Symbol detection method of DCO-OFDM (Direct Current Offset-Orthogonal frequency Division Multiplexing) system
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A detection method and symbol technology, applied in the field of symbol detection of DCO-OFDM systems, can solve the problem of not fully considering the internal structure of the transmitted signal, and achieve the effect of easy implementation and small calculation amount
Active Publication Date: 2014-11-19
SOUTHEAST UNIV
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[0008] Purpose of the invention: In view of the defect that the existing DCO-OFDM system symbol detection method does not fully consider the internal structure of the transmitted signal, the present invention provides a symbol that improves the detection performance by estimating the specific value of the clipping noise and removing it from the received signal Detection method
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Embodiment 1
[0037] Specific parameters are given as follows: the transmitted bits are not channel coded, the modulation method is 16QAM, the number of subcarriers is N=64, and the DC offset is D=2σ, where σ is the variance of the signal sequence x(n), which is assumed to be unilateral here Clipping (that is, A=+∞), the transmission channel is an additive white Gaussian noise (AWGN, Additive White Gaussian Noise) channel, and the single-tap frequency domain equalizer adopts zero-forcing (ZF, Zero Forcing) equalization, that is, on the kth subcarrier The single-tap equalizer coefficient of is 1 / H(k), where H(k) is the transmission coefficient of the kth subchannel; set the number of iterations Nt=2.
[0038] Concrete implementation steps of the present invention are as follows:
[0039] 1), the block diagram of the sending end of the DCO-OFDM system involved in the present invention is as follows figure 1 As shown, the block diagram of the symbol detection method at the receiving end is as...
Embodiment 2
[0053] Specific parameters are given as follows: the transmitted bits have not been channel-coded, the modulation method is 16QAM, the number of subcarriers is N=64, and the DC offset is D=2σ, where σ is the variance of the signal sequence x(n), using bilateral clipping, taking A=5σ, the transmission channel is an Additive White Gaussian Noise (AWGN, Additive White Gaussian Noise) channel, and the single-tap frequency domain equalizer adopts minimum mean square error (MMSE, Minimum Mean Square Error) equalization, that is, the kth subcarrier The single-tap equalizer coefficients are Where H(k) is the transmission coefficient of the kth sub-channel, and the symbol '*' represents the conjugate operation, is the variance of the channel noise; notice that the minimum mean square error equalizer is still a single-tap equalizer; set the number of iterations Nt=2.
[0054] Concrete implementation steps of the present invention are as follows:
[0055] 1), the block diagram of the...
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Abstract
The invention discloses a symbol detection method of a DCO-OFDM (Direct Current Offset-Orthogonal frequency Division Multiplexing) system, belonging to the field of visible light wireless communication. The method is carried out according to the following steps of firstly, preprocessing a received symbol r(n) to obtain an estimated value x(clip)n of a clipped sending signal; secondly, reconstructing clipping noise c(n) and subtracting the clipping noise from the signal x(clip)n to obtain an estimated value x(clip)n of an unclipped sending signal; thirdly, carrying out frequency domain conversion and symbol judgment operation on the x(n), and reconstructing the clipping noise c(n) by utilizing a judged symbol; fourthly, repeating the steps to reach a preset number of iterations; and lastly, demodulating the judged symbol to restore transmitted bits. According to the symbol detection method provided by the invention, the negative effect of the clipping noise on the detection performance can be reduced, an effective signal to noise ratio of a receiving signal is increased, in comparison with the conventional symbol detection method, the better detection performance can be obtained. Meanwhile, the method provided by the invention only needs simple symbol taking operation and DFT/IDFT (Discrete Fourier Transform/Inverse Discrete Fourier Transform) operation and has the advantages of small calculated amount and easiness in implementation.
Description
technical field [0001] The invention belongs to the field of visible light wireless communication, in particular to a symbol detection method of a DCO-OFDM system. Background technique [0002] At present, the 5th generation cellular mobile communication technology is becoming a research hotspot in the field of mobile communication. Compared with the existing communication system, the capacity of the fifth generation cellular mobile communication system will be increased by 1 to 2 orders of magnitude. Therefore, the development of new spectrum resources has become an important way. Visible light is a new spectrum resource with extremely wide bandwidth, and visible light wireless communication technology is also considered an important part of the fifth-generation mobile communication technology. Existing visible light wireless communication technologies mainly use light emitting diode (LED, Light Emitting Diode) or laser as a light source, and adopt an intensity modulation...
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