Title: CWNA Guide to Wireless LANs, Second Edition
1CWNA Guide to Wireless LANs, Second Edition
- Chapter Two
- Wireless LAN Devices and Standards
2Objectives
- List WLAN devices and describe their basic
functions - Explain the different types of communication
standards and why standards are important - List the three major wireless standards and
regulatory agencies and their functions - Describe the different IEEE WLAN standards
3WLAN Devices Wireless Network Interface Card
- Network interface card (NIC) Connects computer
to network so that it can send and receive data - Wireless NICs perform same function, but without
wires - When wireless NICs transmit
- Change computers internal data from parallel to
serial transmission - Divide data into packets and attach sending and
receiving computers address - Determine when to send packet
- Transmit packet
4WLAN Devices Wireless Network Interface Card
(continued)
Network interface card for a wired network
5WLAN Devices Wireless Network Interface Card
(continued)
Wireless NICs for desktop computers (a) PCI
network interface card, (b) standalone USB
device, (c) USB key
6WLAN Devices Wireless Network Interface Card
(continued)
Wireless NICs for laptop computers (a) CardBus
card (b) Mini PCI card
7WLAN Devices Wireless Network Interface Card
(continued)
- For smaller devices, several options
- CardBus or Type II PC Card
- May require a sled
- CompactFlash (CF) card Consists of small circuit
board containing flash memory chips and dedicated
controller chip - Small and consume little power
- SDIO (Secure Digital I/O) or SDIO NOW! Card
Provides high-speed data input/output with low
power consumption
8WLAN Devices Wireless Network Interface Card
(continued)
- A movement towards integrating wireless NICs
- Would eliminate need for external wireless NICs
- Software drivers necessary to allow wireless NIC
and operating system (OS) to interface - Windows XP and PDA OSs have built-in drivers
9WLAN Devices Access Point
- Three major parts
- Antenna and radio transmitter/receiver
- RJ-45 wired network interface
- Special bridging software
- To interface wireless devices to other devices
- Two basic function
- Base station for wireless network
- Bridge between wireless and wired networks
10WLAN Devices Access Point (continued)
An access point acts as a bridge between the
wireless network and a wired network
11WLAN Devices Access Point (continued)
- Range depends on several factors
- Type of wireless network supported
- Walls, doors, and other solid objects
- Number of wireless clients that single AP can
support varies - Theoretically over 100 clients
- No more than 50 for light network use
- No more than 20 for heavy network use
- Power over Ethernet (PoE) Power delivered to AP
through unused wires in standard unshielded
twisted pair (UTP) Ethernet cable
12WLAN Devices Remote Wireless Bridge
- Bridge Connects two network segments together
- Even if they use different types of physical
media - Remote wireless bridge Connects two or more
wired or wireless networks together - Transmit at higher power than WLAN APs
- Use directional antennas to focus transmission in
single direction - Delay spread Minimize spread of signal so that
it can reach farther distances - Have software enabling selection of clearest
transmission channel and avoidance of noise and
interference
13WLAN Devices Remote Wireless Bridge (continued)
Point-to-point remote wireless bridge
14WLAN Devices Remote Wireless Bridge (continued)
Point-to-multipoint remote wireless bridge
15WLAN Devices Remote Wireless Bridge (continued)
- Four modes
- Access point mode Functions as standard AP
- Root mode Root bridge can only communicate with
other bridges not in root mode - Non-root mode Can only transmit to another
bridge in root mode - Repeater mode Extend distance between LAN
segments - Placed between two other bridges
- Distance between buildings using remote wireless
bridges can be up to 18 miles at 11 Mbps or 25
miles transmitting 2 Mbps
16WLAN Devices Remote Wireless Bridge (continued)
Root and non-root modes
17WLAN Devices Remote Wireless Bridge (continued)
Repeater mode
18WLAN Devices Wireless Gateway
- Combines wireless management and security in
single appliance - Authentication
- Encryption
- Intrusion detection and malicious program
protection - Bandwidth management
- Centralized network management
19Wireless Standards Organizations and Regulatory
Agencies
- Three primary standard-setting and regulatory
bodies that play major role in wireless LAN
technology - Institute of Electrical and Electronics Engineers
(IEEE) - Wi-Fi Alliance
- U.S. Federal Communications Commission (FCC)
20Institute of Electrical and Electronics Engineers
(IEEE)
- Establishes standards for telecommunications
- Also covers wide range of IT standards
- Worlds largest technical professional society
- 37 Societies and Councils
