Selective weighted positioning method based on light source RSSI

Abstract

The invention discloses a light source RSSI (Received Signal Strength Indicator)-based selective weighted positioning method, which is realized by adopting an FPGA (Field Programmable Gate Array), and the positioning process mainly comprises the following steps of: screening four signals with the maximum power from different light sources from numerous received signals, selecting any three light sources from the four light sources, ensuring that the three light sources are not collinear, and then selecting one light source from the screened four light sources. Every three light sources form one group, four position coordinates of a receiving end are calculated through an RSSI triangulation positioning algorithm for correcting the weight of the four groups of light sources, and finally the coordinates of the receiving end are accurately estimated through centroid weighting. According to the method, positioning errors caused by light source reflection interference and transmission distance errors in actual use of visible light positioning can be reduced, the influence of environmental factors on signal fluctuation is reduced, the positioning precision is improved, and the method can be implemented on an FPGA hardware platform and has practicability.

Description

Technical Field

[0001] The invention relates to a visible light communication positioning technology, and in particular to a selective weighted positioning method based on light source RSSI. Background Art

[0002] Visible light communication technology (VLC) is a technology that uses LEDs for both lighting and communication. It has great research value and application prospects in future communication fields such as 6G. Visible light communication uses the wavelength of 380nm in the visible light band. ～ 780nm, communication frequency 400THz ～ As an information carrier, 800THz has the advantages of fast data transmission speed, large communication capacity, rich spectrum resources, green and safe. In recent years, with the increasing demand for indoor precise positioning, indoor positioning technology based on VLC has also received widespread attention. In view of the problems of low positioning accuracy and complex system implementation in traditional indoor visible light positioning technology, researchers have proposed a variety of improvement schemes. Among them, the RSSI positioning algorithm is simple to implement, has low equipment complexity, and relatively high positioning accuracy. It is widely used in indoor positioning systems. However, the RSSI positioning algorithm estimates the distance between the transmitter and the receiver mainly through the distance between the three transmitting sources and the receiving end to calculate the receiver's location information. In actual use, the power of the signal will decrease with the increase of the transmission distance, and the environmental factors have a great influence on the signal fluctuation. The three light sources used in this method are collinear, or there will be positioning errors due to the errors in the distance parameters of the three light sources. In addition, there are direct and reflected rays in the transmission of light, which will affect the positioning results. Summary of the invention

[0003] The purpose of the present invention is to provide a selective weighted positioning method based on the RSSI of a light source in view of the deficiencies of the prior art. This method can reduce the positioning error caused by the reflection interference of the light source and the transmission distance error in the actual use of visible light positioning, reduce the influence of environmental factors on signal fluctuations, improve the positioning accuracy, and can be implemented on the FPGA hardware platform, which is practical.

[0004] The technical solution for achieving the purpose of the present invention is:

[0005] A selective weighted positioning method based on light source RSSI comprises the following steps:

[0006] 1) Light source signal screening: Light source signal screening is to select four signals with the largest power from different light sources from a large number of transmitted light source signals, and randomly select three of the four light sources to ensure that the three light sources are not collinear. The specific process is as follows:

[0007] 1-1) Each light source in the room emits a light signal, and the receiving end receives n (n>4) signals. According to the identification information in the signal, the received power Pr of all signals is calculated and the power is sorted. The light source coordinates of the signals sorted from large to small in power are Ti(x i ,y i ,H), i=1,2…n, H is the height of the light source, which is a known fixed value, and the number of light sources is determined;

[0008] 1-2) Filter out the four signals with the strongest power: T1, T2, T3, T4, and determine whether the four light source signals satisfy whether any three light sources are collinear, that is, determine whether the coordinates of the four light sources simultaneously meet the following three conditions:

[0009] a: four horizontal coordinates x i , the number of equal numbers among i=1,2,3,4 is less than 3;

[0010] b: four ordinates y i , the number of equal numbers among i=1,2,3,4 is less than 3;

[0011] c: four x i / y i , among the values ​​of i=1,2,3,4, the number of equal values ​​is less than 3;

[0012] If conditions a, b, and c are met at the same time, T1, T2, T3, and T4 can be used for positioning estimation. If one of the above conditions a, b, and c is not met, it is necessary to replace the weakest signal of the three collinear light sources with the light source T5 sorted in step 1-1), and then perform conditional judgment again until four light sources that meet the conditions are found;

[0013] 2) Weighted RSSI triangulation positioning: From the four light sources selected in step 1), three of them are grouped together, and the four groups of light sources are used to calculate the four position coordinates of the receiving end using the weighted RSSI triangulation positioning algorithm. The specific process is as follows:

[0014] 2-1) After the screening in step 1), the coordinates of the four best light sources are A(x1, y1), B(x2, y2), C(x3, y3), and D(x4, y4). The four light sources A, B, C, and D are combined into four groups: ABC, ABD, ACD, and BCD.

