A random access frequency offset estimation and indication method and a random access frequency offset compensation method

Abstract

The application discloses a random access frequency offset estimation and indication method and a random access frequency offset compensation method, and belongs to the technical field of wireless communication, and comprises the following steps: performing cross-correlation operation on a PRACH preamble and a PRACH reference sequence to obtain a correlation value sequence, extracting peak values and positions of a first peak, a second peak and a third peak, and estimating a noise floor; determining a theoretical double-peak interval, and determining the effective reliability of a current PRACH reference sequence frequency offset measurement according to the matching of the interval between the positions of the first peak and the second peak and the theoretical double-peak interval, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor and a phase slope fitting residual, obtaining a candidate frequency offset and determining a target frequency offset estimation value, calculating a frequency offset change rate and an effective time window, packaging frequency offset information and indicating the frequency offset information and the effective reliability to a terminal. The application solves the problem that the existing technology cannot suppress the abnormal interference of unreliable PRACH peaks on frequency offset estimation.

Description

Technical Field

[0001] This invention relates to a method for estimating and indicating random access frequency offset and a method for compensating random access frequency offset, belonging to the field of wireless communication technology. Background Technology

[0002] In scenarios such as non-terrestrial networks, satellite-connected terminals, satellite relay, and high-speed mobile wireless communications, the uplink frequency of terminals is not yet accurately synchronized in the initial stage of random access. Existing frequency offset estimation schemes typically involve the network side performing correlation detection on the PRACH preamble sent by the terminal and calculating the frequency offset based on the positional relationship of the main peak, secondary peak, and peak within the detection window. Some schemes also incorporate auxiliary information such as ephemeris, terminal coarse position, beam center, historical frequency offset prediction, or group common frequency offset to improve estimation accuracy.

[0003] However, existing solutions do not assess the reliability of the PRACH peak structure. When low signal-to-noise ratio, multipath propagation, adjacent cyclic shift interference, or anomalous peaks occur, the detected second peak is often not a valid second peak in the theoretical bimodal structure, but may be a spurious peak caused by noise, multipath propagation, or interference. Directly using the main peak and the second peak to calculate the frequency offset is prone to outlier errors. Furthermore, existing solutions do not control the selection or fusion of the current measurement, reference frequency offset, and local search based on the reliability of the peak structure; when indicating the frequency offset to the terminal, they typically only provide the numerical value of the frequency offset, lacking auxiliary information such as reliability level, effective time window, or frequency offset change rate, preventing the terminal from flexibly adjusting the uplink compensation strategy based on the reliability of the information. Therefore, existing technologies cannot suppress the anomalous interference caused by unreliable PRACH peaks in frequency offset estimation. Summary of the Invention

[0004] The purpose of this invention is to provide a random access frequency offset estimation and indication method and a random access frequency offset compensation method. By determining the effective reliability of PRACH frequency offset measurement, a candidate frequency offset is obtained by using the current PRACH frequency offset measurement result, or a reference frequency offset or a local CFO search result, or by weighted fusion of the two, according to the reliability classification. The frequency offset information and effective reliability are then indicated to the terminal to solve the problem that the existing technology cannot suppress the abnormal interference of unreliable PRACH peaks on frequency offset estimation.

[0005] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0006] In a first aspect, the present invention provides a random access frequency offset estimation and indication method, executed by the network side, comprising:

[0007] The receiving terminal generates a PRACH preamble based on the Zadoff-Chu sequence;

[0008] Generate the PRACH reference sequence corresponding to the PRACH preamble based on the local PRACH configuration;

[0009] Perform cross-correlation operation on the PRACH preamble and the PRACH reference sequence to obtain the correlation value sequence;

[0010] Extract the peak values ​​and positions of the first, second, and third peaks from the correlation value sequence, and estimate the noise floor;

[0011] The theoretical bimodal spacing is determined by the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain; based on the peak values ​​and positions of the first, second, and third peaks, the effective reliability of the current PRACH reference sequence frequency offset measurement is determined by the matching between the positional spacing of the first and second peaks and the theoretical bimodal spacing, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual.

[0012] When the effective reliability is higher than the first threshold, the current PRACH frequency offset measurement result is used as the candidate frequency offset; when the effective reliability is lower than the second threshold, the reference frequency offset or the local CFO search result centered on the reference frequency offset and located within the preset frequency offset search range is used as the candidate frequency offset; otherwise, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or the local CFO search result centered on the reference frequency offset and located within the preset frequency offset search range to obtain the candidate frequency offset.

[0013] The target frequency offset estimate is determined based on the candidate frequency offsets to calculate the frequency offset change rate and the effective time window;

[0014] The frequency offset information is encapsulated by at least one of the following: target frequency offset estimate, frequency offset unit, frequency offset rate of change, and effective time window. The frequency offset information and effective reliability are then indicated to the terminal.

[0015] Furthermore, the Zadoff-Chu sequence is represented as follows:

[0016] ;

[0017] In the formula, Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, This represents an exponential function with the natural number e as the base. Represents the imaginary unit. Indicates the length of the PRACH sequence. Represents pi;

[0018] The PRACH preamble is represented as follows:

[0019] ;

[0020] In the formula, Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, Indicates the cyclic shift amount. This represents the modulo operation;

[0021] The PRACH reference sequence is represented as follows:

[0022] ;

[0023] In the formula, Indicates the first PRACH reference sequence at each sampling point Indicates the channel complex gain. Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the number of samples with time offset. This indicates the carrier frequency offset to be estimated. Indicates the sampling rate. Indicates the first Noise at each sampling point.

[0024] Furthermore, the relevant value sequence is represented as follows:

[0025] ;

[0026] In the formula, Represents the index of the relevant value sequence. The corresponding sequence of related values, Indicates the first The root sequence number at each sampling point is The complex conjugate term of the PRACH preamble. This indicates the complex conjugate operation.

[0027] Furthermore, the relationship between the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain and the root sequence number is expressed as:

[0028] ;

[0029] In the formula, The root sequence number representing the PRACH reference sequence In PRACH sequence length Multiplicative inverse, This indicates a modular congruence relation.

[0030] Furthermore, the positions of the first peak and the second peak are represented as follows:

[0031] ;

[0032] ;

[0033] In the formula, Indicates the location of the first peak. Indicates the location of the second peak. Represents the integer part of the normalized frequency offset.

[0034] Furthermore, the theoretical bimodal spacing is expressed as:

[0035] ;

[0036] In the formula, This represents the theoretical bimodal distance.

[0037] Furthermore, based on the peak values ​​and positions of the first, second, and third peaks, and according to the matching between the positional distance between the first and second peaks and the theoretical bi-peak distance, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual, the effective reliability of the current PRACH reference sequence frequency offset measurement is determined, including:

[0038] The consistency of the bipeak spacing was calculated based on the positional difference between the first and second peaks and the theoretical bipeak spacing, and the ambiguity of the third peak was calculated based on the peak ratio of the third peak to the second peak.

[0039] The peak signal-to-noise ratio is calculated based on the relative noise floor of the first peak, and the peak structure reliability is generated based on the consistency of the spacing between the two peaks and the ambiguity of the third peak.

[0040] The current measurement reliability is generated based on the phase slope fitting residual, the ambiguity of the third peak, and the consistency of the bi-peak spacing. The peak structure reliability and the current measurement reliability are then fused to determine the effective reliability of the current PRACH reference sequence frequency offset measurement.

[0041] The peak signal-to-noise ratio is expressed as:

[0042] ;

[0043] In the formula, Indicates peak signal-to-noise ratio. Indicates the peak value of the first peak. This indicates that the first peak is relatively low relative to the noise level. Indicates a positive number that is protected against division by zero. Represents a logarithm to the base 10;

[0044] The consistency of the bimodal spacing is expressed as follows:

[0045] ;

[0046] In the formula, This indicates that the spacing between the two peaks is consistent. This represents the function that takes the minimum value. Indicates the length of the PRACH sequence The cyclic distance function below;

[0047] The ambiguity of the third peak is expressed as follows:

[0048] ;

[0049] In the formula, Indicates the degree of ambiguity of the third peak. This indicates the peak value of the third peak. Indicates the peak value of the second peak;

[0050] The reliability of the peak structure is expressed as:

[0051] ;

[0052] In the formula, Indicates the reliability of the peak structure. Represents the first reliability mapping function;

[0053] The current measurement confidence level is expressed as follows:

[0054] ;

[0055] In the formula, This indicates the current reliability of the frequency offset measurement. This represents the second reliability mapping function. This represents the phase slope fitting residual;

[0056] The effective reliability is expressed as:

[0057] ;

[0058] In the formula, Indicates effective reliability. This represents the third reliability fusion function.

[0059] Furthermore, when the effective reliability is higher than the first threshold, the candidate frequency offset is represented as:

[0060] ;

[0061] In the formula, Indicates candidate frequency offset. This indicates the current PRACH frequency offset measurement value;

[0062] When the effective reliability is lower than the second threshold, the candidate frequency offset is expressed as:

[0063] ;

[0064] In the formula, This indicates the reference frequency offset or the reference candidate frequency offset obtained from a local CFO search.

[0065] When the effective reliability is between the first threshold and the second threshold, the candidate frequency offset is expressed as:

[0066] ;

[0067] In the formula, Indicates the fusion weight. , Indicates the second threshold value. Indicates the first threshold value. This indicates the current PRACH frequency offset measurement value.

[0068] Furthermore, frequency offset information and effective reliability are indicated to the terminal through at least one of RAR, MsgB, DCI, MACCE, or RRC signaling.

[0069] Secondly, the present invention provides a random access frequency offset compensation method, executed by a terminal, comprising:

[0070] A PRACH preamble is generated based on the Zadoff-Chu sequence and sent to the network side;

[0071] Receive frequency offset information and effective reliability from the network side, and perform frequency pre-compensation on the uplink signal.

[0072] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0073] 1. This invention determines the theoretical bipeak spacing based on the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain. Based on the matching between the positional spacing of the first and second peaks and the theoretical bipeak spacing, as well as the ambiguity of the third peak relative to the second peak, it determines whether the current peak pair is reliable, reduces the probability of mistaking noise peaks, multipath peaks, or interference peaks as valid second peaks, and identifies the peak selection uncertainty caused by the close positions of the second and third peaks.

