8 results about "Qam constellations" patented technology

The application provides a constellation mapping method and related equipment. The method comprises the following steps: constructing a QAM constellation diagram with a constellation order of 2 M ; constellation points on the QAM constellation diagram are composed of symbol bits and shaping bits, and the constellation points satisfy Gray characteristics; M is an even number; dividing to-be-sent bits into multiple groups of bit sequences with a size of M-1; the bit sequence comprises high-order bits of a first bit and low-order bits except the first bit; sequentially mapping the bit sequence into constellation symbols to obtain a constellation mapping diagram corresponding to the to-be-sent bits; wherein the low-order bits satisfy Gray mapping with the shaping bits, and the high-order bits correspond to the symbol bits. Through the method provided in the application, the bit error rate performance of the trellis shaping symbol during demodulation can be improved without increasing the coding and decoding complexity of any grid shaping.

The application provides a kind of digital signal optical communication method and system based on single pilot symbol, and the sending end periodically inserts X / Y polarized pilot symbol pair, is shaped by orthogonal double binary coding super-Nyquist signal, so that each pair of pilot symbols is merged into equivalent single pilot symbol, phase and amplitude information are retained and mapped to the outermost circle of QAM constellation diagram.Receiving end finds initial pilot symbol sequence based on the characteristics of the highest amplitude of the outermost circle of QAM constellation diagram, constructs sliding window according to the length of the original pilot symbol sequence in the initial pilot symbol sequence to extract sequence, and compares the original pilot symbol sequence to calculate the variance of phase increment, determines the frame starting position based on the minimum variance, and uses pilot symbol to provide accurate initial information and periodic guide decoding for MLSE algorithm.The application can efficiently utilize pilot symbol resources and significantly reduce the complexity of MLSE decoding.

The application discloses an optical OFDM modulation method combining a probability shaping technology and a subcarrier grouping transmission technology, and belongs to the technical field of optical communication, and comprises the following steps: optimizing a QAM constellation diagram based on a probability shaping method, acquiring optimal probability distribution of constellation points, mapping the optimal probability distribution of the constellation points based on a constant distribution matcher, and obtaining OFDM symbols; performing frequency domain symbol transformation on the OFDM symbols, generating transformed frequency domain signals; converting the transformed frequency domain signals into LED group signals based on a filtering block; and processing the LED group signals based on a DCO modulation mode, and completing OFDM modulation. Different subcarriers are modulated on multiple LEDs, so that the peak-to-average power ratio of the OFDM signals modulated on each LED is reduced, and the nonlinear noise interference of the system is further resisted.

Disclosed is a method for implementing a rate-adaptive multi-input single-output visible light communication system, where the visible light communication system includes transmit ends and a receiver end. Binary transmission data streams corresponding to the transmit ends are respectively modulated onto a constellation diagram, and all transmit constellations are loaded onto a signal generator after subjected to digital signal processing, the signal generator outputs analog signals, which are respectively amplified by electrical amplifiers, and then coupled to direct current by biasers, and the light sources corresponding to the transmit ends convert the electric signals obtained by coupling into optical signals. The probabilistic shaping is performed on all the transmit constellations respectively so as to enable same to conform to Maxwell-Boltzmann distribution of a QAM constellation; and geometric shaping is performed on all the transmit constellations at the same time to make a transmit signal power of each transmit end equal.

The application discloses a kind of photonic terahertz communication systems based on semantic compression and weight hierarchical modulation, the external cavity laser ECL1 of the sending end is connected with IQ modulator, provides continuous optical carrier;IQ modulator is simultaneously connected to TX-DSP module, and the compressed sub-block of image is generated by applying semantic compression method, after weight evaluation, compressed sub-block is modulated to basic layer and additional layer in descending order respectively, and SCHM-QAM constellation point baseband signal is obtained, drive IQ modulator to modulate optical carrier, and be coupled with the continuous light wave that external cavity laser ECL2 outputs, after transmission to amplifier, input to single row carrier photoelectric detector and beat frequency, and terahertz signal is obtained, after receiving end receives terahertz signal and local signal are mixed, and after obtaining base frequency signal, input to RX-DSP module, weight hierarchical demodulation and semantic decompression etc. Operation, and the original data is obtained.The application removes redundant information and improves transmission efficiency, improves system transmission capacity, and guarantees information recovery quality.

This invention provides a high-order amplitude-shift keying (APSK) modulation and demodulation method for severe phase noise. In terms of modulation, APSK constellation diagrams exhibit stronger phase noise resistance compared to orthogonal amplitude modulation (QAM). While conventional APSK cannot be Gray-mapped, this invention proposes an APSK constellation diagram where each ring has the same number of constellation points (a power of 2). The phase distribution of constellation points on different rings is identical, and the number of rings is also a power of 2. Adjacent constellation points within the same ring and adjacent constellation points with the same phase differ by only one bit, allowing for Gray-mapping. This constellation diagram can also determine the ring radius through nonlinear optimization, further enhancing its phase noise resistance compared to traditional QAM constellation diagrams. In terms of demodulation, this invention proposes a soft demodulation method, which achieves the same performance as, and does not reduce, maximum likelihood-based soft demodulation, but significantly reduces complexity.

The constellation optimization method for terahertz non-ideal channel based on deep learning belongs to the field of terahertz communication.The method of the present application is as follows: a transmitter based on DFT-s-OFDM modulation is designed to generate a transmission signal; a communication system model for terahertz non-ideal channel is established to obtain a received symbol sequence after the transmission signal is transmitted through the channel and processed by a receiver; a constellation optimization model based on a multi-layer neural network is constructed, a joint loss function containing three types of constraint terms is designed, adaptive optimization training is performed on constellation symbols, and an optimized constellation point sequence suitable for terahertz non-ideal channel is obtained; the optimized constellation points output by the multi-layer neural network are screened and constrained, projected and mapped to a standard QAM constellation to obtain a final constellation diagram satisfying the standard modulation format.The present application can reduce the symbol error rate under the condition of terahertz non-ideal channel, improve the robustness of the system to non-linear distortion and phase noise, and simultaneously consider power efficiency and implementation complexity.

The invention discloses an encryption parameter optimization method for a low peak-to-average ratio in an OFDM (Orthogonal Frequency Division Multiplexing) modulation system, which comprises the following steps of: firstly, carrying out serial-to-parallel conversion and QAM (Quadrature Amplitude Modulation) constellation point mapping on input OFDM communication data, and then generating a pseudorandom sequence by using an initial key generated by a preset parameter through a one-dimensional SINE chaotic mapping model; the method comprises the following steps: performing disturbance encryption on constellation point coordinate data by using a cellular automaton as an iteration rule, performing inverse Fourier transform on ciphertext data, performing peak-to-average ratio calculation, optimizing a secret key through a random multi-neighborhood synchronous search optimization model, generating an optimized secret key and performing secret key updating, and repeating the operations of pseudorandom sequence generation, constellation point data encryption, inverse Fourier transform and peak-to-average ratio calculation until the output data is smaller than the minimum peak-to-average ratio expected value, finally performing cyclic prefix insertion and parallel-to-serial conversion into digital-to-analog conversion data, completing electro-optical conversion and performing data transmission.