Disclosed embodiments relate to wireless communications systems and the operation thereof, and more specifically, to the generation of phase-coherent signaling based on calibration of phase values among ranging nodes in a phase-based Time Difference of Arrival (TDOA) framework so as to substantially eliminate an effect of multipath interference upon coordinate location determination.
Many different applications exist which require the physical location of objects to be determined and/or tracked over time. Examples include asset tracking solutions such as those deployed in hospitals, warehouses, manufacturing facilities and construction locations. Other solutions involve the tracking of people such as in assisted living facilities or various work environments where knowing the physical location of people over time and/or at the current moment is an important characteristic of overall performance.
These applications, often referred to as “Real Time Location Systems” or “RTLS”, are used in any number of scenarios in which the location of one or more physical objects are tracked over time. Typically, the objects being tracked are “tagged” with small wireless capable tags that are attached to the object(s) being tracked. These tags are ideally low cost and transmit using a low power protocol, such as Bluetooth or Bluetooth Low Energy (BLE) or other such a protocol having characteristic low power drain.
Object tracking applications are typically implemented using a user interface which shows the location of the tags in real time in graphical form or via some other reporting format. Location determination of the tags as they move around may be accomplished via various ranging techniques in which the distance between the tag and one or more system components (herein generically referred to as a “beacon”) is determined. The RTLS generally require use of multiple beacons when arriving at the location determination(s). These locations are collectively used to calculate a real time geographical position for the tag, and thus a position for the object(s) being tracked as a result of being attached to or otherwise in the immediate physical vicinity of the tag.
In some RTLS systems, one or more beacons “advertise” their presence via periodic wireless transmissions and when a location determination is required, a predetermined handshaking process occurs between the tag and the beacons with respect to the tag undertakes determination of ranging to a respective beacon or beacons and its location determination based thereon. Alternatively, other RTLS systems function such that the tag instead advertises its presence to the beacon and initiates the handshaking protocol when a location determination is required.
As one might imagine, accurate location determination for objects in these RTLS systems is directly dependent on the accuracy of the ranging values calculated between the tags and each of the beacons. In some systems, a minimum of four (4) beacon-tag ranges is preferred in order to establish a confident geographic coordinate for the tag. If even one of the ranges calculated diverges even minimally from the actual value, the location estimation for the tag can be unusably inaccurate. By way of example, in a hospital environment, while it may not be a requirement to know exactly where in the room a specific piece of equipment is located, at least knowing which room the equipment is in would typically be a minimum requirement. If ranging error is significant enough, the wrong room for a piece of equipment could be reported.
Ranging errors can be caused by a number of factors including environmental conditions such as noise, multi-path channel effects, i.e., multipath interference, clock synchronization and sampling artifacts. Time synchronization and frequency accuracy, or lack thereof, as between the tag and the beacons, can significantly affect ranging accuracy because of the high rate of radio wave propagation. As a result, even small timing errors can cause very significant ranging errors.
In referring to
Relative to the various paradigms for determining ranging, including, for example, Time of Flight (ToF) and Time Difference of Arrival (TDOA), phase, i.e., the angular relationship among transmitted and received signaling for a given frequency and measured time period, may be assessed to determine usable ranging data. Sources of ranging error such as lack of timing synchronization and frequency offset, as discussed above and when existing between transmitted and received signaling, directly effect shift in the aforementioned phase. In other words, phase shift and multipath Mp, when left unaddressed, may skew opportunity to obtain usable ranging data based on implementation of ToF and TDOA frameworks, and also, therefore, an ability to accurately calculate a geographical position of a tag.
In this regard, data compiled when the above frameworks are implemented may be manipulated and/or evaluated to negate the effect of phase shift on applicable ranging measurement data. To do so, however, system transmission components may be required to effectively cooperate to achieve viable phase coherence, i.e., constant or same phase shift, for signaling capable of producing ranging measurement data.
