JP7478171B2 - Terminal and communication method - Google Patents

Description

The present invention relates to a terminal and a communication method in a wireless communication system.

For NR (New Radio) (also known as "5G"), the successor system to LTE (Long Term Evolution), technologies are being considered that meet the requirements of a large-capacity system, high data transmission speed, low latency, simultaneous connection of a large number of terminals, low cost, and low power consumption (for example, non-patent document 1).

Dynamic spectrum sharing (DSS), a technology that allows LTE and NR to coexist in the same band, is being considered (see, for example, Non-Patent Document 2). By allowing different RATs (Radio Access Technologies) to coexist on a single carrier, it becomes possible to flexibly respond to traffic demands at the time of system generation switching.

3GPP TS 38.300 V15.8.0 (2019-12) 3GPP TSG RAN Meeting #86 RP-192678 (2019-12)

In the current DSS specification, signals for synchronization are transmitted separately to LTE terminals and NR terminals. In other words, signals with similar functions are sent to each RAT (Radio Access Technology), which increases the overhead in the entire system.

The present invention has been made in consideration of the above points, and aims to reduce the overhead when multiple RATs (Radio Access Technologies) coexist on a single carrier in a wireless communication system.

According to the disclosed technology, there is provided a terminal having a receiving unit that receives a synchronization signal of a first RAT (Radio Access Technology) and a control unit that uses the synchronization signal to synchronize with a cell of a second RAT, wherein the receiving unit uses a signal of a third RAT for decoding data in the second RAT .

The disclosed technology makes it possible to reduce overhead when multiple RATs (Radio Access Technologies) coexist on a single carrier in a wireless communication system.

1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of downlink channel arrangement using DSS. FIG. 2 is a diagram showing an example of uplink channel allocation using DSS. FIG. 1 is a diagram showing an example (1) of frequency allocation in DSS. A figure showing an example (2) of frequency allocation in DSS. FIG. 1 is a diagram illustrating an example of a channel arrangement for an LTE downlink. A diagram showing an example of channel arrangement for the NR downlink. A diagram showing an example of channel arrangement for LTE and NR downlinks using DSS. FIG. 11 is a diagram for explaining an example of an operation related to a cell search. 1 is a flowchart for explaining an operation example (1) relating to synchronization in an embodiment of the present invention. 11 is a flowchart for explaining an operation example (2) relating to synchronization in the embodiment of the present invention. 1 is a flowchart for explaining an operation example (1) relating to system information acquisition in an embodiment of the present invention. FIG. 11 is a diagram illustrating an example of system information. 11 is a flowchart for explaining an operation example (2) relating to system information acquisition in the embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a functional configuration of a base station 10 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal 20 according to an embodiment of the present invention. 2 is a diagram illustrating an example of a hardware configuration of a base station 10 or a terminal 20 according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applicable is not limited to the following embodiment.

Existing technology is used as appropriate in the operation of the wireless communication system of the embodiment of the present invention. However, the existing technology is, for example, the existing LTE, but is not limited to the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced and systems subsequent to LTE-Advanced (e.g., NR) unless otherwise specified.

In addition, in the embodiment of the present invention described below, terms such as SS (Synchronization signal), PSS (Primary SS), SSS (Secondary SS), PBCH (Physical broadcast channel), PRACH (Physical random access channel), PDCCH (Physical Downlink Control Channel), PDSCH (Physical Downlink Shared Channel), PUCCH (Physical Uplink Control Channel), and PUSCH (Physical Uplink Shared Channel) used in existing LTE are used. This is for convenience of description, and similar signals, functions, etc. may be called by other names. In addition, the above-mentioned terms in NR correspond to NR-SS, NR-PSS, NR-SSS, NR-PBCH, NR-PRACH, etc. However, even if a signal is used in NR, it is not necessarily specified as "NR-".

In addition, in an embodiment of the present invention, the duplex method may be a TDD (Time Division Duplex) method, an FDD (Frequency Division Duplex) method, or another method (e.g., Flexible Duplex, etc.).

In addition, in an embodiment of the present invention, when radio parameters, etc. are "configured," this may mean that predetermined values are pre-configured, or that radio parameters notified from the base station 10 or the terminal 20 are configured.

Figure 1 is a diagram showing an example of the configuration of a wireless communication system in an embodiment of the present invention. As shown in Figure 1, the wireless communication system in the embodiment of the present invention includes a base station 10 and a terminal 20. Although Figure 1 shows one base station 10 and one terminal 20, this is an example and there may be multiple of each.

