CN100382450C - Array antenna channel estimating aftertreatment method - Google Patents

Abstract

The present invention relates to a postprocessing method for channel estimation in array aerials, which comprises the following steps: step 1, training sequences of received data are extracted to be used as channel estimation to obtain the channel impulse response estimation * of the time slot; step 2, by the time delay correlation of DOA that the Borda angle DOA between adjacent time slots changes slowly usually, the postprocessing of channel estimation is executed to obtain processed channel impulse response *pp; step 3, the channel impulse response of each user is acquired, K groups of values are taken out of the channel impulse response by using the channel response window length W of each user as length to from channel estimation corresponding to each user, and subscriber data separated from the received data is detected jointly in a multi-user mode and demodulated. The method of the present invention improves the estimated accuracy of the path position of the channel impulse response of each user, effectively reduces the bit error rate, improves system performance and increases system capacity.

Description

The method of channel estimating reprocessing in a kind of array antenna

Technical field

The present invention relates to channel estimating post-processing approach in an array antenna, relate in particular to the code division multiple access system of communication field, particularly use the TD-SCDMA mobile communication system of aerial array.

Background technology

TD-CDMA (particularly TD-SCDMA) is based on the 3-G (Generation Three mobile communication system) of time division duplex (TDD), and associated detection technique is one of its key technology.Use associated detection technique and can effectively suppress multiple access interference (MAI) and intersymbol interference (ISI), its performance is subjected to the material impact of channel estimation results, and good channel estimation technique becomes the necessary condition of decision joint-detection.Channel estimation technique is not only the precondition that some key technologies realize, but also is the basis that various Measurement Algorithm are achieved, and the whether accurate of it will directly have influence on the performance of this series of algorithms.

Intelligent antenna technology is another key technology of TD-CDMA system, and existing now multiple estimation ripple reaches the method for angle (DOA); Generally DOA changes slowly between adjacent time-slots, therefore can utilize the time delay relevant information of DOA to strengthen the channel estimating reprocessing.

The channel estimation technique of existing TD-CDMA system (particularly TD-SCDMA) generally all is utilization Steiner method of estimation (B.Steiner and P.W.Baier.Low cost channel estimationin the uplink receiver of CDMA mobile radio systems.FRE-QUENZ, vol.47,1993,292-298.), the Steiner estimator is a kind of low-cost channel estimation methods, it passes through the reasonably training sequence of designing user, the linear convolution of complexity is converted into simple circular convolution, utilize the cyclic shift characteristic of matrix, can realize by FFT and IFFT computing.Yet the performance of Steiner estimator is subjected to the influence of receiving terminal additive noise, and its channel response that obtains responds with ideal communication channel and compares, and comprises noise component(s), has certain channel estimation errors.

At this problem, at prior art (Kang Shaoli, Qiu Zhengding, Li Shihe, the improvement of low-cost channel estimation methods in the TD-SCDMA system, the communication journal, Vol.23No.10,2002,108-113.) in, a kind of noise-reduction method of crossing Threshold detection has been proposed, this method has very little amount of calculation, and can make system obtain certain performance improvement, but adopting said method has also increased the false dismissal probability to the signal footpath when reducing the pseudo-footpath of channel estimating, the result of channel estimating reprocessing estimates still to have certain error with actual channel.

At application number is 200410049839.0 (publication numbers: CN1595832A, open March 16 2005 date) in the Chinese patent " a kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna ", disclosed the method that a kind of DOA of utilization has strengthened signal to noise ratio: the DOA that estimates each time delay footpath, calculate the channel estimation value of M array reference point of this time delay then respectively, obtain the average channel estimation value of this reference point on this time delay after average; Just can calculate a channel estimation value according to DOA again through the M of this user on this time delay of array antenna channel post-processing.This method has been improved the estimated accuracy of channel impulse response.

But, above-mentioned several method, lower to the estimation of channel impulse response tap position, so channel estimated accuracy is not very high.

Summary of the invention

Technical problem to be solved by this invention is to provide the method for channel estimating reprocessing in a kind of array antenna, utilize DOA time delay correlation to strengthen the channel estimating reprocessing, strengthened catching to the signal footpath, overcome the influence of noise to channel estimating, improved estimation, improved channel estimated accuracy the channel impulse response tap position.

