JP2013051562A - Base station, mobile station, communication system, communication control method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station which can enhance reception quality in a mobile station in performing downlink communication with different frequency bands by a plurality of antennas.SOLUTION: A base station 100 communicates with a mobile station 300 by at least either a communication method simultaneously using a plurality of frequencies or a communication method using one frequency among the plurality of frequencies. The base station 100 comprises: a DL transmission mode determination unit which determines whether to use a first transmission mode transmitting different information by simultaneously using the plurality of frequencies or a second transmission mode transmitting the same information by simultaneously using the plurality of frequencies, on the basis of communication with the mobile station; and a transmission processing unit for performing downlink transmission for the mobile station 300 by the determined transmission mode.

Description

  The present invention relates to a base station, a mobile station, a communication system, a communication control method, and a program, and more particularly, to a base station, a mobile station, a communication system, a communication control method, and a program that perform communication using carrier aggregation.

  The 3GPP (3rd Generation Partnership Project) is currently studying specifications for LTE-A (Long Term Evolution-Advanced). In LTE-A, it is required to realize higher-speed communication than LTE. For this reason, LTE-A is required to support a wider band than LTE (a band up to 100 MHz exceeding the 20 MHz band of LTE). However, it is difficult to secure a worldwide continuous wide frequency range for LTE-A.

  Therefore, in LTE-A, a carrier aggregation (CA) technique is being studied for the purpose of maintaining compatibility with LTE as much as possible. Carrier aggregation technology secures a bandwidth of up to 100 MHz by performing communication by collecting a plurality of frequency bands, up to 20 MHz, called a component carrier (CC: Component Career), thereby enabling high-speed and large-capacity communication. It is a technology to be realized. Non-Patent Document 1 discloses the carrier aggregation.

  In addition, LTE-A can perform higher-speed and larger-capacity communication by applying a maximum of 8 × 8 MIMO (Multiple Input Multiple Output) technology in the downlink. In such a MIMO technique, it is difficult to receive the MIMO because the propagation path estimation accuracy is deteriorated particularly when the propagation characteristic is poor. For this reason, in LTE-A, reception quality (RSRQ: Reference Signal Received Quality) is improved by switching from the MIMO mode to the transmission diversity mode. That is, the base station transmits the same data from a plurality of transmission antennas without performing carrier aggregation. The mobile station receives the same data with a plurality of antennas. Thereby, the reception quality in a mobile station can be improved.

  For example, when performing downlink communication in the same frequency band using two antennas, the MIMO mode is used near the cell center with good reception quality, and the transmission diversity mode is used at the cell edge with poor reception quality.

Non-Patent Document 2 discloses LTE specifications. More specifically, in Non-Patent Document 2, the base station uses a downlink control information format for the MIMO mode in the MIMO mode, and the base station uses the transmission control format for the transmission diversity mode in the transmission diversity mode. In use, it is disclosed that a base station transmits DL transmission control data. It is also disclosed that the mobile station performs data reception by switching between MIMO and transmission diversity depending on which transmission control format is received by the mobile station.

  Further, when the modes are used properly as described above, there is a case where only the transmission diversity is performed without using the MIMO mode. The transmission mode in the downlink can be limited depending on the capability of the mobile station.

3GPP TR 36.814 V9.0.0 (2010-03), Technical Report, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Further advancements for E-UTRA physical layer aspects (Release 9 ) 3GPP TS 36.212 V9.0.0 (2009-12), Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding (Release 9)

  However, when downlink communication of different frequency bands is performed using a plurality of antennas, no investigation has been made until the reception quality is improved in the mobile station.

  The present invention has been made in view of the above problems, and a base station and a mobile station that can improve reception quality of a mobile station when performing downlink communication in different frequency bands with a plurality of antennas. A communication system, a communication control method, and a program.

  According to an aspect of the present invention, the base station communicates with the mobile station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies. The base station uses any one of a first transmission mode in which information different from each other at a plurality of frequencies is transmitted simultaneously and a second transmission mode in which the same information is transmitted by using a plurality of frequencies at the same time. Determining means based on communication with the mobile station, and transmission processing means for performing downlink transmission to the mobile station in the determined transmission mode.

  Preferably, the base station communicates with the mobile station by carrier aggregation using a plurality of component carriers having different frequency bands. The first transmission mode is a mode in which different information is transmitted using a plurality of component carriers. The second transmission mode is a mode in which the same information is transmitted using a plurality of component carriers.

  Preferably, the determination unit determines the transmission mode based on information representing the reception quality for each component carrier notified from the mobile station.

  Preferably, the determination unit determines whether each reception quality is equal to or higher than a predetermined first threshold value. The determining means determines to use the first transmission mode when it is determined that each reception quality is equal to or higher than the first threshold value.

  Preferably, the determination unit determines whether each reception quality is equal to or higher than a predetermined second threshold value indicating that the reception quality is lower than the first threshold value. The determining means determines to use the second transmission mode when each reception quality is equal to or higher than the second threshold and at least one of the reception qualities is lower than the first threshold.

  Preferably, when communicating with the mobile station in the first transmission mode, the transmission processing means transmits different information using the first format and communicates with the mobile station in the second transmission mode. In some cases, the same information is transmitted using the second format.

  According to another aspect of the present invention, the mobile station communicates with the base station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies. The mobile station transmits any one of a first transmission mode in which different information is transmitted using a plurality of frequencies simultaneously and a second transmission mode in which the same information is transmitted using a plurality of frequencies simultaneously. Is determined based on communication with the base station, and processing means for performing data processing corresponding to the determined transmission mode on information transmitted by the base station.

  Preferably, the mobile station communicates with the base station by carrier aggregation using a plurality of component carriers having different frequency bands. The first transmission mode is a mode in which different information is transmitted using a plurality of component carriers. The second transmission mode is a mode in which the same information is transmitted using a plurality of component carriers.

  Preferably, the mobile station transmits information representing reception quality for each component carrier to the base station.

  Preferably, the determination unit performs the determination based on whether the information transmitted by the base station is information using the first format or information using the second format.

  According to still another aspect of the present invention, a communication system includes a mobile station and a base station, and at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies. A communication system in which a mobile station and a base station communicate. The base station uses any one of a first transmission mode in which different information is transmitted using a plurality of frequencies simultaneously and a second transmission mode in which the same information is transmitted using a plurality of frequencies simultaneously. Is used based on communication with the mobile station. The base station performs downlink transmission to the mobile station in the determined transmission mode. The mobile station determines which transmission mode of the first transmission mode and the second transmission mode is used by the base station based on communication with the base station. The mobile station performs data processing corresponding to the determined transmission mode.

  According to still another aspect of the present invention, a communication control method includes a base station that communicates with a mobile station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies. Is a communication control method. The communication control method includes a first transmission mode in which a base station transmits different information using a plurality of frequencies simultaneously, and a second transmission mode in which the same information is transmitted using a plurality of frequencies simultaneously. Which transmission mode to use is determined based on communication with the mobile station, and the base station performs downlink transmission to the mobile station in the determined transmission mode.

