WIFI PPT
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Transcript of WIFI PPT
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PRESENTED BY:
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Agenda• Introduction• Wi-Fi Technologies• Wi-Fi Architecture• Wi-Fi Network Elements• How a Wi-Fi Network Works• Wi-Fi Network Topologies• Applications of Wi-Fi• Advantages/ Disadvantages of Wi-Fi
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Introduction• Wireless 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 802.11 communications standard for Wireless Local Area Networks (WLANs).
• Wi-Fi Network connect computers to each other, to the Internet and to the wired network.
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The Wi-Fi TechnologyWi-Fi Networks use Radio Technologies to transmit & receive data at high speed:
• IEEE 802.11b• IEEE 802.11a• IEEE 802.11g
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IEEE 802.11b
• Appear in late 1999• Operates at 2.4GHz radio spectrum• 11 Mbps (theoretical speed) - within 30 m
Range• 4-6 Mbps (actual speed)• 100 -150 feet range• Most popular, Least Expensive• Interference from mobile phones and
Bluetooth devices which can reduce the transmission speed.
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IEEE 802.11a• Introduced in 2001• Operates at 5 GHz (less popular) • 54 Mbps (theoretical speed)• 15-20 Mbps (Actual speed)• 50-75 feet range• More expensive• Not compatible with 802.11b
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IEEE 802.11g
• Introduced in 2003• Combine the feature of both standards (a,b)• 100-150 feet range• 54 Mbps Speed• 2.4 GHz radio frequencies• Compatible with ‘b’
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802.11 Physical LayerThere are three sublayers in physical layer:
• Direct Sequence Spread Spectrum (DSSS)• Frequency Hoping Spread Spectrum
(FHSS)• Diffused Infrared (DFIR) - Wide angle
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DSSS• Direct sequence signaling technique divides the 2.4 GHz
band into 11 22-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.
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IEEE 802.11 Data Link LayerThe data link layer consists of two sublayers :
• Logical Link Control (LLC) • Media Access Control (MAC).
802.11 uses the same 802.2 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.
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802.11 Media Access Control• Carrier Sense Medium Access with collision
avoidance protocol (CSMA/CA)• Listen before talking• Avoid collision by explicit Acknowledgement (ACK)• Problem: additional overhead of ACK packets, so
slow performance • Request to Send/Clear to Send (RTS/CTS) protocol
• Solution for “hidden node” problem• Problem: Adds additional overhead by temporarily
reserving the medium, so used for large size packets only retransmission would be expensive
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802.11 Media Access Control(cont.)• Fragmentation• CRC checksum
• Each pkt has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit
• Association & Roaming
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Elements 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.
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How 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.
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Wi-Fi Network Topologies• AP-based topology (Infrastructure Mode)
• Peer-to-peer topology (Ad-hoc Mode)
• Point-to-multipoint bridge topology
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AP-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.
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Peer-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.
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Point-to-multipoint bridge topologyThis 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.
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Wi-Fi Applications• Home• Small Businesses or SOHO• Large Corporations & Campuses• Health Care• Wireless ISP (WISP)• Travellers
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COMPARISIONS: 3G VS WIFI
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Advantages• Mobility• Ease of Installation• Flexibility• Cost• Reliability• Security• Use unlicensed part of the radio spectrum• Roaming• Speed
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Limitations• Interference• Degradation in performance• High power consumption• Limited range
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THANK U
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QUERIES???