Satel SATEL-EASy+ YM6010, Руководство пользователя, Страница: 30 / 85

SATEL-EASy+
User Manual
Version 1.19
29
6.4 Forward Error Correction (FEC)
FEC improves the reliability of data transfer over the radio by adding additional correction
information to the radio messages. Based on that information, the receiving radio modem will
be able to correct erroneous bits provided the ratio of erroneous and correct bits is reasonable.
However, the use of FEC decreases the data throughput, because the amount of transmitted
data increases about 30 % (see Appendix B). FEC should be used on long distance links and/or if
the radio channel is “noisy” in other words suffering from interfering signals.
6.5 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 checksum is verified before data is forwarded
to the serial port. There are two different options for error checking are:
Error check checks data only partially while data is received.
Full CRC16 check adds two checksum characters at the end of the user data message. At the
reception end the receiver receives first the whole package and if the checksum matches the
data message is forwarded to the serial port. If Full CRC16 check is selected it must be set ON for
all radio modems in the same network. Otherwise the checksum characters appear at the end of
user message on the serial port.
6.6 Air Encryption
The product encrypts the data that is transmitted on the air interface with the listed encryption
techniques:
• AES128
•
AES256
Data security is often a concern when using radio communication. Bit encryption (CTR-mode)
on the air-interface ensures privacy in the radio network. The principle of encryption in the radio
path is to collect a certain amount of data to a shift register and manipulate it according to a
certain rule. Every data packet is encrypted individually. Depending on the encryption type, the
process of encryption adds 5-10ms delay in the data flow to each sent data packet (<5
characters in AES128 and <10 in AES256) and must be avoided in the cases where low latency is
the most important requirement.
NOTE!
All radio modems, which are to communicate with each other, must have the same
setting for FEC (ON or OFF). If the transmitting radio modem and the receiving radio modem
has different settings, data will not be received.