TOA anchor-point-free relative positioning method based on RIS, medium, equipment and product
By deploying a RIS reflector in an anchorless environment to assist in measuring the TOA (Time of Arrival) along both the direct and reflected paths, and by combining this with gradient descent to optimize positioning, the ranging error caused by clock offset in anchorless TOA environments is solved, achieving high-precision and low-power positioning.
Patent Information
- Application Number
- CN202511420007.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-01-13
AI Technical Summary
In the TOA anchorless relative positioning method, the unknown clock offset between nodes causes ranging errors, affecting positioning accuracy. Furthermore, the multi-anchor and single-anchor methods are costly and lack flexibility.
By deploying RIS reflectors to assist in measuring the TOA of direct and reflected paths, and combining multiple measurement iterations to solve for node positions, clock offset is eliminated, and the positioning accuracy is optimized using gradient descent.
It improves positioning accuracy, reduces system power consumption, is suitable for flexible anchorless environments, and reduces measurement time and communication overhead.
Smart Images
Figure CN121334840A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless positioning technology, and in particular to a RIS-based TOA (Too-to-Area) anchorless relative positioning method, medium, device, and product. Background Technology
[0002] Relative positioning technology has wide applications in fields such as the Internet of Things, autonomous driving, indoor navigation, and collaborative operations of unmanned systems. This technology is mainly divided into two implementation methods: anchored (multiple anchors and single anchor) and anchorless. Multiple anchors require a large number of precisely synchronized anchor nodes with known locations, leading to high infrastructure costs and poor mobility. Single anchors rely on a central anchor; if the anchor is too far away or damaged, user nodes are prone to losing connection. Anchored methods rely on pre-deployed anchor nodes, resulting in high hardware and maintenance costs and poor flexibility. Anchorless methods rely solely on mutual measurements between nodes to achieve positioning, mainly including TOA (Time of Arrival), AOA (Angle of Arrival), and TDOA (Time Difference of Arrival). Among these, the TOA method has attracted much attention due to its simple principle and intuitive ranging. However, the TOA method faces a core challenge in its implementation: unknown clock offsets between nodes directly introduce ranging errors, severely affecting positioning accuracy. Therefore, this invention proposes a scheme using a RIS reflector to provide additional reflected signal paths to assist positioning. By simultaneously measuring the TOA of the direct path and a reflected path, and combining multiple measurement rounds, the relative positions of the nodes are iteratively solved. This method improves positioning accuracy through multiple iterations and eliminates clock offset between nodes by using the round-trip time difference between two frames of signals in bidirectional TOA ranging, thus achieving high positioning accuracy. Summary of the Invention
[0003] The purpose of this invention is to address the limitations of available path resources and inherent clock skew in TOA (TOA) anchorless relative positioning methods, and to propose a RIS-based TOA anchorless relative positioning method, comprising the following steps: S1. Deploy a wireless network containing N nodes to be located. Within the network coverage area, deploy a RIS and construct a two-dimensional coordinate system for the wireless network. S2. Perform a bidirectional TOA ranging between the two nodes and obtain the time-represented distances of the direct path and the RIS reflection path based on the signal transmission and reception time; measure the distances of the direct path and the RIS reflection path between the two nodes in a two-dimensional coordinate system and obtain the coordinate-represented distances of the direct path and the RIS reflection path. S3. Based on the distance between the direct path and the RIS reflection path in time representation, and the distance between the direct path and the RIS reflection path in coordinate representation, construct the initial node coordinate equation, and construct the maximum likelihood function based on the distance between the direct path and the RIS reflection path in coordinate representation. S4. Using the maximum likelihood function, the problem of solving the node coordinates is transformed into a least squares problem. The node coordinates are located using the gradient descent method. The iteration stops when the convergence criterion is met or the maximum number of iterations is reached.
[0004] Furthermore, the distance of the direct path or reflected path in time is expressed as:
[0005]
[0006] in, The first time represented by time The distance of the direct path between the j-th node and the j-th node. The first time represented by time The distance between the reflection paths of the j-th node and the j-th node. This indicates that the j-th node on the direct path receives the first... The timestamp of the first frame of signal emitted by each node. Indicates the first [item] on the reflection path The timestamp of each node receiving the first frame of signal. Indicates the first The timestamp of the first frame signal emitted by each node. Indicates the first Each node has a clock skew. This indicates that the j-th node has a clock offset. Indicates the first [item] on the direct path The timestamp of the second frame signal received by node j in response to node j. Indicates the first [item] on the reflection path The node receives the first The timestamp of each node's response. This represents the timestamp of the second frame signal received by the j-th node on the direct path. The timestamp of the second frame signal received by the j-th node on the reflection path is represented by c, where c represents the signal transmission speed. Clock skew is eliminated by calculating the round-trip time between two frames of signals.
