UWB time offset synchronization method based on two-factor dynamic adjustment

Abstract

The invention belongs to the technical field of integrated circuits, and discloses a UWB (Ultra Wideband) time offset synchronization method based on two-factor dynamic adjustment, which is based on two-dimensional decision logic of time offset error amplitude and error change rate, combines a hysteresis counting check mechanism, dynamically switches loop amplification coefficients k1 and k2 and a reference coefficient, and realizes time offset synchronization. Accurate adaptation of stable adjustment of conventional errors and quick response of burst errors is realized, and while quick convergence is ensured to cope with time-bias sudden change, steady-state jitter is effectively suppressed, invalid power consumption is reduced, synchronization robustness and communication reliability under a complex channel are remarkably improved, and the overall performance of the system is comprehensively optimized.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology, specifically relating to a UWB time offset synchronization method based on two-factor dynamic adjustment. Background Technology

[0002] Ultra-wideband (UWB) technology uses nanosecond-level non-sinusoidal narrow pulses as its transmission medium. With its significant advantages such as strong anti-interference capabilities, high positioning accuracy, and extremely low power consumption, it occupies an important position in the field of short-range wireless communication. As the technology matures, UWB chips have not only achieved large-scale application in smart terminals and smart cars, but also shown broad prospects in the consumer electronics market, becoming a key technology for enhancing the "spatial awareness" capabilities of devices.

[0003] As a revision of the IEEE 802.15.4 protocol, IEEE 802.15.4a introduced a completely new physical layer scheme. This standard not only improves data transmission rates and communication distances and optimizes interference immunity, but also supports low-rate wireless personal area network applications based on ranging information. It is the first international standard to incorporate precise ranging into the physical layer specification. Figure 1 As shown, the UWB data frame structure specified in IEEE 802.15.4a consists of three parts: a synchronization header (SHR) for synchronization, a physical layer header (PHR) indicating frame information and ranging, and a payload carrying the actual data. The SHR comprises a synchronization sequence SYNC (also commonly called a preamble) and a frame delimiter (SFD), with SYNC occupying the majority of the SHR's length. The standard defines 24 SYNC sequences (sequences 1-8 are 31 characters long, and sequences 9-24 are 127 characters long) and 8 optional numbers of synchronization symbols (ranging from 256 to 2048).

[0004] At a communication rate of 6.8 Mb / s, the system requires a SYNC sequence of length 127. At this point, each symbol in the data portion contains an average of two bursts, while the corresponding value for the SHR portion is 508. This means that the average pulse repetition frequency (MPRF) of the preamble portion is as high as 62.89 MHz, far exceeding the 15.6 MHz of the PHR and payload portions. While the high MPRF supports high-speed transmission, it also exacerbates the risk of signal distortion in multipath environments. Without an effective time offset compensation mechanism to assist channel estimation and matched filtering, it will be difficult to obtain the maximum output signal-to-noise ratio, leading to unpacking failure and severely affecting the stability of the communication system. The automatic time offset compensation module is located between the SHR synchronization module and the demodulation module, and its performance directly determines the accuracy of synchronization frame detection and the quality of data parsing. Current UWB chips need to achieve low-power, low-cost operation in complex and variable channel environments. Traditional frequency offset and time offset compensation schemes are no longer sufficient to meet these requirements, failing to guarantee the system's adaptability and real-time performance. Figure 2 As shown. Problems such as non-convergence or unpacking errors may also occur, severely degrading the performance of UWB baseband communication. Specifically, traditional time offset compensation processing modes have two major flaws: First, the algorithms generally assume that the received signal segment starts at the synchronization part (SYNC), but in actual communication, the signal may start at any position such as the data segment, resulting in insufficient robustness; second, mainstream time offset synchronization algorithms each have limitations. For example, the Muller & Muller algorithm only requires one sampling point for synchronization, making it suitable for high-speed communication, but it has high requirements for carrier frequency accuracy, is complex to implement, and its performance depends on the frequency synchronization accuracy; the late-early gate algorithm has a simple principle and low complexity, but it requires at least three sampling points, has mediocre performance, and cannot adapt to high-speed communication; the traditional Gardner algorithm only requires two sampling points for synchronization and is insensitive to carrier frequency offset and phase shift, but in scenarios with consecutive identical symbols, the synchronization time is prolonged, stability decreases, and performance is significantly degraded. Summary of the Invention

