WO2014012352A1

WO2014012352A1 - Channel estimation method and device

Info

Publication number: WO2014012352A1
Application number: PCT/CN2013/000834
Authority: WO
Inventors: 陈立俊; 邓单
Original assignee: 京信通信系统（中国）有限公司
Priority date: 2012-07-17
Filing date: 2013-07-11
Publication date: 2014-01-23
Also published as: CN103546399B; CN103546399A

Abstract

Disclosed are a channel estimation method and device, comprising: conducting channel estimation on a received pilot frequency sequence to obtain the first sequence of the frequency domain channel estimation; duplicating the first sequence, obtaining a first duplicate and a second duplicate respectively according to the duplicated first sequence, utilizing determined timing information representing the frequency domain phase offset of each channel estimation value in the first sequence to adjust the phases of the first duplicate and the second duplicate, and respectively superimposing the adjusted first duplicate and second duplicate at the low frequency end and the high frequency end of the first sequence, so as to obtain the second sequence of the frequency domain channel estimation, such that when the second sequence is converted into a time domain for time domain denoising, the obtained time domain sequence is consistent with the real time domain channel impulse response of the first sequence, thus avoiding power leakage, and improving channel estimation accuracy while improving channel timing estimation precision.

Description

Channel estimation method and device

Technical field

The present invention relates to the field of mobile communications technologies, and in particular, to a channel estimation method and apparatus. Background technique

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique. The main idea is to divide the non-flat frequency selective channel into many orthogonal sub-ranges in the frequency domain. The channel, the signal bandwidth on each subchannel is smaller than the relevant bandwidth of the channel, so that each subchannel is relatively flat, and the purpose of reducing intersymbol interference caused by multipath effects is achieved. In practical applications, in order to correctly detect the signal, the receiving end needs to perform coherent demodulation on the received signal. Therefore, channel estimation is needed to obtain information such as the amplitude and phase of the channel.

Currently, in OFDM systems, estimation methods based on reference signals (such as pilot or training sequences) and blind estimation methods can be used for channel estimation. The pilot-based channel estimation method generally transmits a specific sequence in the frequency domain known by both communicating parties at the transmitting end to continuously track channel changes. Since the pilot-based channel estimation method is relatively simple and easy to implement, it is widely used.

Taking the uplink communication process of the OFDM-based Long Term Evolution (LTE) communication system as an example, the receiving end uses the pilot sequences known by both the transmitting and receiving parties to accurately reflect the delay of each path of the channel in the time domain. Amplitude phase (time domain channel impulse response), or the amplitude phase of each subcarrier of the channel in the frequency domain (frequency domain channel impulse response). For the Physical Uplink Shared Channel (PUSCH) of the LTE system, as shown in FIG. 1, since it adopts a block pilot structure, each slot (s lot) has a symbol. The pilot sequence is placed. Therefore, when performing channel estimation, the receiving end first needs to estimate the channel response at the pilot position, and then uses the channel response at the pilot position to perform averaging or interpolation in the time domain to obtain a sub- The channel response value of a frame or a time slot.

Currently, the Least Square (LS) algorithm is often used for channel estimation based on pilots. The LS algorithm is relatively simple to implement. The channel estimation can be obtained by directly dividing the frequency domain form of the received sequence by the transmission sequence. However, since the noise in the received signal and the interference between the subcarriers are not considered, the obtained channel estimation includes noise. And interference, resulting in the accuracy of the results as the noise and interference increase, so the estimation accuracy is limited.

In order to reduce the influence of noise and interference on the estimation accuracy of the LS algorithm, the industry has proposed a time domain denoising technique to improve the performance of the LS algorithm to some extent by removing the noise as much as possible by performing domain transformation on the frequency domain channel response. , has been widely used in engineering. The main idea of the LS algorithm after time domain denoising is to convert the frequency domain channel impulse response into a time domain channel impulse response, estimate the noise in the time domain, and then set the threshold according to the estimated noise and pass The threshold denoises and filters the time domain channel impulse response, and then converts the filtered time domain channel impulse response into a frequency domain channel impulse response to obtain a final channel estimation value.

In the time domain denoising operation, if the frequency domain length of the OFDM pilot sequence is not a power of 2, an inverse Fourier inverse Fourier transform (Nove 2) is required. IDFT) / Discrete Fourier Transform (DFT) operation to transform the frequency domain channel impulse response of the pilot sequence to a time domain channel impulse response; however, due to a power-based power of 2 The Inver se Fa st Four Ier Transform (IFFT) / Fast Fourier Transform (FFT) operation is faster than the IDFT/DFT operation, so The frequency domain channel impulse response is complemented by a power of 1 to perform an IFFT/FFT operation using a two-sided zero-padding method.

The frequency domain channel impulse response after zero-padding can be regarded as the original frequency domain channel impulse response multiplied by an ideal rectangular window, and according to the Fourier transform property, the time domain form of the ideal rectangular window is the sine function. The time-domain channel impulse response corresponding to the frequency domain channel impulse response after zero-padding is equal to the original time-domain channel impulse response convolved with a sine function, and the more zero-padding points, the closer the time-domain channel impulse response is to continuous s ine function.

Specifically, taking a pilot sequence of length 12 as an example, if it passes an ideal noise-free time-delayed channel, the obtained frequency domain channel impulse response is a 12-point unit impact corresponding to the 12 subcarriers shown in FIG. 2, That is, the all-one sequence of length 12, after the 12-point DFT operation, the obtained time domain channel impulse response is as shown in FIG. 3, and no side lobes appear in the time domain channel impulse response; The two-side equal-length zero-padding method fills the pilot sequence to 16 points and still passes the ideal noise-free and time-delay-free channel. The resulting frequency domain channel impulse response is shown in Figure 4, after 16-point FFT operation. After that, the obtained time domain channel impulse response is as shown in FIG. 5. At this time, several side lobes appear in the time domain channel impulse response; if the two sides are equal in length, the pilot sequence is zero-padded to 128 points, still pass the ideal noise-free and time-delay-free channel, and its frequency domain channel impulse response is shown in Figure 6. After 128-point FFT operation, the corresponding time-domain channel impulse response is shown in Figure 7. Domain channel impulse response A large number of side lobes appear in it.