In view of such cooperation, however, it would also be advantageous to account for or reconcile such Mp and phase shift, as between beacons, with greater independence among the system transmission components. Doing so, it will be understood, will enhance analysis of signal transmission, and thus increase accuracy in the geolocation of the tag. This way, an optimized RTLS may be deployed to provide any or all of the following, including, for example, proximity sensing, alert systems, jobsite and warehouse asset monitoring, and tracking of assets to be inventoried and for which location must be determined.
It is to be understood that both the following summary and the detailed description are exemplary and explanatory and are intended to provide further explanation of the present embodiments as claimed. Neither the summary nor the description that follows is intended to define or limit the scope of the present embodiments to the particular features mentioned in the summary or in the description. Rather, the scope of the present embodiments is defined by the appended claims.
An embodiment may include a system for generating phase-coherent wireless signaling, including a master beacon (MB) and a slave beacon (SB) each configured to engage in bidirectional wireless communications across channels of a given frequency band, the communications being initiated by the SB in response to detection of an advertisement from the MB, and via transmission to the MB of a first Constant Tone (CT) at each of the channels. In these regards, at each channel, the SB may (a) receive a second CT from the MB in response to receipt by the MB of the first CT, and sample each second CT in in-phase and quadrature (IQ) format, (b) store each IQ sample according to the respective channel therefor, and (c) based on the stored IQ samples, calculate and store a set of one-way channel phase values each defining a calibration factor for calibrating a local oscillator (LO) of the SB to that of the MB.
A further embodiment may include a method in accordance with the aforementioned system.
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate exemplary embodiments and, together with the description, further serve to enable a person skilled in the pertinent art to make and use these embodiments and others that will be apparent to those skilled in the art. Embodiments herein will be more particularly described in conjunction with the following drawings wherein:
The present disclosure will now be described in terms of various exemplary embodiments. This specification discloses one or more embodiments that incorporate features of the present embodiments. The embodiment(s) described, and references in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic. Such phrases are not necessarily referring to the same embodiment. The skilled artisan will appreciate that a particular feature, structure, or characteristic described in connection with one embodiment is not necessarily limited to that embodiment but typically has relevance and applicability to one or more other embodiments.
In the several figures, like reference numerals may be used for like elements having like functions even in different drawings. The embodiments described, and their detailed construction and elements, are merely provided to assist in a comprehensive understanding of the present embodiments. Thus, it is apparent that the present embodiments can be carried out in a variety of ways, and does not require any of the specific features described herein. Also, well-known functions or constructions are not described in detail since they would obscure the present embodiments with unnecessary detail.
The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the present embodiments, since the scope of the present embodiments are best defined by the appended claims.
It should also be noted that in some alternative implementations, the blocks in a flowchart, the communications in a sequence-diagram, the states in a state-diagram, etc., may occur out of the orders illustrated in the figures. That is, the illustrated orders of the blocks/communications/states are not intended to be limiting. Rather, the illustrated blocks/communications/states may be reordered into any suitable order, and some of the blocks/communications/states could occur simultaneously.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedure, Section 2111.03.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
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. Additionally, all embodiments described herein should be considered exemplary unless otherwise stated.
The word “network” is used herein to mean one or more conventional or proprietary networks using an appropriate network data transmission protocol, or other specification and/or guidelines which may be applicable to the transfer of information. Examples of such networks include, PSTN, LAN, WAN, WiFi, LTE, CBRS, and the like.
The phrase “wireless device” is used herein to mean one or more conventional or proprietary devices using radio frequency transmission techniques or any other techniques enabling the transfer of information. Examples of such wireless devices include cellular telephones, desktop computers, laptop computers, handheld computers, electronic games, portable digital assistants, MP3 players, DVD players, or the like.
Bluetooth Low Energy (BLE) networking enables detection and connection among devices that generally do not require continuous connection therebetween in order for an exchange of information in the form of data to occur. Yet, such devices depend upon extended battery life in order that the opportunity for such an exchange may continue to reliably exist. The devices themselves vary in their construction, whether, for example, a sensor, a cellphone, a network access point, or some other object configured to enable and/or provide BLE communication(s) and which is either stationary or mobile, such as a BLUETOOTH tag. In the context of BLE networking, such devices are prescribed by the BLUETOOTH Core Specification 4.0 and are compatible with IEEE 802.15.1, as appropriate.
Embodiments herein may encompass signaling on either a BLE network, or another wireless network so as to demonstrate implementation of the herein discussed phase-coherent signaling, i.e., signaling having constant or same phase shift. Turning now to
System 100 and its components may be configured to be operable in accordance with BLE protocol, such that each of the aforementioned components are configured for BLE communications. System 100 typically includes multiple tags 20—only one is shown in
System 100 may also include one or more access points 40. These access points 40 may also serve in the same capacity as beacons 30 in that their location is known to system 100 and such that they may communicate with tags 20 as described herein for the purpose of location determination as more fully described herein. In addition, access points 40, if present, also provide a connection to network interface 50 which permits data to be shared with and received from other networks such as the internet. This functionality may alternatively be provided by one or more beacons 30 in lieu of access point 40. In one embodiment, data is transmitted and received via backhaul to the internet such that a cloud based application may be accessed by a user via client 60 to view object location information and also to allow the user to configure various aspects related to the functionality of system 100.
Tags 20 are responsible for executing any coordinate location determination process locally and then reporting the location determination to system 100 via a communication to an access point 40 (or a beacon 30).
With reference now to
Additionally, IQ sampling may occur with respect to wireless communications as between multiple ones of beacons 30, as discussed herein. In this respect, each one of beacons 30 may assume a pod configuration including members disposed therein in a master-slave relationship. In particular, each such pod may include at least one first or master beacon (MB) and at least two (2) second or slave beacons (SBs).
It will be understood that each of the tags 20 and beacons 30 may be equipped with all of the necessary hardware and/or software necessary for executing the aforementioned CT enabled communications, as well as the IQ sampling in connection therewith. It will also be understood that each of the tags 20 and beacons 30 may be equipped with all of the necessary hardware and/or software for executing the herein discussed calibration, phase synchronization, ranging, and location determination operations, as applicable and as related to an exchange of CT enabled communications.
As described below, in an effort to achieve phase coherence as between signaling between a SB and a MB, each may engage in TOF sequences to enable the SB to calibrate its local oscillator (LO) to that of the MB when each of the SB and the MB engage in TDOA sequencing with the tag 20.
In a case in which each of the SB and MB engage in bi-directional, i.e., two-way, communications, as in a TOF scenario, for instance, SB may perform a scan within setting 420 to detect those MBs that are enabled to transmit the CT, as will be identified by encoding within a respectively transmitted and received beacon advertisement message from a MB. Upon detection, the SB may initiate a connection with the first detected MB, and transmit signaling in response to the beacon advertisement message received from the MB. In particular, one or more portions of the response signal, as transmitted, may be described by the following:
ej(ω
e is Euler's number,
j is the square root of −1,
ωSB is the angular frequency of the SB's signal, and
φSB is an arbitrary phase shift of the SB's signal.
The response may then be received by the MB as the following:
ej(ω
oSBMB(f,r) is the phase shift introduced during propagation from the SB to the MB, and given as a function of frequency (f) and range (r) by φ(f,r)=−2πfr/c, where c is the speed of light.
The aforementioned responsive, bi-directional signaling as initiated by a SB may be transmitted in response to the SB detecting from the MB advertisement a calibration flag for the purpose of calibrating the local oscillator (LO) of the SB to that of the MB. In this way, the calibration flag serves as a trigger for two-way communications between only the SB and MB, and which are akin to a TOF exchange but different in that the SB does not execute a ranging measurement (though such capability is contemplated). That is, the tag 20 lays dormant upon receipt of a MB advertisement containing the calibration flag, while the SB and MB communications are executed for the purpose of enabling the SB to calibrate its LO phase to that of the MB so as to enable the SB to thwart an effect of multipath interference Mp (as between the MB and the SB) when transmitting its signaling to a tag 20 during TDOA ranging sequences.
