JP2015084528A - Mobile communication system, base station, and user terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system, a base station, and a user terminal which can prevent interference between base stations.SOLUTION: A mobile communication system adopting a frequency division duplex method, comprises: one or a plurality of UE 200 (user terminals) which communicate with a serving cell; and an HeNB 100 (home base station) forming a first cell and a second cell. The first cell uses a pair of first uplink carrier and downlink carrier for communication, and the second cell uses a pair of second uplink carrier and downlink carrier for communication. The HeNB 100 and UE 200 switch the serving cell of the UE 200 between the first cell and the second cell by performing a handover procedure.

Description

  The present invention relates to a mobile communication system, a base station, and a user terminal that employ an FDD scheme.

  3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, has been promoting standardization of LTE Advanced with advanced LTE (Long Term Evolution) since 3GPP Release 10.

  LTE and LTE Advanced can employ frequency division duplex (FDD) or time division duplex (TDD). In the FDD scheme, the carrier (frequency band) differs between uplink and downlink, and communication is performed using a pair of an uplink carrier and a downlink carrier.

  In LTE and LTE Advanced, a home base station, which is a small base station provided in a residence or company, is introduced (see Non-Patent Document 1). The home base station may configure a CSG (Closed Subscriber Group) cell that can be accessed only by a specific user in order to set an access restriction.

  Furthermore, LTE Advanced introduces carrier aggregation in which LTE carriers are positioned as component carriers and a plurality of carriers are used for communication in order to realize a wide band while ensuring backward compatibility with LTE (non-existing). Patent Document 1).

3GPP Technical Specification TS 36.300 V10.4.0

  By the way, the home base station can be installed arbitrarily by the user, unlike the macro base station installed by the station placement design of the operator, which causes interference between the base stations.

  For this reason, in 3GPP Release 11 and later, it is desired to implement a mechanism for avoiding inter-base station interference by applying the carrier aggregation described above.

  Therefore, the present invention provides a mobile communication system, a base station, and a user terminal that can avoid interference between base stations.

  According to a feature of the present invention, there is provided a mobile communication system that employs a frequency division duplex method, and one or a plurality of user terminals that communicate with a serving cell, and bases that constitute the first cell and the second cell The first cell uses a pair of a first uplink carrier and a downlink carrier for communication, and the second cell uses a pair of a second uplink carrier and the downlink carrier. Is used for communication, and the base station and the user terminal are provided with a mobile communication system that switches a serving cell of the user terminal between the first cell and the second cell by a handover procedure.

  According to another feature of the invention, the first cell uses a first radio frame for downlink communication, the second cell uses a second radio frame for downlink communication, and the base The station sets the first radio frame and the second radio frame differently so that the first carrier and the second cell share the downlink carrier in a time division manner. To do.

  According to another feature of the invention, the first radio frame includes a first MBSFN subframe and a first non-MBSFN subframe, and the second radio frame includes a second MBSFN subframe and A second non-MBSFN subframe, wherein the base station overlaps the first non-MBSFN subframe and the second MBSFN subframe on a time axis, and the second non-MBSFN subframe and The frame configurations of the first radio frame and the second radio frame are set so that the first MBSFN subframes overlap on the time axis.

  According to another feature of the invention, the base station adjusts the time division ratio based on traffic conditions in each of the first cell and the second cell. The frame configurations of the radio frame and the second radio frame are reset.

  According to another aspect of the present invention, the first radio frame includes a first specific subframe in which a downlink notification signal is to be transmitted, and the second radio frame is a first radio frame in which a downlink notification signal is to be transmitted. The base station includes the first radio frame and the second radio so that the first specific subframe and the second specific subframe do not overlap on a time axis. Set the frame configuration of each frame.

  According to another aspect of the present invention, the first radio frame includes a plurality of first subframes assigned with subframe numbers, and the second radio frame includes a plurality of first subframes assigned with subframe numbers. The first specific subframe is a subframe having a specific subframe number among the plurality of first subframes, and the second specific subframe is the plurality of second subframes. A subframe having the specific subframe number among the subframes, and the base station includes the plurality of the plurality of subframes so that the first specific subframe and the second specific subframe do not overlap on a time axis. The subframe numbers of the first subframe and the plurality of second subframes are set to be shifted by a predetermined number of subframes.

  According to another feature of the present invention, the user terminal is a process for the handover procedure in switching the serving cell between the first cell and the second cell. The measurement report process for reporting the measurement result of the reception state to the serving cell is omitted.

  According to another aspect of the present invention, the base station has a case where an interference power level in the first uplink carrier is higher than a predetermined level when the serving cell of the user terminal is the first cell. Then, control is performed to switch the serving cell of the user terminal from the first cell to the second cell.

  According to another aspect of the present invention, the base station controls to deactivate the first cell after switching the serving cell of the user terminal from the first cell to the second cell. .

  According to another aspect of the present invention, the base station receives a handover request or a connection request for a new user terminal while switching the serving cell of the user terminal from the first cell to the second cell. The new user terminal is controlled to be accommodated in the second cell.

  According to another feature of the present invention, the base station switches the serving cell of the user terminal from the first cell to the second cell, and then the interference power level in the first uplink carrier is a predetermined level. When it becomes smaller than this, after activating the first cell, control is performed to switch the serving cell of the user terminal from the second cell to the first cell.

  According to another aspect of the present invention, the base station controls to deactivate the second cell after switching the serving cell of the user terminal from the second cell to the first cell. .

  According to another feature of the present invention, the base station makes a handover request or connection request for a new user terminal while switching the serving cell of the user terminal from the second cell to the first cell. The new user terminal is controlled to be accommodated in the first cell.

  According to another aspect of the present invention, the base station performs control so as to preferentially switch a serving cell of a user terminal having a higher priority among the user terminals based on a communication state of the user terminal.

  According to a feature of the present invention, in a mobile communication system employing a frequency division duplex scheme, a base station configuring a first cell and a second cell, wherein a serving cell of a user terminal is set in the first cell by a handover procedure. A control unit configured to control switching between one cell and the second cell, wherein the first cell uses a pair of a first uplink carrier and a downlink carrier for communication, and the second cell The cell is provided with a base station that uses a pair of a second uplink carrier and the downlink carrier for communication.

  According to a feature of the present invention, in a mobile communication system employing a frequency division duplex scheme, a user terminal that communicates with a serving cell, wherein the serving cell is divided into a first cell and a second cell by a handover procedure. The first cell uses a pair of a first uplink carrier and a downlink carrier for communication, and the second cell communicates with a second uplink carrier. A user terminal that uses a pair with the downlink carrier for communication is provided.

