Indoor positioning solutions for wireless communication networks

Abstract

The present invention relates to an indoor positioning system 300 for a wireless communication network 200. The indoor positioning system 300 includes one or more anchor devices 302a-302n, a central entity 306, and one or more tag devices 304a-304n. Transmission of signals 301a-301n by the one or more tag devices 304a-304n is controlled so that one signal 301a is transmitted at a time on a given radio resource, and the tag device 304a transmitting one signal 301a is the tag device 304a to be located. At least one anchor device (302a) of the one or more anchor devices (302a-302n) is configured to receive, via an antenna array (500), a signal (301a) transmitted by a positioned tag device, determine an estimate of a direction of arrival (DOA) based on the received signal (301a) by applying a first power law based algorithm and a second power law based algorithm, respectively, and transmit the estimated DOA together with DOA metadata to a central entity (306). The present invention also relates to an indoor positioning method, an anchor device, a computer program, and a computer-readable medium.

Description

[Technical Field]

[0001] The present invention relates generally to the technical field of wireless communication networks, and more particularly to indoor positioning for wireless communication networks. [Background technology]

[0002] Various direction of arrival (DOA) estimation methods find many applications, such as various indoor positioning systems, including medical devices, radar, navigation, military devices, and the Internet of Things (IoT). Typically, in an IoT wireless communication system supporting indoor positioning, the indoor positioning system may include at least two types of devices (e.g., nodes). The first type of device is a low-cost, battery-powered, and constrained embedded device, such as a tag device, which is the device to be positioned. The second type of device is a so-called anchor device, which is fixed at a known location and is used to locate the tag device. Each anchor device typically has an array of antennas that receive signals transmitted by the tag device.

[0003] The anchor device can estimate the DOA from the signal transmitted by the tag device. The location of the tag device can be determined based on multiple DOAs from different anchor devices. Because conventional DOA estimation methods are inherently complex, a reasonable approach is to perform the DOA estimation in the cloud or in a more powerful processing unit, such as a separate processor, in the anchor device. This is not practical in some network topologies, such as mesh IoT networks. If the DOA estimation is performed in the cloud, the anchor device must constantly forward large chunks of measurement data (i.e., signals) to the cloud (e.g., from one node device in the wireless communication network to another node device in the wireless communication network) through a wireless communication network (e.g., a mesh network such as a mesh IoT network) until the data reaches its destination (i.e., the cloud). This consumes a large amount of radio resources in the wireless communication network and rapidly drains the batteries of the node devices in the wireless communication network. 1A schematically illustrates an example of a conventional DOA estimation method performed in a cloud 102, where an anchor device 104 forwards measurement data (i.e., signals) 101 received from a tag device 106 via a wireless communication network (e.g., a mesh IoT network) 108 to the cloud 102. The exemplary wireless communication network 108 of FIG. 1A includes a plurality of node devices (shown as open circles in FIG. 1A and forming the network 108) and a gateway device 110 acting as a gateway between the mesh IoT network 108 and the cloud 102.

[0004] The size of such chunks of measurement data may depend on the number of samples per antenna, the number of bits per sample, and the number of antennas, but can easily exceed 1 kilobyte. In general, increasing the number of antennas, samples, and bits per sample increases the accuracy of DOA estimation and enables more accurate positioning estimation, potentially increasing the amount of data transferred to the cloud. Another possibility would be to deploy Ethernet cables to the anchor devices. However, this increases deployment costs because a wired connection is required for the anchor devices. Similarly, using wireless broadband, i.e., Wi-Fi, increases the price and deployment costs of the anchor devices because each anchor device must be equipped with a Wi-Fi chip and each anchor device must be within the coverage range of a Wi-Fi access point (AP). Furthermore, transferring measurement data from multiple anchor devices for a large number of tag devices consumes a large amount of Wi-Fi network resources.

[0005] Equipping each anchor device with a more powerful processor unit can reduce the amount of data transferred. However, this increases the cost of the anchor devices. Since the accuracy of DOA-based positioning depends heavily on the density of anchor devices, it can be beneficial to increase the number of anchor devices performing DOA estimation for a single tag device. Therefore, it is clear that the implementation and deployment of low-cost anchor devices are very attractive when using DOA methods in large-scale deployments such as large warehouses, factories, ports, or city-wide deployments.

[0006] FIG. 1B schematically illustrates an example of a conventional DOA estimation method performed by an anchor device 104. The anchor device 104 receives measurement data (i.e., signals) 101 from a tag device 106, performs a conventional DOA estimation method, and transmits the estimated DOA of the received measurement data 101 to a cloud 102 via a wireless communication network (e.g., a mesh IoT network) 108. The cloud 102 then defines a positioning for the tag device 106 based on the estimated DOA. When DOA estimation is performed by the anchor device, the anchor device transfers only, for example, 2 to 8 bytes, rather than kilobytes. However, implementing DOA estimation methods in IoT networks presents real challenges, as such devices are typically constrained embedded systems with limited computational resources. Meanwhile, DOA estimation methods typically consist of complex, resource-intensive, and time-consuming numerical algorithms that can rapidly drain the anchor device's battery, result in unacceptable execution times, and / or result in insufficient computational resources and memory. To achieve even lower cost and easier deployment capabilities in locations where mains power is not readily available, the anchor devices may be battery powered, imposing strict energy consumption requirements on the anchor devices, but in such a scenario Wi-Fi connectivity, Ethernet wiring, and / or separate high-power processing units are not possible.

