Method for hyperbolic tangent companding transform capable of decreasing peak-to-average power ratio (PAPR) of OFDM (orthogonal frequency division multiplexing) signal

Abstract

The invention discloses a method for a hyperbolic tangent companding transform capable of decreasing the peak-to-average power ratio (PAPR) of an OFDM (orthogonal frequency division multiplexing) signal, mainly used for solving the problems of non-constant average power and high error rate in the prior art. The method comprises the following realization steps of: (1) performing a quadrature amplitude modulation on the data bit stream generated by an information source, performing a serial-to-parallel conversion then sampling; (2) performing an inverse fast Fourier transform (IFFT) on an over-sampling signal to obtain an original OFDM signal; (3) establishing a companding function based on a hyperbolic tangent function, performing a companding transform on the original OFDM signal, performing a parallel-to-serial conversion then transmitting the signal; (4) calculating the PAPR of a transmitting signal; (5) performing a serial-to-parallel conversion on a receiving signal, then performing a de-companding transform and a fast Fourier transform (FFT); (6) de-over-sampling a FFT signal to obtain an OFDM demodulation signal; and (7) performing a parallel-to-serial conversion and a quadrature amplitude demodulation on the OFDM demodulation signal, then counting an error rate. The method for a hyperbolic tangent companding transform capable of decreasing the PAPR of an OFDM signal disclosed by the invention can efficiently suppress the PAPR, remarkably decrease the error rate, and keep a constant average power; and the method can be widely applied to a new generation of broadband wireless OFDM communication system.

Description

technical field [0001] The invention belongs to the technical field of wireless communication, relates to a companding transform method for reducing the peak-to-average ratio (PAPR) of an orthogonal frequency division multiplexing OFDM wireless transmission signal, and can be widely applied to various new generation broadband OFDM wireless communication systems. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) modulation technology is a high-speed transmission technology in a wireless environment, and after years of development, this technology is increasingly recognized by people. Because the subcarriers in OFDM modulation are orthogonal, the intersymbol interference of the system can be significantly reduced. Compared with single-carrier modulation, OFDM modulation has higher spectral efficiency. Furthermore, by inserting guard intervals, OFDM modulation can be better resistant to multipath fading. Due to these advantages, OFDM modulation i...

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Problems solved by technology

Therefore, the μ-law companding method will cause the power of the companded signal to reach the saturation region of the power amplifier, thereby causing nonlinear distortion of the power amplified signal; in order to solve the problem of the average signal power increase of the μ-law companding method, Tao Jiang in " Exponential Companding Technique for PAPR Reduction in OFDMSystems” proposed an exponential companding method. The basic idea of ​​this method is to transform the amplitude distribution of the original OFDM signal into a uniform distribution, and to keep the average power constant before and after signal companding by rationally adjusting parameters, but , the uniform distribution goal pursued by this method will increase the large-amplitude signal distribution. Therefore, when the transmitting end adopts a power amplifier with a large nonlinearity, its bit error rate BER performance will deteriorate sharply; Gang Yang in "Using Hyperbolic tangent sigmoid transfer function for companding transform in OFDM system” proposed a hyperbolic tangent companding method. Although this method can obtain different peak-to-average ratio PAPR performance by adjusting the nonlinearity factor, when the required peak-to-average ratio PAPR is relatively hour, its bit error rate BER performance is still very poor

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