  According to still another aspect of the present invention, a communication control method is a mobile station that communicates with a base station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies. Is a communication control method. The communication control method includes a first transmission mode in which a mobile station transmits different information using a plurality of frequencies simultaneously, and a second transmission mode in which the same information is transmitted using a plurality of frequencies simultaneously. Which transmission mode is used by the base station based on communication with the base station, and data processing corresponding to the determined transmission mode for the information transmitted from the base station by the mobile station The step which performs.

  According to still another aspect of the present invention, a communication control method includes a mobile station and a base station, and at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies. A communication control method in a communication system in which a mobile station and a base station communicate with each other. The communication control method includes a first transmission mode in which a base station transmits different information using a plurality of frequencies simultaneously, and a second transmission mode in which the same information is transmitted using a plurality of frequencies simultaneously. Which transmission mode to use is determined based on communication with the mobile station, the base station performs downlink transmission to the mobile station in the determined transmission mode, and the mobile station A step of determining, based on communication with the base station, which one of the first transmission mode and the second transmission mode is used by the base station, and the mobile station corresponds to the determined transmission mode Performing the processed data.

  When the further another situation of this invention is followed, a program makes a computer perform said communication control method.

  According to the present invention, it is possible to improve the reception quality of a mobile station when performing downlink communication in different frequency bands with a plurality of antennas.

It is a figure showing the schematic structure of the communication system. It is a functional block diagram of a base station. It is the figure which showed the data table used for determination of downlink transmission mode. It is a functional block diagram of a mobile station. It is a sequence chart in a communication system. It is another sequence chart in a communication system. It is a flowchart showing the flow of processing in the base station. It is a flowchart showing the flow of processing in a mobile station. It is a figure showing the typical hardware constitutions of the base station. It is a figure showing the typical hardware constitutions of the mobile station.

  The communication system according to each embodiment of the present invention will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<A. System configuration>
FIG. 1 is a diagram showing a schematic configuration of the communication system 1. With reference to FIG. 1, the communication system 1 includes a base station 100 and a mobile station 300. In the communication system 1, the base station 100 and the mobile station 300 communicate with each other by carrier aggregation using a plurality of component carriers having different frequency bands. The mobile station 300 is located in a cell 90 formed by the base station 100.

  Mobile station 300 is, for example, a mobile phone. The mobile station 300 is not limited to a mobile phone, and may be a mobile terminal such as a smartphone or a PDA (Personal Digital Assistants). Further, the mobile station 300 included in the communication system 1 is not limited to one.

  Hereinafter, for convenience of explanation, an example will be described in which two component carriers are used as downlink component carriers and one component carrier is used as an uplink component carrier. Also, the downlink is also referred to as “DL”, the uplink as “UL”, the carrier aggregation as “CA”, the component carrier as “CC”, and the diversity as “DIV”. Of the two component carriers, one component carrier is referred to as “component carrier DL-1”, and the other component carrier is referred to as “component carrier DL-2”.

<B. Base Station 100>
FIG. 2 is a functional block diagram of the base station 100. Referring to FIG. 2, base station 100 includes a receiving antenna 101, receiving unit 102, OFDM (Orthogonal Frequency Division Multiplexing) processing unit 103, UL data processing unit 104, UL data holding unit 105, and transmission unit. 106, a core network 107, a DL reception quality information acquisition unit 108, a DL transmission mode determination unit 109, a reception unit 110, a DL data holding unit 111, a DL transmission control unit 112, and a DL transmission format holding unit 113. A DL transmission information holding unit 114, a CA transmission control unit 115, a DL data arrangement unit 116, a DL data processing unit 117, a DL data processing unit 118, an OFDM processing unit 119, an OFDM processing unit 120, A transmission unit 121, a transmission unit 122, a transmission antenna 123, and a transmission antenna 124 are provided. Hereinafter, the blocks represented by reference numerals 112 to 122 are collectively referred to as “transmission processing unit 150”.

(B1. Communication processing in uplink)
Processing in base station 100 in uplink communication from mobile station 300 to base station 100 will be described.

  The receiving unit 102 receives an UL signal from the mobile station 300 using the antenna 101. The receiving unit 102 sends the UL signal to the OFDM processing unit 103.

  The OFDM processing unit 103 performs OFDM processing on the UL signal received from the receiving unit 102. The OFDM processing unit 103 sends data obtained by performing OFDM processing on the UL signal to the UL data processing unit 104.

  The UL data processing unit 104 acquires user data from the data received from the OFDM processing unit 103. The UL data processing unit 104 sends user data to the UL data holding unit 105. Further, the UL data processing unit 104 sends the user data to the DL reception quality information acquisition unit 108.

  The UL data holding unit 105 holds user data received from the UL data processing unit 104.

  The transmission unit 106 transmits the user data held in the UL data holding unit 105 to the core network 107.

  The DL reception quality information acquisition unit 108 acquires information (hereinafter, also referred to as “DL reception quality information”) indicating the reception quality in the DL transmitted by the mobile station 300 from the user data. DL reception quality information acquisition section 108 sends DL reception quality information to DL transmission mode determination section 109.

  DL transmission mode determination section 109 determines a downlink transmission mode (hereinafter also referred to as “DL transmission mode”) based on DL reception quality information. Specifically, the DL transmission mode determination unit 109 uses two component carriers DL-1 and DL-2 to transmit different information and DL transmission mode and two component carriers DL-1 and DL-2. DL transmission mode that uses the same information to transmit, DL transmission mode that uses only component carrier DL-1, and DL transmission mode that uses only component carrier DL-2. To determine.

  The DL transmission mode in which different information is transmitted using the two component carriers DL-1 and DL-2 is a DL transmission mode using carrier aggregation, and is also referred to as “CA transmission mode” below. A DL transmission mode in which the same information is transmitted by diversity using two component carriers is also referred to as a “CC-DIV transmission mode”. In addition, a DL transmission mode using only the component carrier DL-1 is also referred to as “DL-1 transmission mode”, and a DL transmission mode using only the component carrier DL-2 is also referred to as “DL-2 transmission mode”. “DL-1 transmission mode” and “DL-2 transmission mode” are modes in which “transmission diversity” is performed, respectively. Specifically, the “DL-1 transmission mode” and the “DL-2 transmission mode” are modes in which the same data is transmitted from a plurality of antennas using only one component carrier without performing carrier aggregation. .

  More specifically, the DL transmission mode determination unit 109 receives information on the number of component carriers from the CA transmission control unit 115, and uses the number of component carriers for determination of the DL transmission mode. The DL transmission mode determination method will be described later.

  The DL transmission mode determination unit 109 sends information indicating the determined DL transmission mode (hereinafter also referred to as “DL transmission mode information”) to the DL transmission control unit 112. The DL transmission control unit 112 causes the DL transmission information holding unit 114 to hold DL transmission mode information. Specifically, the DL transmission control unit 112 causes the DL transmission information holding unit 114 to hold DL transmission mode information for each mobile station.

(B2. Communication processing in downlink)
Next, processing in base station 100 in downlink communication from base station 100 to mobile station 300 will be described.

  The receiving unit 110 receives user data addressed to the mobile station 300 transmitted from the core network 107. The receiving unit 110 sends the user data to the DL data holding unit 111.

