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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
Constraints
XTend RF Module User Guide
Low power consumption.
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.
Repeater mode
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