Convergence Technology

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Convergence Technology

• Module 11 Learning Outcomes 5 and 6
• Wi-Fi - Explain the various wireless access
  technologies related to PAN, HAN, LAN, CAN, MAN,
  and WAN networks, including associated cellular
  and wireless network architectures. Describe
  signaling and its importance to wireless
  telecommunications.

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What is a Wireless LAN?

• WLANs use infrared light (IR) or radio
  frequencies (RFs).
• RF is more popular for its longer range, higher
  bandwidth, and wider coverage.
• WLANs use the 2.4-gigahertz (GHz) and 5-GHz
  frequency bands. These bands are reserved in most
  of the world for unlicensed devices.
• However, wireless systems are not completely
  wireless.

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Wireless Evolution
The wireless vendors in 1991 formed Wireless
Ethernet Compatibility Alliance (WECA) which
proposed and built a standard based on
contributed technology. WECA was later changed to
Wi-Fi. In June 1997 IEEE release the first
standard for wireless
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Unlicensed Frequency Bands
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Why Wireless

• Standards Based
• IEEE 802.11 committee and the Wi-Fi Alliance have
  diligently worked to make wireless equipment
  standardized and interoperable
• Increased Data Rates
• Wireless technology will now support the data
  rates and interoperability necessary for LAN
  operation.
• Cost Effective
• The cost of wireless devices has decreased
  greatly, making it an affordable option.

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Wireless
Cost to install wireless between two buildings
will have a one time incur cost of several
thousand dollars. To install a T1 with less
bandwidth, that wireless will cost hundreds of
dollars per month.
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Benefits

• User Mobility
• Scalability
• Flexibility
• Cost Savings
• Installation advantages
• Reliability
• Site to site connectivity (up to 25 miles)

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802.11 WLAN Media

• Infrared light
• 2.4-GHz radio transmission
• Frequency hopping spread spectrum (FHSS)
• Direct sequence spread spectrum (DSSS)
• Orthogonal frequency-division multiplexing (OFDM)
  802.11g
• 5-GHz frequency
• Orthogonal frequency-division multiplexing (OFDM)
  802.11a

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Wireless

• Spread Spectrum is a modulation technique
  developed in 1940s.
• It spreads a transmission signal over a broad
  range of radio frequencies.
• It is used for data communications because
• less susceptible to radio noise
• crate little interferences

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Cellular
Cellular System Topology
MSC

• Types
• TDMA
• CDMA
• GSM

MSC - Mobile Switching Center
- Base Transceiver Station (BTS)
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Components and Technology
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Cisco Aironet 802.11b Client Adapters

• 2.4 GHz
• 802.11b
• 11 Mbps
• Include
• PC Card
• PCI Card
• LMC Card
• Mini PCI

No antenna
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Example of wireless adapter

• 5 GHz/802.11a
• 54 Mbps
• Rate Shifting
• 6, 9, 12, 18, 24, 36, 48, or 54
• Fixed data rates
• User configurable option
• 5 dBi Patch Antenna
• CardBus interface
• Transmit power settings
• 20 mW, 10 mW, and 5 mW

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WLAN Topologies

• A typical use of wireless technology as an add-on
  to a traditional LAN.
• Building to building wireless connectivity can be
  more cost effective and can avoid obstacles faced
  by wired connections.

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WAN Solutions

• Four main requirements for WLAN solution
• High availability
• Through system redundancy
• Redundant AP automatic rate negotiation
• Scalability
• using multiple APs per coverage area
• using multiple frequencies
• AP using load balancing
• Manageability (diagnostic tools)
• Open Architecture
• 802.11a
• 802.11b

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Challenges and Issues
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Interference from other Sites

• Interference from other sites since the 802.11
  standards use unlicensed spectrum.
• Interference cannot always be detected until the
  link is actually implemented.
• Changing channels is the best way to avoid
  interference.

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Power Management

• Power consumption is always an issue with
  laptops.
• There are 3 modes of power for Cisco PC cards
• Constant Awake Mode (CAM)
• Mode is best when power is not an issue such as
  when AC power is available to the device. Default
  mode
• Power save mode (PSP)
• Mode is used when power conservation is the
  utmost importance. The wireless NIC card will go
  to sleep after a period of inactivity
  periodically awake to retrieve buffered data from
  the AP.
• Fast power save mode (FastPSP)
• Combination of CAM PSP. For clients who switch
  between AC DC power.

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Interference from other Devices

• Other devices use these frequencies.
• Physical objects also cause interference.
• In unlicensed bands, the potential for
  interference from another unlicensed user is
  becoming greater. The unlicensed bands are
  allocated on a shared basis.

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Interoperability

• Interoperability issues might influence an admin
  to use a single vendor for all wireless needs.
• Closed networks, such as corporate sites, might
  choose a single-vendor solution in order to
  benefit from increased management utilities and
  vendor accountability.
• In an open network such as a college campus, the
  admin cannot usually dictate hardware selection,
  and must support a variety of hardware solutions.

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Network Security

• As wireless networks grow, the threat of
  intruders from the inside and outside is great.
  Attackers called war drivers are continually
  driving around searching for insecure WLANs to
  exploit.
• IEEE Wired Equivalent Privacy (WEP) with Temporal
  Key Integrity Protocol (TKIP) provides robust
  authentication options with 802.1X to make
  802.11-based wireless LANs secure.
• IEEE has adopted the use of the Advanced
  Encryption Standard (AES) to the data-privacy
  section of the proposed 802.11i standard.

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Installation Site Design Issues

• Obstructions to visual link
• Topographic features
• Curvature of the Earth
• Buildings
• Trees

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Installation and Site Design IssuesWLAN
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HotSpots
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Wi-Fi Manufactures

• Intel Wi-Fi chips
• Microsoft
• Cisco 60 of wired computer networks
• 1999 bought Aironet Wireless Communications for
  800 million.
• 2003, paid 480 million for Linksys.
• is now the leading maker of Wi-Fi gear
• Netgear
• Milpitas, Calif. 58 share of chip market

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Health Issues

• In general, living things should not be subjected
  to RF energy unnecessarily.
• Antenna guidelines
• Do not touch an active antenna.
• Do not stand in front of, or close to, an antenna
  that is radiating a signal.
• Stand to the back or side of any dish-type
  antenna.
• Always assume that any antenna is currently
  energized.
• Small-sized antennas operate at higher
  frequencies, which are more potentially
  hazardous.
• Maintain at least 5 cm (2 in.) between yourself
  and a laptop antenna.

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New Standards

• 802.11g
• Operates in the 2.4 GHz range
• Higher speeds than 802.11b (54 Mbps)
• Uses OFDM modulation
• Backwardly compatible with 802.11b
• Vendor interoperability and standards alignment.
• Increased security and reliability.

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Questions Feel free to contact the creator of
this material

• John Perrine, Professor, Collin County Community
  College, jperrine_at_ccccd.edu

This material is based upon work supported by the
National Science Foundation under Grant No.
0402356. Any opinions, findings, and conclusions
or recommendations expressed in this material are
those of the author(s) and do not necessarily
reflect the views of the National Science
Foundation