Communication Technologies Support to Railway Infrastructure and Operations

GSM-Railways (GSM-R), which is state-of-the-art railway mobile communication technology, is gradually replacing legacy analogue radio systems. Although GSM-R is an unquestionable achievement in terms of European railway interoperability, from a telecommunication point of view, it is an obsolete technology. In the research work presented in this thesis, GSM-R technology is analysed and its main shortcomings are identified, namely: lack of capacity, limited data transmission capabilities, and inefficiency in radio resource usage. Due to these significant disadvantages, alternative mobile technologies are considered to replace GSM-R in the future. This thesis is focused on Long Term Evolution (LTE) as one of the most likely successors to GSM-R. As a technology designed for commercial purposes, LTE has to be investigated specifically in railway environment. Using computer-based simulations, the LTE network is examined in various scenarios modelling typical railway conditions. The transmission performance offered by LTE is analysed under worst-case assumptions in terms of traffic load, base station density, and user speed. The results demonstrate that LTE fulfils transmission requirements set for the two most important railway applications: European Train Control System (ETCS) signalling and railway-specific voice communication. Therefore, LTE is technically capable of replacing GSM-R as the communication network for the European Rail Traffic Management System (ERTMS). Moreover, the simulation results show that LTE offers a significant improvement over GSM-R in terms of transmission capacity and performance. Thus, LTE as a ii railway communication technology would create an opportunity to introduce new business-supporting applications, which could enhance railway operation. The demand for such applications is growing in railways, but the GSM-R networks cannot deliver them. Furthermore, a radio access architecture based on cooperating macro and micro cells is proposed in the thesis. This heterogeneous network architecture, which is novel for railways, may bring numerous advantages, such as high network availability and reduction of inter-cell handover rate for running trains. It also enables railways to use new high-frequency radio bands, which is not a feasible option in the classical railway radio deployments. Simulation results indicate that the macro/micro architecture offers huge capacity increase, which can be used for providing bandwidth-demanding applications, such as video surveillance. All in all, this thesis presents a feasible evolution in the field of railway communications. LTE technology together with the novel heterogeneous architecture may transform railway mobile networks from being a bottleneck of the system into becoming its strong asset.