The DL data holding unit 111 holds user data received from the receiving unit 110.
The DL transmission control unit 112 performs processing for performing downlink transmission based on the DL transmission mode information received from the DL transmission mode determination unit 109. That is, the DL transmission control unit 112 performs processing for performing downlink transmission according to the DL transmission mode determined by the DL transmission mode determining unit 109.

  Specifically, DL transmission control section 112 performs control for executing CA transmission mode when DL transmission mode determining section 109 determines that downlink transmission is performed in CA transmission mode. On the other hand, when the DL transmission mode determination unit 109 determines that the DL transmission control unit 112 performs downlink transmission in the CC-DIV transmission mode, the DL transmission control unit 112 performs control for executing the CC-DIV transmission mode.

  The DL transmission format holding unit 113 has a DL transmission format for the CA transmission mode (that is, a DL transmission format for the MIMO mode), a DL transmission format for the CC-DIV transmission mode, and a DL-1 transmission as DL transmission formats. It holds a DL transmission format for mode and a DL transmission format for DL-2 transmission mode. The DL transmission format is, for example, a DCI (Downlink Control Information) format (control information format).

  In the CA transmission mode, a component carrier used for exchange of control information (PDCCH) is a PCell (Primary Cell). On the other hand, in the case of CC-DIV transmission mode, in the case of DL-1 transmission mode, and in the case of DL-2 transmission mode, since it is not CA, there is no concept (that is, distinction) such as PCell and SCell (Secondary Cell). That is, all the cells used in each transmission mode are used for exchanging control information (that is, corresponding to the PCell in the case of the CA transmission mode).

  As described above, the DL transmission information holding unit 114 holds DL transmission mode information for each mobile station.

  The DL transmission control unit 112 accesses the DL transmission format holding unit 113 and the DL transmission information holding unit 114, acquires the DL transmission format from the DL transmission format holding unit 113, and receives the DL transmission mode information from the DL transmission information holding unit 114. To get. Also, the DL transmission control unit 112 determines the DL transmission mode for each mobile station based on the DL transmission mode information for each mobile station.

  The CA transmission control unit 115 performs transmission control when performing carrier aggregation. Specifically, CA transmission control section 115 controls carrier aggregation transmission to transmission sections 121 and 122, OFDM processing sections 119 and 120, and DL data processing sections 117 and 118. Further, CA transmission control section 115 notifies DL transmission control section 112 and DL transmission mode determination section 109 of the number of downlink carrier components for each mobile station.

  The DL transmission control unit 112 receives information about the number of downlink carrier components for each mobile station from the CA transmission control unit 115. The DL transmission control unit 112 uses the number of carrier components to determine the transmission data amount per transport block.

  The DL transmission control unit 112 sends DL transmission mode information to the DL data arrangement unit 116 and the DL data processing units 117 and 118.

  The DL data arrangement unit 116 receives DL transmission mode information from the DL transmission control unit 112. The DL data arrangement unit 116 acquires DL data for one transport block arranged in each component carrier DL-1 and DL-2 based on the DL transmission mode information. The DL data arrangement unit 116 sends the acquired DL data to the DL data processing units 117 and 118 of each component carrier.

  The base station 100 performs data transmission using the frequency of the first frequency band (first component carrier) by the DL data processing unit 117, the OFDM processing unit 119, the transmission unit 121, and the antenna 123. . In addition, the base station 100 transmits data using the frequency of the second frequency band (second component carrier) using the DL data processing unit 118, the OFDM processing unit 120, the transmission unit 122, and the antenna 124. To do.

  The DL data processing unit 117 performs mapping for performing OFDM processing on the data transmitted from the DL data arranging unit 116 based on the DL transmission format notified from the DL transmission control unit 112. The DL data processing unit 117 sends the mapped data to the OFDM processing unit 119.

  The OFDM processing unit 119 performs OFDM processing on the data sent from the DL data processing unit 117. The OFDM processing unit 119 sends the OFDM processed data to the transmission unit 121.

  Transmitting section 121 transmits data subjected to OFDM processing to mobile station 300 using antenna 123.

  The DL data processing unit 118 performs mapping for performing OFDM processing on the data transmitted from the DL data arrangement unit 116 based on the DL transmission format notified from the DL transmission control unit 112. The DL data processing unit 118 sends the mapped data to the OFDM processing unit 120.

  The OFDM processing unit 120 performs OFDM processing on the data sent from the DL data processing unit 118. The OFDM processing unit 120 sends the OFDM processed data to the transmission unit 122.

  Transmitting section 122 transmits data subjected to OFDM processing to mobile station 300 using antenna 124.

(B3. Determination of downlink transmission mode)
Next, determination of the DL transmission mode in the DL transmission mode determination unit 109 will be described.

  FIG. 3 is a diagram showing a data table 900 used for determining the DL transmission mode. Referring to FIG. 3, the reception quality of component carrier DL-1 is divided into three ranges by threshold value X_CA and threshold value X_CC-DIV (0 <X_CC-DIV <X_CA). Specifically, the reception quality of the component carrier DL-1 is divided into a range of X_CA or more, a range of less than X_CA and greater than or equal to X_CC-DIV, and a range of less than X_CC-DIV.

  Similarly to the reception quality of the component carrier DL-1, the reception quality of the component carrier DL-2 is also divided into three ranges by the threshold value X_CA and the threshold value X_CC-DIV (0 <X_CC-DIV <X_CA). ing.

  DL transmission mode determination section 109 determines DL transmission mode as CA transmission mode when the reception quality of component carrier DL-1 is equal to or higher than threshold value X_CA and the reception quality of component carrier DL-2 is equal to or higher than threshold value X_CA. To do. Also, the DL transmission mode determination unit 109 determines that the DL carrier mode DL-1 reception quality is greater than or equal to the threshold value X_CA, and the component carrier DL-2 reception quality is less than the threshold value X_CA and greater than or equal to the threshold value X_CC-DIV. The transmission mode is determined as CC-DIV transmission mode. Also, the DL transmission mode determination unit 109 sets the DL transmission mode to DL when the reception quality of the component carrier DL-1 is equal to or higher than the threshold value X_CA and the reception quality of the component carrier DL-2 is lower than the threshold value X_CC-DIV. -1 Determine the transmission mode.

  The DL transmission mode determination unit 109 determines the DL transmission mode when the reception quality of the component carrier DL-1 is less than the threshold value X_CA and the threshold value X_CC-DIV or more and the reception quality of the component carrier DL-2 is the threshold value X_CA or more. To CC-DIV transmission mode. Also, the DL transmission mode determination unit 109 has a reception quality of the component carrier DL-1 that is less than the threshold value X_CA and greater than or equal to the threshold value X_CC-DIV, and further that the reception quality of the component carrier DL-2 is less than the threshold value X_CA and the threshold value X_CC-DIV In the above case, the DL transmission mode is determined to be the CC-DIV transmission mode. Also, DL transmission mode determination section 109 has a case where the reception quality of component carrier DL-1 is less than threshold value X_CA and greater than or equal to threshold value X_CC-DIV, and the reception quality of component carrier DL-2 is less than threshold value X_CC-DIV The DL transmission mode is determined as the DL-1 transmission mode.

