Fixed-point terminal multi-state template short packet receiving method, gateway and system

Abstract

This invention discloses a method, gateway, and system for receiving short packets with multi-state templates for fixed-location terminals, belonging to the field of backscatter communication and IoT short packet reception technology. This invention achieves comprehensive reception enhancement at the gateway side: a multi-state echo template library is constructed for fixed-location terminals. When receiving short packets, at least two echo features are extracted to calculate the feature distance and match the optimal template. Based on template differentiation, a three-level window is generated: a main path reception window, a near-end secondary path weighting window, and a late-arriving secondary path suppression window. Hierarchical weighting processing is performed on the echoes. When there is a complete template mismatch, a degradation mode is entered, and terminal presence information is output through a wide window as a safety net. A lifecycle state machine is used to achieve closed-loop management of the entire template process. This invention requires no additional hardware to the terminal, can suppress late-arriving multipath interference, improve the reliability of short packet demodulation, and possesses environmental change survival capabilities and long-term operational stability. It is suitable for backscatter communication scenarios in various fixed asset monitoring applications.

Description

Technical Field

[0001] This invention relates to the fields of backscatter communication and IoT short packet reception technology, and particularly to a method, gateway and system for receiving multi-state template short packets for fixed-point terminals. Background Technology

[0002] Backscatter communication technology, with its passive terminal, low power consumption, and maintenance-free characteristics, is widely used in IoT scenarios such as fixed asset monitoring and facility status acquisition. Terminals are usually permanently installed in cabinets, building structures, or around industrial facilities. Surrounding metal components, sealed panels, wall structures, etc., will generate a large number of reflected multipath components, resulting in severe time delay spread in the backscattered echo.

[0003] Meanwhile, uplink data in such scenarios is mostly in the form of short packets, carrying little state information and extremely short frame length. Delay multipath components are very likely to cause crosstalk of short packet symbols, which in turn leads to demodulation errors and missed data detection, significantly reducing transmission reliability.

[0004] Existing multipath suppression schemes for backscatter communication have the following shortcomings in fixed-location deployment scenarios: First, some schemes deploy channel equalization, multipath estimation, and other processing logic on the terminal side, requiring additional computing and storage units, significantly increasing terminal hardware complexity and power consumption, which conflicts with the low-power design goals of passive and low-power terminals. Second, network-side multipath suppression schemes for dynamic terminals generally adopt real-time channel estimation and adaptive multipath window mechanisms, requiring full-delay domain multipath search and parameter updates for each received signal, resulting in significant computational overhead. Furthermore, existing schemes lack targeted pre-configuration optimization for the relatively stable characteristics of echo multipath at fixed locations within a certain timeframe, leading to unnecessary real-time computational redundancy. Third, fixed locations often have various stable physical environment states (such as cabinet opening / closing, obstruction, etc.), with significant differences in multipath energy distribution under different states. Existing schemes often use a single general-purpose receiving window or a single scene template, failing to adaptively match optimal receiving parameters for various stable environmental states at the location, resulting in insufficient adaptability to scenarios with changing operating conditions. Even if existing solutions employ multipath time windows or channel estimation, they typically do not establish separate receiving templates for different stable physical environment states at the same fixed location. Furthermore, when the current echo does not match any of the existing templates, there is a lack of degradation keep-alive processing and a closed-loop lifecycle management mechanism for template verification, failure, and retraining.

[0005] Therefore, this invention proposes a method, gateway, and system for receiving multi-state template short packets for fixed-location terminals. Summary of the Invention

[0006] This invention provides a method, gateway, and system for receiving short packets with multi-state templates for fixed-location terminals. By constructing a multi-state echo template library indexed by location and state, using echo features to jointly calculate feature distances and match the optimal template, and configuring a three-level time-domain reception window based on template differentiation, the reliability of short packet reception in strong multipath scenarios is improved without increasing the complexity of terminal hardware. At the same time, the real-time computing overhead of the gateway is reduced, and the adaptability to multiple working conditions is improved.

[0007] This invention provides a method for receiving multi-state template short packets for fixed-location terminals, applied to gateway devices, comprising: During the installation and binding, initial network access, or retraining phases of the backscatter terminal, the training backscatter echo returned by the backscatter terminal based on the excitation signal is received. The echo characteristics of the same fixed point terminal under various physical environment conditions are collected, and static echo templates corresponding to each state are generated. A multi-state echo template library indexed by point identifier and state label is constructed. When a backscatter state short packet is received from the terminal, at least two echo features are extracted from the currently received echo, and the feature distances are calculated with the corresponding state templates in the multi-state echo template library. The template with the smallest feature distance is selected as the candidate template. If the feature distance of the candidate template meets the preset matching threshold, it is determined as the target matching template. Based on the target matching template, a differentiated three-level time-domain receiving window is generated, which includes, in sequence, the main path receiving window, the near-end secondary path weighting window, and the late secondary path suppression window; The current echo is processed in stages according to the three-level time domain receiving window to obtain the enhanced received signal and then sent into the short packet demodulation process. If the feature distance of all state templates does not meet the preset matching threshold, the mode is downgraded and a coarse-grained energy decision is performed using a wide window. The terminal in-situ detection result is output, and the template is marked as pending review, triggering the template lifecycle management process.

[0008] Preferably, the state labels in the multi-state echo template library include: open state, closed state, occluded state, and weak coverage state, and each state label corresponds to a different stable physical environment around the point. The static echo template includes at least the main path delay parameter and the multipath energy distribution parameter.

[0009] Preferably, the echo characteristics include at least two of the following: main path drift, late path energy ratio, correlation peak amplitude statistics, window width, link quality level, and phase statistics; The characteristic distance is the weighted sum of the characteristic distances of each echo. The main path drift is calculated based on the difference between the main path delay of the current echo and the template, and the late path energy ratio is calculated based on the ratio of the multipath energy to the total echo energy within a preset delay range after the main path.

