Method and apparatus for eliminating amplitude limiting noise of ACO-OFDM system

A technique of clipping noise and noise estimation, applied in the field of clipping noise elimination, can solve problems such as large peak-to-average signal, system performance degradation, and high requirements for power amplifiers at the transmitting end.

Active Publication Date: 2015-12-02
TSINGHUA UNIV
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Problems solved by technology

[0004] However, the ACO-OFDM time-domain signal has a relatively large peak-to-average value, which places high demands on the power amplifier at the transmitting end. Limiting methods can be used to reduce the peak value of the signal directly at or near the peak amplitude of the OFDM signal. This inevitably produces signal distortion, introduces clipping noise, and degrades system performance

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  • Method and apparatus for eliminating amplitude limiting noise of ACO-OFDM system
  • Method and apparatus for eliminating amplitude limiting noise of ACO-OFDM system
  • Method and apparatus for eliminating amplitude limiting noise of ACO-OFDM system

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Embodiment 1

[0039] Such as figure 1 shown, combined with figure 2 and image 3 , the method for eliminating clipping noise in an ACO-OFDM system according to an embodiment of the present invention is a method for estimating and restoring clipping noise based on compressed sensing that can be applied in an ACO-OFDM system, comprising the following steps:

[0040] S1: Perform ACO-OFDM modulation on the input data sequence to obtain a positive real number time domain sequence, and perform a threshold judgment on the positive real number time domain sequence to limit the part exceeding the predetermined threshold to obtain the transmitted signal, and pass the transmitted signal through LED light for emission.

[0041] Specifically, including:

[0042] S11: Constellation mapping is performed on the input data sequence to obtain constellation mapping symbols, and a Hermitian symmetric structure is formed according to the constellation mapping symbols and the conjugates of the constellation ...

Embodiment 2

[0085] Such as figure 1 shown, combined with figure 2 and image 3 , the method for eliminating clipping noise in an ACO-OFDM system according to an embodiment of the present invention is a method for estimating and restoring clipping noise based on a priori information that can be applied in an ACO-OFDM system, including:

[0086] S1: Perform ACO-OFDM modulation on the input data sequence to obtain a positive real number time domain sequence; perform a threshold judgment on the obtained positive real number time domain sequence, and limit the part exceeding the threshold to obtain a transmission signal; send the transmission signal to the LED Light emission, specifically:

[0087] Constellation mapping is performed on the input data sequence to obtain constellation mapping symbols. Take its conjugate symmetry to form a Hermitian symmetric structure. Only data is transmitted on odd subcarriers, and zeros are transmitted on even subcarriers. After serial-to-parallel conve...

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Abstract

The invention provides a method and apparatus for eliminating amplitude limiting noise of an Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) system. The method includes the steps of: carrying out modulation on input data sequences and obtaining time domain sequences of positive real numbers; carrying out threshold judgment on the time domain sequences of the positive real numbers so as to carry out amplitude limit on the part exceeding a predetermined threshold; obtaining transmitting signals; receiving the transmitting signals and obtaining the time domain signals; transforming the time domain signals and obtaining frequency domain observation sequences; obtaining frequency domain estimation sequences and noise estimation sequences; obtaining observation vectors and observation matrixes of a compressive sensing algorithm from a selection matrix; adopting the compressive sensing algorithm according to a compressive sensing algorithm mode, and obtaining the amplitude limiting noise sequences; and subtracting the amplitude limiting noise sequences from the time domain signals and obtaining the signals after the amplitude limiting noise signals are eliminated. In complex multipath channels having bad amplitude limit noises, the method can accurately and rapidly estimate and eliminate the amplitude limiting noises in high frequency spectrum efficiency, and can improve the system transmission robustness.

Description

technical field [0001] The invention relates to the technical field of digital signal transmission, in particular to a method and device for eliminating clipping noise in an ACO-OFDM system based on compressed sensing. Background technique [0002] Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing) technology, with its advantages of high spectral efficiency, strong anti-multipath interference ability, low complexity of system implementation, bit power allocation and maximum transmission rate according to channel characteristics, etc., is widely used in visible light widely used in communications. [0003] However, because the light intensity cannot have a negative value, for a bipolar signal such as OFDM, it cannot be directly applied to a traditional intensity-modulated optical communication system. One method is to add a DC bias to OFDM when the electro-optical signal is converted, so that the bipolar signal becomes a unipolar signal, ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L25/03H04L27/26
Inventor 杨昉高俊男宋健丁文伯
Owner TSINGHUA UNIV
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