Wireless optical communication low-complexity recombination layering ASE-DMT method and system

Abstract

The invention provides a low-complexity recombination layering ASE-DMT method and system for wireless optical communication. The method comprises the following steps: layering subcarriers according to sequence numbers and virtual and real parts; layering recombination is carried out according to the number of adopted layers, and M layering groups and frequency domain signals of the M layering groups are obtained; performing IFFT operation on the frequency domain signal to generate a time domain signal; introducing a reconstruction signal into the time domain signal to generate a non-negative signal; the non-negative time domain signals corresponding to the M hierarchical groups are superposed, and an RL-ASE-DMT signal is generated; and finally, the RL-ASE-DMT signal is subjected to digital-to-analog conversion and then is input to an optical transmitter to generate an optical signal. According to the RL-ASE-DMT method provided by the invention, the number of times of layer-by-layer detection of a receiving end can be reduced by recombining layering and reducing the number of O-OFDM signal components corresponding to layering, so that the purposes of reducing the complexity and processing time delay of the receiving end are achieved, and meanwhile, relatively good transmission performance is kept.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless optical communication, in particular to a low-complexity recombination layered ASE-DMT method and system for wireless optical communication. BACKGROUND

[0002] At present, wireless spectrum communication is facing the problem of resource shortage, and with the rapid development of light-emitting diode (LED) technology, wireless optical communication is gradually emerging. Wireless optical communication has gradually become a research hotspot due to its advantages of sufficient spectrum resources, wide application field and strong privacy protection. At the same time, optical communication does not involve electromagnetic radiation and will not interfere with traditional radio frequency communication systems, and has been regarded as an effective supplement to wireless spectrum communication.

[0003] In the technology of wireless optical communication, the orthogonal frequency division multiplexing (OFDM) technology is widely used to realize high-speed wireless optical communication transmission due to its high spectrum efficiency and effective anti-interference between codes. Wireless optical communication usually adopts intensity modulation and direct modulation (IM / DD), so the transmitted signal is required to be non-negative real value. Therefore, the traditional OFDM scheme in the field of radio frequency communication cannot be directly applied to wireless optical communication. Wireless optical communication has given birth to a variety of special optical OFDM (O-OFDM) methods. Traditional methods include direct current bias optical OFDM (DCO-OFDM), asymmetric clipping optical OFDM (ACO-OFDM), etc., but these traditional methods have low power or spectrum efficiency.

[0004] In order to solve the problems existing in the traditional method, a layered O-OFDM method is proposed. Typical layered O-OFDM methods include layered ACO-OFDM method (LACO-OFDM), spectrum enhancement-discrete multi-tone injection (ASE-DMT) method, etc. Through these methods, the subcarriers are modulated in layers to generate multi-layer O-OFDM signals and superimposed for transmission, which effectively improves the spectrum efficiency and maintains high power efficiency. However, the receiving end using this method needs to use crosstalk interference cancellation to detect the signal layer by layer, resulting in high complexity and processing delay. Therefore, a direct current bias layered O-OFDM (ABLO-OFDM) method is proposed, which can reduce the complexity of the receiving end design, but the direct current bias layered O-OFDM method will cause the degradation of transmission performance.

[0005] Therefore, the traditional hierarchical DCO-OFDM and ACO-OFDM methods have low power or spectral efficiency, although the hierarchical O-OFDM method can effectively improve the spectral efficiency while maintaining high power efficiency, but will cause high complexity and processing delay. The ABLO-OFDM method can effectively reduce the receiving complexity and processing delay, but compared with the hierarchical O-OFDM method, the transmission performance is degraded. The current wireless optical communication technology lacks a scheme that can balance the receiving complexity and transmission performance. SUMMARY

[0006] In view of the defects and deficiencies of the prior art, the purpose of the present application is to provide a low-complexity recombination hierarchical ASE-DMT method for wireless optical communication, which recombines the hierarchical layers to reduce the number of superimposed O-OFDM signal components, thereby achieving the purpose of reducing the complexity and processing delay of the receiving end, while maintaining good transmission performance.

[0007] According to a first aspect of the purpose of the present application, a low-complexity recombination hierarchical ASE-DMT method for wireless optical communication is provided, which includes the following steps in the signal hierarchical recombination and modulation process at the transmitting end:

[0008] Step 1, layering the subcarriers according to the sequence number and real and imaginary parts, the subcarrier sequence number of the real part is represented as k R , the subcarrier sequence number of the imaginary part is represented as k I , k R =0,1,…,N-1, k I =0,1,…,N-1, N represents the total number of subcarriers; the imaginary part of the subcarriers is used for the first layering, and the subcarrier set of the first layering is represented as φ1={k I |0≤k I ≤N-1,k I ≠0,N / 2}, the real part of the subcarriers is used for subsequent layering, and the subcarrier set of the lth layering is represented as φ l ={k R |k R =2 l-2 (2i+1), i=0,1,…,N / 2 l-1 -1} l≥2;

[0009] Step 2, recombining the layering according to the number of layering used, the sequence number of the recombined layering group is represented as m, the total number of the recombined layering group is represented as M, and the frequency domain signal corresponding to the M layering groups is generated, wherein: when m=1, the first recombined layering group contains the first layer to the l1 layer, wherein l1≥1, and the frequency domain signal corresponding to the first recombined layering group is represented as:

[0010]

[0011] wherein, A k and B k represent the PAM symbol on the imaginary part and the real part of the kth subcarrier respectively, the mth reorganized hierarchical group contains the l m-1 ,…,l m th hierarchical group, wherein, l m ≥l m-1 and m≥2, the frequency domain signal corresponding to the mth reorganized hierarchical group is represented as:

[0012]

[0013] Step 3, after the frequency domain signal corresponding to the reorganized hierarchical group is subjected to IFFT operation, a time domain signal is generated, wherein the time domain signal corresponding to the mth hierarchical group is represented as n=0,1,…,N-1;

[0014] Step 4, the reconstruction signal is introduced to generate a non-negative signal, and the reconstruction signal of the nth time of the mth hierarchical group is represented as then the non-negative time domain signal corresponding to the mth hierarchical group is represented as:

[0015]

[0016] Step 5, the non-negative time domain signals corresponding to the M hierarchical groups are superimposed to generate an RL-ASE-DMT signal represented as:

[0017]

[0018] After the RL-ASE-DMT signal is subjected to digital-to-analog conversion, it is input to an optical transmitter to generate an optical signal.

[0019] According to the second aspect of the object of the application, a low-complexity reorganized hierarchical ASE-DMT system for wireless optical communication is also proposed, which comprises a transmitting end and a receiving end, wherein the transmitting end comprises:

[0020] a subcarrier hierarchical module, configured to hierarchize subcarriers according to sequence numbers and imaginary and real parts respectively, to obtain a set of subcarriers of each hierarchical group;

[0021] a hierarchical reorganization module, configured to reorganize hierarchical groups according to the number of hierarchical groups, to obtain M hierarchical groups and obtain frequency domain signals corresponding to the hierarchical groups;

[0022] an IFFT processing module, configured to generate time domain signals by subjecting the frequency domain signals corresponding to the reorganized hierarchical groups to IFFT operation.

[0023] a non-negative time domain signal generation module, configured to introduce the reconstructed signal into the time domain signal to generate a non-negative time domain signal corresponding to each hierarchical group;

[0024] a signal superposition processing module, configured to superimpose the non-negative time domain signals corresponding to the M hierarchical groups to generate an RL-ASE-DMT signal; and

[0025] an optical signal modulation generation module, configured to generate an optical signal through an optical modulator after digital-to-analog conversion according to the RL-ASE-DMT signal.

[0026] Compared with the prior art, the application proposes a brand-new RL-ASE-DMT method, which utilizes recombination hierarchy to reduce the number of O-OFDM signal components corresponding to each hierarchical group, so that the application can reduce the number of times of layer-by-layer detection at the receiving end, thereby effectively reducing the complexity and processing delay of the receiving end.

[0027] Meanwhile, compared with the traditional DCO-OFDM and ACO-OFDM methods, the application has higher spectrum efficiency, and compared with the ABLO-OFDM method, the wireless optical communication low-complexity recombination hierarchical RL-ASE-DMT method proposed by the application can obtain better transmission performance, effectively balancing the complexity and transmission performance.

[0028] It should be understood that all combinations of the foregoing concepts and additional concepts described in greater detail below can be seen as being part of the inventive subject matter of the present disclosure unless otherwise stated. Additionally, all combinations of claimed subject matter can be seen as being part of the inventive subject matter of the present disclosure.

[0029] The foregoing and other aspects, embodiments and features of the present teachings can be better understood and appreciated from the following description of the embodiments of the present teachings, referenced by the accompanying drawings. Other embodiments of the present teachings, for example, example implementations, can also be understood and appreciated from the following description of the embodiments of the present teachings, referenced by the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical, or nearly identical, component that is illustrated in various figures is represented with a like numeral. For purposes of clarity, not every component is called out in every drawing. Embodiments of various aspects of the present teachings will now be described, by way of example, with reference to the drawings, in which:

[0031] Figure 1 is a schematic block diagram of a transmitting end of a wireless optical communication low-complexity recombination hierarchical ASE-DMT method according to an embodiment of the present application.

[0032] Figure 2 is a principle block diagram of a receiving end of a low-complexity reorganized layered ASE-DMT method of wireless optical communication according to an embodiment of the present application.

[0033] Figure 3 is a comparison diagram of bit error rate (BER) performance of a low-complexity reorganized layered ASE-DMT method of wireless optical communication according to an embodiment of the present application and LACO-OFDM in the prior art. DETAILED DESCRIPTION

[0034] In order to better understand the technical content of the present application, specific embodiments are described below with reference to the accompanying drawings.

[0035] Aspects of the present application are described in the detailed description with reference to the accompanying drawings, in which various embodiments of the application are illustrated. Embodiments of the present application are not necessarily intended to include all aspects of the present application. It should be understood that various concepts and embodiments introduced above and those described in more detail below can be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any particular manner of implementation. Additionally, some aspects of the present application can be utilized independently, or in any suitable combination with other aspects of the present application.

[0036] {Embodiment 1}

[0037] A low-complexity reorganized layered ASE-DMT (RL-ASE-DMT) method of wireless optical communication according to an embodiment of the present application aims to reduce the number of superimposed O-OFDM signal components by recombining the layers, so as to reduce the complexity and processing delay of the receiving end, while maintaining good transmission performance.

[0038] In the RL-ASE-DMT method of the embodiment of the present application, the signal layer recombination and modulation process at the transmitting end includes the following steps, as shown in the accompanying drawings:

[0039] Step 1, layering the subcarriers according to the sequence number and real and imaginary parts, the subcarrier sequence number of the real part is represented as k R , the subcarrier sequence number of the imaginary part is represented as k I , k R =0, 1, …, N-1, k I =0, 1, …, N-1, N represents the total number of subcarriers; the imaginary part of the subcarriers of the first layer is used, and the subcarrier set of the first layer is represented as φ1={k I |0≤k I ≤N-1, k I≠0, N / 2}, and the subsequent layers use the real part of the subcarriers, and the set of subcarriers of the l-th layer is denoted as l = {k R |k R = 2 l-2 (2i+1), i = 0, 1, …, N / 2 l-1 -1}, l ≥ 2;

[0040] Step 2, according to the number of layers used, the reorganization of the layers is carried out, and the serial number of the reorganized layer group is denoted as m, and the total number of the reorganized layer groups is denoted as M, and the frequency domain signal corresponding to the M layer groups is generated, wherein when m = 1, that is, the first reorganized layer group, it contains the first layer to the l1 layer, wherein l1 ≥ 1, and the frequency domain signal corresponding to the first reorganized layer group is denoted as:

[0041]

[0042] wherein A k and B k respectively represent the PAM symbol on the imaginary part and the real part of the k-th subcarrier, the m-th reorganized layer group contains the l m-1 ,…,l m layer, wherein l m ≥l m-1 and m ≥ 2, and the frequency domain signal corresponding to the m-th reorganized layer group is denoted as:

[0043]

[0044] Step 3, after the frequency domain signal corresponding to the reorganized layer group is subjected to IFFT operation, the time domain signal is generated, wherein the time domain signal corresponding to the m-th layer group is denoted as n = 0, 1, …, N-1;

[0045] Step 4, the reconstruction signal is introduced to generate a non-negative signal, and the reconstruction signal of the n-th moment of the m-th layer group is denoted as then the non-negative time domain signal corresponding to the m-th layer group is denoted as:

[0046]

[0047] Step 5, the non-negative time domain signals corresponding to the M layer groups are superimposed to generate the RL-ASE-DMT signal is denoted as:

[0048]

[0049] The RL-ASE-DMT signal is input to an optical transmitter after digital-to-analog conversion to generate an optical signal.

[0050] In a further embodiment, in step 4, for the first layered group, when l1=1, the reconstructed signal for n=0,1,…,N / 2 is represented as:

[0051]

[0052] Further according to the symmetry A reconstructed signal of one RL-ASE-DMT symbol time is generated.

[0053] In a further embodiment, in step 4, when l1>1, and m=1, the reconstructed signal for n=0,1,…,N / 2 is represented as:

[0054]

[0055] wherein,

[0056] Further according to the symmetry A reconstructed signal of one RL-ASE-DMT symbol time is generated; for the mth layered group, and m≥2, the reconstructed signal for n=0,1,…,N / 2 is represented as:

[0057]

[0058] wherein,

[0059] Further according to the symmetry A reconstructed signal of one RL-ASE-DMT symbol time is generated.

[0060] In a further embodiment, the recombination layered RL-ASE-DMT method proposed by the present application adopts a cyclic crosstalk cancellation manner for signal detection at the receiving end.

[0061] As shown in Figure 2 , the processing process at the receiving end includes the following steps:

[0062] First, the transmitted symbol of the first layered group is detected, the reconstructed signal is restored according to the detected symbol, and the reconstructed signal is removed from the received signal; then the transmitted symbol of the second layered group is detected, and the reconstructed signal of the second layered group is further restored and removed;

[0063] The transmitted symbols in the subsequent layered groups are detected in the same manner to achieve detection.

[0064] As shown in Figure 1 ​​​As shown, in the RL-ASE-DMT method proposed in this invention, the number of superimposed O-OFDM signal components is reduced by recombining the subcarrier layers.

[0065] Combination Figure 3 The simulation test results shown demonstrate the performance of the proposed RL-ASE-DMT method and the existing LACO-OFDM method through bit error rate (BER) simulation. In the simulation, symbol transmission is performed using a two-layer approach. In the RL-ASE-DMT method, the two layers can be reassembled into a single group. The complexity and processing latency at the receiver are mainly determined by IFFT and FFT operations. Since the two layers are reassembled into a single group in the RL-ASE-DMT method, the receiver only needs one FFT operation to complete symbol detection. In contrast, the traditional LACO-OFDM method first requires an FFT operation to complete symbol detection for the first layer, and then, based on the detected symbol, additional and sequential IFFT and FFT operations are used to reconstruct the clipping noise of the first layer before completing symbol detection for the second layer. Therefore, for two-layer transmission, the traditional LACO-OFDM method requires additional IFFT and FFT operations to complete signal detection compared to the RL-ASE-DMT method of this invention. The proposed RL-ASE-DMT method significantly reduces receiver complexity and processing latency. Furthermore, combined with… Figure 3 The RL-ASE-DMT method using 2-PAM and 4-PAM can achieve the same spectral efficiency as the LACO-OFDM method using 4-QAM and 16-QAM. As can be seen from the simulation diagram, the RL-ASE-DMT method proposed in this invention has similar BER performance to the traditional LACO-OFDM method. Therefore, the method of this invention maintains the performance advantages of the traditional layered OFDM method while reducing the reception complexity.

[0066] {Example 2}

[0067] Combined with appendix Figure 1 Appendix Figure 2 As shown, the low-complexity reassembly layered ASE-DMT system for wireless optical communication according to an embodiment of the present invention consists of a transmitter and a receiver.

[0068] Combined with appendix Figure 1 As shown, the transmitter includes a subcarrier layering module, a layering and recombination module, an IFET processing module, a non-negative time-domain signal generation module, a signal superposition processing module, and an optical signal modulation generation module.

[0069] The subcarrier layering module is used to layer subcarriers according to their sequence number and virtual / real components, obtaining a set of subcarriers for each layer.

[0070] The hierarchical recombination module is configured to perform hierarchical recombination according to the number of hierarchical layers, to obtain M hierarchical groups and to obtain frequency domain signals corresponding to the hierarchical groups.

[0071] The IFFT processing module is configured to perform IFFT operation on the frequency domain signals corresponding to the recombined hierarchical groups to generate time domain signals.

[0072] The non-negative time domain signal generation module is configured to introduce a reconstruction signal into the time domain signals to generate non-negative time domain signals corresponding to each hierarchical group.

[0073] The signal superposition processing module is configured to superimpose the non-negative time domain signals corresponding to the M hierarchical groups to generate an RL-ASE-DMT signal.

[0074] The optical signal modulation generation module is configured to perform digital-to-analog conversion on the RL-ASE-DMT signal and generate an optical signal through an optical modulator.

[0075] In a further embodiment, the aforementioned subcarrier hierarchical module is configured to obtain the subcarrier set of each hierarchical layer in the following manner:

[0076] The subcarriers are divided into real and imaginary parts according to the sequence number, and the subcarrier sequence number of the real part is represented as k R , and the subcarrier sequence number of the imaginary part is represented as k I , k R =0,1,…,N-1, k I =0,1,…,N-1, N represents the total number of subcarriers, wherein:

[0077] The first hierarchical layer uses the imaginary part of the subcarriers, and the subcarrier set of the first hierarchical layer is represented as φ1={k I |0≤k I ≤N-1,k I ≠0,N / 2};

[0078] The subsequent hierarchical layers use the real part of the subcarriers, and the subcarrier set of the lth hierarchical layer is represented as φ l ={k R |k R =2 l-2 (2i+1), i=0,1,…,N / 2 l-1 -1}, l≥2.

[0079] In a further embodiment, the aforementioned hierarchical recombination module is configured to perform hierarchical recombination in the following manner, to obtain M hierarchical groups and to obtain frequency domain signals corresponding to the hierarchical groups:

[0080] Based on the number of layers used, the layers are recombined. The sequence number of the recombined layer group is denoted as m, and the total number of recombined layer groups is denoted as M. Frequency domain signals corresponding to M layer groups are generated, where:

[0081] When m = 1, that is, the first recombined hierarchical group, which includes the first to the l1th layer, where l1 ≥ 1, the frequency domain signal corresponding to the first recombined hierarchical group is represented as:

[0082]

[0083] Among them, A k and B k Let represent the PAM symbols on the imaginary and real parts of the k-th subcarrier, respectively;

[0084] When m ≥ 2, the m-th recombined stratified group contains the l-th group. m-1 ,…,l m Layer, where l m ≥l m-1 The frequency domain signal corresponding to the m-th recombined hierarchical group is represented as:

[0085]

[0086] In a further embodiment, the aforementioned nonnegative time-domain signal generation module is configured to introduce a reconstructed signal into the time-domain signal in the following manner to generate a nonnegative time-domain signal corresponding to each hierarchical group:

[0087] The nonnegative time-domain signal corresponding to the m-th layer group Represented as:

[0088]

[0089] in, This represents the time-domain signal corresponding to the m-th hierarchical group;

[0090] in, Let represent the reconstructed signal at time n of the m-th hierarchical group, and:

[0091] For the first hierarchical group, when l1 = 1, the reconstructed signal for n = 0, 1, ..., N / 2 is represented as:

[0092]

[0093] Further based on symmetry Generate a reconstructed signal with RL-ASE-DMT symbol time;

[0094] When l1>1 and m=1, for The reconstructed signal is represented as:

[0095]

[0096] wherein,

[0097] further according to the symmetry generating a reconstructed signal of one RL-ASE-DMT symbol time; for the mth hierarchical group, and m≥2, for the reconstructed signal is valued as:

[0098]

[0099] wherein,

[0100] further according to the symmetry generating a reconstructed signal of one RL-ASE-DMT symbol time.

[0101] In a further embodiment, the aforementioned signal superposition processing module is configured to superimpose the non-negative time-domain signals corresponding to the M hierarchical groups in the following manner:

[0102]

[0103] wherein, denotes the RL-ASE-DMT signal.

[0104] As shown in Figure 2 , the receiving end adopts a cyclic crosstalk cancellation method to detect the signal.

[0105] In the embodiment shown in Figure 2 , the processing procedure of the receiving end includes the following steps:

[0106] First, the transmitted symbol of the first hierarchical group is detected, the reconstructed signal is restored according to the detected symbol, and the reconstructed signal is removed from the received signal; then the transmitted symbol of the second hierarchical group is detected, and the reconstructed signal of the second hierarchical group is further restored and removed;

[0107] The transmitted symbols in the subsequent hierarchical groups are detected in the same manner as described above, and the signal detection is realized.

[0108] As an example of the signal detection procedure of the receiving end, taking the transmission of four hierarchical symbols as an example, the RL-ASE-DMT can recombine the first hierarchical group and the second hierarchical group into one group, and the third hierarchical group and the fourth hierarchical group into the second group, and the signal detection procedure of the receiving end includes:

[0109] ​Step one: after the received RL-ASE-DMT signal is subjected to FFT operation, a frequency domain signal is generated, and for the transmission symbol of the first group, since there is no interference of the reconstructed signal, PAM symbol detection can be directly performed, and the PAM symbols transmitted by the first layer and the second layer are detected at the same time;

[0110] Step two: according to the detected PAM symbols of the first group, a time domain signal of the first group is generated after IFFT operation, and a reconstructed signal is generated, and after FFT operation, the frequency domain reconstructed signal corresponding to the first group is restored;

[0111] Step three: the reconstructed signal is removed from the subcarriers corresponding to the second group, and the transmitted PAM symbols of the second group are further detected, so that signal detection is completed.

[0112] As can be seen, for the case of symbol transmission of four layers, the RL-ASE-DMT method proposed by the present application can complete signal detection by using two FFT operations and one IFFT operation, compared with the traditional LACO-OFDM method which needs to use four FFT operations and three IFFT operations to complete signal detection, and at the same time, the related IFFT / FFT modules are serial operation, therefore, the RL-ASE-DMT method can effectively reduce the receiving complexity and processing delay.

[0113] Although the present application has been disclosed as above with reference to the preferred embodiments, it is not intended to limit the present application. Those skilled in the art having ordinary knowledge can make various modifications and decorations without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be subject to the definition of the claims.

Claims

1. A low-complexity reassembly hierarchical ASE-DMT method for wireless optical communication, characterized in that, The reconstructed layered ASE-DMT method includes the following steps in the signal layered reconstruction and modulation process at the transmitting end: Step 1: Divide the subcarriers into layers according to their sequence number and real / imaginary components, and represent the subcarrier sequence number of the real component as k. R The subcarrier index of the imaginary part is represented as k. I k R =0,1,…,N-1,k I =0,1,…,N-1, where N represents the total number of subcarriers; the first layer uses the imaginary part of the subcarriers, and the set of subcarriers in the first layer is represented as φ1={k I |0≤k I ≤N-1,k I ≠0,N / 2}, subsequent layering uses the real part of the subcarriers, and the set of subcarriers in the l-th layer is represented as φ l ={k R |k R =2 l-2 (2i+1), i = 0, 1, ..., N / 2 l-1 -1}, l≥2; Step 2: Based on the number of layers used, perform layer recombination. The sequence number of the recombined layer group is denoted as m, and the total number of recombined layer groups is denoted as M. Generate frequency domain signals corresponding to M layer groups, where: when m = 1, that is, the first recombined layer group, it contains layers 1 to l1, where l1 ≥ 1. The frequency domain signal corresponding to the first recombined layer group is represented as: Among them, A k and B k These represent the PAM symbols on the imaginary and real parts of the k-th subcarrier, respectively. The m-th reassembled hierarchical group contains the l-th... m-1 ,…,l m Layer, where l m ≥l m-1 And m≥2, the frequency domain signal corresponding to the m-th recombined hierarchical group is expressed as: Step 3: After performing an IFFT operation on the frequency domain signals corresponding to the recombined hierarchical groups, a time domain signal is generated, where the time domain signal corresponding to the m-th hierarchical group is represented as... n = 0, 1, ..., N-1; Step 4: Introduce the reconstructed signal to generate a non-negative signal. Represent the reconstructed signal at time n of the m-th layer group as follows: Then the nonnegative time-domain signal corresponding to the m-th layer group Represented as: Step 5: Convert the nonnegative time-domain signals corresponding to the M hierarchical groups. Superimposed to generate RL-ASE-DMT signal Represented as: The RL-ASE-DMT signal is converted from digital to analog and then input to the optical transmitter to generate an optical signal.

2. The low-complexity reassembly layered ASE-DMT method for wireless optical communication according to claim 1, characterized in that, In step 4, for the first hierarchical group, when l1 = 1, the reconstructed signal for n = 0, 1, ..., N / 2 is represented as: Further based on symmetry Generate a reconstructed signal with RL-ASE-DMT symbol time.

3. The low-complexity reassembly layered ASE-DMT method for wireless optical communication according to claim 2, characterized in that, In step 4, when l1>1 and m=1, for The reconstructed signal is represented as: in, Further based on symmetry Generate a reconstructed signal with symbol time of RL-ASE-DMT; for the m-th hierarchical group, and m≥2, for Reconstructed signal The value can be: in, Further based on symmetry Generate a reconstructed signal with RL-ASE-DMT symbol time.

4. The low-complexity reassembly layered ASE-DMT method for wireless optical communication according to any one of claims 1-3, characterized in that, The recombined layered ASE-DMT method uses cyclic crosstalk cancellation for signal detection at the receiving end.

5. The low-complexity reassembly layered ASE-DMT method for wireless optical communication according to claim 4, characterized in that, The processing procedure at the receiving end includes the following steps: First, the transmitted symbols of the first layer group are detected, the reconstructed signal is restored based on the detected symbols, and the reconstructed signal is removed from the received signal; then the transmitted symbols of the second layer group are detected, and the reconstructed signal of the second layer group is further restored and removed. The same method described above is used to detect the transmitted symbols in subsequent hierarchical groups in sequence, thus achieving detection.