[0007] Furthermore, the distance of the direct path represented by the coordinates is:
[0008] The distance of the RIS reflection path, represented by coordinates, is:
[0009] in, The coordinates represent the first The node and the first The distance of the direct path to each node. The coordinates represent the first The node and the first The distance of the RIS reflection path of each node. Indicates the first The coordinates of each node, Indicates the first The coordinates of each node, Indicates the first The node and the first The noise of the direct path to each node follows a Gaussian distribution. , Indicates the first The node and the first The noise in the RIS reflection path of each node follows a Gaussian distribution. .
[0010] Further, initialize the node coordinates:
[0011]
[0012]
[0013]
[0014]
[0015] in, Let U represent the initial coordinates of the m-th node. These are all auxiliary parameters, where K represents the iteration round. Represents the coordinates of the first node and the second node. The distance of the RIS reflection path of each node. Represents the coordinates of the first node and the second node. The distance of the direct path to each node. This represents the estimated ordinate of the first node. Indicates the first The estimated ordinate of each node, Indicates an auxiliary parameter. Indicates the distance from the first node to the second node. The arrival time of the direct path to each node. This represents the known processing delay of the m-th node receiving the signal transmitted by the 1st node. Indicates the distance from the first node to the second node. The arrival time of the reflection path of each node.
[0016] Furthermore, a maximum likelihood function is constructed based on the distance between the direct path and the RIS reflection path represented by coordinates:
[0017]
[0018] And take the logarithm of the maximum likelihood function:
[0019]
[0020] in,
[0021]
[0022]
[0023]
[0024]
[0025]
[0026] Where p and q are auxiliary parameters, and k represents the number of TOA measurements.
[0027] Furthermore, the problem of solving for the nodal coordinates is transformed into a least squares problem, and the objective function of the least squares problem is:
[0028]
[0029]
[0030]
[0031] in, , .
[0032] Furthermore, the node coordinates are located using the gradient descent method, as shown in the formula:
[0033]
[0034]
[0035]
[0036] Convergence criterion is and All are less than the set threshold. Indicates about The maximum value among the absolute values of the gradient components. express about The maximum value among the absolute values of the gradient components; in, Indicates to Gradient descent performs the first Calculations, Indicates to Gradient descent performs the first Calculations, and They represent the first The next iteration and , and They represent the r-th iteration, respectively. and , and Indicates hyperparameters, and They represent respectively to and Operators for performing gradient calculations.
[0037] The present invention also proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described RIS-based TOA anchorless relative positioning method.
[0038] The present invention also proposes an electronic device, including a processor and a memory, wherein the processor and the memory are interconnected, wherein the memory is used to store a computer program, the computer program including computer-readable instructions, and the processor is configured to invoke the computer-readable instructions to execute the above-described RIS-based TOA anchorless relative positioning method.
[0039] The present invention also proposes a computer program product, including a computer program / instruction that, when executed by a processor, implements the steps of the above-described RIS-based TOA anchorless relative positioning method.
[0040] The beneficial effects of the technical solution provided by this invention are: This invention achieves bidirectional TOA (Take-of-Area) anchorless relative positioning through active deployment of RIS (Reflection Path) assistance, enabling multi-path collaborative iteration. It eliminates clock skew by transmitting two frames of signals, obtains signal transmission and reception times through bidirectional TOA, and uses these times to represent the distance between the direct path and the RIS reflection path. Based on two-dimensional coordinates, it calculates the coordinate-represented distance between the direct path and the RIS reflection path. By combining the time-represented and coordinate-represented distance formulas for the direct path and the RIS reflection path with multiple TOA measurements of the direct path and one reflection path, it fully utilizes the acquired path measurement data to construct a maximum likelihood function, transforming the positioning problem into a least-squares problem. Gradient descent is then used to iteratively improve positioning accuracy. This invention uses the direct path and the RIS reflection path, and eliminates clock skew between nodes through two-frame signal transmission, solving the problems of limited available path resources and inherent clock skew in TOA anchorless relative positioning methods, resulting in high-precision positioning. Attached Figure Description
[0041] Figure 1 This is a flowchart of a RIS-based TOA (Too-to-Area) anchorless relative positioning method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the measurement of the direct path and RIS reflection path in the XOY coordinate system according to an embodiment of the present invention; Figure 3 This is a block diagram of an electronic device according to an exemplary embodiment of the present invention. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.
