Product manual
9XTend‐PKG‐R™RS‐232/485RFModem–ProductManualv1.2.4
©2005MaxStream,Inc.ConfidentialandProprietary 45
5.4. Multi-Transmit Mode
Attributes: Reliable Delivery through forced transmission of every RF packet
Every RF packet is sent exactly (MT + 1) times with no delays between packets
Diminish
ed throughput and increased latency
,
d
5.4
Required Parameter Values (TX Modem): MT (Multi-Transmit) >= 1
Other Related Commands: Networking (DT, MK, MY, RN, TT), Serial Interfacing (BR, PK, RB
RO), RF Interfacing (FS)
Recommended Use: Use for applications that require Reliable Delivery without using retries an
acknowledgements.
.1. Connection Sequence
Figure5‐05. Multi‐TransmitModeStateDi
Events up through the ‘Transmit Packet’
process are common to all three RF
Communication O
agram
each of
which will be retransmitted MT times. The Forced Sync (FS)
parameter is ignored in multiple-transmission mode.
The RB and RO parameters are not applied to follow-on
packets, meaning that once transmission has begun, it will
continue uninterrupted until the DI buffer is empty or the
streaming limit (TT) has been reached. As with the first
packet, the payload of each follow-on packet includes up to
the maximum packet size (PK) bytes, and the transmitting
modem checks for more pending data near the end of each
packet. Follow-on packets are not sent until all
retransmissions of the previous packet are finished.
The streaming limit (TT) is specified at the transmitting
modem as the maximum number of bytes that the
transmitting modem can send in one transmission event,
which may consist of many packets. If the TT parameter is
reached, the transmitting modem will force a random delay
of 1 to RN delay slots (exactly 1 delay slot if RN is zero). In
Multi-Transmit mode, each packet is counted only once
when tracking the streaming limit (TT), no matter how
many times it is retransmitted.
When a receiving modem 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 Multi-Transmit event. Thus,
a receiving modem need only receive one of the transmissions, and it will keep off the channel
until the transmitting modem is done. If follow-on packets are coming, the receiving modems will
move to the new frequency and listen for the follow-on packet for a specific period of time.
ptions. Refer to the Transmit
In Multi-Transmit mode, each packet is retransmitted MT
times, for a total of (MT+1) transmissions. There is no
delay between retransmissions, and the transmitting
modem will never receive RF data between retransmissions.
Each retransmission includes an RF initializer. A
transmission event may include follow-on packets,
Mode section [p14] for more information.