Viasat, Inc.

Comtech Aha Corporation

Other

Efficient Channel Coding, Inc.

Visat, Inc.

Thesling, William H.

William H Thesling

Matthew D Nimon

Fan Mo

Donald Wesley Becker

Sameep Dave

Mark Vanderaar

Mark D Dankberg

Russell Fuerst

Mark Kohoot

Jim Keszenheimer

Yuri Zelensky

Richard T Gedney

Mark Dale

Mark J Vanderaar

Methods, systems, and devices are described for modulating data for optical transmissions and demodulating data from optical transmissions. During modulation, bits are mapped to symbols using an 8-ary modulation scheme. The modulation scheme may be based on 8 Phase Shift Keying (8-PSK), Dual Polarization 8-PSK, or 7-1 PSK for which one of the symbols is located at or near the origin of the constellation. Streams with the symbol-mapped bits are modulated onto a waveform in the digital domain that is converted into a waveform in the analog domain before is output for conversion to an optical signal. The streams may be filtered at baseband with at least one discrete pulse-shaping filter. During demodulation, pulse-shaped data received from an optical signal and comprising symbol-mapped bits based on the 8-ary modulation scheme is sampled. The sampled data is filtered with at least one discrete pulse-shaping filter, and then equalized and demodulated.

High data rate optical transport network using 8-psk

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 detecting and correcting a cycle slip occurrence in a coherent receiver. Unique words are used in each received frame to detect phase changes that indicate the occurrence of a cycle slip within a frame. The location of the cycle slip is identified based on measurements made within the frame. Those measurements include phase estimation measurements and reliability measurements. A phase of a portion of the frame subsequent to the identified location of the cycle slip is adjusted to correct for the cycle slip. By combining phase estimates of symbols from both vertical and horizontal polarizations, the location of the cycle slip may be more accurately determined because the measurement windows is less susceptible to thermal noise. The phase estimates are combined by adjusting a phase of the symbols of one polarization to match a phase of the symbols of the other polarization.

Low cycle slip phase recovery for coherent receiver

High data rate optical transport network using 8-PSK

Systems, devices, processors, and methods are described which may be used for the reception of a wireless broadband signal at a user terminal from a gateway via a satellite. A wireless signal may include a series of physical layer frames, each frame including a physical layer header and payload. The received signal is digitized and processed using various novel physical layer headers and related techniques to synchronize the physical layer frames and recover data from physical layer headers for purposes of demodulation and decoding.

False lock detection for physical layer frame synchronization

Systems, devices, processors, and methods are described for the transmission and reception of broadband signals between a gateway and subscriber terminals via satellite. In one set of embodiments, a wireless signal is generated and transmitted including a series of frames including a physical layer header and payload. A sub-channel identifier may be included in the physical layer header to identify the sub-channel for the payload, and allow for various novel filtering techniques at the subscriber terminal. The frames may be generated to be of substantially equal duration. Novel subscriber terminal configurations are described to leverage this formatting.

Method for formatting data of a physical layer frame

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

Symbol timing acquisition is described for a wireless broadband signal received at a user terminal from a gateway via a satellite. In-phase and quadrature channels of the wireless signal may each be sampled at a rate of one sample per symbol. The samples may be interpolated to generate an early interpolation and a late interpolation for each of the samples. A difference measurement is obtained between the early interpolation and the late interpolation for a set of the samples. A number of the difference measurements may be averaged, and symbol timing may be modified based on the average. This process may be continued on an iterative basis to acquire symbol timing.

Symbol timing acquisition using early-late interpolation

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, processors, and methods are described which may be used for the reception of a wireless broadband signal at a user terminal from a gateway via satellite. A physical layer header may be identified, the header including a number of subcode blocks. A phase may be estimated for each of the subcode blocks, and intra-header phase differences may be calculated. The intra-header phase differences may be used to calculate a frequency error, which may be corrected. Frequency errors may be monitored and, when such errors fall below a threshold level, an alternative inter-frame frequency error tracking method may be used.

Delta-theta frequency estimation

Methods, systems, and devices are described for a low complexity interpolator for use in optical transmission systems. An input receives a digitized version of an optical signal, and provides samples of the received signal to a filter module. The filter module filters the input samples according to a set of filter coefficients provided by a memory. The set of filter coefficients are provided based on the output of a numerically controlled oscillator that provides an output corresponding to an accumulation of partial periods of the first sample rate. Filtered data samples are output to a sample block assembler that receives the data samples, removes filtered data samples where it is indicated that the sample is not valid, and outputs valid filtered data samples at the second sample rate and at a fixed number of samples power output period.

Interpolator for high-rate optical communications

Methods, systems, and devices are described for compensating for a coarse frequency offset between a received optical signal and a local oscillator at a demodulator. Multiple samples are received of an output of a discrete Fourier transform performed on the received optical signal. A magnitude of each sample is determined, and the determined magnitudes may be filtered by a digital domain filter. A difference is computed between the determined magnitudes for a first set of the samples and the determined magnitudes for a second set of the samples, and a local oscillator correction factor is generated based on at least the computed difference.

Coarse frequency offset estimation and correction for high-speed optical communications

Methods, systems, and devices are described for estimating a frequency response using a received signal. A first spectral estimation is performed on a digitized representation of an initial version of a wireless signal. A second spectral estimation is performed on the digitized representation of the wireless signal as received from the transmitter. The first spectral estimation is compared with the second spectral estimation to estimate a frequency response. A later signal transmitted from the transmitter may be pre-distorted to compensate for the estimated frequency response. The disclosed frequency response estimation techniques may be used in a satellite communications system.

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Bedford, OH, United States of America

William H Thesling