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    Method and apparatus of low-complexity pattern dependent lookup table pre-compensation
    1.
    发明授权
    Method and apparatus of low-complexity pattern dependent lookup table pre-compensation 有权

    公开(公告)号：US11451329B2

    公开(公告)日：2022-09-20

    申请号：US17157691

    申请日：2021-01-25

    申请人： Jianhong Ke ,  Chuandong Li ,  Xuefeng Tang

    发明人： Jianhong Ke ,  Chuandong Li ,  Xuefeng Tang

    IPC分类号： H04L1/00

    摘要： Methods and systems for performing signal pre-correction of a transmission signal comprising a sequence of symbols using a Pattern Dependent Look-up Table (PDLUT) containing one or more distortion correction values. Upon accessing a distortion correction value from the PDLUT for a symbol of the sequence of symbols, the accessed distortion correction value is quantized into one or more quantized values according to one or more quantizations, thereby reducing the bit-width of the distortion correction value. The transmission signal and the distortion correction value with reduced bit-width may undergo linear correction compensation, such as through a finite impulse response (FIR) filter, independent of one another, where the one or more quantized correction values with reduced bit-width reduce a number of calculation steps performed during linear correction compensation resulting in power savings. The linearly compensated quantized values and the linearly compensated signal are combined to form a pre-corrected signal.

    Method and apparatus for frequency domain equalization with low complexity and loop delay
    2.
    发明授权
    Method and apparatus for frequency domain equalization with low complexity and loop delay 有权

    公开(公告)号：US11108599B1

    公开(公告)日：2021-08-31

    申请号：US16936098

    申请日：2020-07-22

    申请人： Chuandong Li ,  Jianhong Ke

    发明人： Chuandong Li ,  Jianhong Ke

    IPC分类号： H04L25/03 ,  H04B10/61

    摘要： Methods and devices are described for frequency domain equalization with low complexity and loop delay. A transmitter inserts pilot symbols into a data signal at intervals of every n data bits. These pilot symbols are used by a receiver-side frequency-domain equalizer to calculate error levels and equalize the received data signal to effect impairment compensation such as SOP tracking. QPSK or BPSK symbols may be used for the pilot symbols, simplifying error calculation into an addition operation instead of the conventional multiplication operation required by conventional FDEQs. Equalizers are described that may operate in a pilot-assisted mode, a conventional decision-directed mode, or both.

    Apparatuses and methods of far-end transmitter skew monitoring in digital subcarrier multiplexing systems
    4.
    发明授权
    Apparatuses and methods of far-end transmitter skew monitoring in digital subcarrier multiplexing systems 有权

    公开(公告)号：US11581951B1

    公开(公告)日：2023-02-14

    申请号：US17589284

    申请日：2022-01-31

    申请人： Wing Chau Ng ,  Xuefeng Tang ,  Chuandong Li

    发明人： Wing Chau Ng ,  Xuefeng Tang ,  Chuandong Li

    IPC分类号： H04B10/61 ,  H04J14/02 ,  H04B10/516

    摘要： Apparatuses and methods for far-end monitoring of transmitter IQ skew in a DSCM system are described. Soft symbols for a given subchannel and a corresponding mirror subchannel are used as joint inputs to a MIMO equalizer. The hard decision symbols for the given subchannel and mirror subchannel are used as references to compute the equalizer coefficients. An estimated phase or estimated transmitter IQ skew is computed for at least the given subchannel using the equalizer coefficients. The computation is repeated to obtain estimated phase or estimated transmitter skew for all subchannels. The transmitter IQ skew is computed using the estimates from all subchannels. The computation is performed for each polarization. The computed transmitter IQ skew is communicated back to the transmitter via optical path (for correcting the skew).

    Optical transceiver, communication system, and adaptive frequency control method
    5.
    发明授权
    Optical transceiver, communication system, and adaptive frequency control method 有权

    公开(公告)号：US10187155B2

    公开(公告)日：2019-01-22

    申请号：US15352040

    申请日：2016-11-15

    申请人： Zhiping Jiang ,  Chuandong Li ,  Zhuhong Zhang ,  Xuefeng Tang

    发明人： Zhiping Jiang ,  Chuandong Li ,  Zhuhong Zhang ,  Xuefeng Tang

    IPC分类号： H04B10/00 ,  H04B10/40 ,  H04B3/32 ,  H04B10/556 ,  H04Q11/00 ,  H04B10/572 ,  H04B10/61 ,  H04J14/02

    摘要： An optical transceiver is provided with an optical front end for receiving signal light comprising an optical sub-channel, and for providing an electrical signal based on the signal light; a light source optically coupled to the optical front end for providing local oscillator light thereto for mixing with the signal light; an electro-optical modulator coupled to the light source for receiving output light therefrom and for modulating the output light with digital information to obtain modulated light; and a signal processor operably coupled to the optical front end. The signal processor is configured for processing the electrical signal to obtain a frequency offset of the sub-channel; and adjusting an optical frequency of the modulated light based on the frequency offset. When applied to a multiple-access environment, this may allow access nodes to generate optical sub-channels in the uplink direction using the downlink optical signal as an optical frequency reference.

    PARTIALLY DISJOINT EQUALIZATION AND CARRIER RECOVERY
    8.
    发明申请
    PARTIALLY DISJOINT EQUALIZATION AND CARRIER RECOVERY 审中-公开

    公开(公告)号：US20190182082A1

    公开(公告)日：2019-06-13

    申请号：US15838499

    申请日：2017-12-12

    申请人： Nash'at Abughalieh ,  Syed Faisal Ali Shah ,  Chuandong Li

    发明人： Nash'at Abughalieh ,  Syed Faisal Ali Shah ,  Chuandong Li

    IPC分类号： H04L25/03 ,  H04B10/61

    摘要： An apparatus in a signal receiver, such as an optical signal receiver, is provided. An adaptive equalizer provides an equalized output indicative of a received signal. A feedback component receives the equalized output and provides feedback to the adaptive equalizer. A carrier recovery component receives the equalized output from the adaptive equalizer provides estimates of symbols. The carrier recovery component is partially or fully disjoint from the feedback component, thus removing the carrier recovery component from equalizer the feedback loop. The feedback component can include an initial carrier recovery component and a phase rotation and detection component. The initial carrier recovery component generates a carrier recovery output based on the equalized output. The phase rotation and detection component performs a phase rotation based on the carrier recovery output.

    Fractionally spaced adaptive equalizer with non-integer sampling
    10.
    发明授权
    Fractionally spaced adaptive equalizer with non-integer sampling 有权

    公开(公告)号：US09755864B1

    公开(公告)日：2017-09-05

    申请号：US15228592

    申请日：2016-08-04

    申请人： Syed Faisal Ali Shah ,  Chuandong Li ,  Zhuhong Zhang

    发明人： Syed Faisal Ali Shah ,  Chuandong Li ,  Zhuhong Zhang

    IPC分类号： H04L25/03

    CPC分类号： H04L25/03949 ,  H04L25/03063 ,  H04L25/03885

    摘要： An apparatus for performing fractionally spaced adaptive equalization with non-integer sub-symbol sampling has an adaptive equalizer that receives a continuous stream of input data having a non-integer, fractional delay between consecutive samples at a non-integer, sub-symbol rate and outputs a stream of equalized data based on tap weights of taps of the adaptive equalizer that are spaced at an interval corresponding to the non-integer, sub-symbol rate. The tap weights are updated independently of the fractional delay between consecutive samples of the input data using an error signal. An equalizer output alignment component downstream of the adaptive equalizer aligns the stream of equalized data with a corresponding transmitted symbol.