CN106411403B - It is a kind of that transmission of visible light method is lightened based on the ultra-wide that slicing is moved - Google Patents

It is a kind of that transmission of visible light method is lightened based on the ultra-wide that slicing is moved Download PDF

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CN106411403B
CN106411403B CN201610542520.4A CN201610542520A CN106411403B CN 106411403 B CN106411403 B CN 106411403B CN 201610542520 A CN201610542520 A CN 201610542520A CN 106411403 B CN106411403 B CN 106411403B
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ofdm
length
slicing
controlling
bias
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CN106411403A (en
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孔令恺
曹聪聪
李孟超
张思源
吴亮
张在琛
党建
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Southeast University
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114Indoor or close-range type systems
    • H04B10/116Visible light communication
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/501Structural aspects
    • H04B10/502LED transmitters
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/516Details of coding or modulation
    • H04B10/5165Carrier suppressed; Single sideband; Double sideband or vestigial
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B10/00Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50Transmitters
    • H04B10/564Power control
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2626Arrangements specific to the transmitter only

Abstract

Transmission of visible light method is lightened based on the ultra-wide that slicing is moved the invention discloses a kind of, it is characterized by: by not adding the DCO-OFDM time-domain symbol of direct current biasing first multiplied by a controlling elements script, then plus a length is the OFDM subframe of N, and carrying can be more than the negative value of the part information of LED linear range after adding direct current biasing;So that system reaches the stable state unrelated with dc-bias, to adjust light intensity by regulation direct-current bias value and controlling elements, the attainable range that lightens of institute is determined by controlling elements.System performance of the present invention is up to the stable state not influenced by dc-bias size, so as to adjust light intensity simply by regulation direct-current bias value and controlling elements, higher transmission rate is still able to maintain while reaching ultra-wide dimming scope.

Description

It is a kind of that transmission of visible light method is lightened based on the ultra-wide that slicing is moved
Technical field
The invention belongs to technical field of visible light communication, in particular to a kind of wireless optical transmission method.
Background technique
Visible light communication as one of future mobile communications key technology has the spies such as green, safety, wide available frequency band Point is a supplement well for the Radio-Frequency Wireless Communication in short supply for frequency spectrum resource.OFDM technology can not only be effectively Enhance message transmission rate, increases system transmission capacity, and multipath fading and interference can be effectively inhibited, the technology is wide It is general to be applied in Modern wireless communication.
In intensity modulated Direct-detection Optical communication system, the information of required transmission is indicated by the intensity of optical signal, this It can be non-negative unipolar real signal, photoreceiver utilizes square-law detector Direct-detection Optical signal strength or weakness.It is existing several suitable The OFDM mode communicated for intensity modulated, Direct-detection Optical is suggested, comprising: the OFDM (DC-biased based on direct current biasing Optical OFDM, DCO-OFDM), OFDM (Asymmetric clipping the optical OFDM, ACO- of asymmetric trimming OFDM)。
Dimming control technique allows people to adjust room lighting feelings according to oneself requirement to lighting intensity Condition realizes effective energy conservation.In traditional DCO-OFDM system, dimming control technique can be divided into analog-modulated and number is adjusted Two ways processed, i.e., at present the wide continuous current of application adjust (Continuous Current Reduction, CCR) and Pulse width modulates (Pulse Width Modulation, PWM).First method is simple, stablizes, but due to LED light wire Property range limitation so that truncation noise is excessive when light modulation depth is lower or higher, dimming scope very little in this way. What is generallyd use at present is PWM modulation, and this method can adequately utilize the range of linearity of LED light.
Due to the limitation of the LED light range of linearity, when the dc-bias of DCO-OFDM is excessive or too small, the truncation of system Noise is very big, causes the method for adjusting light intensity in system traditional in practical applications by dc-bias that can reach Range it is too small.
Summary of the invention
Transmission of visible light method is lightened based on the ultra-wide that slicing is moved the object of the present invention is to provide a kind of, it is existing to solve Adjusted in traditional system present in technology by dc-bias the method for light intensity attainable range is too small asks Topic.
To achieve the above object, the technical solution adopted by the present invention are as follows:
It is a kind of that transmission of visible light method is lightened based on the ultra-wide that slicing is moved, by the way that script is not added direct current biasing DCO-OFDM time-domain symbol is first multiplied by a controlling elements, and then plus a length is the OFDM subframe of N, carries and added direct current inclined Postponing can be more than the negative value of the part information of LED linear range;So that system reaches the stabilization shape unrelated with dc-bias State, to adjust light intensity by regulation direct-current bias value and controlling elements, the attainable range that lightens of institute is determined by controlling elements It is fixed.
The specific steps of the present invention are as follows:
Step 1 obtains the time-domain signal x [n] for the DCO-OFDM for not adding direct current biasing according to conventional method first, then right Time-domain signal at this time is multiplied by controlling elements α, i.e. xd[n]=α x [n];Then, the OFDM subframe that a length is N is added to use The negative value that direct current biasing can be more than this partial information of LED linear range is added to carry;X after then slicing is movedud[n] and x'ud[n] forms a data pair, wherein n=1,2,3 ..., N-1;
Step 2, then respectively to xud[n] and x'ud[n] the two subframes add cyclic prefix, it is assumed that the length of cyclic prefix Degree is △, then the second subframe will be delayed N+ △ chronomere compared to the first subframe to carry out frame and be multiplexed and finally plus required The dc-bias wanted;The OFDM symbol x " finally sent in this wayud[n] length is 2 (N+ △);
Step 3 through over-sampling and removes cyclic prefix after optical channel, and receiving end obtains the time domain that length is 2N and accords with Number;Removing DC bias DC is gone to rear N number of sequence again, N length is y before defining1[n], rear N length are y'2[n];Then the former is subtracted Go the latter;That is y [n]=y1[n]-y'2[n].;
Step 4 then carries out y [n] serioparallel exchange and to remove removing DC bias DC, then carries out the FFT transform of N point and go forward side by side Row equilibrium can obtain demodulated signal.
Slicing moves the formula of use are as follows:
Wherein, [λminmax] indicating LED linear range, DC is direct current biasing.
The utility model has the advantages that the performance of method of the invention is up to one not by straight compared with traditional DCO-OFDM system The stable state that stream biasing size influences, so as to adjust light by simple regulation direct-current bias value and controlling elements By force.The range that lightens of system is greatly improved.And compared with the PWM method generallyd use, realization of the invention is simpler, Stablize.It is embodied in the following:
1, under conditions of the LED light range of linearity is limited, it is only necessary to be adjusted by adjusting controlling elements and direct current biasing The performance of light intensity, control very simple and system to light intensity is not influenced by direct current biasing size, has reached a stable shape State, so as to so that the range that lightens of system is greatly improved and keeps higher transmission rate simultaneously.
2, it for energy saving and meet the theory of green illumination, realizes under the premise of not losing information transmission reliability Low power illumination regulatory function.Therefore the program has a good application prospect in the low place of some illuminances.
3, the complexity of whole system used in method of the invention is lower, all very easy reality of transmitter and receiver It is existing.
Detailed description of the invention
Fig. 1 is system transmitting terminal block diagram used in method of the invention;
Fig. 2 is system receiving terminal block diagram used in method of the invention;
Fig. 3 is LED light nonlinear model figure;
Fig. 4 is that slicing moves schematic diagram, wherein LED linear range is [0,1], DC=0.3;
Fig. 5 is the time domain waveform finally sent, wherein LED linear range is [0,1], DC=0.3;
Fig. 6 is the frame structure diagram finally sent;
Fig. 7 is in target BER=2*10-3The lower present invention and the accessible spectrum efficiency of tradition DCO-OFDM and light modulation depth Curve graph.
Specific embodiment
The present invention will be further explained with reference to the accompanying drawing.
Transmitting terminal and receiving end the flow chart difference of system used in the present invention are as depicted in figs. 1 and 2.Traditional DCO- OFDM is influenced by truncation noise, and what the method for directly adjusting direct current biasing to adjust light intensity can achieve lightens range very It is limited.And the present invention by will obtained time-domain OFDM symbol multiplied by a controlling elements α, then with one and original OFDM symbol xud The identical subframe x ' of [n] lengthud[n] is loaded beyond the negative value of this partial information of the LED light range of linearity.So that whole system Reach the stable state unrelated with direct current biasing amount, so as to pass through simply adjustment direct current in a very wide range Bias carries out the regulation of light intensity with controlling elements.
More detailed explanation is carried out to method of the invention with reference to the accompanying drawing.
(1) in transmitting terminal, the sub-carrier number of ofdm system is N, is only had in all subcarriersA sub- carrier-wave transmission is effective Data.The binary source sequence that transmitting terminal generates forms frequency domain to be sent by M-ary Quadrature Amplitude modulation (M-QAM) Data, then map that on each subcarrier, and it is made to meet conjugate symmetry and the 0th andA subcarrier data is 0. The final frequency domain data obtained is X=[X (0), X (1) ..., X (N-1)], meets following property:
AndWherein ()*Expression takes complex conjugate.
(2) time-domain signal that frequency-region signal is transformed to real number by N point IFFT is as follows:
Wherein n indicates the position of OFDM time-domain symbol, and j indicates imaginary symbols.
(3) by pre-distortion technology, the nonlinear characteristic of LED light is reduced to the simplification mathematical model of bilateral truncation, such as Shown in Fig. 3.Specific formula is as follows:
Wherein G (s) indicates simplified LED light nonlinear model, [λmin, λmax] indicate LED linear range.
First to time-domain signal at this time multiplied by controlling elements α, i.e. xd[n]=α x [n].Traditional DCO-OFDM added After direct current biasing can by be more than the LED light range of linearity signal directly carry out slicing, this meeting so that work as direct current biasing DC it is smaller or The truncation noise of whole system is very big when higher.And herein, the present invention one length of addition is the OFDM subframe of N to hold Carry the negative value for this partial information that can be shaved.X after then slicing is movedud[n] and x'ud[n] forms a data pair, wherein n =1,2,3 ..., N-1.The formula that specific slicing moves use is as follows:
Wherein, [λminmax] indicating LED linear range, DC is direct current biasing.
The process that slicing is moved is as shown in Figure 4, wherein LED linear range is [0,1], DC=0.3.Again respectively to xud[n] And x'ud[n] the two subframes add cyclic prefix.Assuming that the length of cyclic prefix is △, then the second subframe x'ud[n] compared to First subframe xud[n] sends delay N+ △ chronomere.Finally obtained OFDM symbol time domain waveform and structure difference As shown in Figure 5 and Figure 6.It can be seen that the OFDM symbol length after slicing is moved is extended to original twice.
(4) by through over-sampling and removing cyclic prefix after optical channel, receiving end receives the time-domain symbol that length is 2N. Removing DC bias DC is gone to rear N number of sequence again.Herein, N length is y before defining1[n], rear N length are y'2[n].Then y is used1 [n] subtracts y'2[n] obtains y [n], it may be assumed that y [n]=y1[n]-y'2[n]。
Then y [n] is carried out serioparallel exchange and to remove removing DC bias DC, then is carried out after the FFT transform of N point by equilibrium Device can obtain demodulated signal.
(5) mean value of the OFDM symbol finally sent is ID, and only there are also controlling elements α with direct current biasing DC for this value It is related.Definition light modulation depth η=(IDmin)/(λmaxmin).It, can be with by adjusting direct current biasing there are also the value of controlling elements α Achieve the purpose that adjust light intensity.But the performance of system not will receive the influence of direct current biasing DC size completely, and dimming scope obtains Greatly improve.Realize the low power illumination regulatory function under the premise of not losing information transmission reliability.Therefore the program is one A little low places of illuminance have a good application prospect.
Although the present invention in transmitting terminal to signal multiplied by controlling elements α, receiving end does not need to know this value, this It is because this coefficient may be considered a part of equivalent channel status information, the channel estimator of receiving end can be estimated This equivalent channel status information is counted out so as to the equilibrium of rear end.
Fig. 7 illustrates the present invention accessible spectrum efficiency and light modulation depth in the case where the LED light range of linearity is limited Curve.Simulated environment setting are as follows: NLOS channel, sub-carrier number N=128, E [x2[n]]=1, noise power is -10dbm, LED linear range is [0,1].Target bit is 210-3.DCO-OFDM and the accessible frequency of the present invention are compared in figure Spectrum efficiency and the curve graph for lightening depth.When emulation, the system proposed has carried out likelihood filtering in receiving end, even (y1[n]+y'2[n])∈[λminmax], then y'2[n] is judged as 0.For the justice compared, DCO-OFDM in time domain multiplied by One adaptation coefficient reduces non-linear distortion.As can be seen from the figure the dimming scope of traditional DCO-OFDM is smaller, When lighten depth it is higher or lower when just can not work on.And the performance of system used in the present invention is sufficiently stable, it can be with Reach very big and lighten range, and when lighten depth η > 80% or η < 20%, system used in the present invention can be with The spectrum efficiency reached can be more than DCO-OFDM.Even in extreme circumstances, when such as η=2%, system still be can achieve The spectrum efficiency of 0.75bit/s/Hz.
The above is only a preferred embodiment of the present invention, it should be pointed out that: for the ordinary skill people of the art For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered It is considered as protection scope of the present invention.

