阅读说明：本技术 基站装置、终端装置以及通信方法 (Base station device, terminal device, and communication method ) 是由 留场宏道 山田良太 于 2019-09-06 设计创作，主要内容包括：本发明提供一种能通过抑制基站装置获取高精度的CSI时来自终端装置的反馈的开销来提高频率利用效率或吞吐量的基站装置、终端装置以及通信方法。本发明的一个方案的终端装置具备：接收部,该接收部接收至少一个NZP CSI-RS；以及发送部,该发送部发送至少一个包括CSI的信号,该CSI至少包括RI和PMI,该接收部获取设定该PMI所指定的向量的个数的第一值,在该RI的值超过规定的值的情况下,根据作为该第一值以下的值的第二值来设定该向量的个数。(The invention provides a base station device, a terminal device and a communication method, which can improve frequency utilization efficiency or throughput by suppressing the overhead of feedback from the terminal device when the base station device acquires high-precision CSI. A terminal device according to an aspect of the present invention includes: a receiving section that receives at least one NZP CSI-RS; and a transmitting unit that transmits at least one signal including CSI including at least RI and PMI, wherein the receiving unit acquires a first value that sets the number of vectors designated by the PMI, and sets the number of vectors based on a second value that is a value equal to or less than the first value when the value of RI exceeds a predetermined value.)

1. A terminal device that communicates with a base station device, the terminal device comprising:

a receiving section that receives at least one NZP CSI-RS; and

a transmitting part transmitting at least one signal including CSI,

the CSI includes at least an RI and a PMI,

the receiving unit acquires a first value for setting the number of vectors designated by the PMI,

when the value of the RI exceeds a predetermined value, the number of vectors is set based on a second value that is a value equal to or less than the first value.

2. The terminal device according to claim 1,

the receiving part receives RI limitation information that limits the RI candidates,

and setting the number of vectors specified by the PMI based on the RI restriction information.

3. The terminal device according to claim 1,

the PMIs also include a PMI14 that specifies amplitude coefficients,

the number of candidates for the amplitude coefficient when the value of the RI exceeds a predetermined value is smaller than the number of candidates for the amplitude coefficient when the value of the RI is equal to or smaller than the predetermined value.

4. The terminal device according to claim 1,

the PMIs also include a PMI21 that specifies phase coefficients,

the receiving section receives a bitmap limiting candidates of the phase coefficient.

5. The terminal device according to claim 1,

the reception part receives DCI including trigger information requesting the CSI,

the DCI includes information specifying elements included in the CSI.

6. A base station device that communicates with a terminal device, the base station device comprising:

a receiving section that transmits at least one NZP CSI-RS; and

a transmitting part transmitting at least one signal including CSI,

the CSI includes at least an RI and a PMI,

the transmission unit transmits a signal including a first value for setting the number of vectors designated by the PMI,

when the value of the RI exceeds a predetermined value, the number of vectors is specified based on a second value that is a value equal to or less than the first value.

7. A communication method of a terminal device that communicates with a base station device, the communication method comprising:

receiving at least one NZP CSI-RS;

transmitting a signal including CSI including at least an RI and a PMI;

acquiring a first value for setting the number of vectors specified by the PMI; and

when the value of the RI exceeds a predetermined value, the number of vectors is set based on a second value that is a value equal to or less than the first value.

Technical Field

The present invention relates to a base station apparatus, a terminal apparatus, and a communication method. The present application claims priority based on japanese patent application No. 2018-172520 filed in japan on 9, 14, 2018, and the contents of which are incorporated herein by reference.

Background

Research and development activities related to the fifth generation mobile wireless communication system (5G system) are actively being conducted with the goal of starting commercial services in about 2020. Recently, proposals concerning standard methods for 5G systems (International Mobile Telecommunication-2020 and beyond IMT-2020: 2020 and International Mobile Telecommunications IMT-2020, and beyond) have been reported by International Telecommunication Union Radio communications Sector (ITU-R), which is an International organization for standardization (see non-patent document 1).

In addition to the communication system coping with the rapid increase of data traffic, it is an important issue to secure frequency resources. Therefore, one of the goals of 5G is to achieve ultra-large capacity communication by using a higher frequency band than a frequency band (frequency band) used in LTE (Long term evolution).

It is important to efficiently utilize spatial resources on the basis of improving throughput. In the 5G system, effective use of a Multiple-input Multiple-output (MIMO) technique in which a plurality of antennas are used for transmission and reception is expected (see non-patent document 2). Further, if the base station apparatus can grasp the Channel State Information (CSI) with the terminal apparatus, the efficiency of the MIMO technique is further improved.

As a method for acquiring CSI by the base station apparatus, it is considered to feed back CSI measured by the terminal apparatus to the base station apparatus. For example, the base station apparatus and the terminal apparatus share a codebook including a plurality of vectors indicating the state of the transmission path in advance, and the base station apparatus can grasp the state of the transmission path by selecting a vector closest to the CSI measured by the terminal apparatus from the codebook and feeding back the selected vector to the base station apparatus. In this case, the accuracy of CSI that the base station apparatus can grasp depends on the accuracy of the codebook, and in short, the accuracy of CSI increases in proportion to the number of vectors described in the codebook.

Documents of the prior art

Non-patent document

Non-patent document 1: "IMT Vision-Framework and overall objectives of the future level of IMT for 2020 and beyond," Recommendation ITU-R M.2083-0, Sept.2015.

Non-patent document 2: 3GPP RP-181453, "Enhancement on MIMO for NR," June 2018.

Disclosure of Invention

Problems to be solved by the invention

As explained above, the accuracy of CSI that can be acquired by the base station apparatus greatly depends on the accuracy of the codebook referred to by the terminal apparatus. However, this means that the base station apparatus increases the overhead of feedback from the terminal apparatus in order to acquire CSI with high accuracy. Further, although the transmission environment changes from moment to moment as the terminal device moves and the surrounding environment changes, there is a problem that the CSI acquired by the base station device cannot change following the change in the transmission environment when the delay in feedback increases.

An aspect of the present invention is made in view of the above circumstances, and an object thereof is to provide a base station apparatus, a terminal apparatus, and a communication method capable of improving frequency utilization efficiency and throughput by suppressing overhead of feedback from the terminal apparatus when the base station apparatus acquires CSI with high accuracy.

Technical scheme

The base station apparatus, the terminal apparatus, and the communication method according to one aspect of the present invention for solving the above-described problems are configured as follows.

(1) That is, a terminal device according to an aspect of the present invention is a terminal device that communicates with a base station device, and includes: a receiving section that receives at least one NZP CSI-RS; and a transmitting unit configured to transmit at least one signal including CSI including at least RI and PMI, wherein the receiving unit acquires a first value for setting the number of vectors designated by the PMI, and sets the number of vectors based on a second value that is a value equal to or smaller than the first value when the value of RI exceeds a predetermined value.

(2) A terminal device according to an aspect of the present invention is (i) the terminal device described in (1) above, wherein the receiving unit receives RI restriction information for restricting the RI candidates, and sets the number of vectors designated by the PMI based on the RI restriction information.

(3) A terminal device according to an aspect of the present invention is the terminal device according to the above (1), wherein the PMI further includes a PMI14 that specifies an amplitude coefficient, and the number of candidates for the amplitude coefficient is smaller when the value of the RI exceeds a predetermined value than when the value of the RI is equal to or less than the predetermined value.

(4) A terminal device according to an aspect of the present invention is the terminal device described in (1) above, wherein the PMI further includes a PMI21 that specifies a phase coefficient, and the receiving unit receives a bitmap that restricts candidates for the phase coefficient.

(5) A terminal device according to an aspect of the present invention is (1) described above, wherein the receiving unit receives DCI including trigger information requesting the CSI, the DCI including information specifying elements included in the CSI.

(6) A base station apparatus according to an aspect of the present invention is a base station apparatus that communicates with a terminal apparatus, including: a receiving section that transmits at least one NZP CSI-RS; and a reception unit configured to transmit at least one signal including CSI including at least RI and PMI, wherein the transmission unit is configured to transmit a signal including a first value for setting the number of vectors designated by the PMI, and when the value of RI exceeds a predetermined value, the transmission unit is configured to interpret that the number of vectors is designated based on a second value that is a value equal to or smaller than the first value.

(7) A communication method according to an aspect of the present invention is a communication method for a terminal apparatus that communicates with a base station apparatus, including: receiving at least one NZP CSI-RS; transmitting a signal including CSI including at least an RI and a PMI; acquiring a first value for setting the number of vectors specified by the PMI; and setting the number of vectors based on a second value that is a value equal to or less than the first value when the value of the RI exceeds a predetermined value.

Advantageous effects

According to an aspect of the present invention, since overhead of feedback from the terminal apparatus when the base station apparatus acquires CSI with high accuracy can be suppressed, frequency utilization efficiency or throughput can be improved.

Drawings

Fig. 1 is a diagram showing an example of a communication system according to the present embodiment.

Fig. 2 is a block diagram showing an example of the configuration of the base station apparatus according to the present embodiment.

Fig. 3 is a block diagram showing an example of the configuration of the terminal device according to the present embodiment.

Fig. 4 is a diagram showing an example of a communication system according to the present embodiment.

Fig. 5 is a diagram showing an example of a communication system according to the present embodiment.

Detailed Description

The communication system according to the present embodiment includes: base station devices (transmission device, cell, transmission point, transmission antenna group, transmission antenna port group, component carrier, eNodeB, transmission point, reception point, transmission panel, access point) and terminal devices (terminal, mobile terminal, reception point, reception antenna group, reception antenna port group, UE (user equipment), reception point, reception panel, station). The base station apparatus connected to the terminal apparatus (establishing a radio link) is referred to as a serving cell.

The base station apparatus and the terminal apparatus of the present embodiment are also collectively referred to as a communication apparatus. In the present embodiment, at least a part of the communication method performed by the base station apparatus can be performed by the terminal apparatus. Similarly, in the present embodiment, at least a part of the communication method performed by the terminal apparatus can be performed by the base station apparatus.

The base station apparatus and the terminal apparatus in the present embodiment can perform communication in a frequency band requiring a license (licensed frequency band) and/or a frequency band not requiring a license (unlicensed frequency band).

In the present embodiment, "X/Y" includes "X or Y". In the present embodiment, "X/Y" includes the meaning of "X and Y". In the present embodiment, "X/Y" includes the meaning of "X and/or Y".

[1. first embodiment ]

Fig. 1 is a diagram showing an example of a communication system according to the present embodiment. As shown in fig. 1, the communication system of the present embodiment includes a base station apparatus 1A and a terminal apparatus 2A. The coverage area 1-1 is a range (communication area) in which the base station apparatus 1A can connect to the terminal apparatus. The base station apparatus 1A is also simply referred to as a base station apparatus. The terminal device 2A is also simply referred to as a terminal device.

In fig. 1, the following uplink physical channels are used in uplink wireless communication from the terminal apparatus 2A to the base station apparatus 1A. The uplink physical channel is used to transmit information output from an upper layer.

PUCCH (Physical Uplink Control Channel)

PUSCH (Physical Uplink Shared Channel)

PRACH (Physical Random Access Channel: Physical Random Access Channel)

The PUCCH is used to transmit Uplink Control Information (UCI). Here, the uplink control information includes ACK (positive acknowledgement) or NACK (negative acknowledgement) (ACK/NACK) for Downlink data (Downlink transport block, Downlink-Shared Channel (DL-SCH)). ACK/NACK for downlink data is also referred to as HARQ-ACK, HARQ feedback.

In addition, the uplink control Information includes Channel State Information (CSI) for the downlink. In addition, the Uplink control information includes a Scheduling Request (SR) for requesting resources of an Uplink-Shared Channel (UL-SCH). The channel state information corresponds to: a rank Indicator ri (rank Indicator) specifying a preferred number of spatial multiplexes, a precoding Matrix Indicator pmi (precoding Matrix Indicator) specifying a preferred precoder, a channel Quality Indicator cqi (channel Quality Indicator) specifying a preferred transmission rate, a CSI-RS (Reference Signal ) Resource Indicator CRI (CSI-RS Resource Indicator) indicating a preferred CSI-RS Resource, and an RSRP (Reference Signal Received Power) measured by a CSI-RS or SS (Synchronization Signal), etc.

The channel quality indicator CQI (hereinafter, referred to as a CQI value) can be a preferred modulation scheme (for example, QPSK, 16QAM, 64QAM, 256QAM, or the like) and a coding rate (coding rate) in a predetermined frequency band (as will be described later). The CQI value can be an Index (CQI Index) determined by the change scheme and the coding rate. The CQI value can be determined in advance by the system.

The CRI indicates a CSI-RS resource preferred in reception power/reception quality from among a plurality of CSI-RS resources.

It should be noted that the rank indicator and the precoding quality indicator may be determined in advance by the system. The rank indicator and the precoding matrix indicator may be set to an index determined by the number of spatial multiplexes and precoding matrix information. Note that some or all of the CQI value, PMI value, RI value, and CRI value are also collectively referred to as CSI values.

The PUSCH is used to transmit uplink data (uplink transport block, UL-SCH). In addition, the PUSCH may also be used to transmit ACK/NACK and/or channel state information along with uplink data. In addition, the PUSCH may also be used to transmit only uplink control information.

In addition, the PUSCH is used to transmit RRC messages. The RRC message is information/signal processed in a Radio Resource Control (RRC) layer. In addition, the PUSCH is used to transmit a MAC CE (Control Element). Here, the MAC CE is information/signal processed (transmitted) in a Medium Access Control (MAC) layer.

For example, the power headroom may be included in the MAC CE and reported via PUSCH. That is, the field of the MAC CE may also be used to indicate the level of the power headroom.

The PRACH is used to transmit a random access preamble.

In addition, in the Uplink wireless communication, an Uplink Reference Signal (UL RS) is used as an Uplink physical Signal. The uplink physical signal is not used to transmit information output by an upper layer but is used by a physical layer. Here, the uplink reference signal includes: DMRS (Demodulation Reference Signal), SRS (Sounding Reference Signal), PT-RS (Phase-Tracking Reference Signal).

DMRS is associated with transmission of PUSCH or PUCCH. For example, the base station apparatus 1A performs transmission path correction of PUSCH or PUCCH using DMRS. For example, base station apparatus 1A measures the uplink channel state using SRS. In addition, the SRS is used for observation (sounding) of the uplink. In addition, the PT-RS is used to compensate for phase noise. The uplink DMRS is also referred to as an uplink DMRS.

In fig. 1, the following downlink physical channels are used in downlink wireless communication from the base station apparatus 1A to the terminal apparatus 2A. The downlink physical channel is used to transmit information output from an upper layer.

PBCH (Physical Broadcast Channel; Broadcast Channel)

PCFICH (Physical Control Format Indicator Channel)

PHICH (Physical Hybrid automatic repeat request Indicator Channel; HARQ Indicator Channel)

PDCCH (Physical Downlink Control Channel)

EPDCCH (Enhanced Physical Downlink Control Channel; extended Downlink Control Channel)

PDSCH (Physical Downlink Shared Channel)

The PBCH is used to Broadcast a Master Information Block (Master Information Block: MIB, Broadcast Channel: BCH) common to the terminal apparatuses. The PCFICH is used to transmit information indicating a region (e.g., the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols) used for transmission of the PDCCH. Note that the MIB is also referred to as minimum system information.

The PHICH is used to transmit ACK/NACK for uplink data (transport block, codeword) received by base station apparatus 1A. That is, the PHICH is used to transmit a HARQ indicator (HARQ feedback) indicating ACK/NACK for uplink data. Further, ACK/NACK is also called HARQ-ACK. Terminal device 2A notifies the upper layer of the received ACK/NACK. ACK/NACK is ACK indicating correct reception, NACK indicating incorrect reception, and DTX indicating no corresponding data. In addition, in the case where there is no PHICH for uplink data, terminal apparatus 2A notifies the upper layer of ACK.

The PDCCH and the EPDCCH are used to transmit Downlink Control Information (DCI). Here, a plurality of DCI formats are defined for transmission of downlink control information. That is, a field for downlink control information is defined as a DCI format and mapped to information bits.

For example, as a DCI format for downlink, DCI format 1A for scheduling one PDSCH (transmission of one downlink transport block) in one cell is defined.

For example, the DCI format for the downlink includes: information on resource allocation of the PDSCH, information on MCS (Modulation and Coding Scheme) for the PDSCH, and downlink control information such as a TPC command for the PUCCH. Herein, the DCI format for the downlink is also referred to as a downlink grant (or downlink assignment).

Further, for example, as a DCI format for an uplink, DCI format 0 for scheduling one PUSCH (transmission of one uplink transport block) in one cell is defined.

For example, the DCI format for the uplink includes: uplink control information such as information on resource allocation of PUSCH, information on MCS for PUSCH, and TPC command for PUSCH. The DCI format for the uplink is also referred to as an uplink grant (or uplink allocation).

In addition, the DCI format for the uplink can be used to request (CSI request) Channel State information (CSI; also called reception quality information) for the downlink.

The DCI format for the uplink can be used to indicate setting of an uplink resource for mapping a channel state information report (CSI feedback report) fed back to the base station apparatus by the terminal apparatus. For example, the channel state information report can be used to indicate the setting of an uplink resource that periodically reports channel state information (Periodic CSI). The channel state information report can be used to report a mode setting (CSI report mode) of the channel state information periodically.

For example, the channel state information report can be used to indicate the setting of uplink resources for reporting Aperiodic channel state information (Aperiodic CSI). The channel state information report can be used to report a mode setting (CSI report mode) of the channel state information aperiodically.

For example, the channel state information report can be used to indicate the setting of uplink resources reporting semi-persistent channel state information (semi-persistent CSI). The channel state information report can be used to semi-continuously report the mode setting (CSI report mode) of the channel state information. It should be noted that the semi-persistent CSI report is a CSI report that is periodically reported from activation to deactivation by signals of an upper layer or downlink control information.

The DCI format for the uplink can be used to set the type of the channel state information report that the terminal apparatus feeds back to the base station apparatus. The types of the channel state information report include Wideband CSI (e.g., Wideband CQI) and narrowband CSI (e.g., Subband CQI).

When scheduling resources of a PDSCH using a downlink assignment, a terminal device receives downlink data through the scheduled PDSCH. When scheduling resources of the PUSCH using the uplink grant, the terminal apparatus transmits uplink data and/or uplink control information via the scheduled PUSCH.

The PDSCH is used to transmit downlink data (downlink transport block, DL-SCH). In addition, the PDSCH is used to transmit a system information block type 1 message. The system information block type 1 message is cell-specific (cell-specific) information.

In addition, the PDSCH is used to transmit system information messages. The system information message includes a system information block X other than the system information block type 1. The system information message is cell-specific (cell-specific) information.

In addition, the PDSCH is used to transmit RRC messages. Here, the RRC message transmitted by the base station apparatus may be common to a plurality of terminal apparatuses in the cell. The RRC message transmitted by the base station apparatus 1A may be a dedicated message (also referred to as dedicated signaling) for a certain terminal apparatus 2A. That is, information specific to a certain terminal device (user device-specific) is transmitted using a message specific to the certain terminal device. In addition, the PDSCH is used to transmit MAC CE.

Herein, the RRC message and/or the MAC CE is also referred to as an upper layer signaling (upper layer signaling).

In addition, the PDSCH can be used to request channel state information of the downlink. The PDSCH can be used to transmit uplink resources for mapping a channel state information report (CSI feedback report) fed back from the terminal apparatus to the base station apparatus. For example, the channel state information report can be used to indicate the setting of an uplink resource that periodically reports channel state information (Periodic CSI). The channel state information report can be used to report a mode setting (CSI report mode) of the channel state information periodically.

The downlink channel state information report includes Wideband CSI (e.g., Wideband CSI) and narrowband CSI (e.g., Subband CSI). The wideband CSI calculates one channel state information for the system band of the cell. The narrow-band CSI divides the system band into predetermined units, and calculates one piece of channel state information for the division.

In addition, in Downlink wireless communication, a Synchronization Signal (SS) and a Downlink Reference Signal (DL RS) are used as Downlink physical signals. The downlink physical signal is not used to transmit information output from an upper layer but is used by a physical layer. The Synchronization signals include a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS).

The synchronization signal is used for the terminal apparatus to acquire synchronization of the frequency domain and the time domain of the downlink. In addition, the synchronization Signal is used to measure a received power, a received quality, or a Signal-to-Interference and Noise power Ratio (SINR). The Received Power measured by the Synchronization Signal is referred to as Synchronization Signal-Reference Signal Received Power (SS-RSRP), the Received Quality measured by the Synchronization Signal is referred to as Synchronization Signal-Reference Signal Received Quality (SS-RSRQ), and the SINR measured by the Synchronization Signal is referred to as SS-SINR. The SS-RSRQ is the ratio of the SS-RSRP to the RSSI. The RSSI (Received Signal Strength Indicator) is the total average Received power over a certain observation period. Further, the synchronization signal/downlink reference signal is used for the terminal apparatus to perform transmission path correction of the downlink physical channel. For example, the synchronization signal/downlink reference signal is used for the terminal device to calculate the downlink channel state information.

Here, the downlink reference signal includes: DMRS (Demodulation Reference Signal), NZP CSI-RS (Non-Zero Power Channel State Information-Reference Signal; Non-Zero Power Channel State Information Reference Signal), ZP CSI-RS (Zero Power Channel State Information-Reference Signal; Zero Power Channel State Information Reference Signal), PT-RS, TRS (Tracking Reference Signal; Tracking Reference Signal). The DMRS for the downlink is also referred to as a downlink DMRS. In the following embodiments, when only referred to as CSI-RS, the NZP CSI-RS and/or the ZP CSI-RS are included.

The DMRS is transmitted in subframes and frequency bands used for transmission of the PDSCH/PBCH/PDCCH/EPDCCH associated with the DMRS and is used for demodulation of the PDSCH/PBCH/PDCCH/EPDCCH associated with the DMRS.

The resources of the NZP CSI-RS are set by the base station apparatus 1A. For example, the terminal apparatus 2A performs measurement of a signal (measurement of a channel) or measurement of interference using the NZP CSI-RS. Further, the NZP CSI-RS is used for beam scanning for searching a preferred beam direction, beam recovery for recovery when the reception power/reception quality in the beam direction deteriorates, and the like. The resource of the ZP CSI-RS is set by the base station apparatus 1A. The base station apparatus 1A transmits ZP CSI-RS with zero output. For example, the terminal apparatus 2A measures interference in the resource corresponding to the ZP CSI-RS. The interference measurement resource corresponding to the ZP CSI-RS is also referred to as a CSI-im (interference measurement) resource.

The base station apparatus 1A transmits (sets) the NZP CSI-RS resource setting resource for the NZP CSI-RS. The NZP CSI-RS resource setting comprises one or more NZP CSI-RS resource mappings, CSI-RS resource setting IDs of the NZP CSI-RS resources and part or all of the number of antenna ports. The CSI-RS resource map is information (e.g., resource elements) representing OFDM symbols, subcarriers, within a slot in which CSI-RS resources are configured. The CSI-RS resource setting ID is used for determining NZP CSI-RS resources.

The base station apparatus 1A transmits (sets) CSI-IM resource settings. The CSI-IM resource settings include one or more CSI-IM resource maps and a CSI-IM resource setting ID for each CSI-IM resource. The CSI-IM resource map is information (e.g., resource elements) representing OFDM symbols, subcarriers within a slot in which the CSI-IM resource is configured. The CSI-IM resource setting ID is used to determine the CSI-IM setting resource.

In addition, the CSI-RS is used for measurement of reception power, reception quality, or SINR. The received power measured by the CSI-RS is referred to as CSI-RSRP, the received quality measured by the CSI-RS is referred to as CSI-RSRQ, and the SINR measured by the CSI-RS is referred to as CSI-SINR. It should be noted that CSI-RSRQ is the ratio of CSI-RSRP to RSSI.

In addition, the CSI-RS is transmitted periodically/non-periodically/semi-continuously.

The CSI is set by the terminal apparatus through an upper layer. Examples of the measurement link setting include a report setting as a setting of CSI reporting, a resource setting as a setting of a resource for measuring CSI, and a link setting linking the report setting and the resource setting for CSI measurement. In addition, there are one or more of reporting settings, resource settings, and measurement link settings.

The report setting includes a part or all of a report setting ID, a report setting type, a codebook setting, a CSI report amount, a CQI table, a group-based beam report, a CQI number per report in a low rank. The report setting ID is used to determine the report setting. The report setting type indicates periodic/aperiodic/semi-persistent CSI reports. The CSI report volume means a reported volume (value, type), for example, a part or all of CRI, RI, PMI, CQI, or RSRP. The CQI table indicates a CQI table when CQI is calculated. ON/OFF (active/inactive) is set in the beam report by group. The number of CQIs per report represents the maximum number of CSI reported per CSI. Indicates the maximum number of CQIs per report in the case where the RI is 4 or less. Note that the number of reported CQIs in low rank may be applied when the number of reported CQIs is 2. The codebook settings include the type of codebook and the setting of the codebook. The codebook type indicates a type 1 codebook or a type 2 codebook. Further, the codebook setting includes a setting of a type 1 codebook or a type 2 codebook.

The resource setting includes some or all of a resource setting ID, a synchronization signal block resource measurement list, a resource setting type, and one or more resource set settings. The resource setting ID is used to determine the resource setting. The synchronization signal block resource setting list is a list of resources for which measurement using a synchronization signal is performed. The resource setting type indicates whether the CSI-RS is transmitted periodically, non-periodically, or semi-continuously. In the case of setting to transmit the CSI-RS semi-continuously, the CSI-RS is periodically transmitted from the activation to the deactivation in the signal of the upper layer or the downlink control information.

