A method and system for adaptive cyclic prefix length adjustment

Abstract

The application belongs to the field of wireless communication, and discloses a method and system for adaptive cyclic prefix length adjustment, which comprises the following steps: acquiring system parameters; detecting multipath interference of a wireless environment to obtain multipath interference parameters; setting a system cyclic prefix delay threshold; obtaining a reference delay length of a cyclic prefix according to the cyclic prefix delay threshold requirement and in combination with the actual multipath interference parameters of the environment; determining the cyclic prefix length between each symbol of the system according to the reference delay length of the cyclic prefix, and the cyclic prefix length is not less than the reference delay length; and monitoring the multipath interference of the wireless environment, and repeating the step of adaptively adjusting the cyclic prefix length of the system when the multipath interference changes, otherwise, the monitoring is continued. The cyclic prefix length is determined according to the actual wireless environment, and is not a fixed value defined in advance; the application can well adapt to the demand for effective communication in diversified wireless environments, especially in complex and diverse industrial environments.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of wireless communication technology, and particularly relates to a method and system for adaptive cyclic prefix duration adjustment. Background Technology

[0002] Orthogonal Frequency Division Multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. It is a type of multicarrier modulation that enables parallel transmission of high-speed serial data through frequency division multiplexing. OFDM has good resistance to multipath fading and can support multiple user access, so it is widely used in wireless communication fields such as 4G / 5G mobile communication, WiFi, and power line communication.

[0003] The use of a cyclic prefix (CP) is crucial for reliable OFDM signal transmission. Essentially, a cyclic prefix is ​​a copy of the last part of an OFDM symbol appended to it; it is not used to transmit data itself. The cyclic prefix serves as a guard interval to maintain orthogonality between subcarriers and prevent interference between consecutive OFDM symbols (ISI) and between subcarriers (ICI). CP-OFDM was selected by 3GPP for downlink transmission in the 4G LTE standard and for uplink and downlink transmission in the 5G NR standard.

[0004] The waveform parameters of a CP-OFDM system mainly include subcarrier spacing (SC), cyclic prefix duration, and subframe duration. The waveform parameter set of a CP-OFDM system can be represented as follows: .in, Subcarrier spacing is in Hz, cyclic prefix (CP) duration and subframe duration Typically, the duration is in microseconds (μs) and milliseconds (ms). In practical systems, OFDM is often implemented using Fast Fourier Transform (FFT). Once the subcarrier spacing of the OFDM system is determined, the duration of the FFT symbol without the cyclic prefix is... for, (1) With the addition of the cyclic prefix, the symbol duration of CP-OFDM is also determined. (2) The waveform parameter set design for 3GPP 5GNR is shown in Table 1.

[0005] Table 1 3GPP 5GNR Waveform Parameter Set

[0006] As shown in Table 1 above, when designing the OFDM waveform parameter set, 3GPP ensures that the subcarrier spacing satisfies the following relationship. (3) in This means that the subcarrier spacing in the 3GPP 5G system is set to an integer multiple of 15kHz. Correspondingly, the cyclic prefix (CP) duration for each subcarrier spacing is also determined according to a similar proportional relationship. (4) In the 3GPP protocol, a standard CP is typically set to... The value is μs, which is based on measured data from typical urban and suburban environments, ensuring coverage of approximately 90% of multipath scenarios (latency spread ≤ 4.7 μs). 3GPP fixed this CP value and paired it with a subcarrier spacing of 15 kHz to simplify the design. The CP values ​​corresponding to other subcarrier spacings are determined according to the proportional relationship in formula (4). For mountainous and wide-area coverage scenarios with large latency spread, 3GPP designed an extended CP with a fixed duration of 16.7 μs.

[0007] Since the subcarrier spacing and FFT symbol duration satisfy formula (1), combined with formulas (3) and (4), the CP duration of 3GPP is... The duration of its corresponding symbol The ratio is fixed. That is to say, 3GPP specifies the subcarrier spacing. CP duration A strong coupling relationship with a fixed ratio is introduced between them, as well as between different sets of waveform parameters (such as waveform parameters at 15kHz and 30kHz).

[0008] It is worth noting that 3GPP requires a fixed subframe duration of 1ms when designing the frame structure, with each slot required to contain a fixed 14 CP-OFDM symbols, and the subframe containing an integer number of slots. Under the design requirement of a fixed 1ms subframe duration, the slot duration is not an integer. Therefore, 3GPP uses longer CPs for the first and eighth symbols of each slot to ensure that each slot contains an integer number of slots, thus satisfying the design requirement that the number of slots contained in a 1ms subframe is also an integer. For example, when the subcarrier spacing is 15kHz, the first and eighth symbols of each slot use longer CPs, making the entire slot 1000μs, while the remaining symbols use the same CP length of 4.7μs. Similarly, in the 3GPP standard, the slot durations corresponding to 30kHz, 60kHz, and 120kHz are 500μs, 250μs, and 125μs, respectively.

[0009] The design of the WiFi waveform parameter set does not require a fixed subframe duration, unlike 3GPP which uses a fixed 1ms. The number of symbols transmitted is configured by the Medium Access Control (MAC) layer using the unsigned positive integer parameter LENGTH. Although the WiFi subframe duration is not fixed, its cyclic prefix duration and effective data duration are... The strong coupling relationship remains the same. The proportional strong coupling relationship between the cyclic prefix duration and the corresponding subcarrier spacing of the WiFi series standards is summarized in Table 2.

[0010] Table 2. Strong Coupling Proportional Relationship between WiFi Cyclic Prefix (CP) Duration and Subcarrier Spacing

[0011] As shown in Table 2, the FFT symbol duration is determined by the CP duration and subcarrier spacing of various WiFi standards. The waveform parameter set design method of 3GPP is consistent with the underlying logic and ideas of the waveform parameter set design method, which introduces a strong coupling relationship.

[0012] Adding a cyclic prefix (CP) is primarily to avoid inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by channel delay spread. The magnitude of channel delay spread is mainly determined by the multipath reflection path of the radio wave and has little to do with the specific carrier frequency. Therefore, the CP duration does not necessarily have to be the same as the FFT symbol duration. The binding is a fixed ratio. This artificially introduced strong coupling limits the effectiveness of OFDM systems. Taking 3GPP as an example, when its subcarrier spacing increases to 480kHz, its CP duration decreases proportionally to 0.15μs, making it difficult to effectively avoid inter-symbol interference caused by environmental multipath delays, thus leading to serious interference problems. In addition, 3GPP further requires each frame to contain an integer number of slots, resulting in inconsistent CP durations within the same slot. This design reduces system consistency and effectiveness, and increases the complexity and overhead of the system when adding CP.

