Method for suppressing peak-to-average power ratio of communication system

Abstract

The invention discloses a method for suppressing a peak-to-average power ratio of a communication system, which comprises the following steps that: a sending end allocates power coefficients to users according to channel coefficients of different users; subcarriers of the OFDM system are divided into reserved subcarriers and data subcarriers; the sending end superposes user data needing to be sent to different users according to the corresponding user distribution power coefficients to obtain frequency domain signals; constructing time domain discrete user signals of all OFDM symbol periods, and constructing and solving a user data symbol deviation minimization problem to obtain time domain signals of compensation data; constructing a to-be-sent signal; wherein a time domain signal of the compensation data is sent by utilizing a reserved subcarrier, a time domain discrete user signal is used as user data and is sent through a data subcarrier after being superposed with the time domain signal of the compensation data, and a signal to be sent is sent in the form of an optical signal; and after the receiving end obtains the receiving signal, performing user data detection on the receiving signal to obtain user data required by each user.

Description

Technical Field

[0001] The present invention belongs to the technical field of indoor visible light communication, and in particular relates to a peak-to-average ratio suppression method suitable for a NOMA-VLC system. Background Art

[0002] With the development of network technology and the emergence of a large number of communication devices, spectrum resources have become increasingly scarce. However, improving the utilization rate of spectrum resources is crucial for modern wireless communication systems. Visible light communication (VLC) has entered people's field of vision and received great attention due to its advantages such as rich spectrum resources, large channel capacity and high security. VLC uses data signals to drive photodiodes (LEDs) and uses 380nm~75nm visible light as a carrier for wireless transmission. It can obtain a huge bandwidth of more than 400THz and can effectively solve the problem of spectrum congestion. Specifically, at the transmitting end, VLC uses intensity modulation / direct detection (IM / DD) to modulate the signal on the light intensity and send it out in the form of real numbers. At the receiving end, the user uses PD to convert the light intensity into a voltage signal for demodulation. VLC has the advantages of low deployment cost, high security and confidentiality, no electromagnetic radiation, and no electromagnetic interference. It is widely used in high-speed communication, positioning, sensing and the Internet of Things.

[0003] In order to improve the spectrum efficiency of the system and increase the number of users that can be accommodated simultaneously, non-orthogonal multiple access (NOMA) technology is often used. NOMA enables multiple user information to be superimposed within the same time-frequency resources, improving its spectrum efficiency, and has the advantages of high throughput, high reliability, and low latency. However, this technology of superimposing user signals will cause the VLC system to have a high peak-to-average power ratio (PAPR). In VLC, when these high PAPR signals pass through nonlinear diodes (LEDs), the signals will be severely distorted, resulting in a decrease in the bit error performance of the receiving end. Therefore, the high reception bit error rate caused by the high PAPR of the existing NOMA-VLC system is a problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a method for suppressing peak-to-average ratio of a communication system to overcome the problem of deterioration of the bit error performance of a NOMA-VLC system caused by high PAPR, effectively suppress the PAPR of the NOMA-VLC system, and improve the bit error performance of the system.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A method for suppressing peak-to-average ratio of a communication system, comprising:

[0007] The transmitter allocates power coefficients to users based on their channel coefficients.

[0008] The subcarriers of the OFDM system are divided, and some subcarriers are selected as reserved subcarriers, and the remaining subcarriers are used as data subcarriers;

[0009] The transmitting end superimposes the user data to be sent to different users according to the corresponding user allocation power coefficient to obtain a frequency domain signal;

[0010] The frequency domain signal of the user data is first converted from serial to parallel and then subjected to discrete inverse Fourier transform to obtain the time domain discrete signal of each OFDM symbol period;

[0011] Based on the time domain discrete signal, a time domain discrete user signal of all OFDM symbol periods is constructed, and a user data symbol deviation minimization problem is constructed and solved to obtain a time domain signal of compensated data;

[0012] The signal to be transmitted is constructed by using the time domain signal of the compensation data, the time domain discrete user signals of all OFDM symbol periods and the DC bias; wherein the time domain signal of the compensation data is transmitted using the reserved subcarrier, and the time domain discrete user signal is used as user data, which is superimposed on the time domain signal of the compensation data and then transmitted through the data subcarrier;

[0013] After the signal to be sent is converted into serial and parallel, the LED of the transmitter is driven to send the signal to be sent out in the form of an optical signal;

[0014] The receiving ends of different users receive optical signals through photoelectric receivers respectively, and then perform photoelectric conversion to obtain received signals; user data detection is performed on the received signals to obtain the user data required by each user.

