阅读说明：本技术 一种基于Chirp相关峰值位置偏差趋势估计采样偏差的方法 (Method for estimating sampling deviation based on Chirp correlation peak position deviation trend ) 是由 刘鲲 刘元成 陈丽恒 鲁莎莎 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种基于Chirp相关峰值位置偏差趋势估计采样偏差的方法,包括：采用接收数据与本地基础图样的时域圆周相关来对接收的Chirp信号进行解扩,以查找解扩的相关峰值位置；利用解扩的相关峰值位置,通过迭代方式对峰值位置的移动趋势进行分析以实现对采样偏差的估计。本发明提出的基于Chirp相关峰值位置偏差趋势估计采样偏差的方法,充分利用Chirp信号解扩信息,利用较少的资源开销,联合实现了ppm的估计。(The invention discloses a method for estimating sampling deviation based on Chirp related peak position deviation trend, which comprises the following steps: despreading the received Chirp signal by adopting the time domain circumferential correlation of the received data and the local basic pattern so as to search the position of a despread correlation peak; and analyzing the moving trend of the peak position in an iterative mode by utilizing the despread related peak position so as to realize the estimation of the sampling deviation. The method for estimating the sampling deviation based on the Chirp related peak position deviation trend provided by the invention fully utilizes Chirp signal de-spread information, and jointly realizes ppm estimation by using less resource overhead.)

1. A method for estimating sampling deviation based on Chirp correlation peak position deviation trend is characterized by comprising the following steps: despreading the received Chirp signal by adopting the time domain circumferential correlation of the received data and the local basic pattern so as to search the position of a despread correlation peak; and analyzing the moving trend of the peak position in an iterative mode by utilizing the despread related peak position so as to realize the estimation of the sampling deviation.

2. The method of claim 1, wherein the Chirp signal is a representation of different spread symbols by cyclic shifting of the base pattern.

3. A method according to claim 2, wherein the position of the despread correlation peak is mapped to the spreading symbols.

4. The method of claim 1, further comprising, prior to iteratively analyzing the trend of movement of the peak location to achieve the estimate of the sample bias: averaging the positions of a plurality of correlation peaks received continuously to estimate effective reference peak positions, and analyzing the moving trend of the peak positions according to the effective reference peak positions.

5. The method according to claim 1, wherein the analyzing the trend of the movement of the position of the correlation peak in an iterative manner to achieve the estimation of the sampling deviation comprises: and setting a deviation threshold, screening the reasonability of the moving trend of the relevant peak position, accumulating the trend in an iteration mode to obtain an accumulated deviation value, and converting the accumulated deviation value into a sampling deviation.

6. The method of claim 1, wherein converting the accumulated offset value to a sampling offset specifically comprises: and converting the accumulated offset value into ppm, and converting the ppm into a sampling point compensation value by combining the spread spectrum factor SF and the sampling rate of the Chirp signal.

7. The method according to any of claims 1 to 6, wherein despreading the received Chirp signal using the time-domain circular correlation of the received data with the local base pattern to find the despread correlation peak position comprises: the method comprises the steps of utilizing FFT and IFFT to achieve a circle correlation value Pv of a time domain by using a received Chirp signal Rx and a Local basic pattern Local, and searching a main peak value PvMax and a corresponding correlation peak value position PdMax, wherein the specific implementation formula is as follows: pv ═ ifft (fft (rx) · conj (local)), PvMax ═ max (abs (Pv) · 2) ═ abs (Pv [ PdMax ]. 2).

8. The method of claim 7, wherein the calculation of the correlation peak position comprises an integer part and a fractional part, the integer part being a direct peak index PdInt, and the fractional part PdFrac being a binary interpolation based on the primary peak and the left and right secondary peaks:

the PvMaxEdge0 and the PvMaxEdge1 are respectively a left secondary peak and a right secondary peak;

and updates the correlation peak position: PdMax ═ PdInt + PdFrac.

9. The method of claim 8, wherein iteratively analyzing the trend of the peak locations to estimate the sample bias using the despread correlation peak locations comprises:

firstly, storing correlation peak positions of m continuously received peaks satisfying-PdWin < PdMax [ k ] < PdWin, where k is 1, … m, averaging the stored m peaks to obtain an initial effective peak position Real _ Calc, and firstly succeeding in a symbol value subscript: real _ start ═ m/2+ 1;

setting the current peak value as a current effective peak value Calc ═ PdMax, a symbol index count Idx ═ CntNum, calculating a position accumulated offset sum _ tresVvalue ═ Calc-Real _ Calc, and a symbol index sum _ tresdIdx ═ Idx-Real _ Start;

after the effective initial position is determined, performing deviation rationality judgment on subsequent continuous peak position information PdMax in an iteration mode: abs (PdMax-Calc) < (CntNum-Idx) × DeltaSThr, wherein DeltaSThr is an offset decision threshold of continuous symbols, for a peak value meeting an offset strategy, a position offset sum _ tredValue and a symbol index sum _ tredIdx are accumulated, and the current peak value is updated to be Calc, and the corresponding symbol index is Idx and is used as reference information for judging the rationality of the next iteration offset;

and converting the accumulated position offset sum _ tredvalue into ppm, and converting the ppm into a sampling point compensation value by combining the spreading factor SF and the sampling rate of Chirp.

Technical Field

The invention relates to the technical field of synchronization of wireless spread spectrum communication systems, in particular to a method for estimating sampling deviation based on Chirp related peak position deviation trend.

Background

The synchronization of the spreading codes means that the spread spectrum code signal arriving at the receiver and the local reference spread spectrum signal are exactly consistent in time in the pattern position of the codes and the code clock rate, and if the inconsistency is inconsistent, the symbol synchronization is deviated. When the spreading codes are not completely synchronized, the spread signals cannot be despread, which results in failure of information transmission.

In the current wireless communication receiver, the structure of the software radio system for intermediate frequency digitization is shown in fig. 1, and a frequency source provided by a local oscillator in the structure enables an AD sampler to sample a received analog intermediate frequency signal at a fixed frequency and convert the analog intermediate frequency signal into a digital signal. However, because the sampling clocks of the transmitter and the receiver are generated by different crystal oscillators, when the receiver samples the received signal, a sampling offset (also called a timing offset) is generated, so that the signal sampled by the receiver is not sampled at the optimal sampling point, as shown in fig. 2, and thus a despreading failure of the spreading code is generated.

The above background disclosure is only for the purpose of assisting understanding of the concept and technical solution of the present invention and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for estimating sampling deviation based on Chirp related peak position deviation trend, which fully utilizes Chirp signal de-spread information, utilizes less resource overhead and jointly realizes ppm estimation.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention discloses a method for estimating sampling deviation based on Chirp related peak position deviation trend, which comprises the following steps: despreading the received Chirp signal by adopting the time domain circumferential correlation of the received data and the local basic pattern so as to search the position of a despread correlation peak; and analyzing the moving trend of the peak position in an iterative mode by utilizing the despread related peak position so as to realize the estimation of the sampling deviation.

Preferably, the Chirp signal represents different spread spectrum symbols by cyclic shift of the basic pattern.

Preferably, the position of the correlation peak in which despreading is performed is mapped to the spreading symbols.

Preferably, before analyzing the moving trend of the peak position in an iterative manner to achieve the estimation of the sampling deviation, the method further comprises: averaging the positions of a plurality of correlation peaks received continuously to estimate effective reference peak positions, and analyzing the moving trend of the peak positions according to the effective reference peak positions.

Preferably, the analyzing the moving trend of the correlation peak position in an iterative manner to achieve the estimation of the sampling deviation specifically includes: and setting a deviation threshold, screening the reasonability of the moving trend of the relevant peak position, accumulating the trend in an iteration mode to obtain an accumulated deviation value, and converting the accumulated deviation value into a sampling deviation.

Preferably, converting the accumulated offset value into the sampling offset specifically includes: and converting the accumulated offset value into ppm, and converting the ppm into a sampling point compensation value by combining the spread spectrum factor SF and the sampling rate of the Chirp signal.

Preferably, despreading the received Chirp signal by using time-domain circular correlation between the received data and the local basic pattern to find a despread correlation peak position specifically includes: the method comprises the steps of utilizing FFT and IFFT to achieve a circle correlation value Pv of a time domain by using a received Chirp signal Rx and a Local basic pattern Local, and searching a main peak value PvMax and a corresponding correlation peak value position PdMax, wherein the specific implementation formula is as follows: pv ═ ifft (fft (rx) · conj (local)), PvMax ═ max (abs (Pv) · 2) ═ abs (Pv [ PdMax ]. 2).

Preferably, the calculation of the correlation peak position comprises an integer part and a fractional part, the integer part being the direct peak index PdInt, and the fractional part PdFrac being obtained by binary interpolation based on the primary peak and the left and right secondary peaks:

the PvMaxEdge0 and the PvMaxEdge1 are respectively a left secondary peak and a right secondary peak;

and updates the correlation peak position: PdMax ═ PdInt + PdFrac.

Preferably, the analyzing the moving trend of the peak position in an iterative manner by using the despread correlation peak position to realize the estimation of the sampling deviation specifically includes:

firstly, storing correlation peak positions of m continuously received peaks satisfying-PdWin < PdMax [ k ] < PdWin, where k is 1, … m, averaging the stored m peaks to obtain an initial effective peak position Real _ Calc, and firstly succeeding in a symbol value subscript: real _ start ═ m/2+ 1;

setting the current peak value as a current effective peak value Calc ═ PdMax, a symbol index count Idx ═ CntNum, calculating a position accumulated offset sum _ tresVvalue ═ Calc-Real _ Calc, and a symbol index sum _ tresdIdx ═ Idx-Real _ Start;

after the effective initial position is determined, performing deviation rationality judgment on subsequent continuous peak position information PdMax in an iteration mode: abs (PdMax-Calc) < (CntNum-Idx) × DeltaSThr, wherein DeltaSThr is an offset decision threshold of continuous symbols, for a peak value meeting an offset strategy, a position offset sum _ tredValue and a symbol index sum _ tredIdx are accumulated, and the current peak value is updated to be Calc, and the corresponding symbol index is Idx and is used as reference information for judging the rationality of the next iteration offset;

and converting the accumulated position offset sum _ tredvalue into ppm, and converting the ppm into a sampling point compensation value by combining the spreading factor SF and the sampling rate of Chirp.

Compared with the prior art, the invention has the beneficial effects that: according to the method for estimating the sampling deviation based on the Chirp correlation peak position deviation trend, the despreading of all received Chirp signals is realized by correlating with the time domain circumference of a local basic pattern, so that the local sequence storage is simplified, and the despreading computation amount and time are effectively reduced; and the position information of the despreading peak of the Chirp signal is further fully utilized, so that the despreading and the estimation of ppm are effectively combined by the system, and the calculation resources are reduced.

Drawings

FIG. 1 is a hardware block diagram of a receiver of a software radio;

FIG. 2 is a schematic diagram of sample clock skew;

fig. 3 is a flowchart of a method for estimating a sampling deviation based on a special Chirp correlation peak position deviation trend according to a preferred embodiment of the present invention;

FIG. 4 is a time-frequency diagram of symbols in 4-system;

fig. 5 is a sample bias workflow diagram of an embodiment of the present invention.

Detailed Description

The invention will be further described with reference to the accompanying drawings and preferred embodiments.

The preferred embodiment of the invention discloses a method for estimating sampling deviation based on the position deviation trend of a special Chirp related peak, which comprises the following steps: (1) the special Chirp signal represents different spread spectrum symbols by cyclic shift of a basic pattern; (2) despreading the Chirp signal is realized by adopting time domain circumference correlation of received data and a local basic pattern, and the position of a despread correlation peak has a mapping relation with a spread spectrum symbol; (3) the estimation scheme of the sampling deviation fully utilizes the despreading information-related peak position, and realizes the estimation of the sampling deviation by iteratively analyzing the moving trend of the peak position; (4) the trend determination of the sampling deviation estimation to the peak position is divided into three steps: effectively referring to the estimation of the peak position- > iteratively judging the reasonability of the peak position and accumulating and storing the trend- > converting the accumulated trend into ppm and converting the ppm into a sampling point compensation value by combining the spreading factor SF and the sampling rate of Chirp. The invention fully utilizes the position information of the despreading peak of the Chirp signal, so that the despreading and the estimation of ppm are effectively combined by the system, thereby reducing the calculation resources.

In the wireless spread spectrum communication system according to the preferred embodiment of the present invention, a special Chirp signal is constructed, and a Chirp signal of a certain symbol is used as a basic pattern, and spread spectrum mapping for different symbols is realized by cyclic shift of the basic pattern. At an Rx end, despreading all received Chirp signals is realized by correlating with the time domain circumference of a local basic pattern, so that local sequence storage is simplified, despreading computation amount and time are effectively reduced, and the position of a despreading correlation peak value and a spreading symbol have a mapping relation. Specifically, the method for estimating the sampling deviation based on the special Chirp correlation peak position deviation trend disclosed by the preferred embodiment of the invention has the following characteristics:

1) a special Chirp signal is constructed, the Chirp signal is generated by cyclic shift of a basic pattern, and despreading of the Chirp signal simplifies storage of a local sequence at a receiving end;

2) the sampling deviation estimation is based on trend analysis of the de-spread peak position of a special Chirp signal to realize the estimation of the sampling deviation;

3) the estimation method needs to preset a deviation threshold value, carries out peak value trend rationality screening, carries out trend accumulation in an iterative mode, and finally converts the deviation value into ppm deviation.

The Chirp signals of different symbols are all represented by the Chirp signals after cyclic shift of the basic pattern; at an Rx end, despreading of a Chirp signal is realized by adopting time domain circular correlation of received data and a local basic pattern, and the position of a despreading correlation peak has a mapping relation with a spreading symbol.

Using FFT and IFFT to realize a circle correlation value Pv of a time domain and find a main peak PvMax and a corresponding peak position PdMax by receiving a Chirp signal Rx and a Local basic pattern Local, and specifically realizing the following formulas (1) and (2):

Pv＝ifft(fft(Rx).*conj(Local)) (1)

PvMax＝max(abs(Pv).^2)＝abs(Pv[PdMax].^2) (2)

the calculation of the peak position includes an integer part and a fractional part, the integer part is a direct peak index PdInt, and the fractional part PdFrac is obtained by binary interpolation based on a main peak and left and right secondary peaks (PvMaxEdge0, PvMaxEdge1), which is specifically shown in formula (3). The processing improves the estimation precision while reducing the number of Chirp symbols;

PvMaxEdge0＝Pv[PdInt-1]，PvMaxEdge1＝Pv[PdInt+1]

updating the peak position: PdMax ═ PdInt + PdFrac.

The reference effective initial peak position is determined by averaging, i.e. after starting the estimation algorithm for ppm, the correlation peaks for m peaks received consecutively satisfying-PdWin < PdMax [ k ] < PdWin (k 1, … m) are stored first. Averaging the stored m peaks to obtain an initial effective peak position Real _ Calc, the first successful symbol value subscript: real _ start ═ m/2+ 1.

Setting the current peak value as the current effective peak value Calc ═ PdMax, the symbol index count Idx ═ CntNum, the position cumulative offset sum _ trestvalue ═ Calc-Real _ Calc and the symbol index sum _ tresidx ═ Idx-Real _ Start.

After the effective initial position is determined, iteratively performing deviation rationality judgment on subsequent continuous peak position information PdMax: abs (PdMax-Calc) < (CntNum-Idx). DeltaSThr. And the DeltaSThr is an offset decision threshold of continuous symbols, for the peak value meeting the offset strategy, accumulating a position offset sum _ tredValue and a symbol index sum _ tredIdx, updating the current peak value to be Calc, and updating the corresponding symbol index to be Idx to be used as reference information for the next iteration offset rationality decision.

And converting the accumulated position offset sum _ tredvalue into ppm, and converting the ppm into a sampling point compensation value by combining the spreading factor SF and the sampling rate of Chirp.

The following further describes the method for estimating the sampling deviation based on the trend of the deviation of the position of the special Chirp correlation peak, which is disclosed in the preferred embodiment of the present invention, with specific embodiments.

In this embodiment, the basic pattern of the fm signal is first set to be composed of Up-Chirp and Down-Chirp, as shown in formula (4). Here, the spreading pattern of different symbols is set as a right shift cycle of the base pattern (symbol 0). Of course, the basic pattern of the present invention is not limited to this pattern.

Where A is the amplitude of the signal, μ is the linear spreading slope,starting phases, T, of the first and second segments, respectively_cIs one symbol period; taking M as an example of a 4-ary system, the time-frequency diagram of each symbol is shown in fig. 4: in FIG. 4, the symbol length T is expressed_cIs divided into 4 equal segments, each segment is T long_stepI.e. T_stepIs the step size of the move. Symbol 1 shifted by T relative to symbol 0_stepSymbol 2 shifted by T relative to symbol 1_stepSymbol 3 shifted by T relative to symbol 2_stepAnd the rest is analogized in the same way.

In this embodiment, basic parameters of the system are set: bandwidth BW 125kHz, spreading factor SF 7, symbol period Tc 1.004ms, frequency step f_stepBW/2 SF 976.56 Hz; when Sym is 28, the linear spread spectrum signal will be divided into three segments, wherein the starting frequency f of the first segment₀₁Sym fstep 54.684KHz, start frequency f of the second segment₀₂The starting frequency of the third segment is BW, i.e. the linear spread spectrum signal of Sym28 is:

the working steps of the sampling offset estimation module are described in detail below, and the implementation flow thereof is shown in fig. 5.

In this embodiment, the system configuration is set: the RF is 470MHz, the sampling rate SampleRatio is 4, the symbol sampling point SampleNum is 2^ SF ^ SampleRatio 1.5 is 768, the offset threshold DeltaSStart of the sampling point is 64 (32 times amplification), DeltaSArea is 32, this embodiment takes the Jitter added with 50ppm as an example, and it is assumed that PtDMax thus entered in this embodiment is 64

{-4,3,10,13,19,17,22,-23,21,24,11,20,20,11,43,23,9,43,30,26,41,35,19,52,21,37,41,36,44,54}

S1: the symbol count CntNum of the initial sampling offset estimation is 0, and it is determined whether or not the current peak value PtDMax satisfies the rationality of the peak position. The following conditions were used:

PtDMax∈[-DeltaSStart,DeltaSStart]

if the condition is satisfied, the process proceeds to step S2, and the reset register Sum is 0, Sum _ Index is 0, Calc is 0, Index is 0, Real _ Calc is 0, Real _ Start is 0, and Buf array is initialized; otherwise, continue screening if CntNum counts CntNum ═ 10? If no eligible Buf [ CntNum ] is found yet, the estimation is considered to fail.

Assuming that PtdMax is entered in sequence as {40,45, -4,3,10,13,19,17}, the condition is not satisfied when PtdMax is {45,46}, and then the condition is discarded, and the condition is satisfied when PtdMax is-4, and then CntNum is 3; and initializes all parameters and proceeds to step S2.

S2: determining the validity of the peak position, determining a reasonable range of CntNum as a starting value in step S1, and sequentially updating the peak position PtDMax with Buf array data as follows:

buf [ k ] ═ Buf [ k-1 ]; k is 1,2,3, 4; wherein, Buf [0] ═ PtDMax.

Calculating the difference value between each datum in the DeltaSState 9Buf array, wherein the first effective value is screened out, and the screening condition is as follows:

tmp [ k ] ═ abs (Buf [ k ] -Buf [ k-1]) and Tmp [ k ] ∈ (0, DeltaSArea)

When the conditions are met for the first time, calculating the average value of Buf [0] to Buf [4] and recording the average value as an initial effective value Real _ Calc, wherein the first successful numerical subscript Real _ Start ═ CntNum-2;

record the current valid value: calc ═ PtDMax; subscript count Index ═ CntNum.

Calculating the Sum value: sum + ═ call-Real _ call;

calculate the subscript Sum _ Index value: sum _ Index + ═ Index-Real _ Start;

then step S3 is entered, otherwise, the screening is continued; if the condition is not satisfied, when the counter CntNum is equal to 32, the estimation is considered to fail, and the counter CntNum is reset;

in this embodiment, if Buf [5] ═ {19,13,10,3, -4} is data after the Buf is first filled, Tmp [4] ═ {6,3,7,7}, both of which satisfy the system requirements; therefore, Real _ call is 8, Real _ start is 3, and the current valid value, Calc, is 19, and the subscript count, Index, is 5; sum 11 and Sum _ Index 2.

S3: and determining the effectiveness of the peak value after the iterative processing mode, and accumulating the deviation. The decision mechanism of its validity is as follows:

calculating the difference value between the current P path peak value position PtDMax and the last recorded effective peak value position Calc:

Tmp1＝abs(PtDMax-Calc)

the difference between the current counter CntNum and the last recorded valid peak position Index counter Index is calculated:

Tmp2＝CntNum-Index

judging whether the following conditions are met:

Tmp1≤Tmp2×DeltaSArea

and if the condition is met, updating the latest peak effective value Calc and the peak subscript:

Calc＝PtDMax

Index＝CntNum

and update Sum and Sum _ Index simultaneously:

Sum+＝PtDMax-Real_Calc

Sum_Index+＝CntNum-Real_Start

repeating the above steps until CntNum is equal to CntNumThr, wherein CntNumThr is equal to 30;

here, Sum is 440 after the iteration is completed; sum _ Index 330.

S4: calculating a sampling deviation estimated value:

PPM _ Est _ Calc-Sum/Sum _ Index/SampleNum/magnification

＝440/336/768/32*1e6

＝53.28ppm

The compensation processing of the sampling deviation can be realized by adopting an interpolation filter, or the value index of the buffer is adjusted to correct, and if the scheme adopts the adjustment scheme of the buffer, the number of the adjustment sampling points of each symbol is as follows:

PPM _ Comp/Sum _ Index magnification factor 440/336/32 0.0409

Set SymIdx to 0, SymIdx + +; remain _ ppm is 0;

when floor (SymIdx PPM _ Comp + remaining _ PPM) ═ 1, for the buffered received data, one sampling point is taken forward, the sampling offset is compensated, and the residual offset is updated:

Remain_ppm＝SymIdx*PPM_Comp+Remain_ppm-1，SymIdx＝0。

it can be seen from this embodiment that the present solution can effectively estimate the sampling offset, the estimation error is 3.28ppm, and the estimation error requirements of different systems can be satisfied by adjusting CntNumThr.

In the embodiment of the invention, the despreading peak position information of the Chirp signal is fully utilized, so that the despreading and the estimation of ppm are effectively combined by the system, thereby reducing the calculation resources.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.