CN1589054A - Up self adaption wave beam shorming method based on signal arrival angle detection - Google Patents

Abstract

This invention provides a technology used in the adaptive beam formation of an intelligent antenna system. This invention starts from increasing the convergence speed of the adoptive beam formation iterative algorithm. Since the detection result to the arrival angle of the pilot signal generates a direction vector corresponding to the signal arriving angle, the due-in signal direction vector and the adaptive iterative algorithm as the initial vector of the adaptive beam formation algorithm are used to form the optimum weight vector and the optimum antenna direction map.

Description

A kind of up adaptive beamforming method that detects based on the signal angle of arrival

Technical field

Invention relates to a kind of method of the adaptive beamforming of using in antenna system.Relate in particular to a kind of in wireless communication system the adaptive beamforming method based on reverse pilot signal.

Background technology

Developing rapidly of global traffic, feasible wireless communication technology as the main means of following personal communication is subjected to people and pays close attention to greatly.How to eliminate cochannel effectively and disturb (Co-channel Interference, CCI), multiple access disturbs (Multiple-access Interference, MAI) etc. influence becomes wireless communication system, especially the subject matter of system for restricting capacity etc. in the code division multi-address radio communication system.The processing method of traditional employing equilibrium can not address these problems when the signal propagation delay time is big better.And the employing intelligent antenna technology, the processing by the signal space territory can address these problems preferably.Intelligent antenna technology has become a key technology in the third generation and the later mobile communication system.

Smart antenna using digital signal, produce the spatial orientation wave beam, make antenna main beam aim at the subscriber signal arrival direction, secondary lobe or zero trapping spot are aimed at the interference signal arrival direction, and the useful signal that fully utilizes the mobile subscriber efficiently also suppresses or the purpose of deletion interference signal to reach.The wireless communication system of applying intelligent antenna greatly reduces multiple access and disturbs, and has improved the signal to noise ratio of system.Only the multipath from main lobe direction or big secondary lobe direction just brings interference to useful signal.Applying intelligent antenna can reduce base station transmitting power, saves the cost of system, reduces inter-signal interference and electromagnetic pollution.Applying intelligent antenna can also increase the overlay area of system, improves the power system capacity and the availability of frequency spectrum.

In order to adapt to wireless communications environment, intelligent antenna technology has obtained many research.As United States Patent (USP) U.S.5,887,262 (Smart antenna backwards compatibility indigital cellular systems) and U.S.6,229,486 (Subscriber based smartantenna) have introduced the TDMA wireless communication system of applying intelligent antenna.U.S.6,252,548 (Transceiver arrangement for a smart antenna system in a mobilecommunication base station) have introduced a kind of structure of base station receiver of applying intelligent antenna.

Smart antenna generally is divided into two classes: multi-beam switch antenna and adaptive antenna array.Smart antenna uses digital beam to form (Digital Beamforming) technology and obtains required wave beam forming.

Multi-beam switch antenna utilizes a plurality of parallel beams to cover whole user area, and the sensing of each wave beam is fixed, and beamwidth determines according to array element number that also along with user's moving in the sub-district, the base station switch is selected different wave beams, makes received signal the strongest.

Adaptive antenna array is adjusted antenna array pattern continuously by feedback controling mode.General 4～16 bay structures that adopt, the bay spacing is generally 1/2 wavelength.The bay distribution mode has linear pattern, round, circular ring type and plane etc.Adaptive antenna system adopts Digital Signal Processing to realize the antenna beam figuration, provides different space channels according to the different spaces direction of propagation of subscriber signal, overcomes the influence of interference to system effectively.

