Download Wireless

Wireless Networks
Why go wireless?
•
•
•
•
C
Don’t have to be tied to a
N
, furniture or infrastructure
Can retrieve email, access the Internet , a corporate
database or other info using a cell phone, laptop computer
or handheld computer.
• Lots of wireless zones (
) have been created
– libraries, airports, universities, stores and some entire
cities/towns.
• PCs and laptop computers could access the Internet
without relying on physical wiring.
– Wireless
– Wireless
– Uses low-frequency
/ Access Point Required
Required
to communicate.
Wireless Standards
• 8
(Wi-Fi, for Wireless Fidelity)
• B
802.11
• Allows for faster transmissions and can support
connections over longer distances than Bluetooth.
– 802.11b standard: Up to 11 megabits per second, 300 feet inside
– 802.11g standard:
at a 35 foot indoor range
– 802.11n standard:
with a better range
Bluetooth
• Allows for wireless communications within a limited
distance:
per second, up to
• Less expensive than Wi-Fi chips, consume less
power, easier to build into small devices than run on
batteries such as cell phones, palm-top computers,
and other PDAs.
• Called a “personal area network” (PAN) technology.
Wireless Networks
• Bluetooth: Personal Area Network (PAN)
• 802.11 (Wi-Fi): used in
• Disadvantages of 802.11 wireless LANs
–S
wired LANs
– One person can
point to the detriment of all other wireless users.
– Inherently
. Software tools are easily
available to capture data packets, and thereby
“snoop” on someone’s communications.
– While there are many wireless LANs, your computer
must be specially configured in order to connect to
a specific wireless LAN.
802.11 standards
• 802
: can provide transmission speeds of up to 11
mbps, 300 feet inside, 800 feet outside.
• 802
: can provide transmission speeds of up to
mbps, at a 35 foot indoor range.
• Both the “b” and “g” standards use the same radio
frequency, or wavelength.
– 802
: same transmission speeds as the “g” standard, but it
uses a
(not used by other Wi-Fi users,
microwave ovens and cordless phones)
• Might be good for use in high density/population areas, such as apartment
complexes.
• 802.11n is currently being developed (in use, but not finalized) .
– Expected to provide transmission speeds over
mbps using MIMO
technology (
): signal intensity will also help increase range.
Walt Mossberg Chief Technology columnist for the
WallStreet Journal
Q: I’m wondering about wireless specs for a
laptop. I suspect the “n” version of Wi-Fi is best
but “g” is adequate. Any advice would be
appreciated.
A. It depends on how and where you intend to use
your laptop’s wireless connectivity. The “n”
version of Wi-Fi can be much faster than “g” and
can have much greater range. However, the speed
difference won’t matter much if your sole use is
connecting to the Internet with a typical home or
public hotspot service, since the maximum speed
of these services is almost always well below “g”
and “n” capabilities. But if you are streaming
video at home or backing up large files wirelessly
among computers and networked hard disks on a
home network, you’d be much better off with “n,”
assuming all devices involved support it. The
same goes for range. In a small apartment, it likely
won’t matter. In a large home, it could.
802.11 wireless standards explained
http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htm
http://info.cba.ksu.edu/bkovar/wireless.htm
Researchers explore scrapping and
rebuilding the Internet
• In order to address the problems that were not
envisioned when the Internet was initially
created, some are suggesting rebuilding the
Internet using a
approach.
• S
– The Internet was designed to be open and flexible
and all users were assumed to be trustworthy.
Internet protocols were not designed to authenticate
users and their data. Firewalls and spam filters are
now being used to control security.
– Solution: data not passed along until
• Mobility
– Initially, computers were fixed in location so IP addresses were assigned
to devices in a fixed location. Wireless mobile computing is presenting
challenges related to data flow.
– Solution: R
so that addresses are based on the
device, rather than the location.
• Ubiquity (called
in our class notes)
– When the Internet was first designed, there were relatively few
computers connected to it. The addressing system has become strained
due to the proliferation of personal computers and mobile devices.
– Solution: assign
and have those same
devices connected to an addressed gateway, which is then connected to
routers and the rest of the Internet
• Result is fewer devices to keep track of and improved efficiency.
• These changes may happen over the next 10-15 years. They
(expected to cost
as computer hardware and software and
Internet infrastructure are replaced)
The End