CN110149295A - A method of companding transform United Technologies are spread and normalized based on DFT reduces P-OFDM system PAPR - Google Patents
A method of companding transform United Technologies are spread and normalized based on DFT reduces P-OFDM system PAPR Download PDFInfo
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- CN110149295A CN110149295A CN201910447715.4A CN201910447715A CN110149295A CN 110149295 A CN110149295 A CN 110149295A CN 201910447715 A CN201910447715 A CN 201910447715A CN 110149295 A CN110149295 A CN 110149295A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/3405—Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power
- H04L27/3411—Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set
Abstract
The present invention provides a kind of to be spread and be normalized the method that companding transform United Technologies reduce P-OFDM system PAPR based on DFT, this method includes signal step of transmitting and signal receiving step, signal step of transmitting: pseudo-random binary bit sequence is generated, after being mapped by qam constellation, carry out discrete Fourier transform, obtained signal carries out passing through Fast Fourier Transform (FFT) conversion after interval zero insertion and spread spectrum operation, generate ambipolar time domain complex signal, bipolarity time domain complex signal is subjected to coordinate conversion, by the amplitude and the former complex signal of phase expression under polar coordinate system, companding transform is normalized in amplitude, it adds cyclic prefix and generates real positive base band P-OFDM signal later, optical signal is converted by photoelectric conversion to be sent.The beneficial effects of the present invention are: the present invention, compared to other technologies, computation complexity reduces, and can be effectively reduced signal PAPR, P-OFDM system transmission performance is improved.
Description
Technical field
The present invention relates to technical field of photo communication, more particularly to a kind of DFT that is based on to spread and normalize companding transform joint
The method of technology reduction P-OFDM system PAPR.
Background technique
With the continuous development of the various communication technologys, revolutionary variation is had occurred in the scope of mobile digital terminal, tradition
Access net by huge test, be becoming tight radio spectrum resources day, in this context, collection illumination be in communication in one
Visible light communication come into being, environmentally friendly visible light communication will greatly expand communication spectrum, solve radio spectrum resources
The crisis that will be exhausted.Since orthogonal frequency division multiplexi can effectively antagonize multi-path jamming, reduce intersymbol interference, thus by its
System transmission performance is able to ascend applied to indoor visible light communication field.But in visible light communication system, need reality just
Unipolar signal will be loaded on light carrier by light intensity modulation, and tradition OFDM time-domain signal is that bipolarity plural number is believed
Number, it is therefore desirable to the real positive processing of single polarization is carried out to OFDM, common method will be answered using Hermitan conjugate symmetry property
Number signal is changed into real number signal, realizes single polarization, therefore common system by way of direct current biasing or interval zero insertion
By DCO-OFDM, ACO-OFDM, P-OFDM etc..And in such systems, the band efficiency of P-OFDM is better than ACO-OFDM system
System, PAPR performance and power efficiency are superior to ACO-OFDM and DCO-OFDM system, therefore, indoors in visible light communication system
Using P-OFDM signal, the use of direct current biasing can not only be reduced, and can effective lifting system band efficiency with
PAPR performance, but simultaneously, P-OFDM system still has the higher problem of signal power peak-to-average force ratio, and signal power is effectively reduced
Peak-to-average force ratio is able to ascend system mean power, can not only promotion signal quality, while can be effectively reduced system terminal hardware
Demand and cost needs.Currently, the method for common drop PAPR has pre-distortion method, Choose for user method (Selected
Mapping, SLM) and partial transmission sequence method (Partial Transfer Sequence, PTS).But predistortion can drop
System performance is influenced while PAPR；And SLM and PTS are obtained well by increasing calculation amount to a certain extent
PAPR, enhance overhead.
Summary of the invention
The present invention provides one kind, which to spread and normalize companding transform United Technologies based on DFT, reduces P-OFDM system PAPR
Method and system, while the PAPR for effectively reducing P-OFDM reduce system implementation complexity, to achieve the above object,
The technical solution of the present invention is as follows: a kind of spread and normalized companding transform United Technologies reduction P-OFDM system PAPR based on DFT
Method,
Signal step of transmitting: pseudo-random binary bit sequence is generated, after mapping by qam constellation, carries out discrete Fu
In leaf transformation, obtained signal carry out interval zero insertion and spread spectrum operation after pass through Fast Fourier Transform (FFT) conversion, generate it is bipolar
Property time domain complex signal, bipolarity time domain complex signal is subjected to coordinate conversion, by under polar coordinate system amplitude and phase indicate former
Companding transform, value of the phase mapping between [0,1] is normalized in complex signal, amplitude, and addition cyclic prefix generates reality later
Positive base band P-OFDM signal, is converted into optical signal by photoelectric conversion and is sent；
Signal receiving step: electro-optic conversion is carried out by avalanche photodide in receiving end and obtains Baseband Receiver P-OFDM
Signal, then original bit sequence is restored by inverse process.