[0013] Real-world industrial wireless communication scenarios are complex and demand high real-time performance and reliability. Existing cyclic prefix delay design methods, such as those used in 3GPP and WiFi, artificially introduce a fixed-ratio strong coupling between OFDM symbols and their CPs, resulting in poor adaptability to complex and ever-changing industrial environments. Furthermore, for a given subcarrier spacing, the cyclic prefix duration in 3GPP and WiFi systems is fixed, artificially binding the cyclic prefix length to the subcarrier spacing and solidifying the cyclic prefix duration configuration for that subcarrier spacing. However, multipath interference in real-world wireless environments is not strongly correlated with subcarrier spacing. This design not only lacks flexibility but also introduces unnecessary delays, thus wasting spectrum resources.

[0014] The closest existing technology is Samsung Electronics' patent WO2010050731, which discloses a scheme in which the base station dynamically determines the cyclic prefix (CP) length based on real-time channel conditions and notifies the terminal via a downlink reference signal during a data session. This aims to improve connection robustness while maintaining spectral efficiency. The core process includes: the base station comparing the difference between the new estimated CP and the previously used CP to generate "CP length change information," which is then broadcast in the reference signal; upon receiving the instruction, the terminal adopts the new CP from the next frame and restores symbol synchronization. The document also points out that a "CP length change request" can be triggered in reverse on the mobile station side, forming a bidirectional adaptive closed loop for uplink and downlink, which theoretically reduces inter-symbol interference caused by multipath and improves system throughput.

[0015] However, the scheme still has two major technical problems: (1) It lacks a smoothing or confidence threshold mechanism for the statistical fluctuations of delay spread. It only relies on instantaneous measurement to trigger CP update, which is prone to excessive switching and signaling overhead spikes in fast fading environment; (2) The patent does not provide a quantitative criterion for how to ensure "coverage ≥95% effective power" or limit peak-to-average power ratio (PAPR), nor does it describe the rounding strategy outside the discrete CP level, which may result in residual ISI and decreased spectrum utilization in long multipath or millimeter wave scenarios. Summary of the Invention

[0016] To address the problems existing in the prior art, this invention provides a method and system for adaptive cyclic prefix duration adjustment.

[0017] This invention is implemented as follows: an adaptive cyclic prefix duration adjustment method, characterized in that the adaptive cyclic prefix duration adjustment method specifically includes: S1: Get system parameters.

[0018] S2: Detect multipath interference in the wireless environment and obtain multipath interference parameters.

[0019] S3: Set the system cyclic prefix delay threshold requirement.

[0020] S4: Based on the cyclic prefix delay threshold requirement and combined with the actual multipath interference parameters in the environment, the reference delay duration of the cyclic prefix is ​​obtained.

[0021] S5: Determine the duration of the cyclic prefix between each symbol in the system based on the reference delay duration of the cyclic prefix, and the duration of the cyclic prefix shall not be less than its reference delay duration.

[0022] S6: Monitor the multipath interference situation in the wireless environment. If the multipath interference situation changes, repeat S2 to S5 and adaptively adjust the system cyclic prefix duration. Otherwise, continue monitoring.

[0023] Furthermore, in step S1, the system parameters obtained include, but are not limited to, carrier center frequency, carrier bandwidth, and subcarrier spacing.

[0024] Furthermore, in S2, the multipath interference parameters obtained include, but are not limited to, multipath delay spread, maximum delay, root mean square delay spread, and power delay profile (PDP). The methods for obtaining multipath parameters include, but are not limited to, channel impulse response measurement, frequency domain channel estimation, super-resolution algorithms, spread spectrum technology, and RAKE receivers. The detection of multipath interference in the wireless environment can also be achieved by measuring and estimating the wireless channel, and adaptively acquiring and adjusting the cyclic prefix duration.

[0025] Furthermore, in S3, the system cyclic prefix delay threshold requirement can be, but is not limited to: depending on the multipath energy situation, for example, the set multipath delay threshold can avoid more than 95% of multipath interference energy; the multipath delay threshold can also be the maximum delay, that is, the delay difference between the longest path and the shortest path.

[0026] Furthermore, in S4, the delay obtained according to the cyclic prefix delay threshold requirement is the cyclic prefix reference delay, hereinafter referred to as the reference delay. It can be the delay to avoid more than 95% of multipath interference energy, or it can be the delay difference between the longest path and the shortest path in the environment.

[0027] Furthermore, in step S6, the existing reference signals are used to monitor multipath interference in the wireless environment within the time-frequency resources of the system frame structure. The reference signals include, but are not limited to, any one or more of the following: demodulation reference signal (DMRS), sounding reference signal (SRS), channel state information reference signal (CSI-RS), phase tracking reference signal (PTRS), synchronization signal (SS), and positioning reference signal (PRS).

[0028] Furthermore, in step S6, the existing reference signals are used to monitor multipath interference in the wireless environment within the time-frequency resources of the system frame structure. The reference signals include, but are not limited to, any one or more of the following: Short Training Field (STF) and Long Training Field (LTF).

[0029] Furthermore, in step S6, a multipath delay detection signal is set up in the time-frequency resources of the system frame structure to monitor multipath interference in the wireless environment.

[0030] Furthermore, the multipath delay detection signal in the multipath interference situation can be periodic or non-periodic, and the period of the specific detection signal is configured by the system.

[0031] Furthermore, in the adaptive cyclic prefix duration adjustment method, the system determines a new cyclic prefix duration based on the updated multipath interference parameters and the cyclic prefix delay threshold requirements.

[0032] Furthermore, the cyclic prefix delay threshold can also be set to a specific value, which is set before detecting multipath interference.

[0033] Furthermore, the multipath interference parameters of the system can also be customized.

[0034] Furthermore, the adaptive cyclic prefix duration adjustment method can adaptively determine the cyclic prefix duration by indirectly monitoring the impact of multipath effects. The indirect monitoring methods include, but are not limited to, the quality of channel state information (CSI), the level of bit error rate at the receiver, and the inter-symbol interference situation.

[0035] Another objective of this invention is to provide a system for adaptive cyclic prefix duration adjustment, the system specifically comprising: The parameter acquisition module is used to acquire system parameters.

[0036] The interference detection module is used to detect multipath interference in the wireless environment.

[0037] The delay threshold setting module is used to set the system cyclic prefix delay threshold.

[0038] The cyclic prefix delay determination module is used to adaptively determine the cyclic prefix duration between each symbol in the system based on the multipath interference situation in the wireless environment.

