KR20150009417A

KR20150009417A - Methods for Transmitting and Receiving Channel Quality Information, and Apparatuses Thereof

Info

Publication number: KR20150009417A
Application number: KR1020130161909A
Authority: KR
Inventors: 강승현; 최우진
Original assignee: 주식회사 케이티
Priority date: 2013-06-27
Filing date: 2013-12-23
Publication date: 2015-01-26

Abstract

The present invention provides a method and apparatus for transmitting and receiving channel quality information for a terminal located in an improved coverage area as compared with coverage for a general terminal. The terminal determines the geometry level of the terminal and transmits information on the geometry level of the terminal to the base station. The base station transmits information indicating one of a plurality of CQI (Channel Quality Information) tables to the terminal based on the received signal. Then, the UE and the BS perform CQI feedback using the selected CQI table.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and an apparatus for transmitting channel quality information,

The present invention relates to a method and an apparatus for transmitting and receiving channel quality information in a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving channel quality information for a terminal located in an enhanced coverage area as compared with coverage for a general terminal.

Machine Type Communication (MTC) or Machine to Machine (M2M) is the communication that takes place between a device and an object with no human intervention or minimal intervention. A "machine" may refer to an entity that does not require direct manipulation or intervention by a person, and "MTC" may refer to a form of data communication involving one or more of such machines. Examples of the "machine" include a smart meter equipped with a mobile communication module, a vending machine, and the like. In recent years, a smart phone The mobile terminal having the MTC function is considered as a type of machine.

The MTC terminal can be installed in a place where the radio wave environment is worse than that of a general terminal. Therefore, the coverage of the MTC terminal should be improved to 20 dB or more in comparison with the coverage of the general terminal.

Meanwhile, in a LTE (Long Term Evolution) system, a base station receives CQI (Channel Quality Information) feedback for confirming a channel state from a UE prior to downlink data transmission to the UE. The base station schedules the transmission resource considering the channel state to the terminal with reference to the channel state. This is called channel-dependent scheduling. If the coverage of the MTC terminal is larger than the coverage of the general terminal, existing CQI feedback may not be available for the MTC terminal.

It is an object of the present invention to provide a method and an apparatus capable of transmitting CQI feedback to a base station by an MTC terminal operating at a coverage higher than that of a general terminal.

According to an embodiment of the present invention, there is provided a channel quality information transmission method executed in a terminal of a wireless communication system, the method comprising: determining a geometry level of the terminal; Selecting a CQI table corresponding to a geometry level of the terminal among a plurality of channel quality information (CQI) tables; Receiving a reference signal for estimation of a channel condition from a base station; Determining a corresponding CQI index in the selected CQO table based on the reference signal; And transmitting the determined CQI index to the base station.

According to another embodiment of the present invention, there is provided a channel quality information reception method executed in a base station of a wireless communication system, comprising: receiving information on a geometry level of the terminal from a terminal; Transmitting information indicating one of a plurality of channel quality information (CQI) tables to the terminal; Transmitting a reference signal for channel state estimation to the terminal; And receiving a CQI index determined in the CQI table indicated by the terminal.

According to another embodiment of the present invention, there is provided a terminal for transmitting channel quality information to a base station, the terminal for determining a level of geometry of the terminal, and a terminal for transmitting the channel quality information (CQI) A CQI table corresponding to the CQI table; A receiver for receiving a reference signal for estimating a channel state from the base station; And a transmitter for transmitting a CQI index determined in the selected CQO table based on the reference signal to the base station.

According to another aspect of the present invention, there is provided a base station for receiving channel quality information from a terminal, the base station including: a receiving unit for receiving information about a geometry level of the terminal from the terminal; And a transmitter for transmitting information indicating one of a plurality of channel quality information (CQI) tables to the terminal, wherein the transmitter further transmits a reference signal for estimating a channel state to the terminal, And the receiver further receives a CQI index determined in the CQI table indicated by the terminal.

According to the present invention, a UE can transmit CQI feedback to a base station using one of a CQI table for coverage of a general terminal and a CQI table for coverage of an MTC terminal.

