Base station, wireless terminal, and methods therefor

Abstract

A base station (10, 21) transmits a first indication (421) within a cell (51), the first indication (421) indicating the number of transmission points (31, 32, 33) that may be or are being used in the cell (51), and being transmitted using a signal, physical channel, or message that is received by at least a plurality of wireless terminals (40) in an idle mode. This contributes, for example, to enabling the wireless terminals to know the number of transmission points that may be or are being used in a cell, or the number of beams that may be or are being simultaneously transmitted in the cell at the same time using the same frequency resource.

Description

Base station, wireless terminal, and methods thereof

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to wireless communication systems, and more particularly to beam sweeping transmission of broadcast signals by base stations.

[0002] The 3rd Generation Partnership Project (3GPP®) Fifth Generation (5G) system uses beam sweeping to enable User Equipment (UE) to select the best beam during initial access. Specifically, a gNB transmits multiple Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) blocks (SSBs) as bursts with a fixed periodicity, changing the beam direction for each SSB transmission. One SSB includes a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a PBCH, and a PBCH Demodulation Reference Signal (DMRS).

[0003] An SSB spans four consecutive Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain and 240 consecutive subcarriers (i.e., 20 resource blocks) in the frequency domain. Each SSB in a burst corresponds to a separate beam and is beamformed in a different direction. A set of SSBs in a burst is called an SSB burst set and is transmitted in a half-radio frame, i.e., 5 milliseconds (ms) window. An SSB burst set (i.e., 5 ms duration) typically repeats every two radio frames, i.e., 20 ms. The maximum number of SSBs in an SSB burst set (i.e., 5 ms duration) is specified as four for frequency bands up to 3 GHz, eight for 3-6 GHz, and 64 for 6-52.6 GHz to achieve a trade-off between coverage and resource overhead. Note that the number of SSBs actually transmitted within a cell is configurable and may be less than the maximum number.

[0004] Each SSB within an SSB burst set (5 ms) is assigned an SSB index, which is a unique number starting from 0 and incrementing by 1. As the maximum number of candidate SSBs that can be transmitted within an SSB burst set is 64, the SSB index is signaled to the UE via two parts within the SSB. The SSB index is split into two fields, the first field is carried as part of the PBCH payload, and the second part of the SSB index is carried as part of the PBCH DMRS sequence.

[0005] When synchronizing to the radio access network and performing initial access, the UE needs to retrieve the SSB. In an idle state or mode, i.e., Radio Resource Control (RRC)_IDLE or RRC_INACTIVE, the UE searches for SSBs transmitted within the cell, receives a set of SSB bursts, and selects the SSB with the best reception quality, i.e., the best beam. The SSB index is mapped to available Random Access Channel (RACH) opportunities. The UE informs the network, i.e., the gNB, of its selected SSB beam by transmitting a Physical RACH (PRACH) preamble on the RACH opportunity associated with the selected best beam.

[0006] The 5G specifications by 3GPP regarding the above-mentioned SSB beam sweep are provided, for example, in non-patent documents 1-4.

[0007] 3GPP TS 38.211 V17.2.0 (2022-06), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical channels and modulation (Release 17)", June 2022 3GPP TS 38.212 V17.2.0 (2022-06), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Multiplexing and channel coding (Release 17)", June 2022 3GPP TS 38.213 V17.2.0 (2022-06), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical layer procedures for control (Release 17)", June 2022 3GPP TS 38.331 V17.1.0 (2022-06), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 17)", July 2022

[0008] The inventors anticipate that an extension of the 5G system or a future 6G or beyond system will use millimeter-wave or sub-terahertz frequencies and utilize geographically distributed Transmission Reception Points (TRPs) with overlapping coverage areas to achieve site diversity. Each TRP hosts one or more antenna elements (typically array antennas) and radio frequency (RF) components and can communicate with UEs using beams. A TRP may also be referred to as a Radio Unit (RU), Remote Radio Head (RRH), access point, or distributed antenna. When focusing only on downlink transmissions (e.g., SSB transmissions) by a base station, a TRP may also be referred to as a transmission point.

[0009] However, if multiple TRPs are used in a cell and the number of beams transmitted within the cell increases, the current maximum number of 64 candidate SSB beams may not be sufficient. If all SSB beams transmitted within a cell are swept over different time resources or OFDM symbols, the current constraints on the periodicity of the SSB burst set (i.e., 20 ms) and / or the duration of the SSB burst set (i.e., 5 ms) may need to be relaxed to increase the maximum number of candidate SSB beams beyond 64. Specifically, the periodicity of the SSB bursts may need to be shortened, the duration of the SSB burst set may need to be lengthened, or both. This would result in increased overhead for SSB transmission (i.e., beam sweeping transmission).

[0010] The UE searches for the strongest cell for each frequency (or each frequency band). To determine a suitable cell on which the UE may camp, the UE determines whether the strongest cell satisfies a cell selection criterion, in addition to other conditions. In cell selection in multi-beam operation, the cell measurement quantity is up to the UE implementation. In other words, in cell selection in multi-beam operation, how the UE derives the cell measurement quantity is up to the UE implementation.

[0011] In one implementation, before decoding System Information Block Type 1 (SIB1), the UE may attempt to receive multiple SSBs (i.e., multiple SSB beams) transmitted within the cell and derive the cell measurement quantity as the highest beam measurement quantity value. Each beam measurement quantity may be Synchronization Signal (SS) reference signal received power (SS-RSRP), SS reference signal received quality (SS-RSRQ), or SS signal-to-noise and interference ratio (SS-SINR). If such an implementation is adopted, the UE must attempt to receive SSBs at multiple candidate time-domain locations before it can determine from the information in the decoded SIB1 at which candidate time-domain locations in the SSB burst set SSBs are transmitted. This has the drawback of increasing the UE's power consumption.

[0012] To limit the increase in UE power consumption, it is preferable for the UE to know the time-domain locations at which SSBs are transmitted within the SSB burst set, or to be able to narrow down the candidate time-domain locations at which SSB reception should be attempted within the SSB burst set. By way of example and not limitation, the number of TRPs that may be used or are in use within a cell may be related to the number and arrangement of candidate time-domain locations at which SSBs may be transmitted within the cell. In other words, the number and arrangement of candidate time-domain locations at which SSBs may be transmitted within a cell may depend on the number of TPRs in use within the cell.

[0013] Furthermore, if the maximum number of SSBs (SSB beams) that can be transmitted in a cell is expanded to a sufficiently large number, a problem may arise in that the total size of one or more bitmaps for specifying the SSBs that are actually used becomes large. One approach to address this problem is to impose constraints on the rules for using candidate time-domain positions within an SSB burst set that depend on the number of TRPs used in the cell.

[0014] Alternatively, to reduce SSB transmission overhead, an architecture may be adopted that allows multiple TRPs to simultaneously transmit SSB beams in the same time resource or OFDM symbol. This reduces the radio resources required to transmit different SSB beams and contributes to reducing the overhead of SSB transmission (i.e., beam sweep transmission). Specifically, multiple TRPs may transmit the same PBCH modulation symbols or sets of different PBCH modulation symbols generated from the same PBCH payload or different PBCH payloads in the same time and frequency resource, i.e., resource elements. However, this architecture may cause interference between SSB beams that makes it difficult for the UE to measure the received power or reception quality of each SSB beam.

[0015] To address this issue, it may be effective to transmit TRP-specific or individual PBCH DMRS in time and frequency resources, i.e., resource elements, individually allocated to each TRP. By way of example and not limitation, the arrangement or pattern of resources on which TRP-specific PBCH DMRS are transmitted may depend on the number of TRPs used in a cell. Alternatively, the arrangement or pattern of resources on which TRP-specific PBCH DMRS are transmitted may depend on the number of SSBs (or SSB beams) simultaneously transmitting on the same time and frequency resources in a cell.

[0016] To help solve some of the problems mentioned above, it may be useful to enable UEs to know the number of TRPs (or transmission points) that can be or are being used within a cell. Alternatively, it may be useful to enable UEs to know the number of beams that can or are being transmitted simultaneously on the same time and frequency resources within a cell. More specifically, it may be useful to enable UEs in an idle state or mode (e.g., RRC_IDLE or RRC_INACTIVE or both) to know the number of such transmission points or beams.