[0005] To address the aforementioned technical issues, this invention provides a UWB time offset synchronization method based on dual-factor dynamic adjustment. This method utilizes a dual-dimensional decision logic based on the magnitude and rate of change of the time offset error, combined with a hysteresis counting verification mechanism. It dynamically switches the loop amplification coefficients k1 and k2 with the baseline coefficient, achieving precise adaptation of "smooth adjustment for normal errors and rapid response to sudden errors." While ensuring rapid convergence to cope with sudden time offset changes, it effectively suppresses steady-state jitter, reduces ineffective power consumption, significantly improves synchronization robustness and communication reliability under complex channels, and comprehensively optimizes the overall system performance.

[0006] The present invention discloses a UWB time offset synchronization method based on two-factor dynamic adjustment, comprising the following steps: Step 1: Calculate the number of time-domain sampling points Ls corresponding to the SYNC symbol (i.e., the total number of samples obtained after sampling a single SYNC symbol by the ADC). Select the SYNC sequence consistent with the transmitter as the local reference code. Perform the same repeated extension and time-domain sampling simulation operation as the transmitter on the local reference code to generate a sequence template Sc with a length that perfectly matches Ls. This accurately reproduces the time-domain sampling structure of the SYNC symbol in actual transmission. Step 2: Employ the sampling-point sliding correlation algorithm to analyze the discrete sampled signal containing the SYNC symbol acquired by the receiver. (n is the sampling point index, Ts is the sampling period), and perform related accumulation calculations with the sequence template Sc. Compare with the current maximum value through a comparator to update the maximum value and its position in real time. If the maximum peak value exceeds the preset decision threshold, the coarse synchronization is determined to be successful, and the time corresponding to the peak value is taken as the optimal sampling phase. The improved Gardner timing synchronization algorithm is triggered to perform time-biased synchronization (which is a timing synchronization algorithm with an interpolation closed-loop feedback structure). Step 3: Based on the improved Gardner timing synchronization algorithm, the SYNC symbol synchronization sampling value is first output through the piecewise parabolic interpolation filter of the Gardner feedback loop; then the timing error signal is extracted by the Gardner error detection module, and the error change rate is calculated. Combined with the two-factor threshold judgment strategy, the proportional term coefficient of the loop filter is dynamically selected to generate the NCO control signal to adjust the interpolation position and approach the optimal sampling point, so as to achieve fast and accurate synchronization convergence of UWB time offset.

[0007] Furthermore, in step 1, if the duration of a single SYNC symbol is Tpsym and the sampling period is Ts, then the number of sampling points for a single SYNC symbol is... ; Based on the configuration, the sequence {ck} identical to that of the transmitter is selected as the local code. This process is repeated N times to generate a sequence template Sc of length Ls, mathematically expressed as: , Among them, the repetition factor .

[0008] Furthermore, step 2 specifically involves: When discrete sampled signal When inputting one by one, the receiver will receive the sampled signals. Each time, a sliding window of length Ls is sequentially stored, and related cumulative calculations are performed with the sequence template Sc, as shown in the following formula: , Where Sc(i) is the value of the i-th element in the sequence template Sc; y(i+j) is the received discrete sampled signal. In the diagram, n represents the sample value at time i+j, and n is the sampling point index. g(j) is the correlation value at the current time offset j. When g(j) reaches its maximum value, i.e., a coherent peak appears, it indicates that the receiver has detected the SYNC sequence. This is because the SYNC sequence has good autocorrelation, and a clear coherent peak will appear when SYNC is detected. The maximum value and its position are updated in real time by comparing it with the current maximum value through a comparator. When the maximum peak value exceeds the preset decision threshold, coarse synchronization is determined to be successful, i.e., the position of SYNC is found in the received signal.

