First radio station, second radio station, radio terminal, and communication control method therefor

Abstract

To enable a radio terminal to establish radio connections with cells of a plurality of radio stations, in order to achieve carrier aggregation of cells of different radio stations.SOLUTION: A first radio station that operates a first cell transmits a first request to a second radio station that operates a second cell, the first request being a request for the second cell to prepare for communication with a radio terminal on the second cell while a first radio connection is maintained on the first cell, the first radio connection being established between the first radio station and the radio terminal. The first request includes DRB Identity and E-RAB ID indicating a data path between the radio terminal and S-GW for the communication with the radio terminal on the second cell. The first radio station receives radio resource configuration information of the second cell from the second radio station, and transmits RRC Connection Reconfiguration message including at least the radio resource configuration information to the radio terminal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless communication system in which a wireless station and a wireless terminal communicate with each other by using a plurality of cells. [Background technology]

[0002] In order to improve communication quality degradation caused by the recent rapid increase in mobile traffic and to realize even faster communication, 3GPP (registered trademark) LTE (Long Term Evolution) is standardizing a Carrier Aggregation (CA) function in which a radio base station (eNode B: eNB) and a radio terminal (User Equipment: UE) communicate using multiple cells. Note that the cells that a UE can use in CA are limited to the cells of one eNB (i.e., the cells operated by the eNB).

[0003] The procedure of CA will be described with reference to FIG. 17 (Non-Patent Document 1). FIG. 17 shows an example in which a UE performs CA between a first cell (Cell1) and a second cell (Cell2) operated by an eNB. In step S1, the UE and the eNB establish a radio connection in the first cell (RRC Connection Establishment). In step S2, the UE receives downlink data from the eNB in ​​the first cell (Downlink data on Cell1). Here, the first cell becomes a primary cell (Primary cell: PCell) for the UE.

[0004] In step S3, the eNB determines that it is necessary to configure a secondary cell (SCell) for the UE, and configures the second cell as an SCell in the PCell (RRC Connection Reconfiguration on Cell1 (including Configuration of Cell2 (Secondary cell: SCell)). In step S4, the UE transmits a completion notification to the eNB (RRC Connection Reconfiguration Complete) in response to the completion of the configuration of the second cell, i.e., the preparation for using the second cell is complete.

[0005] In step S5, the eNB transmits a notification of starting use of the second cell to the UE (Cell2 Activation). In step S6, the UE receives downlink data using the first and second cells simultaneously (DL data on Cell1 and Cell2). Note that it is sufficient for the UE in step S6 to be able to use the first and second cells simultaneously for receiving downlink data. In other words, the UE does not need to always receive downlink data in both the first and second cells. Whether to use either one or both of the first and second cells for receiving downlink data is determined based on, for example, the amount of downlink data or the service used by the UE. When the UE transmits uplink data in the second cell, this can also be achieved basically by the same procedure as shown in FIG. 17.

[0006] A UE that performs CA has at least part of the functions of the physical layer and the MAC (Medium Access Control) layer for each integrated cell, but the configuration above the RLC (Radio Link Control) layer is the same as when CA is not performed. Therefore, the core network (Evolved Packet Core: EPC) is not aware of whether the UE is performing CA or not.

[0007] Also, the concept of Inter-eNB CA has been proposed to integrate multiple cells operated by different eNBs in a heterogeneous network (HetNet) environment (Non-Patent Document 2). For example, in Inter-eNB CA, it is considered to use a macro cell operated by a macro base station (Macro eNB: MeNB) and a pico cell operated by a pico base station (Pico eNB: PeNB).

[0008] Furthermore, a method has been proposed in which macrocells, which have a wide coverage area, are used to transmit and receive control signals such as UE mobility management, and picocells, which have relatively good communication quality, are used to transmit and receive data signals such as user data (Non-Patent Document 3). [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] 3GPP TS 36.331 V11.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification", Section 5.3.5, July 2012 [Non-Patent Document 2] 3GPP RWS-120046, Samsung Electronics, "Technologies for Rel-12 and Onwards", 3GPP TSG RAN Workshop on Rel-12 and Onwards Ljubljana, Slovenia, 11-12 June 2012 [Non-Patent Document 3] 3GPP RWS-120010, NTT DOCOMO, "Requirements, Candidate Solutions & Technology Roadmap for LTE Rel-12 Onward", 3GPP TSG RAN Workshop on Rel-12 and Onwards Ljubljana, Slovenia, 11-12 June 2012 Summary of the Invention [Problem to be solved by the invention]

[0010] In conventional carrier aggregation (CA), a wireless terminal (UE) communicates using multiple cells operated by one wireless station (eNB), so that the UE can set multiple cells. On the other hand, in carrier aggregation of multiple cells operated by different eNBs (Inter-eNB CA), the UE needs to perform cell settings (e.g., RRC Connection Setup or RRC Connection Reconfiguration, or both) for communication in each cell so that the UE can simultaneously use multiple cells operated by different eNBs. However, in the current LTE specifications, when a UE has established a wireless connection in a cell of one eNB, it cannot establish a wireless connection in a cell of another eNB.

[0011] Therefore, one object of the present invention is to provide a wireless communication system, a wireless station, a wireless terminal, a communication control method, and a program that enable one wireless terminal to establish wireless connections in cells of multiple wireless stations in order to realize carrier aggregation of multiple cells operated by different wireless stations. [Means for solving the problem]

[0012] In a first aspect, a wireless communication system includes a first wireless station that operates a first cell and a second wireless station that operates a second cell. The first wireless station is configured to request or instruct the second wireless station to prepare for communication with a wireless terminal in the second cell while a first wireless connection with the wireless terminal in the first cell is established. Furthermore, the first wireless station is configured to instruct the wireless terminal or the second wireless station to establish a second wireless connection between the second wireless station and the wireless terminal in the second cell while maintaining the first wireless connection.

[0013] In a second aspect, a first radio station operating a first cell includes a communication control unit that controls communication with a radio terminal with which a first radio connection is established in the first cell. The communication control unit is configured to request or instruct the second radio station to prepare for communication with the radio terminal in the second cell while the first radio connection with the radio terminal in the first cell is established. Furthermore, the communication control unit is configured to instruct the radio terminal or the second radio station to establish a second radio connection between the second radio station and the radio terminal in the second cell while maintaining the first radio connection.

[0014] In a third aspect, a second radio station operating a second cell includes a communication control unit that controls communication with a radio terminal. The communication control unit is configured to prepare for communication with the radio terminal in the second cell in response to an instruction or request from the first radio station while a first radio connection with the radio terminal is established in a first cell operated by the first radio station. Furthermore, the communication control unit is configured to establish a second radio connection between the second radio station and the radio terminal in the second cell in response to an instruction from the first radio station while the first radio connection is maintained.

[0015] In a fourth aspect, a wireless terminal includes a wireless communication unit and a control unit, the control unit being configured to set the second cell while maintaining a first wireless connection with the first wireless station in response to an instruction from the first wireless station or the second wireless station according to the first, second or third aspect.

[0016] In a fifth aspect, a communication control method in a first radio station that operates a first cell includes: (a) requesting or instructing a second radio station to prepare for communication with a radio terminal in a second cell operated by the second radio station while a first radio connection between the first radio station and the radio terminal in the first cell is established; and (b) instructing the radio terminal or the second radio station to establish a second radio connection with the radio terminal in the second cell while maintaining the first radio connection; Includes.

[0017] In a sixth aspect, a communication control method in a second radio station that operates a second cell includes: (a) preparing for communication with a wireless terminal in the second cell in response to an instruction or request from a first wireless station while a first wireless connection with the wireless terminal is established in a first cell operated by the first wireless station; and (b) in response to an instruction from the first radio station, establishing a second radio connection between the second radio station and the radio terminal in the second cell while maintaining the first radio connection; Includes.

[0018] In a seventh aspect, a communication control method in a wireless terminal includes setting up the second cell while maintaining a first wireless connection with the first wireless station in response to an instruction from the first wireless station or the second wireless station relating to the first, second or third aspect described above.

[0019] In an eighth aspect, a program includes a group of instructions for causing a computer to perform the communication control method in a first radio station according to the fifth aspect described above.

[0020] In a ninth aspect, a program includes a group of instructions for causing a computer to perform the communication control method in a second radio station according to the sixth aspect described above.

[0021] In a tenth aspect, a program includes a group of instructions for causing a computer to perform the communication control method in a wireless terminal according to the seventh aspect described above. Effect of the Invention

[0022] According to the above-described aspects, it is possible to provide a wireless communication system, a wireless station, a wireless terminal, a communication control method, and a program that enable a wireless terminal to establish a wireless connection in cells of multiple wireless stations in order to realize carrier aggregation of multiple cells operated by different wireless stations. [Brief description of the drawings]

[0023] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a first wireless station according to the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a second wireless station according to the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a wireless terminal according to the first embodiment. [Diagram 5] 4 is a flowchart showing an example of operation of the first wireless station according to the first embodiment (procedure example 1). [Figure 6] 5 is a flowchart showing an operation example of the second wireless station according to the first embodiment (procedure example 1). [Figure 7] 4 is a flowchart showing an operation example of the wireless terminal according to the first embodiment (procedure example 1). [Figure 8] 1 is a sequence diagram showing an example of a communication control method in a wireless communication system according to a first embodiment (procedure example 1). [Figure 9]5 is a flowchart showing an operation example of the first wireless station according to the first embodiment (procedure example 2). [Figure 10] 6 is a flowchart showing an operation example of the second wireless station according to the first embodiment (procedure example 2). [Figure 11] 5 is a flowchart showing an operation example of the wireless terminal according to the first embodiment (procedure example 2). [Figure 12] 4 is a sequence diagram showing an example of a communication control method in the wireless communication system according to the first embodiment (procedure example 2). FIG. [Figure 13] 13 is a sequence diagram showing an example of a communication control method in a wireless communication system according to a second embodiment (Procedure Example 3). FIG. [Figure 14] 13 is a sequence diagram showing an example of a communication control method in a wireless communication system according to a second embodiment (Procedure Example 4). FIG. [Figure 15] FIG. 11 is a diagram illustrating an example of the configuration of a wireless communication system according to a third embodiment. [Figure 16] FIG. 11 is a sequence diagram showing an example of a communication control method in a wireless communication system according to a third embodiment. [Figure 17] FIG. 1 is a sequence diagram showing a carrier aggregation procedure of LTE (background art). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the following, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as necessary for clarity of explanation.

[0025] <First embodiment> FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. The wireless communication system according to this embodiment includes a first wireless station 1, a second wireless station 2, and a wireless terminal 3. The wireless stations 1 and 2 operate a first cell 10 and a second cell 20, respectively. The wireless stations 1 and 2 are, for example, wireless base stations or base station control stations. The wireless terminal 3 is configured to be able to establish a second wireless connection in the second cell 20 while maintaining a first wireless connection in the first cell 10. This allows the wireless terminal 3 to simultaneously use multiple cells (for example, cells 10 and 20) for transmitting or receiving a signal (for example, user data or control information). In other words, the wireless terminal 3 supports carrier aggregation of multiple cells operated by different wireless stations.

[0026] FIG. 1 illustrates a HetNet environment. Specifically, the first cell 10 illustrated in FIG. 1 has a wider coverage than the second cell 20. FIG. 1 also illustrates a hierarchical cell configuration in which the second cell 20 is arranged in the first cell 10. However, the cell configuration illustrated in FIG. 1 is merely an example. For example, the first and second cells 10 and 20 may have the same degree of coverage. In other words, the wireless communication system according to this embodiment may be applied to a homogeneous network environment.

[0027] In order to allow the wireless terminal 3 to simultaneously use the cells 10 and 20 operated by different wireless stations 1 and 2 for signal reception or transmission, the wireless communication system of this embodiment needs to establish a wireless connection with the wireless terminal 3 in each of the cells 10 and 20. To achieve this, the wireless communication system of this embodiment operates as follows. That is, the wireless station 1 is configured to request or instruct the wireless station 2 to prepare for communication with the wireless terminal 3 in the cell 20 while a first wireless connection with the wireless terminal 3 in the cell 10 is established in order to allow the wireless terminal 3 to simultaneously use the cells 10 and 20 for signal reception or transmission. Furthermore, the wireless station 1 is configured to instruct the wireless terminal 3 or the wireless station 2 to establish a second wireless connection with the wireless terminal 3 in the cell 20 while maintaining the first wireless connection. As a result, in this embodiment, the wireless terminal 3 can establish wireless connections in multiple cells 10 and 20 in order to realize carrier aggregation of the cells 10 and 20 operated by different wireless stations 1 and 2. In addition, the above-mentioned "using multiple cells simultaneously" is not limited to actually receiving or transmitting signals in multiple cells simultaneously, but also includes a state in which multiple cells are both capable of receiving or transmitting signals but actually receiving or transmitting a signal in one of the cells, receiving or transmitting different types of signals in each of the multiple cells, or using each of the multiple cells for either receiving or transmitting a signal, etc.

[0028] In procedure example 1, the wireless station 1 instructs the wireless terminal 3 to establish a second wireless connection in the cell 20. Then, in response to the instruction from the wireless station 1, the wireless terminal 3 sets the cell 20. This allows the wireless terminal 3 to establish a second wireless connection with the wireless station 2 in the cell 20. Here, the wireless station 1 only needs to send the instruction to the wireless terminal 3 via a control connection (e.g., a control channel or a signaling radio bearer (SRB)) between the wireless station 1 and the wireless terminal 3 in the cell 10. This allows the wireless terminal 3 to easily make preparations for communication using the cell 20 of the wireless station 2 while communicating with the wireless station 1 (that is, transmitting or receiving, or both, a signal carrying user data or the like).

[0029] In procedure example 2, the wireless station 1 instructs the wireless station 2 to establish a second wireless connection in the cell 20. In response to the instruction from the wireless station 1, the wireless station 2 instructs the wireless terminal 3 to establish a second wireless connection in the cell 20. Then, in response to the instruction from the wireless station 1, the wireless terminal 3 sets the cell 20. This allows the wireless terminal 3 to establish a second wireless connection with the wireless station 2 in the cell 20. Here, the instruction to establish the second wireless connection from the wireless station 1 to the wireless station 2 may be transmitted simultaneously with an instruction (or request) to prepare for communication with the wireless terminal 3 in the cell 20, or may be used as the instruction (or request) to prepare for communication. In other words, the message of the instruction (or request) to prepare for communication with the wireless terminal 3 in the cell 20 may explicitly or implicitly indicate an instruction to establish the second wireless connection from the wireless station 1 to the wireless station 2. That is, in response to receiving an instruction (or request) to prepare for communication with the wireless terminal 3, the wireless station 2 may prepare for communication with the wireless terminal 3 and instruct the wireless terminal 3 to establish a second wireless connection. The instruction from the wireless station 2 to the wireless terminal 3 may be sent from the wireless station 2 to the wireless terminal 3 via a control connection (e.g., a control channel or a signaling wireless bearer) between the wireless station 1 and the wireless terminal 3 in the cell 10. Furthermore, in order to enable the wireless terminal 3 to receive the instruction sent from the wireless station 2, the wireless station 1 may notify the wireless terminal 3 of wireless resource setting information required for reception in the cell 20 via the control connection in the cell 10.

[0030] In this specification, "establishing a wireless connection" corresponds to, for example, a wireless terminal and a wireless station being in a state where they can communicate with each other, or a state where the wireless terminal and the wireless station are in a state where they share information necessary for communication. Furthermore, "setting a cell in a wireless terminal" corresponds to, for example, a wireless terminal being in a state where a cell is available, or a wireless terminal being in a state where preparations for using a cell are complete. Furthermore, "preparing a wireless station for communication with a wireless terminal" corresponds to, for example, a state where information necessary for a wireless connection with a wireless terminal is held, information necessary for a wireless connection with a wireless terminal is generated, a state where a wireless connection with a wireless terminal is permitted, or a state where communication with a wireless terminal can be accepted.

[0031] In the above-mentioned procedure example 1 and procedure example 2, terminal individual information of the wireless terminal 3 related to the establishment of the first wireless connection or the establishment of the second wireless connection may be sent from the wireless station 1 to the wireless station 2, or from the wireless station 2 to the wireless station 1. Also, in the procedure example 1 and procedure example 2, at least one of wireless connection setting information and wireless access information related to the establishment of the first wireless connection or the establishment of the second wireless connection may be sent from the wireless station 2 to the wireless station 1, or from the wireless station 1 to the wireless station 2.

[0032] The terminal individual information of the wireless terminal 3 related to the establishment of the first wireless connection or the establishment of the second wireless connection may include at least one of the information elements listed below. Wireless device capability information Wireless device identifier information Select network information Bearer information Radio resource control information - Wireless terminal movement history information Service Information

[0033] The wireless connection setting information related to the establishment of the first wireless connection or the establishment of the second wireless connection may include at least one of the information elements listed below. Serving cell information System Information Radio resource setting information Measurement setting information Movement control information Security settings information

[0034] The radio access information related to the establishment of the first radio connection or the establishment of the second radio connection may include at least one of the information elements listed below. Radio Access Identifier information Wireless access resource information

[0035] A possible application of these procedure examples 1 and 2 is when the first wireless station 1 is a wireless station that operates (manages) a cell with a relatively large coverage, and the second wireless station 2 is a low power wireless station (Low Power Node: LPN) that operates (manages) a cell with a small coverage, but is not limited thereto. The LPN may be, for example, a wireless station having the same functions as the wireless station 1, or a new type of network node (New Node) having fewer functions than the wireless station 1. The second cell may also be a new type of cell (New Cell Type) that is different from the conventional one and that includes a new type of carrier (New Carrier Type) that is different from the conventional one as a component.

[0036] Next, a configuration example of the wireless stations 1 and 2 and the wireless terminal 3 according to this embodiment will be described below. FIG. 2 is a block diagram showing a configuration example of the first wireless station 1. The wireless communication unit 11 receives an uplink signal transmitted from the wireless terminal 3 via an antenna. The received data processing unit 13 restores the received uplink signal. The obtained received data is transferred to another network node, for example, a data relay device or a mobility management device of a higher-level network, or another wireless station, via the communication unit 14. For example, the uplink user data received from the wireless terminal 3 is transferred to a data relay device of the higher-level network. Furthermore, the control data of the non-access stratum (NAS) among the control data received from the wireless terminal 3 is transferred to the mobility management device of the higher-level network. Furthermore, the received data processing unit 13 receives the control data to be transmitted to the wireless station 2 from the communication control unit 15, and transmits the control data to the wireless station 2 via the communication unit 14.

[0037] The transmission data processing unit 12 acquires user data addressed to the wireless terminal 3 from the communication unit 14, and performs error correction coding, rate matching, interleaving, etc. to generate a transport channel. Furthermore, the transmission data processing unit 12 adds control information to the data sequence of the transport channel to generate a transmission symbol sequence. The wireless communication unit 11 performs various processes such as carrier modulation, frequency conversion, and signal amplification based on the transmission symbol sequence to generate a downlink signal, and transmits this to the wireless terminal 3. Furthermore, the transmission data processing unit 12 receives control data to be transmitted to the wireless terminal 3 from the communication control unit 15, and transmits this to the wireless terminal 3 via the wireless communication unit 11.

[0038] The communication control unit 15 signals with the wireless station 2 and the wireless terminal 3 to enable the wireless terminal 3 to simultaneously use the cells 10 and 20 for receiving or transmitting user data. That is, the communication control unit 15 transmits a message requesting or instructing the wireless station 2 to prepare for communication with the wireless terminal 3 in the cell 20 via the communication unit 14. Also, the communication control unit 15 transmits a message instructing the establishment of a second wireless connection in the cell 20 to the wireless terminal 3 or the wireless terminal 2 via the wireless communication unit 11 or the communication unit 14. Also, in the case of the above-mentioned procedure example 1, the communication control unit 15 transmits wireless connection setting information related to the cell 20 of the wireless station 2 to the wireless terminal 3. The wireless connection setting information may be transmitted in the same message as the instruction to establish the wireless connection, or may be transmitted in a separate message. In the case of the above-mentioned procedure example 2, the communication control unit 15 may transmit wireless resource setting information related to the cell 20 of the wireless station 2 to the wireless terminal 3.

[0039] Fig. 3 is a block diagram showing a configuration example of the second wireless station 2. The functions and operations of a wireless communication unit 21, a transmission data processing unit 22, a reception data processing unit 23, and a communication unit 24 shown in Fig. 3 are similar to the corresponding elements of the wireless station 1 shown in Fig. 2, i.e., the wireless communication unit 11, the transmission data processing unit 12, the reception data processing unit 13, and the communication unit 14.

[0040] The communication control unit 25 of the wireless station 2 receives a message from the wireless station 1 requesting or instructing preparation for communication with the wireless terminal 3 in the cell 20, and prepares for communication with the wireless terminal 3 in the cell 20 by configuring the wireless communication unit 21 based on the message. In the case of the above-mentioned procedure example 2, the communication control unit 25 transmits wireless connection setting information related to the cell 20 of the wireless station 2 to the wireless terminal 3. The wireless connection setting information may be transmitted in the same message as the instruction to establish a wireless connection, or may be transmitted in a separate message.

[0041] FIG. 4 is a block diagram showing a configuration example of the wireless terminal 3. The wireless communication unit 31 supports carrier aggregation of multiple cells operated by different wireless stations, and can simultaneously use multiple cells (e.g., cells 10 and 20) for transmitting or receiving signals. Specifically, the wireless communication unit 31 receives a downlink signal from the wireless station 1 or the wireless station 2, or both, via an antenna. The received data processing unit 32 restores received data from the received downlink signal and sends it to the data control unit 33. The data control unit 33 uses the received data according to its purpose. In addition, the transmission data processing unit 34 and the wireless communication unit 31 generate an uplink signal using the transmission data supplied from the data control unit 33, and transmit the uplink signal to the wireless station 1 or the wireless station 2, or both.

[0042] The communication control unit 35 of the wireless terminal 3 sets the cell 20 in response to an instruction from the wireless station 1 or the wireless station 2 so that the cells 10 and 20 can be used simultaneously in the wireless communication unit 31. This enables the wireless terminal 3 to communicate with the wireless station 2 while communicating with the wireless station 1 (i.e., transmitting or receiving, or both, a signal carrying user data or the like).

[0043] Next, a specific example of a procedure for establishing a wireless connection with the wireless terminal 3 in the multiple cells 10 and 20 will be described below so that the wireless terminal 3 can simultaneously use the cells 10 and 20. First, the above-mentioned procedure example 1 will be described with reference to Figs. 5 to 8, and then procedure example 2 will be described with reference to Figs. 9 to 12.

[0044] (Example procedure 1) FIG. 5 is a flowchart showing the operation of the wireless station 1 in procedure example 1. In step S101, the wireless station 1 (communication control unit 15) requests or instructs the wireless station 2 to prepare for the wireless terminal 3 belonging to its own cell 10 to perform communication in the cell 20 (that is, transmission or reception, or both, of a signal carrying user data, etc.). In step S102, the wireless station 1 determines whether or not it has received an affirmative response from the wireless station 2 in response to the request or instruction in step S101. As already described, in procedure example 1, the wireless station 1 directly instructs the wireless terminal 3 to establish a second wireless connection in the cell 20. Therefore, when an affirmative response is received (YES in step S102), the wireless station 1 transmits an instruction to establish the second wireless connection to the wireless terminal 3 (step S103). On the other hand, when an affirmative response is not obtained (NO in step S102), the wireless station 1 ends the process in FIG. 5 without instructing the establishment of the second wireless connection.

[0045] 6 is a flowchart showing the operation of the wireless station 2 in procedure example 1. In step S201, the wireless station 2 (communication control unit 25) receives from the wireless station 1 a message instructing or requesting preparation for communication in the cell 20 with the wireless terminal 3 belonging to the cell 10. In step S202, the wireless station 2 determines whether to accept the instruction or request from the wireless station 1. For example, the wireless station 2 may reject the instruction or request from the wireless station 1 when sufficient wireless resources for communication with the wireless terminal 3 cannot be secured due to a high load on the cell 20. When rejecting the instruction or request from the wireless station 1, the wireless station 2 transmits a negative response to the wireless station 1 (step S203), and when accepting the instruction or request, transmits an affirmative response to the wireless station 1 (step S204). When accepting the instruction or request from the wireless station 1, the wireless station 2 prepares for communication in the cell 20 with the wireless terminal 3.

[0046] 7 is a flowchart showing the operation of the wireless terminal 3 in procedure example 1. In step S301, the wireless terminal 3 (communication control unit 35) receives an instruction to establish a second wireless connection from the first wireless station 1. In step S302, in response to the instruction in step S301, the wireless terminal 3 sets a cell 20 and establishes a second wireless connection with the wireless station 2 in the cell 20. In step S303, the wireless terminal 3 reports to the wireless station 1 that the second wireless connection in the cell 20 has been established.

[0047] Fig. 8 is a sequence diagram showing an overall procedure example 1. In step S401, the first wireless station 1 and the wireless terminal 3 establish a first wireless connection in the first cell 10. In step S402, the wireless station 1 communicates with the wireless terminal 3 in the cell 10. In the example of Fig. 8, the wireless station 1 transmits downlink data addressed to the wireless terminal 3 in the cell 10.

[0048] Steps S403 to S406 are procedures for establishing a second wireless connection in the cell 20 for the wireless terminal 3 communicating in the cell 10. That is, in step S403, the wireless station 1 requests or instructs the wireless station 2 to prepare for communication in the cell 20 with the wireless terminal 3. In step S404, the wireless station 2 transmits a response to the request or instruction in step S403 to the wireless station 1. The response is a positive response or a negative response. When transmitting a positive response in step S404, the wireless station 2 prepares for communication in the cell 20 with the wireless terminal 3 based on the request or instruction from the wireless station 1. In step S405, in response to receiving the positive response, the wireless station 1 transmits an instruction to the wireless terminal 3 in the cell 10 to establish a second wireless connection in the cell 20. In step S406, the wireless terminal 3 sets the cell 20 based on the instruction from the wireless station 1. As a result, a wireless connection between the wireless station 2 and the wireless terminal 3 is established in the cell 20.

[0049] Completion of step S406 allows the wireless terminal 3 to use the cells 10 and 20 simultaneously. Therefore, in step S407, for example, the wireless terminal 3 receives downlink data in both the cells 10 and 20. Note that it is sufficient for the wireless terminal 3 in step S407 to be able to use the cells 10 and 20 simultaneously for communication (reception or transmission, or both, of signals carrying user data, etc.). In other words, the wireless terminal 3 does not need to always receive downlink data in both the first and second cells, and does not need to always transmit uplink data. Whether to use either one or both of the cells 10 and 20 for reception or transmission of user data is determined based on, for example, the amount of user data or the service used by the wireless terminal 3.

[0050] For example, if the wireless station 2 is a wireless station having a basic function for communicating with the wireless terminal 3, that is, a wireless station capable of communicating with the wireless terminal 3 independently like the wireless station 1, the wireless station 1 may make a request for communication preparation in step S403 in FIG. 8. On the other hand, if the wireless station 2 is a wireless station having a part (only) of the function for communicating with the wireless terminal 3, the wireless station 1 may make an instruction for communication preparation in step S403. Here, a distinction is made between a "request" and an "instruction" as follows. A "request" is used when the side that has received the request determines whether or not to accept the request. An "instruction" is used when the side that has received the instruction accepts the instruction. A wireless station having a part (only) of the function for communicating with the wireless terminal 3 may be, for example, a wireless station that communicates only user data between the wireless terminal 3 and a higher-level network, or a wireless station that communicates only control system signals between the wireless terminal 3 and a higher-level network. Alternatively, another example of a wireless station that has (only) some of the functions for communicating with wireless terminal 3 may be a wireless station that has the function for communicating with wireless terminal 3 but does not have the function for communicating with a higher-level network.

[0051] 8, the first wireless station 1 may transmit the following information when making the request or the instruction. This information may be transmitted together with the request or the instruction (i.e., in the same message) or in a separate message. Radio connection setting information: e.g. serving cell information; Terminal individual information: For example, wireless terminal capability information, wireless terminal identifier information, selected network identifier information, bearer information, wireless resource control information, wireless terminal movement history information, or service information, or any combination thereof; Radio access information: e.g. radio access identifier information.

[0052] When the wireless station 2 accepts the request or the instruction from the wireless station 1, the wireless station 2 may transmit the following information in step S404 of Fig. 8. This information may be transmitted together with the response to the request or the instruction (i.e., in the same message) or may be transmitted in a separate message. Radio connection setting information: for example, system information, radio resource setting information, measurement setting information, mobility control information, or security setting information, or any combination thereof; Radio access information: for example, radio access identifier information, or radio access resource information, or a combination thereof.

[0053] (Example procedure 2) FIG. 9 is a flowchart showing the operation of the wireless station 1 in procedure example 2. The processes in steps S101 and S102 in FIG. 9 are the same as steps S101 and S102 in procedure example 1 shown in FIG. 5. As already described, in procedure example 2, the wireless station 1 instructs the wireless station 2 to establish a second wireless connection in the cell 20. Also, the instruction to establish the second wireless connection from the wireless station 1 to the wireless station 2 may be used as the instruction (or request) for communication preparation in step S101. The procedure in FIG. 9 shows a case where the instruction to establish the second wireless connection is used as the instruction to prepare for communication in step S101. That is, the message of the instruction (or request) for communication preparation in step S101 explicitly or implicitly indicates the instruction to establish the second wireless connection. Therefore, in the example in FIG. 9, the wireless station 1 does not need to transmit an independent message indicating the instruction to establish the second wireless connection to the wireless station 2. In step S503, the wireless station 1 (communication control unit 15) instructs the wireless terminal 3 to receive information of the second cell 20 in the first cell 10. In step S504, the wireless station 1 determines whether a completion notification of establishment of the second wireless connection has been received from the wireless station 2, and ends the procedure in Fig. 9 on the condition that the completion notification has been received.

[0054] Fig. 10 is a flowchart showing the operation of the wireless station 2 in procedure example 2. The processes in steps S201 to S204 in Fig. 10 are similar to steps S201 to S204 in procedure example 2 shown in Fig. 6. In step S605, the wireless station 2 (communication control unit 25) instructs the wireless terminal 3 to establish a second wireless connection in the cell 20. Then, in response to the completion of the establishment of the second wireless connection, the wireless station 2 transmits a completion notification to the wireless station 1 (steps S606 and S607).

[0055] 11 is a flowchart showing an operation of the wireless terminal 3 in procedure example 2. In step S701, the wireless terminal 3 (communication control unit 35) receives an instruction to receive information of the second cell 20 from the first wireless station 1 in the first cell 10. The wireless terminal 3 performs a receiving operation in the second cell 20 based on the instruction from the wireless station 1. In step S702, the wireless terminal 3 receives an instruction to establish a second wireless connection from the second wireless station 2. In step S703, in response to the instruction in step S701, the wireless terminal 3 sets the cell 20 and establishes a second wireless connection with the wireless station 2 in the cell 20. In step S704, the wireless terminal 3 reports to the wireless station 2 that the second wireless connection in the cell 20 has been established.

[0056] FIG. 12 is a sequence diagram showing an entire procedure example 2. The processes in steps S401 to S404 in FIG. 12 are the same as those in steps S401 to S404 in procedure example 1 shown in FIG. 8. In step S805, the wireless station 1 instructs the wireless terminal 3 to receive information of the second cell 20 in the first cell 10. The instruction in step S805 includes wireless resource setting information of the second cell 20 that is necessary for the wireless terminal 2 to perform a receiving operation in the second cell 20. Furthermore, in step S805, the wireless station 1 may notify information (for example, a gap pattern) that determines a gap period for the wireless terminal 3 to perform a receiving operation in the cell 20. In addition, when the gap period is specified in advance, the wireless terminal 3 may spontaneously set the gap period in response to receiving the wireless resource setting information of the second cell 20 from the wireless station 1. Here, the gap period means a period during which transmission in the first cell 10 to the wireless terminal 3 is stopped in order to receive information in the second cell 20, or a period during which the wireless terminal 3 does not need to receive signals for itself in the first cell.

[0057] In step S806, the wireless station 1 instructs the wireless station 2 to establish a second wireless connection with the wireless terminal 3 in the cell 20. As already described, the instruction in step S806 does not have to be explicitly given. In step S807, the wireless station 2 instructs the wireless terminal 3 to establish a second wireless connection in the cell 20. In step S808, the wireless terminal 3 sets the cell 20 based on the instruction from the wireless station 2. As a result, a wireless connection between the wireless station 2 and the wireless terminal 3 is established in the cell 20. In step S809, the wireless station 2 notifies the wireless station 1 of the completion of the establishment of the second wireless connection. With the completion of step S808, the wireless terminal 3 can use the cells 10 and 20 simultaneously. Therefore, in step S810, for example, the wireless terminal 3 receives downlink data in both the cells 10 and 20.

[0058] <Second embodiment> In this embodiment, an example in which the above-mentioned first embodiment is applied to a 3GPP LTE system will be described. A configuration example of a wireless communication system according to this embodiment may be the same as that shown in FIG. 1. However, wireless stations 1 and 2 correspond to eNBs, and a wireless terminal 3 corresponds to a UE. In addition, transmission and reception of information between wireless stations (i.e., between eNBs) may use a direct interface X2, may use an interface S1 via a core network, or may use a newly defined interface (e.g., X3). The wireless terminal (UE) 3 supports carrier aggregation (Inter-eNB CA) of multiple cells operated by different wireless stations (eNBs). Note that "Inter-eNB CA" here is not limited to actually receiving or transmitting signals in cells of different eNBs at the same time, but includes actually receiving or transmitting a signal in a cell of one of the eNBs while both of the cells of the different eNBs are in a state where signals (e.g., user data or control information) can be received or transmitted, receiving or transmitting different types of signals in each of the cells of the different eNBs, or using each of the cells of the different eNBs for either receiving or transmitting a signal, etc. In the following description, the wireless stations 1 and 2 are referred to as eNB1 and 2, and the wireless terminal 3 is referred to as UE3.

[0059] In this embodiment, the procedure for establishing a wireless connection between each of the cells 10 and 20 and the UE 3 may be the same as that of the first embodiment. That is, the eNB1 requests or instructs the eNB2 to prepare for communication with the UE 3 in the cell 20 while the first wireless connection with the UE 3 in the cell 10 is established. Furthermore, the eNB1 instructs the UE 3 or the eNB2 to establish a second wireless connection with the UE 3 in the cell 20 while maintaining the first wireless connection. When instructing the eNB2 to establish the second wireless connection, the instruction to the eNB2 may be implicit. Thereby, in this embodiment, the UE 3 can establish wireless connections in multiple cells 10 and 20 to realize carrier aggregation of the cells 10 and 20 operated by different eNBs 1 and 2.

[0060] Here, which of eNB1 and eNB2 is used for transmitting downlink user data may be determined according to, for example, the type of service and the required QoS (or QCI). Furthermore, a control signal (Control Plane (CP) signal) may be transmitted from eNB1, and a user data signal (User Plane (UP) signal) may be transmitted from eNB2.

[0061] Procedure Example 3 corresponds to Procedure Example 1 of the first embodiment. In Procedure Example 3, eNB1 instructs UE3 to establish a second wireless connection in the cell 20. In this case, eNB1 may notify UE3 of wireless connection setting information (RRC Connection Reconfiguration information) related to the wireless connection in the cell 20. Then, UE3 configures the cell 20 in response to the instruction from eNB1. This allows UE3 to establish a second wireless connection with eNB2 in the cell 20.

[0062] Procedure Example 4 corresponds to Procedure Example 1 of the second embodiment. In Procedure Example 4, eNB1 instructs eNB2 to establish a second wireless connection in the cell 20. In response to the instruction from eNB1, eNB2 instructs UE3 to establish a second wireless connection in the cell 20. The eNB2 may notify UE3 of wireless connection setting information (RRC Connection Reconfiguration information) related to the wireless connection in the cell 20. Then, in response to the instruction from eNB2, UE3 configures the cell 20. As a result, UE3 can establish a second wireless connection with eNB2 in the cell 20.

[0063] In the above-mentioned procedure examples 3 and 4, at least a part of the UE context information of the UE 3 related to the establishment of the second wireless connection may be sent from the eNB1 to the eNB2 or from the eNB2 to the eNB1. Also, in the procedure examples 3 and 4, at least one of the radio connection setting information (RRC connection reconfiguration information) and the radio access information related to the establishment of the first wireless connection or the establishment of the second wireless connection may be sent from the eNB2 to the eNB1 or from the eNB1 to the eNB2.

[0064] The UE Context information may include at least one of the information elements listed below. UE capability information: e.g. UE radio access capability, UE network capability, or UE security capability, or any combination thereof; UE identification information: e.g., C-RNTI, (S-)TMSI, or shortMAC-I, or any combination of these; UE selected network information: for example, GUMMEI (Globally Unique MME Identifier), eNB UE S1AP ID, MME UE S1AP ID, or CSG ID, or any combination thereof; Bearer information: e.g., E-RAB ID, E-RAB Level QoS Parameters, or UL GTP Tunnel Endpoint ID, or any combination thereof; Radio resource control information (RRC context information): AS-Config, AS-Context, ue-ConfigRelease, or ue-RadioAccessCapabilityInfo, or any combination of these; · UE history information: e.g., Last Visited Cell Information; Service information: For example, QCI, QoS, or MBMS information, or any combination thereof.

[0065] The radio connection reconfiguration information may include at least one of the information elements listed below. Serving Cell information: e.g., Physical Cell ID (PCI), or EUTRAN Cell Global ID (ECGI), or a combination of these; System information: e.g. MIB (Master Information Block) or SIB (System Information Block) x (x=1,2,..) or a combination of these; Radio resource configuration information: e.g., PhysicalConfigDedicated, Mac-Mainconfig, RLC-Config, PDCP-Config, logicalChannelIdentity, drb-Identity, or eps-BearerIdentity, or any combination thereof; Measurement configuration information: e.g., MeasObject, or ReportConfig, or a combination of these; Mobility control information: for example, targetPhysCellId, carrierFreq, or newUE-Identity, or any combination thereof; Security configuration information: For example, SecurityAlgorithmConfig.

[0066] The Radio Access information may include at least one of the information elements listed below. Radio access identification information: e.g., RACH preamble index; Radio access resource information: e.g. PRACH resource configuration.

[0067] A possible application of these procedure examples 3 and 4 is a case where eNB1 is a macro radio base station (Macro eNB: MeNB) that operates (manages) a macro cell with a relatively large coverage, and eNB2 is a low power radio station (Low Power Node: LPN) that operates (manages) a cell with a small coverage, but is not limited thereto. An LPN may be, for example, a pico radio base station (PeNB: Pico eNB) that has the same functions as an MeNB, or a new type of network node (New Node) that has fewer functions than an MeNB. In addition, the second cell (cell 20) may be a new type of cell (New Cell Type) that is different from the conventional one and that includes a new type of carrier (New Carrier Type) that is different from the conventional one as a component.

[0068] Next, specific examples of the above-mentioned procedure example 3 and procedure example 4 will be described below. Fig. 13 is a sequence diagram showing the entire procedure example 3, and Fig. 14 is a sequence diagram showing the entire procedure example 4. In Fig. 13 and Fig. 14, the first cell 10 is displayed as CELL1, and the second cell 20 is displayed as CELL2.

[0069] (Example procedure 3) In step S901, the eNB1 and the UE3 establish a first radio connection in the cell 10 (RRC Connection Establishment). In step S902, the eNB1 communicates with the UE3 in the cell 10. In the example of FIG. 13, the eNB1 transmits downlink data addressed to the UE3 in the cell 10. In step S903, the UE3 or the eNB1 detects or determines the cell 20 (secondary cell discovery or decision). In step S904, the eNB1 requests or instructs the eNB2 operating the cell 20 to prepare for the UE3 belonging to the serving cell 10 to communicate in the cell 20 (i.e., transmit or receive a signal carrying user data or the like, or both). In step S905, the eNB2 transmits a response to the request or instruction in step S904 to the eNB1 (Secondary Cell Preparation Request (or instruction) response). When sending an acknowledgement in step S905, the eNB2 prepares for communication with the UE 3 in the cell 20 based on a request or instruction from the eNB1.

[0070] In step S906, in response to receiving the positive response, the eNB1 transmits an instruction to the UE3 in the cell 10 to establish a second radio connection in the cell 20 (RRC Connection Reconfiguration). The instruction includes radio connection setting information (Secondary Cell configuration) of the second cell 20. In step S907, the UE3 configures the cell 20 based on the instruction from the eNB1. As a result, a radio connection between the eNB2 and the UE3 is established in the cell 20 (RRC Connection Establishment).

[0071] In step S908, the eNB1 transmits a message indicating activation (i.e., start of use) of the cell 20 to the UE 3 in the first cell 10 in order to start carrier aggregation (Secondary Cell Activation). In step S909, the eNB1 notifies the eNB1 that configuration of the cell 20, i.e., the secondary cell for carrier aggregation, is complete (Secondary Cell Configuration Complete). Completion of step S909 enables the UE 3 to perform carrier aggregation in the cells 10 and 20. Thus, in step S910, for example, the UE 3 receives downlink data in both the cells 10 and 20.

[0072] (Example Procedure 4) The processes in steps S901 to S905 in Fig. 14 are the same as those in steps S901 to S905 in Fig. 13. In step S1006, the eNB1 instructs the UE3 to receive information of the second cell 20 in its serving cell 10 (Radio Resource Configuration of Second Cell). In step S1007, the eNB1 instructs the eNB2 to establish a second wireless connection with the UE3 in the cell 20 (Secondary Cell Preparation Complete). In step S1008, the eNB2 instructs the UE3 to establish a second wireless connection in the cell 20 (RRC connection Reconfiguration).

[0073] In step S1009, the UE3 configures the cell 20 based on an instruction from the eNB2. As a result, a radio connection between the eNB2 and the UE3 is established in the cell 20 (RRC Connection Establishment). In step S1010, the eNB2 notifies the eNB1 of the completion of the establishment of the second radio connection (Secondary Cell Configuration Complete). Upon completion of step S1010, the UE3 can perform carrier aggregation in the cells 10 and 20. Therefore, in step S1011, for example, the UE3 receives downlink data in both the cells 10 and 20.

[0074] <Third embodiment> In this embodiment, a modification of the above-mentioned second embodiment will be described. In this embodiment, the setting of bearers between the radio stations 1 and 2 and the upper network, and bearers in the upper network will be described. These bearers are associated with the first and second radio connections (i.e., data radio bearers (Evolved Packet System Radio bearers: EPS RBs)) in the cells 10 and 20 set by the procedure described in the second embodiment for the transfer of user data.

[0075] In the LTE system, the bearer for transferring user data between radio stations (eNB) 1 and 2 and an upper network (Evolved Packet Core: EPC) is the S1 bearer. The S1 bearer is set between a data relay device in the upper network (i.e., a Serving GW: S-GW) and the eNB. In the LTE system, the bearer set between two data relay devices in the EPC, that is, the S-GW and the P-GW (Packet Data Network Gateway), is the S5 / S8 bearer. The EPS RB and the S1 bearer are collectively called a radio access bearer (E-UTRAN Radio Access Bearer: E-RAB). The E-RAB is a bearer for transferring user data between the UE and the EPC via the eNB. Furthermore, the bearer between the P-GW and the UE, including the E-RAB and the S5 / S8 bearer, is called an EPS bearer. The EPS bearer is set for each UE. Also, one UE can use multiple EPS bearers. In this case, multiple EPS bearers for one UEPS are differentiated, for example, by the QoS class of the user data transferred.

[0076] The configuration of the EPS bearer, the E-RAB, and the S1 bearer is controlled by a Mobility Management Entity (MME) in an upper network. Regarding the S1 bearer, the MME communicates with the S-GW and the eNB, and the MME, the S-GW, and the eNB share each other's bearer context (e.g., the IP address of the S-GW, the IP address of the eNB, the endpoint identifiers of the S-GW and the eNB, etc.), thereby configuring the S1 bearer.

[0077] 15 is a block diagram showing a configuration example of a wireless communication system according to this embodiment. An EPC 4, which is a specific example of an upper network, includes an MME 5 and an S / P-GW 6. Each of the eNBs 1 and 2 connects a control connection (S1-MME) to the MME 5 and sets a bearer (S1 bearer) for transferring user data between the MME 5 and the S / P-GW 6.

[0078] Next, a procedure for setting an S1 bearer (or an E-RAB, an EPS bearer) in this embodiment will be described with reference to the sequence diagram of FIG. 16. In FIG. 16, the first cell 10 is displayed as CELL1, and the second cell 20 is displayed as CELL2. In step S1101, an EPS bearer for transferring user data between the UE 3 and the EPC 4 via the cell 10 is set by signaling between the UE 3, the eNB 1, the MME 5, and the S / P-GW 6. In step S1102, the cell 20 is set as a secondary cell so that the UE 3 performs carrier aggregation of the cells 10 and 20 according to the procedure described in the second embodiment. In step S1103, the eNB 2 requests the MME 5 to set a bearer (an S1 bearer, an E-RAB, or an EPS bearer) for transferring user data between the UE 3 and the EPC 4 via the cell 20. As a result, a bearer setup procedure is performed by signaling between UE3, eNB2, MME5, and S / P-GW6. eNB2 sets up an S1 bearer (or E-RAB) according to the bearer setup procedure. In steps S1104 and S1106, S / P-GW6 transfers downlink user data to UE3 to a first S1 bearer associated with eNB1 or a second S1 bearer associated with eNB2. In steps S1105 and S1107, eNB1 and 2 transmit downlink user data received through the S1 bearer to UE3.

[0079] Here, which of eNB1 and eNB2 is used for transmitting downlink user data may be determined according to, for example, the type of service and the required QoS (or QCI). Furthermore, a control signal (Control Plane (CP) signal) may be transmitted from eNB1, and a user data signal (User Plane (UP) signal) may be transmitted from eNB2.

[0080] In the procedure example 3 or procedure example 4 described in the second embodiment, an example is shown in which at least one of the selected network information and the bearer information of the UE3 is transmitted from the eNB1 to the eNB2 when the UE3 requests (or instructs) to prepare for communication in the cell 20. A specific example of the selected network information is GUMMEI, eNB UE S1AP ID, MME UE S1AP ID, or CSG ID, or any combination thereof. A specific example of the bearer information is E-RAB ID, E-RAB Level QoS Parameters, or UL GTP Tunnel Endpoint ID, or any combination thereof. One advantage of transmitting at least one of the selected network information and the bearer information of the UE3 to the eNB2 is that in this embodiment, the eNB2 can trigger bearer setting for transferring user data of the UE3 via the cell 20. That is, the eNB2 may generate a bearer setting request based on at least one of the selected network information and the bearer information, and transmit the request to the MME5. As a result, this embodiment can greatly reduce the load on the UE3 caused by setting up a bearer with a different radio base station.

[0081] <Other embodiments> In the above-described second and third embodiments, the UE 3 may transmit Layer 1 or Layer 2 or both of these control information (L1 / L2 control information) using an uplink physical control channel (PUCCH) in the secondary cell (cell 20). Specifically, the UE 3 may use the PUCCH of the secondary cell (cell 20) to return a response to downlink reception in the secondary cell (cell 20) (e.g., an H-ARQ (Hybrid Automatic Repeat Request) ACK, a CQI (Channel Quality Indicator) / PMI (Precoding Matrix Indicator), or an RI (Rank Indicator)).

[0082] In normal CA in which the same eNB operates multiple cells, all L1 / L2 control information using PUCCH is transmitted by the primary cell. However, if an architecture similar to that of normal CA is adopted in Inter-eNB CA, interworking between eNB1 and eNB2 is required, which may cause processing delays and additional network loads. In contrast, by using the uplink physical control channel of the secondary cell (cell 20) for responding to downlink reception in the secondary cell (cell 20), interworking between eNB1 and eNB2 is not required.

[0083] In the second and third embodiments, the eNB1 may transmit, for example, a random access preamble identifier (RA preamble ID) and a mask value (RA PRACH Mask) used in a physical random access channel (PRACH) to the eNB2. This can reduce access delay in the uplink of the second cell.

[0084] In the second and third embodiments, the terminal identifier (C-RNTI) of the radio link may be the same in the primary cell (cell 10) and the secondary cell (cell 20).

[0085] In the second and third embodiments, a Time Alignment (TA) Timer for determining synchronization of uplink signals (i.e., for synchronization management) may be held for each of the primary cell (cell 10) and the secondary cell (cell 20). Furthermore, when there are multiple secondary cells, one TA Timer may be held for the multiple secondary cells to determine synchronization. Therefore, the primary cell and the secondary cell (or a group of secondary cells) may belong to different timing groups (Timing Advance Groups: TAGs).

[0086] In the second and third embodiments, the eNB2 may transmit MIB (Master Information Block) / SIB (System Information Block) information and security context to the eNB1. This allows the UE3 side to smoothly set up a secondary cell (cell 20).

[0087] Furthermore, in the first to third embodiments, a secondary cell (cell 20) added for carrier aggregation may be used only for a downlink component carrier (CC) or only for an uplink component carrier (CC).

[0088] In the first to third embodiments, the primary cell (cell 10) and the secondary cell (cell 20) may be in different duplex modes. For example, the primary cell (cell 10) may be in FDD (Frequency Division Duplex), and the secondary cell (cell 20) may be in TDD (Time Division Duplex).

[0089] Also, the diagrams illustrated in the first to third embodiments show a heterogeneous network (HetNet) environment. However, these embodiments can also be applied to a homogeneous network. An example of a homogeneous network is a cellular network consisting of macro (or micro) cells of a macro (or micro) base station.

[0090] Furthermore, the communication control methods by the wireless station 1 (communication control unit 15), the wireless station 2 (communication control unit 25), and the wireless terminal 3 (communication control unit 35) described in the first to third embodiments may all be realized using a semiconductor processing device including an Application Specific Integrated Circuit (ASIC). Furthermore, these processes may be realized by causing a computer system including at least one processor (e.g., a microprocessor, a Micro Processing Unit (MPU), a Digital Signal Processor (DSP)) to execute a program. Specifically, one or more programs including a set of instructions for causing a computer system to execute the algorithms shown in the flowcharts and sequence diagrams may be created, and the program may be supplied to a computer.

[0091] The program can be stored and provided to a computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R / W, and semiconductor memory (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, and RAM (random access memory)). The program may also be provided to a computer by various types of transitory computer readable media. Examples of the transitory computer readable media include electric signals, optical signals, and electromagnetic waves. The transitory computer readable media can provide the program to a computer via a wired communication path such as an electric wire and an optical fiber, or via a wireless communication path.

[0092] In the first to third embodiments, the LTE system has been mainly described. However, these embodiments may be applied to wireless communication systems other than the LTE system, such as the 3GPP UMTS (Universal Mobile Telecommunications System), the 3GPP2 CDMA2000 system (1xRTT, HRPD (High Rate Packet Data)), the GSM (Global System for Mobile Communications) system, or the WiMAX system.

[0093] Furthermore, the above-described embodiment is merely an example of application of the technical idea obtained by the inventor of the present invention. In other words, the technical idea is not limited to the above-described embodiment, and various modifications are possible.

[0094] This application claims priority based on Japanese Patent Application No. 2012-223177, filed October 5, 2012, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0095] 1. First Radio Station 2. Second radio station 3. Wireless terminals 10 First Cell 20 Second Cell 15 Communication control section 25 Communication control section 35 Communication control section

Claims

1. 1. A first radio station configured to operate a first cell, comprising: means for transmitting a first request to a second radio station configured to operate a second cell, wherein the first request is configured to request the second radio station to prepare for communication with the radio terminal in the second cell while an established first radio connection between the first radio station and the radio terminal is maintained in the first cell; means for receiving radio resource configuration information of the second cell from the second radio station; means for transmitting a Radio Resource Control (RRC) Connection Reconfiguration message including at least the radio resource configuration information of the second cell to the radio terminal; Equipped with The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. The first radio station.

2. the RRC Connection Reconfiguration message causes the wireless terminal to add the second cell while the established first wireless connection between the wireless terminal and the first wireless station is maintained. A first radio station according to claim 1 .

3. means for instructing at least one of the wireless terminal and the second wireless station to establish a second wireless connection in the second cell; A first radio station according to claim 1 or 2.

4. a means for notifying the second wireless station of at least one of terminal individual information of a wireless terminal related to establishment of the first wireless connection or the second wireless connection, wireless connection setting information related to establishment of the first wireless connection or the second wireless connection, and wireless access information related to the first wireless connection or the second wireless connection; The first radio station according to claim 3 .

5. means for receiving, from the second wireless station, radio access information relating to the first wireless connection or the second wireless connection; The first radio station according to claim 3 .

6. The terminal individual information includes at least one of: (a) wireless terminal capability information; (b) wireless terminal identifier information; (c) selected network information; (d) bearer information; (e) wireless resource control information; (f) wireless terminal movement history information; and (g) service information. The first radio station according to claim 4.

7. The radio connection setting information includes at least one of: (a) serving cell information; (b) system information; (c) radio resource setting information; (d) measurement setting information; (e) mobility control information; and (f) security setting information. The first radio station according to claim 4.

8. The radio access information includes at least one of (a) radio access identifier information and (b) radio access resource information; The first radio station according to claim 4.

9. the instructing means is configured to instruct the second radio station to establish the second radio connection to enable the radio terminal to simultaneously use the first cell and the second cell for signal reception or transmission. The first radio station according to claim 3 .

10. the data path passes through the second wireless station; A first radio station according to any one of claims 1 to 9.

11. the data path is a data path for user data; A first radio station according to any one of claims 1 to 10.

12. a second radio station configured to operate a second cell, means for receiving a first request from a first radio station configured to operate a first cell to the second radio station, wherein the first request is configured to request the second radio station to prepare for communication with the radio terminal in the second cell while an established first radio connection between the first radio station and the radio terminal is maintained in the first cell; means for transmitting radio resource configuration information of the second cell to the first radio station; Equipped with The first radio station is configured to transmit to the radio terminal a Radio Resource Control (RRC) Connection Reconfiguration message including at least the radio resource configuration information of the second cell. The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. Second radio station.

13. means for instructing the wireless terminal to establish a second wireless connection in the second cell; A second radio station according to claim 12.

14. The method further includes receiving, from the first radio station, terminal individual information of the radio terminal related to establishment of the first radio connection or the second radio connection in the second cell. A second radio station according to claim 12 or 13.

15. and means for triggering establishment of a bearer for transferring user data of the wireless terminal between an upper network and the second wireless station based on the terminal individual information. A second radio station according to claim 14.

16. and means for receiving, from the first radio station, at least one of radio connection setting information related to establishment of the first radio connection or a second radio connection in the second cell and radio access information related to the first radio connection or the second radio connection. A second radio station according to any one of claims 12 to 15.

17. a means for notifying the first radio station of at least one of radio connection setting information related to establishment of the first radio connection or a second radio connection in the second cell and radio access information related to the first radio connection or the second radio connection; A second radio station according to any one of claims 12 to 15.

18. the data path passes through the second wireless station; A second radio station according to any one of claims 12 to 17.

19. the data path is a data path for user data; A second radio station according to any one of claims 12 to 18.

20. A wireless terminal, means for establishing a first wireless connection between a first wireless station and the wireless terminal in a first cell operated by the first wireless station; means for receiving, from the first radio station, a Radio Resource Control (RRC) Connection Reconfiguration message including radio resource configuration information of a second cell operated by a second radio station; means for adding the second cell using the radio resource configuration information of the second cell while the established first radio connection is maintained in the first cell; Equipped with the RRC Connection Reconfiguration message is transmitted based on a first request to the second wireless station; the first request is configured to request the second radio station to prepare for communication with the wireless terminal in the second cell; The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. Wireless terminal.

21. the first cell is a primary cell; the second cell is a secondary cell; means for transmitting at least one of layer 1 control information and layer 2 control information using an uplink physical control channel of the second cell; 21. The wireless terminal of claim 20.

22. the data path passes through the second wireless station; 22. A wireless terminal according to claim 20 or 21.

23. the data path is a data path for user data; A wireless terminal according to any one of claims 21 to 22.

24. A communication control method in a first radio station configured to operate a first cell, comprising: transmitting a first request to a second radio station configured to operate a second cell, wherein the first request is configured to request the second radio station to prepare for communication with the wireless terminal in the second cell while an established first wireless connection between the first radio station and the wireless terminal is maintained in the first cell; receiving radio resource configuration information of the second cell from the second radio station; and transmitting a Radio Resource Control (RRC) Connection Reconfiguration message to the wireless terminal, the message including at least the radio resource configuration information of the second cell; Equipped with The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. Communications control method.

25. the data path passes through the second wireless station; The communication control method according to claim 24.

26. the data path is a data path for user data; 26. A communication control method according to claim 24 or 25.

27. A communication control method in a second radio station configured to operate a second cell, comprising: receiving a first request from a first radio station configured to operate a first cell to the second radio station, where the first request is configured to request the second radio station to prepare for communication with the wireless terminal in the second cell while an established first wireless connection between the first radio station and the wireless terminal is maintained in the first cell; and transmitting radio resource configuration information of the second cell to the first radio station; Equipped with The first radio station is configured to transmit to the radio terminal a Radio Resource Control (RRC) Connection Reconfiguration message including at least the radio resource configuration information of the second cell. The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. Communications control method.

28. the data path passes through the second wireless station; 28. The communication control method according to claim 27.

29. the data path is a data path for user data; 29. A communication control method according to claim 27 or 28.

30. A communication control method in a wireless terminal, comprising: establishing a first wireless connection between a first wireless station and the wireless terminal in a first cell operated by the first wireless station; receiving, from the first wireless station, a Radio Resource Control (RRC) Connection Reconfiguration message including radio resource configuration information of a second cell operated by a second wireless station; and adding the second cell using the radio resource configuration information of the second cell while the established first radio connection is maintained in the first cell; Equipped with the RRC Connection Reconfiguration message is transmitted based on a first request to the second wireless station; the first request is configured to request the second radio station to prepare for communication with the wireless terminal in the second cell; The first request includes a Data Radio Bearer (DRB) Identity and an E-UTRAN Radio Access Bearer Identity (E-RAB ID) indicating a data path between the radio terminal and a Serving Gateway (S-GW) for communication with the radio terminal in the second cell. Communications control method.

31. the data path passes through the second wireless station; The communication control method according to claim 30.

32. the data path is a data path for user data; 32. A communication control method according to claim 30 or 31.

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