[0074] 2. This invention determines the effective reliability of the current PRACH reference sequence frequency offset measurement based on the peak signal-to-noise ratio of the first peak relative to the noise floor and the phase slope fitting residual, combined with the matching of the positional distance between the first and second peaks with the theoretical double-peak distance and the ambiguity of the third peak relative to the second peak. The effective reliability is then graded: if it is above a first threshold, the current PRACH frequency offset measurement result is used as a candidate frequency offset; if it is below a second threshold, the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range is used as a candidate frequency offset; if it is between the two, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range to obtain the candidate frequency offset. This improves the stability of frequency offset estimation under conditions of low signal-to-noise ratio, multipath interference, and adjacent cyclic shift interference.

[0075] 3. The present invention encapsulates at least one of the target frequency offset estimate, frequency offset unit, frequency offset change rate, and effective time window into frequency offset information, and indicates the frequency offset information and effective reliability to the terminal, so that the terminal can adjust the uplink compensation strategy according to the effective reliability, and avoid the subsequent uplink signal demodulation performance degradation or access failure due to outlier frequency offset estimation.

[0076] 4. The present invention receives frequency offset information and effective reliability from the network side through the terminal, and performs frequency pre-compensation on the uplink signal according to the effective reliability. This enables the terminal to use the frequency offset information for uplink pre-compensation when the reliability of the frequency offset information is high, and to adjust the compensation range differently or wait for subsequent compensation instructions when the reliability of the frequency offset information is low. This avoids blindly using unreliable frequency offset values ​​for compensation, which may lead to a decrease in uplink signal demodulation performance or access failure. Attached Figure Description

[0077] Figure 1 This is a schematic diagram of a random access frequency offset estimation and indication method provided in an embodiment of the present invention;

[0078] Figure 2 This is a schematic diagram of a random access frequency offset compensation method provided in an embodiment of the present invention;

[0079] Figure 3 This is a schematic diagram comparing the root mean square error of frequency offset estimation between the control method provided in the embodiment of the present invention and the method of the present invention;

[0080] Figure 4 This is a schematic diagram comparing the error probabilities of the control method provided in the embodiment of the present invention and the method of the present invention;

[0081] Figure 5 This is a schematic diagram comparing the frequency offset estimation error distribution of the control method provided in the embodiment of the present invention and the method of the present invention;

[0082] Figure 6 This is a schematic diagram illustrating the relationship between effective reliability and frequency offset estimation error provided in the embodiments of the present invention;

[0083] Figure 7 This is a schematic diagram of the frequency offset estimation trajectory of the continuous PRACH observation window provided in an embodiment of the present invention;

[0084] Figure 8 This is a schematic diagram illustrating the influence of reference frequency offset error provided in an embodiment of the present invention;

[0085] Figure 9 This is a schematic diagram of the PRACH received waveform and phase rotation provided in an embodiment of the present invention;

[0086] Figure 10 This is a schematic diagram of the PRACH-related peak structure provided in an embodiment of the present invention;

[0087] Figure 11 This is a schematic diagram of the recovery of correlation peaks before and after frequency offset compensation provided in an embodiment of the present invention. Detailed Implementation

[0088] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0089] Example 1

[0090] like Figure 1 As shown in the figure, this embodiment introduces a random access frequency offset estimation and indication method, including:

[0091] Step 1: The receiving terminal generates the PRACH preamble based on the Zadoff-Chu sequence.

[0092] In this embodiment, the receiving terminal generates a PRACH preamble based on the Zadoff-Chu sequence. Utilizing the inherent constant amplitude and zero autocorrelation characteristic of the Zadoff-Chu sequence, it provides a raw signal input with periodicity and good correlation, ensuring the distinguishability of the PRACH preamble in the time and frequency domains from the signal's underlying layer. At the same time, relying on its shape-preserving characteristic that it remains a Zadoff-Chu sequence after Fourier transform, it provides the raw data foundation for the receiving end to perform accurate frequency offset detection while maintaining a low peak-to-average power ratio.

[0093] Step 2: Generate the PRACH reference sequence corresponding to the PRACH preamble based on the local PRACH configuration.

[0094] This embodiment generates a PRACH reference sequence corresponding to the PRACH preamble based on the local PRACH configuration. By reconstructing an ideal reference signal that is strictly consistent with the base station configuration locally at the receiving end, the matching template during cross-correlation processing is based entirely on the actual physical layer parameters of the cell. This eliminates the problem of inconsistent reference sequences caused by configuration deviations and provides a distortion-free local reference source for subsequent correlation operations, thereby reducing the frequency offset estimation system error caused by reference sequence mismatch from the source.

[0095] Step 3: Perform cross-correlation operation on the PRACH preamble and the PRACH reference sequence to obtain the correlation value sequence.

[0096] In this embodiment, cross-correlation is performed on the PRACH preamble and the PRACH reference sequence to obtain a correlation value sequence. The coherent accumulation effect of the correlation operation is used to concentrate the signal energy distributed throughout the preamble sequence to the correlation peak position, which significantly improves the amplitude ratio of the effective signal to the background noise. At the same time, the multi-peak structure of the cross-correlation output naturally retains the peak offset information introduced by time-domain multipath propagation or frequency offset.