Claims (3)

1. a kind of lighten transmission of visible light method based on the ultra-wide that slicing is moved, it is characterised in that: pass through not adding script directly The DCO-OFDM time-domain symbol of stream biasing is first multiplied by a controlling elements, and then plus a length is the OFDM subframe of N, carries and adds Cross can be more than after direct current biasing LED linear range part information negative value;So that system reaches unrelated with dc-bias Stable state, to adjust light intensity by regulation direct-current bias value and controlling elements, the attainable range that lightens of institute is by controlling The factor processed determines.
2. according to claim 1 lighten transmission of visible light method based on the ultra-wide that slicing is moved, it is characterised in that: specific Steps are as follows:
Step 1 obtains the time-domain signal x [n] for the DCO-OFDM for not adding direct current biasing according to conventional method first, then at this time Time-domain signal multiplied by controlling elements α, i.e. xd[n]=α x [n];Then, it is the OFDM subframe of N to hold that a length, which is added, Carrying can be more than the negative value of this partial information of LED linear range plus direct current biasing;X after then slicing is movedud[n] and x'ud [n] forms a data pair, wherein n=1,2,3 ..., N-1;
Step 2, then respectively to xud[n] and x'ud[n] the two subframes add cyclic prefix, it is assumed that the length of cyclic prefix is △, then the second subframe will be delayed N+ △ chronomere compared to the first subframe to carry out frame and be multiplexed and finally plus required Dc-bias;The OFDM symbol x " finally sent in this wayud[n] length is 2 (N+ △);
Step 3 through over-sampling and removes cyclic prefix after optical channel, and receiving end obtains the time-domain symbol that length is 2N;Again Removing DC bias DC is gone to rear N number of sequence, N length is y before defining1[n], rear N length are y'2[n];Then after the former being subtracted Person;That is y [n]=y1[n]-y'2[n];
Y [n] is then carried out serioparallel exchange and removes removing DC bias DC by step 4, then is carried out the FFT transform of N point and carried out equal Weighing apparatus can obtain demodulated signal.
3. according to claim 2 lighten transmission of visible light method based on the ultra-wide that slicing is moved, it is characterised in that: step In one, slicing moves the formula of use are as follows:
Wherein, [λminmax] indicating LED linear range, DC is direct current biasing.
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* Cited by examiner, † Cited by third party
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CN110870223A (en) * 2017-06-05 2020-03-06 华为技术有限公司 Dimmable DC biased optical orthogonal frequency division multiplexing
CN107395274B (en) * 2017-06-13 2019-06-18 东南大学 A kind of implementation method of DCO-OFDM visible light communication Transmission system
CN108809433B (en) * 2018-04-04 2020-03-31 东南大学 DCO-OFDM modulation and demodulation method and device with phase modulation
EP3591861A1 (en) * 2018-07-06 2020-01-08 Signify Holding B.V. Optical data transmission system and method
CN109561043B (en) * 2019-01-08 2020-12-22 桂林电子科技大学 Mixed type peak-to-average power ratio suppression method in DCO-OFDM system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103986681A (en) * 2014-05-15 2014-08-13 东南大学 Low peak-to-average ratio wireless light transmission method with clipping moving
CN104184693A (en) * 2014-09-09 2014-12-03 东南大学 DCO-OFDM system direct current bias setting method applicable to visible light communication
CN104639252A (en) * 2013-11-13 2015-05-20 海思光电子有限公司 Method and system for locking offset point of light modulator
CN105515658A (en) * 2015-11-24 2016-04-20 广东顺德中山大学卡内基梅隆大学国际联合研究院 Precoded MIMO-OOFDM visible light communication method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100772504B1 (en) * 2005-12-01 2007-11-01 한국전자통신연구원 OFDM intensity modulation and direct detection apparatus and method with high transmission power efficiency in wire/wireless communication system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104639252A (en) * 2013-11-13 2015-05-20 海思光电子有限公司 Method and system for locking offset point of light modulator
CN103986681A (en) * 2014-05-15 2014-08-13 东南大学 Low peak-to-average ratio wireless light transmission method with clipping moving
CN104184693A (en) * 2014-09-09 2014-12-03 东南大学 DCO-OFDM system direct current bias setting method applicable to visible light communication
CN105515658A (en) * 2015-11-24 2016-04-20 广东顺德中山大学卡内基梅隆大学国际联合研究院 Precoded MIMO-OOFDM visible light communication method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
An Optimum DC-Biasing for DCO-OFDM System;Mingxuan Zhang and Zaichen Zhang;《IEEE COMMUNICATIONS LETTERS》;20140808;第18卷(第8期);第1351-1354页 *

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