JP6279419B2 - User device and cell search method - Google Patents

Description

  The present invention relates to a wireless communication system.

  Currently, the use of LTE (Long Term Evolution) networks is being promoted as a successor to third generation (3G) networks. In the LTE standard, when radio quality deteriorates during communication, a user equipment (User Equipment: UE) reports a radio link failure (Radio Link Failure: RLF), and performs predetermined reconnection to connect to a communicable cell. It is specified to execute the process. For example, when a radio link failure is detected, the user apparatus searches for a communicable frequency or cell, and when a communicable cell is detected, communication is started by the LTE network or the 3G network according to the detected cell.

  An example of operation when a user apparatus communicating with the LTE network detects a radio link failure will be described in more detail. As shown in FIG. 1, first, before LTE communication, a user apparatus in an RRC_IDLE state in which an RRC (Radio Resource Control) connection with the LTE network has not been established receives broadcast information from the LTE base station in the area. When the notification information is received, in step S1, the user device stores the received notification information. The notification information includes, for example, system information such as SIB (System Information Block) and various parameters related to establishment of RRC Connection. Specific examples of parameters related to establishment of RRC Connection include a timer T310 for detecting a radio link failure, a timer T311 indicating a period during which reconnection processing can be performed, and N310 indicating the number of out-of-sync detections. N311 indicating the number of times of detection of synchronization (in-sync). In step S2, when the user instructs the user apparatus to start data communication or voice communication, in step S3, the user apparatus establishes an RRC connection with the LTE base station, shifts to an RRC_CONNECTED state, and performs LTE communication. Start.

  Thereafter, in step S4, when the user detects out-of-sync synchronization with the LTE base station N310 times continuously due to radio quality degradation or the like during LTE communication, the user apparatus starts timer T310. After that, when synchronization (in-sync) is detected N311 times consecutively before the expiration of the timer T310, the user apparatus determines that the radio quality deterioration state has been recovered, stops the timer T310, and continues LTE communication. On the other hand, when the synchronization (in-sync) cannot be detected N311 times continuously by the expiration of the timer T310, the user apparatus detects a radio link failure in step S5. The operation after the detection of the radio link failure differs depending on the establishment state of AS Security. That is, when AS Security has not been established, the user apparatus transitions to the RRC IDLE state, and when AS Security has been established, the user apparatus performs re-establishment of the RRC connection (RRC Connection Re-establishment). In the illustrated operation example, a case where AS Security has been established is shown.

  In step S6, the user apparatus starts a timer T311 and searches for a usable frequency in order to search for a communicable cell. Here, when the LTE cell can be detected (step S8-1), the user apparatus establishes an RRC connection with the base station that provides the LTE cell, so that the RRC Connection Re- Execute establishment and start LTE communication. Alternatively, when a radio access technology (Radio Access Technology: RAT) cell (3G cell in the illustrated example) different from the LTE cell is detected (step S8-2), the user equipment moves to the RRC_IDLE state after the transition to the RRC_IDLE state. An RRC connection is established with a base station that provides a 3G cell, and 3G communication is started. On the other hand, when a communicable cell cannot be detected by the expiration of the timer T311 (step S9) (step S8-3), the user apparatus transitions to the RRC_IDLE state and searches again for a communicable cell in step S10. .

JP2011-10306 Special table 2013-535904

3GPP TS36.331 V12.1.0 (2014-03) 3GPP TS36.304 V12.0.0 (2014-03)

  As described above, when a radio link failure is detected due to degradation of radio quality or the like during LTE communication, the user apparatus searches for a communicable frequency or cell, and communicates with the LTE network or 3G network corresponding to the detected cell. Start. On the other hand, with regard to cell search executed when a radio link failure is detected, the current LTE standard does not stipulate in what order or priority the user apparatus should search for a frequency or cell. Depends on the implementation.

