KR102091714B1 - Method and apparatus for transmission and reception of 256QAM in wireless mobile systems - Google Patents

Abstract

A signal transmission / reception method in a base station of a communication system according to an embodiment of the present specification includes receiving a signal including modulation information supported by a terminal; Transmitting a signal configured to receive data through a specific modulation method to the terminal based on the received signal; Receiving an uplink control channel from the terminal; And determining a channel quality indicator (CQI) analysis method through the received uplink control channel. According to one embodiment of the present specification, data can be transmitted and received using a 256QAM in a mobile communication system, and accordingly, there is an effect of transmitting more data in a faster time. In addition, as a communication method and apparatus using 256QAM compatible with the existing wireless communication system is provided, there is an effect of improving user convenience.

Description

Method and apparatus for transmitting and receiving 256QAM in a wireless mobile communication system {Method and apparatus for transmission and reception of 256QAM in wireless mobile systems}

The present invention relates to a method and apparatus for transmitting and receiving a signal modulated with 256QAM (Quadrature Amplitude Modulation) in a wireless mobile communication system.

Mobile communication systems have evolved from high-speed, high-quality wireless packet data communication systems to provide data services and multimedia services, away from the initial voice-oriented services. Recently, 3GPP's High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), Long Term Evolution Advanced (LTE-A), High Rate Packet Data (HRPD) of 3GPP2, and IEEE Various mobile communication standards such as 802.16 were developed to support high-speed, high-quality wireless packet data transmission services. In particular, the LTE system is a system developed to efficiently support high-speed wireless packet data transmission, and utilizes various wireless access technologies to maximize the capacity of the wireless system. The LTE-A system is an advanced wireless system of the LTE system and has improved data transmission capability compared to LTE.

The LTE generally refers to base station and terminal equipment corresponding to Release 8 or 9 of the 3GPP standard group, and LTE-A refers to base station and terminal equipment corresponding to Release 10 of the 3GPP standard group. The 3GPP standards group is based on this even after standardization of the LTE-A system and is standardizing on subsequent releases with improved performance.

On the other hand, in recent years, for efficient communication, a method has been proposed in which a terminal measures interference and reports it to a base station, and determines a signal transmitted by the base station to the terminal based on the channel state accordingly. Existing 3rd and 4th generation wireless packet data communication systems, such as HSDPA, HSUPA, HRPD, and LTE / LTE-A, adaptive modulation and coding (AMC) method and channel adaptive scheduling to improve transmission efficiency Use techniques such as methods. Using the AMC method, the transmitter can adjust the amount of data to be transmitted according to the channel condition. That is, if the channel condition is not good, the amount of data to be transmitted is reduced to set the probability of reception error to a desired level, and if the channel condition is good, the amount of data to be transmitted is increased to meet the desired level of error and effectively transmit a lot of information. When the channel-sensitive scheduling resource management method is used, the system capacity increases compared to allocating and servicing a channel to a user because the transmitter selectively serves a user with excellent channel status among several users. This increase in capacity is called a multi-user diversity gain. In short, the AMC method and the channel-sensitive scheduling method are methods in which appropriate modulation and coding schemes are applied at a time when it is determined to be most efficient by receiving partial channel state information from a receiver. Based on the AMC method and the channel-sensitive scheduling method, a method capable of transmitting and receiving a large amount of data at high speed is required.

An object of the present invention is to provide a channel quality indicator (CQI) transmission and reception method supporting 256QAM in a mobile communication system based on the LTE-A system, and a modulation and coding scheme (MCS) transmission and reception method in scheduling control information. .

In order to achieve the above-described problem, a method of transmitting and receiving a signal at a base station of a communication system according to an embodiment of the present specification includes receiving a signal including modulation information supported by a terminal; Transmitting a signal configured to receive data through a specific modulation method to the terminal based on the received signal; Receiving an uplink control channel from the terminal; And determining a channel quality indicator (CQI) analysis method through the received uplink control channel.

A signal transmission / reception method in a terminal of a communication system according to another embodiment of the present specification includes transmitting a signal including modulation information supported by the terminal to a base station; Receiving a signal including a setting to transmit data through a specific modulation method from the base station based on the transmitted signal; And transmitting an uplink control channel to the base station, wherein the base station determines a channel quality indicator (CQI) analysis method through the received uplink control channel.

A base station of a communication system according to another embodiment of the present specification receives a signal including modulation information supported by a terminal, and sets a signal configured to receive data through a specific modulation method to the terminal based on the received signal. Transmitting and receiving unit for transmitting and receiving an uplink control channel from the terminal; And a control unit for determining a channel quality indicator (CQI) analysis method through the received uplink control channel.

A terminal of a wireless communication system according to another embodiment of the present specification is a transceiver that can transmit and receive signals with a base station; And transmitting a signal including modulation information supported by the terminal to a base station by controlling the transmission / reception unit, and receiving a signal including a setting for transmitting data through a specific modulation method from the base station based on the transmitted signal. And a control unit transmitting an uplink control channel to the base station, wherein the base station determines a channel quality indicator (CQI) analysis method through the received uplink control channel.

A method of transmitting and receiving a signal at a terminal of a communication system according to another embodiment of the present specification includes receiving a reference signal from a base station; Determining a RI (Rank Indicator) value based on the received reference signal; Determining a modulation method to be used for signal transmission and reception with the base station according to the determined RI value; And transmitting and receiving signals to and from the base station using the determined modulation method.

A method of transmitting and receiving a signal at a base station of a communication system according to another embodiment of the present specification includes transmitting a reference signal to a terminal; Receiving a RI (Rank Indicator) value determined based on the reference signal from the terminal; Determining a modulation method to be used for signal transmission and reception with the terminal based on the received RI value; And transmitting and receiving signals to and from the terminal using the determined modulation method.

According to one embodiment of the present specification, data can be transmitted and received using a 256QAM in a mobile communication system, and accordingly, there is an effect of transmitting more data in a faster time. In addition, as a communication method and apparatus using 256QAM compatible with the existing wireless communication system is provided, there is an effect of improving user convenience.

1 is a diagram showing time and frequency resources in an LTE / LTE-A system.
FIG. 2 is a diagram illustrating radio resources of 1 subframe and 1 RB, which are minimum units that can be scheduled in a downlink in an LTE / LTE-A system.
FIG. 3 is a diagram illustrating that a terminal transmits channel quality indicator (CQI), which is one of channel state information, according to signal energy and interference intensity measured by the terminal.
4 is a diagram for a multi-cell mobile communication system composed of a plurality of cells.
5 is a diagram showing a modulation method that can be used in the embodiment.
6 is a diagram illustrating an AMC between a terminal and a base station according to an embodiment.
7 is a diagram illustrating a HOMI transmitted by a terminal according to an embodiment.
8 is a diagram illustrating a case in which the CQI table switching method 3 proposed in the embodiment is applied.
9 is a diagram illustrating a method for a base station to switch a CQI table according to an embodiment.
10 is a diagram illustrating a method for a terminal to switch a CQI table according to an embodiment.
11 is a diagram for a method of differently analyzing an MCS index according to whether a base station has fallback transmission according to an embodiment.
12 is a diagram illustrating a method of differently interpreting an MCS index according to whether a terminal transmits fallback according to an embodiment.
13 is a diagram showing the components of a base station proposed in an embodiment.
14 is a diagram showing components of a terminal proposed in an embodiment.
15 is a diagram for a base station to determine a CQI analysis method according to a channel state according to an embodiment.
16 is a diagram for a UE to determine a CQI reporting method according to an embodiment.
17 is a diagram illustrating a structure of PUCCH format 2 / 2a / 2b in an LTE system using a normal cyclic prefix.
18 is a diagram illustrating a structure of PUCCH format 2 in an LTE system using an extended cyclic prefix.
19 is a diagram illustrating a method of switching a CQI table based on a cyclic prefix length in the CQI switching method 4 proposed in this specification from a terminal perspective.
20 is a diagram illustrating a method of switching a CQI table based on a cyclic prefix length and the most recent RI value reported by a terminal to a base station in CQI switching method 4 proposed in this specification from a terminal perspective.
21 is a diagram illustrating a method of switching a CQI table based on the most recent RI value reported by the terminal to the base station in the CQI switching method 5 proposed in the present specification from the terminal perspective.
22 is a diagram illustrating a method of switching a CQI table based on the maximum number of layers that can be supported between a base station and a terminal in the CQI switching method 6 proposed in the embodiment of the present specification from a terminal perspective.
23 is a diagram illustrating an MCS notification method based on the maximum number of supported layers between a base station and a terminal in the MCS notification method 3 proposed in an embodiment of the present disclosure from a base station perspective.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the description of the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification.

In addition, in describing the embodiments of the present invention in detail, the OFDM-based wireless communication system, especially the 3GPP EUTRA standard, will be the main target, but the main subject matter of the present invention is another communication system having a similar technical background and channel type. Edo can be applied with a slight modification within a range that does not depart significantly from the scope of the present invention, which will be possible by the judgment of a person skilled in the technical field of the present invention.

In this specification, we propose a method to effectively support 256QAM, which can transfer 8 bits of information, in an LTE-based mobile communication system using one modulation symbol.

The adaptive modulation and coding (AMC) method may also include a function of determining the number or rank of spatial layers of a transmitted signal when used with a multiple input multiple output (MIMO) transmission method. In this case, the AMC method can determine the optimal data rate and consider how many layers will be transmitted using MIMO without simply considering the encoding rate and the modulation method.

Recently, a study to convert CDMA (Code Division Multiple Access), which is a multiple access method used in the 2nd and 3rd generation mobile communication systems, to an orthogonal frequency division multiple access (OFDMA) in the next generation system has been actively conducted. 3GPP and 3GPP2 began to standardize on evolutionary systems using OFDMA. It is known that capacity increase can be expected in the OFDMA method compared to the CDMA method. One of several causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed. Just as a channel gains capacity through a channel-sensitive scheduling method according to a characteristic that changes with time, more capacity gain can be obtained when a channel utilizes different characteristics depending on frequency.