The base station 10 is a communication device that provides one or more cells and performs wireless communication with the terminal 20. The physical resources of a wireless signal are defined in the time domain and the frequency domain, and the time domain may be defined by the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols, and the frequency domain may be defined by the number of subcarriers or the number of resource blocks. The base station 10 transmits a synchronization signal and system information to the terminal 20. The synchronization signal is, for example, NR-PSS and NR-SSS. The system information is, for example, transmitted by NR-PBCH and is also called broadcast information. The synchronization signal and system information may be called SSB (SS/PBCH block). As shown in FIG. 1, the base station 10 transmits a control signal or data to the terminal 20 in DL (Downlink) and receives a control signal or data from the terminal 20 in UL (Uplink). Both the base station 10 and the terminal 20 can transmit and receive signals by performing beamforming. In addition, both the base station 10 and the terminal 20 can apply communication by MIMO (Multiple Input Multiple Output) to DL or UL. In addition, both the base station 10 and the terminal 20 may communicate via a secondary cell (SCell: Secondary Cell) and a primary cell (PCell: Primary Cell) by CA (Carrier Aggregation). Furthermore, the terminal 20 may communicate via a primary cell of the base station 10 and a primary secondary cell (PSCell: Primary Secondary Cell) of another base station 10 by DC (Dual Connectivity).

The terminal 20 is a communication device equipped with a wireless communication function, such as a smartphone, a mobile phone, a tablet, a wearable terminal, or a communication module for M2M (Machine-to-Machine). As shown in FIG. 1, the terminal 20 receives control signals or data from the base station 10 in DL and transmits control signals or data to the base station 10 in UL, thereby utilizing various communication services provided by the wireless communication system. The terminal 20 also receives various reference signals transmitted from the base station 10, and performs measurement of propagation path quality based on the reception results of the reference signals.

Below, we will explain an example of DSS (Dynamic Spectrum Sharing) technology that allows LTE and NR to coexist in the same band. DSS technology allows different RATs (Radio Access Technologies) to coexist on a single carrier, making it possible to flexibly respond to traffic demands at the time of system generation switching.

Figure 2 is a diagram showing an example of downlink channel arrangement by DSS. The time domain shown in Figure 2 corresponds to one subframe of LTE. As shown in Figure 2, in the downlink, "LTE-CRS (Cell specific reference signal)", "LTE-PDCCH" and "LTE-PDSCH" are transmitted as LTE signals or channels. Also, as shown in Figure 2, in the downlink, "NR-PDCCH" and "NR-PDSCH" are transmitted as NR channels. For example, although not shown, physical channels and signals other than these may be arranged. For example, "NR-PDSCH" may include resources in which DM-RS (Demodulation reference signal) is arranged. For example, as shown in Figure 2, "LTE-CRS" may be arranged within the "NR-PDSCH" area.

Figure 3 is a diagram showing an example of uplink channel allocation using DSS. As shown in Figure 3, LTE and NR uplink channels or signals are allocated sharing a frequency band. As shown in Figure 3, for example, from low frequency to high frequency, they are allocated in the following order: "NR-PUCCH", "LTE-PUCCH", "LTE-PRACH", "LTE-PUSCH", "NR-PUSCH", "NR-PRACH", "LTE-PUSCH", "LTE-PUCCH", and "NR-PUCCH". In addition, "LTE-SRS (Sounding Reference Signal)" or "NR-SRS" may be allocated in the frequency region in which "LTE-PUSCH", "NR-PUSCH" and "NR-PRACH" are allocated.

In the above, an example was given in which LTE and NR are frequency multiplexed, but other multiplexing methods may be used, for example time multiplexing or spatial multiplexing.

Figure 4 is a diagram showing an example (1) of frequency allocation in DSS. As shown in Figure 4, LTE is provided by carrier #1, LTE and NR by carrier #2, NR by carrier #3, and NR by carrier #4 from a BS (Base station).

For example, for an NR UE (User Equipment), as in pattern 1 shown in FIG. 4, an LTE PCell (Primary Cell) may be placed on carrier #1, an NR PSCell (Primary Secondary Cell) on carrier #2, an SCell (Secondary Cell) on carrier #3, and an SCell on carrier #4. Also, for example, for an NR UE, as in pattern 2 shown in FIG. 4, an LTE PCell and an NR PSCell may be placed on carrier #2, an SCell on carrier #3, and an SCell on carrier #4. Also, for example, for an NR UE, as in pattern 3 shown in FIG. 4, an NR PCell may be placed on carrier #2, an SCell on carrier #3, and an SCell on carrier #4.

For example, for an LTE UE, an LTE PCell may be placed on carrier #1, as in pattern 1 shown in FIG. 4. Also, for example, for an LTE UE, an LTE PCell may be placed on carrier #2, as in pattern 2 shown in FIG. 4. Also, for example, for an LTE UE, an LTE PCell may be placed on carrier #1 and an LTE SCell on carrier #2, as in pattern 3 shown in FIG. 4. Also, for example, for an LTE UE, an LTE SCell may be placed on carrier #1 and an LTE PCell on carrier #2, as in pattern 4 shown in FIG. 4.

Figure 5 is a diagram showing an example (2) of frequency allocation in DSS. As shown in Figure 5, the BS provides LTE and NR in carrier #1, NR in carrier #2, and NR in carrier #3.

