CN108848048B - Generalized mixed visible light modulation method and device - Google Patents
Generalized mixed visible light modulation method and device Download PDFInfo
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- CN108848048B CN108848048B CN201810847191.3A CN201810847191A CN108848048B CN 108848048 B CN108848048 B CN 108848048B CN 201810847191 A CN201810847191 A CN 201810847191A CN 108848048 B CN108848048 B CN 108848048B
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
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- 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
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- H04B10/114—Indoor or close-range type systems
- H04B10/116—Visible light communication
Abstract
The invention discloses a generalized mixed visible light modulation method and a device, wherein the method comprises the following steps: transmitting the generalized ACO-OFDM signal on a part of odd subcarriers, and multiplying the generalized ACO-OFDM signal by the signal amplification factor; transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers, and multiplying the DCO-OFDM signals by the signal amplification factor; respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out unipolar processing on the transformed ACO-OFDM signal, adding direct current offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted, carrying out amplitude limiting, digital-to-analog conversion and filtering, and controlling visible light driving current to obtain and transmit a visible light communication signal. The method can flexibly allocate system resources, optimize signal amplitude distribution, inhibit signal truncation noise, improve communication performance under dimming constraint, balance spectral efficiency and optical power efficiency, and improve the overall performance of the system.
Description
Technical Field
The invention relates to the technical field of digital signal transmission, in particular to a generalized mixed visible light modulation method and device.
Background
VLC (Visible Light Communication) is a technical means for realizing wireless Communication based on LED illumination, and transmits information by using a Light source to emit a high-frequency signal that cannot be perceived by naked eyes. The LED illumination device has good development prospect due to the characteristics of wide frequency spectrum, green energy conservation, deep coverage and organic combination with illumination.
Compared with the traditional Modulation scheme, such as OOK (On-Off Keying) Modulation and PPM (Pulse Position Modulation), OFDM (Orthogonal Frequency Division multiplexing) Modulation has the advantages of high spectrum efficiency, flexible multiple access and lowest realization complexity, can well resist multipath channel interference, and is a high data rate Modulation mode. For IM/DD (Intensity Modulated/Direct Detection) VLC systems, there are various forms of OFDM, such as DCO-OFDM (DC biased Optical OFDM, Direct current biased Optical orthogonal frequency division multiplexing), ACO-OFDM (asymmetric Clipped Optical OFDM, asymmetric Clipped Optical orthogonal frequency division multiplexing) and ADO-OFDM (asymmetric Clipped DC biased Optical OFDM, asymmetric Clipped Direct current biased Optical orthogonal frequency division multiplexing). Among them, DCO-OFDM modulation is inefficient in terms of optical power by adding a DC bias to make its time domain signal non-negative; ACO-OFDM modulation transmits data symbols only on odd subcarriers, which is not efficient in terms of bandwidth; the ADO-OFDM modulates positive polarity ACO-OFDM signals on odd subcarriers, modulates DCO-OFDM signals on even subcarriers, has bandwidth efficiency superior to that of the ACO-OFDM signals and optical power efficiency superior to that of the DCO-OFDM signals, but because ACO-OFDM and DCO-OFDM time domain signals are both positive numbers, the signal amplitude is easy to be overlarge, the signals enter a system nonlinear area, a truncation phenomenon is generated, and the system performance is deteriorated. In addition, the number of subcarriers occupied by the three modulation methods is fixed, and cannot be changed according to the system requirements.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, an object of the present invention is to provide a generalized hybrid visible light modulation method, which can flexibly allocate system resources, optimize signal amplitude distribution, suppress signal truncation noise, improve communication performance under dimming constraint, balance spectral efficiency and optical power efficiency, and improve overall system performance.
It is another object of the present invention to provide a generalized hybrid visible light modulation device.
In order to achieve the above object, an embodiment of an aspect of the present invention provides a generalized hybrid visible light modulation method, including the following steps: transmitting generalized ACO-OFDM signals on part of odd subcarriers, and multiplying the generalized ACO-OFDM signals by ACO-OFDM signal amplification factors; transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers, and multiplying the DCO-OFDM signals by amplification factors of the DCO-OFDM signals; respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out unipolar processing on the transformed ACO-OFDM signal, and adding direct current offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted; and after amplitude limiting, digital-to-analog conversion and filtering are carried out on the signal frame to be sent, controlling the visible light driving current to acquire and send a visible light communication signal.