1 is an overall configuration diagram of a mobile communication system according to a first embodiment. It is a figure for demonstrating the case where interference in UL arises. It is a figure for demonstrating operation | movement of the mobile communication system at the time of UL interference detection. It is a figure for demonstrating operation | movement of the mobile communication system after completion of the handover procedure which concerns on 1st Embodiment. FIG. 3 is a frame configuration diagram of a radio frame in the mobile communication system according to the first embodiment and the second embodiment. FIG. 4 is a frame configuration diagram of each of a first radio frame used in a first cell and a second radio frame used in a second cell according to the first embodiment and the second embodiment. It is a block diagram of HeNB which concerns on 1st Embodiment and 2nd Embodiment. It is a block diagram of UE which concerns on 1st Embodiment and 2nd Embodiment. It is an operation | movement flowchart of HeNB which concerns on 1st Embodiment. FIG. 10 is an operational flowchart of the HeNB when there is a handover request for a new UE between step S103 and step S109 in FIG. 9. FIG. 10 is an operation flow diagram of the HeNB when there is an access (connection request) from a new UE between step S103 and step S109 in FIG. It is an operation | movement flowchart of UE which concerns on 2nd Embodiment. An example of the state after switching the serving cell of UE from the 1st cell to the 2nd cell by the hand-over procedure demonstrated in 1st Embodiment is shown. It is a figure for demonstrating operation | movement of the mobile communication system when the interference in UL CC (1st UL CC) of a 1st cell reduces. It is a figure for demonstrating operation | movement of the mobile communication system after completion of the handover procedure which concerns on 2nd Embodiment. It is an operation | movement flowchart of HeNB which concerns on 2nd Embodiment. [Fig. 17] Fig. 17 is an operation flowchart of the HeNB when there is a handover request for a new UE between step S203 to step S209 in Fig. 16. FIG. 17 is an operation flowchart of the HeNB when there is an access (connection request) from a new UE between step S203 and step S209 in FIG. It is an operation | movement flowchart of UE which concerns on 2nd Embodiment.

  A first embodiment, a second embodiment, and other embodiments of the present invention will be described with reference to the drawings. In the drawings according to the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

[First Embodiment]
FIG. 1 is an overall configuration diagram of a mobile communication system 1 according to the present embodiment. The mobile communication system 1 employs an FDD scheme.

  As illustrated in FIG. 1, the mobile communication system 1 includes a plurality of home base stations (HeNBs) 100 and a plurality of user terminals (User Equipments: UEs) 200.

  The HeNB 100 is configured based on 3GPP Release 10 or later, but does not support carrier aggregation. That is, the HeNB 100 does not support the use of two component carriers (CC) for downlink (DL) communication simultaneously by the standard. Each CC includes a plurality of resource blocks (RBs) that are resource allocation units.

  In the present embodiment, an environment is assumed in which a plurality of HeNBs 100 having different CSGs are installed, such as an office environment. The HeNB 100-1 configures a CSG cell of CSG # 1, the HeNB 100-2 configures a CSG cell of CSG # 2, and the HeNB 100-3 configures a CSG cell of CSG # 3.

  Each HeNB 100 discriminates CCs used in the vicinity by monitoring radio signals transmitted and received in the vicinity when the power is turned on. And each HeNB100 determines CC different from CC currently used in periphery as CC used by self HeNB.

  The HeNB 100-1 and the HeNB 100-2 are installed close to each other. For this reason, HeNB100-1 and HeNB100-2 use different CC for communication for every uplink (UL) and downlink (DL). In detail, HeNB100-1 uses CC # 1 for UL and CC # 2 for DL. On the other hand, HeNB100-2 uses CC # 3 for UL and CC # 4 for DL.

  UE200-1 belongs to CSG # 1, and is connected to HeNB100-1. That is, UE200-1 makes the CSG cell comprised by HeNB100-1 the serving cell. UE200-1 communicates with HeNB100-1 using CC # 1 for UL and CC # 2 for DL. In FIG. 1, only one UE 200-1 connected to the HeNB 100-1 is illustrated, but a plurality of UEs 200-1 may be provided.

  Moreover, UE200-2 belongs to CSG # 2, and is connected to HeNB100-2. That is, UE200-2 makes the CSG cell comprised by HeNB100-2 the serving cell. UE200-2 communicates with HeNB100-2 using CC # 3 for UL and CC # 4 for DL. In FIG. 1, only one UE 200-2 connected to the HeNB 100-2 is illustrated, but a plurality of UEs 200-2 may be provided.

  The HeNB 100-3 is installed far away from the HeNB 100-1 and the HeNB 100-2. For this reason, HeNB100-3 judges that CC is not being used around by monitoring mentioned above, and determines CC used by self HeNB arbitrarily. As a result, the HeNB 100-3 uses CC # 1 for the UL and CC # 2 for the DL, like the HeNB 100-1.

  UE200-3 belongs to CSG # 3, and is connected to HeNB100-3. That is, UE200-3 makes the CSG cell comprised by HeNB100-3 the serving cell. UE200-3 communicates with HeNB100-3, using CC # 1 for UL and CC # 2 for DL. In FIG. 1, only one UE 200-3 connected to the HeNB 100-3 is illustrated, but a plurality of UEs 200-3 may be provided.

  If the HeNB 100 and the UE 200 are in the positional relationship shown in FIG. 1, no interference occurs in either UL or DL. However, in an environment where a plurality of HeNBs 100 having different CSGs are installed, the UE 200 is not allowed to connect to neighboring HeNBs 100 belonging to different CSGs, and must be connected to distant HeNBs 100 belonging to the same CSG. In this case, interference in the UL occurs.

  FIG. 2 is a diagram for explaining a case where interference in UL occurs.

  As shown in FIG. 2, UE200-3 which belongs to CSG # 3 is the vicinity of HeNB100-1, and is located in the distant place of HeNB100-3. The UE 200-3 connects to a distant HeNB 100-3 belonging to the same CSG, although the radio state is not good.

  The UL signal from the UE 200-3 to the HeNB 100-3 is received not only by the HeNB 100-3 but also by the HeNB 100-1. Moreover, HeNB100-3 and UE200-3 are using CC # 1 for UL similarly to HeNB100-1 and UE200-1. Therefore, the UL signal from the UE 200-3 to the HeNB 100-3 gives strong interference to the HeNB 100-1. As a result, the HeNB 100-1 cannot normally receive the UL signal from the UE 200-1, and communication between the HeNB 100-1 and the UE 200-1 is interrupted.

  FIG. 3 is a diagram for explaining the operation of the mobile communication system 1 when UL interference is detected.

