A method for receiving a signal in a wireless communication system includes: receiving and demodulating a signal transmitted by using a quadrature spatial modulation technology to obtain a complex symbol; and decoding the complex symbol with a spherical decoding detection algorithm. Decoding includes, for the i.sup.th layer of a constellation symbol, discarding the constellation symbol if a calculated radius of the i.sup.th layer is greater than a minimum radius of the i.sup.th layer; otherwise updating the minimum radius of the i.sup.th layer according to the calculated radius; where i is a natural number in a range between Nr and 1; Nr is the number of receiving antennas; and for each constellation symbol that is not discarded, taking a sum of the radii of respective layers of the constellation symbol as the radius of the constellation symbol, and selecting a constellation symbol with the smallest radius as a symbol obtained from the decoding.

Apparatus and methods for performing symbol detection on a plurality of mutually interfering information streams transmitted in a wireless communication system are disclosed. The apparatus comprises a detector configured to receive an input signal comprising a plurality of mutually interfering information streams, and to detect a transmitted symbol for one of the plurality of mutually interfering information streams by searching for a vector solution to an optimization problem, and a detection evaluation module configured to classify the detected symbol as reliable or unreliable, and/or to determine whether current system conditions permit reliable symbol detection and to take a predetermined action to improve the detection reliability according to a result of the determination. In some embodiments a decoding algorithm is then applied to the plurality of detected symbols to recover information from said one of the mutually interfering information streams.

A receiver for receiving a signal including a plurality of symbols through a multiple input multiple output (MIMO) channel, and an operation method of the receiver are provided. The receiver includes a demodulator configured to calculate, for each physical channel, Euclidean distances of one or more of the received symbols with respect to all candidate vectors included in an initial candidate vector set and to output information about the Euclidean distances. A vector set detector may select, based on the information, one of a plurality of candidate vector sets having different sizes, as a subsequent candidate vector set for calculating a log likelihood ratio (LLR) of other symbols of the plurality of symbols or an LLR with respect to a second signal received following the first signal.

An apparatus for deriving a submatrix {tilde over (G)}.sup.1 is described. The apparatus for deriving a submatrix {tilde over (G)}.sup.1 is configured to select an N-elements-column and an N-elements-row of an NN-Matrix G or G.sup.1. The apparatus for deriving a submatrix {tilde over (G)}.sup.1 is configured to rearrange the selected column to the rightest column and the selected row to the lowest row of G or G.sup.1 so as to generate a NN-matrix G.sub.p or G.sub.p.sup.1. The apparatus for deriving a submatrix {tilde over (G)}.sup.1 is configured to calculate a submatrix {tilde over (G)}.sup.1 by ${\tilde{G}}^{-1}=A-\frac{\mathrm{AbcA}}{d^{-1}+c^T\mathrm{Ab}},$
wherein the parameters (N1)(N1)-submatrix A, b, d, c are obtained from the G.sub.p or the G.sub.p.sup.1; wherein $G_p=\left[\begin{array}{cc}\tilde{G}& b\\ c^T& d\end{array}\right],G_p^{-1}=[\begin{array}{cc}A& \tilde{b}\\ {\tilde{c}}^{}\end{array}$

A method for receiving a signal in a wireless communication system includes: receiving and demodulating a signal transmitted by using a quadrature spatial modulation technology to obtain a complex symbol; and decoding the complex symbol with a spherical decoding detection algorithm. Decoding includes, for the i.sup.th layer of a constellation symbol, discarding the constellation symbol if a calculated radius of the i.sup.th layer is greater than a minimum radius of the i.sup.th layer; otherwise updating the minimum radius of the i.sup.th layer according to the calculated radius; where i is a natural number in a range between Nr and 1; Nr is the number of receiving antennas; and for each constellation symbol that is not discarded, taking a sum of the radii of respective layers of the constellation symbol as the radius of the constellation symbol, and selecting a constellation symbol with the smallest radius as a symbol obtained from the decoding.

