WO2022080935A1

WO2022080935A1 - Method and apparatus for performing hybrid beamforming communication in wireless communication system

Info

Publication number: WO2022080935A1
Application number: PCT/KR2021/014338
Authority: WO
Inventors: 정성엽; 최수용; 이동헌
Original assignee: 삼성전자 주식회사; 연세대학교 산학협력단
Priority date: 2020-10-16
Filing date: 2021-10-15
Publication date: 2022-04-21
Also published as: KR20220050681A

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate than a 4G communication system such as LTE. The present disclosure can be applied to intelligent services (for example, smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail businesses, security- and safety-related services, and the like) on the basis of a 5G or 6G communication technology and an IoT-related technology. According to various embodiments of the present disclosure, provided may be a method and apparatus for organically determining scheduling of terminals, a digital transmission beam of the terminals, and an analog reception beam of a base station in a next-generation wireless communication system.

Description

Method and apparatus for performing hybrid beamforming communication in a wireless communication system

The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for performing hybrid beamforming communication using a multi-input multi-output (MIMO) antenna.

Looking back on the progress of wireless communication generations, technologies for mainly human services such as voice, multimedia, and data have been developed. After the commercialization of the 5G (5th-generation) communication system, it is expected that connected devices, which are on an explosive increase, will be connected to the communication network. Examples of things connected to the network may include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction machines, and factory equipment. Mobile devices are expected to evolve into various form factors such as augmented reality glasses, virtual reality headsets, and hologram devices. In the 6th-generation (6G) era, efforts are being made to develop an improved 6G communication system to provide various services by connecting hundreds of billions of devices and things. For this reason, the 6G communication system is called a system after 5G communication (Beyond 5G).

In a 6G communication system that is predicted to be realized around 2030, the maximum transmission speed is tera (that is, 1,000 gigabytes) bps, and the wireless latency is 100 microseconds (μsec). That is, the transmission speed in the 6G communication system is 50 times faster than in the 5G communication system, and the wireless delay time is reduced by one-tenth.

In order to achieve such high data rates and ultra low latency, 6G communication systems use the terahertz band (for example, the 95 gigahertz (95 GHz) to 3 terahertz (3 THz) band). implementation is being considered. In the terahertz band, compared to the millimeter wave (mmWave) band introduced in 5G, the importance of technology that can guarantee the signal reach, that is, the coverage, is expected to increase due to more severe path loss and atmospheric absorption. As major technologies to ensure coverage, new waveforms, beamforming, and massive arrays that are superior in terms of coverage than radio frequency (RF) devices, antennas, orthogonal frequency division multiplexing (OFDM) input and multiple-output (MIMO)), full dimensional MIMO (FD-MIMO), an array antenna, and a multi-antenna transmission technology such as a large scale antenna should be developed. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS) are being discussed to improve the coverage of terahertz band signals.

In addition, in order to improve frequency efficiency and system network, in a 6G communication system, a full duplex technology in which uplink and downlink simultaneously use the same frequency resource at the same time, satellite and Network technology that integrates high-altitude platform stations (HAPS), etc., network structure innovation that supports mobile base stations, etc. and enables optimization and automation of network operation, and dynamic frequency sharing through collision avoidance based on spectrum usage prediction AI-based communication technology that realizes system optimization by utilizing (dynamic spectrum sharing) technology and artificial intelligence (AI) from the design stage and internalizing end-to-end AI support functions, The development of next-generation distributed computing technology that realizes complex services by utilizing ultra-high-performance communication and computing resources (mobile edge computing (MEC), cloud, etc.) is being developed. In addition, through the design of a new protocol to be used in the 6G communication system, the implementation of a hardware-based security environment, the development of mechanisms for the safe use of data, and the development of technologies for maintaining privacy, the connectivity between devices is further strengthened and the network is further enhanced. Attempts to optimize, promote the softwareization of network entities, and increase the openness of wireless communication continue.

Due to the research and development of this 6G communication system, the next hyper-connected experience (the next hyper-connected) through the hyper-connectivity of the 6G communication system, which includes not only the connection between objects but also the connection between people and objects. experience) is expected to become possible. Specifically, the 6G communication system is expected to provide services such as true immersive extended reality (XR), high-fidelity mobile hologram, and digital replica. In addition, services such as remote surgery, industrial automation, and emergency response through security and reliability enhancement are provided through the 6G communication system, so it is applied in various fields such as industry, medical care, automobiles, and home appliances. will be

A device that adjusts the amplitude and phase of a signal when performing beamforming is called a beamformer. The method of applying the beamformer at the radio frequency (RF) stage can be called analog beamforming, and the method applied by the baseband modem can be called digital beamforming.

In addition, in order to combine the advantages of digital beamforming and analog beamforming, digital beamforming is performed based on channel state information (CSI: 　channel 　 state information) in the baseband, and then the analog beam is passed through a radio frequency chain. Hybrid beamforming, a technology for forming, is also being used.

However, in the hybrid beamforming, when the base station determines the analog reception beam of the base station, the interference of channels of each terminal is not considered and the digital transmission beams of the terminals are not taken into account. Accordingly, when the digital transmission beams of the terminals are changed, the channel gain through the analog reception beam of the base station that has been previously selected may be reduced.

In addition, when the base station determines the digital transmission beam of the terminal, the interference of each channel of the terminals is not considered and the analog reception beam of the base station is not considered. Accordingly, when the analog reception beam of the base station is changed, there is a problem in that the channel gain through the digital transmission beam of the terminals that have already been selected is reduced.

The present disclosure has been devised to solve the above problems, and an object of the present disclosure is to organically determine a set of terminals to be scheduled in an arbitrary slot, a digital transmission beam of the terminals, and an analog reception beam of a base station.

A method performed by a base station of a wireless communication system of the present disclosure for solving the above problems includes: receiving, from terminals, a sounding reference signal (SRS); estimating an uplink digital channel for each of the terminals by using the SRS; determining, by using the estimated uplink digital channel, an analog reception beam of the base station for each of the terminals, a digital transmission beam for each of the terminals, and a set of terminals to be scheduled in an arbitrary slot; and transmitting information on the determined digital transmission beam to the scheduled terminals, wherein the digital transmission beam for each of the terminals considers the estimated uplink digital channel and the analog reception beam of the base station. to be determined.

