Labeling diversity of the superposition coding modulation (SCM) of dual-carrier modulation (DCM) of a coded orthogonal frequency-division multiplexed (COFDM) signal is used to reduce its peak-to-average-power ratio (PAPR). The reduction of data throughput owing to DCM is compensated for by quadrupling the number of lattice points in SCM mappings of the quadrature amplitude modulation (QAM) of the carriers of the COFDM signal. The labeling diversity can be such as to minimize PAPR or such as to reduce PAPR less, but improve signal-to-noise (SNR) for reception of the COFDM signal transmitted via an additive-white-Gaussian-noise (AWGN) channel.

Provided are a preamble symbol generation method and receiving method, and a relevant frequency-domain symbol generation method and a relevant device, characterized in that the method comprises: generating a prefix according to a partial time-domain main body signal truncated from a time-domain main body signal; generating the hyper prefix according to the entirety or a portion of the partial time-domain main body signal; and generating time-domain symbol based on at least one of the cyclic prefix, the time-domain main body signal and the hyper prefix, the preamble symbol containing at least one of the time-domain symbols. Therefore, using the entirety or a portion of a certain length of a time-domain main body signal as a prefix, it is possible to implement coherent detection, which solves the issues of performance degradation with non-coherent detection and differential decoding failure under complex frequency selective fading channels; and generating a hyper prefix based on the entirety or a portion of the above truncated time-domain main body signal enables the generated preamble symbol to have sound fractional frequency offset estimation performance and timing synchronization performance.

Provided are a preamble symbol generation method and receiving method, and a relevant frequency-domain symbol generation method and a relevant device, characterized in that the method comprises: generating a prefix according to a partial time-domain main body signal truncated from a time-domain main body signal; generating the hyper prefix according to the entirety or a portion of the partial time-domain main body signal; and generating time-domain symbol based on at least one of the cyclic prefix, the time-domain main body signal and the hyper prefix, the preamble symbol containing at least one of the time-domain symbols. Therefore, using the entirety or a portion of a certain length of a time-domain main body signal as a prefix, it is possible to implement coherent detection, which solves the issues of performance degradation with non-coherent detection and differential decoding failure under complex frequency selective fading channels; and generating a hyper prefix based on the entirety or a portion of the above truncated time-domain main body signal enables the generated preamble symbol to have sound fractional frequency offset estimation performance and timing synchronization performance.

A receiving method for receiving a plurality of carriers and generating one or a plurality of streams. The method includes a first demodulating step of processing a first transmission signal and generating a first demodulation output; a second demodulating step of processing a second transmission signal different from the first transmission signal and generating a second demodulation output; a combining step of generating one stream based on the first demodulation output and the second demodulation output; a selecting step of selecting one among the first demodulation output and the one stream, and generating a selected stream; and a back-end processing step of generating an output for a display from the selected stream and the second demodulation output. In the selecting step, the first demodulation output is selected in a receiving mode in single channel transmission, and the one stream is selected in a receiving mode in multiple channel transmission.

An optical transmitter is operative to generate, from a plurality of encoded client bits, a set of symbols exhibiting non-uniform visitation probabilities in at least one dimension, to encode the set of symbols across a plurality of frequency division multiplexing (FDM) subcarriers, and to transmit an optical signal comprising the plurality of FDM subcarriers across which the set of symbols is encoded. An optical receiver is operative to decode a set of symbol estimates from a plurality of FDM subcarriers, the symbol estimates comprising estimates of symbols exhibiting non-uniform visitation probabilities in at least one dimension, and to recover client bits from the set of symbol estimates.

Provided are a preamble symbol generation method and receiving method, and a relevant frequency-domain symbol generation method and a relevant device. The method includes generating a prefix according to a partial time-domain main body signal truncated from a time-domain main body signal, generating the hyper prefix according to the entirety or a portion of the partial time-domain main body signal, and generating time-domain symbol based on at least one of the cyclic prefix. The time-domain main body signal and the hyper prefix, the preamble symbol includes the time-domain symbols.

System and method for processing an analog signal. For example, a demodulator for processing an analog signal includes one or more analog-to-digital converters configured to receive an analog signal and generate a digital signal based at least in part on the analog signal, and a correlator coupled to the one or more analog-to-digital converters and configured to generate a stream of correlation results including a first plurality of correlation results, a second plurality of correlation results, and a third plurality of correlation results. The first plurality of correlation results is different from the second plurality of correlation results by at least one correlation result, and the second plurality of correlation results is different from the third plurality of correlation results by at least another correlation result.

System for adjusting a reference constellation for demodulating an optical signal include a coherent electro-optical receiver configured to convert a received optical signal to a plurality of electrical signals, an array of analog-to-digital convertors configured to digitize the plurality of electrical signals, and processor logic. The processor logic is configured to process the digitized plurality of electrical signals using a reference constellation to yield a plurality of decoded signals and a signal quality measurement. The reference constellation includes an inphase component equal to an ideal inphase component plus an inphase offset and a quadrature component equal to an ideal quadrature component plus a quadrature offset. The processor logic is configured to determine an optimal inphase offset and optimal quadrature offset. The processor logic is configured to update the reference constellation using the optimal inphase offset and the optimal quadrature offset.

A frequency difference compensation unit (510) generates a carrier recovery signal by compensating for a frequency difference between a local light beam and an optical signal in a plurality of digital signals. A first symbol determination unit (521) determines the symbol position of the carrier recovery signal in which a frequency difference is compensated for, in accordance with the signal arrangement of multi-value modulation. A second symbol determination unit (522) determines the symbol position of the carrier recovery signal in which a frequency difference is compensated for, in accordance with a signal arrangement in which the number of multi-values of the multi-value modulation is reduced. A loop filter unit (540) and a compensation signal generation unit (550) temporarily generates a compensation signal using a determination result of the second symbol determination unit (522), and then regularly generates the compensation signal using a determination result of the first symbol determination unit (521).

A circuit for demodulating an input signal is described. The circuit may be configured to demodulate signals modulated with amplitude-based modulation schemes, such as amplitude shift keying (ASK). The demodulator may comprise a clock extractor configured to generate a clock signal in response to receiving an amplitude-modulated input signal, a phase shifter configured to generate a sampling signal by phase-shifting the clock signal by approximately /2, and a sampler configured to sample the input signal in correspondence to one or more edges (such as one or more falling edges) of the sampling signal. In this way, the amplitude-modulated input signal may be sampled at its peak, or at least near its peak, thus ensuring high signal fidelity.