CN113438193A - Hybrid self-adaptive offset O-OFDM visible light communication system and method - Google Patents

Hybrid self-adaptive offset O-OFDM visible light communication system and method Download PDF

Info

Publication number
CN113438193A
CN113438193A CN202110645780.5A CN202110645780A CN113438193A CN 113438193 A CN113438193 A CN 113438193A CN 202110645780 A CN202110645780 A CN 202110645780A CN 113438193 A CN113438193 A CN 113438193A
Authority
CN
China
Prior art keywords
signal
data
visible light
domain signal
frequency domain
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110645780.5A
Other languages
Chinese (zh)
Other versions
CN113438193B (en
Inventor
李正权
洪焕东
关少义
马可
陆波
丁文杰
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ictehi Technology Development Co ltd
Jiangnan University
Original Assignee
Ictehi Technology Development Co ltd
Jiangnan University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ictehi Technology Development Co ltd, Jiangnan University filed Critical Ictehi Technology Development Co ltd
Priority to CN202110645780.5A priority Critical patent/CN113438193B/en
Publication of CN113438193A publication Critical patent/CN113438193A/en
Application granted granted Critical
Publication of CN113438193B publication Critical patent/CN113438193B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • 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
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • 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
    • H—ELECTRICITY
    • 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
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2697—Multicarrier modulation systems in combination with other modulation techniques
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optical Communication System (AREA)

Abstract

The invention discloses a mixed self-adaptive offset O-OFDM visible light communication system and a method, wherein two visible light communication modulation methods of PAM and QAM are mixed at a transmitting end, original data are grouped, and three groups of data are respectively transmitted and modulated by adopting different subcarriers, so that the frequency spectrum utilization rate of the system is improved; when the non-negativity of the signal is ensured, the adaptive bias is added, so that the requirement of the non-negativity of the signal can be met, and noise generated by introducing the adaptive bias cannot cause interference on signal demodulation under two modulation modes; according to the system and the method, because the receiving end has no influence of amplitude-cutting noise and self-adaptive bias noise, the signal is not required to be subjected to denoising processing, so that the complexity of the system is reduced; according to the technical scheme of the invention, the peak-to-average power ratio (PAPR) of the visible light communication modulation method is compared with that of the conventional visible light communication modulation method, so that the peak-to-average power ratio (PAPR) of the visible light communication modulation method has remarkable advantages, and the power efficiency of the system is improved.