1 is a flow diagram illustrating channel dependent scheduling in a wireless communication system.
2 shows the CQI table specified in 3GPP TS 36.213.
Figure 3 shows the MCS table specified in 3GPP TS 36.213.
Fig. 4 shows a table showing the relationship between the tables of Fig. 2 and Fig.
Figure 5 shows BLER performance for 15 spectral efficiencies used in LTE CQI.
Figure 6 shows the SNR gain according to the number of repetitions.
7 is a flowchart showing a first embodiment of the CQI table setting method of the present invention.
8 is a flowchart showing a second embodiment of the CQI table setting method of the present invention.
FIG. 9 shows a CQI table according to the first embodiment of the method of constructing the CQI table of the present invention.
FIG. 10 shows an example of the CQI table according to FIG.
FIG. 11 shows BLER performance for the CQI table of FIG.
12 shows a CQI table according to the second embodiment of the method of constructing the CQI table of the present invention.
FIG. 13 shows an example of the CQI table according to FIG.
14 shows BLER performance for the CQI table of FIG.
FIG. 15 shows a CQI table according to the third embodiment of the method of constructing the CQI table of the present invention.
FIG. 16 shows BLER performance for the CQI table of FIG. 15. FIG.
17 is a flowchart illustrating a CQI transmission and reception method according to an embodiment of the present invention.
18 is a flowchart illustrating a CQI transmission method of a UE according to an embodiment of the present invention.
19 is a flowchart illustrating a CQI receiving method of a base station according to an embodiment of the present invention.
20 is a block diagram showing a configuration of a terminal according to an embodiment of the present invention.
21 is a block diagram showing a configuration of a base station according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals even though they are shown in different 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 wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and the like.

That is, in the present specification, a base station or a cell has a comprehensive meaning indicating a part or function covered by BSC (Base Station Controller) in CDMA, Node-B in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU communication range, and the like.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-Advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In a system such as LTE and LTE-A, the uplink and downlink are configured based on one carrier or carrier pair to form a standard. The uplink and downlink transmit control information through a control channel such as a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel (PHICH), and a Physical Uplink Control CHannel And a data channel such as a Physical Downlink Shared CHannel (PDSCH), a Physical Uplink Shared CHannel (PUSCH), and the like.

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or transmission / reception point of a signal transmitted from a transmission / reception point, and a transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multiplex transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiplex transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH and PDSCH are transmitted and received'.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

MTC

MTC (Machine Type Communication) means communication between machine and object without human intervention. From the 3GPP (3 ^rd Generation Partnership Project) perspective, a "machine" is a direct manipulation of a person. An "MTC" means that one or more of these machines Means a form of data communication. Typical examples of the machine include a smart meter equipped with a mobile communication module, a vending machine, and the like. In recent years, smart phones that automatically connect to a network and perform communication according to a user's location or situation With the emergence of mobile phones, mobile terminals with MTC functions are also considered as a form of machine.

LTE Low-cost based MTC

As Long Term Evolution (LTE) networks spread, mobile operators want to minimize the number of Radio Access Terminals (RATs) to reduce network maintenance costs. However, the number of MTC products based on the conventional GSM (Global System for Mobile Communications) / GPRS (General Packet Radio Service) network is increasing, and MTC using a low data rate can be provided at a low cost. Therefore, there is a problem that two RATs must be operated respectively because the LTE network is used for the general data transmission and the GSM / GPRS network is used for the MTC. Therefore, It becomes a burden on the profit of the business operator.

In order to solve such a problem, a low-cost MTC terminal using a GSM / GPRS network should be replaced with an MTC terminal using an LTE network, and various requirements for lowering the price of an LTE MTC terminal are disclosed in the 3GPP RAN WG1 standard conference . In addition, the standard meeting is preparing a document (TR 36.888) describing various functions that can be provided to satisfy the above requirements.

In order to support low-cost LTE MTC terminals, the major items related to physical layer specification change, which are currently being discussed in 3GPP, include technologies such as narrowband support, Single RF chain, Half duplex FDD and Long DRX (Discontinued Reception). However, the above methods, which are considered for lowering the price, can reduce the performance of the MTC terminal as compared with the conventional general LTE terminal. Here, a general LTE terminal means a terminal that is not an MTC terminal.

In addition, about 20% of MTC terminals supporting MTC services such as smart metering are installed in a 'Deep indoor' environment such as a basement, so that for successful MTC data transmission, Compared with the coverage of the first embodiment. Further, considering the performance reduction due to the above-mentioned standard change, the coverage of the LTE MTC terminal should be improved by 20 dB or more.

Various methods for robust transmission such as power spectral density (PSD) boosting or low coding rate and time domain repetition are considered for each physical channel in order to improve the coverage while lowering the price of the LTE MTC terminal.