[0015] 2-2) Using RSSI positioning algorithm: The signal receiving power P obtained in step 1-1) is r The emission power P of the light source t Enter formula (1):

[0016]

[0017] in, h is the height of the plane where the mobile receiving end is located. The mobile receiving device is placed horizontally. is 0, and the straight-line distance d between the four light sources and the receiving end is obtained;

[0018] 2-3) The distance obtained in step 2-2) will be larger than the actual distance. In step 2-1), each of the four groups of light sources uses the weighted centroid positioning algorithm to correct the position coordinates. Then the specific coordinate position of the receiving end obtained by each group of light sources is M(x, y, 0) with formula (2):

[0019]

[0020] Among them, ω i is the weight coefficient, and the specific calculation process of point M is:

[0021] 2-3-1) According to the distance between the three light sources and the receiving end, the three-side positioning algorithm is used to calculate the receiver's location information. The coordinates of each light source are A(x1, y1, H), B(x2, y2, H) and C(x3, y3, H). Assuming that the position coordinates of the receiving mobile node are (x, y, 0), and the straight-line distances from the receiving mobile node to the three transmitting light source nodes A, B, and C are d1, d2, and d3, the signal power in the system will decrease as the transmission distance increases, and the calculated distance will be too large, then:

[0022]

[0023] According to the solutions of equations (3), (4) and (5), we can get and The coordinates of the three intersection points;

[0024] 2-3-2) Based on the primary and secondary influence of light sources, the weight coefficient of P1 is Similarly, the coordinates of the final receiving end are:

[0025]

[0026] 2-4) Repeat the calculation of the four groups of light sources in step 2-1) four times through step 2-3) to obtain four specific coordinate positions: M1 (x1, y1), M2 (x2, y2), M3 (x3, y3), M4 (x4, y4);

[0027] 3) Weighted centroid estimation: Use weighted centroid to accurately estimate the coordinates of the receiving end. The specific process is as follows:

[0028] 3-1) Based on the four coordinates M1, M2, M3, and M4 calculated in step 2), the centroid weighted algorithm is used to accurately estimate the coordinates of M (x, y):

[0029]

[0030] W1, W2, W3, W4 are weighting factors, and the weighting factors are:

[0031]

[0032] Where k is the attenuation coefficient, which takes a negative value;

[0033] 3-2) Finally, output the receiving end coordinates M(x,y).

[0034] This technical solution aims at the problems of light source reflection interference and transmission distance error that occur in the actual use of visible light positioning. First, a strong power signal selection method is used to filter out a part of the signals with smaller receiving power, filter out the reflected component, thereby increasing the proportion of the direct component, and screen the light sources so that any three of them are not collinear, which can effectively reduce the positioning error; secondly, the receiving end is positioned through four-point light sources, and any three of them are grouped into a group, which is divided into four groups, and the error caused by the transmission distance is reduced accordingly based on the primary and secondary influence of the light source by improving the weight. Finally, each coordinate value is multiplied by the corresponding weighting factor, and then added to obtain the final position coordinate. The weighting factor is related to the transmission distance. The closer the distance, the larger the weighting factor. The influence of environmental factors on signal fluctuations is reduced to further improve the positioning accuracy.

[0035] This method can reduce the positioning error caused by light source reflection interference and transmission distance error in actual use of visible light positioning, reduce the impact of environmental factors on signal fluctuations, improve positioning accuracy, and can be implemented on an FPGA hardware platform, making it practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the process flow of the embodiment method;

[0037] Figure 2 This is a schematic diagram of the indoor light source layout in the embodiment;

[0038] Figure 3 Schematic diagram of the geometric principle of the RSSI three-side positioning algorithm in the embodiment;

[0039] Figure 4 : It is a simulation diagram of positioning error in the embodiment, wherein Figure (a) is a simulation diagram of positioning error when the receiving end adopts the RSSI algorithm, and Figure (b) is a simulation diagram of positioning error after the receiving end adopts the improved RSSI algorithm;

[0040] Figure 5 Schematic diagram of FPGA implementation in the embodiment. DETAILED DESCRIPTION

[0041] The content of the present invention is further described below in conjunction with the drawings and embodiments, but the present invention is not limited thereto.

