CN106160873B - A kind of phase-shift coding method and realization device based on pulse amplitude modulation system - Google Patents
A kind of phase-shift coding method and realization device based on pulse amplitude modulation system Download PDFInfo
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- 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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/524—Pulse modulation
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- 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
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- 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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
- H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
- H04B10/5561—Digital phase modulation
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- 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
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/67—Optical arrangements in the receiver
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- 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
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/69—Electrical arrangements in the receiver
- H04B10/697—Arrangements for reducing noise and distortion
- H04B10/6971—Arrangements for reducing noise and distortion using equalisation
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Abstract
The invention belongs to technical field of visible light communication, specially a kind of phase-shift coding method and realization device that pulse amplitude modulation system is directly detected based on directly modulation.In the present invention, in system transmitting terminal, the parity symbols of consecutive symbol sequences are used with the phase-shift coding method of contrary sign；In system receiving terminal, the differential decoding method that delay is subtracted each other is carried out to the adjacent-symbol of receiving symbol.Its corresponding realization device includes phase-shift coder, PAM mapping block, string simultaneously/parallel serial conversion module, up-sampling module, LED and its drive module in transmitting terminal；It include differential decoder, serioparallel exchange module, post-equalization module, PAM De-mapping module, clock synchronization module, normalization module, down-sampled module, condenser lens, optical filter and receiver in receiving end.Use apparatus of the present invention and decoding method, intrinsic crosstalk noise between DC component and signal present in the visible light communication system based on pulse amplitude modulation format can effectively be eliminated, increase receiver sensitivity, improves signal transmission quality, effectively improve system performance.And this method realizes that process is simple, is easily integrated.
Description
Technical field
The invention belongs to technical field of visible light communication, and in particular to one kind is based on pulse amplitude modulation (PAM) system
Phase shift (PS) coding method and realization device.
Background technique
Currently, be widely used white light emitting diode (LED, light emitting diode) every field, such as
Illumination, signal transmitting, display etc..It is compared with other Ordinary Light Sources Haves such as incandescent lamp, fluorescent lamps, white light LEDs have higher tune
Bandwidth processed.The many merits such as modulating performance is good in addition, white light LEDs also have, response sensitivity is high.Using these characteristics of LED,
We can modulate the signal on the light of LED sending and transmit, to realize the effective integration of illumination and communication.Visible light
Communication (VLC, Visible Light Communication) is exactly a kind of fast response characteristic realization high speed number using LED
According to the novel green information technology of transmission.
Compared with other wireless communication techniques, that there are also transmission rates is high for VLC technology, safety is good, strong security, without electromagnetism
The advantages that radiating, be environmentally protective, it has also become the hot spot of communications field research in recent years.But its develop there is also some limitations because
Element, one of them important challenge are exactly that the limited bandwidth of LED limits the transmission rate and system performance of VLC system.In order to
Realize the high-speed transfer of VLC system, researcher generally carries out coding tune to initial data using advanced high order modulation technique
System.Wherein, pulse amplitude modulation has obtained extensive research application as a kind of simple and easy modulation system.Also,
In 802.3 joint conference of IEEE 802.1/IEEE in 2015, PAM4 becomes the new mark of IEEE P802.3bs 400Gbs
It is quasi-, it can be seen that PAM modulation technique is a kind of practicability transmission plan for having much potentiality.
But for directly modulating the PAM visible light communication system directly detected, crosstalk is made an uproar between existing signal
Sound can also have certain shadow by severe exacerbation system performance, and due to directly detecting bring intrinsic frequency noise to system performance
It rings.In response to this problem, decoding method proposed by the present invention, by controlling the spectrum shape of encoded signal in transmitting terminal, in receiving end
Phase reducing is carried out to adjacent symbol, can inhibit the DC component and quadratic term noise of signal, mitigates noise to system performance
Deteriorate, lifting system performance.
Summary of the invention
The purpose of the present invention is to provide a kind of based on directly modulating pulse amplitude modulation (PAM) system directly detected
Phase-shift coding method and realization device solve existing PAM modulation skill for realizing the visible light high-speed communication modulated based on PAM
Serious problem is influenced in art by signal crosstalk noise, to improve the transmission performance of system.