[0097] Step 4: Extract the peak values ​​and positions of the first, second, and third peaks from the correlation value sequence, and estimate the noise floor.

[0098] This embodiment extracts the peak values ​​and positions of the first, second, and third peaks from the correlation value sequence and estimates the noise floor. By quantizing and locking the peak intensity and position coordinates of the first three main peaks, the key feature parameters in the time-domain correlation waveform are transformed into measurable numerical variables. At the same time, the noise floor estimated in real time is combined to eliminate the background noise fluctuation interference under different channel environments. This makes all decision quantities based on the relative peak relationship refer to the dynamic noise benchmark, improving the environmental adaptability of the effective reliability judgment of frequency offset measurement.

[0099] Step 5: Determine the theoretical bimodal spacing based on the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain; based on the peak values ​​and positions of the first, second, and third peaks, determine the effective reliability of the current PRACH reference sequence frequency offset measurement according to the matching between the positional spacing of the first and second peaks and the theoretical bimodal spacing, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual.

[0100] This embodiment determines the theoretical bimodal spacing based on the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain. It then determines the effective reliability of the current PRACH reference sequence frequency offset measurement based on the matching of the positional spacing between the first and second peaks with the theoretical bimodal spacing, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual. By introducing the modular inverse operation from algebraic number theory into the calculation of the theoretical bimodal spacing, the frequency offset measurement decision process has a fixed integer ambiguity constraint boundary. Simultaneously, by integrating four dimensions of decision factors—peak position matching, ambiguity exclusion degree, signal-to-noise ratio threshold, and phase linearity—a multi-dimensional joint decision mechanism is constructed from three levels: peak amplitude, time-domain position, and frequency-domain phase slope. This effectively distinguishes between peak shifts introduced by the true frequency offset and spurious peak position changes caused by noise or interference, improving the accuracy and anti-misjudgment capability of the effective reliability characterization results.

[0101] Step 6: Determine candidate frequency offsets based on the effective reliability.

[0102] When the effective reliability is higher than the first threshold, the current PRACH frequency offset measurement result is used as the candidate frequency offset; when the effective reliability is lower than the second threshold, the reference frequency offset or the local CFO search result centered on the reference frequency offset and located within the preset frequency offset search range is used as the candidate frequency offset.

[0103] When the effective reliability is between the first threshold and the second threshold, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or the local CFO search results centered on the reference frequency offset and within the preset frequency offset search range to obtain the candidate frequency offset;

[0104] This embodiment determines candidate frequency offsets based on effective reliability. When the effective reliability is higher than a first threshold, the current PRACH frequency offset measurement result is used as the candidate frequency offset. When the effective reliability is lower than a second threshold, the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range is used as the candidate frequency offset. When the effective reliability is between the first and second thresholds, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range to obtain the candidate frequency offset. By setting dual thresholds, the candidate frequency offset selection is divided into a high-reliability direct pass zone, a low-reliability substitution zone, and an intermediate-state fusion zone. In the high-reliability zone, the original accuracy of the direct measurement value is maintained. In the low-reliability zone, the effective value is substituted using the reference frequency offset or local CFO search to avoid the introduction of erroneous frequency offsets. In the intermediate-state transition zone, weighted fusion is used to achieve a smooth connection between the measured value and the reference value. This ensures both the accuracy of frequency offset estimation under high signal-to-noise ratio conditions and the continuity and stability of frequency offset output under low signal-to-noise ratio or strong interference conditions, avoiding the problem of insufficient applicability of a single decision strategy under different channel qualities.

[0105] Step 7: Determine the target frequency offset estimate based on the candidate frequency offsets to calculate the frequency offset change rate and the effective time window.

[0106] This embodiment determines the target frequency offset estimate based on the candidate frequency offset to calculate the frequency offset change rate and effective time window. By expanding the frequency offset estimate result at the current moment into a dynamic parameter set that includes the frequency offset change rate and effective time window, the frequency offset estimate output is transformed from a single static instantaneous value into dynamic tracking information with the ability to represent the time-domain change trend. This provides the terminal with two additional dimensions of decision-making basis—the rate of change and the available duration—for frequency pre-compensation during uplink transmission, thereby improving the utilization efficiency and timeliness of frequency offset information when updating the frequency tracking loop on the terminal side.

[0107] Step 8: Encapsulate at least one of the following into frequency offset information: target frequency offset estimate, frequency offset unit, frequency offset change rate, and effective time window, and indicate the frequency offset information and effective reliability to the terminal.

[0108] This embodiment encapsulates at least one of the target frequency offset estimate, frequency offset unit, frequency offset change rate, and effective time window into frequency offset information and indicates the frequency offset information and effective reliability to the terminal. By encapsulating multiple frequency offset-related parameters in a structured manner and simultaneously sending the frequency offset information and its corresponding effective reliability to the terminal, the terminal can use each field in the frequency offset information in a differentiated manner according to the priority based on the received effective reliability level. This reduces the computational overhead of the terminal's blind detection of frequency offset while ensuring that the frequency offset information is sent in accordance with the uplink scheduling timing, and at the same time takes into account the balance between frequency offset compensation accuracy and signaling load.