[0017] One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, method, and program for enabling UEs or wireless terminals to know the number of transmission points that can be used or are being used in a cell, or the number of beams that can be transmitted or are being transmitted simultaneously on the same time and frequency resources in a cell. It should be noted that this objective is only one of multiple objectives to be achieved by the multiple embodiments disclosed in this specification. Other objectives or problems and novel features will become apparent from the description of this specification or the accompanying drawings.

[0018] In a first aspect, a base station includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to transmit a first indication in the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, the first indication indicating a number of transmission points that may be used or are being used in the cell.

[0019] In a second aspect, a method performed by a base station includes transmitting a first indication in a cell, the first indication being indicative of a number of transmission points that may be used or are being used in said cell, using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode.

[0020] In a third aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication of a number of transmission points that may be used or are being used in a cell.

[0021] In a fourth aspect, a method performed by a wireless terminal includes receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication of a number of transmission points that may be used or are being used in a cell.

[0022] In a fifth aspect, a base station includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to transmit, via a signal or physical channel within an SSB burst, a first indication indicating a number of one or more subsets of a plurality of subsets of candidate time-domain locations within an SSB burst set that may be used or are being used.

[0023] In a sixth aspect, a method performed by a base station includes transmitting, via a signal or physical channel within an SSB burst set, a first indication indicating the number of one or more subsets of a plurality of subsets of candidate time-domain locations within an SSB burst set that may be used or are being used.

[0024] In a seventh aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive, via a signal or physical channel within an SSB, a first indication of a number of one or more subsets of a plurality of subsets of candidate time-domain locations within an SSB burst set that are potentially used or in use.

[0025] In an eighth aspect, a method performed by a wireless terminal includes receiving, via a signal or physical channel within an SSB, a first indication indicating the number of one or more subsets of a plurality of subsets of candidate time-domain locations within an SSB burst set that may be used or are being used.

[0026] In a ninth aspect, a base station includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to transmit in a cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode a first indication of a number of beams that can be or are being transmitted on the same time and frequency resource in the cell.

[0027] In a tenth aspect, a method performed by a base station includes transmitting a first indication in a cell indicating the number of beams that can be or are being transmitted on the same time and frequency resources in the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode.

[0028] In an eleventh aspect, a wireless terminal includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to receive via a signal, physical channel, or message received by at least a plurality of idle mode wireless terminals a first indication of a number of beams that can be or are being transmitted on the same time and frequency resource within a cell.

[0029] In a twelfth aspect, a method performed by a wireless terminal includes receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication indicating the number of beams that can be or are being transmitted on the same time and frequency resource within a cell.

[0030] A thirteenth aspect is directed to a program, which includes a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to the second, fourth, sixth, eighth, tenth, or twelfth aspect.

[0031] According to the above aspects, it is possible to provide an apparatus, method, and program for enabling UEs or wireless terminals to know the number of transmission points that can be or are being used in a cell or the number of beams that can be or are being transmitted simultaneously on the same time and frequency resources in a cell.

[0032] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to the embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a transmission system of a base station according to the embodiment. FIG. 3 is a diagram illustrating an example of the configuration of a transmission system of a base station according to the embodiment. FIG. 4 is a sequence diagram illustrating an example of signaling between a base station and a UE according to the embodiment. FIG. 5 is a flowchart illustrating an example of an operation of a UE according to the embodiment. FIG. 6 is a diagram illustrating an example of an SSB reception operation by a UE according to the embodiment. FIG. 7 is a sequence diagram illustrating an example of signaling between a base station and a UE according to the embodiment. FIG. 8 is a flowchart illustrating an example of an operation of a UE according to the embodiment. FIG. 9 is a diagram illustrating an example of transmission of a plurality of SSBs according to the embodiment. FIG. 10 is a sequence diagram illustrating an example of signaling between a base station and a UE according to the embodiment. FIG. 11 is a flowchart illustrating an example of an operation of a UE according to the embodiment. FIG. 12 is a diagram illustrating an example of transmission of a plurality of SSBs according to the embodiment. FIG. 13 is a diagram illustrating an example of mapping of a TRP-specific PBCH DMRS in an SSB according to the embodiment. FIG. 14 is a sequence diagram illustrating an example of signaling between a base station and a UE according to the embodiment. FIG. 15 is a flowchart illustrating an example of an operation of a UE according to the embodiment.

[0033] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0034] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different purposes or problems and to achieving different effects.

[0035] The following embodiments are described primarily for the 3GPP 5G system, but may also be applied to other wireless communication systems that support beam sweeping techniques similar to the SSB beam sweeping in the 3GPP 5G system.

[0036] As used herein, depending on the context, "if" may be interpreted to mean "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0037] First, the configurations and operations of several network elements common to several embodiments will be described. Figure 1 illustrates an example configuration of a wireless communication system according to several embodiments. In the example of Figure 1, the wireless communication system includes a Central Unit (CU) 10, Distributed Units (DUs) 21 and 22, TRPs 31 to 35, and UEs 40. The UEs 40 may be referred to by other terms, such as wireless terminals, mobile terminals, mobile stations, or wireless transmit receive units (WTRUs). Each element (network function) illustrated in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0038] The CU 10, the DUs 21 and 22, and the TRPs 31 to 35 correspond to one base station. In other words, one base station includes the CU 10, the DUs 21 and 22, and the TRPs 31 to 35. The base station may also be called a radio access network node, a radio station, or an access point. In a 5G system, the base station may be a gNB.

[0039] The CU 10 may host the RRC, Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols of the gNB (or the RRC and PDCP protocols of the gNB). The CU 10 may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UPs).

[0040] Each of the DUs 21 and 22 hosts the Radio Link Control (RLC) layer and Medium Access Control (MAC) layer of the gNB, and may host part or all of the physical (PHY) layer of the gNB. If each of the DUs 21 and 22 hosts part of the PHY layer, i.e., the high PHY layer, the remaining PHY layer signal processing, i.e., the low PHY layer, is located in the TRPs 31 to 35. In the example of FIG. 1 , the DU 21 is connected to the TRPs 31 to 33, while the DU 22 is connected to the TRPs 34 and 35. The TRPs 31 to 33 provide one cell 51, and the TRPs 34 and 35 provide separate cells 52 and 53, respectively. In other words, the DU 21 provides one cell 51, and the TRPs 31 to 33 correspond to the cell 51. The DU 22 provides a plurality of cells 52 and 53, and the TRPs 34 and 35 correspond to the cells 52 and 53, respectively.

[0041] Each of the TRPs 31 to 35 can communicate with the UEs 40 using a beam. The TRPs 31 to 35 may also be called Radio Units (RUs), Remote Radio Heads (RRHs), access points (APs), or distributed antennas. When focusing only on downlink transmissions (e.g., SSB transmissions) by the base station, the TRPs may also be called transmission points.

[0042] Each of the TRPs 31-35 provides analog RF signal processing. Each TRP may also provide lower PHY layer signal processing. Each TRP includes or is connected to one or more antenna elements (typically array antennas). Each TRP includes RF components coupled to one or more antenna elements. For analog or hybrid beamforming, analog beamforming circuitry may be located between one or more antenna elements or one or more array antennas and the multiple RF chains of each TRP.

[0043] Each TRP may further include a digital front end (DFE). The DFE provides lower PHY layer signal processing and digital radio signal processing. The lower PHY layer signal processing may include, for example, an inverse fast Fourier transform (IFFT) for generating an OFDM signal and an FFT for obtaining subcarrier signal components from a received OFDM signal. The lower PHY layer signal processing may further include cyclic prefix (CP) addition and removal, and physical RACH (PRACH) extraction or filtering. The digital radio signal processing may include, for example, digital pre-distortion (DPD), crest factor reduction (CFR), digital up-conversion (DUC), digital down-conversion (DDC), and transmit and receive baseband channel filters. The DFE may perform digital baseband precoding for beamforming.

