ZigBee backscatter method and system based on environmental bluetooth excitation

Abstract

The application relates to the technical field of backscatter communication and discloses a ZigBee backscatter method and system based on environmental Bluetooth excitation. The method comprises the following steps: an excitation source sends a Bluetooth extended broadcast packet as an excitation signal, and an amplitude modulation signal carrying the channel number of the Bluetooth extended broadcast packet is sent before the excitation signal is sent; a tag demodulates the amplitude modulation signal through an envelope detector, acquires the channel number of the Bluetooth extended broadcast packet, calculates a frequency shift amount according to a dynamic difference value between the listening channel number of a ZigBee receiving end and the channel number of the Bluetooth extended broadcast packet, adjusts the center frequency of a generated backscatter signal through the frequency shift amount; and the ZigBee receiving end receives and demodulates the backscatter signal on a fixed listening channel to obtain tag data. The application uses a Bluetooth excitation signal with a longer duration, improves the data transmission amount of single backscatter, and thus improves the effective throughput.

Description

Technical Field

[0001] This invention relates to the field of backscatter communication technology, and specifically to a ZigBee backscattering method and system based on ambient Bluetooth excitation. Background Technology

[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 have high power consumption. 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 parts: an excitation source, a backscatter tag, and a receiver. The backscatter tag can transmit tag data to the receiver by modifying the excitation signal sent by the excitation source. Because the tag does not actively generate radio frequency signals, its power consumption is much lower than that of active devices. Therefore, if ZigBee backscatter communication can be implemented, ZigBee active devices can be replaced with ZigBee backscatter tags, thereby greatly reducing the communication power consumption of wireless sensor networks.

[0004] To facilitate the deployment of backscattering systems, current research focuses on using commercially available protocol devices as excitation sources. Given the widespread deployment of Bluetooth devices, Bluetooth-excited backscattering communication has become a popular research area. Previously, systems have implemented Bluetooth-excited ZigBee backscattering communication. In this system, the backscattering tag uses ambient Bluetooth signals as excitation signals, carries tag data through phase modulation, and generates a ZigBee-compatible signal through backscattering. A commercial ZigBee device, acting as the receiver, can demodulate the backscattered signal and reconstruct the tag data. This system fully utilizes ubiquitous ambient Bluetooth signals as excitation for ZigBee backscattering communication, significantly reducing the deployment cost of ZigBee backscattering systems.

[0005] However, this system still suffers from low effective throughput. In this system, the Bluetooth excitation source device generates a Bluetooth excitation signal by sending Bluetooth broadcast packets. Because the amount of data carried by a Bluetooth broadcast packet is strictly limited, the corresponding Bluetooth signal duration is short. Using this signal as the excitation signal to carry tag data results in a small amount of tag data being transmitted with each backscatter. Therefore, the effective throughput of this system for backscatter communication is extremely low. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a ZigBee backscattering method and system based on ambient Bluetooth excitation. This invention improves effective throughput by increasing the data transmission volume per backscatter. In the backscattering system of this invention, the Bluetooth excitation source provides the tag with a longer-lasting Bluetooth excitation signal by sending Bluetooth Extended Broadcast packets. The tag carries data on this excitation signal, increasing the data transmission volume per backscatter by 20 times compared to existing systems.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a ZigBee backscattering method based on ambient Bluetooth excitation, comprising:

[0009] 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;

[0010] The tag demodulates the amplitude-modulated signal using an envelope detector to obtain the channel number of the Bluetooth Extended Broadcast packet. The frequency shift 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. After receiving a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel.

[0011] The ZigBee receiver receives and demodulates the backscattered signal on a fixed listening channel to obtain tag data.

[0012] In one embodiment, the amplitude modulation signal encodes the channel number of the Bluetooth Extended Broadcast Packet using 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.

[0013] 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:

[0014] The amplitude-modulated signal data packet includes a preamble field and a payload field; the preamble field is fixed at eight bits 1, corresponding to 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 Broadcast packet specifically includes:

[0016] Calculate the average amplitude of the last 40 sampling points of each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, the current OFDM symbol is determined to be a random OFDM symbol; if the average amplitude is less than or equal to the threshold, the current OFDM symbol is determined to be a constant OFDM symbol.

