Title of Invention: Terminal apparatus, communication method, and integrated circuit Abstract: A technology related to a terminal apparatus, a communication method, and an integrated circuit is provided for efficiently monitoring a status of communication. The terminal apparatus communicates with the base station apparatus by switching between a first frequency and a second frequency in a cell, a timer for monitoring a radio link in the cell starts based on consecutively detecting that out of synchronization occurs a prescribed number of times, the timer stops in the case of switching between the first frequency and the second frequency, and any one of the first frequency and the second frequency is a frequency by which the terminal apparatus has established Radio Resource Control connection. Detailed Description: Part general_description_paragraphs: Part TECHNICAL FIELD: The present invention relates to a terminal apparatus, a communication method, and an integrated circuit. This application claims priority based on JP 775.970.0122 filed on Apr. 26, 2016, the contents of which are incorporated herein by reference. Part BACKGROUND ART: In the 3rd Generation Partnership Project (3GPP), a radio access method and a radio network for cellular mobile communications (hereinafter, referred to as “Long Term Evolution (LTE: registered trademark)”, or “Evolved Universal Terrestrial Radio Access (EUTRA)”) have been studied (Non Patent Literature 1, 2, 3, 4, and 5). In LTE, a base station apparatus is also referred to as an evolved NodeB (eNodeB), and a terminal apparatus is also referred to as User Equipment (UE). LTE is a cellular communication system in which multiple areas covered by the base station apparatuses are deployed to form a cellular structure. A single base station apparatus may manage multiple cells. In the 3GPP, standardization of a radio technology using narrowbands has been studied for the Internet of Things, and deployments that use a resource of a normal LTE carrier (in-band), a guard band (guard band), a band that is not used in normal LTE (standalone), and the like have been considered (Non Patent Literature 6). Additionally, it is considered that an anchor PRB that is mainly used for cell connection (for obtaining system information) and a PRB other than the anchor PRB (non-anchor PRB) are allocated to a terminal apparatus to communicate (Non Patent Literature 7). Part CITATION LIST: Part Non Patent Literature: NPL 1: 3GPP TS 36.211 V13.0.0 (2015-12) http://www.3gpp.org/DynaReport/36211.htm NPL 2: 3GPP TS 36.212 V13.0.0 (2015-12) http://www.3gpp.org/DynaReport/36212.htm NPL 3: 3GPP TS 36.213 V13.0.0 (2015-12) http://www.3gpp.org/DynaReport/36213.htm NPL 4: 3GPP TS 36.321 V13.0.0 (2015-12) http://www.3gpp.org/DynaReport/36321.htm NPL 5: 3GPP TS 36.331 V13.0.0 (2015-12) http://www.3gpp.org/DynaReport/36331.htm NPL 6: RP-151621 New Work Item: NarrowBand IoT (NB-IoT), Qualcomm incorporated http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_69/Docs/RP-151621.zip NPL 7: RP-160183Status Report to TSG http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_71/Docs/RP-160183.zip Part SUMMARY OF INVENTION: Part Solution to Problem: The present invention provides a terminal apparatus capable of efficiently monitoring a status of communication with a base station apparatus, a base station apparatus communicating with the terminal apparatus, a communication method to be used for the terminal apparatus, a communication method to be used for the base station apparatus, an integrated circuit to be mounted on the terminal apparatus, and an integrated circuit to be mounted on the base station apparatus. (1) In order to accomplish the object described above, an aspect of the present invention is contrived to provide the following means. That is, a first aspect of the present invention is a terminal apparatus for communicating with a base station apparatus via a cell, the terminal apparatus communicating with the base station apparatus by switching between a first frequency and a second frequency different from the first frequency in the cell, in which a timer for monitoring a radio link in the cell is common between the first frequency and the second frequency, the timer starts based on consecutively detecting that out of synchronization (out-of-sync) occurs a prescribed number of times, the timer stops in the case of switching between the first frequency and the second frequency, and any one of the first frequency and the second frequency is a frequency by which the terminal apparatus has established Radio Resource Control (RRC) connection. (2) In the first aspect of the present invention, in a case that first out of synchronization is detected on the first frequency and second out of synchronization is detected on the second frequency, even in a case that the first out of synchronization and the second out of synchronization consecutively occur, it is regarded that the first out of synchronization and the second out of synchronization do not consecutively occur. (3) In the first aspect of the present invention, the timer stops based on consecutively detecting in-synchronization (in-sync) a prescribed number of times, and in a case that first in-synchronization is detected on the first frequency and second in-synchronization is detected on the second frequency, even in a case that the first in-synchronization and the second in-synchronization are consecutively detected, it is regarded that the first in-synchronization and the second in-synchronization are not consecutively detected. (4) In the first aspect of the present invention, it is regarded that the first out of synchronization detected on the first frequency and the second out of synchronization detected on the second frequency consecutively occur. (5) In the first aspect of the present invention, the timer stops based on consecutively detecting the in-synchronization (in-sync) the prescribed number of times, and it is regarded that the first in-synchronization detected on the first frequency and the second in-synchronization detected on the second frequency are consecutively detected. (6) A second aspect of the present invention is a terminal apparatus for communicating with a base station apparatus via a cell, the terminal