Abstract:
A method, base station, and terminal employing time division duplex and carrier aggregation are disclosed. The method by the base station includes transmitting, to a terminal, scheduling information on a control channel of a first cell, and transmitting, to the terminal, data on a shared channel of a second cell based on the scheduling information. The scheduling information is transmitted in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is transmitted in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell.

Description:
[0001]    This is a continuation application of a prior application Ser. No. 13/517,388, filed on Jun. 20, 2012, which claimed the benefit under 35 U.S.C. §371 of an International application filed on Dec. 22, 2010, and assigned application number PCT/KR2010/009212, which claimed the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on Dec. 24, 2009 in the Korean Intellectual Property Office and assigned Serial number 10-2009-0130400, the entire disclosures of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a cellular radio communication system and, in particular, to a method and apparatus for defining transmission/reception timing of physical channel in cross-carrier scheduling of TDD system supporting carrier aggregation. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, there are many researches being conducted on the Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier-Frequency Division multiple Access (SC-FDMA) in the cellular communication field. Such a multiple access technology is used to allocate and manage the time-frequency resources for data and/or control information transmission to and from multiple users without overlapping from each other, i.e. orthogonally, so as to makes it possible to discriminate among per-user data and control informations. 
         [0006]    One of the significant features of the cellular communication system is to support scalable bandwidth for providing high speed wireless data service. For example, the Long Term Evolution (LTE) system is capable of supporting various bandwidths, e.g. 20/15/5/3/1.4 Mhz. The mobile carriers can provide their services with one of the available bandwidths. A User Equipment (UE) can operate with various capabilities of minimum 1.4 MHz bandwidth up to 20 MHz bandwidth. Meanwhile, the LTE-Advanced (hereinafter, called LTE-A) system can support high data rate transmission over a wide bandwidth up to 100 MHz for a single UE with carrier aggregation. 
         [0007]    In order to support the high data rate transmission, the LTE-A system requires the bandwidth wider than that of the LTE system while preserving backward compatibility to the legacy systems for supporting the LTE UEs. For the backward compatibility, the system bandwidth of the LTE-A system is divided into a plurality of subbands or component carriers (CC) that can be used for transmission/reception of LTE UEs and aggregated for the high data rate transmission of the LTE-A system with the transmission/reception process of the legacy LTE system per component carrier. 
         [0008]    The scheduling information for the data transmitted on the component carriers is transmitted to the UE in Downlink Control Information (DCI). The DCI is generated in different DCI format according to whether scheduling information is of uplink or downlink, whether the DCI is compact DCI, whether spatial multiplexing with multiple antennas is applied, and whether the DCI is the power control DCI. For example, the DCI format 1 for the control information about downlink data to which Multiple Input Multiple Output (MIMO) is not applied is composed of the following control informations.
       Resource allocation type 0/1 flag: It notifies the UE of whether the resource allocation type is type 0 or type 1. Here, type 0 indicates resource allocation in unit of resource block group (RBG) in bitmap method. In LTE and LTE-A systems, the basic scheduling unit is resource block (RB) representing time and frequency resource, and RBG is composed of a plurality of RBs and basic scheduling unit of in type 0. Type 1 indicates allocation of specific RB in RBG.   Resource block assignment: It notifies the UE of RB allocated for data transmission. At this time, the resource expressed according to the system bandwidth and resource allocation scheme is determined.   Modulation and coding scheme: It notifies the UE of modulation scheme and coding rate applied for data transmission.   HARQ process number: it notifies the UE of HARQ process number.   New data indicator: It notifies the UE of whether the transmission is HARQ initial transmission or retransmission.   Redundancy version: It notifies the UE of redundancy version of HARQ.   TPC command for PUCCH: It notifies the UE of power control command for Physical Uplink Control Channel (PUCCH) as uplink control channel.       
 
         [0016]    The DCI is channel-coded and modulated and then transmitted through Physical Downlink Control Channel (PDCCH). 
         [0017]      FIG. 1  is a diagram illustrating an exemplary case where an eNB schedules downlink data for a UE with two aggregated carriers (CC# 1 , CC# 2 ) in the LTE system. In  FIG. 1 , the DCI  1   101  to be transmitted on the Component Carrier # 1  (CC# 1 )  109  is generated with a format defined in the legacy LTE and channel coded and interleaved so as to be carried by PDCCH  103 . The PDCCH  103  carries the scheduling information about the Physical Downlink Shared Channel  213  as the data channel allocated to the UE on the CC# 1   109 . The DCI  105  transmitted on the component carrier # 2  (CC# 2 )  111  is formatted as defined in the legacy LTE standard, channel-coded, and then interleaved to generate PDCCH  107 . The PDCCH  107  carries the scheduling information about the PDSCH  115  as the data channel allocated to the UE on the CC# 2   111 . 
         [0018]    In the LTE-A system supporting carrier aggregation, the data and/or DCI for supporting the data transmission can be transmitted per component carrier as shown in  FIG. 1 . In case of DCI, however, it can be transmitted on another component carrier different from the component carrier carrying the data, and this is referred to as cross-carrier scheduling. That is, the scheduling information about the data transmitted on the CC# 2  is transmitted on the CC# 1 . The cross-carrier scheduling is described hereinafter in detail with reference to  FIG. 2 . 
         [0019]      FIG. 2  is a diagram illustrating a procedure for scheduling an LTE-A UE using aggregated component carriers # 1  and # 2  (CC# 1  and CC# 2 )  209  and  219 .  FIG. 2  is directed to an exemplary case where the CC# 2   219  experiences significant interference as compared to CC# 1   209  such that it is difficult to satisfy a predetermined DCI reception performance requirement for data transmission on the CC# 2   219 . In this case, the eNB may transmit the DCI on the CC# 1   219 . Since any error occurring in data transmission can be corrected later through HARQ, there is no problem in transmitting data on the CC# 2  although significant interference exists thereon. In order to make it possible to operate as above, it is necessary for the eNB to transmit a carrier indicator (CI) indicating the component carrier targeted by the DCI along with the DCI indicating the resource allocation information and transmission format of the scheduled data. For example, CI=‘00’ indicates CC# 1   209  and, CI=‘01’ indicates CC# 2   219 . 
         [0020]    Accordingly, the eNB combines the DCI  201  indicating resource allocation information and transmission format of the scheduled data  207  and the carrier indicator  202  to generate an extended DCI, performs channel coding, modulation, and interleaving on the extended DCI to generate PDCCH, and maps the PDCCH to the PDCCH region  205  of CC# 1   209 . The eNB also combines the DCI  211  indicating the resource allocation information and transmission format of the data  217  scheduled on CC# 2  and the carrier indicator  212  to generate an extended DCI, performs channel coding, modulation and interleaving on the extended DCI to generate PDCCH, and maps the PDCCH to the PDCCH region  205  of CC# 1   209 . 
         [0021]    The TDD system uses a common frequency for uplink and downlink which are discriminated in time domain. In the LTE TDD system, the uplink and downlink signals are discriminated by subframe. A radio frame can be divided into equal number of uplink and downlink subframes according to the uplink and downlink traffic load, but the number of uplink subframes may greater than that of the downlink subframes and vice versa. In the LTE system, the subframe has a length of 1 ms, 10 subframes form a radio frame. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Uplink- 
                 Subframe number 
               
             
          
           
               
                 downlink 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 0 
                 D 
                 s 
                 u 
                 u 
                 u 
                 D 
                 s 
                 u 
                 u 
                 u 
               
               
                 1 
                 D 
                 s 
                 u 
                 u 
                 D 
                 D 
                 s 
                 u 
                 u 
                 D 
               
               
                 2 
                 D 
                 s 
                 u 
                 D 
                 D 
                 D 
                 s 
                 u 
                 D 
                 D 
               
               
                 3 
                 D 
                 s 
                 u 
                 u 
                 u 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 4 
                 D 
                 s 
                 u 
                 u 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 5 
                 D 
                 s 
                 u 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
                 D 
               
               
                 6 
                 D 
                 s 
                 u 
                 u 
                 u 
                 D 
                 s 
                 u 
                 u 
                 D 
               
               
                   
               
             
          
         
       
     
         [0022]    Table 1 shows TDD configurations (TDD uplink-downlink configurations) defined in LTE standard. In table 1, subframe numbers 0 to 9 indicates the indices of subframes constituting one radio frame. Here, ‘D’ denotes a subframe reserved for downlink transmission, ‘U’ denotes a subframe reserved for uplink transmission, and ‘S’ denotes the special subframe. The DwPTS can carry the downlink control information as the normal subframe does. If the DwPTS is long enough according to the configuration state of the special subframe, it is possible to carry the downlink data too. The GP is the interval required for downlink-to-uplink switch and its length is determined according to the network configuration. The UpPTS can be used for transmitting UE&#39;s Sounding Reference Signal (SRS) for uplink channel state estimation and UE&#39;s Random Access Channel (RACH). 
         [0023]    For example, in case of TDD uplink-downlink configuration# 6 , the eNB can transmit downlink data and/or control information at subframes # 0 , # 5 , and # 9  and uplink data and/control information at subframes # 2 , # 3 , # 4 , # 7 , and # 8 . Here, # indicates number or index. The subframes # 1  and # 6  as special subframes can be used for transmitting downlink control information and/or downlink data selectively and SRS or RACH in uplink. 
         [0024]    Since the downlink or uplink transmission is allowed for specific time duration in the TDD system, it is necessary to define the timing relationship among the uplink and downlink physical channels such as control channel for data scheduling, scheduled data channel, and HARQ ACK/NACK channel (HARQ acknowledgement) corresponding to the data channel. 
         [0025]    In the TDD system, the timing relationship between Physical Downlink Shared Channel (PDSCH) and Physical Uplink Control channel (PUCCH) carrying uplink HARQ ACK/NACK corresponding to the PDSCH or Physical Uplink Shared Channel (PUSCH) is as follows. 
         [0026]    The UE receives the PDSCH transmitted by the eNB at (n−k)th subframe and transmits uplink HARQ ACK/NACK corresponding to the received PDSCH at nth subframe. Here, k denotes an element of a set K, and K is defined as shown in table 2. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 UL- 
                 Subframen 
               
