A channel matrix representing characteristics of a multi-path channel between a transmitter device (210) equipped with multiple transmitter antennas (211, 212, 213, 214, 215) and a receiver device (220, 230, 240) equipped with multiple receiver antennas (221, 222, 231, 232, 241, 242) is determined. The channel matrix is organized in a first number of channel vectors each associated with a different one of the multiple receiver antennas (221, 222, 231, 232, 241, 242). The channel vectors are combined to a smaller second number of linear combinations of the channel vectors and a reduced channel matrix is composed from the linear combinations of the channel vectors. A precoding matrix is determined based on the reduced channel matrix, and multi-antenna transmission by the transmitter device is controlled based on the determined precoding matrix.

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.

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.

Methods and apparatus are disclosed for searching and tracking intercell interference in communication networks. In an exemplary embodiment, a method is provided that includes operations of receiving a noise covariance matrix and generating a beam sub-space from the noise covariance matrix. The beam sub-space includes one or more sub-space beams. The method also includes determining a set of selected sub-space beams having energy levels that exceed a threshold, calculating an Eigenvector decomposition for the set of selected sub-space beams to identify an Eigenspace of interference energy, and tracking the Eigenspace over time.

Embodiments of a method and an apparatus for beamforming are disclosed. In an embodiment, a method for beamforming involves transmitting, by a beamformer to a beamformee, a sounding packet that includes training symbols, receiving, at the beamformee, the sounding packet that includes the training symbols, deriving, at the beamformee, channel estimates from the training symbols included in the sounding packet, computing, at the beamformee, a feedback matrix from the derived channel estimates, transmitting, by the beamformee to the beamformer, a packet that includes two sets of symbols, where the feedback matrix is applied to at least one of the two sets of symbols, receiving, at the beamformer, the packet that includes the two sets of symbols, and operating the beamformer according to the two sets of symbols included in the packet.

A processor coupled to a first communication device produces and transmits a first encoded vector and a second encoded vector to a second communication device via a communication channel that applies a channel transformation to the encoded vectors during transmission. A processor coupled to the second communication device receives the transformed signals, constructs a matrix based on the transformed signals, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. A first symbol of the second encoded vector and a second symbol of the second encoded vector are sent to the first communication device for identification of the message.

This disclosure provides methods, devices and systems for providing channel feedback for multiple spatial streams. In some implementations, the techniques involve generating distinct channel estimates for different respective sets of orthogonal spatial streams. In some implementations, the orthogonality of the different sets of orthogonal spatial streams enables the beamformee to distinguish the spatial streams to provide the separate channel estimates. The beamformee may then determine separate correlations for the different respective sets of spatial streams. In some implementations, the beamformee combines the correlations to determine an average correlation for each of a number of sets of frequency tones. The beamformee may then perform an eigenvalue decomposition on a tone-by-tone basis based on the respective average correlation and the channel estimate obtained for the tone. Because the eigenvalue decomposition may be performed on each of the two sets of spatial streams separately, the complexity involved with performing each eigenvalue decomposition is greatly reduced.

Embodiments of this application disclose a channel estimation method and apparatus, and relate to the field of communications technologies. One example method include: generating and sending indication information, where the indication information is used to indicate L space-frequency basis vectors for constructing an M×N-dimensional space-frequency vector; the space-frequency vector includes M N-dimensional precoding vectors, each precoding vector is used in one of M frequency bands, and the space-frequency vector is generated by performing a weighted combination on L space-frequency component vectors; each of the L space-frequency component vectors is a vector including M×N elements that are in one of the L space-frequency basis vectors, and each of the L space-frequency basis vectors is an N.sub.f×N-dimensional vector; the space-frequency basis vector is a three-dimensional oversampled (DFT) vector; and L≥2, N.sub.f≥M≥1, N≥2, and L, M, N, and N.sub.f are all integers.

An operating method of a power estimation apparatus comprising a fixed antenna and a mobile antenna may comprise: a first operation of obtaining N measurement values by receiving a signal from signal sources using the fixed antenna and the mobile antenna that moves at a speed v from a first point to an Nth point; a second operation of generating a two-dimensional (2D) data collection set comprising N×M measurement values, by repeating the first operation M times; applying an approximation singular value decomposition (SVD) algorithm to the 2D data collection set; and obtaining information of the signal sources based on an application result of the approximation SVD algorithm, wherein N and M are natural numbers.

A communication device is provided that includes a baseband circuit and a transmitter configured to transmit a first signal and a projected signal. The baseband circuit is configured to determine the projected signal based on an estimated signal state information such that an energy of a shaped projected signal is smaller than an energy of a shaped signal. The estimated signal state information is an estimate of a signal state information based on the first signal and a received signal that is received by a receiver of the second communication device. The shaped projected signal is the projected signal received by the receiver of the second communication device and filtered by a filter of the second communication device. The shaped signal is the received signal filtered by the filter of the second communication device.