KR20190017643A - Method for data communication using multiple beamforming in mobile communication system and apparatus for the same - Google Patents

Abstract

A base station operation method in a mobile communication system is disclosed. According to the present invention, a base station operation method comprises the steps of: performing beam management for selecting at least one beam and transmitting different channel status information reference signals (CSI-RSs) for each beam to a terminal through the selected at least one beam; receiving a beam quality report for the at least one beam from the terminal; transmitting at least one CSI-RSs for acquiring channel information set according to a beam management update performing procedure based on the beam quality report to the terminal through the at least one beam; and receiving CSI-RS-based channel state information for obtaining the channel information from the terminal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for data communication using multi-beamforming in a mobile communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication method and apparatus using multi-beamforming in a mobile communication system, and more particularly to a data communication method and a multi- ≪ / RTI >

Fifth generation mobile communications aiming at Gbps (Giga bps) class support, which is at least 10 to 100 times higher data rate than 4th generation mobile communication, are expected to be implemented in the Giga Herz frequency band of several tens of GHz. For example, the implementation is being discussed in the 20 GHz to 60 GHz frequency band (the wavelength at 30 GHz is 10 mm). The fifth generation mobile communication technology is also referred to as millimeter wave (hereinafter referred to as "millimeter wave ") mobile communication technology because the wavelengths in the higher frequency band and the lower frequency band are also expressed in mm.

The fifth generation mobile communication system aims to support a wide bandwidth from 5 MHz to 400 MHz, unlike the conventional 20 MHz maximum bandwidth and a single subcarrier interval of 15 kHz. As described above, in the fifth generation mobile communication system, since it is required to support various frequency bandwidths in various frequency bands, the cell coverage in the case of using the frequency band of several tens of GHz as the carrier frequency band is much smaller than the conventional one, A method of expanding cell coverage using multi-beamforming instead of beam forming has been actively researched. Multibeamforming refers to a multi-antenna technique for transmitting and receiving signals using beams having a plurality of different directivities for covering an entire cell.

Meanwhile, in the case of using multi-beamforming, the beam management procedure including beam quality measurement and the channel information acquisition procedure between the BS and the UE are independent processes or procedures for acquiring information necessary for determining a beam to be used after forming a wireless communication link . Therefore, if the beam management procedure and the channel information acquisition procedure are performed independently, there is a great possibility of overhead of wireless resource waste and related signaling.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an operation method of a base station for reducing efficient radio resource management and signaling overhead in a mobile communication system using multiple beamforming.

Another object of the present invention is to provide an operation method of a mobile communication system using multiple beamforming, which can reduce efficient radio resource management and signaling overhead in a mobile communication system.

It is another object of the present invention to solve the problems described above, and to provide an apparatus for reducing efficient radio resource management and signaling overhead in a mobile communication system using multi-beamforming.

According to another aspect of the present invention, there is provided a method of operating a base station in a mobile communication system, the method comprising: selecting at least one beam and transmitting the CSI-RS channel status information reference signal to a terminal, receiving a beam quality report for the at least one or more beams from the terminal, setting a beam quality update based on the beam quality report, Transmitting at least one CSI-RS for channel information acquisition to the terminal through the at least one beam, and generating CSI-based channel status information (CSI) for obtaining the channel information from the terminal And receiving the data.

The method may further include performing scheduling for data transmission to the UE based on the channel status information.

Here, at least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and an antenna port per CSI-RS resource may be set through upper layer control information.

Here, the beam may correspond to a cell-specific beam or a UE-specific beam.

Here, the beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) reference signal received power).

The number of antenna ports of the CSI-RS resource used in the beam management step may be equal to or greater than the number of antenna ports of the CSI-RS resource required for obtaining the channel information.

If the CSI-RS in the beam management step and the CSI-RS for channel information acquisition have the same spatial characteristic, the step of transmitting quasi-co-location (QCL) information to the UE .

Here, the step of performing the beam management and the step of receiving the channel status information may be performed in one of a periodic, aperiodic, and semi-persistent manner.

Here, the step of receiving the channel state information may be a step of receiving channel state information of two stages, which are performed at the same or different periods.

Here, the channel state information may include at least one of a rank indication (RI), a precoder matrix indication (PMI), a channel quality indication (CQI), and a sounding reference signal (SRS).

According to another aspect of the present invention, there is provided a method of operating a terminal in a mobile communication system, the method comprising: receiving at least one channel status information reference (CSI-RS) through at least one beam selected through a beam- signal from the base station, transmitting a beam quality report based on the at least one CSI-RS received from the base station to the base station, receiving at least one or more CSI- RS, and transmitting channel status information (CSI) to the base station.

At least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and an antenna port per CSI-RS resource is set through the upper layer control information of the base station .

Here, the beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) reference signal received power).

Here, the number of antenna ports of the CSI-RS resource used in the beam management procedure of the BS may be equal to or greater than the number of antenna ports of CSI-RS resources required for channel information acquisition in the BS have.

