Sistem Komunikasi oleh Risanuri Hidayat Sistem Komunikasi Pengantar

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Sistem Komunikasi oleh Risanuri Hidayat Sistem Komunikasi

Sistem Komunikasi oleh Risanuri Hidayat Sistem Komunikasi

Pengantar Telekomunikasi = komunikasi yang dipisahkan oleh jarak Ada 3 komponen utama : •

Pengantar Telekomunikasi = komunikasi yang dipisahkan oleh jarak Ada 3 komponen utama : • Isyarat Komunikasi • Kanal Komunikasi • Jaringan Komunikasi 9/13/2021 Sistem Komunikasi 2

Isyarat Komunikasi 9/13/2021 Sistem Komunikasi 3

Isyarat Komunikasi 9/13/2021 Sistem Komunikasi 3

Isyarat Komunikasi • Sistem Komunikasi harus menyediakan transmisi yang bagus dengan frekuensi 2 di

Isyarat Komunikasi • Sistem Komunikasi harus menyediakan transmisi yang bagus dengan frekuensi 2 di mana spectrum-nya signifikan. • Kanal komunikasi harus bisa melewatkan isyarat dengan range frekuensi 300 Hz s/d 3. 4 k. Hz agar dapat isyarat suara (manusia) dapat terkirim • Sistem telepon menggunakan. LPF 4 k. Hz (Lowpass) • Komponen-komponen frekuensi di dalam gelombang isyarat menjadi Lebar Bidang Isyarat 9/13/2021 Sistem Komunikasi 4

Isyarat Komunikasi • Isyarat Musik mengandung komponen frekuensi signifikan dari 20 Hz sampai 20

Isyarat Komunikasi • Isyarat Musik mengandung komponen frekuensi signifikan dari 20 Hz sampai 20 k. Hz. • Untuk mengirimkan isyarat musik diperlukan LPF dengan Bandwidth 15 k. Hz • Isyarat data biner, interval terkecil antara 0 -1, T, dinamakan interval pengisyaratan (signaling interval) • 1/T dinamakan kecepatan isyarat (signaling rate) dengan satuan bits per second [bps]. • Lebar bidang transmisi pada sistem data biner secara proporsional mendekati bit rate [High data rate = Wider BW of channel] 9/13/2021 Sistem Komunikasi 5

Kanal Komunikasi Ada 2 kanal komunikasi yang dominan dipakai saat ini • Sistem gelombang

Kanal Komunikasi Ada 2 kanal komunikasi yang dominan dipakai saat ini • Sistem gelombang terpandu, menggunakan media fisik, seperti kable – Twisted Pair Cable [ UTP, STP, 10 Base. T[ – Coaxial Cable [thin-coax, thick-coax[ – Optical Fibers [OC-3, OC-12, OC-48[ • Sistem radio, dengan gelombang elektromagnetis 9/13/2021 Sistem Komunikasi 6

Kanal Komunikasi 9/13/2021 Sistem Komunikasi 7

Kanal Komunikasi 9/13/2021 Sistem Komunikasi 7

Kabel Twisted Pair • Total pelemahan (total attenuation) karena kabel tergantung pada panjangnya •

Kabel Twisted Pair • Total pelemahan (total attenuation) karena kabel tergantung pada panjangnya • Pelemahan (isyarat) juga tgt pada frekuensi, akan meningkat dengan bertambahnya frekuensi. Untuk mempertahankan agar pelemahan isyarat tetap rendah, maka diperlukan equalizer [LPF: Low Pass Filter] • Untuk single pair cable [telephone cable], induktor dipakai untuk meningkatkan karakteristik transmisi untuk mendapatkan frekuensi respone yang lebih baik • Pada multi-pair cable, cross-coupling dapat menambah kapasitasi antara 2 konduktor. Hal ini menyebabkan suatu isyarat dapat terganggu karena ada kabel lain. 9/13/2021 Sistem Komunikasi 8

Kabel Coaxial • Dipakai untuk komunikasi yang memerlukan Bandwidth yang lebih besar dari pada.

