CN-116346235-B - Elastic grouping three-layer mixed O-OFDM method based on IM/DD

Abstract

The invention discloses an elastic grouping three-layer mixed O-OFDM method based on IM/DD, which utilizes three-layer O-OFDM signal mixed transmission, meanwhile, subcarrier grouping of a third layer is changeable, can be more flexibly adapted to different channel conditions, and improves the utilization efficiency of subcarriers. Compared with LACO-OFDM, the number of the layers of the FTHO-OFDM is fixed to be three layers, so that the receiver has fixed complexity and processing time delay, the complexity and processing time delay of the receiver are reduced as compared with LACO-OFDM with the number of the layers being larger than three layers, meanwhile, the transmission performance is not obviously reduced, the method is the same as the demodulation mode of LACO-OFDM, and an iterative detection mode is adopted at a receiving end, but under the same spectrum efficiency, as the number of the layers of the method is fixed to be three layers, only two iterations are needed, and for LACO-OFDM with the calculation complexity increased along with the number of the layers, the method is capable of obviously reducing the complexity and processing time delay of the receiver and is more suitable for practical implementation.

Inventors

• LI BAOLONG
• QIAN CHENGCHENG
• WANG CHENGTAO
• LU BO
• DING WENJIE

Assignees

• 南京信息工程大学
• 中科怡海高新技术发展江苏股份公司

Dates

Publication Date

20260512

Application Date

20221228

Claims (10)

1. 1. An elastic packet three-layer hybrid O-OFDM method based on IM/DD, characterized by comprising: acquiring transmission bits, and dividing the transmission bits into three paths; After two paths of transmission bits are subjected to quadrature amplitude modulation and pulse amplitude modulation, serial-parallel conversion is respectively carried out, and the imaginary parts of odd subcarriers and even subcarriers are utilized for carrying out symbol transmission, so that frequency domain signals of ACO-OFDM and PAM-DMT are generated; Converting the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals by IFFT operation, generating non-negative signals by parallel-serial conversion and amplitude limiting operation And Grouping the third transmission bits by adopting an elastic subcarrier grouping method, and calculating to obtain a frequency domain signal Z k ; Performing an N/2 point IFFT operation on the frequency domain signal Z k to generate a time domain signal Z n of Z k ; acquiring an adaptive bias signal b n based on the time domain signal z n ; The adaptive bias signal b n is superimposed on the time domain signal z n to generate a non-negative time domain signal, and is repeated 2 times in the time domain to generate a time domain signal of the third layer O-OFDM Will not be negative signal And Time domain signal of third layer O-OFDM Mixing and superposing to generate FTHO-OFDM signals, and inputting FTHO-OFDM signals into the LED to drive the LED to emit light after digital-to-analog conversion.
2. 2. The IM/DD-based resilient packet three-layer hybrid O-OFDM method of claim 1 wherein non-negative signals are generated by parallel-to-serial conversion and clipping operations And Comprising the following steps: The non-limited time domain signals for ACO-OFDM and PAM-DMT at the nth sample time are denoted x n and y n , n=0, 1, N-1, Generating non-negative signals by parallel-to-serial conversion and clipping operations And Then clipping negative portion operation is indicated.
3. 3. The method for three-layer hybrid O-OFDM of an IM/DD-based resilient packet according to claim 2, wherein grouping the third transmission bits by using a resilient subcarrier grouping method, and calculating to obtain the frequency domain signal Z k , includes: the subcarrier grouping method is expressed as omega= { k|k=2 g-1 (2i+1),i＝0,1,…,N/2 g , g=1, 2,.. G }, wherein G represents the depth of a third layer, and flexible and elastic adjustment of subcarrier grouping of the third layer is realized by adjusting the value of G; On an elastic packet basis, the frequency domain signal is generated by Where P k denotes a PAM symbol allocated to the kth subcarrier.
4. 4. The IM/DD-based resilient packet three-layer hybrid O-OFDM method of claim 3, wherein obtaining the adaptive bias signal b n based on the time domain signal z n comprises: the adaptive bias signal is formed by a time domain signal sequence And Wherein mod () represents a remainder operation, and the adaptive bias signal is represented as b n ,b n , is calculated by the following formula:
5. 5. The IM/DD-based resilient packet three-layer hybrid O-OFDM method of claim 4, wherein the time domain signal of the third layer O-OFDM Expressed as:
6. 6. The method for three-layer hybrid O-OFDM of an IM/DD based resilient packet of claim 5, wherein the non-negative signal is transmitted And Time domain signal of third layer O-OFDM Hybrid superposition, yielding FTHO-OFDM signals, denoted as:
7. 7. The method of claim 1, wherein the method comprises detecting each layer of O-OFDM signal one by iterative detection, converting the received signal into frequency domain signal by FFT operation, detecting ACO-OFDM frequency domain signal first, recovering ACO-OFDM clipping noise from detected symbols of ACO-OFDM, removing ACO-OFDM clipping noise from even subcarriers, detecting PAM-DMT frequency domain signal, recovering PAM-DMT clipping noise from detected symbols of PAM-DMT, removing PAM-DMT clipping noise from real parts of even subcarriers, and detecting third layer O-OFDM frequency domain signal.
8. 8. An IM/DD-based resilient packet three-layer hybrid O-OFDM apparatus comprising: The acquisition module is used for acquiring transmission bits and dividing the transmission bits into three paths; The frequency domain signal generating module is used for respectively carrying out serial-parallel conversion on two paths of transmission bits after quadrature amplitude modulation and pulse amplitude modulation and carrying out symbol transmission by utilizing the imaginary parts of the odd-numbered subcarriers and the even-numbered subcarriers to generate frequency domain signals of ACO-OFDM and PAM-DMT; a non-negative signal acquisition module for converting the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals by IFFT operation, generating non-negative signals by parallel-serial conversion and amplitude limiting operation And The frequency domain signal acquisition module is used for grouping the third transmission bits by adopting an elastic subcarrier grouping method, and calculating to acquire a frequency domain signal Z k ; The time domain signal acquisition module is used for performing N/2 point IFFT operation on the frequency domain signal Z k to generate a time domain signal Z n of Z k ; The adaptive bias signal acquisition module is used for acquiring an adaptive bias signal b n based on the time domain signal z n ; A time domain signal acquisition module of the third layer O-OFDM for superimposing the adaptive bias signal b n on the time domain signal z n to generate a non-negative time domain signal, and repeating the time domain for 2 times to generate a time domain signal of the third layer O-OFDM Hybrid superposition module for adding non-negative signals And Time domain signal of third layer O-OFDM Mixing and superposing to generate FTHO-OFDM signals, and inputting FTHO-OFDM signals into the LED to drive the LED to emit light after digital-to-analog conversion.
9. 9. An electronic device is characterized by comprising a processor and a storage medium; The storage medium is used for storing instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1 to 7.
10. 10. A computer-readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the method according to any one of claims 1-7.

