Network Bulls
www.networkbulls.com
Best Institute for CCNA CCNP CCSP CCIP CCIE Training in India
M-44, Old Dlf, Sector-14 Gurgaon, Haryana, India
Call: +91-9654672192
Various agencies have been around for a very long time to help govern the use of wireless devices,
frequencies, standards, and how the frequency spectrums are used. Table 5.1 shows the current
agencies that help create, maintain, and even enforce wireless standards worldwide.
Because WLANs transmit over radio frequencies, they’re regulated by the same types of
laws used to govern things like AM/FM radios. It’s the Federal Communications Commission
(FCC) that regulates the use of wireless LAN devices, and the Institute of Electrical and Electronics
Engineers (IEEE) takes it from there and creates standards based on what frequencies
the FCC releases for public use.
287
The FCC has released three unlicensed bands for public use: 900MHz, 2.4GHz, and 5.7GHz.
The 900MHz and 2.4GHz bands are referred to as the
Industrial, Scientific, and Medical
(ISM)
bands, and the 5GHz band is known as the
Unlicensed National Information Infrastructure
(UNII) band. Figure 5.1 shows where the unlicensed bands sit within the RF spectrum.
FIGURE 5 . 1
Unlicensed frequencies
So, it follows that if you opt to deploy wireless in a range outside of the three public bands
shown in Figure 5.1, you need to get a specific license from the FCC to do so. Once the FCC
opened the three frequency ranges for public use, many manufacturers were able to start offering
myriad products that flooded the market, with 802.11b/g being the most widely used wireless
network today.
TABLE 5 . 1
Wireless Agencies and Standards
Agency Purpose Web Site
Institute of Electrical and
Electronics Engineers (IEEE)
Creates and maintains operational standards
www.ieee.org
Federal Communications
Commission (FCC)
Regulates the use of wireless devices in
the U.S.
www.fcc.gov
European Telecommunications
Standards
Institute (ETSI)
Chartered to produce common standards
in Europe
www.etsi.org
Wi-Fi Alliance Promotes and tests for WLAN
interoperability
www.wi-fi.com
WLAN Association
(WLANA)
Educates and raises consumer awareness
regarding WLANs
www.wlana.org
AM Broadcast
Cellular
(840MHz)
Visible
light
Sonar
(extremely low)
FM Broadcast Infrared
Wireless
LAN
X-rays
900MHz
band
2.4GHz
band
5GHz
band
5.1 Describe standards associated with wireless media
288
Chapter 5
Explain and select the appropriate administrative tasks
The Wi-Fi Alliance grants certification for interoperability among 802.11 products offered
by various vendors. This certification provides a sort of comfort zone for the users purchasing
the many types of products, although in my personal experience, it’s just a whole lot easier if
you buy all your access points from the same manufacturer!
In the current U.S. wireless LAN market, there are several accepted operational standards
and drafts created and maintained by the IEEE. Let’s take a look at these standards and then
talk about how the most commonly used standards work.
The 802.11 Standards
Taking off from what you learned when reading about Ethernet, wireless networking has its own
802 standards group—remember, Ethernet’s committee is 802.3. Wireless starts with 802.11, and
there are various other up-and-coming standard groups as well, like 802.16 and 802.20. And
there’s no doubt that cellular networks will become huge players in our wireless future. But for
now, we’re going to concentrate on the 802.11 standards committee and subcommittees.
IEEE 802.11 was the first, original standardized WLAN at 1 and 2Mbps. It runs in the
2.4GHz radio frequency and was ratified in 1997 even though we didn’t see many products
pop up until around 1999 when 802.11b was introduced. All the committees listed in Table
5.2 are amendments to the original 802.11 standard except for 802.11F and 802.11T, which
are both stand-alone documents.
TABLE 5 . 2
802.11 Committees and Subcommittees
Committee Purpose
IEEE 802.11a 54Mbps, 5GHz standard
IEEE 802.11b Enhancements to 802.11 to support 5.5 and 11Mbps
IEEE 802.11c Bridge operation procedures; included in the IEEE 802.1D standard
IEEE 802.11d International roaming extensions
IEEE 802.11e Quality of service
IEEE 802.11F Inter-Access Point Protocol
IEEE 802.11g 54Mbps, 2.4GHz standard (backward compatible with 802.11b)
IEEE 802.11h Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC)
at 5Ghz
IEEE 802.11i Enhanced security
289
Exam Objectives
Understand the IEEE 802.11a specification.
802.11a runs in the 5GHz spectrum, and if you
use the 802.11h extensions, you have 23 non-overlapping channels. 802.11a can run up to
54Mbps, but only if you are less than 50 feet from an access point.
Understand the IEEE 802.11b specification.
IEEE 802.11b runs in the 2.4GHz range and
has three non-overlapping channels. It can handle long distances, but with a maximum data
rate of up to 11Mpbs.
Understand the IEEE 802.11g specification.
IEEE 802.11g is 802.11b’s big brother and
runs in the same 2.4GHz range, but it has a higher data rate of 54Mbps if you are less than
100 feet from an access point.
No comments:
Post a Comment