CN102340338B - Method for correcting array antenna channel of a base station in time division duplexing (TDD) mode - Google Patents

Abstract

The invention discloses a method for correcting an array antenna channel of a base station in a time division duplexing (TDD) mode. The method is characterized by comprising the following steps of: in a downlink time slot, N antennae of the base station transmit identical base band signals in N sub-time slots T1, T2, ..., TN; simultaneously, correction equipment receives signals, correlates the signals received in the sub-time slot T1 with the signals received in the sub-time slots T2, T3, ..., TN, and calculates phase values of correlation results; in an uplink time slot, the correction equipment transmits base band signals in turn in sub-time slots R1, R2, ..., RN, wherein e<j(omegaB-omegaM)t> in a formula represents a frequency offset compensation item; and simultaneously, M antennae of the base station receive base band signals, correlates y1<B,n>(t) with yn<B,1>(t), n=2,...N, and calculates phase values of correlation results, wherein Psi2, Psi3, ..., PsiN represent corrected phases of each channel.

Description

Base station array antenna channel correcting method under a kind of tdd mode

Technical field

The present invention relates to wireless communication technology, particularly the bearing calibration of the base station array end antenna channels in a kind of wireless communication system.

Background technology

In multiple antenna communication, the weighting that the signal that the base station need to transmit and receive by the pair array passage carries out amplitude and phase place comes direction and the shape of control antenna wave beam, to realize directional transmissions and the reception to desired user, reach the purpose that improves communication quality and message capacity.At the TDD(time division duplex) in pattern, above-mentioned width phase weight coefficient is under the prerequisite of uplink wireless channel and downlink wireless channel reciprocity, the base station utilizes upward signal to carry out that estimation of channel characteristics calculates.Yet in the array antenna of reality, the transmission characteristic of receiving circuit passage and radiating circuit passage is nonideal, namely there is channel error, and in general, receive path error and transmission channel error are also inconsistent, this has caused the response of receive path and the response of transmission channel is also inconsistent, causes the not reciprocity of up-downgoing channel, as shown in Figure 1.Therefore, realize in the array antenna of reality that wave beam forms, and just must carry out the work of channel correcting.

Existing antenna for base station channel correcting method has wireless feed-in reference signal method and injects the reference signal method.Wireless feed-in reference signal method need to be equipped with a special calibration equipment to the base station.The process of the method receiving channels calibration method is: calibration equipment produces a correction reference signal, and to each antenna of base station, another route feeder line directly is transferred to the base station baseband part to one tunnel process correct detection antenna by transmission of radio links.The correction factor that related operation obtains receive path is carried out by signal and reference signal that each passage is received in the base station.The process of transmitting channel correcting method is: the mutually orthogonal detection signal of each antenna transmission of base station, and by the correct detection antenna reception.Calibration equipment utilizes the orthogonality of each channel transmit signal of base station, by carrying out with the original detection signal in this locality the correction factor that related operation obtains transmission channel, then correction factor is postbacked to the base station.The method proposes strict requirement to the position of correct detection antenna, and in general, the correct detection antenna equates to the distance between each antenna of base station, makes the phase difference that is produced by the locus between each antenna of correction antenna and base station consistent.

Trimming process and the wireless feed-in reference signal method of injecting the reference signal method are very similar, different is, in the trimming process of wireless feed-in method, calibration equipment carries out the signal transmission by Radio Link and each passage of base station, and the Injection Signal rule is to transmit by feeder line and power splitter.Therefore, injecting signal can not be proofreaied and correct the channel error of being introduced by the sky current feed circuit, and power splitter also needs correction error.

Classic algorithm about the antenna for base station channel correcting also has a kind of blind correction method that is proposed by Leshem Amir and Wax Mati.Compare with front two kinds of methods, blind correction method does not need special reference signal, uses general signal to get final product.The radiofrequency signal that each antenna channels receives is divided into A, B two-way through coupler.The A road signal process combiner A of all antennas, the signal of output is designated as y (n); The B road signal of all antennas is subject to the impact of channel error by receiver radio frequency passage to be corrected, and the signal that each output signal is exported after through combiner B is designated as d (n).Calibration equipment uses adaptive algorithm to carry out interative computation, adjusts the correction factor of each passage, makes error e (n) minimum between y (n) and d (n).Can use NLMS(Normalized Least Mean Square, the normalization minimum mean-square error here) scheduling algorithm adjusts correction parameter.Correction and the receive path of transmission channel are similar, repeat no more here.The computation complexity of the method is higher.