  In particular, when a radio link failure due to degradation of radio quality is detected in a situation where there are no LTE cells and only 3G cells, the user equipment quickly searches for 3G cells without searching for LTE cells. It is desirable to resume communication by Further, when the user apparatus searches for an unnecessary frequency, there is a concern about power consumption until a communicable frequency or cell can be detected. For example, as shown in FIG. 2, consider a case where a base station B that provides both an LTE cell and a 3G cell and a user apparatus during LTE communication move to a base station A that provides only a 3G cell. In this case, when the user apparatus detects a radio link failure in LTE communication with the base station B due to degradation of radio quality, it is desirable to preferentially search for a 3G cell provided by the base station A.

  In order to solve the above-described problems, an object of the present invention is to provide a technique for efficiently executing a cell search when a radio link failure is detected.

  In order to solve the above problem, an aspect of the present invention is a user apparatus capable of communicating with both a first wireless communication network and a second wireless communication network, from a base station communicating with the first wireless communication network. An information management unit for managing received information; a radio link failure processing unit for processing a radio link failure in communication with the base station; and the base for timing a period during which reconnection processing for the radio link failure can be performed. A timer management unit for managing a timer notified from the station, and a frequency indicating the frequency of the second radio communication network received from the base station when the timer started in response to detection of the radio link failure expires The present invention relates to a user apparatus having a cell search unit for searching for a communicable cell according to information.

  Another aspect of the present invention is a cell search method by a user apparatus capable of communicating with both a first wireless communication network and a second wireless communication network, wherein information is received from a base station communicating with the first wireless communication network. Receiving, detecting a radio link failure in communication with the base station, and starting a timer notified from the base station to time a period during which reconnection processing can be performed for the radio link failure. And searching for a communicable cell according to frequency information indicating the frequency of the second wireless communication network received from the base station when the timer expires.

  According to the present invention, it is possible to efficiently execute a cell search when a radio link failure is detected.

FIG. 1 is a sequence diagram showing an operation when a radio link failure is detected. FIG. 2 is a schematic diagram illustrating that a UE communicating in an LTE cell has moved in a direction without an LTE area. FIG. 3 is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention. FIG. 4 is a block diagram illustrating a configuration of a user apparatus according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a frequency list notified by LTE_SIB 6 according to an embodiment of the present invention. FIG. 6 is a flowchart showing cell search processing in the user apparatus according to an embodiment of the present invention. FIG. 7 is a diagram illustrating a frequency / cell list according to 3G location performance according to an embodiment of the present invention. FIG. 8 is a flowchart showing cell search processing in a user apparatus according to another embodiment of the present invention. FIG. 9 is a flowchart showing cell search processing in a user apparatus according to still another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In an embodiment to be described later, a user equipment capable of communicating with both wireless communication networks based on different radio access technologies (RAT) is disclosed. In summary, the user apparatus receives 3G cell frequency information (SIB6) and various timers and counters for RRC connection processing as broadcast information from a base station in LTE communication. When a radio link failure is detected in the LTE communication, the user apparatus activates a timer (T311 timer) to measure the period during which reconnection processing can be performed for the radio link failure received as broadcast information, and can communicate with the cell. In order to detect, search for available frequencies. When a communicable cell cannot be detected until the timer expires, the user apparatus preferentially searches for the frequency of the 3G cell received as broadcast information. In another embodiment, after the timer expires, the user apparatus may preferentially search for a 3G cell frequency that has been used before, together with the 3G cell frequency received as the broadcast information. In a further embodiment, during the timer activation, the user equipment may periodically search for a 3G cell frequency that has been used before, together with the 3G cell frequency received as broadcast information.

  Thereby, when an LTE cell is not provided and the user apparatus moves to an area where only the 3G cell is provided, the user apparatus can detect the 3G cell at an early stage and resume communication.

  A radio communication system according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention.

