ZigBee backscattering method and system based on environment Bluetooth excitation

Abstract

The invention relates to the technical field of backscatter communication, and discloses a ZigBee backscatter method and system based on environment Bluetooth excitation. The method comprises the following steps: an excitation source sends a Bluetooth extension broadcast packet as an excitation signal, and sends an amplitude modulation signal carrying a channel number of the Bluetooth extension broadcast packet before sending the excitation signal; the label demodulates the amplitude modulation signal through an envelope detector, obtains a channel number of the Bluetooth extended broadcast packet, calculates a frequency shift amount according to a dynamic difference value between a monitoring channel number of a ZigBee receiving end and the channel number of the Bluetooth extended broadcast packet, and adjusts the center frequency of the generated backscattering signal through the frequency shift amount; and the ZigBee receiving end receives and demodulates the backscattering signal in the fixed monitoring channel to obtain label data. According to the invention, the data transmission quantity of single backscattering is improved by using the Bluetooth excitation signal with longer duration time, so that the effective throughput is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of backscatter communication, and in particular to a ZigBee backscatter method and system based on environmental Bluetooth excitation. Background Art

[0002] In recent years, with the development of the Internet of Things (IoT), ZigBee wireless sensor nodes have been widely used in production and daily life. However, sensor nodes using active ZigBee communication consume high power. This high power consumption has become a major factor limiting the further development of wireless sensor networks.

[0003] To reduce the communication power consumption of wireless sensor networks, implementing ZigBee backscatter communication has become a highly valuable research direction. Backscatter communication is a low-power communication technology. A backscatter system consists of three components: an excitation source, a backscatter tag, and a receiver. Backscatter tags can modify the excitation signal sent by the excitation source to carry tag data, thereby enabling communication to the receiver. Because the tags do not actively generate RF signals, their power consumption is much lower than that of active devices. Therefore, if ZigBee backscatter communication can be implemented, ZigBee backscatter tags can replace ZigBee active devices, significantly reducing the communication power consumption of wireless sensor networks.

[0004] To facilitate the deployment of backscatter systems, current research focuses on using commercial protocol devices as excitation sources. Given the widespread deployment of Bluetooth devices, Bluetooth-stimulated backscatter communication has become a popular research area. Previously, a system implemented ZigBee backscatter communication based on Bluetooth excitation. In this system, backscatter tags use ambient Bluetooth signals as excitation signals, carry tag data through phase modulation, and backscatter to generate a ZigBee-compatible signal. Commercial ZigBee devices, acting as receivers, can demodulate the backscatter signals and recover the tag data. This system fully utilizes the ubiquitous ambient Bluetooth signals as excitation to implement ZigBee backscatter communication, significantly reducing the deployment cost of ZigBee backscatter systems.

[0005] However, this system still suffers from low effective throughput. In this system, the Bluetooth excitation source device generates the Bluetooth excitation signal by sending a Bluetooth advertising packet. Because the amount of data carried by a Bluetooth advertising packet is strictly limited, the corresponding Bluetooth signal duration is short. This signal, used as the excitation signal to carry tag data, carries a small amount of tag data per backscatter transmission. Consequently, the effective throughput of backscatter communication in this system is extremely low. Summary of the Invention

[0006] To address the aforementioned technical issues, the present invention provides a ZigBee backscatter method and system based on ambient Bluetooth excitation. This method improves effective throughput by increasing the data transmission rate per single backscatter shot. The Bluetooth excitation source in the backscatter system of the present invention transmits Bluetooth extended broadcast packets to provide tags with a longer-lasting Bluetooth excitation signal. The tags then carry data on this excitation signal, increasing the data transmission rate per single backscatter shot by 20 times compared to existing systems.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a ZigBee backscattering method based on environmental Bluetooth excitation, comprising: The excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet; The tag demodulates the AM signal through an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; The ZigBee receiving end receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

[0008] In one embodiment, the amplitude modulated signal encodes the channel number of the Bluetooth extended advertising packet through random OFDM symbols and constant OFDM symbols: one random OFDM symbol and one constant OFDM symbol represent bit 1, and two random OFDM symbols represent bit 0.

[0009] In one embodiment, the tag demodulates the amplitude modulated signal using an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, specifically including: The data packet of the amplitude modulated signal includes a preamble field and a payload field; the preamble field is fixed to eight bits 1, and the corresponding signal is eight groups of alternating random OFDM symbols and constant OFDM symbols; the last 40 sampling points of each OFDM symbol corresponding to the preamble field are extracted, and the average amplitude value of the sampling points is used as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended broadcast packet.