Here, the channel state information may include at least one of a rank indication (RI), a precoder matrix indication (PMI), a channel quality indication (CQI), and a sounding reference signal (SRS).

According to another aspect of the present invention, there is provided a terminal of a mobile communication system including at least one processor, a memory storing at least one instruction executed by the at least one processor, A transceiver controlled by a processor, the at least one instruction comprising:

Receiving at least one channel status information reference signal (CSI-RS) from at least one CSI-RS through at least one beam selected through a beam management procedure of the base station using the transceiver, Transmitting a beam quality report based on the CSI-RS based on the beam quality report to the base station, receiving at least one or more CSI-RS based on the beam quality report from the base station, and transmitting channel status information (CSI) .

At least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and an antenna port per CSI-RS resource is set through the upper layer control information of the base station .

Here, the beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) reference signal received power).

Here, the number of antenna ports of the CSI-RS resource used in the beam management procedure of the BS may be equal to or greater than the number of antenna ports of CSI-RS resources required for channel information acquisition in the BS have.

Here, the channel state information may include at least one of a rank indication (RI), a precoder matrix indication (PMI), a channel quality indication (CQI), and a sounding reference signal (SRS).

According to the present invention, in a multi-beamforming mobile communication system, it is possible to efficiently manage radio resources and reduce signaling overhead through interworking of a channel information acquisition procedure and a multi-beam management procedure.

1 is a conceptual diagram showing a first embodiment of a communication system.
2 is a block diagram showing an embodiment of a communication node constituting a communication system.
3 is a conceptual diagram illustrating a hybrid beamforming technique in the fifth generation mobile communication system NR.
FIG. 4 is a flowchart illustrating a procedure for interworking with a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.
5 is a conceptual diagram illustrating interworking of a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.
FIG. 6 is a conceptual diagram illustrating a cycle of performing a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.
7A is a conceptual diagram illustrating a beam management procedure and a multi-step channel information acquisition procedure according to an embodiment of the present invention.
7B is a conceptual diagram illustrating a beam management procedure and a multi-step channel information acquisition procedure according to another embodiment of the present invention.
FIG. 8 is a flowchart illustrating a process of interworking a beam management procedure and a channel information acquisition procedure in an uplink according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a conceptual diagram showing a first embodiment of a communication system.

1, a communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Here, the communication system may be referred to as a "communication network ". Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may be a wireless communication device based on a communication protocol based on a code division multiple access (CDMA) communication protocol, a communication protocol based on a wideband CDMA (WCDMA), a communication protocol based on a time division multiple access (TDMA) based communication protocol, an orthogonal frequency division multiplexing (OFDM) based communication protocol, an OFDMA (orthogonal frequency division multiple access) based communication protocol, a single carrier-FDMA based communication protocol, a non-orthogonal multiple access-based communication protocol, and a space division multiple access (SDMA) -based communication protocol. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing an embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to the network to perform communication. The communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 and communicate with each other. However, each component included in the communication node 200 may not be connected to the common bus 270 but may be connected to the processor 210 via an individual interface or a separate bus. For example, the processor 210 may be coupled to at least one of the memory 220, the transceiver 230, the input interface 240, the output interface 250 and the storage 260 via a dedicated interface .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods in accordance with embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be constituted of at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may comprise at least one of read-only memory (ROM) and random access memory (RAM).

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, a plurality of user equipments ) 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3 and the fourth terminal 130-4 may belong to the coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4 and the fifth terminal 130-5 may belong to the coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5 and the sixth terminal 130-6 may belong to the coverage of the third base station 110-3 . The first terminal 130-1 may belong to the coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the coverage of the fifth base station 120-2.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1 and 120-2 includes a Node B, an evolved Node B, a base transceiver station (BTS) A wireless base station, a radio transceiver, an access point, an access node, a roadside unit (RSU), a digital unit (DU), a cloud digital unit (CDU) , A radio remote head (RRH), a radio unit (RU), a transmission point (TP), a transmission and reception point (TRP), a relay node, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 includes a terminal, an access terminal, a mobile terminal, May be referred to as a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, and the like.

A plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, Each may support cellular communication (e.g., long term evolution (LTE), LTE-A (advanced), etc. defined in 3GPP standards). Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands, or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1 and 120-2 may be connected to each other via an ideal backhaul or a non-ideal backhaul, Or non-idle backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through an idle backhaul or a non-idle backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130 130-2, 130-3, 130-4, 130-5, and 130-6, and transmits the signals received from the terminals 130-1, 130-2, 130-3, 130-4, Lt; / RTI >

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support downlink transmission based on OFDMA, and uplink ) Transmission. Also, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may perform multiple input multiple output (MIMO) transmission (for example, MIMO, MIMO, MIMO, Coordinated Multipoint (CoMP), Carrier Aggregation, Unlicensed Band, Device to Device (D2D) Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may support communication (or ProSe (proximity services) (110-1, 110-2, 110-3, 120-1, 120-2) corresponding to the base stations 110-1, 110-2, 110-3, 120-1, Supported actions can be performed.