[0009] Furthermore, in step 3, the fixed sampling clock frequency of the receiver is... Its output discrete sequence is considered as a sample of the continuous analog signal y(t); due to the time offset between the sampling clock and the received signal, this discrete sequence is an asynchronous sequence; the interpolator's task is to use a polynomial fitting algorithm to calculate the continuous signal y(t) at the synchronization time. The amplitude at the point (where k is the integer index of the output symbol sequence and Ti is the interpolation adjustment interval period); based on the interpolator's operational foundation, interpolation and resampling operations are performed on the asynchronous sequence through the interpolation filter of the feedback loop, outputting the synchronous sampled value at the SYNC symbol decision time: ; in, The output signal of the interpolation filter. and This refers to the support range of the interpolation filter. For local sampling clock cycles, The sequence of numbers after analog-to-digital conversion. Unit impulse response; basic index fractional interval Interpolation filter according to and The value of the input signal is continuously corrected, so that the entire system continuously adjusts the timing through feedback, thereby obtaining the correct interpolation point and the sampled value obtained by interpolation.

[0010] Furthermore, in step 3, the timing error is calculated using the following formula: , , , in, This is a timing error signal. and These represent the timing error estimates calculated independently based on the in-phase component (I-path) and the quadrature component (Q-path), respectively. and These are the sampling point values ​​of the I and Q paths at the corresponding sampling time; When the actual sampling time lags behind the optimal decision point, the midpoint sampled value y(k−1 / 2) is biased towards the energy distribution of the current symbol, resulting in... and If all values ​​are positive, or at least their sum is positive, then the sampling time needs to be adjusted forward (to the left of the time axis) through the interpolation filter to reduce the lag bias. When the actual sampling time precedes the optimal decision point, the midpoint sampled value y(k−1 / 2) is biased towards the energy distribution of the previous sign, leading to... and If all values ​​are negative, or at least their sum is negative, then the sampling time needs to be adjusted backward (to the right of the time axis) through an interpolation filter to reduce the lead bias. When the error signal approaches 0, it indicates that the sampling time is close to the optimal decision point, the time deviation is within the allowable range, and the synchronization loop has entered a stable state.

[0011] Furthermore, in step 3, when the loop filter in the Gardner feedback loop receives the error signal... Then, first cache the error from the previous time step. And calculate the rate of change of error: ; Based on the error amplitude threshold and rate of change threshold Make a judgment: like proportionality coefficient Maintain benchmark value ; like and , use ; like and , use ; Among them, the magnification factor , The SYNC symbol judgment result is verified by a hysteresis counter. When two consecutive SYNC symbols meet the two-factor judgment condition, the corresponding amplification coefficient (k1 or k2) switching operation is executed. When one symbol meets the condition, the reference value is restored. The error signal after being processed by the loop filter is used to control the numerically controlled oscillator NCO.

