WO2013069966A1 - Method for uplink power control of terminal in coordinated multi-point communication system, uplink communication method of transceiving point, transceiving point thereof, and terminal thereof - Google Patents

Abstract

Disclosed are a coordinated multi-point communication system, a communication method thereof, and a device thereof.

Description

Uplink power control method of a terminal and uplink communication method of a transmission / reception point, a transmission / reception point thereof, and the terminal in a cooperative multi-point communication system

The present invention relates to uplink power control in a cooperative multi-point communication system in which two or more transmission / reception points transmit signals in cooperation.

In a wireless communication system, each terminal controls power of a physical channel and a signal such that different uplink physical channels and signals are received at a base station (cell) at an appropriate power.

This uplink power control is a closed loop that directly controls the transmit power of the terminal through an open loop scheme in which the transmit power of the terminal varies according to downlink path loss and an explicit power control command transmitted in downlink. There is a way.

An object of the present invention is to provide an uplink power control method suitable for a heterogeneous network and a method for transmitting information necessary for uplink power control to a terminal.

In one embodiment, a wireless communication system in which a terminal is in cooperative communication with two or more transmission and reception points, receiving reference signals from the transmission and reception points; Measuring reception powers of the received reference signals; Receiving information of reference signal transmission power of the transmission and reception points from at least one of the transmission and reception points; The uplink transmission power in which the uplink transmission power considering the received reference signal transmission power information and the actual path loss obtained from the measured reception powers is required for reception by each of the transmission / reception points. Determining uplink transmit power to be equal to or greater than a maximum value of each of the RS transmit powers; And transmitting a signal with the uplink transmission power through an uplink physical channel.

In another embodiment, in a wireless communication system in which the terminal is a cooperative communication with two or more transmission and reception points, transmitting a reference signal to the terminal; Transmitting transmission power information of the reference signal transmission power information and reference signal of at least one other transmission / reception point to the terminal; And the uplink transmit power considering the received reference signal transmit power information and the actual path loss obtained from the measured receive powers of the reference signal received from the reference signal and at least one other transmission / reception point. Receiving a signal transmitted through an uplink physical channel from the terminal with an uplink transmission power determined to be equal to or greater than a maximum value of each of uplink DM-RS transmission powers required for reception by each of the transmission and reception points. It provides an uplink communication method of a transmission and reception point comprising the step of.

Another embodiment is a wireless communication system in which a terminal is in cooperative communication with two or more transmission and reception points, receiving reference signals from the transmission and reception points, the information of the transmission power of the reference signals of the transmission and reception points one of the transmission and reception points RF unit for receiving from; And the uplink transmit power in consideration of the reference signal transmit power information received by measuring the received powers of the received reference signals and the actual path loss obtained from the measured receive powers. And a processor for determining an uplink transmission power to be equal to or greater than a maximum value of each of uplink DM-RS transmission powers required for reception by each, wherein the RF unit transmits the uplink transmission through an uplink physical channel. Provided is a terminal that transmits a signal with power.

In another embodiment, in a wireless communication system in which a terminal cooperates with two or more transmission / reception points, a reference signal is transmitted to the terminal, and transmission power information of the reference signal and reference signals of at least one other transmission / reception point are transmitted. Transmitting power information to the terminal and receiving the received reference signal transmission power information and the received received powers of the reference signal received from the reference signal and at least one other transmission / reception point through a downlink physical channel The uplink transmission power considering the path loss is an uplink transmission power determined to be equal to or greater than the maximum value of each of the uplink DM-RS transmission powers required for reception by each of the transmission and reception points. An RF unit for receiving a signal transmitted through an uplink physical channel from the terminal; And a processor for controlling uplink transmission from the terminal.

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

2 is a conceptual diagram of a downlink CoMP system according to an embodiment of the present invention.

3 is a conceptual diagram for transmitting a CRS and a physical uplink channel in a COMP system to which the present invention is applied.

4 is a conceptual diagram illustrating CRS and CSI-RS transmission.

5 is a flowchart illustrating a method of controlling uplink power according to an embodiment.

6 is a flowchart illustrating an uplink control method according to another embodiment.

7 is a flowchart of an uplink control method according to another embodiment.

8 is a block diagram illustrating a terminal and a transmission / reception point according to another embodiment.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

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 embodiments of the present invention, 'transmitting a control channel' may be interpreted as meaning that control information is transmitted through a specific channel. Here, the control channel may be, for example, a physical downlink control channel (PDCCH) or a physical uplink control channel (PUCCH).

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

Referring to FIG. 1, the wireless communication system 100 is widely deployed to provide various communication services such as voice and packet data.

The wireless communication system 100 includes at least one transmission / reception point 110. Each transmit / receive point 110 provides a communication service for a specific geographic area or frequency area and may be called a site. A site may be divided into a number of regions 150a, 150b, 150c, which may be called sectors, and these sectors may have different cell IDs.

The user equipment (UE) 120 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 transmission / reception point 110 generally refers to a station communicating with the terminal 120, and may include a component carrier or cell, an evolved-NodeB (eNodeB), a base transceiver system (BTS), an access point, and a femto base station. (Femto eNodeB), home base station (Home eNodeB: HeNodeB), relay (relay), pico base station (Pico eNodeB), remote radio head (hereinafter referred to as "RRH"), any of the hot spot (Hot spot) Can be defined. The transmission / reception point 110 may be defined as a set of antenna ports. The transmission / reception point 110 may transmit information on the set of antenna ports of the transmission / reception point 110 to the terminal through radio resource control (RRC) signaling. Therefore, a plurality of transmission / reception points in one cell may be defined as a set of antenna ports.

Cells 150a, 150b, and 150c should be interpreted in a comprehensive sense to indicate some areas covered by the transmit / receive points 110 and cover all of the various coverage areas such as megacells, macrocells, microcells, picocells, femtocells, and the like. It means. The transmission / reception point 110 may refer to a transmission point for transmitting a signal to provide a communication service, and may receive a signal from the terminal 120 to provide a communication service.

In the present specification, the transmission and reception point 110 and the terminal 120 are two transmission / reception subjects used to implement the technology or technical idea described in this specification, and are used in a comprehensive sense and are not limited by the terms or words specifically referred to. Do not.

Hereinafter, downlink (downlink) means a communication or communication path from the transmission and reception point 110 to the terminal 120, uplink (uplink) indicates a communication or communication path from the terminal 120 to the transmission and reception point 110. it means. In downlink, the transmitter may be part of the transmission / reception point 110 and the receiver may be part of the terminal 120. In uplink, the transmitter may be part of the terminal 120 and the receiver may be part of the transmission / reception point 110.

There is no limitation on the multiple access scheme applied to the wireless communication system 100. 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.

One embodiment of the present invention is asynchronous wireless communication evolving into Long Term Evolution (LTE) and LTE-advanced through GSM, WCDMA, HSPA, and synchronous wireless communication evolving into CDMA, CDMA-2000 and Ultra Mobile Broadband (UMB) Applicable to resource allocation in sectors, etc. The present invention should not be construed as being limited or limited to a specific wireless communication field, but should be construed as including all technical fields to which the spirit of the present invention can be applied.

The wireless communication system 100 to which the embodiments are applied includes a coordinated multi-point transmission / reception system (CoMP system) or a cooperative multi-antenna transmission scheme in which two or more transmission / reception points cooperate to transmit a signal. coordinated multi-antenna transmission system), a cooperative multi-point communication system.

The CoMP system refers to a communication system supporting CoMP or a communication system to which CoMP is applied. CoMP is a technique for adjusting or combining signals transmitted or received by multi transmission / reception (Tx / Rx) points. CoMP can increase data throughput and provide high quality.

