KR20130061586A - Reference signal transmission method and apparatus, and uplink transmission method and apparatus thereof - Google Patents

Abstract

PURPOSE: A reference signal transmitting method, a device thereof, an uplink transmitting method, and a device thereof are provided to control uplink transmission power by considering the path reduction of each multi transmission point by using a reference signal transmitted from the multi transmission point in a CoMP(Cooperative Multi Points Transmission and Receptions) system. CONSTITUTION: A terminal receives information about CSI-RS(Channel State Information-Reference Signal) settings from a BS(Base Station)(S810). The terminal receives information about a DL(DownLink) physical channel from each transmission point of a CoMP cooperative group(S820). The terminal estimates UL(UpLink) path reduction based on CSI-RS and calculates a PMI(Precoding Matrix Indicator)(S830). The terminal applies the calculated UL path reduction to control UL transmission power(S840). [Reference numerals] (AA) Start; (BB) End; (S810) Receive CSI-RS setting information; (S820) Receive information on a downlink physical channel; (S830) Calculate a path loss and a PMI; (S840) Adjust uplink transmission power; (S850) Perform uplink transmission

Description

REFERENCE SIGNAL TRANSMISSION METHOD AND APPARATUS, AND UPLINK TRANSMISSION METHOD AND APPARATUS THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication technology, and more particularly to cooperative multi-point (CoMP) operation using closed loop Multi Input Multi Output (MIMO). It is about.

In order to increase performance and communication capacity of a wireless communication system, multi-cell (or transmission / reception point) cooperation has been introduced. Multiple cell (or transmit / receive point) cooperation is also referred to as cooperative multiple point transmission and reception (CoMP).

CoMP includes a beam avoidance technique in which adjacent cells (or transmit / receive points) cooperate to mitigate interference to a user at a cell (or transmit / receive point) boundary, and a joint transmission technique in which adjacent cells cooperate to transmit the same data. There is this.

Next-generation wireless communication systems, such as Institute of Electrical and Electronics Engineers (IEEE) 802.16m or 3rd Generation Partnership Project (3GPP) long term evolution (LTE) -Advanced, are located at cell boundaries and are subject to severe interference from adjacent cells. In order to solve this problem, CoMP can be considered. Various scenarios are possible with this CoMP.

Meanwhile, the base station transmits a reference signal to the terminal to check the downlink channel state. The terminal receives the reference signal, performs a measurement on the channel state based on the transmission state of the reference signal, and feeds back the result of the measurement to the base station. The base station may estimate the state of the downlink channel based on the feedback measurement result. Similarly, in the CoMP environment, the channel state can be estimated by transmitting the reference signal in downlink. In this case, a solution for how to use the resources of the reference signal between each transmission point constituting the CoMP cooperation set is required.

An object of the present invention is to provide a method and apparatus for controlling uplink transmission power in a CoMP system.

An object of the present invention is to provide a method and apparatus for estimating uplink path attenuation using reference signals transmitted from multiple transmission points in a CoMP system.

An object of the present invention is to provide a method and apparatus for setting a reference signal for controlling uplink transmission power based on a reference signal transmitted from multiple transmission points in a CoMP system.

An object of the present invention is to provide a method and apparatus for transmitting configuration information for transmitting a reference signal from multiple transmission points in a CoMP system.

(1) An embodiment of the present invention is a method of transmitting a reference signal in a Cooperative Multi Point (CoMP) system, comprising: transmitting setting information of a reference signal and based on setting information of the reference signal; And transmitting the reference signal, wherein the configuration information of the reference signal may indicate energy per resource element used for transmitting the reference signal for each transmission point participating in the transmission of the reference signal.

(2) In (1), the configuration information of the reference signal is energy per resource element used for transmission of the reference signal and energy per resource element used for transmission of a downlink physical channel signal transmitted together with the reference signal. The ratio of may be indicated for each transmission point participating in the transmission of the reference signal.

(3) In (1), the energy per resource element used for transmitting the reference signal may be indicated for each antenna port group grouping the antenna ports of the transmission point participating in the transmission of the reference signal.

(4) In (3), the antenna port groups belonging to the same transmission point may be indicated with the same energy per resource element.

(5) The method of (3), wherein the configuration information of the reference signal can indicate a sequence used for transmission of the reference signal for each transmission point having a different cell ID.

(6) In (1), the setting information of the reference signal may include bitmap information indicating the number of transmission points participating in the transmission of the reference signal.

(7) In (6), each bit of the bitmap information corresponds to each antenna port participating in the transmission of the reference signal, and each bit may have a specific bit value when the transmission point changes.

(8) In (6), each bit of the bitmap information may correspond to each antenna port participating in the transmission of the reference signal, and the bit value of each bit may be changed in response to the change of the transmission point.

(9) Another embodiment of the present invention is an uplink transmission method in a cooperative multi-point (CoMP) system, comprising: receiving configuration information of a reference signal and receiving a reference on a downlink physical channel Estimating uplink pathloss using signals, determining uplink transmission power by reflecting the uplink path loss, and performing uplink transmission using the uplink transmission power; The configuration information of the reference signal indicates energy per resource element used for transmission of the reference signal for each transmission point participating in the transmission of the reference signal, and in the estimating uplink path attenuation, each transmission point transmits By using the received power of the reference signal and the transmit power of the reference signal indicated for each transmission point in the configuration information of the reference signal, Uplink path attenuation can be estimated for each transmission point.

(10) In (9), in the uplink transmission power determination step, uplink transmission power for each transmission point may be determined based on the uplink path attenuation estimated for each transmission point.

(11) The method of (9), wherein the configuration information of the reference signal is energy per resource element used for transmission of the reference signal and energy per resource element used for transmission of a downlink physical channel signal transmitted together with the reference signal. The ratio of may be indicated for each transmission point participating in the transmission of the reference signal.

(12) In (9), the configuration information of the reference signal may indicate energy per resource element used for transmission of the reference signal for each antenna port group grouping antenna ports of a transmission point participating in the transmission of the reference signal. Can be.

(13) In (12), the configuration information of the reference signal can indicate the same energy per resource element to antenna port groups belonging to the same transmission point.

(14) Another embodiment of the present invention is a reference signal transmission apparatus, comprising: a radio frequency (RF) unit for transmitting and receiving information, a memory for storing information, and a processor for controlling the RF unit and the memory; Configuration information of a reference signal may be configured, and the configuration information of the reference signal may indicate energy per resource element used for transmission of the reference signal for each transmission point participating in the transmission of the reference signal.

(15) Another embodiment of the present invention is an uplink transmission apparatus, comprising: a radio frequency (RF) unit for transmitting and receiving information, a memory for storing information, and a processor for controlling the RF unit and the memory; Estimating uplink path attenuation for each transmission point using the received power of the reference signal for each transmission point received on the physical channel and the transmission power of the reference signal for each transmission point, and for the transmission power of the reference signal for each transmission point It may be indicated through setting information on the signal.

According to the present invention, the UE can effectively control the uplink transmission power in the CoMP system.

According to the present invention, in the CoMP system, the terminal may control the uplink transmission power in consideration of path attenuation for each multiple transmission point using a reference signal transmitted from the multiple transmission point.

According to the present invention, it is possible to configure a reference signal so that control of uplink transmission power can be performed based on a reference signal transmitted from multiple transmission points in a CoMP system.

1 is a block diagram showing a wireless communication system to which the present invention is applied.
2 schematically illustrates an example in which a CSI-RS is mapped to a resource element in the case of a normal CP.
3 schematically illustrates an example in which a CSI-RS is mapped to a resource element in the case of an extended CP.
4 is a diagram schematically illustrating a method of controlling uplink transmission power.
5 schematically illustrates an example of a transmission point bitmap transmitted by a base station in a system to which the present invention is applied.
FIG. 6 schematically illustrates another example of a transmission point bitmap transmitted by a base station in a system to which the present invention is applied.
7 is a flowchart schematically illustrating a downlink transmission operation by a transmission point of a CoMP cooperative set in a system to which the present invention is applied.
8 and 9 are flowcharts schematically illustrating an operation of a terminal in a system to which the present invention belongs.
10 is a block diagram schematically showing the configuration of a base station in a system to which the present invention is applied.
11 is a block diagram schematically illustrating a configuration of a terminal in a system to which the present invention is applied.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

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

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

Referring to FIG. 1, a wireless communication system 10 is widely deployed to provide various communication services such as voice, packet data, and the like. The wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides a communication service for a specific geographic area or frequency area and may be called a site. The site may be divided into a plurality of regions 15a, 15b, and 15c, which may be called sectors, and the sectors may have different cell IDs.