To achieve these goals, the invention provides the method for channel estimating reprocessing in a kind of array antenna, its characteristics are, comprise the steps:

Step 1 proposes the training sequence that receives data to do channel estimating, obtains the channel impulse response estimation of this time slot

Step 2 is utilized generally between adjacent time-slots ripple to reach angle DOA and is changed the slowly time delay correlation of this DOA, carries out the channel estimating reprocessing, obtains handling the back channel impulse response

Step 3, obtain each user's channel impulse response, be that length is taken out the K class value therefrom, constitute corresponding each user's channel estimating, and will receive the user data that data separating comes out and carry out multi-user's joint-detection and demodulation with each user's the long W of channel response window.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics are, comprise the following steps: in this step 2

Step 21 is calculated average power in each tap

Use thresholding T ₁Right

Do reprocessing, be higher than thresholding T ₁Then be considered as the signal footpath, obtain the signal path position

Step 22 is estimated

The DOA in each footpath;

Step 23 is taken out average power

At thresholding T ₁With another thresholding T ₂Between tap, estimate its DOA, compare with the DOA of a last time slot correspondence position tap, if its difference less than a thresholding T who sets, then directly is judged to this signal footpath; Otherwise be considered as noise path: thus the signal path position taken out

Step 24 is according to the signal path position

With

From

Take out the values of tap of correspondence position, and, obtain the channel estimating reprocessing result of this time slot, promptly handle the back channel impulse response other tap zero setting

Step 25, all DOA directly pass to the next time slot that the respective user uplink service takies with this time slot.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics be, in step 1, and this channel impulse response estimation $\hat{h}=G^{-1}e$ , wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number, e is a training sequence.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics are, above-mentioned channel impulse response estimation

Can further adopt the FFT/IFFT fast method to realize, promptly $\hat{h}=\mathrm{ifft}(\mathrm{fft}\left(e\right)/\mathrm{fft}\left(m\right)),$ The product of G matrix and H matrix is realized with first row and the convolution of H matrix of G matrix in the formula, after doing the first row FFT of G matrix and H matrix and being FFT and multiplying each other, asks IFFT again, and the convolution of the complexity of time domain is converted into efficiently frequency domain FFT/IFFT realization fast.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics are, described thresholding T ₁=r ²σ ², wherein, σ ²The power of noise in the expression channel, the r span is 1.4～1.6; Described another thresholding T ₂=cr ²σ ², σ ²The power of noise in the expression channel, the r span is 1.4～1.6, with T ₁The value unanimity of middle r, c is a threshold parameter, span is 0.5～1; Described thresholding T is the differential seat angle threshold parameter, and span is 0～30 degree.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics are that in step 3, user data arrives receiver by spectrum-spreading and scrambling, air traffic channel, and received signal e can be expressed as:

$\left[\begin{array}{c}{e}^1\\ e^2\\ M\\ e^{\mathrm{Ka}}\end{array}\right]=\left[\begin{array}{c}{A}^1\\ A^2\\ M\\ A^{\mathrm{Ka}}\end{array}\right]d+\left[\begin{array}{c}{n}^1\\ n^2\\ M\\ n^{\mathrm{Ka}}\end{array}\right]$

Wherein, d is the column vector that all users' symbol is formed, the user separately the spread spectrum scrambler and the channel impulse response of reprocessing

Generation system transmission matrix A.

The method of channel estimating reprocessing in the above-mentioned array antenna, its characteristics are, in step 3, with matrix A user data is separated timing, can use in whitened matched filter algorithm WMF, ZF linear block balance device algorithm ZF, these joint detection algorithms of lms algorithm MMSE any.

Adopt the relevant method that strengthens channel post-processing of DOA time delay of utilizing of the present invention, compared with prior art, improve the estimated accuracy of each user's channel impulse response path position, effectively reduced the error rate, improve systematic function, increased power system capacity.

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.

Description of drawings

Fig. 1 is the schematic diagram of the pairing system signal receiving demodulation of the present invention;

Fig. 2 is that the present invention utilizes DOA time delay correlation to strengthen the simple flow chart of channel estimating reprocessing.

Embodiment

The present invention has utilized the relevant characteristic of channel DOA between time slot, has strengthened catching of signal footpath, has overcome the influence of noise to channel estimating, has improved the estimated accuracy of each user's channel impulse response.And be a kind of TD-SCDMA system channel estimation method of simple, better performances, improved the receptivity of uplink receiver.