[0039] The interference monitoring module is used to monitor multipath interference in the wireless environment.

[0040] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows: Taking a typical underwater acoustic wireless environment as an example, the measured maximum multipath delay τ max =20μs, the wireless system adopts BPSK-OFDM modulation, and the relationship between the variation of the cyclic prefix duration and the system bit error rate (BER) is shown in Table 3.

[0041] Table 3 Relationship between Cyclic Prefix (CP) Duration Variation and Bit Error Rate (BER)

[0042] As shown in Table 3, when the cyclic prefix is ​​less than the maximum multipath delay τ max At this time, severe inter-symbol interference occurs, leading to a high bit error rate. As the cyclic prefix delay increases, the system bit error rate decreases. However, when the cyclic prefix delay exceeds τ... max The system bit error rate did not decrease further, while the system spectral efficiency decreased.

[0043] The novel cyclic prefix duration setting method proposed in this invention is only strongly correlated with the multipath interference situation in the actual wireless environment, and has no strong proportional relationship with the OFDM symbol itself. It can well adapt to the needs of effective communication in diverse wireless environments, especially in complex and diverse industrial environments.

[0044] The cyclic prefix duration in this invention is determined based on the actual wireless environment and is not a predefined fixed value. In contrast, the cyclic prefix duration in 4GLET, 5GNR, and WiFi systems is a pre-designed fixed value. As shown in Table 1, the cyclic prefix duration for 3GPP 5GNR with a 15kHz subcarrier spacing is fixed as follows: μs. Then, based on this, for every doubling of the subcarrier spacing, the cyclic prefix duration is reduced by a factor of two.

[0045] In broadband orthogonal frequency division multiplexing (OFDM) systems, inter-symbol interference and out-of-band radiation caused by multipath delay spread have long constrained the improvement of link capacity and spectral efficiency. In typical industrial environments, the combined effects of reflective surfaces, obstacles, and moving targets result in time-varying and complex distributions of channel impulse response lengths. Traditional fixed-length cyclic prefixes often fail to balance stability in high multipath scenarios with cost minimization in low multipath scenarios, thus becoming a bottleneck in system performance.

[0046] To overcome this bottleneck, this method dynamically extracts the main peak and secondary peak from continuously received pilot blocks by performing time-domain correlation processing on the pilot subcarriers, and constructs an accurate channel impulse response model based on the power contribution of multipath paths. This model uses the cumulative power ratio as the core quantitative indicator, which can maintain high reliability and low false alarm rate in scenarios where frequency-selective fading and fast fading coexist.

[0047] In the generation of multipath interference parameters, an exponentially weighted moving average (EWMA) mechanism is introduced to fuse new and old measurement results. This effectively suppresses time delay abrupt changes caused by transient occlusion or rapid fading, and also enables rapid response to sudden environmental changes. This smoothing algorithm utilizes the adjustable time constant to achieve self-adaptation of cyclic prefix threshold delay in various typical industrial application environments (such as subway platforms and indoor industrial parks).

[0048] Once the cyclic prefix threshold delay is determined, it is quantized into an integer multiple of the sampling time interval by combining the discretized configuration of the basic frame structure to derive the cyclic prefix reference delay. This quantization process adheres to the strict requirements of the sampling theorem while also taking into account the subframe alignment rules in the system frame structure, ensuring that threshold mapping can be completed in hardware implementation with minimal storage and control overhead.

[0049] For the pre-set cyclic prefix candidate set under different system carrier bandwidths and frame formats, this method selects the optimal duration through an "rounding up" strategy while satisfying multipath coverage. This ensures that the cyclic prefix length is neither lower than the reference value nor causes unnecessary time overhead due to excessive redundancy. The candidate set incorporates the actual needs of resource block scheduling and frequency domain interpolation in its design, enabling a smooth transition between baseband and RF level switching.

[0050] Finally, to enable unattended industrial deployment, the system continuously monitors the echo signals from the probes on time-frequency resources and automatically recalculates the cyclic prefix reference delay and cyclic prefix duration based on trigger conditions. This monitoring module works in conjunction with the existing link budget and power control unit, enabling adaptive adjustments with millisecond-level latency during drastic environmental changes, significantly improving the system's robustness and spectrum utilization. Attached Figure Description

[0051] Figure 1 This is a flowchart of adaptive acquisition and adjustment of the cyclic prefix duration provided in an embodiment of the present invention.

[0052] Figure 2 This is an example diagram of adaptively acquiring and adjusting the cyclic prefix duration based on channel conditions, provided by an embodiment of the present invention.

[0053] Figure 3 This is a system module diagram of adaptive cyclic prefix duration adjustment provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0055] Example 1: Time-domain dependent base station adaptive with a 95% power threshold.

[0056] Example 1 (Macro-Based Adaptive): The base station physical layer performs sliding window autocorrelation on the reference signal at the beginning of each radio frame. It first locates the main peak and eliminates secondary paths with insufficient confidence in a power-decreasing manner. The "delay Δt" corresponding to the first time the accumulated power reaches 95% of the total power is defined as the cyclic prefix reference threshold. Δt is converted into the discrete-time sample number Ncp, then rounded up to the minimum value greater than or equal to Ncp in the candidate set {64,128,256,512}, and this sample number is used as the new cyclic prefix length. The base station broadcasts this parameter to all active UEs via PDCCH, and it takes effect from the next scheduling cycle. The monitoring unit continuously compares the impulse response of the reference signal. If the accumulated power threshold increases by more than 10% again, a re-estimation is immediately triggered, thereby closing the loop to suppress ISI caused by multipath interference.

[0057] The base station broadcasts this value to all active UEs via the physical downlink control channel (PDCCH) and applies it at the start of the next scheduling cycle; the monitoring unit continuously compares the impulse response changes of the reference signal, and if the threshold increases by more than 10%, it immediately triggers re-estimation, thereby closing the loop to suppress multipath ISI.

[0058] Example 2: FFT Accelerating computations related to convolution.

[0059] In the same scenario, the pilot sequence and the received signal are respectively extended to N. Pointwise FFT, followed by frequency domain multiplication and then IFFT, yields the linear correlation result. The logic for correlation peak search and threshold calculation is consistent with Example 1. Because frequency domain convolution replaces time-domain sliding windowing, the computational complexity is reduced from O(N^2) to O(N^2). 2 The time complexity is reduced to O(N log N), and the correlation time per frame does not exceed 40µs under the conditions of 30kHz subcarrier and 4096-point FFT.

[0060] The hardware implementation uses an FPGA+DSP combination; the FPGA carries a 4096 A point-parallel FFT IP is provided, with a DSP handling peak detection and threshold decision. This combination can be embedded into a baseband board to meet the requirements for FFT / candidate set.

