CN103490825A - Multi-light-source OFDM emitting method and emitter used for visible light communications - Google Patents
Multi-light-source OFDM emitting method and emitter used for visible light communications Download PDFInfo
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Abstract
Disclosed is a multi-light-source OFDM emitting method used for visible light communications. The multi-light-source OFDM emitting method comprises the steps that modulating symbols are divided into N routes through serial-parallel conversion and are modulated onto N routes of sub carrier waves from f<0> to f<N-1> to obtain N routes of subcarrier wave signals, the N routes of subcarrier wave signals are loaded to N LED light sources to respectively generate a light signal, and the LED light sources are separated from one another so that the light signals can be overlapped in space. The invention further provides a multi-light-source OFDM emitter used for visible light communications. The invention further provides a multi-light-source emitter used for visible light communications. The multi-light-source OFDM emitter comprises a serial/parallel conversion module used for converting the modulating symbols into the N routes, a modulating module used for modulating the N routes of signals onto the N routes of subcarrier waves from f<0> to f <N-1> respectively, and the N LED light sources which are used for loading the N routes of subcarrier waves so as to generate the light signals. The multi-light-source OFDM emitter can obviously reduce the requirements for the linear region range of devices, and meanwhile, improve the power efficiency to a certain degree.
Description
Technical field
The invention belongs to communication technical field, particularly for multiple light courcess OFDM launching technique and the transmitter of visible light communication.
Background technology
It is universal rapidly that the LED lighting technology relies on the advantages such as self is energy-conservation, the life-span long, reliable to be able to, and the visible light communication technology based on white light LEDs is also risen thereupon.The visible light communication technology has been utilized the high-speed switch response characteristic of LED, form by load information with illumination light sends by free space, utilize the PD(photodiode simultaneously) etc. electrooptical device receiving optical signals convert the signal of telecommunication to, and then obtaining information.But the band width in physical of LED is limited is a bottleneck of this Technique Popularizing of restriction.
OFDM is a kind of special Multicarrier Transmission Technology, and it is by the parallel low rate symbol that changes into of the information symbol of two-forty, then parallel emission on the subcarrier of a plurality of quadratures.It can reduce the impact that frequency selective fading is brought, and the higher availability of frequency spectrum is arranged, and has greatly weakened the impact that the bandwidth restricted of LED causes to communication performance, in the visible light communication field, is a popular research topic.
As shown in Figure 1, the ingenious part of this structure is traditional ofdm system structured flowchart, by an IFFT, can directly multichannel sub-carrier signal aliasing signal together be calculated, and not need to calculate separately each way carrier wave.In addition, the maturity of FFT/IFFT algorithm is very high, has reduced equally the amount of calculation of this structure.
The typical structure of ofdm system is used for to visible light communication, the emission of signal realizes as shown in Figure 2 with reception, yet, ofdm signal has high peak power, its peak-to-average power ratio (PAPR) is very large, and not only greatly reducing power efficiency (because LED can't modulate the negative value signal, needs to strengthen direct current biasing, perhaps reduce signal amplitude), and the linear zone scope of device has been proposed to harsh requirement (guaranteeing that the serious nonlinear distortions such as amplitude cut-off do not occur signal).
Summary of the invention
In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide multiple light courcess OFDM launching technique and transmitter for visible light communication, can reduce significantly the demand to the linear zone scope of device, improve to a certain extent power efficiency simultaneously.
To achieve these goals, the technical solution used in the present invention is:
A kind of OFDM of the multiple light courcess for visible light communication launching technique, be divided into the N road by modulation symbol through going here and there and changing, and is modulated to respectively N way carrier wave f
0to f
n-1on obtain N way carrier signal, described N way carrier signal is loaded on N LED light source and produces respectively a light signal, the phase mutual edge distance of described LED light source makes described light signal superpose in space.
Wherein said N way carrier wave f
0to f
n-1mutually orthogonal.
When the distance L of receiving terminal and transmitting terminal, much larger than between LED light source during apart from d (L >=10d), receiving terminal reduces ofdm signal with FFT.
Further, can use lookup table technology pre-stored the signal waveform that will send, when producing sub-carrier signal, by the mode of tabling look-up, find corresponding waveform.
Further, each LED light source is all added to direct current biasing, the big or small D that setovers higher than the peak-to-peak value of signal lower than the range of linearity of LED light source.
Further, the phase mutual edge distance of described LED light source is 2-20cm.