[0044] The DU 21 may be connected to each of the TRPs 31 to 33 via an interface conforming to a standard specification such as Common Public Radio Interface (CPRI), enhanced CPRI (eCPRI), or Open Radio Access Network (O-RAN) Fronthaul. Alternatively, the DU 21 may be connected to each of the TRPs 31 to 33 via an interface employing Radio over Fiber (RoF) technology. In this case, the DU 21 may perform all digital signal processing including upper and lower PHY layer signal processing, as well as Digital to Analog (DA) and Analog to Digital (AD) conversion.

[0045] A direct interface, connection, or backhaul may be provided to communicatively connect DU 21 and DU 22. Similarly, a direct interface, connection, or backhaul may be provided to communicatively connect TRPs within a cell or between cells, for example, between TRPs 31 to 33, between TRPs 33 and 34, and between TRPs 34 and 35.

[0046] FIG. 2 conceptually illustrates SSB beam sweeping performed by TRPs 31 to 33 within one cell (cell 51). Each of the TRPs 31 to 33 uses beam sweeping 300 to enable UEs 40 to select the best beam during initial access. Specifically, each TRP transmits multiple SSBs, changing the beam direction for each SSB transmission. One SSB includes PSS, SSS, PBCH, and PBCH DMRS. Note that when multiple TRPs are deployed within one cell, at least one of these TRPs may transmit only one SSB beam. In other words, at least one of the multiple TRPs within a cell may transmit a single SSB beam intermittently in a predetermined direction at a predetermined period without performing beam sweeping.

[0047] FIG. 3 shows an example configuration of a DU 21 and TRPs 31 to 33 that provide one cell (cell 51). In the example of FIG. 3, the DU 21 includes a digital baseband unit 210. The digital baseband unit 210 provides signal processing for the RLC layer, MAC layer, and upper PHY layer. For SSB transmission, the digital baseband unit 210 generates a Broadcast Channel (BCH) transport block containing a Master Information Block (MIB) message and generates a PBCH payload that includes the BCH transport block and additional timing-related PBCH payload bits. In addition, the digital baseband unit 210 performs scrambling, attachment of cyclic redundancy check (CRC) bits, channel coding, and rate matching on the generated PBCH payload. Furthermore, the digital baseband unit 210 performs scrambling on the rate-matched block of bits and maps the scrambled block of bits to multiple modulation symbols (e.g., complex-valued Quadrature Phase Shift Keying (QPSK) symbols).

[0048] Depending on the division of functions between the DU 21 and the TRPs 31 to 33, the digital baseband unit 210 may perform all digital signal processing, including lower PHY layer signal processing, as well as Digital to Analog (DA) and Analog to Digital (AD) conversion.

[0049] In the example of FIG. 3 , each of the TRPs 31 to 33 includes an RF component 310. The RF component 310 is coupled to an antenna 340. In the example of FIG. 3 , the antenna 340 includes multiple antenna elements and is typically an array antenna. The RF component 310 includes an RF transceiver 320 and a beamforming circuit 330. The RF transceiver 320 includes an amplifier and a frequency converter. The beamforming circuit 330 determines a beam direction by adjusting one or both of the phase and amplitude of radio signals supplied to the multiple antenna elements of the antenna 340. The specific beam direction or beam number is specified by the DU 21 or the CU 10. Other beamforming techniques may also be used, and the antenna 340 may be a directional antenna such as a lens antenna or a metamaterial antenna.

[0050] <First Embodiment> A configuration example of a wireless communication system according to this embodiment may be the same as the example described with reference to Figures 1 to 3. This embodiment provides operations of a base station and a UE regarding beam sweep transmission and reception of SSBs.

[0051] Fig. 4 shows an example of signaling between a base station and a UE. A base station (BS) 401 in Fig. 4 may be the CU 10 or the DU 21 described with reference to Figs. 1 to 3. A UE 402 in Fig. 4 may be the UE 40 described with reference to Figs. 1 to 3.

[0052] In step 421, a base station (BS) 401 transmits a first indication in its cell indicating the number of TRPs (or transmission points) that can be used or are being used in the cell using a signal, physical channel, or message that is received by at least a number of UEs in an idle state or mode. A UE 402 in an idle state or mode receives the first indication. The idle state or mode may be RRC_IDLE or RRC_INACTIVE. The first indication of the number of TRPs (or transmission points) may also be referred to as information, data, configuration, or configuration information indicating the number of TRPs (or transmission points).

[0053] The base station 401 may transmit the first indication using a signal or physical channel included in an SSB. Alternatively, the base station 401 may transmit the first indication using SIB1. The base station 401 may transmit the first indication using another SIB. The first indication may be divided into multiple fields and transmitted over multiple signals or physical channels.

[0054] In one implementation, base station 401 may provide the first indication to UE 402 using at least a sequence of synchronization signals, i.e., PSS or SSS, transmitted within an SSB. Additionally or alternatively, base station 401 may provide the first indication to UE 402 using at least a sequence of PBCH DMRS transmitted within an SSB. The PBCH DMRS is used by UE 402 to demodulate PBCH modulation symbols generated from the PBCH payload. Additionally or alternatively, base station 401 may provide the first indication to UE 402 using at least a PBCH payload (e.g., MIB).

[0055] According to the operations described with reference to Figure 4, the base station 401 can enable the UE 402 to know the number of TRPs (or transmission points) that can be or are being used in the cell. Details of various uses by the UE 402 of the first indication and details of the timing of transmission of the first indication suitable for these uses will be described in detail in subsequent embodiments.

[0056] Second Embodiment A configuration example of a wireless communication system according to this embodiment may be the same as the example described with reference to Figures 1 to 3. This embodiment provides details of the operation of a base station and a UE with respect to the signaling indicating the number of TRPs described in the first embodiment.

[0057] FIG. 5 illustrates an example of the operation of a UE (e.g., UE 40). In step 501, the UE receives a first indication, indicating the number of TRPs (or transmission points) that can be used or are being used in a cell, via a signal or physical channel in an SSB. The base station may provide the first indication to the UE using at least a sequence of synchronization signals, i.e., PSS or SSS, transmitted in the SSB. Additionally or alternatively, the base station may provide the first indication to the UE using at least a sequence of PBCH DMRSs transmitted in the SSB. The PBCH DMRSs are used by the UE to demodulate PBCH modulation symbols generated from the PBCH payload. Additionally or alternatively, the base station may provide the first indication to the UE using at least a PBCH payload (e.g., MIB).

[0058] In step 502, the UE determines one or more candidate time-domain locations within the SSB burst set that may be used for SSB transmissions based on the first indication. To enable this, a restriction is imposed on the rules for the base station's use of the candidate time-domain locations within the SSB burst set depending on the number of TRPs used in the cell. Each time-domain location is a time-domain location in a mapping of time and frequency resources (resource elements). The candidate time-domain locations within the SSB burst set may also be referred to as transmission opportunities for SSBs within the SSB burst set. In one example, the candidate time-domain locations within the SSB burst set may be divided into multiple subsets, with each subset associated with a predetermined number of TRP(s). The predetermined number may be one or more. The number of divided subsets may define the maximum number of TRPs available in the cell. The UE may determine which of the divided subsets to use for SSB transmissions based on the number of TRPs indicated in the first indication. Each subset may be contiguous candidate time-domain locations within the set of SSB bursts, or alternatively, each subset may be comprised of multiple candidate time-domain locations that are discretely located within the set of SSB bursts.

[0059] An example of SSB reception operation by a UE is shown in Figure 6. In the example of Figure 6, there are N candidate time-domain positions within one SSB burst set. TRP is divided into N subsets. TRP is the maximum number of TRPs in a cell. The base station TRP, and transmit a first indication on a signal or physical channel within the SSB burst set, indicating a value between . The first indication indicates the number of TRPs that can be used or are being used within the cell. For example, the base station uses the same number of subsets as the number of TRPs indicated in the first indication, starting from the beginning of the SSB burst set. In candidate time-domain positions 610 shaded in FIG. 6, SSBs are transmitted. On the other hand, in candidate time-domain positions 620 not shaded in FIG. 6, SSBs are not transmitted. The duration of the SSB burst set may be, for example, but not limited to, a half radio frame, i.e., 5 ms, which is the same as that of the current NR specification.