[0012] The beneficial effects of this invention are as follows: 1) Optimize the synchronization hierarchy design and improve synchronization accuracy and efficiency through a two-step execution strategy of "coarse synchronization + fine synchronization": First, a sliding correlation algorithm is used to complete coarse synchronization, quickly lock the approximate position of the UWB frame SHR, and control the timing error within a small range, laying the foundation for subsequent accurate compensation; on this basis, an optimized Gardner timing synchronization algorithm is introduced to perform fine synchronization, and subsampling-level timing accuracy is achieved through precise calibration of residual timing offset, effectively making up for the accuracy shortcomings of traditional single synchronization algorithms and fully meeting the core requirement of UWB system for high timing accuracy; 2) Optimize synchronization adaptability and reliability: Utilize the characteristic that the SYNC sequence does not have long strings of consecutive 0 or 1 symbols to form an efficient fit with the working mechanism of the Gardner algorithm. The Gardner algorithm relies on signal inflection points to achieve synchronization, while this sequence characteristic ensures the diversity of time-domain signals and the clarity of inflection points, avoiding false synchronization from the source. At the same time, the precise initial synchronization position provided by the sliding correlation algorithm further reduces the search complexity and error risk of the fine synchronization process, significantly improving the stability and reliability of the synchronization results. 3) Optimize time offset tracking and channel adaptability: Through a two-factor decision logic of "time offset error amplitude + error change rate", the loop reference proportional coefficient c0 is dynamically adjusted to generate amplification coefficients k1 and k2 adapted to different scenarios: in normal small error scenarios, the reference coefficient is maintained to ensure steady-state accuracy; in large error slowly changing scenarios, k1 is activated to accelerate convergence; in large error rapidly changing scenarios, k2 is activated for emergency compensation to achieve fast convergence. This design enhances the system's robustness to complex channels such as multipath interference and low signal-to-noise ratio, while taking into account the simplicity and compatibility of engineering implementation. It significantly improves the accuracy of time offset compensation and scenario adaptability while reducing ineffective power consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the UWB frame structure specified in the IEEE 802.15.4a protocol; Figure 2 This is a flowchart of signal synchronization processing in traditional design; Figure 3 This is a flowchart of the signal synchronization processing part of the present invention using two-factor dynamic adjustment; Figure 4 This is a two-factor decision-making flowchart; Figure 5 It is a loop structure diagram; Figure 6 This is a structural diagram of the improved loop filter module; Figure 7 This is a Farrow structure diagram of a linear interpolation filter; Figure 8 This is the Farrow structure diagram of the piecewise parabolic interpolation filter (β=0.5). Figure 9 These are the impulse response diagrams of linear interpolation filters and piecewise interpolation filters; Figure 10 This is a schematic diagram of the convergence curve before the improvement, where the number of Preamble synchronizations was 2048. Figure 11 This is a schematic diagram of the convergence curve after the Preamble synchronization number is improved to 2048. Figure 12 This is a comparison chart of packet error rates under two different time-biased modules. Detailed Implementation

[0014] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0015] like Figure 3 He Ru Figure 4 As shown, the UWB time offset synchronization method based on two-factor dynamic adjustment described in this invention includes the following steps: Step 1: This invention addresses the case where the UWB system synchronization preamble sequence length is 127 as specified in the IEEE 802.15.4a protocol. With a preamble MPRF of 62.89MHz, a single Symbol contains a fixed 508 effective pulses, and the synchronization count is set to 256, with a signal-to-noise ratio of -5dB. When the signal enters the SHR symbol detection module, the basic parameters of the frequency offset and time offset modules are initialized. A local SYNC (Preamble) sequence consistent with the transmitter is generated according to the IEEE 802.15.4a protocol, with a length matching the transmitter's SYNC period. The duration Tpsym of the preamble symbol and the sampling period Ts, determined by the ADC integration and dump characteristics, are determined based on the basic parameters. Based on these two parameters, the number of sampling points Ls for a single preamble symbol is calculated (formula: Ls = Tpsym / Ts). This value affects the accuracy and matching effect of subsequent template construction. Next, the repetition factor N is calculated (formula N=Ls / Kpbs), and then the sequence consistent with the transmitter is selected as the local code ck according to the configuration. The repetition operation is performed on it N times, and finally a template Sc with a length of Ls is generated. Step 2: When inputting samples y(nTs) one by one, receive discrete sampling signals. The received samples will be divided into continuous segments of length Ls. A sliding correlation algorithm will be used to divide the received samples... The data is sequentially stored in a sliding window matching the template length, and then accumulated with the template sc (y(j) is the received signal sampling sequence, Sc(i) is the local Preamble sequence, Ls is the Preamble length, and j is the sliding step size of one sampling interval). Each time a new g(j) is calculated, a clear coherent peak will appear when the Preamble is detected due to the good autocorrelation of the Preamble sequence. The maximum value and its position are updated in real time by comparing it with the current maximum value through a comparator. When three consecutive Symbols detect a coherent peak, the detection is considered successful, coarse synchronization is completed, and the SYNC position is found in the received signal. Step 3: Based on the improved Gardner timing synchronization algorithm, the SYNC symbol synchronization sampling value is first output through the piecewise parabolic interpolation filter of the Gardner feedback loop; then the timing error signal is extracted by the Gardner error detection module, and the error change rate is calculated. Combined with the two-factor threshold judgment strategy, the proportional term coefficient of the loop filter is dynamically selected to generate the NCO control signal to adjust the interpolation position and approach the optimal sampling point, so as to achieve fast and accurate synchronization convergence of UWB time offset.