  As illustrated in FIG. 3, the wireless communication system 10 includes a user device 100 and base stations 200A and 200B. The wireless communication system 10 supports different RAT networks, such as an LTE network and a 3G network. In the illustrated embodiment, the base station 200A supports only the 3G network, and the base station 200B supports the LTE network and the 3G network. Support both. However, different RAT networks according to the present invention are not limited to LTE networks and 3G networks, and can be applied to any other two or more networks. In the illustrated embodiment, only two base stations 200 </ b> A and 200 </ b> B are shown, but in general, a large number of base stations 200 are arranged to cover the service area of the wireless communication system 10.

  The user apparatus 100 can communicate with networks of different RATs, and can connect to LTE cells and 3G cells provided by the base stations 200A and 200B. Typically, the user apparatus 100 has any appropriate information having a wireless communication function such as a smart phone, a mobile phone, a tablet, a mobile router, a USB (Universal Serial Bus) type terminal, and an embedded module, as illustrated. It may be a processing device. The user apparatus 100 includes a CPU (Central Processing Unit) such as a processor, a memory apparatus such as a RAM (Random Access Memory) and a flash memory, a wireless communication apparatus for transmitting and receiving radio signals to and from the base stations 200A and 200B, and the like. Composed. For example, each function and process of the user device 100 described later may be realized by the CPU processing or executing data or a program stored in the memory device. However, the user apparatus 100 is not limited to the hardware configuration described above, and may be configured by a circuit that realizes one or more of the processes described below.

  Base stations 200 </ b> A and 200 </ b> B (hereinafter may be collectively referred to as base station 200) are networks such as upper stations and servers that are connected to a core network (not shown) by wireless connection with user apparatus 100. The downlink (DL) packet received from the device is transmitted to the user device 100, and the uplink (UL) packet received from the user device 100 is transmitted to the network device. In the illustrated embodiment, base station 200A provides only 3G cells, and base station 200B provides both LTE and 3G cells.

  Next, the configuration of the user apparatus according to an embodiment of the present invention will be described with reference to FIG. The user apparatus 100 according to the present embodiment can communicate with both of two wireless communication networks using different RATs. For example, these two wireless communication networks are referred to hereinafter as a first wireless communication network and a second wireless communication network for convenience, and may be, for example, an LTE network and a 3G network, respectively. The user apparatus 100 communicates with the base station 200B via a cell of the first wireless communication network, and communicates with the base station 200A via a cell of the second wireless communication network. In the following embodiment, it is assumed that the user apparatus 100 is communicating with the base station 200B by a cell (LTE cell or the like) of the first wireless communication network.

  FIG. 4 is a block diagram illustrating a configuration of a user apparatus according to an embodiment of the present invention. As illustrated in FIG. 4, the user apparatus 100 includes an information management unit 110, a radio link failure processing unit 120, a timer management unit 130, and a cell search unit 140.

  The information management unit 110 manages information received from the base station 200B that communicates with the first wireless communication network. The information received from the base station 200B includes frequency information indicating the frequency of the second wireless communication network.

  Here, in an embodiment in which the first wireless communication network is an LTE network or an LTE-Advanced network and the second wireless communication network is a 3G network, the information management unit 110 uses SIB (System) as broadcast information from the base station 200B. Various parameters for information block) and RRC connection are received, and the received broadcast information is stored.

  Specifically, as various parameters for RRC connection, the information management unit 110 includes a timer T310 for detecting a radio link failure, a timer T311 indicating a period in which reconnection processing can be performed, an out-of-synchronization (out-of N310 indicating the number of detections of -sync) and N311 indicating the number of detections of synchronization (in-sync) may be stored. Moreover, the information management part 110 may store SIB6 which shows the information regarding an adjacent 3G cell as frequency information which shows the frequency of a 2nd radio | wireless communication network. In one embodiment, when the SIB is received from the base station 200B, the information management unit 110 extracts the SIB6 from the received SIB, and the frequency information of the adjacent 3G cell indicated by the SIB6 in the LTE_SIB6 list as shown in FIG. May be stored.