[0007] There are several DOA estimation methods, such as Multiple Signal Classification (MUSIC), Space Alternating Generalized Expectation-Maximization (SAGE), Minimum Variance Distortionless Response (MDVR), and Estimation of Signal Parameters via Rotational Invariant Techniques (ESPRIT). ESPRIT is a subspace-based technique with several variations. ESPRIT-based DOA estimation methods offer superior accuracy and performance compared to beamforming-based DOA estimation methods such as MDVR. An alternative approach to DOA estimation based on the maximum likelihood approach offers superior performance compared to subspace-based DOA estimation methods, but maximum likelihood estimation is computationally very expensive compared to the DOA estimation methods mentioned above.

[0008] In theory, DOA estimation methods, such as ESPRIT, can estimate multiple DOAs during their execution. Radar applications, which transmit a sounding signal and measure its own signal as it is received from different reflections, can maximize their capabilities by identifying multiple copies of their own reflected signal. However, in IoT wireless communication systems, anchor devices are employed to locate multiple tag devices. This is practically impossible with low-cost, single-receiver anchor devices operating on a single radio frequency (RF) channel at a given time, such as Bluetooth receivers. That is, if multiple tag devices transmit signals to the anchor device simultaneously and over the same frequency resource (e.g., channel), the signal-to-interference and noise ratio is too low for a single receiving anchor device to reliably detect the transmissions. For example, the anchor device may not be able to reliably decode the tag device's transmitter ID because each transmission interferes with the other transmissions. Therefore, in this scenario, DOA estimation methods can only estimate a single DOA. Summary of the Invention

[0009] The following presents a simplified summary in order to provide a basic understanding of some aspects of various embodiments of the invention. The summary is not an extensive overview of the invention, and is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of example embodiments of the invention.

[0010] An object of the present invention is to provide an indoor positioning system, an indoor positioning method, an anchor device, a computer program, and a computer readable medium for a wireless communication network. Another object of the present invention is to provide an indoor positioning system, an indoor positioning method, an anchor device, a computer program, and a computer readable medium for a wireless communication network that enable simple indoor positioning.

[0011] The object of the invention is achieved by an indoor positioning system, an indoor positioning method, an anchor device, a computer program and a computer readable medium as defined by the respective independent claims.

[0012] According to a first aspect, there is provided an indoor positioning system for a wireless communication network, the indoor positioning system comprising: one or more anchor devices; a central entity that is in bidirectional communication with the one or more anchor devices via the wireless communication network; and one or more tag devices, wherein transmission of signals by the one or more tag devices is controlled such that one signal is transmitted at a time on a given radio resource, the tag device transmitting the one signal being a positioned tag device, and at least one anchor device of the one or more anchor devices is configured to receive the signals transmitted by the positioned tag device via an antenna array, determine an estimate of a direction of arrival (DOA) based on the received signal by applying a first power law based algorithm and a second power law based algorithm, respectively, and transmit the estimated DOA together with DOA metadata to the central entity via the wireless communication network.

[0013] The central entity may be configured to position the tag device based on the received estimated DOA and DOA metadata.

[0014] Control of the transmission of signals by said one or more tag devices may be based on the use of a Medium Access Control (MAC) function.

[0015] The MAC function may include using a random access procedure or a scheduled procedure.

[0016] The first power-based algorithm may be a power method.

[0017] The second power law based algorithm may be an inverse power law or a power law.

[0018] Determining the DOA estimate may include the at least one anchor device being configured to: define a first covariance matrix from IQ samples of the received signal; convert the first covariance matrix to a real covariance matrix; define a signal subspace by applying a first power-law based algorithm to the real covariance matrix; define a second covariance matrix from the defined signal subspace; define DOA information representative of the DOA estimate by applying the second power-law based algorithm to the second covariance matrix; and define the DOA estimate based on the defined DOA information.

[0019] The DOA metadata may include an identifier of the anchor device transmitting the estimated DOA, coordinates of the anchor device transmitting the estimated DOA, an identifier of the positioned tag device, received signal strength indication (RSSI) information, and / or time information.

[0020] According to a second aspect, there is provided an indoor positioning method for a wireless communication network, the method comprising the steps of controlling transmission of signals by one or more tag devices such that one signal is transmitted at a time on a given radio resource, the tag device transmitting the one signal being a positioned tag device, receiving, by at least one anchor device via an antenna array, the signals transmitted by the positioned tag device, determining, by the at least one anchor device via the controller, an estimate of a direction of arrival (DOA) based on the received signals by applying a first power law based algorithm and a second power law based algorithm, respectively, and transmitting, by the at least one anchor device via the radio, the estimated DOA together with DOA metadata to the central entity via the wireless communication network.

[0021] According to a third aspect, there is provided an anchor device for indoor positioning, the anchor device including a radio, an antenna array, and a controller, the anchor device being configured to receive, by the radio, signals transmitted by positioned tag devices via the antenna array, the transmission of signals by one or more tag devices being controlled such that one signal is transmitted at a time on a given radio resource, the tag device transmitting the one signal being a positioned tag device, the anchor device being configured to determine, by the controller, an estimate of a direction of arrival (DOA) based on the received signals by applying a first power law based algorithm and a second power law based algorithm, respectively, and to transmit, by the radio, the estimated DOA together with DOA metadata to the central entity via the wireless communications network.

[0022] According to a fourth aspect, there is provided an indoor positioning method for an anchor device, the method comprising the steps of receiving, by a radio of the anchor device via an antenna array of the anchor device, signals transmitted by a positioned tag device, wherein transmission of signals by one or more tag devices is controlled such that one signal is transmitted at a time on a given radio resource, the tag device transmitting the one signal being a positioned tag device; determining, by a controller of the anchor device, an estimate of a direction of arrival (DOA) based on the received signals by applying a first power law based algorithm and a second power law based algorithm, respectively; and transmitting, by the radio of the anchor device, the estimated DOA together with DOA metadata to the central entity via the wireless communication network.

[0023] According to a fifth aspect, there is provided a computer program comprising instructions that, when the computer program is executed by a computer, cause the computer to perform at least the steps of the method set out above.

[0024] According to a sixth aspect, there is provided a tangible, non-volatile computer readable medium, said computer readable medium comprising the computer program described above.

[0025] Various exemplary, non-limiting embodiments of the present invention, both as to structure and method of operation, as well as additional objects and advantages thereof, will be best understood from the following description of specific exemplary, non-limiting embodiments when read in connection with the accompanying drawings.

[0026] The verbs "to comprise" and "to include" are used in this document as open limitations which neither exclude nor require the presence of unrecited features. Features recited in dependent claims may be freely combined with one another, unless clearly indicated otherwise. Furthermore, it is to be understood that the use of "a" or "an", i.e., the singular, throughout this document does not exclude the plural.

[0027] Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. [Brief explanation of the drawings]

[0028] [Figure 1A] 1 shows a schematic diagram of an example of a conventional cloud-based direction of arrival (DOA) estimation method. [Figure 1B] 1 is a schematic diagram illustrating an example of the implementation of a DOA estimation method in a conventional anchor device. [Figure 2] 1 illustrates an example of a wireless communication environment in which an indoor positioning system may operate. [Figure 3] 1 illustrates a schematic diagram of an example of an indoor positioning system operating in a wireless communication network; [Figure 4] 1 illustrates a schematic diagram of an example of an indoor positioning method for a wireless communication network. [Figure 5] 1 shows a schematic example of dividing an antenna array into two subarrays. [Figure 6] 10 illustrates an example flowchart for determining a DOA estimate by an anchor device. [Figure 7] 1 illustrates a schematic diagram of an example of an operating portion of an anchor device. [Figure 8] 1 shows a schematic diagram of an example of an operating part of a tag device. DETAILED DESCRIPTION OF THE INVENTION

[0029] 2 illustrates an example of a wireless communication environment in which an indoor positioning system 300 may operate. The environment includes a wireless radio communication network (system) 200 that includes multiple wireless radio communication devices (nodes) 202a-202c. The devices 202a-202c operate in the same geographic region, such as within the illustrated environment, and over the same spectrum, which may include one or more frequency bands. Each of the one or more frequency bands may include one or more frequency channels. Use of the same spectrum enables two-way wireless communication between the devices 202a-202c in the network 200, such that a radio transmission transmitted by one device 202a-202c can be received by another device 202a-202c, and vice versa.

[0030] The indoor positioning system 300 may be applied to any wireless communication network 200. Preferably, the indoor positioning system 300 may be applied to a wireless communication network 200 with low capacity and / or low power consumption requirements. Some non-limiting examples of wireless communication networks 200 with low capacity and / or low power consumption requirements to which the indoor positioning system 300 may be applied may include, but are not limited to, a wireless sensor network (WSN), a wireless communication network compliant with the Digital European Cordless Telecommunications (DECT-2020NR) standard, a Bluetooth® Low Energy (BLE) mesh network, a Zigbee® network, a Thread® network, a wireless local area network (WLAN), and / or any other wireless communication network. In many use cases, due to low capacity and / or low power consumption requirements, transferring all measurement data from network nodes (e.g., tag devices) to a central entity (e.g., a cloud entity) with greater processing power is not possible or would cause degradation to other uses or services within the network 200.

[0031] As explained above, each device 202a-202c can provide two-way wireless communication with at least one other device 202a-202c by its radio. This means that each device 202a-202c can operate as a transmitter, a receiver, or a transceiver, provided that each device 202a-202c can send at least one message to and receive at least one message from other devices 202a-202c in network 200.

[0032] Network 200 may also include at least one gateway device 204, e.g., one, two, three, four, or more gateway devices. Each gateway device 204 acts as a gateway between network 200 and other external networks 206 (e.g., a central entity and / or the Internet) and distributes data within and from network 200. Each gateway device 204 communicates with at least one sink device (node) 204a, e.g., one, two, three, four, or more sink devices, and each sink device 202a acts as a wireless interface for a gateway device 204 within network 200. At least one sink device 202a belongs to multiple devices 202a-202c of network 200. Each sink device 202a may be located in physical connection with gateway device 204 or may be located separately in a different part of network 200. If gateway device 204 includes multiple sink devices 202 a, one of them may be located connected to gateway device 204 and the others may be located separately in different parts of network 200.

[0033] Other devices 202b and 202c in network 200 can operate in different fixed or non-fixed roles in network 200. Other devices 202b and 202c in network 200 are router devices (routers) 202b, i.e., devices operating in the role of a router, and non-router devices (non-routers) 202d, i.e., devices operating in the role of a non-router, depending on whether the devices need to participate in data forwarding. Sink devices 202a and router devices 202b in network 200 may participate in routing operations. Each router device 202b maintains connectivity for network 200 and forwards data for other devices 202a-202c as needed. Each non-router device 202c, like sink devices 202a and router devices 202b, can provide two-way communication for transmitting its own data and receiving data directed to it, but the non-router devices 202c do not route data for other devices 202a-202c.

[0034] Network 200 includes devices 202b, 202c for which direct communication with sink device 202a is not possible or is not preferred for all devices 202b, 202c due to wireless conditions, such as long distances between devices 202a, 202c, interference or signal attenuation between devices 202a, 202c, or limited wireless range, in which case it is necessary or preferred for devices 202a, 202c to use multi-link (multi-hop) communication between each of devices 202b, 202c and sink device 202a.

[0035] 3 illustrates schematically an example of an indoor positioning system 300 operating in a wireless communication network 200. The indoor positioning system 300 includes one or more anchor devices 302a-302n, one or more tag devices 304a-304n, and a central entity (e.g., a cloud entity) 306. The central entity 306 is in bidirectional communication with the one or more anchor devices 302a-302n over the wireless communication network 200.

[0036] FIG. 4 schematically illustrates an example indoor positioning method for wireless communications network 200. FIG. 4 illustrates the indoor positioning method in a flow chart. The indoor positioning method is primarily described using one anchor device 302a and one positioned tag device 304a. However, each of the one or more anchor devices 302a-302n may be configured to independently perform one or more method steps (i.e., features) of the indoor positioning method associated with the anchor device, as described below for one anchor device 302a. Similarly, each of the one or more tag devices 304a-304n may be configured to be positioned as described below for one tag device 304a. The indoor positioning method is based on direction of arrival (DOA) estimation.

[0037] In step 410, the transmission of signals 301a-301n by one or more tag devices 304a-304n is controlled so that one signal 301a is transmitted at a time on a given radio resource (e.g., a frequency channel or a code), and the tag device 304a transmitting this one signal 301a is the located tag device 304a. This allows the transmission of signals 301a-301n by one or more tag devices 304a-304n to be controlled so as to avoid collisions between the signals 301a-301n transmitted by the one or more tag devices 304a-304n. Collision avoidance can be performed based on any collision avoidance technique. The given (e.g., predefined) radio resource may depend on the collision avoidance technique applied. For example, the avoidance technique may be based on using multiple frequency channels, in which case transmission of signals 301a-301n by one or more tag devices 304a-304n may be controlled such that only one signal (e.g., signal 301a by tag device 304a) is transmitted on one frequency channel at a time. In other words, only one signal is transmitted on one frequency channel at a time. However, simultaneously, one or more other signals 301b-301n may be transmitted on one or more other frequency channels. In other words, as described, simultaneous transmissions of signals 301a-301n on different frequency channels may be transmitted by one or more tag devices 304a-304c, and each of the simultaneous transmissions of signals 301a-301n on different frequency channels may be received and processed by at least one anchor device 302a. According to another embodiment, the avoidance technique may be based on using Code Division Multiple Access (CDMA), in which case the transmission of signals 301 a-301 n by one or more tag devices 304 a-304 n may be controlled such that each tag device 304 a-304 n is assigned an individual code that also applies to the corresponding signal 301 a-301 n. In other words, the individual code allows only the tag device 304 a-304 n to which it is assigned to transmit using that individual code at one time.Thus, simultaneous transmissions of signals 301a-301n may be transmitted by multiple tag devices 304a-304n assigned different individual codes, and each of the simultaneous transmissions of signals 301a-301n transmitted by multiple tag devices 304a-304n assigned different individual codes may be received and processed by at least one anchor device 302a as described for one signal 301a. Control of the transmission of signals 301a-301n by one or more tag devices 304a-304n may be based on the use of a medium access control (MAC) function. Any type of MAC function may be used that provides a means to identify one or more transmitting tag devices 301a-301n and avoid collisions among the transmitted signals 301a-301n. The MAC function may include, for example, using a random access procedure or a scheduled procedure. In the random access procedure, each router device 202b and sink device 202a in the network 200 announces its random access channel (RACH) resources, i.e., the time slots it will enter, upon receiving data. The RACH resources may be included in beacon messages transmitted by the router / sink devices 202a and 202n. Any device wishing to associate with the router / sink devices 202a and 202b may then transmit its data (e.g., data packets containing measurement data and / or association requests) during those time slots. The random access procedure may include the use of a listen-before-talk (LBT) technique and random backoff. The router / sink devices 202a and 202b announcing the time slots do not know which and how many devices are attempting to use the time slot (i.e., transmit some data). Therefore, devices attempting to transmit data may use LBT and random backoff to avoid collisions. LBT is a short listening period used to verify that no other devices are currently transmitting data on that frequency channel.If the frequency channel is busy (i.e., another device is transmitting data on that frequency channel), a backoff (i.e., a randomized waiting period) is applied before attempting to transmit data again. If the frequency channel is not busy, the device can transmit data. As an alternative to the random access procedure, a scheduled procedure can be used, in which a base station (BS), access point (AP), or router device 202b of network 200 can schedule time reservations for each transmitting device or group of transmitting devices. Using per-device scheduling can avoid the use of LBT. Also, while the features of the indoor positioning method associated with a tag device have been described using a single tag device 304a, each tag device of one or more tag devices 304a-304n may be configured to independently perform one or more features associated with the tag device as described for a single tag device 304a.

[0038] In step 420, the anchor device 302a receives the signal 301a transmitted by the tag device 304a to be located via the antenna array 500. The signal 301a transmitted by the tag device 304a may include, for example, measurement data acquired by the tag device 304a. The antenna array 500 may include multiple antenna elements. For example, the antenna array 500 may be a uniform linear array (ULA) of antennas. Alternatively, the antenna array 500 may be any other antenna array to which the DOA estimation according to the present patent application is applicable. Next, the antenna array 500 is configured to orient the antenna elements of the antenna array 500 at angles θ1, θ2, ..., θ d Assume that the antenna array 500 includes M antenna elements receiving d signals 301a-301n from sources that are far-field sources impinging at an angle θ1. As noted above, only one tag device 304a is transmitting at a time on a given radio resource, so d is one (i.e., d=1). Thus, the antenna elements of the antenna array 500 receive one signal from the located tag device 304a, which is impinging on the antenna elements of the antenna array at an angle θ1. In conventional, or standard, ESPRIT, the antenna elements of the antenna array 500 receive signals at angles θ1, θ2, ..., θd d signals are received from sources impinging on the antenna elements of the antenna array at . Therefore, the DOA estimation described herein can be considered a simplified, or optimized, ESPRIT. Some of the steps of this simplified ESPRIT correspond to those of ESPRIT, and some of the steps of the simplified ESPRIT may differ from those of traditional ESPRIT. While traditional ESPRIT estimates multiple DOAs, this simplified ESPRIT estimates one DOA per radio resource because it controls the transmission of signals by one or more tag devices 304a-304n. Generally, a DOA is the direction of a transmitter (e.g., tag device 304a) measured relative to a line perpendicular to the antenna array 500. The estimated DOA includes an angle of arrival. For example, the angle of arrival may include azimuth, elevation, zenith, or any other angle. Azimuth, elevation, and zenith angles are merely special cases of angle of arrival, which depend on the orientation of the antenna array 500 in three-dimensional space. The signal 301a transmitted by the tag device 304a may be, for example, a narrowband signal propagated in an additive white Gaussian noise (AWGN) channel using a linear and isotropic transmission medium. The following exemplary definitions (e.g., equations) are described for traditional ESPRIT, but the same definitions also apply to simplified ESPRIT, where d=1. The IQ sample of each source (e.g., located tag device 304a) at timestamp t is given by: x(t)=A(t)+n(t) (1) During the ceremony, JPEG2025537733000002.jpg520 is a vector of signals from d sources, JPEG2025537733000003.jpg521 is the spatially correlated additive noise with zero mean, JPEG2025537733000004.jpg417 is the steering matrix, i.e., A=[a(θ1),a(θ2)…a(θd )], (2) In the formula,

[0039]

number

[0040] Similar to conventional ESPRIT, in this simplified ESPRIT, antenna array 500 may be divided into two subarrays 502 and 504. The two subarrays 502 and 504 consist of m=M=1 contiguous antenna elements and M-2 overlapping antenna elements, as shown in FIG. 5, which schematically illustrates an example of dividing antenna array 500 into two subarrays. Subarrays 502 and 504 may be formed by multiplying steering matrix A by:

[0041]

number

[0042] However, instead of computing the rotation operation Φ, as in the conventional ESPRIT, this modified ESPRIT computes the signal subspace U as shown in the following equation: s The subspace rotation operation Ψ can be deduced from:

[0043]

number

[0044] In step 430, the anchor device 302a determines a DOA estimate by applying the first power law based algorithm and the second power law based algorithm, respectively, based on the signal 301a received from the tag device 304a. An example of determining a DOA estimate will now be described with reference to Figure 6, which shows an exemplary flowchart of the determination of a DOA estimate by the anchor device 302a in step 430.

[0045] In step 610, the anchor device 302a derives a first covariance matrix R from the IQ samples of the received signal 301a. xx The radio of the anchor device 302a includes a direct conversion receiver with IQ sampling capability to provide IQ samples of the received signal 301a. The anchor device 302a defines timestamps t1, t2, ..., t n About N samples JPEG2025537733000010.jpg523 The first covariance matrix R xx can be estimated, for example, using the following formula:

[0046]

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[0047] In step 620, the anchor device 302a calculates a first covariance matrix R xx into a real covariance matrix C. The anchor device 302 converts the first covariance matrix R xx can be transformed into a real covariance matrix C:

[0048]

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[0049]

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[0050]

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[0051] In step 630, the anchor device 302a defines, e.g., calculates, a signal subspace by applying a first power-law based algorithm to the real covariance matrix C. The first power-law based algorithm may be a power method. This method simplifies (e.g., optimizes) conventional ESPRIT by taking advantage of the limitation of single-source wireless communication systems (i.e., d=1), as described above. Since d=1, the signal subspace U scontains only one eigenvector, so we can apply the complex and time-consuming eigenvalue decomposition (EVD) as in traditional ESPRIT to obtain the signal subspace U s In EVD, all eigenvectors are calculated. Instead of EVD, we use the signal subspace U s may be defined by applying a first power law (e.g., a power law) to find the eigenvalue with the largest absolute value and its corresponding, i.e., associated, eigenvector, i.e., the signal subspace U s This is a simple numerical algorithm that only requires defining (e.g., calculating) . This saves on execution time and memory footprint. In order to apply the power method, the matrix to which the power method is applied, i.e., the input matrix of the power method, must satisfy a first convergence requirement. More specifically, if the input matrix of the power method satisfies the first convergence requirement, the input matrix will converge to the desired eigenvector. The first convergence requirement includes that the input matrix can be diagonalized, that there is only one eigenvalue with the largest absolute value, and that the eigenvalue is real. For example, JPEG2025537733000018.jpg432 Considering these as eigenvalues, |λ1|>|λ2|≥…≥|λ M |. The matrix C is a real covariance matrix, and therefore is symmetric, diagonalizable, and all its eigenvalues ​​are real. Furthermore, because C is a real covariance matrix, it is positive semidefinite, which means that all its eigenvalues ​​are non-negative. In summary, the power law converges because the input matrix is ​​a real covariance matrix and the DOA is calculated in line-of-sight (LOS). LOS can travel through any medium, including air. In LOS, the signal subspace U s The eigenvalues ​​of are larger than those of the noise subspace, and all the eigenvalues ​​are non-negative. Therefore, the eigenvalues ​​of the noise subspace are s Therefore, the signal subspace U s The eigenvalue of is the largest.

