A handshaking process for time-reversal wireless communication is provided. A first device receives a handshake signal transmitted from a second device through multiple propagation paths, the handshake signal including a preamble and a training sequence, in which the training sequence includes a sequence of symbols known to the first and second devices. A synchronization index is determined based on the preamble, and the training sequence in the handshake signal is identified based on the synchronization index. A channel response signal is determined based on the received training sequence, and a signature waveform that is a time-reversed signal of the channel response signal is generated. A transmission signal is generated based on transmit data and the signature waveform, in which the transmit data are data configured to be transmitted to the second device.

Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, said transmission channel being represented by a channel matrix comprising column vectors, said information symbols carrying information bits, wherein the decoder comprises: a transformation unit (401) configured to determine a set of auxiliary channel matrices, each auxiliary channel matrix being determined by performing a linear combination of at least one of the column vectors of said channel matrix; a decomposition unit (407) configured to determine a decomposition of each auxiliary channel matrix into an upper triangular matrix and an orthogonal matrix; a matrix selection unit (409) configured to select at least one auxiliary channel matrix among said set of auxiliary channel matrices depending on a selection criterion related to the components of said upper triangular matrices.

The decoder being configured to determine an auxiliary signal by multiplying the transpose of the orthogonal matrix corresponding to said selected auxiliary channel matrix by said received signal, the decoder being configured to determine at least one estimate of said vector of information symbols from said auxiliary signal and from the upper triangular matrix corresponding to said selected auxiliary channel matrix by applying a decoding algorithm.

Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, said transmission channel being represented by a channel matrix, wherein the decoder comprises: an initial radius determination unit (307) configured to determine an initial radius; a symbol estimation unit (309) configured to iteratively determine a current radius to search a lattice point inside a current spherical region defined by said current radius, said current radius being initially set to said initial radius, said symbol estimation unit (309) being configured, for each lattice point found in said current spherical region, to store said lattice point in association with a metric, said symbol estimation unit (309) being further configured to update said current radius using a linear function, said linear function having a slope parameter strictly inferior to one,

The decoder being configured to determine at least one estimate of said vector of information symbols from at least one of the lattice points found by the symbol estimation unit (309).

A wireless communication method is provided in which beam training phases alternate with data transmission phases. The method includes estimating a first channel based on a signal received using one or more first training beams in a first beam training phase, and calculating, based on the estimated first channel and a first objective function corresponding to the estimated first channel, a first data beam for a first data transmission phase from the one or more first training beams in the first beam training phase, the first data transmission phase following the first beam training phase.

Methods and systems are described for adaptive channel estimation and equalization in a multicarrier communication system. In one aspect, a channel estimation in a multicarrier communication system is determined. A prediction error is determined based on a difference between the channel estimation and a reference signal. An equalization matrix is formed based on the prediction error.

A method for receiving, at a communications station which has a plurality of antennas, messages from a plurality of users in wireless communication with the communications station, comprising the steps of: (i) receiving, from the users, using the plurality of antennas, time-slotted information chunks formed from the messages of the users, wherein the information chunks are free of any encoded user-identifiers representative of the users transmitting the messages; (ii) after receiving all of the information chunks, estimating vectors representative of respective communication channels between the antennas and the users based on the received information chunks; (iii) grouping the information chunks based on the estimated vectors to form clusters of the information chunks respectively associated with the users; and (iv) recovering the messages of the users from the clusters of the information chunks.

A base station includes a channel estimator, a scheduler, and a controller. The channel estimator estimates a channel matrix with respect to each of a plurality of terminals. The scheduler determines a transmission weight corresponding to each of the plurality of terminals on the basis of the channel matrix that is estimated by the channel estimator such that the transmission weight is orthogonal to a current channel matrix and a past channel matrix of a terminal that is a subject of interference. The controller controls, when the transmission weight is determined by the scheduler, the number of samples of the current channel matrix and the past channel matrix to which the transmission weight is to be orthogonal with respect to each of the terminals.

Disclosed is a method for estimating dense multipath parameters by means of multipolarized broadband extended array responses, which includes: first transmitting multiple different transmitted signal sequences via a multipolarized antenna array, and processing received data in multiple snapshots according to the known transmitted signals, to obtain channel responses of multipolarized antenna components at all frequency points in a frequency band; extending the obtained channel response matrixes of multiple frequency points in multiple snapshots into a large two-dimensional channel response matrix; then, acquiring a delay parameter regarding multipath propagation by using a reference array element, and estimating two-dimensional departure and arrival angles by using a channel matrix subjected to frequency domain smoothing and dimensionality reduction; and afterwards, pairing the estimated departure and arrival angles, and estimating parameters such as the cross-polarization ratios, the initial phases, and the amplitudes of the sub-paths by using the estimated parameters.

A method of selecting a modulation coding scheme (MCS) for transmitting data to a client station (STA). The communications device first predicts the MCS for each of at least two of a plurality of communication modes. The plurality of communication modes may include an open-loop mode and at least one of a single-user multiple-input multiple-output (SU-MIMO) mode or a multiple-user multiple-input multiple-output (MU-MIMO) mode. The communications device then selects one of the plurality of communication modes for transmitting data to the STA based at least in part on the predicted MCSs.

The presently claimed invention relates generally to a method and an apparatus for pilot decontamination for massive MIMO system and, more particularly, to a massive MIMO communication system based on channel estimation with topological interference alignment.