CN108337047A - A kind of time domain hybrid modulation method based on visible light communication system - Google Patents
A kind of time domain hybrid modulation method based on visible light communication system Download PDFInfo
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- CN108337047A CN108337047A CN201810244156.2A CN201810244156A CN108337047A CN 108337047 A CN108337047 A CN 108337047A CN 201810244156 A CN201810244156 A CN 201810244156A CN 108337047 A CN108337047 A CN 108337047A
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- time domain
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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
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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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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
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Abstract
The invention discloses a kind of time domain hybrid modulation method based on visible light communication system, time domain hybrid modulation here refers to being suitably designed a time division multiple frame, to adjust time slot duty ratio of the different modulating format in frame.We use for reference application of the time domain hybrid modulation in fiber optic communication, and the thought of time domain hybrid modulation is proposed in visible light communication.Time domain hybrid modulation in the present invention is using very common switch keying modulation and pulse position modulation, it solves the problems, such as to use technical sophistication, cost and high modulation multiplex equipment in VLC, simplifies the complexity of modulating equipment and ensure that preferable communication performance.In practical applications, it is of great significance in the case that especially VLC is as auxiliary communication system.
Description
Technical field
The present invention relates to a kind of time domain hybrid modulation method based on visible light communication system, and in particular to time domain mixing is adjusted
Method (TDHM, Time Division Hybrid Modulation) processed, TDHM answering in visible light communication system indoors
With belonging to technical field of visible light communication.
Background technology
LED light has the characteristics that long lifespan, energy conservation and environmental protection, is follow-on primary illumination light source.And it is communicated with it
Visible light communication also paid close attention to by more and more people.Visible light communication is since its is environmentally protective, is not necessarily to frequency spectrum certification, transmission
The advantages that rate is high causes the research boom of global range.
In fact, visible light communication is flourishing as effective additional project of radio communication.Currently, visible light is logical
The directly detection of the common modulation system intensity modulateds-of letter system VLC is that modulation signal is loaded directly into the intensity of light.And
It must be the positive real number ＂ of ＂ that the characteristic of light intensity, which determines electric signal to be transmitted also,.That is, the signal in VISIBLE LIGHT SYSTEM
On pulse shaping select permeability, impulse modulation then has advantageous advantage.And it is wanted using carrier modulation in visible light communication
It asks carrier frequency to be higher than bandwidth, nethermost frequency can be lost in this way, and due to using intensity modulated-straight in visible light communication
Detection is connect, the modulated signal needed is necessary for positive real number signal, so being easy to loss information using carrier modulation.Opposite carrier wave
For modulation, baseband modulation meets modulated signal in visible light communication and is the requirement of positive real number signal and will not lose information, because
This uses ON-OFF keying modulation (OOK) and pulse position modulation (PPM) more in early stage is to the research of visible light communication system
Isopulse modulation scheme.
In visible light communication, OOK is the most IM/DD modulation techniques of report.This is because it be in modulation technique very
A kind of scheme being easily understood, position 1 just simply indicate that it can take up entire bit period, can also with a light pulse
It is a part for bit period；Position 0 is just indicated with the bit period of not light pulse.Although OOK modulation schemes are simple to operation,
Low to bandwidth demand, band efficiency is high, and anti-interference ability is stronger, but power utilization and system transfer rate are relatively low.And
PPM is a most attractive selection for visible light communication because of its significant preferable power efficiency.PPM is just
It hands over modulation technique and is a member of impulse modulation family, be a kind of modulation information bit being mapped in pulse position
Form.In the modern times are using term, the PPM signal of a L time slot has and only includes a pulse there are one time slot position.And
The information bit of input determines that who of L time slots is applied.Work as L>When 2, any L-PPM, i.e., needed for the modulation of L time slot
The luminous power wanted will be fewer than OOK, and when L is arbitrarily large, and theoretically the required power of L-PPM can be arbitrarily small.And due to
OOK occupies the frequency band of very little, and PPM occupies prodigious frequency band, so PPM is higher with respect to receiving sensitivity for OOK.With regard to positioning and
For two aspect of communication, low rate can meet positioning requirements, and sensitivity then more demanding in communicating.VLC is positioned at room
Interior auxiliary communication system installs simple modulating equipment additional in existing lighting system, you can realize indoor wireless data transmission,
Have the characteristics that it is inexpensive, simple, energy saving, and the high modulation multiplex equipment of technical sophistication, cost be obviously not suitable for it is this
Positioning.
Invention content
Goal of the invention：It is a kind of based on can the technical problem to be solved by the present invention is to be provided for the deficiency of background technology
The time domain mixed-modulation scheme of light-exposed communication system is a kind of modulation technique being capable of providing flexible data rate, solves
In VLC using technical sophistication, cost again high modulation multiplex equipment the problem of, simplify the complexity of modulating equipment and guarantee
Preferable communication performance.In practical applications, it is of great significance in the case that especially VLC is as auxiliary communication system.