The requirements of low-cost MTC terminal based on LTE are as follows.

● The data transmission rate should satisfy the minimum data transmission rate provided by MTC terminal based on EGPRS (Enhanced GPRS), that is, downlink 118.4kbps and uplink 59.2kbps.

● Frequency efficiency should be improved dramatically compared to GSM / EGPRS MTC terminal.

● The service area provided should not be less than that provided by the GSM / EGPRS MTC terminal.

● Power consumption should not be larger than GSM / EGPRS MTC terminal.

● LTE terminal and LTE MTC terminal should be available at the same frequency.

Reuse existing LTE / SAE networks.

● Perform optimization not only in FDD mode but also in TDD mode.

• Low-cost LTE MTC terminals should support limited mobility and low power consumption modules.

In the conventional LTE system, the base station can distinguish characteristics and types of terminals after receiving UE category and UE capability information RRC messages.

Also, the base station receives CQI (Channel Quality Information) feedback to check the channel state from the UE prior to transmitting the downlink data to the UE. The base station schedules the transmission resource considering the channel state to the terminal with reference to the channel state. This can be referred to as channel-dependent scheduling.

1 is a flow chart illustrating channel-dependent scheduling in a wireless communication system.

Referring to FIG. 1, the BS 20 transmits a reference signal (RS) for channel measurement to the MS 10 (S 110). The reference signals for channel measurement may include Cell-specific RS (CRS), Channel Status Information RS (CSI-RS), and Demodulation RS (DM-RS).

The terminal 10 measures the channel state using the received RS and transmits the channel status information (CSI) to the base station 20 (S120). The CSI may include a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a CQI.

The base station 20 sets the scheduling for the UE 10 using the received CSI and transmits the scheduling information to the UE 10 (S130).

As described above, by using CQI feedback in the conventional LTE system, it is possible to confirm how much level of geometry the UE is in the coverage of the base station. Figure 2 shows a table of CQIs specified in 3GPP TS 36.213.

The general LTE mobile station and the MTC mobile station can be distinguished using the UE category and UE capability information RRC message. Compared to the general LTE terminal, the MTC terminal needs to operate at 20dB improved coverage, so it uses a relatively large amount of transmission resources and increases power consumption.

The base station must receive a channel status report (e.g., CSI feedback or CQI feedback) from the MTC terminal to ascertain to what extent the base station is in the level of geometry within its coverage of the MTC terminal . Therefore, the MTC terminal can not confirm the geometric level of the MTC terminal until the base station receives the CQI feedback. Even in the case of the MTC terminal having a similar geometry level to the general LTE terminal, it is necessary to use more transmission resources than necessary in order to always support enhanced coverage.

In FIG. 2, the CQI index '0' means 'out of range' indicating that the UE has failed to receive the downlink signal from the base station or the channel state is not good enough to prevent the UE from operating.

Even if the base station can know the approximate geometric level of the MTC terminal, if the CQI table of FIG. 2 is used, the MTC terminal located in the improved coverage always feeds back the CQI index '0', that is, 'out of range' , The base station can not perform channel-dependent scheduling.

Spectral efficiency (or efficiency) in the CQI table of FIG. 2 represents the amount of information bits transmitted per modulation symbol as a product of a code rate and a modulation order as transmission efficiency.

3 shows a Modulation and Coding Scheme (MCS) table specified in 3GPP TS36.213. The transmission efficiency of the CQI indexes 2 to 14 of FIG. 2 may correspond to the transmission efficiency of the MCS table of FIG. For example, in FIG. 2, the transmission efficiency when the CQI index is '2' may correspond to the transmission efficiency when the MCS index is '0' in FIG. The relationship between FIG. 2 and FIG. 3 can be summarized as shown in FIG.

FIG. 5 shows BLER (Block Error Rate) performance for 15 transmission efficiencies used in the CQI.

The general LTE mobile station and the MTC mobile station can be distinguished using UE category and UE capability RRC (Radio Resource Control) messages. Compared to general LTE terminals, some MTC terminals may need to operate at 20 dB improved coverage, so that a relatively large amount of transmission resources can be used.

FIG. 6 shows the signal to noise ratio (SNR) gain for each repetition count. For example, considering the improved coverage of 20 dB, 10 * log ₁₀ (100) = 20 dB, it is necessary to repeat the conventional codeword 100 times in order to obtain 20 dB gain, Resources should be used.

Since the increase in the number of iterations is closely related to the amount of required transmission resources, the BS must check the level of geometry of the MTC terminal within its coverage to prevent waste of transmission resources.

