JP2020017976A - Terminal device, wireless communication system, control method, and program - Google Patents

Abstract

To provide a method for determining one cell to which a PUCCH is to be transmitted, in dual connectivity.SOLUTION: A terminal device notifies a first base station device of information on wireless quality of the signal received from a second base station device, for one or more frequency bands of a plurality of frequency bands, and acquires the information indicating a specific frequency band that can transmit a control channel, from the first base station device. In the specific frequency band, first information indicating a predetermined number of frequency bands extracted by the first base station device and second information indicating a frequency band different from the frequency band indicated by the first information are notified to the second base station device in a format that can be distinguished, and the specific frequency band is specified by the second base station device on the basis of the first information and the second information.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a wireless communication system including a plurality of base station devices and a terminal that communicates with the plurality of base station devices.

  In the Third Generation Partnership Project (3GPP), installing a large number of small cells (small cells) using different frequency bands (for example, higher frequency bands than those used in macro cells) within the coverage of large cells (macro cells) Is being discussed. For example, as in the example of FIG. 1, a plurality of small cells using the 3.5 GHz band are placed in the coverage area of the macro cell using the 2 GHz band.

  In LTE Release 12, discussion has begun on a technique called Dual Connectivity in which two types of base stations cooperate in such an environment (Non-Patent Document 1). The two types of base stations are a master eNodeB (master eNB, for example, a base station of a macro cell) and a secondary eNodeB (secondary eNB, for example, a base station of a small cell). In Dual Connectivity, the two types of base stations are connected by a wired or wireless backhaul line. Note that the terminal device can establish a connection with both the master eNB and the secondary eNB, and can receive data from, for example, two base station devices.

  In Dual Connectivity, signaling of a control signal to a terminal device in a downlink direction is performed by a master eNB (Non-Patent Document 1). On the other hand, in the uplink, it is assumed that the control signal from the terminal is transmitted not only to the master eNB but also to the secondary eNB. Here, the master eNB and the secondary eNB can use a plurality of frequency bands each having a certain bandwidth, and the terminal device transmits a control signal in at least one of the plurality of frequency bands. I do. Each of the plurality of frequency bands corresponds to, for example, a component carrier having a bandwidth of 20 MHz. Note that, for example, separate baseband units are assigned to the plurality of frequency bands that can be used by the master eNB and the secondary eNB, respectively, and separate cells (communicable ranges) are formed in each of the plurality of frequency bands. The Rukoto. That is, the master eNB and the secondary eNB are each one base station device, but form a plurality of cells corresponding to a plurality of frequency bands. The set of cells for the master eNB is called an MCG (Master Cell Group), and the set of cells for the secondary eNB is called an SCG (Secondary Cell Group).

3GPP TR 36.842 v12.0.0

  The terminal device must transmit a control channel (PUCCH, physical uplink control channel) to the master eNB and the secondary eNB in one cell of the MCG and one cell of the SCG. Therefore, the master eNB and the secondary eNB need to determine and notify a cell to which the terminal device has to transmit the control channel.

  In this regard, at the 3GPP meeting, an agreement has been formed that, for a certain terminal device, a secondary eNB determines one cell of a plurality of cells included in the SCG to which the PUCCH must be transmitted. . At this time, it has been agreed that the secondary eNB may receive assistance from the master eNB. However, no specific method has been established as to what kind of assistance the secondary eNB should receive from the master eNB and how to select the one cell.

  The present invention has been made in view of the above problems, and has as its object to provide a technique for determining a cell to which a PUCCH can be transmitted in Dual Connectivity.

