阅读说明：本技术 一种超分辨多径数量及时延联合估计方法 (Super-resolution multi-path quantity and time delay joint estimation method ) 是由 夏楠 邢宝辉 崔桐 马昕昕 向润林 李博 赵昕 于 2021-08-26 设计创作，主要内容包括：本发明提供一种超分辨多径数量及时延联合估计方法,包括：建立通用的多径接收信号离散时间系统模型；利用信号的频域变换,构造互谱函数以消除未知源信号波形的影响；对构造的互谱函数波形的超分辨显示进行谱峰搜索；根据互谱函数局部峰值确定多径相对时延及对应幅度值,重建潜在信号与互谱函数进行匹配对应；构造代价函数,通过最大似然估计对多径数量及相应的时延值进行联合估计,得出时间延迟值。本发明提供的超分辨多径数量及时延联合估计方法是一种源信号与多径数量未知的时延估计方法,通过消除源信号波形和干扰的影响,提出了一种新的互谱函数,利用互谱函数的超分辨显示提取时延参数信息,根据时延参数信息重建潜在信号与互谱函数相匹配。(The invention provides a combined estimation method of the number of super-resolution multipath and time delay, which comprises the following steps: establishing a universal multipath received signal discrete time system model; constructing a cross-spectrum function by utilizing the frequency domain transformation of the signal so as to eliminate the influence of the waveform of the unknown source signal; performing spectral peak search on the super-resolution display of the constructed cross-spectral function waveform; determining multipath relative time delay and a corresponding amplitude value according to the local peak value of the cross-spectrum function, and reconstructing a potential signal to match and correspond to the cross-spectrum function; and constructing a cost function, and carrying out joint estimation on the multipath quantity and the corresponding time delay value through maximum likelihood estimation to obtain a time delay value. The invention provides a super-resolution multi-path quantity and time delay combined estimation method, which is a time delay estimation method with unknown source signals and multi-path quantity, and provides a new cross-spectrum function by eliminating the influence of source signal waveforms and interference.)

1. A super-resolution multipath quantity and time delay joint estimation method is characterized by comprising the following steps:

s1, establishing a universal multipath received signal discrete time system model;

s2, constructing a cross-spectrum function by using frequency domain transformation of the signal to eliminate the influence of the waveform of the unknown source signal;

s3, performing spectral peak search on the super-resolution display of the constructed cross-spectral function waveform;

s4, determining multipath relative time delay and a corresponding amplitude value according to the local peak value of the cross-spectrum function, and reconstructing a potential signal to match and correspond to the cross-spectrum function;

and S5, constructing a cost function, and carrying out joint estimation on the multipath quantity and the corresponding time delay value through maximum likelihood estimation to obtain a time delay value.

2. The method for jointly estimating the number of super-resolution multipaths and the time delay according to claim 1, wherein the step S1 is implemented as follows:

s11, modeling the received discrete time domain signal, as follows:

wherein n is 1,2, K, n is a discrete sampling point, K represents the total number of sampling points,is the channel attenuation coefficient between the first source signal to the receiving station,is the channel attenuation coefficient, J, between the second source signal and the receiving station₁The number of multipaths for the first received signal, J₂The number of multipaths for the second received signal,is the time delay value corresponding to each multipath number of the first path receiving signal,is the time delay value, omega, corresponding to each multipath number of the second path of received signal₁(t) is the additive zero mean noise, ω, received in the first path₂(t) is the additive zero mean noise of the second path receptionSound;

s12, performing frequency domain transformation on the discrete time domain signal, wherein the expression is as follows:

wherein K is 1,2₁(k) Is r₁(n) discrete Fourier transform, R₂(k) Is r₂(n) discrete Fourier transform, S (k) is the discrete Fourier transform of s (n), W₁(k) Is omega₁(n) discrete Fourier transform, W₂(k) Is omega₂(n) discrete fourier transform.

3. The method for jointly estimating the number of super-resolution multipaths and the time delay according to claim 1, wherein the step S2 is implemented as follows:

s21, setting a group of time delay points D^l1, 2., N, where N is the total number of points sampled at equal intervals, normalizing the expression in step S12 to obtain the cross-spectrum function as follows:

wherein H represents a conjugate;

s22, dispersing the Fourier sampling average value to suppress the noise part, and makingThe cross-spectral function is rewritten as:

s23, time delay point D set based on the cross-spectrum function of the step S22^lThe spectral peak closest to the true time delay point is larger, i.e. the time delay point D^l＝τ_i-λ_jTime phi^lIs the largest, i.e.:

s24, time delay point D if set^lIf the true time delay value is not approached, the frequency difference still exists, and the average value of the complex sine wave in a plurality of complete cycles is zero.

4. The method for jointly estimating the number of super-resolution multipaths and the time delay according to claim 1, wherein the step S3 is implemented as follows:

s31, let M equal to 1,2^lInformation of corresponding M peaks of |, usingThe function obtains corresponding time delay informationAnd amplitude information

S32, defining interval width delta l and converting phi^lThe value of l is in^*-Δl,l^*+Δl]Set to zero within the range;

s33, if M equals M, it indicates that the number of multipaths matches the set value, otherwise, if M equals M +1, the process returns to step S31.

5. The method for jointly estimating the number of super-resolution multipaths and the time delay according to claim 1, wherein the step S4 is implemented as follows:

as can be seen in step S3, the cross-spectrum function is composed of complex sinusoidal signals, and since the number of paths for each receiving station is unknown through weighting and combining, a set of signals with universality needs to be recovered to process all the possibilities, and in each hypothesis, M is a parameter derived from 1, 2.

Since the amplitude and delay information are known, the reconstructed signal is represented as:

6. the method for jointly estimating the number of super-resolution multipaths and the time delay according to claim 1, wherein the step S5 is implemented as follows:

s51, defining a cost function as follows:

s52, the smaller the output of the cost function is, the greater the similarity between the reconstructed signal and the cross-spectrum function, that is, the reconstructed signal is close to the spectrum with the real time delay, so that the optimal value of each number is searched by minimizing the output of the cost function, where the expression is as follows:

s53, traversing possible values of each cost function to obtain the minimum value, namely obtaining the estimation of the time delay, as follows:

Technical Field

The invention relates to the technical field of digital wireless communication, in particular to a super-resolution multipath quantity and time delay joint estimation method.

Background

Multipath delay estimation is a problem that often occurs in the field of wireless communication such as radar and sonar. Multipath refers to that only one direct path, namely a sending end and a receiving end, exists in the transmission process of signals, and due to factors such as shielding of buildings and reflection of moving vehicles on public roads in the transmission process, signals can be transmitted by other routes different from the direct path, namely, signals are transmitted by a plurality of paths from the sending end to the receiving end. And each path has a relative time difference in arrival time at the receiving station during reception, and this relative time difference is called time delay, and in order to accurately obtain the information of the transmission signal, it is necessary to solve the corresponding time delay value and its attenuation degree.

The current multipath time delay estimation method comprises a correlation method, an improved MUSIC algorithm, an expectation maximization algorithm of correlation entropy and the like.

The correlation method is the most classical method for estimating time delay in radio positioning, has a simpler principle, and is characterized in that correlation matching is carried out according to a source signal and a time delay signal, the matching degree is the maximum when the moving position of the source signal is a time delay value, and a maximum peak value correspondingly appears;

compared with a correlation method, the improved MUSIC algorithm and the expectation maximization algorithm of the correlation entropy are optimized, the improved MUSIC algorithm is a complex sinusoidal signal which is formed by superposing a plurality of complex exponential sinusoidal function harmonics by utilizing a signal, the form of the complex sinusoidal signal is consistent with the form of an arrival signal of the traditional MUSIC algorithm, a time delay value is obtained by utilizing the spectral peak search of the MUSIC algorithm, but the method has the premise that the number of multipath or the actual number of time delay can be estimated in advance, the multipath propagation number of the signal is predicted in advance, and the method has great limitation in practical engineering application.

The expectation maximization algorithm of the correlation entropy uses the maximum correlation entropy criterion to replace the minimum mean square error criterion in the expectation maximization algorithm, the method needs the known source signal, the number of the multipath is needed to be known in the iterative optimization step, and the method has great limitation.

Disclosure of Invention

In light of the above-mentioned technical problems, a method for joint estimation of super-resolution multipath quantity and time delay is provided. The super-resolution multipath quantity and time delay joint estimation method provided by the invention does not need to know a source signal, and the quantity of the multipath does not need to be known, so that the method is in accordance with the actual situation.

The technical means adopted by the invention are as follows:

a super-resolution multipath quantity and time delay joint estimation method comprises the following steps:

s1, establishing a universal multipath received signal discrete time system model;

s2, constructing a cross-spectrum function by using frequency domain transformation of the signal to eliminate the influence of the waveform of the unknown source signal;

s3, performing spectral peak search on the super-resolution display of the constructed cross-spectral function waveform;

s4, determining multipath relative time delay and a corresponding amplitude value according to the local peak value of the cross-spectrum function, and reconstructing a potential signal to match and correspond to the cross-spectrum function;

and S5, constructing a cost function, and carrying out joint estimation on the multipath quantity and the corresponding time delay value through maximum likelihood estimation to obtain a time delay value.

Further, the specific implementation process of step S1 is as follows:

s11, modeling the received discrete time domain signal, as follows:

wherein n is 1,2, K, n is a discrete sampling point, K represents the total number of sampling points,is the channel attenuation coefficient between the first source signal to the receiving station,is the channel attenuation coefficient, J, between the second source signal and the receiving station₁The number of multipaths for the first received signal, J₂The number of multipaths for the second received signal,is the time delay value corresponding to each multipath number of the first path receiving signal,is the time delay value, omega, corresponding to each multipath number of the second path of received signal₁(t) is the additive zero mean noise, ω, received in the first path₂(t) is additive zero mean noise received by the second path;

s12, performing frequency domain transformation on the discrete time domain signal, wherein the expression is as follows:

wherein K is 1,2₁(k) Is r₁(n) discrete Fourier transform, R₂(k) Is r₂(n) discrete Fourier transform, S (k) is the discrete Fourier transform of s (n), W₁(k) Is omega₁(n) discrete Fourier transform, W₂(k) Is omega₂(n) discrete fourier transform.

Further, the specific implementation process of step S2 is as follows:

s21, setting a group of time delay points D^l1, 2., N, where N is the total number of points sampled at equal intervals, normalizing the expression in step S12 to obtain the cross-spectrum function as follows:

wherein H represents a conjugate;

s22, dispersing the Fourier sampling average value to suppress the noise part, and makingThe cross-spectral function is rewritten as:

s23, time delay point D set based on the cross-spectrum function of the step S22^lThe spectral peak closest to the true time delay point is larger, i.e. the time delay point D^l＝τ_i-λ_jTime phi^lIs the largest, i.e.:

s24, time delay point D if set^lIf the true time delay value is not approached, the frequency difference still exists, and the average value of the complex sine wave in a plurality of complete cycles is zero.

Further, the specific implementation process of step S3 is as follows:

s31, let M equal to 1,2^lInformation of corresponding M peaks of |, usingThe function obtains corresponding time delay informationAnd amplitude information

S32, defining interval width delta l and converting phi^lThe value of l is in^*-Δl,l^*+Δl]Set to zero within the range;

s33, if M equals M, it indicates that the number of multipaths matches the set value, otherwise, if M equals M +1, the process returns to step S31.

Further, the specific implementation process of step S4 is as follows:

as can be seen in step S3, the cross-spectrum function is composed of complex sinusoidal signals, and since the number of paths for each receiving station is unknown through weighting and combining, a set of signals with universality needs to be recovered to process all the possibilities, and in each hypothesis, M is a parameter derived from 1, 2.

Since the amplitude and delay information are known, the reconstructed signal is represented as:

further, the specific implementation process of step S5 is as follows:

s51, defining a cost function as follows:

s52, the smaller the output of the cost function is, the greater the similarity between the reconstructed signal and the cross-spectrum function, that is, the reconstructed signal is close to the spectrum with the real time delay, so that the optimal value of each number is searched by minimizing the output of the cost function, where the expression is as follows:

s53, traversing possible values of each cost function to obtain the minimum value, namely obtaining the estimation of the time delay, as follows:

compared with the prior art, the invention has the following advantages:

1. the super-resolution multipath quantity and time delay joint estimation method provided by the invention is convenient to operate and wide in application, a cross-spectrum function is obtained by utilizing the frequency domain transformation of the received signal, the reconstructed potential signal is matched with the cross-spectrum function, and finally the estimation of the multipath time delay value is obtained.

2. The invention provides a combined estimation method of the number of super-resolution multipath and time delay, and provides a novel cross-spectrum function, which realizes super-resolution display of multipath relative time delay under the condition that the waveform of a source signal and the number of multipath are unknown.

3. The invention provides a combined estimation method of the number of super-resolution multipath and time delay, and provides a novel signal reconstruction method.

4. The super-resolution multipath quantity and time delay joint estimation method provided by the invention constructs a new cost function, and performs joint estimation on the multipath quantity and the corresponding time delay value through maximum likelihood estimation.

For the above reasons, the present invention can be widely applied to the fields of digital wireless communication and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of the method of the present invention.

Fig. 2 is a schematic diagram of multipath propagation of a signal according to an embodiment of the present invention.

Fig. 3 is a super-resolution display of signals propagating on multiple paths with signal-to-noise ratios of 15dB according to an embodiment of the present invention.

Fig. 4 is a super-resolution display of signals propagated on multiple paths with signal-to-noise ratios of 5dB according to an embodiment of the present invention.

Fig. 5 is a diagram showing an optimal value of the construction cost function according to the embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The core of the time delay estimation method under the super-resolution multipath condition provided by the invention is a method for jointly estimating the multipath quantity and the time delay value by reconstructing a potential signal model under the condition that the source signal and the multipath quantity are unknown, so that the reconstructed potential signal is matched with the source signal, and the higher the matching similarity is, the more accurate the reconstructed signal is, and the more accurate the corresponding multipath time delay value is. How to accurately reconstruct a potential signal and solve a multi-path delay value needs to solve the following problems to complete the core objective:

(1) the signal model is the premise and the basis of accurate estimation of multipath time delay, and the difficulty of accurate establishment of the signal system model is higher in a complex wireless environment;

(2) in wireless communication, the waveform of a digital modulation signal has great influence on super-resolution display of multipath time delay;

(3) and under the condition that the number of wireless propagation multipath is unknown, the difficulty coefficient for obtaining an accurate multipath time delay estimation result is higher.

The invention solves the technical problems through the following technical scheme:

the invention provides a super-resolution multi-path quantity and time delay combined estimation method, which is a time delay estimation method with unknown source signals and multi-path quantity, and provides a new cross-spectrum function by eliminating the influence of source signal waveforms and interference.

As shown in fig. 1, the present invention provides a super-resolution multipath quantity and time delay joint estimation method, which comprises the following steps:

s1, establishing a universal multipath received signal discrete time system model;

s2, constructing a cross-spectrum function by using frequency domain transformation of the signal to eliminate the influence of the waveform of the unknown source signal;

s3, performing spectral peak search on the super-resolution display of the constructed cross-spectral function waveform;

s4, determining multipath relative time delay and a corresponding amplitude value according to the local peak value of the cross-spectrum function, and reconstructing a potential signal to match and correspond to the cross-spectrum function;

and S5, constructing a cost function, and carrying out joint estimation on the multipath quantity and the corresponding time delay value through maximum likelihood estimation to obtain a time delay value.

In specific implementation, as a preferred embodiment of the present invention, a signal may have multiple paths to propagate due to shielding of buildings or moving objects in a road during propagation, as shown in fig. 2, where a transmitting end has a main path, that is, a direct path, to a receiving end, but due to the influence of reflection, the signal generates 2 and 3 multipath numbers during propagation from the transmitting end, and the signal may cause a deviation of the received signal due to the influence of multipath. The specific implementation process of step S1 is as follows:

s11, modeling the received discrete time domain signal, as follows:

wherein n is 1,2, K, n is a discrete sampling point, K represents the total number of sampling points,is the channel attenuation coefficient between the first source signal to the receiving station,is the channel attenuation coefficient, J, between the second source signal and the receiving station₁The number of multipaths for the first received signal, J₂The number of multipaths for the second received signal,is the time delay value corresponding to each multipath number of the first path receiving signal,is the time delay value, omega, corresponding to each multipath number of the second path of received signal₁(t) is the additive zero mean noise, ω, received in the first path₂(t) is additive zero mean noise received by the second path;

s12, performing frequency domain transformation on the discrete time domain signal, wherein the expression is as follows:

wherein K is 1,2₁(k) Is r₁(n) discrete Fourier transform, R₂(k) Is r₂(n) discrete Fourier transform, S (k) is the discrete Fourier transform of s (n), W₁(k) Is omega₁(n) discrete Fourier transform, W₂(k) Is omega₂(n) discrete fourier transform.

In concrete implementation, as a preferred embodiment of the present invention, it can be known from the discrete fourier transform obtained by the expression in step S12 that the multipath delay information of the received signal exists in the frequency differenceIn the method, because the source signal is unknown and is affected by the waveform, the time delay cannot be calculated in the frequency domain, and to eliminate the effect of the signal waveform, the waveform amplitude of the signal itself needs to be 1 to reduce the deviation. In order to solve the time delay information, the specific implementation process of step S2 is as follows:

s21, setting a group of time delay points D^l1, 2., N, where N is the total number of points sampled at equal intervals, normalizing the expression in step S12 to obtain the cross-spectrum function as follows:

wherein H represents a conjugate;

s22, dispersing the Fourier sampling average value to suppress the noise part, and makingThe cross-spectral function is rewritten as:

s23, time delay point D set based on the cross-spectrum function of the step S22^lThe spectral peak closest to the true time delay point is larger, i.e. the time delay point D^l＝τ_i-λ_jTime phi^lIs the largest, i.e.:

s24, time delay point D if set^lIf the true time delay value is not approached, the frequency difference still exists, and the average value of the complex sine wave in a plurality of complete cycles is zero.

In practical implementation, as a preferred embodiment of the present invention, interference of random noise exists in the received signal, so that a plurality of local maximum values phi appear in the cross-spectrum function^lTherefore, it is difficult to determine which local maxima are the required multipath delay values, because it is not known how many multipaths propagate in the received signal, so a method for searching spectral peaks is proposed, in this embodiment, M peaks are artificially set, but real paths and interference information are not distinguished here, and the specific implementation process of step S3 is as follows:

s31, let M equal to 1,2^lInformation of corresponding M peaks of |, usingThe function obtains corresponding time delay informationAnd amplitude information

S32, defining interval width delta l and converting phi^lThe value of l is in^*-Δl,l^*+Δl]Set to zero within the range;

s33, if M equals M, it indicates that the number of multipaths matches the set value, otherwise, if M equals M +1, the process returns to step S31.

In specific implementation, as a preferred embodiment of the present invention, the specific implementation process of step S4 is as follows:

as can be seen in step S3, the cross-spectrum function is composed of complex sinusoidal signals, and since the number of paths for each receiving station is unknown through weighting and combining, a set of signals with universality needs to be recovered to process all the possibilities, and in each hypothesis, M is a parameter derived from 1, 2.

Since the amplitude and delay information are known, the reconstructed signal is represented as:

in specific implementation, as a preferred embodiment of the present invention, the super-resolution multipath delay estimation method provided by the present invention organically and innovatively provides that the maximum likelihood is combined with the multipath condition, so that the objective function and the constructed signal have the largest similarity as possible, and the specific implementation process of the step S5 is as follows:

s51, defining a cost function as follows:

s52, the smaller the output of the cost function is, the greater the similarity between the reconstructed signal and the cross-spectrum function, that is, the reconstructed signal is close to the spectrum with the real time delay, so that the optimal value of each number is searched by minimizing the output of the cost function, where the expression is as follows:

s53, traversing possible values of each cost function to obtain the minimum value, namely obtaining the estimation of the time delay, as follows:

examples

In order to verify the feasibility of the method, the method tests the multipath digital modulation signals received by 2 receiving stations, the source signal is a BPSK signal, and the BPSK signal is in a state of keeping unchanged in a continuous code element period, so that for the super-resolution condition, namely when the time extension is smaller than the code element duration, the state of the signal in the code element period is kept unchanged, and when the time delay length is smaller, the influence on the code element of the duration is smaller, and the accurate estimation result of the time delay is difficult to obtain.

The source signal is also represented by BPSK signal with sampling frequency f_s＝2×10⁷Hz, sampling interval Ts 1/fs, carrier frequency f_c＝0.2f_sThe code rate is defined as R1 × 10⁶bps, number of sampling points in code element is f_sThe invention adjusts the number of the signals received by two receiving stations respectively, considers four different multipath number conditions, and respectively comprises the following steps:

when the number of the multi-paths of the first path of received signals is 1, the number of the multi-paths of the second path of received signals is also 1;

when the number of the multipath of the first path of received signals is 1, the number of the multipath of the second path of received signals is 2;

when the number of the multi-paths of the first path of received signals is 1, the number of the multi-paths of the second path of received signals is 3;

when the number of the multipath of the first path of received signal is 2, the number of the multipath of the second path of received signal is also 2. So that the multipath number is finally 1,2, 3, 4 and 4 cases;

in the first case: the time delay difference and the attenuation coefficient of the two paths of signals are tau respectively₁₁＝0，α₁₁1 and τ₂₁＝-148，α₂₁＝1；

In the second case: is in the first case increased tau in the second way₂₂＝-153，α₂₂A path 2 multipath signal of 0.8;

in the third case: is that in the second case τ is increased further in the second path₂₃＝-157，α₂₃Path 3 multipath signal equal to 0.7;

in a fourth case: is that in the second case τ is increased further in the first path₁₂＝-9，α₁₂A multipath signal of 0.9.

In the case of multipath number of 2 and above, the relative delay value delta tau₂₁＝|τ₂₂-τ₂₁|＝5＜20；Δτ₃₁＝|τ₂₃-τ₂₂|＝4＜20；Δτ₃₂＝|τ₂₃-τ₂₁|＝9＜20；Δτ₄₁＝|τ₁₂-τ₁₁Where 9 < 20, the delay value is less than the symbol duration is the super-resolution case.

As shown in fig. 3, the time delay value of the super-resolution display of the cross-spectrum function in these 4 cases is shown in the figure, and it can be seen from the figure that the peak value substantially matches the time delay value, and the error is small. It can be seen that the process of the present invention is viable.

In order to verify the universality of the invention, in consideration of the accuracy judgment of the time delay estimation under the condition of low signal-to-noise ratio, the same operations of the multipath quantity are respectively carried out when the signal-to-noise ratio is 5dB, and the result is shown in figure 4, thus the method of the invention is also applicable under the condition of low signal-to-noise ratio. In the super-resolution display of the cross-spectrum function, it can be clearly seen that local small peaks can be generated at other places besides the desired multipath spectrum peaks, because the multipath number is unknown, it is impossible to judge the multipath number according to the peak condition, the invention constructs 6 groups of potential signals by means of the constructed potential signals, and respectively corresponds to 6 different conditions of the multipath number from 1 to 6, and the constructed signals respectively correspond to the cross-spectrum function from the multipath number of 1. The invention utilizes the subtraction of two signals for comparison, the matching degree of the two signals is high, namely the similarity degree is higher, the corresponding obtained result after subtraction is smaller, all the constructed signals are finally traversed, the minimum value taking result is the actual multipath quantity, as shown in figure 5, four curves respectively correspond to the situation that the multipath quantity is 1,2, 3 and 4, the minimum value taking can be clearly seen when the corresponding multipath quantity exists, and the result is consistent with the preset multipath quantity. Accordingly, the time delay value corresponding to the multipath can be obtained.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.