data
Better than ever: secure, reliable data over TEDS
The TETRA Enhanced Data Service (TEDS) is a next-generation TETRA enhancement which can bring data-centric field operations to life. But, as Tero Pesonen explains, its new extension, Direct Access, has features which will offer even more benefits to users
T
he importance of data communication is ever increasing. In field operations, the requirement is quickly changing from better coverage to more, better and faster data. After all, when there is a connection (coverage), the next logical need is for improving the operations. People in the field, as well as field commanders, need a better and more precise picture of the situation. But at the same time, there must not be information overflow. Today, public safety budgets are flat – yet operations may be more demanding, and more costly. It is imperative that daily field routines become more efficient, and this can be done with data. However, not just any data. Before field operations can be founded on data in addition to voice, data must become absolutely reliable. Data has to be as secure, available and dependable as the mission-critical voice link that TETRA systems provide. When field operatives can trust the ready availability of task-related data as much as they trust the ability to communicate with their group, operational models can be changed. And then they can fully take advantage of the information-sharing possibilities that data communications bring.
The answer: TEDS Te TETRA Enhanced Data Service (TEDS) is the TETRA feature that can bring data-centric field operations to life. TEDS is the high speed data part of the ETSI TETRA Release 2 standard. It is a mission-critical data bearer service that is fully integrated into TETRA standard, and so it can be introduced into some vendors’ TETRA systems as a software upgrade. From a technical viewpoint, TEDS is an always-on data
service which provides both Short Data Service (SDS) and IP packet data services. It has quite a clever design: it offers the possibility to use variable channel bandwidths ranging from the current TETRA 25 kHz channels up to 50, 100 and even 150 kHz. In this way it can make use of the entire available spectrum – and even discontinuous spectrum. In practice, a combination of 25 and 50 kHz channels
may be the most common choice, because coverage for TEDS will then be the same as for TETRA voice. Te new high-speed data services can thus be provided over a wide area, without the need to add more base station sites to the network. TEDS has another remarkably clever characteristic: it
strives to maintain the connection as long as possible. To achieve this, it changes its modulation and error coding schemes automatically to more and more robust ones as the link between the TETRA base station and TEDS-capable radio becomes weaker. TEDS uses QAM (Quadrature Amplitude Modulation)
64, 16 and 4, where QAM 4 is the most robust mode. Because WiMAX and LTE use the same modulation, TEDS can be regarded as a member of the same generation. QAM modulation is very-spectrum efficient, which is
important for public safety radio where frequencies are a scarce resource.
Tero Pesonen is a
board member of the TETRA Association. He is also head of Fortecor Business Programme at
Cassidian Systems 12
Many benefits For radio users, TEDS brings two significant benefits: more capacity for data and faster data. On 50 kHz TEDS channels, TEDS yields almost eight times the SDS traffic compared to the TETRA Main Control Channel (MCCH). Te IP data throughput is up to 100 kbit/s – quite an increase over the speed of single-slot TETRA packet data. For owners of TETRA networks, TEDS also brings benefits. Te ability to increase data capacity and speed
TE TRA TODAY Issue 3 May 2011
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