CN108809885B - Novel space orthogonal modulation method based on indoor visible light communication - Google Patents

Novel space orthogonal modulation method based on indoor visible light communication Download PDF

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CN108809885B
CN108809885B CN201810390495.1A CN201810390495A CN108809885B CN 108809885 B CN108809885 B CN 108809885B CN 201810390495 A CN201810390495 A CN 201810390495A CN 108809885 B CN108809885 B CN 108809885B
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nsqm
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李宗艳
单宝玲
李世银
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China University of Mining and Technology CUMT
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits
    • 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
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation

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Abstract

The invention discloses a novel spatial quadrature modulation method based on indoor visible light communication, which comprises the following steps: based on the SQM scheme, according to a maximum likelihood estimation rule, under the condition of not considering the activated LED serial number, giving an estimation expression of a demodulator on a transmission signal; providing an SER expression in an SQM mode by utilizing PEP and UB technologies; according to the SER expression, a BER expression in an SQM mode is given; defining an upper limit expression of BER according to the expression of BER; an SQM optimization problem based on BER upper limit minimization is established, an optimization objective function and corresponding constraint conditions are given, and therefore an NSQM mode based on the number of LEDs at a sending end being 4 is obtained; based on the NSQM mode, a 4-system mapping signal set is designed, a design process of an 8-system mapping signal set is given, a design idea of a 16-system mapping signal set is given, and finally, a 64-system mapping signal set is a superposition of the 4-NSQM and the 16-NSQM. The method improves the transmission reliability of the visible light signals by optimizing the mapping mode of the transmitted light signals.