             
          
           
               
                 DLConfigurati 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 0 
                 — 
                 — 
                 6 
                 — 
                 4 
                 — 
                 — 
                 6 
                 — 
                 4 
               
               
                 1 
                 — 
                 — 
                 7, 6 
                 4 
                 — 
                 — 
                 — 
                 7, 6 
                 4 
                 — 
               
               
                 2 
                 — 
                 — 
                 8, 7, 4, 6 
                 — 
                 — 
                 — 
                 — 
                 8, 7, 4, 6 
                 — 
                 — 
               
               
                 3 
                 — 
                 — 
                 7, 6, 11 
                 6, 5 
                 5, 4 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 4 
                 — 
                 — 
                 12, 8, 7, 11 
                 6, 5, 4, 7 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 5 
                 — 
                 — 
                 13, 12, 9, 8, 7,5, 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 6 
                 — 
                 — 
                 7 
                 7 
                 5 
                 — 
                 — 
                 7 
                 7 
                 — 
               
               
                   
               
             
          
         
       
     
         [0027]      FIG. 3  is a diagram illustrating a timing relationship between PDSCH and uplink HARQ ACK/NACK to show which subframe carries uplink HARQ ACK/NACK corresponding to PDSCH that is transmitted in a downlink subframe or a special subframe in TDD uplink-downlink configuration  6  as defined in table 2. For example, the UE transmits, at subframe # 7  of ith radio frame, the uplink HARQ ACK/NACK corresponding to the PDSCH  301  transmitted by the eNB at subframe # 1  of ith subframe. At this time, the downlink control information (DCI) including the scheduling information on the PDSCH  301  is transmitted through PDCCH of the subframe which also carries PDSCH. For another example, the UE transmits, at the subframe # 4   307  of (i+1)th radio frame, the uplink HARQ ACK/NACK corresponding to PDSCH  305  transmitted by the eNB at subframe # 9  of the ith radio frame. Likewise, the downlink control information (DCI) including the scheduling information on the PDSCH  305  is transmitted through PDCCH of the subframe which also carries PDSCH. 
         [0028]    The LTE adopts an asynchronous HARQ in downlink in which the data retransmission timing is not fixed. That is, when an HARQ ACK fed back by the UE in response to the HARQ initial transmission data transmitted by the eNB is received, the eNB determines the next HARQ retransmission timing freely according to the scheduling operation. The UE buffers the data failed in decoding for HARQ operation and combines the buffered data with the next HARQ retransmission data. In order to keep the reception buffer space to a predetermined level, a maximum number of HARQ processes are defined per TDD uplink-downlink configuration as shown in table 3. One HARQ process is mapped to one subframe in time domain. 
         [0000]    
       
         
               
               
             
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 TDD UL/DL configuration 
                 Maximum number of HARQ processes 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 4 
               
               
                 1 
                 7 
               
               
                 2 
                 10 
               
               
                 3 
                 9 
               
               
                 4 
                 12 
               
               
                 5 
                 15 
               
               
                 6 
                 6 
               
               
                   
               
             
          
         
       
     
         [0029]    Referring to table 3, if it fails to decode the PDSCH  301  transmitted by the eNB at subframe # 0  of the ith radio frame, the UE transmits an HARQ NACK at the subframe # 7  of ith radio frame. Upon receipt of the HARQ NACK, the eNB configures the retransmission data corresponding to PDSCH  301  as PDSCH  309  and transmits the PDSCH  309  along with PDCCH. In the exemplary case of  FIG. 3 , the retransmission data is transmitted in the subframe # 1  of (i+1)th radio frame by taking notice that the maximum number of downlink HARQ processes is 6 in the TDD uplink-downlink configuration # 6  according to the definition of table 3. This means that there are total 6 downlink HARQ processes  311 ,  312 ,  313 ,  314 ,  315 , and  316  between the initial transmission, i.e. PDSCH  301 , and the retransmission, i.e. PDSCH  309 . 
         [0030]    The LTE system adopts synchronous HARQ having fixed data transmission points in uplink unlike the downlink HARQ. That is, the uplink/downlink timing relationship among the Physical Uplink Shared Channel (PUSCH), Physical Downlink Control Channel (PDCCH) followed by the PUSCH, and Physical Hybrid Indicator Channel (PHICH) carrying the downlink HARQ ACK/NACK corresponding to the PUSCH are fixed according to a rule as follows. 
         [0031]    If the PDCCH including DCI format 0 as uplink scheduling control information or the PHICH carrying the downlink HARQ ACK/NACK is received from the eNB at nth subframe, the UE transmits the PUSCH carrying uplink data corresponding to the control information at (n+k)th subframe. Here, k is denoted as shown in table 4. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 TDDUL/DL 
                 DL subframe number n 
               
             
          
           
               
                 Configuratio 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 0 
                 4 
                 6 
                   
                   
                   
                 4 
                 6 
                   
                   
                   
               
               
                 1 
                   
                 6 
                   
                   
                 4 
                   
                 6 
                   
                   
                 4 
               
               
                 2 
                   
                   
                   
                 4 
                   
                   
                   
                   
                 4 
               
               
                 3 
                 4 
                   
                   
                   
                   
                   
                   
                   
                 4 
                 4 
               
               
                 4 
                   
                   
                   
                   
                   
                   
                   
                   
                 4 
                 4 
               
               
                 5 
                   
                   
                   
                   
                   
                   
                   
                   
                 4 
               
               
                 6 
                 7 
                 7 
                   
                   
                   
                 7 
                 7 
                   
                   
                 5 
               
               
                   
               
             
          
         
       
     
         [0032]    If the PHICH carrying downlink HARQ ACK/NACK is received from the eNB at ith subframe, the PHICH corresponds to the PUSCH transmitted by the UE at (i+k)th subframe. Here, k is defined as shown in table 5. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 TDDUL/DL 
                 DL subframe number i 
               
             
          
           
               
                 Configuratio 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
             
          
           
               
                 0 
                 7 
                 4 
                   
                   
                 7 
                 4 
                   
                   
               
               
                 1 
                   
                 4 
                   
                 6 
                   
                 4 
                   
                 6 
               
               
                 2 
                   
                   
                 6 
                   
                   
                   
                 6 
               
               
                 3 
                 6 
                   
                   
                   
                   
                   
                 6 
                 6 
               
               
                 4 
                   
                   
                   
                   
                   
                   
                 6 
                 6 
               
               
                 5 
                   
                   
                   
                   
                   
                   
                 6 
               
               
                 6 
                 6 
                 4 
                   
                   
                 7 
                 4 
                   
                 6 
               
               
                   
               
             
          
         
       
     
