Multi-device ambient backscattering communication using LTE / NR pilot signals.

Abstract

The invention relates to a computer-implemented technique for detecting data transmitted by one or more passive backscattering devices using standardized pilot signals incorporated into an orthogonal frequency-division multiplexing downlink signal.

Description

TARIFF MULTI-DEVICE ENVIRONMENTAL RECORDING USING LTE / NR PILOT SIGNALS SCATTERING COMMUNICATION Technical Area The invention relates to an orthogonal frequency-division multiplexing downlink signal. One or more passive backscattering devices using standardized pilot signals It relates to computer-based techniques for detecting data transmitted by. 10 State of the Art Backscattering communication systems, especially in terms of ultra-low power passive tags, are inherently problematic. It is therefore affected by intermittent transmission and serious synchronization difficulties. 15 In synchronization-centric solutions; dedicated synchronization channels, distributed coding, and Pilot-based symbols that use maximum likelihood estimation in addition to scheduling. Timing shift estimators have been developed [1], [2]. While effective, these approaches, This leads to a significant amount of signaling overhead and computational complexity, and is limited. It offers scalability, making these approaches suitable for large-scale installations. This makes it unfavorable. In medium backscattering systems, primary transmission and backscattering. During signal reception, there is often overlapping, and strong direct path interference (DPI) and weak signal reception are observed. It masks the backscattered signal. As a result, CP-OFDM, due to its widespread use and structural design, Due to its properties, it has been widely utilized and used in various studies to reduce DPI. Empty subcarriers with cyclic prefixes have been used [3]–[6],

[10] ,

[11] . 25 Specifically, a subcarrier-based backscatter scheme uses one bit of information per subcarrier set. [3]; however, this arrangement requires the label to implement a passive notch filter bank. and thus significantly reduce hardware complexity, processing latency, and power consumption. It is increasing. 30 In other studies, the remaining cyclic prefix examples correspond to the OFDM symbol. The intact portion of the cyclic prefix was utilized by correlating it with its cross-sections. [4]–[6]. While effective under ideal conditions, these methods are often ineffective in practice. accurate knowledge of channel delay propagation, which is either absent or changes over time. This requires and limits robustness. 5 In pilot and avant-sequence based approaches, to separate backscatter signals from primary transmissions Pilot subcarriers or antecedent sequences have been reused [7]–[9]; this improves detection. However, using these resources for a different purpose involves channel estimation of the primary system and It impairs synchronization accuracy, reducing backward compatibility and reliability. 10 In frequency domain separation using frequency-shifted keying modulation, the return The scattering signal is shifted outside the bandwidth occupied by the primary signal [8]–

[11] ; However, this method requires receivers to perform additional filtering and adjacent channel scanning. This increases hardware complexity, processing overhead, and energy consumption. Furthermore... In recent studies, on-off switching and frequency-shifted switching schemes have been used, 15 shifts the primary signal energy to pre-allocated empty subcarriers

[11] ; however, open- While switched-mode switching exhibits low reliability, frequency-shifted variants offer significantly better reliability. It increases reliability at the expense of spectral inefficiency. In the context of cellular transporters, LTE is a band 20 that operates via cell-specific reference signals. The backscattering of the medium reaches a speed of only a few bits per second

[12] and probing Reference signal-based designs are a high-order system that performs over a thousand operations per bit. A Bessel receiver is required. In practice, backscattering is not reliable in existing OFDM systems. Integrating them in this way often requires the prior allocation of specific resources. and this leads to inefficient use of the spectrum, higher computational complexity, and an increased 25 This leads to hardware requirements. The limited and dense radio frequency spectrum... Very small, low-cost, and low-complexity passive devices that support machine-type communication. This is especially true given the need for Internet of Things devices. It is of critical importance. Additionally, multi-tag initiative and scalability in real-time large-scale deployments. Difficulties are encountered; to distinguish between simultaneously operating tags. Carrier pattern diversity has been proposed

[13] , however this approach increases signal processing complexity and This is achieved at the cost of additional coordination burden. More importantly, none of the existing OFDM pilot or cyclic prefix-based methods directly This does not completely cancel the road initiative; it only suppresses it approximately, not a single one. It remains consistent with the waveform and requires multiple devices on the reader side without needing additional resources. It does not simultaneously provide energy-neutral passive operation with its separation. In general, the existing solutions; reliability versus spectral efficiency, complexity or scalability 10 This creates a trade-off and involves numerous ultra-low-power Internet of Things (IoT) devices. Synchronized, interference-free, spectrum-efficient, low-powered for the large-scale installations it receives. In terms of implementing complex and cross-standard backscatter communication. This reveals a significant deficiency. Beyond these specific designs, there are also more comprehensive studies on ambient backscattering. the same ongoing relationship between communication range, data rate, reliability and hardware simplicity This confirms the trade-off

[14] . However, the symbiotic radio paradigm, passive devices They are treated as devices sharing the primary spectrum, but for reliable differentiation, the primary spectrum is still required. It is based on the waveform

[15] . 3GPP has a special ultra-low power 20 for future releases. The fact that the Internet of Things has begun to be examined in the radio access network environment as a class of device, The ongoing standardization efforts further highlight the practical importance of this deficiency.

[16] . Among the closest cellular pilot approaches to the current invention, LTE upstream coupling probing systems that utilize a reference signal; cell-specific reference signal. They achieve higher speeds than their designs, but the Bessel rating per bit is 25. This requires a correlation receiver which performs and is computationally heavy

[17] . Together, none of these approaches can simultaneously achieve direct road access while maintaining battery-free operation. It doesn't completely cancel it, it doesn't work the same way across LTE and 5G-NR, and it's a joint pilot program. It does not differentiate between multiple devices that use it; whereas the present invention achieves this. The combination is exactly this. 30 In conclusion, all of the aforementioned problems stem from the emergence of an innovation in the relevant technical field. This has made its inclusion necessary. Brief Description and Objectives of the Invention The main objective of the present invention is to enable one or more direct road signals to be activated in the presence of a relatively strong direct road signal. reliable detection of data transmitted by multiple passive backscattering devices The aim is to develop a computer-based backscatter communication method. Another objective of the invention is to convert an orthogonal frequency-division multiplexed downlink signal to 10 by creating a determinant-based cancellation statistic from standardized pilot subcarriers It is to algebraically cancel the direct route initiative. Another purpose of the invention is to enable the direct cutting of the road channel, with an additional cancellation carrier. the production, use of a filter bank, or the use of specific time or frequency sources 15 The goal is to carry out the cancellation without requiring its allocation. Another objective of the invention is to enable passive backscattering devices; Synchronization Signal Block, side including link synchronization signals and random access predicate sequences, an LTE or 5G New Radio base stations reuse pilot signals already transmitted by the base station. to provide. Another objective of the invention is to encompass pilot subcarriers of a single OFDM symbol containing a reference. to enable the detection of backscatter data from a pilot block and thus related to detection The goal is to reduce coherence time and processing requirements. 25 Another aim of the invention is to achieve backscattering without requiring the cutting of the backscattering channel. The aim is to enable the non-coherent detection of data. Another aim of the invention is to expand multi-device separation to more devices by using multiple receiving antennas. to expand and thus create dense installations containing more than two passive backscattering devices. It is to support. Another purpose of the invention is to expand into logistics, industrial monitoring, smart cities, healthcare, transportation, and smart 5.00 technology. Suitable for applications including homes and other large-scale Internet of Things environments, low-cost The goal is to provide a complex and spectrum-efficient backscattering communication framework. Description of the Figures Related to the Invention The necessary figures and their descriptions are given below to better understand the subject matter of the invention. It has been given. Figure 1. Schematic representation of the system. Figure 2. Schematic representation of the backscattering device. 15 Figure 3. Pilot block structure. Figure 4. Schematic representation of the reader detection chain. Figure 5. Schematic representation of phase-division multiple access. Reference Numbers 20 The parts and components shown in the figures are for reference purposes to facilitate a better understanding of the subject matter of the invention. It is given as follows. 100. Base station 25 101. OFDM modulator and reference pilot addition unit 102. IFFT and cyclic prefixing unit 200. Passive backscattering device 201. Anten 202. Energy collector 30 203. Energy buffer 204. Controller 205. Load modulator / impedance switch 206. Envelope detector 300th Reader 301. Block allocation and synchronization unit 5 302. Determinant cancellation function constructor 303. Direct Road Initiative Cancellation Unit 304. Bit decision unit 305. Phase-division separation layer Detailed Description of the Invention The present invention involves an orthogonal frequency-division multiplexing downlink signal. One or more passive backscattering devices using standardized pilot signals It relates to computer-based techniques for detecting data transmitted by. 15 The invention comprises a base station (100), at least one passive backscattering device (200) and a reader (300). It can be implemented in a cellular communication environment. Base station (100), an LTE base station or It could be a 5G New Radio (NR) base station. The reader (300) is the same as a user equipment. It can be located in the same place, integrated into user equipment, or added to user equipment within 20 days. It can be connected in a way that allows communication. The reader (300) can connect by the computer described herein. a data processing device configured to perform the applied detection procedures It may include. Looking at Figure 1; base station (100) is a downstream 25 containing standardized reference pilots. The downlink transmits an OFDM signal. The downlink OFDM signal is transmitted via an OFDM modulator and The reference pilot is generated by the addition unit (101) and then an inverse speed Fourier transform (IFFT) and cyclic prefixing unit (102) can process it. Standardized reference Pilots; LTE Cell-Specific Reference Signals (CRS), 5G-NR Demodulation Reference The signals (DMRS) or a predetermined time-frequency source of an OFDM transmission 30 It may include other reference signals occupying its elements. The downlink OFDM signal is a direct link represented by the hd direct link channel. It is received by the reader (300) via the same downlink OFDM signal, hf forward. to a passive backscattering device (200) via a forward link represented by a link channel Passive backscattering device (200) reaches by changing the reflection coefficient of an antenna 5 It modulates data onto the downlink signal and performs HB backscattering on the modulated signal. It reflects to the reader (300) via the connection channel. As a result, the signal received by the reader (300) is one received directly from the base station (100). A backscatter generated by a passive backscattering device (200) with a direct path component 10 It includes a composition formed by the overlapping of its components. The direct road component is usually It is significantly more powerful than the backscattering component and therefore, a passive backscattering device. The invention constitutes a direct path interference (DPI) that can cover the data transmitted by (200). a determinant-based cancellation statistic created from standardized pilot subcarriers It addresses this problem by algebraically canceling out the direct road contribution. 15 Multiple passive backscattering devices such as the T1, T2, T3 and T4 devices shown in Figure 1 (200) In a configuration that includes these, the forward connections for each device are hf1 to hf4, and the backward connections for each device are... Scattering junctions can be represented by hb1 to hb4. Multiple passive backscattering devices (200), base The same standardized pilot subcarriers transmitted by station (100) are transmitted simultaneously 20 It can be reused. Looking at Figure 2; a passive backscattering device (200), an antenna (201), an energy collector or rectifier antenna (202), a power buffer (203), a controller (204), a load modulator or It includes an impedance switch (205) and an envelope detector (206). 25 Antenna (201) receives the downlink OFDM signal transmitted by base station (100). At least some of the received radio frequency energy goes to the rectifier that rectifies the received radio frequency signal and converts the energy. to the energy collector or rectifier antenna (202) which supplies electrical energy to its buffer (203) is transmitted. The energy buffer (203); controller (204), load modulator or impedance 30 a capacitor suitable for supplying the switch (205) and envelope detector (206), supercapacitor, rechargeable energy storage element or other electrical storage device It may include. Energy collector or rectifier antenna (202) consists of source elements that include only the pilot, It can harvest energy from the total broadband downlink signal. Therefore, energy harvesting is downlink 5 from the part of the link used for transmitting backscattered data of time-frequency sources It can be carried out over a larger portion of it. Energy harvesting and backscatter data communication, This can be done simultaneously without requiring separate energy harvesting and data transmission stages. Envelope detector (206), synchronization associated signal 10 in the downlink OFDM signal. It can detect bursts. In an LTE configuration, the envelope detector (206) is the primary It can detect the synchronization signal, the secondary synchronization signal, or both. A 5G- In the NR configuration, the envelope detector (206) can detect a synchronization signal block. Detection of the synchronization-related signal is a coherent signal of the passive backscattering device (200). It provides coarse block-level timing without requiring the inclusion of a radio frequency receiver. 15 The controller (204) modulates the load modulator or impedance switch (205) according to the data to be transmitted. It controls the load modulator or impedance switch (205), which is connected to the antenna (201). It changes the electrical charge and thus changes the reflection coefficient of the antenna (201). Therefore, a passive backscattering device (200) can actively generate a radio frequency carrier. Instead, it can modulate data onto the OFDM downlink signal that comes via reflection. Accordingly, the passive backscattering device (200) is a local radio frequency oscillator, power amplifier, It does not need to include a coherent demodulator or channel estimation circuit. Passive backscattering. The device (200) can operate using the energy harvested from the downlink OFDM signal and 25 Therefore, it can be implemented as an energy-neutral or battery-free device. As seen in Figure 3; a pilot block contains multiple OFDM symbols within a single OFDM symbol that includes a reference. It includes pilot samples corresponding to a highly standardized pilot subcarrier. Multiple pilot sub-carriers, while belonging to the same OFDM symbol, may have one or more 30 The resource can be distributed to the block. Each OFDM symbol containing a reference can create its own pilot block. At some point... In cases where the slice contains more than one OFDM symbol with a reference, the referenced symbol OFDM symbols can form successive pilot blocks. Thus, detection is performed on a symbol-by-symbol basis. This can be done over an entire time period or over multiple time periods. It may not require averaging. Passive backscattering device (200) detects a selected antenna impedance state during a pilot block. It can protect. The antenna impedance status can be changed between successive pilot blocks. Pilot block Maintaining a single impedance state throughout, passive feedback of pilot samples within the block 10 It ensures that it is modulated consistently by the scattering device (200). In one configuration, a passive backscattering device (200) uses on-off switching to distribute data. It transmits. In the open state, the load modulator or impedance switch (205) reflects the antenna (201). It creates a backscattering component by adjusting it to an impedance state. In the off state, the load is 15 modulator or impedance switch (205), antenna (201) largely non-reflective or It adjusts to a low-reflection impedance state. In another configuration, the passive backscattering device (200) can also be called D²M. It transmits data using differential determinant modulation. In this configuration, the payload is 20. modulator or impedance switch (205), switching between first and second antipodal load states This is done by maintaining a data bit, load state, between successive pilot blocks, or It is represented by changing the amplitude of the data. Accordingly, the data is represented only in an absolute reflection amplitude. No, it is encoded in the transition between impedance states. Looking at Figure 4; the reader (300), a block separation and synchronization function (301), a Determinant cancellation function constructor (302), a direct path attempt cancellation function (303) and may include a bit decision function (304). These functions are used by one or more data processing devices. with software instructions executed by multiple processors, with programmable logic, or It can be implemented using a combination of these. 30 Block separation and synchronization function (301), an OFDM symbol containing a reference to determine and standardize pilot subcarriers included in the designated OFDM symbol It extracts the corresponding pilot samples. Timing information is available at the following link: OFDM synchronization signals included in the signal and standardized pilot subcarriers They can be obtained from their known locations. 5 The extracted pilot samples form the pilot block. The pilot block is a single OFDM containing the reference. Since the symbol can be created from pilot subcarriers, only that particular symbol is available for processing. Coherence is required for the duration of the OFDM symbol. Determinant cancellation function generator (302) for at least one carrier frequency shift value It creates an inter-carrier interference matrix. The carrier frequency shift value is a trial ε. It may have a value. The carrier-to-carrier interference matrix can be shown as follows: The elements of the carrier interference matrix S(ε) are those resulting from carrier frequency shift and It represents the interference relationships that occur between standardized pilot subcarriers. In one configuration, S(ε) is a sinc inter-carrier interference matrix. Determinant cancellation function generator (302); from the pilot samples received, between carriers interference matrix S(ε) and known pilots corresponding to standardized pilot subcarriers It creates a determinant-based cancellation statistic from the values. In a configuration Determinant-based cancellation statistics are defined as follows: Here, ε represents the trial carrier frequency shift; S(ε) is associated with the standardized pilot subcarriers. a₀, a leading pilot value; c, the inter-carrier interference matrix. A cofactor vector that is related and preferably the first column cofactor vector; B being the pilot 30 It represents a vector created from the samples. Direct path attempt cancellation function (303), for example an identity derived from the Cramér rule including the actual contribution of the direct path component to the determinant-based cancellation statistic. It uses a determinant identity that enables the cancellation of the carrier frequency shift εp. The direct path component and the backscattering component are from the same OFDM downlink signal. is caused by and therefore the reader is exposed to a common carrier frequency shift (300). It remains. Consequently, the true carrier frequency shift is εp, where determinant-based cancellation occurs. The algebraic relationship used in constructing the statistic provides information related to the backscatter component. It eliminates direct road contribution while protecting the road. 10 Unlike techniques that directly estimate and subtract the path component, cancellation is a process that directly estimates the path component. regardless of the power of the component and without interruption of the HD direct link channel. It can be done. The reader (300) can apply a notch filter, generate a cancellation carrier, Empty subcarriers 15 for directly estimating path channel response or retrieving backscatter data There is no need to separate them. The true carrier frequency shift εp is the multiple trial of the determinant-based cancellation statistic. This can be determined by evaluating the carrier frequency shift value. The actual carrier frequency The shift εp is the zero-crossing of the determinant-based cancellation statistic or the minimum magnitude of 20. It can be determined based on the point at which it is located. Multiple values ​​of a determinant-based cancellation statistic in a configuration, for a selected carrier. Frequency shift is calculated across the search interval. Determinant-based cancellation statistics. A carrier frequency shift value corresponding to a zero crossing is the actual carrier frequency shift εp 25 It can be selected as such. In another configuration, the magnitude of the determinant-based cancellation statistic varies across multiple trials. The carrier frequency shift value is determined and corresponds to a minimum magnitude. The carrier frequency shift value is selected. The carrier frequency shift resolution is set to 30. Among the carrier frequency shift values ​​evaluated for improvement, optionally Interpolation can be performed. After canceling the direct path contribution, the bit decision function (304) is determinant-based. It identifies backscatter data based on cancellation statistics. 5 In an on-off switching configuration, the bit decision function (304) is determinant-based cancellation. a normalized magnitude or a normalized ratio based on statistics can calculate. The calculated value is the reflector of the passive backscattering device (200) during the pilot block. To determine whether it is in a reflective or non-reflective state, a threshold value of 10 is used. comparable. The threshold value can be fixed or predetermined, adaptively determined, or pre-determined. It can be derived from one or more pilot blocks. The direct path component is algebraically canceled. Therefore, the threshold value is high and compensates for the variable direct path interference power. 15 It is not necessary. In a differential determinant modulation configuration, for successive pilot blocks Determinant-based cancellation statistics are obtained. A data bit is obtained for successive pilot blocks. Based on the differential relationship between the determinant-based cancellation statistics obtained, 20 It can be determined. Bit decision function (304), determinant-based cancellation of data bits corresponding to successive pilot blocks. It determines the sign of a differential product formed from statistics. A sign is passive. While the backscattering device (200) can show that it maintains the same antipodal charge condition, a contrasting 25 The signal indicates that the passive backscattering device (200) is transitioning from one antipodal charge state to another. It can show. Differential estimation allows for the further estimation of an absolute backscattering channel coefficient. It enables the detection of backscatter data without requiring it. Furthermore, the decision is only 30 It is based not on the magnitude of a single received signal, but on a relationship between successive pilot blocks. This can reduce the detection base associated with damping. Pilot values ​​transmitted by base station (100) are standardized and reader (300) It is known by. Determinant-based cancellation statistics, in the OFDM symbol containing the reference 5 It may not vary depending on the specific pilot sequence used. Accordingly, the pilot subcarriers' LTE CRS In cases where it carries pilot values ​​or 5G-NR DMRS pilot values, it is largely the same. A determinant-based detection method can be used. Therefore, the reader (300) has a different interference cancellation architecture for each cellular standard 10 It can support cross-standard work without requiring pilot locations, pilot sequences, sub-systems. standard-dependent parameters including carrier intervals, symbol durations, or source block layouts While parameters can be provided to the block separation and synchronization function (301), the determinant The cancellation process based on the pilot series remains largely unchanged. The independent work from the pilot series, collaborative. It allows a reader to process LTE CRS and 5G-NR DMRS signals. 15 Standardized pilot subcarriers are used to enable the operation of the primary cellular communication system. It is currently being transmitted. Accordingly, the pilot subcarriers are transmitted by the passive backscattering device (200). The use of a specific time interval, frequency band, pilot sequence, or null subcarrier It does not require allocation. The primary communication system, pilots channel estimation, 20 continue to use for demodulation, synchronization, or other standardized processes. can. In one configuration, the reader (300) has multiple modules that simultaneously modulate the same pilot block. It detects the data transmitted by the passive backscattering device (200). A 25 shown in Figure 5. Phase-division separation layer (305), differences between the effective phases of backscattering channels Based on this, it separates the backscatter data for each device. The first and second passive backscattering devices (200) modulate the same pilot block simultaneously. In this case, the received backscatter component can be represented as follows: 30 Here, b₁ and b₂ are the backscattered signals transmitted by the first and second passive backscattering devices (200), respectively. c₁ and c₂ represent the scattered data values, and respectively, the corresponding complex backscatter coefficients. It is. 5 Each complex backscattering coefficient corresponds to a corresponding forward link channel and a corresponding backscattering coefficient. It may depend on the linkage channel. Accordingly, the complex backscattering coefficients c₁ and c₂ are the first and due to the different physical locations and propagation conditions of the second passive backscattering devices (200) They generally have different sizes and phases. 10 Phase-division separation layer (305) provides an initial access to the relevant complex backscattering coefficients or This is determined during the canal characterization procedure. During this procedure, passive feedback is required. Scattering devices (200) can transmit individually identifiable reflection states or their own It can be activated during access periods; so that the reader (300) can receive the corresponding complex return 15 It enables the estimation of scattering coefficients. Phase-division separation layer (305), complex backscattering coefficients c₁ and c₂ are φ₁ and φ₂ respectively. can determine the phases. The reader (300) can determine a phase between the relevant complex backscattering coefficients. Based on the difference, passive backscattering devices for simultaneous use of the same pilot block (200) 20 You can select or match. Passive backscattering devices with highly orthogonal complex backscattering coefficients (200) It can be matched, if preferred. The phase difference can be selected, for example, to approach 90 degrees. The relevant data values ​​can be separated by constructing a two-to-two separation matrix M and then taking the inverse of this matrix. The determinant of the separation matrix can be proportional to: The separation matrix M is well-conditioned when the absolute value of the sine of the phase difference is relatively high. Accordingly, a phase difference approaching 90 degrees numerically corresponds to the relevant backscatter data values. It improves the separation. Phase-division separation layer (305) takes the superimposed composition to obtain b₁ and b₂ 5 It can be solved by inverting the two-by-two matrix. Thus, the first and second passive backscattering devices (200) can communicate simultaneously using the same time, frequency, pilot and code resources. Separation is achieved by naturally occurring channels rather than through additional spectral allocation or code space allocation. This is achieved by using phase diversity. An example involving two passive backscattering devices operating simultaneously (200) has been described. The meeting is not limited to this. In one configuration, the reader (300) has multiple receiver antennas. It includes each receiving antenna, which provides a different observation of the superimposed backscattered signals. This provides multiple observations to create a higher-dimensional separation matrix. available and thus the same standardized pilot subcarriers of the devices can be used simultaneously 15 In the case where it is used, backscatter data from more than two passive backscatter devices (200) Separation can be ensured. Device selection or grouping depends on a number of conditions, the magnitude of the determinant, phase separation, Based on the power received, the estimated detection reliability or a combination thereof, the reader (300) 20 can be performed by. Reader (300), passive backscattering devices (200), active channel Devices with sufficiently distinguishable phases will be assigned to the relevant pilot blocks such that they are assigned to the same pilot block. can allocate. The reader's (300) data processing device; one or more processors, a memory and a communication 25 It may include an interface. Computer-readable instructions stored in memory; data processing. the device's block separation, synchronization, pilot sample extraction, carrier-to-carrier interference matrix. generating, generating determinant-based cancellation statistics, directly canceling road contribution, and one or more to enable it to perform backscatter data detection operations It can be executed by the processor. 30 The data processing device also detects carrier frequency shift, differential detection, and on / off. Switching detection, initial access operation, estimating complex backscatter coefficients, passive back It can perform scattering device grouping and phase division separation operations. The computer-implemented functions described with reference to the reader (300) are a single 5 This can be performed by a single data processing device or between multiple data processing devices. It can be deployed. For example, the pilot sample extraction process can be performed by a radio front-end processor. While determinant generation and bit detection can be performed, a baseband processor or general This can be accomplished by a purpose-built processor. According to the invention, a data processing system can use any of the method configurations described herein. It includes a data processing device configured to perform this task. The data processing device; reader (300), a user equipment, a baseband processing unit, a network node Or it could form part of another communications apparatus capable of receiving and processing pilot samples. According to the invention, a computer program is processed by a data processing device 15 When executed, the data processing device can use any of the method configurations described here. It contains instructions that enable one to perform an action. A computer program is software or a device. Software can be implemented as machine-readable code or a combination thereof. SOURCES 1. V. Liu et al., “Ambient backscatter: Wireless communication out of thin air,” in Proc. ACM SIGCOMM, 2013, pp. 39–50. 2. H. Dong, Y. Wu et al., “PassiveBLE: Towards fully commodity-compatible BLE backscatter,” 5 arXiv:2503.11490, 2025. 3. M. Nemati et al., “Subcarrier-wise backscatter communications over ambient OFDM for low power IoT,” IEEE Trans. Veh. Technol., vol. 69, no. 11, pp. 13229–13242, 2020. 4. G. Yang and Y.-C. Liang, “Backscatter communications over ambient OFDM signals: Transceiver design and performance analysis,” in Proc. IEEE GLOBECOM, 2016, s. 1–6. 10 5. G. Yang, Y.-C. Liang, R. Zhang and Y. Pei, “Modulation in the air: Backscatter communication over ambient OFDM carrier,” IEEE Trans. Commun., cilt. 66, no. 3, s. 1219–1233, 2018. 6. T. L. Nguyen, Y. Shin, J. Y. Kim and D. I. Kim, “Signal detection for ambient backscatter communication with OFDM carriers,” Sensors, cilt. 19, no. 3, s. 517–531, 2019. 7. R. Takahashi and K. Ishibashi, “Ambient OFDM pilot-aided delay-shift keying and its efficient 15 detection for ultra-low-power communications,” in Proc. IEEE GlobalSIP, 2019, s. 1–5. 8. M. A. ElMossallamy vd., “Non-coherent frequency shift keying for ambient backscatter over OFDM signals,” in Proc. IEEE ICC, 2019, s. 1–6. 9. M. A. ElMossallamy vd., “Backscatter communications over ambient OFDM signals using null subcarriers,” in Proc. IEEE GLOBECOM, 2018, s. 1–6. 20 10. M. A. ElMossallamy vd., “Noncoherent backscatter communications over ambient OFDM signals,” IEEE Trans. Commun., cilt. 67, no. 5, s. 3597–3611, 2019. 11. M. B. Janjua, A. Şahin and H. Arslan, “Interference-free backscatter communications for OFDM-based symbiotic radio,” arXiv:2408.09192, 2024. 12. J. Liao vd., “In-band ambient FSK backscatter communications leveraging LTE cell-specific 25 reference signals,” IEEE J. Radio Freq. Identif., 2023. 13. C. Du and J. Yu, “ConcurScatter: Scalable concurrent OFDM backscatter using subcarrier pattern diversity,” in Proc. IEEE INFOCOM, 2024, s. 1771–1780. 14. N. Van Huynh, D. T. Hoang, X. Lu, D. Niyato, P. Wang, and D. I. Kim, “Ambient backscatter communications: A contemporary survey,” IEEE Commun. Surveys Tuts., cilt. 20, no. 4, s. 2889–30 2922, 2018. 15. Y.-C. Liang, Q. Zhang, J. Wang, and Y. Pei, “Symbiotic radio: Cognitive backscattering communications for future wireless networks,” IEEE Trans. Cogn. Commun. Netw., cilt. 6, no. 4, s. 1242–1255, 2020. 16. 3GPP, “Study on ambient IoT (Internet of Things) in RAN,” TR 38.848, Rel.-18, 2023. 17. J. Liao, X. Zhang, K. Ruttik, R. Jäntti, and Z. Han, “Ambient backscatter communication 5 leveraging the LTE uplink sounding reference signal,” IEEE Internet Things J., 2025.

Claims

REQUESTS 1. Data transmitted by at least one passive backscattering device (200) have an orthogonal frequency Computerized multiplexing is used to detect downlink signals. It is an applied method and is characterized by the following: 5 ● Orthogonal frequency-division multiplexing provides a direct path to the downlink signal. its component and orthogonal frequency by at least one passive backscattering device (200). Multiplexed splitting is created by modulating and reflecting the downlink signal. Receiving a signal containing a backscattering component; 10 ● The number one in an orthogonal frequency-division multiplexing symbol containing a reference. pilot samples taken corresponding to a highly standardized pilot subcarrier the selection and creation of a pilot block; ● Multiple standardized pilot sub-values ​​for at least one carrier frequency shift value. Creating an inter-carrier interference matrix associated with the carrier; 15 ● The contribution of the direct path component to the determinant-based cancellation statistic, directly A carrier frequency shift common to both the path component and the backscattering component. The pilot received will be cancelled by the direct route attempt cancellation procedure (303). from examples, the carrier-to-carrier interference matrix, and standardized pilot sub-assemblies 20 determinant-based cancellation statistics from pilot values ​​corresponding to carriers creation; and ● At least one passive backscatter device based on determinant-based cancellation statistics (200) Detecting backscattered data transmitted by the system.

2. This is a method according to claim 1, where the determinant-based cancellation statistic is 25. The creation of this involves generating a statistic according to the following formula: , where ε is a trial carrier frequency shift; S(ε) is the inter-carrier interference matrix; a₀, a represents a pilot value; c represents a cofactor vector associated with the carrier-to-carrier interference matrix. and B is formed from the pilot samples taken. 30 3. According to claim 1, it is a method where the contribution of the direct path component is the direct path. A determinant identity based on Cramér's rule, regardless of the strength of its component. using algebraic direct path attempt cancellation operation (303) by cancellation is being done.

4. This is a method according to claim 1, where determinant-based cancellation statistics are used. It is invariant according to a pilot sequence carried by standardized pilot subcarriers.

5. A method according to claim 1, where at least one passive backscattering device (200), a load Using a modulator or impedance switch (205) during the pilot block, an antenna 10 to maintain impedance status and antenna impedance status sequentially using pilot blocks It transmits backscattered data by switching between them.

6. This is a method according to claim 1, whereby backscatter data is detected and the determinant is determined. open-15 based on a normalized value of the cancellation statistic and a threshold value. This involves detecting the switched-on behavior.

7. A method according to claim 6, which involves the antenna impedance condition, load modulator, or impedance. The switch (205) is changed between antipodal load states and backscattering Detection of data obtained by bit decision operation (304) for successive pilot blocks 20 Based on the differential relationship between the resulting determinant-based cancellation statistics, a This involves determining the data bit.

8. A method according to claim 7, where data bit determination is done for successive pilot blocks. A differential product formed from the resulting determinant-based cancellation statistics is 25 It involves identifying the symbol. According to claim 9, it is a method of block separation and synchronization (301) OFDM below. This is accomplished by using at least one synchronization signal included in the link signal. It is characterized by 30 10. This is a method according to claim 1, where the received signal is transmitted simultaneously through the same pilot subcarriers. backscatter generated by multiple passive backscattering devices (200) that modulate as It contains scattering components.

11. A method according to claim 10, and also characterized by including the following steps: 5 is being done: ● associated with at least each of the first and second passive backscattering devices (200) Determining complex backscatter coefficients; ● Determining a phase difference between the relevant complex backscattering coefficients; and 10 ● phase of backscatter data of first and second passive backscatter devices (200) Separation based on the difference.

12. A method according to claim 11, where the first and simultaneous use of the pilot block is for... Selection of second passive backscattering devices (200), related complex backscattering 15 due to the fact that the phases of the coefficients are largely orthogonal is being carried out.

13. A method according to claim 11 or 12, where the received signal is transmitted through multiple antennas. It is acquired using and more than two passive return 20 using the same pilot subcarriers. Backscatter data from the scattering device (200) are obtained via multiple antennas. They are distinguished using observations.

14. To perform the steps of the method according to any of the previous requirements. A data processing system containing a configured processor. 25 15. When executed by at least one data processing system, at least one data processing device Instructions that enable the method to be executed according to any of claims 1 through 13. a computer program containing.

16. The computer program is stored on the computer according to Claim 15. a readable data carrier.

Images