User guide

SATELLINE-3AS NMS / NMS Epic / NMS 869 / VHF
User Guide, Version 1.0
50
The radio modems in the Advanced Protocol modes ignore the messages
sent by the radio modems in the Basic Protocol modes and vice versa.
Picture 8.1. Repeater stations extend the coverage of the radio network. The end-to-end latency
increases correspondingly.
8.5
Timing and delays during data transmission
When using a radio modem for data transmission, the use of a radio interface and the radio
modem circuitry itself introduces start-up and data transfer delays. These delays exist when the
radio modem switches from
Standby Mode to Data Transfer Mode and during reception and
transmission of data. See Appendix B for values in each case.
8.6
Data buffering in the radio data modem
A synchronisation signal is transmitted at the beginning of each radio transmission and this
signal is detected by another radio modem, which then turns into receive mode. During the
transmission of the synchronisation signal the radio modem buffers the data to be transmitted
into its memory. Transmission ends when a pause is detected in the data flow sent by the
terminal device, and after all the buffered data has been transmitted. When the data speed of
the serial port is the same or slower than the speed of the radio interface, the internal transmit
buffer memory can not overflow. However, when the serial interface speed exceeds the speed of
the radio interface, data will eventually fill the transmit buffer memory. After the terminal device
has stopped data transmission, it will take a moment for the radio modem to get the buffered
data transmitted and get the transmitter switched off. The maximum size of transmit buffer
memory is one kilobyte (1 kB). If the terminal device does not follow the status of the CTS line