[0010] In one embodiment, using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended advertising packet specifically includes: Calculate the average amplitude of the 40 sampling points after each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, determine that the current OFDM symbol is a random OFDM symbol; if the average amplitude is less than or equal to the threshold, determine that the current OFDM symbol is a constant OFDM symbol.

[0011] In one embodiment, the frequency shift amount is calculated based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , specifically including: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ; It is the monitoring channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel for Bluetooth extended advertising packets for: ; in, is the channel number of the Bluetooth extended advertising packet; Frequency shift for: .

[0012] In a second aspect, the present invention provides a ZigBee backscattering system based on environmental Bluetooth excitation, comprising: Excitation module: the excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet; Backscatter module: The tag demodulates the AM signal through the envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; Receiving module: The ZigBee receiving end receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

[0013] In one embodiment, the amplitude modulated signal encodes the channel number of the Bluetooth extended advertising packet through random OFDM symbols and constant OFDM symbols: one random OFDM symbol and one constant OFDM symbol represent bit 1, and two random OFDM symbols represent bit 0.

[0014] In one embodiment, the tag demodulates the amplitude modulated signal using an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, specifically including: The data packet of the amplitude modulated signal includes a preamble field and a payload field; the preamble field is fixed to eight bits 1, and the corresponding signal is eight groups of alternating random OFDM symbols and constant OFDM symbols; the last 40 sampling points of each OFDM symbol corresponding to the preamble field are extracted, and the average amplitude value of the sampling points is used as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended broadcast packet.

[0015] In one embodiment, using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended advertising packet specifically includes: Calculate the average amplitude of the 40 sampling points after each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, determine that the current OFDM symbol is a random OFDM symbol; if the average amplitude is less than or equal to the threshold, determine that the current OFDM symbol is a constant OFDM symbol.

[0016] In one embodiment, the frequency shift amount is calculated based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , specifically including: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ; It is the monitoring channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel for Bluetooth extended advertising packets for: ; in, is the channel number of the Bluetooth extended advertising packet; Frequency shift amount for: .

[0017] The system in the present invention corresponds to the method, and the specific technical solutions applicable to the method are also applicable to the system.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are: In response to the drawback of low effective throughput of existing ZigBee backscatter systems based on Bluetooth excitation, the present invention proposes to implement ZigBee backscatter communication based on Bluetooth extended broadcast packets. By using a Bluetooth excitation signal with a longer duration, the data transmission volume of a single backscatter is increased, thereby improving the effective throughput. To address the challenge of the non-fixed transmission channel of the Bluetooth extended broadcast packet, the tag in the present invention can dynamically adjust the frequency shift amount according to the Bluetooth extended broadcast packet channel number, thereby ensuring that the transmission channel of the backscatter data packet is constant. The excitation source in the present invention uses a WiFi module to send an amplitude modulated signal to transmit the channel number to the tag, and the tag uses the dynamic threshold demodulation method proposed in the present invention to demodulate the amplitude modulated signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Flowchart of a method in an embodiment of the present invention.

[0020] Figure 2 The following is a comparison diagram of the packet structure of Zigbee data packets carried on Bluetooth advertising packets and Bluetooth extended advertising packets.

[0021] Figure 3 A diagram showing how to extend Bluetooth broadcast events.

[0022] Figure 4 Schematic diagram of a tag dynamic frequency shifting method in an embodiment of the present invention.

[0023] Figure 5 Schematic diagram of an amplitude modulation signal generated by a WiFi module in an embodiment of the present invention.

[0024] Figure 6 Schematic diagram of the demodulation of AM signals using the fixed threshold demodulation method at signal-to-noise ratios of 10dB and 4dB.

[0025] Figure 7 FIG. 1 is a schematic diagram of demodulating an AM signal by dynamically setting a threshold value according to an embodiment of the present invention.

[0026] Figure 8 4 is a comparison chart of channel number error rates in an embodiment of the present invention.