[0017] 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, it includes:

[0018] The channel center frequency of the ZigBee protocol in the 2.4 GHz band for:

[0019] ;

[0020] It is the listening channel number of the ZigBee receiver;

[0021] The center frequency of the Bluetooth data channel in the Bluetooth Extended Broadcast Package. for:

[0022] ;

[0023] in, It is the channel number of the Bluetooth Extended Broadcast packet;

[0024] Frequency shift for:

[0025] .

[0026] Secondly, the present invention provides a ZigBee backscattering system based on ambient Bluetooth excitation, comprising:

[0027] Excitation module: The excitation source sends a Bluetooth Extended Broadcast Packet as an excitation signal, and before sending the excitation signal, it sends an amplitude modulation signal carrying the channel number of the Bluetooth Extended Broadcast Packet;

[0028] Backscatter module: The tag demodulates the amplitude-modulated signal using an envelope detector to obtain the channel number of the Bluetooth Extended Broadcast packet, and calculates the frequency shift 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 a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel.

[0029] Receiver module: The ZigBee receiver receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

[0030] In one embodiment, the amplitude modulation signal encodes the channel number of the Bluetooth Extended Broadcast Packet using 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.

[0031] 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:

[0032] The amplitude-modulated signal data packet includes a preamble field and a payload field; the preamble field is fixed at eight bits 1, corresponding to 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.

[0033] 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 Broadcast packet specifically includes:

[0034] Calculate the average amplitude of the last 40 sampling points of each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, the current OFDM symbol is determined to be a random OFDM symbol; if the average amplitude is less than or equal to the threshold, the current OFDM symbol is determined to be a constant OFDM symbol.

[0035] 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, it includes:

[0036] The channel center frequency of the ZigBee protocol in the 2.4 GHz band for:

[0037] ;

[0038] It is the listening channel number of the ZigBee receiver;

[0039] The center frequency of the Bluetooth data channel in the Bluetooth Extended Broadcast Package. for:

[0040] ;

[0041] in, It is the channel number of the Bluetooth Extended Broadcast packet;

[0042] Frequency shift for:

[0043] .

[0044] 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.

[0045] Compared with the prior art, the beneficial technical effects of the present invention are:

[0046] To address the low effective throughput of existing Bluetooth-excited Zigbee backscattering systems, this invention proposes a method for Zigbee backscattering communication based on Bluetooth Extended Broadcast (EBB) packets. By using a longer-duration Bluetooth excitation signal, the data transmission volume per backscatter is increased, thereby improving the effective throughput. To overcome the challenge of the variable transmission channel of the EBB packets, the tag in this invention dynamically adjusts the frequency shift based on the EBB packet channel number, ensuring a constant backscattered data packet transmission channel. The excitation source in this invention uses a WiFi module to send an amplitude-modulated signal to transmit the channel number to the tag, which then uses the proposed dynamic threshold demodulation method to demodulate the amplitude-modulated signal. Attached Figure Description

[0047] Figure 1 This is a flowchart of the method in an embodiment of the present invention.

[0048] Figure 2 A comparison diagram of the packet structure for carrying Zigbee data packets on Bluetooth Broadcast Packets and Bluetooth Extended Broadcast Packets.

[0049] Figure 3 This is a diagram illustrating Bluetooth Extended Broadcast events.

[0050] Figure 4 This is a schematic diagram of the tag dynamic frequency shifting method in an embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the amplitude modulation signal generated by the WiFi module in an embodiment of the present invention.

[0052] Figure 6 This diagram illustrates the demodulation of amplitude-modulated signals using a fixed threshold demodulation method at signal-to-noise ratios of 10dB and 4dB.

[0053] Figure 7 This is a schematic diagram of dynamically setting a threshold to demodulate the amplitude modulation signal in an embodiment of the present invention.

[0054] Figure 8 This is a comparison chart of channel numbering error rates in an embodiment of the present invention.