[0016] After successfully aligning the received signal at the symbol level using the SYNC function, a small timing offset error remains, affecting the precise adjustment of the signal. To further improve synchronization accuracy, the coarsely synchronized signal segment is passed through the Gardner feedback loop, such as... Figure 5 As shown. The improved loop filter module has the following structural components, as follows: Figure 6 As shown, this invention improves the response speed to time offset abrupt changes and reduces synchronization jitter by adding a real-time error change rate calculation substructure to the traditional loop filtering module and embedding a two-factor threshold determination and hysteresis check unit. The interpolation filter also plays a crucial role in timing synchronization performance. This component performs low-pass filtering and resampling on the digital signal sequence sampled by the local clock to convert it into a digital signal sequence synchronized with the symbol rate. This process effectively solves the problem of aliasing between the sampling rate and the signal spectrum, and is the main signal processing part for adjusting the stability of the Gardner feedback loop. The fixed sampling clock frequency at the receiving end is Ts, and for y(t) in... Resampling is performed at time t, and the interpolation formula is: , Where Ti is the interpolation period, and the basic index is... The fraction interval is The interpolation filter is based on... and The value continuously corrects the input signal, allowing the entire system to continuously adjust the timing through feedback, thereby obtaining the correct interpolation point and the interpolated sampled value. This invention uses a polynomial function to implement the interpolation filter. The polynomial interpolation method constructs an approximate interpolation polynomial based on given discrete data points. This interpolation polynomial is then used to interpolate the given input signal, thus realizing the function of the interpolation filter. This Gardner timing synchronization interpolation filter design selects a piecewise parabolic interpolation filter, which has continuous amplitude and slope, small interpolation error, low timing synchronization jitter, and is suitable for high-precision communication scenarios such as UWB. Figure 7 As shown; however, linear interpolation has large errors, and its synchronization accuracy and stability are relatively weak, such as... Figure 8 As shown; their impact responses are as follows Figure 9 As shown, piecewise parabolic interpolation filters, with their smooth and continuous impulse response, superior frequency domain characteristics, and the engineering advantages of piecewise low-order design, can achieve higher timing synchronization accuracy and anti-interference capability with moderate complexity compared to linear interpolation filters.

[0017] The sampled signal is divided into two paths: the I-path real part of the co-directional component and the Q-path imaginary part of the quadrature component, for processing. This allows for better utilization of signal amplitude and phase information, improving the performance of the synchronization algorithm. Two sampling points are used within each symbol period: the strobe point (optimal sampling point) and the midstrobe point (sampling point between the two observation points). The timing error is calculated using these sampling points, as follows: , , , Timing error signal The magnitude and sign of the value reflect the deviation of the current sampling time from the optimal sampling time. When the actual sampling time lags behind the optimal decision point, the midpoint sample value... It will bias the energy distribution of the current symbol, leading to and All are positive (or at least their sum is positive). In this case, the sampling time needs to be adjusted forward (to the left of the time axis) using an interpolation filter to reduce lag bias. When the actual sampling time leads the optimal decision point, the midpoint sampled value... It will bias the energy distribution towards the previous sign, leading to and All values ​​are negative (or at least their sum is negative). At this point, the sampling time needs to be adjusted backward (to the right of the time axis) using an interpolation filter to reduce the lead error. When the error signal approaches 0, it indicates that the sampling time is close to the optimal decision point, the time offset is within the allowable range (usually subsampling level accuracy), and the synchronization loop enters a stable state.