Even if the base station can not confirm the geometric level of the MTC terminal and the MTC terminal is located at the same geometric level as the general LTE terminal, Can be used.

In addition, even if the base station can know the approximate geometric level of the MTC terminal, when using the conventional CQI table as shown in FIG. 2, the MTC terminal located in the improved coverage always has the CQI index '0' range ', the BS may not be able to perform channel-dependent scheduling for the MTC terminal. In other words, there is only one channel feedback for the area in the extended coverage, and the MTC terminal, which is slightly out of the coverage of a typical LTE terminal, will always use more transmission resources than needed by 20 dB improved coverage.

Hereinafter, a technique for transmitting channel information using different CQI tables according to the geometry of the MTC terminal will be described. Using different CQI tables according to the MTC terminal may have an advantage in terms of transmission resource efficiency.

For example, to successfully transmit data for a 3 dB extended coverage area, approximately twice as much transmission resources should be used, and for data coverage of 20 dB extended coverage area, approximately 100 times transmission resources should be used . Therefore, as the extended coverage is subdivided, the transmission resources can be efficiently used.

The wireless communication system including the base station and the terminal may store at least two preset CQI tables. One of the at least two CQI tables may be the conventional CQI table shown in FIG. For example, the wireless communication system may include a new CQI table (hereinafter referred to as a 'second CQI table') that can be applied in the conventional CQI table (hereinafter referred to as a 'first CQI table'Quot; table ") can be used.

CQI First of the table setting method Example

7 is a flowchart showing a first embodiment of the CQI table setting method of the present invention.

Referring to FIG. 7, the terminal (e.g., MTC terminal) checks its geometry and determines whether it is located in general coverage or extended coverage (S710).

When it is determined that the UE is located in the extended coverage, the UE feeds back the index '0' (i.e., 'out of range') of the first CQI table to the base station in the first CQI feedback transmission (S720).

The BS receiving the index '0' of the first CQI table determines that the UE is located in the extended coverage, and transmits control information indicating that the UE should use the second CQI table (S730). The control information may be transmitted via a downlink control channel (PDCCH or EPDCCH) or through an RRC signaling message.

Then, the terminal and the base station use the second CQI table when transmitting and receiving the subsequent CQI feedback (S740).

On the other hand, when the UE is located in the general coverage, the UE can always perform the CQI feedback using the first CQI table.

The channel state may be changed during communication between the terminal and the base station, and the geometry of the terminal may be changed to expanded coverage. In other words, while the UE is performing CQI feedback with an index that is not '0' in the first CQI table, the UE can feed back the index '0' of the first CQI table by changing the channel status. In this case, the base station can instruct the terminal to use the second CQI table through the above process.

In this embodiment, in a wireless communication system, a first CQI table can be used as a table for channel state feedback, and when a UE is located in an extended coverage and channel state information can not be represented by a first CQI table, If the CQI index is '0'('out of range'), a second CQI table may be used for channel state feedback.

CQI The second of the table setting method Example

8 is a flowchart showing a second embodiment of the CQI table setting method of the present invention.

Referring to FIG. 8, the terminal (e.g., MTC terminal) checks its geometry and determines whether it is located in general coverage or extended coverage (S810).

When it is determined that the terminal is located in the extended coverage, the terminal transmits information indicating that the terminal is located in the extended coverage to the base station (S820). Information indicating that the terminal is located in the extended coverage may be transmitted to the base station before the terminal transmits the initial CQI feedback. Information indicating that the terminal is located in the extended coverage can be delivered through signaling using a one-bit indicator that allows the terminal to distinguish general LTE coverage from extended coverage. Alternatively, the information indicating that the UE is located in the extended coverage may be implicitly delivered through signaling that differentiates the transmission resources of the physical channel according to coverage.

The terminal and the base station use the second CQI table since they transmit / receive the initial CQI feedback (S830).

When the terminal is located in the general LTE coverage and the terminal transmits information indicating that the terminal is located in the general LTE coverage to the base station, the terminal can perform CQI feedback using the first CQI table.

When the UE detects that its coverage is changed from the general LTE coverage to the extended coverage while the UE is performing the CQI feedback using the first CQI table, the UE updates the index of the first CQI table by changing the channel status, 0 'can be fed back. In this case, the BS can instruct the MS to use the second CQI table. The control information may be transmitted via a downlink control channel (PDCCH or EPDCCH) or through an RRC signaling message.

