Patent application number | Description | Published |
20080232488 | WIRELESS COMMUNICATIONS APPARATUS AND METHOD - Detection of information on an OFDM signal involves channel estimation. Following an initial channel estimate, it is desirable to perform smoothing or filtering to achieve a more effective channel estimate. A filter is described which is operable to smooth an initial estimate for a subcarrier by reference to one or more adjacent subcarrier estimates. Extrapolation is used to impose, on a subcarrier, information dependent on one or more other subcarriers in the case that the subcarrier in question is not in use other than use by the filter. | 09-25-2008 |
20080311859 | WIRELESS COMMUNICATION APPARATUS - Channel estimation in a MIMO communications system comprises performing a decomposition of an initial channel matrix estimate associated with a first subcarrier of a plurality thereof defined in the channel to identify eigenvectors associated with that subcarrier of the received signal, and defining a first beamforming transformation to be applied to the received signal on the basis of the eigenvectors. Then, for each of the other subcarriers, an additional decomposition is performed in order to determine a further beamforming transformation for each of said one or more other subcarriers, wherein said additional decompositions are carried out incrementally such that information determined in one of said decompositions contributes to a later executed decomposition. Further described is a method of transmitting from a multiple antenna transmitter defining a plurality of subcarriers in space, and time or frequency, comprising the same iterative process. This transmitting can be carried out using smoothed beamforming applied in accordance with aspects of the invention. | 12-18-2008 |
20090060074 | WIRELESS COMMUNICATIONS APPARATUS - Precoding a plurality of subcarriers in preparation for MIMO transmission is carried out by deriving preceding matrices from available information. When the number of data streams borne by the subcarriers equates to the number of transmit antennas employed in the MIMO transmission, the method comprises deriving, from respective acquired unitary precoder matrices for two of said subcarriers, interpolated precoder matrices for data streams intermediate the two subcarriers. The acquired and interpolated precoder matrices are then applied, as the case may be, at the respective subcarriers. The step of deriving the interpolated precoder matrices comprises determining an overall rotation matrix representing a transformation between the acquired precoder matrices, determining from the overall rotation matrix a further rotation matrix representing a step transformation for interpolation steps between said two subcarriers, and recursively applying said further rotation matrix to derive said interpolated precoder matrices. In the event that the number of data streams is less than the number of transmit antennas employed in said MIMO transmission, the rectangular precoder matrices should first be converted into square unitary matrices. | 03-05-2009 |
20090086836 | WIRELESS TRANSMISSION DEVICE - The invention provides a method and device for managing the use of antennas in a multiple antenna wireless transmission system for OFDM signals. The method includes defining a utility function which comprises a performance metric for transmission. Combinations of antenna and OFDM subcarriers are selected to optimise the utility function under two constraints. The first constraint is that the combinations of antenna and subcarrier include only one antenna for each subcarrier, the second constraint is that the combinations include the same number of subcarriers for each antenna. | 04-02-2009 |
20090202009 | WIRELESS COMMUNICATIONS APPARATUS - Allocation of subcarriers of a wireless communications channel to antennas for transmission of said subcarriers from a multi-antenna transmitter, comprises selecting, for each subcarrier, the antenna with the most effective transmission performance against a predetermined performance criterion; and determining if subcarriers are evenly distributed amongst said antennas. If even distribution does not arise, then a reallocation sequence is performed. This comprises identifying, for an antenna having excessive subcarriers allocated thereto, the subcarriers allocated thereto and reallocating one of said subcarriers as required, said reallocated subcarrier being selected for reallocation on the basis of its impact on transmission performance. | 08-13-2009 |
20110128924 | WIRELESS COMMUNICATIONS APPARATUS AND METHOD - According to one embodiment, antenna allocation or selection in a multi-antenna wireless communications device can be performed at a receiver or an emitter of a wireless communications signal. Selection takes place on the basis of antenna and frequency. Antenna selection in a disclosed embodiment involves a combination of bulk and per tone antenna selection. | 06-02-2011 |
20160043884 | SIGNAL PROCESSING METHOD AND APPARATUS - In an embodiment a method of estimating a sparse signal from a measured signal using a transform matrix is disclosed. The method comprises determining a partial contribution to the sparse signal; determining a residual by subtracting the partial contribution from the measured signal; and iteratively determining further contributions to the sparse signal. An iteration comprises: identifying a first candidate column of the transform matrix, the first candidate column being the column of the transform matrix which is most correlated with the residual at the start of the iteration; calculating a condition indicator, the condition indicator being an indication of the condition of a matrix formed by columns of the transform matrix selected in previous iterations and the first candidate column; comparing the condition indicator with a threshold; if the condition indicator is above the threshold selecting the first candidate column as a selected candidate column; if the condition indicator is below the threshold, identifying a second column of the transform matrix as a second candidate column and selecting the second candidate column as the selected candidate column; determining a contribution to the sparse signal for the iteration from the selected candidate column; and calculating a new residual by subtracting contribution to the sparse signal for the iteration the from the residual at the start of the iteration. | 02-11-2016 |
20160105202 | CODING AND DECODING METHODS AND APPARATUS - According to an embodiment a decoder for decoding a received set of blocks each comprising a plurality of data symbols and a plurality of parity symbols, wherein the received set of blocks is a subset of a complete set of blocks, the complete set of blocks comprising at least one erased block not included in the received set of blocks comprises storage for a coding matrix which is the kronecker product of a totally non-singular matrix with an anti-diagonal matrix; and a processor operable to determine data symbols of the at least one erased block using the encoding matrix. | 04-14-2016 |