WO2016122187A1

WO2016122187A1 - Method for uplink power control in wireless access system supporting unlicensed band and apparatus for supporting same

Info

Publication number: WO2016122187A1
Application number: PCT/KR2016/000814
Authority: WO
Inventors: 김선욱; 안준기; 양석철; 이승민; 이윤정; 황대성
Original assignee: 엘지전자 주식회사
Priority date: 2015-01-26
Filing date: 2016-01-26
Publication date: 2016-08-04

Abstract

The present invention provides methods for uplink power control in a wireless access system supporting an unlicensed band, and apparatuses for supporting the same. As an embodiment of the present invention, a method for performing uplink (UL) power control by a UE in a wireless access system supporting an unlicensed band may comprise the steps of: receiving two or more UL grants including scheduling information; when a licensed band cell (L cell) and an unlicensed band cell (U cell) are included in scheduled serving cells, performing power control on the basis of the sum (P_L) of transmission power required by the L cell, the maximum transmission power (P_u) that can be transmitted by the U cell, a guaranteed power value (P_g) for the U cell, and the maximum transmission power (PCMAX) that can be used by the UE; and transmitting a UL signal in each of the L cell and the U cell on the basis of transmission power derived from the power control, and the scheduling information.

Description

Uplink power control method and apparatus supporting same in wireless access system supporting unlicensed band

The present invention relates to a wireless access system supporting an unlicensed band, and more particularly, to methods of controlling uplink power and apparatuses for supporting the same.

Wireless access systems are widely deployed to provide various kinds 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 multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access) system.

An object of the present invention is to provide methods for efficiently controlling uplink power in a wireless access system supporting an unlicensed band.

It is an object of the present invention to provide methods for solving the hidden node problem in power control in an unlicensed band.

Another object of the present invention is to provide methods for controlling uplink transmission power used between a licensed band cell and an unlicensed band cell.

Still another object of the present invention is to provide methods for controlling transmission power between unlicensed band cells when a terminal transmits an uplink signal through two or more unlicensed band cells.

It is yet another object of the present invention to provide devices which support these methods.

Technical objects to be achieved in the present invention are not limited to the above-mentioned matters, and other technical problems which are not mentioned are those skilled in the art from the embodiments of the present invention to be described below. Can be considered.

The present invention relates to a wireless access system that supports an unlicensed band, and provides methods for controlling uplink power and apparatuses for supporting the same.

According to an aspect of the present invention, a method of performing uplink (UL) power control by a terminal in a wireless access system supporting an unlicensed band includes receiving two or more UL grants including scheduling information and scheduling cells. In the case where a licensed band cell (L cell) and an unlicensed band cell (U cell) are included, the sum of the transmit power required by the L cell (P_L), the maximum value of transmit power that can be transmitted by the U cell (P_u) to ensure power value (P_g) and the UE the maximum available transmission power (P _CMAX) the based on based on the transmission power, and scheduling information derived from the phase and power control for performing power control in L cells and U cells Each may include transmitting a UL signal.

In another aspect of the present invention, a terminal for performing uplink (UL) power control in a wireless access system supporting an unlicensed band may include a receiver, a transmitter, and a processor for supporting UL power control. At this time, the processor controls the receiver to receive two or more UL grants including scheduling information; If the scheduled serving cells include a licensed band cell (L cell) and an unlicensed band cell (U cell), the sum of the transmit power required by the L cell (P_L) and the maximum value of transmit power that can be transmitted by the U cell ( P_u), and a guaranteed power value (P_g) and a terminal U for the cell used to perform power control based on the maximum transmission power value (P _CMAX) as possible; By controlling the transmitter, it may be configured to transmit the UL signal in each of the L cell and the U cell based on the transmission power and the scheduling information derived through the power control.

In this case, P_u may be always set to a value greater than or equal to P_g regardless of P_L.

At this time, P_g may be determined as a ratio of the P _CMAX.

MS may P_g the value in P _CMAX first allocated for the cell, and U, the remainder value for the L cells. In addition, the mobile station then assigns the P_L P _CMAX at first, if the rest of the available power value (P_remain) less than P_g, P_g - may be assigned by the power of the U P_remain cells than the L cells.

In addition, P_g may be set to a value valid only in a subframe scheduled by two or more UL grants.

If two or more U cells are scheduled to the UE, the UE may perform power scaling down on the transmission powers to be allocated to the U cells so that the transmission powers allocated to the U cells do not exceed P_u.

The above-described aspects of the present invention are merely some of the preferred embodiments of the present invention, and various embodiments reflecting the technical features of the present invention will be described in detail by those skilled in the art. Based on the description, it can be derived and understood.

According to embodiments of the present invention has the following effects.

First, uplink power can be efficiently controlled in a wireless access system supporting an unlicensed band.

Second, data transmission and reception can be performed stably by solving a hidden node problem when controlling power in an unlicensed band.

Third, the uplink transmission power can be efficiently controlled by controlling the uplink transmission power used between the licensed band cell and the unlicensed band cell, and the overall data throughput can be increased.

Fourth, the terminal can efficiently transmit data even when two or more unlicensed band cells are allocated by providing methods for controlling the transmission power between two or more unlicensed band cells.

Effects obtained in the embodiments of the present invention are not limited to the above-mentioned effects, and other effects not mentioned above are usually described in the technical field to which the present invention pertains from the description of the embodiments of the present invention. Can be clearly derived and understood by those who have That is, unintended effects of practicing the present invention may also be derived from those skilled in the art from the embodiments of the present invention.

It is included as part of the detailed description to assist in understanding the present invention, and the accompanying drawings provide various embodiments of the present invention. In addition, the accompanying drawings are used to describe embodiments of the present invention in conjunction with the detailed description.

1 is a diagram illustrating a physical channel and a signal transmission method using the same.

2 is a diagram illustrating an example of a structure of a radio frame.

3 is a diagram illustrating a resource grid for a downlink slot.

4 is a diagram illustrating an example of a structure of an uplink subframe.

5 is a diagram illustrating an example of a structure of a downlink subframe.

6 is a diagram illustrating an example of carrier aggregation used in a component carrier (CC) and LTE_A system.

7 shows a subframe structure of an LTE-A system according to cross carrier scheduling.

8 is a diagram illustrating an example of a configuration of a serving cell according to cross carrier scheduling.

9 is a diagram illustrating one of the SRS transmission methods used in embodiments of the present invention.

FIG. 10 is a diagram illustrating an example of a subframe to which a cell specific reference signal (CRS) is allocated, which can be used in embodiments of the present invention.

FIG. 11 is a diagram illustrating an example of subframes in which CSI-RSs that can be used in embodiments of the present invention are allocated according to the number of antenna ports.

FIG. 12 is a diagram illustrating an example in which legacy PDCCH, PDSCH, and E-PDCCH used in an LTE / LTE-A system are multiplexed.

13 is a diagram illustrating an example of a CA environment supported by an LTE-U system.

14 is a diagram for describing a case in which cell coverage according to transmission power is set.

15 is a diagram for describing a method of performing power control in an LAA system.

16 is a diagram for describing a power control method between an L cell and a U cell.

FIG. 17 is a diagram for describing one of methods for performing power control by considering a transmission power for each U cell.

FIG. 18 is a diagram for describing another method of performing power control by considering a transmission power for each U cell.

The apparatus described in FIG. 19 is a means by which the methods described in FIGS. 1 to 18 may be implemented.

The present invention relates to a wireless access system supporting an unlicensed band, and proposes methods for controlling uplink power and apparatuses for supporting the same.

The following embodiments combine the components and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied 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 may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

In the description of the drawings, procedures or steps which may obscure the gist of the present invention are not described, and procedures or steps that can be understood by those skilled in the art are not described.

Throughout the specification, when a part is said to "comprising" (or including) a component, this means that it may further include other components, except to exclude other components unless specifically stated otherwise. do. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have. Also, "a or an", "one", "the", and the like are used differently in the context of describing the present invention (particularly in the context of the following claims). Unless otherwise indicated or clearly contradicted by context, it may be used in the sense including both the singular and the plural.

In the present specification, embodiments of the present invention have been described based on data transmission / reception relations between a base station and a mobile station. Here, the base station is meant as a terminal node of a network that directly communicates with a mobile station. The specific operation described as performed by the base station in this document 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 consisting of a plurality of network nodes including a base station may be performed by the base station or network nodes other than the base station. In this case, 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.

Further, in embodiments of the present invention, a terminal may be a user equipment (UE), a mobile station (MS), a subscriber station (SS), or a mobile subscriber station (MSS). It may be replaced with terms such as a mobile terminal or an advanced mobile station (AMS).

Also, 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 uplink, a mobile station may be a transmitting end and a base station may be a receiving end. Similarly, in downlink, a mobile station may be a receiving end and a base station may be a transmitting end.

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

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced.

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

For example, the term Transmission Opportunity Period (TxOP) may be used in the same meaning as the term transmission period or RRP (Reserved Resource Period). Also, the LBT process may be performed for the same purpose as a carrier sensing (CS) process for determining whether a channel state is idle.

Hereinafter, a 3GPP LTE / LTE-A system will be described as an example of a wireless access system in which embodiments of the present invention can be used.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be applied to various radio access systems.

CDMA may be implemented with a 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 in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA).

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

1. 3GPP LTE/LTE_A 시스템1.3GPP LTE / LTE_A System

In a wireless access system, a terminal receives information from a base station through downlink (DL) and transmits information to the base station through uplink (UL). The information transmitted and received by the base station and the terminal includes general data information and various control information, and various physical channels exist according to the type / use of the information they transmit and receive.

1.1 시스템 일반1.1 System General

1 is a diagram for explaining physical channels that can be used in embodiments of the present invention and a signal transmission method using the same.

When the power is turned off again or a new cell enters the cell, the initial cell search operation such as synchronizing with the base station is performed in step S11. To this end, the UE receives a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH) from the base station, synchronizes with the base station, and obtains information such as a cell ID.

Thereafter, the terminal may receive a physical broadcast channel (PBCH) signal from the base station to obtain broadcast information in a cell.

On the other hand, the terminal may receive a downlink reference signal (DL RS) in the initial cell search step to confirm the downlink channel state.

After completing the initial cell search, the UE receives a physical downlink control channel (PDCCH) and a physical downlink control channel (PDSCH) according to the physical downlink control channel information in step S12. Specific system information can be obtained.

Subsequently, the terminal may perform a random access procedure as in steps S13 to S16 to complete the access to the base station. To this end, the UE transmits a preamble through a physical random access channel (PRACH) (S13), a response message to the preamble through a physical downlink control channel and a corresponding physical downlink shared channel. Can be received (S14). In case of contention-based random access, the UE may perform contention resolution such as transmitting an additional physical random access channel signal (S15) and receiving a physical downlink control channel signal and a corresponding physical downlink shared channel signal (S16). Procedure).

After performing the above-described procedure, the UE subsequently receives a physical downlink control channel signal and / or a physical downlink shared channel signal (S17) and a physical uplink shared channel (PUSCH) as a general uplink / downlink signal transmission procedure. A transmission (Uplink Shared Channel) signal and / or a Physical Uplink Control Channel (PUCCH) signal may be transmitted (S18).

