GE MDS SD Series Technical Manual page 65

Listen Before
Transmit (LBT)
Settings
MDS 05-4846A01, Rev. H
The transceiver provides a legacy collision avoidance scheme called
Listen Before Transmit (LBT). It employs P-Persistent CSMA protocol,
which senses channel usage and inhibits transmission if the channel is
currently in use. CSMA is an abbreviation for Carrier Sense Multiple
Access. This setting is superseded by Packet w/MAC and should only
be used in legacy systems and special use cases. Packet w/MAC is the
preferred method for collision avoidance.
NOTE: The Listen Before Transmit (LBT) feature requires radios to
be configured for Packet Mode operation. Packet w/MAC
operation provides an alternative method for media access.
•
Listen Before Transmit
radio is running in Packet Radio Mode.
• —LBT can be configured to behave in one of two
LBT Behavior
ways; either listen on the radio's transmit frequency (TX) or listen
on the radio's receive frequency (RX). Typically, Remote radios
are configured to
sions with the Master unit. In split frequency operation,
may be preferred. Optimal choices depend on the data trans-
TX
mission characteristics of the connected system.
•
Min/Max Channel Wait (ms)
(in milliseconds) to wait after the channel is free before transmis-
sion is allowed.
Minimum wait time: Normally, the minimum channel wait time
should not be changed from its default setting of
forming advanced operations, such as staggering the responses
from multiple Remotes.
Maximum wait time: Normally, this setting should not be
changed from its default of
operations. Some examples of when this may be beneficial
include:
• There is a need to stagger responses from several Remote
radios.
• The transmission latency from the time the channel is free is
too high, in which case a lower value can be entered.
• Collisions over the air are too high, in which case a higher
value can be entered.
SD Series Technical Manual
—Used to activate or deactivate LBT when the
(the default selection) to avoid colli-
Listen on RX
—These settings refer to the time period
unless performing advanced
100 ms
Listen on
unless per-
0 ms
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