Abstract: A method decodes an optical signal transmitted over an optical channel from a transmitter to a receiver. The receiver receives the transmitted optical signal to produce a digital signal which is filtered in the frequency domain for compensating static effects and/or dynamic effects. The filtering is performed in the frequency domain, while the frequency coefficients of the filter are updated in the time domain by updating at least some of time coefficients of the filter and transforming the time coefficients into the frequency domain.

Abstract: A power encoder includes a pulse width modulator for modulating a signal according to a set of thresholds to produce a pulse width modulated (PWM) signal and a switch mode power amplifier for amplifying the PWM signal by switching states of switching devices according to amplitudes of the PWM signal. At least one or combination of a distribution of values of the voltage thresholds in the set and a distribution of values of a current generated by different switching devices are non-uniform. The set of voltage thresholds includes at least two positive voltage thresholds.

Abstract: A method receives the symbol transmitted over a channel, selects, from a constellation of codewords, a first codeword neighboring the received symbol and a set of second codewords neighboring the first codeword, and determines a relative likelihood of each second codeword being the transmitted symbol with respect to a likelihood of the first codeword being the transmitted symbol. Next, the method determines an approximation of a log-likelihood ratio (LLR) of each data bit in the received symbol as a log of a ratio of a sum of the relative likelihoods of at least some of the second codewords having the same value of the data bit to a sum of the relative likelihoods of at least some of the second codewords having different value of the data bit and decodes the received symbol using the LLR of each data bit.

Abstract: In an advanced adaptive modulation and coding (AMC) scheme, the code rate and the parity-check matrix (PCM) for low-density parity-check (LDPC) codes are adapted according to modulation formats and variable-iteration receivers. The degree distribution for the PCM adaptation is designed by heuristic optimization to minimize the required SNR via an extrinsic information transfer (EXIT) trajectory analysis for finite-iteration decoding. The method uses dynamic window decoding by generating spatially coupled PCM for quasi-cyclic LDPC convolutional coding. The method also provides a way to jointly optimize labeling and decoding complexity for high-order and high-dimensional modulations.

Abstract: The data are communicated from a transmitter to a receiver in a wireless communications network. Data symbols are modulated using a coded modulation to produce modulated symbols and the modulated symbols are precoded using a precoder matrix to produce precoded symbols. The precoder matrix is formed using a rotation matrix including phase angles for at least some elements of the rotation matrix with values determined according to a parametric function of indices of the elements storing the phase angles. Next, the data packets are formed using the precoded symbols and the data packets are transmitted over the wireless network. Multi-stage parametric phase precoding provides full-diversity and full-rate transmissions by using fast-transformable unitary matrices and deterministic diagonal phase rotation, whose phase angles are pre-determined to minimize the union bound for time-selective and frequency-selective fading channels.

Abstract: A method for decoding a codeword transmitted over a channel demodulates data received over the channel to produce an initial estimate of belief messages for bits of the codeword and decodes the codeword using a belief propagation (BP) decoding that iteratively passes the belief messages between a set of variable nodes representing the bits of the codeword and a set of check nodes representing parity-check constraints on the bits of the codeword until a termination condition is met. The BP decoding selects a look-up table based on a probability of the belief messages and maps, using the look-up table, values of at least two incoming belief messages to values of at least one outgoing belief message that forms an incoming belief message in a subsequent iteration of the BP decoding.

Abstract: A method receives the symbol transmitted over a channel, selects, from a constellation of codewords, a first codeword neighboring the received symbol and a set of second codewords neighboring the first codeword, and determines a relative likelihood of each second codeword being the transmitted symbol with respect to a likelihood of the first codeword being the transmitted symbol. Next, the method determines an approximation of a log-likelihood ratio (LLR) of each data bit in the received symbol as a log of a ratio of a sum of the relative likelihoods of at least some of the second codewords having the same value of the data bit to a sum of the relative likelihoods of at least some of the second codewords having different value of the data bit and decodes the received symbol using the LLR of each data bit.

