Patent Publication Number: US-2021185673-A1

Title: Terminal apparatus, base station apparatus, reception method and transmission method

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to a terminal apparatus, a base station apparatus, a reception method and a transmission method. 
     Description of the Related Art 
     3GPP LTE adopts OFDMA (Orthogonal Frequency Division Multiple Access) as a downlink communication scheme. In a radio communication system to which 3GPP LTE is applied, a base station (which may also be called “eNB”) transmits a synchronization signal (Synchronization Channel: SCH) and broadcast signal (Broadcast Channel: BCH) using predetermined communication resources. A terminal (which may also be called “UE”) captures SCH and thereby secures synchronization with the base station. The terminal then reads BCH information and thereby acquires a parameter specific to the base station (e.g., frequency bandwidth) (see NPLs 1, 2 and 3). 
     After completion of the acquisition of the parameter specific to the base station, the terminal sends a connection request to the base station and thereby establishes communication with the base station. The base station transmits control information to the terminal with which communication has been established via a downlink control channel such as PDCCH (Physical Downlink Control Channel) as appropriate. 
     The terminal then performs “blind detection” of a plurality of pieces of control information (which may also be called “downlink control information (DCI)”) included in the received PDCCH signal. That is, the control information includes a CRC (Cyclic Redundancy Check) portion and this CRC portion is masked with a terminal ID of the transmission target terminal by the base station. Therefore, the terminal cannot determine whether or not the received control information is control information intended for the terminal until the terminal demasks the CRC portion with the terminal ID of the terminal itself. When the demasking result shows that CRC calculation is OK, it is determined in this blind detection that the control information is intended for the terminal itself. The downlink control information includes DL (downlink) assignment indicating assignment information of downlink data and UL (uplink) grant indicating assignment information of uplink data, for example. 
     Next, an uplink retransmission control method in 3GPP LTE will be described. In LTE, UL grant which is assignment information of uplink data is transmitted to the terminal by PDCCH. Here, in an FDD (Frequency Division Duplex) system, a UL grant indicates resource assignment within a target subframe which is the fourth subframe from the subframe in which the UL grant is transmitted. 
     Meanwhile, in a TDD (Time Division Duplex) system, a UL grant indicates resource assignment within a target subframe which is the fourth or after the fourth subframe from the subframe in which the UL grant is transmitted. This will be described more specifically using  FIG. 1 . In the TDD system, a downlink component carrier (which may also be called “downlink CC (Component Carrier)”) and an uplink component carrier (which may also be called “uplink CC”) are in the same frequency band, and the TDD system realizes downlink communication and uplink communication by switching between downlink and uplink in a time-division manner. For this reason, in the TDD system, a downlink component carrier can also be expressed as “downlink communication timing in a component carrier.” An uplink component carrier can also be expressed as “uplink communication timing in a component carrier.” Switching between the downlink component carrier and the uplink component carrier is performed based on a UL-DL configuration as shown in  FIG. 1 . The UL-DL configuration is indicated to the terminal by a broadcast signal called “SIB1 (System Information Block Type 1)” (SIB1 indication), the value thereof is the same throughout the entire system and the value is not expected to be changed frequently. In the UL-DL configuration shown in  FIG. 1 , timings in units of subframes (that is, units of 1 msec) are configured for downlink communication (DL: Downlink) and uplink communication (UL: Uplink) per frame ( 10  msec). The UL-DL configuration allows for building a communication system that can flexibly respond to requests for throughput for downlink communication and throughput for uplink communication by changing a subframe ratio between downlink communication and uplink communication. For example,  FIG. 1  illustrates UL-DL configurations (Config# 0  to  6 ) with different subframe ratios between downlink communication and uplink communication. In  FIG. 1 , a downlink communication subframe is represented by “D,” an uplink communication subframe is represented by “U” and a special subframe is represented by “S.” Here, the special subframe is a subframe when a downlink communication subframe is switched to an uplink communication subframe. In the special subframe, downlink data communication may also be performed as in the case of a downlink communication subframe. As shown by a solid line arrow in  FIG. 1  (UL grant-PUSCH timing), a subframe to which uplink data for UL grant (PUSCH: Physical Uplink Shared Channel) is assigned is an uplink communication subframe which is the fourth or after the fourth subframe from the subframe in which the UL grant is indicated, and is uniquely defined as shown in  FIG. 1 . 
     Uplink retransmission control (UL retransmission control) supports non-adaptive retransmission in which retransmission data is assigned to the same resource as a resource to which uplink data is assigned at the time of the last transmission and adaptive retransmission in which retransmission data can be assigned to a resource different from a resource to which uplink data is assigned at the last transmission (e.g., see NPL 4). In non-adaptive retransmission, only PHICH (Physical Hybrid ARQ Indicator CHannel) for transmitting an ACK/NACK signal (response signal) in response to uplink data to the terminal is used as a channel for a retransmission control signal. When requesting the terminal to perform retransmission, the base station transmits a NACK to the terminal using PHICH and transmits an ACK using PHICH when not requesting the terminal to perform retransmission. In non-adaptive retransmission, since the base station can designate retransmission using only PHICH, non-adaptive retransmission has an advantage that the overhead of a control signal transmitted over downlink necessary to designate retransmission is small. 
     Here, in the FDD system, PHICH is indicated to the terminal using a resource within a target subframe which is the fourth subframe from the subframe in which uplink data is transmitted. Meanwhile, in the TDD system, PHICH is indicated to the terminal using a resource within a target subframe which is the fourth or after the fourth subframe from the subframe in which uplink data is transmitted. This will be described more specifically using  FIG. 1 . As shown by a broken line arrow (PUSCH-PHICH timing) in  FIG. 1 , a subframe to which ACK/NACK (PHICH) in response to uplink data (PUSCH) is assigned is a downlink communication subframe or special subframe 4 or more subframes after a subframe in which the uplink data is notified and is uniquely defined as shown in  FIG. 1 . 
     In adaptive retransmission, the base station transmits an ACK using PHICH while designating retransmission and a retransmission resource using UL grant for indicating resource assignment information. UL grant includes a bit called “NDI (New Data Indicator)” and this bit is binary having 0 or 1. The terminal compares an NDI of the received UL grant this time with an NDI of the last UL grant in the same retransmission process (HARQ (Hybrid ARQ) process), determines that new data has been assigned when there is a change in the NDI or determines that retransmission data has been assigned when there is no change in the NDI. Since adaptive retransmission allows the amount of resources and MCS (Modulation and Coding Scheme) to be changed according to a required SINR (Signal-to-Interference and Noise power Ratio) of retransmission data, adaptive retransmission has an advantage that frequency utilization efficiency improves. 
     Since a CRC (Cyclic Redundancy Check) is added to UL grant, a received signal with UL grant has higher reliability than PHICH. For this reason, when the terminal receives PHICH and UL grant, the terminal follows an instruction of UL grant. 
       FIG. 2  shows an example of a procedure for UL retransmission control in the terminal. In  FIG. 2 , in step (hereinafter abbreviated as “ST”)  11 , the terminal determines whether or not there is UL grant. When there is UL grant (ST 11 : YES), the flow proceeds to ST 12  and when there is no UL grant (ST 11 : NO), the flow proceeds to ST 15 . 
     In ST 12 , the terminal compares the NDI of UL grant this time with the NDI of the last UL grant in the same retransmission process and determines whether or not there is any change in the NDI. When there is a change in the NDI (ST 12 : YES), the flow proceeds to ST 13  and when there is no change in the NDI (ST 12 : NO), the flow proceeds to ST 14 . 
     The terminal transmits new data to the base station in ST 13  and transmits retransmission data to the base station through adaptive retransmission in ST 14 . 
     In ST 15 , the terminal determines whether or not PHICH is NACK. When PHICH is NACK (ST 15 : YES), the flow proceeds to ST 16 , and when PHICH is ACK (ST 15 : NO), the flow proceeds to ST 17 . 
     In ST 16 , the terminal transmits retransmission data to the base station through non-adaptive retransmission, and in ST 17 , suspending is applied, so that the terminal suspends retransmission control. 
     Next, a configuration of PHICH will be described. 
     It should be noted that in an LTE system and an LTE-A (LTE-Advanced) system which is an evolved version of LTE, one RB (Resource Block) is made up of 12 subcarriers×0.5 msec and a unit combining two RBs on the time domain is called “RB pair.” Therefore, the RB pair is made up of 12 subcarriers×1 msec. When the RB pair represents a block of 12 subcarriers on the frequency domain, the RB pair may be simply called “RB.” In addition, a unit of 1 subcarrier×1 OFDM symbol is called “1 RE (Resource Element).” 1 REG (Resource Element Group) is made up of 4 REs. 
     First, in coding of PHICH, ACK/NACK (1 bit) is subjected to three-time repetition. The number of PHICHs is one of {1/6, 1/2, 1, 2} times the number of RBs and is indicated by PBCH (Physical Broadcast Channel). The base station can transmit 8 PHICHs in 3 REGs (=12 REs) through code multiplexing and IQ multiplexing with SF (spreading factor)=4. The 8 PHICHs arranged on 3 REGs are called a PHICH group and expressed as “number of PHICH groups (that is, the number of resources) N group   PHICH  is 8.” In the FDD system, the number of PHICH groups N group   PHICH  takes the same value in all subframes. 