         [0033]      FIG. 4  is a diagram illustrating the subframes carrying PUSCH corresponding to the PDCCH or PHICH carried in downlink or special subframe and the subframes carrying PHICH corresponding to the PUSCH according to the definition of tables 4 and 5 in case of TDD uplink-downlink configuration # 1 . For example, the PUSCH corresponding to the PDCCH or PHICH  401  transmitted by the eNB at subframe # 1  of ith radio frame is transmitted by the UE at subframe # 7  of ith radio frame ( 403 ). The eNB transmits PHICH to the UE at subframe # 1  of (i+1)th radio frame ( 405 ). For another example, the PUSCH corresponding to PDCCH or PHICH  407  transmitted by the eNB at subframe # 6  of ith subframe is transmitted by the UE at subframe # 2  of (i+1)th radio frame ( 409 ). The eNB transmits PHICH corresponding to the PUSCH to the UE at subframe # 6  of (i+1)th radio frame ( 411 ). 
         [0034]    In association with PUSCH transmission in LTE TDD system, the downlink transmission of PDCCH or PHICH corresponding to PUSCH is restricted a specific downlink subframe to guarantee minimum transmission/reception processing time of the eNB and UE. For example, in case of the TDD downlink-uplink configuration # 1  of  FIG. 4 , the PDCCH for PUSCH scheduling or the PHICH corresponding to PUSCH is muted at subframes # 0  and # 5 . 
         [0035]    In case of adopting the timing relationship among the physical channels that is designed for the LTE TDD system to the LTE-A system, there is a need of defining extra operation in addition to the legacy timing relationship. In detail, if the cross-carrier scheduling is applied for the case where TDD uplink-downlink configurations of the respective aggregated carriers differ from each other, it is required to define timing relationships between PDCCH and cross-carrier scheduled PDCCH, between cross-carrier scheduled PUSCH and PHICH, and between cross-scheduled PDSCH and uplink HARQ ACK/NACK. 
       DISCLOSURE OF INVENTION 
     Technical Problem 
       [0036]    The present invention has been made in an effort to solve the above problem and it is an object of the present invention to define timing relationships between PDCCH and cross-carrier scheduled PUSCH, between cross-carrier scheduled PUSCH and PHICH, and cross-carrier scheduled PDSCH and uplink HARQ ACK/NACK in the TDD radio communication system securing broad bandwidth through carrier aggregation especially when the TDD uplink-downlink configurations of the aggregated carriers differ from each other. 
       Solution to Problem 
       [0037]    In accordance with an aspect of the present invention, a method by a base station employing time division duplex and carrier aggregation is provided. The method includes transmitting, to a terminal, scheduling information on a control channel of a first cell, and transmitting, to the terminal, data on a shared channel of a second cell based on the scheduling information. The scheduling information is transmitted in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is transmitted in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell. 
         [0038]    In accordance with another aspect of the present invention, a method by a terminal employing time division duplex and carrier aggregation is provided. The method includes receiving, from a base station, scheduling information on a control channel of a first cell, and receiving, from the base station, data on a shared channel of a second cell based on the scheduling information. The scheduling information is received in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is received in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell. 
         [0039]    In accordance with yet another aspect of the present invention, a base station employing time division duplex and carrier aggregation is provided. The base station includes a transceiver which transmits/receives at least one signal, and a controller configured to transmit, to a terminal, scheduling information on a control channel of a first cell, and transmit, to the terminal, data on a shared channel of a second cell based on the scheduling information. The scheduling information is transmitted in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is transmitted in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell. 
         [0040]    In accordance with still another aspect of the present invention, a terminal employing time division duplex and carrier aggregation is provided. The terminal includes a transceiver which transmits/receives at least one signal, and a controller configured to receive, from a base station, scheduling information on a control channel of a first cell, and receive, from the base station, data on a shared channel of a second cell based on the scheduling information. The scheduling information is received in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is received in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell. 
       Advantageous Effects 
       [0041]    As described above, the present invention is capable of mitigating data and control channel transmission error and transmission delay by defining the detailed transmission timings of the physical channels carrying data and control information in the TDD radio communication system securing broad bandwidth through carrier aggregation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]      FIG. 1  is diagram illustrating an exemplary carrier aggregation in an LTE-A system. 
           [0043]      FIG. 2  is a diagram illustrating an exemplary cross-carrier scheduling operation in the LTE-A system supporting carrier aggregation. 
           [0044]      FIG. 3  is a diagram illustrating a timing relationship between PDSCH and uplink HARQ ACK/NACK in TDD uplink-downlink configuration # 6  of the LTE system. 
           [0045]      FIG. 4  is a diagram illustrating a timing relationship among PDSCH/PHICH, PUSCH, and PHICH in TDD uplink-downlink configuration # 1  of the LTE system. 
           [0046]      FIG. 5  is a diagram illustrating a timing relationship between PDSCH and uplink ACK/NACK according to the first embodiment of the present invention. 
           [0047]      FIG. 6  is a flowchart illustrating the eNB procedure according to the first embodiment of the present invention. 
           [0048]      FIG. 7  is a flowchart illustrating the UE procedure according to the first embodiment of the present invention. 
           [0049]      FIG. 8  is a diagram illustrating the timing relationship between PDSCH and uplink HARQ ACK/NACK according to the second embodiment of the present invention. 
           [0050]      FIG. 9  is a flowchart illustrating the eNB procedure according to the second embodiment of the present invention. 
           [0051]      FIG. 10  is a flowchart illustrating the UE procedure according to the second embodiment of the present invention. 
           [0052]      FIG. 11  is a diagram illustrating the timing relationship among PDCCH, PUCCH, and PHICH according to the third embodiment of the present invention. 
           [0053]      FIG. 12  is a flowchart illustrating the eNB procedure according to the third embodiment of the present invention. 
           [0054]      FIG. 13  is a flowchart illustrating the UE procedure according to the third embodiment of the present invention. 
           [0055]      FIG. 14  is a diagram illustrating the timing relationship among PDCCH, PUSCH, and PHICH according to the fourth embodiment of the present invention. 
           [0056]      FIG. 15  is a flowchart illustrating the eNB procedure according to the fourth embodiment of the present invention. 
           [0057]      FIG. 16  is a flowchart illustrating the UE procedure according to the fourth embodiment of the present invention. 
           [0058]      FIG. 17  is a diagram illustrating the eNB apparatus according to the 1st, 2nd, 3rd, and 4th embodiments of the present invention. 
           [0059]      FIG. 18  is a diagram illustrating the UE apparatus according to the 1st, 2nd, 3rd, and 4th embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0060]    Exemplary embodiments of the present invention are described with reference to the accompanying drawings in detail. Detailed description of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. Further, the following terms are defined in consideration of the functionality in the present invention, and may vary according to the intention of a user or an operator, usage, etc. Therefore, the definition should be made on the basis of the overall content of the present specification. 
         [0061]    Although a detailed description of the present invention is given herein with reference to the Advanced E-UTRA (or LTE-A) system supporting carrier aggregation, it will be understood by those skilled in the art that the present invention can be applied even to other communication systems having the similar technical background and channel format, with a slight modification, without departing from the spirit and scope of the present invention. For example, the subject matter of the present invention can be applied to the multicarrier HSPA supporting carrier aggregation. 
         [0062]    The subject matter of the present invention is to define the timing relationship between the PDCCH and cross-carrier scheduled PUSCH, between cross-carrier scheduled PUSCH and PHICH, and cross-carrier scheduled PDSCH and uplink HARQ ACK/NACK in the TDD radio communication system supporting carrier aggregation especially when the TDD uplink-downlink configurations of the aggregated carriers differ from each other. 
         [0063]    In the LTE-A system supporting carrier aggregation, if the component carrier carrying the downlink control information (DCI) and the component carrier carrying the data scheduled by the DCI differ from each other, such a scheduling is referred to as cross-carrier scheduling. The cross-carrier scheduling is applicable for downlink and uplink data transmissions respectively. 
         [0064]    For convenience purpose, the component carrier carrying DCI is referred to as ‘first component carrier’ and the component carrier carrying data scheduled by the DCI is referred to as ‘second component carrier’ in cross-carrier scheduling operation according to the present invention. 
         [0065]    In the LTE-A system supporting carrier aggregation, if the aggregated frequency bands are not consecutive, it is possible to assign different TDD uplink-downlink configurations to the respective component carriers according to a system operation scenario. For example, the first component carrier is configured with equal numbers of uplink and downlink subcarriers in time domain while the second component carrier is configured with a number of downlink subframes greater than that of the uplink subframes to extend the downlink capacity. For another example, by taking notice of compatibility with TD-SCDMA as the conventional  3 G TDD system, the first component carrier is configured with TDD uplink-downlink configuration maintaining compatibility with the TD-SCDMA to avoid interference between TD-SCDMA and LTE TDD system while the second component carrier is configured with the TDD uplink-downlink configuration according to the traffic load without other restriction. 
         [0066]    A descriptions is made of the method for defining the timing relationship among PDCCH, PDSCH, and UL HARQ ACK/NACK in association with DL data transmission first and then the method for defining the timing relationship among PDCCH, PUSCH, and PHICH in association with UL data transmission. The present invention is applicable to the system supporting carrier aggregation to secure broad bandwidth without restriction to the number of aggregate component carriers. 
       First Embodiment 
       [0067]    The first embodiment describes a method for defining timing relationship among PDCCH, PDSCH, and UL HARQ ACK/NACK in association with downlink data transmission in the TDD radio communication system supporting carrier aggregation when the aggregated carriers are configured with different TDD uplink-downlink configurations. 
         [0068]    The description is made in detail hereinafter with reference to the example of  FIG. 5 . 
         [0069]      FIG. 5  shows an example of the TDD system operating with two aggregated component carriers: CC 1   501  with TDD uplink-downlink configuration # 2  and CC 2   503  with TDD uplink-downlink configurations # 6 . Although  FIG. 5  is directed to the example in which CC 1  and CC 2  have the same frame timing, the present invention is applicable to the cases where the radio frame timings of the component carriers mismatch with each other. 
         [0070]    In  FIG. 5 , the PDSCH scheduling operation on the CC 1 , i.e. the operation ruled out the cross-carrier scheduling, is identical with that in the legacy LTE TDD system. For example, transmits the PDCCH  505  for scheduling the PDSCH  507  on the CC 1  at subframe # 3  of the ith radio frame which has been configured as a downlink subframe at the same subframe # 3  on the component carrier CC 1 . The UE transmits the HARQ ACK/NACK  509  corresponding to PDSCH  507  at the subframe # 7  of the ith radio frame which is the fourth subframe after the subframe where the PDSCH  507  is received. As described above, since the LTE system adopts asynchronous HARQ as downlink HARQ, the PDSCH retransmission timing varies according to the eNB scheduling. By taking notice of 10 downlink HARQ processes on the CC 1  as many as the maximum number of downlink HARQ processes in the TDD uplink-downlink configuration # 2  defined in table 3, the eNB transmits the scheduling control information on the data retransmission (i.e. PDCCH  511 ) and the retransmission data (i.e. PDSCH  513 ) at the subframe # 5  of the (i+1)th radio frame which is 7th subframe after the HARQ ACK/NACK transmission timing  509  of the UE. That is, there are 10 downlink HARQ processes between the initial transmission (PDSCH)  507  and retransmission (PDSCH)  513 . 
         [0071]    The operation for scheduling PDSCH to be transmitted on CC 2  is scheduled by PDCCH transmitted on CC 1 , i.e. cross-carrier scheduling, is not defined in the legacy LTE system and thus it is necessary to define such a cross-carrier scheduling operation newly. 
         [0072]    The timing relationship between PDCCH carrying the cross-carrier scheduling information and PDSCH following the PDCCH is defined first. 
         [0073]    In the example of  FIG. 5 , the eNB is to transmit the PDCCH  515  for scheduling PDSCH of CC 2  at subframe # 3  of the ith radio frame which has been configured as downlink subframe on the CC 1 . This is the case where the CC 1  operates as the first component carrier and the CC 2  as the second component carrier. However, the subframe of the CC 2  is configured as uplink subframe at the same timing such that the eNB cannot perform downlink transmission at the corresponding subframe as denoted by reference number  517 . There are two methods to solve this problem as follows.
       Method A: Cross-carrier scheduling is allowed for both the first and second component carriers at the subframe configured as downlink subframe. For example, the PDCCH  519  for cross-carrier scheduling and PDSCH  521  are transmitted on the CC 1  and CC 2  respectively at the subframe # 5  of the ith radio frame which is configured as the downlink subframe on both the CC 1  and CC 2 , the subframe # 5  arriving first after the subframe # 3  of the ith radio frame.   Method B: In case that the first component carrier is of downlink subframe and the second component carrier is of uplink subframe at a certain timing, the PDCCH to be transmitted on the first component carrier is used for cross-carrier scheduling the PDSCH at the downlink subframe of the second component carrier which arrives first since the PDCCH transmission timing on the first component carrier. For example, if the eNB transmits PDCCH  515  for cross-carrier scheduling the PDSCH on the CC 2  at the subframe # 3  of the ith radio frame, the PDSCH  521  is transmitted at the subframe # 5  of the ith radio frame which is the downlink subframe arrives first since the subframe # 3  of the ith radio frame on the CC 2 .       
 