[0042] Example:

[0043] Reference Figure 1 , a selective weighted positioning method based on light source RSSI, comprising the following steps:

[0044] 1) Light source signal screening: Light source signal screening is to select four signals with the largest power from different light sources from a large number of transmitted light source signals, and randomly select three of the four light sources to ensure that the three light sources are not collinear. The specific process is as follows:

[0045] 1-1) Each light source in the room emits a light signal, such as Figure 2 As shown in the figure, in this example, 9 lights are arranged indoors, and the receiving end receives n (n>4) signals. According to the identification information in the signal, the receiving power Pr of all signals is calculated and the power is sorted. The light source coordinates of the signals sorted from large to small in power are Ti(x i ,y i ,H), i=1,2…n, H is the height of the light source, which is a known fixed value, and the number of light sources is determined;

[0046] 1-2) Filter out the four signals with the strongest power: T1, T2, T3, T4, and determine whether the four light source signals satisfy whether any three light sources are collinear, that is, determine whether the coordinates of the four light sources simultaneously meet the following three conditions:

[0047] a: four horizontal coordinates x i , the number of equal numbers among i=1,2,3,4 is less than 3;

[0048] b: four ordinates y i , the number of equal numbers among i=1,2,3,4 is less than 3;

[0049] c: four x i / y i , among the values ​​of i=1,2,3,4, the number of equal values ​​is less than 3;

[0050] If conditions a, b, and c are met at the same time, T1, T2, T3, and T4 can be used for positioning estimation. If one of the above conditions a, b, and c is not met, it is necessary to replace the weakest signal of the three collinear light sources with the light source T5 sorted in step 1-1), and then perform conditional judgment again until four light sources that meet the conditions are found;

[0051] 2) Weighted RSSI triangulation positioning: From the four light sources selected in step 1), three of them are grouped together, and the four groups of light sources are used to calculate the four position coordinates of the receiving end using the weighted RSSI triangulation positioning algorithm. The specific process is as follows:

[0052] 2-1) After the screening in step 1), the coordinates of the four best light sources are A(x1, y1), B(x2, y2), C(x3, y3), and D(x4, y4). The four light sources A, B, C, and D are combined into four groups: ABC, ABD, ACD, and BCD.

[0053] 2-2) Using RSSI positioning algorithm: The signal receiving power P obtained in step 1-1) is r The emission power P of the light source t Enter formula (1):

[0054]

[0055] in, h is the height of the plane where the mobile receiving end is located. The mobile receiving device is placed horizontally. is 0, and the straight-line distance d between the four light sources and the receiving end is obtained;

[0056] 2-3) The distance obtained in step 2-2) will be larger than the actual distance. In step 2-1), each of the four groups of light sources uses the weighted centroid positioning algorithm to correct the position coordinates. Then the specific coordinate position of the receiving end obtained by each group of light sources is M(x, y, 0) with formula (2):

[0057]

[0058] Among them, ω i is the weight coefficient, and the specific calculation process of point M is:

[0059] 2-3-1) If Figure 3 As shown in the figure, according to the distance between the three light sources and the receiving end, the three-side positioning algorithm is used to calculate the receiver's location information. The position coordinates of each light source are A(x1, y1, H), B(x2, y2, H), and C(x3, y3, H). Assuming that the position coordinates of the receiving mobile node are (x, y, 0), and the straight-line distances from the receiving mobile node to the three transmitting light source nodes A, B, and C are d1, d2, and d3, the signal power in the system will decrease as the transmission distance increases, and the calculated distance will be too large, then:

[0060]

[0061] According to equations (3), (4) and (5), we can solve P1(x p1 ,yp1 )、P2(x p2 ,y p2 ) and P3(x p3 ,y p3 ) coordinates of the three intersection points;

[0062] 2-3-2) Based on the primary and secondary influence of light sources, the weight coefficient of P1 is Similarly, the coordinates of the final receiving end are:

[0063]

[0064] 2-4) Repeat the calculation of the four groups of light sources in step 2-1) four times through step 2-3) to obtain four specific coordinate positions: M1 (x1, y1), M2 (x2, y2), M3 (x3, y3), M4 (x4, y4);

[0065] 3) Weighted centroid estimation: Use weighted centroid to accurately estimate the coordinates of the receiving end. The specific process is as follows:

[0066] 3-1) Based on the four coordinates M1, M2, M3, and M4 calculated in step 2), the centroid weighted algorithm is used to accurately estimate the coordinates of M (x, y):

[0067]

[0068] W1, W2, W3, W4 are weighting factors, and the weighting factors are:

[0069]

[0070] Where k is the attenuation coefficient, which takes a negative value;

[0071] 3-2) Finally, output the receiving end coordinates M(x,y).

[0072] In this example, four signals with the highest power from different light sources are selected from numerous transmitted light source signals. Three of the four light sources are randomly selected to ensure that the three light sources are not collinear. The positioning calculation process mainly uses the four selected light sources, each three of which form a group, and the four groups of light sources are used through the weighted RSSI triangulation positioning algorithm to calculate the four position coordinates of the receiving end. Finally, the centroid weighting is used to accurately estimate the receiving end coordinates.

