Placement of RFID Readers in an Environment with a Dense Group of RFID Tags

Abstract

A method and apparatus for placing RFID readers in an RFID environment that includes a dense tag group are described. The RFID readers are deployed using a process that provides an appropriate link margin so that communication with RFID tags can be established in all areas of interest within the RFID environment.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Patent Application No. 63 / 349,303, filed Jun. 6, 2022, which is hereby incorporated by reference in its entirety for all purposes.

Background Art

[0002] Radio Frequency Identification (RFID) tags are low - cost devices that are attached to objects and provide expectations for, among other commercial and medical applications, the automatic tracking, positioning, sales check - out, and inventory of objects. There are passive, semi - active, and active RFID tags that can be wirelessly interrogated by an RFID reader and radiate a wireless RF response to the reader. The response can include information stored in the RFID tag, such as a tag identification number or alphanumeric sequence, and an Electronic Product Code (EPC). Other information may be included in the response.

[0003] Passive RFID tags do not have a battery and are thus typically less costly than semi - active and active RFID tags. Passive RFID tags essentially condition and backscatter the energy from the RF interrogation pulse transmitted by the RFID reader to transmit a response. The cost is lower (e.g., about 1 / 10 of the cost of an active tag), but the response signal from a passive RFID tag weakens as the distance increases. Further, the read range of a passive RFID tag can be significantly smaller than that of an active RFID tag. For example, the read range of a passive tag may be limited to 100 meters in a line - of - sight environment without intervening objects that scatter the interrogation and response signals, while the read range of an active tag may be over 500 meters in the same environment.

[0004] When an RFID reader is configured using a dense group of RFID tags (e.g., at least 10 RFID tags per square meter) and includes an object that scatters RF signals, the RFID reader may not be able to read all the tags even when the tags are located within 100 meters of the reader. Such configurations occur, for example, in warehouses and retail sales facilities. In such cases, it may be necessary to install multiple RFID readers throughout the facility to read all of the tags. SUMMARY OF THE INVENTION

[0005] The described implementation relates to the selection of the location of RFID readers in an environment having dense groups of RFID tags and objects that block, attenuate, and / or scatter RFID signals. The RFID readers are distributed throughout the environment and arranged such that all RFID tags within the environment are read by at least one of the RFID readers. Power calculations can be performed to determine the locations of the RFID readers such that the RFID readers are not spaced unnecessarily close to each other.

[0006] Some implementations relate to ways of placing RFID readers at an installation location and the placed RFID readers. Such ways include measuring the ceiling height of the installation location as well as the positions of walls and / or fixtures, determining intended locations for RFID readers at the installation location based on the ceiling height and the positions of walls and / or fixtures, providing a central controller for RFID readers having a configuration file representing the intended locations for the RFID readers, and installing the RFID readers at the installation location. Once the RFID readers are installed, their actual positions are measured and used to generate an updated configuration file provided to the central controller. The central controller and the RFID readers are commissioned to find RFID tags within the installation location based on (i) signals from RFID tags received by the RFID readers, and (ii) the actual positions of the RFID readers.

[0007] The ceiling height, the positions of walls and / or fixtures, and the actual positions of the RFID readers can be measured by performing LIDAR scans of the installation location before and after installation.

[0008] Determining the intended locations for the RFID readers can include generating a ceiling image representing the floor plan and ceiling height of the installation location and / or identifying potential obstacles based on the ceiling height and / or coverage volume of the RFID readers. The intended locations can be selected such that the coverage volumes of adjacent RFID readers intersect at a (first) predetermined height (e.g., about 1 meter), which may be based on the expected maximum height of RFID tags within the installation location and / or the height of fixtures holding the RFID tags. The coverage volume of an RFID reader adjacent to a wall intersects the wall at a (second) predetermined height (e.g., about 2 meters) or more based on the expected maximum height of RFID tags on fixtures along the wall.

[0009] Determining the intended position of the RFID reader can also include generating different sets of possible sensor positions based on different desired intervals between adjacent sensor positions, determining the coverage and number of sensors for each set of possible sensor positions, and selecting one of the sets of possible sensor positions as the intended position based on the coverage and number of sensors for the different sets of possible sensor positions.

[0010] Installing the RFID reader can include adjusting at least one pitch and / or roll of the RFID reader to an angle of 0.0° ± 0.25°. Mounting the RFID reader can also include connecting each of the RFID readers to a corresponding Ethernet switch and connecting the corresponding Ethernet switch to a central controller. After installing the RFID reader, the angular orientation of the RFID reader can be measured and used to generate an updated configuration file. Optionally, the coverage of the installation location by the RFID reader can be tested before commissioning the central controller and the RFID reader.

[0011] Another implementation relates to a method of placing RFID readers at installation locations and the placed RFID readers, as follows. The corner location is selected such that the coverage volume of the RFID reader at the corner location intersects a wall forming a corner at a first predetermined height or greater, based on the expected maximum height of RFID tags on fixtures along the wall. The perimeter location is selected such that the coverage volume of the RFID reader at the perimeter location intersects the wall at a first predetermined height (e.g., about 2 meters) and intersects an adjacent coverage volume at a second predetermined height (e.g., about 1 meter) or greater, based on the expected maximum height of RFID tags at the installation location. The interior location is selected such that the coverage volume of the RFID reader at the interior location intersects an adjacent coverage volume at a second predetermined height or greater. RFID readers are installed at the corner location, the perimeter location, and the interior location. Next, the RFID readers are test-run to determine the positions of RFID tags within the installation location based on (i) signals from the RFID tags received by the RFID readers and (ii) the actual positions of the RFID readers.

[0012] Optionally, obstacles and / or areas having a ceiling height below a predetermined threshold within the installation location can be identified before selecting the corner location, the perimeter location, and the interior location. After selecting the corner location, the perimeter location, and the interior location and before installing the RFID readers, gaps in the coverage provided by the RFID readers at the corner location, the perimeter location, and the interior location can be identified, and the positions of the RFID readers can be repeatedly added and shifted to reduce and / or remove the gaps. After installing the RFID readers and before test-running them, the actual positions of the RFID readers can be measured. A central controller can be configured with a set file representing the actual positions of the RFID readers for determining the positions of RFID tags.

[0013] Yet other implementations relate to a method for positioning RFID readers in an RFID environment that includes a dense group of RFID tags. The method includes the following steps: receiving floor plan information that describes the extent of the physical space of the RFID environment; determining a first position within the physical space for a plurality of RFID readers, wherein the first position is distributed across the entire physical space in a first pattern; calculating a first plurality of peak radio frequency (RF) power levels at a plurality of positions of interest within the physical space, wherein the first plurality of peak RF power levels are based on the RF fields radiated by the plurality of RFID readers and the first position of the plurality of RFID readers, and each position of interest is a sub-region of the physical space where RFID tags are expected to be present within the RFID environment; determining, for at least a first position of interest of the plurality of positions of interest, that a first peak RF power level of the first plurality of peak RF power levels at the first position of interest does not meet a link margin criterion, wherein the link margin criterion identifies a target power level sufficient to establish communication between at least one of the plurality of RFID readers and an RFID tag located at the first position of interest; in response to the first peak RF power level not meeting the link margin criterion, determining a second position within the physical space for the plurality of RFID readers, wherein the second position is distributed across the entire physical space in a second pattern having an inter-reader spacing of the plurality of RFID readers that is smaller than the inter-reader spacing of the RFID readers in the first pattern; calculating a second plurality of peak RF power levels at a plurality of positions of interest within the physical space, wherein the second plurality of peak RF power levels are based on the RF fields radiated by the plurality of RFID readers and the second position of the plurality of RFID readers; and determining that a second peak RF power level of the second plurality of peak RF power levels for the first position of interest or the second position of interest meets the link margin criterion for at least the first position of interest or the second position of interest of the plurality of positions of interest, wherein the first position of interest or the second position of interest isDetermining the position having the lowest peak RF power level of the second plurality of peak RF power levels, and outputting the second position as an intended position for installing a plurality of RFID readers in response to the second peak RF power level meeting a link margin criterion.

[0014] All combinations of the foregoing concepts and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent) are considered to be part of the subject matter of the invention disclosed herein. In particular, all combinations of the subject matter recited in the claims, which appear at the end of this disclosure, are considered to be part of the inventive subject matter disclosed herein. Terms used in any disclosure incorporated herein by reference and explicitly used herein as well shall be given a meaning that most closely matches the particular concepts disclosed herein.

Brief Description of the Drawings

[0015] Those skilled in the art will understand that the drawings are primarily for illustrative purposes and are not intended to limit the scope of the subject matter of the invention described herein. The drawings are not necessarily to scale, and in some instances, various aspects of the subject matter of the invention disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate understanding of different features. In the drawings, like reference characters generally mean like features (e.g., functionally similar and / or structurally similar components).

