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.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive a sounding reference signal (SRS) configuration that indicates a maximum number of SRS ports and whether the UE is permitted to determine an actual number of SRS ports to be used for SRS transmission that is different from the maximum number of SRS ports. The UE may determine the actual number of SRS ports to be used for SRS transmission based at least in part on the SRS configuration. The UE may transmit one or more SRSs using the actual number of SRS ports. Numerous other aspects are provided.

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 method implemented by a first device operating in a communication system includes obtaining a channel representation of a set of channels between the first device and a second device, the set of channels being over a set of subcarriers, the first device having multiple antenna ports, and the second device having one or multiple antenna ports; determining, by the first device, one or multiple communication filters in accordance with at least the channel representation; and applying, by the first device, the one or multiple communication filters to a communication on at least one of the multiple antenna ports of the first device, the communication being over the set of subcarriers.

Aspects of the disclosure relate to channel estimation and tracking in a wireless communication system. A wireless communication entity estimates a received signal utilizing any suitable process. The wireless communication entity applies a Wavelet decomposition filter to the estimated received signal to generate a channel coefficient estimate. The Wavelet decomposition filter may be configured to employ a Haar mother Wavelet. The wireless communication entity generates a prediction of a future channel estimate at a later time, by characterizing the channel according to a first-order autoregressive model of channel aging. Other aspects, embodiments, and features are also claimed and described.

An operation method of a first receiving node in a distributed communication system may comprise: receiving a signal from a transmitting node; extracting a combined signal vector from a reception signal vector corresponding to a vector of the received signal; obtaining a compressed combined signal vector by extracting a preset number T of combined signal elements from among a plurality of combined signal elements constituting the combined signal vector; quantizing the compressed combined signal vector to obtain a quantized combined signal vector; and transmitting the quantized combined signal vector to a second receiving node included in the distributed communication system.

A communication device is configured to correlate a first signal with a second signal at a designated interval, the second signal corresponding to the first signal and being received by the communication device where the other communication device transmits a signal including a pulse as the first signal, convert a correlation computation result that is a result of correlating the first signal with the second signal at the designated interval into a format including a matrix product of an expanded modal matrix and an expanded signal vector, the expanded modal matrix including a plurality of elements indicating the correlation computation result obtained when assuming that the signals are received at respective set times, the expanded signal vector being a vector including a plurality of elements, each of which indicates whether or not there is a signal received at each of the set times and amplitude and phase of the signal.

A method for enabling hybrid beamforming in a communication system including a transmitter being able to serve a plurality of receivers, wherein a frequency band comprises at least one subcarrier, wherein each receiver is associated to a set Cprec,k of analog precoding codewords, said method comprising: —for each receiver, computing (202) an analog precoding matrix FRF k associated to said receiver; said computation (202) comprising: /a/ for each subcarrier, performing (202a) a Singular Value Decomposition, SVD, on a channel matrix associated to said receiver and to said each subcarrier; /b/ for each subcarrier, determining a first decomposition matrix Vk(1) based on the relative SVD; /c/ determining (303) an analog precoding codeword which optimizes a first function g1(Vk(1), . . . , Vk(L), F) of Vk(1), . . . , Vk(L) and F, for a plurality of F E Cprec,k, wherein L denotes a number of subcarriers.

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.

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.