CN102340338A - 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, the bearing calibration of the base station array end antenna channels in particularly a kind of wireless communication system.

Background technology

In multiple antenna communication; The signal that the base station need transmit and receive through the array passage carries out direction and the shape that the weighting of amplitude and phase place comes the control antenna wave beam; To realize directional transmissions and reception, reach the purpose that improves communication quality and message capacity to desired user.In TDD (time division duplex) pattern, above-mentioned width of cloth phase weight coefficient is under the prerequisite of uplink wireless channel and downlink wireless channel reciprocity, and 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 imperfect, promptly has channel error, and in general; Receive path error and transmission channel error also are inconsistent; This has caused the response of receive path and the response of transmission channel also is 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 be equipped with a special calibration equipment to the base station.The process of this method receive path bearing calibration is: calibration equipment produces a correction reference signal, and one the tunnel passes through transmission of radio links through the correct detection antenna gives each antenna of base station, and another route feeder line directly is transferred to the base station baseband part.The correction factor that related operation obtains receive path is carried out through 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 emission of base station is received by the correct detection antenna.Calibration equipment utilizes the orthogonality of each channel transmit signal of base station, through carrying out the correction factor that related operation obtains transmission channel with the original detection signal in this locality, postbacks correction factor to the base station then.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 between each antenna of correction antenna and base station consistent by the phase difference that the locus produced.

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 through Radio Link and each passage of base station, is to transmit through feeder line and power splitter and inject the signal rule.Therefore, inject signalling and can not proofread and correct the channel error of introducing 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 preceding 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 of all antennas is through combiner A, and the signal of output is designated as y (n); The B road signal of all antennas receives the influence of channel error through receiver radio frequency passage to be corrected, and each is exported the signal of exporting behind the signal process combiner B and 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 the d (n).Can use NLMS (Normalized Least Mean Square, normalization minimum mean-square error) scheduling algorithm to adjust correction parameter here.The correction and the receive path of transmission channel are similar, repeat no more here.The computation complexity of the method is than higher.

Summary of the invention

The object of the present invention is to provide the reception of the antenna for base station under the tdd mode, transmission channel associating bearing calibration in a kind of radio communication, can solve the shortcoming of each method in the 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 is at T1; T2; ..., send the delay that a slot length T is arranged when identical baseband signal

is sent successively during the TN sub-slots in turn;

B) calibration equipment is at T1; T2; ...; The TN time slot receives signal

is done computing cross-correlation with ; 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 the step is at R1; R2; ...; The RN sub-slots sends baseband signal in turn:

delay of a slot length T is arranged when sending successively, is the compensate of frequency deviation item in the formula;

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

With

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

This is each channel correcting phase place of being asked.Wherein, ω _BBe meant the carrier frequency of base station end, ω _MBe meant 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, T}The emission carrier wave first phase that refers to calibration equipment, θ ^{M, R}The 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 RF receiving circuit time-delay of i the passage in base station, τ ^{M, T}The radio-frequency transmissions circuit delay that refers to calibration equipment, τ ^{M, R}Refer to the RF receiving circuit time-delay of calibration equipment,

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

Refer to the spatial transmission time-delay of calibration equipment to 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 this method use is received and dispatched through antenna, therefore can proofread and correct the channel error of being introduced by antenna feeder.

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

3, this method utilizes the characteristics of radio spatial channels reciprocity under the tdd mode to offset the phase effect that the space transmission is introduced, and therefore the locus to the calibration equipment antenna does not have 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

Below in conjunction with accompanying drawing and instantiation the present invention is done further detailed description.

The base station calibration model that the present invention relates to is as shown in Figure 2.The configuration of system is following: 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 _BBe meant the carrier frequency of base station end, ω _MBe meant 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, T}The emission carrier wave first phase that refers to calibration equipment, θ ^{M, R}The 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 RF receiving circuit time-delay of i the passage in base station, τ ^{M, T}The radio-frequency transmissions circuit delay that refers to calibration equipment, τ ^{M, R}Refer to the RF receiving circuit time-delay of calibration equipment,

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

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

In this model, following some hypothesis is arranged: the first, the base station is 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 generally is inconsistent, and the emission mixing first phase of same channels maybe be consistent with reception mixing first phase, maybe be inconsistent, and in order to have more generality, it is inconsistent here all being considered to.The 3rd; Under the tdd mode; Wireless space up channel and wireless space down channel are reciprocity;

this method of promptly thinking is applicable to that under the tdd mode of radio spatial channels reciprocity the channel characteristics that the base station utilizes upward signal to estimate carries out the application situation that downlink wave beam forms.

Often only be concerned about the relative error of passage in the practical application, can select first passage passage as a reference, and expectation obtains the transmit-receive combination correction factor of other passages, make the consistent response of each passage behind the channel correcting.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 reference signal respectively and gives 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) each passage of base station end is at T1; T2; ..., send the delay that a slot length T is arranged when identical baseband signal

is sent successively during the TN sub-slots in turn;

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 the last step at R1, R2 ..., the RN sub-slots sends baseband signal in turn: $x_1^M\left(t\right)=s\left(t\right)e^{j({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t},$ $x_2^M\left(t\right)=s\left(t\right)e^{j[({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_2-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)T]},...,$ $x_N^M\left(t\right)=s\left(t\right)e^{j\left[\right({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)t+{\mathrm{\&Phi;}}_N-{\mathrm{\&Phi;}}_1+({\mathrm{\&omega;}}_B-{\mathrm{\&omega;}}_M)(N-1)T]},$ The delay of a slot length T is arranged successively, in the 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 $y_1^{B,1}\left(t\right),y_1^{B,2}\left(t\right),...,y_1^{B,N}\left(t\right);y_2^{B,1}\left(t\right),y_2^{B,2}\left(t\right),...,y_2^{B,N}\left(t\right);...;y_M^{B,1}\left(t\right),y_M^{B,2}\left(t\right),...,$ $y_M^{B,N}\left(t\right);$ Usually, have

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

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

，n＝1，2，…，N，k＝1，2，…，N

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

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

Use

respectively and

n=2; N; Do cross-correlation, the phase place of getting the computing cross-correlation result can get:

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

Claims (1)

1. the base station array antenna channel correcting method under the 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 is at T1; T2; ..., send the delay that a slot length T is arranged when identical baseband signal

is sent successively during the TN sub-slots in turn;

B) calibration equipment is at T1; T2; ...; The TN time slot receives signal

is done computing cross-correlation with

; 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 the step is at R1; R2; ...; The RN sub-slots sends baseband signal in turn:

delay of a slot length T is arranged when sending successively,

is the compensate of frequency deviation item in the formula;

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

With

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

This is each channel correcting phase place of being asked;

Wherein, ω _BBe meant the carrier frequency of base station end, ω _MBe meant 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, T}The emission carrier wave first phase that refers to calibration equipment, θ ^{M, R}The 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 RF receiving circuit time-delay of i the passage in base station, τ ^{M, T}The radio-frequency transmissions circuit delay that refers to calibration equipment, τ ^{M, R}Refer to the RF receiving circuit time-delay of calibration equipment,

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

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

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