  A terminal device according to an aspect of the present invention is configured such that, when the terminal device connects to the first base station device and the second base station device, the terminal device is selected from a plurality of frequency bands that can be used by the second base station device. In a wireless communication system in which a frequency band in which the terminal device can transmit a control channel to the second base station device specified by the second base station device is notified to the terminal device, Notification means for notifying the first base station apparatus of information on radio quality of a signal received from the second base station apparatus for one or more frequency bands of the plurality of frequency bands. And acquiring means for acquiring information indicating a specific frequency band in which the control channel can be transmitted from the first base station device, wherein the specific frequency band is The first information indicating a predetermined number of frequency bands extracted by one base station apparatus can be distinguished from the second information indicating a frequency band different from the frequency band indicated by the first information. The frequency band is notified to the second base station apparatus in a format, and is a frequency band specified based on the first information and the second information by the second base station apparatus.

  According to the present invention, a method for determining a cell to which a PUCCH can be transmitted in Dual Connectivity is provided.

The conceptual diagram which shows the example of arrangement | positioning of the macro cell and small cell which each use a different frequency band. FIG. 4 is a conceptual diagram showing an example of communication between a terminal and a plurality of eNBs according to Dual Connectivity. FIG. 3 is a diagram illustrating a hardware configuration example of a master eNB and a secondary eNB. FIG. 3 is a block diagram showing a functional configuration example of a master eNB. FIG. 3 is a block diagram showing a functional configuration example of a secondary eNB. FIG. 9 is a sequence diagram illustrating an example of a processing flow.

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

(System configuration)
The wireless communication system according to the present embodiment includes, for example, a master eNB, a secondary eNB, and a terminal device (UE), as illustrated in FIG. Here, the eNB is a base station apparatus (eNodeB), but the corresponding wireless communication system may be other than LTE. Also, the terminal device is a mobile or fixed wireless communication device, and may correspond to a wireless communication system other than LTE. In the wireless communication system according to the present embodiment, the master eNB performs communication using a first frequency band (for example, 2 GHz), and the secondary eNB performs communication using a second frequency band (3.5 GHz). Further, the master eNB and the secondary eNB may be able to use the same frequency band, that is, the first frequency band and the second frequency band may be the same frequency band. Note that the first frequency band and the second frequency band may be different frequency bands and may exist as part of the same frequency band such as a 2 GHz band.

  The master eNB and the secondary eNB can perform communication using a plurality of component carriers (CCs) in the frequency band used by each. Each of the plurality of CCs corresponds to a frequency band having a certain width, for example, 20 MHz. Also, as described above, the master eNB and the secondary eNB form a plurality of communicable cells for each of the plurality of CCs. As described above, since one cell corresponds to one of the CCs, the term “cell” will be used below including the meaning of the corresponding CC (frequency band). In the following discussion, the frequency band corresponding to each cell does not necessarily need to correspond to one CC, and may correspond to a frequency band having a predetermined bandwidth determined in a wireless communication system.

  As described above, a set of cells formed by the master eNB is called an MCG (Master Cell Group), while a set of cells formed by the secondary eNB is called an SCG (Secondary Cell Group). FIG. 2 shows a state in which each of the MCG and the SCG includes five cells. This number is determined based on, for example, the frequency bandwidth that can be used by each of the master eNB and the secondary eNB and the frequency bandwidth of one CC. Communication is performed between the master eNB and the terminal using at least one cell of the MCG. Similarly, in a state where Dual Connectivity is established, communication is performed between the secondary eNB and the terminal using at least one cell of the SCG.

  In Dual Connectivity, communication on a C-plane (control plane) such as transmission of an RRC (Radio Resource Control) message transmitted to a terminal is performed by the master eNB and not by the secondary eNB. A cell in which communication between the master eNB and the terminal in such a control plane is performed is called a PCell. In the PCell, in addition to communication on the control plane, communication on the U-plane (user plane) can also be performed. In addition, the PCell is set for each terminal, and for example, the terminal is guaranteed that the PCell set for itself can transmit uplink data to the master eNB. Note that the terminal can also transmit uplink data in another cell, but, for example, does not transmit data in another cell without transmitting data in the set PCell. Also, the terminal has to transmit PUCCH (Physical Uplink Control Channel) in PCell. Also, the terminal measures the radio quality of the radio signal transmitted from the master eNB or the secondary eNB for at least one of the cell included in the MCG and the cell included in the SCG, and compares the measurement result in the PCell as a master. The eNB can be notified. The radio quality may be, for example, reference signal reception power (RSRP) or reference signal reception quality (RSRQ), but other radio qualities (for example, SIR, SNR, etc.) may be used as radio quality. The terminal may notify the measurement result to the master eNB when a predetermined condition is satisfied, for example, when a radio signal from a cell of the SCG is received at a predetermined power or more, or for example, periodically. May be notified of such a measurement result to the master eNB. The MCG further includes, for example, a downlink serving cell for the terminal, and the master eNB can transmit data to the terminal in the downlink serving cell.

