TETRASUPPLEMENT 09


can still use omnidirectional TETRA 1 channels for speech calls.


Beyond Direct Access Once TETRA terminals are capable of Direct Access to TEDS QAM channels, it raises the possibility of carrying voice calls on the same QAM channels as data to improve efficiency. This would allow closer integration of voice and data in a Direct Access TEDS world, as separate channels to carry the conventional voice channels would no longer be needed. It would also allow some of the benefits of TEDS, in particular the ability to optimise the tradeoff between bit rate (capacity) and range to be applied to voice calls – for example use the low rate, high range service to gain increased rural coverage or to increase site spacing along a railway track, or the high rate, low range service for increased voice capacity at locations with high volumes of traffic. This is one extension to the standard currently under discussion.


Higher data speeds Although the higher speed TEDS services are starting to be deployed now, it is clear that in the future TETRA users will require increasing data


speeds. There will be a mixture of reasons for this: new working practices based around new data applications will drive a need for more capacity, and there is also an increasing demand for video transmission which needs to be satisfied. Some of the capacity improvements can be achieved by deploying the higher bandwidths of TEDS that already exist in the standard, and ETSI TC TETRA is continuously looking at ways to improve throughput, efficiency and range of TEDS. However, it is also apparent that Broadband data speeds will be required for some applications, and the TETRA working groups are actively looking at standardising a broadband addition to the TETRA standard. An obvious question is: ‘Why look at a special technology for TETRA broadband, when there are already existing commercial standards in place?” The answer is that TETRA has some unique characteristics which make it suitable for the professional market – group call communications, fast call set up, high levels of security, full integration of voice and data and so on, and it is important that any broadband technology selected has the same attributes. At the moment, the TETRA community is both actively looking at the


requirements for wideband and broadband data, and researching the technology options in order to ensure that the finally selected, standardised technology has the best fit to provide the fully integrated service in the future that the TETRA market demands. However, one challenge to implementing broadband technologies is the spectrum required especially at low (UHF) frequencies where radio coverage is best, which may mean that TEDS remains the preferred solution for high speed data for the next few years.


David Chater-Lea is Fellow of the Technical Staff, TETRA World Wide Solutions Development, Motorola Solutions UK. He is a senior technologist working for Motorola Solutions in the areas


of advanced system architecture and design. He is Chairman of ETSI TC TETRA WG4, responsible for advanced air interfaces, and is also a specialist in wireless communication system security and Vice Chairman of TC TETRA WG6, responsible for security, and a founder member of the TETRA Association Security and Fraud Prevention Group. David holds a BSc in Electronic and Electrical Engineering from the University of Birmingham and is a Chartered Engineer and a Fellow of the IET. He holds a number of patents in the field of radio communications systems.


Train Radio Systems with TETRA for Bursa Light Railway System


Within the framework of the eight kilometer expansion project of the Light Rail System in Bursa, Turkey, the Tewet Group is replacing the old analogue radio system to a state of the art digital trunked radio system (TETRA). Railtrade, a member of the Tewet Group and its system supplier Rohde & Schwarz Professional Mobile Radio GmbH ensure with this TETRA System an unbroken line of connectivity among urban and main line operators thus enabling a secure and reliable journey for the passengers. Railway transportation operations require


highly flexible and reliable communication in order to provide the staff as well as the passengers with real-time information. The Tetra System in Bursa enables the management of group and private calls, emergency calls, fast access time, data services etc. to guarantee extreme reliability to the requirements and typical needs of railway transportation operators. Railtrade, Tewet, CCE (Member of the Tewet Group) and Rohde & Schwarz planned, delivered and integrated the new Tetra


www.railtrade.de www.eurotransportmagazine.com


Eurotransport Volume 9, Issue 3, 2011


system. The difficulty of this Project is the TETRA System integration and upgrading of the old vehicles to the existing system during the normal Railway operation without service interruption. Safety and security issues in terms of radio communication are important in the railway environment. Additionally, a secure and safe data communication between the Operations Control Centre, all staff and vehicles is another important aspect for an efficient operation, for emergency prevention and in case of emergencies. The following examples are typical for the


use of train radio systems in the Bursa Project: ● Data transfer between trains and the control of operations


● Central traffic control and management ● Transmission of Short Data Service (SDS) for information such as train position and schedule information


● Emergency call communication ● In-train announcements to passengers


● Radio communication for operations, security and maintenance staff


The state of the art TETRA System in Bursa is designed and integrated by Railtrade, Tewet, CCE and Rohde & Schwarz to operate in mission critical environments and delivers the highest reliability and safety which is necessary to ensure smooth and accident-free operation in the railway field. The new line with eight stations allows new residential areas to be accessible, including the University of Bursa. The integration of a state of the art TETRA radio system enables the municipality of Bursa to keep up with the rapid changes in communications and safety technology and safely transform their existing legacy networks into the next generation.


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