[0043] The flowchart of the RIS-based TOA anchorless relative positioning method of this invention is as follows: Figure 1 Specifically, it includes the following steps: S1. Deploy a wireless network containing N nodes to be located. Within the network coverage area, deploy a RIS and construct a two-dimensional coordinate system XOY for the wireless network.
[0044] The Reconfigurable Intelligent Surface (RIS) consists of m×m independently adjustable reflective units. The RIS controller establishes communication links with all nodes in the network for coordinated control. By replacing the passive and uncontrollable natural reflective surface with an actively controllable RIS, and by programming the state of the reflective units of the RIS, a reflection path can be simulated and generated in a single bidirectional signal transmission, thereby improving positioning accuracy through "spatial path diversity".
[0045] S2. Perform a bidirectional TOA ranging between the two nodes and obtain the time-represented distances of the direct path and the RIS reflection path based on the signal transmission and reception time; measure the distances of the direct path and the RIS reflection path between the two nodes in a two-dimensional coordinate system and obtain the coordinate-represented distances of the direct path and the RIS reflection path.
[0046] (1) Two-way TOA ranging With the first The node and the first Taking a single node as an example, the principle of bidirectional TOA ranging is as follows: No. The timestamp of each node sending the first frame signal is: , No. Each node receives the first frame signal and immediately replies with the second frame signal, proceeding directly along the path: the... The node received the first The timestamp of the first frame signal sent by each node is ; On the reflection path: the first The node received the first The timestamp of the first frame signal sent by each node is Direct route: (Number) The timestamp of the node's response to the second frame signal is: ; On the reflection path: the first The timestamp of the node's response to the second frame signal is: Direct route: (Number) The node receives the first The timestamp of each node's response is ; On the reflection path: the first The node receives the first The timestamp of each node's response is . No. The node and the first The clock offsets of each node are respectively and By calculating the round-trip time and eliminating clock skew, an accurate measurement of the direct path distance is obtained.
[0047] Based on time-based path distance calculation, the distances of the direct path and the RIS reflection path, expressed in time, are respectively:
[0048]
[0049] in, The first time represented by time The direct path distance between the j-th node and the j-th node. The first time represented by time The distance of the reflection path between the j-th node and the j-th node. Indicates the first Each node has a clock skew. This indicates that there is a clock offset at the j-th node, and c represents the signal transmission speed.
[0050] In bidirectional TOA ranging communication, the RIS controller keeps all reflection units in an "on" state, but through a pre-set encoding method (such as random phase offset), the RIS generates a comprehensive reflection of the incident signal. The node and the first Each node records the round-trip timestamp of the signal for this communication. Due to the introduction of RIS, this time value corresponds to the transmission delay of the signal through the RIS reflection path, from which a comprehensive reflection path distance measurement can be calculated.
[0051] (2) Measurement of direct path and RIS reflection path represented by XOY coordinates In the XOY coordinate system, reference Figure 2 , Figure 2 This is a schematic diagram of the direct path and RIS reflection path measurement in the XOY coordinate system according to an embodiment of the present invention. The green arrow indicates the first... The node and the first The direct path to each node; the blue arrow indicates a path in the RIS reflection path, node. It is the first The mirror-symmetric nodes are auxiliary nodes introduced to facilitate geometric analysis of reflection paths.
[0052] In the coordinate system constructed above, the distance between nodes is measured based on their coordinates, and the distance between nodes is expressed in coordinate form. The distance of the direct path represented by coordinates is:
[0053] The distance of the RIS reflection path, represented by coordinates, is:
[0054] in, The coordinates represent the first The node and the first The distance of the direct path to each node. The coordinates represent the first The node and the first The distance of the RIS reflection path of each node. Indicates the first The coordinates of each node, Indicates the first The coordinates of each node, Indicates the first The node and the first The noise of the direct path to each node follows a Gaussian distribution. , Indicates the first The node and the first The noise in the RIS reflection path of each node follows a Gaussian distribution. .
[0055] S3. Based on the distance between the direct path and the RIS reflection path in time representation, and the distance between the direct path and the RIS reflection path in coordinate representation, construct the initial node coordinate equation, and construct the maximum likelihood function based on the distance between the direct path and the RIS reflection path in coordinate representation.
[0056] Collect K rounds We then use the data from these K rounds to perform gradient descent iterations. Initialize the node coordinates:
[0057]
[0058]
[0059]
[0060]
[0061] in, U represents the initial estimated coordinates of node m, and This represents the auxiliary parameter, and K represents the iteration round. Represents the coordinates of the first node and the second node. The distance of the RIS reflection path of each node. The coordinates represent the first node and the second node. The distance of the direct path to each node. This represents the estimated ordinate of the first node. This represents the estimated ordinate of the m-th node. Indicates an auxiliary parameter. Indicates the first node and the second node. The arrival time of the direct path to each node. This represents the known processing delay of the m-th node receiving the signal transmitted by the 1st node. Indicates the first node and the second node. The arrival time of the reflection path of each node.
[0062] S4. Using the maximum likelihood function, the problem of solving the node coordinates is transformed into a least squares problem. The node coordinates are located using the gradient descent method. The iteration stops when the convergence criterion is met or the maximum number of iterations is reached.
[0063] Construct a maximum likelihood function based on the distance between the direct path and the RIS reflection path represented by coordinates:
[0064]
[0065] Take the logarithm of the maximum likelihood function:
[0066]
[0067] in,
[0068]
[0069]
[0070]
[0071]
[0072]
[0073] Where p and q represent auxiliary parameters, and k represents the number of TOA measurements.
[0074] The problem of finding the node coordinates is transformed into a least squares problem, and the objective function of the least squares problem is:
[0075]
[0076]
[0077]
[0078] in, , .
[0079] The node coordinates are located using the gradient descent method, as shown in the formula:
[0080]
[0081]
[0082]
[0083] Convergence criterion is and All are less than the set threshold. Indicates about The maximum value among the absolute values of the gradient components. Indicates about The maximum value among the absolute values of the gradient components; in, Describe the objective function In the The gradient of the variable y at the nth iteration Describe the objective function In the During the next iteration, the variables are... gradient, and They represent the (r+1)th iteration. and , and They represent the r-th iteration, respectively. and , and Indicates hyperparameters, and They represent respectively to and Operators for performing gradient calculations.
[0084] The technical solution provided by this invention has the following significant advantages: (1) Free from environmental dependence and highly flexible: This invention does not rely on inherent natural reflective surfaces in the environment. By actively deploying RIS, positioning capabilities can be quickly built in any place where needed (such as indoors, canyons, and urban canyons), making the application scenarios very flexible. Moreover, relative positioning can be achieved without deploying anchor points.
[0085] (2) Significantly improves positioning efficiency: This invention eliminates the clock offset between nodes by using the round-trip time difference between two frames of signals in bidirectional TOA ranging, and obtains positioning by using the information of the reflection path, which greatly reduces measurement time and communication overhead, and reduces system power consumption. It is very suitable for networks that require fast positioning or are energy-constrained.
[0086] (3) Significantly improve positioning accuracy: Make full use of the acquired path measurement data to transform the positioning problem into a least squares problem, and improve the positioning accuracy through gradient descent by iteration. More effective data can better suppress the influence of measurement noise, and obtain higher accuracy positioning results through algorithm optimization.
[0087] In one exemplary embodiment, a computer-readable storage medium is included, which stores a computer program that, when executed by a processor, implements the aforementioned RIS-based TOA anchorless relative positioning method.
[0088] Please see Figure 3 In one exemplary embodiment, the device further includes an electronic device including at least one processor, at least one memory, and at least one communication bus.
[0089] The memory stores a computer program, which includes computer-readable instructions. The processor calls the computer-readable instructions stored in the memory through the communication bus to execute the aforementioned RIS-based TOA anchorless relative positioning method.
[0090] In one exemplary embodiment, a computer program product is proposed, including a computer program / instructions that, when executed by a processor, implement the steps of the RIS-based TOA anchorless relative positioning method described above.
[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A RIS-based TOA (Transit-Oriented Alignment) method without anchor points, characterized in that, Includes the following steps: S1. Deploy a wireless network containing N nodes to be located. Within the network coverage area, deploy a RIS and construct a two-dimensional coordinate system for the wireless network. S2. Perform a bidirectional TOA ranging between the two nodes and obtain the time-represented distances of the direct path and the RIS reflection path based on the signal transmission and reception time; measure the distances of the direct path and the RIS reflection path between the two nodes in a two-dimensional coordinate system and obtain the coordinate-represented distances of the direct path and the RIS reflection path. S3. Based on the distance between the direct path and the RIS reflection path in time representation, and the distance between the direct path and the RIS reflection path in coordinate representation, construct the initial node coordinate equation, and construct the maximum likelihood function based on the distance between the direct path and the RIS reflection path in coordinate representation. S4. Using the maximum likelihood function, the problem of solving the node coordinates is transformed into a least squares problem. The node coordinates are located using the gradient descent method. The iteration stops when the convergence criterion is met or the maximum number of iterations is reached.
2. The RIS-based TOA anchorless relative positioning method according to claim 1, characterized in that, The distance of the direct or reflected path, expressed in terms of time, is: in, The first time represented by time The distance of the direct path between the j-th node and the j-th node. The first time represented by time The distance between the reflection paths of the j-th node and the j-th node. This indicates that the j-th node on the direct path receives the first... The timestamp of the first frame of signal emitted by each node. Indicates the first [item] on the reflection path The timestamp of each node receiving the first frame of signal. Indicates the first The timestamp of the first frame signal emitted by each node. Indicates the first Each node has a clock skew. This indicates that the j-th node has a clock offset. Indicates the first [item] on the direct path The timestamp of the second frame signal received by node j in response to node j. Indicates the first [item] on the reflection path The node receives the first The timestamp of each node's response. This represents the timestamp of the second frame signal received by the j-th node on the direct path. The timestamp of the second frame signal received by the j-th node on the reflection path is represented by c, where c represents the signal transmission speed. Clock skew is eliminated by calculating the round-trip time between two frames of signals.
3. The RIS-based TOA anchorless relative positioning method according to claim 2, characterized in that, The distance of the direct path, represented by the coordinates, is: The distance of the RIS reflection path, represented by coordinates, is: in, The coordinates represent the first The node and the first The distance of the direct path to each node. The coordinates represent the first The node and the first The distance of the RIS reflection path of each node. Indicates the first The coordinates of each node, Indicates the first The coordinates of each node, Indicates the first The node and the first The noise of the direct path to each node follows a Gaussian distribution. , Indicates the first The node and the first The noise in the RIS reflection path of each node follows a Gaussian distribution. .
4. The RIS-based TOA anchorless relative positioning method according to claim 3, characterized in that, Initialize node coordinates: in, Let U represent the initial coordinates of the m-th node. These are all auxiliary parameters, where K represents the iteration round. Represents the coordinates of the first node and the second node. The distance of the RIS reflection path of each node. Represents the coordinates of the first node and the second node. The distance of the direct path to each node. This represents the estimated ordinate of the first node. Indicates the first The estimated ordinate of each node, Indicates an auxiliary parameter. Indicates the distance from the first node to the second node. The arrival time of the direct path to each node. Indicates the first m The known processing delay for each node to receive the signal transmitted by the first node. Indicates the distance from the first node to the second node. The arrival time of the reflection path of each node.
5. The RIS-based TOA anchorless relative positioning method according to claim 3, characterized in that, Construct a maximum likelihood function based on the distance between the direct path and the RIS reflection path represented by coordinates: And take the logarithm of the maximum likelihood function: in, Where p and q are auxiliary parameters, and k represents the number of TOA measurements.
6. The RIS-based TOA anchorless relative positioning method according to claim 5, characterized in that, The problem of finding the node coordinates is transformed into a least squares problem, and the objective function of the least squares problem is: in, , .
7. The RIS-based TOA anchorless relative positioning method according to claim 5, characterized in that, The node coordinates are located using the gradient descent method, as shown in the formula: Convergence criterion is and All are less than the set threshold. Indicates about The maximum value among the absolute values of the gradient components. express about The maximum value among the absolute values of the gradient components; in, Indicates to Gradient descent performs the first Calculations, Indicates to Gradient descent performs the first Calculations, and They represent the first The next iteration and , and They represent the r-th iteration, respectively. and , and Indicates hyperparameters, and They represent respectively to and Operators for performing gradient calculations.
8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, it implements the method as described in any one of claims 1-7.
9. An electronic device, characterized in that, The device includes a processor and a memory interconnected thereto, wherein the memory is used to store a computer program, the computer program including computer-readable instructions, and the processor is configured to invoke the computer-readable instructions to perform the method as described in any one of claims 1-7.
10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-7.