[0016]

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[0017] Overview of the RFID Environment FIG. 1 shows a multi-path RFID environment 100 in which there may be a dense group of passive RFID tags 101 and a plurality of RFID readers 150, also called RFID tag readers, tag readers, or sensors, for communicating face-to-face with all of the RFID tags 101 within the environment 100. The RFID tags 101 can be attached to objects that can be identified and tracked by the RFID tags. The RFID environment 100 can be, for example, within a retail store or a warehouse, although other settings are possible. There may be furnishings 120 within the environment that affect the RF signal (e.g., block, attenuate, and / or scatter the RF signal). The furnishings can include shelves, racks, cabinets, etc. that can be used to hold objects to which at least some of the RFID tags are attached. For example, some furnishings 120 may include metal shelves that hold one or more retail items (not shown in FIG. 1) tagged with RFID tags 101. The furnishings can be arranged in rows in some settings, and aisles separate the rows to allow access to all objects tagged with RFID tags. The RFID environment 100 can be surrounded by walls 110, 112, a ceiling, and a floor, all of which can reflect RF signals from the RFID readers 150 and / or the RFID tags 101. There may be one or more cameras 130 attached to the RFID environment to capture at least a partial image of the environment. The cameras can be communicatively connected to a central controller 140, also called a controller or apparatus that can receive and process images from the cameras 130.

[0018] The RFID reader 150 is preferably installed in the RFID environment 100 so as to be able to communicate with all the RFID tags 101 in the RFID environment 100 in a lump. The RFID reader 150 may communicate with each other and / or with the central controller 140 via one or more Ethernet switches (not shown), and this may also supply power from the central controller 140 to the RFID reader. The central controller 140 may be a computer, laptop, smartphone, or dedicated device having a processor and a non-volatile computer-readable memory adapted to communicate with the RFID reader 150 and issue commands recognizable by the RFID reader 150. The central controller 140 may also receive signals from the RFID reader. For example, the central controller 140 may issue commands to inventory all the RFID tags (and attached items) in the RFID environment 100 or to determine the location of one or more RFID tags 101 (and attached items) within the RFID environment. In response to the commands, the central controller 140 may receive signals from the RFID reader 150 that identifies the RFID tags (and / or attached objects) in the environment 100 and / or may be used to determine the location of the tags and / or attached objects.

[0019] The inventors have recognized and understood that determining the position of the RFID reader 150 prior to their installation presents several challenges. In order to communicate with all of the RFID tags in the environment 100, the RFID reader 150 should be positioned such that each tag can provide a response that is detectable by at least one of the RFID readers 150. Positioning the RFID reader 150 too far away can result in insufficient power at some tag locations, and loss of communication with some of the RFID tags 101 within the environment 100, which are undesirable outcomes. Positioning the RFID reader 150 too close can result in unnecessary RFID readers 150 and associated installation costs. Additionally, physical obstacles at the installation location (e.g., lighting, fire sprinklers, smoke alarms, HVAC vents, etc.) can limit the available locations where the RFID reader 150 can be installed. To assist in the placement of the RFID reader 150 in the RFID environment 100, the inventors have developed a system and process for determining the intended position of the RFID reader 150 prior to installation.

[0020] FIG. 1 also shows the origin and the x and y axes (lower left) of the RFID environmental coordinate system of the RFID tag 101 within the environment 100. In addition to communicating with the RFID tag 101, the RFID reader 150 and the instrument 140 can also find the RFID tag 101 based on the response of the tag. For example, the RFID reader 150 and / or the instrument 140 can estimate or determine the angle of arrival, the received signal strength, and / or the channel of a signal from a given RFID tag 101, and use one or more of those metrics to estimate the position of the RFID tag relative to the RFID reader 150 that received the signal. If the coordinates of the position of the RFID reader within the coordinates are known, the instrument 140 or the reader 150 can convert these relative tag position estimates to absolute tag position estimates, i.e., tag position estimates given in the coordinates of the RFID environmental coordinate system. For example, the instrument 140 can overlay the coordinates of the estimated position of the tag on an app on a smartphone, tablet, or other device showing the estimated position of the tag on a map, or supply them relative to an image of the installation location, or relative to a wall, doorway, or other reference point. By providing absolute coordinates or positions relative to a known fixed origin rather than relative to a given reader, it becomes easier to confirm or average tag position estimates derived from measurements by different sensors and to find the tag and the corresponding object.

[0021] RFID reader / sensor The RFID tag reader 150 can be used in retail stores, warehouses, supply rooms, libraries, museums, galleries or other environments for tracking objects with RFID tags. Generally, the reader 150 is mounted or suspended from the ceiling, for example, at a height in the range of 8 to 20 feet from the floor, so that they send interrogation signals downward towards the RFID tags on shelves, tables, clothing racks, or other storage units. The RFID reader 150 is arranged to provide adequate coverage of the RFID environment 100 on a grid having intervals selected so that it can interrogate tags in all or substantially all of the volume of the RFID environment 100. The RFID tag readers may be arranged in a regular (periodic) pattern or may be distributed irregularly throughout the RFID environment.

[0022] Figures 2A and 2B depict an example of an RFID reader 150 comprising a phased antenna array having four antenna elements 205. The view of Figure 2A is a perspective view from the bottom of the reader 150. The reader 150 also includes a ground plane 220 inside an enclosure 280 that extends across the antenna elements 205 and behind the antenna elements 205 with respect to the radiation direction of the RF beam from the reader. Figure 2A also shows the pitch, roll, and yaw axes of the reader.

[0023] The reader 150 can be mounted or suspended from the ceiling or other structure. The enclosure 280 is generally disk-shaped and can be made of acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), vinyl, or another suitable material that is substantially transparent at the frequencies of the interrogation signal and the response. The enclosure 280 may include a thinner section 282 on the opposite side of the antenna elements 205. These thinner sections 282 can be made less than 1 / 8 inch thick so as to transmit the in-band RF energy between them and the antenna elements 205 without significant attenuation of the transmitted RF energy.

[0024] Figures 2C and 2D illustrate two techniques for attaching the RFID reader 150 to a drop ceiling. A drop ceiling, also referred to as a dropped ceiling, a T-bar ceiling, or a suspended ceiling, is a secondary ceiling suspended from a main ceiling or other overhead structure. Drop ceilings are very common in retail and office environments. A drop ceiling typically has a suspension grid 230 suspended from a main ceiling or overhead structure and defining square and / or rectangular openings or cells. The suspension grid can be made of metal or plastic and is configured to hold ceiling tiles. In the United States and Canada, these openings are typically 24 inches by 24 inches (610 mm by 610 mm) or 24 inches by 48 inches (610 mm by 1220 mm) and accommodate ceiling tiles and lighting fixtures. In some cases, fluorescent lights are the same size as those that fit within the grid. In Europe, the grid opening sizes are typically 600 mm by 600 mm or 600 mm by 1200 mm. Ceiling tiles and fixtures may be slightly (5 mm) smaller than the grid opening size (e.g., 595 mm by 595 mm or 595 mm by 1195 mm, 5 mm smaller in Europe).

[0025] The antenna element 205 can be attached within the opening, above the opening, or below the opening of the suspension grid 230 of the suspended ceiling. In FIG. 2C, the leader 150 is housed within a box 240 that fits within the opening and is held in place by the suspension grid 230. The antenna element 205 may be at approximately the same height as the grid 230, and the ground plane 220 may be located above the grid 230. In some cases, an aesthetic panel 232 can be used to cover all or part of the RFID reader 150 and the opening of the grid 230. The aesthetic panel 232 can be made of plastic such as ABS, PVC, vinyl, or mixtures thereof, and can be made thin to slightly attenuate RF signals to and from the antenna element 205.

[0026] An alternative mounting arrangement is shown in FIG. 2D, where the RFID reader 150 is mounted so as to extend below the grid 230. Such a mounting arrangement may be used when the suspension grid 230 contains metal that can interfere with RF signals to and from the antenna element 205. In either mounting arrangement, the box 240 can house and / or connect to other components such as the adjustable mount 210 shown in FIG. 2E, as well as Ethernet cables, power cables, etc. for communicating with other readers 150 and the central controller 140.

[0027] One way to assist in the alignment of the RFID reader 150 is to attach them using an adjustable mount 210, as shown in FIG. 2E. The adjustable mount may be attached to the ceiling, to a box 240 as in FIGS. 2C or 2D, or to other overhead structures 250, and the RFID reader 150 can be attached to the adjustable mount 210. The adjustable mount can provide three or more degrees of freedom (e.g., three rotational degrees of freedom and one mechanical (vertical) degree of freedom) to adjust the position and / or orientation of the RFID reader 150. In some implementations, the adjustable mount can be used to adjust the pitch, yaw, and roll of the RFID reader about the axes of rotation shown in FIG. 2A. The extent of these adjustments can level the RFID reader (e.g., with respect to the floor of the RFID environment) and align it with the x, y, z coordinate system of the RFID environment 100 (e.g., as shown in FIG. 1). The adjustable mount 210 can also be used to raise and lower the reader 150 and, if possible, translate it in a plane parallel to the floor or ceiling.

