ULTRASOUND LOCATION SYSTEM USING A DOUBLE SYMMETRICAL TRANSMISSION SEQUENCE

Abstract

A system for locating a target in a location (150), the system comprising: a plurality of ultrasonic transmitters (110) positioned within the location (150) according to a physical layout, each ultrasonic transmitter (110) in the plurality of ultrasonic transmitters (110) being configured to transmit ultrasonic spacing pulses within the location (150) for reception by the target; and a backend controller (130) comprising a processor and a memory, wherein the backend controller (130) is communicatively coupled to the plurality of ultrasonic transmitters (110), wherein the backend controller (130) is configured to activate the ultrasonic transmitters (110) in a symmetry mode comprising a plurality of symmetry ultrasonic transmitter groups, wherein the ultrasonic transmitters (110) in each symmetry ultrasonic transmitter group have symmetry across a plurality of symmetry lines (318, 320) in the location (150), wherein the backend controller (130) is configured to control each symmetry ultrasonic transmitter group to transmit a respective spacing pulse during a symmetry mode time frame, wherein the backend controller (130) is further configured to receive location signal information in each symmetry mode time frame of the symmetry mode, and wherein the backend controller (130) is further configured to determine the location of the target in the location (150) in response to the location signal information received during the symmetry mode.

Description

Background of the invention

[0001] The background description contained herein is intended to provide a general context for the disclosure. Works of the presently named inventors, to the extent described in this background section, as well as aspects of the description that could not be considered prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0002] A system using ultrasonic transmitters can determine the location of devices capable of receiving ultrasonic signals, e.g., devices such as mobile devices located in a retail, factory, or warehouse environment. The ultrasonic transmitter typically includes an emitter (e.g., transducer or speaker) capable of transmitting ultrasonic energy in a short pulse that can be received by a transducer (e.g., microphone) in the mobile device. For example, today's unmodified smartphones have audio hardware and circuitry capable of receiving ultrasonic signals in the 20-22 kHz frequency range. Furthermore, the use of multiple ultrasonic transmitters in the environment can be used to provide a specific position of a particular device using techniques known in the art, including triangulation, trilateration, multilateration, and the like.

[0003] In an ultrasonic positioning system, the frequency of a transmitter's transmission is a key design parameter, not only setting the repetition rate for position updates but also determining the overall position accuracy when measuring a device moving within a sensing area. Ultrasonic pulses must be distributed in a timely manner so that reflections decay below the detection threshold before a new pulse signal is transmitted and a new measurement is taken. These times, called reverberation times, can amount to several hundred milliseconds in a typical retail environment.

[0004] However, existing ultrasonic positioning systems lack transmitter scheduling in several respects. The concept of scale is particularly problematic. As retail, factory, and warehouse facilities increase in size, ultrasonic positioning systems are becoming larger. However, the size of an ultrasonic positioning system, for example, to cover an entire retail space, may require a large number of tracking transmitters; and the larger the number of transmitters, the greater the time required to sequence each of the transmitters in succession. For this reason, the update rate and position accuracy are reduced.

[0005] US 2006 / 0 077 759 A1 describes a method and system for monitoring and determining the position of objects and / or living beings within an area, such as a room in a building or a road tunnel. The system comprises a plurality of identification tags equipped with an ultrasonic receiver and a radio transmitter, which are attached to the objects to be monitored. The identification tags receive ultrasonic signals and measure their arrival time. This information, along with the ID code of the identification tags, is transmitted wirelessly to a central unit, which calculates the position of each individual identification tag.

[0006] US 6,816,437 B1 describes a method and apparatus for determining orientation. The position and orientation of a mobile unit are determined using ultrasonic waves received from transmitters with a known location. The orientation is determined based on the phase difference of the detected ultrasonic wave at multiple receivers of the mobile unit. Signals from multiple beacons can be processed to calculate the X, Y, and Z position as well as the speed of sound. The receivers are arranged at a distance of more than half a wavelength of the ultrasonic wave, and signals from multiple receivers are processed to eliminate phase ambiguities due to multiple wavelengths. Ambiguities resulting from the symmetry of the receivers can be resolved using two non-collinear sets of collinear receivers.

