Transcript 2 saluran transmisi

DASAR
TELEKOMUNIKASI
2
Elfitrin Syahrul
Universitas Gunadarma
Transmission media
I.
Guided media / wireline
 metalik atau optis
karakteristik yang
jelas sangat berbeda
II.
Unguided media / wireless
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I. Guided media
1. Transmisi metal (metallic transmission)
a. Twisted pair
Keuntungan utama twisted pair
 Minimal skill
 Simpel tool
 Star wiring topologies
1.
2.
3.
4.
Kategori 3 ( 4 pairs unshielded telephone wiring – dgn pjg kabel bisa
beberapa mil utk transmisi 3000 Hz, utk DSL standarnya lebih kecil
Kategori 5 ( 4 pairs shielded LAN wiring, utk ethernet 10 Mbps diatas 100 m)
Kategori 5E (4 pairs shielded LAN wiring, dispesifikasikan utk full duplex 10
Mbps Ethernet, tp juga bisa utk ethernet 100 Mbps diatas 100 m)
Kategori 6 (4 pairs shielded LAN wiring, utk 100 Mbps 100 m menggunakan 1
pair utk masing2 arah dikomersialkan utk ethernet 1 Gbps dengan 2 pairs utk
masing2 arah.
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b. Coaxial Cable
 RG-58 (3/8 inch diameter luar kabel digunakan utk jarak dekat utk
frekuensi 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 atau
aplikasi komunikasi data frekuensi radio (RF).
Kabel metalik mempunyai faktor propagasi antara 0,80 dan 0,95 yang
bervariasi berdasarkan tipe, fabrikasi, material
karakteristik impedansi saluran transmisi metal (kabel) harus “matched”,
sehingga energi maksimum dapat ditransfer dari sumber (source) ke kabel dan
dari kabel ke beban (load) utk menghindari refleksi. Terminasi “mismatched”
akan menyebabkan data hilang (loss).
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2. non-metallic transmission
Fiber optik
Fiber optik menggunakan gel. Elektromagnetik (gelas/kaca atau kadangkadang plastik) untuk menghantarkan informasi/pesan.
Panjang gel yang digunakan adalah cahaya tampak (500 nm) atau
mendekati spektrum infrared (790 nm, 850 nm, 1310 nm, atau 1550 nm)
dengan panjang gelombang yang lebih luas akan dapat mencapai jarak
yang 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 meningkatkan
bit rate 100 x melalui single fiber akan
tetapi dengan biaya terminal yang cukup
tinggi
 Peralatan yang digunakan oleh transmisi FO adalah
light emitting diode (LED) dan laser dengan tradeoff
antara biaya versus jarak dan bandwidth.
 Aplikasi telekomunikasi pada umumnya
menggunakan single mode fiber dan laser, kenapa?
 tugas …..!!!!!!
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FO
•Loss pada FO  chromatic dispersion (ketika menggunakan LED),
intermodal dispersion (biasanya pada multi-mode fiber), dan Rayleigh
Scattering (penyerapan karena ketidak murnian kaca)
•Tidak ada radiasi loss atau gangguan dari luar  Total Internal
Reflection.
•Tapping tanpa physical access ke fiber sangat sulit
•Cross-talk hampir tidak memungkinkan terjadi dan distances-bandwidth
product  sangat tinggi, 100s kali (atau lebih) baik dari metallic
transmission.
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OPTICAL FIBER LINKS
 Undersea cables
 Terrestrial long haul telecommunications
transmission
 Inter-building computer communications
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Infrared
Data Communications Infrared through the air systems
have been around for many years. We all have used one
in our homes daily for many years now. (Think TV)
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Laser
"unguided"
transmission but
usually considered
point-to-point through
the use of lasers and
lens systems to
constrain the optical
path to a very narrow
beam.
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The beams are often so narrow that mounting of transmitters and
receivers on roofs is discouraged due to tilting of the roof surface
because of heating of the side of the building in sunlight.
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Unguided media –
masih 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's
Equations--happens for all alternating currents in wires. All
metallic transmission media are antennas!
 Efficiently built and installed antennas transmit radio signals
when built to be an appreciable fraction of the operating
wavelength or larger.
 Propagation is characteristic of the wavelength due to terrestrial
factors and possible antenna construction at various sizes.
 Radio signals are made and used practically as low at KHz
frequencies (imagine the wavelength and antenna sizes
needed) up to 100 GHz or where practical transmitting and
receiving electronics is not available.
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WIRELESS/RADIO POINTS - 2
 Various modulation techniques are used depending on
application.
 Impairments depend on wavelength, modulation system
employed, and atmospheric absorption, multipath distortion and
other reflection caused problems, and even refraction causing
phenomena.
 Co-channel and adjacent channel interference can limit cause
problems in channelized systems. Unlicensed (but legal)
services are increasingly greatly, and spread spectrum
techniques (especially in unlicensed bands) are exploding in
use. 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 the
same. Thank Maxwell for showing this.
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Lower frequencies/longer wavelengths require large antennas, propagate via
ionosphere reflections (e.g. worldwide short wave radio); higher frequencies such
as 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 ke
bulan). 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 ketinggian
11,000 mil merotasi bumi 2x sehari  actually exactly twice per
sidereal day.
 Geosynchronous satellites  world wide data communications link
(alternatif fiber optik).
 Waktu propagasi cukup tinggi dibandingkan media transmisi
lainnya  “mengganggu" protokol  very low effective data rates
 transmisi satelit tidak sesuai utk aplikasi/sistem komunikasi
tertentu.
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This ring of allowable locations
(i.e. 23,000 miles above the
equator) for geosynchronous
satellites is known as, "The Clarke
Belt", in honor of science fiction
author Sir Arthur C. Clarke, who is
said to have devised the concept.
Clarke is now in his 80s and lives in Sri Lanka, the only non-native with
permanent residency status there. He is ailing but still actively publishing-his new book just came out--and participates in a weekly web cast. He
also 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 surface
from each satellite, but footprints can be constrained much smaller by
directional antenna techniques as well as longitude at which a given satellite
is assigned.
•Very northern and southern locations are problematical but possible with
large 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 for
geosynchronous satellites but frequency reuse limit satellite spacing to 1
degree 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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