2CONTENTS Introduction Wi-Fi Technologies Wi-Fi Architecture Wi-Fi Network ElementsHow a Wi-Fi Network WorksWi-Fi Network TopologiesApplications of Wi-FiWi-Fi SecurityAdvantages/ Disadvantages of Wi-Fi
3INTRODUCTIONWireless Technology is an alternative to Wired Technology , which is commonly used, for connecting devices in wireless mode.Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE communications standard for Wireless Local Area Networks (WLANs).Wi-Fi Network connect computers to each other, to the internet and to the wired network.
4The Wi-Fi TechnologyWi-Fi Networks use Radio Technologies to transmit & receive data at high speed. The name comes from the IEEE committee that standardized it.IEEE bIEEE aIEEE g
5IEEE 802.11b Appear in late 1999 Operates at 2.4GHz radio spectrum 11 Mbps (theoretical speed) - within 30 m Range4-6 Mbps (actual speed)feet rangeMost popular, Least ExpensiveInterference from mobile phones and Bluetooth devices which can reduce the transmission speed.
6IEEE 802.11a Introduced in 2001 Operates at 5 GHz (less popular) 54 Mbps (theoretical speed)15-20 Mbps (Actual speed)50-75 feet rangeMore expensiveNot compatible with b
7IEEE gIntroduced in 2003Combine the feature of both standards (a,b)feet range54 Mbps Speed2.4 GHz radio frequenciesCompatible with ‘b’Use OFDM Technology
8802.11 Physical Layer There are three sub layers in physical layer: Direct Sequence Spread Spectrum (DSSS)Frequency Hoping Spread Spectrum (FHSS)Diffused Infrared (DFIR) - Wide angle
9DSSSDirect sequence signaling technique divides the 2.4 GHz band into MHz channels. Adjacent channels overlap one another partially, with three of the 11 being completely non-overlapping. Data is sent across one of these 22 MHz channels without hopping to other channels.
10IEEE Data Link LayerThe data link layer consists of two sublayers :Logical Link Control (LLC)Media Access Control (MAC).uses the same LLC and 48-bit addressing as other 802 LANs, allowing for very simple bridging from wireless to IEEE wired networks, but the MAC is unique to WLANs.
11Elements of a WI-FI Network Access Point (AP) - The AP is a wireless LAN transceiver or “base station” that can connect one or many wireless devices simultaneously to the Internet.Wi-Fi cards - They accept the wireless signal and relay information. They can be internal and external. (e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)Safeguards - Firewalls and anti-virus software protect networks from uninvited users and keep information secure.
12How a Wi-Fi Network Works Basic concept is same as Walkie talkies.A Wi-Fi hotspot is created by installing an access point to an internet connection.An access point acts as a base station.When Wi-Fi enabled device encounters a hotspot the device can then connect to that network wirelessly.A single access point can support up to 30 users and can function within a range of 100 – 150 feet indoors and up to 300 feet outdoors.Many access points can be connected to each other via Ethernet cables to create a single large network.
14AP-based topology The client communicate through Access Point. BSA-RF coverage provided by an AP.ESA-It consists of 2 or more BSA.ESA cell includes 10-15% overlap to allow roaming.
15Peer-to-peer TOPOLOGY AP is not required.Client devices within a cell can communicate directly with each other.It is useful for setting up of a wireless network quickly and easily.
16Point-to-multipoint bridge TOPOLOGY This is used to connect a LAN in one building to a LANs in other buildings even if the buildings are miles apart.These conditions receive a clear line of sight between buildings. The line-of-sight range varies based on the type of wireless bridge and antenna used as well as the environmental conditions.
20Wi-Fi APPLICATION Home Small Businesses or SOHO Large Corporations & CampusesHealth CareWireless ISP (WISP)Travellers
21Wi-Fi SecurityThe requirements for Wi-Fi network security can be broken down into two primary components:AuthenticationUser AuthenticationServer AuthenticationPrivacy
22Wi-Fi Security Techniques Service Set Identifier (SSID)Wired Equivalent Privacy (WEP)802.1X Access ControlWireless Protected Access (WPA)IEEE i
23ADVANTAGES Mobility Ease of Installation Flexibility Cost Reliability SecurityUse unlicensed part of the radio spectrumRoamingSpeed
24LIMITATION Interference Degradation in performance High power consumptionLimited range
25CONCLUSIONFor now Wi-Fi provides broad band internet access to specially outfitted PCs and Laptops. But in future may be hotspots be wireless.By Wi-Fi our time and money are saved.The technologies have help Wi-Fi “Hotspots are becoming more popular throught urban envirnment.”