Viasat, Inc.

Visat, Inc.

Effect Photonics B.v.

Sameep Dave

Fan Mo

William H Thesling

Yuri Zelensky

Murat Arabaci

Matthew D Nimon

Russell Fuerst

Jim Keszenheimer

William H Miller

Mark Kohoot

Lawrence W Esker

Eric A Fowlie

A system and method of creating frames comprised of blocks, where each block comprises data symbols corresponding to a higher order quadrature modulation format and support symbols corresponding to a lower order modulation format. One or more of the blocks can further comprise markers comprising distinct symbol patterns. The markers can mark the start of each frame and/or another location in the frame. The support symbols can be in a common location in each block.

Systems and methods for creating in a transmitter a stream of symbol frames configured for efficient processing in a receiver

A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame. Each sample block can comprise a first region that contains first samples corresponding to the selected first modulation format or overhead samples regardless of the selected first modulator format or an index of the sample block in the frame; a second region that contains second samples corresponding to a second modulation format regardless of the selected first modulator format or an index of the sample block in the frame; and a third region in which whether the samples are first samples or second samples depends on the selected first modulation format or the index of the sample block in the frame. The system estimates first metrics according to the selected first modulation format for each of the first samples and second metrics according to the second modulation format for each of the second samples. The system also estimates both first metrics and second metrics for each of the third samples and then selects valid ones of the first metrics and second metrics for the third samples in accordance with the selected first modulation format or the index of the sample block in the frame.

Generating metrics from samples of a received signal in a communications receiver supporting multiple operating modes

One example includes an equalizer system. The system includes a filter system configured to receive digital sample blocks associated with an input signal and to provide equalized digital sample blocks associated with the respective digital sample blocks based on adaptive tap weights. Each of the digital sample blocks includes samples and each of the equalized digital sample blocks includes equalized samples. The system also includes a sample set selector to select a subset of equalized samples from each of the equalized digital sample blocks at the output of the filter and an error estimator configured to implement an error estimation algorithm on the subset of the equalized samples to determine a residual error associated with the equalized samples. The system further includes a tap weight generator configured to generate the adaptive tap weights in response to the residual error and to provide the adaptive tap weights to the filter.

Adaptive equalizer system

Methods, systems, and devices are described for modulating and demodulating data on optical signals. During modulation, at least one stream of symbol mapped bits is filtered with at least one pulse shaping filter to reduce a bandwidth of the stream of bits and to pre-compensate for at least one identified non-ideal transmission condition. The filtered bits are modulated onto a waveform in the digital domain, and the modulated filtered bits are transmitted to digital-to-analog converter. The output of the digital-to-analog converter is converted to an optical signal. During demodulation, a received optical signal is sampled at a first sampling rate at an ADC, downsampled to a lower sampling rate for filtering, filtered with at least one discrete pulse-shaping filter, upsampled for equalization and demodulation, and then equalized and demodulated.

DAC-based optical modulator and demodulator

Methods, systems, and devices are described for soft-decision decoding of data received from optical signals and encoded using a forward error correction (FED) code. A first reliability information is determined for a subset of the bits corresponding to each symbol transmitted using differentially-encoded 16 Quadrature Amplitude Modulation (16-Qam). A second reliability information is determined for a remaining subset of the bits. The first reliability information is based on log likelihood ration (LLR) calculations used for soft-decision FEC decoding of data transmitted using differentially-encoded Quadrature Phase-Shift Keying (QPSK), while the second reliability information is based on LLR calculations used for soft-decision FEC decoding of data transmitted using coherently-encoded 16-QAM. The second reliability information may be pre-calculated and accessed from a lookup table based on a location of the respective symbol in a complex in-phase and quadrature plane. They symbols are then decoded using the two sets of reliability information.