[0060] The UE powers on at timing A shown in FIG. 6 and searches for an SSB. If the SSB is successfully received, the UE obtains a first indication at timing B shown in FIG. 6. The first indication indicates the number of TRPs that can be used or are being used in the cell. This allows the UE to recognize the number of subsets on which the SSB is transmitted. The UE then detects an SSB index from the received SSB. The SSB index is associated with the candidate time-domain location (and subset) on which the SSB is transmitted. This allows the UE to determine the candidate time-domain locations on which the SSBs may be transmitted. The UE may attempt SSB reception at the candidate time-domain locations (period C shown in FIG. 6) and stop SSB reception at other candidate time-domain locations. This operation can help reduce the increase in UE power consumption.

[0061] Third Embodiment A configuration example of a wireless communication system according to this embodiment may be similar to the example described with reference to Figures 1 to 3. This embodiment provides details of the operation of a base station and a UE with respect to the signaling indicating the number of TRPs described in the first and second embodiments. More specifically, this embodiment provides a method for reducing the amount of information or the number of bits required to indicate to a UE the candidate time-domain locations from which SSBs are actually transmitted.

[0062] Fig. 7 shows an example of signaling between a base station and a UE. A base station 701 in Fig. 7 may be the CU 10 or the DU 21 described with reference to Figs. 1 to 3. A UE 702 in Fig. 7 may be the UE 40 described with reference to Figs. 1 to 3.

[0063] In step 721, the base station 701 transmits a first indication in the cell, indicating the number of TRPs (or transmission points) that can be used or are being used in the cell, using a signal, physical channel, or message that is received by at least a plurality of UEs in idle state or mode. In step 722, the base station 701 transmits a second indication that is used in combination with the first indication to indicate the time-domain locations that are being used for SSB transmissions within the SSB burst set. The second indication is information that is common to a plurality of TRPs. The UE 702 receives the first indication and the second indication.

[0064] The second indication may be transmitted in a signal, physical channel, or message different from that in which the first indication is transmitted. For example, the first indication may be transmitted via a signal or physical channel within an SSB, while the second indication is transmitted in SIB1. Alternatively, the second indication may be transmitted in the same signal, physical channel, or message as the first indication. For example, both the first indication and the second indication may be transmitted in SIB1.

[0065] Similar to the example described in the second embodiment, the candidate time-domain locations in the SSB burst set may be divided into subsets, with each subset associated with a predetermined number of TRP(s). The predetermined number may be one or more. In this case, the second indication may indicate one or more candidate time-domain locations that are common to the TRPs and that are used for SBB transmissions within each subset.

[0066] 8 illustrates an example of the operation of a UE (e.g., UE 40 or 702). In step 801, the UE receives a first indication indicating the number of TRPs that may be used or are being used in a cell. In step 802, the UE receives a second indication indicating one or more time-domain locations that are common to multiple TRPs and that are being used for SBB transmissions within each subset of the SSB burst set. In step 803, the UE determines the candidate time-domain locations that are actually being used for SBB transmissions within the SSB burst set based on the first and second indications.

[0067] The second indication may include a first bitmap and a second bitmap. The first bitmap indicates which of the multiple groups in each subset of the SSB burst set are used. In other words, the first bitmap indicates which one or more groups in each subset are active. In contrast, the second bitmap indicates which one or more time-domain positions in the active groups are transmitting SSBs. The first and second bitmaps may be included in the "ssb-PositionsInBurst" field in SIB1. The names of the first and second bitmaps may be the "groupPresenceCommon" and "inOneGroupCommon" fields, respectively. A value of 0 in the first bitmap may indicate that no SSB transmission is performed in the corresponding group according to the second bitmap. In this case, a value of 1 in the first bitmap indicates that one or more SSBs are transmitted in the corresponding group according to the second bitmap. A value of 0 in the second bitmap may indicate that the corresponding SSB is not transmitted. In this case, a value of 1 in the second bitmap indicates that the corresponding SSB is being transmitted.

[0068] Figure 9 shows a second example of a display for indicating the time domain positions actually used within an SSB burst set. In the example of Figure 9, there are N candidate time domain positions within an SSB burst set. TRPThe time-domain positions are divided into subsets, each consisting of 64 candidate time-domain positions. A second indicator is used to indicate which one or more of the 64 candidate time-domain positions in each subset are in use. In the example of FIG. 9, the "groupPresenceCommon" field and the "inOneGroupCommon" field are each an 8-bit bitmap. Eight time-domain positions constitute one group. In the example of FIG. 9, the "groupPresenceCommon" field indicates that all eight groups are active, and the "inOneGroupCommon" field indicates that the first, third, fifth, and seventh time-domain positions within each group are active. In candidate time-domain positions 910 that are shaded in FIG. 9, SSBs are transmitted. In candidate time-domain positions 920 that are not shaded in FIG. 9, SSBs are not transmitted.

[0069] The signaling described in this embodiment contributes to reducing the amount of information, or the number of bits, required to indicate to a UE the candidate time-domain locations from which SSBs are actually being transmitted. As an example, consider the case where the maximum number of TRPs in a cell is 32, and therefore the SSB burst set is divided into 32 subsets. Further, assume that each subset consists of 64 candidate time-domain locations, as in FIG. 9 . If two 8-bit bitmaps similar to the second representation shown in FIG. 9 were provided for each of the 32 subsets, a total data size of 512 bits would be required to indicate the active candidate time-domain locations within the SSB burst set. In contrast, the first representation in this embodiment only requires a 5-bit string. Meanwhile, the second representation only requires a 16-bit string consisting of the two 8-bit bitmaps shown in FIG. 9 . Therefore, the total bit length of the first and second representations is only 21 bits.

[0070] As already explained, each subset in an SSB burst set may be associated with two or more TRPs. In other words, SSBs can be transmitted from two or more TRPs at multiple candidate time-domain locations within one subset. In this case, the base station may transmit a third indication within the cell indicating the number of TRPs with which each subset is associated. The first, second, and third indications may be transmitted via different signals, physical channels, or messages. Alternatively, two or all of the first, second, and third indications may be transmitted via the same signal, physical channel, or message. For example, the first indication may be transmitted via a signal or physical channel within the SSB, while the second and third indications are transmitted via SIB1. Alternatively, the first, second, and third indications may all be transmitted via SIB1.

[0071] Figure 10 shows a variation of the example shown in Figure 9. In the example of Figure 10, one subset is associated with two TRPs. Therefore, the total number of subsets N in one SSB burst set is half the maximum number of TRPs in a cell, i.e., N TRP / 2.

[0072] It should be noted that in some implementations, it is not necessary for the UE to know the number of TRPs that may be used or are in use in a cell. As can be seen from the example described with reference to FIG. 10, in some implementations, it is sufficient for the UE to know the number of subsets that may be used or are in use in a cell. Therefore, the transmission of the first indication by the base station (step 421 in FIG. 4 or step 721 in FIG. 7) may be modified as shown in FIG. 11. In step 1121 of FIG. 11, the base station 1101 transmits a first indication via a signal or physical channel in an SSB burst set, indicating the number of one or more subsets that may be used or are in use among a plurality of subsets of candidate time domain locations in an SSB burst set. To indicate active candidate time domain locations in the subset, the base station may further transmit a second indication as described with reference to FIGS. 7 to 10. The UE 1102 may receive the first indication and may further receive the second indication.

[0073] FIG. 12 illustrates an example of the operation of a UE (e.g., UE 40 or 1102). In step 1201, the UE receives a first indication via a signal or physical channel within an SSB burst set. The first indication indicates the number of one or more subsets of candidate time-domain locations within an SSB burst set that may be used or are in use. In step 1202, the UE determines one or more candidate time-domain locations within the SSB burst set that may be used for SSB transmission based on the first indication. In other words, the UE determines one or more subsets that are active for SSB transmission based on the first indication. The UE may also receive a second indication as described with reference to FIGS. 7-10. In this case, the UE may determine one or more active subsets based on the first indication and one or more active candidate time-domain locations within each active subset based on the second indication.

