WO2013100541A1

WO2013100541A1 - Method and apparatus for controlling transmission power in wireless communication system

Info

Publication number: WO2013100541A1
Application number: PCT/KR2012/011434
Authority: WO
Inventors: 김종남; 리지안준
Original assignee: 주식회사 팬택
Priority date: 2011-12-29
Filing date: 2012-12-26
Publication date: 2013-07-04
Also published as: KR20130077387A

Abstract

The present invention relates to a method and an apparatus for controlling transmission power in a wireless communication system. To that end, a method for controlling power is disclosed in the present specification comprising the steps of: determining whether an uplink channel, which is transmitted from a second server cell belonging to a different band than a first serving cell, has priority over a sounding reference signal (SRS) for power allocation at a point in time overlapping with a transmission time of an SRS, the SRS being a reference signal used for estimating the status of an uplink in the first serving cell; and scaling the power for the SRS or the uplink channel in accordance with the determination regarding priority. In an environment of simultaneous transmission of SRS and PUSCH or PUCCH from multiple uplink component carriers, the uplink power is effectively controlled by allocating power sequentially according to priority, and thus the performance of the multiple component carrier is improved.

Description

Method and apparatus for controlling transmission power in wireless communication system

The present invention relates to wireless communications, and more particularly, to a method and apparatus for controlling transmission power in a wireless communication system.

One of the most important requirements of the next generation wireless communication system is that it can support high data rate requirements. To this end, various technologies such as Multiple Input Multiple Output (MIMO), Cooperative Multiple Point Transmission (CoMP), and relay are being studied, but the most basic and stable solution is to increase the bandwidth.

When a wireless communication system intends to support broadband, one or more carriers having a bandwidth smaller than the target broadband may be collected to form a broadband. In this case, one or more component carriers are aggregated to support broadband. For example, if one component carrier corresponds to a bandwidth of 5 MHz, four carriers are aggregated to support a maximum bandwidth of 20 MHz. Such a system using carrier aggregation is called a multiple component carrier system. In a multi-component carrier system, a terminal can simultaneously transmit or receive one or a plurality of carriers according to its capacity. Each independent operating band is defined as a component carrier (CC).

In a multi-component carrier system, a UE transmits a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), or a sounding reference signal through a plurality of CCs. SRS) may be transmitted. When the UE transmits a PUCCH, PUSCH or SRS on each of a plurality of CCs, the transmit power of the PUCCH, PUSCH or SRS may be limited by the maximum transmit power of the UE. The UE should be able to efficiently allocate and / or control the power for the PUCCH, PUSCH, and SRS.

The present invention provides a method and apparatus for controlling transmission power in a wireless communication system.

Another object of the present invention is to provide an apparatus and a method for performing power scaling when an SRS and another uplink signal are transmitted on a band-served aggregated serving cell.

Another technical problem of the present invention is to provide an apparatus and method for performing power scaling according to priority between an SRS and another uplink signal.

According to an aspect of the present invention, there is provided a power control method by a terminal in a multi-component carrier system. The method belongs to a band different from the first serving cell at a point of time overlapping with a transmission time of a sounding reference signal (SRS), which is a reference signal used to estimate a state of an uplink on the first serving cell. Determining whether an uplink channel transmitted on a second serving cell has a higher priority in power allocation than the sounding reference signal, and based on the determination result of the priority, the sounding reference signal or the uplink Performing power scaling on the channel.

In the power scaling, when the sounding reference signal has a higher priority than the uplink channel, power is first assigned to the sounding reference signal and the remaining power is allocated to the uplink channel, and the sounding reference signal is assigned to the uplink channel. If the priority is lower than the link channel, power may be allocated to the uplink channel first, and the remaining power may be allocated to the sounding reference signal.

In the situation where a plurality of uplink component carriers simultaneously transmit SRS, PUSCH or PUCCH, power can be efficiently controlled by sequentially assigning power according to priority, thereby improving performance of a multi-component carrier system. Can be.

1 is a block diagram showing a wireless communication system to which the present invention is applied.

2 and 3 schematically show the structure of a radio frame to which the present invention is applied.

4 shows a structure of an uplink subframe.

5 is a diagram illustrating states of serving cells configured in a terminal in a multi-component carrier system according to an embodiment of the present invention.

6 shows transmission timing of component carriers.

7 is a flowchart illustrating an uplink power control operation by a terminal according to an embodiment of the present invention.

8 is an explanatory diagram illustrating a method of performing power scaling based on priorities according to an embodiment of the present invention.

9 is an explanatory diagram illustrating a method of performing power scaling based on priorities according to another embodiment of the present invention.

10 is an explanatory diagram illustrating a method of performing power scaling based on priority according to another example of the present invention.

11 is an explanatory diagram illustrating a method of performing power scaling based on priority according to another example of the present invention.

12 is a flowchart illustrating an uplink power control operation by a terminal according to another embodiment of the present invention.

13 is a configuration diagram of a terminal according to an embodiment of the present invention.

Hereinafter, some embodiments will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even though they are shown in different drawings. The present specification describes a communication network, and the work performed in the communication network is performed in the process of controlling the network and transmitting data in a system (for example, a base station) that manages the communication network, or a terminal linked to the network. Work can be done in

According to the embodiments of the present invention, the term 'transmitting a channel' may be interpreted to mean that information mapped through the channel or mapped to the channel is transmitted. Here, the channel may be, for example, a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH) or a physical channel. It may include a physical uplink shared channel (PUSCH).

