Reference Manual

3. Configuring Point-to-MultiPoint Networks
FGR3
User-Reference Manual
LUM0110AA Rev Jan-2019 Page 79 of 143 Copyright © 2019FreeWave
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3.7.5. Master Packet Repeat
Note: When using the radio in Modbus RTU mode, the Master Packet Repeat setting must match
in every radio, regardless of whether the network is in Point-to-Point or MultiPoint mode.
Master Packet Repeat
Setting Description
Default Setting 3
Options Any number between 0 and 9.
Terminal Menu (5) Edit MultiPoint Parameters > (1) Master Packet Repeat
Description: In a Point-to-MultiPoint network, Slave radios do not acknowledge transmissions
from the Master.
l If Slave radios did acknowledge all data transmissions, in a large network, the
Master would soon become overwhelmed with acknowledgments from the
Slaves.
l Without acknowledgments, 100% confidence every Slave radio has received
every packet cannot be met.
l To address this issue, change the Master Packet Repeat parameter,
assigning a value between 0 (the packet is transmitted once) to 9 (the packet
is transmitted 10 times).
For networks with solid RF links, this parameter should be set to a low value
(e.g.,1 or 2).
l If a network has some weak or marginal links it should be set with higher
values.
l If a Slave radio receives a good packet from a Master more than once it
discards the repeated packets.
l Similarly, after a MultiPoint Repeater receives a good packet from the Master,
it discards any further repeated packets.
l In turn, the Repeater sends the packet out to the next Repeater or Slaves the
number of times corresponding to its own Master Packet Repeat setting.
Increasing the Master Packet Repeat setting increases the probability of a
packet getting through, but also increases latency in the network because each
packet from the Master or Repeater is being sent multiple times.
Note: Therefore, it is important to find the optimal mix between network
robustness, throughput, and latency.
In general, a setting of 2 to 3 works well for most well designed networks.
The Master Packet Repeat parameter may be set to 0 if the user software is
capable of, or requires acknowledgment.
In this case, if the Master sends a packet that the Slave radio does not receive,
the user software controls the retries as needed.