FreeWave LRS-455-EU, Руководство пользователя

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LRS-455-EU Data Transceiver Users Manual
LUM0032AA Rev A Version 1.0 17
MultiPoint Parameters
When installing MultiPoint networks it is important to do some up front planning. Unlike Point-to-Point
networks, a Point-to-MultiPoint network requires several parameters are set consistently on all
transceivers in the network. This includes RF Data Rate and Min and Max Packet Size.
Note:
If several independent MultiPoint networks are to be located in close proximity the planning
becomes more critical. In such cases, it becomes very important to include as much frequency
and time diversity as possible through use of different Min and Max Packet Size. In some
instances the use of the MultiMaster Sync option may be required.
Edit MultiPoint Parameters
(0) R
EPEATERS
The Repeaters selection must be set to On if a repeater is to be used in the network. However, if the
network will not utilize a repeater, FreeWave recommends setting Repeaters to Off to provide higher
throughput.
(1) M
ASTER
P
ACKET
R
EPEAT
In a Point-to-MultiPoint network, Slaves do not acknowledge transmissions from the Master. If Slaves did
acknowledge all data transmissions, in a large network, the Master would soon become overwhelmed
with acknowledgments from the Slaves. Without acknowledgements, 100% confidence every Slave has
received every packet cannot be met. To address this issue, the user may modify the 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 to 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
Increasing the Master Packet Repeat setting will increase the probability of a packet getting through, but
will also increase latency in the network because each packet from the Master is being sent multiple
times. Therefore, it is important to find the optimal mix between network robustness, throughput, and
latency. In general, a setting of 0 to 1 will work well for most well designed licensed band networks.
Note:
The Master Packet Repeat may be set to 0 if the user software is capable of, or requires
acknowledgment. In this case if a packet sent by the Master and not received by the Slave, the
user software will control the retries as needed.