Topik bahasan - muamalkhoerudin.files.wordpress.com · Jaringan Komputer (IF8505) Physical layer 2 ... – Media transmisi kabel – Media transmisi tanpa kabel – Komunikasi satelit

1

Jaringan Komputer (IF8505)Physical layer

2

Topik bahasan

• Dasar teori komunikasi data• Jenis media transmisi

– Media transmisi kabel– Media transmisi tanpa kabel– Komunikasi satelit

• Contoh sistem komunikasi:– PSTN– Sistem telpon mobile– TV Kabel

2

3

Topik bahasan




4

Dasar teori komunikasi data

• Informasi/data dikirimkan berupa sinyal, misalnya pada medium kabel, berupaarus/tegangan sebagai fungsi dari waktu, g(t)

• Setiap sinyal, selalu dinyatakan sebagaikomposisi dari gelombang sinusoida yang jumlahnya tak terhingga, dengan menggunakanformula fourier:

)2cos()2sin(21)(

11

nftbnftactgn

nn

n ππ ∑∑∞

=

∞

=

++=

3

5

• Square wave:

• Triangular wave:

• Sawtooth wave:

Contoh

...)5cos513cos

31(cos4

−+− tttA ωωωπ

...)5cos2513cos

91(cos8

2 +++ tttA ωωωπ

...)3sin312sin

21(sin2

−+− tttA ωωωπ

6

• Sinyal (c) adalahkomposisi dari sinyal– (a): sin( 2 ft )– (b) 1/3 sin ( 2 (3f)t )

4

7

• Dengan mengetahuifrekuensi sinyalkomponennya, kita dapatmenggambarkan sinyalyang sama dalam domain frekuensi– (a) sinyal yang sama

dengan slide sebelumnya– (b) sinyal berupa sebuah

kotak yang memiliki lebar x

8

Teori dasar komunikasi data

• Komponen sinyal yang diperlukan untukmembentuk sebuah sinyal tertentu dapat takterbatas

• Setiap media memiliki keterbatasan dalammengirimkan sinyal. Umumnya hanya beberapakomponen frekuensi awal yang tidak mengalamipelemahan.

• Lebar frekuensi yang dapat diteruskan sebuahmedia tanpa mengalami pelemahan yang berartidisebut sebagai bandwidth

5

9

Bandwidth-Limited Signals

A binary signal and its root-mean-square Fourier amplitudes.(b) – (c) Successive approximations to the original signal.

10

Bandwidth-Limited Signals (2)

(d) – (e) Successive approximations to the original signal.

6

11

Bandwidth-Limited Signals (3)

Hubungan antara data rate dengan harmonik untuk saluranyang memiliki bandwidth 3000 Hz (saluran telpon)

12

Topik bahasan




7

13

Guided Transmission Data

• Twisted Pair• Coaxial Cable• Fiber Optics

14

Twisted Pair

(a) Category 3 UTP.(b) Category 5 UTP.

8

15

Twisted pair

• Twisting: menghindari kabel beroperasi sebagai antena• Cat 3: digunakan untuk komunikasi telpon (max 16 MHz)• Cat 5: digunakan untuk jaringan LAN/ethernet (max 100

MHz)• Sinyal analog: memerlukan repeater setiap 5-6 km• Sinyal digital: memerlukan repeater setiap 2-3 km• murah

16

Coaxial Cable

A coaxial cable.

9

17

Coaxial cable

• Mampu menangani frekuensi lebih tinggidibandingkan TP

• Kapasitas bandwidth dapat mencapai 1GHz• Analog: transmisi TV, telpon jarak jauh

(digantikan fiber sekarang)• Digital: jaringan ethernet. Memerlukan repeater

setiap < 1 km

18

Fiber Optics

(a) Side view of a single fiber.(b) End view of a sheath with three fibers.

10

19

Fiber Optics

• Kapasitas besar, hingga ratusan GBps• Berukuran lebih kecil dan ringan• Pelemahan sinyal tidak besar, memerlukan

repeater setelah lebih dari puluhan km

20

Fiber Optics

(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.

(b) Light trapped by total internal reflection.

11

21

Transmission of Light through Fiber

Attenuation of light through fiber in the infrared region.

22

Fiber Cables (2)

A comparison of semiconductor diodes and LEDsas light sources.

12

23

Wireless Transmission

• The Electromagnetic Spectrum• Radio Transmission• Microwave Transmission• Infrared and Millimeter Waves• Lightwave Transmission

24

The Electromagnetic Spectrum

The electromagnetic spectrum and its uses for communication.λf = c

13

25

Radio Transmission

(a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth.