  When the reception quality of the component carrier DL-1 is less than the threshold value X_CC-DIV and the reception quality of the component carrier DL-2 is equal to or higher than the threshold value X_CA, the DL transmission mode determination unit 109 sets the DL transmission mode to DL-2. Determine the transmission mode. Also, the DL transmission mode determination unit 109 has the reception quality of the component carrier DL-1 less than the threshold value X_CC-DIV, and the reception quality of the component carrier DL-2 is less than the threshold value X_CA and the threshold value X_CC-DIV. In the above case, the DL transmission mode is determined to be the DL-2 transmission mode. Also, DL transmission mode determination section 109 has a case where the reception quality of component carrier DL-1 is less than threshold value X_CC-DIV, and the reception quality of component carrier DL-2 is less than threshold value X_CC-DIV The process of switching to another component carrier is executed. However, in the present embodiment, since there are only two component carriers DL-1 and DL-2, the switching is not performed.

  As described above, the base station 100 determines which transmission mode to set among the CA transmission mode, the CC-DIV transmission mode, and the transmission diversity mode (DL-1 transmission mode, DL2 transmission mode) for each frequency. It is determined based on the communication quality of the band.

<C. Mobile station 300>
FIG. 4 is a functional block diagram of mobile station 300. Referring to FIG. 4, mobile station 300 includes receiving antennas 301 and 302, receiving units 303 and 304, OFDM processing units 305 and 306, DL reception quality measuring units 307 and 308, and DL transmission format detection. Units 309 and 310, DL data processing units 311 and 312, DL reception control unit 313, CA reception control unit 314, DL data synthesis unit 315, application unit 316, DL reception quality holding unit 317, UL A data processing unit 318, an OFDM processing unit 319, a transmission unit 320, and a transmission antenna 321 are provided.

(C1. Communication processing in downlink)
Processing in the mobile station 300 in downlink communication from the base station 100 to the mobile station 300 will be described.

  The mobile station 300 uses the antenna 301, the reception unit 303, the OFDM processing unit 305, the DL transmission format detection unit 309, and the DL data processing unit 311 to perform the first frequency band (first component carrier). Data reception using frequency is performed. In addition, the mobile station 300 uses the antenna 302, the reception unit 304, the OFDM processing unit 306, the DL transmission format detection unit 310, and the DL data processing unit 312 to transmit the second frequency band (second component carrier). ) Is used for data transmission.

  The CA reception control unit 314 performs reception control when performing carrier aggregation. Specifically, CA reception control section 314 controls carrier aggregation reception for receiving sections 303 and 304, OFDM processing sections 305 and 306, and DL data processing sections 311 and 312.

  The receiving unit 303 receives a signal transmitted from the base station 100 using the antenna 301. The reception unit 303 sends the received signal to the OFDM processing unit 305 and the DL reception quality measurement unit 307.

  DL reception quality measuring section 307 measures the reception quality of the signal received by receiving section 303. The DL reception quality measurement unit 307 sends information indicating the reception quality as a result of the measurement (that is, DL reception quality information) to the DL reception quality holding unit 317.

  The OFDM processing unit 305 performs OFDM processing on the signal transmitted from the receiving unit 303. The OFDM processing unit 305 sends data obtained by OFDM processing (hereinafter also referred to as “OFDM processed data”) to the DL transmission format detection unit 309 and the DL data processing unit 311.

  The DL transmission format detection unit 309 detects the DL transmission format from the OFDM processed data sent from the OFDM processing unit 305. The DL transmission format detection unit 309 sends the detected DL transmission format to the DL data processing unit 311 and the DL reception control unit 313.

  The DL data processing unit 311 receives the OFDM processed data sent from the OFDM processing unit 305. The DL data processing unit 311 receives the DL transmission format sent from the DL transmission format detection unit 309. The DL data processing unit 311 extracts user data from the OFDM processed data based on the DL transmission format. The DL data processing unit 311 sends the extracted user data to the DL data synthesis unit 315.

  The receiving unit 304 receives a signal transmitted from the base station 100 using the antenna 302. Receiving section 304 sends the received signal to OFDM processing section 306 and DL reception quality measuring section 308.

  DL reception quality measuring section 308 measures the reception quality of the signal received by receiving section 304. The DL reception quality measurement unit 308 sends information (DL reception quality information) indicating the reception quality as a measurement result to the DL reception quality holding unit 317.

  The OFDM processing unit 306 performs OFDM processing on the signal transmitted from the receiving unit 304. The OFDM processing unit 306 sends the OFDM processed data obtained by the OFDM processing to the DL transmission format detection unit 310 and the DL data processing unit 312.

  The DL transmission format detection unit 310 detects the DL transmission format from the OFDM processed data sent from the OFDM processing unit 306. The DL transmission format detection unit 310 sends the detected DL transmission format to the DL data processing unit 312 and the DL reception control unit 313.

  The DL data processing unit 312 receives the OFDM processed data sent from the OFDM processing unit 306. The DL data processing unit 312 receives the DL transmission format sent from the DL transmission format detection unit 310. The DL data processing unit 312 extracts user data from the OFDM processed data based on the DL transmission format. The DL data processing unit 312 sends the extracted user data to the DL data synthesis unit 315.

  The DL reception control unit 313 determines the DL transmission mode based on the DL transmission format sent from the DL transmission format detection unit 309. That is, the DL reception control unit 313 uses the two component carriers DL-1 and DL-2 and the same CA transmission mode in which the two component carriers DL-1 and DL-2 are used. Based on the DL transmission format, the base station 100 determines which DL transmission mode of the CC-DIV transmission mode for transmitting information is used.

  The DL reception control unit 313 determines the DL transmission mode by, for example, brand decoding. Note that in the case of a configuration in which the DL transmission mode is determined by blind decoding, information is not necessary because the transmission format is specified from the base station 100. Further, when the same control information (PDCCH) and the same data (PDSCH) are transmitted between the component carrier DL-1 and the component carrier DL-2, the received information is compared, and when the received information is the same, CC-DIV If the received information is different, the DL reception control unit 313 may be configured to determine CA.

  The DL data combining unit 315 receives the determination result of the DL transmission mode used by the base station 100 from the DL reception control unit 313. The determination result is information representing one of the CA transmission mode, CC-DIV transmission mode, DL-1 transmission mode, and DL-2 transmission mode.

  Based on the determination result, the DL data combining unit 315 combines user data sent from the DL data processing units 311 and 312 of the component carriers DL-1 and DL-2. Specifically, DL data combining section 315 performs data combination for carrier aggregation when the DL transmission mode is the CA transmission mode. In addition, when the DL transmission mode is the CC-DIV transmission mode, the DL data combining unit 315 performs data combination for CC-DIV. When the DL transmission mode is the DL-1 transmission mode or the DL-2 transmission mode, the DL data combining unit 315 does not need to combine user data.

  When the DL transmission mode is the CA transmission mode or the CC-DIV transmission mode, the DL data combining unit 315 sends the combined user data to the application unit 316. When the DL transmission mode is the DL-1 transmission mode, the DL data combining unit 315 sends the user data sent from the DL data processing unit 311 to the application unit 316. When the DL transmission mode is the DL-2 transmission mode, the DL data combining unit 315 sends the user data sent from the DL data processing unit 312 to the application unit 316.

