Bluetooth backscatter data recovery method and system based on double sideband information compensation

Abstract

This invention relates to the field of backscatter communication technology, and discloses a Bluetooth backscatter data recovery method and system based on double-sideband information compensation. The method includes: synchronizing the tag with the excitation source to determine the modulation start point and the excitation source symbol boundary; the tag uses the excitation source signal as a carrier, carries tag data on the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-sideband backscatter signal and a right-sideband backscatter signal; the receiving end performs Gaussian frequency shift keying demodulation on the carrier signal, the left-sideband backscatter signal, and the right-sideband backscatter signal to obtain carrier bits, left-sideband demodulation bits, and right-sideband demodulation bits; and recovering the tag data using a three-channel gating recovery method or a two-channel differential recovery method. This invention not only exhibits excellent robustness under different signal-to-noise ratio environments, but can also be directly implemented based on standard commercial Bluetooth receivers.

Description

Technical Field

[0001] This invention relates to the field of backscatter communication technology, and specifically to a Bluetooth backscatter data recovery method and system based on double-sideband information compensation. Background Technology

[0002] In recent years, the Internet of Things (IoT) has flourished, enabling comprehensive connectivity between people, machines, and things. However, with the increasing number of nodes, the power consumption of wireless communication nodes has become increasingly prominent. Backscatter communication, which transmits data by reflecting and modulating existing signals in the environment, significantly reduces communication power consumption. Bluetooth backscatter, in particular, is of significant research value due to its low protocol power consumption and wide device distribution. Bluetooth backscatter communication systems are mainly divided into two categories based on the type of Bluetooth excitation source: controlled excitation source-based Bluetooth backscatter requires the excitation source to transmit a specific bit sequence, while uncontrolled excitation source-based Bluetooth backscatter allows the excitation source to transmit arbitrary bit sequences, which better reflects the realities of Bluetooth signals in the environment.

[0003] Uncontrolled backscatter communication based on ambient Bluetooth signals has significant application value because it does not require modification of existing infrastructure. Current technologies typically employ a single-sideband (SSB) demodulation architecture, where a single receiver listens to the backscatter channel and XORs the demodulated bits with the original carrier bits to recover the tag data. However, research has revealed demodulation incompleteness in the traditional SSB architecture under Bluetooth Gaussian Frequency Shift Keying (GFSK) modulation: due to the superposition of frequency shifts required for codeword conversion and frequency shifting at the physical layer, under certain bit combinations (such as when both the carrier and tag data are 1), the generated backscatter signal will produce non-standard frequency components (such as +3) that exceed the standard protocol range. This causes the standard demodulator to malfunction, creating a demodulation dead zone and severely affecting the accuracy of tag data recovery. Summary of the Invention

[0004] To address the demodulation dead zone problem in existing single-sideband Bluetooth backscatter systems, this invention provides a Bluetooth backscatter data recovery method and system based on double-sideband information compensation. It aims to utilize the double-sideband (DSB) characteristics of the backscatter signal and proposes two double-sideband demodulation architectures to achieve accurate recovery of tag data under full-bit combination, thereby improving the reliability of data transmission and better meeting the data transmission requirements of low-power wireless transmission systems.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a Bluetooth backscatter data recovery method based on double-sideband information compensation, comprising: The tag is synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. The receiver performs Gaussian frequency shift keying demodulation on the carrier signal, the left-side backscattered signal, and the right-side backscattered signal to obtain the carrier bit C and the left-side demodulated bit C. and the right side with demodulation bits When C=1, choose Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the label data.

[0006] In one embodiment, according to the first aspect, the receiving end performs Gaussian frequency shift keying demodulation on the carrier signal, the left-side backscattered signal, and the right-side backscattered signal, specifically including: Gaussian frequency shift keying demodulation employs a continuous phase differential summation algorithm. The formula for calculating the cumulative phase sum of all adjacent sampling points within one symbol period is: ; ; Where sum represents the cumulative phase within a symbol, N is the number of sampling points within a symbol, and S[n] represents the signal at the nth sampling point. Let S[n] represent the conjugate of S[n], and D represent the demodulation bit. This indicates the phase angle calculation.

[0007] In one embodiment, according to the first aspect, tag data is recovered by configuring three receiving ends; The first receiver listens to the carrier channel and obtains the carrier bit C; the second and third receivers respectively listen to the left-band backscatter signal channel and the right-band backscatter signal channel and obtain the left-band demodulation bit. and the right side with demodulation bits ; When C=1, select Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the tag data, specifically including: ; To recover the label data, This is an XOR operation.

[0008] Secondly, the present invention provides a Bluetooth backscatter data recovery method based on double-sideband information compensation, comprising: The tag is synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. The receiver performs Gaussian frequency shift keying demodulation on the left-band and right-band backscattered signals to obtain the left-band demodulated bits. and the right side with demodulation bits , directly and Perform an XOR operation to restore the tag data.

[0009] In one embodiment, according to the first or second aspect, the tag is time-synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary, specifically including: The tag uses energy rising edge detection for coarse synchronization and employs a cross-correlation algorithm based on the preamble of the excitation source signal for precise synchronization. Let the locally stored reference preamble sequence be s[k], k=0,1,…,L 1. L is the length of the preamble sequence, k represents the symbol index, and the excitation source signal received by the tag is down-converted and sampled to obtain the discrete complex baseband sequence r[k]. The tag performs a sliding correlation operation on the excitation source signal and calculates the correlation metric at the time delay index d. : ; in, The complex conjugate of s[k] is represented by the time delay index d that maximizes Λ[d], which yields an estimate of the synchronization position. : ; The modulation start point is obtained by corresponding to the end of the preamble sequence or a known reference point. The tag determines the starting boundary of the excitation source symbol based on the modulation start point.

[0010] In one embodiment, according to the first or second aspect, the step of carrying tag data onto a carrier wave to generate a backscattered signal, and performing a frequency shift operation on the backscattered signal to generate a left-band backscattered signal and a right-band backscattered signal, specifically includes: The tag switches frequencies via an RFID switch. Switching load impedance, the time-varying reflection coefficient of the tag Since it is a real-periodic signal in the time domain, the spectrum of the time-varying reflection coefficient contains positive frequency components. and negative frequency components Excitation source signal Multiplying the reflection coefficient in the time domain is equivalent to a convolution operation in the frequency domain, producing sum-frequency components. and difference frequency components The sum-frequency component forms a right-side backscattered signal, and the difference-frequency component forms a left-side backscattered signal; the switching frequency... Based on the tag data value, when the tag data is bit 1... When the tag data is bit 0, , The label represents a preset channel shift amount introduced to deflect the backscattered signal away from the original carrier channel to avoid co-channel interference. The modulation frequency offset is used for codeword conversion.

[0011] In one embodiment, according to the first aspect, the receiving end performs Gaussian frequency shift keying demodulation on the left-side backscattered signal and the right-side backscattered signal, specifically including: Gaussian frequency shift keying demodulation employs a continuous phase differential summation algorithm. The formula for calculating the cumulative phase sum of all adjacent sampling points within one symbol period is: ; ; Where sum represents the cumulative phase within a symbol, N is the number of sampling points within a symbol, and S[n] represents the signal at the nth sampling point. Let S[n] represent the conjugate of S[n], and D represent the demodulation bit. This indicates the phase angle calculation.

[0012] In one embodiment, according to the first aspect, tag data is recovered by configuring two receiving ends; The two receivers respectively monitor the left-band backscatter signal channel and the right-band backscatter signal channel to obtain the left-band demodulation bits. and the right side with demodulation bits ; The direct and Perform an XOR operation to recover the tag data, specifically including: .

[0013] Thirdly, a system for implementing the Bluetooth backscatter data recovery method based on double-sideband information compensation according to any embodiment of the first aspect includes: The synchronization module is used to synchronize the tag with the excitation source in time and determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. At the receiving end, Gaussian frequency shift keying demodulation is performed on the carrier signal, the left-side band backscattered signal, and the right-side band backscattered signal to obtain the carrier bit C and the left-side band demodulated bit C. and the right side with demodulation bits When C=1, choose Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the label data.

[0014] Fourthly, a system for implementing the Bluetooth backscatter data recovery method based on double-sideband information compensation according to any embodiment of the second aspect, comprising: The synchronization module is used to synchronize the tag with the excitation source in time and determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. At the receiving end, Gaussian frequency shift keying demodulation is performed on the backscattered signals from the left and right bands to obtain the demodulated bits from the left band. and the right side with demodulation bits , directly and Perform an XOR operation to restore the tag data.

[0015] The system and method in this invention correspond to each other; the specific technical solutions applicable to the method are also applicable to the system.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are: This invention utilizes the natural left and right sideband symmetry of backscattered signals for dynamic information compensation, fundamentally eliminating the demodulation dead zone caused by illegal frequency components in traditional single-sideband architectures. It achieves high tag data recovery accuracy under noise-free conditions with full-bit combination. At the same time, the scheme supports two flexible architectures: three-channel gating and two-channel differential. It not only exhibits excellent robustness under different signal-to-noise ratio environments, but can also be directly implemented based on standard commercial Bluetooth receivers without the need for customized dedicated chips, significantly reducing system deployment costs and hardware overhead. Attached Figure Description

[0017] Figure 1This is a diagram illustrating the architecture of the three-channel gating method of the present invention. Figure 2 This is a diagram of the dual-channel differential method architecture of the present invention; Figure 3 The time-domain observation diagram of the instantaneous frequency of the right channel in a traditional single-sideband scheme; Figure 4 The standard demodulator output probability diagram for the right channel under different carrier / tag data combinations in a traditional single-sideband scheme; Figure 5 Accuracy of tag data recovery under noise-free conditions for three schemes; Figure 6 Average tag recovery accuracy of three schemes under different signal-to-noise ratio conditions; Figure 7 This is a flowchart of the method of the present invention. Detailed Implementation

[0018] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] like Figure 7 As shown, a Bluetooth backscatter data recovery method based on double-sideband information compensation according to the present invention includes the following steps: S1, the tag synchronizes with the excitation source in time to determine the modulation start point and the excitation source symbol boundary; S2, the tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal; S3, the receiver performs Gaussian frequency shift keying demodulation on the carrier signal, the left-side band backscattered signal, and the right-side band backscattered signal to obtain the carrier bit C and the left-side band demodulated bit C. and the right side with demodulation bits When C=1, choose Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the tag data; or, directly... and Perform an XOR operation to restore the tag data.

[0020] Based on the double-sideband characteristics of backscatter communication, this invention proposes two tag data recovery methods for uncontrolled Bluetooth excitation source environments. The core of these methods lies in utilizing the left and right symmetrical double-sidebands naturally generated by the backscatter signal under Gaussian Frequency Shift Keying (GFSK) modulation, and eliminating the demodulation dead zone present in the traditional single-sideband architecture through multi-channel parallel reception and logical fusion.

[0021] The present invention will be described in detail below in several parts.

[0022] 1. Synchronize the tag and excitation source to determine the modulation start point and symbol boundary.

[0023] In backscatter communication, the tag itself does not generate a carrier wave; instead, it reflects or absorbs the excitation source signal by switching its antenna impedance. To ensure that the reflected signal can be correctly demodulated by the receiver, the tag must first achieve time synchronization with the excitation source to obtain a timing reference, thereby determining the modulation start point and the boundaries of the excitation source symbols / frames. Synchronization methods can be based on the characteristics of the excitation source and the tag's power consumption constraints, employing energy rising edge detection for coarse synchronization, or using a preamble for precise time synchronization, or a combination of both.

[0024] Coarse synchronization based on rising edge energy detection is a low-power, low-complexity blind detection scheme commonly used for tag wake-up and initial triggering. The tag continuously monitors the short-term energy of the signal received at the antenna end; when the excitation source begins to transmit, the received energy rapidly increases. A typical circuit structure includes an envelope detector, a low-pass filter, and a voltage comparator.

[0025] Precise synchronization of the preamble using the excitation source signal typically employs a cross-correlation algorithm. Let the local reference preamble sequence stored in the tag be s[k], k=0,1,…,L 1, where L is the sequence length. The excitation source signal received by the tag is down-converted and sampled to obtain a discrete complex baseband sequence r[k].

[0026] The tag performs a sliding correlation operation on the received excitation source signal and calculates the correlation metric at the time delay index d. : (1) in Let represent the complex conjugate of s[k]. The label obtains the estimated synchronization position d' by finding the delay index d that maximizes Λ[d]. (2) d' corresponds to the end of the preamble sequence or a known reference point, and the tag uses this to determine the precise starting boundary of the excitation source symbol.

[0027] 2. Tag backscatter modulation, which loads its own tag data onto the backscatter signal.

[0028] First, let's explain the principle of tag backscatter modulation. Assume the excitation source signal... As shown in formula (3), the amplitude is The frequency is (Includes two frequencies) and ), phase is When the tag is intended to introduce a frequency offset, the RF switch needs to be controlled at the desired frequency. Switching the load impedance will affect the reflection coefficient. As shown in equation (4), the backscattered signal It can be expressed by formula (5), where the frequency of the backscattered signal is... for : (3) (4) (5) It should be noted that formulas (3) to (5) above use the mathematical representation of a complex signal, which is a common method for simplifying theoretical analysis and system design. In this model, the frequency is... The complex exponential excitation signal and its frequency are Multiplying the complex exponential switching signals results in a mathematical expression with a frequency of . The single complex exponential component is shown in Equation (5).

[0029] However, in actual physical circuits, the backscattered signal radiated by the tag antenna is a real signal. A signal with a frequency of... Real signals (e.g.) ) and a frequency of Real signals (e.g., representing RF switches at frequency) Switching signal When multiplying in the time domain, according to the product-to-sum formula, two frequency components will be generated: ; These two components correspond to the carrier wave in the spectrum. The right side band on the right and the left side band on the left.

[0030] Therefore, in formula (5) of the present invention In physical implementation, this frequency component corresponds to the backscattered signal on the right band; while the symmetrical backscattered signal on the left band ( The product of multiplication of real signals is naturally generated by the physical properties of multiplying real signals.

[0031] Secondly, tag modulation requires the introduction of two frequency offsets: the frequency offset for codeword conversion. Frequency shifting technology The following will explain them in turn.

[0032] First, for a tag to perform codeword conversion, it needs to convert one codeword in the codebook into another valid codeword, ensuring that the codeword in the backscattered signal remains in the codebook. The receiver can then determine the tag data based on this change introduced by the tag in the backscattered signal. Bluetooth signals typically use GFSK modulation, utilizing two different frequencies to carry information. Corresponding to bit 0, frequency Corresponding to bit 1. Where It is the center frequency of the Bluetooth channel; This is the one-sided frequency offset, typically 250Hz. Therefore, the codebook for the Bluetooth signal is... The codeword conversion logic that the tag can use is as follows: When the tag transmits 1, a frequency offset needs to be introduced. For example This makes the original frequency of The signal is converted to a frequency of The signal, originally at a frequency of signal conversion The signal; when the tag transmits 0, no frequency offset is introduced. .

[0033] Second, the tag needs to frequency shift the backscattered signal. To avoid severe interference from the excitation source signal in the original channel, a new channel is used. The value must be an integer multiple of the channel bandwidth (e.g., 2MHz according to the Bluetooth Low Energy standard).

[0034] These two frequency offsets will be superimposed in the reflection coefficient, from which we can determine the switching frequency of the RF switch appearing in formulas (4) and (5). It is a value that changes based on the tag data. Specifically, when the tag wants to transmit bit 1, for When the tag wants to transmit 0, for .

[0035] 3. The receiver uses a continuous phase differential summation algorithm to demodulate GFSK.

[0036] The receiver uses a standard GFSK demodulator to demodulate the backscattered signal, and calculates all adjacent sampling points within one symbol period using the continuous phase differential summation algorithm for decision-making. The continuous phase differential summation algorithm is shown in formulas (6) and (7): (6) (7) Where sum represents the cumulative phase within a symbol, k is the number of sampling points within a symbol, and S[n] represents the signal (IQ value) at the nth sampling point. Let S[n] represent the conjugate of the nth digit. D represents the demodulation result (0 / 1) at the receiver. This indicates the phase angle calculation.

[0037] 4. Tag data recovery.

[0038] This invention proposes two architectures utilizing the double-sideband characteristics of backscattered signals: a three-channel gating recovery method (Scheme A) and a two-channel differential recovery method (Scheme B). Gating refers to the digital logic operation of selectively using one channel from the parallel input demodulated bit stream based on the value of the carrier bit C.

[0039] Option A, Three-Channel Gating Recovery Method: The architecture of the three-channel gating method is as follows: Figure 1 As shown in the diagram, the architecture includes a transmitter (excitation source), tags, and a processing unit consisting of three parallel receivers.

[0040] Receiver 1 listens to the original carrier channel (center frequency is ); receivers 2 and 3 respectively monitor the left and right backscattered signal channels (center frequencies are respectively). and ).

[0041] The backscattering double sidebands are symmetrical, and when one sideband produces an illegal codeword, the other sideband always produces a legal codeword.

[0042] Restore tag data The logic is shown in formula (8). The demodulation module uses the carrier bit C output by receiver 1 as the selection criterion: if C=1 (positive frequency codeword), the demodulation bit on the left side is selected. Perform XOR recovery; if C=0, strobe the demodulated bits on the right-hand side. Perform XOR recovery: (8) Here, ⊕ represents the bitwise XOR operation.

[0043] Scheme A uses dynamic gating to avoid channels in the demodulation dead zone in real time, ensuring logical integrity.

[0044] Option B, dual-channel differential recovery method: The architecture of the dual-channel differential method is as follows: Figure 2 As shown. The processing end only requires two parallel receivers to listen to the backscattered signals from the left and right bands, respectively.

[0045] The demodulation result of illegal codewords is predictable. Standard demodulators typically use the sign of the phase accumulation over a symbol period for decision-making. For example, when both the carrier and tag data are 1, an illegal codeword is generated. Although not standard However, it still falls within the positive frequency domain, the phase accumulation within the symbol is positive, and the demodulation result of the standard demodulator is 1.

[0046] Without referencing the original carrier bits, as shown in formula (9), the original demodulated bit streams of the left and right sideband channels are directly XORed, and the influence of the carrier data is offset by the dual-path differential effect, and the tag data is directly extracted.

[0047] (9) Scheme B reduces the hardware overhead and synchronization complexity of the receiver, and has extremely high engineering practical value.

[0048] Through the above technical solution, the present invention realizes a complete signal processing flow of tag synchronization with uncontrolled excitation sources in the environment, backscatter modulation of tag data, GFSK demodulation at the receiving end, and tag data recovery based on double-sideband, effectively solving the tag data recovery bottleneck caused by illegal codewords in the prior art.

[0049] Table 1 shows a comparison between the two schemes of the present invention and the existing FreeRider scheme.

[0050] Table 1

[0051] Traditional single-sideband schemes have dead zones: Figure 3 This demonstrates the time-domain distribution of the instantaneous frequency of the right channel after the tag introduces a frequency offset when using a traditional single-sideband scheme. Figure 3 It can be seen that when both the carrier and tag data are bit 1, the frequency offset of the synthesized signal reaches [value missing]. This far exceeds the standard Bluetooth demodulation range. Figure 4 This demonstrates the probability that the standard demodulator output of the right channel will be 1 under different carrier / tag data combinations when using a traditional single-sideband scheme. Figure 4 As can be seen, the standard demodulator still identifies it as bit 1, which makes it impossible to restore the correct XOR logic through the single-sideband signal, verifying that the traditional single-sideband solution has a dead zone when recovering Bluetooth tag data.

[0052] This invention proposes two tag data recovery methods utilizing the double-sideband characteristics of backscattered signals in Bluetooth backscattering systems facing uncontrolled excitation sources, aiming to improve the accuracy of tag data recovery and the reliability of data transmission. Specific advantages are as follows: (1) Eliminating demodulation dead zone: Experiments have shown that ( Figure 5The two schemes proposed in this invention can achieve 100% tag recovery accuracy under noise-free conditions, completely solving the failure problem of traditional single-sideband schemes under specific bit combinations (accuracy of 0%). Figure 5 The logical correctness of the three schemes was compared under the condition of eliminating noise interference. The horizontal axis of the figure represents different combinations of carrier data (C) and tag data to be transmitted (T), and the vertical axis represents the recovery accuracy of tag data.

[0053] (2) High robustness: Simulation results show that in an environment where the signal-to-noise ratio (SNR) is greater than 10dB, both schemes can quickly converge to 100% accuracy.

[0054] (3) Strong commercial compatibility: This invention can be implemented based on standard commercial Bluetooth receivers (such as the nRF52840 series), without the need for customized dedicated chips, which greatly reduces the system deployment cost. (4) Performance classification: In low SNR environment, the three-channel gating scheme shows better robustness than the two-channel differential scheme and can be flexibly selected according to the application scenario.

[0055] Figure 6 Simulation results under different signal-to-noise ratio (SNR) environments are presented. Observing the curves, it can be seen that the traditional single-sideband method, limited by the physical defect of the demodulation dead zone, cannot achieve an average accuracy exceeding 75% even at extremely high SNRs (because one of the four combinations inevitably fails). The proposed three-channel gating and two-channel differential schemes exhibit significant performance advantages. As the SNR increases above 10dB, both of these improved schemes based on double-sideband demodulation can quickly converge to 100% accuracy. Another finding is that in the low SNR region (e.g., -5dB to 5dB), the three-channel gating scheme demonstrates the best robustness, with an accuracy slightly higher than the two-channel differential scheme. This figure compares the performance of the three schemes under Gaussian white noise conditions with different SNRs, verifying that the two double-sideband methods proposed in this invention have certain robustness and still outperform the traditional single-sideband method in noisy environments.

[0056] Example: This embodiment aims to verify the feasibility of achieving high-precision tag data recovery in Bluetooth backscatter communication oriented towards uncontrolled excitation sources by using multiple standard commercial receivers in conjunction with double-sideband recovery logic.

[0057] 1. Experimental system setup.

[0058] The verification platform constructed in this embodiment mainly consists of the following parts: Excitation source (transmitter): A commercial Bluetooth 5.0 core board is used, configured to send uncontrolled GFSK modulated data packets (such as PRBS9 pseudo-random sequences) to simulate Bluetooth traffic in a real environment.

[0059] Tag: An FPGA prototype is used to control an RF switch to perform backscatter modulation on the Bluetooth signal. The tag then uses frequency shifting technology to move the original signal to a preset double-sideband channel.

[0060] Processing end (multi-channel receiver architecture): When using a three-channel gating architecture ( Figure 1 This requires three standard commercial Bluetooth receivers (such as Nordic nRF52840 or TI CC2640 series). Receiver 1 is tuned to the original carrier frequency. Receiver 2 and receiver 3 are respectively tuned to the center frequency of the left band. and the center frequency on the right ( (Integer multiples of channel bandwidth). When using a dual-channel differential architecture ( Figure 2 Only two standard commercial Bluetooth receivers are needed, tuned to the center frequency of the left and right bands respectively.

[0061] Data processing logic unit: After the digital baseband chip at the receiving end completes the standard GFSK demodulation, it aggregates the output bit stream to the microcontroller (MCU) or host computer for final XOR recovery logic processing.

[0062] 2. Tag data recovery process.

[0063] (1) Multi-channel data acquisition: Each commercial receiver independently executes the demodulation process of the standard Bluetooth protocol stack. Due to the characteristics of uncontrolled sources, when the carrier frequency and tag data frequency are superimposed to form an illegal codeword (such as +3), When one of the receivers listening to the backscatter channel outputs a bit stream, it will contain unexpected results from the traditional single-sideband method.

[0064] (2) Information compensation and recovery on both sides: Gating and Restoration: The logic module reads the carrier bit C output by the carrier receiver in real time. If C=1, the left-side bit stream is gated for logic restoration; if C=0, the right-side bit stream is gated. This dynamic gating avoids the demodulation dead zone present in the single-sideband architecture.

[0065] Differential recovery: Without acquiring the carrier bits, the bit streams demodulated from the left and right receivers are directly XORed. This utilizes the predictability of illegal codewords under the standard demodulator's decision logic (e.g., +3). (Identified as bit 1), the tag data is directly extracted by differentially canceling the influence of carrier data.

[0066] 3. Robustness simulation verification.

[0067] Simulation experiments based on the above commercial receiver model show that (e.g.) Figure 5 , Figure 6 (as shown) Logical completeness: Under fully random bit combinations, both double-sideband schemes proposed in this embodiment can solve the problem that the accuracy of traditional single-sideband schemes drops to 0% under specific combinations (such as carrier data being 1 and tag data being 1), achieving a theoretical recovery rate of 100%.

[0068] Robustness: In a white gas noise environment, both the three-channel gating and two-channel differential schemes exhibit excellent stability when the SNR increases to above 10dB. However, the three-channel gating scheme shows slightly better bit error rate performance in low SNR environments than the two-channel differential scheme, making it more suitable for applications with extremely high communication quality requirements.

[0069] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0070] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the flowcharts of the accompanying drawings may include multiple steps or stages, which are not necessarily completed at the same time, but may be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0071] Based on the description of the above method embodiments, the present invention also provides a system. The system may be a system that uses software (applications), modules, components, servers, clients, etc., using the methods described in the embodiments of this specification, combined with necessary implementation hardware. Since the implementation schemes and methods for solving the problem are similar, the specific system implementations in the embodiments of this specification can be found in the implementations of the foregoing methods, and repeated details will not be described again. Although the system described in the embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0074] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for recovering Bluetooth backscatter data based on double sideband information compensation, characterized in that, include: The tag is synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. The receiver performs Gaussian frequency shift keying demodulation on the carrier signal, the left-side backscattered signal, and the right-side backscattered signal to obtain the carrier bit C and the left-side demodulated bit C. and the right side with demodulation bits ; When C=1, choose Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the label data.

2. The Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 1, characterized in that, The receiver performs Gaussian frequency shift keying demodulation on the carrier signal, the left-side backscattered signal, and the right-side backscattered signal, specifically including: Gaussian frequency shift keying demodulation employs a continuous phase differential summation algorithm. The formula for calculating the cumulative phase sum of all adjacent sampling points within one symbol period is: ； ； Where sum represents the cumulative phase within a symbol, N is the number of sampling points within a symbol, and S[n] represents the signal at the nth sampling point. Let S[n] represent the conjugate of S[n], and D represent the demodulation bit. This indicates the phase angle calculation.

3. The Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 1, characterized in that, Tag data can be recovered by configuring three receivers; The first receiver listens to the carrier channel and obtains the carrier bit C; the second and third receivers respectively listen to the left-band backscatter signal channel and the right-band backscatter signal channel and obtain the left-band demodulation bit. and the right side with demodulation bits ; When C=1, select Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the tag data, specifically including: ； To recover the label data, This is an XOR operation.

4. A Bluetooth backscatter data recovery method based on double-sideband information compensation, characterized in that, include: The tag is synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. The receiver performs Gaussian frequency shift keying demodulation on the left-band and right-band backscattered signals to obtain the left-band demodulated bits. and the right side with demodulation bits , directly and Perform an XOR operation to restore the tag data.

5. A Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 1 or 4, characterized in that, The tag is time-synchronized with the excitation source to determine the modulation start point and the excitation source symbol boundary, specifically including: The tag uses energy rising edge detection for coarse synchronization and employs a cross-correlation algorithm based on the preamble of the excitation source signal for precise synchronization. Let the locally stored reference preamble sequence be s[k], k=0,1,…,L 1. L is the length of the preamble sequence, k represents the symbol index, and the excitation source signal received by the tag is down-converted and sampled to obtain the discrete complex baseband sequence r[k]. The tag performs a sliding correlation operation on the excitation source signal and calculates the correlation metric at the time delay index d. : ； in, The complex conjugate of s[k] is represented by the time delay index d that maximizes Λ[d], which is used to obtain an estimate of the synchronization position. : ； The modulation start point is obtained by corresponding to the end of the preamble sequence or a known reference point. The tag determines the starting boundary of the excitation source symbol based on the modulation start point.

6. A Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 1 or 4, characterized in that, The step of mounting tag data onto a carrier wave to generate a backscatter signal, and then performing a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal, specifically includes: The tag switches frequencies via an RFID switch. Switching load impedance, the time-varying reflection coefficient of the tag Since it is a real-periodic signal in the time domain, the spectrum of the time-varying reflection coefficient contains positive frequency components. and negative frequency components Excitation source signal Multiplying the reflection coefficient in the time domain is equivalent to a convolution operation in the frequency domain, producing sum-frequency components. and difference frequency components The sum-frequency component forms a right-side backscattered signal, and the difference-frequency component forms a left-side backscattered signal; the switching frequency... Based on the tag data value, when the tag data is bit 1... When the tag data is bit 0, , The label represents a preset channel shift amount introduced to deflect the backscattered signal away from the original carrier channel to avoid co-channel interference. The modulation frequency offset is used for codeword conversion.

7. The Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 4, characterized in that, The receiver performs Gaussian frequency shift keying demodulation on the backscattered signals from the left and right bands, specifically including: Gaussian frequency shift keying demodulation employs a continuous phase differential summation algorithm. The formula for calculating the cumulative phase sum of all adjacent sampling points within one symbol period is: ； ； Where sum represents the cumulative phase within a symbol, N is the number of sampling points within a symbol, and S[n] represents the signal at the nth sampling point. Let S[n] represent the conjugate of S[n], and D represent the demodulation bit. This indicates the phase angle calculation.

8. The Bluetooth backscatter data recovery method based on double-sideband information compensation according to claim 4, characterized in that, Tag data can be recovered by configuring two receivers; The two receivers respectively monitor the left-band backscatter signal channel and the right-band backscatter signal channel to obtain the left-band demodulation bits. and the right side with demodulation bits ; The direct and Perform an XOR operation to recover the tag data, specifically including: 。 9. A system for implementing the Bluetooth backscatter data recovery method based on double-sideband information compensation as described in claim 1, 2, or 3, characterized in that, include: The synchronization module is used to synchronize the tag with the excitation source in time and determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. At the receiving end, Gaussian frequency shift keying demodulation is performed on the carrier signal, the left-side band backscattered signal, and the right-side band backscattered signal to obtain the carrier bit C and the left-side band demodulated bit C. and the right side with demodulation bits ; When C=1, choose Perform an XOR operation with C to recover the tag data. When C=0, select... Perform an XOR operation with C to recover the label data.

10. A system for implementing the Bluetooth backscatter data recovery method based on double-sideband information compensation as described in claim 4, 7, or 8, characterized in that, include: The synchronization module is used to synchronize the tag with the excitation source in time and determine the modulation start point and the excitation source symbol boundary; The tag uses the excitation source signal as a carrier, loads the tag data onto the carrier to generate a backscatter signal, and performs a frequency shift operation on the backscatter signal to generate a left-band backscatter signal and a right-band backscatter signal. At the receiving end, Gaussian frequency shift keying demodulation is performed on the backscattered signals from the left and right bands to obtain the demodulated bits from the left band. and the right side with demodulation bits , directly and Perform an XOR operation to restore the tag data.

Images