Kabel Coaxial • Dipakai untuk komunikasi yang memerlukan Bandwidth yang lebih besar dari pada. Twisted pair • Pelemahan (attenuation) meningkat kira-kira mendekati akar kuadrat frekuensi, sehingga untuk jarak yang jauh dibutuhkan penapisan • Efek kulit (“Skin Effect”), yaitu banyak isyarat dgn frekuensi yang tinggi akan hilang di dekat permukaan. Dibutuhkan penambahan ukuran kabel untuk BW yang lebih besar • BW Isyarat bisa mencapai 60 MHz [140 Mbps digital transmission] • Crosstalk sangat berkurang pada kabel coaxial 9/13/2021 Sistem Komunikasi 9

Fiber Optis 9/13/2021 Sistem Komunikasi 10

Fiber Optis 9/13/2021 Sistem Komunikasi 10

Fiber Optis [1] • Yang paling sederhana : inti fiber [sekitar 50 micron diameter]

Fiber Optis [1] • Yang paling sederhana : inti fiber [sekitar 50 micron diameter] dengan index bias n 1, dilapisi fiber dengan index bias yang lebih kecil n 2 • Cahaya berjalan sepanjang inti 9/13/2021 Sistem Komunikasi 11

Snell’s Law of Refraction • Critical angle = sin-1 n 2/n 1 9/13/2021 Sistem

Snell’s Law of Refraction • Critical angle = sin-1 n 2/n 1 9/13/2021 Sistem Komunikasi 12

Total Internal Reflection 9/13/2021 Sistem Komunikasi 13

Total Internal Reflection 9/13/2021 Sistem Komunikasi 13

Multimode Step Index • The pulse spreading places a limit on the transmission rate

Multimode Step Index • The pulse spreading places a limit on the transmission rate over a fiber of given length • Hence, the effective bandwidth of MMS fiber depends on length and on the index difference [n 1 -n 2] and it is normally used for a short haul systems 9/13/2021 Sistem Komunikasi 14

Multimode Graded Index • The fiber bandwidth is greatly improved with the parabolic refractive

Multimode Graded Index • The fiber bandwidth is greatly improved with the parabolic refractive index profile which gradually reduces from a maximum at the center to the core-cladding interface • The pulse spreading is very much reduced compared with a step index fiber because all rays paths having almost the same propagation delay 9/13/2021 Sistem Komunikasi 15

Single Mode Step Index • Single mode step index is known as “Monomode” •

Single Mode Step Index • Single mode step index is known as “Monomode” • By making a core diameter and index difference sufficiently small, there will be only one possible mode travel in the fiber. • Thus, pulse spreading due to mode velocity difference cannot exist • Single mode step index is the fastest mode in optical communications • Due to the complexity of manufacturing, a single mode fiber optic cable is therefore the most expensive one 9/13/2021 Sistem Komunikasi 16

Radio Systems • An Electromagnetic wave is launched from an antenna at the transmitter,

Radio Systems • An Electromagnetic wave is launched from an antenna at the transmitter, propagates through the atmosphere an on arrival at the receiver is picked up by a receiving antenna • There are five major of Radio Propagation. 1 Line of Sight. 2 Surface wave or ground wave. 3 Ionospheric propagation. 4 Tropospheric scattering. 5 Free space propagation 9/13/2021 Sistem Komunikasi 17

Radio Propagation • Line of Sight – Omidirectional : is used for radio broadcasting

Radio Propagation • Line of Sight – Omidirectional : is used for radio broadcasting – Directional : is used for point-to-point radio communication link • Surface wave or ground wave – A radio wave travels along the curvature of the earth as a result of currents flowing in the ground • Ionospheric propagation – Radio wave can refracted by the ionosphere and returned to the surface some considerable distance from the transmitter – This is because the gradual reduction with height of the refractive index in the ionosphere 9/13/2021 Sistem Komunikasi 18

Radio Propagation[1[ • Tropospheric scattering – Radio wave can be scattered by small particles