(C2. Uplink communication processing)
Next, processing in mobile station 300 in uplink communication from mobile station 300 to base station 100 will be described.

The application unit 316 sends UL data to the UL data processing unit 318.
The UL data processing unit 318 performs mapping for performing OFDM processing on the UL data transmitted from the application unit 316. The UL data processing unit 318 performs mapping for performing OFDM processing on the DL reception quality information transmitted from the DL reception quality holding unit 317 simultaneously with the mapping for the UL data. The UL data processing unit 318 sends the mapped data to the OFDM processing unit 319.

  The OFDM processing unit 319 performs OFDM processing on the data transmitted from the UL data processing unit 318. The OFDM processing unit 319 sends the OFDM processed data to the transmission unit 320.

  The transmission unit 320 transmits the OFDM processed data transmitted from the OFDM processing unit 319 to the base station 100 using the antenna 321.

<D. Data processing>
FIG. 5 is a sequence chart in the communication system 1. Specifically, FIG. 5 is a sequence chart when the DL transmission mode is switched from the CA transmission mode to the CC-DIV transmission mode.

  Referring to FIG. 5, as an initial state of the sequence, CA communication is performed between base station 100 and mobile station 300 using component carriers DL-1 and DL-2 in the downlink, and component carrier UL− in the uplink. Suppose that communication by 1 is performed.

  When the reception quality of component carrier DL-1 and component carrier DL-2 is good (reception quality ≧ threshold value X_CA), communication system 1 periodically repeats step Sα. Step Sα includes step S2, step S4, and step S6.

  Specifically, in step S2, mobile station 300 measures DL reception quality. In step S4, the mobile station 300 notifies the DL reception quality information to the base station 100. In step S6, base station 100 determines the DL transmission mode based on the DL reception quality information. In addition, since the reception quality of component carrier DL-1 and component carrier DL-2 is favorable, base station 100 does not change the DL transmission mode.

  Here, it is assumed that the reception quality of the component carrier DL-1 and the component carrier DL-2 is deteriorated. Precisely, it is assumed that the reception quality of the component carrier DL-1 and / or the component carrier DL-2 is a value that falls within the range of CC-DIV shown in FIG.

  In this case, in step S8, the mobile station 300 continues to measure the DL reception quality. In step S10, the mobile station 300 notifies the base station 100 of DL reception quality information. In step S12, base station 100 determines a DL transmission mode based on DL reception quality information. Specifically, the base station 100 determines the DL transmission mode as the CC-DIV transmission mode. In step S14, the base station 100 changes the DL transmission mode from the CA transmission mode to the CC-DIV transmission mode.

  Thereafter, between the base station 100 and the mobile station 300, CC-DIV communication using the component carriers DL-1 and DL-2 is performed on the downlink, and communication using the component carrier UL-1 is performed on the uplink.

  Note that the DL transmission mode change notification (response and response confirmation) using the L3 message may be performed between the mobile station 300 and the base station 100.

  FIG. 6 is a sequence chart in the communication system 1. Specifically, FIG. 6 is a sequence chart when the DL transmission mode is switched from the CC-DIV transmission mode to the CA transmission mode.

  Referring to FIG. 6, as an initial state of the sequence, CC-DIV communication by component carriers DL-1 and DL-2 is performed in the downlink between base station 100 and mobile station 300, and component carrier is transmitted in the uplink. It is assumed that communication by UL-1 is performed.

  When the reception quality of the component carrier DL-1 and the component carrier DL-2 is poor, the communication system 1 repeats Step Sβ. To be precise, when the reception quality of the component carrier DL-1 and the component carrier DL-2 is a value that falls within the range of CC-DIV shown in FIG. 3, the communication system 1 periodically performs step Sβ. Repeat. Step Sβ includes step S102, step S104, and step S106.

  Specifically, in step S102, the mobile station 300 measures DL reception quality. In step S104, the mobile station 300 notifies the DL reception quality information to the base station 100. In step S106, base station 100 determines the DL transmission mode based on the DL reception quality information. In addition, since the reception quality of component carrier DL-1 and component carrier DL-2 becomes a value that falls within the range of CC-DIV shown in FIG. 3, base station 100 does not change the DL transmission mode.

  Here, it is assumed that the reception quality of the component carrier DL-1 and the component carrier DL-2 is good (reception quality ≧ threshold X_CA). In this case, in step S108, the mobile station 300 continues to measure the DL reception quality. In step S110, the mobile station 300 notifies the DL reception quality information to the base station 100. In step S112, base station 100 determines the DL transmission mode based on the DL reception quality information. Specifically, base station 100 determines the DL transmission mode as the CA transmission mode. In step S114, the base station 100 changes the DL transmission mode from the CC-DIV transmission mode to the CA transmission mode.

  Thereafter, between the mobile station 300 and the base station 100, CA communication by the component carriers DL-1 and DL-2 is performed in the downlink, and communication by the component carrier UL-1 is performed in the uplink.

  Note that the DL transmission mode change notification (response and response confirmation) using the L3 message may be performed between the mobile station 300 and the base station 100.

  FIG. 7 is a flowchart showing a process flow in the base station 100. Referring to FIG. 7, in step S202, base station 100 determines whether or not reception quality is notified from mobile station 300. Specifically, base station 100 determines whether or not DL reception quality information has been received.

  In step S204, the base station 100 determines the DL transmission mode based on the DL reception quality information. In step S206, the base station 100 determines whether it is necessary to change the DL transmission mode.

  If base station 100 determines that the DL transmission mode needs to be changed (YES in step S206), base station 100 changes the DL transmission mode to the DL transmission mode determined from the current DL transmission mode in step S208. On the other hand, when base station 100 determines that it is not necessary to change the DL transmission mode (NO in step S206), the process proceeds to step S212.

  In step S210, the base station 100 resumes communication with the mobile station 300 in the changed DL transmission mode. In step S212, the base station 100 determines whether communication with the mobile station 300 has ended. If base station 100 determines that communication with mobile station 300 has not ended (NO in step S212), base station 100 advances the process to step S202. On the other hand, when base station 100 determines that communication with mobile station 300 has ended (YES in step S212), base station 100 ends a series of processing with mobile station 300.

  FIG. 8 is a flowchart showing a process flow in the mobile station 300. Referring to FIG. 8, in step S302, mobile station 300 determines whether or not data has been received from base station 100. If mobile station 300 determines that data has been received (YES in step S302), mobile station 300 measures the reception quality of the data in step S304. On the other hand, when mobile station 300 determines that data has not been received (NO in step S302), the process proceeds to step S312.

  In step S306, the mobile station 300 notifies the reception quality to the base station 100. Specifically, the mobile station 300 transmits DL reception quality information to the base station 100. In step S308, the mobile station 300 determines whether or not the DL transmission mode has been changed. Specifically, the mobile station 300 determines whether or not the DL transmission mode has been changed by determining the DL transmission mode based on the detection results by the DL transmission format detection units 309 and 310.

