WO2023170809A1

WO2023170809A1 - Base station device and terminal device

Info

Publication number: WO2023170809A1
Application number: PCT/JP2022/010217
Authority: WO
Inventors: フィテンチェン; 剛史下村; 慎一郎相川; 好明太田; 貴子堀
Original assignee: 富士通株式会社
Priority date: 2022-03-09
Filing date: 2022-03-09
Publication date: 2023-09-14

Abstract

According to the present invention, it is possible to notify a terminal of a change in the antenna arrangement of a base station device without delay. The base station device can change the number of antenna ports used for transmitting radio signals. The base station device comprises: a plurality of antenna ports; a control information generation unit that generates control information related to the arrangement of transmission antenna ports used for transmitting radio signals among the plurality of antenna ports; and a control information transmission unit that transmits control information to the terminal. The control information generation unit generates first control information representing a first arrangement of transmission antenna ports and second control information representing a second arrangement of transmission antenna ports different from the first arrangement. The control information transmission unit transmits the first control information to the terminal by a first method and then transmits second control information to the terminal by a second method different from the first method.

Description

Base station equipment and terminal equipment

The present invention relates to a base station device and a terminal device used in a mobile communication system.

There is a need to reduce the power consumption of communication equipment in mobile communication systems. For example, in RAN (Radio Access Network) #94-e plenary meeting, reduction of network power was considered.

FIG. 1 shows an example of a method for reducing power consumption of a base station in the spatial domain. Here, the base station (gNB) is assumed to include multiple radio transceiver circuits and multiple antennas. Furthermore, the base station can change the number of wireless transceiver circuits and multiple antennas used depending on the traffic. Specifically, when the traffic between the base station and the terminal (UE) decreases, the base station controls one or more radio transceiver circuits to be turned off and also reduces the number of multiple antennas used. do. In other words, dynamic antenna adaptation according to traffic is realized. As a result, power consumption of the base station is reduced. Note that this method is described in, for example, Non-Patent Document 1.

The base station sets parameters for transmitting wireless signals to the terminal based on the state of the channel between the base station and the terminal. Specifically, the base station notifies the terminal of the antenna arrangement of the base station. The terminal estimates the state of the channel between the base station and the terminal using reference signals transmitted from the base station. At this time, the terminal creates channel state information (CSI) representing the state of the channel based on the antenna arrangement of the base station. This channel state information is transmitted from the terminal to the base station. The base station then sets parameters for transmitting wireless signals based on the channel state information. That is, CSI feedback realizes downlink transmission according to channel conditions.

However, in the conventional technology, when the antenna arrangement of a base station is changed, it may take a long time to notify the terminal of the new antenna arrangement. If this notification is delayed, appropriate channel state information will not be created in the terminal, and the base station will not be able to set appropriate parameters. As a result, communication quality may deteriorate.

An object of one aspect of the present invention is to provide a method of notifying a terminal of a change in the antenna arrangement of a base station device without delay.

A base station device according to one aspect of the present invention can change the number of antenna ports used to transmit wireless signals. This base station device includes a plurality of antenna ports, a control information generation unit that generates control information related to the arrangement of a transmission antenna port used for transmitting a wireless signal among the plurality of antenna ports, and A control information transmitter that transmits information to the terminal. The control information generation unit generates first control information representing a first arrangement of the transmitting antenna ports, and second control information representing a second arrangement of the transmitting antenna ports that is different from the first arrangement. generate. The control information transmitter transmits the first control information to the terminal using a first method, and then transmits the second control information to the terminal using a second method different from the first method. .

According to the above aspect, a change in antenna arrangement of a base station device can be notified to a terminal without delay.

FIG. 2 is a diagram illustrating an example of a method for reducing power consumption of a base station in the spatial domain. FIG. 1 is a diagram showing an example of a base station device according to an embodiment of the present invention. It is a figure showing an example of composition of an antenna. FIG. 6 is a diagram illustrating an example of a change in antenna arrangement when the number of wireless transceivers operating in a base station is reduced. FIG. 3 is a diagram showing an example of CSI feedback. FIG. 3 is a diagram illustrating an example of a CSI feedback sequence. FIG. 6 is a diagram illustrating an example of a CSI feedback sequence when the antenna arrangement changes. FIG. 3 is a diagram showing an example of a CSI feedback sequence according to an embodiment of the present invention. FIG. 3 is a diagram illustrating an example of resources for transmitting DCI. 1 is a diagram showing an example of a terminal device according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a codebook. FIG. 3 is a diagram illustrating an example of antenna arrangement supported by a base station. FIG. 3 is a diagram illustrating an example of a codebook subset restriction list. FIG. 3 is a diagram illustrating an example of a description related to a CSI report. FIG. 7 is a diagram illustrating an example of a CSI feedback sequence according to a third embodiment. FIG. 7 is a diagram showing an example of a CSI feedback sequence according to a fourth embodiment.

FIG. 2 shows an example of a base station device according to an embodiment of the present invention. The base station device 1 according to the embodiment of the present invention includes a control unit 11, a plurality of radio transceivers (TRX_1 to TRX_n) 12, a switch circuit 13, and a memory 14. Note that the base station device 1 is, for example, a gNB, although it is not particularly limited. Furthermore, the base station device 1 may include other circuits, elements, and functions not shown in FIG. 2. Furthermore, in the following description, a base station device may be simply referred to as a "base station."

The control unit 11 connects to the core network via an interface. Further, the control unit 11 controls wireless communication with one or more terminals (UE) located within the cell of the base station 1. At this time, the control unit 11 can dynamically control the number of radio transceivers 12 used by the base station 1 according to the traffic within the cell. Note that the functions of the control section 11 will be explained later.

Each wireless transceiver 12 includes one or more antenna elements. Then, the wireless transceiver 12 uses the antenna element to transmit a downlink signal generated by the control unit 11 to the terminal, and receives an uplink signal transmitted from the terminal. The downlink signal includes a data signal and a control signal. Further, the downlink signal is transmitted via, for example, a PDSCH (Physical Downlink Shared Channel) or a PDCCH (Physical Downlink Control Channel). Uplink signals include data signals and control signals. Further, the uplink signal is transmitted via, for example, a PUSCH (Physical Uplink Shared Channel) or a PUCCH (Physical Uplink Control Channel).

The switch circuit 13 controls the wireless transceiver 12 to turn on or off according to instructions from the control unit 11. For example, when there is a lot of traffic within the cell of the base station 1, the switch circuit 13 may control all the radio transceivers 12 to be in the on state according to instructions from the control unit 11. Furthermore, when the traffic decreases, the switch circuit 13 may control some of the wireless transceivers 12 to turn off according to instructions from the control unit 11.

FIG. 3 shows a configuration example of an antenna included in the base station 1. In this example, each wireless transceiver 12 includes three antenna elements. Note that in FIG. 3, an x mark represents one antenna element. Furthermore, each antenna element has two ports in order to realize polarization multiplexing.

In the example shown in FIG. 3(a), the base station 1 includes one antenna panel. 4×4 antenna circuits are mounted within this antenna panel. Each antenna circuit is connected to a corresponding wireless transceiver 12, respectively. That is, in this example, the base station 1 includes 16 wireless transceivers 12.

Here, the antenna arrangement of the base station 1 is expressed using logical antenna elements as necessary. In this example, an antenna circuit connected to one radio transceiver 12 is represented as one logical antenna element. Therefore, in this case, the base station 1 will be equipped with 16 logical antenna elements. Note that the logical antenna element is sometimes called an antenna port. The antenna arrangement is represented by three parameters Ng, N1, and N2. Ng represents the number of antenna panels. N1 represents the number of antenna elements arranged in the horizontal direction. N2 represents the number of antenna elements arranged in the vertical direction. Alternatively, N1 represents the number of antenna ports arranged in the horizontal direction. N2 represents the number of antenna ports arranged in the vertical direction. Therefore, the antenna arrangement shown in FIG. 3(a) is expressed as "(Ng, N1, N2)=(1, 4, 4)".

In the example shown in FIG. 3(b), the base station 1 includes two antenna panels. 4×2 antenna circuits are mounted in each antenna panel. Therefore, the antenna arrangement shown in FIG. 3(b) is expressed as "(Ng, N1, N2)=(2, 4, 2)".

FIG. 4 shows an example of a change in antenna arrangement when the number of wireless transceivers 12 operating in the base station 1 is reduced. In this example, the base station 1 has an antenna shown in FIG. 3(a). Then, eight of the 16 wireless transceivers 12 are controlled to be in the off state. As a result, the antenna arrangement of base station 1 is changed from (1, 4, 4) to (1, 4, 2).

In this way, the base station 1 can dynamically control the number of radio transceivers 12 used by the base station 1, depending on the traffic within the cell. At this time, the antenna arrangement of the base station 1 changes. Then, the base station 1 notifies the terminal of the change in antenna arrangement.

FIG. 5 shows an example of CSI feedback. In this example, base station (gNB) 1 performs precoding transmission. In precoding transmission, the directivity of a transmission signal is controlled by multiplying a combination of a data sequence and a transmission antenna by a precoding weight. Here, in order to realize suitable precoding transmission, base station 1 needs to recognize the state of the channel between base station 1 and the terminal. Therefore, the base station 1 recognizes the channel state by CSI feedback.

The base station 1 transmits a CSI reference signal to the terminal for each antenna. The terminal estimates the channel state based on the received CSI reference signal. Here, the terminal includes a codebook. The codebook stores predetermined precoding weight matrix candidates. Then, the terminal selects a suitable precoding weight matrix from the codebook according to the estimated channel state. Note that the selected precoding weight matrix is identified using a PMI (Precoding Matrix Indicator).

The terminal creates a CSI report representing the state of the channel. The CSI report includes the above-mentioned PMI. Further, the CSI report includes a CQI (Channel Quality Indicator) and an RI (Rank Indicator). CQI represents downlink reception quality and is used by base station 1 to select a modulation scheme and code. The RI specifies the preferred number of transmission streams. The terminal then transmits the CSI report to the base station 1.

The base station 1 controls signal transmission to the terminal based on the CSI report. That is, CSI feedback is realized. Specifically, base station 1 performs precoding according to PMI, selects a modulation scheme and code based on CQI, and determines the number of transmission streams based on RI.

