KR102045621B1 - Method and apparatus for operating antenna subset in next generation mobile communication network - Google Patents

Abstract

One disclosure of the present specification provides a method for a terminal to feed back channel information to operate an antenna subset of a base station. The method includes estimating a channel with a base station having a plurality of transmit antennas; Feeding back information according to the channel estimation; The method may include receiving data from the base station through one or more transmit antennas belonging to a first subset of the plurality of transmit antennas. Here, one or more transmit antennas belonging to the first subset may be determined by the fed back information.

Description

METHOD AND APPARATUS FOR OPERATING ANTENNA SUBSET IN NEXT GENERATION MOBILE COMMUNICATION NETWORK}

The present invention relates to next generation mobile communication.

With the success of long term evolution (LTE) / LTE-Advanced (LTE-A) for 4G mobile communications, interest in future mobile communications, namely 5G (so-called 5G) mobile communications, is increasing. It's going on.

As defined by the International Telecommunication Union (ITU), “5th generation (5G)” mobile communication means delivering data rates of up to 20 Gbps and immersive transmission rates of at least 100 Mbps anywhere. The official name is “IMT-2020” and it aims to be commercialized worldwide in 2020.

The ITU presents three usage scenarios, such as Enhanced Mobile BroadBand (eMBB) massive Machine Type Communication (MMTC) and Ultra Reliable and Low Latency Communications (URLLC).

First, URLLC relates to usage scenarios that require high reliability and low latency. For example, services such as autonomous driving, factory automation, and augmented reality require high reliability and low latency (eg, less than 1 ms). Currently, latency of 4G (LTE) is statistically 21-43ms (best 10%) and 33-75ms (median). This is insufficient to support a service requiring a delay of less than 1ms. Therefore, to support the URLLC usage scenario, a PER (packet error rate) of 10-5 or less and a latency of 1ms are required. The delay time is defined as a delay time between the MAC layer of the UE and the MAC layer of the network. The 3GPP standards group is currently standardizing in two ways: to reduce latency and to increase reliability for URLLC support. First of all, as a method of reducing the delay time, the radio frame structure is defined by defining a transmission time interval (TTI) of 1 ms or less, the HARQ scheme is adjusted in the L2 layer, and the direction of initial access procedure and scheduling are examined. As a method of improving reliability, multiple connectivity, multi-link diversity in frequency / spatial dimension, and data redundancy in higher layers are considered.

Next, eMBB usage scenarios relate to usage scenarios that require mobile ultra-wideband.

In order to achieve high data rates, beamforming, massive array multiple input and output (FD-MIMO), array antenna, and analog are used in 5G mobile communication systems. Analog beamforming and large scale antenna techniques are discussed. In addition, a discussion on non-orthogonal multiple access (NOMA) technology for enabling the service of a large number of terminals is being made. While the conventional OFDMA scheme is a concept of allocating resources orthogonally to users by dividing time and frequency for each user, the NOMA is intended to increase bandwidth efficiency by allowing multiple users to use the same resource.

Meanwhile, multi-user MIMO technology can increase bandwidth efficiency. This is a method of supporting multiple users with the same resource by using the spatial characteristics of multiple antennas. Increasing the number of antennas at the receiving end can increase bandwidth efficiency by increasing the number of users that can be supported at the same time, and in particular, the number of antennas that can be physically integrated in the high frequency band can be increased.

As such, in order to realize the ultra-wideband in the next generation mobile communication system, the number of antennas is expected to be increased more than in the existing LTE system.

However, the increase in the number of antennas means that the channel vector between one transmitting end and the receiving end is increased in dimension by the number of antennas. Therefore, the increase in the number of antennas has a problem of increasing the amount of information that the user must feed back to the transmitter.

Republic of Korea Patent Application No. 10-2015-0084312 (name: beamforming apparatus and method using an antenna array in a wireless communication system) in the 5G mobile communication system, one transmitting end grouping a plurality of antenna elements, and one beam per group It proposes a method of forming and transmitting. In detail, a plurality of antenna elements are connected to one digital chain, and an analog beamforming method is used as a beam forming technique rather than a digital beamforming method. Korean Patent Registration No. 10-1003560 (name: apparatus and method for generating antenna subset information, and a multi-input multi-output communication system having the apparatus) selects a transmitting and receiving antenna to be used between one transmitting end and the receiving end, We propose a method for transmitting and receiving data. US patent application Ser. No. 11 / 072,339 (named antenna split multiple access) states that when there are three or more nodes, one node conveys information to the other two nodes through different antennas and each receiving node uses a receiver such as VBLAST. We propose a method for removing interference signal components and restoring original data. In the present invention, there is a difference as a technique including a NOMA scheme including a splitting of a transmitting antenna, multiple data for each divided antenna group, or a multi-user beam forming technique. On the other hand, even in the orthogonal multiple access (OMA) method of multiplexing data of multiple users using multiple antennas, a loss of beam gain is lost during orthogonalization of beams for each user for interference control between multiple users. May occur. This has a problem that the loss rate may increase as the number of antennas increases. In addition, when a non-orthogonal multiple access (NOMA) technique is applied to a communication system having a large number of antennas, an increase in the number of antennas may cause performance degradation. For example, in order to apply NOMA on downlink, when transmitting data to two or more users in one beam from one transmitter, scheduling of users having the same channel direction should be performed. However, in the case of user scheduling having the same channel direction, as the number of antennas increases, the number of dimension of the channel vector increases, which may reduce the correspondence of the channel directions of arbitrary users.

Accordingly, the present disclosure aims to solve various problems that may occur when increasing the number of antennas in a next generation mobile communication system.

In order to achieve the above object, one disclosure of the present specification provides a method for a user equipment to feed back channel information to operate an antenna subset of a base station. The method includes estimating a channel with a base station having a plurality of transmit antennas; Feeding back information according to the channel estimation; The method may include receiving data from the base station through one or more transmit antennas belonging to a first subset of the plurality of transmit antennas. Here, one or more transmit antennas belonging to the first subset may be determined by the fed back information.

The plurality of transmit antennas may be divided into a plurality of subsets. In this case, each subset may be used for beamforming downlink data transmission to the corresponding UE.

The channel estimating step may include estimating a channel for all of the plurality of transmit antennas of the base station. The feedback may include feeding back channel estimation results for all of the plurality of transmit antennas. In this case, the first subset may be selected by the base station based on channel estimation results for all of the plurality of transmit antennas.

The channel estimating may include estimating, by the terminal, a channel for all of a plurality of transmit antennas of the base station. The feedback may include selecting, by the terminal, the first subset based on channel estimation results for all of the plurality of transmit antennas, and receiving, by the terminal, information about the selected first subset according to the channel estimation. Feedback to the base station with information.

The method may further include receiving, by the terminal, information about the number of antenna ports of the base station and selection criteria of the antenna ports from the base station. In this case, the channel estimating step includes the terminal selecting an antenna port corresponding to the selection criterion by the number of antenna ports, and the terminal selecting the selected antenna port to the base station together with the information according to the channel estimation. Feedback may be included.

The method may further comprise receiving information for all of the plurality of subsets when the plurality of transmit antennas are divided into a plurality of subsets.

The method may further include receiving information on one or more subsets when the plurality of transmit antennas are divided into a plurality of subsets. In this case, the channel estimating may include performing channel estimation on antenna ports belonging to the one or more specific subsets.

The method may further include receiving information on one or more subsets when the plurality of transmit antennas are divided into a plurality of subsets. In this case, the information on the specific subset may include a number of transport layers, a precoding matrix, the number of antenna ports allocated to the terminal, antenna port index information allocated to the terminal, and a non-orthogonal multiple access (NOMA) scheme. According to the number of terminals simultaneously serviced, an antenna port index used for another terminal in addition to the antenna port index assigned to the terminal, information on a modulation order and hatching rate used to transmit data to the terminal, According to the NOMA scheme, it may include one or more of information on a modulation order and a coding rate for other terminals that receive a service together.

In order to achieve the above object, one disclosure of the present specification provides a terminal for feeding back channel information. The terminal and the transceiver; It may include a processor for controlling the transceiver. The processor comprising: estimating a channel with a base station having a plurality of transmit antennas; Feeding back information according to the channel estimation; A process of receiving data from the base station through one or more transmit antennas belonging to a first subset of the plurality of transmit antennas may be performed. Here, one or more transmit antennas belonging to the first subset may be determined by the fed back information.

In order to achieve the above object, one disclosure of the present specification also provides a base station. The base station may include a transceiver that includes a plurality of transmit antennas, and a processor that controls the transceiver. The processor may signal information about the plurality of transmit antennas to the terminal through the transceiver. The processor may receive channel information on the plurality of transmit antennas from the terminal through the transceiver. The processor may transmit downlink data to the terminal through one or more transmit antennas belonging to a first subset selected based on the channel information among the plurality of transmit antennas.

According to the present disclosure, the problems of the prior art are solved.

In addition, the invention according to the disclosure of the present specification is not grouping the antenna elements, but in a group that can be used to divide the antenna by grouping the digital chain or physical antenna and applying a digital beamforming scheme to enable multiple access, the prior patent application There is a difference from the number 10-2015-0084312.

In addition, the invention according to the disclosure of the present specification is different from the conventional patent No. 10-1003560 in that the antenna is divided and service and multiplex one or more receiving end for each divided antenna subset.

In addition, the present invention according to the present disclosure can be applied in the conventional US patent application No. 11 / 072,339 in that it is possible to apply the NOMA method including the splitting of the transmitting antenna, the multiple data for each divided antenna group or a multi-user beam forming technique There is a difference.

1 is a wireless communication system.
2 shows a structure of a radio frame according to FDD in 3GPP LTE.
3 shows an example of a subframe type in NR.
4 is a conceptual diagram of a multiple access technique utilizing antenna subsets in accordance with one disclosure of the present specification.
5 is a flowchart exemplarily illustrating a procedure of determining an antenna subset by a base station according to the first scheme of the first disclosure.
6 is a flowchart exemplarily illustrating a procedure of determining an appropriate antenna subset based on an estimated channel by a terminal according to the second scheme of the first disclosure.
7A and 7B are flowcharts illustrating a procedure of determining, by the terminal, N antenna ports satisfying a selection condition according to the third method of the first disclosure.
8 is an exemplary flowchart illustrating a procedure according to the first scheme of the second disclosure.
9 is an exemplary flow diagram illustrating a procedure in accordance with a second approach of the second disclosure.
10 is a block diagram illustrating a wireless communication system in which the disclosure of the present specification is implemented.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. In addition, the technical terms used in the present specification should be interpreted as meanings generally understood by those skilled in the art unless they are specifically defined in this specification, and are overly inclusive. It should not be interpreted in the sense of or in the sense of being excessively reduced. In addition, when the technical terms used herein are incorrect technical terms that do not accurately represent the spirit of the present invention, it should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In this application, terms such as “consisting of” or “having” should not be construed as necessarily including all of the various components, or various steps described in the specification, some of which include some or some of the steps It should be construed that it may not be, or may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein 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 the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but other components may be present in between. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and should not be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

The term base station, which is used hereinafter, generally refers to a fixed station for communicating with a wireless device, and includes an evolved-nodeb (eNodeB), an evolved-nodeb (eNB), a base transceiver system (BTS), and an access point (e. Access Point) may be called.

Further, hereinafter, the term UE (User Equipment), which is used, may be fixed or mobile, and may include a device, a wireless device, a terminal, a mobile station, and a user terminal (UT). Other terms may be referred to as a subscriber station (SS) and a mobile terminal (MT).

1 is a wireless communication system.

As can be seen with reference to FIG. 1, a wireless communication system includes at least one base station (BS) 20. Each base station 20 provides a communication service for a particular geographic area (generally called a cell) 20a, 20b, 20c. The cell can in turn be divided into a number of regions (called sectors).

The UE typically belongs to one cell, and the cell to which the UE belongs is called a serving cell. A base station that provides a communication service for a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication service for a neighbor cell is called a neighbor BS. The serving cell and the neighbor cell are determined relatively based on the UE.

Hereinafter, downlink means communication from the base station 20 to the UE 10, and uplink means communication from the UE 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the UE 10. In uplink, the transmitter may be part of the UE 10 and the receiver may be part of the base station 20.

Hereinafter, the LTE system will be described in more detail.

2 is 3GPP In LTE  A structure of a radio frame according to FDD is shown.

Referring to FIG. 2, a radio frame includes 10 subframes, and one subframe includes two slots. Slots in a radio frame are numbered from 0 to 19 slots. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

The structure of the radio frame is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe may be variously changed.

Meanwhile, one slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols. How many OFDM symbols are included in one slot may vary depending on a cyclic prefix (CP).

One slot includes N _RB resource blocks (RBs) in the frequency domain. For example, in the LTE system, the number of resource blocks (RBs), that is, N _RB may be any one of 6 to 110.

A resource block (RB) is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block may include 7x12 resource elements (REs). Can be.

<Next Generation Mobile Communication Network>

Thanks to the success of commercialization of mobile communication based on 4G LTE / international mobile telecommunications (IMT) standard, research on next generation mobile communication (5th generation mobile communication) is underway. The fifth generation of mobile communication systems aims at higher capacity than current 4G LTE, and can increase the density of mobile broadband users, support device-to-device (D2D), high reliability, and machine type communication (MTC). 5G R & D also targets lower latency and lower battery consumption than 4G mobile communication systems to better implement the Internet of Things. New radio access technology (New RAT or NR) may be proposed for such 5G mobile communication.

In the NR, it may be considered that reception from the base station uses a downlink subframe, and transmission to the base station uses an uplink subframe. This approach can be applied to paired and unpaired spectra. A pair of spectrum means that two carrier spectrums are included for downlink and uplink operation. For example, in a pair spectrum, one carrier may include a downlink band and an uplink band paired with each other.

3 is At NR  An example of a subframe type is shown.

The transmission time interval (TTI) shown in FIG. 3 may be called a subframe or slot for NR (or new RAT). The subframe (or slot) of FIG. 3 may be used in a TDD system of NR (or new RAT) to minimize data transmission delay. As shown in FIG. 3, the subframe (or slot) includes 14 symbols, like the current subframe. The symbol at the beginning of the subframe (or slot) may be used for the DL control channel, and the symbol at the end of the subframe (or slot) may be used for the UL control channel. The remaining symbols may be used for DL data transmission or UL data transmission. According to such a subframe (or slot) structure, downlink transmission and uplink transmission may proceed sequentially in one subframe (or slot). Accordingly, downlink data may be received in a subframe (or slot), and an uplink acknowledgment (ACK / NACK) may be transmitted in the subframe (or slot). The structure of such a subframe (or slot) may be referred to as a self-contained subframe (or slot). Using the structure of such a subframe (or slot), there is an advantage that the time taken to retransmit the received error data is reduced, thereby minimizing the final data transmission latency. In such a self-contained subframe (or slot) structure, a time gap may be required for the transition process from transmit mode to receive mode or from receive mode to transmit mode. To this end, some OFDM symbols when switching from DL to UL in the subframe structure may be set to a guard period (GP).

Disclosures herein

According to one disclosure of the present specification, unlike a method of beamforming by using an entire antenna in an existing LTE system base station, data transmission for multiple users may be performed based on an antenna subset.

4 is Full-blown  Antenna according to start of work Subset  Of multiple access technologies Conceptual diagram .

As shown in FIG. 4, when the base station has a plurality of antennas, the antenna may be divided into a plurality of antenna groups or subsets, multiple data may be transmitted for each subset, and services may be provided to the user for each subset.

More specifically, as shown in FIG. 4, when the base station has 8 antennas and the terminal has 2 antennas, the base station transmits to the user 3 through a beam using all 8 antennas, that is, the antenna subset 3 at the transmitting end. Provide service to users 1 and 2 via antenna subset 1 (i.e. antenna 1 through antenna 4) consisting of four antennas at the same time, and user 4 through antenna subset 2 (ie antenna 5 through antenna 8) To provide services.

As shown in FIG. 4, user 4 simultaneously receives two data streams based on antenna subset 2, each user may simultaneously receive one or more data based on each antenna subset. That is, each antenna subset transmits one or more data simultaneously for one or more users.

As such, one disclosure of the present specification provides a technique of dividing an entire antenna into a plurality of antenna groups or subsets in one base station, and performing beamforming for specific users for each antenna group or subset group. In this case, antennas included in each antenna subset may overlap, and users served by each subset may overlap.

Hereinafter, when describing the contents of the present specification, for convenience of description, the signals and channels used in the LTE / LTE-A will be described based on the names of the present specification. The contents of the present specification are wireless communication using multiple antennas as well as LTE / LTE-A. If the system is applicable.

I. First Initiation: Antenna of Base Station Subset  If not predefined

If the corresponding antenna subset of the base station is not defined in advance, the operation can be performed in the following manner.

I-1. First Scheme of the First Initiation: An Antenna Base Station Based on Feedback Channel Information of a Terminal; Subset  If you decide

When the base station does not define the antenna subset in advance, when the base station determines and operates the antenna subset based on the feedback channel information of the terminal, the operation procedure of the base station and the terminal is as follows.

5 is an antenna of a base station according to the first scheme of the first disclosure. Subset  A flowchart illustrating an example of a decision making process.

Referring to FIG. 5, the determination of the antenna subset to be used for the terminal 100 is performed by the base station 200. To this end, the base station needs to know information about the channel between the base station and the terminal for each antenna port. Accordingly, the base station 200 signals the configuration information on a reference signal (RS) for each transmission antenna port to the terminal 100. The base station 200 transmits a reference signal RS to the terminal 100.

Then, the terminal 100 performs channel estimation for each antenna port using the received reference signal RS. The terminal 100 feeds back Channel Status Information (CSI) including the estimated channel result to the base station. The estimated channel result may be transmitted to the base station through an uplink control channel, for example, a physical uplink control channel (PUCCH). Alternatively, the estimated channel result may be piggybacked on an uplink data channel, for example, a physical uplink shared channel (PUSCH), and transmitted to the base station. Alternatively, the estimated channel result may be transmitted to the base station through MAC-CE.

Various methods may be used as the feedback method of the channel state information (CSI). For example, a method in which a terminal feeds back an estimated analog channel value for each transmitting antenna port to a base station, and a method for feeding back information on an estimated channel based on a codebook when there is a shared codebook between base stations and terminals. In order to reduce the feedback overhead, select only a few of the selected values in the codebook with the larger channel component values and select the corresponding value information and the analog channel component values corresponding to the corresponding values. There may be a method of informing the base station of the information on the sparse channel by feedback.

The base station 100 determines the antenna subset based on the feedback channel state information (CSI). That is, the base station 200 schedules a user to use each antenna subset. The base station 200 signals the scheduled antenna subset related information to the corresponding user. The base station 200 performs beamforming using the antenna subset, and transmits downlink data to the terminal 100.

The information related to the antenna subset includes the number of transport layers, the precoding matrix, the number of antenna ports assigned to the user, the antenna port index information assigned to the user, the number of users simultaneously served together according to the NOMA scheme, and the user. Antenna port index used for other users in addition to the specified antenna port index, information on the modulation order / hatching rate used by the base station to transmit data to the user, and other users provided with the service according to the NOMA method. The modulation order / coding rate for the may be included.

The antenna subset information may be included in a downlink control channel, for example, in downlink control information (DCI) in a physical downlink control channel (PDCCH) of LTE / LTE-A and transmitted to the terminal. The downlink data may be transmitted through a downlink data channel, for example, a physical downlink shared channel (PDSCH) of LTE / LTE-A. In this case, the PDCCH and the PDSCH through which the DCI including the antenna subframe information is transmitted may be transmitted on the same subframe or may be transmitted on another subframe.

Alternatively, the antenna subset information may be delivered through a higher layer signal, such as a radio resource control (RRC) signal or a medium access control element (MAC-CE).

I-2. Second Scheme of the First Initiation: When the UE determines an appropriate antenna subset based on the estimated channel

According to the second method of the first disclosure of the present specification, in a situation where the base station does not define the antenna subset in advance, the terminal performs channel estimation and determines an appropriate antenna subset based on the estimated channel. The terminal feeds back information about the determined antenna subset to a base station. Specifically, this will be described with reference to FIG. 6.

6 shows an appropriate antenna based on a channel estimated by a terminal according to the second scheme of the first disclosure. Subset  A flowchart illustrating an example of a decision making process.

Referring to FIG. 6, the base station 200 signals configuration information on a reference signal (RS) to the terminal. In addition, the base station 200 transmits a reference signal (RS) for each transmit antenna port.

Then, the terminal 100 performs channel estimation for each antenna port using the received reference signal RS. The terminal 100 determines an antenna subset based on the estimated channel result. Specifically, the terminal 100 determines antenna ports corresponding to the antenna subset based on the estimated channel result.

The terminal 100 feeds back information on the determined antenna subset to the base station 200. Information on the determined antenna subset may be included in channel status information (CSI) and transmitted to the base station. The CSI may further include the estimated channel result. Information on the determined antenna subset may be transmitted to the base station through an uplink control channel, for example, PUCCH. Alternatively, the information on the determined antenna subset may be piggybacked on an uplink data channel, for example, a PUSCH, and transmitted to the base station. Alternatively, the information on the determined antenna subset may be transmitted through the MAC-CE.

The terminal 100 may determine the plurality of antenna subsets, and feed back the plurality of antenna subsets to the base station 200. In this case, the base station 200 determines an antenna subset that is optimal for the terminal 100 among the plurality of antenna subsets. In addition, the base station 200 signals the determined information on the optimal antenna subset to the terminal 100.

Meanwhile, when the terminal 100 determines only one antenna subset and feeds back one antenna subset to the base station 200, the base station 200 determines that the antenna subset determined by the terminal 100 is the terminal. Review once again whether it is optimal for (100). If the antenna subset determined by the terminal 100 is not optimal, the base station 200 determines another optimal antenna subset, and then signals the terminal 100 with information on the determined optimal antenna subset. . Determination of the optimal antenna subset in the base station by transmitting the reference signal (RS) configuration information and transmission of the reference signal (RS) in FIG. This is possible. However, if the antenna subset determined by the terminal 100 is optimal, the base station 200 signals to the terminal 100 an indication of accepting the antenna subset determined by the terminal 100.

The base station 200 performs beamforming using the antenna subset, and transmits downlink data to the terminal 100.

I-2-1. First of Second Measures of the First Disclosure Example

As an embodiment of the second method of determining the antenna subset based on the channel result estimated by the terminal 100, a codebook may be shared between the base station and the terminal.

For example, suppose a base station has eight antennas, where the base station antenna port index is 1-8. In addition, it is assumed that the base station transmits a plurality of data streams to one terminal. Assume that the type of codebook shared between the base station and the terminal is a 2 by 2 codebook and a 4 by 4 size codebook. And, assume that there are various codebooks for each size. Here, a 2 by 2 codebook is used by a base station to transmit two data streams to one user using two antennas. The 4 by 4 codebook is used by a base station to transmit four data streams to one user using four antennas.

In this case, after estimating the channel, the terminal 100 may determine antenna subset information and channel information as shown in Table 1 below. In Table 1, for each codebook size, the user selects an antenna port index having a good channel for data multiplexing among eight antenna port indexes. In order to transmit channel information on the selected antenna port, channel direction information consisting of two and four antennas and a channel quality indicator (CQI) for each channel direction are included in the feedback channel state information (CSI). . At this time, the information on the two and four channel direction means the channel direction information (CDI), LTE standard PMI (Precoding Matrix Indicator) or codebook index can be utilized. In this case, the codebook index or PMI refers to an index indicating one codebook of 2 by 2 size or the entire codebook of 4 by 4 size. When each codeword or code vector is an index, a plurality of codebook indexes are fed back. It should be included in the channel state information (CSI). That is, when two data streams are transmitted, two code vector indices must be included in the feedback channel state information (CSI). The channel quality indicator (CQI) may be utilized in the existing LTE / LTE-A, and various metric such as received SINR and SNR may be used.

Codebook size Antenna port index Channel State Information (CSI) fed back 2 x 2 1, 4 Channel direction indictor (CDI) for transmitting two data streams, eg PMI or codebook index
-CQI for each CDI 4x4 2, 4, 5, 8 Channel direction indictor (CDI) for transmitting four data streams, eg PMI or codebook index
-CQI for each CDI

I-2-2. Second of the second scheme of the first disclosure Example

As a second embodiment of the second scheme, when each user receives one data stream from a base station in a multi-user environment, each terminal only feeds back a codeword index for one data stream as shown in Table 2 below. do.

Codebook size Antenna port index Channel State Information (CSI) fed back 2 x 2 1, 4 Channel direction indictor (CDI) for transmission of one data stream, eg PMI or codebook index
-CQI for each CDI 4x4 2, 4, 5, 8 Channel direction indictor (CDI) for transmission of one data stream, eg PMI or codebook index
-CQI for each CDI

In the embodiments described with reference to Tables 1 and 2 above, one antenna port index set and one channel information set are fed back for downlink data transmission. However, the number may be a plurality of base stations. After receiving the feedback of the channel state information (CSI), it may determine an antenna port and a precoding index to use for the user terminal.

I-3. Third Scheme of First Initiation: When the UE determines an appropriate antenna port based on the estimated channel

According to the third scheme of the first disclosure, instead of the base station defining the antenna subset in advance, the base station informs the terminal of the selection condition of the antenna port, the terminal selects N antenna ports that satisfy the selection condition, Information about the selected N antenna ports may be fed back to the base station.

7A and 7B are flowcharts illustrating a procedure of determining N antenna ports for a terminal to satisfy a selection condition according to a third method of the first disclosure.

Referring to FIG. 7A, the base station 200 may include feedback setting information of the terminal, that is, information about the number N of antenna ports to be selected by the terminal and information about a criterion (eg, a threshold) for selecting the antenna port. Transmit to the terminal 100. For example, after the base station 200 determines the information, the determination result may be delivered to the terminal 100, or the base station 200 and the terminal 100 may determine the information in consultation. The base station 200 may transmit the information to the terminal 100 through an upper layer signal, for example, an RRC signal or a MAC-CE. Subsequently, the base station 200 signals configuration information on a reference signal (RS) to the terminal. In addition, the base station 200 transmits a reference signal (RS) for each transmit antenna port.

Alternatively, as shown in FIG. 7B, when the base station 100 transmits reference signal (RS) configuration information to the terminal 200, the base station 100 may include necessary information for subset determination. That is, when the base station 200 does not request a feedback operation related to a specific antenna subset configuration from the terminal, only the general RS configuration information is transmitted. However, when the base station 200 requests a terminal operation related to antenna subset determination, the terminal 100 feeds back information on one or more antenna subsets configured with specific antenna ports to the base station 200. Therefore, the base station transmits feedback configuration information for antenna subset determination together with reference signal (RS) configuration information to the terminal. In this case, the feedback configuration information may include on / off indication information on whether or not the terminal participates in the determination of the antenna subset. The specific number of antenna ports to be fed back (N), condition information for selecting an antenna port of the terminal, and the like may be included.

The terminal 100 performs channel estimation, that is, channel measurement through the reference signal. The terminal 100 selects antenna ports corresponding to the selection condition by the number N. The terminal 100 feeds back channel state information (CSI) including the index of the selected antenna port and a channel estimation value for each antenna port, to the base station 200. The channel state information (CSI) may further include a CDI. The estimated channel value for each antenna port may be quantized in various forms and then fed back.

The base station 200 determines an antenna subset including one or more of the feedback N antenna ports. Specifically, the base station 200 may decide to include only some of the N antenna ports in the antenna subset or include all of the N antenna ports.

In addition, the base station 200 signals the determined information on the optimal antenna subset to the terminal 100.

The base station 200 performs beamforming using the antenna subset, and transmits downlink data to the terminal 100.

II. Second initiation: the base station is antenna Subset  If you predefine

As in the foregoing first disclosure, if the base station does not determine the antenna subset in advance, the amount of information to be fed back to the terminal may be increased and the complexity may be increased. Therefore, the second disclosure proposes methods in which the base station presets the antenna subset and utilizes it. Or, the second disclosure places a constraint on determining the antenna subset, and thus suggests a way for the antenna subset to be determined accordingly. In the following description, the information about the determined antenna subset is transmitted to the terminal by the base station. However, instead of the information on the determined antenna subset, the base station transmits the constraint information to be used when determining the antenna subset to the terminal. It is possible. The constraint information includes a constraint on the selection of a particular antenna port.

II-1. Base station antenna On subset  Do not share information about

First, when the base station has previously defined the antenna subset, but does not share it with the terminal, this is not very different from the first first disclosure. In this case, therefore, the contents of the first disclosure will be followed.

II-2. Base station defined antenna On subset  If you share information about

In order to efficiently support the multiple access technology using the antenna subset proposed herein, the base station may signal information about the antenna subsets currently used for all terminals in the cell to the terminal in the following manner.

Passing antenna subset related information through MIB

-Transmission of antenna subset related information through SIB

-Transmission of antenna subset related information through RRC signal

-Transmission of antenna subset related information through MAC-CE

-Delivery of antenna subset related information through DCI

The base station may share information about the antenna subset with the terminal using one or a combination of two or more of the above schemes. That is, the base station may transmit the subset related information when the terminal transitions to the RRC connection state after the initial access process or the initial access process. When the subset related information is 3 bits, for example, it may be expressed as shown in the following table.

Antenna subset index
(3 bits) Antenna subset 000 1 ^st antenna subset: antenna port index 1-8 001 1 ^st antenna subset: antenna port index 1-4 2 ^nd antenna subset: antenna port index 5-8 010 1 ^st antenna subset: antenna port index 1-8 2 ^nd antenna subset: antenna port index 1-4 3 ^rd antenna subset: antenna port index 5-8 011 1 ^st antenna subset: antenna port index 1-2 2 ^nd antenna subset: antenna port index 3-4 3 ^rd antenna subset: antenna port index 5-8 100 1 ^st antenna subset: antenna port index 1-4 2 ^nd antenna subset: antenna port index 5-6 3 ^rd antenna subset: antenna port index 7-8 101 1 ^st antenna subset: antenna port index 1-2 2 ^nd antenna subset: antenna port index 3-4 3 ^rd antenna subset: antenna port index 5-6 4 ^th antenna subset: antenna port index 7-8 110 1 ^st antenna subset: antenna port index 1-2 2 ^nd antenna subset: an antenna port index 3-4 3 ^rd antenna subset: antenna port index 5-6 4 ^th antenna subset: antenna port index 7-8 5 ^th antenna subset: antenna port index 1-4 111 1 ^st antenna subset: antenna port index 1-2 2 ^nd antenna subset: antenna port index 3-4 3 ^rd antenna subset: antenna port index 5-6 4 ^th antenna subset: antenna port index 7-8 5 ^th antenna subset: antenna port index 5-8

Table 3 above shows an example in which the number of antennas of a base station is 8 and 3 bits are used for each antenna subset indication. Referring to Table 3, the base station may use eight kinds of antenna subsets. Each antenna subset may include two, four, eight antenna ports. Table 3 contains only the indexes of the antenna ports included in the antenna subset, but is simultaneously used according to the number of transmission layers, the precoding matrix, the number of antenna ports assigned to the user, the antenna port index information assigned to the user, and the NOMA scheme The number of users receiving the service, the antenna port index used for other users in addition to the antenna port index assigned to the user, the modulation order / code rate for the user's own data, and the data transmission for other users. The modulation order / code rate, etc. may be included, and thus may be configured in various forms including related information. Such information can be utilized as an interference control for the terminal.

8 and 9 illustrate methods of signaling and utilizing information of the base station to the terminal.

8 is an exemplary flowchart illustrating a procedure according to the first scheme of the second disclosure.

Referring to FIG. 8, the base station 200 signals information about antenna subsets to the terminal 100.

The base station 200 signals configuration information on a reference signal (RS) to the terminal. In addition, the base station 200 transmits a reference signal (RS) for each transmit antenna port.

The terminal 100 performs channel estimation on all antenna ports belonging to the plurality of antenna subsets. In addition, the terminal 100 feeds back the results of all channel estimation to the base station 200.

The base station 200 schedules user terminals for each antenna subset based on the feedback channel estimation result. That is, the base station 200 determines the antenna subset for each user terminal. In other words, the base station 200 matches the user terminal with the corresponding antenna subset. In addition, the base station 200 transmits information on the antenna subset to the corresponding user terminal. In this case, the information on the scheduled antenna subsets delivered to the corresponding user terminal may be indicated by using (using) the antenna subset indicators shown in Table 3. . Information about the scheduled antenna subset may be included in the DCI in the PDCCH. Alternatively, information can be transmitted by RRC or MAC-CE.

9 is an exemplary flow diagram illustrating a procedure in accordance with a second approach of the second disclosure.

Referring to FIG. 9, according to the second method of the second disclosure, the base station 200 may reduce complexity by allowing the terminal 100 to perform channel estimation on only antenna ports within a specific antenna subset. . Specifically, it is as follows.

Referring to FIG. 9, the base station 200 signals information about antenna subsets to the terminal 100.

The base station 200 signals configuration information on a reference signal (RS) to the terminal. In addition, the base station 200 signals information about a specific antenna subset to the terminal 100.

The base station 200 transmits a reference signal RS only through an antenna port belonging to the specific antenna subset.

The terminal 100 performs channel estimation only on the antenna ports belonging to the specific antenna subset. In addition, the terminal 100 feeds back the results of all channel estimation to the base station 200. If there are a plurality of specific antenna subsets signaled from the base station 200, the terminal 100 performs channel estimation on antenna ports belonging to the plurality of antenna subsets, and the result of the channel estimation is determined by the base station. Feedback to 200.

The base station 200 schedules user terminals for each antenna subset based on the feedback channel estimation result. That is, the base station 200 determines the antenna subset for each user terminal. In other words, the base station 200 matches the user terminal with the corresponding antenna subset. In addition, the base station 200 transmits information about the scheduled antenna subset to the user terminal.

Meanwhile, the terminal 100 may also perform channel estimation on antenna ports belonging to other antenna subsets in addition to the antenna subset signaled by the base station, and may also feedback the result of the channel estimation. The channel estimation at this time is an interference channel estimation.

Meanwhile, when there are a plurality of specific antenna subsets signaled by the base station 200, the at least one antenna subset may be for the terminal to measure and feed back interference with other user terminals. In addition, the information on the antenna subset scheduled from the base station to the terminal may include scheduled antenna subset information for the terminal other than the terminal, this information may be utilized for interference control.

On the other hand, Table 3 may be simplified by simply expressing the number of antenna ports. If there is existing shared codebook information (when antenna port number information is mapped for each codebook index), an indication of the number of antenna ports may be performed using the codebook index. In the case of indicating the antenna subset using the codebook, the process of transmitting information on the antenna subset in FIGS. 8 and 9 is already performed in the codebook sharing process and can be omitted. In this case, when the base station delivers information on the antenna subset to be actually used to the terminal, the base station may transmit the codebook index scheduled by the base station and / or the number of antenna ports and / or antenna port indexes used.

Embodiments of the present invention described so far may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. Specifically, it will be described with reference to the drawings.

Degree 10 is  Representing a wireless communication system implemented in the present disclosure Block diagram .

The base station 200 includes a processor 201, a memory 202, and an RF unit 203. The memory 202 is connected to the processor 201 and stores various information for driving the processor 201. The RF unit 203 is connected to the processor 201 to transmit and / or receive a radio signal. The processor 201 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 201.

The terminal 100 includes a processor 101, a memory 102, and an RF unit 103. The memory 102 is connected to the processor 101 and stores various information for driving the processor 101. The RF unit 103 is connected to the processor 101 and transmits and / or receives a radio signal. The processor 101 implements the proposed functions, processes and / or methods.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

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

Claims (16)

A method of receiving data from a base station,
Estimating a channel with a base station having a plurality of transmit antennas;
Feeding back information according to the channel estimation;
If the plurality of transmit antennas of the base station is divided into a plurality of subsets, receiving information about one or more subsets;
Receiving data from the base station via one or more transmit antennas belonging to a first subset of the plurality of transmit antennas,
Wherein one or more transmit antennas belonging to the first subset are determined by the fed back information, and
The information on the subset includes information related to an antenna to be used for another terminal. The method of claim 1,
Each subset is used for beamforming downlink data transmission to a corresponding terminal. The method of claim 1,
The channel estimating step includes estimating a channel for all of a plurality of transmit antennas of the base station;
The feedbacking includes feeding back channel estimation results for all of the plurality of transmit antennas.
And wherein the first subset is selected by the base station based on channel estimation results for all of the plurality of transmit antennas. The method of claim 1,
The channel estimating step includes the terminal estimating a channel for all of the plurality of transmit antennas of the base station.
The feedback may include selecting, by the terminal, the first subset based on channel estimation results for all of the plurality of transmit antennas, and receiving, by the terminal, information about the selected first subset. And feeding back to the base station. The method of claim 1,
Receiving, by the terminal, information about the number of antennas of the base station and selection criteria of the antennas from the base station;
The channel estimating step includes the terminal selecting the antennas corresponding to the selection criteria by the number of antennas, and the terminal feeding back the selected antennas to the base station with the information according to the channel estimation. Characterized in that the method. The method of claim 1, wherein the information on the received subset includes information on all of the plurality of subsets. The method of claim 1,
Wherein the channel estimating comprises performing channel estimation on antennas belonging to the one or more subsets. The method of claim 1,
The information on the one or more subsets may be simultaneously used according to the number of transport layers, a precoding matrix, the number of antennas to be allocated to the terminal, antenna index information to be allocated to the terminal, and a non-orthogonal multiple access (NOMA) scheme. The number of terminals to be serviced, the antenna index to be used for other terminals in addition to the antenna index to be allocated to the terminal, information on the modulation order and coding rate to be used to transmit data to the terminal, and the service together according to the NOMA scheme. And at least one of information on a modulation order and a coding rate to be used for another terminal to be provided.
A terminal for receiving data from a base station,
A transceiver;
A processor for controlling the transceiver;
Estimating a channel with a base station having a plurality of transmit antennas;
Feeding back information according to the channel estimation;
Receiving information on one or more subsets when the plurality of transmit antennas of the base station are divided into a plurality of subsets;
Receiving data from the base station through one or more transmit antennas belonging to a first subset of the plurality of transmit antennas,
Wherein one or more transmit antennas belonging to the first subset are determined by the fed back information, and
And the information about the subset includes information related to an antenna to be used for another terminal. 10. The terminal of claim 9, wherein each subset is used for beamforming downlink data transmission to a corresponding terminal. The method of claim 9, wherein the terminal
The channel estimating step further performs a process of estimating a channel for all of the plurality of transmit antennas of the base station.
The process of performing the feedback by the processor includes feeding back a channel estimation result for all of the plurality of transmit antennas.
And wherein the first subset is selected by the base station based on channel estimation results for all of the plurality of transmit antennas. The method of claim 9,
The process of performing the channel estimation by the processor includes estimating a channel for all of the plurality of transmit antennas of the base station.
The performing of the feedback by the processor may include selecting the first subset based on channel estimation results of all of the plurality of transmit antennas, and converting the information on the selected first subset into information based on the channel estimation. Terminal comprising a process of feeding back together. The method of claim 9,
The processor further performs a process of receiving information about the number of antennas and the selection criteria of the antennas,
The process of performing the channel estimation by the processor includes selecting an antenna meeting the selection criterion by the number of antennas, and feeding back the selected antenna with the information according to the channel estimation. Terminal. The method of claim 9,
And the information on the received subset includes information on all of the plurality of subsets. The method of claim 9,
Wherein the processor performing the channel estimation comprises performing channel estimation on antennas belonging to the one or more subsets. delete

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