- Publish technically focused journals, magazines,
and proceedings - Work on over 800 standards
- Best known for its work in establishing standards
for computer networks - Project 802
21Institute of Electrical and Electronics Engineers
(continued)
Current IEEE 802 committees
22Wi-Fi Alliance
- Wireless Ethernet Compatibility Alliance (WECA)
Consortium of wireless equipment manufacturers
and software providers formed to promote wireless
network technology - Three goals
- Encourage wireless manufacturers to use IEEE
802.11 technologies - Promote and market these technologies to
consumers at home, and in small and large
organizations - Test and certify that wireless products adhere to
the IEEE 802.11 standards
23Wi-Fi Alliance (continued)
- WECA changed name to Wi-Fi Alliance in 2002
- Reflected name of certification that it uses
(Wi-Fi) to verify that products follow IEEE
standards - Only products that pass Wi-Fi Alliance tests may
be referred to as Wi-Fi Certified - Wi-Fi Alliance now allows businesses to apply to
be registered as a Wi-Fi ZONE - Qualifies them to be placed in online database of
wireless hotspot locations - Can be accessed through Alliances Web site
24Federal Communications Commission (FCC)
Responsibilities
- Primary regulatory agency for wireless
communications in U.S. and territorial
possessions - Independent government agency
- Directly responsible to Congress
- Broad range of responsibilities
- Develop and implement regulatory programs
- Process applications for licenses and other
filings - Analyze complaints
- Conduct investigations
- Take part in congressional hearings
25FCC Regulating the Radio Frequency Spectrum
- FCC regulates radio frequency spectrum
- Entire range of all radio frequencies
- Spectrum divided into 450 different bands
- U.S. obligated to comply with international
spectrum allocations - FCC license normally required to send and receive
on a specific frequency - License-exempt spectrum or unregulated bands
Bands that are available nationwide to all users - Created to foster development of new devices
26FCC Regulating the Radio Frequency Spectrum
(continued)
Common radio frequency bands
27FCC Regulating the Radio Frequency Spectrum
(continued)
- Two unregulated bands used for WLANs
- Industrial, Scientific, and Medical (ISM) band
- Unlicensed National Information Infrastructure
(U-NII) band Intended for devices that provide
short-range, high-speed wireless digital
communications - Negative features of unregulated bands
- Devices from different vendors may attempt to use
same frequency - Can cause interference and unpredictability
28FCC Regulating the Radio Frequency Spectrum
(continued)
Unlicensed bands
29Types of Wireless LANs
- Since late 1990s, IEEE has approved four
standards for wireless LANs - IEEE 802.11
- IEEE 802.11b
- IEEE 802.11a
- IEEE 802.11g
- IEEE 802.11n expected to be approved by 2006
30IEEE 802.11
- Specified that wireless transmission could take
place via infrared (IR) or radio signals - Infrared Transmissions
- Can send data by the intensity of the infrared
light wave - Light spectrum All types of light
- Infrared light Can be used for wireless
transmissions - Invisible
- Emitter Device that transmits a signal
- Detector Device that receives a signal
31IEEE 802.11 (continued)
- Radio Wave Transmissions
- Radio waves can penetrate through objects
- Provides mobility
- Radio waves travel longer distances
- Can be used indoors and outdoors
- Radio waves can travel at much higher speeds than
infrared transmissions - IEEE 802.11 standard outlining radio wave
transmissions has become preferred method for
wireless LANs
32IEEE 802.11b
- 802.11 standards 2 Mbps bandwidth not sufficient
for most network applications - 802.11b amendment added two higher speeds (5.5
Mbps and 11 Mbps) to original 802.11 standard - Uses ISM band
- Supports wireless devices up to 115 meters (375
feet) apart - Radio waves decrease in power over distance
- 802.11b standard specifies that, when devices out
of range to transmit at 11 Mbps, devices drop
transmission speed to 5.5 Mbps
33IEEE 802.11a
- IEEE 802.11a standard specifies maximum rated
speed of 54 Mbps - Also supports 48, 36, 24, 18, 12, 9,and 6 Mbps
transmissions using U-NII band - 802.11a and 802.11b published at same time
- 802.11a came to market later due to technical
issues and high production cost - Range of 802.11a is less than that of 802.11b
34IEEE 802.11g
- Effort to combine best features of 802.11a and
802.11b - Data transfer rates to 54 Mbps
- Support devices up to 115 meters apart
- 802.11g standard specifies that devices operate
entirely in ISM frequency
35Projected IEEE 802.11n
- Currently in evaluation stage
- Top speed of 802.11n standard will be anywhere
from 100 Mbps to 500 Mbps - Ratification may not occur until 2006
- Devices based on standard may appear prior to
that - 802.11 pre-N