XBee‐PRO®900HP/XBee‐PRO®XSCRFModules
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• Transmitting a unicast with an unknown route
• Transmitting a unicast with a broken route.
Note: The timeouts in this section are theoretical timeouts and not precisely accurate. The application should pad the
calculated maximum timeouts by a few hundred milliseconds. When using API mode, Tx Status API packets should be the
primary method of determining if a transmission has completed.
Unicast One Hop Time
A building block of many of the calculations presented below is the unicastOneHopTime. As its name indi-
cates, it represents the amount of time it takes to send a unicast transmission between two adjacent
nodes. It is dependent upon the %H setting. It is defined as follows:
unicastOneHopTime=%H
Transmitting a broadcast
A broadcast transmission must be relayed by all routers in the network. The maximum delay would be
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*%8
Transmitting a unicast with a known route
When a route to a destination node is known the transmission time is largely a function of the number of
hops and retries. The timeout associated with a unicast assumes the maximum number of hops is neces-
sary (as specified by NH). The timeout can be estimated in the following manner:
knownRouteUnicast=2*NH*MR*unicastOneHopTime
Transmitting a unicast with an unknown route
If the route to the destination is not known the transmitting module will begin by sending a route discovery.
If the route discovery is successful and a route is found then the data is transmitted. The timeout associ-
ated with the entire operation can be estimated as follows:
unknownRouteUnicast=BroadcastTxTime+NH*unicastOneHopTime +knownRouteUnicast
Transmitting a unicast with a broken route
If the route to a destination node has changed since the last time a route discovery was completed a node
will begin by attempting to send the data along the previous route. After it fails a route discovery will be ini-
tiated and, upon completion of the route discovery, the data will be transmitted along the new route. The
timeout associated with the entire operation can be estimated as follows:
brokenRouteUnicast=BroadcastTxTime+NH*unicastOneHopTime +2*knownRouteUnicast
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