Summary of the invention

The object of the present invention is to provide the reception of the antenna for base station under tdd mode, transmission channel associating bearing calibration in a kind of radio communication, can solve the shortcoming of each method in background technology.

For reaching above purpose, the present invention takes following technical scheme to be achieved:

Base station array antenna channel correcting method under a kind of tdd mode, the calibration model of employing are that a cover antenna number is the multi-antenna base station of N and the calibration equipment of a single antenna, and time division duplex is adopted in transmitting-receiving, it is characterized in that, comprises the steps:

A) descending time slot, each passage of base station end be at T1, T2 ..., the TN sub-slots sends identical baseband signal in turn

The delay of a slot length T is arranged during transmission successively;

B) calibration equipment is at T1, T2 ..., the TN time slot receives signal

Will

With

Do computing cross-correlation, cross correlation results is got phase value, obtain

C) ascending time slot, calibration equipment is according to b) phase place of trying to achieve in step is at R1, R2 ..., the RN sub-slots sends baseband signal in turn:

The delay of a slot length T is arranged successively, in formula during transmission

It is the compensate of frequency deviation item;

D) N of a base station antenna is at R1, R2 ..., the baseband signal that the RN sub-slots receives is respectively $y_1^{B,1}\left(t\right),y_1^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,y_1^{B,N}\left(t\right);y_2^{B,1}\left(t\right),y_2^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,y_2^{B,N}\left(t\right);\&CenterDot;\&CenterDot;\&CenterDot;;y_N^{B,1}\left(t\right),y_N^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,$ $y_N^{B,N}\left(t\right),$ Afterwards will

With

N=2 ..., N does cross-correlation, and cross correlation results is got phase value, can get:

…

This is each required channel correcting phase place.Wherein, ω _BRefer to the carrier frequency of base station end, ω _MRefer to the carrier frequency of calibration equipment,

Finger base station i (i=1,2 ..., N) the emission carrier wave first phase of individual passage,

The reception carrier first phase that refers to i the passage in base station, θ ^M,TThe emission carrier wave first phase that refers to calibration equipment, θ ^M,RThe reception carrier first phase that refers to calibration equipment,

The radio-frequency transmissions circuit delay that refers to i the passage in base station,

Refer to the radio-frequency (RF) receiving circuit time-delay of i the passage in base station, τ ^M,TThe radio-frequency transmissions circuit delay that refers to calibration equipment, τ ^M,RRefer to the radio-frequency (RF) receiving circuit time-delay of calibration equipment, Refer to i of base station antenna to the spatial time-delay of calibration equipment antenna,

Refer to that calibration equipment is to the spatial time-delay of i the antenna in base station.

Compare with existing antenna for base station channel correcting method, the invention has the beneficial effects as follows:

1, the reference signal of the method use is received and dispatched by antenna, therefore can proofread and correct the channel error of being introduced by antenna feeder.

2, the method is united consideration with the error of transmission channel and receive path, and flow process is simple, and efficient is higher.

3, the method utilizes the characteristics of radio spatial channels reciprocity under tdd mode to offset the phase effect that the space transmission is introduced, and therefore the locus of calibration equipment antenna is not had special requirement, and is simple to operate, the performance robust.

Description of drawings

Fig. 1 is the up-downgoing channel model in the related time division duplex multiple antenna communication of the inventive method.

Fig. 2 is the model of the related antenna for base station multipath correction of the inventive method.

Fig. 3 is the structure of time slot figure of the related bearing calibration of the inventive method.

Embodiment

The present invention is described in further detail below in conjunction with accompanying drawing and instantiation.

The base station calibration model that the present invention relates to as shown in Figure 2.The configuration of system is as follows: the base station end uses N antenna to receive and dispatch, and the pattern of time division duplex is adopted in transmitting-receiving, and each antenna uses independently transceiver channel, and calibration equipment adopts the single antenna transmitting-receiving.Wherein, ω _BRefer to the carrier frequency of base station end, ω _MRefer to the carrier frequency of calibration equipment, Finger base station i (i=1,2 ..., N) the emission carrier wave first phase of individual passage,

The reception carrier first phase that refers to i the passage in base station, θ ^M,TThe emission carrier wave first phase that refers to calibration equipment, θ ^M,RThe reception carrier first phase that refers to calibration equipment,

The radio-frequency transmissions circuit delay that refers to i the passage in base station,

Refer to the radio-frequency (RF) receiving circuit time-delay of i the passage in base station, τ ^M,TThe radio-frequency transmissions circuit delay that refers to calibration equipment, τ ^M,RRefer to the radio-frequency (RF) receiving circuit time-delay of calibration equipment,

Refer to i of base station antenna to the spatial time-delay of calibration equipment antenna,

Refer to that calibration equipment is to the spatial time-delay of i the antenna in base station.