apparatus communicating with the base station apparatus by switching between a third frequency and a fourth frequency different from the third frequency in the cell, in which, in a case of monitoring a radio link in the cell, detection for out of synchronization (out-of-sync) is performed only by any one of the third frequency and the fourth frequency, and any one of the third frequency and the fourth frequency is a frequency by which the terminal apparatus has established Radio Resource Control (RRC) connection. (7) In the second aspect of the present invention, a timer for monitoring the radio link in the cell starts based on consecutively detecting that the out of synchronization occurs a prescribed number of times on the third frequency, and the timer stops in a case of switching from the third frequency to the fourth frequency. (8) In the second aspect of the present invention, the timer for monitoring the radio link in the cell starts based on consecutively detecting that the out of synchronization occurs the prescribed number of times on the third frequency, the timer suspends detection for the out of synchronization in a case of switching from the third frequency to the fourth frequency, and the timer suspends detection for the out of synchronization in a case of switching from the third frequency to the fourth frequency and resumes the detection for the out of synchronization in a case of returning from the fourth frequency to the third frequency. (9) In the second aspect of the present invention, it is regarded that the out of synchronization detected immediately before the suspension and out of synchronization detected immediately after the resumption are consecutively detected. (10) A third aspect of the present invention is a communication method to be applied to a terminal apparatus for communicating with a base station apparatus via a cell, the communication method including at least a step of communicating with the base station apparatus by switching between a first frequency and a second frequency different from the first frequency in the cell, in which a timer for monitoring a radio link in the cell is common between the first frequency and the second frequency, the timer starts based on consecutively detecting that out of synchronization (out-of-sync) occurs a prescribed number of times, the timer stops in the case of switching between the first frequency and the second frequency, and any one of the first frequency and the second frequency is a frequency by which the terminal apparatus has established Radio Resource Control (RRC) connection. (11) A fourth aspect of the present invention is an integrated circuit to be mounted on a terminal apparatus for communicating with a base station apparatus via a cell, the integrated circuit allowing the terminal apparatus to perform a function of communicating with the base station apparatus by switching between a first frequency by which the terminal apparatus establishes Radio Resource Control (RRC) connection and a second frequency different from the first frequency in the cell, in which a timer for monitoring a radio link in the cell is common between the first frequency and the second frequency, the timer starts based on consecutively detecting that out of synchronization (out-of-sync) occurs a prescribed number of times, the timer stops in the case of switching between the first frequency and the second frequency, and any one of the first frequency and the second frequency is a frequency by which the terminal apparatus has established the Radio Resource Control (RRC) connection. (12) A fifth aspect of the present invention is a communication method to be applied to a terminal apparatus for communicating with a base station apparatus via a cell, the communication method including at least a step of communicating with the base station apparatus by switching between a third frequency and a fourth frequency different from the third frequency in the cell, in which, in a case of monitoring a radio link in the cell, detection for out of synchronization (out-of-sync) is performed only by any one of the third frequency and the fourth frequency, and any one of the third frequency and the fourth frequency is a frequency by which the terminal apparatus has established Radio Resource Control (RRC) connection. (13) A sixth aspect of the present invention is an integrated circuit to be mounted on a terminal apparatus for communicating with a base station apparatus via a cell, the integrated circuit allowing the terminal apparatus to perform a function of communicating with the base station apparatus by switching between a third frequency and a fourth frequency different from the third frequency in the cell, in which, in a case of monitoring a radio link in the cell, detection for out of synchronization (out-of-sync) is performed only by any one of the third frequency and the fourth frequency, and any one of the third frequency and the fourth frequency is a frequency by which the terminal apparatus has established Radio Resource Control (RRC) connection. Part Advantageous Effects of Invention: According to the present invention, the terminal apparatus is capable of efficiently monitoring a status of communication with the base station apparatus. Part DESCRIPTION OF EMBODIMENT: An embodiment of the present invention will be described below. A radio communication system according to the present embodiment will be described. Long Term Evolution (LTE) (registered trademark) and the Narrow Band Internet of Things (NB-IoT) may be defined as different Radio Access Technologies (RAT). The NB-IoT may be defined as a technology included in LTE. The present embodiment may be applied to the NB-IoT, but may be applied to LTE or other RATs. FIG. 1 is a conceptual diagram of the radio communication system according to the present embodiment. In FIG. 1, the radio communication system includes terminal apparatuses 2A and 2B and base station apparatuses 3A and 3B. The terminal apparatuses 2A and 2B are also referred to as a terminal apparatus 2. A base station apparatus 3 includes the base station apparatuses 3A and 3B. The base station apparatuses 3A and 3B may be defined as different apparatuses. The base station apparatus 3 may include a core network