Methods, systems, and devices for wireless communications are described. Some wireless communications systems may utilize beamforming techniques to process wireless communications transmitted in millimeter wave (mmW) frequency ranges. In such cases, a user equipment (UE) may perform lattice reduction (LR)-based preprocessing for a received resource element (RE), which allows the UE to utilize demapping techniques (e.g., minimum mean square error (MMSE)-based demapping techniques or successive interference cancellation (SIC) demapping techniques) that are less computationally-complex than conventional demapping techniques (e.g., maximum likelihood (ML)-based demapping techniques) while providing a similar performance as conventional techniques. Further, due to mmW systems' robustness to time-dispersion, the UE may apply the same LR to multiple REs across multiple symbols in the time domain and across multiple sub-carriers in the frequency domain. The computational cost of performing the LR calculation may be spread across multiple REs and further increase the efficiency of utilizing low-complexity demapping techniques.

A decoder for decoding a signal received through a transmission channel represented by a channel matrix using a search sphere radius. The decoder comprises a radius determination device for determining a search sphere radius from a preliminary radius. The radius determination device is configured to: i. apply a machine learning algorithm to input data derived from the received signal, the channel matrix and a current radius, the current radius being initially set to the preliminary radius, which provides a current predicted number of lattice points associated with the current radius; ii. compare the current predicted number of lattice points to a given threshold; iii. update the current radius if the current predicted number of lattice points is strictly higher than the given threshold, the current radius being updated by applying a linear function to the current radius; Steps i to iii are iterated until a termination condition is satisfied, the termination condition being related to the current predicted number, the radius determination device being configured to set the search sphere radius to the current radius in response to the termination condition being satisfied.

Certain aspects of the disclosure are directed to a method for communicating data from a transmitting circuit to a receiving circuit over a noisy channel. The method can be performed by logic circuitry, and can include encoding data, for transmission over the noisy channel. The data can be encoded, as a shaped-coded modulation signal by shaping the signal based on an amplitude selection algorithm that leads to a symmetrical input and by constructing a trellis having a bounded-energy sequence of amplitude values selected by computing and storing a plurality of channel-related energy constraints based on use of a nonlinear-estimation process, and therein providing an index for the bounded-energy sequence of amplitudes. The method can also include receiving over the noisy channel, the shaped-coded modulation signal, and decoding the data from the shaped-coded modulation signal by using the index to reconstruct the bounded-energy sequence of amplitudes.

Certain aspects of the disclosure are directed to a method for communicating data from a transmitting circuit to a receiving circuit over a noisy channel. The method can be performed by logic circuitry, and can include encoding data, for transmission over the noisy channel. The data can be encoded, as a shaped-coded modulation signal by shaping the signal based on an amplitude selection algorithm that leads to a symmetrical input and by constructing a trellis having a bounded-energy sequence of amplitude values selected by computing and storing a plurality of channel-related energy constraints based on use of a nonlinear-estimation process, and therein providing an index for the bounded-energy sequence of amplitudes. The method can also include receiving over the noisy channel, the shaped-coded modulation signal, and decoding the data from the shaped-coded modulation signal by using the index to reconstruct the bounded-energy sequence of amplitudes.

There is provided a decoder (310) for sequentially decoding a data signal received through a transmission channel in a communication system, the received data signal carrying transmitted symbols, the decoder comprising a symbol estimation unit (311) configured to determine estimated symbols representative of the transmitted symbols carried by the received signal from information stored in a stack, the stack being filled by iteratively expanding child nodes of a selected node of a decoding tree comprising a plurality of nodes, each node of the decoding tree corresponding to a candidate component of a symbol of the received data signal and each node being associated with a predetermined metric, the stack being filled at each iteration with at least some of the expanded child nodes and being ordered by increasing values of the metrics associated with the nodes, the selected node for each iteration corresponding to the node having the lowest metric in the stack. The decoder further comprises a stack reordering activation monitoring unit (313) configured to monitor at least one stack reordering activation condition and, in response to a stack reordering activation condition being verified, to cause the symbol estimation unit to: reduce the metric associated with each node stored in the stack by a quantity, reorder the stack by increasing value of the reduced metric, and remove a set of nodes from the reordered stack so as to maintain a number N of nodes in the reordered stack, the maintained nodes corresponding to the N nodes having the lowest metrics in the reordered stack.