XBP24-DMWIT-250 Digi International, XBP24-DMWIT-250 Datasheet - Page 23

• Manufacturer Part Number: XBP24-DMWIT-250
• Description: XBEE-PRO MESH 2.4 EXTENDED
• Manufacturer: Digi International
• Series: XBEE-PRO™r

Specifications of XBP24-DMWIT-250

• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: ISM
• Applications: General Purpose
• Power - Output: 18dBm
• Sensitivity: -100dBm
• Voltage - Supply: 2.8 V ~ 3.4 V
• Current - Receiving: 55mA
• Current - Transmitting: 250mA
• Data Interface: PCB, Through Hole
• Antenna Connector: On-Board, Wire Whip
• 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: Q4542387

XBee/XBee‐PRO DigiMesh 2.4 RF Modules
Note: Data throughput measurements were made setting the serial interface rate to 115200 bps, and measuring the time
to send 100,000 bytes from source to destination. During the test, no route discoveries or failures occurred.
Broadcast Addressing
Routing
Route Discovery
Throughput
Broadcast transmissions will be received and repeated by all routers in the network. Because ACKs are not used the origi-
nating node will send the broadcast multiple times. By default a broadcast transmission is sent four times. Essentially the
extra transmissions become automatic retries without acknowledgments. This will result in all nodes repeating the trans-
mission four times as well. In order to avoid RF packet collisions, a random delay is inserted before each router relays the
broadcast message. (See NN parameter for details on changing this random delay time.) Sending frequent broadcast trans-
missions 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 algo-
rithm 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 mes-
sage will reach its destination or be forwarded to an intermediate router which will route the message on to its destination.
A message with a broadcast address is broadcast to all neighbors. All routers receiving the message 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 with-
out ever receiving an ACK. This results in the source node initiating RD.
RD begins by the source node broadcasting a route request (RREQ). Any router that receives the RREQ that is not the ulti-
mate 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.
Throughput in a DigiMesh network can vary by a number of variables, including: number of hops, encryption enabled/dis-
abled, sleeping end devices, failures/route discoveries. Our empirical testing showed the following throughput performance
in a robust operating environment (low interference).
1 hop, Encryption Disabled
3 hop, Encryption Disabled
6 hop, Encryption Disabled
1 hop, Encryption Enabled
3 hop, Encryption Enabled
6 hop, Encryption Enabled
Configuration
© 2010 Digi International, Inc.
Data Throughput
27.0 kbps
10.9 kbps
5.78 kbps
20.5 kbps
9.81 kbps
4.7 kbps
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