Wireless LAN’s Brent Leopold Geoff Guist. History of WLAN’s Have been around for almost 40 years...
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Transcript of Wireless LAN’s Brent Leopold Geoff Guist. History of WLAN’s Have been around for almost 40 years...
Wireless LAN’s
Brent Leopold
Geoff Guist
History of WLAN’s
Have been around for almost 40 years First WLAN came together in 1971 Project called ALOHNET Originally WLAN hardware was so expensive
that it was only used where cabling was difficult or impossible
Today it is very common
How WLAN’s Work
Supplement wired LAN’s Send radio waves to transmit a signal to an
access point Access point is connected to an ethernet
switch by a UTP cord Requires a wireless network interface card
(NIC) to connect to access point
How WLAN’s Work
Internal NIC External NIC
How WLAN’s Work
The radio transmission requires an antenna in order to send and receive information Omni directional Dish Antenna
Dish Antenna
How WLAN’s Work
Radio transmissions are sent out as a frequency
Service Bands High Bandwidth = Broadband Low Bandwidth = Narrowband Spread Spectrum
Frequency Hopping Spread Spectrum FHSS enables the user to choose from a large
number of frequency channels (75 or more in the US.). With this flexibility modems can be programmed to hop around virtually any electrical interference or interfering object. For example, if transmission is blocked at one frequency, the modem will automatically hop to the next frequency in the pattern, so reliable communications is maintained. FHSS modems remain synchronized at all times, so their latency can be very low.
Direct Sequence Spread Spectrum In DSSS, the stream of information to be transmitted
is divided into small pieces, each of which is allocated across to a frequency channel across the spectrum. A data signal at the point of transmission is combined with a higher data-rate bit sequence (also known as a chipping code) that divides the data according to a spreading ratio. The redundant chipping code helps the signal resist interference and also enables the original data to be recovered if data bits are damaged during transmission.
How WLAN’s Work
Advantages
Freedom No Cables Increased Productivity User Friendly Environment
Disadvantages
Lack of Security Electromagnetic interference Propagation and attenuation
Penalty's for Hackers
Illinois Case Man stole neighbor’s access Charged $250
Florida Case Charged with unauthorized access to a computer
network Man was found guilty and charged with a third-
degree felony
802.11 WLAN Standards
802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients
802.11a 802.11b 802.11g
Emerging Wireless Technology 802.11n
This new technology is said to transmit signals at 100 Mbps or more in the 5 Gigahertz band
Radio frequency Ids (RFIDs) A way to read UPC bar codes by radio over short
distances Ultra Wideband (UWB) transmission systems
Transmit signals across a much wider frequency than conventional systems and are usually very difficult to detect
Emerging Wireless Technology Fourth-generation (4G) station
Instead of using multiple pieces of hardware (many different NICs), 4G stations are focusing on software-defined radio, which will be reconfigured by software instead of hardware