The 802.11 Standard and Its Variations
Generally, the core 802.11 standard is intended to specify a
way for computers to network using the 2.4GHz and 5GHz free spectrums I just
explained. (When computers network, it is said that they are forming a local area network, or LAN. When computers network
wirelessly, it is called a Wireless LAN, or WLAN.)
The 802.11b Standard
When you say "Wi-Fi" today, you probably mean 802.11b, which is
a subset of the general 802.11 standard. Most Wi-Fi devices that are currently
in operation are using 802.11b. However, technology moves quickly, and 802.11g
is gaining momentum fast.
The full 802.11b specification document is more than 500 pages
long, but here are the key things to know about 802.11b:
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The 802.11b standard uses the 2.4GHz spectrum.
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The 802.11b standard uses a technology called Direct Sequence
Spread Spectrum (DSSS) to minimize interference with other devices transmitting
on the 2.4GHz spectrum.
-
The 802.11b standard has a theoretical throughput speed of 11
megabytes per second (Mbps).
The 11Mbps speed compares favorably with the 10Mbps throughput
of a conventional 10BASE-T wired Ethernet network, which may be what you are
used to using at work. It is certainly faster than even the fastest broadband
Internet connections.
 |
Another factor that slows down 802.11b Wi-Fi is that
transmissions are in duplex mode, which means
that communication consists of a query and a response (rather than simultaneous
communication). This slows down speeds noticeably. |
However, for a variety of reasons Wi-Fi connections rarely
achieve anything like its theoretical maximum (encryption slows 802.11b down,
for one thing). Weak connectivity also slows Wi-Fi down. Even so, Wi-Fi
connections should be fine for everyday uses such as file sharing or sharing an
Internet connection. There may be some extremely demanding applications that
Wi-Fi speeds are not good enough for, but I am hard put to think of any.
The most important thing you should take away regarding the
speed of 802.11b Wi-Fi is that for most users 11Mbps is good enough. The 802.11b
Wi-Fi connection is rarely slower than other parts of the system it is in, such
as the network it is connected to, or access to the Internet.
I'll be telling you a little more about transmission speeds of
802.11b related to other wireless standards later in this chapter.
The 802.11a and 802.11g Standards
The 802.11a and 802.11g standards are different variants of
802.11 that can be thought of as 802.11b's smarter, younger brothers. The
802.11a standard uses the 5GHz band for transmission, which minimizes the
possibility of interference with the plethora of 2.4GHz devices out there (think
microwaves, garage door openers, and so on) and promises a theoretic throughput
of 24Mbps.
Still newer than 802.11a, 802.11g operates on the 2.4GHz
spectrum and boasts throughput as fast as 54Mbps.
In other words, both 802.11a and 802.11g show the promise of
being considerably faster than 802.11b.
The 802.11a standard poses some compatibility issues with
802.11b. But at least one vendor, Atheros Communications, makes 802.11a
equipment that is backward- compatible with 802.11b. (Atheros also makes a
"tri-mode" chipset that uses 802.11a, 802.11b, and 802.11g.) The chief advantage
of 802.11a is that it will run into less interruption from other devices because
it does not use the crowded 2.4GHz band.
Moving to 802.11a has some pluses and minuses, but moving to
802.11g is a no-brainer—because 802.11g systems are backward-compatible with
802.11b, and faster. This backward compatibility of 802.11g devices is a
requirement for Wi-Fi certification.
Neither 802.11a nor 802.11g are starting to become mainstream,
with prices a bit higher than for 802.11b. In fact, the 802.11g standard is
replacing 802.11b as the standard for new equipment (it is preferred to 802.11a
because of its backward compatibility). Pretty soon, 802.11g will be the de
facto Wi-Fi standard that is at the "sweet" price point, and other, faster Wi-Fi
standards—such as the proposed 802.11n—will be the new contender knocking at the
door.
You'll find more information about evaluating whether 802.11a
or 802.11g Wi-Fi hardware is right for you in Chapter 8, "Adding Wi-Fi to a Mobile Computer," and Chapter 13, "Buying a Wi-Fi Access Point
or Router."
The 802.11i Standard
The IEEE is in the process of developing a new security
standard for 802.11 that is named 802.11i. The Wi-Fi Alliance has released a
subset of the 802.11i standard that the Alliance has developed called "Wi-Fi
Protected Access."
Products that successfully complete the Wi-Fi Alliance testing
required for meeting its version of the 802.11i standard will be called "Wi-Fi
Protected Access" certified.
Wi-Fi Protected Access provides a stronger level of encryption
and authentication than is built into the current Wi-Fi standards. This means
that Wi-Fi networks will be better protected from unauthorized access and other
security problems. Wi-Fi Protected Access is intended to replace WEP encryption
built into current Wi-Fi.
The new standard is also intended to be "software
implementable." This means that current Wi-Fi products should be upgradeable to
Wi-Fi Protected Access by running a software patch—new hardware will not be
required.
The Wi-Fi Protected Access standard is currently available, and
a number of manufacturers have announced that their products will support it.
However, most products on the market do not support this standard yet. For more
about Wi-Fi and security, please see Part V, "Securing Your Wi-Fi Computer and
Network."
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