CN113176534A - Gaussian beam tracking method based on free space optical communication - Google Patents

Gaussian beam tracking method based on free space optical communication Download PDF

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CN113176534A
CN113176534A CN202110456865.9A CN202110456865A CN113176534A CN 113176534 A CN113176534 A CN 113176534A CN 202110456865 A CN202110456865 A CN 202110456865A CN 113176534 A CN113176534 A CN 113176534A
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laser
transmitter
receiver
sinθ
cosθ
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朱秉诚
蒋佩霖
徐安梓
王钒锰
何卓旻
程天
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Southeast University
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Southeast University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/16—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
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  • Optical Communication System (AREA)

Abstract

The invention discloses a Gaussian beam tracking method based on Free Space Optical (FSO) communication. The method is divided into a time domain and a space domain, laser is transmitted according to a transmitter, a receiver can measure the laser power of the laser, the transmitter transmits the laser with directional parameters in different time periods, the receiver obtains K samples, and the relative coordinate of a user can be obtained based on the measured values. The invention has high calculation efficiency, only needs the solution of a linear equation set, and can be realized by a low-cost signal processing unit. Meanwhile, the requirement on a feedback link is reduced, and an iterative process is not relied on.

Description

Gaussian beam tracking method based on free space optical communication
Technical Field
The invention relates to the technical field of visible light positioning, in particular to a Gaussian beam tracking method based on Free Space Optical (FSO) communication.
Background
In the past decades, communication rates have been increasing and communication systems are utilizing higher frequency bands to cover millimeter waves, terahertz waves and light waves. The higher the frequency, the narrower the signal beam, and thus the higher the directional gain. However, a narrow beam places higher demands on tracking speed and robustness.
Most existing FSO tracking systems utilize charge coupled devices, silicon photovoltaic panels, or free-spinning heads, and these tracking methods do not consider the limitation of tracking speed or how to reduce the workload of the feedback link. Therefore, the existing FSO tracking system cannot support high-mobility nodes, and is difficult to be applied to equipment with certain requirements on tracking speed.
Disclosure of Invention
The invention mainly solves the technical problems that the existing FSO tracking system is slow in tracking speed or large in workload of feedback link, and provides a Gaussian beam tracking method based on Free space optical (Free spatial optical) communication. The algorithm is computationally efficient, requiring only the solution of a linear system of equations, which can be implemented with a low cost signal processing unit. Meanwhile, the requirement on a feedback link is reduced, and an iterative process is not relied on.
The invention comprises the following steps:
step 1: the transmitter emits laser light to form a laser spot on the receiving plane. The plane distance between the transmitter plane and the receiver plane is d, and the receiver center coordinate is (ρ)r,θr) The center coordinate of the laser point is (rho)l,θl). The transmitter points to the origin of the plane in which the receiver is located. When d is large, let ρ bel cosθlD and rhol sinθlWhen the/d is sufficiently small (less than 0.01), the deflection angle can be approximated as
Figure BDA0003040808540000011
Step 2: the spatial distribution of the received intensity at a distance d from the transmitter is
Figure BDA0003040808540000021
PrIs the laser power measured by the receiver; a is a constant dependent on the propagation distance d and the transmission power Pt(ii) a σ is a distribution parameter of laser intensity at a unit distance from the emitter; σ d is a distribution parameter of the laser intensity at distance d, i.e. the laser spot diameter increases linearly with d.
And step 3: the sampling process is divided into K time segments, and in the K time segment, the transmitter transmits a directional parameter (rho)l, kcosθl,k/d,ρl,ksinθl,kLaser of/d), the receiver can obtain K samples in K time periods:
Figure BDA0003040808540000022
Figure BDA0003040808540000023
wherein deltakN (0,1) is additive Gaussian noise.
Dividing the kth and the (k-1) th equations in the above equation to obtain a linear equation system:
Figure BDA0003040808540000024
wherein
Figure BDA0003040808540000025
Is a sample of the optical power measured at time k,