The generalized mixed visible light modulation method can flexibly adjust the proportion of the positive/negative ACO-OFDM signals according to different requirements of a system, and avoids the phenomenon that the superposed signals enter a non-linear area of the system to generate truncation and deteriorate the performance of the system due to overlarge signal amplitude; in addition, the number of sub-carriers allocated to the ACO-OFDM and the DCO-OFDM can be flexibly adjusted to balance the bandwidth efficiency and the optical power efficiency of the system.
In addition, the generalized hybrid visible light modulation method according to the above embodiment of the present invention may further have the following additional technical features:
further, in one embodiment of the invention, the generalized ACO-OFDM and the DCO-OFDM signals satisfy Hermitian symmetry structure.
Further, in one embodiment of the present invention, the generalized ACO-OFDM signal includes: and the positive polarity ACO-OFDM signal or the negative polarity ACO-OFDM signal obtained by carrying out zero setting on the positive part of the bipolar signal before the ACO-OFDM signal is subjected to asymmetric amplitude limiting and retaining the negative part of the bipolar signal.
Further, in an embodiment of the present invention, the method further includes: and changing the generalized ACO-OFDM signal into a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal frame by frame according to the system requirement.
Further, in an embodiment of the present invention, the method further includes: and changing the number of the sub-carriers occupied by the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to the system requirement.
Further, in one embodiment of the present invention, the ACO-OFDM subcarrier number is at least zero and at most not more than half of the total subcarrier number.
Further, in one embodiment of the present invention, the number of DCO-OFDM subcarriers is at least half of the number of all subcarriers and at most does not exceed the number of all subcarriers.
Further, in an embodiment of the present invention, the method further includes: and changing the amplification factors of the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to system requirements.
Further, in one embodiment of the present invention, the visible light communication signal has a minimum signal amplitude of 0 and a maximum signal amplitude of the maximum linear operating current of the LED.
In order to achieve the above object, another embodiment of the present invention provides a generalized hybrid visible light modulation device, including: the generalized ACO-OFDM modulation module is used for transmitting generalized ACO-OFDM signals on part of odd subcarriers and multiplying the generalized ACO-OFDM signals by an ACO-OFDM signal amplification factor; the DCO-OFDM modulation module is used for transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers and multiplying the DCO-OFDM signals by an amplification factor; the signal fusion module is used for respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out unipolar processing on the transformed ACO-OFDM signal, and adding direct current offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted; and the signal sending module is used for controlling the visible light driving current after carrying out amplitude limiting, digital-to-analog conversion and filtering on the signal frame to be sent so as to acquire and send the visible light communication signal.
The generalized mixed visible light modulation device can flexibly adjust the proportion of the positive/negative ACO-OFDM signals according to different requirements of a system, and avoids the phenomenon that the superposed signals enter a non-linear area of the system to generate truncation and deteriorate the performance of the system due to overlarge signal amplitude; in addition, the number of sub-carriers allocated to the ACO-OFDM and the DCO-OFDM can be flexibly adjusted to balance the bandwidth efficiency and the optical power efficiency of the system.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow diagram of a generalized hybrid visible light modulation method according to one embodiment of the present invention;
FIG. 2 is a flow diagram of a generalized hybrid visible light modulation method according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating generalized ACO-OFDM signaling according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a DCO-OFDM signal transmission signal according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating the effect of a generalized hybrid visible light modulation method according to a first embodiment of the present invention;
FIG. 6 is a diagram illustrating the effect of a generalized hybrid visible light modulation method according to a second embodiment of the present invention;
FIG. 7 is a diagram illustrating the effect of a generalized hybrid visible light modulation method according to a third embodiment of the present invention;
FIG. 8 is a schematic diagram of a generalized hybrid visible light modulation device according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The generalized mixed visible light modulation method and apparatus proposed according to the embodiments of the present invention will be described below with reference to the accompanying drawings, and first, the generalized mixed visible light modulation method proposed according to the embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a flow diagram of a generalized hybrid visible light modulation method of one embodiment of the present invention.
