An IM / DD-based elastic packet three-layer hybrid O-OFDM method

Abstract

The application discloses an elastic packet three-layer hybrid O-OFDM method based on IM / DD, utilizes three-layer O-OFDM signal hybrid transmission, meanwhile, the subcarrier grouping of the third layer is variable, can more flexibly adapt to different channel conditions, and improves the utilization efficiency of the subcarrier. Compared with LACO-OFDM, the number of FTHO-OFDM layers is fixed to three, therefore, the receiver has fixed complexity and processing delay, will not increase with the number of layers, compared with LACO-OFDM with the number of layers greater than three, reduces the complexity and processing delay of the receiver, at the same time, the transmission performance does not obviously reduce, the demodulation mode of the application and LACO-OFDM is same, both adopt the iterative detection mode at the receiving end, but under the same spectrum efficiency, since the number of layers of the application is fixed to three, therefore, only needs to iterate twice, for LACO-OFDM with the increasing complexity with the number of layers, the application significantly reduces the complexity and processing delay of the receiver, and is more suitable for actual implementation.

Description

Technical Field

[0001] This invention relates to a flexible packet three-layer hybrid O-OFDM method based on IM / DD, belonging to the field of optical communication technology. Background Technology

[0002] In the field of optical communication, intensity modulation direct detection (IM / DD) is a popular modulation method that uses light intensity to transmit information. It boasts advantages such as simplicity and low cost, and is widely used in optical fiber communication, wireless optical communication, and other optical communication fields. Meanwhile, orthogonal spectrum multiplexing (OFDM) technology offers advantages such as high spectral efficiency and effective resistance to inter-symbol interference. Therefore, in the field of optical communication, optical OFDM (O-OFDM) based on IM / DD has become a popular technology.

[0003] In IM / DD-based systems, the transmitted signal is constrained to be non-negative, leading to the development of various O-OFDM methods. Typical examples include DC-biased O-OFDM (DCO-OFDM), asymmetric clipping O-OFDM (ACO-OFDM), hybrid ACO-OFDM (HACO-OFDM), adaptive biased O-OFDM (ABO-OFDM), and three-layer hybrid O-OFDM (THO-OFDM). DCO-OFDM uses a DC bias to ensure non-negativity, offering simplicity but lower power efficiency. Therefore, the more power-efficient ACO-OFDM method was proposed. While it uses clipping to generate the signal, ACO-OFDM utilizes only half of the subcarriers for transmission, resulting in lower spectral efficiency. To improve spectral efficiency, HACO-OFDM superimposes a pulse amplitude modulated discrete multitone (PAM-DMT) signal onto the ACO-OFDM signal, enhancing spectral efficiency. However, in HACO-OFDM, one-quarter of the subcarrier resources remain unutilized. The ABO-OFDM method adaptively adds an offset signal based on the signal amplitude, achieving high power efficiency while significantly reducing reception complexity. However, ABO-OFDM suffers from the same problem as HACO-OFDM: it fails to achieve efficient subcarrier utilization. THO-OFDM uses three O-OFDM methods for hybrid transmission to improve subcarrier utilization, but its subcarrier utilization is fixed at 87.5%, still failing to fully utilize subcarrier resources. Currently, although there are O-OFDM methods that can fully utilize subcarrier resources, such as layered ACO-OFDM (LACO-OFDM), the excessive number of layers leads to high reception complexity and processing delay. While a low-complexity adaptive offset layered O-OFDM (ABLO-OFDM) method exists, the cost of reduced complexity is a significant decrease in transmission performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a flexible three-layer hybrid O-OFDM method based on IM / DD. This method utilizes the hybrid transmission of three layers of O-OFDM signals, and the subcarrier grouping of the third layer is variable, enabling more flexible adaptation to different channel conditions and improving subcarrier utilization efficiency. Compared to LACO-OFDM, FTHO-OFDM has a fixed number of layers (three), therefore the receiver has a fixed complexity and processing delay that does not increase with the number of layers. Compared to LACO-OFDM with more than three layers, this reduces receiver complexity and processing delay without significantly reducing transmission performance.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a flexible grouping three-layer hybrid O-OFDM method based on IM / DD, comprising:

[0007] Obtain the transmission bits and divide them into three paths;

[0008] After the two transmission bits are subjected to orthogonal amplitude modulation and pulse amplitude modulation, they are converted from serial to parallel and the imaginary parts of the odd and even subcarriers are used for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT.

[0009] The frequency domain signals of ACO-OFDM and PAM-DMT are converted into time domain signals through IFFT operation, and non-negative signals are generated through parallel-to-serial conversion and clipping operation. and

[0010] The third transmission bits are grouped using a flexible subcarrier grouping method, and the frequency domain signal Z is calculated and obtained. k ;

[0011] For frequency domain signal Z k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ;

[0012] Based on time-domain signal z n Obtain the adaptive bias signal b n ;

[0013] The adaptive bias signal b n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM.

[0014] Non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

[0015] Furthermore, non-negative signals are generated through parallel-to-serial conversion and limiting operations. and include:

[0016] Let the unlimited time-domain signals of ACO-OFDM and PAM-DMT at the nth sampling time be represented as x. n and y n n = 0, 1, ..., N-1,

[0017] Non-negative signals are generated through parallel-to-serial conversion and limiting operations. and This indicates the negative part of the clipping operation.

[0018] Furthermore, the third transmission bits are grouped using a flexible subcarrier grouping method, and the frequency domain signal Z is calculated and obtained. k ,include:

[0019] The subcarrier grouping method is expressed as: Ω={k|k=2 g-1 (2i+1), i = 0, 1, ..., N / 2 g ,g=1,2,…,G}, where G represents the depth of the third layer. By adjusting the value of G, the flexible and elastic adjustment of the third layer subcarrier groups can be achieved.

[0020] Based on flexible grouping, the frequency domain signal is generated by the following formula.

[0021]

[0022] Among them, P k This represents the PAM symbol assigned to the k-th subcarrier.

[0023] Furthermore, based on the time-domain signal z n Obtain the adaptive bias signal b n ,include:

[0024] The adaptive bias signal is composed of a time-domain signal sequence. and q = 0, 1, ..., 2 G+1 The minimum value of -1 determines the value, where mod() represents the remainder operation, and the adaptive bias signal is represented as b. n b nCalculate using the following formula:

[0025]

[0026] Furthermore, the time-domain signal of the third layer O-OFDM Represented as:

[0027]

[0028] Furthermore, non-negative signals and and the time-domain signal of the third layer O-OFDM The mixed superposition generates an FTHO-OFDM signal, represented as:

[0029]

[0030] Furthermore, an iterative detection method is adopted to detect each layer of O-OFDM signals one by one. The received signals are converted into frequency domain signals through FFT operation. First, ACO-OFDM frequency domain signal detection is performed. The ACO-OFDM clipping noise is restored based on the detection symbol of ACO-OFDM. After removing the ACO-OFDM clipping noise from the even subcarriers, PAM-DMT frequency domain signal detection is performed. The PAM-DMT clipping noise is restored based on the detection symbol of PAM-DMT. After removing the PAM-DMT clipping noise from the real part of the even subcarriers, the third layer of O-OFDM frequency domain signal detection is performed.

[0031] In a second aspect, the present invention provides a flexible packet three-layer hybrid O-OFDM device based on IM / DD, comprising:

[0032] The acquisition module is used to acquire the transmitted bits and divide the transmitted bits into three paths.

[0033] The frequency domain signal generation module is used to convert the two transmitted bits through orthogonal amplitude modulation and pulse amplitude modulation, and then perform serial-to-parallel conversion and use the imaginary parts of odd and even subcarriers for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT.

[0034] The non-negative signal acquisition module is used to convert the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals through IFFT operations, and generate non-negative signals through parallel-to-serial conversion and clipping operations. and

[0035] The frequency domain signal acquisition module is used to group the third-channel transmitted bits using a flexible subcarrier grouping method and calculate and acquire the frequency domain signal Z. k ;

[0036] The time-domain signal acquisition module is used to acquire the frequency-domain signal Z. k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ;

[0037] An adaptive bias signal acquisition module is used to acquire bias signals based on time-domain signal z. n Obtain the adaptive bias signal b n ;

[0038] The third-layer O-OFDM time-domain signal acquisition module is used to acquire the adaptive bias signal b. n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM.

[0039] Hybrid overlay module, used to combine non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

[0040] Thirdly, the present invention provides an electronic device, including a processor and a storage medium;

[0041] The storage medium is used to store instructions;

[0042] The processor is configured to operate according to the instructions to perform the steps of the method according to any of the preceding claims.

[0043] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the preceding methods.

[0044] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0045] This invention provides a three-layer hybrid O-OFDM method based on IM / DD flexible packetization. Compared with traditional methods such as ACO-OFDM, HACO-OFDM, ABO-OFDM, and THO-OFDM, this invention can achieve the same spectral efficiency as LACO-OFDM, thereby fully utilizing subcarrier resources. Furthermore, the third-layer subcarriers enable flexible packetization, allowing for flexible adjustment of the number of subcarrier groups used for data transmission as needed, thus providing additional degrees of freedom for communication.

[0046] This invention uses the same demodulation method as LACO-OFDM, employing iterative detection at the receiver. However, at the same spectral efficiency, since the number of layers in this invention is fixed at three, only two iterations are required. Compared to LACO-OFDM, where computational complexity increases with the number of layers, this invention significantly reduces receiver complexity and processing latency, making it more suitable for practical implementation.

[0047] Furthermore, when using more subcarriers for transmission, this invention outperforms LACO-OFDM in terms of peak-to-average power ratio (PAPR), indicating better performance in suppressing nonlinear distortion. Considering the nonlinearity of LEDs, this invention demonstrates superior bit error rate (BER) performance, effectively improving the transmission performance of optical communication. Attached Figure Description

[0048] Figure 1 This is a block diagram of the transmitter structure in this invention;

[0049] Figure 2 This is a block diagram of the receiver structure in this invention;

[0050] Figure 3 A comparison chart of PAPR performance for different O-OFDM schemes;

[0051] Figure 4 For different O-OFDM schemes in different E b BER performance diagram under / N0. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0053] Example 1

[0054] This embodiment introduces a flexible grouping three-layer hybrid O-OFDM method based on IM / DD, including:

[0055] Obtain the transmission bits and divide them into three paths;

[0056] After the two transmission bits are subjected to orthogonal amplitude modulation and pulse amplitude modulation, they are converted from serial to parallel and the imaginary parts of the odd and even subcarriers are used for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT.

[0057] The frequency domain signals of ACO-OFDM and PAM-DMT are converted into time domain signals through IFFT operation, and non-negative signals are generated through parallel-to-serial conversion and clipping operation. and

[0058] The third transmission bits are grouped using a flexible subcarrier grouping method, and the frequency domain signal Z is calculated and obtained. k ;

[0059] For frequency domain signal Z k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ;

[0060] Based on time-domain signal z n Obtain the adaptive bias signal b n ;

[0061] The adaptive bias signal b n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM.

[0062] Non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

[0063] Furthermore, non-negative signals are generated through parallel-to-serial conversion and limiting operations. and include:

[0064] Let the unlimited time-domain signals of ACO-OFDM and PAM-DMT at the nth sampling time be represented as x. n and y n n = 0, 1, ..., N-1,

[0065] Non-negative signals are generated through parallel-to-serial conversion and limiting operations. and This indicates the negative part of the clipping operation.

[0066] The flexible grouping three-layer hybrid O-OFDM method based on IM / DD provided in this embodiment involves the following steps in its application process:

[0067] Step 1: The proposed FTHO-OFDM method employs a three-layer O-OFDM signal hybrid transmission mode. The first two layers of FTHO-OFDM are ACO-OFDM and PAM-DMT signals. The two transmission bits first undergo Quadrature Amplitude Modulation (QAM) and Pulse Amplitude Modulation (PAM), then undergo serial-to-parallel conversion and use the imaginary parts of odd and even subcarriers for symbol transmission, generating frequency domain signals for ACO-OFDM and PAM-DMT. These are then converted to time domain signals through IFFT operations. The unlimited time domain signals of ACO-OFDM and PAM-DMT at the nth sampling time are represented as x. n and y n For n = 0, 1, ..., N-1, non-negative signals are further generated through parallel-to-serial conversion and amplitude limiting operations. and This indicates the negative part of the clipping operation;

[0068] Step 2: The third-layer O-OFDM uses a flexible subcarrier grouping method. Let k represent the subcarrier index and N represent the total number of subcarriers in the system. The subcarrier grouping of the third-layer O-OFDM can be represented as Ω = {k | k = 2}. g-1 (2i+1), i = 0, 1, ..., N / 2 g Let g = 1, 2, ..., G, where G represents the depth of the third layer. By adjusting the value of G, the subcarrier grouping of the third layer can be flexibly adjusted. Based on this flexible grouping, the frequency domain signal can be generated using the following formula.

[0069]

[0070] Among them, P k This represents the PAM symbol assigned to the k-th subcarrier. Further, for the frequency domain signal Z... k If k = 0, 1, ..., N / 2, perform an N / 2-point IFFT operation to generate Z. k The time-domain signal is represented as z. n n = 0, 1, ..., N / 2-1;

[0071] Step 3: Generate a non-negative signal using an adaptive bias. The adaptive bias signal is derived from a time-domain signal sequence. and q = 0, 1, ..., 2 G+1 The minimum value of -1 determines the value, where mod() represents the remainder operation, and the adaptive bias signal is represented as b. n b n Calculate using the following formula:

[0072]

[0073] Step 4: Apply the adaptive bias signal b n Superimposed on z n This generates a nonnegative time-domain signal, which is repeated twice in the time domain to produce the time-domain signal of the third layer O-OFDM, denoted as . It can be represented as

[0074]

[0075] Step 5: Mix and superimpose the O-OFDM signals from the three layers to generate an FTHO-OFDM signal, represented as...

[0076]

[0077] After the FTHO-OFDM signal is converted from digital to analog, it is further input to the LED to drive it to emit light;

[0078] Step 6: The receiver uses an iterative detection method to detect each layer of O-OFDM signal one by one. The received signal is converted into a frequency domain signal through FFT operation. First, the signal detection of the first layer ACO-OFDM is performed. The ACO-OFDM clipping noise is restored according to the detection symbol of ACO-OFDM. After removing the ACO-OFDM clipping noise from the even subcarrier, the signal detection of the second layer PAM-DMT is performed. The PAM-DMT clipping noise is restored according to the detection symbol of PAM-DMT. After removing the PAM-DMT clipping noise from the real part of the even subcarrier, the signal detection of the third layer O-OFDM is performed.

[0079] Figure 1 The diagram shows a transmitter architecture for a three-layer hybrid O-OFDM method based on IM / DD flexible grouping. As can be seen, to achieve the same spectral efficiency, an L-layer LACO-OFDM transmitter requires L IFFT operations, while the proposed FTHO-OFDM transmitter only requires three IFFT operations. Therefore, this invention has lower hardware implementation complexity.

[0080] Figure 2 The diagram shows the receiver structure of the three-layer hybrid O-OFDM method based on IM / DD elastic grouping. At the receiver, although both FTHO-OFDM and LACO-OFDM use iterative detection, the number of iterations is significantly less than that of LACO-OFDM because the number of layers in this invention is fixed at three. Therefore, this invention has lower reception complexity and processing latency than LACO-OFDM.

[0081] Figure 3The graph compares the PAPR performance of the proposed FTHO-OFDM method with that of LACO-OFDM. The horizontal axis PAPR0 represents the set range of PAPR transformation, and the vertical axis represents the complementary cumulative distribution function curve Pr[PAPR>PAPR0], indicating the probability that the system PAPR distribution is greater than PAPR0. The FTHO-OFDM methods with G=1, G=2, and G=3 have the same spectral efficiency as those with L=3, L=4, and L=5. Furthermore, it can be seen that, under the same spectral efficiency, for a given PAPR0, when G=1 and G=2, the Pr[PAPR>PAPR0] of FTHO-OFDM is the same as that of LACO-OFDM, indicating the same PAPR performance. When G=3, FTHO-OFDM has a lower PAPR than LACO-OFDM, meaning that the present invention is superior in terms of nonlinear resistance.

[0082] Figure 4 For different O-OFDM schemes in different E b As can be seen from the figure, under the same spectral efficiency, the present invention can achieve BER performance similar to that of LACO-OFDM, ensuring the reliability of transmission.

[0083] This invention proposes a flexible three-layer hybrid O-OFDM (FTHO-OFDM) method, which utilizes the hybrid transmission of three layers of O-OFDM signals. Furthermore, the subcarrier grouping of the third layer is variable, enabling more flexible adaptation to different channel conditions and improving subcarrier utilization efficiency. Compared to LACO-OFDM, FTHO-OFDM has a fixed number of layers (three), therefore, the receiver has a fixed complexity and processing delay that does not increase with the number of layers. Compared to LACO-OFDM, which has more than three layers, this reduces receiver complexity and processing delay without significantly degrading transmission performance.

[0084] Example 2

[0085] This embodiment provides a flexible packet three-layer hybrid O-OFDM device based on IM / DD, including:

[0086] The acquisition module is used to acquire the transmitted bits and divide the transmitted bits into three paths.

[0087] The frequency domain signal generation module is used to convert the two transmitted bits through orthogonal amplitude modulation and pulse amplitude modulation, and then perform serial-to-parallel conversion and use the imaginary parts of odd and even subcarriers for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT.

[0088] The non-negative signal acquisition module is used to convert the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals through IFFT operations, and generate non-negative signals through parallel-to-serial conversion and clipping operations. and

[0089] The frequency domain signal acquisition module is used to group the third-channel transmitted bits using a flexible subcarrier grouping method and calculate and acquire the frequency domain signal Z. k ;

[0090] The time-domain signal acquisition module is used to acquire the frequency-domain signal Z. k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ;

[0091] An adaptive bias signal acquisition module is used to acquire bias signals based on time-domain signal z. n Obtain the adaptive bias signal b n ;

[0092] The third-layer O-OFDM time-domain signal acquisition module is used to acquire the adaptive bias signal b. n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM.

[0093] Hybrid overlay module, used to combine non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

[0094] Example 3

[0095] This embodiment provides an electronic device, including a processor and a storage medium;

[0096] The storage medium is used to store instructions;

[0097] The processor is configured to operate according to the instructions to perform the steps of the method according to any one of Embodiment 1.

[0098] Example 4

[0099] This embodiment provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described in Embodiment 1.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible grouping three-layer hybrid O-OFDM method based on IM / DD, characterized in that, include: Obtain the transmission bits and divide them into three paths; After the two transmission bits are subjected to orthogonal amplitude modulation and pulse amplitude modulation, they are converted from serial to parallel and the imaginary parts of the odd and even subcarriers are used for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT. The frequency domain signals of ACO-OFDM and PAM-DMT are converted into time domain signals through IFFT operation, and non-negative signals are generated through parallel-to-serial conversion and clipping operation. and The third transmission bits are grouped using a flexible subcarrier grouping method, and the frequency domain signal Z is calculated and obtained. k ; For frequency domain signal Z k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ; Based on time-domain signal z n Obtain the adaptive bias signal b n ; The adaptive bias signal b n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM. Non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

2. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 1, characterized in that, Non-negative signals are generated through parallel-to-serial conversion and limiting operations. and include: Let the unlimited time-domain signals of ACO-OFDM and PAM-DMT at the nth sampling time be represented as x. n and y n n = 0, 1, ..., N-1, Non-negative signals are generated through parallel-to-serial conversion and limiting operations. and This indicates the negative part of the clipping operation.

3. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 2, characterized in that, The third transmission bits are grouped using a flexible subcarrier grouping method, and the frequency domain signal Z is calculated and obtained. k ,include: The subcarrier grouping method is expressed as: Ω={k|k=2 g-1 (2i+1), i = 0, 1, ..., N / 2 g ,g=1,2,…,G}, where G represents the depth of the third layer. By adjusting the value of G, the flexible and elastic adjustment of the third layer subcarrier groups can be achieved. Based on flexible grouping, the frequency domain signal is generated by the following formula. Among them, P k This represents the PAM symbol assigned to the k-th subcarrier.

4. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 3, characterized in that, Based on time-domain signal z n Obtain the adaptive bias signal b n ,include: The adaptive bias signal is composed of a time-domain signal sequence. and The minimum value is determined by mod(), where mod() represents the remainder operation, and the adaptive bias signal is represented as b. n b n Calculate using the following formula:

5. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 4, characterized in that, The time-domain signal of the third layer O-OFDM Represented as:

6. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 5, characterized in that, Non-negative signals and and the time-domain signal of the third layer O-OFDM The mixed superposition generates an FTHO-OFDM signal, represented as:

7. The IM / DD-based flexible grouping three-layer hybrid O-OFDM method according to claim 1, characterized in that, An iterative detection method is adopted to detect each layer of O-OFDM signals one by one. The received signals are converted into frequency domain signals through FFT operation. First, ACO-OFDM frequency domain signal detection is performed. The ACO-OFDM clipping noise is restored based on the detection symbol of ACO-OFDM. After removing the ACO-OFDM clipping noise from the even subcarriers, PAM-DMT frequency domain signal detection is performed. The PAM-DMT clipping noise is restored based on the detection symbol of PAM-DMT. After removing the PAM-DMT clipping noise from the real part of the even subcarriers, the third layer of O-OFDM frequency domain signal detection is performed.

8. A flexible grouping three-layer hybrid O-OFDM device based on IM / DD, characterized in that, include: The acquisition module is used to acquire the transmitted bits and divide the transmitted bits into three paths. The frequency domain signal generation module is used to convert the two transmitted bits through orthogonal amplitude modulation and pulse amplitude modulation, and then perform serial-to-parallel conversion and use the imaginary parts of odd and even subcarriers for symbol transmission to generate frequency domain signals of ACO-OFDM and PAM-DMT. The non-negative signal acquisition module is used to convert the frequency domain signals of ACO-OFDM and PAM-DMT into time domain signals through IFFT operations, and generate non-negative signals through parallel-to-serial conversion and clipping operations. and The frequency domain signal acquisition module is used to group the third-channel transmitted bits using a flexible subcarrier grouping method and calculate and acquire the frequency domain signal Z. k ; The time-domain signal acquisition module is used to acquire the frequency-domain signal Z. k Perform an N / 2-point IFFT operation to generate Z. k The time-domain signal z n ; An adaptive bias signal acquisition module is used to acquire bias signals based on time-domain signal z. n Obtain the adaptive bias signal b n ; The third-layer O-OFDM time-domain signal acquisition module is used to acquire the adaptive bias signal b. n Superimposed on the time-domain signal z n This generates a nonnegative time-domain signal, which is then repeated twice in the time domain to produce the time-domain signal of the third-layer O-OFDM. Hybrid overlay module, used to combine non-negative signals and and the time-domain signal of the third layer O-OFDM The mixture is superimposed to generate an FTHO-OFDM signal. After the FTHO-OFDM signal is converted from digital to analog, it is input to the LED to drive it to emit light.

9. An electronic device, characterized in that: Including processor and storage media; The storage medium is used to store 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. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the program implements the steps of the method according to any one of claims 1 to 7.

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