Huawei Technologies Co., Limited

Future Wei Technologies, Inc.

Mahdi Zamani

Zhuhong Zhang

Chuandong Li

Jeebak Mitra

Hossein Najafi

Ahikam Aharony

Demin Yao

Chen Chen

Mehdi Torbatian

Weikun Hou

Aspects of the present disclosure are directed in part to a receiver DSP unit including an equalization module. The equalization module includes a trellis-based equalization module that may utilize multiple trellis-based processors (TBP), which can each be individually adaptively configured for performing a trellis-based equalization. The design of the TBPs allows them to be configured for compensating a residual Inter-Symbol Interference (ISI) as well as compensating a residual Phase Noise (PN). ISI is an example of an additive impairment and PN is an example of a multiplicative impairment that communication systems, particularly high speed transmission systems such as coherent optical systems, can suffer from.

Trellis based processing for robust digital multiband transmission

An optical channel between a coherent optical transmitter and a coherent optical receiver may include one or more components that act as a bandpass filter with a passband that is narrower than the signal bandwidth. Such a narrow filter may significantly attenuate the signal content close to the band edge of the data signal. As a result, timing error detection may work less effectively, and therefore clock recovery may be less effective or fail. Methods and systems are disclosed in which a single optical carrier is used to transmit a data signal that has multiple bands, and timing error detection is performed at the receiver using one or more inner bands of the multiple bands. The timing error detection may therefore be made more robust to the effects of the narrow filtering.

Method and apparatus for robust clock recovery in coherent optical systems

An apparatus comprises a front end configured to receive an optical signal, and convert the optical signal into a plurality of digital signals, and a processing unit coupled to the front end and configured to determine a best-match chromatic dispersion (CD) estimate in the optical signal by optimizing a cost function based on signal peaks of the plurality of digital signals.

Chromatic dispersion estimation for digital coherent optical receivers

A digital signal processing method and apparatus is described. The digital processing apparatus comprises a coarse carrier recovery module for performing a coarse carrier compensation of a received modulated signal; and a trellis-based equalization module selectable between a first mode for performing a trellis-based equalization to compensate a residual inter-symbol interference of the received modulated signal and a second mode for performing a trellis-based equalization to compensate a residual phase noise of the received modulated signal.

Apparatus and method for unified mitigation of correlative additive and multiplicative noise

Optical network devices and method for optical network communications in discrete multi-tone (DMT) are provided. A serial information signal is converted to groups of bits and loaded to parallel processing branches based on bit rates of the parallel processing branches. Each branch is configured to encode the associated group of data bits on the associated tone. A first bit rate and modulation and power allocation to a first branch of the branches may be different from a second bit rate and modulation and power allocation to a second branch of the branches. To recover the incoming data, the encoded signal may be parallel-processed using branches with different demodulation formats and provide the serial data stream.

Method and system for discrete multi-tone transmission with multiple modulations

Provided is an apparatus and method for transmitting and receiving polarized signals. Wireless communication with multiple polarized signals may experience greater attenuation on one polarized signal than another polarized signal. The polarized signal that is more attenuated limits overall throughput for the wireless communication. According to an embodiment of the invention, signals undergo rotation processing with a transformation involving a rotation matrix prior to transmission. Each polarized signal that is transmitted is based on a different weighted combination of the signals. The rotation processing can be performed with an objective that signals recovered at a receiver have comparable signal quality, which can increase overall throughput. In some implementations, the rotation processing is performed based on feedback to dynamically adjust the rotation processing.

Apparatus and method for transmitting and receiving polarized signals

Provided is an apparatus and method for transmitting and receiving wireless signals. A transmitting apparatus has a signal processor and a transmitter. The signal processor is configured to generate a signal having a middle channel and at least one side channel. The transmitter is configured to wirelessly transmit the signal subject to a spectral mask that has shoulder regions. According to an embodiment of the invention, the signal processor generates the signal such that each side channel is positioned in one of the shoulder regions of the spectral mask. In this manner, bandwidth from the shoulder regions can be utilized by one or more side channels. Also provided is a receiving apparatus having a receiver configured to wirelessly receive the signal, and a signal processor configured to process the signal.

Apparatus and method for transmitting and receiving wireless signals subject to a spectral mask

A method and apparatus for performing residual phase noise compensation is described. A coarse carrier compensation of a received modulated signal is performed to obtain a coarse carrier compensated signal and a trellis-based residual carrier recovery is performed to estimate a residual phase noise of the coarse carrier compensated signal. The coarse carrier compensated signal is compensated based on the estimated residual phase noise.

Method and apparatus for residual phase noise compensation

The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [&#x2212;&#x3c0;,&#x3c0;] such that the summation of a function of PMF values where the function is convex or concave between 0 and 1 can be utilized to determine an a frequency offset to be used by the coherent receiver.

Method and apparatus with improved estimation accuracy and robustness for fine frequency offset estimation in coherent receivers

A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4&#xd7;4 matrix to generate four modulated symbols, wherein the 4&#xd7;4 matrix comprises 16 tap-vectors.

Linear dispersion polarization-time codes and equalization in polarization multiplexed coherent optical system

System and method embodiments are provided for bit loading for optical Discrete Multi-Tone Transmission (DMT). In an embodiment, a method for bit loading for optical DMT transmission or reception includes receiving, at a processor, a bit data stream, wherein the bit data stream comprises a plurality of subcarriers; assigning, with the processor, a code rate to each of a plurality of forward error correction (FEC) encoders/decoders according to a mapping of a signal-to-noise-ratio (SNR) to a code rate for each of the subcarriers or subcarrier groups, wherein each FEC encoder/decoder corresponds to a respective one of the subcarriers or a respective subcarrier group; and assigning, with the processor, a modulation format to each subcarrier or each subcarrier group according to a mapping of an SNR for each subcarrier or subcarrier group to a bit number for a corresponding subcarrier or subcarrier group.

Bit loading for optical discrete multi-tone transmission

An apparatus comprising an optical receiver configured to receive a plurality of orthogonal frequency-division-multiplexed (OFDM) symbols comprising a first OFDM symbol and a second OFDM symbol, and a processor coupled to the optical receiver and configured to generate a first decoded signal based on the first OFDM symbol, estimate a plurality of channel parameters adaptively based on the first decoded signal, generate a second decoded signal based on the second OFDM symbol, wherein the second decoded signal is generated using the plurality of channel parameters, and wherein phase recovery is performed on the first OFDM symbol using a number of pilot subcarriers prior to generating the first decoded signal.

Channel estimation for optical orthogonal frequency division multiplexing systems

The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [&#x2212;&#x3c0;,&#x3c0;] such that the summation of square of PMF (PMF sum-square) values is minimized. However at the actual frequency offset, the signal phase is no longer uniformly distributed over [&#x2212;&#x3c0;,&#x3c0;]; in other words the signal phase will take some specific values in [&#x2212;&#x3c0;,&#x3c0;], therefore a peak PMF sum-square value will result. This peak PMF value provides an indication of the actual offset frequency of the received signal.

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Ottawa, Canada

Mahdi Zamani