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Wireless LANs Class Goals Planning a home wireless network Selecting wireless equipment Installation and configuring wireless devices Issues relating to boosting range and increasing throughput Security Playing internet games Using wireless gear on the road

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Wireless LANs

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class goals
Class Goals
  • Planning a home wireless network
  • Selecting wireless equipment
  • Installation and configuring wireless devices
  • Issues relating to boosting range and increasing throughput
  • Security
  • Playing internet games
  • Using wireless gear on the road
  • Sharing audio-visual devices in the home
  • What is Wireless?The term wireless refers to telecommunication technology, in which radio waves, infrared waves and microwaves, instead of cables or wires, are used to carry a signal to connect communication devices.
  • These devices include pagers, cell phones, portable PCs, computer networks, location devices, satellite systems and handheld digital assistants.
  • Wireless networking is the transmission of data using a physical topology, not direct physical links.
wireless everywhere
Wireless everywhere
  • Computers
    • Wi-Fi
    • Bluetooth
    • Wireless Wans – CDMA, GSM, WiMAX
  • HDTV
    • Wi-Fi
    • Zigbee – New technology
    • UWB (universal wideband) for video, surround sound and zigbee controls
  • AV equipment
    • Wi-Fi
    • Zigbee
    • UWB
  • Cell Phones
    • Wi-Fi – VOIP
    • Bluetooth
  • Cars
    • Wi-Fi
    • Bluetooth
    • Onstar
    • Lo-Jack
  • Planes
wireless landscape
Wireless Landscape

WiMAX as a last-mile alternative for remote areas not currently served by DSL or cable

wireless data networks

2.5 GHz Service

Circuit and Packet Data

Cellular, CDPD, Mobitex, DataTac

Broadband PCS

Narrowband PCS

Wireless Data Networks

50 Mbps

802.11 is WiFi

WAP is small handhelds

Spread Spectrum Wireless LANs

10 Mbps

Infrared Wireless LANs

2 Mbps

1 Mbps

Data Rates

56 Kbps

19.6 Kbps

Narrow Band Wireless LANs


9.6 Kbps



Coverage Area

wireless signals
Wireless Signals
  • Wireless communications use waves that travel through space
  • The electromagnetic spectrum or electromagnetic waves require no medium for movement
    • Waves travel freely through space at speed of light or 186,000 miles per second
    • Figure 2-1 shows the electromagnetic spectrum
  • Wireless signals use infrared light and radio waves
ways to use home wireless
Ways to use Home Wireless
  • Data transfer
  • Audio – IPOD, music
  • Voices – VOIP
  • Home control
  • Security surveillance
  • Bluetooth wireless technology is a short-range radio technology.
  • Bluetooth wireless technology makes it possible to transmit signals over short distances between telephones, computers and other devices and thereby simplify communication and synchronization between devices.
  • The Bluetooth wireless technology comprises hardware, software and interoperability requirements.
  • Transmits at up to 1 Mbps over a distance of 33 feet and is not impeded by physical barriers
bluetooth blue snarfing
Bluetooth – Blue Snarfing
  • Blue-snarfing, the technique leaves no trace of intrusion, steals the contents of a cellphone's address book , or even gain access to a user's laptop.
  • "Bluejacking" allows a user to send an anonymous and unauthorized message to another cell user. It has become primarily a means of entertainment for some individuals in crowded places - who'll send anonymous comments like "I like your tie" to people nearby.

Bluetooth was named after the 10th century Danish King Harold Bluetooth, who was responsible for unifying Scandinavia

advantages and disadvantages of wireless home networks

Freedom – work anywhere

Quick, effortless installation

No cables to buy

Save cabling time and hassle

Easy to expand

Available in Hotspots at coffee shops, businesses, airports

Great on the road


Higher cost

Slower speed

Shorter range

Least efficient way to move large amounts of data

Less Secure

Advantages and Disadvantages of Wireless Home Networks

Linksys Home

hot spots and hot zones
Hot Spots and Hot Zones
  • Hotspots – an area with publicly available high-speed Internet access via a Wi-Fi network.
    • Personal, retail, libraries, hospitality, airports, convention centers
  • Hot Zones – a wireless network that covers a few square miles instead of just a few hundred feet
    • Universities, corporate campuses, economic zones, municipal networks
  • Check Southern California Free Net.
    • Check WiFi Planet
a few san diego hotspots
A few San Diego HotSpots