For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 can transmit a signal based on the SU-MIMO scheme And may receive a signal from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, the fourth terminal 130-4, And the fifth terminal 130-5 may receive signals from the second base station 110-2 by the MU-MIMO scheme. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 can transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, The terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP method. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6) and the CA scheme. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 coordinates D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5, the fourth terminal 130-4 and the fifth terminal 130-5 may be coordinated by the coordination of the second base station 110-2 and the third base station 110-3, Can be performed.

Next, multi-beamforming techniques will be described. Here, even when a method (for example, transmission or reception of a signal) to be performed in the first communication node among the communication nodes is described, the corresponding second communication node is equivalent to the method performed in the first communication node (E.g., receiving or transmitting a signal). That is, when the operation of the terminal is described, the corresponding base station can perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, the corresponding terminal can perform an operation corresponding to the operation of the base station.

3 is a conceptual diagram illustrating a hybrid beamforming technique in the fifth generation mobile communication system NR.

Referring to FIG. 3, a hybrid beamforming technique, which is one of the large capacity multi-antenna techniques used in an NR (New Radio) system (hereinafter referred to as NR), which is one of the fifth generation mobile communication system standard specifications, is shown .

NR, which supports system operation in the frequency band up to 100 GHz, is considering a beam-forming method using a large-capacity multi-antenna as a method for solving the problem of a radio signal reaching distance which is a fundamental problem of high frequency band communication. Such beamforming includes an analog beamforming method and a digital beam forming method.

The digital beamforming scheme uses a plurality of radio frequency (RF) paths based on a multiple input multiple output (MIMO) antenna and a digital precoder or a codebook to generate a beamforming gain gain. The digital beamforming scheme requires a digital to analog converter (DAC) or an analog to digital converter (ADC) and requires the same number of transceiver units (TXRUs) as the antenna elements, The complexity of antenna implementation is greatly increased.

The analog beamforming scheme achieves beamforming gain through a number of analog devices and antenna arrays, such as a phase shifter, a power amplifier (PA), and a variable gain amplifier (VGA). In the analog beamforming scheme, since a plurality of antenna elements are connected to one transceiver unit through a phase shifter, even if the antenna elements are increased to increase the beam forming gain, the resulting complexity is not significantly increased. However, since the analog beamforming adjusts the phase shifter in time, the frequency resource utilization efficiency is limited.

A hybrid beam forming system that is a combination of a digital beam forming system and an analog beam forming system includes a digital signal processor 310 (corresponding to digital beamforming) for a baseband signal, (340) and the amplifier (350) together. In addition, the hybrid beam forming method can generate a directional beam in the RF unit 360 to compensate for path attenuation, and obtain multiple input / output gains through additional beam forming in the digital domain. As a result, in order to apply the hybrid beam forming method, the beam forming precision and the implementation complexity must be compromised. The TXRU (transceiver) 330 is a transceiver.

On the other hand, in addition to the beam forming method, an important technique in NR beamforming is a technique for channel state information acquisition. Since the quality of acquired channel information has a great effect on the system performance, acquisition of channel information is one of the most important parts in utilizing multi beamforming. The acquisition of channel information includes a reference signal (RS) design for channel information measurement and channel state information (CSI) reporting.

 In NR, the use of hybrid CSI-RS, which is a combined form of UE-specific RS and non-UE-specific RS, is also considered for channel information measurement, and interference measurement and channel reciprocity The use of RS for measurement is also considered. In this regard, in NR, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a precoding type indicator (PTI), a rank indicator, a CRI (CSI-RS a variety of channel information reporting methods such as an implicit feedback method for reporting resource indicator information as well as explicit feedback for reporting quantized or actual channel information and interference information feedback are considered in NR have.

On the other hand, when cell coverage is increased through beamforming in the NR, a common control channel and a common control channel, which are commonly transmitted to all UEs in a cell, as well as a dedicated control channel and dedicated data transmitted to each UE in the cell, Are also transmitted in a beam-forming manner. However, in this case, the common signal including the common control channel and the synchronous signal can not be transmitted to the entire cell area through one transmission, and the signal is transmitted through multiple beams over a plurality of times for a predetermined time (referred to as beam sweeping). At this time, the beam used for transmission can be determined through the channel information acquisition procedure described above. NR also performs beam management to select and adjust the transmission beam faster than channel information acquisition as needed.

The beam management means that the base station determines and adjusts the beam to be applied to the physical channel or the signal based on the beam quality information reported from the terminal. More specifically, when the terminal measures the quality of a plurality of beams of a base station through reception of a reference signal from the base station and transmits beam quality information to the base station, the base station performs beam management using the measured quality. The beam quality information may be a CSI obtained through a reference signal or a reference signal received power (RSRP) of a reference signal. Also, the beam quality information may be one or more beam index information preferred by the UE.

