Methods, systems, and devices for wireless communications are described. In some examples, a user equipment (UE) may receive a control message indicating a set of sampling beams defined for the UE. The UE may measure a set of received signal strengths for communications from a wireless node associated with a set of linear combinations of sampling beams from the set of sampling beams defined at the UE. The UE may calculate a set of entries of a channel covariance matrix based on the set of received signal strengths of the set of linear combinations of the sampling beams from the set of sampling beams defined for the UE. As such, the UE may communicate with the wireless node based on applying a set of beam weights to an antenna array of the UE. In some examples, the set of beam weights may be based on the channel covariance matrix.

A machine learning based method for channel estimation for a multiple-input multiple-output, MIMO, system, the method including receiving a measured signal y[k] at a receiver of the system; finding subcarriers k of the measured signal y[k]; estimating, with a convolutional neural network, CNN, channel amplitudes ĝ[k] of the measured signal y[k]; reconstructing a channel Ĥ[k], between the receiver and a transmitter of the system, based on the channel amplitudes ĝ[k] and a low resolution whiten measurement matrix Y.sub.w; and adjusting a parameter of the system based on the reconstructed channel Ĥ[k]. The channel amplitudes ĝ[k] are simultaneously estimated by the CNN.

A control device for a wireless communication system is configured to obtain a first channel estimation for a first client device and a second channel estimation for a second client device, to allocate a common resource block (RB) for concurrent wireless transmission between a first network node and the first client device using a first radio access technology (RAT) and between a second network node and the second client device using a second RAT based on the first channel estimation and the second channel estimation. The control device is further configured to allocate a first precoder for the common RB for the first client device and a second precoder for the common RB for the second client device. The first precoder and the second precoder are configured for spatially multiplexing the concurrent wireless transmission.

A time-frequency block-sparse channel estimation method based on compressed sensing includes the following steps. Step 1: A channel model is established. Step 2: According to the channel model obtained in Step 1, a sparse signal estimation value is solved by a compressed sensing method to further calculate an index set. Step 3: According to the index set obtained in Step 2, a channel matrix estimation value is solved. The method provides a generalized block adaptive gBAMP algorithm, which uses time-frequency joint block sparsity of a massive MIMO system to further optimize selection of an index set in an algorithm iteration process to improve stability of the algorithm. Then, without a specified threshold parameter, based on an F norm, an adaptive iteration stop condition is determined based on a residual, and the validity of the method is proved.

An operation method of a base station in a time division duplex communication system includes: a step for setting a time period in which a terminal can transmit an uplink in a downlink period; a step for generating a sparse vector signal including information about the time period; and a step for transmitting the sparse vector signal to the terminal. In addition, an operation method of the terminal in the time division duplex communication system includes: a step for receiving a part of a sparse vector signal from the base station; a step for recovering the received sparse vector signal by compressed sensing; and a step for transmitting uplink data in a time period instructed in a downlink period based on the basis of the recovered signal.

A method for estimating Multiple Input Multiple Output, MIMO, channel state information for a radio link between a first radio node including a number N, N≥2, of receiving antenna ports and a second radio node including a number M, M≥2, of transmitting antenna ports. The method includes obtaining partial channel state information from a reference signal transmitted by a number X, 1≤X<M, of said transmitting antenna ports and received by all of said receiving antenna ports, said partial channel state information providing a measure for the N×X propagation channels between all of said receiving antenna ports and said transmitting antenna ports. Also disclosed are corresponding devices and computer programs. Also disclosed is a method for controlling transmission based on estimated channel state information.

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 method for controlling a combined waveform, representing a combination of at least two signals having orthogonal frequency multiplexed signal components, comprising: receiving information defining the at least two signals; transforming the information defining each signal to a representation having orthogonal frequency multiplexed signal components, such that at least one signal has at least two alternate representations of the same information, and combining the transformed information using the at least two alternate representations, in at least two different ways, to define respectively different combinations; analyzing the respectively different combinations with respect to at least one criterion; and outputting a respective combined waveform or information defining the waveform, representing a selected combination of the transformed information from each of the at least two signals selected based on the analysis.

The present disclosure provides communication apparatus and communication method for channel estimation. The communication apparatus comprises a transmitter, which in operation, transmits a physical layer protocol data unit (PPDU) to one or more other communication apparatus in a multiple-input multiple-output (MIMO) wireless network, the PPDU including a long training field (LTF) that facilitates the one or more other communication apparatus to estimate respective channels for respective communications with the communication apparatus; and a controller, which in operation, establishes the number of LTF symbols (NLTF) for generating the LTF in the PPDU, wherein the NLTF depends on a maximum value (NSTSMAX) of the number of space-time streams for each resource unit (RU) in the PPDU.

Techniques are described for carrier frequency offset (CFO) and channel estimation of orthogonal frequency division multiplexing (OFDM) transmissions over multiple-input multiple-output (MIMO) frequency-selective fading channels. A wireless transmitter forms blocks of symbols by inserting training symbols within two or more blocks of information-bearing symbols. The transmitter applies a hopping code to each of the blocks of symbols to insert a null subcarrier at a different position within each of the blocks of symbols, and a modulator outputs a wireless signal in accordance with the blocks of symbols. A receiver receives the wireless signal and estimates the CFO, and outputs a stream of estimated symbols based on the estimated CFO.