A pose estimation method for a multi-led-multi-pd visible light system

Abstract

The present application relates to the technical field of wireless communication, in particular to a kind of pose estimation method of multi-led-multi-pd visible light system.The present application includes establishing multi-led-multi-pd system, system contains N t LED and a receiver containing N r PD, first define the coordinates and direction of all pd in the receiver frame, then it is converted into multi-led-multi-pd system frame;Based on DCO-OFDM modulation mode modulation signal, first generate OFDM signal, then add a direct current bias on the generated OFDM signal;Then feed to LED, to comply with intensity modulation / direct detection, it is assumed that direct current component of received signal is removed by built-in hardware component before digital-analog conversion, then AC coupling is carried out;Typical frame structure is used, for multi-led-multi-pd system, direct current bias version MIMO-OFDM scheme is used, synchronization algorithm is used to realize frame synchronization, communication state information is calculated, and pose is estimated assuming that appropriate synchronization algorithm is used to realize frame synchronization.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a pose estimation method for a multi-LED-multi-PD visible light system. Background Technology

[0002] With the development of wireless communication, people's demand for communication is increasing, and it has spread to various industries. Compared with traditional light sources, LEDs can be modulated at high frequencies, which has led to research into visible light communication and positioning systems. The many advantages of visible light systems, such as lower energy consumption and deployment costs, and no electromagnetic interference, have made them a hot topic in academia and industry.

[0003] The channel of a visible light system is highly dependent on the receiver's pose, i.e., its position and orientation; neglecting pose will limit the performance of the visible light system. Much work assumes the receiver is pointing upwards or parallel to the ceiling, or assumes prior knowledge of the orientation, such as by using an external orientation estimation device. However, these stringent assumptions are difficult to achieve in reality. In the case of mobile users, it is nearly impossible to keep the receiver perfectly parallel to the ceiling, and external orientation estimation devices are limited in accuracy due to cost or size constraints, making them not always feasible.

[0004] Furthermore, most studies on positioning implicitly assume that the transmit power is known. However, due to manufacturing defects, temperature drift, aging during use, and dust, the power current (PI) characteristics of LEDs can deviate slightly from the design value. Therefore, the transmit power is not entirely clear. Existing research has found that power uncertainty has a significant impact on the positioning performance of VLP systems. To address this issue, some researchers have proposed an estimator that considers unknown power and pose, where orientation is represented by a unit vector, and power is represented by coefficients of a scaled orientation vector. This algorithm first estimates the scale vector and then separates the corresponding unit vector, orientation coefficients, and power coefficients. The simple vector representation method used in this approach is suitable for a single PD receiver, but for multi-antenna receivers, the strategy of combining power coefficients into an orientation vector lacks degrees of freedom. Therefore, the power uncertainty for receivers with multiple PDs remains unresolved. Summary of the Invention

[0005] To address the problems mentioned in the background, a multi-LED / multi-PD DCO-OFDM communication system is designed, and the system structure and frame structure are presented. Using LOS amplitude estimation, a joint estimator for receiver pose and PI coefficients is proposed. The PI coefficients are estimated as interference parameters to account for power uncertainty, which is transformed into a least-squares problem solved using the Gauss-Newton method. This method effectively optimizes the orientation matrix using the manifold optimization principle. Monte Carlo simulation results verify the effectiveness of the designed algorithm.

[0006] This invention is achieved through the following technical solution: a pose estimation method for a multi-LED-multi-PD visible light system, comprising the following steps:

[0007] Step 1: Establish a multi-LED-multi-PD system, the system contains N t LEDs and a collection of N r For each PD receiver, the coordinates and orientations of all PDs are first defined in the receiver frame, and then transformed into a multi-LED-multi-PD system frame.

[0008] Step 2: Modulate the signal based on the DCO-OFDM modulation method, including:

[0009] At the transmitting end, an OFDM signal is first generated, and then a DC bias is added to the generated OFDM signal; then it is fed to the LED to conform to intensity modulation / direct detection, which is the mainstream modulation scheme for visible light systems.

[0010] At the receiving end, assuming that the DC component of the received signal is removed by built-in hardware components before digital-to-analog conversion, and then AC coupling is performed; the signal received after AC coupling has the following expression:

[0011]

[0012] In the formula, k is the subcarrier index, and s k For data symbols, Symbol length T sym The length T of the OFDM block u =NT s With the length T of the cyclic prefix (CP) g =N g T s The sum of T s Sampling time;

[0013] Step 3: Employing a typical frame structure, for multi-LED-multi-PD systems, a DC-biased version of the MIMO-OFDM scheme is used.