Figure BDA0003040808540000026
are the estimated coordinates of the receiver.
And 4, step 4: solving the system of linear equations can yield the relative coordinates of the user.
Has the advantages that: the invention has high calculation efficiency, only needs the solution of a linear equation set, and can be realized by a low-cost signal processing unit. Meanwhile, the requirement on a feedback link is reduced, and an iterative process is not relied on.
Drawings
Fig. 1 is a schematic diagram of a transmitter and a receiver.
Fig. 2 is a schematic diagram of a time domain method.
FIG. 3 is a schematic diagram of a spatial domain method.
Fig. 4 is a schematic diagram of the relative relationship between the relative coordinates of the user calculated by the present invention and the actual relative coordinates of the user in a noise-free environment.
Fig. 5 is a schematic diagram of the relative relationship between the relative coordinates of the user determined by using the scheme and the actual relative coordinates of the user in a noise environment.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The transmitter emits laser light as shown in fig. 1, forming a spot on the receiving plane. The plane distance between the transmitter plane and the receiver plane is d, and the receiver center coordinate is (ρ)r,θr) The coordinates of the center of the point are (rho)l,θl). The transmitter points to the origin of the plane in which the receiver is located. When d is large, the deflection angle can be approximated by
Figure BDA0003040808540000031
Received power at a distance d from the transmitter of
Figure BDA0003040808540000032
Where a is dependent on the distance d and the transmit power PtA constant of (d); σ is a distribution parameter of laser intensity per unit distance from the transmitter; σ d is a distribution parameter of the laser intensity at the distance transmitter d.
As shown in the time domain method of fig. 2, the transmitter angle is adjusted at multiple time instants, and assuming that there are K transmitted signals at different time instants, the transmitter transmission angle is (ρ) during the kth time periodl,kcosθl,k/d,ρl,ksinθl,kLaser of/d), the receiver can obtain K samples in K time periods:
Figure BDA0003040808540000033
wherein deltakN (0,1) is additive Gaussian noise.
The above equation for k and k-1 is divided by the system of linear equations:
Figure BDA0003040808540000034
wherein
Figure BDA0003040808540000035
Is a sample of the optical power measured at time k,
Figure BDA0003040808540000036
are the estimated coordinates of the receiver.
By transforming the above equation, one can derive:
Figure BDA0003040808540000041
wherein
Figure BDA0003040808540000042
Figure BDA0003040808540000043
Figure BDA0003040808540000044
Known from linear algebra knowledge
Figure BDA0003040808540000045
Solving using MATLAB software
Figure BDA0003040808540000046
The relative coordinates of the user, i.e. the user position on the receiving surface, can be derived.
In order to reduce the time of the time domain method, a space domain method as shown in fig. 3 can be adopted, and K transmitters are used for simultaneously transmitting gaussian beams with different wavelengths, and the calculation method is the same as the time domain method.
The following further describes our scheme with reference to specific embodiments.
Fig. 4 shows the relative relationship of the user relative coordinates calculated using the present invention and the user's actual relative coordinates in a noise-free environment, in this case, three sets of data are used to locate the user, i.e., K3 and (ρ ═ 3 &)l,kcosθl,k,ρl,ksinθl,k) K is distributed at equal intervals of 1,2,3
Figure BDA0003040808540000047
On a unit circle with a center, the results in fig. 4 show that: in a noise-free environment, the relative coordinates of the user calculated by the invention are completely consistent with the actual relative coordinates of the user, which means that the algorithm is unbiased.
Fig. 5 shows the relative coordinates of a user determined using the scheme in a noisy environment, in this case introducing additive noise into the environment, and keeping other conditions constant, versus the actual relative coordinates of the user, the results in fig. 5 showing: the relative coordinates of the user calculated by the invention can still be matched with the actual relative coordinates of the user even under a noise environment, which means that the invention can still realize accurate tracking of the user even if certain interference factors exist in the environment.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations. The foregoing examples or embodiments are merely illustrative of the present invention, which may be embodied in other specific forms or in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims should be construed to be included therein.