1 is a diagram showing time and frequency resources in an LTE / LTE-A system.

Referring to FIG. 1, radio resources transmitted by a base station (or 'eNB') to a terminal are divided into resource block (RB) units on a frequency axis and subframe units on a time axis. The RB is generally composed of 12 subcarriers in the LTE / LTE-A system and occupies a band of 180 kHz. On the other hand, a subframe (subframe) generally consists of 14 OFDM symbol periods in the LTE / LTE-A system and occupies a time period of 1 msec. In performing the scheduling, the LTE / LTE-A system may allocate resources in subframe units on the time axis and RB units on the frequency axis.

FIG. 2 is a diagram illustrating radio resources of 1 subframe and 1 RB, which are minimum units that can be scheduled in a downlink in an LTE / LTE-A system.

The radio resource shown in FIG. 2 consists of one subframe on the time axis and one RB on the frequency axis. This radio resource consists of 12 subcarriers in the frequency domain and 14 OFDM symbols in the time domain to have a total of 168 natural frequencies and time locations. In LTE / LTE-A, each natural frequency and time location in FIG. 2 is referred to as a RE (resource element).

A plurality of different types of signals may be transmitted to the radio resource shown in FIG. 2 as follows.

1. CRS (Cell Specific RS): a reference signal transmitted for all UEs belonging to one cell

2. DMRS (Demodulation Reference Signal): a reference signal transmitted for a specific terminal

3. PDSCH (Physical Downlink Shared Channel): A data channel transmitted through a downlink, used by a base station to transmit traffic to a terminal, and a RE in which a reference signal is not transmitted in the data region of FIG. 2 is used. Sent by

4. CSI-RS (Channel Status Information Reference Signal): This is a reference signal transmitted for terminals belonging to one cell, and is used to measure the channel status. Multiple CSI-RSs can be transmitted to one cell.

5. Other control channels (PHICH (Physical Hybrid-ARQ Indicator Channel), PCFICH (Physical Control Format Indicator Channel), PDCCH (Physical Downlink Control Channel)): The terminal receives the control information needed to receive the PDSCH (Physical Downlink Shared Channel) ACK / NACK transmission for providing or operating HARQ for uplink data transmission

In addition to the above signals, in the LTE-A system, zero power CSI-RS can be set so that CSI-RSs transmitted by different base stations can be received without interference from terminals of a corresponding cell. The zero power CSI-RS (muting) can be applied at a location where the CSI-RS can be transmitted, and in general, the UE skips the radio resource and receives a traffic signal. In LTE-A system, zero power CSI-RS (muting) is also called muting in another term. Because of the nature of zero power CSI-RS (muting), it is applied to the position of CSI-RS and the transmission power is not transmitted.

In FIG. 2, CSI-RS may be transmitted using a part of positions indicated by A, B, C, D, E, E, F, G, H, I, J according to the number of antennas transmitting CSI-RS. You can. In addition, zero power CSI-RS (muting) can also be applied to some of the positions indicated by A, B, C, D, E, E, F, G, H, I, and J. In particular, CSI-RS can be transmitted in 2, 4, or 8 REs depending on the number of antenna ports being transmitted. When the number of antenna ports is 2, CSI-RS is transmitted to half of a specific pattern in FIG. 2, and when the number of antenna ports is 4, CSI-RS is transmitted to all of the specific patterns, and when the number of antenna ports is 8, two patterns are used. CSI-RS is transmitted. On the other hand, in case of zero power CSI-RS (muting), it is always done in one pattern unit. That is, zero power CSI-RS (muting) can be applied to a plurality of patterns, but if CSI-RS and the location do not overlap, it cannot be applied to only a part of one pattern. However, it can be applied to a part of one pattern only when the position of CSI-RS and the position of zero power CSI-RS (muting) overlap.

In a cellular system, a reference signal must be transmitted to measure a downlink channel state. In the case of the Long Term Evolution Advanced (LTE-A) system of 3GPP, the UE measures a channel state between the base station and itself using a CSI-RS (Channel Status Information Reference Signal) transmitted by the base station. In the channel state, several factors should be basically considered, and this includes the amount of interference in the downlink. The amount of interference in the downlink includes an interference signal generated by an antenna belonging to an adjacent base station, thermal noise, and the like, and is important for the UE to determine the channel condition of the downlink. For example, when a transmitting antenna transmits from a single base station to a single terminal, the terminal determines the energy per symbol that can be received in the downlink from the reference signal received from the base station and the amount of interference to be simultaneously received in the section receiving the corresponding symbol. You have to decide Es / Io by judging. The determined Es / Io is notified to the base station so that the base station can determine which data transmission rate is to be performed by the base station in the downlink.

FIG. 3 is a diagram illustrating that a terminal transmits channel quality indicator (CQI), which is one of channel state information, according to signal energy and interference intensity measured by the terminal.

In FIG. 3, channel estimation is performed by measuring a downlink reference signal such as a terminal CSI-RS, and the Es (reception signal energy) according to a radio channel such as 300 is calculated using this. In addition, the terminal calculates the strength of interference and noise, such as 310, using a downlink reference signal or separate resources for interference and noise measurement. In LTE, a CRS, a downlink reference signal, is used for interference and noise measurement, or an interference measurement resource is set by a base station to a terminal, so that signals measured in the radio resource are assumed to be interference and noise. Using the received signal energy, the intensity of interference and noise obtained in this way, the terminal determines the maximum data transmission speed that can be received at a constant success rate from the corresponding signal-to-interference and noise ratio and notifies the base station. . The base station that the terminal is notified of the maximum data transmission rate that can be supported by the signal-to-interference and noise ratio uses this to determine the actual data transmission rate of the downlink data signal to be transmitted to the terminal. In this way, the maximum data transmission rate that a terminal can receive at a constant success rate by a terminal is called a channel quality indicator (CQI) in the LTE standard. In general, since the radio channel changes with time, the terminal periodically notifies the base station of the CQI or whenever the base station requests it from the base station. The request from the base station to the terminal may be performed through one or more of periodic and aperiodic methods.

4 is a diagram for a multi-cell mobile communication system composed of a plurality of cells.

Referring to FIG. 4, in a multi-cell mobile communication system, macro cells performing high output transmission and small cells performing low output transmission may be mixed as shown in FIG. 4. At this time, the service area or coverage area in which each cell performs transmission and reception to the terminal varies according to the transmission power of the corresponding cell. For example, the coverage area generated by the transmitter 400 transmitting a high power signal has a wide area such as 410, while the coverage area generated by the transmitter 420 transmitting a low power signal has a narrow area such as 430. As shown in FIG. 4, macro cells and small cells that are mixed within a limited area may generate mutual interference and degrade each performance. The small cell in this patent includes a cell having a separate cell ID in a separate multi-cell system and a remote radio head (RRH) that has the same cell ID as a macro cell and is dispersed within the coverage area of the corresponding macro cell.

In general, in a mobile communication system, macro cells and small cells are used for different purposes. In the case of a macro cell, it is used to guarantee the mobility of a terminal or to solve a shadow area by using a point having a wide coverage. On the other hand, in the case of small cells, it is deployed in a densely populated area and is used to perform high-speed data transmission in limited areas. In particular, in the case of a small cell, it is often placed indoors, and at this time, the signal of the macro cell placed outdoors is effectively blocked, and the terminal may experience a very high signal-to-interference and noise ratio.

As mentioned above, a mobile communication system such as LTE improves system performance by using AMC to determine data transmission speed by adapting according to channel conditions. The AMC selects the highest data transmission rate that can be received while maintaining a constant reception success rate in consideration of the channel state experienced by the terminal among a plurality of data transmission rates defined by a plurality of modulation methods and data amounts, and transmits the data to the corresponding terminal. Table 1 summarizes the downlink data transmission rate using 6 RB bandwidth for AMC in LTE. More specifically, Table 1 shows a Modulation Coding Scheme (MCS) level of downlink data transmission with 6RB bandwidth.

In Table 1, a total of 29 MCS levels are defined, and each MCS index is defined by modulation order and transport block size. The transport block size corresponds to the size of the amount of information transmitted in a given bandwidth, and the unit is bits. That is, in Table 1, MCS index 28 means that a total of 4392 bits are transmitted in a bandwidth of 6RB (180kHz * 6 = 1080kHz). Modulation order means the number of bits carried on one modulation symbol when each transmitted modulation method is applied. LTE Release 11 and earlier releases support modulation orders 2, 4, and 6 as shown in Table 1 above.

5 is a diagram showing a modulation method that can be used in the embodiment.

Referring to FIG. 5, it is possible to consider using 256QAM of FIG. 5 in addition to modulation orders 2, 4, and 6 used in LTE. As a result, the use of 256QAM has the following effects.

-Higher data transmission rate can be realized by using higher modulation order

-Optimized transmission / reception for a wider range of received signal energy-to-noise and interference ratios using more modulation orders

In LTE Release 11 and earlier releases, data transmission and reception using QPSK, 16QAM, and 64QAM is performed as shown in FIG. 5 for modulation orders 2, 4, and 6. In general, a higher modulation order has the advantage of being able to transmit more data, but also has the disadvantage that a higher received signal energy to noise and interference ratio is required. Particularly, in the case of 256QAM of FIG. 5, sufficient reception performance can be supported only at a very high received signal energy to noise and interference ratio. It is also a disadvantage that the complexity of the receiver of the terminal increases to satisfy the received signal energy to noise and interference ratio. Noise is generated according to the number of quantization bits in the ADC (Analog to Digital Converter) of the terminal. In order to suppress this, the number of quantization bits must be increased, and additional complexity and power consumption of the terminal are inevitable.