The resource set setting includes a part or all of a resource set setting ID, a resource repetition, and information representing one or more CSI-RS resources. The resource set setting ID is used to determine resource set setting. The resource repetition means ON/OFF (valid/invalid) of the resource repetition within the resource set. In the case where the resource repetition is ON, it means that the base station apparatus uses a fixed (same) transmission beam in each of the plurality of CSI-RS resources within the resource set. In other words, in the case where the resource repetition is ON, the terminal apparatus assumes that the base station apparatus uses a fixed (same) transmission beam in each of the plurality of CSI-RS resources within the resource set. When the resource repetition is OFF, it means that the base station apparatus does not use a fixed (same) transmission beam in each of the plurality of CSI-RS resources within the resource set. In other words, in the case where the resource repetition is OFF, the terminal apparatus assumes that the base station apparatus does not use a fixed (same) transmission beam in each of the plurality of CSI-RS resources within the resource set. The information indicating the CSI-RS resources includes one or more CSI-RS resource setting IDs and one or more CSI-IM resource setting IDs.

The measurement link setting includes a part or all of a measurement link setting ID, a report setting ID, and a resource setting ID, and the report setting is linked with the resource setting. The measurement link setup ID is used to determine the measurement link setup.

An MBSFN (Multimedia Broadcast multicast service Single Frequency Network) RS transmits in the entire band of the subframe for transmission of the PMCH. The MBSFN RS is used for performing PMCH demodulation. And the PMCH transmits at an antenna port for transmitting the MBSFN RS.

Here, the downlink physical channel and the downlink physical signal are also collectively referred to as a downlink signal. The uplink physical channel and the uplink physical signal are also collectively referred to as an uplink signal. In addition, the downlink physical channel and the uplink physical channel are also collectively referred to as a physical channel. Also, the downlink physical signal and the uplink physical signal are also collectively referred to as a physical signal.

Moreover, BCH, UL-SCH, and DL-SCH are transport channels. A channel used in the MAC layer is referred to as a transport channel. Further, a Unit of a Transport channel used in the MAC layer is also referred to as a Transport Block (TB) or a MAC PDU (Protocol Data Unit). A transport block is a unit of data that the MAC layer delivers (transmitter) to the physical layer. In the physical layer, a transport block is mapped to a codeword, and encoding processing and the like are performed for each codeword.

Further, the base station apparatus can aggregate a plurality of Component Carriers (CCs) for communication for a terminal apparatus supporting Carrier Aggregation (CA) so as to perform transmission in a wider frequency band. In carrier aggregation, one Primary Cell (PCell; Primary Cell) and one or more Secondary cells (scells; Secondary cells) are set as a set of serving cells.

In Dual Connectivity (DC), a Master Cell Group (MCG) and a Slave Cell Group (SCG) are set as a serving Cell Group. The MCG is composed of a PCell and optionally one or more scells. Further, the SCG is composed of a primary SCell (pscell) and one or more scells as options.

The base station apparatus can perform communication using a radio frame. A radio frame is composed of a plurality of subframes (subintervals). When the frame length is expressed in terms of time, for example, the radio frame length may be 10 milliseconds (ms), and the subframe length may be 1 ms. In this example, the radio frame is composed of 10 subframes.

Further, the slot is composed of 14 OFDM symbols. The OFDM symbol length can vary according to the subcarrier spacing, and thus the slot length can be replaced with the subcarrier spacing. Further, a minislot may be composed of fewer OFDM symbols than a slot. The slot/minislot can become a scheduling unit. The terminal device can know the slot-based scheduling/the micro slot-based scheduling from the position (configuration) of the first downlink DMRS. In slot-based scheduling, a first downlink DMRS is configured to the 3 rd or 4 th symbol of a slot. In the micro-slot based scheduling, a first downlink DMRS is mapped to a first symbol of scheduled data (resource, PDSCH).

Further, a resource block is defined by 12 consecutive subcarriers. In addition, the resource elements are defined by indices of the frequency domain (e.g., subcarrier indices) and indices of the time domain (e.g., OFDM symbol indices). Resource elements are classified as: uplink resource elements, downlink elements, flexible resource elements, reserved resource elements. In the reserved resource elements, the terminal apparatus neither transmits an uplink signal nor receives a downlink signal.

In addition, multiple Subcarrier spacing (SCS) is supported. For example, SCS 15/30/60/120/240/480 kHz.

The base station apparatus/terminal apparatus can perform communication in a licensed band or an unlicensed band. The base station device/terminal device can communicate with at least one SCell that is a licensed band that is a PCell and operates in an unlicensed band by carrier aggregation. The base station apparatus/terminal apparatus can perform communication by dual connection in which the master cell group performs communication in the licensed frequency band and the slave cell group performs communication in the unlicensed frequency band. In addition, the base station apparatus/terminal apparatus can perform communication only in the PCell in the unlicensed band. Further, the base station apparatus/terminal apparatus can communicate only in the unlicensed band by CA or DC. Note that, the case where the Licensed band is a PCell and communication is performed by a cell (SCell, PSCell) that assists the unlicensed band by, for example, CA, DC, or the like is also referred to as LAA (Licensed-Assisted Access). The case where the base station apparatus/terminal apparatus performs communication only in the Unlicensed band is also referred to as Unlicensed-independent access (ULSA). The case where the base station apparatus/terminal apparatus performs communication only in the Licensed band is also referred to as Licensed Access (LA).

Fig. 2 is a schematic block diagram showing the configuration of the base station apparatus according to the present embodiment. As shown in fig. 2, the base station apparatus includes: an upper layer processing unit (upper layer processing step) 101, a control unit (control step) 102, a transmission unit (transmission step) 103, a reception unit (reception step) 104, a transmission/reception antenna 105, and a measurement unit (measurement step) 106. The upper layer processing unit 101 includes a radio resource control unit (radio resource control step) 1011 and a scheduling unit (scheduling step) 1012. The transmission unit 103 includes: an encoding unit (encoding step) 1031, a modulation unit (modulation step) 1032, a downlink reference signal generation unit (downlink reference signal generation step) 1033, a multiplexing unit (multiplexing step) 1034, and a radio transmission unit (radio transmission step) 1035. The receiving unit 104 includes: a radio reception unit (radio reception step) 1041, a demultiplexing unit (demultiplexing step) 1042, a demodulation unit (demodulation step) 1043, and a decoding unit (decoding step) 1044.

The upper layer processing unit 101 performs processing of a Medium Access Control (MAC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Radio Resource Control (RRC) layer. The upper layer processing unit 101 generates information necessary for controlling the transmission unit 103 and the reception unit 104, and outputs the information to the control unit 102.

The upper layer processing unit 101 receives information related to the terminal device, such as a function (UE capability) of the terminal device, from the terminal device. In other words, the terminal apparatus transmits its own function to the base station apparatus by the upper layer signal.

In the following description, the information on the terminal device includes information indicating whether or not the terminal device supports a predetermined function, or information indicating that the terminal device has introduced a predetermined function and completed a test. In the following description, whether or not a predetermined function is supported includes whether or not the introduction and the test for the predetermined function are completed.

For example, when a terminal device supports a predetermined function, the terminal device transmits information (parameter) indicating whether or not the predetermined function is supported. When a terminal device does not support a predetermined function, the terminal device does not transmit information (parameter) indicating whether or not the predetermined function is supported. That is, whether or not the predetermined function is supported is notified by transmitting information (parameter) indicating whether or not the predetermined function is supported. Note that information (parameter) indicating whether or not a predetermined function is supported may be notified using 1 bit of 1 or 0.

The radio resource controller 1011 generates or acquires downlink data (transport block) of the PDSCH placed on the downlink, system information, RRC message, MAC CE, and the like from an upper node. The radio resource controller 1011 outputs the downlink data to the transmitter 103 and outputs other information to the controller 102. The radio resource control unit 1011 manages various setting information of the terminal apparatus.

The scheduler 1012 specifies the frequency and subframe to which the physical channel (PDSCH and PUSCH) is allocated, the coding rate, modulation scheme (or MCS), transmission power, and the like of the physical channel (PDSCH and PUSCH). The scheduling unit 1012 outputs the determined information to the control unit 102.

The scheduling unit 1012 generates information for scheduling of physical channels (PDSCH and PUSCH) based on the scheduling result. The scheduling unit 1012 outputs the generated information to the control unit 102.

The control unit 102 generates a control signal for controlling the transmission unit 103 and the reception unit 104 based on information input from the upper layer processing unit 101. The control unit 102 generates downlink control information based on the information input from the upper layer processing unit 101 and outputs the downlink control information to the transmission unit 103.

The transmission unit 103 generates a downlink reference signal from the control signal input from the control unit 102, encodes and modulates the HARQ indicator, the downlink control information, and the downlink data input from the upper layer processing unit 101, multiplexes the PHICH, the PDCCH, the EPDCCH, the PDSCH, and the downlink reference signal, and transmits the signal to the terminal device 2A via the transmission/reception antenna 105.

The coding unit 1031 codes the HARQ indicator, the downlink control information, and the downlink data input from the upper layer processing unit 101 by using a predetermined coding scheme such as block coding, convolutional coding, Turbo coding, LDPC (Low density parity check) coding, Polar coding, or the like, or codes the HARQ indicator, the downlink control information, and the downlink data by using a coding scheme determined by the radio resource control unit 1011. The modulator 1032 modulates the coded bits input from the encoder 1031 by a modulation scheme that is preset or determined by the radio resource controller 1011, such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature amplitude modulation), 64QAM, or 256 QAM.

The downlink reference signal generation unit 1033 generates a sequence known to the terminal apparatus 2A, which is obtained by a rule set in advance based on a physical cell identifier (PCI, cell ID) for identifying the base station apparatus 1A, and the like, as a downlink reference signal.

The multiplexing unit 1034 multiplexes the modulated symbols of the respective channels, the generated downlink reference signal, and the downlink control information. That is, the multiplexing unit 1034 allocates the modulated symbols of each channel, the generated downlink reference signal, and the downlink control information to the resource elements.

The radio transmission unit 1035 performs Inverse Fast Fourier Transform (IFFT) on the multiplexed modulation symbols and the like to generate OFDM symbols, adds Cyclic Prefixes (CP) to the OFDM symbols to generate baseband digital signals, converts the baseband digital signals into analog signals, removes unnecessary frequency components by filtering, up-converts the transmission frequency, amplifies the power, outputs the amplified signals, and transmits the amplified signals to the transmission/reception antenna 105. The transmission power at this time is based on information set via the control unit 102.

The reception unit 104 separates, demodulates, and decodes the reception signal received from the terminal device 2A via the transmission/reception antenna 105 based on the control signal input from the control unit 102, and outputs the decoded information to the upper layer processing unit 101. The receiving unit 104 also has a function (step) of performing carrier sense.

The radio receiving unit 1041 down-converts an uplink signal received via the transmitting/receiving antenna 105 into a baseband signal, removes unnecessary frequency components, controls the amplification level so as to maintain the signal level appropriately, performs quadrature demodulation based on the in-phase component and the quadrature component of the received signal, and converts the quadrature-demodulated analog signal into a digital signal.

The radio receiver 1041 removes a portion corresponding to the CP from the converted digital signal. The radio receiving unit 1041 performs Fast Fourier Transform (FFT) on the CP-removed signal to extract a signal in the frequency domain, and outputs the signal to the demultiplexing unit 1042.

The demultiplexing unit 1042 separates the signal input from the radio receiving unit 1041 into signals such as PUCCH, PUSCH, and uplink reference signal. The separation is determined in advance by the base station apparatus 1A through the radio resource control unit 1011, and is performed based on the allocation information of the radio resource included in the uplink grant notified to each terminal apparatus 2A.

The demultiplexer 1042 compensates the transmission path of the PUCCH and the PUSCH. Further, the demultiplexing section 1042 separates the uplink reference signal.

The demodulator 1043 performs Inverse Discrete Fourier Transform (IDFT) on the PUSCH to acquire modulation symbols, and demodulates the received signal using a modulation scheme such as BPSK, QPSK, 16QAM, 64QAM, and 256QAM for each modulation symbol of the PUCCH and PUSCH, which is set in advance or which is notified to the terminal apparatus 2A in advance by the apparatus itself through an uplink grant.

The decoding unit 1044 decodes the demodulated coded bits of the PUCCH and PUSCH at a coding rate which is set in advance in a preset coding scheme, set in advance, or notified to the terminal apparatus 2A by the apparatus itself through an uplink grant, and outputs the decoded uplink data and uplink control information to the upper layer processing unit 101. When retransmitting the PUSCH, the decoding unit 1044 performs decoding using the coded bits stored in the HARQ buffer and the demodulated coded bits input from the upper layer processing unit 101.

The measurement unit 106 observes the received signal and obtains various measurement values such as RSRP, RSRQ, and RSSI. Further, the measurement unit 106 obtains reception power, reception quality, and a preferred SRS resource index from the SRS transmitted from the terminal apparatus.

Fig. 3 is a schematic block diagram showing the configuration of the terminal device according to the present embodiment. As shown in fig. 3, the terminal device includes: an upper layer processing unit (upper layer processing step) 201, a control unit (control step) 202, a transmission unit (transmission step) 203, a reception unit (reception step) 204, a measurement unit (measurement step) 205, and a transmission/reception antenna 206. The upper layer processing unit 201 is configured to include a radio resource control unit (radio resource control procedure) 2011 and a schedule information interpretation unit (schedule information interpretation procedure) 2012. The transmission unit 203 is configured to include: an encoding unit (encoding step) 2031, a modulation unit (modulation step) 2032, an uplink reference signal generation unit (uplink reference signal generation step) 2033, a multiplexing unit (multiplexing step) 2034, and a radio transmission unit (radio transmission step) 2035. The receiving unit 204 includes: a radio reception unit (radio reception step) 2041, a demultiplexing unit (demultiplexing step) 2042, and a signal detection unit (signal detection step) 2043.

The upper layer processing section 201 outputs uplink data (transport block) generated by a user operation or the like to the transmitting section 203. The upper layer processing unit 201 performs processing of a Medium Access Control (MAC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Radio Resource Control (RRC) layer.

The upper layer processing unit 201 outputs information indicating the functions of the terminal device supported by the terminal device itself to the transmission unit 203.

The radio resource control unit 2011 manages various setting information of the terminal apparatus itself. The radio resource control unit 2011 also generates information on each channel allocated to the uplink, and outputs the information to the transmission unit 203.

The radio resource control unit 2011 obtains the setting information transmitted from the base station apparatus and outputs the setting information to the control unit 202.

The scheduling information interpreter 2012 interprets the downlink control information received via the receiver 204 and determines scheduling information. The schedule information interpreter 2012 generates control information for controlling the receiver 204 and the transmitter 203 based on the schedule information and outputs the control information to the controller 202.

The control unit 202 generates a control signal for controlling the reception unit 204, the measurement unit 205, and the transmission unit 203 based on information input from the upper layer processing unit 201. The control unit 202 outputs the generated control signal to the receiving unit 204, the measuring unit 205, and the transmitting unit 203 to control the receiving unit 204 and the transmitting unit 203.

The control unit 202 controls the transmission unit 203 to transmit the CSI/RSRP/RSRQ/RSSI generated by the measurement unit 205 to the base station apparatus.

The reception unit 204 separates, demodulates, and decodes a reception signal received from the base station apparatus via the transmission/reception antenna 206 based on the control signal input from the control unit 202, and outputs the decoded information to the upper layer processing unit 201. The reception unit 204 also has a function (step) of performing carrier sense.

The radio receiving unit 2041 down-converts the downlink signal received via the transmitting/receiving antenna 206 into a baseband signal, removes unnecessary frequency components, controls the amplification level so as to maintain the signal level appropriately, performs quadrature demodulation based on the in-phase component and quadrature component of the received signal, and converts the quadrature-demodulated analog signal into a digital signal.

The radio receiving unit 2041 removes a portion corresponding to the CP from the converted digital signal, performs fast fourier transform on the signal from which the CP is removed, and extracts a signal in the frequency domain.

The demultiplexer 2042 separates the extracted signal into PHICH, PDCCH, EPDCCH, PDSCH, and downlink reference signals, respectively. The demultiplexing unit 2042 compensates the channels of the PHICH, PDCCH, and EPDCCH based on the estimated value of the channel of the desired signal obtained by the channel measurement, detects downlink control information, and outputs the downlink control information to the control unit 202. Further, the controller 202 outputs the PDSCH and the channel estimation value of the desired signal to the signal detector 2043.

The signal detector 2043 performs signal detection using the PDSCH and the channel estimation value, and outputs the result to the upper layer processor 201.

The measurement unit 205 obtains CSI/RSRP/RSRQ/RSSI and the like by performing various measurements such as CSI measurement, RRM (Radio Resource manager) measurement, RLM (Radio Link Monitoring) measurement and the like.

The transmission unit 203 generates an uplink reference signal from the control signal input from the control unit 202, encodes and modulates uplink data (transport block) input from the upper layer processing unit 201, multiplexes the PUCCH, the PUSCH, and the generated uplink reference signal, and transmits the multiplexed signal to the base station apparatus via the transmission/reception antenna 206.

The encoding unit 2031 performs encoding such as convolutional encoding, block encoding, Turbo encoding, LDPC encoding, Polar encoding, and the like on the uplink control information or uplink data input from the upper layer processing unit 201.

The modulation unit 2032 modulates the coded bits input from the coding unit 2031 in a modulation scheme notified by downlink control information such as BPSK, QPSK, 16QAM, 64QAM, or the like, or in a modulation scheme preset for each channel.

The uplink reference signal generation unit 2033 generates a sequence determined by a preset rule (formula) based on a physical Cell identifier (referred to as physical Cell identity: PCI, Cell ID, and the like) for identifying the base station apparatus, a bandwidth in which the uplink reference signal is arranged, a cyclic shift notified by the uplink grant, a parameter value for generation of a DMRS sequence, and the like.

The multiplexing unit 2034 multiplexes the PUCCH and PUSCH signals and the generated uplink reference signal for each transmission antenna port. That is, the multiplexing unit 2034 allocates the PUCCH, PUSCH signal, and the generated uplink reference signal to the resource elements for each transmission antenna port.

The radio transmission unit 2035 performs OFDM modulation on the multiplexed signal by Inverse Fast Fourier Transform (IFFT), generates an OFDMA symbol, adds a CP to the generated OFDMA symbol to generate a baseband digital signal, converts the baseband digital signal into an analog signal, removes an unnecessary frequency component, converts the analog signal into a carrier frequency by up-conversion, amplifies power, and transmits the amplified power to the transmission/reception antenna 206.

The terminal apparatus is not limited to the OFDMA system, and may perform modulation of the SC-FDMA system.

In the case of ultra-large capacity communication such as ultra-high definition video transmission, it is desired to perform ultra-wideband transmission that effectively utilizes a high frequency band. Transmission in the high frequency band requires compensation for path loss and beamforming becomes important. In an environment where a plurality of terminal apparatuses exist in a certain limited area, when a super-large capacity communication is required for each terminal apparatus, it is effective to configure a base station apparatus as a high-density Ultra-high-density network (Ultra-dense network). However, when the base station apparatus is arranged at a high density, although the SNR (Signal to noise power ratio) is greatly improved, strong interference due to beamforming may be generated. Therefore, in order to realize a super-capacity communication to all terminal apparatuses in a limited area, interference control (avoidance, suppression, removal) by beam forming and/or coordinated communication by a plurality of base stations need to be considered.

Fig. 4 shows an example of a downlink communication system of the present embodiment. The communication system shown in fig. 4 includes: base station apparatus 3A, base station apparatus 5A, and terminal apparatus 4A. Terminal apparatus 4A can set base station apparatus 3A and/or base station apparatus 5A as a serving cell. In addition, when the base station apparatus 3A or the base station apparatus 5A includes a plurality of antennas, the plurality of antennas can be divided into a plurality of sub-arrays (panels, sub-panels), and transmission/reception beamforming can be applied to each sub-array. In this case, each sub-array may include a communication device, and the configuration of the communication device is the same as that of the base station device shown in fig. 2 unless otherwise specified. When the terminal apparatus 4A includes a plurality of antennas, the terminal apparatus 4A can perform transmission or reception by beamforming. In addition, when the terminal apparatus 4A includes a plurality of antennas, the plurality of antennas can be divided into a plurality of sub-arrays (panels, sub-panels), and different transmission/reception beamforming can be applied to each sub-array. Each sub-array may include a communication device, and the configuration of the communication device is the same as that of the terminal device shown in fig. 3 unless otherwise specified. The base station apparatus 3A and the base station apparatus 5A are also simply referred to as base station apparatuses. The terminal apparatus 4A is also simply referred to as a terminal apparatus.

The synchronization signal is used to determine a preferred transmission beam of the base station apparatus and a preferred reception beam of the terminal apparatus. The base station apparatus transmits synchronization signal blocks (SS block, SSB) composed of PSS, PBCH, SSS. In the synchronization signal block burst set period set by the base station apparatus, one or more synchronization signal blocks are transmitted in the time domain, and a time index is set for each synchronization signal block. A synchronization signal block with the same time index within a synchronization signal block burst set period may be considered to be transmitted from the same location (quasi co-located): QCL to some extent as if the terminal device considers the synchronization signal block to be the same in delay spread, doppler shift, average gain, average delay, spatial receive parameters, and/or spatial transmit parameters. The spatial reception parameter is, for example, a spatial relationship of channels, an Angle of Arrival (Angle of Arrival), or the like. The spatial transmission parameter is, for example, a spatial relationship of channels, a transmission Angle (reception), or the like. That is, the terminal device can assume that: in the synchronization signal block burst set period, synchronization signal blocks having the same time index are transmitted through the same transmission beam, and synchronization signal blocks having different time indexes are transmitted through different beams. Therefore, if the terminal apparatus reports information indicating the time index of a preferred synchronization signal block within the synchronization signal block burst set period to the base station apparatus, the base station apparatus can know the transmission beam suitable for the terminal apparatus. In addition, the terminal device can obtain a reception beam suitable for the terminal device using the synchronization signal blocks of the same time index in different synchronization signal block burst set periods. Accordingly, the terminal apparatus can associate the time index of the synchronization signal block with the reception beam direction and/or the sub-array. When a plurality of sub-arrays are provided, the terminal device may use a different sub-array when connecting to a different cell.

In addition, in order to determine the transmission beam of the preferred base station apparatus and the reception beam of the preferred terminal apparatus, CSI-RS may be used. The base station apparatus can set the setting information using the signal of the upper layer. For example, the setting information includes part or all of resource setting and report setting.

The resource setting includes a resource setting ID, a resource setting type, and/or one or more CSI-RS resource set settings. The resource setting ID is used to determine the resource setting. The resource setting type indicates an operation in a time domain of resource setting. Specifically, the resource setting is a setting for transmitting the CSI-RS aperiodically (aperiodically), periodically (period), or semi-continuously (semi-continuously). The CSI-RS resource set setting includes a CSI-RS resource set setting ID and/or one or more CSI-RS resource settings. The CSI-RS resource set setting ID is used to determine CSI-RS resource set setting. The CSI-RS resource setting includes a part or all of a CSI-RS resource setting ID, a resource setting type, an antenna port number, a CSI-RS resource mapping, and power offsets of the CSI-RS and the PDSCH. The CSI-RS resource setting ID is used for determining CSI-RS resource setting, and the CSI-RS resource establishes association by using the CSI-RS resource setting ID. The CSI-RS resource map indicates resource elements (OFDM symbols, subcarriers) of CSI-RS within a configuration slot.

The resource setting is for CSI measurement or RRM measurement. The terminal device receives the CSI-RS from the set resource, calculates CSI from the CSI-RS, and reports the CSI to the base station device. Further, in the case where the CSI-RS resource set setting includes a plurality of CSI-RS resource settings, the terminal apparatus receives CSI-RS with the same reception beam at each CSI-RS resource and calculates CRI. For example, in the case where the CSI-RS resource set setting includes K (K is an integer of 2 or more) CSI-RS resource settings, the CRI represents N CSI-RS resources that are preferable from among the K CSI-RS resources. Wherein N is a positive integer less than K. When CRI indicates a plurality of CSI-RS resources, the terminal device may report CSI-RSRP measured for each CSI-RS resource to the base station device in order to indicate which CSI-RS resource is good in quality. If the CSI-RS is beamformed (precoded) in different beam directions for transmission on the plurality of set CSI-RS resources, the base station apparatus can know the transmission beam direction suitable for the base station apparatus of the terminal apparatus from the CRI reported from the terminal apparatus. On the other hand, the reception beam direction of the preferred terminal apparatus may be determined using the CSI-RS resource in which the transmission beam of the base station apparatus is fixed. For example, the base station apparatus transmits, to a certain CSI-RS resource, information indicating whether or not a transmission beam of the base station apparatus is fixed and/or a period of time during which the transmission beam is fixed. The terminal device can obtain a preferred reception beam direction from the CSI-RS received in each of the different reception beam directions on the CSI-RS resource for which the transmission beam is fixed. It should be noted that the terminal device may report the CSI-RSRP after determining the preferred receive beam direction. When the terminal device includes a plurality of sub-arrays, the terminal device may select a preferred sub-array when determining a preferred reception beam direction. It should be noted that the preferred receiving beam direction of the terminal device may be associated with the CRI. Further, when the terminal apparatus reports a plurality of CRIs, the base station apparatus can fix the transmission beam on the CSI-RS resource associated with each CRI. At this time, the terminal apparatus can determine a preferred reception beam direction for each CRI. For example, the base station apparatus can associate a downlink signal/channel and CRI to transmit. In this case, the terminal device must receive using a reception beam associated with the CRI. In addition, different base station apparatuses can transmit CSI-RS in the set plurality of CSI-RS resources. In this case, the network side can know which base station apparatus the communication quality from is good through the CRI. In addition, when the terminal apparatus includes a plurality of sub-arrays, reception can be performed by the plurality of sub-arrays at the same timing. Therefore, if the base station apparatus associates a CRI with each of a plurality of layers (codewords and transport blocks) by downlink control information or the like and transmits the CRI, the terminal apparatus can receive a plurality of layers using sub-arrays and reception beams corresponding to the CRI. However, in the case of using an analog beam, when the reception beam direction used at the same timing in one sub-array is one, the terminal apparatus may receive using a plurality of reception beams when two CRIs corresponding to one sub-array of the terminal apparatus are simultaneously set. To avoid this problem, for example, the base station apparatus groups a plurality of set CSI-RS resources, and obtains the CRI using the same sub-array in the group. Further, if different sub-arrays are used between groups, the base station apparatus can know a plurality of CRIs that can be set at the same timing. It is noted that the set of CSI-RS resources may be a set of CSI-RS resources. The QCL may be CRI that can be set at the same timing. At this time, the terminal apparatus may establish an association with the QCL information to transmit the CRI. For example, if the terminal apparatus discriminates between the CRI of the QCL and the CRI not of the QCL for reporting, the base station apparatus may set the CRI not of the QCL to the same timing instead of the CRI of the QCL. The base station apparatus may request CSI for each subarray of each terminal apparatus. In this case, the terminal apparatus reports CSI for each sub-array. When a plurality of CRIs are reported to the base station apparatus, the terminal apparatus may report only CRIs that are not QCLs.

The report setting is a setting regarding CSI reporting, including a report setting ID, a report setting type, and/or a report value (amount). The report setting ID is used to determine the report setting. The reported value (amount) is the reported CSI value (amount). The report setting type is a setting in which the report setting reports the CSI value (quantity) aperiodically (aperiodic), periodically (period), or semi-continuously (semi-persistent).

When reporting CSI aperiodically or semi-continuously, the base station apparatus transmits a trigger (trigger information) for starting reporting of the CSI to the terminal apparatus. The trigger may be DCI or signaling of an upper layer.

In order to identify a transmission beam of a preferred base station apparatus, a codebook defining candidates of a predetermined precoding (beamforming) matrix (vector) is used. The base station apparatus transmits the CSI-RS, and the terminal apparatus obtains a preferred precoding (beamforming) matrix from the codebook and reports the precoding matrix to the base station apparatus as a PMI. Thereby, the base station apparatus can know the transmission beam direction suitable for the terminal apparatus. In the codebook, there are a precoding (beamforming) matrix for combining antenna ports and a precoding (beamforming) matrix for selecting antenna ports. When a codebook for selecting antenna ports is used, the base station apparatus can use different transmission beam directions for each antenna port. Therefore, if the terminal apparatus reports with the preferred antenna port as the PMI, the base station apparatus can know the preferred transmission beam direction. The preferred reception beam of the terminal apparatus may be a reception beam direction associated with the CRI, or the preferred reception beam direction may be determined again. In the case where a codebook for selecting antenna ports is used and a preferred reception beam direction of the terminal apparatus adopts a reception beam direction associated with the CRI, it is desirable that the reception beam direction for receiving the CSI-RS is received in the reception beam direction associated with the CRI. Even when the reception beam direction associated with the CRI is used, the terminal apparatus can associate the PMI with the reception beam direction. In addition, when a codebook for selecting antenna ports is used, each antenna port can be transmitted from a different base station apparatus (cell). In this case, if the terminal apparatus reports the PMI, the base station apparatus can know with which base station apparatus (cell) the communication quality is good. In this case, antenna ports of different base station apparatuses (cells) may be used without QCL.

In case of reporting CSI through PUSCH or in case of reporting sub-band CSI through PUCCH, CSI is split into two parts for reporting. In addition, the CSI report includes a type 1CSI report and a type 2CSI report. In type 1CSI reporting, CSI based on a type 1 codebook (also referred to as type 1CSI) is reported. In type 2CSI reporting, CSI based on a type 2 codebook (also referred to as type 2CSI) is reported. In addition, the two parts are also referred to as a first part (part 1, CSI part 1) and a second part (part 2, CSI part 2). Note that the first part has higher priority than the second part CSI report. For example, in the case where the RI is 4 or less, the first part includes a part or all of the sum of the first RI and the second RI (or the second RI), the second CRI, the first CRI, and the CQI based on the second CRI (or the second CQI). The second part comprises a part or all of the first CRI, the first RI, the first CQI, the first PMI and the second PMI. In case the RI is greater than 4, the first part includes a part or all of the sum of the first RI and the second RI (or the second RI), the second CRI, the second CQI. The second part comprises a part or all of the first CRI, the first RI, the first CQI, the first PMI and the second PMI. Note that CSI may be divided into three parts. The third part is also referred to as the third part (part 3, CSI part 3). The third portion has a lower priority than the second portion. At this time, the first part includes a part or all of the sum of the first RI and the second RI (or the second RI), the second CRI, the first CRI, and the CQI based on the second CRI (or the second CQI). The second part comprises a part or all of the first CRI, the first RI and the first CQI. The third part comprises a part or all of the first PMI and the second PMI.

Note that the terminal apparatus may report the CSI based on the first CRI and the CSI based on the second CRI by dividing each of the two parts. Note that the two parts of the CSI based on the first CRI are also referred to as a first part 1 and a first part 2. Furthermore, the two parts of the CSI based on the second CRI are also referred to as second part 1 and second part 2. It should be noted that the first part 1 includes a part or all of the first CRI, the first RI, and the first CQI. Further, the first part 2 includes a first PMI. In addition, the second part 1 includes a part or all of the second CRI, the second RI, and the second CQI. Further, the second part 2 includes a second PMI. The priority of CSI may be set higher in the order of the second part 1, the first part 1, the second part 2, and the first part 2. At this time, the terminal apparatus reports CSI with a long period (less change) for each of the second CRI and the first CRI, and the base station apparatus and the terminal apparatus can communicate using the minimum parameters relating to the first CRI and the second CRI. In addition, the priority of CSI can be set higher in the order of the second part 1, the second part 2, the first part 1, and the first part 2. At this time, the terminal apparatus preferentially reports the complete CSI in the second CRI, whereby the base station apparatus and the terminal apparatus can communicate using detailed parameters related to the second CRI.

In addition to the serving cell, the terminal apparatus 4A may receive an interference signal from a neighboring cell (neighboring cell interference). The interference signal is a PDSCH, PDCCH or reference signal of a neighbor cell. In this case, it is effective to remove or suppress the interference signal in the terminal apparatus. As a way of removing or suppressing the interfering signal, the following may be applied: an E-MMSE (Enhanced-Minimum Mean Square Error) that estimates a channel of an interfering signal and suppresses by linear weighting, an interference canceller that generates and removes a replica of the interfering signal, an MLD (Maximum Likelihood Detection) that searches for transmission signal candidates of all desired signals and interfering signals and detects a desired signal, an R-MLD (Reduced complexity-MLD: Reduced complexity-Maximum Likelihood Detection) that reduces transmission signal candidates and sets an amount of computation lower than the MLD, and the like. Channel estimation of the interfering signal, demodulation of the interfering signal, or decoding of the interfering signal is required to apply these approaches. Therefore, in order to effectively remove or suppress the interference signal, the terminal device needs to know parameters of the interference signal (neighbor cell). Therefore, the base station apparatus may transmit (set) assistance (Assist) information including parameters of the interference signal (neighbor cell) to the terminal apparatus in order to Assist the terminal apparatus in removing or suppressing the interference signal. One or more auxiliary information is set. The auxiliary information includes, for example: some or all of the physical cell ID, the virtual cell ID, the power ratio (power offset) of the reference signal to the PDSCH, the scrambling ID of the reference signal, QCL information (quaternary co-location information), CSI-RS resource setting, the number of CSI-RS antenna ports, subcarrier spacing, resource allocation granularity, resource allocation information, DMRS setting, DMRS antenna port number, number of layers, TDD DL/UL configuration, PMI, RI, Modulation scheme, and MCS (Modulation and coding scheme). The virtual cell ID is an ID virtually assigned to a cell, and there may be cells having the same physical cell ID but different virtual cell IDs. The QCL information is information on QCLs for a predetermined antenna port, a predetermined signal, or a predetermined channel. When the long-section characteristic of the channel for the transmission symbol at one of the two antenna ports can be estimated from the channel for the transmission symbol at the other antenna port, these antenna ports are referred to as QCLs. The long interval characteristics include: delay spread (delay spread), Doppler spread (Doppler spread), Doppler shift (Doppler shift), average gain, average delay, spatial reception parameters, and/or spatial transmission parameters. That is, when the two antenna ports are QCLs, the terminal device can consider that the long section characteristics of the antenna ports are the same. The subcarrier spacing represents a candidate for the subcarrier spacing of the interfering signal or the subcarrier spacing that may be used in its frequency band. When the subcarrier spacing included in the assistance information is different from the subcarrier spacing used for communication in the serving cell, the terminal apparatus may not remove or suppress the interference signal. Candidates of subcarrier spacing that may be used in their frequency bands may represent commonly used subcarrier spacings. For example, a subcarrier spacing of a low frequency such as that used for high-reliability low-delay communication (emergency communication) may not be included in a subcarrier spacing that is generally used. The resource allocation granularity indicates the number of resource blocks for which precoding (beamforming) does not change. DMRS settings indicate PDSCH mapping types and DMRS additional configurations. DMRS resource allocation varies according to PDSCH mapping type. For example, for PDSCH mapping type a, the DMRS is mapped to the third symbol of the slot. Also, for example, for PDSCH mapping type B, DMRS is mapped to the first OFDM symbol of the assigned PDSCH resources. The additional configuration of the DMRS indicates whether or not there is an additional DMRS configuration or an added configuration. A part or all of the parameters included in the auxiliary information are transmitted (set) by an upper layer signal. In addition, some or all of the parameters included in the auxiliary information are transmitted using downlink control information. When each parameter included in the assistance information indicates a plurality of candidates, the terminal device blindly detects a preferred parameter from the candidates. In addition, the terminal apparatus blindly detects parameters that are not included in the auxiliary information.

When a terminal apparatus performs communication using a plurality of reception beam directions, the interference situation around the terminal apparatus varies greatly depending on the reception beam directions. For example, an interfering signal that is stronger in one receive beam direction may be weaker in another receive beam direction. The assistance information of a cell having a low possibility of strong interference is meaningless, and may cause useless calculation when determining whether or not a strong interference signal is received. Therefore, the auxiliary information is preferably set for each reception beam direction. However, the base station apparatus does not necessarily know the reception direction of the terminal apparatus, and therefore, the information related to the reception beam direction may be associated with the auxiliary information. For example, since the terminal apparatus can associate CRI with the reception beam direction, the base station apparatus can transmit (set) one or more pieces of assistance information for each CRI. Further, since the terminal apparatus can associate the time index of the synchronization signal block with the reception beam direction, the base station apparatus can transmit (set) one or more pieces of auxiliary information per the time index of each synchronization signal block. Further, since the terminal apparatus can associate the PMI (antenna port number) with the reception beam direction, the base station apparatus can transmit (set) one or more pieces of auxiliary information for each PMI (antenna port number). In addition, when the terminal apparatus includes a plurality of sub-arrays, since there is a high possibility that the reception beam direction changes for each sub-array, the base station apparatus can transmit (set) one or a plurality of pieces of auxiliary information for each index associated with the sub-array of the terminal apparatus. Further, when a plurality of base station apparatuses (transmitting/receiving points) communicate with a terminal apparatus, the terminal apparatus is highly likely to communicate in a reception beam direction different from that of each base station apparatus (transmitting/receiving point). Therefore, the base station apparatus transmits (sets) one or more pieces of auxiliary information for each piece of information indicating the base station apparatus (transmission/reception point). The information indicating the base station apparatus (transmitting/receiving point) may be a physical cell ID or a virtual cell ID. When different DMRS antenna port numbers are used in the base station apparatus (transmitting/receiving point), information indicating the DMRS antenna port numbers and DMRS antenna groups is information indicating the base station apparatus (transmitting/receiving point).

The number of pieces of assistance information set by the base station apparatus for each CRI may be common. Here, the number of pieces of assistance information refers to the type of assistance information, the number of elements of each piece of assistance information (for example, the number of candidates for a cell ID), and the like. The base station apparatus sets the maximum value for the number of pieces of auxiliary information set for each CRI, and can set the auxiliary information for each CRI within the range of the maximum value.

When the reception beam direction of the terminal apparatus changes, the transmission antenna is highly likely not to be QCL. Therefore, the above-mentioned side information can be associated with the QCL information. For example, when the base station apparatus transmits (sets) the assistance information of a plurality of cells, the terminal apparatus can be instructed with a cell that is QCL (or a cell that is not QCL).

The terminal apparatus uses the supplementary information associated with CRI used for communication with the serving cell to remove or suppress the interference signal.

The base station apparatus can set the auxiliary information associated with the reception beam direction (CRI/time index/PMI/antenna port number/sub-array of the synchronization signal block) and the auxiliary information not associated with the reception beam direction (CRI/time index/PMI/antenna port number/sub-array of the synchronization signal block). In addition, the assistance information associated with the reception beam direction and the assistance information not associated with the reception beam direction may be selectively used according to the capability and category of the terminal apparatus. The capability, class of the terminal device may indicate whether the terminal device supports receive beamforming. In addition, the side information associated with the reception beam direction and the side information not associated with the reception beam direction may also be selectively used according to the frequency band. For example, the base station apparatus does not set the auxiliary information associated with the reception beam direction when the frequency is lower than 6 GHz. For example, the base station apparatus sets the auxiliary information associated with the reception beam direction only at a frequency higher than 6 GHz.

It should be noted that the CRI may be associated with the CSI resource set setting ID. In the case of indicating the CRI to the terminal apparatus, the base station apparatus may indicate the CRI to the terminal apparatus together with the CSI resource set setting ID. When the CSI resource set setting ID is associated with one CRI or one reception beam direction, the base station apparatus may set the auxiliary information for each CSI resource set setting ID.

In order to know the neighbor cell associated with the reception beam direction of the terminal apparatus, the base station apparatus requests the terminal apparatus for neighbor cell measurement. The neighbor cell measurement request includes information associated with the reception beam direction of the terminal apparatus and a cell ID. When receiving the adjacent cell measurement request, the terminal device measures the RSRP, RSRQ, and RSSI of the adjacent cell, and reports the measured RSRP, RSRQ, and RSSI to the base station device together with information related to the reception beam direction of the terminal device. The information related to the reception beam direction of the terminal device is information indicating the CRI, the time index of the synchronization signal block, and the sub-array of the terminal device or the base station device (transmitting/receiving point).

Further, in the case where the terminal device moves, the surrounding environment may change from moment to moment. Therefore, it is desirable that the terminal device observe the surrounding channel conditions, interference conditions, and the like at predetermined timing and report them to the base station device. The reporting results are reported in a periodic report or event-dependent report. In the case of the periodic reporting, the terminal device periodically measures RSRP/RSRQ of the synchronization signal or CSI-RS to report. In the case of event-dependent reporting, the event ID is associated with the condition of the report. The event ID has, for example, the following contents, and further sets threshold values (threshold value 1 and threshold value 2, if necessary) and offset values necessary for conditional calculation.

Event A1: the measurement result of the serving cell is better than the set threshold.

Event A2: the measurement result of the serving cell is worse than the set threshold.

Event A3: the measurement result of the neighbor cell is better than the offset value set by the measurement result of the PCell/PSCell.

Event A4: and the measurement result of the adjacent cell is better than the set threshold value.

Event A5: the measurement result of the PCell/PSCell is worse than the set threshold 1, and the measurement result of the neighbor cell is better than the set threshold 2.

Event A6: the measurement result of the neighboring cell is better than the offset value set by the measurement result of the SCell.

Event C1: a case where a measurement result at the CSI-RS resource is better than a set threshold value.

Event C2: the measurement result at the CSI-RS resource is better than the case of the measurement result offset at the set reference CSI-RS resource.

Event D1: and the measurement result of the CSI-RS resource different from the CRI is better than the set threshold value.

Event D2: a measurement result of the CSI-RS resource associated with the CRI is worse than a set threshold value.

Event D3: the measurement result of the reception beam direction not associated with the CRI is better than the set threshold.

Event D4: the measurement result of the SS block index used for synchronization is worse than the set threshold.

Event D5: the measurement result of SS block indexes not used for synchronization is worse than the set threshold.

Event E1: the base station apparatus determines that the elapsed time after the wave has passed a threshold value. Event E2: the terminal device determines that the elapsed time after the wave has passed the threshold.

The terminal device reports SS-RSRP/SS-RSRQ/CSI-RSRP/CSI-RSRQ/RSSI as a measurement result when reporting is performed based on the report setting.

Fig. 5 shows an example of an uplink communication system of the present embodiment. The communication system shown in fig. 5 includes: base station apparatus 7A, base station apparatus 9A, and terminal apparatus 6A. Terminal apparatus 6A can set base station apparatus 7A and/or base station apparatus 9A as a serving cell. In addition, when the base station apparatus 7A or the base station apparatus 9A includes a plurality of antennas, the plurality of antennas can be divided into a plurality of sub-arrays (panels, sub-panels), and transmission/reception beamforming can be applied to each sub-array. In this case, each sub-array may include a communication device, and the configuration of the communication device is the same as that of the base station device shown in fig. 2 unless otherwise specified. When the terminal apparatus 6A includes a plurality of antennas, the terminal apparatus 6A can perform transmission or reception by beamforming. In addition, when the terminal device 6A includes a plurality of antennas, the plurality of antennas can be divided into a plurality of sub-arrays (panels, sub-panels), and different transmission/reception beamforming can be applied to each sub-array. Each sub-array may include a communication device, and the configuration of the communication device is the same as that of the terminal device shown in fig. 3 unless otherwise specified. The base station apparatus 7A and the base station apparatus 9A are also simply referred to as base station apparatuses. The terminal device 6A is also simply referred to as a terminal device.

In the uplink, the SRS is used to determine a preferred transmission beam for the terminal apparatus and a preferred reception beam for the base station apparatus. The base station apparatus can transmit (set) the setting information on the SRS using the upper layer signal. The setting information includes one or more SRS resource set settings. The SRS resource set setting includes an SRS resource set setting ID and/or one or more SRS resource settings. The SRS resource set setting ID is used to determine SRS resource set setting. The SRS resource setting comprises the following steps: an SRS resource setting ID, an SRS antenna port number, an SRS transmission interval (Comb), SRS resource mapping, SRS frequency hopping, and an SRS resource setting type. The SRS resource setting ID is used to determine SRS resource setting. The SRS transmission interval indicates a frequency interval of the comb-shaped spectrum and a position (offset) within the frequency interval. The SRS resource map indicates an OFDM symbol position and an OFDM symbol number at which the SRS is arranged in the slot. SRS hopping is information indicating hopping of SRS. The SRS resource setting type indicates an operation in a time domain in which the SRS resource is set. Specifically, the setting of the SRS resource indicates whether the SRS resource setting is a setting for transmitting the SRS aperiodically (aperiodic), a setting for transmitting the SRS periodically (period), or a setting for transmitting the SRS semi-continuously (semi-persistent).

When a plurality of SRS resources are set, if each SRS resource transmits in a different transmission beam direction, the base station apparatus can determine a preferred SRS resource. The base station apparatus transmits (instructs) an SRS Resource Indicator (SRI) which is information indicating the SRS Resource to the terminal apparatus, and the terminal apparatus can know that the transmission beam direction transmitted by the SRS Resource is preferable. In order to obtain a preferred reception beam of the base station apparatus, the base station apparatus may request the terminal apparatus to transmit the same transmission beam for a predetermined period of time. The terminal device transmits in the same transmission beam direction as the transmission beam direction transmitted by the indicated SRI in the indicated time slot and the indicated SRS resource in response to a request from the base station device.

When a terminal apparatus includes a plurality of sub-arrays, it can communicate with a plurality of base station apparatuses (transmitting/receiving points). In the example of fig. 5, terminal apparatus 6A can set base station apparatus 7A and base station apparatus 9A as serving cells. In this case, the terminal apparatus 6A is highly likely to have a transmission beam direction suitable for communication with the base station apparatus 7A different from a transmission beam direction suitable for communication with the base station apparatus 9A. Therefore, if the terminal apparatus 6A transmits in different transmission beam directions by different sub-arrays, it can communicate with the base station apparatus 7A and the base station apparatus 9A at the same timing.

When a terminal apparatus transmits an SRS through a plurality of antenna ports in a certain SRS resource, the terminal apparatus can use different transmission beam directions for each antenna port. In this case, if the base station apparatus instructs the terminal apparatus to transmit at the preferred antenna port number, the terminal apparatus can know the preferred transmission beam direction. The base station apparatus may instruct the terminal apparatus to transmit the pmi (tpmi) using the codebook for selecting the antenna port. The base station apparatus can indicate to the terminal apparatus which codebook to refer to. The terminal apparatus can refer to the indicated codebook to use the transmission beam direction corresponding to the antenna port number shown by the TPMI.

When the terminal apparatus includes a plurality of sub-arrays and can transmit at the same timing using the plurality of sub-arrays, different antenna port numbers may be assigned to the sub-arrays. At this time, if the terminal apparatus transmits SRS from different antenna ports of the sub-array using the transmission beam and receives TPMI from the base station apparatus, the terminal apparatus can know a preferred sub-array and transmission beam direction. Therefore, the terminal apparatus can associate TPMI with the sub-array and the transmission beam direction.

When a terminal apparatus communicates with a plurality of base station apparatuses (transmitting/receiving points), the same signal (data) may be transmitted to each base station apparatus (transmitting/receiving point), or different signals (data) may be transmitted. When a terminal device communicates with a plurality of base station devices (transmitting and receiving points) using the same signal (data), the reception quality can be improved by combining signals received by the plurality of base station devices (transmitting and receiving points), and therefore, it is desirable that the plurality of base station devices (transmitting and receiving points) perform reception processing in cooperation with each other.

The base station apparatus can schedule the PUSCH using the DCI. When a terminal apparatus communicates with a plurality of base station apparatuses, each base station apparatus can transmit DCI used for scheduling of a PUSCH. The DCI includes SRI and/or TPMI, and the terminal apparatus can know a transmission beam suitable for the base station apparatus. Further, when the terminal apparatus communicates with a plurality of base station apparatuses, the terminal apparatus can transmit PUSCH to the plurality of base station apparatuses using DCI from one base station apparatus. For example, when DCI includes control information for a plurality of layers (codewords and transport blocks) and SRI and/or TPMI is indicated (set) for each layer, each layer is transmitted using a transmission beam suitable for each base station apparatus. Thus, the terminal apparatus can transmit different signals (data) to the plurality of base station apparatuses when receiving one DCI. In addition, when the DCI includes one layer of control information and a plurality of SRIs and/or TPMIs are indicated (set) for one layer, the terminal apparatus transmits one layer (same data) using different transmission beams. Thus, the terminal apparatus can transmit the same signal (data) to the plurality of base station apparatuses when receiving one DCI.

When a terminal device transmits the same timing to a plurality of base station devices, it is desirable that each base station device know the communication quality with the terminal device at the same timing. Therefore, the base station apparatus can instruct (trigger) a plurality of SRIs and SRS resources corresponding to the SRIs with one DCI. That is, if the terminal apparatus transmits the SRS in the transmission beam direction corresponding to each SRI at the same timing, each base station apparatus can know the communication quality with the terminal apparatus at the same timing.

When the sub-array of the terminal device uses only one transmission beam direction at the same timing, the terminal device transmits to a plurality of base station devices using different sub-arrays at the same timing. In this case, when the base station apparatus instructs (sets) two SRIs with one DCI, the terminal apparatus may not be able to perform transmission corresponding to the two SRIs at the same timing when the two SRIs are associated with the same sub-array. To avoid this problem, for example, the base station apparatus may request, from the terminal apparatus: a plurality of SRS resources are grouped and set, and SRS are transmitted using the same sub-array within a group. Further, if different sub-arrays are used between groups, the base station apparatus can know a plurality of SRIs that can be set at the same timing. It is noted that the group of SRS resources may be a set of SRS resources. It should be noted that SRS (SRS resource) settable at the same timing may not be QCL. At this time, the terminal device may establish an association with the QCL information to transmit the SRS. For example, if the terminal apparatus discriminates between SRS that is QCL and SRS that is not QCL for transmission, the base station apparatus may set SRI that is QCL to the same timing, but set SRI that is not QCL to the same timing. The base station apparatus may request SRS for each subarray of each terminal apparatus. In this case, the terminal apparatus transmits the SRS for each sub-array.

When the terminal device indicates two SRIs that cannot be transmitted from the base station device at the same timing, the terminal device may request the base station device to perform the beam recovery procedure for transmitting beam selection again. This beam recovery process is performed when the communication quality is significantly degraded due to off-tracking of the transmission and reception beams between the terminal apparatus and the base station apparatus, and the terminal apparatus needs to acquire a new connection destination (transmission beam of the base station apparatus) in advance. The terminal apparatus according to the present embodiment is in a state where the transmission beam itself is secured, but can use a beam recovery procedure in order to eliminate a state where two SRIs are set, which cannot be transmitted at the same timing.

The terminal device of the present embodiment may include a plurality of antennas (antenna panels) in which independent beamforming is set. The terminal device of the present embodiment can use a plurality of antenna panels. Of course, the terminal device can use the plurality of antenna panels by switching them, but if the antenna panels are not selected appropriately, the transmission quality is significantly reduced particularly in high-frequency transmission. Therefore, the terminal apparatus can perform beam scanning (probing) with the base station apparatus in order to select the beam forming set in the antenna. The terminal apparatus of the present embodiment can transmit an SRS for performing the beam scanning.

The base station apparatus according to the present embodiment can notify the terminal apparatus of information indicating duality (correlation, inverse) of transmission (channel) characteristics of downlink and uplink. As information on transmission characteristics, the base station apparatus can notify the terminal apparatus of information indicating Beam correlation (Beam correlation), Spatial correlation information (Spatial correlation information), and reception parameters). Here, the beam correspondence includes: information indicating the correlation between reception beamforming (spatial domain reception filter, reception weight, reception parameter, reception spatial parameter) used when the terminal device receives a downlink signal and transmission beamforming (spatial domain transmission filter, transmission weight, transmission parameter, transmission spatial parameter) used when the terminal device transmits an uplink signal.

The base station apparatus can set a beam association for each signal transmitted from each terminal apparatus. For example, the base station apparatus can notify the terminal apparatus of information indicating beam correspondence to the SRS transmitted by the terminal apparatus. The base station apparatus can notify the terminal apparatus of SRS spatial correlation information (SRS-SpatialRelationInfo). When the SRS spatial correlation information indicates a predetermined signal (value, state), the terminal apparatus can transmit the SRS using beamforming associated with the predetermined signal. For example, when the SRS spatial correlation information specifies the synchronization signals (SSB and PBCH), the terminal apparatus can transmit the SRS using the reception beamforming used when receiving the synchronization signals. Similarly, the base station apparatus can notify the terminal apparatus of spatial correlation information on other signals (for example, PUCCH/PUSCH/RS/RACH and the like) transmitted by the terminal apparatus and other signals (for example, PDCCH/PDSCH/RS) received by the terminal apparatus. That is, the base station apparatus can notify the terminal apparatus of the spatial correlation information between the first signal and the second signal. The terminal device can transmit the second signal (or receive the second signal) using the reception parameter of the received first signal (or the transmission parameter of the transmitted first signal) when receiving the spatial correlation information between the first signal and the second signal and recognizing that the spatial correlation information ensures spatial correlation between the first signal and the second signal.

QCLs include at least the following four types, each of which is considered to be the same parameter different. The base station apparatus and the terminal apparatus can set any one of the following QCL types for the antenna ports (or signals associated with the antenna ports), and can also set a plurality of QCL types at the same time.

QCL type a (QCL type a): doppler shift, Doppler spread, average delay, and delay spread

QCL type B (QCL type B): doppler shift, Doppler spread

QCL type C (QCL type C): doppler shift, average delay

QCL type D (QCL type D): spatial Rx (space Rx)

When the PDSCH resources are scheduled using the downlink assignment, the terminal apparatus can set reception beamforming for receiving the PDSCH. In this case, the terminal apparatus can acquire information associated with the reception beamforming from the DCI describing the downlink assignment. For example, the terminal apparatus can acquire a Transmission Configuration Indication (TCI) from the DCI. The TCI represents information that the QCL of the antenna port through which the PDSCH is transmitted has established association. The terminal device can set reception beamforming for receiving the PDSCH (or the DMRS associated with the PDSCH) by reading the TCI. For example, when the DMRS associated with the SSB and PDSCH in the TCI is set to the QCL as the reception parameter, the terminal apparatus can use the reception beam used when receiving the SSB fed back to the index of the base station apparatus for reception of the PDSCH. When the terminal device is not ready to acquire DCI before the reception of the PDSCH is started (before a frame including the PDSCH is received by the terminal device) (when the value of the scheduling offset indicating the time difference between the scheduling information and the PDSCH is smaller than a predetermined value), the terminal device can receive the PDSCH according to TCI default set as default. Note that TCI-default is 1 of 8 set TCIs. In addition, the terminal apparatus can set reception beamforming based on the setting of the TCI default when receiving the PDCCH.

In order to identify a transmission beam of a preferred base station apparatus, a codebook defining candidates of a predetermined precoding (beamforming) matrix (vector) is used. The base station apparatus transmits the CSI-RS, and the terminal apparatus obtains a preferred precoding (beamforming) matrix from the codebook and reports the precoding matrix to the base station apparatus as a PMI. Thereby, the base station apparatus can know the transmission beam direction suitable for the terminal apparatus. In the codebook, there are a precoding (beamforming) matrix for combining antenna ports and a precoding (beamforming) matrix for selecting antenna ports. When a codebook for selecting antenna ports is used, the base station apparatus can use different transmission beam directions for each antenna port. Therefore, if the terminal apparatus reports with the preferred antenna port as the PMI, the base station apparatus can know the preferred transmission beam direction. The preferred reception beam of the terminal apparatus may be a reception beam direction associated with the CRI, or the preferred reception beam direction may be determined again. In the case where a codebook for selecting antenna ports is used and a preferred reception beam direction of the terminal apparatus adopts a reception beam direction associated with the CRI, it is desirable that the reception beam direction for receiving the CSI-RS is received in the reception beam direction associated with the CRI. Even when the reception beam direction associated with the CRI is used, the terminal apparatus can associate the PMI with the reception beam direction. In addition, when a codebook for selecting antenna ports is used, each antenna port can be transmitted from a different base station apparatus (cell). In this case, if the terminal apparatus reports the PMI, the base station apparatus can know with which base station apparatus (cell) the communication quality is good. In this case, antenna ports of different base station apparatuses (cells) may be used without QCL.

The terminal apparatus of the present embodiment notifies the base station apparatus of a plurality of PMIs. The terminal apparatus according to the present embodiment can notify the base station apparatus of the PMI1 as the first PMI and the PMI2 as the second PMI.

The PMI1 can also be a PMI11 as an eleventh PMI, a PMI12 as a twelfth PMI, a PMI13 as a thirteenth PMI, and a PMI14 as a fourteenth PMI.

The PMI11 can also be constituted by q1 (the one hundred eleventh PMI, PMI111) as an element relating to the first dimension and q2 (the one hundred twelfth PMI, PMI112) as an element relating to the second dimension. q1 can represent an orthogonal matrix referenced by v as a vector in the first dimension. The orthogonal matrix referred to by v is a DFT matrix given by the number N1 of CSI-RS ports in the first dimension of the base station apparatus, but the base station apparatus may oversample the DFT matrix by the number O1 of oversamples in the first dimension. This is because there are O1 orthogonal matrices referenced by v, and therefore, q1 is an indicator indicating an orthogonal matrix referenced by v among the O1 orthogonal matrices. On the other hand, q2 is an indicator of an orthogonal matrix referred to by u as a vector of the second dimension. The base station apparatus can oversample the DFT matrix given by the number N2 of CSI-RS ports of the second dimension by the oversampling number O2 for the second dimension. q2 is an indicator indicating an orthogonal matrix referenced by v among the O2 orthogonal matrices. When the terminal apparatus performs feedback assuming a plurality of layers, the orthogonal matrix indicated by the PMI11 can be shared between the layers. The terminal device according to the present embodiment can also notify the PMI11 on a layer-by-layer basis.

The PMI12 may be an indicator indicating at least one of a plurality of vectors possessed by a matrix selected by the PMI 11. The terminal device can notify the base station device of a vector given by a kronecker product of v, which is a vector of the first dimension, and u, which is a vector of the second dimension. u and v are vectors selected from DFT matrices of size N1 and size N2, respectively, and thus there are N1 × N2 candidates for the vector given by the kronecker product of v and u. The terminal apparatus of the present embodiment can feed back to the base station apparatus a plurality of vectors given by the kronecker product of v and u. The number of vectors that the terminal device can feed back is set by the base station device according to L1(L1, first value) representing the first vector number. L1 can be notified to the terminal apparatus by signaling of an upper layer. Thus, when C (x, y) is a combination function indicating the number of combinations when y are selected from the total number x, the terminal apparatus feeds back to the base station apparatus C (N1N1, L) candidates of vector combinations. The PMI12 may be an indicator indicating that there is any one of candidates for a combination of C (N1N1, L) vectors. The base station apparatus according to the present embodiment may include a polarized antenna, but may use a vector selected by the PMI12 in common. Similarly to PMI11, the PMI12 can be shared by terminal apparatuses between layers. The terminal apparatus can also notify the PMI12 between layers.

The base station apparatus can set the value of L1 based on the number of ports of the CSI-RS. As will be described later, the base station apparatus may set the value of L1 based on information other than the number of ports of the CSI-RS.

The PMI13 may be an indicator indicating a strongest vector for the terminal apparatus among the L1 vectors notified by the PMI 12. When the base station apparatus includes a polarized wave antenna, the base station apparatus is an indicator that indicates the strongest vector among 2 × L1 vectors including polarized waves. The terminal apparatus can notify the base station apparatus of the PMI13 for each layer. The terminal device of the present embodiment may select one layer and notify the strongest vector in the layer. In this case, the terminal apparatus can notify the base station apparatus of the selected layer as well. The terminal device can always notify the strongest vector in layer 1.

The PMI14 is an indicator indicating an amplitude coefficient by which the L1 vectors designated by the PMI12 can be multiplied. Note that since the PMI14 can also calculate an amplitude coefficient for each polarized wave, the PMI14 in this case is an indicator indicating an amplitude coefficient by which (2 × L1) vectors are multiplied.

The amplitude coefficient can be a value obtained by dividing the interval between 0 and 1 into predetermined particle sizes. For example, the terminal device of the present embodiment uses 3 bits of information, and converts 0 to 64^-1/2、32^-1/2、16^-1/2、8^-1/2、4^-1/2、2^-1/2Either one of 1 and 1 is reported to the base station apparatus as an amplitude coefficient related to (2 × L1) vectors indicated by the PMI 12. The terminal apparatus can notify the PMI14 for each layer. The terminal device according to the present embodiment can notify the PMI14 as a common value between layers. The PMI14 can be represented by (2L-1) elements (k) of the amplitude coefficient representing the amount of each vector indicated by the PMI12⁽¹⁾ ₀(fourteenth (0) PMI, PMI14(0)), k⁽¹⁾ ₁(fourteenth (1) PMI, PMI14(1) … … k⁽¹⁾ _2L-1(fourteenth (2L-1) PMI, PMI14 (2L-1)). Further, elements can be defined per layer.

PMI21 can represent the phase coefficients for the (2 × L1) vectors indicated by PMI 12. The phase coefficient can be an angle obtained by dividing an angle of 360 ° into predetermined particle sizes. For example, when the 360 ° is divided into four, the terminal apparatus can notify the base station apparatus of any one of the phase coefficients indicating four angles of 0 °, 90 °, 180 °, and 270 ° as the phase coefficient. The base station apparatus can notify the NPSK to the terminal apparatus as a value indicating the granularity of the phase coefficient. The base station apparatus can notify any one of 2, 4, and 8 as the NPSK. The terminal apparatus can notify the base station apparatus of the PMI21 for each layer. The terminal apparatus can notify the base station apparatus of a value common to the PMI21 between layers.

PMI22 can represent the amplitude coefficients for the (2 × L1) vectors indicated by PMI 12. PMI14 can also represent amplitude coefficients, but in PMI22, amplitude coefficients are indicated per subband. Thus, the terminal apparatus can feed back the PMI22 when the base station apparatus requests feedback of CSI for each subband. The terminal apparatus can notify the base station apparatus of the PMI22 for each layer. The terminal apparatus can notify the base station apparatus of a value common to the PMI22 between layers. PMI22 can be represented by (2L-1) elements (k) of the phase coefficient of each vector indicated by PMI12⁽²⁾ ₀(twenty-second (0) PMI, PMI22(0)), k⁽²⁾ ₁(the second twelve (1) PMI, PMI22(1) … … k⁽¹⁾ _2L-1(the twenty-second (2L-1) PMI, PMI22 (2L-1)). The elements constituting the PMI22 can be defined per layer.

The terminal apparatus of the present embodiment can notify the base station apparatus of a Rank Indicator (RI) indicating the number of layers desired by the apparatus itself as CSI. The terminal apparatus according to the present embodiment can change the feedback of the PMI based on the value of the RI notified to the base station apparatus.

The terminal apparatus notifies the RI/CQI/PMI suitable for the apparatus itself based on a reference signal such as NZP-CSI-RS. When the terminal device feeds back RI >1 to the base station device, the terminal device feeds back PMI corresponding to the number of RIs to the base station device. Note that, when the setting of the PMI is not fed back, the PMI may not be fed back even when RI > 1. The terminal apparatus feeding back RI >1 to the base station apparatus implies that the transmission environment is an environment where high throughput can be expected, but at the same time, it means that overhead of feedback of PMI and CQI may increase.

Therefore, the base station apparatus and the terminal apparatus according to the present embodiment can control the information to be fed back based on the RI fed back by the terminal apparatus.

The base station apparatus according to the present embodiment can restrict the rank number considered when the terminal apparatus performs feedback to the terminal apparatus. The base station apparatus can restrict the rank number considered by the terminal apparatus by signaling of an upper layer (for example, typeII-RI ■ Restriction (type 2RI ■ Restriction, hereinafter also referred to as RI Restriction, RI Restriction information)). On the other hand, the base station apparatus can notify the terminal apparatus of L1 by upper layer signaling such as RRC.

Therefore, the base station apparatus according to the present embodiment can set the value of L1 according to the upper limit of the rank factor considered by the terminal apparatus when the codebook setting instruction type 2 codebook is used. That is, depending on whether or not the rank factor considered by the terminal device exceeds a predetermined value, the upper limit of the value of L1 that can be notified by the base station device changes. For example, when the base station apparatus sets the upper limit of the rank factor considered by the terminal apparatus to 2 by upper layer signaling (e.g., codebook setting), the base station apparatus can set the upper limit of the value of L1 to 4. When the base station apparatus sets the upper limit of the rank factor considered by the terminal apparatus to 4 by upper layer signaling (codebook setting), the base station apparatus can set the upper limit of the value of L1 to 2.

Further, the terminal apparatus can acquire (judge) the value of L1 from the base station apparatus by signaling of an upper layer. The terminal device of the present embodiment can replace the value of L1 with the value of RI fed back. That is, the terminal apparatus can determine whether the value of L1 under consideration uses the value itself notified by the base station apparatus or uses a value (the second value of L, the second value) smaller than the value notified by the base station apparatus, based on whether or not the value of RI fed back exceeds a predetermined value. For example, the terminal apparatus may set 4 as the value of L1 in the base station apparatus. When the predetermined value is 2, the terminal device calculates the other feedback value with reference to the value L1 when the value RI <3 is fed back as RI, but the terminal device may calculate the other feedback value as the second value L (that is, a value smaller than the value L1 notified from the base station device) when the value RI >2 is fed back as RI.

The method of limiting the value of L according to the RI value can be selected whether to set according to the RI maximum value or the L1 maximum value. Hereinafter, the same applies to any of the methods described in the present embodiment.

The terminal apparatus can notify the base station apparatus of information to be referred to by the terminal apparatus by feeding back the PMI 11. For example, the PMI11 can notify the base station apparatus of a matrix composed of a plurality of vectors. The base station apparatus can restrict information referred to by the PMI11 by upper layer signaling. For example, when there are 4 types of modes of candidates for the PMI111 (i.e., matrix candidates) constituting the PMI11, the base station apparatus can notify the terminal apparatus of candidates that may not be considered among the 4 types of modes by a bitmap.

The base station apparatus according to the present embodiment can restrict the information itself notified by the PMI 11. For example, when the PMI11 indicates a matrix including a plurality of vectors, the base station apparatus can notify the terminal apparatus of the possibility of not considering candidates among the plurality of vectors constituting the matrix by a bitmap through signaling (or a control signal such as DCI) of an upper layer. For example, in the case where the information indicated by the PMI11 indicates 4 vectors, the base station apparatus can notify the terminal apparatus of candidates of vectors that may not be considered among the 4 vectors by a bitmap. It is needless to say that, when a vector that the terminal device can not consider is generated, the amount of information fed back by the terminal device can be reduced based on the vector.

The method of limiting the amount of information of the PMI11 may be determined whether or not to be set according to the value of RI fed back by the terminal apparatus or the upper limit of RI that can be fed back and is notified to the terminal apparatus by the base station apparatus, or may be set for each RI. For example, when the restriction of the PMI11 is set by the base station apparatus, and when the value of RI notified by the terminal apparatus exceeds a predetermined value (for example, 2), the terminal apparatus can feed back the PMI11 in consideration of the restriction of the amount of information. When the RI limit is set by the base station apparatus and the maximum value of RI set by the RI limit exceeds a predetermined value, the PMI11 can be fed back in consideration of the above-described information amount limit.

Further, the base station apparatus can still restrict the candidates of the PMI14 by signaling of an upper layer. The PMI14 can indicate coefficients (amplitude coefficient, amplitude weight) set for each vector selected according to the PMI12, but the base station apparatus can also set the maximum value of the coefficients by upper layer signaling.

The terminal device of the present embodiment can change the maximum value of the coefficient in accordance with the value of the RI notified. For example, when the base station apparatus sets the maximum value of the coefficient to 1 by upper layer signaling, the terminal apparatus can set the maximum value of the coefficient to a value smaller than 1 (for example, 2-^(1/2)) The PMI14 can be calculated and fed back to the base station apparatus.

Further, the base station apparatus can limit not only the maximum value of the amplitude coefficient but also candidate values of the amplitude coefficient that can be fed back by the terminal apparatus. For example, when 8 candidates of amplitude coefficients that can be fed back by the terminal apparatus are set, the base station apparatus can restrict candidate values of amplitude coefficients considered by the terminal apparatus by using an 8-bit bitmap.

The terminal device uses the N notified by the base station device as the candidate of the phase coefficient fed back by the PMI21_PSKTo be determined. The base station apparatus can consider {2, 4, 8} as N_PSKIs used as a candidate of (1). According to N_PSKThe phase difference (angular difference) between the candidate values of the phase coefficient fed back from the terminal device varies depending on the value of (2), and 360 DEG/N_PSKIs the phase difference.

The base station apparatus can restrict the phase coefficient considered in the PMI21 to its candidates. The base station apparatus according to the present embodiment can limit N according to the RI limit when the upper limit of the RI value considered by the terminal apparatus exceeds a predetermined value_PSKThe value of (c). For example, the base station apparatus can limit N to a value exceeding 2 in the case where RI is limited to_PSKThe value of (A) is set to 4 or less. In addition, the terminal device can change the considered N when the value of RI fed back exceeds a predetermined value_PSKThe value of (c). For example, in N notified by the base station apparatus through RRC_PSKWhen the value of (3) is 8 and the value of RI fed back by the terminal device exceeds a predetermined value (e.g., 2), N is set_PSKIs set to 4 (i.e., a value smaller than the value notified by RRC) to calculate and feed back the PMI 21.

In addition, the base stationThe device can also restrict its candidates to the phase coefficients considered in PMI21 through a bitmap. For example, N is set in the base station apparatus_PSKIn the case of 8, the phase coefficient considered by the terminal device in the PMI21 may be restricted by an 8-bit bitmap.

Further, the subband of the feedback phase coefficient may not be limited. For example, the base station apparatus can set the frequency density of the feedback phase coefficient by signaling (e.g., codebook setting) of an upper layer. For example, the frequency density is 1, 2, 3. When the frequency density is 1, the terminal apparatus feeds back the phase coefficient in all subbands. In the case of a frequency density of 2, the phase coefficient is fed back at a ratio of 1 out of 2 subbands. In the case of a frequency density of 3, the phase coefficient is fed back at a ratio of 1 out of 3 subbands. Therefore, if the sub-band fed back according to the frequency density is reduced, the amount of feedback information is reduced.

The terminal apparatus can notify the amplitude coefficient for each subband (also referred to as subband amplitude coefficient) by the PMI 22. However, since feedback is performed for each subband, the overhead of the feedback is extremely large. Therefore, the base station apparatus according to the present embodiment can set whether or not feedback is permitted for each subband based on the value of RI notified from the terminal apparatus. That is, the base station apparatus can permit the terminal apparatus to notify the amplitude coefficient for each subband only when the value of RI notified from the terminal apparatus is equal to or less than a predetermined value.

Further, the subband to which the subband amplitude coefficient is fed back may not be limited. For example, the base station apparatus can set the frequency density of the feedback subband amplitude coefficient by signaling (e.g., codebook setting) of an upper layer. For example, the frequency density is 1, 2, 3. When the frequency density is 1, the terminal apparatus feeds back the amplitude coefficient in all subbands. In the case of a frequency density of 2, the amplitude coefficient is fed back at a ratio of 1 out of 2 subbands. In the case of a frequency density of 3, the amplitude coefficient is fed back at a ratio of 1 out of 3 subbands. Therefore, if the sub-band fed back according to the frequency density is reduced, the amount of feedback information is reduced. The frequency densities of the phase coefficients and the subband amplitude coefficients may be the same or different. The frequency density of the subband amplitude coefficients is used when the subband amplitude coefficients are ON in the upper layer signaling (for example, codebook setting). In the case where the subband amplitude coefficient is OFF, the amplitude coefficient is not considered in all subbands.

In addition, in order to reduce the amount of information, amplitude coefficients (wideband amplitude coefficients or subband amplitude coefficients) can be commonly used between spatial layers. For example, when the base station apparatus sets information for setting the amplitude coefficient to be common between spatial layers in signaling (for example, codebook setting) of an upper layer, the terminal apparatus reports one amplitude coefficient in one CSI report (including CSI portion 1 and CSI portion 2).

The above-described information amount reduction method can be set semi-statically by the base station apparatus through upper layer signaling or determined in advance between the base station apparatus and the terminal apparatus, that is, fixedly. The base station apparatus of the present embodiment can also dynamically notify the terminal apparatus of the information amount reduction method.

The base station apparatus according to the present embodiment can record information of the information amount reduction method in a trigger for requesting feedback of CSI to the terminal apparatus. That is, information of the information amount reduction method can be written in DCI as a trigger for requesting CSI feedback. The base station apparatus may set a plurality of information amount reduction methods in advance for the terminal apparatus, and record information indicating whether to consider which CSI feedback among the plurality of information amount reduction methods set in advance is associated with DCI as a trigger for requesting CSI feedback.

The base station apparatus according to the present embodiment can notify the terminal apparatus of the element requested in the CSI feedback. For example, the base station apparatus can notify the terminal apparatus of information indicating which of the PMIs constituting the first PMI and the second PMI is included in the CSI feedback, by DCI or upper layer signaling.

In the above-described information amount reduction method, the base station apparatus can be set to the terminal apparatus commonly between layers, or can be set for each layer. That is, when the terminal apparatus performs CSI feedback with RI being 3, it is possible to set: the information amount reduction method is not performed for PMIs corresponding to layer 1 and layer 2, and is performed for PMIs corresponding to layer 3. The base station apparatus can set whether or not to set the information amount reduction method for each layer in the terminal apparatus, and can notify the terminal apparatus of the maximum number of layers for which the information amount reduction method is to be considered. When the maximum number of layers for which consideration is given to the information amount reduction method is started is set to 3, for example, the terminal device can set: the information amount reduction method is not performed for PMIs corresponding to layer 1 and layer 2, and is performed for PMIs corresponding to layer 3.

The base station apparatus can notify the terminal apparatus of L1. Since the number of vectors that can be synthesized is increased when the value of L1 is large, CSI can be fed back with high accuracy, but of course, the overhead of CSI feedback also increases. Therefore, the base station apparatus according to the present embodiment can set the value of L1 in association with the value associated with the other CSI feedback. For example, the base station apparatus can be based on O considered in PMI111(PMI112)₁(O₂) Value of (d), N considered in PMI12₁And N₂Set the value of L1. For example, the base station apparatus can be based on N₁And N₂Whether or not either or both of them exceed a predetermined value determines the maximum value of L1 that can be set.

The number of candidates of the vector selectable in the PMI12 is based on N₁And N₂Given the product of, the value of L1 may be N₁And N₂A value of the product of (a). In addition, the base station apparatus of the present embodiment may be provided with more than N₁And N₂The value of the product of (d) is taken as the value of L1. This means that the terminal device can select the same vector through the PMI 12. By setting as described above, even when the candidate value of the amplitude coefficient fed back from the PMI14 is small, the terminal apparatus can flexibly change the amplitude coefficient that can be set in the vector selected from the PMI12 (in short, selecting the same vector and simply adding corresponds to multiplying the vector by the amplitude coefficient 2). Thus, even if the feedback amount of the PMI14 is reduced (for example, the candidate value is reduced by a bitmap), the reduction of the feedback accuracy can be minimized.

[2. common to all embodiments ]

The program that operates in the apparatus according to the present invention may be a program that controls a Central Processing Unit (CPU) or the like to function as a computer in order to realize the functions of the embodiments according to the present invention. The program or information processed by the program is temporarily stored in a volatile memory such as a Random Access Memory (RAM), a nonvolatile memory such as a flash memory, a Hard Disk Drive (HDD), or other storage device system.

Note that a program for realizing the functions of the embodiments of the present invention may be recorded in a computer-readable recording medium. The program recorded in the recording medium may be read into a computer system and executed. The term "computer system" as used herein refers to a computer system built in the apparatus and includes hardware such as an operating system and peripheral devices. Further, the "computer-readable recording medium" may be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a medium that dynamically stores a program for a short time, or another recording medium that is readable by a computer.

Further, each functional block or each feature of the apparatus used in the above-described embodiments may be mounted on or executed by an electronic circuit such as an integrated circuit or a plurality of integrated circuits. A circuit designed in a manner to perform the functions described herein may include: general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other programmable logic elements, discrete gate or transistor logic, discrete hardware components, or combinations thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional type of processor, controller, microcontroller, or state machine. The electronic circuit may be a digital circuit or an analog circuit. Further, in the case where an integrated circuit technology that replaces an existing integrated circuit appears as a result of progress in semiconductor technology, one or more aspects of the present invention can also use a new integrated circuit based on the technology.

The present invention is not limited to the above-described embodiments. In the embodiments, although an example of the device is described, the invention of the present application is not limited to this, and can be applied to fixed or non-movable electronic devices installed indoors and outdoors, for example, terminal devices or communication devices such as AV equipment, kitchen equipment, cleaning/washing equipment, air conditioning equipment, office equipment, vending machines, and other living equipment.

While the embodiments of the present invention have been described in detail with reference to the drawings, the specific configurations are not limited to the embodiments, and design changes and the like are included without departing from the scope of the present invention. The present invention can be variously modified within the scope shown in the claims, and embodiments obtained by appropriately combining the claims disclosed in the respective different embodiments are also included in the technical scope of the present invention. The present invention also includes a configuration in which elements having similar effects to those described in the above embodiments are replaced with each other.

Industrial applicability of the invention

The present invention is applicable to a base station apparatus, a terminal apparatus, and a communication method.