As a further improvement of the present invention, signal step of transmitting includes the following steps:
Step 1: a string of binary bit sequences are randomly generated in lower MATLAB module online, by serial to parallel conversion it
Afterwards, M-QAM constellation mapping is carried out, the road L constellation mapping symbol data are obtained, is carried out in L point discrete Fourier after leaf transformation DFT, to
Odd positions interval zero insertion and zero padding spread spectrum operation are carried out to data sequence；
Step 2: carrying out N point quick Fourier to the sub-carrier signal for completing spread spectrum converts IFFT, time domain bipolarity is generated
Complex signal, N/2 time domain complex signal carries out coordinate conversion before extracting, and the complex signal conversion poling under cartesian coordinate system is sat
The amplitude and phase of mark system are indicated；
Step 3: companding transform is normalized to the range signal of acquisition, meanwhile, the phase of acquisition is reflected by [0,2 π]
[0,1] is incident upon to be indicated；
Step 4: amplitude signal and phase signal are combined, one group of unipolarity reality positive signal is formed, it is added
Cyclic prefix generates the real P- for just spreading and normalizing companding transform United Technologies based on DFT of unipolarity by parallel serial conversion
OFDM baseband signal；
Step 5: being put after the base band P-OFDM signal generated is loaded into arbitrary waveform generator (AWG) through electric amplifier
Greatly, then after adjustable electrical attenuator, driving laser diode realizes electro-optic conversion, the P-OFDM based on DFT spread spectrum of acquisition
Optical signal, freedom of entry space are transmitted.
As a further improvement of the present invention, in the first step, odd positions interval is carried out to data sequence D and is inserted
Zero, data are expressed as after zero insertionAt this point, the data length is 2L, with laggard
Row zero padding operation.
As a further improvement of the present invention, in the second step, it is fast that N point is carried out to the sub-carrier signal for completing spread spectrum
Fast Fourier transformation IFFT, generating time domain bipolarity complex signal can indicate are as follows:Wherein,
As a further improvement of the present invention, in the second step, N/2 time domain complex signal carries out coordinate turn before extracting
It changes, the amplitude and phase that the complex signal under cartesian coordinate system is converted into polar coordinate system is indicated, wherein range signal can
To indicate are as follows:Wherein
As a further improvement of the present invention, in the third step, the temporal amplitude by normalizing companding transform is believed
It number can indicate are as follows:
WhereinMin (A) expression takes minimum radius to believe
Number value, max (A) expression take maximum-amplitude signal value.
As a further improvement of the present invention, in the third step, the phase signal for mapping to [0,1] can be indicated
Are as follows:
Wherein
As a further improvement of the present invention, in the 4th step, amplitude signal and phase signal are combined,
Form one group of unipolarity reality positive signal are as follows:
As a further improvement of the present invention, signal receiving step includes:
Step 6: received optical signal carries out photoelectric conversion, the electric signal warp of acquisition by avalanche photodide (APD)
Digital oscilloscope (DSO) acquisition feeding line lower module is crossed to be handled；
Step 7: online in lower processing module, to the electric signal of acquisition by after synchronization process, carry out serioparallel exchange with
After going cyclic prefix to operate, N/2 symbol is as reception range signal, rear N/2 before extracting to received unipolarity time-domain symbol
A symbol is as phase signal；
Step 8: the range signal and phase signal that extract unipolarity time-domain symbol are normalized respectively, then
By coordinate inverse conversion, the bipolarity complex signal that is converted under cartesian coordinate system；
Step 9: carrying out L point after carrying out N point quick Fourier transformation FFT by the time domain complex signal of acquisition, remove Z-operation
Discrete inverse Fourier transform IDFT, then carry out M-QAM demodulation and go here and there to handle to restore original binary bit sequence.
As a further improvement of the present invention, in the 7th step, N/2 before being extracted to received unipolarity time-domain symbol
A symbol is indicated as range signal is received are as follows:N/2 symbol conduct after extraction
Phase signal can indicate are as follows:
As a further improvement of the present invention, in the 8th step, the amplitude for extracting unipolarity time-domain symbol is carried out
The range signal obtained after normalized can indicate:
Wherein
It can indicate the signal that phase signal is normalized is received are as follows:
Wherein
As a further improvement of the present invention, in the 8th step: by coordinate inverse conversion, by the list under polar coordinate system
The bipolarity complex signal that polarity amplitude and phase signal is converted under cartesian coordinate system can indicate are as follows:Wherein
The beneficial effects of the present invention are: the present invention can be effectively reduced signal PAPR, same phase compared to traditional P-OFDM
Than can reduce computation complexity in the prior art, overhead is saved, system transmission performance is improved.