Description

Hybrid self-adaptive offset O-OFDM visible light communication system and method
Technical Field
The invention relates to a visible light communication system and a method of hybrid self-adaptive offset O-OFDM, belonging to the technical field of wireless optical communication.
Background
The visible light communication combines the LED technology with information transmission, does not occupy radio frequency spectrum resources, and can provide a high-speed and large-capacity communication method for an indoor wireless communication network. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique with a high spectrum utilization rate, can effectively resist multipath fading and inter-signal interference in a wireless transmission process, is simple to implement, and has been widely applied to visible light communication.
Visible light communication systems typically employ intensity modulated direct detection (IM/DD) and therefore visible light communication can only transmit positive real signals. In the prior art, a signal modulation method of an asymmetric amplitude-cut optical orthogonal frequency division multiplexing (ACO-OFDM) ensures non-negativity of a signal by amplitude-cutting the signal, but because the technique only modulates odd subcarriers, all subcarriers are not fully utilized to transmit data, so that the frequency spectrum utilization rate is still low.
The method for improving the spectrum utilization rate generally comprises the following steps: more sub-carrier resources are utilized to transmit data, i.e. more sub-carriers are modulated to transmit data, and more sub-carriers use QAM modulation to transmit data. However, in the signal modulation method of the hybrid asymmetric amplitude-cut optical orthogonal frequency division multiplexing (HACO-OFDM), although both odd subcarriers and even subcarriers are utilized and the even subcarriers all use PAM modulation, only the imaginary part of the even subcarriers is modulated to transmit data, which may result in that the spectrum utilization rate may not achieve the optimal effect, and amplitude-cut noise affects signal demodulation, such that the system complexity increases and the peak-to-average power ratio (PAPR) of the signal is high.
Disclosure of Invention
In order to solve the problems of low frequency spectrum utilization rate, high peak-to-average power ratio (PAPR) and high system complexity in the prior art of visible light communication, the invention provides a visible light communication system and a method of hybrid self-adaptive offset optical orthogonal frequency division multiplexing (O-OFDM), which not only can increase the frequency spectrum utilization rate, but also can reduce the PAPR, simultaneously reduces the system complexity and improves the power efficiency. The technical scheme of the hybrid self-adaptive offset O-OFDM visible light communication system and the method provided by the invention is as follows.
According to the visible light communication system of the mixed self-adaptive offset O-OFDM, the visible light communication system comprises a transmitting end and a receiving end, and the transmitting end is connected with the receiving end through a VLC optical channel;
the transmitting end includes: the system comprises a data distributor, a hybrid self-adaptive bias modulator, a digital-to-analog converter and an LED; the data distributor, the hybrid adaptive bias modulator, the digital-to-analog converter and the LED are connected in sequence;
the receiving end includes: the device comprises a photoelectric converter, an analog-to-digital converter, a hybrid self-adaptive bias demodulator and a data combiner; the photoelectric converter, the analog-to-digital converter, the hybrid self-adaptive bias demodulator and the data combiner are sequentially connected.
According to the visible light communication system, at the transmitting end, the data distributor calculates and divides original data D into data D1, data D2 and data D3; the data D1, the data D2 and the data D3 are all modulated by the hybrid adaptive bias modulator, the hybrid adaptive bias modulator further includes a quadrature amplitude modulator (QAM modulator) and a pulse amplitude modulator (PAM modulator), and the data D1, the data D2 and the data D3 are modulated by the hybrid adaptive bias modulator respectively as follows: data D1 is transmitted by being loaded on a subcarrier with a sequence of 2m +1 and forms a QAM signal through a QAM modulator, data D2 is transmitted by being loaded on a subcarrier with a sequence of 4m +2 and forms a QAM signal through the QAM modulator, and data D3 is transmitted by being loaded on a subcarrier with a sequence of 4m and forms a PAM signal through the PAM modulator.
Further, at a transmitting end, the hybrid adaptive bias modulator cuts the modulated PAM signal, time domain signals obtained by Fourier inverse transformation of the two groups of QAM signals after superposition and time domain signals obtained by Fourier inverse transformation of the cut PAM signal are superposed, and adaptive bias s is introducednEnsuring non-negativity of the signal and introducing an adaptive bias snThe noise does not affect the signal demodulation, and the mixed signal z is finally outputn。
According to the system, at a receiving end, the hybrid self-adaptive offset demodulator further comprises a PAM demodulator and a QAM demodulator; mixed signal z at transmitting endnConverted by a digital-to-analog converter and transmitted to a receiving end, and converted into a mixed signal z by an analog-to-digital convertern' hybrid adaptive bias demodulator for hybrid signal zn' the process of demodulating is as follows: mixed signal znObtaining a PAM signal and two groups of QAM signals through Fourier transform, simultaneously outputting the PAM signal and the QAM signals, and obtaining a demodulated PAM signal D3' through a PAM demodulator by the PAM signal; the two groups of QAM signals pass through a QAM demodulator to obtain two groups of demodulated QAM signals D1 'and D2'; and (3) the two groups of demodulated QAM signals D1 'and D2' and the demodulated PAM signal D3 'are subjected to a data combiner to obtain demodulated original data D'.
The invention provides a visible light communication method, which is applied to a transmitting end of a visible light communication system of O-OFDM (orthogonal frequency division multiplexing) with hybrid self-adaptive offset, and comprises the following steps:
the method comprises the following steps: original transmission data D is calculated and divided into three groups of data D1, D2 and D3 through a data distributor, the three groups of data are respectively modulated by a hybrid adaptive bias modulator, the data D1 are transmitted only in subcarriers with the sequence of 2m +1 and are modulated by a QAM modulator, and a frequency domain signal X is obtained1Data D2 is transmitted only in the subcarrier with the sequence of 4m +2 and modulated by a Quadrature Amplitude Modulator (QAM) modulator to obtain a frequency domain signal X2Data D3 is transmitted only in subcarriers with sequence 4m and modulated by PAM modulator to obtain frequency domain signal Y, where m is 0,1, …, NN is the number of subcarriers, and the number of subcarriers used for transmitting signals in each group is N;