[0028] Placement and Installation of RFID Readers at the Installation Site FIG. 3A shows a process 350 for placing the RFID reader 150 at an installation site such as a retail store, warehouse, office, library, medical facility, or other site that stores or houses RFID tags. The process 350 is generally performed in five stages or phases: (1) site survey and design, (2) installation preparation, (3) installation, (4) testing, and (5) commissioning. These phases are typically performed sequentially, with some tasks occurring at the installation site and other tasks occurring at the installation site or elsewhere.

[0029] The configuration begins, as part of the site survey and design phase, by acquiring an initial LIDAR scan (step 352) and an image (step 354) of the installation location, using a portable LIDAR scanner and a camera, respectively. These representations should show the ceiling, walls, floor, and fixtures in sufficient detail and with a sufficiently fine spatial resolution (e.g., 6 inches, 3 inches, 1 inch, or finer) to identify and locate vents, sprinkler heads, and other potential obstacles on the ceiling, walls, and floor. The LIDAR scan and image can be uploaded to a server, or a distributed collection of servers that host software and infrastructure and are accessible via the Internet or another suitable computer network, such that they can be accessed off-site. (Such a distributed server collection is typically referred to as the cloud.) Optionally, the LIDAR scan and / or image can be annotated with information regarding, for example, physical obstacles and / or installation issues.

[0030] Next, optionally, after the LIDAR scan is properly aligned or otherwise verified, information about the installation location is extracted from the LIDAR scan and the image (procedure 356) for use in generating a map or plan of the location where the sensor is to be installed. In particular, a person using a properly programmed computer can extract, for example, in the form of a computer-aided design (CAD) line drawing (e.g., a.dxf file), the walls, doorways, and / or other aspects of the floor plan or other representation of the installation location from the LIDAR scan. This user can also create an image or map of the ceiling, such as those in FIGS. 3B and 3C, based on the LIDAR scan indicating the ceiling height (distance from the floor). The ceiling image can be shaded or colored to indicate the ceiling height along a regular grid, for example, with an interval between adjacent grid points of about 0.25 meters, along a square, triangular, or hexagonal grid along the ceiling. The ceiling image is used to adjust the planned position of the sensor, as described below. The user also creates a fixture image from the installation location image for use in specifying different zones and determining the coordinates of those zones. Optionally, the user can upload the floor plan, ceiling image, and fixture image to the cloud.

[0031] Uploading a floor plan, a ceiling image, and a fixture image to the server triggers the generation of zone coordinate artifacts or zone layouts that include boxes and labels for each zone (procedure 358), including both customers and RFID / Stateful Inventory (SI) zones. Typical stateful inventory zones include checkout, transition, and warehouse zones, and customer zones can include or have other uses such as, for example, men's dressing rooms, clearance items. For details of SI, see, for example, International Application PCT / US2023 / 061645 titled "Stateful Inventory for Monitoring RFID Tags" (incorporated herein by reference in its entirety for all purposes). Boxes and labels can be used to visualize zones (e.g., on a map or image) and to associate estimated tag positions and other positions with different zones. The zone coordinate artifacts are saved for use in adjusting sensor positions and providing appliances and sensors, as described below.

[0032] When the floor plan is posted to the cloud, it can trigger the automatic generation of an initial installation map of possible sensor positions (procedure 360) by a server or another processor that executes instructions stored in non-volatile computer memory. This installation map provides the absolute dimensions of sensor positions, including stateful inventory sensors that cover stateful inventory zones (e.g., entrances) at the installation location. The sensor positions can be overlaid on an initial LIDAR scan and used to create both an appliance configuration file (such as a JSON file) and a model of the installation location (such as in glTF file format) that represents the installed sensors, walls, rooms, zones, and zone labels at the installation location.

[0033] The setup map can be generated from a floor plan, a ceiling image, zone coordinate artifacts, and models of the RFID reader's antenna pattern, range / coverage range, or coverage volume. For example, the antenna pattern can be a cone with a 60-degree apex angle or a square pyramid with a curved profile (e.g., as described in FIGS. 5A - 5F shown below). This initial setup map can be calculated according to a common approach where sensors are placed on a regular grid overlaid on the ceiling representation. The grid can have an inter-sensor spacing along the ceiling that depends on the sensor height, the sensor's coverage volume, range, antenna pattern, and the desired overlap of the coverage volume or antenna pattern from adjacent sensors at a particular height (e.g., about 1 meter above the floor). Optionally, the spacing between sensors can be scaled (e.g., made shorter or longer) by applying an appropriate tag sensitivity scaling factor, which is the farthest horizontal distance at which a sensor can activate a tag (e.g., the distance measured along the floor or ceiling from the sensor position to the tag position), to the coverage volume or sensor range.

[0034] Next, the user can adjust the sensor positions within the initial installation map to resolve potential coverage issues and / or interference with other objects (procedure 362). For example, the user can identify and eliminate invalid sensor positions, such as positions that are too low (e.g., less than 3 meters in height) or too close to fixtures, sprinklers, pipes, HVAC ducts, vents, or other obstacles. The user can also adjust sensor positions for aesthetic reasons and / or provide desired coverage in areas or zones with high or low traffic. For example, the user can add or remove sensors, or change the sensor spacing / sensor density in zones where tags are expected to be more or less densely, moved, and / or queried frequently. The user can make these changes to provide the desired overlap between the coverage volumes / antenna patterns of adjacent sensors, ensure that the number of sensors per square foot of ceiling is above or below a predetermined threshold, and / or reveal undesirable tag orientations or positions.

[0035] When the user finishes adjusting the sensor positions, the adjusted sensor positions are maintained within the finalized installation map (procedure 364). The user can add reference points with dimensions near each sensor to help the installer more easily find each sensor position during installation. Suitable reference points include, but are not limited to, easily distinguishable objects or features such as ventilation holes, sprinkler heads, lights, exit signs, entrances and exits. As another method, or additionally, reference points can be automatically generated or selected. For example, what can be automatically selected can include the wall closest to the desired sensor position. The wall selected for use as a reference point may have a normal vector offset by at least 60 degrees in the x and y directions of the installation location to provide sufficient dimensions. The installer can use the finalized installation map, along with information about the electrical circuit (e.g., amperage) at the installation location, to generate a parts list for the installation hardware as part of the installation preparation.

[0036] While continuing with the installation preparation, the installer collects information about each sensor intended for installation at the installation location, including the model number, serial number, and media access control (MAC) address, for example, by a scan bar code or quick response (QR) code on the sensor or its package. This metadata is uploaded to a server, which uses it to determine the Internet Protocol (IP) address of the Power-over-Ethernet (PoE) switch used to connect the appliance / controller to the sensors installed at the installation location. The switch can be configured manually or automatically.

[0037] The technician or installer uses a Progressive Web App (PWA) to obtain the certificate of the controller and provides this certificate to the server that stores the sensor installation information (procedure 366). If the controller is connected to the LAN at the installation location, the controller is automatically connected to the server and fully provided. During this stage of the provision, the controller downloads a new image from the cloud and restarts with that image. The controller also downloads configuration data from the server, including the sensor serial number, MAC address, configuration file (e.g., JSON configuration file), and the final installation map with sensors assigned to locations by serial number and / or MAC address. The controller also activates an RFID MAC schedule generator that generates three schedules for the sensors to follow when transmitting and receiving signals for (1) the sensor test operation schedule, (2) the coverage test operation schedule, and (3) the normal day / night operation schedule. The first two schedules are used for testing (described below in procedure 378), and the third schedule is used after the trial operation (procedure 380).

[0038] Installation preparation may also include providing one or more RFID test tags (procedure 368) for testing and commissioning the installed appliances and sensors. These RFID test tags, also called cards, facilitate arranging sensors in parallel at several installation locations at once. Each set or kit of RFID tags can have a unique kit number and can include several RFID test tags (e.g., 10, 25, 50, 75, 100 tags, or a number around that, or one RFID test tag per sensor).

[0039] Each RFID test tag is a passive RFID test tag that stores the corresponding set or kit number and a unique EPC. The kit number is useful for sorting RFID test tags from different kits, and the EPC helps installers or testers place a specific RFID test tag at a specific location within the installation site. Kits can be provided by uploading a file containing the EPC and the corresponding card numbers to a server.

[0040] At this point, the sensors, appliances, and switches can be installed at the installation site (step 370). The appliances, switches, and optional patch panels can be installed in a rack within a closet or other back-of-house space. Once the appliance is connected to the LAN, the provisioning is completed by downloading the image from the server as described above. The installer places the sensors in the store according to the finalized installation map and matches the serial numbers of the sensors to the annotated locations on the finalized installation map. The installer attaches the sensors at those locations to ensure that each sensor is set to the desired height, pitch, and roll (pitch and roll are perpendicular to each other and are rotations about axes parallel to the ceiling / floor). The mounting brackets can enable the installer to adjust the height, pitch, and / or roll of the sensor so that it fits within the desired tolerances, for example, up to a pitch angle and roll angle of 0.0° ± 0.25°. Deviations from the desired pitch and roll angles can reduce sensor performance, especially for sensors installed above the floor.