     Meanwhile, in the TDD system, as shown in  FIG. 3A , a factor (m i ) of number of PHICH groups is defined in each UL-DL configuration and each downlink communication subframe or special subframe. The total number of PHICH groups (=number of PHICH groups N group   PHICH × factor m i  of the number of PHICH groups) is changed for each subframe using this factor. In the FDD system, the factor of number of PHICH groups is always 1 irrespective of subframes. 
     The reason that the total number of PHICHs varies from one subframe to another in the TDD system will be described using  FIG. 3B .  FIG. 3B  illustrates the number of subframes before a PHICH received by the terminal in subframe #n is associated with a PUSCH transmitted by the terminal. Blanks in  FIG. 3B  indicate that there are no PHICHs. For example, as shown in  FIG. 3B , PHICH in subframe # 1  of Config# 0  is associated with PUSCH transmitted in subframe # 7  which is 4 subframes earlier (see  FIG. 1 ). In subframe # 1  of Config# 0 , since PUSCH in one subframe is associated with PHICH in one subframe, factor m i  of the number of PHICH groups is assumed to be 1 as in the case of the FDD system (see  FIG. 3A ). On the other hand, as shown in  FIG. 3B , PHICH in subframe # 0  of Config# 0  is associated with PUSCHs transmitted in subframe # 3  which is 7 subframes earlier and in subframe # 4  which is 6 subframes earlier respectively. That is, in subframe # 0  of Config# 0 , the terminal receives PHICHs corresponding to two PUSCHs. Thus, in subframe # 0  of Config# 0 , twice as many resources for PHICH (hereinafter referred to as “PHICH resources”) as those in subframe # 1  of Config# 0  are required, and therefore factor m i  of the number of PHICH groups is considered to be 2 (see  FIG. 3A ). 
     In  FIG. 3B , two PHICHs intended for the same terminal received in the same subframe (e.g., subframes # 0  and  5 ) are distinguished by parameter I PHICH . For example, in subframe # 0  of Config# 0 , PHICH corresponding to PUSCH 7 subframes earlier corresponds to I PHICH =0 and PHICH corresponding to PUSCH 6 subframes earlier corresponds to I PHICH =1. The same applies to subframe # 5  of Config# 0 . For PHICHs in other UL-DL configurations and subframes, I PHICH  is always 0. 
     A PHICH resource is represented by a combination {n group   PHICH , n seq   PHICH  } of an index of the total number of PHICH resources n group   PHICH  and an index of orthogonal sequence n seq   PHICHH . The index of the total number of PHICH resources n group   PHICH  and the index of orthogonal sequence n seq   PHICH  are expressed by following equations 1 and 2 respectively. 
         n   PHICH   group =( I   PRB_BA   +n   DMRS )mod  N   PHICH   group   +I   PHICH   N   PHICH   group    (Equation 1)
 
         n   PHICH   seq =(└ I   PRB_BA   /N   PHICH   group   ┘+n   DMRS )mod 2 N   SF   PHICH    (Equation 2)
 
     Here, N PHICH   SF  is a spreading factor (SF) that varies depending on the length of a CP (Cyclic Prefix). I PRB_RA  is a minimum value of a PRB (Physical RB) index to which PUSCH corresponding to PHICH is assigned. Meanwhile, n DMRS  is a cyclic shift value of DMRS (Demodulation Reference Signal) included in UL grant that indicates PUSCH corresponding to PHICH. Since I PRB_RA  and n DMRS  depend on assignment of UL grant and PUSCH, a PHICH resource can be said to be implicitly indicated (implicit signaling) based on the assignment of UL grant and PUSCH. The determined PHICH resource is divided for every value of I PHICH . For example, in subframe # 0  of Config# 0 , PHICH corresponding to PUSCH  7  subframes earlier and PHICH corresponding to PUSCH  6  subframes earlier are designed such that the PHICH resources do not conflict with each other. 
     Mapping of PHICH depends on a cell ID. Therefore, it is difficult to control interference of PHICH with other cells and PHICH may interfere with PDCCH and/or CRS (Cell-specific Reference Signal) in other cells. All of 3 REGs making up PHICH may be arranged on OFDM symbol # 0  (not shown) or 3 REGs may be arranged one for each of OFDM symbols # 0 , # 1  and # 2  as shown in  FIG. 4 . Information indicating which PHICH arrangement is used is indicated to the terminal using a broadcast signal. 
     The number of OFDM symbols ( 1  to  3 ) occupied by PDCCH is determined based on the value of CFI (Control Format Indicator) indicated by PCFICH (Physical Control Format Indicator Channel) arranged on OFDM symbol # 0 . Moreover, when detecting PDCCH, the terminal performs blind detection on some resources in resource regions except resources occupied by PCFICH, PHICH and reference signals (hereinafter may also be referred to as “PDCCH resources”) of resource regions corresponding to the number of OFDM symbols indicated by CFI from OFDM symbol # 0 . 
     In the LTE-A system, studies are being carried out on changing UL-DL configuration (hereinafter referred to as “TDD eIMTA (enhancement for DL-UL Interference Management and Traffic Adaptation),” which may also be referred to as “dynamic TDD” or “flexible TDD”). Exemplary purposes of TDD eIMTA include provision of a service that meets the needs of users by flexible changes of a UL/DL ratio or reduction in power consumption at a base station by increasing the UL ratio in a time zone when traffic load is low. As a method of changing UL-DL configuration, the following methods are under study in accordance with the purpose of change: (1) method using indication of an SI (System Information) signaling base, (2) method using indication of an RRC (higher layer) signaling base, (3) method using indication of a MAC (Media Access Control layer) signaling base and (4) method using indication of an L1 (Physical Layer) signaling base. 
     Method ( 1 ) is to change the least frequent UL-DL configuration. Method ( 1 ) is suitable for a case where the purpose is to reduce power consumption at a base station by increasing the UL ratio, for example, in a time zone when traffic load is low (e.g., midnight or early morning). Method ( 4 ) is to change the most frequent UL-DL configuration change. The number of terminals connected is smaller in a small cell such as a pico cell than in a large cell such as a macro cell. In a pico cell, UL/DL traffic in the entire pico cell is determined depending on the level of UL/DL traffic in a small number of terminals connected to the pico cell. For this reason, UL/DL traffic in the pico cell fluctuates drastically with time. Thus, method ( 4 ) is suitable for a case where UL-DL configuration is changed to follow a time fluctuation of UL/DL traffic in a small cell such as a pico cell. Method ( 2 ) and method ( 3 ) are positioned between method ( 1 ) and method ( 4 ) and suitable for a case where UL-DL configuration is changed with medium frequency. 
     CITATION LIST 
     Non-Patent Literature 
     NPL 1 
     3GPP TS 36.211 V10.1.0, “Physical Channels and Modulation (Release 10),” March 2011 
     NPL 2 
     3GPP TS 36.212 V10.1.0, “Multiplexing and channel coding (Release 10),” March 2011 
     NPL 3 
     3GPP TS 36.213 V10.1.0, “Physical layer procedures (Release 10),” March 2011 
     NPL 4 
     R1-074811, “Semi-static Configuration of Non-adaptive and Adaptive HARQ in E-UTRA Downlink” 
     BRIEF SUMMARY 
     Technical Problem 
     A case will be considered where a terminal using an SIB1-indicated UL-DL configuration (hereinafter may be referred to as “non-TDD eIMTA terminal” or “legacy terminal”) coexists with a terminal that supports TDD eIMTA using UL-DL configuration which is different from the SIB1-indicated UL-DL configuration (hereinafter may be referred to as “TDD eIMTA terminal”). 
     As shown in  FIG. 3B , the LTE system and LTE-A system define PUSCH timing corresponding to PHICH for each UL-DL configuration (timing relating to uplink retransmission control). Moreover, as shown in  FIG. 3A , factor (m i ) of the number of PHICH groups is defined in association with PHICH reception timing in a terminal. Therefore, the timing relating to uplink retransmission control and a factor of the number of PHICH groups may differ between a legacy terminal using SIB1-indicated UL-DL configuration and a TDD eIMTA terminal using UL-DL configuration which is different from the SIB1-indicated UL-DL configuration. 
       FIGS. 5A and 5B  illustrate an example of a case where the factor of the number of PHICH groups differs between the legacy terminal and the TDD eIMTA terminal. 
       FIG. 5A  shows an example of a case where Config# 0  is set in the legacy terminal and Config# 2  is set in the TDD eIMTA terminal. That is, the factor (m i ) of the number of PHICH groups corresponding to Config# 0  shown in  FIG. 3A  is defined in the legacy terminal for every subframe and the factor (m i ) of the number of PHICH groups corresponding to Config# 2  shown in  FIG. 3A  is defined in the TDD eIMTA terminal for every subframe. 