For example, for an NR UE, as in pattern 1 shown in FIG. 5, an LTE PCell and an NR SCell may be placed on carrier #1, an NR PSCell on carrier #2, and an NR SCell on carrier #3. Also, for example, for an NR UE, as in pattern 2 shown in FIG. 5, an LTE PCell and an NR PSCell may be placed on carrier #1, an NR PSCell on carrier #2, and an NR SCell on carrier #3. Also, for example, for an NR UE, as in pattern 3 shown in FIG. 5, an NR PCell may be placed on carrier #1, an NR PSCell on carrier #2, and an NR SCell on carrier #3.

For example, for an LTE UE, an LTE PCell may be placed on carrier #1, as in pattern 1 shown in FIG. 5.

Table 1 shows examples of LTE and NR synchronization signals or reference signals for different purposes.

As shown in Table 1, signals are specified for the same or similar purposes in LTE and NR. For rough synchronization, LTE uses LTE-PSS/SSS, and NR uses NR-PSS/SSS. For highly accurate synchronization, LTE uses CRS, and NR uses NR-TRS. NR-TRS may be called NR-CSI (Channel State Information)-RS for tracking. For downlink propagation path estimation, LTE uses LTE-CRS/CSI-RS, and NR uses NR-CSI-RS. For uplink propagation path estimation, LTE uses LTE-SRS, and NR uses NR-SRS. For phase noise estimation, no signal is set for this purpose in LTE, and NR uses NR-PT (Phase tracking)-RS. For data decoding, LTE-CRS/DM-RS is used in LTE, and NR-DM-RS is used in NR. For broadcast signal decoding, CRS is used in LTE, and NR-PBCH-DM-RS is used in NR.

Note that even if the names are the same, the physical signal configuration may be different. For example, the physical signal configuration of LTE CSI-RS and NR CSI-RS is different.

Figure 6 is a diagram showing an example of channel arrangement for the LTE downlink. The time domain shown in Figure 6 corresponds to one LTE subframe, and the frequency domain corresponds to one resource block. As shown in Figure 6, LTE-CRS is transmitted as a reference signal, and LTE-PDCCH is transmitted as a control signal.

Figure 7 is a diagram showing an example of channel arrangement for the NR downlink. The time domain shown in Figure 7 corresponds to one slot of NR, the frequency domain corresponds to one resource block, and the subcarrier spacing is 15 kHz. As shown in Figure 7, NR-DM-RS is transmitted as a reference signal, and NR-PDCCH is transmitted as a control signal.

Figure 8 shows an example of channel allocation for LTE and NR downlinks using DSS. Under the current DSS specifications, signals with the same purpose are transmitted to LTE terminals and NR terminals, respectively. As shown in Figure 8, transmitting LTE signals and NR signals, respectively, increases overhead and reduces resources for transmitting data.

Therefore, overhead can be reduced by sharing some signals and/or channels between RATs. For example, the terminal 20 may receive NR signals using LTE-CRS. Also, for example, the terminal 20 may establish synchronization with an NR cell using LTE-SS.

Figure 9 is a diagram for explaining an example of operation related to cell search. The broadcast information is a cell-specific operational parameter, and all terminals 20 that wish to be present in the cell must obtain the broadcast information. After cell search, the terminal 20 obtains the broadcast information via the BCCH.

As shown in FIG. 9, after the terminal 20 is powered on, the terminal 20 performs carrier frequency, SCH (Synchronization Channel) symbol synchronization, and local ID detection using the PSS as the first stage of cell search. The local ID is one of the parameters that specifies the physical cell ID. For example, the local ID may be one of the values {0, 1, 2}.

Following the first cell search stage, the terminal 20 performs radio frame synchronization and cell group ID detection as a second stage using SSS. For example, the cell group ID may be one of the values {0, 1, 2, ..., 335}.

Following the second cell search stage, the terminal 20 performs broadcast information reception via the PBCH and PDSCH. The broadcast information is the minimum system information specific to the cell and is composed of the MIB (Master Information Block) and the SIB (System Information Block).

MIB is the minimum information required to receive SIB, and the transmission period is specified by the standard. SIB is broadcast information other than MIB, and includes common channel information, regulatory information, and basic information required for cell reselection. The transmission period of SIB can be changed by setting, with some exceptions. The above PSS, SSS, and PBCH may be called SSB (SS/PBCH block) in NR.

Here, the terminal 20 may reduce the amount of NR-SSB signals by establishing synchronization with the NR cell using LTE-PSS/SSS. For example, when an NR cell is added, information related to LTE-PSS/SSS may be notified to the terminal 20. The information related to LTE-PSS/SSS may be, for example, a center frequency (absolute radio-frequency channel number, ARFCN).

Figure 10 is a flowchart for explaining an operation example (1) related to synchronization in an embodiment of the present invention. In step S11, the terminal 20 starts an NR cell addition operation. In step S12, the terminal 20 receives information necessary for receiving LTE-SS. Step S12 may be executed prior to step S11. In step S12, the terminal 20 may receive information necessary for receiving LTE-SS from the NR base station 10, or may receive information necessary for receiving LTE-SS from the LTE base station 10. Next, the terminal 20 receives LTE-SS based on the information received in step S12 (S13). Next, the terminal 20 performs NR synchronization using LTE-SS (S14). By performing NR synchronization using LTE-SS, the signal amount of NR-SS can be reduced.