[0109] Example 2

[0110] Based on the same inventive concept as Embodiment 1, this embodiment describes the implementation steps of a random access frequency offset estimation and indication method, including:

[0111] Step 1: The receiving terminal generates the PRACH preamble based on the Zadoff-Chu sequence.

[0112] In this embodiment, the Zadoff-Chu sequence is represented as:

[0113] ;

[0114] In the formula, Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, This represents an exponential function with the natural number e as the base. Represents the imaginary unit. Indicates the length of the PRACH sequence. It represents pi (π).

[0115] Step 2: Generate the PRACH reference sequence corresponding to the PRACH preamble based on the local PRACH configuration.

[0116] In this embodiment, the PRACH preamble is represented as:

[0117] ;

[0118] In the formula, Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, Indicates the cyclic shift amount. This indicates the modulo operation.

[0119] In this embodiment, the PRACH reference sequence is represented as:

[0120] ;

[0121] In the formula, Indicates the first PRACH reference sequence at each sampling point Indicates the channel complex gain. Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the number of samples with time offset. This indicates the carrier frequency offset to be estimated. Indicates the sampling rate. Indicates the first Noise at each sampling point.

[0122] Step 3: Perform cross-correlation operation on the PRACH preamble and the PRACH reference sequence to obtain the correlation value sequence.

[0123] In this embodiment, the correlation value sequence is represented as:

[0124] ;

[0125] In the formula, Represents the index of the relevant value sequence. The corresponding sequence of related values, Indicates the first The root sequence number at each sampling point is The complex conjugate term of the PRACH preamble. This indicates the complex conjugate operation.

[0126] Step 4: Extract the peak values ​​and positions of the first, second, and third peaks from the correlation value sequence, and estimate the noise floor.

[0127] Step 5: Determine the theoretical bimodal spacing based on the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain; based on the peak values ​​and positions of the first, second, and third peaks, determine the effective reliability of the current PRACH reference sequence frequency offset measurement according to the matching between the positional spacing of the first and second peaks and the theoretical bimodal spacing, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual.

[0128] Step 5.1: Calculate the consistency of the double peak spacing based on the position difference between the first peak and the second peak and the theoretical double peak spacing, and calculate the ambiguity of the third peak based on the peak ratio of the third peak to the second peak.

[0129] Step 5.2: Calculate the peak signal-to-noise ratio based on the relative noise floor of the first peak, and generate the peak structure reliability based on the consistency of the spacing between the two peaks and the ambiguity of the third peak.

[0130] Step 5.3: Generate the current measurement reliability based on the phase slope fitting residual, the ambiguity of the third peak, and the consistency of the bi-peak spacing. Then, fuse the peak structure reliability and the current measurement reliability to determine the effective reliability of the current PRACH reference sequence frequency offset measurement.

[0131] In this embodiment, the relationship between the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain and the root sequence number is expressed as:

[0132] ;

[0133] In the formula, The root sequence number representing the PRACH reference sequence In PRACH sequence length Multiplicative inverse, This indicates a modular congruence relation.

[0134] In this embodiment, the theoretical bimodal spacing is expressed as:

[0135] ;

[0136] In the formula, This represents the theoretical bimodal distance.

[0137] In this embodiment, the positions of the first peak and the second peak are respectively represented as follows:

[0138] ;

[0139] ;

[0140] In the formula, Indicates the location of the first peak. Indicates the location of the second peak. Represents the integer part of the normalized frequency offset.

[0141] In this embodiment, the peak signal-to-noise ratio is expressed as:

[0142] ;

[0143] In the formula, Indicates peak signal-to-noise ratio. Indicates the peak value of the first peak. This indicates that the first peak is relatively low relative to the noise level. Indicates a positive number that is protected against division by zero. It represents a logarithm with base 10.

[0144] In this embodiment, the consistency of the bimodal spacing is represented as:

[0145] ;

[0146] In the formula, This indicates that the spacing between the two peaks is consistent. This represents the function that takes the minimum value. Indicates the length of the PRACH sequence The cyclic distance function.

[0147] In this embodiment, the ambiguity of the third peak is represented as:

[0148] ;

[0149] In the formula, Indicates the degree of ambiguity of the third peak. This indicates the peak value of the third peak. This indicates the peak value of the second peak.

[0150] In this embodiment, the peak structure reliability is expressed as:

[0151] ;

[0152] In the formula, Indicates the reliability of the peak structure. This represents the first reliability mapping function.

[0153] In this embodiment, the current measurement confidence level is represented as:

[0154] ;

[0155] In the formula, This indicates the current reliability of the frequency offset measurement. This represents the second reliability mapping function. This represents the phase slope fitting residual.

[0156] In this embodiment, the effective reliability is expressed as:

[0157] ;

[0158] In the formula, Indicates effective reliability. This represents the third reliability fusion function.

[0159] Step 6: Determine the candidate frequency offset based on the effective reliability.

[0160] When the effective reliability is higher than the first threshold, the current PRACH frequency offset measurement result is used as the candidate frequency offset; the candidate frequency offset is expressed as:

[0161] ;

[0162] In the formula, Indicates candidate frequency offset. This indicates the current PRACH frequency offset measurement value.

