Introduced here is at least one technique to better estimate interference at a receiver. The technique includes receiving a plurality of reference signals, which each have information indicative of noise. Thus, the technique further includes, for each reference signal, determining a noise estimation and determining a distance metric and log-likelihood ratio (LLR) of the noise estimation. Once the distance metric and LLR of each reference signal is determined, the receiver can determine a final LLR based on the distance metric and LLR of each reference signal. In this manner, a final LLR is determined. This technique can be applied by any device operating on MIMO technology.

A method of detecting u symbol transmitted over a communication channel in a multiple input-multiple output communication system. The method includes receiving a plurality of symbols transmitted over a communication channel of a multiple input-multiple output communication system. A sphere radius is initialized based on attributes of the communication channel. A first matrix of possible transmitted signals is defined as well as a second matrix of receiv ed symbols. The matrix of possible transmitted signals is searched using a breadth-first search (BFS). Each level of the search tree is analyzed utilizing matrix multiplication to determine selected symbols satisfying the initialized sphere radius. A maximum likelihood solution is of the transmitted symbols is derived based on the selected symbols.

A device for determining a received signal as minimum values of a set of values, the device comprising a processor configured to: load a first set of values in a register; identify a maximum value of the first set of values and a minimum value of the first set of values; in the register, replace the maximum value by a value of a second set of values and simultaneously replace the minimum value by a new value, calculated based on the minimum value, to receive an updated first set of values; and repeat previous steps until all values of the updated first set of values are replaced by values of the second set of values.

Communication device adapted for receiving a MIMO signal is provided. The device comprises a first detector adapted to perform a first symbol detection on the MIMO signal using a first detection method, a detection error determination unit adapted to determine a first detection error of the first symbol detection, a detection error judging unit adapted to determine if the first detection error is above or below a detection threshold, and a second detector, adapted to perform a second symbol detection on the MIMO signal using a second detection method, if the detection error judging unit has determined that the first detection error is above the detection threshold. The communication device is adapted to use results of the symbol detection as final symbol detection results, if the detection error judging unit has determined that the first detection error is below the detection threshold.

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.

A receiver decodes received data streams based on a subset of candidate decoding constellation points. A first stage of a decoder of the receiver selects a subset of candidate decoding constellation points by identifying a decoded value for an initial data stream of the set of data streams. A second stage then applies MMSE error detection to each of the constellation points in the selected subset, and calculates an error metric based on the MMSE error detection results. The decoder selects the constellation points having the lowest error metrics, and uses the selected constellation points as an initial set of points for decoding the next data stream to be decoded.

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.

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).

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.

A multiple-phase multiple-input multiple-output (MIMO) detector and a method thereof are disclosed. The multiple-phase MIMO detector includes a first MIMO detection module that performs a first MIMO detection operation on an input signal; a second MIMO detection module that is coupled in series with the first MIMO detection module and performs a second MIMO detection operation on the input signal; and a control module that is coupled to the second MIMO detection module and controls whether the second MIMO detection module operates. Complexity of the first MIMO detection module is lower than or equal to that of the second MIMO detection module.