  As illustrated in FIG. 3, when the HeNB 100-1 according to the present embodiment detects interference in the UL (that is, when the interference power level exceeds a predetermined level), the CSG cell configured so far (hereinafter, referred to as “interference power level”) , A new CSG cell (hereinafter referred to as a “second cell”).

  The second cell differs from the first cell in the CC used for UL (hereinafter referred to as “UL CC”), and the CC used for DL (hereinafter referred to as “DL CC”) is the first. The same cell as For example, the second cell uses CC # 5 for UL and CC # 1 for DL. In addition, the second cell has a cell ID different from that of the first cell and has the same CSG ID as the first cell.

  After the configuration of the second cell, the HeNB 100-1 and the UE 200-1 switch the serving cell of the UE 200-1 from the first cell to the second cell by a handover procedure. The handover procedure is performed in accordance with “10 Mobility” described in Non-Patent Document 1, for example.

  As a result, the HeNB 100-1 and the UE 200-1 use another CC (that is, CC # 5) for UL communication instead of the CC in which interference in the UL is detected (that is, CC # 1). , Interference in the UL is avoided.

  FIG. 4 is a diagram for explaining the operation of the mobile communication system 1 after completion of the handover procedure.

  As illustrated in FIG. 4, after switching the serving cell of the UE 200-1 from the first cell to the second cell, the HeNB 100-1 deactivates the first cell. Deactivation of the first cell means, for example, stopping transmission of a DL signal (including a reference signal, cell ID, CSG ID, and the like) from the first cell. In addition, when there are a plurality of UEs 200-1, the HeNB 100-1 deactivates the first cell after switching the serving cells of all the UEs 200-1 from the first cell to the second cell.

  Although interference in the UL is avoided in this way, the first cell and the second cell use the same DL CC, so that interference in the DL occurs between the first cell and the second cell. obtain.

  For this reason, in this embodiment, the HeNB 100-1 uses a radio frame (hereinafter referred to as a DL frame) used by the first cell for DL communication so that the first DL and the second cell share the same DL CC in a time division manner. , The configuration of the "first radio frame") and the configuration of the radio frame used by the second cell for DL communication (hereinafter referred to as "second radio frame") are set differently. .

  FIG. 5 is a frame configuration diagram of a radio frame in the mobile communication system 1. The radio frames shown in FIG. 5 are provided side by side in the time direction.

  As shown in FIG. 5, the radio frame is composed of 10 subframes arranged in the time direction, and each subframe is composed of 2 slots. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. A subframe number is sequentially assigned to each subframe in the radio frame. Each slot includes 6 or 7 OFDM symbols in the time direction, and includes a plurality of RBs in the frequency direction.

  The HeNB 100 transmits a DL broadcast signal in a specific subframe in the radio frame. The DL notification signal is a synchronization signal, system information, or the like. The synchronization signal includes a primary synchronization signal (PSS) and a secondary synchronization signal (SSS).

  The PSS is mapped to the last OFDM symbol in each slot of the subframe with the subframe number # 0 and the subframe with the # 5, and the SSS is the second OFDM symbol from the end of the same slot (that is, immediately before the PSS). Maps to a symbol.

  When the UE 200 normally receives the PSS and the SSS, the UE 200 can discover and synchronize with the cell. When the UE 200 normally receives the system information from the cell after the cell search is completed, the UE 200 acquires information necessary for communication in the cell from the system information, and performs a connection process (access and registration) to the cell. ).

  The system information includes a master information block (MIB) and a system information block (SIB). The MIB is transmitted using a physical broadcast channel (PBCH) mapped to a subframe whose subframe number is # 0. The MIB includes information necessary for receiving the SIB. The SIB is transmitted using a physical downlink shared channel (PDSCH). The SIB includes information necessary for accessing the cell. SIB1 is mapped to subframe # 5, and SIB2 and subsequent are mapped to subframes described in SIB1.

  FIG. 6 is a frame configuration diagram of each of the first radio frame used in the first cell and the second radio frame used in the second cell. 6 indicate subframes, and a hatched subframe is an MBSFN (Multicast / Broadcast Single Frequency Network) subframe that can be set for MBMS (Multimedia Broadcast Multicast Services). On the other hand, the subframes without hatching are subframes that cannot be set as MBSFN subframes (hereinafter referred to as “non-MBSFN subframes”). The frame configuration shown in FIG. 6 is applied at least in a period from the configuration (activation) of the second cell to the deactivation of the first cell.

  As shown in FIG. 6, the first radio frame includes a first MBSFN subframe (subframe numbers # 1, # 2, # 3, # 6, # 7, and # 8) and a first non-MBSFN subframe. (Subframe numbers # 0, # 4, # 5, # 9). The second radio frame includes a second MBSFN subframe (subframe number # 1, # 2, # 3, # 6, # 7, # 8) and a second non-MBSFN subframe (subframe number # 0, # 4, # 5, # 9).

  The HeNB 100-1 includes a first non-MBSFN subframe (subframe numbers # 0, # 4, # 5, and # 9 of the first radio frame) and a second MBSFN subframe (subframe of the second radio frame). Number # 1, # 2, # 6, # 7) overlap on the time axis, and the second non-MBSFN subframe (second radio frame subframe number # 0, # 4, # 5, # 9) and the first MBSFN subframe (subframe numbers # 2, # 3, # 7, # 8 of the first radio frame) overlap on the time axis, Set the frame configuration of each radio frame.

  As a result, normal communication with the UE 200 is possible in the non-MBSFN subframe in one radio frame, and normal communication as the MBSFN subframe cannot be performed for the subframe overlapping with the non-MBSFN subframe in the other radio frame. Put it in a state. As a result, a single downlink carrier can be shared in a time division manner in the first cell and the second cell.

  In FIG. 6, some MBSFN subframes (subframe numbers # 1 and # 6) in the first radio frame and some MBSFN subframes (subframe numbers # 8 and # 6 in the second radio frame). # 3) overlaps on the time axis. One of the MBSFN subframes that overlaps on the time axis can be set as a normal subframe (non-MBSFN subframe).

  In the present embodiment, the HeNB 100-1 adjusts the time division ratio based on the traffic situation in each of the first cell and the second cell, so that the first radio frame and the second radio frame are adjusted. Reset each frame configuration. Specifically, among MBSFN subframes that overlap on the time axis, the MBSFN subframe corresponding to the cell with the higher traffic is set as a normal subframe (non-MBSFN subframe). As a result, in the cell having the higher traffic among the first cell and the second cell, more normal subframes (non-MBSFN subframes) can be used, and the communication capacity can be increased.