Description

Novel space orthogonal modulation method based on indoor visible light communication
Technical Field
The invention relates to a modulation method of visible light signals in an indoor visible light communication scene, in particular to a novel spatial orthogonal modulation method based on indoor visible light communication.
Background
Visible Light Communication (VLC) is receiving attention for its significant advantages in energy efficiency and indoor wireless communication, and its basic principle: the transmitting end adopts a Light Emitting Diode (LED) to transmit information data, signals reach the receiving end after being transmitted by an optical channel, and the receiving end adopts a Photodiode (PD) detector to directly detect the optical signals. However, it is noteworthy that: based on the unipolar characteristic of the signal in the VLC system, the constraint problem that the signal adopts intensity modulation/direct detection exists. Therefore, in order to overcome the above challenges and achieve high efficiency and reliability of information transmission, Spatial Modulation (SM), multilevel quadrature amplitude modulation (M-QAM), and Spatial Quadrature Modulation (SQM) have become important research contents in VLC modulation technology.
The basic principle of the SQM technique is: converting the M-QAM signal into a signal meeting the requirements of a VLC system on the real and positive characteristics of the signal, activating and sending the serial number of an LED by a sending signal, and sending information data through the LED; the receiving end needs to consider the estimation of the serial number of the LED activated by the transmitting end in the process of estimating the transmitted optical signal based on the maximum likelihood criterion. Therefore, in an indoor visible light communication scene, on the basis of the SQM, how to optimize a mapping mode for sending an optical signal and further realize high efficiency and reliability of visible light signal transmission is always a research focus of experts.
The scheme is developed in order to obtain a high-efficiency and reliable modulation mode suitable for indoor visible light communication.
Disclosure of Invention
The invention aims to provide a novel space orthogonal modulation method based on indoor visible light communication, which improves the transmission reliability of visible light signals by optimizing the mapping mode of transmitting light signals.
In order to achieve the above purpose, the solution of the invention is:
a novel spatial orthogonal modulation method based on indoor visible light communication comprises the following steps:
step A, based on an SQM scheme, according to a maximum likelihood estimation rule, under the condition of not considering an activated LED serial number, an estimation expression of a demodulator on a transmission signal is given;
step B, utilizing PEP and UB technologies to provide an SER expression in an SQM mode;
step C, according to the SER expression, by analyzing the characteristics of the transmitted signals, a BER expression in the SQM mode is given;
step D, defining an upper limit expression of the BER according to the expression of the BER;
step E, an SQM optimization problem based on BER upper limit minimization is established, an optimization objective function and corresponding constraint conditions are given, and therefore the number N of LEDs based on a sending end is obtainedtNSQM mode of 4;
step F, designing a 4-system mapping signal set based on an NSQM mode;
step G, based on the NSQM mode, giving a design flow of an 8-system mapping signal set;
step H, based on the NSQM mode, giving a design idea of a 16-system mapping signal set;
and step I, based on the NSQM mode, the 64-system mapping signal set is the superposition of the 4-NSQM and the 16-NSQM.
The specific steps of the step B are as follows:
step B1, utilizing PEP and UB technology, giving an initial SER expression as follows:
Figure BDA0001643331550000021
wherein P(s)m→sk) Represents: transmitting a symbol of smIs determined as a symbol skThe corresponding PEP; the number of modulation symbols is M;
step B2, based on the visible light channel characteristic H, includes: p(s)m→sk|H)＝P(D(y,sk)>D(y,sm) | H), wherein D (y, s)m) Is y and smThe Euclidean distance between them is defined as:
Figure BDA0001643331550000022
yl represents an optical signal detected by the l-th PD, NrIndicates the number of receiving end PDs, HlLine i representing H;
step B3, obtaining an SER expression:
Figure BDA0001643331550000023
wherein
Figure BDA0001643331550000024
σ2P is the average transmitted optical power per symbol, and γ is the responsivity of the photodetector, which is the variance of gaussian noise in the visible channel.
The specific steps of the step F are as follows:
in step F1, according to the SQM method, the 4-ary signal set of NSQM is defined as:
Figure BDA0001643331550000025
step F2, disregarding HlUnder the conditions of influence, all possible euclidean distance forms are given:
Figure BDA0001643331550000031
step F3, according to the optimization objective function and the corresponding constraint conditions, under the condition that α is 1 and β is 0, obtaining all the optimized possible euclidean distances as:
Figure BDA0001643331550000032
step F4, obtaining the 4-ary signal set of NSQM as:
Figure BDA0001643331550000033
the step G comprises the following specific steps:
step G1, the 8-ary NSQM signal set is:
Figure BDA0001643331550000034
and define η ═ α/β;
step G2, disregarding HlUnder the conditions of influence, all possible euclidean distances are given:
Figure BDA0001643331550000035
the formula is related to η;
g3, calculating an optimization factor eta according to the optimization objective function and the corresponding constraint conditionoptAnd realizing the optimal design of modulation.
The specific steps of the step H are as follows:
step H1, gives two sets of 4-ary NSQM signals:
Figure BDA0001643331550000036
Figure BDA0001643331550000037
definition eta ═ alpha/beta；
Step H2, the 16-ary NSQM signal set is:
Figure BDA0001643331550000038
the signal operation is a superposition operation of a plurality of numbers;
step H3, calculating an optimization factor eta according to the optimization objective function and the corresponding constraint conditionoptAnd realizing the optimal design of modulation.