It can be seen from FIG. 3, FIG. 5 and FIG. 7 that when the frequency domain channel impulse response is complemented by the power of 2 and the time domain channel impulse response is converted by the zero-padding method, the real time domain channel rushing is caused. The power of the response is leaked throughout the time domain, ie the side lobes of the sine function contain information on the time domain channel impulse response. If time domain denoising is performed on the time domain channel impulse response at this time, all points outside the length of the cyclic prefix (Cyc l ic Pref ix , CP ) are zeroed, which may cause partial information of the real time domain channel impulse response to be lost, corresponding Ground, it will also destroy the frequency domain channel impulse response after time domain denoising, thus reducing the accuracy of channel estimation.

In addition, for some systems using OFDM technology, when performing channel estimation, certain accuracy needs to be determined. Estimated to adjust the communication parameters. If the length of the pilot sequence used for channel estimation is short, the IDFT operation of the frequency domain channel estimation result is performed, and the number of points in the obtained time domain channel impulse response is also small, thereby resulting in insufficient accuracy of timing estimation. Unable to meet the communication needs. Taking the 10 MHz LTE system using OFDM technology as an example, since the pilot sequence of 12-point length is used, if the frequency domain channel estimation result of the pilot sequence is subjected to IDFT operation, the obtained time domain channel impulse response is 12 In the point, each point can only represent ^1WS · ¹⁰²⁴ = 5.56 X 1 (Γ ³ ms, while LTE

15360 - 12

1 - 1 074

The system requires at least 128 points in the time domain, that is, each point must represent at least ⁱ = 52 \^ms, that is,

15360- 128

When the length of the pilot sequence used for channel estimation is too short, the timing estimation accuracy is obviously insufficient. In this case, the length of the frequency domain channel impulse response of the pilot sequence can also be increased by zero-padding the frequency domain channel impulse response of the pilot sequence, thereby increasing the number of times of the pilot sequence time domain channel impulse response. The effect of improving the timing estimation accuracy to a certain extent is achieved, but if the length of the frequency domain channel impulse response is increased by zero-padding the frequency domain channel impulse response, the frequency domain channel will still be rushed. When the response is transformed into the time domain to perform time domain denoising, a power leakage occurs, which results in partial information loss of the real time domain channel impulse response, which causes the channel estimation performance to be degraded.

In summary, in the prior art, by performing zero-padding on the frequency domain channel impulse response of the pilot sequence, it is possible to perform an IFFT/FFT operation, thereby improving the channel estimation operation rate, or The frequency domain channel impulse response of the pilot sequence is zero-padded to improve the accuracy of the channel timing estimation. If the frequency domain channel impulse response after zero-padding is converted to the time domain, the converted time-domain channel impact will result. In response to the power leakage phenomenon, that is, the converted time domain channel impulse response has a large side lobes, and the side lobes contain useful signals. If the time domain channel impulse response is time-domain denoised, the real time will be caused. Part of the information of the domain channel impulse response is lost, thereby reducing the accuracy of the channel estimation.

Summary of the invention

The embodiment of the present invention provides a channel estimation method and device, which are used to solve the problem of zero-frequency channel impulse response in the prior art and perform power-time denoising operation on the frequency domain channel impact response. Part of the information of the time domain channel impulse response is lost, thereby reducing the problem of channel estimation accuracy.

A channel estimation method includes:

Performing channel estimation on the received pilot sequence to obtain a first sequence of frequency domain channel estimates, where the first sequence includes at least one channel estimation value that is consecutively arranged;

Determining timing information indicating a phase offset of each channel estimate in the first sequence in the frequency domain; Performing a copy operation on the first sequence, and respectively obtaining a first copy and a second copy according to the copied first sequence, respectively performing phase adjustment on the first copy and the second copy by using the determined timing information, and Adding the adjusted first copy to the low frequency end of the first sequence, and adding the adjusted second copy to the high frequency end of the first sequence to obtain a second sequence of frequency domain channel estimation;

After transforming the second sequence into the time domain for time domain denoising, transforming it into the frequency domain to obtain a channel estimation result. A channel estimation apparatus includes:

a frequency domain channel estimation module, configured to perform channel estimation on the received pilot sequence, to obtain a first sequence of frequency domain channel estimates, where the first sequence includes at least one channel estimation value that is consecutively arranged;

a timing information determining module, configured to determine timing information indicating a phase offset of each channel estimation value in the frequency domain in the frequency domain;

a first sequence adding module, configured to perform a copy operation on the first sequence obtained by the frequency domain channel estimation module, and obtain a first copy and a second copy respectively according to the copied first sequence, and respectively use the determined timing information Phase-adjusting the first copy and the second copy, adding the adjusted first copy to the low frequency end of the first sequence, and adding the adjusted second copy to the high of the first sequence At the frequency end, obtaining a second sequence of frequency domain channel estimates;

And a second sequence processing module, configured to transform the second sequence into a time domain for time domain denoising, and then transform the frequency into a frequency domain to obtain a channel estimation result.