step two: frequency domain signal X by hybrid adaptive bias modulator1And frequency domain signal X2Superposing to obtain a frequency domain signal X, and carrying out inverse Fourier transform on the frequency domain signal X to obtain a time domain signal XnPerforming inverse Fourier transform on the frequency domain signal Y to obtain a time domain signal YnAnd for the time domain signal ynCutting to obtain a cut time domain signal qnThen superimpose the time domain signal xnAnd a clipped time domain signal qnTo obtain a mixed signal wnThen adding adaptive bias snEnsuring the mixed signal wnAnd causes the introduction of an adaptive bias snThe noise does not affect the signal demodulation, and finally a new mixed signal z is obtainedn；
Step three: mixing signal z by a hybrid adaptive bias modulatornAnd adding a cyclic prefix, transmitting the cyclic prefix to a digital-to-analog converter (DAC) to obtain an analog signal, driving the LED to emit light by the analog signal, converting the light into a light signal, and transmitting the light signal to a receiving end through a VLC channel.
According to the visible light communication method of the present invention, the first step for the transmitting end further comprises the following detailed steps:
a1: the first group of data D1 is transmitted only in the subcarrier with the sequence of 2m +1 and modulated by a QAM modulator, the modulated signal is subjected to serial-parallel conversion and then mapping and Hermite symmetry to obtain a frequency domain signal X1(ii) a The second group of data D2 is transmitted only in the subcarrier with the sequence of 4m +2 and modulated by a QAM modulator, the modulated signal is subjected to serial-parallel conversion and then mapping and Hermite symmetry to obtain a frequency domain signal X2；
A2: the third group of data D3 is transmitted only in subcarriers with a sequence of 4m and modulated by a PAM modulator, the modulated signals are subjected to serial-to-parallel conversion, and then mapped and hermitian symmetric to obtain frequency domain signals Y (m is 0,1, …, N/8, where N is the number of subcarriers, and the number of subcarriers used for transmitting signals in each group is N).
According to the visible light communication method of the present invention, optionally, the step a1 further includes the following detailed steps:
b1: frequency domain signal X1Expressed as:
Figure BDA0003109523760000031
wherein N is the number of subcarriers, QiRepresenting a QAM signal. And the modulated signal satisfies the following equation in the time domain:
Figure BDA0003109523760000032
b2: frequency domain signal X2Expressed as:
Figure BDA0003109523760000033
wherein N is the number of subcarriers, QiRepresenting a QAM signal.
According to the visible light communication method of the present invention, optionally, the step a2 further includes the following detailed steps:
b1: the frequency domain signal Y is represented as:
Figure BDA0003109523760000034
wherein N is the number of subcarriers, PiRepresenting a PAM signal. And the following equation is satisfied in the time domain of the modulated signal:
Figure BDA0003109523760000041
according to the visible light communication method of the present invention, optionally, the step two for the transmitting end includes the following detailed steps:
c1: the frequency domain signal X is represented as:
Figure BDA0003109523760000042
wherein N is the number of subcarriers, QiRepresents a QAM signal;
c2: time domain signal ynPerforming clipping operation to obtain a time domain signal qnThe specific process comprises the following steps:
Figure BDA0003109523760000043
in the formula (I), the compound is shown in the specification,
Figure BDA0003109523760000044
indicating y after clippingnValue of (a), qnRepresenting the clipped time domain signal.
C3: superimposed time domain signal xnAnd a clipped time domain signal qnTo obtain a mixed signal wnThe specific expression is as follows:
wn＝xn+qn,n＝0,1,…,N-1；
c4: adding adaptive bias snEnsuring the mixed signal wnAnd causes the introduction of an adaptive bias snThe noise does not affect the signal demodulation, and finally a new mixed signal z is obtainednThe specific expression is as follows:
zn＝wn+sn,n＝0,1,…,N-1。
according to the visible light communication method of the present invention, optionally, the step C4 further includes the following detailed steps:
e1: adaptive biasing snThe following conditions are satisfied:
Figure BDA0003109523760000045
sn+wn≥0,n＝0,1,…,N-1；
e2: synthesis of E1 to obtain an adaptive bias snFinally, the conditions are met:
Figure BDA0003109523760000046
the invention also provides a visible light communication method, which is applied to a receiving end of a visible light communication system of the hybrid self-adaptive offset O-OFDM, and comprises the following steps:
the method comprises the following steps: the photoelectric converter receives the optical signal transmitted by VLC channel and converts it into electric signal, after the electric signal passes through analog-to-digital converter (ADC), the mixed signal z of receiving end is obtainedn' mixing the mixed signal z by a hybrid adaptive bias demodulatorn' demodulating, removing cyclic prefix, for mixed signal znPerforming Fourier transform (FFT) to obtain a receiving end frequency domain signal X 'and a frequency domain signal Y', and separating the frequency domain signal X 'according to the superposition rule of a transmitting end to obtain a frequency domain signal X'1And frequency domain signal X'2Finally, three groups of frequency domain signals X 'are output'1，X'2And Y';
step two: the frequency domain signal Y 'is subjected to a PAM demodulator to obtain a demodulated PAM signal D3', and the frequency domain signal X 'is obtained'1And frequency domain signal X'2Sending the signals into a QAM demodulator to obtain demodulated QAM signals D1 'and D2' respectively;
step three: and recovering the original data D 'by passing the three groups of demodulated signals D3' and D2 'and D1' through a data combiner.
According to the visible light communication method of the present invention, optionally, the step one for the receiving end further includes the following detailed steps:
f1: the frequency domain signal X 'is separated according to the superposition rule of the transmitting ends'1And frequency domain signal X'2The specific process is as follows:
the transmitting end transmits the frequency domain signal X only with the modulation sequence of 2m +1 subcarriers1And the frequency domain signal superposition transmitted in 4m +2 subcarriers by using only the modulation sequence (wherein m is 0,1, …, N/8, N is the number of subcarriers, and each group is used for transmittingThe number of subcarriers of the input signal is N), and a frequency domain signal X is obtained; when the receiving end separates the frequency domain signal X ', according to the sequence rule corresponding to the modulation subcarrier of the transmitting end, namely the signal carried by the subcarrier with the sequence of 2m +1 in the frequency domain signal X ' is the frequency domain signal X '1The signal carried by the subcarrier with the sequence of 4m +2 in the frequency domain signal X 'is a frequency domain signal X'2。
The invention has the beneficial effects that:
