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Wi-Fi Technology

Wi-Fi Technology. By. P. Victer Paul Dear, We planned to share our eBooks and project/seminar contents for free to all needed friends like u.. To get to know about more free computerscience ebooks and technology advancements in computer science. Please visit....

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Wi-Fi Technology

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  1. Wi-Fi Technology

  2. By. P. Victer Paul Dear, We planned to share our eBooks and project/seminar contents for free to all needed friends like u.. To get to know about more free computerscience ebooks and technology advancements in computer science. Please visit.... http://free-computerscience-ebooks.blogspot.com/ http://recent-computer-technology.blogspot.com/ http://computertechnologiesebooks.blogspot.com/ Please to keep provide many eBooks and technology news for FREE. Encourage us by Clicking on the advertisement in these Blog.

  3. Introduction • Wi-Fi Technologies • Wi-Fi Architecture • Wi-Fi Network Elements • How a Wi-Fi Network Works • Wi-Fi Network Topologies • Wi-Fi Configurations • Applications of Wi-Fi Agenda

  4. 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. Introduction • Wireless Network Design • Radio Modes • Bridged Networking

  5. Any wireless network can be thought of as a combination of one or more of these types of connections: • Point-to-Point • Point-to-Multipoint • Multipoint-to-Multipoint WIRELESS NETWORK DESIGN

  6. The simplest connection is the Point-to-Point link. These links can be used to extend a network over great distances. POINT TO POINT

  7. When more than one computer communicates with a central point, this is a Point-to-Multipoint network. POINT TO MULTIPOINT

  8. When any node of a network may communicate with any other, this is a multipoint-to-multipoint network(also known as an ad-hoc or mesh network). MULTIPOINT TO MULTIPOINT

  9. Wi-Fi cards can be operated in one of these modes: • Master(Access Point) Managed(also known as client or station) Ad-hoc. • Monitor. • Other proprietary modes(e.g. Mikrotik Nstreme). Radios may only operate in one mode at a time. Radio Modes

  10. Master mode (also called AP or infrastructure mode) is used to create a service that looks like a traditional access point. • The wireless card creates a network with a specified name (called the SSID) and channel, and offers network services on it. • Wireless cards in master mode can only communicate with cards that are associated with it in managed mode. master Mode

  11. Managed mode is sometimes also referred to as client mode. • Wireless cards is managed mode will join a network created by a master, and will automatically change their channel to match it. • Clients using a given access point are said to be associated with it. • Managed mode cards do not communicate with each other directly, and will only communicate with an associated master. managed Mode

  12. Ad-hoc mode creates a multipoint-to-multipoint network when there is no master or AP available. • In ad-hoc mode, each wireless card communicates directly with its neighbors. • Nodes must be in range of each other to communicate, and must agree on a network name and channel. ad-hoc mode

  13. Monitor mode is used by some tools (such as Kismet) to passively listen to all radio traffic on a given channel. • This is useful for analyzing problems on a wireless link or observing spectrum usage in the local area. • Monitor mode is not used for normal communications. Monitor mode

  14. In a simple local area wireless network, a bridged architecture is usually adequate. Advantages: Very simple configuration Roaming works very well. Disadvantages: Increasingly inefficient as nodes are added. All broadcast traffic is repeated Virtually unusable on very large wide-area networks. Bridged networking

  15. Large networks are built by applying routing between nodes. Static routing is often used on point-to-point links Dynamic routing (such as RIP or OSPF) can be used on larger networks, although they are not designed to work with imperfect wireless links Mesh routing Protocols (OLSR, HSLS,AODV) work very well with wireless networks, particularly when using radios in ad-hoc mode. Routed networking

  16. Wi-Fi Networks use Radio Technologies to transmit & receive data at high speed: • IEEE 802.11b • IEEE 802.11a • IEEE 802.11g The Wi-Fi Technology

  17. 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. IEEE 802.11b

  18. 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 IEEE 802.11a

  19. 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’ IEEE 802.11g

  20. There are three sublayers in physical layer: Direct Sequence Spread Spectrum (DSSS) Frequency Hoping Spread Spectrum (FHSS) Diffused Infrared (DFIR) - Wide angle 802.11 Physical Layer

  21. 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. DSSS

  22. The 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. IEEE 802.11 Data Link Layer

  23. 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 802.11 Media Access Control

  24. Power Management • MAC supports power conservation to extend the battery life of portable devices • Power utilization modes • Continuous Aware Mode • Radio is always on and drawing power • Power Save Polling Mode • Radio is “dozing” with access point queuing any data for it • The client radio will wake up periodically in time to receive regular beacon signals from the access point. • The beacon includes information regarding which stations have traffic waiting for them • The client awake on beacon notification and receive its data 802.11 Media Access Control(cont.)

  25. Fragmentation • CRC checksum • Each pocket has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit • Association & Roaming 802.11 Media Access Control(cont.)

  26. 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. Elements of a WI-FI Network

  27. 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. How a Wi-Fi Network Works

  28. AP-based topology (Infrastructure Mode) Peer-to-peer topology (Ad-hoc Mode) Point-to-multipoint bridge topology Wi-Fi Network Topologies

  29. 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. AP-based topology

  30. 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. Peer-to-peer topology

  31. 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. Point-to-multipoint bridge topology

  32. Wi-Fi Configurations

  33. Wi-Fi Configurations

  34. Wi-Fi Configurations

  35. Home • Small Businesses or SOHO • Large Corporations & Campuses • Health Care • Wireless ISP (WISP) • Travellers Wi-Fi Applications

  36. Thank You

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