         [0076]    If the PDSCH  521  is received at the subframe # 5  of the ith radio frame on the CC 2 , the UE transmits uplink HARQ ACK/NACK  523  at the subframe # 2  of the (i+1)th radio frame after 7 subframes according to the TDD uplink-downlink configuration # 6  as defined in table 2. That is, the UE receives PDSCH from the eNB and, since component carrier on which the uplink HARQ ACK/NACK is to be transmitted in correspondence to the PDSCH is identical, applies the rule determined in the legacy LTE TDD system according to the TDD uplink-downlink configuration applied to the second component carrier. 
         [0077]    If the uplink HARQ ACK/NACK  523  indicates NACK, then eNB retransmits PDCCH with the determination on whether to perform cross-carrier scheduling again. However, the PDSCH retransmission is performed on the same component carrier as the PDSCH initial transmission. If it is determined to perform cross-carrier scheduling on the PDSCH retransmission, the eNB transmits the scheduling information (PDCCH)  525  for the data transmission at the subframe # 6  of the (i+1)th radio frame after 4 subframes from the HARQ ACK/NACK transmission  523  of the UE on the CC 1  by taking notice of 6 HARQ processes as many as the maximum downlink HARQ processes of the TDD uplink-downlink configuration # 6  defined in table 3. 
         [0078]    Since the subframe is configured as downlink subframe on the CC 2  at the same timing, the eNB transmits the retransmission data (PDSCH)  513  at the subframe # 6  of the (i+1)th radio frame to the UE. 
         [0079]    Summering the operation of the first embodiment, the timing relationship between PDCCH carrying the cross-carrier scheduling information and the PDSCH can be determined with one of methods A and B. The timing relationship between the PDSCH received from the eNB and the HARQ ACK/NACK transmitted by the UE in uplink is determined with the application of the rule defined in the legacy LTE TDD system according to the TDD uplink-downlink configuration applied to the second component carrier. 
         [0080]      FIG. 6  shows an eNB procedure according to the first embodiment. In order to transmit data to the UE, the eNB determines whether to perform cross-carrier scheduling at step  601 . If it is determined not to perform cross-carrier scheduling, the eNB generates and transmits PDCCH and PDSCH to the UE on the same component carrier at the same subframe at step  607 . The eNB receives uplink HARQ ACK/NACK from the UE according to the timing relationship between the PDSCH and uplink HARQ ACK/NACK defined in the legacy LTE system for the component carrier at step  609 . If it is determined to perform cross-carrier scheduling at step  601 , the eNB generates and transmits PDCCH on the first component carrier and generates and transmits PDSCH on the second component carrier. At this time, the PDCCH and PDSCH transmission timings are determined according to one of the methods A and B. The eNB and UE use one of the methods A and B which is agreed in advance through negotiation. The eNB receives the uplink HARQ ACK/NACK from the UE according to the timing relationship between the PDSCH and uplink HARQ ACK/NACK which is defined in the legacy LTE system for the second component carrier on which the PDSCH has been transmitted at step  605 . If the HARQ ACK/NACK received at step  609  or  605  indicates NACK, the eNB performs retransmission of the PDSCH and, otherwise if ACK, transmits new PDSCH. The eNB returns the procedure to step  601  to determine whether to perform the cross-carrier scheduling for PDSCH retransmission or new PDSCH transmission and continues the rest steps according to the determination result. 
         [0081]      FIG. 7  is a UE procedure according to the first embodiment. The UE receives PDCCH from the eNB at step  701 . Since it is impossible to know the timing when and the component carrier on which the eNB transmits the PDCCH, the UE attempts detecting PDCCH on all aggregated component carrier at every subframe. The UE performs CRC with unique UE-ID allocated to itself on the PDCCH and, if the PDCCH carries the scheduling information on it, determines whether the scheduling information is the cross-carrier scheduling information at step  703 . If the carrier indicator (CI) included in the PDCCH indicates the component carrier on which the PDCCH has been transmitted at step  703 , the UE determines that the cross-carrier scheduling is not applied and thus the procedure goes to step  709 . At step  709 , the UE receives PDSCH at the subframe on the component carrier on which the PDCCH has been transmitted. The UE transmits uplink HARQ ACK/NACK according to the timing relationship between the PDSCH and uplink HARQ ACK/NACK defined in the legacy LTE system for the component carrier identified at step  709 . If the CI included in the PDCCH indicates a component carrier different form the component carrier on which the PDCCH has been transmitted, the UE determines that cross-carrier scheduling is applied and thus the procedure goes to step  705 . At step  705 , the UE receives PDSCH on the second component carrier indicated by the CI. Here, the PDSCH reception timing is determined according to one of the methods A and B. The eNB and UE selects one of the methods A and B through negotiation in advance. The UE transmits uplink HARQ ACK/ACK according to the timing relationship between the PDSCH and uplink HARQ ACK/NACK defined in the legacy LTE system for the second component carrier on which the PDSCH has been received at step  707 . The UE returns the procedure to step  701  after step  707  or  711  and, if the HARQ ACK/ACK indicates NACK, prepares receipt of the PDSCH retransmission and, otherwise if ACK, prepares receipt of new PDSCH. 
         [0082]    The first embodiment may be modified in various ways. For example, unlike the methods A and B, it is possible to designate the subframe for carrying PDSCH on the second component carrier which is cross-carrier scheduled by the PDCCH with n-bit subframe indicator. In case of using 2-bit subframe indicator, the PDCCH including the subframe indicator set to 00 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives first since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 01 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives second since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 10 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives third since the PDCCH transmission timing, and the PDCCH including the subframe indicator set to 11 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives fourth since the PDCCH transmission timing. 
       Second Embodiment 
       [0083]    The second embodiment describes another method for defining timing relationship among PDCCH, PDSCH, and UL HARQ ACK/NACK in association with downlink data transmission in the TDD radio communication system supporting carrier aggregation when the aggregated carriers are configured with different TDD uplink-downlink configurations. 
         [0084]    The description is made in detail hereinafter with reference to the example of  FIG. 8 . 
         [0085]      FIG. 8  shows an example of the TDD system operating with two aggregated component carriers: CC 1   801  with TDD uplink-downlink configurations # 2  and CC 2   803  with TDD uplink-downlink configuration # 6 . Although  FIG. 8  is directed to the example in which CC 1  and CC 2  have the same frame timing, the present invention is applicable to the cases where the radio framing timings of the component carriers mismatch with each other. 
         [0086]    In  FIG. 8 , the PDSCH scheduling operation on the CC 1 , i.e. the operation ruled out the cross-carrier scheduling, is identical with that in the legacy LTE TDD system. Accordingly, detailed description thereon is omitted herein as in the first embodiment of  FIG. 5 . 
         [0087]    In the second embodiment, a procedure for scheduling the PDSCH of CC 2  by the PDCCH of CC 1 , i.e. cross-carrier scheduling procedure, is defined with some difference from the first embodiment. 
         [0088]    The timing relationship between PDCCH carrying the cross-carrier scheduling information and the scheduled PDSCH are defined with the methods A and B as described in the first embodiment. 
         [0089]    In the example of  FIG. 8 , the eNB is to transmit PDCCH  815  scheduling PDSCH of CC 2  at subframe # 8  of the ith radio frame which is configured as a downlink subframe on the CC 1 . That is, this is the case where the CC 1  operates as the first component carrier and the CC 2  operates as the second component carrier. However, since the subframe of the CC 2  is configured as an uplink subframe at the same timing, the eNB cannot perform downlink transmission at the corresponding subframe as denoted by reference number  817 . In order to solve this problem, the method A is to transmit the PDCCH  819  for cross-carrier scheduling and the scheduled PDSCH  821  on the respective component carriers CC 1  and CC 2  simultaneously at the subframe # 9  of the ith radio frame which is the first downlink subframe, on both the CC 1  and CC 2 , arriving after the subframe # 8  of the ith radio frame. Another method B is to transmit the PDCCH  815  for cross-carrier scheduling the PDSCH on the CC 2  at the subframe # 8  of the ith radio frame on the CC 1  and then transmit the PDSCH  821  at the subframe # 9  of the ith radio frame which is the downlink subframe arrives first after the subframe # 8  of the ith radio frame on the CC 2 . 
         [0090]    The second embodiment defines the uplink HARQ ACK/NACK transmission timing corresponding to the PDSCH  821  in different way from the first embodiment. That is, the UE does not follow the timing relationship according to the TDD uplink-downlink configuration # 6  of the CC 2  carrying the PDSCH  821  which is defined for the legacy LTE system but transmits the uplink HARQ ACK/NACK at the uplink subframe of the CC 2  which arrives first after at least j subframes since the subframe at which the PDSCH  821  is received. Here, j is set to a value large enough for guaranteeing the minimum signal processing time of the UE, i.e. 4 subframes in general. Accordingly, in the example of  FIG. 8 , the uplink HARQ ACK/NACK  823  is transmitted at the subframe # 3  of the (i+1)th radio frame. 
         [0091]    If it is determined that the uplink HARQ ACK/NACK  823  indicates NACK, the eNB determines whether to perform cross-carrier scheduling for PDSCH retransmission. However, the PDSCH retransmission is performed on the same component carrier as the initial transmission of the PDSCH. In case of cross-carrier scheduling the PDSCH retransmission, the eNB schedules the PDSCH retransmission at the downlink subframe of the CC 1  which arrives after at least j subframes since the subframe at which the HARQ ACK/NACK  823  has been received. As aforementioned, since the downlink HARQ is asynchronous HARQ, the PDCCH for scheduling the PDSCH retransmission is possible at any downlink subframe after at least j subframes since subframe carrying the uplink HARQ ACK/NACK  823 .  FIG. 8  shows the exemplary case in which the eNB transmits the PDCCH  825  at the subframe # 8  of the (i+1)th radio frame which is the downlink subframe of the CC 1  which arrives after 4 subframes since the receipt of the uplink HARQ ACK/NACK  823 . At this time, since the CC 2  is of uplink subframe at the timing when the PDCCH  825  is transmitted in downlink on the CC 1 , the eNB cannot perform PDSCH retransmission. According to method B, the eNB performs PDSCH retransmission  827  on the CC 2  at the subframe # 9  of the (i+1)th radio frame. 