The phase-shift coding method provided by the invention that PAM system is directly detected based on directly modulation, to the surprise of original signal
Even symbol uses the phase-shift coding mode of contrary sign, uses the differential decoding mode for postponing to subtract each other, specific table to signal is received
It is existing are as follows: the low frequency component for controlling the PAM signal of base band transmission its frequency spectrum inhibits between its DC component and signal to signal is received
Crosstalk noise.
Specifically, carrying out phase-shift coding in transmitting terminal to the modulated signal of PAM, modulated PAM symbol being divided into
Different block of symbols, every group of block of symbols includes two continuous symbols, and second symbol is the anti-of first symbol.Wherein send out
Penetrate the Baseband PAM signal in k-th of the block of symbols in endWithIt can respectively indicate are as follows:
Wherein,Indicate the symbol of PAM mapping.
In receiving end, differential decoding is carried out to signal, obtains photoelectric current.Photoelectric current in the kth group block of symbols of receiving endIt may be expressed as:
Wherein, coefficientIndicate the intensity rate of PAM baseband signal；WithRespectively indicate LED bias voltage and
Backward voltage；WithRespectively indicate the noise electricity in kth group block of symbols in 2k-1 and 2k symbol
Stream.
The invention also discloses it is a kind of based on directly modulate PAM system phase-shift coding and differential decoding realization device,
Including corresponding transmitting terminal and receiving end；It include phase-shift coder, PAM mapping block, string simultaneously/parallel-serial conversion in the transmitting terminal
Module up-samples module, LED and its drive module；It include differential decoder in the receiving end, serioparallel exchange module is rear equal
Weigh module, PAM De-mapping module, and clock synchronization module normalizes module, down-sampled module, condenser lens, optical filter and reception
Machine；Wherein:
The phase-shift coder, for carrying out phase-shift coding to signal；
The PAM mapping block, the coded modulation for signal；
String simultaneously/the parallel serial conversion module, for the sequence transformation before and after Signal coding；
The up-sampling module, the up-sampling for signal；
The LED and its drive module, for will launch in signal loading to LED and by free space；
The differential decoder, for carrying out differential decoding to signal；
The serioparallel exchange module is used for the decoded sequence transformation of signal；
The post-equalization module, for the equilibrium to decoded signal；
The PAM De-mapping module, for PAM signal to be demodulated to binary bit stream；
The clock synchronization module, for receive signal carry out Clock Extraction with it is synchronous；
The normalization module, for doing mean power normalized to reception signal；
The down-sampled module, for the down-sampled of signal；
The condenser lens, optical filter and receiver, for optical signal reception and convert optical signals to electric signal.
The present invention using wavelength-division multiplex (WDM) technology transmitted on three wave bands of red, green, blue different wave length based on phase shift
The PAM signal of coding carries out corresponding differential decoding in receiving end, it can be achieved that phase-shift coding PAM signal is in visible light communication system
High-speed transfer in system.
The workflow of apparatus of the present invention is as follows:
In transmitting terminal:
(1) PAM mapping block carries out PAM mapping to original binary bit stream, generates the PAM signal of more level；
(2) up-sampling module carries out 2 times of up-samplings to the PAM symbol after mapping, prepares for the serial to parallel conversion of signal；
(3) serioparallel exchange module carries out serial to parallel conversion to signal, and serial signal is divided into two-way parallel signal, compiles for phase shift
Code is prepared；
(4) second road signal of input is negated and postpones T/2 bit by phase-shift coder；
(5) parallel two paths of signals is merged into signal all the way by parallel serial conversion module, so that closely following after each code element signal
Its inverted signal；
(6) up-sampling module up-samples the signal after coding, for inputting arbitrary waveform generator (AWG)；
(7) signal that LED and its drive module emit AWG passes through preequalization plate, electric amplifier and alternating current-direct current coupling with this
Transmitting signal and bias voltage are coupled on RGB (RGB) LED by clutch, and launch by free space.
In receiving end:
(1) receiver distinguishes the transmission signal of three different-wavebands of red, green, blue by condenser lens, optical filter, then leads to
It crosses receiver and received optical signal is converted into electric signal, and signal is acquired with complete with the real-time oscilloscope of high-speed sampling
At the processed offline of next step；
(2) the signal progress clock that clock synchronization module acquires oscillograph is synchronous, finds signal heads；
(3) normalization module normalizes reception signal with mean power；
(4) down-sampled module is down-sampled to 4 times of signal progress is received；
(5) serial signal is converted into parallel two paths of signals by serioparallel exchange module, is prepared for differential decoding；
(6) parallel second road signal is postponed T/2 bit by differential decoder, and after subtracting delay with first via signal
Second road signal obtains decoded signal；
(7) post-equalization module carries out post-equalization to decoded signal with the intersymbol interference of thermal compensation signal；
(8) PAM signal demapping is binary bit stream by PAM De-mapping module.
The beneficial effects of the present invention are: the visible light biography of PAM modulated signal is carried out using phase-shift coding and differential decoding
It is defeated, the crosstalk noise received between DC component and signal in signal can be effectively suppressed, improve the sensitivity of receiver.The present invention
Suitable for visible light communication field, crosstalk noise severe exacerbation system in the visible light communication system for solving to modulate based on PAM
The problem of performance of uniting, the greatly transmission performance of lifting system.
Detailed description of the invention
The PAM signal schematic representation of Fig. 1 phase-shift coding proposed by the present invention.
Fig. 2 PAM system implementation device schematic diagram proposed by the present invention based on phase-shift coding.
Application schematic diagram of Fig. 3 present invention in the visible light communication system based on WDM.
The PAM signal of Fig. 4 phase-shift coding proposed by the present invention and uncoded PAM signal spectrum comparison diagram.
The uncoded PAM-8 receipt signal frequency spectrum of Fig. 5.
The PAM-8 receipt signal frequency spectrum of Fig. 6 phase-shift coding proposed by the present invention.
The PAM-8 of Fig. 7 phase-shift coding proposed by the present invention directly decode after signal spectrum.
Signal spectrum after the PAM-8 differential decoding of Fig. 8 phase-shift coding proposed by the present invention.
Fig. 9 is uncoded, phase-shift coding and directly decodes and the PAM-8 signal constellation (in digital modulation) figure of phase-shift coding and differential decoding.
The PAM-8 signal of phase-shift coding is in differential decoding and bit error rate performance when directly decoding in the transmission of Figure 10 feux rouges
With the research of bit rate variation.
The PAM-8 signal of phase-shift coding in Figure 11 green light transmission is in differential decoding and bit error rate performance when directly decoding
With the research of bit rate variation.
The PAM-8 signal of phase-shift coding in Figure 12 blue transmission is in differential decoding and bit error rate performance when directly decoding
With the research of bit rate variation.
The PAM-8 signal error rate performance of phase-shift coding and differential decoding is with grinding than distance change in the transmission of Figure 13 feux rouges
Study carefully.
The PAM-8 signal error rate performance of phase-shift coding and differential decoding is with grinding than distance change in Figure 14 green light transmission
Study carefully.
The PAM-8 signal error rate performance of phase-shift coding and differential decoding is with grinding than distance change in Figure 15 blue transmission
Study carefully.
Specific embodiment
To make the object, technical solutions and advantages of the present invention clearer, below in conjunction with attached drawing to each reality of the invention
The mode of applying is explained in detail.
The purpose of the present invention is to provide a kind of based on directly modulating the pulse amplitude modulation system (PAM) directly detected
Phase shift (PS) coding method and its realization device in visible light communication system.This method can reduce system intrinsic noise and signal
Between influence of the crosstalk noise to system, improve system performance, obtain higher transmission rate.We will be from principle analysis and experiment
Specific embodiment is discussed in detail in terms of transmission two.
One, principle analysis
Coding schematic diagram proposed by the present invention is as shown in Fig. 1.In the phase-shift coder of transmitting terminal, by continuous symbol
It is divided into different blocks, includes two code elements in every group of block of symbols, make the symbol of second symbol and first symbol completely opposite.
In set of symbols, first group of first symbol is, second symbol in first group be, and so on, in kth group
A symbol be, second symbol。
Baseband PAM signal after coding may be expressed as:
(1)
(2)
Wherein,Indicate the symbol of PAM mapping.