The control information transmitted from the terminal to the base station is collectively referred to as uplink control information (UCI). UCI includes Hybrid Automatic Repeat and reQuest Acknowledgement / Negative-ACK (HARQ-ACK / NACK), Scheduling Request (SR), Channel Quality Indication (CQI), Precoding Matrix Indication (PMI), and Rank Indication (RI). .

In the LTE system, UCI is generally transmitted periodically through the PUCCH, but may be transmitted through the PUSCH when control information and traffic data should be transmitted at the same time. In addition, the UCI may be aperiodically transmitted through the PUSCH by the request / instruction of the network.

2 shows a structure of a radio frame used in embodiments of the present invention.

2 (a) shows a frame structure type 1. The type 1 frame structure can be applied to both full duplex Frequency Division Duplex (FDD) systems and half duplex FDD systems.

One radio frame has a length of Tf = 307 200 * Ts = 10 ms, an equal length of Tslot = 15360 * Ts = 0.5 ms, and consists of 20 slots indexed from 0 to 19. One subframe is defined as two consecutive slots, and the i-th subframe includes slots corresponding to 2i and 2i + 1. That is, a radio frame consists of 10 subframes. The time taken to transmit one subframe is called a transmission time interval (TTI). Here, Ts represents a sampling time and is represented by T _s = 1 / (15 kHz x 2048) = 3.2552 x 10 ^-8 (about 33 ns). The slot includes a plurality of OFDM symbols or SC-FDMA symbols in the time domain and a plurality of resource blocks in the frequency domain.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. Since 3GPP LTE uses OFDMA in downlink, the OFDM symbol is for representing one symbol period. The OFDM symbol may be referred to as one SC-FDMA symbol or symbol period. A resource block is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot.

In a full-duplex FDD system, 10 subframes may be used simultaneously for downlink transmission and uplink transmission during each 10ms period. At this time, uplink and downlink transmission are separated in the frequency domain. On the other hand, in the case of a half-duplex FDD system, the terminal cannot transmit and receive at the same time.

The structure of the radio frame described above is just one example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the number of OFDM symbols included in the slot may be variously changed.

2 (b) shows a frame structure type 2. Type 2 frame structure is applied to the TDD system. One radio frame has a length of Tf = 307200 * Ts = 10ms and consists of two half-frames having a length of 153600 * Ts = 5ms. Each half frame consists of five subframes having a length of 30720 * Ts = 1ms. The i-th subframe consists of two slots each having a length of Tslot = 15360 * Ts = 0.5ms corresponding to 2i and 2i + 1. Here, Ts represents a sampling time and is represented by T _s = 1 / (15 kHz x 2048) = 3.2552 x 10 ^-8 (about 33 ns).

The type 2 frame includes a special subframe consisting of three fields: a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). Here, the DwPTS is used for initial cell search, synchronization or channel estimation in the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

Table 1 below shows the structure of the special frame (length of DwPTS / GP / UpPTS).

Table 1

3 is a diagram illustrating a resource grid for a downlink slot that can be used in embodiments of the present invention.

Referring to FIG. 3, one downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes seven OFDM symbols, and one resource block includes 12 subcarriers in a frequency domain, but is not limited thereto.

Each element on the resource grid is a resource element, and one resource block includes 12 × 7 resource elements. The number NDL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

4 shows a structure of an uplink subframe that can be used in embodiments of the present invention.

Referring to FIG. 4, an uplink subframe may be divided into a control region and a data region in the frequency domain. The control region is allocated a PUCCH carrying uplink control information. In the data area, a PUSCH carrying user data is allocated. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH. The PUCCH for one UE is allocated an RB pair in a subframe. RBs belonging to the RB pair occupy different subcarriers in each of the two slots. The RB pair assigned to this PUCCH is said to be frequency hopping at the slot boundary.

5 shows a structure of a downlink subframe that can be used in embodiments of the present invention.

Referring to FIG. 5, up to three OFDM symbols from the OFDM symbol index 0 in the first slot in the subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which the PDSCH is allocated. to be. One example of a downlink control channel used in 3GPP LTE includes a Physical Control Format Indicator Channel (PCFICH), a PDCCH, and a Physical Hybrid-ARQ Indicator Channel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe and carries information about the number of OFDM symbols (ie, the size of the control region) used for transmission of control channels within the subframe. The PHICH is a response channel for the uplink and carries an ACK (Acknowledgement) / NACK (Negative-Acknowledgement) signal for a hybrid automatic repeat request (HARQ). Control information transmitted through the PDCCH is called downlink control information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information or an uplink transmission (Tx) power control command for a certain terminal group.

1.2 PDCCH(Physical Downlink Control Channel)1.2 Physical Downlink Control Channel (PDCCH)

1.2.1 PDCCH 일반1.2.1 PDCCH General

The PDCCH includes resource allocation and transmission format (ie, DL-Grant) of downlink shared channel (DL-SCH) and resource allocation information (ie, uplink grant (UL-) of uplink shared channel (UL-SCH). Grant)), paging information on a paging channel (PCH), system information on a DL-SCH, and an upper-layer control message such as a random access response transmitted on a PDSCH. It may carry resource allocation, a set of transmission power control commands for individual terminals in a certain terminal group, information on whether Voice over IP (VoIP) is activated or the like.

A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH consists of an aggregation of one or several consecutive control channel elements (CCEs). The PDCCH composed of one or several consecutive CCEs may be transmitted through the control region after subblock interleaving. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups (REGs). The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

1.2.2 PDCCH 구조1.2.2 PDCCH Structure

A plurality of multiplexed PDCCHs for a plurality of terminals may be transmitted in a control region. The PDCCH is composed of one or more consecutive CCE aggregations (CCE aggregation). CCE refers to a unit corresponding to nine sets of REGs consisting of four resource elements. Four Quadrature Phase Shift Keying (QPSK) symbols are mapped to each REG. Resource elements occupied by a reference signal (RS) are not included in the REG. That is, the total number of REGs in the OFDM symbol may vary depending on whether a cell specific reference signal exists. The concept of REG, which maps four resource elements to one group, can also be applied to other downlink control channels (eg, PCFICH or PHICH). If REG not assigned to PCFICH or PHICH is N _REG , the number of CCEs available in the system is N _CCE = floor (N _REG / 9), and each CCE has an index from 0 to N _CCE -1.

In order to simplify the decoding process of the UE, the PDCCH format including n CCEs may start with a CCE having an index equal to a multiple of n. That is, when the CCE index is i, it may start from a CCE satisfying imod (n) = 0.

The base station may use {1, 2, 4, 8} CCEs to configure one PDCCH signal, wherein {1, 2, 4, 8} is called a CCE aggregation level. The number of CCEs used for transmission of a specific PDCCH is determined by the base station according to the channel state. For example, one CCE may be sufficient for a PDCCH for a terminal having a good downlink channel state (close to the base station). On the other hand, in case of a UE having a bad channel state (when it is at a cell boundary), eight CCEs may be required for sufficient robustness. In addition, the power level of the PDCCH may also be adjusted to match the channel state.

Table 2 below shows a PDCCH format, and four PDCCH formats are supported as shown in Table 2 according to the CCE aggregation level.

TABLE 2

PDCCH Format	CCE Count (n)	REG Count	PDCCH Bit Count
0	One	9	72
One	2	18	144
2	4	36	288
3	8	72	576

The reason why the CCE aggregation level is different for each UE is because a format or a modulation and coding scheme (MCS) level of control information carried on the PDCCH is different. The MCS level refers to a code rate and a modulation order used for data coding. Adaptive MCS levels are used for link adaptation. In general, three to four MCS levels may be considered in a control channel for transmitting control information.

Referring to the format of the control information, control information transmitted through the PDCCH is referred to as downlink control information (DCI). According to the DCI format, the configuration of information carried in the PDCCH payload may vary. The PDCCH payload means an information bit. Table 3 below shows DCI according to DCI format.

TABLE 3

DCI format	Contents
Format
0	Resource grants for PUSCH transmissions (uplink)
Format 1	Resource assignments for single codeword PDSCH transmission ( transmission modes 1, 2 and 7)
Format 1A	Compact signaling of resource assignments for sigle codeword PDSCH (all modes)
Format 1B	Compact resource assignments for PDSCH using rank-1 closed loop precoding (mode 6)
Format 1C	Very compact resource assignments for PDSCH (eg, paging / broadcast system information)
Format 1D	Compact resource assignments for PDSCH using multi-user MIMO (mode 5)
Format 2	Resource assignments for PDSCH for closed loop MIMO operation (mode 4)
Format 2A	resource assignments for PDSCH for open loop MIMO operation (mode 3)
Format 3 / 3A	Power control commands for PUCCH and PUSCH with 2-bit / 1-bit power adjustment
Format
4	Scheduling of PUSCH in one UL cell with multi-antenna port transmission mode

Referring to Table 3, a DCI format includes a format 0 for PUSCH scheduling, a format 1 for scheduling one PDSCH codeword, a format 1A for compact scheduling of one PDSCH codeword, and a very much DL-SCH. Format 1C for simple scheduling, format 2 for PDSCH scheduling in closed-loop spatial multiplexing mode, format 2A for PDSCH scheduling in open-loop spatial multiplexing mode, for uplink channel There are formats 3 and 3A for the transmission of Transmission Power Control (TPC) commands. DCI format 1A may be used for PDSCH scheduling, regardless of which transmission mode is configured for the UE.

The PDCCH payload length may vary depending on the DCI format. In addition, the type and length thereof of the PDCCH payload may vary depending on whether it is a simple scheduling or a transmission mode set in the terminal.

The transmission mode may be configured for the UE to receive downlink data through the PDSCH. For example, the downlink data through the PDSCH may include scheduled data, paging, random access response, or broadcast information through BCCH. Downlink data through the PDSCH is related to the DCI format signaled through the PDCCH. The transmission mode may be set semi-statically to the terminal through higher layer signaling (eg, RRC (Radio Resource Control) signaling). The transmission mode may be classified into single antenna transmission or multi-antenna transmission.

The terminal is set to a semi-static transmission mode through higher layer signaling. For example, multi-antenna transmission includes transmit diversity, open-loop or closed-loop spatial multiplexing, and multi-user-multiple input multiple outputs. ) Or beamforming. Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in multiple transmit antennas. Spatial multiplexing is a technology that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data from multiple transmit antennas. Beamforming is a technique of increasing the signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions in multiple antennas.

The DCI format is dependent on a transmission mode configured in the terminal (depend on). The UE has a reference DCI format that monitors according to a transmission mode configured for the UE. The transmission mode set in the terminal may have ten transmission modes as follows.

(1) transmission mode 1: single antenna port; Port 0

(2) Transmission Mode 2: Transmit Diversity

(3) Transmission Mode 3: Open-loop Spatial Multiplexing

(4) Transmission Mode 4: Closed-loop Spatial Multiplexing

(5) Transmission Mode 5: Multi-User MIMO

(6) Transmission mode 6: closed loop, rank = 1 precoding

(7) Transmission mode 7: Precoding supporting single layer transmission not based on codebook

(8) Transmission mode 8: Precoding supporting up to two layers not based on codebook

(9) Transmission mode 9: Precoding supporting up to eight layers not based on codebook

(10) Transmission mode 10: precoding supporting up to eight layers, used for CoMP, not based on codebook

1.2.3 PDCCH 전송1.2.3 PDCCH Transmission

The base station determines the PDCCH format according to the DCI to be transmitted to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. In the CRC, a unique identifier (for example, a Radio Network Temporary Identifier (RNTI)) is masked according to an owner or a purpose of the PDCCH. If it is a PDCCH for a specific terminal, a unique identifier (eg, C-RNTI (Cell-RNTI)) of the terminal may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier (eg, P-RNTI (P-RNTI)) may be masked to the CRC. If the system information, more specifically, the PDCCH for the System Information Block (SIB), a system information identifier (eg, a System Information RNTI (SI-RNTI)) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the UE.

Subsequently, the base station performs channel coding on the control information added with the CRC to generate coded data. In this case, channel coding may be performed at a code rate according to the MCS level. The base station performs rate matching according to the CCE aggregation level allocated to the PDCCH format, modulates the coded data, and generates modulation symbols. At this time, a modulation sequence according to the MCS level can be used. The modulation symbols constituting one PDCCH may have one of 1, 2, 4, and 8 CCE aggregation levels. Thereafter, the base station maps modulation symbols to physical resource elements (CCE to RE mapping).

1.2.4 블라인드 디코딩(BS: Blind Decoding)1.2.4 Blind Decoding (BS)

A plurality of PDCCHs may be transmitted in one subframe. That is, the control region of one subframe includes a plurality of CCEs having indices 0 to N _{CCE, k} −1. Here, N _{CCE, k} means the total number of CCEs in the control region of the kth subframe. The UE monitors the plurality of PDCCHs in every subframe. Here, monitoring means that the UE attempts to decode each of the PDCCHs according to the monitored PDCCH format.

In the control region allocated in the subframe, the base station does not provide information on where the PDCCH corresponding to the UE is. In order to receive the control channel transmitted from the base station, the UE cannot know where the PDCCH is transmitted in which CCE aggregation level or DCI format. Therefore, the UE monitors the aggregation of PDCCH candidates in a subframe. Find the PDCCH. This is called blind decoding (BD). Blind decoding refers to a method in which a UE de-masks its UE ID in a CRC portion and then checks the CRC error to determine whether the corresponding PDCCH is its control channel.

In the active mode, the UE monitors the PDCCH of every subframe in order to receive data transmitted to the UE. In the DRX mode, the UE wakes up in the monitoring interval of every DRX cycle and monitors the PDCCH in a subframe corresponding to the monitoring interval. A subframe in which PDCCH monitoring is performed is called a non-DRX subframe.

In order to receive the PDCCH transmitted to the UE, the UE must perform blind decoding on all CCEs present in the control region of the non-DRX subframe. Since the UE does not know which PDCCH format is transmitted, it is necessary to decode all PDCCHs at the CCE aggregation level possible until blind decoding of the PDCCH is successful in every non-DRX subframe. Since the UE does not know how many CCEs the PDCCH uses for itself, the UE should attempt detection at all possible CCE aggregation levels until the blind decoding of the PDCCH succeeds.

In the LTE system, a search space (SS) concept is defined for blind decoding of a terminal. The search space means a PDCCH candidate set for the UE to monitor and may have a different size according to each PDCCH format. The search space may include a common search space (CSS) and a UE-specific / dedicated search space (USS).

In the case of the common search space, all terminals can know the size of the common search space, but the terminal specific search space can be set individually for each terminal. Accordingly, the UE must monitor both the UE-specific search space and the common search space in order to decode the PDCCH, thus performing a maximum of 44 blind decoding (BDs) in one subframe. This does not include blind decoding performed according to different CRC values (eg, C-RNTI, P-RNTI, SI-RNTI, RA-RNTI).

Due to the limitation of the search space, the base station may not be able to secure the CCE resources for transmitting the PDCCH to all the terminals to transmit the PDCCH in a given subframe. This is because resources remaining after the CCE location is allocated may not be included in the search space of a specific UE. A terminal specific hopping sequence may be applied to the starting point of the terminal specific search space to minimize this barrier that may continue to the next subframe.

Table 4 shows the sizes of the common search space and the terminal specific search space.

Table 4

PDCCH Format	CCE Count (n)	Candidate count in CSS	Candidate Count in USS
0	One	-	6
One	2	-	6
2	4	4	2
3	8	2	2

In order to reduce the load of the UE according to the number of blind decoding attempts, the UE does not simultaneously perform searches according to all defined DCI formats. Specifically, the terminal always performs a search for DCI formats 0 and 1A in the terminal specific search space (USS). In this case, the DCI formats 0 and 1A have the same size, but the UE may distinguish the DCI formats by using a flag used for distinguishing the DCI formats 0 and 1A included in the PDCCH. In addition, a DCI format other than DCI format 0 and DCI format 1A may be required for the UE. Examples of the DCI formats include 1, 1B, and 2.

In the common search space (CSS), the UE may search for DCI formats 1A and 1C. In addition, the UE may be configured to search for DCI format 3 or 3A, and DCI formats 3 and 3A have the same size as DCI formats 0 and 1A, but the UE uses a CRC scrambled by an identifier other than the UE specific identifier. The DCI format can be distinguished.

Search space

Set level

PDCCH candidate set according to the. The CCE according to the PDCCH candidate set m of the search space may be determined by Equation 1 below.

Equation 1

Here, M ^(L) represents the number of PDCCH candidates according to CCE aggregation level L for monitoring in search space,

to be. i is an index designating an individual CCE in each PDCCH candidate in the PDCCH, and i = 0, ..., L-1.

N _s represents a slot index in a radio frame.

As described above, the UE monitors both the UE-specific search space and the common search space to decode the PDCCH. Here, the common search space (CSS) supports PDCCHs having an aggregation level of {4, 8}, and the UE specific search space (USS) supports PDCCHs having an aggregation level of {1, 2, 4, 8}. . Table 5 shows PDCCH candidates monitored by the UE.

Table 5

Referring to Equation 1, Y _k is set to 0 for two aggregation levels, L = 4 and L = 8 for a common search space. On the other hand, for the UE-specific search space for the aggregation level L, Y _k is defined as in Equation 2.

Equation 2

here,

And n _RNTI represents an RNTI value. Further, A = 39827 and D = 65537.

2. 캐리어 병합(CA: Carrier Aggregation) 환경 2. Carrier Aggregation (CA) Environment

2.1 CA 일반2.1 CA General

3GPP LTE (3rd Generation Partnership Project Long Term Evolution (Rel-8 or Rel-9) system (hereinafter referred to as LTE system) is a multi-carrier modulation (MCM) that divides a single component carrier (CC) into multiple bands. Multi-Carrier Modulation) is used. However, in the 3GPP LTE-Advanced system (hereinafter, LTE-A system), a method such as Carrier Aggregation (CA) may be used in which one or more component carriers are combined to support a wider system bandwidth than the LTE system. have. Carrier aggregation may be replaced with the words carrier aggregation, carrier matching, multi-component carrier environment (Multi-CC) or multicarrier environment.

In the present invention, the multi-carrier means the aggregation of carriers (or carrier aggregation), wherein the aggregation of carriers means not only merging between contiguous carriers but also merging between non-contiguous carriers. In addition, the number of component carriers aggregated between downlink and uplink may be set differently. The case where the number of downlink component carriers (hereinafter referred to as 'DL CC') and the number of uplink component carriers (hereinafter referred to as 'UL CC') is the same is called symmetric merging. This is called asymmetric merging. Such carrier aggregation may be used interchangeably with terms such as carrier aggregation, bandwidth aggregation, spectrum aggregation, and the like.

Carrier aggregation, in which two or more component carriers are combined, aims to support up to 100 MHz bandwidth in an LTE-A system. When combining one or more carriers having a bandwidth smaller than the target band, the bandwidth of the combining carrier may be limited to the bandwidth used by the existing system to maintain backward compatibility with the existing IMT system.

For example, the existing 3GPP LTE system supports {1.4, 3, 5, 10, 15, 20} MHz bandwidth, and the 3GPP LTE-advanced system (i.e., LTE-A) supports the above for compatibility with the existing system. Only bandwidths can be used to support bandwidths greater than 20 MHz. In addition, the carrier aggregation system used in the present invention may support carrier aggregation by defining a new bandwidth regardless of the bandwidth used in the existing system.

In addition, the carrier aggregation may be divided into an intra-band CA and an inter-band CA. Intra-band carrier merging means that a plurality of DL CCs and / or UL CCs are located adjacent to or in proximity to frequency. In other words, it may mean that the carrier frequencies of the DL CCs and / or UL CCs are located in the same band. On the other hand, an environment far from the frequency domain may be referred to as an inter-band CA. In other words, it may mean that the carrier frequencies of the plurality of DL CCs and / or UL CCs are located in different bands. In this case, the terminal may use a plurality of radio frequency (RF) terminals to perform communication in a carrier aggregation environment.

The LTE-A system uses the concept of a cell to manage radio resources. The carrier aggregation environment described above may be referred to as a multiple cell environment. A cell is defined as a combination of a downlink resource (DL CC) and an uplink resource (UL CC), but the uplink resource is not an essential element. Accordingly, the cell may be configured with only downlink resources or with downlink resources and uplink resources.

For example, when a specific UE has only one configured serving cell, it may have one DL CC and one UL CC. However, when a specific terminal has two or more configured serving cells, it may have as many DL CCs as the number of cells and the number of UL CCs may be the same or smaller than that. Alternatively, the DL CC and the UL CC may be configured on the contrary. That is, when a specific UE has a plurality of configured serving cells, a carrier aggregation environment in which a UL CC has more than the number of DL CCs may be supported.

Carrier coupling (CA) may also be understood as the merging of two or more cells, each having a different carrier frequency (center frequency of the cell). The term 'cell' in terms of carrier combining is described in terms of frequency, and should be distinguished from 'cell' as a geographical area covered by a commonly used base station. Hereinafter, the above-described intra-band carrier merging is referred to as an intra-band multi-cell, and inter-band carrier merging is referred to as an inter-band multi-cell.

The cell used in the LTE-A system includes a primary cell (P cell) and a secondary cell (S cell). The PCell and the SCell may be used as serving cells. In case of the UE that is in the RRC_CONNECTED state but the carrier aggregation is not configured or does not support the carrier aggregation, there is only one serving cell composed of the PCell. On the other hand, in case of a UE in RRC_CONNECTED state and carrier aggregation is configured, one or more serving cells may exist, and the entire serving cell includes a PCell and one or more SCells.

Serving cells (P cell and S cell) may be configured through an RRC parameter. PhyS cell Id is a cell's physical layer identifier and has an integer value from 0 to 503. SCell Index is a short identifier used to identify SCell and has an integer value from 1 to 7. ServCellIndex is a short identifier used to identify a serving cell (P cell or S cell) and has an integer value from 0 to 7. A value of 0 is applied to the P cell, and the S cell Index is given in advance to apply to the S cell. That is, a cell having the smallest cell ID (or cell index) in ServCellIndex becomes a P cell.

