CN108900462A - A method of reducing indoor visible light DCO-OFDM system peak-to-average power ratio - Google Patents
A method of reducing indoor visible light DCO-OFDM system peak-to-average power ratio Download PDFInfo
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- CN108900462A CN108900462A CN201811133147.2A CN201811133147A CN108900462A CN 108900462 A CN108900462 A CN 108900462A CN 201811133147 A CN201811133147 A CN 201811133147A CN 108900462 A CN108900462 A CN 108900462A
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- visible light
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- indoor visible
- average power
- power ratio
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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
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
- H04B10/114—Indoor or close-range type systems
- H04B10/116—Visible light communication
Abstract
The invention discloses a kind of method for reducing indoor visible light DCO-OFDM system peak-to-average power ratio, broadband subcarrier is become multiple narrow-band sub-carriers by M filter by transmitting terminal；Receiving end is come out WBSR wideband signal recovery by squeeze theorem, M filter and Signal averaging.Present system power utilization is high；Non-linear distortion caused by LED can be resisted, the bit error rate of system is reduced；Indoor normal illumination can be maintained while communication, be conducive to avoid human eye caused by scintillation in single optical source system uncomfortable.
Description
Technical field
The invention belongs to indoor visible light communication technical fields, and in particular to a kind of reduction indoor visible light DCO-OFDM system
The method of system peak-to-average power ratio.
Background technique
Visible light communication (Visible Light Communication, VLC), which refers to, utilizes 400-700nm visible light wave
The light of section is as information carrier, without the transmission medium of the wire channel such as optical fiber, directly transmits the communication of optical signal in air
Mode.Compared with infrared, bluetooth, WI-FI and other technology for radio frequency, VLC has the advantage below such as：(1) will not hurt
Evil eye-safe；(2) frequency spectrum resource is abundant, and permits without radio-frequency spectrum；(3) transmission power is high；(4) not dry vulnerable to electromagnetism
It disturbs；(5) green and environmental protection.So following lead in Internet of Things, smart city (family), aviation, navigation, subway, high-speed rail, interior
The fields such as boat and underground work all have wide application prospect.By orthogonal frequency division multiplexing (Orthogonal Frequency
Division Multiplexing, OFDM) modulation technique be applied to not only can be further improved in VLC system transmission speed
The ability of rate and anti-multipath jamming, and there is the higher availability of frequency spectrum than single-carrier modulated mode, but inevitably
The problem of bringing height power ratio (Peak to Average Power Ratio, PAPR), LED (Light Emitting
Diode, LED) nonlinear characteristic can make to have the unipolarity ofdm signal of high PAPR to generate non-linear distortion, seriously affect and be
The transmission reliability of system.
Currently, the method for reducing ofdm system PAPR mainly has three kinds of direct clipping, non-distortion and coding.Though direct clipping
It is so simple easily to realize, but serious band outward leakage can be caused.Partial transmission sequence (Partial Transmit Sequence,
PTS) and selected mapping method (Selective Mapping, SLM) is two kinds of typical non-distortion methods, since PTS is using dedicated
Reserved resource in channel or OFDM symbol carries out side information transmission, can not only bring under data rate in this way
Drop, but also the raising again of PAPR can be caused.SLM needs to search for all possible phase factor combination, preamble bit
It needs to transmit, so equally existing the problem that band efficiency is low and system complexity is high.Pilot aided method is a kind of coding class
The method for reducing ofdm system PAPR, although error rate of system performance is better than SLM under high order modulation, transmission speed is lower.It is another
The method of kind common coding class reduction PAPR is index nonlinear compression method, this method not only error rate of system performance
Deteriorate very fast and very serious with outer subcarriers power leakage.
Summary of the invention
The object of the present invention is to provide a kind of methods for reducing indoor visible light DCO-OFDM system peak-to-average power ratio, solve
DCO-OFDM system power utilization rate existing in the prior art is low and transmission reliability is low problem.
The technical scheme adopted by the invention is that a kind of side for reducing indoor visible light DCO-OFDM system peak-to-average power ratio
Broadband subcarrier is become multiple narrow-band sub-carriers by M filter by method, transmitting terminal；Receiving end passes through squeeze theorem, M filter
Wave device and Signal averaging come out WBSR wideband signal recovery.
The features of the present invention also characterized in that：
It is specifically implemented according to the following steps：
Step a：Indoor visible light communication platform is built, indoor visible light channel is established；Acquire data；Letter is carried out to data
Source code generates binary data stream；
Step b：Quadrature amplitude modulation, serial/parallel conversion and conjugate pair are successively carried out to the binary data stream that step a is obtained
Claim mapping, obtains complex signal vector；
Step c：The complex signal vector that step b is obtained is divided into M sub- carrier wave sets, obtains M complex conjugate symmetry vector；
Step d：IFFT transformation is carried out to the M complex conjugate symmetry vector that step c is obtained, obtains M bipolarity time domain letter
Number vector.
