A) TDD, Synchronised case

Base stations of synchronised TDD systems on both sides of the border line with centre frequencies not aligned for all PCIs or with centre frequencies aligned and for preferential PCIs may be used without coordination with a neighbouring country if the mean field strength of each cell produced by the base station does not exceed the values of 67 dBμV/m/5 MHz at a height of 3 m above ground at the border line between countries and 49 dBμV/m/5 MHz at a height of 3 m above ground at a distance of 6 km inside the neighbouring country. Base stations of synchronised TDD systems on both sides of the border line with centre frequencies aligned and for non-preferential PCIs may be used without coordination with a neighbouring country if the mean field strength of each cell produced by the base station does not exceed the value of 49 dBμV/m/5 MHz at a height of 3 m above ground at the border line between countries.

The following table gives an overview of the trigger values of the field strength at a height of 3 m above ground between synchronised TDD systems:

B) TDD, Unsynchronised case

The following table gives an overview of the trigger values of the field strength at a height of 3 m above ground for preferential frequency blocks of unsynchronised TDD systems:

For field strength predictions, the calculations should be made according to Appendix B. In the case of channel bandwidth other than 5 MHz, a factor of 10 x log10 (channel bandwidth[4] /5 MHz), should be added to the field strength levels.

For this band, due to the low field strength level in the unsynchronised case, in order to enable the field strength measurement, a conversion factor of 23 dB from 3 m to 10 m could be applied for suburban environment.

GUIDANCE FOR OPERATORS FOR DEPLOYMENT IN BORDER AREAS

This section lists different techniques as a guidance for operators that can be used to reduce the interference across the border in case of both TDD and FDD systems. In the context of TDD systems, while these techniques decrease the interference, they may not be sufficient to enable unsynchronised operation of TDD networks across the border.

Antenna tilting and restricted beamforming:5 The downtilt of the base station antennas is adjusted such that there is suppression of all signals towards the horizon, thereby reducing the horizon component of interference to the base stations. In the case of advanced antenna system (AAS) antennas at the base stations, configured elevation-domain codeword subset restriction may also be used to decrease the interference to the base stations across the border.

Downlink power reduction: Another possible solution could be to reduce the downlink power on the base station sectors which are facing the border or located at sites near the border. One of the main advantages of this technique is that there is less interference radiated across the border. Moreover, since the difference between the uplink and downlink transmit powers is smaller, there is reduced UL/DL imbalance in a cell. The direct consequence of this technique is that the downlink to uplink interference becomes less problematic as there is a smaller area with vulnerable user equipment (UE). Also, smaller cells can be deployed closer to the border, providing a stronger uplink. Additionally, the performance degradation due to downlink power reduction can be compensated for by link adaptation.

Minimum inter-cell interference scheduling: The selection of start Physical Resource Blocks (PRB) or Resource Block Group (RBG) in the scheduler can be enhanced to reduce the inter-cell interference. This can be accomplished through restricted or randomised distributed PRB scheduling in uplink or RBG scheduling in downlink.

FDD6:

The 3510-3590 MHz band may be used for MFCN FDD systems downlink without coordination if the mean field strength of each cell produced by the base station does not exceed:

• if FDD systems are used in the neighbouring country, a value of 67 dBμV/m/5 MHz at a height of 3 m above ground level at the border line between countries and a value of 49 dBμV/m/5 MHz at a height of 3 m above ground level at a distance of 6 km inside the neighbouring country.

• if TDD systems are used in the neighbouring country, a value of 32 dBμV/m/5 MHz at a height of 3 m above ground level at the border line between countries.

TDD Downlink only scenario should be considered as FDD downlink scenario. For field strength predictions, the calculations should be made according to Appendix B. In cases of other frequency block sizes 10*log10(frequency block size / 5 MHz) should be added to the field strength values.

If neighbouring administrations wish to agree on frequency coordination based on preferential frequencies, whilst ensuring equitable treatment of different operators within a country, the Authority will add these into the mutual agreements.

As per ECC/REC (11)05 of the 26th May 2011, the cross border operation between TDD and between TDD and FDD systems, stations of IMT systems may be operated without coordination if the mean field strength produced by the cell (all transmitters within the sector) does not exceed the value of 21 dBμV/m/5 MHz at 10% time, 50% of locations at 3 metres above ground level at the border line. Adjusting this value by the ratio of the propagation attenuations in the bands, i.e., 20 × log10(3400 MHz / 2500 MHz) = 2.7 dB, the adjusted mean field strength produced by the cell (all transmitters within the sector) does not exceed the value of 23.7 dBμV/m/5 MHz.

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1https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi81bOFz6P2AhUwQUEAHe1YD IgQFnoECAIQAQ&url=https%3A%2F%2Fextranet.crasa.org%2Fzip-agm.php%3Fid%3D332&usg=AOvVaw1bVAuEnE8a2iJnP20F_b_2

2 https://www.itu.int/en/ITU-D/Projects/ITU-EC-ACP/HIPSSA/Documents/FINAL%20DOCUMENTS/FINAL%20DOCS%20ENGLISH/hcm4a_agreement.pdf.pdf

3 PowerPoint Presentation (itu.int) https://www.itu.int/en/ITU-D/Regional- Presence/AsiaPacific/Documents/Events/2017/May%20BKK/Presentations/HCM%20and%20HCM4A%20B KK%2020170504%20IB.pdf

4 Unoccupied occupied bandwidth

5 https://docdb.cept.org/download/1777

6 As per an older version of ECC/REC/ (15)01 dated 05 February 2016 (the latest version does not include this information).