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Title:
ENHANCED TIME DIFFERENCE OF ARRIVAL IN RADIO FREQUENCY WIRELESS COMMUNICATIONS
Document Type and Number:
WIPO Patent Application WO/2019/112647
Kind Code:
A1
Abstract:
This disclosure describes systems, methods, and devices related to enhanced time difference of arrival techniques for radio frequency time of flight indoor device positioning. A device may identify a first radio frequency pulse received from a tag device at a first time of arrival. The device may identify a second radio frequency pulse received from the tag device at a second time of arrival. The device may identify a third radio frequency pulse received from another anchor device at a third time of arrival, wherein the third radio frequency pulse is a reflection of the second radio frequency pulse. The device may determine a time difference of arrival (TDOA) based at least in part on a first time of arrival, a second time of arrival, a third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

Inventors:
TSCHIRSCHNITZ MAXIMILIAN (DE)
WAGNER MARCEL (DE)
Application Number:
PCT/US2018/040545
Publication Date:
June 13, 2019
Filing Date:
July 02, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
INTEL IP CORP (US)
International Classes:
G01S5/06; H04W64/00
Foreign References:
US20170219700A12017-08-03
US20150087330A12015-03-26
US20160223641A12016-08-04
US20160334498A12016-11-17
US20120293371A12012-11-22
Attorney, Agent or Firm:
GRIFFIN, Malvern U. III et al. (US)
Download PDF:
Claims:
CLAIMS

What is claimed is:

1. A device, the device comprising storage and processing circuitry configured to: identify a first radio frequency (RF) pulse received from a tag device at a first time of arrival;

identify a second RF pulse received from the tag device at a second time of arrival; identify a third RF pulse received from a first anchor device at a third time of arrival, wherein the third RF pulse is a reflection of the second RF pulse; and

determine a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the fourth time of arrival is associated with an arrival of the first RF pulse at the first anchor device, wherein the fifth time of arrival is associated with an arrival of the second RF pulse at the first anchor device, wherein the time of departure is associated with a time when the first anchor device sends the third RF pulse, and wherein the first TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

2. The device of claim 1, wherein to determine the first TDOA comprises the storage and the processing circuitry being further configured to:

determine a first difference between the third time of arrival and the first time of arrival;

determine a second difference between the time of departure and the fifth time of arrival;

determine a processing time between the third time of arrival and the second time of arrival;

determine a reflection interval between the time of departure and the fourth time of arrival; and

determine the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

3. The device of claim 2, wherein the first TDOA is smaller than the processing time and the reflection interval.

4. The device of claim 1, wherein the storage and processing circuitry are further configured to determine a position of the tag device based at least in part on the first TDOA.

5. The device of claim 4, wherein the storage and processing circuitry are further configured to identify a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

6. The device of claim 4, wherein to determine the position of the tag device comprises the storage and processing circuitry being further configured to:

identify a second frame received from a second anchor device;

identify a third frame received from a third anchor device;

determine a second TDOA based at least in part on the second frame;

determine a third TDOA based at least in part on the third frame; and

determine the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

7. The device of claim 6, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

8. The device of claim 6, wherein the first TDOA is associated with a first hyperbolic curve, wherein the second TDOA is associated with a second hyperbolic curve, and wherein the third TDOA is associated with a third hyperbolic curve, wherein to determine the position of the tag device further comprises the storage and processing circuitry being further configured to determine an intersection of the first hyperbolic curve, the second hyperbolic curve, and the third hyperbolic curve.

9. The device of claim 1, further comprising a transceiver configured to transmit and receive wireless signals.

10. The device of claim 9, further comprising one or more antennas coupled to the transceiver.

11. A non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: identifying, at a first anchor device, a first radio frequency (RF) pulse received from a tag device at a first time of arrival;

identifying a second RF pulse received from the tag device at a second time of arrival; causing to send a third RF pulse at a time of departure, wherein the third RF pulse is a reflection of the second RF pulse; and

determining a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, a third time of arrival, a fourth time of arrival, a fifth time of arrival, and the time of departure, wherein the third time of arrival is associated with an arrival of the first RF pulse at a second anchor device, wherein the fourth time of arrival is associated with an arrival of the second RF pulse at the second anchor device, wherein the fifth time of arrival is associated with an arrival of the third RF pulse at the second anchor device, and wherein the first TDOA indicates a difference between the first time of arrival and the third time of arrival.

12. The non-transitory computer-readable medium of claim 11, wherein determining the first TDOA comprises:

determining a first difference between the fifth time of arrival and the third time of arrival;

determining a second difference between the time of departure and the second time of arrival;

determining a processing time between the fifth time of arrival and the fourth time of arrival;

determining a reflection interval between the time of departure and the first time of arrival; and

determining the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

13. The non-transitory computer-readable medium of claim 12, wherein the first TDOA is smaller than the processing time and the reflection interval.

14. The non-transitory computer-readable medium of claim 11, the operations further comprising determining a position of the tag device based at least in part on the first TDOA.

15. The non-transitory computer-readable medium of claim 14, the operations further comprising identifying a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

16. The non-transitory computer-readable medium of claim 14, wherein determining the position of the tag device comprises:

identifying a second frame received from a third anchor device;

identifying a third frame received from a fourth anchor device;

determining a second TDOA based at least in part on the second frame;

determining a third TDOA based at least in part on the third frame; and

determining the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

17. The non-transitory computer-readable medium of claim 16, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

18. The non-transitory computer-readable medium of claim 16, wherein the first TDOA is associated with a first hyperbolic curve, wherein the second TDOA is associated with a second hyperbolic curve, and wherein the third TDOA is associated with a third hyperbolic curve, wherein determining the position of the tag device further comprises determining an intersection of the first hyperbolic curve, the second hyperbolic curve, and the third hyperbolic curve.

19. A method comprising:

identifying, by processing circuitry of a first anchor device, a first radio frequency (RF) pulse received from a tag device at a first time of arrival;

identifying a second RF pulse received from the tag device at a second time of arrival; identifying a third RF pulse received from a second anchor device at a third time of arrival, wherein the third RF pulse is a reflection of the second RF pulse; and determining a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the fourth time of arrival is associated with an arrival of the first RF pulse at the other anchor device, wherein the fifth time of arrival is associated with an arrival of the second RF pulse at the other anchor device, wherein the time of departure is associated with a time when the other anchor device sends the third RF pulse, and wherein the first TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

20. The method of claim 19, wherein determining the first TDOA comprises:

determining a first difference between the third time of arrival and the first time of arrival;

determining a second difference between the time of departure and the fifth time of arrival;

determining a processing time between the third time of arrival and the second time of arrival;

determining a reflection interval between the time of departure and the fourth time of arrival; and

determining the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

21. The method of claim 19, wherein the first TDOA is smaller than the processing time and the reflection interval.

22. The method of claim 19, further comprising determining a position of the tag device based at least in part on the first TDOA.

23. The method of claim 22, further comprising identifying a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

24. The method of claim 22, wherein determining the position of the tag device comprises: identifying a second frame received from a third anchor device;

identifying a third frame received from a fourth anchor device;

determining a second TDOA based at least in part on the second frame;

determining a third TDOA based at least in part on the third frame; and

determining the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

25. The method of claim 24, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

Description:
ENHANCED TIME DIFFERENCE OF ARRIVAL IN RADIO FREQUENCY

WIRELESS COMMUNICATIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application 62/596,586, filed December 8, 2017, the disclosure of which is incorporated herein by reference as if set forth in full. TECHNICAL FIELD

[0002] This disclosure generally relates to systems and methods for wireless communications and, more particularly, to synchronization-less time difference of arrival (TDOA) in radio frequency (RF) time of flight (ToF) indoor positioning.

BACKGROUND

[0003] Wireless devices are becoming widely prevalent and are increasingly requesting positioning. Part of providing location-based services includes positioning the mobile device. A mobile device's position may be determined from time measurements taken from radio signals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a network diagram illustrating an example network environment, in accordance with one or more example embodiments of the present disclosure.

[0005] FIG. 2 A depicts an illustrative schematic diagram for a two-way ranging approach to ranging operations.

[0006] FIG. 2B depicts an illustrative schematic diagram for time difference of arrival (TDOA) operations.

[0007] FIG. 3A depicts an illustrative schematic diagram for a Whistle algorithm for ranging operations.

[0008] FIG. 3B depicts an illustrative schematic diagram for a modified Whistle TDOA for a radio frequency system, in accordance with one or more example embodiments of the present disclosure.

[0009] FIG. 4A depicts an illustrative schematic diagram for enhanced Whistle TDOA in an RF time of flight (ToF) indoor positioning system, in accordance with one or more example embodiments of the present disclosure. [0010] FIG. 4B depicts an illustrative schematic diagram for enhanced Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure.

[0011] FIG. 5 A depicts an illustrative schematic diagram for enhanced Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure.

[0012] FIG. 5B depicts an illustrative schematic diagram for regular Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure.

[0013] FIG. 6A illustrates a flow diagram of illustrative process for enhanced double- pulse-whistle (DPW) TDOA in indoor RF systems, in accordance with one or more example embodiments of the present disclosure.

[0014] FIG. 6B illustrates a flow diagram of illustrative process for enhanced DPW TDOA in indoor RF systems, in accordance with one or more example embodiments of the present disclosure.

[0015] FIG. 7 illustrates a functional diagram of an exemplary communication station that may be suitable for use as a user device, in accordance with one or more example embodiments of the present disclosure.

[0016] FIG. 8 illustrates a block diagram of an example machine upon which any of one or more techniques (e.g., methods) may be performed, in accordance with one or more example embodiments of the present disclosure.

DETAILED DESCRIPTION

[0017] Example embodiments described herein provide certain systems, methods, and devices for enhanced synchronization-less Whistle time difference of arrival (TDOA) in radio frequency (RF) time of flight (ToF) indoor device positioning. The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, algorithm, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0018] Indoor positioning/ranging operations, in which devices may determine device locations within an indoor environment, are a useful technique when global navigation satellite system (GNSS) services may be unavailable or may lack precision, for example. Whereas GNSS services may locate a device within a few meters, such location determinations may not be precise enough for some applications.

[0019] A ToF approach for ranging operations may be used to achieve more precise indoor positioning determinations of devices. ToF approaches may involve measuring a signal transmission time between two devices and determining a distance between the devices based on a known signal speed. A ToF system may rely on devices which may be fixed or mobile, and whose positions may be known at a given time. Anchor devices may determine a location of a tag device, which may be mobile and battery-powered.

[0020] For example, because radio waves (e.g., RF waves) propagate at approximately the speed of light, a distance d between a receiver and a transmitter may be calculated by multiplying the time it takes for a radio signal to reach the receiver by a value c, where c represents the speed of light. If the position of the transmitter is known, then it is known that a receiver of the transmitter’s signals is within a radius of the transmitter. If the receiver may determine d for at least three transmitters, the receiver's position may be determined to be the intersection of three circles, in which the center point of each respective circle represents the location of each respective transmitter, and the radius of each respective circle represents the respective distance between the transmitter and the receiver. This positioning technique is referred to as ToF positioning. In ToF-based indoor positioning there are many approaches to measure distances between a tag device and anchor devices.

[0021] One ToF approach is two way ranging (TWR), which refers to an approach in which signals between two nodes (e.g., devices A and B) are exchanged to estimate the distance between the nodes. For example, node A sends a signal to node B at time t l B receives the signal at time t 2 , uses a processing time D b , and sends a signal back to node A at time t 3 . Node A in turn measures the arrival time t 4 , and, after a processing delay D a , sends a signal back to node B at time t 5 . Nodes A and B then calculate R a = t 4 — t 4 and R b = t 7 — t 3 , which may be used for the calculation of d = - (R a — D a + R b — D b ), where d is the time of flight between A and B, and thus d*c provides the distance between nodes A and B with c representing the speed of light (e.g., 3xl0 8 meters/second).

[0022] Typically, an advantage of TWR is that no clock synchronization (e.g., of anchor device clocks) is needed and thus, very low infrastructure requirements may be required. A disadvantage of TWR is that the ranging operations may be performed between two nodes and thus, a significant amount of communication may be needed to range (e.g., determine the location of) one tag device using multiple anchor devices. The significant amount of communication for TWR ranging may increase latency and reduce communication channel capacity, (e.g., the amount of tags which can be ranged in a system).

[0023] Another approach for ToF-based indoor positioning operations is TDOA. TDOA refers to an approach in which a signal emitted by a tag device may be received at different times by different anchor devices. For example, a tag device may transmit an omnidirectional signal. Nearby anchor devices may have timing mechanisms (e.g., clocks/oscillators) and may note the time of arrival of received signals from other anchor devices and from tag devices. Using an exchange of frames, the anchor devices may communicate the times of arrival and departure of signals, which the anchor devices may use to determine TDOA. Anchor devices may also communicate with an external server to exchange timing information used to determine TDOA at either the anchor devices or at a server. The exchange of frames with relevant timing information for TDOA determinations may occur in messages over a channel, radio, or medium that is the same as or different from the channel used to perform ToF operations.

[0024] In particular, because the difference in distance between a tag device and anchor devices of known locations may result in multiple possible locations for the tag device, the possible combinations of tag device locations may be represented by a hyperbolic curve. To determine a tag device’s exact location on the hyperbolic curve, multiple curves may be used to determine an intersection of the curves (e.g., multiple measurements between different pairs of anchor devices may be used). The difference between distances of two devices (e.g., anchor devices) to another device (e.g., a tag device) may represent a focal length of a hyperbola, and the intersection of multiple hyperbolas may indicate a tag device’s location. Therefore, the use of frames may allow anchor devices to communicate times of arrival and departure so that the anchor devices (e.g., three or more) may determine TDOA based on the different distances of the anchor devices from the tag. Given the locations of the anchor devices and the TDOA, the set of possible tag positions may be represented by a hyperbola. Using three anchor devices, three TDOAs may be determined (e.g., a TDOA for the first and second devices, a TDOA for the first and third devices, a TDOA for the second and third devices), allowing for a determination of the location of the tag in three-dimensional space based on the intersection of the hyperbolic curves associated with the TDOAs. The TDOA information may be exchanged by anchor devices to aggregate the information and allow an anchor device to perform TDOA calculations. An external server may also collect TDOA information from anchor devices to perform TDOA calculations and/or to communicate TDOA information with anchor devices. [0025] An advantage of TDOA is that overhead related to ranging messages may be very low, (e.g., only one broadcast of a signal from a tag to all anchors may be sufficient). A disadvantage of TDOA may be that the clocks of the anchors may need to be synchronized to provide precision and accuracy in ranging determinations. Such clock synchronization may require significant infrastructure. Another common challenge of ToF systems may be that the tag runs on battery power, so a low-power operation may be needed to conserve tag battery power. For example, Ultra Wideband (UWB) communication may require a device receiver to scan the bandwidth, thereby using significant energy. By allowing a device (e.g., a tag) to be in a transmit-only mode, however, the device may use less resources in a TDOA operation. UWB communication is an example of such a scheme, but other RF-based ToF systems like Wi-Fi FTM may benefit from TDOA as well.

[0026] In some TDOA systems, no clock synchronization is needed. For example, a TDOA system known as indoor positioning and indoor navigation (IPIN) assumes that only the anchors are communicating (e.g., transmitting), and the tags are listening only (e.g., a receive only mode). Another TDOA system may be used in Ultrasound applications, and is known as“Whistle.” In Whistle, tags are not in listening mode, but rather are only sending. In addition, clocks of the anchors may not need to be synchronized, resulting in low protocol overhead compared to TWR. A disadvantage of IPIN is that all tags may need to have a receive mode enabled all the time and thus, device battery may drained quickly. A disadvantage of Whistle is that Whistle may not be useful for RF signals unless clock drift issues are addressed. For example, tags in Whistle may use an affordable crystal oscillator which fulfills a drift (e.g., <= 20ppm). The error of a Whistle approach with such clocks may be highly dependent on signal velocity and the size of a reflection interval (e.g., a time between when an anchor receives a tag signal and sends a reflection of that signal to another anchor device). If for example, the reflection interval is lms, the clock drift is already 20ns. For sound signals, this drift may be irrelevant because sound propagates at a velocity of ~330m/s. However, radio signals (e.g., RF signals) travel with speed of light, (e.g., in 20ns around 7m), so a ranging measurement may be heavily distorted in Whistle. Therefore, Whistle may not be applicable to RF-based TDOA application scenarios unless modified to address timing issues.

[0027] Therefore, it may be beneficial to enhance TDOA operations for better use in RF- based scenarios.

[0028] Example embodiments of the present disclosure relate to systems, methods, and devices for enhanced synchronization-less TDOA for wireless communications. [0029] In one or more embodiments, enhanced synchronization-less TDOA may not require a clock synchronization between any devices. Enhanced synchronization-less TDOA may only require tag devices to send short pulses for ranging operations without the tag devices needing to be in a receive mode, thereby conserving power resources on tag devices. Enhanced synchronization-less TDOA may keep communication channel usage low in comparison with other methods (e.g., TWR), thereby facilitating efficient use of a higher number of tag devices than other methods may allow.

[0030] In one or more embodiments, enhanced synchronization-less TDOA in an RF ToF indoor positioning system may extend an existing approach (e.g., Whistle) to work with RF systems associated with severe timing requirements.

[0031] In one or more embodiments, enhanced synchronization-less TDOA in an RF ToF indoor positioning system may allow for building an indoor positioning system with low power tags and very low infrastructure needs. The enhanced synchronization-less TDOA in an RF ToF indoor positioning system may enhance existing TDOA algorithms by removing a need for clock synchronization, and by reducing the amount of communication needed between anchors and tags (e.g., compared to TWR), thereby facilitating the locating of a higher number of tags.

[0032] In one or more embodiments, enhanced synchronization-less TDOA in an RF ToF indoor positioning system may eliminate the need to synchronize nodes, and also may allow for the development of more reliable, redundant positioning systems. In enhanced synchronization-less TDOA, the amount of anchors in the system may have no effect on the positioning frequency, meaning the system may be scalable without losses on any number of anchors, thereby facilitating the operation of larger and more dynamic positioning systems (e.g., factories, convention centers, shopping malls).

[0033] The above descriptions are for purposes of illustration and are not meant to be limiting. Numerous other examples, configurations, processes, algorithms, etc., may exist, some of which are described in greater detail below. Example embodiments will now be described with reference to the accompanying figures.

[0034] FIG. 1 is a network diagram illustrating an example network environment, according to some example embodiments of the present disclosure. Wireless network 100 may include one or more user devices 120 and one or more access points(s) (AP) 102, which may communicate in accordance with IEEE 802.11 communication standards. The user device(s) 120 may be mobile devices that are non-stationary (e.g., not having fixed locations) or may be stationary devices. [0035] In some embodiments, the user devices 120 and the AP 102 may include one or more computer systems similar to that of the functional diagram of FIG. 7 and/or the example machine/system of FIG. 8.

[0036] One or more illustrative user device(s) 120 and/or AP(s) 102 may be operable by one or more user(s) 110. It should be noted that any addressable unit may be a station (STA). An STA may take on multiple distinct characteristics, each of which shape its function. For example, a single addressable unit might simultaneously be a portable STA, a quality-of- service (QoS) STA, a dependent STA, and a hidden STA. The one or more illustrative user device(s) 120 and the AP(s) 102 may be STAs. The one or more illustrative user device(s) 120 and/or AP(s) 102 may operate as a personal basic service set (PBSS) control point/access point (PCP/AP). The user device(s) 120 (e.g., 124, 126, or 128) and/or AP(s) 102 may include any suitable processor-driven device including, but not limited to, a mobile device or a non-mobile, e.g., a static, device. For example, user device(s) 120 and/or AP(s) 102 may include, a user equipment (UE), a station (STA), an access point (AP), a software enabled AP (SoftAP), a personal computer (PC), a wearable wireless device (e.g., bracelet, watch, glasses, ring, etc.), a desktop computer, a mobile computer, a laptop computer, an ultrabook™ computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, an internet of things (IoT) device, a sensor device, a PDA device, a handheld PDA device, an on-board device, an off-board device, a hybrid device (e.g., combining cellular phone functionalities with PDA device functionalities), a consumer device, a vehicular device, a non-vehicular device, a mobile or portable device, a non-mobile or non-portable device, a mobile phone, a cellular telephone, a PCS device, a PDA device which incorporates a wireless communication device, a mobile or portable GPS device, a DVB device, a relatively small computing device, a non-desktop computer, a“carry small live large” (CSLL) device, an ultra mobile device (UMD), an ultra mobile PC (UMPC), a mobile internet device (MID), an “origami” device or computing device, a device that supports dynamically composable computing (DCC), a context-aware device, a video device, an audio device, an A/V device, a set-top-box (STB), a blu-ray disc (BD) player, a BD recorder, a digital video disc (DVD) player, a high definition (HD) DVD player, a DVD recorder, a HD DVD recorder, a personal video recorder (PVR), a broadcast HD receiver, a video source, an audio source, a video sink, an audio sink, a stereo tuner, a broadcast radio receiver, a flat panel display, a personal media player (PMP), a digital video camera (DVC), a digital audio player, a speaker, an audio receiver, an audio amplifier, a gaming device, a data source, a data sink, a digital still camera (DSC), a media player, a smartphone, a television, a music player, or the like. Other devices, including smart devices such as lamps, climate control, car components, household components, appliances, etc. may also be included in this list.

[0037] As used herein, the term“Internet of Things (IoT) device” is used to refer to any object (e.g., an appliance, a sensor, etc.) that has an addressable interface (e.g., an Internet protocol (IP) address, a Bluetooth identifier (ID), a near-field communication (NFC) ID, etc.) and can transmit information to one or more other devices over a wired or wireless connection. An IoT device may have a passive communication interface, such as a quick response (QR) code, a radio-frequency identification (RFID) tag, an NFC tag, or the like, or an active communication interface, such as a modem, a transceiver, a transmitter-receiver, or the like. An IoT device can have a particular set of attributes (e.g., a device state or status, such as whether the IoT device is on or off, open or closed, idle or active, available for task execution or busy, and so on, a cooling or heating function, an environmental monitoring or recording function, a light-emitting function, a sound-emitting function, etc.) that can be embedded in and/or controlled/monitored by a central processing unit (CPU), microprocessor, ASIC, or the like, and configured for connection to an IoT network such as a local ad-hoc network or the Internet. For example, IoT devices may include, but are not limited to, refrigerators, toasters, ovens, microwaves, freezers, dishwashers, dishes, hand tools, clothes washers, clothes dryers, furnaces, air conditioners, thermostats, televisions, light fixtures, vacuum cleaners, sprinklers, electricity meters, gas meters, etc., so long as the devices are equipped with an addressable communications interface for communicating with the IoT network. IoT devices may also include cell phones, desktop computers, laptop computers, tablet computers, personal digital assistants (PDAs), etc. Accordingly, the IoT network may be comprised of a combination of “legacy” Internet-accessible devices (e.g., laptop or desktop computers, cell phones, etc.) in addition to devices that do not typically have Internet-connectivity (e.g., dishwashers, etc.).

[0038] The user device(s) 120 and/or AP(s) 102 may also include mesh stations in, for example, a mesh network, in accordance with one or more IEEE 802.11 standards and/or 3 GPP standards.

[0039] Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to communicate with each other via one or more communications networks 130 and/or 135 wirelessly or wired. The user device(s) 120 may also communicate peer-to-peer or directly with each other with or without the AP(s) 102. Any of the communications networks 130 and/or 135 may include, but not limited to, any one of a combination of different types of suitable communications networks such as, for example, broadcasting networks, cable networks, public networks (e.g., the Internet), private networks, wireless networks, cellular networks, or any other suitable private and/or public networks. Further, any of the communications networks 130 and/or 135 may have any suitable communication range associated therewith and may include, for example, global networks (e.g., the Internet), metropolitan area networks (MANs), wide area networks (WANs), local area networks (LANs), or personal area networks (PANs). In addition, any of the communications networks 130 and/or 135 may include any type of medium over which network traffic may be carried including, but not limited to, coaxial cable, twisted-pair wire, optical fiber, a hybrid fiber coaxial (HFC) medium, microwave terrestrial transceivers, radio frequency communication mediums, white space communication mediums, ultra-high frequency communication mediums, satellite communication mediums, or any combination thereof.

[0040] Any of the user device(s) 120 (e.g., user devices 124, 126, 128) and AP(s) 102 may include one or more communications antennas· The one or more communications antennas may be any suitable type of antennas corresponding to the communications protocols used by the user device(s) 120 (e.g., user devices 124, 126 and 128), and AP(s) 102. Some non-limiting examples of suitable communications antennas include Wi-Fi antennas, Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards compatible antennas, directional antennas, non-directional antennas, dipole antennas, folded dipole antennas, patch antennas, multiple-input multiple-output (MIMO) antennas, omnidirectional antennas, quasi- omnidirectional antennas, or the like. The one or more communications antennas may be communicatively coupled to a radio component to transmit and/or receive signals, such as communications signals to and/or from the user devices 120 and/or AP(s) 102.

[0041] Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform directional transmission and/or directional reception in conjunction with wirelessly communicating in a wireless network. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform such directional transmission and/or reception using a set of multiple antenna arrays (e.g., DMG antenna arrays or the like). Each of the multiple antenna arrays may be used for transmission and/or reception in a particular respective direction or range of directions. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform any given directional transmission towards one or more defined transmit sectors. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform any given directional reception from one or more defined receive sectors.

[0042] MIMO beamforming in a wireless network may be accomplished using RF beamforming and/or digital beamforming. In some embodiments, in performing a given MIMO transmission, user devices 120 and/or AP(s) 102 may be configured to use all or a subset of its one or more communications antennas to perform MIMO beamforming.

[0043] Any of the user devices 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may include any suitable radio and/or transceiver for transmitting and/or receiving radio frequency (RF) signals in the bandwidth and/or channels corresponding to the communications protocols utilized by any of the user device(s) 120 and AP(s) 102 to communicate with each other. The radio components may include hardware and/or software to modulate and/or demodulate communications signals according to pre-established transmission protocols. The radio components may further have hardware and/or software instructions to communicate via one or more Wi-Fi and/or Wi-Fi direct protocols, as standardized by the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards. In certain example embodiments, the radio component, in cooperation with the communications antennas, may be configured to communicate via 2.4 GHz channels (e.g., 802.1 lb, 802. llg, 802.11h, 802.1 lax), 5 GHz channels (e.g., 802.11h, 802.llac, 802.llax), or 60 GHZ channels (e.g., 802.l lad, 802.llay). In some embodiments, non-Wi-Fi protocols may be used for communications between devices, such as Bluetooth, dedicated short-range communication (DSRC), Ultra-High Frequency (UHF) (e.g., IEEE 802.llaf, IEEE 802.22), white band frequency (e.g., white spaces), or other packetized radio communications. The radio component may include any known receiver and baseband suitable for communicating via the communications protocols. The radio component may further include a low noise amplifier (LNA), additional signal amplifiers, an analog-to- digital (A/D) converter, one or more buffers, and digital baseband.

[0044] In one or more embodiments, a device (e.g., AP 102 or user devices 120) may send one or more signals 142 (e.g., RF pulses) to one another. The signals 142 may be transmitted as part of a ranging operation. For example, the signals 142 may be RF pulses used as sounding signals (e.g., from a tag device), and may be sent omnidirectionally so that multiple devices (e.g., anchor devices) may receive the signals 142. The anchor devices may record the times of arrival of the signals 142 and may send one or more frames 144 to communicate those times of arrival to other anchor devices. The anchor devices may determine a TDOA between each other and the tag device using the times of arrival. Given the locations of two anchor devices and their TDOA, the possible locations of a tag device may be represented by a hyperbolic curve. In a multi-dimensional space (e.g., two-dimensional), an approximate/estimated intersection of three hyperbolas may yield the position of the tag device, for example. This means that three anchor devices may determine three TDOAs between them, which may be used to determine tag device location. [0045] FIG. 2 A depicts an illustrative schematic diagram 200 for a TWR approach for ranging operations.

[0046] Referring to FIG. 2A, the TWR approach may be double sided, meaning two nodes may each transmit to each other. In particular, device 202 and device 204 may communicate with one another. For example, at time ti, device 202 may send signal 206, which may be received by device 204 at time t 2 . After a processing time Db, device 204 may send signal 208 at time t 3 , which may be received by device 202 at time t 4 . After a processing time Da, device 202 may send signal 210 at time ts, which may be received by device 204 at time t 6 . Either device 202 or device 204 may initiate a frame exchange in which one or more frames 212 (e.g., in the same or a different channel) may be exchanged between device 202 and device 204. The frames 212 may indicate times of arrival (e.g., t 2 , U, te) and times of departure (e.g., ti, t 3 , ts). Each signal between device 202 and device 204 (e.g., signal 206, signal 208, signal 210) may have a time of flight d, which represents the time for each signal to travel between device 202 and device 204.

[0047] Using the timing data, device 202 and device 204 may estimate the distance between them. Device 202 and device 204 may calculate R a = t 4 — t t and R b = t 7 — 1 3 , which may be used for the calculation of d = - (R a — D a + R b — D b ), where d is the ToF between device 202 and device 204. Thus, d*c gives the distance between A and B with c representing the speed of light.

[0048] Typically, the advantage of TWR is that no clock synchronization is needed and therefore very low infrastructure requirements apply. A disadvantage of TWR is that the ranging is always performed between two nodes (e.g., device 202 and device 204), and therefore a significant amount of communication is needed to range one tag device with four anchors (e.g., device 202 and device 204 may be anchor devices). TWR may result in high latency and reduced channel capacity (e.g., the amount of tags which can be ranged in a system).

[0049] FIG. 2B depicts an illustrative schematic diagram 250 for TDOA operations.

[0050] Referring to FIG. 2B, there is shown a TDOA with three anchor devices: device 252, device 254, and device 256. The anchor devices may determine the location of tag device 258 using TDOA. Tag device 258 may send an omnidirectional signal 260 which may be received by each of the anchor devices at different times. Curve 262 solves the TDOA between device 252 and device 254. Curve 264 solves the TDOA between device 252 and device 256. Curve 266 solves the TDOA between device 254 and device 256. Curve 262, curve 264, and curve 266 may be hyperbolic curves representing possible locations of tag device 258 based on the respective TDOAs. The intersection of curve 262, curve 264, and curve 266 may represent the location of tag device 258. The intersection may not be the exact intersection, for example, but may be an approximation.

[0051] An advantage of TDOA is that the communication overhead requirements may be relatively low. For example, a single broadcast of a signal (e.g., signal 26) from tag device 258 to all anchors may be sufficient to perform position calculations. A disadvantage of TDOA is that clocks of the anchors (e.g., device 252, device 254, device 256) may need to be synchronized.

[0052] FIG. 3A depicts an illustrative schematic diagram 300 for a Whistle algorithm for ranging operations.

[0053] The basic idea of Whistle is shown in FIG. 3A. Whistle uses a TDOA approach typically used in an ultrasound application. Applying Whistle to wireless device communications, device 302 and device 304 may be anchors determining a position of tag device 306. Device 302 may have a microphone 309 and a speaker 310, and device 304 may have a microphone 312 and a speaker 314. Tag device 306 may send signal S omnidirectionally, and signal S may be received by device 302 and by device 304 at different times. For example, device 302 may receive signal S at time t Ai (e.g., at microphone 309), and device 304 may receive signal S at time tei (e.g., at microphone 312), which may be a different time of arrival. Due to processing time, signal S may be detected by device 302 at time t A 2. Similarly, signal S may be detected by device 304 at time t B 2. Device 302 may function as a mirror device, meaning device 302 may send signal S’ (e.g., device 302 may send a sound signal using speaker 310), which may be a reflection of signal S. Device 302 may send signal S’ at time t A 3, and time t A4 may be the time signal S’ arrives at device 302 (e.g., at microphone 309). Signal S’ may arrive at device 304 at time t B 3 (e.g., at microphone 312), which may be a different time of arrival than t A4 . Due to processing delay, signal S’ may be detected by device 302 at time t A 5 and may be detected by device 304 at time t B 4. After the detection of signal S and signal S’, device 302 and device 304 may exchange one or more frames 308 (e.g., in the same or a different channel) which may indicate the times of arrival and times of departure so that the TDOA may be determined.

[0054] For example, because a time D a (e.g., the time between device 302 receiving signal S and reflecting with signal S’) may be known by device 304 along with a distance d AB between device 302 and device 304, B can calculate the TDOA value by TAB — ki - T B2 s + T A2 s— the velocity of the signal. (Note: d AA may represent the difference between a microphone and loudspeaker of device 302, where the microphone is used to receive signal S and signal S’ , and the loudspeaker is used to send signal S’).

[0055] Referring to FIG. 3A, t A4 — t A3 may represent the time from the signal S’ being sent from device 302’ s speaker 310 to device 302’ s microphone 309 to be heard by device 302. The calculation of the TDOA value T AB * which describes the TDOA of the signal S at device

302 and device 304 may be performed as follows: where d AB is the distance between device 302 and device 304, d AA is the distance between microphone 309 and speaker 310 of device 302, v is the speed of sound, (e.g., -343 m/s). It is important to understand that S’ is not issued by the tag device 306, but rather is reflected by device 302. Once the TDOA is determined for device 302 and device 304 with respect to tag device 306, a hyperbolic curve may represent the location of tag device 306. If other TDOAs are determined with other devices, then the intersection of the hyperbolic curves associated with respective TDOAs may identify the position of the tag device 306. The intersection may not be the exact intersection, but an approximation.

[0056] In one or more embodiments, if a third anchor device (not shown) were listening to signal S and S’ , and if the positions of device 302, device 304, and the third anchor device were known (e.g., a priori), the position of tag device 306 may be determined on a two-dimensional plane. No additional reflective signal exchange would be necessary.

[0057] However, applying Whistle TDOA in RF systems like UWB and Wi-Fi FTM may lead to high measurement error, so enhancements may be beneficial to improve accuracy and precision. For example, an enhanced Whistle TDOA may assume no difference between a sender and receiver component of an anchor device (e.g., d AA may be 0). In addition, in RF systems, the estimated time of arrival and time of departure may be very accurate due to the signal velocity, so t A 2, t B 2, T AS , and t B 4 may not be needed. Also, because S’ is a reflective signal of signal S, signal S’ may be removed from the process flow may equal d, wherein v = c, the speed of light. The enhancements of Whistle TDOA as shown in FIG. 3A may be represented by the modified TDOA process shown in FIG. 3B.

[0058] FIG. 3B depicts an illustrative schematic diagram 350 for a modified Whistle TDOA for an RF system, in accordance with one or more example embodiments of the present disclosure. [0059] Referring to FIG. 3B, device 352 and device 354 may be anchor devices which may perform a TDOA analysis to determine the position of tag device 356. At time tO, tag device 356 may send omnidirectionally signal 358, which may be received by device 352 at time ti and by device 354 at time t 2 , which may be a different time of arrival than time tl. After a reflection interval D t> , device 354 at time t 3 may send a reflection of signal 358 (e.g., signal 360), which may require a ToF d to arrive at device 352 at time t 4 . In order for device 352 and device 354 to determine TDOA, device 352 and device 354 may exchange one or more frames 362 (e.g., in the same or a different channel) indicating the times of arrival and times of departure associated with signal 358 and signal 360.

[0060] Once the TDOA is determined for device 352 and device 354 with respect to tag device 356, a hyperbolic curve may represent the location of tag device 356. If other TDOAs are determined with other devices, then the intersection of the hyperbolic curves associated with respective TDOAs may identify the position of the tag device 356. The intersection may not be the exact intersection, but an approximation.

[0061] The following calculations show that the modified Whistle TDOA approach without additional enhancements may lead to a very high estimation error. The main source of the error is the size of the reflection interval D b . The error calculation for a basic Whistle TDOA Algorithm is as follows. Signal 358 and signal 360 may be RF pulses/signals.

[0062] Let t 2 —t 1 = d, then D b — R a = d + d. The drift of a clock of device 352 and a clock of device 354 may be represented by e A and e B respectively. It may assumed that e A and ee remain constant over a short time period (e.g., 1 ms). The relationship between the real time t r and any local time measured at device 302, t A , may be modeled by t r = t A (1 + e A ) and for device 304 in a similar manner. For delta without any drifting, d = D b — R a — d, and for the clock drifting case d = D b — R a — d. (Note: The time d is calculated from the a-priori known distance between device 352 and device 354, and it is assumed that that this is error free because it can be measured with external means.). It may be concluded that d— d = D b

[0063] Assuming that d + d are in order of magnitude of lOOns and e a is at most 20ppm, only the term D b (e a — e b ) contributes to the estimation error. With 20 ppm a worst case estimation of e a — e b = 40ppm . With D b being in order of magnitude of lms, the error introduced by clock drifts is around 20ns. This is already ~7m propagation of RF signal and therfeore leads to a very high position estimation inaccuracy, which makes the basic Whistle algorithm useless for RF-based ToF measurements. Therefore, it may be beneficial to enhance the Whistle TDOA algorithm for more accurate use with RF systems.

[0064] FIG. 4A depicts an illustrative schematic diagram 400 for enhanced Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure. The enhanced Whistle TDOA may be referred to as a Double-Pulsed- Whistle (DPW) TDOA algorithm.

[0065] Referring to FIG. 4 A, device 402 and device 404 may be anchor devices which may determine the position of tag device 406. Tag device 406 may at time tO send omnidirectionally signal 408 (e.g., a first pulse), which may arrive at device 402 at time ti and may arrive at device 404 at time t 2 . After a reflection interval D t> , device 404 may send at time t 3 a reflection of signal 408 (e.g., signal 410), which may have a ToF between device 404 and device 402 of d, and may arrive at device 402 at time I4. At time t , tag device 406 may send a second pulse (e.g., signal 412) omnidirectionally, and signal 412 may arrive at device 402 at time t 6 and at device 404 at time t 7 . A signal propagation time d may represent the time between time ti and time t 2 , and between time t 6 and time t 7 . After the two pulses have arrived at device 402 and device 404 in addition to the arrival of a reflective signal (e.g., signal 410), device 402 and device 404 may communicate one or more frames 414 (e.g., in the same or a different channel or using a different radio over wire, etc.), which may include indications of the times of arrival and departure. Signal 408, signal 410, and signal 412 may be RF signals/pulses.

[0066] Once the TDOA is determined for device 402 and device 404 with respect to tag device 406, a hyperbolic curve may represent the location of tag device 406. If other TDOAs are determined with other devices, then the intersection of the hyperbolic curves associated with respective TDOAs may identify the position of the tag device 406. The intersection may not be the exact intersection, but an approximation.

[0067] FIG. 4B depicts an illustrative schematic diagram 450 for enhanced Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure. The enhanced Whistle TDOA may be referred to as a DPW TDOA algorithm.

[0068] Referring to FIG. 4B, there is shown DPW with reflection occurring after two pulse signals have been sent by a tag. For example, device 452 and device 454 may be anchor devices which may determine the position of tag device 456. Tag device 456 at time to may send signal 458 (e.g., a first pulse) omnidirectionally, and signal 458 may arrive at device 452 at time ti and at device 454 at time t 2 . The difference between time ti and time t 2 may refer to a signal propagation d. At time t , tag device 456 may send a second pulse (e.g., signal 460) omnidirectionally, and signal 460 may arrive at device 452 at time t 6 and at device 454 at time t 7 . The difference between time t 6 and time t 7 may refer to signal propagation d. After a reflection interval D b from time t 2 to time t 3 , device 454 may send a reflection of signal 460 (e.g., signal 462) at time t 3 . Signal 462 may arrive at device 452 at time U, and signal 462 may have a ToF between device 454 and device 452 of value d. Signal 458, signal 460, and signal 462 may be RF signals/pulses. After the arrivals of signal 458, signal 460, and signal 462, device 452 and device 454 may exchange one or more frames 464 (e.g., in the same or a different channel) which may include indications of the times of flight and departure to be used in the TDOA calculations.

[0069] Once the TDOA is determined for device 452 and device 454 with respect to tag device 456, a hyperbolic curve may represent the location of tag device 456. If other TDOAs are determined with other devices, then the intersection of the hyperbolic curves associated with respective TDOAs may identify the position of the tag device 456. The intersection may not be the exact intersection, but an approximation.

[0070] Referring to FIGs. 4A and 4B, device 404 and device 454 may be mirror devices, and device 402 and device 452 may be in a receive/listening mode in which device 402 and device 454 may not need to transmit. Tag device 406 and tag device 456 may not need to receive any signals in order for the respective tag devices to be located in the enhanced DPW process.

[0071] In one or more embodiments, dependency on local clocks of device 402, device 404, device 452, and device 454 (e.g., anchor devices) and the reflection interval D b may be reduced significantly so that the accuracy of the TDOA and position measurements are improved.

[0072] With the TDOA enhancements, the schematic diagram 400 has an analogy to the TWR described above, yet there are clear differences. For example, in TWR one of the nodes is a tag (e.g., tag device 406), the other node an anchor (e.g., device 402 or device 404), whereas in DPW, device 402 and device 404 both are anchors, and tag device 406 is the tag. In DPW, device 402 is not sending anything in contrast to TWR, where one device has to reply to the other device. In TWR, the round trip time is estimated and assumed to be 2d where d is unknown, but in DPW, d + d may be estimated and used to calculate d because d is known, since the anchor positions are known.

[0073] In one or more embodiments, once TDOA value d is determined for two anchor devices (e.g., device 402 and device 404) with respect to a tag device (e.g., tag device 406), a hyperbolic curve representing the possible locations of the tag device may be compared with other hyperbolic curves based on other TDOA values of other anchor devices (not shown). The intersection of multiple hyperbolic curves may represent the location of the tag device (e.g., as shown in FIG. 2B). The intersection may not be the exact intersection, but an approximation.

[0074] Still referring to FIG. 4A and FIG. 4B, in DPW, clock drift effects are reduced, thereby improving accuracy of TDOA and position determinations. DPW also may allow more efficient channel use. The difference becomes clear when FIG. 4A is considered and it may be realized that the“reflection” of signal S may happen not only after the first signal of S but also after the second signal (e.g., signal 460 in FIG. 4B). This is depicted in FIG. 5A. Note that the signal d may be the reflection of the second signal sent by the tag device (e.g., signal 462 may be a reflection of signal 460 as shown in FIG. 4B). The calculations applied to schematic diagram 450 of FIG. 4B may possible if it is considered that D a and R a are negative.

[0075] In one or more embodiments using DPW’s enhanced synchronization-less TDOA, R a = d + d + D b and R b = d + d + D a . From this, it may be concluded that R a R b = (d + d + D b )(d + d + D a ) <=> R a R b — D a D b = (d + 6)(d + d + D a + D b ). Then, using the relationship R a = d + d + D b and R b = d + d + D a results in two equations: R a R b — D a D b = (d + 6)(R a + D a ), and R a R b — D a — D b = (d + 6)(R b + D b ). The formula for d may be calculated as d = RaR D ° ) same time the

fact that R a + D a = R b + D b , the final estimation for d may be derived —

2 R R D p ) value d is a“thought” or virtual signal propagation,

(R a + D a + R b + D b )

it may be negative as well. A negative d is not a problem as long as D b and D a are much larger than d. However, the error correction applied to a TWR scheme may be remodeled for usage with DPW. From the DPW calculation above, it can be concluded that the TDOA value d =

T A A B B may be calculated

[0076] Referring to FIG. 4A and 4B, it may be shown that error for DPW is significantly reduced from the Whistle approach. For example, denote k A = (1 + e A ) and k B = (1 + e B ), resulting in d = k A ke RaR b DaD b d = k d

k A Ra+Da

Therefore d— d = d— k A 6 + e A 6 = 2e A 6 , d— d = k B 6 + e B 6 = 2e B 6 . If d is in order of magnitude of lOOns, the overall error is «100 pico seconds, and thus negligible, meaning a significant improvement by reduced error in comparison with the Whistle TDOA approach without enhancements. Also, because device 402 and device 452 are only listening, the same algorithm may be performed in parallel with an arbitrary amount of anchors, because except for device 404 and device 454 (e.g., the respective mirror devices), all anchors only need to listen to the signals. Thus, assuming that another anchor device also is listening to signal 408 or signal 458, a single DPW flow may be sufficient to locate tag device 406 or tag device 456 with TDOA. This allows DPW to be much more scalable in terms of a number of tags operating per system because of low protocol overhead and low energy consumption of tags.

[0077] Still referring to FIG. 4A and FIG. 4B, there is shown differences between DPW and the Whistle method. In particular, the influence of clock drifts on DPW is much smaller than regular Whistle. In addition, regular Whistle is not usable for RF based ToF schemes due to its lack of accuracy when applied to an RF scheme. In addition, the channel use of DPW is significant lower than that associated with regular Whistle. For example, DPW needs only 3/4 of the signals used by regular Whistle, as shown with respect to FIG. 5 A and FIG. 5B, explained further below. DPW is not only more accurate than regular Whistle, DPW also allows for locating more tags per second or locating the same amount of tags using less signal transmissions and therefore energy saving when less signals are sent.

[0078] FIG. 5 A depicts an illustrative schematic diagram 500 for enhanced Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure.

[0079] FIG. 5B depicts an illustrative schematic diagram 550 for regular Whistle TDOA in an RF ToF indoor positioning system, in accordance with one or more example embodiments of the present disclosure.

[0080] Referring to FIG. 5A, there is shown a DPW flow. Device 502 and device 504 may be anchors which may determine the location of tag device 506. Tag device 506 omnidirectionally may send signal 508, which may arrive at device 502 and at device 504 at different times. Device 504 may be a mirror device and may send a reflection of signal 508 (e.g., signal 510), which may arrive at device 502. Tag device 506 omnidirectionally may send signal 512, which may arrive at device 502 and at device 504 at different times. Tag device 506 omnidirectionally may send signal 514, which may arrive at device 502 and at device 504 at different times. Device 504 may send a reflection of signal 514 (e.g., signal 516), which may arrive at device 502. The sequence may continue, as tag device 506 omnidirectionally may send another signal 518, which may arrive at device 502 and at device 504 at different times. Tag device 506 may omnidirectionally send another signal 520, which may arrive at device 502 and at device 504 at different times. Device 504 may send a reflection of signal 520 (e.g., signal 522), which may arrive at device 502. Tag device 506 may send signal 524 and signal 526 omnidirectionally, each of which may be received by device 502 and by device 504 at different times. Device 504 may send a reflection of signal 526 (e.g., signal 528), which may be received by device 502. Tag device 506 may send signal 530 omnidirectionally, and so on. Multiple ranging operations may be performed. For example, ranging operation Rl may include the sending of signal 508 through the final time of arrival of signal 512 at device 504 (e.g., two pulses and a reflective signal). Ranging operation R2 may include the sending of signal 512 through the final time of arrival of signal 516 at device 502 (e.g., two pulses and a reflective signal). Ranging operation R3 may include the sending of signal 514 through the final time of arrival of signal 518 at device 504. Ranging operation R4 may include the sending of signal 518 through the time of arrival of signal 522 at device 502.

[0081] Referring to FIG. 5B, there is shown a regular Whistle flow. Device 552 and device 554 may be anchors which may determine the location of tag device 556. For ranging operation Rl, tag device 556 omnidirectionally may send signal 558, which may arrive at device 552 and at device 554 at different times. Device 554 may be a mirror device and may send a reflection of signal 558 (e.g., signal 560), which may arrive at device 502. For ranging operation R2, tag device 556 may send another signal (e.g., signal 562), which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 564), which may arrive at device 552. For ranging operation R3, tag device 556 may send signal 566, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 568), which may arrive at device 552. For ranging operation R4, tag device 556 may send signal 570, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 572), which may arrive at device 552. For a subsequent ranging operation, tag device 556 may send signal 574, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 576), which may arrive at device 552. For a subsequent ranging operation, tag device 556 may send signal 578, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 580), which may arrive at device 552. For a subsequent ranging operation, tag device 556 may send signal 582, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 584), which may arrive at device 552. For a subsequent ranging operation, tag device 556 may send signal 586, which may arrive at device 552 and at device 554 at different times. Device 554 may send another reflective signal (e.g., signal 588), which may arrive at device 552. The sequence of signals and reflective signals may be associated with respective ranging operations. For example, ranging operation Rl may include signal 558 and signal 560. Ranging operation R2 may include signal 562 and signal 564. Ranging operation R3 may include signal 566 and signal 568. Ranging operation R4 may include signal 570 and signal 572.

[0082] The DPW approach of FIG. 5A reflects every second signal. For example, signal 516 is a reflective signal sent after signal 512 and signal 514 (e.g., a double pulse followed by a reflective signal). Using one signal (e.g., signal 514) with reflection (e.g., signal 516) and one signal without reflection (e.g., signal 512) in a DPW operation, DPW may perform n-l ranging operations using n signals from tag device 506. While there may be no significant difference with a regular Whistle approach as shown in FIG. 5B, as the regular Whistle approach may perform n ranging operations with n signals from tag device 556, one important difference between DPW and regular Whistle is that DPW may reflect every second signal while regular Whistle reflects every signal. Therefore, DPW needs fewer signals than Regular Whistle to perform the same amount of ranging operations (e.g., three reflective signals in DPW for four ranging operations versus four reflective signals for four ranging operations in regular Whistle) . The efficiency of DPW’ s synchronization- less TDOA in an RF TOF indoor positioning system is an improvement over the regular Whistle method, and the clock drift for anchors is significantly smaller with the DPW method’s enhancements.

[0083] FIG. 6A illustrates a flow diagram of illustrative process 600 for enhanced DPW TDOA in indoor RF systems, in accordance with one or more example embodiments of the present disclosure.

[0084] At block 602, processing circuitry of a device (e.g., the user device(s) 120 and/or the AP 102 of FIG. 1) may identify a first RF pulse (e.g., signal 458 of FIG. 4B) received from a tag device (e.g., tag device 456 of FIG. 4B) at a first time of arrival (e.g., time ti of FIG. 4B). The device may be an anchor device (e.g., device 452 of FIG. 4B), and may be in a receive/listening only mode for ranging operations associated with determining a location of the tag device.

[0085] At block 604, the processing circuitry of the device may identify a second RF pulse (e.g., signal 460 of FIG. 4B) received from the tag device at a second time of arrival (e.g., time t¾ of FIG. 4B). The second RF pulse may be part of a double pulse sequence along with the first RF pulse. Both the first and second RF pulses may be sent omnidirectionally by the tag device so that any anchor device within range of the tag device may receive the pulses. This way, the device may perform ranging operations with multiple anchor devices in order to better estimate the location of the tag device in three-dimensional space.

[0086] At block 606, the processing circuitry of the device may identify a third RF pulse (e.g., signal 462 of FIG. 4B) received from another anchor device (e.g., device 454) at a third time of arrival (e.g., time U of FIG. 4B), wherein the third RF pulse may be a reflection of the second RF pulse. The reflection signal may be part of the same ranging operation as the first and second RF pulses, and the sequence of two pulses plus the reflection signal may be used to determine the location of the tag device.

[0087] At block 608, the processing circuitry of the device may determine a TDOA based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure. The TDOA may indicate a difference between the first time of arrival and the fourth time of arrival. The fourth time of arrival may be the time at which the first RF pulse arrives at the other anchor device. The fifth time of arrival may be the time at which the second RF pulse arrives at the other anchor device. The time of departure may be the time at which the other anchor device sends the third RF pulse (e.g., the reflective signal). Knowing the location of the device and the other anchor device, the device may determine the TDOA using the arrival/departure time information of the signals in the DPW ranging operation. The TDOA may be associated with a hyperbolic curve representing the possible locations of the tag device. If the device also performs ranging operations with other anchor devices, the device may receive such timing information of the DPW ranging operations using signals from the same tag device, and may determine respective TDOAs associated with hyperbolic curves. The intersection of the curves may indicate the location of the tag device. The intersection may not be the exact intersection, but an approximation.

[0088] The anchor device may identify a frame (e.g., frames 464 of FIG. 4B) including an indication of a fourth time of arrival (e.g., time t 2 of FIG. 4B) at which the first RF pulse is received by the other anchor device, an indication of a fifth time of arrival (e.g., time t 7 of FIG. 4B) at which the second RF pulse is received by the other anchor device, and an indication of a time of departure (e.g., time t 3 of FIG. 4B) at which the third RF pulse is sent by the other anchor device. The frame may be part of a communication sequence which may be initiated by the device or by the other anchor device, and may be between anchor devices and/or an external server which may collect TDOA information from anchor devices. The frame alternatively may be a different type of frame with any format used in Wi-Fi RF systems (e.g., as defined by the IEEE 802.11 communication standards). The frame may include time of arrival and time of departure information for each anchor device. For example, for the device to be able to determine TDOA with the other anchor device with respect to the tag device, the timing information of the two pulse signals and the reflection signals with respect to their arrival at and departure from the other anchor device may be provided to the device (and vice versa, the timing information of the signals at the device may be provided to the other anchor device) in an exchange of frames. Using the timing information, the device may determine the TDOA, which may then be used to estimate the location of the tag device.

[0089] To determine the TDOA, the processing circuitry of the device may determine a first difference (e.g., R a of FIG. 4B) between the third time of arrival (e.g., t4 of FIG. 4B) and the first time of arrival (e.g., ti of FIG. 4B), may determine a second difference (e.g., R b of FIG. 4B) between the time of departure (e.g., t 3 of FIG. 4B) and the fifth time of arrival (e.g., t 7 of FIG. 4B), may determine a processing time (e.g., D a of FIG. 4B) between the third time of arrival (e.g., t4 of FIG. 4B) and the second time of arrival (e.g., t ¾ of FIG. 4B), may determine a reflection interval (e.g., D b of FIG. 4B) between the time of departure (e.g., t 3 of FIG. 4B) and the fourth time of arrival (e.g., t 2 of FIG. 4B), and may determine the TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval. The TDOA may be smaller than the processing time and the reflection interval.

[0090] FIG. 6B illustrates a flow diagram of illustrative process 650 for enhanced DPW TDOA in indoor RF systems, in accordance with one or more example embodiments of the present disclosure.

[0091] At block 652, processing circuitry of a device (e.g., the user device(s) 120 and/or the AP 102 of FIG. 1) may identify a first RF pulse (e.g., signal 458 of FIG. 4B) received from a tag device (e.g., tag device 456) at a first time of arrival (e.g., time t 2 of FIG. 4B). The device may be performing a DPW ranging operation to determine the location of the tag device.

[0092] At block 654, the processing circuitry of the device may identify a second RF pulse (e.g., signal 460 of FIG. 4B) received from the tag device at a second time of arrival (e.g. time t 7 of FIG. 4B). The second RF pulse may be part of a double pulse sequence along with the first RF pulse. Both the first and second RF pulses may be sent omnidirectionally by the tag device so that any anchor device within range of the tag device may receive the pulses. This way, the device may perform ranging operations with multiple anchor devices in order to better estimate the location of the tag device in three-dimensional space.

[0093] At block 656, the processing circuitry of the device may cause the device to send a third RF pulse (e.g., signal 462) at a time of departure (e.g., time t 3 of FIG. 4B), wherein the third RF pulse is a reflection of the second RF pulse (e.g., signal 460 of FIG. 4B). The reflection signal may be part of the same ranging operation as the first and second RF pulses, and the sequence of two pulses plus the reflection signal may be used to determine the location of the tag device.

[0094] At block 658, the processing circuitry of the device may determine a TDOA based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, the fourth time of arrival, the fifth time of arrival, and the time of departure, wherein the TDOA indicates a difference between the first time of arrival and the third time of arrival. Knowing the location of the device and the other anchor device, the device may determine the TDOA using the arrival/departure time information of the signals in the DPW ranging operation. The TDOA may be associated with a hyperbolic curve representing the possible locations of the tag device. If the device also performs ranging operations with other anchor devices, the device may receive such timing information of the DPW ranging operations using signals from the same tag device, and may determine respective TDOAs associated with hyperbolic curves. The intersection of the curves may indicate the location of the tag device. The intersection may not be the exact intersection, but an approximation.

[0095] The processing circuitry of the device may identify a frame received from a second anchor device (e.g., device 452 of FIG. 4A), and the frame may include an indication of a third time of arrival (e.g., time ti of FIG. 4B) at which the first RF pulse is received by the second anchor device, an indication of a fourth time of arrival (e.g., time t 6 of FIG. 4B) at which the second RF pulse is received by the second anchor device, and an indication of a fifth time of arrival (e.g., time t4 of FIG. 4B) at which the third RF pulse is received by the second anchor device. The frame may be part of a sequence which may be initiated by the device or by the other anchor device. The frame alternatively may be a different type of frame with any format used in Wi-Fi RF systems (e.g., as defined by the IEEE 802.11 communication standards). The frame may include time of arrival and time of departure information for each anchor device. For example, for the device to be able to determine TDOA with the other anchor device with respect to the tag device, the timing information of the two pulse signals and the reflection signals with respect to their arrival at and departure from the other anchor device may be provided to the device (and vice versa, the timing information of the signals at the device may be provided to the other anchor device) in an exchange of frames. Using the timing information, the device may determine the TDOA, which may then be used to estimate the location of the tag device.

[0096] For example, the processing circuitry of the device may determine a first difference between the fifth time of arrival and the third time of arrival (e.g., R a of FIG. 4B), may determine a second difference between the time of departure and the second time of arrival (e.g., R b of FIG. 4B), may determine a processing time between the fifth time of arrival and the fourth time of arrival (e.g., D a of FIG. 4B), may determine a reflection interval between the time of departure and the first time of arrival (e.g., D b of FIG. 4B), and may determine the TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval. The TDOA may be smaller than the processing time and the reflection interval.

[0097] FIG. 7 shows a functional diagram of an exemplary communication station 700 in accordance with some embodiments. In one embodiment, FIG. 7 illustrates a functional block diagram of a communication station that may be suitable for use as an AP 102 (FIG. 1) or a user device 120 (FIG. 1) in accordance with some embodiments. The communication station 700 may also be suitable for use as a handheld device, a mobile device, a cellular telephone, a smartphone, a tablet, a netbook, a wireless terminal, a laptop computer, a wearable computer device, a femtocell, a high data rate (HDR) subscriber station, an access point, an access terminal, or other personal communication system (PCS) device.

[0098] The communication station 700 may include communications circuitry 702 and a transceiver 710 for transmitting and receiving signals to and from other communication stations using one or more antennas 701. The communications circuitry 702 may include circuitry that can operate the physical layer (PHY) communications and/or media access control (MAC) communications for controlling access to the wireless medium, and/or any other communications layers for transmitting and receiving signals. The communication station 700 may also include processing circuitry 706 and memory 708 arranged to perform the operations described herein. In some embodiments, the communications circuitry 702 and the processing circuitry 706 may be configured to perform operations detailed in FIGs. 2A, 2B, 3A, 3B, 4A, 4B, 5 A, 5B, 6 A, and 6B.

[0099] In accordance with some embodiments, the communications circuitry 702 may be arranged to contend for a wireless medium and configure frames or packets for communicating over the wireless medium. The communications circuitry 702 may be arranged to transmit and receive signals. The communications circuitry 702 may also include circuitry for modulation/demodulation, upconversion/downconversion, filtering, amplification, etc. In some embodiments, the processing circuitry 706 of the communication station 700 may include one or more processors. In other embodiments, two or more antennas 701 may be coupled to the communications circuitry 702 arranged for sending and receiving signals. The memory 708 may store information for configuring the processing circuitry 706 to perform operations for configuring and transmitting message frames and performing the various operations described herein. The memory 708 may include any type of memory, including non-transitory memory, for storing information in a form readable by a machine (e.g., a computer). For example, the memory 708 may include a computer-readable storage device, read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices and other storage devices and media.

[0100] In some embodiments, the communication station 700 may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), a wearable computer device, or another device that may receive and/or transmit information wirelessly.

[0101] In some embodiments, the communication station 700 may include one or more antennas 701. The antennas 701 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated for spatial diversity and the different channel characteristics that may result between each of the antennas and the antennas of a transmitting station.

[0102] In some embodiments, the communication station 700 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

[0103] Although the communication station 700 is illustrated as having several separate functional elements, two or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may include one or more microprocessors, DSPs, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio- frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements of the communication station 700 may refer to one or more processes operating on one or more processing elements.

[0104] Certain embodiments may be implemented in one or a combination of hardware, firmware, and software. Other embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory memory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. In some embodiments, the communication station 700 may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

[0105] FIG. 8 illustrates a block diagram of an example of a machine 800 or system upon which any one or more of the techniques (e.g., methodologies) discussed herein may be performed. In other embodiments, the machine 800 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 800 may operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, the machine 800 may act as a peer machine in peer-to-peer (P2P) (or other distributed) network environments. The machine 800 may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a wearable computer device, a web appliance, a network router, a switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine, such as a base station. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0106] Examples, as described herein, may include or may operate on logic or a number of components, modules, or mechanisms. Modules are tangible entities (e.g., hardware) capable of performing specified operations when operating. A module includes hardware. In an example, the hardware may be specifically configured to carry out a specific operation (e.g., hardwired). In another example, the hardware may include configurable execution units (e.g., transistors, circuits, etc.) and a computer readable medium containing instructions where the instructions configure the execution units to carry out a specific operation when in operation. The configuring may occur under the direction of the executions units or a loading mechanism. Accordingly, the execution units are communicatively coupled to the computer-readable medium when the device is operating. In this example, the execution units may be a member of more than one module. For example, under operation, the execution units may be configured by a first set of instructions to implement a first module at one point in time and reconfigured by a second set of instructions to implement a second module at a second point in time.

[0107] The machine (e.g., computer system) 800 may include a hardware processor 802 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 804 and a static memory 806, some or all of which may communicate with each other via an interlink (e.g., bus) 808. The machine 800 may further include a power management device 832, a graphics display device 810, an alphanumeric input device 812 (e.g., a keyboard), and a user interface (UI) navigation device 814 (e.g., a mouse). In an example, the graphics display device 810, alphanumeric input device 812, and UI navigation device 814 may be a touch screen display. The machine 800 may additionally include a storage device (i.e., drive unit) 816, a signal generation device 818 (e.g., a speaker), an enhanced positioning device 819, a network interface device/transceiver 820 coupled to antenna(s) 830, and one or more sensors 828, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensor. The machine 800 may include an output controller 834, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.)).

[0108] The storage device 816 may include a machine readable medium 822 on which is stored one or more sets of data structures or instructions 824 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 824 may also reside, completely or at least partially, within the main memory 804, within the static memory 806, or within the hardware processor 802 during execution thereof by the machine 800. In an example, one or any combination of the hardware processor 802, the main memory 804, the static memory 806, or the storage device 816 may constitute machine-readable media.

[0109] The enhanced positioning device 819 may carry out or perform any of the operations and processes (e.g., process 600 of FIG. 6A and process 650 of FIG. 6B) described and shown above.

[0110] In one or more embodiments, the enhanced positioning device 819 may facilitate enhanced synchronization-less TDOA, which may not require a clock synchronization between any devices. Enhanced synchronization-less TDOA may only require tag devices to send short pulses for ranging operations without the tag devices needing to be in a receive mode, thereby conserving power resources on tag devices. Enhanced synchronization-less TDOA may keep communication channel usage low in comparison with other methods (e.g., TWR), thereby facilitating efficient use of a higher number of tag devices than other methods may allow.

[0111] In one or more embodiments, the enhanced positioning device 819 may facilitate enhanced synchronization- less TDOA in an RF ToF indoor positioning system, and may extend an existing approach (e.g., Whistle) to work with RF systems associated with severe timing requirements.

[0112] In one or more embodiments, the enhanced positioning device 819 may facilitate enhanced synchronization- less TDOA in an RF ToF indoor positioning system, and may allow for building an indoor positioning system with low power tags and very low infrastructure needs. The enhanced synchronization-less TDOA in an RF ToF indoor positioning system may enhance existing TDOA algorithms by removing a need for clock synchronization, and by reducing the amount of communication needed between anchors and tags (e.g., compared to TWR), thereby facilitating the locating of a higher number of tags.

[0113] In one or more embodiments, the enhanced positioning device 819 may facilitate enhanced synchronization-less TDOA in an RF ToF indoor positioning system, and may eliminate the need to synchronize nodes, and also may allow for the development of more reliable, redundant positioning systems. In enhanced synchronization-less TDOA, the amount of anchors in the system may have no effect on the positioning frequency, meaning the system may be scalable without losses on any number of anchors, thereby facilitating the operation of larger and more dynamic positioning systems (e.g., factories, convention centers, shopping malls).

[0114] It is understood that the above are only a subset of what the enhanced positioning device 819 may be configured to perform and that other functions included throughout this disclosure may also be performed by the enhanced positioning device 819.

[0115] While the machine -readable medium 822 is illustrated as a single medium, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 824.

[0116] Various embodiments may be implemented fully or partially in software and/or firmware. This software and/or firmware may take the form of instructions contained in or on a non-transitory computer-readable storage medium. Those instructions may then be read and executed by one or more processors to enable performance of the operations described herein. The instructions may be in any suitable form, such as but not limited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. Such a computer-readable medium may include any tangible non-transitory medium for storing information in a form readable by one or more computers, such as but not limited to read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; a flash memory, etc.

[0117] The term“machine-readable medium” may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 800 and that cause the machine 800 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting machine-readable medium examples may include solid-state memories and optical and magnetic media. In an example, a massed machine-readable medium includes a machine -readable medium with a plurality of particles having resting mass. Specific examples of massed machine-readable media may include non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD- ROM disks.

[0118] The instructions 824 may further be transmitted or received over a communications network 826 using a transmission medium via the network interface device/transceiver 820 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communications networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), plain old telephone (POTS) networks, wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, and peer-to-peer (P2P) networks, among others. In an example, the network interface device/transceiver 820 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 826. In an example, the network interface device/transceiver 820 may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple- output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term“transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine 800 and includes digital or analog communications signals or other intangible media to facilitate communication of such software. The operations and processes described and shown above may be carried out or performed in any suitable order as desired in various implementations. Additionally, in certain implementations, at least a portion of the operations may be carried out in parallel. Furthermore, in certain implementations, less than or more than the operations described may be performed.

[0119] The word“exemplary” is used herein to mean“serving as an example, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. The terms“computing device,” “user device,” “communication station,” “station,” “handheld device,” “mobile device,”“wireless device” and“user equipment” (UE) as used herein refers to a wireless communication device such as a cellular telephone, a smartphone, a tablet, a netbook, a wireless terminal, a laptop computer, a femtocell, a high data rate (HDR) subscriber station, an access point, a printer, a point of sale device, an access terminal, or other personal communication system (PCS) device. The device may be either mobile or stationary.

[0120] As used within this document, the term“communicate” is intended to include transmitting, or receiving, or both transmitting and receiving. This may be particularly useful in claims when describing the organization of data that is being transmitted by one device and received by another, but only the functionality of one of those devices is required to infringe the claim. Similarly, the bidirectional exchange of data between two devices (both devices transmit and receive during the exchange) may be described as“communicating,” when only the functionality of one of those devices is being claimed. The term“communicating” as used herein with respect to a wireless communication signal includes transmitting the wireless communication signal and/or receiving the wireless communication signal. For example, a wireless communication unit, which is capable of communicating a wireless communication signal, may include a wireless transmitter to transmit the wireless communication signal to at least one other wireless communication unit, and/or a wireless communication receiver to receive the wireless communication signal from at least one other wireless communication unit.

[0121] As used herein, unless otherwise specified, the use of the ordinal adjectives“first,” “second,”“third,” etc., to describe a common object, merely indicates that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

[0122] The term“access point” (AP) as used herein may be a fixed station. An access point may also be referred to as an access node, a base station, an evolved node B (eNodeB), or some other similar terminology known in the art. An access terminal may also be called a mobile station, user equipment (UE), a wireless communication device, or some other similar terminology known in the art. Embodiments disclosed herein generally pertain to wireless networks. Some embodiments may relate to wireless networks that operate in accordance with one of the IEEE 802.11 standards.

[0123] Some embodiments may be used in conjunction with various devices and systems, for example, a personal computer (PC), a desktop computer, a mobile computer, a laptop computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, a personal digital assistant (PDA) device, a handheld PDA device, an on board device, an off-board device, a hybrid device, a vehicular device, a non- vehicular device, a mobile or portable device, a consumer device, a non-mobile or non-portable device, a wireless communication station, a wireless communication device, a wireless access point (AP), a wired or wireless router, a wired or wireless modem, a video device, an audio device, an audio- video (A/V) device, a wired or wireless network, a wireless area network, a wireless video area network (WVAN), a local area network (LAN), a wireless LAN (WLAN), a personal area network (PAN), a wireless PAN (WPAN), and the like.

[0124] Some embodiments may be used in conjunction with one way and/or two-way radio communication systems, cellular radio-telephone communication systems, a mobile phone, a cellular telephone, a wireless telephone, a personal communication system (PCS) device, a PDA device which incorporates a wireless communication device, a mobile or portable global positioning system (GPS) device, a device which incorporates a GPS receiver or transceiver or chip, a device which incorporates an RFID element or chip, a multiple input multiple output (MIMO) transceiver or device, a single input multiple output (SIMO) transceiver or device, a multiple input single output (MISO) transceiver or device, a device having one or more internal antennas and/or external antennas, digital video broadcast (DVB) devices or systems, multi standard radio devices or systems, a wired or wireless handheld device, e.g., a smartphone, a wireless application protocol (WAP) device, or the like.

[0125] Some embodiments may be used in conjunction with one or more types of wireless communication signals and/or systems following one or more wireless communication protocols, for example, radio frequency (RF), infrared (IR), frequency-division multiplexing (FDM), orthogonal FDM (OFDM), time-division multiplexing (TDM), time-division multiple access (TDMA), extended TDMA (E-TDMA), general packet radio service (GPRS), extended GPRS, code-division multiple access (CDMA), wideband CDMA (WCDMA), CDMA 2000, single-carrier CDMA, multi-carrier CDMA, multi-carrier modulation (MDM), discrete multi- tone (DMT), Bluetooth®, global positioning system (GPS), Wi-Fi, Wi-Max, ZigBee, ultra- wideband (UWB), global system for mobile communications (GSM), 2G, 2.5G, 3G, 3.5G, 4G, fifth generation (5G) mobile networks, 3 GPP, long term evolution (LTE), LTE advanced, enhanced data rates for GSM Evolution (EDGE), or the like. Other embodiments may be used in various other devices, systems, and/or networks.

[0126] Example 1 may be a device comprising memory and processing circuitry configured to: identify a first radio frequency (RF) pulse received from a tag device at a first time of arrival; identify a second RF pulse received from the tag device at a second time of arrival; identify a third RF pulse received from a first anchor device at a third time of arrival, wherein the third RF pulse is a reflection of the second RF pulse; and determine a time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the fourth time of arrival is associated with an arrival of the first RF pulse at the first anchor device, wherein the fifth time of arrival is associated with an arrival of the second RF pulse at the first anchor device, wherein the time of departure is associated with a time when the first anchor device sends the third RF pulse, and wherein the first TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

[0127] Example 2 may include the device of example 1 and/or some other example herein, wherein to determine the first TDOA comprises the storage and the processing circuitry being further configured to: determine a first difference between the third time of arrival and the first time of arrival; determine a second difference between the time of departure and the fifth time of arrival; determine a processing time between the third time of arrival and the second time of arrival; determine a reflection interval between the time of departure and the fourth time of arrival; and determine the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

[0128] Example 3 may include the device of example 2 and/or some other example herein, wherein the first TDOA is smaller than the processing time and the reflection interval.

[0129] Example 4 may include the device of example 1 and/or some other example herein, wherein the storage and processing circuitry are further configured to determine a position of the tag device based at least in part on the first TDOA.

[0130] Example 5 may include the device of example 4 and/or some other example herein, wherein the storage and processing circuitry are further configured to identify a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

[0131] Example 6 may include the device of example 4 and/or some other example herein, wherein to determine the position of the tag device comprises the storage and processing circuitry being further configured to: identify a second frame received from a second anchor device; identify a third frame received from a third anchor device; determine a second TDOA based at least in part on the second frame; determine a third TDOA based at least in part on the third frame; and determine the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

[0132] Example 7 may include the device of example 6 and/or some other example herein, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

[0133] Example 8 may include the device of example 6 and/or some other example herein, wherein the first TDOA is associated with a first hyperbolic curve, wherein the second TDOA is associated with a second hyperbolic curve, and wherein the third TDOA is associated with a third hyperbolic curve, wherein to determine the position of the tag device further comprises the storage and processing circuitry being further configured to determine an intersection of the first hyperbolic curve, the second hyperbolic curve, and the third hyperbolic curve.

[0134] Example 9 may include the device of example 1 and/or some other example herein, further comprising a transceiver configured to transmit and receive wireless signals.

[0135] Example 10 may include the device of example 9 and/or some other example herein, further comprising one or more antennas coupled to the transceiver.

[0136] Example 11 may include a non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: identifying, at a first anchor device, a first radio frequency (RF) pulse received from a tag device at a first time of arrival; identifying a second RF pulse received from the tag device at a second time of arrival; causing to send a third RF pulse at a time of departure, wherein the third RF pulse is a reflection of the second RF pulse; and determining a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, a third time of arrival, a fourth time of arrival, a fifth time of arrival, and the time of departure, wherein the third time of arrival is associated with an arrival of the first RF pulse at a second anchor device, wherein the fourth time of arrival is associated with an arrival of the second RF pulse at the second anchor device, wherein the fifth time of arrival is associated with an arrival of the third RF pulse at the second anchor device, and wherein the first TDOA indicates a difference between the first time of arrival and the third time of arrival.

[0137] Example 12 may include the non-transitory computer-readable medium of example

11 and/or some other example herein, wherein determining the first TDOA comprises: determining a first difference between the fifth time of arrival and the third time of arrival; determining a second difference between the time of departure and the second time of arrival; determining a processing time between the fifth time of arrival and the fourth time of arrival; determining a reflection interval between the time of departure and the first time of arrival; and determining the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

[0138] Example 13 may include the non-transitory computer-readable medium of example

12 and/or some other example herein, wherein the first TDOA is smaller than the processing time and the reflection interval.

[0139] Example 14 may include the non-transitory computer-readable medium of example 11 and/or some other example herein, the operations further comprising determining a position of the tag device based at least in part on the first TDOA.

[0140] Example 15 may include the non-transitory computer-readable medium of example 14 and/or some other example herein, the operations further comprising identifying a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

[0141] Example 16 may include the non-transitory computer-readable medium of example 14 and/or some other example herein, wherein determining the position of the tag device comprises: identifying a second frame received from a third anchor device; identifying a third frame received from a fourth anchor device; determining a second TDOA based at least in part on the second frame; determining a third TDOA based at least in part on the third frame; and determining the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

[0142] Example 17 may include the non-transitory computer-readable medium of example 16 and/or some other example herein, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

[0143] Example 18 may include the non-transitory computer-readable medium of example 16 and/or some other example herein, wherein the first TDOA is associated with a first hyperbolic curve, wherein the second TDOA is associated with a second hyperbolic curve, and wherein the third TDOA is associated with a third hyperbolic curve, wherein determining the position of the tag device further comprises determining an intersection of the first hyperbolic curve, the second hyperbolic curve, and the third hyperbolic curve.

[0144] Example 19 may include a method comprising: identifying, by processing circuitry of a first anchor device, a first radio frequency (RF) pulse received from a tag device at a first time of arrival; identifying a second RF pulse received from the tag device at a second time of arrival; identifying a third RF pulse received from a second anchor device at a third time of arrival, wherein the third RF pulse is a reflection of the second RF pulse; and determining a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the fourth time of arrival is associated with an arrival of the first RF pulse at the other anchor device, wherein the fifth time of arrival is associated with an arrival of the second RF pulse at the other anchor device, wherein the time of departure is associated with a time when the other anchor device sends the third RF pulse, and wherein the first TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

[0145] Example 20 may include the method of example 19 and/or some other example herein, wherein determining the first TDOA comprises: determining a first difference between the third time of arrival and the first time of arrival; determining a second difference between the time of departure and the fifth time of arrival; determining a processing time between the third time of arrival and the second time of arrival; determining a reflection interval between the time of departure and the fourth time of arrival; and determining the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

[0146] Example 21 may include the method of example 19 and/or some other example herein, wherein the first TDOA is smaller than the processing time and the reflection interval.

[0147] Example 22 may include the method of example 19 and/or some other example herein, further comprising determining a position of the tag device based at least in part on the first TDOA.

[0148] Example 23 may include the method of example 22 and/or some other example herein, further comprising identifying a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

[0149] Example, 24 may include the method of example 22 and/or some other example herein, wherein determining the position of the tag device comprises: identifying a second frame received from a third anchor device; identifying a third frame received from a fourth anchor device; determining a second TDOA based at least in part on the second frame; determining a third TDOA based at least in part on the third frame; and determining the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

[0150] Example, 25 may include the method of example 24 and/or some other example herein, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

[0151] Example 26 may include an apparatus comprising means for: identifying, by processing circuitry of a first anchor device, a first radio frequency (RF) pulse received from a tag device at a first time of arrival; identifying a second RF pulse received from the tag device at a second time of arrival; identifying a third RF pulse received from a second anchor device at a third time of arrival, wherein the third RF pulse is a reflection of the second RF pulse; and determining a first time difference of arrival (TDOA) based at least in part on the first time of arrival, the second time of arrival, the third time of arrival, a fourth time of arrival, a fifth time of arrival, and a time of departure, wherein the fourth time of arrival is associated with an arrival of the first RF pulse at the other anchor device, wherein the fifth time of arrival is associated with an arrival of the second RF pulse at the other anchor device, wherein the time of departure is associated with a time when the other anchor device sends the third RF pulse, and wherein the first TDOA indicates a difference between the first time of arrival and the fourth time of arrival.

[0152] Example 27 may include the apparatus of example 26 and/or some other example herein, wherein determining the first TDOA comprises: determining a first difference between the third time of arrival and the first time of arrival; determining a second difference between the time of departure and the fifth time of arrival; determining a processing time between the third time of arrival and the second time of arrival; determining a reflection interval between the time of departure and the fourth time of arrival; and determining the first TDOA based at least in part on the first difference, the second difference, the processing time, and the reflection interval.

[0153] Example 28 may include the apparatus of example 26 and/or some other example herein, wherein the first TDOA is smaller than the processing time and the reflection interval.

[0154] Example 29 may include the apparatus of example 26 and/or some other example herein, further comprising determining a position of the tag device based at least in part on the first TDOA. [0155] Example 30 may include the apparatus of example 29 and/or some other example herein, further comprising identifying a first frame comprising an indication of the fourth time of arrival, an indication of the fifth time of arrival, and an indication of the time of departure.

[0156] Example, 31 may include the apparatus of example 29 and/or some other example herein, wherein determining the position of the tag device comprises: identifying a second frame received from a third anchor device; identifying a third frame received from a fourth anchor device; determining a second TDOA based at least in part on the second frame; determining a third TDOA based at least in part on the third frame; and determining the position of the tag device based at least in part on the first TDOA, the second TDOA, and the third TDOA.

[0157] Example 32 may include the apparatus of example 31 and/or some other example herein, wherein the second frame is associated with a time of arrival of the first RF pulse received by the third anchor device and wherein the third frame is associated with a time of arrival of the first RF pulse received by the fourth anchor device.

[0158] Example 33 may include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of a method described in or related to any of examples 1-32, or any other method or process described herein.

[0159] Example 34 may include an apparatus comprising logic, modules, and/or circuitry to perform one or more elements of a method described in or related to any of examples 1-32, or any other method or process described herein.

[0160] Example 35 may include a method, technique, or process as described in or related to any of examples 1-32, or portions or parts thereof.

[0161] Example 36 may include an apparatus comprising: one or more processors and one or more computer readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform the method, techniques, or process as described in or related to any of examples 1-32, or portions thereof.

[0162] Example 37 may include a method of communicating in a wireless network as shown and described herein.

[0163] Example 38 may include a system for providing wireless communication as shown and described herein.

[0164] Example 39 may include a device for providing wireless communication as shown and described herein. [0165] Embodiments according to the disclosure are in particular disclosed in the attached claims directed to a method, a storage medium, a device and a computer program product, wherein any feature mentioned in one claim category, e.g., method, can be claimed in another claim category, e.g., system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject- matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.

[0166] The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.

[0167] Certain aspects of the disclosure are described above with reference to block and flow diagrams of systems, methods, apparatuses, and/or computer program products according to various implementations. It will be understood that one or more blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and the flow diagrams, respectively, may be implemented by computer-executable program instructions. Likewise, some blocks of the block diagrams and flow diagrams may not necessarily need to be performed in the order presented, or may not necessarily need to be performed at all, according to some implementations.

[0168] These computer-executable program instructions may be loaded onto a special- purpose computer or other particular machine, a processor, or other programmable data processing apparatus to produce a particular machine, such that the instructions that execute on the computer, processor, or other programmable data processing apparatus create means for implementing one or more functions specified in the flow diagram block or blocks. These computer program instructions may also be stored in a computer-readable storage media or memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage media produce an article of manufacture including instruction means that implement one or more functions specified in the flow diagram block or blocks. As an example, certain implementations may provide for a computer program product, comprising a computer- readable storage medium having a computer-readable program code or program instructions implemented therein, said computer-readable program code adapted to be executed to implement one or more functions specified in the flow diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational elements or steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide elements or steps for implementing the functions specified in the flow diagram block or blocks.

[0169] Accordingly, blocks of the block diagrams and flow diagrams support combinations of means for performing the specified functions, combinations of elements or steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, may be implemented by special-purpose, hardware-based computer systems that perform the specified functions, elements or steps, or combinations of special-purpose hardware and computer instructions.

[0170] Conditional language, such as, among others,“can,”“could,”“might,” or“may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language is not generally intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.

[0171] Many modifications and other implementations of the disclosure set forth herein will be apparent having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.