A mobile station (MS) 12 may be fixed or mobile and may be a user equipment (UE), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, (personal digital assistant), a wireless modem, a handheld device, and the like. The base station 11 generally refers to a station communicating with the terminal 12, and includes an evolved-nodeb (eNodeB), a base transceiver system (BTS), an access point, an femto base station, and a domestic base station. (Home eNodeB: HeNodeB), relay (relay), Remote Radio Head (Remote Radio Head (RRH)) may be called in other terms. 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 the downlink, the transmitter may be part of the base station 11, and the receiver may be part of the terminal 12. In the 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. (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA , OFDM-CDMA, and the like. 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 wireless communication system 10 may be a Coordinated Multi Point (CoMP) 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.

The transmission / reception point may be defined as any of a component carrier or a cell, or a base station (macro cell, Pico eNodeB, Femto eNodeB, etc.), or a remote radio head (RRH). Alternatively, the transmission / reception point may be defined as a set of antenna ports. The transceiver may transmit information about the set of antenna ports to the terminal through radio resource control (RRC) signaling. Therefore, a plurality of transmission points (TPs) in one cell may be defined as a set of antenna ports. The intersection between the set of antenna ports is always empty.

Each base station or cells may constitute multiple transmission / reception 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. A mode in which a CoMP system communicates using CoMP is called a CoMP mode, and a mode other than the CoMP system is called a normal mode or a non-CoMP mode.

The terminal 12 may be a CoMP terminal. The CoMP terminal is a component of the CoMP system and performs communication with a CoMP cooperating set. Like the CoMP system, the CoMP terminal may operate in the CoMP mode or in the normal mode. The CoMP cooperative set is a set of transmit / receive points that directly or indirectly participate in data transmission on a time-frequency resource for a CoMP terminal.

Participating directly in data transmission or reception means that the transmitting and receiving points actually transmit data to or receive data from the CoMP terminal in the corresponding time-frequency resource. Indirect participation in data transmission or reception means that the transmit / receive points do not actually transmit or receive data to or from the CoMP terminal in the corresponding time-frequency resource, but contribute to making decisions about user scheduling / beamforming. .

The CoMP terminal may simultaneously receive signals from the CoMP cooperative set or transmit signals simultaneously to the CoMP cooperative set. At this time, the CoMP system minimizes the interference effect between the CoMP cooperation sets in consideration of the channel environment of each cell constituting the CoMP cooperation 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 base station, 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.

In the case of JP, the data for the terminal is available at at least one transmit / receive point of the CoMP cooperative set in some time-frequency resource. JP includes Joint Transmission (JT, hereinafter referred to as 'JT') and Dynamic Point Selection (DPS, hereinafter referred to as 'DPS').

JT means that data is simultaneously transmitted from multiple transmission / reception points belonging to a CoMP cooperative set to one terminal or a plurality of terminals in time-frequency resources. In the case of JT, multiple cells (multi-transmitting / receiving points) transmitting data to one terminal perform transmission using the same time / frequency resource.

In the case of DPS, data transmission is performed from one transmission / reception point of a CoMP cooperative set in time-frequency resources. The transmission and reception point may be changed for each subframe in consideration of interference. The data to be transmitted is simultaneously available at multiple 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 cooperation set for time-frequency resources, and user scheduling is determined by coordination between the transmit and receive points of the CoMP cooperation set.

In the case of CB, it is also determined by cooperation between the transmitting and receiving points of the CoMP cooperation 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 can be changed by selecting a transmission / reception point semi-statically.

As mentioned above, it is also possible to mix JP and CS / CB. For example, some transmit / receive points in the CoMP cooperative set may transmit data to the target terminal according to JP, and other transmit / receive points in the CoMP cooperative set may perform CS / CB.

The transmission and reception point to which the present invention is applied may include a 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.

Meanwhile, a multi-input multi-output (MIMO) system, also called a multi-antenna system, improves transmission and reception data transmission efficiency by using a multi-transmission antenna and a multi-reception antenna.

In the data transmission / reception process performed in the MIMO system, the base station may receive data from N users and output K streams to be transmitted at one time. In a MIMO system, a base station may determine a terminal and a transmission rate to transmit to an available radio resource by using channel information transmitted to or from each terminal. For example, a code rate is extracted by extracting channel information from feedback information. , Modulation and Coding Scheme (MCS) may be selected.

Information fed back from the terminal to the base station for the operation of the MIMO system includes control information such as channel quality indicator (CQI), channel state information (CSI), channel covariance matrix (CCM), precoding weight (PW), and channel rank (CR). May be included.

The CSI may include a channel matrix between transceivers, a channel correlation matrix, a quantized channel matrix or a quantized channel correlation matrix, and a PMI. The CQI may be a signal to noise ratio (SNR), a signal to interference and noise ratio (SINR), a signal to interference ratio, or the like, between the transceivers.

The UE may estimate a channel, select a precoding matrix that maximizes channel performance, and report a precoding matrix indicator (PMI) for the selected precoding matrix. The base station may select a precoding matrix indicated by the fed back PMI from the codebook and use it for data transmission.

The MIMO method that uses precoding weights according to channel conditions is called CL (Closed-Loop) MIMO method. This is called. In the CL MIMO scheme, the transmitting side, for example, the base station corresponds to a channel state by utilizing channel state information (CSI) transmitted from the receiving side, for example, the terminal. CSI may be transmitted including the PMI.

Meanwhile, 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, and compensates for a distortion of a signal caused by a sudden environmental change. The process of restoring the signal is called channel estimation. It is also necessary to measure the channel state of the cell or other cell to which the terminal belongs. In general, a reference signal (RS) known to each other is used by a transceiver for channel estimation or channel state measurement.

Since the receiver knows the information of the reference signal, the receiver can estimate the channel based on the reference signal of the received signal and compensate the channel value to accurately obtain the data sent from the transmitter. If p is the reference signal transmitted from the transmitter, channel information that the reference signal undergoes during transmission, h is thermal noise generated at the receiver, and n is the signal received at the receiver, it can be expressed as y = h · p + n . . Since the reference signal p is already known by the receiver, if the LS (Least Square) scheme is used, the channel information

) Can be estimated.

&Quot; (1) "

Here, the channel estimation value estimated using the reference signal p

The

Value, so for accurate estimation of the h value

It is necessary to converge to zero. By using a large number of reference signals

It is possible to estimate the channel by minimizing the influence of the channel.

Reference signals are generally transmitted in sequence. The reference signal sequence may be any sequence without any particular limitation. The reference signal sequence may use a PSK-based computer generated sequence (PSK) -based computer. Examples of PSKs include Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). Alternatively, the reference signal sequence may use a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence. Examples of the CAZAC sequence include a ZC-based sequence, a ZC sequence with a cyclic extension, a truncation ZC sequence (ZC sequence with truncation), and the like . Alternatively, the reference signal sequence may use a PN (pseudo-random) sequence. Examples of PN sequences include m-sequences, computer generated sequences, Gold sequences, and Kasami sequences. Also, the reference signal sequence may use a cyclically shifted sequence.

The downlink reference signal includes a cell-specific RS (CRS), an MBSFN reference signal, a UE-specific RS, a positioning reference signal (PRS), and channel state information (CSI). And a reference signal (CSI-RS).

In a multi-antenna system, resource elements used for reference signals of one antenna are not used for reference signals of other antennas. To avoid interference between antennas. For example, only one reference signal may be transmitted per antenna.

The CSI-RS of the downlink reference signal may be used for estimation of channel state information. The CSI-RS is located in the frequency domain or the time domain, and channel quality indicator (CQI), precoding matrix indicator (PMI) and A rank indicator (RI) and the like may be reported from the terminal as channel state information.

Table 1 schematically shows an example of defining configuration information (CSI-RS-Config) of the CSI-RS. The configuration information about the CSI-RS is an information element used to specify the CSI-RS configuration and is individually transmitted to each terminal using the CSI-RS.