As such, and when referring to
A description of the process for initiating and exchanging CTs between a SB and a MB that enables the noted calibration to occur is now provided. The first step is for the MB to transmit an advertisement message to all SBs within range. This is represented at “A” on the MB timeline at the top (see also step 710). Such messages are periodically and repetitively transmitted until such time as acknowledged by a respectively designated SB (as identified in the MB's advertisement according to the pod configuration thereof).
The acknowledgement may comprise a request by the identified SB to begin the calibration process in response to the SB detecting from the MB advertisement a calibration flag indicating that the purpose of the advertisement is phase calibration with the particularly identified SB (see step 720) via, for instance, its media access control (MAC) address. This acknowledgement and request is represented at “B” on the timeline for the SB.
Upon receipt of the request, MB then acknowledges the request at “C” by sending an acknowledgement message to the SB. Following this, SB sends a pilot signal (defining a single CT) to the MB at “D,” to enable the MB to detect offset between local oscillator (LO) frequencies corresponding to the SB and the MB, and to synchronize frequency with the SB at “D′.” In accordance with this CT and resulting synchronization, the MB and the SB may then engage in a series of hops, at E and E′, so that each of the MB and the SB may set its relative gain. Substantially simultaneously with transmission of the pilot signal, the SB sends a “Start” message to the MB to initiate the timing that ought to control the calibration process and begin following gain setting at the MB and/or the SB. This message starts the hop frame timer which allows the MB and the SB to synchronize timing for the series of CT calibration hops which is about to come. In particular, the LOs for both the SB and the MB must remain in synch and locked during the duration of each hop, i.e., the LOs may lay dormant in between hops. In a preferred embodiment of the invention, a BLE chip manufactured by Nordic Semiconductor, such as the nRF52833 Bluetooth v4.2 and BT5 chip may be employed in both the MB and the SB to provide PPI (Programmable Peripheral Interconnect) and LO capabilities as desirable for implementing the teachings provided by the embodiments herein.
As noted, once the start message is received by the MB, the hop frame timer is triggered for both the MB and the SB via, for example a PPI interface. Once synchronized and gain has been set, the SB and the MB begin to exchange CT tones across the given frequency band for the purpose of generating signaling to enable the SB to establish a set, i.e., library, of phase response calibration factors to be used in calibrating its LO with that of the MB during TDOA sequencing with the tag 20 (see step 730). This is shown as across the set of boxes corresponding to “F” for the MB and as similarly illustrated with respect to the SB at “F′,” and referred to hereinafter as SB-MB calibration, in accordance with the exemplary calibration hops, as shown. That is, the SB may initiate a respective exchange for a given channel with a first CT, and receive from the MB a second CT thereof. In one embodiment, the band is traversed with a 1 MHz sample rate across a 100 MHz bandwidth, resulting in 100 tone exchanges to be made, although more or less samples could be used across a wider or narrower band and/or in a different licensed or unlicensed band without departing from the scope or spirit of the embodiments herein. At the conclusion of the SB-MB calibration and before ending the SB-MB operations at step 750, each of the SB and the MB may thereafter engage in TDOA sequencing, at step 740, to enable the tag 20 to ascertain relative phase shift as to their signaling and corresponding PLD with respect to the tag 20 as basis for its determination of a respective coordinate location within space 420.
