Wilan LIBRA 5800 AP, User Manual

Page: 136 / 156

Glossary
136 Libra 5800 Series User Guide
dBi
dBi is antenna gain referenced to an isotropic radiator. This a theoretical antenna that radiates
equally in all directions, like the sun.
Wi-LAN references antenna gain in dBi. The conversion factor is 0 dBd = 2.14 dBi
dBm
A power measurement with respect to one milliwatt. This is an absolute measure of power rather
than a relative measure such as a gain or a loss.
Default Gateway IP Address
This is the address of the gateway from the wireless network to the wired one. All packets bound for
a destination on the wireless network must go here first. All packets meant for the next network must
leave from here.
diffraction
Diffraction occurs when a radio signal bounces off 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 .
dipole
An antenna fed from the center. Antenna gains are often measured in relation to a standard dipole.
downtilt
Some antennas have a 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. A downtilt or uptilt may be required when there is a significant
deviation between the elevation of the remote sites and the base site.
dynamic time allocation (DTA)
A process for determining how active a CPE is. A poll allows a unit a brief time to respond before
considering that remote an idle one.
E
EEPROM
Electrically Erasable, Programmable Read Only Memory: Non-volatile memory, it must be removed
from board to be erased.
EIRP
Effective Isotropically Radiated Power. EIRP is the amount of power transmitted to the air by the
antenna. EIRP levels depend on the power of the radio transmitter, the type of antenna, and the
losses incurred in the antenna cable.
ERP
Effective Radiated Power. The power radiating from an antenna taking into account the output power
from the transmitter plus the antenna gain, less connector and cable losses.