[0018] The calculated I-channel and Q-channel timing error signals and The error signal is input into the loop filter. The loop filter's function is to smooth the error signal, remove noise and interference, and adjust the amplitude and phase characteristics of the error signal according to system requirements. When the loop filter receives the error signal e(k), it first buffers the error from the previous time step. And calculate the rate of change of error. Then, based on the error amplitude threshold and rate of change threshold To determine, T is the UWB symbol period: if proportionality coefficient Maintain benchmark value ;like and , use ;like and , use Where k1=1.5 and k2=2.0. At the same time, a hysteresis counter is used to switch to the amplification factor only when two consecutive symbols meet the condition, and to restore the reference value when one symbol meets the condition. The error signal after being processed by the loop filter is used to control the numerically controlled oscillator (NCO).

[0019] The NCO adjusts the phase and frequency of its output clock signal based on the received error signal, thereby controlling the interpolation filter to perform interpolation operations on the I and Q signals. The purpose of interpolation is to insert new sampling points between the original sampling points based on the current timing error, so that the sampling time gradually approaches the optimal sampling time. By continuously repeating the above process—calculating the timing error, performing loop filtering, and adjusting the NCO and interpolation filter—the timing error e(k) gradually decreases, eventually converging to a very small range. When the timing error meets the preset accuracy requirements, high-precision fine synchronization is considered to have been achieved. At this point, the sampling times of the I and Q signals are very close to the optimal decision time and can be used for subsequent accurate signal demodulation.

[0020] So far, steps 1 to 5 constitute a complete automatic time offset compensation loop. Repeating steps 1 to 5 will complete the time offset tracking and compensation of the UWB signal under the current channel environment.

[0021] The method described in this invention was used to conduct simulation experiments in an algorithm simulation system for UWB chips. The simulation system includes a frame generation module, a pulse formation module, a simulation channel module, an AD module, a synchronization module, a time offset compensation module, and a depacketization module. The actual effectiveness of the method described in this invention was verified through data packet transmission and reception simulations.

[0022] (1) Simulation experiments to verify the effectiveness of the time-biased compensation algorithm;

[0023] According to the IEEE 802.15.4a protocol for HRP-UWB communication systems, the simulation system's transmitter is configured to operate in BPRF mode with a data rate of 6.80 Mbps. In this mode, the MPRF of the preamble is 62.89 MHz, and the MPRF of the data portion is 15.60 MHz. To simulate a complex channel environment with high noise levels, the simulation channel is configured with a signal-to-noise ratio (SNR) of -5 dB, a time offset of 10 PPM (Percent Per Million), and a data packet length of 60 bytes. The IEEE 802.15.4a protocol uses a 127-bit preamble sequence with sequence number 18, and an 8-bit SFD sequence with sequence number 2 for simulation testing.

[0024] In digital baseband time-off synchronization simulation tests, the convergence curve is the core basis for intuitively evaluating the stability of the module under the current channel environment, and its morphological characteristics can directly reflect the effectiveness of the time-off compensation mechanism.

[0025] For ultra-wideband (UWB) systems, synchronization convergence time is a key performance indicator affecting their adaptability to low-power applications. In typical low-power devices such as IoT sensors and positioning tags, the power consumption control of the baseband chip directly determines the device's battery life: if the time-off synchronization convergence time is too long, the chip will continuously maintain a high computational load, significantly increasing ineffective power consumption, which contradicts the design intent of "low power consumption and long standby time" for such devices. At the same time, an excessively long convergence process may also prolong the signal demodulation preparation cycle, indirectly affecting the real-time performance and reliability of data transmission. Therefore, precise control of the synchronization convergence time is not only an important dimension for measuring the performance of the time-off synchronization algorithm, but also a core prerequisite for the engineering implementation of UWB technology in low-power scenarios.

