An iterative two dimension equalizer usable in a receiver of orthogonal time frequency space (OTFS) modulated signals is described. In one configuration of the equalizer, a forward path generates, from received time-frequency domain samples and a channel estimate, estimates of data bits and likelihood numbers associated with the estimates of data bits, generated by delay-Doppler domain processing. In the feedback direction, the estimates of data bits are used to generate symbol estimates and autocorrelation matrix estimate in the time domain. In another configuration, a soft symbol mapper is used in the feedback direction for directly generating the feedback input symbol estimate without having to generate estimates of data bits.

A method includes: generating a trellis; generating one or more predicted symbols using a first non-linear model; computing and saving two or more branch metrics using a priori log-likelihood ratio (LLR) information, a channel observation, and the one or more predicted symbols; if alpha forward recursion has not yet completed, generating alpha forward recursion state metrics using a second non-linear model; if beta backward recursion has not yet completed, generating beta backward recursion state metrics using a third non-linear model; if sigma forward recursion has not yet completed, generating sigma forward recursion state metrics using the branch metrics, the alpha state metrics, and the beta backward recursion state metrics; generating extrinsic information comprising a difference of a posteriori LLR information and the a priori LLR information; computing and feeding back the a priori LLR information; and calculating the a posteriori LLR information.

A method for detecting a sent sequence, a receiver, and a receiving device in order to simplify an algorithm for detecting a sent sequence and improve detection efficiency. The method for detecting a sent sequence includes determining a maximum possible candidate value of each element in N elements of a received element sequence to obtain N maximum possible candidate values, where N is a positive integer, determining state sequences corresponding to the N maximum possible candidate values as reserved sequences to obtain N groups of reserved sequences, performing likelihood computation on the N groups of reserved sequences, and setting a reserved sequence that is in the N groups of reserved sequences and is most consistent with the element sequence as a detected sent sequence.

A method and apparatus for adapting, in parallel, two operating parameters associated with an equalizer circuit is disclosed. A control circuit may be configured to initialize a first operating parameter to an initial value, and modify a second operating parameter based upon the initial value of the first parameter. In response to determining a peak amplitude of an output signal of the equalizer circuit is less than a threshold value, the control circuit may be further configured to select a new value for the first operating parameter and adapt, in response to the change in the first operating parameter, the second operating parameter based on a performance metric of the equalizer circuit.

Provided are a sub-carrier estimation method in a multi-carrier communication system and an apparatus. The method includes: receiving a data frame transmitted by a transmitting end, and extracting a training sequence from the data frame; performing fast Fourier transform operation on the training sequence and a preset reference sequence, respectively, to obtain frequency domain data of the training sequence and frequency domain data of the reference sequence, and conjugately multiplying the two kinds of frequency domain data; extracting real part of conjugate multiplication result; averaging values in each column of an MN array, respectively, to obtain an output array of 1 row and N columns; and estimating, according to the value in each column of the output array of 1 row and N columns, whether valid data is transmitted over N sub-carriers corresponding to the output array of 1 row and N columns.

Maximum likelihood bit-stream generation and detection techniques are provided using the M-algorithm and Infinite Impulse Response (IIR) filtering. The M-Algorithm is applied to a target input signal X to perform Maximum Likelihood Sequence Estimation on the target input signal X to produce a digital bit stream B, such that after filtering by an IIR filter, the produced digital stream Y produces an error signal satisfying one or more predefined requirements. The predefined requirements comprise, for example, a substantially minimum error. In an exemplary bit detection implementation, the target input signal X comprises an observed analog signal and the produced digital stream Y comprises a digitized output of a receive channel corresponding to a transmitted bit stream. In an exemplary bit stream generation implementation, the target input signal X comprises a desired transmit signal and the produced digital stream Y comprises an estimate of the desired transmit signal.

Methods and apparatuses for direct sequence detection can receive an input signal over a communication channel. Next, the input signal can be sampled based on a clock signal to obtain a sampled voltage. A set of reference voltages can be generated based on a main cursor, a set of pre-cursors, and a set of post-cursors associated with the communication channel. Each generated reference voltage in the set of reference voltages can correspond to a particular sequence of symbols. A sequence corresponding to the sampled voltage can be selected based on comparing the sampled voltage with the set of reference voltages.

An iterative two dimension equalizer usable in a receiver of orthogonal time frequency space (OTFS) modulated signals is described. In one configuration of the equalizer, a forward path generates, from received time-frequency domain samples and a channel estimate, estimates of data bits and likelihood numbers associated with the estimates of data bits, generated by delay-Doppler domain processing. In the feedback direction, the estimates of data bits are used to generate symbol estimates and autocorrelation matrix estimate in the time domain. In another configuration, a soft symbol mapper is used in the feedback direction for directly generating the feedback input symbol estimate without having to generate estimates of data bits.

A method for receiving, by a terminal, a signal on the basis of a non-orthogonal multiple access scheme in a wireless communication system comprises the steps of: receiving, from a base station, control information including information on a codebook selected for the terminal among pre-defined codebooks for non-orthogonal multiple access and information on a codeword selected from the selected codebook; receiving, from the base station, data for the terminal according to scheduling of the control information; and detecting data for the terminal by performing a multi-user detection (MUD) scheme on the basis of the information on the selected codebook and the information on the selected codeword.

A method and apparatus for adapting, in parallel, two operating parameters associated with an equalizer circuit is disclosed. A control circuit may be configured to initialize a first operating parameter to an initial value, and modify a second operating parameter based upon the initial value of the first parameter. In response to determining a peak amplitude of an output signal of the equalizer circuit is less than a threshold value, the control circuit may be further configured to select a new value for the first operating parameter and adapt, in response to the change in the first operating parameter, the second operating parameter based on a performance metric of the equalizer circuit.