Step e：Clipping, parallel/serial conversion plus direct current biasing are successively carried out to the time domain signal vector that step d is obtained；It obtains
M unipolarity time domain signal vector, and respectively drive the corresponding LED light source of transmitting terminal and shine；It sends signal to indoor visible
Optical channel realizes the parallel transmission of signal；
Step f：The optical signal received is passed through K electric signal by receiving end, and removes direct current biasing；Wherein, K >=M；
Step g：Serial/parallel conversion, FFT transform are successively carried out to signal, obtain K complex signal vector；
Step h：The K complex signal vector obtained to step g carries out squeeze theorem, obtain complex signal that M recover to
Amount；
Step i：Useful complex signal in M complex signal vector that step h is obtained is extracted；
Step j：The M useful complex signals that step i is obtained are overlapped；QAM demodulation is carried out to signal, is restored out
Binary bit stream.
In step a, indoor visible light communication platform includes transmitting terminal, Transmission system and receiving end；
Transmitting terminal includes sequentially connected IP Camera, video encoder, QAM modulation device, shift register a, DSP mould
Block a；DSP module is connect with several filters respectively；Each filter a successively connects with OFDM modulator, driving circuit, light source
It connects；
Transmission system is the channel being made of air；
Receiving end includes several photodetectors, each photodetector successively with shift register b, ofdm demodulator
Connection；The quantity of photodetector is greater than or equal to the quantity of filter；Several ofdm demodulators are detected with that can realize ZF
DSP module b connection；DSP module b is connect with several filters b respectively；Several filters b is folded with that can realize signal
The DSP module c connection added；DSP module c is connect with qam demodulator；Ofdm demodulator, the quantity of filter b are consistent.
The RJ45 network interface connection of QAM modulation device and video encoder.
Light source is HL2000 commercialization white LED light source.
The model PDA10A-EC of photodetector.
It further include error analyzer, error analyzer is connect with qam demodulator.
The model AV5232 of error analyzer.
The beneficial effects of the invention are as follows：
(1) system power utilization rate is high.OFDM broadband signal is divided into multiple narrow band signals, it is carried out be conjugated it is symmetrical and
The standard deviation of bipolarity real-valued signal after Fourier transformation is obviously reduced, and required direct current biasing is obviously reduced, for sending out
The power specific gravity for penetrating useful signal is obviously increasing, and the effective received signal to noise ratio in receiving end significantly improves.
(2) non-linear distortion caused by LED is resisted, the bit error rate of system is reduced.It will be multiple narrow by means of spatial degrees of freedom
Parallel transmission is carried out in different LED transmitting terminals with ofdm signal load, spatial multiplexing gain spatially makes the bit error rate of system
Performance is further improved in entire SNR ranges internal ratio DCO-OFDM.
(3) indoor normal illumination can be maintained while communication, is conducive to avoid in single optical source system caused by scintillation
Human eye is uncomfortable.
Detailed description of the invention
Fig. 1 is the flow chart for the method that the present invention reduces indoor visible light DCO-OFDM system peak-to-average power ratio；
Fig. 2 is the structure of the communication system for the method that the present invention reduces indoor visible light DCO-OFDM system peak-to-average power ratio
Schematic diagram；
Fig. 3 is the communication system transmitting terminal for the method that the present invention reduces indoor visible light DCO-OFDM system peak-to-average power ratio
Structural block diagram；
Fig. 4 is the receiving terminal of communication system for the method that the present invention reduces indoor visible light DCO-OFDM system peak-to-average power ratio
Structural block diagram.
In figure, 1. IP Cameras, 2. video encoders, 3.QAM modulator, 4. shift register a, 5.DSP module a,
6. filter a, 7.OFDM modulator, 8. driving circuits, 9. light sources, 10. photodetectors, 11. shift register b, 12.OFDM
Demodulator, 13.DSP module b, 14. filter b, 15.DSP module c, 16.QAM demodulators, 17. error analyzers.
Specific embodiment
The following describes the present invention in detail with reference to the accompanying drawings and specific embodiments.
The method that the present invention reduces indoor visible light DCO-OFDM system peak-to-average power ratio, transmitting terminal pass through M filter
Broadband subcarrier is become into multiple narrow-band sub-carriers；Broadband is believed by squeeze theorem, M filter and Signal averaging receiving end
It number recovers.
Realize the present invention reduce indoor visible light DCO-OFDM system peak-to-average power ratio method system include transmitting terminal,
Transmission system and receiving end (as shown in Figure 2)；
Transmitting terminal include sequentially connected IP Camera 1, video encoder 2, QAM modulation device 3, shift register a4,
DSP module a5；DSP module 5 is connect with M filter 6 respectively；Each filter a6 successively with OFDM modulator 7, driving circuit
8, light source 9 connects (as shown in Figure 3)；
Transmission system is the channel being made of air；
Receiving end includes K electric explorer 10, each photodetector 10 successively with shift register b11, OFDM demodulation
Device 12 connects, and K >=M；K ofdm demodulator 12 is connect with that can realize the DSP module b13 of ZF detection；DSP module b13 points
It is not connect with K filter b14；K filter b14 is connect with DSP module c15, and DSP module c15 and qam demodulator 16 connect
It connects；Qam demodulator 16 is connect with error analyzer 17；Wherein, DSP module c15 can realize Signal averaging；QAM modulation device 3 and view
The RJ45 network interface connection of frequency encoder 2；Light source 9 is HL2000 commercialization white LED light source；The model of photodetector 10
PDA10A-EC；The model AV5232 (as shown in Figure 4) of error analyzer 17；
The present invention reduce indoor visible light DCO-OFDM system peak-to-average power ratio method, as shown in Figure 1, specifically according to
Lower step is implemented：
Step a：Indoor visible light communication platform is built, indoor visible light channel is established；Number is acquired by IP Camera 1
According to；Message sink coding is carried out to data by video encoder 2, generates binary data stream, such as
101001101011000100010……。
Step b：Quadrature amplitude modulation (Quadrature is successively carried out to the binary data stream that step a is obtained
Amplitude Modulation, QAM) obtain the complex signal vector X that length is N/2-1D=[X1,X2,…,Xk], wherein k=
1,2 ..., N/2-1, N are the length of inverse Fourier transform (Inverse Fourier Transform, IFFT)；To XDIt carries out
Serial/parallel (Serial/Parallel, S/P) conversion and conjugation symmetrical mapping, obtain the complex signal vector that length is NWherein, quadrature amplitude modulation is real by QAM modulation device 3
It is existing；Serial/parallel conversion is realized by shift register a4；Conjugation is symmetrically mapping through DSP module a5 realization.
Step c：The complex signal vector that step b is obtained is passed through into M filter a6 respectively and realizes space subcarrier grouping, is obtained
The complex conjugate symmetry vector for being N to M length：
…
Wherein L=N/2-1.
Step d：IFFT transformation is carried out by OFDM modulator 7 to the M complex conjugate symmetry vector that step c is obtained, obtains M
A length is the bipolarity time domain signal vector x of N1,x2,…xM。
Step e：Clipping is successively carried out to the time domain signal vector that step d is obtained by driving circuit 8, parallel/serial conversion, is added
Direct current biasing obtains the unipolarity time domain signal vector that M length is N, and drives corresponding LED light source 9, realize signal and
Row transmission.
Step f：The optical signal received is become electric signal by K photodetector 10 by receiving end, and removes direct current
Biasing.
Step g：Serial/parallel conversion is carried out to signal by shift register b11；Signal is carried out by ofdm demodulator 12
FFT transform obtains K complex signal vector.
Step h：Squeeze theorem (Zero is carried out to the K complex signal vector that step g is obtained by DSP module b13
Forcing, ZF) remove influence of the channel to signal, obtain the M complex signal vectors recovered：
…
Step i：The M complex signal vector that step h is obtained pass through respectively M frequency domain filter b14 extract it is therein
Useful complex signal：
…
Step j：The M useful complex signals that step i is obtained are overlapped by DSP module c15, obtaining length is N/2-
1 complex signalQAM demodulation, two to be restored out are carried out to the signal by qam demodulator 16
System bit stream；
Step k：The bit error rate of system is calculated by error analyzer 17.
Wherein, the RJ45 network interface connection of QAM modulation device 3 and video encoder 2；Light source 9 is HL2000 commercialization white light LEDs light
Source；Photodetector 10 is PDA10A-EC；Error analyzer 17 is AV5232.
The present invention reduce indoor visible light DCO-OFDM system peak-to-average power ratio method the advantages of be：
(1) system power utilization rate is high.OFDM broadband signal is divided into multiple narrow band signals, it is carried out be conjugated it is symmetrical and
The standard deviation of bipolarity real-valued signal after Fourier transformation is obviously reduced, and required direct current biasing is obviously reduced, for sending out
The power specific gravity for penetrating useful signal is obviously increasing, and the effective received signal to noise ratio in receiving end significantly improves.
