Dynamic compensation method for reducing LED (Light Emitting Diode) nonlinear distortion of visible light Flip-OFDM (Orthogonal Frequency Division Multiplexing) communication system

Abstract

The invention relates to a dynamic compensation method for reducing LED (Light Emitting Diode) nonlinear distortion of a visible light Flip-OFDM (Orthogonal Frequency Division Multiplexing) communication system. The method comprises the following steps: segmenting a modulated subcarrier data vector into a plurality of non-overlapped subsequences; multiplying by a corresponding weighting coefficient, extending to be a hermitian symmetric sequence and then performing IFFT (Inverse Fast Fourier Transform); selecting a weighting coefficient for keeping the negative signal amplitude of a combined signal to be minimum; decomposing the polarity of the combined signal into a Flip-OFDM positive signal and a flip negative signal and limiting the amplitude; carrying an end cut signal of the positive signal at a zero signal position corresponding to the flip negative signal as a compensation signal; restoring the positive signal by a receiving end through the compensation signal. By using the method, PAPR (Peak to Average Power Ratio) in the Flip-OFDM system can be effectively suppressed, and the LED nonlinear distortion is reduced, so that the usability and the reliability of the system are greatly improved.

Description

technical field [0001] The invention relates to a dynamic compensation method for reducing LED nonlinear distortion in a visible light Flip-OFDM communication system. Background technique [0002] Visible light communication (VLC) has the advantages of high transmission power, no electromagnetic interference, no spectrum certification, and energy saving. It can effectively alleviate the problem of radio spectrum resource depletion, and has attracted more and more attention in recent years. Given that Orthogonal Frequency Division Multiplexing (OFDM) technology has the advantages of high spectral efficiency, strong bandwidth scalability, anti-multipath fading, and flexible allocation of spectrum resources, applying OFDM technology to VLC can effectively increase the transmission rate of the system. In VLC, the optical signal modulation method of intensity modulation / direct detection requires that the Orthogonal Frequency Division Multiplexing (OFDM) signal must be a real sign...

AI Technical Summary

Problems solved by technology

[0003] However, in the VLC system, the signal conversion characteristics of the LED are nonlinear, and the high peak-to-average ratio (PAPR) of OFDM has a high requirement for the quasi-linear dynamic range of the LED. When the quasi-linear dynamic range of the LED cannot meet the OFDM signal When required, the signal will be distorted, causing the spectrum of the superimposed signal to change, resulting in the destruction of the orthogonality between the sub-channels, resulting in mutual interference, and reducing system performance

At present, there are mainly two types of methods to reduce PAPR: 1) signal predistortion methods, such as clipping method and companding method, which are simple and practical but will cause signal distortion and lead to distortion; 2) non-signal predistortion methods, such as Coding method, Selective Mapping (SLM) method, Partial Transmission Sequence (PTS) method, etc. The coding method has a good effect on suppressing PAPR, but the number of coding patterns available is small. SLM and PTS focus on reducing the occurrence of peaks. In terms of probability, it does not focus on reducing the maximum value of the signal amplitude, and cannot completely avoid the occurrence of high peak signals in the system

The above methods are all designed for the PAPR problem of the general OFDM communication system. When applied to the visible light Flip-OFDM communication system, the unipolarity of the signal is not considered. In large cases, the PAPR suppression performance is limited, resulting in serious nonlinear distortion of the LED, which seriously restricts the performance of the communication system

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