[0061] Example 3: Exponentially weighted moving average (EWMA) stable cyclic prefix.

[0062] In high-speed train coverage areas, rapid channel fading causes significant inter-frame threshold jitter. The base station compares the latest threshold τ(t) with the historical smoothed value τ(t). 1) Perform EWMA with α=0.2: τ'(t)=0.2·τ(t)+0.8·τ(t) 1) The smoothed results are then mapped to the candidate set to determine the final loop prefix, avoiding frequent switching that causes UE synchronization overhead.

[0063] The monitoring thread checks BER and CQI every 5 frames; if BER remains below the threshold and CQI increases, the first-level candidate prefix is ​​allowed to be shortened; otherwise, it is lengthened, thus implementing an indirect monitoring + fine-tuning strategy.

[0064] Example 4: SoC chip with embedded loop prefix control coprocessor.

[0065] To support edge small base stations, a 28nm SoC was designed, with a core containing a multipath correlation coprocessor (MCE), a programmable threshold table, and a DMA controller. The MCE completes FFT multiplication within a 10ms cycle. IFFT Peak detection outputs a threshold value into a threshold table and drives the digital front end (DFE) to update the peak value (CP).

[0066] The SoC integrates 2MB of SRAM to store the most recent 128 frames of CIR; the clock unit provides a 307.2MHz reference; and the on-chip hardware AES engine ensures PDCCH signaling encryption. This chip can be installed in macro base stations, indoor distributed RRHs, or enterprise-grade APs.

[0067] Example 5: MUSIC super-resolution time delay spectrum estimation.

[0068] In urban high-rise street valleys, an 8×8 MIMO antenna array is used, and MUSIC spectrum estimation is performed on the received pilot covariance matrix. An accurate delay list is obtained through peak search, and a threshold is calculated based on a 95% total power threshold. This is then compared with FFT. Convolutional combinations can maintain the same bit error rate performance at a 3dB lower signal-to-noise ratio.

[0069] Threshold delay is converted into integer sampling points through linear interpolation and entered into the candidate set mapping; each beam of the array antenna is estimated independently, and the maximum value is finally taken as the global prefix to ensure that even the worst link is protected.

[0070] Example 6: BER Adaptive driver for the UE side.

[0071] On a CPE terminal, the PHY layer continuously calculates the BER after demodulation. When the BER is higher than 10 for three consecutive subframes... -3 Furthermore, when the CSI report CQI drops below level 2, the UE autonomously reports a "prefix insufficiency" indication. Upon receiving this, the base station immediately sends a new CP (+0.5µs) and implements it in the next frame.

[0072] If BER is consistently below 10 -4 Furthermore, with CQI upgrades, it is recommended that the UE shorten the prefix. This closed loop satisfies the indirect monitoring scenario.

[0073] Example 7: Beam-level control in large-scale MIMO scenarios.

[0074] The 64T64R base station performs cluster estimation of CIR based on beam and calculates the threshold for each cluster. The scheduler takes the maximum value of all beam thresholds as the unified CP; at the same time, it records the margin of each beam for subsequent beamforming / power allocation optimization.

[0075] The probe signal is inserted into the DMRS hole and the echo is obtained by reflecting the idle symbol; if the monitoring unit finds that the threshold of a certain beam spikes by more than 10%, it triggers a local CP increase or reschedules the user.

[0076] Example 8: Non-terrestrial network (NTN) satellite base station scenario.

[0077] In the LEO satellite base station link, the round-trip delay varies greatly; the on-board baseband performs fast threshold estimation according to the frame period and encapsulates the target CP value in the PDCCH DCI format, and sends it to the ground UE in a 5ms period.

[0078] Due to power consumption limitations on the satellite, the relevant calculations use Rad. Hard ASIC; the threshold candidate set is set to {256,512, 1024 sampling points} to cover a delay of 30–120µs, which meets the requirements of large echo scenarios.

[0079] Example 9: RAKE receiver-assisted V2X broadband communication.

[0080] In 60GHz car In the road-to-road (V2X) system, the roadside unit uses RAKE to merge signals from each path and outputs a time delay list; the system accumulates the power of this list to obtain a 95% threshold, and converts it into a CP with 128–256 sampling points.

[0081] The vehicle UE does not need to estimate independently; it only needs to receive the latest CP value from the roadside PDCCH, which reduces the computation on the vehicle side.

[0082] Example 10: Spreading code autocorrelation multipath identification.

[0083] in Wi Fi7 Enhanced Edition (16K) FFT, CMU In the Preamble, the access point utilizes the good autocorrelation of the spreading code to perform cyclic correlation between the transmitted sequence and the echo, and takes a 95% threshold after locating the main and secondary peaks. Due to the short code length, estimation can be completed within 1µs.

[0084] This threshold reference value is obtained through HE. SIG B-field broadcast; the access point also supports EWMA smoothing to avoid frequent CP switching when multiple users access randomly.

[0085] Example 11: Machine learning prediction + trigger-based adjustment.

[0086] The LSTM network is trained in the cloud, and 10 frames of historical CIR, UE speed, frequency offset and other features are input to predict the threshold of the next frame. If the difference between the predicted CP and the real-time estimated CP is less than 5%, the predicted value is used directly to reduce real-time computation.

[0087] If the difference exceeds the limit or a sudden change in the threshold is detected, the system reverts to the real-time estimation in Example 1. This hybrid approach reduces the DSP load by 40% while maintaining the same BER.

[0088] Example 12: TDD Distributed RRH + Forward Synchronization.

[0089] Distributed Massive In a MIMO system, the Rectangular Rate Hull (RRH) is responsible for CIR measurement; CP calculation and decision-making are completed in a centralized BBU, and the target CP duration is written back to the RRH via the eCPRI link. Local clock drift is synchronized via IEEE 1588v2 to ensure RRH's stability. BBU timed consistency.

[0090] RRH uses a threshold-based hardware timer to insert CPs into downlink symbols; when the BBU updates the CP, RRH switches to the new value within one frame, realizing the distributed configuration of base station equipment.

[0091] like Figure 1 As shown, this embodiment of the invention provides a method for adaptive cyclic prefix duration adjustment, which specifically includes: S1: Get system parameters.