[0026] Time offset error has a cumulative characteristic. If the synchronization algorithm responds late, the accumulation of error will lead to symbol sampling misalignment, demodulation constellation shift, and ultimately convergence failure. Figure 10 This demonstrates the convergence process of the traditional scheme at 2048 Preamble synchronization attempts. Due to the rapid accumulation of errors, convergence fails, ultimately resulting in synchronization failure. Figure 11 The convergence curve of the present invention is shown: the time offset is initially controlled within ±1ns by sliding correlation coarse synchronization, and the subsequent two-factor dynamic scaling c0 mechanism of Gardner loop can match the time offset change trend in real time, which solves the problem of convergence failure due to insufficient number of Preamble synchronizations in traditional methods.

[0027] Simulation results show that the proposed solution, through a hierarchical architecture of "sliding correlation coarse synchronization fast acquisition + dual-factor dynamic scaling c0 fine tuning", not only solves the problem of short-term preamble convergence failure in traditional solutions, but also avoids the power consumption risk of excessively long convergence time under long-term preamble. It can dynamically adapt to the time offset variation characteristics of complex UWB multipath channels and improve the synchronization robustness of the baseband chip in complex environments.

[0028] (2) Verification of the performance of the partial synchronization scheme under different signal-to-noise ratios;

[0029] The core advantage of this invention compared to traditional time-off synchronization methods lies in its ability to adaptively match synchronization requirements under different signal-to-noise ratio (SNR) scenarios by dynamically adjusting c0 using a two-factor approach. At high SNR, a baseline c0 ensures accuracy, while at low SNR, a graded amplification factor enhances anti-interference capabilities. This overcomes noise interference with time-off estimation and avoids performance degradation of fixed coefficients at low SNR, balancing low power consumption and communication reliability. Based on the IEEE 802.15.4a protocol specification, the simulation system's transmitter is still configured in BPRF mode with a data rate of 6.80 Mbps. In this configuration, the MPRF of the preamble is 62.89 MHz, and the MPRF of the data portion is 15.60 MHz. To simulate a complex channel environment with high noise levels, the initial signal-to-noise ratio was configured as -5dB, with a step value of -1dB, cutoff to -15dB, and a time offset of 10PPM (Percent Per Million). The simulation test used an SFD sequence with sequence number 18 and a length of 127 bits as the preamble and sequence number 2 and a length of 8 bits as the SFD sequence in the IEEE 802.15.4a protocol. The data packet length was 60 bytes, and 1000 data packets were tested each time.

[0030] Figure 12 The performance comparison between the conventional solution and the solution of this invention in receiving BPRF mode signals is demonstrated: when the signal-to-noise ratio (SNR) is greater than -13dB, the solution of this invention receives 1000 data packets without any packet errors or bit errors; when the SNR drops to -14dB, the system packet error rate is only 3%; and the overall performance only deteriorates significantly when the SNR is below -16dB. In contrast, the conventional solution exhibits packet errors when the SNR is below -5dB. The solution of this invention achieves a 7-8dB improvement in SNR performance compared to the conventional solution, ensuring that the UWB communication baseband can still operate stably in complex environments with high noise and strong multipath propagation.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to further limit the present invention. All equivalent changes made based on the description and drawings of the present invention are within the protection scope of the present invention.

Claims

1. A method for UWB time offset synchronization based on double-factor dynamic adjustment, characterized in that, The method comprises the following steps: Step 1, calculate the number of time domain sampling points Ls corresponding to the SYNC symbol, select the same SYNC sequence as the local reference code as the transmitting end, and generate a sequence template Sc with the same length as Ls by performing the same repeated expansion and time domain sampling simulation operation on the local reference code. Step 2, using the sampling point by sampling point sliding correlation algorithm, the discrete sampling signal containing the SYNC symbol collected by the receiving end correlation accumulation calculation is performed with the sequence template Sc, comparison is performed with the current maximum value through a comparator, and the maximum value and its position are updated in real time; if the maximum peak value exceeds a preset decision threshold, it is determined that the coarse synchronization is successful, and the time corresponding to the peak value is taken as the optimal sampling phase; Step 3, based on the improved Gardner timing synchronization algorithm, first output the SYNC symbol synchronization sampling value through the segmented parabolic interpolation filter of the Gardner feedback loop; then extract the timing error signal through the Gardner error detection module, and then calculate the error rate, combine the double-factor threshold judgment strategy to dynamically select the loop filter proportional term coefficient, generate the NCO control signal to adjust the interpolation position and approach the best sampling point, and finally realize the fast and accurate synchronization convergence of the UWB time offset.

