CN1595832A - A TD-CDMA system demodulation method based on array antenna - Google Patents

Abstract

The invention discloses an antenna array-based time division-code division multiple access (TD-CDMA) system demodulating method, including the steps: obtaining original estimated values of all time delay paths of each user by channel estimation of single antenna; according to original channel estimated values of every two adjacent antennas, calculating the phase difference between their channel estimations, then calculating the corresponding M-1estimated values of incident angle in this time delay, and averaging and obtaining an average estimated value of incident angle of this time delay; then calculating M estimated values of array reference point, averaging and obtaining the average channel estimated value of the array reference point in this time delay; thus able to calculate M processed channel estimated values of a user in this time delay; making the above processing on all time delay paths of each user, and finally output the reconstructed channel estimated values and data sequences together for making data demodulation. It can reduce the channel estimated error of TD-CDMA system on array receiving conditions, simple and easy to implement and high-efficiency.

Description

A kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna

Technical field

Base band demodulating technology, especially this system of the present invention relates to receiver in TD-CDMA Time Division-Code Division Multiple Access (TD-CDMA) mobile communication system estimate and post-processing technology based on the Fast Channel of array antenna.

Background technology

TD-CDMA, particularly TD SDMA (TD-SCDMA) are based on the 3-G (Generation Three mobile communication system) of time division duplex (TDD), wherein relate to a lot of key technologies, as Fast Channel estimation technique, associated detection technique, intelligent antenna technology etc.In the TD-CDMA system, Fast Channel estimates to have important effect with post-processing technology.It is some key technologies, the basis that for example precondition of realizations such as smart antenna, joint-detection, synchronous detecting, or various Measurement Algorithm is achieved, its whether accurate performance that will have influence on this series of algorithms.Therefore, reducing channel estimation error, promptly weaken or eliminate noise in the channel response, is the problem that presses for solution.

The channel estimation technique of existing TD-CDMA system (particularly TD-SCDMA) generally all is utilization Steiner method of estimation (STEINER B, BAIER P.Low cost channel estimation inthe uplink receiver of CDMA mobile radio systems, Frequenz, 1993,47 (12): 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, can realizes by fast Fourier transform (FFT) and inverse fast fourier transform (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), just channel estimation errors; Can enlarge noise power simultaneously, cause the relative input of output signal to noise ratio that a certain amount of loss is arranged.

The communication journal, 2002,23 (10): in disclosed among the 125-130. " improvement of low-cost channel estimation methods in the TD-SCDMA system ", proposed a kind of noise-reduction method of crossing Threshold detection, this method has very little amount of calculation, and can make system obtain certain performance improvement.

But above-mentioned 2 kinds of methods all are based on the channel estimating and the post-processing technology of single antenna.And adopt the situation of array antenna received to compare with the employing single-antenna case, when reaching identical gain, each antenna in the array can be operated on the lower signal to noise ratio.This just means with single-antenna case compares, and adopts the performance for estimating channel that obtains under the situation of array antenna received poorer.By emulation shows to TD-SCDMA system uplink reception technique (adopting many antennas MMSE-BLE technology), adopt the above-mentioned noise-reduction method estimation channel of crossing Threshold detection to compare with direct employing ideal communication channel, its performance loss is about 4dB.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna, can reduce the channel estimation errors of TD-CDMA system under the array received condition.

In order to solve the problems of the technologies described above, the invention provides a kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna, may further comprise the steps:

(a) will carry out the channel estimating of single antenna to the training sequence that obtains after the radio frequency signal processing, obtain the original channel estimated value in all effective time delay footpaths of all users;

(b), calculate the phase difference of each adjacent antenna channel estimating according to the original channel estimated value of each adjacent antenna correspondence on this user's time delay;

(c) calculated the estimated value of M-1 incidence angle of this time delay correspondence by this phasometer, calculate the estimated value of average incidence angle on this time delay again, wherein M is the antenna number;

(d) according to estimated value, the original channel estimated value of this time delay correspondence and the array characteristic of described array antenna of this average incidence angle, calculate the channel estimation value of M array reference point respectively, calculate the average channel estimation value of this reference point on this time delay again;

(e) according to estimated value, the average channel estimation value of reference point and the array characteristic of described array antenna of this average incidence angle, obtain a channel estimation value through the M of this user on this time delay of array antenna channel post-processing;

(f) all effective time delays of all users are directly carried out the processing of step (b) to (e), obtain through the channel estimation value in all effective time delays footpaths of all users of array antenna channel post-processing and the data sequence that obtains after to the radio frequency signal processing is sent into data demodulation module together and carried out the user data demodulation.