[0092] System parameters such as subcarrier spacing, OFDM symbol duration, sampling rate, carrier center frequency, carrier bandwidth, and the maximum allowed cyclic prefix duration follow specific communication standards (5G, WiFi, Bluetooth, Zigbee, Lora). When a base station or access point (AP) initiates or connects to the network, it configures its operating parameters based on system information blocks or signaling messages received from the network. The network dynamically or semi-statically broadcasts signaling (system information, Radio Resource Control (RRC) configuration) through the base station, instructing terminals to use specific parameter values ​​(bandwidth, subcarrier spacing) within the standard's allowed range.

[0093] S2: Detect multipath interference in the wireless environment and obtain multipath interference parameters; the methods for obtaining multipath parameters may include, but are not limited to: 1) Channel Impulse Response (CIR) measurement.

[0094] step: (1) Sending probe signals: Use broadband signals (such as pulse, chirp signals or pseudo-random sequences) to excite the channel.

[0095] (2) Received signal processing: The time domain correlation between the received signal and the transmitted signal is extracted by matched filtering or cross-correlation algorithm.

[0096] (3) Extracting multipath peaks: Detect the peak values ​​of the cross-correlation results. Each peak corresponds to a multipath component, and the peak spacing is the time delay difference.

[0097] 2) Frequency domain channel estimation (OFDM system).

[0098] step: (1) Pilot insertion: A known pilot is inserted into a specific subcarrier of an OFDM symbol.

[0099] (2) Frequency domain channel estimation: Channel frequency response (CFR) is estimated by pilot signals.

[0100] (3) IFFT conversion: Convert CFR to time domain CIR and extract multipath delay.

[0101] 3) Super-resolution algorithm (high-precision scene) method.

[0102] (1) MUSIC algorithm: Construct a high-resolution time delay spectrum by utilizing the orthogonality between the signal subspace and the noise subspace.

[0103] (2) ESPRIT algorithm: Based on the rotation invariance of the signal, the computational complexity is reduced.

[0104] 4) Spread spectrum technology and RAKE receiver.

[0105] Principle: Multipath separation is achieved by utilizing the autocorrelation properties of spreading codes.

[0106] step: (1) Transmit spread spectrum signals (such as CDMA pseudocode).

[0107] (2) The receiver detects the components with different time delays by using a sliding correlator.

[0108] The RAKE receiver combines multipath signals and records the time delay.

[0109] S3: Set the system cyclic prefix delay threshold requirement; the system cyclic prefix delay threshold requirement can be, but is not limited to: depending on the multipath energy situation, for example, the set cyclic prefix delay threshold can be the delay to avoid more than 95% of multipath interference; the cyclic prefix delay threshold can also be the maximum delay difference, that is, the delay difference between the longest path and the shortest path.

[0110] S4: Based on the cyclic prefix delay threshold requirement and the actual multipath interference parameters in the environment, obtain the reference delay of the cyclic prefix. According to the system-set cyclic prefix delay threshold requirement, such as avoiding more than 95% of multipath interference, and combined with the obtained power delay distribution (PDP) of the multipath paths, the specific delay value that meets the delay threshold requirement can be obtained as the reference delay of the cyclic prefix. Alternatively, the system-set cyclic prefix delay threshold requirement can be the maximum delay difference in the environment. Combining this with the obtained multipath delay distribution, the specific value of the cyclic prefix reference delay can be obtained through the delay difference between the longest and shortest paths.

[0111] S5: Determine the cyclic prefix duration between each symbol in the system based on the cyclic prefix reference delay duration, and the cyclic prefix duration shall not be less than its reference delay duration; the cyclic prefix reference delay obtained through step S4 is affected by the complex and ever-changing wireless environment and can be any value, which is not conducive to engineering implementation. The final cyclic prefix delay can be determined by rounding up; or the nearest delay parameter that is not less than the cyclic prefix reference delay can be found from the system's cyclic prefix delay parameter set as the cyclic prefix delay.

[0112] S6: Monitor the multipath interference situation in the wireless environment. If the multipath interference situation changes, repeat S2 to S5 and adaptively adjust the system cyclic prefix duration. Otherwise, continue monitoring.

[0113] For any wireless communication system, multipath interference in the wireless environment can be monitored using existing reference signals or pilot signals within the time-frequency resources of the system frame structure. Specifically, for 5G systems, their rich set of reference signals, such as demodulation reference signals (DMRS), sounding reference signals (SRS), channel state information reference signals (CSI-RS), phase tracking reference signals (PTRS), synchronization signals (SS), and positioning reference signals (PRS), can be used to extract and update multipath parameters, thereby monitoring multipath interference. For WiFi systems, their own pilot or reference signals, such as short training sequence signals (STF) and long training sequence signals (LTF), can be used to extract and update multipath parameters, thereby monitoring multipath interference. For any wireless communication system, a multipath delay detection signal can be set in the time-frequency resources of the system frame structure to monitor multipath interference in the wireless environment. The multipath delay detection signal can be periodic or aperiodic. The specific period of the detection signal is configured by the system. The triggering conditions for aperiodic signals can be, but are not limited to: a large number of errors in the receiver signal, a significant decrease in the signal-to-interference and noise ratio (SINR), and a significant decrease in the channel estimation quality.

[0114] like Figure 2As shown, the cyclic prefix duration can be adaptively adjusted through indirect monitoring. Specific indirect monitoring methods for multipath interference in the wireless environment include, but are not limited to, monitoring the quality of channel state information, the receiver bit error rate (BER), and inter-symbol interference. Taking channel state information monitoring as an example, when the system detects a deterioration in channel state information, the cyclic prefix duration is increased; conversely, the cyclic prefix duration remains unchanged or is appropriately reduced to adapt to the environment. 5G systems can conveniently obtain channel state information through CSI-RS channel measurement. Similarly, when the receiver BER increases, the system increases the cyclic prefix duration until the BER design requirements are met; conversely, if the system BER exceeds the design requirements, the cyclic prefix duration remains unchanged or is appropriately reduced.

[0115] In wideband OFDM systems, a fixed cyclic prefix duration cannot adaptively adjust to the real-time delay spread of the wireless channel, revealing its limitations in two extreme scenarios: First, in long multipath environments such as valleys or street "canyons," existing CPs are insufficient to cover the effective channel impulse response, leading to a significant increase in inter-symbol crosstalk and inter-subcarrier interference. Second, in open or line-of-sight (LoS) scenarios, excessively long CPs waste time and transmit power budget, reducing spectral efficiency and coarsening scheduling granularity. This lack of adaptability is the core technical pain point of current unified CP configuration schemes. It is necessary to first identify the physical layer metrics obtainable in real-time on the system side, including static parameters such as subcarrier spacing, symbol length, sampling rate, modulation order, and the maximum CP insertion length supported by the transceiver. These parameters define the adjustable range of the CP, the modulation bandwidth, and the maximum tolerable channel delay spread, laying the boundary conditions for subsequent dynamic calculations. At the same time, the base station or terminal should also record the bit error rate, reference signal received power (RSRP / RSRQ / RSSI: Reference Signal Received Power / Reference Signal Received Quality / Received Signal Strength Indicator) and channel estimation matrix in the most recent frames in order to correct the noise baseline in subsequent multipath detection.

[0116] Multipath interference quantization cannot rely solely on static statistics of power attenuation distribution. Instead, a sliding window detection mechanism based on correlation peak difference and threshold self-localization should be employed: the receiver first performs time-domain correlation on the pilot resource block to extract the positions of the main peak and several sub-peaks, and calculates the weighted delay spread based on the proportion of sub-peak power accumulation in the main peak power. Then, it combines noise variance to perform confidence screening of weak paths, obtaining a refined effective channel impulse response length τ_eff. This τ_eff, as a "multipath interference parameter" in a real-world environment, better meets the needs of instantaneous link scheduling than the traditional RmsDelaySpread.

[0117] To avoid frequent switching caused by instantaneously high secondary paths, the algorithm introduces a pseudo-random dither and an exponentially weighted moving average in addition to τ_eff to generate a smooth threshold τ_thr. This threshold is essentially the maximum residual delay spread that the system can tolerate, covering 95% of the effective power while also considering the power amplifier peak-to-average power ratio (PAPR) and synchronization overhead. By controlling the threshold update rate, drastic fluctuations can be suppressed during rapid fading in high-speed channels, while maintaining sensitive adaptation in low-speed mobile scenarios.

[0118] Once τ_thr is obtained, both the transmitting and receiving ends quantize it to the nearest integer multiple N_cp·T_s based on the sampling time interval T_s. If this value falls outside the preset set of multiple CP candidate levels {N0, N1, ...}, a rounding-up strategy is adopted to ensure that the CP duration is always ≥ τ_thr. Subsequently, the base station broadcasts the new CP configuration number to the relevant terminals through the Physical Downlink Control Channel (PDCCH) or dedicated signaling, and the terminal takes effect from the next frame. This "one-frame delay" strategy is compatible with the current 3GPP frame structure and does not disrupt the air interface protocol timing.

[0119] The system continuously monitors the channel-related peak distribution. If the detected deviation of τ_eff from the current τ_thr exceeds a set range (e.g., ±8T_s), the threshold is recalculated and a CP update process is triggered; otherwise, only relevant statistics are refreshed to reduce control plane overhead. Experiments show that in outdoor 700MHz large-area macro base station scenarios, this method improves the average throughput by 11.3% compared to the fixed CP scheme, while in long multipath scenarios such as subway tunnels, the block error rate is reduced by more than 47%, verifying its robustness and efficiency advantages in different wireless environments.

[0120] The S1 process involves acquiring system parameters including, but not limited to, carrier center frequency, carrier bandwidth, and subcarrier spacing. In practice, system parameters such as carrier center frequency, carrier bandwidth, and subcarrier spacing are often known information.

[0121] S2 obtains multipath interference parameters including, but not limited to: multipath delay spread, maximum delay, root mean square delay spread, and power delay distribution (PDP). Methods for obtaining multipath parameters include: (1) Channel impulse response (CIR) measurement.

[0122] (1.1) Transmitting multipath delay probe signal: Excite the channel using a wideband signal (such as a pulse, chirp signal or pseudo-random sequence); the multipath delay probe signal can also be an existing reference signal of the system, including but not limited to demodulation reference signal (DMRS), probe reference signal (SRS), channel state information reference signal (CSI-RS), phase tracking reference signal (PTRS), synchronization signal (SS), positioning reference signal (PRS), short training sequence signal (STF) and long training sequence signal (LTF) any one or more.

[0123] (1.2) Received signal processing: The time-domain correlation between the received signal and the transmitted signal is extracted by matched filtering or cross-correlation algorithm.

[0124] (1.3) Extracting multipath peaks: Detect the peak values ​​of the cross-correlation results. Each peak corresponds to a multipath component, and the peak spacing is the time delay difference.

[0125] (2) Frequency domain channel estimation (OFDM system).

[0126] (2.1) Pilot insertion: A known pilot is inserted into a specific subcarrier of an OFDM symbol.

[0127] (2.2) Frequency domain channel estimation: Channel frequency response (CFR) is estimated by pilot signals.

[0128] (2.3) IFFT conversion: Convert CFR to time domain CIR and extract multipath delay.

[0129] (3) Super-resolution algorithm (high-precision scene).

[0130] (3.1) MUSIC algorithm: Construct a high-resolution time delay spectrum by utilizing the orthogonality between the signal subspace and the noise subspace.

[0131] (3.2) ESPRIT algorithm: Based on the rotation invariance of the signal, the computational complexity is reduced.

[0132] (4) Spread spectrum technology and RAKE receiver, using the autocorrelation characteristics of the spreading code to separate multipath.

[0133] (4.1) Transmit spread spectrum signals (such as CDMA pseudocode).

[0134] (4.2) The receiver detects the components with different time delays by using a sliding correlator.

[0135] (4.3) The RAKE receiver merges multipath signals and records the time delay.

[0136] The S3 requirement for the system cyclic prefix delay threshold can be, but is not limited to, depending on the multipath energy situation, such as setting a cyclic prefix delay threshold that can avoid more than 95% of multipath interference energy; the cyclic prefix delay threshold can also be the maximum delay difference, that is, the delay difference between the longest path and the shortest path.

[0137] The cyclic prefix reference delay obtained in S4 according to the cyclic prefix delay threshold requirement can be the delay to avoid more than 95% of multipath interference energy, or it can be the delay difference between the longest path and the shortest path in the environment.

[0138] In S5, the reference delay of the cyclic prefix in the actual system can be any value, which is not conducive to engineering implementation. For example, the determined cyclic prefix can be the rounded-up value of its reference delay; the determined cyclic prefix delay can also be the delay in the system's cyclic prefix delay parameter set that is not less than and is closest to the reference delay, which is convenient for engineering implementation.

[0139] In one embodiment of the present invention, a detection signal specifically designed for monitoring multipath interference in the wireless environment is included in the time-frequency resources of the system frame structure. The system extracts multipath interference parameters based on the detection signal, including but not limited to: multipath delay spread, maximum delay, root mean square delay spread, and power delay distribution (PDP). Existing multipath interference parameters are then updated. Accordingly, the system determines the system cyclic prefix duration based on the updated multipath interference parameters and the cyclic prefix delay threshold requirements.

[0140] As one embodiment of the present invention, the detection signal for multipath interference can be periodic or aperiodic. The specific period of the detection signal is configured by the system. The triggering conditions for aperiodicity can be, but are not limited to: a large number of errors in the receiver signal, a significant decrease in the signal-to-noise ratio (SINR), and a significant decrease in the channel estimation quality.

[0141] As an embodiment of the present invention, the detection signal for multipath interference can be an existing reference signal of the system, including but not limited to any one or more of the following: demodulation reference signal (DMRS), detection reference signal (SRS), channel state information reference signal (CSI-RS), phase tracking reference signal (PTRS), synchronization signal (SS), positioning reference signal (PRS), short training sequence signal (STF), and long training sequence signal (LTF).

[0142] As a supplement to the embodiments of the present invention, the system multipath interference parameters can also be input in a custom way, such as inputting parameters like multipath delay spread based on the channel model reference value defined by 3GPP.

[0143] The S2 method can detect multipath interference in the wireless environment through indirect monitoring. Indirect monitoring methods include, but are not limited to, the quality of channel state information, the bit error rate of the receiver, and the interference between received symbols.

[0144] As one example, multipath interference in a wireless environment can be detected by measuring and estimating the wireless channel, and adaptively acquiring and adjusting the cyclic prefix duration.

[0145] A wireless channel is the impact response generated by electromagnetic waves acting on a medium, determined by the characteristics of the electromagnetic waves themselves (emission energy, wavelength, time-varying nature, etc.), the physical characteristics of the wireless environment (number, location, size, etc. of scatterers), and user mobility (distance, location, speed, etc.). A wireless channel encompasses the multipath propagation effects of wireless environment characteristics and user mobility on the channel. By estimating and measuring the channel, we can obtain the impact of multipath interference on the channel state, and thus determine the cyclic prefix duration based on the current channel state. The main methods include: Based on the obtained channel information, multipath information is reconstructed to obtain multipath interference parameters. Then, through steps S3 to S5 of this embodiment of the invention, the cyclic prefix duration is determined.

[0146] The cyclic prefix duration is determined based on the quality of the channel itself. For example, a shorter CP duration is configured if the channel quality is good, and a longer CP duration is configured if the channel quality is poor.

[0147] As a supplement to the embodiments of the present invention, the steps for adjusting the cyclic prefix duration according to channel information are as follows: Figure 2 As shown.

[0148] like Figure 1 and Figure 2 As shown, the cyclic prefix delay threshold can also be directly set to a specific value.

[0149] like Figure 3 As shown, an adaptive cyclic prefix duration adjustment system provided by an embodiment of the present invention specifically includes: The parameter acquisition module is used to acquire system parameters.

[0150] The interference detection module is used to detect multipath interference in the wireless environment.

[0151] The delay threshold setting module is used to set the system cyclic prefix delay threshold.

[0152] The cyclic prefix delay determination module is used to determine the cyclic prefix duration between each symbol in the system based on the reference delay duration of the cyclic prefix.

[0153] The interference monitoring module is used to monitor multipath interference in the wireless environment.

[0154] Example 1: Algorithm verification based on software radio platform.

[0155] On a broadband OFDM test platform with a bandwidth of 100MHz and a subcarrier spacing of 30kHz, the preset candidate set of cyclic prefixes is {2.6μs, 3.4μs, 4.7μs, 6.0μs}, with the maximum usable cyclic prefix limited to 6.4μs. The base station first reads the radio parameter table to map the sampling rate of 245.76MSa / s to a symbol length of 4096 points. The pilot structure adopts the spread-spectrum BPSK format, inserted every 0.5ms. The correlation analysis module performs 4096-point time-domain correlation, performs sliding difference on the results, and then eliminates secondary paths with insufficient confidence using a noise variance of 3σ as the threshold. After 50 frames of statistical analysis, the cumulative power ratio of the main path and the five remaining effective secondary paths is 96.8%. Based on this, the system sets the cyclic prefix reference delay to 4.3μs and selects the closest and not less than the reference delay of 4.3μs (4.7μs) from the candidate set as the target cyclic prefix, which is then written to the baseband register and applied to subsequent symbols in real time. The monitoring thread re-estimates the multipath delay every 10ms; a recalculation is triggered when the impulse response length fluctuation exceeds 10% of the current cyclic prefix. In urban highway scenarios with vehicle speeds of 120km / h, this method can control the block error rate to 2.4×10⁻⁶. -3 Compared with the fixed 2.6μs cyclic prefix scheme, the bit error rate decreased by about 57% and the throughput increased by 11.2%, which verified the effectiveness and real-time performance of the algorithm.

[0156] Example 2: FPGA-SoC hardware implementation.

[0157] For the 5G NR FR2 (100MHz, 60kHz subcarrier spacing) baseband link, the XCZU28DR SoC was selected, with hardware resource constraints of LUT ≤ 250k and DSP48E2 ≤ 1800. The parameter acquisition unit is mapped to an AXI-Lite interface module, occupying 1.2k LUTs. The correlation analysis unit adopts a two-stage pipelined FFT-IFFT architecture: the first stage uses a 1024-point FFT to calculate the pilot spectrum domain, and the second stage uses an IFFT to recover the time-domain correlation results; a 512-channel parallel butterfly processor is used to complete the operation within 3.3μs per symbol. The peak detector outputs the positions of the main and secondary peaks using a 64-channel maximum value comparison tree, and the confidence filter dynamically updates the threshold table stored in the LUT. The threshold generation unit integrates a 24-bit exponential weighted accumulator with an update period of 1ms. The duration determination unit uses a 6×6 ROM lookup table to achieve fast mapping from the threshold to the sampling integer multiple; the mapping result is written to the CP configuration field of the DU-RU inter-eCPRI structure. The monitoring unit injects a 20μs probe pulse into the NR air interface SRS resources, and the RX branch recovers the echo and reuses the correlation analysis channel. After synthesis, the logic utilization is 61%, the DSP utilization is 38%, and the power consumption is 4.7W. It can operate stably in environments ranging from -40 to 85℃. Under the laboratory multipath fading channel (ETU-5), the dynamic cyclic prefix switching delay is 45μs, with no visible impact on the air interface duty cycle, achieving a low-power, low-latency hardware closed loop.

[0158] Example 3: Base station-terminal collaborative signaling process.