(b) In the HF band, they bounce off the ionosphere.

26

Politics of the Electromagnetic Spectrum

The ISM bands in the United States.

14

27

Lightwave Transmission

Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here.

28

Communication Satellites

• Geostationary Satellites• Medium-Earth Orbit Satellites• Low-Earth Orbit Satellites• Satellites versus Fiber

15

29

Communication Satellites

Communication satellites and some of their properties, includingaltitude above the earth, round-trip delay time and number of

satellites needed for global coverage.

30

Communication Satellites (2)

The principal satellite bands.

16

31

Communication Satellites (3)

VSATs using a hub.

32

Low-Earth Orbit SatellitesIridium

(a) The Iridium satellites from six necklaces around the earth.(b) 1628 moving cells cover the earth.

(a) (b)

17

33

Globalstar

(a) Relaying in space.(b) Relaying on the ground.

34

Topik bahasan




18

35

Public Switched Telephone System• Structure of the Telephone System• The Local Loop: Modems, ADSL and

Wireless• Trunks and Multiplexing• Switching

36

Structure of the Telephone System

(a) fully-interconnected network.(b) Centralized switch.(c) Two-level hierarchy.

19

37

Structure of the Telephone System (2)

A typical circuit route for a medium-distance call.

38

Major Components of the Telephone System

• Local loopsAnalog twisted pairs going to houses and businesses

• TrunksDigital fiber optics connecting the switching offices

• Switching officesWhere calls are moved from one trunk to another

20

39

The Local Loop: Modems, ADSL, and Wireless

The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.

Three major problems: attenuation, distortion & noise

40

Modem

• Digital signal requires a wide frequency spectrum for transmission, which is unsuitable to be used on telephone line

• Modem translates digital data to/from analogue form for transmission over analogue media

• Codec: a software module that can also be used to translate between analogue and digital form

• Modems are used for twisted pair, coaxial cable, fibre optics, radio and satellite transmission

21

41

Modems

(a) A binary signal(b) Amplitude modulation

(c) Frequency modulation(d) Phase modulation

42

Modems (2)

(a) QPSK: 1 symbol = 2 bit(b) QAM-16: 1 symbol = 4 bit(c) QAM-64: 1 symbol = 6 bit

22

43

Modems (3)

(a) V.32 for 9600 bps. (TCM)(b) V32 bis for 14,400 bps. (QAM-128)

(a) (b)

44

Modems (4)

• A modem/connection that allows traffic in both directions is called full duplex

• A connection that allows traffic either way, only one way at a time: half duplex

• A connection that allows traffic only one way is called simplex

• V.90 modem: capable of transmitting 33.6 kbps upstream & 56 kbps downstream

• V92: 48 kbps upstream & 56 kbps downstream

23

45

Digital Subscriber Lines

Bandwidth versus distanced over category 3 UTP for DSL.

46


• DSL service criteria– Work over existing cat 3 twisted pair local loops– Must not affect existing telephones and fax services– Much faster than 56 kbps– Always on, no per-minute charge

• Initial solution:– Dividing 1.1 MHz spectrum into 3 bands: POTS,

upstream & downstream• Better solution:

– Dividing 1.1 MHz into 256 channels of 4312.5 Hz each (Discrete multitone)

24

47

Digital Subscriber Lines (2)

Operation of ADSL using discrete multitonemodulation.

48


• Many providers choose to allocate more bandwidth for downstream -> Asymmetric DSL

• Use a modulation scheme similar to V.34, with sampling rate 4000 baud, and 15 bits per baud (symbol)

25

49

Digital Subscriber Lines (3)

A typical ADSL equipment configuration.

50

Wireless Local Loops

Architecture of an LMDS system.

26

51

Trunks & Multiplexing

• Multiplexing allows the carrying of multiple signals on a single medium.

• e,.g. : frequency division multiplexing, time division multiplexing

52

Frequency Division Multiplexing

(a) The original bandwidths.(b) The bandwidths raised in frequency.(b) The multiplexed channel.

27

53

Frequency Division Multiplexing

• Filters are used at receiver to separate channels and remove carriers

• CCITT standards: 12 of 4 kHz voice channels are multiplexed into 60 kHz – 108 kHz called group

• 5 groups (60 voice channels) form supergroup• 5 supergroups form mastergroup

54

Wavelength Division Multiplexing

Wavelength division multiplexing.

28

55

Time Division Multiplexing

The T1 carrier (1.544 Mbps).Analog signals are converted into digital by using PCM

56

Time Division Multiplexing (2)

Delta modulation.

29

57


Multiplexing T1 streams into higher carriers.

58


Two back-to-back SONET frames.

30

59


SONET and SDH multiplex rates.

60

Circuit Switching

(a) Circuit switching.(b) Packet switching.

31

61

Message Switching

(a) Circuit switching (b) Message switching (c) Packet switching

62

Packet Switching

A comparison of circuit switched and packet-switched networks.

32

63

The Mobile Telephone System

• First-Generation Mobile Phones: Analog Voice

• Second-Generation Mobile Phones: Digital Voice

• Third-Generation Mobile Phones:Digital Voice and Data

64

Analog voice: AMPS

• Dikembangkan oleh Bell Labs pada tahun 1982• Menggunakan sistem cell: area geografis dibagi menjadi

sel-sel kecil berukuran 10-20 km:– Frequency reuse– Handset dapat menggunakan daya lebih rendah untuk

mengakses base station• Pada setiap saatnya, seorang pengguna akan berada

pada lokasi sel tertentu.• Proses perpindahan pengguna dari satu sel ke sel

lainnya pada saat terjadi percakapan aktif disebutsebagai hand-off.

• Soft hand-off: tanpa melalui pemutusan hubungan• Hard hand-off: hubungan dengan base lama terputus

dahulu, sebelum tersambung ke base station baru

33

65

Advanced Mobile Phone System

(a) Frequencies are not reused in adjacent cells. Frequencies are reused for every 7 cells

(b) To add more users, smaller cells can be used.

66

Channel CategoriesFrequency allocation: 824-849 MHz (mobile to base

station), 869-894 MHz (base station to mobile)The 832 channels (30 kHz wide) are divided into

four categories:• Control (base to mobile) to manage the system• Paging (base to mobile) to alert users to calls for

them• Access (bidirectional) for call setup and channel

assignment• Data (bidirectional) for voice, fax, or data

34

67

Channel allocation

• Control, access & paging dikelompokkanbersama menjadi control channel.

• 832 channel (full duplex) dibagi 2 (untuk 2 provider pada area yg sama), masing2 416 channel

• 21 channel digunakan untuk control (data/digital: 10 kbps) 1 channel untuk setiap sel, 395 untukuser (voice), dibagi per sel. Untuk alokasi seldengan faktor 7, maka per sel mendapat 395/7 = 57 channel

68

Call management

• Saat handset dinyalakan: scan 21 control channel untukmencari sinyal terkuat (memilih sel)

• Handset kemudian mengirim informasi serial number handset & nomor telpon

• MTSO mencatat informasi pengguna & lokasinya• Untuk memanggil: handset mengirimkan nomor tujuan

via access channel. Jika ada channel tersedia, base station mengalokasikan channel data tersebut, danhandset mendengarkan channel untuk melakukanpanggilan

35

69

D-AMPS Digital Advanced Mobile Phone System

(a) A D-AMPS channel with three users.(b) A D-AMPS channel with six users.

70

GSMGlobal System for Mobile

Communications

GSM uses 124 frequency channels, each of which uses an eight-slot TDM system

36

71

GSM (2)

A portion of the GSM framing structure.

72

CDMA – Code Division Multiple Access

(a) Binary chip sequences for four stations(b) Bipolar chip sequences (c) Six examples of transmissions(d) Recovery of station C’s signal

37

73

Third-Generation Mobile Phones:Digital Voice and Data

Basic services an IMT-2000 network should provide

• High-quality voice transmission• Messaging (replace e-mail, fax, SMS, chat,

etc.)• Multimedia (music, videos, films, TV, etc.)• Internet access (web surfing, w/multimedia.)

74

Cable Television

• Community Antenna Television• Internet over Cable• Spectrum Allocation• Cable Modems• ADSL versus Cable

38

75

Community Antenna Television

An early cable television system.

76

Internet over Cable

Cable television

39

77

Internet over Cable (2)

The fixed telephone system.

78

Spectrum Allocation

Frequency allocation in a typical cable TV system used for Internet access

40

79

Cable Modems

Typical details of the upstream and downstream channels in North America.

Topik bahasan - muamalkhoerudin.files.wordpress.com · Jaringan Komputer (IF8505) Physical layer 2 ... – Media transmisi kabel – Media transmisi tanpa kabel – Komunikasi satelit

Documents