By AC-DC coupling device by the PAM signal modulation to LED light after coding, the signal of LED transmitting be may be expressed as:
(3)
Wherein,WithRespectively indicate the bias current and reverse current of LED；CoefficientIndicate the intensity of PAM signal；Indicate the luminous centre frequency of LED；Indicate unit coefficient；Indicate the time.
After free space transmission, receive signal may be expressed as: the signal of LED transmitting
(4)
Wherein,Indicate additive white Gaussian noise.
Receiver can convert optical signals to electric signal.Since receiver uses square-law to detect, then kth group symbol
In signal code can approximate representation are as follows:
(5)
(6)
(7)
Wherein,It is that first item indicates to receive the direct current point of signal in noise formula (5) that receiver is introduced into
Amount, Section 2 indicate that signal component, Section 3 indicate the crosstalk noise between signal, and Section 4 is its as listed by equation (6)
His noise.AWGN is indicated in formula (6) to the beat frequency noise of AWGN, Section 2 indicates signal to the beat frequency noise of AWGN.
Section 2 photoelectric current in k-th of block of symbols can be indicated with formula (7).Subtract each other behaviour by equation (5) and equation (7)
Make, the photoelectric current that can be obtained in k-th of block of symbols is as follows:
(8)
Wherein, first item indicates signal, and Section 2 indicates noise.Compare equation (8) and equation (5), it is possible to find signal
DC component and quadratic term crosstalk noise can all be completely eliminated, and receive one times of enhanced strength of signal, that is, receive clever
3dB can be improved in sensitivity.It can be seen that the signal-to-noise ratio of system can be effectively improved using phase-shift coding and differential decoding method, thus
Improve system performance.
Two, transmission experiment
In order to test feasibility of this method in visible light communication system, we use the direct tune based on phase-shift coding
The realization device of PAM system processed has carried out transmission confirmatory experiment.The schematic device and system architecture figure of the system are respectively as attached
Shown in Fig. 2 and attached drawing 3.Its realization device includes transmitting terminal and receiving end.
Include phase-shift coder, PAM mapping block, string simultaneously/parallel serial conversion module, LED and its driving in the transmitting terminal
Module etc..It comprises the steps of:
Step 101:PAM mapping block carries out PAM mapping to original binary bit stream, generates the PAM letter of more level
Number；
Step 102: up-sampling module carries out 2 times of up-samplings to the PAM symbol after mapping, does for the serial to parallel conversion of signal
Prepare；
Step 103: serioparallel exchange module carries out serial to parallel conversion to signal, serial signal is divided into two-way parallel signal, is
Phase-shift coding is prepared；
Step 104: the second road signal of input is negated and postpones T/2 bit by phase-shift coder；
Step 105: parallel two paths of signals is merged into signal all the way by parallel serial conversion module, so that each code element signal
Its inverted signal is closely followed afterwards；
Step 106: up-sampling module up-samples the signal after coding, for inputting arbitrary waveform generator
(AWG).
The signal of AWG transmitting is passed through preequalization plate, electric amplifier and friendship with this by step 107:LED and its drive module
Transmitting signal and bias voltage are coupled on RGB (RGB) LED by DC coupler, and launch by free space.
Include differential decoder, PAM De-mapping module, serioparallel exchange module, receiver module etc. in the receiving end.Packet
Containing following steps:
Step 201: receiver module distinguishes the transmission of three different-wavebands of red, green, blue by condenser lens, optical filter
Then received optical signal is converted to electric signal by receiver by signal, and with the real-time oscilloscope of high-speed sampling to signal
It is acquired to complete the processed offline of next step；
Step 202: the signal of oscillograph acquisition is carried out clock and synchronized, finds signal heads by clock synchronization module；
Step 203: normalization module is normalized to signal is received with mean power；
Step 204: down-sampled module, to receiving, 4 times of signal progress is down-sampled；
Step 205: serial signal is converted into parallel two paths of signals, prepared for differential decoding by serioparallel exchange module；
Step 206: parallel second road signal is postponed T/2 bit, and is subtracted and prolonged with first via signal by differential decoder
The second road signal to lag, obtains decoded signal；
Step 207: post-equalization module carries out post-equalization to decoded signal with the intersymbol interference of thermal compensation signal；
PAM signal demapping is binary bit stream by step 208:PAM De-mapping module.
The division of each step in present embodiment, be intended merely to describe it is clear, when realization can be merged into a step or
Person splits certain steps, is decomposed into multiple steps, as long as comprising identical logical relation, all in protection model of the invention
In enclosing.
It will be understood by those skilled in the art that the respective embodiments described above are to realize specific embodiments of the present invention,
And in practical applications, can to it, various changes can be made in the form and details, without departing from the spirit and scope of the present invention.
The signal transmission that we tested above-mentioned experimental provisions in the free space that distance is 1 ~ 2m.Fig. 4 is the present invention
The PAM signal of the phase-shift coding of proposition and uncoded PAM signal spectrum comparison diagram.It is low in spectrogram after coding can be seen
Frequency ingredient is inhibited, and radio-frequency component is retained as far as possible, this spectrum shape is conducive to resist the low frequency in visible light channel transmission
Decaying.
Fig. 5 is the uncoded PAM-8 receipt signal frequency spectrum after the free space transmission of 1m.It can be seen that the frequency spectrum has
Very big DC component, and have very strong signal fadeout and distortion at frequency spectrum low frequency.This is because visible light channel is at low frequency
There is very big signal decaying.And the AC-DC coupling device in this experimental provision cannot pass through the DC component of signal, received spectrum
In DC component be by receiver square-law detection introduce fixed frequency noise component(s).Therefore, for uncoded reception
Signal, performance impairment is serious, cannot directly transmit in visible light channel.
Fig. 6 is the uncoded PAM-8 receipt signal frequency spectrum after the free space transmission of 1m.The frequency spectrum is in 400MHz
Bandwidth in it is all relatively flat.
Fig. 7 is the signal spectrum after the PAM-8 of phase-shift coding proposed by the present invention is directly decoded.The frequency spectrum exists by receiving
The DC component and more rich low-frequency noise that the detection of machine square-law introduces.
Fig. 8 is the signal spectrum after the PAM-8 differential decoding of phase-shift coding proposed by the present invention.Direct current is not present in the frequency spectrum
Component, and noise intensity is greatly inhibited.
Fig. 9 is uncoded, phase-shift coding and directly decodes and the PAM-8 signal constellation (in digital modulation) figure of phase-shift coding and differential decoding.
It can be seen that uncoded signal performance is worst, original signal cannot be solved completely；The signal that phase shift S is encoded and directly decoded
It；The signal performance of phase-shift coding and differential decoding is optimal, can recover original signal.
The present invention is also tested at different rates, and the signals of three kinds of color optical transports of red, green, blue is directly decoding and poor
Bit error rate performance in the case of decomposition code, respectively as shown in figs. 10,11 and 12.It can be seen that under 7% FEC thresholding, Difference Solution
The total rate of signal of code is up to 3.375Gb/s(feux rouges: 1.35Gb/s；Green light: 0.975Gb/s；Blue light: 1.05Gb/s)；Directly
The decoded total rate of signal is all 600Mb/s up to the rate of tri- kinds of color of light of 1.8Gb/s().Therefore pass through differential decoding, speed
Rate improves 1.575Gb/s.
In addition, being also tested for the change of signal bit error rate performance in different distance of three kinds of color optical transports of red, green, blue
Change, respectively as shown in Figure 13, Figure 14, Figure 15.Under the transmission range of 1m, 1.5m and 2m, transmission rate is respectively 3.375Gb/
S, 3.225-Gb/s and 2.925-Gb/s.
Above-mentioned transmission experiment demonstrates phase-shift coding scheme and implementing device in the visible light communication system modulated based on PAM
Feasibility and inhibiting effect to system noise, system performance, which can get, greatly to be promoted.
Claims (3)
1. a kind of based on the phase-shift coding method for directly modulating the pulse amplitude modulation system directly detected, it is characterised in that original
The parity character of beginning signal uses the phase-shift coding mode of contrary sign, uses the differential decoding side for postponing to subtract each other to signal is received
Formula；Specific manifestation are as follows: the low frequency component for controlling the PAM signal of base band transmission its frequency spectrum inhibits its direct current point to signal is received
Crosstalk noise between amount and signal；
In transmitting terminal, continuous transmitting signal is divided into different block of symbols, each code element block includes two adjacent symbols, and
Second symbol is the anti-of first symbol；Wherein, the Baseband PAM signal in k-th of block of symbols of transmitting terminalE 2k-1 (t)WithE 2k (t)It respectively indicates are as follows:
Wherein,a k Indicate the symbol of PAM mapping；
Photoelectric current in receiving end, kth group block of symbolsI bk (t)It indicates are as follows:
Wherein, coefficient a indicates the intensity rate of PAM baseband signal；V 0 WithV a Respectively indicate the bias voltage and backward voltage of LED；WithRespectively indicate the noise current in kth group block of symbols in 2k-1 and 2k symbol.
2. a kind of realization device based on the phase-shift coding method for directly modulating the pulse amplitude modulation system directly detected, including
Corresponding transmitting terminal and receiving end；It is characterized by: in the transmitting terminal include phase-shift coder, PAM mapping block, string simultaneously/
Parallel serial conversion module up-samples module, LED and its drive module；It include differential decoder, serioparallel exchange mould in the receiving end
Block, post-equalization module, PAM De-mapping module, clock synchronization module normalize module, down-sampled module, and condenser lens filters
Piece and receiver；Wherein:
The phase-shift coder, for carrying out phase-shift coding to signal；
The PAM mapping block, the coded modulation for signal；
String simultaneously/the parallel serial conversion module, for the sequence transformation before and after Signal coding；
The up-sampling module, the up-sampling for signal；
The LED and its drive module, for will launch in signal loading to LED and by free space；
The differential decoder, for carrying out differential decoding to signal；
The serioparallel exchange module is used for the decoded sequence transformation of signal；
The post-equalization module, for the equilibrium to decoded signal；
The PAM De-mapping module, for PAM signal to be demodulated to binary bit stream；
The clock synchronization module, for receive signal carry out Clock Extraction with it is synchronous；
The normalization module, for doing mean power normalized to reception signal；
The down-sampled module, for the down-sampled of signal；
The condenser lens, optical filter and receiver, for optical signal reception and convert optical signals to electric signal.
3. realization device as claimed in claim 2, it is characterised in that: the workflow of device is as follows:
In transmitting terminal:
(1) PAM mapping block carries out PAM mapping to original binary bit stream, generates the PAM signal of more level；
(2) up-sampling module carries out 2 times of up-samplings to the PAM symbol after mapping, prepares for the serial to parallel conversion of signal；
(3) serioparallel exchange module carries out serial to parallel conversion to signal, and serial signal is divided into two-way parallel signal, is done for phase-shift coding
Prepare；
(4) second road signal of input is negated and postpones T/2 bit by phase-shift coder；
(5) parallel two paths of signals is merged into signal all the way by parallel serial conversion module, so that anti-immediately following it after each code element signal
Signal；
(6) up-sampling module up-samples the signal after coding, for inputting arbitrary waveform generator AWG；
(7) signal that LED and its drive module emit AWG passes through preequalization plate, electric amplifier and AC-DC coupling device with this,
Transmitting signal and bias voltage are coupled on RGB (RGB) LED, and launched by free space；
In receiving end:
(1) receiver distinguishes the transmission signal of three different-wavebands of red, green, blue by condenser lens, optical filter, then by connecing
Received optical signal is converted to electric signal by receipts machine, and is acquired under completion with the real-time oscilloscope of high-speed sampling to signal
The processed offline of one step；
(2) the signal progress clock that clock synchronization module acquires oscillograph is synchronous, finds signal heads；
(3) normalization module normalizes reception signal with mean power；
(4) down-sampled module is down-sampled to 4 times of signal progress is received；
(5) serial signal is converted into parallel two paths of signals by serioparallel exchange module, is prepared for differential decoding；
(6) parallel second road signal is postponed T/2 bit by differential decoder, and subtracts second after postponing with first via signal
Road signal, obtains decoded signal；
(7) post-equalization module carries out post-equalization to decoded signal with the intersymbol interference of thermal compensation signal；
(8) PAM signal demapping is binary bit stream by PAM De-mapping module.
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| CN110266396B (en) * | 2019-06-21 | 2020-08-25 | 上海交通大学 | Optical PAM-4 signal receiver and all-optical quantization method |
| CN110727681B (en) * | 2019-09-27 | 2022-07-08 | 北京智道合创科技有限公司 | Data storage method and device |
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