  The radio link failure processing unit 120 processes a radio link failure in communication with the base station 200B. Specifically, when detecting a radio link failure in communication with base station 200B, radio link failure processing unit 120 instructs cell search unit 140 to search for a communicable cell. For example, when the first wireless communication network is an LTE network or an LTE-Advanced network, the radio link failure processing unit 120 is out of synchronization with the base station 200B that provides an LTE cell N310 times consecutively due to radio quality degradation or the like (out When -of-sync) is detected, the T310 timer is started. After that, when synchronization (in-sync) is detected N311 times consecutively before the expiration of the T310 timer, the radio link failure processing unit 120 determines that the radio quality degradation state has been recovered, stops the T310 timer, and stops the base station Communication with 200B is continued. On the other hand, if synchronization (in-sync) cannot be detected N311 times consecutively before the expiration of the T310 timer, the radio link failure processing unit 120 determines that a radio link failure has occurred and searches for a communicable cell. The cell search unit 140 is instructed to do so. When a communicable cell is detected by a cell search process as described later, the radio link failure processing unit 120 executes a connection process on the detected cell. On the other hand, when a communicable cell cannot be detected, the radio link failure processing unit 120 determines that the user apparatus 100 is out of service from both the first radio communication network and the second radio communication network.

  The timer management unit 130 manages the timer notified from the base station 200B in order to measure the period during which reconnection processing for a radio link failure can be performed. Here, when the radio link failure processing unit 120 detects a radio link failure, the timer management unit 130 starts the timer. For example, when the first wireless communication network is an LTE network or an LTE-Advanced network, the timer may be a T311 timer broadcast from the base station 200B. When the cell search unit 140 detects a communicable cell while the timer started by the cell search process as described later is counted, the timer management unit 130 stops and resets the timer. On the other hand, when the timer expires without detecting a communicable cell, timer management unit 130 notifies cell search unit 140 of the expiration of the timer.

  When the timer started in response to the detection of the radio link failure expires, the cell search unit 140 searches for a communicable cell according to the frequency information indicating the frequency of the second radio communication network received from the base station 200B. In an embodiment in which the first radio communication network is an LTE network or an LTE-Advanced network and the second radio communication network is a 3G network, the cell search unit 140 is started with a T311 timer started in response to detection of a radio link failure. Is expired, the frequency shown in the LTE_SIB6 list storing the 3G frequency information of SIB6 broadcast from the base station 200B is preferentially searched.

  Specifically, when a radio link failure is detected by the radio link failure processing unit 120, the cell search unit 140 uses the LTE cell and 3G cell frequencies to detect communicable cells while the timer is activated. Search for possible frequencies. When a communicable cell can be detected before the timer expires, the cell search unit 140 notifies the radio link failure processing unit 120 of the detected cell. On the other hand, if no cell is detected before the timer expires, the cell search unit 140 searches for the frequency of the 3G cell in the LTE_SIB6 list held by the information management unit 110 with priority. Thereafter, when a communicable 3G cell is detected by the priority search, the cell search unit 140 notifies the radio link failure processing unit 120 of the detected 3G cell. On the other hand, when a communicable 3G cell cannot be detected from the 3G frequency shown in the LTE_SIB6 list, the cell search unit 140 searches again for available frequencies including the LTE and 3G frequencies. Thereafter, when a communicable cell can be detected by the re-search, the cell search unit 140 notifies the radio link failure processing unit 120 of the detected cell. On the other hand, when a communicable cell cannot be detected, the radio link failure processing unit 120 determines that the user device 100 is outside the network area.

  Next, cell search processing when a radio link failure is detected in a user apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 6 is a flowchart showing cell search processing in the user apparatus according to an embodiment of the present invention. This process is started when the user apparatus 100 communicates with the base station 200B via the LTE cell. As described above, when the user apparatus 100 is located in the base station 200B, the user apparatus 100 acquires various parameters (T310, T311, N310, N311, etc.) for SIB or RRC connection by broadcast information. The information management unit 110 manages the acquired information.