Claims (4)

1. A Gaussian beam tracking method based on free space optical communication is characterized by comprising the following steps:
1) the transmitter transmits laser to form a laser spot on a receiving plane; the plane distance between the transmitter plane and the receiver plane is d, and the receiver center coordinate is (ρ)r,θr) The center coordinate of the laser point is (rho)l,θl) (ii) a When d is large enough that ρlcosθlD and rholsinθlWhen each of the values of/d is less than 0.01, the deflection angle is expressed as
Figure FDA0003040808530000011
2) The spatial distribution of the received intensity at a distance d from the transmitter is
Figure FDA0003040808530000012
PrIs the laser power measured by the receiver; a is a constant, the magnitude of a is inversely proportional to the propagation distance d, and is related to the transmission power PtIs in direct proportion; σ is a distribution parameter of laser intensity at a unit distance from the transmitter; σ d is a distribution parameter of laser intensity at distance d; let ρ belcosθlD and rholsinθlAll d are smallAt 0.01, the laser direction of the transmitter can be obtained as (ρ)lcosθl/d,ρlsinθl/d)；
3) The transmitter transmits the directional parameter (p)l,kcosθl,k/d,ρl,ksinθl,kLaser of/d), receiver obtains K samples:
Figure FDA0003040808530000013
wherein deltakN (0,1) is additive Gaussian noise;
the equation (1) for the k-th and k-1 time periods is divided to yield a system of linear equations:
Figure FDA0003040808530000014
wherein
Figure FDA0003040808530000015
Is a sample of the optical power measured at time k,
Figure FDA0003040808530000016
is the estimated coordinates of the receiver;
4) and solving the linear equation system (2) to obtain the relative coordinates of the user.
2. The Gaussian beam tracking method based on free-space optical communication as claimed in claim 1, wherein there is only one transmitter, and in step 3), the transmitter adjusts the transmission angle at K different time instants, and in the kth time period, the transmitter transmits the orientation parameter (ρ)l,kcosθl,k/d,ρl,ksinθl,kD), the receiver obtains K samples in K time periods.
3. The Gaussian beam tracking method based on free-space optical communication as claimed in claim 1, characterized in thatIn step 3), K transmitters are used to simultaneously transmit Gaussian beams with different wavelengths, and the transmission angle of the kth transmitter is (rho)l,kcosθl,k/d,ρl,ksinθl,kLaser of/d).
4. The Gaussian beam tracking method based on free-space optical communication according to claim 1, wherein the specific steps of step 4) include:
transforming the system of linear equations (2) to obtain:
Figure FDA0003040808530000021
wherein
Figure FDA0003040808530000022
Figure FDA0003040808530000023
Figure FDA0003040808530000024
Known from linear algebra knowledge
Figure FDA0003040808530000031
Solving using MATLAB software
Figure FDA0003040808530000032
The user position on the receiving surface is derived.
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WO2024083562A1 (en) 2022-10-20 2024-04-25 Signify Holding B.V. Method for beam alignment in optical wireless communication systems

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CN104407505A (en) * 2014-11-25 2015-03-11 东南大学 Holographic calculation method for suppressing laser speckle effect
CN204389019U (en) * 2015-02-05 2015-06-10 中国工程物理研究院应用电子学研究所 A kind of high resolving power multiwavelength laser intensity distribution detection device
CN109274432A (en) * 2018-08-29 2019-01-25 西安电子科技大学 Coherent tracking system and compensation method based on free space optical communication
CN111628822A (en) * 2020-06-04 2020-09-04 清华大学 Approximate calculation method for single scattering path loss in ultraviolet light communication non-line-of-sight link
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CN103471817A (en) * 2013-09-27 2013-12-25 重庆大学 Rapid measurement device and method for multi-field space luminosity distribution
CN104407505A (en) * 2014-11-25 2015-03-11 东南大学 Holographic calculation method for suppressing laser speckle effect
CN204389019U (en) * 2015-02-05 2015-06-10 中国工程物理研究院应用电子学研究所 A kind of high resolving power multiwavelength laser intensity distribution detection device
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CN111628822A (en) * 2020-06-04 2020-09-04 清华大学 Approximate calculation method for single scattering path loss in ultraviolet light communication non-line-of-sight link
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WO2024083562A1 (en) 2022-10-20 2024-04-25 Signify Holding B.V. Method for beam alignment in optical wireless communication systems

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