(2) non-linear distortion caused by LED is resisted, the bit error rate of system is reduced.It will be multiple narrow by means of spatial degrees of freedom
Parallel transmission is carried out in different LED transmitting terminals with ofdm signal load, spatial multiplexing gain spatially makes the bit error rate of system
Performance is further improved in entire SNR ranges internal ratio DCO-OFDM.
(3) indoor normal illumination can be maintained while communication, is conducive to avoid in single optical source system caused by scintillation
Human eye is uncomfortable.
Claims (8)
1. a kind of method for reducing indoor visible light DCO-OFDM system peak-to-average power ratio, which is characterized in that transmitting terminal passes through M
Broadband subcarrier is become multiple narrow-band sub-carriers by filter；It receiving end will by squeeze theorem, M filter and Signal averaging
WBSR wideband signal recovery comes out.
2. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as described in claim 1, which is characterized in that
It is specifically implemented according to the following steps：
Step a：Indoor visible light communication platform is built, indoor visible light channel is established；Acquire data；Information source volume is carried out to data
Code generates binary data stream；
Step b：Quadrature amplitude modulation, serial/parallel conversion and conjugation is successively carried out to the binary data stream that step a is obtained symmetrically to reflect
It penetrates, obtains complex signal vector；
Step c：The complex signal vector that step b is obtained is divided into M sub- carrier wave sets, obtains M complex conjugate symmetry vector；
Step d：The M complex conjugate symmetry vector obtained to step c carries out IFFT transformation, obtain M bipolarity time-domain signal to
Amount.
Step e：Clipping, parallel/serial conversion plus direct current biasing are successively carried out to the time domain signal vector that step d is obtained；Obtain M
Unipolarity time domain signal vector, and respectively drive the corresponding LED light source of transmitting terminal and shine；Send signal to indoor visible light letter
The parallel transmission of signal is realized in road；
Step f：The optical signal received is divided into K electric signal by receiving end, and removes direct current biasing；Wherein, K >=M；
Step g：Serial/parallel conversion, FFT transform are successively carried out to signal, obtain K complex signal vector；
Step h：Squeeze theorem is carried out to the K complex signal vector that step g is obtained, obtains the M complex signal vectors recovered；
Step i：Useful complex signal in M complex signal vector that step h is obtained is extracted；
Step j：The M useful complex signals that step i is obtained are overlapped；QAM demodulation, two to be restored out are carried out to signal
System bit stream.
3. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 2, which is characterized in that
In step a, the indoor visible light communication platform includes transmitting terminal, Transmission system and receiving end；
The transmitting terminal includes sequentially connected IP Camera (1), video encoder (2), QAM modulation device (3), shift LD
Device a (4), DSP module a (5)；DSP module (5) is connect with several filters (6) respectively；Each filter a (6) successively with
OFDM modulator (7), driving circuit (8), light source (9) connection；
The Transmission system is the channel being made of air；
The receiving end includes several photodetectors (10), each photodetector (10) successively with shift register b
(11), ofdm demodulator (12) connects；The quantity of photodetector (10) is greater than or equal to the quantity of filter (6)；Several
Ofdm demodulator (12) is connect with that can realize the DSP module b (13) of ZF detection；DSP module b (13) is filtered with several respectively
Device b (14) connection；Several filters b (14) is connect with that can realize the DSP module c (15) of Signal averaging；DSP module c
(15) it is connect with qam demodulator (16)；Ofdm demodulator (12), the quantity of filter b (14) are consistent.
4. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 3, it is characterised in that：
The RJ45 network interface connection of the QAM modulation device (3) and video encoder (2).
5. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 3, it is characterised in that：
The light source (9) is HL2000 commercialization white LED light source.
6. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 3, it is characterised in that：
The model PDA10A-EC of the photodetector (10).
7. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 3, it is characterised in that：
It further include error analyzer (17), error analyzer (17) is connect with qam demodulator (16).
8. reducing the method for indoor visible light DCO-OFDM system peak-to-average power ratio as claimed in claim 3, it is characterised in that：
The model AV5232 of the error analyzer (17).
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| CN112565152A (en) * | 2020-12-25 | 2021-03-26 | 重庆理工大学 | Peak-to-average power ratio reduction method and device for visible light communication OFDM system |
| CN112564799A (en) * | 2020-12-01 | 2021-03-26 | 江苏科技大学 | Method for inhibiting peak-to-average power ratio of visible light MIMO-OFDM system |
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| CN114745244A (en) * | 2022-04-24 | 2022-07-12 | 南京邮电大学 | Flicker suppression method under OFDM modulation mode in visible light communication |
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