according to the visible light communication system and method of the invention, at the transmitting end, the original data D is divided into three groups: data D1, data D2 and data D3, three groups of data D1, D2 and D3 are respectively modulated by a hybrid adaptive bias modulator, data D1 is transmitted by being loaded to a subcarrier with a sequence of 2m +1 and forms a QAM signal by a QAM modulator, data D2 is transmitted by being loaded to a subcarrier with a modulation sequence of 4m +2 and forms a QAM signal by the QAM modulator, and data D3 is transmitted by being loaded to a subcarrier with a modulation sequence of 4m and forms a PAM signal by the PAM modulator; therefore, the real part and the imaginary part of the subcarrier with the sequence of 4m +2 in the even number of subcarriers are modulated and data are transmitted, and the subcarrier with the sequence of 4m only modulates the imaginary part to transmit the data, so that the frequency spectrum utilization rate of the system is improved.
According to the visible light communication system and the method, at the transmitting end, the hybrid adaptive bias modulator cuts the modulated PAM signal, two groups of QAM signals and the cut PAM signal are superposed, adaptive bias is introduced to ensure the non-negativity of the signals, and the adaptive bias s is introducednThe noise does not affect the signal demodulation, and the mixed signal z is finally outputn. Therefore, the signal superposition modulated by the hybrid adaptive bias modulator in the transmitting end is directly superposed without other devices; the above-mentioned cutting operation can also be directly implemented, and has no need of other devices.
According to the visible light communication system and method, at the transmitting end, the clipping noise caused by the hybrid adaptive bias modulator clipping the PAM signal only affects the real part of the subcarrier with the sequence of 4m and does not affect the imaginary part of the subcarrier with the sequence of 4m, and the data D3 is transmitted only by modulating the imaginary part of the subcarrier with the sequence of 4m, so that the PAM signal is clipped without considering the effect of the clipping noise.
According to the mixed self-adaptive offset O-OFDM visible light communication system and method, the two visible light communication modulation methods of PAM and QAM are mixed, data are grouped, and three groups of data are respectively transmitted and modulated by adopting different subcarriers, so that the frequency spectrum utilization rate of the system is improved; in addition, the self-adaptive bias is added in the process of ensuring the nonnegativity of the signals, so that the requirement of the nonnegativity of the signals is met, and noise generated by the self-adaptive bias is introduced to not interfere with the signal demodulation under the two modulation modes; because the receiving end has no influence of amplitude-cutting noise and self-adaptive bias noise, the signal is not required to be subjected to denoising processing, so that the complexity of the system is reduced; according to the technical scheme of the invention, the peak-to-average power ratio (PAPR) of the modulation method has obvious advantages in comparison with the conventional visible light communication modulation method, and the power efficiency of the system can be improved compared with the conventional HACO-OFDM system.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a hybrid adaptive offset O-OFDM visible light communication system of the present invention;
FIG. 2 is a graph comparing bit error rates of hybrid adaptive offset O-OFDM systems and HACO-OFDM systems of the present invention;
FIG. 3 is a PAPR complementary cumulative distribution function graph of the hybrid adaptive offset O-OFDM system and HACO-OFDM system of the present invention;
FIG. 4 is a graph comparing power efficiency of hybrid adaptive offset O-OFDM system and HACO-OFDM system of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The first embodiment is as follows:
fig. 1 is a schematic diagram illustrating a principle of a hybrid adaptive offset O-OFDM visible light communication system according to the present invention.
According to the visible light communication system of the hybrid adaptive offset O-OFDM of the present embodiment, the visible light communication system includes a transmitting end and a receiving end, and the transmitting end is connected to the receiving end through a VLC optical channel; the transmitting end includes: the system comprises a data distributor, a hybrid self-adaptive bias modulator, a digital-to-analog converter and an LED; the data distributor, the hybrid adaptive bias modulator, the digital-to-analog converter and the LED are connected in sequence; the receiving end includes: the device comprises a photoelectric converter, an analog-to-digital converter, a hybrid self-adaptive bias demodulator and a data combiner; the photoelectric converter, the analog-to-digital converter, the hybrid self-adaptive bias demodulator and the data combiner are sequentially connected.
According to the visible light communication system of the present embodiment, at the transmitting end, the data distributor calculates and divides the original data D into data D1, data D2, and data D3; the data D1, the data D2 and the data D3 are all modulated by a hybrid adaptive bias modulator, the hybrid adaptive bias modulator further comprises a quadrature amplitude modulator (QAM modulator) and a pulse amplitude modulator (PAM modulator), the data D1, the data D2 and the data D3 are all modulated by the hybrid adaptive bias modulator, and the modulation process is as follows:
the data D1 is transmitted by being loaded on a subcarrier with the sequence of 2m +1 and forms a QAM signal through a QAM modulator, the data D2 is transmitted by being loaded on a subcarrier with the sequence of 4m +2 and forms a QAM signal through the QAM modulator, and the data D3 is transmitted by being loaded on a subcarrier with the sequence of 4m and forms a PAM signal through the PAM modulator.
Further, at the transmitting end, the hybrid adaptive bias modulator cuts the modulated PAM signal, and then the two groups of PAM signals are subjected to clipping processingSuperposing a time domain signal obtained by Fourier inverse transformation of a QAM signal after superposition and a time domain signal obtained by Fourier inverse transformation of a cut PAM signal, and introducing self-adaptive bias snEnsuring non-negativity of the signal and introducing an adaptive bias snThe noise does not affect the signal demodulation, and the mixed signal z is finally outputn。
According to the system, at a receiving end, the hybrid self-adaptive offset demodulator further comprises a PAM demodulator and a QAM demodulator; mixed signal z at transmitting endnConverted by a digital-to-analog converter and transmitted to a receiving end, and converted into a mixed signal z by an analog-to-digital convertern' hybrid adaptive bias demodulator for hybrid signal zn' the process of demodulating is as follows:
