KR101007448B1 - Channel Quality Indicator Detection Apparatus and Method - Google Patents

Abstract

An apparatus for detecting a channel quality indicator according to an aspect of the present invention capable of determining whether to update a CQI by using a signal-to-noise ratio (SNR) of a reception channel of a CQI fed back from a terminal is a channel fed back from the terminal. A correlation calculator configured to calculate a correlation with respect to an index of each channel quality indicator by using a channel quality indicator (CQI); On the basis of the correlation calculated by the correlation calculator, a global maximum value, which is an index of the channel quality indicator corresponding to the largest correlation among the indexes of all channel quality indicators, and a largest correlation among some channel quality indexes. A maximum value determiner that determines a local maximum value that is an index of a corresponding channel quality indicator; And a channel quality indicator manager for updating a previous channel quality indicator using any one of the global maximum value and the local maximum value.

CQI, Feedback, Detection, Reliability

Description

Apparatus and Method for Detecting Channel Quality Indicator

The present invention relates to wireless communication technology, and more particularly, to a technology for detecting a channel quality indicator in a wireless communication system.

In the wireless communication system, the terminal measures the quality of the radio link to generate a channel quality indicator (hereinafter, referred to as "CQI"), and transmits the generated CQI to the base station. Meanwhile, the base station checks the CQI transmitted from the terminal, and then modulates the data according to the channel state of the terminal using adaptive modulation and coding (AMC) based on the identified CQI. And coding.

Here, the AMC scheme refers to a data transmission scheme for improving data transmission efficiency of the entire cell by determining a modulation scheme and a coding scheme of different data channels according to channel conditions between the base station and the terminal. The AMC scheme has a plurality of modulation schemes and a plurality of coding schemes, and modulates and codes a data channel signal by combining the modulation schemes and coding schemes.

In the wireless communication system, when the UE transmits such a CQI to the base station, it does not adopt a method of checking and correcting an error such as a cyclic redundancy check (CRC), and thus, if the radio link to which the CQI is transmitted is poor, The problem is that CQI is not completely reliable.

In addition, if the MCS level of the UE is determined based on an unreliable CQI, the data transmitted from the base station cannot be decoded by the terminal, or the data transmitted by the base station can be received and decoded by the terminal. The lower the problem, the more serious the problem.

The present invention is to solve the above-mentioned problems, the apparatus for detecting the channel quality indicator that can determine whether to update the CQI using the signal-to-noise ratio (SNR) of the received channel of the CQI fed back from the terminal; It is a technical task to provide a method.

Another object of the present invention is to provide an apparatus and method for detecting a channel quality indicator capable of updating a previous CQI using a plurality of indexes determined by using a CQI value fed back from a terminal among the CQI indexes. do.

In accordance with an aspect of the present invention, an apparatus for detecting a channel quality indicator according to an aspect of the present invention uses a channel quality indicator (CQI) fed back from a terminal to correlate an index of each channel quality indicator. Correlation calculation unit for calculating a; On the basis of the correlation calculated by the correlation calculator, a global maximum value, which is an index of the channel quality indicator corresponding to the largest correlation among the indexes of all channel quality indicators, and a largest correlation among some channel quality indexes. A maximum value determiner that determines a local maximum value that is an index of a corresponding channel quality indicator; And a channel quality indicator manager for updating a previous channel quality indicator using any one of the global maximum value and the local maximum value.

According to another aspect of the present invention, there is provided a method for detecting a channel quality indicator, comprising: calculating a signal-to-noise ratio of a channel to which a channel quality indicator is fed back from a terminal; Calculating a correlation of indices of respective channel quality indicators using the channel quality indicator fed back from the terminal when the calculated signal-to-noise ratio is greater than a threshold; And selecting a channel quality indicator using any one of a global maximum value and a local maximum value determined based on the correlation among the indices of the respective channel quality indicators.