     Here, attention is focused on factors of the numbers of PHICH groups in subframes (SF)# 0 ,  1 ,  5  and  6  which are downlink communication subframes (D) or special subframes (S) in both terminals. It can be seen that a factor of the number of PHICH groups in each subframe differs between the legacy terminal and the TDD eIMTA terminal. For example, in subframe # 0 , the TDD eIMTA terminal recognizes that there is no PHICH resource (factor  0 ), whereas the legacy terminal recognizes that there are PHICH resources corresponding to factor  2  of the number of PHICH groups. 
     As described above, each terminal (legacy terminal or TDD eIMTA terminal) performs blind detection of PDCCH in some resource regions except resources occupied by PCFICH, PHICH and reference signals out of resource regions corresponding to the number of OFDM symbols indicated by CFI from OFDM symbol # 0 . However, when the total number of PHICH groups (=number of PHICH groups×factor relating to number of PHICH groups) recognized by the terminal does not match the number of PHICH resources assumed by the base station, a blind detection range of PDCCH in the terminal may be different from the assumption made by the base station. For this reason, the terminal can neither correctly receive PHICH nor downlink control information (DCI) included in PDCCH intended for the terminal. That is, the base station cannot correctly indicate downlink control information (DCI) using PDCCH to the legacy terminal and the TDD eIMTA terminal in a single subframe. Thus, to correctly indicate DCI using PDCCH to the legacy terminal and the TDD eIMTA terminal, the base station needs to use subframes while classifying subframes into a legacy terminal subframe and a TDD eIMTA terminal subframe, which therefore causes a problem of involving large scheduling constraints regarding DCI. 
       FIG. 5B  shows an exemplary case where Config# 3  is set in a legacy terminal and Config# 0  is set in a TDD eIMTA terminal. It can also be seen in  FIG. 5B  that both terminals have problems similar to those in  FIG. 5A  in subframes # 0 ,  1 ,  5  and  6  which are downlink communication subframes or special subframes. 
     An object of the present invention is to provide a terminal apparatus, a base station apparatus, a reception method and a transmission method capable of suppressing scheduling constraints on downlink control information (DCI) for both terminals in the base station when terminals in which different UL-DL configurations are set coexist. 
     Solution to Problem 
     A terminal apparatus according to an aspect of the present invention is a terminal apparatus capable of changing setting of a configuration pattern of subframes which make up a single frame to one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication, the terminal apparatus including: a receiving section that receives a signal transmitted from a base station apparatus; and a demultiplexing section that demultiplexes the signal into a response signal assigned to a first resource identified based on a number of resources associated with the first subframe in which the signal has been received, and downlink control information assigned to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, the demultiplexing section uses a number of resources associated with the first subframe of the second configuration pattern. 
     A base station apparatus according to an aspect of the present invention includes: a generation section that generates a response signal for uplink data transmitted from a terminal apparatus in which one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication is set, each configuration pattern including subframes which make up one frame; an assignment section that assigns a response signal to a first resource identified based on a number of resources associated with the first subframe in which the response signal is transmitted, and downlink control information to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern; and a transmitting section that transmits a signal including the response signal and the downlink control information, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, the assignment section uses a number of resources associated with the first subframe of the second configuration pattern for the terminal apparatus. 
     A reception method according to an aspect of the present invention is a method for a terminal apparatus capable of changing setting of a configuration pattern of subframes which make up a single frame to one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication, the method including: receiving a signal transmitted from a base station apparatus; and demultiplexing the signal into a response signal assigned to a first resource identified based on a number of resources associated with the first subframe in which the signal has been received, and downlink control information assigned to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, a number of resources associated with the first subframe of the second configuration pattern is used. 
     A transmission method according to an aspect of the present invention includes: generating a response signal for uplink data transmitted from a terminal apparatus in which one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication is set, each configuration pattern including subframes which make up one frame; assigning a response signal to a first resource identified based on a number of resources associated with the first subframe in which the response signal is transmitted, and downlink control information to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern; transmitting a signal including the response signal and the downlink control information; and using, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, a number of resources associated with the first subframe of the second configuration pattern for the terminal apparatus. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to suppress scheduling constraints on downlink control information (DCI) for both terminals in the base station when terminals in which different UL-DL configurations are set coexist. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a diagram provided for describing UL-DL configuration and uplink communication retransmission control timing in TDD; 
         FIG. 2  is a flowchart illustrating an uplink communication retransmission control procedure; 
         FIGS. 3A and 3B  illustrate factors of PHICH group number for UL-DL configuration; 
         FIG. 4  illustrates an example of mapping of PHICHs; 
         FIGS. 5A and 5B  are diagrams provided for describing problems with respect to different UL-DL configurations; 
         FIG. 6  is a block diagram illustrating a main configuration of a base station according to an embodiment of the present invention; 
         FIG. 7  is a block diagram illustrating a main configuration of a terminal according to the embodiment of the present invention; 
         FIG. 8  is a block diagram illustrating a configuration of the base station according to the embodiment of the present invention; 
         FIG. 9  is a block diagram illustrating a configuration of the terminal according to the embodiment of the present invention; 
         FIGS. 10A and 10B  are diagrams provided for describing a method of determining factors of the numbers of PHICH groups according to case  1  of the embodiment of the present invention; 
         FIGS. 11A and 11B  are diagrams provided for describing factors of the numbers of PHICH groups according to method  1  of case  2  of the embodiment of the present invention; 
         FIGS. 12A and 12B  are diagrams provided for describing problems associated with case  2  of the embodiment of the present invention; 
         FIGS. 13A and 13B  are diagrams provided for describing factors of the numbers of PHICH groups according to method  2  of case  2  of the embodiment of the present invention; 
         FIGS. 14A and 14B  are diagrams provided for describing factors of the numbers of PHICH groups according to method  3  of case  2  of the embodiment of the present invention; 
         FIG. 15  is a diagram provided for describing problems associated with case  2  of the embodiment of the present invention; 
         FIG. 16  is a diagram provided for describing problems associated with case  2  of the embodiment of the present invention; and 
         FIG. 17  is a diagram provided for describing factors of the numbers of PHICH groups according to method  4  of case  2  of the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Throughout the embodiment, the same elements are assigned the same reference numerals and any duplicate description of the elements is omitted. 
       FIG. 6  is a main configuration diagram of base station  100  according to the present embodiment. In base station  100 , PHICH generation section  103  generates a response signal (ACK/NACK signal) in response to uplink data transmitted from a terminal in which one of a plurality of configuration patterns (UL-DL configurations) of subframes making up one frame is set, the plurality of configuration patterns including a first subframe used for downlink communication (downlink communication subframe or special subframe) and a second subframe used for uplink communication (uplink communication subframe). Note that the number of resources (total number of PHICH groups) to which response signals are assigned is associated with the first subframe included in UL-DL configuration. Signal assignment section  106  assigns a response signal to a first resource (PHICH resource) identified based on the number of resources associated with the first subframe in which the response signal is transmitted and assigns downlink control information (DCI) to a second resource (PDCCH resource). Radio transmitting section  107  transmits the signal to which response signal and downlink control information are assigned. 
     Here, when both timing of a first configuration pattern set in the above terminal (TDD eIMTA terminal) and timing of a second configuration pattern set in the other terminal (non-TDD eIMTA terminal) whose UL-DL configuration setting cannot be changed are the first subframes, signal assignment section  106  uses the number of resources associated with the first subframe of the second configuration pattern for the terminal (TDD eIMTA terminal). 
       FIG. 7  is a main configuration diagram of terminal  200  according to the present embodiment. Terminal  200  is a terminal that can change the setting of one of a plurality of configuration patterns (UL-DL configurations) of subframes making up one frame, the plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication. Note that the number of resources (total number of PHICH groups) to which response signals in response to uplink data are assigned is associated with the first subframe included in UL-DL configuration. Radio receiving section  202  receives a signal transmitted from base station  100 . Signal demultiplexing section  203  demultiplexes the signal into a response signal assigned to a first resource (PHICH resource) identified based on the number of resources associated with the first subframe in which the signal is received and downlink control information assigned to a second resource (PDCCH resource). 
     Here, when both timing of the first configuration pattern set in terminal  200  (TDD eIMTA terminal) and timing of the second configuration pattern set in the other terminal apparatus (non-TDD eIMTA terminal) whose UL-DL configuration setting cannot be changed are the first subframes, signal demultiplexing section  203  uses the number of resources associated with the first subframe of the second configuration pattern. 
     [Configuration of Base Station  100 ] 
       FIG. 8  is a block diagram illustrating a configuration of base station  100  according to the embodiment of the present invention. 
     In  FIG. 8 , using CRC or the like, error determining section  101  determines whether or not there is any error in a data signal (uplink data) received from error correction decoding section  111  which will be described later. The determination result is outputted to control information generation section  102 . 
     When there is a data signal to be transmitted over the downlink, control information generation section  102  determines a resource to which the data signal is assigned and generates DL assignment which is assignment information. When there is a data signal to be assigned to the uplink, control information generation section  102  determines a resource to which the data signal is assigned and generates UL grant which is assignment information. Note that control information generation section  102  determines whether or not to cause the terminal to retransmit the signal (that is, uplink data), based on the determination result received from error determining section  101 . The generated assignment information is outputted to signal assignment section  106  as information to be transmitted via PDCCH (or EPDCCH). The DL assignment is also outputted to signal assignment section  106  as control information for transmitting downlink data. The UL grant is outputted to radio receiving section  109  to receive uplink data. 
