CN-120034416-B - Radio optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing

CN120034416BCN 120034416 BCN120034416 BCN 120034416BCN-120034416-B

Abstract

The invention discloses a radio optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing, and relates to the technical field of wireless communication. The method comprises the following steps of S1, preprocessing input signal data, including mapping, design of modulation symbols and symmetrical construction, generating frequency domain signals, S2, mapping the frequency domain signals to a time domain based on real discrete affine Fourier transform, generating an imitated radio frequency division multiplexing (AFDM) signal, S3, asymmetrically cutting the AFDM signal, transmitting the AFDM signal to a receiving end through an optical communication channel, and reversely reducing the AFDM signal, including recovery of the cut signal and demodulation of the data, S4, deriving a new c 1 parameter range based on design of real DAFT kernel function, and realizing complete separation of signal paths with different delays in a DAFT domain to achieve full diversity. The invention solves the problem of signal distortion caused by multipath effect in optical communication.

Inventors

MAO TIANQI
Yuan Jiuda
LIU JIAYUE
ZHENG DEZHI
QIN TONG
GAO ZHEN
Lv Yuezu
LIANG XIAO

Assignees

北京理工大学

Dates

Publication Date: 20260508
Application Date: 20250219

Claims (10)

1. A radio optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing is characterized by comprising the following specific steps: s1, preprocessing input optical communication signal data at a transmitting end, wherein the preprocessing comprises mapping of frequency domain data, design of modulation symbols and symmetrical construction of the data, and generating frequency domain signals meeting specific conditions; Step S2, mapping the frequency domain signal generated in the step S1 to a time domain based on the real discrete affine Fourier transform DAFT to generate an imitated radio frequency division multiplexing AFDM time domain signal; s3, performing asymmetric clipping on the AFDM time domain signal generated in the step S2 by utilizing the characteristic of odd half-wave symmetry, setting the negative value part of the AFDM time domain signal to zero, and transmitting the signal to a receiving end through an optical communication channel; step S4, deducing a new one based on the design of the real DAFT kernel function A range of parameters enabling complete separation of signal paths with different delays in the DAFT domain, achieving full diversity, wherein, Is a free parameter in the modulation design.
2. The method of claim 1, wherein in step S1, the input optical communication signal data is mapped onto frequency domain subcarriers to form frequency domain symbols, and in order to ensure that the frequency domain signals are real numbers, the frequency domain symbols are set to be in a conjugate symmetric form, and the formula is as follows: ; Wherein, the The symbol representing the kth subcarrier, Is that Is used to determine the complex number of the conjugate, The symbol of the N-k sub-carriers, N is the number of sub-carriers.
3. The radio optical transmission method based on asymmetric limiting optical imitated radio frequency division multiplexing as claimed in claim 2, wherein, to meet the requirement of asymmetric clipping, data is only loaded on odd numbered subcarriers, and even numbered subcarriers are set to zero, and the formula is as follows: ; 。
4. the method for wireless optical transmission based on asymmetric limiting optical multiplexing-imitated radio frequency division according to claim 1, wherein in step S2, the frequency domain signal generated in step S1 is mapped to a time domain by using a real discrete affine fourier transform DAFT to generate an imitated radio frequency division multiplexing AFDM time domain signal, which specifically comprises the following steps: In step S21, the calculation formula of the kernel function of the discrete affine fourier transform DAFT is as follows: ; The calculation formula of the inverse transformation is as follows: ; Wherein, the In order to input a signal to the device, In order to output the signal, As the number of sub-carriers, For a length of DAFT of the transition, Is a free parameter in the modulation design, m is an output signal index, n is an input signal index, and j is an imaginary number; Step S22, adjusting the kernel function of the discrete affine Fourier transform DAFT, and removing the complex exponential kernel function Item, will Replaced by The calculation formula of the adjusted discrete affine fourier transform DAFT kernel function is as follows: ; the time domain signal generated by the adjusted kernel function is a real number, and the multipath separation capability of the discrete affine fourier transform DAFT is reserved.
5. The method for wireless optical transmission based on asymmetric limiting optical imitated radio frequency division multiplexing as claimed in claim 4, wherein, The calculation formula of (2) is as follows: 。
6. The radio optical transmission method based on asymmetric amplitude limiting optical imitated radio frequency division multiplexing as claimed in claim 4, wherein in the step S3, the asymmetric cutting ACO is performed on the AFDM time domain signal generated in the step S2 by utilizing the characteristic of odd half-wave symmetry, and the specific steps are as follows: step S31, due to the time domain signal The negative half part of the system does not carry effective information, and the negative part is forced to be zero by asymmetric clipping, and the formula is as follows: ; Wherein, the Is the signal after cutting, t is the continuous time variable of the signal; And S32, demodulating and restoring the received optical signals to realize accurate recovery of data, wherein the receiving end restores the received optical signals to electric signals through a photoelectric converter Photodetector, and restores the clipped negative half-part signals by using the known characteristic of odd half-wave symmetry according to the following formula: ; Wherein, the The signal is recovered, and T is the signal period; inverse transformation is carried out on the real DAFT kernel function, the frequency domain symbol is restored, and the calculation formula is as follows: ; and extracting the original input data by using conjugate symmetry among frequency domain symbols and odd subcarrier allocation rules.
7. The method for wireless optical transmission based on asymmetric limiting optical radio frequency division multiplexing as claimed in claim 6, wherein in step S4, the offset distances of the left shift logic and the non-zero elements in the channel matrix are deduced, and the mapping relation of the signal paths in DAFT domains is described in combination with the right shift logic, specifically comprising the following steps: step S41, performing left shift and right shift caused by the real kernel function; step S42, deducing a new And the parameter range realizes full diversity and ensures that paths of right shift and left shift are not overlapped and paths of left shift and right shift are not overlapped.
8. The method for wireless optical transmission based on asymmetric limiting optical radio frequency division multiplexing as claimed in claim 7, wherein in step S41, the left shift and the right shift caused by the real kernel function are as follows: In step S411, in the conventional AFDM, The range of (c) is derived as follows: The elements of the channel matrix are: ; Wherein, the ; When (when) In the time-course of which the first and second contact surfaces, ; Right shift logic is composed of The offset is introduced as follows: ; Wherein, the Is the delay of the i-th path, For the channel matrix element of the i-th path, 、 For the frequency domain index, As a function of the frequency domain contribution, For the doppler shift of the i-th path, Is the offset of the ith path; in step S412, the real kernel function introduces left shift logic, and in ACO-AFDM, the kernel function is replaced with: ; left shift logic is composed of Introduced, its channel matrix elements become: ; Wherein, the ; When (when) When (1): ; wherein the new offset is: ; left shift logic is composed of Introduced, the non-zero elements of the channel matrix are left offset from diagonal A plurality of positions.
9. The method for radio optical transmission based on asymmetric limiting optical imitated radio frequency division multiplexing as claimed in claim 7, wherein in step S42, a new one is provided The parameter range derivation steps are as follows: step S421, non-overlapping between right shift paths Range derivation: From the derivation of the original AFDM, the right shift is defined by the following formula: ; In order to avoid overlapping between right shift paths, it is required to satisfy: ; Order the Ensuring non-overlapping, right-shifted paths The range needs to satisfy: ; Step S422, non-overlapping between left shift paths The range is derived as follows: The shift range for the left shift is: ; In order to avoid overlapping between left shift paths, the following needs to be satisfied ; Similarly, assuming a minimum delay difference of 1 between paths, a left shift is obtained to ensure no overlap between paths The range is as follows: 0; step S423, non-overlapping between the left shift path and the right shift path In order to avoid overlapping between the left shift path and the right shift path, the range derivation needs to satisfy that the maximum value of all right shift paths is smaller than N/2 and the absolute value of all left shift paths is also smaller than N/2; step S424, right shift and left shift of no overlap between own paths is required to satisfy The non-overlapping between the left shift path and the right shift path needs to satisfy: ; Wherein, the Is the maximum time delay of a plurality of paths, and finally The range of (2) is: 0 ; The ACO-AFDM channel matrix is completely separated in DAFT domains, so that full diversity is achieved.
10. The method for wireless optical transmission based on asymmetric limiting optical rf-like multiplexing as claimed in claim 9, wherein in step S423, the maximum value of the rightward shift is: ; making it less than N/2: ; And (3) finishing to obtain: 0 ; The left offset is: ; Order the The method comprises the following steps of: ; And (3) finishing to obtain: 0 。

Description

Radio optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing Technical Field The invention relates to the technical field of wireless communication, in particular to a wireless optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing. Background With the rapid development of modern communication technology, optical communication has become an important component in the communication field by virtue of high speed, large capacity, low loss and the like. However, optical communication systems require that the signal transmitted in the channel must be non-negative real numbers, subject to physical characteristics. This unique requirement places higher standards on modulation and waveform design techniques. The existing Orthogonal Frequency Division Multiplexing (OFDM) technology is widely used in wireless communication due to its high spectral efficiency and robustness to frequency selective fading. However, the direct application of conventional OFDM to optical communication systems may face challenges, such as signal complex form and higher peak-to-average power ratio (PAPR) not meeting the non-negative requirements of the signal. For this reason, researchers have proposed asymmetric clipping optical orthogonal frequency division multiplexing (ACO-OFDM) technology, and generate non-negative real signals through asymmetric clipping, so as to meet the transmission requirements of optical communications. However, the ACO-OFDM has problems of reduced spectrum efficiency, insufficient anti-interference capability under multipath channel, and the like, and has certain limitations in scenes with obvious multipath effects such as multimode optical fiber communication and free space optical communication. Radio frequency division multiplexing (AFDM) has shown unique advantages in wireless communications as an emerging multi-carrier modulation technique based on Discrete Affine Fourier Transforms (DAFT). The AFDM can effectively separate the delay of a multipath channel, reduce interference, realize high diversity gain by utilizing the time-frequency sparsity of the channel, and improve the fading resistance and the system reliability. In addition, the AFDM receiving end can adopt a simple linear detection algorithm, and has lower implementation complexity. However, the successful experience of AFDM in wireless communication cannot be directly migrated to the field of optical communication, mainly because the generated signal is in complex form, and the requirement of optical communication on non-negative real signals is not satisfied. To solve this problem, additional signal processing means such as biasing or nonlinear transformation are required, but this significantly increases the complexity and power consumption of the system, limiting its practical application. The existing optical communication modulation technology, such as ACO-OFDM, can meet the non-negative requirement, but has limited anti-interference capability under the complex multipath channel scene, while AFDM has technical advantages under the multipath environment, but is difficult to be applied to an optical communication system due to the problem of non-negative signal. This technical bottleneck limits the performance improvement of optical communication systems in complex multipath environments. How to introduce the advantages of the AFDM technology into the field of optical communication and solve the problem of non-negative constraint of signals is a key problem to be overcome in the current urgent need. Disclosure of Invention The invention aims to provide a wireless optical transmission method based on asymmetric amplitude limiting optical imitated radio frequency division multiplexing, which solves the problems of non-negative constraint and multipath interference of signals in an optical communication system by combining the multipath component separation capacity of AFDM with a non-negative processing mode of ACO-OFDM, realizes efficient and reliable signal transmission, and is particularly suitable for complex scenes with obvious multipath effects such as multimode optical fiber communication, free space optical communication and the like. In order to achieve the above purpose, the invention provides a wireless optical transmission method based on asymmetric amplitude limiting optical imitation radio frequency division multiplexing, which comprises the following specific steps: s1, preprocessing input optical communication signal data at a transmitting end, wherein the preprocessing comprises mapping of frequency domain data, design of modulation symbols and symmetrical construction of the data, and generating frequency domain signals meeting specific conditions; Step S2, mapping the frequency domain signal generated in the step S1 to a time domain based on the real discrete affine Fourier transform DAFT to