[0027] Figure 9 1 is a comparison chart of different backscattering technologies in embodiments of the present invention and the effective throughput of the present invention. DETAILED DESCRIPTION

[0028] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] A ZigBee backscattering method based on environmental Bluetooth excitation in the present invention includes the following steps: S1, an excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulated signal carrying the channel number of the Bluetooth extended broadcast packet; S2, the tag demodulates the AM signal through the envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; S3, the ZigBee receiving end receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

[0030] The following first introduces the advantages of implementing backscatter communication based on Bluetooth extended advertising packets and the challenges faced in implementing this method. Thereafter, the overall architecture and specific implementation of the present invention will be introduced.

[0031] 1. Advantages and challenges of implementing backscatter based on Bluetooth extended broadcast packets.

[0032] This paper compares the packet structures of Bluetooth advertising packets and Bluetooth extended advertising packets and demonstrates that implementing ZigBee backscatter communication based on Bluetooth extended advertising packets can increase effective throughput by approximately 20 times compared to the original backscatter method. This paper then describes the process of Bluetooth devices transmitting Bluetooth extended advertising packets using frequency hopping and analyzes the challenges of implementing backscatter communication based on extended advertising packets.

[0033] (1) Advantages of backscatter communication based on Bluetooth extended broadcast packets: The Bluetooth 5.0 standard introduces Bluetooth Extended Advertisement Packets. Compared to standard Bluetooth Advertisement Packets, these packets carry more valid data and have a longer signal duration. Using the Bluetooth signal corresponding to the Bluetooth Extended Advertisement Packet as the excitation signal, each backscattered packet can transmit more tag data. Figure 2This paper presents a comparison of the packet structures of ZigBee packets carried over Bluetooth advertising packets and Bluetooth extended advertising packets. The payload of a Bluetooth advertising packet can only carry 37 bytes of data. When a ZigBee packet is carried over the signal corresponding to a Bluetooth advertising packet, a single backscattering operation can only transmit 3 bytes of valid data. However, the payload of a Bluetooth extended advertising packet can carry 255 bytes of data. When a ZigBee packet is carried over the signal corresponding to a Bluetooth extended advertising packet, a single backscattering operation can transmit 58 bytes of valid data. In summary, compared to the original method of implementing ZigBee backscatter using Bluetooth advertising packets, implementing backscatter communication based on Bluetooth extended advertising packets can increase the effective data transmission capacity per backscattering operation, thereby increasing the effective throughput by approximately 20 times.

[0034] (2) Challenges in implementing backscatter communication based on Bluetooth extended broadcast packets: Bluetooth devices use frequency hopping technology to transmit Bluetooth extended broadcast packets, and the transmission channel of Bluetooth extended broadcast packets is not fixed. Figure 3 This section shows the process by which a Bluetooth device sends a Bluetooth Extended Advertising packet during a Bluetooth Extended Advertising event. The Bluetooth device sends an advertising packet on the advertising channel (channel 37) and then sends the Bluetooth Extended Advertising packet on a randomly selected channel from among the 37 data channels (channels 0 to 36). The channel number of the Bluetooth Extended Advertising packet is recorded in the advertising packet.

[0035] The non-fixed transmission channel of Bluetooth extended advertising packets presents a challenge for implementing backscattering in the present invention. This is because the channel of the backscattered data packet is related to the channel of the original excitation signal. Using the signal corresponding to the non-fixed channel of the Bluetooth extended advertising packet as the excitation signal will result in an unstable transmission channel for the backscattered data packet, which in turn prevents the receiving device from stably receiving it.

[0036] 2. Tag dynamic frequency shift strategy.

[0037] The center frequency of the Bluetooth excitation signal can be calculated from the transmission channel of the Bluetooth extended advertising packet. The center frequency of the ZigBee receiver's monitoring channel can also be calculated from the ZigBee channel number. Knowing the channel number allows the tag to set the correct frequency shift.

[0038] In order to realize backscatter communication based on Bluetooth extended broadcast packet, the present invention designs a tag dynamic frequency shift strategy, see Figure 4. In order to solve the problem that the transmission channel of the Bluetooth extended broadcast packet is not fixed, the tag in the present invention can dynamically adjust the frequency shift amount according to the channel number of the Bluetooth extended broadcast packet, thereby ensuring that the transmission channel of the backscattered data packet is constant. The present invention adds a WiFi module to the excitation source device to generate an amplitude modulated signal. The excitation source first sends an amplitude modulated signal before sending the Bluetooth extended broadcast packet, and carries the channel number of the next Bluetooth extended broadcast packet in it. The tag uses an envelope detector to demodulate the amplitude modulated signal, obtain the channel number, and set the frequency shift amount according to the channel number in the subsequent backscattering process.

