Repeater Mode - Digi XBee User Manual

Network configurations
Multi-transmit mode connection sequence
In Multi-transmit mode, the device re-transmits each packet MT times, for a total of (MT+1)
transmissions. There is no delay between retransmissions, and the TX (transmitting) device never
receives RF data between retransmissions. Each retransmission includes an RF initializer. A
transmission event may include follow-on packets, each of which retransmit MT times. Devices ignore
the Forced Sync (FS) parameter in Multi-Transmit Mode.
The firmware does not apply the RB and RO parameters to follow-on packets, meaning that once
transmission has begun, it continues without interruption until the DIN buffer is empty or the device
reaches the streaming limit (TT parameter). As with the first packet, the payload of each follow-on
packet includes up to the maximum packet size (PK parameter) bytes, and the TX device checks for
more pending data near the end of each packet. The device does not send follow-on packets until it
finishes all retransmissions of the previous packet.
The TX device specifies the streaming limit (TT) as the maximum number of bytes that the TX device
can send in one transmission event, which may consist of many packets. If the device reaches the TT
parameter limit, the TX device forces a random delay of 1 to RN delay slots (exactly 1 delay slot if RN is
zero). In Multi-transmit mode, the firmware counts each packet only once when tracking the
streaming limit (TT), no matter how many times it is retransmitted.
When an RX (receiving) device receives a Multi-transmit packet, it calculates the amount of time
remaining in the Multi-transmit event, and inhibits its own transmissions for the duration of the Multi-
transmit event, plus a random number of delay slots between 0 and (RN-1). If the local RN parameter
is zero, the delay is only for the calculated duration of the event. An RX device only needs to receive
one of the transmissions, and it keep the channel off until the TX device is complete. If follow-on
packets are coming, the RX devices move to the new frequency and listen for the follow-on packet for
a specific period of time.

Repeater mode

Use Repeater mode in networks where you need intermediary devices to relay data to devices beyond
the transmission range of the base device.
Characteristics Low power consumption.
Constraints
XBee®/XBee-PRO XTend Compatible (XTC) RF Module User Guide
Minimizes interference
Tags each RF packet with a unique Packet ID (PID).
Each repeater only repeats a packet once (the PID tracks the packet).
Increases latency and decreases throughput. The number of hops determine
latency and throughput, not the number of repeaters. Multiple repeaters within
range of a source node count as one hop.
All RF packets propagate to every device in the network (filtering rules apply).
Packet destination addresses (DT) determine which packets the device sends out
the serial port and/or retransmits.
Broadcast communications: each packet comes out every node exactly once.
Addressed communications: all devices see every packet. Only the devices with a
matching address forward it to the DOUT buffer.
Requires that each device have a unique MY parameter.
System must introduce only one packet at a time to the network for transmission.
The PK parameter determines the maximum number of bytes.
Each hop (H) decreases network throughput by a factor of 1/(H+1). Additional
repeaters add network redundancy without decreasing throughput.
Basic communications
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