CN102780656A - Method and device for eliminating multi-symbol subcarrier jamming and performing channel estimation jointly - Google Patents

Abstract

The invention discloses a method and a device for eliminating multi-symbol subcarrier jamming and performing channel estimation jointly. The method comprises the following steps of: obtaining a slope matrix of a multipath channel by utilizing two pilot frequency data successively received on a same subcarrier; obtaining a nodal increment matrix of the multipath channel by utilizing the pilot frequency subjected to slope matrix removal; and determining a time-domain model of the multipath channel for channel estimation by utilizing the slope matrix and the nodal increment matrix. According to the method, the time-domain model of the multipath channel is established, so that the frequency response of each subcarrier channel can be accurately obtained, and the subcarrier jamming can be effectively eliminated.

Description

A kind of many symbols subcarrier interference is eliminated combination channel estimating method and device

Technical field

The present invention relates to the method for time varying channel lower channel modeling, particularly many symbols subcarrier interference is eliminated combination channel estimating method and relevant apparatus thereof.

Background technology

OFDM (Orthogonal Frequency-Division Multiplexing; OFDM) be a kind of special multi-carrier modulation technology, it can become the low-speed parallel data stream modulates and to mutually orthogonal subcarrier, transmit with high-speed data-flow through serial to parallel conversion; So; The duration of each symbol increases, and through adding Cyclic Prefix (Cyclic Prefix-CP), can the linear convolution of signal and channel be converted into circular convolution; Receiving terminal adopts the frequency-domain equalizer of single order, to eliminate anti-intersymbol interference (Inter-Symbol Interference-ISI).See from the frequency domain angle; Because OFDM sub-carriers interval is less than the coherence bandwidth of channel; So OFDM can be good at contrary frequency selectivity decline and narrow band interference, and the OFDM technology easily with multiple-input and multiple-output (Multiple Input and Multiple Output---MIMO) combine employing power division and adaptive modulation technology; Can obtain the branch collection and the spatial multiplexing gain in space, at utmost satisfy the requirement of channel capacity transmission.So the OFDM technology has become WLAN (Wireless Local Area Network-WLAN), the key technology of WiMax (Worldwide Interoperability for Microwave Access) and 3GPP Long Term Evolution (LTE).

Because high speed railway construction will be crossed over landform such as Plain, hills, cause the radio propagation multi-path environment comparatively complicated.The OFDM technology is applied to the high-speed railway broadband wireless access, mainly is to consider that OFDM can be good at the decline of contrary frequency selectivity.The channel estimating of multi-carrier OFDM technology is normally inserted pilot tone in the frequency domain or the time domain of transmission symbol, uses interpolation to accomplish channel estimating at receiving terminal.But the normal channel method of estimation exists precision and the not enough situation of band efficiency under the time varying channel condition, so, need further research channel estimation methods, improve systematic function, reduce the channel estimating expense.

Disturb (Inter-Carrier Interference ICI) self elimination method between subcarrier; Promptly at the ofdm system transmitting terminal; Signal is carried out particular design and coding, when it is transmitted under the time varying channel condition, disturb even receive ICI; Carry out special decoding at receiving terminal and handle, also can resist subcarrier preferably.It is at transmitting terminal modulating data to be mapped on the adjacent subcarrier with certain weight coefficient that classical ICI disturbs from the main thought of eliminating, and makes that the influence of ICI is minimum; To superpose with corresponding weight coefficient at receiving terminal, further reduce the influence of ICI.Through cancelling out each other of ICI on the adjacent sub-carrier; Can improve the performance of system greatly, but this method shortcoming is the availability of frequency spectrum only 50%, and system adopts the differential modulation mode; Though do not need channel estimating; But can not satisfy high order modulation requirements such as QAM, these shortcomings do not satisfy the high efficiency of transmission in the modern communications, have restricted its application in reality.

Summary of the invention

The object of the present invention is to provide a kind of many symbols subcarrier interference to eliminate combination channel estimating method and device, can solve better and reduce the channel estimating expense and eliminate the problem of disturbing between the OFDM sub-carriers.