The beam management procedure and the channel information acquisition procedure described above are processes defined independently of each other, and the method of performing each procedure such as signaling, feedback information, CSI-RS resource configuration, and the like is different. However, the configuration that acquires the information needed to determine the beam used to transmit the signal and channel after establishing the wireless communication link is common to both procedures. Therefore, if both procedures are performed independently, the CSI-RS resource, signaling and feedback overhead may overlap. Next, integration of the beam management procedure and the channel information acquisition procedure according to an embodiment of the present invention for solving such a problem will be described.

FIG. 4 is a flowchart illustrating a procedure for interworking with a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.

Referring to FIG. 4, it is shown that a beam management procedure and a channel information acquisition procedure are interworked and processed between a base station and a terminal. As described above, in performing beam management in a multi-beam-based mobile communication system, beams to be applied to a physical channel or a signal are determined and adjusted based on the beam quality information reported from the terminal.

In operation S410, the base station may perform beam management to select and adjust one or more transmission beams and one or more reception beams (hereinafter, referred to as multiple beams) forming a radio link with the terminal before receiving the beam quality report. The base station may allocate different CSI-RSs to the selected multiple beams and transmit them to the terminal (S420). The beam used in performing the beam management may be a cell-specific beam or a UE-specific beam and may be a wideband beam or a narrow-band beam. The CSI-RS can be used to manage this feature beam.

The CSI-RS is a reference signal transmitted from the base station to the UE. The CSI-RS is used for estimating channel state information required for channel-dependent scheduling, link adaptation, and transmission setup related to multi-antenna transmission. The pattern of the CSI-RS according to the beam, the number of CSI-RS resources and the number of antenna ports per CSI-RS resource are set by a higher layer of the base station, Lt; / RTI >

Here, the antenna port is an abstract concept and does not necessarily correspond to a specific physical antenna. Each downlink transmission is performed through a specific antenna port, and each antenna port is distinguished and announced to the UE. The terminal also assumes that when two transmission signals are transmitted from the same antenna port, they pass through the same radio channel. In the downlink, each antenna port actually corresponds to a specific RS. Therefore, the terminal can estimate a channel corresponding to a specific antenna port using a specific RS, and can extract detailed channel state information on a channel corresponding to a specific antenna port.

개의 안테나포트로 이루어져 있다.If one CSI-RS resource is mapped in one beam and a total of K _B CSI-RS resources are set in the base station, the base station may use K _B beams for beam management. At this time, the CSI-RS resources set for each beam are

Antenna ports.

Then, the terminal receives a reference signal such as a CSI-RS transmitted through multiple beams of the base station, measures the quality of a plurality of beams of the base station, measures beam quality information such as one or more beam index information and channel state information Information to the base station (S430). This is called beam quality reporting. As described above, the beam quality information may be CSI (channel status information) obtained through a reference signal or RSRP of a reference signal. Or the beam quality report may be a CSI-RS resource indicator (CRI), a wideband / narrowband precoding matrix indicator (PMI), a rank indicator (RI), or a channel quality indicator (CQI).

The beam quality report may be transmitted on the uplink control channel and / or the uplink data channel of the radio link formed by the beam. Also, even if the beam is selected by the base station through the CSI during the beam quality report, other information such as RSRP may be additionally provided according to the needs of the base station.

The CSI provides the Node B with the base station scheduling information in order to assist scheduling according to the downlink channel of the Node B, and the Node B makes a downlink scheduling decision based on the CSI. The CSI may be composed of one or more of a rank indication (RI), a precoder matrix indication (PMI), and a channel-quality indication (CQI).

The RI is a recommendation value for a rank used for transmission, and provides information on the number of layers desired to be used for downlink transmission to the corresponding terminal. The PMI provides information on what precoding matrices are desired to be used for DL-SCH transmission. The CQI means the highest possible modulation and coding scheme (MCS) for PDSCH transmissions that can be received with a block error rate (BLER) of less than 10% when the recommended RI and PMI are used.

The CSI reporting to the base station of the terminal is performed by a combination of RI, PMI, and CQI. Exactly which information is included in the CSI depends on the transmission mode set by the terminal. For example, RI and PMI need not be reported unless the terminal is in a spatial multiplexing transmission mode. In an embodiment of the present invention, the beam quality report may report the wideband PMI (i ₁ ^(B) ), RI ^(B) , and CRI ^{( B)} . The reason for using the wideband PMI (i ₁ ^(B) ) and RI ^(B) as the beam quality report is to reduce the overhead in the channel information acquisition procedure, and to specify the beamforming used in the channel information acquisition procedure To do so. Since CRI ^{( B)} is the information for indicating the selected CSI-RS resource, beam quality report for beam selection and determination at the base station can be referred to.

Meanwhile, an embodiment of a codebook for generating a PMI used in an embodiment of the present invention is as follows.

W = W ₁ W ₂ is possible as a form of the entire codebook for generating the PMI used in the embodiment of the present invention. W ₁ can be expressed as a kronecker product of a horizontal domain vector and a vertical domain vector. In this case, each domain vector is based on oversampled DFT vectors and is generally defined as a long-term wideband. W ₂ can be defined as a short-term wideband or a short-term subband according to the base station, and the shape can be defined as a selection and co-phasing matrix .

The codebook W ₁ can be expressed by Equation (1) and the codebook W ₂ can be expressed by Equation (2).

로 정의될 수 있고, W₂에 해당하는 인덱스는 i₂로 정의될 수 있다.The reason for dividing the codebook into two parts is to simplify the implementation by allowing the terminal to apply different time band filtering to the two parts when forming the PMI. PMI is fed back to the base station in the form of an index, and the index corresponding to W ₁ is

, And the index corresponding to W ₂ can be defined as i ₂ .

Another example of a form of codebook for generating a PMI is a method of adding a term related to amplitude control in addition to a selection and co-phasing term to W ₂ , In the case of using multiple panels, W ₁ and W _{2, as} well as W ₃ , which controls the co-phasing and amplitude between the panels, may be added. However, the present invention is not limited to the above-described codebooks, and various types of codebooks for generating PMIs are available.

Upon receipt of the beam quality report from the terminal, the base station updates the beam management based on the received beam quality report (S440). That is, the base station can determine, adjust, and adjust the beam to be applied to the physical channel or the signal based on the beam quality information reported from the terminal.

If you are to apply the beam quality as RSRP reported as an example select one beam N _B, the RSRP is sorted from largest beam sequentially may select the N _B beams. At this time, the CRI ^{( B)} can be configured to inform the CSI-RS resource position corresponding to the selected N _B beams. Or the CQI required to derive the PMI.

The base station that has performed the beam management update may transmit the CSI-RS used to acquire the channel information of the UE to the UE by changing the beam (S450). As described above, the CSI-RS is a reference signal transmitted from a base station to a mobile station. After receiving the reference signal, the mobile station estimates channel state information required for scheduling according to a channel, link adaptation, .

A cell-specific RS (CRS) is also used to acquire channel state information, but the CSI-RS is used to allow the terminal to acquire CSI for at least eight antenna ports, unlike the CRS. In an initial version of the 3GPP LTE and LTE-A mobile communication systems, it is necessary to perform detailed channel estimation to perform coherent demodulation for different downlink transmissions and to perform downlink adaptation and scheduling All of the functions that need to acquire channel status information have been performed through CRS.

CRS, however, must be transmitted very tightly in the time and frequency domain to allow channel estimation necessary for coherent demodulation even for very rapidly changing channels. Also, in order to enable the UEs to acquire the channel state information in a predetermined period, it should always be transmitted in all subframes regardless of whether there is data to be transmitted. For these reasons, the CRS can not use beamforming towards a particular terminal and must be transmitted in the entire cell area.

On the other hand, CSI-RS can be set to terminal specific. The number of CSI-RSs used by a particular terminal and the CSI-RS settings that define the detailed structure are given for each terminal. Also, the CSI-RS may be the same for a group of terminals or all terminals in a cell, which means that all terminals can use the same CSI-RS to obtain CSI in the cell. That is, both the beam management procedure and the channel information acquisition procedure according to the embodiment of the present invention can be performed through the CSI-RS. At this time, the configuration of the CSI-RS used in the beam management procedure and the channel information acquisition procedure May be different. Also, if a demodulation reference signal (DM-RS) for channel estimation of a UE and a CSI-RS for acquiring channel state information of the UE are used, the DM-RS can be transmitted only when there is data to be transmitted. Foaming can be used.

The terminal receiving the CSI-RS from the base station can transmit channel state information (CSI), which is a state of the radio channel section, to the base station (S460). Specifically, the MS estimates a channel state from the CSI-RS to be transmitted CSI, such as the ^{_{subband PMI (i 1 (c)}} , i 2 (c)), CQI, RI (c), CRI (c) to the base station (Where superscript C indicates that the information is CSI reporting information different from the beam quality reporting information described above). The procedure of transmitting the CSI-RS to the base station that has performed the beam management update and transmitting the CSI to the base station by receiving the CSI-RS may be referred to as a channel information acquisition procedure. The CSI-RS transmitted by the base station in the channel information acquisition procedure may be different from the CSI-RS transmitted from the base station in the above-described beam management procedure. The base station may receive the CSI from the UE to acquire channel information, and may perform scheduling for data transmission in step S470.

Meanwhile, the CSI-RS transmitted from the base station to the mobile station through the beam management procedure and the CSI-RS transmitted from the base station to the mobile station through the channel information acquisition procedure are transmitted to the mobile station with the same or similar spatial characteristics, The base station can set quasi-co-location (QCL) information in the space and transmit it to the terminal.

