KR20130089312A - Apparatus and method of sounding reference signal calibration - Google Patents

Apparatus and method of sounding reference signal calibration Download PDF

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KR20130089312A
KR20130089312A KR1020120010573A KR20120010573A KR20130089312A KR 20130089312 A KR20130089312 A KR 20130089312A KR 1020120010573 A KR1020120010573 A KR 1020120010573A KR 20120010573 A KR20120010573 A KR 20120010573A KR 20130089312 A KR20130089312 A KR 20130089312A
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base station
calibration
correction factor
incorporated
update information
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Korean (ko)
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고은석
김은용
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삼성전자주식회사
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Priority to PCT/KR2013/000839 priority patent/WO2013115600A1/en
Publication of KR20130089312A publication Critical patent/KR20130089312A/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/10—Monitoring; Testing of transmitters
    • H04B17/11—Monitoring; Testing of transmitters for calibration
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

PURPOSE: A method of sounding reference signal calibration and an apparatus for carrying out the same are provided to keep the phases of complex constant values of multiple cell calibration the same or keep the phases and sizes the same concurrently between several base stations for a single terminal. CONSTITUTION: A control unit (320) determines whether there is a base station to be incorporated in a base station cooperative combination and if there is a base station to be incorporated, calculates a second calibration correction factor for the base station to be incorporated. The control unit generates calibration update data constituted by a value of the difference between a first calibration correction factor and the second calibration correction factor, and applies the calculated second calibration correction factor to sounding calibration. A storage unit (330) stores the second calibration correction factor and the calibration update data. [Reference numerals] (310) Communication unit; (320) Control unit; (325) Calibration correction factor calculation unit; (327) Calibration renew information generation unit; (330) Storage unit

Description

Sounding reference signal calibration method and apparatus for performing the same {APPARATUS AND METHOD OF SOUNDING REFERENCE SIGNAL CALIBRATION}

The present invention relates to a calibration method of a sounding reference signal (Sounding Reference Signal) for a system using a multiple input multiple output (MIMO) in a multi-cell environment.

Recently, a technique for reducing interference using cooperation between base stations in order to reduce inter-cell interference has been studied. Various MIMO (Multiple Input Multiple Output) techniques have been considered as a method of reducing inter-cell interference through cooperation between base stations. In particular, many MIMO techniques have been proposed that extend various MIMO techniques used in a single cell to multiple base stations.

In order to use the base station cooperative MIMO scheme, feedback of channel information from each terminal is required. The feedback amount of channel information is proportional to the performance of the MIMO scheme. That is, CSI (Channel State Information) information feedback with a large amount of feedback is required to maximize the performance of the base station cooperative MIMO scheme.

The time division duplex (TDD) system may obtain feedback of channel information using a sounding reference signal. In other words, in the base station cooperative MIMO scheme, several base stations may simultaneously acquire channel information using the sounding reference signal transmitted by the terminal. This method is called a multi-cell sounding technique. Thus, the amount of feedback for base station cooperative MIMO is effectively reduced.

In order to use a multi-cell sounding scheme in a TDD system, each base station and a terminal must perform a calibration for synchronizing a transmission and a reception RF chain. The calibration method for using the multi-cell sounding technique is as follows.

Each base station estimates an uplink channel using a sounding reference signal transmitted by the selected reference terminal. The base stations perform calibration using the estimated uplink channel and the downlink channel fed back by the reference terminal.

In this technique, when performing multi-cell calibration, all base stations performing base station cooperation must be calibrated at once. However, base stations cooperating in the base station cooperative MIMO scheme may be dynamically changed. That is, the cooperative base stations are not fixed, and the combination of cooperative base stations may vary according to channel conditions and supporting terminals. In this case, whenever the combination of cooperative base stations is changed, the calibration of all base stations must be performed again. In addition, it is necessary to select a reference terminal for multi-cell calibration. In a real environment, it is not easy to select a terminal having good uplink and downlink channel conditions with all base stations. Therefore, whenever the combination of cooperative base stations is changed, the reference terminal should be selected again. This causes a problem of increased control overhead and feedback overhead.

Accordingly, the present invention proposes a method for calibrating a sounding reference signal in a TDD system and an apparatus for performing the same.

In order to solve the above problems, the sounding reference signal calibration method according to the present invention includes performing a calibration with at least one base station for configuring a base station cooperative combination, and storing a first calibration correction factor calculated accordingly; Determining whether a base station to be incorporated in the base station cooperative combination exists; calculating a second calibration correction factor with the base station to be incorporated, if the base station to be incorporated exists; and wherein the first calibration correction factor and the first Generating calibration update information, which is a difference value between the two calibration correction factors, and applying the calculated second calibration correction factors to sound calibration.

In addition, in order to solve the above problems, the sounding reference signal calibration apparatus according to the present invention performs a calibration with at least one base station for configuring a base station cooperative combination, calculates a first calibration correction factor accordingly, and performs the base station cooperative operation. It is determined whether there is a base station to be incorporated in the combination. If the base station to be incorporated exists, a second calibration correction factor is calculated with the base station to be incorporated, and a difference value between the first calibration correction factor and the second calibration correction factor. And a controller configured to generate in calibration update information, to apply the calculated second calibration correction factor to a sounding calibration, and to store the second calibration correction factor and the calibration update information.

According to the present invention, in calibration of multi-cell sounding, a phase of calibration complex constant values between several base stations may be kept the same for one terminal, or phase and magnitude may be maintained at the same time. Through this, the performance of the base station cooperative MIMO scheme using multi-cell sounding can be maintained.

1 illustrates a multi-cell structure in accordance with the present invention.
2 illustrates a signal flow for performing calibration between multiple cells according to an embodiment of the present invention.
3 is a diagram illustrating a configuration of a base station according to an embodiment of the present invention.
4 illustrates a method of performing sounding reference signal calibration according to an embodiment of the invention.

Hereinafter, the operation principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

1 is a diagram illustrating a multi-cell structure according to the present invention.

Referring to FIG. 1, it is assumed here that cooperative TDD (Time Division Duplex) downlink communication is communication by a plurality of base stations. In addition, it is assumed that the number of antennas of all base stations is N B and the number of antennas of all terminals is N M. This is assumed to describe the present invention. Even though each base station and the terminal have different numbers of antennas, the method described in the present invention can be applied in the same way.

It is assumed that the total number of base stations participating in calibration is K, and there is one terminal in each cell managed by the K base stations. Base stations BS1 101, BS2 102, BS3 103 are grouped into a first base station cooperative combination 110 for calibration. Here, the multi-cell calibration correction factors of the BS1 101, the BS2 102, and the BS3 103, which have been multi-cell calibrated, are calculated through Equation 1.

Figure pat00001

here,

Figure pat00002
Is the multi-cell calibration correction factor for the K base station,
Figure pat00003
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the base station after the single cell base station calibration of the K-th base station is applied. And
Figure pat00004
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after the single cell terminal calibration of the selected reference terminal is applied. Using the multi-cell calibration correction factor thus obtained, it is possible to keep the calibration complex constant values of the various base stations the same.

The combination of cooperative base stations is changed according to the channel situation and the supporting terminal, so that BS2 102 is excluded from the first base station cooperative combination 110. BS4 104 is newly incorporated into the first base station cooperative association 110, and the BS1 101, BS3 103, and BS4 104 are grouped into the second base station cooperative association 120. Even in this case, it is necessary to calculate the multi-cell calibration correction factor to maintain the same calibration complex constant value among several base stations, and to obtain base station cooperative MIMO performance gain. To do this, a new calibration correction factor is calculated between the base stations included in the base station cooperative combination and the base stations adjacent to the base stations to be incorporated. In addition, calibration update information which is a difference between a calibration correction factor calculated at the first base station cooperative combination and a calibration correction factor calculated at the second base station cooperative combination is generated. The generated calibration update information is transmitted to other base stations constituting the base station cooperative combination. Even if a new base station is incorporated, a calibration complex constant value between each base station may be kept the same using calibration update information without calculating a calibration correction factor between all base stations.

For example, assume that BS4 104 to be incorporated and the base station in proximity to BS4 104 are BS1 101. First, a base station close to BS4 104 to be incorporated is selected. In this case, the base station adjacent to BS4 104 becomes BS1 101. Next, a terminal capable of calibrating BS4 104 and BS1 101 is selected.

Using the complex constant value transmitted from the selected terminal, the multi-cell calibration correction factor between BS4 104 and BS1 101 is calculated. BS1 101 compares the calibration correction factor calculated by changing to the base station cooperative combination 120 and the calibration correction factor calculated by the existing base station cooperative combination 110. BS1 101 generates calibration update information necessary for updating the calibration correction factor with other base stations. BS1 101 transmits the generated calibration update information to BS3 103, which is a neighboring cooperative base station, through the backhaul. Upon receiving this, BS3 103 updates the calibration correction factor using the calibration update information. Each base station BS1 101, BS3 103, BS4 104 applies the updated calibration correction factor to the sounding calibration.

2 is a diagram illustrating a signal flow for performing calibration between multiple cells according to an embodiment of the present invention.

Referring to FIG. 2, in operation 210, the first base station, the second base station, and the third base station perform multi-cell calibration with the first base station cooperative combination. In this case, the multi-cell calibration correction factor according to the first base station cooperative combination is calculated through Equation 2.

Figure pat00005

here,

Figure pat00006
Is the first multi-cell calibration correction factor for the K-th base station,
Figure pat00007
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the base station after the single cell base station calibration of the K-th base station is applied. And
Figure pat00008
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after the single cell terminal calibration is applied to the selected reference terminal.

The second base station is excluded according to the channel condition and the supporting terminal, and the fourth base station is incorporated into a new base station cooperative combination. Then, in step 220, the cooperative cell is changed to the first base station, the third base station, and the fourth base station to form a second base station cooperative combination.

In step 230, the fourth base station selects a base station for multi-cell calibration. To this end, the fourth base station may select a base station near its own neighbor using a neighbor cell list such as a cell ID. Herein, although the fourth base station selects a base station for multi-cell calibration, the present invention is not limited thereto. That is, a Mobility Management Entity (MME) such as a Self Organization Network (SON) server may select and notify a base station having the same scheduling condition or a base station located in the vicinity.

Next, the first base station and the fourth base station calculate the multi-cell calibration correction factor in step 240. Here, the multi-cell calibration correction factor between the first base station and the fourth base station is calculated by Equation 3.

Figure pat00009

here,

Figure pat00010
Is the new second multi-cell calibration correction factor for the K-th base station, as a new base station is incorporated,
Figure pat00011
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the base station after the single cell base station calibration of the K-th base station is applied. And
Figure pat00012
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after a single cell terminal calibration is applied to the selected reference terminal to perform multi-cell calibration between the first base station and the fourth base station to be incorporated.

Next, the first base station generates calibration update information according to the multi-cell calibration correction factor changed in step 250. In this case, the calibration update information may be generated through Equation 4.

Figure pat00013

here

Figure pat00014
Denotes calibration update information.

The first base station transmits the calibration update information generated in step 260 to the third base station constituting the second base station cooperative combination through the backhaul. Then, the third base station updates the calibration correction factor using the calibration update information received in step 270. That is, the third base station updates the multi-cell calibration correction factor through equation (5).

Figure pat00015

Through these processes, the first base station, the third base station, and the fourth base station configured with the new second base station cooperative combination have the same calibration correction factor as shown in Equation (6).

Figure pat00016

Therefore, when a new base station cooperative combination is configured, the same calibration effect can be obtained without going through the conventional calibration process. Although not shown in the figure, the first base station, the third base station, and the fourth base station that have updated the multi-cell calibration correction factor apply the updated calibration correction factor to the sounding calibration.

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

Referring to FIG. 3, the base station includes a communication unit 310, a control unit 320, and a storage unit 330.

The communication unit 310 may receive a signal for requesting multi-cell calibration received from another base station. Also, the communication unit 310 receives a signal including calibration update information from another base station and transmits the signal to the control unit 320.

The controller 320 may control the operation and state of all the components constituting the base station. In this case, the controller 320 calculates a first calibration correction factor by performing a multi-cell calibration according to the base station cooperative combination. When the base station cooperative combination is changed, the controller 320 calculates a new second calibration correction factor between base stations to be incorporated. Next, the controller 320 may generate calibration update information, which is a difference between the first calibration correction factor and the new second calibration correction factor, and transmit the calibration update information to other base stations configuring the base station cooperative combination. To this end, the controller 320 includes a calibration correction factor calculator 325 and a calibration update information generator 327.

The calibration correction factor calculator 325 calculates a multi-cell calibration correction factor between cooperative base stations according to Equation 7 according to the base station cooperative combination.

Figure pat00017

here,

Figure pat00018
Is the first multi-cell calibration correction factor for the K-th base station,
Figure pat00019
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the base station after the single cell base station calibration of the K-th base station is applied. And
Figure pat00020
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after the single cell terminal calibration is applied to the selected reference terminal.

When a new base station is incorporated into the base station cooperative combination according to the channel condition and the supporting terminal, the calibration correction factor calculator 325 calculates a second calibration correction factor according to the new base station cooperative combination. Here, the second calibration correction factor is calculated by the equation (8).

Figure pat00021

here,

Figure pat00022
Is the new second calibration correction factor for the Kth base station, as a new base station is incorporated,
Figure pat00023
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the base station after the single cell base station calibration of the K-th base station is applied. And
Figure pat00024
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after the single cell terminal calibration is applied to the selected reference terminal to calculate the second calibration correction factor.

Next, the calibration correction factor calculator 325 may update the calibration correction factor through Equation 9 by using the calibration update information received through the communication unit 310.

Figure pat00025

here

Figure pat00026
Denotes calibration update information.

The calibration update information generator 327 may generate calibration update information according to the changed multi-cell calibration correction factor. In this case, the calibration update information may be generated through Equation 10.

Figure pat00027

here

Figure pat00028
Denotes calibration update information. And
Figure pat00029
Is the first multi-cell calibration correction factor for the K-th base station,
Figure pat00030
Denotes a new second calibration correction factor for the K-th base station by incorporating a new base station. to the next
Figure pat00031
Is a complex constant value generated between the transmit RF chain and the receive RF chain of the terminal after the single cell terminal calibration is applied to the reference terminal selected for calculating the first multicell calibration correction factor. Finally
Figure pat00032
Is a complex constant value generated between the transmitting RF chain and the receiving RF chain of the terminal after the single cell terminal calibration is applied to the selected reference terminal to calculate the second calibration correction factor.

With these configurations, when a new base station cooperative combination is configured, the same calibration effect can be obtained without going through a conventional calibration process. The controller 320 applies the updated calibration correction factor to the sounding calibration.

The storage unit 330 may store programs and data necessary for the overall operation of the base station. The storage unit 330 may store a calibration correction factor calculated when the base station performs a multi-cell calibration under the control of the controller 320. In addition, the storage unit 330 may store calibration update information generated according to a change of a calibration correction factor under the control of the controller 320. The storage unit 330 may store an equation for calculating a calibration correction factor and calibration update information under the control of the controller 320.

4 illustrates a method of performing sounding reference signal calibration according to an embodiment of the present invention.

Referring to FIG. 4, in step 410, the base station performs calibration with at least one base station managing at least one neighboring cell for configuring a base station cooperative combination, and stores the first multi-cell calibration correction factor calculated accordingly. . Next, the base station determines whether there is a base station managing a cell to be incorporated by changing the base station cooperative combination according to the channel state or the supporting terminal in step 415.

If there is a cell to be incorporated, the base station selects a terminal capable of performing multi-cell calibration with the base station to be incorporated in step 420. Next, the base station calculates a second multi-cell calibration correction factor with the base station managing the cell to be incorporated in step 425. In step 430, the base station generates calibration update information using the first multi-cell calibration correction factor and the second multi-cell calibration correction factor. Next, the base station transmits the calibration update information generated in step 435 to other base stations constituting the changed base station cooperative combination. In this case, the base station was one of the base stations constituting the base station cooperative combination, but does not transmit calibration update information to the excluded base station as the base station cooperative combination is changed.

In step 415, if the cell to be included is not identified, the base station determines whether calibration update information is received through the backhaul from another base station in step 440. If calibration update information is received, the base station updates the first calibration correction factor to the second calibration correction factor using the calibration update information received in step 445.

However, if the calibration update information is not received, the base station determines in step 450 whether the group to be incorporated according to the base station cooperative combination change is confirmed. If the group to be incorporated is identified, the base station selects adjacent base stations located in the vicinity of the base stations constituting the modified base station cooperative combination in step 455. At this time, the base station selects a base station close to its periphery by using a neighbor cell list such as a cell ID, or a mobility management entity (MME) such as a self organization network (SON) server has a base station or a periphery having the same scheduling condition. The base station can be selected and informed. Next, the base station calculates a multi-cell calibration correction factor with the base station selected in step 460.

Finally, the base station applies the multi-cell calibration correction factor calculated in step 470 to the sounding calibration.

When the cooperative base station is changed through these processes, even if the calibration for all base stations is not performed, the phase of the multi-cell calibration complex constant value between the multiple base stations for one terminal is kept the same. Therefore, the performance of the base station cooperative MIMO scheme using multi-cell sounding can be maintained.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims, and equivalents thereof.

Claims (10)

In the sounding reference signal calibration method in the base station,
Performing calibration with at least one base station for configuring the base station cooperative combination, and storing the first calibration correction factor calculated accordingly;
Determining whether a base station to be incorporated into the base station cooperative combination exists;
Calculating a second calibration correction factor with the base station to be incorporated if the base station to be incorporated exists;
Generating calibration update information which is a difference value between the first calibration correction factor and the second calibration correction factor;
And applying the calculated second calibration correction factor to a sounding calibration. The process of claim 1, wherein the generating of the calibration update information comprises:
And transmitting the calibration update information to another base station constituting the base station cooperative combination. The method of claim 1,
If there is no base station to be incorporated, determining whether calibration update information is received from another base station constituting the base station cooperative combination;
And if the calibration update information is received, updating the first calibration correction factor using the calibration update information. The method of claim 1,
If there is no base station to be incorporated, checking whether there is a group to be incorporated according to a base station cooperative combination change;
Selecting an adjacent base station among base stations constituting the changed base station cooperative combination, if the group to be incorporated exists;
And calculating a calibration correction factor with the selected neighbor base station. The process of claim 1, wherein the calculating of the second calibration correction factor with the base station to be incorporated includes:
Sounding reference signal calibration method comprising the step of selecting a terminal capable of performing a multi-cell calibration with the base station to be incorporated. Perform calibration with at least one base station for configuring a base station cooperative combination, calculate a first calibration correction factor accordingly, determine whether a base station to be incorporated into the base station cooperative combination exists, and if the base station to be incorporated exists, Calculating a second calibration correction factor with the base station to be incorporated, generating calibration update information that is a difference between the first calibration correction factor and the second calibration correction factor, and sounding the calculated second calibration correction factor A control unit to be applied to the calibration,
And a storage unit for storing the second calibration correction factor and the calibration update information. The method according to claim 6,
And a communication unit for transmitting the calibration update information to another base station constituting the base station cooperative combination under the control of the control unit. 7. The apparatus of claim 6, wherein the control unit
If the base station to be incorporated does not exist, it is determined whether calibration update information is received from another base station constituting the base station cooperative combination, and when the calibration update information is received, the first calibration correction factor is used by using the calibration update information. Sounding reference signal calibration device, characterized in that for updating. 7. The apparatus of claim 6, wherein the control unit
If the base station to be incorporated does not exist, check whether there is a group to be incorporated according to the base station cooperative combination change; A sounding reference signal calibration device, comprising: calculating a calibration correction factor with an adjacent base station. 7. The apparatus of claim 6, wherein the control unit
Sounding reference signal calibration device, characterized in that for selecting a terminal capable of performing a multi-cell calibration with the base station to be incorporated.
KR1020120010573A 2012-02-02 2012-02-02 Apparatus and method of sounding reference signal calibration KR20130089312A (en)

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