There is an advantage that supporting more types of modulation orders can improve a system performance by supporting a wider range of received signal energy to noise and interference ratios. That is, compared to a system supporting only modulation order 2 and 4, a system supporting modulation order 2, 4, and 6 can support a wider range of received signal energy-to-noise and interference ratios, and the performance improvement effect is expected. You can. The following two problems exist in the problem of supporting more types of modulation orders in the LTE system.

-Increased amount of channel status information that the terminal notifies the base station

-The base station increases the amount of control channel information to notify the user of downlink transmission

6 is a diagram illustrating an AMC between a terminal and a base station according to an embodiment.

Referring to FIG. 6, an AMC between a terminal and a base station can be described in more detail to explain the above problem. The terminal receives the downlink reference signal CSI-RS transmitted from the base station at 600 and an interference measurement resource (IMR), which is a radio resource for measuring interference, as 610, and uses this to generate channel state information as 620. As information included in the channel state information generated by the terminal, CQI exists, and the CQI refers to a maximum data transmission speed that the terminal can support. In LTE Release 11 system, the CQI has 4 bits of information and is defined as the following table. More specifically, Table 2 below shows CQIs defined in LTE Release 11 and earlier releases.

It can be seen that the CQI defined in LTE Release 11 and the previous Release of Table 2 supports modulation up to 64QAM and 256QAM. That is, when using the above Table 2, the terminal can support the actual 256QAM, and there is no method to notify the base station even if the signal received with 256QAM can be decoded with the required reception performance because the channel state is good.

Another reason why 256QAM cannot be supported in LTE Release 11 is PDCCH / E-PDCCH (Physical Downlink Control Channel /), which is a control channel containing scheduling information for a data channel, PDSCH (Physical Downlink Shared Channel), from the base station to the UE. This is because 256QAM can be specified in the control information notified to the UE through the Enhanced Physical Downlink Control Channel. The terminal is informed of whether the PDSCH has been transmitted to it and in which modulation method the PDSCH has been transmitted by decoding the PDCCH / E-PDCCH and receiving the control information carried therein. The problem is that there is no function to notify 256QAM in the control information defined in Release 11. Table 1 summarizes the modulation order and the number of information bits of the PDSCH defined in LTE / LTE-A Release 11. The base station notifies the UE of the modulation order of the PDSCH and the number of bits of the information amount by notifying the UE of the modulation index value in Table 1 above. It can be seen that there is no MCS index specifying 256QAM.

As mentioned above, in order to support 256QAM in the downlink in LTE / LTE-A system, CQI must be newly defined. The method to newly define CQI to support 256QAM is as follows.

-New CQI definition method 1: Expand the scope of spectral efficieny designated by 4 bits of CQI

-New CQI definition method 2: CQI information amount is extended from 4 bits to 5 bits to support 256QAM

-New CQI definition method 3: The range of spectral efficiency indicated by CQI is variably operated to support up to 256QAM

The CQI definition method 1 proposed in the present specification is a method of using 4 bits like the conventional CQI, but allowing the CQI to designate up to 256QAM. As a result, in this method, in order to specify 256QAM, compared to the existing CQI definition method, less dense spectral efficiency is specified, so that channel state information is less accurate. Table 3 is a newly defined CQI table by applying CQI definition method 1.

Comparing Table 3 and Table 2, it can be seen that Table 3 added three CQI indexes specifying 256QAM after excluding three of the CQI indexes reporting the spectral efficiency of Table 2. However, the number of CQI indexes to be excluded may vary according to embodiments. The advantage of CQI definition method 1 is that the terminal can notify the base station to 256QAM by using 4 bits, but the accuracy of channel state information is relatively decreased as the average distance between spectral efficiencies specified by CQI indexes increases. It has the disadvantage of being. The CQI definition method 1 may be notified to the terminal of its application by upper layer signaling. That is, when the base station determines that a function capable of transmitting 256QAM is implemented and the terminal also determines that a function capable of receiving 256QAM is implemented, the base station notifies the UE to apply the CQI definition method 1 as higher layer signaling. . Conversely, the base station may notify the UE to switch from the CQI definition method 1 to the conventional CQI definition method using higher layer signaling.

The CQI definition method 2 proposed in this specification is to enlarge the information amount of the CQI from 4 bits to 5 bits. In this case, since the spectral efficiency that can be specified by the CQI is a total of 32, 256QAM can be supported without the disadvantage that the accuracy of channel state information is reduced compared to the above method 1. On the other hand, the disadvantage of Method 2 is that an additional 1 bit of information is required compared to the existing CQI. That is, since the UE needs to transmit 5 bit CQI in uplink instead of the existing 4 bit CQI in order to support method 2, additional uplink overhead and UE transmit power are inevitable.

The CQI definition method 3 proposed in the present specification is to adaptively change the CQI range designated by the CQI of the corresponding 4 bits, although the UE maintains the information amount of the CQI as 4 bits and the same.

According to an embodiment, in the CQI definition method 3, two CQI tables are basically operated. However, three or more CQI tables may be operated in other embodiments. In an embodiment, the first of the two CQI tables may use the conventional CQI table of Table 2, which cannot specify 256QAM. The second of the two CQI tables can use a CQI table that can specify 256QAM. Table 4 may be proposed as an example of a CQI table capable of designating 256QAM.

The CQI table in Table 4 is designed to support spectral efficiency assuming 256QAM at CQI indexes 11, 12, 13, 14, and 15. However, the number of CQI indexes specifying 256QAM may be differently set according to embodiments. In Table 4, R1, R2, R3, R4, and R5 are channel coding rates when 256QAM is applied, and S1, S2, S3, S4, and S5 are spectral efficiency when 256QAM is applied. In general, when supporting 256QAM, the spectral efficiency is higher than when supporting 64QAM. That is, the values of S1, S2, S3, S4, and S5 are higher than 5.5547 in Table 4 above. In order to notify spectral efficiency when using 256QAM, CQI indexes that designate low spectral efficiency for QPSK of Table 2 above may be excluded. As described above, when adaptively changing and using the CQI table in Table 2 and the CQI table in Table 4, the spectral efficiency value that the terminal can notify to the base station varies depending on which CQI table is used. That is, when the UE uses the CQI table of Table 2, the spectral efficiency of the low region can be notified to the base station, but the spectral efficiency of the high region corresponding to 256QAM cannot be notified to the base station.

The advantage of the CQI definition method 3 is that it can support 256QAM by using a 4 bit CQI, and unlike the CQI definition method 1, there is no problem that the accuracy of channel state information is deteriorated. On the other hand, CQI definition method 3, unlike CQI definition method 1 or CQI definition method 2, a method of switching between two CQI tables should be additionally introduced. In this specification, a method of switching between two CQI tables is proposed.

-CQI table switching method 1: Switching method using higher layer signaling

-CQI table switching method 2: Switching method using physical layer signaling

-CQI table switching method 3: downlink scheduling information and a switching method using ACK / NACK for this

The CQI table switching method 1 proposed in the present invention is performed using higher layer signaling. In this method, the UE initially uses the CQI table of Table 2, and when it is determined that it can support 256QAM as a result of measuring its downlink channel state, it notifies the base station using higher level signaling. After receiving the upper signaling of the terminal that it can support 256QAM, the base station determines whether to switch the CQI table to the corresponding terminal and notifies the terminal. Here, the process of determining whether the base station switches the CQI table to the UE may be omitted. If this process is omitted, the base station switches as requested by the terminal without a separate switching determination process. The use of the CQI table (second CQI table) of Table 4 and then switching to the CQI table (first CQI table) of Table 2 can also be accomplished by requesting the terminal to switch to the base station.

Another method of switching the CQI table using upper signaling is a method in which the base station determines whether to switch the CQI table based on the signal transmitted by the UE and notifies the UE using the higher signaling. According to an embodiment, the base station may determine whether to switch the CQI table by measuring the strength of the uplink signal of the terminal and notify the terminal to the terminal using higher level signaling. According to an embodiment, when it is determined that the base station is sufficiently close to the base station by measuring the reception strength of the signal transmitted by the terminal in the uplink, the base station signals the UE to use the second CQI table supporting 256QAM to the UE. You can notify the terminal by using. In addition to the method of measuring the reception strength of the signal transmitted by the terminal in the uplink, control information that the terminal notifies the base station in relation to the downlink state may be used. As the control information that the terminal notifies the base station regarding the downlink state, one or more of RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality) and CQI values that the UE measures and notifies by cell is used. You can. RSRP is a measure of the reception strength of a downlink reference signal transmitted from a specific cell, and RSRQ is a measurement in consideration of the reception strength and interference strength of a downlink reference signal transmitted from a specific cell. In addition, CQI is the maximum transmission data rate that the terminal can support in the downlink as mentioned above. RSRP, RSRQ, and CQI are all measured values of a downlink reference signal, and the terminal notifies the base station. The base station combines one or more of these values to determine whether the corresponding terminal is in a channel state capable of supporting 256QAM. .

As in the switching method 1, when the base station determines that the terminal should be switched to the first CQI table, the base station may notify the user of the switching using higher layer signaling.

In general, the upper layer signaling has an additional time delay in the transmission and reception process compared to the physical layer signaling. However, since the channel situation is changed from a situation in which 256QAM cannot be supported to a situation in which it can be supported, it is a phenomenon that occurs every tens of msec, rather than every msec, so it can be adequately switched to higher layer signaling.

The CQI table switching method 2 proposed in this specification may be performed using physical layer signaling.

The terminal periodically transmits to the base station which of the two CQI tables to be used in the uplink periodically using physical layer signaling. In the present invention, the physical layer signaling may be referred to as High Order Modulation Index (HOMI).

7 is a diagram illustrating a HOMI transmitted by a terminal according to an embodiment.

Referring to FIG. 7, the terminal periodically transmits HOMI, such as 700 and 740. The HOMI is defined as follows. In the first embodiment, the first CQI table indicates an existing CQI table, and the second CQI table indicates a CQI table capable of designating 256QAM according to an embodiment.

-HOMI = 0: CQI index is determined according to the first CQI table (Table 2) and transmitted.