QCL is also an essential element for antenna port configuration. When receiving the CSI-RS for channel state information estimation, the terminal receiving the QCL information, which is an essential element in setting the antenna port, assumes the same reception spatial correlation between the beam management procedure and the channel information acquisition procedure, . The QCL can be set for a single beam and can be set for multiple beams. Next, a description will be made of a specific operation procedure for interworking of beam management and channel information acquisition according to an embodiment of the present invention.

5 is a conceptual diagram illustrating interworking of a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.

Referring to FIG. 5, when a specific CSI-RS resource is selected through the beam management procedure, the CSI-RS resource for the new channel information acquisition is created using the base station. More specifically, a beam management update procedure for selecting and adjusting two beams 520 and 540 through a beam quality report from the terminal when the CSI-RSs are selected by selecting four beams 520, 530, 540 and 550 in the beam management procedure 510 Can be performed. That is, the four beam that is the target of a beam management in a beam control procedure (K _B = 4) Select the beam 1 520 and the beam 3 540 of a through-beam quality report from (CSI-RS resource 1 and CSI-RS Resource 3 is selected) and can be adjusted.

Next, the base station selects two beams (570-1, 570-2, 580-1, 580-2) from four beams (K _c = 4) for channel information acquisition in the channel information acquisition procedure 560 And transmit the CSI-RS. Through this procedure, the base station can select and adjust the beam for the CSI-RS transmission so that it can receive a finer range of CSI from the terminal.

Assuming that beam 1 (beam for transmitting CSI-RS resource 1) is selected in the beam management procedure in FIG. 5 and the number of antenna ports of the CSI-RS resource 1 is P ₁ , The number of antenna ports of the CSI-RS for acquiring channel information related to the beam management procedure may be P ₁₁ , P ₁₂ , ..., P _1n . Where P ₁ ≥ P ₁₁ + P ₁₂ + ... + P _1n .

That is, the number of antenna ports of the CSI-RS resource used in the beam management procedure may be equal to or greater than the number of antenna ports of the CSI-RS resource required for channel information acquisition.

If the example in beam control procedures in the CSI-RS resources corresponding beam 1 1 is selected for transmitting the P ₁ of CSI-RS for antenna ports, this is to adjust the beam 1, beam ₁₁ and beam _12, ..., _1n beam . The beam ₁₁ is a beam for transmitting P ₁₁ CSI-RS antenna ports corresponding to the CSI-RS resource 1 in the channel information acquisition procedure, and the beam ₁₂ is a beam for transmitting P ₁₁ (The number n of antenna ports of the CSI-RS for channel information acquisition is assumed to be n = 2 for convenience of explanation).

5, if beam 4 (beam for transmitting CSI-RS resource 4) is selected in the beam management procedure and the number of antenna ports of the corresponding CSI-RS resource 4 is P ₄ , The number of antenna ports of the CSI-RS for acquiring channel information related to the beam management procedure may be P ₄₁ , P ₄₂ , ..., P _4n . Where P ₄ ≥ P ₄₁ + P ₄₂ + ... + P ₄ n.

If the example in beam control procedures in the CSI-RS resource 4 P ₄ the beams 4 has been selected to send the CSI-RS antenna port on, to adjust the beam 4, beams _41, beam _42, ..., _4n beam is . The beam ₄₁ is a beam for transmitting P ₄₁ CSI-RS antenna ports corresponding to the CSI-RS resource 1 in the channel information obtaining procedure, and the beam ₄₂ is a beam for transmitting P ₄₁ (The number n of antenna ports of the CSI-RS for channel information acquisition is assumed to be n = 2 for convenience of explanation). Meanwhile, as described above, the CSI-RS configuration in the beam management procedure and the CSI-RS configuration in the channel information acquisition procedure may be different.

The base station transmits CSI-RS for channel information acquisition via the beam 1 and the beam 4 to the terminal through the procedure described above, and the terminal can receive the CSI and transmit the CSI to the base station by deriving the CSI. In this case, in the embodiment of FIG. 5, four beams are selected in the beam management procedure, and beam 1 and beam 3 are selected as the beam for acquiring channel information through the beam quality report. However, the present invention is not limited thereto The number of beams selected in the beam management procedure and the beam selection method for acquiring channel information may be variously changed. Next, the operation cycle of the beam management procedure and the channel information acquisition procedure will be described.

FIG. 6 is a conceptual diagram illustrating a cycle of performing a beam management procedure and a channel information acquisition procedure according to an embodiment of the present invention.

