Various embodiments disclosed herein provide for a reciprocity based channel state information acquisition scheme for frequency division duplex wireless communications systems. By converting channel state information from a traditional frequency-time domain to a Delay-Doppler domain, the channel state information feedback overhead can be reduced since the multi-path of radio propagation is reciprocal in terms of each ray and each cluster of antenna elements. Since the surrounding objects create the same multipath fading for both uplink and downlink transmissions, modeling the channel state information in the Delay-Doppler domain, and adjusting the sign of the Doppler value (negative/positive) can account for the multipath characteristics in both uplink and downlink.

Methods, systems, and devices for spectral sharing wireless systems, wherein multiple user devices share time and frequency resources for uplink and/or downlink transmissions, are described. One example method includes transmitting transmission symbols from the network station to at least one user device by processing through a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected to have the transmission symbols receivable at the at least one user device to appear as if the transmission symbols are processed by a second precoder different from the first precoder.

Facilitating sparsity adaptive feedback in the delay doppler domain in advanced networks (e.g., 4G, 5G, 6G, and beyond) is provided herein. Operations of a method can comprise determining, by a first device comprising a processor, a channel covariance matrix in a time-frequency domain based on a channel estimation associated with reference signals received from a second device. The method also can comprise decomposing, by the first device, the channel covariance matrix into a group of component matrices. Further, the method can comprise transforming, by the first device, respective matrices of the group of component matrices into respective covariance matrices in a delay doppler domain. The method also can comprise determining, by the first device, channel state information feedback in the delay doppler domain.

Noise and interference may be estimated at a user equipment (UE) in a system that may support transmissions having different transmission time intervals (TTIs). The UE may perform a channel estimation for a first set of transmissions having a first TTI based at least in part on an estimated interference from a second set of transmissions having a second TTI that is shorter than the first TTI. The UE may perform channel estimation for orthogonal frequency division multiplexing (OFDM) symbols of the first set of transmissions. The first set of transmissions may then be demodulated based at least in part on the channel estimation for the first set of transmissions. Noise and interference may also be estimated based on one or more null tones within one or more OFDM symbols of the allocated resources.

An OFDM system generates a channel estimate in the time domain for use in either a frequency domain equalizer or in a time domain equalizer. Preferably channel estimation is accomplished in the time domain using a locally generated reference signal. The channel estimator generates an initial estimate from a cross correlation between the time domain reference signal and an input signal input to the receiver and generates at least one successive channel estimate. Preferably the successive channel estimate is determined by vector addition (or subtraction) to the initial channel estimate. The at least one successive channel estimate reduces the minimum mean square error of the estimate with respect to a received signal.

MMSE-IRC receiver may be used to suppress inter-cell interference for improving the cell-edge user throughput in cellular wireless communication systems. But MMSE-IRC performance is limited by estimation errors, namely, channel estimation error and covariance matrix estimation error. It is important to have an accurate covariance matrix estimation scheme, so that maximum gain from MMSE-IRC receiver may be achieved. In order to have accurate estimation, covariance matrix may be averaged across channel bandwidth in frequency domain. A method and apparatus are disclosed that adaptively determine the averaging bandwidth employed for covariance matrix estimation based on the detected delay spread and SNR. Based on the present disclosure, the throughput performance of MMSE-IRC receiver may be improved by adaptively using suitable sub-band length in frequency domain averaging of covariance matrix estimation.

A method performed by a communication device includes generating an initial channel estimate of a channel for a current time step with a Kalman filter based on a first signal received at the communication device. The method also includes inferring, with a neural network, a residual of the initial channel estimate of the current time step. The method further includes updating the initial channel estimate of the current time step based on the residual.

Bayesian Inference based communication receiver employs Markov-Chain Monte-Carlo (MCMC) sampling for performing several of the main receiver functionalities. The channel estimator estimates the multipath channel coefficients corresponding to a signal received with fading. The symbol demodulator demodulates the received signal according to a QAM constellation, so as to generate a demodulated signal, and estimate the transmitted symbols. The decoder reliably decodes the demodulated signals to generate an output bit sequence, factoring in redundancy induced at a certain code rate. A universal sampler may be configured to use MCMC sampling for generating estimates of channel coefficients, transmitted symbols or decoder bits, for aforementioned functionalities, respectively. The samples may then be used in one or more of the receiver tasks: channel estimation, signal demodulation, and decoding, which leads to a more scalable, reusable, power/area efficient receiver.

An operating method of a communication device for providing a beamformed transmission signal to a plurality of terminals may include determining a target transmission vector based on an area restriction condition for each of the plurality of terminals, generating a beam selection matrix for selecting some of a plurality of antennas based on the target transmission vector and a beam selection condition, generating a precoding matrix based on the target transmission vector and the beam selection matrix, and generating a transmission signal based on the beam selection matrix and the precoding matrix.

Systems, apparatus, and methods for channel estimation and data detection. In one exemplary embodiment, the data is obtained in a two-phase transmission structure that alternates known data with unknown data according to a regular or otherwise pre-determined time interval. Then, the receiver iteratively updates a postulated channel, and provides a predicted channel to the next time slot. Conceptually, the exemplary techniques iteratively improve its postulates for channel condition and data over multiple time slots. More directly, instead of linear detection and decoding of a pilot for channel estimation in each time slot, the exemplary techniques described herein use postulated channel conditions to attempt data detection and use the recovered data from data detection (unknown data) to re-postulate the channel conditions, etc. until channel conditions are stable and/or the next time slot is ready for processing.