SG 4- some key areas of study -

• Sharing between:

  • non-GSO FSS networks and GSO networks
  • different non-GSO FSS networks

• Power limits

• Mitigation techniques

  • orbital avoidance
  • optimization of satellite constellation
  • satellite diversity
  • optimization of antenna patterns

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• With increasing use of NGSO satellites (in LEO), SG 4 studies sharing between NGSO networks and GSO networks that use the same frequency bands (picture 1); also between different NGSO networks. Due to the changing geometry associated with NGSO systems (satellites are moving relative to Earth and GSO), interference potential is high and the quantification of potential interference very complicated (picture 2).

• Power limits established with which NGSO systems should operate in order to protect other services but these limits are usually not enough and so …..

• Interference mitigation techniques are necessary in order to avoid unacceptable interference. [2 cases: (i) NGSO systems sharing with other networks using the GSO (e.g. FSS, BSS), (ii) between different non-GSO networks.] Examples of interference mitigation techniques are: orbital avoidance (turning off transmissions to or from a sat in the NGO when the angle between its boresight and a GSO sat falls below an agreed value); optimization of sat constellation (optimizing sat positions to provide an evenly distributed service on Earth’s surface); [adaptive power control]; satellite diversity (selection of the sat with least interference potential); [homogeneous orbits (using same parameter values for sats of different systems (e.g. power) which leads to improved efficiency)]; optimum antenna patterns at both sat and ES (e.g. low ant side-lobes); [alternate polarization].