Nonlinear Clipping Estimation Method Based on Preamble Sequence of Visible Light Dco-ofdm Communication System

Abstract

The invention discloses a leader sequence of a visible light DCO-OFDM communication system, comprising a ZC sequence and 30 OFDM symbols. The 30 OFDM symbols are divided into three groups in sequence. The OFDM symbols are obtained by carrying out IFFT on original bit streams modulated on sub-carriers. DA for transmission is the DA with n-bit symbols. The three groups of OFDM symbols are multiplied by amplitude factors 2 <n-4 >, <square root 2>*2 <n-4 > and n <2-3 >, thereby generating three groups of classification amplitudes. An original ZC sequence is multiplied by the amplitude factor consistent with the first classification amplitude, thereby obtianing the ZC sequence. The invention also discloses a method for carrying out nonlinear amplitude limit estimation and channel parameter estimation by employing the leader sequence provided by the invention. The leader sequence provided by the invention can be periodically and discontinuously sent in a time domain; only little transmitting power is occupied; the visible light communication system can work in a linear working area of an LED; and the accurate signal to noise ratio condition is provided for the system approximately in real time.

Description

technical field [0001] The invention relates to a visible light DCO-OFDM communication system, in particular to a preamble sequence, a nonlinear limit estimation method and a channel parameter estimation method of the visible light DCO-OFDM communication system. Background technique [0002] With the continuous development of social economy, people's requirements for the quality of life are getting higher and higher. At the same time, the communication field begins to pursue a "green" and "high-speed" communication technology. Visible light communication technology, as an alternative to the above, is gradually becoming a hot spot in the research field. It uses laser devices or LED devices to achieve high-speed information transmission through modulation of light intensity, which meets people's requirements for high-speed information transmission while meeting daily work lighting. This technology has the advantages of free broadband spectrum resources independent of radio fr...

AI Technical Summary

Problems solved by technology

The frequency domain symbols of DCO-OFDM also satisfy conjugate symmetry, but it does not require the value on even subcarriers to be 0, 1 / 2 subcarriers are used to transmit effective symbols, and the spectrum utilization rate is high, but it is used to make the time domain The signal is positive, and an additional DC bias needs to be added to the signal output by the IFFT

[0004] In the DCO-OFDM visible light communication system, it is necessary to add an additional DC bias to the OFDM signal to make the time domain signal a positive value; if the DC bias is too high, the positive value of the time domain signal exceeds the linear range of the LED , there will be up-clipping, which will also affect the performance of the visible light communication system

At present, in the visible light communication scenario where the LED bias and linear range of the transmitter are unknown, there is no clear way to adjust the LED bias and the power of the transmitted OFDM signal, so that the indoor visible light communication system works in the linear working area of ​​the LED.

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