Further, the method of above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: in the described step (a), training sequence is carried out also carry out simple thresholding reprocessing after the channel estimating of single antenna, obtain described original channel estimated value.

Further, the method for above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: when described step (b) is calculated adjacent antenna channel estimating phase difference, have only the situation of an incidence angle to calculate by this user on this time delay.

Further, the method for above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: in the described step (c), be that the estimated value of a described M-1 incidence angle is carried out arithmetic average, obtain the estimated value of described average incidence angle.

Further, the method of above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: in the described step (d), be that channel estimation value to described M array reference point carries out arithmetic average, obtain the average channel estimation value of this reference point on this time delay.

Further, the method for above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: the channel estimation value in each step is the estimated value of channel impulse response.

Further, the method for above-mentioned TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna can have following characteristics: described array reference point is the geometric center point of described array antenna.

By the TD-SCDMA standard testing channel that provides based on 3GPP is carried out a large amount of emulation, simulation result shows, adopt method and apparatus of the present invention to carry out the array antenna channel post-processing, compare, (BER=10 for example under identical error performance with the prior art of not carrying out this processing ^-3) obtained the gain about 2dB, noise reduces greatly.Simultaneously, this method and device have compared with prior art just increased very small amount of complexity, and are simple and easy to realize that efficient is higher, and has finally improved the receptivity of uplink receiver.Be specially adapted to the outdoor macro honeycomb environment.

Description of drawings

Fig. 1 is the functional block diagram of the embodiment of the invention based on the TD-CDMA system uplink receiving system of array.

Fig. 2 A and Fig. 2 B are respectively the array antenna schematic diagrames of ring array and linear array.

Fig. 3 is the flow chart of estimation of embodiment of the invention device D respective channels and reprocessing.

Embodiment

For reaching the purpose of the up receiving system receptivity of final raising, method provided by the present invention is mainly on the basis of conventional single antenna channel estimation and thresholding reprocessing, utilize the characteristics of array antenna, increase array antenna channel post-processing technology, reduce the noise power in the channel impulse response that estimates, channel estimation errors is reduced greatly, thereby improve the performance of data demodulates.

Be elaborated below in conjunction with the technical scheme of accompanying drawing to the embodiment of the invention:

As shown in Figure 1, present embodiment is made up of the following several parts that connect successively based on the TD-CDMA system uplink receiving system of array: the data of array received antenna 1, radio frequency, intermediate frequency and A/D ARRAY PROCESSING module 2, each time slot and training sequence separation module 3, channel estimating and post-processing module 4, data demodulation module 5.Wherein, array received antenna 1 can comprise forms such as linear array or ring array, and shown in Fig. 2 A and Fig. 2 B, present embodiment is that the even ring array with unit 8 is an example.Channel estimating and post-processing module 4 can be divided into single antenna channel estimation module 41 and array antenna channel post-processing module 42 again.

The up receiving system of present embodiment may further comprise the steps the Signal Processing process:

Step 110, array antenna receiver apparatus is sensed radiofrequency signal, exports baseband digital I through after radio frequency, intermediate frequency and the A/D ARRAY PROCESSING module;

Step 120, this baseband digital I is isolated training sequence and data sequence in each prominent method through after the data and training sequence separation module of each time slot,

Step 130 after the single antenna channel estimation module receives training sequence, is carried out conventional single antenna channel and is estimated and simple thresholding reprocessing, draws the channel estimation value in all time delay footpaths of all users;

Step 140 is sent the described channel estimation value that obtains into array antenna channel post-processing module and is carried out reprocessing, calculates the channel estimation value through all effective time delay footpaths of all users of array antenna channel post-processing;

Step 150, to deliver to data demodulation module simultaneously through the channel estimation value in all effective time delays footpaths of all users of array antenna channel post-processing and isolated described data sequence and carry out the user data demodulation, export all users' demodulating data, can adopt associated detection technique or 2D-RAKE technology.

Above-mentioned steps 110～130, and step 150 can adopt routine techniques to handle.Present embodiment adopts aforesaid single antenna channel to estimate and the thresholding post-processing technology in step 130.

Below emphasis is discussed the concrete computational methods of step 140, as shown in Figure 3, be may further comprise the steps:

Step 210, the original channel estimated value that obtains according to step 130, calculate the phase difference of this user efficient channel estimated value on certain time delay of each adjacent antenna correspondence, go out the estimated value (supposition this user on time delay has only an incidence angle, and antenna amount is M) of M-1 incidence angle of this time delay correspondence again according to this phase difference estimation

Estimate that through single antenna channel the channel estimation value that obtains with simple thresholding reprocessing can be expressed as:

I=1 wherein, 2 ..., W represents i time delay footpath; K=1,2 ..., K represents k user; M=1,2 ..., M represents m antenna.Even ring array with tool representative in the TD-SCDMA system is an example, establish k user i effectively the true impulse response of time delay reference point (center of circle) directly be h _{I, k} ^(o), then estimate Can be expressed as:

${\hat{h}}_{i,k,m}=h_{i,k}^{\left(o\right)}\·e^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\mathrm{\θ}}_{i,k})}+n_m---\left(1\right)$

Wherein: θ _{I, k}The incidence angle of representing i time delay footpath of k user, n _mThe expression noise jamming, β=2 π R/ λ, wherein: R is an annular radii, λ is a carrier wavelength.This formula is different under the array antenna of different formation, but all can carry out the computing of follow-up each step.

The phase difference of adjacent antenna channel estimating is:

$\mathrm{\Δ}{h}_{i,k,m}=\frac{{\hat{h}}_{i,k,m+1}}{{\hat{h}}_{i,k,m}}$

$=\frac{h_{i,k}^{\left(o\right)}\·e^{-\mathrm{j\β}\cos (2\mathrm{\πm}/M-{\mathrm{\θ}}_{i,k})}+n_{m+1}}{h_{i,k}^{\left(o\right)}\·e^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\mathrm{\θ}}_{i,k})}+n_{m+1}}$

$\≅e^{-j\·\mathrm{\β}[\cos (2\mathrm{\πm}/M-{\mathrm{\θ}}_{i,k})-\cos (2\mathrm{\π}(m-1)/M-{\mathrm{\θ}}_{i,k})]---\left(2\right)}$

Therefore, just can calculate M-1 the incidence angle θ in i time delay footpath of k user according to (2) formula _{I, k}Estimated values theta _{I, k, m}

Step 220 is carried out arithmetic average to M-1 the incidence angle that estimates, and calculates the estimated value of average incidence angle on this time delay;

The incidence angle θ in i time delay footpath of k user _{I, k}Mean estimates θ _{I, k}For:

${\stackrel{-}{\mathrm{\θ}}}_{i,k}=\frac{1}{M-1}\underset{m=1}{\overset{M-1}{\mathrm{\Σ}}}{\stackrel{-}{\mathrm{\θ}}}_{i,k,m}---\left(3\right)$

Step 230 is a reference point with the center of circle of ring array, according to the original channel estimation value of the estimated value of this average incidence angle, this time delay correspondence and the even array characteristic of ring array, calculates the channel estimation value of M reference point respectively;

Calculate θ _{I, k}After, because The noise, we do not know h in fact _{I, k} ^(o), carry out h below _{I, k} ^(o)Estimation.According to formula (1), can get:

$h_{i,k}^{\left(o\right)}={\hat{h}}_{i,k,m}/[e^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\mathrm{\θ}}_{i,k})}+n_m]---\left(4\right)$

According to (3) formula and (4) formula, then m the antenna in i time delay footpath of k user is to h _{I, k} ^(o)Estimated value h _{I, k, m} ^(o)For:

${\stackrel{-}{h}}_{i,k,m}^{\left(o\right)}={\hat{h}}_{i,k,m}/e^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\stackrel{-}{\mathrm{\θ}}}_{i,k})}$

$={\hat{h}}_{i,k,m}{e}^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\stackrel{-}{\mathrm{\θ}}}_{i,k})}---\left(5\right)$

Will

With the θ that calculates _{I, k}The substitution following formula can obtain i M h directly of k user _{I, k} ^(o)Estimated value h _{I, k, m} ^(o)

Step 240 is carried out arithmetic average to the channel estimation value of M reference point estimating, calculates the average channel estimation value of reference point correspondence on this time delay;

K user i time delay footpath h _{I, k} ^(o)The average channel estimation value h of reference point _{I, k} ^(o)For:

${\stackrel{-}{h}}_{i,k}^{\left(o\right)}=\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\stackrel{-}{h}}_{i,k,m}^{\left(o\right)}---\left(6\right)$

Step 250 according to the estimated value of the average incidence angle that obtains and the average channel estimation value of reference point, and the even steering vector characteristic of ring array, reconstructs this user corresponding M channel impulse response value on this time delay, promptly new channel estimation value;

With h _{I, k} ^(o)And θ _{I, k}Substitution (1) formula can calculate through i time delay of k user M channel estimation value directly of array antenna channel post-processing as follows:

${\hat{h}}_{i,k,m}={\stackrel{-}{h}}_{i,k}^{\left(o\right)}\·e^{-j\·\mathrm{\β}\cos (2\mathrm{\π}(m-1)/M-{\stackrel{-}{\mathrm{\θ}}}_{i,k})}---\left(7\right)$

Step 260 is to all effective diameters of this user, repeating step 210～250;

Step 270, to all validated users, repeating step 210～160 can obtain the channel estimation value through all effective time delay footpaths of all users of array antenna channel post-processing, just can send into the E module then and carry out data demodulates.

When the array antenna of linear array or other form was carried out the array antenna channel post-processing, though array characteristic difference, concrete formula difference can adopt the method in the above-mentioned steps equally.

Claims (7)

1, a kind of method of the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna may further comprise the steps:

(a) will carry out the channel estimating of single antenna to the training sequence that obtains after the radio frequency signal processing, obtain the original channel estimated value in all effective time delay footpaths of all users;

(b), calculate the phase difference of each adjacent antenna channel estimating according to the original channel estimated value of each adjacent antenna correspondence on this user's time delay;

(c) calculated the estimated value of M-1 incidence angle of this time delay correspondence by this phasometer, calculate the estimated value of average incidence angle on this time delay again, wherein M is the antenna number;

(d) according to estimated value, the original channel estimated value of this time delay correspondence and the array characteristic of described array antenna of this average incidence angle, calculate the channel estimation value of M array reference point respectively, calculate the average channel estimation value of this reference point on this time delay again;

(e) according to estimated value, the average channel estimation value of reference point and the array characteristic of described array antenna of this average incidence angle, obtain a channel estimation value through the M of this user on this time delay of array antenna channel post-processing;

(f) all effective time delays of all users are directly carried out the processing of step (b) to (e), obtain through the channel estimation value in all effective time delays footpaths of all users of array antenna channel post-processing and the data sequence that obtains after to the radio frequency signal processing is sent into data demodulation module together and carried out the user data demodulation.

2, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1, it is characterized in that, in the described step (a), training sequence is carried out also carry out simple thresholding reprocessing after the channel estimating of single antenna, obtain described original channel estimated value.

3, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1, it is characterized in that, when described step (b) is calculated adjacent antenna channel estimating phase difference, have only the situation of an incidence angle to calculate by this user on this time delay.

4, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1 is characterized in that, in the described step (c), is that the estimated value of a described M-1 incidence angle is carried out arithmetic average, obtains the estimated value of described average incidence angle.

5, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1, it is characterized in that, in the described step (d), be that the channel estimation value to described M array reference point carries out arithmetic average, obtain the average channel estimation value of this reference point on this time delay.

6, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1 is characterized in that the channel estimation value in each step is the estimated value of channel impulse response.

7, the method for the TD-CDMA Time Division-Code Division Multiple Access system demodulation based on array antenna as claimed in claim 1 is characterized in that described array reference point is the geometric center point of described array antenna.

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