GE MDS SD Series Technical Manual page 56

48
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NOTE: The Listen Before Transmit (LBT) feature requires radios to
be configured for Packet Mode operation. Packet with MAC
operation provides an alternative media access method.
• —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
lisions with the Master unit. In peer-to-peer configurations,
may be preferred. Optimal choices depend on the data trans-
on TX
mission characteristics of the connected system.
•
Min/Max Channel Wait
(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 100 ms unless performing advanced
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.
Note that the lower the value of the Maximum Wait Time, the
higher the chances of collisions occurring over-the-air. Con-
versely, the higher the value of the Maximum Wait Time, the
higher the transmission latency.
• —Provides a setting for the maximum time to wait (in
Timeout (ms)
milliseconds) for the channel to become free. When this time is
exceeded, the radio follows the action defined in the
setting (either
on Timeout
•
Packet Action on Timeout
once the timeout period has expired and the channel is still not
available. If set to
transmission of the packet is attempted despite the channel being
busy.
•
Clear Channel RSSI (dBm)
a carrier signal on the radio's operating frequency. If a carrier is
present, transmission is inhibited. The
allows a threshold to be set which, when equaled or exceeded,
declares the channel busy and therefore unavailable for transmit-
ting.
SD Series Technical Manual
(the default selection) to avoid col-
Listen on RX
(ms)—These settings refer to the time period
or ).
Drop Send
—Determines what to do with a packet
, the packet is discarded. If set to
Drop
—LBT works by sensing the presence of
Clear Channel RSSI
MDS 05-4846A01, Rev. D
Listen
ms unless per-
0
Packet Action
,
Send
setting