P cell refers to a cell operating on a primary frequency (or primary CC). The UE may be used to perform an initial connection establishment process or to perform a connection re-establishment process, and may also refer to a cell indicated in a handover process. In addition, the P cell refers to a cell serving as a center of control-related communication among serving cells configured in a carrier aggregation environment. That is, the terminal may receive and transmit a PUCCH only in its own Pcell, and may use only the Pcell to acquire system information or change a monitoring procedure. E-UTRAN (Evolved Universal Terrestrial Radio Access) changes only the Pcell for the handover procedure by using an RRC ConnectionReconfigutaion message of a higher layer including mobility control information to a UE supporting a carrier aggregation environment. It may be.

The S cell may refer to a cell operating on a secondary frequency (or, secondary CC). Only one PCell may be allocated to a specific UE, and one or more SCells may be allocated. The SCell is configurable after the RRC connection is established and may be used to provide additional radio resources. PUCCH does not exist in the remaining cells excluding the P cell, that is, the S cell, among the serving cells configured in the carrier aggregation environment.

When the E-UTRAN adds the SCell to the UE supporting the carrier aggregation environment, the E-UTRAN may provide all system information related to the operation of the related cell in the RRC_CONNECTED state through a dedicated signal. The change of the system information may be controlled by the release and addition of the related SCell, and at this time, an RRC connection reconfigutaion message of a higher layer may be used. The E-UTRAN may transmit specific signaling having different parameters for each terminal, rather than broadcasting in the related SCell.

After the initial security activation process begins, the E-UTRAN may configure a network including one or more Scells in addition to the Pcells initially configured in the connection establishment process. In the carrier aggregation environment, the Pcell and the SCell may operate as respective component carriers. In the following embodiments, the primary component carrier (PCC) may be used in the same sense as the PCell, and the secondary component carrier (SCC) may be used in the same sense as the SCell.

FIG. 6 is a diagram illustrating an example of carrier aggregation used in a component carrier (CC) and an LTE_A system used in embodiments of the present invention.

6 (a) shows a single carrier structure used in an LTE system. Component carriers include a DL CC and an UL CC. One component carrier may have a frequency range of 20 MHz.

6 (b) shows a carrier aggregation structure used in the LTE_A system. 6 (b) shows a case where three component carriers having a frequency size of 20 MHz are combined. Although there are three DL CCs and three UL CCs, the number of DL CCs and UL CCs is not limited. In case of carrier aggregation, the UE may simultaneously monitor three CCs, receive downlink signals / data, and transmit uplink signals / data.

If N DL CCs are managed in a specific cell, the network may allocate M (M ≦ N) DL CCs to the UE. In this case, the UE may monitor only M limited DL CCs and receive a DL signal. In addition, the network may assign L (L ≦ M ≦ N) DL CCs to allocate a main DL CC to the UE, in which case the UE must monitor the L DL CCs. This method can be equally applied to uplink transmission.

The linkage between the carrier frequency (or DL CC) of the downlink resource and the carrier frequency (or UL CC) of the uplink resource may be indicated by a higher layer message or system information such as an RRC message. For example, a combination of DL resources and UL resources may be configured by a linkage defined by SIB2 (System Information Block Type2). Specifically, the linkage may mean a mapping relationship between a DL CC on which a PDCCH carrying a UL grant is transmitted and a UL CC using the UL grant, and a DL CC (or UL CC) and HARQ ACK on which data for HARQ is transmitted. It may mean a mapping relationship between UL CCs (or DL CCs) through which a / NACK signal is transmitted.

2.2 크로스 캐리어 스케줄링(Cross Carrier Scheduling)2.2 Cross Carrier Scheduling

In a carrier aggregation system, there are two types of a self-scheduling method and a cross carrier scheduling method in terms of scheduling for a carrier (or carrier) or a serving cell. Cross carrier scheduling may be referred to as Cross Component Carrier Scheduling or Cross Cell Scheduling.

Self-scheduling is transmitted through a DL CC in which a PDCCH (DL Grant) and a PDSCH are transmitted in the same DL CC, or a PUSCH transmitted according to a PDCCH (UL Grant) transmitted in a DL CC is linked to a DL CC in which a UL Grant has been received. It means to be.

In cross-carrier scheduling, a DL CC in which a PDCCH (DL Grant) and a PDSCH are transmitted to different DL CCs, or a UL CC in which a PUSCH transmitted according to a PDCCH (UL Grant) transmitted in a DL CC is linked to a DL CC having received an UL grant This means that it is transmitted through other UL CC.

Whether to perform cross-carrier scheduling may be activated or deactivated UE-specifically and may be known for each UE semi-statically through higher layer signaling (eg, RRC signaling).

When cross-carrier scheduling is activated, a carrier indicator field (CIF: Carrier Indicator Field) indicating a PDSCH / PUSCH indicated by the corresponding PDCCH is transmitted to the PDCCH. For example, the PDCCH may allocate PDSCH resource or PUSCH resource to one of a plurality of component carriers using CIF. That is, when the PDCCH on the DL CC allocates PDSCH or PUSCH resources to one of the multi-aggregated DL / UL CC, CIF is set. In this case, the DCI format of LTE Release-8 may be extended according to CIF. In this case, the set CIF may be fixed as a 3 bit field or the position of the set CIF may be fixed regardless of the DCI format size. In addition, the PDCCH structure (same coding and resource mapping based on the same CCE) of LTE Release-8 may be reused.

On the other hand, if the PDCCH on the DL CC allocates PDSCH resources on the same DL CC or PUSCH resources on a single linked UL CC, CIF is not configured. In this case, the same PDCCH structure (same coding and resource mapping based on the same CCE) and DCI format as in LTE Release-8 may be used.

When cross carrier scheduling is possible, the UE needs to monitor the PDCCHs for the plurality of DCIs in the control region of the monitoring CC according to the transmission mode and / or bandwidth for each CC. Therefore, it is necessary to configure the search space and PDCCH monitoring that can support this.

In the carrier aggregation system, the terminal DL CC set represents a set of DL CCs scheduled for the terminal to receive a PDSCH, and the terminal UL CC set represents a set of UL CCs scheduled for the terminal to transmit a PUSCH. In addition, the PDCCH monitoring set represents a set of at least one DL CC that performs PDCCH monitoring. The PDCCH monitoring set may be the same as the terminal DL CC set or may be a subset of the terminal DL CC set. The PDCCH monitoring set may include at least one of DL CCs in the terminal DL CC set. Alternatively, the PDCCH monitoring set may be defined separately regardless of the UE DL CC set. The DL CC included in the PDCCH monitoring set may be configured to always enable self-scheduling for the linked UL CC. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring set may be configured UE-specifically, UE group-specifically, or cell-specifically.

When cross-carrier scheduling is deactivated, it means that the PDCCH monitoring set is always the same as the UE DL CC set. In this case, an indication such as separate signaling for the PDCCH monitoring set is not necessary. However, when cross-carrier scheduling is activated, it is preferable that a PDCCH monitoring set is defined in the terminal DL CC set. That is, in order to schedule PDSCH or PUSCH for the UE, the base station transmits the PDCCH through only the PDCCH monitoring set.

7 illustrates a subframe structure of an LTE-A system according to cross carrier scheduling used in embodiments of the present invention.

Referring to FIG. 7, three DL component carriers (DL CCs) are combined in a DL subframe for an LTE-A terminal, and DL CC 'A' represents a case in which a PDCCH monitoring DL CC is configured. If CIF is not used, each DL CC may transmit a PDCCH for scheduling its PDSCH without CIF. On the other hand, when the CIF is used through higher layer signaling, only one DL CC 'A' may transmit a PDCCH for scheduling its PDSCH or PDSCH of another CC using the CIF. At this time, DL CCs 'B' and 'C' that are not configured as PDCCH monitoring DL CCs do not transmit the PDCCH.

8 is a diagram illustrating an example of a configuration of a serving cell according to cross carrier scheduling used in embodiments of the present invention.

In a radio access system supporting carrier combining (CA), a base station and / or terminals may be composed of one or more serving cells. In FIG. 8, the base station can support a total of four serving cells, such as A cell, B cell, C cell, and D cell, and terminal A is composed of A cell, B cell, and C cell, and terminal B is B cell, C cell, and the like. It is assumed that the D cell and the terminal C is configured as a B cell. In this case, at least one of the cells configured in each terminal may be configured as a P cell. In this case, the PCell is always in an activated state, and the SCell may be activated or deactivated by the base station and / or the terminal.

The cell configured in FIG. 8 is a cell capable of adding a cell to a CA based on a measurement report message from a terminal among cells of a base station, and may be configured for each terminal. The configured cell reserves the resources for the ACK / NACK message transmission for the PDSCH signal transmission in advance. An activated cell is a cell configured to transmit a real PDSCH signal and / or a PUSCH signal among configured cells, and performs CSI reporting and SRS (Sounding Reference Signal) transmission. A de-activated cell is a cell configured not to transmit or receive a PDSCH / PUSCH signal by a command or timer operation of a base station, and also stops CSI reporting and SRS transmission.

2.3 CA 환경 기반의 CoMP 동작2.3 CoMP operation based on CA environment

Hereinafter, a cooperative multi-point (CoMP) transmission operation that can be applied to embodiments of the present invention will be described.

In the LTE-A system, CoMP transmission may be implemented using a carrier aggregation (CA) function in LTE. 9 is a conceptual diagram of a CoMP system operating based on a CA environment.

In FIG. 9, it is assumed that a carrier operating as a PCell and a carrier operating as an SCell may use the same frequency band as the frequency axis, and are allocated to two geographically separated eNBs. In this case, the serving eNB of the UE1 may be allocated to the Pcell, and the neighboring cell which gives a lot of interference may be allocated to the Scell. That is, the base station of the P cell and the base station of the S cell may perform various DL / UL CoMP operations such as joint transmission (JT), CS / CB, and dynamic cell selection with respect to one UE.

9 shows an example of combining cells managed by two eNBs for one UE (e.g. UE1) as a Pcell and an Scell, respectively. However, as another example, three or more cells may be combined. For example, some of the three or more cells may be configured to perform a CoMP operation on one terminal in the same frequency band, and other cells to perform a simple CA operation in another frequency band. At this time, the Pcell does not necessarily participate in CoMP operation.

2.4 참조신호(RS: Reference Signal)2.4 Reference Signal

Hereinafter, reference signals that can be used in embodiments of the present invention will be described.

10 shows an allocation structure of a CRS when a system supports four antennas. In 3GPP LTE / LTE-A system, CRS is used for decoding and channel state measurement. Accordingly, the CRS is transmitted over the entire downlink bandwidth in all downlink subframes in a cell supporting PDSCH transmission, and is transmitted in all antenna ports configured in the eNB.

Specifically, the CRS sequence is mapped to complex-valued modulation symbols used as reference symbols for antenna port p in slot n _s .

The UE can measure the CSI using the CRS, and can decode the downlink data signal received through the PDSCH in a subframe including the CRS using the CRS. That is, the eNB transmits the CRS at a predetermined position in each RB in all RBs, and the UE detects the PDSCH after performing channel estimation based on the CRS. For example, the UE measures the signal received at the CRS RE. The UE may detect the PDSCH signal from the PD to which the PDSCH is mapped by using a ratio of the reception energy for each CRS RE to the reception energy for each RE to which the PDSCH is mapped.

As such, when the PDSCH signal is transmitted based on the CRS, the eNB needs to transmit the CRS for all RBs, which causes unnecessary RS overhead. In order to solve this problem, the 3GPP LTE-A system further defines a UE-specific RS (hereinafter, UE-RS) and a channel state information reference signal (CSI-RS) in addition to the CRS. UE-RS is used for demodulation and CSI-RS is used to derive channel state information.

Since UE-RS and CRS are used for demodulation, they can be referred to as demodulation RS in terms of use. That is, the UE-RS may be regarded as a kind of DM-RS (DeModulation Reference Signal). In addition, since the CSI-RS and the CRS are used for channel measurement or channel estimation, the CSI-RS and CRS may be referred to as RS for channel state measurement in terms of use.

The CSI-RS is a downlink reference signal introduced in the 3GPP LTE-A system not for demodulation purposes but for measuring a state of a wireless channel. The 3GPP LTE-A system defines a plurality of CSI-RS settings for CSI-RS transmission. In subframes in which CSI-RS transmission is configured, the CSI-RS sequence is mapped according to complex modulation symbols used as reference symbols on antenna port p.

FIG. 11 (a) shows 20 CSI-RS configurations 0 to 19 available for CSI-RS transmission by two CSI-RS ports among CSI-RS configurations, and FIG. 11 (b) shows CSI-RS configurations. Of the configurations, 10 CSI-RS configurations available through four CSI-RS ports 0 through 9 are shown, and FIG. 11 (c) shows 5 available by eight CSI-RS ports among the CSI-RS configurations. Branch CSI-RS configuration 0-4 are shown.

Here, the CSI-RS port means an antenna port configured for CSI-RS transmission. Since the CSI-RS configuration varies depending on the number of CSI-RS ports, even if the CSI-RS configuration numbers are the same, different CSI-RS configurations are obtained when the number of antenna ports configured for CSI-RS transmission is different.

On the other hand, unlike the CRS configured to be transmitted every subframe, the CSI-RS is configured to be transmitted every predetermined transmission period corresponding to a plurality of subframes. Therefore, the CSI-RS configuration depends not only on the positions of REs occupied by the CSI-RS in a resource block pair but also on the subframe in which the CSI-RS is configured.

In addition, even if the CSI-RS configuration numbers are the same, if the subframes for CSI-RS transmission are different, the CSI-RS configuration may be regarded as different. For example, if the CSI-RS transmission period (T _CSI-RS ) is different or the start subframe (Δ _CSI-RS ) configured for CSI-RS transmission in one radio frame is different, the CSI-RS configuration may be different.

Hereinafter, the CSI-RS configuration depends on (1) the CSI-RS configuration to which the CSI-RS configuration number is assigned, and (2) the CSI-RS configuration number, the number of CSI-RS ports, and / or subframes in which the CSI-RS is configured. In order to distinguish between them, the configuration of the latter 2 is called a CSI-RS resource configuration. The setting of the former 1 is also referred to as CSI-RS configuration or CSI-RS pattern.

When eNB informs UE of CSI-RS resource configuration, the number of antenna ports, CSI-RS pattern, CSI-RS subframe configuration I _CSI-RS , CSI used for transmission of _CSI-RSs UE assumption on reference PDSCH transmitted power for feedback (CSI) can be informed about P _c , zero power CSI-RS configuration list, zero power CSI-RS subframe configuration, etc. .

CSI-RS Subframe Configuration Index I _CSI-RS is information for specifying the subframe configuration period T _CSI-RS and subframe offset Δ _CSI-RS for the presence of _CSI-RSs . Table 4 below illustrates CSI-RS subframe configuration index I _CSI-RS according to T _CSI-RS and Δ _CSI-RS .

Table 6

CSI-RS-SubframeConfig I _CSI-RS	CSI-RS periodicity T _CSI-RS (subframes)	CSI-RS subframe offset Δ _CSI-RS (subframes)
0-4	5	I _CSI-RS
5-14	10	I _CSI-RS -5
15-34	20	I _CSI-RS -15
35-74	40	I _CSI-RS -35
75-154	80	I _CSI-RS -75

At this time, subframes satisfying Equation 3 below are subframes including the CSI-RS.

Equation 3

UE set to a transmission mode defined after 3GPP LTE-A system (for example, transmission mode 9 or another newly defined transmission mode) performs channel measurement using CSI-RS and PDSCH using UE-RS Can be decoded.

2.5 Enhanced PDCCH (EPDCCH)2.5 Enhanced PDCCH (EPDCCH)

In a 3GPP LTE / LTE-A system, when defining a cross carrier scheduling (CCS) operation in a combined situation for a plurality of component carrier (CC) cells, one scheduled CC (CC) is defined. In other words, the scheduled CC may be preset to receive DL / UL scheduling only from another scheduling CC (ie, to receive a DL / UL grant PDCCH for the scheduled CC). In this case, the scheduling CC may basically perform DL / UL scheduling on itself. In other words, a search space (SS) for a PDCCH for scheduling a scheduled / scheduled CC in the CCS relationship may exist in a control channel region of all scheduling CCs.

Meanwhile, in an LTE system, FDD DL carriers or TDD DL subframes use the first n (n <= 4) OFDM symbols of each subframe to transmit PDCCH, PHICH, and PCFICH, which are physical channels for transmitting various control information. And use the remaining OFDM symbols for PDSCH transmission. In this case, the number of OFDM symbols used for transmission of control channels in each subframe may be delivered to the UE dynamically through a physical channel such as PCFICH or in a semi-static manner through RRC signaling.

Meanwhile, in the LTE / LTE-A system, the PDCCH, which is a physical channel for transmitting DL / UL scheduling and various control information, has a limitation such as being transmitted through limited OFDM symbols. Thus, the PDCCH is transmitted through an OFDM symbol separate from the PDSCH, such as a PDCCH. An extended PDCCH (ie E-PDCCH) may be introduced, which is more freely multiplexed by PDSCH and FDM / TDM scheme instead of the control channel. FIG. 12 is a diagram illustrating an example in which legacy PDCCH, PDSCH, and E-PDCCH used in an LTE / LTE-A system are multiplexed.

2.6 제한된 CSI 측정2.6 Limited CSI Measurement

In order to reduce the influence of interference between cells in a wireless network, cooperative operations may be performed between network entities. For example, during a particular subframe in which Cell A transmits data, cells other than Cell A transmit only common control information, but do not transmit data, thereby minimizing interference to users receiving data in Cell A. can do.

In this way, it is possible to reduce the influence of interference between cells by transmitting only a minimum of common control information from other cells except cells that transmit data at a specific moment through cooperation between cells in the network.

To this end, when two CSI measurement subframe sets CCSI, 0 and CCSI, 1 are configured in an upper layer, the UE may perform a resource-restricted measurement (RRM) operation. In this case, it is assumed that the CSI reference resources corresponding to the two measurement subframe sets belong to only one of the two subframe sets.

Table 7 below shows an example of a higher layer signal for setting a CSI subframe set.

TABLE 7

Table 7 shows an example of a CQI-Report Cofig message transmitted to set a CSI subframe set. At this time, the CQI report configuration message includes aperiodic CQI report (cqi-ReportAperiodic-r10) IE, nomPDSCH-RS-EPRE-Offset IE, periodic CQI report (cqi-ReportPeriodci-r10) IE, PMI-RI report (pmi-RI- Report-r9) IE and CSI subframe pattern configuration (csi-subframePatternConfig) IE may be included. In this case, the CSI subframe pattern configuration IE includes a CSI measurement subframe set 1 information (csi-MeasSubframeSet1) IE and a CSI measurement subframe set 2 information (csi-MeasSubframeSet2) IE indicating a measurement subframe pattern for each subframe set.

Herein, the CSI measurement subframe set 1 (csi-MeasSubframeSet1-r10) information element (IE) and the CSI measurement subframe set 2 (csi-MeasSubframeSet2-r10) IE are 40 bit bitmap information and belong to each subframe set. Represents information about a subframe. In addition, the aperiodic CQI report (CQI-ReportAperiodic-r10) IE is an IE for performing the setting for aperiodic CQI reporting to the terminal, the periodic CQI report (CQI-ReportPeriodic-r10) IE is set for the periodic CQI reporting IE is done.

nomPDSCH-RS-EPRE-Offset IE

Indicates a value. At this time, the actual value is

Value * 2 is set to [dB]. In addition, the PMI-RI Report IE indicates that PMI / IR reporting is configured or not. EUTRAN configures the PMI-RI Report IE only when the transmission mode is set to TM8, 9 or 10.

3. LTE-U 시스템3. LTE-U system

3.1 LTE-U 시스템 구성3.1 LTE-U system configuration

Hereinafter, methods for transmitting and receiving data in a carrier combining environment of a licensed band, an LTE-A band and an unlicensed band, will be described. In the embodiments of the present invention, the LTE-U system refers to an LTE system supporting CA conditions of the licensed band and the unlicensed band. The unlicensed band may be a Wi-Fi band or a Bluetooth (BT) band.

13 is a diagram illustrating an example of a CA environment supported by the LTE-U system.

Hereinafter, for convenience of description, assume a situation in which the UE is configured to perform wireless communication in each of a licensed band and an unlicensed band using two component carriers (CCs). Of course, even if three or more CCs are configured in the UE, the methods described below may be applied.

In embodiments of the present invention, a licensed CC (LCC: Licensed CC) is a major carrier (can be referred to as a primary CC (PCC or PCell)), an unlicensed carrier (Unlicensed CC: UCC) is a sub-carrier Assume a case of (Secondary CC: SCC or S cell). However, embodiments of the present invention may be extended to a situation in which a plurality of licensed bands and a plurality of unlicensed bands are used in a carrier combining method. In addition, the proposed schemes of the present invention can be extended to not only 3GPP LTE system but also other system.

FIG. 13 illustrates a case in which one base station supports both a licensed band and an unlicensed band. That is, the terminal can transmit and receive control information and data through a PCC, which is a licensed band, and can also transmit and receive control information and data through an SCC, which is an unlicensed band. However, the situation shown in FIG. 13 is one example, and embodiments of the present invention may be applied to a CA environment in which one terminal accesses a plurality of base stations.

For example, the terminal may configure a P-cell and a macro base station (M-eNB: Macro eNB) and a small cell (S-eNB: Small eNB) and an S cell. At this time, the macro base station and the small base station may be connected through a backhaul network.

In embodiments of the present invention, the unlicensed band may be operated in a contention based random access scheme. In this case, an eNB and / or a transmission point (TP) supporting an unlicensed band may first perform a carrier sensing (CS) process before data transmission and reception. The CS process is a process of determining whether the corresponding band is occupied by another entity.

For example, the base station eNB and / or TP of the SCell checks whether the current channel is busy or idle. If it is determined that the corresponding band is idle, the base station and / or the TP is a scheduling grant through the (E) PDCCH of the Pcell in the case of the cross carrier scheduling scheme or the PDCCH of the Scell in the case of the self scheduling scheme. Transmits to the terminal to allocate resources, and may attempt to transmit and receive data.

The CS process may be performed the same as or similar to that of the List Before Talk (LBT) process. The LBT process is a process in which a base station of a Pcell checks whether a current state of a Ucell (a cell operating in an unlicensed band) is busy or idle. For example, when there is a clear channel assessment (CCA) threshold set by a preset or higher layer signal, when an energy higher than the CCA threshold is detected in the U-cell, it is determined to be busy or otherwise idle. do. When the Ucell is determined to be idle, the base station of the Pcell transmits a scheduling grant (ie, DCI, etc.) through the (E) PDCCH of the Pcell or through the PDCCH of the Ucell to schedule resources for the Ucell. The data can be transmitted and received through the U cell.

In this case, the base station and / or the TP may set a transmission opportunity (TxOP) section consisting of M consecutive subframes. Here, the base station may inform the UE of the M value and the use of the M subframes in advance through a higher layer signal, a physical control channel, or a physical data channel through a Pcell. A TxOP period consisting of M subframes may be called a reserved resource period (RRP).

4. 상향링크 송신 전력 결정 방법4. Uplink transmission power determination method

In embodiments of the present invention, the terminal determines the transmission power in transmitting UL signals (eg, uplink data (PUSCH), reference signal (RS) and / or control signal (SRS, PUCCH), etc.) to the base station How to do this is described.

In FIG. 14, the solid line indicates coverage when the transmission power P1 and the dotted line indicates the coverage when the transmission power P2. In addition, it is assumed that the UE is geographically located near the base station eNB while being relatively far from the WiFi AP.

As such, in the case of the UE located near the eNB, successful signal transmission is possible even with a smaller power than the cell edge UE in the UL transmission. In the LTE / LTE-A system, a relatively low power is allocated to a UE located near an eNB through power control in order to reduce battery consumption of the UE. However, in the LAA system operating in the unlicensed band, as shown in the example of FIG. 14, the UE may be vulnerable to a hidden node problem by reducing the transmission power of the UE.

For example, if the UE transmits data using the power of P2 (> P1), the WiFi AP that detects the data transmission may not attempt to transmit, but the UE transmits using the power of P1 (<P2). If the WiFi AP does not detect the transmission, it may attempt to transmit in the unlicensed band. This may cause severe interference from the eNB's point of view, and the eNB may not successfully receive data transmitted by the UE. In order to reduce such a hidden node problem, it may be advantageous in the LAA system not to significantly reduce the UL transmission power through power control even for a UE located near the eNB.

In FIG. 15, resource scheduling including power control may use a self carrier scheduling (SCS) scheme or a cross carrier scheduling (CCS) scheme. In FIG. 15, when scheduling information is transmitted in subframe SF #n, UL data transmission may be performed in SF # n + k.

Referring to FIG. 15, a UE that has received a UL grant including scheduling information for each of Ucell1 and Ucell2 at time SF #n is UL at time SF # n + k (eg, k = 4). May be configured to perform CCA immediately before (or immediately after) SF # n + k for transmission. As shown in FIG. 15A, when both Ucell1 and Ucell2 are determined to be in an idle state, the UE may perform UL transmission for both Ucells that have received the UL grant. However, as shown in FIG. 15B, when the Ucell1 is in the idle state and the Ucell2 is in the busy state, the UE may not perform the UL signal transmission even if the UE has received the UL grant for the Ucell2.

The power value required for the UL signal transmission in the Ucell1 or the Ucell2 that receives the UL grant is defined as P_u1 or P_u2. In the case of FIG. 15A, the UE may transmit a UL signal using the power of P_u1 in U cell 1 and a UL signal using the power of P_u2 in U cell 2 at SF # n + 4. . However, in the case of FIG. 15B, since the UE2 is busy at the time of SF # n + 4, the UE may not transmit the UE2.

Embodiments of the present invention can be applied to the case of carrier combination of an L cell defined in the license band and a U cell defined in the unlicensed band. In this regard, a general carrier combining technique of primary and secondary cells supported by the same or different base stations, and a DC in which one terminal is connected to two or more serving cells managed by separate base stations In the dual connectivity technology, there is a carrier coupling technology between a master cell group (MCG) and a secondary cell group (SCG).

In this case, the general carrier combining technology and the DC technology are technologies defined in a license band. Accordingly, the terminal may transmit the UL signal by controlling the transmission power of the Pcell and the Scell based on the power information transmitted from the base station. In this case, since both the Pcell and the Scell (or MCG and SCG) operate in the license band and the processing time (for example, 1ms) for determining the UL transmission power is guaranteed, the terminal transmit power of the Pcell and the Scell. There's enough time to handle it.

However, in a LAA system that supports both a licensed band cell and an unlicensed band cell in the same base station, a CS process (or CCA, LBT process, etc.) performed in an unlicensed band is performed for a very short time (a few tens of us). Since it may be difficult to ensure the processing time for calculating the UL transmission power for the terminal to perform the UL signal transmission.

In more detail, it is typically assumed that an LTE / LTE-A system supporting a licensed band takes about 1 ms in processing time for determining UL transmission power. Therefore, when considering the operation characteristics of the unlicensed band in which signal transmission is determined depending on whether the channel is idle or busy during the CCA process (or CS process, LBT process, etc.) of several tens of us, Accordingly, it may be practically difficult to calculate and apply UL transmit power immediately for each serving cell.

In other words, since the U cell 2 is busy as shown in FIG. 15 (b), the UE does not need to use the power of P_u2 preset for the U cell 2, so that the UE uses the corresponding power (ie, P_u2) as the U cell. It may not be possible to utilize 1 or L cell.

Therefore, hereinafter, methods for configuring the UL transmission power between the L-cell and the U-cell or the U-cell by the LAA terminal in such an environment will be described in detail.

4.1 전력 제한 케이스4.1 Power Limit Case

Embodiments of the present invention relate to power control methods for unlicensed UL transmission, and may be particularly applicable to power limited cases. P_u is defined as the maximum amount of power available in one or more U-cells at a specific time in view of a specific UE. If the UE receives the U cell that has received the UL grant at that time, the U cell 1 and the U cell 2, P_u1 + P_u2> P_u is defined as a power limit case. In other words, when P_sum is defined as “the sum of transmit powers required for UL signal transmission of one or more U cells,” P_sum> P_u corresponds to a power limit case.

For such a power limited case, if the UE performs power scale down assuming that the UE transmits UL signals in all U cells, not only may it be vulnerable to the hidden node problem described in FIG. 14, but also a CCA result. Accordingly, it may not be able to transmit the UL signal in all U cells. In addition, in consideration of the power processing time, it is also practically impossible to utilize the power of the U cell, which is not transmitted by the terminal, in the transmission of the UL signal for other cells.

Embodiments of the present invention intend to propose a power control method for the UL signal transmission in the LAA system to solve this problem.

4.2 L셀과 U셀간 전력 제어4.2 Power Control Between L-cell and U-cell

The UE may be configured to simultaneously perform UL signal transmission for one or more licensed band cells (Lcell) and one or more unlicensed band cells (Ucell) at a specific time. For example, a UL carrier coupling (CA) situation may occur between one or more Lcells and Ucells. Hereinafter, methods for allocating transmission power between one or more L cells and one or more U cells will be described. However, for convenience of description, it will be described assuming one L cell and one U cell, but the technical features described below may be equally applicable to a situation in which a plurality of L cells and a plurality of U cells are carrier coupled.

When the L cell and the U cell are allocated to the terminal, the terminal may be configured to allocate the transmission power for the L cell first, and then utilize the remaining power in the U cell.

In embodiments of the present invention, the sum of the transmission power required for UL signal transmission in all L cells that receive the UL grant including uplink scheduling information is defined as P_L, and the maximum output power available to the terminal at the time of UL signal transmission Define maximum output power as P _CMAX .

If P_L> If P _CMAX terminal without assigning a power include U cells, it is possible to perform the power scale-down for the P_L. On the other hand P_L remaining power of, if <P P _CMAX _CMAX - may be assigned to P_L the UL transmission in a cell U. In other words, P = P_u _CMAX - a P_L.

4.2.1 L셀과 U셀간 전력 제어 방법-14.2.1 Power control method between L cell and U cell

If the UE allocates the transmit power of the L cell first and then utilizes only the remaining power in the U cell, if the P_L value is large, UL transmission is not possible in the U cell because there is no remaining power even if the UL grant for the U cell is received. Even when transmitting, only a very low power can be tolerated. Therefore, in order to compensate for this, the U cells may be set so that a certain power is always guaranteed. This can be defined as guaranteed power.

That is, no matter how large the P_L value, the UE can always guarantee a certain level of power for the UL signal transmission in the U-cell. Hereinafter, methods for calculating guaranteed power will be described.

(1) 제1방법(1) Method 1

If the guaranteed power is defined as P_g in the U cell, P_u and P_g may be set to always satisfy the relationship of P_u> = P_g.

(2) 제2방법(2) Second method

Guaranteed power can also be defined as a percentage of the P _CMAX value. If you define the 30% of the P _CMAX value to ensure power, it may be set to P_g = P * _CMAX 30%. As a method of guaranteeing the guaranteed power, the insufficient amount of power of the U cell may be set to derive from the transmit power allocated to the L cell. For example, if the guaranteed power of 30% of the P value _CMAX and P_L = P _CMAX * 80%, the reducing the P_L value below P _CMAX * 70% can satisfy the relationship P_u> = P_g.

(3) 제3방법(3) Third method

As another method of guaranteeing the guaranteed power, it is possible to equally scale the U-cell power and the L-cell power above the guaranteed power. 30% of the guaranteed power value P _CMAX and is described for example P_L = P * _CMAX and 80%, P = P_u _CMAX * For 50%. When the guarantee U or more power cell power P _CMAX * 20% and the sum of Lcell power equivalent to scaling so that the _{P CMAX * 70%, P_L =} P CMAX * 56%, P_u = P CMAX * is set to (30 + 14)% Can be.

(4) 제4방법(4) Fourth method

In the first to third methods of guaranteeing guaranteed power for the above-described U cell, a particular serving cell may be set as an exception.

Assuming a carrier combining situation for two serving cells of a cell #x and a U cell, if the UE simultaneously transmits an UL signal in the cell #x and the U cell (for example, PUCCH transmission and / or PUSCH on Cell # x) For reasons such as UCI piggyback), the guaranteed power for the U cell may not be guaranteed.

In this case, P_g may be set to a valid value only for SF scheduled by receiving the UL grant for the Ucell. Referring to FIG. 15, the UE may have no UL signal to transmit to the U cell at SF # n + 3 and an UL signal to transmit to the U cell at SF # n + 4. In this case, the terminal may consider only the P value _CMAX without considering the value P_g SF # n + 3 has received UL scheduling grant to perform a UL power control for the L cells. On the other hand, SF # n + 4 in P_L value is received through the UL Scheduling Grant may perform the UL power control for the L cells so as not to exceed _CMAX P_g {P}.

4.2.2 L셀과 U셀간 전력 제어 방법-24.2.2 Power Control Method between L Cell and U Cell

The embodiments to be described below will be described on the assumption that there are several UL transmission power values preset for each serving cell, and that the UE can select and transmit one transmission power among various values according to a specific situation. In this case, the UE may use the remaining power allocated to the Ucells that do not perform UL transmission because of the busy state of the CCA in other cells (eg, Lcell and / or Ucell).

The following embodiments are described with reference to FIG. 15. In this section, it is assumed that L cells are scheduled to two or more terminals in FIG. 15, and may be set to L cell 1, L cell 2, L cell 3,.

If the UE is scheduled for the UL transmit power for Lcell2 (not shown) and Ucell1 through the UL grant received at the time of SF #n, the UE transmits the Lcell according to whether the UE transmits the UL signal in Ucell1. Two power values of 2 can be set in advance. For example, if the UE determines that the channel state of Ucell1 is busy at time of SF # n + 4 and does not transmit the UL signal, the UE may allocate more UL transmit power to Lcell2. If the channel state of the Ucell1 is determined to be idle, the UE may attempt to transmit the UL signal by allocating the UL transmission power to the Ucell1 and the Lcell2. This method can be extended even in a situation where several U cells are scheduled at the same time.

For example, if Lcell2, Ucell1, and Ucell2 are scheduled to the UE at the same time, the UE pre-transmits four transmit power values for Lcell2 according to a combination according to whether UL signals are transmitted to each Ucell. You can set it. In addition, the UE may preset the transmission power value for the UL signal transmission in the Ucell2 according to whether or not the UL signal is transmitted in the Ucell1.

In addition, these methods can be extended and applied in a situation where several L cells and several U cells are scheduled at the same time. If the Lcell2, the Lcell3 and the Ucell1 are scheduled to the UE at the same time, the UE previously sets two or more UL transmit power values according to the combination according to whether or not the UL signal is transmitted from the Ucell1 to the Lcell2 and Each can be set in Lcell3. For example, if the Ucell1 is busy and the terminal does not transmit the UL signal through the Ucell1, the UE equally distributes the transmission power values set on the Ucell1 to the Lcell2 and the Lcell. It can be set to assign to three.

FIG. 16 illustrates a transmission power control method between the L cell and the U cell described in Section 4.2 from a terminal perspective. In embodiments of the present invention, P_u value means the sum of the transmission power required for the UL signal transmission in the U cells scheduled by the terminal or the maximum value of the amount of transmission power available in the U cell, P_g is the U cells scheduled by the terminal The sum of the transmission powers guaranteed by

Referring to FIG. 16, the terminal may receive one or more UL grants in SF # n. In this case, the one or more UL grants may be UL grants related to one or more L cells and / or U cells (S1610).

When the terminal receives one or more UL grants, the terminal may identify which serving cell the scheduled serving cell is. For example, the UE may check the scheduled L-cell and U-cell (S1620).

If the terminal is scheduled for both the L cell and the U cell, the processor of the terminal calculates the guaranteed power P_g guaranteed in the U cell. Thereafter, the processor of the terminal compares the P_u value required for U cell transmission with the guaranteed power P_g value of the U cell (S1630).

In step S1630, if the P_u value is greater than or equal to the P_g value, the UE may perform power control using the P_L value and the P_u value required for UL signal transmission in the L cell (S1640).

In step S1630, if the P_u value is less than the P_g value, the UE may perform power control using the P_L value and P_g value required for the UL signal transmission in the L cell. For example, the terminal assignment for the cells U P_g first value in the maximum transmission power P _CMAX a terminal is used by the method described above in Section 4.2.1, the first to fourth methods, and the remaining values for L cells Can be assigned (S1650).

Further, in S1650 step, the terminal may be assigned a power of as much as after allocating P_L in P _CMAX first, one if the remaining power level (P_remain) is less than P_g, P_g-P_remain soluble in U-cell non-L cells .

In step S1620, when the UE is scheduled only for the L cell without the U cell, the terminal may perform power control for the L cell using P_L (S1660, S1670).

4.3 U셀들간 전송 전력 제어 방법4.3 Transmission Power Control Method between U Cells

The P_L and P_u values can be calculated by the methods described in Section 4.2. In this case, the P_u value, which is the sum of the amount of power that the UE can transmit on the U cells, may have one of the following values.

(1) if there is no L-cell transmission: P_u = P _CMAX

(2) L If the cell transmission: P_u = P _CMAX - P_L or P _CMAX - P_g or more power values

The following embodiments are for UL transmit power control methods for U cells in a power limited case when P_u value is given as (1) or (2).

4.3.1 전력 스케일 다운 방법4.3.1 Power Scale Down Method

After allocating UL transmit power for all U cells that have received (ie, scheduled) UL grants, the UE scales the power so that the sum of UL transmit powers for U cells does not exceed P_u in a power limiting case where P_sum> P_u. You can do the down. In this case, power scaling down may be collectively performed on the transmission power of all U cells.

For example, the UE may determine a w value that satisfies w * P_sum <= P_u. The terminal may perform power scaling down on each U cell by using the determined w value.

Referring to FIG. 15A, the UE may transmit a UL signal with a w * P_u1 value for the Ucell1 and a UL signal with a w * P_u2 value for the Ucell2.

However, referring to FIG. 15 (b), the UE transmits a UL signal with a transmit power of w * P_u1 on Ucell1, but does not use w * P_u2 allocated to Ucell2 because Ucell2 is busy. The UL transmission can be given without.

After all, the UE performs power scaling down assuming that the scheduled Ucell1 and the Ucell2 can transmit UL signals. However, when a channel of a Ucell is busy due to CCA, the UE is assigned a transmit power. Even if it is possible to drop the transmission of the UL signal. Accordingly, the UE may be configured to perform power control (or power scaling) based on all scheduled U cells, not allocating transmit power only to U cells performing actual transmission.

4.3.2 다수의 U셀에 대한 전력 스케일 다운 방법4.3.2 Power Scaling Down for Multiple U Cells

In the case of the method as described in Section 4.3.1, when the number of U-cells scheduled in the terminal increases, the terminal may need to scale down too much power. In this case, since the transmission power for the U cell is weakened, it may be exposed to a hidden node problem.

Hereinafter, transmission power control methods that allow only a certain level of power scale-down so as not to be exposed to a hidden node problem due to scaling down will be described.

The terminal may be pre-assigned a power scaling threshold T through higher layer signaling. The power required for UL signal transmission in a specific Ucellx is defined as P_ux. At this time, the power scaling threshold T means a maximum ratio value that can power down P_ux. That is, if the UE sets the UL transmit power lower than T * P_ux in the Ucellx, this means that a hidden node problem may occur.

If P_u> = T * P_sum, the UE may perform power scale down as described in Section 4.3.1. On the other hand, if P_u <T * P_sum, the UE may give up UL signal transmission on all scheduled Ucells.

As another aspect of this embodiment, the transmit power threshold T may be set to a minimum transmit power value rather than a ratio value. For example, after performing the method described in Section 4.3.1, the UE can perform CCA and UL signal transmission only when P_ux used in a specific Ucellx is equal to or greater than the T value.

4.3.3 U셀에 대한 전송 전력을 스케일링하지 않는 방법4.3.3 How to not scale transmit power for Ucell

If scaling down is allowed for the transmit power for U cells as described in Sections 4.3.1 and 4.3.2, the transmit power set for each U cell becomes too small, which may be vulnerable to the hidden node problem as described above.

To solve this problem, power scaling down may be set to not allow for transmitting UL signals in U cells. For example, even in the case of P_u1 + P_u2> P_u in the example of FIG. 15, the terminal does not perform power scaling down. In this case, it is assumed that P_u1 and P_u2 are smaller than P_u, respectively.

If the UE has both CCell result Ucell1 and Ucell2 at the SF # n + 4 time, the UE may drop the UL transmission on all Ucells. If only one U cell of the two cells is in an idle state as shown in FIG. 15B, the UE may transmit a UL signal using P_u1 in the U cell 1 and stop the UL transmission in the U cell 2. If Ucell1 is busy and Ucell2 is idle, the UE may transmit a UL signal using P_u2 in Ucell2.

In this case, if the methods described in Sections 4.3.1 to 4.3.2 are applied, the UE uses the power scaled down UL transmission power such as w * P_u1 or w * P_u2 when transmitting the UL signal. Compared to the method, smaller transmission power can be used.

However, when the Ucell1 and the Ucell2 are both in the idle state, the UE may be configured to select one of the Ucells and perform UL signal transmission. This is because P_u1 + P_u2> P_u, and it is practically impossible to redistribute power in the same manner as in Sections 4.3.1 to 4.3.2 for several tens of CCA hours.

That is, the terminal may not perform transmission power scaling down even in a power limited case. For example, when the total sum of powers for UL signal transmission is smaller than P_u in several U cells that are idle as a result of CCA, the UE may transmit a UL signal using power allocated for the corresponding U cells. However, when the total sum of powers for the UL signal transmission is greater than P_u, the UE may drop the UL transmission in some of the corresponding U cells and transmit the UL signal using the preset power in some.

When the CCA resultant channel for the scheduled Ucells is idle, the UE determines whether to transmit or drop the UL signal in the Ucells as follows.

(1) 방법1(1) Method 1

The UE may randomly select only one U cell among idle U cells among scheduled U cells, or may arbitrarily select several U cells until the total sum of transmission powers is not greater than P_u.

Alternatively, the maximum number of U cells that can be transmitted to the UL at a corresponding time by higher layer signaling (for example, K) may be preset. In this case, the UE may arbitrarily select up to K U cells until the sum of the transmit powers used in the U cells is not greater than P_u, and transmit a UL signal through the selected U cells.

(2) 방법2(2) Method 2

Power required for UL signal transmission in a specific Ucellx may be defined as P_ux. In this case, the UE may select only one U cell x having the largest P_ux and transmit a UL signal.

Alternatively, the terminal may sort in descending order (or ascending order) in P_ux order, and select a maximum number of U cells in which the total sum of the transmit powers of the selected U cells does not become larger than P_u.

Alternatively, if the maximum number of U cells that can be transmitted to the UL at that time (for example, K) is set in advance by a higher layer signal (eg, RRC, etc.), when the terminal is not larger than P_u Up to K U cells can be selected up to (in the order of U cells sorted in P_ux order).

(3) 방법3(3) Method 3

Priorities for the Ucells may be defined in advance by higher layer signaling. For example, the priority of Ucell2 may be set higher than that of Ucell1 in FIG. 15. In this case, when both Ucell1 and Ucell2 are idle, the terminal may select the Ucell1 having the highest priority and transmit the UL signal.

If more than one U cell is scheduled in the terminal, the terminal selects the U cells in the order of high priority, but until the sum of transmit powers does not exceed P_u (up to K if K is set). ) You can choose.

If there are U cells having the same priority, method 1 or method 2 may be followed. In this case, when the U cells having the same priority are the lowest priority, the terminal may drop transmission of the corresponding U cells.

(4) 방법4(4) Method 4

If the sum of the transmission powers to be used in the scheduled Ucells in the power limit case is larger than the P_u value allowed for the terminal, the terminal may be configured to drop the UL transmission in all the Ucells.

4.3.4 일반 케이스에 확장 적용 방법4.3.4 How to apply extensions to common cases

In cases where the K value is set in advance by the higher layer signal in section 4.3.3, the methods (1) to (3) can be extended even if they are not in the power limiting case. For example, when a base station triggers an aperiodic SRS (A-SRS) in a radio access system that combines and services five or more multiple carriers, multiple A-s within one UL grant to reduce signal overhead. You can set up triggers for SRS. That is, specific U cell indexes may be mapped for each state indicated by the A-SRS trigger. For example, when the A-SRS trigger is set to '01', this indicates that the UE transmits the A-SRS through the Ucell1 and the Ucell2. When the A-SRS trigger is set to '10', the Ucell3 It can indicate that the UE transmits the A-SRS through the Ucell4.

However, due to the nature of the unlicensed band, the UE may transmit the SRS only when it is in an idle state according to the CCA result for each U cell, so that specifying the U cell index in advance may not be significant. Therefore, by specifying only the number of U cells to transmit the UL signal, it may be preferable that the UE is configured to transmit SRS only for the K U cells that can transmit the CCA result among the scheduled U cells.

In this case, it is assumed that the number of U cells scheduled by the UE is M (> K), and the transmission power P_sum required for transmitting UL signals through all M U cells is smaller than P_u. When N UEs (K <N <= M) of M U cells are determined to be idle, the UE selects K U cells in which the sum of transmit powers of N does not exceed P_u to select UL signals. Can transmit In this case, the UE may select any K of N U cells.

The methods of section 4.3.3 may not apply on Ucells that can transmit without LBT. For example, in FIG. 15, if the UE is continuously transmitting UL signals from SF # n + 3, which is before SF # n + 4 in Ucell1, the UE transmits UL signals in SF # n + 4 without LBT. Can be. For another example, when another UE or eNB is configured to perform CS instead of the UE, the UE may transmit a UL signal without LBT.

4.3.5 각 U셀에 따른 송신 전력 제어 방법4.3.5 Transmission power control method according to each U cell

In the embodiments described below, if the transmit power P_ux required for the UL signal transmission of a specific Ucellx is larger than P_u, which is the sum of the transmit powers for all scheduled Ucells, the terminal is described in Section 4.3.3. CCA may not be performed for the Ucellx after excluding the aforementioned methods from power control in advance. That is, the terminal may be configured to perform the methods described in Sections 4.3.1 to 4.3.3 above only for U cells whose P_ux is not greater than P_u.

Referring to FIG. 17, the terminal may be scheduled for UL of one or more Ucellx (S1710).

If the terminal is scheduled for one or more Ucellx, the terminal compares the total power P_u of the transmission power of the corresponding Ucellx and the transmission power required for all scheduled Ucells (S1720).

If P_ux <= P_u, the UE may perform power control for the corresponding Ucellx by applying the methods performed in Sections 4.3.1 to 4.3.3 (S1730).

In step S1720, if P_ux> P_u, the UE does not perform a CCA (or CS, LBT, etc.) process in the Ucellx and does not perform UL transmission (S1740).

The UE may be assigned a power scale threshold T previously defined by higher layer signaling similarly to the method described in Section 4.3.2. The UE may use the allocated power scale threshold T as a scaling factor without excluding all Ucellx from UL power control because P_ux is greater than P_u.

Referring to FIG. 18, the terminal may be scheduled for UL of one or more Ucellx (S1810).

If the terminal is scheduled for one or more Ucellx, the terminal compares the total power P_u of the transmission power of the corresponding Ucellx and the transmission power required for all scheduled Ucells (S1820).

If P_ux <= P_u, the UE may perform power control on the corresponding Ucellx by applying the methods performed in Sections 4.3.1 to 4.3.3 (S1840).

In step S1820, if P_ux> P_u, the terminal compares the scaled T * P_ux value with P_u using the received power scale threshold T (S1840).

At this time, if T * P_ux <= P_u, the terminal may use the T * P_ux value as the UL transmission power for the Ucellx. That is, the UE may perform power control by applying the methods described in Sections 4.3.1 to 4.3.3 based on the T * P_ux value (S1850).

If T * P_ux> P_u, the UE does not perform the CCA (or CS, LBT, etc.) process in the Ucellx and also does not perform UL transmission (S1860).

In the methods described with reference to FIGS. 17 and 18, if P_ux is greater than or equal to a predetermined value, the UE may exclude P_ux value from the U-cell power control in advance. In this case, a case where UL signal transmission is impossible on all U cells scheduled by the UE may occur.

To compensate for this, when all P_ux is equal to or greater than a predetermined value (for example, P_u in FIG. 17, P_u or T * P_u in FIG. 18), the UE performs power scale-down only for one specific U cell and the corresponding U cell. Phase CCA and UL signal transmission may be allowed.

For example, when there are Ucell1 and Ucell2 scheduled by the UE as shown in FIG. 15, both P_u1 and P_u2 may be larger than P_u. That is, P_u1> P_u and P_u2> P_u. In this case, the terminal may perform power scaling down so that only one of the scheduled U cells (for example, P_u1 of U cell 1) is equal to or less than P_u. That is, the terminal may set the w value to satisfy w * P_u1 <= P_u. In addition, when the channel is idle by performing the CCA on the Ucell1, the UE may perform UL signal transmission with a power of w * P_u1. This method may also be applied to the method described with reference to FIG. 18. That is, the terminal may perform UL signal transmission with the power of T * w * P_u1.

As such, when all P_ux is greater than or equal to a certain value, the UE performs power scaling down on only one specific U cell, and the method of selecting one particular U cell by the UE is described in the above-described method (1) to 4.3.3. (3) is applicable.

For example, the terminal selects any one U cell as in Method (1), or selects one U cell whose P_ux is maximum (or minimum) as in Method (2), or As such, it may be configured to select one U-cell having the highest priority according to a preset priority.

As another aspect of the present invention, in the above-described embodiments described in Section 4.3.2 and FIG. 17, the power scaling threshold T may be set differently according to the UL transmission signal. For example, the T value applied at PUSCH transmission may be greater than the T value applied at SRS transmission. As another example, the T value may be set to a different value for each UE and / or for each U cell.

5. 구현 장치5. Implement device

A UE may operate as a transmitting end in uplink and a receiving end in downlink. In addition, an e-Node B (eNB) may operate as a receiving end in uplink and a transmitting end in downlink.

That is, the terminal and the base station may include

transmitters

1940 and 1950 and

receivers

1950 and 1970 to control the transmission and reception of information, data and / or messages, respectively. Or

antennas

1900 and 1910 for transmitting and receiving messages.

In addition, the terminal and the base station may each include a processor (1920, 1930) for performing the above-described embodiments of the present invention and a memory (1980, 1990) that can temporarily or continuously store the processing of the processor, respectively. Can be.

Embodiments of the present invention can be performed using the components and functions of the above-described terminal and base station apparatus. For example, the processor of the terminal may perform UL power control based on the above-described methods when the scheduled serving cells are L cells and / or U cells. The processor of the base station transmits a UL grant for scheduling L cells and / or U cells to the terminal, and the UL grant includes P _CMAX necessary for power control, power scale threshold T, and / or weight w for power scale down. Can be. However, P _CMAX , T, w values, etc. may be transmitted to the UE through higher layer signaling rather than the UL grant. For details, reference may be made to the contents described in Sections 1 to 4 described above.

The transmitter and the receiver included in the terminal and the base station include a packet modulation and demodulation function, a high speed packet channel coding function, an orthogonal frequency division multiple access (OFDMA) packet scheduling, and a time division duplex (TDD) for data transmission. Packet scheduling and / or channel multiplexing may be performed. In addition, the terminal and the base station of FIG. 19 may further include a low power radio frequency (RF) / intermediate frequency (IF) unit.

Meanwhile, in the present invention, the terminal is a personal digital assistant (PDA), a cellular phone, a personal communication service (PCS) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA) phone, an MBS. A Mobile Broadband System phone, a hand-held PC, a notebook PC, a smart phone, or a Multi Mode-Multi Band (MM-MB) terminal may be used.

Here, a smart phone is a terminal that combines the advantages of a mobile communication terminal and a personal portable terminal, and may mean a terminal incorporating data communication functions such as schedule management, fax transmission and reception, which are functions of a personal mobile terminal, in a mobile communication terminal. have. In addition, a multimode multiband terminal can be equipped with a multi-modem chip to operate in both portable Internet systems and other mobile communication systems (e.g., code division multiple access (CDMA) 2000 systems, wideband CDMA (WCDMA) systems, etc.). Speak the terminal.

Embodiments of the invention may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

In the case of a hardware implementation, the method according to embodiments of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs). Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above. For example, software code may be stored in

memory units

1980 and 1990 and driven by

processors

1920 and 1930. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

The invention can be embodied in other specific forms without departing from the spirit and essential features of the invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention. In addition, the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship or may be incorporated as new claims by post-application correction.

Embodiments of the present invention can be applied to various wireless access systems. Examples of various radio access systems include 3rd Generation Partnership Project (3GPP), 3GPP2 and / or IEEE 802.xx (Institute of Electrical and Electronic Engineers 802) systems. Embodiments of the present invention can be applied not only to the various radio access systems, but also to all technical fields to which the various radio access systems are applied.

Claims

In a method of performing uplink (UL) power control by a terminal in a wireless access system supporting an unlicensed band,

Receiving at least two UL grants including scheduling information;

When the scheduled serving cells include a licensed band cell (L cell) and an unlicensed band cell (U cell), the sum of the transmit power required by the L cell (P_L) and the maximum transmit power that can be transmitted by the U cell value (P_u), comprising: performing power control as a guaranteed power value (P_g) and the maximum transmission power value (P CMAX) available for the terminal is used in the cell-based U; And

And transmitting a UL signal in each of the L cell and the U cell based on the transmission power and the scheduling information derived through the power control.
The method of claim 1,

And wherein P_u is always set to a value greater than or equal to P_g regardless of P_L.
The method of claim 1,

The P_g is, UL power control method that is determined by the ratio between the P CMAX.
The method of claim 3,

The P CMAX the P_g first value assigned to the cell at U, and,, UL power control method of allocating a remainder to the L cells.
The method of claim 1,

The P_g is set to a value valid only in a subframe scheduled by the two or more UL grants.
The method of claim 1,

When two or more U cells are scheduled to the terminal, the UL power control method is configured such that transmission powers allocated to the U cells do not exceed P_u by performing power scaling down on transmission powers to be allocated to the U cells. .
In a wireless access system supporting an unlicensed band, a terminal performing uplink (UL) power control may include:

receiving set;

transmitter; And

Including a processor for supporting the UL power control,

The processor is:

Control the receiver to receive two or more UL grants including scheduling information;

When the scheduled serving cells include a licensed band cell (L cell) and an unlicensed band cell (U cell), the sum of the transmit power required by the L cell (P_L) and the maximum transmit power that can be transmitted by the U cell value (P_u), and performs the power control to ensure the power value (P_g) and the maximum transmission power value (P CMAX) available for the terminal is used in the cell-based U;

And control the transmitter to transmit UL signals in the L cell and the U cell based on the transmission power and the scheduling information derived through the power control.
The method of claim 7, wherein

The P_u is always set to a value greater than or equal to the P_g regardless of the P_L.
The method of claim 7, wherein

The P_g, the terminal that is determined by the ratio between the P CMAX.
The method of claim 9,

A terminal to a value in the P P_g CMAX is first allocated for the U cells, the remainder value for the L cells.
The method of claim 7, wherein

The P_g is set to a value valid only in a subframe scheduled by the two or more UL grants.
The method of claim 7, wherein

When two or more U cells are scheduled to the terminal, the terminal is configured to perform power scaling down on transmission powers to be allocated to the U cells so that the transmission powers allocated to the U cells do not exceed P_u.