[0041] The installer can connect the sensors to the switches with Ethernet cables or other connectors that provide both power and network connectivity (e.g., PoE connections). Alternatively, the sensors can be connected wirelessly (e.g., via a WiFi connection) to the appliances and powered by a separate power source or connection.

[0042] Once the sensor is installed, the installer performs a post-installation LIDAR scan (step 372) of the installation location and takes a photo of the installed sensor (step 374). The post-installation LIDAR scan provides the actual (absolute) position of the installed sensor. Ideally, the actual position should match the desired position specified by the final installation map. However, in practice, the actual position may deviate from the desired position due to, for example, obstacles that could not be predicted during the site survey and design, installation difficulties, inaccuracies in the installation map or site survey data (e.g., images or LIDAR scans), or installation errors. Since each sensor positions an RFID tag relative to itself, knowing the actual position of each sensor enables the relative RFID tag position measurements of the sensors to be accurately and precisely transformed, for example, onto an absolute coordinate system having an origin at one corner of the installation location.

[0043] The image of the installed sensor provides evidence of proper installation and shows the orientation of the sensors relative to each other. In particular, the image shows the yaw, or rotation about an axis perpendicular to the floor / ceiling, of the sensor, as indicated, for example, by a clocking mark or other reference mark (e.g., logo) on the outer housing of each sensor. The yaw mark or clocking mark indicates the yaw or rotational orientation of the sensor's antenna array for use in transforming the relative angle of arrival determined by that sensor into the absolute coordinate system.

[0044] The post-installation LIDAR scan and image are uploaded to a server and can be used to determine the position and yaw angle of each sensor within the absolute coordinate system of the installation location (step 376). This information can be used to update the configuration files of the sensors and / or instruments, which are updated and exported to the sensors and / or instruments by the server.

[0045] As described above, each sensor can be assigned and installed at a specific location, for example, by the serial number of the sensor. This can be easily done when attaching a small number of RFID readers to a small space, but when attaching many sensors to a large space, it may take time to match the serial number of each reader to a specific installation location. Alternatively, the position of the RFID reader can be discovered after installation. For example, the controller 140 can instruct one of the RFID readers 150b (which may have a unique network address) to emit a signal for other RFID readers to detect. The relative position of the emitting reader 150b can be determined based on, for example, the received signal strength, signature, and / or angle of arrival of the signal detected by other RFID readers. Once the relative positions and identities of all the readers in the RFID environment 100 are determined, the installation positions (which may be output by process 200) can be mapped to each RFID reader 150 in the RFID environment 100.

[0046] The installed sensors can be tested to ensure that they are functioning properly (procedure 378) before being used to locate and interrogate RFID tags at unknown locations in the installation site. For example, the installer can place cards from an RFID test tag kit throughout the store (e.g., card #1 is directly below sensor #1, card #2 is directly below sensor #2, etc.). With the cards in their predetermined positions, the sensors read the cards according to a sensor test operation schedule, transfer the measurements to the instrument, which processes the data as needed and transfers the results to the server. The server uses the data to determine whether the sensors passed the test. If the results indicate that all cards are located below the corresponding sensors, the sensors and the instrument pass the test.

[0047] The sensor can also be tested to ensure it provides the desired / intended coverage of the installation location. To test the coverage, the installer places it around the installation location, for example, on a fixture or table and in areas where RF coverage is suspect. The sensor attempts to read all cards according to the coverage test operation schedule without necessarily estimating the position of the cards. If other RFID tags are present, the sensor may filter or query responses from the cards. The sensor passes the coverage test if it can read a preselected number or percentage (e.g., 90%, 95%, or 99%) of the cards. The installer can also test the power connection, durability, network connection, and the ability to connect a mobile device to the controller via an app.

[0048] As a final test, the sensor can start tracking and determining the location of unknown RFID tags entering, exiting, and / or moving within the installation location, for example, according to the normal day / night operation schedule. The sensor's measurements can be compared to RFID tag measurements collected with a handheld RFID scanner over several hours, days, or weeks. If the sensor's measurements match the measurements collected with the handheld RFID scanner (e.g., within a specific percentage or threshold), the sensor is test-run (procedure 380) and put into service.

[0049] Determination of the Installation Location of the RFID Reader There are several issues related to the selection of the location of RFID reader 150 within RFID environment 100. Ideally, RFID reader 150 should be laid out such that each possible location of RFID tag 101 within RFID environment 100 can be read and positioned by one or more RFID readers 150. This desire for complete and reliable coverage implies a denser layout of RFID readers 150. At the same time, RFID readers 150 should be placed fewer in number in locations that are easily accessible in order to reduce or minimize the overall system cost and installation cost. Further, for example, in order to compensate for the movement or reorientation of fixture 120 or other obstacles within RFID environment 100, it should not be necessary to move RFID reader 150 after it is installed. Moving one RFID reader 150 can interrupt system operation, incur additional costs, and potentially lead to the need to move other RFID readers 150.

[0050] With these issues in mind, there are several strategies for selecting the locations of RFID readers 150 and installing the RFID readers 150 at those locations. In a common approach, for example, the RFID readers 150 are arranged in a grid (e.g., a square or hexagonal grid) at intervals determined based on their mounting heights, their ranges / coverage volumes, and the desired overlap at a given height between adjacent RFID readers 150. The grid spacing / sensor density can be adjusted based on the expected tag density and / or the expected usage for a portion of the RFID environment 100. For example, the sensors may be grouped closer together above the sales floor, entrances, and / or exits, and may be spaced further apart in a warehouse or loading area. The common approach generally provides good overall coverage across the space, can be easily automated, and typically involves less manual inspection. Generally, it is not affected by the movement or rearrangement of fixtures, but if the sensor density is too low, there may be areas with missing coverage, or if the sensor density is too high, it may be expensive to install.

[0051] In a targeted approach, the position of the RFID reader 150 is customized based on, for example, the expected use and / or tag density, based on the physical layout of the RFID environment 100 and / or the desired coverage of a particular area or zone of the RFID environment 100. A targeted sensor layout can include sensors grouped closer together in zones with more sensors / higher tag density, as well as sensors directly above specific locations, such as POS, entrances, or exits. Targeted layouts often provide better sensor coverage in difficult areas (e.g., zones with high tag traffic or zones with irregular shapes) and tend not to have too many or too few sensors for the desired coverage. On the other hand, targeted layouts tend to take more time to generate (it is more difficult to generate them automatically) and involve more verification of sensor placement. Also, they tend to be susceptible to changes in RFID system performance due to changes in fixture positions and / or the spatial distribution of tags within the RFID environment 100.

[0052] A targeted approach for determining or selecting the position of an RFID reader tends to work well in an RFID environment using fixed or static fixtures (i.e., fixtures that do not move or do not move very frequently). Using information about the size, position, and orientation of static fixtures, the automatic sensor placement process can consider the static fixtures when determining possible sensor positions. The size, position, and orientation information of static fixtures can be determined from sufficiently detailed architectural drawings or floor plans, or from measurements of the RFID environment. If the fixtures are attached or fixed to walls, floors, or ceilings, their positions can be estimated or derived from architectural drawings or floor plans.

[0053] A hybrid approach to determining the appropriate RFID reader positions within an RFID environment incorporates elements of both general and targeted approaches. The targeted approach may be employed in specific zones such as exits, checkouts, receipts, shipments, and / or warehouse areas, as well as other zones having strict guidelines for sensor placement. Even with a targeted approach, the sensor positions can be automatically determined for zones having strict guidelines for sensor placement. A general approach (e.g., selection of a predetermined grid, two-dimensional array, or other geometric pattern of sensor positions) may be applied to the sales floor / front-of-house zone, or to a warehouse or other RFID environment.

[0054] Antenna Pattern and Coverage Volume of an RFID Reader The coverage volume of an RFID reader affects how close the RFID readers should be to each other in order to read all of the RFID tags within the RFID environment. The coverage volume, also called the coverage pattern, is the volume within which the RFID reader can reliably activate passive RFID tags. In other words, an RFID sensor can reliably activate passive RFID tags within its coverage volume, but may not be able to reliably activate passive RFID tags outside of its coverage volume. In practice, for example, due to attenuation or scattering by other objects (multipath) within the coverage volume, or coupling between RFID tags, there may be RFID tags that cannot be activated even within the coverage volume. For this reason, it may be more convenient to define the coverage volume of a sensor as the locus of points or positions at which the sensor can deliver or project a certain amount of RF power (e.g., the activation threshold power of a passive RFID tag plus some margin to account for multipath or unfavorable tag orientation).

[0055] The range of an RFID sensor depends on its transmission power, the amount of power required to turn on a passive RFID tag, and especially attenuation. Generally, the maximum transmission power is adjusted, and the minimum amount of power required to turn on a passive RFID tag depends on the RFID tag, its orientation, and its proximity to other RFID tags or metallic objects. Attenuation can vary according to distance, scattering, etc. If desired, the range can be scaled by a sensitivity factor or buffered by a link margin, as described below with respect to FIG. 9.

[0056] The range also depends on the antenna of the RFID reader. Most RFID readers have a directional antenna, i.e., an antenna that preferentially radiates and receives RF waves in several directions. This direction selectivity can be characterized by a radiation pattern, also called an antenna pattern or far-field pattern, which represents the angular dependence of the intensity of the RF waves radiated by the antenna. Reciprocity ensures that the sensitivity of the antenna to incoming signals as a function of direction, also called its reception pattern, is identical to its radiation pattern. This direction dependence means that an RFID reader with a directional antenna has a range that can vary with direction / angle. The shape of the sensor coverage volume depends on the range and radiation pattern of the RFID reader's antenna (array). Generally, the coverage volume should be or be similar to the antenna pattern cut off at a distance from the sensor / antenna equal to the range.

[0057] The antenna pattern of the reader 150 can be determined empirically or from the specifications provided for the RFID reader 150. In some cases, the radiation pattern can be determined primarily based on the antenna configuration of the reader and how it operates (e.g., whether the antenna includes an array of antennas and whether they are used to generate a stationary radiation pattern or a swept beam). In some implementations, the RFID reader 150 can have a phased array antenna that enables beamforming and steering.

[0058] FIG. 4A shows an RF beam 410 radiated by an RFID reader 150 mounted on a ceiling and directed in several directions. In this example, the beam is directed in five different directions in a series of emissions. The five different directions are the -z direction (an inclination angle of 0 degrees -90 and azimuth angle), and four directions having inclination angles of 45-45 degrees, 135 degrees, 225 degrees, and 315 degrees, which are linear. The inclination angle is measured with respect to the x-y plane, and the azimuth angle is measured from the x-axis of the x-y plane. Other implementations of process 200 can use other radiation directions and a greater or lesser number of emissions.

[0059] FIGS. 4B and 4C are simulations of sensor performance as a function of height and the number of effective beam steering sectors. FIG. 4B is a plot of sensor reach versus the height at which the sensor is mounted for four and eight effective beam steering sectors (lower trace and upper trace, respectively). The additional beam steering sectors are at higher altitudes. FIG. 4B shows that the range is affected by the sensor height, as well as the number and elevation of the beam steering sectors. FIG. 4C is a plot of the sensor reach scale value versus the difference in amplitude of the detected tag responses for sensors having four or eight effective beam steering sectors (steeper trace and shallower trace, respectively). Again, the additional beam steering sectors are at higher altitudes.

[0060] Automatic Sensor Placement Figures 5A - 5F show diagrams of an automatic sensor placement process that can be used to generate a sensor installation map (steps 360, 362, and 364 of FIG. 3A). Automatic sensor placement is a hybrid or targeted approach that, depending on its implementation, uses inputs related to the physical and logical zone layout of an installation location (e.g., LIDAR scans, images, and / or floor plans) to identify a sensor placement that maximizes system performance while minimizing the number of sensors. Sensors installed according to the installation map or sensor layout generated by this automatic sensor process should be able to read and position at least 99% of the RFID tags at the installation location.

[0061] Figures 5A - 5D show a model of the coverage volume of an RFID reader 150 having a four - element square antenna array. The model has a pyramidal - like shape with a curved contour. This represents how much power is delivered to different xyz positions as a function of transmit power, antenna gain, and path loss (attenuation) when the sensor is mounted on the ceiling. If desired, a margin level can be applied to the coverage volume to account for tag antenna characteristics, multipath, and / or other non - idealities.

[0062] FIG. 5A shows a cross-section of the coverage volume surrounding a square and an irregular hexagon. The square cross-section is a reasonable approximation of the coverage area at a given distance from the antenna array / floor height. Both the square and the hexagon are convenient shapes for tiling a two-dimensional surface (e.g., the floor or a plane parallel to and above the floor). FIG. 5B shows a side view of the antenna pattern projected onto the floor and the shelf. The reach or distance to the most distant detectable RFID tag position from sensor 150 decreases at a shallower elevation angle and directly below sensor 150. As shown in the figure of FIG. 5B, the floor and the shelf attenuate or block the signal, reducing the sensor reach. From this geometry, the horizontal reach of the sensor can be calculated as given by the difference between the target reading area (estimated tag height) of the sensor and the height of the sensor, as shown in FIGS. 5C and 5D.

[0063] By modeling the coverage volume encompassed by the antenna pattern to have a curved contour with the square cross-sections shown in FIGS. 5A - 5D, the solution for the sensor layout is simplified and the sensors can be placed on a square grid or array with a pitch or spacing determined by the desired overlap between adjacent antenna patterns / coverage volumes. For sensor 150 in the middle of a store or other relatively open space, the sensor spacing may be selected such that the sensor reach is equal to half the spacing between adjacent sensors 150. The square cross-section estimation / approximation also means that the sensor reach can be calculated from a single input, namely the difference between the sensor height and the fixture height.

[0064] The automatic sensor placement process also takes in information about the installation location as input. This information can include information about fixtures, such as the number, shape, size, placement, and whether they are reconfigured regularly or frequently. This information can also include the expected height of tags on the floor. When determining coverage, the automatic sensor placement process takes these heights into account and positions the sensors so that tags within a given height of the floor receive sufficient power (power with margins applied for multipath and tag orientation) to be activated.

[0065] If the installation location is a retail store, for example, there may typically be tables and racks that are usually about 1 meter or less and can be rearranged regularly, and shelves fixed to the wall that are about 2 meters or less. In this example, therefore, the sensors should be placed such that the coverage volume or antenna pattern intersects or overlaps at a minimum height of 1 meter and intersects the wall at a minimum height of 2 meters. Other installation locations may have fixed fixtures and / or antenna patterns that overlap at other heights (e.g., 50 cm, 75 cm, 1.25 m, 1.5 m, etc.) and / or intersect the wall at other heights (e.g., 1.5 m, 1.75 m, 2.25 m, 2.5 m, etc.). Additionally, the overlap of the antenna patterns and the wall intersection heights may vary in different rooms or different areas across the installation location, for example, depending on the fixtures and the floor plan. In practice, the automatic sensor placement can process the desired overlap and wall intersection heights as minimum heights and position the sensors such that their coverage patterns overlap and / or intersect the wall above the desired overlap and wall intersection heights.

[0066] FIG. 6A shows a floor plan derived from a LIDAR scan of an exemplary installation location (e.g., steps 352, 354, and 356 of FIG. 3A). This floor plan shows walls, support columns / posts, and doorways. This can be divided into zones and overlaid in absolute (location-specific) coordinates having an origin fixed at one corner of the store, for example. This coordinate system is the coordinate system used to indicate the location of RFID tags located by the sensor.

[0067] FIG. 6B shows a shadowed image of the ceiling derived from a LIDAR scan of an exemplary installation location (e.g., steps 352, 354, and 356 of FIG. 3A). The shadowing indicates changes in ceiling height.

[0068] FIG. 6C shows a shadowed floor plan showing different zones. These zones can be manually identified and labeled using a properly programmed computer, tablet, or smartphone (step 358 of FIG. 3A). Each zone can correspond to a different room or different section of a larger space. In the case of a retail store, the zone coordinate artifact can indicate whether the zone is front of house (FOH) or back of house (BOH), as well as the shape, size, and location of the zone. Zones specialized for a particular sensor placement or a stateful inventory can include exits, packing areas, holding areas, cash wraps, and incoming shipments.

[0069] The zone coordinate artifact can be exported in JSON format for use in an automated sensor placement. The JSON file can include the coordinates of these zones, as well as metadata related to the zone name, type, and desired sensor placement. The zone coordinate artifact can be used for both automated sensor placement and the creation of a three-dimensional (3D) model of the installation location. Some of the data included in the zone layout is not utilized for sensor placement, such as zone names and labels.

[0070] Automatic sensor placement uses zone coordinates or zone coordinate artifacts within a zone layout to identify areas within an installation location where sensors are to be placed. Generally, sensors are placed only in zoned locations. Sensors may be omitted from some zones such as office zones or information technology zones. Sensors in stateful inventory zones such as exits, registers, transition areas, and receipts may be placed in highly specialized locations such as above each entrance or register.

[0071] As shown in FIGS. 5A - 5D, a pyramid - like antenna pattern / coverage model increases the coverage volume as the height of the sensor increases. Thus, placing sensors at the highest possible positions serves to increase or maximize the coverage volume of each sensor and potentially enables providing the desired coverage using fewer sensors. With this in mind, automatic sensor placement includes the analysis of a color - coded ceiling image or other representations of the ceiling height for identifying the ceiling and obstacle heights. The ceiling image or other representation can be divided into a grid (e.g., a square grid with a 0.25 m grid spacing) that indicates the maximum height of the sensor for each grid square, and the grid spacing is based on the ceiling height as well as the size and shape of the sensor's coverage volume. A higher ceiling, for example, may allow sensors to be placed further apart, so a larger grid spacing may be used. Since the ceiling height can vary for a given installation location, the grid spacing can also vary, having a shorter spacing for lower ceiling heights and a longer spacing for higher ceiling heights. The maximum sensor height for each grid square is lower than the lowest point of the ceiling directly above it, and nearby ceiling obstacles need to be taken into account.

[0072] FIG. 7A illustrates an obstacle 700 of a sensor 150 mounted on a ceiling having the antenna patterns of FIGS. 5A-5D. Considering the antenna pattern, there should be a clearance angle of at least 30 degrees between the bottom of the obstacle 700 and the horizontal plane (ceiling or floor) for a satisfactory sensor placement.

[0073] Once the maximum sensor height is identified for each grid square on the ceiling, sensor positions that are too low, blocked, or otherwise inappropriate are excluded. In particular, positions that are below a desired minimum height (e.g., 3 m) or directly under small obstacles such as light fixtures, sprinkler heads, or HVAC vents are excluded from consideration. These inappropriate positions may be identified by a large difference between the local height and the surrounding ceiling height. FIG. 7B shows the floor plan of FIG. 6A shaded to indicate the altitude or height of the effective (appropriate) positions of the sensors (the unshaded areas are inappropriate).

[0074] FIGS. 8A-8J show how the desired positions for the sensors are selected in an automatic sensor placement from the effective or appropriate positions for the sensors in FIG. 7B. The automatic sensor placement typically functions room by room through the following steps. If the installed RFID system operates according to a stateful inventory process, the sensors can be placed in the designated stateful inventory zones. Stateful inventory is a process that supports the retail operations and inventory accuracy of the RFID system. For details of stateful inventory, see International Application No. PCT / US2023 / 061645, filed on January 31, 2023, entitled "Stateful Inventory for Monitoring RFID Tags". This is hereby incorporated by reference in its entirety for all purposes.

[0075] Typical stateful inventory zones include exits, checkouts, and receipts. Each of these areas or zones should have specially placed sensors, such as an exit sensor in front of the entrance / exit, or a receipt sensor in the center of the receipt area. Stateful inventory zones are identified by zone coordinate artifacts before automatic sensor placement. Determining the sensor positions in the stateful inventory zones first can avoid duplication of unnecessary sensors and ensure that the stateful inventory zones can obtain an optimal sensor placement.

[0076] When sensor positions are found in the stateful inventory zones, sensor positions near the corners are selected. There are many possible sensor configurations across the open section of the room, and each corner of the room can be optimally covered by a corresponding sensor with an antenna pattern that has an approximately square cross-section as shown in Figure 8A. Using the sensor height from the ceiling map (Figure 7B), the sensor coverage model (Figures 5A - 5D), and the assumption or target that the antenna pattern of the sensor should intersect the wall at a predetermined height (e.g., 2 meters), it is possible to identify the position where the antenna pattern of the sensor placed at the highest possible height intersects the adjacent wall at the predetermined height. Figure 8B shows the ceiling height shaded and the possible positions of the sensors to cover the corners of the installation location.

[0077] Figures 8C and 8D show how the sensor positions around each room of the installation location are then found. Again, the sensors around the perimeter should be arranged such that their antenna patterns intersect at a (first) predetermined height on the wall and overlap with the adjacent antenna patterns at a (second, perhaps different) predetermined height (e.g., 1 meter). The first predetermined height can be the maximum height of a shelf or other fixture along the wall, the expected highest position of an RFID tag along the wall, and the second predetermined height can be, for example, the maximum height of a table, rack, or other fixture on the floor, the expected height of an RFID tag on the sales floor. In other words, each perimeter position is a position where the antenna pattern of the sensor will intersect one wall and one sensor. Unlike the corner placement, the perimeter placement step loops repeatedly until no new perimeter positions can be identified, resulting in the coverage map shown in Figure 8D in this example. At this point, the selected perimeter positions may not align perfectly around the installation location due to ceiling obstructions, height limitations, or excessive overlap, but gaps or excessive overlap between sensor patterns are addressed in subsequent steps of the automatic sensor placement process.

[0078] Once the corner and wall - along sensor positions are identified, as shown in Figures 8E and 8F, the sensors can be repeatedly placed inside the installation location (room). As described above, the sensors on the floor should overlap in coverage around the second predetermined height (e.g., 1 meter), allowing these sensors to be slightly spaced apart from the perimeter sensors. The repetition continues using the antenna pattern overlap criterion until no more (ideal) sensor positions can be found, even if there are still gaps in the sensor coverage.

[0079] Once the internal or floor sensor positions are determined, any gaps in sensor coverage can be filled by repeatedly adding sensor positions to fill the coverage gaps and shifting existing sensor positions to fill the coverage gaps. Iterating between these steps reduces or eliminates coverage gaps, spreads sensor coverage, and overlaps it more evenly. In the first iteration shown in Figure 8G, large coverage gaps are identified as areas for new sensor positions. The sensor positions are placed near the center of each gap, and the gaps are subdivided into multiple sections if they are too large to be covered by a single sensor. After this first iteration of adding sensor positions, some coverage gaps may still exist, and Figure 8H shows the circles around the gaps within the coverage. Figure 8H (right) also shows that shifting one or more sensor positions can reduce or eliminate these gaps. The shift takes into account nearby walls, uncovered gaps, and overlapping areas, and a small iterative shift to any sensor position increases the total area covered within the store. This part of the automatic sensor placement process continues until no additional coverage can be obtained by shifting the sensors. Since the final coverage gaps can be very small, adding new sensor positions to these areas can lead to concentrated areas of sensor overlap, which can result in uneven sensor coverage at the installation location. The final coverage shift distributes the sensor overlap more uniformly across the installation location, providing consistent coverage and a greater tolerance for performance or installation errors.

[0080] Figures 8I and 8J illustrate the final step of an automatic sensor placement that (purely) identifies and removes redundant sensor / sensor positions. A sensor position is redundant if the sensor installed at that position has an antenna pattern that completely overlaps with the antenna patterns of other sensors. This situation can occur through the gap filling and sensor shifting processes because a sensor added to fill a gap can shift other sensors, resulting in excessive overlap between antenna patterns / coverage volumes. If this situation occurs, the sensor with the minimum coverage volume or the lowest (in height) sensor can be removed from the sensor layout, and the layout can be adjusted as needed (e.g., some or all of the sensor positions can be shifted). The final sensor coordinates can be exported, for example, in JSON format, and if needed, for additional configuration, dedicated SI sensors are shown to the backend (step 364).

[0081] If time, memory, and processing power permit, the automatic sensor placement for a given installation location can be performed either simultaneously or sequentially using different input parameters, such as the overlap height of different antenna patterns or the spacing between sensor positions. By performing the automatic sensor placement with different inputs, a sensor layout with equal or similar coverage for installation locations with different numbers of sensors can be obtained. By using a range of inputs (e.g., different spacings between adjacent sensors) to generate multiple layouts for the installation location, then determining the coverage and number of sensors for each layer, and comparing these layouts with each other, it is possible to select the layout with the desired coverage and the lowest number of sensors.

[0082] Alternative methods for determining the installation position of RFID readers Figure 9 shows a process 900 for determining the RFID reader position in installation locations such as retail stores, warehouses, museums, art galleries, etc. Process 900 can be applied to general-purpose, target, and / or hybrid approaches and can be implemented at least in part by a processor adapted with code that models the antenna pattern of RID reader 150 or the radiation of the RF field from RFID reader 150. Process 900 may begin with receiving a floor plan or other representation of RFID environment 100 to which RFID reader 150 is attached, such as a LIDAR scan (step 902). The floor plan may include the dimensions of the floor space where RFID tags 101 are located and the ceiling height of the floor space. In some implementations, RFID reader 150 is essentially mounted at the ceiling level, but the reader may be suspended from the ceiling and mounted at a lower level, or mounted above the ceiling panel.

[0083] The process can continue with calculating the antenna pattern of each RFID reader 150, or other representation of the volume within which each RFID reader 150 can transmit and detect an RF field (step 906). These patterns may depend on the parameters of the RFID reader, their antennas, and how the readers operate (e.g., at one or more frequencies). In some cases, the radiation pattern of reader 150 can be determined empirically or from the specifications provided for RFID reader 150. In some cases, the antenna pattern can be determined primarily based on the antenna configuration of the reader and how it operates (e.g., whether the antenna includes an array of antennas and whether they are used to generate a stationary radiation pattern or a swept beam). In some implementations, RFID reader 150 can have a phased array antenna that enables beamforming and steering.

[0084] The RF field calculated for a single RFID reader 150 can be determined from different emissions into the free space around the reader. In a first approximation, the RF field is calculated without considering signal scattering objects or signal attenuation objects that may be located within the RFID environment 100 at the installation location. The calculated RF field is for voxels at different x r , y r , z r positions around the RFID reader, the positions of which are determined with respect to the position of the RFID reader (e.g., x r = 0, y r = 0, z r = 0). As an example, the x r , y r , z r positions are spaced 1 foot apart (defining a 1 cubic foot voxel) and can extend under and around the RFID reader 150 from the peak field value to the position where the field or power level is half or 1 / 4 of the peak field or power level, although other cutoff criteria may be used. The field value for each voxel can be the peak calculated RF field calculated for the voxel by any of the radiation beams. For example, if three radiation beams generate an RF field in a voxel, the value of the highest RF field among the three beams is selected as the peak RF field of the voxel. When multiple beams are radiated into the voxel simultaneously, the RF field of the voxel is the sum of the RF fields from the beams that generate an RF field within the voxel.

[0085] In some implementations, the RF field calculated for one RFID reader 150 can be attenuated (procedure 910) to account for signal scattering objects and / or signal attenuation objects that may be present within the RFID environment 100. The attenuation factor can be a value in the range of 0.05 to 0.95 and may depend on the details of the RFID environment 100 and the tagged objects. For example, the attenuation factor may depend on the number of fixtures and / or equipment within the environment, the materials from which those fixtures and / or equipment are made, the proximity of the tagged item to the wall, the maximum density of the tagged items, etc. Once implemented, the attenuation factor can be used to account for the expected forward link loss and reverse link loss of the RFID environment 100 between the RFID reader 150 and the RFID tag 101. In some cases, as further described below, the attenuation (procedure 910) of the calculated RF field may not be performed, and the signal loss can be accounted for when evaluating the link margin (procedure 922).

[0086] Process 300 can continue with the selection of the initial reader position (procedure 914). When used in a common approach for determining the sensor position, the initial position may be on a rectangular (e.g., square) grid pattern with intervals selected automatically or by the user. The initial interval between RFID readers 150 can be 10 feet, 15 feet, 20 feet, or any other suitable trial value. Other grid patterns (e.g., hexagonal) and intervals (e.g., from half of the desired sensor reach to the desired sensor reach, where the sensor reach is the sensor range projected on a plane parallel to the ceiling or floor and at a specific distance from the ceiling or floor) can also be used.

[0087] Using the test positions of each RFID reader 150 and the calculated RF field values, the power at the voxels of different x, y, z positions of interest throughout the RFID environment can be calculated. The x, y, z positions can be, for example, one foot apart, although other spacings can also be used. The x, y, z positions can be at the center of voxels having external dimensions equal to the spacing between the x, y, z positions. Since only one RFID reader 150 and one focused beam can be active at a time, the power at each x, y, z position of interest is proportional to the square of the maximum calculated RF field generated at that position from any one of the RFID readers 150 that radiate the RF field to that position.

[0088] The positions of interest in the RFID environment 100 are the positions where RFID tags can reside during (business) operations in the RFID environment. In some retail environments, such positions of interest can be from 6 inches above the floor to 7 feet above the floor, including within the aisles through which tags can be transported. In some cases, the positions of interest may be intentionally further restricted. For example, in settings where tags and attached objects are densely packed on shelves or where tags or objects are on metal shelves and not all of them can be read, it may be sufficient to have positions of interest restricted only to the aisles where individual tags can be detected when placed on or removed from the shelves.

[0089] Once power values are determined for all x, y, z positions (P x、y、z ) of the objects of interest in the RFID environment 100, it can be determined (procedure 922) whether all RFID tags within the RFID environment can be interrogated and communicated using the power level having the lowest value. To communicate with an RFID tag, the RFID tag needs to receive sufficient power P min at its x, y, z position to operate the tag to backscatter a signal having sufficient power to be detected by the RFID readers 150 within the environment 100. Expressed in this way, P minincorporates several factors that affect the forward link from the RFID reader 150 to the RFID tag 101 and the reverse link from the RFID tag to the RFID reader. For example, P min describes the forward path loss and reverse path loss, tag sensitivity, and reader sensitivity. P min represents the threshold amount of power at the voxel to establish communication with the RFID tag at the voxel.

[0090] To make communication with the RFID tag more reliable, link margin can be used. The link margin is provided for each x, y, z position or voxel of interest within the RFID environment 100 to determine the target amount of power P c (P min exceeding) to ensure the establishment of communication between the RFID reader and the RFID tag at that position. Without being bound by a particular theory, the link margin can be described by the following equation.

[0091]

Equation

[0092]

Equation

[0093] The forward path loss and reverse path loss, tag sensitivity, and reader sensitivity are P minAs described, when the link margin m is used, the attenuation of the leader's field (step 910) may be omitted. In some cases, the attenuation of the leader's field (step 910) can be implemented and the link margin can be set to zero (m = 0). Of course, in some cases, both attenuation and link margin can be used.

[0094] Using the selected link margin value m and the target power P c it is possible to determine (step 922) whether there is an appropriate link margin for each x, y, z position within the RFID environment 100 by comparing the calculated power P x、y、z at that position with the target power P c at that position. If there is no appropriate link margin, the position of the RFID reader can be changed (step 914), (for example, by reducing the distance between the readers), and the operation of calculating the power value (step 918) and determining whether there is an appropriate link margin (step 922) for each position can be performed.

[0095] If an appropriate link margin is established for all cells of interest in the RFID environment, process 900 may continue with a determination (procedure 924) as to whether there are physical obstacles (such as sprinklers, lights, smoke detectors, etc.) at one or more of the intended leader positions. In some cases, the location of the physical obstacle can be determined from the floor plan or other representation of the RFID environment 100. In some implementations, the location of the physical obstacle may not be known until on-site installation begins. If it is determined that a physical obstacle is at the intended location of the RFID reader 150, the location of the reader may be changed (procedure 914), for example, to the nearest available location. The power value may then be recalculated (procedure 918), and the link margin may be re-evaluated (procedure 922). In some cases, the change due to the physical obstacle can prompt a repositioning of all RFID readers 150 within the environment 100 to obtain an appropriate link margin. For example, by iterating loop 930 of process 900, an appropriate link margin can be established for all voxels of interest. If an appropriate link margin is established for all voxels of interest in the RFID environment 100 and there are no obstacles at the intended locations of the RFID readers 150, the reader locations may be output (procedure 928) for subsequent use by installers placing the readers in the environment.

[0096] To improve the placement of the RFID readers 150, there may be improvements to process 900. One improvement could be to place at least one of the RFID readers 150 directly above areas of very high traffic, such as beside a door or passage between the retail area and the warehouse, above the checkout area, and / or above an exit from the RFID environment. RFID readers in such locations can detect the movement of tags (e.g., into and out of the retail space).

[0097] Another improvement could be to set the distance between the wall and the RFID reader to be less than the distance between the RFID readers. The inventors have found that RFID tags near the wall can be more difficult to read due to reflections from the wall. By placing the RFID reader closer to the wall, the readability of RFID tags near the wall can be improved. As an example, the RFID readers 150 may be 16 feet apart from each other on the RFID environment 100. However, the peripheral RFID readers may be 6 feet apart from the walls bounding the RFID environment. In some cases, the shortest distance from the RFID reader 150 to the walls 110, 112 can be the fractional part of the distance between the RFID readers. The fractional part can have a value in the range of, for example, approximately or exactly 0.4 to approximately or exactly 0.9.

[0098] In some implementations, the RFID reader 150 can be located near areas where RFID tags are likely to be densely packed (e.g., on multiple shelves within stacked shelves). For example, it can be beneficial to position some of the readers above and within a horizontal distance of 2 feet (or other horizontal distances between approximately or exactly 5 feet and approximately or exactly 0 feet) of a stacked shelf holding a dense group of RFID tags. Placing the RFID reader near such a dense group of tags can increase the RF signal strength to and from the RFID tags within the dense group compared to the RF signal to RFID tags located in a sparser group far from the RFID reader.

[0099] Conclusion Although various embodiments of the invention have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions described herein and / or for obtaining one or more of the results and / or advantages thereof, and each of such variations and / or modifications is to be regarded as within the scope of the embodiments of the invention described herein. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are meant to be illustrative, and that the actual parameters, dimensions, materials, and / or configurations will depend upon the particular use or uses for which the teachings of the invention are employed. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Accordingly, the foregoing embodiments are presented by way of example only, and it is understood that embodiments of the invention may be practiced otherwise than as specifically described and claimed within the scope of the appended claims and their equivalents. Embodiments of the invention disclosed herein are directed to each and every individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the scope of the invention disclosed herein if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0100] Also, various inventive concepts may be embodied as one or more methods, and examples thereof have been provided. The acts performed as part of the method may be ordered in any suitable way. As a result, embodiments may be constructed in which acts are performed in an order different than that illustrated, including performing some acts simultaneously, even if shown as consecutive acts in the illustrative embodiments.

[0101] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in incorporated documents by reference, and / or ordinary meanings of defined terms.