Referring to FIG. 6, the beam management procedure and the channel information acquisition procedure may be periodic, aperiodic, or semi-persistent. For example, when the beam management procedure and the channel information acquisition procedure are periodically performed, the following conditions can be satisfied. A beam management procedure may be periodically performed. The period M 640 includes an offset Y 620 between the beam management procedure and CSI-RS transmission for channel information acquisition, CSI-RS transmission for channel information acquisition, (Y + N < M). In this case, the offset X 610 between the beam management procedure and the reception of the beam quality report from the terminal may be larger than the offset Y between the beam management procedure and the CSI-RS transmission for obtaining the channel information (X <Y).

The setup information for the cycle for performing the beam management procedure and the channel information acquisition procedure is transmitted to the UE through control information such as radio resource control (RRC), medium access control (CE) control element (DCC), and downlink control information Lt; / RTI &gt; Next, a description will be given of a method for increasing the efficiency in interworking with the beam management procedure by performing the channel information acquisition procedure in multiple steps.

FIG. 7A is a conceptual diagram illustrating a beam management procedure and a multi-step channel information acquisition procedure according to an embodiment of the present invention. FIG. 7B is a conceptual diagram illustrating a beam management procedure and a multi-step channel information acquisition procedure according to another embodiment of the present invention. to be.

7A and 7B, the beam management procedure and the channel information acquisition procedure linked to the beam management procedure are performed by two or more steps, and the cycle of the beam management procedure and the two-step channel information acquisition procedure are variously set. The two-stage channel information acquisition procedure and the beam management procedure can set various operations. That is, the beam management procedure and the channel information acquisition procedure (the first channel information acquisition procedure and the second channel information acquisition procedure) can be set to be periodic, aperiodic or semi-persistent.

At this time, the setting information of the second channel information obtaining procedure is dependent on the setting information of the beam management procedure associated with the first channel information obtaining procedure or the first channel information obtaining procedure. For example, if the beam management procedure and the first channel information acquisition procedure are set non-periodically, the second channel information acquisition procedure can not be periodically set and must be set non-periodically. As another example, if the beam management procedure and the first channel information acquisition procedure are periodically set, the second channel information acquisition procedure can not be set non-periodically and must be periodically set. The setup information for the cycle for performing the beam management procedure and the channel information acquisition procedure is transmitted to the UE through control information such as radio resource control (RRC), medium access control (CE) control element (DCC), and downlink control information Lt; / RTI &gt;

According to the embodiment of the present invention shown in FIGS. 7A and 7B, a beam management procedure is performed according to a predetermined period (TB), a channel information acquisition procedure is divided into two steps (a first channel information acquisition procedure, 2 channel information acquisition procedure) Each channel information acquisition procedure can also be performed at a specific period (the cycle of the first channel information acquisition procedure is TC1 and the cycle of the second channel information acquisition procedure is TC2). In the embodiment of FIG. 7A, the beam management procedure and the channel information acquisition procedure are performed. In this case, the channel information acquisition procedure includes two steps (first channel information acquisition procedure and second channel information acquisition procedure) Lt; / RTI > The execution period (TB) 710 of the beam management procedure may be similar to the execution period TC1 720 of the first channel information acquisition procedure and the execution period TC2 730 of the second channel information acquisition procedure May be shorter than the first channel information acquisition performing cycle 720 (TB? TC1> TC2).

In the second channel information acquisition procedure, the CSI-RS used in the first channel information acquisition procedure may be used, or the newly set CSI-RS may be used thereafter. When the two-step channel information acquisition procedure is used, the long-term channel information is acquired through the first channel information acquisition procedure, the short-period channel information is acquired through the second channel information acquisition procedure, And perform scheduling for transmission.

In another embodiment of the present invention shown in FIG. 7B, the beam management procedure and the channel information acquisition procedure are performed. In this case, the channel information acquisition procedure includes two steps (a first channel information acquisition procedure and a second channel information acquisition procedure) The second channel information acquisition procedure may be performed prior to the first channel information acquisition procedure.

 The execution period (TB) 740 of the beam management procedure may be similar to the execution period (TC1) 750 of the first channel information acquisition procedure and the execution period (TC2) 760 of the second channel information acquisition procedure May be shorter than the first channel information acquisition execution cycle (TC1) 750 procedure (TB≈TC1> TC2). Meanwhile, the channel information acquisition procedure may include two or more channel information acquisition procedures that are dependent on the first channel information acquisition procedure.

As described above, the setting information for the period for performing the beam management procedure and the channel information acquisition procedure may include control information such as radio resource control (RRC), medium access control (CE) control element (CE), and downlink control information (DCI) Lt; / RTI &gt; Although the embodiments of the present invention have been described in terms of the downlink, the present invention is also applicable to the uplink. Next, a description will be made of an interworking procedure of a beam management procedure and a channel information acquisition procedure in an uplink according to an embodiment of the present invention.

FIG. 8 is a flowchart illustrating a process of interworking a beam management procedure and a channel information acquisition procedure in an uplink according to an embodiment of the present invention.

Referring to FIG. 8, it is shown that a beam management procedure and a channel information acquisition procedure are interworked between a base station and a terminal using SRS information from a terminal. If the base station determines that it has not normally received the uplink data from the terminal, it can instruct beam management to be performed on the downlink control channel. The concrete procedure is as follows.

In operation S810, the base station may perform beam management to select and adjust one or more transmission beams and one or more reception beams (hereinafter, referred to as multi-beams) that form a wireless link with the terminal before receiving the beam quality report.

According to the beam management procedure, the UE may beam-form a sounding reference signal (SRS) resource to the base station (S820).

The base station can measure the uplink beam quality by receiving the SRS from the UE, and perform the beam management update based on the measured SRS (S830). The base station can inform the UE of the updated beam information, and the terminal can beam-form SRS for channel estimation using the updated beam information and transmit the beamformed signal to the base station (S840). The base station can estimate the uplink channel information by receiving the SRS for channel estimation from the UE. Then, the base station can perform scheduling for uplink data transmission (S850).

The methods according to the present invention can be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software.

Examples of computer readable media include hardware devices that are specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (20)

A method of operating a base station in a mobile communication system,
Performing beam management for selecting at least one beam and for transmitting different CSI-RS (CSI-RS) for each beam through the selected one or more beams to the terminal;
Receiving a beam quality report for the at least one beam from the terminal;
Transmitting one or more CSI-RSs for acquiring channel information set according to a beam management update performing procedure based on the beam quality report to the terminal through the at least one beam; And
And receiving CSI-based channel status information (CSI) for obtaining the channel information from the terminal. The method according to claim 1,
And performing scheduling for data transmission to the terminal based on the channel state information. The method according to claim 1,
Wherein at least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and information about an antenna port per CSI-RS resource is set through upper layer control information, . The method according to claim 1,
Wherein the beam corresponds to a cell-specific beam or a UE-specific beam. The method according to claim 1,
The beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) received power. &lt; / RTI &gt; The method according to claim 1,
Wherein the number of antenna ports of the CSI-RS resource used in the beam management step is greater than or equal to the number of antenna ports of the CSI-RS resource required for obtaining the channel information. The method according to claim 1,
And transmitting the quasi-co-location (QCL) information to the terminal when the CSI-RS in the beam management step and the CSI-RS for obtaining the channel information have the same spatial characteristic , A method of operating a base station. The method according to claim 1,
Wherein performing the beam management and receiving the channel state information is performed in one of a periodic, aperiodic, and semi-persistent manner. The method of claim 8,
Wherein the step of receiving the channel state information is a two-step channel state information reception step performed at equal or different intervals. The method according to claim 1,
Wherein the channel state information comprises at least one of a rank indication (RI), a precoder matrix indication (PMI), a channel quality indication (CQI), and a sounding reference signal (SRS). A method of operating a terminal in a mobile communication system,
Receiving at least one channel status information reference signal (CSI-RS) from the base station through at least one beam selected through a beam management procedure of the base station;
Transmitting a beam quality report based on the at least one CSI-RS received from the base station to the base station;
Receiving at least one or more CSI-RSs based on the beam quality report from the base station; And
And transmitting channel status information (CSI) to the base station. The method of claim 11,
Wherein at least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and an antenna port per CSI-RS resource is set through upper layer control information of the base station, Lt; / RTI &gt; The method of claim 11,
The beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) received power. &lt; / RTI &gt; The method of claim 11,
The number of antenna ports of the CSI-RS resource used in the beam management procedure of the BS is greater than or equal to the number of antenna ports of the CSI-RS resource required for channel information acquisition in the BS, How it works. The method of claim 11,
Wherein the channel state information includes at least one of a rank indication, a precoder matrix indication, a channel-quality indication, and a sounding reference signal. 21. A terminal of a mobile communication system, comprising: at least one processor; a memory storing at least one instruction executed by the at least one processor; and a transceiver controlled by the at least one processor, silver,
Receiving at least one channel status information reference signal (CSI-RS) from the base station through at least one beam selected through a beam management procedure of the base station using the transceiver;
Transmitting a beam quality report based on the at least one CSI-RS received from the base station to the base station;
Receiving at least one or more CSI-RSs based on the beam quality report from the base station; And
And transmitting channel status information (CSI) to the base station. 18. The method of claim 16,
Wherein at least one of a signal pattern for the CSI-RS, a number of CSI-RS resources, and an antenna port per CSI-RS resource is set through upper layer control information of the base station, . 18. The method of claim 16,
The beam quality report includes a CSI-RS resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator (RI), a channel quality indicator (CQI) received power. 18. The method of claim 16,
Wherein the number of antenna ports of the CSI-RS resource used in the beam management procedure of the BS is equal to or greater than the number of antenna ports of CSI-RS resources required to acquire channel information in the BS. 18. The method of claim 16,
Wherein the channel state information comprises at least one of a rank indication, a precoder matrix indication, a channel-quality indication, and a sounding reference signal.

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