Detailed description of the invention
Fig. 1 is that the present invention is based on DFT spread spectrums and normalization companding transform P-OFDM baseband signal transmitting block diagram；
Fig. 2 is P-OFDM visible light communication system block diagram of the invention；
Fig. 3 is that the present invention is based on DFT spread spectrums and normalization companding transform P-OFDM baseband signal to receive block diagram；
Fig. 4 is the time domain waveform before and after present invention normalization companding transform, and Fig. 4 (a) is that could be used without being normalized
The time domain waveform of companding transform, Fig. 4 (b) are the time domain waveform being normalized after companding transform；
Fig. 5 is the present invention and tradition P-OFDM, DC-OFDM PAPR comparison diagram.
Specific embodiment
The invention discloses one kind, which to spread and normalize companding transform United Technologies based on DFT, reduces P-OFDM system PAPR
Method technical solution of the present invention specific steps are illustrated below in conjunction with attached drawing.
Step 1: as shown in Figure 1, a string of binary bit sequences are randomly generated, by string in lower MATLAB module online
And after converting, M-QAM constellation mapping is carried out, multichannel bit information is mapped in different sub-carrier, the road L constellation mapping is obtained
Symbol data q=[q0, q1..., qL-1]；
Step 2: the road L symbol data then carries out leaf (DFT) in L point discrete Fourier and converts, and obtains data sequence D=[D0,
D1..., DL-1]；
Step 3: odd positions interval zero insertion is carried out to data sequence D, data can be expressed as after zero insertionAt this point, the data length is 2L, zero padding spread spectrum operation is then carried out, is grown
Degree is that the data-signal of N can indicate are as follows:Its
In,
Step 4: the transformation of N point quick Fourier (IFFT) is carried out to the sub-carrier signal for completing spread spectrum, it is bipolar to generate time domain
Property complex signal, can indicate are as follows:Wherein
Step 5: N/2 time domain complex signal before extractingCoordinate conversion is carried out, Descartes is sat
The amplitude and phase that complex signal under mark system is converted into polar coordinate system are indicated；
Step 6: range signal is expressed asWhereinIt is normalized what companding transform obtained
Range signal isWherein
It is rightPhase signal it then mapped into [0,1] by [0,2 π] be indicated
Wherein
Step 7: amplitude signal and phase signal are combined, and form one group of unipolarity reality positive signalThe signal contrast before and after companding transform is normalized
For figure as shown in figure 4, wherein Fig. 4 (a) is the signal graph that companding transform is not normalized, Fig. 4 (b) is that companding change is normalized
Signal graph after alternatively；Cyclic prefix is added to signal x, after carrying out parallel serial conversion, it is real just based on joint DFT to generate unipolarity
The P-OFDM baseband signal of spread spectrum.Based on the P-OFDM signal PAPR and tradition P-OFDM of joint DFT spread spectrum, DCO-OFDM signal
PAPR correlation curve as shown in figure 5, it can be found that compared to traditional P-OFDM system, the present invention is in 10-3, PAPR performance
Improve about 4dB, compared to DCO-OFDM, PAPR performance improvement about 6.5dB of the present invention.
Step 8: as shown in Fig. 2, after the base band P-OFDM signal generated is loaded into arbitrary waveform generator (AWG), warp
Electric amplifier amplification, then after adjustable electrical attenuator, driving laser diode realizes electro-optic conversion, acquisition is expanded based on DFT
The P-OFDM optical signal of frequency and normalization companding transform United Technologies is sent into free space and is transmitted.
Step 9: received optical signal carries out photoelectric conversion, the electric signal warp of acquisition by avalanche photodide (APD)
It crosses under the laggard line of digital oscilloscope (DSO) acquisition and handles.
Step 10: as shown in figure 3, online in lower MATLAB module, after passing through synchronization process to the electric signal of acquisition, into
Row serioparallel exchange is operated with cyclic prefix is removed, and extracts the amplitude of unipolarity time-domain symbol
And phaseThe range signal of acquisition is after it is normalized respectivelyWhereinPhase signal isWherein
Step 11: by coordinate inverse conversion, by under polar coordinate system unipolar amplitude and phase signal be converted into Descartes
Bipolarity complex signal under coordinate system:
Wherein
Step 12: carrying out Fast Fourier Transform (FFT) (FFT) conversion to frequency domain data for the time domain complex signal of acquisition, and to obtaining
Frequency-region signal by going after Z-operation, carry out discrete inverse Fourier transform (IDFT), then carry out M-QAM demodulation with and go here and there
Processing restores original binary bit sequence.
The present invention can be effectively reduced signal PAPR compared to traditional P-OFDM, compared to other technologies, due to only with
DFT and IDFT and normalized, hardware realization is simpler, and computation complexity reduces, and system cost reduces, and system passes
Defeated performance improves.
