User's Manual

SATELLINE-4Pro
User Guide v0.93 DRAFT
57
10.3.3 Repeater chain using dual addressing
If the terminal devices cannot add address chains to the beginning of the data packets, a network
with several repeaters may still be realised by using dual addressing. In dual addressing each link
(see arrows below in figure) is given a unique address, which will prevent duplication of messages
and endless loops in the network. The terminal devices need not add anything to the data.
Usually the primary transmit address is used in transmission (TX1). The secondary transmit address
(TX2) is used only if the Repeater Mode is used and the packet to be repeated was received using
the secondary reception address (RX2).
In the following example two repeaters are used. It should be noted that each link (arrow) might be
uniquely defined with the help of radio modem numbers and data transfer directions. The Repeater
Mode should be switched ON only in the radio modems acting as repeaters to prevent the packets
from remaining in endless loops in the network.
Repeaters may also act as ordinary substations; in that case the terminal device must wait until the
message has reached the end of the repeater chain before sending data.
10.3.4 Redundant repeater chain
Reliability of a radio data communication system can be improved significantly by designing
redundant equipment setup for master and repeater stations. The two repeater chains are separated
by proper dual addressing setup. Slave stations need to be able to communicate with the master
through the both repeater chains. By using the "TX address auto switch" function, the slave station
modem directs the reply message to the repeater chain from which the request has been received.
If "TX address auto switch" has been set ON, radio modem checks out the RX address of the received
message. When one of the RX addresses is recognised, all the messages coming in from the serial
interface will be sent to the air with matching TX address. The use of "TX address auto switch"
function is not recommended if Repeater Function is set ON.
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(21)
21
32
23
12
32
43
34
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rxd
txd
rxd
txd
Modem 1
master
Modem 2
repeater
Modem 3
repeater
Modem 4
TX1
RX1
TX2
RX2
Addresses: