CN115314092B - Pearson coefficient-based multi-array visible light OGSM-MIMO antenna selection method - Google Patents

Abstract

The invention discloses a Pearson coefficient-based multi-array visible light OGSM-MIMO antenna selection method, which specifically comprises the following steps: building a visible light indoor communication link system model; establishing a mathematical model of a channel comprising a direct line-of-sight link LOS and a first order reflection link NLOS; determining the mounting interval of LEDs and dividing positioning areas; collecting the received illuminance RSS value of each LED and the actual coordinates of the reference point at the positioning point, and storing the RSS value and the actual coordinates into a fingerprint library; determining a fingerprint library of the positioning areas, and calculating a Pearson coefficient between any LED combination and the photoelectric detector in any one of the positioning areas according to the fingerprint library of the positioning areas; and taking the corresponding LED combination with high correlation as an actually activated antenna combination. The invention does not depend on the system channel characteristics, realizes the multiplexing of the time domain and the space domain, improves the error code performance, ensures the reliability and simultaneously improves the application range of OGSM-MIMO systems.

Description

A multi-array visible light OGSM-MIMO antenna selection method based on Pearson coefficient

Technical Field

The invention belongs to the technical field of visible light indoor communication and relates to a multi-array visible light OGSM-MIMO antenna selection method based on Pearson coefficient.

Background technique

In visible light indoor lighting scenarios, in order to take into account both lighting and communication, a multi-array light source layout model is usually adopted. Especially in large scenes, the number of LED arrays will increase sharply, making the reliability of the traditional OGSM-MIMO system unable to be guaranteed. Based on this, in order to ensure reliability while further improving the applicability of the OGSM-MIMO system, the researchers introduced an antenna selection method.

At present, traditional antenna selection methods mainly include random antenna selection method and norm-based antenna selection method. The random selection method is the lower limit of evaluating the system performance of the antenna selection method; the norm-based antenna selection method is based on a known channel, but in reality, due to external environmental interference, the channel is a time-varying channel.

Summary of the invention

In order to solve the above problems, the present invention provides a multi-array visible light OGSM-MIMO antenna selection method based on Pearson coefficient, which does not rely on system channel characteristics, realizes time domain and space domain multiplexing, improves bit error performance, and solves the problems existing in the prior art.

The technical solution adopted by the present invention is a multi-array visible light OGSM-MIMO antenna selection method based on the Pearson coefficient, which is specifically performed in the following steps:

Step 1: Determine the indoor space parameters, build a visible light indoor communication link system model, and establish a three-dimensional coordinate system in the indoor space;

Step 2, establish a channel mathematical model including the direct line-of-sight link LOS and the first-order reflection link NLOS;

Step 3: Based on the channel mathematical model including LOS and NLOS, the installation spacing of the LEDs is determined by the two conditions of the standard deviation of the illuminance on the receiving plane and the minimum RSS value of the illuminance on the receiving plane, and then the positioning area is divided;

Step 4: Select several positioning points in the positioning area, collect the received RSS value of the illuminance of each LED and the actual coordinates of the reference point at the positioning point, and store them in the fingerprint library;

Step 5: Determine the fingerprint library of the positioning area;

Step 6: Calculate the Pearson coefficient between any LED combination and the photodetector in any positioning area according to the fingerprint library of the positioning area;

Step 7: Based on the Pearson coefficient between any LED combination and the photodetector, the corresponding LED combination with high correlation is used as the actually activated antenna combination.

Furthermore, in step 2, the illuminance E of any M LED light sources received by any photodetector is:

Where D represents the distance between the receiving end of any photodetector and the LED light source, D′ represents the distance between the receiving end of any photodetector and the secondary light source generated by the LED light source; _Ej is the direct horizontal illuminance of the jth photodetector under multiple light sources, _E′j is the reflected light illuminance of the jth photodetector under multiple secondary light sources, I( _φi ) is the light intensity from a single light source to any point, _φi represents the emission angle of the i-th LED, represents the incident angle of the jth photodetector, I _i ' is the reflected light intensity from a single light source to any point, and β represents the emission angle of the secondary light source.

Furthermore, in step 3, the comfort range illuminance RSS of the illuminance received by the human eye is 300lx to 1500lx.

Furthermore, in step 4, the fingerprint library is:

f _n ={S _n ,(x _n , _yn ,z _n ),t _n |n=1,2,…,N}

In the formula, represents the received light illuminance from each LED _m at the nth photodetector PD _n ; (x _n , y _n , z _n ) represents the coordinate position of the nth photodetector, in m; t _n represents the number of light exposures received by the nth photodetector;

LED _m represents the mth LED, m=1, 2, ..., M; LED _m is represented by:

LED _m = {R _m ,(x _m ,y _m ,z _m )|m = 1,2,…,M}

Wherein, R _m represents the central luminous intensity of the mth LED, unit: lx; (x _m , y _m , z _m ) is the coordinate position of the mth LED, unit: m.

Furthermore, in step 5, the fingerprint library fn _,k of the positioning area is determined according to the fingerprint library _fn in step 4, that is, the set of average illuminances of the LED combination received by the nth photodetector in any positioning area, as shown in the following formula:

f _n,k = {S _n,k , (x _n,k , yn _,k , z _n,k ), t _n,k | n = 1, 2, …, N _k }

Where, Sn _,k represents the received light illumination received by the nth photodetector in the kth positioning area from the mth LED in the kth positioning area, (xn _,k , _yn,k , _zn,k ) represents the coordinate position of the nth photodetector PD in the kth area, unit: m;

The position LED _m,k of the mth LED in the kth positioning area is expressed as:

LED _m,k = {R _m,k , (x _m,k , y _m,k , z _m,k ) | m = 1, 2, …, M _k }

Throughout, R _m,k represents the central luminous intensity of the mth LED in the kth region, unit: lx; (x _m,k , y _m,k , z _m,k ) represents the coordinate position of the mth LED in the kth region, unit: m.

Furthermore, in step 6, the Pearson coefficient ρ(LED _m,k ,f _n,k ) between any LED combination and the photodetector in the kth positioning area is expressed as:

In the formula, is the average illuminance of the actual LED combination received by the nth photodetector of the kth localization area fingerprint library; σ represents the sample standard deviation, /> It means that the nth photodetector in the kth positioning area receives the light intensity of the mth LED.

The beneficial effects of the present invention are:

The embodiment of the present invention combines the visible light communication link model, the LED channel diffuse reflection model, and the mathematical model of the correlation between the visible light OGSM-MIMO system and the Pearson coefficient to fit the indoor channel environment, and adopts an antenna selection method based on the Pearson coefficient to select antennas for the OGSM-MIMO system. The correlation of the Pearson coefficients between the photoelectric detector (PD) ends at different positions and the activated transmitting antennas is used to select the optimal antenna combination, which does not rely on the system channel characteristics, thereby realizing multiplexing of the time domain and the space domain, and improving the system's bit error performance.

The embodiments of the present invention can also be applied to large-scale OGSM-MIMO systems, reducing the amount of calculation, and are not limited to indoor optical communications, but can also be applied to optical fields such as lasers.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG. 1 is a visible light communication link model in an embodiment of the present invention.

FIG. 2 is a diffuse reflection model of an LED channel in an embodiment of the present invention.

FIG. 3 is an OGSM-MIMO system model based on antenna selection according to an embodiment of the present invention.

FIG4 is a simulation diagram of the bit error rate of the OGSM-MIMO system with different antenna selection methods.

FIG5 is a simulation diagram of theoretical bit error performance of an OGSM-MIMO system based on the Pearson coefficient according to an embodiment of the present invention.

FIG6 is an analysis of the bit error rate of the OGSM-MIMO system based on the Pearson coefficient under different conditions in an embodiment of the present invention.

Detailed ways

The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Example

A multi-array visible light OGSM-MIMO antenna selection method based on Pearson coefficient comprises the following steps:

Step 1, determine the indoor space parameters, as shown in Figure 1, take a 4m×4m×3m indoor room as the experimental simulation model, build a visible light indoor communication link system model, and establish a three-dimensional coordinate system with a corner of the indoor space as the coordinate origin.

Step 2: Establish a channel mathematical model including the direct line-of-sight link LOS and the first-order reflection link NLOS, as shown in FIG2 ; wherein the light intensity I(φ _i ) from a single light source to any point is defined as:

I(φ _i )＝I ₀ cos ^r φ _i (1)

Where _I0 represents the central luminous intensity of the LED, _φi represents the emission angle of the i-th LED, r is the radiation pattern of the light source, and the value range of r is 0 to 2. The value represents the number of reflections, 0 means no reflection is considered, and 2 means 2 reflections.

Then the direct horizontal illumination _Ej of the jth PD under multiple light sources is:

In the formula, represents the incident angle of the jth PD, _Eij represents the illuminance of the i-th LED received by the j-th PD, ( _xj , _yj , 0) represents the coordinates of the j-th PD, and ( _Xi , _Yi , _Zi ) represents the coordinates of the i-th LED. In Figure 2, _Dj represents the coordinates of the j-th PD, W represents the width of any area in Figure 1, and H=3 represents the indoor height of 3m.

Assume that the secondary light source generated by any LED light source is point P, and the coordinates of point P can be expressed as P(X ₁ ,0,Z ₁ ). Similarly, the reflected light intensity I′ _i from a single light source to any point is defined as:

I′ _i = kI _i cos ^m-1 β (3)

In the formula, _Ii represents the light intensity of the i-th LED directly irradiating to point P, k is the reflection coefficient of the wall, β represents the emission angle of the secondary light source, and m is the radiation mode of the light source. Then the reflected light illuminance _E'j of the j-th PD under multiple secondary light sources is:

_E′ij represents the illuminance of the i-th LED received by the j-th PD.

Then the illuminance E of any M LED light sources received by any PD end is:

Wherein, D represents the distance between any PD end and the LED light source, and D′ represents the distance between any PD end and the secondary light source generated by the LED light source.

In the embodiment, That is, the illuminance E of any M LED light sources received by any PD end is:

Formula (5) makes the difference in the illuminance received by the PD from different LEDs more obvious, and the Pearson coefficient correlation is more different. This is because walls in real life also reflect light, which can better simulate the real environment.

Step 3: Determine the installation spacing of each LED based on the LED channel diffuse reflection model (including the channel mathematical model of LOS and NLOS) established in step 2 and divide the positioning area according to the RSS value (illuminance) of the receiving bottom surface.

Different installation spacing of LEDs leads to different RSS values. Finally, the installation spacing of LEDs is determined by two conditions: the standard deviation of the illumination on the receiving plane and the minimum RSS value on the receiving plane, and then the division of the positioning area is determined. The international lighting standard stipulates that the comfortable range of illumination received by the human eye is 300lx to 1500lx. According to the illumination generated by LEDs in different areas, the optimal illumination area is selected. The simulated environment is closer to real life and the factors considered are more comprehensive.

Step 4: Select several positioning points in the positioning area, collect the received RSS values of each LED and the actual coordinates of the reference point at the positioning points, and store them in the fingerprint library; wherein, there are M LEDs, the mth LED is recorded as LED _m , m = 1, 2, ..., M; which can be expressed as:

LED _m = {R _m ,(x _m ,y _m ,z _m )|m = 1,2,…,M} (6)

Where R _m represents the central luminous intensity of the mth LED, unit: lx; (x _m ,y _m ,z _m ) is the coordinate position of the mth LED, unit: m. There are N PDs in the positioning area, and the nth PD is recorded as PD _n , n = 1, 2…, N, then the light intensity received from the LED _m signal at PD _n can be recorded as Therefore, the fingerprint library can be defined as:

f _n = {S _n , (x _n , _yn , z _n ), t _n | n = 1, 2, …, N} (7)

In the formula, _fn represents the set of different LED light intensities received by different PD receiving ends. represents the received light illuminance from each LED at PD _n ; ( _xn , _yn , _zn ) represents the coordinate position of the PD, unit: m; _tn represents the number of times the PD receives light.

Step 5: Determine the fingerprint library of the positioning area. According to the LED light source layout model divided in step 3, select any area divided; assuming that the indoor bottom surface is divided into k positioning areas, denoted as f _n,k , k∈{1,2,…,K}, then the fingerprint library of the positioning area is defined as:

f _n,k = {S _n,k ,(x _n,k ,yn _,k ,z _n,k ),t _n,k | _nk = 1,2,…, _Nk } (8)

f _n,k represents the set of average light illumination received by the nth PD in the kth positioning area from the LED combination; Sn _,k represents the received light illumination received by PD _n in the kth positioning area from LED _m,k , ( _xn,k , _yn,k , zn _,k ) represents the coordinate position of the nth photodetector PD in the kth area, unit: m; _tn,k represents the number of light illuminations received by the nth photodetector PD in the kth positioning area.

The position LED _m,k of the mth LED in the kth positioning area is expressed as:

LED _m,k = {R _m,k ,(x _m,k ,y _m,k ,z _m,k )|m = 1,2,…,M _k } (9)

Wherein, R _m,k represents the central luminous intensity of the mth LED in the kth region, unit: lx; (x _m,k ,y _m,k ,z _m,k ) represents the coordinate position of the kth region PD, unit: m.

Step 6: Select any area divided in step 5, and calculate the Pearson coefficient between any LED combination and the photodetector in the area according to the fingerprint library in step 4.

The Pearson correlation coefficient is a linear correlation coefficient, which is defined as the ratio of the covariance of two points to the product of the standard deviation. The value of the Pearson coefficient is between -1 and 1. The larger the value, the higher the correlation. Therefore, it can be used as a selection criterion for antenna combinations. The correlation coefficient ρ(LED _m,k ,f _n,k ) between any LED combination in the kth partition and the fingerprint library PD is expressed as:

In the formula, is the average illuminance of the actual LED combination received by the nth PD in the kth partition fingerprint library; m LEDs with high similarity are used as the transmitting antenna combination; σ represents the sample standard deviation, which is the parameter of the original formula of the Pearson coefficient; It means that the nth PD in the kth area receives the illuminance of the mth LED.

According to the VLC communication link model, it is assumed that there are 6 LEDs in the kth partition fingerprint library, and the central luminous intensity is 21 (lx). Then the LED information can be expressed according to formula (9):

Through the visible light communication model, the received light intensity of each PD can be obtained. Assuming there are two PDs, the coordinate information is expressed as (0.8, 0.8, 0) and (0.8, 1.6, 0). Then, the receiving end receives 6 LEDs respectively, and there are 12 types of received light intensity. The partition fingerprint library is expressed according to formula (8):

In the formula, considering the noise interference in real life, the average of three measurements is taken, and the average illumination value when t _n = 3 is, for example Since there are 6 LEDs and 2 PD receiving ends, in the OGSM-MIMO system, that is, the transmitting antenna _Nt = 6, the receiving antenna _Nr = 2, and assuming that the activated transmitting antenna (LED) _Na = 2, there are a total of 15 antenna combinations in the OGSM-MIMO system. However, the actual antenna combination of OGSM-MIMO must satisfy the integral power of 2, so the actual antenna combination is to select 8 of the 15. According to formulas (10), (11), and (12), the Pearson coefficient set can be obtained:

Step 7, select the corresponding antenna combination as the actually activated antenna combination through the Pearson coefficient correlation calculated in step 6, so as to obtain the optimal communication effect; the number of antenna combinations is constrained by an integer power of 2, because after the constraint condition, each antenna combination will correspond to the same number of modulation signal combinations; the embodiment of the present invention changes from activating all antennas to activating some antennas, and only needs to consider the best antennas at the transmitting antenna end, which not only reduces the impact of multipath interference on communication quality, but also reduces the impact of the number of antennas on bit error performance, reduces multipath interference, improves bit error performance, overcomes the impact of the relationship between the number of antennas and inter-channel interference on communication quality, and at the same time, the amount of calculation is small, and the amount of calculation for large-scale OGSM-MIMO systems with more antennas is still very small, and the applicability is stronger.

