CN-117176531-B - Peak-to-average ratio reduction method of OFDM system

Abstract

The invention relates to a peak-to-average ratio reducing method of an OFDM system, which comprises the steps of firstly, taking an OFDM signal PAPR as an objective function, taking the maximum error vector on the data subcarrier and the power of the reserved subcarrier as constraint conditions, establishing an original optimization problem, secondly, utilizing an ADMM algorithm to decompose the original problem into three sub-problems, and alternately solving and repeatedly iterating each sub-problem until a global optimal solution is obtained. Compared with the prior art, the invention has the advantages of avoiding the increase of the error rate of the system caused by overlarge introduced interference, obtaining better peak-to-average ratio reducing effect and the like.

Inventors

• YANG FENG
• ZENG NI
• DING LIANGHUI
• WANG TIANLE

Assignees

• 上海交通大学
• 中国电子科技集团公司第十研究所

Dates

Publication Date

20260505

Application Date

20220527

Claims (6)

1. 1. A method for peak-to-average power ratio reduction in an OFDM system, comprising the steps of: 1) Performing OFDM modulation on an original signal; 2) The method comprises the steps of restraining PAPR by utilizing a TR technology, expanding a frequency domain elimination signal C to a data subcarrier, adding maximum EVM constraint to interference of the frequency domain elimination signal C on the data subcarrier, and obtaining a vector D on a data subcarrier set; 3) Input of original OFDM frequency domain signal Sum time domain signal Vector D of frequency domain peak value eliminating signal C on data subcarrier set, vector B on reserved subcarrier set, time domain transmitting signal after TR Lagrange multiplier Initial value of (1) EVM preset threshold, power preset threshold, penalty coefficient Simplified IFFT matrix And And total number of iterations According to a TR algorithm based on the maximum EVM constraint, calculating and obtaining a frequency domain peak value elimination signal C; in step 2), the frequency domain OFDM signal is divided into N sub-carriers Each reserved sub-carrier Adding maximum EVM constraint to data subcarriers to limit maximum in-band distortion caused by introduced interference in the data subcarriers, thereby obtaining an original optimization problem: In the formula, A threshold value is preset for the EVM, Presetting a threshold for power, matrix And Are binary diagonal arrays with dimensions of Corresponding to the data subcarrier position and the reserved subcarrier position respectively; defining a simplified IFFT matrix And The dimensions are respectively And Decomposing the optimized variable C into a vector D on a data subcarrier set and a vector B on a reserved subcarrier set, wherein the optimized variable of the original problem does not meet the use condition of an ADMM algorithm, performing variable substitution on the optimized variable, and introducing equality constraint The equivalence problem is obtained: In step 3), the augmented Lagrangian function of the original problem is decomposed into terms of 、 And The functions of the three variables are solved alternately and iterated repeatedly for the three objective functions until a global optimal solution is obtained, and the expression of the Lagrangian function is: The iteration steps are as follows: 。
2. 2. the method for reducing peak-to-average power ratio of an OFDM system according to claim 1, wherein the specific contents of step 1) are: For the original frequency domain signal Performing OFDM modulation to obtain a frequency domain OFDM signal, performing IFFT transformation on the frequency domain OFDM signal, and obtaining a time domain OFDM signal.
3. 3. The method for reducing peak-to-average ratio of an OFDM system according to claim 1, wherein in step 3), the specific step of the TR algorithm based on the maximum EVM constraint includes: A) Input of original OFDM frequency domain signal Sum time domain signal Vector D of frequency domain peak value eliminating signal C on data subcarrier set, vector B on reserved subcarrier set, time domain transmitting signal after TR Lagrange multiplier Initial value of (1) EVM preset threshold, power preset threshold, penalty coefficient Simplified IFFT matrix And And total number of iterations ; B) Order the Iterating; C) Solving the sub-problem a and updating ; D) Solving the sub-problem b, updating ; E) Solving the sub-problem c and updating ; F) Calculation of ; G) Output of , 。
4. 4. The method for reducing peak-to-average power ratio of OFDM system as set forth in claim 3, wherein solving the sub-problem a updates The specific steps of (a) include: c1 Calculation of (c) ; C2 Instruction) command Iterating; C3 Calculation of (c) 。
5. 5. The method for reducing peak-to-average power ratio of OFDM system as set forth in claim 3, wherein solving the sub-problem b updates The specific steps of (a) include: D1 Calculation of (c) ; D2 Calculation of (c) ; D3 Calculation of (c) 。
6. 6. The method for reducing peak-to-average power ratio of OFDM system as set forth in claim 3, wherein solving the sub-problem c updates The specific steps of (a) include: e1 Calculation of (c) ; E2 Using linear Bregman algorithm 。

