Dynamic reconfiguration of CSI-RS resources for CSI reporting is described for full dimension multiple input, multiple output (FD-MIMO) systems. While a larger number of channel state information (CSI) reference signal (CSI-RS) resources with independent resource configuration are configured and associated with a CSI process, only a subset of resources that are activated by additional signaling are used for CSI measurement and reporting. The set of activated CSI-RS resources may include only a single CSI-RS resource. Both periodic and aperiodic CSI reporting may then be based on the same set of the activated CSI-RS resources. Medium access control (MAC) control elements may be used to provide activation/deactivation of the CSI-RS resources. Additionally, CSI reporting may be based on both the activated CSI-RS resources and the associated number of antenna ports.

Systems and methods are described for radio frequency (RF) calibration in a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”) exploiting uplink/downlink channel reciprocity. The RF calibration is used to compute open-loop downlink precoder based on uplink channel estimates, thereby avoiding feedback overhead for channel state information as in closed-loop schemes. For example, a MU-MAS of one embodiment comprises a wireless cellular network with one or multiple beacon stations, multiple client devices and multiple distributed antennas operating cooperatively via precoding methods to eliminate inter-client interference and increase network capacity.

Systems and methods are described for radio frequency (RF) calibration in a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”) exploiting uplink/downlink channel reciprocity. The RF calibration is used to compute open-loop downlink precoder based on uplink channel estimates, thereby avoiding feedback overhead for channel state information as in closed-loop schemes. For example, a MU-MAS of one embodiment comprises a wireless cellular network with one or multiple beacon stations, multiple client devices and multiple distributed antennas operating cooperatively via precoding methods to eliminate inter-client interference and increase network capacity.

Methods, systems, and devices for wireless communication are described. In multi-user (MU) multiple-input multiple-output (MIMO) wireless communications systems, a base station may perform signaling to indicate information related to ports assigned to one or more UEs. The base station may also signal information regarding ports shared with other UEs, which the UE may use when performing channel estimation. In some examples, the base station may signal a number of ports used per sub-band to the UE or a number of demodulation reference signal (DMRS) ports used by the UE. The base station may signal a sub-set of a total number of ports that are shared by other UEs overlapping with the resource allocation of the UE. The signaling may indicate a number of combs used by the base station in the resource allocation for the UE.

Methods, systems, and devices for wireless communication are described. In multi-user (MU) multiple-input multiple-output (MIMO) wireless communications systems, a base station may perform signaling to indicate information related to ports assigned to one or more UEs. The base station may also signal information regarding ports shared with other UEs, which the UE may use when performing channel estimation. In some examples, the base station may signal a number of ports used per sub-band to the UE or a number of demodulation reference signal (DMRS) ports used by the UE. The base station may signal a sub-set of a total number of ports that are shared by other UEs overlapping with the resource allocation of the UE. The signaling may indicate a number of combs used by the base station in the resource allocation for the UE.

A user matching and power distribution methods for a MIMO-NOMA downlink communication system is provided. The user matching method includes: dividing all users into a strong user group and a weak user group according to a channel gain sorting result; and sequentially selecting a user in the strong user group, calculating a correlation coefficient between the user and each user in the weak user group, selecting a weak user with the highest correlation coefficient as a weak user in a cluster where the strong user is located, and excluding matched users from respective user groups, until the matching between all strong users and weak users are completed. The present invention enables weak users in a cluster to experience less inter-cluster interference in scenarios where the channel correlation between users is relatively low, thereby improving the total throughput of the communication system.

Certain aspects relate to methods and apparatus for wireless communication. The apparatus generally includes a first interface configured to output one first frame for transmission to solicit CSI feedback from each of one or more first wireless nodes associated with a first BSS and from each of one or more second wireless nodes associated with a second BSS, a second interface configured to obtain the CSI feedback solicited from the first and second wireless nodes, and a processing system configured to generate data frames for the first wireless nodes based on the CSI feedback solicited from the first wireless nodes, and one or more nulling frames based on the CSI feedback solicited from the second wireless nodes. The first interface is configured to simultaneously output the data frames for beamformed transmission to the first wireless nodes, and the nulling frames for beamformed transmission to the second wireless nodes.

Certain aspects relate to methods and apparatus for wireless communication. The apparatus generally includes a first interface configured to output one first frame for transmission to solicit CSI feedback from each of one or more first wireless nodes associated with a first BSS and from each of one or more second wireless nodes associated with a second BSS, a second interface configured to obtain the CSI feedback solicited from the first and second wireless nodes, and a processing system configured to generate data frames for the first wireless nodes based on the CSI feedback solicited from the first wireless nodes, and one or more nulling frames based on the CSI feedback solicited from the second wireless nodes. The first interface is configured to simultaneously output the data frames for beamformed transmission to the first wireless nodes, and the nulling frames for beamformed transmission to the second wireless nodes.

A method, system and apparatus are disclosed. According to one or more embodiments, a network node is provided. The network node includes processing circuitry configured to receive channel state information, CSI, from each of a plurality of wireless devices and determine at least one null space based on the received CSI from each of the plurality of wireless devices. The processing circuitry is further configured to determine a common precoding matrix index, PMI, where a common beamforming vector is not in the at least one null space and cause a multicast broadcast transmission to the plurality of wireless devices using at least the common PMI.

Provided are a method of transmitting a dedicated reference signal (DRS), a method of receiving a DRS, and a feedback method of a terminal. The method of transmitting a DRS includes determining a DRS transmitting resource for at least one terminal which is a target of transmission, and transmitting the DRS using the determined transmission resource and notifying the terminal of information about layer used by the terminal. The method of receiving a DRS includes determining a DRS receiving resource, receiving information about layer used by a terminal from a serving cell base station, and receiving the DRS for the terminal using the determined reception resource and the information about layer. Accordingly, a terminal can find the position and sequence of its DRS. In particular, in the case of multi-user multiple input multiple output (MU-MIMO) or joint scheduling, it is possible to prevent or remove signal interference using the DRS of another terminal.