Data Services and facilities
The TETRA standard has always provided for the transmission of data as well as voice. The use of status messaging and Short Data Service (SDS) provide very efficient methods for quickly sharing information with little impact on voice traffic or IP data. Many SDS applications have been developed specifically to increase operational efficiency. As some organisations and agencies also use mobile data services and applications on public carriers, TETRA is well positioned to offer a complementary or alternative bearer that is far more resilient and secure.
Key to the success of implementing an effective mobile data capability is to start with a realistic expectation of the data speeds, and a willingness to adapt operational procedures to take full advantage of the data. The objectives should be to generate good decisions and outcomes. TETRA data speeds are modest when compared to 3G or LTE/4G but are more than capable of carrying many of the applications vital to public safety and industrial needs. Well engineered applications which minimise the transmitted data and manage the information efficiently at either end have been shown to be very effective over TETRA. These include database look-up, picture messaging, and location-based services.
TETRA data speeds continue to evolve and have long since increased with the provision of Multi-Slot Packet Data (MSPD), providing speeds similar to GPRS. TETRA Enhanced Data Service (TEDS) brings EDGE-like speeds to TETRA. TEDS better manages data traffic in busy TETRA networks and maintains high availability for voice. In addition TEDS enables richer data applications such as video, image and mapping services.
The deployment of public mobile broadband services will stimulate the demand for similar high speed data services from the critical communications user community. However, it is essential that these users continue to benefit from the resilience, functionality and coverage already delivered by TETRA voice networks. TETRA and TEDS deliver low and medium speed data capability that meet these criteria and enable many of the data services through the use of efficient applications.
TETRA provide a Short Data Service which allows the transmission of up to 256 bytes data payload. The most common use of such a service is text messaging which thanks to the Transport Layer facility can also be provided with additional functions such as, for instance, message received and consumed reports.
TETRA provides also a status messaging function which allows the transmission of pre-coded status through which a user on the field can, for instance, quickly and easily update Control Room operators about his/her current operational status.
Short Data Service (SDS)
The TETRA Short Data Service can also be used to convey user application data (e.g. for mobile positioning or diagnostic/telemetry).
IP Packet Data
For application data transmission TETRA also provides an IP based packet switched data transfer service supporting all typical IP facilities such as, for instance, data acknowledgement and re-transmission. The maximum data throughput is about 13-14 Kbit/s in case all4 timeslots of a single TETRA carrier are used for data transmission.
Mobile positioning (with Location Information Protocol)
The most common use of TETRA Short Data Service facility is probably mobile positioning for which TETRA does not only provide a simple bearer but, thanks to its SDS Transport Layer facility, can also offer an ad-hoc Location Information protocol (LIP) which supports an interoperable data transfer protocol and format.
TETRA Enhanced Data Service (TEDS)
TEDS is the wideband data transmission service introduced in TETRA Release 2 and provides an alternative and more efficient IP based data transmission service. TEDS exploits different modulation schemes and frequency bandwidths (from 25 KHz up to 150 KHz) if compared with TETRA Release 1 and therefore needs specific frequency allocation and network design strategies. With adaptive selection of modulation schemes, RF channel bandwidths and coding according to propagation conditions, user bit rates in the region of 10 to 500 kbits/s can be expected.
Peripheral Equipment Interface (PEI)
In order to build an open data application environment, TETRA also provides a standardised interface protocol to be used for the connection of external data equipment terminals to TETRA radios (e.g. so that the same application can be used with different manufacturers’ terminals).