[0039] Specifically, the frequency shift It should be the difference between the center frequency of the ZigBee monitoring channel and the center frequency of the Bluetooth extended advertising packet transmission channel, that is: ;(1) The channel center frequency of the ZigBee protocol can be calculated from the channel number. The calculation formula for the channel center frequency of the ZigBee protocol in the 2.4 GHz frequency band is shown in formula (2). It is the monitoring channel number of the ZigBee receiver.

[0040] ; (2) Similarly, the channel center frequency of the Bluetooth protocol can also be calculated from the channel number. Since the Bluetooth extended broadcast packet is transmitted on the Bluetooth data channel, only the calculation method of the center frequency of the Bluetooth data channel is discussed, as shown in formula (3). It is the channel number of the Bluetooth extended advertising packet.

[0041] ; (3) In summary, the tag can calculate the frequency shift amount based on the number of the ZigBee receiver's monitoring channel and the number of the Bluetooth extended broadcast packet transmission channel. , the calculation formula is shown in formula (4).

[0042] (4) The ZigBee receiver's listening channel is set by the system and is known to the tag. The transmission channel of the Bluetooth extended advertising packet is transmitted to the tag via an amplitude-modulated signal. Therefore, the tag can determine the ZigBee receiver's listening channel number and the Bluetooth extended advertising packet's channel number and set the correct frequency shift accordingly.

[0043] The present invention achieves backscatter communication by dynamically adjusting the frequency shift amount and using Bluetooth extended broadcast packets transmitted via frequency hopping. Because Bluetooth extended broadcast packets correspond to longer signal durations, this method increases the data transmission rate per single backscatter and significantly improves the effective throughput of the system.

[0044] 3. The tag dynamically sets the threshold to demodulate the AM signal.

[0045] The tag is equipped with an envelope detector that can be used to demodulate the amplitude modulated signal transmitted by the WiFi module. This invention proposes a method for demodulating the AM signal by dynamically setting a threshold. This demodulation method enables the tag to recover the channel number carried by the AM signal with a low error rate under various signal-to-noise ratios.

[0046] The WiFi module can generate an amplitude modulated signal by sending constant OFDM symbols and random OFDM symbols. Constant OFDM symbols indicate that the data carried in the current OFDM symbol is constant (for example, all 0s), and random OFDM symbols indicate that the data carried in the current OFDM symbol is random. Figure 5 As shown, the amplitude of the signal corresponding to the random OFDM symbol is relatively balanced, while the signal corresponding to the constant OFDM symbol has a high-amplitude sampling point at the beginning, with smaller amplitudes at the remaining sampling points. Because the amplitudes of the time domain signals corresponding to the two OFDM symbols differ significantly, an amplitude-modulated signal can be generated by transmitting these two OFDM symbols. The amplitude-modulated signal transmitted by the present invention uses one random OFDM symbol and one constant OFDM symbol to represent a bit 1, and two random OFDM symbols to represent a bit 0.

[0047] The traditional method demodulates the AM signal by setting a fixed threshold. By comparing the amplitude of the sampling point with the threshold, the data carried in the AM signal is restored. However, since the overall amplitude of the signal will change when the signal-to-noise ratio changes, the fixed threshold demodulation method is extremely susceptible to noise interference. Figure 6 As shown in (a) and (b) in Figure 1, when the signal-to-noise ratio (SNR) is 10dB, setting the threshold to 1 can effectively distinguish between random OFDM symbols and constant OFDM symbols (because the amplitudes of many sampling points in random OFDM symbols are greater than 1, while the amplitudes of very few sampling points in constant OFDM symbols are greater than 1). However, when the SNR drops to 4dB, the overall signal amplitude increases, and a large number of sampling points in constant OFDM symbols also have amplitudes greater than 1, causing the originally set threshold to become ineffective.

[0048] In order to enable the tag to demodulate the AM signal with a low error rate under various signal-to-noise ratios, the present invention proposes a demodulation method with a dynamically set threshold. Figure 7As shown. The data packet carried by the AM signal contains a preamble field. The data carried by this field is fixed to eight bits of 1. Random OFDM symbols and constant OFDM symbols appear alternately in the corresponding signal. The tag will sample the signal corresponding to this field, taking the last 40 sampling points of each symbol in the field and calculating the average amplitude of all the sampling points. Thereafter, the tag will use this average value as the threshold to demodulate the subsequent AM signal. When demodulating the AM signal, the last 40 sampling points of each symbol are taken to calculate the average amplitude. If the average amplitude is greater than the threshold, the symbol is determined to be a random OFDM symbol; otherwise, it is determined to be a constant OFDM symbol.

[0049] Simulation experiments were conducted in MATLAB to verify the feasibility and superiority of the method proposed in this invention. The experimental results show that the error rates of demodulating the AM signal and restoring the channel number under different signal-to-noise ratios are compared between the traditional fixed threshold demodulation method and the dynamic threshold demodulation method proposed in this invention. Figure 8 As shown. Experimental results show that the dynamic threshold demodulation method proposed in the present invention is more resistant to noise interference than the traditional fixed threshold demodulation method, and the error rate of channel number restoration is 1 to 2 orders of magnitude lower on average. When the signal-to-noise ratio is greater than 6 dB, the error rate of channel number restoration by the dynamic threshold demodulation method will be less than 1%. In addition, the present invention measures the effective throughput of the backscatter communication of the present invention through simulation experiments. The experimental results are shown in Figure 2. Figure 9 Experimental results show that, compared to existing backscatter technologies (Interscatter and BumbleBee), the backscatter communication implemented by the present invention using Bluetooth extended advertising packets can increase the effective throughput by approximately 20 times. The effective throughput of backscatter communication in the present invention can reach up to 23.2 kbps.

[0050] The dynamic threshold demodulation method proposed in this invention calculates a threshold based on the sampling results of the signal corresponding to the preamble field. Once the appropriate threshold is calculated, subsequent signals are demodulated. As the signal-to-noise ratio and the overall signal amplitude change, the threshold set by the tag is also adjusted. Compared to fixed-threshold demodulation methods, the dynamic threshold demodulation method proposed in this invention can set the appropriate threshold for each signal-to-noise ratio, providing better resistance to noise interference.

[0051] The technical solution of the present invention is described in more detail below with reference to an embodiment.

[0052] The present invention performs simulation experiments in MATLAB R2024b to verify the feasibility and superiority of the present invention.

[0053] The AM signal demodulation experiment uses the wlanWaveformGenerator function in the WLAN toolbox to generate the WiFi protocol signal, the awgn function in the Communications toolbox to add noise to the signal, and the envelope function in the Signal Processing toolbox to perform envelope detection.

[0054] The backscatter experiment uses the bleWaveformGenerator function in the Bluetooth toolbox to send Bluetooth extended advertising packets and generate Bluetooth protocol signals. The awgn function in the Communications toolbox is used to add noise to the signal. The PHYDecoderOQPSKNoSync function in the Communications toolbox is used to simulate a ZigBee receiver and demodulate the backscattered signal.

[0055] The backscatter communication process works as follows. The source device first sets the transmission channel for the Bluetooth Extended Advertisement Packet and then sends a Wi-Fi AM signal containing the channel number. The source device then transmits the Bluetooth Extended Advertisement Packet on the specified channel. The tag uses an envelope detector to demodulate the Wi-Fi AM signal and obtain the channel number for the next Bluetooth Extended Advertisement Packet. The tag then calculates the frequency shift based on this channel number to ensure that the backscattered signal is transmitted on the channel monitored by the receiving device. The tag then applies a phase shift to the excitation signal to carry the tag data. The Zigbee receiver samples the signal and demodulates it based on the sign of the phase shift between adjacent sampling points to recover the tag data.

[0056] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown in sequence as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps 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 multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times. The order of execution of these steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a portion of the steps or stages in other steps.

[0057] Based on the description of the above method embodiments, the present invention also provides a system. The system can be a system that uses the software (application), module, component, server, client, etc. of the method described in the embodiments of this specification and is combined with the necessary implementation hardware. Based on the same innovative concept, the system in one or more embodiments provided by the embodiments of the present disclosure is as described in the following embodiments. Since the implementation scheme and method for solving the problem of the system are similar, the implementation of the specific system of the embodiments of this specification can refer to the implementation of the aforementioned method, and the repeated parts will not be repeated. As used below, the term "module" or "module" refers to a combination of software and / or hardware that can realize the predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0058] A ZigBee backscattering system based on environmental Bluetooth excitation, comprising: An excitation module, wherein the excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet; Backscatter module, the tag demodulates the amplitude modulated signal through the envelope detector, obtains the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; The receiving module, the ZigBee receiving end receives and demodulates the backscattered signal in a fixed monitoring channel to obtain tag data.

[0059] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0060] 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 embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be embraced herein, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0061] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A ZigBee backscattering method based on environmental Bluetooth excitation, characterized in that: include: The excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet; The tag demodulates the AM signal through an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; The ZigBee receiving end receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

2. A ZigBee backscattering method based on environmental Bluetooth excitation according to claim 1, characterized in that: The AM signal encodes the channel number of the Bluetooth extended advertising packet through random OFDM symbols and constant OFDM symbols: one random OFDM symbol and one constant OFDM symbol represent bit 1, and two random OFDM symbols represent bit 0.

3. The ZigBee backscattering method based on environmental Bluetooth excitation according to claim 1, characterized in that: The tag demodulates the amplitude modulated signal through an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, specifically including: The data packet of the amplitude modulated signal includes a preamble field and a payload field; the preamble field is fixed to eight bits 1, and the corresponding signal is eight groups of alternating random OFDM symbols and constant OFDM symbols; the last 40 sampling points of each OFDM symbol corresponding to the preamble field are extracted, and the average amplitude value of the sampling points is used as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended broadcast packet.

4. The ZigBee backscattering method based on ambient Bluetooth excitation according to claim 3, characterized in that: The method of using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended advertising packet specifically includes: Calculate the average amplitude of the 40 sampling points after each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, determine that the current OFDM symbol is a random OFDM symbol; if the average amplitude is less than or equal to the threshold, determine that the current OFDM symbol is a constant OFDM symbol.

5. The ZigBee backscattering method based on environmental Bluetooth excitation according to claim 1, characterized in that: The frequency shift amount is calculated based on the dynamic difference between the monitoring channel number of the ZigBee receiving end and the channel number of the Bluetooth extended broadcast packet , specifically including: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ； It is the monitoring channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel for Bluetooth extended advertising packets for: ； in, is the channel number of the Bluetooth extended advertising packet; Frequency shift for: 。 6. A ZigBee backscatter system based on ambient Bluetooth excitation, characterized in that: include: Excitation module: the excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and before sending the excitation signal, sends an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet; Backscatter module: The tag demodulates the AM signal through the envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, and calculates the frequency shift amount based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the Bluetooth extended broadcast packet. , after receiving the Bluetooth extended broadcast packet, adjusting the center frequency of the generated backscatter signal by the frequency shift amount to keep the transmission channel constant; Receiving module: The ZigBee receiving end receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

7. The ZigBee backscatter system based on ambient Bluetooth excitation according to claim 6, characterized in that: The AM signal encodes the channel number of the Bluetooth extended advertising packet through random OFDM symbols and constant OFDM symbols: one random OFDM symbol and one constant OFDM symbol represent bit 1, and two random OFDM symbols represent bit 0.

8. The ZigBee backscatter system based on ambient Bluetooth excitation according to claim 6, characterized in that: The tag demodulates the amplitude modulated signal through an envelope detector to obtain the channel number of the Bluetooth extended broadcast packet, specifically including: The data packet of the amplitude modulated signal includes a preamble field and a payload field; the preamble field is fixed to eight bits 1, and the corresponding signal is eight groups of alternating random OFDM symbols and constant OFDM symbols; the last 40 sampling points of each OFDM symbol corresponding to the preamble field are extracted, and the average amplitude value of the sampling points is used as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended broadcast packet.

9. The ZigBee backscatter system based on ambient Bluetooth excitation according to claim 8, characterized in that: The method of using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field to obtain the channel number of the Bluetooth extended advertising packet specifically includes: Calculate the average amplitude of the 40 sampling points after each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, determine that the current OFDM symbol is a random OFDM symbol; if the average amplitude is less than or equal to the threshold, determine that the current OFDM symbol is a constant OFDM symbol.

10. The ZigBee backscatter system based on ambient Bluetooth excitation according to claim 6, characterized in that: The frequency shift amount is calculated based on the dynamic difference between the monitoring channel number of the ZigBee receiving end and the channel number of the Bluetooth extended broadcast packet , specifically including: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ； It is the monitoring channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel for Bluetooth extended advertising packets for: ； in, is the channel number of the Bluetooth extended advertising packet; Frequency shift for: 。

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