Transmisi Data dan Pengkodean Data

Komunikasi Data dan Jaringan Komputer Teknik Telekomunikasi

Politeknik Negeri Ujung Pandang

• Konsep pengiriman informasi baik sinyal analog maupun

digital

• Media transmisi kabel atau nonkabel atau wireless.

• Komponen-komponen yang terdapat pada suatu sinyal yaitu

frekwensi, amplitudo dan fasa serta peranan bandwidth

pada system pengiriman data

Konsep Transmisi Data

• Transmisi data terjadi di antara pemancar dan penerima

melalui beberapa media transmisi

• Media transmisi digolongkan sebagai guided dan unguided

• Guided media > gelombang dikendalikan sepanjang jalur

fisik, contohnya kabel twisted pair, kabel koaksial dan fiber

optic

• Unguided media menyediakan alat untuk mengirimkan

gelombang-gelombang elektromagnetik namun tidak

mengendalikannya contoh permbatan gelombang di udara

dan laut

Sinyal dan Bandwidth

•

Sinyal dan Bandwidth

• Bandwidth > lebar dari spectrum, biasa disebut

lebar saluran atau kanal

• Mis: suatu system telekomunikasi bekerja pada

frekwensi 1,5Mhz s/d 2Mhz, artinya system

tersebut mempunyai bandwidth 0,5Mhz

Media Transmisi

• Wired

– Copper Coaxial, Twisted Pair (UTP, sTP)

– Fiber Optic

• Wireless

– Bluetooth, Wi Fi

Cable Specifications

• Cables have different specifications and expectations

pertaining to performance.

Cable Specifications

• 10BASE-T

– speed of transmission at 10 Mbps

– type of transmission is baseband, or digitally

interpreted

– T stands for twisted pair

Cable Specifications

• 10BASE5

– Speed of transmission at 10 Mbps

– Type of transmission is baseband

– 5 represents the capability of the cable to allow the signal to travel for approximately 500 meters before attenuation could disrupt the ability of the receiver to appropriately interpret the signal being received.

– often referred to as Thicknet

Cable Specifications

• 10BASE2

– speed of transmission at 10 Mbps

– type of transmission is baseband

– The 2, in 10BASE2, represents the capability of the cable to allow the signal to travel for approximately 200 meters, before attenuation could disrupt the ability of the receiver to appropriately interpret the signal being received. 10BASE2 is often referred to as Thinnet.

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Coaxial Cable

Coaxial Cable

• Advantages:

– Requires fewer repeaters than twisted pair

– Less expensive than fiber

– It has been used for many years for many types of data communication, including cable television

• Disadvantages:

– More expensive and more difficult to install than twisted pair

– Needs more room in wiring ducts than twisted pair

Shielded Twisted Pair (STP and ScTP)

STP – Shielded Twisted Pair ScTP – Screened Twisted Pair

Unshielded Twisted Pair (UTP)

• Unshielded twisted-pair cable (UTP) is a four-pair wire medium used in a variety of networks.

• TIA/EIA-568-A contains specifications governing cable performance.

• RJ-45 connector

Kapasitas Saluran

• Data rate : Merupakan rate, dalam bit per detik (bps), pada data

yang mana dikomunikasikan

• Bandwidth : Merupakan lebar band dari sinyal yang

ditransmisikan, dinyatakan dalam siklus per detik atau Hertz.

• Menurut Nyquist kapasitas saluran C :

C = 2 BW log2 M

• Claude Shannon menyatakan bahwa kapasitas saluran

maksimum diperoleh melalui persamaan :

C = BW log2 (1 + S/N)

Pengkodean Data

• Data digital, digital transmisi

• Data analog, digital transmisi

• Data digital, analog transmisi

• Data analog, analog transmisi

Data Digital, Digital Transmisi

Data Digital, Digital Transmisi

• Nonreturn to Zero-level (NRZ-L)

0 = Level tertinggi

1 = Level terendah

• Nonreturn to Zero-Inverted (NRZ-I)

0 = tanpa transisi pada permulaaninterval (satu bit waktu)

1 = transisi pada permulaan interval bipolar

• Bipolar- AMI

0 = tanpa sinyal pada jalur

1 = level positif atau negatif, alternatif untuk satu yang berturut-turut

• Pseudoternary

0 = level positif atau negatif, alternatif untuk 0 yang berturut-turut

1 = tanpa sinyal pada jalur

Data Digital, Digital Transmisi

• Manchester

0 = transisi dari tinggi ke rendah dipertengahan interval

1 = transisi dari rendah ke tinggi di pertengahan interval

• Diffrential Manchester

Selalu terdapat tarnsisi di pertengahan interval

0 = transisi dipermulaan interval

1 = tidak ada transisi di permulaan interval

Data Digital, Analog Transmisi

• Amplitudo Shift Keying (ASK)

• Frequency Shift Keying (FSK)

• Phase Shift Keying (PSK)

Data Analog, Digital Tranmisi

• Proses digitasi :PCM (Pulse Code Modulation), Delta modulation, DPCM

(Diffrensial PCM), PDM (Pulse Duration Modulation) dan PTM (Pulse

Time Modulation

Data Analog, Analog Transmisi

• Modulasi analog : AM, FM maupun PM

Kode Karakter

• Kode Morse

• Baudot

• EBCDIC

• ASCII