[0010] Preferably, the three-level time-domain receiving window is configured based on the principal path delay in the target matching template: The main path receiving window covers the time domain interval where the main path peak is located, in order to retain the effective signal of the main path; The proximal secondary path weighted window covers the proximal reflection multipath region after the main path, and the weighting coefficient is determined by the proportion of proximal multipath energy in the target matching template; The late secondary path suppression window covers the time delay interval outside the near secondary path weighting window and is used to suppress late multipath interference caused by far-end reflections.

[0011] Preferably, the downgraded reception mode includes: A wide receiving window covering the entire effective time delay range is used to perform echo energy accumulation and existence determination; If the energy accumulation result meets the in-situ decision threshold, the terminal in-situ identifier and the reception reliability degradation flag are output, and the complete short packet demodulation result is not output. Synchronously trigger the template pending review status mark, and record the number of consecutive mismatches and the duration of the mismatch.

[0012] Preferably, each static echo template is configured with a lifecycle management field, including template version number, training timestamp, validity period, and reliability score. The template lifecycle is managed according to a state machine transition between initialization state, valid state, pending review state, invalid state, and retraining state, including: After the template is initially generated, it enters the initialization state. After passing the verification, it transitions to the valid state. When the number of consecutive matching failures reaches the first threshold, the system transitions to a pending review state. When the number of consecutive matching failures reaches the second threshold or the validity period is exceeded, it becomes invalid. The failed template triggers the retraining process, which re-acquires training echoes, generates a new template, and then returns to the initialization state. When the template is in the pending verification state, the gateway device will continuously attempt template matching during subsequent reception. If multiple matches are successful consecutively and the credibility score rises back above the threshold, the system returns to the valid state. If the mismatch persists, the system will transition to a failure state and trigger retraining.

[0013] Preferably, the training backscatter echo is generated by the terminal by switching the radio frequency impedance state. In this case, the passive terminal switches the impedance according to a preset training sequence when triggered by an excitation signal, and the semi-passive terminal extends the length of the training sequence or increases the number of repetitions when the local energy storage meets a preset threshold, thereby enhancing the detectability of the echo.

[0014] This invention provides a multi-state template short packet receiving gateway for fixed-location terminals, comprising: The excitation and radio frequency transceiver unit is used to send excitation signals to the backscatter terminal and receive the backscattered echoes returned by the terminal. The template library construction unit is used to extract echo features under various states from the training echoes, generate static echo templates, and build a multi-state echo template library indexed by point location and state. The template matching unit is used to extract the echo features of the current echo, calculate the feature distance with each state template in the template library, and filter the target matching template that meets the matching threshold. The three-level window generation unit is used to generate three-level time-domain receiving windows—main path receiving window, near-end secondary path weighted window, and late secondary path suppression window—based on the target matching template differentiation. The graded receiving and processing unit is used to perform graded weighting processing on the echo according to the three-level time domain receiving window and output the enhanced received signal. The downgrade decision unit is used to perform a wide-window coarse-grained energy decision when all templates fail to match, output the terminal in-situ detection result, set the template to be reviewed, and trigger template lifecycle management. The demodulation processing unit is used to perform short packet detection, demodulation, and verification on the enhanced received signal.

[0015] Preferably, it also includes: a template lifecycle management unit, used to maintain the version number, training timestamp, validity period, and credibility score fields of each template, control the state transition of the template between the initialization state, the valid state, the pending review state, the invalid state, and the retraining state, and trigger the template retraining process.

[0016] This invention provides a multi-state template short packet receiving system for fixed-location terminals, comprising: at least one fixedly deployed backscatter terminal, used to return training echoes and state short packets via backscattering under the triggering of an excitation signal; a gateway device, used to execute the multi-state template short packet receiving method described above; and a monitoring platform, communicatively connected to the gateway device, used to receive short packet demodulation results, terminal location information, and template status data reported by the gateway.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: Multi-state adaptation, stronger adaptability to working conditions: A multi-state echo template library is built for various stable physical environments around fixed points. At least two features, such as the main path drift and the energy ratio of the late path, are used to jointly calculate the feature distance and match the template. It can adaptively match the current environmental state to output the optimal receiving parameters, thereby improving the short packet demodulation success rate in various working conditions such as cabinet opening and closing, and whether there is obstruction.

[0018] Three-level window hierarchical processing for more refined multipath suppression: The design employs a three-level window structure consisting of a main path receiving window, a near-end secondary path weighting window, and a late secondary path suppression window. The window parameters are configured differently depending on the matching template. This approach retains the diversity gain of effective near-end multipaths while accurately suppressing far-end late multipath interference. Compared to the general single-window solution, this approach offers finer processing granularity and a more significant improvement in the received signal-to-interference-plus-noise ratio.

[0019] Zero overhead for the terminal and good deployment compatibility: All template construction, matching calculation and window processing logic are deployed on the gateway side. The terminal only needs to perform standard backscatter impedance switching action. No new hardware and algorithms are required. It fully retains the low power consumption and maintenance-free characteristics of passive terminals and can be directly adapted to the existing terminal system with low deployment cost.

[0020] Template pre-storage and reuse improve gateway computation efficiency: By leveraging the long-term stability of fixed-point channels, templates can be collected once and reused for a long time. During normal reception, pre-stored templates can be directly called to generate three-level windows, eliminating the need to perform full-domain multipath search and complete channel estimation for each reception, thus reducing the real-time computation load and power consumption of the gateway.

