An Empirical Approach for MNOs to Achieve Unhindered 5G 3.5GHz TDD Operation at the Cross Borders

5G New Radio (NR) spectrum usage specification through the adoption of Time Division Duplexing (TDD) caters for flexibility in uplink and downlink bandwidth allocation, on the expense of interference and potential service degradation in cases of unsynchronised TDD operations among neighbouring networks. As the 5G NR in N78 has become the first major rollout of TDD cellular networks in Europe, the formalization of the appropriate approach to guarantee harmonization and unhindered TDD operations especially in cross-border areas between neighboring countries where the National Regulation Authorities (NRAs) recommendations do not have effect, becomes a key consideration for Mobile Network Operators (MNOs). This paper presents the work carried-out as part of the 5G SEAGUL project by the MNOs COSMOTE and A1BG to analyze the implications incurred, by providing a subtle synopsis of the relevant best practices and proposing a stepwise approach for streamlining the necessary activities and negotiations among the MNOs. The paper contains the results of the subsequent real-life validation in the field, the Greece (GR)-Bulgaria (BG) borders including performance measurements.