Spread Spectrum Wireless Data Transceiver User Manual
frequency and time diversity as possible through use of different frequency keys, min and max
packet sizes, and hop tables.
Edit MultiPoint Parameters
Selecting (5) Edit MultiPoint Parameters from the main menu displays the following window.
(0)
N
UMBER
R
EPEATERS
In a MultiPoint network it is critical to transmission timing to configure this parameter correctly. The value
should be 0 if there are no Repeaters in the network and 1 if Repeaters are present. This parameter
must be set to the same value in all transceivers in a MultiPoint network.
(1)
M
ASTER
P
ACKET
R
EPEAT
In Point-to-Point operation FreeWave transceivers acknowledge every data packet transmitted. In a
Point-to-MultiPoint network, the Slaves do not acknowledge transmissions from the Master. If the Slaves
acknowledged all data transmissions from the Master in a large MultiPoint system, then the system
capacity would be spent on the Master listening for acknowledgments from the Slaves. Without
acknowledgements from the Slaves, 100% confidence does not exist that every Slave has received every
packet from the Master. To address this issue, the user may modify Master Packet Repeat setting,
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 with a low value such as 0 or 1. If a network
has some weak or marginal links it should be set with higher values. If a Slave receives a good packet
from a Master more than once it will discard the repeated packets. Similarly, once a MultiPoint Repeater
receives a good packet from the Master, it will discard any of the repeated packets. In turn, the Repeater
will send the packet out to the next Repeater or Slaves the number of times corresponding to
its
Master
Packet Repeat setting. For more information on this, see the next section, Master Packet Repeat in
MultiPoint Systems with Repeaters.
It is important to keep in mind that increasing the Master packet repeat will increase the probability of a
packet getting through, but will also increase latency in the system because each packet from the Master
or Repeater is being sent multiple times. Therefore, it is important to find the optimal mix between system
robustness, throughput, and latency. In general a setting of 2 to 3 will work well for most systems.
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