A precoding method, a precoding apparatus, a Frequency Domain Equalization (FDE) method, and an FDE apparatus are provided in the embodiments of the present invention. The precoding method includes: performing offset modulation for a transmitting signal vector; calculating a precoding matrix according to the offset-modulated transmitting signal vector and a receiver decision signal vector, where the precoding matrix is used for performing precoding for the transmitting signal vector; and performing precoding for the transmitting signal vector according to the precoding matrix. Linear precoding is performed by using the offset-modulated signal on the transmitter, and therefore, the interference caused by multiple antennas and multipath propagation is reduced, the system BER is reduced, and the complexity of implementation is low.

Disclosed is a 5G or pre-5G communication system to be provided for supporting a data transfer rate higher than that of a 4G communication system, such as LTE, and subsequent systems. The present invention relates to a method for transmitting and receiving a QAM signal in a filter bank-based multicarrier communication system, and an apparatus therefor. Particularly, the present invention provides an efficient transmission and reception method and apparatus capable of obtaining high performance in the transmission of a QAM signal without intrinsic interference in a multi-path delay channel environment in a filter bank-based multicarrier communication system. Accordingly, the present invention relates to a transmission method in a filter bank-based multicarrier (FBMC) communication system, and an apparatus therefor, the method comprising the steps of: spreading each of two QAM signals divided into a plurality of groups to a plurality of signals on a frequency axis; intersecting at least one signal, which is overlapped with a spread signal of an adjacent QAM signal among the plurality of spread signals, with the spread signal of the adjacent QAM signal; filtering, by each of the plurality of groups, the plurality of spread signals of which at least one signal has been intersected; and transmitting the plurality of filtered spread signals by being overlapped on a time axis.

This disclosure relates to a 5G or a pre-5G communication system to be provided to support a higher data rate following 4G communication systems such as LTE. A method according to one embodiment of the present invention is a method for attenuating interference of a signal received in a receiver of a filter bank multicarrier (FBMC) system, the method comprising the steps of: separately extracting data and a reference signal in a received FMBC symbol; obtaining a diagonal element channel of a desired symbol through a channel estimation from the extracted reference signal; generating an interference channel matrix of a non-diagonal component of the desired symbol, a diagonal component and a non-diagonal component of an interference symbol using a channel estimated diagonal component; reconfiguring to a banded channel matrix using an interference channel matrix; and attenuating the interference contained in the extracted data using the reconfigured banded channel matrix information and filter information of a transmitter of the filter bank multicarrier system.

The present invention adopts a configuration such that when cooperative reception by a plurality of base stations is not applied, a reference signal sequence determined from a selection baseline value corresponding to the number of a sequence group allocated to a cell belonging to the device in question is selected from among a plurality of selection baseline values as a reference signal sequence for non-cooperative reception, whereas when cooperative reception by a plurality of base stations is applied, a reference signal sequence determined from one or more intermediate selection baseline values set between two adjacent selection baseline values corresponding to the number of a sequence group allocated individually to a terminal device is selected among the plurality of selection baseline values as a reference signal sequence for cooperative reception differing from the reference signal sequence for non-cooperative reception.

A multiple-input multiple-output (MIMO) receiver comprises a MIMO frequency-domain equalizer, which comprises a MMSE filter for mitigating inter-symbol interference and an adder for mitigating inter-antenna interference, a MIMO detector and a MIMO decoder for processing a received MIMO signal and for estimating transmit bits. The receiver comprises a feedback path from the decoder to the detector for providing soft-information on the transmit bits to the detector and an additional feedback path from the decoder to the MIMO frequency-domain equalizer for providing soft-information to the MMSE filter and to the adder of the equalizer.

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.

A method and structure for equalization in coherent optical receivers. Block-based LMS (BLMS) algorithm is one of the many efficient adaptive equalization algorithms used to (i) increase convergence speed and (ii) reduce implementation complexity. Since the computation of the equalizer output and the gradient of the error are obtained using a linear convolution, BLMS can be efficiently implemented in the frequency domain with the constrained frequency-domain BLMS (FBLMS) adaptive algorithm. The present invention introduces a novel reduced complexity constrained FBLMS algorithm. This new approach replaces the two discrete Fourier transform (DFT) stages required to evaluate the DFT of the gradient error, by a simple frequency domain filtering. Implementation complexity can be drastically reduced in comparison to the standard constrained FBLMS. Furthermore, the new approach achieves better performance than that obtained with the unconstrained FBLMS in ultra-high speed coherent optical receivers.

Methods, systems and devices for lattice reduction in decision feedback equalizers for orthogonal time frequency space (OTFS) modulation are described. An exemplary wireless communication method, implementable by a wireless communication receiver apparatus, includes receiving a signal comprising information bits modulated using OTFS modulation scheme. Each delay-Doppler bin in the signal is modulated using a quadrature amplitude modulation (QAM) mapping. The method also includes estimating the information bits based on an inverse of a single error covariance matrix of the signal, with the single error covariance matrix being representative of an estimation error for all delay-Doppler bins in the signal.

A method of modulating a series of input digital symbols of a first modulation scheme is provided. The method is implemented by a transmitter and includes receiving a sequential series of samples of the digital symbols in a first domain of the first modulation scheme. The first domain is one of the time domain and the frequency domain. The method further includes determining a dual of the first modulation scheme. The dual has a second modulation scheme in a second domain that is different from the first domain the second domain is the other of the time domain and the frequency domain. The method further includes applying a 90 degree rotational operation to the second modulation scheme to generate a rotational modulation format, modulating the series of digital symbols with the generated rotational modulation format, and outputting the modulated series of digital symbols to a receiver.