[0014] In the preamble section, we assume that all LEDs are in sequence with S.s Transmitted on all subcarriers for indexing, each LED transmits by N t A distinct and unique training sequence composed of OFDM symbols is used to estimate the effective channel response of these subcarriers;

[0015] The expression for the received sample at the m-th PD (after removing the guard interval) is:

[0016]

[0017] In the formula, the vec(·) operator represents the column vectorization of the matrix;

[0018] In the formula, It is the kth OFDM symbol of the received signal at the m-th PD. l k subcarriers l ∈S s ;

[0019] In the formula, K = |S s |, T l =T[k l ];

[0020] For N t A matrix consisting of training sequences of LEDs;

[0021] Let be the channel matrix, where

[0022] h m,n,l =h m,n [k l [The m-th PD and the n-th led are in the k-th position] l The channel frequency response at each subcarrier, k l ∈S s ;

[0023] Step 4: Use a synchronization algorithm to achieve frame synchronization and calculate the communication status information. For communication purposes, assume that an appropriate synchronization algorithm is used to achieve frame synchronization. The expression for the communication status information is:

[0024]

[0025] In the formula, This is the Moore-Penrose pseudo-inverse; the communication state information at this point is used for equalization, therefore based on H... m m∈{1,...,N r We use this to estimate the pose of {R,r}.

[0026] In step 1, the receiver frame includes:

[0027] The coordinates d of the m-th PD m,0 From relative to the origin O r The relative vector representation;

[0028] The normal vector n of the m-th PD P,m,0 The normal vector n0 relative to the receiving plane and the rotation matrix R P,m ∈SO(3) means that n P,m,0 =R P,m n0.

[0029] In step 1, the multi-LED-multi-PD system framework includes:

[0030] The coordinates of the receiver are r, which is the position of the receiver's centroid, and the direction is R∈SO(3). The normal n of the receiver is represented by n=Rn0;

[0031] The coordinates and normal of the m-th PD are represented by r. P,m =r+d m and n P,m =Rn P,m,0 In the formula d m It is a vector relative to r by d m =Rd m,0 express;

[0032] Assume the coordinates of the nth LED in the system are The normal to the nth LED is That is, the radiation direction of the LED, and the coordinates and normal of the LED are known to the receiver.

[0033] In step 2, the signal received after AC coupling is expressed as follows: This includes the constraints imposed by intensity modulation / direct detection, i.e. and s -N / 2 =0, meaning only the positive half of the subcarrier can be used to transmit data;

[0034] Let S s ={l∈N + If :l<N / 2} is the index set of allowed subcarriers, then At a frequency of k / T u The effective channel frequency response at the evaluation point, i.e.

[0035] An effective channel is a combination of the actual channel and the transceiver front end, i.e. Where h(f) is the frequency response of the actual channel h(t), and g(f) simulates the overall impact of the transceiver front end. Since g(f) is usually limited in bandwidth, aliasing after sampling is avoided by selecting an appropriate sampling rate.

[0036] Assuming complete synchronization and discarding the CP component, the Discrete Fourier Transform (DFT) y[k] of the sampled signal is expressed as:

[0037]

[0038] In the formula, for have:

[0039] The beneficial effects of this invention are: by utilizing the optimization principle of manifolds, the orientation matrix is ​​effectively optimized, and Monte Carlo simulation results verify the effectiveness of the designed algorithm. Attached Figure Description

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] Figure 1 This invention provides a system framework for multiple LEDs and multiple PDs.

[0042] Figure 2 This is the receiver frame provided by the present invention.

[0043] Figure 3 This is a schematic diagram of the MIMO-OFDM principle framework provided by the present invention.

[0044] Figure 4 This is the frame structure of the MIMO-OFDM system provided by the present invention; Detailed Implementation

[0045] The embodiments of the present invention will be further described in detail below with reference to specific drawings and examples. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0046] A pose estimation method for a multi-LED-multi-PD visible light system includes the following steps:

[0047] Step 1: Establish a multi-LED-multi-PD system, such as Figure 1 The system shown contains N t LEDs and a collection of N r For a receiver with multiple photodetectors (PDs), first define the coordinates and orientations of all PDs within the receiver frame, as shown in the example below. Figure 2 As shown, it is then converted into a multi-LED-multi-PD system framework;

[0048] Step 2: Modulate the signal based on the DCO-OFDM modulation method, including:

[0049] At the transmitting end, an OFDM signal is first generated, and then a DC bias is added to the generated OFDM signal; then it is fed to the LED to conform to intensity modulation / direct detection, which is the mainstream modulation scheme for visible light systems.

