A method includes estimating an uplink channel for a terminal device, based on an amount of antennas used by an access node for transmitting signals to the terminal device, antennas used for receiving the transmitted signals at the terminal device, and sub-bands used for transmitting the signals. Based on the estimation, a channel covariance matrix is determined for a precoder comprised in a transmitter of the access node by determining a limited number of elements of a full dimensional channel covariance matrix, which is different than the channel covariance matrix. The limited number of elements are elements corresponding to i-th row and j-th column of the channel covariance. Correlation computation is performed for the limited number of elements. Elements of the full-dimensional channel covariance matrix that are excluded from the limited number of elements are determined and set to be zero. Precoding is performed using the determined channel covariance matrix.

Multi-stage distributed beamforming for distributed mosaic wireless networks is provided. Embodiments described herein present systems, devices, and methods that provide increased range, data rate, and robustness to interference and jamming. A distributed mosaic wireless network includes a transmitter, a receiver, and one or more distributed clusters of radios referred to herein as mosaics or relay mosaics. Each mosaic consists of several distributed, cooperative radio transceivers (e.g., mosaic nodes) that relay a signal sent by the transmitter towards the receiver. In some embodiments, a single-stage beamforming technique is implemented whereby the transmitter sends a signal to a first mosaic, which then relays this signal by beamforming to the receiver. In some embodiments, a multi-stage beamforming technique is implemented whereby the transmitter sends a signal to a first mosaic, which then relays this signal by beamforming to a second mosaic, which then relays this signal by beamforming to the receiver.

An angular domain channel estimation method based on matrix reconstruction for a symmetrical nonuniform array is a combined two-stage channel estimation and channel equalization scheme provided based on an SNLA model. In a first stage, a matrix reconstruction method is used to estimate a path AOA, and compared with traditional channel estimation based on ULA, the matrix reconstruction method achieves a higher resolution ratio. In a second stage, an LS method is used to obtain a path gain. According to the angular domain channel estimation method, a mean square error of channel estimation, a bit error of data transmission and complexity of a traditional scheme are significantly reduced. A simulation result indicates that compared with the traditional method, the angular domain channel estimation method can achieve a lower MSE and BER.

Methods and apparatuses for canonical model (CM) based channel status information enhancement. A base station includes a transceiver configured to receive a reference signal from a user equipment (UE) and a processor operably coupled to the transceiver. The processor is configured to perform a linear transformation based on the received reference signal, select a basis set based on the linear transformation, select a set of kernels based on the selected basis set and the linear transformation, and reconstruct a channel based on the selected set of kernels.

The present disclosure relates in general to telecommunications. In one of its aspects, the technology presented herein concerns a method, implemented in an Access Point (AP), for transmitting data intended for a terminal in a cell-free massive Multiple-Input and Multiple-Output (MIMO) communications system. The AP is grouped into a cluster together with other APs and the cluster operates autonomously. The cluster is connected to, and managed by, one Central Processing Unit (CPU). A message that the AP is selected to serve the terminal and data intended for said terminal are received from the CPU. Power control is independently conducted, exclusively considering the terminals that are served by the AP itself. Thereafter, said intended data is transmitted to the terminal.

An angular domain channel estimation method based on matrix reconstruction for a symmetrical nonuniform array is a combined two-stage channel estimation and channel equalization scheme provided based on an SNLA model. In a first stage, a matrix reconstruction method is used to estimate a path AOA, and compared with traditional channel estimation based on ULA, the matrix reconstruction method achieves a higher resolution ratio. In a second stage, an LS method is used to obtain a path gain. According to the angular domain channel estimation method, a mean square error of channel estimation, a bit error of data transmission and complexity of a traditional scheme are significantly reduced. A simulation result indicates that compared with the traditional method, the angular domain channel estimation method can achieve a lower MSE and BER.

A receiver for receiving OFDM signals with a channel estimation means is disclosed. The channel estimation means estimates the channel at pilot locations by least squares estimation at pilot locations in subcarriers that include pilot symbols. Using the estimates of the channel at pilot locations, it estimates the channel for each subcarrier containing the pilot symbols, using linear interpolation. It estimates the channel for the sub-frame by interpolating the channel estimates estimated for the sub-carriers including the pilot locations, by using Minimum Mean Square Estimation that uses an auto-covariance matrix. An auto-covariance matrix generator generates the auto-covariance matrix. It generates an auto-covariance matrix based on, an extended cyclic prefix, an estimate of the channel in the time domain estimated by performing an Inverse Discrete Fourier Transform on the channel estimated as above and an average tap power calculated based on the estimate of the channel in the time domain.

This application provides a method for obtaining downlink channel information. The method includes: performing precoding weighting on M CSI-RSs of each of N sub-cycles, where each sub-cycle is a quantity of measurement pilot subframes for bearing and transmitting the M CSI-RSs; sending the M weighted CSI-RSs to UE; receiving M PMIs and M CQIs that are sent by the UE and that correspond to the M CSI-RSs, where the M PMIs and the M CQIs are obtained by the UE by separately measuring the M weighted CSI-RSs based on a set a rank 1 precoding codebooks corresponding to the predetermined antenna quantity; obtaining M signal-to-noise ratios of a downlink channel of the UE according to the M CQIs; obtaining M equivalent codebooks according to the M PMIs and weights of the precoding weighting; and obtaining a covariance matrix according to the M signal-to-noise ratios and the M equivalent codebooks.

Disclosed are: a MIMO transmitter communication method estimating a channel correlation for REs on the basis of information regarding channels of REs contained in a resource region allocable to a MIMO receiver, allocating a part of the resource region as a resource for the MIMO receiver in consideration of the estimated channel correlation, and transmitting a downlink signal to the MIMO receiver through the allocated resource; and a MIMO transmitter.

The present disclosure relates to methods and devices for mitigating inter-cluster interference in clusters where one or more network nodes are transmitting in coordination using several transceiver antennas. In particular the disclosure relates to improved precoder algorithms to be used for coordinated multipoint transmission applications. The disclosure also relates to corresponding computer programs. The disclosure proposes a method, performed in a coordination unit in a communication system, of mitigating inter-cluster interference, wherein the coordination unit is configured to coordinate transmissions in a cluster comprising one or more wireless devices and one or more network nodes, wherein the one or more network nodes are transmitting in coordination to the wireless devices in the cluster using several transceiver antennas. The method comprises receiving, for each transceiver antenna in each of the one or more network nodes, a signal comprising pre-defined sounding sequences transmitted by the one or more wireless devices of the cluster and sounding channel interference from one or more wireless devices outside the cluster. The method further comprises estimating, from the received signal, the sounding channel interference from the wireless devices outside the cluster. The method also comprises determining downlink precoder weights, for use when transmitting from the transceiver antennas of the cluster, using the estimated sounding channel interference from the one or more wireless devices outside the cluster.