     If a signal need not be retransmitted to the terminal on the basis of the determination result received from error determining section  101  or a signal is adaptively retransmitted, control information generation section  102  instructs PHICH generation section  103  to generate an ACK. Meanwhile, if a signal is non-adaptively retransmitted to the terminal, control information generation section  102  instructs PHICH generation section  103  to generate a NACK. 
     PHICH generation section  103  generates an ACK/NACK signal (ACK or NACK) according to an instruction from control information generation section  102 . 
     Error correction coding section  104  performs error correction coding on a transmission data signal (that is, a downlink data signal) and outputs the coded signal to modulation section  105 . 
     Modulation section  105  modulates the signal received from error correction coding section  104  and outputs the modulated signal to signal assignment section  106 . 
     Signal assignment section  106  assigns the modulated signal received from modulation section  105  to a corresponding resource based on the DL assignment received from control information generation section  102 . In addition, signal assignment section  106  assigns DCI including the DL assignment and UL grant received from control information generation section  102  to a PDCCH resource region of (PDCCH region) (or an EPDCCH resource region (EPDCCH region)). Furthermore, when an ACK/NACK signal is outputted from PHICH generation section  103 , signal assignment section  106  assigns the ACK/NACK signal to the PHICH resource region. More specifically, signal assignment section  106  assigns an ACK/NACK signal to a PHICH resource identified based on a factor of the number of PHICH groups (that is, total number of PHICH groups associated with the subframe) defined for a subframe in which the ACK/NACK signal is transmitted (downlink communication subframe or special subframe) and assigns DCI to a PDCCH resource other than at least a PHICH resource in a predetermined resource region (region determined by the abovementioned CFI). One of a plurality of UL-DL configurations (e.g., Config# 0  to # 6 ) is set in the terminal that has transmitted uplink data corresponding to the above ACK/NACK signal. Details of the assignment operation by signal assignment section  106  will be described later. 
     In this way, a transmission data signal, control information (assignment information (DL assignment, UL grant) or the like) and PHICH signal (ACK/NACK signal) are assigned to predetermined resources and a transmission signal is thereby generated. The generated transmission signal is outputted to radio transmitting section  107 . 
     Radio transmitting section  107  applies predetermined radio transmission processing such as up-conversion to the transmission signal received from signal assignment section  106  and transmits the transmission signal via antenna  108 . 
     Radio receiving section  109  receives a signal transmitted from the terminal via antenna  108  and applies predetermined radio reception processing such as down-conversion to the received signal. Radio receiving section  109  then demultiplexes the signal transmitted from the terminal using the UL grant received from control information generation section  102  and outputs the signal to demodulation section  110 . 
     Demodulation section  110  applies demodulation processing to the signal received from radio receiving section  109  and outputs the demodulated signal thus obtained to error correction decoding section  111 . 
     Error correction decoding section  111  decodes the demodulated signal received from demodulation section  110  and obtains a received data signal. The received data signal obtained is also outputted to error determining section  101 . 
     [Configuration of Terminal  200 ] 
       FIG. 9  is a block diagram illustrating a configuration of terminal  200  according to the present embodiment. 
     In  FIG. 9 , radio receiving section  202  receives a signal transmitted from base station  100  via antenna  201 , applies predetermined radio reception processing such as down-conversion and outputs the signal subjected to the radio reception processing to signal demultiplexing section  203 . 
     Signal demultiplexing section  203  extracts a PHICH region signal (ACK/NACK signal) and a PDCCH region signal (control information) from the signal received from radio receiving section  202  and outputs the extracted PHICH region signal and PDCCH region signal to PHICH receiving section  206  and control information receiving section  207 , respectively. More specifically, signal demultiplexing section  203  demultiplexes the received signal into control information (DCI) assigned to a PDCCH resource other than at least a PHICH resource of ACK/NACK signal assigned to the PHICH resource (number of resources and resource position) identified based on a factor of the number of PHICH groups defined in a subframe in which radio receiving section  202  receives the received signal (downlink communication subframe or special subframe) (that is, total number of PHICH groups associated with the subframe) and predetermined resource region (region determined by the aforementioned CFI). Details of the demultiplexing operation by signal demultiplexing section  203  will be described later. 
     Signal demultiplexing section  203  extracts a signal assigned to a data resource indicated by the DL assignment received from control information receiving section  207  which will be described later (that is, downlink data signal) from the received signal and outputs the extracted signal to demodulation section  204 . 
     Demodulation section  204  demodulates the signal received from signal demultiplexing section  203  and outputs the demodulated signal to error correction decoding section  205 . 
     Error correction decoding section  205  decodes the demodulated signal received from demodulation section  204  and outputs the received data signal obtained. 
     PHICH receiving section  206  determines whether the PHICH region signal extracted by signal demultiplexing section  203  is ACK or NACK. The determination result is outputted to control information receiving section  207 . 
     Control information receiving section  207  performs blind decoding on the PDCCH region signal extracted by signal demultiplexing section  203  and thereby extracts control information (e.g., DL assignment or UL grant) intended for terminal  200 . Control information receiving section  207  outputs the extracted DL assignment to signal demultiplexing section  203  and outputs the UL grant to signal assignment section  210 . 
     Control information receiving section  207  also functions as a retransmission control section. When the determination result received from PHICH receiving section  206  is NACK and no UL grant is detected, control information receiving section  207  outputs a signal indicating non-adaptive retransmission (retransmission indication signal) to signal assignment section  210 . Meanwhile, when the determination result received from PHICH receiving section  206  is an ACK and no UL grant is detected, control information receiving section  207  does not output any signal indicating the assignment to signal assignment section  210 . 
     Error correction coding section  208  performs error correction coding on a transmission data signal (that is, uplink data) and outputs the coded signal to modulation section  209 . 
     Modulation section  209  modulates the signal outputted from error correction coding section  208  and outputs the modulated signal to signal assignment section  210 . 
     Upon receiving UL grant from control information receiving section  207 , signal assignment section  210  compares an NDI of the UL grant (NDI of the UL grant this time) with the NDI of the last UL grant in the same retransmission process, determines, when there is any change in the NDI, that new data has been assigned and assigns a modulated signal of the new data outputted from modulation section  209  to data resources according to the UL grant. Meanwhile, when there is no change in the NDI, signal assignment section  210  determines that retransmission data has been assigned and assigns the modulated signal of the retransmission data outputted from modulation section  209  to data resources according to the UL grant. Upon receiving a retransmission indication signal from control information receiving section  207 , signal assignment section  210  assigns the modulated signal of the retransmission data outputted from modulation section  209  to data resources according to the last UL grant in the same retransmission process. The assigned signal is outputted to radio transmitting section  211  as a transmission signal. 
     Radio transmitting section  211  applies predetermined radio transmission processing such as up-conversion to the transmission signal received from signal assignment section  210  and transmits the transmission signal via antenna  201 . 
     [Operations of Base Station  100  and Terminal  200 ] 
     Operations of base station  100  and terminal  200  having the above-described configurations will be described in detail. Here, a TDD eIMTA terminal (terminal  200 ) whose UL-DL configuration setting can be changed and a non-TDD eIMTA terminal (including a legacy terminal) whose UL-DL configuration setting cannot be changed coexist within the same cell covered by base station  100 . A case where the UL-DL configuration of terminal  200 , which is a TDD eIMTA terminal, is a downlink communication subframe or special subframe will be described separately using two cases. 
     &lt;Case  1 &gt;: 
     Where UL-DL configuration of the non-TDD eIMTA terminal is a downlink communication subframe or special subframe, and 
     &lt;Case  2 &gt;: 
     where UL-DL configuration of the non-TDD eIMTA terminal is an uplink communication subframe. 
     &lt;Case  1 &gt; 
     A method of determining the number of PHICH resources by base station  100 , and a method of determining the total number of PHICH groups and a method of detecting the PDCCH by terminal  200  (TDD eIMTA terminal) will be described using  FIG. 10 . 
     The UL-DL configurations of terminals in  FIG. 10A  and  FIG. 10B  correspond to the UL-DL configurations of terminals in  FIG. 5A  and  FIG. 5B , respectively. In  FIG. 10A , although a factor of the number of PHICH groups in subframe # 3 ,  4 ,  8  and  9  of the TDD eIMTA terminal is represented by “x,” the value of “x” may be determined using one of the methods in &lt;Case  2 &gt; which will be described later. 
     Here, the TDD eIMTA terminal (terminal  200 ) is first connected to a cell that supports TDD eIMTA using UL-DL configuration which is SIB1-indicated as UL-DL configuration for connection to a cell. The TDD eIMTA terminal may be changed to a different UL-DL configuration based on an instruction of base station  100  in the cell after the cell connection. That is, the TDD eIMTA terminal can receive not only a UL-DL configuration for TDD eIMTA (that is, UL-DL configuration which is set in the TDD eIMTA terminal yet different from SIB1-indicated UL-DL configuration) but also an SIB1-indicated UL-DL configuration (that is, UL-DL configuration set in the non-TDD eIMTA terminal). In contrast, a non-TDD eIMTA terminal including a legacy terminal can receive an SIB1-indicated UL-DL configuration, but need not receive a UL-DL configuration for TDD eIMTA or cannot receive any UL-DL configuration in the first place. 
     Thus, at timing of case  1 , base station  100  secures the number of PHICH resources and the PHICH resource position according to the factor of the number of PHICH groups based on the SIB1-indicated UL-DL configuration irrespective of the current UL-DL configuration of terminal  200  for the TDD eIMTA terminal (terminal  200 ). Base station  100  sets a PDCCH region based on the secured PHICH region. 
     Meanwhile, at timing of case  1 , terminal  200  detects PDCCH assuming that the number of PHICH resources and the PHICH resource position are secured according to the factor of the number of PHICH groups based on the SIB1-indicated UL-DL configuration irrespective of the current UL-DL configuration of terminal  200 . 
     That is, at timing of case  1  at which both the UL-DL configuration set in the TDD eIMTA terminal and the UL-DL configuration set in the non-TDD eIMTA terminal are downlink communication subframes or special subframes, base station  100  (e.g., signal assignment section  106 ) and terminal  200  (e.g., signal demultiplexing section  203 ), in order to eliminate a difference in recognition of the total number of PHICH groups between the TDD eIMTA terminal and the non-TDD eIMTA terminal, identify resource regions of PHICH and PDCCH using the factor of number of PHICH groups defined in the UL-DL configuration (SIB1-indicated UL-DL configuration) set in the non-TDD eIMTA terminal for the TDD eIMTA terminal. In other words, at timing of case  1 , base station  100  and terminal  200  use the total number of PHICH groups (number of PHICH resources) associated with the timing of the UL-DL configuration set in the non-TDD eIMTA terminal. 
     More specifically, in subframes # 0 ,  1 ,  5  and  6  corresponding to case  1  in  FIG. 10A , base station  100  (signal assignment section  106 ) sets the factor (m i ) of number of PHICH groups for the TDD eIMTA terminal (terminal  200 ) to the same number ((m i =2, 1, 2, 1) in that order) as the factor (m i ) of the number of PHICH groups set in the legacy terminal (non-TDD eIMTA terminal). Thus, in subframes # 0 ,  1 ,  5  and  6  shown in  FIG. 10A , base station  100  sets the same total number of PHICH groups (=number of PHICH groups×factor of number of PHICH groups) for the TDD eIMTA terminal and the non-TDD eIMTA terminal. Thus, in subframes # 0 ,  1 ,  5  and  6  shown in  FIG. 10A , base station  100  sets the same PDCCH region for the TDD eIMTA terminal and the non-TDD eIMTA terminal. Thus, the PDCCH blind detection range is the same for the TDD eIMTA terminal and the non-TDD eIMTA terminal. 
     Meanwhile, terminal  200  (signal demultiplexing section  203 ) assumes the factor of number of PHICH groups in subframes # 0 ,  1 ,  5  and  6  shown in  FIG. 10A  to be the same number as the factor of the number of PHICH groups recognized by the legacy terminal (factor defined in the SIB1-notified UL-DL configuration) (2, 1, 2, 1 in that order), not the factor of the number of PHICH groups corresponding to Config# 2  set in terminal  200 . Thus, in subframes # 0 ,  1 ,  5  and  6  shown in  FIG. 10A , terminal  200  detects PDCCH intended for terminal  200  in the same PDCCH region (blind detection range) as that of the legacy terminal. 
     Similarly, in subframes # 0 ,  1 ,  5  and  6  shown in  FIG. 10B , base station  100  and terminal  200  set the factor of PHICH group number of terminal  200  to the same number ( 1 ,  0 ,  0 ,  0  in that order) as the factor of the number of PHICH groups recognized by the legacy terminal and perform assignment processing and demultiplexing processing (and detection processing) in PHICH and PDCCH, respectively. 
     [Effects] 
     In this way, at timing of case  1 , the difference in recognition of the total number of PHICH groups between the TDD eIMTA terminal and non-TDD eIMTA terminal is eliminated and the numbers of PHICH resources assumed by each terminal and base station  100  match. Thus, in the same subframe, base station  100  can correctly indicate DCI using PDCCH to the TDD eIMTA terminal and the non-TDD eIMTA terminal. Moreover, the TDD eIMTA terminal (terminal  200 ) and non-TDD eIMTA terminal can detect PDCCH intended for terminal  200  in the same subframe. In this way, base station  100  need not divide a subframe to be used in the TDD eIMTA terminal and non-TDD eIMTA terminal, and so there is no scheduling constraint regarding DCI. 
     [PDCCH Detection Method and PHICH Detection Method] 
     Next, in case  1 , the operations of terminal  200  relating to PDCCH detection and PHICH detection will be described in detail in each of combinations (a) to (d) of the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA set in terminal  200  (TDD eIMTA terminal) and the factor of the number of PHICH groups corresponding to the UL-DL configuration SIB1-indicated to the legacy terminal (non-TDD eIMTA terminal). 
     In any combinations (a) to (d) which will be described later, terminal  200  performs blind detection of PDCCH in some resource regions except PCFICH resources, reference signal resources and PHICH resources secured using a method which will be described later out of resource regions (predetermined resource regions) corresponding to the number of OFDM symbols indicated by CFI from OFDM symbol # 0 . 
     (a) When the factor of number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 0 and the SIB1-indicated factor of the number of PHICH groups is 1 or 2 
     In the subframes, terminal  200  secures, for PHICH, PHICH resources (number of PHICH resources and corresponding PHICH resource positions) identified based on the factor of the number of PHICH groups ( 1  or  2 ) defined in the SIB1-indicated UL-DL configuration for PDCCH detection. However, since there is no PHICH intended for terminal  200 , terminal  200  need not perform PHICH detection. 
     (b) When the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 1 and the SIB1-indicated factor of the number of PHICH groups is 2 
     In the subframes, terminal  200  secures, for PHICH, PHICH resources (number of PHICH resources and corresponding PHICH resource positions) identified based on factor  2  of the number of PHICH groups defined in the SIB1-indicated UL-DL configuration for PDCCH detection. Furthermore, terminal  200  performs PHICH detection. Therefore, both adaptive retransmission and non-adaptive retransmission are available as the uplink data retransmission method for terminal  200 . 
     (c) When the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 1 or 2 and the SIB1-indicated factor of PHICH group number is 0 
     In the subframes, terminal  200  does not secure any PHICH resource for PDCCH detection. Terminal  200  does not perform PHICH detection either. Therefore, only adaptive retransmission is available as the uplink data retransmission method for terminal  200 . 
     (d) When the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 2 and the SIB1-indicated factor of the number of PHICH groups is 1 
     In the subframes, terminal  200  secures, for PHICH, PHICH resources (number of PHICH resources and corresponding PHICH resource positions) identified based on factor  1  of the number of PHICH groups defined in the SIB1-indicated UL-DL configuration for PDCCH detection. Moreover, terminal  200  performs PHICH detection only for one piece of uplink data (assumed to be first uplink data) of two pieces of uplink data corresponding to PHICH received in the subframes and does not perform PHICH detection on the other uplink data (assumed to be second uplink data). Therefore, as the uplink data retransmission method for terminal  200 , both adaptive retransmission and non-adaptive retransmission are available for the first uplink data and only adaptive retransmission is available for the second uplink data. 
     Alternatively, terminal  200  secures, for PHICH corresponding to the first uplink data, PHICH resources (number of PHICH resources and corresponding PHICH resource positions) identified based on factor  1  of the number of PHICH groups defined in the SIB1-indicated UL-DL configuration for PDCCH detection. Furthermore, terminal  200  determines a PHICH resource corresponding to the second uplink data based on the PHICH resource corresponding to the first uplink data. More specifically, when a PHICH resource for the first uplink data is determined by a parameter set (I PRB_RA , n DMRS ), terminal  200  determines a PHICH resource corresponding to the second uplink data using a parameter set (I PRB_RA +1, n DMRS ). In this case, both non-adaptive retransmission and adaptive retransmission are available for both the first uplink data and the second uplink data. Here, I PRB_RA  represents a leading PRB of uplink data assignment. For this reason, there is a high possibility that I PRB_RA +1 representing PRB neighboring the PRB corresponding to I PRB_RA  may also be occupied by the uplink data. That is, the possibility that base station  100  may assign uplink data whose leading PRB is the PRB corresponding to I PRB_RA +1 to other terminals except terminal  200  is low. Therefore, even when base station  100  uses a PHICH resource corresponding to I PRB_RA +1 in addition to a PHICH resource corresponding to I PRB_RA  for terminal  200 , it is possible to reduce the possibility of producing constraints on scheduling for other terminals. 
     The operations relating to PDCCH detection and PHICH detection by terminal  200  in each combination (a to d) have been described. As in the case of the operation of aforementioned terminal  200 , base station  100  performs PDCCH and PHICH resource assignment and retransmission control for terminal  200 . 
     &lt;Case  2 &gt; 
     The method of determining the number of PHICH resources in base station  100 , the method of determining the total number of PHICH groups in terminal  200  (TDD eIMTA terminal) and the PDCCH detection method will be described with reference to  FIG. 11  to  FIG. 17 . 
     In case  2 , since the UL-DL configuration of the non-TDD eIMTA terminal is an uplink communication subframe, the TDD eIMTA terminal need not follow the factor used by the non-TDD eIMTA terminal and defined in the SIB1-indicated UL-DL configuration, that is, the total number of PHICH groups. Focusing on this aspect, methods  1  to  4  of setting the total number of PHICH groups (factor of the number of PHICH groups) for the TDD eIMTA terminal will be described hereinafter. 
     (Method  1 ) 
     In method  1 , the total number of PHICH groups is determined based on UL-DL configuration for TDD eIMTA. That is, at the timings corresponding to case  2 , base station  100  and terminal  200  use the factor of the number of PHICH groups defined for the timing of UL-DL configuration set in terminal  200 . In other words, at the timings corresponding to case  2 , base station  100  and terminal  200  use the total number of PHICH groups associated with the timing of UL-DL configuration set in terminal  200 . 
     Method  1  will be described using  FIG. 11 . Note that UL-DL configuration of each terminal in  FIG. 11A  corresponds to the UL-DL configuration of each terminal in  FIG. 10A . In  FIG. 11A , the timings corresponding to case  2  (when timing at the TDD eIMTA terminal is a downlink communication subframe or special subframe, and timing at the non-TDD eIMTA terminal is an uplink communication subframe) are subframes # 3 ,  4 ,  8  and  9 . 
     At the timings corresponding to case  2 , when base station  100  performs downlink communication, base station  100  secures PHICH resources (number of PHICH resources and PHICH resource positions) based on the factor of the number of PHICH groups defined in the current UL-DL configuration of terminal  200  (Config# 2  in  FIG. 11A ) for terminal  200  (TDD eIMTA terminal). That is, as shown in  FIG. 11B , in subframes # 3 ,  4 ,  8  and  9 , base station  100  secures PHICH resources identified based on a factor (m i ) of PHICH groups of 1, 0, 1 and 0, respectively for terminal  200 . Furthermore, base station  100  sets PDCCH resources based on the secured PHICH resources. 
     Meanwhile, at the timings corresponding to case  2 , terminal  200  determines the factor of the number of PHICH groups based on the factor of the number of PHICH groups defined in UL-DL configuration for TDD eIMTA (Config# 2  in  FIG. 11A ) currently set in terminal  200 . That is, as shown in  FIG. 11B , in subframes # 3 ,  4 ,  8  and  9 , terminal  200  detects PHICH and PDCCH assuming that PHICH resources (number of PHICH resources and corresponding PHICH resource positions) identified based on the factor (m i ) of PHICH groups of 1, 0, 1 and 0 have been secured. 
     [Effects] 
     In this way, base station  100  can apply non-adaptive retransmission using an optimum total number of PHICH groups for terminal  200  using UL-DL configuration for TDD eIMTA, that is, by securing just enough PHICH resources. 
     [PDCCH Detection Method and PHICH Detection Method] 
     Next, operations relating to PDCCH detection and PHICH detection by terminal  200  will be described in detail. 
     (a) When factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 0. 
     In the subframes, terminal  200  does not secure any PHICH resources for PDCCH detection. In addition, terminal  200  need not perform PHICH detection because there is no PHICH intended for terminal  200 . 
     (b) When factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 1 or 2 
     In the subframes, for PDCCH detection, terminal  200  secures PHICH resources (number of PHICH resources and corresponding PHICH resource position) identified based on the factor of the number of PHICH groups (1 or 2) defined in UL-DL configuration for TDD eIMTA for PHICH. Furthermore, terminal  200  performs PHICH detection. Therefore, both adaptive retransmission and non-adaptive retransmission are available as the uplink data retransmission method for terminal  200 . 
     (Method  2 ) 
     In method  2 , the total number of PHICH groups is determined based on a maximum value for each subframe in all UL-DL configurations (e.g., Config# 0  to Config# 6 ). That is, at the timings corresponding to case  2 , base station  100  and terminal  200  use a maximum value in factors of the numbers of PHICH groups defined for the timings of a plurality of UL-DL configurations. In other words, at timings corresponding to case  2 , base station  100  and terminal  200  use a maximum value among the total numbers of PHICH groups associated with the plurality of UL-DL configurations, respectively. 
     Before describing method  2 , premises and problems will be described using  FIG. 12 . 
     Method  2  assumes a case where there are two TDD eIMTA terminals in addition to the non-TDD eIMTA terminal (legacy terminal) using SIB1-indicated UL-DL configuration. Method  2  also assumes that mutually different UL-DL configurations which are also different from SIB1-indicated UL-DL configuration are set in two TDD eIMTA terminals. 
     For example, in  FIG. 12A , TDD eIMTA terminal  1  in which Config# 2  is set and TDD eIMTA terminal  2  in which Config# 1  is set exist in addition to the legacy terminal in which Config# 0  is set. In  FIG. 12 , when timings of the TDD eIMTA terminal are downlink communication subframes or special subframes and timings of the non-TDD eIMTA terminal (legacy terminal) are uplink communication subframes (subframes # 3 ,  4 ,  8  and  9 ), the factor of the number of PHICH groups is set based on method  1  for each TDD eIMTA terminal. That is, in TDD eIMTA terminal  1 , the factors of the numbers of PHICH groups in subframes # 3 ,  4 ,  8  and  9  are 1, 0, 1 and 0 as shown in  FIG. 12B . In TDD eIMTA terminal  2 , the factors of the numbers of PHICH groups in subframes # 4  and  9  are 1 and 1 as shown in  FIG. 12B . 
     Here, in TDD eIMTA terminal  1  and TDD eIMTA terminal  2 , attention is focused on the factors of the number of PHICH groups in subframes # 4  and  9  in which timings of both terminals are downlink communication subframes or special subframes. It is seen that the factor of the number of PHICH groups in each subframe differs between TDD eIMTA terminal  1  and TDD eIMTA terminal  2 . Thus, as described in  FIGS. 5A and 5B , since base station  100  cannot simultaneously perform scheduling for both TDD eIMTA terminal  1  and TDD eIMTA terminal  2  in subframes # 4  and  9 , there are constraints on scheduling regarding DCI. 
     As shown in  FIG. 12A , in addition to the non-TDD eIMTA terminal (legacy terminal) using SIB1-indicated UL-DL configuration, there are two TDD eIMTA terminals and mutually different UL-DL configurations which are also different from SIB1-indicated UL-DL configuration are set for the two TDD eIMTA terminals, in which case following two cases I and II are considered. 
     Case I: System assumed to be operated using three or more different UL-DL configurations within one cell. 
     Case II: When UL-DL configuration settings are simultaneously changed for a plurality of TDD eIMTA terminals, the terminal cannot receive an instruction for changing the UL-DL configuration setting due to a reception failure in some of the plurality of TDD eIMTA terminals. 
     As described above, the TDD eIMTA terminal can receive SIB1-indicated UL-DL configuration in addition to UL-DL configuration for TDD eIMTA intended for terminal  200 . Meanwhile, it is assumed that each TDD eIMTA terminal cannot receive UL-DL configuration for TDD eIMTA intended for other TDD eIMTA terminals. 
     Thus, in method  2 , as shown in  FIG. 13A , when the timings of the non-TDD eIMTA terminal (legacy terminal) are uplink communication subframes and timing of at least one of all UL-DL configurations other than SIB1-notified UL-DL configuration is a downlink communication subframe or special subframe (subframes # 3 ,  4 ,  7 ,  8  and  9  in  FIG. 13A ), when base station  100  performs downlink communication (subframes # 3 ,  4 ,  8  and  9  in  FIG. 13A ), base station  100  secures, for these TDD eIMTA terminals, PHICH resources (number of PHICH resources and PHICH resource positions) assuming a maximum value of factors of the number of PHICH groups defined in all UL-DL configurations (Config# 0  to  6 ) in the subframes as the factor of the number of PHICH groups in the subframes. Meanwhile, when timings of SIB1-indicated UL-DL configuration are uplink communication subframes and timings of the UL-DL configuration set in the terminal are downlink communication subframes or special subframes, terminal  200  (TDD eIMTA terminal) identifies the number of PHICH resources and a corresponding PHICH resource position assuming a maximum value of the factors of the number of PHICH groups defined in all UL-DL configurations (Config# 0  to  6 ) in the subframes as the factor of the number of PHICH groups in the subframes and detects PDCCH. 
     For example, according to  FIG. 13B , since the factor of the number of PHICH groups in subframe # 3  is  1  in Config# 2  and  0  in Config# 5 , the maximum value is 1. Similarly, since the factor of the number of PHICH groups in subframe # 8  is always 1 in Config# 2  to  5 , the maximum value is 1. Since the factor of the number of PHICH groups in subframe # 7  is always 0 in Config# 3  to  5 , the maximum value is 0. The same applies to other subframes # 4  and  9 . 
     Note that method  2  is applicable to above two cases I and II. 
     [Effects] 
     This allows base station  100  to eliminate the difference in recognition of the total number of PHICH groups among a plurality of TDD eIMTAs and determine PHICH resources, thereby making it possible to perform PDCCH scheduling for the plurality of TDD eIMTA terminals, and at the same time allowing each TDD eIMTA terminal to detect PDCCH in the same subframe. It is also possible to secure just enough PHICH resources for all TDD eIMTA terminals. 
     In the above description, the “maximum value of the factor of the number of PHICH groups among all UL-DL configurations (Config# 0  to  6 )” has been assumed, but, for example, when base station  100  indicates, to the plurality of TDD eIMTA terminals, a set of UL-DL configuration candidates that can be changed by TDD eIMTA (e.g., Config# 0  to  2  in  FIG. 13A ) beforehand or when a set of UL-DL configuration candidates that can be changed by TDD eIMTA is predefined for SIB1-notified UL-DL configuration (e.g., only Config# 0  to  2  are available to TDD eIMTA for SIB1-indicated Config# 0  in  FIG. 13A ), the “maximum value of the factor of the number of PHICH groups among all UL-DL configurations (Config# 0  to  2 ) that can be changed” may be used for the TDD eIMTA terminal. By determining the maximum value of the factor of the number of PHICH groups exclusively for some UL-DL configurations, base station  100  can secure PHICH resources using the total number of PHICH groups which is more suitable for each TDD eIMTA terminal and can thereby improve the resource utilization efficiency. 
     [PDCCH Detection Method and PHICH Detection Method] 
     Next, operations relating to PDCCH detection and PHICH detection by terminal  200  will be described. 
     (a) When the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 0 and the maximum value of the factor of the number of PHICH groups among all UL-DL configurations is 1.
         In the subframes, terminal  200  secures, for PDCCH, a PHICH resource (number of PHICH resources and corresponding PHICH resource position) identified based on factor  1  of the number of PHICH groups (maximum value in the subframes) for PDCCH detection. However, since there is no PHICH intended for terminal  200 , terminal  200  need not perform PHICH detection.       

     (b) When the factor of the number of PHICH groups corresponding to UL-DL configuration for TDD eIMTA is 1 and the maximum value of the factor of the number of PHICH groups among all UL-DL configurations is 1.
         In the subframes, terminal  200  secures, for PDCCH, a PHICH resource (number of PHICH resources and corresponding PHICH resource position) identified based on factor  1  of the number of PHICH groups (maximum value in the subframes) for PDCCH detection. Furthermore, terminal  200  performs PHICH detection. Therefore, both adaptive retransmission and non-adaptive retransmission are available as the uplink data retransmission method for terminal  200 .       

     (Method  3 ) 
     The total number of PHICH groups is determined based on the minimum value for each subframe in all UL-DL configurations. That is, at timings corresponding to case  2 , base station  100  and terminal  200  use a minimum value among the factors of the numbers of PHICH groups defined for the timings of a plurality of UL-DL configurations. In other words, at timings corresponding to case  2 , base station  100  and terminal  200  use a minimum value among the total numbers of PHICH groups associated with a plurality of UL-DL configurations respectively. 
     Note that the premise of method  3  is the same as that of method  2  (e.g.,  FIGS. 12A and 12B ). 
     In method  3 , as shown in  FIG. 14A  and  FIG. 14B , when timings of the non-TDD eIMTA terminal (legacy terminal) are uplink communication subframes and timings of at least one of TDD eIMTA terminals in which mutually different UL-DL configurations for TDD eIMTA are set in all UL-DL configurations other than SIB1-indicated UL-DL configuration are downlink communication subframes or special subframes (subframes # 3 ,  4 ,  7 ,  8  and  9  in  FIG. 14A ), and when base station  100  performs downlink communication (subframes # 3 ,  4 ,  8  and  9  in  FIG. 14A ), base station  100  secures, for these TDD eIMTA terminals, PHICH resources (number of PHICH resources and PHICH resource positions) assuming the minimum value among the factors of the numbers of PHICH groups defined in all UL-DL configurations (Config# 0  to  6 ) in the subframes as the factor of the number of PHICH groups in the subframes. When timings of SIB1-indicated UL-DL configuration are uplink communication subframes and timings of UL-DL configuration set in the terminal are downlink communication subframes or special subframes, terminal  200  (TDD eIMTA terminal) identifies the number of PHICH resources and corresponding PHICH resource positions assuming the minimum value among the factors of the numbers of PHICH groups defined in all UL-DL configurations (Config# 0  to  6 ) in the subframes as the factor of the number of PHICH groups in the subframes and detects PDCCH. 
     For example, according to  FIG. 14B , the factor of the number of PHICH groups in subframe # 3  is  1  in Config# 2  and  0  in Config# 5 , and therefore the minimum value is 0. Similarly, the factor of the number of PHICH groups in subframe # 8  is always 1 in Config# 2  to  5 , and therefore the minimum value is 1. Moreover, the factor of the number of PHICH groups in subframe # 7  is always 0 in Config# 3  to  5 , and therefore the minimum value is 0. The same applies to other subframes # 4  and  9 . 
     Note that method  3  is applicable to above-described two cases I and II. 
     [Effects] 
     In this way, as in the case of method  2 , base station  100  can determine PHICH resources by eliminating differences in recognition of the total number of PHICH groups among a plurality of TDD eIMTAs. Thus, base station  100  can perform PDCCH scheduling for the plurality of TDD eIMTA terminals in the same subframe, and at the same time each TDD eIMTA terminal can detect PDCCH in the same subframe. It is also possible to prevent PHICH resources from being excessively secured for the TDD eIMTA terminal. 
     In the above description, the “minimum value of the factor of the number of PHICH groups among all UL-DL configurations (Config# 0  to  6 )” has been assumed, but, for example, when base station  100  notifies the plurality of TDD eIMTA terminals of a set of UL-DL configuration candidates that can be changed by TDD eIMTA (e.g., Config# 0  to  2  in  FIG. 14A ) beforehand or when a set of UL-DL configuration candidates that can be changed by TDD eIMTA is predefined for SIB1-notified UL-DL configuration (e.g., only Config# 0  to  2  are available to TDD eIMTA for SIB1-notified Config# 0  in  FIG. 14A ), the “minimum value of the factor of the number of PHICH groups among all UL-DL configurations (Config# 0  to  2 ) that can be changed” may be used for the TDD eIMTA terminal. In this case, in  FIG. 14B , the factors of numbers of PHICH groups in subframes # 3 ,  4 ,  8  and  9  are  1 ,  0 ,  1  and  0 , respectively. Determining the minimum value of the factor of the number of PHICH groups exclusively for some UL-DL configurations allows base station  100  to secure PHICH resources using the total number of PHICH groups which is more suitable for each TDD eIMTA terminal, and can thereby improve the resource utilization efficiency. 
     (Method  4 ) 
     In method  4 , the total number of PHICH groups is always 0. That is, in base station  100  and terminal  200 , the demultiplexing section sets the factor of the number of PHICH groups to 0 at timings corresponding to case  2 . In other words, base station  100  and terminal  200  set the total number of PHICH groups to 0 at timings corresponding to case  2 . 
     Before describing method  4 , premises and problems will be described using  FIG. 15  and  FIG. 16 . 
     As shown in  FIG. 15 , method  4  assumes that a non-TDD eIMTA terminal (legacy terminal) using SIB1-indicated UL-DL configuration is located in cell  2  adjacent to cell  1  to which a TDD eIMTA terminal is connected. 
     In  FIG. 15 , the TDD eIMTA terminal and the non-TDD eIMTA terminal (legacy terminal) are located in proximity to each other, but the terminals are connected to different cells. Here, suppose that the legacy terminal connected to cell  2  is performing uplink communication based on SIB1-indicated UL-DL configuration. At the same time, suppose that the TDD eIMTA terminal connected to cell  1  is performing downlink communication based on UL-DL configuration for TDD eIMTA. 
     At this time, since the TDD eIMTA terminal and the legacy terminal are located in proximity to each other, the legacy terminal provides large inter-terminal interference (inter-UE interference) to the TDD eIMTA terminal. 
       FIG. 16  illustrates, in a time sequence of one frame, the case shown in  FIG. 15  where inter-UE interference has occurred. Note that in  FIG. 16 , in addition to the TDD eIMTA terminal connected to cell  1  and legacy terminal  1  connected to cell  2 , there is legacy terminal  2  connected to cell  1 . In  FIG. 16 , it is assumed that the SIB1-indicated UL-DL configuration is identical (Config# 0 ) between cell  1  and cell  2 . 
     Attention is focused on timings of legacy terminal  2  connected to cell  1  and legacy terminal  1  connected to cell  2  which are uplink communication subframes and timings of the TDD eIMTA terminal which are downlink communication subframes or special subframes (subframes # 3 ,  4 ,  8  and  9  in  FIG. 16 ). In this case, in cell  1 , when the subframes are used for downlink communication, operation is performed such that legacy terminal  2  connected to cell  1  does not perform uplink communication. Meanwhile, in cell  1 , even when the subframes are used for downlink communication, communication in cell  2  may be operated independently of cell  1 , and therefore legacy terminal  1  connected to cell  2  may perform uplink communication. At this time, the TDD eIMTA terminal connected to cell  1  receives large inter-UE interference from legacy terminal  1  connected to cell  2 . 
     At this time, the TDD eIMTA terminal is more likely to be unable to correctly receive PHICH and PDCCH in the subframes due to inter-UE interference. Meanwhile, as described above, since a CRC is added to UL grant, a received signal of UL grant has higher reliability than PHICH. For this reason, UL grant is more resistant to interference than PHICH. 
     Thus, in method  4 , when timings of the non-TDD eIMTA terminal (legacy terminal) are uplink communication subframes and timings of the TDD eIMTA terminal (terminal  200 ) are downlink communication subframes or special subframes, base station  100  does not assign PHICH to terminal  200  and terminal  200  does not detect PHICH in the subframes. That is, since PHICH detection is not performed in the subframes, as shown in  FIG. 17 , base station  100  and terminal  200  set the factor of the number of PHICH groups for terminal  200  to 0 (total number of PHICH groups is 0). In this case, only adaptive retransmission is available as the uplink data retransmission method for terminal  200 . 
     [Effects] 
     In this way, since only retransmission (adaptive retransmission) based on interference-resistant PDCCH is carried out for terminal  200  (TDD eIMTA terminal), it is possible to perform highly reliable uplink communication retransmission control even when aforementioned inter-UE interference occurs. Moreover, since it is not necessary to secure unnecessary PHICH resources for terminal  200 , the resource utilization efficiency can be improved. 
     The embodiment of the present invention has been described so far. 
     [Other Embodiments] 
     (1) In the above embodiment, as the method of indicating a UL-DL configuration for TDD eIMTA set in a TDD eIMTA terminal (terminal  200 ), one of the following indication methods may be adopted: method of indicating an RRC (higher layer) signaling base, method of indicating a MAC (Media Access Control layer) signaling base and method of indicating a L1 (Physical Layer) signaling base. When UL-DL configuration for TDD eIMTA set in a TDD eIMTA terminal is different from SIB1-notified UL-DL configuration used in a non-TDD eIMTA terminal (legacy terminal), the method of indicating an SI (System Information) signaling base may be adopted as the method of indicating UL-DL configuration for TDD eIMTA set in the TDD eIMTA terminal. 
     (2) “UL-DL configuration for TDD eIMTA set in a TDD eIMTA terminal” has been described in the above embodiment. However, this is based on the premise that “UL-DL configuration for TDD eIMTA set in the TDD eIMTA terminal” and “UL-DL configuration referencing timing relating to uplink control that defines the factor of the number of PHICH groups (that is, PHICH reception timing corresponding to uplink data (PUSCH)” are the same. 
     However, in an LTE-A system, according to TDD inter-band CA (Carrier Aggregation), when different UL-DL configurations are indicated among a plurality of component carriers to which carrier aggregation is applied, UL-DL configuration that indicates a subframe configuration within one frame may be different from UL-DL configuration referencing timing relating to uplink control (hereinafter, may also be referred to as “UL-DL configuration for timing reference”). 
     When TDD inter-band CA is operated in combination with TDD eIMTA, “UL-DL configuration for TDD eIMTA set in the TDD eIMTA terminal” in the above embodiment is different from “UL-DL configuration for timing reference” referenced by the TDD eIMTA terminal. Therefore, in the above embodiment, the “UL-DL configuration for TDD eIMTA set in the TDD eIMTA terminal” may be regarded as “UL-DL configuration at timing relating to uplink control referenced by the TDD eIMTA terminal.” 
     (3) Each of the embodiments has been described with antennas, but the present invention can be applied to antenna ports in the same manner. 
     The term “antenna port” refers to a logical antenna including one or more physical antennas. In other words, the term “antenna port” does not necessarily refer to a single physical antenna, and may sometimes refer to an array antenna formed of a plurality of antennas and/or the like. 
     For example, LTE does not specify the number of physical antennas forming an antenna port, but specifies an antenna port as a minimum unit allowing each base station to transmit a different reference signal. 
     In addition, an antenna port may be specified as a minimum unit for multiplication of precoding vector weighting. 
     (4) In the foregoing embodiments, the present invention is configured with hardware by way of example, but the present invention can be also implemented by software in conjunction with hardware. 
     In addition, the functional blocks used in the descriptions of the embodiments are typically implemented as LSI devices, which are integrated circuits. These functional blocks may be formed as individual chips, or part or all of the functional blocks may be integrated into a single chip. The term “LSI” is used herein, but the terms “IC,” “system LSI,” “super LSI” or “ultra LSI” may be used as well depending on the level of integration. 
     In addition, the circuit integration is not limited to LSI and may be achieved by dedicated circuitry or a general-purpose processor other than an LSI. After fabrication of LSI, a field programmable gate array (FPGA), which is programmable, or a reconfigurable processor, which allows reconfiguration of connections and settings of circuit cells in LSI may be used. 
     Should a circuit integration technology replacing LSI appear as a result of advancements in semiconductor technology or other technologies derived from the technology, the functional blocks could be integrated using such a technology. Another possibility is the application of biotechnology and/or the like. 
     As has been descried above, a terminal apparatus according to the present disclosure is a terminal apparatus capable of changing setting of a configuration pattern of subframes which make up a single frame to one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication, the terminal apparatus including: a receiving section that receives a signal transmitted from a base station apparatus; and a demultiplexing section that demultiplexes the signal into a response signal assigned to a first resource identified based on a number of resources associated with the first subframe in which the signal has been received, and downlink control information assigned to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, the demultiplexing section uses a number of resources associated with the first subframe of the second configuration pattern. 
     In the terminal apparatus according to the disclosure, when the timing of the first configuration pattern is the first subframe and the second configuration pattern is the second subframe, the demultiplexing section uses the number of resources associated with the first subframe of the first configuration pattern. 
     In the terminal apparatus according to the disclosure, when the timing of the first configuration pattern is the first subframe and the second configuration pattern is the second subframe, the demultiplexing section uses a maximum value of the numbers of resources associated with the first subframes of the plurality of configuration patterns, respectively. 
     In the terminal apparatus according to the disclosure, when the timing of the first configuration pattern is the first subframe and the second configuration pattern is the second subframe, the demultiplexing section uses a minimum value of the numbers of resources associated with the first subframes of the plurality of configuration patterns, respectively. 
     In the terminal apparatus according to the disclosure, when the timing of the first configuration pattern is the first subframe and the second configuration pattern is the second subframe, the demultiplexing section sets the number of resources to 0. 
     A base station apparatus according to the present disclosure includes: a generation section that generates a response signal for uplink data transmitted from a terminal apparatus in which one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication is set, each configuration pattern including subframes which make up one frame; an assignment section that assigns a response signal to a first resource identified based on a number of resources associated with the first subframe in which the response signal is transmitted, and downlink control information to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern; and a transmitting section that transmits a signal including the response signal and the downlink control information, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, the assignment section uses a number of resources associated with the first subframe of the second configuration pattern for the terminal apparatus. 
     A reception method according to the present disclosure is a method for a terminal apparatus capable of changing setting of a configuration pattern of subframes which make up a single frame to one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication, the method including: receiving a signal transmitted from a base station apparatus; and demultiplexing the signal into a response signal assigned to a first resource identified based on a number of resources associated with the first subframe in which the signal has been received, and downlink control information assigned to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern, in which, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, a number of resources associated with the first subframe of the second configuration pattern is used. 
     A transmission method according to the present disclosure includes: generating a response signal for uplink data transmitted from a terminal apparatus in which one of a plurality of configuration patterns including a first subframe used for downlink communication and a second subframe used for uplink communication is set, each configuration pattern including subframes which make up one frame; assigning a response signal to a first resource identified based on a number of resources associated with the first subframe in which the response signal is transmitted, and downlink control information to a second resource, while a number of resources to which a response signal for uplink data is assigned is associated with the first subframe included in the configuration pattern; transmitting a signal including the response signal and the downlink control information; and using, when both timing of a first configuration pattern set in the terminal apparatus and timing of a second configuration pattern set in another terminal apparatus whose setting of a configuration pattern cannot be changed are the first subframes, a number of resources associated with the first subframe of the second configuration pattern for the terminal apparatus. 
     The disclosure of Japanese Patent Application No. 2012-236768, filed on Oct. 26, 2012, including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful in mobile communication systems, for example. 
     REFERENCE SIGNS LIST 
       100  Base station 
       200  Terminal 
       101  Error determining section 
       102  Control information generation section 
       103  PHICH generation section 
       104 ,  208  Error correction coding section 
       105 ,  209  Modulation section 
       106 ,  210  Signal assignment section 
       107 ,  211  Radio transmitting section 
       108 ,  201  Antenna 
       109 ,  202  Radio receiving section 
       110 ,  204  Demodulation section 
       111 ,  205  Error correction decoding section 
       203  Signal demultiplexing section 
       206  PHICH receiving section 
       207  Control information receiving section