  As described above, the first radio frame includes a subframe (hereinafter referred to as a “first specific subframe”) to which a DL broadcast signal (MIB / SIB / PSS / SSS) is to be transmitted. The radio frame includes a subframe (hereinafter referred to as “second specific subframe”) to which a DL broadcast signal (MIB / SIB / PSS / SSS) is to be transmitted. Specifically, the first specific subframe is a subframe with subframe numbers # 0 and # 5 in the first radio frame, and the second specific subframe is a subframe in the second radio frame. The subframes have frame numbers # 0 and # 5.

  The HeNB 100-1 sets the frame configurations of the first radio frame and the second radio frame so that the first specific subframe and the second specific subframe do not overlap on the time axis. That is, it sets so that the sub-frame which should transmit DL alerting | reporting signal (MIB / SIB / PSS / SSS) does not overlap with a 1st radio frame and a 2nd radio frame.

  In the present embodiment, the HeNB 100-1 is configured so that the first specific subframe and the second specific subframe do not overlap each other on the time axis. The frame number is set by shifting by a predetermined number of subframes. Specifically, subframe number # 0 in the second radio frame has an offset of three subframes with reference to subframe number # 0 in the first radio frame.

  Next, the configuration of the HeNB 100 will be described. Since HeNB100-1-HeNB100-3 are comprised similarly, the structure of HeNB100-1 is demonstrated here. FIG. 7 is a block diagram of the HeNB 100-1.

  As illustrated in FIG. 7, the HeNB 100-1 includes an antenna 101, a radio communication unit 110, a network communication unit 120, a storage unit 130, and a control unit 140.

  The wireless communication unit 110 is configured to perform wireless communication via the antenna 101. For transmission, the radio communication unit 110 performs up-conversion and amplification of the baseband signal input from the control unit 140 and outputs the radio signal from the antenna 101. For reception, the radio communication unit 110 performs amplification and down-conversion of the reception signal input from the antenna 101, and then outputs a baseband signal to the control unit 140.

  The network communication unit 120 communicates with a core network (Evolved Packet Core: EPC) using the S1 interface. Moreover, the network communication part 120 performs communication (communication between base stations) with other HeNB using an X2 interface.

  The storage unit 130 is configured using, for example, a memory, and stores various types of information used for control and the like by the control unit 140. The storage unit 130 is, for example, the center frequency of each CC (CC # 1 to CC # N) and each CC (CC # 1) as information on each CC (CC # 1 to CC # N) that can be used in the mobile communication system. ~ CC # N) and other information. The memory | storage part 130 memorize | stores CSG ID which identifies CSG (namely, CSG # 1) to which HeNB100-1 belongs, and each cell ID of a 1st cell and a 2nd cell.

  The control unit 140 is configured using, for example, a processor, and controls various functions of the HeNB 100.

  The control unit 140 measures (monitors) the state of the radio signal received by the radio communication unit 110 for each CC based on the information about the CC stored in the storage unit 130 when the HeNB 100-1 is turned on. The CC used in is determined. And the control part 140 determines CC different from CC currently used in periphery as CC used in HeNB100-1. Note that the control unit 140 periodically performs monitoring even after determining the UL CC and DL CC.

  After determining the UL CC and DL CC, the control unit 140 transmits information indicating the UL CC (information on the center frequency and bandwidth) and information indicating the DL CC (information on the center frequency and bandwidth) to the SIB. The radio communication unit 110 is controlled so as to be periodically broadcast as an information element (IE) in its own cell. Moreover, the control part 140 controls the radio | wireless communication part 110 so that cell ID and CSG ID of the cell (1st cell) which HeNB100-1 comprises may be broadcast periodically.

  After accommodating UE200-1 in a 1st cell, the control part 140 allocates RB with respect to each of UL and DL to UE200-1 by a scheduler function. Specifically, the control unit 140 determines an RB to be allocated to the UE 200-1 from a plurality of RBs included in the UL CC of the first cell, and includes a plurality of RBs included in the DL CC of the first cell. The RB to be assigned to the UE 200-1 is determined from the inside. Then, the control unit 140 controls the radio communication unit 110 to transmit the determined UL and DL allocation RBs to the UE 200-1 on the physical downlink control channel (PDCCH).

  After accommodating UE 200-1 in the first cell, control unit 140 measures the interference power level in the UL CC of the first cell based on the reception state in radio communication unit 110. The control unit 140 determines the UL CC of the second cell when the interference power level exceeds a predetermined level. Specifically, based on the result of monitoring the surrounding CC usage, a CC that is not used in the vicinity or a CC with a low UL interference power level is determined as the UL CC of the second cell.

  The control unit 140 may determine the UL CC of the second cell based on the result of monitoring performed when the power is turned on, or may determine the UL CC of the second cell based on the result of monitoring performed periodically. You may decide. Alternatively, after determining handover to the second cell, monitoring may be performed again, and the UL CC of the second cell may be determined based on the monitoring result. Below, the case where UL CC of a 2nd cell is determined based on the result of the monitoring performed periodically is demonstrated.

  When determining the UL CC of the second cell, the control unit 140 configures (activates) the second cell and sets the frame configurations of the first radio frame and the second radio frame described above. . The activation of the second cell starts transmission of a DL signal (including a reference signal, cell ID, CSG ID, etc.) from the second cell, and CC information (second This means processing for controlling the wireless communication unit 110 to start transmission of information on the center frequency and bandwidth of each of the UL CC and DL CC of the cell. CC information from the second cell is transmitted as an SIB IE.

  In addition, the control unit 140 transmits information indicating the frame configuration of the first radio frame after the change in the first cell, and transmits information indicating the frame configuration of the second radio frame in the second cell. The wireless communication unit 110 is controlled. The information indicating the frame configuration means a list of subframe numbers of the MBSFN subframe described above and information on the offset of the subframe described above.

  Further, the control unit 140 performs measurement control for the UE 200-1. For example, the control unit 140 controls the radio communication unit 110 to transmit measurement control information for controlling to omit the measurement report process to the UE 200-1. The measurement report process is a process for a handover procedure, and is a process for reporting a reception state measurement result in the UE 200-1 to the serving cell. As described above, since the UE 200-1 performs a handover to the second cell, the measurement report process is unnecessary. Therefore, overhead can be reduced by omitting the measurement report processing.

  Alternatively, instead of omitting the measurement report process, the control unit 140 wirelessly transmits an offset value such that the measurement result for the second cell is higher than the measurement result for the first cell to the UE 200-1. The communication unit 110 may be controlled. If a measurement report indicating that the measurement result for the second cell is higher than the measurement result for the first cell is received from the UE 200-1, the UE 200-1 is handed over to the second cell according to a normal handover procedure. be able to.

  And the control part 140 starts the handover procedure of UE200-1.

  First, the control unit 140 controls the radio communication unit 110 so as to prepare for acceptance of the UE 200-1 in the second cell. Specifically, a predetermined communication context in the first cell is taken over by the second cell, and an RB for the UE 200-1 is secured in the second cell.

  Secondly, the control unit 140 controls the radio communication unit 110 to transmit a handover command for instructing handover to the second cell to the UE 200-1.

  3rdly, the control part 140 accommodates UE200-1 which accessed the 2nd cell with the hand-over command in a 2nd cell. As a result, the serving cell of UE 200-1 is switched from the first cell to the second cell.

  When there are a plurality of UEs 200-1, the control unit 140 performs a handover procedure for each UE 200-1. Here, the control unit 140 performs control so as to preferentially switch the serving cell of the UE 200-1 having a higher priority among the plurality of UEs 200-1 based on the respective communication states of the plurality of UEs 200-1. This is because when a plurality of UEs 200-1 collectively perform handover, overhead and processing load increase, and handover failure may occur. In addition, UE200-1 with high priority is UE200-1 which is not in DRX state, UE200-1 with large buffer amount notified by a buffer status report (BSR), QCI (QoS Class Identifier), for example. It means UE200-1 whose QoS shown is high.

  In addition, when there is a handover request or a connection request for a new UE in the middle of switching the serving cell from the first cell to the second cell for each of the plurality of UEs 200-1, the control unit 140 Is controlled to be accommodated in the second cell. Specifically, when the network communication unit 120 receives a handover request for requesting acceptance of a UE from the outside (another HeNB or another eNB) on the X2 interface or the S1 interface, the control unit 140 In addition, if the handover request requests a handover to the first cell, the handover request is rejected, and if the handover request requests a handover to the second cell, the handover request Allow. In addition, when the wireless communication unit 110 receives an access (connection request) from a new UE, the control unit 140 denies the access and accesses the first cell if the access is an access to the first cell. If is an access to the second cell, the access is permitted.

  The control unit 140 switches the serving cell of all UEs 200-1 to the second cell, and when there is no UE 200-1 accommodated in the first cell, the DL signal from the first cell (reference signal or 1st cell is deactivated by stopping transmission of cell ID, CSG ID, etc.).

  Then, the control unit 140 initializes the setting of the MBSFN subframe in the second radio frame used in the second cell, and uses at least a part of the MBSFN subframe as a normal subframe (non-MBSFN subframe). It can be so. In addition, the control unit 140 controls the radio communication unit 110 to transmit information indicating the frame configuration of the second radio frame after initialization in the second cell.

  Next, the configuration of UE 200 will be described. Since UE200-1 to UE200-3 are configured similarly, the configuration of UE200-1 will be described here. FIG. 8 is a block diagram of the UE 200-1.

  As illustrated in FIG. 8, the UE 200 includes an antenna 201, a wireless communication unit 210, a storage unit 220, and a control unit 230.

  The wireless communication unit 210 is configured to perform wireless communication via the antenna 201. For transmission, the radio communication unit 210 performs up-conversion and amplification of the baseband signal input from the control unit 230 and outputs the radio signal from the antenna 201. For reception, the radio communication unit 210 performs amplification and down-conversion of the reception signal input from the antenna 201, and then outputs a baseband signal to the control unit 230.

  The storage unit 220 is configured using, for example, a memory, and stores various types of information used for control by the control unit 230 and the like. Further, the storage unit 220 stores the CSG ID of the CSG to which the UE 200-1 belongs (that is, CSG # 1).

  The control unit 230 is configured using, for example, a processor, and controls various functions of the UE 200-1.

  The control unit 230 measures the state of the radio signal received by the radio communication unit 210 and acquires the cell ID and CSG ID included in the radio signal. And the control part 230 is a state in which radio | wireless communication is possible, Comprising: The cell (1st cell comprised by HeNB100-1) which transmits CSG ID which corresponds to CSG ID memorize | stored in the memory | storage part 220 is shown. Determine as serving cell and try to connect. In addition, the control unit 230 acquires the SIB received by the wireless communication unit 210 from the first cell, and determines the UL CC and DL CC of the second cell based on the SIB.

  After being accommodated by the first cell, the control unit 230 determines an allocation RB based on allocation information received on the PDCCH by the wireless communication unit 210 from the first cell, and performs communication (data) using the allocation RB. The wireless communication unit 210 is controlled to perform transmission / reception.

  When the wireless communication unit 210 receives an SIB including information indicating the frame configuration of the changed first radio frame from the first cell, the control unit 230 receives a normal subframe (non-MBSFN subframe) of the first radio frame. The wireless communication unit 210 is controlled to perform communication using a frame. Here, the information indicating the frame configuration is a list of subframe numbers of the MBSFN subframe of the first radio frame.

  Furthermore, when the wireless communication unit 210 receives measurement control information for controlling to omit the measurement report process from the first cell, the control unit 230 controls to omit the measurement report process. As described above, the measurement report process is a process for the handover procedure, and is a process for reporting the measurement result of the reception state in the UE 200-1 to the serving cell.

  Alternatively, when the wireless communication unit 210 receives an offset value from the first cell such that the measurement result for the second cell is higher than the measurement result for the first cell, the control unit 230 performs measurement for the second cell. A measurement report that the measurement result for the second cell is higher than the measurement result for the first cell by adding the offset value to the result or subtracting the offset value from the measurement result for the first cell. The wireless communication unit 210 is controlled to transmit to the first cell.

  Thereafter, when the wireless communication unit 210 receives a command for instructing handover to the second cell from the first cell, the control unit 230 causes the wireless communication unit 210 to receive the SIB from the second cell. Control. Then, the control unit 230 includes CC information (information on the center frequencies and bandwidths of the UL CC and DL CC of the second cell) and information indicating the frame configuration of the second radio frame included in the SIB. Based on this, the wireless communication unit 210 is controlled to access the second cell and perform the connection process with the second cell. In addition, the control unit 230 controls to disconnect the connection with the first cell.

  When the wireless communication unit 210 receives information indicating the frame configuration of the second radio frame after initialization after being accommodated by the second cell from the second cell, the control unit 230 receives the second radio frame. The wireless communication unit 210 is controlled to perform communication in a normal subframe (non-MBSFN subframe).

  Next, the operation of the mobile communication system according to the present embodiment will be described in the order of the operation of the HeNB 100-1 and the operation of the UE 200-1. Here, an operation of handing over UE 200-1 to the second cell when communication between the first cell of HeNB 100-1 and UE 200-1 is performed will be described.