mixed signal znObtaining a PAM signal and two groups of QAM signals through Fourier transform, simultaneously outputting the PAM signal and the QAM signals, and obtaining a demodulated PAM signal D3' through a PAM demodulator by the PAM signal; the two groups of QAM signals pass through a QAM demodulator to obtain two groups of demodulated QAM signals D1 'and D2'; and recovering original data D 'by the data combiner from the two groups of demodulated QAM signals D1' and D2 'and the demodulated PAM signal D3'.
The embodiment provides a visible light communication method, which is applied to a transmitting end of a visible light communication system of O-OFDM (orthogonal frequency division multiplexing) with hybrid adaptive bias, and the method comprises the following steps:
the method comprises the following steps: original transmission data D is calculated and divided into three groups of data D1, D2 and D3 through a data distributor, the three groups of data are respectively modulated by a hybrid adaptive bias modulator, the data D1 are only transmitted in subcarriers with the sequence of 2m +1 and are modulated by a QAM modulator, and a frequency domain signal X is obtained1Data D2 is transmitted only in subcarrier with sequence of 4m +2 and modulated by QAM modulator to obtain frequency domain signal X2Data D3 is transmitted only on subcarriers with sequence of 4m and modulated by a PAM modulator, so as to obtain a frequency domain signal Y (m is 0,1, …, N/8, where N is the number of subcarriers, and the number of subcarriers used for transmitting signals in each group is N);
step two: by mixingCombining adaptive bias modulator to convert frequency domain signal X1And frequency domain signal X2Superposing to obtain a frequency domain signal X, and carrying out inverse Fourier transform on the frequency domain signal X to obtain a time domain signal XnPerforming inverse Fourier transform on the frequency domain signal Y to obtain a time domain signal YnAnd for the time domain signal ynCutting to obtain a cut time domain signal qnThen superimpose the time domain signal xnAnd a clipped time domain signal qnTo obtain a mixed signal wnThen adding adaptive bias snEnsuring the mixed signal wnAnd causes the introduction of an adaptive bias snThe noise does not affect the signal demodulation, and finally a new mixed signal z is obtainedn；
Step three: hybrid adaptive bias modulator for mixing signal znAnd adding a cyclic prefix, transmitting the cyclic prefix to a digital-to-analog converter (DAC) to obtain an analog signal, driving the LED to emit light by the analog signal, converting the light into a light signal, and transmitting the light signal to a receiving end through a VLC channel.
According to the visible light communication method of the present embodiment, the first step for the transmitting end further includes the following detailed steps:
a1: the first group of data D1 is transmitted only in the subcarrier with the sequence of 2m +1 and modulated by a QAM modulator, the modulated signals are subjected to serial-parallel conversion and then are mapped and Hermite-symmetric to obtain a frequency domain signal X1(ii) a The second group of data D2 is transmitted only in the subcarrier with the sequence of 4m +2 and modulated by a QAM modulator, the modulated signal is subjected to serial-parallel conversion and then mapping and Hermite symmetry to obtain a frequency domain signal X2；
A2: the third group of signals D3 are transmitted only in the imaginary part of the subcarrier with the sequence of 4m and modulated by a PAM modulator, the modulated signals are subjected to serial-to-parallel conversion, and then mapped and hermitian symmetric to obtain a frequency domain signal Y (m is 0,1, …, N/8, where N is the number of subcarriers, and the number of subcarriers used for transmitting signals in each group is N).
According to the visible light communication method of this embodiment, optionally, the step a1 further includes the following detailed steps:
b1: frequency domain signal X1Expressed as:
Figure BDA0003109523760000081
where N is the number of subcarriers, LiRepresenting a QAM signal. And the modulated signal satisfies the following equation in the time domain:
Figure BDA0003109523760000082
b2: frequency domain signal X2Expressed as:
Figure BDA0003109523760000083
in which N is the number of subcarriers, IiRepresenting a QAM signal. And the modulated signal satisfies the following equation in the time domain:
Figure BDA0003109523760000084
according to the visible light communication method of this embodiment, optionally, the step a2 further includes the following detailed steps:
b1: the frequency domain signal Y is represented as:
Figure BDA0003109523760000091
wherein N is the number of subcarriers, PiRepresents a PAM signal; and the modulated signal satisfies the following equation in the time domain:
Figure BDA0003109523760000092
according to the visible light communication method of this embodiment, optionally, the step two for the transmitting end includes the following detailed steps:
c1: the frequency domain signal X is represented as:
Figure BDA0003109523760000093
wherein N is the number of subcarriers, QiRepresenting a QAM signal. And the modulated signal satisfies the following equation in the time domain:
Figure BDA0003109523760000094
c2: time domain signal ynPerforming clipping operation to obtain a time domain signal qnThe specific process comprises the following steps:
Figure BDA0003109523760000095
in the formula (I), the compound is shown in the specification,
Figure BDA0003109523760000096
indicating y after clippingnValue of (a), qnRepresenting the clipped time domain signal.
C3: superimposed time domain signal xnAnd a clipped time domain signal qnTo obtain a mixed signal wnThe specific expression is as follows:
wn＝xn+qn,n＝0,1,…,N-1。
c4: adding adaptive bias snEnsuring the mixed signal wnAnd causes the introduction of an adaptive bias snThe noise does not affect the signal demodulation, and finally a new mixed signal z is obtainednThe specific expression is as follows:
zn＝wn+sn,n＝0,1,…,N-1。
according to the visible light communication method of the present embodiment, the step C4 further includes the following detailed steps:
e1: adaptive biasing snShould satisfy the followingA piece:
Figure BDA0003109523760000097
sn+wn≥0,n＝0,1,…,N-1；
e2: synthesis of E1 to obtain an adaptive bias snThe conditions should be met finally:
Figure BDA0003109523760000101
the embodiment also provides a visible light communication method, which is applied to a receiving end of a hybrid adaptive offset O-OFDM visible light communication system, and the method includes the following steps:
the method comprises the following steps: the photoelectric converter receives the optical signal transmitted by VLC channel, converts it into electric signal, and after the electric signal passes through analog-to-digital converter (ADC), the mixed signal z of receiving end is obtainedn' mixing the mixed signal z by a hybrid adaptive bias demodulatorn' demodulating, removing cyclic prefix, for mixed signal znPerforming Fourier transform (FFT) to obtain a receiving end frequency domain signal X 'and a frequency domain signal Y', and separating the frequency domain signal X 'according to the superposition rule of a transmitting end to obtain a frequency domain signal X'1And frequency domain signal X'2Finally, three groups of frequency domain signals X 'are output'1，X'2And Y';
