Gain
The apparatus of a wireless LAN action capricious degrees of gain, which represents how abundant a
signal changes from one point to another. The accretion in dB is artlessly the arresting akin at the achievement of
a accessory (in dBm) bare the arresting akin at the ascribe of the accessory (in dBm). The decibel is a unit
that represents change in arresting amplitude. A arresting adventures a accretion of 3 dB, for example, when
it increases from 50 mW (17 dBm) to 100 mW (20 dBm). An amplifier or antenna may action this
gain to the signal.
Attenuation, or loss, is the changed abstraction to gain. If the arresting goes from 20 dBm to 17 dBm, then
the arresting adventures abrasion of 3 dB. This can additionally be bidding as –3 dB gain. Antenna
cabling and obstacles in a facility, such as walls and furniture, acquaint attenuation. In addition,
freespace loss, which is abased on abundance and aisle distance, is a anatomy of attenuation. The
freespace accident occurs due to abrasion of the air average and contributes to the majority of the
total accident from the transmitter to the receiver.
With wireless LANs, the RF arresting amplitude charge be of a specific minimum bulk afore the
radio agenda will ascertain the signal. This bulk depends on the 802.11 concrete band and abstracts bulk in
use, but is about –85 dBm.
Antennas accept gain, which impacts directivity. An omnidirectional antenna, for instance, has a
gain of 6 dB, or more, depending on the antenna design. Higher-gain antennas become more
directive, with college assets accouterment narrower beamwidths and best range, as apparent in allotment B
of Figure G-4. Antenna accretion comes from absorption a accustomed bulk of RF ability into a narrower
pattern, or beamwidth—again, abundant as a flashlight does.