DCO-OFDM modulation-demodulation method and device added with phase modulation
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A technology of phase modulation and modulation method, applied in modulation carrier system, transmission system, free space transmission and other directions, can solve problems such as inter-symbol interference
Active Publication Date: 2018-11-13
上海瀚芯实业发展合伙企业(有限合伙)
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[0003] The visible light channel is a multipath cha
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Embodiment 1
[0096] Such as figure 1 As shown, this embodiment provides a DCO-OFDM method adding phase modulation, the method comprising:
[0097] (1) At the sending end, the data to be sent is subjected to QAM mapping, subcarrier allocation and conjugate symmetry to generate a signal X;
[0098] (2) IFFT processing the signal X to generate time-domain data x;
[0099] (3) Process the time-domain data x with a phase modulator 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 a scaling factor, so that the range of Cx[k] is limited to [-ω, ω]; θ∈[-ω, ω] is a rotation factor, in order to prevent phase ambiguity, 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 adding phase modulation, the system includes a modulation device and a demodulation device, the modulation device includes a mapping and carrier allocation module, an IFFT module, a phase modulator, a cyclic prefix adding module, and a digital-to-analog conversion device, low-pass filter, DC bias, zero limiter, optical modulator LED, demodulation device including 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 functions of each module are: the mapping and carrier allocation module is used to perform QAM mapping, subcarrier allocation and conjugate symmetry on the data to be sent to generate signal X; 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 gener...
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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 invention relates to signal modulation technology, in particular to a DCO-OFDM modulation and demodulation method and device with phase modulation added. Background technique [0002] As a multi-carrier modulation technology in broadband high-speed wireless transmission scenarios, OFDM can divide a wide bandwidth into several mutually orthogonal flat-fading sub-bands to transmit signals, so that at the receiving end, it is no longer necessary In order to avoid multipath interference, the equalization processing, plus OFDM adopts fast discrete Fourier transform IFFT and FFT to realize the signal processing of OFDM modulation and demodulation, which is easy to implement by digital signal processing, which greatly reduces the receiver of complexity. In addition, since the spectrum resource is broadened into many sub-bands, the efficiency of multi-user resource allocation is greatly improved. Due to the above-mentioned advantages of OFDM modulation, ...
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