-HOMI = 1: CQI index is determined according to the second CQI table (Table 4) and transmitted.

That is, when the terminal transmits the HOMI with a value of 0, it generates and transmits the CQI index at 710, 720, or 730 using the first CQI table. Accordingly, when the base station determines that the HOMI is 0, it is assumed that the base station generates and transmits a CQI index using the first CQI table until the next HOMI is received. Accordingly, when the base station determines that the HOMI of 700 is 0, the CQI indexes of 710, 720, and 730 are analyzed using the first CQI table. On the other hand, when the base station determines that the UE has transmitted the HOMI as 1, as in 740, the corresponding base station uses the second CQI table to interpret the CQI of 750. For example, when the base station determines that the HOMI of 700 is 0, when CQI index 12 is received at 710, it is interpreted as spectral efficiency corresponding to 64QAM using Table 2, whereas when CQI index 12 is received at 740, Using Table 4, it is interpreted as spectral efficiency corresponding to 256QAM.

In addition, the base station may transmit to the UE which of the two CQI tables to be used in downlink using physical layer signaling. The downlink transmitted by the base station to the terminal may be transmitted periodically or aperiodically. More specifically, the base station can measure the channel state and determine which of the CQI tables to use based on this. In addition, the base station may transmit information related to the CQI table used to the terminal. According to an embodiment, when it is determined that the determined channel state can use 256QAM, the base station may notify the terminal to use the second CQI table through physical layer signaling. One of the methods of notifying the UE to use either the first CQI table or the second CQI table through physical layer signaling is to use an MCS index value notifying the UE. The UE determines which CQI table to use based on whether the MCS level notified by the base station exceeds a certain level. Likewise, the base station can determine which CQI table the UE transmits is generated according to which CQI table based on which level the MCS level that the UE has notified has exceeded. For example, when the MCS that is the basis for determining which CQI table to use is '10', the UE applies the second CQI table to the CQI generated later when the base station notifies the MCS equal to or higher than the corresponding MCS. Similarly, the base station assumes that the CQI generated by the terminal is generated by the second CQI table when the MCS notified to the terminal is higher than '10'. The method of determining whether to switch based on the MCS as described above is to switch to the second CQI table when in a relatively good channel state and switch to the first CQI table when in a relatively low channel state. This method can be applied when the higher the MCS level represents, the higher the spectral efficiency, and the higher the MCS level, the higher the MCS level may be based on the spectral efficiency or the number of transport block size bits transmitted. have. In addition, a method for determining by using a part of control information included in downlink control information (DCI) that the base station notifies the UE using PDCCH or E-PDCCH may be defined.

The CQI table switching method 3 proposed in this specification does not use a separate higher layer signaling or physical layer signaling related to switching and implicitly determines CQI talbe switching based on a control signal defined in an existing LTE / LTE-A system. will be.

8 is a diagram illustrating a case in which the CQI table switching method 3 proposed in the embodiment is applied.

Referring to FIG. 8, switching is performed between the first CQI table and the second CQI table by using scheduling information transmitted by the base station and ACK / NACK transmitted by the UE. That is, the terminal observes the modulation order of the PDSCH transmitted to the base station within a predetermined time period. It can be assumed that the CQI table is switched when the modulation order of the PDSCH transmitted within this period and the ACK / NACK therefor satisfy the predetermined conditions. The base station also switches the method of interpreting the CQI transmitted by the terminal in response to the determination that the terminal switches in this way. As an embodiment of this, the UE using the first CQI table transmits ACK when the modulation order of the PDSCH scheduled to itself is 50% or higher during 50 msec time intervals and transmits ACK when 90% or higher of the PDSCH transmitted by 64 QAM. It is assumed that the CQI uses the second CQI table. On the other hand, the UE using the second CQI table transmits CQI when the modulation order of the PDSCH scheduled to itself during the period of 100 msec is less than 50% or 64QAM or less than 90% of the PDSCH transmitted with 64QAM, and then transmits ACK. Suppose to use the first CQI table. Numerical values used in the determination criteria may be determined differently according to embodiments.

In the CQI table switching method shown in FIG. 8, the base station and the terminal determine whether to switch the CQI table using a ratio of 64QAM among modulation orders of PDSCHs scheduled for a specific terminal and a ratio of ACK among ACK / NACK. In addition to this method, it is also possible to determine whether the CQI table is switched by considering only the ratio of 64QAM among the modulation orders of the PDSCH at the base station and the UE. That is, the UE switches to the second CQI table when the ratio of 64QAM is above a certain level when using the first CQI table, and switches to the first CQI table when the ratio of 64QAM is below a certain level when using the second CQI table.

When the CQI table switching method 2 or the CQI table switching method 3 is applied, when an error occurs in the base station or the terminal, the system performance may be degraded by interpreting the CQI transmitted by the terminal using the wrong CQI table. In preparation for such an error, a second CQI table supporting 256QAM that can reduce the effect of reception error may be proposed in Table 5 below.

The difference between Table 5 and Table 4 is that in Table 5, the spectral efficieny value specified by some CQI index is the same as the spectral efficieny value specified by some CQI index of the first CQI table. The value of the CQI Index specifying 256QAM proposed in the embodiment may be determined differently in other embodiments. That is, in Table 5 and Table 2, the modulation order and spectral efficiency specified by CQI index 15 in CQI index 5 are the same. Table 5 differs from Table 2 in that the CQI index specifying the low spectral efficiency region is changed to specify the spectral efficiency when 256QAM is used. For this reason, even if an error occurs in the process of receiving the HOMI from the base station, the base station misinterprets only when the terminal notifies the changed CQI index. That is, even if the base station incorrectly determines that the UE transmits HOMI = 1 as HOMI = 0, when the UE notifies the base station of CQI index 15 in CQI index 5 of 5, the CQI index is not misinterpreted. .

As mentioned above, another necessary for supporting 256QAM in the LTE system is to support the MCS notification method capable of designating 256QAM. In LTE Release 11 and earlier releases, the base station does not notify the UE that the PDSCH of 256QAM has been transmitted to the UE, and thus, 256QAM cannot be actually supported. A method of notifying that the PDSCH transmitted to the UE is modulated with 256QAM is as follows.

-MCS notification method 1 supporting 256QAM: Control information for notifying MCS is extended from 5 bits to 6 bits.

-MCS notification method supporting 256QAM 2: Linking the range of control information to notify MCS with CQI conversion

In the MCS notification method 1 supporting 256QAM, control information for notifying the MCS is extended from the existing 5 bits to 6 bits. In this case, 256QAM can be notified, but as the amount of control information of 1 bit increases, performance decreases or additional transmission energy is allocated to achieve the same performance as before.

In the MCS notification method 2 supporting 256QAM, the base station changes the MCS definition method as the terminal changes the CQI definition method. That is, when changing between two CQI tables according to the CQI definition method 3, when the UE generates and notifies the CQI using the first CQI table that does not support 256QAM, the base station transmits to the conventional MCS table shown in Table 1 above. Accordingly, an MCS index is created. In addition, the terminal also interprets the MCS index according to the conventional MCS table. On the other hand, if the UE generates and notifies by using the second CQI table supporting 256QAM, the base station generates an MCS index according to the MCS table supporting 256QAM. In addition, the terminal also interprets the MCS index according to the MCS table supporting 256QAM. Table 6 is an example of an MCS table supporting 256QAM. The MCS table in Table 6 may be determined differently in the Modulation Order, TBS Index, and TBS Size according to the MCS Index, which is designated according to an embodiment.

The MCS notification method 2 can also be applied when using the CQI definition method 1. When the base station notifies the UE to use the CQI definition method 1, the UE also changes the method of interpreting the MCS index notified by the base station to a method supporting 256QAM, and conversely, interprets the MCS index when notifying the base station to use the conventional CQI definition method. The method of changing is also a conventional method. Also, according to an embodiment, the CQI analysis method and the MCS analysis method may be determined as independent methods.

In the LTE system, the terminal is configured to support a transmission mode designated by the base station. In the Release 11 LTE system, a total of 10 transmission modes are supported, and each transmission mode has a difference depending on how to transmit a PDSCH using multiple antennas in the downlink. For example, transmission mode 9 supports MIMO transmission of PDSCH using up to 8 transmission antennas, and transmission mode 2 supports transmission diversity transmission of PDSCH using up to 4 transmission antennas. The transmission mode is specified separately for each terminal, and the format of control information that the terminal should receive varies depending on the transmission mode. In addition to the transmission mode and the LTE / LTE-A system, fallback transmission is also supported. The fallback transmission is designed to transmit data to a terminal having a poor channel condition. For example, if the downlink transmission method according to the transmission mode is not suitable for the channel state of the terminal, the base station uses the fallback transmission to change the transmission mode of the terminal to more suitable. In addition, the fallback transmission maintains a stable communication function between the terminal and the base station in a section in which the configuration of the terminal is changed. As an example, when the base station changes the transmission mode using higher layer signaling, it takes time for the base station to be convinced that it is actually applied to the terminal after transmitting the upper layer signaling. In the time period, the base station cannot determine which transmission mode the terminal itself determines. By using fallback transmission in this time period, the base station can transmit downlink data to the terminal. In an embodiment, an MCS Index interpretation method may be determined according to whether fallback transmission is used.

As mentioned above, different DCI formats are used when a base station transmits a PDSCH according to a transmission mode set to a terminal and when transmitting a PDSCH according to a fallback transmission. The DCI format means a format in which control information is configured in the control channel PDCCH / E-PDCCH in LTE. As an example, transmission mode 9 uses DCI format 2C. On the other hand, the fallback transmission uses DCI format 1A. The UE can determine whether the PDSCH transmitted to itself is a transmission according to a transmission mode or a fallback transmission by distinguishing the DCI format.

