Apparatus and methods for finding a vector solution to a tree search problem are disclosed. In some embodiments, the apparatus and methods can be used for sphere decoding. The tree search is performed by: obtaining a tree graph; identifying a plurality of nodes in the tree graph that are likely to be part of the solution to the tree graph; partitioning the tree graph into a plurality of sub-trees, each sub-tree including one or more of the identified nodes; processing the plurality of sub-trees in parallel by allocating one or more of the processing elements to each of the sub-trees; and determining the solution based on results of the sub-tree processing.

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.

An OFDM transmitter comprising an input for acquiring or receiving a signal to be transmitted, an output for transmitting a PAPR reduced version of the signal, a processor and memory storing code for execution by the processor. The processor, when executing the code, is configure to determine a plurality of possible values of tone reservation, hereinafter referred to as TR, tones for use in TR based PAPR reduction and to perform a tree search over some or all of the possible values under a first constraint that the average power per TR tone does not exceed the average power per tone used for data transmission and a second constraint that selected values for the TR tones reduce PAPR.

The disclosure discloses a path detection method including after obtaining an equalizing signal of a received signal, Maximum Likelihood (ML) path detection and ML complementary set path detection are performed on the equalizing signal according to the pre-set maximum number of reserved nodes and maximum number of expanded branches of each layer; in the process of the detections, an accumulated path measurement value is calculated after finishing the search of each layer and each path, and the accumulated path measurement value is compared with a pre-set search measurement threshold; when the accumulated path measurement value is less than the search measurement threshold, the search of this path is continued; otherwise the search of this path is finished and the search of the next path is started until all the paths are searched. The disclosure also discloses a path detection device, Sphere Decoding (SD) detection device and computer storage medium.

Embodiments of the invention provide a decoder (10) for decoding a signal received through a transmission channel in a communication system, the signal carrying information symbols selected from a given set of values and being associated with a signal vector, the transmission channel being represented by a channel matrix. The decoder comprises : a sub-block division unit (12) configured to divide the received signal vector into a set of sub-vectors in correspondence with a division of a matrix related to said channel matrix ; at least one weighting coefficient calculation unit (14) configured to calculate a sub-block weighting coefficient for each sub-vector, at least one symbol estimation unit (11) for recursively determining estimated symbols representative of the transmitted symbols carried by the data signal from information stored in a stack.

The at least one symbol estimation unit is configured to apply at least one iteration of a sequential decoding algorithm, the sequential decoding algorithm comprising iteratively filling a stack by 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 at least a part of the received signal and each node being assigned an initial metric. The symbol estimation unit is further configured to calculate a modified metric for at least one node of the expanded child nodes from the metric associated with the at least one node and from the sub-block weighting coefficient calculated for the sub-vector to which the at least one node belongs, symbol estimation unit being configured to assign the modified metric to the at least one node.

The apparatus may be a wireless device such as a UE configured to receive an indication of at least one shaping operation associated with one or more additional wireless devices in a plurality of wireless devices, where each of the plurality of wireless devices is associated with MU-MIMO communication, and where the first wireless device is included in the plurality of wireless devices. The apparatus may be configured to receive a DL transmission associated with the MU-MIMO communication, perform a demodulation of the DL transmission based on the indication, and output a result of the demodulation of the DL transmission for at least one of a transmission to at least one other wireless device or a local storage at the first wireless device.

Embodiments of the invention concern a method of equalizing (S9), in a turbo equalizing system (S10), by sphere decoding (S11) a signal transmitted over a channel by a multiple input multiple output system, comprising: receiving (S3) said transmitted signal, building (S4) at least one search tree, providing (S6) likelihoods of bits, for said transmitted signal, from said built search tree(s) and from said received transmitted signal, wherein equalizing method (S9) also comprises receiving feedback signal from a channel decoder (S8) of said turbo equalizing system (S10), and wherein said feedback signal is used to build (S4) said search tree(s).

Embodiments of the invention provides a decoder for decoding a signal received through a transmission channel in a communication system, said signal carrying information symbols selected from a given alphabet and being associated with a signal vector, said transmission channel being represented by a channel matrix, wherein said decoder comprises: a sub-block division unit (301) configured to divide the received signal vector into a set of sub-vectors in correspondence with a division of a matrix related to said channel matrix; a candidate set estimation unit (305) for recursively determining candidate estimates of sub-blocks of the transmitted signal corresponding to said sub-vectors, each estimate of a given sub-block being determined from at least one candidate estimate of the previously processed sub-blocks, wherein said candidate set estimation unit is configured to determine a set of candidate estimates for at least one sub-block of the transmitted signal by applying at least one iteration of a decoding algorithm using the estimates determined for the previously processed sub-blocks, the number of candidate estimates determined for said sub-block being strictly inferior to the cardinal of the alphabet and superior or equal to two, the decoder further comprising a signal estimation unit (306) for calculating an estimate of the transmitted signal from said candidate estimates determined for said sub-blocks.

A receiver estimates a vector of emitted symbols over a MIMO transmission channel which is emitted by emitting antennas. The receiver receives a vector of received symbols on receiving antennas. Estimation of the vector of emitted symbols is made by calculating a metric associated with a criterion for each vector of a subset of all possible vectors of emitted symbols and selecting an estimation for said vector of emitted symbols as the vector of emitted symbols among said subset which minimizes said metric.

Systems and methods are disclosed for detecting a symbol in large-scale multiple-input multiple-output communication systems. The detection is based on an improved lattice-reduction-aided K-best algorithm. The detection finds K best candidate symbols with minimum costs for each layer based on a priority queue and an on-demand expansion. In a complex domain, the detection may include a 2-dimensional Schnorr-Euchner expansion or, in the alternative, a two-stage 1-dimensional Schnorr-Euchner expansion.