The present invention also provides a kind of OFDM of the multiple light courcess for visible light communication transmitter, comprising:
For the modulation symbol conversion being divided into to the serial/parallel modular converter on N road;
For described N road signal is modulated to respectively to N way carrier wave f
0to f
n-1on modulation module;
And for loading described N way carrier wave to produce N LED light source of light signal;
The phase mutual edge distance of wherein said LED light source makes described light signal superpose in space.
Further, transmitter of the present invention also comprises the memory module that stores signal waveform to be sent and the enquiry module that connects memory module and serial/parallel modular converter.
Further, transmitter of the present invention also comprises the direct current biasing module be added on each LED light source.
Compared with prior art, the invention has the beneficial effects as follows:
1) reduce the peak-to-average power ratio of signal, thereby reduce the demand to the linear zone scope of device.
2) reduce the power that direct current biasing consumes, improve the power efficiency of transmitter.
The accompanying drawing explanation
Fig. 1 is the typical structure schematic diagram of ofdm system.
Fig. 2 is the emission and reception schematic diagram of signal in visible light communication.
Fig. 3 is the basic structure schematic diagram of OFDM transmitter of the present invention.
Fig. 4 is the schematic diagram of OFDM transmitter of the present invention.
Fig. 5 is 16QAM signal constellation and mapping of the present invention.
Fig. 6 is a kind of LED light source schematic diagram that loads 4 way carrier waves.
Embodiment
Describe embodiments of the present invention in detail below in conjunction with drawings and Examples.
The present invention abandons using IFFT to produce the time-domain signal of multichannel subcarrier aliasing, but uses multiple light courcess to produce.Wherein, each light source produces separately the single sub-carrier signal.Close proximity between each light source, the light signal of generation has individual overlapping in space.When the distance of receiver and transmitter be greater than light source directly apart from the time, receiver can reduce ofdm signal with FFT.
The basic structure of OFDM transmitter as shown in Figure 3, comprises for modulation symbol conversion is divided into to the serial/parallel modular converter on N road, for described N road signal is modulated to respectively to N way carrier wave f
0to f
n-1on modulation module, for loading described N way carrier wave with the enquiry module of N the LED light source that produces light signal, the memory module that stores signal waveform to be sent and connection memory module and serial/parallel modular converter and being added in the direct current biasing module on each LED light source, the phase mutual edge distance of wherein said LED light source makes described light signal superpose in space.
Launching technique of the present invention, as shown in Figure 4, modulation symbol still is divided into the N road through serial/parallel conversion, is modulated to respectively N way carrier wave f
0to f
n-1on obtain N way carrier signal.These subcarriers are mutually quadratures
n way carrier signal is loaded on N LED light source that leans on very closely.These light signals superpose in space, and receiver can receive the superposed signal of these light signals and restore the symbol on each way carrier wave by FFT.
In order to make up the defect that causes amount of calculation to rise because abandoning IFFT, when producing sub-carrier signal, the present invention has used lookup table technology (LUT).The signal waveform that will send is left in memory device in advance, when producing signal, by the mode of tabling look-up, find corresponding waveform.
It is the same that the signal that the present invention sends sends with the OFDM classical architecture, is all digital signal.
By IFFT, calculating be N the superposed signal on time domain point, and in the present invention, each light source calculates separately N the sub-carrier signal on time domain point.
The value of symbol that for example will send is X
k, the subcarrier of use is f
l, so, needing in advance stored value in memory device is X
k,
data, N altogether.
Owing to adopting digital signal, the number of the symbol of modulating is limited (for example 64QAM has 64 symbols), is designated as q, and so, every way carrier wave is when a symbol of transmission, and time domain waveform has possibility in q.For every kind of possibility, need to calculate N point.One total N subcarrier, therefore, be limited to N on the data volume that needs to store
2q.
According to the mode of sign map, memory space has the space of continuing optimization.Such as for QAM, as shown in Figure 5, can utilize the symmetry of planisphere, memory space is reduced to original 1/4.
Fig. 6 is a kind of LED light source schematic diagram that loads 4 way carrier waves, four lamp pearls 5 are arranged in Lamp cup 6, respectively the first LED light source 1, the second LED light source 2, the 3rd LED light source 3 and the 4th LED light source 4, spacing all is controlled between 2-20cm each other, so that the light signal produced can be overlapping in space.
Because LED light source can't send the negative value signal, each light source adds separately direct current biasing.Setovering big or small D will be higher than the peak-to-peak value of signal lower than the range of linearity of LED light source.Because different sub carrier adds respectively direct current biasing, so the more traditional IFFT scheme of direct current biasing is much lower.The biasing size of supposing l light source is D
l, ignore the protection interval, the biasing size that the IFFT scheme needs so is
The relation that power with respect to amplitude is square.Because
therefore the present invention program's direct current power is lower than traditional IFFT scheme.Especially, if D
0=D
1=...=D
n-1=D,
direct current power can drop to the 1/N of traditional scheme.
Claims (10)
1. the OFDM of the multiple light courcess for a visible light communication launching technique, be divided into the N road by modulation symbol through going here and there and changing, and is modulated to respectively N way carrier wave f
0to f
n-1on obtain N way carrier signal, it is characterized in that, described N way carrier signal is loaded on N LED light source and produces respectively a light signal, and the phase mutual edge distance of described LED light source makes described light signal superpose in space.
2. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 1, is characterized in that, described N way carrier wave f
0to f
n-1mutually orthogonal.
3. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 1, is characterized in that, when the distance L of receiving terminal and transmitting terminal, much larger than between LED light source during apart from d, receiving terminal reduces ofdm signal with FFT.
4. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 3, is characterized in that, while between the distance L of described receiving terminal and transmitting terminal and LED light source, apart from d, meeting L >=10d, receiving terminal reduces ofdm signal with FFT.
5. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 1, is characterized in that, uses lookup table technology pre-stored the signal waveform that will send, and when producing sub-carrier signal, by the mode of tabling look-up, finds corresponding waveform.
6. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 1, is characterized in that, each LED light source is all added to direct current biasing, the big or small D that setovers higher than the peak-to-peak value of signal lower than the range of linearity of LED light source.
7. the OFDM of the multiple light courcess for visible light communication launching technique according to claim 1, is characterized in that, the phase mutual edge distance of described LED light source is 2-20cm.
8. the OFDM of the multiple light courcess for a visible light communication transmitter, is characterized in that, comprising:
For the modulation symbol conversion being divided into to the serial/parallel modular converter on N road;
For described N road signal is modulated to respectively to N way carrier wave f
0to f
n-1on modulation module;
And for loading described N way carrier wave to produce N LED light source of light signal;
The phase mutual edge distance of wherein said LED light source makes described light signal superpose in space.
9. the OFDM of the multiple light courcess for visible light communication transmitter according to claim 8, is characterized in that, also comprises the memory module that stores signal waveform to be sent and the enquiry module that connects memory module and serial/parallel modular converter.
10. the OFDM of the multiple light courcess for visible light communication transmitter according to claim 8 or claim 9, is characterized in that, also comprises the direct current biasing module be added on each LED light source.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106992814A (en) * | 2017-06-02 | 2017-07-28 | 东南大学 | A kind of visible ray multi-carrier communications systems emitter design method based on distributed multiple light courcess |
| CN109818633A (en) * | 2018-12-19 | 2019-05-28 | 武汉船舶通信研究所（中国船舶重工集团公司第七二二研究所） | The signal transmitting method and device synthesized based on SCPC array and symbol space |
| CN109831270A (en) * | 2019-01-28 | 2019-05-31 | 钟林晟 | A kind of visible optical privacy communication system and encryption method |
| CN110048773A (en) * | 2019-03-15 | 2019-07-23 | 哈尔滨工业大学（深圳） | Visible light communication method, signal processing method, system and storage medium |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3060912A1 (en) * | 2016-12-21 | 2018-06-22 | Universite de Bordeaux | DEVICE FOR GENERATING A DIGITAL SIGNAL MODULE AND SYSTEM FOR GENERATING AN ANALOGUE SIGNAL MODULE |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106992814A (en) * | 2017-06-02 | 2017-07-28 | 东南大学 | A kind of visible ray multi-carrier communications systems emitter design method based on distributed multiple light courcess |
| CN106992814B (en) * | 2017-06-02 | 2019-05-28 | 东南大学 | A kind of visible light multi-carrier communications systems transmitter design method based on distributed multiple light courcess |
| CN109818633A (en) * | 2018-12-19 | 2019-05-28 | 武汉船舶通信研究所（中国船舶重工集团公司第七二二研究所） | The signal transmitting method and device synthesized based on SCPC array and symbol space |
| CN109818633B (en) * | 2018-12-19 | 2021-03-02 | 武汉船舶通信研究所（中国船舶重工集团公司第七二二研究所） | Signal transmitting method and device based on SCPC array and symbol space synthesis |
| CN109831270A (en) * | 2019-01-28 | 2019-05-31 | 钟林晟 | A kind of visible optical privacy communication system and encryption method |
| CN109831270B (en) * | 2019-01-28 | 2022-01-04 | 钟林晟 | Visible light secret communication system and encryption method |
| CN110048773A (en) * | 2019-03-15 | 2019-07-23 | 哈尔滨工业大学（深圳） | Visible light communication method, signal processing method, system and storage medium |
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