Network node and method for in-field antenna calibration

A network node in a wireless communication system, the network node comprising an antenna array and a number of transceiver chipsets, the antenna array comprising a number of antenna subarrays and the antenna subarrays are arranged in a number of subarray groups, SAGs, and the number of SAGs are coupled to the number of transceiver chipsets, respectively, the network node is configured to perform a two-step calibration, the two-step calibration comprising:

• during a first step calibration:
• obtaining, at a system power-up, compensation values for the number of antenna subarrays comprised in a SAG, the compensation values representing relative phase and amplitude differences between the antenna subarrays in the same SAG for two or more subcarriers;
• and
• compensating phase and amplitude for the antenna subarrays in each SAG based on the compensation values during the system power-up;
• and
• during a second step calibration:
• estimating a channel-state information for the number of antenna subarrays in a SAG at a subcarrier based on a received signal from a user equipment, UE, the channel-state information being represented by a combined channel data matrix comprising channel data contributed from a communication channel between the network node and user equipment and channel data contributed from antenna calibration error between the number of antenna subarrays comprised in the antenna array;
• calculating a relative antenna calibration error between the number of SAGs for each SAG based on the estimated channel state information;
• and
• compensating one or both phase and amplitude for the antenna subarrays in each SAG based on the relative antenna calibration error between the number of SAGs for each SAG.

A computer storage medium storing a computer program comprising program code which, when the computer program is executed by a computer, causes the computer to carry out a method for antenna calibration for a network node, the network node comprising an antenna array and a number of transceiver chipsets, the antenna array comprising a number of antenna subarrays and the antenna subarrays are arranged in a number of subarray groups, SAGs, and the number of SAGs are coupled to the number of transceiver chipsets, respectively, the network node being configured to perform a two-step calibration, the two-step calibration comprising:

• during a first step calibration:
• obtaining, at a system power-up, compensation values for the number of antenna subarrays comprised in a SAG, the compensation values representing relative phase and amplitude differences between the antenna subarrays in the same SAG for two or more subcarriers;
• and
• compensating phase and amplitude for the antenna subarrays in each SAG based on the compensation values during the system power-up;
• and
• during a second step calibration:
• estimating a channel-state information for the number of antenna subarrays in a SAG at a subcarrier based on a received signal from a user equipment, UE, the channel-state information being represented by a combined channel data matrix comprising channel data contributed from a communication channel between the network node and user equipment and channel data contributed from antenna calibration error between the number of antenna subarrays comprised in the antenna array;
• calculating a relative antenna calibration error between the number of SAGs for each SAG based on the estimated channel state information;
• and
• compensating one or both phase and amplitude for the antenna subarrays in each SAG based on the relative antenna calibration error between the number of SAGs for each SAG.