[0021] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall system architecture of the present invention; Figure 2 This is a schematic diagram of the initialization process of the multi-state echo template library of the present invention; Figure 3 This is a schematic diagram of the three-level time-domain receiving window based on the main path delay of the present invention; Figure 4This is a schematic diagram comparing the echo multipath energy distribution before and after the hierarchical windowing process of the present invention. Figure 5 This is a schematic diagram of the short packet hierarchical reception and processing flow based on multi-template matching of the present invention; Figure 6 This is a schematic diagram of the template lifecycle state machine and mismatch closed-loop management process of the present invention; Figure 7 This is a structural diagram of a multi-state template short packet receiving gateway for fixed-location terminals according to the present invention. Detailed Implementation

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] This invention provides a method for receiving multi-state template short packets for fixed-location terminals, applied to gateway devices, comprising: During the installation and binding, initial network access, or retraining phases of the backscatter terminal, the training backscatter echo returned by the backscatter terminal based on the excitation signal is received. The echo characteristics of the same fixed point terminal under various physical environment conditions are collected, and static echo templates corresponding to each state are generated. A multi-state echo template library indexed by point identifier and state label is constructed. When a backscatter state short packet is received from the terminal, at least two echo features are extracted from the currently received echo, and the feature distances are calculated with the corresponding state templates in the multi-state echo template library. The template with the smallest feature distance is selected as the candidate template. If the feature distance of the candidate template meets the preset matching threshold, it is determined as the target matching template. Based on the target matching template, a differentiated three-level time-domain receiving window is generated, which includes, in sequence, the main path receiving window, the near-end secondary path weighting window, and the late secondary path suppression window; The current echo is processed in stages according to the three-level time domain receiving window to obtain the enhanced received signal and then sent into the short packet demodulation process. If the feature distance of all state templates does not meet the preset matching threshold, the mode is downgraded and a coarse-grained energy decision is performed using a wide window. The terminal in-situ detection result is output, and the template is marked as pending review, triggering the template lifecycle management process.

[0026] Preferably, the state labels in the multi-state echo template library include: open state, closed state, occluded state, and weak coverage state, and each state label corresponds to a different stable physical environment around the point. The static echo template includes at least the main path delay parameter and the multipath energy distribution parameter.

[0027] Preferably, the echo characteristics include: main path drift, late path energy ratio, correlation peak amplitude statistics, and phase statistics; The characteristic distance is the weighted sum of the characteristic distances of each echo. The main path drift is calculated based on the difference between the main path delay of the current echo and the template, and the late path energy ratio is calculated based on the ratio of the multipath energy to the total echo energy within a preset delay range after the main path.

[0028] Preferably, the three-level time-domain receiving window is configured based on the principal path delay in the target matching template: The main path receiving window covers the time domain interval where the main path peak is located, in order to retain the effective signal of the main path; The proximal secondary path weighted window covers the proximal reflection multipath region after the main path, and the weighting coefficient is determined by the proportion of proximal multipath energy in the target matching template; The late secondary path suppression window covers the time delay interval outside the near secondary path weighting window and is used to suppress late multipath interference caused by far-end reflections.

[0029] Preferably, the downgraded reception mode includes: A wide receiving window covering the entire effective time delay range is used to perform echo energy accumulation and existence determination; If the energy accumulation result meets the in-situ decision threshold, the terminal in-situ identifier and the reception reliability degradation flag are output, and the complete short packet demodulation result is not output. Synchronously trigger the template pending review status mark, and record the number of consecutive mismatches and the duration of the mismatch.

[0030] Preferably, the training backscatter echo is generated by the terminal by switching the radio frequency impedance state. In this case, the passive terminal switches the impedance according to a preset training sequence when triggered by an excitation signal, and the semi-passive terminal extends the length of the training sequence or increases the number of repetitions when the local energy storage meets a preset threshold, thereby enhancing the detectability of the echo.

[0031] This invention provides a multi-state template short packet receiving system for fixed-location terminals, such as... Figure 1 As shown, it includes: at least one fixed backscatter terminal, used to return training echoes and status short packets via backscattering when triggered by an excitation signal; at least one gateway device, used to execute the multi-state template short packet receiving method described in any one of the claims; and a monitoring platform, communicatively connected to the gateway device, used to receive short packet demodulation results, terminal presence information, and template status data reported by the gateway.

[0032] It should be noted that the training backscatter echo is generated by the terminal by switching the RF impedance state, according to the following rules: Training sequence format: A 127-bit m-sequence is used as the standard training sequence with a chip rate of 1 Mbps. The sequence has good autocorrelation properties and is used for correlation detection and extraction of multipath distribution. Passive terminal: When triggered by the gateway excitation signal, it switches between high and low reflection impedance according to the preset training sequence and sends the training sequence 4 times. The gateway improves the detection accuracy through multiple averaging. Semi-passive terminal: When the local energy storage voltage is ≥2.5V, the echo amplitude is improved by optimizing the impedance switching ratio, and the training sequence is repeatedly sent 8 times to further improve the template extraction accuracy; when the energy storage is insufficient, the passive terminal rules are followed to avoid excessive energy consumption.

[0033] The backscatter terminal is fixedly deployed at the monitoring point and does not communicate directly with the monitoring platform. It interacts with the gateway device only through a backscatter wireless link. The terminal receives the excitation signal sent by the gateway and reflects the status data back to the gateway in short packets by switching the radio frequency impedance. The terminal forms include passive terminals and semi-passive terminals, both of which only perform basic impedance switching responses and do not perform complex calculations such as channel estimation and multipath equalization.

[0034] The gateway device is the core processing device on the network side. It integrates a multi-state echo template library, a three-level window processing module, a degradation decision module, a template lifecycle management module, and a short packet demodulation module. It is responsible for echo signal reception, feature extraction, template matching, hierarchical window processing, degradation keep-alive, and short packet parsing.

[0035] The monitoring platform connects to the gateway via wired or wireless networks (Ethernet, mobile communication, industry private networks, etc.) and receives short packet demodulation results, terminal location information and template status data reported by the gateway, thereby realizing visualized management of assets across the entire domain.

[0036] like Figure 2 As shown, template library initialization is performed during terminal installation, initial network access, or retraining phases. The specific process is as follows: Complete the physical installation and identity binding of the terminal and the location, and record the correspondence between the location identifier and the terminal identifier; The gateway device sends excitation signals or calibration commands to the target terminal; The terminal generates training backscatter echoes according to a preset training sequence by switching the radio frequency impedance state. The gateway receives training echoes, obtains power delay distribution through relevant detection, and identifies the energy distribution of main path peak, near-end multipath, and late-arriving multipath. Under the current physical environment conditions, parameters such as main path delay, multipath energy distribution, recommended parameters for each level of window, and link quality are extracted to generate a static echo template corresponding to this state. Switch the physical environment status around the location, repeat the above steps, and collect template data under various statuses; Configure lifecycle fields (version number, training timestamp, validity period, initial confidence score) for each template, and store them in the multi-state echo template library by location identifier and status label index.

[0037] For passive terminals, training echoes can be generated simply by switching between high and low reflection impedances when triggered by an excitation signal; for semi-passive terminals, the training sequence can be extended and the number of repetitions increased when local energy storage is sufficient, thereby improving template extraction accuracy.

[0038] The status labels of the multi-state echo template library can be configured according to the on-site working conditions. Typical statuses include open, closed, obstructed, and weak coverage, which correspond to different stable physical environments around the point, ensuring that the optimal template can be matched under different working conditions.

[0039] Regarding the mathematical model of the echo channel: the backscattered echo received by the gateway device from the fixed-point terminal is the superposition of the main path, several secondary paths, and noise, which can be expressed as: , where: i is the i-th fixed point terminal; Let be the time-domain echo signal of the i-th terminal received by the gateway at time t; The total number of valid multipath paths for the i-th terminal; For the process The terminal baseband transmits signals with time delay offset; Let be the complex amplitude of the k-th path, including amplitude attenuation and phase shift, where k=0 corresponds to the principal path; Let be the arrival delay for the k-th path; This is the background noise signal.

[0040] Because the terminals are fixedly deployed at designated locations, the main path delay... Furthermore, the time delay distribution of the main secondary diameter remains relatively stable over a long period of time, so it can be extracted and solidified into a static echo template for that location during the installation or initial network connection phase.

[0041] Regarding related detection and power delay distribution: The gateway device will receive the echoes and perform correlation detection with the local reference training sequence to obtain the echo energy at different time delay locations: , ,in: The cross-correlation output of the i-th terminal echo and the local reference sequence is a time-delay domain function, with the path delay as the independent variable. ; (t τ) represents the time delay offset. The conjugate delay form of the subsequent local reference training sequence; The power delay distribution is used to characterize the echo energy intensity at different delay locations. Gateway devices use the power delay distribution to identify the distribution of the main path peak, near-end secondary path, and late-arriving secondary path.

[0042] Regarding the estimation of the main path delay: In one implementation, the main path delay can be taken as the delay corresponding to the strongest peak in the power delay distribution: ,in: The arrival time delay of the main path is the real-time estimate of the current echo; argmax indicates the value of the independent variable that makes the function reach its maximum value.

[0043] In scenarios with strong multipath propagation and where the strongest peak value does not necessarily correspond to the earliest effective path, the earliest effective peak value method can also be used to calculate the main path delay. ,in: The maximum power value of the PDP within the effective search range; The effective peak threshold coefficient is 0 < λ ≤ 1, and the preferred value range is 0.3 to 0.8. The effective latency search range for the i-th terminal is determined by the maximum distance between the terminal and the gateway and the maximum latency spread of the system.

[0044] Regarding the definition of a multi-template set: For the i-th fixed-point terminal, the gateway device can store a multi-state echo template set under various states. : Each state template : , ,in, For terminal identification, For installation point identification, For service gateway device identification, Let m be the main path delay of the i-th terminal in state m. The multipath energy distribution in state m. The width of the multipath feature window in state m. This represents the link quality level under state m. The principal diameter phase in state m. For environmental status labels (open / closed / occluded / weakly covered); It should be noted that the status labels in the template library are based on quantitative indicators of the physical environment surrounding the location. In this embodiment, four typical stable states are defined, and the classification criteria are as follows: Open state: There are no obstructions within 0.5m around the point, the energy of the direct path accounts for ≥70% of the total echo energy, and there are no strong reflectors; Closed state: The point is located in a closed metal cabinet / box, the direct path energy accounts for ≤30%, the multipath reflection from the inner metal wall is dominant, and the time delay spread is ≥100ns; Blocked state: There are non-metallic obstructions (wood, plastic, walls, etc.) in front of the point. The total echo energy is reduced by 10dB~20dB compared with the open state at the same distance. The multipath structure does not change significantly. Weak coverage: The location is at the edge of the gateway coverage, the total echo energy is attenuated by more than 20dB compared to the open state, and the signal-to-noise ratio is ≤6dB.

[0045] Status labels can be expanded according to on-site working conditions. All statuses correspond to repeatable and quantifiable physical environments, avoiding subjective judgment.

[0046] In the minimum implementation, the static echo template includes at least a principal diameter delay. and multipath energy distribution The main diameter amplitude, main diameter phase, and main-to-secondary diameter energy ratio can be selected as optional features.

[0047] Multipath energy distribution It can be further defined as the set of power at several sampling offsets relative to the main path delay: ,in, , ,..., This multipath energy distribution, relative to the main path delay, is used to describe the near-end secondary path, the late secondary path, and the stable reflection components formed by the metal tank, fire cabinet, and wall after the main path.

[0048] like Figure 6 As shown, each static echo template follows a unified lifecycle state machine to achieve closed-loop management throughout the entire process: Initialization state: After the template is generated for the first time, it enters the initialization state. The gateway verifies the template matching accuracy by receiving multiple samples. If the accuracy reaches the qualified threshold, it is marked as valid. If the verification fails, the data is collected and trained again.

[0049] Valid state: The template state during normal operation, which can be used for template matching and window generation in regular short packet reception; Increase the credibility score each time a match is successful, and decrease the credibility score each time a match fails.

[0050] Pending review status: When the number of consecutive matching failures reaches the first threshold, or the credibility score drops to the warning threshold, the template enters the pending review status; In this state, the template can still participate in matching, but a review and statistics process is initiated simultaneously to record subsequent matching results.

[0051] Failure State: When the number of consecutive failed matches reaches the second threshold, or the template exceeds the preset validity period, or the credibility score drops to the failure threshold, the template enters the failure state and no longer participates in regular matching.

[0052] Retraining state: The failed template automatically or manually triggers the retraining process, re-collects training echoes, generates a new version of the template, and returns to the valid state after verification, completing one life cycle closed loop.

[0053] In the template lifecycle management field, the version number increments with retraining, the training timestamp records the generation time, the validity period is configured according to the stability of the on-site environment, and the credibility score is dynamically updated based on the historical matching success rate, thereby realizing quantitative control of template quality.

[0054] like Figure 5 As shown, the complete processing flow for receiving normal short packets is as follows: The gateway sends a read command or excitation signal, and the terminal returns a short status packet via backscatter. The gateway receives the echo signal and extracts the echo characteristics of the current echo, typically including the main path drift and the energy ratio of the late path, and can also combine relevant peak amplitude statistics, phase statistics, etc. The feature distance is calculated one by one between the current echo feature and all state templates of this point in the template library. The feature distance is the weighted sum of the distances of each component. The template with the smallest feature distance is selected as the candidate template. If the feature distance of the candidate template is less than or equal to the preset matching threshold, it is determined as the target matching template. Based on the main path delay and multipath distribution parameters in the target matching template, a three-level time domain receiving window is generated. The width and weight of each level of window are configured differently by the template parameters. The echo signal is processed in a three-level window: full retention in the main aperture window, weighted accumulation in the near-end secondary aperture window, and weighted filtering in the late secondary aperture window. The processed enhanced signal is sent into the short packet detection, demodulation, decoding and verification process to finally parse out the terminal status data. If the feature distance of all templates is greater than the matching threshold, then the system enters the degraded reception mode.

[0055] Feature distance calculation method: The gateway device calculates the feature distance between the current echo feature and each state template. The feature distance is a weighted sum of multiple feature distances, expressed as: ,in: Let β1 be the feature distance between the current echo of the i-th terminal and the state template m; β1~β5 are the weight coefficients of each feature, satisfying β1+β2+β3+β4+β5=1. At least two features can be selected to participate in the calculation according to the scenario, and the weight coefficients of unused features are set to 0. The reference weight range is: β1=0.25~0.45, β2=0.25~0.45, β3=0.10~0.25, β4=0.05~0.15, β5 = 0~0.20; Preset a reference delay spread width for the system (normalized baseline, taking the maximum effective delay spread value of the system). Let the main path delay be the current state of the i-th terminal. The multipath energy distribution under the current state. The width of the multipath feature window in the current state. This represents the link quality level under the current conditions. The maximum effective delay search range (system maximum delay extension) is preset for this point. The main path phase in the current state; The specific definitions of the distances for each component are as follows: Main diameter drift distance: calculated based on the normalized difference between the current echo and the template's main diameter delay, reflecting the degree of offset of the main diameter position; Normalized multipath energy distribution distance (·) is represented as: ,in, , , , L represents the number of effective paths. and These represent the 1st, 2nd, 3rd, 4th, and 5th sampled components of the current state and the mth state in the multipath energy distribution of the i-th terminal, respectively.

[0056] Link quality difference function (·) is represented as: ,in, This represents the maximum possible value for the link quality level. The minimum value is used. The method of classifying the link quality level can be pre-configured by the system, for example, it can be divided into levels 1-3, 1-5, or 1-10.

[0057] Phase ring distance (·) is represented as: ; The gateway device selects the template with the shortest distance. ,when When using a template Generate multipath feature windows when all template distances are greater than 10 ... However, if the limit has not been exceeded consecutively, the union of candidate template windows can be used as a conservative receiving window; when the distance between all templates is greater than the limit for k consecutive times... When this occurs, template retraining is triggered or a template mismatch indication is output, where, The preset matching threshold can be determined based on the training samples, the ambient noise level, and the required mismatch rate; in one embodiment, 0.25 is acceptable.

[0058] like Figure 3 , Figure 4 As shown, the three-level time-domain receiving window is arranged sequentially along the time-domain axis based on the main path delay of the target matching template, so as to realize differentiated processing of multipath with different delays.

[0059] Definition of time-domain interval for a three-level window: Main path receiving window: Centered on the peak value of the main path, it covers the main time domain interval of the main path signal. The signal weight within the window is 1, and it is fully retained and participates in the demodulation decision to ensure the full utilization of the effective energy of the main path.

[0060] Near-end sub-path weighting window: immediately after the main path receiving window, it covers the near-end multipath range generated by the nearby reflector; the window weight is determined by the energy proportion and phase stability of the corresponding multipath in the template, and the stable near-end multipaths are weighted and accumulated, and the receiving performance is improved by using multipath diversity gain.

[0061] Late-arrival secondary path suppression window: covers all late-arrival delay intervals outside the near-end secondary path weighting window, corresponding to late-arrival multipaths generated by far-end walls and metal structures; the signal weights within the window are set to low values ​​or zero, and late-arrival multipaths are deweighted or completely filtered out to eliminate their crosstalk to short packet symbols.

[0062] All three time-domain receiving windows use the principal diameter delay of the target matching template. Based on this, the axes are arranged sequentially according to the time delay axis, and the boundary calculation rules are as follows: Main diameter receiving window : Among them, forward protection interval Main diameter rearward width The weight coefficient within the window is always 1, and the effective signal of the main path is fully retained. For the corresponding chip duration period; Proximal secondary diameter weighted window : Among them, the near-end boundary Determined by the template parameters, the time delay width is taken from the near-end multipath segments with the top 80% energy percentage in the template; in this embodiment, the typical value is 10. Window weighting coefficient Linear mapping of template proximal multipath energy proportion: ,in, The total energy of the near-end multipath is given. The higher the proportion of near-end multipath energy, the larger the weighting coefficient, thus making full use of diversity gain. This represents the total energy of all multipath components, meaning only the total energy of the multipath components is counted, excluding the principal path. The total energy of the late secondary path.

[0063] Late secondary path suppression window : The remaining interval of the effective delay spread of the window coverage template, and the suppression coefficient. The default value is 0.1; in scenarios with strong multipath interference, it can be set to 0 to completely filter out late multipath signals.

[0064] The total window width is bound to the template's effective delay extension, typically 30. It corresponds to a 300ns delay range at a 100MHz sampling rate, which can cover the multipath delay extension of most fixed-point scenarios.

[0065] Window weight functions can be defined: ,in, Main path receiving window, For the proximal secondary diameter weighted window, For late secondary path suppression window; The weighting coefficient for the proximal accessory diameter. This is the late-arriving secondary diameter suppression coefficient. When... At that time, the late secondary path was completely filtered out; In such cases, latecomers participate in the judgment with a lower weight.

[0066] The gateway device's windowing of relevant outputs can be represented as follows: ,in, This is the original related output; This is the output after windowing.

[0067] The processed echo can be represented as: ,in, Match the i-th terminal with the i-th terminal After template number 1, the time-delay domain cross-correlation output is enhanced by a three-level window and has the dimension of voltage V. The two-dimensional output is obtained by performing a sliding cross-correlation between the original echo and the local reference sequence, with the path delay as the independent variable. With sampling time t.

[0068] Using the aforementioned window weight function, the gateway device can choose to completely filter out the secondary paths outside the window, or perform soft weighting on the secondary paths outside the window, based on hardware or algorithm implementation.

[0069] Regarding the comparison of signal-to-interference-plus-noise ratio (SIR) before and after window opening: The SIR before and after window processing can be expressed as follows: ; ; in, Indicates the signal-to-interference-to-noise ratio before window opening processing; This indicates the signal-to-interference-plus-noise ratio after windowing processing; This represents the average noise power of the additive white Gaussian noise at the receiving end. Indicates the complex amplitude of the kth secondary radius; ( ) represents the window weight of the delay position corresponding to the k-th L-path. Since the late secondary path outside the window satisfies... ( ) < 1, therefore The secondary diameter interference term in the middle is less than The secondary path interference term in the middle, thus making Higher than This demonstrates that the present invention can improve the reliability of short packet reception by determining the three-level time-domain reception window through target matching templates and by reducing or suppressing late secondary paths.

[0070] The core of this invention does not lie in limiting specific OOK or BPSK demodulation algorithms, but in generating multipath feature windows based on static templates and performing windowing processing on D2R short packet echoes. The following decision methods are only optional embodiments.

[0071] For OOK or energy-modulated short packets, the windowed energy within the b-th bit interval can be calculated: ; The judgment rule is as follows: Among them, threshold Defined as: ,in, This indicates an idle window, a low-reflection state, or the average energy of a 0-symbol sign. Indicates a high reflectivity state or average energy with a symbol of 1; These are threshold interpolation coefficients, preferably between 0.4 and 0.6. The first state can be "reflection-enabled / high energy / conduction-enabled state", typically corresponding to bit 1; the second state can be "non-reflection-enabled / low energy / off state", typically corresponding to bit 0. The single-bit duration is the signal duration corresponding to a single binary bit (bit "0" or bit "1") in OOK modulation. This represents the number of chips corresponding to a single bit.

[0072] The three-level window parameters corresponding to different state templates are different. For example, in the closed state, late multipath is richer, and the corresponding suppression window range is larger and the suppression weight is lower; in the open state, the proportion of near-end multipath is high, and the corresponding weighted window width is wider and the weight is higher, so as to achieve accurate adaptation of window parameters to environmental state.

[0073] When a sudden change occurs in the surrounding environment of a location, causing all status templates to fail to match, the system does not force the use of the most recent template for fine-tuning, but automatically switches to a degraded receiving mode: The gateway enables a wide reception window covering the entire effective delay range to accumulate energy across the entire echo range; The energy decision threshold is used to determine whether the terminal is in place. If the threshold is met, the terminal is in place and the reception reliability degradation flag is output to ensure that the terminal can still be confirmed to be online during sudden environmental changes and to avoid complete loss of connection. In degraded mode, complete short packet demodulation results are not output; only basic in-situ detection capabilities are retained. At the same time, all templates at the corresponding points are marked as pending verification, and the template status verification process is initiated.

[0074] It is suitable for scenarios with frequent changes in environmental conditions. It can still provide basic keep-alive capability when fine demodulation fails, forming a hierarchical receiving system that prioritizes fine demodulation and provides a fallback keep-alive capability.

[0075] For example, in a scenario where cabinet facilities are deployed in a corridor, a passive backscatter terminal is installed on each facility, and the gateway device is deployed in the corridor or low-voltage shaft area. During the installation phase, maintenance personnel bind the terminal to the location. The gateway collects training echoes under two typical states: cabinet door open and cabinet door closed. Through relevant detection, the power delay distribution is obtained, and features such as main path delay, multipath energy distribution, and three-level window parameters are extracted to generate static echo templates for the corresponding states. After configuring the lifecycle field, the templates are stored in the multi-state echo template library for that location. During routine inspections, the gateway sends read commands to the cabinet group periodically, and the terminal returns status short packets via backscatter. After receiving the echoes, the gateway extracts two features: the main path drift and the proportion of late-arriving path energy. It calculates the feature distance to each state template, automatically matches the target template corresponding to the current state, and generates differentiated three-level time-domain receiving windows. The main path window retains the main path signal, the near-end secondary path window weighted and merges the effective reflection components, and the late-arriving secondary path window filters out late reflections generated by the cabinet and walls, effectively reducing bit errors caused by multipath. When a sudden abnormal change in the cabinet door status causes a complete mismatch of templates, the gateway automatically enters a degraded mode, confirms the terminal's presence through wide-window energy judgment, and sets the template to a pending verification state; if the state remains stable, retraining is triggered to generate a new state template and update the template library.

[0076] For example, in densely populated fixed-point short-packet reception scenarios in underground warehouses, asset terminals are densely deployed along walls and shelves, creating a complex multipath environment with surrounding metal vehicles, shelves, and walls. During deployment, the gateway triggers terminal training in batches by region, generating a multi-state echo template library for each fixed point, including open, obstructed, and weak coverage states. For points with severe obstruction and weak signals, semi-passive terminals are used, sending enhanced training sequences when local energy storage is sufficient to improve template extraction accuracy and initial reliability score. During daily monitoring, the gateway calls a dedicated template library for each point for matching, generating a three-level receiving window to classify echoes, and distinguishing echoes from adjacent points by combining terminal identifiers to avoid misjudgments caused by neighboring point reflections. For points that are in a long-term obstructed state, the system automatically extends the validity period of the corresponding template and optimizes the reliability score weight. When the surrounding environment of a point changes over a long period or the template continues to mismatch, the template gradually transitions to a pending review or invalid state according to the state machine, automatically triggering a retraining process, updating the template parameters, and putting it back into use to ensure long-term stable operation of densely populated points.

[0077] For a single terminal in a single environment, the template generation steps are as follows: The gateway continuously collects 8 frames of valid training echoes and removes invalid frames with a signal-to-noise ratio of less than 8dB. Perform cross-correlation on each frame of echo to obtain the corresponding power delay distribution; The earliest effective peak value method is used to estimate the principal path delay, where the threshold coefficient is set to 0.6. Based on the main path delay, the energy values ​​of the last 30 sampling points of the main path are extracted to form the original multipath energy vector; The arithmetic mean of the results from the 8 frames is taken to obtain the average multipath energy distribution under this state. Calculate the total effective delay spread width: starting from the peak of the main path, the delay width corresponding to when the cumulative energy accounts for 90% of the total energy; Calculate the nominal total echo energy: the sum of energy within the effective time delay range; The multipath energy vector is normalized to obtain the normalized multipath energy distribution vector; Write the template lifecycle field: the version number is initially V1.0, the training timestamp records the current system time, the validity period is 30 days by default, and the initial credibility score is set to 80 points.

[0078] After generating the initial template, it must pass validation before it can enter the valid state. A matching test is performed using 10 additional echo frames collected under the same conditions. If the matching success rate is ≥90%, the verification is passed. For templates that fail validation, re-acquire training echoes and generate new templates; Templates that pass verification are stored in the multi-state echo template library according to the index of "location ID + status label".

[0079] In this embodiment, the execution flow of the downgraded receiving mode is as follows: Enable a wide receive window that covers the entire effective delay range. The window width is equal to the maximum delay spread of the system, and the weight within the window is always 1. Perform global energy accumulation on the current echo and calculate the total energy value; Preset in-service decision threshold ,in, The duration of a single frame; B is the noise one-sided power spectral density; B is the receiving system bandwidth; coefficient 9 is the amplitude domain. The criterion corresponds to the square relationship of the energy domain; If the total energy is greater than or equal to the in-situ decision threshold, then the "terminal in-situ" flag is output along with the "reception reliability degraded" flag, and the complete short packet demodulation result is not output. If the total energy is less than the in-situ decision threshold, then output a "terminal suspected to be offline" flag and report it to the monitoring platform; Simultaneously mark all templates at this location as pending review, record the number of consecutive mismatches and the duration of the mismatch, and trigger the template lifecycle management process.

[0080] In this embodiment, the quantitative implementation rules for template lifecycle management are as follows: Credibility scoring rules: Each template is configured with a credibility score ranging from 0 to 100, and the dynamic update rules are as follows: Among them, a successful match Match failed ; Validity period rules: Dynamic validity period: ,in, Assign a credibility score, with a value range of 0 to 100. This represents the score increment after a single match. The template has a dynamic validity period, in days. The base validity period is 90 days by default; As a baseline for credibility, a score of 80 is used. State transition quantization threshold: The template transitions through a state machine from initialization state, valid state, pending review state, invalid state, and retraining state, with the following trigger thresholds: Initialized state → Valid state: Template verification matching success rate ≥ 90%; Valid state → pending verification state: consecutive matching failures ≥ 5 times, or confidence score ≤ 50 points; Pending review status → Valid status: Successful matching ≥ 5 times consecutively, and the credibility score rises back to 70 points or above; Pending review status → Invalid status: consecutive matching failures ≥15 times, or confidence score ≤15 points; Failure state → Retraining state: The gateway automatically sends a training command, triggering the terminal to resend the training sequence; Retraining state → Initialization state: Reacquire training echoes to generate a new version template, with the version number incremented.

[0081] Retraining interaction process: When template-triggered retraining occurs, the interaction process between the gateway and the terminal is as follows: The gateway sends a retraining instruction to the target terminal, which includes an identifier for the number of training sequences. After receiving the instruction, the terminal switches the impedance according to the rules to send the training sequence; The gateway collects training echoes and generates a new version template, which replaces the old template after verification. The old template will be converted to historical archive status and retained for 7 days for retrospective analysis.

[0082] This invention provides a multi-state template short packet receiving gateway for fixed-location terminals, such as... Figure 7 As shown, it includes: The excitation and radio frequency transceiver unit is used to send excitation signals to the backscatter terminal and receive the backscattered echoes returned by the terminal. The template library construction unit is used to extract echo features under various states from the training echoes, generate static echo templates, and build a multi-state echo template library indexed by point location and state. The template matching unit is used to extract at least two echo features of the current echo, calculate the feature distance with each state template in the template library, and filter the target matching template that meets the matching threshold. The three-level window generation unit is used to generate three-level time-domain receiving windows—main path receiving window, near-end secondary path weighted window, and late secondary path suppression window—based on the target matching template differentiation. The graded receiving and processing unit is used to perform graded weighting processing on the echo according to the three-level time domain receiving window and output the enhanced received signal. The downgrade decision unit is used to perform a wide-window coarse-grained energy decision when all templates fail to match, output the terminal in-situ detection result, set the template to be reviewed, and trigger template lifecycle management. The demodulation processing unit is used to perform short packet detection, demodulation, and verification on the enhanced received signal.

[0083] Preferably, it also includes: a template lifecycle management unit, used to maintain the version number, training timestamp, validity period, and credibility score fields of each template, control the state transition of the template between the initialization state, the valid state, the pending review state, the invalid state, and the retraining state, and trigger the template retraining process.

[0084] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for receiving multi-state template short packets for fixed-location terminals, applied to gateway devices, characterized in that: include: During the installation and binding, initial network access, or retraining phases of the backscatter terminal, the training backscatter echo returned by the backscatter terminal based on the excitation signal is received. The echo characteristics of the same fixed point terminal under various physical environment conditions are collected, and static echo templates corresponding to each state are generated. A multi-state echo template library indexed by point identifier and state label is constructed. When a backscatter state short packet is received from the terminal, at least two echo features are extracted from the currently received echo, and the feature distances are calculated with the corresponding state templates in the multi-state echo template library. The template with the smallest feature distance is selected as the candidate template. If the feature distance of the candidate template meets the preset matching threshold, it is determined as the target matching template. Based on the target matching template, a differentiated three-level time-domain receiving window is generated, which includes, in sequence, the main path receiving window, the near-end secondary path weighting window, and the late secondary path suppression window; The current echo is processed in stages according to the three-level time domain receiving window to obtain the enhanced received signal and then sent into the short packet demodulation process. If the feature distance of all state templates does not meet the preset matching threshold, the mode is downgraded and a coarse-grained energy decision is performed using a wide window. The terminal in-situ detection result is output, and the template is marked as pending review, triggering the template lifecycle management process.

2. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, The state labels in the multi-state echo template library include: open state, closed state, obstructed state and weak coverage state, and each state label corresponds to a different stable physical environment around the point. The static echo template includes at least the main path delay parameter and the multipath energy distribution parameter.

3. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, The echo characteristics include at least two of the following: main path drift, late path energy ratio, correlation peak amplitude statistics, window width, link quality level, and phase statistics. The characteristic distance is the weighted sum of the characteristic distances of each echo. The main path drift is calculated based on the difference between the main path delay of the current echo and the template, and the late path energy ratio is calculated based on the ratio of the multipath energy to the total echo energy within a preset delay range after the main path.

4. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, The three-level time-domain receiving window is configured based on the principal path delay in the target matching template: The main path receiving window covers the time domain interval where the main path peak is located, in order to retain the effective signal of the main path; The proximal secondary path weighted window covers the proximal reflection multipath region after the main path, and the weighting coefficient is determined by the proportion of proximal multipath energy in the target matching template; The late secondary path suppression window covers the time delay interval outside the near secondary path weighting window and is used to suppress late multipath interference caused by far-end reflections.

5. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, The downgraded reception mode includes: A wide receiving window covering the entire effective time delay range is used to perform echo energy accumulation and existence determination; If the energy accumulation result meets the in-situ decision threshold, the terminal in-situ identifier and the reception reliability degradation flag are output, and the complete short packet demodulation result is not output. Synchronously trigger the template pending review status mark, and record the number of consecutive mismatches and the duration of the mismatch.

6. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, Each static echo template is configured with lifecycle management fields, including template version number, training timestamp, validity period, and reliability score. The template lifecycle is managed according to a state machine transition from initialization state, valid state, pending review state, invalid state, to retraining state, including: After the template is initially generated, it enters the initialization state. After passing the verification, it transitions to the valid state. When the number of consecutive matching failures reaches the first threshold, the system transitions to a pending review state. When the number of consecutive matching failures reaches the second threshold or the validity period is exceeded, it becomes invalid. The failed template triggers the retraining process, which re-acquires training echoes, generates a new template, and then returns to the initialization state. When the template is in the pending verification state, the gateway device will continuously attempt template matching during subsequent reception. If multiple matches are successful consecutively and the credibility score rises back above the threshold, the system returns to the valid state. If the mismatch persists, the system will transition to a failure state and trigger retraining.

7. The method for receiving multi-state template short packets for fixed-location terminals according to claim 1, characterized in that, The training backscatter echo is generated by the terminal by switching the radio frequency impedance state. The passive terminal switches the impedance according to a preset training sequence when triggered by an excitation signal. The semi-passive terminal extends the length of the training sequence or increases the number of repetitions when the local energy storage meets a preset threshold, thereby enhancing the detectability of the echo.

8. A multi-state template short packet receiving gateway for fixed-location terminals, characterized in that, include: The excitation and radio frequency transceiver unit is used to send excitation signals to the backscatter terminal and receive the backscattered echoes returned by the terminal. The template library construction unit is used to extract echo features under various states from the training echoes, generate static echo templates, and build a multi-state echo template library indexed by point location and state. The template matching unit is used to extract the echo features of the current echo, calculate the feature distance with each state template in the template library, and filter the target matching template that meets the matching threshold. The three-level window generation unit is used to generate three-level time-domain receiving windows—main path receiving window, near-end secondary path weighted window, and late secondary path suppression window—based on the target matching template differentiation. The graded receiving and processing unit is used to perform graded weighting processing on the echo according to the three-level time domain receiving window and output the enhanced received signal. The downgrade decision unit is used to perform a wide-window coarse-grained energy decision when all templates fail to match, output the terminal in-situ detection result, set the template to be reviewed, and trigger template lifecycle management. The demodulation processing unit is used to perform short packet detection, demodulation, and verification on the enhanced received signal.

9. The multi-state template short packet receiving gateway for fixed-location terminals according to claim 8, characterized in that, The template lifecycle management unit is used to maintain the version number, training timestamp, validity period, and credibility score fields of each template, and to control the state transition of the template between the initialization state, the valid state, the pending review state, the invalid state, and the retraining state, and to trigger the template retraining process.

10. A multi-state template short packet receiving system for fixed-location terminals, characterized in that, include: At least one fixed backscattering terminal is used to return training echoes and short state packets via backscattering when triggered by an excitation signal. At least one gateway device according to claim 8 or 9 is used to execute the multi-state template short packet receiving method according to any one of claims 1-7; a monitoring platform is communicatively connected to the gateway device and is used to receive short packet demodulation results, terminal presence information and template status data reported by the gateway.

Images