         [0092]    Summering the second embodiment, the timing relationship between PDCCH carrying the cross-carrier scheduling information and the scheduled PDSCH is determined based on one of methods A and B. The timing relationship between the PDSCH which the UE receives form the eNB and the HARQ ACK/NACK which the UE transmits in uplink is determined in such a way that the uplink HARQ ACK/NACK is transmitted at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe at which the PDSCH has been received regardless of the TDD uplink-downlink configuration applied to the second component carrier. 
         [0093]      FIG. 9  is shows the eNB procedure according to the second embodiment. In order to transmit data to a UE, the eNB determines whether to perform cross-carrier scheduling at step  901 . If it is determined not to perform cross-carrier scheduling, the eNB generates PDCCH and PDSCH and transmits the PDCCH and PDSCH to the UE on the same component carrier and at the same subframe at step  907 . The eNB receives uplink HARQ ACK/NACK from the UE according to the timing relationship between the PDSCH and uplink HARQ ACK/NACK which is applied to the component carrier carrying the PDCCH and PDSCH (step  907 ) as defined in the legacy LTE system at step  909 . If it is determined to perform cross-carrier scheduling at step  901 , the eNB generates and transmits PDCCH on the first component carrier and generates and transmits PDSCH on the second component carrier at step  903 . At this time, the PDCCH and PDSCH transmission timings are determined according to one of the methods A and B. The method to be used for determining the PDCCH and PDSCH transmission timings are agreed between the eNB and the UE in advance. The eNB receives uplink ACK/NACK at the uplink subframe of the second component carrier arriving first after at least j subframes since the subframe at which the PDSCH has been transmitted regardless of the timing relationship between the PDSCH and uplink HARQ ACK/NACK applied to the second component as defined in legacy LTE system. Here, j is set to a value large enough for guaranteeing the minimum signal procession time of the UE, 4 subframes in general. If the HARQ ACK/NACK received at steps  909  or  905  indicates NACK, the eNB performs PDSCH retransmission and, otherwise, new PDSCH transmission. Afterward, the eNB returns the procedure to step  901  to determine whether to perform cross-carrier scheduling for the PDSCH retransmission or new PDSCH transmission and continues the procedure according to the determination result. 
         [0094]      FIG. 10  shows the UE procedure according to the second embodiment. The UE receives PDCCH from the eNB at step  1001 . Since the UE has no information on the time and PDCCH on which the eNB transmits the PDCCH, it attempts detecting PDCCH on every aggregated component carrier at every subframe. The UE performs CRC on the received PDCCH with unique UE-ID allocated to it and, if the PDCCH carries the scheduling information for the UE, determines whether cross-carrier scheduling has been applied at step  1003 . At step  1003 , if the carrier indicator (CI) included in the PDCCH indicates the component carrier on which the PDCCH has been transmitted, the UE determines that no cross-carrier scheduling has been applied and thus the procedure goes to step  1009 . At step  1009 , the UE receives PDSCH at the same subframe where the PDCCH is received. The UE transmits uplink HARQ ACK/NACK according to the timing relationship between the PDCCH and uplink HARQ ACK/NACK according to the TDD uplink-downlink configuration applied to the component carrier carrying both the PDCCH and PDSCH as defined in the legacy LTE system at step  1011 . If the CI included in the PDCCH indicates a component carrier different from the one on which the PDCCH has been transmitted at step  1003 , the UE determines that the cross-carrier scheduling has been applied and thus the procedure goes to step  1005 . At step  1005 , the UE receives the PDSCH on the second component carrier indicated by the CI. The PDSCH reception timing is determined according to one of methods A and B. The method to be used for determining the PDCCH and PDSCH transmission timings are agreed between the eNB and the UE in advance. The UE transmits uplink HARQ ACK/NACK at the uplink subframe of the second component carrier which arrives first after least j subframes since the subframe on which the PDSCH has been received regardless of the timing relationship between the PDSCH and uplink HARQ ACK/NACK of the TDD uplink-downlink configuration applied to the second component carrier as defined for the legacy LTE system. 
         [0095]    The second embodiment can be modified in various ways. For example, unlike the methods A and B, it is possible to designate the subframe for carrying PDSCH on the second component carrier which is cross-carrier scheduled by the PDCCH. For example, it is possible to add an n-bit subframe indicator to the PDCCH to map with the subframe of the PDSCH scheduled by the PDCCH. That is, when using the 2-bit subframe indicator, In case of using 2-bit subframe indicator, the PDCCH including the subframe indicator set to 00 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives first since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 01 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives second since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 10 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives third since the PDCCH transmission timing, and the PDCCH including the subframe indicator set to 11 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives fourth since the PDCCH transmission timing. 
       Third Embodiment 
       [0096]    The third embodiment describes a method for defining timing relationship among PDCCH, PUSCH, and PHICH in association with uplink data transmission in the TDD radio communication system securing broad bandwidth through carrier aggregation especially when the aggregated carriers are configured with different TDD uplink-downlink configurations. 
         [0097]    The description is made in detail hereinafter with reference to the example of  FIG. 11 . 
         [0098]      FIG. 11  shows an example of the TDD system operating with two aggregated component carriers: CC 1   1101  with TDD uplink-downlink configuration # 3  and CC 2   1103  with TDD uplink-downlink configuration # 6 . Although  FIG. 11  is directed to the example in which CC 1  and CC 2  have the same frame timing, the present invention is applicable to the cases where the radio framing timings of the component carriers mismatch with each other. 
         [0099]    The LTE system adopts synchronous HARQ having the fixed data transmission timing in uplink. Accordingly, the uplink/downlink timing relationship among the PUSCH, PDCCH followed by the PUSCH, and the PHICH carrying downlink HARQ ACK/NACK corresponding to the PUSCH has to be fixed according to an predetermined rule. 
         [0100]    In the LTE TDD system, the minimum signal processing time of the eNB or UE is secured in association with PUSCH transmission in such a way that the downlink transmission of the PDCCH corresponding to the PUSCH or the PHICH is restricted to specific downlink subframe according to a TDD uplink-downlink configuration. For example, in case of the TDD uplink-downlink configuration # 3  of  FIG. 11 , the downlink transmission of the PDCCH for scheduling the PUSCH or the PHICH corresponding to the PUSCH is muted at the subframes # 1 , # 5 , # 6 , and # 7 . In case of the TDD uplink-downlink configuration # 6 , the above restriction is not applied to any subframe. 
         [0101]    In  FIG. 11 , the PDSCH scheduling operation on the CC 1 , i.e. the operation ruled out the cross-carrier scheduling, is identical with that in the legacy LTE TDD system. For example, the eNB transmits the PDCCH  1109  for scheduling PUSCH  1111  of CC 1  on the CC 1  carrying the PUSCH  1111  at the subframe # 8  of the ith radio frame which is configured as a downlink subframe. The UE transmits the PUSCH  1111  at the subframe # 2  of the (i+1)th radio frame after four subframes since the receipt of the PDCCH  1109  according to the timing relationship of the TDD uplink-downlink configuration # 3  defined in table 4. Afterward, the eNB generates HARQ ACK/NACK corresponding to the PUSCH  1111  transmitted by the UE and transmits it in the PHICH  1113  at the subframe # 8  of the (i+1)th radio frame after 6 subframes since the subframe on which the PUSCH  1111  has been received according to the timing relationship of the TDD uplink-downlink configuration # 3  defined in table 5. In case of scheduling the PUSCH retransmission, the PDCCH  1115  including the scheduling information is transmitted at the same subframe as the PHICH  1113 . 
         [0102]    As described above, since the transmission of PUSCH for scheduling PUSCH and the PHICH corresponding to the PUSCH is restricted at the subframes # 1 , # 5 , # 6 , and # 7  in the TDD uplink-downlink configuration # 3 , it is impossible to transmit the PDCCH  1105  for scheduling PUSCH on the CC 1  at the subframe # 5  of the ith radio frame. 
         [0103]    The operation for scheduling PUSCH of CC 2  by PDCCH of CC 1 , i.e. the cross-carrier scheduling operation, is need to be defined newly for covering the operations that are not shown in the legacy LTE system. In more detail, the PDCCH, PUSCH, and PHICH transmission related to uplink data transmission are not limited to specific component carrier but performed in order of PDCCH transmission to the eNB on the first component carrier, PUSCH transmission to the UE on the second component carrier, and PHICH transmission to the eNB on the first component carrier in the cross carrier, scheduling such that it is difficult to apply the timing relationship designed for the legacy LTE system under the assumption of one component carrier. 
         [0104]    First, the timing relationship between PDCCH carrying cross-carrier scheduling information and PUSCH scheduled by the PDCCH is defined. 
         [0105]    In the example of  FIG. 11 , the eNB is to transmit PDCCH  1107  for scheduling PUSCH of CC 2  at the subframe # 5  of the ith radio frame which is configured as downlink subframe on the CC 1 . That is, this is the case where the CC 1  operates as the first component carrier and the CC 2  operates as the second component carrier. In this case, the subframe # 5  of the ith radio frame on the CC 1  is the subframe at which PDCCH transmission is restricted according to the TDD uplink-downlink configuration # 3  applied to the CC 1  as described above. However, the transmission of the PDCCH for scheduling the PUSCH of the CC 2  through cross-carrier scheduling is permitted even at the restricted subframes on the CC 1  so as to secure flexibility of the cross-carrier scheduling. 
         [0106]    The UE transmits the PUSCH  1117  at the uplink subframe of the CC 2  which arrives first after at least j subframes since the subframe on which the PDCCH  1107  has been received regardless of the timing relationship of the TDD uplink-downlink configuration # 6  applied to the CC 2  on which the PDCCH  1101  has been received as defined in the legacy LTE system. Here, j is set to a value large enough for guaranteeing the minimum signal processing time of the UE, i.e. 4 subframes in general. Accordingly, in the example of  FIG. 11 , transmits the PUSCH  1117  at the subframe # 2  of the (i+1)th radio frame which is the uplink subframe arriving first after 4 subframes since the receipt of the PDCCH  1107  on the CC 2 . 
         [0107]    If the PUSCH  1117  is received, the eNB determines whether to transmit ACK or NACK and feeds back the determination result to the UE through PHICH. In case of NACK, then eNB transmits the PDCCH for scheduling the PUSCH at the same subframe as the PHICH to the UE. At this time, the eNB determines whether to perform cross-carrier scheduling. However, the PUSCH retransmission is performed on the same component carrier as the initial transmission of the PUSCH. In case of applying the cross-carrier scheduling for PUSCH retransmission, the eNB transmit both the PHICH and PDCCH at the downlink subframe of the CC 1  which arrives first after at least j subframes since the subframe on which the PUSCH  1117  has been received so as to secure the minimum signal processing time of the eNB.  FIG. 11  shows the exemplary case in which the eNB transmits the PHICH  1121  and PDCCH  1119  at the subframe # 6  of the (i+1)th radio frame on the CC 1  which is the downlink subframe arriving first after 4 subframes since the receipt of the PUSCH  1117 . 
