Method and apparatus are provided for estimating first downlink (DL) channel information of first DL channels in accordance with reference signals received on first uplink (UL) channels, the first UL channels being a subset of available UL channels, and the first DL channels corresponding to the first UL channels. Channel feedback is received for a set of DL channels, and second DL channel information is estimated in accordance with the estimated first DL channel information and the received channel feedback.

According to one aspect, a network node is provided. The network node including processing circuitry configured to: estimate a spatial spectrum associated with a plurality of wireless devices, determine active spatial directions for the plurality of wireless devices based at least on the estimated spatial spectrum, and determine Multiple User-Multiple Input Multiple Output, MU-MIMO, pairing based at least on the determined active spatial directions.

Transmission quality is improved in an environment in which direct waves dominate in a transmission method for transmitting a plurality of modulated signals from a plurality of antennas at the same time. All data symbols used in data transmission of a modulated signal are precoded by hopping between precoding matrices so that the precoding matrix used to precode each data symbol and the precoding matrices used to precode data symbols that are adjacent to the data symbol in the frequency domain and the time domain all differ. A modulated signal with such data symbols arranged therein is transmitted.

Methods are disclosed for improving communications on feedback transmission channels, in which there is a possibility of bit errors. The basic solutions to counter those errors are: proper design of the CSI vector quantizer indexing (i.e., the bit representation of centroid indices) in order to minimize impact of index errors, use of error detection techniques to expurgate the erroneous indices and use of other methods to recover correct indices.

Methods, systems, and devices for wireless communications are described. A first wireless device may receive a request for beamforming information associated with line-of-sight (LoS) multiple input multiple output (MIMO) communication from a second wireless device. The first wireless device may generate a channel estimation matrix for a channel between rectangular antenna arrays of the respective wireless devices, the channel estimation matrix including one or more quadratic terms for the LoS MIMO communication. The first wireless device may generate a first sub-matrix and a second sub-matrix based on the channel estimation matrix. The first wireless device may transmit an indication of a set of precoders for the LoS MIMO communication, the set of precoders based on a symmetry associated with the first and second sub-matrices, and may receive the LoS MIMO communication from the second wireless device based on the set of precoders.

A method and apparatus are provided in which a set of reference signals is received (2102), and a set of channel signatures for a multiple antenna communication channel is estimated (2104). Channel state information including a set of quality metrics is calculated (2106). In response to the set of quality metrics satisfying a criterion, the baseline receiver for the multiple antenna communication channel is selected (2108). In response to the set of quality metrics not satisfying the criterion, the alternative receiver for the multiple antenna communication channel is selected (2110). The selectable alternative receiver for the multiple antenna communication channel at the user equipment is based on a set of integer linear combinations, where each integer linear combination is based on at least a pair of channel signatures from the estimated set of channel signatures (2112).

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.

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.

A method of communication performed by a first apparatus with respect to a second apparatus in a wireless local area network (WLAN) system including the first apparatus and the second apparatus, includes: transmitting a null data packet (NDP) based on a first protocol standard to the second apparatus; receiving a first feedback frame including information on an estimated first channel and phase information from the second apparatus in response to the NDP; performing beamforming with respect to the second apparatus by reflecting the phase information in the information on the estimated first channel; and transmitting a beamformed physical layer protocol data unit (PPDU) to the second apparatus.

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.