As shown in fig. 1, the generalized hybrid visible light modulation method includes the following steps:
in step S101, the generalized ACO-OFDM signal is transmitted on a part of the odd subcarriers and multiplied by an ACO-OFDM signal amplification factor.
In one embodiment of the invention, generalized ACO-OFDM satisfies Hermitian symmetry structure.
Further, in one embodiment of the invention, the number of ACO-OFDM subcarriers is at least zero and at most not more than half of the number of all subcarriers.
It will be appreciated that as shown in fig. 2, embodiments of the present invention first transmit the generalized ACO-OFDM signal over a portion of the odd subcarriers and multiply by the ACO-OFDM signal amplification factor, such as shown in fig. 3. The generalized ACO-OFDM signal meets an Hermitian symmetric structure, and the number of the generalized ACO-OFDM subcarriers is at least zero and at most not more than half of the number of all the subcarriers.
Further, in one embodiment of the present invention, the generalized ACO-OFDM signal includes: and the positive polarity ACO-OFDM signal or the negative polarity ACO-OFDM signal is obtained by carrying out zero setting on the positive part of the bipolar signal before the ACO-OFDM signal is subjected to asymmetric amplitude limiting and retaining the negative part of the bipolar signal.
In step S102, the DCO-OFDM signal is transmitted on the even subcarriers and the remaining odd subcarriers and multiplied by the DCO-OFDM signal amplification factor.
In one embodiment of the invention, the DCO-OFDM signal satisfies the Hermitian symmetry structure.
Further, in one embodiment of the present invention, the number of DCO-OFDM subcarriers is at least half of the number of all subcarriers and at most does not exceed the number of all subcarriers.
It is to be understood that, as shown in fig. 2, the embodiment of the present invention transmits DCO-OFDM signals on even subcarriers and the remaining odd subcarriers and multiplies the DCO-OFDM signal amplification factor, for example, as shown in fig. 4. The DCO-OFDM signal meets an Hermitian symmetrical structure, the number of DCO-OFDM subcarriers is at least half of the number of all subcarriers, and the number of DCO-OFDM subcarriers does not exceed the number of all subcarriers at most.
In step S103, discrete fourier transform is performed on the generalized ACO-OFDM signal and the DCO-OFDM signal, unipolar processing is performed on the transformed ACO-OFDM signal, and dc offset is added to the transformed DCO-OFDM signal, so as to obtain a signal frame to be transmitted.
It can be understood that, as shown in fig. 2, in the embodiment of the present invention, discrete fourier transform is performed on the generalized ACO-OFDM signal and the DCO-OFDM signal, unipolar processing is performed on the transformed ACO-OFDM signal, and a dc offset is added to the transformed DCO-OFDM signal, and the converted ACO-OFDM signal and the transformed DCO-OFDM signal are added to obtain a signal frame to be transmitted.
Further, in an embodiment of the present invention, the method of an embodiment of the present invention further includes: and changing the generalized ACO-OFDM signal into a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal frame by frame according to the system requirement.
Further, in an embodiment of the present invention, the method of an embodiment of the present invention further includes: and changing the number of the sub-carriers occupied by the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to the system requirement.
Further, in an embodiment of the present invention, the method of an embodiment of the present invention further includes: and changing the amplification factors of the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to the system requirement.
Specifically, the embodiment of the invention respectively carries out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal. And carrying out amplitude limiting processing on the converted ACO-OFDM signal, adding direct current offset to the converted DCO-OFDM signal, and adding the direct current offset and the DCO-OFDM signal to obtain a signal frame to be transmitted. The generalized ACO-OFDM signal can be changed to a positive-polarity ACO-OFDM signal or a negative-polarity ACO-OFDM signal frame by frame according to system requirements, where the negative-polarity ACO-OFDM signal refers to: and carrying out zero setting on the positive part of the bipolar signal before the ACO-OFDM signal is subjected to asymmetric amplitude limiting, and reserving the negative part of the bipolar signal. And, the number of sub-carriers occupied by the generalized ACO-OFDM signal and the DCO-OFDM signal can be changed frame by frame according to the system requirement. Further, the amplification factors of the generalized ACO-OFDM signal and the DCO-OFDM signal can be changed from frame to frame according to the system requirements.
In step S104, after performing amplitude limiting, digital-to-analog conversion, and filtering on the signal frame to be transmitted, the visible light driving current is controlled to obtain and transmit the visible light communication signal.