         [0108]    Summarizing the procedure of the third embodiment, first, first, although the PDCCH and PHICH transmissions are restricted at a specific subframe on the first component carrier according to the legacy LTE system rule, the PDCCH transmission for cross-carrier scheduling and the PHICH transmission on the second component carrier are permitted at the restricted subframe. Second, the timing relationship between the PDCCH carrying the carrier scheduling information on the first component carrier and the PUSCH to be transmitted by the UE on the second component carrier is configured such that the UE transmits the PUSCH at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which the PDCCH has been received. Third, the timing relationship between the PUSCH transmitted on the second component carrier and the PHICH transmitted on the first component carrier in correspondence to the PUSCH is configured such that the eNB transmits the PHICH and PDCCH at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe on which the PUSCH has been received. 
         [0109]      FIG. 12  shows the eNB procedure according to the third embodiment. In order to transmit data to a UE, the eNB determines whether to perform cross-carrier scheduling at step  1201 . If it is determined not to perform cross-carrier scheduling, the eNB generates and transmits PDCCH at step  1209 . The eNB receives the PUSCH on the same component carrier as the PDCCH according to the timing relationship between the PDCCH and PUSCH which is applied to the component carrier of step  1209  as defined in the legacy LTE system at step  1211 . The eNB transmits PHICH on the same component carrier according to the timing relationship between PUSCH and PHICH which is applied to the component carrier of steps  1209  and  1211  as defined in the legacy LTE system at step  1213 . 
         [0110]    If it is determined to perform cross-carrier scheduling at step  1201 , the eNB generates and transits PDCCH on the first component carrier at step  1203 . In this case, although it is the subframe at which PDCCH transmission is restricted on the first component carrier according to the rule of the legacy LTE system, the PDCCH for the cross-carrier scheduling on the second component carrier is permitted to be transmitted at the same subframe. The eNB receives the PUSCH at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which the PDCCH has been transmitted at step  1205 . Here, j is set to a value large enough for guaranteeing the minimum signal procession time of the UE, 4 subframes in general. The eNB transmits PHICH at the downlink subframe of the first component carrier which arrives after at least j subframes since the subframe at which the PUSCH has been received. 
         [0111]    If the PHICH transmitted at step  1207  or  1213  carries NACK, the PUSCH retransmission is triggered and, otherwise if ACK, new PUSCH transmission is triggered. Afterward, the eNB returns the procedure to step  1201  to determine whether to perform cross-carrier scheduling on the PUSCH retransmission or the new PUSCH transmission and continues the procedures according to the determination result. At this time, the PDCCH for scheduling the PUSCH retransmission is transmitted on the same component carrier and at the same subframe as the PHICH transmitted at step  1207  or  1213 . 
         [0112]      FIG. 13  shows the UE procedure according to the third embodiment. The UE receives PDCCH from the eNB at step  1301 . Since the UE has no information on the time and PDCCH on which the eNB transmits the PDCCH, it attempts detecting PDCCH on every aggregated component carrier at every subframe. The UE performs CRC on the received PDCCH with unique UE-ID allocated to it and, if the PDCCH carries the scheduling information for the UE, determines whether cross-carrier scheduling has been applied at step  1303 . At step  1303 , if the carrier indicator (CI) included in the PDCCH indicates the component carrier on which the PDCCH has been transmitted, the UE determines that no cross-carrier scheduling has been applied and thus the procedure goes to step  1309 . At step  1309 , the UE transmits PUSCH according to the timing relationship between PDCCH and PUSCH which is applied to the component carrier on which the PDCCH has been transmitted as defined in the legacy LTE system. The UE receives the PHICH on the same component carrier according to the timing relationship between the PUSCH and PHICH which is applied to the component carrier of step  1309  as defined in the legacy LTE system at step  1311 . If the CI included in the PDCCH indicates a component carrier different from the component carrier on which the PDCCH has been transmitted, the UE determines that cross-carrier scheduling has been applied and thus the procedure goes to step  1305 . At step  1305 , the UE transmits PUSCH on the second component carrier indicated by the CI. The UE transmits the PUSCH at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which he PDCCH has been received. Here, j is set to a value large enough for guaranteeing the minimum signal processing time of the UE, i.e. 4 subframes in general. The UE receives the PHICH at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the PUSCH has transmitted at step  1307 . 
         [0113]    If the PHICH received at step  1307  or  1311  indicates HARQ NACK, the UE performs PUSCH retransmission and, otherwise, if ACK, new PUSCH transmission. Afterward, the UE returns the procedure to step  1301  to received PDCCH from the eNB and continue the procedure as described above. At this time, the UE receives the PDCCH for scheduling PUSCH retransmission on the same component carrier and at the same subframe where the PHICH has been transmitted at step  1307  or  1311 . 
         [0114]    The third embodiment can be modified in various ways. It is possible to designate the subframe for carrying PDSCH on the second component carrier which is cross-carrier scheduled by the PDCCH. For example, it is possible to add an n-bit subframe indicator to the PDCCH to map with the subframe of the PDSCH scheduled by the PDCCH. However, the subframe carrying PDCCH is configured to occur after at least j subframes as described above, That is, when using the 2-bit subframe indicator, in case of using 2-bit subframe indicator, the PDCCH including the subframe indicator set to 00 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives first after at least j subframes since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 01 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives second after at least j subframes since the PDCCH transmission timing, the PDCCH including the subframe indicator set to 10 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives third after at least j subframes since the PDCCH transmission timing, and the PDCCH including the subframe indicator set to 11 indicates cross-carrier scheduling for the PDSCH at the downlink subframe of the second component carrier which arrives fourth after at least j subframes since the PDCCH transmission timing. 
       Fourth Embodiment 
       [0115]    The fourth embodiment describes another method for defining timing relationship among PDCCH, PUSCH, and PHICH in association with uplink data transmission in the TDD radio communication system securing broad bandwidth through carrier aggregation especially when the aggregated carriers are configured with different TDD uplink-downlink configurations. 
         [0116]    The description is made in detail with reference to the example of  FIG. 14 . 
         [0117]      FIG. 14  shows an example of the TDD system operating with two aggregated component carriers: CC 1   1401  with TDD uplink-downlink configuration # 3  and CC 2   1403  with TDD uplink-downlink configuration # 6 . Although  FIG. 14  is directed to the example in which CC 1  and CC 2  have the same frame timing, the present invention is applicable to the cases where the radio framing timings of the component carriers mismatch with each other. 
         [0118]    As aforementioned, The LTE system adopts synchronous HARQ having the fixed data transmission timing in uplink. Accordingly, the uplink/downlink timing relationship among the PUSCH, PDCCH followed by the PUSCH, and the PHICH carrying downlink HARQ ACK/NACK corresponding to the PUSCH has to be fixed according to an predetermined rule. 
         [0119]    In the LTE TDD system, the minimum signal processing time of the eNB or UE is secured in association with PUSCH transmission in such a way that the downlink transmission of the PDCCH corresponding to the PUSCH or the PHICH is restricted to specific downlink subframe according to a TDD uplink-downlink configuration. For example, in case of the TDD uplink-downlink configuration # 3  of  FIG. 14 , the downlink transmission of the PDCCH for scheduling the PUSCH or the PHICH corresponding to the PUSCH is muted at the subframes # 1 , # 5 , # 6 , and # 7 . In case of the TDD uplink-downlink configuration # 6 , the above restriction is not applied to any subframe. 
         [0120]    In  FIG. 14 , the PDSCH scheduling operation on the CC 1 , i.e. the operation ruled out the cross-carrier scheduling, is identical with that in the legacy LTE TDD system. Since this is identical with example of not performing cross-carrier scheduling in the third embodiment of  FIG. 11 , detailed description thereon is omitted herein. 
         [0121]    In the fourth embodiment, the procedure for scheduling PUSCH of CC 2  by the PDCCH of CC 1 , i.e. the cross-carrier scheduling procedure, is not specified in the legacy LTE standard and thus it is necessary to define such a cross-carrier scheduling operation newly. In cross-carrier scheduling, the PDCCH, PUSCH, and PHICH transmissions are not fixed on specific component carriers but performed in order of PDCCH transmission to the eNB on the first component carrier, PUSCH transmission to the UE in correspondence to the PDCCH on the second component carrier, and PHICH transmission to the eNB on the first component carrier, and thus it is difficult to apply the timing relationship designed under the assumption of the legacy LTE system using single component carrier. 
         [0122]    The timing relationship between the PDCCH carrying the cross-carrier scheduling and the PUSCH in correspondence to the PDCCH is defined first. 
         [0123]    In the example of  FIG. 14 , the eNB is to schedule the UE to transmit the PUSCH  1417  at the subframe # 2  of the (i+1)th radio frame which is configured as an uplink subframe on the CC 2 . In this case, the eNB&#39;s transmission timing of the PDCCH for scheduling the PUSCH  1417  is determined such that the PDCCH is transmitted at the subframe nearest to the UE&#39;s PUSCH  1417  transmission timing among the downlink subframes on CC 1  before at least j subframes preceding the transmission timing of the PUSCH  1417 . Here, j is set to a value large enough for guaranteeing the minimum signal processing time of the UE, i.e. 4 subframes in general. Accordingly, in the example of  FIG. 14 , the eNB transmits the PDCCH  1407  at the subframe # 8  of the ith radio frame which is nearest to the UE&#39;s PUSCH  1417  transmission timing among downlink subframes before 4 subframes preceding the transmission timing of the PUSCH  1417  on the CC 2  which is to be scheduled by the eNB. Through this operation, it is possible to secure the time duration of at least j subframes between the PDCCH and PUSCH transmissions while maintaining the transmission interval to the least, resulting in improvement of eNB&#39;s scheduling efficiency. 
