672 results about "Soft information" patented technology

The disclosed technology provides a less resource intensive way to decode a parity check code using a modified min-sum algorithm. For a particular parity check constraint that includes n variable nodes, an LDPC decoder can compute soft information for one of the variable nodes based on combinations of soft information from other variable nodes, wherein each combination includes soft information from at most a number d of other variable nodes. In one embodiment, soft information from one of the other variable nodes is used in a combination only if it corresponds to a non-most-likely value for the other variable node.

Methods and apparatus for scaling soft values as part of an error correction decoding process are described. Accurate decoding depends on use of the appropriate scale factor. Selection and use of the scale factor to scale soft values is designed to improve and/or optimize decoder performance without the need for prior knowledge of the correct scale factor or the actual channel conditions at the time the signal from which the soft values were obtained was transmitted through a communications channel. The techniques of the present invention assume that the soft values to be processed were transmitted through a communications channel having a quality that can be accurately described by a channel quality value. A scale factor is determined from the distribution of soft values to be scaled and an assumption that the channel through which they were transmitted was of the quality corresponding to a preselected channel quality value.

A novel and useful apparatus for and method of multiple input multiple output (MIMO) detection for use in MIMO based communication systems. The mechanism of the invention performs a simplified tree search utilizing a single stage expansion of the most likely first symbol candidates, in the case of a 2×2 MIMO system. The invention also provides a refinement mechanism that is operative to significantly improve the soft information (i.e. log likelihood ratio) of the list of candidates. To improve the soft information, the mechanism applies one or more refinements rounds to generate additional candidates for both first and second detected symbols.

In a GSM/EDGE Single Antenna Interference Cancellation (SAIC) operation environment, a mobile station is required to operate in a wide range of interference levels. An SAIC linear equalizer that takes advantage of the GMSK signal structure performs better than a conventional Maximum Likelihood Sequence Estimation (MLSE) equalizer in high interference levels, while it performs worse in low interference levels. A dynamic selection between the SAIC linear equalizer and the MLSE equalizer for each received burst is achieved to provide the optimal performance across the entire required operation environments. The dynamic selection is based on the estimated noise plus interference energy relative to the total received signal energy. The soft information calculated by the two categories of equalizers is properly scaled to generate soft information with balanced magnitude.

A process for signal detection in EDGE cellular systems is presented with the step of wireless channel estimation, a time-reversed signal processor, a soft-output Viterbi signal detector consisting of forward and reverse block processing, a MAP decoder that exchange soft information with the equalizer. Claim 1. A signal detection mechanism to demodulate received data frame that includes an accurate estimator to obtain channel responses, a forward filter and a FIR decision feedback filter to be used in soft-output equalizer, a time-reversal device storing received data in a time-reversed order for reverse block processing, an interference removal apparatus in both forward and reverse processing blocks, and a soft-input soft-output reduced state equalizer that utilizes the forward processing and reversed time processing blocks to generate iterative soft-output signals to the forward error correction decoder within the receiver system.

Error correction coding using soft information and interleaving. A symbol interleaved ECC signal (which can be a symbol interleaved multi-level ECC signal) initially undergoes detection (e.g., such as using SOVA detection) to generate soft information. A decoder uses the soft information to generate estimates of at least one symbol (or at least one bit) of the symbol interleaved multi-level ECC signal. Initially, each of the interleaves of the symbol interleaved multi-level ECC signal undergo decoding to determine whether or not any of the interleaves has correctable errors. If not, then a receiving device can request re-transmission of the symbol interleaved multi-level ECC signal from a transmitting device (or a re-read from media of a hard disk drive (HDD)). Interleaves having uncorrectable errors are associated with interleaves having correctable errors. Uncorrectable errors can be corrected via the use of erasure pointers or bit-flipping, among other means.

Systems and methods are provided for decoding signal vectors in multiple-input multiple-output (MIMO) systems, where the receiver has received one or more signal vectors from the same transmitted vector. The symbols of the received signal vectors are combined, forming a combined received signal vector that may be treated as a single received signal vector. The combined signal vector is then decoded using a maximum-likelihood decoder. In some embodiments, the combined received signal vector may be processed prior to decoding. Systems and methods are also provided for computing soft information from a combined signal vector based on a decoding metric. Computationally intensive calculations can be extracted from the critical path and implemented in preprocessors and/or postprocessors.

Systems and methods are provided for implementing various aspects of a Reed-Solomon (RS) error-correction system. A detector can provide a decision-codeword from a channel and can also provide soft-information for the decision-codeword. If the decision-codeword corresponds to an inner code and an RS code is the outer code, a soft-information map can process the soft-information for the decision-codeword to produce soft-information for a RS decision-codeword. A RS decoder can employ the Berlekamp-Massey algorithm (BMA), list decoding, and a Chien search, and can include a pipelined architecture. A threshold-based control circuit can be used to predict whether list decoding will be needed and can suspend the list decoding operation if it predicts that list decoding is not needed.