[0050] At the receiving end, assuming that the DC component of the received signal is removed by built-in hardware components before digital-to-analog conversion, and then AC coupling is performed; the signal received after AC coupling has the following expression:

[0051]

[0052] In the formula, k is the subcarrier index, and s k For data symbols, Symbol length T sym The length T of the OFDM block u =NT s With the length T of the cyclic prefix (CP) g =N g T s The sum of T s Sampling time;

[0053] Step 3: Use a typical frame structure, such as Figure 4 As shown, for multi-LED-multi-PD systems, a DC-biased version of the MIMO-OFDM solution is adopted, such as... Figure 3 As shown;

[0054] In the preamble section, we assume that all LEDs are in sequence with S. s Transmitted on all subcarriers for indexing, each LED transmits by N t A distinct and unique training sequence composed of OFDM symbols is used to estimate the effective channel response of these subcarriers;

[0055] The expression for the received sample at the m-th PD (after removing the guard interval) is:

[0056]

[0057] In the formula, the vec(·) operator represents the column vectorization of the matrix;

[0058] In the formula, It is the kth OFDM symbol of the received signal at the m-th PD. l k subcarriers l ∈S s ;

[0059] In the formula, K = |S s |, T l =T[k l ];

[0060] For N t A matrix consisting of training sequences of LEDs;

[0061] Let be the channel matrix, where

[0062] h m,n,l =h m,n [k l [The m-th PD and the n-th led are in the k-th position] l The channel frequency response at each subcarrier, k l ∈S s ;

[0063] Step 4: Use a synchronization algorithm to achieve frame synchronization and calculate the communication status information. For communication purposes, assume that an appropriate synchronization algorithm is used to achieve frame synchronization. The expression for the communication status information is:

[0064]

[0065] In the formula, This is the Moore-Penrose pseudo-inverse; the communication state information at this point is used for equalization, therefore based on H... m m∈{1,...,N r We use this to estimate the pose of {R,r}.

[0066] In step 1, the receiver frame includes:

[0067] The coordinates d of the m-th PD m,0 From relative to the origin O r The relative vector representation of (the centroid of the receiver);

[0068] The normal vector n of the m-th PD P,m,0 The normal vector n0 relative to the receiving plane and the rotation matrix R P,m ∈SO(3) means that n P,m,0 =R P,m n0.

[0069] In step 1, the multi-LED-multi-PD system framework includes:

[0070] The coordinates of the receiver are r, which is the position of the receiver's centroid, and the direction is R∈SO(3). The normal n of the receiver is represented by n=Rn0;

[0071] The coordinates and normal of the m-th PD are represented by r. P,m =r+d m and n P,m =Rn P,m,0 In the formula d m It is a vector relative to r by d m =Rd m,0 express;

[0072] Assume the coordinates of the nth LED in the system are The normal to the nth LED is That is, the radiation direction of the LED, and the coordinates and normal of the LED are known to the receiver.

[0073] In step 2, the signal received after AC coupling is expressed as follows: This includes the constraints imposed by intensity modulation / direct detection, i.e. and s -N / 2 =0, meaning only the positive half of the subcarrier can be used to transmit data;

[0074] Let S s ={l∈N + If :l<N / 2} is the index set of allowed subcarriers, then At a frequency of k / T u The effective channel frequency response at the evaluation point, i.e.

[0075] An effective channel is a combination of the actual channel and the transceiver front end, i.e. Where h(f) is the frequency response of the actual channel h(t), and g(f) simulates the overall impact of the transceiver front end. Since g(f) is usually limited in bandwidth, aliasing after sampling is avoided by selecting an appropriate sampling rate.

[0076] Assuming complete synchronization and discarding the CP component, the Discrete Fourier Transform (DFT) y[k] of the sampled signal is expressed as:

[0077]

[0078] In the formula, for have: Assume that the statistical measure of uncertainty is unknown and is used to represent the uncertainty of transmission power;

[0079] By jointly estimating the PI coefficients and pose, the estimated parameters Θ = {R, r, α} t} includes pose {R, r} and PI coefficients {α} t};

[0080] The estimator is designed based on the least squares principle. Essentially, the maximum likelihood principle is applied to the assumed Gaussian distribution model, which is: in

[0081] estimated value The expression is:

[0082] in,

[0083] estimate This is transformed into a constrained nonlinear least squares (NLS) problem, and its expression is:

[0084]

[0085] st R T R = RR T =I,det(R)=+1

[0086] In the formula, ||α t -1|| 2 and λ 2 These are the additional adjustment term and weights, respectively, indicating that the uncertainty of the PI coefficient is constrained, R∈SO(3); the Gauss-Newton algorithm is used to estimate R on the popular SO(3),

[0087] Use iterative updates to estimate Θ = {R, r, α} t}, its expression is:

[0088]

[0089] The operator (·) in the formula ^ Rotate vector Convert to a partially symmetric matrix (Δ) R ) ^ ∈so(3);

[0090] exp(·) is the matrix exponential function;

[0091] Growth Step Calculated by the following expression:

[0092]

[0093] In the formula, β represents the step size;