apparatus. The terminal apparatus 2A and the base station apparatus 3A communicate with each other by using the NB-IoT. The terminal apparatus 2B and the base station apparatus 3B communicate with each other by using the NB-IoT. Time Division Duplex (TDD) and/or Frequency Division Duplex (FDD) is applied to the radio communication system in the present embodiment. In the present embodiment, a single serving cell is configured for the terminal apparatus 2. The serving cell configured for the terminal apparatus 2 is also referred to as an NB-IoT cell. The configured single serving cell may be a primary cell. The primary cell is a serving cell in which an initial connection establishment procedure has been performed, a serving cell in which a connection re-establishment procedure has been started, or a cell indicated as a primary cell during a handover procedure. A carrier corresponding to a serving cell in a downlink is referred to as a downlink component carrier. A carrier corresponding to the serving cell in an uplink is referred to as an uplink component carrier. The downlink component carrier and the uplink component carrier are collectively referred to as a component carrier. The present embodiment may be applied to three scenarios/modes of standalone, guard band, and in-band. In the standalone mode, a channel bandwidth of the NB-IoT cell is not included in a channel bandwidth of a LTE cell. In the guard band mode, the channel bandwidth of the NB-IoT cell is included in a guard band of the LTE cell. In the in-band mode, the channel bandwidth of the NB-IoT cell is included in a transmission bandwidth of the LTE cell. For example, the guard band of the LTE cell is included in the channel bandwidth of the LTE cell, but is not included in the transmission bandwidth of the LTE cell. The present embodiment is applicable to any of the modes. Physical channels and physical signals in the present embodiment will be described. In FIG. 1, the following downlink physical channels are used for downlink radio communication from the base station apparatus 3 to the terminal apparatus 2. The downlink physical channels are used by a physical layer for transmission of information output from a higher layer. Narrowband Physical Broadcast CHannel (NPBCH) Narrowband Physical Downlink Control CHannel (NPDSCH) Narrowband Physical Downlink Shared CHannel (NPDSCH) The NPBCH is used to broadcast system information that is commonly used by the terminal apparatuses 2. The NPDCCH is used to transmit Narrow Band Downlink Control Information (DCI) that is used for scheduling of the NPDSCH and downlink control information that is used for scheduling of the Narrowband Physical Uplink Shared CHannel (NPUSCH), The downlink control information may include HARQ information. Cyclic Redundancy Check (CRC) parity bits to be attached to the downlink control information are scrambled with a Cell-Radio Network Temporary Identifier (C-RNTI), a Temporary C-RNTI, or a Semi Persistent Scheduling (SPS) C-RNTI. The C-RNTI and the SPS C-RNTI are identifiers for identifying a terminal apparatus within a cell. The Temporary C-RNTI is used during the contention based random access procedure. Adding the RNTI to the downlink control information is also referred to as the RNTI being included in the NPDCCH. The C-RNTI is used to control the NPDSCH or the NPUSCH in one subframe. The SPS C-RNTI is used to periodically allocate a resource for the NPDSCH or the NPUSCH. The Temporary C-RNTI is used to schedule retransmission of a random access message 3 and transmission of a random access message 4. The NPDSCH is used for transmission of downlink data (DownLink Shared CHannel (DL-SCH)). In FIG. 1, the following downlink physical signals are used for the downlink radio communication from the base station apparatus 3 to the terminal apparatus 2. The downlink physical signals are not used for transmission of information output from the higher layer, but are used by the physical layer. Narrowband Synchronization signal (NSS) Narrowband Downlink Reference Signal (NDL-RS) The NSS is used in order for the terminal apparatus 2 to establish synchronization in terms of frequency and time in the downlink of the NB-IoT cell. The NSS includes a Narrowband Primary Synchronization Signal (NPSS) and a Narrowband Secondary synchronization Signal (NSSS). The NSSS is generated based on a Narrowband Physical layer Cell Identity (NPCI) of the NB-IoT cell. The terminal apparatus 2 may obtain the NPCI of the NB-IoT cell from the NSS. The NDL-RS is used in order for the terminal apparatus 2 to perform channel compensation on the downlink physical channel in the NB-IoT cell. The NDL-RS may be used in order for the terminal apparatus 2 to calculate downlink channel state information in the NB-IoT cell. Additionally, in a case of the in-hand mode NB-IoT, a LTE cell-specific downlink reference signal (LTE-Cell specific Reference Signal (LTE-CRS)) may be used to perform the channel compensation on the downlink physical channel in the NB-IoT cell. In addition, the LTE-CRS may be used in order for the terminal apparatus 2 to calculate the downlink channel state information in the NB-IoT cell. In FIG. 1, the following uplink physical channels are used for uplink radio communication from the terminal apparatus 2 to the base station apparatus 3. The uplink physical channels are used by a physical layer for transmission of information output from a higher layer. Narrowband Physical Random Access Channel (NPRACH) Narrowband Physical Uplink Shared CHannel (NPUSCH) The NPUSCH may be used for transmission of uplink data (Uplink-Shared CHannel (UL-SCH)) and/or uplink control information. The uplink control information includes a Hybrid Automatic Repeat reQuest ACKnowledgment (HARQ-ACK) corresponding to the NPDSCH (downlink data). In the present embodiment, transmitting the NPUSCH once corresponds to one or multiple subcarriers. For example, the number of the subcarriers for transmitting the NPUSCH once is selected from 1, 3, 6, or 12. Transmission of a different NPUSCH may correspond to a different subcarrier. The transmission of the different NPUSCH may correspond to the different number of subcarriers. In FIG. 1, the following uplink physical signal is used for the uplink radio