CN107769851A - A kind of LED localization methods and system based on mixing OFDM - Google Patents
A kind of LED localization methods and system based on mixing OFDM Download PDFInfo
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- H—ELECTRICITY
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- 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
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Abstract
The invention discloses a kind of LED localization methods and system based on mixing OFDM, this method is combined mixing OFDM LED location algorithms with system, modulates strange carrier wave using ACO OFDM, PAM DMT modulate the imaginary part of even carrier wave, and the coordinate of receiver is determined using RSS.The LED localization methods and system based on mixing OFDM of the present invention, improves the positioning precision under the influence of multi-path jamming, while improve transmission rate and the availability of frequency spectrum.
Description
Technical Field
The invention relates to the field of position location, in particular to the aspect of LED location, and more particularly to a method and a system for LED location based on hybrid OFDM.
Background
The location service determines the actual geographical location of the mobile user through the cooperation of the mobile terminal and the wireless network, thereby providing the information service which is needed by the user and is related to the location. In order to improve the accuracy of indoor positioning, people adopt technologies such as infrared positioning, ultrasonic positioning, radio frequency identification positioning and the like, but the traditional indoor positioning technology cannot completely meet the requirements of users in the aspects of system cost, stability, positioning accuracy and the like. With the development of Light-emitting diode (LED) lighting technology, Visible Light Communication (VLC) technology has also been developed, and indoor positioning and navigation technology based on Visible Light Communication has become a hot point for research. Compared with the traditional radio frequency positioning and other wireless positioning technologies, the indoor positioning based on the LED visible light communication has the advantages of high transmitting power, high positioning precision, wide use occasions, no electromagnetic interference, energy conservation and the like.
However, in practical applications, LED positioning systems are affected by multipath interference in Indoor environment, and an article "Impact of multipath interference on the positioning accuracy" published in 2016, volume 34, volume 10 of the journal of "outer of Lightwave Technology" researches the influence of multipath interference on the positioning accuracy, and the result shows that the multipath interference greatly reduces the positioning accuracy, so the multipath interference needs to be considered in the positioning algorithm. Unlike conventional radio frequency wireless communication, VLC uses intensity-modulated direct-detection (IM/DD), requiring that the transmitted signal carried by the optical intensity must be non-negative and real. Direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) obtains a non-negative transmission signal by superimposing direct current biases, a smaller direct current bias causes a larger amplitude limiting noise, and a larger direct current bias reduces power efficiency. Asymmetric amplitude-limited optical orthogonal frequency division multiplexing (ACO-OFDM) only modulates odd carriers, pulse amplitude modulation-discrete multi-audio modulation (PAM-DMT) only modulates carrier imaginary parts, the two parts both obtain non-negative transmission signals through zero amplitude limitation, amplitude-limited noise only affects unmodulated carrier parts, but the zero amplitude limitation enables half energy of a transmitting end to be consumed in the unmodulated carrier parts, so that the ACO-OFDM and the PAM-DMT have 3dB performance loss compared with the traditional bipolar OFDM. A method for hybrid transmission of ACO-OFDM and DCO-OFDM is provided in Journal of lightwave technology, volume 31, 2013, Journal 7, Armstrong J.Comparison of ACO-OFDM, DCO-OFDM and ADO-OFDM in IM/DD Systems, so that the transmission rate is improved. In order to further improve the spectrum utilization and reduce the transmission complexity, the hybrid orthogonal frequency division multiplexing-Based IM/DD Optical Wireless System, published in journal of Optical Communications and networks in 6, 4 of 2014, proposes a method for hybrid transmission of ACO-OFDM and PAM-DMT.
Most of the current LED positioning Systems use LEDs as transmitters, photodetectors fixed on a target as receivers, and calculate the coordinates of the receivers by Using the distance between the transceivers, which is obtained by Using Time-of-Arrival (TOA) (refer to "acquisition of Time-of-Arrival Technology" published in 2013, 31, 20, Using visual light With Application in indicator Localization Systems), Time-difference-of-Arrival (TDOA) (refer to IEEE Transactions convergence electronics, 2011, 57, 4, TDOA-boundary acquisition Systems) (refer to IEEE Transactions correlation and RSS signal reception Systems), and Cybernetics, Part C (Applications and Reviews), three articles, Survey of Wireless Industration Techniques and Systems, published in 2007 at 37 6, and article, Optics Express, published at 2015 23, 16, expansion of the effect of diffusion recovery dynamics Systems based on RSSI-VLC. RSS estimates distance by the energy attenuation of the transmitted signal and is widely used because of its simple principle. An article, "interior location estimation with Optical-based orthogonal frequency division multiplexing communications", published by "Optical Engineering" at volume 55, 5, 2016, proposes an algorithm for combining ACO-OFDM with a positioning system, but the positioning accuracy of the algorithm still needs to be further improved, and the problem that half of the energy of a transmitting end of an ACO-OFDM system is consumed in an unmodulated carrier part generally exists, and 3dB performance loss is generated.
Disclosure of Invention
In view of the above technical problems, the present invention provides a hybrid OFDM-based LED positioning system and method.
According to one aspect of the present invention, to solve the technical problem, the present invention provides a method for positioning an LED based on hybrid OFDM, comprising the following steps:
s1, the plurality of LED transmitters respectively superpose respective ACO-OFDM signals and PAM-DMT signals and then respectively transmit the signals;
wherein, the ACO-OFDM signal is obtained by the following method: modulating an input signal on an odd carrier by M-ary quadrature amplitude modulation to generate complex data with the length of N/4, setting all even carriers to zero, setting all first and N/2 th sub-carriers to zero, and converting the even carriers and the N/2 th sub-carriers into serial codes to perform amplitude limiting operation to obtain the complex data, wherein M is the size of a constellation diagram, and N is the number of the sub-carriers;
the PAM-DMT signal is obtained by the following method: modulating an input signal on an imaginary part of an even carrier by adopting an M-element pulse amplitude modulation method, setting all odd carriers to be zero, and converting the odd carriers into serial codes to carry out amplitude limiting operation to obtain the input signal;
the input signal contains the coordinates of the transmitter in the horizontal plane;
s2, the receiver respectively estimates PAM-DMT signals according to the received signals of each transmitter, and respectively reconstructs PAM-DMT signals according to the respectively estimated PAM-DMT signals;
and S3, the receiver calculates the coordinates of the receiver in the horizontal plane according to the reconstructed PAM-DMT signals of the transmitters and the corresponding coordinates.
Further, in step S2 of the LED positioning method of the present invention, the method for estimating the PAM-DMT signal of each transmitter comprises the steps of:
s21, carrying out Fourier transform on the signal received by the receiver to obtain an odd sequence, and carrying out inverse ACO-OFDM operation to obtain an estimated ACO-OFDM signal;
s22, calculating to obtain amplitude limiting noise on the even carrier wave according to the estimated ACO-OFDM signal;
s23, calculating the difference value of the clipping noise on the even sequence and the even carrier wave after Fourier transform is carried out on the signal received by the receiver, and taking the imaginary part of the difference value as the estimated value of the PAM-DMT signal.
Further, in step S3 of the LED positioning method of the present invention, the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
in the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,the propagation coefficient of the optical filter for the ith LED,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
Further, in the LED positioning method of the present invention, the signal transmitting direction of the transmitter and the signal receiving direction of the receiver are both perpendicular to the ground, and the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
wherein C is a preset constant and the size of C satisfies the requirement
In the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,propagation coefficient of optical filter for ith LED, hiThe vertical distance between the ith receiver and the transmitter,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
Further, in the LED positioning method of the present invention, the input signal further includes identification information of the transmitter, so that a receiver receiving the identification information can distinguish coordinates of the transmitters.
According to another aspect of the present invention, to solve the technical problems, there is provided a hybrid OFDM-based LED positioning system, including:
the control modules are respectively arranged on the transmitters and used for respectively controlling the transmitters to respectively superpose respective ACO-OFDM signals and PAM-DMT signals and then respectively transmit the signals;
the ACO-OFDM signal is obtained through a first transmitting unit, the first transmitting unit is used for modulating an input signal on an odd carrier through M-ary quadrature amplitude modulation to generate complex data with the length of N/4, all even carriers are set to zero, the first and the N/2 th sub-carriers are also set to zero, and then the complex data are converted into serial codes to carry out amplitude limiting operation to obtain the ACO-OFDM signal, wherein M is the size of a constellation diagram, and N is the number of the sub-carriers;
the PAM-DMT signal is obtained through a second transmitting unit, the second transmitting unit is used for modulating an input signal on an imaginary part of an even carrier wave by adopting an M-element pulse amplitude modulation method, all odd carrier waves are set to zero, and then the input signal is converted into a serial code to carry out amplitude limiting operation to obtain the PAM-DMT signal;
the input signal contains the coordinates of the transmitter in the horizontal plane;
a signal reconstruction module, located on the receiver, for estimating a PAM-DMT signal according to the received signal of each transmitter, and reconstructing a PAM-DMT signal according to the estimated PAM-DMT signals;
and the position calculation module is positioned on the receiver and used for calculating the coordinates of the receiver in the horizontal plane according to the reconstructed PAM-DMT signals of all the transmitters and the corresponding coordinates.
Further, the signal reconstruction module of the LED positioning system of the present invention estimates the PAM-DMT signal for each transmitter using the following units:
the ACO-OFDM signal estimation unit is used for carrying out Fourier transform on the signal received by the receiver to obtain an odd sequence and carrying out inverse ACO-OFDM operation to obtain an estimated ACO-OFDM signal;
the even carrier amplitude limiting noise calculation unit is used for calculating amplitude limiting noise on the even carrier according to the estimated ACO-OFDM signal;
and the PAM-DMT signal estimation unit is used for calculating the difference value of amplitude-limiting noise on the even sequence and the even carrier wave obtained after Fourier transform is carried out on the signal received by the receiver, and taking the imaginary part of the difference value as the estimated value of the PAM-DMT signal.
Further, in the position calculation module of the LED positioning system of the present invention, the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
in the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,the propagation coefficient of the optical filter for the ith LED,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf of the angle of view of the light concentratorAngle, n is the refractive index of the light concentrator.
Furthermore, in the LED positioning system of the present invention, the signal transmitting direction of the transmitter and the signal receiving direction of the receiver are both perpendicular to the ground, and the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
wherein C is a preset constant and the size of C satisfies the requirement
In the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,propagation coefficient of optical filter for ith LED, hiThe vertical distance between the ith receiver and the transmitter,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
Further, in the LED positioning system of the present invention, the input signal further includes identification information of the transmitter, so that the receiver receiving the identification information can distinguish the coordinates of each transmitter.
The invention discloses a mixed OFDM-based LED positioning method and a system, which are combined with a mixed OFDM LED positioning algorithm, utilize ACO-OFDM to modulate the imaginary part of odd carriers and PAM-DMT to modulate the imaginary part of even carriers, and use RSS to determine the coordinates of a receiver. The LED positioning method and system based on the hybrid OFDM improve the positioning accuracy under the influence of multipath interference and simultaneously improve the transmission rate and the frequency spectrum utilization rate.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flow chart of one embodiment of a hybrid OFDM based LED positioning method of the present invention;
fig. 2 is a state diagram of the hybrid OFDM-based LED positioning method of fig. 1 according to the present invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Fig. 1 and 2 are a flowchart of an embodiment of the hybrid OFDM-based LED positioning method according to the present invention and a usage state diagram of the hybrid OFDM-based LED positioning method in fig. 1, respectively. The method is particularly suitable for indoor positioning, and the hybrid OFDM-based LED positioning method in fig. 1 will be described below with reference to fig. 2.
In fig. 2, the rectangular parallelepiped is a room 6 meters long, 6 meters wide, and 4.2 meters high, four LED bulbs are arranged on the ceiling of the room, each bulb is used as an independent light emitter to emit a unique ID (identification) code and a position coordinate, the position coordinate of this embodiment is expressed by coordinates (x, y, z), x represents the coordinate of x axis, y represents the coordinate of y axis, z represents the coordinate of z axis, and in addition to the coordinates (x, y) included in the horizontal plane, a height coordinate z is included, and each position information is (2,2,4.2), (2,4,4.2), (4,2,4.2), and (4,4,4.2), respectively. In other embodiments, the height coordinate may not be transmitted to the receiver through the transmitter, but may be preset in the transmitter directly in a preset manner.
S1, at each transmitter, the System uses ACO-OFDM to modulate the imaginary part of odd carrier and PAM-DMT to modulate the imaginary part of even carrier, two paths of signals are generated separately and then combined into one signal for transmission (refer to Journal of Optical communications and Networking in 2014, 6, published article "hybrid assisted logic OFDM-Based IM/DD Optical Wireless System" in the Journal of Japan).
Specifically, the obtaining mode of the ACO-OFDM signal is as follows: modulating an input signal containing transmitter ID codes and position coordinates on an odd carrier through M-ary quadrature amplitude modulation (M-QAM) to generate complex data with the length of N/4, and setting all even carriers to be zero, wherein the even carriers are zeroIn the above description, M is the size of the constellation diagram, and N is the number of subcarriers. In addition, to satisfy the hermitian symmetry rule to ensure that the output signal is true, the first and nth/2 subcarriers are also set to zero. At this time, the generated signalIs an input signal of N-point Inverse Fast Fourier Transform (IFFT), wherein ()*And the complex conjugate of the vector is expressed, and then the complex conjugate is converted into a serial code to carry out amplitude limiting operation to obtain the ACO-OFDM signal. The PAM-DMT signal adopts M-ary Pulse Amplitude Modulation (PAM) method to modulate the input signal on the imaginary part of the even carrier, all odd carriers are set to zero, the input signal of IFFT isAnd then converting the signal into a serial code to carry out amplitude limiting operation to obtain a PAM-DMT signal. How to convert to string code and how to perform the slicing operation are well known in the art and will not be described in detail herein.
After obtaining the non-negative signal through the amplitude limiting operation, the two parts of signals are added together, and a Cyclic Prefix (CP) is inserted, and finally the signals enter the optical channel for transmission.
S2, at the receiver, after removing the CP from the received signal, performing Fast Fourier Transform (FFT) to obtain an even sequence and an odd sequence corresponding to each transmitter, where the even sequence is reven、caco、cpam、nevenOf which the odd sequence is rodd、caco、cpam、noddA sum of where roddAnd revenACO-OFDM and PAM-DMT signals, respectively, cacoAnd cpamClipping noise, n, for ACO-OFDM and PAM-DMT, respectivelyoddAnd nevenRepresents Additive White Gaussian Noise (AWGN) in the optical channel.
And then carrying out inverse ACO-OFDM operation on the odd sequence to obtain an estimated ACO-OFDM signal.
And calculating to obtain the amplitude limiting noise on the even carrier wave according to the estimated ACO-OFDM signal. This step is common knowledge in the art.
And calculating the difference value of the amplitude limiting noise on the even sequence and the even carrier, and taking the imaginary part of the difference value as the estimated value of the PAM-DMT signal.
Through the PAM technology, the estimation signal can be reconstructed into a PAM-DMT signal, the reconstructed signal eliminates the amplitude limiting noise which affects the real part of the even carrier in the PAM-DMT signal, the estimation precision is higher, and finally the receiver coordinate is calculated according to the reconstructed PAM-DMT signal and the coordinate of each transmitter. Since the receiver is located on the ground and has a z-axis coordinate of 0, only the x-axis and y-axis coordinates of the receiver need to be calculated.
The specific implementation manner of acquiring the coordinates of the x-axis and the y-axis of a group of receivers by using the parameters corresponding to any group of transmitters is as follows.
Obtaining an average value P of the power of the PAM-DMT signal of the reconstructed ith LEDtAverage value P of transmission power of PAM-DMT signal of ith LEDriLambertian order m ═ ln2/ln (cos Ψ)1/2) Half-power angle psi for emitting signal LED1/2Physical areas A, D of a photodetector for receiving a signaliIs the distance, θ, between the receiver and the ith transmitteriFor the ith LED emission angle,the angle of incidence of the ith receiver with respect to its normal direction,the propagation coefficient of the optical filter for the ith LED,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
Then r is calculated according to the following formulai：
Where h is the vertical distance between the transmitter and the receiver.
The coordinates of the receiver in the horizontal plane are then calculated:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riI is 1, 2, …, n is the horizontal distance between the receiver and the ith transmitter, and n is the number of transmitters.
In the above-mentioned Di 2In the formula of (2)1/2、m、Φc、TsN and A are system parameters which are generally obtained by human presetting, and cos (theta)i)、Will be different according to the different transmitting direction of the transmitter and the receiving direction of the receiver。
In this embodiment, the transmitting direction of the transmitter and the receiving direction of the receiver are perpendicular to the ceiling, and in this case:
since the height h of the receiver is fixed, a simplified formula for the distance between the receivers can be obtained as:
from the above formula (3):
wherein, C is a constant obtained by calculating the system parameters in the following table in formula (2) for the corresponding part, wherein the specific calculation formula of C is as follows:
in the present embodiment, the sizes of the partial parameters are shown in the following table.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. An LED positioning method based on hybrid OFDM is characterized by comprising the following steps:
s1, the plurality of LED transmitters respectively superpose respective ACO-OFDM signals and PAM-DMT signals and then respectively transmit the signals;
wherein, the ACO-OFDM signal is obtained by the following method: modulating an input signal on an odd carrier by M-ary quadrature amplitude modulation to generate complex data with the length of N/4, setting all even carriers to zero, setting all first and N/2 th sub-carriers to zero, and converting the even carriers and the N/2 th sub-carriers into serial codes to perform amplitude limiting operation to obtain the complex data, wherein M is the size of a constellation diagram, and N is the number of the sub-carriers;
the PAM-DMT signal is obtained by the following method: modulating an input signal on an imaginary part of an even carrier by adopting an M-element pulse amplitude modulation method, setting all odd carriers to be zero, and converting the odd carriers into serial codes to carry out amplitude limiting operation to obtain the input signal;
the input signal contains the coordinates of the transmitter in the horizontal plane;
s2, the receiver respectively estimates PAM-DMT signals according to the received signals of each transmitter, and respectively reconstructs PAM-DMT signals according to the respectively estimated PAM-DMT signals;
and S3, the receiver calculates the coordinates of the receiver in the horizontal plane according to the reconstructed PAM-DMT signals of the transmitters and the corresponding coordinates.
2. The LED positioning method according to claim 1, wherein the estimation method of the PAM-DMT signal of each transmitter in step S2 comprises the steps of:
s21, carrying out Fourier transform on the signal received by the receiver to obtain an odd sequence, and carrying out inverse ACO-OFDM operation to obtain an estimated ACO-OFDM signal;
s22, calculating to obtain amplitude limiting noise on the even carrier wave according to the estimated ACO-OFDM signal;
s23, calculating the difference value of the clipping noise on the even sequence and the even carrier wave after Fourier transform is carried out on the signal received by the receiver, and taking the imaginary part of the difference value as the estimated value of the PAM-DMT signal.
3. The LED positioning method according to claim 1, wherein in step S3, the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the level of the ith transmitterAbscissa and ordinate of (a), riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
<mrow> <msub> <mi>r</mi> <mi>i</mi> </msub> <mo>=</mo> <msqrt> <mrow> <msubsup> <mi>D</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>-</mo> <msup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> <mo>,</mo> </mrow>
in the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,propagation coefficient of optical filter for ith LED, hiThe vertical distance between the ith receiver and the transmitter,is the gain, magnitude of the light concentrator of the ith LEDIs determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
4. The LED positioning method according to claim 1, wherein the signal transmitting direction of the transmitter and the signal receiving direction of the receiver are perpendicular to the ground, and the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
<mrow> <msub> <mi>r</mi> <mi>i</mi> </msub> <mo>=</mo> <msqrt> <mrow> <msup> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>C</mi> <mo>&CenterDot;</mo> <msub> <mi>h</mi> <mi>i</mi> </msub> <mo>&CenterDot;</mo> <msub> <mi>P</mi> <mi>t</mi> </msub> </mrow> <msub> <mi>P</mi> <mrow> <mi>r</mi> <mi>i</mi> </mrow> </msub> </mfrac> <mo>)</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> <mo>-</mo> <msup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> <mo>,</mo> <mrow> <mo>(</mo> <mi>i</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mn>3</mn> <mo>,</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow>
wherein C is a preset constant and the size of C satisfies the requirement
In the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,propagation coefficient of optical filter for ith LED, hiThe vertical distance between the ith receiver and the transmitter,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
5. The LED location method of claim 1, wherein the input signal further includes the transmitter identification information, such that a receiver receiving the identification information can distinguish the coordinates of the respective transmitters.
6. A hybrid OFDM-based LED positioning system, comprising:
the control modules are respectively arranged on the transmitters and used for respectively controlling the transmitters to respectively superpose respective ACO-OFDM signals and PAM-DMT signals and then respectively transmit the signals;
the ACO-OFDM signal is obtained through a first transmitting unit, the first transmitting unit is used for modulating an input signal on an odd carrier through M-ary quadrature amplitude modulation to generate complex data with the length of N/4, all even carriers are set to zero, the first and the N/2 th sub-carriers are also set to zero, and then the complex data are converted into serial codes to carry out amplitude limiting operation to obtain the ACO-OFDM signal, wherein M is the size of a constellation diagram, and N is the number of the sub-carriers;
the PAM-DMT signal is obtained through a second transmitting unit, the second transmitting unit is used for modulating an input signal on an imaginary part of an even carrier wave by adopting an M-element pulse amplitude modulation method, all odd carrier waves are set to zero, and then the input signal is converted into a serial code to carry out amplitude limiting operation to obtain the PAM-DMT signal;
the input signal contains the coordinates of the transmitter in the horizontal plane;
a signal reconstruction module, located on the receiver, for estimating a PAM-DMT signal according to the received signal of each transmitter, and reconstructing a PAM-DMT signal according to the estimated PAM-DMT signals;
and the position calculation module is positioned on the receiver and used for calculating the coordinates of the receiver in the horizontal plane according to the reconstructed PAM-DMT signals of all the transmitters and the corresponding coordinates.
7. The LED locator system of claim 6, wherein the signal reconstruction module estimates the PAM-DMT signal for each transmitter using:
the ACO-OFDM signal estimation unit is used for carrying out Fourier transform on the signal received by the receiver to obtain an odd sequence and carrying out inverse ACO-OFDM operation to obtain an estimated ACO-OFDM signal;
the even carrier amplitude limiting noise calculation unit is used for calculating amplitude limiting noise on the even carrier according to the estimated ACO-OFDM signal;
and the PAM-DMT signal estimation unit is used for calculating the difference value of amplitude-limiting noise on the even sequence and the even carrier wave obtained after Fourier transform is carried out on the signal received by the receiver, and taking the imaginary part of the difference value as the estimated value of the PAM-DMT signal.
8. The LED positioning system of claim 6, wherein the coordinates of the receiver in the horizontal plane in the position calculation module are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
<mrow> <msub> <mi>r</mi> <mi>i</mi> </msub> <mo>=</mo> <msqrt> <mrow> <msubsup> <mi>D</mi> <mi>i</mi> <mn>2</mn> </msubsup> <mo>-</mo> <msup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> <mo>,</mo> </mrow>
in the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,the propagation coefficient of the optical filter for the ith LED,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
9. The LED positioning system of claim 6, wherein the signal transmitting direction of the transmitter and the signal receiving direction of the receiver are perpendicular to the ground, and the coordinates of the receiver in the horizontal plane are calculated by the following formula:
Q＝(MTM)-1MTN，
wherein,and Q is the receiver coordinate, X, of the solutioni、YiIs the abscissa and ordinate of the horizontal plane of the ith transmitter, riIs the horizontal distance between the receiver and the ith transmitter, i is 1, 2, …, n is the number of transmitters, riCalculated by the following formula:
<mrow> <msub> <mi>r</mi> <mi>i</mi> </msub> <mo>=</mo> <msqrt> <mrow> <msup> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>C</mi> <mo>&CenterDot;</mo> <msub> <mi>h</mi> <mi>i</mi> </msub> <mo>&CenterDot;</mo> <msub> <mi>P</mi> <mi>t</mi> </msub> </mrow> <msub> <mi>P</mi> <mrow> <mi>r</mi> <mi>i</mi> </mrow> </msub> </mfrac> <mo>)</mo> </mrow> <mrow> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> <mo>-</mo> <msup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> <mo>,</mo> <mrow> <mo>(</mo> <mi>i</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mn>3</mn> <mo>,</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow>
wherein C is a preset constant and is full ofFoot
In the formula, PtAveraging the power of the reconstructed PAM-DMT signal for the ith LED, PriThe mean value of the emission power of the PAM-DMT signal of the ith LED has a Lambert order of m-ln 2/ln (cos Ψ)1/2)，Ψ1/2Is the half-power angle of the LED used to transmit the signal, A is the physical area of the photodetector used to receive the signal, DiIs the distance, θ, between the receiver and the ith transmitteriFor the emission angle of the ith lamp,the angle of incidence of the ith receiver with respect to its normal direction,propagation coefficient of optical filter for ith LED, hiThe vertical distance between the ith receiver and the transmitter,is the gain of the light concentrator for the ith LED, the magnitude of which is determined by the formula:
wherein phicHalf the angle of view of the light concentrator, n is the refractive index of the light concentrator.
10. The LED location system of claim 6, wherein the input signal further includes the transmitter identification information, such that a receiver receiving the identification information can distinguish the coordinates of the respective transmitters.
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| CN109324311A (en) * | 2018-09-29 | 2019-02-12 | 中山大学 | A kind of bimodulus LED localization method and system based on different Lambertian radiation lobe moduluses |
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| CN111711593A (en) * | 2020-06-22 | 2020-09-25 | 西安电子科技大学 | OFDM/OQAM-based modulation method for visible light communication system |
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