Telefonaktiebolaget Lm Ericsson (publ)

Nxp B.v.

Özgün Paker

Arie Geert Cornelis Koppelaar

Sebastien Mouy

Petrus Josephus Franciscus Hoeven

Sebastian Eckert

Aspects of the present disclosure may involve use of a radio frequency receiver and in such a receiver, tracking multipath gains and delays of multipath reflections corresponding to an OFDM multipath transmission channel. The gains and delays are based on time-domain evolution of the channel impulse response. Multipath reflections are searched for and then used to calculate channel correlation information to provide channel estimations to aid in mitigating or cancelling distortion of the received signal.

Processing signals to account for multipath-reflection phenomena in RF communications

Signal equalization is provided, according to certain aspects, by a frequency-domain equalization circuit, a noise-whitening filter and a noise predictor. A sequencer is used to control ordering of the equalization circuit, a noise-whitening filter and a noise predictor. The equalization circuit provides equalization the frequency domain by converging on symbols of the input signal. The noise-whitening filter and the noise predictor filter colored noise from a signal responsive to the equalization circuit. The sequencer controls operation of the noise-whitening filter by detecting an indication of convergence of the symbols from input signal and causing the noise-whitening filter to commence suppression of colored noise from a signal derived from an output by the equalization circuit.

Signal-equalization with noise-whitening filter

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

Equalization in the receiver of a multiple input multiple output system

A sphere decoder based turbo equalizer is described. A method comprises assorting in a first vector Quadrature Amplitude Modulation, QAM, symbols on a particular tree level based on first distance properties, assorting in a second vector QAM symbols on the particular tree level based on second distance properties, selecting the QAM symbol with the minimum second distance property in the second vector, wherein said selecting comprises labeling the selected QAM symbol as protected, identifying the selected QAM symbol in the first vector assorted by distance properties, pruning the first vector by eliminating all QAM symbols having a larger first distance property compared to the selected QAM symbol, wherein said pruning is restricted to QAM symbols not being labeled as protected, and repeating the steps d-e selecting the QAM symbol with the next minimum second distance property.

Method performed by a sphere decoder based turbo equalizer

A receiver () for receiving for receiving encoded data transmitted simultaneously as a plurality of M different sequences of transmitted symbols from different transmit antennas using a plurality of m modulation levels, where M and m are integers and each of the transmitted symbols represents a plurality of bits of the encoded data, comprises a demodulator () arranged to provide N received symbol combinations by receiving at a plurality of N receive antennas (), where N is an integer, the plurality of M different sequences of transmitted symbols, wherein each received symbol combination comprises M simultaneously received ones of the transmitted symbols. An equalizer () is arranged to generate from the N received symbol combinations M pre-processed signals by performing interference cancellation, in which interference cancellation a different symbol of the respective received symbol combination is a wanted signal and the other symbols of the respective received symbol combination are interfering signals. The equalizer () is also arranged to generate from each of the M pre-processed signals a list of up to m initial candidate symbol combinations by, for each of the up to m initial candidate symbol combinations, selecting a first initial symbol indicative of a different one of the m modulation levels and selecting M&#x2212;1 further initial symbols. The equalizer () is further arranged to generate from the lists of initial candidate symbol combinations an initial estimate of the transmitted symbols. A decoder () is arranged to decode bits represented by the initial estimate of the transmitted symbols.

Turbo equalisation

Sphere decoding of signals for MIMO detection involves a first distance processor arranged to determine a distance between symbols of a received symbol vector and possible transmit symbols, in a search sequence according to a search tree. A line from root to leaf of the search tree represents a possible transmit symbol vector and the sequence of processing root level symbols can be ordered with respect to increasing distance without explicit sorting of the root level symbols based on distance calculations. A next symbol in the sequence is determined, based on a symbol currently being processed by the first distance processor, and a second distance processor determines the distance in respect of the next symbol in the search sequence for the same possible transmit symbol vector, in parallel with the determining of the distance in respect of the current symbol by the first distance processor.

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Waalre, Netherlands

Özgün Paker