communication from the terminal apparatus 2 to the base station apparatus 3. The uplink physical signal is not used for transmission of information output from the higher layer, but is used by the physical layer. Narrowband Downlink Reference Signal (NUL-RS) The NUL-RS may be used in order for the base station apparatus 3 to perform channel compensation of the uplink physical channel in the NB-IoT cell. The NUL-RS may be used in order for the terminal apparatus 2 to calculate the uplink channel state information in the NB-IoT cell. The NUL-RS may be mapped to a subcarrier identical to the corresponding NPUSCH. The NUL-RS is time-multiplexed with the NPUSCH. The NUL-RS is also referred to as a DeModulation Reference Signal (DMRS), an uplink reference signal, or a reference signal. The downlink physical channels and the downlink physical signals are collectively referred to as a downlink signal. The uplink physical channels and the uplink physical signals are collectively referred to as an uplink signal. The downlink physical channels and the uplink physical channels are collectively referred to as a physical channel. The downlink physical signals and the uplink physical signals are collectively referred to as a physical signal. The DL-SCH is a transport channel. A channel used in a Medium Access Control (MAC) layer is referred to as a transport channel. A unit of the transport channel used in the MAC layer is also referred to as a Transport Block (TB) or a MAC Protocol Data Unit (PDU). A Hybrid Automatic Repeat reQuest (HARQ) is controlled for each transport block in the MAC layer. The transport block is a unit of data that the MAC layer delivers to the physical layer. In the physical layer, the transport block is mapped to a codeword and subjected to coding processing on a codeword-by-codeword basis. The base station apparatus 3 and the terminal apparatus 2 exchange (transmit and/or receive) a signal in the higher layer. For example, the base station apparatus 3 and the terminal apparatus 2 may transmit and/or receive, in a Radio Resource Control (RRC) layer, RRC signaling (also referred to as a Radio Resource Control message (RRC message) or Radio Resource Control information (RRC information)). Furthermore, the base station apparatus 3 and the terminal apparatus 2 may transmit and/or receive, in the Medium Access Control (MAC) layer, a MAC Control Element (CE), Here, the RRC signaling and/or the MAC CE is also referred to as higher layer signaling. The NPDSCH is used to transmit the RRC signaling and the MAC CE. Here, the RRC signaling transmitted from the base station apparatus 3 by using the NPDSCH may be signaling common to multiple terminal apparatuses 2 in a cell. The RRC signaling transmitted from the base station apparatus 3 by using the NPDSCH may be signaling dedicated (specified) to a certain terminal apparatus 2 (also referred to as dedicated signaling or UE specific signaling). A cell-specific parameter may be transmitted by using the signaling common to the multiple terminal apparatuses 2 in the cell or the signaling dedicated to the certain terminal apparatus 2. A UE-specific parameter may be transmitted by using the signaling dedicated to the certain terminal apparatus 2. The physical channels (NPDCCH, NPDSCH, and NPUSCH) corresponding to identical data (a transport block) may be repeatedly transmitted in consecutive subframes. A Repetition Level (RL) of the physical channel may be controlled for each physical channel. The repetition level 1 means that the physical channel corresponding to the identical data is not repeatedly transmitted. The repetition level larger than 1 means that the physical channel corresponding to the identical data is repeatedly transmitted. That is, the repetition level is associated with a length of one transmission instance/attempt/bundle of the physical channel in a time domain. The repetition level may be at least based on some or all of the downlink control information, the RRC signalling, the MAC CE, and a coverage level. The coverage level includes at least a first coverage level and a second coverage level. The coverage level may include three or more coverage levels. The coverage level is associated with the repetition level. The terminal apparatus 2 for which the first coverage level is configured may transmit and/or receive the physical channel having the repetition level which is X or smaller. The terminal apparatus 2 for which the first coverage level is configured may not transmit and/or receive the physical channel having the repetition level which is larger than X. The terminal apparatus 2 for which the second coverage level is configured may transmit and/or receive the physical channel having the repetition level which is larger than X. For example, X may be 1 or 3. The terminal apparatus 2 may configure the coverage level based on information received from the base station apparatus 3 and Reference Signal Received Power (RSRP) of the signal (NDL-RS) received from the base station apparatus 3. Here, the above information may be the downlink control information, the RRC signalling or the MAC CE. A radio network according to the present embodiment will be described. A communicable range (communication area) at each frequency controlled by a base station apparatus 3 is regarded as a cell. Here, the communication area covered by the base station apparatus 3 may be different in size and shape for each frequency. Moreover, the covered area may be different for each frequency. A radio network, in which cells having different types of base station apparatuses 3 and different cell radii coexist in an area by using the identical frequency or different frequencies to form a single communication system, is referred to as a heterogeneous network. The terminal apparatus 2 operates by regarding the inside of a cell as a communication area. In a case that the terminal apparatus 2 moves from one cell to another cell, the terminal apparatus 2 moves to an appropriate different cell through a cell re-selection procedure at the time of having no radio connection (also referred to as an idle state, or an RRC_IDLE state) and through a handover procedure at the time of having radio connection (also referred a connected state, or an RRC_CONNECTED state). The