According to an aspect of the present invention, provide a kind of many symbols subcarrier interference to eliminate combination channel estimating method, having comprised:

A) utilize two pilot datas that receive in succession on the same subcarrier, obtain the slope matrix of multipath channel;

B) utilize the pilot data of having eliminated said slope matrix, obtain the intercept matrix of multipath channel;

C), confirm to be used for the Model in Time Domain of the multipath channel of channel estimating according to said slope matrix and said intercept matrix.

Further, said steps A) be specially:

The pilot data

of the symbol n that receives in succession on the same subcarrier P and the pilot data

of symbol n+1 are carried out subtraction, obtain difference

Utilize said difference Obtain the slope matrix of multipath channel ${\tilde{C}}_1=\frac{1}{N+N_{\mathrm{Cp}}}{\left(\mathrm{Diag}\left(S^p\right)\right)}^{-1}{F}_L^{-1}(Y_{n+1}^p-Y_n^p);$

Wherein, N is that invert fast fourier transformation is counted N _CpBe the length of the Cyclic Prefix of symbol,

Be submatrix contrary of FFT matrix, (diag (S ^p)) ^-1Be local pilot signal S ^pDiagonal matrix contrary.

Further, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then said Confirm through following formula:

${\tilde{C}}_1=\frac{1}{N+N_{\mathrm{cp}}}{F}_L^{-1}(Y_{n+1}^p-Y_n^p)$

Further, said step B) be specially:

With comprising in the channel frequency response Part and local pilot signal S ^pDo multiplying, and use said pilot data

Do subtraction with said multiplication result, be eliminated

Pilot data

Using the

get the intercept of the multipath channel matrix

Further, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then said

Confirm through following formula:

${\tilde{C}}_2=F_L^{-1}{Y}_n^{\′p}$

Further, the Model in Time Domain of said multipath channel is confirmed through following formula:

$h(n,l)=c_1^l\·n+c_2^l$

Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath, and the Model in Time Domain of symbol n comprises the slope matrix

of L slope composition and the intercept matrix

that L intercept

formed

Further, said slope matrix

and said intercept matrix

also are used for eliminating the subcarrier interference that receives data.

Further, said method also comprises:

The Model in Time Domain of the multipath channel that utilization obtains obtains channel frequency response, and channel is carried out equilibrium treatment, obtains each sub-carrier channels frequency response.

According to a further aspect in the invention, provide a kind of many symbols subcarrier interference to eliminate the combined channel estimation unit, having comprised:

Slope matrix generation module is used to utilize two pilot datas that receive in succession on the same subcarrier, obtains the slope matrix of multipath channel;

Intercept matrix generation module is used to utilize the pilot data of having eliminated said slope matrix, obtains the intercept matrix of multipath channel;

The model generation module is used for according to said slope matrix and said intercept matrix, confirms to be used for the Model in Time Domain of the multipath channel of channel estimating.

Further, the Model in Time Domain of said multipath channel is confirmed through following formula:

$h(n,l)=c_1^l\·n+c_2^l$

Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath, and the Model in Time Domain of symbol n comprises the slope matrix

of L slope

composition and the intercept matrix

that L intercept

formed

Compared with prior art; Beneficial effect of the present invention is: the method that the invention provides a kind of linear channel modeling; And pass through channel under the situation that a symbol period internal linear changes; Adopt ICI to eliminate the combined channel estimation approach, when accurately obtaining each sub-carrier channels response, can effectively eliminate ICI again.

Description of drawings

Fig. 1 is that many symbols subcarrier interference that the embodiment of the invention provides is eliminated the combination channel estimating method flow chart;

Fig. 2 be the embodiment of the invention provide normalization Doppler less than 0.1 o'clock, channel is the linear change sketch map in time;

Fig. 3 is the OFDM pilot configuration figure that the embodiment of the invention provides;

Fig. 4 is that many symbols subcarrier interference that the embodiment of the invention provides is eliminated the combined channel estimation unit.

Embodiment

, should be appreciated that following illustrated preferred embodiment only is used for explanation and explains the present invention, and be not used in qualification the present invention a preferred embodiment of the present invention will be described in detail below in conjunction with accompanying drawing.

Fig. 1 is that many symbols subcarrier interference that the embodiment of the invention provides is eliminated the combination channel estimating method flow chart, and is as shown in Figure 1.In the present embodiment, at first the characteristic of the multipath channel Model in Time Domain of linear time-varying is described, based on said model ICI of the present invention is eliminated combination channel estimating method then and describe.

Utilization of the present invention is as normalization Doppler frequency deviation f _N≤0.1 o'clock; The multipath channel tap of time-variant multipath channel is satisfied the condition that is linear change and is carried out the linear channel modeling in an OFDM symbol period; As shown in Figure 2, can get the expression formula of slope and intercept in the channel variation parameter after the conversion, but promptly become linear time-variant channel when the multipath channel modeling; And when receiving terminal can obtain the distinguishable multipath number L of channel, the Model in Time Domain of multipath channel can be write as

Wherein, With

Be slope and the intercept that the current sign tap changes.And the frequency domain of multipath channel can be write as:

$Y\left[m\right]=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}X\left[k\right]H_l^{m-k}{e}^{-j2\mathrm{\Πlk}/N}+W\left[m\right]$

$=X\left[m\right]\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(\frac{N-1}{2}{c}_1^l+c_2^l)e^{-j2\mathrm{\Πlm}/N}+\underset{\underset{k\≠m}{k=0}}{\overset{N-1}{\mathrm{\Σ}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}X\left[k\right]\left(\frac{-c_1^l}{1-e^{-j2\mathrm{\Π}(k-m)/N}}\right)e^{-j2\mathrm{\Πlk}/N}+W\left[m\right]$

Wherein, the reception data that comprise pilot data on Y [m] the expression m sub-carrier positions, the transmission data on X [m] the expression m sub-carrier positions, W [m] representes noise section, N is expressed as IFFT and counts.

Under Novel OFDM symbol pilot configuration as shown in Figure 3, suppose that number (exponent number) L of the distinguishable multipath of multipath channel is that communication system is known, in ofdm system, selecting the L number of sub-carrier for use is pilot sub-carrier, all the other subcarriers are used to carry data.Therefore, be 2L (every distinguishable multipath has slope and two parameters of intercept) because exponent number is the unknown parameter of multipath channel of the linear time-varying of L, from the frequency domain angle, the individual local pilot signal S of L ^p=[S (0) ..., S (L-1)] ^TCan be write as with the relation of channel frequency response (comprising ICI)

Wherein,

Transform to frequency domain through the multipath channel Model in Time Domain and obtain, Be noise section, here for the number that guarantees equation with the identical of unknown number number and all be 2L.Estimate through many symbols of frequency domain combined channel, obtain the running parameter in the multipath channel time-varying characteristics, transform to frequency domain and be channel frequency response, then carry out equilibrium, promptly can obtain each sub-carrier channels frequency response accurately this moment, can eliminate ICI again.

The step of eliminating combination channel estimating method based on the ICI of said model comprises:

Step 101: utilize two pilot datas that receive in succession on the same subcarrier, obtain the slope matrix of multipath channel;

Step 102: utilize the pilot data of having eliminated said slope matrix, obtain the intercept matrix of multipath channel;

Step 103:, confirm to be used for the Model in Time Domain of the multipath channel of channel estimating according to said slope matrix and said intercept matrix.

Said step 101 is specially: the pilot data

of the symbol n that receives in succession on the same subcarrier P and the pilot data

of symbol n+1 are carried out subtraction; Obtain difference

wherein,

and

be expressed as noise section.Utilize said difference

Obtain the slope matrix of multipath channel

Wherein, N is that invert fast fourier transformation is counted N _CpBe the length of the Cyclic Prefix of symbol,

Be submatrix contrary of FFT matrix, (diag (S ^p)) ^-1Be local pilot signal S ^pDiagonal matrix contrary.

Further, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then I=diag (S ^p), said

Can be reduced to

That is to say, utilize the linear change rule of channel response, calculate the conversion slope in each distinguishable footpath of bar

Utilize the slope matrix

Can eliminate the part ICI that receives in the data.

Said step 102 is specially: with comprising in the channel frequency response Part and local pilot signal S ^pDo multiplying, and use said pilot data

Do subtraction with said multiplication result, be eliminated

Pilot data

Utilize said

Obtain the intercept matrix of multipath channel

That is to say the slope matrix that step 102 utilizes step 101 to calculate

Eliminate

In the slope part, utilize to eliminate the slope part then

Calculate the pilot data of eliminating slope part (eliminating part ICI disturbs)

Promptly eliminate pilot data

In part ICI disturb, wherein,

Utilize said then

Calculate the linear intercept matrix that changes in distinguishable footpath

Further, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then I=diag (S ^p), said Can be reduced to

Utilize the intercept matrix

Can eliminate and receive remaining ICI in the data.

In the said step 103; The Model in Time Domain of multipath channel is confirmed through formula

; Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath; The intercept matrix that the Model in Time Domain of symbol n comprises slope matrix

that L slope

formed and L intercept

composition furtherly; The variation characteristic of the multipath channel that slope matrix that utilization is calculated

and intercept matrix

become in the time of can obtaining; It is carried out Fourier transform; Be channel frequency response; Just can directly carry out equilibrium treatment to channel; Promptly can obtain each sub-carrier channels frequency response accurately this moment, effectively eliminated ICI simultaneously to receiving the influence of data.

Fig. 4 has shown many symbols subcarrier interference elimination combined channel estimation unit that the embodiment of the invention provides, and is as shown in Figure 4, comprises slope matrix generation module, intercept matrix generation module, model generation module, wherein:

Said slope matrix generation module is used to utilize two pilot datas that receive in succession on the same subcarrier, obtains the slope matrix of multipath channel.That is to say that said slope matrix generation module utilizes the linear change rule of channel response, calculate the slope matrix in distinguishable footpath

Wherein, N is that invert fast fourier transformation is counted N _CpBe the length of the Cyclic Prefix of symbol,

Be submatrix contrary of FFT matrix, (diag (S ^p)) ^-1Be local pilot signal S ^pDiagonal matrix contrary,

With

Be the pilot data of the symbol n that receives in succession on the same subcarrier P and the pilot data of symbol n+1.Said slope matrix generation module utilizes that its slope matrix that calculates

can be eliminated

to receiving the influence of data, promptly eliminates part ICI to receiving the influence of data.

Said intercept matrix generation module is used to utilize the pilot data of having eliminated said slope matrix, obtains the intercept matrix of multipath channel.That is to say that said slope matrix generation module calculates the linear slope matrix that changes in distinguishable footpath

Said intercept matrix generation module utilizes said slope matrix generation module to calculate

With comprising in the channel frequency response

Part and local pilot signal S ^pDo multiplying, and use said pilot data Do subtraction with said multiplication result, so that eliminate said To pilot data

Influence, also just can be to pilot data

Eliminate part ICI, further utilize the pilot data of eliminating part ICI

Calculate the linear intercept matrix that changes in distinguishable footpath

The intercept matrix that said intercept matrix generation module utilizes it to calculate Can eliminate To receiving the influence of data, promptly eliminate residue ICI to receiving the influence of data.

Said model generation module is used for according to said slope matrix and said intercept matrix, confirms to be used for the Model in Time Domain of the multipath channel of channel estimating.The Model in Time Domain of said multipath channel is confirmed through following formula:

$h(n,l)=c_1^l\·n+c_2^l$

Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath, and the Model in Time Domain of symbol n comprises the slope matrix

of L slope composition and the intercept matrix

that L intercept

formed

Said model generation module utilizes said slope matrix generation module to calculate the multipath channel variation characteristic that intercept matrix that slope matrix

and said intercept matrix generation module calculate becomes when obtaining, and promptly confirms the Model in Time Domain of multipath channel.It is carried out Fourier transform, be channel frequency response, just can directly carry out the multipath channel equilibrium, promptly can obtain each sub-carrier channels frequency response accurately this moment, effectively eliminated ICI again to receiving the influence of data.

