Control of reference signaling for calibration of a D-MIMO system

A non-transitory computer readable medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit of a control node for a distributed multiple-input multiple-output (D-MIMO) system and the computer program configured to cause execution of a method when the computer program is run by the data processing unit, the method comprising, during a calibration process with over-the-air reference signaling between at least two of a plurality of access points, the calibration process comprising a plurality of reference signaling occasions, for at least one particular reference signaling occasion:

• dynamically selecting, among the plurality of access points and based on information obtained by measurements performed during a previous reference signaling occasion, a first access point, the information obtained by measurements performed during the previous reference signaling occasion comprising one or more of:
• a respective channel coherence time for the first access point relative to each of one or more other access points among the plurality of access points;
• and
• a respective reference signaling reliability for the first access point relative to each of one or more other access points among the plurality of access points, the respective reference signaling reliability for the first access point being based on signal strength measurements performed by the first access point;
• and
• controlling the first access point to act as a reference signal transmitter during the particular reference signaling occasion.

An apparatus for a control node for a distributed multiple-input multiple-output (D-MIMO) system comprising a plurality of access points, the apparatus comprising controlling circuitry configured to cause, during a calibration process with over-the-air reference signaling between at least two access points of the plurality of access points, the calibration process comprising a plurality of reference signaling occasions, for at least one particular reference signaling occasion:

• dynamic selection, among the plurality of access points and based on information obtained by measurements performed during a previous reference signaling occasion, of a first access point, the information obtained by measurements performed during the previous reference signaling occasion comprising one or more of:
• a respective channel coherence time for the first access point relative to each of one or more other access points among the plurality of access points;
• and
• a respective reference signaling reliability for the first access point relative to each of one or more other access points among the plurality of access points, the respective reference signaling reliability for the first access point is based on signal strength measurements performed by the first access point;
• and
• control of the first access point to act as a reference signal transmitter during the particular reference signaling occasion.