The TETRA Short Data Service (SDS) is a data service that is comparable with the Short Data Message (SMS) of GSM. A TETRA SDS message can carry up to 140 byte data per message. SDS message carrying different types of information are separated via a protocol identifier. A range of protocol identifiers are defined in the ETSI TETRA specification.
A variety of applications can use the SDS service to carry information. The most common usage is the sending an message that is entered via the keypad of the subscriber. But for example the LIP (Location Information Protocol) location information messages that carry the GPS location from the subscriber to the mapping application are usually also transported via SDS messages.
SDS message can be send between subscribers, between subscriber and dispatcher and subscriber and fixed host in the network. SDS messages can be send to individual subscribers or broadcasted on a number of basestations to all subscriber using that basestation. Short data messages between subscriber and fixed host makes it possible for an application to receive SDS message and based on their content do something with the received information. For example when the SDS message contained to GPS location of the subscriber the location can be displayed on a map. Or for example when the SDS message contains the water level the water level can be displayed and monitored. SDS messages are often used as transport mechanism for telemetry applications.
TETRA Short Data Message are transported via the Control Channel of a basestation. The control channel is also used for signalling of the voice traffic. To prevent overload of the control channel SDS message need to be used carefull. Contact TETRA-Consultancy to learn about the limitations.
TETRA SDS user cases
TETRA Short Data Service (SDS) used between two mobile radio’s
The user enters his message using the keypad on the mobile radio and sends it the the destination address (ISSI) of the recipient. Two messaging within the TETRA network is possible.