  • Sorrento Valley Food Court - corner of Mira Mesa Boulevard and Scranton Road near the 5/805 junctionSorrento Mesa area building campus near Karl StraussSanta Fe Depot - Amtrak StationOne America Plaza - 600 West BroadwayGelato Vero Caffe - 3753 India St. - 619-295-9269Influx - 1948 BroadwayLittle Italy Wi-Fi - free for introductory period - India Street between Cedar & FirUniversity of San Diego campusMount Etna Park - 4741 Mount Etna DriveBest Western Hacienda - lobby area - Old TownGolden Hill neighborhood - 4 locations - near 2035, 2426 Broadway, 26th and Broadway, 2302 C StSherman Heights neighborhood - 20th between Island and J StreetTravel University International - 3870 Murphy Canyon Road Suite 310 - 858-292-9755 Aztec Coin Laundry - 6931 El Cajon BlvdLestat's Coffee House - 3343 Adams Avenue - (619) 282-0437San Diego Public Library locations (eventual plans for all branches)Mission Valley Branch - 2123 Fenton ParkwayPoint Loma/Hervey Branch - 3701 Voltaire St.San Diego Technical Bookstore - 7512 Clairemont Mesa Blvd. - (858) 279-4990It's a Grind Coffeeshop - 13350 Camino Del Sur, Suite 9. - 858.780.2601Bandwidth Bay project provides access at the outdoor sitting area on the east side of the building at 225 BroadwayHotel Del Coronado - lobby area - Coronado Island
wi fi
  • Wi-Fi™ Alliance
    • Wireless Fidelity Alliance
    • 170+ members
    • Over 350 products certified
  • Wi-Fi’s™ Mission
    • Certify interoperability of WLAN products (802.11)
    • Wi-Fi™ is tested and given the “stamp of approval”
    • Promote Wi-Fi™ as the global standard
ieee 802 11 standards activities
IEEE 802.11 Standards Activities
  • 802.11a: 5GHz, 54Mbps
  • 802.11b: 2.4GHz, 11Mbps
  • 802.11d: Multiple regulatory domains
  • 802.11e: Quality of Service (QoS)
  • 802.11f: Inter-Access Point Protocol (IAPP)
  • 802.11g: 2.4GHz, 54Mbps
  • 802.11h: Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC)
  • 802.11i: Security
  • 802.11j: Japan 5GHz Channels (4.9-5.1 GHz)
  • 802.11k: Measurement
802 11

Electromagnetic Spectrum – any particular spot on the spectrum is defined by its wave length and frequency.

  • Introduced in 1990
  • Defined cable-free local area network with either fixed or mobile locations that transmit at either 1 or 2 Mbps which was insufficient for most network applications
  • A new standard was developed for sending packetsized data traffic over radio waves in the unlicensed 2.4 Ghz band.
  • Unlicensed, means it does not have to be certified by the FCC, and devices could possible share the bandwidth with other devices such as cordless phones, baby monitors etc.
physical layer osi model
Physical Layer OSI Model
  • Defines how bits and bytes are transferred to and from the physical medium, in the case, radio waves of the electromagnetic spectrum.
  • If the device shares same physical layer (radio frequency) implementations, they can communicate.

802.11b and 802.11g share the same frequency

unlicensed band
Unlicensed Band
  • 2.4 GHz frequency range is an unlicensed band.
  • No license is required from FCC.
  • However, approval is required for:
    • Amount of power
    • Antennas must meet standards.
  • Industrial, Scientific, and Medical (ISM) band approved by FCC in 1985
    • Devices transmit at 11 Mbps
  • Unlicensed National Information Infrastructure (U-NII) approved by FCC in 1996
    • Used for short-range, high-speed wireless digital communications
frequency hopping spread spectrum fhss
Frequency Hopping Spread Spectrum (FHSS)
  • Frequency hopping spread spectrum (FHSS) uses a range of frequencies, changing frequencies during transmission
    • A short burst is transmitted at one frequency and then another at a different frequency, etc.
    • Figure 2-31 demonstrates FHSS transmission

More immune to interference

Hedy Lamar and George Anthell conceived the idea of FHSS during World War II to keep Germans from jamming radios that guided warships

dsss modulation
DSSS Modulation
  • Modulation describes how data is added to the radio waves
  • Demodulation is the reverse – Modem
  • Due to FCC Regulations, US can only use 11 channels with 3 non-overlapping
  • Has real work throughput of 5 Mbps

11 Channels – each channel 22 MHz wide

1 set of 3 non-overlapping channels

14 Channels – each channel 22 MHz wide

4 sets of 3 non-overlapping channels, only one set used at a time

channels 2 4 ghz dsss
Channels- 2.4 GHz DSSS
  • 802.11b also defines how the radio waves behave.
  • 802.11b uses DSSS which uses one channel for transmission.
  • 11 Mbps data rate
  • 3 access points can occupy same area

11 Channels – each channel 22 MHz wide

1 set of 3 non-overlapping channels

14 Channels – each channel 22 MHz wide

4 sets of 3 non-overlapping channels, only one set used at a time

  • Orthogonal Frequency Division Multiplexing (OFDM) - Dating to 1960s, it’s primary role is to split high-speed digital signal into several slower signals running in parallel
    • Sending device breaks transmission into pieces and sends it over channels in parallel
    • Receiving device combines signals to re-create the transmission
  • OFDM modulation – independent and well-separated that fills the airwaves but distinct enough to demodulate.
  • Enough bandwidth to handel HDTV.