To be described in detail method of the present invention below:

At first, data are done transmitting terminal handle, (being equivalent to wireless channel) launched in spread spectrum, scrambling (grouping scrambling), modulation and raised cosine filtering by eating dishes without rice or wine.

Then, from receive data, isolate the training sequence received signal, finish channel estimating and channel post-processing each user.The training sequence that receives can be expressed as

e＝Gh+n (1)

Wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number, and h is user's a channel impulse response, and n is a white Gaussian noise.

Finish the maximal possibility estimation of channel impulse response h with formula (2)

Promptly

$\hat{h}={\left(G^{*T}G\right)}^{-1}{G}^{*T}e---\left(2\right)$

Because the G matrix is the ring shift right matrix, has

$\hat{h}=G^{-1}e---\left(3\right)$

Therefore, utilize the cyclic shift characteristic of matrix, above-mentioned channel estimating can adopt the FFT/IFFT fast method to realize, thereby has improved arithmetic speed significantly.

As shown in the formula (4):

$\hat{h}=\mathrm{ifft}(\mathrm{fft}\left(e\right)/\mathrm{fft}\left(m\right))---\left(4\right)$

To channel impulse response

The power of each tap judge, if more than or equal to the threshold value that is provided with, then keep the position of this tap: otherwise, remove the response of this tap.The channel impulse response that we claim this method to obtain is a post process channel response.

The sign indicating number design of TD-SCDMA system, frame structure, spreading rate etc. provide feasibility for interference mitigation technology.Because generally, it is unconspicuous that the DOA in each footpath of the channel estimating between a last time slot and the next time slot changes, and the DOA information of front and back time slot can be utilized, so we utilize DOA time delay correlation to improve channel estimating.

Be the estimation of channel impulse response, we can further utilize DOA time delay correlation, and multi-slot smoothly strengthens the channel estimating reprocessing.At first power is higher than threshold T ₁The footpath be judged to signal footpath, then power is higher than another threshold T ₂And be lower than threshold T ₁The footpath take out, estimate its DOA, for each bar power at T ₂With T ₁Between the footpath, judge that in conjunction with the DOA in corresponding footpath on the adjacent time-slots of this user uplink business this directly is user's signal footpath, still the false footpath that causes by noise jamming.Judgment principle is: if the DOA of this footpath adjacent time-slots differs (at angle on the circle) in certain limit T, we think that promptly this directly is signal footpath, otherwise for noise jamming cause directly false.

Thresholding T wherein ₁=R ²σ ², σ ²The power of noise in the expression channel, the r span is 1.4～1.6, concrete value can be done fine setting by emulation or experiment; T ₂=cr ²σ ², σ ²The power of noise in the expression channel, the r span is 1.4～1.6, with T ₁The value unanimity of middle r, c is a threshold parameter, and span is 0.5～1, and concrete value can be obtained by emulation or experiment: T is the differential seat angle threshold parameter, and span is 0～30 degree, concrete value can be obtained by emulation or experiment.

Specifically, a kind of method of utilizing time delay D OA relevant information to strengthen channel post-processing of the present invention, it comprises the following steps:

The first step: the training sequence that will receive data proposes to do channel estimating.The maximal possibility estimation of channel impulse response, $\hat{h}=G^{-1}e.$

Second step: carry out this step of channel estimating reprocessing and can comprise following substep again:

(1) calculates average power in each tap

Be higher than thresholding T ₁Then be considered as the signal footpath, obtain the signal path position

(2) utilize existing a certain method (as the fixed beam search) to estimate

Each footpath DOA;

(3) find out average power

At thresholding T ₁With thresholding T ₂Between tap, take out its DOA, compare with the DOA of a last time slot correspondence position tap, if its difference (angle on the circle) less than a thresholding T who sets, then directly is judged to this signal footpath; Otherwise be considered as noise path.Take out the signal path position

(4) according to the signal path position

With

From Take out the values of tap of correspondence position, and, this channel estimation results that obtains is designated as other tap zero setting (thinking noise path)

, obtain the channel estimating reprocessing result of this time slot;

(5) DOA with all footpaths of this time slot passes to the next time slot that the respective user uplink service takies.

The 3rd step: the channel impulse response that obtains each user therefrom is that length is taken out the channel estimating (the long W of being of each user's channel response window) that the K class value has just constituted corresponding each user with W.

Enforcement below in conjunction with Fig. 1,2 pairs of technical schemes of the present invention is described in further detail:

At first, data are done transmitting terminal handle, spread spectrum, scrambling, modulation and raised cosine filtering are launched by antenna.

The training sequence that receives data is proposed to do channel estimating, and data portion is carried out multi-user's joint-detection demodulation, finishes data separating.

Then, from receive data, isolate the training sequence received signal, finish channel estimating and channel estimating reprocessing each user.The training sequence that receives can be expressed as

e＝Gh+n (5)

Wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number, and h is user's a channel impulse response, and n is a white Gaussian noise.

Finish the maximal possibility estimation of channel impulse response h with formula (6)

Promptly

$\hat{h}={\left(G^{*T}G\right)}^{-1}{G}^{*T}e---\left(6\right)$

Because the G matrix is the ring shift right matrix, has

$\hat{h}=G^{-1}e---\left(7\right)$

Therefore above-mentioned channel estimating can adopt the FFT/IFFT fast method to realize, thereby has improved arithmetic speed significantly, as shown in the formula:

$\hat{h}=\mathrm{ifft}(\mathrm{fft}\left(e\right)/\mathrm{fft}\left(m\right))---\left(8\right)$

The product of G matrix and H matrix is realized with first row of G matrix and the convolution of H matrix in the formula, after doing the first row FFT of G matrix and H matrix and being FFT and multiplying each other, asks IFFT again, and the convolution of the complexity of time domain is converted into efficiently frequency domain FFT/IFFT realization fast.

Be the estimation of channel impulse response, we can utilize the time delay correlation of DOA, further differentiate

Be user's signal footpath, the still false footpath that causes by noise jamming, i=1 wherein, L, W, W are that the channel impulse response window is long.

Earlier with a thresholding T ₁To the channel estimating power average value in each tap

Do judgement, will be recorded as greater than the tap position of thresholding

Use existing a certain method (as the fixed beam search) to estimate again

The DOA in each footpath finds out average power

At thresholding T ₁With thresholding T ₂Between tap, take out its DOA, compare with the DOA of a last time slot correspondence position tap, if its difference (angle on the circle) less than a thresholding T who sets, then directly is judged to this signal footpath; Otherwise be considered as noise path.Take out the signal path position

According to the signal path position

With

From

Take out the values of tap of correspondence position, and, this channel estimation results that obtains is designated as other tap zero setting (thinking noise path)

Obtain the channel estimating reprocessing result of this time slot.

User data arrives receiver by spectrum-spreading and scrambling, air traffic channel, and received signal e can be expressed as:

$\left[\begin{array}{c}{e}^1\\ {\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="C20051013062300121.png,C20051013062300131.png"\; state="\{\{state\}\}">e</figure-callout>}}^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ e^{\mathrm{Ka}}\end{array}\right]=\left[\begin{array}{c}{A}^1\\ {\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="C20051013062300121.png,C20051013062300131.png"\; state="\{\{state\}\}">A</figure-callout>}}^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ A^{\mathrm{Ka}}\end{array}\right]d+\left[\begin{array}{c}{n}^1\\ {\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C20051013062300121.png,C20051013062300131.png"\; state="\{\{state\}\}">n</figure-callout>}}^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ n^{\mathrm{Ka}}\end{array}\right]---\left(9\right)$

D is the column vector that all users' symbol is formed, the user separately the spread spectrum scrambler and the channel impulse response of reprocessing

Generation system transmission matrix A.

To the user data demodulation, can use whitened matched filter algorithm (WMF) with matrix A, ZF linear block balance device algorithm (ZF), lms algorithm multiple joint detection algorithms such as (MMSE).Here be that example is carried out data estimation with the lms algorithm, have

$\hat{d}={(A^H{R_n}^{-1}A+{R_d}^{-1})}^{-1}{A}^H{R_n}^{-1}e---\left(10\right)$

The present invention also can combine with other channel estimating reprocessing enhancement techniques, carry out the improvement of systematic function together as the channel estimation methods in application number be 200410049839.0 Chinese patent " a kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna " in (publication number: CN1595832A, open March 16 2005 date).After using channel estimating reprocessing Enhancement Method of the present invention, utilize the method in this patent to carry out the channel estimating reprocessing again, will obtain bigger performance gain.

The present invention is applicable to all cdma systems, particularly TDD-CDMA system and SCDMA system.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (7)

1. the method for channel estimating reprocessing in the array antenna is characterized in that, comprises the steps:

Step 1 proposes the training sequence that receives data to do channel estimating, obtains the channel impulse response estimation of this time slot

Step 2 is utilized the time delay correlation of slow this DOA of DOA variation between adjacent time-slots generally, carries out the channel estimating reprocessing, obtains handling the back channel impulse response DOA is that ripple reaches the angle;

Step 3, obtain each user's channel impulse response, be that length is taken out the K class value therefrom, constitute corresponding each user's channel estimating, and will receive the user data that data separating comes out and carry out multi-user's joint-detection and demodulation with each user's the long W of channel response window.

2. the method for channel estimating reprocessing is characterized in that in the array antenna according to claim 1, comprises the following steps: in this step 2

Step 21 is calculated average power in each tap

Use thresholding T ₁Right

Do reprocessing, be higher than thresholding T ₁Then be considered as the signal footpath, obtain the signal path position

Step 22 is estimated

The DOA in each footpath;

Step 23 is taken out average power At thresholding T ₁With another thresholding T ₂Between tap, estimate its DOA, compare with the DOA of a last time slot correspondence position tap, if its difference less than a thresholding T who sets, then directly is judged to this signal footpath; Otherwise be considered as noise path; Thereby take out the signal path position

Step 24 is according to the signal path position

With

From

Take out the values of tap of correspondence position, and, obtain the channel estimating reprocessing result of this time slot, promptly handle the back channel impulse response other tap zero setting

Step 25, all DOA directly pass to the next time slot that the respective user uplink service takies with this time slot.

3. the method for channel estimating reprocessing is characterized in that in the array antenna according to claim 2, in step 1, and this channel impulse response estimation $\hat{h}=G^{-1}e,$ Wherein, the G matrix is the ring shift right matrix that is made of a basic Midamble sign indicating number, and e is a training sequence.

4. the method for channel estimating reprocessing is characterized in that in the array antenna according to claim 3, above-mentioned channel impulse response estimation

Can further adopt the FFT/IFFT fast method to realize, promptly $\hat{h}=\mathrm{ifft}(\mathrm{fft}\left(e\right)/\mathrm{fft}\left(m\right)),$ The product of G matrix and H matrix is realized with first row and the convolution of H matrix of G matrix in the formula, after doing the first row FFT of G matrix and H matrix and being FFT and multiplying each other, asks IFFT again, and the convolution of the complexity of time domain is converted into efficiently frequency domain FFT/IFFT realization fast.

5. the method for channel estimating reprocessing is characterized in that in the array antenna according to claim 3, described thresholding T ₁=r ²σ ², wherein, σ ²The power of noise in the expression channel, the r span is 1.4～1.6; Described another thresholding T ₂=cr ²σ ², σ ²The power of noise in the expression channel, the r span is 1.4～1.6, with T ₁The value unanimity of middle r, c is a threshold parameter, span is 0.5～1; Described thresholding T is the differential seat angle threshold parameter, and span is 0～30 degree.

6. the method for channel estimating reprocessing is characterized in that in the array antenna according to claim 5, and in step 3, user data arrives receiver by spectrum-spreading and scrambling, air traffic channel, and received signal can be expressed as:

$\left[\begin{array}{c}{e}^1\\ e^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ e^{\mathrm{Ka}}\end{array}\right]=\left[\begin{array}{c}{A}^1\\ A^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ A^{\mathrm{Ka}}\end{array}\right]d+\left[\begin{array}{c}{n}^1\\ n^2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ n^{\mathrm{Ka}}\end{array}\right]$

Wherein, d is the column vector that all users' symbol is formed, the user separately the spread spectrum scrambler and the channel impulse response of reprocessing

Generation system transmission matrix A.

7. the method for channel estimating reprocessing in the array antenna according to claim 6, it is characterized in that, in step 3, with matrix A user data is separated timing, can use in whitened matched filter algorithm WMF, ZF linear block balance device algorithm ZF, these joint detection algorithms of lms algorithm MMSE any.

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