The beneficial effects of the invention are:

An embodiment of the present invention provides a channel estimation method and apparatus, which obtains a first sequence of frequency domain channel estimation by performing channel estimation on a received pilot sequence, and obtains a first copy and a first copy according to the copied first sequence, respectively. a second copy, and determining, by using the determined timing information indicating a phase offset of each channel estimation value in the frequency domain in the frequency domain, phase adjustment of the first copy and the second copy, respectively, and adjusting the A copy and a second copy are respectively added to the low frequency end and the high frequency end of the first sequence to obtain a second sequence of frequency domain channel estimation, so that the second sequence is transformed into the time domain for time domain denoising The obtained time domain sequence conforms to the real time domain channel impulse response of the first sequence, thereby avoiding power leakage, thereby solving the frequency domain channel of the pilot sequence existing in the prior art while improving channel channel estimation accuracy. When the impulse response is zero-padded and time-domain denoised, there is a side lobes containing useful signals in the time-domain channel impulse response, resulting in power dissipation. Resulting in real time-domain channel impulse response of partial information loss and reduce the problem of channel estimation accuracy. DRAWINGS

1 is a schematic diagram of a PUSCH block pilot structure of an LTE system in the prior art; Figure 2 is a diagram showing a frequency domain channel impulse response of a 12-point pilot sequence under an ideal channel;

Figure 3 shows the time domain channel impulse response of the 12-point pilot sequence under the ideal channel;

Figure 4 shows the resulting frequency domain channel impulse response when the 12-point pilot sequence is zeroed to 16 points on the ideal channel.

Figure 5 shows the resulting time domain channel impulse response when the 12-point pilot sequence is zeroed to 16 points on the ideal channel.

Figure 6 shows the resulting frequency domain channel impulse response when the 12-point pilot sequence is zeroed to 128 points on the ideal channel.

Figure 7 shows the time-domain channel impulse response of the 12-point pilot sequence when it is zeroed to 128 points on the ideal channel.

FIG. 8 is a schematic flowchart diagram of a channel estimation method according to Embodiment 1 of the present invention;

FIG. 9 is a schematic structural diagram of a channel estimation apparatus according to Embodiment 2 of the present invention. detailed description

The embodiments of the present invention will be further described below in conjunction with the drawings, but the present invention is not limited to the following embodiments.

Embodiment 1:

FIG. 8 is a schematic flowchart diagram of a channel estimation method according to Embodiment 1 of the present invention, where the method includes the following steps:

Step 101: Perform channel estimation on the received pilot sequence to obtain a first sequence of frequency domain channel estimates, where the first sequence includes at least one channel estimation value that is consecutively arranged.

In this step 101, the received pilot sequence may be subjected to channel estimation by using an LS channel estimation method, and the obtained first sequence of the frequency domain channel estimation may be expressed as:

H _LS = Χ ¹ Υ = Η + Χ ¹ Ν , where is the first sequence of frequency domain channel estimation, X is the pilot vector transmitted by the transmitting end, and Y is the pilot vector after the channel received by the receiving end, ^N Is noise and / or interference, H is the frequency domain response of the channel.

Specifically, the first sequence of the frequency domain channel estimation includes at least one channel estimation value that is consecutively arranged, that is, the first sequence may be specifically represented as 0 _LS =[^ ··· H _n · · · H^ ] Where Μ = 1, 2· · · 7 , N _c is the number of subcarriers, and A „ represents the channel estimate on the subcarrier”.

It should be noted that the number of channel estimation values in the first sequence is the sequence number of the first sequence. Step 102: Determine timing information indicating a phase offset of each channel estimation value in the first sequence in the frequency domain. The timing information is a phase offset added to the first sequence caused by the timing error, and may be an average phase offset of each channel estimation value in the frequency domain in the first sequence.

Further, the timing information can be determined by:

Manner 1: According to the order of the channel estimation values in the first sequence, the first sequence is divided into two sub-sequences including the same number of channel estimation values, and each channel estimation value in the subsequent sub-sequence is determined respectively. The sum of the determined phase offsets is averaged with respect to the phase offset of the channel estimation values of the same position in the previous subsequence, and the obtained average phase offset is used as timing information.

Specifically, if the first sequence is and = H, H, the determined timing information can be expressed as:

Where m=\, 2--'N _c , N _r is the number of subcarriers, indicating that the channel estimation value on the subcarrier m is conjugated.

For example: When N _f is 12, the timing information may be expressed as: 1

Φ" ■ phase Σ m+N _c '2 H.

m=\

1

.phase ∑H _m+b {H _n

12/2

.phase H ₇ -(H,)*+H ₈ - H ₂ )' +H _g - (H ₃ )* + ή. (A ₄ )* +H _n -(H ₅ )* + H _n -(H ₆ )*J Mode 2: determining the phase-bias complex number of the average phase offset, and determining according to the phase-bias complex number The phase offset base number is used as timing information.

Specifically, after determining an average phase offset of each channel estimation value in the first sequence in the frequency domain, the extracted

N _C I2 *

The phase-bias complex number a + _y'.b= i^ _ra+jV( . _/2 .(A _ffl ) , where α is the real part of the phase-biased complex number, and 6 is the imaginary part of the phase-biased complex number, and The phase offset base number extracted by the complex phase is used as timing information, and the phase offset base number can be expressed as: C = exp( -N _c

= (exp(7-N _c /2

,

Exp(yN _c /2. • phase H—

N _c /2 exp(i'-N _r 12.——· phase (a + jb)

N 2

=^exp(j■ phase (^a + -b))"

₌ a + J'b

, ja ² +b ² a ² +b ²

Step 103: Perform a copy operation on the first sequence, and obtain a first copy and a second copy respectively according to the copied first sequence, and respectively phase the first copy and the second copy by using the determined timing information. Adjusting, adding the adjusted first copy to the low frequency end of the first sequence, and adding the adjusted second copy to the high frequency end of the first sequence to obtain a second sequence of frequency domain channel estimation .

Specifically, the channel estimation values included in the first sequence are subjected to a copy operation to obtain a copied first sequence (or referred to as a first sequence copy;), and the channel estimation included in the copied first sequence The value is the same as the order of the channel estimation values included in the first sequence and the number is equal.

