nascent IEEE proposal for a 100M bit/sec wireless standard.
By "100M bit/sec," the IEEE means throughput, what
users see when they transfer a file, for example, as distinct
from the data rate, which is the raw speed before you subtract
the overhead associated with the protocol.
is an important distinction because wireless overhead can add
up to a significant percentage of the data - in the case of
802.11, typically more than half of the data rate. An 802.11b
access point, rated at 11M bit/sec, typically gives a throughput
of less than 6M bit/sec, often far less. The 802.11a and 802.11g
hardware can give users about 18M to 22M bit/sec. The data rate
for both is 54M bit/sec.
makers have been boosting WLAN throughput to around 100M bit/sec
for some time. The catch is: You have to have the same chips
in both the client and the access point, and high throughput
sacrifices conformity to the 802.11 specification. Network executives
already seem to be discounting high-throughput claims that are
based on their WLAN experience. "Unless you are sitting
right under the access point, you just don't get the maximum
throughput," says Dewitt Latimer, deputy CIO and CTO at
University of Notre Dame in South Bend, Ind.
throughput falls off more or less rapidly the farther a client
device moves from an access point. TheÂ drop depends on
how much metal, wood, concrete and other construction materials
is between the two devices. In addition, in almost every case
today, an access point is a shared medium: whatever throughput
it can deliver is divvied up among however many users connect
to that one access point.
practical applications, such as three students sitting under
a tree working on a paper [with wireless notebooks], tend to
be insensitive to bandwidth. I don't think high throughput WLANs
will be a big driver until we see things like streaming media
applications being untethered."
Wireless LAN throughput on the rise, Network World Fusion, 09/29/03.