         [0124]    If the PUSCH  1417  is received, the eNB determines whether to transmit ACK or NACK and feeds back the ACK or NACK to the UE through PHICH. In case of NACK, the eNB transmits the PDCCH for rescheduling the PUSCH to the UE along with the PHICH. At this time, the eNB determine whether to perform cross-carrier scheduling again. However, the PUSCH retransmission is performed on the same component carrier as the initial transmission of the PUSCH. In case that the cross-carrier scheduling is performed for the PUSCH retransmission, the eNB transmits the PHICH and PDCCH at the downlink subframe of CC 1  which arrives first after at least j subframes since the subframe at which the PUSCH  1417  has been received, so as to secure its minimum signal processing time.  FIG. 14  shows an example in which the eNB transmits the PHICH  1421  and PDCCH  1419  at the subframe # 6  of the (i+1)th radio frame as a downlink subframe of the CC 1  which arrives first after 4 subframes since the receipt of the PUSCH  1117 . In this case, the subframe # 6  of the (i+1)th radio frame on the CC 1  corresponds to the subframe at which PDCCH and PHICH transmission is restricted according to the TDD uplink-downlink configuration # 3  as aforementioned. Through cross-carrier scheduling, however, the PDCCH for scheduling PUSCH of the CC 2  and the PHICH carrying HARQ ACK/NACK on the CC 2  are permitted to be transmitted at the restricted subframe of the CC 1  to secure flexibility of the cross-carrier scheduling. 
         [0125]    Summarizing the procedure of the fourth embodiment, first, although the PDCCH and PHICH transmissions are restricted at a specific subframe on the first component carrier according to the legacy LTE system rule, the PDCCH transmission for cross-carrier scheduling and the PHICH transmission on the second component carrier are permitted at the restricted subframe. Second, the timing relationship between the PDCCH carrying the carrier scheduling information on the first component carrier and the PUSCH to be transmitted by the UE on the second component carrier is configured such that the eNB transmits the PDCCH at the subframe nearest to the PUSCH transmission timing among the downlink subframes of the first component carrier before at least j subframes proceeding the UE&#39;s PUSCH transmission timing Third, the timing relationship between the PUSCH transmitted by the UE on the second component carrier and the PHICH transmitted by the eNB on the first component carrier in correspondence to the PUSCH is configured such that the eNB transmits PHICH and PDCCH at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the PUSCH has been received. 
         [0126]      FIG. 15  shows the eNB procedure according to the fourth embodiment. In order to transmit data to a UE, the eNB determines whether to perform cross-carrier scheduling at step at step  1501 . If it is determined not to perform cross-carrier scheduling, the eNB generates and transmits PDCCH at step  1509 . The eNB receives the PUSCH on the same component carrier as the PDCCH according to the timing relationship between the PDCCH and PUSCH which is applied to the component carrier of step  1509  as defined in the legacy LTE system at step  1511 . The eNB transmits PHICH on the same component carrier according to the timing relationship between PUSCH and PHICH which is applied to the component carrier of steps  1509  and  1511  as defined in the legacy LTE system at step  1513 . 
         [0127]    If it is determined to perform cross-carrier scheduling at step  1501 , the eNB generates and transits PDCCH on the first component carrier at step  1503 . In this case, the eNB transmits the PDCCH at the subframe nearest to the UE&#39;s PUSCH transmission timing among the downlink subframes of the first component carrier before at least j subframes preceding the UE&#39;s PUSCH transmission timing on the second component carrier. Here, j is set to a value large enough for guaranteeing the minimum signal procession time of the UE, 4 subframes in general. Although it is the frame at which PDCCH transmission is restricted on the first component carrier according to the legacy LTE system rule, the PDCCH transmission for cross-carrier scheduling on the second component carrier is permitted at the restricted subframe on the first component carrier. The eNB receives PUSCH at the scheduled timing on the second component carrier at step  1050 , the timing being determined in transmitting the PDCCH. the eNB transmits PHICH at the downlink subframe carrier of the first component carrier which arrives after at least j subframes since the subframe on which the PUSCH has been received. 
         [0128]    If the PHICH transmitted at step  1507  or  1513  carries HARQ NACK, the eNB schedules the PUSCH retransmission and, otherwise if the PHICH carries HARQ ACK and if there is the data to be transmitted by the UE, new PUSCH transmission. Afterward, the eNB returns the procedure to step  1501  to determine whether to perform cross-carrier scheduling for the PUSCH retransmission or the new PUSCH transmission and continue the procedure according to the determination result. At this time, the PDCCH for scheduling the PUSCH retransmission is transmitted on the same component carrier at the same subframe as the PHICH. 
         [0129]      FIG. 16  shows the UE procedure according to the fourth embodiment. The UE receives PDCCH from the eNB at step  1601 . Since the UE has no information on the time and PDCCH on which the eNB transmits the PDCCH, it attempts detecting PDCCH on every aggregated component carrier at every subframe. The UE performs CRC on the received PDCCH with unique UE-ID allocated to it and, if the PDCCH carries the scheduling information for the UE, determines whether cross-carrier scheduling has been applied at step  1603 . At step  1303 , if the carrier indicator included in the PDCCH indicates the component carrier on which the PDCCH has been transmitted, the UE determines that no cross-carrier scheduling has been applied and thus the procedure goes to step  1609 . At step  1609 , the UE transmits PUSCH according to the timing relationship between PDCCH and PUSCH which is applied to the component carrier on which the PDCCH has been transmitted according to the timing relationship between the PDCCH and PUSCH as defined in the legacy LTE system. The UE receives the PHICH on the same component carrier according to the timing relationship between the PUSCH and PHICH which is applied to the component carrier of step  1609  as defined in the legacy LTE system at step  1611 . If the carrier indicator included in the PDCCH indicates a component carrier different from the component carrier on which the PDCCH has been transmitted, the UE determines that cross-carrier scheduling has been applied and thus the procedure goes to step  1605 . At step  1605 , the UE transmits PUSCH on the second component carrier indicated by the carrier indicator. The UE transmits the PUSCH at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which the PDCCH has been received. Here, j is set to a value large enough for guaranteeing the minimum signal processing time of the UE, i.e. 4 subframes in general. The UE receives the PHICH at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the PUSCH has transmitted at step  1607 . 
         [0130]    If the PHICH received at step  1607  or  1611  indicates HARQ NACK, the UE performs PUSCH retransmission and, otherwise, if ACK, new PUSCH transmission. Afterward, the UE returns the procedure to step  1601  to received PDCCH from the eNB and continue the procedure as described above. At this time, the UE receives the PDCCH for scheduling PUSCH retransmission on the same component carrier and at the same subframe where the PHICH has been transmitted at step  1607  or  1611 . 
         [0131]      FIG. 17  shows the eNB apparatus according to the 1st, 2nd, 3rd, and 4th embodiments of the present invention. Referring to  FIG. 17 , the eNB apparatus comprises a transmission part including a PDCCH block  1705 , a PDSCH block  1716 , a PHICH block  1724 , a multiplexer  1715 ; a reception part including a PUSCH block  1730 , and PUCCH block  1739 , and demultiplexer  1749 ; a carrier aggregation and timing controller  1701 ; and a scheduler  1703 . The PDCCH block  1705  of the transmission part includes a DCI formatter  170107 , a channel coder  1709 , a rate matcher  1711 , and a modulator  1713 ; the PDSCH block  1716  includes a data buffer  1717 , a channel coder  1719 , a rate matcher  1721 , and a modulator  1723 ; and the PHICH block  1724  includes an HARQ ACK/NACK generator  1725 , a PHICH generator  1727 , and a modulator  1729 . The PUSCH block  1730  of the reception part includes a demodulator  1737 , de-rate matcher  1735 , channel decoder  1733 , and data acquirer  1731 ; and the PUCCH block  1739  includes a demodulator  1747 , a de-rate matcher  1745 , a channel decoder  1743 , an ACK/NACK or CQI acquirer  1741 . 
         [0132]    The carrier aggregation and timing controller  1701  determines whether to apply carrier aggregation and the timing relationship among the physical channels based on the data amount to be transmitted and resource amount available in the system and notifies the scheduler  1703 , the PUSCH block  1730 , and PUCCH block  1739  of the determination result. The timing relationship is determined by the method according to the embodiment of the present invention. 
         [0133]    In detail, the carrier aggregation and timing controller  1701  according to the first and second embodiments controls such that the downlink control channel is transmitted through the first component carrier and the downlink data channel scheduled by the downlink control channel is transmitted on the second component carrier based on the transmission timing rule in performing the cross-carrier scheduling. In this case, the carrier aggregation and timing controller  1701  may control such that the downlink control channel and the downlink data channels are transmitted at the subframe configured as downlink subframe on both the first and second component carriers. The carrier aggregation and timing controller  1701  also may control such that the downlink data channel is transmitted at the downlink subframe of the second component carrier which arrives first since the subframe at which the downlink control channel has been transmitted on the first component carrier. 
         [0134]    The carrier aggregation and timing controller  1701  according to the first embodiment may control such that the uplink retransmission ACK/NACK signal transmitted by the UE in accordance with the TDD uplink-downlink configuration predetermined on the second component carrier. 
         [0135]    Also, the carrier aggregation and timing controller  1701  according to the second embodiment may control such that the uplink retransmission ACK/NACK signal transmitted by the UE at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which the downlink data channel has been received. 
         [0136]    Also, the carrier aggregation and timing controller  1701  according to the third embodiment may controls such that the downlink control channel is transmitted at a certain subframe of the first component carrier and the uplink data channel scheduled by the downlink control channel is transmitted at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe at which the downlink control channel has been transmitted, in performing the cross-carrier scheduling. In this case, the carrier aggregation and timing controller  1701  may control such that the retransmission ACK/NACK signal at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the uplink data channel has been received. 
