Methods and systems for CSI-RS port selection for CSI-reporting

A method in a wireless device served by a network node of a wireless communication network, the method comprising:

• receiving, from the network node, a Channel State information-Reference Signal (CSI-RS) setup comprising K CSI-RS configurations,
• wherein K>1 and each CSI-RS configuration is comprising N CSI-RS ports and an antenna configuration of the network node with P antenna ports, wherein N is defined in 1<N<P and multiple of 2;
• determining a subset of Q antenna ports from the P antenna ports, wherein Q<P;
• determining whether feedback of a first type or a second type is enabled;
• if feedback of the first type is enabled, measuring channel information based on the reference signals associated with the subset of antenna ports for periodic CSI reporting;
• if feedback of the second type is enabled, measuring channel information based on signals associated with the P antenna ports for aperiodic Class-A CSI reporting;
• and
• reporting the measured channel information to the network node,
• wherein each CSI-RS port in the predetermined set is associated with an identifier, and
• wherein one of the following holds:
• the identifier is explicitly stated in a feedback signal;
• the identifier is implicitly derivable from an internal structure of a feedback signal;
• and
• the identifier is implicitly derivable from a resource used for transmitting a feedback signal.

A network node comprising:

• an antenna array with controllable polarization;
• and one or more processors, the one or more processors configured to:
• select a subset of Channel State Information-Reference Signal (CSI-RS) ports from a predetermined set of P CSI-RS ports for receiving channel information,
• wherein P is an integer equal to or greater than 2,
• wherein the predetermined set of P CSI-RS ports comprises a first number P1 of CSI-RS ports with a first polarization state and a second number P2 of CSI-RS ports with a second polarization state,
• wherein the first and second polarization states are distinct, and
• wherein each CSI-RS port corresponds to a combination of a set of resource elements and an antenna port of said antenna array;
• populate the subset with Q CSI-RS ports in such manner that the ratio of CSI-RS ports respectively having the first and second polarization states is equal to the ratio of the first and second numbers;
• determine whether feedback of a first type or a second type is enabled;
• if feedback of the first type is to be enabled, transmit reference signals on CSI-RS ports from the subset of CSI-RS ports for periodic CSI reporting;
• and
• if feedback of the second type is to be enabled, transmit reference signals on CSI-RS ports from the predetermined set of CSI-RS ports for aperiodic Class-A CSI reporting,
• wherein each CSI-RS port in the predetermined set is associated with an identifier, and
• wherein one of the following holds:
• the identifier is explicitly stated in a feedback signal;
• the identifier is implicitly derivable from an internal structure of a feedback signal;
• and
• the identifier is implicitly derivable from a resource used for transmitting a feedback signal.

A wireless device configured to be served by a network node in a wireless communication network, the wireless device comprising:

• one or more processors, the one or more processors configured to:
• receive, from the network node, a Channel State information-Reference Signal (CSI-RS) setup comprising K CSI-RS configurations,
• wherein K>1 and each CSI-RS configuration is comprising N CSI-RS ports and an antenna configuration of the network node with P antenna ports, wherein N is defined in 1<N<P and multiple of 2;
• determine a subset of Q antenna ports from the P antenna ports, wherein Q<P;
• determine whether feedback of a first type or a second type is enabled;
• if feedback of the first type is to be enabled, measure channel information based on the reference signals associated with the subset of Q antenna ports for periodic CSI reporting;
• if a feedback of the second type is to be enabled, measure channel information based on the reference signals associated with the P antenna ports for aperiodic Class-A CSI reporting;
• and
• report the measured channel information to the network node,
• wherein each CSI-RS port in the predetermined set is associated with an identifier, and
• wherein one of the following holds:
• the identifier is explicitly stated in a feedback signal;
• the identifier is implicitly derivable from an internal structure of a feedback signal;
• and
• the identifier is implicitly derivable from a resource used for transmitting a feedback signal.