[0073] like Figure 4As shown in the figure, the estimation simulation diagram of the two-dimensional positioning coordinates of the receiving end is carried out in a room within 5m*5m*3m. (a) is the positioning error simulation diagram when the receiving end adopts the RSSI algorithm. Figure (b) is the positioning error simulation diagram after the receiving end adopts the improved RSSI algorithm. It can be clearly seen that the positioning error has been reduced. Under the same environment, the positioning error is about 27.16cm when the RSSI algorithm is used, and the positioning error after using this method is 10.38cm. The schematic diagram of FPGA implementation in this example is shown in Figure 5 shown.

Claims

1. A selective weighted positioning method based on light source RSSI, characterized in that: The steps include: 1) Light source signal screening: Light source signal screening is to select four signals with the largest power from different light sources from a large number of transmitted light source signals, and randomly select three of the four light sources to ensure that the three light sources are not collinear. The specific process is as follows: 1-1) Each light source in the room transmits a light signal, and the receiving end receives n signals, n>4. According to the identification information in the signal, the receiving power P of all signals is calculated. r And sort the power, the light source coordinate of the signal sorted from large to small is T i (x i ,y i ,H), i=1,2…n, H is the height of the light source, which is a known fixed value, and the number of light sources is determined; 1-2) Filter out the four signals with the strongest power: T1, T2, T3, T4, and determine whether the four light source signals satisfy whether any three light sources are collinear, that is, determine whether the coordinates of the four light sources simultaneously meet the following three conditions: a: four horizontal coordinates x i , the number of equal numbers among i=1,2,3,4 is less than 3; b: four ordinates y i , the number of equal numbers among i=1,2,3,4 is less than 3; c: four x i / y i , among the values ​​of i=1,2,3,4, the number of equal values ​​is less than 3; If conditions a, b, and c are met at the same time, T1, T2, T3, and T4 can be used for positioning estimation. If one of the above conditions a, b, and c is not met, it is necessary to replace the weakest signal of the three collinear light sources with the light source T5 sorted in step 1-1), and then perform conditional judgment again until four light sources that meet the conditions are found; 2) Weighted RSSI triangulation positioning: From the four light sources selected in step 1), three of them are grouped together, and the four groups of light sources are used to calculate the four position coordinates of the receiving end using the weighted RSSI triangulation positioning algorithm. The specific process is as follows: 2-1) After the screening in step 1), the coordinates of the four best light sources are A(x1, y1), B(x2, y2), C(x3, y3), and D(x4, y4). The four light sources A, B, C, and D are combined into four groups: ABC, ABD, ACD, and BCD. 2-2) Using RSSI positioning algorithm: The signal receiving power P obtained in step 1-1) is r The emission power P of the light source t Enter formula (1): in, h is the height of the plane where the mobile receiving end is located. The mobile receiving device is placed horizontally. is 0, and the straight-line distance d between the four light sources and the receiving end is obtained; 2-3) The distance obtained in step 2-2) will be larger than the actual distance. In step 2-1), each of the four groups of light sources uses the weighted centroid positioning algorithm to correct the position coordinates. Then the specific coordinate position of the receiving end obtained by each group of light sources is M(x, y, 0) with formula (2): Among them, ω i is the weight coefficient, and the specific calculation process of point M is: 2-3-1) According to the distance between the three light sources and the receiving end, the three-side positioning algorithm is used to calculate the receiver's location information. The coordinates of each light source are A(x1, y1, H), B(x2, y2, H), and C(x3, y3, H). Assuming that the position coordinates of the receiving mobile node are (x, y, 0), and the straight-line distances from the receiving mobile node to the three transmitting light source nodes A, B, and C are d1, d2, and d3, the signal power in the system will decrease as the transmission distance increases, and the calculated distance will be too large, then: According to the solutions of equations (3), (4) and (5), we can get and The coordinates of the three intersection points; 2-3-2) Based on the primary and secondary influence of light sources, the weight coefficient of P1 is Similarly, the coordinates of the final receiving end are: 2-4) Repeat the calculation of the four groups of light sources in step 2-1) four times through step 2-3) to obtain four specific coordinate positions: M1 (x1, y1), M2 (x2, y2), M3 (x3, y3), M4 (x4, y4); 3) Weighted centroid estimation: Use weighted centroid to accurately estimate the coordinates of the receiving end. The specific process is as follows: 3-1) Based on the four coordinates M1, M2, M3, and M4 calculated in step 2), the centroid weighted algorithm is used to accurately estimate the coordinates of M (x, y): W1, W2, W3, W4 are weighting factors, and the weighting factors are: Where k is the attenuation coefficient, which takes a negative value; 3-2) Finally, output the receiving end coordinates M(x,y).

Images