Referring to FIG. 1, the wireless communication system 10 is widely deployed to provide various communication services such as voice and packet data. The wireless communication system 10 includes at least one base station (BS) 11. Each base station 11 provides a communication service for a particular geographic area or frequency area (generally called a cell) 15a, 15b, 15c.

Cells

15a, 15b, and 15c may in turn be divided into a number of regions (called sectors).

The user equipment (UE) 12 may be fixed or mobile, and may include a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, and a PDA. (personal digital assistant), wireless modem (wireless modem), a handheld device (handheld device) may be called other terms. The base station 11 generally refers to a station that communicates with the terminal 12, and includes an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, an femto eNB, and a home. It may be referred to by other terms such as a base station (HeNB), a relay, a remote radio head (RRH), and the like.

Cells

15a, 15b, and 15c should be interpreted in a comprehensive sense indicating some areas covered by the base station 11, and encompass all of the various coverage areas such as megacells, macrocells, microcells, picocells, and femtocells. to be.

Hereinafter, downlink refers to a communication or communication path from the base station 11 to the terminal 12, and uplink refers to a communication or communication path from the terminal 12 to the base station 11. . In downlink, the transmitter may be part of the base station 11 and the receiver may be part of the terminal 12. In uplink, the transmitter may be part of the terminal 12 and the receiver may be part of the base station 11. There is no limitation on the multiple access scheme applied to the wireless communication system 10. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), OFDM-FDMA, OFDM-TDMA For example, various multiple access schemes such as OFDM-CDMA may be used. These modulation techniques demodulate signals received from multiple users of a communication system to increase the capacity of the communication system. The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme transmitted using different times or a frequency division duplex (FDD) scheme transmitted using different frequencies.

The layers of the radio interface protocol between the terminal and the base station are based on the lower three layers of the Open System Interconnection (OSI) model, which is well known in the communication system. It may be divided into a second layer L2 and a third layer L3. Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel.

There are several physical channels used in the physical layer. The PDCCH includes a resource allocation and transmission format of a downlink shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), a random access response message transmitted on a PDSCH, Resource allocation of the same upper layer control message, a set of transmission power control (TPC) commands for individual terminals in a certain terminal group, etc. may be carried. A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs.

Control information of the physical layer mapped to the PDCCH is referred to as downlink control information (DCI). That is, DCI is transmitted through the PDCCH. The DCI may include an uplink or downlink resource allocation field, an uplink transmission power control command field, a control field for paging, a control field for indicating a random access response (RA response), and the like.

DCI has different uses according to its format, and fields defined in DCI are also different. Table 1 shows DCIs according to various formats.

Table 1

DCI format	Explanation
0	Used for scheduling of PUSCH (Uplink Grant)
One	Used for scheduling one PDSCH codeword in one cell
1A	Used for simple scheduling of one PDSCH codeword in one cell and random access procedure initiated by PDCCH command
1B	Used for simple scheduling of one PDSCH codeword in one cell using precoding information
1C	Used for brief scheduling of one PDSCH codeword and notification of MCCH change
1D	Used for simple scheduling of one PDSCH codeword in one cell containing precoding and power offset information
2	Used for PDSCH scheduling for UE configured in spatial multiplexing mode
2A	Used for PDSCH scheduling of UE configured in long delay CDD mode
2B	Used in transmission mode 8 (double layer transmission)
2C	Used in transmission mode 9 (multi-layer transmission)
3	Used to transmit TPC commands for PUCCH and PUSCH with power adjustment of 2 bits
3A	Used to transmit TPC commands for PUCCH and PUSCH with single bit power adjustment
4	Used for scheduling of PUSCH (Uplink Grant). In particular, it is used for PUSCH scheduling for a terminal configured in a spatial multiplexing mode.

Referring to Table 1, DCI format 0 is uplink scheduling information, format 1 for scheduling one PDSCH codeword, format 1A for compact scheduling of one PDSCH codeword, and very simple of DL-SCH. Format 1C for scheduling, format 2 for PDSCH scheduling in closed-loop spatial multiplexing mode, format 2A for PDSCH scheduling in open-loop spatial multiplexing mode, and uplink channel Formats 3 and 3A for transmission of a transmission power control (TPC) command.

Each field of the DCI is sequentially mapped to _n information bits a ₀ to a _n-1 . For example, if DCI is mapped to information bits of a total of 44 bits in length, each DCI field is sequentially mapped to a ₀ to a ₄₃ . DCI formats 0, 1A, 3, and 3A may all have the same payload size. DCI format 0 may be called an uplink grant.

2 and 3, a radio frame includes 10 subframes. One subframe includes two slots. The time (length) of transmitting one subframe is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

One slot may include a plurality of symbols in the time domain. For example, in the case of a wireless system using Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink, the symbol may be an Orthogonal Frequency Division Multiplexing Access (SC-FDMA) symbol. Meanwhile, the representation of the symbol period in the time domain is not limited by the multiple access scheme or the name. For example, the plurality of symbols in the time domain may be orthogonal frequency division multiple access (OFDMA) symbols, symbol intervals, etc. in addition to the SC-FDMA symbols.

One slot includes a plurality of subcarriers in the frequency domain and seven SC-FDMA symbols in the time domain. A resource block (RB) is a resource allocation unit. If a resource block includes 12 subcarriers in the frequency domain, one resource block may include 7 × 12 resource elements (REs).

