WO2022115391A1 - Method of srs assisted dl csi acquisition for 4t6r transceiver architecture - Google Patents

Abstract

A terminal is disclosed that is in communication with a base station (BS). The terminal includes a plurality of antenna ports (APs) coupled to a transmitter that transmits one or more sounding reference signals (SRSs) to the BS and a processor that controls switching of the plurality of APs for the one or more SRS transmissions. In other aspects, a method for a terminal and a system are also disclosed.

Description

METHOD OF SRS ASSISTED DL CSI ACQUISITION FOR 4T6R TRANSCEIVER ARCHITECTURE TECHNICAL FIELD [0001] One or more embodiments disclosed herein relate to a method of sounding reference signal (SRS)-assisted downlink (DL) channel state information (CSI) acquisition for up to 8 antenna ports. BACKGROUND [0002] The current new radio (NR) standard supports SRS switching for only up to 4 antennas. [0003] On the other hand, the NR standard begins to contemplate how to identify the requirement of supporting SRS switching for up to 8 antennas in NR multiple-input and multiple-output (MIMO) technologies for Rel. 17. [0004] A MIMO work item description (WID) for Rel.17 indicates the following items, which are not yet determined: [0005] Enhancement on SRS, targeting both frequency range FR1 and FR2: [0006] a. Identify and specify enhancements on aperiodic SRS triggering to facilitate more flexible triggering and/or DCI overhead/usage reduction; [0007] b. Specify SRS switching for up to 8 antennas (e.g., xTyR, x = {1, 2, 4} and y = {6, 8}); and [0008] c. Evaluate and, if needed, specify the following mechanism(s) to enhance SRS capacity and/or coverage: SRS time bundling, increased SRS repetition, and partial sounding across frequency CITATION LIST NON-PATENT REFERENCE [0009] [Non-Patent Reference 1] 3GPP RP 193133, “New WID: Further enhancements on MIMO for NR”, Dec., 2019 [Non-Patent Reference 2] 3GPP TS 38.214, “NR; Physical procedure for data (Release 16)” SUMMARY [0010] One or more embodiments provide a method of SRS switching extended to support up to 8 antenna ports. [0011] In general, one or more embodiments disclosed herein relate to terminal in communication with a base station (BS) that includes a plurality of antenna ports (APs) coupled to a transmitter that transmits one or more sounding reference signals (SRSs) to the BS and a processor that controls switching of the plurality of APs for the one or more SRS transmissions. [0012] In one aspect of the terminal, the plurality of APs comprises at least 8 APs. [0013] In one aspect of the terminal, the plurality of APs have a 4T6R configuration. [0014] In one aspect of the terminal, the processor further controls the switching based on a configuration information. [0015] In one aspect of the terminal, the configuration information is predetermined. [0016] In one aspect of the terminal, the configuration information is signaled by Downlink Control Information (DCI) or higher-layer signaling. [0017] In one aspect of the terminal, an allocated power differs for the plurality of APs based on an SRS configuration information. [0018] In general, one or more embodiments disclosed herein relate to a method for a terminal in communication with a base station (BS) that includes transmitting, using a plurality of antenna ports (APs), one or more sounding reference signals (SRSs) to the BS; and [0019] controlling switching of the plurality of APs for the one or more SRS transmissions. [0020] The method according to claim 8, wherein an allocated power differs for the plurality of APs based on an SRS configuration information. [0021] In general, one or more embodiments disclosed herein relate to a system that includes a base station and a terminal, where the terminal includes a plurality of antenna ports (APs) coupled to a transmitter that transmits one or more sounding reference signals (SRSs) to the BS and a processor that controls switching of the plurality of APs for the one or more SRS transmissions. [0022] Other embodiments and advantages of the present invention will be recognized from the description and figures. BRIEF DESCRIPTION OF THE DRAWINGS [0023] FIG. 1 shows an example of a UE transceiver architecture 2T4R. [0024] FIG. 2 shows an example antenna structure. [0025] FIG. 3 shows an example of a SRS resource configuration. [0026] FIG. 4 shows an example of SRS transmissions. [0027] FIG. 5 shows an example of AP combinations for transmitting SRS. [0028] FIG.6 shows an example transceiver architecture and an example SRS resource configuration. [0029] FIG. 7 shows an example antenna structure. [0030] FIG. 8 shows an example SRS resource configuration. [0031] FIG.9 shows an example of a wireless communication system according to one or more embodiments. [0032] FIG. 10 shows an example of a configuration of a BS according to one or more embodiments. [0033] FIG.11 shows an example of a configuration of a UE according to one or