Abstract: A method generates constant modulus multi-dimensional modulations for coherent optical communications by first projecting points in a constellation of the code onto a Poincare sphere or its higher-dimensional hyper-sphere. By using meta-heuristic procedures, nonlinear programming and gradient search methods, constellation points in the hyper-sphere are optimized in certain criteria, such as maximizing the minimum Euclidean distance, minimizing the union bound, minimizing the bit-error rate, minimizing the required signal-to-noise ratio, maximizing the nonlinear fiber reach, maximizing the phase noise tolerance, and maximizing the mutual information. Some methods use parametric unitary space-time block codes such as Grassmannian packing, and filter impulse response as well as unitary rotation over adjacent code blocks to generate near-constant modulus waveform, not only at the symbol timing, but also over the entire time.

Abstract: A method modulates data for optical communication by first encoding the data using a forward error correction (FEC) encoder to produce encoded data, which are encoded using a block encoder to produce block encoded data such that Lee distances between code words that represent the block encoded data are increased. The block encoded data are mapped to produce mapped data such that Euclidian distances between the constellation points are increased. Then, the mapped data are modulated in a transmitter to a modulated signal for an optical channel.

Abstract: A method for transmitting data over an optical super-channel partitions the data unequally into a set of data streams for transmission over the set of sub-channels of the super-channel, such that a size of a first data stream for transmission over a first sub-channel is different than a size of a second data stream of the data for transmission over a second sub-channel. The method encodes each data stream of the data with an error correction code (ECC) having different ECC rates to produce a set of encoded data streams and transmits concurrently the set of encoded data streams over the set of sub-channels of the super-channel. Accordingly, the method uses an adaptive ECC for optical super-channels, such that a first ECC rate for encoding the first data stream is different than a second ECC rate for encoding the second data stream.

Abstract: An optical manipulator includes a first section for propagating an optical signal with multiple polarization modes including a transverse electric (TE) mode and a transverse magnetic (TM) mode and a second section for propagating separately the TE mode and the TM mode of the optical signal. The optical manipulator also includes a multi-mode interference (MMI) section having a groove with a first refractive index less than a second refractive index of the MMI section. The groove extends along an entire length of the MMI section to partition the MMI section into two connected channels including a first channel and a second channel. The first section is connected to the first channel and the second section is connected to both the first and the second channels.

Abstract: A method decodes an optical signal transmitted over an optical channel from a transmitter to a receiver. The receiver receives the transmitted optical signal to produce a digital signal including data symbols and pilot symbols, and determines filtering coefficients based on an error between amplitudes of the received pilot symbols and amplitudes of transmitted pilot symbols, while ignoring errors between phases of the received pilot symbols and phases of the transmitted pilot symbols. The amplitudes and the phases of the transmitted pilot symbols are known at the transmitter and the receiver. The receiver filters the digital signal according to the filtering coefficients to produce a filtered signal with equalized amplitude and an unconstrained phase demodulates and decodes the filtered signal to produce an estimate of the transmitted optical signal.

Abstract: A method decodes a block of data received over a communication channel. The method determines an initial estimate of bits in the block using a QR decomposition (QRD-M) method decoding the bits in the block sequentially by reducing an accumulated distance between the initial estimate and the bits of the block. Then, the method determines the block using a likelihood ascent (LAS) method that iteratively updates the bits of the block starting from the initial estimate.

Abstract: A system and method provides high-quality video streaming in wireless video communications. The system includes a digital codec, an analog codec, and a power controller. The output of the digital and analog encoders are superposed and transmitted to a receiver employing a digital and analog decoders over a wireless channel. The method uses high-order modulation for digital encoded data, optimal power allocation for digital and analog data, optimal subcarrier assignment to enhance a water-filling gain, and compressive sensing to reduce packet loss during wireless communications. In addition, the system provides an optimal power allocation for multi-view texture and depth information taken by multiple cameras to improve video quality according to channel quality, camera geometry, and a free-viewpoint rendering procedure based on analysis with polynomial fitting.