[0055] Figure 9 This is a comparison chart of different backscattering techniques in the embodiments of the present invention and the effective throughput of the present invention. Detailed Implementation

[0056] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0057] The ZigBee backscattering method based on ambient Bluetooth excitation in this invention includes the following steps:

[0058] S1, 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;

[0059] S2, the tag demodulates the amplitude-modulated signal using 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 a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel.

[0060] S3, the ZigBee receiver receives and demodulates the backscatter signal on a fixed listening channel to obtain tag data.

[0061] The following section first introduces the advantages of backscatter communication based on Bluetooth Extended Broadcast Packets, as well as the challenges in implementing this method. Following this, the overall architecture and specific implementation of this invention will be described.

[0062] 1. Advantages and challenges of implementing backscatter based on Bluetooth Extended Broadcast Packet.

[0063] The following section compares the packet structures of Bluetooth Broadcast packets and Bluetooth Extended Broadcast packets, demonstrating that compared to the original backscattering method, implementing ZigBee backscatter communication based on Bluetooth Extended Broadcast packets can improve the effective throughput by approximately 20 times. Subsequently, this invention will describe the process of Bluetooth devices transmitting Bluetooth Extended Broadcast packets via frequency hopping and analyze the challenges faced in implementing backscatter communication based on Extended Broadcast packets.

[0064] (1) Advantages of implementing backscatter communication based on Bluetooth extended broadcast packets:

[0065] The Bluetooth 5.0 standard introduced the Bluetooth Extended Broadcast Packet (EBPS). Compared to a regular Bluetooth Broadcast Packet, the EBPS can carry more valid data, and its signal duration is also relatively longer. Using the Bluetooth signal corresponding to the EBPS as the excitation signal, each backscatter can transmit more tag data. Figure 2 This section compares the packet structures of Bluetooth Broadcast packets and Bluetooth Extended Broadcast packets carrying ZigBee data packets. The Bluetooth Broadcast packet's payload can only carry 37 bytes of data, and with ZigBee data packets embedded in the corresponding signal, only 3 bytes of valid data can be transmitted per backscatter. In contrast, the Bluetooth Extended Broadcast packet's payload can carry 255 bytes of data, and with ZigBee data packets embedded in the corresponding signal, 58 bytes of valid data can be transmitted per backscatter. Therefore, compared to the original method of implementing ZigBee backscatter using Bluetooth Broadcast packets, implementing backscatter communication based on Bluetooth Extended Broadcast packets can increase the effective data transmission volume per backscatter, thereby increasing the effective throughput by approximately 20 times.

[0066] (2) Challenges faced in implementing backscatter communication based on Bluetooth extended broadcast packets:

[0067] 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 demonstrates the process of a Bluetooth device sending a Bluetooth Extended Broadcast packet during a Bluetooth Extended Broadcast event. The Bluetooth device will send a broadcast packet on the broadcast channel (channel 37), and then randomly select one of the 37 data channels (channels 0 to 36) to send the Bluetooth Extended Broadcast packet. The channel number of the Bluetooth Extended Broadcast packet is recorded in the broadcast packet.

[0068] The variable transmission channel of Bluetooth Extended Broadcast packets (EBBS) presents a challenge to this invention in implementing backscattering. This is because the channel of the backscattered data packet is channel-dependent on the original excitation signal. Using the signal corresponding to the EBBS packet with its variable channel as the excitation signal will result in an unstable transmission channel for the backscattered data packet, thus preventing stable reception by the receiving device.

[0069] 2. Tag dynamic frequency shifting strategy.

[0070] The center frequency of the Bluetooth excitation signal can be calculated from the transmission channel of the Bluetooth Extended Broadcast packet. The center frequency of the ZigBee receiver's listening channel can also be calculated from the ZigBee channel number. The tag can be set with the correct frequency shift amount given the channel number.

[0071] To achieve backscatter communication based on Bluetooth Extended Broadcast packets, this invention designs a tag dynamic frequency shifting strategy, see [link to relevant documentation]. Figure 4 To address the issue of the non-fixed transmission channel of Bluetooth Extended Broadcast (EBB) packets, the tag in this invention dynamically adjusts the frequency shift based on the channel number of the BEBB packet, thereby ensuring a constant transmission channel for backscattered data packets. This invention incorporates a WiFi module into the excitation source device to generate an amplitude-modulated (AM) signal. The excitation source sends an AM signal before transmitting the BEBB packet, carrying the channel number of the next BEBB packet within it. The tag demodulates the AM signal using an envelope detector to obtain the channel number and sets the frequency shift based on the channel number during subsequent backscattering.

[0072] Specifically, frequency shift amount It should be the difference between the center frequency of the ZigBee listening channel and the center frequency of the Bluetooth Extended Broadcast packet transmission channel, i.e.:

[0073] (1)

[0074] The channel center frequency of the ZigBee protocol can be calculated from the channel number. The formula for calculating the channel center frequency of the ZigBee protocol in the 2.4 GHz band is shown in formula (2). It is the listening channel number of the ZigBee receiver.

[0075] (2)

[0076] Similarly, the channel center frequency of the Bluetooth protocol can also be calculated from the channel number. Since Bluetooth Extended Broadcast packets are transmitted on the Bluetooth data channel, only the calculation method for the center frequency of the Bluetooth data channel will be discussed, as shown in formula (3). It is the channel number of the Bluetooth Extended Broadcast Packet.

[0077] (3)

[0078] In summary, the tag can calculate the frequency shift based on the ZigBee receiver's listening channel number and the Bluetooth Extended Broadcast packet transmission channel number. The calculation formula is shown in formula (4).

[0079] (4)

[0080] The ZigBee receiver's listening channel is set by the system and is known to the tag. The Bluetooth Extended Broadcast packet's transmission channel is transmitted to the tag via an amplitude-modulated signal. Therefore, the tag can obtain the ZigBee receiver's listening channel number and the Bluetooth Extended Broadcast packet's channel number, and set the correct frequency shift accordingly.

[0081] This invention achieves backscatter communication by dynamically adjusting the frequency shift amount and utilizing Bluetooth Extended Broadcast packets transmitted via frequency hopping. Because the Bluetooth Extended Broadcast packets correspond to a relatively long signal duration, this method increases the data transmission volume of a single backscatter and significantly improves the system's effective throughput.

[0082] 3. The tag dynamically sets the threshold to demodulate the amplitude modulation signal.

[0083] The tag is equipped with an envelope detector, which can be used to demodulate amplitude-modulated signals transmitted by the WiFi module. This invention proposes a method for demodulating amplitude-modulated signals by dynamically setting a threshold. By employing this demodulation method, the tag can recover the channel number carried by the amplitude-modulated signal with a low error rate at various signal-to-noise ratios.

[0084] A WiFi module can generate amplitude-modulated signals by sending constant OFDM symbols and random OFDM symbols. A constant OFDM symbol indicates that the data carried within the current OFDM symbol is constant (e.g., all zeros), while a random OFDM symbol indicates that the data carried within the current OFDM symbol is random. For example... Figure 5 As shown, the amplitude of the signal corresponding to the random OFDM symbol is relatively uniform, while the signal corresponding to the constant OFDM symbol has a high-amplitude sampling point at the beginning, and the amplitudes of the remaining sampling points are smaller. Because the amplitudes of the time-domain signals corresponding to the two types of OFDM symbols are significantly different, an amplitude-modulated signal can be generated by sending these two OFDM symbols. The amplitude-modulated signal transmitted in this invention uses one random OFDM symbol and one constant OFDM symbol to represent bit 1, and two random OFDM symbols to represent bit 0.

[0085] Traditional methods demodulate amplitude-modulated (AM) signals by setting a fixed threshold, then reconstruct the data carried in the AM signal by comparing the amplitude of the sampled points with the threshold. However, because the overall amplitude of the signal changes with the signal-to-noise ratio (SNR), the fixed-threshold demodulation method is highly susceptible to noise interference. Figure 6 As shown in (a) and (b), 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 a large number of sampling points in random OFDM symbols have amplitudes greater than 1, while a very small number of sampling points in constant OFDM symbols have amplitudes 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.