[0163] When the effective reliability is lower than the second threshold, the reference frequency offset or the local CFO search result centered on the reference frequency offset and within the preset frequency offset search range is used as the candidate frequency offset.

[0164] ;

[0165] In the formula, This indicates the reference frequency offset or the reference candidate frequency offset obtained from the local CFO search.

[0166] When the effective reliability is between the first threshold and the second threshold, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or the local CFO search result centered on the reference frequency offset and within the preset frequency offset search range to obtain a candidate frequency offset; the candidate frequency offset is represented as:

[0167] ;

[0168] In the formula, Indicates the fusion weight. , Indicates the second threshold value. Indicates the first threshold value. This indicates the current PRACH frequency offset measurement value.

[0169] Step 7: Determine the target frequency offset estimate based on the candidate frequency offsets to calculate the frequency offset change rate and the effective time window.

[0170] Step 8: Encapsulate at least one of the target frequency offset estimate, frequency offset unit, frequency offset change rate, and effective time window into frequency offset information, and indicate the frequency offset information and effective reliability to the terminal through at least one of RAR, MsgB, DCI, MACCE, or RRC signaling.

[0171] Example 3

[0172] Based on the same inventive concept as other embodiments, such as Figure 2 As shown, this embodiment introduces a random access frequency offset compensation method based on embodiment 1 or 2, which is executed by the terminal and includes:

[0173] Step 1: Generate a PRACH preamble based on the Zadoff-Chu sequence and send it to the network side.

[0174] This embodiment generates a PRACH preamble based on the Zadoff-Chu sequence and sends it to the network side. It utilizes the constant amplitude and zero autocorrelation characteristic of the Zadoff-Chu sequence to generate a preamble waveform at the terminal side, so that the transmitted preamble maintains a flat power spectral density in the frequency domain to reduce the peak-to-average power ratio. At the same time, the combination of the root sequence number and time-domain cyclic shift provides the network side with a distinguishable random access signature sequence, providing the network side with a source of original signals with deterministic generation parameters and a standard time-frequency structure for frequency offset estimation.

[0175] Step 2: Receive frequency offset information and effective reliability from the network side, and perform frequency pre-compensation on the uplink signal.

[0176] This embodiment receives frequency offset information and effective reliability from the network side and performs frequency pre-compensation on the uplink signal. By acquiring frequency offset information from the network side, including frequency offset estimate, frequency offset change rate, and effective time window, and combining it with the simultaneously received effective reliability level, the usability confidence level of the current frequency offset information is determined. Within the effective time window, a frequency adjustment amount in the opposite direction is applied to the uplink transmitted signal, so that the residual frequency offset of the uplink signal is pre-canceled before reaching the network side receiver. At the same time, based on the level of effective reliability, it is determined whether to use the change rate in the frequency offset information for tracking compensation. This avoids the terminal blindly performing pre-compensation when the frequency offset information is unreliable, thus introducing additional frequency errors. In this way, the frequency offset estimation result from the network side is transformed into the compensation action of the uplink transmission on the terminal side, realizing closed-loop control of frequency offset correction.

[0177] Figure 3 and Figure 4 A performance comparison between the control method and the method of the present invention is shown; Figure 5 The frequency offset estimation error distribution is shown to illustrate that the method of the present invention has a more concentrated error distribution and fewer outlier errors compared to the control method; Figure 6 The relationship between effective reliability and frequency offset estimation error is shown to illustrate that effective reliability can reflect whether the current measurement is reliable; Figure 7 The frequency offset estimation trajectory within a continuous PRACH observation window is shown to illustrate that the method of the present invention has a smoother tracking effect; Figure 8 The impact of reference frequency offset error on estimation performance is shown to illustrate that the method of the present invention can still make robust selection or fusion through effective reliability when there is reference frequency offset error. Figure 9 The PRACH received waveform and phase rotation are shown to illustrate the effect of frequency offset on the received signal. Figure 10 The structure of the PRACH correlation peaks is shown to illustrate that the first peak, second peak, third peak, and noise floor are used together in reliability calculations. Figure 11The results show the recovery effect of correlation peaks before and after frequency offset compensation, illustrating that the method of the present invention can improve the concentration of correlation peaks after compensation. The control method uses a PRACH frequency offset measurement process without introducing peak structure reliability, third peak ambiguity, reference frequency offset fusion, and local search control. The method of the present invention uses effective reliability control to select or weight fusion between the current PRACH frequency offset measurement result, the reference frequency offset, and the local CFO search results. Simulation results are shown in Table 1.

[0178] Table 1: Simulation Results

[0179] As can be seen from the above results, under the conditions of low signal-to-noise ratio, multipath interference, and adjacent cyclic shift interference set in this embodiment, the root mean square error of frequency offset estimation of the method of the present invention is lower than that of the control method, and it can reduce the probability of large errors in the medium-to-high signal-to-noise ratio range. For example, at 10dB, the probability of a large error of the control method is 0.458, while that of the method of the present invention is 0.180; at 14dB, the probability of a large error of the control method is 0.072, while that of the method of the present invention is 0.020. Figures 5 to 11 It can be further seen that the method of the present invention suppresses abnormal peaks and unreliable measurements through peak structure reliability and effective reliability, making the error distribution more concentrated, continuous tracking smoother, and restoring a more obvious correlation peak structure after frequency offset compensation. The present invention can also adopt the following alternative implementation methods: the current PRACH frequency offset measurement result can be obtained by one or more of the following methods: PRACH phase slope, PRACH bimodal analytical estimation, local CFO search, or neural network estimation; the effective reliability can be calculated by segmented threshold, weighted summation, table lookup, Bayesian fusion, or machine learning model; the ambiguity of the third peak can be expanded to the entropy of the first K peaks, peak concentration, or inter-peak spacing consistency index; the frequency offset information indication method can be terminal-specific, beam-level, group-common, or cell-common; frequency offset compensation can be performed by the terminal, or pre-compensation or joint compensation can be performed by the network-side receiver.

[0180] Example 4

[0181] Based on the same inventive concept as other embodiments, this embodiment describes a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implement the steps of the methods of Embodiment 1 or 2 described above.

[0182] Example 5

[0183] Based on the same inventive concept as other embodiments, this embodiment introduces a computer program product, including computer instructions that, when executed by a processor, implement the steps of the methods described in Embodiment 1 or 2 above.

[0184] In summary, this invention determines the theoretical bipeak spacing based on the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain. Based on the matching between the positional spacing of the first and second peaks and the theoretical bipeak spacing, as well as the ambiguity of the third peak relative to the second peak, it determines whether the current peak pair is reliable, reducing the probability of mistaking noise peaks, multipath peaks, or interference peaks as valid second peaks, and identifying the peak selection uncertainty caused by the close positions of the second and third peaks.

[0185] This invention determines the effective reliability of the current PRACH reference sequence frequency offset measurement based on the peak signal-to-noise ratio of the first peak relative to the noise floor and the phase slope fitting residual, combined with the matching of the positional distance between the first and second peaks with the theoretical bi-peak distance and the ambiguity of the third peak relative to the second peak. The effective reliability is then graded: if it is above a first threshold, the current PRACH frequency offset measurement result is used as a candidate frequency offset; if it is below a second threshold, the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range is used as a candidate frequency offset; if it is between these two thresholds, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or a local CFO search result centered on the reference frequency offset and within a preset frequency offset search range to obtain the candidate frequency offset. This improves the stability of frequency offset estimation under conditions of low signal-to-noise ratio, multipath interference, and adjacent cyclic shift interference.

[0186] This invention encapsulates at least one of the target frequency offset estimate, frequency offset unit, frequency offset change rate, and effective time window into frequency offset information, and indicates the frequency offset information and effective reliability to the terminal, so that the terminal can adjust the uplink compensation strategy according to the effective reliability, and avoid the subsequent uplink signal demodulation performance degradation or access failure due to outlier frequency offset estimation.

[0187] This invention enables the terminal to receive frequency offset information and effective reliability indicated by the network side, and to perform frequency pre-compensation on the uplink signal based on the effective reliability. This allows the terminal to use the frequency offset information for uplink pre-compensation when the reliability of the frequency offset information is high, and to adjust the compensation range differently or wait for subsequent compensation instructions when the reliability of the frequency offset information is low. This avoids blindly using unreliable frequency offset values ​​for compensation, which could lead to a decrease in uplink signal demodulation performance or access failure.

[0188] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0189] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0190] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0191] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0192] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for estimating and indicating random access frequency offset, characterized in that, Executed by the network side, including: The receiving terminal generates a PRACH preamble based on the Zadoff-Chu sequence; Generate the PRACH reference sequence corresponding to the PRACH preamble based on the local PRACH configuration; Perform cross-correlation operation on the PRACH preamble and the PRACH reference sequence to obtain the correlation value sequence; Extract the peak values ​​and positions of the first, second, and third peaks from the correlation value sequence, and estimate the noise floor; The theoretical bimodal spacing is determined by the multiplicative inverse of the root sequence number of the PRACH reference sequence in the PRACH reference sequence length modulus domain; based on the peak values ​​and positions of the first, second, and third peaks, the effective reliability of the current PRACH reference sequence frequency offset measurement is determined by the matching between the positional spacing of the first and second peaks and the theoretical bimodal spacing, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual. When the effective reliability is higher than the first threshold, the current PRACH frequency offset measurement result is used as the candidate frequency offset; when the effective reliability is lower than the second threshold, the reference frequency offset or the local CFO search result centered on the reference frequency offset and located within the preset frequency offset search range is used as the candidate frequency offset; otherwise, the current PRACH frequency offset measurement result is weighted and fused with the reference frequency offset or the local CFO search result centered on the reference frequency offset and located within the preset frequency offset search range to obtain the candidate frequency offset. The target frequency offset estimate is determined based on the candidate frequency offsets to calculate the frequency offset change rate and the effective time window; The frequency offset information is encapsulated by at least one of the following: target frequency offset estimate, frequency offset unit, frequency offset rate of change, and effective time window. The frequency offset information and effective reliability are then indicated to the terminal.