In adaptive antenna array system, the base station is signal and the interference signal according to the targeted customer who receives, according to certain judgment criteria, make some cost function minimum (such as, but not limited to the least mean-square error of echo signal), thereby the weighing vector of adaptive adjustment aerial array, and finally obtain optimum weighing vector, form the optimal antenna directional diagram.Adaptive algorithm takes the mode of piece or iteration to carry out usually.In iterative algorithm, the setting of initial weighing vector can influence the convergence rate of adaptive algorithm to a great extent.So,, will improve the convergence rate and the efficient of adaptive algorithm if before the beam shaping iterative algorithm, can select the initial weight vector of the weighing vector of a suboptimum according to known signal message as iterative algorithm.

In traditional adaptive antenna array system, at different signal characteristics (being the different signal angles of arrival), standard adaptive beamforming algorithm all adopts identical initial weighing vector to carry out adaptive iterative computation to upgrade weighing vector.This will certainly increase wherein the amount of calculation to the iterative computation in most signal processing, thereby increases the Signal Processing time.

So far, all be to adopt identical initial weighing vector to carry out adaptive beam shaping in the antenna system.More is adopts complete " 1 " vector as initial weighing vector (this supposes tentatively that just the angle of arrival of signal is 0 degree or 180 degree, just adjust by the adaptive beamforming algorithm then and upgrade).And be not set with initial targetedly weighing vector at the different signal angles of arrival.So, cause the iterative algorithm convergence rate of adaptive beamforming algorithm very slow.

In recent years, the existing iterative convergence speed of much being devoted to improve the adaptive beamforming algorithm about the research of intelligent antenna technology, as Coherent LMS Algorithms (IEEECOMMUNICATIONS LETTERS, VOL.4, NO.3, MARCH 2000) a kind of relevant LMS algorithm based on pilot channel has been proposed, compared with the LMS algorithm of standard, under identical adaptive algorithm step-length condition, can improve the convergence rate of adaptive algorithm greatly.

Conventional art usually adopts complete " 1 " vector initial weighing vector as spatial weighting, that is to say that incipient the time addition obtains output signal then to the signal times that receives on each bay and separately initial weighted value " 1 ".Comparing with this output signal with based on the reference signal that pilot tone obtains obtains error signal, and the adjustment weighing vector that adopts adaptive algorithm to repeat then meets the demands less than some threshold values up to error signal.

From above-mentioned process as can be seen, the speed of convergence rate is decided by three aspects: the setting of the convergence rate of adaptive algorithm itself, algorithm iteration step-length and initial weighing vector.

Summary of the invention

The present invention considers from the setting aspect of initial weighing vector, a kind of adaptive beamforming method of practicality and high efficiency has been proposed, adaptive beamforming convergence of algorithm speed be can improve greatly, thereby the conversion speed and the ability of adaptive antenna array improved.

Characteristics of the present invention are, to the signal characteristic of different echo signals---the angle of arrival of signal, generate corresponding direction vector, and the direction vector of echo signal and the initial weighing vector that is set at correspondence.Initial weighing vector like this is a kind of spatial weighting vector of suboptimum, initial weighing vector compared with complete " 1 ", only need the seldom iterative computation of number of times, the spatial weighting vector of this suboptimum just can converge to optimum spatial weighting vector, so improved adaptive beamforming convergence of algorithm speed greatly.

The present invention proposes a kind of method of the adaptive beamforming that is applied to antenna system newly.(201～20M) pilot signals that receive at first are input to the signal angle of arrival and the joint-detection network that arrives time delay to intelligent antenna array, promptly 21, detect the incident direction (being the signal angle of arrival) that obtains this pilot signal by the angle of arrival, utilize the angle of arrival of this pilot signal further can obtain direction vector corresponding to this pilot signal, and the direction vector addition of echo signal as initial spatial weighting vector (212); Obtain the time delay (211) of this reception pilot signal simultaneously by time delay detection, thereby further obtain its corresponding reference signal (231); On the other hand, (201～20M) uplink pilot signal that receive, initial space weighing vector (212) and reference pilot signal (231) etc. are as the input of adaptive beamforming unit (22) for intelligent antenna array, make adaptive algorithm control sub unit (32) to meet the demands less than the threshold value of a certain setting until echo signal (241) of also adjudicating through beam shaping and the error signal between the reference signal (231) by adaptive adjustment spatial weighting vector, the spatial weighting vector of this moment just can be thought optimum spatial weighting vector.Among the figure, the effect of input and judgement (24) is beam shaping signal (221) to be adjudicated obtain judgement output (241).