appropriate cell in general indicates a cell that is determined that access from the terminal apparatus 2 is not prohibited based on information specified by the base station apparatus 3, and that has downlink reception quality satisfying a predefined condition. The base station apparatus 3 manages a cell that is an area where the terminal apparatus 2 is capable of communicating, for each frequency. A single base station apparatus 3 may manage multiple cells. In a case that the terminal apparatus 2 can communicate with a certain base station apparatus 3, the cell configured so as to be used for the communication with the terminal apparatus 2 is referred to as a “Serving cell”, while the other cells that are not used for the communication are referred to as “Neighboring cells”, among the cells of the base station apparatus 3. A structure of a radio protocol according to the present embodiment will be described. FIG. 4 is a diagram illustrating a protocol stack of a User-Plane or U-Plane (UP) handling user data of the terminal apparatus 2 and the base station apparatus 3, in a radio network (EUTRAN) of EUTRA. In addition, FIG. 5 is a diagram illustrating a protocol stack of a Control-Plane or C-Plane (CP) handling control data. In FIGS. 4 and 5, a PHYsical layer (PHY layer) uses the physical channels to provide a transmission service to a higher layer. The PHY layer is connected with a Medium Access Control layer (MAC layer), which is a higher layer, via the transport channels. The data is exchanged via the transport channels between layers, that is, the MAC layer and the PHY layer. The data is transmitted and/or received via the physical channels between the PHY layers of the terminal apparatus 2 and the base station apparatus 3. The MAC layer maps various logical channels to the various transport channels. The MAC layer is connected with a Radio Link Control layer (RLC layer), which is a higher layer, via the logical channels. The logical channels are roughly classified depending on the type of the transmitted information, specifically, classified into the control channels transmitting the control information and the traffic channels transmitting the user information. The MAC layer has a function to control the PHY layer in order to perform Discontinuous Reception and Transmission (DRX and DTX), a function to perform the random access procedure, a function to report transmit power information, a function to perform the HARQ control, and the like. The RLC layer performs segmentation or concatenation of the data received from the higher layer to adjust its data size so that a lower layer can appropriately transmit the data. The RLC layer also has a function to guarantee Quality of Service (QoS) demanded by each data. In other words, the RLC layer has a function of data re-transmission control or the like. A Packet Data Convergence Protocol layer (PDCP layer) has a header compression function to compress unnecessary control information in order to efficiently transmit an IP packet, which is the user data, in a radio segment. The PDCP layer also has a data encryption function. A Radio Resource Control layer (RRC layer) is present in the Control-Plane protocol stack. The RRC layer performs configurations and reconfigurations of Radio Bearers (RBs) to control the logical channels, the transport channels, and the physical channels. RBs are classified into a Signaling Radio Bearer (SRB) and a Data Radio Bearer (DRB), and the SRB is used as a path for transmitting an RRC message, which is the control information. The DRB is used as a path for transmitting the user data. Each RB is configured between the RRC layers of the base station apparatus 3 and the terminal apparatus 2. The PHY layer corresponds to a physical layer as the first layer in the layered structure of the generally known Open Systems Interconnection (OSI) model. The MAC layer, the RLC layer, and the PDCP layer correspond to a data link layer as the second layer in the OSI model. The RRC layer corresponds to a network layer as the third layer in the OSI model. Signalling protocols used between the network and the terminal apparatus 2 are divided into an Access Stratum (AS) protocol and a Non-Access Stratum (NAS) protocol. For example, the protocol in the RRC layer and its lower layers is the Access Stratum protocol used between the terminal apparatus 2 and the base station apparatus 3. Further, the protocol in Connection Management (CM), Mobility Management (MM), or the like of the terminal apparatus 2 is the Non-Access Stratum protocol, and is used between the terminal apparatus 2 and a Core Network (CN). For example, as illustrated in FIG. 5, communication using the Non-Access Stratum protocol is transparently performed via the base station apparatus 3 between the terminal apparatus 2 and a Mobility Management Entity (MME). An anchor PRB and a non-anchor PRB according to the present embodiment will be described. An NB-IoT cell includes multiple PRBs (or channels or carriers) in a frequency direction, the NPSS, the NSSS, the NPBCH and other system information of the multiple PRBs are transmitted, and the PRB used by the terminal apparatus 2 for establishing RRC connection is referred to as the anchor PRB (or anchor channel, anchor carrier). Additionally, the PRB (channel, carrier) by which some or all of the NPSS, the NSSS, and the NPBCH are not transmitted is referred to as the non-anchor PRB (or non-anchor channel, non-anchor carrier). The terminal apparatus 2 that has established the RRC connection by using the anchor PRB may continue to communicate by changing the anchor PRB to the non-anchor PRB, based on an RRC connection reconfiguration message indicated from the base station apparatus 3 (for example, physical configuration message for the NB-IoT (PhysicalConfigDedicated-NB)), or other notifications. For example, the terminal apparatus 2, in a case that information on a frequency (carrier) of the PRB (non-anchor PRB) to be used for transmission and/or reception in the future is indicated, may promptly start to use the indicated frequency, after transmitting an acknowledgement in response to reception of the last transport block in a case that the MAC layer transports one RRC message. Moreover, in a case that there exist the multiple PRBs by which the NPSS, the NSSS, the NPBCH, and other system information are transmitted, the terminal apparatus 2 may configure the PRB, by which the RRC connection has been established, as the anchor PRB, and may configure the other PRB, by which the NPSS, the NSSS, the NPBCH, and other system information are transmitted, as the non-anchor PRB. The random access procedure described later may be performed only by the anchor PRB. In this case, the terminal apparatus 2 that is in communication by the non-anchor PRB returns from the non-anchor PRB to the anchor PRB to perform the random access procedure, in a case that the random access procedure is indicated by the base station apparatus 3 (PDCCH order) or other conditions for performing the random access procedure are satisfied. Radio Link Monitoring (RLM) according to the present embodiment will described. An example of an operation that the terminal apparatus 2 having e RRC connection detects a radio link failure will be described. The terminal apparatus 2 obtains information such as a value (t310) of a timer (T310) for detecting physical layer problems of a serving cell (the anchor PRB and/or the non-anchor PRB), a threshold value N310 of the number of times detecting out-of-sync, and a threshold value N311 of the number of times detecting in-sync via broadcast information or the RRC message for each user from a serving base station apparatus 3. In addition, the value of the timer and the threshold value of the number of times may be configured to default values. Moreover, the timer may be common between the anchor PRB and the non-anchor PRB, or may be independent. Furthermore, the value of the timer and the threshold value of the number of times may be configured to a common value between the anchor PRB and the non-anchor PRB, or may be configured to independent values. In order to monitor the radio link, a physical layer processing unit of the terminal apparatus 2, based on information such as reception power of the received reference signal (NDL-RS and/or LTE-CRS) and/or NSS (NPSS and/or NSSS), in a case that it is estimated that radio link quality of the serving cell has been a specified threshold value (Qout) or smaller over a specified period (for example, TEvaluate_Qout=200 ms), notifies a processing unit of a Radio Resource Control (RRC) layer, which is the higher layer, of “out-of-sync”. Additionally, the physical layer processing unit, based on the information such as the reception power of the received reference signal, in a case that it is estimated that the radio link quality of the serving cell has been a specified threshold value (Qin) or larger over a specified period (for example, TEvaluate_Qin=100 ms), notifies the processing unit of the Radio Resource Control layer, which is the higher layer, of “in-sync”. Note that the physical layer processing unit may notify the higher layer of out-of-sync or in-sync after a specified interval (for example, TReport_sync=10 ms) or longer. In addition, the terminal apparatus 2 may be notified of information on a signal that may be assumed to be transmitted by using the non-anchor PRB via the RRC message or other signalling from the base station apparatus 3. For example, in a case that the NPSS is transmitted by using only the anchor PRB, and in a case that the non-anchor PRB for a certain terminal apparatus 2 is the anchor PRB for another terminal apparatus 2, the reception power can be measured by using the NPSS even in a case of the non-anchor PRB. Alternatively, for example, in a case that a transmission period of the NPSS and/or the NSSS by using the non-anchor PRB is a subset of a transmission period by using the anchor PRB, and in a case that the non-anchor PRB for a certain terminal apparatus 2 is the anchor PRB for another terminal apparatus 2, the reception power can be measured based on the transmission period of the NPSS and/or the NSSS by using the anchor PRB even in a case of the non-anchor PRB. Therefore, the terminal 2 may be allowed to obtain some or all pieces of the following information (A) to (F) from the base station apparatus 3. (A) Information indicating whether the LTE-CRS is transmitted by using the non-anchor PRB or not (B) Information indicating whether the NPSS is transmitted by using the non-anchor PRB or not (C) Information indicating whether the NSSS is transmitted by using the non-anchor PRB or not (D) Resource information on the NPSS and/or the NSSS that is transmitted by using the non-anchor PRB (E) Information indicating whether an identical type of signal to the anchor PRB (for example, the LTE-CRS, and/or the NPSS and/or the NSSS) is transmitted by using the non-anchor PRB or not (F) Information indicating whether transmission power of the NSS and/or the NDL-RS that is transmitted by using the non-anchor PRB is identical to that of the anchor PRB or not Here, for example, the threshold value (Qout) may be defined as a level at which reception in a radio link of the downlink is not reliable and a hypothetical transmission block error rate for the downlink control channel (NPDCCH) based on a predetermined parameter becomes 10%. Additionally, for example, the threshold value (Qin) may be defined as a level at which radio link quality of the downlink is significantly high, the reception is reliable compared with the condition at Qout and a hypothetical transmission block error rate for the downlink control channel based on a predetermined parameter becomes 2%. Moreover, in a case that the threshold value Qout and the threshold value Qin are defined, different formats for the NPDCCH may be assumed. More specifically, the threshold value Qout may be defined as a level at which the block error rate for the NPDCCH, considered some or all of the following conditions (A) to (D), becomes a predetermined rate. (A) The DCI format for the NPDCCH is made to be a specified format. (B) The repetition number of times for the NPDCCH is made to be a specified number of times (for example, a maximum repetition number of times (Rmax) for the PDCCH, which is indicated via the RRC message). (C) Which reference signal is used for demodulation (for example, the NPDCCH is demodulated by using the NDL-RS and the LIE-CRS in a case a cell identity for LTE and a cell identity for the NB-IoT are identical in the in-band, and in a case that the LTE-CRS and the NDL-RS have the identical number of antennas and a port number is one or two in the in-band, or the NPDCCH is demodulated by using only the NDL-RS in a case of not being in the in-band, in a case that the cell identity for LIE and the cell identity for the NB-IoT are different in the in-band, in a case that the LTE-CRS and the NDL-RS have the different numbers of antennas in the in-band, and in a case that the LTE-CRS and the NDL-RS have the identical number of antennas but the port number is not one or two in the in-band). (D) A transmission power ratio between the NPDCCH and the reference signal (the NDL-RS and/or the LTE-CRS) (for example, a condition is configured by whether the NDL-RS for the anchor PRB is boosted or not, the antenna port number for the LTE-CRS in a case that the LTE-CRS is used, or the like). In addition, the threshold value Qin may be defined as a level at which the block error rate for the NPDCCH, considered some or all of the following conditions (A) to (D), becomes a predetermined rate. (A) The DCI format for the NPDCCH is made to be a specified format. (B) The repetition number of times for the NPDCCH is made to be a specified number of times (for example, which may be made to be a maximum repetition number of times (Rmax) for the PDCCH which is indicated via the RRC message, or a value smaller than Rmax). (C) Which reference signal is used for demodulation (for example, only the NDL-RS is used to demodulate the NPDCCH, or the like). (D) A transmission power ratio between the NPDCCH and the reference signal (the NDL-RS and/or the LTE-CRS) (for example, a condition is that the anchor PRB is not boosted, and/or the LTE-CRS is not used, or the like). The NSS (the NPSS and/or the NSSS) is transmitted by using the anchor PRB. The base station apparatus 3 may transmit information for indicating whether the NSS (the NPSS and/or the NSSS) is transmitted by using the non-anchor PRB or not to the terminal apparatus 2. The NSS (the NPSS and/or the NSSS) may be used for monitoring the radio link using the anchor PRB. The NSS (the NPSS and/or the NSSS) may be used for monitoring the radio link on the non-anchor PRB, in a case the NSS (the NPSS and/or the NSSS) is transmitted by using the non-anchor PRB. In a case the NSS (the NPSS and/or the NSSS) is used for monitoring the radio link, the base station apparatus 3 may transmit power ratio information for indicating (i) a power ratio between the reference signal (the NDL-RS and/or the LTE-CRS) and the NSS (the NPSS and/or the NSSS), and/or (ii) a power ratio between the NPDCCH and the NSS (the NPSS and/or the NSSS), to the terminal apparatus 2. In a case that the terminal apparatus 3 has not received the above power ratio information, the terminal apparatus 3 may regard that the power of the reference signal (the NDL-RS and/or the LTE-CRS) and the power of the NSS (the NPSS and/or the NSSS) are identical. In a case that the terminal apparatus 3 has not received the above power ratio information, the terminal apparatus 3 may regard that the power of the NPDCCH and the power of the NSS (the NPSS and/or the NSSS) are identical. The above power may be power per one resource element. Additionally, the physical layer processing unit of the terminal apparatus 2 may notify the higher layer of only out-of-sync or in-sync, which occurs on the anchor PRB, may notify the higher layer of only out-of-sync or in-sync, which occurs on the non-anchor PRB, and may notify the higher layer of out-of-sync or in-sync, which occurs during reception in a cell (that is, a cell in which either the anchor PRB or the non-anchor PRB is received). In a case that the physical layer processing unit notifies the higher layer of out-of-sync or in-sync, which occurs during reception in a cell, the physical layer processing unit may notify the higher layer of information capable of determining in which of the cells using the anchor PRB or the non-anchor PRB out-of-sync or in-sync occurs. In a case that a radio resource control layer processing unit of the terminal apparatus 2 consecutively receives out-of-sync that is notified from the physical layer processing unit the predetermined number of times (N310), the radio resource control layer processing unit may allow the timer (T310) to start or restart counting. Additionally, in a case that the radio resource layer processing unit of the terminal apparatus 2 consecutively receives in-sync the predetermined number of times (N311), the radio resource layer processing unit may allow the timer (T310) to stop counting. Furthermore, in a case that the timer (T310) expires without stopping of counting, the radio resource control layer processing unit of the terminal apparatus 2 may shift to an idle mode or perform an RRC connection re-establishment procedure. For example, operations of the terminal apparatus 2 may be different depending on a state of establishing AS security. First, in a case that the AS security has not been established, the terminal apparatus 2 shifts to an RRC_IDLE mode, and in a case that the AS security has been established, the terminal apparatus 2 performs the RRC connection re-establishment procedure. Although the above is an example of a case that the DRX is not configured in the terminal apparatus 2, in a case that the DRX is configured in the terminal apparatus 2, the radio resource control layer processing unit of the terminal apparatus 2 may configure for the physical layer processing unit so that a period for measuring the radio link quality and an interval of notification to the higher layer have different values from those of a case that the DRX is not configured. Note that even in a case that the DRX is configured, while the above timer (T310) is counting, the period for measuring the radio link quality to estimate in-sync and the interval of notification to the higher layer have identical values to those of the case that the DRX is not configured. Note that some or all of the timer value (t310), the threshold values (Qin, Qout), the numbers of times (N310, N311), the periods (TEvaluate_Qout, TEvaluate_Qin), or the interval (TReport_sync) may be independent values between the anchor PRB and the non-anchor PRB. Some or all of the timer value (t310), the threshold values (Qin, Qout), the numbers of times (N310, N311), the periods (TEvaluate_Qout, TEvaluate_Qin), or the interval (TReport_sync) may be broadcasted as system information from the base station apparatus 3, may be individually configured for the terminal apparatus 2 via the RRC message or the like, or may be a combination of them. Radio Link Monitoring (RLM) according to the present embodiment will be described in more detail. First, an example that the independent timers between the anchor PRB and the non-anchor PRB are used will be described using FIGS. 8 to 10. Where, N310=2, and N311=2 for the anchor PRB and the non-anchor PRB. In FIGS. 8 to 10, horizontal axes indicate time. At P80 in FIG. 8, based on a case that the terminal apparatus 2 receiving by the non-anchor PRB (PRB-Na1) consecutively detects N310 out-of-sync twice (N310=2), the timer T310 starts. Then, at P81, in-sync is detected once. After that, because of indication for performing the random access procedure from the base station apparatus 3 or other reasons, the terminal apparatus 2 shifts to the anchor PRB (PRB-A). At this time, T310 for PRB-Na1 is suspended, and counted time and count numbers of times of out-of-sync and in-sync are retained. At P82 on the anchor PRB (PRB-A), out-of-sync and in-sync are newly counted, and in a case that out-of-sync is consecutively detected twice (N310=2), a timer, which is independent of the suspended timer for the non-anchor PRB, starts. Additionally, in a case that in-sync is consecutively detected twice (N311=2), the timer T310 for the anchor PRB stops. In a case that the terminal apparatus 2 returns to the non-anchor PRB (PRB-Na1) at P83, the suspended timer T310 resumes. In this example, since the timer T310 suspends in a state that in-sync has been detected once at P81, it is regarded that in-sync is consecutively detected twice (N311=2) based on a case in-sync is detected on the non-anchor PRB at P84 again, so that the timer T310 for the non-anchor PRB stops. Furthermore, in a case that the terminal apparatus 2 returns to the anchor PRB (PRB-A), since the timer T310 suspends in a state that out-of-sync has been detected once at P82, it is regarded that out-of-sync is consecutively detected twice (N310=2) based on a case out-of-sync is detected on the anchor PRB at P85 again, so that the timer T310 for the anchor PRB starts. That is, even in a case that out-of-syn or in-sync is detected on the anchor PRB (PRB-A) between P81 and P84, it is regarded that detection at P81 and detection at P84 are consecutive. As another example, at P90 in FIG. 9, based on a case that the terminal apparatus 2 receiving by the non-anchor PRB (PRB-Na1) consecutively detects N310 out-of-sync twice (N310=2), the timer T310 starts. Then, in-sync is detected claudia90@example.net. After that, because of indication for performing the random access procedure from the base station apparatus 3 or other reasons, the terminal apparatus 2 shifts to the anchor PRB (PRB-A). At this time, T310 for PRB-Na1 is suspended, and counted time is retained and the count numbers of times of out-of-sync and in-sync are reset. At P92 on the anchor PRB (PRB-A), out-of-sync and in-sync are newly counted, and in a case that out-of-sync is consecutively detected twice (N310=2), a timer, which is independent from the suspended timer for the non-anchor PRB, starts. Additionally, in a case that in-sync is consecutively detected twice (N311=2), the timer T310 for the anchor PRB stops. In a case that the terminal apparatus 2 returns to the non-anchor PRB (PRB-Na1) at P93, the suspended timer T310 resumes. In this example, since a state that in-sync has been detected once at P91 is reset because of suspension, in a case that in-sync is consecutively detected twice (N311=2) on the non-anchor PRB at P94, the timer T310 for the non-anchor PRB stops. Furthermore, in a case that the terminal apparatus 2 returns to the anchor PRB (PRB-A), the count number of times of out-of-sync on the anchor PRB is reset, so that, in a case that out-of-sync is detected on the anchor PRB at P95, the detection of out-of-sync is regarded as the first time. As another example, at P100 in FIG. 10, based on a case that the terminal apparatus 2 receiving by the non-anchor PRB (PRB-Na1) consecutively detects out-of-sync twice (N310=2), the timer T310 starts. Then, in-sync is detected claudia90@example.net. After that, because of indication for performing the random access procedure from the base station apparatus 3 or other reasons, the terminal apparatus 2 shifts to the anchor PRB (PRB-A). At this time, T310 for PRB-Na1 is suspended, and counted time and count numbers of times of out-of-sync and in-sync are retained. At P102 on the anchor PRB (PRB-A), out-of-sync and in-sync are newly counted, and in a case that out-of-sync is consecutively detected twice (N310=2), a timer, which is independent from the suspended timer for the non-anchor PRB, starts. Additionally, in a case that in-sync is consecutively detected twice (N311=2), the timer T310 for the anchor PRB stops. In a case that the terminal apparatus 2 shifts to the non-anchor PRB (PRB-Na2) different from the non-anchor PRB (PRB-Na1) at P103, the suspended timer T310 stops and the count numbers of times of out-of-sync and in-sync are reset. That is, in a case that the terminal apparatus 2 shifts to the non-anchor PRB (PRB-Na2) different from the non-anchor PRB (PRB-Na1) before shifting to the anchor PRB, the timer T310 and the count number of times for the non-anchor PRB are reset. Furthermore, in a case that the terminal apparatus 2 returns to the anchor PRB (PRB-A), since the timer T310 and the count number of times for the anchor PRB are not reset and the timer T310 suspends in a state that out-of-sync has been detected once at P102, it is regarded that out-of-sync is consecutively detected twice (N310=2) in a case out-of-sync is detected on the anchor PRB at
{'bibliographic_information': "{'country': 'US', 'doc-number': '16095914', 'kind': 'B2', 'date': '20170215', 'invention_title': 'Terminal apparatus, communication method, and integrated circuit'}", 'source_file': './grant/2021/ipg210706.xml', 'source_data': 'USPTO-Grant'}