more embodiments. DETAILED DESCRIPTION [0034] Embodiments of the present invention will be described in detail below with reference to the drawings. Like elements in the various figures are denoted by like reference numerals for consistency. [0035] In the following description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. In the below discussion, although alternative embodiments are discussed one skilled in the art will appreciate that various embodiments or alternatives may be combined. [0036] UE Sounding Procedure for DL CSI Acquisition [0037] For sounding the DL channel, SRS resource set(s) with usage set to ‘antenna switching’ can be considered. [0038] A number of ports of an SRS resource in an SRS resource set with usage set to ‘antenna switching’ is based on available Tx ports at a UE [0039] FIG. 1 shows an example of UE transceiver architecture for 2T4R (i.e., 2 Tx ports, 4 Rx ports). For DL CSI acquisition, the UE is configured with 2 SRS resources each with 2-ports (equal to the number of Tx ports). [0040] According to Sec. 6.2.1.2 of TS 38.214, for 2T4R, up to two SRS resource sets may be configured with a different value for the higher layer parameter resourceType in SRS- ResourceSet set, where each SRS resource set has two SRS resources transmitted in different symbols. Additionally, each SRS resource in a given set consisting of two SRS ports and the SRS port pair of the second resource are associated with a different UE antenna port pair than the SRS port pair of the first resource. [0041] UE transceiver architectures that consider antenna switching for channel sounding (for up to 4 antennas) are: [0042] 1T2R, 2T4R, 1T4R, 1T4R/2T4R, or T=R. [0043] A UE capability of handling different transceiver architectures is reported using supportedSRS-TxPortSwitch parameter. Feasible capability combinations are as follows: • 't1r2' for 1T2R • 't1r1-t1r2' for 1T=1R/1T2R • 't2r4' for 2T4R • 't1r4' for 1T4R • 't1r1-t1r2-t1r4’ for 1T=1R/1T2R/1T4R • 't1r4-t2r4' for 1T4R/2T4R • 't1r1-t1r2-t2r2-t2r4' for 1T=1R/1T2R/2T=2R/2T4R • 't1r1-t1r2-t2r2-t1r4-t2r4' for 1T=1R/1T2R/2T=2R/1T4R/2T4R • 't1r1' for 1T=1R • 't2r2' for 2T=2R • 't1r1-t2r2' for 1T=1R/2T=2R • 't4r4' for 4T=4R • 't1r1-t2r2-t4r4' for 1T=1R/2T=2R/4T=4R [0044] Next, how different SRS resource allocation configurations assist in acquiring DL CSI for different transceiver architectures will be described below. [0045] First Embodiment [0046] According to a First Embodiment as shown in Fig. 2, an example antenna structure has 4 transceivers and 6 Rx antenna ports (APs). In embodiments in accordance with Fig. 2, AP₂, AP₃, AP₄, and AP₅ are connected to two of the transceiver (Tx) chains via an RF switching network. [0047] Additionally, in accordance with the First Embodiment, Fig. 3 describes an example SRS resource configuration. Fig. 3 shows an SRS resource set having two SRS resources each with 4-ports. Each port in a given SRS resource may be uniquely associated with an antenna port (AP). Note here that, with this SRS resource configuration, two APs (out of 6 available APs) have to transmit the SRS two times. As such, note that in the example AP and AP_! transmit SRS two times. Colors and/or shading represent the APs and their corresponding SRS ports. Note here that 15 different AP combinations can be considered for two SRS transmission times. These combinations may include: [0048] {AP₀, AP₁}, {AP₀, AP₂ }, {AP₀, AP₃}, {AP₀, AP₄}, {AP₀, AP₅}, {AP₁, AP₂ }, {AP₁, AP₃}, [0049] {AP₁, AP₄}, {AP₁, AP₅}, { AP₂ , AP₃}, { AP₂ , AP₄}, { AP₂ , AP₅}, {AP₃, AP₄}, {AP₃, AP₅}, [0050] {AP₄, AP₅} [0051] Second Embodiment [0052] According to a Second Embodiment, Fig. 4 shows an example NW configuration of antenna ports for multiple SRS transmission. At the outset, note here that the APs that transmit SRS two times can achieve better channel estimation performance. Hence, those skilled in the art may appreciate an importance for the NW and UE to have a common understanding about which APs are configured with multiple SRS transmissions. [0053] According to the Second Embodiment, APs for multiple SRS transmissions are pre-configured in the specification(s), e.g., APs with the x largest (smallest) port indices are associated with SRS resource 1 whereas the x smallest (largest) port indices are associated with SRS resource 2. Here x can be pre-determined in the specification(s) or higher-layer configured. [0054] Fig. 4 shows an example of when x=2. Since x=2, the two largest port indices for SRS resource 1 are 2 and 3 while the two smallest port indices for SRS resource 2 are 2 and 3. [0055] Second Embodiment Alternative 1 [0056] According to an alternative implementation of the Second Embodiment, examples are described of a NW configuration of antenna ports for multiple SRS transmission. Using higher-layer signaling or x-bits in DCI, the NW explicitly configures APs for multiple SRS transmission, e.g., using bits in DCI where N_AP and P are the number of

available APs and the number of ports for multiple SRS transmissions, respectively. In this example, the NW explicitly configures which APs should transmit SRS multiple times. [0057] Second Embodiment Alternative 2 [0058] In an alternative implementation of the Second Embodiment, it is possible that using a bitmap the NW explicitly configures APs for multiple SRS transmissions, e.g., assuming N_AP = 6 and P = 2, the NW can explicitly configure APs 2 and 3 for multiple SRS transmission using the bitmap: 011000. [0059] Second Embodiment Alternative 3 ^{[0060] In an alternative implementation of the Second Embodiment, with} periodic/semi-persistent SRS resources, the NW can assign different APs for multiple SRS transmissions at different time occasions. An example is shown in Fig. 5. [0061] In the example, AP combinations for transmitting SRS two times at different ^{time occasions are in the following order: {AP} ₂ ^{, AP} ₃ ^{}, {AP} ₀ ^{, AP} ₁ ^{}, {AP} ₄ ^{, AP} ₅ ^}. [0062] The alternative implementations of the Second Embodiment also may implement one or more of the following options. [0063] In a first option, as discussed under the Second Embodiment and Second Embodiment Alternative 1, the NW configures which APs transmit SRS two times within the initial slot. Afterwards, based on some pre-defined rule, a UE can switch to other AP combinations in subsequent slots in a cycle. ^{[0064] In a second option, using higher-layer signaling or DCI, the NW configures the} order of AP combinations for multiple SRS transmissions at different time slots within a cycle. [0065] Third Embodiment [0066] According to a Third Embodiment, examples are described of reporting of antenna ports for multiple SRS transmissions as part of the UE Capability. That is, as part of UE capability reporting and based on the UE antenna structure, a UE can report, explicitly or implicitly, which APs perform multiple SRS transmissions. Subsequently, that information can be used at the NW side to estimate channels associated with different APs. [0067] Third Embodiment Alternative 1 [0068] In an alternative implementation of the Third Embodiment, using x-bits within its capability reporting, the UE explicitly reports which APs can achieve multiple SRS transmission, e.g., using bits where N_AP and P are the number of available

APs and number of ports for multiple SRS transmission, respectively, and the UE explicitly reports to the NW which APs can perform multiple SRS transmissions. [0069] Third Embodiment Alternative 2 [0070] In an alternative implementation of the Third Embodiment, using a bitmap within its capability reporting, the UE explicitly reports which APs can achieve multiple SRS transmission, e.g., assuming N_AP = 6 and P = 2, the UE explicitly reports to the NW that AP 2 and 3 are capable of multiple SRS transmission using the bitmap: 011000. [0071] Third Embodiment Alternative 3 [0072] In an alternative implementation of the Third Embodiment, the UE explicitly or implicitly reports/indicates its antenna structure to the NW. [0073] Third Embodiment Alternative 4 [0074] In an alternative implementation of the Third Embodiment, the UE explicitly or implicitly reports/indicates to the NW what SRS resource configurations it can support. [0075] Fourth Embodiment [0076] According to a Fourth Embodiment, examples are described of SRS resource association(s) with SRS antenna ports. An SRS resource configuration with reference to Fig. 5 is contemplated that may take into account the antenna structure described in Fig. 2. [0077] An SRS resource set is described having two SRS resources where one has 4- ports and the other one has 2-ports. Each port in a given SRS resource is uniquely associated with an AP. Note here that each AP gets only one opportunity to transmits SRS (i.e., unlike the previous case where 2 APs transmit SRS two times.) In the example captured in FIG. 6: AP_" , AP_# , AP and AP_! are associated with a 4-port SRS resource while AP₄ and AP₅ are associated with a 2-port SRS resource. There are 6 different AP combinations that can be associated with the 2-port SRS resource: { AP₂ , AP₃}, {AP₄, AP₅}, { AP₂ , AP₄}, { AP₂ , AP₅}, {AP₃, AP₄}, {AP₃, AP₅}. [0078] Fifth Embodiment [0079] According to a Fifth Embodiment, examples are described of the association of APs with SRS resources. As a first example, the association of APs with SRS resources are pre-configured in the specification(s), e.g., the two APs with the x largest (smallest) port indices out of 4 APs connected via RF switching network are associated with the 2-port SRS resource. Here x can be pre-determined in the specification(s) or higher-layer configured. [0080] Fifth Embodiment Alternative 1 [0081] In an alternative implementation of the Fifth Embodiment, using higher layer signaling or x-bits in DCI, the NW explicitly configures APs for 2-port or 4-port SRS transmission, e.g., using bits in DCI, the NW explicitly configures two out of

four APs connected via an RF switching network, with a 2-port SRS resource. [0082] Fifth Embodiment Alternative 2 [0083] In an alternative implementation of the Fifth Embodiment, using a bitmap the NW explicitly configures APs for 2-port or 4-port SRS transmission, e.g., the NW explicitly configures { AP₂ , AP₃} out of AP₂ , AP₃, AP₄, AP₅ with a 2-port SRS resource using the bitmap: 1100. [0084] Fifth Embodiment Alternative 3 [0085] In an alternative implementation of the Fifth Embodiment, during its capability reporting, a UE explicitly or implicitly reports which APs can be associated with a 2-port SRS resource. [0086] Sixth Embodiment [0087] According to a Sixth Embodiment, examples are described of Power Allocation for 4-port and 2-port SRS Transmissions. A same power allocation may be provided for all APs irrespective of the number of ports in each SRS resource, e.g., assuming total available power is P, each AP can be assigned P/4 power. This means, for 4-port SRS resource transmission, the total available power P is used whereas for 2-port SRS resource transmission, only P/2 power is used. [0088] Sixth Embodiment Alternative 1 [0089] In an alternative implementation of the Sixth Embodiment, it is possible to allocate different power for different APs based on the number of ports in each SRS resource, e.g., assuming total power available is P, each AP associated with a 4-port SRS resource is allocated with P/4 power, while each AP associated with 2-port SRS resource is allocated with P/2 power. This means, for both 4-port and 2-port SRS resource transmissions that the total available power can be used. [0090] Seventh Embodiment [0091] According to a Seventh Embodiment, an example antenna structure has 4 transceivers and 6 APs. In embodiments in accordance with Fig. 7, all of AP₀, AP₁, AP₂, AP₃, AP₄, and AP₅ are connected to the transceiver (Tx) chains via an RF switching network. Note that, for configuration of APs associated with multiple SRS transmissions, the Second Embodiment and Third Embodiment discussed previously can be considered here. [0092] Additionally, in accordance with the Seventh Embodiment, Fig. 8 describes an example SRS resource configuration. Fig. 8 shows an SRS resource set having two SRS resources each with 4-ports. Each port in a given SRS resource is uniquely associated with an AP. Note here that, with this SRS resource configuration, two APs (out of 6 available APs) have to transmit a SRS two times. As such, note that in the example AP and AP_! transmit the SRS two times. Colors and/or shading represent the APs and their corresponding SRS ports. Note that, for configuration of APs associated with multiple SRS transmissions, the discussion within the Second and Third Embodiments can be considered here. [0093] Wireless Communication System [0094] FIG. 9 is a wireless communications system 1 according to one or more embodiments of the present invention. The wireless communication system 1 includes a UE 10, a BS 20, and a core network 30. The wireless communication system 1 may be a NR system. The wireless communication system 1 is not limited to the specific configurations described herein and may be any type of wireless communication system such as an LTE/LTE-Advanced (LTE-A) system. [0095] The BS 20 may communicate uplink (UL) and downlink (DL) signals with the UE 10 in a cell of the BS 20. The DL and UL signals may include control information and user data. The BS 20 may communicate DL and UL signals with the core network 30 through backhaul links 31. The BS 20 may be gNodeB (gNB). The BS 20 may be referred to as a network (NW) 20. For example, the BS 20 may transmit DL signals such as a CSI-RS and DCI. [0096] The BS 20 includes antennas, a communication interface to communicate with an adjacent BS 20 (for example, X2 interface), a communication interface to communicate with the core network 30 (for example, S1 interface), and a CPU (Central Processing Unit) such as a processor or a circuit to process transmitted and received signals with the UE 10. Operations of the BS 20 may be implemented by the processor processing or executing data and programs stored in a memory. However, the BS 20 is not limited to the hardware configuration set forth above and may be realized by other appropriate hardware configurations as understood by those of ordinary skill in the art. Numerous BSs 20 may be disposed so as to cover a broader service area of the wireless communication system 1. [0097] The UE 10 may communicate DL and UL signals that include control information and user data with the BS 20 using Multi Input Multi Output (MIMO) technology. The UE 10 may be a mobile station, terminal, mobile terminal, user terminal, a smartphone, a cellular phone, a tablet, a mobile router, or information processing apparatus having a radio communication function such as a wearable device. The wireless communication system 1 may include one or more UEs 10. For example, the UE 10 may transmit UL signals such as an SRS and CSI report. [0098] The UE 10 includes a CPU such as a processor, a RAM (Random Access Memory), a flash memory, and a radio communication device to transmit/receive radio signals to/from the BS 20 and the UE 10. For example, operations of the UE 10 described below may be implemented by the CPU processing or executing data and programs stored in a memory. However, the UE 10 is not limited to the hardware configuration set forth above and may be configured with, e.g., a circuit to achieve the processing described below. [0099] Configuration of BS The BS 20 according to embodiments of the present invention will be described below with reference to FIG. 10. FIG. 10 is a diagram illustrating a schematic configuration of the BS 20 according to embodiments of the present invention. The BS 20 may include a plurality of antennas (antenna element group) 201, amplifier 202, transceiver (transmitter/receiver) 203, a baseband signal processor 204, a call processor 205 and a transmission path interface 206. [00101] User data that is transmitted on the DL from the BS 20 to the UE 20 is input from the core network, through the transmission path interface 206, into the baseband signal processor 204. [00102] In the baseband signal processor 204, signals are subjected to Packet Data Convergence Protocol (PDCP) layer processing, Radio Link Control (RLC) layer transmission processing such as division and coupling of user data and RLC retransmission control transmission processing, Medium Access Control (MAC) retransmission control, including, for example, HARQ transmission processing, scheduling, transport format selection, channel coding, inverse fast Fourier transform (IFFT) processing, and precoding processing. Then, the resultant signals are transferred to each transceiver 203. As for signals of the DL control channel, transmission processing is performed, including channel coding and inverse fast Fourier transform, and the resultant signals are transmitted to each transceiver 203. [00103] The baseband signal processor 204 notifies each UE 10 of control information (system information) for communication in the cell by higher layer signaling (e.g., Radio Resource Control (RRC) signaling and broadcast channel). Information for communication in the cell includes, for example, UL or DL system bandwidth. [00104] In each transceiver 203, baseband signals that are precoded per antenna and output from the baseband signal processor 204 are subjected to frequency conversion processing into a radio frequency band. The amplifier 202 amplifies the radio frequency signals having been subjected to frequency conversion, and the resultant signals are transmitted from the antennas 201. [00105] As for data to be transmitted on the UL from the UE 10 to the BS 20, radio frequency signals are received in each antennas 201, amplified in the amplifier 202, subjected to frequency conversion and converted into baseband signals in the transceiver 203, and are input to the baseband signal processor 204. [00106] The baseband signal processor 204 performs FFT processing, IDFT processing, error correction decoding, MAC retransmission control reception processing, and RLC layer and PDCP layer reception processing on the user data included in the received baseband signals. Then, the resultant signals are transferred to the core network through the transmission path interface 206. The call processor 205 performs call processing such as setting up and releasing a communication channel, manages the state of the BS 20, and manages the radio resources. [00107] Configuration of UE [00108] The UE 10 according to embodiments of the present invention will be described below with reference to FIG. 11. FIG. 11 is a schematic configuration of the UE 10 according to embodiments of the present invention. The UE 10 has a plurality of UE antenna S101, amplifiers 102, the circuit 103 comprising transceiver (transmitter/receiver) 1031, the controller 104, and an application 105. [00109] As for DL, radio frequency signals received in the UE antenna S101 are amplified in the respective amplifiers 102, and subjected to frequency conversion into baseband signals in the transceiver 1031. These baseband signals are subjected to reception processing such as FFT processing, error correction decoding and retransmission control and so on, in the controller 104. The DL user data is transferred to the application 105. The application 105 performs processing related to higher layers above the physical layer and the MAC layer. In the downlink data, broadcast information is also transferred to the application 105. [00110] On the other hand, UL user data is input from the application 105 to the controller 104. In the controller 104, retransmission control (Hybrid ARQ) transmission processing, channel coding, precoding, DFT processing, IFFT processing and so on are performed, and the resultant signals are transferred to each transceiver 1031. In the transceiver 1031, the baseband signals output from the controller 104 are converted into a radio frequency band. After that, the frequency-converted radio frequency signals are amplified in the amplifier 102, and then, transmitted from the antenna 101. [00111] Another Example [00112] The above examples and modified examples may be combined with each other, and various features of these examples may be combined with each other in various combinations. The invention is not limited to the specific combinations disclosed herein. [00113] Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

CLAIMS What is claimed is: 1. A terminal in communication with a base station (BS), comprising: a plurality of antenna ports (APs) coupled to a transmitter that transmits one or more sounding reference signals (SRSs) to the BS; and a processor that controls switching of the plurality of APs for the one or more SRS transmissions.

2. The terminal according to claim 1, wherein the plurality of APs comprises at least 8 APs.

3. The terminal according to claim 1, wherein the plurality of APs have a 4T6R configuration.

4. The terminal according to any one of claims 1 to 3, wherein the processor further controls the switching based on a configuration information.

5. The terminal according to claim 4, wherein the configuration information is predetermined.

6. The terminal according to claim 4, wherein the configuration information is signaled by Downlink Control Information (DCI) or higher-layer signaling.

7. The terminal according to claim 1, wherein an allocated power differs for the plurality of APs based on an SRS configuration information.

8. A method for a terminal in communication with a base station (BS), comprising: transmitting, using a plurality of antenna ports (APs), one or more sounding reference signals (SRSs) to the BS; and controlling switching of the plurality of APs for the one or more SRS transmissions.

9. The method according to claim 8, wherein the plurality of APs comprises at least 8 APs.

10. The method according to claim 8, wherein the plurality of APs have a 4T6R configuration.

11. The method according to any one of claims 8 to 10, wherein the terminal further controls the switching based on a configuration information.

12. The method according to claim 11, wherein the configuration information is predetermined.

13. The method according to claim 11, wherein the configuration information is signaled by Downlink Control Information (DCI) or higher-layer signaling.

14. The method according to claim 8, wherein an allocated power differs for the plurality of APs based on an SRS configuration information.

15. A system comprising: a base station; and a terminal, comprising: a plurality of antenna ports (APs) coupled to a transmitter that transmits one or more sounding reference signals (SRSs) to the BS; and a processor that controls switching of the plurality of APs for the one or more SRS transmissions.

16. The system according to claim 15, wherein the plurality of APs comprises at least 8 APs.

17. The system according to claim 15, wherein the plurality of APs have a 4T6R configuration.

18. The system according to any one of claims 15 to 17, wherein the processor further controls the switching based on a configuration information.

19. The system according to claim 18, wherein the configuration information is predetermined.

20. The system according to claim 18, wherein the configuration information is signaled by Downlink Control Information (DCI) or higher-layer signaling.