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.
The user enters his message using the keypad on the mobile radio and sends it the the destination address (ISSI) of the control room dispatcher. Two messaging within the TETRA network is possible.
The mobile radio contains a GPS receiver and send the GPS location using a SDS message to the Geographical Information System (GIS) were the location of the mobile radio is displayed on a map.
TETRA Short Data Service (SDS) used for database query
The enters for example a vehicle licence plate number using a SDS to a central database where the licence plate number is queried and the name of the car owner is send back to the mobile radio.
Or the fire brigade types in the number on a truck that indicates the type of transported material, this is send to the database were the type of material is checked and it is send back if the material is hazardous.
TETRA Short Data Service (SDS) used for telemetry
It is possible to connect a computer to the PEI (Peripheral Equipment Interface) of a subscriber and send for example the water level of a watertank via SDS to a central database.
