252 results about "Maximum likelihood detection" patented technology

A MIMO OFDM system includes a plurality of space-time encoders for encoding respective data blocks with independent space-time codes. The transformed data block signals are transmitted by a plurality of transmit antennas and received by a plurality of receive antennas. The received data is pre-whitened prior to maximum likelihood detection. In one embodiment, successive interference cancellation can be used to improve system performance. Channel parameter estimation can be enhanced by weighting the channel impulse response estimates based upon a deviation from average.

A repeatable run-out (RRO) detector employs one or more digital interpolators to interpolate asynchronous sample values representing an RRO address mark (AM) and RRO data, an asynchronous maximum-likelihood (AML) detector to detect the RRO AM, and a RRO data decoder to decode the RRO data. The AML detector employs an AML algorithm, such as a Viterbi algorithm, to detect the series of peaks of the RRO AM based on detection of the entire sequence of observed peaks. AML detection selects one of either the asynchronous or interpolated sample sequences that are closest in distance to the ideal RRO AM sample sequence. Once the RRO AM is detected, the AML detector provides a RRO AM found signal as well as the selected one of the sample sequences having the best phase for detecting and decoding the RRO data.

Detection for a MIMO (multiple-input, multiple-output) wireless communications system with symbols iteratively detected in subsets with maximum likelihood hard decisions within subsets. Previously detected subsets of symbols are used to regenerate corresronding input signals for interference cancellation. With a 4-transmitter antenna, 4-receiver antenna system, two subsets of two symbols are possible with the first two symbols detected with zero-forcing or MMSE soft estimates which feed maximum likelihood hard decisions; and the hard decision for the first two symbols are used for interference cancellation followed by zero-forcing or MMSE soft estimates for the second two symbols which then feed further maximum likelihood hard decisions.

A maximum likelihood detection (MLD) method is disclosed. Received data is processed to obtain preliminary parameters. An initial radius r is determined. r² is multiplied by a corresponding scaling factor according to a partial Euclidean distance (PED) constraint function to determine the upper limit values of PED for each layer. It is examined whether a sub-lattice exceeds a search scope according to the upper limit values of PED for each layer to search a better solution by utilizing the preliminary parameters.

The invention discloses an SIM-OFDM communication method, and belongs to the communication anti-jamming technical field. The mapping method of subcarrier index modulation is improved at a transmitting end, namely a novel mapping method is introduced, so that subcarriers in each subblock are mutually independent, in this way, the minimum Euclidean distance is increased, and system performance is improved; at a receiving end, with respect to the complexity of maximum likelihood detection, a novel frequency domain detection technology is provided, hence, the maximum likelihood detection performance is achieved, and meanwhile the complexity can be extremely lowered.

Maximum likelihood detection of signals in a MIMO receiver. A system transformation is obtained by selecting a weighting matrix that when linearly transforming a channel utilized for wireless communication, results in a particular transformed triangular matrix. The weighting matrix is then used to provide a transformed vector for a received signal that allows a search in one constellation. In searching the constellation recursion values are used to calculate the Euclidean distances between set points of the constellation and the location on the constellation corresponding to the received signal for both bit values 0 and 1. Minimum Euclidean distances are determined for bit values 0 and 1 and the difference of the minimum Euclidean distances is used to compute the maximum likelihood value for bits contained in the received signal.

The invention provides an LC-DSM algorithm (low-complexity differential detection algorithm). Firstly, a symbolic matrix is constructed at the transmitting end of a differential spatial modulation system by applying a bit filling scheme and a transmission bit calculation formula, and a receiving signal is obtained at the receiving end through differential transformation and transmitting. Then a search mode of detection by column is adopted on a receiving matrix based on the equation structure of a differential maximum likelihood detection algorithm to perform signal decision column by column so that a transmitting symbol and the sequence number of a transmitting antenna are obtained. Finally information bits are obtained through inverse mapping according to the corresponding relation of the bit and the transmitting symbol and the bit and the sequence number of the transmitting antenna. The method is obtained by combination of the low-complexity detection algorithm under spatial modulation and the equation structure formed by the maximum likelihood detection algorithm under the differential spatial modulation system. The research indicates that complexity is greatly reduced relative to the differential maximum likelihood detection algorithm by using the LC-DSM algorithm under the premise of guaranteeing no loss of algorithm performance.

The invention provides a method and apparatus for estimating flat fading channel in CDMA communication system, said method is implemented by using an adaptive forward prediction technique based on lattice filter and maximum likelihood technique of Viterbi algorithm. The adaptive lattice filter is used to carry out prediction of LS criteria on channel fading, and a maximum likelihood detection technique completes Viterbi algorithm in accordance with a channel fading value obtained by the prediction, thus obtaining final estimation and decision about the transmitting signals. The present invention has the advantages that it can obtain accurate result for channel estimation and sequence decision when it operates in the fast fading channel, and overcome fast fading influence due to motion speed up of mobile station, thereby satisfying mobile station speed and corresponding receiving performance required in 3G mobile communication.

