CN1917396A - Method for estimating angle of arrival wave, and assigning form for wave packet - Google Patents

Abstract

In the invention, for the sub frame, repeat the following steps: according to the channel estimation of each user on each antenna, calculating the covariance matrix of antenna array channel matrix of each user; in the angular coverage of antenna array, calculating the uplink receiving power transients and the received power recursion average value; search the maximum value of the uplink received power recursion average value corresponding to each user; based on it, generating the downlink beam-forming weighted value to implement beam-forming; calculating the fluctuating value of the Direction of Arrival (DOA) estimation between neighboring subframes; according to the up and down threshold of the received power forgetting factor, using the fluctuating value of DOA estimation of each user to self adapt the corresponding forgetting factor.

Description

A kind of ripple reaches the method for angle estimation and wave beam forming

Technical field

The present invention relates to a kind of ripple and reach angle (DOA, Direction Of Arrival) method of estimation and wave beam forming relates in particular to the up link DOA estimation of employing intelligent antenna technology in S-CDMA (CDMA) communication system and the method for downlink beamforming.

Background technology

The spatial character and the Digital Signal Processing of the smart antenna using signal transmission of prior art, can realize up link DOA estimation and downlink beamforming, thereby reach the purpose that reduces noise jamming, increase capacity, expansion covering, improves communication quality, reduction transmitting power and raising wireless data transmission rate.

Under certain user moving speed condition, for the synchronous CDMA communications system that adopts time division duplex (TDD) mode, its uplink and downlink channel satisfies symmetrical requirement, if adopt smart antenna, the up link DOA that then can realize each user according to the channel estimating of aerial array correspondence estimates, and then finish downlink beamforming, solve problems such as anti-multipath interference and anti-multiple access interference preferably.

Estimate and the implementation of wave beam forming, present engineering applicable cases according to DOA, mainly take dynamic multi-beam scan mode at present, in the angle of coverage scope, search for the received power (average) of each user on all directions with predetermined angle step, wherein the maximum corresponding orientation angles of received power (average) is the strongest direction of user uplink link power, and this also can think the direction of downlink beamforming.

In mobile communication system, wireless channel is very complicated, and to communication environments such as the reflection with various barriers, refraction, scattering and multipaths, the randomness of wireless channel propagation characteristic is very big from simple line-of-sight propagation.Along with the increase of distance between base station and the user terminal, will cause the signal strength signal intensity of radio magnetic wave obviously to weaken simultaneously.And user terminal is bigger with respect to the direction of motion and the speed influence to received signal of base station.Above-mentioned factor makes the base band algorithm of base station fluctuation or sudden change may occur when the DOA of estimating user, and the scope of fluctuation or sudden change may be very big, thereby causes the direction of wave beam forming to occur fluctuation or sudden change too.Yet in practice, user's true bearing fluctuation on a large scale or sudden change can not occur within a certain period of time, therefore can be at first that the received power of all directions is carried out recurrence is average, search for the received power of recurrence after average then, the orientation angles of its maximum correspondence is the direction of downlink beamforming.

In following document, introduced prior art about smart antenna:

[1] patent " time division SCDMA wireless communication system and communication means thereof " with smart antenna. Chinese patent, notification number: CN1053313C, the day for announcing: on June 7th, 2000

[2] patent " a kind of method of estimating the fixed beam space arrival direction ". Chinese patent, publication number: CN1535048A, the day for announcing: on October 6th, 2004

[3] patent " space characteristics of cdma wireless communication extracts and the direction of arrival of signal method of estimation ". Chinese patent, publication number: CN1585318A, the day for announcing: on February 23rd, 2005

[4]Liberti?J?C，Rappaport?T?S.Smart?Antennas?for?WirelessCommunications：IS-95?and?Third?Generation?CDMA?Applications.PrenticeHall?PTR

Document [1] combines smart antenna array with technology such as synchronization CDMA and TDD, provided a kind of time division SCDMA wireless communication system with smart antenna; Document [2] has provided a kind of method of estimating fixed beam space DOA, forms the method for estimation that DOA is asked in a kind of progressively classification refinement by changing the single-stage search into multi-pass decoding, is satisfying reduction system-computed amount under the condition of angular resolution; The space characteristics that document [3] has provided a kind of cdma wireless communication extracts and the direction of arrival of signal method of estimation, separate and choose the space impulse response of main propagation path during from each subscriber channel empty the impulse response result, estimate the space characteristics and the corresponding arrival direction of every main propagation path in view of the above; Document [4] has been systematically discussed intelligent antenna technology and algorithm thereof in conjunction with the characteristics of cdma system.