For example, if the first sequence includes a channel estimation value of (/^, _{3⁄4 4} ), after the copy operation is performed, the channel estimation value included in the obtained first sequence of the replica is also Η ₂ Η Η _Α ).

Specifically, the first copy is obtained according to the first sequence of the copy, the first copy is phase-adjusted by using the determined timing information, and the adjusted first copy is added to the low-frequency end of the first sequence, including:

Determining the number of channel estimation values to be added at the low frequency end of the first sequence and the number of channel estimation values in the first sequence, and determining the first sequence of the copied codes obtained by Μ/Ν and The remaining C channel estimation values obtained by the M/N in the copied first sequence are used as the first copy, and the first copy is phase-adjusted by using the determined timing information, and the adjusted first copy is added. At the low frequency end of the first sequence, where the C channel estimation values are consecutive last C channel estimation values in the first sequence of the copy;

Specifically, obtaining a second copy according to the copied first sequence, and performing phase adjustment on the second copy by using the determined timing information, and adding the adjusted second copy to the high frequency end of the first sequence, including :

Determining the number M of channel estimation values of the second replica that need to be added at the high frequency end of the first sequence and the number N of channel estimation values in the first sequence, and copying the quotients A obtained by M/N The first sequence and the first sequence copied a remainder of the C channel estimates obtained by M/N in the column as a second copy, phase adjustment of the second copy using the determined timing information, and adding the adjusted second copy to the first sequence The high frequency end, wherein the C channel estimation values are consecutive first C channel estimation values in the first sequence of the copy;

Wherein, in the first copy and the second copy, a distance between the first copied A sequence and the first sequence is smaller than a distance between the C channel estimated values and the first sequence; and, in the first copy And in the second copy, for the first sequence of A replicas, the copied sequence of the first sequence is located at a farther distance from the first sequence, the phase adjustment amplitude is larger, and the phase adjustment amplitude is greater than the C channel estimation values. The first sequence of any of the copies.

Specifically, if the timing information is extracted according to the method in step 102, the adjusted first copy VL that needs to be added at the low end of the first sequence 0 according to the timing information and the first sequence may be Expressed as:

LS

Where P = \, 2"' N _PAD , N _PAD = {N _FFT - N _C , /2 , N^ is the number of points of the fast Fourier transform; accordingly, according to the timing information and the first sequence Η obtained in the second copy need VR after the end of the first sequence added to adjust 0L _S can be expressed as: VR = VR VR VR, pad

LS

W modWc - 1

m. dW _c

Where = 1,2' N , N _pad =, N _N _C , I2, A is the number of points of the fast Fourier transform _FFT . Further, if the timing information is extracted according to the second method in step 102, the adjusted first copy VL that needs to be added at the low frequency end of the first sequence according to the timing information and the first sequence H _ts may be Expressed as:

H LS

C ² ) H LS

C* H LS Wherein, ρ = 1 · 'Ν correspondingly, according to the timing information and the first sequence 0, the adjusted second replica VR that needs to be added at the high frequency end of the first sequence H _1S can be expressed as:

C H LS

C ² H LS c H LS

W modW _c - 1

HN _pad modN _c

q = \,2---N

among them

It should be noted that, the number of channel estimation values of the adjusted first copy that need to be added at the low frequency end of the first sequence and the adjusted second copy of the channel that need to be added at the high frequency end of the first sequence The number of estimates is equal.

Further, after the adjusted first copy or the adjusted second copy is added to the low frequency end or the high frequency end of the first sequence, the obtained second sequence of frequency domain channel estimates can be expressed as:

^H LS = VL H _LS VR where VL is the first replica added at the low frequency end, VR is the second replica added at the high frequency end, and the VL and the VR are equal in length.

If the number of channel estimation values of the first sequence (that is, the sequence number of the first sequence) is N _e , and the lengths of VL and VR are, then the adjusted first copy or the second copy is added to the After the low frequency end or the high frequency end of the first sequence, the number of channel estimation values of the obtained second sequence, that is, the sequence number of the second sequence is N _e + 2 'N _pad . It should be noted that the sequence number of the second sequence may be a power of 2 or a power of 2, and preferably, the number of sequence points of the second sequence is a power of 2.

Further, if the sequence number of the second sequence is a power of 2, the sequence number of the second sequence + ² .^^ is not limited to the nearest power of ² to N _e , but may be the number of sequence points determined according to the system timing estimation, for example, if the system is TDD-LTE (Time Division Duplexing - Long Term) Evolution, time division duplex-long-term evolution system, and the bandwidth is 10MHz, the sequence number of the second sequence may be 128, so that the channel timing estimation is maximized under the premise of ensuring a high channel estimation operation rate. Precision.

Specifically, when the sequence number N of the first sequence is 12 and the sequence number N _c +2' N _pad of the second sequence is 128, it is known from the calculation that the low frequency end of the first sequence is needed. Or the number of sequence points N _pad in the adjusted first copy or the adjusted second copy added at the high frequency end is 58. At this time, the adjusted first copy VL added at the low frequency end of the first sequence may be represented. for:

VL = VL VL,

■H

H

H,

H, φ>-Η,

e...-, ,-H,

e K e . ² .(w.0 _LS

= [e-^^-H ₃ ,...,e-^ ^r '' ⁾ -H ₁₁ ,e-^ That is, the first four copies of the quotient obtained from 58/12 and the above The adjusted first replica is obtained by using the remaining 10 channel estimation values obtained by 58/12 in a sequence of replicas as the first replica, and performing phase adjustment using the determined timing information, where the 10 channels are obtained. The estimated value is consecutively arranged in the first sequence of copies 10 channel estimates;

And, in the first copy or the adjusted first copy, the distance between the four first sequence copies (or the adjusted first sequence copy) and the first sequence is smaller than the first sequence copy (or adjusted) The distance between the 10 channel estimates in the first sequence of copies and the first sequence; for example, in the adjusted first copy VL, the four adjusted copies of the first sequence e_ ( ^AW >.0) _LS , _E - ³ ' ^(A ' ^RT -H _LS , _e - ^J - ^2iN ^-H _LS and e - ^Ί · ! ^ are spaced from the first sequence by less than the 10 adjusted channel estimates, eg _E ^'(K , _e - H^).^ ₄ and _e - ^5(AW ). ₁₂ The distance from the first sequence.

