Wilan LIBRA 5800 AP, User Manual

Page: 137 / 156

June 2003 Rev 0 137
ESD
Electrostatic Discharge. Caused by static electricity. ESD Protection should be used to protect
electronic components from damage.
F
fade margin
The amount by which the system gain plus the total antenna gain exceed the path loss is called the
fade margin. The fade margin is the number of dB that the received signal strength exceeds the
minimum receiver sensitivity.
FEC
Forward Error Correction. A method of correcting data errors without retransmission.
filtering
Filtering in remote stations limits certain data packets.
Flash
A type of electrically erasable non-volatile memory that can easily be erased without removal from a
unit. Using Flash, the Access Point can be upgraded in the field.
Fresnel zone
The line of sight between two antennas. It consists of one of a theoretically infinite number of a
concentric ellipsoids of revolution that define volumes in the radiation pattern of a usually circular
aperture.
• The cross section of the first Fresnel zone is circular. Subsequent Fresnel zones are annular in
cross-section, and concentric with the first.
• Odd-numbered Fresnel zones have relatively intense field strengths and even-numbered Fresnel
zones are nulls.
• Fresnel zones result from diffraction by the circular aperture.
front to back ratio (F/B)
Directional antennas focus the signal in a forward path, reducing the signal in the opposite direction.
The proportion between the two is called the front-to-back ratio. A higher gain antenna typically has a
greater F/B ratio.
frost loading
A concern of antenna operation affected by low temperatures.
ftp
File Transfer Protocol. A method of copying files from one site to another. An operator of Wi-LAN
equipment might use ftp to download software upgrades.