In this CoMP system, transmission / reception points may provide a service by allocating the same frequency resource at the same time when attempting cooperative transmission / reception to one user terminal 120. That is, the transmission / reception points selected as the cooperative transmission / reception points at the same time may transmit and receive data with one user terminal 120 using the same frequency resource.

Each transmit / receive point or cells may constitute multiple transmit / receive points. For example, the multiple transmit / receive points may be macro cells that form a homogeneous network. In addition, the multiple transmission / reception points may be RRHs having a macro cell and high transmission power. In addition, the multiple transmission / reception points may be RRHs having low transmission power in the macro cell and the macro cell region.

The CoMP system may selectively apply CoMP. That is, the CoMP system may or may not apply CoMP to a communication operation. In the CoMP system, a mode in which a transmission / reception point and a terminal perform communication using CoMP is referred to as a CoMP mode, and a mode not otherwise referred to as a normal mode or a non-CoMP mode.

The terminal 120 may be a CoMP terminal. The CoMP terminal is a component of the CoMP system and performs communication with a CoMP cooperating set or a CoMP set. Like the CoMP system, the CoMP terminal may operate in the CoMP mode or in the normal mode. The CoMP set may be a set of transmission / reception points that directly or indirectly participate in data transmission in a certain time-frequency resource for the CoMP terminal. In addition, the CoMP terminal may apply a multi-user multi-antenna (MU-MIMO) scheme as well as a single-user multi-antenna (SU-MIMO) scheme. Although the terminal 120 receives data from the transmission and reception points, respectively, since the frequency bands for receiving the association data are the same, the terminal 120 may be regarded as receiving data from one transmission and reception point.

Participating directly in data transmission or reception means that transmission / reception points actually transmit data to or receive data from a CoMP terminal in a corresponding time-frequency resource. Indirect participation in data transmission or reception may mean that the transmit / receive points do not actually transmit or receive data to or from the CoMP terminal at that time-frequency resource, but contribute to making a decision about user scheduling / beamforming. Can be.

The CoMP terminal may simultaneously receive signals from the CoMP set or transmit signals to the CoMP set at the same time. At this time, the CoMP system may minimize the interference effect between the CoMP sets in consideration of the channel environment of each cell constituting the CoMP set.

When operating a CoMP system, various scenarios are possible. The first CoMP scenario is CoMP, which is composed of a homogeneous network among a plurality of cells in one transmission / reception point, and may be referred to as intra-site CoMP. The second CoMP scenario is CoMP, which consists of a homogeneous network for one macro cell and one or more high-power RRHs. The third CoMP scenario and the fourth CoMP scenario are CoMPs that consist of a heterogeneous network for one macro cell and one or more low-power RRHs in the macro cell region. In this case, when the physical cell IDs of the RRHs are not the same as the physical cell IDs of the macro cells, they correspond to the third CoMP scenario and the same cases correspond to the fourth CoMP scenario.

CoMP's category includes Joint Processing (JP) and Coordinated Scheduling / Beamforming (CS / CB). It is also possible to mix CS and CB.

JP stands for Joint Transmission (JT), Dynamic Point Selection (DPS), or Dynamic Point Scheduling / Dynamic. point blanking, DPS / DPB).

JT refers to simultaneous data transmission from multiple transmission / reception points belonging to a CoMP set to one terminal or a plurality of terminals in time-frequency resources. In the case of JT, multiple cells (multiple transmission / reception points) for transmitting data to one terminal may perform transmission using the same time / frequency resource.

In the case of DPS, data transmission may be performed from one transmission / reception point of a CoMP set in time-frequency resources. The transmission and reception points may be changed for each subframe in consideration of interference. The data to be transmitted is simultaneously available at a plurality of transmit and receive points. DPS includes Dynamic Cell Selection (DCS).

In the case of CS, data is transmitted from one transmit / receive point in a CoMP set for time-frequency resources, and uplink or downlink scheduling for a terminal may be determined by coordination between transmit / receive points of the CoMP set. have.

In the case of CB, uplink or downlink scheduling for the UE is determined by cooperation between the transmission and reception points of the CoMP set. By the CB (Coordinated Beamforming) it is possible to avoid the interference occurring between the terminals of the neighbor cell.

The CS / CB may include a semi-static point selection (SSPS) that may select (change) a transmission / reception point semi-statically.

As described above, CoMP may be operated in a manner in which JP and CS / CB are mixed. For example, some transmit / receive points in the CoMP set may transmit data to the target terminal according to JP, and other transmit / receive points in the CoMP set may perform CS / CB.

The transmission and reception points to which the present invention is applied may include a base station (macro base station or micro base station (local base station)), a cell, or an RRH. That is, the base station or the RRH may be a transmission / reception point. Meanwhile, the plurality of base stations may be multiple transmission / reception points, and the plurality of RRHs may be multiple transmission / reception points. Of course, the operation of all base stations or RRH described in the present invention can be equally applied to other types of transmission and reception points.

There is a radio interface protocol between a terminal and a transmission / reception point. Of course, the operation of all base stations or RRH described in the present invention can be equally applied to other types of transmission and reception points.

Layers of a radio interface protocol between a terminal and a transmission / reception point are based on the lower three layers of the Open System Interconnection (OSI) model, which is well known in a 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 physical downlink control channel (PDCCH) is a resource allocation and transmission format of a downlink shared channel (DL-SCH), a resource of an uplink shared channel (UL-SCH). Resource allocation of upper layer control messages, such as allocation information, random access responses transmitted on a physical downlink shared channel (PDSCH), and transmission power control for individual terminals in any terminal group : TPC) can carry a set of commands. A plurality of PDCCHs may be mapped and transmitted in a control region of a subframe, 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.

The transmission / reception point 110 transmits at least one of a control signal and data through a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH). Channels corresponding to the PDCCH and PDSCH may include a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH). The terminal 120 transmits at least one of a control signal and data through the PUCCH and the PUSCH. Hereinafter, a situation in which a signal is transmitted and received through a channel such as a PUCCH, a PUSCH, a PDCCH, and a PDSCH may be described in the form of 'sending and receiving a PUCCH, a PUSCH, a PDCCH, and a PDSCH.'

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 a wireless system using orthogonal frequency division multiple access (OFDMA) in downlink (DL), the symbol may be an orthogonal frequency division multiplexing (OFDM) 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 a Single Carrier-Frequency Division Multiple Access (SCFDMA) symbol, a symbol interval, etc. in addition to the OFDM symbol.

The number of OFDM symbols included in one slot may vary depending on the length of a cyclic prefix (CP). For example, in case of a normal CP, one slot may include 7 OFDM symbols, and in case of an extended CP, one slot may include 6 OFDM symbols.

A resource block (RB) is a resource allocation unit and includes a time-frequency resource corresponding to one slot on the time axis and 180 kHz on the frequency axis. For example, if one slot includes seven symbols on the time axis and 180 kHz on the frequency axis includes 12 subcarriers, one resource block may include 7 * 12 resource elements (REs). Can be.

The resource element represents the smallest time-frequency unit to which a modulation symbol of a data channel or a modulation channel of a control channel is mapped.

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 addition, it is also necessary to measure the channel state (channel state) for the cell to which the terminal belongs or other cells. In general, a reference signal (RS) that is known between a terminal and a transmission / reception point is used for channel estimation or channel state measurement.

The downlink reference signal includes a cell-specific RS (CRS), a Multimedia Broadcast and Multicast Single Frequency Network (MBSFN) reference signal, a UE-specific RS (UE) -specific RS, and a positioning reference signal (PRS) RS and Channel State Information RS (CSI-RS).

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 may be called a demodulation RS (DM-RS) because it is mainly used for data demodulation of a specific terminal or a specific terminal group. have.

The MBSFN reference signal is a reference signal for providing a multimedia broadcast multicast service (MBMS), and the PRS may be used as a reference signal for position measurement of the terminal.

CSI-RS may be used for estimation of channel information. The CSI-RS is placed in the frequency domain or time domain. Channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), etc. may be used as channel information when necessary through channel state estimation using CSI-RS. It may be reported from the terminal. The CSI-RS may be transmitted on one or more antenna ports.

The uplink data channel (hereinafter referred to as "PUSCH") is transmitted in a region excluding the PUCCH and SRS regions of the system band. PUCCH includes ACK (Acknowledge) / NACK (Negative ACK) for HARQ (Hybrid Automatic Repeat reQuest) operation, RI (Rank Indicator), channel status information for downlink data scheduling, Precoding Matrix Indicator (PMI), and Channel Quality (CQI). Indication) information, and the like, and the SRS is a signal for acquiring uplink channel information for each user and adjusting uplink transmission timing for the entire system.

The feedback method of the channel state information includes a method of periodically transmitting using a PUCCH and a method of periodically transmitting using a PUSCH allocated for feedback according to a request of a transmission / reception point.

2 is a conceptual diagram of a downlink CoMP system according to an embodiment of the present invention.

Referring to FIG. 2, in the cooperative multi-point communication system according to an exemplary embodiment, transmission / reception points 210, 212, 214, and 216 and a terminal 220 may perform cooperative communication. For example, the serving cell (or transmit / receive point) for the terminal 220 may be a first transmit / receive point 210 which is a macro cell, a second transmit / receive point 212 that is RRH1, a third transmit / receive point 214 that is RRH2, and an RRH3, respectively. It may be a fourth transmission / reception point 216.

In this case, only four transmission / reception points 210, 212, 214, and 216 are exemplarily described as transmission / reception points participating in the cooperative communication, but two, three, five, or more transmission / reception points are cooperative with the terminal 220. You can also participate in the communication.

Each of the transmission / reception points illustrated in FIGS. 1 and 2, for example, the transmission / reception point 210 may include an antenna array including two or more antennas. Although the transmission / reception point 210 is described as an example, other macro or micro base stations described with reference to FIGS. 1 and 2 may be the same. Likewise, the terminal 220 illustrated in FIGS. 1 and 2 may also include an antenna array including two or more antennas.

In this case, the antenna arrays of the transmission and reception point 210 and the terminal 220 are dual polarized antenna arrays in which two antennas having different polarizations are alternately installed in order to arrange more antennas in a limited space in a communication system. ) Can be used. In the above embodiment, a dual polarization antenna array has been described as an example, but the present invention is not limited thereto. For example, it may be a multi-polarized antenna array, such as a triple polarized wave or quadrupole antenna array. In addition, the transmitting and receiving point and the terminal is not limited to including a multi-polarized antenna array, such as a single polarized antenna, and may include two or more multi-polarized antenna arrays and a linear array antenna, a combination thereof. . In this case, the transmission / reception point 210 and the terminal 220 may both use two or more multiple polarized antenna arrays for communication or may selectively use some of them.

The transmit / receive points 210, 212, 214, and 216 precode data symbols using their precoding matrix, and transmit 2n precoded data symbols (n is 1 or a natural number greater than 1) through the antenna array. Can propagate into the air.

Meanwhile, the transmit / receive points 210, 212, 214, and 216 may use a dual structure precoding (precoder) matrix of W = W ₁ * W ₂ , or a single structure precoding (precoder) matrix.

In this case, W ₁ is a block diagonal matrix of [X _n 0; 0X _n ]. W ₂ is a matrix that performs beam selection and performs co-phasing to correct for phase mismatch between antenna groups.

In this case, the transmission / reception points 210, 212, 214, and 216 precode data symbols using their precoding matrix using channel information received from the UE, for example, CQI / PMI / RI. 2n precoded data symbols (n is 1 or a natural number greater than 1) may propagate into the air through the antenna array.

In the wireless communication system described with reference to FIGS. 1 and 2, a plurality of transmit and receive points form independent cells, and perform uplink / downlink transmission using the same band between each cell. In this case, uplink power control may be performed to control inter-cell interference occurring during uplink transmission or intra-cell interference occurring between terminals in cells using the same band.

3 is a conceptual diagram for transmitting a CRS and a physical uplink channel in a COMP system to which the present invention is applied.

Referring to FIG. 3, a first transmission / reception point eNB capable of performing transmission over an entire macro cell region and a plurality of second to fourth transmission / reception points 1 controlled by the eNB and performing low power transmission (1) ˜3 low power RRHs have cell IDs or share the same cell IDs, and the eNB may perform CRS transmission.

Referring to FIG. 3, each transmission / reception point 310, 312, 314, 316 may have an independent cell ID. Or, it may have a common cell ID. Different resources can be used to send CRS. The terminal 320 performs PDCCH reception through the eNB, which is the first transmission / reception point 310, and receives a PDSCH from the second to fourth transmission / reception points 312, 314, and 316, which are RRH1 to RRH3, by a downlink CoMP operation. can do.

The terminal 320 to perform uplink transmission may estimate the path loss by measuring the reception power of the CRS transmitted by the eNB, which is the first transmission / reception point 310, and comparing the measured power and the CRS transmission power. .

The estimated path loss is a long term measurement. Assuming that the path loss is similar to the path loss generated in the uplink transmission, each terminal can determine the uplink transmission power. In this process, considering the difference between downlink path loss and uplink path loss, a value determined by a higher layer,

Is used, the transmission power of the terminal may be determined in consideration of a transmission power control command (TPC command) that is notified through transmission of control information of the eNB or transmission of control information of the RRH.

When each UE transmits a PUCCH in cell (c), the transmit power (P _{PUCCH, C} (i)) of the PUCCH in subframe (i) may be determined by Equation 1 below.

In the above-described part, transmitting a signal in a cell may mean that a signal is received at a transmitting / receiving point covering the cell so that the transmitting / receiving point covering the cell may grasp information included in the corresponding signal. In addition, the reception here does not mean that the signal is received by interference but may mean that the signal is received according to the purpose of the signal transmitted by the terminal as a desired signal.

[Equation 1]

In Equation 1, P _{CMAX, c} (i) is the maximum transmit power of the terminal 320 in the subframe (i) (in) in the cell (c), and the PUCCH transmit power is the maximum of the terminal 320. Limited by transmit power.

P _{0_PUCCH} is a factor for the received power that should be guaranteed in transmitting the PUCCH. P _{0_PUCCH} is a factor for reception power required to obtain a reception signal-to-interference and noise ratio (SINR) required at a transmission / reception point, and is determined by a PUCCH format.

PL _c is an estimate of the downlink path loss calculated by the terminal 320 with respect to the cell c, and PL _c = (Reference Signal Received Power (RSRP)). Determined by the equation.

h (n _CQI , n _HARQ, n _SR ) is n _CQI corresponding to the number of information bits for channel quality information ( _CQI ), n _HARQ and subframe (i), which is the number of HARQ bits transmitted in subframe (i) A power offset by n _SR indicating whether a scheduling request (SR) is configured for the UE. Δ _{F_PUCCH} (F) is an offset determined by the PUCCH format (F). Δ _TxD (F ′) is an offset considering the case where the terminal 10 is configured to transmit PUCCH in two antenna ports.

g (i) is a value for directly adjusting the PUCCH transmit power through an explicit transmit power control command. g (i) is cumulative and increases or decreases by a certain amount. g (i) may be included in the downlink scheduling assignment or may be provided on a special PDCCH which simultaneously provides a transmission power control command to multiple terminals. For example, it may correspond to DCI format 3 / 3A. g (i) may be used to compensate for uplink multipath fading not reflected in downlink path loss, and to compensate for a change in uplink interference not reflected in P _{0_PUCCH} .

In the wireless communication system, when each terminal 320 does not simultaneously transmit a PUSCH for the cell c with the PUCCH, the transmit power of the _PUSCH (P _{PUSCH, c} (i)) in the subframe (i) is Can be determined by Equation 2.

[Equation 2]

In the wireless communication system, when each terminal 320 transmits a PUSCH simultaneously with the PUCCH, the transmission power P _{PUSCH, c} (i) of the PUSCH in the subframe i may be determined by Equation 3 below. .

[Equation 3]

In Equations 2 and 3, P _{CMAX, c} (i) is the maximum transmit power of the terminal 320 in the subframe (i) in the cell (c),

Is the linear value of P _{CMAX, c} (i).

Is a linear value of P _PUCCH (i) defined in equation (1). Referring to Equation 2, when the PUSCH is not transmitted simultaneously with the PUCCH, the PUSCH transmission power is limited by the maximum transmission power of the terminal 320. Referring to Equation 3, when the PUSCH is simultaneously transmitted with the PUCCH, the PUSCH transmission power is limited by a limit value of the transmission power of the PUCCH at the maximum transmission power of the terminal 320.

M _{PUSCH, c} (i) is the bandwidth of the PUSCH resource allocation expressed as the number of valid resource blocks for cell (c) and subframe (i). Allocation of more resource blocks requires higher transmit power.

P _{0_PUSCH, c} (j) is a factor for the received power that should be guaranteed in transmitting the PUSCH. P _{0_PUSCH} is a factor for reception power required to obtain a reception SINR required at a transmission and reception point, and is determined by a PUSCH format and the like. P _{0_PUSCH} is a value determined based on the interference level at the transmission / reception point and the interference may vary depending on the system construction situation, and may vary depending on time since the load in the network changes over time. J = 0 for PUSCH (re) transmission for semi-persistent grant, j = 1 for PUSCH (re) transmission for dynamic scheduled grant, random J = 2 for PUSCH (re) transmission for random access response grant.

α _c (j) represents the extent to which the path loss is compensated. If α _c (j) is 1, path loss is completely compensated, and if α _c (j) is less than 1, path loss is not completely compensated. α _c (j) ∈ {0,0.4,0.5,0.6,0.7,0.8,0.9,1} when j = 0 or 1 and α _c (j) = 1 when j = 2.

PL _c is a downlink path loss estimated value calculated by the terminal 320 with respect to the cell c, and PL _c = (reference signal transmitted power-reference signal received power (RSRP)) It can be determined by the equation.

ΔTF, c (i) is an offset determined by the Modulation and Coding Scheme (MCS) for cell c.

f _c (i) is a value for directly adjusting the PUSCH transmit power through an explicit transmit power control command. f _c (i) is a cumulative value, increasing or decreasing by a specific amount. f _c (i) may be included in an UL scheduling grant.

For example, a second transmission / reception point 312 whose terminal 320 is RRH1 may be located nearby. In this case, when there is a situation in which an uplink channel having a small path loss exists between the second transmission / reception point 312 and the terminal 320, the uplink transmission of the terminal 320 toward the first transmission / reception point eNB is performed by the second transmission / reception. Serious interference can be caused to point 312. For example, the terminal may be located far from the first transmission / reception point eNB compared to the distance to other transmission / reception points. In this case, when the terminal 320 performs high power uplink transmission to the first transmission / reception point eNB, the uplink transmission of the terminal 320 is different RRHs (eg, RRH2 and RRH3). (314, 316) may cause interference.

In the example of FIG. 3, since the terminal 320 receives the CRS through the first transmission / reception point eNB, the path loss is measured based on the first transmission / reception point 310 regardless of whether the uplink CoMP is operated. Uplink transmission based on this measurement may cause severe uplink interference to one or multiple RRHs, eg, second to fourth transmit / receive points 312, 314, 316. That is, power control suitable for uplink CoMP operation cannot be performed.

4 illustrates CRS and CSI-RS transmission. Unlike CRS, in case of CSI-RS, even if multiple transmit / receive points share the same cell ID, CSI-RS can transmit each transmit / receive point separately. Liver path attenuation measurements are possible. In an embodiment of FIG. 4, the UE may control uplink transmission power through path loss estimation using CSI-RS along with path loss estimation using CRS described in FIG. 3.

5 is a flowchart illustrating a method of controlling uplink power according to an embodiment.

Referring to FIGS. 4A and 5, at least a first transmission / reception point 410 controlling a plurality of transmission / reception terminals constituting a CoMP set may perform downlink or uplink CoMP operation with the terminal 420. One transmission / reception point, for example, the second to fourth transmission / reception points 412, 414, and 416 may be searched for (S501).

In this case, the CoMP system according to another embodiment is a cooperative multi-point communication system described with reference to FIG. 4, but is not limited thereto. Of course, the transmission and reception points participating in the cooperative communication may be four, as shown in FIGS. 4 and 5, but the present invention is not limited thereto and may be two, three, five, or more. However, for convenience of description, transmission and reception points participating in the cooperative communication will be described as the first to fourth transmission and reception points 410, 412, 414, and 416 as illustrated in FIGS. 4 and 5.

In operation S501, the first transmission / reception point 410 may designate the second to fourth transmission / reception points 412, 414, and 416 for performing downlink to the terminal 420, and the second to fourth transmission / reception points for performing downlink. 412, 414, and 416 may be changed by the first transmission / reception point 410 according to an environment change of the system.

In operation S501, the first transmission / reception point 410 may designate second to fourth transmission / reception points 412, 414, and 416 that receive uplink data from the terminal 420, and receive the uplink data. The fourth transmission / reception point 412, 414, 416 may be changed by the first transmission / reception point 410 according to an environment change of the system.

Accordingly, the first transmission / reception point 410 searches for all transmission / reception points that may transmit / receive data with the terminal 420 as well as the transmission / reception point for transmitting / receiving data with the current terminal 420, and then at least one transmission / reception point that is optimal. To the terminal. In this case, allocating a transmission / reception point means that the terminal 420 informs the terminal 420 of information necessary to receive a signal from each transmission / reception point. The first transmission / reception point 410 capable of controlling other transmission / reception points may transmit information on a CoMP set (CoMP set) to cooperatively transmit a higher layer message, for example, radio resource control (RRC) signaling and downlink. It may transmit to the terminal 420 through the control channel.

Next, the first transmission / reception point 410 may transmit the terminal specific reference signal transmission power information and the terminal specific reference signal configuration information of the searched second to fourth transmission / reception points 412, 414, and 416 to the terminal 420. (Step S502). The terminal specific reference signal may be, for example, CSI-RS or DM-RS.

If the UE-specific reference signal is a CSI-RS, the first transmission / reception point 410 stores CSI-RS transmission power information and CSI-RS configuration information of the searched second and third transmission / reception points 412 and 414 in step S502. It may be transmitted to the terminal 420.

The CSI-RS transmission power information and the CSI-RS configuration information may be stored in a table in the terminal 420 or preset in the system so that the terminal 420 may know in advance.

In a wireless communication system, the CSI-RS is transmitted on one, two, four or eight antenna ports using patterns p = 15, p = 15,16, p = 15-18, p = 15-22, respectively. In step S502, the first transmission / reception point 410 transmits information on CSI-RS transmission power for eight antenna ports of the first transmission / reception point 410, and the second to fourth transmission / reception points 412, 414, 416 Information about the CSI-RS transmit power for four or less antenna ports may be transmitted.

In addition, the first transmission / reception point 410 may transmit information on the number of antenna ports and the CSI-RS pattern of each of the second to fourth transmission / reception points 412, 414, and 416. For the information on the CSI-RS pattern, higher layer signaling, for example, RRC (Radio Resource Control) signaling may be used.

For example, the CRS transmission power and the CSI-RS transmission power transmitted from the first transmission / reception point 410 to the terminal by higher layer signaling, for example, RRC signaling, are 43 dBM and transmitted from the second transmission / reception point 412. CSI-RS transmit power is 23 dBM.

The above-described CSI-RS transmission power information and CSI-RS configuration information may be transmitted in RRC (Radio Resource Control) format as a higher layer. Alternatively, they may be transmitted in the form of system information.

The terminal may perform measurement of the CSI-RS reception power transmitted by each transceiver through the above-described information on the CSI-RS transmission, and compares each of the notified transceiver CSI-RS transmission powers with the reception power. The path attenuation between the CSI-RS transmitting and receiving terminal and the corresponding terminal can be measured.

In another embodiment, path attenuation measurement may be performed using DM-RS, which is one of the terminal specific reference signals. In operation S502, the first transmission / reception point S502 may transmit DM-RS transmission power information and DM-RS configuration information of the first transmission / reception point and the searched second and third transmission / reception points 412 and 414 to the terminal 420. Can be. DM-RS transmission power information and DM-RS configuration information may be stored in a table in the terminal 420. The terminal may perform the reception power measurement and the path attenuation measurement of the transmitting and receiving terminal DM-RS using the table information.

In a situation where each transmit / receive point shares the same cell ID, the terminal 420 may receive one or more transmit power control (TPC) commands through the first transmit / receive point 410 or another transmit / receive end (S510). ).

The TPC command may be included in a response message for the preamble for random access or transmitted through a physical downlink control channel (PDCCH). PDCCH may have various formats according to downlink control information (DCI), and a TPC command transmitted according to the format may be different. For example, the terminal 420 may include PDCCHs of various formats, such as a format for downlink scheduling, a format for uplink scheduling, a TPC-only format for an uplink data channel (PUSCH), and a TPC-only format for an uplink control channel (PUCCH). Can be received. In addition, the TPC command may be used to determine transmit power for each component carrier, transmit power for a component carrier group, or transmit power for an entire component carrier. In addition, the TPC command may be used to determine the transmit power for each signal (eg, PUSCH, PUCCH, etc.). The TPC command includes PDCCHs in various formats such as a format for downlink scheduling, a format for uplink scheduling, a TPC-only format for an uplink data channel (eg, PUSCH), and a TPC-only format for an uplink control channel (eg, PUCCH). Can be received via.

The terminal 420 receives a cell specific reference signal and / or a UE specific RS, for example, at least one reference signal RS among CRS, CSI-RS, and DM-RS. In operation 511, the terminal may receive the received data from the receiver 410.

In addition, the terminal 420 may be configured with an uplink CoMP set (for example, the second to fourth transmission and reception points (412, 414, 416)) terminal specific reference signal (UE specific RS) from the transmission and reception point, for example For example, CSI-RS and / or DM-RS may be received (S512, S514, and S516).

The terminal 420 may perform a substantial path loss for a specific plurality of transmission / reception points r (0 ≦ r <R) based on one or more reference signals among CRS, CSI-RS, or DM-RS.

Can be calculated (S520).

In step S520, the terminal 420 receives the CRS through the first transmission / reception point 410 (eNB) capable of controlling the second to fourth transmission / reception points (for example, 1 to 3 RRHs) and based on the CRS. The path loss from the first transmission / reception point 410 may be calculated.

In an environment in which at least one transmit / receive point has the same cell ID, other transmit / receive points except for the first transmit / receive point 410 do not transmit CRS, and thus, path loss from other transmit / receive points cannot be measured using the CRS. .

When the terminal 420 knows the transmission power of the CSI-RS or the DM-RS of the second to fourth transmission / reception points 412, 414, and 416 in step S520, the terminal 10 transmits the CSI-RS or DM-RS. The downlink path loss may be calculated from the second to fourth transmit / receive points 412, 414, and 416 capable of driving Uplink CoMP by measuring the received power of.

In more detail, each transmission / reception point 410, 412, 414, 416 including the first transmission / reception point may be distinguished from other transmission / reception points by a CSI-RS or DM-RS configuration, for example, a sequence, ports ( ports, mapping, or subframes, and information about the CSI-RS or DM-RS configuration may be notified to the terminal 420.

Based on the CSI-RS or DM-RS configuration, the terminal 420 may measure path loss for at least one transmission / reception point, and perform uplink transmission power control based on the measurement result.

In other words, in Equation 1 to 3, a path loss calculated for a specific transmit / receive point r based on one or more reference signals among CRS, CSI-RS, or DM-RS,

(Reference Signal Received Power (RSRP)).

In a wireless communication system, the CRS is transmitted in all resource blocks, and each resource block includes 12 subcarriers on the frequency axis and 0.5 ms slot on the time axis. In contrast, the CSI-RSs are transmitted at intervals of 5, 10, 20, 40, or 80 subframes, and each subframe has a size of 1 ms. The DM-RS exists for PDSCH demodulation only when PDSCH transmission is related to a corresponding antenna port, and the DM-RS is transmitted only to a resource block to which a corresponding PDSCH is mapped.

Therefore, CRS has a larger time coverage than CSI-RS and a greater frequency coverage than DM-RS. Therefore, for the transmitting end transmitting the CRS, it is possible to calculate the path loss using the CRS instead of the CSI-RS or the DM-RS.

In the following embodiment, it is assumed in FIG. 4A that the CSI-RS or CRS transmitted by the fourth transmission / reception point 416 corresponding to RRH3 is not received by the terminal 420 due to a path loss.

For example, when the UE 420 performs uplink cooperative transmission to three transmit / receive points 410, 412, and 414 through uplink CoMP, in FIG. 4B, the PUCCH and the PUSCH receive multiple transmit / receive points. You get multiple point reception gain. In this case, when considering multiple point reception gain, the transmission power of the terminal 420 uses less transmission power than the non-CoMP case in which only the first transmission / reception point 410 corresponding to the serving cell receives the uplink transmission. Thus, the terminal 420 performs uplink transmission, and interference of uplink transmission of the terminal 420 on the fourth transmission / reception point 416 may be reduced.

Alternatively, when the path loss between the terminal 420 and the second transmission and reception point 412 and the third transmission and reception point 414 is smaller than the path loss between the terminal 420 and the first transmission and reception point 410, the terminal 420 Uplink transmission can be further lowered such that the uplink transmission is received at the second transmission / reception point 412 and the third transmission / reception point 414 and the reception is not suitable at the first transmission / reception point 410.

When uplink transmission of the terminal 420 is received at the first to third transmission and reception points 410, 412, and 414 to obtain multiple point reception gains, reception reliability of PUSCH and PUCCH is increased. Assuming that the reception reliability of the DM-RS is sufficiently high that there is no influence due to a channel estimation error, the PUSCH / PUCCH reception power after multiple points reception combining is determined by each of the transmission and reception points 410,. 412 and 414) The sum of the respective PUSCH / PUCCH received powers may be given as follows.

[Equation 4]

In this case, if the reception reliability of the DM-RS is sufficiently high, the reception power of the DM-RS may not be considered.

When interpreted as a reduction due to the substantial path loss of the transmission power of the terminal 420, the substantial path loss may be defined as follows.

 [Equation 5]

In equation (5)

(0 or a natural number where 0 ≦ r <R) is a path loss calculated for a specific transmission / reception point r based on one or more reference signals of CRS, CSI-RS, or DM-RS.

Next, the terminal 420 may calculate the actual path loss calculated for a specific plurality of transmission / reception points r (0 ≦ r <R) based on one or more reference signals among CRS, CSI-RS, or DM-RS.

In consideration of the uplink transmission power can be controlled (S521).

The actual path loss calculated by equation (5)

), When controlling the uplink transmission power, it is possible to ensure sufficient reception reliability by using a lower transmission power.

When each UE transmits the PUCCH for the cell (c), the actual path loss calculated by Equation 5 in subframe (i)

), The transmission power P _{PUCCH, C} (i) of the _PUCCH may be determined by Equation 6 below.

[Equation 6]

In a wireless communication system, when each terminal 420 does not transmit a PUSCH for a cell c simultaneously with a PUCCH, a substantial path loss calculated by Equation 5 in subframe (i)

Transmission power of the PUSCH

) May be determined by Equation 7 below.

[Equation 7]

In the wireless communication system, when each terminal 420 simultaneously transmits the PUSCH for the cell c with the PUCCH, the substantial path loss calculated by the equation (5) in the subframe (i)

Transmission power of the PUSCH

) May be determined by Equation 8 below.

[Equation 8]

This substantial path loss (

) May represent a path loss when the terminal 420 assumes a maximum of multiple points reception gain.

Next, when the transmission power for the uplink physical channel is controlled, the terminal 420 generates an uplink physical channel having the corresponding transmission power, and then the terminal 420 generates each transmission / reception point 410 through the generated uplink physical channel. 412, 414, (S530, S532, S534).

Although not limited thereto, the control of the transmission power for the uplink physical channel may be performed in the frequency domain before the inverse fast Fourier transform (IFFT). In this case, the control of the transmission power may be performed in units of subcarriers, for example, may be performed by multiplying a weight by a modulation value mapped to a subcarrier. The weights can be multiplied using a diagonal matrix (power diagonal matrix) where each element represents a value related to transmit power. In the case of a multiple input multiple output (MIMO) system, the transmit power may be controlled by using a weighted precoding matrix, or by multiplying a pre-coded modulation value by a power diagonal matrix. Therefore, even when a plurality of physical channels are included in the frequency band to which the same IFFT is applied, the transmission power of each physical channel can be easily controlled.

In addition to / in addition to power control in the frequency domain, control of the transmit power for the uplink physical channel may be performed in the time domain after the IFFT. In particular, transmission power control in the time domain may be achieved in various functional blocks. As an example, the transmit power control may be performed in the DAC block and / or the RF block.

In the present specification, the simultaneous or the same time period may include the same transmission time interval (TTI) or subframe, but is not limited thereto.

The uplink power control method in the CoMP system according to an embodiment has been described above with reference to FIG. 5, and the uplink power control method in the CoMP system according to another embodiment will now be described with reference to FIG. 6. In this case, since other steps in the uplink power control method in the CoMP system according to another embodiment described with reference to FIG. 6 are the same as those described with reference to FIG. 5, only the uplink power control step will be described in detail.

6 is a flowchart illustrating an uplink control method according to another embodiment.

Referring to FIG. 6, as described with reference to FIG. 5, for a specific transmission / reception point r (0 ≦ r <R) based on one or more reference signals among CRS, CSI-RS, or DM-RS in step S520. Substantial path loss (

Calculate For example, if it is interpreted as a reduction due to the substantial path loss of the transmission power of the terminal 420, the substantial path loss may be defined as in Equation 5.

Next, in step S521, the terminal 420 may calculate the actual path loss calculated by considering the cooperative reception gain of a plurality of specific transmission / reception points based on one or more reference signals among CRS, CSI-RS, or DM-RS.

) To control the uplink transmission power of the PUSCH.

In step S610, the terminal 420 is the actual path loss calculated by the equation (5)

In the case where the UE transmits the PUCCH to a plurality of transmission / reception points in the cell (c), the transmission power (P _{PUCCH, C} (i)) and the PUSCH of the PUCCH are not simultaneously transmitted in the subframe (i). Transmit power of the PUSCH (

), When the PUSCH is transmitted simultaneously with the PUCCH, the transmit power of the PUSCH (

) May be determined by Equations 6 to 8, respectively.

Next, since all transmission and reception points should be able to estimate the channel by receiving the DM-RS, the transmission power of the uplink DM-RS of the UE 420 (

Determine (S620).

In order to guarantee the 'maximum multiple reception point combined gain', the transmission power should be controlled such that the DM-RS received at each reception point has sufficient reliability or reception power to perform channel estimation.

If the PUSCH transmit power and DM RS transmit power are the same, the received power of the PUSCH for each transmit / receive point r such that the DM-RS received at each transmit / receive point has sufficient reliability or receive power to perform channel estimation.

) Is the maximum received power of DM-RS (

Is expressed as

[Equation 9]

In other words, the reception power of the PUSCH of each transmission / reception point must have sufficient reliability or reception power, that is, transmission power required for reception, for uplink DM-RSs received by each transmission / reception point to perform channel estimation. Since all transmit / receive points should be able to estimate the channel by receiving the DM-RS, the transmit power request value of the uplink DM-RS of the user equipment (

) Should be the maximum of the transmit powers of the uplink DM-RS of each transmit / receive point.

[Equation 10]

In equation (10)

Is a factor for the reception power, i.e., the transmission power value required for reception, that should be guaranteed to obtain the reception SINR in transmitting the uplink DM-RS of the terminal 420 for a specific transmission / reception point r.

Denotes the degree to which the path loss is compensated. In other words

Is a scaling parameter for applying the path loss measured through the downlink reference signal to the uplink.

Is a downlink path loss estimate calculated by the terminal 420 for a specific transmit / receive point r.

Is an offset determined for a specific transmit / receive point r. The above offset may be determined by a modulation and coding scheme (MCS) of a transmission PUSCH / PUCCH, or may be determined by high layer signaling.

Next, the terminal 420 determines an uplink transmission power that is larger than a maximum value of transmission powers required for reception of each of the uplink DM-RSs received by each of the transmission and reception points (S630).

In other words, in step S630, the terminal 420 transmits an uplink DM-RS, and the transmission / reception points 410, 412, 414, and 416 receive the uplink DM-RS and use the uplink DM-RS. The terminal 420 determines the uplink transmission power so as to have the reliability of performing the link physical channel estimation.

For example, when the terminal 420 controls the transmission power, if the transmission power of the PUSCH and the uplink DM-RS are the same, the uplink transmission power of the terminal 420 (

) Is a transmit power request value of the uplink DM-RS of the UE 420 as represented by Equation (11).

May be greater than).

[Equation 11]

In general terms, the selection of the transmission / reception points constituting the uplink CoMP may be selected in the order of high reliability of the received signal or in the order of low path loss. That is, if the number of transmit / receive points constituting the uplink CoMP increases, the transmit power required for PUSCH transmission decreases due to the increase of the combined gain, while performing DM-RS transmission for the transmit / receive point having a larger path loss. The transmit power requirement to support estimation can increase.

The transmission power for supporting channel estimation through DM-RS while guaranteeing 'maximum multiple transmit / receive point combined gain' includes transmission power and uplink for supporting PUSCH transmission for each transmit / receive point r (0≤r <R). The maximum value of the transmission power request values of the DM-RS is defined as follows.

[Equation 12]

In Equation 12, f _c (i) is a value for directly adjusting the PUSCH transmit power through an explicit transmit power control command.

In other words, while guaranteeing the 'maximum multiple transmit / receive point combined gain', the transmit power (

Is the transmit power of the PUSCH considering the actual path loss when obtaining the maximum multiple transmit / receive point combined gain.

And a transmit power request value of an uplink DM-RS of a terminal for supporting channel estimation through a DM-RS necessary to obtain the combined gain (

) Is the maximum value.

Next, referring to FIG. 5, when transmission power for an uplink physical channel is controlled in S530, S532, and S534, the terminal 420 generates an uplink physical channel, and then the terminal 420 generates the uplink physical channel. Each transmit and receive point (410, 412, 414) through the corresponding transmission power (

Send the signal to).

The uplink power control method in the CoMP system according to another embodiment has been described with reference to FIGS. 5 and 6, and the PUSCH considering the combining gain and the DM-RS reliability in consideration of the coupling gain will now be described with reference to FIG. 7. The uplink power control method in which the UE controls the uplink transmission power in consideration of the transmission power and flexibly performs transmission / reception point selection in this process will be described.

7 is a flowchart of an uplink control method according to another embodiment.

As described with reference to FIG. 5, in operation S520, substantial path loss for a plurality of specific transmission / reception points based on one or more reference signals among CRS, CSI-RS, or DM-RS (

) Can be calculated.

Next, in step S521, the terminal 420 may calculate a substantial path loss calculated for a plurality of specific transmission / reception points based on one or more reference signals among CRS, CSI-RS, or DM-RS.

), The uplink transmission power may be controlled.

Referring to FIG. 7, in detail, the method for controlling uplink power according to another embodiment requires that all transmission / reception points 410, 412, and 414 receive the DM-RS to estimate the channel, thereby uplink DM of the terminal 420. RS transmit power (

And uplink transmit power greater than the maximum of the required transmit powers of each of the uplink DM-RSs to be received by each of the transmit and receive points 410, 412, 414.

It may include a step (S720) to determine. Operation S720 is the same as operation S610 and operation S620 described with reference to FIG. 6.

In other words, for the CoMP set indicated by the first transmit / receive point 410 that is responsible for any or serving cell.

And

Can be calculated.

Next, in consideration of the actual path loss, the uplink transmission power for transmitting a signal through the uplink physical channel (

) And the maximum value of the required transmit powers of each of the uplink DM-RSs to be received by each of the transmit and receive points (

) Can be compared (S730).

In consideration of the actual path loss, the uplink transmission power for transmitting a signal through the uplink physical channel (

) Is the maximum value of the received powers of each of the uplink DM-RSs to be received by each of

Greater than) means that the uplink transmit power is sufficient to support accurate channel estimation. In this case, R = R + 1, that is, an additional transmission / reception point that is a target of uplink transmission may be added or increased to the CoMP set (S735). After that, at S720

And

Can be recalculated.

Since the transmission and reception points with a larger path loss than the existing transmission and reception points were added,

The value increases while the combined gain of additional transmit / receive points

The value can be decreased. Compare these two values

If the value is larger, these additional transmit / receive points may be included in the CoMP set.

Next, it may be determined whether the number R of transmission / reception points added to the CoMP set is less than or equal to the total number M of transmission / reception points receiving the downlink reference signals (S737).

On the other hand, if the number (R) of the transmission and reception points added to the CoMP set in step S737 is less than or equal to the total number (M) of the transmission and reception points receiving the downlink reference signals, steps S720 and S730 may be repeated. On the other hand, if the number R of transmit / receive points added to the CoMP set in step S737 is greater than the total number of transmit / receive points M receiving the downlink reference signals (M), steps S740 and S730 will not be repeated. Can be performed. If the number R of transmit / receive points added to the CoMP set is larger than the total number M of transmit / receive points receiving downlink reference signals, this may mean that there are no more transmit / receive points. No more transmit / receive points that can be added, all transmit / receive points recognized by the terminal 420 is defined as a CoMP set or all transmit / receive points within a category allowed by the first transmit / receive point 410 corresponding to the serving cell. It may mean that it is included in the CoMP set.

In step S730

Value is

If the number (R) of transmission / reception points added to the CoMP set is greater than or greater than the total number (M) of transmission / reception points receiving the downlink reference signals (S737), the terminal 420 may add a transmission / reception point before adding another transmission / reception point. R-1) transmission / reception points may be selected as a CoMP set (S740). In step S740, the terminal 420 measures the path loss, and when the uplink CoMP transmission, can set the CoMP set to the minimum transmission power.

In step S740, the terminal 420 may transmit the set CoMP set information to the first transmission / reception point 410 corresponding to the serving cell periodically or aperiodically. For example, the terminal 420 may periodically transmit CoMP set information that is periodically set to the serving transmission / reception point 410. For another example, the terminal 420 transmits aperiodic CoMP set information to the first transmission / reception point 410 aperiodically only when it is triggered to feed back the CoMP set information set from the first transmission / reception point 410. Can be.

Next, the terminal 420 transmits uplink transmission power (R-1) defined in Equation 11 to (R-1) transmission / reception points.

) May be determined (S750). In other words, calculated for the R transmission and reception points in step S750

this

If not greater than (R-1) calculated for the transmit and receive points

The uplink transmission power can be determined.

However, according to Equation 12 (

A value of + fc (i)) is calculated for (R-1) transmit / receive points

Is greater than (

The value of + fc (i) may be determined as the final uplink transmission power of the terminal 420.

Next, referring to FIG. 5, when transmission power for an uplink physical channel is determined in S530, S532, and S534, the terminal 420 generates an uplink physical channel and then generates a corresponding transmission power through an uplink physical channel generated.

Uplink transmission may be performed.

8 is a block diagram illustrating a terminal and a transmission / reception point according to another embodiment.

Referring to FIG. 8, the terminal 800 may include a terminal RF unit 805 and a terminal processor 810.

The terminal RF unit 805 receives a reference signal from two or more transmission / reception points and receives information on the transmission power of the reference signals of the transmission / reception points from one of the transmission / reception points 850 and through the uplink physical channel. As described with reference to FIG. 7, a signal may be transmitted using uplink transmission power. In addition, the terminal RF unit 805 may transmit CoMP set information in which at least one transmission / reception point is configured as a CoMP set.

As described with reference to FIGS. 4 to 7, the terminal processor 810 determines an uplink transmission power for transmitting a signal through an uplink physical channel, generates an uplink physical channel, and then uplinks the uplink transmission power with the determined uplink transmission power. It may be controlled to transmit a signal through a physical channel.

In more detail, as described above with reference to FIGS. 4 through 7, the terminal processor 810 determines a UL transmission power for transmitting a signal through an UL physical channel and at least a power controller 812 for controlling the UL transmission power. It may include all or part of the CoMP set determination unit 814 for generating CoMP set information consisting of a CoMP set of one transmission point.

In detail, the power controller 812 considers information on the transmission power of the received reference signals and the actual path loss obtained from the measured reception powers of the reference signals received through the downlink physical channel from the transmission and reception points. The uplink transmission power for transmitting a signal through the uplink physical channel can be determined based on Equations 6 to 8.

Meanwhile, the power control unit 812 may determine the uplink transmission power so that the uplink DM-RS received by the transmission / reception points has reliability to perform uplink physical channel estimation. For example, the power control unit 812 may use the uplink transmit power equal to or greater than the maximum value of each of the uplink DM-RSs received by each of the transmit and receive points based on Equations 10 and 11, respectively. Can be determined.

In addition, the power control unit 812 considers uplink transmission power for transmitting a signal through an uplink physical channel in consideration of a substantial path loss.

) And the maximum transmit power required of uplink DM-RSs to be received by each of the transmit and receive points (

),

this

If greater, add another transmit / receive point to the CoMP set

Is calculated,

this

Is not larger than before adding another send / receive point

or (

The uplink transmission power may be determined as the maximum value of the + fc (i)) value (f _c (i) is a value for directly controlling the PUSCH transmission power through an explicit transmission power control command).

CoMP set determination unit 814 is described with reference to FIG.

Remind me

If it is not larger, CoMP set information including a CoMP set may be generated as at least one transmit / receive point before adding another transmit / receive point.

The transmission / reception point 850 may include a transmission / reception point RF unit 855 and a transmission / reception point processor 860.

The transmission / reception point RF unit 855 transmits a reference signal to the terminal 800, transmits transmission power information of its reference signal and transmission power information of the reference signal of at least one other transmission / reception point to the terminal, and transmits uplink. The power signal may be transmitted through the uplink physical channel.

The transmit / receive point processor 860 from the terminal 800

this

If not greater than CoMP set determination unit 862 for determining CoMP set information consisting of a CoMP set of at least one transmit and receive point before adding another transmit and receive points, and a reference signal generator 864 for generating a reference signal, control information B may include some or all of the information generating unit 866 for generating system information.

The terminal 800 and the transmission / reception point 860 described with reference to FIG. 8 have been described as including a CoMP set determination unit 814 and a CoMP set determination unit 862, respectively. As described with reference to FIG. 7, when the UE 420 performs CoMP set determination, the UE 800 includes a CoMP set determination unit 814, but otherwise, at least one of the UE 800 and the transmission / reception point 860. One may include a CoMP set determination unit.

In the case of uplink CoMP performing uplink transmission to a plurality of transmission / reception points, an interference problem may cause more serious performance degradation. In particular, when uplink transmission is performed in a heterogeneous network in which a physical boundary between cells is ambiguous, more serious interference may occur regardless of whether CoMP is driven or not.

In order to solve this interference problem, the above-described embodiments provide a method and apparatus for recognizing transmission and reception points adjacent to the terminal and determining power required for performing uplink transmission to the transmission and reception points and determining an appropriate transmission power. Can provide. Multiple point reception gains obtained by measuring a substantial path loss for a plurality of transmission and reception points and performing uplink transmission to the plurality of transmission and reception points by the power control method and apparatus according to the above-described embodiment gain) can be inferred and used for power control.

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 by these embodiments. 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.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority under No. 10 (2011) 119 (a) (35 USC § 119 (a)) of the Patent Application No. 10-2011-0115447, filed with Korea on November 7, 2011. All content is incorporated by reference in this patent application. In addition, if this patent application claims priority for the same reason for countries other than the United States, all its contents are incorporated into this patent application by reference.

Claims (12)

1. Receiving reference signals from the transmission and reception points in a wireless communication system in which the terminal is a cooperative communication with two or more transmission and reception points;

   Measuring reception powers of the received reference signals;

   Receiving information of reference signal transmission power of the transmission and reception points from at least one of the transmission and reception points;

   The uplink transmission power in which the uplink transmission power considering the received reference signal transmission power information and the actual path loss obtained from the measured reception powers is required for reception by each of the transmission / reception points. Determining uplink transmit power to be equal to or greater than a maximum value of each of the RS transmit powers; And

   Uplink power control method of a terminal comprising transmitting a signal with the uplink transmission power through an uplink physical channel.
2. The method of claim 1,

   One of the two or more transmission / reception points is an eNodeB, at least another is an RRH, and a reference signal from the eNodeB is at least one of a cell specific reference signal, a terminal specific reference signal, and a channel state information reference signal, and a reference signal from the RRH. Is at least one or more of a terminal specific reference signal and a channel state information reference signal.
3. The method of claim 1,

   The uplink physical channel is a method for controlling uplink power of a terminal, characterized in that the PUCCH and / or PUSCH.
4. The method of claim 1,

   Uplink transmission power determined in consideration of the actual path loss (hereinafter, referred to as "

   

   And maximum values of transmit powers of the uplink DM-RS required for reception by each of the transmission / reception points (hereinafter, “”).

   

   Comparing “); and

   remind

   

   this

   

   If greater, add additional transmit / receive points to the CoMP set

   

   , And

   Calculated Remind

   

   this

   

   If there are no send / receive points that are greater than or can be added anymore, before adding the additional send / receive points to the CoMP set

   

   or (

   

   and determining the uplink transmission power to a maximum value of + fc (i)), wherein f _c (i) is a value for directly controlling a PUSCH transmission power through an explicit transmission power control command. UL power control method.
5. The method of claim 4, wherein

   remind

   

   Remind me

   

   If there is no transmit / receive point that can be added to a larger or no more, configure a CoMP set with at least one transmit / receive point before adding the additional transmit / receive point to the CoMP set, and transmit the CoMP set information to one of the transmit / receive points. Uplink power control method of a terminal further comprising the step.
6. In a wireless communication system in which two or more transmission and reception points and the terminal cooperative communication,

   Transmitting a reference signal to the terminal;

   Transmitting transmission power information of the reference signal transmission power information and reference signal of at least one other transmission / reception point to the terminal; And

   The uplink transmission power considering the received reference signal transmission power information and the actual path loss obtained from the measured reception powers of the reference signal received from the reference signal and at least one other transmission / reception point, Receiving a signal transmitted through an uplink physical channel from the terminal with the uplink transmission power determined to be equal to or greater than the maximum value of each of the uplink DM-RS transmission powers required for reception by each of the transmission and reception points. Uplink communication method of a transmission and reception point comprising the step.
7. The method of claim 6,

   The reference signal is uplink communication method of the transmission and reception point, characterized in that at least one of the CRS or CSI-RS.
8. The method of claim 6,

   The determined uplink transmission power is determined by the terminal in consideration of the actual path loss (Path Loss).

   

   And the maximum value of uplink DM-RS transmit powers required to be received by each of the transmit / receive points (hereinafter,

   

   "),

   remind

   

   this

   

   If greater, add additional transmit / receive points to the CoMP set

   

   , And

   Calculated Remind

   

   this

   

   If there are no transmit / receive points that are greater than or can be added anymore, before adding the additional transmit / receive points to the CoMP set.

   

   or (

   

   + f _c (i)) is determined as the maximum value, and f _c (i) is a value for directly adjusting the PUSCH transmission power through an explicit transmission power control command. .
9. The method of claim 8,

   From the terminal to the

   

   Remind me

   

   If there is no transmit / receive point that can be added larger or no longer, uplink communication method of a transmit / receive point further comprising receiving CoMP set information including at least one transmit / receive point prior to adding another transmit point. .
10. In a wireless communication system in which two or more transmission and reception points and the terminal cooperative communication,

    An RF unit for receiving reference signals from the transmission / reception points and receiving information on transmission power of reference signals of the transmission / reception points from one of the transmission / reception points; And

    The uplink transmission power considering the received reference signal transmission power information received by measuring the reception powers of the received reference signals and the actual path loss obtained from the measured reception powers, respectively, are respectively transmitted and received points. A processor for determining the uplink transmission power to be equal to or greater than the maximum value of each of the uplink DM-RS transmission powers required for reception by

    The RF unit is characterized in that for transmitting a signal in the uplink transmission power through an uplink physical channel.
11. The method of claim 10,

    The RF unit takes uplink transmission power to transmit a signal through an uplink physical channel in consideration of the substantial path loss.

    

    And maximum values of transmit powers of an uplink DM-RS to be received by each of the transmit / receive points (hereinafter, “”).

    

    "),

    remind

    

    this

    

    If greater, add additional transmit / receive points to the CoMP set

    

    , And

    Calculated Remind

    

    this

    

    If there are no transmit / receive points that are greater than or can be added anymore, before adding the additional transmit / receive points to the CoMP set.

    

    or (

    

    The uplink transmission power is determined as a maximum value of + fc (i)), and f _c (i) is a value for directly controlling a PUSCH transmission power through an explicit transmission power control command. .
12. In a wireless communication system in which two or more transmission and reception points and the terminal cooperative communication,

    Transmits a reference signal to the terminal, transmits transmission power information of the reference signal and transmission power information of a reference signal of at least one other transmission / reception point to the terminal, and receives the received reference signal transmission power information and the reference signal and The uplink transmission power in consideration of the actual path loss obtained from the measured reception powers of the reference signal received through the downlink physical channel from at least one other transmission / reception point is determined by each of the transmission / reception points. An RF unit for receiving a signal transmitted through an uplink physical channel from the terminal with an uplink transmission power determined to be equal to or greater than a maximum value of each of uplink DM-RS transmission powers required for reception; And

    Transmitting and receiving point comprising a processor for controlling uplink transmission from the terminal.

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