  FIG. 9 is an operation flowchart of the HeNB 100-1 according to the present embodiment.

  As shown in FIG. 9, in step S101, after accommodating UE 200-1 in the first cell, control unit 140 monitors the UL interference power level for each CC based on the reception state in radio communication unit 110. .

  In step S102, the control unit 140 confirms whether or not the interference power level in the UL CC (first UL CC) of the first cell exceeds a predetermined level. When the interference power level in the UL CC of the first cell exceeds a predetermined level (step S102; YES), the process proceeds to step S103. On the other hand, when the interference power level in the UL CC of the first cell does not exceed the predetermined level (step S102; NO), the process returns to step S101.

  In step S103, based on the result of monitoring in step S101, the control unit 140 selects a CC that is not used in the vicinity or a CC with a low UL interference power level as the UL CC (second UL CC) of the second cell. ). In addition, the control unit 140 configures (activates) the second cell and sets the frame configurations of the first radio frame and the second radio frame described above.

  In step S104, control unit 140 transmits information indicating the frame configuration of the changed first radio frame in the first cell, and transmits information indicating the frame configuration of the second radio frame in the second cell. The wireless communication unit 110 is controlled to do so.

  In step S105, the control unit 140 performs measurement control for the UE 200-1. For example, the control unit 140 controls the radio communication unit 110 to transmit measurement control information for controlling to omit the measurement report process to the UE 200-1. Alternatively, instead of omitting the measurement report process, the control unit 140 wirelessly transmits an offset value such that the measurement result for the second cell is higher than the measurement result for the first cell to the UE 200-1. The communication unit 110 may be controlled.

  In step S106 to step S108, the control unit 140 performs a handover procedure for the UE 200-1.

  First, in step S106, the control unit 140 prepares for reception of the UE 200-1 in the second cell.

  Secondly, in step S107, the control unit 140 controls the radio communication unit 110 to transmit a handover command for instructing handover to the second cell to the UE 200-1.

  Thirdly, in step S108, the control unit 140 accommodates the UE 200-1 that has accessed the second cell by the handover command in the second cell. As a result, the serving cell of UE 200-1 is switched from the first cell to the second cell.

  In step S109, the control unit 140 confirms whether or not the handover procedure to the second cell has been completed for all the UEs 200-1. When the handover procedure to the second cell is completed for all UEs 200-1 (step S109; YES), the process proceeds to step S110. On the other hand, when there is a UE 200-1 that has not completed the handover procedure to the second cell (step S109; NO), the process returns to step S106, and the handover procedure for the UE 200-1 is performed.

  In performing the handover procedure of the plurality of UEs 200-1, the control unit 140 determines the UE 200-1 having the highest priority among the plurality of UEs 200-1 based on the communication state of the plurality of UEs 200-1. Control to switch the serving cell with priority.

  In step S110, the control unit 140 deactivates the first cell by stopping transmission of a DL signal (including a reference signal, a cell ID, a CSG ID, and the like) from the first cell.

  In step S111, the control unit 140 initializes the setting of the MBSFN subframe in the second radio frame so that at least a part of the MBSFN subframe can be used as a normal subframe (non-MBSFN subframe). Then, control unit 140 controls radio communication unit 110 to transmit information indicating the frame configuration of the second radio frame after initialization in the second cell.

  In addition, between step S103 to step S109, when there is a handover request or connection request for a new UE, the control unit 140 performs control so that the new UE is accommodated in the second cell.

  FIG. 10 is an operation flow diagram of the HeNB 100-1 when there is a handover request for a new UE between Step S103 and Step S109. Specifically, the network communication unit 120 receives a handover request for requesting acceptance of a UE from the outside (another HeNB or another eNB) on the X2 interface or the S1 interface.

  As shown in FIG. 10, in step S121, the control unit 140 requests the handover to the second cell based on the cell ID of the target cell included in the handover request received by the network communication unit 120. Check if it is what you want to do. If the handover request is a request for handover to the second cell (step S121; YES), the process proceeds to step S122. On the other hand, when the handover request is a request for handover to the first cell (step S121; NO), the process proceeds to step S123.

  In step S122, the control unit 140 determines that the handover request is permitted, and transmits a positive response (ACK) to the handover request to the transmission source of the handover request over the X2 interface or the S1 interface. The communication unit 120 is controlled.

  On the other hand, in step S123, the control unit 140 determines to reject the handover request, and transmits a negative response (NACK) to the handover request to the transmission source of the handover request on the X2 interface or the S1 interface. The network communication unit 120 is controlled.

  FIG. 11 is an operation flowchart of the HeNB 100-1 when there is an access (connection request) from a new UE between step S103 and step S109. Specifically, the radio communication unit 110 receives a random access preamble for the first cell or the second cell from the new UE.

  As shown in FIG. 11, in step S131, the control unit 140 determines whether the random access preamble requests access to the second cell based on the random access preamble received by the wireless communication unit 110. To check. If the random access preamble is a request for access to the second cell (step S131; YES), the process proceeds to step S132. On the other hand, when the random access preamble is a request for access to the first cell (step S131; NO), the process proceeds to step S133.

  In step S132, the control unit 140 determines to permit the random access preamble, and controls the radio communication unit 110 to transmit a random access response that is an acknowledgment to the random access preamble to the new UE.

  On the other hand, in step S133, the control unit 140 determines to reject the random access preamble, and controls the radio communication unit 110 not to transmit a random access response that is an acknowledgment to the random access preamble to the new UE. To do.

  FIG. 12 is an operation flowchart of the UE 200-1 according to the present embodiment.

  As illustrated in FIG. 12, in step S151, when the wireless communication unit 210 receives the SIB including the information indicating the frame configuration of the changed first radio frame from the first cell, the control unit 230 receives the first radio frame. The radio communication unit 210 is controlled to perform communication in a normal subframe (non-MBSFN subframe) of the radio frame.

  In step S152, when the wireless communication unit 210 receives measurement control information for controlling to omit the measurement report process from the first cell, the control unit 230 controls to omit the measurement report process. Alternatively, when the wireless communication unit 210 receives an offset value from the first cell such that the measurement result for the second cell is higher than the measurement result for the first cell, the control unit 230 performs measurement for the second cell. A measurement report that the measurement result for the second cell is higher than the measurement result for the first cell by adding the offset value to the result or subtracting the offset value from the measurement result for the first cell. May be controlled to transmit to the first cell.

  In step S153, the radio communication unit 210 receives a command for instructing handover to the second cell from the first cell.

  In step S154, the control unit 230 controls the wireless communication unit 210 to receive the SIB from the second cell. Then, the control unit 230 includes CC information (information on the center frequencies and bandwidths of the UL CC and DL CC of the second cell) and information indicating the frame configuration of the second radio frame included in the SIB. Based on this, the wireless communication unit 210 is controlled to access the second cell and perform the connection process with the second cell. In addition, the control unit 230 controls to disconnect the connection with the first cell.

  In step S155, the control unit 230 receives the information indicating the frame configuration of the second radio frame after initialization after being accommodated by the second cell from the second cell. The radio communication unit 210 is controlled to perform communication in a normal subframe (non-MBSFN subframe) of the radio frame.

  As described above, in the mobile communication system adopting the FDD scheme, the HeNB 100-1 includes the first cell using the pair of the first UL CC and the DL CC for communication, the second UL CC, and the relevant And a second cell that uses the pair with the DL CC for communication. When detecting interference in the first UL CC, the HeNB 100-1 and the UE 200-1 switch the serving cell of the UE 200-1 from the first cell to the second cell by the handover procedure. Thereby, it replaces with 1st UL CC by which the interference in UL was detected, will use 2nd UL CC for UL communication, and the interference in UL is avoided.

  In addition, after detecting the interference in 2nd UL CC after switching the serving cell of UE200-1 from a 1st cell to the 2nd cell, the interference in UL is carried out by implementing the process mentioned above anew. Avoided.

[Second Embodiment]
Hereinafter, the difference between the second embodiment and the first embodiment will be mainly described.

  FIG. 13 illustrates an example of a state after the serving cell of the UE 200-1 is switched from the first cell to the second cell by the handover procedure described in the first embodiment.

  As shown in FIG. 13, after the serving cell of UE 200-1 is switched from the first cell to the second cell by the handover procedure, UL interference is caused to the UL CC (first UL CC) of the first cell. The given UE 200-3 has moved far away from the HeNB 100-1.

  In this case, since the interference power level in the UL CC of the first cell (first UL CC) has been sufficiently reduced, by returning to the UL CC determined at the time of power-on, the initial level in harmony with the neighboring cells It is preferable to keep the state.

  Therefore, in this embodiment, when the interference in the first UL CC is reduced after switching the serving cell of the UE 200-1 from the first cell to the second cell by the handover procedure, the HeNB 100-1 and the UE 200-1 The serving cell of UE 200-1 is switched from the second cell to the first cell by the handover procedure.

  FIG. 14 is a diagram for explaining the operation of the mobile communication system 1 when interference in the UL CC (first UL CC) of the first cell is reduced.

  As illustrated in FIG. 14, the HeNB 100-1 according to the present embodiment detects interference reduction in the first UL CC (that is, CC # 1) (that is, the interference power level is lower than a predetermined level). Case), the first cell is configured in addition to the second cell. The first cell is the same as that described in the first embodiment.

  After the configuration of the first cell, the HeNB 100-1 and the UE 200-1 switch the serving cell of the UE 200-1 from the second cell to the first cell by a handover procedure.

  FIG. 15 is a diagram for explaining the operation of the mobile communication system 1 after the handover procedure according to the present embodiment is completed.

  As illustrated in FIG. 15, after switching the serving cell of the UE 200-1 from the second cell to the first cell, the HeNB 100-1 deactivates the second cell. Deactivation of the second cell means, for example, stopping transmission of a DL signal (including a reference signal, cell ID, CSG ID, and the like) from the second cell. In addition, when there are multiple UEs 200-1, the HeNB 100-1 deactivates the second cell after switching the serving cells of all the UEs 200-1 from the second cell to the first cell.

  In the present embodiment as well, as in the first embodiment, the same DL CC is used in the first cell and the second cell during the period in which the first cell and the second cell exist at the same time. The configuration of the first radio frame and the configuration of the second radio frame are set differently so as to be shared by division (see FIG. 6).

  Next, the operation of the mobile communication system according to the present embodiment will be described in the order of the operation of the HeNB 100-1 and the operation of the UE 200-1. Here, an operation of handing over UE 200-1 to the first cell when communication between the second cell of HeNB 100-1 and UE 200-1 is performed will be described.

  FIG. 16 is an operation flowchart of the HeNB 100-1 according to the present embodiment.

  As shown in FIG. 16, in step S201, after accommodating UE 200-1 in the second cell, control unit 140 monitors the UL interference power level for each CC based on the reception state in radio communication unit 110. .

  In step S202, the control unit 140 confirms whether or not the interference power level in the UL CC (first UL CC) of the first cell is lower than a predetermined level. When the interference power level in the first UL CC becomes smaller than the predetermined level (step S202; YES), the process proceeds to step S203. On the other hand, when the interference power level in the first UL CC is not smaller than the predetermined level (step S202; NO), the process returns to step S201.

  In step S203, the control unit 140 configures (activates) the first cell, and sets the frame configurations of the first radio frame and the second radio frame described above.

  In step S204, control unit 140 transmits information indicating the frame configuration of the changed second radio frame in the second cell, and transmits information indicating the frame configuration of the first radio frame in the first cell. The wireless communication unit 110 is controlled to do so.

  In step S205, the control unit 140 performs measurement control for the UE 200-1. For example, the control unit 140 controls the radio communication unit 110 to transmit measurement control information for controlling to omit the measurement report process to the UE 200-1. Alternatively, instead of omitting the measurement report process, the control unit 140 wirelessly transmits an offset value such that the measurement result for the first cell is higher than the measurement result for the second cell to the UE 200-1. The communication unit 110 may be controlled.

  In step S206 to step S208, the control unit 140 performs a handover procedure for the UE 200-1.

  First, in step S206, the control unit 140 prepares for receiving the UE 200-1 in the first cell.

  Secondly, in step S207, the control unit 140 controls the radio communication unit 110 to transmit a handover command for instructing handover to the first cell to the UE 200-1.

  Thirdly, in step S208, the control unit 140 accommodates the UE 200-1 that has accessed the first cell by the handover command in the first cell. As a result, the serving cell of UE 200-1 is switched from the second cell to the first cell.

  In step S209, the control unit 140 confirms whether or not the handover procedure to the first cell has been completed for all the UEs 200-1. When the handover procedure to the first cell is completed for all UEs 200-1 (step S209; YES), the process proceeds to step S210. On the other hand, when there is a UE 200-1 that has not completed the handover procedure to the first cell (step S209; NO), the process returns to step S206, and the handover procedure for the UE 200-1 is performed.

  In performing the handover procedure of the plurality of UEs 200-1, the control unit 140 determines the UE 200-1 having the highest priority among the plurality of UEs 200-1 based on the communication state of the plurality of UEs 200-1. Control to switch the serving cell with priority.

  In step S210, the control unit 140 deactivates the second cell by stopping transmission of a DL signal (including a reference signal, a cell ID, a CSG ID, and the like) from the second cell.

  In step S211, the control unit 140 initializes the setting of the MBSFN subframe in the first radio frame so that at least a part of the MBSFN subframe can be used as a normal subframe (non-MBSFN subframe). Then, control unit 140 controls radio communication unit 110 to transmit information indicating the frame configuration of the first radio frame after initialization in the first cell.

  In addition, between step S203 and step S209, when there is a handover request or connection request for a new UE, the control unit 140 performs control so that the new UE is accommodated in the first cell.

  FIG. 17 is an operation flow diagram of the HeNB 100-1 when there is a handover request for a new UE between Step S203 and Step S209. Specifically, the network communication unit 120 receives a handover request for requesting acceptance of a UE from the outside (another HeNB or another eNB) on the X2 interface or the S1 interface.

  As shown in FIG. 17, in step S221, the control unit 140 requests the handover to the first cell based on the cell ID of the target cell included in the handover request received by the network communication unit 120. Check if it is what you want to do. If the handover request is a request for handover to the first cell (step S221; YES), the process proceeds to step S222. On the other hand, when the handover request is a request for handover to the second cell (step S221; NO), the process proceeds to step S223.

  In step S222, the control unit 140 determines that the handover request is permitted, and transmits a positive response (ACK) to the handover request to the transmission source of the handover request over the X2 interface or the S1 interface. The communication unit 120 is controlled.

  On the other hand, in step S223, the control unit 140 determines to reject the handover request, and transmits a negative response (NACK) to the handover request to the transmission source of the handover request on the X2 interface or the S1 interface. The network communication unit 120 is controlled.

  FIG. 18 is an operation flow diagram of the HeNB 100-1 when there is an access (connection request) from a new UE between step S203 and step S209. Specifically, the radio communication unit 110 receives a random access preamble for the first cell or the second cell from the new UE.

  As illustrated in FIG. 18, in step S231, the control unit 140 determines whether the random access preamble requests access to the first cell based on the random access preamble received by the wireless communication unit 110. To check. If the random access preamble is a request for access to the first cell (step S231; YES), the process proceeds to step S232. On the other hand, if the random access preamble is a request for access to the second cell (step S231; NO), the process proceeds to step S233.

  In step S232, the control unit 140 determines to allow the random access preamble, and controls the radio communication unit 110 to transmit a random access response that is an acknowledgment to the random access preamble to the new UE.

  On the other hand, in step S233, the control unit 140 determines to reject the random access preamble, and controls the radio communication unit 110 not to transmit a random access response that is an acknowledgment to the random access preamble to the new UE. To do.

  FIG. 19 is an operation flow diagram of the UE 200-1 according to the present embodiment.

  As illustrated in FIG. 19, in step S251, when the wireless communication unit 210 receives the SIB including information indicating the frame configuration of the changed second radio frame from the second cell, the control unit 230 receives the second radio frame. The radio communication unit 210 is controlled to perform communication in a normal subframe (non-MBSFN subframe) of the radio frame.

  In step S <b> 252, when the wireless communication unit 210 receives measurement control information for controlling to omit the measurement report process from the second cell, the control unit 230 controls to omit the measurement report process. Alternatively, when the wireless communication unit 210 receives an offset value from the second cell such that the measurement result for the first cell is higher than the measurement result for the second cell, the control unit 230 performs the measurement for the first cell. A measurement report indicating that the measurement result for the first cell is higher than the measurement result for the second cell by adding the offset value to the result or subtracting the offset value from the measurement result for the second cell. The wireless communication unit 210 may be controlled to transmit to the second cell.

  In step S253, the radio communication unit 210 receives a command for instructing handover to the first cell from the second cell.

  In step S254, the control unit 230 controls the wireless communication unit 210 to receive the SIB from the first cell. Then, the control unit 230 includes CC information (information on the center frequencies and bandwidths of the UL CC and DL CC of the first cell) and information indicating the frame configuration of the first radio frame included in the SIB. Based on this, the wireless communication unit 210 is controlled to access the first cell and perform the connection process with the first cell. In addition, the control unit 230 controls to disconnect the connection with the second cell.

  In step S <b> 255, when the wireless communication unit 210 receives information indicating the frame configuration of the first radio frame after initialization after being accommodated by the first cell, The radio communication unit 210 is controlled to perform communication in a normal subframe (non-MBSFN subframe) of the radio frame.

  As described above, in the mobile communication system adopting the FDD scheme, the HeNB 100-1 includes the first cell using the pair of the first UL CC and the DL CC for communication, the second UL CC, and the relevant And a second cell that uses the pair with the DL CC for communication. If the interference in the first UL CC is reduced after switching the serving cell of the UE 200-1 from the first cell to the second cell by the handover procedure, the HeNB 100-1 and the UE 200-1 perform the UE 200- Switch one serving cell from the second cell to the first cell. Thereby, since it can return to UL CC determined at the time of power activation, the initial state in harmony with the surrounding cell can be maintained.

[Other Embodiments]
As described above, the present invention has been described according to each embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In each of the above-described embodiments, an example has been described in which a handover procedure for changing the UL CC is performed using the detection of interference in the UL as a trigger. However, a handover procedure for changing the UL CC may be performed using the congestion detection in the UL as a trigger. For example, when congestion occurs in the UL, the UL communication capacity increases by performing a handover procedure so as to change to a UL CC having a wide bandwidth, so that congestion in the UL can be eliminated. Note that the presence or absence of congestion in the UL can be determined based on, for example, whether or not the RB usage rate in the UL exceeds a predetermined value.

  Moreover, in embodiment mentioned above, although HeNB which is 1 type of a base station was demonstrated to an example, not only HeNB but a macro base station (MeNB) and a pico base station (PeNB) are good also as a base station which concerns on this invention. .

  Furthermore, in the future, it is assumed that one CC is divided and each divided carrier is handled as a new CC. However, the component carrier (CC) in this specification includes such a new CC. Shall be.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein.

Claims (2)

A base station constituting a first cell and a second cell,
The first cell uses a first uplink carrier and downlink carrier pair for communication,
The base station, wherein the second cell uses a pair of a second uplink carrier and the downlink carrier for communication. A user terminal that communicates with a serving cell,
The serving cell includes a first cell and a second cell;
The first cell uses a first uplink carrier and downlink carrier pair for communication,
The user terminal, wherein the second cell uses a pair of a second uplink carrier and the downlink carrier for communication.

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