According to the present invention, the CQI fed back is updated only when the signal-to-noise ratio of the received channel of the CQI fed back from the terminal is greater than the threshold, and the correlation for each CQI index is calculated using the CQI fed back from the terminal. In addition, since the previous CQI is updated using one or more indexes determined using the correlation of each CQI index among the CQI indexes, the reliability of the CQI may be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram of a base station including a channel quality indicator detection device according to an embodiment of the present invention. As shown, the base station includes a channel quality indicator detection apparatus 100, a plurality of channel estimators 110a to 110n, a plurality of noise measuring units 112a to 112n, and a scheduler.

First, the channel quality indicator detecting apparatus 100 receives a channel quality indicator (CQI, hereinafter referred to as 'CQI') fed back from the terminal to update the previous CQI, as shown. The calculator 102, the correlation calculator 104, the maximum value determiner 106, and the CQI manager 108 are included.

First, the SNR calculator 102 calculates a signal-to-noise ratio (SNR) of a reception channel of a CQI fed back from a terminal. In one embodiment, the SNR calculator 102 may include a plurality of channel weights. The SNR of the CQI reception channel is calculated by using the estimated values of the CQI reception channels estimated by the governments 110a through 110n and the noise values of the CQI reception channels measured by the plurality of noise measuring units 112a through 112n.

The SNR calculator 102 may calculate the SNR of the CQI reception channel using the method described in Equation 1 below.

는 i번째 수신 안테나의 u번째 타일의 채널 이득을 나타내고,

는 i번째 수신 안테나에서 노이즈 성분의 표준편차를 나타내는 것으로서, 수학식 1에서 분자에 기재된 항목은 각 채널 추정부(110a~110n)에 의해 산출되고, 분모에 기재된 항목은 각 노이즈 측정부(112a~112n)에 의해 산출된다.In Equation 1

Denotes the channel gain of the u-th tile of the i-th receive antenna,

Denotes the standard deviation of the noise component in the i-th reception antenna, wherein the items described in the numerator in Equation 1 are calculated by the channel estimators 110a to 110n, and the items described in the denominator are the noise measurements 112a to. 112n).

Next, the correlation calculator 104 calculates a correlation with respect to the index of each CQI using the CQI fed back from the terminal. Here, the CQI is divided into a plurality of categories according to contents included in the CQI, as shown in FIG. 4, and each category corresponds to any one of two types, and the total CQI is 64 CQI indexes. It consists of.

Hereinafter, the category and type of the CQI will be described with reference to FIG. 4. As shown in FIG. 4, the categories of CQI include Physical CINR (PCINR), Effective CINR (ECINR), Anchor BS Report, MIMO Mode, Band Width Request (BWR), and Band AMC Transition.

First, the PCINR represents information on the carrier to interference and noise ratio (CINR) of the channel measured by the terminal, and these categories include CQI indexes 0 to 31.

ECINR represents the MCS level applicable to the terminal, and the category includes CQI indexes 0 to 15.

The Anchor BS Report indicates information transmitted when Macro Diversity Handover (MDHO) or Fast BS Switching (FBSS) is required. These categories include CQI indexes 32 to 39. .

The MIMO mode indicates a MIMO mode applicable to the terminal, such as STTD or SM, and includes CQI indexes 40 to 58.

Band width ratio (BWR) indicates information transmitted by the UE for requesting bandwidth, and includes Extended RtPS Bandwidth Request and Indication Flag Feedback information. These categories include CQI indexes 59 and 60.

The Band AMC Transition indicates information on switching from the normal subchannel to the AMC, switching from the AMC to the basic subchannel, and switching the AMC band, and includes CQI indexes 61 to 63.

Meanwhile, as shown in FIG. 4, the types of PCINR, ECINR, and MIMO Mode among the categories are periodic types, and this type indicates a category in which a period in which the UE transmits a CQI including corresponding content is predetermined. The types of BS Report, BWR, and Band AMC Transition are aperiodic types, and this type indicates a category in which the UE transmits a CQI including corresponding content to the base station aperiodically.

As such, the correlation calculator 104 calculates a correlation for each CQI index shown in FIG. 4 using the CQI fed back from the terminal. In one embodiment, the correlation calculator 104 may calculate the correlation for the index in each CQI using the method described in Equation 2 below in calculating the correlation for each CQI index.

은 수신 CQI r과 j번째 CQI 인덱스에 대한 상관도를 나타내고,

는 i번째 수신 안테나의 u번째 타일의 채널 이득 행렬의 복소 행렬을 나타내며,

는 j 번째 코드 인덱스에 따른 u 번째 타일에 매핑되는 CQI 심볼 벡터의 허미션(Hermitian) 행렬을 나타내고,

는 i번째 수신 안테나를 통해 수신된 u번째 타일의 CQI를 나타낸다.In equation (2)

Denotes a correlation between the received CQI r and the j th CQI index,

Denotes the complex matrix of the channel gain matrix of the u-th tile of the i-th receive antenna,

Denotes a Hermitian matrix of CQI symbol vectors mapped to the u th tile according to the j th code index,

Denotes the CQI of the u-th tile received through the i-th receive antenna.

는 아래의 수학식 3과 같이 정의될 수 있다.Meanwhile, in Equation 2

May be defined as in Equation 3 below.

는 j 번째 코드 인덱스에 따른 u 번째 타일에 매핑되는 CQI 심볼 벡터를 나타내며,

는 i번째 수신 안테나를 통해 수신된 U번째 타일에서의 노이즈를 나타낸다.Here, the channel gain of the u th tile of the i th reception antenna is shown.

Denotes a CQI symbol vector mapped to the u th tile according to the j th code index,

Denotes noise in the U-th tile received through the i-th receive antenna.

The correlation calculator 104 may calculate the correlation for each CQI index by using the real term of the product of the factors as described above in Equation 2 above.

Next, the maximum value determiner 106 determines a global maximum value and a local maximum value among correlations for each CQI index calculated by the correlation calculator 104. Here, the maximum value determining unit 106 determines the CQI index having the largest correlation among all the CQI indexes, that is, the 64 CQI indexes, as the global maximum value.

In addition, the maximum value determining unit 106 is the CQI index having the largest correlation among the correlations for the CQI index of each category for each category corresponding to a category whose type is a periodic type among the categories including the CQI index. Is determined as the local maximum. That is, the maximum value determining unit 106 determines the CQI index having the highest correlation among 32 CQI indexes belonging to the PCINR, the CQI index having the highest correlation among the 15 CQI indexes belonging to the ECINR, and 19 CQIs belonging to the MIMO Mode. The CQI index with the highest correlation among the indexes is determined as the local maximum value.

That is, the maximum value determining unit 106 determines one global maximum value and four local maximum values among correlations for each CQI index. However, this is only one embodiment. If the number of categories of the CQI is changed or the type of each category is changed, the number of local maximum values may be changed.

Next, the CQI management unit 108 determines whether to update the previous CQI using the SNR calculated by the SNR calculating unit 102 described above, and when determining to update the previous CQI, the maximum value determining unit 106. Update the previous CQI using the global maximum value or the local maximum value determined by.

Specifically, the CQI management unit 108 determines whether the SNR calculated by the SNR calculation unit 102 is greater than the threshold, and determines to update the previous CQI when it is larger than the threshold, and does not update the previous CQI when it is smaller than the threshold. Decide to keep without.

Here, if the SNR is smaller than the threshold, the CQI is not updated because the SNR is smaller than the threshold because the channel situation is not good and the reliability of the received CQI may not be high.

Therefore, when the CQI management unit 108 determines not to update the previous CQI, the global maximum value and the local maximum value are not needed to update the previous CQI. Therefore, the correlation calculation unit for obtaining the global maximum value and the local maximum value may be performed. 104 and the maximum value determining unit 106 may operate only when the CQI management unit 108 determines to update the previous CQI.