  If mobile station 300 determines that the DL transmission mode has been changed (YES in step S308), in step S310, mobile station 300 performs data processing corresponding to the changed DL transmission mode. The data processing is, for example, processing performed in the DL data processing unit 311, the DL data processing unit 312, and the DL data synthesis unit 315. On the other hand, when mobile station 300 determines that there is no change in the DL transmission mode (NO in step S308), the process proceeds to step S312.

  In step S312, the mobile station 300 determines whether communication with the base station 100 has ended. If the mobile station 300 determines that communication with the base station 100 has not ended (NO in step S312), the process proceeds to step S302. On the other hand, when mobile station 300 determines that communication with base station 100 has ended (YES in step S312), mobile station 300 ends a series of processing with base station 100.

  As described above, the communication system 1 does not transmit / receive different information signals using two component carriers, but transmits the same information signal using two component carriers. Further, in the communication system 1, combining is performed by the mobile station 300 on the receiving side. Further, the base station 100 of the communication system 1 generates a transmission format for CC diversity.

  Conventionally, when performing downlink communication in the same frequency band with two antennas, the MIMO mode is used near the cell center with good reception quality, and the transmission diversity mode is used at the cell edge with poor reception quality. The communication system 1 according to the present embodiment has a configuration extended to the case where downlink communication in different frequency bands is performed using two antennas, performs CA communication in the vicinity of a cell center with good reception quality, and has a cell edge with poor reception quality. Then, CC diversity (CC-DIV) is performed.

<E. Hardware configuration>
FIG. 9 is a diagram illustrating a typical hardware configuration of base station 100. In FIG. 9, a configuration corresponding to 2 × 2 MIMO of 3 sectors is taken as an example. Referring to FIG. 9, base station 100 includes a plurality of antennas 1301, 1302, 1311, 1312, 1321 and 1322, a plurality of radio processing units 1500 a, 1500 b and 1500 c, and a control / baseband unit 1800.

  Each of the wireless processing units 1500a, 1500b, and 1500c includes duplexers 1501 and 1502, power amplifiers 1503 and 1504, low noise amplifiers 1505 and 1506, transmission circuits 1507 and 1508, reception circuits 1509 and 1510, and an orthogonal modulation / demodulation unit 1511. Is provided. The control / baseband unit 1800 includes a baseband circuit 1810, a control device 1820, a power supply unit 1850, a timing control unit 1830, and a communication interface 1840. The control device 1820 includes a CPU 1821, ROM 1822, RAM 1823, nonvolatile memory 1824, and HDD (Hard Disk Drive) 1825.

  The orthogonal modulation / demodulation unit 1511 performs orthogonal modulation / demodulation on an OFDM (Orthogonal Frequency Division Multiplexing) signal processed by the baseband circuit 1810 and converts it into an analog signal (RF (Radio Frequency) signal). The transmission circuits 1507 and 1508 convert the RF signal generated by the orthogonal modulation / demodulation unit 1511 into a frequency to be transmitted as a radio wave. The receiving circuits 1509 and 1510 convert the received radio wave into a frequency processed by the orthogonal modulation / demodulation unit 1511.

  The power amplifiers 1503 and 1504 amplify the RF signals generated by the transmission circuits 1507 and 1508 in order to transmit them from the antennas 1301, 1302, 1311, 1312, 1321, and 1322. The low noise amplifier amplifies the weak radio wave received by the antenna and passes it to the receiving circuits 1509 and 1510.

  The control device 1820 performs control of the entire base station 100, call control protocol, and control monitoring. The timing control unit 1830 generates various clocks used in the base station 100 based on a reference clock extracted from a transmission path or GPS (Global Positioning System).

  The communication interface 1840 connects a transmission line such as Ethernet (registered trademark), processes a protocol such as IPsec (Security Architecture for Internet Protocol), IPv6 (Internet Protocol Version 6), and transfers IP packets.

  The baseband circuit 1810 performs conversion (modulation / demodulation) between an IP packet exchanged using the communication interface 1840 and an OFDM signal (baseband signal) to be placed on the radio. The baseband signal is exchanged with the wireless processing units 1500a, 1500b, 1500c. The power supply unit 1850 converts the voltage supplied to the base station 100 into a voltage used inside the base station 100.

  The processing in the base station 100 is realized by each hardware and software executed by the CPU 1821. Such software may be stored in advance in the HDD 1825 or the like. Further, the software may be stored in a memory card (not shown) or other storage medium and distributed as a program product. Alternatively, the software may be provided as a program product that can be downloaded by an information provider connected to the so-called Internet. Such software is read from the storage medium by an IC card reader / writer or other reading device, or downloaded via the communication interface 1840 and then temporarily stored in the HDD 1825. The software is read from the HDD 1825 by the CPU 1821 and is further stored in the nonvolatile memory 1824 in the form of an executable program. The CPU 1821 executes the program.

  Each component which comprises the base station 100 shown by the figure is general. Therefore, it can be said that the essential part of the present invention is the software stored in the HDD 1825, the nonvolatile memory 1824, the memory card or other storage medium, or the software that can be downloaded via the network. Since the operation of each hardware of base station 100 is well known, detailed description will not be repeated.

  The recording media are not limited to DVD-ROM, CD-ROM, FD (Flexible Disk), and hard disk, but are magnetic tape, cassette tape, optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc), optical card, mask ROM, EPROM (Electronically Programmable Read-Only Memory), EEPROM (Electronically Erasable Programmable Read-Only Memory), flash ROM, etc. . The recording medium is a non-transitory medium that can be read by a computer.

  The program here includes not only a program directly executable by the CPU but also a program in a source program format, a compressed program, an encrypted program, and the like.

  FIG. 10 is a diagram illustrating a typical hardware configuration of mobile station 300. Referring to FIG. 10, mobile station 300 includes antennas 3006, 3007, 3008, and 3009, RF circuits 3101 and 3102, baseband circuit 3103, GPS receiver 3104, application processor 3105 that executes a program, A ROM (Read Only Memory) 3106, a RAM (Random Access Memory) 3107, a NAND flash memory 3108, a display 3109, a camera 3110, a microphone 3111, a speaker 3112, and an operation for receiving an instruction input by a user A key 3113, a communication IF (Interface) 3114, an IC (Integrated Circuit) card reader / writer 3115, and a power supply unit 3116 are provided.

  The GPS receiver 3104 includes an antenna 3141, an RF circuit 3142, and a baseband circuit 3143. The GPS receiver 3104 receives a GPS satellite signal using the antenna 3141. Furthermore, the GPS receiver 3104 outputs the processing results (that is, current location information) in the RF circuit 3142 and the baseband circuit 3143 to the application processor 3105.

  Antennas 3006 to 3009, RF circuits 3101 and 3102, and baseband circuit 3103 are used for wireless communication with other mobile terminals, fixed telephones, and PCs (Personal Computers) via a base station. Specifically, antennas 301 and 302, RF circuits 3101 and 3102, and baseband circuit 3103 are used for mobile station 300 to perform communication using a mobile phone network.

  The flash memory 3108 is a nonvolatile semiconductor memory. The flash memory 3108 volatilely stores various programs for controlling the mobile station 300 and various data such as data generated by the mobile station 300 and data acquired from an external device of the mobile station 300.

  The components 3103 to 3116 are connected to each other by a data bus. A memory card 3151 is attached to the IC card reader / writer 3115.

  The processing in the mobile station 300 is realized by each hardware and software executed by the application processor 3105. Such software may be stored in advance in the flash memory 3108. The software may be stored in a memory card 3151 or other storage medium and distributed as a program product. Alternatively, the software may be provided as a program product that can be downloaded by an information provider connected to the so-called Internet. Such software is read from the storage medium by an IC card reader / writer 3115 or other reading device, or downloaded via the antennas 3006 to 3009, the RF circuits 3101 and 3102, and the baseband circuit 3103 or the communication IF 3114. Then, it is temporarily stored in the flash memory 3108. The software is read from the flash memory 3108 by the application processor 3105 and further stored in the flash memory 3108 in the form of an executable program. The application processor 3105 executes the program.

  Each component which comprises the mobile station 300 shown by the figure is general. Therefore, it can be said that the essential part of the present invention is software stored in the flash memory 3108, the memory card 3151 or other storage medium, or software that can be downloaded via a network. Since the operation of each hardware of mobile station 300 is well known, detailed description will not be repeated.

  The recording media are not limited to DVD-ROM, CD-ROM, FD (Flexible Disk), and hard disk, but are magnetic tape, cassette tape, optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc), optical card, mask ROM, EPROM (Electronically Programmable Read-Only Memory), EEPROM (Electronically Erasable Programmable Read-Only Memory), flash ROM, etc. . The recording medium is a non-transitory medium that can be read by a computer.

  The program here includes not only a program directly executable by the CPU but also a program in a source program format, a compressed program, an encrypted program, and the like.

<F. Summary of Base Station 100>
(1) As described above, the base station 100 communicates with the mobile station 300 by carrier aggregation using two component carriers DL-1 and DL-2 having different frequency bands. DL transmission mode determination section 109 of base station 100 transmits different information using two component carriers when the reception qualities of component carriers DL-1 and DL-2 are both equal to or higher than threshold value X_CC-DIV. Based on the communication with the mobile station 300, which DL transmission mode is used among the CA transmission mode and the CC-DIV transmission mode in which the same information is transmitted using two component carriers is determined. Further, the transmission processing unit 150 of the base station 100 performs downlink transmission to the mobile station 300 in the determined DL transmission mode.

  Therefore, base station 100 can improve the reception quality of mobile station 300 when performing downlink communication in different frequency bands with a plurality of antennas. Typically, the base station 100 can improve the reception quality of the mobile station 300 in an environment where the reception quality is low, such as the cell edge of the base station 100.

  (2) More specifically, the DL transmission mode determination unit 109 determines the DL transmission mode based on the DL reception quality information of the component carrier DL-1 and the component carrier DL-2 notified from the mobile station 300. Thus, the base station 100 uses the reception quality for each component carrier in determining the DL transmission mode. Therefore, the base station 100 can improve the reception quality of the mobile station 300 as compared with the configuration using only the reception quality of one component carrier.

  (3) More specifically, the DL transmission mode determination unit 109 determines whether each reception quality is equal to or higher than a threshold value X_CA. When the DL transmission mode determination unit 109 determines that each reception quality is equal to or higher than the threshold value X_CA, the DL transmission mode determination unit 109 determines to use the CA transmission mode. Therefore, base station 100 can set the DL transmission mode to the CA transmission mode only when the reception quality of component carrier DL-1 and the reception quality of component carrier DL-2 are both good.

  (4) More specifically, the DL transmission mode determination unit 109 determines whether each reception quality is equal to or higher than a predetermined threshold value X_CC-DIV that represents that the reception quality is lower than the threshold value X_CA. The DL transmission mode determination unit 109 determines to use the CC-DIV transmission mode when each reception quality is equal to or higher than the threshold value X_CC-DIV and at least one of the reception qualities is lower than the threshold value X_CA.

  Therefore, the base station 100 sets the DL transmission mode to the CC-DIV transmission mode when at least one of the reception quality of the component carrier DL-1 and the reception quality of the component carrier DL-2 is not good (when the threshold is X_CC-DIV or more). Can be set to

  By the way, when at least one of the reception quality of the component carrier DL-1 and the reception quality of the component carrier DL-2 is poor (less than the threshold value X_CC-DIV), the base station 100 hardly obtains the effect of CC diversity. Therefore, the base station 100 does not perform CC diversity when at least one of the reception quality of the component carrier DL-1 and the reception quality of the component carrier DL-2 is poor, thereby simplifying data processing and power consumption. Can be reduced.

  (5) More specifically, DL transmission mode determination section 109 selects the DL transmission format for CA transmission mode (that is, DL transmission format for MIMO mode) when communicating with mobile station 300 in the CA transmission mode. Information different from each other is transmitted to the mobile station 300. In addition, when the DL transmission mode determination unit 109 communicates with the mobile station 300 in the CC-DIV transmission mode, the DL transmission mode determination unit 109 transmits the same information using the DL transmission format for the CC-DIV transmission mode.

  Therefore, the mobile station 300 can determine whether the DL transmission mode is the CA transmission mode or the CC-DIV transmission mode by identifying the DL transmission format.

<G. Summary of Mobile Station 300>
(1) As described above, the mobile station 300 communicates with the base station 100 by carrier aggregation using two component carriers DL-1 and DL-2 having different frequency bands. The mobile station 300 transmits the same information using two component carriers DL-1 and DL-2 and the CA transmission mode in which different information is transmitted using the two component carriers DL-1 and DL-2. Based on communication with the base station 100, the base station 100 uses which DL transmission mode of the CC-DIV transmission mode is used. The mobile station 300 performs data processing corresponding to the determined DL transmission mode on the information transmitted by the base station 100.

  Therefore, when base station 100 performs downlink communication in different frequency bands with a plurality of antennas, mobile station 300 can improve reception quality. Typically, in an environment where the reception quality is low, such as the cell edge of the base station 100, the mobile station 300 can improve the reception quality of the mobile station 300.

  (2) The mobile station 300 transmits each DL reception quality information of the component carrier DL-1 and the component carrier DL-2 to the base station 100. Therefore, the reception quality of mobile station 300 can be improved as compared with the configuration in which base station 100 uses only the reception quality of one component carrier to determine the DL transmission mode.

  (3) Whether the information transmitted from the base station 100 is information using the DL transmission format for the CA transmission mode or information using the DL transmission format for the CC-DIV transmission mode. Based on the above, the DL transmission mode is determined. Therefore, the mobile station 300 can determine whether the DL transmission mode of the base station 100 is the CA transmission mode or the CC-DIV transmission mode.

<H. Modification>
(1) Without providing threshold value X_CC-DIV, when at least one of the reception quality of component carrier DL-1 and the reception quality of component carrier DL-2 is equal to or lower than threshold value X_CA, the DL transmission mode is changed from the CA transmission mode to CC-DIV The base station 100 may be configured to change to the transmission mode.

  (2) The case where two component carriers are used in the downlick has been described as an example, but is not limited to two. Any configuration that uses two or more component carriers may be used. Further, the case where one component carrier is used in the uplink has been described as an example, but the number is not limited to one.

  (3) In the above description, the configuration for determining the DL transmission mode based on the reception quality (RSRQ) has been described. The communication system 1 may be configured to determine the DL transmission mode based on a reception level (RSRP: Reference Signal Received Power) instead of the reception quality.

  (4) In the above description, the configuration in which the mobile station 300 and the base station 100 communicate by carrier aggregation using a plurality of component carriers having different frequency bands has been described as an example. However, the present invention is not limited to this. is not. The mobile station 300 and the base station 100 may be configured to communicate with at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies. Here, “using a plurality of frequencies simultaneously” means using a plurality of frequencies for transmission or reception of certain one data. In addition, at least one of a communication scheme that uses at least two of three or more predetermined frequencies simultaneously and a communication scheme that uses one of the three or more frequencies, the mobile station The communication system 1 may be configured such that 300 and the base station 100 communicate with each other.

  The embodiment disclosed this time is an exemplification, and the present invention is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 communication system, 100 base station, 102, 110, 303, 304 reception unit, 103, 119, 120, 305, 306, 319 OFDM processing unit, 104, 318 UL data processing unit, 117, 118, 311, 312 DL data Processing unit, 105 UL data holding unit, 111 DL data holding unit, 106, 121, 122, 320 transmission unit, 107 core network, 108 reception quality information acquisition unit, 109 transmission mode determination unit, 112 DL transmission control unit, 115 CA Transmission control unit, 113 DL transmission format holding unit,
114 DL transmission information holding unit, 116 DL data arrangement unit, 150 transmission processing unit, 300 mobile station, 307, 308 DL reception quality measurement unit, 309, 310 DL transmission format detection unit, 313 DL reception control unit, 314 CA reception control Unit, 315 DL data synthesis unit, 316 application unit, 317 DL reception quality holding unit, 900 data table, 1500a, 1500b, 1500c wireless processing unit, 1501, 1502 duplexer, 1503, 1504 power amplifier, 1505, 1506 low noise amplifier, 1507 , 1508 transmission circuit, 1509, 1510 reception circuit, 1511 quadrature modulation / demodulation unit, 1800 baseband unit, 1810, 3103, 3143 baseband circuit, 1820 controller, 1822 ROM, 1823 RAM, 182 Non-volatile memory, 1830 timing control unit, 1840 communication interface, 1850 power supply unit, 3101, 3102, 3142 RF circuit, 3105 application processor, 3108 flash memory, 3109 display, 3115 IC card reader / writer, 3116 power supply unit, 3151 memory card, DL, UL Component carrier.

Claims (15)

A base station that communicates with a mobile station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies,
Use any one of a first transmission mode in which different information is transmitted simultaneously using the plurality of frequencies and a second transmission mode in which the same information is transmitted using the plurality of frequencies simultaneously. Determining means for determining whether or not based on communication with the mobile station;
A base station comprising transmission processing means for performing downlink transmission to the mobile station in the determined transmission mode. The base station communicates with the mobile station by carrier aggregation using a plurality of component carriers having different frequency bands from each other,
The first transmission mode is a mode in which different information is transmitted using the plurality of component carriers,
The base station according to claim 1, wherein the second transmission mode is a mode in which the same information is transmitted using the plurality of component carriers.   The base station according to claim 2, wherein the determination unit determines the transmission mode based on information representing reception quality for each component carrier notified from the mobile station. The determining means includes
Determining whether each of the reception qualities is equal to or higher than a predetermined first threshold;
The base station according to claim 3, wherein when it is determined that each of the reception qualities is equal to or higher than the first threshold, the base station determines to use the first transmission mode. The determining means includes
Determining whether each of the reception qualities is equal to or higher than a predetermined second threshold value indicating that the reception quality is lower than the first threshold value;
The decision to use the second transmission mode is made when each of the reception qualities is greater than or equal to the second threshold and at least one of the reception qualities is less than the first threshold. 4. A base station according to 4. The transmission processing means includes
When communicating with the mobile station in the first transmission mode, transmit the different information using the first format,
The base station according to any one of claims 1 to 5, wherein when performing communication with the mobile station in the second transmission mode, the same information is transmitted using a second format. A mobile station that communicates with a base station in at least one of a communication scheme that uses a plurality of frequencies simultaneously and a communication scheme that uses one of the plurality of frequencies,
Any one of the first transmission mode in which different information is transmitted simultaneously using the plurality of frequencies and the second transmission mode in which the same information is transmitted using the plurality of frequencies at the same time is selected. A judging means for judging whether the base station is using or not based on communication with the base station;
A mobile station comprising processing means for performing data processing corresponding to the determined transmission mode for information transmitted by the base station. The mobile station communicates with the base station by carrier aggregation using a plurality of component carriers having different frequency bands from each other,
The first transmission mode is a mode in which different information is transmitted using the plurality of component carriers,
The mobile station according to claim 7, wherein the second transmission mode is a mode in which the same information is transmitted using the plurality of component carriers.   The mobile station according to claim 8, wherein the mobile station transmits information representing reception quality for each component carrier to the base station.   The determination unit performs the determination based on whether the information transmitted by the base station is information using a first format or information using a second format. The mobile station described in 1. A communication system comprising a mobile station and a base station, wherein the mobile station and the base station communicate with each other in at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies. Because
The base station
Use any one of a first transmission mode in which different information is transmitted simultaneously using the plurality of frequencies and a second transmission mode in which the same information is transmitted using the plurality of frequencies simultaneously. Is determined based on communication with the mobile station,
Performing downlink transmission to the mobile station in the determined transmission mode;
The mobile station
Determining which transmission mode of the first transmission mode or the second transmission mode is used by the base station based on communication with the base station;
A communication system that performs data processing corresponding to the determined transmission mode. A communication control method in a base station that communicates with a mobile station in at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies,
Either of a first transmission mode in which the base station transmits different information using the plurality of frequencies simultaneously and a second transmission mode in which the same information is transmitted using the plurality of frequencies simultaneously Determining whether to use the transmission mode according to communication with the mobile station;
A communication control method comprising: the base station performing downlink transmission to the mobile station in the determined transmission mode. A communication control method in a mobile station that communicates with a base station in at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies,
Any one of a first transmission mode in which the mobile station transmits different information using the plurality of frequencies simultaneously and a second transmission mode in which the same information is transmitted using the plurality of frequencies simultaneously Determining whether the base station is using the transmission mode based on communication with the base station;
A communication control method comprising: a step in which the mobile station performs data processing corresponding to the determined transmission mode for information transmitted by the base station. A communication system comprising a mobile station and a base station, wherein the mobile station and the base station communicate with each other in at least one of a communication method using a plurality of frequencies simultaneously and a communication method using one of the plurality of frequencies. A communication control method in
Either of a first transmission mode in which the base station transmits different information using the plurality of frequencies simultaneously and a second transmission mode in which the same information is transmitted using the plurality of frequencies simultaneously Determining whether to use the transmission mode according to communication with the mobile station;
The base station performing downlink transmission to the mobile station in the determined transmission mode;
Determining, based on communication with the base station, whether the mobile station is using the transmission mode of the first transmission mode or the second transmission mode;
A communication control method comprising: the mobile station performing data processing corresponding to the determined transmission mode.   A program for causing a computer to execute the communication control method according to claim 12.

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