The self-adaptive processing algorithm that uses among the present invention can adopt various algorithm to realize, such as, but not limited to lowest mean square (LMS) algorithm, and recursive least-squares (RLS) algorithm etc.

According to structure proposed by the invention, system should comprise following major part: an intelligent antenna array (201～20M), signal angle of arrival and signal arrive time delay joint-detection network (21), an adaptive beamforming unit (22), a reference signal recovery unit (23) and input and decision unit (24).

Description of drawings

Below in conjunction with drawings and Examples the present invention is elaborated:

What Fig. 1 described is the direction dictates of the structure chart and the angle of arrival of linear antenna arrays.

The functional structure of the adaptive beamforming that is based on angle of arrival detection that Fig. 2 describes.

What Fig. 3 described is the functional structure chart of adaptive beamforming unit.

Embodiment

At first, the apparatus structure of system of the present invention being done some specifies.

Referring to Fig. 1, what represent among the figure is the direction dictates of the structure chart and the angle of arrival of linear antenna arrays.Generally speaking, the spacing in the aerial array between array element is half of wavelength, promptly ^λ/ ₂Usually, linear antenna arrays be to be initial point in coordinate diagram with a rightmost array element 101, the coordinate of a promptly rightmost bay 101 is (0,0), the rest may be inferred for remaining.On the regulation of incident angle, usually all be that the normal direction with aerial array is the incidence angle zero degree, on the right side of normal angle greater than zero, be minus angle on the left side of normal.

Referring to Fig. 2, the functional structure chart of the adaptive beamforming that is based on angle of arrival detection shown in the figure.The intelligent antenna array that this system is made up of M array element (201～20M), signal time delay and angle of arrival joint-detection unit (21), adaptive beamforming unit (22), pilot reference signal recovery unit (23) form with input and decision unit modules such as (24).(201～20M) pilot signals that receive obtain signal time delay (211) through signal time delay and angle of arrival joint-detection to intelligent antenna array, thereby recover to obtain pilot reference signal (231) through pilot reference signal.Simultaneously, by detecting the angle of arrival of echo signal, thereby obtain the direction vector of angle of arrival correspondence and as initial space weighing vector (212).Reference signal and initial space weighing vector are imported into adaptive beamforming unit (22) as the known conditions of adaptive beamforming algorithm.(201～20M) pilot signals that receive are through the processing of adaptive beamforming unit (22) for intelligent antenna array, obtain beam shaping signal (221), this signal is input to input and decision unit (24), court verdict (241) is sent back to adaptive beamforming unit (22) again and produces new spatial weighting vector sum court verdict according to the adaptive beamforming algorithm, carries out so repeatedly meeting the demands less than a certain threshold value up to error signal.

Referring to Fig. 3, shown in the figure simple knot composition of adaptive beamforming unit.This unit compares subelement (33) by adaptive algorithm subelement (31), adaptive algorithm control sub unit (32) and signal and forms.(301～30M) pilot signals that receive obtain the output signal behind the beam shaping after through adaptive algorithm subelements (31) to intelligent antenna array, this signal obtains decision signal (333) after judgement, this signal be sent to signal relatively subelement (33) reference signal (332) that deducts input obtain error signal (331), error signal (331) is imported into adaptive algorithm control sub unit (32), and whether adaptive algorithm control sub unit (32) satisfies condition according to error signal judges whether less than a certain threshold value that also needs call (promptly producing control signal 321) the adaptive beamforming algorithm upgrades the spatial weighting vector.If do not need, just current spatial weighting vector is exported as the optimal spatial weighing vector; If desired, then the adaptive algorithm subelement (31) of error signal (331) input is calculated the spatial weighting vector that makes new advances again.

Below in conjunction with an example the concrete application flow of the present invention once at wireless communication system is described.With cdma2000 1x EV-DV system is example, owing to there is Reverse Pilot Channel, in upward signal was handled, the adaptive beamforming after antenna system can improve based on pilot channel was used for shape beam the reception to other channels then.

Suppose that the received signal of Reverse Pilot Channel is as follows through after the beam shaping:

Y＝W ^HX (1)

Wherein, W (k)=[w ₁(k) w ₂(k) ... w _M(k)] ^HIt is the weighing vector of aerial array;

And

X(k)＝As(k)+n(k) (2)

It is aerial array (201～20M) the pilot signal that receives; Wherein, $A\left(\mathrm{\θ}\right)={[1e^{-j{\mathrm{\φ}}_2\left(\mathrm{\θ}\right)}\·\·{\·e}^{-j{\mathrm{\φ}}_M\left(\mathrm{\θ}\right)}]}^H$ It is direction vector corresponding to this signal; S (k) is the reverse pilot signal of transmission; What n (k) represented is white Gauss noise and the interference signal that comes from other users.

Before beam shaping, utilize aerial array received signal X (t), can finish detection, thereby obtain angle of arrival θ the reverse pilot signal angle of arrival _DoAUtilize the angle of arrival, system can obtain the direction vector A (θ of this angle of arrival correspondence _DoA).

The direction vector addition that to desire received signal then obtain direction vector and, and this direction vector with as the initial weight vector W (0) of adaptive beamforming algorithm:

So far, just can utilize least mean-square error (LMS) algorithm of iteration to carry out the weight vector renewal of adaptive beamforming:

$W(k+1)=W\left(k\right)+\frac{1}{2}\mathrm{\μX}(\tilde{H}-W{\left(k\right)}^{H}X)----\left(4\right)$

Wherein,

Be with reference to reverse pilot signal, the base station just obtains it by time delay detection before beam shaping; μ is the step-length of iterative algorithm.

Call formula (4) by limited number of time and be weighted the vector renewal, during one of condition below satisfying, algorithm finishes, and just can obtain optimum weighing vector W _Opt

(1) error function $e\left(k\right)=\tilde{H}-W{\left(k\right)}^{H}X$ Mould square Δ less than certain fixed gate limit value.

$\mathrm{\Δ}=e\×e^H=(\tilde{H}-W^{H}X){(\tilde{H}-W^{H}X)}^H$

$={\tilde{H}\tilde{H}}^H-W^{H}X{\tilde{H}}^H-\tilde{H}{X}^{H}W+W^H{\mathrm{XX}}^{H}W----\left(6\right)$

(2) iterations of least mean-square error (LMS) algorithm is greater than certain fixed gate limit value.

As can be seen, idiographic flow of the present invention is:

1) (incidence angle of the signal that receives on 201～20M) is carried out the angle of arrival and is detected to intelligent antenna array;

2) according to the direction vector of signal angle of arrival generation corresponding to each signal;

3) the pairing direction vector addition of echo signal is obtained direction vector and, and this direction vector with as initial space weighing vector (212);

4) thus smart antenna array is listed the echo signal that receives to be arrived time delay detection and obtains reference pilot signal (231) corresponding to this target pilot signal;

5) with 3) in the initial space valency weight vector (212), 4 that obtains) in the reference signal (231) that obtains and aerial array (signal that receives on 201～20M) is input to adaptive beamforming unit (22);

6) under the control of adaptive algorithm control sub unit (32), based on 5) in initial conditions, call the adaptive beamforming algorithm iteration and calculate optimal spatial weighing vector under the current time.

In sum, the present invention has following advantage:

1. can effectively improve adaptive beamforming convergence of algorithm speed.

2. this method is fit to any type of real network, is not subjected to the restriction of real network form characteristics.

3. this method is when improving efficiency of algorithm, the decline that does not bring intelligent antenna performance.

In a word, the present invention has reduced required iterations and the time of standard adaptive beamforming algorithm widely, and it is a kind of practicality, adaptive beamforming algorithm efficiently.

Claims (7)

1. an adaptive beamforming method that is used for antenna system is characterized in that, when echo signal being utilized adaptive algorithm carry out adaptive beamforming, the angle of arrival that is based on echo signal detects, and sets corresponding initial space weighing vector.

2. the adaptive beamforming method that is used for antenna system described in claim 1, it is characterized in that, by an intelligent antenna array (201～20M), signal angle of arrival and signal arrive time delay joint-detection unit (21), an adaptive beamforming unit (22), a pilot reference signal recovery unit (23) and input and decision unit compositions such as (24).(201～20M) pilot signals that receive at first are input to the signal angle of arrival and the joint-detection unit (21) that arrives time delay to intelligent antenna array, detect the incident direction (being the signal angle of arrival) that obtains this pilot signal by the angle of arrival, utilize the angle of arrival of this pilot signal further can obtain corresponding to the initial weighing vector (212) of this signal at the spatial weighting network; Recover to obtain the reference signal (231) of this reception pilot signal simultaneously by time delay detection and pilot reference signal; On the other hand, (201～20M) signals that receive, initial space weighing vector (212) and reference pilot signal (231) etc. can make the adaptive renewal spatial weighting of adaptive algorithm control sub unit (32) vector until finally obtaining optimum spatial weighting vector as the input of adaptive beamforming unit (22) to intelligent antenna array.

3. the angle of arrival that utilizes pilot signal described in claim 2 obtains the method for initial space weighing vector, it is characterized in that, for an incoming signal, the result who utilizes the angle of arrival to detect, generation is input to adaptive beamforming unit (22) with this direction vector as initial space weighing vector (212) then corresponding to the direction vector of this angle of arrival; Corresponding to K incoming signal, utilize the testing result of the angle of arrival, generation is corresponding to the direction vector separately of K signal, then these direction vector additions obtain a direction vector and, this direction vector and just can be used as initial space weighing vector (212) and be input to adaptive beamforming unit (22).

4. the adaptive beamforming method that is used for antenna system described in claim 1 is characterized in that, the adaptive beamforming algorithm that has adopted the based target signal angle of arrival to detect is such as, but not limited to least mean-square error (LMS) algorithm etc.

5. the adaptive beamforming method that is used for antenna system described in claim 1 is characterized in that, has adopted the adaptive beamforming method based on pilot signal.

6. the adaptive beamforming calculation method described in claim 5 based on pilot signal, it is characterized in that, receiving terminal by to pilot signal time delay (211) thus detection generate the reference signal (231) that receives pilot signal corresponding to this, and this reference signal is input to adaptive beamforming unit (22) compares with decision signal (241) and produce error signal (331).

7. the adaptive beamforming method that is used for antenna system described in claim 1 is characterized in that implementation step is:

1) (incidence angle of the signal that receives on 201～20M) is carried out the angle of arrival and is detected to intelligent antenna array;

2) according to the direction vector of signal angle of arrival generation corresponding to each signal;

3) the pairing direction vector addition of echo signal is obtained direction vector and, and this direction vector with as initial space weighing vector (212);

4) thus smart antenna array is listed the echo signal that receives to be arrived time delay detection and obtains reference signal (231) corresponding to this echo signal;

5) with 3) in the initial space weighing vector (212), 4 that obtains) in the reference signal (231) that obtains and aerial array (signal that receives on 201～20M) is input to adaptive beamforming unit (22);

6) under the control of adaptive algorithm control sub unit (32), based on 5) in initial conditions, call the adaptive beamforming algorithm iteration and calculate optimal spatial weighing vector under the current time.

Images