In addition, a method performed by a terminal of a wireless communication system according to another embodiment of the present disclosure includes: transmitting, to a base station, a sounding reference signal (SRS); receiving, from the base station, information on a digital transmission beam; and transmitting data to the base station by using a digital transmit beam corresponding to the information on the digital transmit beam, wherein the digital transmit beam includes an uplink digital channel estimated by the base station and a function of the base station. It is characterized in that it is determined in consideration of the analog reception beam.

In addition, a base station of a wireless communication system according to another embodiment of the present disclosure includes a transceiver; and receiving a sounding reference signal (SRS) from the terminals through the transceiver, estimating an uplink digital channel for each of the terminals using the SRS, and using the estimated uplink digital channel, Determines a set of terminals to be scheduled in an analog reception beam of the base station for each of the terminals, a digital transmission beam for each of the terminals, and a set of terminals to be scheduled in an arbitrary slot, and sends the determined digital transmission beam to the scheduled terminals. The information is transmitted through the transceiver, and the digital transmission beam for each of the terminals includes a control unit that is determined in consideration of the estimated uplink digital channel and the analog reception beam of the base station.

In addition, the terminal of the wireless communication system according to another embodiment of the present disclosure includes a transceiver; and transmitting a sounding reference signal (SRS) to the base station through the transceiver, and receives information on the digital transmission beam from the base station through the transceiver, and provides the base station with digital information corresponding to the digital transmission beam information. Transmitting data through the transceiver using a transmission beam, wherein the digital transmission beam comprises a control unit determined in consideration of an uplink digital channel estimated by the base station and an analog reception beam of the base station do.

According to an embodiment of the present disclosure, there is an effect of organically determining a set of terminals to be scheduled in an arbitrary slot, a digital transmission beam of terminals, and an analog reception beam of a base station, and an analog reception beam of a base station with better performance and A digital transmission beam of the terminal may be selected.

In addition, when there is channel reciprocity, the same effect can be obtained by using channel reciprocity.

1 is a diagram illustrating a wireless communication system according to an embodiment of the present disclosure.

2 is a diagram illustrating a scenario in which an operation embodiment of a base station and a terminal is determined in consideration of channel reciprocity and power of a terminal in a wireless communication system according to an embodiment of the present disclosure.

3 is a diagram illustrating an operation sequence of a base station and a terminal in the wireless communication system according to the first embodiment of the present disclosure.

4 is a diagram illustrating an operation sequence of a base station and a terminal in a wireless communication system according to a second embodiment of the present disclosure.

5 is a diagram illustrating an operation sequence of a base station in the wireless communication system according to the first embodiment of the present disclosure.

6 is a diagram illustrating an operation sequence of a terminal in the wireless communication system according to the first embodiment of the present disclosure.

7 is a diagram illustrating an operation sequence of a base station in a wireless communication system according to a second embodiment of the present disclosure.

8 is a diagram illustrating an operation sequence of a terminal in a wireless communication system according to a second embodiment of the present disclosure.

9 is a diagram illustrating a method of organically determining a set of terminals to be scheduled in an analog reception beam of a base station, a digital transmission beam of terminals, and an arbitrary slot in a wireless communication system according to an embodiment of the present disclosure.

10 is a diagram illustrating a tabu search algorithm used to determine an analog reception beam of a base station and a digital transmission beam of terminals in a wireless communication system according to an embodiment of the present disclosure.

11 is a diagram illustrating an example of a third party search algorithm in a wireless communication system according to an embodiment of the present disclosure.

12 is a diagram illustrating a semi-orthogonal user scheduling (SUS) algorithm used to determine a set of terminals to be scheduled in an arbitrary slot in a wireless communication system according to an embodiment of the present disclosure.

13 is a block diagram illustrating an internal structure of a terminal according to an embodiment of the present disclosure.

14 is a block diagram illustrating an internal structure of a base station according to an embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

In describing the embodiments, descriptions of technical contents that are well known in the technical field to which the present disclosure pertains and are not directly related to the present disclosure may be omitted. This is to more clearly convey the gist of the present disclosure without obscuring the gist of the present disclosure by omitting unnecessary description.

For the same reason, some components may be exaggerated, omitted, or schematically illustrated in the accompanying drawings. In addition, the size of each component may not fully reflect the actual size. The same reference numbers may be assigned to the same or corresponding elements in each figure.

Advantages and features of the present disclosure, and a method for achieving them may become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. The present disclosure is not limited to the embodiments disclosed below, and may be implemented in various different forms. Only the present embodiments are provided so that the disclosure of the present disclosure is complete, and to fully inform those of ordinary skill in the art to which the present disclosure belongs, the scope of the disclosure, and the present disclosure is defined by the scope of the claims can be Like reference numerals may refer to like elements throughout.

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It may also be possible for the functions recited in blocks to occur out of order in some alternative implementations. For example, two blocks shown one after another may be performed substantially simultaneously, or the blocks may sometimes be performed in the reverse order according to a corresponding function.

At this time, the term '~ unit' used in an embodiment of the present disclosure means software or hardware components such as FPGA or ASIC, and '~ unit' may perform certain roles. However, '~ part' may not mean limited to software or hardware. '~' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Accordingly, as an example, '~' indicates components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to play one or more CPUs in a device or secure multimedia card. Also, in an embodiment, '~ unit' may include one or more processors.

For convenience of description below, the present disclosure may use terms and names defined in the 3rd generation partnership project long term evolution (3GPP LTE) standard. However, the present disclosure is not limited by the terms and names, and may be equally applied to systems conforming to other standards.

Beam sweeping may refer to a method of covering the entire cell area while changing a beam by changing a direction to cover one wide cell area using analog beamforming. In order to select an analog beam from a hybrid beam composed of an analog beam and a digital beam, the base station or the terminal may transmit a reference signal (RS) while changing the analog beam.

