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SATEL OY
// SATELLAR MANUAL // RADIO UNIT // USER GUIDE // V. 1.8
6. Data transmission
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6. Data transmission
In order to transfer data, the RU must be configured to operate in one of the following modes
–
Basic, TX priority
–
Basic, RX priority
–
Basic, repeater
–
Source routing, master (supported with FSK-radio)
–
Source routing, slave (supported with FSK-radio)
–
Packet routing
–
Link Based Modulation (supported with QAM-radio)
–
Automatic QAM Modulation (supported with QAM-radio)
These are called network protocol modes. Basic mode with TX priority is the traditional transparent mode
of data transmission, where the RU is effectively replacing a cable between two Data Terminal Equip-
ments. In basic mode with RX priority the transmission is disabled as long as there is a reception ongoing.
In repeater mode the data received from the radio path is buffered and then forwarded back to the radio
path. Repeater mode is used to extend the radio coverage.
Source routing (supported only with FSK-radio) is needed when the network topology is more compli-
cated than just a point-to-point connection between two stations (possibly added by a repeater station).
This mode requires polling type protocols with fixed station address length and position in the message,
based on RS-232, -422, and -485.
Packet routing is typically in use when the RU is working together with the CU. The CU interfaces with the
DTE using the IP protocol stack and acts as an IP router. The RU is seen as a virtual network interface and
does not need to be especially configured for the IP traffic. However, settings related to medium access
control (see explanation later in this chapter) must be done and routing tables must be filled. As explained
earlier, the RU can act as a radio router station without the CU also in cases where IP data is transferred.
Only when a local Ethernet connection is needed the CU must be used.
6.1 Basic mode with TX priority
When the RU operates in basic mode with TX priority, the Data Terminal Equipment (DTE) is connected to
the serial data connector (D9). Data transfer starts immediately when the first byte of data comes from the
DTE and stops when the data ends. The RU does not store the data anywhere and does not rearrange it at
all. It just sends the data that it gets as input. The radio link between the two DTE is done without routers
or repeaters in between. This mode is a simple point-to-point connection where the connecting cable is
replaced by a radio link. The DTE is fully responsible for the traffic control: it decides when to transmit,
interprets the incoming data for correctness and decides further transmission is needed.
