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XStream‐PKG‐T™TelephoneRFModem–ProductManualv5.x00[2006.02.24]

4.3. Acknowledged Communications

4.3.1. Acknowledged Mode

Characteristics: Reliable delivery through positive acknowledgements for each packet

Throughput, latency and jitter vary depending on the quality of the channel

and the strength of the signal.

Recommended Use: Acknowledge Mode configuration is appropriate when reliable delivery is

required between modems. If messages are smaller than 256 bytes, use RB and RO commands

to align RF packets with application packets.

Required Parameter Values (TX Modem): RR (Retries) >= 1

Related Commands: Networking (DT, MK, RR), Serial Interfacing (PK, RN, TT, RO, RB)

Table4‐04. SampleNetworkProfile

Modem Parameter Settings (assume default values for parameters not listed)

All

ATRR A [set number of Retries to 0x0A]

ATRN 5 [set number of Delay Slots to 5]

Connection Sequence

Figure4‐06. AcknowledgedModeStateDiagramÆ

After sending a packet while

in Acknowledged Mode, the

transmitting modem listens

for an ACK

(acknowledgement). If it

receives the ACK, it will either

send a subsequent packet (if

more transmit data is

pending), or will wait for

exactly RN random delay slots

before allowing another

transmission (if no more data

is pending for transmission).

If the transmitting modem

does not receive the ACK

within the allotted time, it will

retransmit the packet with a

new RF initializer following the

ACK slot. There is no delay

between the first ACK slot and

the first retransmission.

Subsequent retransmissions

incur a delay of a random

number of delay slots,

between 0 and RN. If RN is

set to 0 on the transmitting

modem, there are never any

back-off delays between

retransmissions. Note that

during back-off delays, the

transmitting modem will go

into Idle Mode and may

receive RF data. This can h

the effect of increasing the ba

retransmit) mode as long as it is receiving RF data.

ave

ck-off delay, as the radio cannot return to RF transmit (or

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