         [0137]    Also, the carrier aggregation and timing controller  1701  according to the fourth embodiment may control such that the downlink control channel is transmitted at a certain subframe of the first component carrier and the uplink data channel is received at the uplink subframe of the second component carrier which is scheduled by the downlink control channel, in performing the cross-carrier scheduling. In this case, the downlink control channel is transmitted at the subframe nearest to the subframe at which the uplink data channel is received among the downlink subframes of the first component carrier before at least j subframes preceding the subframe of the second component carrier at which the uplink data channel is received. The carrier aggregation and timing controller  1701  also may control such that the retransmission ACK/NACK signal is transmitted at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the uplink data channel has been received. 
         [0138]    The PDCCH block  1705  generates a DCI by mans of the DCI formatter  1710 , adds error correction capability to the DCI by means of the channel coder  1709 , matches rate to the resource amount to which the DCI is mapped by means of the rate matcher  1711 , modulates the rate match result by means of the modulator  1713 , and multiplexes the modulation result with other signals by means of the multiplexer  1715 , under the control of the scheduler. 
         [0139]    The PDSCH block  1716  reads out the data to be transmitted from the data buffer  1717 , adds error correction capability to the data by means of the channel coder  1719 , matches the rate to the resource amount to which the data is mapped by means of the rate-matcher  1721 , modulates the rate match result by means of the modulator  1723 , and multiplexes the modulation result with other signals by means of the multiplexer  1715 . 
         [0140]    The PHICH block  1724  generates HARQ ACK/NACK corresponding to the PUSCH received from the UE by means of the HARQ ACK/NACK generator  1725  under the control of the scheduler  1703 . The HARQ ACK/NACK is formatted to be suitable for the PHICH channel structure by means of the PHICH formatter  1727 , modulated by means of the modulator  1729 , and then multiplexed with other signals by means of the multiplexer  1715 . 
         [0141]    The multiplexed signals converted to OFDM signals to be transmitted to the UE. 
         [0142]    The PUSCH block  1730  of the reception part separates the PUSCH signal form the signal received from UE by means of the demultiplexer  1749 , demodulates the PUSCH by means of the demodulator  1737 , de-rate matches the demodulation result to the signal before the rate matching by means of the de-rate matcher  1735 , decodes the de-rate match result by means of the decoder  1733 , and acquires the PUSCH by means of the data acquirer  1731 . The data acquirer  1731  notifies the scheduler  1703  of the decoding result, i.e. whether error is detected, to control downlink HARQ ACK/NACK generation and notifies the carrier aggregation and timing controller  1701  of the decoding result, i.e. whether error is detected, to adjust downlink HARQ ACK/NACK transmission timing. 
         [0143]    The PUCCH block  1730  separates PUCCH signal from the signal received from the UE by means of the demultiplexer  1749 , demodulates the PUCCH signal by means of the demodulator  1747 , decodes the demodulation result by means of the channel decoder  1733 , and acquires uplink ACK/NACK or CQI by means of the uplink ACK/NACK or CQI acquirer  1741 . The acquired ACK/NACK or CQI is provided to the scheduler  1703  so as to be used for determining PUSCH retransmission and modulation and coding scheme (MCS). The acquired uplink ACK/NACK is provided to the carrier aggregation and timing controller  1701  so as to be used for PDSCH transmission timing adjustment. 
         [0144]      FIG. 18  shows the UE apparatus according to the 1st, 2nd, 3rd, and 4th embodiments of the present invention. Referring to  FIG. 18 , the UE comprises a transmitter including a PUCCH block  1805 , a PUSCH block  1816 , and a multiplexer  1815 ; a receiver including a PHICH block  1824 , a PDCCH block  1839 , and a demultiplexer  1849 ; and a carrier aggregation and timing controller  1801 . The PUCCH block  1805  of the transmitter includes a UCI formatter  1807 , a channel coder  1809 , and a modulator  1813 ; and the PUSCH block  1816  includes a data buffer  1818 , a channel coder  1819 , a rate matcher  1821 , and a modulator  1823 . The PHICH block  1824  of the receiver includes an HARQ ACK/NACK acquirer  1825  and a modulator  1829 ; the PDSCH block  1830  includes a demodulator  1837 , a de-rate matcher  1835 , a channel coder  1833 , and a data acquirer  1831 ; and the PDCCH block  1839  includes a demodulator  1847 , a de-rate matcher  1845 , a channel coder  1843 , and a DCI acquirer  1841 . 
         [0145]    The carrier aggregation and timing controller  1801  checks carrier aggregation state of the UE based on the DCI received from the eNB to determine the carrier for receiving the PDSCH in the cross-carrier scheduling and transmission/reception timing relationship among the physical channels and notifies the PUCCH block  1805 , PUSCH block  1816 , PHICH block  1824 , PDSCH block  1830 , and PDCCH block  1839  of the determination result. The timing relationship is determined according to the method described in the embodiments of the present invention. 
         [0146]    According to the first and second embodiments, the carrier aggregation and timing controller  1801  controls such that, in cross-carrier scheduling, the downlink control channel is received on the first component carrier and the downlink data channel, which is scheduled by the downlink control channel, on the second component carrier according to a predetermined transmission timing rule of the downlink control can data channels. In this case, the carrier aggregation and timing controller  1701  may control such that the downlink control channel and the downlink data channel are received at the subframe which is configured as downlink subframe on both the first and second component carrier. The carrier aggregation and timing controller  1701  also may control such that the downlink data channel is received at the downlink subframe of the second component carrier which arrives first since the downlink control channel has been transmitted. 
         [0147]    Particularly according to the first embodiment, the carrier aggregation and timing controller may control such that the uplink retransmission ACK/NACK signal is transmitted to the eNB according to a TDD uplink-downlink configuration predetermined on the second component carrier. 
         [0148]    According to the second embodiment, the carrier aggregation and timing controller may controls such that the uplink retransmission ACK/NACK signal is transmitted to the eNB at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe at which the downlink data channel has been received. 
         [0149]    According to the third embodiment, the carrier aggregation and timing controller may controls such that, in cross-carrier scheduling, the downlink control channel is received at a certain subframe of the first component carrier and the uplink data channel scheduled by the downlink control channel is transmitted at the uplink subframe of the second component carrier which arrives first after at least j subframes since the subframe on which the downlink control channel has been transmitted. In this case, the carrier aggregation and timing controller may control such that the retransmission ACK/NACK signal is received at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the uplink data channel has been received. 
         [0150]    According to the fourth embodiment, the carrier aggregation and timing controller may controls such that, in cross-carrier scheduling, the downlink control channel is received at a certain subframe of the first component carrier and the uplink data channel, which is scheduled by the downlink control channel, at the uplink subframe of the second component carrier. In this case, the downlink control channel is received at the subframe nearest to the subframe carrying the uplink data channel among the downlink subframes of the first component carrier before at least j subframes preceding the subframe of the second component carrier at which the uplink data channel is received. According to the fourth embodiment, the carrier aggregation and timing controller controls such that the retransmission ACK/NACK signal is received at the downlink subframe of the first component carrier which arrives first after at least j subframes since the subframe at which the uplink data channel is received. 
         [0151]    The PUCCH block  1805  generates HARQ ACK/NACK or CQI based on the Uplink Control Information (UCI) by means of the UCI formatter  1807  under the timing control of the carrier aggregation and timing controller  1701 , adds error correction capability to the UCI by means of the channel coder  1809 , modulates the channel-coded result by means of the modulator  1813 , and multiplexes the modulation result with other signals by means of the multiplexer  1815 . 
         [0152]    The PUSCH block  1816  reads out data from the data buffer  1818  under the timing control of the carrier aggregation and timing controller  1801 , adds error correction capability to the data by means of the channel coder  1819 , rate-matches the channel-coding result to the resource amount for actual mapping, modulates the rate-match result by means of the modulator  1823 , and multiplex the modulation result with other signals by means of the multiplexer  1815 . 
         [0153]    The multiplexed signals are converted into Single Carrier Frequency Division Multiple Access (SC-FDMA) signal to be transmitted to the eNB. 
         [0154]    The PHICH block  1824  of the receiver separates PHICH signal from the signal transmitted by the UE by means of the demultiplexer  1849 , demodulates the PHICH signal by means of the demodulator  1829 , and acquires HARQ ACK/NACK corresponding to PUSCH by means of the HARQ ACK/NACK acquirer  1825 . The HARQ ACK/NACK information corresponding to the PUSCH is delivered to the carrier aggregation and timing controller  1801  so as to be used for determining PUSCH retransmission timing of the UE. 
         [0155]    The PDSCH block  1830  separates PDSCH signal from the signal transmitted by the eNB by means of the demultiplexer  1849 , demodulates the PDSCH signal by means of the demodulator  1837 , de-rate matches the demodulation result to the symbols before being rate-matched, decodes the de-rate match result by mean of the channel decoder  1833 , and acquires PDSCH data by means of the data acquirer  1831 . The data acquire  1831  notifies the PUCCH block  1805  of the decoding result erroneous or not to generate uplink HARQ ACK/NACK and notifies the carrier aggregation and timing controller  1801  of the decoding result so as to determine the uplink HARQ ACK/NACK transmission timing. 
         [0156]    The PDCCH block  1839  separates PDCCH signal from the signal transmitted by the eNB by means of the demultiplexer  1849 , demodulates the PDCCH signal by means of the demodulator  1847 , decodes the demodulation result by means of the channel decoder  1833 , and acquires DCI by means of the DCI acquirer  1841 . The DCI is delivered to the carrier aggregation and timing controller  1801  to determine the PUSCH transmission timing of the UE. 
         [0157]    While embodiments of the present invention have been shown and described in the specification and drawings to illustrate and explain the present invention, it should be understood that the present invention is not limited to these specific embodiments. That is, it is obvious to those skilled in the art that various changes and modification may be made therein without departing from the technical concept of the invention.