In general, and with reference to
In referring to
ZSBMB=e−j(ω
wherein
ωSB and φSB respectively represent the SB's LO angular frequency and phase;
ωMB and φMB respectively represent the MB's LO angular frequency and phase;
Δωt0 approximates 0 as each of the SB and MB LOs are synchronized (as discussed above, i.e., prior to their exchange of tones);
t0 represents the reception time of the CT at the MB;
φm represents multipath interference between the SB and the MB; and
φSBMB represents a phase shift of the CT while travelling a distance d between from the SB to the MB, and is given by:
At each channel, the SB, as shown at step 830, IQ samples each MB CT, in response to ZSBMB, as ZMBSB and stores each sample for each channel of the band. Based on these stored samples, the SB further calculates therefrom a respective phase angle, e.g., ∠ZMBSB radians, and associates the same to its stored sample.
At this stage, the SB has compiled a library of two-way channel phase responses given the two-way communications according to the SB-MB calibration as discussed above. As such, and as is understood that phrase repeats modulo-2π, it is necessary to, at step 840, unwrap the two-way responses (see Itoh, Kazuyoshi. (1982). Analysis of the phase unwrapping problem. Applied optics. 21. 2470. 10.1364/AO.21.002470, for exemplary unwrapping technique(s)) and halve those responses so as to derive, upon re-wrapping, a one-way channel response which may be applicable during TDOA sequencing as between the SB and the tag 20. Thus, upon the conclusion of the SB-MB calibration, as indicated at step 850, the SB has compiled a library of one-way channel phase response values defining respective channel calibration factors for use in TDOA sequencing with the tag 20. Each such factor may be a function of the propagation phase shift as between the MB and the SB as well as the Mp component φm so as to be given by the following:
Zcal=ej(ϕ
As has been discussed above, transmissions from the MB to the SB may often occasion instances of multipath interference Mp such that signaling of a CT received at the SB may be given by the following:
ZMBSB=ej(ω
That is, and with reference to
So as to account for, i.e., substantially remove, the phase shift resulting from Mp experienced in transmission from the MB to the SB, the SB draws upon its library of catalogued listing of phase response calibration factors for the respective communications channel. More specifically, the SB invokes, as at 940, the respective calibration factor for a given channel as the subtrahend relative to the measured ∠ZMBSB. This way, phase coherence between the MB and the SB may be given by the following:
∠ZMBSB−∠Zcal=φMB−φSB+φMBSB+φm−φMBSB−φm=PMB−φSB=ΔLOMB/SB,
wherein ΔLOMB/SB represents the difference in phase values as between the LOs of the MB and the SB so as to define a phase synchronization adjustment value for a given channel.
Thus, as may be appreciated, invocation of Zcal as against ZMBSB substantially eliminates not only the phase shift attributable to multipath interference Mp, but also that which is attributable to propagation between the MB and the SB. Accordingly, the SB is now equipped to, prior to ending its TDOA sequence for a given channel at step 960, adjust its LO by Δ LOMB/SB at step 950 to achieve phase coherence with the MB. Samples thus received from the SB at the tag 20 as a third CT given by ZSBT=ej(ω
Thus, relative to signaling from the MB being received by the tag 20 as ZMBT=ej(ω
In referring to
U.S. Pat. No. 10,985,787, entitled, “System and Method For Generating Phase-Coherent Signaling When Ranging Between Wireless Communications Nodes,” and U.S. Pat. No. 11,105,917, entitled, “System and Method For Generating Phase-Coherent Signaling When Ranging Between Wireless Communications Nodes and To Account For Phase Shift Therebetween” are each incorporated herein by reference in their entireties relative to aspects as are discussed herein other than the provided MB-SB calibration, and provide for manner of providing phase-coherent signaling as between a MB and a SB relative to a tag's determination of its coordinate location. However, as discussed, calibration according to the present embodiments further refines such phase synchronization given the simultaneous and substantial elimination of (1) artifacts due to multipath interference, (2) phase shift owing to propagation, and (3) effect of various radio non-idealities among beacons.
In view of the above, it will be understood that the presently discussed embodiments enable phase coherence among signaling providing basis for the calculation of ranging data between, for example, a tag and one or more beacons in the context of phase-based TDOA measurement. As such, efficacy in calculation of such ranging data at the tag may be heightened since phase coherence may be established remotely, i.e., away from the tag and at a single transmission source such as a beacon. Additionally, and due to an ability of a beacon, such as a SB, to establish such phase coherence, processing burden on the tag is reduced, thus increasing opportunity for extended operating, i.e., battery, capacity when calculating its coordinate location and/or moving between locations.
The present embodiments are not limited to the particular embodiments illustrated in the drawings and described above in detail. Those skilled in the art will recognize that other arrangements could be devised. The present embodiments encompass every possible combination of the various features of each embodiment disclosed. One or more of the elements described herein with respect to various embodiments can be implemented in a more separated or integrated manner than explicitly described, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. While the present embodiments have been described with reference to specific illustrative embodiments, modifications and variations of the present embodiments may be constructed without departing from the spirit and scope of the present embodiments as set forth in the following claims.
While the present embodiments have been described in the context of the embodiments explicitly discussed herein, those skilled in the art will appreciate that the present embodiments are capable of being implemented and distributed in the form of a computer-usable medium (in a variety of forms) containing computer-executable instructions, and that the present embodiments apply equally regardless of the particular type of computer-usable medium which is used to carry out the distribution. An exemplary computer-usable medium is coupled to a computer such the computer can read information including the computer-executable instructions therefrom, and (optionally) write information thereto. Alternatively, the computer-usable medium may be integral to the computer. When the computer-executable instructions are loaded into and executed by the computer, the computer becomes an apparatus for practicing the embodiments. For example, when the computer-executable instructions are loaded into and executed by a general-purpose computer, the general-purpose computer becomes configured thereby into a special-purpose computer. Examples of suitable computer-usable media include: volatile memory such as random access memory (RAM); nonvolatile, hard-coded or programmable-type media such as read only memories (ROMs) or erasable, electrically programmable read only memories (EEPROMs); recordable-type and/or re-recordable media such as floppy disks, hard disk drives, compact discs (CDs), digital versatile discs (DVDs), etc.; and transmission-type media, e.g., digital and/or analog communications links such as those based on electrical-current conductors, light conductors and/or electromagnetic radiation.
Although the present embodiments have been described in detail, those skilled in the art will understand that various changes, substitutions, variations, enhancements, nuances, gradations, lesser forms, alterations, revisions, improvements and knock-offs of the embodiments disclosed herein may be made without departing from the spirit and scope of the embodiments in their broadest form.
Number | Name | Date | Kind |
---|---|---|---|
5477199 | Montreuil | Dec 1995 | A |
5548617 | Patel et al. | Aug 1996 | A |
6084932 | Veintimilla | Jul 2000 | A |
6097766 | Okubo et al. | Aug 2000 | A |
6236675 | Bedingfield et al. | May 2001 | B1 |
6480555 | Renard et al. | Nov 2002 | B1 |
6665308 | Rakib et al. | Dec 2003 | B1 |
6771590 | Marchok et al. | Aug 2004 | B1 |
7024331 | Jones et al. | Apr 2006 | B2 |
7228228 | Bartlett et al. | Jun 2007 | B2 |
7474677 | Trott | Jan 2009 | B2 |
9253727 | Luna et al. | Feb 2016 | B1 |
9264099 | Sapio et al. | Feb 2016 | B1 |
9449202 | Clare et al. | Sep 2016 | B2 |
9652955 | Ray et al. | May 2017 | B1 |
9660768 | Sapio et al. | May 2017 | B2 |
9775157 | Luna et al. | Sep 2017 | B2 |
9860882 | Sapio et al. | Jan 2018 | B2 |
10070479 | Ray et al. | Sep 2018 | B1 |
10182487 | Mohan et al. | Jan 2019 | B2 |
10234536 | Luna et al. | Mar 2019 | B2 |
10237913 | Wohler et al. | Mar 2019 | B2 |
10244373 | Bloechi et al. | Mar 2019 | B2 |
10244377 | Bloechi et al. | Mar 2019 | B2 |
10264436 | Wohler et al. | Apr 2019 | B1 |
10484932 | Bloechl et al. | Nov 2019 | B2 |
10499196 | Bloechi et al. | Dec 2019 | B2 |
10506498 | Bloechl et al. | Dec 2019 | B1 |
10708970 | Bloechl et al. | Jul 2020 | B2 |
10798547 | Gold et al. | Oct 2020 | B2 |
10845451 | Bloechi | Nov 2020 | B1 |
10862520 | Bloechl | Dec 2020 | B1 |
10873949 | Li et al. | Dec 2020 | B1 |
10887860 | Bloechi | Jan 2021 | B1 |
10985787 | Bloechi | Apr 2021 | B1 |
10986467 | Bloechl et al. | Apr 2021 | B1 |
11105917 | Bloechl | Aug 2021 | B1 |
20010001616 | Rakib et al. | May 2001 | A1 |
20070186258 | Dapper | Aug 2007 | A1 |
20070274477 | Chen | Nov 2007 | A1 |
20120032855 | Reede et al. | Feb 2012 | A1 |
20120276921 | Németh | Nov 2012 | A1 |
20130343490 | Wertz et al. | Dec 2013 | A1 |
20140192729 | Kim et al. | Jul 2014 | A1 |
20140270032 | Liu et al. | Sep 2014 | A1 |
20140301494 | Hsu et al. | Oct 2014 | A1 |
20150215880 | Rafique et al. | Jul 2015 | A1 |
20160057565 | Gold | Feb 2016 | A1 |
20160113013 | Dark et al. | Apr 2016 | A1 |
20160218833 | Sapio et al. | Jul 2016 | A1 |
20160323886 | Luna et al. | Nov 2016 | A1 |
20170127403 | Sapio et al. | May 2017 | A1 |
20170153323 | Luna et al. | Jun 2017 | A1 |
20170251390 | Gold et al. | Aug 2017 | A1 |
20170263032 | Cricri et al. | Sep 2017 | A1 |
20180139565 | Norris et al. | May 2018 | A1 |
20180157330 | Gu et al. | Jun 2018 | A1 |
20180367942 | Bloechl et al. | Dec 2018 | A1 |
20180367973 | Bloechl et al. | Dec 2018 | A1 |
20180368206 | Wohler et al. | Dec 2018 | A1 |
20190124474 | Bloechl et al. | Apr 2019 | A1 |
20190159109 | Bloechl et al. | May 2019 | A1 |
20190253282 | Hadaschik et al. | Aug 2019 | A1 |
20200022607 | Pratt et al. | Jan 2020 | A1 |
20200028530 | Shapira et al. | Jan 2020 | A1 |
20200053719 | Sadiq et al. | Feb 2020 | A1 |
20200113006 | Bloechl et al. | Apr 2020 | A1 |
20200178054 | Simileysky | Jun 2020 | A1 |
20210289364 | Patel | Sep 2021 | A1 |
20210410149 | Xia | Dec 2021 | A1 |
Entry |
---|
U.S. Appl. No. 17/036,128, filed Sep. 2020, Bloechl. |
U.S. Appl. No. 17/036,079, filed Sep. 2020, Bloechl et al. |
Gustafsson et al., “Positioning using time-difference of arrival measurements,” Proceedings of International Conference on Acoustics, Speech and Signaling Processing, vol. 6, pp. 553-556, Apr. 2003. |
International Search Report and Written Opinion issued in application No. PCT/US2021/043621, dated Jan. 4, 2022. |
Unknown, “Bluetooth Core Specification v5.1 Feature Overview,” https://www.bluetooth.com/wp-content/uploads/2019/03/1901_Feature_Overview_Brief_FINAL.pdf, Jan. 2019, retrieved on Sep. 25, 2020. |
International Search Report and Written Opinion issued in application No. PCT/US2021/043626, dated Jan. 5, 2022. |