Systems and methods for determining a tag location

Abstract

Systems (100) and methods (400) for Radio Frequency Identification ("RFID") security tags. The methods comprise: concurrently reading the RFID security tags and locator tags to obtain unique identifiers thereof and Received Signal Strength indicator ("RSSI") measurements therefore, where the RFID security tags are respectively coupled to inventory items located within a facility and the locator tags are placed at locations within the facility so as to respectively define a plurality of Zones Of Interest ("ZOls") in which inventory items may reside; and determining which ZOI of the plurality of ZOIs each said RFID security tag resides within based at least on the RSSI measurements, a number of times each locator tag was read, read times specifying when the locator tags were read, differences in read times for the locator tags, and known locations of the locator tags.

Description

SYSTEMS AND METHODS FOR DETERMINING A TAG LOCATIONFIELD OF THE INVENTION

[0001] This document relates generally to systems and methods for determining a taglocation. More particularly, this document relates to Radio Frequency Identification ("RFID")based systems and methods for determining a tag location using a handheld reader, locator tagsand a software algorithm.BACKGROUND OF THE INVENTION

[0002] RFID technology has conventionally been used in the identification and tracking ofproducts, equipment, and other articles. For example, RFID systems are commonly used inElectronic Article Surveillance ("EAS") and in logistical and inventory systems for monitoringgoods and equipment and recording information on the target item. An RFlD system typicallyincludes an RFID reader and an RFID device such as a tag or label. The RFID reader maytransmit a Radio-Frequency ("RF") carrier signal to the RFID device. The RFID device mayrespond to the RF carrier signal (or interrogator signal) with a data response signal (orauthentication reply signal) encoded with information stored on the RFID device. RFID devicesmay store information such as a unique identifier or an Electronic Product Code ("EPC")associated with an article or item.

[0003] The RFID technology allows business owners and other persons to rapidly and / orcontini~ously( a) identify products, assets and people, (b) count products, assets and people, and(c) track locations of products, assets and people. As such, the RFID technology offerssignificant benefits over a physical inventory counting process. By leveraging the RFlDtechnology to increase inventory accuracy, retailers are better able to perform replenishment,service customer requests, manage product recalls or any other activities that rely on inventorydata. Products on the market today to aid in determining a product's identification and / orlocation are too expensive, bulky and / or heavy. For example, some handheld RFID tag readersare bulky, heavy and need to be physically carried by a person through a facility. Cellphoneintegrated RFlD tag readers are expensive since a special dongle is needed for enabling the RFIDtag reading operations.

[0004] Despite the advantages of the above described RFID solutions, they do not provideknowledge of where in a facility the inventory is kept. Knowledge of this can help retailers in anumber of ways. Therefore there is a need for an i~nprovedi nventory solution.SUMMARY OF THE. INVENTION

[0005] The present disclosure concerns implementing systems and methods for locatingRFID security tags. The methods involve concurrently reading the RFID security tags andlocator tags to obtain unique identifiers thereof and Received Signal Strength Indicator ("RSSI")measurements therefore. The RFID security tags are respectively coupled to inventory itemslocated within a facility. The locator tags are placed at locations within the facility so as torespectively define a plurality of Zones Of Interest ("ZOIs") in which inventory items mayreside. Thereafter, a determination is made as to which ZOI of the plurality of ZOIs each RFIDsecurity tag resides within. This determination is based at least on the RSSI measurements, anumber of times each locator tag was read, read times specifying when the locator tags wereread, differences in read times for the locator tags, and known locations of the locator tags.Accuracy of the determining may be increased using barcodes.

[0006] In some scenarios, the method further comprises identifying and eliminating eachstray locator tag based on at least one of the number of times the stray locator tag was read, anRSSI measured for the stray locator tag, and a difference in read times between the stray locatortag and another locator tag.

[0007] In those or other scenarios, the duration of time a handheld reader spent reading RFIDsecurity tags and locator tags in each ZOI of the plurality of ZOIs is determined. The duration oftime is determined based on Start Read Time ("SRT") and End Read Time ("ERT). The SRTco~nprises(a ) a read time of a locator tag which was the first locator tag read in a given ZOI or(b) a read time that creates a largest difference during a change between reading location tags ina first ZOI and reading tags in a second ZOI. The ERT comprises (a) a read time of a locator tagwhich was the last locator tag read in any given ZOI or (b) a read time prior to a read time thatcreates a largest difference during a change between reading location tags in a first ZOI andreading tags in a second ZOI. Next, it is determined whether read times for each RFlD securitytag fall within the duration of time. lf the read times for tlie RFID security tag do fall within theduration of time, then a conclusion is made that the RFID security tag is located within the ZOI.

[0008] In some scenarios, a conclusion may be made that at least one RFID security tagresides in at least a first ZOI and a second ZOI. In this case, the IiFID security tag is assigned tothe first ZOI when the RFID security tag's total number of reads and average signal strengthassociated with the first ZOI have higher values than the RFlD security tag's total number ofreads and average signal strength associated with the second ZOI, respectively. In another case,the RFlD security tag is assigned to the second ZOI when the total number of reads and averagesignal strength associated with the second ZOI is higher than those associated with the first ZOI.In contrast, tlie RFID security tag is assigned to the first or second ZOI in which other inventoryitems belonging to the same product category as the inventory object to which the RFlD securitytag is coupled, when the RFID security tag's total number of reads and average signal strengthassociated with both ZOIs cannot clearly distinguish where it belongs to.DESCRIPTION OF THE DRAWINGS

[0009] Embodiments will be described with reference to the following drawing figures, inwhich like numerals represent like items throughout the figures, and in which:[OOlO] FIG. 1 is an illustration of an exemplary system that is useful for ~~nderstandintlgiepresent invention.[OOllj FIG. 2 is a block diagram of an exemplary architecture for a handheld reader.

[0012] FIG. 3 is a block diagram of an exemplary architecture for an exemplary RemoteProcessing Unit ("RPU").

[0013] FIGS. 4A-4B (collectively referred to herein as "FIG. 4") provide a flow diagram ofan exemplary method for determining a tag location.DETAILED DESCRIPTION OF THE INVENTION

[0014] It will be readily understood that the components of the embodiments as generallydescribed herein and illustrated in the appended figures co~lld be arranged and designed in a widevariety of different configurations. Thus, the following more detailed description of variousembodiments, as represented in the figures, is not intended to limit the scope of the presentdisclosure, but is merely representative of various embodiments. While the various aspects ofthe embodiments are presented in drawings, the drawings are not necessarily drawn to scaleunless specifically indicated.

[0015] The present invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodiments are to be considered in allrespects only as illustrative and not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by this detailed description. All changes which come withinthe meaning and range of equivalency of the claims are to be embraced within their scope.

[0016] Reference throughout this specification to features, advantages, or similar languagedoes not imply that all of the features and advantages that may be realized with the presentinvention should be or are in any single embodiment of the invention. Rather, language referringto the features and advantages is understood to mean that a specific feature, advantage, orcharacteristic described in connection with an embodiment is included in at least oneembodiment of the present invention. Thus, discussions of the features and advantages, andsimilar language, throughout the specification may, but do not necessarily, refer to the sameembodiment.

[0017] Furthermore, the described features, advantages and characteristics of the inventionmay be combined in any suitable manner in one or Inore embodiments. One skilled in therelevant art will recognize, in light of the description herein, that the invention can be practicedwithout one or more of the specific features or advantages of a particular embodiment. In otherinstances, additional features and advantages may be recognized in certain embodiments thatmay not be present in all embodiments of the invention.

[0018] Reference throughout this specification to "one embodiment", "an embodiment", orsimilar language means that a particular feature, struct~~roer, cliaracteristic described inconnection with the indicated embodiment is included in at least one embodiment ofthe presentinvention. Thus, the phrases "in one embodiment", "in an embodiment", and sitnilar languagethroughout this specification may, but do not necessarily, all refer to the same embodiment.5

[0019] As used in this document, the singular form "a", "an", and "the" include pluralreferences unless the context clearly dictates otherwise. Unless defined otherwise, all technicaland scientific terms used herein have the same meanings as commonly understood by one ofordinary skill in the art. As used in this document, the term "comprising" means "including, butnot limited to".

[0020] As noted above, RFlD solutions have been traditionally used to maintain inventoryaccuracy within a facility. However, there is no simple solution that provides knowledge ofwliere in the facility this inventory is kept. Knowledge of this can help retailers in a number ofways.

[0021] Some indoor positioning techniques involve the use of Wi-Fi, Bluetooth, RFID, LightEmitting Diodes ("LEDs"), andlor magnetic fields. Global Positioning Systems ("GPSs") havemet the need for outdoor location sensing. However, when it comes to indoor areas, GPS is notreliable due to poor reception of satellite signals. RFID solutions usually consist of using ahandheld reader that scans the RFID tags attached to the products, identifies each product, andmaintains an inventory of the products.100221 'The proposed solution described herein can be easily and cost-effectivelyincorporated into any existing RFlD solution that is used for inventory tracking. This solutionwould use a combination of locator tags and a software algorithm. The location tags provide ameans for identifying a smaller region of a facility where inventory is kept. The softwarealgorithm ~lsesi gnal strength measurements, number of reads, and read times to determine alocation of each prod~lcto which an RFID tag is attached, as described below.I00231 Most solutions, that have tried to resolve the location oftags within facilities, havegenerally needed external hardware, which is required to be incorporated into the facility'sinfrastructure. The present solutiori described herein has tlie only requirement of inexpensivelocator tags to be attached to certain regions in tlie facility where merchandise is kept. Thisrequirement will not change the facility setup. Any handheld reader and backend software that isbeing used for inventory counting can still be used with changes to only the software thereof.The novelty of the present solution lies it1 the software algorithm that uses various parameterscollected during inventory counting in order to determine the location oftags.6

[0024] Accordingly, the present disclosure concerns systems and methods for locating RFIDtags within a facility. The methods generally involve: disposing locator tags (e.g., fixed passiveRFID tags and / or barcode labels) throughout at least a postion of a facility at strategic locatio~iswhere items are generally kept (e.g., shelves, tables, etc.). The unique location identifiers andlocations of the locator tags are known and stored in a data store for later use in determining anitem's location. Notably, the locator tag set-up is the only extra one-time step that needs to beperformed before inventory counting is performed. Since the locator tags can be implementedusing passive RFID tags and / or barcode labels, the cost of the present solution is relatively low.I00251 After setting-up the locator tags, a handheld reader is used for reading the locator andRFID security tags' unique identifiers and measuring signal strengths of received signalstrans~nittedt herefrom. The handheld reader also keeps track of the number of reads and readtimes. The locator and RFID security tags' unique identifiers, signal strength measurements,number of reads and read times is sent to an RPU. The RPU uses the signal strengthmeasureme~itsr,e ad times and number of reads of the locator and RFID security tags todetermine which RFID security tags are in proximity to each of the locator tags. Thisinformation allows the RPU to know where the RFID security tags reside within a facility sincethe locations of the locator tags are known.(00261 Exemplary System(00271 Referring now to FIG. 1, there is provided a schematic illustration of an exemplarysystem 100 that is ~~seffuolr understanding the present invention. The present invention isdescribed lierei~in relation to a retail store environment. The present invention is not limited inthis regard, and can be used in other environments. For example, the present invention can beused in distribution centers, factories and other commercial environments. Notably, the presentinvention can be employed in any environment in which objects and / or items need to be locatedand / or tracked.(0028J The system 100 is generally configured to allow improved object and / or item locatingwithin a facility using various types of communication and sensor technologies. As shown inFIG. I , systeni 100 comprises a Retail Store Facility ("RSF") 128 in which display equipment102,; . . ., 102hI is disposed. The display equipment is provided for displaying objects (or items)71101-llON, 1161-116N to customers of the retail store. The display equipment can include, but isnot limited to, shelves, article display cabinets, promotional displays, fixtures and / or equipmentsecuring areas of the RSF 128. The RSF can also include emergency equipment (not shown),checkout counters and an EAS system (not shown). Emergency equipment, checkout counters,and EAS systems are well known in the art, and therefore will not be described lierein.I00291 Locator tags 1081, . . ., loghq are located at strategic locations within the RSF 128. Insome scenarios, the locator tags are disposed on display equipment 1021, . . ., 102~4a,s shown inFIG. 1. Additionally or alternatively, the locator tags are disposed on emergency equipment,checkout counters, walls, ceilings, and / or EAS system equipment (e.g., pedestals near andentrancelexit of the RSF). Locator tags are well known in the art, and therefore will not bedescribed herein. Still, it should be understood that the locator tags are generally configured tofacilitate a periodic or continuous determination of locations of the objects within the RSF 128.In this regard, the locator tags may include passive RFID tags.

[0030] In some scenarios, more than one locator tag is attached to each piece of displayequipment for increasing the accuracy of the RFID tag locating. For example, one or morelocator tags log1, . . ., are placed on or in proximity to each piece of display equipment forimproving location accuracy by providing additional location data. Accordingly, a locator tag isplaced on each side of a table or shelf. Alternatively or additionally, a locator tag is placed oneach shelf of multi-shelf display equipment. A locator tag can include, but is not limited to, anRFID tag mounted on a wall, ceiling, ground or equipment for which a location is known. Thelocator tag is oriented to be easily read. The present invention is not limited to the particulars ofthis example.

[0031] Additionally or alternatively, the accuracy is further increased by disposing barcodelabels on the display equipment. A barcode can identify display equipment without ambiguity asits scanning is based on line-of-sight. In barcode scenarios, a user needs to toggle between thefollowing two operational modes of a handheld reader 120: a barcode reading mode; and a tagreading mode. The barcode would need to be read prior to proceeding to scan the locator andRFID tags.I00321 The locator tags log1,. . ., 1 0 8a~re positioned so as to define respective ZOIs orregions. The locations of the ZOls are known. Each ZOI is identified by the location Identifier("ID") transmitted from a respective locator tag. The locator tags can be arranged so that theirZOIs do or do not overlap. Each ZOI contains the items to be inventoried and located. The sizeof the ZOI depends on the location accuracy. In some exemplary cases, the ZO1 is less than aone (1) meter radius. The RSF 128 has a plurality of ZOIs. A single Z01 could encompass asingle shelf, rack or table. The present invention is not limited to the particulars of this example.(00331 By correlating RFID tag reads and the location ID received from a locator tag, it ispossible to determine the location of objects 1101, . . ., llON, 1161, . . ., 116w within the RSF 128.In this regard, it should be understood that information is stored in a data store 126 that specifiesthe known locations of the locator tags in three dimensional space, locator tag identifiers, ZOIsrespectively associated with the locator tag identifiers, RFlD tag identifiers, and informationspecifying product categories associated with the objects to which the RFID tags are respectivelycoupled. This information can be stored in the data store 126 using a RPU 124. RPU 124 willbe described in more detail below in relation to FIG. 2.100341 A handheld reader 120 is provided for communicating with the locator tags log1, . . .,1 0 8a~nd RFID tags 1121,. . ., 112N, 118], . . ., 1 1 8 ~I.n this regard, the handheld reader 120 isdesigned to transmit signals to and receive signals from the locator tags and / or RFID tags whenplaced with the ZOls, respectively. Each locator and RFID tag has a unique ID associatedtherewith. When the handheld reader 120 reads a locator or RFID tag, it obtains the unique ID.Information is stored in database 126 which specifies the known locations of the locator tags.Accordingly, RFlD tags 1121,. . ., 112N read in time proximity with a locator tag can be assignedto the approximate same location (e.g., a particular shelf, table or other piece of displayequipment).

[0035] As noted above, the handheld reader 120 is generally configured to read RFID tags1121, . . ., 112w, 1181, . . ., llgN and the locator tags 1081, . . ., 108kl. The RFID tags 1121-112N,1181-118Na re respectively coupled to the objects 110,-llON,1 161-116N.T he RFlD and locatortags are described herein as comprising single-technology tags that are only RFlD enabled. Thepresent invention is not limited in this regard. The RFlD and locator tags can alternatively oradditionally comprise dual-technology tags that have both EAS and RFID capabilities.I00361 In some scenarios, the handheld reader 120 operates in a static configuration. Theoperator sets the power and other RFID parameters before reading tags to inventorying the same.'The whole inventory of tags is performed with the configuration set at the start of theinventorying process.

[0037] In other scenarios, the handheld reader 120 operates in a dynamic configuration. Thehandheld reader 120 dynamically adapts its parameters based on whether or not it is presentwithin a ZOI. When the handheld reader 120 is not present within a Z01, the handheld reader120 operates in a default mode, i.e., using a maximum power and reading RFID tags only once toensure inventory accuracy in a timely manner. When the handheld reader 120 is within a 201,the handheld reader 120 operates in a location mode, i.e., it toggles between reads at high powerand reads at low power. The power used to read an RFID tag is inversely proportional to a taglocation confidence factor. That is, the lower the power used to read an RFlD tag, the higher thetag location confidence. High power reads ensure inventory accuracy, while low power readsallow location accuracy. In location mode, an RFID tag can be read multiple times to allow thecorrelation logic to re-allocate an RFID tag from one location to another. The power can bedynamically ad-justed depending on the RFID tag density being read. As inventory accuracy hasto be maintained, the power applied in location mode can be reduced in case of dense tagpopulation, and vice versa.

[0038] Notably, locator tags are read multiple times during an inventory coulit of a ZOI. Theread time for each read is captured. In some scenarios, the received signal strength typically fallswithin -30 dBm to -80 dBm for a handheld reader of output power 800 mW. Signals of strength-30 dBm are typically considered relatively strong signals and indicate that a locator tag is lessthan a foot away fi-om the handheld reader. AS the signal strength recedes towards -80 dBm, itsuggests that the signal is fading and that the locator tag is further away from the handheldreader. Filters may be applied by the RPU 124 to ignore tag reads ofrelatively low signalstrength.lo0391 During operation of system 100, RFID tag location is performed by allocating a ZOIto each RFID tag. The ZOI is identified by the location ID received from a locator tag when theRFID tags' are being read by the handheld reader 120. As the locator tag's position is knownand associated with a unique location ID, the physical location of the RFID tag is deduced andlocated as being within the ZOI of the locator tag.

[0040] In some scenarios, two or more ZOIs overlap or RFID tags may be read from anadjacent ZOI, which causes cross-reads to occur. A cross-read is a tag read from a first ZOI to asecond ZOI. Cross-reads cause location conflicts and may reduce location accuracy. In order toresolve location conflicts, a location confidence is computed for each location ID and for eachtag involved. The location confidence is computed based on the number of reads, an averageRSSI, a max RSSI and the handheld reader's power level at the time of a tag read. The taglocation is deducted from the location ID having the highest location confidence value. AnRFID tag can be declared between multiple locations if there is no clear winner based on thelocation confidences.

[0041] An RFID tag 112,, . . ., 112* may be used as a locator tag if its determined location isconsidered as having a high degree of confidence. In this scenario, the locator tag reads adjustthe location confidence for each RFID tag read in close time proximity. Tag reads around thesame time as a locator tag have a higher probability to be in the same ZO1 as the locator tag. Thelocator tag reads are also used to provide approximate positions within the ZOI reducing thelocation granularity. The locator tag reads also help to approximate the height of the surroundingRFID tags enabling three dimensional mapping.

[0042] The tag location in regards to locator tags is perfonned when both tags have beenread at a relatively lower power (short range). Since the usage of low power reduces theinventory accuracy andlor slows down the process, it should be performed only when necessary.The handheld reader 120 will operate in default mode most of the time (i.e., read using arelatively liigli power), and operate in location mode only when close to objects (i.e., read using arelatively low power). The location mode is triggered when a locator tag is read along arelatively high JISSI. The location mode is maintained for a certain period of time. The timeperiod is renewed when a reader trigger event reoccurs. A low power read on a locator tag isalso an event renewing the location mode period.

[0043] The location mode can also be triggered by detecting the proximity of items orobstacles. In this case, the handheld reader is equipped with a proximity sensor 152 (e.g., anacoustic sensor or infrared sensor). 'The proximity sensor 152 detects the distance from thehandheld reader to the RFID tags being read. A distance threshold value can be applied totrigger the location mode. The distance can be used to adjust the read power of the handheldreader. 'The distance can be used to compute more precise tag locations.

[0044] The tag locations are achieved by considering tag reads in close time proximity with alocator tag read as approximately in the same location. The lower the read power used, thehigher the tag location confidence. The location confidence is computed based on the number ofreads, an average RSSI, a maximum RSSI and the handheld reader's power level used to read theRFID tags. An RFlD tag's location is deduced from the locator tag position having clearly thehigher location confidence value. An RFlD tag can be declared between multiple locations ifthere is no clear winner based on the location confidences.

[0045] Alternatively, a different logic is employed that consists of recoding a time windowcentered on the timestamp of each locator tag read. All those time windows chronologicallyaligned create a tirneline of the handheld reader's location as each time window corresponds to atag locator for whicli its location is I<nown.

[0046] For each RFID tag, the read having the highest RSSI is selected and the timestamp ofthis read is used with the timeline. If the timestamp is included in a recorded time window of thetimeline, the location is deduced from the location of the corresponding locator tag.I00471 When two time windows overlap, tlie one created f'rom the read having the highestRSSI takes over tlie overlapping time period. The applied time window widths can be adjustedbased on the RSSl locator tag reads. The higher the RSSI, the wider the time window and viceversa. As a result, a tag locator read having higher RSSl takes priority while a tag locator readoccurring at lower RSSI wo~tld have their time window reduced or filtered.

[0048] The ZOI coverage and locator tag positions have to be known to enable tag location.This mapping can be done by taking physical measurements. Additionally or alternatively, afingerprint technique is employed. Using the handheld reader 120 with a touch screen, a userrecords received location IDS while pinpointing (his)her position on a map displayed on thetouch screen. By doing so, the 201s are mapped to physical locations and maintained in adatabase. The same process can be applied to locator tags. A user scans a locator tag whilepinpointing (her)his location on the map. The scanning can be done by: reading a twodimensional barcode printed on a locator tag; and / or RFID reads at very close range to thelocator tag.I00491 Referring now to FIG. 2, there is provided a detailed block diagram of an exemplaryarchitecture for a handheld reader 200. Handheld reader 120 of FIG. 1 is the same as or similarto handheld reader 200. As such, the discussion of handheld reader 200 is sufficient forunderstanding handheld reader 120.

[0050] Handheld reader 200 may include more or less components that that shown in FIG. 2.However, the components shown are sufficient to disclose an illustrative embodimentimplementing the present invention. Some or all of the components of the handheld reader 200can be implemented in hardware, software and / or a combination of hardware and software. Thehardware includes, but is not limited to, one or more electronic circuits. The electronic circuitmay comprise passive components (e.g., capacitors and resistors) and active components (e.g.,processors) arranged and / or programmed to implement the methods disclosed herein.(00511 The hardware architecture of FIG. 2 represents an embodiment of a representativehandheld reader 200 configured to facilitate improved object locating within an RSF (e.g., RSF128 of FIG. I ) . In this regard, the handheld reader 200 comprises an RF enabled device 250 forallowing data to be exchanged with an external device (e.g., locator tags logr, ..., logM, andlorRFID tags 112], ..., 11zN, 118], ..., llgN of FIG. 1) via RF technology. The components 204-216 shown in FIG. 2 may be collectively referred to herein as the RF enabled device 250, andinclude a power source 212 (e.g., a battery).(00521 The RF enabled device 250 comprises an antenna 202 for allowing data to beexchanged with the external device via RF technology (e.g., RFID technology or other RF based13technology). The external device may comprise locator tags 1081, ..., 10SM, and / or RFID tags112,, ..., llS1, ..., llgN of FIG. I. In this case, the antenna 202 is configured to transmitRF carrier signals (e.g., interrogation signals) to the listed external devices, and / or transmit dataresponse signals (e.g., authentication reply signals) generated by the RF enabled device 250. Inthis regard, the RF enabled device 250 comprises an RF transceiver 208. RFID transceivers arewell known in the art, and therefore will not be described herein. However, it should beunderstood that the RF transceiver 208 receives RF signals including information from thetransmitting device, and forwards the same to a logic controller 210 for extracting theinformation therefrom.100531 In scenarios where the location determination is made by the handheld reader, theextracted information can be used to determine the location of an object (e.g., object 1101, . . .,l l O ~1,1 6], . . ., or 116No f FIG. I) within a facility (e.g., RSF 128 of FIG. I). Accordingly, thelogic controller 210 can store the extracted information in memory 204, and execute algorithmsusing the extracted information. For example, the logic controller 210 can correlate RFID tagreads with locator tag reads to determine the location of the object within the facility.

[0054] Notably, memory 204 may be a volatile memory and / or a non-volatile memory. Forexample, the memory 204 can include, but is not limited to, a Random Access Memory("RAM"), a Dynamic Random Access Memory ("DRAM"), a Static Random Access Memory(TRAM"), a Read-Only Memory ("ROM") and a flash memory. The memory 204 may alsocomprise unsecure memory and / or secure memory. The phrase "unsecure memory", as usedherein, refers to memory configured to store data in a plain text form. The phrase "securememory", as used herein, refers to memory configured to store data in an encrypted form and / ormemory having or being disposed in a secure or tamper-proof enclosure.100551 Instructions 222 are stored in memory for execution by the RF enabled device 250and that cause the RF enabled device 250 to perform any one or more of the methodologies ofthe present disclosure. The instructions 222 are generally operative to facilitate determinationsas to where RFID tags are located within a facility. Other functions of the RF enabled device250 will become apparent as tlie discussion progresses.

[0056] The handheld reader 200 may also comprise an optional barcode reader 260. Thebarcode reader 260 is generally configured to: read barcodes to obtain barcode information inresponse to a command signal; parsing unique IDS from barcode information; andcommunicating the unique IDS to the RF enabled device 250. The command signal can begenerated by the RF enabled device 250 and sent to the barcode reader 260 in response to anoperator's depression of a trigger 270.(00571 The handheld reader 200 may further comprise an optional proximity sensor 262(e.g., an acoustic sensor or infrared sensor). The proximity sensor 262 detects the distance fromthe handheld reader 200 to the RFID tags being read (e.g., RFID tags 1121, ..., l l g l , ...,1 1 8o~f FIG. 1). A distance threshold value can be applied to trigger the location mode. Thedistance can be used to adjust the read power of the handheld reader. The distance can be usedto compute more precise tag locations.

[0058] Referring now to FIG. 3, there is provided a detailed block diagram of an exemplaryarchitecture for a RPU 300. RPU 124 of FIG. 1 is the same as or substantially similar to RPU300. As such, the following discussion of RPU 300 is sufficient for understanding RPU 124.I00591 Notably, the RPU 300 may include more or less components than those shown inFIG. 3. However, the components shown are sufficient to disclose an illustrative embodimentimplementing the present invention. The hardware architecture of FIG. 3 represents oneembodiment of a representative RPU configured to facilitate the provision of a three di~nensionalmap showing locations of RFID tags (e.g., RFID tags 1121,. . ., 1 1 2 ~l,l g l , . . ., llSNo f FIG. I )within an RSF (e.g., RSF 128 of FIG. I ) . As such, the RPU 300 of FIG. 3 implements at least aportion of a method for providing such tag locations in accordance with embodiments of thepresent invention. Some or all the components of the RPU 300 can be i~nplementeda s hardware,software andlor a co~nbination of hardware and software. The hardware includes, but is notlimited to, one or more electronic circuits. The electronic circuits can include, but are not limitedto, passive components (e.g., resistors and capacitors) andlor active components (e.g., amplifiersand / or microprocessors). The passive andlor active components can be adapted to, arranged toandlor program~ned to perform one or Inore of the methodologies, procedures, or firnctionsdescribed herein.

[0060] As shown in FIG. 3, the RPU 300 comprises a user interface 302, a CentralProcessing Unit ("CPU") 306, a system bus 310, a memory 312 connected to and accessible byother portions of RPU 300 through system bus 310, and hardware entities 314 connected tosystem bus 310. The user interface can include input devices (e.g., a keypad 350) and outputdevices (e.g., speaker 352, a display 354, andlor light emitting diodes 356), which facilitate usersoftwareinteractions for controlling operations of the RPU 300.

[0061] At least some of the hardware entities 314 perform actions involving access to anduse of me~nory3 12, which can be a Random Access Memory ("RAM"), a disk driver and / or aCompact Disc Read Only Memory ("CD-ROM"). I-Iardware entities 314 can include a diskdrive unit 316 comprising a computer-readable storage medium 318 on which is stored one ormore sets of instructions 320 (e.g., software code) configured to implement one or more of themethodologies, procedures, or functions described herein. The instructions 320 can also reside,co~npletelyo r at least partially, within the memory 312 and / or within the CPU 306 duringexecution thereof by the RPU 300. The memory 312 and the CPU 306 also can constitutemachine-readable media. The term "machine-readable media", as used here, refers to a singlemedium or multiple media (e.g., a centralized or distributed database, and / or associated cachesand RPUs) that store the one or more sets of instructions 320. The term "machine-readablemedia", as used here, also refers to any medium that is capable of storing, encoding or carrying aset of instructions 320 for execution by the RPU 300 and that cause the RPU 300 to perform anyone or more of the methodologies of the present disclosure.

[0062] In some embodiments of the present invention, the hardware entities 314 include anelectronic circuit (e.g., a processor) programmed for facilitating the provision of a threedimensional map showing locations of RFID tags within a facility. In this regard, it should beunderstood that the electronic circuit can access and run a location determining application 324installed on the RPU 300. The software application 324 is generally operative to facilitate: thedetermination of RFID tag locations within a facility; and the mapping of the RFlD tag locationsin a virtual three dimensional space. Other functions of the software application 324 willbecome apparent as the discussion progresses.

[0063] Notably, the RPU 300 can act as a learning system that keeps a history of locator tagreads, signal strengths, average read counts, average read durations and product categories / types16respectively associated with ZOIs (or regions). The history information can be used in furtherlocation identification processes to define reference points against which RFID tag locations canbe resolved.10064j Exemplary Methods For Locating An Object In A Facility

[0065] Referring now to FIG. 4, there is provided a flow diagram of an exemplary method400 for determining a location of an object within a facility. Method 400 begins with step 402and continues with step 404 where an inventory counting process is performed using a handheldreader (e.g., handheld reader 120 of FIG. 1). Inventory counting processes are well known in theart, and therefore will not be described in detail herein. Still, it should be understood that theinventory counting process involves reading RFlD tags (e.g., RFID tags 1121, . . ., 112N, 1181, . .., 1 1 8o~f FIG. 1) coupled to inventory objects (e.g., ob-jects 1101, . . ., llON,1 161, . . ., 116* ofFIG. 1).

[0066] During tlie inventory counting process, multiple reads of locator tags (e.g., locatortags log1, . . ., of FIG. 1) are performed as shown by step 406. The read times for thelocator tag reads are captured in step 408. Next in step 410, a search is performed to identifylocator tags which were consecutively read by the handheld reader. Stray locator tags are thenidentified based on the number of times a locator tag was read, a signal strength (or RSSI)measured for the locator tag, and / or a difference in read times between the locator tag andanother locator tag. Read information associated with tlie identified stray locator tags is theneliminated from further analysis, as shown by step 412. Generally, when the user moves fromone region to another the difference in tlie locator tag read times is much larger than that of thelocator tag reads within a region.

[0067] Notably, tlie signal strength (or RSSI) typically has a value within -30 dBm and -80dBm for a handheld reader of oi~tpip~otw er 800 mW. Signals of strength -30 dBm are typicallyvery strong signals and indicate tliat a tag is less than a foot away. As the signal strength recedestowards -80 dBm, it suggests tliat the signal is fading and tliat the tag is further away from theliandheld reader. Filters niay be applied so that tag reads of relatively low signal strength areignored.

[0068] Referring again to FIG. 4, step 414 involves analyzing the data associated with theconsecutive locator tag reads to identify the ZOI (or region) associated with the unique identifierof the locator tag. Once the ZOI (or region) is identified, the duration of time spent in that ZOI(or region) is determined in step 416. In this regard, a Start Read Time ("SRT") and an EndRead Time ("ERT") for the identified ZOI (or region) are determined. The SRT is either (a) theread time of the first tag in case of the identified ZOI (or region) (i.e., in the below samples ofTable 1 the SRT would be TI for location marked by LocRagl) or (b) the read time that createsthe largest difference during change of location (i.e., in the below Table 1, if T7-T6 produces thelargest difference di~ringlo cation change then T7 would be the SRT for location marked byLocTag2). The ERT is either (a) the read time prior to the one that creates the largest differenceduring change of locator tag read in the sequence (i.e., in the below Table 1, if T7-T6 producesthe largest difference during location change then T6 would be the ERT for location marked byLocrTagl) or (b) the read time of the last tag in case of the last ZOI (or region) (i.e., in the belowTable 1 it would be T13 for location marked Loctag2).100691 Evident from the below Table I, the inventory counting in the location marked byLocTagl spanned from TI to T6. The inventory counting for location marked by LocTag2spanned from T7 to TI 3. The accuracy of the read time duration is important because we needto know the boundary of each region correctly.TABLE 1Tag Read SequenceLocTag lTag lTag2-Tag3Read TimesTILocTag 1.-'fag4DeltaT2T3---. - -T4T2-T 1T3-T2T4-'T3T5T6T7T5 -T4T6-T5T7-T6location identification using the read times thereof.Tag6LocTag2Tag7Tag8Tag9LocTag2

[0071] In some scenarios, a particular RFlD tag may be associated with two or more ZOIs(or regions), as shown by step 422. This may be due to the problem of cross-reads (i.e., locatortags from other ZOIs being read while reading RFID tags in a particular ZOI). If the RFID tag isassociated with only one ZOI (or region) [422:NO], then step 424 is performed where method400 continues with step 436 of FIG. 4B. Step 436 will be described below.

[0070] Referring again to FIG. 4, various steps are performed to determine which RFID tags(e.g., RFID tags 112], . . ., 118],. . ., 1 1 8o~f FIG. 1) are located within the ZOI (orregion). These steps include step 418 where read data is analyzed to deter~iiinew hether RFIDtag read times fall within the time period defined by the SRT and ERT. A conclusion is madethat the RFlD tags, having read times falling within the time period, are located within the Z01(or region), as shown by step 420. From the above Table 1, Tagl-Tag4 lie in the region markedLocTagl and Tag5-Tag9 lie in the region marked LocTag2. This is the first level of RFID tagT8T9T10T11T12TI3I00721 In contrast, if the RFlD tag is associated with two or more ZOIs (or regions)[422:YES], then a second level of tag location identification is applied as shown by steps 426-T8-T7T9-T8T 10-T9'TI 1 -TI 0TI 2-TllT13-TI2428. Step 426 involves making a determination as to whether or not both the number of readsand average signal strength values obtained for the RFID tag in a first ZOI (or region) are higherthan that obtained for tlie RFID tag in other second ZOIs (or regions). If both the number ofreads and average signal strength values obtained for the RFlD tag in the first ZOI (or region) arehigher than that obtained for the RFlD tag in the second ZOls (or regions) [426:YES], then aconclusion is made in step 428 that the IiFID tag is located within the first ZOI (or region).After making such a conclusion, method 400 continues with step 436 of FIG. 4B. Step 436 will19be described below. If the number of reads value and / or average signal strength value obtainedfor the RFID tag in the first ZOI (or region) islare lower than that obtained for the RFID tag inthe second ZOIs (or regions) [426:NO], then method 400 continues with decision step 427 ofFIG 4B.

[0073] As shown in FIG. 4B, step 427 involves determining whether both the number ofreads and average signal strength of both the first and second ZOIs are inconclusive. If it isdetermined that both the number of reads and average signal strength of both the first and secondZOIs are not inconclusive [427:NO], then step 428 is performed where a conclusion is made thatthe RFID tag is located within the second ZOI. In contrast, if both the number of reads andaverage signal strength of both ZOls are determined to be inconclusive [427: YES], then method400 continues with steps 430-434 of FIG. 4B in which a third level of RFID tag locationidentification is performed.(00741 As shown in FIG. 4B, steps 430-434 involve: determining a product category of theobject to which the RFID tag is coupled; identifying the ZOI (or region) in which objectsbelonging to the same product category are kept; and concluding that the RFID tag is locatedwithin the identified Z01 (or region). The premise for the third level of RFID tag locationidentification is that objects belonging to the same product category are kept in the same ZOI (orregion) of a facility (e.g., a warehouse facility). Using this premise, for an RFID tag whoselocation determination is still ambiguous, an increased probability of being in a particular regionis achieved by knowing the product categoryltype of the object to which the RFID tag is coupledand associating the RFID tag with the ZOI (or region) holding objects of the productcategory / type.

[0075] Upon completing step 434, step 436 is performed where the RFlD tag's location isstored in a data store (e.g., data store 126 of FIG. I ) . A three dimensional map is generated instep 438 showing the locations of the RFlD tags in a three dimensional space. 'The threedimensional map is then presented to an operator of the handheld reader and / or other electronicdevice (e.g., RPU 124 of FIG. 1). Subsequently, step 442 is performed where method 400 endsor other processing is performed (e.g., return to step 402 of 121G. 4A).100761 All of the apparatus, methods, and algorithms disclosed and claimed herein can bemade and executed without undue experimentation in light of the present disclosure. While theinvention has been described in terms of preferred embodiments, it will be apparent to thosehaving ordinary skill in the art that variations may be applied to the apparatus, methods andsequence of steps of the method without departing from the concept, spirit and scope of theinvention. More specifically, it will be apparent that certain components may be added to,combined with, or substituted for the components described herein while the same or similarresults would be achieved. All such similar substitutes and modifications apparent to thosehaving ordinary skill in the art are deemed to be within the spirit, scope and concept of theinvention as defined.

[0077] The features and functions disclosed above, as well as alternatives, may be combinedinto many other different systems or applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements may be made by those skilled in the art,each of which is also intended to be encompassed by the disclosed embodiments.

Claims

We claim:

1. A method for locating Radio Frequency Identification ("RFID") security tags,comprising:concurrently reading the RFID security tags and locator tags to obtain unique identifiersthereof and Received Signal Strength Indicator ("RSSI") lneasuretnents tlierefore, where theRFID security tags are respectively coupled to inventory items located within a facility and thelocator tags are placed at locations within the facility so as to respectively define a plurality ofZones Of Interest ("ZOIs") in which inventory items may reside; anddetermining which ZOI of the plurality of 201s each said RFID security tag resideswithin based at least on the RSSI measurements, a number of times each locator tag was read,read times specifying when the locator tags were read, differences in read times for the locatortags, and known locations of the locator tags.

2. The method according to claim 1, further comprising identifying and eliminating eachstray locator tag based on at least one of the number of times the stray locator tag was read, anRSSI measured for the stray locator tag, and a difference in read times between the stray locatortag and another locator tag.

3. The lnethod according to claim 1, further comprising determining the duration of time ahandheld reader spent reading RFID security tags and locator tags in each ZOI of the plurality ofZOls.

4. The method according to claim 3, wherein the duration oftirne is determined based onStart Read Time ("SRT") comprising (a) a read time of a locator tag whic11 was the first locatortag read in an given ZOI or (b) a read time that creates a largest difference during a changebetween reading location tags in a first ZOI and reading tags in a second ZOI.

5. The lnethod according to claim 3, wherein the duration of time is determined based on anEnd Read Time ("ERT) comprising (a) a read time of a locator tag which was the last locator tagread in any given ZOI or (b) a read time prior to a read time that creates a largest differenceduring a change between reading location tags in a first ZOI and reading tags in a second ZOI.

6. The method according to claim 3, f~~rthceorm prising determining whether read times foreach RFID security tag fall within the duration of time.

7. The method according to claim 6, further comprising concluding that the RFID securitytags, having read times that fall within the duration of time, are located within the ZOI.

8. The method according to claim 1, further comprising:identifying at least one RFID security tag which has been determined to reside in at leasta first ZOI and a second ZOI; andassig~lingth e RFID security tag to the first ZOI when the RFID security tag's totalnumber of reads and average signal strength associated with the first ZOI have higher valuesthan the RFID security tag's total number of reads and average signal strength associated withthe second ZOI, respectively.

9. The method according to claim 1 , further comprising:identifying at least one RFID sec~~rittayg which has been determined to reside in at leasta first ZOI and a second 201;determining a product category of an inventory item to which the RFID security tag iscoupled; andassigning the RFID security tag to the first or second 201 in which other inventory itemsbelonging to the prod~~ccatt egory are stored.

10. The method according to claim 1, fi~rtlierc omprising increasing an accuracy of saiddetermining using barcodes.I I . A system, comprising:a plurality of RFID security tags respectively coupled to inventory items located within afacility;a pl~~raliotyf locator tags placed at locations within the facility so as to respectivelydefine a plurality of Zones Of Interest ("ZOls") in ~vhich inventory items may reside;an RFlD reader configul.ed to conc~~rrentrleya d the RFID security tags and the locatortags to obtain unique identifiers thereof and Received Signal Strength Indicator ("RSSI")measurements therefore; and2 3a processing unit executing programming instructions which cause the processor todetermine which ZOI of the plurality of 201s each said RFID security tag resides within based atleast on the RSSI measurements, a number of times each locator tag was read, read timesspecifying when the locator tags were read, differences in read times for the locator tags, and12. The system according to claim 1 1, wherein the processing unit is further caused toidentify and eliminate each stray locator tag based on at least one of the number of times thestray locator tag was read, an RSSI measured for the stray locator tag, and a difference in readtimes between the stray locator tag and another locator tag.

13. Tlie systeln according to claim 1 1, wherein the processing unit is further caused todetermine the duration of time a handheld reader spent reading RFID security tags and locatortags in each ZOI of the plurality of ZOIs.

14. Tlie system according to claim 13, wherein the duration of time is determined based onStart Read Time ("SRT") colnprising (a) a read time of a locator tag which was the first locator15. The systeln according to claim 13, wherein the duration of time is determined based onan Elid Read Time ("ER7') colnprising (a) a read time of a locator tag which was the last locatortag read in any given ZOI or (b) a read time prior to a read time that creates a largest difference16. The system according to clailn 13, wherein the processing unit is furtlier caused todetermine wlietlier read times for each RFID security tag fall within the duration of time.

17. I'lie system according to claim 16, wherein the processing unit is further caused toconclude that tlic RI-'ID security tags, having read times that fall within the duration of time, are18. The system according to claim I I, wherein the processing unit is further caused to:identify at least one RFlD security tag which has been determined to reside in at least afirst Z01 and a second ZOI; andassign the RFID security tag to the first ZOI when the RFID security tag's total numberof reads and average signal strength associated with the first ZOI have higher values than theRFID security tag's total number of reads and average signal strength associated with the second19. The system according to claim 11, wherein the processing unit is further caused to:identify at least one RFID security tag which has been determined to reside in at least adetermine a product category of an inventory item to which the RFID security tag isassign the RFID security tag to the first or second ZOI in which other inventory itemsbelonging to the product category are stored.

20. The system according to claim 11, wherein barcodes are used to increase an accuracy ofthe determination as to which ZOI of the plurality of ZOIs each said RFID security tag resides.