In this specification, it is proposed that the method of interpreting the MCS index by the UE is differently applied depending on whether the PDSCH received by the UE is fallback transmission or another transmission in the transmission mode. In this case, if the base station incorrectly determines the HOMI transmitted by the UE, the influence of the incorrect determination may be limited to interpretation of the DCI format according to the transmission mode. That is, the UE determines whether the PDSCH is transmitted by fallback transmission or transmission mode, and if it is determined that it is transmitted by fallback transmission, applies a conventional MCS index analysis method and determines that it is made according to the transmission mode. The MCS index analysis method proposed in the present invention can be applied. The summary is as follows.

-A terminal receiving DCI format 1A and receiving control information for PDSCH applies a conventional MCS index analysis method

-The terminal receiving the DCI format according to the transmission mode and receiving control information on the PDSCH applies a new MCS index analysis method

The LTE system supports normal cyclic prefix and extended cyclic prefix. In general, a cyclic prefix is introduced for the purpose of removing adjacent symbol interference in an OFDM-based wireless communication system. The longer the time, the longer the length is advantageous in a relatively larger cell. The normal cyclic prefix supported in the LTE system is designed for small and medium-sized cells in which the delay spread of the reflected wave is small in time, and extended cyclic is designed for large cells in which the delay spread of the reflected wave is large in time. Another method of interpreting the MCS index is to analyze whether the cyclic prefix set by the base station is an extended cyclic prefix or a normal cyclic prefix. If the base station has set a normal cyclic prefix, the base station has a function to transmit 256QAM, and the terminal also has a function to receive 256QAM, the terminal uses a new MCS index analysis method. On the other hand, when the base station sets an extended cyclic prefix, the terminal uses a conventional MCS index analysis method regardless of whether a function capable of receiving 256QAM is implemented or a function capable of transmitting 256QAM at the base station. When the extended cyclic prefix is set in this way, the conventional MCS index analysis method is used because the extended cyclic prefix itself is designed for a large cell, so it is very unlikely that 256QAM can be used.

9 is a diagram illustrating a method for a base station to switch a CQI table according to an embodiment.

9, in step 900, the base station establishes a connection with the terminal.

In step 910, the base station connected to the terminal may receive the UE capability of the terminal from the corresponding terminal. In an embodiment, the UE capability includes control information on whether the terminal can support 256QAM.

If the terminal can receive 256QAM, the base station is configured to receive the 256QAM to the terminal in step 920. This is to inform the UE that there may be a PDSCH to which 256QAM modulation is applied in some of the PDSCHs to be transmitted in the future. According to an embodiment, step 920 may be performed by a method in which the base station determines a transmission mode to the terminal.

Thereafter, the base station receives an uplink control channel transmitted by the terminal in step 930. The uplink control channel transmitted by the UE in step 930 may be control information including one or more of CQI and HOMI, ACK / NACK control information for a downlink PDSCH, and control information including one or more of RSRP and RSRQ. .

In step 940, it is determined whether to change the CQI table using the control channel and the control information carried on the control channel. As an example, when determining a change based on HOMI, the base station determines which CQI table to apply according to the value of the HOMI.

The base station changes the CQI table as in step 950 or maintains the CQI table as in step 960 according to the result determined in step 940. In a subsequent step, the base station may interpret the CQI that the UE will shear based on the CQI table determined in the process 950 or 960.

10 is a diagram illustrating a method for a terminal to switch a CQI table according to an embodiment.

Referring to FIG. 10, in step 1000, the terminal establishes a connection with the base station.

Then, in step 1010, the UE notifies its UE capability of the base station. This includes information on whether the terminal can receive 256QAM.

Subsequently, in step 1020, the UE is configured to receive the PDSCH transmitted in 256QAM from the base station in the future. According to an embodiment, the setting may be transmitted through higher level signaling or physical signaling. In the embodiment of FIG. 10, it is assumed that the UE performs downlink measurement and changes the CQI table.

To this end, the UE measures a downlink channel as in step 1030, generates channel status information (CSI) for this, and notifies the base station.

During the process, if it is determined that the CQI table is changed in 1040, the UE notifies the base station as in step 1050. Similarly, if it is determined that the CQI table is not changed, the base station is notified that the CQI table is maintained as in step 1060. Such notification is made by the above HOMI or higher layer signaling. Thereafter, the terminal generates a CQI according to the CQI table it notifies as in step 1070 and notifies the base station.

11 is a diagram illustrating a method of differently analyzing an MCS index according to whether a base station has fallback transmission according to an embodiment.

Referring to FIG. 11, in step 1100, the base station determines that a new CQI definition method has been applied. The new CQI definition method may include a CQI definition method capable of transmitting and receiving signals using 256QAM. As mentioned above, in this case, in the PDSCH transmission by the transmission mode, the UE may apply a new MCS analysis method.

Thereafter, in step 1110, the base station determines whether to perform PDSCH transmission by the fallback transmission or PDSCH transmission by the transmission mode.

If it is determined in step 1110 that the PDSCH transmission by the fallback transmission is performed, the base station determines the MCS index to be transmitted to the UE using the existing MCS definition method as in step 1120, and transmits to the PDCCH or E-PDCCH of DCI format 1A in step 1140. Also, it is transmitted to the UE together with the PDSCH.

On the other hand, if it is determined in step 1110 that the PDSCH transmission by the transmission mode is performed, the base station determines the MCS index to be transmitted to the UE using the new MCS definition method as in step 1130, and in step 1140, loads the PDSCH in the DCI format suitable for the transmission mode. And sends it to the terminal.

In the embodiment, when transmitting the PDSCH by the fallback transmission, the base station can analyze the same as the existing MCS analysis regardless of the type of MCS analysis previously applied. Through the analysis method of this embodiment, it is possible to transmit and receive data with less error.

12 is a diagram illustrating a method of differently interpreting an MCS index according to whether a terminal transmits fallback according to an embodiment.

Referring to FIG. 12, in step 1200, the UE determines that a new CQI definition method is applied.

Thereafter, in step 1210, the UE determines whether the PDSCH received by the UE is due to fallback transmission or transmission mode. The method for the UE to determine this may include a method of determining depending on which of DCI format 1A and DCI format determined according to transmission mode is received. When DCI format 1A is assumed and blind decoding is successfully performed, the UE assumes that DCI format 1A is received and PDSCH is made by fallback transmission. On the other hand, if the decoding is successfully performed by performing blind decoding by assuming the DCI format determined according to the transmission mode, the UE assumes that the corresponding DCI format is received and the PDSCH is made by the transmission mode.

In the case of the fallback transmission mode, the UE assumes an existing MCS analysis method as in step 1220 and decodes the PDSCH by interpreting the MCS index carried in the PDCCH / E-PDCCH in step 1240.

On the other hand, in transmission mode, the UE assumes a new MCS analysis method as in step 1230 and decodes the PDSCH by interpreting the MCS index carried in the PDCCH / E-PDCCH in step 1240. The new MCS analysis method may include an MCS analysis method that can be used when transmitting and receiving data using 256QAM.

In the embodiment of FIG. 12, the UE may decode the PDSCH using the existing MCS analysis method regardless of the previously applied MCS analysis method according to whether or not the fall back transmission mode is applied. In this way, errors in data transmission and reception can be further reduced.

13 is a diagram showing the components of a base station proposed in an embodiment.

Referring to FIG. 13, the base station may include at least one of a base station controller 1300, a control channel transmitter 1310, a data channel transmitter 1320, and an uplink channel receiver 1330.

When the CQI analysis method and the MCS definition method are changed in the base station control unit 1300 of the base station transceiver, how to interpret the CQI and determine the MCS based on the change. That is, the base station control unit 1300 receives the uplink signal transmitted by the terminal through the uplink channel receiving unit 1330 and the received signal may include a CQI index transmitted by the terminal in the uplink. The base station analyzes the CQI index transmitted by the terminal according to an appropriate CQI analysis method and uses it for scheduling of the terminal. The CQI analysis method may be analyzed through an existing CQI analysis method or a new CQI analysis method according to an embodiment. The new CQI analysis method may include a CQI analysis method capable of transmitting and receiving signals using 256QAM proposed in the embodiment.

In addition, the base station determines the MCS index according to the MCS definition method of a specific terminal and transmits it to the terminal using the control channel transmitter 1310, and transmits the PDSCH to the terminal using the data channel transmitter 1320 accordingly. The MCS definition method of the specific terminal may include one or more of an existing MCS definition method and a new MCS definition method. The new MCS definition method may include an MCS definition method capable of transmitting and receiving data using 256QAM proposed in the embodiment.

In addition, the base station may further include a transceiver capable of transmitting and receiving a higher level signal.

14 is a diagram showing components of a terminal proposed in an embodiment.

Referring to FIG. 14, the terminal may include at least one of a terminal control unit 1400, an uplink channel transmission unit 1410, a control channel reception unit 1420, and a data channel reception unit 1430.

When the CQI definition method and the MCS analysis method are changed in the terminal control unit 1400 of the terminal transceiver, how to define the CQI index and how to interpret the MCS index based on this. The CQI index definition method may include one or more of an existing CQI definition method and a new CQI definition method. The new CQI definition method may include a CQI definition method capable of transmitting and receiving data through 256QAM.

That is, the terminal control unit 1400 may be notified of the MCS index transmitted by the base station through the control channel receiving unit 1420 and may receive the PDSCH through the data channel receiving unit 1430 using the same. Also, an appropriate CQI index is determined according to a CQI definition method and transmitted to the base station through the uplink channel transmitter 1420.

In addition, the terminal may further include a transceiver capable of transmitting and receiving a higher level signal.

15 is a diagram for a base station to determine a CQI analysis method according to a channel state according to an embodiment.

15, in step 1510, the base station establishes a connection with the terminal.

The base station connected to the terminal may receive the UE capability of the terminal from the corresponding terminal in step 1520. In an embodiment, the UE capability includes control information on whether the terminal can support 256QAM.

If the UE can receive 256QAM, the base station sets to receive 256QAM to the UE in step 1530. This is to inform the UE that there may be a PDSCH to which 256QAM modulation is applied in some of the PDSCHs to be transmitted in the future. According to an embodiment, step 1520 may be performed by a method in which the base station determines a transmission mode to the terminal.

Thereafter, in step 1540, the base station can measure the channel state. The channel state measurement may be performed based on channel state information reported by the terminal.

In step 1550, the base station may determine whether a new CQI analysis method can be applied based on the channel state measured in step 1540. The new CQI analysis method may include a CQI analysis method capable of transmitting and receiving data through 256QAM. According to an embodiment, the base station may determine to apply a new CQI analysis method when the channel state is good enough to transmit and receive data using 256QAM. Determining the good case may include a case in which the channel state is a specific state or more.

In step 1550, if the channel condition satisfies the condition, in step 1560, the base station may notify the terminal to apply a new CQI analysis method. More specifically, the base station may inform the terminal to apply a new CQI analysis method through at least one of upper layer signaling and physical layer signaling.

In step 1550, if the channel condition does not satisfy the condition, in step 1570, the base station may notify the terminal to apply the existing CQI analysis method. More specifically, the base station may notify the terminal to apply the existing CQI analysis method through at least one of upper layer signaling and physical layer signaling. According to an embodiment, as a result of the determination of the base station in step 1550, the process may be performed as a process of notifying the terminal only when an analysis method different from the existing CQI analysis method is used.

16 is a diagram for a UE to determine a CQI reporting method according to an embodiment.

Referring to FIG. 16, in step 1610, the UE may perform channel measurement for CQI reporting. The channel measurement may be performed based on a signal received by the terminal from a base station.

In step 1620, the UE may determine whether the CQI report according to the measured channel information is a periodic CQI report or an aperiodic CQI report.

If the determination result is a periodic CQI report, in step 1630, the UE can report the CQI by variably using the existing CQI analysis method and the new CQI analysis method proposed in the embodiment of the present specification. More specifically, the new CQI analysis method includes a CQI analysis method capable of transmitting and receiving data using 256QAM, and a CQI index can be delivered using the same number of bits as the existing CQI analysis method. According to the embodiment

If the result of the determination is aperiodic CQI reporting, in step 1640, the UE may report the CQI to the base station using a 5 bit CQI. More specifically, in the embodiment, in the case of aperiodic CQI reporting, the UE needs to report more accurate CQI information to the base station, and in the case of aperiodic CQI reporting, the number of executions is less than that of periodic CQI reporting, so more bits are allocated to CQI reporting. Since there is no problem in allocating, the terminal can report the CQI to the base station using, for example, a 5 bit CQI table.

The base station may also apply a method of interpreting the CQI differently according to whether the CQI reported by the UE is periodic or aperiodic. According to an embodiment, the base station analyzes the CQI index using the same number of bits as the existing CQI analysis method when the periodic CQI report corresponds to the method reported by the terminal, and when the aperiodic CQI report CQI index can be interpreted through the assigned CQI table.

[Example 2]

The LTE system supports normal cyclic prefix and extended cyclic prefix. When the base station and the terminal use an extended cyclic prefix, as shown in FIG. 2, one subframe may be composed of 12 OFDM symbols in the time domain, unlike one subframe composed of 14 OFDM symbols in the normal cyclic prefix. Therefore, a range of radio resources that can be used by a base station and a terminal is limited when using an extended cyclic prefix than when using a normal cyclic prefix. For example, in the current LTE system, the UE is designed to simultaneously transmit CQI and precoding matrix indicator (PMI) up to 13 bits using PUCCH (Physical Uplink Control Channel) format 2 / 2a / 2b.

17 is a diagram illustrating a structure of PUCCH format 2 / 2a / 2b in an LTE system using a normal cyclic prefix.

Referring to FIG. 17, in a base station using a normal cyclic prefix, a UE can transmit CQI and PMI of up to 13 bits using symbols other than symbols for transmitting a reference signal. If ACK / NACK is simultaneously transmitted with CQI and PMI, ACK / NACK is transmitted to the second reference signal position located in one slot.

18 is a diagram illustrating a structure of PUCCH format 2 in an LTE system using an extended cyclic prefix.

Referring to FIG. 18, when an extended cyclic prefix is used by a base station and a terminal, there is one symbol for a reference signal in one slot. Therefore, when ACK / NACK is simultaneously transmitted with CQI and PMI, reference is different from that of the normal cyclic prefix. ACK / NACK cannot be transmitted using signal. Therefore, for a base station using an extended cyclic prefix, the UE jointly transmits CQI, PMI and ACK / NACK and simultaneously transmits them. Therefore, the UE may transmit information including at least one of CQI and PMI within a range of up to 11 bits to a base station using an extended cyclic prefix. As a result, unlike the normal cyclic prefix case, a case in which a CQI table of 5 bits or more cannot be transmitted through a PUCCH may occur for a base station using an extended cyclic prefix. Therefore, the CQI table switching method can be defined as follows based on the difference in the cyclic prefix length used by the base station and the terminal.

-CQI table switching method 4: switching method based on the cyclic prefix length used by the base station and the terminal

The CQI table conversion method 4 proposed in the embodiment of the present specification may determine CQI table conversion based on a cyclic prefix length.

More specifically, the terminal and the base station can switch the CQI table used based on the length of the cyclic prefix used for signal transmission and reception.

In an embodiment, when the base station has a function capable of transmitting 256QAM, and the terminal also has a function capable of receiving 256QAM, the base station and the terminal for the base station using the extended cyclic prefix are shown in Table 2 above. The existing CQI transmission method can be used without supporting 256QAM by referring to the CQI table, or 256QAM can be supported without additional information by referring to the reinterpreted 4bit CQI table such as Table 3, Table 4, and Table 5 above. .

When the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the base station and the terminal use a normal cyclic prefix, a 5-bit CQI table as in CQI definition method 2 above, or 256QAM can be supported by referring to the CQI table having more bits.

In an embodiment, when using an extended cyclic prefix, it is possible to consider using an existing CQI table that does not support 256QAM, and when using a normal cyclic prefix, selecting and using one of CQI tables that support 256QAM. The CQI table used for may be variously applied according to an embodiment.

The advantage of the CQI table switching method 4 is that it can be used by switching the 4 bit CQI table or 5 bit CQI table according to the length of the cyclic prefix. Through this, 256QAM can be supported. In addition, since the base station and the terminal can accurately distinguish the cyclic prefix length of the base station, the CQI table switching process is clear.

19 is a diagram illustrating a method of switching a CQI table based on a cyclic prefix length in the CQI switching method 4 proposed in this specification from a terminal perspective.

Referring to FIG. 19, in step 1900, the UE may check the cyclic prefix length of the base station.

In step 1910, whether to switch the CQI table is determined based on the cyclic prefix of the base station obtained in step 1900. If the cyclic prefix length of the base station is extended cyclic prefix according to the result determined in step 1910, the UE proceeds to step 1920 to refer to the existing 4 bit CQI table as shown in Table 2, or replay as shown in Tables 3, 4, and 5 4 bit CQI may be transmitted by referring to the analyzed 4 bit CQI table.

On the other hand, if the length of the cyclic prefix of the base station is normal cyclic prefix according to the result determined in step 1910, the process proceeds to step 1930, and the terminal refers to a CQI table having a 5-bit CQI table or more bits as in CQI switching method 2. CQI is transmitted.

Table 7 is a table showing the maximum number of bits that can be transmitted through PUCCH transmission when an extended cyclic prefix is used when using a 5bit CQI table.

Table 7 defines the maximum number of bits that a terminal can transmit through PUCCH transmission according to a PUCCH transmission mode state when a base station and a terminal using an extended cyclic prefix use a 5 bit CQI table.

That is, in the case of index 7 in Table 7, the terminal transmits a total of 7 bits of information to the base station including the 5 bit CQI value and the 2 bit PMI value. As mentioned above, in the LTE system, the maximum number of bits that a terminal can transmit through PUCCH transmission is limited to 11 bits for a base station using an extended cyclic prefix. Accordingly, as shown in Table 7, the 5bit CQI table cannot be switched in PUCCH transmission modes such as indexes 9, 11, and 15.

 Also, in the case of index 4, when the L value is 2 or more, it is impossible to switch the 5bit CQI table in PUCCH transmission mode. Here, L is a value representing a subband index transmitted for a specific frequency band when the UE delivers a CQI value in subband units to a base station, and a value is determined according to the system bandwidth. In Table 7, the RI (rank indication) indicates the most recently reported RI value based on the transmission time of the corresponding CQI / PMI, and in the LTE system supporting a plurality of transmit and receive antennas, the channel status of the base station and the terminal. This is a value used when reporting the number or rank of spatial layers that can be received through to the base station.

In the case of a base station using an extended cyclic prefix as shown in the indexes 4, 9, 11, and 15 of Table 7, the PUCCH transmission mode in which the UE cannot switch the 5bit CQI table commonly has the most recently reported RI value greater than 1 Occurs on. In other words, if the most recently reported RI value of 1 in the base station using the extended cyclic prefix is 1, the terminal can transmit 5 bit CQI. Accordingly, when the base station has a function capable of transmitting 256QAM and the terminal also has a function capable of receiving 256QAM, when the latest RI reported by the terminal for the base station using the extended cyclic prefix is greater than 1 , The base station and the terminal do not support 256QAM by referring to the CQI table shown in Table 2 above, or 256QAM without additional information by referring to the reinterpreted 4bit CQI table such as Table 3, Table 4, and Table 5 above. can do.

When the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the latest RI reported by the terminal to the base station using the extended cyclic prefix is not greater than 1, the 256QAM may be supported by referring to a 4bit CQI table such as Table 3, Table 4, and Table 5 of the above, or by referring to a 5bit CQI table such as CQI definition method 2 or a CQI table having more bits.

20 is a diagram illustrating a method of switching a CQI table based on a cyclic prefix length and an RI value reported by a terminal to a base station in the CQI switching method 4 proposed in this specification from a terminal perspective. Preferably, the RI value may be the most recently reported RI value to the base station.