The antenna combination selected in the embodiment of the present invention is applied to the OGSM-MIMO system, as shown in FIG3 . The actual antenna combination is known, and the L-PAM modulation mode is adopted, and the modulation order L=2, then the OGSM-MIMO system mapping table is shown in Table 1.

Table 1 OGSM-MIMO mapping based on antenna selection

In Figure 3, _xu represents the transmitted signal, such as the data stream composed of input bits in Table 1, _x1,u represents the number of bits mapped by the antenna combination, x2 _,u represents the number of bits mapped by the constellation, and x1 _,u and x2 _,u can be obtained through the theoretical formula of the OGSM-MIMO system. _yu represents the signal received by the receiving end. Nt represents that the transmitting end has Nt transmitting antennas, and Nr represents that the receiving end has Nr receiving antennas. ML represents the maximum likelihood detection algorithm, s/p and p/s represent serial-to-parallel conversion and parallel-to-serial conversion respectively, OGSM is optical generalized spatial modulation, Symbol modulation represents symbol modulation, Symboldemodulation represents symbol demodulation, Antenna modulation represents antenna modulation, and Antenna demodulation represents antenna demodulation.

The performance of the multi-array visible light OGSM-MIMO antenna selection method based on the Pearson coefficient is analyzed compared with other traditional antenna selection methods.

As shown in FIG4 , the number of activated antennas at the transmitting end is _Na = 2, the number of receiving PD end is _Nr = 2, and the modulation mode is 2PAM. It can be seen from the simulation results that, compared with the antenna selection method based on the norm (Norm selection) and the random selection method (Random selection), the OGSM-MIMO system bit error rate performance based on the Pearson coefficient antenna selection method of the present invention is better; when the bit error rate (BER) reaches 10 ^-3 , the OGSM-MIMO system bit error performance (37.8dB) is improved by 2.2dB and 4dB compared with the Norm selection (40dB) and the Random selection (41.8dB), respectively.

As shown in Figure 5, the modulation mode adopts 2PAM, the number of activated antennas _Na at the transmitting end is 2, 3, and 4 respectively, and the receiving antenna _Nr = 2. From the simulation results, it can be seen that: 1) when the signal-to-noise ratio is relatively low, the theoretical bit error rate of the OGSM-MIMO system is higher than the actual bit error rate, and when the signal-to-noise ratio is relatively high, the theoretical bit error rate and the actual bit error rate basically coincide. 2) Under the same modulation mode, increasing the number of transmitting antennas will reduce the bit error performance; this shows that the embodiment of the present invention further improves the scope of application of the OGSM-MIMO system while increasing the number of activated transmitting antennas to ensure reliability.

As shown in Figure 6, the number of active antennas at the transmitting end is _Na = 2, the number of receiving antennas is _Nr = 6, and the OGSM-MIMO system modulation uses 2PAM, 4PAM, and 8PAM. From the simulation results and the OGSM-MIMO system, it can be seen that: as the modulation order increases, the transmission rate will be improved, but the bit error performance will decrease; when the bit error rate reaches ^10-3 , the 2PAM modulation mode reduces the transmission rate by 2bpcu and 4bpcu respectively compared with the 4PAM and 8PAM modulation modes, but the bit error performance is improved by about 2dB and 4dB.

The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims (5)

1. The multi-array visible light OGSM-MIMO antenna selection method based on the Pearson coefficient is characterized by comprising the following steps of:

step 1, determining indoor space parameters, building a visible light indoor communication link system model, and building a three-dimensional coordinate system in an indoor space;

Step 2, establishing a channel mathematical model comprising a direct line-of-sight link LOS and a first-order reflection link NLOS;

Step 3, determining the mounting interval of the LEDs based on a channel mathematical model comprising LOS and NLOS through two conditions of the standard deviation of illuminance of a receiving plane and the minimum value of illuminance RSS of the receiving plane, and dividing a positioning area;

step 4, selecting a plurality of positioning points in the positioning area, collecting the received illuminance RSS value of each LED and the actual coordinates of the positioning points at the positioning points, and storing the RSS value and the actual coordinates of the positioning points into a fingerprint library;

Step 5, determining a fingerprint library of the positioning area;

Step 6, calculating Pearson coefficients between any LED combination and the photoelectric detector in any one positioning area according to the fingerprint library of the positioning area;

Step 7, based on the Pearson coefficient between any LED combination and the photoelectric detector, the corresponding LED combination with high relativity is used as an actually activated antenna combination;

In the step 6, the Pearson coefficient ρ (LED _m,k,f_n,k) between any LED combination and the photodetector in the kth positioning region is expressed as:

Where R _m,k represents the center emission intensity of the mth LED of the kth region, The nth photodetector which is the kth positioning area fingerprint database receives the average illuminance of the actual LED combination; sigma represents the sample standard deviation,/>Indicating that the kth positioning area nth photodetector received the illumination of the mth LED.

2. The method for selecting the multi-array visible light OGSM-MIMO antenna based on the Pearson coefficients according to claim 1, wherein the illuminance E of any M LED light sources received by any one of the photodetectors in step 2 is:

wherein D represents the distance between the receiving end of any one photoelectric detector and the LED light source, and D' represents the distance between the receiving end of any one photoelectric detector and the secondary light source generated by the LED light source; e _j is the direct horizontal illumination of the jth photodetector under multiple light sources, E _j' is the reflected illumination of the jth photodetector under multiple light sources, I (phi _i) is the light intensity from a single light source to any point, phi _i represents the emission angle of the ith LED, Representing the angle of incidence of the jth photodetector, I _i' is the reflected intensity of the single light source to any point, and β represents the emission angle of the secondary light source.

3. The method for selecting the multi-array visible light OGSM-MIMO antenna based on the Pearson coefficients according to claim 1, wherein in the step 3, the illuminance RSS of the human eye in the comfortable range of illuminance is 300 lx-1500 lx.

4. The method for selecting the multi-array visible light OGSM-MIMO antenna based on the Pearson coefficients according to claim 1, wherein in the step 4, the fingerprint library is:

f_n＝{S_n,(x_n,y_n,z_n),t_n|n＝1,2,L,N}

In the method, in the process of the invention, Representing the received illuminance from each LED _m at the nth photodetector PD _n; (x _n,y_n,z_n) represents the coordinate position of the nth photodetector, in units: m; t _n represents the number of times of illumination received by the nth photodetector;

The LED _m represents an mth LED, m=1, 2, l, m; LED _m is represented as:

LED_m＝{R_m,(x_m,y_m,z_m)|m＝1,2,…,M}

Wherein, R _m represents the central luminous intensity of the mth LED, unit: lx; (x _m,y_m,z_m) is the coordinate position of the mth LED in units: m.

5. The method for selecting a multi-array visible light OGSM-MIMO antenna based on Pearson coefficients according to claim 1, wherein in step 5, the fingerprint library f _n,k of the positioning area is determined according to the fingerprint library f _n in step 4, that is, the average illuminance set received by the nth photodetector in any positioning area from the LED combinations is expressed by the following formula:

f_n,k＝{S_n,k,(x_n,k,y_n,k,z_n,k),t_n,k|n＝1,2,L,N_k}

Where S _n,k denotes the received illuminance from the nth LED in the kth positioning area received by the nth photodetector in the kth positioning area, (x _n,k,y_n,k,z_n,k) denotes the coordinate position of the nth photodetector PD in the kth area in units of: m;

The position of the mth LED in the kth positioning area LED _m,k is denoted as:

LED_m,k＝{R_m,k,(x_m,k,y_m,k,z_m,k)|m＝1,2,…,M_k}

Wherein R _m,k represents the center emission intensity of the m-th LED of the k-th region, in units of: lx; (x _m,k,y_m,k,z_m,k) represents the coordinate position of the mth LED in the kth region, in units of: m.