A system and method of timing estimation for use in a digital receiver within a communication system. An algorithm calculates the timing offset by evaluating the spectral component at the symbol clock frequency. The spectral component is generated using a nonlinearity operation. However, the maximum likelihood non-data-aided timing estimation equation reveals an alternative approximation for the logarithm of the hyperbolic cosine function present in the maximum likelihood equation, which offers a compromise between implementation complexity and variance performance. The estimated timing offset is then fed to a timing correction unit, which calculates the data samples corresponding to the sampling clock phase and removes the redundant samples. The ideal sampled signal is then forwarded to additional synchronization and functional units for further processing.

Disclosed is a method for increasing a data transfer rate without an increase in the whole bandwidth using intrinsic spreading codes and orthogonal codes. The method uses interleaving, OFDM modulation/demodulation, and maximum likelihood detection (MLD) to overcome the effects of multipath fading or signal interference, determines grouped optimal values by a grouping method of dividing the intrinsic spreading codes in series, and calculates an integrated optimal value for all the intrinsic spreading codes using the grouped optimal values, thereby reducing the complexity of MLD according to the length of the intrinsic spreading code and acquiring an improved performance.

An apparatus and a method for canceling interference based on Maximum Likelihood (ML) at a receiver of a multi-antenna system are provided. The method includes estimating a channel using a signal received over one or more receiver antennas; generating one or more weights using the estimated channel to cancel interference; detecting a candidate symbol having the shortest Euclidean distance through Maximum Likelihood using a first weight; and soft-decoding the candidate symbol using a second weight. Therefore, by receiving the signal based on the ML under the interference, the system capacity can be increased and the reception performance can be enhanced.

The invention provides a signal transmission and detection method of an environment backscattering system; the system comprises an environment radio source for emitting a source radio frequency signal, a label for receiving the source radial signal and reflecting the radio frequency signal and a reader for receiving the source radio frequency signal and the radio signal, wherein the label continuously emits an equiprobable binary character loaded on the source radio frequency signal; the binary character is corresponding to if the label reflects the radio frequency signal; the reader judges if the received signal is the binary character emitted by the label on the basis of a maximum likelihood detection method or a joint energy detection method. The method is simple in practice, good in performance, and very strong in practicability.

The invention discloses a multi-symbol detecting and symbol synchronizing method based on CPM (critical path method) modulation. The arithmetic comprises the following steps: determining the starting time of receiving the baseband signal symbol so as to carry out multi-symbol detection treatment; generating local likelihood detecting codes; adopting a single-symbol cycle lead-lag likelihood detection arithmetic to extract phase discrimination information; carrying out clock regeneration by a loop filter circuit; controlling the lead-lag likelihood detection circuit by the regeneration clock, thus achieving the aim of completing high-quality symbol synchronization. The method has the following effective technical effects: the method is based on the maximum likelihood detection so as to ensure the synchronous performance under the low signal-to-noise ratio condition; the time window of the likelihood detection of symbol synchronization is a symbol cycle, and the likelihood detection matching baseband has simple waveform, so that the engineering is convenient to realize.

A Maximum Likelihood (ML) detection apparatus and method in a wireless communication system are provided, in which a Euclidean distance are calculated using at least one of channel matrix information, noise power information and modulation order information of each stream, Pairwise Error Rate (PER) are calculated using the Euclidean distance, an error probability of the each stream is calculated using the PER, the error probability of the each stream is ordered and sorted, and ML detection is performed using a result of the ordering and sorting.

The invention discloses an interference suppression method for a multi-user MIMO collaborative relay system, mainly solving the problem that each user has multiple antennas in a common-channel multi-user relay system. The interference suppression method comprises the steps that: a user determines a beamforming vector by adopting a signal space alignment method, and sends out a signal after weighting the signal with the beamforming vector in a multiple-access time slot; a relay constructs a precoding matrix based on an orthogonal projection principle, and amplifies and sends the received signal after precoding; the user receives the signal and suppresses interference signals between user pairs by adopting a decoding vector, and conducts a maximum likelihood detection to obtain the needed signal. According to the invention, a network transmission rate and a resource utilization rate are improved, diversity gains of multiple antennas are achieved, channel fading resisting capability of the system is enhanced, and a bit error ratio is decreased. Further, the interference suppression method of the invention can be applied in a transmission mode under centralized management and control of a wireless ad hoc network and base station, wherein data can be exchanged directly through user-relay-user mode.