[0007] There is a need for an improved ultrasonic positioning system capable of detecting large coverage areas. Brief description of the different views of the drawings

[0008] The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the several views, together with the detailed description below, are incorporated in and constitute a part of the specification and serve to further illustrate embodiments of concepts incorporating the claimed invention and to explain various principles and advantages of such embodiments. Fig. 1 is a block diagram of an ultrasonic positioning system according to an exemplary embodiment. Fig. Figure 2 is a block diagram showing a top view of the ultrasonic transmitters of Fig. 1 and illustrates the physical layout configuration of the transmitters in a location according to an exemplary embodiment. Fig. 3 is a flowchart illustration according to an exemplary embodiment. Fig. Figure 4 is a diagram showing a plan view of a symmetric mode array of the transmitters of Fig. 2, in an example of a double symmetry mode. Fig. Figure 5 is a diagram showing a plan view of a subspace grouping of the transmitters of Fig. 2, in an example of a subspace mode. Fig. 6 is a graphical representation of a timing diagram showing a double symmetry mode and a subspace mode in an exemplary embodiment. Fig. Figure 7 is a diagram showing a plan view of a double symmetry mode in which the symmetry lines fall on the lines of transmitters and not between the lines of transmitters, as in Fig. 4 shown. Fig. Figure 8 is a diagram showing a plan view of a subspace mode in which the symmetry lines fall on the lines of transmitters and not between the lines of transmitters, as in Fig. 5 shown. Fig. 9 is a diagram showing a plan view of a double symmetry mode of a location which is configured differently from the location of Fig. 2, and shows that patterns of the double symmetry mode and the subspace mode can be transposed horizontally and vertically to cover differently designed locations.

[0009] Those skilled in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to enhance understanding of embodiments of the present invention.

[0010] The apparatus and method components have been represented, where appropriate, by conventional symbols in the drawings showing only those specific details relevant to an understanding of the embodiments of the present invention, so as not to obscure the disclosure with details that would be readily apparent to those skilled in the art having recourse to the description herein. Detailed description of the invention

[0011] According to some embodiments of the present invention, an improved technique is described to enable faster and more accurate localization of a mobile device within a scanning area, such as a retail location, warehouse, or factory. In particular, a location system uses a unique reconfiguration of transmitters to more quickly identify the position of one or more mobile devices. The location system coordinates the operation of the transmitters in a grouped manner to transmit ultrasonic spacing pulses in the form of pulsed signals, such as acoustic pulses or short tones. The sequencing of these pulsed signals can be performed in an optimized and static manner, allowing the sequencing to achieve the same performance speeds regardless of the number of transmitters in a location and the size of the locations.

[0012] Although an ultrasonic positioning system should be highly accurate, this accuracy decreases with increasing numbers of transmitters. However, the configuration and parallel sequencing techniques presented herein can help enable the use of an increased number of transmitters without compromising the time required to identify a target (e.g., a mobile device) or, accordingly, the positional accuracy of that identification.

[0013] In some embodiments, a location system includes a backend controller that controls the operation of a plurality of ultrasonic transmitters distributed throughout a location. The backend controller controls these transmitters to transmit pulsed signals sequentially, using specific groups of transmitters that transmit simultaneously according to one or more lines of symmetry. These transmitters, operated in what is referred to herein as a symmetry mode, are grouped together to establish symmetry along different lines of symmetry. An exemplary implementation of a symmetry mode is a double symmetry mode, where the transmitters in a location are grouped based on two-axis symmetry, e.g., based on both a horizontal line of symmetry and a vertical line of symmetry.That is, in some examples, the transmitters are divided into groups, where each transmitter group has a biaxial symmetry and where each group contains a different collection of the transmitters in the location.

[0014] For ultrasonic transmitters configured in symmetry mode, the backend controller instructs the transmitters of the first group to fire, i.e., to send pulse signals in the form of acoustic pulses, tones, etc. After the first group of transmitters fires, another group is triggered to fire. The backend controller controls this process by instructing each group of transmitters to fire sequentially, one after the other, in their respective assigned time slots.

[0015] In some examples, the backend controller determines the symmetry lines, whether biaxial with vertical and horizontal lines or other symmetry lines, by first dividing a location into n subspaces, where n is an integer equal to or greater than 2. These subspaces can be determined at runtime by the backend controller, they can be pre-stored in a layout configuration file accessed by the backend controller during initialization, or they can be pre-stored and updated during operation. In some examples, a layout configuration file stores the subspace data for the location, data specifying the symmetry transmitter groups, and data specifying the subspace transmitter groups.

[0016] In symmetric mode, each transmitter group can be structured so that the entire location is covered when the transmitter group fires. This can be achieved by forming each transmitter group so that it includes at least one transmitter in each of the sub-spaces of the location. When each transmitter group fires, all sub-spaces are examined simultaneously. The backend controller instructs this sequential examination until all transmitter groups in symmetric mode have fired.

