KR20050087378A - Advanced calibration method and device for adaptive smart antenna in wireless communication system - Google Patents

Abstract

The present invention provides a method and apparatus for correcting distortion of the smart antenna due to nonlinear characteristics in a base station of a wireless communication system using a smart antenna, wherein a transmission signal is generated on the cell side after generating a correction signal. The correction signal is sequentially transmitted to the receiver for each antenna path through the wireless area, and at the receiver, the correction value is found by applying a correction signal finally received from the transmitter and a gain change value corresponding to each antenna path. Correct the distortion of the smart antenna.

Description

Advanced calibration method and device for adaptive smart antenna in wireless communication system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system, and more particularly, to a calibration method and apparatus for improving performance of a smart antenna for efficiently using radio resources.

Radio resources used for wireless communication are gradually becoming saturated not only by existing voice service users but also by data service users who are increasing. Accordingly, new technologies are needed for the efficient use of limited radio resources. One example of a technique for efficiently using such a radio resource is a smart antenna technology.

The smart antenna technology reduces signal-to-noise ratio (SNR) because all wireless terminal stations in the same base station are not only interfered with signals for serving themselves but also for serving other terminal stations. Can be. However, the smart antenna technology can minimize the interference to the terminal stations in different directions by actively detecting the position of the terminal station and applying directionality to the transmission / reception signal even if the terminal station exists in the same base station.

In order to apply the direction in the desired direction, unlike conventional systems using one unidirectional antenna, since multiple antennas are used, a control technique based on the phase difference and magnitude difference of each antenna is required. . This technique is applied in the digital part of the base station system, and the control result must be transmitted to the physical antenna just before being radiated to the wireless environment without any change. However, the phase difference and magnitude difference applied by an amplifier, a converter (up / down converter), a front end unit (FEU), and a cable having non-linear characteristics of a base station system are subject to distortion. To compensate for this distortion, smart antenna technology performs a calibration technique.

The smart antenna technology will determine the overall performance of the smart antenna technology of the accuracy of the correction. That is, the performance of smart antenna technology can be improved by minimizing directional accuracy and phase mismatch. This principle applies equally to the forward as well as the reverse direction. The operation of the calibration task applied to the smart antenna technology will be described.

1 is a block diagram illustrating an apparatus for smart antenna correction in a conventional base station system.

Referring to FIG. 1, a digital signal (channel card) processor (calibration signal processor) 10 transmits a signal to the RF coupler (RF coupler) 20 of the physical antenna portion. The RF coupler 20 then processes the received signal for each antenna 30 and retransmits it in the Sunni direction.

The retransmitted signal passes through elements having nonlinear characteristics such as amplifiers, FEUs, converters, and cables in the non-linear system 40 to reach the processor 10 in which the correction signal is generated and demodulates. Will go through. Through this process, the wireless communication system measures a phase difference and a magnitude difference on a reception path of each antenna through which a correction signal passes. The measured result is applied as a correction value when the beamforming coefficient of the smart antenna is generated so that the correct beam is formed in the physical antenna.

The interpretation of the correction signal by the demodulation will be described.

The demodulator of the wireless communication system demodulates the received signal to obtain an average magnitude and phase as shown in Equations 1 and 2 below.

Then, the minimum values of M _i obtained by Equations 1 and 2 are normalized as shown in Equation 3 below.

The reciprocal of the value obtained in Equation 3 is obtained to obtain a final correction signal result value as shown in Equation 4 below.

In this case, the constant is multiplied by the number of significant digits.

On the other hand, as shown in FIG. 2, the correction execution time is performed in 80 ms as a basic unit, and the transmission direction is sequentially performed by the time difference for each path, and the reception is performed at the same time. Therefore, the transmission direction is increased in proportion to the number of paths requiring correction. Here, the execution time refers to the time before the transmission and reception direction of the correction technique is completed and the following execution starts as shown in Equation 5 below.

Execution time = (80ms) * {(Transmission signal average section) * (Number of transmission direction paths) + (Receive signal average section) + Margin}

In recent years, the AGC is applied to the converter in the transmission / reception direction of the nonlinear characteristic system, and the operation of the AGC interferes with the correction signal. That is, as different gains are applied to each antenna transmission / reception direction to be compared, the reference value of magnitude correction becomes unclear and an error occurs in the correction. In addition, correction of the correction technique is necessary because the operation of the automatic gain regulator may cause a change in phase.