TABLE 1

Referring to Table 1, the CSI-RS is set through parameters such as antennaPortsCount, subframeConfig, resourceConfig, and p-c.

The CSI-RS may be transmitted on one or more antenna ports. In Table 1, antennaPortsCount represents the number of antenna ports used for transmitting CSI-RS, where an1 is one antenna port, an2 is two antenna ports, an4 is four antenna ports, and an8 is eight antenna ports. Instruct it to use.

p-C indicates the ratio of energy per PDSCH resource element (EPRE) to energy per CSI-RS resource element (EPRE) when the UE induces CSI feedback. p-C has a value in the range of [-8, 15] dB and increases and decreases in 1 dB increments. The p-C-base station is a case where the transceiver point is a base station, which is a p-C for the CSI-RS transmitted by the base station. p-C-RRH is a case where the transmission / reception point is RRH, and is p-C for CSI-RS transmitted by RRH.

subframeConfig indicates the timing at which the CSI-RS is transmitted. For example, subframeConfig may indicate a subframe in which the CSI-RS is transmitted.

In addition, resourceConfig indicates a pattern of the CSI-RS. The CSI-RS may have a certain pattern according to the antenna port.

2 schematically illustrates an example in which a CSI-RS is mapped to a resource element in the case of a normal CP. The CSI-RS mapping shown in FIG. 2 is an example of CSI configuration 0 for a normal CP, where R _p represents a resource element used for CSI-RS transmission at an antenna port P. FIG.

3 schematically illustrates an example in which a CSI-RS is mapped to a resource element in the case of an extended CP. The mapping of CSI-RS shown in FIG. 3 relates to CSI configuration 0 for extended CP. As shown in FIG. 2 and FIG. 3, the CSI-RS may be mapped to resource elements in a predetermined pattern according to the antenna port transmitted.

Table 2 is an example of PDSCH configuration information. Table 2 shows a case in which information included in an RRC message, for example, a system information block (SIB) 2, used to specify a common or terminal specific PDSCH configuration, is an element of PDSCH configuration information.

<Table 2>

In the case of Table 2, the PDSCH configuration information element includes a PDSCH-ConfigCommon field and a PDSCH-ConfigDedicated field. p-a is a terminal specific parameter and p-b is a cell specific parameter. referenceSignalPower indicates a downlink reference signal transmission power and is provided in units of dBm. From this, energy per resource element (EPRE) of the downlink reference signal may be derived. In this case, the downlink reference signal transmission power is defined as a linear average of power contributions of all resource elements carrying the CRS or CSI-RS within an operating system bandwidth. In the case of CoMP mode, it is assumed that the EPREs for all transmission and reception points are the same.

Table 3 is another example of PDSCH configuration information. Table 3 shows a case in which the EPREs for the base station and the RRH are set differently in the case of the CoMP mode.

<Table 3>

Referring to Table 3, an energy per resource element (EPRE) value different from a base station eNB and an RRH is set in the PDSCH-ConfigCommon field. Here, the EPRE values between the eNB and the RRH are different, but the EPRE values are the same between the RRHs.

Table 4 is another example of PDSCH configuration information. Table 4 shows a case where EPREs for each transmission / reception point are set differently.

TABLE 4

Referring to Table 4, an energy per resource element (EPRE) value different from a base station eNB, RRH1, and RRH2 is set in the PDSCH-ConfigCommon field.

In the CoMP system, a plurality of cells or transmission / reception points may transmit a reference signal, for example, a CSI-RS, to the terminal. In the CoMP system, the reference signal sequence may be determined cell-specifically. In particular, one macro cell in the fourth scenario, which is a CoMP environment where the cell IDs of the transmitting and receiving points (for example, RRHs) that are cooperative with the specific transmitting and receiving points (for example, macro cells) are the same. Within the same reference signal sequence is used for generation of the reference signal. This means that all of the transmission and reception points (eg, RRHs) belonging to the same cooperative set as the macro cell transmit the reference signal using the same reference signal sequence.

4 is a diagram schematically illustrating a method of controlling uplink transmission power.

Referring to FIG. 4, the UE derives a downlink reference signal, that is, energy per resource element (EPRE) of the CSI-RS from referenceSignalPower in the PDSCH-ConfigCommon field, or energy per resource element (EPRE) of the CSI-RS from the pC value. ), And calculates a reference signal received power (RSRP) (S410).

RSRP may be defined as a linear average over the power contributions of all resource elements carrying the CSI-RS within the considered measurement frequency bandwidth. In this case, RSRP may be defined using CRS instead of CSI-RS. Here, CRS is defined for antenna ports 0 to 3, and CSI-RS is defined for antenna ports 15 to 22. Therefore, R ₁₅ refers to the CSI-RS present in the antenna port 15 (see FIGS. 2 and 3).

RSRP may be specifically obtained by the following procedure. The terminal acquires measurement samples by filtering at the physical layer level, and filters the measurement samples at a higher layer level as shown in the following equation.

&Quot; (2) &quot;

In Equation 2, M _n is the most recent measurement sample, F _n is the measurement to be reported by the measurement report, F _n-1 is the measurement reported by the previous measurement report, and a is 1/2 ^{where (k / 4)} k is the filter coefficient used for filtering.

The measurement sample is a measurement value in units of subframes and is a variable required to derive RSRP or RSRQ (Reference Signal Received Quality). Alternatively, the measurement sample means a measurement value for the subframe selected by the measurement rule defined in the wireless system among the measurement values for all the subframes received by the terminal. The measurement sample may be obtained at a physical layer of the terminal, and filtering may be performed at a higher layer of the terminal, for example, a radio resource control (RRC) layer.

The measurement sample may be acquired continuously every subframe, but may be obtained discontinuously as long as the capacity of the terminal or a condition defined by the system is satisfied. That is, after one measurement sample is obtained, another measurement sample may be obtained after a predetermined interval of time. In this case, measurement samples are not obtained for some subframes. The spacing section may be periodic or aperiodic.

Meanwhile, RSRQ may be defined as a ratio between RSRP and Received Signal Strength Indicator (RSSI) as shown in Equation 3 below.

&Quot; (3) &quot;

Here, N is the number of resource elements of the carrier RSSI measurement bandwidth of the radio access network. In Equation 3, the measurements of the numerator and the denominator are performed on the same set of resource blocks. RSSI includes a linear average of the total received power. The total received power is observed only within an OFDM symbol that includes reference symbols within the measurement bandwidth and is a value obtained over N resource blocks. If the UE receives signaling indicating RSRQ measurement at a higher layer, RSSI measurement is performed for all OFDM symbols in the subframe in which the RSRQ measurement is indicated.

The terminal calculates a pathloss (PL) estimate between the transmitting and receiving point and the terminal from the EPRE value of the CSI-RS and the RSRP (S415). The path attenuation estimate can be obtained by Equation 4 below.

&Quot; (4) &quot;

Referring to Equation 4, PL _C is an estimated downlink path attenuation value for the serving cell C calculated by the terminal in dB unit. referenceSignalPower is an EPRE value of a downlink reference signal provided from a higher layer, in dBm. The link determination between referenceSignalPower and RSRP used for serving cell C selected as the reference serving cell and PL _C calculation is configured by pathlossReferenceLinking, which is a higher layer parameter. The reference serving cell configured by the path attenuation reference link information includes a primary serving cell (PCell) or an uplink component carrier (UL CC) and a secondary serving cell (corresponding) in which an SIB2 connection is established. It may be a downlink SCC of a serving cell (SCell).

As in the fourth scenario, when a plurality of transmission / reception points transmit CRS using the same physical cell ID in the CoMP cooperative set, the CRS, which is a reference for RSRP measurement, is the same at the plurality of transmission / reception points. Therefore, the terminal cannot distinguish the path loss estimate for each transmission / reception point based on the CRS. However, according to the definition of the path attenuation estimate, RSRP should be measured separately for each transmission / reception point. In particular, since the DPS is supported in the CoMP mode, the UE can accurately control the uplink transmission power by knowing the path attenuation estimate for each transmission / reception point. For example, in the CoMP system as shown in FIG. 7, it is assumed that the path attenuation expectation value is PL1 at the transmission / reception point 1 and the path attenuation prediction value is PL2 at the transmission / reception point 2. The CoMP terminal may dynamically perform uplink transmission for either or both of the transmission point 1 and the transmission point 2 or both based on the DPS. In this case, when the PL1 and the PL2 are not distinguished, the terminal may erroneously recognize the path attenuation expected value for the transceiver point 2 as the PL1 and calculate an uplink transmission power.

On the other hand, when using the CSI-RS as a reference for RSRP measurement as in steps S410 and S415, since the path attenuation estimates are distinguished for each transmission / reception point, the terminal may calculate the accurate uplink transmission power for each transmission / reception point.

As described above, in the situation where the UE can derive the path attenuation estimates distinguished from each other for each transmission / reception point, it must be determined which path attenuation estimate is to be used to derive the uplink transmission power. As an example, the terminal may select one transmission / reception point among multiple transmission / reception points as a target for uplink transmission according to the DPS operation. At this time, the terminal applies the path attenuation estimate calculated based on the signal received from the selected transmission / reception point to the derivation of uplink transmission power. That is, the terminal may calculate a path attenuation estimate for the transmission / reception point for which the uplink radio link is selected by the terminal itself without extra signaling from the transmission / reception point, in particular, the base station, and apply it to derivation of uplink transmission power.

As another example, the terminal uses the path attenuation estimate for the transceiver point set as the first serving cell to derive uplink transmit power for the transceiver point selected according to the DPS operation. This corresponds to a case in which the UE cannot select one transmission / reception point as a target for uplink transmission according to the DPS operation in the CoMP mode. Therefore, the terminal adjusts the path attenuation estimate of the transceiver point selected by the DPS operation from the base station through TPC signaling. The TPC signaling may proceed through a DCI format 3 / 3A signal.

The terminal calculates uplink transmission power from the path loss estimate for the serving cell C (S420). The uplink physical channel includes a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH). The uplink transmission power may be controlled differently according to the uplink physical channel to transmit.

In the case of the PUSCH, the uplink transmission power P _{PUSCH, C (i)} is scaled by the number of antennas for which at least one PUSCH transmission is performed and the number of antennas configured according to the transmission scheme. C is a serving cell to perform uplink transmission, and i is a number of a subframe in which uplink transmission is performed with power P _{PUSCH, C (i)} . The adjusted total uplink transmission power is equally divided and allocated to the antennas performing at least one PUSCH transmission.

PUSCH transmission power is further divided into i) a case in which PUSCH and PUCCH are not transmitted simultaneously for any serving cell C and ii) a case in which both PUSCH and PUCCH are simultaneously transmitted.

In case of i), the UE calculates an uplink transmission power P _{PUSCH, C (i)} defined by Equation 5 in subframe i for the serving cell C.

<Equation 5>

In case of ii), the UE calculates an uplink transmission power P _{PUSCH, C (i)} defined by Equation 6 in subframe i for the serving cell C.

<Equation 6>

Referring to Equations 5 and 6, P _{CMAX, C (i)} is the maximum terminal transmission power configured for the serving cell C,

Is the linear conversion of dB values. Meanwhile,

Is a value obtained by linearly converting P _{PUCCH (i)} . M _{PUSCH, C (i)} is a value representing the bandwidth of a resource allocated with a PUSCH in subframe i for the serving cell C as the number of resource blocks.

P _{0_PUSCH, C (i)} is the sum of P _{0_NOMINAL_PUSCH, C (j)} and P _{0_UE_PUSCH, C (j)} for the serving cell C. For example, in case of semi-persistent grant PUSCH (re) transmission, j = 0. On the other hand, in case of dynamic scheduled grant PUSCH (re) transmission, j = 1. If j = 0 or 1, it is signaled by a higher layer. And, in case of random access response grant PUSCH (re) transmission, j = 2. In addition, in case of random access response grant PUSCH (re) transmission, P _{0_UE_PUSCH, C (2)} = 0 and P _{0_NOMINAL_PUSCH, C (2)} = P _{0_PRE + ΔPREAMBLE_Msg3} . Here parameters preambleInitialReceivedTargetPower (P _{0_PRE} ) and Δ _{PREAMBLE_Msg3} are signaled from higher layer.

If j = 0 or 1, one of the values of α _C ∈ {0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} is P _{PUCCH, C (i)} by the 3-bit parameter provided in the upper layer _. Can be selected as α _C to determine. When j = 2, α _C (j) = 1.

Δ _{TF, C (i)} is Δ _{TF, C (i)} = ₁₀ log ₁₀ ((2 ^{BPRE · Ks} −1) · β ^PUSCH _offset ), which is affected by the modulation and coding scheme (MCS). Parameter to reflect. Here, K _S is a parameter provided as deltaMCS-Enabled in the upper layer for each serving cell C. In transmission mode 2, which is a mode for transmit diversity, K _S = 0. If only control information is transmitted through the PUSCH without UL-SCH data, BPRE = O _CQI / N _RE , and in all other cases, BPRE =

to be. Where C is the number of code blocks and K _r is the size of the code blocks.

Also, O _CQI is the number of CQI / PMI bits including the number of CRC bits, and N _RE is the number of determined resource elements. That is, N _RE = M _sc ^{PUSCH-initialN} _symb ^{PUSCH-initial} .

If only control information is transmitted without UL-SCH data through the PUSCH, β ^PUSCH _offset = β ^CQI _offset is set. Otherwise, it is always set to 1.

δ _{PUSCH, C} is a correction value. In addition, it is determined by referring to a TPC command present in DCI format 0 or 4 for the serving cell C or a TPC command in DCI format 3 / 3A that is coded and transmitted jointly with other terminals. In DCI format 3 / 3A, cyclic cyclic check (CRC) parity bits are scrambled with TPC-PUSCH-RNTI, so only UEs to which the RNTI value is assigned can be identified. In this case, when an arbitrary terminal is configured with a plurality of serving cells, a different TPC-PUSCH-RNTI value may be allocated to each serving cell to distinguish each serving cell. Alternatively, a different TPC-PUSCH-RNTI value may be assigned to each transmit / receive point to distinguish between the transmit and receive points.

f _c (i) represents the PUSCH power control adjustment state for the current serving cell C, and is defined as in Equation 7 below.

<Equation 7>

Equation (7) is the case in which accumulation is enabled by a higher layer for serving cell C or when DCI format 0 scrambled by a temporary C (Cell) -RNTI is included in the PDCCH. . here,

Is a TPC command in DCI format 0/4 or 3 / 3A in the PDCCH that was transmitted in the subframe in subframe #iK _PUSCH , and f _c (0) is the first value after the cumulative reset. In relation to the K _PUSCH value, in case of FDD, K _PUSCH is 4, and when TDD is 1 to 6, K _PUSCH values are shown in the following table.

<Table 5>

Referring to Table 5, the portion marked with '-' is a DL subframe, and the portion indicated with a number is an UL subframe.

In case of TDD configuration # 0, if there is a PDCCH scheduling PUSCH transmission in subframe # 2 or subframe # 7, a LSB (Least Significant Bit) value of a 2-bit UL index in DCI format 0/4 in the PDCCH If is set to '1' K _PUSCH is 7. K _PUSCH values in all other cases are shown in Table 5 above. The 2-bit UL index is used to schedule UL subframes that cannot be scheduled in Table 5.

Meanwhile, the UE attempts to decode the PDCCH in all subframes except when the DRX operation is performed. This includes the PDCCH of DCI format 0/4 for the C-RNTI of the UE or DCI format 0 for the SPS C-RNTI and DCI format 3 / 3A for the TPC-PUSCH-RNTI of the UE.

If DCI format 0/4 and DCI format 3 / 3A for the serving cell C are simultaneously received in the same subframe, the terminal should use only δ _{PUSCH, C} of DCI format 0/4.

For a certain subframe _, δ _{PUSCH, C} is 0dB when there is no TPC command for the serving cell C, during DRX operation, or when the corresponding subframe is an UL subframe of TDD. When the TPC command fields in DCI format 0/3/4 are 0, 1, 2, and 3, respectively, the accumulated δ _{PUSCH, C} dB values are -1,0,1,3, respectively. If the PDCCH of DCI format 0 is approved as an SPS activation or release PDCCH, δ _{PUSCH, C} is 0 dB. When the TPC command fields in DCI format 3A are 0 and 1, respectively, the accumulated δ _{PUSCH and C} dB values are −1 and 1, respectively.

If the UE reaches P _CMAX, C for the serving cell C, the positive TPC command will not accumulate. If the terminal reaches the minimum power, negative TPC commands will not accumulate.

If the P _{0_UE_PUSCH, C} value for the serving cell C is changed by a higher layer or the terminal receives a random access response message for the main serving cell, the terminal will reset the accumulation.

In Equation 7, f _c (i) is equal to Equation 8 when accumulation is deactivated by the higher layer with respect to the serving cell C.

<Equation 8>

here,

Is transmitted on DCI format 0/4 in PDCCH for serving cell C in subframe #iK _PUSCH . The K _PUSCH value is 4 for FDD and is given as shown in Table 2 in TDD UL / DL configuration # 1 to # 6.

In TDD UL / DL configuration # 0, if PUSCH transmission in subframe # 2 or subframe # 7 is scheduled and the LSB of the 2-bit UL index of DCI format 0/4 in the PDCCH is set to '1', K _PUSCH is 7. Otherwise, K _PUSCH is given as shown in Table 2 above.

If DCI format 0/4 in the PDCCH for serving cell C is not decoded, DRX occurs, or subframe #i is not an UL subframe in TDD, f _c (i) is equal to f _c (i-1). same.

If the P _{0_UE_PUSCH, C} value is changed by the higher layer and the serving cell C is the main serving cell, or the P _{0_UE_PUSCH, C} value is received by the higher layer and the serving cell C is the secondary serving cell, f _c (0) Is zero. In other cases, if the serving cell C is the main serving cell, f _c (0) = ΔP _rampup + δ _msg2 , where δ _msg2 is a TPC command indicated by a random access response. The TPC command is present in 3 bits in the DCI in the PDCCH for indicating the location of the PDSCH including the RAR MAC CE. In addition, ΔP _rampup is provided by the upper layer and is for the total power ramp-up from the first preamble to the last preamble.

The terminal transmits the PUSCH to the reception point at the calculated uplink transmission power (S425).

The terminal also uses the CSI-RS to simply compensate for path attenuation and calculate uplink transmission power, and feeds back information measured based on the CSI-RS to the base station. Information fed back to the base station (CSI feedback) may include control information such as channel quality indicator (CQI), channel state information (CSI), channel covariance matrix (CCM), precoding weight (PW), channel rank (CR), and the like. .

The CSI may include a channel matrix between transceivers, a channel correlation matrix, a quantized channel matrix or a quantized channel correlation matrix, and a PMI. The CQI may be a signal to noise ratio (SNR), a signal to interference and noise ratio (SINR), a signal to interference ratio, or the like, between the transceivers.

The UE may estimate a channel, select a precoding matrix that maximizes channel performance, and report a precoding matrix indicator (PMI) for the selected precoding matrix. The base station may select a precoding matrix indicated by the fed back PMI from the codebook and use it for data transmission.

The MIMO method that uses precoding weights according to channel conditions is called CL (Closed-Loop) MIMO method, and the MIMO method that uses precoding weights according to certain rules regardless of channel condition is called Open-Loop (MO) method. This is called. In the CL MIMO scheme, the transmitting side, for example, the base station corresponds to a channel state by utilizing channel state information (CSI) transmitted from the receiving side, for example, the terminal. CSI may be transmitted including the PMI.

Meanwhile, in order to support the CoMP environment, multiple non-zero-power CSI-RS resources should be configured in the terminal through dedicated signaling such as an RRC message, even for at least CSI feedback. In this case, if the settings shown in Table 1 are used as they are, it is difficult to accurately reflect that different path attenuations may occur for transmission from each transmission / reception point. Thus, a problem arises in that the uplink transmission power cannot be accurately adjusted. In addition, since the same CSI-RS resource and the same CSI-RS configuration are used for different transmission and reception points, the situation where the ratio of PDSCH EPRE and CSI-RS EPRE is different for each transmission and reception point is not reflected. Thus, a problem arises that accurate CQI feedback is difficult to achieve.

Therefore, the aforementioned problems can be solved by adding a field indicating a CSI-RS EPRE value or a field indicating a p-C value to the CSI-RS configuration for each transmission / reception point in the CoMP cooperation set.

By instructing different CSI-RS EPREs for each transmission / reception point, path attenuation that reflects the actual channel state can be calculated for each transmission / reception point. In this case, for a given PDSCH EPRE, different CSI-RS EPREs are indicated for each transmission / reception point, and thus different p-c values are set for each transmission / reception point.

In addition, different p-c may be indicated for each transmission / reception point. Since the p-c value is indicated for each transmission / reception point, path attenuation reflecting the actual channel state can be calculated. In this case, for a given PDSCH EPRE, different p-c is indicated for each transmit / receive point, so that different CSI-RS EPRE values can be set for each transmit / receive point.

In addition, a field indicating a CSI-RS EPRE value and a field indicating a pc value may be added to the CSI-RS configuration for each transmission / reception point in the CoMP cooperation set. By using the CSI-RS EPRE and the pc for each transmission and reception point, different path attenuations may be calculated for each transmission and reception point and adjusted to reflect the uplink transmission power.

Not only when different CSI-RS resources are used, but also when each transmission point uses the same CSI-RS resource, the CSI-RS EPRE, PC, or CSI-RS EPRE and pc are indicated for each transmission point. Can be indicated together.

Table 6 schematically shows an example in which multiple transmission points use one CSI-RS resource in a CoMP system to which the present invention is applied.

<Table 6>

As shown in Table 6, even when a plurality of transmission points use one CSI-RS resource, that is, one CSI-RS pattern, a field indicating a CSI-RS EPRE for each transmission point may be included in the CSI configuration. In addition, as described above, a field indicating pc for each transmission point may be included in the CSI configuration, and a field indicating CSI-RS EPRE for each transmission point and a field indicating pc may be included in the CSI configuration. . As described above, the CSI configuration may be delivered to the terminal through higher layer signaling such as an RRC message.

Table 7 schematically shows an example of a CSI configuration including a CSI-RS EPRE field and a p-c field in a CoMP system to which the present invention is applied.

<Table 7>

In Table 7, an antennaPortCount indicating the number of antenna ports, a resourceConfig indicating a CSI-RS resource, and a subframeConfig indicating a CSI-RS transmission timing are as described in Table 1.

The referenceSignalPower added to the CSI configuration of Table 7 is a field indicating the EPRE of the CSI-RS and indicates the CSI-RS EPRE for at least one antenna port. In addition, p-C is also a field indicating the ratio of PDSCH EPRE to CSI-RS EPRE and indicates p-C for at least one antenna port.

In an environment in which the PDSCH EPRE for the CSI-RS EPRE may have different values for each RRH, as shown in Table 6, in order to support multiple RRHs using the same CSI-RS resource, different transmission points using multiple pcs are used. Different pcs may be allocated to each antenna fork.

Table 8 schematically shows an example of indicating pc / EPRE for each antenna port transmitting CSI-RS in order to support multiple transmission points using one CSI-RS resource in a CoMP system to which the present invention is applied. will be. In the example of Table 8, for convenience of description, only two fields added to the CSI-RS configuration, a field for EPRE and a field for p-c are considered.

<Table 8>

The example in Table 8 describes the CSI-RS configuration in antenna port units. In this case, EPRE values and p-c values are included in the CSI-RS configuration for each antenna port.

If the example of Table 8 is specifically applied to the CSI-RS configuration, it may be represented as shown in Table 9. Table 9 is an example of CSI-RS configuration in which the example of Table 8 is shown together with other CSI-RS parameters.

<Table 9>

Table 10 schematically illustrates an example of indicating pc / EPRE for each group of antenna ports transmitting CSI-RSs to support multiple transmission points using one CSI-RS resource in a CoMP system to which the present invention is applied. It is shown as. In the example of Table 10, only two fields added to the CSI-RS configuration, a field for EPRE and a field for p-c are considered for convenience of description.

<Table 10>

The example in Table 10 illustrates the CSI-RS configuration in units of two antenna ports. That is, all antenna ports are divided into groups, each group including two antenna ports, each having an EPRE and p-c value. For example, EPRE1 and p-c1 are set for a group of antenna ports 15 and 16, EPRE2 and p-c2 are set for a group of antenna ports 17 and 18, and for a group of antenna ports 19 and 20, EPRE3 and p-c3 are set, and for groups of antenna ports 21 and 22, EPRE4 and p-c4 are set. Even if two different groups belong to the same transmission point, the two groups may have different EPRE and p-c values. For example, for an RRH having four antenna ports, when dividing the antenna ports into two groups, the two groups may have different EPREs and p-c.