step two: the frequency domain signal Y 'is subjected to a PAM demodulator to obtain a demodulated PAM signal D3', and the frequency domain signal X 'is obtained'1And frequency domain signal X'2Sending the signals into a QAM demodulator to obtain demodulated QAM signals D1 'and D2' respectively;
step three: and recovering the original data D 'by passing the three groups of demodulated signals D3' and D2 'and D1' through a data combiner.
According to the present embodiment, the adaptive bias s is introduced in the step C4nThe specific proving process that the brought noise does not affect the signal demodulation is as follows:
Figure BDA0003109523760000102
F1：
Figure BDA0003109523760000103
f2: for k being odd, e-jπk-1, giving the following formula:
Figure BDA0003109523760000104
f3: for k 4m +2, and when k is even, e-jπk1, the following formula is obtained:
Figure BDA0003109523760000111
f4: for k 4m, and when k is even, e-jπk1, the following formula is obtained:
Figure BDA0003109523760000112
f5: as can be seen from the above verification process, the adaptively biased noise only affects the real part of the subcarrier with the sequence of 4m, while the scheme of the present embodiment only modulates the imaginary part of the subcarrier with the sequence of 4m, so the adaptively biased noise also does not affect the demodulation thereof.
According to the visible light communication method of the present embodiment, the first step for the receiving end further includes the following detailed steps:
g1: the frequency domain signal X 'is separated according to the superposition rule of the transmitting ends'1And frequency domain signal X'2The specific process is as follows:
the transmitting end transmits the frequency domain signal X only with the modulation sequence of 2m +1 subcarriers1And the frequency domain signal which is transmitted in 4m +2 subcarriers by only modulation sequence (wherein m is 0,1, …, N/8, N is subcarrierThe number of subcarriers used for transmitting signals in each group is N), and a frequency domain signal X is obtained; when the receiving end separates the frequency domain signal X ', according to the sequence rule corresponding to the modulation subcarrier of the transmitting end, namely the signal carried by the subcarrier with the sequence of 2m +1 in the frequency domain signal X ' is the frequency domain signal X '1The signal carried by the subcarrier with the sequence of 4m +2 in the frequency domain signal X 'is a frequency domain signal X'2。
FIG. 2 is a graph comparing error rates of hybrid adaptive offset O-OFDM and HACO-OFDM according to the present invention, wherein the error rates of the proposed scheme and HACO-OFDM are compared under 3 modulation conditions of 16QAM-4PAM, 64QAM-4PAM, 256QAM-4PAM, respectively. It can be known from the curves in fig. 2 that, as the number of QAM modulations increases, the error rate performance of the two modulation schemes gets closer and closer, and although the error rate performance of the scheme proposed by the present invention slightly decreases compared with the HACO-OFDM error rate performance under different modulation conditions, the spectrum utilization rate of the scheme proposed by the present invention is more advantageous than the HACO-OFDM, and the power efficiency is also higher than the HACO-OFDM.
FIG. 3 is a graph of peak-to-average power ratio (PAPR) complementary cumulative distribution functions of hybrid adaptive offset O-OFDM and HACO-OFDM according to the present invention, wherein the curves of Complementary Cumulative Distribution Functions (CCDF) of HACO-OFDM under the conditions of 16QAM-4PAM and 64QAM-4PAM are almost overlapped, and the curves of Complementary Cumulative Distribution Functions (CCDF) of the scheme proposed in the present invention under the conditions of 16QAM-4PAM and 64QAM-4PAM are also almost overlapped, which shows that the PAPRs of HACO-OFDM under different modulation conditions are almost identical, and the scheme proposed in the present invention is also identical, and under the same conditions, the PAPRs of the two different modulation modes are compared, the scheme proposed in the present invention is reduced by about 2.8dB compared with that of HACO-OFDM, which shows that the scheme of the present invention significantly reduces the PAPR of the system.
Fig. 4 is a graph comparing the power efficiency of hybrid adaptive offset O-OFDM and HACO-OFDM of this embodiment, and it can be seen from the graph that when the bit rate/normalized bandwidth is in the range of 3 to 9, the system of the present invention achieves the bit error rate target with lower requirement, so the system of this embodiment has more advantage in power efficiency, and as the bit rate/normalized bandwidth increases, the telecommunication noise ratio required to achieve the bit error rate target is much lower than that of the HACO-OFDM system, which shows that in a large bit rate/normalized range, the system of this embodiment has higher power efficiency compared to HACO-OFDM.
According to the mixed self-adaptive offset O-OFDM visible light communication system and method, data are grouped by mixing two visible light communication modulation methods of PAM and QAM, three groups of data are respectively transmitted and modulated by adopting different subcarriers, the real part and the imaginary part of a subcarrier with a sequence of 4m +2 in an even number of subcarriers are modulated to transmit the data, the subcarrier with the sequence of 4m still only modulates the imaginary part to transmit the data, and the spectrum utilization rate of the system is improved; in addition, the self-adaptive bias is added in the process of ensuring the nonnegativity of the signals, so that the requirement of the nonnegativity of the signals is met, and noise generated by the self-adaptive bias is introduced to not interfere with the signal demodulation under the two modulation modes; because the receiving end has no influence of amplitude-cutting noise and self-adaptive bias noise, the signal is not required to be subjected to denoising processing, so that the complexity of the system is reduced; further, as can be seen from the above description, according to the technical solution of the present invention, the peak-to-average power ratio (PAPR) comparison with the conventional visible light communication modulation method is also significantly advantageous, and the power efficiency of the system can be improved compared with HACO-OFDM.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. The visible light communication system of the O-OFDM with the hybrid self-adaptive bias comprises a transmitting end and a receiving end, wherein the transmitting end is connected with the receiving end through a VLC optical channel;
the transmitting end includes: the system comprises a data distributor, a hybrid self-adaptive bias modulator, a digital-to-analog converter and an LED; the data distributor, the hybrid adaptive bias modulator, the digital-to-analog converter and the LED are connected in sequence;
the receiving end includes: the device comprises a photoelectric converter, an analog-to-digital converter, a hybrid self-adaptive bias demodulator and a data combiner; the photoelectric converter, the analog-to-digital converter, the hybrid adaptive bias demodulator and the data combiner are sequentially connected.
2. The visible light communication system of claim 1, wherein the hybrid adaptive bias modulator further comprises a QAM modulator and a PAM modulator;
at the transmitting end, the data distributor calculates and divides original data D into data D1, data D2 and data D3; the data D1, the data D2, and the data D3 are all modulated by the hybrid adaptive bias modulator as follows:
the data D1 are transmitted by being loaded on a subcarrier with a sequence of 2m +1 and form a QAM signal through the QAM modulator, the data D2 are transmitted by being loaded on a subcarrier with a sequence of 4m +2 and form a QAM signal through the QAM modulator, and the data D3 are transmitted by being loaded on a subcarrier with a sequence of 4m and form a PAM signal through the PAM modulator.
3. The visible light communication system according to claim 2, wherein at the transmitting end, the hybrid adaptive bias modulator performs clipping processing on the modulated PAM signal, then superimposes a time domain signal obtained by performing inverse fourier transform on two groups of QAM signals after superimposing and a time domain signal obtained by performing inverse fourier transform on the clipped PAM signal, and introduces an adaptive bias snEnsuring non-negativity of the signal and introducing an adaptive bias snThe noise does not affect the signal demodulation, and the mixed signal z is outputn。
4. The visible light communication system according to claim 1, wherein at the receiving end, the hybrid adaptive bias demodulator further comprises a PAM demodulator and a QAM demodulator; mixed signal z of the transmitting endnConverted by the D/A converter and transmitted to the receiving end, and converted into a mixed signal z by the A/D convertern'。
5. The visible light communication system according to claim 1, wherein the hybrid adaptive bias demodulator is configured to demodulate the hybrid signal zn' the process of demodulating is as follows:
the mixed signal znObtaining a PAM signal and two groups of QAM signals through Fourier transform, simultaneously outputting the PAM signal and the QAM signals, and obtaining a demodulated PAM signal D3' through a PAM demodulator by the PAM signal; the two groups of QAM signals pass through a QAM demodulator to obtain two groups of demodulated QAM signals D1 'and D2'; and recovering original data D 'by the data combiner from the two groups of demodulated QAM signals D1' and D2 'and the demodulated PAM signal D3'.
6. A visible light communication method, applied to a transmitting end of a visible light communication system of hybrid adaptive offset O-OFDM, comprising the steps of:
the method comprises the following steps: original transmission data D is calculated and divided into three groups of data D1, data D2 and data D3 through a data distributor, the three groups of data are respectively modulated by a hybrid adaptive bias modulator, the data D1 are only transmitted in subcarriers with the sequence of 2m +1 and are modulated by a QAM modulator, and a frequency domain signal X is obtained1The data D2 is transmitted only in the subcarrier with the sequence of 4m +2 and is modulated by a QAM modulator to obtain a frequency domain signal X2The data D3 is transmitted only in subcarriers with a sequence of 4m and modulated by a PAM modulator, so as to obtain a frequency domain signal Y, where m is 0,1, …, N/8, N is the number of subcarriers, and the number of subcarriers used for transmitting signals in each group is N;
step two: frequency domain signal X by the hybrid adaptive bias modulator1And frequency domain signal X2Superposing to obtain a frequency domain signal X, and carrying out inverse Fourier transform on the frequency domain signal X to obtain a time domain signal XnPerforming inverse Fourier transform on the frequency domain signal Y to obtain a time domain signal YnAnd for the time domain signal ynCutting to obtain a cut time domain signal qnThen superimpose the time domain signal xnAnd a clipped time domain signal qnTo obtain a mixed signal wnThen adding adaptive bias snEnsuring the mixed signal wnAnd causes the introduction of an adaptive bias snThe noise does not affect the signal demodulation and a new mixed signal z is obtainedn；
Step three: mixing the signal z by the hybrid adaptive bias modulatornAnd adding a cyclic prefix, transmitting the cyclic prefix to a digital-to-analog converter to obtain an analog signal, driving the LED to emit light by the analog signal, converting the light into a light signal, and transmitting the light signal to a receiving end through a VLC channel.
7. The visible light communication method according to claim 6, wherein the hybrid adaptive bias modulator, when modulating data,
and modulating the real part and the imaginary part of the subcarrier with the sequence of 4m +2 in the even number of subcarriers and transmitting data, wherein the subcarrier with the sequence of 4m only modulates the imaginary part to transmit the data so as to improve the frequency spectrum utilization rate of the system.
8. The visible light communication method according to claim 6,
introduced adaptive bias snThe following conditions are satisfied:
Figure FDA0003109523750000021
sn+wn≥0,n＝0,1,…,N-1。
9. the visible light communication method according to claim 8,
the adaptive bias snFinally, the conditions are met:
Figure FDA0003109523750000031
10. a visible light communication method is applied to a receiving end of a visible light communication system of hybrid self-adaptive offset O-OFDM, and the method comprises the following steps:
the method comprises the following steps: the photoelectric converter receives the optical signal transmitted by the VLC channel and converts the optical signal into an electric signal, and the electric signal is processed by an analog-to-digital converter (ADC) to obtain a mixed signal z of a receiving endn' mixing the mixed signal z by a hybrid adaptive bias demodulatorn' demodulating, removing cyclic prefix, mixing signal znPerforming Fourier transform (FFT) to obtain a receiving end frequency domain signal X 'and a frequency domain signal Y', and separating the frequency domain signal X 'according to the superposition rule of a transmitting end to obtain a frequency domain signal X'1And frequency domain signal X'2And finally three groups of frequency domain signals X 'are output'1，X'2And Y';
step two: the frequency domain signal Y 'is subjected to a PAM demodulator to obtain a demodulated PAM signal D3', and the frequency domain signal X 'is obtained'1And frequency domain signal X'2Sending the signals into a QAM demodulator to obtain demodulated QAM signals D1 'and D2' respectively;
step three: the three demodulated signals D3 'and D2' and D1 'are transmitted to a data combiner, and the original data D' is recovered by the data combiner.
CN202110645780.5A 2021-06-10 2021-06-10 Hybrid self-adaptive offset O-OFDM visible light communication system and method Active CN113438193B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110645780.5A CN113438193B (en) 2021-06-10 2021-06-10 Hybrid self-adaptive offset O-OFDM visible light communication system and method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110645780.5A CN113438193B (en) 2021-06-10 2021-06-10 Hybrid self-adaptive offset O-OFDM visible light communication system and method