6. A low-complexity reassembly hierarchical ASE-DMT system for wireless optical communication, characterized in that, Includes a transmitter and a receiver, wherein the transmitter includes: The subcarrier layering module is used to layer subcarriers according to their sequence number and virtual / real components, obtaining a set of subcarriers for each layer. The layered recombination module is used to recombine layers according to the number of layers, obtain M layered groups, and obtain the frequency domain signal of the corresponding layered group; The IFET processing module is used to perform IFFT operations on the frequency domain signal corresponding to the recombined hierarchical group to generate a time domain signal. The nonnegative time-domain signal generation module is used to introduce a reconstructed signal into the time-domain signal to generate a nonnegative time-domain signal corresponding to each layer group; The signal superposition processing module is used to superimpose the non-negative time-domain signals corresponding to M hierarchical groups to generate an RL-ASE-DMT signal; and The optical signal modulation generation module is used to generate an optical signal by performing digital-to-analog conversion on the RL-ASE-DMT signal and then using an optical modulator.

7. The low-complexity reassembly layered ASE-DMT system for wireless optical communication according to claim 6, characterized in that, The subcarrier layering module is configured to obtain the subcarrier set for each layer in the following manner: The subcarriers are layered according to their sequence number and their real / imaginary components. The sequence number of the subcarrier in the real component is represented as k. R The subcarrier index of the imaginary part is represented as k. I k R =0,1,…,N-1,k I =0,1,…,N-1, where N represents the total number of subcarriers, and: The first layer uses the imaginary part of the subcarriers, and the set of subcarriers in the first layer is represented as φ1={k I |0≤k I ≤N-1,k I ≠0, N / 2}; Subsequent layering uses the real part of the subcarriers, and the set of subcarriers in the l-th layer is represented as φ. l ={k R |k R =2 l-2 (2i+1), i = 0, 1, ..., N / 2 l-1 -1}, l≥2.

8. The low-complexity reassembly layered ASE-DMT system for wireless optical communication according to claim 6, characterized in that, The hierarchical recombination module is configured to perform hierarchical recombination in the following manner to obtain M hierarchical groups and obtain the frequency domain signals of the corresponding hierarchical groups: Based on the number of layers used, the layers are recombined. The sequence number of the recombined layer group is denoted as m, and the total number of recombined layer groups is denoted as M. Frequency domain signals corresponding to M layer groups are generated, where: When m = 1, that is, the first recombined hierarchical group, which includes the first to the l1th layer, where l1 ≥ 1, the frequency domain signal corresponding to the first recombined hierarchical group is represented as: Among them, A k and B k Let represent the PAM symbols on the imaginary and real parts of the k-th subcarrier, respectively; When m ≥ 2, the m-th recombined stratified group contains the l-th group. m-1 ,…,l m Layer, where l m ≥l m-1 The frequency domain signal corresponding to the m-th recombined hierarchical group is represented as:

9. The low-complexity reassembly hierarchical ASE-DMT system for wireless optical communication according to claim 6, characterized in that, The nonnegative time-domain signal generation module is configured to introduce a reconstructed signal into the time-domain signal in the following manner to generate a nonnegative time-domain signal corresponding to each hierarchical group: The nonnegative time-domain signal corresponding to the m-th layer group Represented as: in, This represents the time-domain signal corresponding to the m-th hierarchical group; in, Let represent the reconstructed signal at time n of the m-th hierarchical group, and: For the first hierarchical group, when l1 = 1, the reconstructed signal for n = 0, 1, ..., N / 2 is represented as: Further based on symmetry Generate a reconstructed signal with RL-ASE-DMT symbol time; When l1>1 and m=1, for The reconstructed signal is represented as: in, Further based on symmetry Generate a reconstructed signal with symbol time of RL-ASE-DMT; for the m-th hierarchical group, and m≥2, for Reconstructed signal The value can be: in, Further based on symmetry Generate a reconstructed signal with RL-ASE-DMT symbol time.

10. The low-complexity reassembly hierarchical ASE-DMT system for wireless optical communication according to claim 6, characterized in that, The signal superposition processing module is configured to process the nonnegative time-domain signals corresponding to the M layer groups in the following manner. The signals are superimposed to generate an RL-ASE-DMT signal: in, This indicates the RL-ASE-DMT signal.

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