[0102] As used in this specification and the claims, the indefinite articles "a" and "an" should be understood to mean "at least one" unless clearly indicated otherwise.

[0103] The phrase "and / or" as used in this specification and the claims means "either or both" of the associated components, i.e., components that exist conjunctively in some cases and disjunctively in other cases. The multiple components listed with "and / or" should be construed in the same manner, i.e., as "one or more" of the components connected in parallel. Regardless of whether or not specifically identified elements are related, other components may optionally exist in addition to the components specifically identified by the "and / or" clause. Thus, by way of non-limiting example, a reference to "A and / or B" can, when used in conjunction with open-ended grammar such as "comprising", refer in one embodiment to only A (optionally including components other than B), in another embodiment to only B (optionally including components other than A), and in yet another embodiment to both A and B (optionally including other components).

[0104] As used in this specification and the claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be construed as inclusive, i.e., including the number of components or at least one of the list, but including more than one, and optionally including additional items not in the list. Only terms that clearly indicate the contrary, such as "only one of", "exactly one of", or "consisting of" when used in the claims, refer to exactly one element of the number of components or the list. Generally, the term "or" as used in this specification shall be construed to indicate an exclusive alternative (i.e., "either one or the other but not both") only when preceded by an exclusive term such as "any one of", "only one of", "only one and no more of", or "exactly one of". "Consisting essentially of" shall have the ordinary meaning as used in the field of patent law when used in the claims.

[0105] As used in this specification and the claims, the phrase "at least one" with respect to a list of one or more components should be understood to mean at least one component selected from any one or more of the components in the list of components, but does not necessarily include each and every component specifically listed in the list of components, nor does it exclude any combination of the components in the list of components. This definition also allows for the optional presence of components other than those specifically identified in the list of components referred to by the phrase "at least one", whether or not such other components are related to the specifically identified components. Thus, by way of non-limiting example, "at least one of A and B" (or equivalently "at least one of A or B", or equivalently "at least one of A and / or B") can, in one embodiment, refer to at least one, optionally one or more, A, where B is absent (and optionally includes components other than B); in another embodiment, to at least one, optionally one or more, B, where A is absent (and optionally includes components other than A); and in yet another embodiment, to at least one, optionally one or more, A, and at least one, optionally one or more, B (and optionally includes other components), and so forth.

[0106] In the claims, as well as in the above specification, all transitional phrases such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", "consisting of", and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are to be considered closed or semi-closed transitional phrases, respectively, as defined in the Manual of Patent Examining Procedure of the United States Patent and Trademark Office, Section 2111.03.

Claims

1. A method of placing a radio frequency identification (RFID) reader at an installation location, comprising: measuring the ceiling height of the installation location and the positions of walls and / or fixtures; determining an intended position of the RFID reader at the installation location based on the ceiling height and the positions of the walls and / or the fixtures; providing a central controller for the RFID reader using a configuration file representing the intended position for the RFID reader; installing the RFID reader at the installation location; measuring an actual position of the RFID reader; providing an updated configuration file representing the actual position of the RFID reader to the central controller; commissioning the central controller and the RFID reader to find RFID tags within the installation location based on signals from the RFID tags received by the RFID reader and the actual position of the RFID reader. A method as described above.

2. The method of claim 1, wherein measuring the ceiling height and the positions of the walls and / or fixtures includes performing a first LIDAR scan of the installation location, and measuring the actual position of the RFID reader includes performing a second LIDAR scan of the installation location.

3. The method of claim 1, wherein determining the intended position of the RFID reader includes generating a floor plan of the installation location and a ceiling image representing the ceiling height.

4. The method of claim 1, wherein determining the intended position of the RFID reader includes identifying potential obstacles based on the ceiling height and / or coverage volume of the RFID reader.

5. The method of claim 1, wherein determining the intended position of the RFID reader includes selecting the intended position such that the coverage volumes of adjacent RFID readers intersect at a predetermined height, based on the expected maximum height of RFID tags within the installation location.

6. Determining the intended position of the RFID reader includes selecting the intended position such that the coverage volume of the RFID reader adjacent to the wall intersects the wall at a predetermined height or more, based on the expected maximum height of the RFID tag on the fixture along the wall. The method according to claim 1.

7. Determining the intended position of the RFID reader includes selecting the intended position such that the coverage volumes of adjacent RFID readers intersect at a predetermined height or more. The method according to claim 1.

8. The method according to claim 7, wherein the predetermined height is based on the height of the fixture holding the RFID tag.

9. Determining the intended position of the RFID reader includes generating different sets of possible sensor positions based on different desired intervals between adjacent sensor positions, determining the coverage and number of sensors for each of the different sets of possible sensor positions, and selecting one of the different sets of possible sensor positions as the intended position based on the coverage and number of sensors for the different sets of possible sensor positions The method according to claim 1.

10. Installing the RFID reader at the installation location includes adjusting at least one pitch and / or roll of the RFID reader to an angle of 0.0° ± 0.25°. The method according to claim 1.

11. Installing the RFID reader at the installation location includes connecting each of the RFID readers to a corresponding Ethernet switch, and connecting the corresponding Ethernet switch to the central controller The method according to claim 1.

12. After installing the RFID reader, further includes measuring the angular orientation of the RFID reader, wherein the updated configuration file further represents the angular orientation of the RFID reader. The method according to claim 1.

13. Before commissioning the central controller and the RFID reader, further includes testing the coverage of the installation location by the RFID reader. The method according to claim 1.

14. An RFID tag reader arranged according to the method of claim 1.

15. A method of placing a radio frequency identification (RFID) reader at an installation location, comprising: selecting a corner position such that the coverage volume of the RFID reader at the corner position forms a corner above a first predetermined height, intersecting a wall based on the expected maximum height of RFID tags on fixtures along the wall; selecting a peripheral position such that the coverage volume of the RFID reader at the peripheral position intersects the wall at the first predetermined height and intersects an adjacent coverage volume above a second predetermined height based on the expected maximum height of the RFID tags at the installation location; selecting an interior position such that the coverage volume of the RFID reader at the interior position intersects an adjacent coverage volume above the second predetermined height; installing the RFID reader at the corner position, peripheral position, and interior position; test-running the RFID reader to find RFID tags within the installation location based on signals from the RFID tags received by the RFID reader and the actual position of the RFID reader. A method as described above.

16. The method of claim 15, wherein the first predetermined height is about 2 meters and the second predetermined height is about 1 meter.

17. The method of claim 15, further comprising identifying obstacles and / or areas within the installation location having a ceiling height below a predetermined threshold before selecting the corner position, peripheral position, and interior position.

18. Before installing the RFID reader, identifying gaps in coverage provided by the RFID reader at the corner position, peripheral position, and interior position; repeatedly adding and shifting the position of the RFID reader to reduce and / or eliminate the gaps. The method of claim 15, further comprising the steps above.

19. After installing the RFID reader and before test-running the RFID reader, measuring the actual position of the RFID reader; providing a central controller having a configuration file representing the actual position of the RFID reader. The method further includes the steps above. ​ Determining the RFID tag is the method according to claim 15 based on the configuration file.

20. An RFID reader arranged according to the method according to claim 15.

21. A method for positioning a radio frequency identification (RFID) reader in an RFID environment including an RFID tag group, comprising: Receiving floor plan information describing the extent of the physical space of the RFID environment; Determining a first position within the physical space for a plurality of RFID readers, the first position being distributed throughout the physical space in a first pattern; Calculating first plural peak radio frequency (RF) power levels at a plurality of positions of interest within the physical space, the first plural peak RF power levels being based on an RF field radiated by the plurality of RFID readers and the first positions of the plurality of RFID readers, each position of interest being a sub-region of the physical space where an RFID tag is expected to be present within the RFID environment; Determining, for at least a first position of interest of the plurality of positions of interest, that a first peak RF power level of the first plural peak RF power levels at the first position of interest does not meet a link margin criterion, the link margin criterion identifying a target power level for establishing communication between at least one RFID reader of the plurality of RFID readers and an RFID tag located at the first position of interest; In response to the first peak RF power level not meeting the link margin criterion, determining a second position within the physical space for the plurality of RFID readers, the second position being distributed throughout the physical space in a second pattern having an inter-reader spacing of the plurality of RFID readers that is smaller than the inter-reader spacing of the RFID readers in the first pattern; Calculating second plural peak RF power levels at the plurality of positions of interest within the physical space, the second plural peak RF power levels being based on the RF field radiated by the plurality of RFID readers and the second positions of the plurality of RFID readers; Determining, for at least the first or second of the plurality of positions of interest, that a second peak RF power level of the second plurality of peak RF power levels for the first or second position of interest meets the link margin criteria for the first or second position of interest, wherein the first or second position of interest is a position having the lowest peak RF power level of the second plurality of peak RF power levels; Outputting, in response to the second peak RF power level meeting the link margin criteria, the second position as an intended position for installing the plurality of RFID readers; A method comprising.

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