When the base station determines the analog reception beam of the base station, the plurality of terminals may transmit a reference signal to the base station, and the base station may receive the reference signal while changing the analog reception beam. Thereafter, the base station may determine the analog reception beam of the base station by using at least one of a received signal strength indicator (RSSI), reference signal received quality (RSRQ), and reference signals received power (RSRP) through the received reference signal.

However, when the base station determines the analog reception beam, it does not consider the interference of each channel of the terminals and does not consider the digital transmission beams of the terminals. Accordingly, when the digital transmission beams of the terminals are changed, the channel gain through the analog reception beam of the base station that has been previously selected may be reduced.

In addition, when the base station determines the digital transmission beam of the terminal, the plurality of terminals may transmit a sounding reference signal (SRS) to the base station, and the base station may estimate the channel of each terminal using the received SRS. . The base station may determine the digital transmission beams of the terminals through the estimated channel. The base station may transmit digital transmission beam information for the terminals to the terminals through a transmitted precoding matrix indicator (TPMI), and the terminals transmit data to the base station using a digital transmission beam corresponding to the received digital transmission beam information. can do.

However, when the base station determines the digital transmission beam of the terminal, the interference of channels of each terminal is not considered and the analog reception beam of the base station is not considered. Accordingly, when the analog reception beam of the base station is changed, the channel gain through the digital transmission beam of the terminals that have already been selected may be reduced.

In order to solve this problem, according to an embodiment of the present disclosure, there is an effect of organically determining a set of terminals to be scheduled in an arbitrary slot, a digital transmission beam of the terminals, and an analog reception beam of a base station, and a channel gain It is possible to determine the better analog reception beam of the base station and the digital transmission beam of the terminal.

Hereinafter, operations of the base station and the terminal according to the first and second embodiments of the present invention for solving the above object will be described in detail with reference to the drawings.

Referring to FIG. 1 , a wireless network environment in a wireless communication system may include a plurality of terminals 120 and a base station 110 . Depending on the network type, the base station 110 may include an inode ratio (“eNodeB” or “eNB”), a 5 ^th generation node B, a transmission reception point (TRP) in addition to a “base station”. may be used instead. Also for convenience, the base station 110 may be used to mean network infrastructure components that provide wireless access to remote terminals in the following description. In addition, depending on the network type, the terminal 120 is a "mobile station", "subscriber station", "remote terminal", " Other well-known terms such as "wireless terminal", or "user device" may be used.

The wireless network environment includes a downlink that is a link from the base station 110 to the terminals 120 and an uplink that is a link from the terminals 120 to the base station 110 . can do.

The base station 110 may include a plurality of antennas 116 . The base station 110 may perform transmission through downlink or reception through uplink through the antenna 116 . That is, the antenna 116 may be a transmission/reception (TX/RX) common antenna. Also, the terminals 120 may include a plurality of antennas 126 . The antenna 126 may be a transmit/receive (TX/RX) common antenna.

In FIG. 1 , the antennas of the base station 110 and the terminals 120 have been described as a common transmission/reception antenna, but the present invention is not limited thereto. Accordingly, the base station 110 and the terminals 120 according to various embodiments of the present disclosure may not include a common transmit/receive antenna. In other words, the base station 110 and the terminals 120 may include a transmission antenna and a reception antenna physically separated.

The base station 110 may transmit downlink data to the terminals 120 through the antenna 116 . The base station 110 may determine any one downlink transmission beam from among a plurality of downlink transmission beams having different directions for transmission of downlink data. Also, the base station 110 may use the uplink beam search result for a downlink beam search procedure. In other words, the base station 110 may determine a beam used for uplink reception as a downlink transmission beam by using channel reciprocity.

Also, the base station 110 may receive uplink data from the terminals 120 through the antenna 116 . The base station 110 may determine any one uplink reception beam from among a plurality of uplink reception beams having different directions in order to receive uplink data. Also, the base station 110 may use a downlink beam search result for an uplink beam search procedure. In other words, the base station 110 may determine a beam used for downlink transmission as an uplink reception beam by using channel reciprocity.

The terminals 120 may transmit uplink data to the base station 110 through the antenna 126 . The terminals 120 may determine any one uplink transmission beam from among a plurality of uplink transmission beams having different directions for transmission of uplink data. Also, the terminals 120 may use the downlink beam search result for the uplink beam search procedure. In other words, the terminals 120 may determine a beam used for downlink reception as an uplink transmission beam by using channel reciprocity.

Also, the terminals 120 may receive downlink data from the base station 110 through the antenna 126 . In order to receive downlink data, the terminals 120 may determine any one downlink reception beam from among a plurality of downlink reception beams having different directions. Also, the terminals 120 may use the uplink beam search result for a downlink beam search procedure. In other words, the terminals 120 may determine a beam used for uplink transmission as a downlink reception beam by using channel reciprocity.

Beamforming may mean modulating the amplitude and phase of a signal transmitted and received by each antenna in a state in which a plurality of antenna patterns are overlapped. Through beamforming, a signal may be strongly transmitted and received in a specific direction, and a signal may be transmitted/received weakly in other directions. That is, signals transmitted and received from a plurality of antennas may be operated as beams in a specific direction, and signals may be transmitted/received strongly by operating as if a single antenna. Through this, cell coverage can be expanded and transmission speed can be improved.

In beamforming, a device that adjusts the amplitude and phase of a signal may be referred to as a beamformer. Analog beamforming (analog　beamforming, 114) refers to a method of adjusting the beamformer in the RF (radio frequency)

chain

118, 128, and digital beamforming (digital　beamforming, 112, 122) is to convert the beamformer to baseband ( baseband) refers to the method controlled by the modem.

In the analog beamforming 114, since the beamformer operates in the

RF chains

118 and 128, a beam cannot be formed in several directions at the same time, but can transmit and receive only in a specific direction. In addition, regardless of the number of antennas, only one transceiver is required to transmit a signal to the baseband modem, so hardware resources required for implementation may be less and baseband processing may be simple. Therefore, it is easier to implement compared to digital beamforming, and power consumption and implementation cost may be low.

