Passive intermodulation aware beamforming

1. An apparatus, comprising:

at least one processor; and

at least one non-transitory memory

storing instructions that when executed by the at least one processor, cause the apparatus to:

for each beam direction of a set of beam directions of an antenna array of a communication system, determining a level of a passive intermodulation signal at a receiver of the communication system, the passive intermodulation signal being caused by a set of signals transmitted with the antenna array in the beam direction;

identifying one or more beam directions of the set of beam directions whose determined passive intermodulation level is higher than a predefined threshold; and

adapting a beamforming of signals in at least part of the identified beam directions to mitigate the passive intermodulation level at the receiver,

wherein the signals comprise signalling with a receiving device having a direction that coincides with at least one direction of the identified one or more beam directions, and

wherein the adapting comprises generating one or more beam directions which are closest directions to the direction of the receiving device and which do not coincide with the at least one direction of the identified beam directions.

2. The apparatus of claim 1 , wherein the at least one non-transitory memory is storing instructions that when executed by the at least one processor, cause the apparatus to perform adapting beamforming settings of transmitting antenna elements of the antenna array in accordance with the generated directions, the at least part of the identified beam directions being the one direction of the identified beam directions.

3. The apparatus of claim 2 , wherein the one or more generated beam directions are beam directions of a first beam of a subset of the signals to the receiving device, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting further comprising adapting beamforming settings of the transmitting antenna elements for forming a second beam for another subset of the signals to another receiving device, the second beam having a direction different from the generated directions.

4. The apparatus of claim 2 , the signals further comprising uplink signals from a transmitting device, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting further comprising adapting beamforming settings of receiving antenna elements of the antenna array for forming a beam having a direction of the transmitting device different from the one direction of the identified beam directions.

5. The apparatus of claim 1 , the signals comprising downlink signals to the receiving device, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting comprising adapting beamforming settings of transmitting antenna elements of the antenna array for notching a beam in each direction of the at least part of the identified beam directions.

6. The apparatus of claim 5 , the at least part of the identified beam directions being a direction that coincides with the direction of the receiving device.

7. The apparatus of claim 5 , the at least part of the identified beam directions being a direction that does not coincide with the direction of the receiving device and that is one of: a closest direction to the direction of the receiving device or a direction having a highest determined passive intermodulation level.

8. The apparatus of claim 5 , the signals further comprising uplink signals from a transmitting device, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting further comprising adapting beamforming settings of receiving antenna elements of the antenna array for forming a beam having a direction of the transmitting device different from the at least part of the identified beam directions.

9. The apparatus of claim 1 , the signals comprising uplink signals from a transmitting device, a direction of the transmitting device does not coincide with the at least part of the identified beam directions, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting comprising adapting beamforming settings of receiving antenna elements of the antenna array for notching a beam in each direction of the at least part of the identified beam directions.

10. The apparatus of claim 9 , the at least part of the identified beam directions being a direction that does not coincide with the direction of the transmitting device and that is one of: a closest direction to the direction of the transmitting device or a direction having a highest determined passive intermodulation level.

11. The apparatus of claim 9 , the signals further comprising downlink signals to the transmitting device, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting comprising adapting beamforming settings of transmitting antenna elements of the antenna array for notching a beam in each direction of the at least part of the identified beam directions.

12. The apparatus of claim 1 , the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform selecting the at least part of the identified beam directions based on the passive intermodulation levels.

13. The apparatus of claim 1 , for each identified beam direction of the at least part of the identified beam directions, the at least one non-transitory memory storing instructions that when executed by the at least one processor, cause the apparatus to perform the adapting comprising adapting weightings of magnitudes and/or phases associated with the identified beam direction.

14. A system comprising:

an antenna array,

a receiver,

a transmitter, and

an apparatus, the apparatus being configured for:

for each beam direction of a set of beam directions of the antenna array, determining a level of a passive intermodulation passive intermodulation signal at the receiver, the passive intermodulation signal being caused by a set of signals transmitted with the antenna array in the beam direction;

identifying beam directions of the set of beam directions whose passive intermodulation level is higher than a predefined threshold; and

adapting a beamforming of signals in at least part of the identified beam directions to mitigate the passive intermodulation level at the receiver,

wherein the signals comprise signalling with a receiving device having a direction that coincides with at least one direction of the identified one or more beam directions, and

wherein the adapting comprises generating one or more beam directions which are closest directions to the direction of the receiving device and which do not coincide with the at least one direction of the identified beam directions.

15. The system of claim 14 , wherein the antenna array comprises a number of antenna elements higher than a predefined minimum number of antenna elements.

16. A method for a communication system, comprising:

for each beam direction of a set of beam directions of an antenna array of the communication system, determining a level of a passive intermodulation passive intermodulation signal at a receiver of the communication system, the passive intermodulation signal being caused by a set of signals transmitted with the antenna array in the beam direction;

identifying beam directions of the set of beam directions whose passive intermodulation level is higher than a predefined threshold; and

adapting a beamforming of signals in at least part of the identified beam directions to mitigate the passive intermodulation level at the receiver,

wherein the signals comprise signalling with a receiving device having a direction that coincides with at least one direction of the identified one or more beam directions, and

wherein the adapting comprises generating one or more beam directions which are closest directions to the direction of the receiving device and which do not coincide with the at least one direction of the identified beam directions.

17. The method of claim 16 , wherein the determining of the passive intermodulation levels and the identifying steps are performed in an offline calibration step, wherein the adapting step is performed in a real-time operation of the communication system.

18. A computer program encoded on a non-transitory computer readable medium comprising instructions stored thereon for causing an apparatus to perform at least the following:

for each beam direction of a set of beam directions of an antenna array of a communication system, determining a level of a passive intermodulation, signal at a receiver of the communication system, the passive intermodulation signal being caused by a set of signals transmitted with the antenna array in the beam direction;

identifying beam directions of the set of beam directions whose passive intermodulation level is higher than a predefined threshold; and

adapting a beamforming of signals in at least part of the identified beam directions to mitigate the passive intermodulation level at the receiver,

wherein the signals comprise signalling with a receiving device having a direction that coincides with at least one direction of the identified one or more beam directions, and

wherein the adapting comprises generating one or more beam directions which are closest directions to the direction of the receiving device and which do not coincide with the at least one direction of the identified beam directions.