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SATEL OY
// SATELLAR MANUAL // RADIO UNIT // USER GUIDE // V. 1.8
6. Data transmission
3
–
Set all the radio parameters as required (unless already set in the factory): radio
frequency, channel spacing, RF output power, modulation method, forward
error correction (FSK)/trellis coding (QAM) and encryption.
6.2 Basic mode with RX priority
Basic mode with RX priority is similar to TX priority. The difference is in how the RU reacts to the incom-
ing data from the DTE: when the priority is TX the transmission is started without delay even when there
is a reception ongoing while in RX priority the transmission is started just after the reception has been
completed.
An example of how to use priority settings in a simple network is shown in the figure below.
SA00043
No radio
coverage
between B
and C
Station A
(RU+CU)
Priority TX
TD
RD
PWR
STAT
RU-14500
0
RX
TX
CTS
RTS
USB
ETH
PWR
STAT
CU-1U210
0
OK
Station B
(RU)
Priority RX
TD
RD
PWR
STAT
RX
TX
CTS
RTS
Station C
(RU)
Priority RX
TD
RD
PWR
STAT
RX
TX
CTS
RTS
Figure 6.1 Priority settings in a simple network
Station ‘A’ has a radio link to stations ‘B’ and ‘C’. It sends control commands to these. Stations ‘B’ and ‘C’
respond by sending either status information or acknowledgement messages. They cannot hear each
other’s radio transmissions. Control commands from station ‘A’ are of high priority, so station ‘A’ needs to
start sending despite it has an incoming message. Therefore station ‘A’ is set to priority TX while the others
are set to priority RX.
Priority settings help if the radio coverage is as described in the figure above, i.e. if station ‘B’ and ‘C’ can-
not hear each others’ transmissions. Consider a situation where station ‘B’ is sending to ‘A’ and ‘A’ then
needs to send a high priority message to station ‘C’ while it still has reception ongoing from ‘B’. Due to
priority setting to TX it is possible but if stations ‘B’ and ‘C’ are within each others’ radio coverage the two
simultaneous messages from ‘A’ and ‘B’ collide at ‘C’ and therefore the message from ‘A’ is probably not