Description

Peak-to-average ratio reduction method of OFDM system Technical Field The invention relates to the technical field of wireless communication, in particular to a peak-to-average power ratio (PAPR) reducing method of an Orthogonal Frequency Division Multiplexing (OFDM) system. Background The basic idea of OFDM is to convert a high-rate serial data stream into multiple low-rate parallel sub-data streams by a serial-to-parallel (S/P) conversion operation, and then modulate onto multiple orthogonal sub-carriers for parallel transmission. The parallel transmission system greatly expands the pulse width of the symbol and improves the performance of resisting severe transmission conditions such as multipath fading and the like. The OFDM system signal is formed by superposing a plurality of subcarrier signals, when the phases of all the subcarriers are similar or identical, the subcarrier superposition is caused to generate a high-power signal in the process of inverse Fourier transformation, so that a large peak-to-average power ratio (PAPR) occurs. The method has the advantages that the high requirement is put on the linearity of the amplifier in the transmitter, if the peak value of the signal waveform is not in the linear dynamic range of the power amplifier, distortion is brought to the signal, the frequency spectrum of the superimposed signal is changed, so that orthogonality among all sub-channel signals is destroyed, mutual interference is generated, and the overall performance of the system is affected. The TR algorithm (reserved subcarrier technique) is a widely applied PAPR suppression algorithm, and divides N subcarriers into data subcarriers and reserved subcarriers, the data subcarriers are used for transmitting information, the reserved subcarriers are used for generating peak cancellation signals to reduce the PAPR of the final signal, and only the signal at the position of the data subcarriers needs to be demodulated at the receiving end, so that the effect of the reserved subcarriers is avoided. However, the conventional TR algorithm has high operational complexity and limited ability to reduce the PAPR, and a practical method is required to improve the TR algorithm. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide a method for reducing the peak-to-average ratio of an OFDM system. The aim of the invention can be achieved by the following technical scheme: a method for peak-to-average power ratio reduction in an OFDM system, the method comprising the steps of: and S1, performing OFDM modulation on the original signal. S2, suppressing PAPR by using TR technology, expanding the frequency domain elimination signal C to the data sub-carrier, adding maximum EVM constraint to the interference of the frequency domain elimination signal C on the data sub-carrier, obtaining vector D on the data sub-carrier set, and defining TR problem based on the maximum EVM constraint in the OFDM system by combining the maximum in-band distortion constraint on the data sub-carrier and the power constraint on the reserved sub-carrier. S3, inputting an original OFDM frequency domain signal X and a time domain signal X, a vector D of a frequency domain peak value eliminating signal C on a data subcarrier set, a vector B on a reserved subcarrier set, a time domain transmitting signal y after TR, an initial value (D 1,B1,y1,u1) of a Lagrange multiplier u, an EVM preset threshold value, a power preset threshold value, penalty coefficients (alpha, beta and rho), simplified IFFT matrixes Q D and Q B and a total iteration number K, and calculating and obtaining the frequency domain peak value eliminating signal C according to a TR algorithm based on the maximum EVM constraint. Further, the specific content of S1 is: And carrying out OFDM modulation on the original frequency domain signal X= [ X 0,X1,...,XN-1]T ] to obtain a frequency domain OFDM signal, and carrying out IFFT transformation on the frequency domain OFDM signal to obtain a time domain OFDM signal. Further, in S2, the frequency domain OFDM signal has N subcarriers, which is divided into N r reserved subcarriers and N-N r data subcarriers, and the maximum EVM constraint is added to limit the maximum in-band distortion caused by the introduced interference in the data subcarriers, thereby obtaining the original optimization problem: Wherein alpha is an EVM preset threshold value, beta is a power preset threshold value, the matrixes M D and M R are binary diagonal arrays, and the dimensions are N multiplied by N, and correspond to the data subcarrier position and the reserved subcarrier position respectively; Defining simplified IFFT matrixes Q D and Q B, wherein the dimensions are LN× (N-N r) and LN×N r respectively, decomposing an optimization variable C into a vector D on a data subcarrier set and a vector B on a reserved subcarrier set, performing variable substitution on the optimization variable of the original problem