KR102098826B1 - Method for controlling a modulation and coding scheme and base station using the same - Google Patents

Abstract

The present application relates to a method of changing a modulation and coding scheme in a base station and a base station, and a method of changing a modulation and coding scheme in a base station according to an embodiment of the present invention is received from a user terminal set to 64QAM (Quadrature Amplitude Modulation). An MCS index determination step of determining whether to increase the MCS index set in the user terminal by using a channel quality indicator (CQI) and a block error rate (BLER) of a channel; When the MCS index is increased, a confirmation step of checking whether 256QAM is applicable in the increased MCS index; A TBS comparison step of extracting and comparing TBS (Transport Block Size) in 64QAM and TBS in 256QAM corresponding to the increased MCS index when the 256QAM is applicable; And if the TBS in the 256QAM is greater than the TBS in the 64QAM, set the user terminal to use the second CQI table corresponding to the 256QAM, and apply the increased MCS index to the 256QAM, and corresponding down. It may include a setting step of transmitting the link signal to the user terminal.

Description

{Method for controlling a modulation and coding scheme and base station using the same}

The present application relates to a base station capable of maximizing downlink speed and a method of changing modulation and coding schemes at the base station.

Wireless access systems have been widely deployed to provide various types of communication services such as voice and data. In general, a wireless access system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, and a single carrier frequency (SC-FDMA). division multiple access) system.

This application intends to provide a base station capable of maximizing downlink speed and a method of changing modulation and coding schemes in the base station.

The method of changing the modulation and coding method in the base station according to an embodiment of the present invention uses channel quality indicator (CQI) and block error rate (BLER) of a channel received from a user terminal set to 64QAM (Quadrature Amplitude Modulation) The MCS index determination step of determining whether to increase the MCS index set in the user terminal; When the MCS index is increased, a confirmation step of checking whether 256QAM is applicable in the increased MCS index; A TBS comparison step of extracting and comparing TBS (Transport Block Size) in 64QAM and TBS in 256QAM corresponding to the increased MCS index when the 256QAM is applicable; And if the TBS in the 256QAM is greater than the TBS in the 64QAM, set the user terminal to use the second CQI table corresponding to the 256QAM, and apply the increased MCS index to the 256QAM, and corresponding down. It may include a setting step of transmitting the link signal to the user terminal.

Here, in the MCS index determination step, if the CQI increases or the CQI is constant but the BLER decreases, the MCS index may be increased.

Here, the checking step may determine whether the 256QAM is applicable in the increased MCS index by using the second MCS table table corresponding to the 256QAM.

Here, the TBS comparison step extracts TBS at 64QAM and TBS at 256QAM, respectively, from the first MCS table table corresponding to the 64QAM and the second MCS table table corresponding to the 256QAM, respectively. To compare with each other.

Here, in the setting step, when the TBS in the 256QAM is less than or equal to the TBS in the 64QAM, the user terminal is configured to use the first CQI table corresponding to the 64QAM, and the MCS index increased to the 64QAM By applying, a corresponding downlink signal can be transmitted to the user terminal.

Here, in the method of changing the MCS at the base station according to an embodiment of the present invention, when the user terminal is set to use the second CQI table, a CQI receiving step of receiving a CQI according to the second CQI table from the user terminal It may further include.

The method of changing the modulation and coding method in the base station according to an embodiment of the present invention uses channel quality indicator (CQI) and block error rate (BLER) of a channel received from a user terminal set to 256QAM (Quadrature Amplitude Modulation) The MCS index determination step of determining whether to decrease the MCS index set in the user terminal; When the MCS index is decreased, a checking step of checking whether 64QAM is applicable in the reduced MCS index; A TBS comparison step of comparing the transport block size (TSB) in 64QAM corresponding to the reduced MCS index and the data transmission rate in 256QAM corresponding to the reduced MCS index when the 64QAM is applicable; And if the TBS in the 64QAM is greater than the data transmission rate in the 256QAM, the user terminal is set to use the first CQI table corresponding to the 64QAM, and the reduced MCS index is applied to the 64QAM, and the corresponding down It may include a setting step of transmitting a link signal to the user terminal.

Here, in the MCS index determination step, if the CQI decreases or the CQI is constant but the BLER increases, the MCS index may be decreased.

Here, the checking step may check whether the 64QAM is applicable in the reduced MCS index using the first MCS table table corresponding to the 64QAM.

Here, the TBS comparison step includes: extracting TBS in 64QAM corresponding to the reduced MCS index from the first MCS table table corresponding to the 64QAM; Extracting TBS at 256QAM corresponding to the reduced MCS index from the second MCS table table corresponding to the 256QAM, and multiplying the extracted TBS at 256QAM by (1-BLER) to calculate the data transmission rate; And comparing the TBS in the 64QAM and the data transmission rate in the 256QAM.

Here, in the setting step, if the TBS in the 64QAM is less than or equal to the data transmission rate in the 256QAM, the user terminal is configured to use the second CQI table corresponding to the 256QAM, and the reduced MCS index in the 256QAM By applying, a corresponding downlink signal can be transmitted to the user terminal.

Here, in the method of changing the modulation and coding method in the base station according to an embodiment of the present invention, when the user terminal is set to use the first CQI table, the CQI according to the first CQI table from the user terminal The receiving CQI may further include a receiving step.

The base station according to an embodiment of the present invention uses a channel quality indicator (CQI) received from a user terminal set to 64QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of a channel, and the MCS index set in the user terminal MCS index determining unit to determine whether the increase; When increasing the MCS index, a checking unit to check whether 256QAM is applicable in the increased MCS index; A TBS comparison unit for extracting and comparing TBS (Transport Block Size) in 64QAM and TBS in 256QAM corresponding to the increased MCS index when the 256QAM is applicable; And if the TBS in the 256QAM is greater than the TBS in the 64QAM, set the user terminal to use the second CQI table corresponding to the 256QAM, and apply the increased MCS index to the 256QAM, and corresponding down. It may include a setting unit for transmitting a link signal to the user terminal.

The base station according to an embodiment of the present invention uses a channel quality indicator (CQI) received from a user terminal set to 256QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of a channel, and the MCS index set in the user terminal MCS index determining unit to determine whether the reduction; When reducing the MCS index, a confirmation unit to determine whether 64QAM is applicable in the reduced MCS index; When the 64QAM is applicable, a TBS (Transport Block Size) in 64QAM corresponding to the reduced MCS index and a TBS comparison unit comparing data transmission rates in 256QAM corresponding to the reduced MCS index; And if the TBS in the 64QAM is greater than the data transmission rate in the 256QAM, the user terminal is set to use the first CQI table corresponding to the 64QAM, and the reduced MCS index is applied to the 64QAM, and the corresponding down It may include a setting unit for transmitting a link signal to the user terminal.

In addition, not all the features of the present invention are listed in the solution means of the above-mentioned subject. Various features of the present invention and the advantages and effects thereof may be understood in more detail with reference to specific embodiments below.

According to a method of changing a modulation and coding scheme in a base station and a base station according to an embodiment of the present invention, when a modulation and coding scheme of a user terminal is changed, only a section in which a downlink rate gain occurs can be changed. Therefore, unnecessary waste of resources can be prevented and downlink speed can be maximized.

1 is a schematic diagram showing a cellular network system according to an embodiment of the present invention.
2 is a block diagram showing a base station according to an embodiment of the present invention.
3 is a graph showing data transmission rates for 64QAM and 256QAM.
4 and 5 are flowcharts illustrating a method of changing modulation and coding scheme in a base station according to an embodiment of the present invention.

The following embodiments are combinations of components and features of the present invention in a predetermined form. Each component or feature can be considered to be optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some components and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention can be changed. Some configurations or features of one embodiment may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

In the description of the drawings, procedures or steps that may obscure the subject matter of the present invention are not described, and procedures or steps that are understandable at the level of those skilled in the art are not described.

In the present specification, embodiments of the present invention have been mainly described in relation to data transmission and reception between a base station and a mobile station. Here, the base station has a meaning as a terminal node of a network that directly communicates with a mobile station. Certain operations described in this document as being performed by a base station may be performed by an upper node of the base station in some cases.

That is, various operations performed for communication with a mobile station in a network composed of a plurality of network nodes including a base station may be performed by a base station or other network nodes other than the base station. At this time, the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an advanced base station (ABS), or an access point.

In addition, in the embodiments of the present invention, a user terminal is a user equipment (UE), a mobile station (MS), a subscriber station (SS), and a mobile subscriber station (MSS). , Mobile Terminal or Advanced Mobile Station (AMS).

Further, the transmitting end refers to a fixed and / or mobile node that provides a data service or a voice service, and the receiving end refers to a fixed and / or mobile node that receives a data service or a voice service. Therefore, in the uplink, a mobile station can be a transmitting end and a base station can be a receiving end. Likewise, in the downlink, a mobile station can be a receiving end, and a base station can be a transmitting end.

Embodiments of the present invention can be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802.xx system, 3GPP (3rd Generation Partnership Project) system, 3GPP LTE system and 3GPP2 system, and in particular, the present invention. Embodiments of 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.321 and / or 3GPP TS 36.331 documents may be supported. That is, obvious steps or parts not described in the embodiments of the present invention may be described with reference to the documents. Also, all terms disclosed in this document may be described by the standard document.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION The detailed description set forth below, in conjunction with the accompanying drawings, is intended to describe exemplary embodiments of the invention, and is not intended to represent the only embodiments in which the invention may be practiced.

Further, specific terms used in the embodiments of the present invention are provided to help understanding of the present invention, and the use of these specific terms may be changed to other forms without departing from the technical spirit of the present invention. .

The following technologies are various such as code division multiple access (CDMA), frequency division multiple access (FDMA), timedivision multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). It can be applied to a wireless access system.

CDMA may be implemented by radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented with wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA).

UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) using EUTRA, and adopts OFDMA in the downlink and SC-FDMA in the uplink. The LTE-A (Advanced) system is an improved 3GPP LTE system. In order to clarify the description of the technical features of the present invention, embodiments of the present invention mainly describe a 3GPP LTE / LTE-A system, but can also be applied to an IEEE 802.16e / m system.

1 is a schematic diagram showing a cellular network system according to an embodiment of the present invention.

Referring to FIG. 1, a cellular network system according to an embodiment of the present invention may include a base station 100 and a user terminal 1.

Hereinafter, a cellular network system according to an embodiment of the present invention will be described with reference to FIG. 1.

The user terminal 1 may be a communication device that receives wireless communication services such as voice calls and data communication through the base station 100, and according to an embodiment, a user equipment (UE), a mobile station (MS), UT ( It can be called in other terms such as User Terminal (SS) and Subscriber Station (SS). The user terminal 1 may include a conventional mobile phone such as a cellular phone, a PCS phone, a GSM phone, a CDMA-2000 phone, a WCDMA phone, a smart phone and a tablet PC that are recently actively used, and a mobile phone using a 4G network. have.

The user terminal 1 may be connected to the base station 100 to receive a wireless communication service, wherein the reference signal received power (RSRP) transmitted through the downlink and the quality of the reference signal (RSRQ: reference) signal received quality) and the like, the measurement result may be reported to the base station 100 periodically or event triggered.

Here, the user terminal 1 may transmit channel quality indication (CQI) as a result of the measurement. The CQI is determined by the received signal quality of the terminal, which can generally be determined based on the measurement of the downlink reference signal. That is, the user terminal 1 can report the channel information according to the downlink channel condition through the uplink, and the base station 100 uses the downlink channel information received from each user terminal 1 to each user. For each terminal 1, an appropriate time / frequency resource and modulation and coding scheme (MCS) may be determined for data transmission. Here, the modulation and coding scheme set by the base station may include QPSK (Quadrature Phase Shift Keying), 16 QAM (16 Quadrature Amplitude Modulation), 64 QAM, 256 QAM, etc., respectively, of the 2nd, 4th, 6th, 8th order It can have a modulation order.

Meanwhile, the user terminal 1 may generate a CQI corresponding to each measurement result using a preset CQI table. In the CQI table, each CQI corresponding to the downlink channel, modulation and coding scheme (MCS) corresponding to the CQI may be displayed. Here, as the condition of the downlink channel is good, the CQI may increase, and the modulation order of the supported modulation and coding scheme may also increase.

CQI may be displayed in 4 bits, and when the user terminal 1 supports modulation and coding of 256QAM, a range for CQI for applying 256QAM may be newly defined. That is, in order to support the added 256QAM while maintaining the consistency with respect to the existing 64QAM, the user terminal 1 may further include a CQI table corresponding to 256QAM. Hereinafter, a CQI table corresponding to 64QAM is referred to as a first CQI table, and a CQI table corresponding to 256QAM is referred to as a second CQI table.

Specifically, the first CQI table may be represented as Table 1 below, and the second CQI table may be represented as Table 2 below.

CQI table for 64QAM CQI index modulation code rate x 1024 efficiency 0 out of range One QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5 QPSK 449 0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.9141 9 16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM 666 3.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948 5.5547

CQI table for 256QAM CQI index modulation code rate x 1024 efficiency 0 out of range One QPSK 78 0.1523 2 QPSK 193 0.3770 3 QPSK 449 0.8770 4 16QAM 378 1.4766 5 16QAM 490 1.9141 6 16QAM 616 2.4063 7 64QAM 466 2.7305 8 64QAM 567 3.3223 9 64QAM 666 3.9023 10 64QAM 772 4.5234 11 64QAM 873 5.1152 12 256QAM 711 5.5547 13 256QAM 797 6.2266 14 256QAM 885 6.9141 15 256QAM 948 7.4063

The base station 100 may be a communication device that provides wireless communication services such as voice calls and data communication to the user terminal 1 located in the cell, and according to an embodiment, a fixed station, Node B, eNode B (eNB), advanced base station (ABS), or access point (access point).

The base station 100 may receive downlink channel information from the user terminal 1, and modulate and code a modulation (MCS) method for data transmission for each user terminal 1 using the received downlink channel information. Can be set.

Specifically, the base station may set the MCS for each user terminal 1 using a preset MCS table. The MCS table may include an MCS index, a modulation order applied according to the MCS index, and a TBS index. Here, the base station 100 may apply a higher MCS index as the condition of the downlink channel to the user terminal 1 is higher, and a higher modulation order MCS may be set as the MCS index is higher. Here, the modulation orders 2, 4, 6, and 8 correspond to QPSK, 16QAM, 64QAM, and 256QAM, respectively, and a Transport Block Size (TBS) index corresponding to each MCS index may be set. Thereafter, if a separate TBS table table is used, a TBS value corresponding to a TBS index can be extracted.

Meanwhile, when the user terminal 1 supports up to 256QAM, an MCS table for applying 256QAM may be newly defined. That is, in order to maintain the consistency with respect to the existing 64QAM, and to support the added 256QAM, the base station 100 may further include an MCS table corresponding to 256QAM. Hereinafter, an MCS table corresponding to 64QAM is referred to as a first MCS table, and an MCS table corresponding to 256QAM is referred to as a second MCS table.

Specifically, the first MCS table may be represented as Table 3 below, and the second MCS table may be represented as Table 4 below.

MCS table for 64QAM

MCS Index

Modulation Order

TBS Index

0 2 0 One 2 One 2 2 2 3 2 3 4 2 4 5 2 5 6 2 6 7 2 7 8 2 8 9 2 9 10 4 9 11 4 10 12 4 11 13 4 12 14 4 13 15 4 14 16 4 15 17 6 15 18 6 16 19 6 17 20 6 18 21 6 19 22 6 20 23 6 21 24 6 22 25 6 23 26 6 24 27 6 25 28 6 26 / 26A 29 2 reserved 30 4 31 6

MCS table for 256QAM

MCS Index

Modulation Order

TBS Index

0 2 0 One 2 2 2 2 4 3 2 6 4 2 8 5 4 10 6 4 11 7 4 12 8 4 13 9 4 14 10 4 15 11 6 16 12 6 17 13 6 18 14 6 19 15 6 20 16 6 21 17 6 22 18 6 23 19 6 24 20 8 25 21 8 27 22 8 28 23 8 29 24 8 30 25 8 31 26 8 32 27 8 33 / 33A 28 2
reserved 29 4 30 6 31 8

Conventionally, if the user terminal 1 supports 256QAM, it is always set to utilize the second CQI table, or if the transmitting CQI is greater than or equal to a preset value, the CQI is transmitted using the second CQI table instead of the first CQI table. Did.

However, when the user terminal 1 always uses the second CQI table, the timing of changing the MCS can be set differently compared to the case where the first CQI table is used. That is, when referring to the second CQI table, MCS with a higher modulation order is applied faster than when referring to the first CQI table. In this case, unnecessary resource waste such as poor transmission efficiency occurs. Can cause problems.

In addition, when the second CQI table is used only when the value is greater than or equal to a preset CQI value, only CQI is uniformly compared to determine whether to switch to 256QAM. There may be a problem such as a case where there is no gain in the link speed.

Specifically, as shown in FIG. 3, it is advantageous to operate at 256QAM (L1) in the A section at downlink speed, but it may be more advantageous to operate at 64QAM (L2) in the C section. However, in section B, the speeds of 64QAM (L2) and 256QAM (L1) are similar to each other, and considering the BLER of the channel, it may be advantageous to operate with 64QAM (L2). However, when the preset CQI value is located in the B section, it may operate as 256 QAM in the B section, and in this case, a loss may occur in the downlink speed according to the channel environment such as the BLER of the channel. .

In order to solve the above-mentioned problems, the base station 100 according to an embodiment of the present invention may refer to each MCS and convert it to 256QAM only for a section in which a gain occurs in a downlink rate.

Hereinafter, a base station according to an embodiment of the present invention will be described with reference to FIG. 2.

2 is a block diagram showing a base station according to an embodiment of the present invention.

2, the base station 100 according to an embodiment of the present invention includes an MCS index determination unit 110, a confirmation unit 120, a TBS comparison unit 130, a setting unit 140, and a CQI receiving unit 150 ). Here, an embodiment in which the base station 100 converts the modulation and coding scheme from 64QAM to 256QAM will be described.

The MCS index determination unit 110 may determine whether to increase or decrease the MCS index set in the user terminal 1 by using the CQI received from the user terminal 1 and the BLER of the channel. Here, an MCS to be applied to each user terminal 1 may be determined according to the MCS index, and each MCS may be set according to a channel environment. Accordingly, the MCS index determination unit 110 may determine each MCS index using the CQI received from the user terminal and the BLER measured by the base station.

When the MCS of the user terminal 1 is converted from 64QAM to 256QAM, the MCS of the user terminal 1 may be set to 64QAM, and the user terminal 1 is transmitting CQI according to the first CQI table. You can.

Here, the MCS index determination unit 110 may increase the MCS index when the CQI received from the user terminal 1 increases. Since the increase in CQI corresponds to a case where the channel environment of the user terminal 1 is improved, the MCS index determination unit 110 may increase the MCS index.

In addition, the MCS index determination unit 110 may maintain the CQI constant, but may increase the MCS index even when the BLER decreases. The lower BLER corresponds to a case where the reception rate for the data signal transmitted by the user terminal 1 is improved, so that an effect such as a faster transmission speed can be obtained. Accordingly, the MCS index determiner 110 may increase the MCS index when the BLER decreases while the CQI is kept constant.

When the MCS index is increased, the verification unit 120 may check whether 256QAM can be applied to the increased MCS index. Increasing the MCS index means that the channel environment of the user terminal 1 is improved, so the confirmation unit 120 can check whether it can be switched from 64QAM to 256QAM. Here, since the user terminal 1 is currently set to 64QAM by the first MCS table, the verification unit 120 may check the MCS corresponding to the increased MCS index using the second MCS table.

First, the verification unit 120 may search for the MCS corresponding to the increased MCS index in the second MCS table. As a result of the search, if it is determined that the MCS corresponding to the increased MCS index corresponds to 256QAM, the verification unit 120 may determine that 256QAM is applicable to the user terminal 1. That is, the verification unit 120 may check whether 256QAM is applicable in the increased MCS index using the second MCS table table.

However, in some cases, the user terminal 1 may not support 256QAM MCS. In this case, it is possible to first check whether the application of 256QAM of the user terminal 1 is applicable, by using the supportable MCS information of the user terminal 1 received from the user terminal 1 upon initial access. In this case, without needing to check the second MCS table table, the user terminal 1 can confirm that 256QAM is not applied.

If it is confirmed that 256QAM is applicable to the user terminal 1, the TBS comparison unit 130 extracts TBS (Transport Block Size) in 64QAM and TBS in 256QAM corresponding to the increased MCS index and compares them. have. Specifically, the TBS comparator 130, from the first MCS table table corresponding to 64QAM and the second MCS table table corresponding to 256QAM, respectively, TBS at 64QAM and TBS at 256QAM corresponding to the increased MCS index. It can be extracted and compared with each other.

As shown in FIG. 3, even when switching from 64QAM to 256QAM in section B, there may be no significant gain in downlink speed. Therefore, it is possible to determine which is advantageous in the downlink transmission rate by directly comparing TBS in the case of operating according to 64QAM and switching to 256QAM, respectively. In this case, after extracting the TBS index corresponding to the increased MCS index from each of the first MCS table table and the second MCS table table, the TBS value corresponding to each TBS index is searched in the separately provided TBS table, Each TBS can be extracted.

Here, the larger the TBS, the more information is transmitted at a time, so the larger the TBS, the faster the downlink transmission rate can be viewed. Therefore, by comparing the TBS for each case in the TBS comparison unit 130, it is possible to determine which of the 64QAM operation and 256QAM operation is more advantageous.

The setting unit 140 may set the user terminal 1 to use the second CQI table corresponding to 256QAM when the TBS in 256QAM is greater than the TBS in 64QAM. In addition, by applying an increased MCS index to 256QAM, a corresponding downlink signal can be transmitted to the user terminal 1. That is, since the downlink transmission speed is faster when operating in 256QAM, the setting unit 140 may set the user terminal 1 to operate in 256QAM.

On the other hand, if the TBS in 256QAM is less than or equal to the TBS in 64QAM, the user terminal 1 may be configured to use the first CQI table corresponding to 64QAM. In addition, by applying an increased MCS index to 64QAM, a corresponding downlink signal can be transmitted to the user terminal 1. That is, rather than switching to 256QAM, since operating at 64QAM is advantageous for downlink transmission speed, the setting unit 140 may set the user terminal 1 to operate at 64QAM. Additionally, the setting unit 140 may allow the TBS in the 256QAM to operate as 64QAM even when the TBS in the 64QAM is the same, because when applying the 64QAM, relatively few BLERs may appear.

The CQI receiving unit 150 may receive information about a channel state such as CQI from the user terminal 1. That is, when the user terminal 1 is set by the setting unit 140 to use the first CQI table or the second CQI table, the CQI receiving unit 150 sets the first CQI table or the first set from the user terminal 1, respectively. 2 CQI according to the CQI table may be received.

On the other hand, depending on the embodiment, it is also possible for the base station 100 to convert the modulation and coding scheme from 256QAM to 64QAM. In this case, the MCS of the user terminal 1 may be set to 256QAM, and may transmit CQI according to the second CQI table.

The MCS index determination unit 110 may determine whether the MCS index set in the user terminal 1 is reduced using the CQI received from the user terminal 1 and the BLER of the channel. Here, the MCS index determination unit 110 may decrease the MCS index when the CQI transmitted by the user terminal 1 decreases or when the CQI remains constant but the BLER increases. That is, when the channel environment is deteriorated, such as a decrease in CQI or an increase in BLER, the MCS index determiner 110 may decrease the MCS index to improve the downlink speed.

When the MCS index decreases, the verification unit 120 may check whether 64QAM is applicable in the reduced MCS index. Specifically, the verification unit 120 may check whether 64QAM is applicable in the reduced MCS index by using the first MCS table table corresponding to 64QAM. If it is impossible to apply to 64QAM, a reduced MCS index according to 256QAM can be applied.

In the TBS comparison unit 130, when 64QAM is applicable, a data transmission rate in TQ (Transport Block Size) in 64QAM corresponding to the reduced MCS index and 256QAM corresponding to the reduced MCS index may be compared. Specifically, the TBS comparison unit 130 may first extract the TBS in 64QAM corresponding to the reduced MCS index from the first MCS table table corresponding to 64QAM. Thereafter, the TBS in 256QAM corresponding to the reduced MCS index from the second MCS table table corresponding to 256QAM can be extracted, and the TBS in the extracted 256QAM is multiplied by (1-BLER) to calculate the data transmission rate. Here, since the TBS in 64QAM and the data transmission rate in 256QAM are extracted, the TBS comparator 130 can compare the sizes of each other.

In the setting unit 140, if the TBS in 64QAM is greater than the data transmission rate in 256QAM, the user terminal 1 may be set to operate in 64QAM. That is, the user terminal 1 may be set to use the first CQI table corresponding to 64QAM, and a reduced MCS index may be applied to 64QAM to transmit the corresponding downlink signal to the user terminal 1.

On the other hand, when the TBS in 64QAM is less than or equal to the data transmission rate in 256QAM, the user terminal 1 may be set to operate in 256QAM. That is, the user terminal 1 is set to use the second CQI table corresponding to 256QAM, and the reduced MCS index is applied to 256QAM, so that the corresponding downlink signal can be transmitted to the user terminal 1.

The CQI receiving unit 150 may receive information about a channel state such as CQI from the user terminal 1. That is, when the user terminal 1 is set by the setting unit 140 to use the first CQI table or the second CQI table, the CQI receiving unit 150 sets the first CQI table or the first set from the user terminal 1, respectively. 2 CQI according to the CQI table may be received.

4 is a flowchart illustrating a method of changing a modulation and coding scheme in a base station according to an embodiment of the present invention, and shows an embodiment of converting from 64QAM to 256QAM.

Referring to Figure 4, the modulation and coding method change method in the base station according to an embodiment of the present invention, MCS index determination step (S110), confirmation step (S120), TBS comparison step (S130), setting step (S141) , S142) and CQI receiving step (S150).

Hereinafter, a modulation and coding method change method in a base station according to an embodiment of the present invention will be described with reference to FIG. 4.

In the MCS index determination step S110, it is possible to determine whether to increase the MCS index set in the user terminal by using the CQI received from the user terminal and the BLER of the channel. Specifically, in the MCS index determination step S110, when the CQI received from the user terminal 1 increases or the CQI remains constant, the MCS index may be increased when the BLER decreases. Meanwhile, the present embodiment corresponds to a case in which the MCS of a user terminal is converted from 64QAM to 256QAM, so the MCS of the user terminal may be set to 64QAM, and the user terminal may transmit CQI according to the first CQI table. have.

In the checking step (S120), if the MCS index is increased, it can be checked whether 256QAM can be applied to the increased MCS index. Since the MCS index increases means that the channel environment of the user terminal is improved, it is possible to check whether it can be switched from 64QAM to 256QAM through the checking step S120. In the checking step (S120), the MCS corresponding to the increased MCS index can be searched in the second MCS table, and if the MCS corresponding to the increased MCS index is found to correspond to 256QAM, 256QAM is applicable to the user terminal. You can judge that. That is, it is possible to check whether 256QAM is applicable in the increased MCS index using the second MCS table table.

In the TBS comparison step (S130), if it is determined that 256QAM is applicable to the user terminal, TBS (Transport Block Size) in 64QAM corresponding to the increased MCS index and TBS in 256QAM may be extracted and compared. Specifically, from the first MCS table table corresponding to 64QAM and the second MCS table table corresponding to 256QAM, TBS at 64QAM and TBS at 256QAM corresponding to the increased MCS index can be extracted and compared with each other.

Depending on the channel environment, even when switching from 64QAM to 256QAM, there may be a case where there is no significant gain in downlink speed. Therefore, through the TBS comparison step (S130), it is possible to directly compare the TBS in the case of operating according to 64QAM and 256QAM by switching to 256QAM, and determine which is advantageous in the downlink transmission rate. In this case, after extracting the TBS index corresponding to the increased MCS index from each of the first MCS table table and the second MCS table table, the TBS value corresponding to each TBS index is searched in the separately provided TBS table, Each TBS can be extracted.

Here, the larger the TBS, the more information is transmitted at a time, so the larger the TBS, the faster the downlink transmission rate can be viewed. Therefore, by comparing the TBS for each case through the TBS comparison step (S130), it is possible to determine which is more advantageous in the case of operating in actual 64QAM or in case of operating in 256QAM.

Thereafter, if the TBS in 256QAM is greater than the TBS in 64QAM, the user terminal may be set to use the second CQI table corresponding to 256QAM through the setting step S141. In addition, by applying an increased MCS index to 256QAM, a corresponding downlink signal can be transmitted to a user terminal. That is, since the downlink transmission speed is faster when operating in 256QAM, the user terminal 1 may be set to operate in 256QAM in the setting step S141.

On the other hand, if the TBS in 256QAM is less than or equal to the TBS in 64QAM, the user terminal may be configured to use the first CQI table corresponding to 64QAM through the setting step S142. In addition, by applying an increased MCS index to 64QAM, a corresponding downlink signal can be transmitted to the user terminal. That is, rather than switching to 256QAM, operating at 64QAM is advantageous for downlink transmission speed, so that the user terminal can be set to operate at 64QAM through the setting step S142.

When the user terminal is set to use the first CQI table or the second CQI table, the CQI receiving step (S150) may receive the CQI according to the first CQI table or the second CQI table set from the user terminal, respectively. That is, when the user terminal is set to use the second CQI table through the setting step S141, the CQI according to the second CQI table may be received.

5 is a flowchart illustrating a method of changing a modulation and coding scheme in a base station according to an embodiment of the present invention, and shows an embodiment of converting from 256QAM to 64QAM.

Referring to Figure 5, the modulation and coding method change method in the base station according to an embodiment of the present invention, MCS index determination step (S210), confirmation step (S220), TBS comparison step (S230), setting step (S240) ) And CQI receiving step (S250).

Hereinafter, a method of changing modulation and coding scheme in a base station according to an embodiment of the present invention will be described with reference to FIG. 5.

In the MCS index determination step (S210), it is possible to determine whether the MCS index set in the user terminal is reduced by using the CQI received from the user terminal and the BLER of the channel. Here, in the MCS index determination step (S210), when the CQI transmitted by the user terminal decreases or the CQI remains constant, but the BLER increases, the MCS index may be decreased. That is, if the channel environment is deteriorated, such as a decrease in CQI or an increase in BLER, the MCS index can be decreased to improve downlink speed.

In the checking step S220, when the MCS index decreases, it is possible to check whether 64QAM is applicable in the reduced MCS index. Specifically, using the first MCS table table corresponding to 64QAM, it is possible to check whether 64QAM is applicable in the reduced MCS index, and if it is impossible to apply to 64QAM, the reduced MCS index is applied according to 256QAM. can do.

In the TBS comparison step (S230), if 64QAM is applicable, the data transmission rate in TQ (Transport Block Size) in 64QAM corresponding to the reduced MCS index and 256QAM corresponding to the reduced MCS index may be compared. In the TBS comparison step (S230), first, the TBS in 64QAM corresponding to the reduced MCS index may be extracted from the first MCS table table corresponding to 64QAM. Thereafter, the TBS in 256QAM corresponding to the reduced MCS index can be extracted from the second MCS table table corresponding to 256QAM, and the TBS in the extracted 256QAM is multiplied by (1-BLER) to calculate the data transmission rate. Here, since the data transmission rate in TQ of 64QAM and 256QAM are extracted, each size can be compared with each other.

If the TBS in 64QAM is greater than the data transmission rate in 256QAM, the user terminal may be set to operate in 64QAM through a setting step (S241). That is, the user terminal may be set to use the first CQI table corresponding to 64QAM, and the reduced downlink signal may be transmitted to the user terminal by applying the reduced MCS index to 64QAM.

On the other hand, if the TBS in 64QAM is less than or equal to the data transmission rate in 256QAM, the user terminal may be configured to operate in 256QAM through the setting step S242. That is, the user terminal may be set to use the second CQI table corresponding to 256QAM, and the reduced MCS index may be applied to 256QAM to transmit the corresponding downlink signal to the user terminal.

When the user terminal is configured to use the first CQI table or the second CQI table, the CQI receiving step (S250) may receive the CQI according to the first CQI table or the second CQI table, respectively, set from the user terminal. That is, when the user terminal is set to use the first CQI table through the setting step S241, the CQI according to the first CQI table may be received.

The present invention is not limited by the above-described embodiments and the accompanying drawings. For those skilled in the art to which the present invention pertains, it will be apparent that components according to the present invention can be substituted, modified and changed without departing from the technical spirit of the present invention.

1: user terminal 100: base station
110: MCS index determination unit 120: confirmation unit
130: TBS comparison unit 140: setting unit
150: CQI receiver

Claims (14)

As a method for changing the modulation and coding scheme (MCS: Modulation and Coding Scheme) in the base station,
An MCS index determination step of determining whether to increase the MCS index set in the user terminal by using a channel quality indicator (CQI) received from a user terminal set to 64QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of the channel;
When the MCS index is increased, a confirmation step of checking whether 256QAM is applicable in the increased MCS index;
A TBS comparison step of extracting and comparing TBS (Transport Block Size) in 64QAM and TBS in 256QAM corresponding to the increased MCS index when the 256QAM is applicable; And
If the TBS in the 256QAM is greater than the TBS in the 64QAM, the user terminal is configured to use the second CQI table corresponding to the 256QAM, and the increased MCS index is applied to the 256QAM, and corresponding downlink Method for changing the modulation and coding method in the base station comprising a setting step of transmitting a signal to the user terminal.
The method of claim 1, wherein the determining of the MCS index
When the CQI is increased or the CQI is constant but the BLER is decreased, the method of changing the modulation and coding scheme at the base station is characterized in that the MCS index is increased.
The method of claim 1, wherein the confirmation step
A method of changing a modulation and coding scheme in a base station, characterized in that it is checked whether the 256QAM is applicable in the increased MCS index by using a second MCS table table corresponding to the 256QAM.
The method of claim 1, wherein the TBS comparison step
Characterized in that the TBS in 64QAM and TBS in 256QAM are respectively extracted from the first MCS table table corresponding to the 64QAM and the second MCS table table corresponding to the 256QAM, and compared with each other. A method of changing the modulation and coding scheme at a base station.
The method of claim 1, wherein the setting step
When the TBS in the 256QAM is less than or equal to the TBS in the 64QAM, the user terminal is configured to use the first CQI table corresponding to the 64QAM, and the increased MCS index is applied to the 64QAM, thereby corresponding A method of changing modulation and coding scheme in a base station, characterized in that a downlink signal is transmitted to the user terminal.
The method of claim 5,
When the user terminal is set to use the second CQI table, the CQI receiving step of receiving a CQI according to the second CQI table from the user terminal further comprises a modulation and coding scheme change in the base station Way.
As a method for changing the modulation and coding scheme (MCS: Modulation and Coding Scheme) in the base station,
An MCS index determination step of determining whether the MCS index set in the user terminal is reduced by using a channel quality indicator (CQI) received from a user terminal set to 256QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of the channel;
When the MCS index is decreased, a checking step of checking whether 64QAM is applicable in the reduced MCS index;
A TBS comparison step of comparing the transport block size (TSB) in 64QAM corresponding to the reduced MCS index and the data transmission rate in 256QAM corresponding to the reduced MCS index when the 64QAM is applicable; And
If the TBS in the 64QAM is greater than the data transmission rate in the 256QAM, the user terminal is configured to use the first CQI table corresponding to the 64QAM, and the reduced MCS index is applied to the 64QAM, and the corresponding downlink A method of changing a modulation and coding method in a base station comprising a setting step of transmitting a signal to the user terminal.
The method of claim 7, wherein the MCS index determining step
When the CQI decreases or the CQI is constant but the BLER increases, the method of changing the modulation and coding scheme at the base station is characterized in that the MCS index is decreased.
The method of claim 7, wherein the confirmation step
A method of changing a modulation and coding scheme in a base station, characterized in that it is checked whether the 64QAM is applicable in the reduced MCS index using a first MCS table table corresponding to the 64QAM.
The method of claim 7, wherein the TBS comparison step
Extracting TBS in 64QAM corresponding to the reduced MCS index from the first MCS table table corresponding to the 64QAM;
Extracting TBS in 256QAM corresponding to the reduced MCS index from the second MCS table table corresponding to the 256QAM, and multiplying the extracted TBS in 256QAM by (1-BLER) to calculate the data transmission rate; And
And comparing the TBS in the 64QAM with the data transmission rate in the 256QAM.
The method of claim 7, wherein the setting step
If the TBS in the 64QAM is less than or equal to the data transmission rate in the 256QAM, the user terminal is set to use the second CQI table corresponding to the 256QAM, and the reduced MCS index is applied to the 256QAM, thereby corresponding A method of changing modulation and coding scheme in a base station, characterized in that a downlink signal is transmitted to the user terminal.
The method of claim 11,
If the user terminal is set to use the first CQI table, the CQI receiving step of receiving the CQI according to the first CQI table from the user terminal further comprises a modulation and coding scheme change in the base station Way.
An MCS index determination unit for determining whether to increase or decrease the MCS index set in the user terminal by using a channel quality indicator (CQI) received from a user terminal set to 64QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of the channel;
When increasing the MCS index, a checking unit to check whether 256QAM is applicable in the increased MCS index;
A TBS comparison unit for extracting and comparing TBS (Transport Block Size) in 64 QAM and TBS in 256 QAM corresponding to the increased MCS index when the 256 QAM is applicable; And
If the TBS in the 256QAM is greater than the TBS in the 64QAM, the user terminal is configured to use the second CQI table corresponding to the 256QAM, and the increased MCS index is applied to the 256QAM, and corresponding downlink A base station including a setting unit for transmitting a signal to the user terminal.
An MCS index determination unit determining whether to decrease the MCS index set in the user terminal by using a channel quality indicator (CQI) received from a user terminal set to 256QAM (Quadrature Amplitude Modulation) and a block error rate (BLER) of the channel;
When reducing the MCS index, a confirmation unit to determine whether 64QAM is applicable in the reduced MCS index;
When the 64QAM is applicable, a TBS (Transport Block Size) in 64QAM corresponding to the reduced MCS index and a TBS comparison unit comparing data transmission rates in 256QAM corresponding to the reduced MCS index; And
If the TBS in the 64QAM is greater than the data transmission rate in the 256QAM, the user terminal is configured to use the first CQI table corresponding to the 64QAM, and the reduced MCS index is applied to the 64QAM, and the corresponding downlink A base station including a setting unit for transmitting a signal to the user terminal.

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