The resource element represents the smallest frequency-time unit to which the modulation symbol of the data channel or the modulation symbol of the control channel is mapped. If there are M subcarriers on one SC-FDMA symbol, and one slot includes N SC-FDMA symbols, one slot includes MxN resource elements.

In a wireless communication system, it is necessary to estimate an uplink channel or a downlink channel for data transmission / reception, system synchronization acquisition, channel information feedback, and the like. The process of restoring a transmission signal by compensating for distortion of a signal caused by a sudden change in channel environment is called channel estimation. In general, a reference signal (RS) known to a terminal and a transceiver is mutually used for channel estimation or channel state measurement.

Since the terminal knows the information of the reference signal, the terminal can estimate the channel based on the received reference signal and compensate the channel value to accurately obtain the data sent from the transmission / reception point. When the reference signal from the reception point (transmission and reception point) p, a reference signal is the channel information h, the thermal noises generated in a terminal n, y to the signal terminal receives experienced during transmission La y = h · p can be expressed as: + n In this case, since the reference signal p is already known by the terminal, when the LS (Least Square) method is used, channel information (

) Can be estimated.

Equation 1

Here, the channel estimate estimated using the reference signal p

Is

Depends on the value, so to get an accurate estimate of

You need to converge to zero. By using a large number of reference signals

The channel can be estimated by minimizing the effects of

The reference signal may be allocated to all subcarriers or may be allocated between data subcarriers for transmitting data. In a method in which a reference signal is allocated to all subcarriers, a signal of a specific transmission timing is composed of only a reference signal such as a preamble in order to obtain a gain of channel estimation performance. According to a method in which a reference signal is allocated between data subcarriers, a data transmission amount can be increased.

In downlink, a cell-specific RS (CRS), a UE-specific RS, a positioning reference signal (PRS) and a channel state information (CSI) reference signal (CSI-RS) Etc. are defined.

The CRS is a reference signal transmitted to all terminals in a cell and used for channel estimation. The CRS may be transmitted in all downlink subframes in a cell supporting PDSCH transmission. The UE specific reference signal is a reference signal received by a specific terminal or a specific terminal group in a cell, and is mainly used for data demodulation of a specific terminal or a specific terminal group, and thus may be called a demodulation RS (DMRS). The PRS may be used for location measurement of the terminal. The PRS may be transmitted only through resource blocks in a downlink subframe allocated for PRS transmission. CSI-RS may be used for estimation of channel state information. The CSI-RS is placed in the frequency domain or time domain. Channel quality indicator (CQI), precoding matrix indicator (PMI) and rank indicator (RI) rank information such as channel quality indicator (CQI), if necessary through the estimation of the channel state using the CSI-RS As reported from the terminal. The CSI-RS may be transmitted on one or more antenna ports.

In uplink, a demodulation reference signal (DMRS) and a sounding reference signal (SRS) are defined. DMRS is associated with transmission of PUSCH or PUCCH, and SRS is not correlated with PUSCH or PUCCH. SRS is a signal that the base station receives from the terminal for use in uplink scheduling. SRS is used in the physical layer and does not carry information originating from higher layers. The SRS may be transmitted in the last symbol of each subframe. With respect to the transmission of the SRS may be configured specifically for the terminal, the SRS may be transmitted periodically (periodic) or aperiodic (aperiodic).

4 shows a structure of an uplink subframe.

Referring to FIG. 4, the uplink subframe includes two slots on the time axis, and each slot includes seven SC-FDMA symbols. The uplink subframe includes a PUCCH and a PUSCH using different frequencies. The uplink subframe may be divided into a region to which a PUCCH is allocated and a region to which a PUSCH is allocated.

Control information of the physical layer mapped to the PUCCH is called uplink control information (UCI). That is, the UCI is transmitted through the PUCCH. UCI includes scheduling request (SR), acknowledgment / non-acknowledgement (ACK / NACK) signal for hybrid ARQ (HARQ), channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), etc. It may include various kinds of control information. PUCCH carries various kinds of control information according to a format. For example, uplink control information having a different number of bits per subframe may be transmitted according to a modulation scheme. For example, when using BPSK (Binary Phase Shift Keying), 1-bit uplink control information can be transmitted on PUCCH, and when using QPSK (Quadrature Phase Shift Keying), 2-bit uplink control information is PUCCH. Can be sent over the air.

PUCCH for one UE uses one resource block occupying a different frequency in each of two slots in a subframe. Two slots use different resource blocks (or subcarriers) in a subframe. Two resource blocks allocated to the PUCCH are said to be frequency hopping at a slot boundary.

SRS can be transmitted in the last SC-FDMA symbol interval, the PUCCH in the last SC-FDMA symbol is puncturing. At this time, the UE transmits data using 13 SC-FDMA symbols, and performs a preprocessing process such as rate matching for the remaining SC-FDMA symbols and transmits a sounding reference signal.

Referring to FIG. 5, the system bandwidth includes bands A and B, band A includes a main serving cell (PCell) and a first secondary serving cell (SCell 1), and band B includes a second secondary serving. It includes a cell (SCell 2) and a third secondary serving cell (SCell 3). The terminal may be configured with any one of the first secondary serving cell and the third secondary serving cell, including a main serving cell. Carrier aggregation of the primary serving cell and the first secondary serving cell is intra-band aggregation. Similarly, the carrier aggregation of the second secondary serving cell and the third secondary serving cell is the aggregation in the B band. On the other hand, carrier aggregation between the main serving cell and the second secondary serving cell and carrier aggregation between the primary serving cell and the third secondary serving cell are inter-band aggregation. Carrier aggregation between the first secondary serving cell and the second secondary serving cell, and carrier aggregation between the first secondary serving cell and the third secondary serving cell are inter-band aggregation.

6 shows transmission timing of component carriers.

Referring to FIG. 6, the system bandwidth includes bands A and B, band A includes a main serving cell (PCell) and a first secondary serving cell (SCell 1), and band B includes a second secondary serving. It includes a cell (SCell 2) and a third secondary serving cell (SCell 3).

Regarding uplink transmission, a timing difference Td may exist between a band A and a band B in terms of frequency characteristics or a transmission path for a base station. For example, when the UE simultaneously transmits signals on the first secondary serving cell and the second secondary serving cell, the base station receives a signal of the first secondary serving cell by Td later than a signal of the second secondary serving cell due to a timing difference. . Therefore, the UE should transmit the signal of the first secondary serving cell earlier by Td. This is called timing alignment (TA) to accelerate or lag the uplink transmission.

Since there is almost no difference in frequency characteristics or transmission paths within one band, there is little timing difference even if band aggregation is achieved. However, if the bands are different, there are differences in frequency characteristics and transmission paths. Therefore, if band aggregation is achieved, timing differences may occur.

For example, in FIG. 6, when carrier aggregation (that is, interband aggregation) is performed between the first secondary serving cell and the second secondary serving cell, the SRS in the first secondary serving cell is determined by the second secondary serving cell due to the timing difference. SRS is sent at different times. In other words, the SRS in the first secondary serving cell may be transmitted simultaneously with the PUSCH or the PUCCH in the second secondary serving cell, and the PUSCH or the PUCCH in the first secondary serving cell and the SRS in the second secondary serving cell are simultaneously transmitted. May be When simultaneous transmission of the uplink channel and the SRS exceeds the maximum value of the uplink power of the terminal, the terminal should be able to set the transmission power of the uplink channel and the transmission power of the SRS within the maximum value. This is manifested by uplink power control which sets the amount of power to be allocated to the uplink channel or SRS.

Referring to FIG. 7, the terminal calculates a transmit power P _SRS of an _SRS , a transmit power P _UL of an uplink channel, and a transmit power P _DMRS of a _DMRS (S700). It is assumed that an aggregated multi-component carrier is configured in the terminal, and a timing difference exists between the multi-component carriers. The uplink channel includes at least one of a PUCCH and a PUSCH.

The terminal is the maximum transmission power of the sum of the total uplink transmission power of the terminal P _SRS , P _UL and P _DMRS

It is determined whether to exceed (S705). Where i is the subframe index. If the total uplink transmission power of the terminal is the maximum transmission power

If exceeded, the terminal performs power scaling (S710). Increasing or decreasing the transmit power of the uplink channel, the transmit power of the DMRS, or the transmit power of the SRS by a certain ratio is called power scaling. One example of power scaling is to multiply the original transmit power by a scaling factor w. For example, power scaling of P _SRS , P _UL, and P _DMRS results in wP _SRS , wP _UL, and wP _DMRS , respectively. Here, w may have a value of 0 ≦ w ≦ 1, and power scaling may be called uplink power control.

In one embodiment, the power scaling scales the transmit power of one uplink channel, the transmit power of a DMRS, or the transmit power of an SRS, and the transmit power of another uplink channel, the transmit power of a DMRS, or the transmit power of an SRS. It does not scale. For example, the transmit power P _SRS of the _SRS may be scaled to wP _SRS or the transmit power P _PUSCH of the _PUSCH may be scaled to wP _PUSCH .

What is to be scaled and what is not is selected based on priority. Priority provides a criterion for efficiently allocating limited uplink power to uplink channels, DMRSs, and SRSs.

Scaling the power of the uplink channel, DMRS or SRS based on the priority, the terminal scales the transmission power of the lower priority uplink channel, the transmission power of the DMRS or the transmission power of the SRS, the priority is higher It does not scale the transmission power of the high uplink channel, the transmission power of the DMRS or the transmission power of the SRS. That is, the terminal maintains the first transmission power of the uplink channel having the higher priority, the first transmission power of the DMRS, or the first transmission power of the SRS. And the second transmission power remaining at the maximum transmission power except for the first transmission power is greater than the third transmission power of the uplink channel having the lower priority, the third transmission power of the DMRS, or the third transmission power of the SRS. In this case, power is allocated to an uplink channel having a low priority, DMRS or SRS. On the other hand, if the second transmission power is smaller than the third transmission power, the terminal allocates zero power to the uplink channel, DMRS or SRS having a lower priority. That is, the UE does not transmit or drop the uplink channel, DMRS or SRS having a lower priority.

Priority may be defined in SC-FDMA symbol units or dimensions, or may be defined in subframe units or dimensions. First, in the SC-FDMA symbol dimension, priority is defined based on the type of information transmitted by the SC-FDMA symbol. For example, the type of information transmitted by the SC-FDMA symbol includes data, DMRS, SRS, and the like. The priority in the SC-FDMA symbol dimension may be DMRS> SRS> data. Next, in the subframe dimension, priority is defined based on the type of information transmitted by each subframe. For example, the type of information transmitted in the subframe includes PUSCH, PUCCH, SRS, and the like. In the subframe dimension, the priority may be PUCCH> SRS> PUSCH.

In another embodiment, the power scaling includes scaling transmission power of all uplink channels and transmission power of SRS by a predetermined ratio. In this case, power scaling may be independent of priority. This power scaling is called power scaling based on reduction sharing.

Thereafter, the process of transmitting the SRS by the terminal is not shown in the figure, but proceeds to the following procedure. The terminal generates an SRS sequence and multiplies the generated sequence of SRS by an amplitude scaling factor β _SRS to conform to the scaled SRS transmission power wP _SRS , and multiplies the β _SRS by the SRS. After sequentially mapping r ^P _SRS (0) to resource elements on antenna port p, SC-FDMA symbols are generated and transmitted to the base station.

As described above, when the uplink channel and the SRS are simultaneously transmitted on different component carriers, a method of scaling the transmission power or the SRS of the uplink channel at a constant rate may be applied.

Hereinafter, when priority is defined at the SC-FDMA symbol dimension, a method of scaling power in the case of being defined at the subframe dimension is disclosed.

1. Power scaling when priorities are defined at the SC-FDMA symbol dimension

If the priority is defined in the SC-FDMA symbol dimension, it is equivalent to the concept that the transmission power is allocated in SC-FDMA symbol units. Types of information transmitted by the SC-FDMA symbol include data, DMRS, SRS, and the like. In determining the priority at the SC-FDMA symbol dimension, for example, the priority may be determined based on the reliability of the data transmission.

In case of an SC-FDMA symbol in which uplink control information or data (PUCCH or PUSCH without DMRS) is transmitted, transmission is performed in the corresponding SC-FDMA symbol according to coding rate, modulation, or diversity characteristics. Even if data is not received, data can be recovered to some extent through data transmitted in another SC-FDMA symbol. Accordingly, the priority of the SC-FDMA symbol to which data is transmitted may be set lower than that of other uplink signals.

However, if the DMRS fails to receive the transmitted SC-FDMA symbol, the entire uplink channel cannot be received. Therefore, it is preferable that the priority of the SC-FDMA symbol to which DMRS is transmitted is higher than the SC-FDMA symbol to which data is transmitted. According to this, the priority in the SC-FDMA symbol dimension may be DMRS> SRS> data.

Equations

2 and 3 express power allocation in consideration of priorities in the SC-FDMA symbol dimension.

Equation 2

Equation 3

Referring to Equations 2 and 3,

Denotes a linear value of x. therefore,

Is the linear value of P _CMAX . c is the index of the serving cell, P _{PUCCH, DMRS} is the power of the PUCCH including the DMRS, P _{PUSCH, DMRS} is the power of the PUSCH including the DMRS. In Equation 2, the first allocation for the uplink power allocation of the UE and the next for the DMRS of the PUSCH, the next allocation for the DMRS of the PUSCH, the remaining power is scaled by the scaling factor w to the SRS transmission power of each serving cell c Is assigned. In Equation 3, SC-FDMA symbols transmitting data not including DMRS are allotted power to data including DMRS and SC-FDMA symbols transmitting SRS, and the remaining power is scaled by a scaling factor w. And is allocated to transmission of PUSCH or PUCCH of each serving cell.

Since power allocation is made in fast Fourier transform (FFT) units, the UE may allocate resources independently for each SC-FDMA symbol that is a unit of FFT. Therefore, in a situation where the timing difference between serving cells occurs, in order to use the power available to the UE more efficiently, the unit of power allocation should be defined in symbol units. 8 and 9 are examples of power allocation when Equation 2 and Equation 3 are actually applied.

Referring to FIG. 8, a first secondary serving cell SCell 1 and a second secondary serving cell SCell 2 are configured by carrier aggregation in a terminal, and Td is divided between the first secondary serving cell and the second secondary serving cell. Assume that there is a timing difference. The SC-FDMA symbol i in which the SRS is transmitted in the first secondary serving cell overlaps the SC-FDMA symbol j in which the PUSCH or PUCCH not including the DMRS is transmitted in the first secondary serving cell. In this interval, the UE sets the transmit power of the SRS to PSRS and sets the remaining power to the transmit power P _DATA of PUSCH or PUCCH. On the other hand, in the SC-FMDA symbols j-1, j + 1, etc., which are not transmitted simultaneously with the SRS, the UE sets the transmission power of the PUSCH or the PUCCH to P _DATA .

One limitation may be applied when allocating remaining power for transmission of the SRS and allocating the remaining power for transmission of the PUSCH or the PUCCH. For example, when the modulation scheme of the PUSCH is QPSK, the remaining power after transmitting the SRS is allocated to the data transmission of the PUSCH. When the modulation scheme of the PUSCH is 16QAM or 64QAM, the SRS is allocated and the remaining power is not allocated to the transmission of the PUSCH. Do not. The reason for this is as follows. If the modulation scheme of the PUSCH is QPSK, information is transmitted through the phase and amplitude (magnitude) does not affect the information. As a result, the signal size may be reduced when transmitting with less power, but may not affect information detection. On the other hand, when not only phases but also amplitudes, such as 16QAM or 64QAM, are used for the transmission of information, it is preferable not to transmit since they may cause distortion when transmitted with less power.

Referring to FIG. 9, the SC-FDMA symbol i in which the SRS is transmitted in the first secondary serving cell overlaps the SC-FDMA symbol j in which the DMRS is transmitted through the PUSCH or the PUCCH in the second secondary serving cell. In this interval, the UE preferentially allocates power PDMRS to DMRS according to priority and does not allocate power for transmission of SRS. That is, the SRS is punctured or dropped or muted by rate matching or zero power is allocated.

Referring to FIG. 10, a first secondary serving cell SCell 1 and a second secondary serving cell SCell 2 are configured in one terminal by carrier aggregation, and the first secondary serving cell and the second secondary serving cell are configured. There is a timing difference in uplink time.

The index of the last SC-FDMA symbol of subframe n in the first secondary serving cell is i, and this SC-FDMA symbol is located between j-1 and j SC-FDMA symbols of subframe n in the second secondary serving cell. do. In the carrier aggregation environment, the transmission start point of each serving cell is determined in consideration of the transmission delay of the terminal. If the serving cells are configured with carrier aggregation between bands in one terminal, the transmission delay in each band may be different. As shown in FIG. 10, the transmission start point may not match.

As such, when symbol timings between serving cells do not match, a power allocation scheme for each symbol should be defined. Here, the priority (for example, DMRS> SRS> data) defined in the SC-FDMA symbol dimension may be equally applied. In FIG. 10, the SRS is transmitted in the SC-FDMA symbol i and the DM-1 is not present in the j-1 and j SC-FDMA symbols of the second secondary serving cell which overlaps with the SC-FDMA symbol i simultaneously (PUCCH or PUSCH). ) Is sent.

The UE performs power scaling in consideration of the PUSCH required power of the SC-FDMA symbol i-1 of the first secondary serving cell and the PUSCH required power of the SC-FDMA symbol j-1 of the second secondary serving cell The transmission power P _j-1 in the SC-FDMA symbol of _j-1 is obtained (0 ≦ w (i) ≦ 1). Here, the transmission power P _j-1 in the SC-FDMA symbol of _j-1 is expressed by the following equation.

Equation 4

Thereafter, the terminal obtains P _j through power scaling in SC-1 and j-1 SC-FDMA symbols i-1 and j SC-FDMA symbols. If power is allotted for transmission of the SRS and P ₃ = 0, the UE processes data in SC-1 FDMA symbols j-1 and j as rate matching.

Referring to FIG. 11, unlike in FIG. 10, an SRS is transmitted in an SC-FDMA symbol i in the first secondary serving cell and SC-1 in the second secondary serving cell overlapping with an SC-FDMA symbol i simultaneously. In the -FDMA symbol, data without a DMRS (PUCCH or PUSCH) and data including a DMRS are transmitted, respectively.

The UE performs power scaling in consideration of the PUSCH required power of the SC-FDMA symbol i-1 of the first secondary serving cell and the PUSCH required power of the SC-FDMA symbol j-1 of the second secondary serving cell The transmission power w (i) P ₃ of the SC-FDMA symbol of j-1 is obtained (0 ≦ w (i) ≦ 1). The UE obtains the scaled SRS transmission power P ′ _SRS in consideration of simultaneous transmission of the SRS in the first secondary serving cell and the DMRS in the second secondary serving cell. This is the same as Equation 5.

Equation 5

Here, P _SRS means the SRS transmission power set before scaling. The transmit power P _j-1 in the SC-FDMA symbol of _j-1 is represented by the following equation.

Equation 6

Subsequently, the UE obtains P _j through power scaling in the same manner as the power scaling method in the SC-FDMA symbols i-1 and j-1 in SC-FDMA symbols _i and _j , respectively. If power is allotted for transmission of the SRS and P ₃ = 0, the UE processes data in SC-1 FDMA symbols j-1 and j as rate matching.

2. Power scaling when priorities are defined in subframe dimensions

If the priority is defined in the subframe dimension, it is equivalent to the concept that the transmission power is allocated in subframe units. Since data is transmitted in units of one subframe, transmission power is also allocated in units of subframes. Therefore, power scaling should be defined even if the priority is defined in the subframe dimension. When the SRS and the uplink channel PUCCH or PUSCH are simultaneously transmitted on different serving cells, power is allocated according to the priority by dividing the SRS and the PUSCH or the SRS and the PUCCH.

For example, the transmission of the PUSCH may determine whether the base station receives data transmitted by the terminal through reception of a physical HARQ indicator channel (PHICH), and the terminal may retransmit if the base station does not receive the data. However, in the case of PUCCH, since the terminal transmits ACK / NACK of data received from the base station or transmits channel information between the base station and the terminal, more reliable transmission is required. Therefore, the transmission priority of the SRS may be determined by assigning a higher priority to the PUSCH and then lowering the PUCCH. Accordingly, the power allocation priority between SRS, PUCCH, and PUSCH may be PUSCH <SRS <PUCCH.

As an embodiment, when SRS and PUSCH or SRS and PUCCH are simultaneously transmitted on different serving cells, the power allocated to the SRS and PUSCH or PUCCH according to the priority when the different serving cells are maintained in symbol synchronization is It is defined by the following equation.

Equation 7

Equation 8

Referring to Equations 7 and 8, there is no change in power during one subframe, which is a transmission unit of the channel, in a method according to the priority between the SRS and the channel (PUSCH or PUCCH). That is, when the power required for SRS transmission is allocated in consideration of the priority between the PUCCH and the SRS (Equation 7), and the transmission power of the PUSCH is scaled and allocated according to the remaining power (Equation 8), one sub-sub is maintained. Constant power is maintained during the frame.

In another embodiment, when SRS and PUSCH or SRS and PUCCH are simultaneously transmitted on different serving cells, when different serving cells are not kept in symbol synchronization as shown in FIG. The power allocated to the PUSCH or PUCCH is defined by the following equation.

Equation 9

Referring to Equation 9, P _{subframe n} represents the transmission power of _{subframe n} of the second secondary serving cell. Referring to FIGS. 10 and 11 to explain Equation 9, since the PUSCH has a lower priority than the SRS, the UE corresponds to the required power of the subframe n of the first secondary serving cell and the subframe n of the second secondary serving cell. Obtain w ₁ (i) P _{1 according} to the calculation. In this case, w ₁ (i) is a scaling factor that is equally applied to two subframes. Then, w ₂ (i) P ₂ is calculated according to the required power of subframe n + 1 of the first secondary serving cell and subframe n of the second secondary serving cell.

As another embodiment, when SRS and PUSCH or SRS and PUCCH are simultaneously transmitted on different serving cells, the SRS according to the priority when the different serving cells do not maintain symbol synchronization as shown in FIG. 10 or 11 And power allocated to PUSCH or PUCCH is defined by the following equation.

3. Power Scaling Based on Reduction Sharing

Power scaling based on reduced sharing includes an operation of scaling the transmission power of all uplink channels and the transmission power of SRS by a predetermined ratio. That is, it means that all uplink channels and SRS are shared to participate in power reduction.

In one embodiment, the terminal prioritizes power allocation to the PUCCH, and the remaining power is allocated to the SRS and the PUSCH at a constant rate by power scaling. This is to give priority to the PUCCH because it requires transmission of higher reliability than SRS and PUSCH. This is expressed as the following equation.

Equation 10

In another embodiment, when SRS and PUSCH or SRS and PUCCH are simultaneously transmitted on different serving cells, the SRS is based on a reduced sharing when the different serving cells do not maintain symbol synchronization as shown in FIG. 10 or 11. And power allocated to PUSCH or PUCCH is defined by the following equation.

Equation 11

Referring to Equation 11, the transmission power is allocated in _subframe units, and P _{subframe n} represents the transmission power of _{subframe n} of the second secondary serving cell. Referring to FIGS. 10 and 11 to explain Equation 11, the UE determines w ₁ (i) P ₁ according to the required power of subframe n of the first secondary serving cell and subframe n of the second secondary serving cell. Obtain In this case, w ₁ (i) is a scaling factor that is equally applied to two subframes. Then, w ₂ (i) P ₂ is calculated according to the required power of subframe n + 1 of the first secondary serving cell and subframe n of the second secondary serving cell. In addition, the terminal obtains w _SRS (i) P _SRS according to the required power of the SRS and subframe n of the second secondary serving cell.

12 is a flowchart illustrating an uplink power control operation by a terminal according to another embodiment of the present invention. This is power scaling based on priority.

Referring to FIG. 12, the terminal recognizes a difference in uplink transmission and timing (S1200). Here, the terminal may be configured with a plurality of serving cells located in different bands, and the plurality of serving cells may be configured by carrier aggregation. The uplink transmission includes a PUSCH or PUCCH transmission that does not include DMRS (called data transmission), a PUSCH or PUCCH transmission that includes DMRS, and an SRS transmission.

The terminal determines whether simultaneous transmission of the SRS and another uplink channel occurs (S1205). If the SRS and the other uplink transmission occurs at the same time, the terminal determines whether the other uplink transmission is DMRS (S1210). If the other uplink transmission is DMRS, the terminal preferentially allocates power to DMRS (S1215), for example, allocates power to SRS as shown in Equation 2 (S1220), for example, As described above, power is allocated to the PUSCH or the PUCCH not including the DMRS (S1225).

In step S1210, if the other uplink transmission is not DMRS, this indicates that the other uplink transmission is data transmission, and thus, the UE preferentially allocates power to the SRS as shown in Equation 2 (S1220), For example, as shown in Equation 3, power is allocated to the PUSCH or the PUCCH not including the DMRS (S1225).

In step S1205, if simultaneous transmission of the SRS and another uplink channel does not occur, the terminal determines whether data transmission exists (S1230). If data transmission exists, the terminal allocates power to data (S1225). ). If there is no data transmission, the terminal terminates the procedure.

Referring to FIG. 13, the terminal 1400 includes a receiver 1305, a terminal processor 1310, and a transmitter 1320. The terminal processor includes a power controller 1311 and a signal generator 1312.

The receiver 1305 receives a downlink signal received from a base station (not shown). The downlink signal includes RRC configuration information related to transmission of DCI and SRS, which are physical layer signals.

The power control unit 1311 has a maximum transmission power in which the sum of the total uplink transmission power P _SRS , P _UL, and P _DMRS is added.

It is determined whether to exceed the total uplink transmission power of the terminal is the maximum transmission power

When exceeding, the terminal performs power scaling. An example of power scaling is as follows.

As an example, when the SRS, PUSCH, and PUCCH are transmitted on a plurality of serving cells belonging to different bands, the power controller 1311 may perform power scaling of the SRS, PUSCH, or PUCCH based on the priority. As another example, when the SRSs, PUSCHs, and PUCCHs are transmitted on a plurality of serving cells belonging to different bands, the power control unit 1311 may perform power scaling of the SRSs, PUSCHs, or PUCCHs based on a reduction sharing. . When the power control unit 1311 performs power scaling based on the priority defined in the SC-FDMA symbol dimension, the power control unit 1311 may determine the SRS, PUSCH, or PUCCH according to Equation 2 to Equation 6, for example. Perform power scaling.

When the power control unit 1311 performs power scaling based on the priority defined in the subframe dimension, the power control unit 1311 performs power scaling of the SRS, PUSCH, or PUCCH according to, for example, Equations 7 to 9 below. Do this.

When the power control unit 1311 performs power scaling based on the reduction sharing, the power control unit 1311 performs power scaling of the SRS, PUSCH, or PUCCH, for example, according to Equation 10 or Equation 11.

The signal generator 1312 generates an SRS sequence, multiplies the generated sequence of _SRSs by a magnitude scaling factor β _SRS to match the SRS transmission power wP _SRS scaled by the power controller 1311, and β β _SRS is After the sequence of the multiplied SRS is sequentially mapped to the resource elements on the antenna port p from r ^P _SRS (0), an SC-FDMA symbol is generated and sent to the transmitter 1320.

The transmitter 1320 transmits SC-FDMA symbols generated on the plurality of serving cells to the base station with a timing difference between the serving cells.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited thereto. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims

In a power control method by a terminal in a multi-component carrier system,

A second serving belonging to a band different from the first serving cell at a point of time overlapping with a transmission time of a sounding reference signal (SRS), which is a reference signal used to estimate an uplink state on the first serving cell; Determining a priority in power allocation between an uplink channel transmitted on a cell and the sounding reference signal; And

Performing power scaling on the sounding reference signal or the uplink channel based on the determination result of the priority;

The power scaling is,

If the sounding reference signal has a higher priority than the uplink channel, power is first allocated to the sounding reference signal, and a smaller power among the remaining power and the transmission power of the uplink channel is allocated to the uplink channel.

If the sounding reference signal has a lower priority than the uplink channel, allocating power to the uplink channel first and allocating zero power to the sounding reference signal.
The method of claim 1, wherein the determining of the priority comprises:

And when the uplink channel is transmitted with a data demodulation reference signal (DMRS), which is a reference signal used for uplink data demodulation, determining that the uplink channel has a higher priority than the sounding reference signal. Characterized in that, the power control method.
The method of claim 1, wherein the determining of the priority comprises:

If the uplink channel is not transmitted with a data demodulation reference signal (DMRS), which is a reference signal used for uplink data demodulation, it is determined that the uplink channel has a lower priority than the sounding reference signal. Characterized in that the power control method.
The method of claim 2 or 3,

The priority is characterized in that the power is determined in units of Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbols or in units of subframes.
The method of claim 1, wherein performing power scaling comprises:

The transmission power of the sounding existing signal is scaled by a scaling factor so that the transmission power of the sounding reference signal is reduced to the remaining power, or the transmission power of the uplink channel is reduced to the remaining power. And scaling the transmit power of the uplink channel by the scaling factor.
The method of claim 1,

And if the sum of the transmission power of the uplink channel and the transmission power of the sounding reference signal exceeds an uplink maximum transmission power, the power scaling is performed.
The method of claim 1,

The uplink channel includes a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH), the power control method.
A terminal for controlling power in a multi-component carrier system,

An uplink channel transmitted on a second serving cell belonging to a band different from the first serving cell at a time point when the sounding reference signal, which is a reference signal used for estimating an uplink state, on the first serving cell overlaps with the transmission time point. And a power control unit configured to determine a priority in power allocation between the sounding reference signals and perform power scaling on the sounding reference signal or the uplink channel based on the determination result of the priority.

The power scaling performed by the power control unit,

If the sounding reference signal has a higher priority than the uplink channel, power is first allocated to the sounding reference signal, and a smaller power among the remaining power and the transmission power of the uplink channel is allocated to the uplink channel.

If the sounding reference signal has a lower priority than the uplink channel, power is allocated to the uplink channel first, and 0 power to the sounding reference signal, characterized in that the terminal.
The method of claim 8, wherein the determining of the priority by the power control unit comprises:

And when the uplink channel is transmitted with a data demodulation reference signal (DMRS), which is a reference signal used for uplink data demodulation, determining that the uplink channel has a higher priority than the sounding reference signal. Characterized in that, the terminal.
The method of claim 8, wherein the determining of the priority by the power control unit comprises:

If the uplink channel is not transmitted with a data demodulation reference signal (DMRS), which is a reference signal used for uplink data demodulation, it is determined that the uplink channel has a lower priority than the sounding reference signal. Terminal, characterized in that.
The method of claim 9 or 10, wherein the power control unit,

Characterized in that the priority is determined in units of a single carrier-frequency division multiple access (SC-FDMA) symbol or in units of subframes.
The method of claim 8, wherein the power controller performs the power scaling.

The transmission power of the sounding existing signal is scaled by a scaling factor so that the transmission power of the sounding reference signal is reduced to the remaining power, or the transmission power of the uplink channel is reduced to the remaining power. And scaling the transmit power of the uplink channel by the scaling factor.
The power control unit of claim 8, wherein the power control unit.

And if the sum of the transmission power of the uplink channel and the transmission power of the sounding reference signal exceeds an uplink maximum transmission power, performing power scaling.
The method of claim 8,

The uplink channel is characterized in that it comprises a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH).