User's Manual

SATELLINE-3AS

User Guide, Version 2.2

3.4 Error correction

Another new feature of the SATELLINE-3AS is the addition of an error correction mode called the

FEC-method (F

Forward E

Error C

Correction). FEC-function is switched ON (or OFF) by using the

Programming Mode. When activated, the FEC-function will cause the SATELLINE-3AS to

automatically add additional error correction information, which increases the amount of

transmitted data by 30 %. It is used by the receiving radio modem to correct erroneous bits - as

long as the ratio of correct and erroneous bits is reasonable.

Error correction improves the reliability of data transfer via the radio interface especially in

unfavourable conditions. FEC-function should be used when link distances are long and/or if

there are many disturbances in the radio channels used. The use of the FEC-function will,

however decrease the data transfer throughput of data by about 30 %. For a listing of exact

delays introduced by using FEC-function, see Chapters 15.1 and 15.2.

To switch the FEC-function ON in the Programming Mode, select:

1) Error correction ON

3.5 Error checking

When the error checking is switched on, the radio modem will add a checksum to the

transmitted data. When the data is received, the checksums are verified before data is

forwarded to the serial port. Erroneous data will be rejected.

Switching the error checking ON in the Programming Mode, select:

2) Error check ON

3.6 Dual Band version

SATELLINE-3AS(d) radio modem is also available as a special "Dual Band" version. The radio

transceiver of the Dual Band version offers two times two MHz frequency bands, and radio

modem can be reprogrammed to operate at any channel within those two bands. Frequency

bands are tuned at the factory and the maximum separation between the highest and the lowest

frequency is 12 MHz (see the diagram on next page).

The centre frequency (fc) is set to the middle of the two frequency bands at the factory. When

using the SL-commands please note that SL&F=nnn.nnnn is the only command for frequency

NOTE!

ll radio modems which are to communicate with each other must have the same setting fo

FEC (ON or OFF). If the transmitting radio modem and the receiving radio modem have

different settings, data will not be received correctly.