The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be said that
Specific implementation of the invention is only limited to these instructions.For those of ordinary skill in the art to which the present invention belongs, exist
Under the premise of not departing from present inventive concept, a number of simple deductions or replacements can also be made, all shall be regarded as belonging to of the invention
Protection scope.
Claims (10)
1. a kind of method for spreading and normalizing companding transform United Technologies based on DFT and reduce P-OFDM system PAPR, feature
It is, comprising:
Step 1: a string of binary bit sequences are randomly generated in lower MATLAB module online, after serial to parallel conversion, into
Row M-QAM constellation mapping, obtains the road L constellation mapping symbol data, carries out in L point discrete Fourier after leaf transformation DFT, to obtaining data
Sequence carries out odd positions interval zero insertion and zero padding spread spectrum operation；
Step 2: carrying out N point quick Fourier to the sub-carrier signal for completing spread spectrum converts IFFT, time domain bipolarity plural number is generated
Signal, N/2 time domain complex signal carries out coordinate conversion before extracting, and the complex signal under cartesian coordinate system is converted into polar coordinate system
Amplitude and phase be indicated；
Step 3: companding transform is normalized to the range signal of acquisition, meanwhile, the phase of acquisition is mapped to by [0,2 π]
[0,1] it is indicated；
Step 4: amplitude signal and phase signal are combined, one group of unipolarity reality positive signal is formed, circulation is added to it
Prefix generates the real P-OFDM base for just spreading and normalizing companding transform United Technologies based on DFT of unipolarity by parallel serial conversion
Band signal；
Step 5: amplifying after the base band P-OFDM signal generated is loaded into arbitrary waveform generator through electric amplifier, then passing through can
After adjusting electrical attenuator, driving laser diode realization electro-optic conversion, the P-OFDM optical signal based on DFT spread spectrum of acquisition, into
Enter free space to be transmitted；
Step 6: received optical signal carries out photoelectric conversion by avalanche photodide, the electric signal of acquisition shows by number
The acquisition of wave device is sent into line lower module and is handled；
Step 7: after passing through synchronization process to the electric signal of acquisition, carrying out serioparallel exchange online in lower processing module and going to follow
After ring prefix operation, as range signal is received, latter N/2 accords with N/2 symbol before extracting to received unipolarity time-domain symbol
Number be used as phase signal；
Step 8: the range signal and phase signal that extract unipolarity time-domain symbol are normalized respectively, then pass through
Coordinate inverse conversion, the bipolarity complex signal being converted under cartesian coordinate system；
Step 9: it is discrete to carry out L point after carrying out N point quick Fourier transformation FFT by the time domain complex signal of acquisition, remove Z-operation
Inverse Fourier transform IDFT, then carry out M-QAM demodulation and go here and there to handle to restore original binary bit sequence.
2. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in second step, the transformation of N point quick Fourier is carried out to the sub-carrier signal for completing spread spectrum
IFFT, generating time domain bipolarity complex signal can indicate are as follows:Wherein,
3. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in second step, N/2 time domain complex signal carries out coordinate conversion before extracting, by cartesian coordinate
The amplitude and phase that complex signal under system is converted into polar coordinate system are indicated, and wherein range signal can indicate are as follows:Wherein
4. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in third step, the temporal amplitude signal by normalizing companding transform can be indicated are as follows:
WhereinMin (A) expression takes minimum radius signal value,
Max (A) expression takes maximum-amplitude signal value.
5. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that the phase signal in third step, mapping to [0,1] can indicate are as follows:
Wherein
6. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in the 4th step, amplitude signal and phase signal are combined, form one group of unipolarity
Real positive signal are as follows:
7. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in the 5th step, after the base band P-OFDM signal of generation is loaded into arbitrary waveform generator,
Amplify through electric amplifier, then after adjustable electrical attenuator, driving laser diode realize electro-optic conversion, acquisition based on DFT
The P-OFDM optical signal of spread spectrum, freedom of entry space are transmitted.
8. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in the 7th step, N/2 symbol is as reception before extracting to received unipolarity time-domain symbol
Range signal indicates are as follows:N/2 symbol, can be with table as phase signal after extraction
It is shown as:
9. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in the 8th step, obtained after the amplitude for extracting unipolarity time-domain symbol is normalized
The range signal obtained can indicate:
Wherein
It can indicate the signal that phase signal is normalized is received are as follows:Wherein
10. according to claim 1 spread and normalized companding transform United Technologies reduction P-OFDM system based on DFT
The method of PAPR, which is characterized in that in the 8th step: by coordinate inverse conversion, by the unipolar amplitude and phase under polar coordinate system
The bipolarity complex signal that signal is converted under cartesian coordinate system can indicate are as follows:Wherein
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