Funk-Electronic Piciorgros GmbH
TGW-100/TGW-100R
V2.71 - Page 29 of 59
3.1
Data Communication by SDS
Data communication by SDS does not necessarily require an IP switch within the
TETRA network: therefore it is compatible even with smaller installations. SDS Data
communication takes place only through the Control Channel (MCCH). Therefore no
additional timeslots or RF-Carriers are required for data communication.
The TGW-100 supports a maximum SDS length of 2047 bits (254 bytes) in accordance
with the ETSI specification. However, since not all TETRA infrastructures support this
length, users can set a lower maximum length for SDS data blocks. If the data block to
be transferred is longer than the maximum SDS length, it is split into several SDS data
blocks by the transmitting TGW-100 and automatically re-assembled by the receiving
TGW-100. This fragmentation/de fragmentation of data blocks is transparent to the
terminal equipment connected to the TGW-100 at either end, and makes the TGW-100
compatible even with older TETRA networks. In this respect, radio data communication
through TGW-100 modems behaves like wire communication, with minimum
transmission delay. If a TGW-100 receiving data detects a checksum error, the entire
data block is discarded.
SDS data communication supports data communication only via the serial interfaces:
RS-232 or RS-422/485. Transfer and routing of IP packets is not possible
The serial interface settings of TGW-100 modems on the same TETRA network do not
have to be the same. Therefore it is no problem if the master modem is set for 38400
bps, 8N1, - while the slave is set for 9600 bps, 8E1. For performance-critical
applications the serial interface should be set for the highest possible baud rate
compatible with the terminal equipment, as this naturally minimizes data
communication delay time.
As every TETRA infrastructure manufacturer uses an own proprietary protocol to send
and receive SDS and Status message with a direct connection to the switch, the used
infrastructure must be supported by the TGW-100. Please contact Piciorgros for a list of
supported infrastructures.
