Development and Application of a Methodology for Optimizing Frequency Spectrum Usage in the Design of LTE-1800 TDD Radio Access Networks

Relevance of the research topic is simultaneously driven by technical, industry, and regulatory factors. First, mission-critical operational radiocommunications are a fundamental element in ensuring the safety and controllability of railway infrastructure; at the same time, current GSM-R-based solutions are reaching their limits in capacity and functionality. Second, spectrum scarcity and fragmentation in the 1785–1805 MHz band, as well as the need for its coexistence with other radio networks, necessitate spectrally efficient planning methods and the reduction of mutual interference. Existing radio planning practices are generally poorly adapted to the specifics of railways, increasing the risks of coverage shortfalls, degradation of handover performance, and failure to meet latency regulations. The comprehensive methodology proposed in this study for LTE‑1800 TDD delivers measurable reductions in mutual interference, expands zones of reliable coverage, ensures compliance with <50 ms latency for critical services, and enables rational use of scarce spectrum. Accordingly, the topic has high practical relevance for the modernization of existing lines, the design of new sections, and the phased migration to FRMCS/5G. The main objective of the study is to develop and substantiate a comprehensive methodology for designing digital systems of operational railway radiocommunications based on the LTE‑1800 TDD standard under limited spectrum resources and stringent requirements for reliability and latency. Results: mutual interference reduced by up to 30 %, the radius of reliable coverage increased by up to 15 % through antenna system optimization, guaranteed compliance with <50 ms signal delay requirements for control systems; the effectiveness of adaptive bandwidth selection is demonstrated. Adaptive multi-stage LTE‑1800 TDD planning for operational railway communications delivers measurable improvements in interference immunity, coverage, and latency under spectrum constraints and can serve as a practical design standard. Scientific novelty: an integrated methodology with adaptive branching and a set of application-specific correction factors for the railway environment is proposed, ensuring simultaneous fulfillment of latency, robustness, and spectral efficiency requirements amid spectrum scarcity. Practical significance: the methodology has been implemented in real-world design practice, improving the reliability of critical services and the efficiency of spectrum use.

railway transport, LTE, high-speed highways, radio access network design, radio communications