Using TEDS Direct Access, a radio will register not on the TETRA MCCH but directly on the TEDS carrier. As long as the TEDS service is available, the radio will perform cell re-selection from one TEDS carrier to another, without ever visiting the conventional TETRA side. It may seem a small difference, but this mechanism can deliver great results.

Quality of service: because the dedicated TEDS data radios do not use the MCCH, the TEDS data services are independent from voice services and have separate Quality of Service (QoS). In other words, voice services will not suffer, however much TEDS data traffic is in the system – and vice versa. If there is congestion on either side, only the overloaded service has to be adjusted.

Cost-efficient dedicated data networks: Direct Access helps in building extremely cost efficient, dedicated TEDS data networks. If only narrowband or wideband data needs to be delivered, all carriers in the network can be TEDS data carriers.

More scalability for cell sizes: if a network has only a few voice users but needs extreme data capacity, TEDS Direct Access makes it possible to build extra wide coverage, low-capacity cells for voice and smaller, high-capacity cells for data.

As the adoption of TEDS expands, more benefits from Direct Access will be discovered. For example, ETSI’s TC-TETRA is currently studying the potential of voice services over QAM (TEDS) channels, since this would yield better spectrum efficiency. TETRA and TEDS will continue to evolve for years and years to come.

CASE IN POINT: RADIO NETWORK FOR DATA TRANSMISSION ONLY

TEDS Direct Access is a great opportunity for a TETRA network owner who only needs data, or is only allowed to use data. (For example, the existing analogue trunked network may not yet be amortized, and the frequency regulator has thus granted the network owner a licence for data only.)

Building a dedicated data network based on TEDS Direct Access has several benefits for such an owner. All carriers in the base stations can be dedicated to TEDS, therefore yielding maximal data capacity. But the network itself is still a complete TETRA network, and so voice services can be introduced in the same network if the owner develops the need or gets permission for voice.

What’s more, it may be possible to activate voice services on a base station area over a remote connection (this depends on the technical details of the network).

CASE IN POINT: SMART GRIDS FOR ELECTRICAL POWER COMPANIES

A Smart Grid is an intelligent power distribution and generation system. It can sense system overloads and reroute power automatically to prevent or minimize outages. It can also respond autonomously to manage supplies quickly and efficiently.

Smart Grids are changing the landscape of power and energy business. Before, large systems provided power for a great number of users, but Smart Grids will make smaller-scale power generation and storage economically feasible. For example, solar panels or small wind turbines on the rooftops generate electricity; charging stations for electric cars store electricity locally.

In the future, electricity consumers’ power meters will be read automatically. The measurements will help the consumers’ appliances optimize their power consumption according to tariffing. A growing amount of signalling will flow back and forth as the electricity grid is kept in balance, optimizing power generation and minimizing the use of non-renewable energy.

How to transfer all this data for Smart Grids? Commercial wireless networks do not meet the availability or security requirements; and until now, mission-critical radio networks such as TETRA did not have the ability to handle the required data volumes.

Enter TEDS Direct Access. Power and energy companies can build a dense network of miniature-size TEDS base stations, possibly with a single carrier. Such a network would be most cost-effective, because miniature base stations could be installed in existing facilities and cabinets. The cells would be small, requiring only small, cheap antennas, and frequencies could be reused, so the increase in capacity would fit into the available spectrum.

CASE IN POINT: EMERGENCY SERVICES AT A MAJOR INCIDENT

A fire has broken out in a shopping mall. Arson is suspected. Units from police, fire and ambulance services need to co-ordinate their own operations and joint efforts. Data and information are in high demand: the command centre needs video footage from the scene of the fire, while the police units need to view pictures of suspects. Ambulance services deliver patient data to the hospital, and the fire chief assigns hydrants and entry points to the arriving units.

The locations of all participants are updated frequently and shared. A joint mobile command post is being set up.
Mobile phone networks are overloaded and cannot reliably serve the people near the location of the fire. The public authorities use their mission-critical TETRA radio network, which continues to provide a great service.
(中国集群通信网 | 责任编辑：陈晓亮)