Intercepting RFID uhf signals for determining the proximity of RFID tags

Abstract

The present disclosure provides a system, a device, and method for determining proximity of at least one Radio Frequency Identification (RFID) tag. The system includes at least one RFID reader, at least one RFID tag, one or more listening devices, and a computing device. Each listening device comprises a receiver configured to intercept RF signals exchanged between the RFID reader and RFID tag, a processor with a software controller configured to analyze the intercepted RF signals and generate a data signal, and a communication interface configured to send the data signal. The software controller extracts first parameters related to the RFID reader and second parameters related to the RFID tag. The computing device receives the data signals including the first and second parameters from each listening device, processes them, and determines the proximity of the RFID tag relative to at least one known location.

Description

INTERCEPTING RFID UHF SIGNALS FOR DETERMINING THE PROXIMITY OF RFID TAGSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Number 63 / 561,841 filed onMarch 6, 2024 which is incorporated herein in its entirety.FIELD OF INVENTION

[0002] The present disclosure relates to the field of Radio Frequency Identification (RFID) systems. More specifically, it pertains to systems and methods for determining the proximity of RFID tags using intercepted RFID Ultra High Frequency (UHF) signals.BACKGROUND

[0003] Radio Frequency Identification (RFID) systems typically include RFID readers and RFID tags. RFID readers communicate with RFID tags via radio frequency (RF) transmissions to gather data stored on the tags. This data may include information about items associated with the tags, such as product details, shipping information, or inventory data.

[0004] Traditional RFID readers may rely on their own measurements, such as Received Signal Strength Indicator (RSSI) values, to estimate tag locations. However, this approach may be unreliable due to factors such as multipath propagation, signal interference, and environmental obstacles. Conventional RFID systems may encounter challenges in accurately determining a tag's proximity to a reader or read zone. Current RFID readers may often rely solely on data received directly from tags to estimate how close a tag might be to a read zone or area. This approach may lead to difficulties in precisely tracking and monitoring tagged items.

[0005] Various solutions have been proposed to improve RFID localization accuracy, including the use of multiple readers and advanced signal processing techniques. However, these solutions may require significant infrastructure investments, complex system integration.

[0006] Some existing RFID systems may utilize readers with phased array antennas to approximate tag locations. These systems may collect tag IDs, time stamps, RSSI values, and read rates in response to RF signals broadcast to tags. The collected data may then be compared with different antenna states to estimate item locations. However, achieving high accuracy in these systems may be challenging, as the data utilized may pertain only to the direct interaction between the reader and tag.

[0007] In some cases, erroneous data in RFID systems may indicate that an item has shifted to a new location even when it has not physically moved. Factors such as multipath effects, interference, environmental changes, and signal propagation delays may introduce inaccuracies in signal reception and processing, leading to errors in determining tag proximity.

[0008] Some existing loss prevention and self-checkout systems may use higher power settings in RFID readers to improve tag detection. While this approach may extend the read field and enable identification of tags beyond an exit gate, it may make it difficult for the reader to distinguish whether a tag is within the exit area, obscured, or simply positioned at a distance.

[0009] There may be a need for improved systems and methods to overcome these limitations and accurately determine RFID tag proximity. Furthermore, there may be a need for compact and cost- effective solutions that can enhance the capabilities of existing RFID infrastructure.SUMMARY

[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0011] The present disclosure provides a system and a method for determining the proximity of RFID tags using intercepted RFID UHF signals.

[0012] In some embodiments, the system for determining the proximity of RFID tags may include at least one RFID reader, at least one RFID tag, and at least one listening device. Each listening device may include a receiver configured to intercept RF signals exchanged between the RFID reader and RFID tag, a processor with a software controller to analyze the intercepted RF signals and generate a data signal, and a communication interface configured to send the data signal. The system may also include a computing device configured to receive the data signal, process it, and determine the proximity of the RFID tag relative to at least one known location based on the processed data signal.

[0013] In some embodiments, the method for determining the proximity of RFID tag may include intercepting RF signals exchanged between an RFID reader and an RFID tag using at least one listening device, analyzing the intercepted RF signals, generating a data signal based on the analyzed RF signals, sending the data signal to a computing device, and determining the proximity of the RFID tag relative to at least one known location based on the processed data signal.

[0014] In some embodiments, the present disclosure provides a listening device for determining proximity of RFID tags. The listening device may include a receiver configured to intercept RF signals exchanged between at least one RFID reader and at least one RFID tag, and a processor comprising a software controller. The processor may be configured to analyze the intercepted RF signals to extract first parameters related to the RFID reader and second parameters related to the RFID tag, where the analysis comprises demodulation and processing of the intercepted RF signals. The processor may further determine the proximity of the RFID tag relative to at least one known location based on the processed data signal based on the extracted parameters.

[0015] The systems and methods described herein may improve accuracy in determining RFID tag proximity by utilizing data from multiple listening devices positioned at different locations. This approach may enhance the capabilities of existing RFID infrastructure and enable more precise tracking and monitoring of tagged items in various environments, including retail stores, selfcheckout areas, and shipment verification systems.BRIEF DESCRIPTION OF FIGURES

[0016] Non-limiting and non-exhaustive examples are described with reference to the following figures.

[0017] FIG. la illustrates a system for determining the proximity of RFID tags, in accordance with an embodiment;

[0018] FIG. lb illustrates a block diagram of a listening device, in accordance with an embodiment;

[0019] FIG. 2 illustrates a flow chart of a method for determining the proximity of RFID tags, in accordance with an embodiment;

[0020] FIG. 3 illustrates a retail system that includes multiple components for RFID tag detection and monitoring, in accordance with an embodiment;

[0021] FIG. 4 illustrates a checkout system for monitoring RFID tags, in accordance with an embodiment; and

[0022] FIG. 5 illustrates a shipment verification system for monitoring boxes in a shipping area, in accordance with an embodiment.DETAILED DESCRIPTION

[0023] Before the present subject matter is described in further detail, it is to be understood that the subject matter is not limited to the particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describingparticular embodiments only and is not intended to be limiting because the scope of the present subject matter will be limited only by the appended claims.

[0024] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure applies. It may be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0025] The following detailed description illustrates various embodiments of the present subject matter and ways in which they may be implemented. Although a limited number of the exemplary methods and materials are described herein for clarity, those of ordinary skill in the art to which this disclosure applies will understand that other methods and materials for carrying out or practicing the present subject matter are also possible.

[0026] As used herein, the term "RFID" refers to Radio Frequency Identification.

[0027] As used herein, the term "RFID reader" refers to a device that includes one or more antennas that emit Radio Frequency (RF) signals and receive signals back from the RFID tag.

[0028] As used herein, the term "RFID tag" refers to a label that includes an antenna and a chip that may be attached to a product, which provides a means of product identification.

[0029] As used herein, the term "Return Signal Strength Indicator ( RSSI )" refers to a measurement of strength or intensity of RF signals received by a receiver when hearing a response from the RFID tag.

[0030] As used herein, the term "listening device" refers to a device that intercepts RF signals exchanged between at least one RFID reader and at least one RFID tag, and sends data signal to a computing device after demodulation and processing.

[0031] As used herein, the term "receiver" refers to a component that is part of the listening device, and it intercepts RF signals exchanged between at least one RFID reader and at least one RFID tag.

[0032] As used herein, the term "communication interface" refers to a component that is part of the listening device, and it sends data signals to the computing device via a communication network.

[0033] As used herein, the term "delta value" refers to the difference calculated by subtracting a first RSSI value from a second RSSI value.

[0034] As used herein, the term "read rate" refers to the number of RFID tags successfully read per unit of time.

[0035] As used herein, the term "path loss" refers to the attenuation of RF signal strength that occurs as the signal propagates through space between the RFID reader, RFID tag, and listening devices.

[0036] As used herein, the term "antenna array" refers to a configuration of multiple antennas within a single listening device, arranged to enable spatial diversity in signal reception and processing.

[0037] As used herein, the term "time stamp" refers to a recorded time related to the RFID tag and the RFID reader, indicating when a specific RF signal is exchanged between the RFID reader and the RFID tag.

[0038] As used herein, the term "response rate" refers to how frequently the RFID tag responds to the RFID reader over time. This may be measured as the number of successful tag responses to reader queries within a specific time interval.

[0039] As used herein, the term "phase angle" refers to the phase difference between RF signals received at multiple antennas of an antenna array in a listening device.

[0040] As used herein, the term "proximity zone" may refer to a defined area or region within the operational range of the RFID system where the presence, position, or movement of RFID tags is monitored and analyzed. A proximity zone may be established using various parameters including, but not limited to, signal strength thresholds, calculated distances from one or more listening devices or RFID readers, angular information derived from multiple listening devices, and user- defined spatial boundaries. Proximity zones may be static or dynamic, and may be adjusted based on operational requirements, environmental factors, or historical data. For example, a proximity zone may encompass a specific shelf in a retail environment, a designated area around a checkout counter, or a defined region within a shipping facility. The system may utilize data from multiple listening devices to accurately determine whether an RFID tag is within a particular proximity zone, enabling precise tracking and monitoring of tagged items within the specified area.

[0041] These and other features, aspects, embodiments, and advantages of the present subject matter will be better understood with reference to the below stated description and appended claims. These definitions are provided to introduce a selection of concepts in a simplified form. These definitions are not intended to identify key or essential features of the claimed or disclosed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0042] FIG. la illustrates a system 100 for determining the proximity of RFID tags, in accordance with an embodiment. The system 100 comprises one or more components including, but not limited to, one or more listening devices 101, 105, 106 and 107, at least one RFID system, and a computing device 108. For example, the system 100 may be implemented in, but not limited to, a retailenvironment, a self-checkout system, a loss prevention system, a shipment verification system 400, and the like. In one embodiment, the one or more listening devices 101, 105, 106 and 107 are stationary. In other embodiment, each of the one or more listening devices 101, 105, 106 and 107 can be implemented as a mobile device with a known location using any location identification technology such as Ultra-Wideband (UWB) technology.

[0043] Referring to FIG. la and FIG. lb, each of the one or more listening devices 101, 105, 106 and 107 includes a receiver 124, a communication interface 123, and a processor 120 comprising a software controller 121. The RFID system comprises at least one RFID reader 102 and at least one RFID tag 104. The RFID reader 102 includes a reader antenna 103. The RFID tag 104 includes a tag antenna (not shown in Figure) and a chip (not shown in Figure). The RFID reader 102 is configured to transmit RF signals through its reader antenna 103. The communication between RFID reader 102 and RFID tag 104 is primarily governed by a Gen 2 Ultra High Frequency (UHF) Communication protocol. The receiver 124 of the listening device is configured to intercept the RF signals exchanged between the RFID reader 102 and the RFID tag 104 by capturing electromagnetic waves with its antenna 122, then amplifying and filtering these signals. The receiver 124 is configured to intercept RF signals exchanged between the RFID reader and at least one RFID tag using the Gen 2 UHF Communication protocol. The listening device converts the RF signals to digital data through analog-to-digital conversion. The digital data is then demodulated and processed to extract the first parameters and second parameters. These intercepted RF signals, inter alia, include : i)query signals from the at least one RFID reader 102 to the at least one RFID tag 104; ii)response signals from the at least one RFID tag 104 to the at least one RFID reader 102; ill) Random Number 16 (RN16) signals; iv) Acknowledge (ACK) signals; v) Electronic Product Code (EPC) signals; vi) any command signal from the at least one RFID reader 102 to the at least one RFID tag 104; vii) any response signal from the at least one RFID tag 104 to the at least one RFID reader 102; and viii) any other signals exchanged as part of RFID communication protocols or a combination thereof as may be feasible.

[0044] The system 100 for determining the proximity of RFID tag is designed to determine a given RFID tag's proximity without requiring any modifications to existing RFID tags or readers as used in many applications and thus allowing for seamless integration with current RFID infrastructure. The system 100 utilizes standard RFID communication protocols as mentioned herein before.

[0045] The computing device 108 is implemented as an algorithm-implemented computing device 108, a cloud-based server, or a laptop. The communication between the listening devices and the computing device 108 is facilitated through a communication network (not shown in figure). The communication network may include, but not limited to, direct interconnections such as socket connections and wired connections (e.g., Ethernet, USB, RS-232), Local Area Network (LAN), Wide Area Network (WAN), Controller Area Network (CAN), LoRa (Long Range), Transmission Control Protocol / lnternet Protocol (TCP / IP), MQ.TT (Message Queuing Telemetry Transport), Wi-Fi, Bluetooth Low Energy (BLE), Zigbee, Ultra-Wideband (UWB), Thread, and other suitable protocols.

[0046] In some embodiments, the software controller 121 of each of the one or more listening devices 101, 105, 106 and 107 may be implemented in hardware such as the processor 120 and / or software or a combination thereof. The software controller 121 of each of the one or more listening devices 101, 105, 106 and 107 is configured to analyze the intercepted RF signals to extract the first parameters and the second parameters. The analysis includes demodulation and processing of the intercepted RF signals to extract the first parameters and the second parameters. The software controller 121 is configured to generate a data signal based on the extracted first parameters and the second parameters. The data signal, inter alia, includes at least one of:I) a first Return Signal Strength Indicator (RSSI) value; ii) a second RSSI value; ill) read rates; iv) Electronic Product Codes (EPC) of tags; v) phase angle information; vi) RFID reader name; vii), RFID reader port; viii) RFID tag ID; ix) a time stamp related to the RFID tag 104 and the RFID reader 102; x) a read rate of at least one RFID tag 104 over time;xi) a response rate of the RFID tag 104 to the RFID reader 102, xii) a command sent to the RFID tag 104, and a response from the RFID tag 104.

[0047] The first parameters of the intercepted RFI signal are related to the at least one RFID reader 102. The second parameters are related to the at least one RFID tag 104.

[0048] In an exemplary embodiment, consider the system 100 for determining the proximity of RFID tags, including the one or more components such as the one or more listening devices 101, 105, 106 and 107, the at least one RFID system, and the computing device 108 are being implemented in the retail store environment. Each of the listening devices 101, 105, 106 and 107 are positioned at a certain distance from each other, as shown in FIG. la. The RFID reader 102 is positioned in proximity to a listening device 101. The RFID tag 104 is directly adhered to or attached to a product item (not shown in Figure). The product holding the RFID tag 104 is placed near the listening devices 105 and 107 and away from the listening devices 101 and 106.

[0049] Each of the listening devices 101, 105, 106 and 107 is configured to intercept RF signals exchanged between the at least one RFID reader 102 and the at least one RFID tag 104. These intercepted RF signals, as mentioned earlier, inter alia, include query signals from the at least one RFID reader 102 to the at least one RFID tag 104, response signals from the at least one tag 104 to the at least one RFID reader 102, Random Number 16 (RN16) signals, Acknowledge (ACK) signals, Electronic Product Code (EPC) signals, any command signal from the at least one RFID reader 102 to the at least one RFID tag 104, any response signal from the at least one RFID tag 104 to the at least one RFID reader 102, and any other signals exchanged as part of RFID communication protocols. For example, each of the listening devices 101, 105, 106, and 107 is configured to intercept the query signal from the at least one RFID reader 102 and a response signal to the query signal generated by the at least RFID tag 104.

[0050] Each of the listening devices 101, 105, 106, and 107 uses its own software controller 121 to measure RSSI values upon intercepting the response signal generated by the RFID tag 104. RSSI, or Received Signal Strength Indicator, is a measurement of the power level of the response signal, typically expressed in dBm (decibels per milliwatt). This power level indicates the strength of the received signal. The power level of the response signal varies based on the proximity of the RFID tag 104 to the listening devices. For example, the power level received at the listening device 107 is high when the RFID tag 104 is near to listening device 107, and the power level received at the listening device 101 is low when the RFID tag 104 is far from listening device 101.

[0051] The RSSI value or power level is typically influenced by free space loss and additional losses due to obstacles, reflections, diffraction, and environmental conditions. The response signalundergoes loss or attenuation, or reduction in the strength of the response signal as it propagates in free space. For example, the RSSI value received at listening device 107 is different from RSSI value received at listening devices 101 and 106 because the at least one RFID tag 104 is near to the listening device 107 and away from the listening devices 101 and 106.

[0052] For example, the RSSI value can range from -30 to -92 dBm. The listening device 107 may receive an RSSI value of -30 dBm, the listening device 105 may receive -28 dBm, and the listening devices 101 and 106 may receive -89 dBm and -90 dBm, respectively. The listening devices 107 and 105 receive a stronger response signal, and the listening devices 101 and 106 receive a low response signal because the distance between the listening device 107 or 105 and the at least one RFID tag 104 is less compared to the distance between the at least one RFID tag 104 and other listening device 101 or 106. This variation in RSSI values is primarily due to the signal attenuation that occurs as the RF waves travel through space. The signal strength decreases as the distance increases, resulting in lower RSSI values for more distant listening devices. Additionally, obstacles in the signal path, such as walls or shelving units, or other objects in the retail environment (not shown in the figure), may further reduce the signal strength, contributing to the lower RSSI values received by listening devices 101 and 106. The RSSI value range -30 to -92 dBm is only an example and should not be considered as a limitation. Similarly, the response time of the at least one RFID tag 104 varies as the distance between the tag and each of the one or more listening devices 101, 105, 106 and 107 varies. Combining data from strategically placed listening devices allows an enhanced ability to detect and localize RFID tags in complex environments with obstacles, reflections, and signal interference. Furthermore, this is highly advantageous to have reduced susceptibility to environmental factors owing to the multipath effects than direct reader-tag communications of the conventional art and practices.

[0053] The computing device 108 receives the data signals comprising the first and second parameters from each of the one or more listening devices 101, 105, 106 and 107. The computing device 108 then processes the data signal to determine the proximity of the RFID tag 104 relative to at least one known location using one or more proximity determination techniques. The at least one known location is pre-stored in a memory (not shown in figure) or database (not shown in Figure) associated with the computing device 108, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the method is implemented. The computing device 108utilizes data signals from one or more listening devices 101, 105, 106 and 107 positioned at different locations, each providing the extracted first parameters related to the RFID reader 102 and second parameters related to the RFID tag 104. By processing the data signals from each of the one or more listening devices 101, 105, 106 and 107, the computing device 108 determines the tag's proximity more accurately than any conventional systems that rely predominantly on direct reader-tag communications. The multi-faceted perspectives offered by the one or more listening devices 101, 105, 106 and 107 allow the system to account for practical factors such as signal strength variations and environmental conditions, resulting in a more precise determination of the RFID tag's proximity. Improved accuracy in determining tag proximity by utilizing data from multiple listening devices positioned at different locations is resulted here compared to relying solely on a single RFID reader's measurement.

[0054] As mentioned hereinbefore, the computing device 108 employs one or more proximity determination techniques to determine the RFID tag's proximity. The one or more proximity determination techniques, inter alia, include, but are not limited to:I) delta value calculation; ii) path loss calculation; ill) data combination from multiple receivers; and iv)angle of signal approach calculation.

[0055] According to one embodiment, the computing device 108 utilizes one or more proximity determination techniques, individually or in combination, to enhance the accuracy of tag proximity determination. In some embodiments, the computing device 108 employs a delta value calculation technique to determine the location and movement of RFID tags relative to the at least one known location. Using the delta value calculation technique, the computing device 108 analyzes variations in RSSI values over time or between multiple listening devices to determine the proximity and movement of RFID tags relative to the at least one known location. Instead of relying on absolute signal strength or fixed distance measurements, the computing device 108 uses the delta value calculation technique to analyze changes in RSSI values to determine tag proximity and movement. The computing device 108 calculates a delta value by subtracting the first RSSI value from the second RSSI value. The first RSSI value represents the strength of the signal received by the RFID reader 102 from the RFID tag 104, while the second RSSI value represents the strength of the signal received directly by the listening devices 101, 105, 106 and 107 from the RFID tag 104. The listening devices positioned closer to the RFID reader 102, such as the listening devices 101 and 106, provide more accurate data about the first RSSI value, as theycan more precisely measure the strength of the signal received by the RFID reader 102 from the RFID tag 104 compared to the other listening devices 105 and 107. The proximity of the RFID tag 104 is then determined based on the delta value. A positive delta value indicates the RFID tag 104 is closer to the RFID reader 102, while a negative delta value suggests the RFID tag 104 is closer to the listening devices 105 and 107.

[0056] In another embodiment, the magnitude of the delta value may correlate with the confidence level of the proximity estimate. The amount the delta value deviates from zero represents the level of confidence in determining the RFID tag's relative position. When the delta value is close to zero, the RFID tag 104 is approximately equidistant from the RFID reader 102 and the listening devices 101, 105, 106, and 107, indicating a lower confidence estimate. As the delta value deviates further from zero, the confidence in determining the RFID tag's relative position increases. A larger deviation from zero indicates higher confidence in determining whether the RFID tag is closer to the RFID reader or closer to the listening devices, enabling more precise localization of the RFID tag.

[0057] The computing device 108 interprets RFID tag's movement based on changes in the delta value over time. A shift from positive to negative delta values (or vice versa) may indicate the tag 104 crossing a threshold between the RFID reader 102 and the listening devices 101, 105, 106, and 107, potentially signifying passage through a predefined zone. Increasing positive delta values suggest movement toward the RFID reader 102 and / or away from the listening devices 101, 105, 106, and 107, while increasing negative values indicate movement in the opposite direction, according to an embodiment herein. The delta value calculation technique, thus, offers advantages over static distance measurements, allowing for more accurate tracking of tag movement and position.

[0058] In some embodiments, the system 100 may employ specific calibration procedures to optimize its performance. During initial setup, each listening device may undergo a calibration process where it measures and records the signal characteristics from known RFID tag positions. The recorded signal characteristics are used to create a baseline for signal propagation in the specific environment. The computing device 108 may then use learning algorithms to continuously refine its proximity calculations based on this calibration data and ongoing measurements. For example, the delta-value calculation may be fine-tuned using these calibrations to account for environmental factors specific to each installation.

[0059] In some embodiments, the computing device 108 calculates path losses between antennas of the RFID reader 102, the RFID tag 104, and the one or more listening devices 101, 105, 106, and107. It measures signal strengths at each antenna 103, 122 and compares the calculated path losses with the measured signal strengths to determine the proximity of the RFID tag 104 relative to the at least one known location.

[0060] In some embodiments, the computing device 108 combines data of a single RFID tag 104 corresponding to signals detected by two different receivers. These receivers are selected from: (i) a receiver of the RFID reader 102 as measured by a first listening device positioned in proximity to the RFID reader 102 and the receiver 124 of a second listening device, or (ii) the receivers 124 of first and second listening devices. By calculating the RFID tag's 104 proximity based on this combined data, where at least one of the receivers is independent from the RFID reader 102, the system 100 achieves improved accuracy in localization. In one embodiment, the first listening device positioned in proximity to the RFID reader 102 is configured to intercept both signals transmitted by the RFID reader 102 to the RFID tag 104 and signals received by the RFID reader 102 from the RFID tag 104, while the receiver 124 of the second listening device is configured to intercept RF signals directly from the RFID tag 104. In another embodiment, the receivers 124 of first and second listening devices are configured to intercept RF signals directly from the RFID tag 104, wherein both listening devices operate independently from the RFID reader 102.

[0061] In some implementations, each of the one or more listening devices 101, 105, 106, and 107 comprises an antenna array with multiple antennas 122. The software controller 121 of each listening device 101, 105, 106, and 107 is configured to receive Radio Frequency (RF) signals communicated between the RFID reader 102 and the RFID tag 104 at the multiple antennas 122 and calculate an angle of signal approach based on phase differences between the received RF signals. The computing device 108 then determines the proximity of the RFID tag 104 based on the calculated angles of signal approach from multiple listening devices. The angle of signal approach enables more precise spatial localization of tags, offering an advantage over systems that rely solely on signal strength measurements.

[0062] In some embodiments, the system 100 provides flexible methods for defining and adjusting one or more proximity zones. Through the computing device's interface (not shown in Figures), users can define custom proximity zones based on physical layouts or operational requirements. These zones may be configured using a combination of signal strength thresholds, calculated distances, and angular information from multiple listening devices. The system may also employ adaptive zone adjustment algorithms that automatically refine zone boundaries based on historical data and detected movement patterns. For example, in a retail environment as shown in Figure 3, the system could automatically adjust the boundaries of a "shelf zone" based on observed customer interactions, ensuring accurate tracking of items removed from or returned tothe shelf. The proximity zones may also be a "fitting room," a "shopping area," a "product storage area," or a combination thereof.

[0063] The computing device 108 applies these proximity determination techniques to the processed data signals received from each of the one or more listening devices 101, 105, 106, and 107. Each data signal contains the first parameters and the second parameters, such as the first RSSI value, the second RSSI value, read rates, Electronic Product Codes (EPC) of RFID tags, the phase angle information, the RFID reader name, RFID reader port, RFID tag ID, the time stamp related to the RFID tag 102 and the RFID reader 104, the read rate of at least one RFID tag over time, the response rate of the RFID tag 102 to the RFID reader 104, the command sent to the RFID tag 102, and the response from the RFID tag 102. The computing device 108 uses these first and the second parameters as inputs for the proximity determination techniques. For example, in the delta value calculation, the first and second RSSI values from the data signals are used to calculate the delta value. In the path loss calculation, the measured signal strengths contained in the data signals are compared with the calculated path losses. For data combinations from multiple receivers, the computing device 108 processes data signals from different listening devices to enhance the accuracy of the proximity determination. In the angle of signal approach calculation, the phase angle information from the data signals is used to determine the angle of the RFID tag 104 relative to the at least one known location. By applying these techniques to the processed data signals, the computing device 108 can accurately determine the proximity of the RFID tag 104 relative to the at least one known location using the delta value calculation, path loss calculation, data combination from multiple receivers, and angle of signal approach calculation. In one embodiment, upon analyzing the first parameters and second parameters, the computing device 108 suggests that a retail operator or staff member modify settings of the at least one RFID reader 102 to improve performance. The suggestion (i.e., setting parameters) can be presented through a computing device interface (not shown in Figure) associated with the computing device 108.

[0064] In an alternative embodiment, a listening device (101, 105, 106, and 107) for determining proximity of RFID tags comprises a receiver 124 and a processor 120 with a software controller 121. The receiver 124 intercepts RF signals exchanged between at least one RFID reader 102 and at least one RFID tag 104, potentially using a Gen 2 Ultra High Frequency (UHF) Communication protocol. These intercepted signals may include query signals, response signals, Random Number 16 (RN16) signals, Acknowledge (ACK) signals, Electronic Product Code (EPC) signals, and other command or response signals. The processor 120 analyzes the intercepted RF signals through demodulation and processing to extract first parameters related to the RFID reader 102 and second parameters related to the RFID tag 104. The first and second parameters may include RSSIvalues, read rates, EPCs, phase angle information, RFID reader name and port, RFID tag ID, time stamps, response rates, commands, and responses. The processor 120 then determines the proximity of the RFID tag 104 to the at least one known location based on these extracted parameters using one or more proximity determination techniques. The at least one known location is pre-stored in a memory (not shown in figure) or a database (not shown in figure) associated with the listening device, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the method is implemented. The one or more proximity determination techniques may involve delta value calculation by subtracting RSSI values, path loss calculation, data combination from multiple receivers, and angle of signal approach calculation. For enhanced accuracy, the listening device may include an antenna array with multiple antennas 122, allowing the processor 120 to calculate the angle of signal approach based on phase differences between received signals. This listening device can be implemented in various environments such as retail store environments, self-checkout gated areas, and shipment verification systems.

[0065] FIG.2 illustrates a method for determining the proximity of RFID tags implemented using the system 100, in accordance with an embodiment. The method includes several steps performed by various components of the system 100.

[0066] At step 201, intercepting, by the at least one listening device (101, 105, 106, or 107), RF signals exchanged between the at least one RFID reader 102 and the at least one RFID tag 104 104. These intercepted RF signals may include query signals from the RFID reader 102 to the RFID tag 104, response signals from the RFID tag 104 to the RFID reader 102, Random Number 16 (RN16) signals, Acknowledge (ACK) signals, Electronic Product Code (EPC) signals, and any other signals exchanged as part of RFID communication protocols. In some implementations, the RF signals are intercepted using a Gen 2 Ultra High Frequency (UHF) Communication protocol.

[0067] Step 202 includes analyzing, by a software controller 121 of the at least one listening device (101, 105, 106, or 107), the intercepted RF signals. This analysis includes extracting first parameters and second parameters, wherein the extracting comprises demodulating and processing the intercepted RF signals. The first parameters are related to the at least one RFID reader 102, while the second parameters are related to the at least one RFID tag 104.

[0068] Step 203 includes generating, by the software controller, a data signal based on the analyzed RF signals. The data signal includes at least one of: a first Return Signal Strength Indicator (RSSI) value, a second RSSI value measured, read rates, Electronic Product Codes (EPC) of tags, phase angle information, RFID reader name, RFID reader port (antenna), RFID tag ID, a time stamp related to the RFID tag 104 and the RFID reader 102, a read rate of at least one RFID tag 104 over time, a response rate of the RFID tag 104 to the RFID reader 102, a command sent to the RFID tag 104, and a response from the RFID tag 104.

[0069] Step 204 includes sending, by the at least one listening device (101, 105, 106, or 107), the data signal using the communication interface 123.

[0070] Step 205 includes receiving, by a computing device 108, the data signal from the at least one listening device (101, 105, 106, or 107) via the communication network.

[0071] Step 206 includes processing, by the computing device 108, the received data signal.

[0072] Step 207 includes determining, by the computing device 108, a proximity of the at least one RFID tag 104 relative to the at least one known location based on the processed data signal. The at least one known location is pre-stored in a memory or database associated with the computing device 108, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the method is implemented. The proximity determination uses one or more proximity determination techniques, wherein the one or more proximity determination techniques include:(i) calculating a delta value by subtracting the first RSSI value from the second RSSI value and determining the proximity based on this delta value;(ii) calculating path losses between receivers of the RFID reader 102, the RFID tag 104, and the at least one listening device (101, 105, 106, or 107), measuring signal strengths at each receiver, and comparing the calculated path losses with the measured signal strengths to determine the proximity of the at least one RFID tag 104.(ill) combining data of a single RFID tag 104 corresponding to signals detected by two different receivers. These receivers are selected from either (i) a receiver of the RFID reader 102 (not shown in Figure) as measured by a first listening devicepositioned in proximity to the RFID reader 102 and a receiver 124 of a second listening device, or (ii) receivers 124 of first and second listening devices. The tag's proximity is calculated based on the combined data. Wherein in scenario (i), the first listening device intercepts both signals transmitted by the RFID reader 102 to the RFID tag 104 and signals received by the RFID reader 102 from the RFID tag 104, while the second listening device intercepts RF signals directly from the RFID tag 104. Wherein in scenario (ii), the receivers 124 of first and second listening devices intercept RF signals directly from the RFID tag 104, with both listening devices operating independently from the RFID reader 102.(iv) for a system where each listening device 101, 105, 106, and 107 comprises an antenna array with multiple antennas, receiving signals at multiple antennas of an antenna array of each listening device 101, 105, 106, and 107, calculating an angle of signal approach based on phase differences between the received signals by the processor 120 of each of the one or more listening device (101, 105, 106, and 107), and determining the proximity of the at least one RFID tag 104 based on the calculated angles of signal approach from multiple listening devices.

[0073] FIG.3 shows an example implementation of a system 300 in a retail store environment, in accordance with an embodiment. The system 300 includes one or more listening devices 302, 303, 305, 306, and 307, at least one RFID reader 301, a first RFID tag 304, and a second RFID tag 310. The first RFID tag 304 is attached or adhered to a first product (not shown in Figure 3) placed on a table 308, while the second RFID tag 310 is attached or adhered to a second product (not shown in Figure 3) placed on a shelf 309. Each of the listening devices 302, 303, 305, 306, and 307 are positioned at fixed locations, as shown in Figure 3, with listening device 306 positioned close to or on table 308 and listening device 307 positioned close to or on shelf 309. The RFID reader 301 is configured to transmit an RF signal. Both the first and the second RFID tags 304 and 310 receive this transmitted signal and send corresponding response signals. Each listening device 302, 303, 305, 306, and 307 is configured to intercept the transmitted signal from RFID reader 301 and the response signals from tags 304 and 310.

[0074] The listening device 306 intercepts a higher RSSI value for the first RFID tag 304 than other listening devices 302, 303, 305, and 307, but a lower RSSI value for RFID reader 301 compared to listening devices 302 and 303 due to its distance from the RFID reader 301. Similarly, listening device 307 intercepts a higher RSSI value for the second RFID tag 310 than other listening devices302, 303, 305, and 306. Combining collected data from each of the one or more listening devices302, 303, 305, 306, and 307 increases the level of data accuracy.

[0075] The system 300 accounts for signal attenuation due to path loss as RF signals propagate through the retail environment. RSSI values received by each of the one or more listening devices 302, 303, 305, 306, and 307 vary based on their distance from the first and the second tags 304 and 310 and RFID reader 301, as well as obstacles in the signal path. This variation in signal strength across multiple listening devices enables more accurate determination of tag locations. The strategic placement of the listening devices 306 and 307 near the table 308 and shelf 309 respectively allows for enhanced RF signal interception and improved tag detection efficacy in those specific areas. The system 300 also considers signal distortion caused by shelf 309 and other store fixtures. The presence of shelf 309 may cause signal reflections, diffractions, or absorptions that affect RF signals exchanged between RFID reader 301, tags 304 and 310, and listening devices. By having multiple listening devices positioned at different locations, the system 300 can compensate for these distortions and provide a more accurate assessment of tag locations, even when signals are partially obstructed or altered by store fixtures.

[0076] FIG.4 shows an example implementation of a system 400 at a self-checkout counter in a retail store environment, in accordance with an embodiment. The system 400 includes one or more listening devices 401, 406, 413, and 411, a first RFID reader 402 including a reader antenna 403, a second reader 405 including a reader antenna 404, a first RFID tag 408, a second RFID tag 409, and a third RFID tag 410. Each RFID tag is attached or adhered to a product (not shown in Figure). The first RFID reader 402 is positioned on the left side of the checkout exit, and the second RFID reader 405 is positioned on the right side, with 407 representing a checkout path for customers. A customer (not shown in Figure) picks a product and moves along the checkout path 407.

[0077] Each of the one or more listening devices 401, 406, 413, and 411 is positioned at a fixed location as shown in FIG.4. Listening device 401 is positioned on the left side of the self-checkout counter and in front of the first RFID reader 402. Listening device 406 is positioned on the right side of the self-checkout counter and in front of the second RFID reader 405. The listening device 411 is positioned on the left side of the self-checkout counter, behind the first RFID reader 402, and is close to or on the shelf 309. The listening device 413 is positioned on the right side of the self-checkout counter and behind the second RFID reader 405. The first RFID reader 402 and the second RFID reader 405 are configured to transmit RF signals. The RFID tags 408, 409, and 410 receive these transmitted signals and send corresponding response signals back to the readers 402 and 405.

[0078] Each of the one or more listening devices 401, 406, 413, and 411 intercepts the RF signals exchanged between the RFID readers 402, 405 and the tags 408, 409, and 410. These intercepted signals are then analyzed by the software controller 121 (as shown in Figure lb) in each of the one or more listening device 401, 406, 413, and 411. Based on this analysis, each of the one or more listening devices 401, 406, 413, and 411 generates a data signal containing first and second parameters.

[0079] The computing device (not shown in Figure 4) receives these data signals from each of the one or more listening devices 401, 406, 413, and 411. It then processes and combines these first and the parameters received from each of the one or more listening devices 401, 406, 413, and 411 to determine the proximity of the RFID tags' 408, 409 and 410 locations relative to the at least one known location of the RFID readers 402, 405 and the checkout counter. This combined processing increases the confidence level of the proximity determination. For example, by processing the data signals received from each of the one or more listening devices, the computing device 108 can determine that the first RFID tag 408 is outside the self-checkout counter.

[0080] FIG.5 shows an example implementation of a shipment verification system 500, in accordance with an embodiment. The system 500 includes one or more listening devices 501, 506, 513, and 511, a first RFID reader 502 including a reader antenna 503, a second reader 505 including a reader antenna 504, all or most of which are disposed within a shipping area. The system 500 is designed to track and monitor the movement of RFID-tagged items through an entry and exit gate. In this example, three RFID tags are shown: a first RFID tag 508, a second RFID tag 509, and a third RFID tag 510. These tags may be attached to boxes, packages, or other items, though the specific items are not shown in FIG.5. The first RFID reader 502 is positioned on a right side of the entry and exit gate, the second reader 505 is positioned on a left side, and 507 represents a path through which tagged items may pass into and out of the shipping area.

[0081] Each of the one or more listening devices 501, 506, 513, and 511 are positioned at fixed locations near the entry and exit gate, as shown in FIG.5. Listening device 501 is positioned on the right side of the gate and in front of the first RFID reader 502. Listening device 506 is positioned on the left side and in front of the second RFID reader 505. The listening device 511 is positioned on the right side and behind the first RFID reader 502. The listening device 513 is positioned on the left side and behind the second reader 505. It will be appreciated that this positioning is for illustrative purposes only, and embodiments contemplate alternative arrangements suitable for specific shipping areas.

[0082] The first RFID reader 502 and the second RFID reader 505 are configured to transmit RF signals. The RFID tags 508, 509, and 510 receive these signals and send corresponding response signals to the RFID readers 502, 505. Each of the one or more listening devices 501, 506, 513, and 511 are configured to intercept both the transmitted signals from the RFID readers 502, 505 and the response signals from the RFID tags 508, 509, and 510. The listening devices demodulate these intercepted RF signals to extract first and second parameters, which may include, but are not limited to, RSSI values, unique identifiers, time stamps, read rates, and response rates for each tag. The computing device (as shown in FIG. la) receives these extracted parameters from each of the one or more listening devices and determines the proximity of each tagged item as it enters or exits the shipping area via the gate, relative to the at least one known locations of the readers 502 and 505. The use of multiple listening devices provides additional data points, increasing the accuracy in verifying the proximity of each tagged item and improving overall monitoring of the movement of items entering or exiting the shipping area.

[0083] In some embodiment, the system 100 and the architecture thereunder is designed for scalability, allowing it to be deployed in environments of varying sizes and complexities. The distributed nature of the listening devices enables easy expansion of coverage areas by simply adding more devices to the network. The computing device 108 is capable of processing data from a large number of listening devices simultaneously, using parallel processing techniques to maintain real-time performance as the system scales. In large-scale deployments, such as extensive warehouse operations or multi-story retail environments, the system can be segmented into zones, each with its own set of listening devices and local processing units, all reporting to a central computing device. This hierarchical structure allows the system to scale efficiently, maintaining high accuracy and responsiveness even in very large or complex RFID environments.Example listening device implementation

[0084] The RSSI value or power level is typically influenced by a free space loss and a path loss. The free space loss refers to an attenuation or reduction in the strength of a radiofrequency (RF) signal as it propagates through free space (a vacuum or air) without any obstacles or interference. This occurs because the electromagnetic waves spread out as they travel, leading to a decrease in signal intensity with distance. Path loss refers to the overall reduction in signal strength as a signal travels from transmitter to the receiver in the system. The path loss includes various factors such as free space loss, additional losses due to obstacles, reflections, diffraction, and environmental conditions.

[0085] During the implementation stage, it is crucial to consider factors such as the free space loss and the path loss. These crucial factors aid in estimating the signal strength at various distances and optimizing listening device configurations for reliable communication. The estimation may be accomplished using the formulas provided below:Friis Free-Space Path Loss (FSPL): = 20logl0 (d) + 20logl0 (f) + 20logl0 (4 ?r / c)-GTx- GRX) . (i) where, d = Distance between the antennas. f = FrequencyG (Tx) = The Gain of the Transmitting Antenna.G (Rx) = The Gain of the Receiving Antenna. c = Speed of light in vacuum ( Meters per Second).RSSI = P t - P L ( d ) . (ii) where, Pt: a signal transmission power,P L ( d ):path loss when the distance is d.A = P t - P L ( d ) . (ill)'A' indicates the signal strength which is received from listening devices at a distance.

[0086] It should be apparent, however, to those of ordinary skill in the art to which this subject matter pertains that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the disclosure. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced

Claims

CLAIMSWe claim:

1. A system for determining the proximity of RFID tags, comprising: at least one RFID reader; at least one RFID tag; at least one listening device, wherein each listening device comprises: a receiver configured to intercept RF signals exchanged between the RFID reader and at least one RFID tag; a processor comprising a software controller configured to analyze the intercepted RF signals and generate a data signal; and a communication interface configured to send the data signal; and a computing device configured to: receive the data signal from the at least one listening device; process the received data signal; and determine proximity of the at least one RFID tag relative to at least one known location based on the processed data signal.

2. The system of claim 1, wherein the proximity of the at least one RFID tag relative to the at least one known location is determined using one or more proximity determination techniques.

3. The system of claim 2, wherein the one or more proximity determination techniques comprise at least one of: a delta value calculation by subtraction of a first RSSI value from a second RSSI value; path loss calculation; data combination from multiple receivers; and angle of signal approach calculation.

4. The system of claim 1, wherein the software controller is configured to: analyze the intercepted RF signals to extract first parameters and second parameters, wherein the analysis comprises demodulation and processing of the intercepted RF signals;generate the data signal based on the extracted first parameters and second parameters; and send, using the communication interface, the data signal comprising the first parameters and the second parameters to the computing device.

5. The system of claim 1, wherein the receiver is configured to intercept RF signals exchanged between the at least one RFID reader and at least one RFID tag using a Gen 2 Ultra High Frequency (UHF) Communication protocol.

6. The system of claim 4, wherein the first parameters are related to the at least one RFID reader.

7. The system of claim 4, wherein the second parameters are related to the at least one RFID tag.

8. The system of claim 1, wherein the intercepted RF signals comprise one or more of: a query signal from the at least one RFID reader to the at least one RFID tag; a response signal from the at least one RFID tag to the at least one RFID reader; a Random Number 16 (RN16) signal from the at least one RFID tag to the at least one RFID reader; an Acknowledge (ACK) signal from the at least one RFID reader to the at least one RFID tag; an Electronic Product Code (EPC) signal from the at least one RFID tag to the at least one RFID reader; any command signal from the at least one RFID reader to the at least one RFID tag; any response signal from the at least one RFID tag to the at least one RFID reader; and any other signal exchanged between the at least one RFID reader and the at least one RFID tag as part of RFID communication protocols.

9. The system of claim 1, wherein the data signal includes at least one of: a first Return Signal Strength Indicator (RSSI) value, a second RSSI value measured, read rates, Electronic Product Codes (EPC) of tags, phase angle information, RFID reader name, RFID reader port (antenna), RFID tag ID, a time stamp related to the RFID tag and the RFID reader, a read rate of at least one RFID tag over time, a response rate of the RFID tag to the RFID reader, a command sent to the RFID tag, and a response from the RFID tag.

10. The system of claim 1, wherein to determine the proximity of the at least one RFID tag relative to at least one known location , the computing device is further configured to: calculate a delta value by subtracting the first RSSI value from the second RSSI value; and determine the proximity of the at least one RFID tag relative to the at least one known location based on the delta value.

11. The system of claim 1, wherein to determine the proximity of the at least one RFID tag relative to the at least one known location , the computing device is further configured to: calculate path losses between receivers of the RFID reader, the RFID tag, and the at least one listening device; measure signal strengths at each receiver; and compare the calculated path losses with the measured signal strengths to determine the proximity of the at least one RFID tag.

12. The system of claim 1, wherein to determine the proximity of the at least one RFID tag relative to the at least one known location , the computing device is further configured to: combine data of a single RFID tag corresponding to signals detected by two different receivers, wherein the two receivers are selected from: (i) a receiver of the RFID reader as measured by a first listening device positioned in proximity to the RFID reader and a receiver of a second listening device, or (ii) receivers of first and second listening devices; and calculate the tag's proximity based on the combined data.

13. The system of claim 12, wherein: the first listening device positioned in proximity to the RFID reader is configured to intercept both signals transmitted by the RFID reader to the RFID tag and signals received by the RFID reader from the RFID tag; and the second listening device is configured to intercept RF signals directly from the RFID tag.

14. The system of claim 12, wherein: the receivers of first and second listening devices are configured to intercept RF signals directly from the RFID tag, wherein both the first and second listening devices operate independently from the RFID reader.

15. The system of claim 1, wherein: each listening device comprises an antenna array with multiple antennas; the processor of each listening device is further configured to: receive signals at the multiple antennas; and calculate an angle of signal approach based on phase differences between the received signals; the computing device is further configured to determine the proximity of the at least one RFID tag based on the calculated angles of signal approach from multiple listening devices.

16. The system of claim 1, wherein the system is implemented in at least one of: a retail store environment; a self-checkout gated area; and a shipment verification system.

17. The system of claim 1, wherein the at least one known location is pre-stored in a memory or database associated with the computing device, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the system is implemented.

18. A method for determining the proximity of RFID tags in a system comprising at least one RFID reader, at least one RFID tag, at least one listening device, and a computing device, the method comprising: intercepting, by the at least one listening device, RF signals exchanged between the at least one RFID reader and the at least one RFID tag; analysing, by the at least one listening device, the intercepted RF signals; generating, by the at least one listening device, a data signal based on the analyzed RF signals; sending, by the at least one listening device, the data signal; receiving, by the computing device, the data signal from the at least one listening device;processing, by the computing device, the received data signal; and determining, by the computing device, a proximity of the at least one RFID tag relative to at least one known location based on the processed data signal.

19. The method of claim 18, wherein determining the proximity of the at least one RFID tag comprises using one or more proximity determination techniques.

20. The method of claim 19, wherein the one or more proximity determination techniques comprise at least one of: calculating a delta value by subtracting the first RSSI value from the second RSSI value; calculating path loss; combining data from multiple receivers; and calculating an angle of signal approach.

21. The method of claim 18, wherein analyzing the intercepted RF signals comprises: extracting first parameters and second parameters, wherein the extracting comprises demodulating and processing the intercepted RF signals; generating the data signal based on the extracted first parameters and second parameters; and sending, by the at least one listening device, the data signal comprising the first parameters and the second parameters to the computing device. generating the data signal based on the extracted first parameters and second parameters.

22. The method of claim 18, wherein intercepting RF signals comprises intercepting RF signals exchanged between the at least one RFID reader and at least one RFID tag using a Gen 2 Ultra High Frequency (UHF) Communication protocol.

23. The method of claim 21, wherein the first parameters are related to the at least one RFID reader.

24. The method of claim 21, wherein the second parameters are related to the at least one RFID tag.

25. The method of claim 18, wherein the intercepted RF signals comprise one or more of: a query signal from the at least one RFID reader to the at least one RFID tag;a response signal from the at least one RFID tag to the at least one RFID reader; a Random Number 16 (RN16) signal from the at least one RFID tag to the at least one RFID reader; an Acknowledge (ACK) signal from the at least one RFID reader to the at least one RFID tag; an Electronic Product Code (EPC) signal from the at least one RFID tag to the at least one RFID reader; any command signal from the at least one RFID reader to the at least one RFID tag; any response signal from the at least one RFID tag to the at least one RFID reader; and any other signal exchanged between the at least one RFID reader and the at least one RFID tag as part of RFID communication protocols.

26. The method of claim 18, wherein the data signal includes at least one of: a first Return Signal Strength Indicator (RSSI) value, a second RSSI value measured, read rates, Electronic Product Codes (EPC) of tags, phase angle information, RFID reader name, RFID reader port (antenna), RFID tag ID, a time stamp related to the RFID tag and the RFID reader, a read rate of at least one RFID tag over time, a response rate of the RFID tag to the RFID reader, a command sent to the RFID tag, and a response from the RFID tag.

27. The method of claim 18, wherein determining the proximity comprises: calculating a delta value by subtracting the first RSSI value from the second RSSI value; and determining the proximity of the at least one RFID tag relative to the at least one known location based on the delta value.

28. The method of claim 18, wherein determining the proximity comprises: calculating path losses between receivers of the RFID reader, the RFID tag, and the at least one listening device; measuring signal strengths at each receiver; and comparing the calculated path losses with the measured signal strengths to determine the proximity of the at least one RFID tag.

29. The method of claim 18, wherein determining the proximity comprises:combining data of a single RFID tag corresponding to signals detected by two different receivers, wherein the two receivers are selected from: (i) a receiver of the RFID reader as measured by a first listening device positioned in proximity to the RFID reader, and a receiver of a second listening device, or (ii) receivers of first and second listening devices; and calculating the tag's proximity based on the combined data.

30. The method of claim 29, wherein: intercepting, by the first listening device positioned in proximity to the RFID reader, both signals transmitted by the RFID reader to the RFID tag and signals received by the RFID reader from the RFID tag; and intercepting, by the second listening device, RF signals directly from the RFID tag.

31. The method of claim 29, wherein: intercepting, by the receivers of first and second listening devices, RF signals directly from the RFID tag, wherein both listening devices operate independently from the RFID reader.

32. The method of claim 18, further comprising: receiving signals at multiple antennas of an antenna array of each listening device; calculating, by the processor of each listening device, an angle of signal approach based on phase differences between the received signals; and determining, by the computing device, the proximity of the at least one RFID tag based on the calculated angles of signal approach from multiple listening devices.

33. The method of claim 18, wherein the method is implemented in at least one of: a retail store environment; a self-checkout gated area; and a shipment verification system.

34. The method of claim 18, wherein the at least one known location is pre-stored in a memory or database associated with the computing device, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the method is implemented.

35. A listening device for determining proximity of RFID tags, comprising: a receiver to intercept RF signals exchanged between at least one RFID reader and at least one RFID tag; a processor comprising a software controller configured to: analyze the intercepted RF signals to extract first parameters and second parameters, wherein the analysis comprises demodulation and processing of the intercepted RF signals; wherein the first parameters are related to the at least one RFID reader and the second parameters are related to the at least one RFID tag; and determine the proximity of the at least one RFID tag relative to at least one known location based on the extracted first parameters and second parameters.

36. The listening device of claim 35, wherein the proximity of the at least one RFID tag relative to the at least one known location is determined using one or more proximity determination techniques.

37. The listening device of claim 36, wherein the one or more proximity determination techniques comprise at least one of: a delta value calculation by subtraction of a first RSSI value from a second RSSI value; path loss calculation; data combination from multiple receivers; and angle of signal approach calculation.

38. The listening device of claim 35, wherein the receiver intercepts RF signals exchanged between the at least one RFID reader and at least one RFID tag using a Gen 2 Ultra High Frequency (UHF) Communication protocol.

39. The listening device of claim 35, wherein the intercepted RF signals comprise one or more of: a query signal from the at least one RFID reader to the at least one RFID tag; a response signal from the at least one RFID tag to the at least one RFID reader; a Random Number 16 (RN16) signal from the at least one RFID tag to the at least one RFID reader; an Acknowledge (ACK) signal from the at least one RFID reader to the at least one RFID tag;an Electronic Product Code (EPC) signal from the at least one RFID tag to the at least one RFID reader; any command signal from the at least one RFID reader to the at least one RFID tag; any response signal from the at least one RFID tag to the at least one RFID reader; and any other signal exchanged between the at least one RFID reader and the at least one RFID tag as part of RFID communication protocols.

40. The listening device of claim 35, wherein the extracted first parameters and second parameters include at least one of: a first Return Signal Strength Indicator (RSSI) value, a second RSSI value measured, read rates, Electronic Product Codes (EPC) of tags, phase angle information, RFID reader name, RFID reader port, RFID tag ID, a time stamp related to the RFID tag and the RFID reader, a read rate of at least one RFID tag over time, a response rate of the RFID tag to the RFID reader, a command sent to the RFID tag, and a response from the RFID tag.

41. The listening device of claim 35, wherein to determine the proximity, the processor: calculates a delta value by subtraction of the first RSSI value from the second RSSI value; and determines the proximity of the at least one RFID tag relative to the at least one known location based on the delta value.

42. The listening device of claim 35, wherein to determine the proximity, the processor: calculates path losses between receivers of the RFID reader, the RFID tag, and the listening device; measures signal strengths at each receiver; and compares the calculated path losses with the measured signal strengths to determine the proximity of the at least one RFID tag.

43. The listening device of claim 35, further comprising an antenna array with multiple antennas, wherein the processor: receives signals at the multiple antennas; and calculates an angle of signal approach based on phase differences between the received signals.

44. The listening device of claim 35, wherein the listening device is implemented in at least one of: a retail store environment; a self-checkout gated area; and a shipment verification system.

45. The of listening device of claim 35, wherein the at least one known location is pre-stored in a memory or a database associated with the listening device, and comprises at least one of: a location of at least one of the listening devices, a location of the RFID reader, a location of a fixture, a location of a predefined zone, a location of an entry or exit point, a location of a transaction area, a location of a product storage or display area, a location of a customer interaction area, a location of a product handling area, a location of a shipping or receiving area, or a location of a known reference point, within the environment where the listening device is implemented.

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