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Wireless Networks ppt

wireless networks ppt

What is wireless

  • A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier.
  • The last link with the users is wireless, to give a network connection to all users in a building or campus.
  • The backbone network usually uses cables

Common topologies in wireless networks

The wireless LAN connects to a wired LAN

  • There is a need of an access point that bridges wireless LAN traffic into the wired LAN.
  • The access point (AP) can also act as a repeater for wireless nodes, effectively doubling the maximum possible distance between nodes.

Complete Wireless Networks

  • The physical size of the network is determined by the maximum reliable propagation range of the radio signals.
  • Referred to as ad hoc networks
  • Are self-organizing networks without any centralized control
  • Suited for temporary situations such as meetings and conferences.

How are wlans different

  • They use specialized physical and data link protocols
  • They integrate into existing networks through access points which provide a bridging function
  • They let you stay connected as you roam from one coverage area to another
  • They have unique security considerations
  • They have specific interoperability requirements
  • They require different hardware
  • They offer performance that differs from wired LANs.

Physical and data link layers

Physical Layer:

  • The wireless NIC takes frames of data from the link layer, scrambles the data in a predetermined way, then uses the modified data stream to modulate a radio carrier signal.

Data Link Layer:

  • Uses Carriers-Sense-Multiple-Access with Collision Avoidance (CSMA/CA).

Parts of wireless LAN

  • Network Card (NIC)
    • Radio that attached to computer.
    • Cisco Aironet 350
  • Access Points
    • Radio equipment that connects to the wireless network.
    • Cisco Aironet 350 & 1200
  • Repeaters
    • Extends the range of wireless network.
  • Bridges
    • Used to link different sites.  Uses ‘line of sight’.

Different standards in wireless networks

  • 802.11 -- applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band.
  • 802.11a -- an extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5GHz band.
  • 802.11b (also referred to as 802.11 High Rate or Wi-Fi) -- an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band.
  • 802.11g -- applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band.


  • Pros
    • Range
      • 300 ft. in a building
      • 1000 ft. outside
    • Well accepted standard
    • Low Cost
    • Availability of Equipment
      • AP’s, NIC’s, & Accessories
    • Interoperability
      • 802.11b works with the new 802.11g equipment
  • Cons
    • RF Interference
    • Lower Throughput
      • 1-11 MBit (Up to 22 MBit with special equipment.)
      • Only 4 Step-downs


  • Pros
    • Speed!
      • 54 MBit
      • Support for high bandwidth applications.  Ex:  voice, video, & large image files.
    • Less Interference
      • Standards such as 802.11b & 802.11g are in the 2.5 GHz band, which is getting congested. 
    • More End-Users
      • 802.11a AP’s can handle more users because of the increased throughput.
  • Cons
    • Cost
      • Higher cost of equipment.
      • More equipment needed
    • Coverage
      • High Bandwidth (5 GHz)  affects range.
      • Range of 60 ft.
    • Inoperability
      • 802.11b is already widely accepted and ‘a’ operates on a different frequency than ‘b’ & ‘g’.  They will not work together.


  • Pros
    • Faster
      • 54 MBit
    • Interoperability
    • Fledgling support
      • Companies such as Cisco, Linksys, Apple, & D-link have ‘g’ equipment.
    • Same advantages as ‘b’.
  • Cons
    • No definite standard yet.
      • Established in the year 2003
    • “Pre-standard” equipment is not guaranteed to work.
wireless standards ppt

RF Interference

  • For 2.4 GHz wireless LANs, there are several sources of interfering signals, including microwave ovens, wireless phones, Bluetooth enabled devices, and other wireless LANs.
  • The most damaging of these are 2.4 GHz wireless phones that people are starting to use in homes and some companies.
  • If one of these phones is in use within the same room as an 802.11b wireless LAN, then expect poor wireless LAN performance.
  • Microwave ovens operating within 10 feet or so of an access point or radio-equipped user will generally just cause 802.11b performance to drop.
  • Bluetooth enabled devices, such as laptops and PDAs, will also cause performance degradations if operating in close proximately to 802.11 stations, especially if the 802.11 station is relatively far (i.e., low signal levels) from the station that it's communicating with.
  • The 802.11 and 802.15 standards groups, however, are working on a standard that will enable the coexistence of Bluetooth and 802.11 devices.
  • Other wireless LANs, such as one that your neighbor may be operating, can cause interference unless you coordinate the selection of 802.11b channels.

Wireless Security

  • MAC ID Filtering
  • Static IP Filtering
  • Regular WEP (Wired Equivalent Privacy)
  • WPA v1 (Wi-Fi Protected Access)
  • TKIP (Temporal Key Integrity Protocol)
  • EAP (Extensible Authentication Protocol)
  • WAPI (WLAN Authentication and Privacy Infrastructure)

Smart Cards, USB Tokens and software tokens

  • These are very strong form of security.
  • When combined with some server software, the hardware or software card or token will use its internal identity code combined with a user entered PIN to create a powerful algorithm that will very frequently generate a new encryption code.
  • The server will be time synced to the card or token. This is a very secure way to conduct wireless transmissions.
  • Companies in this area make USB tokens, software tokens, and smart cards. They even make hardware versions that double as an employee picture badge.
  • Currently the safest security measures are the smart cards / USB tokens. However, these are expensive.
  • The next safest methods are WPA2 or WPA with a RADIUS server.
  • Any one of the three will provide a good base foundation for security.
  • The third item on the list is to educate both employees and contractors on security risks and personal preventive measures.
  • It is also IT's task to keep the company workers' knowledge base up-to-date on any new dangers that they should be cautious about.
  • If the employees are educated, there will be a much lower chance that anyone will accidentally cause a breach in security by not locking down their laptop or bring in a wide open home access point to extend their mobile range.
  • Employees need to be made aware that company laptop security extends to outside of their site walls as well.
  • This includes places such as coffee houses where workers can be at their most vulnerable. T
  • he last item on the list deals with 24/7 active defense measures to ensure that the company network is secure and compliant.

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Wireless Networks ppt wireless security ppt

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