[0094] It is η with respect to Θ. r N t ×(6+N t The Jacobian matrix is ​​expressed as follows:

[0095]

[0096] It is η m,n 1×(6+N) of Θ t The Jacobian matrix is ​​expressed as follows:

[0097]

[0098] The first 6 elements are:

[0099]

[0100] The expression is:

[0101]

[0102] α t Jacobian matrix of Θ It is N t ×(6+N t The expression for a matrix is:

[0103]

Claims

1. A pose estimation method for a multi-LED-multi-PD visible light system, characterized in that, Includes the following steps: Step 1: Establish a multi-LED-multi-PD system, the system contains N t LEDs and a collection of N r For each PD receiver, the coordinates and orientations of all PDs are first defined in the receiver frame, and then transformed into a multi-LED-multi-PD system frame. Step 2: Modulate the signal based on the DCO-OFDM modulation method, including: At the transmitting end, an OFDM signal is first generated, and then a DC bias is added to the generated OFDM signal; It is then fed to the LED to meet intensity modulation / direct detection, which is the mainstream modulation scheme for visible light systems; At the receiving end, assuming that the DC component of the received signal is removed by built-in hardware components before digital-to-analog conversion, and then AC coupling is performed; the signal received after AC coupling has the following expression: In the formula, k is the subcarrier index, and s k For data symbols, Symbol length T sym The length T of the OFDM block u =NT s With the length T of the cyclic prefix (CP) g =N g T s The sum of T s Sampling time; Step 3: Employing a typical frame structure, for multi-LED-multi-PD systems, a DC-biased version of the MIMO-OFDM scheme is used. In the preamble section, we assume that all LEDs are in sequence with S. s Transmitted on all subcarriers for indexing, each LED transmits by N t A distinct and unique training sequence composed of OFDM symbols is used to estimate the effective channel response of these subcarriers; The expression for the received sample at the m-th PD (after removing the guard interval) is: In the formula, the vec(·) operator represents the column vectorization of the matrix; In the formula, It is the k-th OFDM symbol of the received signal at the m-th PD. l k subcarriers l ∈S s ; In the formula, K = |S s |, T l =T[k l ]; For N t A matrix consisting of training sequences of LEDs; Let be the channel matrix, where h m,n,l =h m,n [k l [The m-th PD and the n-th led are in the k-th position] l The channel frequency response at each subcarrier, k l ∈S s ; Step 4: Use a synchronization algorithm to achieve frame synchronization and calculate the communication status information. For communication purposes, assume that an appropriate synchronization algorithm is used to achieve frame synchronization. The expression for the communication status information is: In the formula, This is the Moore-Penrose pseudo-inverse; the communication state information at this point is used for equalization, therefore based on H... m m∈{1,...,N r We use this to estimate the pose of {R,r}.

2. The pose estimation method for a multi-LED-multi-PD visible light system according to claim 1, characterized in that: In step 1, the receiver frame includes: The coordinates d of the m-th PD m,0 From relative to the origin O r The relative vector representation; The normal vector n of the m-th PD P,m,0 The normal vector n0 relative to the receiving plane and the rotation matrix R P,m ∈SO(3) means that n P,m,0 =R P,m n0.

3. The pose estimation method for a multi-LED-multi-PD visible light system according to claim 1, characterized in that: In step 1, the multi-LED-multi-PD system framework includes: The coordinates of the receiver are r, which is the position of the receiver's centroid, and the direction is R∈SO(3). The normal n of the receiver is represented by n=Rn0; The coordinates and normal of the m-th PD are represented by r. P,m =r+d m and n P,m =Rn P,m,0 In the formula d m It is a vector relative to r by d m =Rd m,0 express; Assume the coordinates of the nth LED in the system are The normal to the nth LED is That is, the radiation direction of the LED, and the coordinates and normal of the LED are known to the receiver.

4. The pose estimation method for a multi-LED-multi-PD visible light system according to claim 1, characterized in that: In step 2, the signal received after AC coupling is expressed as follows: This includes the constraints imposed by intensity modulation / direct detection, i.e. and s -N / 2 =0, meaning only the positive half of the subcarrier can be used to transmit data; Let S s ={l∈N + If :l<N / 2} is the index set of allowed subcarriers, then At a frequency of k / T u The effective channel frequency response at the evaluation point, i.e. An effective channel is a combination of the actual channel and the transceiver front end, i.e. Where h(f) is the frequency response of the actual channel h(t), and g(f) simulates the overall impact of the transceiver front end. Since g(f) is usually limited in bandwidth, aliasing after sampling is avoided by selecting an appropriate sampling rate. Assuming complete synchronization and discarding the CP component, the Discrete Fourier Transform (DFT) y[k] of the sampled signal is expressed as: In the formula, for have:

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