XBP09-DPUIT-156 Digi International, XBP09-DPUIT-156 Datasheet - Page 25

• Manufacturer Part Number: XBP09-DPUIT-156
• Description: MODULE XBEE PRO W/U.FL
• Manufacturer: Digi International
• Series: XBEE-PRO™r

Specifications of XBP09-DPUIT-156

• Frequency: 902MHz ~ 928MHz
• Data Rate - Maximum: 156kbps
• Modulation Or Protocol: FHSS
• Applications: ISM
• Power - Output: 17dBm (50mW)
• Sensitivity: -100dBm
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Receiving: 80mA
• Current - Transmitting: 210mA
• Data Interface: PCB, Through Hole
• Antenna Connector: U.FL
• Operating Temperature: -40°C ~ 85°C
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 602-1168

XBee‐PRO® 900 RF Modules
Data Transmission and Routing
Unicast Addressing
Broadcast Addressing
Routing
Route Discovery
When transmitting while using Unicast communications, reliable delivery of data is accomplished
using retries and acknowledgements. The number of retries is determined by the MR (Network
Retries) parameter. RF data packets are sent up to MR + 1 times and ACKs (acknowledgements)
are transmitted by the receiving node upon receipt. If a network ACK is not received within the
time it would take for a packet to traverse the network twice, a retransmission occurs.
To send Unicast messages, set the DH and DL on the transmitting module to match the
corresponding SH and SL parameter values on the receiving module.
Broadcast transmissions will be received and repeated by all nodes in the network. Because ACKs
are not used the originating node will send the broadcast multiple times as configured by the MT
parameter. Essentially the extra transmissions become automatic retries without
acknowledgments. A node which receives multiple copies of the same packet will discard the
duplicates. This will result in all nodes repeating the transmission MT+1 times as well. In order to
avoid RF packet collisions, a random delay is inserted before each node relays the broadcast
message. (See the NN parameter for details on changing this random delay time.) Sending
frequent broadcast transmissions can quickly reduce the available network bandwidth and as such
should be used sparingly.
The broadcast address is a 64 bit address with the lowest 16 bits set to 1. The upper bits are set to
0. To send a broadcast transmission set DH to 0 and DL to 0xFFFF. In API mode the destination
address would be set to 0x000000000000FFFF.
A module within a mesh network is able to determine reliable routes using a routing algorithm and
table. The routing algorithm uses a reactive method derived from AODV (Ad-hoc On-demand
Distance Vector). An associative routing table is used to map a destination node address with its
next hop. By sending a message to the next hop address, either the message will reach its
destination or be forwarded to an intermediate node which will route the message on to its
destination. A message with a broadcast address will be received by all neighbors. All receiving
neighbors will rebroadcast the message MT+1 times and eventually the message will reach all
corners of the network. Packet tracking prevents a node from resending a broadcast message
more than MT+1 times.
If the source node doesn’t have a route to the requested destination, the packet is queued to
await a route discovery (RD) process. This process is also used when a route fails. A route fails
when the source node uses up its network retries without ever receiving an ACK. This results in
the source node initiating RD.
RD begins by the source node broadcasting a route request (RREQ). Any node that receives the
RREQ that is not the ultimate destination is called an intermediate node.
Intermediate nodes may either drop or forward a RREQ, depending on whether the new RREQ has
a better route back to the source node. If so, information from the RREQ is saved and the RREQ is
updated and broadcast. When the ultimate destination receives the RREQ, it unicasts a route reply
(RREP) back to the source node along the path of the RREQ. This is done regardless of route
quality and regardless of how many times an RREQ has been seen before.
This allows the source node to receive multiple route replies. The source node selects the route
with the best round trip route quality, which it will use for the queued packet and for subsequent
packets with the same destination address.
© 2009 Digi International, Inc.
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