Soft-decision decoding of differential 16-QAM

Methods, systems, and devices are described for filtering data from an optical signal to compensate for chromatic dispersion in an optical path. Samples of different polarizations are filtered in the frequency domain with a matched filter by time-sharing a conversion module. The conversion module first converts a set of samples to the frequency domain for filtering when in a Fast Fourier Transform (FFT) configuration and then converts the filtered set of samples back to the time domain when in an Inverse FFT (IFFT) configuration. The size of the FFT in the FFT configuration and of the IFFT in the IFFT configuration is the same as the size of the samples being processed by the conversion module to enable both configurations to be based on a set of constant multipliers. Both configurations may be based on a pipelined architecture to sequentially process the samples in an efficient manner.

Low power low complexity chromatic dispersion compensation

Methods, systems, and devices are described for formatting of data streams to be transmitted over fiber optic channels, and for processing received optical signals. A data transmission device may include a digital coding and modulation module that encodes a digital data stream, inserts unique words into the digital data stream, and modulates the encoded data stream and unique words onto optical channels for transmission over an optical fiber. A demodulation and decoding device may include a unique word identification module that identifies the unique words inserted in each optical channel stream, determines one or more characteristics of the plurality of optical channels based on the unique words, and provides the one or more characteristics to one or more other modules in the demodulator and decoding device.

Frame formatting for high rate optical communications

Methods, systems, and devices are described for equalizing data from an optical signal. Samples are filtered with at least one filter to compensate for polarization mode dispersion in an optical path. The filtered samples may be used to determine errors based on a difference between a radius of a recovered symbol and a target radius. A parameter may be assigned to one or more of the errors and properties of the at least one filter may be updated based on the assigned parameters. The parameter may be assigned from a small set of parameters based on at least one threshold value. Outputs generated from the filtered samples may also be assigned a parameter from a different set of parameters. The parameter assigned to the output may be used to update the particular set of taps of the at least one filter from which the output was generated.

Simplified polarization mode dispersion equalization

Methods, systems, and devices are described for forward error correction for flash memory. Encoded data from flash memory may be used to generate a number of data streams. At each of a number of error detection sub-modules operating in parallel, a different one of the data streams is processed. Each error detection sub-module may detect whether a portion of the respective received stream contains an error, and forward the portion to an error correction module. The error correction module, physically separate from the error detection sub-modules, may correct the forwarded portions of the respective received streams containing an error. The age and error rate associated with the flash memory may be monitored, and a coding rate or other aspects may be dynamically adapted to account for these factors.

Forward error correction with parallel error detection for flash memories

Methods, systems, and devices are described for decoding data using a low-density parity check (LDPC) decoder. An edge memory in the LDPC decoder is configured to have a first bank and a second bank of memory partitions. The first bank stores extrinsic information for edges for a first set of N check nodes and the second bank stores extrinsic information for edges for a second set of N check nodes. The first and second banks are concurrently accessed to process 2N check nodes in parallel. The first and second sets of N check nodes may respectively correspond to odd-numbered and even-numbered check nodes from the 2N check nodes processed in parallel by the LDPC decoder. The LDPC decoder operation may include initializing channel soft information into a memory different from the edge memory and the use of incremental changes in the extrinsic information to update the extrinsic information.

High-speed LDPC decoder

Methods, systems, and devices are described for a digital demodulator device for processing received optical signals. The device may include a quadrature error filter that receives a digitized version of an optical signal, and removes quadrature errors to generate a filtered series of data samples. The device may also include a frequency offset removal module for performing frequency rotation on the filtered series of data samples. The device may include a chromatic dispersion compensation module which removes chromatic dispersion from horizontal and vertical polarization channels. The device may include a polarization mode dispersion (PMD)/polarization dependent loss (PDL) compensation module which compensates for interference caused by PMD and PDL. The device may also include a phase recovery module configured to track and correct phase.

Digital demodulator architecture

Systems, devices, and methods are disclosed for a novel LDPC decoder. An architecture is described to implement a novel sequence of bit node processing (BNP) and check node processing (CNP) operations. More specifically, the BNP may be split into two parts: a BNP accumulator and a BNP extrinsic information calculator. This separation of processing modules may provide for fewer read and write operations to and from edge memory.

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Hinckley, OH, United States of America

Sameep Dave