In the digital beamforming (112, 122), the beamformer operates in a baseband modem, and the RF chain (118, 128) and the antenna can transmit/receive a signal to which beamforming is applied in the baseband. Therefore, when multiple users in a cell are in different locations, beamforming for each user can be separately applied through baseband signal processing. In the case of LTE and 5G wireless communication systems using an orthogonal frequency division multiple access (OFDMA: 　orthogonal 　 frequency division 　 multiple access) method, beamforming may be applied by allocating different frequency resources for each user in a cell. Therefore, beamforming may be possible for several users at the same time, and in this case, digital beamforming may be used more flexibly than analog beamforming. On the other hand, since the number of transceivers that transmit signals from each antenna to the baseband modem through the RF chain is as many as the number of antennas, it may require more hardware resources than analog beamforming and baseband processing may be complicated.

Accordingly, hybrid beamforming combining the advantages of the

digital beamforming

112 and 122 and the analog beamforming 114 may be used. As shown in FIG. 1, the beamformer operates on the RF chain and the baseband modem to perform digital beamforming (112, 122) based on channel state information (CSI: channel state information) in the baseband, and analog beamforming through the RF chain (114) techniques can be used.

Also, in FIG. 1 , the number of terminals 120 is X in total, and the number of scheduled terminals may be K. The terminals 120 are

Antenna 126 can be used, and the base station 110

Antenna 116 may be used.

In addition, the base station 110 may use M RF chains 118 , and the analog channel 130 between the k-th terminal 120 and the base station 110 is

may be, and the digital transmission beam 122 of the k-th terminal 120 is

can be

In addition, it may be said that the number of analog reception beams that the base station can select is N. The analog reception beam 114 of the m-th RF chain 118 of the base station is

may be, and each RF chain 118 has a selectable analog receive beam.

can be thus,

may be, and the entire analog reception beam 114 may be represented by the following [Equation 1].

In addition, the digital channel between the k-th terminal 120 and the base station 110 is

may be defined, and the effective channel between the k-th terminal 120 and the base station 110 may be defined by the following [Equation 2].

The number determined above is an arbitrary number, and the present disclosure is not limited to the number described above.

Referring to FIG. 2 , operations of a base station and a terminal using channel reciprocity and operations of a base station and a terminal not using channel reciprocity can be divided according to whether channel reciprocity is used or not.

In an environment where it is difficult to use channel reciprocity, an operation of organically determining a set of terminals to be scheduled in an arbitrary slot, digital transmission beams of terminals, and analog reception beams of the base station by estimating an uplink data channel in the base station (first example) can be done.

The base station can determine whether the available transmit power for the terminals to repeatedly transmit the SRS is sufficient, and when the available transmit power is not sufficient, the terminals estimate the downlink digital channel and use the channel reciprocity, The base station may perform an operation (the second embodiment) of organically determining a set of terminals to be scheduled in an arbitrary slot, a digital transmission beam of the terminals, and an analog reception beam of the base station

According to FIG. 2 , the base station may determine 210 whether channel reciprocity can be used by the base station and the terminal. When channel reciprocity cannot be used, the base station and the terminal may operate as in the first embodiment 231 . When channel reciprocity is available, the base station may receive a report on available power headroom (PH) capable of repeatedly transmitting SRS from UEs, and corresponds to the case where the available transmission power is greater than a specific value. It can be determined 220 whether or not. When the available transmission power of the terminals is greater than a specific value, the base station and the terminal may operate as in the first embodiment 231, and when the available transmission power of the terminals is less than a specific value, the second embodiment 233 ), the base station and the terminal can operate. Specific operations of the first and second embodiments will be described below.

Whether or not channel reciprocity can be used 210 may be determined according to a wireless communication environment. Examples of the wireless communication environment may include a time division duplex (TDD) communication environment, a frequency division duplex (FDD) communication environment, and the like.

Since the TDD communication environment is a method in which uplink transmission and downlink transmission are divided and transmitted in the time domain, uplink and downlink may exist in the same frequency band. In such a TDD communication environment, if the coherence time (a time during which a channel can be assumed to be constant) is sufficiently long, it can be assumed that the channels of the uplink and the downlink are the same, and the base station and the terminal can use channel reciprocity. Conversely, when the coherence time is short in the TDD communication environment, since it may not be possible to assume that the channels of the uplink and the downlink are the same, the base station and the terminal may not be able to use channel reciprocity.

In addition, the FDD communication environment is a method in which uplink transmission and downlink transmission are divided and transmitted in the frequency domain. Therefore, since the frequency bands of the uplink and the downlink are different from each other, it may not be possible to assume that the channels are the same, and channel reciprocity may not be available.

The method for determining the channel reciprocity is not limited to the above case.

In relation to the case 220 when the base station determines whether the available transmit power (PH) at which the terminals can repeatedly transmit the SRS is greater than a specific value (220), the terminals report to the base station the available transmit power (PH) of the terminals can do. The available transmit power (PH) of the terminals may be obtained by subtracting the power (Ppusch+Ppucch) currently used for the uplink of the terminals from the maximum transmit power (Pc,max) of the terminals. Through this, the base station can determine whether the available transmission power at which the terminals can repeatedly transmit the SRS is greater than a specific value.

3 is an operation sequence for organically determining a set of terminals 120 to be scheduled in an arbitrary slot in uplink transmission, a digital transmission beam of the terminals 120, and an analog reception beam of the base station 110 As such, a detailed description of each operation is as follows.

In step S310 , the base station 110 may transmit a control message to the terminals 120 to instruct the terminals 120 to repeatedly transmit a sounding reference signal (SRS) to the base station 110 .

Upon receiving the control message, the terminals 120 repeatedly transmit a sounding reference signal (SRS) to the base station 110 in the uplink direction in step S312, and the base station 110 transmits an analog reception beam.

SRS can be received by changing .

The base station 110 in step S314, a digital channel including the analog reception beam of the base station 110

can be estimated. In addition, the base station 110 uses the estimated digital channels, a digital transmit beam for each of the terminals 120 , an analog receive beam of the base station 110 , and a set of terminals 120 to be scheduled in an arbitrary slot. can be organically determined through a tabu search algorithm and a semi-orthogonal user selection (SUS) algorithm.

In step S316 , the base station 110 may transmit information on the scheduled digital transmission beams of the terminals 120 to the corresponding terminals through a transmitted precoding matrix indicator (TPMI).

Upon receiving the information on the digital transmission beam, the terminals 120 apply a precoding matrix corresponding to the received TPMI to the complex symbol generated according to the type of signal or the state of the channel in step S318 to the base station 110 data can be transmitted.

The complex symbol may be modulated using a method such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), or 16QAM/64QAM (quadrature amplitude modulation) according to a signal type or channel state. The modulated complex symbol may be multiplied by a precoding matrix and assigned to an antenna, and the processed transmission signal is each time-mapped to a frequency resource element and then an orthogonal frequency division multiple access (OFDMA) signal generator. can be transmitted through each antenna.

4 illustrates a process in which a base station organically determines a set of terminals 120 to be scheduled in an arbitrary slot, a digital transmit beam of the terminals 120, and an analog receive beam of the base station 110 using channel reciprocity. As illustrated, a detailed description of each operation is as follows.

In step S410, the base station 110 transmits an analog transmission beam of a CSI-RS (channel state information-reference signal) in the downlink direction.

can be transmitted to the terminal by changing

Each terminal receiving the CSI-RS

In step S412, 120 may obtain downlink digital channel information (CSI). CSI includes CQI (channel quality information), PMI (precoding matrix indicator), CRI (CSI-RS resource indicator) SSBRI (SS / PBCH resource block indicator), LI (layer indicator), RI (rank indicator) or L1-RSRP ( There may be several components such as reference signal received power). The terminal uses CSI, and a downlink digital channel including an analog transmission beam of the base station 110

can be estimated In addition, through a physical uplink shared channel (PUSCH) or a physical uplink control channel (PUCCH), each terminal 120 transmits a downlink digital channel including an analog transmission beam of the base station 110 .

may be transmitted to the base station 110 .

In step S414 , the base station 110 may convert the downlink digital channel into an uplink digital channel using channel reciprocity, and may convert the downlink analog transmission beam of the base station 110 into an uplink reception beam. . The base station 110 uses the converted digital channels, a digital transmit beam for each of the terminals 120, an analog receive beam of the base station 110, and a set of terminals 120 to be scheduled in an arbitrary slot. can be organically determined through a tabu search algorithm and a semi-orthogonal user selection (SUS) algorithm.

In step S416 , the base station 110 may transmit information on the scheduled digital transmission beams of the terminals 120 to the corresponding terminals through a transmitted precoding matrix indicator (TPMI).

The terminals 120 receiving the information on the digital transmission beam apply a precoding matrix corresponding to the received TPMI to the complex symbol generated according to the type of signal or the state of the channel in step S418 to the base station 110 data can be transmitted.

Referring to FIG. 5 , a flowchart of a detailed operation of a base station in the first embodiment is shown, and each step is divided and expressed as follows.

In step S510 , the base station 110 may transmit a control message for SRS transmission to the terminals 120 to instruct the terminals 120 to repeatedly transmit the SRS to the base station 110 .

The base station 110 in step S520, the analog reception beam from the terminals

SRS can be received by changing . And the base station 110 in step S530, a digital channel including the analog reception beam of the base station 110

can be estimated.

The base station 110 uses the estimated digital channels in step S540, a digital transmit beam for each of the terminals 120, an analog receive beam of the base station 110, and the terminals 120 to be scheduled in an arbitrary slot. can be organically determined through the tabu search algorithm and the semi-orthogonal user selection (SUS) algorithm. In step S550 , the base station 110 may transmit information on the digital transmission beam to the scheduled terminals through the TPMI. And, in step S560, the base station 110 may receive data from the terminals to be scheduled in any slot, and the data is determined by the base station 110 according to an embodiment of the present invention, and is transmitted to the TPMI notified to the terminal. It is transmitted based on

Referring to FIG. 6 , a flowchart of a specific terminal operation in the first embodiment is shown, and each step is divided and expressed as follows.

The terminal 120 may receive a control message for SRS transmission from the base station in step S610. Using the control message, the terminal 120 may repeatedly transmit the SRS to the base station in step S620.

In step S630 , the terminal 120 may receive information about the digital transmission beam from the base station through the TPMI. The information on the digital transmission beam is determined by the base station, and is to be scheduled in a digital transmission beam for each of the terminals 120, an analog reception beam of the base station 110, and an arbitrary slot using estimated digital channels. The set of terminals 120 is organically determined through a tabu search algorithm and a semi-orthogonal user selection (SUS) algorithm.

Upon receiving the information on the digital transmission beam, the terminal 120 applies a precoding matrix corresponding to the received TPMI to the complex symbol generated according to the type of signal or the state of the channel in step S640 to the base station 110. data can be transmitted.

Referring to FIG. 7 , a flowchart of a detailed operation of a base station in the second embodiment is shown, and each step is divided and expressed as follows.

In step S710, the base station 110 transmits the CSI-RS to the terminals as an analog transmission beam.

can be transmitted to the terminal by changing And, the base station 110, in step S720, a downlink digital channel including the analog transmission beam of the base station 110 through PUSCH or PUCCH.

can receive

In step S730 , the base station 110 may convert the downlink digital channel into an uplink digital channel using channel reciprocity, and may convert the downlink analog transmission beam of the base station 110 into an uplink reception beam. .

In step S740, the base station 110 uses the converted digital channels, the digital transmit beam for each of the terminals 120, the analog receive beam of the base station 110, and the terminals 120 to be scheduled in an arbitrary slot. ) can be organically determined through a tabu search algorithm and a semi-orthogonal user selection (SUS) algorithm.

In step S750 , the base station 110 may transmit information on the digital transmission beam of the scheduled terminals 120 to the corresponding terminals through a transmitted precoding matrix indicator (TPMI).