Compared with Table 8, in the case of Table 10, four EPRE and p-c parameters are transmitted, thereby reducing transmission overhead.

If the example of Table 10 is specifically applied to the CSI-RS configuration, it may be represented as shown in Table 11. Table 11 is an example of CSI-RS configuration in which the example of Table 10 is shown together with other CSI-RS parameters.

<Table 11>

In order to further reduce the transmission overhead, reference values for EPRE and p-c may be determined in the CSI-RS configuration, and differences between the reference values may be transmitted so that EPRE and p-c for each antenna port or antenna port group may be indicated. For example, reference values for a predetermined EPRE and p-c may be separately determined in the CSI-RS configuration, and a difference value for the reference values may be indicated for each antenna port or antenna port group. In addition, in the CSI-RS configuration, one antenna port or antenna port group may be set as a reference antenna port or a reference antenna port group, and a difference value between EPRE and p-c of the reference antenna port or reference antenna port group may be transmitted. In this case, the original values of EPRE and p-c of the reference antenna port or the reference antenna port group may be transmitted as they are. Alternatively, EPRE and p-c of the reference antenna port or reference antenna port group may be set as reference values, and a value of 0 may be indicated as a difference between EPRE and p-c of the reference antenna port or reference antenna port group and the reference value.

Table 12 shows another example of indicating pc / EPRE for each group of antenna ports transmitting CSI-RS to support multiple transmission points using one CSI-RS resource in a CoMP system to which the present invention is applied. It is shown schematically. In the example of Table 12, only two fields added to the CSI-RS configuration, a field for EPRE and a field for p-c are considered for convenience of description.

<Table 12>

In Table 12, an example of dividing the transmission points of the CoMP cooperation group into two groups is given as an example. Referring to Table 12, the first group including the antenna ports 15 and 16 is taken as a reference group, and EPRE and p-c for the first group are set to indicate original values.

In this case, the EPRE for another antenna port group may transmit a difference value ΔEPRE from the EPRE for the first group. For example, if the EPRE for the first antenna port group is called EPRE 1 and the EPRE for the second antenna port group is called EPRE 2, the difference value ΔEPRE12 of the EPRE indicated for the second antenna port group is EPRE2 to EPRE1. This can be

In addition, p-c for another antenna port group transmits a difference value Δp-c from p-c for the first group. For example, if pc for the first antenna port group is p-c1 and pc for the second antenna port group is p-c2, the difference value Δp-c12 of pc indicated for the second antenna port group is p. -c2-p-c1.

In the example of Table 12, the case where the antenna port group includes two antenna ports has been described, but the present invention is not limited thereto. For example, when the EPRE and p-c are configured for each antenna port and the antenna port group includes three or more antenna ports, the method of transmitting the difference value with respect to the reference value may be applied in the same manner as described above.

In addition, in the example of Table 12, the difference value is transmitted based on the first antenna port group, but the present invention is not limited thereto. For example, the second and subsequent antenna port groups or antenna ports may be referenced. Also, instead of referring to the EPRE and pc for the antenna port or antenna port group, a separate reference EPRE and pc may be set so that a difference value for the reference EPRE and pc is indicated for all the antenna ports or antenna port groups. It may be.

Meanwhile, the base station may transmit a bitmap (hereinafter, referred to as a 'transmission point bitmap' for convenience of description) indicating how many transmission points of the CoMP cooperation set use the same CSI-RS resource. The transport point bitmap may be transmitted through higher layer signaling. For example, the transmission point bitmap may be transmitted in addition to the RRC message in which the CSI-RS configuration is transmitted.

Table 13 schematically shows another example of indicating pc / EPRE for each antenna port transmitting CSI-RS to support multiple transmission points using one CSI-RS resource in a CoMP system to which the present invention is applied. . In the example of Table 13, for convenience of description, only two fields added to the CSI-RS configuration, a field for EPRE and a field for p-c are considered.

<Table 13>

Table 14 shows another example of indicating pc / EPRE for each group of antenna ports transmitting CSI-RS in order to support multiple transmission points using one CSI-RS resource in a CoMP system to which the present invention is applied. It is shown schematically. In the example of Table 14, for convenience of description, only two fields added to the CSI-RS configuration, a field for EPRE and a field for p-c are considered.

TABLE 14

In the examples of Tables 13 and 14, antenna ports 15-18 belong to RRH1, antenna ports 19 and 20 belong to RRH2, and antenna ports 21 and 22 belong to RRH3.

In this way, the base station can inform the user equipment of the transmission point (RRH) and the antenna ports using one CSI-RS resource using the transmission point bitmap. As described above, the transmission point bitmap may be transmitted in addition to the RRC message through which the CSI-RS configuration is transmitted.

5 schematically illustrates an example of a transmission point bitmap transmitted by a base station in a system to which the present invention is applied. In the example of FIG. 5, the transmission point bitmap reflecting the settings of Table 13 or Table 14 is shown.

In the example of FIG. 5, each bit of the transmission point bitmap 510 corresponds to an antenna port. A bit having a value of 0 in the transmission point bitmap 510 indicates that there is no change in the transmission point, and a bit having a value of 1 indicates that there is a change in the transmission point.

Referring to Figure 5 and Table 13 / Table 14, the transmission point bitmap 510 has a value of 1 in the first bit (antenna port 15), indicating that the transmission point begins with RRH1 and then to antenna port 18. Indicates that there is no change in the transfer point. The transmission point bitmap 510 then indicates that the transmission points at antenna port 19 and antenna port 21 are changed to RRH2 and RRH3, respectively.

FIG. 6 schematically illustrates another example of a transmission point bitmap transmitted by a base station in a system to which the present invention is applied. Also in the example of FIG. 6, the transmission point bitmap reflecting the settings in Table 13 or Table 14 is shown.

In the example of FIG. 6, each bit of the transmission point bitmap 610 corresponds to an antenna port. Unlike the transmission point bitmap of FIG. 5, in the transmission point bitmap 610 of FIG. 6, if there is no change in the transmission point, the previous bit is maintained. Has That is, when the bit value is changed from 0 to 1 or when the bit value is changed from 1 to 0, this indicates that the transmission point is changed.

Referring to FIG. 6 and Table 13 / Table 14, transmission point bitmap 610 indicates that the first four antenna ports (antenna ports 15-18) belong to the same transmission point, followed by two consecutive antenna ports. Indicates that belongs to the same transmission point.

Through the bitmap as described above, the base station can inform the terminal of the situation (situation) that the transmission is performed.

Meanwhile, in the fourth CoMP scenario among the above-described CoMP scenarios, physical cell IDs of transmission points (eg, RRHs) in the CoMP cooperation set are the same. On the other hand, in the case of the first to third CoMP scenarios, the physical cell IDs of the transmission points in the CoMP cooperative set are different. Transmission points having different physical cell IDs may transmit different patterns of CSI-RS.

Specifically, the reference signal sequence that can be used to generate the CSI-RS

May be defined as in Equation 9.

&Quot; (9) &quot;

Here, n _S is the number of slots in a radio frame, and l is the number of OFDM symbols in the slot. Also,

Denotes the maximum number of downlink resource blocks. In Equation 9, c (i) is a scrambling code, which is a pseudo random sequence defined by a length-31 gold sequence, and is initialized as shown in Equation 10 at the start of each OFDM symbol. .

&Quot; (10) &quot;

In Equation 10, N _CP has a value of 1 in the case of a normal cyclic prefix (CP) and a value of 0 in the case of an extended CP. In addition, N ^cell _ID indicates a cell ID (physical layer cell ID) in the physical layer.

Referring to Equations 9 and 10, transmission points having different cell IDs have different c _init . Therefore, the reference signal sequence of the CSI-RS transmitted by the transmission points having different cell IDs is different, so that the pattern of the CSI-RS may be different. That is, transmission points having different cell IDs may transmit CSI-RSs using different CSI-RS resources.

Accordingly, when the first to third CoMP scenarios are applied, the base station may inform the terminal of the c _init value of each transmission point. In this case, the c _init value may be added as one field value in the CSI-RS configuration and set for each antenna port or transmission point (eg, RRH).