FIG. 6 shows an example of a CSI feedback sequence. In this embodiment, first, the base station (gNB) 1 transmits an RRC (Radio Resource Control) message to the terminal (UE). This RRC message specifies the configuration of the CSI report. Further, this RRC message includes information representing the antenna arrangement of the base station 1. The antenna arrangement is expressed using, for example, the three parameters Ng, N1, and N2 described with reference to FIGS. 3 and 4. Further, this RRC message includes resource information representing resources for the terminal to receive a CSI reference signal (CSI-RS) and resources for the terminal to transmit a CSI report. The resource information specifies, for example, time and frequency. In this case, this RRC message corresponds to a trigger that instructs the terminal to create a CSI report. The RRC message may be an RRC reconfiguration message, an RRC stop message, or an RRC release message.

Note that the RRC message may specify multiple sets of parameters Ng, N1, and N2 as antenna placement candidates. The RRC message may also specify resource candidates for CSI reference signals and CSI reports. Here, when antenna placement candidates and resource candidates are specified, the base station 1 transmits a MAC Control Element (MAC-CE) to the terminal following the RRC message. This MAC-CE specifies one set of parameters corresponding to the actual antenna arrangement from among multiple sets of parameters Ng, N1, and N2. Furthermore, this MAC-CE specifies a resource to actually be used from among the resource candidates. In this case, this MAC-CE corresponds to a trigger that instructs the terminal to create a CSI report.

The base station 1 transmits a CSI reference signal to the terminal using the PDSCH. The CSI reference signal is used by the terminal to create a CSI report, as described with reference to FIG. Note that the resources (time and frequency) for transmitting the CSI reference signal are notified from the base station 1 to the terminal by an RRC message or MAC-CE. Therefore, the terminal can receive the CSI reference signal.

The terminal creates a CSI report based on the CSI reference signal received from the base station 1. Here, the CSI report includes PMI, CQI, and RI, as described above. The terminal then transmits the created CSI report to the base station 1.

The base station 1 determines downlink parameters based on the CSI report. Specifically, the precoding weight, modulation method, code, number of transmission streams, etc. are determined based on the CSI report. Then, the base station 1 transmits downlink data to the terminal according to the determined parameters.

In this way, the terminal creates a CSI report and transmits it to the base station 1. At this time, the terminal creates a CSI report based on the antenna arrangement of the base station 1. Therefore, when the terminal does not correctly recognize the antenna arrangement of the base station 1, inappropriate PMI, CQI, or RI will be notified to the base station 1. In this case, the quality of the downlink may deteriorate.

FIG. 7 shows an example of a CSI feedback sequence when the antenna arrangement changes. Note that the initial state of the antenna arrangement is notified from the base station 1 to the terminal by an RRC message or MAC-CE shown in FIG.

FIG. 7(a) shows a sequence in which periodic CSI reporting is performed. In this case, the CSI report is initiated by the RRC message. After this, CSI reporting is performed repeatedly until an RRC message indicating reconfiguration is sent. Then, when the antenna arrangement of the base station 1 changes, an RRC message representing the new antenna arrangement is transmitted from the base station 1 to the terminal. This allows the terminal to recognize the latest antenna arrangement.

FIG. 7(b) shows a sequence in which a semi-persistent CSI report is performed. In this case, CSI reporting is started by MAC-CE (activation). Thereafter, CSI reporting is repeatedly executed until a MAC-CE (deactivation) is sent to invalidate the settings. Then, when the antenna arrangement of base station 1 changes, base station 1 sends a MAC-CE (deactivation) to the terminal to disable the settings related to the previous antenna arrangement, and activates the settings related to the new antenna arrangement. MAC-CE (activation) to be sent to the terminal. This allows the terminal to recognize the latest antenna arrangement.

However, in the sequence shown in FIG. 7, it may take a long time from when the antenna arrangement is changed at the base station 1 until the terminal recognizes the new antenna arrangement. That is, a delay may occur between the base station 1 and the terminal. For example, in the sequence shown in FIG. 7(a), a change in antenna arrangement is notified by an RRC message. However, RRC messages are sent at intervals of tens of milliseconds to hundreds of milliseconds in many cases. Therefore, it may take a long time from when the antenna arrangement at the base station 1 is changed until the base station 1 transmits the next RRC message. Furthermore, RRC messages are processed in higher layers. Therefore, it may take a long time from when the terminal receives the RRC message until the terminal recognizes the change in antenna arrangement. If the actual antenna arrangement at the base station 1 differs from the antenna arrangement recognized by the terminal, inappropriate PMI, CQI, or RI will be notified to the base station 1. Note that this problem may similarly occur in the case shown in FIG. 7(b).

FIG. 8 shows an example of a CSI feedback sequence according to an embodiment of the present invention. Note that FIG. 8(a) shows a sequence in which a periodic CSI report is performed, and FIG. 8(b) shows a sequence in which a semi-persistent CSI report is performed.

The method of notifying the terminal of the initial state of the antenna arrangement of the base station 1 is substantially the same in FIGS. 7 and 8. That is, the initial state of the antenna arrangement of the base station 1 is notified to the terminal by an RRC message or MAC-CE. Note that the terminal receives three parameters Ng, N1, and N2 representing the antenna arrangement through this notification. Therefore, the terminal can recognize the number of antenna panels of the base station 1.

When the antenna arrangement of the base station 1 changes, the base station 1 uses downlink control information (DCI) to notify the terminal of the changed antenna arrangement. DCI can use existing formats (Format0_0, Format0_1, Format0_2). In this case, new fields are added to the existing format. Information representing the changed antenna arrangement is then written into a new field. Alternatively, a new DCI format may be defined to notify the terminal of the changed antenna arrangement.

The DCI does not need to include resource information representing resources for CSI reference signals and CSI reports. In this case, the terminal receives the CSI reference signal from the PDSCH notified by the RRC message, and also transmits the CSI report on the PUSCH or PUCCH notified by the RRC message. Alternatively, the terminal receives the CSI reference signal from the PDSCH specified by the MAC-CE, and also transmits the CSI report on the PUSCH or PUCCH specified by the MAC-CE.

The base station 1 may reconfigure resources for the CSI reference signal and CSI report. In this case, the DCI includes resource information representing resources for CSI reference signals and CSI reporting. Then, the terminal receives a CSI reference signal from the PDSCH notified by the DCI, and also transmits a CSI report on the PUSCH or PUCCH notified by the DCI.

FIG. 9 shows an example of resources for transmitting DCI. In this embodiment, radio frames are transmitted between the base station 1 and the terminal. The length of the radio frame is 10 msec. A radio frame is composed of 10 subframes. Therefore, the length of the subframe is 1 msec. Each subframe is composed of one or more slots. For example, when the subcarrier frequency spacing (SCS) is 15 kHz, a subframe consists of one slot. Furthermore, when the subcarrier frequency interval is 30 kHz, a subframe is composed of two slots. Each slot consists of 14 symbols in the time domain. Note that FIG. 9 shows a case where the subcarrier frequency interval is 15 kHz.

Each frame includes resources for transmitting DCI. In this example, DCI is transmitted using the first symbol and the second symbol. Note that the CSI reference signal is transmitted using the fifth symbol and the ninth symbol.

In this way, the DCI is stored in each slot constituting a radio frame and transmitted from the base station 1 to the terminal. Therefore, when changing the antenna arrangement, the base station 1 can notify the terminal of the changed antenna arrangement without delay.

Next, the functions of the control unit 11 of the base station 1 will be described with reference to FIG. 2. The control unit 11 includes an uplink signal processing unit 21, a TRX control unit 22, an RS transmission unit 23, a control information generation unit 24, a control information transmission unit 25, and a precoder 26. Note that the control unit 11 may include other functions not shown in FIG. 2.

The uplink signal processing unit 21 processes uplink signals transmitted from the terminal. In this embodiment, the uplink signal processing unit 21 can receive a CSI report transmitted from a terminal. The CSI report represents the state of the channel between the base station 1 and the terminal, and includes PMI, CQI, and RI.

The TRX control unit 22 determines the number of wireless transceivers 12 in the on state based on the traffic within the cell of the base station 1. That is, when traffic is low, in order to reduce power consumption of the base station 1, the TRX control unit 22 turns off one or more radio transceivers 12 to reduce the number of radio transceivers 12 in the on state. . Note that the TRX control unit 22 controls the number of wireless transceivers 12 in the on state by controlling the switch circuit 13. Here, the antenna element connected to the off-state wireless transceiver 12 is not used in communication with the terminal. Therefore, controlling the number of wireless transceivers 12 in the on state changes the number and arrangement of antenna elements used to transmit wireless signals. Note that an antenna element used to transmit a wireless signal is sometimes referred to as a "transmission antenna element."

The RS transmitter 23 transmits a CSI reference signal to the terminal. CSI reference signals are transmitted with known power and are used by terminals to detect channel conditions. Note that the CSI reference signal is transmitted using a predetermined symbol of each slot, for example, as shown in FIG.

The control information generation unit 24 generates control information to be transmitted to the terminal. In this embodiment, control information related to CSI feedback will be described.

In the sequence shown in FIG. 8(a), the control information includes information transmitted by the RRC message and information transmitted by the DCI. Here, the initial setting information (first control information) transmitted by the RRC message includes the following information.
(1) Information representing the initial state of antenna arrangement (2) Information representing downlink resources for transmitting CSI reference signals (3) Information representing uplink resources for transmitting CSI reports

The change information (second control information) transmitted by the DCI includes the following information. However, the information transmitted by the DCI does not have to include the following (2) and (3).
(1) Information representing the changed antenna arrangement (2) Information representing downlink resources for transmitting CSI reference signals (3) Information representing uplink resources for transmitting CSI reports

The initial state of the antenna arrangement is determined in advance as, for example, default information. Additionally, as the number of wireless transceivers 12 in the on state changes, the number and arrangement of antenna elements used to transmit wireless signals also change. That is, the control information generation unit 24 determines a new antenna arrangement based on the number of wireless transceivers 12 in the on state.

In the sequence shown in FIG. 8(b), the control information includes the RRC message, information transmitted by the MAC-CE, and information transmitted by the DCI. Here, the initial setting information (first control information) transmitted by the RRC message and MAC-CE includes the following information.
(1) Information representing antenna placement candidates (2) Information specifying the initial state antenna placement from antenna placement candidates (3) Information representing downlink resources for transmitting CSI reference signals (4) Information representing uplink resources for transmitting CSI reports

The change information (second control information) transmitted by the DCI includes the following information. However, the information transmitted by the DCI does not have to include the following (2) and (3).
(1) Information specifying the changed antenna arrangement from antenna arrangement candidates (2) Information representing downlink resources for transmitting CSI reference signals (3) Information indicating uplink resources for transmitting CSI reports Information representing the resource

The control information transmitter 25 transmits the control information generated by the control information generator 24 to the terminal. Specifically, in the sequence shown in FIG. 8A, the control information transmitter 25 transmits initial setting information to the terminal using an RRC message, and transmits change information to the terminal using DCI. Furthermore, in the sequence shown in FIG. 8(b), the control information transmitting unit 25 transmits initial setting information to the terminal using the RRC message and MAC-CE, and transmits change information to the terminal using DCI. .

The precoder 26 controls the directivity of the signal transmitted to the terminal based on the CSI report received from the terminal. In this embodiment, precoder 26 multiplies the combination of data sequence and transmit antenna by a precoding weight matrix based on the PMI included in the CSI report.

The control unit 11 that provides the above-mentioned functions is realized by, for example, a processor. In this case, the processor executes the control program stored in the memory 14 to control the uplink signal processing section 21, the TRX control section 22, the RS transmission section 23, the control information generation section 24, the control information transmission section 25, and provides the functions of the precoder 26.

FIG. 10 shows an example of a terminal device according to an embodiment of the present invention. The terminal device 3 according to the embodiment of the present invention includes a wireless receiving section 31, a wireless transmitting section 32, a control section 33, and a memory 37. The terminal device 3 is, for example, a UE (User Equipment). Furthermore, the terminal device 3 may include other circuits, elements, and functions not shown in FIG. Furthermore, in the following description, a terminal device may be simply referred to as a "terminal."

The radio receiving unit 31 receives a downlink signal transmitted from the base station 1. Downlink signals include data signals, control signals, and reference signals. The wireless transmitter 32 transmits an uplink signal to the base station 1. Uplink signals include data signals, control signals, and reference signals. The control unit 33 includes a downlink signal processing unit 34, a channel estimation unit 35, and a CSI generation unit 36. Note that the control unit 33 may include other functions not shown in FIG.

The downlink signal processing unit 34 processes downlink signals transmitted from the base station 1. In this embodiment, the downlink signal processing unit 34 can process RRC messages, MAC-CE, and DCI. Specifically, the downlink signal processing unit 34 determines the antenna arrangement of the base station 1, the resources allocated to the CSI reference signal, and the resources allocated to the CSI report based on the RRC message (and MAC-CE). To detect. Furthermore, when the antenna arrangement changes in the base station 1, the downlink signal processing unit 34 detects the new antenna arrangement based on the DCI.

The channel estimation unit 35 estimates the state of the channel between the base station 1 and the terminal 3 based on the CSI reference signal. For example, attenuation, phase rotation, delay, etc. occurring in the channel are estimated.

The CSI generation unit 36 generates a CSI report based on the channel state estimated by the channel estimation unit 35. The CSI report includes PMI, CQI, and RI, as described above. Among these parameters, PMI represents an optimal precoding weight matrix selected from codebook 38 stored in memory 37.

FIG. 11 shows an example of the codebook 38. The codebook 38 stores candidates for precoding weight matrices used by the precoder 26 of the base station 1. Here, candidates for the precoding weight matrix are prepared for each antenna arrangement supported by the base station 1. For example, for the antenna arrangement "N1=2, N2=1", weight matrix candidates A1, A2, . ．．．． are prepared, and weight matrix candidates B1, B2, . ．．．． is available. Candidates for the precoding weight matrix are created in advance by simulation or measurement.

The CSI generation unit 36 extracts candidates corresponding to the antenna arrangement of the base station 1 from the codebook 38. Then, the CSI generation unit 36 selects a precoding weight matrix that provides the maximum throughput after precoding from the extracted candidates based on the channel state estimated by the channel estimation unit 35. For example, when the antenna arrangement notified from the base station 1 to the terminal 3 is "N1=2, N2=1", weight matrix candidates A1, A2, . ．．．． is extracted. Then, weight matrix candidates A1, A2, . ．．．． The optimal weight matrix is selected from among. PMI represents the precoding weight matrix selected in this way.

The terminal 3 transmits a CSI report including PMI, CQI, and RI to the base station 1. Then, the base station 1 controls the downlink based on the CSI report, as described above. For example, the precoder 26 controls downlink directivity using a precoding weight matrix specified by the PMI notified from the terminal 3.

The control unit 33 that provides the above-mentioned functions is realized by, for example, a processor. In this case, the processor provides the functions of the downlink signal processing unit 34, channel estimation unit 35, and CSI generation unit 36 by executing the control program stored in the memory 37.

<First embodiment>
The CSI feedback sequence in the first embodiment is as shown in FIG. That is, as shown in FIG. 8(a), the base station (gNB) 1 notifies the terminal (UE) 3 of the initial state of the antenna arrangement using an RRC message. In the sequence shown in FIG. 8(b), the initial state of the antenna arrangement is notified using the RRC message and MAC-CE. Note that by notification of the initial state of the antenna arrangement, the terminal 3 can detect the number of antenna panels (that is, whether it is a single panel or a multi-panel). After this, when the antenna arrangement of base station 1 changes, base station 1 notifies terminal 3 of the new antenna arrangement using DCI.

FIG. 12 shows an example of antenna arrangement supported by the base station 1. FIG. 12(a) shows a case in which the base station 1 includes one antenna panel, and FIG. 12(b) shows a case in which the base station 1 includes a plurality of antenna panels.

When the base station 1 includes one antenna panel, 13 antenna arrangement patterns are provided as shown in FIG. 12(a). The number of CSI antenna ports represents the number of logical antenna ports that transmit CSI reference signals. The antenna arrangement is represented by a combination of the number N1 of antenna elements arranged in the horizontal direction and the number N2 of antenna elements arranged in the vertical direction. Further, the antenna arrangement is represented by a combination of the number N1 of antenna ports arranged in the horizontal direction and the number N2 of antenna ports arranged in the vertical direction.

In this case, the antenna arrangement can be represented by a 4-bit index. In this example, 13 antenna arrangement patterns are represented by "0000" to "1100". Then, when the antenna arrangement changes, the base station 1 sets an index corresponding to the new antenna arrangement in a predetermined area of the DCI. For example, when the antenna arrangement changes from "N1=4, N2=4" to "N1=4, N2=2", "0101" is set in a predetermined area of the DCI. Then, the base station 1 transmits this DCI to the terminal 3. Thereby, the terminal 3 recognizes the new antenna arrangement. Note that it is assumed that the terminal 3 has previously acquired the information showing the correspondence shown in FIG. 12 from the base station 1.

When the base station 1 includes multiple antenna panels, eight antenna arrangement patterns are provided, as shown in FIG. 12(b). Furthermore, five antenna arrangement patterns are added to accommodate the case where the base station 1 uses only one antenna panel among the plurality of antenna panels. That is, a total of 13 antenna placement patterns are provided. Therefore, in this case as well, the antenna arrangement can be represented by a 4-bit index. For example, as shown in Figure 12(b), when the antenna arrangement changes from "Ng = 2, N1 = 4, N2 = 2" to "Ng = 1, N1 = 4, N2 = 2", the DCI Using this, "1011" is notified to the terminal 3.

Note that in the example shown in FIG. 12, the antenna arrangement is expressed using a 4-bit index, but the first embodiment is not limited to this configuration. That is, the antenna arrangement may be represented by an index of 5 bits or more.

In this way, in the first embodiment, when the antenna arrangement of the base station 1 changes, information representing the new antenna arrangement is notified from the base station 1 to the terminal 3 using DCI. Here, the DCI is stored and transmitted within each slot constituting a radio frame. Therefore, the terminal 3 can detect a change in the antenna arrangement of the base station 1 without delay. As a result, correct channel state information is fed back to the base station 1, so communication quality does not deteriorate even when the antenna arrangement is changed.

<Second embodiment>
The CSI feedback sequence in the second embodiment is as shown in FIG. That is, the base station (gNB) 1 notifies the terminal (UE) 3 of antenna placement candidates and the initial state of the antenna placement using the RRC message (and MAC-CE). Thereafter, when the antenna arrangement of the base station 1 changes, the base station 1 uses the DCI to notify the terminal 3 of the identification index of the new antenna arrangement.

FIG. 13 shows an example of a codebook subset restriction list. The codebook subset restriction list represents, for each antenna arrangement of the base station 1, a weight matrix that can be used by the base station 1 or a weight matrix that cannot be used by the base station 1. For example, as shown in FIG. 11, it is assumed that eight weight matrix candidates A1 to A8 are stored in the codebook 38 for the antenna arrangement "N1=2, N2=1". Further, as shown in FIG. 13, 8-bit restriction information is set for the antenna arrangement "N1=2, N2=1". Each bit of restriction information corresponds to a weight matrix candidate stored in codebook 38. That is, the first bit of the restriction information corresponds to the weight matrix candidate A1, and the eighth bit of the restriction information corresponds to the weight matrix candidate A8.

Weight matrix candidates corresponding to bits whose restriction information is "1" can be selected when creating CSI. Weight matrix candidates corresponding to bits whose restriction information is "0" are not allowed to be selected when creating CSI. For example, when the antenna arrangement is "N1=2, N2=1", the first to fourth bits are "1" and the fifth to eighth bits are "0". In this case, when generating the CSI, the terminal 3 selects the optimal weight matrix (ie, PMI) from among the weight matrix candidates A1 to A4.

Note that in the codebook subset restriction list, an index is given to each antenna arrangement. That is, each antenna arrangement may be identified by an index.

The base station 1 transmits the codebook subset restriction list shown in FIG. 13 to the terminal 3 using an RRC message. Here, in the sequence shown in FIG. 8A, default information representing the initial state of the antenna arrangement is set for the codebook subset restriction list. In the example shown in FIG. 13, the initial state of the antenna is "N1=8, N2=2". Furthermore, in the sequence shown in FIG. 8(b), the terminal 3 is notified of the initial state of the antenna arrangement by the MAC-CE following the RRC message. The terminal 3 stores the codebook subset restriction list acquired from the base station 1 in the memory 37.

When the antenna arrangement of the base station 1 changes, the base station 1 uses the DCI to transmit an index that identifies the new antenna arrangement to the terminal 3. Then, by searching the codebook subset restriction list using the received index, the terminal 3 recognizes the new antenna arrangement and acquires restriction information corresponding to the new antenna arrangement. Thereafter, when the terminal 3 receives the CSI reference signal, it selects a weight matrix within the range specified by the restriction information.

For example, when the antenna arrangement changes from "N1=8, N2=2" to "N1=2, N2=1", the base station 1 notifies the terminal 3 of the index "0". In this case, the terminal 3 detects that the new antenna arrangement is "N1=2, N2=1" and the corresponding restriction information is "11110000". Then, when generating the CSI, the terminal 3 selects the optimal weight matrix (ie, PMI) from among the weight matrix candidates A1 to A4 corresponding to the first to fourth bits of the restriction information.

FIG. 14 shows an example of a description related to a CSI report. In this example, a description related to a codebook (CodebookConfig) is provided in a description related to a CSI report (CSI-ReportConfig). And CodebookSubsetRestriction is set in CodebookConfig. Note that this description is transmitted from the base station 1 to the terminal 3 using an RRC message.

As described above, in the second embodiment, at the start of communication, a plurality of processing patterns (in the example, a codebook subset restriction list) are used to control the processing of the terminal 3 according to the antenna arrangement of the base station 1. is notified from the base station 1 to the terminal 3. Then, when the antenna arrangement of the base station 1 changes, an index representing the new antenna arrangement is notified from the base station 1 to the terminal 3 using the DCI. Furthermore, the terminal 3 creates a CSI report using a processing pattern corresponding to the notified index and transmits it to the base station 1. Therefore, even when changing the antenna arrangement, the terminal 3 can create the CSI report requested by the base station 1 without delay.

<Third embodiment>
FIG. 15 shows an example of a CSI feedback sequence according to the third embodiment. Also in the third embodiment, when the antenna arrangement of the base station 1 changes, DCI including information representing the new antenna arrangement is transmitted from the base station 1 to the terminal 3. Then, the terminal 3 creates a CSI report based on the new antenna arrangement and transmits it to the base station 1.

However, in the third embodiment, the terminal 3 transmits an ACK/NACK signal to the base station 1 indicating whether or not the DCI was correctly received. In this embodiment, the terminal 3 transmits an ACK signal to the base station 1 when information representing the antenna arrangement can be acquired from a predetermined area in the received DCI. On the other hand, when information representing the antenna placement cannot be obtained from a predetermined area in the received DCI, or when the value in the predetermined area in the received DCI does not represent the antenna placement, Terminal 3 transmits a NACK signal to base station 1.

Upon receiving the ACK signal from the terminal 3, the base station 1 transmits a CSI reference signal to the terminal 3, as shown in FIG. 15(a). After that, the base station 1 waits for a CSI report transmitted from the terminal 3. On the other hand, upon receiving the NACK signal from the terminal 3, the base station 1 retransmits the DCI including information representing the antenna arrangement to the terminal 3, as shown in FIG. 15(b). This retransmission procedure is realized by, for example, HARQ (Hybrid automatic repeat request). In this way, according to the third embodiment, the terminal 3 can reliably recognize the change in the antenna arrangement of the base station 1, and therefore can create a highly accurate CSI report.

<Fourth embodiment>
FIG. 16 shows an example of a CSI feedback sequence according to the fourth embodiment. Also in the fourth embodiment, when the antenna arrangement of the base station 1 changes, DCI including information representing the new antenna arrangement is transmitted from the base station 1 to the terminal 3. However, in this embodiment, when the antenna arrangement of base station 1 changes from Config_1 to Config_2, terminal 3 cannot receive DCI.

In the sequence shown in FIG. 16(a), the DCI includes information representing the CSI reference signal resource in addition to information representing the changed antenna arrangement. However, in this example, terminal 3 cannot receive this DCI. On the other hand, the base station 1 starts a timer when transmitting the DCI. Then, the base station 1 transmits the CSI reference signal to the terminal 3 using the resource notified using the DCI. However, since the terminal 3 has not received the DCI, it does not recognize the resource of the CSI reference signal. That is, the terminal 3 cannot receive the CSI reference signal. Therefore, since the terminal 3 does not create a CSI report, the base station 1 cannot receive the CSI report.

After this, when the timer expires, the base station 1 determines that the terminal 3 has not received the DCI. Then, the base station 1 retransmits the DCI. Here, it is assumed that the terminal 3 receives this DCI. In this case, the terminal 3 can receive subsequent CSI reference signals. Therefore, the terminal 3 creates a CSI report, and the base station 1 receives the CSI report.

In the sequence shown in FIG. 16(b), the DCI includes information representing the changed antenna arrangement, but does not include information representing the resources of the CSI reference signal. That is, the CSI reference signal is transmitted according to the initial settings. Then, the terminal 3 cannot receive the DCI, similar to the case shown in FIG. 16(a).

The base station 1 transmits the CSI reference signal to the terminal 3 based on the changed antenna arrangement. Here, the terminal 3 can receive this CSI reference signal. Therefore, the terminal 3 creates a CSI report. However, since the terminal 3 does not receive the DCI, it does not recognize that the antenna arrangement has changed. Therefore, the terminal 3 creates a CSI report corresponding to the antenna arrangement before the change. In this embodiment, although the antenna arrangement of the base station 1 has changed from Config_1 to Config_2, the terminal 3 creates a CSI report for Config_1.

In this case, the base station 1 receives an incorrect CSI report. Here, the bit length of the CSI report depends on the antenna arrangement of the base station 1. Therefore, the base station 1 can determine whether an appropriate CSI report has been created in the terminal 3 based on the bit length of the received CSI report. In this example, base station 1 determines that terminal 3 has created an inappropriate CSI report. Therefore, the base station 1 executes the DCI retransmission procedure. In this manner, also in the fourth embodiment, the terminal 3 can reliably recognize the change in the antenna arrangement of the base station 1, and therefore can create a highly accurate CSI report.

Additionally, if the information transmitted by the DCI includes information representing uplink resources for transmitting the CSI report, the base station 1 cannot receive the CSI report using the specified resource. As a result, the base station 1 determines that an inappropriate CSI report has been created in the terminal 3. In this case, the base station 1 may perform a DCI retransmission procedure.

1 Base station device 3 Terminal device 11 Control section 12 Wireless transceiver 21 Uplink signal processing section 22 TRX control section 23 RS transmission section 24 Control information generation section 25 Control information transmission section 26 Precoder 33 Control section 35 Channel estimation section 36 CSI generation section 38 code book

Claims

A base station device capable of changing the number of antenna ports used to transmit wireless signals, the base station device comprising:
multiple antenna ports,
a control information generation unit that generates control information related to the arrangement of transmitting antenna ports used for transmitting wireless signals among the plurality of antenna ports;
a control information transmitter that transmits the control information to a terminal,
The control information generation unit generates first control information representing a first arrangement of the transmitting antenna ports, and second control information representing a second arrangement of the transmitting antenna ports that is different from the first arrangement. generate,
The control information transmitter transmits the first control information to the terminal using a first method, and then transmits the second control information to the terminal using a second method different from the first method. A base station device characterized by:
The plurality of antenna ports are K×L antenna ports in which K antenna ports are arranged in a first direction and L antenna ports are arranged in a second direction,
As the transmitting antenna ports, N1 antenna ports are selected from the K antenna ports in the first direction, and N2 antenna ports are selected from the L antenna ports in the second direction. The base station apparatus according to claim 1, wherein at this time, the second control information includes information identifying a combination of N1 and N2.
the plurality of antenna ports are housed in M antenna panels;
Each antenna panel accommodates K×L antenna ports, with K antenna ports arranged in a first direction and L antenna ports arranged in a second direction;
Ng antenna panels are selected from the M antenna panels as the transmitting antenna ports, and in each selected antenna panel, N1 antenna ports are selected from the K antenna ports in the first direction. and when N2 antenna ports are selected from the L antenna ports in the second direction, the second control information includes information identifying the combination of N1, N2, and Ng. The base station device according to claim 1, characterized in that it includes:
The first control information includes a plurality of candidates for the arrangement of the transmitting antenna port, and information specifying one corresponding to the first arrangement from among the plurality of candidates,
The base station apparatus according to claim 1, wherein the second control information includes information specifying one corresponding to the second arrangement from among the plurality of candidates.
a receiving unit that receives channel state information generated by the terminal based on the first control information or the second control information;
The base station apparatus according to claim 1, further comprising a precoder that multiplies a signal to be transmitted to the terminal by a corresponding weight matrix based on the channel state information.
The first control information includes information representing a weight matrix used by the precoder or a weight matrix not used by the precoder for each arrangement of the transmitting antenna elements supported by the base station device,
The base station apparatus according to claim 5, wherein the second control information includes information specifying the second arrangement.
The control information transmitter transmits the first control information to the terminal using RRC (Radio Resource Control), and transmits the second control information to the terminal using DCI (Downlink Control Information). The base station device according to any one of claims 1 to 6, wherein the base station device transmits.
When the base station apparatus does not receive a report corresponding to the second control information from the terminal within a predetermined time from when the control information transmitter transmits the second control information, the control information transmitter , the base station device retransmits the second control information to the terminal.
When the base station apparatus receives a report that does not correspond to the second control information from the terminal after the control information transmitter transmits the second control information, the control information transmitter transmits the second control information. The base station apparatus according to claim 1, further comprising: retransmitting control information of the base station to the terminal.
A terminal device that communicates with a base station device that can change the number of antenna elements used to transmit wireless signals,
The base station device includes:
multiple antenna ports,
a control information generation unit that generates control information related to the arrangement of transmitting antenna ports used for transmitting wireless signals among the plurality of antenna ports;
a control information transmitter that transmits the control information to the terminal device,
The control information generation unit generates first control information representing a first arrangement of the transmitting antenna ports, and second control information representing a second arrangement of the transmitting antenna ports that is different from the first arrangement. generate,
The control information transmitter transmits the first control information to the terminal device using a first method, and then transmits the second control information to the terminal device using a second method different from the first method. send,
The terminal device is
During the period from receiving the first control information to receiving the second control information, the state of the channel between the base station device and the terminal device is determined based on the first control information. a channel state information generation unit that generates channel state information representing the channel state information and, after receiving the second control information, generates the channel state information based on the second control information;
A terminal device comprising: a transmitter that transmits the channel state information generated by the channel state information generator to the base station device.