Networking methods Data transmission and routing
XBee® SX 868 RF Module User Guide
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Note The timeouts in this documentation are theoretical timeouts and are not precisely accurate.
Your application should pad the calculated maximum timeouts by a few hundred milliseconds. When
you use API operating mode, use Extended Transmit Status - 0x8B as the primary method to
determine if a transmission is complete.
Unicast one hop time
unicastOneHopTime is a building block of many of the following calculations. It represents the
amount of time it takes to send a unicast transmission between two adjacent nodes. The amount of
time depends on the parameter.
Transmit a broadcast
All of the routers in a network must relay a broadcast transmission.
The maximum delay occurs when the sender and receiver are on the opposite ends of the network.
The NH and %H parameters define the maximum broadcast delay as follows:
BroadcastTxTime = NH * NN * %8
Unless BH < NH, in which case the formula is:
BroadcastTxTime = BH * NN * %8
Transmit a unicast with a known route
When a device knows a route to a destination node, the transmission time is largely a function of the
number of hops and retries. The timeout associated with a unicast assumes that the maximum
number of hops is necessary, as specified by the NH command.
You can estimate the timeout in the following manner:
knownRouteUnicastTime=2*NH*MR*unicastOneHopTime
Transmit a unicast with an unknown route
If the transmitting device does not know the route to the destination, it begins by sending a route
discovery. If the route discovery is successful, then the transmitting device transmits data. You can
estimate the timeout associated with the entire operation as follows:
unknownRouteUnicastTime=BroadcastTxTime+
(NH*unicastOneHopTime)+knownRouteUnicastTime
Transmit a unicast with a broken route
If the route to a destination node changes after route discovery completes, a node begins by
attempting to send the data along the previous route. After it fails, it initiates route discovery and,
when the route discovery finishes, transmits the data along the new route. You can estimate the
timeout associated with the entire operation as follows:
brokenRouteUnicastTime=BroadcastTxTime+(NH*unicastOneHopTime)+
(2*knownRouteUnicastTime)
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