Wilan LIBRA 5800 AP, User Manual

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Glossary
142 Libra 5800 Series User Guide
Q
QAM
Quadrature Amplitude Modulation. A kind of modulation that varies signal amplitude.
R
Reed-Solomon
A way of accomplishing Forward Error Correction. Reed-Solomon describes a data block in such a
way that errors in the data block can be detected and repaired without retransmission.
remote unit
A unit that can communicate with a base station or other remote units. A remote unit forms a wireless
link between a network segment and a base station. CPEs are the remote units in the BWS system.
RF
Radio Frequency. RF communication uses electromagnetic waves propagated through space.
Because of varying characteristics, radio waves of different lengths are used for different purposes
and are usually identified by their frequency.
RF Center Frequencies
Wi-LAN Broadband Wireless Access Systems sometimes use two center frequencies. The AP
transmits on one and the CPEs transmit on another.
RF Station ID
This is a configurable number, from one to 2,048, that identifies an AP or CPE to the network.
RS-232
RS-232 in this document is generally refers to the DB-9 connector that attaches a PC to an IDU. RS-
232 also refers to standards for serial communications, which define the voltages, currents, data
rates, and other factors about the signals to be used, as well as single-ended, differential, multi-drop
operation.
RSSI
Received Signal Strength Indicator. Strength of received signal expressed in dB. The Access Point
measures RSSI as a fade margin value.
S
sensitivity
The minimum signal strength required for usable performance, expressed in dBm.
shadowing
Shadowing is a form of diffraction typically caused by antennas being mounted too close to a
structure, where they lose a portion of the signal lobe due to reflection. The receiving antenna is in a
shadowed area. To minimize shadowing, mount the antenna higher.