Table 15 schematically shows an example of indicating pc / EPRE and c _init for each antenna port transmitting CSI-RS in order to support a plurality of transmission points having different cell IDs in a CoMP system to which the present invention is applied. . In the example of Table 15, only two fields added to the CSI-RS configuration, a field for EPRE, a field for pc, and a field for c _init are considered for convenience of description.

<Table 15>

If the example of Table 15 is specifically applied to the CSI-RS configuration, it may be represented as shown in Table 16. Table 16 shows an example of CSI-RS configuration in which the example of Table 15 is shown together with other CSI-RS parameters.

<Table 16>

Table 17 shows an example of indicating pc / EPRE and c _init for each group of antenna ports transmitting CSI-RS in order to support multiple transmission points having different cell IDs in a CoMP system to which the present invention is applied. It is shown schematically. In the example of Table 17, only two fields added to the CSI-RS configuration, a field for EPRE, a field for pc, and a field for c _init are considered for convenience of description.

TABLE 17

In the example of Table 17, the transmission points of the CoMP cooperation group are divided into two groups, and EPRE, p-c, and cinit are indicated for each group.

Table 18 schematically shows an example of indicating pc / EPRE and c _init for each group of antenna ports transmitting CSI-RS to support a plurality of transmission points having different cell IDs in a CoMP system to which the present invention is applied. It is shown as. In the example of Table 18, only two fields added to the CSI-RS configuration, a field for EPRE, a field for pc, and a field for c _init are considered for convenience of description.

<Table 18>

In the example in Table 18, with the first group containing antenna ports 15 and 16 as the reference group, the values of EPRE and pc are indicated for the first group, and EPRE and pc for the other antenna port group are the first group. Transmits the difference value ΔEPRE and Δp-c with EPRE and pc for.

Even when the difference value is used to transmit the EPRE and the pc, the value of c _init may be indicated by the original value for each antenna port group as shown in the example of Table 18. In addition, unlike in the example of Table 18, c _init , like other parameters (EPRE, pc), also has a c _init value for an antenna port group other than the reference group (the first antenna port group in the example of Table 15). You can also specify a difference value for _init .

7 is a flowchart schematically illustrating a downlink transmission operation by a transmission point of a CoMP cooperative set in a system to which the present invention is applied. Referring to FIG. 7, the base station sets a CSI-RS in an environment to which CoMP is applied and transmits it to the terminal (S710). The base station may deliver the CSI-RS configuration to the terminal through higher layer signaling such as an RRC message.

As described above, the CSI-RS configuration may include EPRE / pc for each antenna port or antenna port group in addition to antennaPortsCount, subframeConfig, and resourceConfig. In addition, the CSI-RS configuration may indicate c _init for each antenna port or antenna port group when the first CoMP scenario or the third CoMP scenario is applied. The CSI-RS configuration may indicate the EPRE / pc for the corresponding antenna port or antenna port group as a difference value with respect to the reference value. In addition, the base station may transmit the CSI-RS transmission status (eg, RRHs participating in the transmission) to the terminal through a bitmap. The CSI-RS configuration and the transmission method of the CSI-RS configuration according to the present invention have been described above in detail.

Subsequently, the base station selects an antenna port group (S720). The base station selects an antenna port group to participate in CSI-RS transmission among antenna ports belonging to transmission points of the CoMP cooperative set. The antenna port group includes at least one antenna port. How many antenna ports the antenna port group includes or which antenna ports the antenna port group includes may be determined by the CSI-RS configuration.

In addition, different antenna port groups may belong to the same RRH. For example, if RRH1 includes antenna ports 15-18, antenna port group 1 may include antenna ports 15 and 16, and antenna port group 2 may include antenna ports 17 and 18.

Subsequently, each transmission point checks which antenna port group their antenna ports belong to (S730). Scheduling between RRHs may be determined by coordination between the transmit / receive points (RRHs) of the CoMP cooperative set as described above. The contents of the CSI-RS configuration set in the base station may be delivered to the RRH through a wired or wireless connection between the base station and the RRH.

Each transmission point transmits the CSI-RS according to the CSI-RS configuration for the antenna port group to which each antenna port belongs (S740).

8 is a flowchart schematically illustrating an operation of a terminal in a system to which the present invention belongs. Referring to FIG. 8, the terminal receives information on the CSI-RS configuration from the base station (S810). The CSI-RS configuration may be delivered to the terminal through higher layer signaling such as an RRC message. In this case, the UE may also receive PDSCH configuration information. The CSI-RS configuration indicates values of EPRE and p-c for each antenna port group including at least one antenna port for antenna ports participating in downlink transmission.

The information on the CSI-RS configuration information and the PDSCH configuration information has been described in detail above.

The terminal then receives the information on the downlink physical channel from each transmission point of the CoMP cooperative set (S820). Information transmitted through the downlink physical channel includes a CSI-RS.

The UE may estimate uplink path loss based on the received CSI-RS and calculate information constituting CSI such as PMI (S830). The UE may estimate uplink path attenuation based on the set values of the received CSI-RS and CSI-RS configuration. The specific method of calculating the path attenuation by the UE and the method of configuring information to be included in the CSI feedback are also described above.

The terminal controls the uplink transmission power by reflecting the calculated path attenuation (S840). As a method of controlling uplink transmission power by reflecting path attenuation, examples of Equations 5 and 6 may be used.

The terminal performs uplink transmission using the uplink transmission power controlled above (S850). In this case, the terminal may transmit the CSI including the information calculated based on the CSI-RS to the base station. The CSI may include PMI information for downlink transmission from each transmission point.

Meanwhile, in FIG. 8, when an operation of controlling uplink transmission power in one process is referred to as a first operation and an operation of configuring CSI feedback information is referred to as a second operation, a terminal operation in which the first operation and the second operation are combined. It assumes each step of the process and explains it. However, this is an example of the present invention is not limited thereto. For example, each step of the first operation and each step of the second operation may be configured in a different combination from FIG. 8. In other words, the UE may divide the operation of controlling uplink transmission power using the CSI-RS and the operation of configuring the CSI feedback information.

FIG. 9 is a flowchart illustrating an operation of a terminal described with reference to FIG. 8 divided into control of uplink transmission power and configuration of CSI information.

Referring to FIG. 9, the terminal receives the CSI-RS configuration as described with reference to FIG. 8 (S910).

The UE may then measure RSRP based on the CSI-RS received on the physical channel from each transmission point (S920). RSRP may be defined as a linear average over the power contributions of all resource elements carrying the CSI-RS within the considered measurement frequency bandwidth. The terminal may calculate the RSRQ as shown in Equation 3 based on the calculated RSRP.

Subsequently, the terminal may estimate path attenuation based on the RSRQ (S930). A detailed method of obtaining the path attenuation is as described in Equation 4.

Subsequently, the terminal controls uplink transmission power using the calculated path attenuation (S940). A detailed method of controlling uplink transmission power is as described above.

On the other hand, the terminal generates a CSI based on the CSI-RS received on the physical channel from each transmission point (S950). The CSI may include a channel matrix between transceivers, a channel correlation matrix, a quantized channel matrix or a quantized channel correlation matrix, and a PMI. The CQI may be a signal to noise ratio (SNR), a signal to interference and noise ratio (SINR), a signal to interference ratio, or the like, between the transceivers. The UE may estimate a channel, select a precoding matrix that maximizes channel performance, and report PMI for the selected precoding matrix. In this case, the precoding matrix may reflect the channel state from each transmission point in the CoMP cooperative set participating in the CSI-RS transmission.

The terminal performs uplink transmission with uplink transmission power calculated based on the CSI-RS (S960). Uplink transmission includes transmission of CSI feedback information configured based on CSI-RS.

10 is a block diagram schematically showing the configuration of a base station in a system to which the present invention is applied. Referring to FIG. 10, the base station 1000 includes an RF unit 1010, a memory 1020, and a processor 1030.

The base station 1000 transmits and receives information through the RF unit 1010. The RF unit 1010 may include a plurality of antennas and support MIMO operation. The base station 1000 may be connected to transmission and reception points (eg, RRHs) constituting a CoMP cooperation set through the RF unit 1010. In addition, the base station 1000 may be connected to a transmitting and receiving point constituting a CoMP cooperation set through a wired network.

The memory 1020 may store information necessary for the base station 1000 to perform communication or to control the network. For example, the memory 1020 may store setting information of a network. For example, reference signal configuration information such as CSI-RS configuration may be stored, and configuration information regarding physical channel transmission may be stored, such as PDSCH configuration. In addition, the memory 1020 may store information such as a codebook for operating the MIMO system.

The processor 1030 implements the functions, processes and / or methods proposed by the present invention. For example, the processor 1030 may control the overall operation of the base station 1000 and may perform scheduling for CoMP operation. In addition, the processor 1030 may be connected to the RF unit 1010 and the memory 1020 to control operations of the RF unit 1010 and the memory 1020.

The processor 1030 may include a setting unit 1040, a scheduling unit 1050, and a control unit 1060. The setting unit 1040 may perform setting necessary for network operation and uplink / downlink transmission. For example, the setting unit 1040 may set a reference signal such as a CSI-RS. In addition, the setting unit 1040 may perform setting for transmission of a downlink physical channel. The parameters set by the setting unit 1040 may be applied cell-specifically or terminal-specifically. For example, the CSI-RS configuration set by the configuration unit 1040 is cell-specific, and each of the RRHs in the cell transmits the CSI-RS according to the CSI-RS configuration. The details of the CSI-RS setting performed by the setting unit 1040 in relation to the present invention are as described above.

The scheduling unit 1050 performs an operation necessary for uplink / downlink scheduling and / or cooperative scheduling (CS) of the CoMP system. In addition, the controller 1060 controls the operation of the other modules associated with it.

11 is a block diagram schematically illustrating a configuration of a terminal in a system to which the present invention is applied. Referring to FIG. 11, the terminal 1100 includes an RF unit 1110, a memory 1120, and a processor 1130.

The terminal 1100 transmits and receives information through the RF unit 1110. The RF unit 1110 may include a plurality of antennas and may support a MIMO operation and a CoMP operation. The terminal 1100 may receive information transmitted from a transmission / reception point (eg, RRH) constituting a CoMP cooperation set through the RF unit 1110 and transmit information to the transmission / reception points.

The memory 1120 may store information necessary for the terminal 1000 to perform communication. For example, the memory 1020 may store various setting information. For example, reference signal configuration information such as CSI-RS configuration may be stored, and configuration information regarding physical channel transmission may be stored, such as PDSCH configuration. The information about the configuration may be transmitted from the base station through higher layer signaling such as an RRC message.

The processor 1130 implements the functions, processes, and / or methods proposed by the present invention. For example, the processor 1130 may be connected to the RF unit 1110 and the memory 1120 to control the operation of the RF unit 1110 and the memory 1120.

The processor 1130 may include a path attenuation calculator 1140, an uplink power controller 1150, a CSI component 1160, and a controller 1170. The path attenuation calculator 1140 estimates the path attenuation through the RSRP and the EPRE calculated using the received CSI-RS. The uplink power controller 1150 controls the uplink transmission power by reflecting the path attenuation calculated by the path attenuation calculator 1140. The CSI configuration unit 1160 configures CSI information to be transmitted as a feedback signal to the base station based on the received CSI-RS. The CSI information may include information indicating a channel state such as PMI. The controller 1170 may control the operation of other linked modules.

As described above, according to the present invention, the base station may divide antenna ports of transmission points participating in CSI-RS transmission in a CoMP cooperative set into antenna port groups and configure EPRE for each antenna port. Correspondingly, the terminal may estimate path attenuation for each antenna port group using the EPRE set for each antenna port group. The EPRE may be set for each antenna port, and in this case, it may be considered that the antenna port group includes one antenna port. The terminal may control uplink transmission power for each antenna port group by using the estimated path attenuation for each antenna port group. In this case, the same transmit power may be set for the antenna port group belonging to the same transmission / reception point.

Meanwhile, in the above examples of Tables 8 to 18, the PC is configured with the EPRE for each antenna port or antenna port group as the CSI-RS configuration, but the pc is configured with the EPRE for controlling uplink transmission power. There is no need. As described above in Table 6, in the CSI-RS, only EPREs may be configured for each antenna port or antenna port group, and EPREs and p-c may be set together.

When the CSI-RS configuration includes pc information for each antenna port or antenna port group, the UE transmits a downlink physical channel (eg, PDSCH) using EPRE and pc for each antenna port or antenna port group. The power EPRE can be calculated. The terminal may control the uplink physical transmission power based on the calculated transmission power of the downlink physical channel (eg, PDSCH). At this time, the control of the transmission power may be made in a predetermined predetermined step size unit in a predetermined power range. For example, the terminal may control the transmit power of the uplink physical channel in units of 1 dB in the range of [-8, 15] dB by considering the calculated transmit power of the PDSCH together with the received power of the PDSCH.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (15)

In the Cooperative Multi Point (CoMP) system,
Transmitting setting information of a reference signal; And
Transmitting a reference signal based on the configuration information of the reference signal,
The reference signal configuration information indicates the energy per resource element used for transmitting the reference signal for each transmission point participating in the transmission of the reference signal. The method of claim 1, wherein the configuration information of the reference signal is a ratio of energy per resource element used for transmission of the reference signal and energy per resource element used for transmission of a downlink physical channel signal transmitted together with the reference signal. And indicating each transmission point participating in the transmission of the reference signal. The method of claim 1, wherein the energy per resource element used for transmitting the reference signal is indicated for each antenna port group grouping antenna ports of a transmission point participating in the transmission of the reference signal. 4. The method of claim 3, wherein the antenna port groups belonging to the same transmission point are indicated with the same energy per resource element. The method of claim 3, wherein the configuration information of the reference signal indicates a sequence used for transmission of the reference signal for each transmission point having a different cell ID. The method of claim 1, wherein the configuration information of the reference signal includes bitmap information indicating the number of transmission points participating in the transmission of the reference signal. The reference signal transmission of claim 6, wherein each bit of the bitmap information corresponds to each antenna port participating in the transmission of the reference signal, and each bit has a specific bit value when a transmission point changes. Way. 7. The method of claim 6, wherein each bit of the bitmap information corresponds to each antenna port participating in the transmission of the reference signal, and the bit value of each bit is changed in response to a change in transmission point. Signal transmission method. In the Cooperative Multi Point (CoMP) system,
Receiving setting information of a reference signal;
Estimating uplink pathloss using reference signals received on a downlink physical channel;
Determining an uplink transmission power by reflecting the uplink path attenuation; And
Performing uplink transmission with the uplink transmission power;
The configuration information of the reference signal indicates the energy per resource element used for transmission of the reference signal for each transmission point participating in the transmission of the reference signal,
In estimating the uplink path attenuation,
An uplink path attenuation for each transmission point is estimated using the reception power of the reference signal transmitted by each transmission point and the transmission power of the reference signal indicated for each transmission point in the configuration information of the reference signal. Transmission method. The method of claim 9, wherein in the uplink transmission power determination step,
And uplink transmission power for each transmission point is determined based on the estimated uplink path attenuation for each transmission point. 10. The method of claim 9, wherein the configuration information of the reference signal is a ratio of energy per resource element used for transmission of the reference signal and energy per resource element used for transmission of a downlink physical channel signal transmitted together with the reference signal. Uplink transmission method characterized by indicating for each transmission point participating in the transmission of the reference signal. 10. The method of claim 9, wherein the configuration information of the reference signal indicates the energy per resource element used for transmission of the reference signal for each antenna port group grouping the antenna ports of the transmission point participating in the transmission of the reference signal. Uplink transmission method. The uplink transmission method of claim 12, wherein the configuration information of the reference signal indicates energy per resource element to antenna port groups belonging to the same transmission point. RF (Radio Frequency) unit for transmitting and receiving information;
A memory for storing information; And
It includes a processor for controlling the RF unit and the memory,
The processor configures setting information of a reference signal,
The reference signal configuration information indicates the energy per resource element used for transmitting the reference signal for each transmission point participating in the transmission of the reference signal. RF (Radio Frequency) unit for transmitting and receiving information;
A memory for storing information; And
It includes a processor for controlling the RF unit and the memory,
The processor estimates an uplink path attenuation for each transmission point using the received power of each reference signal received on a physical channel and the transmission power of the reference signal for each transmission point,
The transmission power of the reference signal for each transmission point is indicated by the configuration information for the reference signal.

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