On the applicability of TETRA for direct train-to-train beaconing

TETRA has been designed with reliable voice communications under critical environmental and operational conditions in primary focus. However, there is more to TETRA than being a mobile radio for police and rescue forces. In this talk we will elaborate on the particular suitability of TETRA for a direct train-to-train communication as part of an innovative railway collision avoidance system. We will show that not only the TETRA frequency band has principal advantages being used for train-to-train communications, but also the TETRA DMO mode is key to a system design for a network of beaconing trains. Comprehensive simulations have shown that the performance requirements of safety applications such as the railway collision avoidance systems can be met by TETRA. The simulative results have been validated with a measurement campaign in an area covering urban as well as sub-urban, rural and mountainous pre-alpine area in south Germany using an implementation of the cooperative railway collision avoidance system adopting common of-the-shelf TETRA devices. The measurement results proved that TETRA is suitable to achieve the necessary range, reliability, throughput and update delay characteristics. From the statistics of the measurement it could be ensured that a safety factor of more than seven times the braking distance between any two approaching trains have been made aware of any other train in its vicinity, which allows – together with a proper, track selective positioning sub-system – the railway collision safety system to act as an excellent safety overlay system