In addition, since the correction technique is executed periodically (10 to 60 seconds), the assumption that there is no sudden change of the system in the middle of execution is given priority. However, in practice, nonlinear characteristics such as automatic gain regulators may have their characteristics changed drastically by the instantaneous environment. Therefore, there is a need for a method that can apply the information about the calibration technique. In particular, since the correction of each antenna is performed parallax when the transmission direction correction technique is applied, there is a problem in that if the change of the automatic gain controller (AGC) is severe with time, the effect thereof is large.

Accordingly, an object of the present invention is to provide a method and apparatus for correcting non-linear characteristic devices so that the characteristics are not changed due to environmental changes in smart antenna technology.

Another object of the present invention is to provide a method and an apparatus for correcting by applying AGC operation information in a converter among devices having nonlinear characteristics in a wireless communication system in a smart antenna technology.

The method for achieving the above object of the present invention is a method for correcting the distortion of the smart antenna due to nonlinear characteristics in a base station of a wireless communication system using a smart antenna, the transmission side, And subsequently transmitting the generated correction signal through the cell bus to the receiver for each antenna path sequentially through a wireless area, and at the receiving side, a gain corresponding to a final correction signal received from the transmitter and each antenna path. And applying a change value to find a correction value.

And an apparatus for achieving the objects of the present invention, in a wireless communication system using a smart antenna, a base station apparatus for correcting the distortion of the smart antenna due to non-linear characteristics, generating a correction signal, and the final from the transmitting side A correction signal processor that finds a correction value using the received correction signal and a gain change value corresponding to each antenna path, up- and down-converting the correction signal, and automatically adjusts the correction signal received for each antenna path Receiving a nonlinear characteristic unit sequentially transmitting a gain change value to the correction signal processor, a correction signal generated from the correction signal processor, and sequentially transmitting the received correction signal to the nonlinear characteristics unit for each antenna path. And a wireless coupler.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention to be described later is a method of reducing the distortion of the correction signal by minimizing the influence of the automatic gain controller (AGC: Auto Gain Controller) is applied in the converter of the base station system, and the operation information of the AGC The gain change value is continuously divided into a method of receiving / applying the algorithm in the correction technique and a method of transmitting direction in which the AGC value is temporarily fixed or the AGC is stopped while the correction technique is applied. First, the structure of a base station system according to an embodiment of the present invention will be described.

3 is a diagram illustrating a structure of a base station system according to an embodiment of the present invention.

Referring to FIG. 3, a base station system generates a correction signal and obtains a correction value, and the correction signal is distorted by a nonlinear characteristic, and a gain change value is transmitted to the correction signal processor 110. The non-linear characteristic unit 120 and the RF coupler 130 for transmitting the generated correction signal to the receiver for each antenna 130 path are configured.

The nonlinear characteristic unit 120 includes an up-converter 121 for up-converting the generated correction signal to an RF signal, and a transmission / reception terminal 122 for receiving an RF signal through the RF coupler 130. And a down converter 123 converting the received RF signal into a baseband signal and transmitting the converted RF signal to the correction signal processor 110.

The correction signal processor 110 includes a modulator 111 for generating a correction signal for performing beamforming, a demodulator 112 for demodulating a received signal, and a beamformer 113 for beamforming the demodulated signal. do.

An upper controller 150 is connected between the down converter 123 and the demodulator 112. When the down converter 123 receives the correction signal of the RF signal,

In the base station system configured as described above, two correction schemes of the smart antenna technology will be described. First, a method of continuously applying gain change information of AGC according to the principles of the present invention will be described.

The down converter 123 of the base station system is controlled by an upper system. That is, it operates under the control of the upper system by information such as shape information, alarm information, or attenuation value. However, the automatic gain control (AGC) information is not reported high, and only hardware ON / OFF can be done. In this system flow, the gain change information of the AGC is reported as higher than other information so that this information can be used for the correction technique. Since each antenna and a reception path are mapped one-to-one, when the above information is used, a more accurate correction value is obtained when a gain change value corresponding to each path is used for normalization of magnitude in a correction technique. You can find

In addition, when receiving the change information of the AGC that occurs between the period of the correction is performed, it is possible to apply to the portion that was not previously compensated for a faster and more accurate correction.

Equation 1 may be expressed as Equation 6 in consideration of a gain value A _I of the automatic gain controller.

The method of delivering gain information of AGC to a block performed by a correction technique in the converter is as follows.

In the base station system, the information of the converter is uploaded to the upper control block through the cell bus, and the signal can be transmitted between the control block and the block to which the correction technique is applied through the ATM. In addition, new signal paths can be added between the converter and the correction technology block if separate design considerations are taken into account.

Next, a description will be given of a method of temporarily fixing the gain applied to the AGC according to the principle of the present invention.

In the case of the calibration technique transmission direction, the path where the calibration signal reaches the physical antenna and back to the system is the same. However, since the phase difference and the magnitude difference are sequentially executed by the time difference of each path, it is troublesome to apply the gain change value of the AGC at each moment.

In the current smart antenna technology, a path for returning the correction signal in the transmission direction back to the system is implemented separately so that a constant gain is maintained for the time that the AGC does not affect the CDMA signal or the correction is performed. This can improve the accuracy of the calibration technique. In the case of receiving correction technology, the CDMA signal may be affected. Therefore, it is necessary to consider whether the effect is applied.

With reference to the accompanying drawings, a correction operation according to an embodiment of the present invention according to the above two methods will be described.

4 is a flowchart illustrating a correction operation of a smart antenna technology in a base station system according to an embodiment of the present invention.

In step 410, the base station system generates a calibration signal through the modulator 111. The correction signal is a signal that is distinguished from the CDMA signal, and there are various methods of generating the correction signal, such as a method using a Walsh code and a PN code, and a detailed description thereof will be omitted.

 In step 420, the base station system converts the generated correction signal into an RF signal through the up converter 121 and transmits the converted signal to the RF coupler 130 through an RF cable. In this case, the correction signal is a signal in a transmission direction but is converted into a reception RF signal because it is a signal used for correction of a reception path.

In step 430, the base station system distributes one signal received through the RF coupler 130 for each antenna 140 port and transmits the signal to the transmission / reception terminal 122. In this case, since the RF cable which is phase matched between the RF coupler 130 and the antenna 140 is used, there is no need to pass a correction signal. In step 440, the base station system transmits the correction signal to the down converter 123 through the front end unit (FEU) 122 through the RF cable for each antenna path. Here, a low-noise amplifier (LNA) exists in the transmission and reception terminal 150, but gives only a constant gain in the same way as the amplifier in the transmission direction.

In step 450, the down converter 123 in the base station system transmits the received signal to the demodulator 112. At this time, the automatic gain controller (AGC) is operated, which causes the correction signal to be distorted. In step 460, the demodulator 112 in the base station system finally receives the correction signal.

In step 470, the base station system receives a gain change value of the automatic gain adjuster until the correction signal generated by the modulator 111 is received by the demodulator 112. Here, the method for receiving the gain value in the down converter 123 is to control the down converter 123 through a cell bus (Cell-Bus) according to the first embodiment of the present invention as shown in FIG. There is a method of receiving this information (what information?) From the upper controller 150 and lowering it back to the demodulator 112. Alternatively, there is a method of directly transmitting from the down converter 123 to the demodulator 112 according to the second embodiment of the present invention as shown in FIG. 5. The method according to the first embodiment has a path already implemented in the current system, and the method according to the second embodiment should implement an additional path.

In step 480, the base station system calculates a phase difference and a magnitude difference on each path by using the final received correction signal and the gain change value in the demodulator 112.

Then, in step 490, the base station system performs correction by applying the value (compensation value) calculated in step 480 to the final result value of the smart antenna technology through the beamformer 113.

 Smart antenna technology is the key to how exactly the phase difference and signal size difference generated in the baseband of the base station according to the position of the terminal can be applied to the multi-antenna which is the final part of the system. It can improve the performance of antenna technology.

The correction signal also moves along the same path as the CDMA signal. In other words, the generation of the correction signal acts as interference affecting the CDMA signal. Therefore, it is effective to perform the calibration for a short time only when necessary. Therefore, since the correction can be performed by applying only the gain change value of the automatic gain controller using the correction result value once performed due to the correction according to the embodiment of the present invention, it is possible to avoid adding / repeating the correction signal.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention can improve the transmission / reception performance of the smart antenna technology by continuously receiving / applying a gain change value which is operation information of the automatic gain controller.

In addition, the transmission direction has an effect of minimizing the effect of the correction signal on the CDMA signal by temporarily fixing the value of the automatic gain adjuster while the correction technique is applied.

1 is a block diagram showing an apparatus for smart antenna correction in a conventional base station system,

2 is a diagram illustrating a time for performing correction of a general smart antenna technology;

3 is a diagram showing the structure of a base station system according to a first embodiment of the present invention;

4 is a diagram showing the structure of a base station system according to a second embodiment of the present invention;

5 is a flow diagram illustrating the calibration operation of the smart antenna technology in the base station system in accordance with an embodiment of the present invention.

Claims (11)

In a base station of a wireless communication system using a smart antenna, a method for correcting the distortion of the smart antenna due to nonlinear characteristics, Transmitting, by the transmitting side, generating the correction signal through the cell bus and sequentially transmitting the generated correction signal to the receiving side for each antenna path through the wireless domain; And at the receiving side, searching for a correction value by applying a correction signal finally received from the transmitting side and a gain change value corresponding to each antenna path. The method of claim 1, The correction signal is transmitted to the receiving end for each antenna path through a wireless cable without passing through the antenna, and the method is characterized in that the transmitting side is converted into a receiving radio signal used for correction of the receiving path. The method of claim 1, wherein the finding of the correction value comprises: Receiving the correction signal for each antenna path from the transmitting side; Receiving a gain change value of the distorted correction signal due to a nonlinear characteristic until the correction signal is finally received; Calculating a phase difference and a magnitude difference on each antenna path; And normalizing the gain change value to the calculated value. The method of claim 3, The gain change value is received directly from a down converter for down converting the correction signal. The method of claim 3, The gain change value is received from a down converter for down converting the correction signal through an upper control unit for controlling the down converter. In a wireless communication system using a smart antenna, a base station apparatus for correcting the distortion of the smart antenna due to nonlinear characteristics, A correction signal processor which generates a correction signal and finds a correction value using a correction signal finally received from the transmitting side and a gain change value corresponding to each antenna path; A nonlinear characteristic unit configured to up- and down-convert the correction signal, and to automatically adjust the correction signal received for each antenna path to transmit a gain change value to the correction signal processor; And a wireless coupler which sequentially receives correction signals generated from the correction signal processor and transmits the sequentially received correction signals to the nonlinear features for each antenna path. The method of claim 6, The correction signal is transmitted to the receiver for each antenna path through a wireless cable without passing through the antenna, and the apparatus is characterized in that the transmitting side is converted into a radio signal of the receiving side used to correct the receiving path. The method of claim 6, And an upper control unit for obtaining a gain change value of the correction signal and transmitting the gain change value to the nonlinear characteristic unit, and transmitting the gain change value received from the voice unit back to the correction signal processor. The method of claim 6, wherein the correction signal processor, A modulator for generating the correction signal; And a demodulator for finding a correction value using a final correction signal received from the nonlinear characteristic unit and a gain change value corresponding to each antenna path. The method of claim 9, wherein the demodulator, Until the correction signal is finally received, the gain change value of the distorted correction signal due to nonlinear characteristics is received, the phase difference and magnitude difference on each antenna path are calculated, and the gain change value is applied to the calculated value and normalized. The device, characterized in that. The method of claim 6, wherein the non-linear characteristic portion, An upconverter for upconverting the correction signal generated from the correction signal processor; A transmission and reception termination unit for receiving a correction signal for each antenna path from the wireless coupler; And a down converter which down-converts the correction signal received from the transmission / reception terminal, receives a gain change value of the correction signal and transmits it to the correction signal processor.