[0015] Furthermore, the transmitting end allocates power coefficients to users according to channel coefficients of different users, including:

[0016] Arrange the channel coefficients of the users from large to small, that is, |h1|≥|h2|≥…≥h M |,h m is the channel coefficient of the mth (m=1,…,M)th user, and then the power coefficient α is allocated to the mth user m , the selection of power allocation coefficient is related to the channel coefficient and satisfies |α M |≥|α M-1 |≥…≥|α1| and

[0017] Furthermore, the subcarriers of the OFDM system are divided, and some subcarriers are selected as reserved subcarriers and the remaining subcarriers are selected as data subcarriers, including:

[0018] Note that OFDM has a total of N subcarriers. To ensure that the time domain signal transmitted through the driver LED is a real number, the 0th and subcarrier is not used for data transmission, and the subcarriers and The data on the subcarriers are conjugate symmetrical; subcarriers, arbitrarily select N r subcarriers as reserved subcarriers, and the remaining subcarriers as data subcarriers.

[0019] Furthermore, the transmitting end superimposes the user data to be sent to different users according to the corresponding user allocation power coefficients to obtain a frequency domain signal, including:

[0020] Set the total number of OFDM symbol periods L. In the lth (L≥l≥1) OFDM symbol period, the user data to be sent to different users is allocated power coefficient α according to the corresponding user. m The frequency domain signal V(l) = [V u,1 (l),…,V u,N (l)] T , among which The frequency domain signal on the subcarriers satisfies V u,k (l)=(V u,N-k (l)) * , V u,k (l) represents the kth OFDM symbol period in the lth OFDM symbol period The frequency domain signal on the subcarriers, (·) * represents the conjugate operator; if but where s m,k (l) is the 4-quadrature amplitude modulation data modulation symbol of the m-th user on the k-th subcarrier in the l-th OFDM symbol period, if Then V u,k (l) = 0; They represent the data subcarrier set and the reserved subcarrier set respectively.

[0021] Furthermore, the problem of constructing the user data symbol deviation minimization is expressed as:

[0022]

[0023] st||FV c +v|| ∞ ≤A s

[0024] ||FV c +v|| F ≤v|| F

[0025]

[0026] Where minimize means minimizing the objective function, st, represents the constraint condition, V c represents the frequency domain signal of the compensation data to be solved; F represents the inverse discrete Fourier transform matrix, v represents the time domain discrete user signal of all OFDM symbol periods, A s Indicates the maximum signal amplitude allowed by the LED as a transmitter in the system, ||·|| ∞ represents the infinite norm of the matrix, ||·|| F represents the F-norm of the matrix, (·) * represents the conjugate operator, V c,N-k (l) represents the frequency domain signal of the compensation data on the Nkth subcarrier in the lth OFDM symbol period, V c,k (l) represents the frequency domain signal of the compensation data on the kth subcarrier in the lth OFDM symbol period, Represents the imaginary part operator, V c,0 (l) and They represent the 0th subcarrier and the 1st subcarrier in the 1st OFDM symbol period respectively. The frequency domain signal of the compensated data on the subcarriers.

[0027] Furthermore, the problem of minimizing the user data symbol deviation is solved to obtain a time domain signal of the compensated data, including:

[0028] The user data sign deviation minimization problem P1 is transformed into an equivalent problem P2:

[0029]

[0030] st,||vec(v c )+vec(v)|| ∞ ≤A s

[0031] vec(v c )+vec(v)||2≤||vec(v)||2

[0032] where v c =FV c The frequency domain signal V representing the compensation data c The corresponding time domain signal, (vec(·) represents the matrix vectorization operator, ||·||2 represents the 2-norm of the vector, and F′ represents the Fourier transform matrix;

[0033] The time domain signal v of the compensation data is obtained by solving the interior point method in convex optimization theory c .

[0034] Furthermore, the performing of user data detection on the received signal to obtain user data required by each user includes:

[0035] For the case where there are two users in the NOMA system, the process of user data detection is as follows:

[0036] The received signal of user 1 is expressed as y1=vec(y1)=h1vec(v tx )+n, where y1 is the received signal after serial-to-parallel conversion, h1 represents the channel coefficient of user 1, and n represents Gaussian noise; y1 is converted serially to parallel to obtain y1=h1v tx +n, where n is the noise signal after serial-to-parallel conversion; FFT transformation is performed on y1, and the received data on N carriers in L OFDM symbol periods is expressed as Y1=[y1(1),…,y1(L)]=F′y1, where y1(l)=[y 1,1 (l),…,y 1,N (l)] T represents the received data of NOMA user 1 on N carriers in the lth (L≥l≥1) OFDM symbol period, y 1,k (l) represents the data symbol received by user 1 on the kth subcarrier in the lth OFDM symbol period, and then the kth subcarrier in the lth OFDM symbol period The data symbols on the subcarriers are judged, that is:

[0037]

[0038] Among them, s 1,k (l) represents the data symbol of user 1 on the kth subcarrier in the lth OFDM symbol period, j represents the imaginary symbol, represents the real part operator, represents the imaginary part operator. Then the data symbols on N subcarriers in all OFDM symbol periods of user 1 constitute the complete user data s1 of user 1;

[0039] For user 2, serial interference cancellation is used to eliminate user 1's user data s1, expressed as Y2 = F'y2-s1, where y2 = h2v tx +n is the user data on N carriers in L OFDM symbol periods received by user 2, h2 represents the channel coefficient of NOMA user 2, and after obtaining y2, the data symbol is judged in the same way as user 1 to obtain the user data of user 2.

[0040] A NOMA-VLC system adopts the communication system peak-to-average ratio suppression method.

[0041] A terminal device comprises a processor, a memory and a computer program stored in the memory; when the processor executes the computer program, the peak-to-average ratio suppression method of the communication system is implemented.

[0042] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the communication system peak-to-average ratio suppression method is implemented.

[0043] Compared with the prior art, the present invention has the following technical features:

[0044] The principle of the present invention is to add an optimized compensation signal on the basis of the reserved subcarrier, and to obtain the improvement of the signal PAPR suppression performance and the bit error performance under LED peak clipping by changing the amplitude and phase of the transmitter symbol. First, the reserved subcarrier is selected in the NOMA-VLC system, and secondly, the compensation signal is introduced to further reduce the signal peak, while ensuring that the total power of the transmitted signal remains unchanged and the user data constellation point offset is minimized. Compared with the existing methods, the present invention can significantly reduce the peak-to-average ratio of the transmission signal and improve the bit error performance of the system under the LED peak constraint. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The NOMA-VLC system model diagram for two users;

[0046] Figure 2 This is the IV curve model diagram of LED;

[0047] Figure 3 The constellation diagram of the transmitted signal, where (a) is direct peak clipping and (b) is preprocessing;

[0048] Figure 4 It is a time domain signal waveform comparison chart;

[0049] Figure 5 This is a comparison diagram of the signal-to-noise ratio and bit error performance of the present invention;

[0050] Figure 6 This is a comparison diagram of LED peak constraint and signal-to-noise ratio gain of the present invention;

[0051] Figure 7 A schematic diagram comparing the BER of the peak-to-average ratio suppression solution and the ASDST solution provided by the present invention with the variation of LED peak value. DETAILED DESCRIPTION

[0052] The present invention provides a method for suppressing peak-to-average ratio of a communication system, wherein the communication is in the form of a NOMA-VLC system, and there are M users in the system; the method comprises:

[0053] Step 1: The transmitter allocates power coefficients to users according to their channel coefficients.

[0054] Arrange the channel coefficients of the users from large to small, that is, |h1|≥|h2|≥…≥h M |,h m is the channel coefficient of the mth (m=1,…,M)th user, and then the power coefficient α is allocated to the mth user m , used for superposition in the power domain. The selection of the power allocation coefficient is related to the channel coefficient and needs to satisfy |α M |≥|α M-1 |≥…≥|α1| and

[0055] Step 2: divide the subcarriers of the OFDM system, select some subcarriers as reserved subcarriers, and use the remaining subcarriers as data subcarriers.

[0056] Note that OFDM has a total of N subcarriers. To ensure that the time domain signal transmitted through the driver LED is a real number, the 0th and subcarrier is not used for data transmission, and the subcarriers and The data on the subcarriers are conjugate symmetrical; subcarriers, arbitrarily select N r subcarriers as reserved subcarriers, and the remaining subcarriers as data subcarriers; reserved subcarriers are used to transmit PAPR compensation data, and data subcarriers are used to transmit superimposed data of user data and PAPR compensation data; PAPR compensation data is used to reduce the PAPR of the system; the data subcarrier set and the reserved subcarrier set are respectively represented as

[0057] Step 3: The transmitting end superimposes the user data to be sent to different users according to the corresponding user allocation power coefficients to obtain a frequency domain signal.

[0058] Set the total number of OFDM symbol periods L. In the lth (L≥l≥1) OFDM symbol period, the user data to be sent to different users is allocated power coefficient α according to the corresponding user. m The frequency domain signal V(l) = [V u,1 (l),…,V u,N (l)] T , among which The frequency domain signal on the subcarriers satisfies V u,k (l)=(V u,N-k (l)) * , V u,k (l) represents the kth OFDM symbol period in the lth OFDM symbol period The frequency domain signal on the subcarriers, (·)* represents the conjugate operator; if but where s m,k (l) is the 4-quadrature amplitude modulation (4-QAM) data modulation symbol of the m-th user on the k-th subcarrier in the l-th OFDM symbol period, if Then V u,k (l)=0.

[0059] Step 4: frequency domain signal V(l)=[V u,1 (l),…,V u,N (l)] T First, perform serial-to-parallel conversion S / P, and then perform discrete inverse Fourier transform (IFFT) to obtain the time domain discrete signal v(l)=FV(l) of the lth OFDM symbol period, where F represents the discrete Fourier inverse transform matrix, as shown below

[0060]

[0061] Where N represents the total number of OFDM subcarriers, e represents a natural constant, and j represents an imaginary symbol.

[0062] Step 5: Use the time domain discrete signal to construct the time domain discrete user signal v = [v(1), ..., v(L)] of all OFDM symbol periods T , construct the user data symbol deviation minimization problem, that is, the PAPR compensation data modulus minimization problem:

[0063]

[0064] st||FV c +v|| ∞ ≤A s

[0065] ||FV c +v|| F ≤||v|| F

[0066]

[0067] Where minimize means minimizing the objective function, st, represents the constraint condition, V c A represents the frequency domain signal of the compensation data to be solved, which is used to reduce the PAPR of the transmission signal; s Indicates the maximum signal amplitude allowed by the LED as a transmitter in the system, ||·|| ∞ represents the infinite norm of the matrix, ||·|| F represents the F-norm of the matrix, (·) *represents the conjugate operator, V c,N-k (l) represents the frequency domain signal of the compensation data on the Nkth subcarrier in the lth OFDM symbol period, V c,k (l) represents the frequency domain signal of the compensation data on the kth subcarrier in the lth OFDM symbol period, Represents the imaginary part operator, V c,0 (l) and They represent the 0th subcarrier and the 1st subcarrier in the 1st OFDM symbol period respectively. The first and second constraints ensure the amplitude and energy of the transmitted signal; the third and fourth constraints ensure that the compensation signal is a real number, (||V c || ∞ is the maximum offset distance of data symbols.

[0068] Transform P1 into an equivalent problem P2:

[0069]

[0070] st,||vec(v c )+vec(v)|| ∞ ≤A s

[0071] ||vec(v c )+vec(v)||2≤||vec(v)||2

[0072] where v c =FV c The frequency domain signal V representing the compensation data c The corresponding time domain signal, (vec(·) represents the matrix vectorization operator, ||·||2 represents the 2-norm of the vector, and F′ represents the Fourier transform matrix, is as follows

[0073]

[0074] Wherein, N represents the total number of OFDM subcarriers, e represents a natural constant, and j is an imaginary number symbol.

[0075] This problem is a semi-positive programming problem, and the solution v is obtained by the interior point method in convex optimization theory. c .

[0076] Step 6: Construct the signal v to be sent tx =v+v c +v bias ; Among them, the DC bias v bias Used to adjust the transmitter's LED voltage signal during transmission, which is determined by the transmitter's LED model; compensate the data's time domain signal vc The reserved subcarrier is used for transmission, and the discrete user signal v in the time domain is used as user data, which is superimposed with v c Then sent through the data subcarrier;

[0077] Treat the sent signal v tx After the parallel-to-serial conversion P / S, the LED driving the transmitter sends out the signal to be sent in the form of an optical signal.

[0078] Step 6: The receiving ends of different users receive optical signals through photoelectric receivers PD respectively, and then perform photoelectric conversion to obtain received signals; user data detection is performed on the received signals to obtain user data required by each user.

[0079] Take the demodulation process of a two-user NOMA system as an example:

[0080] The received signal of user 1 is expressed as y1=vec(y1)=h1vec(v tx )+n, where y1 is the received signal after serial-to-parallel conversion, h1 represents the channel coefficient of user 1, and n represents Gaussian noise; y1 is converted serially to parallel to obtain y1=h1v tx +n, where n is the noise signal after serial-to-parallel conversion; FFT transformation is performed on y1, and the received data on N carriers in L OFDM symbol periods is expressed as Y1=[y1(1),…,y1(L)]=F′y1, where y1(l)=[y 1,1 (l),…,y 1,N (l)] T represents the received data of NOMA user 1 on N carriers in the lth (L≥l≥1) OFDM symbol period, y 1,k (l) represents the data symbol received by user 1 on the kth subcarrier in the lth OFDM symbol period, and then the kth subcarrier in the lth OFDM symbol period The data symbols on the subcarriers are judged, that is:

[0081]

[0082] Among them, s 1,k (l) represents the data symbol of user 1 on the kth subcarrier in the lth OFDM symbol period, j represents the imaginary symbol, surface

[0083] Shows the real part operator, represents the imaginary part operator. Then the data symbols on N subcarriers in all OFDM symbol periods of user 1 constitute the complete user data s1 of user 1.

[0084] For user 2, serial interference cancellation SIC is used to eliminate user 1's user data s1, expressed as Y2 = F'y2-s1, where y2 = h2v tx +n is the user data on N carriers in L OFDM symbol periods received by user 2, h2 represents the channel coefficient of NOMA user 2. After y2 is obtained, the data symbol is judged in the same way as user 1 (replace y1 in the previous text with y2, and then use the same operation) to obtain the user data of user 2.

[0085] Example:

[0086] In one embodiment of the present invention, the number of OFDM subcarriers is set to 64, the number of reserved subcarriers is set to 2, and both NOMA users use 4-QAM modulation; the LED model used as the driver is XM(-(L2, measure the LED to determine its amplitude range, A s =0.104V.

[0087] The power allocation coefficients α1=0.8 and α2=0.2 for NOMA users are selected, and Nr=2 subcarriers (the 4th and 5th) are randomly selected as reserved subcarriers.

[0088] Figure 5 The bit error rate (BER) performance comparison of different schemes when the power allocation is α1 = 0.8 and α2 = 0.2 is shown. Without adding compensation signal, user 1 (BER reaches 10 -3 The required signal-to-noise ratio (SNR) is 17.3 dB, while user 2 (BER reaches 10 -3 The required SNR is 19.1 dB. Compared with the case without preprocessing, user 1 and user 2 obtain 1 dB and 7 dB signal-to-noise ratio gains respectively.

[0089] Figure 6 Demonstrated user BER reached 10 -3 When α1=0.7 and As=0.121,

[0090] The SNR gains of user 1 and user 2 are both 4.4 dB. When α1 = 0.6 and As = 0.155, the SNR gains of user 1 and user 2 are both 3.0 dB.

[0091] Figure 7 The performance comparison between the proposed method and the adaptive symbol decomposition for serial transmission (ASDST) scheme is shown. Compared with the ASDST scheme, when As = 0.104v, the SNR gain of user 1 is 4.8dB, and the SNR gain of user 2 is 3.8dB. It can be seen that the performance of the patented scheme is improved compared with the traditional scheme.

[0092] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for suppressing peak-to-average ratio of a communication system, characterized in that: include: The transmitter allocates power coefficients to users based on their channel coefficients. The subcarriers of the OFDM system are divided, and some subcarriers are selected as reserved subcarriers, and the remaining subcarriers are used as data subcarriers; The transmitting end superimposes the user data to be sent to different users according to the corresponding user allocation power coefficient to obtain a frequency domain signal; The frequency domain signal of the user data is first converted from serial to parallel and then subjected to discrete inverse Fourier transform to obtain the time domain discrete signal of each OFDM symbol period; Based on the time domain discrete signal, a time domain discrete user signal of all OFDM symbol periods is constructed, and a user data symbol deviation minimization problem is constructed and solved to obtain a time domain signal of compensated data; The signal to be transmitted is constructed by using the time domain signal of the compensation data, the time domain discrete user signals of all OFDM symbol periods and the DC bias; wherein the time domain signal of the compensation data is transmitted using the reserved subcarrier, and the time domain discrete user signal is used as user data, which is superimposed on the time domain signal of the compensation data and then transmitted through the data subcarrier; After the signal to be sent is converted into serial and parallel, the LED of the transmitter is driven to send the signal to be sent out in the form of an optical signal; The receiving ends of different users receive optical signals through photoelectric receivers respectively, and then perform photoelectric conversion to obtain received signals; user data detection is performed on the received signals to obtain the user data required by each user.

2. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: The transmitting end allocates power coefficients to users according to channel coefficients of different users, including: Arrange the channel coefficients of the users from large to small, that is, |h1|≥|h2|≥…≥|h M |,h m is the channel coefficient of the mth (m=1,…,M)th user, and then the power coefficient α is allocated to the mth user m , the selection of power allocation coefficient is related to the channel coefficient and satisfies |α M |≥|α M-1 |≥…≥|α1| and 3. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: The subcarriers of the OFDM system are divided, and some subcarriers are selected as reserved subcarriers and the remaining subcarriers are selected as data subcarriers, including: Note that OFDM has a total of N subcarriers. To ensure that the time domain signal transmitted through the driver LED is a real number, the 0th and subcarrier is not used for data transmission, and the subcarriers and The data on the subcarriers are conjugate symmetrical; subcarriers, arbitrarily select N r subcarriers as reserved subcarriers, and the remaining subcarriers as data subcarriers.

4. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: The transmitting end superimposes the user data to be sent to different users according to the corresponding user allocation power coefficients to obtain a frequency domain signal, including: Set the total number of OFDM symbol periods L. In the lth (L≥l≥1) OFDM symbol period, the user data to be sent to different users is allocated power coefficient α according to the corresponding user. m The frequency domain signal V(l) = [V u,1 (l),…,V u,N (l)] T , among which The frequency domain signal on the subcarriers satisfies V u,k (l)=(V u,N-k (l)) * , V u,k (l) represents the kth OFDM symbol period in the lth OFDM symbol period The frequency domain signal on the subcarriers, (·) * represents the conjugate operator; if but where s m,k (l) is the 4-quadrature amplitude modulation data modulation symbol of the m-th user on the k-th subcarrier in the l-th OFDM symbol period, if Then V u,k (l) = 0; They represent the data subcarrier set and the reserved subcarrier set respectively.

5. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: The problem of constructing the user data symbol deviation minimization is expressed as: P1: s.t.||FV c +v|| ∞ ≤A s ||FV c +v|| F ≤||v|| F Where minimize means minimizing the objective function, st, represents the constraint condition, V c represents the frequency domain signal of the compensation data to be solved; F represents the inverse discrete Fourier transform matrix, v represents the time domain discrete user signal of all OFDM symbol periods, A s Indicates the maximum signal amplitude allowed by the LED as a transmitter in the system, ||·|| ∞ represents the infinite norm of the matrix, || · || F represents the F-norm of the matrix, (·) * represents the conjugate operator, V c,N-k (l) represents the frequency domain signal of the compensation data on the Nkth subcarrier in the lth OFDM symbol period, V c,k (l) represents the frequency domain signal of the compensation data on the kth subcarrier in the lth OFDM symbol period, Represents the imaginary part operator, V c,0 (l) and They represent the 0th subcarrier and the 1st subcarrier in the 1st OFDM symbol period respectively. The frequency domain signal of the compensated data on the subcarriers.

6. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: Solve the problem of minimizing the user data symbol deviation to obtain the time domain signal of the compensated data, including: The user data sign deviation minimization problem P1 is transformed into an equivalent problem P2: st,||vec(v c )+thing(v)|| ∞ ≤A s ||thing(in c )+vec(v)||2≤vec(v)||2 where v c =FV c The frequency domain signal V representing the compensation data c The corresponding time domain signal, (vec(·) represents the matrix vectorization operator, ||·||2 represents the 2-norm of the vector, and F′ represents the Fourier transform matrix; The time domain signal v of the compensation data is obtained by solving the interior point method in convex optimization theory c .

7. The method for suppressing peak-to-average ratio of a communication system according to claim 1, characterized in that: The performing user data detection on the received signal to obtain user data required by each user includes: For the case where there are two users in the NOMA system, the process of user data detection is as follows: The received signal of user 1 is expressed as y1=vec(y1)=h1vec(v tx )+n, where y1 is the received signal after serial-to-parallel conversion, h1 represents the channel coefficient of user 1, and n represents Gaussian noise; y1 is converted serially to parallel to obtain y1=h1v tx +n, where n is the noise signal after serial-to-parallel conversion; FFT transformation is performed on y1, and the received data on N carriers in L OFDM symbol periods is expressed as Y1=[y1(1),…,y1(L)]=F′y1, where y1(l)=[y 1,1 (l),…,y 1,N (l)] T represents the received data of NOMA user 1 on N carriers in the lth (L≥l≥1) OFDM symbol period, y 1,k (l) represents the data symbol received by user 1 on the kth subcarrier in the lth OFDM symbol period, and then the kth subcarrier in the lth OFDM symbol period The data symbols on the subcarriers are judged, that is: Among them, s 1,k (l) represents the data symbol of user 1 on the kth subcarrier in the lth OFDM symbol period, j represents the imaginary symbol, represents the real part operator, represents the imaginary part operator. Then the data symbols on N subcarriers in all OFDM symbol periods of user 1 constitute the complete user data s1 of user 1; For user 2, serial interference cancellation is used to eliminate user 1's user data s1, expressed as Y2 = F'y2-s1, where y2 = h2v tx +n is the user data on N carriers in L OFDM symbol periods received by user 2, h2 represents the channel coefficient of NOMA user 2, and after obtaining y2, the data symbol is judged in the same way as user 1 to obtain the user data of user 2.

8. A NOMA-VLC system, characterized in that: The system adopts the peak-to-average ratio suppression method of the communication system according to any one of claims 1-7.

9. A terminal device comprising a processor, a memory and a computer program stored in the memory; characterized in that: When the processor executes the computer program, the peak-to-average ratio suppression method for a communication system according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, wherein a computer program is stored in the medium; characterized in that: When the computer program is executed by a processor, the peak-to-average ratio suppression method for a communication system according to any one of claims 1 to 7 is implemented.

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