It can be understood that, in the embodiment of the present invention, after performing amplitude limiting, digital-to-analog conversion and filtering on a signal frame to be transmitted, a visible light driving current is controlled, and a visible light communication signal is obtained and transmitted.
Further, in one embodiment of the present invention, the visible light communication signal has a minimum signal amplitude of 0 and a maximum signal amplitude of the maximum linear operating current of the LED.
For the sake of understanding, the generalized hybrid visible light modulation method will be further explained with reference to the drawings and the specific embodiments.
In a first embodiment of the present invention, as shown in fig. 5, a generalized hybrid visible light modulation method comprises the steps of:
step 1: the method for transmitting the generalized ACO-OFDM signal on the part of the odd subcarriers and multiplying the generalized ACO-OFDM signal by the amplification factor of the ACO-OFDM signal specifically comprises the following steps:
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd multiplying it by the ACO-OFDM signal amplification factor alphaAPost modulation is numbered as
Where N is the number of subcarriers. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein m represents the mth frame, XAi∈{Xk}。
Step 2: transmitting DCO-OFDM signals on even subcarriers and residual odd subcarriers, and multiplying the DCO-OFDM signals by amplification factors of the DCO-OFDM signals, specifically comprising:
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd multiplying it by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of the array. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein, XDi∈{Xk}。
And step 3: respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out amplitude limiting processing on the transformed ACO-OFDM signal, adding direct current offset to the transformed DCO-OFDM signal, and adding the direct current offset and the transformed DCO-OFDM signal to obtain a signal frame to be transmitted, wherein the method specifically comprises the following steps:
on one hand, for the generalized ACO-OFDM signal, the positive polarity ACO-OFDM signal or the negative polarity ACO-OFDM signal can be selected frame by frame according to the system requirement, specifically:
the positive polarity ACO-OFDM signal frame generation method comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mThe bipolar signal is subjected to asymmetric amplitude limiting to set the negative part of the bipolar signal to zero and keep the positive part of the bipolar signal to obtain a positive polarity ACO-OFDM signal frame
Further, of frames of negative polarity ACO-OFDM signalsThe generation method comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mPerforming asymmetric amplitude limiting on the bipolar signal to set the positive part of the bipolar signal to zero and reserve the negative part of the bipolar signal to obtain a negative ACO-OFDM signal frame
On the other hand, for the DCO-OFDM signal, the signal frame generation method comprises the following steps: to XD,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the DCO-OFDM time domain bipolar signal x 'is obtained through fast Fourier inverse transformation'D,mAdding DC bias to the bipolar signal to cancel out the negative part of the bipolar signal, and setting the signal still being negative to 0 to obtain frame x of DCO-OFDM signalD,m。
Further, the m-th frame to be signaled is: x is the number ofm＝xD,m+xA,m。
Specifically, in the present embodiment, the odd frame employs a negative polarity ACO-OFDM signal, and the amplification factor of the generalized ACO-OFDM signal in the odd frame takes αA1(ii) a The even frame adopts positive polarity ACO-OFDM signal, and the amplification factor of generalized ACO-OFDM signal in the even frame is alphaA2In which α isA2≠αA1. Furthermore, each frame of DCO-OFDM signal amplification factor takes alphaD。
And 4, step 4: and carrying out amplitude limiting, digital-to-analog conversion and filtering on the superposed signal frame, then controlling the visible light driving current, obtaining a visible light communication signal and then sending the visible light communication signal. In one embodiment of the present invention, the minimum signal amplitude of the visible light communication signal is 0, and the maximum signal amplitude is the maximum linear operating current of the LED.