After the scheme is adopted, aiming at the problem that the BER of signal transmission is high in the existing SQM mode in indoor visible light communication, compared with the existing SQM technology, the signal estimation expression based on the maximum natural criterion is given under the condition that the estimation of the activated LED serial number is not considered, the optimization problem of error upper limit minimization is established based on the SQM mode at the dead point, the optimization objective function and the constraint condition are given, the signal mapping mode of multi-system NSQM is further designed, the BER performance of signal transmission is effectively improved, the information transmission quality in the indoor visible light communication scene is improved, and the signal transmission method is suitable for user nodes in indoor visible light communication.
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FIG. 1 is a graph comparing bit error rate performance of 4-NSQM and 8-NSQM proposed in the present invention with that of existing 4-SQM and 8-SQM;
FIG. 2 is a graph comparing the bit error rate performance of the proposed 16-NSQM and 64-NSQM of the present invention with that of the existing 16-SQM and 64-SQM.
Detailed Description
The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.
The invention provides a novel space orthogonal modulation method based on indoor visible light communication, which comprises the following steps:
step A): based on the existing space orthogonal modulation (SQM) scheme, according to the maximum likelihood estimation rule, under the condition of not considering the activated LED serial number, giving an estimation expression of a demodulator to a transmission signal;
step B): a Symbol Error Rate (SER) expression in an SQM mode is given by utilizing a Pairwise Error Probability (PEP) and a Uniform Boundary (UB) technology;
step C): according to the SER expression, a Bit Error Rate (BER) expression in an SQM mode is given by analyzing the characteristics of a transmitted signal;
step D): defining an upper limit expression of BER according to the expression of BER;
step E): an SQM optimization problem based on BER upper limit minimization is established, an optimization objective function and corresponding constraint conditions are given, and therefore the number N of LEDs based on a transmitting end is obtainedtA Novel Spatial Quadrature Modulation (NSQM) approach of 4;
step F): designing a 4-system mapping signal set based on an NSQM mode;
step G): based on the NSQM mode, a design flow of an 8-system mapping signal set is given.
Step H): based on the NSQM mode, the design idea of the 16-system mapping signal set is given.
Step I): based on the NSQM mode, the 64-system mapping signal set is the superposition of the 4-NSQM and the 16-NSQM.
Wherein, the specific steps of the step B are as follows:
step B1): using PEP and UB techniques, the initial SER expression is given as:
Figure BDA0001643331550000051
wherein P(s)m→sk) Represents: transmitting a symbol of smIs determined as a symbol skThe corresponding PEP; the number of modulation symbols is M;
step B2): based on the visible light channel characteristics H, the method comprises the following steps: p(s)m→sk|H)＝P(D(y,sk)>D(y,sm) | H), wherein D (y, s)m) Is y and smThe Euclidean distance between them is defined as:
Figure BDA0001643331550000052
yl represents an optical signal detected by the l-th PD, NrIndicates the number of receiving end PDs, HlLine i representing H;
step B3): obtaining an SER expression:
Figure BDA0001643331550000053
wherein
Figure BDA0001643331550000054
σ2P is the average transmitted optical power per symbol, and γ is the responsivity of the photodetector, which is the variance of gaussian noise in the visible channel.
The specific steps of the step F are as follows:
step F1): according to the SQM approach, the 4-ary signal set of NSQM is defined as:
Figure BDA0001643331550000055
step F2): in the case of HlUnder the conditions of influence, all possible euclidean distance forms are given:
Figure BDA0001643331550000056
step F3): according to the optimization objective function and the corresponding constraint conditions, under the condition that alpha is 1 and beta is 0, all the optimized possible Euclidean distances are obtained as follows:
Figure BDA0001643331550000057
step F4): the 4-ary signal set for NSQM is obtained as:
Figure BDA0001643331550000058
the specific steps of the step G are as follows:
step G1): the 8-ary NSQM signal set can be written as:
Figure BDA0001643331550000061
and define η ═ α/β;
step G2): in the case of HlInfluence ofGiven all possible euclidean distances:
Figure BDA0001643331550000062
the formula is related to η;
step G3): according to the optimization objective function and the corresponding constraint conditions, the optimization factor eta can be calculatedoptAnd realizing the optimal design of modulation.
The specific steps of the step H are as follows:
step H1): two sets of 4-ary NSQM signals are given:
Figure BDA0001643331550000063
Figure BDA0001643331550000064
definition eta ═ alpha/beta
Step H2): the 16-ary NSQM signal set is:
Figure BDA0001643331550000065
the signal operation is a superposition operation of complex numbers.
Step H3): according to the optimization objective function and the corresponding constraint conditions, the optimization factor eta can be calculatedoptAnd realizing the optimal design of modulation.
In summary, the invention provides a novel spatial quadrature modulation method based on indoor visible light communication, which aims at the characteristics of transmission signals in visible light communication, establishes an optimization problem of error upper limit minimization by analyzing the bit error rate performance in the SQM mode under the condition of omitting the estimation of the activated LED serial number, and provides an optimized objective function and constraint conditions, thereby optimizing the mapping form of the transmission signals, providing a multilevel signal mapping form in the NSQM mode, and improving the bit error rate performance of information transmission. As can be seen from FIG. 1, the bit error rate is 10 under certain simulation parameters-4Compared with the existing corresponding SQM scheme, the proposed 4-NSQM and 8-NSQM schemes respectively have the advantages ofPerformance gains of 4.5dB and 1.5 dB; as can be seen from FIG. 2, the bit error rate is 10 under certain simulation parameters-5Compared with the existing corresponding SQM scheme, the proposed 16-NSQM and 64-NSQM schemes respectively have performance gains of about 2.3dB and 1.0 dB; furthermore, from fig. 1 and 2, it can be seen that: under the condition of high signal-to-noise ratio, the corresponding bit error rate performance can be accurately described by using the derived error upper limit.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.

Claims (1)

1. A novel space orthogonal modulation method based on indoor visible light communication is characterized by comprising the following steps:
step A, based on an SQM scheme, according to a maximum likelihood estimation rule, under the condition of not considering an activated LED serial number, an estimation expression of a demodulator on a transmission signal is given;
step B, utilizing PEP and UB technologies to provide an SER expression in an SQM mode; the method comprises the following specific steps:
step B1, utilizing PEP and UB technology, giving an initial SER expression as follows:
Figure FDA0003055638170000011
wherein P(s)m→sk) Represents: transmitting a symbol of smWhile the decision symbol is skThe corresponding PEP; the number of modulation symbols is M;
step B2, based on the visible light channel characteristic H, includes: p(s)m→sk|H)＝P(D(y,sk)＞D(y,sm) | H), wherein D (y, s)m) Is y and smThe Euclidean distance between them is defined as:
Figure FDA0003055638170000012
ylindicating the light signal detected by the l-th PD, NrIndicates the number of receiving end PDs, HlLine i representing H;
step B3, obtaining an SER expression:
Figure FDA0003055638170000013
wherein
Figure FDA0003055638170000014
σ2Is the variance of gaussian noise in the visible light channel, ρ is the average transmitted optical power per symbol, γ is the responsivity of the photodetector;
step C, a BER expression in an SQM mode is given according to the SER expression;
step D, defining an upper limit expression of the BER according to the expression of the BER;
step E, an SQM optimization problem based on BER upper limit minimization is established, an optimization objective function and corresponding constraint conditions are given, and therefore the number N of LEDs based on a sending end is obtainedtNSQM mode of 4;
step F, designing a 4-system mapping signal set based on an NSQM mode; the method comprises the following specific steps:
in step F1, according to the SQM method, the 4-ary signal set of NSQM is defined as:
Figure FDA0003055638170000015
step F2, disregarding HlUnder the conditions of influence, all possible euclidean distances are given:
Figure FDA0003055638170000021
step F3, according to the optimization objective function and the corresponding constraint conditions, under the condition that α is 1 and β is 0, obtaining all the optimized possible euclidean distances as:
Figure FDA0003055638170000022
step F4, obtaining the 4-ary signal set of NSQM as:
Figure FDA0003055638170000023
step G, based on the NSQM mode, giving a design flow of an 8-system mapping signal set; the method comprises the following specific steps:
step G1, the 8-ary NSQM signal set is:
Figure FDA0003055638170000024
and define η ═ α/β;
step G2, disregarding HlUnder the conditions of influence, all possible euclidean distances are given:
Figure FDA0003055638170000025
the formula is related to η;
g3, calculating an optimization factor eta according to the optimization objective function and the corresponding constraint conditionoptRealizing the optimal design of modulation;
step H, based on the NSQM mode, giving a design idea of a 16-system mapping signal set; the method comprises the following specific steps:
step H1, gives two sets of 4-ary NSQM signals:
Figure FDA0003055638170000026
Figure FDA0003055638170000027
definition η ═ α/β;
step H2, the 16-ary NSQM signal set is:
Figure FDA0003055638170000028
the signal operation is a superposition operation of a plurality of numbers;
step H3, according to the optimized objective function and the corresponding constraint conditionBy calculating the optimization factor etaoptRealizing the optimal design of modulation;
and step I, based on the NSQM mode, the 64-system mapping signal set is the superposition of the 4-NSQM and the 16-NSQM.
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Publication number Priority date Publication date Assignee Title
CN103840886A (en) * 2014-01-24 2014-06-04 清华大学 Precoding method based on multiple light sources in visible light communication
CN104243033A (en) * 2014-09-15 2014-12-24 东南大学 Spatial modulation transmitting method suitable for visible light communication
CN105517153A (en) * 2015-12-22 2016-04-20 北京邮电大学 Channel control method and device in indoor visible light communication
CN105991508A (en) * 2016-05-13 2016-10-05 深圳市统先科技股份有限公司 8QAM modulation method and system thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5325526B2 (en) * 2008-10-17 2013-10-23 三星電子株式会社 Visible light communication system and visible light communication method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103840886A (en) * 2014-01-24 2014-06-04 清华大学 Precoding method based on multiple light sources in visible light communication
CN104243033A (en) * 2014-09-15 2014-12-24 东南大学 Spatial modulation transmitting method suitable for visible light communication
CN105517153A (en) * 2015-12-22 2016-04-20 北京邮电大学 Channel control method and device in indoor visible light communication
CN105991508A (en) * 2016-05-13 2016-10-05 深圳市统先科技股份有限公司 8QAM modulation method and system thereof

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