[0074] <Fourth embodiment> A configuration example of a wireless communication system according to this embodiment may be the same as the example described with reference to Figures 1 to 3. This embodiment provides details of the operation of a base station and a UE with respect to the signaling indicating the number of TRPs described in the first embodiment.

[0075] FIG. 13 illustrates an example of the operation of a UE (e.g., UE 40). In step 1301, the UE receives a first indication, indicating the number of TRPs (or transmission points) that can be used or are being used in a cell, via a signal or physical channel in an SSB. The base station may provide the first indication to the UE using at least a sequence of synchronization signals, i.e., PSS or SSS, transmitted in the SSB. Additionally or alternatively, the base station may provide the first indication to the UE using at least a sequence of PBCH DMRSs transmitted in the SSB. The PBCH DMRSs are used by the UE to demodulate PBCH modulation symbols generated from the PBCH payload. Additionally or alternatively, the base station may provide the first indication to the UE using at least a PBCH payload (e.g., MIB).

[0076] In step 1302, the UE determines, based on the first indication, the location within a resource grid of time and frequency resources individually allocated for each TRP on which the TRP-specific PBCH DMRS is transmitted. The location within the resource grid of these time and frequency resources may also be referred to as the arrangement, mapping pattern, transmission pattern, or allocation pattern of these time and frequency resources within the resource grid. A resource grid is a time-frequency representation of radio resources available for transmission. A resource grid is a collection of resource elements or resource blocks available for transmission, i.e., consisting of subcarriers in the frequency domain and OFDM symbols in the time domain. A resource grid may be characterized or defined by the full or whole carrier bandwidth in the frequency domain and a subframe in the time domain.

[0077] In this embodiment, the base station controls each of multiple TRPs in a cell to transmit a TRP-specific PBCH DMRS on a first set of time and frequency resources, each set being separate for each TRP. The TRP-specific PBCH DMRS is used by UEs to demodulate one of the same or different sets of modulation symbols generated from the same PBCH payload or different PBCH payloads. In other words, the base station transmits the DMRS used to demodulate the same or different sets of modulation symbols generated from the same PBCH payload or different PBCH payloads from each of multiple transmission points on a first set of time and frequency resources, each set being separate for each transmission point. The first set of time and frequency resources may be a set of resource elements.

[0078] Furthermore, the base station controls the TRPs in the cell to transmit the same or different sets of PBCH modulation symbols on the same second set of time and frequency resources. In other words, the base station transmits the same or different sets of PBCH modulation symbols from multiple transmission points on the same second set of time and frequency resources. The second set of time and frequency resources may be a set of resource elements.

[0079] The UE receives TRP-specific PBCH DMRS on a first set of time and frequency resources that is separate for each TRP, and further receives one of the same or different sets of PBCH modulation symbols on a second set of time and frequency resources that is common to multiple TRPs.

[0080] In some implementations, the UE may estimate an individual channel response between each TRP and the UE based on reception of the TRP-specific PBCH DMRS and use the individual channel response to demodulate and decode the PBCH payload from one of the different sets of PBCH modulation symbols. Depending on the UE's location, the UE may receive SSB transmissions from multiple TRPs simultaneously, but the UE may be able to demodulate the PBCH payload of one SSB received with greater power.

[0081] In another implementation, the UE may estimate an individual channel response between each TRP and the UE based on reception of a TRP-specific PBCH DMRS, calculate a composite channel response using multiple individual channel responses between multiple TRPs and the UE, and then demodulate and decode the same PBCH payload from the same set of PBCH modulation symbols using the composite channel response.

[0082] Figure 14 shows an example of SSB transmission by two TRPs in one SSB burst set. In the example of Figure 14, the maximum number of candidate time-domain positions where each TRP can transmit SSBs in one SSB burst set is L max The number of SSBs each TRP actually transmits is configurable and may be less than the maximum number. Two TRPs #0 and #1 share the same candidate time-domain location within the SSB burst set and transmit PBCH 1430 and PBCH 1440 in the same time and frequency resources (resource elements). However, the two TRPs #0 and #1 transmit their respective TRP-specific PBCH DMRSs 1410 and 1420 in different time and frequency resources (resource elements) within each candidate time-domain location.

[0083] By way of example and not limitation, L maxThe number of SSB beams may be 64, the same as in the current NR specification. The duration of an SSB burst set may also be a half radio frame, i.e., 5 ms, the same as in the current NR specification. Even in this case, in the example of FIG. 14 , two TRPs #0 and #1 can transmit a total of up to 128 SSB beams in one SSB burst set. Additionally, the UE can obtain received power or quality measurements for each of the TRP-specific PBCH DMRSs 1410 and 1420 by measuring different time and frequency resources (resource elements).

[0084] Figure 15 shows an example of mapping of TRP-specific PBCH DMRS within an SSB. In the example of Figure 15, one SSB is extended to span five consecutive OFDM symbols in the time domain. The frequency-domain resources occupied by the SSB in Figure 15 are 240 subcarriers or 20 resource blocks, the same as those of SSBs in the existing NR specifications. In the example of Figure 15, the TRP-specific PBCH DMRS for one TRP is mapped to a set of resource elements 1500. Multiple resource elements 1500 are located in the same OFDM symbol #1 in the time domain and are spaced 10 subcarriers apart from one another in the frequency domain. That is, in the example of Figure 15, the 240 resource elements in OFDM symbol #1 can transmit TRP-specific PBCH DMRSs for up to 10 TRPs. The resource element numbers to which the TRP-specific PBCH DMRS for each TRP is mapped can be expressed as follows: Here, TRP ID is 0 or more and N TRP is an integer smaller than N TRP is the maximum number of TRPs in a cell. In the example of Figure 15, N TRP is 10.

[0085] The base station may change the time and frequency resources (e.g., resource elements) to which the TRP-specific PBCH DMRS is mapped within an SSB depending on or in response to the number of TRPs (or transmission points) that may be used or are being used within the cell. In other words, the base station may change the placement or mapping of the TRP-specific PBCH DMRS within an SSB based on the number of TRPs that may be used or are being used within the cell. In yet another way, the base station may change the placement or mapping of the TRP-specific PBCH DMRS within an SSB depending on or in response to the number of TRPs that may be or are being simultaneously transmitted in one candidate time-domain position within the SSB burst set. Alternatively, the base station may change the placement or mapping of the TRP-specific PBCH DMRS within an SSB depending on or in response to the number of SSBs or beams that may be or are being simultaneously transmitted in one candidate time-domain position within the SSB burst set. The UE may assume that the placement or mapping of the TRP-specific PBCH DMRS within an SSB will be changed in this manner.

[0086] In this case, similar to the first embodiment, the base station informs the UE of the number of TRPs that can be used or are being used in the cell. This enables the UE to determine the placement or mapping of the TRP-specific PBCH DMRS. That is, as described with reference to Figure 13, the UE can determine the location in the resource grid of the time and frequency resources individually allocated for each TRP where the TRP-specific PBCH DMRS is transmitted, based on the first indication.

[0087] It should be noted that in some implementations, it is not necessary for the UE to know the number of TRPs that can be or are being used in a cell. In some implementations, the placement or mapping of the TRP-specific PBCH DMRS within an SSB may be changed depending on the number of SSBs or beams that can be or are being simultaneously transmitted on the same time and frequency resources of a candidate time-domain location within the SSB burst set. In this case, as shown in step 1621 of FIG. 16 , the base station 1601 may signal to the UE 1602 a first indication indicating the number of SSBs or beams that can be or are being simultaneously transmitted on the same time and frequency resources. Then, based on the first indication, the UE 1602 may determine the location within the resource grid of the time and frequency resources individually allocated for each TRP at which the TRP-specific PBCH DMRS is transmitted.

[0088] Fifth Embodiment A configuration example of a wireless communication system according to this embodiment may be the same as the example described with reference to Figures 1 to 3. This embodiment provides details of the operation of a base station and a UE with respect to the signaling indicating the number of TRPs described in the first embodiment.

[0089] FIG. 17 illustrates an example of the operation of a UE (e.g., UE 40). In step 1701, the UE receives a first indication indicating the number of TRPs (or transmission points) that can be used or are being used in a cell. The base station may provide the first indication to the UE using at least a sequence of synchronization signals, i.e., PSS or SSS, transmitted in an SSB. Additionally or alternatively, the base station may provide the first indication to the UE using at least a sequence of PBCH DMRSs transmitted in an SSB. The PBCH DMRSs are used by the UE to demodulate PBCH modulation symbols generated from the PBCH payload. Additionally or alternatively, the base station may provide the first indication to the UE using at least a PBCH payload (e.g., MIB). Additionally or alternatively, the base station may provide the first indication to the UE using at least configuration information in SIB1.

[0090] In step 1702, the UE increases or decreases the number of reception quality information items reported to a radio access network (e.g., a base station) according to or depending on the number of TRPs indicated by the first indication. In other words, the UE determines the number of reception quality information items reported to the radio access network based on the number of TRPs indicated by the first indication. More specifically, the UE may increase the number of reported reception quality information items as the number of TRPs increases, and decrease the number of reported reception quality information items as the number of TRPs decreases.

[0091] According to the operation described with reference to Figure 17, the UE can set an appropriate number of reporting items according to the number of TRPs, which can reduce the transmission overhead of measurement reports from the UE to the radio access network (e.g., base station).

[0092] Next, exemplary configurations of the CU 10, DUs 21 and 22, TRPs 31 to 35, and UE 40 shown in Fig. 1 will be described below. Fig. 18 is a block diagram showing an exemplary configuration of the CU 10. The configurations of the DUs 21 and 22 may also be similar to the configuration shown in Fig. 18. In addition, the configurations of the base stations (e.g., base stations 401, 701, 1101, 1601, etc.) described in the above embodiments may also be similar to the configuration shown in Fig. 18.

[0093] 18, the CU 10 includes a network interface 1801, a processor 1802, and a memory 1803. The network interface 1801 is used to communicate with network nodes (e.g., DUs, and control plane (CP) nodes and / or user plane (UP) nodes in a core network). The network interface 1801 may include multiple interfaces. The network interface 1801 may include, for example, an optical fiber interface for communication between the CU and DU and a network interface compliant with the IEEE 802.3 series.

[0094] The processor 1802 may include multiple processors. If the CU 10 is a CU-CP, the processor 1802 performs, for example, control plane processing, such as processing related to NGAP, RRC, E1AP, and F1AP signaling. If the CU 10 includes a CU-UP, the processor 1802 performs, for example, termination of the NG-U interface, termination of the F1-U interface, and data processing for the SDAP and PDCP layers.

[0095] In the case of the DUs 21 and 22, the processor 1802 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. For example, the processor 1802 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. The digital baseband signal processing may include signal processing for the RLC, MAC, and PHY layers. The control plane processing may include processing of MAC CEs and DCIs. The processor 1802 may include a digital beamformer module for beamforming. The digital beamformer module may include a multi-input multi-output (MIMO) encoder and precoder.

[0096] The memory 1803 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1803 may include storage located remotely from the processor 1802. In this case, the processor 1802 may access the memory 1803 via the network interface 1801 or another I / O interface.

[0097] The memory 1803 may store one or more software modules (computer programs) 1804 including instructions and data for performing the processing by the CU 10 described in the above-described embodiments. In some implementations, the processor 1802 may be configured to read and execute the one or more software modules 1804 from the memory 1803 to perform the processing by the CU 10 described in the above-described embodiments.

[0098] FIG. 19 is a block diagram showing an example configuration of the TRPs 31 to 35. Referring to FIG. 19, each of the TRPs 31 to 35 includes an RF transceiver 1901, a network interface 1903, a processor 1904, and a memory 1905. The RF transceiver 1901 performs analog RF signal processing for communication with UEs. The RF transceiver 1901 may include multiple transceivers. The RF transceiver 1901 is coupled to an antenna array 1902 and a processor 1904. The RF transceiver 1901 receives modulation symbol data from the processor 1904, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1902. The RF transceiver 1901 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1902 and provides the baseband receive signal to the processor 1904. The RF transceiver 1901 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0099] The network interface 1903 is used to communicate with network nodes (e.g., DUs, other TRPs). The network interface 1903 may include multiple interfaces. For example, the network interface 1903 may include an optical fiber interface for DU-TRP communication (and inter-TRP communication) and a network interface compliant with the IEEE 802.3 series.

[0100] The processor 1904 may include one or more processors. The processor 1904 may include a DFE and a controller. The DFE provides lower PHY layer signal processing and digital radio signal processing.

[0101] The memory 1905 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, SRAM or DRAM, or a combination thereof. The non-volatile memory is, for example, MROM, EEPROM, flash memory, or a hard disk drive, or any combination thereof. The memory 1905 may include storage located remotely from the processor 1904. In this case, the processor 1904 may access the memory 1905 via the network interface 1903 or an I / O interface (not shown).

[0102] The memory 1905 may store one or more software modules (computer programs) 1906 including instructions and data for performing at least a portion of the processing by the TRPs 31 to 35 described in the above embodiments. In some implementations, the processor 1904 may be configured to read and execute the software modules 1906 from the memory 1905 to perform at least a portion of the processing by the TRPs 31 to 35 described in the above embodiments.

[0103] FIG. 20 is a block diagram showing an example configuration of a UE 40. An RF transceiver 2001 performs analog RF signal processing for communication with TRPs. The RF transceiver 2001 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 2001 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 2001 is coupled to an antenna array 2002 and a baseband processor 2003. The RF transceiver 2001 receives modulation symbol data (or OFDM symbol data) from the baseband processor 2003, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 2002. The RF transceiver 2001 also generates a baseband receive signal based on the receive RF signal received by the antenna array 2002 and provides the baseband receive signal to the baseband processor 2003. The RF transceiver 2001 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0104] The baseband processor 2003 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communications. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0105] For example, the digital baseband signal processing by the baseband processor 2003 may include signal processing of the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer. Also, the control plane processing by the baseband processor 2003 may include processing of the Non-Access Stratum (NAS) protocol, the RRC protocol, MAC CEs, and DCIs.

[0106] The baseband processor 2003 may perform MIMO encoding and precoding for beamforming.

[0107] The baseband processor 2003 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 2004, which will be described later.

[0108] The application processor 2004 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 2004 may include multiple processors (multiple processor cores). The application processor 2004 executes a system software program (operating system (OS)) and various application programs (e.g., a call application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 2006 or a memory not shown, thereby realizing various functions of the UE 40.

[0109] In some implementations, the baseband processor 2003 and the application processor 2004 may be integrated on a single chip, as indicated by the dashed line (2005) in Figure 20. In other words, the baseband processor 2003 and the application processor 2004 may be implemented as a single System on Chip (SoC) device 2005. An SoC device is sometimes called a system Large Scale Integration (LSI) or chipset.

[0110] The memory 2006 is volatile memory, nonvolatile memory, or a combination thereof. The memory 2006 may include multiple physically independent memory devices. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The nonvolatile memory is MROM, EEPROM, flash memory, a hard disk drive, or any combination thereof. For example, the memory 2006 may include an external memory device accessible from the baseband processor 2003, the application processor 2004, and the SoC 2005. The memory 2006 may also include an internal memory device integrated within the baseband processor 2003, the application processor 2004, or the SoC 2005. Furthermore, the memory 2006 may include memory within a Universal Integrated Circuit Card (UICC).

[0111] The memory 2006 may store one or more software modules (computer programs) 2007 including instructions and data for performing the processing by the UE 40 described in the above-described embodiments. In some implementations, the baseband processor 2003 or the application processor 2004 may be configured to read and execute the software modules 2007 from the memory 2006, thereby performing the processing by the UE 40 described in the above-described embodiments using the drawings.

[0112] It should be noted that the control plane processing and operations performed by the UE 40 described in the above embodiment can be realized by elements other than the RF transceiver 2001 and the antenna array 2002, namely, at least one of the baseband processor 2003 and the application processor 2004, and the memory 2006 storing the software module 2007.

[0113] As described with reference to Figures 18, 19, and 20, each of the processors included in the CUs, DUs, TRPs, and UEs according to the above-described embodiments can execute one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0114] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0115] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0116] (Supplementary Note 1) A base station comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to transmit, within the cell, a first indication indicating a number of transmission points that can be used or are being used within the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode. (Supplementary Note 2) The base station according to Supplementary Note 1, wherein the signal, physical channel, or message is a signal or physical channel included in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB). (Supplementary Note 3) The base station according to Supplementary Note 1 or 2, wherein the at least one processor is configured to send the first indication using a sequence of synchronization signals. (Supplementary Note 4) The base station according to Supplementary Note 3, wherein the synchronization signal is a Primary Synchronization Signal (PSS) or a Secondary Synchronization Signal (SSS). (Supplementary Note 5) The base station according to Supplementary Note 1 or 2, wherein the at least one processor is configured to send the first indication using a sequence of demodulation reference signals for demodulating modulation symbols generated from a broadcast channel payload. (Supplementary Note 6) The base station according to Supplementary Note 5, wherein the demodulation reference signal is a Physical Broadcast Channel (PBCH) Demodulation Reference Signal (DMRS). (Supplementary Note 7) The base station according to Supplementary Note 1 or 2, wherein the at least one processor is configured to send the first indication using a broadcast channel payload. (Supplementary Note 8) The base station according to Supplementary Note 7, wherein the broadcast channel payload is a Physical Broadcast Channel (PBCH) payload. (Supplementary Note 9) The base station according to Supplementary Note 1, wherein the signal, physical channel, or message is a System Information Block Type 1 (SIB1).(Supplementary Note 10) The base station according to any one of Supplements 1 to 9, wherein the at least one processor is configured to transmit the first indication via a signal or physical channel within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and the first indication is used by a wireless terminal to determine one or more candidate time-domain locations that may be used for SBB transmissions within an SSB burst set. (Supplementary Note 11) The base station according to any one of Supplements 1 to 10, wherein the at least one processor is further configured to transmit a second indication within the cell, the second indication being used in combination with the first indication to indicate time-domain locations used for SBB transmissions within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set. (Supplementary Note 12) The base station according to Supplementary Note 11, wherein a plurality of candidate time-domain locations in the SSB burst set are divided into a plurality of subsets, each subset being associated with one or more transmission points, and the second indication indicates one or more time-domain locations that are common to a plurality of transmission points and are used for SSB transmissions in each subset. (Supplementary Note 13) The base station according to Supplementary Note 11 or 12, wherein the first indication is transmitted via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and the second indication is transmitted via System Information Block Type 1 (SIB1). (Supplementary Note 14) The base station according to Supplementary Note 12, wherein the at least one processor is further configured to transmit a third indication within the cell, indicating the number of transmission points with which each subset is associated.(Supplementary Note 15) The base station according to Supplementary Note 14, wherein the first indication is transmitted via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and the second indication and the third indication are transmitted via System Information Block Type 1 (SIB1). (Supplementary Note 16) The base station according to any one of Supplements 1 to 15, wherein the first indication is used by a wireless terminal to determine a position in a resource grid of time and frequency resources individually allocated for each transmission point on which a transmission point-specific demodulation reference signal is transmitted. (Supplementary Note 17) A method performed by a base station, comprising transmitting in a cell a first indication indicating the number of transmission points that can be used or are being used in the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode. (Supplementary Note 18) A program for causing a computer to perform a method for a base station, the method comprising transmitting, in a cell, a first indication indicating a number of transmission points that can be used or are being used within the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode. (Supplementary Note 19) A wireless terminal comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to receive, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, the first indication indicating the number of transmission points that can be used or are being used within the cell. (Supplementary Note 20) The wireless terminal of Supplementary Note 19, wherein the signal, physical channel, or message is a signal or physical channel included in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB).(Supplementary Note 21) The wireless terminal of Supplementary Note 19 or 20, wherein the at least one processor is configured to receive the first indication via a sequence of synchronization signals. (Supplementary Note 22) The wireless terminal of Supplementary Note 21, wherein the synchronization signal is a Primary Synchronization Signal (PSS) or a Secondary Synchronization Signal (SSS). (Supplementary Note 23) The wireless terminal of Supplementary Note 19 or 20, wherein the at least one processor is configured to receive the first indication via a sequence of demodulation reference signals for demodulating modulation symbols generated from a broadcast channel payload. (Supplementary Note 24) The wireless terminal of Supplementary Note 23, wherein the demodulation reference signal is a Physical Broadcast Channel (PBCH) Demodulation Reference Signal (DMRS). (Supplementary Note 25) The wireless terminal of Supplementary Note 19 or 20, wherein the at least one processor is configured to receive the first indication via a broadcast channel payload. (Supplementary Note 26) The wireless terminal of Supplementary Note 25, wherein the Broadcast Channel payload is a Physical Broadcast Channel (PBCH) payload. (Supplementary Note 27) The wireless terminal of Supplementary Note 19, wherein the signal, physical channel, or message is a System Information Block Type 1 (SIB1). (Supplementary Note 28) The wireless terminal of any one of Supplements 19 to 27, wherein the at least one processor is configured to receive the first indication via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and wherein the at least one processor is configured to determine, based on the first indication, one or more candidate time-domain locations that may be used for SBB transmissions within an SSB burst set.(Supplementary Note 29) The wireless terminal of any one of Supplements 19 to 28, wherein the at least one processor is further configured to receive a second indication used in combination with the first indication to indicate time-domain locations used for SBB transmissions within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set. (Supplementary Note 30) The wireless terminal of Supplementary Note 29, wherein a plurality of candidate time-domain locations within the SSB burst set are divided into a plurality of subsets, each subset being associated with one or more transmission points, and the second indication is common to a plurality of transmission points and indicates one or more time-domain locations used for SBB transmissions within each subset. (Supplementary Note 31) The wireless terminal of Supplementary Note 29 or 30, wherein the at least one processor is configured to determine time-domain locations actually used for SSB transmissions within the SSB burst set based on the first indication and the second indication. (Supplementary Note 32) The wireless terminal of any one of Supplements 29 to 31, wherein the first indication is transmitted via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and the second indication is transmitted via System Information Block Type 1 (SIB1). (Supplementary Note 33) The wireless terminal of Supplementary Note 30, wherein the at least one processor is further configured to transmit a third indication in the cell, the third indication indicating a number of transmission points with which each subset is associated. (Supplementary Note 34) The wireless terminal of Supplementary Note 33, wherein the first indication is transmitted via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), and the second indication and the third indication are transmitted via System Information Block Type 1 (SIB1).(Supplementary Note 35) The wireless terminal of any one of Supplements 19 to 34, wherein the at least one processor is configured to determine, based on the first indication, a position in a resource grid of time and frequency resources allocated to each transmission point individually for transmitting a transmission point-specific demodulation reference signal. (Supplementary Note 36) The wireless terminal of any one of Supplementary Notes 19 to 35, wherein the at least one processor is configured to increase or decrease a number of reception quality information items reported to a radio access network in response to a number of transmission points that can be used or are being used in the cell as indicated by the first indication. (Supplementary Note 37) A method performed by a wireless terminal, comprising receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication indicating the number of transmission points that can be used or are being used in a cell. (Supplementary Note 38) A program for causing a computer to perform a method for a wireless terminal, the method comprising receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication indicating the number of transmission points that can be used or are being used in a cell. (Supplementary Note 39) A base station comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to transmit, via a signal or physical channel within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set, a first indication indicating a number of one or more subsets that may be used or are in use among a plurality of subsets of candidate time-domain locations within an SSB burst set. (Supplementary Note 40) The base station of Supplementary Note 39, wherein the first indication is used by a wireless terminal to determine one or more candidate time-domain locations that may be used for SSB transmissions within the SSB burst set. (Supplementary Note 41) The base station of Supplementary Note 39 or 40, wherein each of the plurality of subsets is associated with one or more transmission points.(Supplementary Note 42) The base station according to any one of Supplements 39 to 41, wherein the at least one processor is further configured to transmit a second indication indicating one or more time-domain locations used for SBB transmission within each subset. (Supplementary Note 43) The base station according to Supplementary Note 42, wherein the second indication is transmitted via a System Information Block Type 1 (SIB1). (Supplementary Note 44) A method performed by a base station, comprising transmitting, via a signal or physical channel within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), a first indication indicating a number of one or more subsets of candidate time-domain locations that may be used or are being used, out of a plurality of subsets of candidate time-domain locations within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set. (Supplementary Note 45) A program for causing a computer to perform a method for a base station, the method comprising transmitting, via a signal or physical channel within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) a first indication indicating a number of one or more subsets that may be used or are in use among a plurality of subsets of candidate time-domain locations within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set. (Supplementary Note 46) A wireless terminal, comprising: at least one memory; and at least one processor coupled to the at least one memory, the at least one processor configured to receive, via a signal or physical channel within the SSB, a first indication indicating a number of one or more subsets that may be used or are in use among a plurality of subsets of candidate time-domain locations within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set.(Supplementary Note 47) The wireless terminal of Supplementary Note 46, wherein the at least one processor is configured to determine one or more candidate time-domain locations that may be used for SBB transmissions within the SSB burst set based on the first indication. (Supplementary Note 48) The wireless terminal of Supplementary Note 46 or 47, wherein each of the plurality of subsets is associated with one or more transmission points. (Supplementary Note 49) The wireless terminal of any one of Supplements 46 to 48, wherein the at least one processor is further configured to receive a second indication indicating one or more time-domain locations used for SBB transmissions within each subset. (Supplementary Note 50) The wireless terminal of Supplementary Note 49, wherein the second indication is transmitted via System Information Block Type 1 (SIB1). (Supplementary Note 51) The wireless terminal of Supplementary Note 49 or 50, wherein the at least one processor is configured to determine time-domain locations actually used for SSB transmissions within the SSB burst set based on the first indication and the second indication. (Supplementary Note 52) A method performed by a wireless terminal, comprising receiving, via a signal or physical channel within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), a first indication indicating a number of one or more subsets of a plurality of subsets of candidate time-domain locations within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set that are potentially used or in use. (Supplementary Note 53) A program for causing a computer to perform a method for a wireless terminal, the method comprising receiving, via a signal or physical channel within an SSB, a first indication indicating a number of one or more subsets of a plurality of subsets of candidate time-domain locations within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set that are potentially used or in use.(Supplementary Note 54) A base station comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to transmit within the cell a first indication indicating the number of beams that can be transmitted or are being transmitted on the same time and frequency resource within the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode. (Supplementary Note 55) The base station of Supplementary Note 54, wherein the first indication is used by the wireless terminals to determine a position within a resource grid of time and frequency resources individually allocated for each transmission point on which a transmission point-specific demodulation reference signal is transmitted. (Supplementary Note 56) The base station of Supplementary Note 54 or 55, wherein the signal, physical channel, or message is a signal or physical channel included in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB). (Supplementary Note 57) The base station according to Supplementary Note 56, wherein the at least one processor is configured to send the first indication using a Primary Synchronization Signal (PSS) or a Secondary Synchronization Signal (SSS) sequence transmitted in the SSB. (Supplementary Note 58) The base station according to Supplementary Note 56, wherein the at least one processor is configured to send the first indication using a Physical Broadcast Channel (PBCH) Demodulation Reference Signal (DMRS) sequence transmitted in the SSB. (Supplementary Note 59) The base station according to Supplementary Note 56, wherein the at least one processor is configured to send the first indication using a Physical Broadcast Channel (PBCH) payload transmitted in the SSB.(Supplementary Note 60) A method performed by a base station, comprising transmitting a first indication in a cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, the first indication indicating a number of beams that can be transmitted or are being transmitted on the same time and frequency resources within the cell. (Supplementary Note 61) A program for causing a computer to perform a method for a base station, the method comprising transmitting a first indication in the cell using a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, the first indication indicating a number of beams that can be transmitted or are being transmitted on the same time and frequency resources within the cell. (Supplementary Note 62) A wireless terminal, comprising: at least one memory; and at least one processor coupled to the at least one memory, the at least one processor configured to receive a first indication indicative of the number of beams that can be transmitted or are being transmitted on the same time and frequency resources within the cell via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode. (Supplementary Note 63) The wireless terminal of Supplementary Note 62, wherein the at least one processor is configured to determine, based on the first indication, a position within a resource grid of time and frequency resources allocated individually to each transmission point on which a transmission point-specific demodulation reference signal is transmitted. (Supplementary Note 64) The wireless terminal of Supplementary Note 62 or 63, wherein the signal, physical channel, or message is a signal or physical channel included in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB). (Supplementary Note 65) The wireless terminal of Supplementary Note 64, wherein the at least one processor is configured to receive the first indication via a sequence of Primary Synchronization Signals (PSS) or Secondary Synchronization Signals (SSS) transmitted within the SSB.(Supplementary Note 66) The wireless terminal of Supplementary Note 64, wherein the at least one processor is configured to receive the first indication via a Physical Broadcast Channel (PBCH) Demodulation Reference Signal (DMRS) sequence transmitted in the SSB. (Supplementary Note 67) The wireless terminal of Supplementary Note 64, wherein the at least one processor is configured to receive the first indication via a Physical Broadcast Channel (PBCH) payload transmitted in the SSB. (Supplementary Note 68) A method performed by a wireless terminal, comprising receiving via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode a first indication indicating a number of beams that can be transmitted or are being transmitted on the same time and frequency resource in a cell. (Supplementary Note 69) A program for causing a computer to perform a method for a wireless terminal, the method comprising receiving via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode a first indication indicating a number of beams that can be transmitted or are being transmitted on the same time and frequency resource in a cell.

[0117] This application claims priority based on Japanese Patent Application No. 2022-143673, filed September 9, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0118] 10 CU 21, 22 DU 31, 32, 33, 34, 35 TRP 40 UE 51, 52, 53 Cell 1802 Processor 1803 Memory 1904 Processor 1905 Memory 2003 Baseband processor 2004 Application processor 2006 Memory

Claims

1. A method for providing a method for a mobile station, comprising: receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in an idle mode, a first indication of a number of transmission points that may be used or are being used within a cell; Wireless terminal.

2. The signal, physical channel, or message is a signal or physical channel contained within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB), The wireless terminal of claim 1.

3. the means for receiving is configured to receive the first indication via a sequence of synchronization signals.

3. A wireless terminal according to claim 1 or 2.

4. the means for receiving is configured to receive the first indication via a sequence of demodulation reference signals for demodulating modulation symbols generated from a broadcast channel payload.

3. A wireless terminal according to claim 1 or 2.

5. The receiving means is configured to receive the first indication via a signal or physical channel in a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB); The wireless terminal further comprises means for determining, based on the first indication, one or more candidate time domain locations that may be used for an SBB transmission within an SSB burst set.

3. A wireless terminal according to claim 1 or 2.

6. the means for receiving is further configured to receive a second indication used in combination with the first indication to indicate a time domain location being used for an SBB transmission within a Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) block (SSB) burst set.

3. A wireless terminal according to claim 1 or 2.

7. The method further comprises means for determining, based on the first indication, a position in a resource grid of time and frequency resources individually assigned to each transmission point at which a transmission point specific demodulation reference signal is transmitted.

3. A wireless terminal according to claim 1 or 2.

8. The present invention further comprises means for increasing or decreasing a number of reception quality information items reported to a radio access network depending on a number of transmission points that can be used or are being used in the cell as indicated by the first indication.

3. A wireless terminal according to claim 1 or 2.

9. receiving, via a signal, physical channel, or message received by at least a plurality of wireless terminals in idle mode, a first indication of a number of transmission points that may be used or are being used in a cell; A method performed by a wireless terminal.

10. A method for transmitting a first indication of a number of transmission points available or in use in a cell using a signal, physical channel or message received by at least a plurality of wireless terminals in idle mode, comprising: Base station.