The terminal and the base station use the second CQI table when transmitting and receiving CQI feedback thereafter.

Hereinafter, an embodiment for configuring the second CQI table will be described.

Second CQI First of the table configuration method Example

In the first embodiment of the second CQI table configuration method, a terminal (for example, an MTC terminal) located in the extended coverage can construct a new CQI table (second CQI table) to transmit channel information. Various methods of increasing the number of transmission resources, such as repetition transmission and TTI (Transmission Time Interval) bundling, may be considered to achieve data transmission in the extended coverage area. Such a method can reduce the coding rate. The ratio of the number of transmission resources to be increased is defined as a parameter a, and a new CQI table (second CQI table) can be constructed as shown in FIG. 9 using the parameter a.

In FIG. 9, y may select one of the transmission efficiency values that can be considered when transmitting data in normal LTE coverage (see FIG. 2), and x may be a code rate multiplied by 1024 to configure the transmission efficiency . Transmission efficiency can be defined as the minimum transmission efficiency value of general LTE coverage. For example, referring to FIG. 2, it is possible to use y = 0.1523, x = 78 based on the minimum transmission efficiency of the first CQI table. Or, referring to FIG. 3, it is possible to use y = 0.2344 and x = 120 based on the transmission efficiency corresponding to the MCS index.

Once the values of x and y are determined, the rate of increase α _i of the transmission resource can be defined for each CQI index i so that the extended coverage can be subdivided. When α _i is defined, the link performance gains corresponding to the adjacent CQI indexes can be configured to have a relatively even difference.

At least one CQI index in the second CQI table may be defined to be able to feed back the case of being out of extended coverage. For example, in FIG. 9, the CQI index '0' may indicate 'out of range'.

Also, the CQI index '15' may indicate 'Higher SE range'. That is, the CQI index '15' may indicate that the UE is located in the coverage of the general LTE UE. When the base station receives the CQI index '15' of the second CQI table from the terminal, the base station can transmit information indicating the use of the first CQI table to the terminal.

FIG. 10 shows an example of a second CQI table according to the present embodiment, and FIG. 11 shows BLER performance for 14 transmission efficiencies used in the CQI of FIG.

In Fig. 10, x = 78 and y = 0.1523, and α _i is 100, 71.5, 51.5, 37, 26.5, 19, 14, 10, 7.5, 5.5, 4, 3, 2 and 1.5 for i = 1 to 14 . Referring to FIG. 11, it can be seen that the difference in the required SNR values for adjacent CQI indexes in the extended coverage area is set at relatively equal intervals.

Second CQI The second of the table configuration method Example

FIG. 12 shows a CQI table according to the second embodiment of the second CQI table configuration method.

Referring to FIG. 12, in the second embodiment of the second CQI table configuration method, the CQI indexes 0 to 12 of the second CQI table can be configured in a manner similar to the first embodiment. That is, the CQI index '0' may indicate 'out of range'. The CQI indexes 1 to 12 may be configured by selecting values of x, y, and? _I such that link performance gains corresponding to adjacent CQI indexes are configured to have a comparatively uniform difference.

Meanwhile, the CQI indexes 13 to 15 of the second CQI table can be set to indicate CQI feedback corresponding to the minimum transmission efficiency for each modulation order. That is, the CQI index '13' indicates that the transmission efficiency is at least 0.1523 with QPSK, the CQI index '14' indicates 16QAM at least the transmission efficiency is 1.4766, and the CQI index '15' indicates 64QAM at least the transmission efficiency is 2.7305 have. That is, the CQI index '13' indicates that the CQI feedback can be performed using the CQI index (indexes 1 to 6) corresponding to QPSK in the first CQI table, and the CQI index '14' The CQI index '15' indicates that the CQI index corresponding to 64QAM (index 10 to 15) in the first CQI table is used, and the CQI index ' Lt; RTI ID = 0.0 > CQI < / RTI > feedback.

In this case, if the UE feeds back one of the CQI indexes 13 to 15 of the second CQI table, the BS can determine that the UE is located in the coverage of the general LTE UE, and transmit the CQI feedback The control information can be transmitted. Also, before the UE performs the CQI feedback using the first CQI table, the base station can grasp the approximate geometry of the UE. The base station can use this to more efficiently allocate resources.

FIG. 13 shows an example of a second CQI table according to the present embodiment, and FIG. 14 shows BLER performance for 12 transmission efficiencies used in the CQI of FIG.