Publications (2)

Publication Number Publication Date
CN113438193A true CN113438193A (en) 2021-09-24
CN113438193B CN113438193B (en) 2022-08-23

Family

ID=77755539

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110645780.5A Active CN113438193B (en) 2021-06-10 2021-06-10 Hybrid self-adaptive offset O-OFDM visible light communication system and method

Country Status (1)

Country Link
CN (1) CN113438193B (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120087668A1 (en) * 2009-06-15 2012-04-12 Huawei Technologies Co., Ltd. Method and device for generating and receiving oofdm signal, and wavelength-division multiplexing system
CN107395277A (en) * 2017-08-04 2017-11-24 苏州大学 A kind of visible light communication system based on ADO OFDM
CN107395276A (en) * 2017-08-04 2017-11-24 苏州大学 A kind of visible light communication system of the ADO OFDM based on innovatory algorithm
CN109787685A (en) * 2019-03-21 2019-05-21 东南大学 The adaptive ebb ratio method of visible optical OFDM system based on tone reservation
CN110212981A (en) * 2019-05-30 2019-09-06 江南大学 A kind of visible light communication transmission method mixing single carrier and multi-carrier modulation
CN111327359A (en) * 2020-03-02 2020-06-23 兰州理工大学 Method for inhibiting visible light communication LED nonlinear distortion amplitude limiting noise

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120087668A1 (en) * 2009-06-15 2012-04-12 Huawei Technologies Co., Ltd. Method and device for generating and receiving oofdm signal, and wavelength-division multiplexing system
CN107395277A (en) * 2017-08-04 2017-11-24 苏州大学 A kind of visible light communication system based on ADO OFDM
CN107395276A (en) * 2017-08-04 2017-11-24 苏州大学 A kind of visible light communication system of the ADO OFDM based on innovatory algorithm
CN109787685A (en) * 2019-03-21 2019-05-21 东南大学 The adaptive ebb ratio method of visible optical OFDM system based on tone reservation
CN110212981A (en) * 2019-05-30 2019-09-06 江南大学 A kind of visible light communication transmission method mixing single carrier and multi-carrier modulation
CN111327359A (en) * 2020-03-02 2020-06-23 兰州理工大学 Method for inhibiting visible light communication LED nonlinear distortion amplitude limiting noise

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BAOLONG LI等: "Interference-Free Hybrid Optical OFDM With Low-Complexity Receiver for Wireless Optical Communications", 《IEEE COMMUNICATIONS LETTERS》 *
李超等: "基于DCO-OFDM与PAM-DMT的混合传输系统性能研究", 《电视技术》 *

Also Published As

Publication number Publication date
CN113438193B (en) 2022-08-23

Similar Documents

Publication Publication Date Title
Muller et al. A novel peak power reduction scheme for OFDM
EP2504940B1 (en) Wireless data communications
CN111525956B (en) Interference-free HACO-OFDM modulation method based on IM-DD in wireless optical communication system
CN107395277A (en) A kind of visible light communication system based on ADO OFDM
CN110661576B (en) Adaptive offset OFDM modulation method based on IM-DD in wireless optical communication system
CN104683277A (en) Receiving and transmitting devices and methods, front end circuit, modulator and receiving/transmitting system
CN106453191A (en) LED visible light orthogonal multicarrier communication method with low peak average power ratio
CN113328964B (en) VOOK-fused adjustable light orthogonal hybrid ACO-OFDM method
CN112511238A (en) Adaptive bias layered optical OFDM method based on IM/DD
CN114726439B (en) Visible light communication single carrier and multi-carrier modulation method based on KK relation
CN113193913B (en) Visible light communication system and method based on MPPM and self-adaptive bias
CN111711593B (en) OFDM/OQAM-based modulation method for visible light communication system
CN112653647B (en) Multi-carrier signal modulation method
CN109067686A (en) Method for transmitting signals based on binary phase shift keying modulation and orthogonal frequency division multiplexi
CN113438193B (en) Hybrid self-adaptive offset O-OFDM visible light communication system and method
EP2704388B1 (en) Reduction of peak-to-average ratio in ofdm systems
CN113542179B (en) Mixed light OFDM method based on time domain preprocessing
CN112671686B (en) Method, device and system for inhibiting peak-to-average power ratio of orthogonal frequency division multiplexing signal
CN213461748U (en) Broadband power line carrier communication system based on OFDM technology
KR20060028150A (en) Real-time papr reduction method by the combination of phase rotation and selective mapping and system for transmitting data using the same
Orović et al. Analysis of power consumption in OFDM systems
CN108809433B (en) DCO-OFDM modulation and demodulation method and device with phase modulation
CN108023851B (en) Synchronous signal transmitting and receiving device and method based on super-Nyquist filtering
CN114844565A (en) PAM-DMT modulation-based low-complexity visible light communication system and method
CN115834317B (en) Enhanced distortion cancellation hybrid O-OFDM transmission method

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant