)a. Twisted pair

1. Kategori 3 ( 4 pairs unshielded telephone wiring dgn pjg kabel bisabeberapa mil utk transmisi 3000 Hz, utk DSL standarnya lebih kecil

2. Kategori 5 ( 4 pairs shielded LAN wiring, utk ethernet 10 Mbps diatas 100 m)3. Kategori 5E (4 pairs shielded LAN wiring, dispesifikasikan utk full duplex 10

Mbps Ethernet, tp juga bisa utk ethernet 100 Mbps diatas 100 m)

4. Kategori 6 (4 pairs shielded LAN wiring, utk 100 Mbps 100 m menggunakan 1pair utk masing2 arah dikomersialkan utk ethernet 1 Gbps dengan 2 pairs utkmasing2 arah.

Keuntungan utama twisted pair Minimal skill

Simpel tool Star wiring topologies


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b. Coaxial Cable

RG-58 (3/8 inch diameter luar kabel digunakan utk jarak dekat utkfrekuensi radio dan ethernet LAN 10 Mbps

RG-75 (1/2 inch OD cable utk kabel TV diatas 500+ MHz)

Tujuan khusus lainnya digunakan utk jarak jauh seperti LAN atauaplikasi komunikasi data frekuensi radio (RF).

Kabel metalik mempunyai faktor propagasi antara 0,80 dan 0,95 yangbervariasi berdasarkan tipe, fabrikasi, material

karakteristik impedansi saluran transmisi metal (kabel) harus matched,

sehingga energi maksimum dapat ditransfer dari sumber (source) ke kabel dandari kabel ke beban (load) utk menghindari refleksi. Terminasi mismatched

akan menyebabkan data hilang (loss).


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Fiber optik

2. non-metallic transmission

Fiber optik menggunakan gel. Elektromagnetik (gelas/kaca atau kadang-

kadang plastik) untuk menghantarkan informasi/pesan.

Panjang gel yang digunakan adalah cahaya tampak (500 nm) ataumendekati spektrum infrared (790 nm, 850 nm, 1310 nm, atau 1550 nm)dengan panjang gelombang yang lebih luas akan dapat mencapai jarakyang lebih panjang dengan loss yang kecil sekitar 3 dB per km atau malah

lebih kurang.


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Keuntungan fiber optik


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Fiber optik


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Beberapa fakta penting Fiber optik

Teknik Dense Wavelength Division

Multiplex (DWDM) dapat meningkatkanbit rate 100 x melalui single fiber akantetapi dengan biaya terminal yang cukup

tinggi

Peralatan yang digunakan oleh transmisi FO adalahlight emitting diode (LED) dan laser dengan tradeoffantara biaya versus jarak dan bandwidth.

Aplikasi telekomunikasi pada umumnyamenggunakan single mode fiber dan laser, kenapa?

tugas ..!!!!!!


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FO

Loss pada FOchromatic dispersion (ketika menggunakan LED),intermodal dispersion (biasanya pada multi-mode fiber), dan RayleighScattering (penyerapan karena ketidak murnian kaca)

Tidak ada radiasi loss atau gangguan dari luarTotal InternalReflection.

Tapping tanpa physical access ke fiber sangat sulit

Cross-talk hampir tidak memungkinkan terjadi dan distances-bandwidthproductsangat tinggi, 100s kali (atau lebih) baik dari metallictransmission.


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OPTICAL FIBER LINKS

Undersea cables

Terrestrial long haul telecommunicationstransmission

Inter-building computer communications


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Infrared

Data Communications Infrared through the air systemshave been around for many years. We all have used onein our homes daily for many years now. (Think TV)


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Laser

"unguided"transmission butusually consideredpoint-to-point throughthe use of lasers and

lens systems toconstrain the opticalpath to a very narrowbeam.


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The beams are often so narrow that mounting of transmitters andreceivers on roofs is discouraged due to tilting of the roof surfacebecause of heating of the side of the building in sunlight.


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Unguided mediamasih lanjutan lho!!

WIRELESS, RADIO, PCS, atau CORDLESS TELEPHONY

Akan dibahas dalam suatu mata kuliah khusus !!!!!


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WIRELESS/RADIO POINTS - 1

Electromagnetic radiation--as we learned from Maxwell'sEquations--happens for all alternating currents in wires. Allmetallic transmission media are antennas!

Efficiently built and installed antennas transmit radio signalswhen built to be an appreciable fraction of the operatingwavelength or larger.

Propagation is characteristic of the wavelength due to terrestrialfactors and possible antenna construction at various sizes.

Radio signals are made and used practically as low at KHzfrequencies (imagine the wavelength and antenna sizesneeded) up to 100 GHz or where practical transmitting andreceiving electronics is not available.


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WIRELESS/RADIO POINTS - 2

Various modulation techniques are used depending onapplication.

Impairments depend on wavelength, modulation systememployed, and atmospheric absorption, multipath distortion andother reflection caused problems, and even refraction causingphenomena.

Co-channel and adjacent channel interference can limit cause

problems in channelized systems. Unlicensed (but legal)services are increasingly greatly, and spread spectrumtechniques (especially in unlicensed bands) are exploding inuse. Full characterization is not known.


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The Electromagnetic Spectrum

Above "light" frequencies used by optical communications comes ultra-violet, X-rays,and eventually cosmic rays. They're all electromagnet radiation, mathematically thesame. Thank Maxwell for showing this.


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Lower frequencies/longer wavelengths require large antennas, propagate viaionosphere reflections (e.g. worldwide short wave radio); higher frequencies suchas microwave have highly directional antennas, require "line of sight"transmission, and are used for point to point and satellite transmission.


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Satelit

1. GEOSYNCHRONOUS SATELLITES (GSO)

23.300 mil diatas bumi (3x diameter bumi dan 1/10 jarak kebulan). Periode orbital rotasi bumi (diatas equator "stationary

Low Earth satellites spt Space Station mengelilingi buni dalam 90 minute (bulan 28 hari ), dan satelit GPS pada ketinggian11,000 mil merotasi bumi 2x sehari actually exactly twice persidereal day.

Geosynchronous satellites world wide data communications link(alternatif fiber optik).

Waktu propagasi cukup tinggi dibandingkan media transmisilainnya mengganggu" protokol very low effective data rates transmisi satelit tidak sesuai utk aplikasi/sistem komunikasitertentu.


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This ring of allowable locations(i.e. 23,000 miles above theequator) for geosynchronous

satellites is known as, "The ClarkeBelt", in honor of science fictionauthor Sir Arthur C. Clarke, who issaid to have devised the concept.

Clarke is now in his 80s and lives in Sri Lanka, the only non-native withpermanent residency status there. He is ailing but still actively publishing--his new book just came out--and participates in a weekly web cast. Healso hosts a science program on public television.


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GEOSYNCHRONOUS SATELLITE COVERAGE & BANDWIDTH

Coverage for each satellite can be for about 1/3 to 1/4 the Earth's surfacefrom each satellite, but footprintscan be constrained much smaller bydirectional antenna techniques as well as longitude at which a given satelliteis assigned.

Very northern and southern locations are problematical but possible withlarge ground antennas mounted high enough to have a distant horizon to"see" the satellite.

Each satellite has a number of 6 MHz channels, each called a "transponder",that relays ground transmissions received on one frequency called an "uplink"to a paired "downlink" frequency.

A number of frequency bands are allocated internationally forgeosynchronous satellites but frequency reuse limit satellite spacing to 1degree at best. There are a lot of geosynchronous satellites in the Clarke Belt,mostly filling up all the usable longitudes.


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Geosynchronous Orbit

Geosynchronous (adj.): geo-, earth and synchronous, going on at the same rate and exactly together.

A satellite in geosynchronous orbit circles the earth once each day. The time it takes for a satellite to orbit the

earth is called its period. For a satellite's orbit period to be one day, it must be approximately 35,786 kilometers

(19,323 nautical miles or 22,241 statute miles) above the earth's surface. That is a lot higher than the Shuttle ever

goes (usually about 300 kilometers).

To stay over the same spot on earth, a geostationary satellite also has to be directly above the equator.


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Tugas

Makalah sekitar 2500 kata mengenai :

WIRELESS, RADIO, PCS, CORDLESS TELEPHONY,

Atau MEO & LEO

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