The present invention relates to a method in a receiver for decoding at least two received communication signals, wherein the communication signals are modulated, pre-coded by a discrete Fourier transform and transmitted by means of single-carrier frequency division multiple access scheme (SC-FDMA). The method comprises the steps of: performing an antenna combining and equalization on a signal observed at the receiver; performing inverse discrete Fourier transform on a model of the observed signal; whitening a time domain model of the observed signal; and jointly detecting the received at least two communication signals by performing soft value calculations based on maximum likelihood detection of a whitened time domain model using a whitened time domain channel estimate.

Disclosed is a wavelet domain value de-noising method for the maximum likelihood estimator based on the wavelet de-noising algorithm, comprising the following: a known signal is inserted into a fixed pilot; through IDFT, a data is parallel-serial transformed, and after a cyclic prefix is added, the data is discretized and molded and is sent into a radio frequency channel; a filter wave is matched with the received data, and a received pilot data is extracted; a frequency response of a pilot point is obtained, then a channel time domain and a frequency domain shock response are estimated to complete the maximum likelihood estimation, and hMLE is obtained; the maximum likelihood estimation is decomposed by the wavelet; the threshold value of the wavelet coefficient decomposed in each grade is quantified and reconstructed; when the difference value of the maximum likelihood estimation of the wavelet and the traditional maximum likelihood estimation approximately obeys the gaussian distribution at utmost, the maximum likelihood channel estimation of the wavelet; and the channel estimation value is applied to the space-time decoding. The invention does not need the distribution function of the known channel, the improvement of the estimation accuracy brings the decline of the error rate of the STBC decode, and the invention is easy to be realized without the prior statistical information of the channel, and is not limited to a certain channel environment.

A wireless receiver detects signals generated with a multiple-input, multiple-output (MIMO) transmitter. The receiver applies maximum-likelihood detection (MLD) for soft-output signal detection, where an MLD exhaustive search across all candidate vectors is performed recursively by computing and accumulating the differences between, for example, the Euclidean metrics of consecutive candidate tests. Difference terms used for the accumulation are also calculated recursively. An ordering of candidates, such as by a triangular-waveform shaped ordering, is employed such that only one candidate variable is changed between any two consecutive candidate evaluations, leading to a reduced set of computations.

The invention relates to a detection method for multi-user signal in a large-scale multi-antenna system and belongs to the technical field of wireless communication. The method adopts the obtained CSI to detect the multi-user information at the base station side. The method has low complexity and good error bit rate performance, which is close to the error bit rate performance of the optimal MMSE detection within a few iterations. The method adopts the Lanczo iterative algorithm for obtaining the system of linear equations for avoiding the mode of obtaining MMSE orthogonal matrix by directly using large-scale matrix inversion mode, the detection calculating complexity is greatly reduced; in addition, the method can calculate LLR value of each information bit in lower complexity as the input of the decoder and the joint detection decoding performance is obviously improved. The complexity is obviously reduced while the ratio of the user number K and the base station antenna number N is certain and the number tends to infinity, and the error bit rate performance can gradually reach to the maximum likelihood detection (optimal) performance.

An apparatus and method for detecting a signal in a receiver by maximum likelihood (ML) are provided, in which symbols are detected according to the number of transmit antennas of a transmitter and a modulation scheme, channels are estimated, an equivalent channel matrix corresponding to the estimated channels is determined, a permuted equivalent channel matrix is determined by multiplying the equivalent channel matrix by a predetermined permutation matrix, the permuted equivalent channel matrix is QR decomposed, a hard decision is performed on predetermined symbols among the detected symbols using a received signal resulting from the QR decomposition, and the log likelihood ratios (LLRs) of the hard-decided symbols are determined.

The invention relates to the field of communication anti-jamming technologies, in particular to spatial modulation (Spatial Modulation, SM) technologies, signal vector detection algorithms (Signal Vector Detection, SVD), hard-limiter maximum-likelihood detection algorithms (Hard-Limiter Maximum-Likelihood Detection, HL-ML Detection) and related multiple input multiple output (Multiple Input Multiple Output, MIMO) technologies. By adopting a spatial modulation and detection method with low complexity, through arranging a reasonable threshold, the signal vector detection algorithm and the hard-limiter maximum-likelihood detection algorithm are combined, and the complexity for detection is greatly reduced under the condition that the BER (Basic Error Rate) performance obtained through detection is extremely close to optimal algorithm ML detection.

Various aspects of a method for minimum mean square error soft interference cancellation (MMSE-SIC) based sub-optimal maximum likelihood (ML) detection for a multiple input multiple output (MIMO) wireless system may comprise selecting at least one constellation point in a constellation map based on at least one of a plurality of received symbols. A number of the at least one constellation point may be less than or equal to a number of previously selected constellation points in a previous constellation map. At least one of the plurality of received symbols may be decoded based on the selected at least one constellation point.