[0017] Once all symmetry mode transmitter groups have fired, the backend controller can determine the target's position through triangulation, trilateration, and / or multilateration based on the tracking data received from the target. For example, the target can record a timestamp each time a pulse signal is received at the target. Thus, the target would perform a timestamp for each symmetry mode transmitter group according to each transmitter group's timeframe. The target sends the timestamps to the backend controller over a wireless network. The backend controller records these timestamps and uses triangulation, trilateration, and / or multilateration to identify which symmetry mode transmitter group is closest to the target.

[0018] In some further exemplary embodiments, after transmitting the pulse signals during the symmetry mode, the backend controller may switch the transmitters to a second mode in which the transmitters are grouped in a different grouping pattern. This second grouping pattern may be derived from the same subspaces n stored in the layout configuration file. Or this second grouping pattern may be derived from a different configuration of the transmitters in the location. In both cases, the transmitters in this second mode are grouped in a so-called subspace mode, in which the transmitters do not exhibit the same multiaxial symmetry as in the symmetry mode. Indeed, in some examples of the subspace mode, the transmitters in a group do not exhibit symmetry among themselves; only the group itself may exhibit symmetry with other groups, or even the group itself may exhibit no symmetry.As in symmetry mode, in any case in subspace mode each transmitter group transmits its pulse signals during an assigned time frame, and the time frames for the different groups are triggered one after the other until all transmitter groups of the subspace mode have fired.

[0019] As in symmetry mode, the backend controller can collect timestamp information from the target through the sequential group firing of subspace mode. From this information, the backend controller determines which transmitter group in subspace mode is closest to the target.

[0020] The backend controller collects location signal information (e.g., timestamp information) in response to the pulse signals of both the symmetry mode and the subspace mode, and the backend controller determines a location of the target, e.g., by triangulation, trilateration, and / or multilateration.

[0021] The techniques described herein enable various performance advantages. By using a symmetry mode configuration, particularly a double symmetry mode, the system can contribute to the faster identification of a moving target, such as a mobile device. For example, double mirror symmetry (i.e., a transmitter firing array configuration with horizontal and vertical symmetry, as in Fig. 4) ensures that an observer (e.g., a transmitter) is always closer to an object (e.g., a target or a mobile device) than the observer is to that object's mirror image. Furthermore, the symmetry mode ensures that all subspaces of a location are scanned simultaneously, reducing the time until retransmission by a given transmitter and thus ensuring that the entire location is seemingly covered with each pulse.

[0022] Any number of targets in a location can be located using the present techniques. By way of example, the target to be located may be a mobile device from a variety of business and personal electronic platforms, such as cellular telephones, mobile stations, mobile units, mobile nodes, user equipment, subscriber equipment, subscriber stations, mobile computers, access terminals, remote terminals, terminal equipment, cordless handsets, gaming devices, personal computers, and personal digital assistants, and the like, all hereinafter referred to as a device. Each device includes a processor, which may be further coupled to a keyboard, speaker, microphone, display, signal processors, and other functions as are known in the art and therefore not shown.

[0023] Fig. 1 is a block diagram of an ultrasonic positioning system according to this document. An ultrasonic transponder, such as a piezoelectric speaker or emitter 116, may be implemented in an ultrasonic transmitter 110. The transmitter may transmit a short ultrasonic pulse (e.g., an ultrasonic pressure wave 20) for ambient listening by a mobile device 100. The mobile device 100 may include a transducer, such as an existing microphone 106, for receiving the pulse 20. The mobile device also includes existing audio circuitry to convert the pulse into an electrical signal 108. The mobile device also includes an existing processor 102 for converting and processing the signal. The processor 102 may also be coupled to a wireless local area network interface 104 to wirelessly communicate with other devices in a communications network.

[0024] The communications network may include local and wide area wireless networks, wired networks, or other IEEE 802.11 or Wi-Fi™ wireless communications systems, including virtual and extended virtual networks. The communications network is contemplated to include a backend controller / scheduler 130 that performs network control and provides location determinations. The backend controller 130 further controls the operation of each of the ultrasonic transmitters 110 to operate synchronously and configures the transmitters 110 to transmit ultrasonic pulses (also referred to herein as pulses) according to a double symmetry configuration, as explained in some embodiments herein. The backend controller 130 may be connected to a network switch 120 that may be wired (e.g., an Ethernet interface connection) or wireless (e.g., IEEE 802.11 or Wi-Fi™) may be connected to the plurality of ultrasonic transmitters 110, and to at least one wireless communication link, such as a wireless access point 125, used to communicate with the mobile devices 100.

[0025] To enable more precise positioning, for example, using a time-of-flight technique, a large number of ultrasonic transmitters 110 can be used in an environment, each transmitter carrying an emitter 116. For discreetness and clear signaling, the transmitters can be mounted on a ceiling of the environment, where the position of each transmitter is fixed and known to the backend controller 130. The configuration of Fig. 1 can use time-of-flight information from multiple pulses from different transmitters 110 to locate the mobile device 100. Since the position and location of these transmitters 110 are known and fixed, the various signals received by the mobile device's microphone from each transmitter can be used to locate and track the mobile device's position using a suitable location technique, such as triangulation, trilateration, or multilateration.

[0026] In practice, the mobile device 100 may not know which specific transmitter is the one transmitting the ultrasonic pulse. Therefore, the backend controller 130 controls the operation of the transmitters 110, whereby the backend controller knows which transmitter group is transmitting at a given time and the layout of the transmitters in that group. The backend controller 130 has stored the information that the layout of the transmitters in symmetric mode differs from the layout in subspace mode, for example. The backend controller has stored these layouts, for example, in configuration files.

[0027] As further explained, the backend controller 130 may include a scheduler and communicate with each of the ultrasonic transmitters to group the transmitters based on various reconfigurations of the transmitter groups. To optimize the range of the transmitter groupings, the groupings may be defined by double symmetry, where all transmitters in a given group exhibit symmetry across two selected lines or planes of symmetry (e.g., one horizontal and one vertical).

[0028] After receiving a pulse from a group of transmitters, device 100 can communicate with backend controller 130 over the communications network through access point 125 that device 100 has received the pulse. Backend controller 130 will then know that the pulse came from the respective transmitter group by tracking the time frame over which the pulse signals were transmitted and comparing that time frame with the timestamp received from the target, where that timestamp represents the time at which the target device 100 receives the pulse signal. This process repeats for the next transmitter group, the next transmitter group after that, and so on, until all transmitter groups in symmetry mode have transmitted their respective pulse signals.The backend controller 130 receives and stores the timestamps received in each sequential time frame, from which the backend controller 130 determines the position of the target in the location or at least determines which of the symmetry mode transmitter groups of the device 100 is closest.

[0029] Fig. Figure 2 illustrates an exemplary environment (location) 150 in which a plurality of ultrasonic transmitters 110 are arranged, only some of which are labeled for convenience. An example of the mobile device (MD) 100 is also shown. The transmitters 110 are shown in a physical layout configuration in a location, such as a building.

[0030] Fig. 3 illustrates a flowchart depicting an exemplary process 200 performed by or under the control of the backend controller 130 to achieve optimized localization of the mobile device 100 within the environment 150. The backend controller (block 202) obtains initial physical layout data for the ultrasonic transmitters 110 and for the environment 150. This physical layout data may include the position of the transmitters 110 within the environment 150, the number of transmitters 110, and, in some examples, the dimensions of the environment 150.

[0031] The backend controller (block 204) takes the physical layout data and divides the environment 150 into virtual subregions or subspaces. As used herein, subspaces do not have to be physical spaces. The subspaces can be areas within the environment 150. Each subspace can have the same size in area, or the subspaces can have different sizes. In some examples, the subspaces do not represent areas; rather, a subspace simply defines a particular grouping of neighboring transmitters 110 with a corresponding firing or transmitting sequence in the location. In examples where the environment 150 is divided, this division can be based on the layout data of the transmitters 110, the layout data of the environment 150, or the layout data from both. In some embodiments, the backend controller divides the environment 150 into equally sized areas of the same geometry (e.g.,"Cells"), such as rectangular, square, or diamond-shaped cells. In other examples, the backend controller may divide the environment 150 into cells with different but complementary geometries, e.g., some cells with rectangular shapes and others with complementary square shapes.

[0032] Fig. Figure 4 illustrates an example of a subspace layout used by the backend controller (through block 204) for the environment 150. As shown, the transmitters 110 of the environment 150 are divided into nine (9) subspaces 300-316, each of equal size and square shape. To reconfigure the transmitters 110 into these subspaces 300-316, orthogonal symmetry lines were used. A first symmetry line 318 corresponds to vertically running lines, while a second symmetry line 320 corresponds to horizontally running lines. The number of symmetry lines determines the number of subspaces. In the example shown, the symmetry lines 318 and 320 are orthogonal to each other, which facilitates the implementation of a double symmetry reconfiguration described further.While for this particular example the symmetry lines run along the vertical and horizontal alignment, in fact any number of orthogonal symmetry lines can be created, such as a symmetry rotated by 45°.

[0033] The subspaces 300-316 can be stored in a layout configuration file accessed by the backend controller 130. In other examples, however, the subspaces 300-316 are determined by the backend controller 130 at runtime.

[0034] With the subspaces set, the backend controller 130 operates the transmitters in two different pulse signal modes to identify the location of the mobile device 100, a symmetry mode and a subspace mode.

[0035] To operate in symmetry mode, the backend controller 130 assigns each of the transmitters 110 to one of several symmetry mode transmitter groups (block 206). Fig. Figure 4 illustrates an example in which the backend controller 130 has divided the total group of transmitters 110 into nine (9) different groups, each labeled Group 1, 2, 3, ...., 7, 8 and 9. All transmitters reconfigured into the double symmetry group 1 are in Fig. 4 is marked with 1. The backend controller 130 is configured to assign each transmitter to only one of these symmetry groups, and so that each subspace has only one transmitter from each symmetry group within that subspace. For example, subspace 300 has nine (9) transmitters, and in double symmetry mode, the backend controller has configured these nine transmitters so that each one is assigned to a different symmetry transmitter group. In the example shown, the symmetry is double symmetry.

[0036] With further reference to Fig. 2, the backend controller has assigned the transmitters 110 at block 206 such that a double symmetry is created around the symmetry lines 318 and 320. In the illustrated example, this double symmetry is of a specific type, referred to herein as double mirror symmetry. By configuring the transmitters in a double symmetry configuration, the backend controller ensures that each transmitter in a group is symmetrical to every other transmitter in that group, i.e., symmetrical about axis 318 and symmetrical about axis 320. For example, considering subspace 300, transmitter 110 assigned to group 3 is symmetrical about axial line 320 with the group 3 transmitter in subspace 306. Likewise, the group 3 transmitter in subspace 300 is symmetrical about line 318 with the group 3 transmitter in subspace 302. This double symmetry is achieved for each transmitter across the entire environment 150.

[0037] In symmetry mode, the backend controller (block 208) instructs a first group of transmitters to transmit an ultrasonic pulse signal. In some examples, the backend controller is configured to wait for and receive response signals from the mobile device, where the response signals indicate when the mobile device has received the pulse signal. In some embodiments, the backend controller instructs only one symmetry transmitter group (groups 1-9 in Fig. 4) to transmit simultaneously. After each transmitter group has transmitted a pulse signal, the next transmitter group transmits its pulse signal. The backend controller can repeat the process until each group has transmitted a pulse signal.

[0038] The firing order of the different transmitter groups can vary. The double symmetry mode ensures that the entire environment 150 can be quickly examined without having to activate transmitter groups in a specific order. In some embodiments, the transmitter groups can be activated according to a sequence pattern of group 1, then group 2, 3, 4, 5, 6, 7, 8, and 9; in other examples, the sequence pattern could be group 2, then group 4, 6, 8, 1, 3, 5, 7, and 9; in other examples, any other sequence pattern could be used. While in these examples each group is activated once before repeating the groups, in some embodiments transmitter groups can be activated variably, e.g., following a non-consumable sequence, such as group 1, then group 2, 1, 2, 4, and 5, until the mobile device is sufficiently located.

[0039] The backend controller at block 208 controls the process to separately activate each of the transmitter groups to transmit pulse signals. This process occurs for each transmitter group under control of the backend processor so that upon completion of block 208, the backend controller has received timestamps from the mobile device corresponding to all transmitter groups of the symmetry mode. After all transmitter groups have fired during the double symmetry mode, the backend controller then determines which transmitter group had the ultrasonic transmitter closest to the target. For example, if transmitter group 3 has the shortest time of flight (i.e., the time from the pulse to the received timestamp) of all transmitter groups, then the backend controller determines that one of the transmitters in group 3 is closest to the actual location of the mobile device.

[0040] The backend controller then transitions to a second mode, e.g., a subspace mode, in which the backend controller reconfigures the transmitters 110 into a subspace layout configuration, e.g., that of block 204. In subspace mode 210, the backend controller instructs each subspace of transmitters to separately and sequentially transmit pulse signals to further determine which subspace the mobile device 100 is in and where it is located within that subspace.

[0041] Fig. Figure 5 illustrates an example of each of the transmitters 110 configured in groups defined by subspaces 300-316 (block 210). In subspace mode (block 212), the backend controller instructs each of the transmitter groups, groups 10-18 in the illustrated example, to transmit pulse signals. As in double symmetry mode, each subsequent group is controlled to wait for an update period (e.g., 200 ms) before transmitting its respective pulse.

[0042] In subspace mode, the transmitters transmit pulse signals for each subspace group, and the mobile device records a timestamp of when the pulse signal is received. If a mobile device is not in a particular subspace, the mobile device cannot record a timestamp during a period. If a mobile device is in a different subspace but close to the subspace currently active, the mobile device can record a timestamp, where this timestamp represents a flight time longer than the flight time of the subspace group that actually contains the mobile device.

[0043] In the illustrated example, the process repeats for multiple subspaces, such as for each of the subspaces, and identifies a corresponding subspace in which the mobile device is located. The target records a timestamp upon receiving the pulse signal and sends this timestamp to the backend controller (block 212). The backend controller records the received timestamps as the transmitter groups are fired in sequential order.

[0044] From the received timestamp information, the backend controller determines the location of the mobile device 100 at block 214 in both symmetry mode and subspace mode. For example, the backend controller identifies which double-symmetry transmitter group generated the shortest flight time and which subspace generated the shortest flight time. Since the subspace has only one transmitter from each double-symmetry transmitter group, the backend controller is able to determine the subspace and a corresponding transmitter within the subspace closest to the mobile device.

[0045] Fig. Figure 6 illustrates an example of a timing diagram of the pulse signal transmissions of the transmitter group for both the double symmetry mode and the subspace mode, for example the embodiment of the Fig. 4 and Fig. 5. Each double-symmetry transmitter group transmits its pulse signal over a respective double-symmetry time frame, which is represented in the example as a 200 ms time frame. After all groups 1-9 in double-symmetry mode have transmitted their pulse signals during their respective 200 ms time frames and the resulting location signal information has been obtained, the backend controller reconfigures the transmitters to subspace mode, and each subspace group 10-18 transmits its pulse signals according to this mode during their respective 200 ms time frames.

[0046] In the illustrated embodiment, the entire tracking process takes approximately 200 ms x 18 group time frames, or 3.6 seconds. The time period depends on the size of the environment, the number of transmitter groups, and the subspace mode. As those skilled in the art will realize, the ultrasonic tracking technique described herein can result in a significantly shortened tracking cycle, as opposed to sequentially activating each transmitter in the location, which in the above example would take 200 ms x 81 individual transmitter time frames, or 16.2 seconds. Therefore, the dual symmetry and subspace transmitter activation technique described herein facilitates the deployment of the large number of ultrasonic tracking transmitters that may be required to cover large locations.

[0047] While in the illustrated example, the subspace configuration used by block 210 matches the subspace configuration used by block 204, in other examples, a different subspace configuration may be used for block 210. For example, the backend controller may use transmitter groups that are larger or smaller for block 210 than those of block 204, where in some examples, the size change may be determined dynamically based on the location information data received in double symmetry mode.

[0048] In the exemplary embodiments of the Fig. 4 and Fig. 5, the symmetry lines between adjacent transmitters bisect each other vertically and horizontally. In other embodiments, symmetry lines may be aligned with transmitters, e.g., with symmetry lines aligned with columns and rows of transmitters, as in Fig. 7, which shows transmitter groups for a double symmetry mode, and as in Fig. 8, which shows transmitter groups in subspace mode, where transmitters aligned with symmetry lines are not included in the subspace pulses.

[0049] The techniques described herein are scalable and can be adapted to any number of environmental layouts. Fig. Figure 9 illustrates another exemplary environment in which a backend controller has configured transmitters in a double symmetry configuration, accounting for an aisle or other space between two adjacent rectangular-shaped rooms. The operation of the tracking system for this configuration would be consistent with the other examples herein.

[0050] In some embodiments, the backend controller can operate the double symmetry mode and the subspace mode in any order. Furthermore, the sequential firing of the transmitter groups in the double symmetry mode (or those in the subspace mode) can be changed depending on the location. In some embodiments, the firing order of the transmitter groups can be changed to adapt to the size and shape of the location itself. For example, a location can be Fig. 9 have a different order of time frames for groups with double symmetry than that of Fig. 4 and Fig. 5. A configuration file can be called from the backend control and used, for example, to specify the order of the transmitter groups for different locations.

[0051] Any number of transmitter groups can be used for the double symmetry and subspace modes. Furthermore, the backend controller can use a different total number of double symmetry groups than the total number of subspace groups. Furthermore, the geometric shape and size of the double symmetry groups can differ from the geometric shape and size of the subspace groups. The backend controller can determine optimized shapes and sizes of transmitter groups based, for example, on the physical layout configuration of the transmitters and the location.

[0052] In the foregoing description, specific embodiments have been described. However, one of ordinary skill in the art will recognize that various modifications and changes may be made without departing from the scope of the invention as defined in the following claims. Accordingly, the description and figures are to be considered in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present teachings.

[0053] The benefits, advantages, solutions to problems, and any elements that may result in the occurrence or enhancement of a benefit, advantage, or solution are not to be construed as critical, required, or essential features or elements in any or all of the claims. The invention is defined solely by the appended claims, including any amendments made during the pendency of this application and all equivalents of the granted claims.

[0054] Furthermore, in this document, relational terms such as first and second, upper and lower, and the like may be used merely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has," "having," "comprising," "includes," "includes," or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, product, or apparatus that comprises, has, has, or contains a list of elements not only includes those elements, but may also include other elements not expressly listed or inherent in such process, method, product, or apparatus. An element that is preceded by "comprises," "has," "has," or "includes"a" does not exclude, without further limitation, the existence of additional identical elements in the process, method, product, or apparatus comprising, having, including, or containing the element. The terms "a" and "an" are defined as one or more unless expressly stated otherwise herein. The terms "substantially," "generally," "approximately," "about," or any other version thereof are defined as being approximately understood by one of ordinary skill in the art, and in one non-limiting embodiment, the term is defined as within 10%, in another embodiment, within 5%, in another embodiment, within 1%, and in yet another embodiment, within 0.5%. The term "coupled," as used herein, is defined as being connected, but not necessarily directly and not necessarily mechanically.A device or structure that is “constructed” in a particular way is at least constructed that way, but may also be constructed in ways that are not listed.

[0055] It should be understood that some embodiments may be comprised of one or more generic or specialized processors (or "processing devices") such as microprocessors, digital signal processors, custom processors, and field-programmable gate arrays (FPGAs), and unique stored program instructions (including both software and firmware) controlling the one or more processors to, in conjunction with certain non-processor circuitry, implement some, most, or all of the functions of the method and / or apparatus described herein. Alternatively, some or all of the functions may be implemented by a state machine that does not have stored program instructions, or in one or more application-specific integrated circuits (ASICs) in which each function, or some combination of certain functions, are implemented as user-defined logic.Of course, a combination of the two approaches can be used.

[0056] Furthermore, an embodiment may be implemented as a computer-readable storage medium having computer-readable code stored thereon for programming a computer (e.g., including a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage media include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (read-only memory), a PROM (programmable read-only memory), an EPROM (erasable programmable read-only memory), an EEPROM (electrically erasable programmable read-only memory), and a flash memory.It is further believed that, notwithstanding possible significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, one of ordinary skill in the art will readily be able to generate such software instructions and programs and ICs with minimal experimentation when guided by the concepts and principles disclosed herein.

[0057] The Summary of Disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is provided with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Further, it can be seen from the foregoing Detailed Description that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This manner of disclosure should not be construed to reflect an intent that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims demonstrate, inventive subject matter lies in fewer than all of the features of a single disclosed embodiment.Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as separately claimed subject matter.

Claims

[1] A system for locating a target in a location (150), the system comprising: a plurality of ultrasonic transmitters (110) positioned within the location (150) according to a physical layout, each ultrasonic transmitter (110) in the plurality of ultrasonic transmitters (110) being configured to transmit ultrasonic spacing pulses within the location (150) for reception by the target; and a backend controller (130) comprising a processor and a memory, wherein the backend controller (130) is communicatively coupled to the plurality of ultrasonic transmitters (110), wherein the backend controller (130) is configured to activate the ultrasonic transmitters (110) in a symmetry mode comprising a plurality of symmetry ultrasonic transmitter groups, wherein the ultrasonic transmitters (110) in each symmetry ultrasonic transmitter group have symmetry across a plurality of symmetry lines (318, 320) in the location (150), wherein the backend controller (130) is configured to control each symmetry ultrasonic transmitter group to transmit a respective spacing pulse during a symmetry mode time frame, wherein the backend controller (130) is further configured to receive location signal information in each symmetry mode time frame of the symmetry mode, and wherein the backend controller (130) is further configured to determine the location of the target in the location (150) in response to the location signal information received during the symmetry mode. [2] The system of claim 1, wherein the backend controller (130) is further configured to: activating the ultrasonic transmitters (110) in a subspace mode comprising a plurality of subspace ultrasonic transmitter groups that differ from the plurality of symmetric ultrasonic transmitter groups, wherein the backend controller (130) is configured to control each subspace ultrasonic transmitter group to transmit a respective spacing pulse during a subspace mode time frame, wherein the backend controller (130) is further configured to receive location signal information in each subspace mode time frame, and wherein the backend controller (130) is further configured to determine the position of the target in the location (150) in response to the location signal information received during the symmetry mode and the location signal information received during the subspace mode. [3] The system of claim 2, wherein the backend controller (130) is configured to receive the location signal information received during the symmetry mode and the location signal information received during the subspace mode from the target. [4] The system of claim 3, wherein the location signal information received during the symmetry mode and the location signal information received during the subspace mode are timestamp data of the target. [5] The system of claim 1, wherein the symmetry mode is a double symmetry mode such that each symmetry ultrasonic transmitter group has symmetry about two orthogonal axes. [6] The system of claim 5, wherein the two orthogonal axes are a horizontal axis in the location (150) and a vertical axis in the location (150). [7] The system of claim 5, wherein the double symmetry mode is defined by a plurality of repeating geometric cells. [8] The system of claim 7, wherein the repeating geometric cells are repeating rectangular cells, square cells, or repeating diamond-shaped cells. [9] A method for locating a target in a location (150) with a plurality of ultrasonic transmitters (110) positioned within the location (150), the method comprising: Activating the plurality of ultrasonic transmitters (110) in a symmetry mode comprising a plurality of symmetry ultrasonic transmitter groups using a backend controller (130) communicatively coupled to the plurality of ultrasonic transmitters (110), wherein the ultrasonic transmitters (110) in each symmetry ultrasonic transmitter group have symmetry across a plurality of symmetry lines (318, 320) in the location (150), Transmitting ultrasonic spacing pulses in the location (150) during a symmetry mode time frame using the plurality of ultrasonic transmitters (110) activated in the symmetry mode; Receiving location signal information in each symmetry mode time frame; and Determining the position of the target in the location (150) in response to the location signal information received during the symmetry mode. [10] The method of claim 9, further comprising: activating the ultrasonic transmitters (110) using the backend controller (130) in a subspace mode comprising a plurality of subspace ultrasonic transmitter groups different from the plurality of symmetry ultrasonic transmitter groups; transmitting ultrasonic spacing pulses in the location (150) during a sub-space mode time frame using the plurality of ultrasonic transmitters (110) activated in the sub-space mode; Receiving location signal information in each subspace mode time frame; and Determining the location of the target in the location (150) in response to the location signal information received during the symmetry mode and the location signal information received during the subspace mode. [11] The method of claim 10, further comprising: Receiving, at the backend controller (130), the location signal information received from the target during the symmetry mode; and Receiving, at the backend controller (130), the location signal information received from the target during the subspace mode. [12] The method of claim 11, wherein the location signal information received during the symmetry mode and the location signal information received during the subspace mode comprise timestamp data from the target. [13] The method of claim 9, wherein the symmetry mode is a double symmetry mode such that each symmetry ultrasonic transmitter group has symmetry about two orthogonal axes. [14] The method of claim 13, wherein the two orthogonal axes are a horizontal axis in the location (150) and a vertical axis in the location (150). [15] The method of claim 13, wherein the double symmetry mode is defined by a plurality of repeating geometric cells. [16] The method of claim 15, wherein the repeating geometric cells are repeating rectangular cells, square cells, or repeating diamond-shaped cells. [17] An ultrasonic location system for locating a target in a location (150), the system comprising: a plurality of ultrasonic transmitters (110) positioned within the location (150), each ultrasonic transmitter (110) configured to transmit ultrasonic spacing pulses for reception by the target in the location (150); and a backend controller (130) comprising at least one processor and at least one memory, wherein the backend controller (130) is communicatively coupled to the plurality of ultrasonic transmitters (110), wherein the backend controller (130) is configured to actuate the ultrasonic transmitters (110) in different ultrasonic transmitter groups to transmit ultrasonic spacing pulses, wherein each ultrasonic transmitter group has symmetry across one or more lines of symmetry (318, 320) in the location (150), wherein the backend controller (130) is further configured to actuate each ultrasonic transmitter group in a sequential order over a respective time frame, and wherein the backend controller (130) is configured to receive location signal information in each time frame and determine a location of the target in the location (150) from the received location signal information obtained from the plurality of ultrasonic transmitter groups.

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