When calculating the recursive average of received power, if forgetting factor is configured to definite value, then be difficult to adapt to the situation of change of different communication environments, still do not have at present by adjusting forgetting factor adaptively and realize that ripple reaches the method for angle estimation and wave beam forming.

Summary of the invention

The object of the present invention is to provide a kind of ripple to reach the method for angle estimation and wave beam forming, technical problem to be solved is: the ripple that provides a kind of self adaptation to adjust forgetting factor reaches the method for angle estimation and wave beam forming, can solve real-time and the contradiction between the stability and the problem of DOA estimation and wave beam forming effectively, thereby increase the DOA estimation stability to a certain extent, thereby improve the performance of wave beam forming.

A kind of ripple reaches the method for angle estimation and wave beam forming, may further comprise the steps:

A, according to the channel estimating of each user on each antenna, calculate the covariance matrix of each user's aerial array channel estimating;

B, in the angle of coverage scope of aerial array, calculate the corresponding in different directions up link received power instantaneous value of each user with predetermined angle step;

C, in the angle of coverage scope of aerial array, the up link received power instantaneous value corresponding in different directions according to each user calculates the received power recursive average;

D, search for the maximum of the up link received power recursive average of each user's correspondence, the orientation angles of its maximum correspondence is this user's up link DOA estimated result, and generate this user's downlink beamforming weights in view of the above, realize wave beam forming;

E, calculate the undulating value that each user's adjacent sub-frame DOA estimates;

F, the undulating value that utilizes each user DOA to estimate are adjusted thresholding and are adjusted thresholding down according to going up of received power forgetting factor, and self adaptation is adjusted corresponding received power forgetting factor;

G, subframe numbers increase progressively, and repeating said steps a to f handles next subframe.

Described step f also comprises: adjust thresholding on the received power forgetting factor or adjust thresholding down if the undulating value that a certain user Bo Da angle is estimated has reached, then self adaptation is adjusted this user's received power forgetting factor; Otherwise the received power forgetting factor remains unchanged.

Described method, wherein, described go up to adjust thresholding and adjust the value of thresholding down and aerial array-the 3dB beamwidth is designated as W _BRelevant, the described span of adjusting thresholding that goes up is

The described span of adjusting thresholding down is

And following adjustment thresholding is not less than adjusts thresholding.

A kind of ripple provided by the present invention reaches the method for angle estimation and wave beam forming, overcome the shortcoming that received power recurrence average forgetting factor is configured to definite value, real-time and the contradiction between the stability and the problem of DOA estimation and wave beam forming have been solved, provided the method for a kind of DOA estimation and wave beam forming, increase the DOA estimation stability to a certain extent, thereby improved the performance of wave beam forming; Exist under sighting distance footpath, the multipath number is few, communication environments the is more satisfactory situation, DOA estimated result fluctuation or suddenly change lessly by adjusting forgetting factor, increases instantaneous value shared ratio in recursive average, helps the variation of real-time tracking user location; Multipath obviously, ignore apart from footpath, communication environments under the relatively more abominable or complicated situation, DOA estimated result fluctuation or suddenly change morely by adjusting forgetting factor, has reduced instantaneous value shared ratio in recursive average.

Description of drawings

Fig. 1 is the realization module frame chart of DOA estimation of the present invention and beam form-endowing method;

Fig. 2 is the flow chart of DOA estimation of the present invention and beam form-endowing method.

Embodiment

Below in conjunction with accompanying drawing, will carry out comparatively detailed explanation to preferred embodiment of the present invention.

A kind of ripple of the present invention reaches the method for angle estimation and wave beam forming, be DOA estimation and the beam form-endowing method that a kind of self adaptation is adjusted forgetting factor, can be along with the average forgetting factor of recurrence be adjusted in the variation of actual channel communication environments adaptively, and realize that according to the recursive average of received power up link DOA estimates and downlink beamforming.The basic technical scheme of the inventive method may further comprise the steps:

A, according to the channel estimating of each user on each antenna, calculate the covariance matrix of each user's aerial array channel estimating;

B, in the angle of coverage scope of aerial array, calculate the corresponding in different directions up link received power instantaneous value of each user with predetermined angle step;

C, in the angle of coverage scope of aerial array, the up link received power instantaneous value corresponding in different directions according to each user calculates the received power recursive average;

D, search for the maximum of the up link received power recursive average of each user's correspondence, the orientation angles of its maximum correspondence is this user's up link DOA estimated result, and generate this user's downlink beamforming weights in view of the above, realize wave beam forming;

E, calculate the undulating value that each user's adjacent sub-frame DOA estimates;

F, the undulating value that utilizes each user DOA to estimate are adjusted thresholding and are adjusted thresholding down according to going up of received power forgetting factor, and self adaptation is adjusted corresponding received power forgetting factor;

G, subframe numbers increase progressively, and repeating said steps a to f handles next subframe.

Described go up to adjust thresholding and adjust the value of thresholding down and aerial array-the 3dB beamwidth is designated as W _BRelevant.Generally, the span of adjusting thresholding on is

The span of adjusting thresholding down is And following adjustment thresholding is not less than adjusts thresholding.

As shown in Figure 1, the realization module of DOA estimation of the present invention and beam form-endowing method comprises:

1) aerial array (101)

2) multichannel amplifying unit (102)

3) multichannel transmitting-receiving letter machine unit (103)

4) channel estimating unit (104)

5) uplink baseband processing unit (105)

6) covariance matrix generation unit (106)

7) DOA estimation unit (107)

8) shape-endowing weight value generation unit (108)

9) down beam shaping unit (109)

For up link, multichannel amplifying unit (102) is operated in the LNA large model, and wireless signal is received by aerial array (101), is sent to multichannel transmitting-receiving letter machine unit (103) after amplifying through multichannel amplifying unit (102); Multichannel transmitting-receiving letter machine unit (103) carries out radiofrequency signal converting digital baseband signal to after the processing such as filtering, down-conversion, analog to digital conversion;

Channel estimating unit (104) is used for realizing each user's channel impulse response estimation, thereby obtains the information such as amplitude, phase place, multipath of channel; The output of multichannel transmitting-receiving letter machine unit (103) and channel estimating unit (104) is sent to uplink baseband processing unit (105) respectively, realizes that up link receives the demodulation work of data;

Covariance matrix generation unit (106) utilizes the channel estimation results of each user on aerial array of channel estimating unit (104) output to generate corresponding covariance matrix;

DOA estimation unit (107) is finished estimation to each user uplink link DOA according to the output of covariance matrix generation unit (106), and the DOA estimated result is sent to shape-endowing weight value generation unit (108);

Shape-endowing weight value generation unit (108) calculates according to each user DOA estimated result and generates corresponding downstream link beam shape-endowing weight value;

Down beam shaping unit (109) carries out beam forming processing based on shape-endowing weight value to each user's downlink base band data; Multichannel transmitting-receiving letter machine unit (103) carries out converting analog radio-frequency signal to after the processing such as digital to analog conversion, up-conversion, filtering to the base band figuration data of down beam shaping unit (109) output; For down link, multichannel amplifying unit (102) is operated in the power amplification pattern, and radiofrequency signal is amplified the back through multichannel amplifying unit (102) and launched by aerial array (101).

As shown in Figure 2, the method concrete steps of DOA estimation of the present invention and wave beam forming are as follows:

Step 201 according to the channel estimating of each user on each antenna, is calculated the covariance matrix of each user's aerial array channel estimating.

At aerial array, the channel estimate matrix of k user, a n subframe is

$H^{\left(k\right)}\left(n\right)={\left[\begin{array}{cccc}{h}_1^{(k,1)}\left(n\right)& h_2^{(k,1)}\left(n\right)& \·\·\·& h_W^{(k,1)}\\ h_1^{(k,2)}\left(n\right)& h_2^{(k,2)}\left(n\right)& \·\·\·& h_W^{(k,2)}\\ \·\·\·& \·\·\·& \·\·\·& \·\·\·\\ h_1^{(k,\mathrm{Ka})}\left(n\right)& h_2^{(k,\mathrm{Ka})}\left(n\right)& \·\·\·& h_W^{(k,\mathrm{Ka})}\left(n\right)\end{array}\right]}_{\mathrm{Ka}\×W}---\left(1\right)$

K _aThe expression antenna number, W represents that channel estimation window is long.Its covariance matrix is expressed as

$R_{\mathrm{HH}}^{\left(k\right)}\left(n\right)=H^{\left(k\right)}\left(n\right)\·{\left(H^{\left(k\right)}\left(n\right)\right)}^H---\left(2\right)$

Step 202 in the angle of coverage scope of aerial array, is calculated the corresponding in different directions up link received power instantaneous value of each user with certain angle step.

θ _iSteering vector a (θ on the direction _i) be expressed as

$a\left({\mathrm{\θ}}_i\right)={\left[\begin{array}{cccc}{e}^{-j{\mathrm{\γ}}_1\left({\mathrm{\θ}}_i\right)},& e^{-j{\mathrm{\γ}}_2\left({\mathrm{\θ}}_i\right)},& ...,& e^{-j{\mathrm{\γ}}_{\mathrm{Ka}}\left({\mathrm{\θ}}_i\right)}\end{array}\right]}^T---\left(3\right)$

In the formula

θ _i＝θ ₁+i·Δθ (4)

θ wherein ₁The start angle of expression search, Δ θ are represented the angle step of searching for.

So, k user, a n subframe, at θ _iUp link received power instantaneous value corresponding on the direction is

$P^{\left(k\right)}({\mathrm{\θ}}_i,n)={\left(a\left({\mathrm{\θ}}_i\right)\right)}^H{R}_{\mathrm{HH}}^{\left(k\right)}\left(n\right)a\left({\mathrm{\θ}}_i\right)---\left(5\right)$

Step 203, in the angle of coverage scope of aerial array, the up link received power instantaneous value corresponding in different directions according to each user calculates the received power recursive average.

K user, at θ _iOn the direction, the up link received power recursive average of a n subframe correspondence is expressed as

$\stackrel{\‾}{P^{\left(k\right)}({\mathrm{\θ}}_i,n)}=(1-p^{\left(k\right)}\left(n\right))\·\stackrel{\‾}{P^{\left(k\right)}({\mathrm{\θ}}_i,n-1)}+p^{\left(k\right)}\left(n\right)\·P^{\left(k\right)}({\mathrm{\θ}}_i,n)---\left(6\right)$

P in the formula ^(k)(n) the received power forgetting factor of k user of expression, a n subframe, p ^(k)(l)=p ₀, p ₀Initial value for the received power forgetting factor.

Step 204, search for the maximum of the up link received power recursive average of each user's correspondence, the orientation angles of its maximum correspondence is this user's up link DOA estimated result, and generates this user's downlink beamforming weights in view of the above, realizes wave beam forming.

Search for the maximum of the up link received power recursive average of k user's correspondence, the orientation angles of its maximum correspondence is this user's up link DOA estimated value, is expressed as

${\mathrm{\θ}}_{\mathrm{DOA}}^{\left(k\right)}\left(n\right)=\underset{{\mathrm{\θ}}_i}{\arg }\left[\max \left(\stackrel{\‾}{P^{\left(k\right)}({\mathrm{\θ}}_i,n)}\right)\right]---\left(7\right)$

Corresponding downlink beamforming weights are

$w^{\left(k\right)}\left(n\right)=a\left({\mathrm{\θ}}_{\mathrm{DOA}}^{\left(k\right)}\left(n\right)\right)---\left(8\right)$

K user's downlink beamforming output is expressed as

y ^(k)(t，n)＝(w ^(k)(n)) ^Hx ^(k)(t，n) (9)

X in the formula ^(k)(t, n) k user's of expression emission data.

Step 205 is calculated the undulating value that each user's adjacent sub-frame DOA estimates.

The undulating value of k user's adjacent sub-frame DOA estimated result is expressed as

$F^{\left(k\right)}\left(n\right)=|{\mathrm{\θ}}_{\mathrm{DOA}}^{\left(k\right)}\left(n\right)-{\mathrm{\θ}}_{\mathrm{DOA}}^{\left(k\right)}(n-1)|---\left(10\right)$

Step 206, the undulating value that utilizes each user DOA to estimate is adjusted thresholding and is adjusted thresholding down according to going up of received power forgetting factor, and self adaptation is adjusted corresponding received power forgetting factor.

Adjust thresholding on the received power forgetting factor or adjust thresholding down if the undulating value that a certain user DOA estimates has reached, then self adaptation is adjusted this user's received power forgetting factor; Otherwise the received power forgetting factor remains unchanged.

The self adaptation regulation rule of forgetting factor is expressed as

S in the formula _pBe the adjustment step-length of received power forgetting factor, T _p ¹And T _p ²Be respectively the following adjustment thresholding and the last adjustment thresholding of received power forgetting factor, p _Min, p _MaxBe respectively the minimum value and the maximum of received power forgetting factor.

Last adjustment thresholding and adjust the value of thresholding down and aerial array-the 3dB beamwidth (is designated as W _B) relevant.Generally, adjust thresholding T on _p ²Span be

Under adjust thresholding T _p ¹Span be $\frac{W_B}{4}~2W_B;$ $T_p^1\≥T_p^2;$ Forgetting factor is adjusted step-length S _pSpan be 0～0.5; The minimum value p of forgetting factor _MinSpan be 0～1, the maximum p of forgetting factor _MaxSpan be 0～1.

Step 207, subframe numbers increases progressively, and repeating step 201 to step 206 is handled next subframe.

In sum, the present invention has provided a kind of self adaptation and has adjusted the method that the ripple of forgetting factor reaches angle estimation and wave beam forming, can solve real-time and the contradiction between the stability and the problem of DOA estimation and wave beam forming effectively.Ripple provided by the present invention reaches the method for angle estimation and wave beam forming can adjust the average forgetting factor of recurrence adaptively along with the variation of actual channel communication environments.Calculate the recursive average of received power, realize that according to the received power recursive average up link DOA estimates and downlink beamforming, and the undulating value that utilizes each user DOA to estimate, upper and lower adjustment thresholding according to the received power forgetting factor, self adaptation is adjusted corresponding forgetting factor, can increase the DOA estimation stability to a certain extent, thereby improve the performance of wave beam forming.

The inventive method exists under sighting distance footpath, the multipath number is few, communication environments the is more satisfactory situation, the DOA estimated result fluctuates or suddenlys change less, by adjusting forgetting factor, instantaneous value shared ratio in recursive average is increased, help the variation of real-time tracking user location; Multipath obviously, ignore apart from footpath, communication environments under the relatively more abominable or complicated situation, DOA estimated result fluctuation or suddenly change morely by adjusting forgetting factor, has reduced instantaneous value shared ratio in recursive average.

Should be noted that; the present invention is applicable to S-CDMA (CDMA) communication system; be particularly useful for TD-SCDMA system (1.28Mcps TDD) and 3.84Mcps TDD system in the 3-G (Generation Three mobile communication system); but be applicable to the frequency division multiple access of employing synchronization CDMA and the system of time division multiple access too; any have a signal processing; the technical staff of knowledge background such as communication; reach the method for angle estimation and wave beam forming according to the ripple that is equal to of the inventive method design; it all should be included in thought of the present invention and the scope, should belong within the protection range of claims of the present invention.

Claims (3)

1, a kind of ripple reaches the method for angle estimation and wave beam forming, may further comprise the steps:

A, according to the channel estimating of each user on each antenna, calculate the covariance matrix of each user's aerial array channel estimating;

B, in the angle of coverage scope of aerial array, calculate the corresponding in different directions up link received power instantaneous value of each user with predetermined angle step;

C, in the angle of coverage scope of aerial array, the up link received power instantaneous value corresponding in different directions according to each user calculates the received power recursive average;

D, search for the maximum of the up link received power recursive average of each user's correspondence, the up link ripple that the orientation angles of its maximum correspondence is this user reaches the angle estimated result, and generate this user's downlink beamforming weights in view of the above, realize wave beam forming;

E, calculate each user's adjacent sub-frame ripple and reach the undulating value that the angle is estimated;

F, the undulating value that utilizes each user Bo Da angle to estimate are adjusted thresholding and are adjusted thresholding down according to going up of received power forgetting factor, and self adaptation is adjusted corresponding received power forgetting factor;

G, subframe numbers increase progressively, and repeating said steps a to f handles next subframe.

2, method according to claim 1 is characterized in that, described step f also comprises:

Adjust thresholding on the received power forgetting factor or adjust thresholding down if the undulating value that a certain user Bo Da angle is estimated has reached, then self adaptation is adjusted this user's received power forgetting factor; Otherwise the received power forgetting factor remains unchanged.

3, method according to claim 1 is characterized in that, described go up to adjust thresholding and adjust the value of thresholding down and aerial array-the 3dB beamwidth is designated as W _BRelevant, the described span of adjusting thresholding that goes up is

The described span of adjusting thresholding down is

And following adjustment thresholding is not less than adjusts thresholding.

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