Figure 11 is a flowchart for explaining an example operation (2) related to synchronization in an embodiment of the present invention. In step S21, terminal 20 starts an NR cell addition operation. In step S22, terminal 20 determines whether the DSS flag is ON or not. The DSS flag is a flag indicating whether DSS is being executed or not. If the DSS flag is ON (YES in S22), proceed to step S23, and if the DSS flag is OFF (NO in S22), proceed to step S24.

In step S23, the terminal 20 performs NR synchronization using LTE-SS. Meanwhile, in step S24, the terminal 20 performs NR synchronization using NR-SS. When DSS is being executed, the signal volume of NR-SS can be reduced by performing NR synchronization using LTE-SS.

Figure 12 is a flowchart for explaining an example (1) of operation related to acquiring system information in an embodiment of the present invention. A terminal 20 that performs NR synchronization using LTE-SS without receiving NR-SSB cannot obtain information acquired through NR-SSB. Therefore, the information acquired through NR-SSB may be notified to the terminal 20.

In step S31, the terminal 20 receives an NR cell addition instruction. Next, the terminal 20 acquires information obtained from the NR-SSB via the NR cell addition instruction (S32).

The information obtained from the NR-PSS or NR-SSS of the NR-SSB may include, for example, at least one of the following 1)-3).

1) Cell ID information 2) Time synchronization information For example, the presence or absence of time synchronization with an LTE cell may be notified. For example, the time difference with an LTE cell may be notified. Also, for example, the terminal 20 may assume that the LTE cell and the NR cell are time synchronized.
3) Frequency synchronization information For example, the presence or absence of frequency synchronization with an LTE cell may be notified. For example, the frequency difference with an LTE cell may be notified. Also, for example, the terminal 20 may assume that the LTE cell and the NR cell are frequency synchronized.

The information obtained from the NR-PBCH in the NR-SSB may include, for example, at least one of the following 1)-3).

1) Information regarding the SFN of NR When the SFNs of LTE and NR are synchronized, a flag indicating that the SFNs of LTE and NR are synchronized may be set. Also, when the SFNs of LTE and NR are synchronized, the offset of the SFNs of LTE and NR may be notified. The terminal 20 may determine the transmission timing of the PRACH based on the SFN of NR.

2) Information regarding SFN of NR When the SFNs of LTE and NR are not synchronized, the offset of the LTE radio frame and the NR radio frame may be notified. Also, when the SFNs of LTE and NR are not synchronized, the offset of the SFNs of LTE and NR may be notified.

3) Other information acquired from PBCH Fig. 13 is a diagram showing an example of system information. As shown in Fig. 13, information a) to f) acquired from PBCH may be notified.
a) Information indicating subcarrier spacing b) Offset between SSB and subcarrier c) Information indicating the position of DM-RS d) PDCCH configuration for receiving SIB1 e) Information indicating whether the cell is restricted f) Information indicating whether intra-frequency reselection is permitted

Figure 14 is a flowchart for explaining an operation example (2) related to acquiring system information in an embodiment of the present invention. The information acquired by the above-mentioned NR-SSB may be notified to the terminal 20 via LTE notification information.

In step S41, the terminal 20 receives the LTE-MIB or LTE-SIB. Next, the terminal 20 acquires information obtained from the NR-SSB via the LTE-MIB or LTE-SIB (S42).

The embodiment of the present invention has been described mainly with reference to a case where the first RAT and the second RAT are in DSS mode, but DSS is not necessarily required. For example, when DSS is not applied, synchronization may be established in the second RAT based on the synchronization signal of the first RAT.

The embodiments of the present invention can be applied regardless of the distinction between uplink, downlink, transmission or reception. Uplink signals and channels and downlink signals and channels can be read as interchangeable terms. Uplink feedback information and downlink control signaling can be read as interchangeable terms.

In the above-described embodiment, the signaling from the base station 10 to the terminal 20 or the signaling from the terminal 20 to the base station 10 is not limited to an explicit method and may be notified by an implicit method. Also, no signaling may be performed and may be uniquely specified in the specifications.

In the above-mentioned embodiments, the signaling from the base station 10 to the terminal 20 or the signaling from the terminal 20 to the base station 10 may be signaling of different layers such as RRC signaling, signaling by MAC-CE, or signaling by DCI, or may be signaling by broadcast information (MIB (Master Information Block), SIB (System Information Block)). Also, for example, RRC signaling and signaling by DCI may be combined, RRC signaling and signaling by MAC-CE may be combined, or RRC signaling, signaling by MAC-CE, and signaling by DCI may be combined.