The base station 110 may receive data from the terminals to be scheduled in the arbitrary slot in step S760, and the data is determined by the base station 110 according to an embodiment of the present invention and based on the TPMI notified to the terminal will be transmitted.

Referring to FIG. 8 , a flowchart of a specific terminal operation in the second embodiment is shown, and each step is divided and expressed as follows.

The terminal 120 may receive the CSI-RS from the base station in step S810. Then, in step S820 , the terminal 120 may obtain downlink digital channel information (CSI) through the received CSI-RS. CSI includes CQI (channel quality information), PMI (precoding matrix indicator), CRI (CSI-RS resource indicator) SSBRI (SS / PBCH resource block indicator), LI (layer indicator), RI (rank indicator) or L1-RSRP ( There may be several components such as reference signal received power). The terminal uses CSI, and a downlink digital channel including an analog transmission beam of the base station 110

can be estimated

In step S830, the terminal 120 sends a downlink digital channel including an analog transmission beam of the base station 110 to the base station 110 through PUSCH or PUCCH.

can be sent.

In step S840, the terminal 120 may receive information on the digital transmission beam from the base station through the TPMI. The information on the digital transmission beam is determined by the base station 110, and a digital transmission beam for each of the terminals 120, an analog reception beam of the base station 110, and an arbitrary slot using estimated digital channels. The set of terminals 120 to be scheduled in . is organically determined through a tabu search algorithm and a semi-orthogonal user selection (SUS) algorithm.

Upon receiving the information on the digital transmission beam, the terminal 120 applies a precoding matrix corresponding to the received TPMI to the complex symbol generated according to the type of signal or the state of the channel in step S850 to the base station 110 . data can be transmitted.

Referring to FIG. 9 , in the first and second embodiments, a specific method for determining an analog reception beam of a base station, a digital transmission beam of terminals, and a set of terminals to be scheduled in an arbitrary slot is disclosed.

As a first step, the base station may select an analog reception beam of the base station using the estimated digital channel.

The initial value of the analog reception beam 114 may be selected based on a value at which the digital channel gain is the maximum, and the equation for selecting the analog reception beam having the maximum digital channel gain is as shown in Equation 3 below.

In [Equation 3], X represents the total number of terminals sharing time and frequency resources,

denotes an analog channel between the k-th terminal and the base station,

is the analog reception beam of the base station,

denotes a digital channel between the k-th terminal and the base station.

In a second step, the base station may select a digital transmit beam for each of the terminals using the estimated digital channel and the analog receive beam of the base station.

The effective channel by multiplying the digital channel of each terminal by the digital transmission beam of the terminal

can be formed, and the digital transmission beam of the terminal that maximizes the gain of the effective channel can be obtained. The following [Equation 4] shows an expression for this.

In the above [Equation 4],

is the digital transmission beam of the k-th terminal,

denotes an effective channel between the k-th terminal and the base station.

In a third step, the base station may select a set of terminals to be scheduled in an arbitrary slot in consideration of the estimated digital channel, the analog receive beam of the base station, and the digital transmit beam. The base station may determine a set of terminals to be scheduled in an arbitrary slot by using a semi-orthogonal user selection (SUS) technique for an effective channel. SUS is a technique of selecting a set of terminals having a corresponding parameter equal to or greater than a preset reference value by comparing orthogonality of effective channel vectors of each terminal to each other through a parameter. [Equation 5] below shows an expression for an effective channel.

In a fourth step, the base station may select the analog reception beam of the base station again from a sum-rate point of view using a tabu search algorithm. The taboo search algorithm is an algorithm that compares the current solution with neighboring candidate groups and updates it, and prevents repeated finding of the same solution, which will be described below.

As the fifth step, the third to fourth steps can be repeated as many times as the inner iteration number. (910)

As the sixth step, the second to fifth steps can be repeated as many times as the number of outer iterations. (920)

The taboo search algorithm is an algorithm for solving a given optimization problem regardless of the type of optimization problem. Since existing optimization algorithms basically operate based on neighboring solution search, there may be a characteristic of proceeding only in the direction of improvement of the current solution. Due to this characteristic, it is possible to frequently converge to a local optimum. In order to solve the problem of convergence to such a local optimal point, the other search algorithm can separately store information about the local optimal point, and can avoid the local optimal point based on this information. In this case, the information on the local optimum may be referred to as tabu. In other words, it is an algorithm that updates the current solution by comparing it with neighboring candidate groups, and it is possible to avoid falling into local optimization by repeatedly searching for the same solution.

Referring to FIG. 11 , a process of finding an optimal solution using the other search algorithm may be as follows. Candidate optimal solution, updated from candidate solution 1 (1151) to candidate solution 2 (1153) in Region 1 (1110), updated to candidate solution 3 (1155) in Region 2 (1120), and candidate solution in Region 3 (1130) Year 4 (1157) may be updated. As the optimal solution in Region 4 (1140), it may be possible with candidate solution 1 (1151) and candidate solution 5 (1159). Convergence to the local optimal solution can be avoided by searching for candidate solutions excluding the optimal solution in the tabular list of .

Referring to FIG. 10 , a flowchart of a search algorithm for other parts may be known.

The other search algorithm may go through an initialization step in step S1010. An initial candidate solution may be set, p indicating the current number of taboo list checks may be set to 0, and an i value indicating the current number of iterations may be set to 0. In addition, parameters M (maximum number of repetitions) and P (length of taboo list) to be compared can be set. These values are arbitrary values and are not limited to the values described above.

In addition, the other search algorithm may find a neighboring solution of the determined candidate solution in step S1020.

The taboo search algorithm may select the most optimal solution from among the found neighboring solutions in step S1030 and determine whether it is more optimal than a solution in the existing taboo list. If it is determined that the new candidate solution is the optimal solution, it may be set as the new candidate solution. Since the candidate solution is newly updated, the number of current taboo list checks (p) can be increased by one.

In addition, in step S1040, the other search algorithm may determine whether the current number of other part list checks (p) is greater than a predetermined P (length of the other part list). This is because the number of candidate solutions that can be stored in the taboo list is set to P.

In the taboo search algorithm, in step S1050, if the current taboo list check count (p) is greater than a predetermined P (length of the taboo list), the first stored candidate solution among the candidate solutions stored in the existing taboo list is deleted, A new candidate solution can be stored. This may be done according to a first-in-first-out method.

In addition, the taboo search algorithm may store the new candidate solutions in the taboo list in order in step S1060.

The taboo search algorithm may increase the current number of iterations (i) by 1 in step S1070.

The other search algorithm may determine whether the current number of repetitions is greater than the maximum number of repetitions in step S1080. If the current number of repetitions is greater than the maximum number of repetitions, the search is terminated, and if the current number of repetitions is smaller than the maximum number of repetitions, steps S1020 to S1080 may be performed again.

Referring to FIG. 12 , the set of terminals may be estimated by using the SUS algorithm in consideration of the influence of interference between channels between the terminals and the base station. The steps of the SUS algorithm are as follows.

The SUS algorithm may select a user having the highest channel gain in step S1210 and add it to the user set U.

In step S1220, the SUS algorithm determines the size of the channel and semi-orthogonality component for U (

) can be added to U by selecting the largest user.

In the SUS algorithm, in step S1230, the number of users is smaller than a specific value (K), and the size of the component (

) is greater than a specific value (L). The number of users is less than a certain value (K), and the size of the component (

) is greater than the specific value L, step 1220 may be performed again. If the number of users is greater than a certain value (K), or the size of the component (

) is less than the specific value L, the corresponding operation may be terminated.

Through this, it is possible to estimate a set of terminals considering the influence of orthogonality and interference between channels between the terminals and the base station.

According to an embodiment of the present disclosure, there is an effect of organically determining a set of terminals to be scheduled in an arbitrary slot, a digital transmission beam of the terminals, and an analog reception beam of a base station, and an analog reception beam of a base station having a better channel gain and a digital transmission beam of the terminal may be determined.

Referring to FIG. 13 , the terminal may include a transceiver 1310 , a controller 1320 , and a storage 1330 . In the present disclosure, the controller may be defined as a circuit or an application specific integrated circuit or at least one processor.

The transceiver 1310 may transmit/receive signals to and from other network entities. The transceiver 1310 may transmit system information to, for example, a base station, and may transmit a synchronization signal or a reference signal.

The controller 1320 may control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the controller 1320 may control a signal flow between blocks to perform an operation according to the procedure described above with reference to FIGS. 1 to 12 . Specifically, the controller 1320 may control the operation proposed by the present disclosure in the wireless communication system according to the embodiment of the present disclosure.

The storage unit 1330 may store at least one of information transmitted/received through the transceiver 1310 and information generated through the control unit 1320 . For example, the storage unit 1330 may store information according to the above-described embodiment.

Referring to FIG. 14 , the base station may include a transceiver 1410 , a controller 1420 , and a storage 1430 . In the present disclosure, the controller may be defined as a circuit or an application specific integrated circuit or at least one processor.

The transceiver 1410 may transmit/receive signals to and from other network entities. The transceiver 1410 may transmit system information to, for example, a base station, and may transmit a synchronization signal or a reference signal.

The controller 1420 may control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the controller 1420 may control a signal flow between blocks to perform an operation according to the procedure described above with reference to FIGS. 1 to 12 . Specifically, the controller 1420 may control the operation proposed by the present disclosure in the wireless communication system according to the embodiment of the present disclosure.

The storage unit 1430 may store at least one of information transmitted/received through the transceiver 1410 and information generated through the control unit 1420 . For example, the storage unit 1430 may store information according to the above-described embodiment.

Methods according to the embodiments described in the claims or specifications of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in a computer-readable storage medium may be configured to be executable by one or more processors in an electronic device. One or more programs may include instructions for causing an electronic device to execute methods according to embodiments described in a claim or specification of the present disclosure.

Such programs (software modules, software) include random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable ROM (EEPROM: electrically erasable programmable read only memory), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs), or other types of It may be stored in an optical storage device or a magnetic cassette. Alternatively, it may be stored in a memory composed of a combination of some or all thereof. In addition, each configuration memory may be included in plurality.

In addition, the program accesses through a communication network consisting of a communication network such as the Internet, an intranet, a local area network (LAN), a wide LAN (WLAN), or a storage area network (SAN), or a combination thereof. It may be stored in an attachable storage device that can be accessed. Such a storage device may be connected to a device implementing an embodiment of the present disclosure through an external port. In addition, a separate storage device on the communication network may be connected to the device implementing the embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, elements included in the disclosure are expressed in the singular or plural according to the specific embodiments presented. However, the singular or plural expression is appropriately selected for the context presented for convenience of description, and the present disclosure is not limited to the singular or plural component, and even if the component is expressed in plural, it is composed of the singular or singular. Even an expressed component may be composed of a plurality of components.

On the other hand, the embodiments of the present disclosure disclosed in the present specification and drawings are only presented as specific examples to easily explain the technical content of the present disclosure and help the understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is apparent to those of ordinary skill in the art to which the present disclosure pertains that other modified examples can be implemented based on the technical spirit of the present disclosure. In addition, each of the above embodiments may be operated in combination with each other as needed. For example, the base station and the terminal may be operated by combining parts of one embodiment and another embodiment of the present disclosure. For example, a base station and a terminal may be operated by combining parts of a plurality of embodiments of the present disclosure. In addition, although the above embodiments have been presented based on the FDD LTE system, other modifications based on the technical idea of the embodiment may be implemented in other systems such as the TDD LTE system, 5G or NR system.

Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.

Claims

A method performed by a base station of a wireless communication system, comprising:

Receiving a sounding reference signal (SRS) from the terminals;

estimating an uplink digital channel for each of the terminals by using the SRS;

determining, by using the estimated uplink digital channel, an analog reception beam of the base station for each of the terminals, a digital transmission beam for each of the terminals, and a set of terminals to be scheduled in an arbitrary slot; and

and transmitting information on the determined digital transmission beam to the scheduled terminals.
The method of claim 1, wherein the analog reception beam of the base station for each of the terminals is determined in consideration of the estimated uplink digital channel and

The digital transmission beam for each of the terminals is determined in consideration of the estimated uplink digital channel and the analog reception beam of the base station for each of the terminals, and

The set of terminals to be scheduled is determined in consideration of the estimated uplink digital channel, an analog reception beam of the base station for each of the terminals, and a digital transmission beam for each of the terminals.
3. The method of claim 2, wherein the analog reception beam of the base station for each of the terminals and the digital transmission beam for each of the terminals are determined based on a tabu search algorithm, and

The set of terminals to be scheduled is determined based on a semi-orthogonal user selection (SUS) algorithm.
According to claim 3, wherein the search algorithm for determining the analog reception beam of the base station for each of the terminals and a digital transmission beam for each of the terminals,

[Equation 6]

[Equation 6]

determines the analog reception beam with the maximum digital channel gain using
represents the analog channel between the k-th terminal and the base station,
represents the analog reception beam of the base station,
represents a digital channel between the k-th terminal and the base station, and

The determined analog reception beam and the following [Equation 7]

[Equation 7]

Determine the digital transmission beam for which the effective channel gain is maximized using
represents the digital transmission beam of the k-th terminal,
is an effective channel between the k-th terminal and the base station.
The method of claim 4, wherein a semi-orthogonal user selection (SUS) algorithm for determining a set of terminals to be scheduled comprises:

Comparing the orthogonality of the effective channels of the terminals and the base station, the method characterized in that the orthogonality determines a set of terminals equal to or greater than a preset reference value.
The method of claim 1, wherein before receiving the SRS,

determining channel reciprocity; and

Further comprising the step of measuring the power of the terminals,

The base station, when there is no channel reciprocity or the power of the terminals is greater than a specific value, the method characterized in that for transmitting the control message for the SRS transmission to the terminal.
7. The method of claim 6,

If there is the channel reciprocity and the power of the terminals is less than a specific value,

transmitting, to the terminals, a channel state information reference signal (CSI-RS);

receiving, from the terminals, downlink digital channel information for each of the terminals;

converting the downlink digital channel information into uplink digital channel information using the channel reciprocity, and converting a downlink analog transmission beam of the base station into an uplink analog reception beam;

determining, by using the uplink digital channel information, an analog reception beam of the base station for each of the terminals, a digital transmission beam for each of the terminals, and a set of terminals to be scheduled in an arbitrary slot; and

and transmitting information on the determined digital transmission beam to the scheduled terminals.
8. The method of claim 7,

The analog reception beam of the base station for each of the terminals is determined in consideration of the uplink digital channel information,

The digital transmission beam for each of the terminals is determined in consideration of the estimated uplink digital channel and the analog reception beam of the base station for each of the terminals,

The set of terminals to be scheduled is determined in consideration of the estimated uplink digital channel, an analog reception beam of the base station for each of the terminals, and a digital transmission beam for each of the terminals.
The method of claim 1, wherein the information on the digital transmission beam is transmitted through a transmitted precoding matrix indicator (TPMI).
A method performed by a terminal of a wireless communication system, comprising:

transmitting a sounding reference signal (SRS) to the base station;

receiving, from the base station, information on a digital transmission beam; and

Transmitting data to the base station by using a digital transmission beam corresponding to information on the digital transmission beam,

The digital transmit beam is determined in consideration of an uplink digital channel estimated by the base station and an analog receive beam of the base station.
11. The method of claim 10, wherein the analog reception beam of the base station and the digital transmission beam of the terminal are determined based on a tabu search algorithm,

The other search algorithm for determining the analog reception beam of the base station and the digital transmission beam of the terminal,

[Equation 8]

[Equation 8]

determines the analog reception beam with the maximum digital channel gain using
represents the analog channel between the k-th terminal and the base station,
represents the analog reception beam of the base station,
represents a digital channel between the k-th terminal and the base station, and

The determined analog reception beam and the following [Equation 9]

[Equation 9]

Determine the digital transmission beam for which the effective channel gain is maximized using
represents the digital transmission beam of the k-th terminal,
is an effective channel between the k-th terminal and the base station.
11. The method of claim 10, before transmitting the SRS,

determining channel reciprocity;

measuring the power of the terminal; and

The method further comprising the step of receiving a control message for the SRS transmission from the base station when there is no channel reciprocity or when the power of the terminal is greater than a specific value.
13. The method of claim 12,

If there is the channel reciprocity and the power of the terminal is less than a specific value,

receiving, from the base station, a channel state information reference signal (CSI-RS);

estimating a downlink digital channel for the base station by using the CSI-RS;

transmitting downlink digital channel information to the base station;

receiving, from the base station, information on a digital transmission beam; and

Transmitting data to the base station by using a digital transmission beam corresponding to information on the digital transmission beam,

The digital transmission beam is determined by the base station in consideration of the converted uplink digital channel and the analog reception beam of the base station using the channel reciprocity.
In a base station of a wireless communication system,

transceiver; and

Receiving a sounding reference signal (SRS) from the terminals through the transceiver, estimating an uplink digital channel for each of the terminals using the SRS, and using the estimated uplink digital channel, the Determining an analog reception beam of the base station for each of the terminals, a digital transmission beam for each of the terminals, and a set of terminals to be scheduled in an arbitrary slot, and information on the determined digital transmission beam to the scheduled terminals Base station, characterized in that it comprises a control unit for transmitting through the transceiver.
In the terminal of a wireless communication system,

transceiver; and

Transmitting a sounding reference signal (SRS) to a base station through the transceiver, receiving information on a digital transmission beam from the base station through the transceiver, and digital transmission corresponding to information on the digital transmission beam to the base station Using a beam to transmit data through the transceiver, the digital transmission beam includes a control unit determined in consideration of an uplink digital channel estimated by the base station and an analog reception beam of the base station,

The terminal according to claim 1, wherein the analog reception beam of the base station and the digital transmission beam of the terminal are determined based on a tabu search algorithm.