In this model, following several presupposition is arranged: the first, the base station is the centralized aerial array, each passage uses the crystal oscillator of homology, therefore can think that the carrier frequency of each passage is consistent; The second, the frequency mixer first phase of each passage is generally inconsistent, and the emission mixing first phase of same channels may be consistent with reception mixing first phase, may be inconsistent, and in order to have more generality, it is inconsistent here all being considered to.The 3rd, under tdd mode, wireless space up channel and wireless space down channel are reciprocity, namely think

The method is applicable under the tdd mode of radio spatial channels reciprocity, and the base station utilizes the channel characteristics that upward signal estimates to carry out the application situation that downlink wave beam forms.

Often only be concerned about the relative error of passage in practical application, can select first passage as the reference passage, and expectation obtains the transmit-receive combination correction factor of other passages, make after channel correcting the response of each passage consistent.Therefore the phase calibration of other passage is:

…

Fig. 3 is the structure of time slot figure of bearing calibration.In descending time slot, base station passage 1 is followed each passage at T1 at T0 sub-slots emission frame head, T2 ..., the TN time slot sends respectively reference signal to calibration equipment; In ascending time slot, the many antennas in base station receive the signal that calibration equipment postbacks simultaneously.Below in conjunction with Fig. 3, method of the present invention is elaborated.

1) descending time slot

A) end each passage in base station is at T1, T2 ..., send in turn identical baseband signal during the TN sub-slots

The delay of a slot length T is arranged during transmission successively;

B) calibration equipment is at T1, T2 ..., the signal that the TN time slot receives is:

$y_1^M\left(t\right)=x_1^{B,1}\left(t\right)e^{j({\mathrm{\&omega;}}_{B}t+{\mathrm{\&theta;}}_1^{B,T})}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_1^{B,T}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_1^{B,M}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}^{M,R}}{e}^{-j({\mathrm{\&omega;}}_{M}t+{\mathrm{\&theta;}}^{M,R})}$

$=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&theta;}}_1^{B,T}-{\mathrm{\&omega;}}_B({\mathrm{\&tau;}}_1^{B,T}+{\mathrm{\&tau;}}_1^{B,M}+{\mathrm{\&tau;}}^{M,R})-{\mathrm{\&theta;}}^{M,R})}$

$=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_1)}$

$y_2^M\left(t\right)=x_2^{B,2}\left(t\right)e^{j({\mathrm{\&omega;}}_B(t+T)+{\mathrm{\&theta;}}_2^{B,T})}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_2^{B,T}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_2^{B,M}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}^{M,R}}{e}^{-j({\mathrm{\&omega;}}_M(t+T)+{\mathrm{\&theta;}}^{M,R})}$

$=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&theta;}}_2^{B,T}-{\mathrm{\&omega;}}_B({\mathrm{\&tau;}}_2^{B,T}+{\mathrm{\&tau;}}_2^{B,M}+{\mathrm{\&tau;}}^{M,R})-{\mathrm{\&theta;}}^{M,R}+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)T)}$

$=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_2+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)T)}$

…

$y_N^M\left(t\right)=x_N^{B,N}\left(t\right)e^{j({\mathrm{\&omega;}}_B(t+(N-1)T)+{\mathrm{\&theta;}}_N^{B,T})}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_N^{B,T}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}_N^{B,M}}{e}^{-j{\mathrm{\&omega;}}_B{\mathrm{\&tau;}}^{M,R}}{e}^{-j({\mathrm{\&omega;}}_M(t+(N-1)T)+{\mathrm{\&theta;}}^{M,R})}$ $=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&theta;}}_N^{B,T}-{\mathrm{\&omega;}}_B({\mathrm{\&tau;}}_N^{B,T}+{\mathrm{\&tau;}}_N^{B,M}+{\mathrm{\&tau;}}^{M,R})-{\mathrm{\&theta;}}^{M,R}+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)(N-1)T)}$

$=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_N+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)(N-1)T)}$

By

Can estimate frequency deviation (ω _B-ω _M); Will

Respectively with

Do computing cross-correlation, cross correlation results is got phase value, can obtain

2) ascending time slot

A) calibration equipment according to the phase place of trying to achieve in previous step at R1, R2 ..., the RN sub-slots sends baseband signal in turn: $x_1^M\left(t\right)=s\left(t\right)e^{j({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t},x_2^M\left(t\right)=s\left(t\right)e^{j[({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_2-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)T]},\&CenterDot;\&CenterDot;\&CenterDot;,$ $x_N^M\left(t\right)=s\left(t\right)e^{j[({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_N-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)(N-1)T]},$ The delay of a slot length T is arranged successively, in formula during transmission

It is the compensate of frequency deviation item;

B) N of a base station antenna is at R1, R2 ..., the baseband signal that the RN sub-slots receives is respectively $y_1^{B,1}\left(t\right),y_1^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,y_1^{B,N}\left(t\right);y_2^{B,1}\left(t\right),y_2^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,y_2^{B,N}\left(t\right);\&CenterDot;\&CenterDot;\&CenterDot;;y_N^{B,1}\left(t\right),y_N^{B,2}\left(t\right),\&CenterDot;\&CenterDot;\&CenterDot;,$ $y_N^{B,N}\left(t\right);$ Usually, have

$y_k^{B,n}\left(t\right)=s\left(t\right)e^{j(({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_k-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)(k-1)T)}{e}^{j({\mathrm{\&omega;}}_M(t+(N+k-1)T+T_{\mathrm{TTG}})+{\mathrm{\&theta;}}^{M,T})}$

$e^{-j{\mathrm{\&omega;}}_B({\mathrm{\&tau;}}^{M,T}+{\mathrm{\&tau;}}_n^{M,B}+{\mathrm{\&tau;}}_n^{B,R})}{e}^{-j({\mathrm{\&omega;}}_B(t+(N+k-1)T+T_{\mathrm{TTG}})+{\mathrm{\&theta;}}_n^{B,R})}$

$=s\left(t\right)e^{j({\mathrm{\&Phi;}}_k-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_M-{\mathrm{\&omega;}}_B)(\mathrm{NT}+T_{\mathrm{TTG}})+{\mathrm{\&theta;}}^{M,T}-{\mathrm{\&omega;}}_B({\mathrm{\&tau;}}^{M,T}+{\mathrm{\&tau;}}_n^{M,B}+{\mathrm{\&tau;}}_n^{B,R})-{\mathrm{\&theta;}}_n^{B,R})}$

$=s\left(t\right)e^{j{\mathrm{\&psi;}}_k^n}$

，n＝1，2，…，N，k＝1，2，…，N

Use respectively

With

N=2 ..., N does cross-correlation, and the phase place of getting the computing cross-correlation result can get:

…

This is each required channel correcting phase place.Can know, the base station need to be preserved 2 (N-1) segment data and be carried out computing cross-correlation.

Claims (1)

1. the base station array antenna channel correcting method under a tdd mode, the calibration model of employing is that a cover antenna number is the multi-antenna base station of N and the calibration equipment of a single antenna, time division duplex is adopted in transmitting-receiving, it is characterized in that, comprises the steps:

A) descending time slot, each passage of base station end be at T1, T2 ..., the TN sub-slots sends identical baseband signal in turn

The delay of a slot length T is arranged during transmission successively;

B) calibration equipment is at T1, T2 ..., the TN time slot receives signal

Will

With

Do computing cross-correlation, cross correlation results is got phase value, obtain

C) ascending time slot, calibration equipment is according to b) phase place of trying to achieve in step is at R1, R2 ..., the RN sub-slots sends baseband signal in turn:

The delay of a slot length T is arranged successively, in formula during transmission

It is the compensate of frequency deviation item;

D) N of a base station antenna is at R1, R2 ..., the baseband signal that the RN sub-slots receives is respectively

Afterwards will

With

N=2 ..., N does cross-correlation, and cross correlation results is got phase value, can get

...

This is each required channel correcting phase place;

Wherein, ω _BRefer to the carrier frequency of base station end, ω _MRefer to the carrier frequency of calibration equipment,

The reception carrier first phase that refers to i the passage in base station,

Refer to the radio-frequency (RF) receiving circuit time-delay of i the passage in base station,

Refer to that calibration equipment is to the spatial time-delay of i the antenna in base station.

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