User guide

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SATELLINE-3AS NMS / NMS Epic / NMS 869 / VHF

User Guide, Version 1.0

NETWORK PROTOCOL MODES

SATELLINE-3AS NMS can operate in one of the following network protocol modes, which

determine the way the radio modem handles and buffers data:

• Basic - RX Priority (transmit after receive)

• Basic - TX Priority (transmit immediately)

• Basic - Repeater (store & forward all)

• Advanced - Master (routing supported)

• Advanced - Slave (routing supported)

NMS, network addresses or routing is supported ONLY in the

Advanced

Master

and

Advanced Slave

Protocol modes

Any radio modem in

Advanced Master

or Advanced Slave

mode acts also as a repeater station automatically depending on the

message.

The three

Basic

modes require that the user equipment perform the above-mentioned functions.

The radio modems in the Advanced Protocol modes ignore the messages

sent by the radio modems in the Basic Protocol modes and vice versa.

7.1

Basic - RX Priority

SATELLINE-3AS NMS works as a plain transparent radio modem in the

Basic - RX Priority

mode

i.e. it does NOT support routing or NMS features.

RX Priority

here means that a radio modem tries to receive all data currently in the air. If a

terminal device outputs data to be transmitted it will be buffered. The radio modem will wait

until the reception has stopped before transmitting the buffered data. This will result in timing

slacks to the system, but decreases the number of collisions on the air, which is particularly

useful in systems based on multiple random accesses.

Note:

In case the terminal device enters an SL command, any radio reception will be terminated

and the SL command will be handled immediately.

Note:

The diagnostic functions are disabled in the

Basic - RX Priority

mode.

7.2

Basic - TX Priority

Basic-TX priority

mode means that a terminal device attached to a radio modem determines the

timing of the transmission precisely. The transmitter is switched on immediately when the

terminal device is starting to output data.

If the radio modem is already receiving data from the radio interface and data to be

transmitted is detected on the TD line, the radio modem will stop the reception and switch to the

transmit state. Thus there is no need to use RTS line to control the timing of

transmission/reception.