Bab I

2. Bab I Pengenalan Wireless LAN

3. Seluk-Beluk Wireless LAN • Pertumbuhan sangat pesat dan terlihat seperti fashion dalam industri network • Wireless LAN sangat fleksibel dalam implementasi, mampu menghemat waktu dan uang perusahaan ketika memerlukan fleksibilitas perpindahan • Harga teknologi wireless semakin turun dan kualitas semakin bagus, menawarkan koneksi yang tidak mahal bagi perusahaan/kampus untuk menghubungkan antar gedung • Sekarang, banyak bisnis yang mengimplementasikan wireless dalam networknya

4. Standart Wireless LAN • IEEE 802.11 (tahun 1997) • Standart asli wireless LAN • Transfer data paling lambat • IEEE 802.11 a (tahun 1999) • Transfer data lebih cepat. • frekuensi band : 5 GHz • Tidak kompatibel dengan lainnya, • IEEE 802.11 b • Transfer data lebih cepat • Dikenalkan sebagai Wi-FiTM oleh WECA • IEEE 802.11 g • Transfer data sama cepat dengan IEEE 802.11 a • Kompatibel dengan IEEE 802.11 b

5. Wi-Fi Standards Standard Speed Freq band Notes • 802.11 2 Mbps 2.4 GHz (1997) 802.11a 54 Mbps 5 GHz (1999) 802.11b 11 Mbps 2.4 GHz • 802.11g 54 Mbps 2.4 GHz

6. Wireless network design • Point-to-Point • Point-to-Multipoint • Multipoint-to-Multipoint

7. Point to Point • The simplest connection. • Atau peer to peer

8. Point to Multipoint When more than one computer communicates with a central point, this is a point-to-multipoint network.

9. Multipoint to Multipoint When any node of a network may communicate with any other, this is a multipoint-to-multipoint network (also known as mesh network)

10. WLAN Architecture • Ad-hoc • Mesh • Infrastructure

11. WLAN Architecture—Ad Hoc Mode • Ad-Hoc mode: Peer-to-peer setup where clients can connect to each other directly. Generally not used for business networks.

12. WLAN Architecture--Mesh Every client in the network also acts as an access or relay point,

13. WLAN Architecture—Infrastructure Mode To Wired Network

14. Infrastructure vs. Adhoc Networks infrastructure network AP: Access Point AP AP wired network AP ad-hoc network Source: Schiller

15. Infrastructure network • There is an Access Point (AP), which becomes the hub of a “star topology.” • Any communication has to go through AP. If a Mobile Station (MS), like a computer, a PDA, or a phone, wants to communicate with another MS, it needs to send the information to AP first, then AP sends it to the destination MS • Multiple APs can be connected together and handle a large number of clients. • Used by the majority of WLANs in homes and businesses.

16. Comparison of Two Structures Infrastructure Ad hoc Expansion X Flexibility X Control X Routing X Coverage X Reliability X

17. Fresnel Zone & Line of Sight

18. Satuan Ukuran • Watts (W) • Miliwatt (mW) • Decibels (dB) • dBm

19. Perbandingan ukuran

20. Spectrum Technology

21. Narrow Band Transmission • Teknologi komunikasi yang menggunakan cukup spektrum frekuensi untuk membawa signal data • High peak power • Range frekuensi kecil Spread Spectrum Technology • Menggunakan range frekuensi yang lebar • Mengurangikemungkinan data corrupt . • Low peak power • Kelebihan • Karenasinyalnyaseperti noise, shg Susah dideteksi • Susah dimodulasitanpaalatkhusus

22. Penggunaan Spread Spectrum • Wireless Local Area Networks • Wireless Personal Area Networks • Wireless Metropolitan Area Networks

23. Antennas, continued • Antennas come in all shapes and styles: • Omni-directional: • Vertical Whip • Ceiling mount • Directional: • Yagi (“Pringles can”) • Wall mounted panel • Parabolic dish

24. Spread spectrum in 802.11 • It is a requirement imposed by the regulatory authorities for devices in ISM band in order to reduce interference. • There is also limitations on transmitted power. • We discuss two methods specified in 802.11, FHSS and DSSS.

25. Teknologi Spread Spectrum ada 2 teknik : • Direct Sequence Spread Spectrum (DSSS) • Frequency Hopping Spread Spectrum (FHSS)

26. Frequency Hopping in 802.11 • The frequency can hop over 78 hopping channels each separated by 1 MHz. • The first channel, Channel 0, starts at 2.402 GHz. • Channel 1 is at 2.403 GHz, • Channel 2, 2.404 GHz, and • so on up to Channel 77 at 2.479 GHz (US, Canada, and Europe standards). • These frequencies are divided into three patterns of 26 hops each corresponding channel numbers (0, 3, 6, 9, …, 75), (1, 4, 7, 10, …, 76), (2, 5, 8, 11, …, 77), see p. 454, Fig. 11.5. • Three APs can coexist without any hop collision, that results in a threefold increase in the capacity of the cell. • Hop rate = 2.5 hops per second. (hop=loncatan turun-naik)

27. DSSS DSSS mempunyai bandwidth 26 MHz (wideband) • Frekuensi kerja (ISM band) 2.4 GHz terbagi ke dalam 11 overlapping channels spaced by 5 MHz. • The coverage areas of two access points (Basic Service Sets, BSS) may overlap to increase capacity. For example, up to 8 users can use VoIP simultaneously through one access point. With two overlapping APs, 16 users can talk simultaneously. But the two APs have to use non-overlapping channels. Modulasi yang digunakan pada FHSS dan DSSS adalalah Gaussian frequency shift keying (GFSK)

29. Modulation

30. Wireless LANInfrastructure Devices

31. Access Point

32. Install AP dalam wired network

33. 3 Mode Konfigurasi AP • Root Mode • Repeater Mode • Bridge Mode

34. Root Mode

35. Bridge Mode

36. Repeater Mode

37. Wireless Bridge

38. Penggunaan Wireless Bridge

39. mode komunikasi wireless bridge • Root Mode • Salah satu bridge harus diset sebagai root bridge • Bisa berkomunikasi dengan non-root bridge lainnya • Tidak bisa berkomunikasi dengan root bridge lainnya • Non-root Mode • Komunikasi bisa ke root bridge • Access Point Mode • Punya kemampuan memperbolehkan client connect • Repeater Mode • Berada diantara 2/lebih bridge • Memperpanjang segmen wireless bridge

40. Peralatan yang berhubungan dengan wireless bridge • Fixed or Detachable Antennas • Advanced Filtering Capabilities • Removable (modular) Radio cards • Variable Output Power • Varied Types of Wired Connectivity

41. Wireless Workgroup Bridges

42. Penggunaan Wireless Workgroup Bridges

43. Wireless LAN client devices • PCMCIA & compact flash cards • Ethernet & serial converters • USB Adapters • PCI & ISA Adapters

44. PCMCIA & Converter

45. Wireless Adapters

46. Wireless LANs: Characteristics • Types • Infrastructure based • Adhoc • Advantages • Flexible deployment • Minimal wiring difficulties • More robust against disasters (earthquake etc) • Disadvantages • Low bandwidth compared to wired networks (1-10 Mbit/s) • Proprietary solutions (kepemilikan) • Need to follow wireless spectrum regulations

47. Infrared uses IR diodes, diffuse light, multiple reflections (walls, furniture etc.) Advantages simple, cheap, available in many mobile devices no licenses needed simple shielding possible Disadvantages interference by sunlight, heat sources etc. many things shield or absorb IR light low bandwidth Example IrDA (Infrared Data Association) interface available everywhere Radio typically using the license free ISM band at 2.4 GHz Advantages experience from wireless WAN and mobile phones can be used coverage of larger areas possible (radio can penetrate walls, furniture etc.) Disadvantages very limited license free frequency bands shielding more difficult, interference with other electrical devices Example WaveLAN, HIPERLAN, Bluetooth Transmission: Infrared vs. Radio Source: Schiller