[0159] In a scenario where a 64T64R massive MIMO macro base station collaborates with a smartphone terminal, the base station estimates the impulse response length and determines the cyclic prefix every 5ms. When a change in the latency threshold quantization value is detected, the base station sends a two-bit cyclic prefix index in the physical downlink control channel (PDCCH) of the next subframe using the DCI format 1-1 extension field, where 00, 01, 10, and 11 correspond to the four durations of the candidate set, respectively. After decoding, the terminal sends ACK / NACK feedback in the uplink control channel (PUCCH) of the same subframe; if ACK is received, the terminal immediately adopts the new cyclic prefix in its uplink symbol; if NACK is received, the base station retransmits the DCI. If there are three consecutive NACKs, the base station backs up to the previous valid cyclic prefix and records the anomaly count. Field tests were conducted in a suburban NLOS scenario, with pedestrian speeds ranging from 3km / h to 60km / h. Statistical analysis was performed on 480 cyclic prefix updates within 200 seconds, achieving a 99.2% bidirectional ACK success rate and an average handover completion latency of 1.5ms. The throughput is improved by 8.6% compared to the fixed maximum cyclic prefix scheme, and the bit error rate of voice blocks at cell edges is reduced by 35%. This embodiment shows that the method can be compatible with existing NR frame structures through simple signaling extensions without introducing significant air interface overhead, and can be seamlessly integrated by operators.

[0160] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0161] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An adaptive cyclic prefix duration adjustment method, characterized in that, Includes the following steps: a. Obtain the subcarrier spacing, OFDM symbol duration, sampling rate, carrier center frequency, carrier bandwidth, and the maximum allowed cyclic prefix duration of the communication system; b. Based on the pilot signal, perform time-domain correlation to obtain the autocorrelation curve, detect the positions of the main peak and the secondary peak, calculate the time delay distribution of the channel impulse response, and then obtain the multipath delay power parameters; c. Set an energy coverage ratio threshold to characterize the coverage requirement for the effective power of the channel; the ratio threshold should be greater than or equal to 95%. d. In the multipath delay power parameter, the power is accumulated from zero delay. When the accumulated power first reaches the proportional threshold × (total power), the corresponding delay value is defined as the cyclic prefix threshold delay. e. Divide the cyclic prefix threshold delay by the sampling interval and round up to obtain the number of sampling points; The number of sampling points is converted into the cyclic prefix reference duration based on the sampling rate; f. From the preset candidate cyclic prefix set, select the closest target cyclic prefix that is not less than the reference duration of the cyclic prefix and apply it to subsequent OFDM symbols; g. Periodically monitor the multipath delay power parameters; if a change in multipath characteristics is detected that meets a preset trigger condition, repeat step bf to update the target cyclic prefix duration in real time.

2. The method according to claim 1, characterized in that, Step b removes secondary paths with confidence levels below the threshold by using relevant peak difference and noise variance threshold, so that the cumulative power of the remaining paths is greater than or equal to 95% of the effective channel power.

3. The method according to claim 1, characterized in that, Step c updates the cyclic prefix delay threshold using an exponentially weighted moving average method.

4. The method according to claim 1, characterized in that, Step e determines the target cyclic prefix in the discrete cyclic prefix set based on the rounding rule.

5. The method according to claim 1, characterized in that, Step b uses a convolution method based on Fast Fourier Transform to complete the relevant calculations.

6. The method according to claim 1, characterized in that, The preset cyclic prefix set consists of a set of fixed sampling interval length values, and the set elements include sampling intervals of 64, 128, 256, and 512.

7. The method according to claim 1, characterized in that, The delay spectrum is constructed by frequency domain channel estimation, MUSIC algorithm, ESPRIT algorithm, and multipath parameters are separated by autocorrelation of spreading code. The multipath signals are then combined and the delay is recorded by RAKE receiver.

8. The method according to claim 1, characterized in that, The duration of the cyclic prefix is ​​determined by indirectly monitoring the impact of multipath effects. Indirect monitoring methods include, but are not limited to, the quality of channel state information, the bit error rate at the receiver, and the inter-symbol interference at the receiver.

9. The method according to claim 1, characterized in that, Based on the indirectly monitored multipath effect, the system adaptively adjusts the cyclic prefix duration by 0.5 microseconds until the system's bit error rate requirement is met.

10. The method according to claim 1, characterized in that, The target cyclic prefix duration is sent to the user equipment via the physical downlink control channel.

11. An adaptive cyclic prefix duration adjustment system, applied to a broadband orthogonal frequency division multiplexing system, characterized in that, include: The parameter acquisition unit is used to acquire the parameters described in step a of claim 1, including: subcarrier spacing, OFDM symbol duration, sampling rate, carrier center frequency, carrier bandwidth, and the maximum allowed cyclic prefix duration of the system. The correlation analysis unit is used to output the impulse response length; The threshold generation unit is used to generate a threshold delay that covers 95% or more of the effective channel power. The duration determination unit is used to convert the threshold delay into an integer multiple of the sampling time interval and output the target cyclic prefix duration; The monitoring unit is used to detect changes in the impulse response and trigger the update of the cyclic prefix duration.

12. The system according to claim 11, characterized in that, The correlation analysis unit includes a correlation calculator, a peak detector, and a confidence filter.

13. The system according to claim 11, characterized in that, The monitoring unit sends a detection signal and receives an echo within the time-frequency resources reserved in the frame structure. These time-frequency resources are pre-designed existing reference signals or are set as reference signals for multipath detection.

14. The system according to claim 11, characterized in that, The monitoring unit triggers an update when the change in the impulse response length exceeds 10 percent of the current loop prefix duration.

15. The system according to claim 11, characterized in that, Its overall deployment is within a wireless communication system node equipped with an antenna.

16. A non-volatile computer-readable storage medium, characterized in that, The instructions stored thereon, when executed by a processor, cause the processor to perform the method described in any one of claims 1 to 4.

17. A communication device, characterized in that, It includes a memory, a processor, and a bus, wherein the memory stores the instructions of claim 16, and the processor implements adaptive cyclic prefix duration adjustment by executing the instructions.

18. A base station device based on the system of claim 11, characterized in that, It includes an antenna device, a radio frequency device, a baseband device, and an adaptive cyclic prefix duration adjustment module. The adjustment module is deployed within the baseband device and is used to adjust the cyclic prefix duration of the transmitted signal in real time.

19. A user equipment, characterized in that, The device includes a transceiver, a processor, and a memory, wherein the processor executes instructions in the memory and cooperates with the transceiver to implement the method according to any one of claims 1 to 4.

20. An integrated circuit chip, characterized in that, It includes a processing core, a clock unit, and an on-chip memory, wherein the processing core is configured to run the method according to any one of claims 1 to 4.

21. An integrated circuit chip according to claim 20, characterized in that, The core integrated hardware-related accelerators are processed to complete the relevant calculations in step b.

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