Referring to FIG. 20, in step 2000, the UE can check the cyclic prefix length of the base station.

Based on the cyclic prefix of the base station obtained in step 2000, it is determined whether to switch the CQI table in step 2010.

If the cyclic prefix length of the base station is normal cyclic prefix according to the result determined in step 2010, the terminal proceeds to step 2030 and transmits a 4bit CQI with reference to the reinterpreted 4bit CQI table as shown in Tables 3, 4, and 5, or , CQI is transmitted by referring to the CQI table having a 5 bit CQI table or more bits as in the CQI switching method 2 above.

If the cyclic prefix length of the base station determined in step 2010 is extended cyclic prefix, the process proceeds to step 2020 to check the RI of the terminal.

The terminal may determine whether to switch the CQI table in step 2040 based on the RI value checked in step 2020.

If the RI value is greater than 1 according to the result determined in step 2040, the UE proceeds to step 1650 to refer to the existing 4bit CQI table shown in Table 2, or the 4bit reinterpreted as shown in Tables 3, 4, and 5 4bit CQI may be transmitted by referring to the CQI table. If the RI value is not greater than 1 according to the result determined in the process 2040, the process proceeds to the process 2030 and transmits a 4 bit CQI with reference to the reinterpreted 4 bit CQI table as shown in Tables 3, 4, and 5, or the CQI. As in the switching method 2, the CQI may be transmitted by referring to the CQI table having a 5 bit CQI table or more bits.

In this embodiment, the UE determines the CQI table to be referred to based on the type of cyclic prefix used and the RI value reported by the UE, and the CQI table referred to in this case is a table including the CQI table proposed in this specification. It can be variously determined.

[Example 3]

The LTE system supports a plurality of transmit and receive antennas. At this time, the number or rank of spatial layers of a signal transmitted through a plurality of antennas varies according to a channel state of a base station and a terminal. Therefore, for correct system operation, the terminal should check the number or rank of spatial layers that can be received through the channel state of the base station and the terminal and report it to the base station. In the LTE system, the number or rank of spatial layers that can be received by the UE can be reported to the base station through rank indication (RI). In general, a higher modulation order has the advantage of being able to transmit more data, but a higher received signal energy-to-noise and interference ratio is required compared to a modulation method of 64QAM or less. In particular, in the case of 256QAM, sufficient reception performance can be supported only at a very high received signal energy to noise and interference ratio. If a signal modulated with 256QAM is transmitted through a plurality of layers, a higher received signal energy-to-noise and interference ratio is required due to the influence of additional inter-layer interference. In addition, since the transmission efficiency when transmitting a signal modulated with 256QAM through one layer and transmitting a signal modulated with 16QAM through two layers are the same, a very high received signal energy to noise and interference ratio is required as described above. The use of 256QAM to be can be limited according to the RI value. Therefore, the CQI table can be switched based on the most recent RI value reported by the UE to the base station.

-CQI table switching method 5: A switching method based on the most recent RI value reported by the UE to the base station

In CQI table switching method 5 proposed in the embodiment of the present specification, CQI table switching is performed based on the RI value reported by the UE to the base station, and the RI value is the latest RI value reported by the UE to the BS. It can contain.

In an embodiment, when the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the latest RI value reported by the terminal to the base station is greater than 1, the base station and the terminal are 256QAM is not supported by referring to the CQI table shown in Table 2, or 256QAM can be supported without additional information by referring to the reinterpreted 4bit CQI table such as Table 3, Table 4, and Table 5 above. When the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the latest RI value reported by the terminal to the base station is not greater than 1, Table 3 and Table 4 above. , And 256QAM without additional information by referring to the reinterpreted 4bit CQI table such as Table 5, or 256QAM by referring to the 5bit CQI table such as CQI definition method 2 or CQI table consisting of more bits. have.

21 is a diagram illustrating a method of switching a CQI table based on the most recent RI value reported by the terminal to the base station in the CQI switching method 5 proposed in the present specification from the terminal perspective. In an embodiment, the RI value is described based on the most recent RI value reported by the UE to the base station, but is not limited thereto.

Referring to FIG. 21, in step 2100, the UE measures a channel state between base stations to check the latest RI value to report to the base station.

In step 2100, the UE determines whether to switch the CQI table in step 2110 based on the obtained RI value.

The UE proceeds to step 2120 when the RI value obtained in step 2100 is greater than 1 according to the result determined in step 2110 and refers to an existing 4bit CQI table shown in Table 2, or Table 3, Table 4, Table 5 4bit CQI is transmitted by referring to the reinterpreted 4bit CQI table.

If the RI value obtained in step 2100 is not greater than 1 according to the result determined in step 2110, the process proceeds to step 2130 and refers to a CQI table having a 5-bit CQI table or a CQI table having more bits than the CQI conversion method 2 Can send.

In this embodiment, the terminal determines a reference CQI table based on the RI value reported to the base station, and in this case, the reference CQI table may be variously determined from a table including the CQI table proposed in this specification.

[Example 4]

In LTE systems of Release 12 and higher, base stations and terminals supporting LTE Release 11 and earlier Release characteristics, as well as base stations and terminals supporting a plurality of transmit and receive antennas and 256QAM, and base stations and terminals supporting a single transmit, receive antenna and 256QAM Various types of base stations and terminals may coexist. Accordingly, a plurality of transmit and receive antennas and a base station supporting 256QAM and a single transmit, receive antenna and a terminal supporting 256QAM, or a single transmit, receive antenna and a base station supporting 256QAM and a plurality of transmit, receive antennas and 256QAM are supported. It is possible to transmit data between terminals, and the spatial layer or rank at this time is limited to 1, and higher transmission efficiency can be obtained when the base station and the terminals use 256QAM. On the other hand, base stations and terminals capable of using multiple transmit and receive antennas have the same transmission efficiency when transmitting the same data in 16QAM modulation through 2 layers and 256QAM modulation through 1 layer. The use of 256QAM, which requires a high received signal energy to noise and interference ratio, may be limited.

Therefore, the CQI table can be switched based on the maximum supportable layers between the base station and the terminal.

-CQI table switching method 6: A switching method based on the maximum number of supported layers between a base station and a terminal

In the CQI table switching method 6 proposed in the embodiment of the present specification, the CQI table switching is performed based on the maximum number of supported layers between the base station and the terminal.

The maximum number of layers that can be supported between the base station and the terminal is determined as a minimum value between the number of antenna ports of the base station and the maximum downlink MIMO capability determined by the UE capability of the terminal. For example, when the terminal uses transmission mode 9 or higher, the maximum number of antenna ports transmitting the CSI-RS of the base station and the maximum downlink MIMO capability determined by the UE capability by the UE is the smallest possible value between the base station and the terminal. The number of layers is determined. When the UE uses transmission mode 8 or lower, the maximum number of supported layers between the base station and the UE is determined as a minimum value between the number of antenna ports transmitting the CRS of the base station and the maximum downlink MIMO capability determined by the UE capability. Accordingly, when the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the maximum number of layers that can be supported between the base station and the terminal is 1, Table 3, Table 4 and Table above It is possible to support 256QAM without additional information by referring to a 4bit CQI table such as 5, or 256QAM by referring to a 5bit CQI table such as CQI definition method 2 or a CQI table using more bits. When the base station has a function to transmit 256QAM and the terminal also has a function to receive 256QAM, when the maximum number of layers that can be supported between the base station and the terminal is greater than 1, use the CQI table shown in Table 2 above. Therefore, 256QAM is not supported or 256QAM can be supported without additional information by referring to the 4bit CQI table such as Table 3, Table 4 and Table 5 above.

22 is a diagram illustrating a method of switching a CQI table based on the maximum number of layers that can be supported between a base station and a terminal in the CQI switching method 6 proposed in the embodiment of the present specification from a terminal perspective.

Referring to FIG. 22, in step 2200, the terminal checks the number of antenna ports of the base station according to its transmission mode. For example, if the transmission mode of the terminal is 9 or more, the antenna configuration of the base station can be checked based on the number of antenna ports transmitting the CSI-RS of the base station. If the transmission mode of the terminal is less than 9, the antenna configuration can be checked based on the number of antenna ports transmitting the CRS of the base station.

In step 2210, the number of layers may be checked in step 2200. More specifically, the terminal checks the number of supported layers between the base station and the terminal with a minimum value of the measured number of base station antenna ports and the maximum downlink MIMO capability supported by the terminal's UE capability.

Based on the maximum number of supported layers between the base station and the terminal obtained in step 2210, it is determined whether to switch the CQI table in step 2220.

If the number of supported layers between the base station and the terminal determined in step 2220 is greater than 1, the process proceeds to step 2230 to transmit a 4bit CQI with reference to the existing 4bit CQI table shown in Table 2 or to Table 3, Table 4 and Table 5 above. With reference to the 4bit CQI table, etc., 256QAM can be supported without additional information.

When the number of supported layers between the base station and the terminal determined in step 2220 is 1, the process proceeds to step 2240, and as shown in the method 2 of CQI switching, refer to the 4bit CQI table such as Table 3, Table 4 and Table 5 without additional information amount. CQI is transmitted by supporting 256QAM, referring to a 5-bit CQI table, or referring to a CQI table having a bit of 5 bits or more.

[Example 5]

The MCS notification method may be determined based on the maximum supportable layers between the base station and the terminal.

-MCS notification method supporting 256QAM 3: Notification method based on the maximum number of supported layers between the base station and the terminal

In the MCS notification method 3 supporting 256QAM proposed in the embodiment of the present specification, MCS notification is performed based on the maximum number of supported layers between the base station and the terminal. As in the fourth embodiment, the maximum number of layers that can be supported between the base station and the terminal is determined as a minimum value between the number of antenna ports of the base station and the maximum downlink MIMO capability determined by the UE capability of the terminal. Therefore, both the base station and the terminal can know the same number of maximum supportable layers between the base station and the terminal. Accordingly, when the base station has a function capable of transmitting 256QAM and the terminal also has a function capable of receiving 256QAM, when the maximum number of layers that can be supported between the base station and the terminal is greater than 1, the base station is shown in Table 1 above. An MCS index can be generated according to a conventional MCS table.

At this time, since the maximum number of layers supported between the base station and the terminal known to the terminal is also greater than 1, the terminal interprets the MCS index according to the conventional MCS table shown in Table 1, or the base station supports 256QAM as shown in Table 6 above. MCS index is generated according to the reinterpreted 5bit MCS table.

On the other hand, if the maximum number of layers that can be supported between the base station and the terminal is 1, the base station generates an MCS index according to the reinterpreted 5bit MCS table supporting 256QAM as shown in Table 6 above, or an MCS index according to an MCS table of 6bit or more. do. At this time, since the maximum number of layers supported between the base station and the terminal known to the terminal is also 1, the terminal interprets the MCS index according to the MCS table supporting 256QAM as shown in Table 6 or the MCS index according to the MCS table of 6 bits or more.

23 is a diagram illustrating an MCS notification method based on the maximum number of supported layers between a base station and a terminal in the MCS notification method 3 proposed in an embodiment of the present disclosure from the perspective of a base station.

Referring to FIG. 23, in step 2300, the base station can check the number of layers that can be supported between the base station and the terminal, and more specifically, the base station is a minimum value of the maximum antenna downlink MIMO capability supported by the antenna configuration of the base station and the UE capability of the terminal. It is possible to check the number of layers that can be supported between the base station and the terminal.

The MCS notification method is determined in step 2310 based on the maximum number of supported layers between the base station and the terminal acquired in step 2300.

If the number of supported layers between the base station and the terminal determined in step 2310 is greater than 1, proceed to step 2320 to refer to an existing 5 bit MCS table shown in Table 1, or reinterpreted 5 bit supporting 256QAM as shown in Table 6 above. The MCS index is transmitted to the UE by referring to the MCS table or by referring to an MCS table of 6 bits or more.

When the number of supported layers between the base station and the terminal determined in step 2310 is 1, refer to the reinterpreted 5bit MCS table as shown in Table 6, or transmit the MCS index to the terminal by referring to the MCS table of 6bit or more. At this time, since the UE also knows the same number of layers that can be supported between the base station and the UE through processes 2200 and 2210 of FIG. 22 as the base station, the MCS index can be interpreted by referring to the same MCS table as the base station.

On the other hand, in the specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms have been used, they are merely used in a general sense to easily describe the technical contents of the present invention and to help understand the invention. It is not intended to limit the scope of the invention. It is obvious to those skilled in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (30)

In the method of the base station of the communication system,
Receiving information on modulation supported by the terminal;
Transmitting setting information for setting data to be received through a specific modulation method to the terminal based on the information on the modulation;
Receiving an uplink control channel from the terminal; And
And determining a channel quality indicator (CQI) table for interpretation of CQI index information transmitted from the terminal, wherein the CQI table is one of a plurality of predefined CQI tables. According to claim 1,
The plurality of predefined CQI tables include a first CQI table supporting 256 QAM and a second CQI table not supporting 256 QAM. According to claim 1,
The receiving of the uplink control channel includes receiving channel state information from the terminal,
Determining the CQI table comprises the step of determining a CQI table to use a higher modulation order than a preset modulation order when the received channel state information is greater than or equal to a specific reference value. Way. According to claim 1,
And transmitting information on the determined CQI table to the terminal through an upper layer signal or a physical layer signal. According to claim 1,
The step of receiving the control channel includes receiving information on the CQI table determined by the terminal,
The determining of the CQI table includes determining a CQI table according to the table determined by the terminal. According to claim 1,
The step of receiving the control channel includes receiving a periodic or aperiodic CQI report from the terminal,
Determining the CQI table comprises the step of deciding to use a CQI table that allocates a larger number of bits than the periodic report when the CQI report is an aperiodic CQI report. In the method in the terminal of the communication system,
Transmitting a signal including information on modulation supported by the terminal to a base station;
Receiving setting information including a setting for transmitting data through a specific modulation method from the base station based on the information on the modulation; And
And transmitting an uplink control channel to the base station.
The base station determines a channel quality indicator (CQI) table for interpretation of CQI index information transmitted from the terminal, and the CQI table is one of a plurality of predefined CQI tables. The method of claim 7,
The plurality of predefined CQI tables include a first CQI table supporting 256 QAM and a second CQI table not supporting 256 QAM. The method of claim 7,
The transmitting of the uplink control channel includes transmitting channel state information to the base station,
And the base station determines a CQI table to use a modulation order higher than a preset modulation order when the received channel state information is greater than or equal to a specific reference value. The method of claim 7,
And receiving information on the CQI table determined by the base station from the base station through an upper layer signal or a physical layer signal. The method of claim 7,
The step of transmitting the control channel includes transmitting information including information on a CQI table determined by the terminal to the base station,
The base station determines a CQI table according to the CQI table determined by the terminal. The method of claim 7,
The step of transmitting the control channel includes transmitting a periodic or aperiodic CQI report to the base station,
The base station uses a CQI table that allocates more bits than the periodic report when the CQI report is an aperiodic CQI report. In the base station of the communication system,
Receives information on the modulation supported by the terminal, and transmits configuration information set to receive data through a specific modulation method to the terminal based on the information on the modulation, and receives an uplink control channel from the terminal Transceiver; And
A base station including a control unit, which determines a channel quality indicator (CQI) table for interpretation of CQI index information transmitted from the terminal, wherein the CQI table is one of a plurality of predefined CQI tables. The method of claim 13,
The plurality of predefined CQI tables include a first CQI table supporting 256 QAM and a second CQI table not supporting 256 QAM. The method of claim 13,
The transceiver receives channel state information from the terminal,
Wherein the step of the control unit, if the received channel state information is more than a specific reference value, the base station characterized in that to determine the CQI table to use a higher modulation order than the preset modulation order (modulation order). The method of claim 13,
The transmission / reception unit transmits information on the determined CQI table to a terminal through an upper layer signal or a physical layer signal. The method of claim 14,
The transmitting and receiving unit is characterized in that it receives the information on the CQI table determined by the terminal,
The control unit determines that the CQI table is a base station, characterized in that for determining the CQI table according to the table determined by the terminal. The method of claim 14,
The transmitting and receiving unit is characterized in that it receives a periodic or aperiodic CQI report from the terminal,
The control unit determines that the step of determining the CQI table is to use a CQI table that allocates a larger number of bits than the periodic report when the CQI report is an aperiodic CQI report. In the terminal of the wireless communication system,
A transmitting and receiving unit capable of transmitting and receiving signals with a base station; And
The control unit transmits and receives a signal including information on modulation supported by the terminal to the base station by controlling the transceiver, and receives configuration information from the base station to transmit data through a specific modulation method based on the information on the modulation, It includes a control unit for transmitting an uplink control channel to the base station,
The base station determines a channel quality indicator (CQI) table for interpretation of CQI index information transmitted from the terminal, and the CQI table is one of a plurality of predefined CQI tables. The method of claim 19,
The plurality of predefined CQI tables include a first CQI table supporting 256 QAM and a second CQI table not supporting 256 QAM. The method of claim 19,
The control unit is characterized in that for transmitting the channel state information to the base station,
The base station determines that the CQI table to use a higher modulation order than a preset modulation order when the received channel state information is greater than or equal to a specific reference value. The method of claim 19,
The control unit receives the information on the CQI table determined by the base station from the base station through a higher layer signal or a physical layer signal. The method of claim 19,
The control unit transmits information including information on the CQI table determined by the terminal to the base station,
The base station determines the CQI table according to the CQI table determined by the terminal. The method of claim 19,
The control unit is characterized in that for transmitting a periodic or aperiodic CQI report to the base station,
When the CQI report is the aperiodic CQI report, the base station uses a CQI table that allocates more bits than the periodic report. In the method in the terminal of the communication system,
Receiving a reference signal from a base station;
Determining a RI (Rank Indicator) value based on the received reference signal;
Determining a modulation method to be used for signal transmission and reception with the base station according to the determined RI value; And
And transmitting and receiving signals to and from the base station using the determined modulation method.
The signal transmission and reception method
Further comprising the step of determining the number of layers used for signal transmission and reception with the base station,
The determining of the modulation method comprises determining a modulation method to be used for signal transmission and reception with the base station based on at least one of the RI value and the number of layers. The method of claim 25,
The signal transmission and reception method
Further comprising the step of determining the cyclic prefix value used for signal transmission and reception with the base station;
The determining of the modulation method may include determining a modulation method to be used for signal transmission and reception with the base station based on the RI value and the cyclic prefix value. The method of claim 25,
The signal transmission and reception method,
And determining a modulation coding scheme (MCS) used for signal transmission and reception with the base station based on the number of layers. A method in a base station of a communication system,
Transmitting a reference signal to the terminal;
Receiving a RI (Rank Indicator) value determined based on the reference signal from the terminal;
Determining a modulation method to be used for signal transmission and reception with the terminal based on the received RI value; And
And transmitting and receiving signals to and from the terminal using the determined modulation method.
The signal transmission and reception method
Further comprising the step of determining the number of layers (layer) used for signal transmission and reception with the terminal,
The determining of the modulation method comprises determining a modulation method to be used for signal transmission and reception with the terminal based on at least one of the RI value and the number of layers. The method of claim 28,
The signal transmission and reception method
Further comprising the step of determining the cyclic prefix value used to transmit and receive signals with the terminal;
The determining of the modulation method includes determining a modulation method to be used for signal transmission and reception with the terminal based on the RI value and the cyclic prefix value. The method of claim 25,
The signal transmission and reception method,
And determining a modulation coding scheme (MCS) used for signal transmission and reception with the terminal based on the number of layers.

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