Technical solution：A kind of time domain hybrid modulation method based on visible light communication system, specifically comprises the following steps：
Step 1, a string of random original bit streams are generated；
Step 2, original bit stream is become into M+K system bit streams by serial to parallel conversion；
Step 3, it then by the K system bit streams in each group of M+K system bit stream by L-PPM encodes；
Step 4, respectively by the result of process L-PPM coding mappings and M systems bit stream by emission filter, corresponding
Time slot on generate and be integrally formed TDM frame after signal pulse and send, calculate signal-to-noise ratio and the bit error rate, a TDM frame is by N
A time slot is constituted, and N is the natural number more than 2；
Step 5, the value of the M and K in 2,3 and 4 are changed the step, step 1-4 is repeated, comparison system uses different time domains
The obtained signal-to-noise ratio of hybrid modulation receiving terminal and its bit error rate.
Further, in step 2, original bit flows through the number of M and K in the M+K system bit streams obtained by serial to parallel conversion
Value can be set.
Further, in step 3, the K system bits in the M+K system bit streams through each group obtained by serial to parallel conversion
Stream is encoded by L-PPM, and the mapping of K system bit streams is become L-PPM sequence of time slots.
Further, the timeslot number L=2^K of L-PPM sequence of time slots.
Further, in step 4, emission filter exports rectangular pulse response wave shape.
Further, in step 4, " 1 " representative has signal in the bit stream of M systems, and " 0 " represents no signal.
Advantageous effect：
1, it on the basis of the single modulation of visible light communication system indoors of the invention, proposes by ON-OFF keying modulation (OOK)
The thought of time domain hybrid modulation is constituted with two kinds of modulation systems of pulse position modulation (PPM).With OOK easy to operate and PPM modulation
It compares, time domain hybrid modulation has both the spectrum efficiency of OOK and the high advantage of power utilization of PPM, and effectively improves system
Transmission rate, improve the anti-interference ability of system.
2, the method for the present invention solves the problems, such as to use technical sophistication, cost and high modulation multiplex equipment, letter in VLC
The complexity of modulating equipment is changed and ensure that preferable communication performance, in practical applications, especially VLC is as subsidiary communications
It is of great significance in the case of system
Description of the drawings
Fig. 1 is the functional block diagram of time domain hybrid modulation visible light communication system application indoors；
Fig. 2 is the practical block diagram of time domain hybrid modulation；
Fig. 3 is the functional block diagram of time domain hybrid modulation.
Specific implementation mode
Further explanation is done to the present invention below in conjunction with the accompanying drawings.
The thinking of the present invention is to propose a kind of time domain hybrid modulation method based on visible light communication system, is to existing
The improvement of the modulation scheme of visible light communication system.Here time domain hybrid modulation refers to being suitably designed a time division multiplexing
Frame, to adjust time slot duty ratio of the different modulating format in frame.We use for reference time domain hybrid modulation in fiber optic communication
Using the thought of proposition time domain hybrid modulation (TDHM) in visible light communication.Time domain mixing applied in fiber optic communication is adjusted
System uses quadrature amplitude modulation (QAM), but the time domain hybrid modulation based on visible light communication system in the present invention is adopted
It is very common switch keying modulation (OOK) and pulse position modulation (PPM).The method of the present invention, which solves, uses skill in VLC
Art is complicated, cost again high modulation multiplex equipment the problem of, simplify the complexity of modulating equipment and ensure that preferable logical
Believe performance.In practical applications, it is of great significance in the case that especially VLC is as auxiliary communication system.
Part in attached drawing 1 labelled in dotted line is the particular content of attached drawing 2, is produced after the time domain hybrid modulation of attached drawing 2
Raw OOK/PPM time domain hybrid modulation electric signals, become optical signal by time domain Hybrid-modulated Signal using driving circuit and LED and exist
It is sent in indoor wireless channels, receiving terminal is received by PD, the optical signal received is converted to last after electric signal
Restore original bit stream information by matched filter, then by modes such as judgements.
Attached drawing 2 is the practical block diagram of time domain hybrid modulation, a string of random original bit streams is generated first, by original bit
Stream becomes M+K system bit streams by serial to parallel conversion, then the K system bit streams in each group of M+K system bit stream are passed through L-
PPM is encoded, respectively by the result of process L-PPM coding mappings and M systems bit stream by emission filter, in corresponding time slot
A TDM frame is integrally formed after upper generation signal pulse to send.
Attached drawing 3 is the functional block diagram of time domain hybrid modulation, that is, a time division multiple frame is suitably designed, by adjusting OOK
OOK/PPM time domain Hybrid-modulated Signals are constituted with time slot duty ratios of the PPM in frame.