802.11g uses same frequencies as 802.11b, same channel assignments and same modulation, therefore backward compatible.

802.11b slows the 802.11g network.

802.11a uses wider channels, has more channels, and most importantly, 8 non-overlapping channels.

Downside – shorter range and inertia

wlan devices
WLAN Devices

In-building Infrastructure

Access Points

  • Combo (802.11a and 802.11b)
  • (802.11b)
  • (802.11b) not shown


wlan devices29
WLAN Devices


  • 2.4 GHz client adapter (802.11b)
  • 5 GHz client adapter (802.11a)
  • Workgroup bridge (802.11b)


  • 2.4GHz
  • 5 GHz Antennas
cable accessories wireless ip phone
Cable, Accessories, Wireless IP Phone

Cable and Accessories

  • Low Loss Cable
  • Antenna Mounts
  • Lightening Arrestor
  • Wireless IP Phone
optional 2 4ghz antennas for long range
Optional 2.4GHz Antennas for Long Range
  • 13.5 dBi Yagi
    • Distances over
      • 7.3 miles @ 2 Mbps
      • 11.7 Km @ 2 Mbps
      • 3.6 miles @ 11 Mbps
      • 5.8 Km @ 11 Mbps
  • 21 dBi Solid Dish
    • For distances up to
      • 25+ miles @ 2 Mbps
      • 40+ Km @ 2 Mbps
      • 20.5 miles @ 11 Mbps
      • 33 Km @ 11 Mbps

Note: Distances include 50 feet of low loss cable and 10 dB fade margin

ad hoc topology
Ad Hoc Topology
  • Peer-to-Peer (Ad Hoc) Topology
    • Can consist of 2 or more PCs with wireless network adapters.
    • Sometimes called an Independent BSS (IBSS).
    • Limited range.
802 11 authentication and association
802.11 Authentication and Association
  • The 802.11 standard includes rudimentary authentication and confidentiality controls.
    • Authentication is handled in its most basic form by the 802.11 access point (AP).
      • It forces the clients to perform a handshake when attempting to “associate” to the AP. Association is the process needed before the AP will allow the client to talk across the AP to the network.
      • Association occurs only if the client has all the correct parameters needed such as the service set identifier (SSID) in the handshake.
802 11 security tools
802.11 Security Tools
  • WEP
  • WPA,
  • 802.11i
  • SSID
  • MAC Filtering
  • VPN
  • Userid and Password
the security attack recon and access
The Security Attack—Recon and Access

War Chalking, War Driving, War Flying, Blue Snarfing

wireless lan security war driving
Wireless LAN Security - War Driving

“War Driving”

Hacking into WEP

War driving (drive-by hacking or LAN-jacking) is a play on “war dialing”. War dialing, in turn, comes from the 1983 movie War Games, now a classic in computer cracking circles.

Literally, war driving is using a laptop‘s to pick up unsecured wireless networks for anonymous and free high-speed Internet access, akin to stealing long-distance phone service.

war chalking
War Chalking
  • Welcome to Warchalking! Warchalking is the practice of marking a series of symbols on sidewalks and walls to indicate nearby wireless access. That way, other computer users can pop open their laptops and connect to the Internet wirelessly. It was inspired by the practice of hobos during the Great Depression to use chalk marks to indicate which homes were friendly.
war flying
War Flying
  • War flying uses airplanes to find the wireless access points. The obvious advantage is the extra height provides an unobstructed line.
  • Some people think war driving is illegal. Actually accessing someone's network is illegal, but detecting the network is not. You can think of war driving as walking up to a house, and checking to see if the door is unlocked. If you find an unlocked door, you write down the address and move to the next house. It becomes illegal when you open the door and walk in, which is similar to accessing the Internet through a AP without the owner's permission.
wlan security hierarchy
WLAN Security Hierarchy

Enhanced Security


TKIP/WPA Encryption,

Mutual Authentication,

Scalable Key Mgmt., etc.

Basic Security

Open Access

40-bit or 128-bitStatic WEP Encryption

No Encryption, Basic Authentication

Home Use


Public “Hotspots”

VirtualPrivateNetwork (VPN)

Business Traveler, Telecommuter

Remote Access


The actual performance of your wireless network depends on a number of factors, including:

  • In an Infrastructure environment, your distance from the access point. As you get farther away, the transmission speed will decrease.
  • Structural interference. The shape of your building or structure, the type of construction, and the building materials used may have an adverse impact on signal quality and speed.
  • The placement and orientation of the wireless devices.
radio signal interference
Radio Signal Interference

Since the frequency is unlicensed, any device operating in the 2.4 GHz spectrum may cause network interference with a 802.11b wireless device. Some devices that may prove troublesome include 2.4 GHz cordless phones, microwave ovens, adjacent public hotspots, and neighboring 802.11b wireless LANs.

interference cont
Interference (cont.)





Fluorescent Lighting

Microwave Ovens

Electrical Transformers