  On the other hand, in the SCG, a cell for transmitting an RRC message like PCell is not set, but a cell in which a PUCCH must be transmitted by a terminal is set for each terminal. Here, this cell is called a primary SCell (pSCell). Note that the terminal can also transmit the PUCCH in a cell other than the pSCell, but need not transmit the PUCCH in a cell other than the pSCell, but must transmit the PUCCH in the pSCell. The SCG also includes, for example, a serving cell for the downlink similarly to the MCG, and can transmit data to the terminal in the serving cell for the downlink. Also, the MCG and the SCG do not require that all cells be used for communication with the terminal. For example, as shown by a blank square in FIG. 2, any one of PCell, pSCell, and a serving cell for downlink Some cells do not correspond to the above. Then, the master eNB and the secondary eNB do not communicate with the terminal in such a cell, for example.

(Overview)
As described above, the PCell and the pSCell are selected and set from the MCG and the SCG, respectively, for each terminal, and information on the setting is notified to the terminal by, for example, an RRC message via the master eNB. As for pSCell, as described above, an agreement is formed in 3GPP by the secondary eNB selecting from SCG. Then, at this time, the secondary eNB may make this selection using the assist information notified from the master eNB. However, a specific method for this selection, what information should be used as assist information, and the like have not been determined at present.

  Therefore, in the following, a specific method of selecting a pSCell by the secondary eNB with the assistance of the master eNB will be proposed.

(Configuration of Master eNB and Secondary eNB)
FIG. 3 illustrates a hardware configuration example of the master eNB and the secondary eNB (base station device) according to the present embodiment. The master eNB and the secondary eNB include, for example, a CPU 301, a ROM 302, a RAM 303, an external storage device 304, and a communication device 305. In the master eNB and the secondary eNB, the CPU 301 executes a program for realizing each function of the master eNB and the secondary eNB as described below, which is recorded in, for example, the ROM 302, the RAM 303, or the external storage device 304.

  Then, the master eNB and the secondary eNB control the communication device 305 by, for example, the CPU 301 to perform communication between the master eNB and the secondary eNB and the terminal or communication between the eNBs between the master eNB and the secondary eNB. Note that the master eNB and the secondary eNB may include dedicated hardware for executing each function, or may execute a part by hardware and execute the other part by a computer that operates a program. Further, all functions may be executed by a computer and a program.

  Although FIG. 3 shows that the master eNB and the secondary eNB have one communication device 305, there may be more than one communication device 305, or the communication device 305 may include a plurality of communication devices. It may be configured. That is, for example, the master eNB and the secondary eNB may have a communication device for communication between eNBs and a communication device for communication with terminals.

  Also, the master eNB and the secondary eNB may prepare a communication device for communication with the terminal for each CC. Note that the communication device 305 may include a plurality of units for baseband processing, and may be configured to transmit signals in a plurality of CCs generated by the units using one antenna. In this case, for example, by assigning identification information (global ID) for uniquely specifying the unit, one CC for one eNB can be specified by the global ID. Note that a cell ID may be assigned to each frequency band (CC). In this case, by specifying two pieces of identification information of a cell ID and an ID for specifying an eNB, one CC for one eNB is determined. Can be specified.

  Subsequently, a functional configuration of the master eNB will be described. FIG. 4 is a block diagram illustrating a functional configuration example of the master eNB according to the present embodiment. The master eNB includes, for example, a wireless communication unit 401, a wired communication unit 402, a wireless quality information acquisition unit 403, and an assist information generation unit 404.

  The wireless communication unit 401 is a functional unit for performing wireless communication, and establishes a wireless connection with, for example, a terminal to perform wireless communication. That is, the wireless communication unit 401 establishes a connection with the terminal in one or more of the plurality of cells included in the MCG. Then, the wireless communication unit 401 selects, for example, one cell as the PCell from one or more cells for establishing a connection, and notifies the terminal by an RRC message. The terminal recognizes the PCell that has to transmit the PUCCH according to the RRC message. Then, wireless communication section 401 receives PUCCH from the terminal in PCell. In addition, the wireless communication unit 401 transmits data to the terminal in the PCell or, for example, in a downlink serving cell. Further, wireless communication section 401 receives data from the terminal in the PCell or in another cell in addition thereto. The wireless communication unit 401 can further receive, for example, a measurement report (Measurement Report) including information such as reference signal reception power (RSRP) or reference signal reception quality (RSRQ) from the terminal. The received measurement report is input to wireless quality information acquisition section 403.

  The wired communication unit 402 is a functional unit for performing wired communication, and establishes a connection with, for example, a secondary eNB to perform wired communication. For example, the wired communication unit 402 notifies the secondary eNB of the assist information generated by the assist information generating unit 404 described later when the secondary eNB selects pSCell. Note that the master eNB and the secondary eNB may be connected by, for example, a fixed wireless line or the like instead of a wired line. In this case, the wired communication unit 402 may not be necessary. In addition, when there is a wireless section in the middle of the connection between the master eNB and the secondary eNB, the wired communication unit 402 may exist to establish a wired connection with the end point of the wireless section in the middle. Good.

  The wireless quality information acquisition unit 403 acquires information related to the wireless quality of the wireless signal received by the terminal, for one or more cells included in the plurality of cells included in the SCG, received by the wireless communication unit 401. That is, the radio quality information acquisition unit 403 acquires, for example, information on RSRP or RSRQ as radio quality information in the terminal. This wireless quality information is acquired for each terminal. The acquired wireless quality information is input to the assist information generation unit 404.

  The assist information generation unit 404 generates assist information based on the wireless quality information. The generated assist information is transmitted to the secondary eNB via the wired communication unit 402. The assist information generation unit 404 generates, for example, assist information including the radio quality information of each of the cells for which the radio quality information has been acquired from a certain terminal. In this case, the identification information of the cell and the radio quality information are associated with each other and included in the assist information in order to clearly indicate what radio quality was obtained in which cell. Note that the assist information is generated separately for each of the plurality of terminals, for example. Note that the assist information generating unit 404 may form a signal in which assist information corresponding to a plurality of terminals is integrated into one, and transmit the signal to the secondary eNB via the wired communication unit 402.

  The assist information generation unit 404 is, for example, a candidate cell extraction unit that extracts some of the cells included in the SCG as candidate cells to be selected as a pSCell by the secondary eNB, based on the radio quality information. 405 may be further included.

  The candidate cell extracting unit 405 extracts, for example, a predetermined number of cells having higher radio quality from the plurality of cells included in the SCG as the above-mentioned partial cells, based on the radio quality information. In addition, the candidate cell extracting unit 405 may, for example, extract, from the plurality of cells included in the SCG, a cell whose wireless quality exceeds a predetermined value as a part of the cells based on the wireless quality information. . Furthermore, at this time, when the number of cells whose radio quality exceeds a predetermined value exceeds a predetermined number, the candidate cell extracting unit 405 may selectively extract a predetermined number of cells. At this time, for example, the candidate cell extracting unit 405 may randomly select and extract a predetermined number of cells from cells whose radio quality exceeds a predetermined value, or A number of cells may be selected and extracted.

  The assist information generating unit 404 generates assist information by including information for identifying some extracted cells. The information for specifying this cell is, for example, identification information for identifying each cell in the secondary eNB. In this case, by transmitting identification information about a certain cell to the secondary eNB, the one cell in the secondary eNB can be specified by a combination of the destination and the identification information. Similarly, the information for specifying the cell may be configured to include the identification information of the secondary eNB and the identification information of the cell. As described above, a certain cell in a certain secondary eNB can be uniquely specified by a combination of the identification information of the secondary eNB and the identification information of the cell. Further, different IDs are assigned to the cells of each eNB, and if there is identification information that can uniquely identify any cell in any eNB, the identification information is used as information for identifying the cell. You may be. For example, a unit for baseband processing for each cell is assigned a global ID for uniquely specifying the unit. Therefore, this global ID can be used as information for specifying a cell.

  The assist information generating unit 404 may include the information for specifying the extracted part of the cells in the assist information in an order according to the rank of the radio quality. For example, among the five cells, the first cell, the second cell, and the fourth cell are extracted as the above-described partial cells, and the radio qualities are the fourth cell, the first cell, The case where the cell is the second cell will be described. In this case, the assist information generation unit 404 causes the assist information to include information for specifying cells in the order of, for example, “4”, “1”, and “2”. Upon receiving this information, the secondary eNB can grasp that the fourth cell has the best radio quality, and subsequently the radio quality of the first cell and the second cell decreases. . Therefore, the secondary eNB may select the fourth cell as a cell in which the terminal has to transmit the PUCCH, for example, because the fourth cell is considered to be the cell having the best PUCCH reception quality. it can. Note that the assist information generation unit 404 may include, for example, information that specifies cells in an order such as “2”, “1”, and “4” in the assist information. Also in this case, the secondary eNB receives the information, so that the fourth cell has the best radio quality, and subsequently the radio quality of the first cell and the second cell decreases. Can be grasped.

  Note that the assist information generating unit 404 may generate assist information by adding, to the extracted cells, information on the order of the order of the radio quality. For example, in the above case, the assist information generation unit 404 adds information “2” for the first cell, “3” for the second cell, and “1” for the fourth cell, and outputs the assist information. May be generated. Further, the assist information may include, for example, a field that includes information of the rank of the radio quality for each cell, and the assist information generating unit 404 stores the numerical value of the rank in this field, Assist information may be generated. That is, for example, the assist information generation unit 404 sets “2” in the field for the first cell, “3” in the field for the second cell, “1” in the field for the fourth cell, Assist information may be generated by storing the information. The assist information generation unit 404 may, for example, store “0” in a field for a cell having a rank higher than a predetermined number.

  In addition, the assist information generating unit 404 may generate assist information including information on the radio quality of some of the extracted cells. That is, for example, when the first cell, the second cell, and the fourth cell among the five cells are extracted as the above-described partial cells, for example, the values of RSRP or RSRQ for these cells are Included and assist information is generated. Note that a value other than RSRP or RSRQ may be used as the radio quality. In this case, since the order of the radio quality is clear based on the information of the radio quality, it is not necessary to include the information of the above-mentioned order, but this information may be included together. This is because the master eNB may not know how the secondary eNB uses the assist information.

  Subsequently, a functional configuration of the secondary eNB will be described. FIG. 5 is a block diagram illustrating a functional configuration example of the secondary eNB according to the present embodiment. The secondary eNB includes, for example, a wireless communication unit 501, a wired communication unit 502, an assist information acquisition unit 503, and a pSCell selection unit 504.

  The wireless communication unit 501 is a functional unit for performing wireless communication, and establishes a wireless connection with, for example, a terminal to perform wireless communication. That is, the wireless communication unit 501 establishes a connection with a terminal in one or more of a plurality of cells included in the SCG. Then, the wireless communication unit 501 receives the PUCCH from the terminal in the pSCell, for example, one cell selected by the pSCell selection unit 504 among the one or more cells that establish a connection. In addition, the wireless communication unit 501 transmits data to the terminal in the pSCell or the serving cell for downlink, for example. Further, wireless communication section 501 receives data from the terminal in pSCell or in another cell in addition thereto.

  The wired communication unit 502 is a functional unit for performing wired communication, and establishes a connection with, for example, a master eNB to perform wired communication. The wired communication unit 502 receives, for example, data such as assist information transmitted from the master eNB. Note that the master eNB and the secondary eNB may be connected by a wireless line such as a wireless entrance instead of a wired line. In this case, the wired communication unit 502 need not be provided. Further, when there is a wireless section in the middle of the connection between the master eNB and the secondary eNB, the wired communication unit 502 may exist to establish a wired connection with the end point of the wireless section in the middle. Good.

  The assist information acquiring unit 503 acquires assist information from a signal from the master eNB received via the wired communication unit 502, for example. The acquired assist information is input to the pSCell selection unit 504. In addition, the assist information acquisition unit 503 may wait for the arrival of assist information from the master eNB. Good.

  Based on the input assist information, pSCell selecting section 504 selects a pSCell for a terminal corresponding to the assist information from a plurality of cells included in the SCG. The pSCell selecting unit 504, for example, when the assist information includes information that specifies some cells extracted by the master eNB among the plurality of cells included in the SCG, Select pSCell from some cells. When the assist information indicates the order of the radio quality for some of the cells in the assist information, the pSCell selecting unit 504 may select, for example, the cell with the highest radio quality as the pSCell. Here, the pSCell selecting unit 504 selects a cell having the next highest radio quality as the pSCell, for example, when the number of terminals having the cell having the highest radio quality as the pSCell is equal to or more than a predetermined number, for example. Is also good.

  Further, if the assist information includes information on radio quality such as the value of RSRP or RSRQ in each cell, the pSCell selecting unit 504 determines whether the value of the radio quality is equal to or more than a predetermined value. May be selected from among pSCells. Further, the pSCell selecting unit 504 may select the cell having the highest radio quality included in the assist information as the pSCell by giving priority to the cell having the highest radio quality. That is, for a cell having the highest radio quality, for example, when the number of terminals having the cell as the pSCell is equal to or more than a predetermined number, a cell having the next highest radio quality may be selected as the pSCell. Note that when the terminal measures the radio quality for all cells of the SCG, all the values may be included in the assist information. A cell whose quality value is equal to or greater than a predetermined value may be selected as pSCell.

  The information of the cell selected by the pSCell selection unit 504 is notified to the master eNB via, for example, the wired communication unit 502. Note that the pSCell selection unit 504 may control the wireless communication unit 501 using the selected pSCell.

  When receiving the information of the selected cell via the wired communication unit 402, the master eNB generates an RRC message to set the pSCell, and transmits the generated RRC message via the wireless communication unit 401 to the terminal. Send to

(Processing flow)
Subsequently, the flow of processing executed by the master eNB, the secondary eNB, and the terminal in the wireless communication system will be described. FIG. 6 is a sequence diagram illustrating an example of a processing flow according to the present embodiment. At the start of the processing in FIG. 6, it is assumed that the connection setting between the terminal and the master eNB, such as which cell becomes a PCell among a plurality of cells included in the MCG, has been completed. I do.

  In the process, first, the terminal observes the radio signals received from the master eNB and the secondary eNB, and measures the radio quality (S601). Note that the measurement of the radio quality can be performed for one or more cells included in the MCG and one or more cells included in the SCG. Here, the radio quality measurement is mainly performed for the cells included in the SCG. It suffices if measurements are taken. This measurement may be performed when a predetermined event occurs, for example, when the terminal enters a range of any cell formed by the secondary eNB. It should be noted that the predetermined event is determined by the setting of the wireless communication system, and it is apparent that the predetermined event is not limited to entering the range of any cell formed by the secondary eNB. Subsequently, the terminal notifies the master eNB of at least the radio quality measured for the SCG (S602). The notification of the radio quality is performed in the PCell included in the MCG.

  After acquiring the information on the radio quality, the master eNB subsequently generates assist information for the secondary eNB to select pSCell (S603). At this time, the assist information includes, for example, information for identifying a predetermined number of cells from the higher radio quality of the radio signal received by the terminal. Further, the assist information may be information for specifying a cell whose wireless quality exceeds a predetermined value. Further, when there are a predetermined number or more cells whose radio quality exceeds a predetermined value, the assist information may be information for specifying a predetermined number of cells selected from the cells. The information for specifying a cell can be as shown in some examples described above, and can be, for example, a global ID that uniquely specifies a unit for baseband processing corresponding to the cell. If the assist information includes information for specifying a plurality of cells, the information for specifying the cells is included in an order according to the order of the radio quality of those cells, and the assist information is generated. Is also good. Further, the assist information may be configured by a value of radio quality (for example, RSRP or RSRQ) measured by the terminal for each cell included in the SCG. In this case, for example, if the radio quality was not measured for some cells, the same value as when the radio quality was the lowest value is included as radio quality information for the some cells. Is also good. Further, as described above, the assist information includes wireless quality information on a predetermined number of cells or cells whose wireless quality exceeds a predetermined value, and may not include wireless quality information on other cells. Thereafter, the master eNB notifies the generated assist information to the secondary eNB (S604).

  The secondary eNB uses the notified assist information to select pSCell, which is a cell in which the terminal has to transmit the PUCCH (S605). Here, the secondary eNB does not necessarily have to use the notified assist information, and may or may not use the assist information as occasion demands. For example, when the accuracy of the radio quality information used when the assist information is generated is low, the secondary eNB may not use the information. In this case, the master eNB may determine this accuracy information and notify the secondary eNB, for example, according to the reception quality of the wireless signal when the notification of the wireless quality in S602 is performed. In addition, depending on the setting of the secondary eNB, whether the secondary eNB uses or does not use the assist information notified from the master eNB may be determined.

  Note that this selection of pSCell may be executed again for a terminal for which pSCell has already been set. That is, based on the radio quality of the radio signal from each cell included in the SCG in each terminal, the above selection for resetting the pSCell in each terminal may be performed. At this time, the secondary eNB may also select a cell (secondary SCell, sSCell) used for communication with the terminal.

  When selecting the pSCell, the secondary eNB notifies the master eNB of information indicating the selected pSCell (S606). If the sSCell has been determined in S605, information indicating the sSCell may also be notified to the master eNB in this notification. This notification may be transmitted, for example, as an inter eNB RRC message (Inter eNB RRC message).

  Upon receiving the notification of the information indicating the pSCell for a terminal, the master eNB transmits an RRC message (for example, an RRCConnectionReconfiguration message) for wireless connection setting for the terminal (S607). By this message, information indicating the pSCell to which the terminal should transmit the PUCCH is notified to the terminal. After that, the terminal sets wireless communication so as to transmit the PUCCH in the notified pSCell. Then, in response to the completion of the wireless connection setting, the terminal transmits, for example, an RRCConnectionReconfigurationComplete message (S608), and ends this processing.

  Thus, in the present embodiment, based on the radio quality measured by the terminal, the master eNB generates assist information that can be used when the secondary eNB selects pSCell for the terminal. Then, the secondary eNB receives the provision of the assist information from the master eNB, and selects pSCell based on the information. According to such a method, it becomes possible to select pSCell such that the communication quality of the PUCCH transmitted from the terminal to the secondary eNB is improved.

Claims (8)

When the terminal device connects to the first base station device and the second base station device, the terminal device is specified by the second base station device from a plurality of frequency bands that can be used by the second base station device. In a wireless communication system in which a frequency band in which the terminal device can transmit a control channel to the second base station device is notified to the terminal device, the terminal device,
Notifying means for notifying the first base station device of information on radio quality of a signal received from the second base station device, for one or more frequency bands of the plurality of frequency bands,
Acquiring means for acquiring, from the first base station apparatus, information indicating a specific frequency band in which the control channel can be transmitted;
Has,
The specific frequency band indicates first information indicating a predetermined number of frequency bands extracted by the first base station device, and a frequency band different from the frequency band indicated by the first information. The second information is notified to the second base station device in a form that can be distinguished from the second information, and the second information is transmitted by the second base station device in a frequency band specified based on the first information and the second information. is there,
A terminal device characterized by the above-mentioned.   The terminal device according to claim 1, wherein the information on radio quality related to a signal received from the second base station device is information on which frequency is valid.   The terminal device according to claim 1, wherein the predetermined number is a plurality.   The terminal device according to any one of claims 1 to 3, wherein the number of frequency bands indicated by the second information is plural. The information on the radio quality includes at least one of reference signal reception power and reference signal reception quality,
The terminal device according to claim 1, wherein: When the terminal device connects to the first base station device and the second base station device, the terminal device is specified by the second base station device from a plurality of frequency bands that can be used by the second base station device. A radio communication system in which a frequency band in which the terminal device can transmit a control channel to the second base station device is notified to the terminal device,
The terminal device,
A first notifying unit for notifying the first base station apparatus of information regarding radio quality of a signal received from the second base station apparatus for at least one of the plurality of frequency bands. When,
A first acquisition unit that acquires, from the first base station apparatus, information indicating a specific frequency band in which the control channel can be transmitted;
Has,
The first base station device comprises:
From the terminal device, a second acquisition unit that acquires information on the radio quality,
Extracting means for extracting a predetermined number of frequency bands from the plurality of frequency bands,
A format capable of distinguishing the first information indicating the predetermined number of frequency bands extracted by the extracting means from the second information indicating a frequency band different from the frequency band indicated by the first information A second notifying means for notifying the second base station device with
Has,
The second base station device includes:
A third obtaining unit that obtains the first information and the second information from the first base station device;
Specifying means for specifying the specific frequency band based on the information obtained by the third obtaining means;
A third notifying unit that notifies the terminal device of the specific frequency band specified by the specifying unit via the first base station device;
A wireless communication system comprising: When the terminal device connects to the first base station device and the second base station device, the terminal device is specified by the second base station device from a plurality of frequency bands that can be used by the second base station device. A control method executed by the terminal device in a wireless communication system in which a frequency band in which the terminal device can transmit a control channel to the second base station device is notified to the terminal device,
A notification step of notifying the first base station apparatus of information regarding radio quality of a signal received from the second base station apparatus, for one or more frequency bands of the plurality of frequency bands,
From the first base station apparatus, an acquisition step of acquiring information indicating a specific frequency band in which the control channel can be transmitted;
Has,
The specific frequency band indicates first information indicating a predetermined number of frequency bands extracted by the first base station device, and a frequency band different from the frequency band indicated by the first information. The second information is notified to the second base station device in a form that can be distinguished from the second information, and the second information is transmitted by the second base station device in a frequency band specified based on the first information and the second information. is there,
A control method characterized in that: When the terminal device connects to the first base station device and the second base station device, the terminal device is specified by the second base station device from a plurality of frequency bands that can be used by the second base station device. In a wireless communication system in which a frequency band in which the terminal device can transmit a control channel to the second base station device is notified to the terminal device, a computer provided in the terminal device includes:
The first base station device, for one or more frequency bands of the plurality of frequency bands, to notify information about radio quality related to a signal received from the second base station device,
From the first base station device, to obtain information indicating a specific frequency band in which the control channel can be transmitted,
A program,
The specific frequency band indicates first information indicating a predetermined number of frequency bands extracted by the first base station device, and a frequency band different from the frequency band indicated by the first information. The second information is notified to the second base station device in a form that can be distinguished from the second information, and the second information is transmitted by the second base station device in a frequency band specified based on the first information and the second information. is there,
A program characterized by that:

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