In the above-mentioned embodiment, LTE and NR are described, but the present invention may be applied to a communication system beyond NR (e.g., called "6G"). For example, the above-mentioned embodiment may be applied to coexistence technology of NR and 6G.

Similarly, in general, a next-generation system may receive signals and/or channels of a previous-generation system. For example, the systems may span multiple generations. For example, a system may apply a reference signal of a system two generations ago. Reference signals of multiple generations may be applied. For example, a system may apply a reference signal of a system two generations ago for synchronization, and a reference signal of a system one generation ago for data decoding. Similarly, the application of this technology does not have to be based on differences in RATs between generations. That is, in general, it may be applied to different RATs.

Although the above describes a future system applying signals and/or channels of a past system, the opposite may also be true: a past system applying signals and/or channels of a future system.

In the above embodiments, "data" may refer to the PDSCH, the PDCCH, or the PBCH. Also, "data" may refer to an uplink signal and/or channel.

The above-described embodiments may be combined with each other. The features shown in the above-described embodiments may be combined with each other in various combinations. Such combinations are not limited to the specific combinations disclosed.

According to the above-described embodiment, the terminal 20 can reduce resources used for a synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added. In addition, the terminal 20 can acquire information acquired from a synchronization signal or system information in the RAT of the cell to be added in the different RAT.

In other words, in a wireless communication system, it is possible to reduce overhead when multiple RATs (Radio Access Technologies) coexist on a single carrier.

(Device configuration)
Next, a functional configuration example of the base station 10 and the terminal 20 that execute the processes and operations described above will be described. The base station 10 and the terminal 20 include functions for implementing the above-mentioned embodiments. However, the base station 10 and the terminal 20 may each include only a part of the functions in the embodiments.

<Base Station 10>
Fig. 15 is a diagram showing an example of the functional configuration of the base station 10 in the embodiment of the present invention. As shown in Fig. 15, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 15 is merely an example. The names of the functional divisions and functional units may be any as long as they can execute the operations related to the embodiment of the present invention.

The transmitting unit 110 has a function of generating a signal to be transmitted to the terminal 20 side and transmitting the signal wirelessly. The transmitting unit 110 also transmits inter-network node messages to other network nodes. The receiving unit 120 has a function of receiving various signals transmitted from the terminal 20 and acquiring, for example, information of a higher layer from the received signals. The transmitting unit 110 also has a function of transmitting NR-PSS, NR-SSS, NR-PBCH, DL/UL control signals, etc. to the terminal 20. The receiving unit 120 also receives inter-network node messages from other network nodes.

The setting unit 130 stores preset setting information and various setting information to be transmitted to the terminal 20. The contents of the setting information include, for example, information related to DSS settings.

The control unit 140 performs control related to the setting of the DSS as described in the embodiment. The control unit 140 also controls communication by the DSS. A functional unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and a functional unit related to signal reception in the control unit 140 may be included in the receiving unit 120.

<Terminal 20>
Fig. 16 is a diagram showing an example of a functional configuration of the terminal 20 in the embodiment of the present invention. As shown in Fig. 16, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 16 is merely an example. The names of the functional divisions and functional units may be any as long as they can execute the operations related to the embodiment of the present invention.

The transmitter 210 creates a transmission signal from the transmission data and transmits the transmission signal wirelessly. The receiver 220 wirelessly receives various signals and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving NR-PSS, NR-SSS, NR-PBCH, DL/UL/SL control signals, etc. transmitted from the base station 10. For example, the transmitter 210 transmits PSCCH (Physical Sidelink Control Channel), PSSCH (Physical Sidelink Shared Channel), PSDCH (Physical Sidelink Discovery Channel), PSBCH (Physical Sidelink Broadcast Channel), etc. to another terminal 20 as D2D communication, and the receiver 220 receives PSCCH, PSSCH, PSDCH, PSBCH, etc. from the other terminal 20.

The setting unit 230 stores various setting information received from the base station 10 by the receiving unit 220. The setting unit 230 also stores setting information that is set in advance. The contents of the setting information include, for example, information related to DSS settings.

The control unit 240 performs control related to the setting of the DSS as described in the embodiment. The control unit 240 also controls communication by the DSS. A functional unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and a functional unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

(Hardware configuration)
The block diagrams (FIGS. 15 and 16) used in the description of the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. The method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically coupled, or may be realized using two or more devices that are physically or logically separated and directly or indirectly connected (for example, using wires, wirelessly, etc.). The functional block may be realized by combining the one device or the multiple devices with software.

Functions include, but are not limited to, judgement, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, election, establishment, comparison, assumption, expectation, regard, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs the transmission function is called a transmitting unit or transmitter. In either case, as mentioned above, there are no particular limitations on the method of implementation.

For example, the base station 10, terminal 20, etc. in one embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. FIG. 17 is a diagram showing an example of the hardware configuration of the base station 10 and terminal 20 in one embodiment of the present disclosure. The above-mentioned base station 10 and terminal 20 may be physically configured as a computer device including a processor 1001, a memory device 1002, an auxiliary memory device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

In the following description, the term "apparatus" may be interpreted as a circuit, device, unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the devices shown in the figure, or may be configured to exclude some of the devices.

Each function in the base station 10 and the terminal 20 is realized by loading a specific software (program) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of the reading and writing of data in the memory device 1002 and the auxiliary memory device 1003.

The processor 1001, for example, operates an operating system to control the entire computer. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

The processor 1001 reads out a program (program code), a software module, or data, etc., from at least one of the auxiliary storage device 1003 and the communication device 1004 to the storage device 1002, and executes various processes according to the program. As the program, a program that causes a computer to execute at least a part of the operations described in the above-mentioned embodiment is used. For example, the control unit 140 of the base station 10 shown in FIG. 15 may be stored in the storage device 1002 and realized by a control program that runs on the processor 1001. Also, for example, the control unit 240 of the terminal 20 shown in FIG. 16 may be stored in the storage device 1002 and realized by a control program that runs on the processor 1001. Although the above-mentioned various processes have been described as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The program may be transmitted from a network via a telecommunication line.

The storage device 1002 is a computer-readable recording medium, and may be composed of at least one of, for example, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electrically Erasable Programmable ROM), a RAM (Random Access Memory), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to one embodiment of the present disclosure.

The auxiliary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other suitable medium including at least one of the storage device 1002 and the auxiliary storage device 1003.

The communication device 1004 is hardware (transmitting/receiving device) for communicating between computers via at least one of a wired network and a wireless network, and is also called, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc., to realize at least one of, for example, Frequency Division Duplex (FDD) and Time Division Duplex (TDD). For example, a transmitting/receiving antenna, an amplifier unit, a transmitting/receiving unit, a transmission line interface, etc. may be realized by the communication device 1004. The transmitting/receiving unit may be implemented as a transmitting unit and a receiving unit that are physically or logically separated.

The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that accepts input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that performs output to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one configuration (e.g., a touch panel).

In addition, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

In addition, the base station 10 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

(Summary of the embodiment)
As described above, according to an embodiment of the present invention, there is provided a terminal having a receiving unit that receives a synchronization signal of a first RAT (Radio Access Technology), and a control unit that uses the synchronization signal to synchronize with a cell of a second RAT.

With the above configuration, the terminal 20 can reduce resources used for the synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added. In other words, in a wireless communication system, it is possible to reduce overhead when multiple RATs (Radio Access Technologies) coexist on a single carrier.

The second RAT may be transmitted on the same carrier as the first RAT. The terminal 20 can reduce the amount of signaling related to NR synchronization by performing NR synchronization of the same carrier using an LTE signal.

When adding a cell of the second RAT, the receiving unit may receive information necessary for receiving the synchronization signal, and receive the synchronization signal based on the information. With this configuration, the terminal 20 can reduce resources used for the synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added.

When adding a cell of the second RAT, the receiving unit may receive information necessary for receiving the synchronization signal, and receive the synchronization signal based on the information. With this configuration, the terminal 20 can reduce resources used for the synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added.

The control unit may use the synchronization signal to synchronize with a cell of the second RAT transmitted on the same carrier as the first RAT, based on information indicating whether the first RAT and the second RAT coexist on the same carrier. With this configuration, the terminal 20 can reduce resources used for the synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added.

The receiving unit may receive an instruction to add a cell of the second RAT and acquire information acquired from a synchronization signal and a block of broadcast information of the second RAT included in the instruction. With this configuration, the terminal 20 can acquire, in a different RAT, information acquired from a synchronization signal or system information in the RAT of the cell to be added.

The receiving unit may receive broadcast information of the first RAT and acquire information acquired from a synchronization signal and a block of broadcast information of the second RAT included in the broadcast information. With this configuration, the terminal 20 can acquire information acquired from a synchronization signal or system information in the RAT of the cell to be added in a different RAT.

In addition, according to an embodiment of the present invention, a communication method is provided in which a terminal executes a reception procedure for receiving a synchronization signal of a first RAT (Radio Access Technology) and a control procedure for synchronizing with a cell of a second RAT using the synchronization signal.

With the above configuration, the terminal 20 can reduce resources used for the synchronization signal in the RAT of the cell to be added by synchronizing with the cell using a synchronization signal of a RAT different from the RAT of the cell to be added. In other words, in a wireless communication system, it is possible to reduce overhead when multiple RATs (Radio Access Technologies) coexist on a single carrier.

(Supplementary description of the embodiment)
Although the embodiment of the present invention has been described above, the disclosed invention is not limited to such an embodiment, and those skilled in the art will understand various modifications, modifications, alternatives, replacements, and the like. Although the description has been given using specific numerical examples to facilitate understanding of the invention, unless otherwise specified, those numerical values are merely examples and any appropriate value may be used. The division of items in the above description is not essential to the present invention, and items described in two or more items may be used in combination as necessary, and items described in one item may be applied to items described in another item (as long as there is no contradiction). The boundaries of functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries of physical parts. The operations of multiple functional units may be physically performed by one part, or the operations of one functional unit may be physically performed by multiple parts. The order of processing procedures described in the embodiment may be changed as long as there is no contradiction. For convenience of processing description, the base station 10 and the terminal 20 have been described using functional block diagrams, but such devices may be realized by hardware, software, or a combination thereof. The software operated by the processor possessed by the base station 10 in accordance with an embodiment of the present invention and the software operated by the processor possessed by the terminal 20 in accordance with an embodiment of the present invention may each be stored in random access memory (RAM), flash memory, read only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server or any other suitable storage medium.

In addition, the notification of information is not limited to the aspects/embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), higher layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling, broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals, or combinations thereof. In addition, the RRC signaling may be called an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, etc.

Each aspect/embodiment described in this disclosure may be applied to at least one of systems using LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), FRA (Future Radio Access), NR (new Radio), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth (registered trademark), and other appropriate systems, and next-generation systems extended based on these. In addition, multiple systems may be combined (for example, a combination of at least one of LTE and LTE-A with 5G, etc.).

The processing steps, sequences, flow charts, etc. of each aspect/embodiment described herein may be reordered unless inconsistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

In this specification, a specific operation performed by the base station 10 may be performed by its upper node in some cases. In a network consisting of one or more network nodes having a base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and other network nodes other than the base station 10 (e.g., MME or S-GW, etc., but are not limited to these). Although the above example shows a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (e.g., MME and S-GW).

The information or signals described in this disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer). They may be input and output via multiple network nodes.

The input and output information, etc. may be stored in a specific location (e.g., memory) or may be managed using a management table. The input and output information, etc. may be overwritten, updated, or added to. The output information, etc. may be deleted. The input information, etc. may be transmitted to another device.

In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean (true or false) value, or a comparison of numerical values (e.g., comparison with a predetermined value).

Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Additionally, software, instructions, information, etc. may be transmitted and received via a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and/or wireless technologies (such as infrared, microwave), then these wired and/or wireless technologies are included within the definition of a transmission medium.

The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

Note that the terms described in this disclosure and the terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of the channel and the symbol may be a signal (signaling). Also, the signal may be a message. Also, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

As used in this disclosure, the terms "system" and "network" are used interchangeably.

In addition, the information, parameters, etc. described in this disclosure may be expressed using absolute values, may be expressed using relative values from a predetermined value, or may be expressed using other corresponding information. For example, radio resources may be indicated by an index.

The names used for the above-mentioned parameters are not limiting in any way. Moreover, the formulas etc. using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not limiting in any way.

In this disclosure, terms such as "base station (BS)", "radio base station", "base station device", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "transmission/reception point", "cell", "sector", "cell group", "carrier", and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the entire coverage area of the base station can be divided into multiple smaller areas, and each smaller area can also provide communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head). The term "cell" or "sector" refers to a part or the entire coverage area of at least one of the base station and base station subsystems that provide communication services in this coverage.

In this disclosure, terms such as "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" may be used interchangeably.

A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a moving body, the moving body itself, etc. The moving body may be a vehicle (e.g., a car, an airplane, etc.), an unmanned moving body (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may include a device that does not necessarily move during communication operation. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

In addition, the base station in the present disclosure may be read as a user terminal. For example, each aspect/embodiment of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, the terminal 20 may be configured to have the functions possessed by the above-mentioned base station 10. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals (for example, "side"). For example, the uplink channel, downlink channel, etc. may be read as a side channel.

Similarly, the user terminal in this disclosure may be interpreted as a base station. In this case, the base station may be configured to have the functions of the user terminal described above.

As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. In addition, "judgment" and "decision" can include considering resolving, selecting, choosing, establishing, comparing, etc., to be a "judgment" or "decision." In other words, "judgment" and "decision" can include considering some action to be a "judgment" or "decision." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

The terms "connected" and "coupled", or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access". As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using at least one of one or more wires, cables, and printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and light (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

The reference signal may also be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

Any reference to elements using designations such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must precede the second element in some way.

The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

When used in this disclosure, the terms "include," "including," and variations thereof are intended to be inclusive, similar to the term "comprising." Additionally, the term "or," as used in this disclosure, is not intended to be an exclusive or.

A radio frame may be composed of one or more frames in the time domain. Each of the one or more frames in the time domain may be called a subframe. A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

The numerology may be a communication parameter that applies to at least one of the transmission and reception of a signal or channel. The numerology may indicate, for example, at least one of the following: Subcarrier Spacing (SCS), bandwidth, symbol length, cyclic prefix length, Transmission Time Interval (TTI), number of symbols per TTI, radio frame structure, a particular filtering operation performed by the transceiver in the frequency domain, a particular windowing operation performed by the transceiver in the time domain, etc.

A slot may consist of one or more symbols in the time domain (such as an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, etc.). A slot may be a time unit based on numerology.

A slot may include multiple minislots. Each minislot may consist of one or multiple symbols in the time domain. A minislot may also be called a subslot. A minislot may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called PDSCH (or PUSCH) mapping type B.

Radio frame, subframe, slot, minislot, and symbol all represent time units for transmitting signals. Radio frame, subframe, slot, minislot, and symbol may each be referred to by a different name.

For example, one subframe may be called a Transmission Time Interval (TTI), multiple consecutive subframes may be called a TTI, or one slot or one minislot may be called a TTI. In other words, at least one of the subframe and the TTI may be a subframe (1 ms) in existing LTE, a period shorter than 1 ms (e.g., 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, a base station schedules each terminal 20 by allocating wireless resources (such as frequency bandwidth and transmission power that can be used by each terminal 20) in TTI units. Note that the definition of TTI is not limited to this.

A TTI may be a transmission time unit for a channel-coded data packet (transport block), a code block, a code word, etc., or may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the time interval (e.g., the number of symbols) in which a transport block, a code block, a code word, etc. is actually mapped may be shorter than the TTI.

In addition, when one slot or one minislot is called a TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit of scheduling. In addition, the number of slots (minislots) constituting the minimum time unit of scheduling may be controlled.

A TTI having a time length of 1 ms may be called a normal TTI (TTI in LTE Rel. 8-12), normal TTI, long TTI, normal subframe, normal subframe, long subframe, slot, etc. A TTI shorter than a normal TTI may be called a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

Note that a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length exceeding 1 ms, and a short TTI (e.g., a shortened TTI, etc.) may be interpreted as a TTI having a TTI length less than the TTI length of a long TTI and equal to or greater than 1 ms.

A resource block (RB) is a resource allocation unit in the time domain and frequency domain, and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in an RB may be the same regardless of the numerology, for example, 12. The number of subcarriers included in an RB may be determined based on the numerology.

In addition, the time domain of an RB may include one or more symbols and may be one slot, one minislot, one subframe, or one TTI in length. One TTI, one subframe, etc. may each be composed of one or more resource blocks.

In addition, one or more RBs may be referred to as a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, an RB pair, etc.

A resource block may also be composed of one or more resource elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol.

A Bandwidth Part (BWP), which may also be referred to as a partial bandwidth, may represent a subset of contiguous common resource blocks (RBs) for a given numerology on a given carrier, where the common RBs may be identified by an index of the RB relative to a Common Reference Point of the carrier. PRBs may be defined in a BWP and numbered within the BWP.

The BWP may include a BWP for UL (UL BWP) and a BWP for DL (DL BWP). One or more BWPs may be configured for a UE within one carrier.

At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a given signal/channel outside the active BWP. Note that the terms "cell", "carrier", etc. in this disclosure may be read as "BWP".

The above-mentioned structures of radio frames, subframes, slots, minislots, and symbols are merely examples. For example, the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, as well as the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, and other configurations can be changed in various ways.

In this disclosure, where articles have been added by translation, such as a, an, and the in English, this disclosure may include that the nouns following these articles are in the plural form.

In this disclosure, the term "A and B are different" may mean "A and B are different from each other." In addition, the term may mean "A and B are each different from C." Terms such as "separate" and "combined" may also be interpreted in the same way as "different."

Each aspect/embodiment described in this disclosure may be used alone, in combination, or switched depending on the implementation. In addition, notification of specific information (e.g., notification that "X is the case") is not limited to being done explicitly, but may be done implicitly (e.g., not notifying the specific information).

In this disclosure, the DSS flag is an example of information indicating whether the first RAT and the second RAT coexist on the same carrier. The SSB is an example of a block of synchronization signals and broadcast information.

Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Control unit 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Control unit 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device

Claims (7)

A receiving unit that receives a synchronization signal of a first RAT (Radio Access Technology);
A control unit that synchronizes with a cell of a second RAT using the synchronization signal,
The receiving unit is a terminal that uses a signal of a third RAT for decoding data in the second RAT. The terminal according to claim 1, wherein the second RAT is transmitted on the same carrier as the first RAT. The terminal according to claim 1, wherein the receiver receives information necessary for receiving the synchronization signal when adding a cell of the second RAT, and receives the synchronization signal based on the information. The terminal according to claim 1, wherein the control unit uses the synchronization signal to synchronize with a cell of the second RAT transmitted on the same carrier as the first RAT, based on information indicating whether the first RAT and the second RAT coexist on the same carrier. The terminal according to claim 1, wherein the receiving unit receives an instruction to add a cell of the second RAT and acquires information obtained from a block of a synchronization signal and broadcast information of the second RAT included in the instruction. The terminal according to claim 1, wherein the receiving unit receives broadcast information of the first RAT and acquires information obtained from a synchronization signal and a block of broadcast information of the second RAT included in the broadcast information. A receiving procedure for receiving a synchronization signal of a first RAT (Radio Access Technology);
a control procedure for synchronizing with a cell of a second RAT using the synchronization signal;
and a procedure of using a signal of a third RAT for decoding data in the second RAT, the procedure being performed by a terminal.

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