Wireless LAN Pertemuan 16 Matakuliah: H0484/Jaringan Komputer Tahun: 2007

Bina Nusantara Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menggunakan LAN -Nirkabel

Bina Nusantara Outline Materi Ad-Hoc Infra structure Standards

Bina Nusantara MAC layers in IEEE standard

Bina Nusantara Wireless LAN Specifications b b802.11g802.11a Data Transfer RateUp to 22MbpsUp to 11MbpsUp to 54Mbps Frequency2.4GHz 5GHz Compatibiliy802.11b802.11g802.11b802.11a only

Bina Nusantara b Wireless LAN Utilise Direct Sequence Spread Spectrum (DSSS) technology Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Frequency range of DSSS is between 2.4 to GHz No. of channels at different part of the world varies (S.E.A. : 13 channels) Each channel bandwidth is approximately 20MHz

Bina Nusantara Access Components Client (PCMCIA card) External Antena Access Points Enterprise Access Point Residential Gateways Access Servers (Public Access) Outdoor Routers (Outdoor)

Bina Nusantara FHSS

Bina Nusantara DSSS

Bina Nusantara Two Modes in b Ad-Hoc Mode (also known as “peer-to-peer” mode) Screen Monitor II PC equipped with wireless LAN adapter Notebooks equipped with wireless LAN adapters

Bina Nusantara Infrastructure Mode Screen Monitor II Wired File Server Wired Ethernet Network Gateway to Internet Internet Wired Computer with printer sharing Hardware Access Point Wireless Network PC equipped with wireless LAN adapter Notebooks equipped with wireless LAN adapters Two Modes in b

Bina Nusantara Security Issue Access Control – By MAC Address, only the authorised network card (with correct MAC address) can access the network Data Privacy (Wired Equivalent Privacy -WEP) – Protect the data while it is transferred from one station to another – Encryption between wireless devices to prevent eavesdropping – Rely on a secret key that is shared between the client machines and the access points – The secret key (64/128-bit) is used to encrypt packets before transmitted – b+ supports secret key with 64/128/256-bit

Bina Nusantara Understanding the Antennas Type of Antenna – Omni, Patch, Panel, Yagi, etc Indoor or Outdoor Gain (dBi) – The higher the gain, the further the coverage distance Half Power Beam Width (HPBW) – Horizontal & Vertical

Bina Nusantara Antennas Characteristics Antenna Gain Accomplished by compressing the radiation pattern of the antenna into a narrower beamwidth and focusing the energy toward one direction. Defined as the ratio between radiation intensity of the main lobe and the radiation intensity of an isotropic radiator (having the same input power). Antenna Gain is expressed in dBi. Gain = Focus.

Bina Nusantara Position of Antenna Omni Antenna Best Coverage Side View Best Coverage Top View antenna HPBW/ Horizontal = HPBW/Vertical

Bina Nusantara Line of Sight Optical line of sight: – An imaginary straight line connecting the antennas on both sides of the link. Clear Line of Sight: – When no physical objects obstruct viewing one antenna from the location of the other. Clearance: – The distance between the optical Line of Sight and the nearest obstacle. Fresnel Zone: – The area of a circle around the line of sight.