Although preceding text specify the present invention, the invention is not restricted to this, those skilled in the art of the present technique can carry out various modifications according to principle of the present invention.Therefore, all modifications of doing according to the principle of the invention all are to be understood that to falling into protection scope of the present invention.

Claims (10)

1. symbol subcarrier interference more than a kind is eliminated combination channel estimating method, it is characterized in that, comprising:

A) utilize two pilot datas that receive in succession on the same subcarrier, obtain the slope matrix of multipath channel;

B) utilize the pilot data of having eliminated said slope matrix, obtain the intercept matrix of multipath channel;

C), confirm to be used for the Model in Time Domain of the multipath channel of channel estimating according to said slope matrix and said intercept matrix.

2. many symbols subcarrier interference according to claim 1 is eliminated combination channel estimating method, it is characterized in that said steps A) be specially:

The pilot data

of the symbol n that receives in succession on the same subcarrier P and the pilot data of symbol n+1 are carried out subtraction, obtain difference

Utilize said difference

Obtain the slope matrix of multipath channel ${\tilde{C}}_1=\frac{1}{N+N_{\mathrm{Cp}}}{\left(\mathrm{Diag}\left(S^p\right)\right)}^{-1}{F}_L^{-1}(Y_{n+1}^p-Y_n^p);$

Wherein, N is that invert fast fourier transformation is counted N _CpBe the length of the Cyclic Prefix of symbol, Be submatrix contrary of FFT matrix, (diag (S ^p)) ^-1Be local pilot signal S ^pDiagonal matrix contrary.

3. many symbols subcarrier interference according to claim 2 is eliminated combination channel estimating method, it is characterized in that, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then said

Confirm through following formula:

${\tilde{C}}_1=\frac{1}{N+N_{\mathrm{cp}}}{F}_L^{-1}(Y_{n+1}^p-Y_n^p)$

4. many symbols subcarrier interference according to claim 1 is eliminated combination channel estimating method, it is characterized in that said step B) be specially:

With comprising in the channel frequency response

Part and local pilot signal S ^pDo multiplying, and use said pilot data Do subtraction with said multiplication result, be eliminated

Pilot data

Utilize said

Obtain the intercept matrix of multipath channel

5. method according to claim 4 is characterized in that, if local pilot signal S ^pThe modulation of employing binary phase shift keying, then said

Confirm through following formula:

${\tilde{C}}_2=F_L^{-1}{Y}_n^{\′p}$

6. method according to claim 1 is characterized in that, the Model in Time Domain of said multipath channel is confirmed through following formula:

$h(n,l)=c_1^l\·n+c_2^l$

Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath, and the Model in Time Domain of symbol n comprises the slope matrix

of L slope composition and the intercept matrix

that L intercept

formed

7. method according to claim 1; It is characterized in that said slope matrix and said intercept matrix also are used for eliminating the subcarrier interference that receives data.

8. method according to claim 1 is characterized in that, said method also comprises:

The Model in Time Domain of the multipath channel that utilization obtains obtains channel frequency response, and channel is carried out equilibrium treatment, obtains each sub-carrier channels frequency response.

9. symbol subcarrier interference more than a kind is eliminated the combined channel estimation unit, it is characterized in that, comprising:

Slope matrix generation module is used to utilize two pilot datas that receive in succession on the same subcarrier, obtains the slope matrix of multipath channel;

Intercept matrix generation module is used to utilize the pilot data of having eliminated said slope matrix, obtains the intercept matrix of multipath channel;

The model generation module is used for according to said slope matrix and said intercept matrix, confirms to be used for the Model in Time Domain of the multipath channel of channel estimating.

10. device according to claim 9 is characterized in that, the Model in Time Domain of said multipath channel is confirmed through following formula:

$h(n,l)=c_1^l\·n+c_2^l$

Wherein, N representes symbol; 0＜l≤L; L is the number of distinguishable multipath, and the Model in Time Domain of symbol n comprises the slope matrix of L slope

composition and the intercept matrix

that L intercept

formed

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