Version 1.0 Rev B - 08/00
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dBd
dBd is antenna gain referenced over a half-wave dipole which is an antenna that has a
donut shaped radiation pattern.
Gain of a Standard Dipole = 2.14 dBi.
dBi
dBi is antenna gain referenced over an isotropic radiator which is a theoretical antenna
that radiates equally in all directions (e.g. the sun).
Wi-LAN references antenna gain in dBi. The conversion factor is:
0 dBd = 2.14 dBi
dBm
A power measurement referenced to one milliwatt. This is an absolute measure of power
rather than a relative measure such as a gain or a loss.
diffraction
Diffraction occurs when a radio signal reflects or bounces off of a solid object. The level
of diffraction could lead to connectivity problems if the remaining signal level is too low.
Two types of diffraction are
shadowing
and
multipath
.
downtilt
Some antennas have either an associated downtilt or an uptilt. The tilt further focuses the
signal either downward or upward with respect to the horizon. A tilt may be either
electrically built into the antenna or achieved mechanically with the mounting gear. An
downtilt or uptilt may be required when there is a significant deviation between the
elevation of the remote site(s) and the base site.
dynamic polling
A polling protocol in which idle units are not polled as frequently as active units. Since
less time is spent polling idle remotes, there are more available resources for active units
and overhead is reduced.
E
EEPROM
Electrically Erasable, Programable Read Only Memory: Non-volatile memory, but must
be removed from board to be erased.
EIRP
Effective Isotropically Radiated Power. EIRP is the amount of power that is transmitted to
the air from the antenna. EIRP levels depend on the power of the radio transmitter, the size
of the antenna, and the losses incurred in the antenna cable. To remain license exempt the
EIRP must remain under 4 watts or 36 dBm in Canada and the United States for
point-to-multipoint applications. In Europe, this value is reduced to 100 mW or to
20 dBm.
Note:
EIRP = Power out of unit — Power lost in cable + Gain in power from Antenna