In a second embodiment of the present invention, as shown in fig. 6, the generalized hybrid visible light modulation method comprises the steps of:
step 1: the method for transmitting the generalized ACO-OFDM signal on the part of the odd subcarriers and multiplying the generalized ACO-OFDM signal by the amplification factor of the ACO-OFDM signal specifically comprises the following steps:
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd multiplying it by the ACO-OFDM signal amplification factor alphaAPost modulation is numbered as
Where N is the number of subcarriers. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein m represents the mth frame, XAi∈{Xk}。
Step 2: transmitting DCO-OFDM signals on even subcarriers and residual odd subcarriers, and multiplying the DCO-OFDM signals by amplification factors of the DCO-OFDM signals, specifically comprising:
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd multiplying it by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of the array. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein, XDi∈{Xk}。
And step 3: respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out amplitude limiting processing on the transformed ACO-OFDM signal, adding direct current offset to the transformed DCO-OFDM signal, and adding the direct current offset and the transformed DCO-OFDM signal to obtain a signal frame to be transmitted, wherein the method specifically comprises the following steps:
on one hand, for the generalized ACO-OFDM signal, the positive polarity ACO-OFDM signal or the negative polarity ACO-OFDM signal can be selected frame by frame according to the system requirement, specifically:
the positive polarity ACO-OFDM signal frame generation method comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mThe bipolar signal is subjected to asymmetric amplitude limiting to set the negative part of the bipolar signal to zero and keep the positive part of the bipolar signal to obtain a positive polarity ACO-OFDM signal frame
Furthermore, the generating method of the negative polarity ACO-OFDM signal frame comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mPerforming asymmetric amplitude limiting on the bipolar signal to set the positive part of the bipolar signal to zero and reserve the negative part of the bipolar signal to obtain a negative ACO-OFDM signal frame
On the other hand, for the DCO-OFDM signal, the signal frame generation method comprises the following steps: to XD,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the DCO-OFDM time domain bipolar signal x 'is obtained through fast Fourier inverse transformation'D,mAdding DC bias to the bipolar signal to cancel out the negative part of the bipolar signal, and setting the signal still being negative to 0 to obtain frame x of DCO-OFDM signalD,m。
Further, the m-th frame to be signaled is: x is the number ofm＝xD,m+xA,m。
Specifically, in the present embodiment, the even frame employs the negative polarity ACO-OFDM signal, the odd frame employs the positive polarity ACO-OFDM signal, and the amplification factors of the generalized ACO-OFDM signals are each αA. Further, each frame DCO-OFDM signal amplification factorAll take alphaD
And 4, step 4: and carrying out amplitude limiting, digital-to-analog conversion and filtering on the superposed signal frame, then controlling the visible light driving current, obtaining a visible light communication signal and then sending the visible light communication signal. In one embodiment of the present invention, the minimum signal amplitude of the visible light communication signal is 0, and the maximum signal amplitude is the maximum linear operating current of the LED.
In a third embodiment of the present invention, as shown in fig. 7, the generalized hybrid visible light modulation method comprises the steps of:
step 1: the method for transmitting the generalized ACO-OFDM signal on the part of the odd subcarriers and multiplying the generalized ACO-OFDM signal by the amplification factor of the ACO-OFDM signal specifically comprises the following steps:
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd multiplying it by the ACO-OFDM signal amplification factor alphaAPost modulation is numbered as
Where N is the number of subcarriers. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein m represents the mth frame, XAi∈{Xk}。
Step 2: transmitting DCO-OFDM signals on even subcarriers and residual odd subcarriers, and multiplying the DCO-OFDM signals by amplification factors of the DCO-OFDM signals, specifically comprising:
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd multiplying it by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers outside the number. Further, taking the conjugate of the compound to form a Hermitian symmetrical structure, namely:
wherein, XDi∈{Xk}。
And step 3: respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out amplitude limiting processing on the transformed ACO-OFDM signal, adding direct current offset to the transformed DCO-OFDM signal, and adding the direct current offset and the transformed DCO-OFDM signal to obtain a signal frame to be transmitted, wherein the method specifically comprises the following steps:
on one hand, for the generalized ACO-OFDM signal, the positive polarity ACO-OFDM signal or the negative polarity ACO-OFDM signal can be selected frame by frame according to the system requirement, specifically:
the positive polarity ACO-OFDM signal frame generation method comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mThe bipolar signal is subjected to asymmetric amplitude limiting to set the negative part of the bipolar signal to zero and keep the positive part of the bipolar signal to obtain a positive polarity ACO-OFDM signal frame
Furthermore, the generating method of the negative polarity ACO-OFDM signal frame comprises the following steps: to XA,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the ACO-OFDM time domain bipolar signal x is obtained through fast inverse Fourier transformA,mPerforming asymmetric amplitude limiting on the bipolar signal to set the positive part of the bipolar signal to zero and reserve the negative part of the bipolar signal to obtain a negative ACO-OFDM signal frame
On the other hand, for the DCO-OFDM signal, the signal frame generation method comprises the following steps: to XD,mAfter the OFDM data block with the length of N is obtained through serial-parallel conversion, the DCO-OFDM time domain bipolar signal x 'is obtained through fast Fourier inverse transformation'D,mAdding DC bias to the bipolar signal to cancel the bipolar signalAnd setting the still negative signal to 0 to obtain frame x of the DCO-OFDM signalD,m。
Further, the m-th frame to be signaled is: x is the number ofm＝xD,m+xA,m。
Specifically, in the present embodiment, the even frame employs the negative polarity ACO-OFDM signal, and the amplification factor of the generalized ACO-OFDM signal in the even frame takes αA1(ii) a The odd frame adopts positive polarity ACO-OFDM signal, and the amplification factor of generalized ACO-OFDM signal in the odd frame takes alphaA2In which α isA2≠αA1. Further, the amplification factor of the odd frame DCO-OFDM signal takes alphaD1The even number frame DCO-OFDM signal amplification factor takes alphaD2In which α isD2≠αD1。
And 4, step 4: and carrying out amplitude limiting, digital-to-analog conversion and filtering on the superposed signal frame, then controlling the visible light driving current, obtaining a visible light communication signal and then sending the visible light communication signal. In one embodiment of the present invention, the minimum signal amplitude of the visible light communication signal is 0, and the maximum signal amplitude is the maximum linear operating current of the LED.
According to the generalized mixed visible light modulation method provided by the embodiment of the invention, the proportion of positive/negative ACO-OFDM signals can be flexibly adjusted according to different requirements of a system, and the phenomenon that the superposed signals enter a nonlinear area of the system due to overlarge amplitude to generate truncation and deteriorate the performance of the system is avoided; in addition, the number of sub-carriers allocated to the ACO-OFDM and the DCO-OFDM can be flexibly adjusted to balance the bandwidth efficiency and the optical power efficiency of the system.
Next, a generalized mixed visible light modulation device proposed according to an embodiment of the present invention is described with reference to the drawings.
FIG. 8 is a schematic diagram of a generalized hybrid visible light modulation device according to an embodiment of the present invention.
As shown in fig. 8, the generalized hybrid visible light modulation device 10 includes: the system comprises a generalized ACO-OFDM modulation module 100, a DCO-OFDM modulation module 200, a signal fusion module 300 and a signal transmission module 400.
The generalized ACO-OFDM modulation module 100 is configured to transmit a generalized ACO-OFDM signal on a part of odd subcarriers and multiply the amplification factor of the ACO-OFDM signal. The DCO-OFDM modulation module 200 is used to transmit DCO-OFDM signals on even subcarriers and the remaining odd subcarriers and multiply the amplification factor of the DCO-OFDM signals. The signal fusion module 300 is configured to perform discrete fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, perform unipolar processing on the transformed ACO-OFDM signal, and add dc offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted. The signal sending module 400 is configured to control the visible light driving current after performing amplitude limiting, digital-to-analog conversion, and filtering on a signal frame to be sent, so as to obtain and send a visible light communication signal. The device 10 of the embodiment of the invention can flexibly allocate system resources, optimize signal amplitude distribution, inhibit signal truncation noise, improve communication performance under dimming constraint, balance spectral efficiency and luminous power efficiency and improve the overall performance of the system.
It should be noted that the foregoing explanation of the embodiment of the generalized mixed visible light modulation method is also applicable to the generalized mixed visible light modulation device of the embodiment, and is not repeated here.
According to the generalized mixed visible light modulation device provided by the embodiment of the invention, the proportion of positive/negative ACO-OFDM signals can be flexibly adjusted according to different requirements of a system, and the phenomenon that the superposed signals enter a nonlinear area of the system due to overlarge amplitude to generate truncation and deteriorate the performance of the system is avoided; in addition, the number of sub-carriers allocated to the ACO-OFDM and the DCO-OFDM can be flexibly adjusted to balance the bandwidth efficiency and the optical power efficiency of the system.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (6)
1. A method of generalized hybrid visible light modulation comprising the steps of:
transmitting generalized ACO-OFDM signals on part of odd subcarriers, and multiplying the generalized ACO-OFDM signals by ACO-OFDM signal amplification factors;
transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers, and multiplying the DCO-OFDM signals by amplification factors of the DCO-OFDM signals;
respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out unipolar processing on the transformed ACO-OFDM signal, and adding direct current offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted; the generalized ACO-OFDM and DCO-OFDM signals satisfy a Hermitian symmetry structure, the generalized ACO-OFDM signals including: a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal obtained by carrying out zero setting on a positive part of a bipolar signal before the ACO-OFDM signal is subjected to asymmetric amplitude limiting and reserving a negative part of the bipolar signal; changing the generalized ACO-OFDM signal into a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal frame by frame according to system requirements; changing the number of sub-carriers occupied by the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to system requirements; and
after amplitude limiting, digital-to-analog conversion and filtering are carried out on the signal frame to be sent, visible light driving current is controlled so as to obtain and send visible light communication signals;
transmitting generalized ACO-OFDM signals on part of odd subcarriers, and multiplying the generalized ACO-OFDM signals by ACO-OFDM signal amplification factors; transmitting the DCO-OFDM signal on the even subcarriers and the remaining odd subcarriers and multiplying by the amplification factor of the DCO-OFDM signal, comprising:
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even number subcarriers outside the number;
wherein N is the number of subcarriers.
2. The generalized hybrid visible light modulation method according to claim 1, wherein the number of generalized ACO-OFDM subcarriers is at least zero and at most not more than half of the number of all subcarriers.
3. The method of claim 1, wherein the number of DCO-OFDM subcarriers is at least half of the number of all subcarriers and at most not more than the number of all subcarriers.
4. The method of generalized hybrid visible light modulation according to claim 1, further comprising:
and changing the amplification factors of the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to system requirements.
5. The method of claim 1, wherein the visible light communication signal has a minimum signal amplitude of 0 and a maximum signal amplitude of the LED maximum linear operating current.
6. A generalized hybrid visible light modulation device, comprising:
the generalized ACO-OFDM modulation module is used for transmitting generalized ACO-OFDM signals on part of odd subcarriers and multiplying the generalized ACO-OFDM signals by an ACO-OFDM signal amplification factor;
the DCO-OFDM modulation module is used for transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers and multiplying the DCO-OFDM signals by an amplification factor;
the signal fusion module is used for respectively carrying out discrete Fourier transform on the generalized ACO-OFDM signal and the DCO-OFDM signal, carrying out unipolar processing on the transformed ACO-OFDM signal, and adding direct current offset to the transformed DCO-OFDM signal to obtain a signal frame to be transmitted; the generalized ACO-OFDM and DCO-OFDM signals satisfy a Hermitian symmetry structure, the generalized ACO-OFDM signals including: a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal obtained by carrying out zero setting on a positive part of a bipolar signal before the ACO-OFDM signal is subjected to asymmetric amplitude limiting and reserving a negative part of the bipolar signal; changing the generalized ACO-OFDM signal into a positive polarity ACO-OFDM signal or a negative polarity ACO-OFDM signal frame by frame according to system requirements; changing the number of sub-carriers occupied by the generalized ACO-OFDM signal and the DCO-OFDM signal frame by frame according to system requirements; and
the signal transmitting module is used for controlling visible light driving current after carrying out amplitude limiting, digital-to-analog conversion and filtering on the signal frame to be transmitted so as to acquire and transmit a visible light communication signal;
the generalized ACO-OFDM modulation module is used for transmitting generalized ACO-OFDM signals on part of odd subcarriers and multiplying the generalized ACO-OFDM signals by an ACO-OFDM signal amplification factor; the DCO-OFDM modulation module is used for transmitting DCO-OFDM signals on even subcarriers and the rest odd subcarriers and multiplying the DCO-OFDM signals by an amplification factor; the method comprises the following steps:
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even subcarriers except the one with the number of
On odd subcarriers of (1);
data ofObtaining constellation mapping symbol X after QPSK constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the ACO-OFDM signalAPost modulation is numbered as
On odd subcarriers of (1);
obtaining constellation mapping symbol X after data is subjected to 16QAM constellation mappingkAnd mapping the constellation to symbol XkMultiplying by the amplification factor alpha of the DCO-OFDM signalDPost modulation is in the division of 0 th and second
All even number subcarriers outside the number;
wherein N is the number of subcarriers.
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