In FIG. 13, x = 78 and y = 0.1523, and? _I is 100, 68, 46, 31.5, 21.5, 14.5, 10, 6.5, 4.5, 3, 2 and 1.5 for i = 1-12. Referring to FIG. 14, it can be seen that the difference in the required SNR values for the adjacent CQI indexes in the extended coverage area is set at relatively equal intervals.

Second CQI The second of the table configuration method Example

15 shows a CQI table according to the third embodiment of the second CQI table configuration method.

In this embodiment, the second CQI table may be configured to include both general LTE coverage and extended coverage. Therefore, the UE located in the MTC terminal or the extended coverage performs CQI feedback using the second CQI table, and the UE does not use the first CQI table and the second CQI table Can be used to perform CQI feedback.

Referring to FIG. 5, the required SNR of BLER = 0.1 for the CQI index '1' having the lowest transmission efficiency in the first CQI table is about -8 dB, and when the coverage is expanded by 20 dB, the required SNR is -28 dB .

In addition, since the required SNR of BLER = 0.1 for the CQI index '3' in the first CQI table is about -4 dB, transmission efficiency for eight CQI indexes is defined at intervals of 3 dB from -28 dB to -4 dB .

Also, since the SNR 3 dB gain has a repetition effect of twice, the rate of increase α _i of the transmission resource can be expressed by an exponential form of 2.

For the general LTE coverage, if the transmission efficiency for the CQI index is transmitted at the required SNR at 3 dB intervals, a value equal to or similar to the transmission efficiency (see FIG. 3) of the conventional specific MCS index can be set.

In the example of FIG. 15, the CQI indices 1 to 8 of the second CQI table are indexes that can be used when the UE is located in the extended coverage, and the CQI indexes 9 to 15 are used when the UE is located in general LTE coverage It can be indexed.

The CQI index '9' of the second CQI table corresponds to the index '2' of the MCS table, the CQI index '10' of the second CQI table corresponds to the index '5' of the MCS table, The index '11' corresponds to the index '8' of the MCS table, the CQI index '12' of the second CQI table corresponds to the index '12' of the MCS table, The CQI index '14' of the second CQI table corresponds to the index '19' of the MCS table, and the CQI index '15' of the second CQI table corresponds to the index '15' '.

Alternatively, the CQI index '9' of the second CQI table corresponds to the index '3' of the first CQI table, the CQI index '11' of the second CQI table corresponds to the index '6' of the first CQI table, The CQI index '13' of the second CQI table corresponds to the index '9' of the first CQI table and the CQI index '15' of the second CQI table corresponds to the index '12' of the first CQI table.

FIG. 16 shows BLER performance for 15 transmission efficiencies used in the CQI of FIG. Referring to FIG. 16, it can be seen that the difference in required SNR values for adjacent CQI indexes is set at 3 dB intervals.

17 is a flowchart illustrating a CQI transmission and reception method according to an embodiment of the present invention.

Referring to FIG. 17, the terminal 10 determines its own geometric level (S1710).

The terminal 10 that has determined the level of its own geometry transmits information on its own geometry level to the base station 20 (S1720).

In one example, the terminal 10 may transmit information on its own geometric level to the base station 20 using the CQI index of the first CQI table. When any one of the CQI indexes '1' to '15' of the first CQI table is transmitted, the base station 20 may determine that the terminal 10 is located in the general LTE coverage. When the CQI index '0' of the first CQI table is transmitted, the base station 20 may determine that the terminal 10 is located in the extended coverage.

In another example, the terminal 10 may send information to the base station 20 indicating that it is located in the extended coverage. This information may be transmitted using signaling including a one-bit indicator, or may be implicitly delivered using the transmission resources of the physical channel.

The base station 20 receives the information about the geometric level from the terminal 10 and transmits information indicating the one of the plurality of CQI tables to the terminal 10 based on the information about the geometric level in operation 1730.

When the base station 20 determines that the terminal 10 is located in the extended coverage, the base station 20 may transmit information indicating that the terminal 10 should perform CQI feedback using the second CQI table .

The second CQI table may indicate a lower transmission efficiency than the first CQI table.

In one example, the second CQI table includes a plurality of CQI indexes indicating a lower transmission efficiency in the extended coverage, an index indicating 'out of range', and a transmission efficiency included in the first CQI table At least one index that is < / RTI >

In another example, the second CQI table may be a table that is available in both general LTE coverage and extended coverage. That is, in the second CQI table, some CQI indexes are available indexes in extended coverage, and other CQI indexes may be indexes available in general LTE coverage.