2. The UWB time offset synchronization method based on double-factor dynamic adjustment according to claim 1, characterized in that, In step 1, the duration of a single SYNC symbol is Tpsym, and the sampling period is Ts, then the number of sampling points of a single SYNC symbol is ; According to the configuration selection and the same sequence {ck} as the transmitting end, execute N times of repeated operation to generate a sequence template Sc with a length of Ls, and the mathematical expression is: ， wherein the repetition factor .

3. The UWB time offset synchronization method based on double-factor dynamic adjustment according to claim 2, characterized in that, Step 2 is specifically: When the discrete sampling signal The receiver will receive the sampling signal Each time, the length of the sliding window Ls is stored in sequence, and the correlation accumulation calculation is performed with the sequence template Sc, and the formula is as follows: ， where Sc(i) is the value of the i-th element in the sequence template Sc; y(i+j) is the received discrete sampling signal where y(i+j) is the sample value at time i+j, n is the sampling point index; g(j) is the correlation value at the current time offset j, when g(j) reaches the maximum value, i.e. the coherent peak, it indicates that the receiver has detected the SYNC sequence; through the comparator, the maximum value and its position are updated in real time; when the maximum peak exceeds the preset decision threshold, it is determined that the coarse synchronization is successful, i.e. the position of the SYNC in the received signal is found.

4. The UWB time offset synchronization method based on double-factor dynamic adjustment according to claim 3, characterized in that, In step 3, the segmented parabolic interpolation filter of the Gardner feedback loop is used to perform interpolation operation and resampling operation on the non-synchronous sequence to output the synchronization sampling value at the SYNC symbol judgment time: ； wherein is the output signal of the interpolation filter, and is the support range of the interpolation filter, is the digital sequence after analog-digital conversion, is the unit impulse response; basic index , fractional interval ; the interpolation filter constantly corrects the input signal according to the values of and , so as to obtain the correct interpolation point and the sampling value obtained by interpolation.

5. The UWB time offset synchronization method based on double-factor dynamic adjustment according to claim 3, characterized in that, In step 3, the timing error calculation formula is as follows: ， ， ， wherein is a timing error signal, and respectively represent timing error estimates independently calculated based on the in-phase component, i.e. I-path, and the quadrature component, i.e. Q-path, and are the sample point values of the I-path and Q-path corresponding to the sampling instant, respectively. When the actual sampling time lags behind the optimal decision point, the midpoint sampling value The energy distribution is biased towards the current symbol, resulting in and are positive, or at least their sum is positive, then the sampling time needs to be adjusted forward, i.e. left on the time axis, by an interpolation filter to reduce the lag bias. When the actual sampling time is ahead of the optimal decision point, the midpoint sampling value The energy distribution is biased towards the previous symbol, resulting in and are both negative, or at least their sum is negative, then the sampling time needs to be adjusted to the right of the time axis, i.e. backward, by an interpolation filter to reduce the advance bias. The error signal approaches 0, indicating that the sampling time has approached the optimal judgment point, the time offset is within the allowable range, and the synchronization loop enters a stable state.

6. The UWB time offset synchronization method based on double-factor dynamic adjustment according to claim 5, characterized in that, In step 3, when the loop filter in the Gardner feedback loop receives the error signal After that, first buffer the error at the previous time And calculate the error rate of change: ; based on an error magnitude threshold and a rate of change threshold to make a determination If , the proportionality coefficient maintain the reference value ; If and , using ; If and , using ; Wherein, k1 and k2 are amplification coefficients; the hysteresis counter is used to check the SYNC symbol judgment result, when the double-factor judgment condition is met for the continuous 2 SYNC symbols, the switching operation of the corresponding amplification coefficient is executed, 1 symbol meets the condition to restore the reference value, and the error signal processed by the loop filter is used to control the numerical control oscillator NCO.

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