CN102664835A - Multicell channel estimation method based on interference elimination route by route - Google Patents

Abstract

The invention relates to a multicell channel estimation method based on interference elimination route by route, provides a thought of interference elimination based ona route, and in this thought framework, provides two specific methods which can be used to eliminate interference. After analysis, the multicell channel estimation method based on interference elimination route by route not only can get a channel impulse response with high accuracy, but also has a low computational complexity. Therefore, the method provided by the invention can getthe channel impulse response with high accuracy in the case of low computational complexity, and a good basis for joint detection is provided.

Description

Based on multi-cell channel estimation method by the footpath interference eliminated

Technical field

The present invention relates to the CDMA mobile telecommunication technical field, be specifically related to a kind of based on multi-cell channel estimation method by the footpath interference eliminated.

Background technology

TD-SCDMA (Time Division-Synchronous Code Division Multiple-Access) is one of 3G (Third Generation) Moblie technical standard, adopts time division duplex.TD-SCDMA has adopted many advanced persons' the communication technology, like smart antenna, dynamic channel allocation, joint-detection etc.

In the TD-SCDMA of 3GPP standard system, data transmit with burst form.Midamble sign indicating number (also being called as training sequence) length is 144chips, be to be inserted in the middle of two 352chips data fields, is used for receiving terminal and carries out channel estimating.Have 128 accurate quadratures in the TD-SCDMA system but not completely orthogonal basic midamble sequence, they are divided into 32 groups.In each sub-district, choose one in four basic midamble sequences of base station from given group.Adjacent cell uses accurate quadrature but not completely orthogonal midamble sequence, and the midamble sign indicating number of same sub-district different user is to be obtained through cyclic shift by certain basic midamble sequence.In the multi-cell downlink transmitting scene of identical networking, the signal that user side (UE) is received not only comprises the signal that this cell base station sends, and has also comprised the signal that send the adjacent cell base station.Therefore, when UE carried out channel estimating, the nonorthogonality of midamble sequence had just caused presence of intercell interference.In like manner; In many cell uplinks transmitting scene of identical networking; The signal that base station end is received not only comprises the signal that this community user sends; And comprised the signal that the adjacent cell user sends, when channel estimating was carried out in the base station, the nonorthogonality of midamble sequence can cause presence of intercell interference equally.

Traditional Steiner channel estimation methods can adopt FFT/IFFT to simplify calculating.Because when estimating the channel impulse response of a certain sub-district, the signal of other community users is all handled as white noise, the gross power of noise and interference is excessive, has therefore influenced the accuracy of channel estimating.Thereby use the Steiner algorithm only can obtain the relatively poor channel impulse response of initial accuracy (CIR), but this initial CIR can be used as the input of precise channels algorithm for estimating more.

Parallel interference elimination algorithm based on chip just is to use traditional Steiner algorithm to obtain initial CIR, and initial CIR is carried out noise reduction process.The midamble signal of reconstruct adjacent cell then, and with its CIR behind noise reduction one by one chip ground remove.Because this parallel interference removing method chip one by one carries out, so computation complexity is higher.In the traditional combined channel algorithm for estimating of another kind, channel estimate matrix is made up of the interference user in the adjacent cell, though precision of channel estimation is improved, need carry out matrix inversion operation in the estimation procedure, and computation complexity is high.

Summary of the invention

In order to overcome the deficiency that above-mentioned prior art exists; The object of the present invention is to provide a kind of based on multi-cell channel estimation method by the footpath interference eliminated; Really realized providing the multi-cell channel estimation method of a kind of high accuracy, low complex degree, promptly based on multi-cell channel estimation method by the footpath interference eliminated.

In order to achieve the above object, the technical scheme that the present invention adopted is:

A kind of based on the multi-cell channel estimation method by the footpath interference eliminated, step is following:

Step 1: adopt following formula

$\hat{h}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(e_{\mathrm{mid}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basic}}\right)}\right)$

Obtain the initial cir value of current service cell

Wherein, e _MidThe midamble sequence that the expression receiving terminal is received, m _BasicThe basic midamble sequence that use the expression sub-district;

Step 2: initial CIR is carried out noise reduction process, select power among the initial CIR and surpass the element of setting thresholding, thereby separation and Extraction goes out the predominating path of each sub-district;

Step 3: the sub-district to current service cell is adjacent is also adopted the method for step (1) and (2) successively, obtains adjacent sub-district through the CIR after the noise reduction process and its predominating path;

Step 4: pursue and directly eliminate adjacent area interference, and then obtain final CIR.

When the method for the area interference that described elimination is adjacent was the parallel interference removing method, the step of carrying out interference eliminated was following:

Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

$y={[{\tilde{h}}_1\left(0\right),{\tilde{h}}_1\left(1\right),\·\·\·,{\tilde{h}}_1(N_1-1),{\tilde{h}}_2\left(0\right),{\tilde{h}}_2\left(1\right),\·\·\·,{\tilde{h}}_2(N_2-1)\·\·\·,{\tilde{h}}_n\left(0\right),{\tilde{h}}_n\left(1\right),\·\·\·,{\tilde{h}}_n(N_n-1)]}^T$

Wherein is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

Step 3: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path

To the path

Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

$R_{\mathrm{ij}}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basicj}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basici}}\right)}\right)$

Calculate;

Step 4: the initial value β that iteration is set ⁽⁰⁾=y sets the predefine stopping criterion for iteration, comprises maximum iteration time, the precision of channel estimation requirement;

Step 5: obtain β according to following iterative formula ^(l), l=0,1

β ^(l)=y-Bβ ^(l-1),l＝1,2,…,∞.

Step 6: if β ^(l)Meet predefined stopping criterion for iteration, then iteration finishes, otherwise returns step (3);

Step 7: with iteration β as a result ^(l)In the predominating path substitution of each sub-district through among the CIR of noise reduction process, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.

When the method for the area interference that described elimination is adjacent was method for eliminating serial interference, the step of carrying out interference eliminated was following:

Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

$y={[{\tilde{h}}_1\left(0\right),{\tilde{h}}_1\left(1\right),\·\·\·,{\tilde{h}}_1(N_1-1),{\tilde{h}}_2\left(0\right),{\tilde{h}}_2\left(1\right),\·\·\·,{\tilde{h}}_2(N_2-1)\·\·\·,{\tilde{h}}_n\left(0\right),{\tilde{h}}_n\left(1\right),\·\·\·,{\tilde{h}}_n(N_n-1)]}^T$

Wherein

is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

Step 3: the y matrix that step 1 obtains in eliminating to parallel interference, sort from big to small and select power maximum diameter h by power _i, i is more than or equal to 1 integer smaller or equal to n;

Step 4: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path

To the path

Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

$R_{\mathrm{ij}}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basicj}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basici}}\right)}\right)$

Calculate;

Step 5: according to following formula, by directly eliminating h _iTo other footpaths h _jInterference.

h _j＝h _j-R _jih _i

Step 6: to the rearrangement of y matrix, remove the footpath of having selected, select the power maximum diameter, return step 4, till all footpaths all had been selected in the y matrix, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.

The invention has the advantages that the thinking that a kind of interference eliminated based on the path is provided, under this thinking framework, the concrete grammar of two kinds of operable interference eliminated is provided.Through analyzing, not only can obtain high-precision channel impulse response based on multi-cell channel estimation method, and have lower computation complexity by the footpath interference eliminated.Therefore method provided by the invention can obtain high-precision channel impulse response under the situation of low computation complexity, and then good basis is provided for joint-detection.

Description of drawings

Fig. 1 is the TD-SCDMA burst structure.

Fig. 2 is two cell system models.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is done more detailed explanation.

Based on the multi-cell channel estimation method by the footpath interference eliminated, step is following:

Step 1: adopt following formula

$\hat{h}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(e_{\mathrm{mid}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basic}}\right)}\right)$

Obtain the initial cir value of current service cell

Wherein, e _MidThe midamble sequence that the expression receiving terminal is received, m _BasicThe basic midamble sequence that use the expression sub-district;

Step 2: initial CIR is carried out noise reduction process, select power among the initial CIR and surpass the element of setting thresholding, thereby separation and Extraction goes out the predominating path of each sub-district;

Step 3: the sub-district to current service cell is adjacent is also adopted the method for step (1) and (2) successively, obtains adjacent sub-district through the CIR after the noise reduction process and its predominating path;

Step 4: pursue and directly eliminate adjacent area interference, and then obtain final CIR.

During the method parallel interference removing method of the area interference that described elimination is adjacent, the step of carrying out interference eliminated is following:

Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

$y={[{\tilde{h}}_1\left(0\right),{\tilde{h}}_1\left(1\right),\·\·\·,{\tilde{h}}_1(N_1-1),{\tilde{h}}_2\left(0\right),{\tilde{h}}_2\left(1\right),\·\·\·,{\tilde{h}}_2(N_2-1)\·\·\·,{\tilde{h}}_n\left(0\right),{\tilde{h}}_n\left(1\right),\·\·\·,{\tilde{h}}_n(N_n-1)]}^T$

Wherein

is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

Step 3: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path

To the path Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

$R_{\mathrm{ij}}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basicj}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basici}}\right)}\right)$

Calculate;

Step 4: the initial value β that iteration is set ⁽⁰⁾=y sets the predefine stopping criterion for iteration, comprises maximum iteration time, the precision of channel estimation requirement;

Step 5: obtain β according to following iterative formula ^(l), l=0,1

β ^(l)=y-Bβ ^(l-1),l＝1,2,…,∞.

Step 6: if β ^(l)Meet predefined stopping criterion for iteration, then iteration finishes, otherwise returns step (3);

Step 7: with iteration β as a result ^(l)In the predominating path substitution of each sub-district through among the CIR of noise reduction process, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.

When the method for the area interference that described elimination is adjacent was method for eliminating serial interference, the step of carrying out interference eliminated was following:

Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

$y={[{\tilde{h}}_1\left(0\right),{\tilde{h}}_1\left(1\right),\·\·\·,{\tilde{h}}_1(N_1-1),{\tilde{h}}_2\left(0\right),{\tilde{h}}_2\left(1\right),\·\·\·,{\tilde{h}}_2(N_2-1)\·\·\·,{\tilde{h}}_n\left(0\right),{\tilde{h}}_n\left(1\right),\·\·\·,{\tilde{h}}_n(N_n-1)]}^T$

Wherein

is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

Step 3: the y matrix that step 1 obtains in eliminating to parallel interference, sort from big to small and select power maximum diameter h by power _i, i is more than or equal to 1 integer smaller or equal to n;

Step 4: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path

To the path Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

$R_{\mathrm{ij}}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basicj}}\right)}{\mathrm{FFT}\left(m_{\mathrm{basici}}\right)}\right)$

Calculate;

Step 5: according to following formula, by directly eliminating h _iTo other footpaths h _jInterference.

h _j＝h _j-R _jih _i

Step 6: to the rearrangement of y matrix, remove the footpath of having selected, select the power maximum diameter, return step 4, till all footpaths all had been selected in the y matrix, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.

Be example with two cell pattern shown in Figure 2 particularly, wherein, the midamble sign indicating number that current service cell was suitable for is m ₁, the midamble that adjacent cell uses is m ₂Supposing has 4 users in current service cell, and also there are 4 users the adjacent service sub-district.Maximum number of user is 8 (K in a certain time slot _Cell=8), the length of CIR is 16 (W=16).Under the Pedestrian A (PedA) and two kinds of channels of Vehi cular A (VehA) that M.1225 Rec.ITU-R defines, adopt respectively based on multi-cell channel estimation method by the footpath interference eliminated.The channel parameter of two kinds of channels is as shown in table 1.Other parameter of simulating scenes is as shown in table 2.

Table 1

Table 2

Parameter	Value
		Noise?Power	-104dBm
Noise?Figure	9dB
		NodeB?Power	34dBm
PhyCH?Power	22dBm

[0081]?

Antenna?Gain	11dB
		Cell?Radius	866m

Suppose that the predominating path number of current service cell is N through extracting ₁, the predominating path number of adjacent sub-district is N ₂

Adopt the parallel interference removing method to carry out interference eliminated, step is following:

(1) obtains comprising the channel impulse response y of presence of intercell interference, by N ₁+ N ₂The individual element of selecting can be expressed as:

$y={[{\tilde{h}}_1\left(0\right),{\tilde{h}}_1\left(1\right),\·\·\·,{\tilde{h}}_1(N_1-1),{\tilde{h}}_2\left(0\right),{\tilde{h}}_2\left(1\right),\·\·\·,{\tilde{h}}_2(N_2-1)]}^T$

Wherein

is the predominating path of Serving cell, and

is the predominating path of adjacent sub-district.

(2) obtain (N ₁+ N ₂) * (N ₁+ N ₂) interference matrix B, B=R-E.Matrix R representes the weighing factor between each footpath, minizone, wherein r _IjExpression path j is to the weighing factor of path i.Because only exist presence of intercell interference, and do not have the interference in the sub-district.So diagonal blocks N in the R matrix ₁* N ₁Matrix and N ₂* N ₂Matrix is 1 except diagonal entry, and other elements are 0.Contrary diagonal piece is represented the weighing factor matrix R of Serving cell to adjacent sub-district respectively ₁₂And adjacent sub-district is to the weighing factor matrix R of Serving cell ₂₁, can calculate by following respectively formula.

$R_{12}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basic}2}\right)}{\mathrm{FFT}\left(m_{\mathrm{basic}1}\right)}\right)$

$R_{21}=\mathrm{IFFT}\left(\frac{\mathrm{FFT}\left(m_{\mathrm{basic}1}\right)}{\mathrm{FFT}\left(m_{\mathrm{basic}2}\right)}\right)$

(3) the initial value β of iteration is set ⁽⁰⁾=y sets the predefine stopping criterion for iteration, like maximum iteration time, and precision of channel estimation requirement etc.

(4) obtain β according to the iterative formula in the parallel interference removal process (4) ^(l), l=0,1 ...

(5) if β ^(l)Meet predefined stopping criterion for iteration, then iteration finishes, otherwise returns step (4)

(6) with iteration β as a result ^(l)In before N ₁Among the CIR of the Serving cell of the substitution process noise reduction process that individual element is corresponding, obtain the final CIR of Serving cell.In like manner, with iteration β as a result ^(l)Middle back N ₂Among the CIR of the adjacent sub-district of the substitution process noise reduction process that individual element is corresponding, obtain the final CIR of adjacent sub-district.

Adopt method for eliminating serial interference to carry out interference eliminated, step is following:

(1) the y matrix that obtains to step 1 in the parallel interference elimination sorts by power from big to small; ,

(2) select power maximum diameter h _i

(3) the R matrix that is obtained by step 2 in the parallel interference elimination is according to the formula in the serial interference elimination step (3), by directly eliminating h _iTo other footpaths h _jInterference.

(4) to the rearrangement of y matrix, remove the footpath of having selected, select the power maximum diameter, return step 3, till all footpaths all had been selected in the y matrix.

Adopt MSE (mean square error) and coefficient correlation ρ to weigh channel estimated accuracy in this scheme.

Wherein

$\mathrm{mse}=\sqrt{E\left({(\hat{h}-h).}^2\right)}$

$\mathrm{\ρ}=\left|\frac{\mathrm{cov}(\hat{h},h)}{\sqrt{\mathrm{cov}(\hat{h},h)\mathrm{cov}(h,h)}}\right|.$

The invention has the advantages that the thought that a kind of interference eliminated based on the path is provided, under this thought frame, provide two kinds to eliminate by the footpath parallel interference and by the footpath method for eliminating serial interference.Through simulation analysis; Not only can improve the accuracy of channel estimating based on multi-cell channel estimation method by the footpath interference eliminated; And with by the chip interference elimination method, compel zero integrated processes and compare with the least mean-square error unified algorithm, have lower computation complexity.Therefore method provided by the invention can obtain high-precision channel impulse response under the situation of low computation complexity, and then good basis is provided for joint-detection.

Claims (3)

1. One kind based on by the footpath interference eliminated multi-cell channel estimation method, it is characterized in that step is following:

   Step 1: adopt following formula

   Obtain the initial cir value of current service cell

   

   Wherein, e _MidThe midamble sequence that the expression receiving terminal is received, m _BasicThe basic midamble sequence that use the expression sub-district;

   Step 2: initial CIR is carried out noise reduction process, select power among the initial CIR and surpass the element of setting thresholding, thereby separation and Extraction goes out the predominating path of each sub-district;

   Step 3: the sub-district to current service cell is adjacent is also adopted the method for step (1) and (2) successively, obtains adjacent sub-district through the CIR after the noise reduction process and its predominating path;

   Step 4: pursue and directly eliminate adjacent area interference, and then obtain final CIR.
2. 2. according to claim 1 based on by the footpath interference eliminated multi-cell channel estimation method, it is characterized in that the method for the area interference that described elimination is adjacent is carried out interference eliminated for the parallel interference removing method, step is following:

   Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

   Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

   

   Wherein

   

   is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

   Step 3: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path To the path

   

   Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

   

   Calculate;

   Step 4: the initial value β that iteration is set ⁽⁰⁾=y sets the predefine stopping criterion for iteration, comprises maximum iteration time, the precision of channel estimation requirement;

   Step 5: obtain β according to following iterative formula ^(l), l=0,1

   β ^(l)=y-Bβ ^(l-1),l=1,2,…,∞.

   Step 6: if β ^(l)Meet predefined stopping criterion for iteration, then iteration finishes, otherwise returns step (3);

   Step 7: with iteration β as a result ^(l)In the predominating path substitution of each sub-district through among the CIR of noise reduction process, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.
3. 3. according to claim 1ly it is characterized in that based on the multi-cell channel estimation method by the footpath interference eliminated method of the area interference that described elimination is adjacent is carried out interference eliminated for adopting method for eliminating serial interference, step is following:

   Step 1: at first set the employed midamble sign indicating number of current service cell and be designated as m ₁, the midamble that use adjacent sub-district is designated as m respectively ₂, m ₃..., m _n, the predominating path number of current service cell and adjacent sub-district respectively is N ₁, N ₂..., N _n, wherein n is the integer greater than 1;

   Step 2: obtain comprising the channel impulse response y of presence of intercell interference, promptly by N=N ₁+ N ₂+ ... + N _nThe individual element of selecting is formed, and is expressed as:

   Wherein is followed successively by the predominating path of current service cell and adjacent sub-district, and i is more than or equal to 1 integer smaller or equal to n;

   Step 3: the y matrix that step 1 obtains in eliminating to parallel interference, sort from big to small and select power maximum diameter h by power _i, i is more than or equal to 1 integer smaller or equal to n;

   Step 4: obtain the interference matrix B of N * N, B=R-E, matrix R represent the weighing factor matrix between current service cell and adjacent each footpath, minizone, and wherein E is a unit matrix, R _IjThe expression path

   

   To the path

   

   Weighing factor, j is more than or equal to 1 integer smaller or equal to n, wherein i sub-district to the weighing factor matrix of j sub-district by following formula

   

   Calculate;

   Step 5: according to following formula, by directly eliminating h _iTo other footpaths h _jInterference.

   h _j＝h _j-R _jih _i

   Step 6: to the rearrangement of y matrix, remove the footpath of having selected, select the power maximum diameter, return step 4, till all footpaths all had been selected in the y matrix, obtain the final CIR of the process interference eliminated of a plurality of sub-districts.

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