Apparatus and methods are provided for calculating soft information in a multi-level modulation scheme using one or more nearest neighbors. The nearest neighbors correspond to signal points in a signal constellation set nearest to the value of a received signal. The nearest neighbors of a received signal can be found by using a second symbol-to-signal point mapping for the signal constellation set that is different from the mapping actually used by the signal modulator. The second symbol mapping can be used to simplify the discover of nearest neighbors. Once the nearest neighbors are found in the second symbol mapping, the nearest symbols can be translated back into the actual symbol mapping using, for example, table lookup. The nearest neighbors in the actual symbol mapping can then be used to compute soft information in the form of, for example, log-likelihood ratios (LLRs).

The invention discloses an SOQPSK (shaping offset quadrature phase shift keying) carrier synchronization method based on pilot frequency and soft information combined assistance, mainly solves the problem in the existing short frame burst communication system carrier synchronization technique that the complexity is high and the carrier deviation estimation range is small. The implementation steps are as follows: firstly, according to pilot frequency assistant maximum likelihood carrier synchronization method, the rough estimation values of carrier frequency deviation and phase deviation are obtained, and the phase rough estimation value is used to revise the receiving signals; then, the frequency deviation one dimensional fine estimation interval, and phase deviation one dimensional fine estimation interval are respectively determined; and in the frequency deviation and phase deviation fine estimation intervals, according to the rule of maximizing the mean square value obtained during demodulation of soft information by SOQPSK, one dimensional search is performed to obtain the precise estimation value of carrier frequency deviation and phase deviation. A small amount of pilot frequency overhead is utilized, large carrier deviation with comparatively low operation complexity is revised, effective carrier synchronization is realized, nearly ideal bit-error performance of coherent demodulation is obtaind, and the method is suitable for the short frame burst communication system.

A communications channel is provided, which includes a receive path having an iterative decoder and an ECC decoder. The iterative decoder has a soft channel detector with a soft output. The ECC decoder is coupled to decode bits produced from soft information received from the soft output and operates on the bits in a bit order that is the same as that on the soft output.

A flash memory controller, a computer readable medium and a method for generating reliability information using a hard information interface, the method may include performing multiple read attempts, while using the hard information interface, of a plurality of flash memory cells to provide multiple read results; wherein each flash memory cell is read by providing a reference voltage to the flash memory cell; wherein a same reference voltage is provided during the multiple read attempts; and generating, for each flash memory cell, reliability information based upon multiple read results of the flash memory cell.

Analog iterative decoders are provided that are based on the so-called min-sum algorithm (also referred to as max-sum or max-product, Max-Log-MAP or BP-based decoding) and can be used to decode powerful coding schemes such as low-density parity-check (LDPC) codes and turbo codes. The circuits can be implemented by standard CMOS technology, which means lower fabrication cost and/or simpler design compared to previously reported analog iterative decoders that are based on BiCMOS or sub-threshold CMOS technology. Soft information is passed among variable nodes and parity-check nodes. A low-voltage high-swing Max WTA circuit is also provided. The circuit can be implemented by short channel MOSFET transistors and yet provide a reasonably high degree of accuracy. Applications include soft computing, and analog signal processing, in general. A Min WTA circuit can also be built based on this circuit by subtracting the input currents from a large reference current.

The invention discloses a system and a method for realizing iterative timing synchronization of a continuous phase modulation (CMP) signal; the system is provided with a sender, and is composed of a maximum likelihood detector, a de-interleaver, a channel decoder and an information destination which are connected in order, and an interleaver which is used for interleaving an output signal of the channel decoder and feeding back the interleaved output signal to the maximum likelihood detector; a built-up circuit of the maximum likelihood detector comprises a match filter set, a demodulator, and a timing synchronization loop circuit arranged between the match filter set and the demodulator; a detecting method based on a maximum likelihood criterion is used for demodulating the received CPM signal, detecting and computing a timing error value and adjusting the time delay, and outputting a bit likelihood ratio of each symbol. Based on a timing error detecting method of the maximum likelihood criterion, a soft information assistance fed back by the channel decoder is used for realizing the timing synchronization to obtain an accurate timing deviation estimation; meanwhile, an iterativeprocess is used between the demodulation and the decoding to maximally improve an error bit ratio of the system; and the system and method for realizing iterative timing synchronization of the CMP signal can be applied in long-distance communication with the requirement of high performance.

Methods and apparatus for scaling soft values as part of an error correction decoding process are described. Accurate decoding depends on use of the appropriate scale factor. Selection and use of the scale factor to scale soft values is designed to improve and/or optimize decoder performance without the need for prior knowledge of the correct scale factor or the actual channel conditions at the time the signal from which the soft values were obtained was transmitted through a communications channel. The techniques of the present invention assume that the soft values to be processed were transmitted through a communications channel having a quality that can be accurately described by a channel quality value. A scale factor is determined from the distribution of soft values to be scaled and an assumption that the channel through which they were transmitted was of the quality corresponding to a preselected channel quality value.

In one embodiment, the present invention can be used to correct one more error in an extended codeword encoded with a block code and a single parity check code than the block code is able to correct. In one embodiment, a communications device includes a decoder that has a soft decoder to receive an extended codeword and a strength of each bit of the extended codeword, and to produce a codeword by soft decoding the extended codeword using the received strengths, and a block decoder coupled to the soft decoder to produce a corrected codeword by block decoding the codeword using an error correcting block code.