On the other hand, when the base station 20 determines that the terminal 10 is located in the general LTE coverage, the base station 20 transmits information instructing the terminal 10 to perform CQI feedback using the first CQI table . For example, when the coverage of the terminal 10 is changed from the extended coverage to the general LTE coverage, the terminal 10 can transmit information indicating to perform CQI feedback using the first CQI table.

Upon receiving the information indicating one of the plurality of CQI tables, the terminal 10 selects a CQI table based on the information (S1740). When the terminal 10 receives a reference signal (e.g., CRS, CSI-RS, DM-RS, etc.) for channel state estimation from the base station 20 (S1750) The corresponding CQI index is determined in the selected CQI table (S1760), and the index determined by the base station 20 is transmitted (S1770).

18 is a flowchart illustrating a CQI transmission method of a UE according to an embodiment of the present invention.

Referring to FIG. 18, the terminal determines its own geometric level (S1810).

The terminal that has determined the level of its own geometry transmits information on its own geometry level to the base station (S1820).

In one example, the UE can transmit information on its own geometric level to the BS using the CQI index of the first CQI table. When any one of the CQI indexes '1' to '15' of the first CQI table is transmitted, the base station can determine that the UE is located in the general LTE coverage. When the CQI index '0' of the first CQI table is transmitted, the BS can determine that the UE is located in the extended coverage.

In another example, the terminal may send information to the base station informing that it is located in the extended coverage. This information may be transmitted using signaling including a one-bit indicator, or may be implicitly delivered using the transmission resources of the physical channel.

The terminal receives information indicating one of a plurality of CQI tables from the base station (S1830).

When the base station determines that the terminal is located in the extended coverage, the base station may transmit information instructing the terminal to perform CQI feedback using the second CQI table.

On the other hand, when the BS determines that the UE is located in the general LTE coverage, the BS can transmit information indicating that the UE should perform CQI feedback using the first CQI table. For example, if the coverage of the terminal is changed from extended coverage to general LTE coverage, the terminal may transmit information indicating to perform CQI feedback using the first CQI table.

Upon receiving the information indicating one of the plurality of CQI tables, the terminal selects the CQI table based on the information (S1840). When the terminal receives a reference signal (e.g., CRS, CSI-RS, etc.) for channel state estimation from the base station (S1850), the terminal determines a corresponding CQI index in the selected CQI table based on the reference signal S1860), and transmits the index determined by the base station (S1870).

19 is a flowchart illustrating a CQI transmission method of a UE according to an embodiment of the present invention.

Referring to FIG. 19, the base station receives information on the geometric level of the terminal from the terminal (S1910).

The base station transmits information indicating one of the plurality of CQI tables to the terminal (S1920).

Then, the base station transmits a reference signal (e.g., CRS, CSI-RS, etc.) for channel state estimation to the base station (S1930) and receives the corresponding CQI index from the selected CQI table determined based on the reference signal (S1940).

20 is a block diagram showing a configuration of a terminal according to an embodiment of the present invention. 20, the terminal 2000 includes a controller 2010, a transmitter 2020, and a receiver 2020.

The control unit 2010 can determine the level of the geometry of the terminal.

The transmitter 2020 can transmit information on the geometry level of the terminal to the base station.

In one example, the transmitter 2020 can transmit information on the geometry level of the CQI to the base station using the CQI index of the first CQI table. When any one of the CQI indexes '1' to '15' of the first CQI table is transmitted, the base station can determine that the UE is located in the general LTE coverage. When the CQI index '0' of the first CQI table is transmitted, the BS can determine that the UE is located in the extended coverage.

In another example, the transmitter 2020 may send information to the base station informing that the terminal is located in the extended coverage. This information may be transmitted using signaling including a one-bit indicator, or may be implicitly delivered using the transmission resources of the physical channel.

The receiving unit 2030 can receive information indicating one of a plurality of CQI tables from the base station (S1830).

After receiving the information indicating one of the plurality of CQI tables, the control unit 2010 selects the CQI table based on the information. When the receiving unit 2030 receives a reference signal (e.g., CRS, CSI-RS, etc.) for channel state estimation from the base station, the control unit 2010 obtains a corresponding CQI index in the selected CQI table based on the reference signal And the transmission unit 2020 transmits the index determined by the base station.

21 is a flowchart showing a configuration of a base station according to an embodiment of the present invention. 21, the base station 2100 includes a control unit 2100, a transmitting unit 2120, and a receiving unit 2130.

The receiving unit 2130 can receive information on the geometric level of the terminal from the terminal.

The control unit 2110 selects one of the plurality of CQI tables based on the information about the geometry level of the terminal, and the transmitting unit 2120 can transmit information indicating one of the plurality of CQI tables to the terminal.

The transmitting unit 2120 transmits a reference signal (e.g., CRS, CSI-RS, etc.) for channel state estimation to the UE, and the receiving unit 2130 receives the reference signal from the selected CQI table determined based on the reference signal. Lt; / RTI >

The table presented in the above embodiment is merely an example, and the present invention is not limited thereto. Although the above embodiment describes two CQI tables including the first CQI table and the second CQI table, the present invention is not limited to this, and it is also possible to use three or more CQI tables. Although the above embodiment describes the case of the MTC terminal as an example, the present invention can also be applied to terminals other than the MTC terminal. For example, when a general terminal other than the MTC terminal feeds back the CQI index '0' ('out of range') of the conventional CQI table to the base station, the base station uses a CQI table other than the conventional CQI table, Feedback can be performed.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and portions of the standard documents are added to or contained in the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

Claims

A channel quality information transmission method executed in a terminal of a wireless communication system,
Determining a geometry level of the terminal;
Selecting a CQI table corresponding to a geometry level of the terminal among a plurality of channel quality information (CQI) tables;
Receiving a reference signal for estimation of a channel condition from a base station;
Determining a corresponding CQI index in the selected CQO table based on the reference signal; And
And transmitting the determined CQI index to the base station.

The method according to claim 1,
And transmitting information on the geometry level of the terminal to the base station.

The method according to claim 1,
Further comprising the step of receiving information indicating the selected CQI table from the base station.

The method according to claim 1,
Transmitting an index indicating 'out of range' in the first CQI table to the base station; And
Further comprising the step of receiving information indicating a second CQI table indicating an efficiency lower than that of the first CQI table from the base station.

The method according to claim 1,
Wherein the plurality of CQI tables include a first CQI table and a second CQI table indicating an efficiency lower than the first CQI table,
Wherein the second CQI table includes a CQI index indicating 'out of range' and a CQI index indicating that the first CQI table is used.

A method for receiving channel quality information performed at a base station of a wireless communication system,
Receiving an index indicating 'out of range' in a first CQI table from a terminal;
Transmitting information indicating a second CQI table indicating an efficiency lower than the first CQI table to the UE;
Transmitting a reference signal for channel state estimation to the terminal; And
And receiving a CQI index determined in the CQI table indicated by the terminal.

The method according to claim 6,
Wherein the second CQI table includes a CQI index indicating 'out of range' and a CQI index indicating that the first CQI table is used.

A terminal for transmitting channel quality information to a base station,
A controller for determining a geometry level of the terminal and selecting a CQI table corresponding to a geometric level of the terminal among a plurality of channel quality information (CQI) tables;
A receiver for receiving a reference signal for estimating a channel state from the base station; And
And a transmitter for transmitting a CQI index determined in the selected CQO table to the base station based on the reference signal.

9. The method of claim 8,
Wherein the transmitter further transmits information on the geometry level of the terminal to the base station.

9. The method of claim 8,
Wherein the receiver further receives information indicating the selected CQI table from the base station.

9. The method of claim 8,
The transmitter further transmits an index indicating 'out of range' in the first CQI table to the base station,
Wherein the receiver further receives information indicating a second CQI table indicating an efficiency lower than the first CQI table from the base station.

9. The method of claim 8,
Wherein the plurality of CQI tables include a first CQI table and a second CQI table indicating an efficiency lower than the first CQI table,
Wherein the second CQI table includes a CQI index indicating 'out of range' and a CQI index indicating using the first CQI table.

A base station for receiving channel quality information from a terminal,
A receiver for receiving an index indicating 'out of range' in the first CQI table from the terminal; And
And a transmitter for transmitting information indicating a second CQI table indicating an efficiency lower than that of the first CQI table to the terminal,
Wherein the transmitter further transmits a reference signal for estimating a channel state to the terminal,
Wherein the receiver further receives a CQI index determined in the CQI table indicated by the terminal.

14. The method of claim 13,
Wherein the second CQI table includes a CQI index indicating 'out of range' and a CQI index indicating using the first CQI table.