Description

Elastic grouping three-layer mixed O-OFDM method based on IM/DD Technical Field The invention relates to an elastic grouping three-layer hybrid O-OFDM method based on IM/DD, belonging to the technical field of optical communication. Background In the field of optical communication, intensity modulation direct detection (IM/DD) is a popular modulation method, which transmits information by means of intensity of light, has the advantages of simple implementation and low cost, and is widely applied to the optical communication fields such as optical fiber communication, wireless optical communication and the like. Meanwhile, the Orthogonal Frequency Division Multiplexing (OFDM) technology has the advantages of high frequency spectrum efficiency, capability of effectively resisting inter-code crosstalk and the like, so that the optical OFDM (O-OFDM) based on the IM/DD is a popular technology in the field of optical communication. In IM/DD based systems, the transmission signal is defined to be non-negative, thus promoting a variety of O-OFDM methods, typical representatives including dc offset O-OFDM (DCO-OFDM), asymmetric limiting O-OFDM (ACO-OFDM), hybrid ACO-OFDM (HACO-OFDM), adaptive offset O-OFDM (ABO-OFDM), three-layer hybrid O-OFDM (THO-OFDM), etc. The DCO-OFDM adopts a mode of adding direct current offset to ensure non-negativity, is simple to realize and has lower power efficiency, so that an ACO-OFDM method with more efficient power is proposed, and the ACO-OFDM method is generated by adopting a limiting mode and only utilizes half of sub-carriers for transmission, thereby having lower frequency spectrum efficiency. In order to improve the spectrum efficiency, HACO-OFDM is superimposed with pulse amplitude modulation discrete multitone (PAM-DMT) signals on the basis of ACO-OFDM signals, so that the spectrum efficiency is improved, but in HACO-OFDM, 1/4 of subcarrier resources are still not utilized. The ABO-OFDM method adds offset signals in a self-adaptive manner according to the amplitude of signals, so that high-efficiency power efficiency is realized, and meanwhile, the receiving complexity is greatly reduced. However, ABO-OFDM has the same problems as HACO-OFDM, and fails to realize efficient use of subcarriers. The THO-OFDM utilizes three O-OFDM for hybrid transmission to improve the subcarrier utilization, but the subcarrier utilization of the THO-OFDM is fixed to 87.5%, and the subcarrier resources are still not fully utilized. Currently, although there is an O-OFDM method capable of fully utilizing subcarrier resources, such as hierarchical ACO-OFDM (LACO-OFDM), a higher reception complexity and processing delay are caused due to an excessive number of layers. While there are low complexity adaptive bias layered O-OFDM (ABLO-OFDM) approaches, the cost of complexity reduction is a significant drop in transmission performance. Disclosure of Invention The invention aims to overcome the defects in the prior art, and provides an elastic grouping three-layer hybrid O-OFDM method based on IM/DD, which utilizes three-layer O-OFDM signal hybrid transmission, meanwhile, the subcarrier grouping of the third layer is variable, can be more flexibly adapted to different channel conditions, and improves the utilization efficiency of subcarriers. Compared with LACO-OFDM, the number of the layering of the FTHO-OFDM is fixed to be three layers, so that the receiver has fixed complexity and processing time delay, the complexity and the processing time delay of the receiver are reduced compared with LACO-OFDM with the layering number being larger than three layers without increasing the layering number, and meanwhile, the transmission performance is not obviously reduced. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: in a first aspect, the present invention provides an IM/DD-based resilient packet three-layer hybrid O-OFDM method, including: acquiring transmission bits, and dividing the transmission bits into three paths; After two paths of transmission bits are subjected to quadrature amplitude modulation and pulse amplitude modulation, serial-parallel conversion is respectively carried out, and the imaginary parts of odd subcarriers and even subcarriers are utilized for carrying out symbol transmission, so that frequency domain signals of ACO-OFDM and PAM-DMT are generated; Converting the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals by IFFT operation, generating non-negative signals by parallel-serial conversion and amplitude limiting operation And Grouping the third transmission bits by adopting an elastic subcarrier grouping method, and calculating to obtain a frequency domain signal Z k; Performing an N/2 point IFFT operation on the frequency domain signal Z k to generate a time domain signal Z n of Z k; acquiring an adaptive bias signal b n based on the time domain signal z n; The adaptive bias signal b n is superim