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.
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.
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
Unlicensed Frequency Bands
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.
The cost of wireless devices has decreased greatly, making it an affordable option.
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.
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
Cellular Cellular System Topology MSC MSC - Mobile Switching Center - Base Transceiver Station (BTS)
Components and Technology
Cisco Aironet 802.11b Client Adapters
Example of wireless adapter
6, 9, 12, 18, 24, 36, 48, or 54
Fixed data rates
User configurable option
5 dBi Patch Antenna
Transmit power settings:
20 mW, 10 mW, and 5 mW
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.
Four main requirements for WLAN solution:
Through system redundancy
Redundant AP automatic rate negotiation
using multiple APs per coverage area
using multiple frequencies
AP using load balancing
Manageability (diagnostic tools)
Challenges and Issues
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.
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.
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.
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.
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.
Installation & Site Design Issues
Obstructions to visual link:
Curvature of the Earth
Installation and Site Design Issues—WLAN
Intel – Wi-Fi chips
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
Milpitas, Calif.; 58% share of chip market
In general, living things should not be subjected to RF energy unnecessarily.
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.
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.
Questions: Feel free to contact the creator of this material
John Perrine, Professor, Collin County Community College, email@example.com
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