An apparatus includes a first communication device with multiple antennas, operably coupled to a processor and configured to access a codebook of transformation matrices. The processor generates a set of symbols based on an incoming data, and applies a permutation to each of the symbols to produce a set of permuted symbols. The processor transforms each of the permuted symbols based on at least one primitive transformation matrix, to produce a set of transformed symbols. The processor applies, to each of the transformed symbols, a precode matrix selected from the codebook of transformation matrices to produce a set of precoded symbols. The codebook of transformation matrices is accessible to a second communication device. The processor sends a signal to cause transmission, to the second communication device, of multiple signals, each representing a precoded symbol from the set of precoded symbols, each of the signals transmitted using a unique antenna from the plurality of antennas.

Aspects of the disclosure relate to a multi-antenna wireless user equipment (UE) calculating a covariance matrix corresponding to a covariance of signals received from each of its antennas. The UE further calculates the eigenvectors of the covariance matrix, and transmits feedback including information corresponding to the eigenvectors. Based on this information, a base station can determine to alter a number of beams for transmitting information to the UE, efficiently improving the reliability of transmission to the UE. Other aspects, embodiments, and features are also claimed and described.

A method of generating channel estimates of a communication channel in an OFDM system includes receiving reference symbols from at least one time-frequency observation block of a predetermined block size infrequency and time. Subspace-transformed reference symbols are generated from the received reference symbols. The subspace-transformed reference symbols are subspace filtered to generate a channel estimate for a communication channel target time. A latency between a communication channel time instant of a currently received reference symbol and the communication channel target time is smaller than the observation block size in time.

Device, methods and systems for aspects of channel estimation for orthogonal time frequency space (OTFS) modulation in wireless systems are described. In an aspect, a method for wireless communication may include receiving, using multiple receive antennas, from a number of user devices, non-orthogonal pilots wherein at least some transmissions of the non-orthogonal pilots from GT different user devices overlap in at least some time and frequency resources, estimating individual pilots from the number of user devices by computing a pilot separation filter for each antenna, and estimating the wireless channel at time and frequency resources used by the non-orthogonal pilots by filtering the receiving signal at the multiple receiver antennas.

Embodiments of a method in a base station for precoding a downlink transmission are disclosed. In some embodiments, the method comprises obtaining, for a time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to a wireless device and projecting the estimate of the channel matrix onto one or more sets of spatial orthonormal functions, thereby obtaining respective sets of coefficients. The method further comprises, for each set of spatial orthonormal functions, filtering the set of coefficients for the time instant k based on a filtering parameter that is specific to a downlink channel to be transmitted. The method further comprises generating beamforming weights using the filtered set of coefficients for at least one of the sets of spatial orthonormal functions, and precoding the downlink channel using the beamforming weights.

A method for estimating angle of arrival (AoA) of signals in a wireless communication system applied in an apparatus can estimate multiple AOAs of multiple paths on one channel tap using a transmitting scheme of beamformed multiple transmissions at the transmitting side. In the transmitting scheme, the equivalent channels for paths with multiple AoAs can be viewed as random, and a subspace-based algorithm is applied for AoA estimation.

An apparatus implemented in an access point (AP) participates in joint soundings together with one or more other APs in a joint multi-AP (JMAP) configuration to receive joint feedbacks from a plurality of stations (STAs) responding to the joint soundings. The apparatus then performs transmissions in a coordinated multi-AP (CMAP) configuration with the one or more other APs or in a single-AP configuration with no other AP based on the joint feedbacks received while in the JMAP configuration.

A wireless communication method includes receiving, by a first wireless device during a training phase, reference tones using a first number of resource elements from a transmitter of a second wireless device, wherein the first wireless device comprises multiple receiving antennas, estimating, by the first wireless device, from the receiving the reference tones, a second order statistics of wireless channels between the multiple receiving antennas and the transmitter of the second wireless device, and performing channel estimation, during an operational phase subsequent to the training phase, using the second order statistics and reference tones received on a second number of resource elements, wherein the second number is less than the first number.

A channel state information reporting method and apparatus are described. The method can include a terminal device obtaining first indication information and sending the first indication information to a network device. The network device receives the first indication information, where the first indication information indicates a differential value between channel state information of a first antenna port set and channel state information of a second antenna port set. The first antenna port set includes x antenna ports of the terminal device, the second antenna port set includes m antenna ports of the terminal device, and the first antenna port set is different from the second antenna port set. The channel state information reporting method and apparatus in embodiments of this application help improve accuracy of channel state information obtained by a network device, and improve data transmission performance.

A communication device for providing an explicit channel state information, CSI, feedback in a wireless communication system includes a transceiver to receive, from a transmitter a radio signal via a radio time-variant frequency MIMO channel, the radio signal including downlink reference signals according to a reference signal configuration, and downlink signals including the reference signal configuration, and a processor. The processor estimates the CSI using measurements on the downlink reference signals of the radio channel according to the reference signal configuration over one or more time instants/slots, constructs a frequency-domain channel tensor using the CSI estimate, performs a higher-order principal component analysis, HO-PCA, on the channel tensor, identifies a plurality of dominant principal components of the channel tensor, thereby obtaining a compressed channel tensor, and reports to the transmitter the explicit CSI including the dominant principal components of the channel tensor.