On the other hand, if the calculated SNR is greater than the threshold, the CQI management unit 108 determines that the received CQI is reliable and updates the previous CQI using the above-described global maximum or local maximum.

First, the CQI manager 108 determines the type of the global maximum value, and if the type of the global maximum value is an aperiodic type, updates the previous CQI using the global maximum value.

On the other hand, when the type of the global maximum value is a periodic type, the CQI management unit 108 determines whether the global maximum value is included in the CQI index set that is to be received in the current frame, and if so, determines the global maximum value. To update the previous CQI.

In addition, if the type of the global maximum value is a periodic type, but the global maximum value is not included in the CQI index set to be received in the current frame, the CQI management unit 108 updates the previous CQI using any one of the local maximum values. . At this time, the CQI management unit 108 is included in the CQI index set to be received in the current frame among the local maximum values determined by the above-described maximum value determining unit 106 in updating the previous CQI using the local maximum value. The local maximum may be used to update the previous CQI.

4 is a diagram showing a simulation result of the performance of the above-described channel quality indicator detection apparatus. FIG. 4A illustrates a message error rate (MER) of a base station measured by changing a threshold for SNR. As shown in FIG. 4A, the higher the threshold for SNR is, the better the performance is.

On the other hand, Figure 4b is a view showing the MER of the base station measured while changing the CQI index set, it can be seen that the performance varies depending on the number of CQI index set or CQI index included in the CQI index set as shown. .

Referring back to FIG. 1, the plurality of channel estimators 110a through 110n serve to estimate a channel through which the CQI is received through each receive antenna, and the plurality of noise measuring units 112a through 112n each receive antenna. Through the CQI serves to measure the noise on the channel received.

Next, the scheduler 114 determines which rule to distribute available radio resources to each terminal based on the CQI detected by the channel quality indicator detection apparatus 100 described above, and the data of each user every frame. The subchannels are allocated and managed in the entire burst region of the uplink subframe and the downlink subframe of the current frame for transmission and reception. That is, after finding a channel having optimal performance for each terminal, scheduling is performed so that a channel having optimal performance is allocated to a user terminal.

In the above-described embodiment, the channel quality indicator detection apparatus 100 is described as being included in the base station as a separate component, but in the modified embodiment, the channel quality indicator detection apparatus 100 is provided to the base station as a separate component. Not included, the function performed by the channel quality indicator detection apparatus 100 may be implemented in the PHY layer processing unit or the MAC layer processing unit of the base station. For example, the functions performed by the SNR calculator 102, the correlation calculator 104, and the maximum value determiner 106 may be implemented in the physical layer processor, and the functions of the CQI manager 108 may be implemented in the MAC layer processor. Could be implemented.

Hereinafter, the channel quality indicator detection method according to the present invention will be described with reference to FIGS.

2 is a flowchart illustrating a method of detecting a channel quality indicator according to an embodiment of the present invention.

First, the CQI fed back from the terminal is received (S200). Thereafter, the CQI receives the estimated channel and measures the noise of the CQI received channel (S210).

Next, the SNR of the channel from which the CQI is received is calculated using the estimated channel and the measured noise (S220). In one embodiment, the SNR of the channel on which the CQI is received may be calculated using the method described in Equation 1 above.

Next, it is determined whether the calculated SNR is greater than the threshold (S230). When the calculated SNR is smaller than the threshold, it is determined that the previous CQI is maintained without updating (S240). Here, if the SNR is smaller than the threshold, maintaining the previous CQI without updating it is because the channel situation is poor and the received CQI cannot be trusted.

On the other hand, when the SNR calculated as a result of the determination in S230 is larger than the threshold, the correlation degree for the index of each CQI is calculated using the received CQI (S250). Here, the index of each CQI, the category to which each CQI index belongs, and the type of each category are shown in FIG. 5, and the correlation for the index of each CQI may be calculated using Equation 2 described above.

Thereafter, the global maximum value and the local maximum value of each CQI index are determined using correlations with respect to the index of each CQI (S260). In one embodiment, the global maximum value may be determined as the CQI index having the largest correlation among all the CQI indexes, that is, the correlations for the 64 CQI indexes.

In addition, the local maximum value corresponds to the CQI index, that is, the PCINR having the largest correlation among the CQI indexes belonging to each category for each category corresponding to a category whose type is a periodic type among the categories including the CQI index. The CQI index with the highest correlation among the 32 CQI indexes belonging to it, the CQI index with the highest correlation among the 15 CQI indexes belonging to ECINR, and the CQI index with the highest correlation among the 19 CQI indexes belonging to MIMO Mode. have.

Finally, the previous CQI is updated using the global maximum value or the local maximum value determined in S260 (S270).

Hereinafter, a method of updating a previous CQI using a global maximum value or a local maximum value will be described in detail with reference to FIG. 3.

First, the type of the global maximum value is determined (S300). That is, it is determined whether the type of the global maximum value is an aperiodic type or a periodic type.

As a result of the determination, when the type of the global maximum value is an aperiodic type, the previous CQI is updated using the global maximum value (S310).

On the other hand, if it is determined in S300 that the type of the global maximum value is a periodic type, it is determined whether the global maximum value is included in the CQI index set to be received in the current frame (S320). As a result of the determination, when the global maximum value is included in the CQI index set to be received in the current frame, the previous CQI is updated using the global maximum value (S330).

That is, since the index of the CQI received from the terminal is one of the CQI indexes expected to be received in the current frame, it is determined that the index is reliable and updates the previous CQI.

As a result of the determination in S320, when the global maximum value is not included in the CQI index set to be received in the current frame, the previous CQI is updated using any one of the local maximum values (S330). Specifically, the CQI is updated by using the local maximum value included in the CQI index set to be received in the current frame among the local maximum values.

The channel quality indicator detection method described above may be implemented in the form of program instructions that can be executed by various computer means, and recorded in a computer-readable recording medium. In this case, the computer-readable recording medium may include program instructions, data files, data structures, and the like, alone or in combination. On the other hand, the program instructions recorded on the recording medium may be those specially designed and configured for the present invention or may be available to those skilled in the art of computer software.

The computer-readable recording medium includes a magnetic recording medium such as a magnetic medium such as a hard disk, a floppy disk and a magnetic tape, an optical medium such as a CD-ROM and a DVD, a magnetic disk such as a floppy disk, A magneto-optical media, and a hardware device specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. The recording medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, or the like.

In addition, program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

On the other hand, those skilled in the art will understand that the present invention described above can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

1 is a schematic block diagram of a base station including a channel quality indicator detection device according to an embodiment of the present invention.

2 is a flowchart showing a method for detecting a channel quality indicator according to an embodiment of the present invention.

3 is a flowchart illustrating a method of updating a channel quality indicator in accordance with an embodiment of the present invention.

4 is a diagram showing a simulation result for the performance of the channel quality indicator detection method according to the present invention.

5 shows a category and a type of each CQI index.

<Explanation of symbols for the main parts of the drawings>

100: channel quality indicator detection device 102: SNR calculator

104: correlation calculation unit 106: maximum value determination unit

108: CQI management

Claims (20)

A correlation calculation unit configured to calculate a correlation with respect to an index of each channel quality indicator by using a channel quality indicator (CQI) fed back from the terminal; On the basis of the correlation calculated by the correlation calculator, a global maximum value, which is an index of the channel quality indicator corresponding to the largest correlation among the indexes of all channel quality indicators, and a largest correlation among some channel quality indexes. A maximum value determiner that determines a local maximum value that is an index of a corresponding channel quality indicator; And And a channel quality indicator manager for updating a previous channel quality indicator by using any one of the global maximum value and the local maximum value. The method of claim 1, The local maximum value is an index of a channel quality indicator corresponding to the largest correlation among the correlations of the indexes of the channel quality indicators belonging to each category for each category corresponding to a cyclic type. Indicator detection device. The method of claim 2, The category may include at least one of physical CINR (PCINR), Effective CINR (ECINR), Anchor BS report, MIMO Mode, Band Width Request (BWR), and B-AMC Transition. The method of claim 1, And, if the global maximum value is an unsolicited type, updating the previous channel quality indicator using the global maximum value. The method of claim 1, The channel quality indicator management unit uses the global maximum value if the index of the channel quality indicator fed back from the terminal is included in the index set of the scheduled channel quality indicator when the global maximum value is a periodic type. And update the previous channel quality indicator. The method of claim 1, The channel quality indicator manager, if the global maximum value is a periodic type and the index of the channel quality indicator fed back from the terminal is not included in the index set of the scheduled channel quality indicator, the previous channel quality using the local maximum value. And updating the indicator. 7. The method of claim 6, wherein when there are a plurality of local maximums, And the channel quality indicator manager updates the previous channel quality indicator by using a local maximum value included in a scheduled channel quality indicator index set among the local maximum values. The method of claim 1, The channel quality indicator manager is configured to update the previous channel quality indicator by using a signal to noise ratio (SNR) of a channel in which a channel quality indicator fed back from the terminal is received before the update of the previous channel quality indicator. And channel quality indicator detection device. The method of claim 8, The channel quality indicator manager, if the signal-to-noise ratio is less than a threshold, maintains the previous channel quality indicator without updating, and if the signal-to-noise ratio is greater than a threshold, one of the global maximum value and the local maximum value. And updating the previous channel quality indicator by using the channel quality indicator. The method of claim 1, And a signal-to-noise ratio calculation unit for calculating a signal-to-noise ratio of the channel from which the channel quality indicator fed back from the terminal is received. The method of claim 10, And the signal-to-noise ratio calculation unit calculates the signal-to-noise ratio of the channel using the estimated value of the channel and the noise value measured in the channel. The method of claim 1, The correlation calculator and the maximum value determiner belong to a physical layer, and the channel quality indicator manager belongs to a MAC layer. Calculating a signal-to-noise ratio of the channel to which the channel quality indicator is fed back from the terminal; Calculating a correlation of indices of respective channel quality indicators using the channel quality indicator fed back from the terminal when the calculated signal-to-noise ratio is greater than a threshold; And Selecting a channel quality indicator by using any one of a global maximum value and a local maximum value determined based on the correlation among the indexes of the respective channel quality indicators. . The method of claim 13, And if the signal to noise ratio is less than the threshold, retain a previous channel quality indicator. The method of claim 13, The global maximum value is an index of a channel quality indicator corresponding to the largest correlation among the correlations for the indexes of the channel quality indicators, and the local maximum value is a channel quality belonging to each category for each category corresponding to a periodic type. And a channel quality indicator index corresponding to the largest correlation among the correlations for the indexes of the indicators. The method of claim 15, The category may include at least one of Physical CINR (PCINR), Effective CINR (ECINR), Anchor BS Report, MIMO Mode, Band Width Request (BWR), and B-AMC Transition. The method of claim 13, And in the channel quality indicator selection step, selecting the channel quality indicator using the global maximum value when the global maximum value is an aperiodic type. The method of claim 13, wherein in the channel quality indicator selection step: When the global maximum value is a periodic type, if the index of the channel quality indicator fed back from the terminal is included in the scheduled channel quality indicator index set, the channel quality indicator is selected using the global maximum value. And if the index of the channel quality indicator fed back from the terminal is not included in the scheduled channel quality indicator index set, selecting the channel quality indicator using the local maximum value. The method of claim 18, When selecting the channel quality indicator using the local maximum value, when there are a plurality of local maximum values, selecting the channel quality indicator using a local maximum value included in a scheduled index set among the local maximum values. Characterized in that the channel quality indicator detection method. The method of claim 13, In the signal-to-noise ratio calculation step, the signal-to-noise ratio of the channel is calculated using the estimated value of the channel and the noise value measured in the channel.

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