Topik bahasan. IF3291 Jaringan Komputer & Pengamanannya Physical layer. Dasar teori komunikasi data Jenis media transmisi. Contoh sistem komunikasi:

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1 IF3291 Jaringan Komputer & Pengamanannya Physical layer Achmad Imam Kistijantoro Semester II 2006/2007 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 1

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 3 Dasar teori komunikasi data Informasi/data dikirimkan berupa sinyal, misalnya pada medium kabel, berupa arus/tegangan sebagai fungsi dari waktu, g(t) Setiap sinyal, selalu dinyatakan sebagai komposisi dari gelombang sinusoida yang jumlahnya tak terhingga, dengan menggunakan formula fourier: 1 g( t) = c + 2 n= 1 a sin(2πnft) + n n= 1 b cos(2πnft) n 4 2

3 Contoh Square wave: 4A 1 1 (cos ωt cos 3ωt + cos 5ωt...) π 3 5 Triangular wave: 8A 1 1 (cos ωt + cos 3ωt + cos 5ωt π Sawtooth wave: 2 A (sin ωt π 1 sin 2...) 1 2ωt + sin 3ωt...) 3 5 Sinyal (c) adalah komposisi dari sinyal (a): sin( 2 ft ) (b) 1/3 sin ( 2 (3f)t ) 6 3

4 Dengan mengetahui frekuensi sinyal komponennya, kita dapat menggambarkan sinyal yang sama dalam domain frekuensi (a) sinyal yang sama dengan slide sebelumnya (b) sinyal berupa sebuah kotak yang memiliki lebar x 7 Teori dasar komunikasi data Komponen sinyal yang diperlukan untuk membentuk sebuah sinyal tertentu dapat tak terbatas Setiap media memiliki keterbatasan dalam mengirimkan sinyal. Umumnya hanya beberapa komponen frekuensi awal yang tidak mengalami pelemahan. Lebar frekuensi yang dapat diteruskan sebuah media tanpa mengalami pelemahan yang berarti disebut sebagai bandwidth 8 4

5 Bandwidth-Limited Signals A binary signal and its root-mean-square Fourier amplitudes. (b) (c) Successive approximations to the original signal. 9 Bandwidth-Limited Signals (2) (d) (e) Successive approximations to the original signal. 10 5

6 Bandwidth-Limited Signals (3) Hubungan antara data rate dengan harmonik untuk saluran yang memiliki bandwidth 3000 Hz (saluran telpon) 11 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 12 6

7 Guided Transmission Data Twisted Pair Coaxial Cable Fiber Optics 13 Twisted Pair (a) Category 3 UTP. (b) Category 5 UTP. 14 7

8 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 15 Coaxial Cable A coaxial cable. 16 8

9 Coaxial cable Mampu menangani frekuensi lebih tinggi dibandingkan TP Kapasitas bandwidth dapat mencapai 1GHz Analog: transmisi TV, telpon jarak jauh (digantikan fiber sekarang) Digital: jaringan ethernet. Memerlukan repeater setiap < 1 km 17 Fiber Optics (a) Side view of a single fiber. (b) End view of a sheath with three fibers. 18 9

10 Fiber Optics Kapasitas besar, hingga ratusan GBps Berukuran lebih kecil dan ringan Pelemahan sinyal tidak besar, memerlukan repeater setelah lebih dari puluhan km 19 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 Transmission of Light through Fiber Attenuation of light through fiber in the infrared region. 21 Fiber Cables (2) A comparison of semiconductor diodes and LEDs as light sources

12 Wireless Transmission The Electromagnetic Spectrum Radio Transmission Microwave Transmission Infrared and Millimeter Waves Lightwave Transmission 23 The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication. λf = c 24 12

13 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. 25 Politics of the Electromagnetic Spectrum The ISM bands in the United States

14 Lightwave Transmission Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here. 27 Communication Satellites Geostationary Satellites Medium-Earth Orbit Satellites Low-Earth Orbit Satellites Satellites versus Fiber 28 14

15 Communication Satellites Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage. 29 Communication Satellites (2) The principal satellite bands

16 Communication Satellites (3) VSATs using a hub. 31 Low-Earth Orbit Satellites Iridium (a) (b) (a) The Iridium satellites from six necklaces around the earth. (b) 1628 moving cells cover the earth

17 Globalstar (a) Relaying in space. (b) Relaying on the ground. 33 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 34 17

18 Public Switched Telephone System Structure of the Telephone System The Local Loop: Modems, ADSL and Wireless Trunks and Multiplexing Switching 35 Structure of the Telephone System (a) fully-interconnected network. (b) Centralized switch. (c) Two-level hierarchy

19 Structure of the Telephone System (2) A typical circuit route for a medium-distance call. 37 Local loops Major Components of the Telephone System Analog twisted pairs going to houses and businesses Trunks Digital fiber optics connecting the switching offices Switching offices Where calls are moved from one trunk to another 38 19

20 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 39 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 40 20

21 Modems (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation 41 Modems (2) (a) QPSK: 1 symbol = 2 bit (b) QAM-16: 1 symbol = 4 bit (c) QAM-64: 1 symbol = 6 bit 42 21

22 Modems (3) (a) (b) (a) V.32 for 9600 bps. (TCM) (b) V32 bis for 14,400 bps. (QAM-128) 43 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 44 22

23 Digital Subscriber Lines Bandwidth versus distanced over category 3 UTP for DSL. 45 Digital Subscriber Lines 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 Hz each (Discrete multitone) 46 23

24 Digital Subscriber Lines (2) Operation of ADSL using discrete multitone modulation. 47 Digital Subscriber Lines 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) 48 24

25 Digital Subscriber Lines (3) A typical ADSL equipment configuration. 49 Wireless Local Loops Architecture of an LMDS system

26 Trunks & Multiplexing Multiplexing allows the carrying of multiple signals on a single medium. e,.g. : frequency division multiplexing, time division multiplexing 51 Frequency Division Multiplexing (a) The original bandwidths. (b) The bandwidths raised in frequency. (b) The multiplexed channel

27 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 53 Wavelength Division Multiplexing Wavelength division multiplexing

28 Time Division Multiplexing The T1 carrier (1.544 Mbps). Analog signals are converted into digital by using PCM 55 Time Division Multiplexing (2) Delta modulation

29 Time Division Multiplexing (3) Multiplexing T1 streams into higher carriers. 57 Time Division Multiplexing (4) Two back-to-back SONET frames

30 Time Division Multiplexing (5) SONET and SDH multiplex rates. 59 Circuit Switching (a) Circuit switching. (b) Packet switching

31 Message Switching (a) Circuit switching (b) Message switching (c) Packet switching 61 Packet Switching A comparison of circuit switched and packet-switched networks

32 The Mobile Telephone System First-Generation Mobile Phones: Analog Voice Second-Generation Mobile Phones: Digital Voice Third-Generation Mobile Phones: Digital Voice and Data 63 Analog voice: AMPS Dikembangkan oleh Bell Labs pada tahun 1982 Menggunakan sistem cell: area geografis dibagi menjadi sel-sel kecil berukuran 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 disebut sebagai hand-off. Soft hand-off: tanpa melalui pemutusan hubungan Hard hand-off: hubungan dengan base lama terputus dahulu, sebelum tersambung ke base station baru 64 32

33 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. 65 Channel Categories Frequency allocation: MHz (mobile to base station), 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 66 33

34 Channel allocation Control, access & paging dikelompokkan bersama 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 untuk user (voice), dibagi per sel. Untuk alokasi sel dengan faktor 7, maka per sel mendapat 395/7 = 57 channel 67 Call management Saat handset dinyalakan: scan 21 control channel untuk mencari 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, dan handset mendengarkan channel untuk melakukan panggilan 68 34

35 D-AMPS Digital Advanced Mobile Phone System (a) A D-AMPS channel with three users. (b) A D-AMPS channel with six users. 69 GSM Global System for Mobile Communications GSM uses 124 frequency channels, each of which uses an eight-slot TDM system 70 35

36 GSM (2) A portion of the GSM framing structure. 71 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 72 36

37 Third-Generation Mobile Phones: Digital Voice and Data Basic services an IMT-2000 network should provide High-quality voice transmission Messaging (replace , fax, SMS, chat, etc.) Multimedia (music, videos, films, TV, etc.) Internet access (web surfing, w/multimedia.) 73 Cable Television Community Antenna Television Internet over Cable Spectrum Allocation Cable Modems ADSL versus Cable 74 37

38 Community Antenna Television An early cable television system. 75 Internet over Cable Cable television 76 38

39 Internet over Cable (2) The fixed telephone system. 77 Spectrum Allocation Frequency allocation in a typical cable TV system used for Internet access 78 39

40 Cable Modems Typical details of the upstream and downstream channels in North America