Abstract: The embodiments of the invention provide methods to deal with problems of cycle slips, angular skew, and residual phase noise for high-speed optical communications employing any arbitrary high-order multi-dimensional modulation formats. The embodiments use a slip process analyzer, a skew angle estimator, and a phase noise variance estimator to provide feedforward soft-decision information of a carrier phase recovery (CPE) for more accurate likelihood calculation based on a high-order hidden Markov model (HMM). The log-likelihood calculation can be done jointly in dual polarization with joint Markov state transition. Some embodiments use a kernel filter or a particle filter for log-likelihood calculation.

Abstract: An optical manipulator includes a first section for propagating an optical signal with multiple polarization modes including a transverse electric (TE) mode and a transverse magnetic (TM) mode and a second section for propagating separately the TE mode and the TM mode of the optical signal. The optical manipulator also includes a multi-mode interference (MMI) section having a groove with a first refractive index less than a second refractive index of the MMI section. The groove extends along an entire length of the MMI section to partition the MMI section into two connected channels including a first channel and a second channel. The first section is connected to the first channel and the second section is connected to both the first and the second channels.

Abstract: A method decodes an optical signal transmitted over an optical channel from a transmitter to a receiver. The receiver receives the transmitted optical signal to produce a digital signal including data symbols and pilot symbols, and determines filtering coefficients based on an error between amplitudes of the received pilot symbols and amplitudes of transmitted pilot symbols, while ignoring errors between phases of the received pilot symbols and phases of the transmitted pilot symbols. The amplitudes and the phases of the transmitted pilot symbols are known at the transmitter and the receiver. The receiver filters the digital signal according to the filtering coefficients to produce a filtered signal with equalized amplitude and an unconstrained phase demodulates and decodes the filtered signal to produce an estimate of the transmitted optical signal.

Abstract: The data are communicated from a transmitter to a receiver in a wireless communications network. Data symbols are modulated using a coded modulation to produce modulated symbols and the modulated symbols are precoded using a precoder matrix to produce precoded symbols. The precoder matrix is formed using a rotation matrix including phase angles for at least some elements of the rotation matrix with values determined according to a parametric function of indices of the elements storing the phase angles. Next, the data packets are formed using the precoded symbols and the data packets are transmitted over the wireless network. Multi-stage parametric phase precoding provides full-diversity and full-rate transmissions by using fast-transformable unitary matrices and deterministic diagonal phase rotation, whose phase angles are pre-determined to minimize the union bound for time-selective and frequency-selective fading channels.

Abstract: The transmission of data from a transmitter to a receiver over an optical super-channel including a set of sub-channels of different frequencies includes partitioning the data into a set of data streams including one data stream for each sub-channel and partitioning each data stream into a set of sub-streams. Each sub-stream of each data stream is encoded with different forward error correction (FEC) codes to produce a set of encoded sub-streams for each data stream, and the set of encoded sub-streams of each data stream are superimposed with different powers to produce a set of encoded data streams. The set of encoded data streams is multiplexed to produce an optical signal transmitted over the set of sub-channels of the optical super-channel.

Abstract: In an advanced adaptive modulation and coding (AMC) scheme, the code rate and the parity-check matrix (PCM) for low-density parity-check (LDPC) codes are adapted according to modulation formats and variable-iteration receivers. The degree distribution for the PCM adaptation is designed by heuristic optimization to minimize the required SNR via an extrinsic information transfer (EXIT) trajectory analysis for finite-iteration decoding. The method uses dynamic window decoding by generating spatially coupled PCM for quasi-cyclic LDPC convolutional coding. The method also provides a way to jointly optimize labeling and decoding complexity for high-order and high-dimensional modulations. The problem to use a large number of different LDPC codes for various modulation formats and variable-iteration decoding is also dealt with by linearly dependent PCM adaptation across iteration count to keep using a common generator matrix.