Adding phase modulation to dco-ofdm modulation, demodulation method and device
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A technology of phase modulation and modulation method, which is applied in the direction of modulated carrier system, multi-frequency code system, digital transmission system, etc., and can solve problems such as intersymbol interference
Active Publication Date: 2020-03-31
白盒子(上海)微电子科技有限公司
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[0003] The visible light channel is a multipath channel, which will generate inter-symbol interference
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Embodiment 1
[0096] Such as figure 1 As shown, this embodiment provides a DCO-OFDM method with phase modulation, and the method includes:
[0097] (1) At the transmitting end, QAM mapping, sub-carrier allocation and conjugate symmetry are performed on the data to be sent to generate signal X;
[0098] (2) Perform IFFT processing on signal X to generate time domain data x;
[0099] (3) Use a phase modulator to process the time domain data x to generate a sequence p with a peak-to-average ratio of 0dB:
[0100] p={P[k]|k=0,1,...,N-1}
[0101] P[k]=e j(Cx[k]+θ )
[0102] In the formula, C is the scaling factor, which limits the range of Cx[k] to between [-ω,ω]; θ∈[-ω,ω] is the rotation factor. To prevent phase blur, let ω=2π / 3, x[k] is the element in x.
[0103] (4) Extract the real part sequence r and the imaginary part sequence i from the sequence p, and add a cyclic prefix respectively;
[0120] This embodiment provides a DCO-OFDM system with phase modulation. The system includes a modulation device and a demodulation device. The modulation device includes a mapping and carrier distribution module, an IFFT module, a phase modulator, a cyclic prefix addition module, and a digital-to-analog conversion. Converter, low-pass filter, DC bias, zero limiter, light modulator LED, demodulation device includes photodiode, DC blocking module, low-pass filter, analog-to-digital converter, cyclic prefix removal module, phase Demodulator, FFT transformation module and equalization and demapping module.
[0121] Among them, the function of each module is: the mapping and carrier allocation module is used to generate signal X after QAM mapping, sub-carrier allocation and conjugate symmetry of the data to be sent; the IFFT module is used to perform IFFT processing on signal X to generate time-domain data x; The phase modulator is used to process the time-domain data x to generate a...
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Abstract
The invention discloses a DCO-OFDM modulation-demodulation method and device added with phase modulation, and a method and system including modulation and demodulation. The DCO-OFDM modulation-demodulation method comprises the following steps: at a sending end, producing time domain data x by performing IFFT processing, and obtaining a sequence by processing the time domain data x by adopting a phase modulator; respectively adding cyclic prefix on each of a real number part r and a virtual number part I of the sequence p, and producing time domain analog signals r(t) and i(t) through a digital-to-analog converter DAC and a low-pass filter; adding DC bias on the r(t) and i(t), enabling the amplitude limiting as zero if the obtained signal still has negative value, thereby producing rDCO(t)and iDCO(t); inputting the signals rDCO(t) and iDCO(t) into two optical modulator LEDs, converting electric signals into optical signals, and enabling the optical signals to achieve a receiver throughan optical channel; at a receiving end, performing DC blocking processing on two optical signals after the PD; sampling two analog signals through the low-pass filter and an ADC, and removing the cyclic prefixes to obtain the sequences as shown in description, wherein the formula as shown in description is used as the real part, and the formula as shown in description is used as a virtual part, thereby obtaining the sequence as shown in description; and obtaining the time domain data as shown in description through one phase demodulator, wherein the processing on the time domain data as showin description is similar to the traditional DCO-OFDM scheme. The DCO-OFDM modulation-demodulation method disclosed by the invention is lower in signal-to-noise ratio and higher in BER performance.
Description
Technical field [0001] The present invention relates to signal modulation technology, in particular to a DCO-OFDM modulation and demodulation method and device with phase modulation. Background technique [0002] OFDM, as a multi-carrier modulation technology in broadband high-speed wireless transmission scenarios, can divide a wide bandwidth into several mutually orthogonal flat fading sub-bands to transmit signals. Therefore, at the receiving end, it is no longer needed In order to avoid multipath interference, the equalization processing, plus OFDM uses fast discrete Fourier transform IFFT and FFT to achieve OFDM modulation and demodulation signal processing, easy to use digital signal processing method to achieve, greatly reducing the receiver Complexity. In addition, because the spectrum resources are broadbandized into many sub-bands, the efficiency of multi-user resource allocation is greatly improved. Due to the above advantages of OFDM modulation, OFDM modulation techn...
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