2. The random access frequency offset estimation and indication method according to claim 1, characterized in that, The Zadoff-Chu sequence is represented as follows: ； In the formula, Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, This represents an exponential function with the natural number e as the base. Represents the imaginary unit. Indicates the length of the PRACH sequence. Represents pi; The PRACH preamble is represented as follows: ； In the formula, Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the first The root sequence number at each sampling point is The Zadoff-Chu sequence, Indicates the cyclic shift amount. This represents the modulo operation; The PRACH reference sequence is represented as follows: ； In the formula, Indicates the first PRACH reference sequence at each sampling point Indicates the channel complex gain. Indicates the first The root sequence number at each sampling point is The PRACH preamble. Indicates the number of samples with time offset. This indicates the carrier frequency offset to be estimated. Indicates the sampling rate. Indicates the first Noise at each sampling point.

3. The random access frequency offset estimation and indication method according to claim 1, characterized in that, The relevant value sequence is represented as follows: ； In the formula, Represents the index of the relevant value sequence. The corresponding sequence of related values, Indicates the first The root sequence number at each sampling point is The complex conjugate term of the PRACH preamble. This indicates the complex conjugate operation.

4. The random access frequency offset estimation and indication method according to claim 1, characterized in that, The relationship between the multiplicative inverse of the root sequence number of the PRACH reference sequence in the modulus domain of the PRACH reference sequence and the root sequence number is expressed as: ； In the formula, The root sequence number representing the PRACH reference sequence In PRACH sequence length Multiplicative inverse, This indicates a modular congruence relation.

5. The random access frequency offset estimation and indication method according to claim 1, characterized in that, The positions of the first peak and the second peak are respectively represented as follows: ； ； In the formula, Indicates the location of the first peak. Indicates the location of the second peak. Represents the integer part of the normalized frequency offset.

6. The random access frequency offset estimation and indication method according to claim 1, characterized in that, The theoretical bimodal spacing is expressed as: ； In the formula, This represents the theoretical bimodal distance.

7. The random access frequency offset estimation and indication method according to claim 1, characterized in that, Based on the peak values ​​and positions of the first, second, and third peaks, and according to the matching between the positional distance between the first and second peaks and the theoretical bi-peak distance, the ambiguity of the third peak relative to the second peak, the peak signal-to-noise ratio of the first peak relative to the noise floor, and the phase slope fitting residual, the effective reliability of the current PRACH reference sequence frequency offset measurement is determined, including: The consistency of the bipeak spacing was calculated based on the positional difference between the first and second peaks and the theoretical bipeak spacing, and the ambiguity of the third peak was calculated based on the peak ratio of the third peak to the second peak. The peak signal-to-noise ratio is calculated based on the relative noise floor of the first peak, and the peak structure reliability is generated based on the consistency of the spacing between the two peaks and the ambiguity of the third peak. The current measurement reliability is generated based on the phase slope fitting residual, the ambiguity of the third peak, and the consistency of the bi-peak spacing. The peak structure reliability and the current measurement reliability are then fused to determine the effective reliability of the current PRACH reference sequence frequency offset measurement. The peak signal-to-noise ratio is expressed as: ； In the formula, Indicates peak signal-to-noise ratio. Indicates the peak value of the first peak. This indicates that the first peak is relatively low relative to the noise level. Indicates a positive number that is protected against division by zero. Represents a logarithm to the base 10; The consistency of the bimodal spacing is expressed as follows: ； In the formula, This indicates that the spacing between the two peaks is consistent. This represents the function that takes the minimum value. Indicates the length of the PRACH sequence The cyclic distance function below; The ambiguity of the third peak is expressed as follows: ； In the formula, Indicates the degree of ambiguity of the third peak. This indicates the peak value of the third peak. Indicates the peak value of the second peak; The reliability of the peak structure is expressed as: ； In the formula, Indicates the reliability of the peak structure. Represents the first reliability mapping function; The current measurement confidence level is expressed as follows: ； In the formula, This indicates the current reliability of the frequency offset measurement. This represents the second reliability mapping function. This represents the phase slope fitting residual; The effective reliability is expressed as: ； In the formula, Indicates effective reliability. This represents the third reliability fusion function.

8. The random access frequency offset estimation and indication method according to claim 1, characterized in that, When the effective reliability is higher than the first threshold, the candidate frequency offset is represented as: ； In the formula, Indicates candidate frequency offset. This indicates the current PRACH frequency offset measurement value; When the effective reliability is lower than the second threshold, the candidate frequency offset is expressed as: ； In the formula, This indicates the reference frequency offset or the reference candidate frequency offset obtained from a local CFO search. When the effective reliability is between the first threshold and the second threshold, the candidate frequency offset is expressed as: ； In the formula, Indicates the fusion weight. , Indicates the second threshold value. Indicates the first threshold value. This indicates the current PRACH frequency offset measurement value.

9. The random access frequency offset estimation and indication method according to claim 1, characterized in that, Frequency offset information and effective reliability are indicated to the terminal through at least one of RAR, MsgB, DCI, MACCE or RRC signaling.

10. A random access frequency offset compensation method, characterized in that, Executed by the terminal, including: A PRACH preamble is generated based on the Zadoff-Chu sequence and sent to the network side; Receive frequency offset information and effective reliability from the network side, and perform frequency pre-compensation on the uplink signal.

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