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 MIMO symbol detection and search method, a decoding circuit and a receiving antenna system are provided. The signal detection and search method includes the following steps. A symbol search tree is obtained, and a plurality of candidate symbols at each layer of the symbol search tree are sorted. The candidate symbols are traversed in sequence at each layer of the symbol search tree. At each layer of the symbol search tree, if a cumulative partial Euclidean distance is greater than or equal to a threshold, un-scanned candidate symbols are excluded. If the cumulative partial Euclidean distance is less than the threshold, the threshold is updated by the cumulative partial Euclidean distance. When all of the candidate symbols have been calculated, an estimated symbol combination is outputted, and the scan of the symbol search tree is terminated.

Methods are disclosed for improving communications on feedback transmission channels, in which there is a possibility of bit errors. The basic solutions to counter those errors are: proper design of the CSI vector quantizer indexing (i.e., the bit representation of centroid indices) in order to minimize impact of index errors, use of error detection techniques to expurgate the erroneous indices and use of other methods to recover correct indices.

The present disclosure provides techniques for bandwidth constrained communication systems with frequency domain information processing. A bandwidth constrained equalized transport (BCET) communication system can include a transmitter, a communication channel, and a receiver. The transmitter can include a pulse-shaping filter that intentionally introduces memory into a signal in the form of inter-symbol interference, an error control code (ECC) encoder, a multidimensional fast Fourier transform (FFT) processing block that processes the signal in the frequency domain, and a first interleaver. The receiver can include an information-retrieving equalizer, a deinterleaver with an ECC decoder, and a second interleaver joined in an iterative ECC decoding loop. The communication system can be bandwidth constrained, and the signal can comprise an information rate that is higher than that of a communication system without intentional introduction of the memory at the transmitter.

A receiver includes a decision feed forward equalization (DFFE) system coupled to a partial response (PR) system. The partial response system generates, based on a digital signal that includes pre-cursor intersymbol interference (ISI) and post-cursor ISI introduced by a communication channel, a detected signal including a set of detected symbol values. The detected signal is equalized to a partial response. The DFFE system includes a PR inverter to generate a set of estimated transmitted symbol values based on the set of detected symbol values and DFFE circuitry to cancel the pre-cursor ISI and the post-cursor ISI from the detected signal using the set of estimated transmitted symbols and a set of tap coefficients to obtain a compensated signal and a set of compensated symbol values.

A sequence detection device includes a decision-feedback equalizer (DFE), a combining circuit, a decision circuit, and a sequence detection circuit. The DFE processes a symbol decision signal to generate a first equalized signal. The combining circuit combines a data signal and the first equalized signal to generate a sample signal. The decision circuit performs hard decision upon the sample signal to generate the symbol decision signal. The sequence detection circuit performs sequence detection upon the data signal to generate and output a symbol sequence. Regarding the sequence detection, the sequence detection circuit selects branches for branch metric calculation according to at least the symbol decision signal.

A receiver includes a decision feed forward equalization (DFFE) system that generates, based on a digital signal that includes at least one intersymbol interference (ISI) value introduced by a communication channel, a detected signal including a set of detected symbol values. The DFFE system cancels the at least one ISI value from the detected signal using the set of estimated transmitted symbols and a set of tap coefficients to obtain a compensated signal and a set of compensated symbol values.

An apparatus including a processor configured to receive a digital communication signal having a plurality of transmitted layers. The processor is configured to determine an estimated channel matrix based on the digital communication signal, determine a first estimated transmitted symbol vector and a mean square error matrix based on a linear analysis of the received digital communication signal. A first set of bit LLR are determined based on a LMMSE type detector and a second set of bit LLR are determined based on a novel simplified tree search process. The two sets of bit LLR are then combined and used to detect the data in the received communication signal. The simplified tree search process uses a specially formed channel shortening process to determine a set of shortened channel correlation matrices that allow the second set of bit LLR to be determined using an alternative marginalized tree search process.

In a receiver of Quadrature Amplitude Modulation (QAM) signal, the received QAM signal is divided into multiple Quadrature Phase Shift Keying (QPSK) symbol streams. A Maximum Likelihood Symbol Estimation (MLSE) is performed on each QPSK symbol stream to recover information bits in the received QAM signal. In one advantageous aspect, complexity of implementation can be reduced by performing MLSE on QPSK signals instead of QAM signals.

Methods, systems, and computer program products for decoding a received data signal in a communication system by iteratively constructing a decoding tree, each node of said decoding tree corresponding to a component of a symbol of said data signal, and being associated with a metric, the construction of the decoding tree implementing at least one iteration of the following steps, for a current node of the tree stored in the top of a stack: generating (102) a reference child node of said current node from said vector representing the received data signal, from the reference child node, generating (106) a first neighbor child node by subtracting a positive integer parameter from the value of the reference node, and a second neighbor child node by adding said positive integer parameter to the value of the reference child node; storing (108) in said stack three child nodes deriving from the reference child node and from said first and second neighbor child nodes, each child node being stored in the stack in association with node information comprising a predetermined metric, the nodes in the stack being ordered by increasing values of metrics; removing (109) the current node from said stack; selecting (111) the top node of said stack as the new current node;
wherein said method further comprises determining an estimation of said data signal from the node information stored in said stack.