[0086] To enable the tag to demodulate amplitude-modulated signals with a low error rate across various signal-to-noise ratios, this invention proposes a demodulation method with dynamically set thresholds. The method is as follows: Figure 7As shown, the data packet carried by the amplitude-modulated signal contains a preamble field. This field carries eight fixed bits of 1, and the corresponding signal alternates between random OFDM symbols and constant OFDM symbols. The tag samples the signal corresponding to this field, taking the last 40 samples of each symbol in the field, and calculates the average amplitude of all the samples. The tag then uses this average as a threshold to demodulate subsequent amplitude-modulated signals. When demodulating the amplitude-modulated signal, the last 40 samples of each symbol are used 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.

[0087] Simulation experiments were conducted in MATLAB to verify the feasibility and superiority of the proposed method. The error rates of demodulating amplitude-modulated signals and restoring channel numbers under different signal-to-noise ratios were compared between the traditional fixed-threshold demodulation method and the dynamic-threshold demodulation method proposed in this invention. The experimental results are as follows: Figure 8 As shown in the figure. Experimental results show that the dynamic threshold demodulation method proposed in this invention is more resistant to noise interference than the traditional fixed threshold demodulation method, and the error rate of channel number reconstruction 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 reconstruction using the dynamic threshold demodulation method will be less than 1%. In addition, the effective throughput of the backscatter communication proposed in this invention was measured through simulation experiments, and the experimental results are shown in the figure. Figure 9 As shown in the figure. Experimental results show that, compared with existing backscattering technologies (Interscatter, BumbleBee), the backscattering communication implemented by this invention using Bluetooth Extended Broadcast Packets can increase the effective throughput by about 20 times. The effective throughput of the backscattering communication of this invention can reach up to 23.2 kbps.

[0088] 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, and then demodulates subsequent signals after calculating a suitable threshold. When the signal-to-noise ratio changes, or the overall signal amplitude changes, the threshold set by the tag will also be adjusted. Compared to fixed-threshold demodulation methods, the dynamic threshold demodulation method proposed in this invention can set appropriate thresholds at various signal-to-noise ratios, thus better resisting noise interference.

[0089] The technical solution of the present invention will be described in more detail below with reference to an embodiment.

[0090] The feasibility and superiority of this invention were verified through simulation experiments in MATLAB R2024b.

[0091] The amplitude modulation signal demodulation experiment uses the wlanWaveformGenerator function in the WLAN toolbox to generate WiFi protocol signals, the awgn function in the Communications toolbox to add noise to the signals, and the envelope function in the Signal Processing toolbox to implement envelope detection.

[0092] The backscatter experiment uses the bleWaveformGenerator function in the Bluetooth toolbox to send Bluetooth Extended Broadcast 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 backscatter signal.

[0093] The backscatter communication workflow is as follows: The excitation source device first sets the transmission channel for the Bluetooth Extended Broadcast (EBB) packet, then sends a WiFi amplitude-modulated (AM) signal carrying the channel number. The excitation source device then transmits the Bluetooth BEBB packet on the set channel. The tag demodulates the WiFi AM signal using an envelope detector to obtain the transmission channel number for the next Bluetooth BEBB packet. The tag then calculates the frequency shift based on this channel number to ensure the backscatter signal is transmitted on the channel monitored by the receiving device. The tag carries its data by applying a phase shift to the excitation signal. The Zigbee receiver samples the signal and demodulates it based on the sign of the phase shift between adjacent sampling points to reconstruct the tag data.

[0094] 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.

[0095] 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. Based on the same innovative concept, the systems in one or more embodiments provided in this disclosure are as described in the following embodiments. Since the implementation schemes and methods for solving the problem are similar, the specific system implementations in the embodiments of this specification can refer to the implementations of the foregoing methods, and repeated details will not be repeated. As used below, the terms "module" or "module group" refer to a combination of software and / or hardware capable of performing a predetermined function. Although the systems described in the following embodiments are preferably implemented in software, hardware implementations, or a combination of software and hardware, are also possible and contemplated.

[0096] A ZigBee backscattering system based on ambient Bluetooth excitation, comprising:

[0097] The excitation module sends a Bluetooth Extended Broadcast Packet as an excitation signal from the excitation source, and before sending the excitation signal, it sends an amplitude modulation signal carrying the channel number of the Bluetooth Extended Broadcast Packet.

[0098] The backscatter module uses an envelope detector to demodulate the amplitude-modulated signal, obtains the channel number of the Bluetooth Extended Broadcast packet, and calculates the frequency shift 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 a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel.

[0099] The receiving module, a ZigBee receiver, receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

[0100] 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.

[0101] 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.

[0102] 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 ZigBee backscattering method based on ambient 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, it sends an amplitude modulation signal carrying the channel number of the Bluetooth Extended Broadcast packet; the data packet of the amplitude modulation 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 tag demodulates the amplitude-modulated signal using an envelope detector to obtain the channel number of the Bluetooth Extended Broadcast packet: extract the last 40 sampling points of each OFDM symbol corresponding to the preamble field, and use 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 Broadcast packet. 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. After receiving a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel. The ZigBee receiver receives and demodulates the backscattered signal on a fixed listening channel to obtain tag data.

2. The ZigBee backscattering method based on ambient Bluetooth excitation according to claim 1, characterized in that, The amplitude modulation signal encodes the channel number of the Bluetooth Extended Broadcast Packet using 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 ambient Bluetooth excitation according to claim 1, characterized in that, The step of using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field and obtain the channel number of the Bluetooth Extended Broadcast packet specifically includes: Calculate the average amplitude of the last 40 sampling points of each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, the current OFDM symbol is determined to be a random OFDM symbol; if the average amplitude is less than or equal to the threshold, the current OFDM symbol is determined to be a constant OFDM symbol.

4. The ZigBee backscattering method based on ambient 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 receiver and the channel number of the Bluetooth extended broadcast packet. Specifically, it includes: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ； It is the listening channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel in the Bluetooth Extended Broadcast Package. for: ； in, It is the channel number of the Bluetooth Extended Broadcast packet; Frequency shift for: 。 5. A ZigBee backscattering 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, it sends an amplitude modulation signal carrying the channel number of the Bluetooth Extended Broadcast Packet; the data packet of the amplitude modulation 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; Backscattering module: The tag demodulates the amplitude-modulated signal using an envelope detector to obtain the channel number of the Bluetooth Extended Broadcast Packet (BBS); it extracts the last 40 sampling points of each OFDM symbol corresponding to the preamble field, uses the average amplitude value of these sampling points as a threshold to demodulate the signal corresponding to the payload field, and obtains the channel number of the BBS; it calculates the frequency shift based on the dynamic difference between the monitoring channel number of the ZigBee receiver and the channel number of the BBS. After receiving a Bluetooth extended broadcast packet, the center frequency of the generated backscattered signal is adjusted by the frequency shift amount to maintain a constant transmission channel. Receiver module: The ZigBee receiver receives and demodulates the backscattered signal on a fixed monitoring channel to obtain tag data.

6. A ZigBee backscattering system based on ambient Bluetooth excitation according to claim 5, characterized in that, The amplitude modulation signal encodes the channel number of the Bluetooth Extended Broadcast Packet using 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.

7. A ZigBee backscattering system based on ambient Bluetooth excitation according to claim 5, characterized in that, The step of using the average amplitude value of the sampling points as a threshold to demodulate the signal corresponding to the payload field and obtain the channel number of the Bluetooth Extended Broadcast packet specifically includes: Calculate the average amplitude of the last 40 sampling points of each OFDM symbol in the signal corresponding to the payload field. If the average amplitude is greater than the threshold, the current OFDM symbol is determined to be a random OFDM symbol; if the average amplitude is less than or equal to the threshold, the current OFDM symbol is determined to be a constant OFDM symbol.

8. A ZigBee backscattering system based on ambient Bluetooth excitation according to claim 5, characterized in that, 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, it includes: The channel center frequency of the ZigBee protocol in the 2.4 GHz band for: ； It is the listening channel number of the ZigBee receiver; The center frequency of the Bluetooth data channel in the Bluetooth Extended Broadcast Package. for: ； in, It is the channel number of the Bluetooth Extended Broadcast packet; Frequency shift for: 。

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