  As illustrated in FIG. 6, in step S101, the radio link failure processing unit 120 detects a radio link failure in LTE communication with the base station 200B. For example, the radio link failure processing unit 120 starts the T310 timer when detecting out-of-sync with the base station 200B for N310 times consecutively. After that, when the synchronization (in-sync) is detected N311 times before the expiration of the T310 timer, the radio link failure processing unit 120 determines that the radio quality degradation state has been recovered, stops the T310 timer, and Continue communication with station 200B. On the other hand, if synchronization (in-sync) cannot be detected N311 times consecutively before the expiration of the T310 timer, the radio link failure processing unit 120 determines that a radio link failure has occurred.

  In step S102, the timer management unit 130 starts a timer. In one embodiment, in response to detection of a radio link failure, the timer management unit 130 starts a T311 timer, and the cell search unit 140 uses a frequency that can be used by the user apparatus 100 to detect a communicable cell. Search for bands.

  In step S103, it is determined whether the cell search unit 140 has detected a communicable cell before the timer expires. If the cell search unit 140 can detect a communicable cell before the timer expires (S103: YES), the radio link failure processing unit 120 executes reconnection processing on the detected cell in step S106. For example, when the detected cell is an LTE cell, the radio link failure processing unit 120 executes an RRC connection re-establishment process on the detected cell. On the other hand, when the detected cell is a 3G cell, the radio link failure processing unit 120 transitions to the RRC_IDLE state, and performs RRC connection establishment processing (RRC Connection Establishment) on the detected cell. On the other hand, when the cell search unit 140 cannot detect a communicable cell before the timer expires (S103: NO), the cell search unit 140 preferentially uses the 3G frequency notified by the broadcast information in step S104. Search for.

  In step S105, it is determined whether the cell search unit 140 has detected a communicable 3G cell. When the cell search unit 140 can detect a communicable 3G cell (S105: YES), the radio link failure processing unit 120 executes connection processing on the detected 3G cell in step S106. On the other hand, when the cell search unit 140 cannot detect a communicable 3G cell (S105: NO), in step S107, the cell search unit 140 uses frequency bands (LTE and 3G frequencies) that can be used by the user apparatus 100. Regardless of whether the cell is communicable with the LTE cell or the 3G cell. If the cell search unit 140 can detect a communicable LTE cell or 3G cell (S108: YES), the radio link failure processing unit 120 executes connection processing for the detected LTE cell or 3G cell in step S106. To do. On the other hand, when the cell search unit 140 cannot detect any communicable cell (S108: NO), the radio link failure processing unit 120 determines in step S109 that the user apparatus 100 is out of the network area.

  Next, cell search processing when a radio link failure is detected in a user apparatus according to another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the user apparatus 100 preferentially searches for a frequency or cell that has been used before, together with the frequency of the SIB6 notified by the broadcast information. In other words, in this embodiment, the information management unit 110 maintains a 3G in-zone performance list indicating the cell ID and frequency of the 3G cell that has been in the area as shown in FIG. 7 and is in the 3G cell. The cell ID and frequency of the 3G cell acquired by this are sequentially added to the 3G in-zone performance list. The cell search unit 140 uses the LTE_SIB6 list shown in FIG. 5 and the 3G in-zone performance list shown in FIG. 7 to preferentially search the frequencies shown in these two lists.

  FIG. 8 is a flowchart showing cell search processing in a user apparatus according to another embodiment of the present invention. This process is started when the user apparatus 100 communicates with the base station 200B via the LTE cell. As described above, when the user apparatus 100 is located in the base station 200B, the user apparatus 100 acquires various parameters (T310, T311, N310, N311, etc.) for SIB and RRC connection by broadcast information. . Moreover, the user apparatus 100 acquires the frequency of the 3G cell when the user apparatus 100 is located in the 3G cell. The information management unit 110 manages the received broadcast information and registers the acquired 3G cell frequency in the 3G in-zone performance list.

  As shown in FIG. 8, in step S201, the radio link failure processing unit 120 detects a radio link failure in LTE communication with the base station 200B. For example, the radio link failure processing unit 120 starts the T310 timer when detecting out-of-sync with the base station 200B for N310 times consecutively. After that, when the synchronization (in-sync) is detected N311 times before the expiration of the T310 timer, the radio link failure processing unit 120 determines that the radio quality degradation state has been recovered, stops the T310 timer, and Continue communication with station 200B. On the other hand, if synchronization (in-sync) cannot be detected N311 times consecutively before the expiration of the T310 timer, the radio link failure processing unit 120 determines that a radio link failure has occurred.

  In step S202, the timer management unit 130 starts a timer. In one embodiment, in response to detection of a radio link failure, the timer management unit 130 starts a T311 timer, and the cell search unit 140 uses a frequency that can be used by the user apparatus 100 to detect a communicable cell. Search for bands.

  In step S203, it is determined whether the cell search unit 140 has detected a communicable cell before the timer expires. If the cell search unit 140 can detect a communicable cell before the timer expires (S203: YES), the radio link failure processing unit 120 executes reconnection processing on the detected cell in step S206. For example, when the detected cell is an LTE cell, the radio link failure processing unit 120 executes an RRC connection re-establishment process on the detected cell. On the other hand, when the detected cell is a 3G cell, the radio link failure processing unit 120 transitions to the RRC_IDLE state, and performs RRC connection establishment processing (RRC Connection Establishment) on the detected cell. On the other hand, if the cell search unit 140 cannot detect a communicable cell by the expiration of the timer (S203: NO), the cell search unit 140, together with the 3G frequency notified by the broadcast information in step S204, The frequency of the 3G cell communicated before shown in the area achievement list is preferentially searched.

  In step S205, it is determined whether the cell search unit 140 has detected a communicable 3G cell. When the cell search unit 140 can detect a communicable 3G cell (S205: YES), the radio link failure processing unit 120 executes reconnection processing on the detected 3G cell in step S206. On the other hand, when the cell search unit 140 cannot detect a communicable 3G cell (S205: NO), in step S207, the cell search unit 140 uses frequency bands (LTE and 3G frequencies) that can be used by the user apparatus 100. Regardless of whether the cell is communicable with the LTE cell or the 3G cell. When the cell search unit 140 can detect a communicable LTE cell or 3G cell (S208: YES), the radio link failure processing unit 120 executes connection processing for the detected LTE cell or 3G cell in step S206. To do. On the other hand, when the cell search unit 140 cannot detect any communicable cell (S208: NO), the radio link failure processing unit 120 determines in step S209 that the user apparatus 100 is outside the network area.

  In still another embodiment, the cell search unit 140 does not wait until the timer expires, and the 3G communicated before being indicated in the 3G in-zone performance list together with the frequency of the 3G cell notified by the broadcast information during the timer activation. You may search the frequency of a cell. For example, while the timer is activated, the cell search unit 140 may periodically search for the frequency of the 3G cell communicated before indicated in the 3G in-zone performance list together with the frequency of the 3G cell notified by the broadcast information. . For this reason, the timer management unit 130 has a temporary timer (T_tempA) whose expiration time is shorter than the timer described above. That is, the temporary timer (T_tempA) is set to a value equal to or less than the T311 timer broadcast from the base station 200B.

  FIG. 9 is a flowchart showing cell search processing in a user apparatus according to still another embodiment of the present invention.

  As shown in FIG. 9, in step S301, the radio link failure processing unit 120 detects a radio link failure in LTE communication with the base station 200B. For example, the radio link failure processing unit 120 starts the T310 timer when detecting out-of-sync with the base station 200B for N310 times consecutively. Thereafter, when synchronization (in-sync) is detected N311 times before the expiration of the T310 timer, the radio link failure processing unit 120 determines that the wireless quality failure state has been recovered, and stops the T310 timer. On the other hand, if synchronization (in-sync) cannot be detected N311 times consecutively before the expiration of the T310 timer, the radio link failure processing unit 120 determines that a radio link failure has occurred.

  In step S302, the timer management unit 130 starts a timer. In one embodiment, in response to detection of a radio link failure, the timer management unit 130 starts a T311 timer, and the cell search unit 140 uses a frequency that can be used by the user apparatus 100 to detect a communicable cell. Search for bands.

  In step S303, the timer management unit 130 starts a temporary timer. In one embodiment, in response to detecting a radio link failure, timer manager 130 activates a T_tempA timer with an expiration time shorter than the T311 timer.

  In step S304, the timer management unit 130 determines whether the timer has expired. If the timer has expired (S304: YES), it is determined in step S305 whether the cell search unit 140 has detected a communicable cell. If the cell search unit 140 can detect a communicable cell before the timer expires (S305: YES), the radio link failure processing unit 120 executes reconnection processing on the detected cell in step S311. For example, when the detected cell is an LTE cell, the radio link failure processing unit 120 executes an RRC connection re-establishment process on the detected cell. On the other hand, when the detected cell is a 3G cell, the radio link failure processing unit 120 transitions to the RRC_IDLE state, and executes an RRC connection establishment process (RRC Connection Establishment) on the detected cell. On the other hand, if the cell search unit 140 cannot detect a communicable cell before the timer expires (S305: NO), the cell search unit 140 determines that the 3G cell frequency notified by the broadcast information is 3G in step S306. The frequency of the 3G cell communicated before shown in the in-zone performance list is searched. In step S307, it is determined whether the cell search unit 140 has detected a communicable 3G cell. When the cell search unit 140 can detect a communicable 3G cell (S307: YES), the radio link failure processing unit 120 executes reconnection processing on the detected 3G cell in step S311. On the other hand, when the cell search unit 140 cannot detect a communicable 3G cell (S307: NO), in step S308, the cell search unit 140 uses the frequency bands (LTE and 3G frequencies) that the user apparatus 100 can use. Regardless of whether the cell is communicable with the LTE cell or the 3G cell. When the cell search unit 140 can detect a communicable LTE cell or 3G cell (S309: YES), the radio link failure processing unit 120 executes connection processing for the detected LTE cell or 3G cell in step S311. To do. On the other hand, when the cell search unit 140 cannot detect any communicable cell (S309: NO), the radio link failure processing unit 120 determines in step S310 that the user apparatus 100 is out of the network area.

  On the other hand, while the timer does not expire (S304: NO), in step S312, it is determined whether the cell search unit 140 has detected a communicable cell before the temporary timer expires. If the cell search unit 140 can detect a communicable cell before the temporary timer expires (S312: YES), the radio link failure processing unit 120 executes reconnection processing on the detected cell in step S311. For example, when the detected cell is an LTE cell, the radio link failure processing unit 120 executes an RRC connection re-establishment process on the detected cell. On the other hand, when the detected cell is a 3G cell, the radio link failure processing unit 120 transitions to the RRC_IDLE state, and executes an RRC connection establishment process (RRC Connection Establishment) on the detected cell. On the other hand, if the cell search unit 140 cannot detect a communicable cell before the provisional timer expires (S312: NO), the cell search unit 140, in step S313, along with the frequency of the 3G cell notified by the broadcast information, The frequency of the 3G cell communicated before shown in the 3G in-zone performance list is searched. For example, the cell search unit 140 may periodically search for the frequency of the 3G cell communicated before indicated in the 3G in-zone performance list together with the frequency of the 3G cell notified by the broadcast information while the timer is activated. .

  In step S314, it is determined whether the cell search unit 140 has detected a communicable 3G cell. If the cell search unit 140 can detect a communicable 3G cell (S314: YES), the radio link failure processing unit 120 executes reconnection processing on the detected 3G cell in step S311. On the other hand, if the cell search unit 140 cannot detect a communicable 3G cell (S314: NO), the cell search unit 140 uses the frequency bands (LTE and 3G frequencies) that can be used by the user apparatus 100 in step S315. Regardless of whether the cell is communicable with the LTE cell or the 3G cell. When the cell search unit 140 can detect a communicable LTE cell or 3G cell (S316: YES), the radio link failure processing unit 120 executes connection processing for the detected LTE cell or 3G cell in step S311. To do. On the other hand, when the cell search unit 140 cannot detect any communicable cell (S316: NO), the process returns to step S303, and the timer management unit 130 restarts the temporary timer and performs the above-described process. repeat.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the specific embodiment mentioned above, In the range of the summary of this invention described in the claim, various deformation | transformation・ Change is possible.

DESCRIPTION OF SYMBOLS 10 Wireless communication network 100 User apparatus 110 Information management part 120 Radio link failure processing part 130 Timer management part 140 Cell search part 200 Base station

Claims (10)

A user device capable of communicating with both the first wireless communication network and the second wireless communication network,
An information management unit for managing information received from a base station communicating with the first wireless communication network;
A radio link failure processing unit for processing a radio link failure in communication with the base station;
A timer management unit for managing a timer notified from the base station in order to measure a period in which reconnection processing can be performed for the radio link failure;
A cell search unit for searching for a communicable cell according to frequency information indicating a frequency of the second radio communication network received from the base station when the timer started in response to detection of the radio link failure expires; ,
A user device. The first wireless communication network is an LTE (Long Term Evolution) network or an LTE-Advanced network,
The second wireless communication network is a third generation (3G) network;
The timer is a T311 timer broadcast from the base station,
The user apparatus according to claim 1, wherein the frequency information is 3G frequency information of SIB (System Information Block) 6 broadcast from the base station. The information management unit stores frequency information indicating a frequency of the second wireless communication network in which the user apparatus has been previously located,
3. The user apparatus according to claim 1, wherein the cell search unit further searches for the communicable cell according to frequency information indicating a frequency of the second wireless communication network in which the cell is located previously. The timer management unit manages a temporary timer that times a period shorter than the timer notified from the base station,
When the temporary timer started in response to detection of the radio link failure expires, the cell search unit can communicate with the cell according to the frequency information indicating the frequency of the second radio communication network received from the base station. The user device according to claim 1, wherein the user device is searched.   The user apparatus according to any one of claims 1 to 4, wherein when the cell search unit detects the communicable cell, the radio link failure processing unit executes a connection process on the detected cell.   When the communicable cell could not be detected, the cell search unit searches for the communicable cell from frequencies that can be used by the user device in the first wireless communication network and the second wireless communication network. The user apparatus as described in any one of Claims 1 thru | or 5.   When the cell search unit cannot detect the communicable cell from the frequency that can be used by the user apparatus in the first radio communication network and the second radio communication network, the radio link failure processing unit The user apparatus according to claim 6, wherein the user apparatus determines that the user apparatus is out of range from both the first wireless communication network and the second wireless communication network. A cell search method by a user apparatus capable of communicating with both a first wireless communication network and a second wireless communication network,
Receiving information from a base station communicating via the first wireless communication network;
Detecting a radio link failure in communication with the base station;
Starting a timer notified from the base station in order to time a period during which reconnection processing for the radio link failure can be performed;
When the timer expires, searching for a communicable cell according to frequency information indicating the frequency of the second wireless communication network received from the base station;
A cell search method comprising: The first wireless communication network is an LTE (Long Term Evolution) network or an LTE-Advanced network,
The second wireless communication network is a third generation (3G) network;
The timer is a T311 timer broadcast from the base station,
The cell search method according to claim 8, wherein the frequency information is 3G frequency information of SIB (System Information Block) 6 broadcast from the base station. Storing the frequency information indicating the frequency of the second wireless communication network in which the user apparatus was previously located;
The cell search according to claim 8 or 9, wherein the step of searching for the communicable cell further searches for the communicable cell according to frequency information indicating a frequency of the second wireless communication network that has been previously located. Method.

Images