Much about in the design of the modulation scheme of visible light communication, we are especially common be OOK and PPM etc. some
Simple pulse modulation scheme.In the document about visible light communication that we can know about, document proposed from when
All it is the thought of single modulation in the angle in domain, but for single modulation, the excellent of Different Modulations cannot be taken into account
Disadvantage.Although OOK modulation schemes are simple to operation, low to bandwidth demand, band efficiency is high, strong antijamming capability, work(
Rate utilization rate and system transfer rate are relatively low；PPM is one for visible light communication because of its significant preferable power efficiency
A most attractive selection, however PPM modulation technology is since receiving terminal is that demodulated signal requires time slot and sign synchronization, although
Power efficiency is improved relative to OOK, but is to increase bandwidth demand and more complexities as cost.The present invention combines
The advantages of two kinds of modulation schemes, is suitably designed a time division multiple frame, by adjusting difference using time domain hybrid modulation
Time slot duty ratio of the modulation format in frame constitutes the modulation of time domain hybrid orthogonal amplitude.Present invention visible light communication system indoors
On the basis of single modulation, the thought that time domain hybrid modulation is made of two kinds of modulation systems of OOK and PPM is proposed.With it is easy to operate
OOK is compared with PPM modulation, and time domain hybrid modulation has both the spectrum efficiency of OOK and the high advantage of power utilization of PPM, and
The transmission rate for effectively improving system improves the anti-interference ability of system.
The present invention proposes the thought of time domain hybrid modulation, as shown in Figure 2.Ensureing that system has certain anti-interference ability
In the case of, so that system transfer rate is reached maximization.
A kind of time domain hybrid modulation method based on visible light communication system, as shown in Fig. 2：It is specific to include following step
Suddenly：
Step 1, a string of random original bit streams to be generated；
Step 2, original bit stream is become into (M+K) system bit stream by serial to parallel conversion；The value M's and K of wherein M and K
Numerical value can not be changeless numerical value, and M and K determine that the ratio of OOK and PPM in a TDM frame, such as M can take
2, K can also take 2；
Step 3, it then by the K system bit streams in each group of (M+K) system bit stream by L-PPM encodes；That is L-PPM is compiled
The mapping of K system bit streams is become L-PPM sequence of time slots by code device, and L-PPM timeslot numbers are L=2^K；
Step 4, shape will be integrated by emission filter by the result and M system bit streams of L-PPM coding mappings respectively
It is sent at a TDM frame, as shown in Fig. 3；Emission filter is a filter with rectangular pulse response wave shape, M into
" 1 ", which represents, in the bit stream of system signal, and " 0 " represents no signal.
Step 5, the value of the M and K in 2,3 and 4 are changed the step, step 1-4 is repeated, comparison system uses different time domains
The obtained signal-to-noise ratio of hybrid modulation receiving terminal and its bit error rate.
From above-mentioned processing it is found that a kind of new modulation scheme-time domain mixing in visible light communication system proposed by the present invention
Modulation can be different neatly to obtain according to the distribution of two different modulation formats ratio shared in a TDM frame
Spectrum efficiency, and for the multi-carrier modulation that can reach high communication data rate the time domain hybrid modulation complexity
It can reduce very much.The method of the present invention solves the problems, such as in VLC using technical sophistication, cost high modulation multiplex equipment again,
It simplifies the complexity of modulating equipment and ensure that preferable communication performance.In practical applications, especially VLC is logical as auxiliary
It is of great significance in the case of letter system.
The above is only a preferred embodiment of the present invention, it is noted 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 (6)
1. a kind of time domain hybrid modulation method based on visible light communication system, which is characterized in that specifically comprise the following steps：
Step 1, a string of random original bit streams are generated；
Step 2, original bit stream is become into M+K system bit streams by serial to parallel conversion；
Step 3, it then by the K system bit streams in each group of M+K system bit stream by L-PPM encodes；
Step 4, respectively by the result of process L-PPM coding mappings and M systems bit stream by emission filter, when corresponding
Generated in gap and be integrally formed TDM frame after signal pulse and send, calculate signal-to-noise ratio and the bit error rate, a TDM frame be by it is N number of when
Gap is constituted, and N is the natural number more than 2；
Step 5, the value of the M and K in 2,3 and 4 are changed the step, step 1-4 is repeated, comparison system is mixed using different time domains
Modulate the obtained signal-to-noise ratio of receiving terminal and its bit error rate.
2. a kind of time domain hybrid modulation method based on visible light communication system according to claim 1, it is characterised in that：
In step 2, original bit flows through the numerical value of M and K in the M+K system bit streams obtained by serial to parallel conversion and can set.
3. a kind of time domain hybrid modulation method based on visible light communication system according to claim 1, it is characterised in that：
In step 3, the K system bit streams in the M+K system bit streams through each group obtained by serial to parallel conversion are encoded by L-PPM,
The mapping of K system bit streams is become into L-PPM sequence of time slots.
4. a kind of time domain hybrid modulation method based on visible light communication system according to claim 1, it is characterised in that：
The timeslot number L=2^K of L-PPM sequence of time slots.
5. a kind of time domain hybrid modulation method based on visible light communication system according to claim 1, it is characterised in that：
In step 4, emission filter exports rectangular pulse response wave shape.
6. a kind of time domain hybrid modulation method based on visible light communication system according to claim 1, it is characterised in that：
In step 4, " 1 " representative has signal in the bit stream of M systems, and " 0 " represents no signal.
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| CN111935750A (en) * | 2020-08-21 | 2020-11-13 | 苏州大学 | Capacity optimization method of mobile wireless optical communication system, communication method and system |
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