Radio Propagation[1[ • Tropospheric scattering – Radio wave can be scattered by small particles in the lower atmosphere to provide over-the-horizon radio communication • Free space propagation – Wave can propagate without the aid of a physical medium and this is how light from the Sun and other stars reaches the Earth 9/13/2021 Sistem Komunikasi 19

Communication Network • The communication cannot takes place in isolation • Each source and

Communication Network • The communication cannot takes place in isolation • Each source and destination needs to have at least one connection to make communication happen • The classic example of communication network are : Switched Network Data Network Integrated Services Digital Network 9/13/2021 Sistem Komunikasi 20

Switched Network • Switching center can produce all possible connections required but not all

Switched Network • Switching center can produce all possible connections required but not all at once • The statistical properties of the communication requirements of large user groups are relied upon to effect an economy • The idea of a star connection can be extended to form a star of star hierarchical network • the central switching center must provide a sufficient communication capacity to allow several message to be transferred simultaneously • This is achieved by combining several message waveforms to form a single composite message and it is known as “multiplexing” [TDM, FDM [ 9/13/2021 Sistem Komunikasi 21

Data Network • A protocol is a well-defined procedure to enable terminals/nodes to communicate

Data Network • A protocol is a well-defined procedure to enable terminals/nodes to communicate effectively over a network • Ring topology allows any nodes to communicate to any other nodes by simply applying signals to the ring • This is essence of a form of Local Area Network [LAN] used for computer/data communications • Data circulate around the ring in packets, a packet being a sequence of binary digits • Protocol layering of OSI reference model provide the standard for data network 9/13/2021 Sistem Komunikasi 22

Protocol Layering • Layer 1 • Layer 2 • Layer 3 • Layer 4

Protocol Layering • Layer 1 • Layer 2 • Layer 3 • Layer 4 • Layer 5 • Layer 6 • Layer 7 9/13/2021 Physical Data link Network Transport Session Presentation Application Sistem Komunikasi [Please[ [Do[ [Not[ [Throw[ [Sausage[ [Pizza[ [Away[ 23

ISDN • Increasingly, both signal transmission and switching are implemented using digital data technique

ISDN • Increasingly, both signal transmission and switching are implemented using digital data technique and the telephone systems are rapidly moving to a digital network • In addition, there is an increasing need for the wide range of telecommunication services ; data transmission, E-mail, Video conference, etc. • In combining a various services and make these available on a single network with the continued expansion of digital transmission and switching • It gives rise to form an Integrated Services Digital Network [ISDN [ 9/13/2021 Sistem Komunikasi 24

Satuan ukuran Common Unit of measurement : Gain & Loss Current Gain [Ai] Voltage

Satuan ukuran Common Unit of measurement : Gain & Loss Current Gain [Ai] Voltage Gain [Av] Power Gain [G] Power Loss [L] = = Io/Ii Vo/Vi Po/Pi Pi/Po Note: G = 1/L or L = 1/G 9/13/2021 Sistem Komunikasi 25

Satuan Decibels [d. B] • Power Gain expressed in d. B : G[d. B]

Satuan Decibels [d. B] • Power Gain expressed in d. B : G[d. B] = 10 log G 9/13/2021 Sistem Komunikasi 26

Satuan d. Bw dan d. Bm • d. Bw dan d. Bm digunakan untuk

Satuan d. Bw dan d. Bm • d. Bw dan d. Bm digunakan untuk menyatakan daya absolute dengan referensi 1 Watt (untuk d. Bw) dan 1 milliwatt (untuk d. Bm) • Contoh, daya P=100 W – Dinyatakan dlm d. Bw = = = – Dinyatakan dlm d. Bm = = 10 10 20 10 10 10 50 log P/P[ref] log 100 W/1 W d. Bw log P/P[ref] log 100 W/1 m. W log 105 m. W/1 m. W d. Bm Catatan : d. Bm = d. Bw + 30 9/13/2021 Sistem Komunikasi 27