[0052] In step 640, the anchor device 302a calculates the signal subspace U sDefine a second covariance matrix E from: The second covariance matrix E can be defined using the following formula:

[0053]

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[0054] In step 650, the anchor device 302a defines DOA information Y, which represents a DOA estimate, by applying a second power-law based algorithm to the second covariance matrix. The second power-law based algorithm may be an inverse power law. Alternatively, the second power-law based algorithm may be a power law. Since d=1, the size of the second covariance matrix E is 2x2. As a result, the right submatrix of the eigenvector matrix V, i.e., [V 12 V 22 ] T is a vector of size 2. Since these elements are scalars, the submatrix is ​​[v 12 v 22 ] T Instead of applying EVD, which is a complex numerical technique (as in conventional ESPRIT), the anchor device 302a applies a second power law based algorithm to the second covariance matrix E. For example, the anchor device 302a may apply an inverse power law to the second covariance matrix E, which finds the smallest magnitude eigenvalue and its corresponding eigenvector, i.e., the vector [v 12 v 22 ] T Define and calculate, for example:

[0055] For the inverse power method to be applicable, the matrix to which the inverse power method is applied, i.e., the input matrix of the inverse power method, must satisfy the second convergence requirement. The second convergence requirement is that the input matrix is ​​non-singular and has only one smallest real eigenvalue in the modulus. For example, when d=1, |λ1|>|λ2|. Since the second covariance matrix E is a real covariance matrix, the second covariance matrix E is a real symmetric matrix with real eigenvalues; more specifically, the second covariance matrix E is positive semidefinite. Vector K1U S and K2U S If the are linearly independent, then the second covariance matrix E may be positive definite. In this case, the second covariance matrix E is non-singular. However, JPEG2025537733000022.jpg423 If , the second covariance matrix E may be "nearly singular" (ill-conditioned). To ensure that the second covariance matrix E is always non-singular, it must be transformed into a positive definite matrix. Taking advantage of the positive semidefinite property of the second covariance matrix E, it can be transformed into a positive definite matrix by applying a well-known simple method involving small perturbations, i.e., JPEG2025537733000023.jpg422 where α must be a small positive number to approximate the perturbed matrix to the unperturbed matrix. Assuming that the perturbed matrix E has only one smallest eigenvalue, the inverse power method can be applied. Preferably, the anchor device 302a defines only the eigenvectors. This is because this simplified ESPRIT does not require the use of eigenvalues ​​in determining the DOA estimates, which is one advantage of simplified ESPRIT over traditional ESPRIT. The inverse power method requires computing the solution to a linear equation at each iteration, which requires an iterative algorithm for solving a linear system, such as Gaussian elimination or LU (Lower-Upper) decomposition. The linear system can be considered to have the following elements:

[0056]

number

[0057] However, since E is of size 2x2, an iterative algorithm is not necessary and instead the solution to the linear equation can be analytically found using

[0058]

number

[0059] Since the solution to the linear equations can be found analytically, there is no need to use numerical techniques such as Gaussian elimination algorithms to solve the linear system. As mentioned earlier, the output of the inverse power method is the eigenvector associated with the smallest eigenvalue of the covariance matrix E, i.e., [v 12 v 22 ] T The DOA information Y can be calculated as follows:

[0060]

number

[0061] As mentioned above, the power method can be applied instead of the inverse power method as an algorithm based on the second power method. E is a 2x2 real symmetric matrix with well-defined eigenvalue assumptions, so its two eigenvectors are orthogonal to each other. Therefore, applying the power method to the second covariance matrix E yields the vector JPEG2025537733000027.jpg412 Any vector orthogonal to v may be the eigenvector corresponding to the smallest eigenvalue. However, the execution time, accuracy, and memory consumption of using the power method to define the DOA information are essentially the same as using the inverse power method.

[0062] In step 660, the anchor device 302a defines a DOA estimate based on the defined DOA information Y. The DOA estimate may be defined, for example, using the following equation:

[0063]

number

[0064] In step 440, the anchor device 302a transmits (e.g., reports) the estimated DOA together with DOA metadata to a central entity 306 (e.g., a cloud entity) via the wireless communications network 200 for positioning of the tag device 304a. The estimated DOA and DOA metadata are transmitted to the central entity 306, for example, in a measurement report including the estimated DOA and DOA metadata. The anchor device 302a may perform the above-described DOA estimation multiple times (i.e., two or more times) to estimate multiple DOAs (i.e., two or more DOAs). In that case, the measurement report may include the multiple estimated DOAs. Alternatively, each estimated DOA of the multiple DOAs may be reported in a separate measurement report. In other words, if the anchor device 302a estimates multiple DOAs, one or more of the multiple estimated DOAs may be included in the same measurement report. The DOA metadata may include, for example, an identifier of the anchor device 302a transmitting the estimated DOA, the coordinates of the anchor device 302a transmitting the estimated DOA, an identifier of the positioned tag device 304a, received signal strength indication (RSSI) information, and / or time information. The time information may be, for example, the DOA estimation time or the time since the DOA estimation. If the time information includes the time since the DOA estimation, the anchor device 302a may have already set the time information in the measurement report to a value greater than zero because some time may have elapsed between the DOA estimation and transmitting the DOA estimate to the central entity 306. Alternatively or additionally, each router device 202b in the wireless communication network 200 may add the time used to transmit the measurement report to the time since the DOA estimation. If the indoor positioning system 300 knows the location of each anchor device 302a, the identifier of the anchor device 302a transmitting the estimated DOA may substantially limit the location of the already-positioned tag device. The RSSI information may be used, for example, to estimate whether the tag device 304a is closer or farther from the anchor device 302a. Alternatively or additionally, the RSSI information may also be useful if the DOA estimation is unsuccessful for some reason. The DOA metadata may be associated with at least one estimated DOA.For example, simplified DOA metadata containing only the identifier of the positioned tag device 304a may be subsequently reported along with the estimated DOAs.

[0065] Furthermore, the indoor positioning method may further include, in response to receiving a measurement report from the anchor device 302a including the estimated DOA and DOA metadata, positioning the tag device 304a by the central entity 306 (e.g., by a cloud entity) based on the received estimated DOA and DOA metadata. This is shown by step 450 in FIG. 4. The central entity 306 may define a rough estimate of the position of the positioned tag device 304a if it knows the position (and possibly RSSI information) of the anchor device 302a. However, using the estimated DOA received from the anchor device 302a may improve the accuracy of the defined estimate of the position of the positioned tag device 304a. To be able to determine the true direction of the positioned tag device 304a relative to the anchor device 302a transmitting the estimated DOA, the anchor device 302a may need to be installed in a particular orientation (e.g., horizontal and / or vertical) and / or may need a particular part to always point in a particular compass direction (e.g., north). Alternatively or additionally, the use of multiple antenna arrays 500 or the use of an antenna array 500 having a shape capable of estimating two or more DOAs in different directions can be applied to provide more data for positioning purposes. For example, an L-shaped antenna array 500 formed with two rows of antenna elements can be used to estimate a DOA consisting of angles in two directions. The positioning of the tag device 304a by the central entity 306a using the received estimated DOA and DOA metadata can be based on any known positioning calculation method.According to an exemplary positioning calculation method, the central entity 306 may position the tag device 304a by first defining an estimate (with a rough accuracy, e.g., to an accuracy of 100 meters, depending on the radio used) of the location of the anchor device 302a transmitting the estimated DOA, then using the estimated DOA to determine the direction or area of ​​the positioned tag device 304a relative to the anchor device 302a transmitting the estimated DOA (e.g., a particular compass direction, e.g., northwest), and finally using RSSI information to estimate the distance of the positioned tag device 304a relative to the anchor device 302a transmitting the estimated DOA (e.g., less than a few meters, e.g., less than 5 meters). Alternatively, multiple anchor devices 302a-302n can be used to triangulate the precise location of the positioned tag device 304a based on measurement reports transmitted from the multiple anchor devices 302a-302n. The use of multiple anchor devices 302a-302n (ie, measurement reports transmitted by multiple anchor devices 302a-302b) further improves the accuracy of the defined estimate of the location of the positioned tag device 304a.

[0066] 7 illustrates a schematic of anchor devices 302a-302n that communicate within network 200 and that are capable of performing the associated functions (steps) of the indoor positioning method as described above. In other words, the devices described are those that operate as anchor devices 302a-302n and are capable of performing the features of the indoor positioning method associated with anchor device 302a as described above.

[0067] Anchor devices 302a to 302n each include a controller (control unit) 730 that controls the operation of each of its units 732, 734, 736, 738, and 740 so that anchor devices 302a to 302n operate as described above.

[0068] The controller 730 includes a processor 732 that executes operator-driven and / or computer program-driven instructions and processes data to run applications. The processor 732 may include at least one processor, such as one, two, three, four, or more processors.

[0069] The controller 730 also includes a memory 734 for storing and retaining data. The data may be instructions, computer programs, and data files. The memory 734 may include at least one memory, such as one, two, three, four, or more memories.

[0070] Anchor devices 302a-302n also include a radio (wireless communication unit, data transfer unit) 736 and an antenna (antenna unit) 738 that are used by controller 730 to transmit commands, requests, messages, and data to at least one other device in indoor positioning system 300 and / or network 200 via antenna 738. Radio 736 also receives commands, requests, and data from at least one other device in indoor positioning system 300 and / or network 200 via antenna 738. Antenna unit 738 includes at least antenna array 500. Communication between radio 736 of anchor devices 302a-302n and other devices in indoor positioning system 300 and / or network 200 is provided wirelessly via antenna 738.

[0071] Anchor devices 302a to 302n may further include a power supply (power supply unit) 740. Power supply 740 includes components for supplying power to anchor devices 302a to 302n, such as a battery and a regulator.

[0072] The memory 734 stores at least a radio communication (RC) application 742 for operating (controlling) the radio 736 and a power supply (PS) application 744 for operating the power supply 740 .

[0073] The memory 734 also stores a computer program (CP) (i.e., computer software, computer application) 746 that, when executed (implemented) by the controller 730 in a computer, such as anchor device 302a-302n, uses at least one of components 736, 738, 740 to perform the operations of anchor device 302a-302n described above, at least in the context of the preceding figures.

[0074] The computer program 746 may be stored on a tangible, non-volatile computer readable storage medium, such as a compact disc (CD) or universal serial bus (USB) type storage device.

[0075] 8 illustrates a schematic diagram of tag devices 304a-304n that are capable of communicating in network 200 and performing the associated functions (steps) of the indoor positioning method as described above. In other words, apparatuses are described that operate as tag devices 304a-304n and that are capable of performing the features of the indoor positioning method associated with tag device 304a as described above.

[0076] The tag devices 304a to 304n each include a controller (control unit) 830 that controls the operation of each of the units 832, 834, 836, 838, and 840 thereof so that the tag devices 304a to 304n operate as described above.

[0077] The controller 830 includes a processor 832 that executes operator-driven and / or computer program-driven instructions and processes data to run applications. The processor 832 may include at least one processor, for example, one, two, three, four, or more processors.

[0078] The controller 830 also includes a memory 834 for storing and retaining data. The data may be instructions, computer programs, and data files. The memory 834 may include at least one memory, such as one, two, three, four, or more memories.

[0079] The tag devices 304a-304n also include a radio (wireless communication unit, data transfer unit) 836 and an antenna (antenna unit) 838 that the controller 830 uses to transmit commands, requests, messages, and data to at least one other device in the indoor positioning system 300 and / or network 200 via the antenna 838. The radio 836 also receives commands, requests, and data from at least one other device in the indoor positioning system 300 and / or network 200 via the antenna 838. Communication between the radios 836 of the tag devices 304a-304n and other devices in the indoor positioning system 300 and / or network 200 is provided wirelessly via the antenna 838.

[0080] The tag devices 304a to 304n may further include a power supply (power supply unit) 840. The power supply 840 includes components for supplying power to the tag devices 304a to 304n, such as a battery and a regulator.

[0081] The memory 834 stores at least a radio communication (RC) application 842 for operating (controlling) the radio 836 and a power supply (PS) application 844 for operating the power supply 840.

[0082] The memory 834 also stores a computer program (CP) (i.e., computer software, computer application) 846 which, when executed (implemented) by the controller 830 in a computer, such as tag devices 304a-304n, uses at least one of the components 836, 838, 840 to perform the operations of the tag devices 304a-304n described above, at least in the context of the previous figures.

[0083] The computer program 846 may be stored on a tangible, non-volatile computer readable storage medium, such as a compact disc (CD) or universal serial bus (USB) type storage device.

[0084] The specific examples provided in the above description should not be construed as limiting the scope and / or interpretation of the appended claims. Any example lists or groups provided in the above description are not exhaustive unless expressly indicated otherwise.

Claims

1. An indoor positioning system (300) for a wireless communication network (200), comprising: one or more anchor devices (302a-302n); a central entity (306) in bidirectional communication with the one or more anchor devices (302a-302n) over the wireless communication network (200); one or more tag devices (304a-304n), wherein transmission of signals (301a-301n) by said one or more tag devices (304a-304n) is controlled such that one signal (301a) is transmitted at a time on a given radio resource, and the tag device (304a) transmitting said one signal (301a) is a tag device (304a) to be located; Including, At least one anchor device (302a) of the one or more anchor devices (302a-302n) receiving, via an antenna array (500), the signal (301a) transmitted by the target tag device; determining an estimate of a direction of arrival (DOA) based on the received signal (301 a) by applying a first power law based algorithm and a second power law based algorithm, respectively; transmitting the estimated DOA together with DOA metadata to the central entity (306) via the wireless communication network (200); An indoor positioning system (300) configured to:

2. The indoor positioning system (300) of claim 1, wherein the central entity (306) is configured to position the tag device (304a) based on the received estimated DOA and DOA metadata.

3. The indoor positioning system (300) according to claim 1 or 2, wherein the control of the transmission of signals (301a-301n) by the one or more tag devices (304a-304n) is based on the use of a Medium Access Control (MAC) function.

4. The indoor positioning system (300) of claim 3, wherein the MAC function includes using a random access procedure or a scheduled procedure.

5. The indoor positioning system (300) of any one of claims 1 to 4, wherein said first power-based algorithm is a power law.

6. The indoor positioning system (300) of any one of claims 1 to 5, wherein the second power law based algorithm is an inverse power law or a power law.

7. The determination of the DOA estimate is performed by the at least one anchor device (302a): defining 301a a first covariance matrix from IQ samples of the received signal; converting the first covariance matrix to a real covariance matrix; defining a signal subspace by applying a first power-based algorithm to the real covariance matrix; defining a second covariance matrix from the defined signal subspace; applying the second power law based algorithm to the second covariance matrix to define DOA information representing an estimate of the DOA; defining an estimate of the DOA based on the defined DOA information; The indoor positioning system (300) of any one of claims 1 to 6, further comprising:

8. The DOA metadata includes an identifier of the anchor device (302a) transmitting the estimated DOA, coordinates of the anchor device (302a) transmitting the estimated DOA, an identifier of the positioned tag device (304a), received signal strength indication (RSSI) information, and / or time information. An indoor positioning system (300) according to any one of claims 1 to 7.

9. An indoor positioning method for a wireless communication network (200), comprising: controlling (410) the transmission of signals (301 a-301 n) by one or more tag devices (304 a-304 n) so that one signal (301 a) is transmitted at a time on a given radio resource, the tag device (304 a) transmitting the one signal (301 a) being a tag device to be located; receiving (420) the signal (301a) transmitted by said located tag device (304a) via an antenna array (500) by at least one anchor device (302a); determining (430), by the at least one anchor device (302a), an estimate of a direction of arrival (DOA) based on the received signal (301a) by applying a first power law based algorithm and a second power law based algorithm, respectively; transmitting (440) the estimated DOA together with DOA metadata by the at least one anchor device (302a) to a central entity (306) via the wireless communications network (200); An indoor positioning method including each step.

10. An anchor device (302a-302n) for indoor positioning, a wireless communication device (736); an antenna array (500); a controller (730); Including, The anchor devices (302a to 302n) receiving, by the radio communication device (736), via the antenna array (500), a signal (301 a) transmitted by a tag device (304 a) to be located; and controlling transmission of the signals (301 a-301 n) by one or more tag devices (304 a-304 n) so that one signal (301 a) is transmitted at a time on a given radio resource, the tag device (304 a) transmitting the one signal (301 a) being the tag device to be located (304 a); determining, by the controller (730), an estimate of a direction of arrival (DOA) based on the received signal (301 a) by applying a first power law based algorithm and a second power law based algorithm, respectively; transmitting, by said radio (736), said estimated DOA together with DOA metadata to a central entity (306) over a wireless communications network (200); The anchor devices (302a to 302n) are configured to:

11. An indoor positioning method for anchor devices (302a-302n), comprising: receiving (420) a signal (301 a) transmitted by a tag device (304 a) to be located via an antenna array (500) of the anchor device (302 a-302 n) by a radio transmitter (736) of the anchor device (302 a-302 n); controlling transmission of the signals (301 a-301 n) by one or more tag devices (304 a-304 n) so that one signal (301 a) is transmitted at a time on a given radio resource, the tag device (304 a) transmitting the one signal (301 a) being the tag device (304 a); determining (430) an estimate of a direction of arrival (DOA) based on the received signal (301 a) by applying a first power law based algorithm and a second power law based algorithm, respectively, by a controller (730) of the anchor device (302 a-302 n); transmitting (440) the estimated DOA together with DOA metadata via the radio (736) of the anchor device (302a-302n) to a central entity (306) over a wireless communications network (200); An indoor positioning method including each step.

12. A computer program (746) comprising instructions, which when executed by a computer, cause the computer to perform at least the steps of the method of claim 11.

13. 13. A tangible, non-volatile computer readable medium containing the computer program of claim 12.

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