Meanwhile, in the first copy, for the first sequence of four copies, the phase sequence adjustment amplitude is larger as the first sequence copy located farther from the first sequence, for example, the phase adjustment range of ε^ΚΗ is larger than

Phase adjustment amplitude; for the 10 channel estimation values, the phase adjustment amplitude is greater than any of the first sequence copies, for example, the phase adjustment amplitude of _e - „ / ^ ₂ is greater than _e - H , e - ^{/ 3} ' ⁽ ^^-H _LS , e— (K _LS and

_E ^(AW ).H The phase adjustment amplitude of the _TS .

The adjusted first copy VR added at the high frequency end of the first sequence can be expressed as:

VR = VR, VR VR

H LS

''2·(Λ' _Γ ·ί>)

H LS

LS

• H,

H

LS

LS e 4.(w _r .(*).

LS

• ^e ^ 10”

= [e (^ 0 _LS , e ^(A ' ^f .AA _LS ,...' ⁴ .(w(.. _LS , _e ( ,,..., e ⁵ . ₉ , e ⁵ · A _io ) Similarly, 58 / 12 obtained the first sequence of the quotient and the remaining 10 channel estimates obtained by 58 / 12 in the first sequence of copies as the second copy, and using the determined timing information for phase adjustment, The adjusted second copy, wherein the 10 channel estimation values are consecutively ranked first 10 channel estimation values in the first sequence of copies;

And, in the second copy or the adjusted second copy, the distance between the four first sequence copies and the first sequence is smaller than the distance between the ten channel estimation values and the first sequence;

Meanwhile, in the second copy, for the first sequence of four copies, the phase sequence adjustment amplitude is larger for the first sequence of the further position of the first sequence; and the phase adjustment is performed for the ten channel estimation values. The amplitude is greater than the phase adjustment amplitude of any of the first sequence of copies.

Further, the adjusted first copy VL added at the low frequency end of the first sequence may also be expressed as: VL = VL

modN _c )+l

σ H LS

= [(C5)* .73⁄4,.."(C5)* . , (C5)* ' A ₂ ,(C4)* .0 _LS ,...,(C2)* . _LS ,(C1)* - H _LS ] Correspondingly, the adjusted second copy VR added at the high frequency end of the first sequence can also be expressed as: VR = VR

C H LS

C ² H LS

c ¹ HN _pad modN _c -\

Mo N _c

C H LS

C ² H LS

C ⁴ H LS

C ⁵ f,

C -^io-i

C ⁵ . H _]0

=[CH _LS , C ² H _LS ,...,C ⁴ H _LS ,C ⁵ ·//,,...,C ⁵ / ₉ ,C ⁵ - _]0 ]

Step 104: Transform the frequency domain channel estimated second sequence into a time domain for time domain denoising, and then transform the frequency domain to a frequency domain to obtain a channel estimation result.

Specifically, this step 104 includes the following three sub-steps:

Step 1: Perform an inverse discrete Fourier transform on the second sequence of the frequency domain channel estimation to obtain a first sequence of time domain channel estimates.

The resulting first sequence of time domain channel estimates can be expressed as

Wherein, an inverse discrete Fourier transform is performed on a vector, which is a second sequence of frequency domain channel estimation.

The inverse discrete Fourier transform may be a normal inverse discrete Fourier transform, and if the first copy and the second copy are added after the continuous phase adjustment, the second sequence of the obtained frequency domain channel estimation is obtained. The number of sequence points is ² . N2013/000834

16

In the power of the power, the inverse discrete Fourier transform in this step may be a fast Fourier transform in the discrete Fourier transform.

The second step: performing a time domain denoising operation on the first sequence of the time domain channel estimation to obtain a second sequence of time domain channel estimation.

The first sequence of time domain channel estimates before time domain denoising can be expressed as: h. ■·· h _n ··■ hn = \,2-(N _c +2-N _nad ); The second sequence of time domain channel estimates after noise can be expressed as:

l,2-(N _c +2-N _pad )

Specifically, the time domain denoising operation may be performed on the first sequence of the time domain channel estimation by:

(1), in the first sequence of the time domain channel estimation, the sequence value corresponding to the sequence index whose sequence index value is greater than the CP length value is set to zero, and the corresponding mathematical expression is: h„ ^h "" ^{= ι} ...^ where, £^ is the length of .

0 else

(2) setting, in the first sequence of the time domain channel estimation, a sequence index value corresponding to a sequence index whose value is greater than a CP length value and smaller than a difference between a total index value of the sequence and a CP length value, and corresponding to The mathematical expression is:

h _n n = \---L _cp

_{h "= h n, Ν.} + 2.υ ΓΡ +, ··· ίΝ Γ + 2 · Ν ρα, wherein ^ is the CP length.

0 else

Step 3: Perform a discrete Fourier transform on the second sequence of the time domain channel estimation to obtain a channel estimation result. The obtained channel estimation result can be expressed as specifically! ! ^-^^^^, where (*) indicates a discrete Fourier transform on a vector, which is the second sequence of time domain channel estimation.

The discrete Fourier transform may be a normal discrete Fourier transform. If the first copy and the second copy are added after the continuous phase adjustment, the sequence number of the second sequence of the obtained frequency domain channel estimation is obtained. When the power is 2, the discrete Fourier transform in this step may be a fast Fourier transform in the discrete Fourier transform. Embodiment 2:

As shown in FIG. 9, FIG. 9 is a schematic structural diagram of a channel estimation apparatus according to Embodiment 2 of the present invention, where the channel estimation apparatus includes a frequency domain channel estimation module 11, a timing information determining module 12, a first sequence adding module 13, and a second sequence processing. Module 14, wherein:

The frequency domain channel estimation module 11 is configured to perform channel estimation on the received pilot sequence to obtain a first sequence of frequency domain channel estimation, where the first sequence includes at least one channel estimation value that is consecutively arranged; specifically Channel estimation The meter can be estimated for the LS channel. When the channel estimation of the received pilot sequence is performed by using the LS channel estimation, the obtained first sequence of the frequency domain channel estimation can be expressed as:

H _LS =Χ ¹ Υ = Η + Χ'Ν , where 0 is the first sequence of frequency domain channel estimation, X is the pilot vector transmitted by the transmitting end, and Y is the pilot vector after the channel received by the receiving end. ^N is noise and/or interference, and H is the frequency domain response of the channel. Further, the first sequence may be expressed as ··· H _n ■■■ ^], where " = 1, 2...N _C , N _c is the number of subcarriers,

Α,, represents the channel estimate on the subcarrier.

The timing information determining module 12 is configured to determine timing information indicating a phase offset of each channel estimation value in the frequency domain in the frequency domain; specifically, the timing information is added to the first sequence caused by a timing error The phase offset may be an average phase offset of the channel estimates in the first sequence in the frequency domain.

Further, the timing information determining module 12 may determine the timing information by: manner 1: dividing the first sequence into the same quantity according to an order of arrangement of channel estimation values in the first sequence The two sub-sequences of the channel estimation value respectively determine the phase offset of each channel estimation value in the subsequent sub-sequence relative to the channel estimation value of the same position in the previous sub-sequence, and average the sum of the determined phase offsets, The resulting average phase offset is used as timing information.

Specifically, if the first sequence is and = "··· Η _η ■■■ , the timing information 0 determined by the timing information determining module 12 can be expressed as: φ =

Where m = \, 2'-'N _c , N _e is the number of subcarriers, and (Α _Μ )' represents the conjugate of the channel estimate / ^ on the subcarrier.

Manner 2: determining a phase offset complex number of the average phase offset, and using the phase offset base number determined according to the phase offset complex number as timing information.

Specifically, after determining an average phase offset 0 of each channel estimation value in the frequency domain in the first sequence, extracting a phase partial complex number a + .6= _{m+ 2} . (^), where α is a phase The real part of the partial complex number, 6 is the imaginary part of the phase-biased complex number, and the phase-bias base number extracted according to the phase-shift complex number is used as timing information, and the phase-offset base number can be expressed as: T N2013/000834

18

C = exp(/ - N _c - ^)

= (exp (; - N _c / 2 - ^)) ²

a ² + b ²

The first sequence adding module 13 is configured to perform a copy operation on the first sequence obtained by the frequency domain channel estimation module 11, and obtain the first copy and the second copy respectively according to the copied first sequence, and use the determined timing information. Phase adjusting the first copy and the second copy respectively, adding the adjusted first copy to the low frequency end of the first sequence, and adding the adjusted second copy to the first At the high frequency end of the sequence, a second sequence of frequency domain channel estimates is obtained.

Specifically, the first sequence adding module 13 is configured to perform a copy operation on each channel estimation value included in the first sequence, to obtain a copied first sequence, that is, a first sequence copy, where the first sequence is copied. The included channel estimate is the same as the order of the channel estimates included in the first sequence and the number is equal.

Specifically, the first sequence adding module 13 is configured to obtain a first copy according to the copied first sequence, and perform phase adjustment on the first copy by using the determined timing information, where the adjusted first A copy is added at the low end of the first sequence:

Determining the number M of channel estimation values to be added at the low frequency end of the first sequence and the number N of channel estimation values in the first sequence, and the first sequence of the quotients of the quotients obtained by M/N and The remaining C channel estimation values obtained by the M/N in the copied first sequence are used as the first copy, and the first copy is phase-adjusted by using the determined timing information, and the adjusted first copy is added. At the low frequency end of the first sequence, where the C channel estimation values are consecutive last C channel estimation values in the first sequence of the copy;

Similarly, the first sequence adding module 13 is configured to obtain a second copy according to the copied first sequence, and perform phase adjustment on the second copy by using the determined timing information, and the adjusted second copy is performed. Added at the high frequency end of the first sequence:

Determining the number M of channel estimation values of the second replica that need to be added at the high frequency end of the first sequence and the number N of channel estimation values in the first sequence, and copying the quotients A obtained by M/N a first sequence and a remainder of the C channel estimates obtained by M/N in the copied first sequence as a second copy, phase adjustment of the second copy using the determined timing information, and adjusting A second copy is added to the high frequency end of the first sequence, wherein the C channel estimates are consecutive first C channel estimates in the first sequence of the copy.

Wherein, in the first copy and the second copy, the distance between the first sequence of A copies and the first sequence is less than Determining the distance between the C channel estimation values and the first sequence; and, in the first copy and the second copy, for the first sequence of the A copies, the first copy of the first sequence is located farther away The sequence has a larger phase adjustment amplitude; for the C channel estimation values, the phase adjustment amplitude is greater than any of the copied first sequences.

Specifically, if the timing information determining module 12 performs the extraction of the timing information according to the mode 1, the first sequence adding module 13 obtains the required sequence in the first sequence H _ts according to the timing information and the first sequence. The adjusted first copy VL added at the low end can be expressed as:

VL = VL ... VL VL

e ■H

LS

e H LS where P = U _pad , N _pad =, N _FFT - N _c , n , _OT is the number of points of the fast Fourier transform; accordingly, the first sequence adding module 13 is based on the timing information and the A sequence of adjusted second copies VR that need to be added at the high frequency end of the first sequence 0 can be expressed as: P

WO 2014/012352

20

VR VR _q ... VR _Npi

H LS

!.(Wc. H LS (" ^ 1).(Λ^)Ά

e LS e -H,

modW _c - 1

nodN _c ” q:\,2 -N _pad N _pad N _FFT - N _r ) / 2, N _FFT Fast Fourier Transform FFT points. among them

The timing information determining module 12 performs timing information extraction according to the second method, and the first sequence adding force 'block ₁₃ according to the timing information and the first sequence, obtains the need in the first sequence 歹' 6 6 _LS The frequency of the end of the adjustment 'the first copy of the VL is:

VL = ··· VL VL

4

twenty one

Wherein, P = HN _pad ; correspondingly, the first sequence adding module 13 obtains an adjusted second required at the high frequency end of the first sequence H _ts according to the timing information and the first sequence The copy VR is:

VR = VR, VR VR

C H LS

C ² H LS

LS

c "w

modW _c -l

"w /w _c ]

c •HN _pai moAN _c J

It should be noted that the number of channel estimation values of the first replica that need to be added at the low frequency end of the first sequence is equal to the number of channel estimation values of the second replica that need to be added at the high frequency end of the first sequence. .

Further, after the adjusted first copy or the second copy is added to the low frequency end or the high frequency end of the first sequence, the second sequence of the frequency domain channel estimation obtained by the first sequence adding module 13 is obtained. It can be expressed as:

Wherein VL is the adjusted first copy added at the low frequency end, and VR is the adjusted second copy added at the high frequency end, and the VL and the VR are equal in length.

If the sequence number of the first sequence is N _e and the length of VL and VR is N^, after the adjusted first copy or the second copy is added to the low frequency end or the high frequency end of the first sequence The number of channel estimation values of the obtained second sequence, that is, the sequence number of the second sequence is N _e + 2.N . It should be noted that the sequence number of the second sequence may be a power of 2 or a power of 2, and preferably, the number of sequence points of the second sequence is a power of 2.

Further, if the sequence number of the second sequence is a power of ² , the sequence number of the second sequence ^ + 2 · ^^ / is not limited to the nearest power of ² , but may also be determined according to the system timing estimation needs, for example, if the system is a TDD-LTE system and the bandwidth is 10MHz, then The sequence number of the second sequence may be I ²⁸ , so that the accuracy of the channel timing estimation is maximized under the premise of ensuring a high channel estimation operation rate.

The second sequence processing module 14 is configured to transform the second sequence into a time domain for time domain denoising, and then transform it into a frequency domain to obtain a channel estimation result.

Further, the second sequence processing module 14 includes a conversion submodule 141 and a time domain denoising submodule 142. The conversion sub-module 141 is configured to transform the second sequence of the frequency domain channel estimation into a time domain, and transform a second sequence after transforming into a time domain and performing a time domain denoising operation to the frequency domain; The time domain denoising sub-module 142 is configured to perform time domain denoising on the second sequence of the frequency domain channel estimation transformed into the time domain.

Specifically, the conversion sub-module 141 is configured to perform inverse discrete Fourier transform on the second sequence of the frequency domain channel estimation to obtain a first sequence of time domain channel estimation, and, for the time domain denoising sub-module 142. The second sequence of the obtained time domain channel estimation is subjected to discrete Fourier transform to obtain a channel estimation result.

Specifically, the first sequence of the time domain channel estimation obtained by the conversion submodule 141 may be represented as h _LS = "' (H _LS ) , where -^*) represents an inverse discrete Fourier transform on a vector. , fi _LS is a second sequence of frequency domain channel estimation; the inverse discrete Fourier transform may be a normal inverse discrete Fourier transform, if the first copy and the second copy are added after continuous phase adjustment When the sequence number of the second sequence of the obtained frequency domain channel estimation is a power of 2, the inverse discrete Fourier transform may be a fast Fourier transform in the discrete Fourier transform.

The channel estimation result obtained by the conversion sub-module 141 may be H), where

A vector performs a discrete Fourier transform, and ^ ₈ is a second sequence of time domain channel estimates; the discrete Fourier transform can be a normal discrete Fourier transform, if the continuous phase is continuously phase adjusted After the addition operation of the copy and the second copy, the discrete Fourier transform may be fast in the discrete Fourier transform when the sequence number of the second sequence of the obtained frequency domain channel estimation is a power of 2 Fourier transform.

The time domain denoising sub-module 142 is specifically configured to perform a time domain denoising operation on the first sequence of the time domain channel estimation obtained by the conversion sub-module 141 to obtain a second sequence of time domain channel estimation. Specifically, the time domain denoising sub-module 142 may perform a time domain denoising operation on the first sequence of the time domain channel estimation by:

(1), in the first sequence of the time domain channel estimation, the sequence value corresponding to the sequence index whose sequence index value is greater than the CP length value is set to zero, and the corresponding mathematical expression is: h„ ^h "" ⁼ " ^Lcp ' where _CT is the CP length.

I 0 else

h _n n = l - - - L _CP

h.. = h _n (N _c + 2 - N _pad - L _{cp +} l) - (N _{c +} 2 - N _pad ) , where ' _CT is CP length.

0 else

An embodiment of the present invention provides a channel estimation method and apparatus, which obtains a first sequence of frequency domain channel estimation by performing channel estimation on a received pilot sequence, and obtains a first copy and a first copy according to the copied first sequence, respectively. a second copy, and determining, by using the determined timing information indicating a phase offset of each channel estimation value in the frequency domain in the frequency domain, phase adjustment of the first copy and the second copy, respectively, and adjusting the A copy and a second copy are respectively added to the low frequency end and the high frequency end of the first sequence to obtain a second sequence of frequency domain channel estimation, so that the frequency domain channel estimation second sequence is transformed into the time domain When domain denoising, the obtained time domain channel impulse response has no side lobes, which conforms to the real time domain channel impulse response of the first sequence of frequency domain channel estimation, avoiding power leakage, thereby improving the accuracy of channel timing estimation. The invention solves the problem that the frequency domain channel impulse response of the pilot sequence existing in the prior art is zero-padded and time-domain denoising is performed, because the time domain channel Hit exist side lobe response contains useful signal, resulting in power leakage leading to real time domain channel impulse response of partial information loss and reduce the problem of channel estimation accuracy, improved channel estimate was accurate. At the same time, since the timing information extraction operation is adopted in the embodiment of the present invention, the direct calculation of the phase is avoided, the implementation efficiency of the system hardware is improved, and the resource consumption is reduced.

Those skilled in the art will appreciate that embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) in which computer usable program code is embodied.

The present invention has been described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. To implement the functions specified in one or more blocks of a flow or a flow and/or block diagram of a flowchart ―

twenty four - -

Device.

The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more of the flow or in one or more of the flow charts and/or block diagrams of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

The above is only a preferred embodiment of the present invention, and it is obvious that those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and the modifications

Claims

Rights request

A channel estimation method, comprising:

Determining timing information indicating a phase offset of each channel estimate in the first sequence in the frequency domain;

Performing a copy operation on the first sequence, and respectively obtaining a first copy and a second copy according to the copied first sequence, respectively performing phase adjustment on the first copy and the second copy by using the determined timing information, and Adding the adjusted first copy to the low frequency end of the first sequence, and adding the adjusted second copy to the high frequency end of the first sequence to obtain a second sequence of frequency domain channel estimation;

After transforming the second sequence into the time domain for time domain denoising, transforming it into the frequency domain to obtain a channel estimation result.

2. The channel estimation method according to claim 1, wherein:

The timing information is an average phase offset of each channel estimation value in the first sequence in the frequency domain.

3. The channel estimation method according to claim 2, wherein the manner of determining the timing information is specifically:

Determining, according to the order of the channel estimation values in the first sequence, the first sequence into two sub-sequences including the same number of channel estimation values, respectively determining each channel estimation value in the subsequent sub-sequence relative to the former a phase offset of channel estimation values at the same position in a subsequence, averaging the determined phase offsets, and using the obtained average phase offset as timing information; or

Determining a phase offset complex number of the average phase offset, and using the phase offset base number determined according to the phase partial complex number as timing information.

The channel estimation method according to claim 1, wherein the first copy is obtained according to the copied first sequence, and the first copy is phase-adjusted by using the determined timing information, and the adjusted first copy is obtained. Adding to the low frequency end of the first sequence specifically includes:

Obtaining a second copy according to the first sequence of the copy, and performing phase adjustment on the second copy by using the determined timing information, and adding the adjusted second copy to the high frequency end of the first sequence, specifically including: Determining the number M of channel estimation values of the second replica to be added at the high frequency end of the first sequence and the number N of channel estimation values in the first sequence, and copying the quotients A obtained by M/N a first sequence and a remainder of the C channel estimates obtained by M/N in the copied first sequence as a second copy, phase adjustment of the second copy using the determined timing information, and adjusting A second copy is added to the high frequency end of the first sequence, wherein the C channel estimates are consecutive first C channel estimates in the first sequence of the copy.

5. The channel estimation method according to claim 4, wherein:

In the first copy and the second copy, the distance between the first sequence of A copies and the first sequence is less than the distance between the C channel estimates and the first sequence.

6. The channel estimation method according to claim 5, wherein:

In the first copy and the second copy, for the first sequence of A copies, the copied first sequence located further away from the first sequence has a larger phase adjustment amplitude; for the C channel estimates , the phase adjustment amplitude is greater than the first sequence of any of the copies.

7. The channel estimation method according to claim 6, wherein:

The total number of channel estimation values in the second sequence is a power of two.

The channel estimation method according to claim 1, wherein after the second sequence is transformed into the time domain, the time domain denoising operation is performed by:

In the time domain sequence obtained after transforming the second sequence into the time domain, the sequence value corresponding to the sequence index whose sequence index value is greater than the cyclic prefix CP length value is set to zero; or

In the time domain sequence obtained after transforming the second sequence into the time domain, the sequence value corresponding to the sequence index whose sequence index value is smaller than the difference between the total index value of the sequence and the CP length value and larger than the CP length value is set to zero.

A channel estimation apparatus, comprising:

a second sequence processing module, configured to transform the second sequence into a time domain for time domain denoising, and then transform the In the frequency domain, the channel estimation result is obtained.

10. The channel estimation apparatus according to claim 9, wherein:

The timing information determined by the timing information determining module is an average phase offset of the channel estimation values in the first sequence in the frequency domain.

The channel estimation apparatus according to claim 10, wherein the timing information determining module is specifically configured to determine the timing information by:

The channel estimation apparatus according to claim 9, wherein the first sequence adding module obtains the first copy according to the copied first sequence, and performs phase adjustment on the first copy by using the determined timing information. Adding the adjusted first copy to the low frequency end of the first sequence, specifically including:

The first sequence adding module obtains a second copy according to the copied first sequence, and performs phase adjustment on the second copy by using the determined timing information, and adds the adjusted second copy to the high of the first sequence. The frequency end includes:

13. The channel estimation apparatus according to claim 12, wherein:

In the first copy and the second copy, the distance between the first replicated A sequence and the first sequence is less than the distance between the C channel estimate values and the first sequence.

14. The channel estimation apparatus according to claim 13, wherein:

The channel estimation apparatus according to claim 14, wherein:

The channel estimation apparatus according to claim 9, wherein the second sequence processing module performs time domain denoising operation by transforming the second sequence into a time domain by: