Patent Publication Number: US-2020304265-A1

Title: Method and apparatus for transmitting srs in wireless cellular mobile communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application of prior U.S. application Ser. No. 15/028,616, filed on Apr. 11, 2016, is a U.S. National Stage application under 35 U.S.C. § 371 of an International application number PCT/KR2014/009539, filed on Oct. 10, 2014, which is based on and claimed priority of a Korean patent application number 10-2013-0121346, filed on Oct. 11, 2013, and Korean patent application number 10-2014-0012251, filed on Feb. 3, 2014, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to cellular wireless communication systems, and more particularly, to a method for a terminal to transmit Sounding Reference Signal (SRS) to a base station in a communication system configured to support the carrier aggregation of a component carrier using a Frequency Division Duplex (FDD) scheme and a component carrier using a Time Division Duplex (TDD) scheme. 
     BACKGROUND ART 
     Wireless communication systems that were providing voice-based services have evolved to broadband wireless communication systems that are capable of providing packet data services based on high quality and high speed, such as: Long Term Evolution (LTE), High Speed Packet Access (HSPA) defined in 3rd Generation Partnership Project (3GPP); Ultra Mobile Broadband (UMB), High Rate Packet Data (HRPD) defined in 3rd Generation Partnership Project 2 (3GPP2); the communication standard IEEE 802.16e; etc. 
     The LTE system, as a typical example of the broadband wireless communication systems, employs Orthogonal Frequency Division Multiplexing (OFDM) in the downlink and Single Carrier-Frequency Division Multiple Access (SC-FDMA) in the uplink. The Multiple Access performs allocation and management of time-frequency resources to carry data and control information according to users, so as not to overlap with each other, i.e., so as to achieve orthogonality between them, thereby distinguishing data or control information between respective users. 
       FIG. 1  is a diagram showing the basic structure of a radio resource area on the time-frequency domain, transmitting data or control information through an uplink of an LTE system. 
     In LTE systems, uplink (UL) refers to a radio link through which UE transmits data or control signals to evolved Node B (eNB) (base station) and downlink (DL) refers to a radio link through which eNB transmits data or controls signals to UE. 
     As shown in  FIG. 1 , the horizontal and vertical axes represent the time and frequency domains, respectively. The minimum unit of transmission on the time domain is an SC-FDMA symbol. N symb  SC-FDMA symbols (N represents the number of symbols), indicated by the reference number  102 , form one slot  106 . Two slots  106  form one subframe  105 . 10 subframes  105  form one radio frame  107 . The slot has a length of 0.5 ms. The subframe has a length of 1.0 ms. The radio frame has a length of 10 ms. The minimum unit of transmission on the frequency domain is a subcarrier. 
     The basic unit of resource on the time-frequency domain is a Resource Element (RE)  112  and is represented by an SC-FDMA symbol index and a subcarrier index. The Resource Block (RB)  108  (or Physical Resource Block (PRB)) is defined as successive N symb  SC-FDMA symbols  102  on the time domain and successive N RB   SC  subcarriers  110  on the frequency domain. Therefore, one RB  108  includes REs of N symb ×N RB   SC , denoted as N symb ×N RB   SC  REs  112 . In general, the minimum unit of data is an RB  108  and the system transmission bandwidth forms RBs of N RB  in total, denoted as N RB  RB  108 . The overall system transmission bandwidth is subcarriers of N RB ×N RB   SC  in total, denoted as N RB ×N RB   SC  subcarriers  104 . Generally, in LTE systems, N symb =7 and N RB   SC =12. 
     The LTE system employs a Hybrid Automatic Repeat reQuest (HARQ) scheme for retransmitting data, which has failed in decoding in the initial transmission, via the physical layer. HARQ is a scheme that allows a receiver to transmit, when not correctly decoding data from a transmitter, information (NACK) indicating the decoding failure to the transmitter so that the transmitter can perform re-transmission of the data from the physical layer. The receiver combines the data re-transmitted from the transmitter with the existing data for which decoding has failed, thereby increasing the capability of data reception. When correctly decoding data, the receiver transmits information (ACK) indicating the success of decoding to the transmitter so that the transmitter can perform transmission of new data. 
     In broadband wireless communication systems, one of the important factors in providing high transmission rate wireless data services is the ability to support scalable bandwidths. For example, LTE systems are capable of supporting various bandwidths, such as 20/15/10/5/3/1.4 MHz, etc. Therefore, service operators are capable of selecting a particular one of the various bandwidths and providing services via the bandwidth. There are various types of user equipment (UE) devices that are capable of supporting bandwidths from a minimum of 1.4 MHz to a maximum of 20 MHz. 
       FIG. 2  is a diagram showing the structure of an LTE-A system supporting carrier aggregation. 
     As shown in  FIG. 2 , eNB (base station)  202  supports the aggregation of two component carriers, CC # 1  and CC # 2 . CC # 1  has a frequency f 1  and CC # 2  has a frequency f 2  that differs from f 1 . CC # 1  and CC # 2  are included in the same eNB  202 . The eNB  102  provides coverage  104  and  106  corresponding to the component carrier CC # 1  and CC # 2 , respectively. The LTE-A system capable of supporting carrier aggregation performs transmission of data and transmission of control information related to the transmission of data, according to component carriers, respectively. The configuration shown in  FIG. 2  may also be applied to the aggregation of uplink carriers in the same way as the aggregation of downlink carriers. 
     The carrier aggregation system divides component carriers into Primary Cell (Pcell) and Secondary Cell (Scell) and manages them. Pcell refers to a cell that provides the basic radio resources to UE and serves as a standard cell allowing UE to perform operations such as the initial access, a handover, etc. Pcell includes a downlink primary frequency (or Primary Component Carrier (PCC)) and an uplink primary frequency. Scell refers to a cell that provides additional radio resources to UE along with Pcell. Scell includes a downlink secondary frequency (or Secondary Component Carrier (SCC)) and an uplink secondary frequency. In the present disclosure, unless otherwise indicated, the terms ‘cell’ and ‘component carrier’ will be used interchangeably with each other. 
     The Frequency Division Duplex (FDD) scheme employs different frequencies for downlink and uplink. In contrast, the Time Division Duplex (TDD) scheme employs the same frequency for downlink and uplink but performs transmission and reception of uplink/downlink signals at different times. The LTE TDD scheme transmits uplink or downlink signals at different times according to subframes. Therefore, on the time domain, according to traffic load of uplink and downlink, the LTE TDD is capable of: dividing subframes to uplink/downlink equally and managing them; or assigning more subframes to either downlink or uplink and managing them. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 plink- 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 downlink 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
            
           
           
               
               
            
               
                    onfigura- 
                 Subframe number 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 tion 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
                 
                   
                 
               
               
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 
                   
                 
               
               
                   
               
               
                     indicates data missing or illegible when filed 
               
            
           
         
       
     
     Table 1 shows the TDD uplink-downlink configuration defined as in LTE. In table 1, ‘D’ denotes a subframe configured for downlink transmission, ‘U’ denotes a subframe configured for uplink transmission, and ‘S’ represents a Special subframe including a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot (UpPTS). 
       FIG. 3  is a diagram showing the structure of a special subframe for an LTE TDD system. 
     Referring to  FIG. 3 , DwPTS  301  is used to transmit control information via downlink like a general subframe. When DwPTS  301  has a sufficient length according to configuration states of a special subframe, it can be used to transmit downlink data. GP  302  is a section for accepting the transition of transmission signals from a downlink to an uplink, and its length is determined according to the network settings, etc. UpPTS  303  contains one or two SC-FDMA symbols and is used to transmit Sounding Reference Signal (SRS) of UE which eNB needs to estimate an uplink channel state or a random access preamble of UE to perform random access. 
     The special subframe has a length of 1 ms like the general subframe. According to the settings of eNB, DwPTS  301  includes 3 to 12 OFDM symbols and UpPTS  303  includes 1 or 2 SC-FDMA symbols. GP  302  has a time interval obtained by subtracting the length of DwPTS  301  and UpPTS  303  from the overall length of the special subframe, 1 ms. 
     As described in table 1, the special subframe may be set to subframe # 1  or subframe # 6  according to the TDD uplink-downlink configuration. 
     For example, for TDD uplink-downlink configuration # 6 , subframe # 0 , # 5 , and # 9  may transmit downlink data and control information, and subframe # 2 , # 3 , # 4 , # 7 , and # 8  may transmit uplink data and control information. Subframe # 1  and # 6  corresponding to the special subframe may transmit downlink control information and further downlink data according to conditions. Sounding Reference Signal (SRS) or RACH may be transmitted via the uplink. 
     eNB estimates an uplink channel state from an SRS transmitted from UE. In general, an SRS may be located in the last SC-FDMA symbol of a subframe. In an LTE system using a TDD scheme, the UpPTS section of the special subframe may transmit SRS over a maximum of two SC-FDMA symbols. eNB may determine a subframe, available to transmit an SRS, and an SC-FDMA symbol in the UpPTS, available to transmit an SRS, and inform UE of the settings via signaling. 
     A conventional LTE-A system configured to support carrier aggregation has a limitation to apply the same duplex scheme to individual component carriers. That is, it aggregates component carriers using the FDD scheme to each other or component carriers using the TDD scheme to each other. 
     In order to perform carrier aggregation using duplex schemes that differs from each other according to component carriers, the present invention provides a method for UE to transmit an SRS via a special subframe. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present invention has been made to address the above problems and disadvantages, and to provide at least the advantages described below. Accordingly, the present invention provides a method for UE to transmit a Sounding Reference Signal (SRS) to eNB in a communication system configured to support the carrier aggregation of a component carrier using Frequency Division Duplex (FDD) scheme and a component carrier using Time Division Duplex (TDD) scheme. 
     This section, Technical Problem, is merely intended to provide a few aspects of the present invention. It should be understood that the features and advantages of the present invention are not limited to those in the foregoing description, and the other features and advantages not described above will become more apparent from the following description. 
     Solution to Problem 
     In accordance with an aspect of the present invention, the present invention provides a communication method of a terminal in a communication system configured to support the carrier aggregation of a component carrier using a Frequency Division Duplex (FDD) scheme and a component carrier using a Time Division Duplex (TDD) scheme. The method includes: receiving setup information regarding SRS transmission from a base station; receiving scheduling information regarding uplink data from the base station; determining whether simultaneous transmission of the SRS and the uplink data occurs; and when simultaneous transmission of the SRS and the uplink data occurs, setting the transmission of the uplink data or the SRS so that the sum of the transmission powers of the first symbol and the second symbol of an FDD cell and the first symbol and the second symbol of a TDD cell does not exceed the maximum transmission power of the terminal. The timing of the first symbol of the FDD cell corresponds to the timing of the first symbol of the TDD cell. The timing of the second symbol of the FDD cell corresponds to the timing of the second symbol of the TDD cell. 
     In accordance with another aspect of the present invention, the present invention provides a communication method of a base station in a communication system configured to support the carrier aggregation of a component carrier using a Frequency Division Duplex (FDD) scheme and a component carrier using a Time Division Duplex (TDD) scheme. The method includes: transmitting setup information regarding SRS transmission to a terminal; and transmitting scheduling information regarding uplink data to the terminal. The setup information regarding SRS transmission and the scheduling information regarding uplink data comprises information for setting, when simultaneous transmission of the SRS and the uplink data occurs, the transmission of the SRS or the uplink data so that the sum of the transmission powers of the first symbol and the second symbol of an FDD cell and the first symbol and the second symbol of a TDD cell does not exceed the maximum transmission power of the terminal. The timing of the first symbol of the FDD cell corresponds to the timing of the first symbol of the TDD cell. The timing of the second symbol of the FDD cell corresponds to the timing of the second symbol of the TDD cell. 
     In accordance with another aspect of the present invention, the present invention provides a terminal of a communication system configured to support the carrier aggregation of a component carrier using a Frequency Division Duplex (FDD) scheme and a component carrier using a Time Division Duplex (TDD) scheme. The terminal includes: a communication unit for communicating with a base station; and a controller for: receiving setup information regarding SRS transmission from the base station; receiving scheduling information regarding uplink data from the base station; determining whether simultaneous transmission of the SRS and the uplink data occurs; and setting, when simultaneous transmission of the SRS and the uplink data occurs, the transmission of the uplink data or the SRS so that the sum of the transmission powers of the first symbol and the second symbol of an FDD cell and the first symbol and the second symbol of a TDD cell does not exceed the maximum transmission power of the terminal. The timing of the first symbol of the FDD cell corresponds to the timing of the first symbol of the TDD cell. The timing of the second symbol of the FDD cell corresponds to the timing of the second symbol of the TDD cell. 
     In accordance with another aspect of the present invention, the present invention provides a base station of a communication system configured to support the carrier aggregation of a component carrier using a Frequency Division Duplex (FDD) scheme and a component carrier using a Time Division Duplex (TDD) scheme. The base station includes: a communication unit for communicating with a terminal; and a controller for transmitting setup information regarding SRS transmission and scheduling information regarding uplink data to the terminal. The setup information regarding SRS transmission and the scheduling information regarding uplink data comprises information for setting, when simultaneous transmission of the SRS and the uplink data occurs, the transmission of the SRS or the uplink data so that the sum of the transmission powers of the first symbol and the second symbol of an FDD cell and the first symbol and the second symbol of a TDD cell does not exceed the maximum transmission power of the terminal. The timing of the first symbol of the FDD cell corresponds to the timing of the first symbol of the TDD cell. The timing of the second symbol of the FDD cell corresponds to the timing of the second symbol of the TDD cell. 
     Advantageous Effects of Invention 
     The present invention defines an SRS transmission method of UE in a wireless communication system and enables the UE to efficiently transmit the uplink data. 
     It should be understood that the advantageous effects of the present invention are not limited to those in the foregoing description, and the other effects not described above will become more apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing the basic structure of an uplink time-frequency domain of an LTE system. 
         FIG. 2  is a diagram showing the structure of an LTE-A system supporting carrier aggregation. 
         FIG. 3  is a diagram showing the structure of a special subframe for an LTE TDD system. 
         FIG. 4  is a diagram showing an example when a special subframe of a TDD cell and a subframe of an FDD cell overlap with each other in terms of time. 
         FIG. 5  is a diagram showing Method  1  according to a first embodiment of the present invention. 
         FIG. 6  is a diagram showing Method  2  according to a first embodiment of the present invention. 
         FIG. 7  is a diagram showing Method  3  according to a first embodiment of the present invention. 
         FIG. 8  is a diagram showing Method  4  according to a first embodiment of the present invention. 
         FIG. 9  is a diagram showing Method  1  according to a second embodiment of the present invention. 
         FIG. 10  is a diagram showing Method  2  according to a second embodiment of the present invention. 
         FIG. 11  is a diagram showing Method  3  according to a second embodiment of the present invention. 
         FIG. 12  is a diagram showing Method  1  according to a third embodiment of the present invention. 
         FIG. 13  is a diagram showing Method  2  according to a third embodiment of the present invention. 
         FIG. 14  is a diagram showing Method  3  according to a third embodiment of the present invention. 
         FIG. 15  is a diagram showing Method  4  according to a third embodiment of the present invention. 
         FIG. 16  is a diagram showing Method  1  according to a fourth embodiment of the present invention. 
         FIG. 17  is a diagram showing Method  2  according to a fourth embodiment of the present invention. 
         FIG. 18  is a diagram showing Method  3  according to a fourth embodiment of the present invention. 
         FIG. 19  is a diagram showing a method according to a fifth embodiment of the present invention. 
         FIG. 20  is a flowchart that describes operations of eNB according to an embodiment of the present invention. 
         FIG. 21  is a flowchart that describes operations of UE according to an embodiment of the present invention. 
         FIG. 22  is a block diagram showing a transmitting device of UE according to an embodiment of the present invention. 
         FIG. 23  is a block diagram showing a receiving device of eNB according to an embodiment of the present invention. 
         FIG. 23  is a block diagram showing a receiver of eNB according to an embodiment of the present invention. 
         FIG. 24  is a diagram showing a method according to a sixth embodiment of the present invention. 
         FIG. 25  is a flowchart that describes operations of eNB according to a sixth embodiment of the present invention. 
         FIG. 26  is a flowchart that describes operations of UE according to a sixth embodiment of the present invention. 
         FIG. 27  is a block diagram showing a transmitting device of UE according to another embodiment of the present invention. 
         FIG. 28  is a block diagram showing a receiving device of eNB according to another embodiment of the present invention. 
     
    
    
     MODE FOR THE INVENTION 
     Embodiments of the present invention are described in detail referring to the accompanying drawings. Detailed descriptions of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the invention. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The term ‘eNB’ refers to an entity configured to assign resources to UE, and is used in the sense of at least one of the following: eNode B, eNB, Node B, Base Station (BS), radio access unit, base station controller, node on a network. 
     The term ‘terminal’ is used in the sense of: User Equipment (UE), Mobile Station (MS), cellular phone, smartphone, computer, or multimedia system capable of performing a communication function. 
     Embodiments of the present invention are described based on E-UTRA (or called LTE) or Advanced E-UTRA (or called LTE-A) system; however, it should be understood that the present invention can also be applied to various types of communication systems which have the technical background and channel forms similar to those of the present invention. 
     It will be appreciated to those skilled in the art that embodiments of the present invention can be modified without departing from the scope and sprit of the present invention and the modifications can also be applied to other types of communication systems. 
     In the present disclosure, a method for UE to transmit a Sounding Reference Signal (SRS) via a special subframe is defined to perform carrier aggregation using duplex schemes that differ from each other according to component carriers. 
     In the following description, embodiments of the present invention to resolve the conventional problems are explained in detail. 
       FIG. 4  is a diagram showing an example when a special subframe of a TDD cell and a subframe of an FDD cell overlap with each other in terms of time. 
     Referring to  FIG. 4 , in a carrier aggregation system configured to aggregate a cell (or a component carrier) using Frequency Division Duplex (FDD) scheme and a cell (or a component carrier) using Time Division Duplex (TDD) scheme and to manage the carrier aggregation, an example is shown where a special subframe  408  of a TDD cell  402  and a subframe  403  of an FDD cell  401  overlap with each other in terms of time. For the TDD cell  402 , the UpPTS  407  of the special subframe  408  is set to have a length of two SC-FDMA symbols. It is assumed that UE is scheduled by eNB for uplink data transmission to perform transmission of: Physical Uplink Shared Channel (PUSCH) during the interval of the subframe  403  of the FDD cell  401 ; and SRS during the interval of UpPTS  407  of the special subframe  408  of the TDD cell  402 . 
     PUSCH refers to a physical channel carrying uplink data that UE transmits to eNB. In order to estimate the PUSCH, Reference Signals (RSs)  409  and  410  are transmitted. Therefore, the PUSCH is mapped to intervals  411 ,  412 , and  413  in the subframe  403 , except for symbols where the RSs  409  and  410  and located, and is then transmitted to eNB. 
     eNB determines the settings, such as a condition as to whether one or two SRS symbols are transmitted during the interval of UpPTS  407 , a symbol in UpPTS  407  to transmit one SRS, etc., and informs UE of the settings via higher-layer signaling. 
     In this case, UE needs to simultaneously transmit a PUSCH via the FDD cell  401  and an SRS via the TDD cell  402  during the interval corresponding to the UpPTS  407 , and this may cause a problem that the sum of the PUSCH transmission power and the SRS transmission power exceeds the maximum allowable transmission power of UE. Therefore, there is a need to define specified transmission methods for PUSCH and SRS. 
     First Embodiment 
     In a first embodiment, specified operations are defined when UE needs to simultaneously transmit a PUSCH to an FDD cell and an SRS to a TDD cell, under the condition shown in  FIG. 4 . The first embodiment provides a method for UE to transmit two SRS symbols to a TDD cell during a UpPTS interval. 
     1) Method  1   
       FIG. 5  is a diagram showing Method  1  according to a first embodiment of the present invention. 
     According to Method  1 , UE transmits only the second one of the two SRS symbols to be transmitted via a TDD cell  502 , without transmitting the first SRS symbol; and performs rate matching for a PUSCH to be transmitted via an FDD cell  501  within the last symbol interval in a subframe, thereby transmitting the PUSCH. Channel coding is generally performed to add an error correcting capability to data that UE needs to transmit. UE adjusts the size of output bit stream channel-encoded to match with the amount of resource scheduled by eNB, and maps the output bit stream to a time-frequency resource, which is called a rate-matching. 
     Referring to  FIG. 5 , Method  1  is described below. UE transmits the second SRS symbol  509 , without transmitting the first SRS symbol  508 , during the UpPTS interval  507  corresponding to the time interval of two SC-FDMA symbols in the special subframe  504  of the TDD cell  502 . For the FDD cell  501 , UE does not transmit PUSCH in the interval  510  of the last SC-FDMA symbol which overlaps with the transmission time point of the second SRS symbol  509  of the UpPTS interval  507 . UE is capable of performing rate matching for channel-encoded uplink data during a time interval, except for the last SC-FDMA symbol location  510  and RS symbol locations  512  and  513 , within a corresponding subframe  503  of the FDD cell  501 , thereby configuring and transmitting a PUSCH ( 511 ). Therefore, from the point of view of UE transmitting uplink signals, a case is avoided where simultaneous uplink signal transmissions to the FDD cell  501  and the TDD cell  502  occur at a certain time point during the interval of the subframe  503  of the FDD cell  501  or the special subframe  504  of the TDD cell  502 , thereby resolving the problem that the sum of the PUSCH transmission power and the SRS transmission power exceeds the maximum allowable transmission power of UE. Method  1  has a feature so that it does not transmit each of PUSCH and SRS, symbol by symbol, and thus does not cause excessive transmission loss in transmitting each of the PUSCH and SRS. 
     2) Method  2   
       FIG. 6  is a diagram showing Method  2  according to a first embodiment of the present invention. 
     Referring to  FIG. 6 , Method  2  is described below. According to Method  2 , UE transmits both the first SRS symbol  608  and the second SRS symbol  609  during the UpPTS interval  607  corresponding to the time interval of two SC-FDMA symbols in the special subframe  604  of the TDD cell  602 . For the FDD cell  601 , UE does not transmit PUSCH in intervals  610  and  611  of the last, two SC-FDMA symbols which overlap with transmission time points of the first SRS symbol  608  and the second SRS symbol  609  in the UpPTS interval  607 . UE is capable of performing rate matching for channel-encoded uplink data during a time interval, except for the intervals  610  and  611  of the last two SC-FDMA symbols and RS symbol locations  613  and  614 , within a corresponding subframe  603  of the FDD cell  601 , thereby configuring and transmitting a PUSCH ( 612 ). Unlike the SRS, when an error occurs in PUSCH transmitted via a current subframe, the error can be corrected by HARQ and re-transmission. As described above, Method  2  has a feature so that it prioritizes the transmission of SRS whenever possible. 
     3) Method  3   
       FIG. 7  is a diagram showing Method  3  according to a first embodiment of the present invention. 
     Referring to  FIG. 7 , Method  3  is described below. According to Method  3 , UE does not transmit the first SRS symbol  708  and the second SRS symbol  709  during the UpPTS interval  707  corresponding to the time interval of two SC-FDMA symbols in the special subframe  704  of the TDD cell  702 . For the FDD cell  701 , UE is capable of performing rate matching for channel-encoded uplink data over SC-FDMA symbols, except for the RS symbol locations  711  and  712 , within a subframe  703 , thereby configuring and transmitting a PUSCH ( 710 ). Method  3  has a feature so that it prioritizes the transmission of PUSCH over the transmission of SRS. 
     4) Method  4   
       FIG. 8  is a diagram showing Method  4  according to a first embodiment of the present invention. 
     Referring to  FIG. 8 , Method  4  is described below. According to Method  4 , UE transmits both the first SRS symbol  808  and the second SRS symbol  809  during the UpPTS interval  807  corresponding to the time interval of two SC-FDMA symbols in the special subframe  804  of the TDD cell  802 . For the FDD cell  801 , UE performs rate matching for channel-encoded uplink data over SC-FDMA symbols, except for the RS symbol locations  811  and  812 , within a subframe  803 , thereby configuring and transmitting a PUSCH ( 810 ). 
     In this case, the PUSCH transmission power or the SRS transmission power is adjusted so that the sum of the PUSCH transmission power and the SRS transmission power can be maintained within the maximum allowable transmission power of UE, during the UpPTS interval  807  where uplink signals are simultaneously transmitted to the FDD cell  801  and TDD cell  802 . For example, when the PUSCH transmission has priority, the SRS transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE, during UpPTS interval  807 . Alternatively, when the SRS transmission has priority, the PUSCH transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE, during UpPTS interval  807 . Alternatively, each of the SRS transmission power and the PUSCH transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE, during UpPTS interval  807 . 
     In general, the PUSCH transmission power is constantly maintained within one subframe transmitting PUSCH, thereby simplifying operations of the receiver. Therefore, according to an embodiment, when PUSCH transmission power is adjusted during the SC-FDMA symbol interval overlapping with the UpPTS interval  807  and PUSCH is transmitted, the value of adjusted PUSCH transmission power can also be applied to the interval of the remaining symbols transmitting PUSCH in the subframe as well as the SC-FDMA symbol interval overlapping with the UpPTS interval  807 . 
     When transmission power of UE is adjusted, eNB is capable of: determining a condition as to whether it prioritizes the SRS signal transmission or the PUSCH signal transmission or equalizes the SRS signal transmission and the PUSCH signal transmission regardless of the priority; and then informing the UE of the condition via higher-layer signaling. 
     In addition, one of the Method  1  to Method  4  is pre-defined as a method to be applied or eNB informs UE of the pre-defined method via higher-layer signaling. Alternatively, in another embodiment, one of the Method  1  to Method  4  may be defined as a method to be applied according to a condition as to whether the PUSCH transmission is initial transmission or re-transmission. For example, when the PUSCH transmission is initial transmission, Method  3  where the PUSCH transmission has priority is applied. When the PUSCH transmission is re-transmission, Method  2  where the SRS transmission has priority is applied. When the PUSCH transmission is re-transmission, the receiver of the eNB has a higher probability of successfully decoding PUSCH via an HARQ process combining the initially transmitted PUSCH with the re-transmitted PUSCH. Therefore, the SRS transmission has a relatively high priority in re-transmitting PUS CH. 
     Second Embodiment 
     In a second embodiment, specified operations are defined when UE needs to simultaneously transmit a PUSCH to an FDD cell and an SRS to a TDD cell, under the condition shown in  FIG. 4 . The second embodiment provides a method for UE to transmit two SRS symbols to a TDD cell and a PUSCH and an SRS to an FDD cell, during a UpPTS interval. 
     1) Method  1   
       FIG. 9  is a diagram showing Method  1  according to a second embodiment of the present invention. 
     Referring to  FIG. 9 , Method  1  is described below. According to Method  1 , of the two SRS symbols to be transmitted via a TDD cell  902 , UE transmits only the second SRS symbol  909 , without transmitting the first SRS symbol  908 . In addition, Method  1  maps an SRS to be transmitted via an FDD cell  901  to the last symbol in a subframe  903  and transmits the result to the FDD cell  901  ( 910 ). Additionally, Method  1  performs rate matching for data to be transmitted to the FDD cell  901  during a time interval, except for RS symbol locations  912  and  913  and the last symbol location  910 , transmitting an SRS in the subframe  903 , thereby configuring and transmitting a PUSCH ( 911 ). 
     In this case, UE is capable of adjusting transmission power of SRS  910  transmitted to an FDD cell  901  and transmission power of SRS  909  transmitted to a TDD cell  902 , respectively, so that the sum of the transmission power of SRS  910  and the transmission power of SRS  909  does not exceed the maximum allowable transmission power of UE. The quantity of SRS transmission power to be adjusted may be determined according to the priority. For example, when SRS symbols  910  and  909 , transmitted to an FDD cell  901  and a TDD cell  902 , respectively, have the same degree of importance, the transmission power of SRS  910  transmitted to an FDD cell  901  and the transmission power of SRS  909  transmitted to a TDD cell  902  is reduced by the same proportion, so that the sum of the adjusted transmission power of SRS  910  and the adjusted transmission power of SRS  909  does not exceed the maximum allowable transmission power of UE. When SRS  910  transmitted to an FDD cell  901  has priority, the transmission power of SRS  909  transmitted to a TDD cell  902  is reduced by a relatively larger proportion and the transmission power of SRS  910  transmitted to an FDD cell  901  is reduced by a relatively smaller proportion or not reduced, so that the sum of the adjusted transmission power of SRS  910  and the adjusted transmission power of SRS  909  does not exceed the maximum allowable transmission power of UE. According to embodiments, eNB may determine the priority between SRSs to be transmitted and inform UE of the determined priority via higher-layer signaling. 
     2) Method  2   
       FIG. 10  is a diagram showing Method  2  according to a second embodiment of the present invention. 
     Referring to  FIG. 10 , Method  2  is described below. According to Method  2 , UE transmits both the first SRS symbol  1008  and the second SRS symbol  1009  during the UpPTS interval  1007  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1004  of the TDD cell  1002 . 
     SRS to be transmitted to an FDD cell  1001  is mapped to the last symbol  1001  in a subframe  1003  and then transmitted thereto. Like Method  1 , UE is capable of adjusting transmission power of SRS  1010  transmitted to an FDD cell  1001  and transmission power of SRS  1009  transmitted to a TDD cell  1002 , respectively, according to the priority between SRSs to be transmitted, so that the sum of the transmission power of SRS  1010  and the transmission power of SRS  1009  does not exceed the maximum allowable transmission power of UE. 
     For uplink data to be transmitted to an FDD cell  1001 , UE performs rate matching for channel-encoded uplink data over intervals except for RS symbol locations  1013  and  1014  and an interval overlapping with the UpPTS interval  1007  within a subframe  1003 , thereby configuring and transmitting a PUSCH ( 1012 ). Therefore, uplink signal transmission is not performed for the last second symbol  1011  of the subframe  1003 . 
     Method  2  has a feature so that it transmits two SRS symbols to a TDD cell  1002  whenever possible, despite PUSCH transmission loss which may be caused due to the decrease in the number of symbols configuring a PUSCH transmitted to the FDD cell  1001 , thereby allowing eNB to relatively precisely measure a channel state of the TDD cell  1002 . 
     3) Method  3   
       FIG. 11  is a diagram showing Method  3  according to a second embodiment of the present invention. 
     Referring to  FIG. 11 , Method  3  is described below. According to Method  3 , UE transmits both the first SRS symbol  1108  and the second SRS symbol  1109  during the UpPTS interval  1107  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1104  of the TDD cell  1102 . In addition, for an FDD cell  1101 , Method  3  maps an SRS to the last symbol  1110  in a subframe  1103  and transmits the result. Additionally, Method  3  performs rate matching for channel-encoded uplink data during a time interval, except for RS symbol locations  1112  and  1113  and the symbol  1110  to which the SRS is mapped, in the subframe  1103 , thereby configuring and transmitting a PUSCH ( 1111 ). 
     In this case, UE is capable of adjusting transmission power of an uplink signal transmitted to an FDD cell  1101  and transmission power of an uplink signal transmitted to a TDD cell  1102 , respectively, so that the sum of the transmission power of an uplink signal transmitted to an FDD cell  1101  and transmission power of an uplink signal transmitted to a TDD cell  1102  does not exceed the maximum allowable transmission power of UE, during the UpPTS interval  1107  where the uplink signal transmissions to the FDD cell  1101  and the TDD cell  1102  are simultaneously performed. In addition, like Method  1 , Method  3  defines the priority according to cells or types of uplink transmission signal, and adjusts the transmission power based on the defined priority. 
     In general, the PUSCH transmission power is constantly maintained within one subframe transmitting PUSCH, thereby simplifying operations of the receiver. Therefore, according to an embodiment, when PUSCH is transmitted with adjusted PUSCH transmission power during the SC-FDMA symbol interval overlapping with the UpPTS interval  1107 , the value of adjusted PUSCH transmission power can also be applied to the interval of the remaining symbols transmitting PUSCH in the subframe as well as the SC-FDMA symbol interval overlapping with the UpPTS interval  1107 . 
     Like the first embodiment, the second embodiment is implemented in such a way that one of the Method  1  to Method  3  is pre-defined as a method to be applied or eNB informs UE of the pre-defined method via higher-layer signaling. Alternatively, in another embodiment, one of the Method  1  to Method  3  may be defined as a method to be applied according to a condition as to whether the PUSCH transmission is initial transmission or re-transmission. For example, when the PUSCH transmission is initial transmission, Method  1  where the PUSCH transmission has priority is applied. When the PUSCH transmission is re-transmission, Method  2  where the SRS transmission has priority is applied. When the PUSCH transmission is re-transmission, the receiver of the eNB has a higher probability of successfully decoding PUSCH via an HARQ process combining the initially transmitted PUSCH with the re-transmitted PUSCH. Therefore, the SRS transmission has a relatively high priority in re-transmitting PUSCH. 
     The first and second embodiments may also be modified in such a way to define operations regarding a case that UE transmits a PUSCH to an FDD cell and a random access preamble to a TDD cell during the interval of UpPTS  2  symbol. In general, PUSCH is processed for its additional error correction by the HARQ process. When the transmission time points of the PUSCH and the random access preamble overlap with each other, the modifications may prioritize the transmission of a random access preamble. Since the length of a random access preamble in a UpPTS interval is fixed to an interval of 2 symbols, the modifications may also employ Method  2  and Method  4  of the first embodiment and Method  2  and Method  3  of the second embodiment, which can transmit  2  symbol unlink signals in UpPTS. In this case, its detailed description can be substituted by those of the first and second embodiments where the SRS is only replaced with a random access preamble. In order to prevent the reception performance degradation of a random access preamble, the transmission power of a random access preamble may be maintained to a constant value during the UpPTS interval. 
     Third Embodiment 
     In a third embodiment, specified operations are defined when UE needs to simultaneously transmit a PUSCH to an FDD cell and an SRS to a TDD cell, under the condition shown in  FIG. 4 . The third embodiment provides a method for UE to transmit an SRS symbol at the first symbol location to a TDD cell during a UpPTS interval. 
     1) Method  1   
       FIG. 12  is a diagram showing Method  1  according to a third embodiment of the present invention. 
     According to Method  1 , UE transmits PUSCH to be transmitted to an FDD cell  1201  thereto by using the entire symbol in a subframe, without transmitting an SRS symbol to be transmitted to a TDD cell  1202 . Referring to  FIG. 12 , Method  1  is described below. UE does not transmit an SRS symbol  1208  required to be transmitted, in a special subframe  1204  of a TDD cell  1202 . For the FDD cell  1201 , UE performs rate matching for channel-encoded uplink data over an interval of symbols that excludes RS symbol locations  1210  and  1211  from the entire symbol in the subframe  1203 , including an interval overlapping with the UpPTS interval  1207 , thereby configuring and transmitting a PUSCH ( 1209 ). Therefore, from the point of view of UE transmitting uplink signals, a case is avoided where simultaneous uplink signal transmissions to the FDD cell  1201  and the TDD cell  1202  occur at a certain time point during the interval of the subframe  1203  or the special subframe  1204 , thereby resolving the problem that the sum of the PUSCH transmission power and the SRS transmission power exceeds the maximum allowable transmission power of UE. Method  1  has a feature so that it does not transmit SRS of a TDD cell  1202  and thus prioritizes the transmission of PUSCH. 
     2) Method  2   
       FIG. 13  is a diagram showing Method  2  according to a third embodiment of the present invention. 
     Referring to  FIG. 13 , Method  2  is described below. According to Method  2 , UE transmits an SRS symbol  1308  at the first symbol location of the UpPTS interval  1307  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1304  of the TDD cell  1302 . For the FDD cell  1301 , UE does not transmit PUSCH in an interval  1310  of an SC-FDMA symbol which overlaps with the transmission time point of the SRS symbol  1308  during the UpPTS interval  1307 . UE performs rate matching for channel-encoded uplink data, during time intervals  1309  and  1311 , except for RS symbol locations  1312  and  1313  and SC-FDMA symbol location  1310  overlapping with the transmission time point of the SRS symbol  1308 , within a corresponding subframe  1303  of the FDD cell  1301 , thereby configuring and transmitting a PUSCH. 
     3) Method  3   
       FIG. 14  is a diagram showing Method  3  according to a third embodiment of the present invention. 
     Referring to  FIG. 14 , Method  3  is described below. According to Method  3 , UE transmits an SRS symbol  1408  at the first symbol location during the UpPTS interval  1407  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1404  of the TDD cell  1402 . For the FDD cell  1401 , UE performs rate matching for channel-encoded uplink data over intervals, except for RS symbol locations  1412  and  1413  and the last two SC-FDMA symbols  1410  and  1411  within the subframe  1403  overlapping with a transmission time point of the UpPTS  1407 , thereby configuring and transmitting a PUSCH ( 1409 ). Method  3  has a feature so that it prioritizes the transmission of SRS over the transmission of PUSCH. 
     4) Method  4   
       FIG. 15  is a diagram showing Method  4  according to a third embodiment of the present invention. 
     Referring to  FIG. 15 , Method  4  is described below. According to Method  4 , UE transmits an SRS symbol  1508  at the first symbol location during the UpPTS interval  1507  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1504  of the TDD cell  1502 . For the FDD cell  1501 , UE performs rate matching for channel-encoded uplink data over symbols except for the RS symbol locations  1511  and  1512 , within a subframe  1503 , thereby configuring and transmitting a PUSCH ( 1410 ). 
     In this case, the PUSCH transmission power or the SRS transmission power is adjusted so that the sum of the PUSCH transmission power and the SRS transmission power can be maintained within the maximum allowable transmission power of UE in the location of an SRS symbol  1508  of the UpPTS interval  1507  where uplink signals are simultaneously transmitted to the FDD cell  1501  and the TDD cell  1502 . For example, when the PUSCH transmission has priority, the SRS transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE in the location of the SRS symbol  1508 . Alternatively, when the SRS transmission has priority, the PUSCH transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE in the location of the SRS symbol  1508 . Alternatively, each of the SRS transmission power and the PUSCH transmission power is adjusted to a value less than a required level of transmission power, so that the sum of the PUSCH transmission power and the SRS transmission power is maintained within the maximum allowable transmission power of UE in the location of the SRS symbol  1508 . 
     In general, the PUSCH transmission power is constantly maintained within one subframe transmitting PUSCH, thereby simplifying operations of the receiver. Therefore, according to an embodiment, when PUSCH transmission power is adjusted in the location of the SRS symbol  1508  and PUSCH is transmitted, the value of adjusted PUSCH transmission power can also be applied to the interval of the remaining symbols transmitting PUSCH in the subframe as well as the SC-FDMA symbol interval overlapping with the location where the SRS symbol  1508  is transmitted during the UpPTS interval  1507 . 
     When the transmission power of UE is adjusted, eNB is capable of determining a condition as to whether it prioritizes the SRS signal transmission or the PUSCH signal transmission or equalizes the SRS signal transmission and the PUSCH signal transmission regardless of the priority, and then informing the UE of the condition via higher-layer signaling. 
     In addition, one of the Method  1  to Method  4  is pre-defined as a method to be applied or eNB informs UE of the pre-defined method via higher-layer signaling. Alternatively, in another embodiment, one of the Method  1  to Method  4  may be defined as a method to be applied according to a condition as to whether the PUSCH transmission is initial transmission or re-transmission. For example, when the PUSCH transmission is initial transmission, Method  1  where the PUSCH transmission has priority is applied. When the PUSCH transmission is re-transmission, Method  2  or Method  3  where the SRS transmission has priority is applied. When the PUSCH transmission is re-transmission, the receiver of the eNB has a higher probability of successfully decoding PUSCH via an HARQ process combining the initially transmitted PUSCH with the re-transmitted PUSCH. Therefore, the SRS transmission has a relatively high priority in re-transmitting PUSCH. 
     Fourth Embodiment 
     In a fourth embodiment, specified operations are defined when UE needs to simultaneously transmit a PUSCH to an FDD cell and an SRS to a TDD cell, under the condition shown in  FIG. 4 . The fourth embodiment provides a method for UE to transmit an SRS symbol at the first symbol location to a TDD cell and a PUSCH and an SRS to an FDD cell, during a UpPTS interval. 
     1) Method  1   
       FIG. 16  is a diagram showing Method  1  according to a fourth embodiment of the present invention. 
     Referring to  FIG. 16 , Method  1  is described below. According to Method  1 , UE maps an SRS to be transmitted to an FDD cell  1601  to the last symbol in a subframe  1603  and transmits the result to the FDD cell  1601 , without transmitting an SRS symbol to be transmitted to a TDD cell  1602  ( 1610 ). Additionally, Method  1  performs rate matching for data to be transmitted to the FDD cell  1601  during a time interval, except for RS symbol locations  1612  and  1613  and the last symbol interval  1610  transmitting an SRS in the subframe  1603 , thereby configuring and transmitting a PUSCH ( 1611 ). Method  1  has a feature so that it prioritizes the transmission of uplink signals, i.e., the transmission of PUSCH and SRS, to the FDD cell  1601  to have priority. 
     2) Method  2   
       FIG. 17  is a diagram showing Method  2  according to a fourth embodiment of the present invention. 
     Referring to  FIG. 17 , Method  2  is described below. According to Method  2 , UE transmits an SRS symbol  1708  at the first symbol location of the UpPTS interval  1707  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1704  of the TDD cell  1702 . 
     According to Method  2 , UE maps an SRS to be transmitted to an FDD cell  1701  to the last symbol in a subframe  1703  and transmits the result to the FDD cell  1701  ( 1710 ). For uplink data to be transmitted to an FDD cell  1701 , UE performs rate matching for channel-encoded uplink data over intervals except for RS symbol locations  1712  and  1713  and a UpPTS interval  1707  within a subframe  1703 , thereby configuring and transmitting a PUSCH ( 1711 ). Therefore, uplink signal transmission is not performed for the last second symbol  1709  of the subframe  1703 . 
     Method  2  has a feature so that it transmits SRS symbols to a TDD cell  1702  whenever possible, despite PUSCH transmission loss which may be caused due to the decrease in the number of symbols configuring a PUSCH transmitted to the FDD cell  1701 , thereby allowing eNB to measure a channel state of the TDD cell  1702 . 
     3) Method  3   
       FIG. 18  is a diagram showing Method  3  according to a fourth embodiment of the present invention. 
     Referring to  FIG. 18 , Method  3  is described below. According to Method  3 , UE transmits an SRS symbol  1808  at the first symbol location during the UpPTS interval  1807  corresponding to the time interval of two SC-FDMA symbols in the special subframe  1804  of the TDD cell  1802 . In addition, for an FDD cell  1801 , Method  3  maps an SRS to the last symbol  1810  in a subframe  1803  and transmits the result. Additionally, Method  3  performs rate matching for channel-encoded uplink data during time intervals, except for RS symbol locations  1811  and  1812  and the symbol  1810  to which the SRS is mapped, in the subframe  1803  of the FDD cell  1801 , thereby configuring and transmitting a PUSCH ( 1809 ). 
     In this case, UE is capable of adjusting transmission power of an uplink signal transmitted to an FDD cell  1801  and transmission power of an uplink signal transmitted to a TDD cell  1802 , respectively, so that the sum of the transmission power of an uplink signal transmitted to an FDD cell  1801  and transmission power of an uplink signal transmitted to a TDD cell  1802  does not exceed the maximum allowable transmission power of UE, in the SRS symbol location  1808  of the TDD cell  1802  where the uplink signal transmissions to the FDD cell  1801  and the TDD cell  1802  are simultaneously performed. In addition, like Method  4  of the third embodiment, Method  3  defines the priority according to cells or types of uplink transmission signals, and adjusts the transmission power based on the defined priority. 
     In general, the PUSCH transmission power is constantly maintained within one subframe transmitting PUSCH, thereby simplifying operations of the receiver. Therefore, according to an embodiment, when PUSCH transmission power is adjusted in a location in an FDD cell  1801 , corresponding to a location of the SRS symbol  1808 , and the PUSCH is transmitted, the value of adjusted PUSCH transmission power can also be applied to the interval of the remaining symbols transmitting PUSCH in the subframe as well as the SC-FDMA symbol interval overlapping with the location where the SRS symbol  1808  is transmitted, during the UpPTS interval  1807 . 
     When the transmission power of UE is adjusted, eNB is capable of determining a condition as to whether it prioritizes the SRS signal transmission or the PUSCH signal transmission or equalizes the SRS signal transmission and the PUSCH signal transmission regardless of the priority, and then informing the UE of the condition via higher-layer signaling. 
     In addition, like the first embodiment, one of the Method  1  to Method  3  may be pre-defined as a method to be applied or eNB may inform UE of the pre-defined method via higher-layer signaling. Alternatively, in another embodiment, one of the Method  1  to Method  3  may be defined as a method to be applied according to a condition as to whether the PUSCH transmission is initial transmission or re-transmission. For example, when the PUSCH transmission is initial transmission, Method  1  where the PUSCH transmission has priority is applied. When the PUSCH transmission is re-transmission, Method  2  where the SRS transmission has priority is applied. When the PUSCH transmission is re-transmission, the receiver of the eNB has a higher probability of successfully decoding PUSCH via an HARQ process combining the initially transmitted PUSCH with the re-transmitted PUSCH. Therefore, the SRS transmission has a relatively high priority in re-transmitting PUSCH. 
     Fifth Embodiment 
     In a fifth embodiment, specified operations are defined when UE needs to simultaneously transmit a PUSCH containing Uplink Control Information (UCI) to an FDD cell and an SRS to a TDD cell, under the condition shown in  FIG. 4 . 
     Uplink Control Information (UCI) refers to control information that UE transmits to eNB via uplink. UCI contains: ACK/NACK representing a condition as to whether downlink data transmitted from eNB to UE fails; Channel Quality Indicator (CQI) representing a status of downlink channel; Rank Indicator (RI) representing a rank of downlink channel; Pre-coding Matrix Indicator (PMI) representing pre-coding information; etc. The ACK/NACK and RI are required to have a relatively high reception capability, compared with the other factors. Therefore, when ACK/NACK and RI are multiplexed with uplink data on PUSCH, the mapping located on the time domain is fixed to be near the RS. This results in a relatively high channel estimation gain, and also a relatively high reception capability. 
       FIG. 19  is a diagram showing a method according to a fifth embodiment of the present invention. 
     Referring to  FIG. 19 , ACK/NACK may be multiplexed with uplink data in locations of symbols  1915  and  1916  and symbols  1919  and  1920 , immediately adjacent to RS  1909  and RS  1910 , respectively, in the subframe. RI may be multiplexed with uplink data in the locations of symbols  1914 ,  1917 ,  1918 , and  1921  adjacent to the mapping locations of the ACK/NACK. 
     When an SRS is transmitted during the UpPTS interval  1907  of the TDD cell  1902 , the first to fourth embodiments have part of the methods that are not capable of performing uplink signal transmission to the location of the symbol  1921  to which the RI can be mapped. Therefore, when the RI is multiplexed with uplink data and the result is transmitted, a method capable of guaranteeing transmission of the symbol  1921  may be employed, e.g., Method  1 , Method  3 , and Method  4  of the first embodiment; Method  1  and Method  3  of the second embodiment; Method  1  and Method  4  of the third embodiment; and Method  1  and Method  3  of the fourth embodiment. 
       FIG. 20  is a flowchart that describes operations of eNB according to an embodiment of the present invention. 
     Referring to  FIG. 20 , the eNB is capable of setting a transmission period, resources for SRS transmission, etc., as control information regarding SRS transmission of UE, and notifies the UE of the settings in operation  2001 . The control information may be configured via higher-layer signaling. 
     The eNB assigns a schedule to UE so that UE can transmit PUSCH in the n th  subframe (subframe n) in operation  2002 . The eNB determines whether the transmission time points of SRS and PUSCH of the UE overlap with each other within the n th  subframe in operation  2003 . 
     When the eNB ascertains that the transmission time points of SRS and PUSCH of the UE do not overlap with each other within the n th  subframe in operation  2003 , it is capable of receiving PUSCH transmitted from the UE, in the n th  subframe in operation  2005 . 
     On the other hand, when the eNB ascertains that the transmission time points of SRS and PUSCH of the UE overlap with each other within the n th  subframe in operation  2003 , it is capable of receiving PUSCH and SRS from the UE, by using methods of the first to fifth embodiments in operation  2004 . Since those methods were described above, their detailed description is omitted below. A method to be applied may be pre-determined between UE and eNB. Alternatively, eNB informs UE of the pre-defined method via higher-layer signaling. The process of higher-layer signaling may be performed before operation  2002  where eNB makes a schedule to enable UE to transmit PUSCH in operation  2002 . 
       FIG. 21  is a flowchart that describes operations of UE according to an embodiment of the present invention. 
     Referring to  FIG. 21 , the UE is capable of obtaining a transmission period, resources for SRS transmission, etc., as control information regarding SRS transmission, from eNB in operation  2101 . The control information may be configured via higher-layer signaling. 
     The UE is scheduled by eNB to transmit PUSCH in the n th  subframe (subframe n) in operation  2102 . The UE determines whether the transmission time points of SRS and PUSCH overlap with each other within the n th  subframe in operation  2103 . 
     When the UE ascertains that the transmission time points of SRS and PUSCH do not overlap with each other within the n th  subframe in operation  2103 , it is capable of transmitting PUSCH in the n th  subframe in operation  2105 . 
     On the other hand, when the UE ascertains that the transmission time points of SRS and PUSCH overlap with each other within the n th  subframe in operation  2103 , it is capable of transmitting SRS and PUSCH, using methods of the first to fifth embodiments, in the n th  subframe in operation  2104 . Since its detailed description was described in the previous embodiments, it is omitted below. 
       FIG. 22  is a block diagram showing a transmitting device of UE according to an embodiment of the present invention. 
     For the sake of the convenience, detailed descriptions of well-known functions and structures incorporated herein are omitted to avoid obscuring the subject matter of the invention. Referring to  FIG. 22 , UE is capable of including an FDD cell transmitter  2230 , a TDD cell transmitter  2250  and a controller  2210 . The FDD cell transmitter  2230  includes a PUSCH block  2231 , a multiplexer  2233 , and a transmitting RF block  2235 . The TDD cell transmitter  2250  includes an SRS block  2251 , a multiplexer  2253 , and a transmitting RF block  2255 . The controller  2210  is capable of controlling the components, included in the FDD cell transmitter  2230  and the TDD cell transmitter  2250 , to perform operations related to the PUSCH transmission and SRS transmission by the UE, using the methods of the embodiments described above, referring to control information received from the eNB. 
     The PUSCH block  2231  of the FDD cell transmitter  2230  creates PUSCH for uplink data by performing processes, such as channel-encoding, modulation, etc. When the UE has uplink transmission signals to be transmitted to an FDD cell, the multiplexer  2233  multiplexes the uplink transmission signals with the created PUSCH. The transmitting RF block  2235  processes the multiplexed signals and transmits the processed signals to the eNB. 
     The SRS block  2251  of the TDD cell transmitter  2250  creates an SRS signal according to the settings of eNB. When the UE has uplink transmission signals to be transmitted to a TDD cell, the multiplexer  2253  multiplexes the uplink transmission signals with the created SRS signal. The transmitting RF block  2255  processes the multiplexed signals and transmits the processed signals to the eNB. 
       FIG. 23  is a block diagram showing a receiving device of eNB according to an embodiment of the present invention. 
     Referring to  FIG. 23 , the eNB is capable of including an FDD cell receiver  2330 , a TDD cell receiver  2350  and a controller  2310 . The FDD cell receiver  2330  includes a PUSCH block  2331 , a de-multiplexer  2333 , and a receiving RF block  2335 . The TDD cell receiver  2350  includes an SRS block  2351 , a de-multiplexer  2353 , and a receiving RF block  2355 . The controller  2310  is capable of controlling the components, included in the FDD cell receiver  2330  and the TDD cell receiver  2350 , to perform operations of the eNB related to the reception of SRS and PUSCH transmitted from the UE, using the methods of the embodiments described above. 
     The FDD cell receiver  2330 : processes signals received from the UE via the receiving RF block  2335 ; separates a PUSCH signal from the processed signals via the de-multiplexer  2333 ; and performs processes, such as demodulation, channel-decoding, etc., via the PUSCH block  2331 , thereby obtaining uplink data. 
     The TDD cell receiver  2350 : processes signals received from the UE via the receiving RF block  2355 ; separates an SRS signal from the processed signal via the de-multiplexer  2353 ; and obtains uplink channel status information via the SRS block  2351 . 
     Sixth Embodiment 
       FIG. 24  is a diagram showing a method according to a sixth embodiment of the present invention. 
     In a sixth embodiment, specified operations are defined when UE needs to simultaneously transmit Uplink Control Information (UCI) to an FDD cell  2401 , via a Physical Uplink Control Channel (PUCCH)  2411  for transmitting control information, and an SRS to a TDD cell  2402 . Since the UCI was described, in detail, in the fifth embodiment, its description is omitted below. 
     1) Method  1   
     Method  1  is related to a case where the transmission interval of SRS is the last one symbol within a subframe. 
     Referring to  FIG. 24 , when the transmission time points of PUCCH  2411  and SRS  2409  overlaps with each other within the same subframe, this case employs a shortened PUCCH format where the last one symbol interval  2410  of the PUCCH  2411  within the subframe is not used for transmission. Therefore, UE is capable of transmitting UCI in the shortened PUCCH format during the time interval except for the last symbol interval  2410 . UE transmits an SRS  2409  during the last symbol interval of the subframe. This process can prevent a case where PUCCH  2411  and SRS  2409  are simultaneously transmitted at the same time point, thereby maintaining the sum of instantaneous transmission power of UE within the maximum allowable transmission power of UE. 
     The UE may be previously notified, from eNB, via signaling, of a condition as to whether it can use the shortened PUCCH format. According to an embodiment, when UE is notified from eNB that it is not allowed to use the shortened PUCCH format and the transmission time points of PUCCH and SRS overlap with each other within the same subframe, it transmits PUCCH during the entire time interval of the subframe; however, it may not transmit SRS. 
     2) Method  2   
     Method  2  is related to a case where the transmission interval of SRS is the last two symbols or the second-to-last symbol within a subframe. 
     As shown in  FIG. 4 , when the UpPTS  407  in a special subframe of the TDD cell  402  is set to have a length corresponding to two SC-FDMA symbols, and SRS transmission to the TDD cell  402  is performed over the two symbols of the UpPTS  407  or in the first symbol interval of the UpPTS  407 , there is a need to define operations that differ from those of the Method  1 . 
     That is, when UE is notified from eNB that it is allowed to use the shortened PUCCH format and the transmission time points of PUCCH  2411  and SRS overlap with each other within the same subframe, the UE is capable of transmitting UCI in the shortened PUCCH format during the time interval except for the last one symbol interval  2410  of the subframe. UE transmits the SRS  2409  of the TDD cell  2402  in the last symbol interval of the subframe. UE does not transmit an SRS of the TDD cell  2402  which has been planned to be transmitted in the interval of the second-to-last symbol  2408  within the subframe. 
     On the other hand, when UE is notified from eNB that it is not allowed to use the shortened PUCCH format and the transmission time points of PUCCH and SRS overlap with each other within the same subframe, it transmits PUCCH  2411  during the entire time interval of the subframe but does not transmit SRS. 
     Referring to  FIG. 24 , when UE is set to use the shortened PUCCH format, a detailed description regarding Method  2  is provided as follows. 
     In a condition where UE is set to use the shortened PUCCH format, the UE does not transmit the first SRS symbol  2408  but transmits the second SRS symbol  2409  during the UpPTS interval  2407  corresponding to a time interval of the two SC-FDMA symbols in the special subframe  2404  of the TDD cell  2402 . In this case, for the FDD cell  2401 , UE does not transmit PUCCH in the last SC-FDMA symbol interval  2410  overlapping with the transmission time point of the second SRS symbol  2409  of the UpPTS interval  2407 . In addition, UE is capable of: configuring PUCCH  2411  in the shortened PUCCH format, from channel-encoded UCI, during a time interval except for the last SC-FDMA symbol location  2410  and RS symbol locations  2412  and  2413 , within a corresponding subframe  2403  of an FDD cell  2401 ; and transmitting it. According to embodiments, RS symbol locations  2412  and  2413  in transmission of PUCCH may differ from RS symbol locations (e.g.,  512  and  513  shown in  FIG. 5 ) in transmission of PUSCH. 
       FIG. 25  is a flowchart that describes operations of eNB according to a sixth embodiment of the present invention. 
     Referring to  FIG. 25 , the eNB sets control information related PUCCH transmission of UE and notifies the UE of the settings in operation  2501 . The control information may contain a condition as to whether UE is allowed to use a shortened PUCCH format, etc. According to embodiments, the control information may be configured via higher-layer signaling. 
     The eNB is capable of setting control information regarding SRS transmission of UE, such as a transmission period, resources for SRS transmission, etc., and notifies the UE of the settings in operation  2502 . According to embodiments, the control information may be configured via higher-layer signaling. 
     The embodiment may also be modified in such a way that operation  2502  is performed earlier than operation  2501  or they are simultaneously performed. 
     The eNB determines whether the transmission time points of SRS and PUCCH for UCI transmission of the UE overlap with each other within the n th  subframe (subframe #n) used to receive uplink signals from the UE in operation  2503 . The eNB may determine the SRS transmission time point of the UE based on the information set in operation  2502 . According to embodiments, when the eNB transmits downlink data to the UE at a time point of subframe #n-4 corresponding to subframe #n, it detects that the UE has sent the subframe #n containing HARQ-ACK/NACK via PUCCH. 
     When the eNB ascertains that the transmission time points of SRS and PUCCH of the UE do not overlap with each other in operation  2503 , it is capable of receiving PUCCH transmitted from the UE via the subframe #n in operation  2506 . In this case, the PUCCH is a general PUCCH which does not have a shortened PUCCH format. 
     On the other hand, when the eNB ascertains that the transmission time points of SRS and PUCCH of the UE overlap with each other in subframe #n in operation  2503 , it determines whether the UE is set to use a shortened PUCCH format in operation  2504 . 
     When the eNB ascertains that the UE is set to use a shortened PUCCH format in operation  2504 , it is capable of receiving SRS and PUCCH in the shortened PUCCH format from the UE, according to Method  1  or Method  2  of the sixth embodiment, in operation  2505 . That is, when the transmission interval of SRS is the last one symbol within a subframe, the eNB is capable of receiving SRS and PUCCH via Method  1  of the sixth embodiment. When the transmission interval of SRS is the last two symbols or the second-to-last symbol in a special subframe, the eNB is capable of receiving SRS and PUCCH via Method  2  of the sixth embodiment. Since the detailed description was explained in the previous embodiments, it is omitted below. 
     On the other hand, when the eNB ascertains that the UE is not set to use a shortened PUCCH format in operation  2504 , it is capable of receiving PUCCH transmitted from the UE in operation  2506 . In this case, the PUCCH is a general PUCCH which does not have a shortened PUCCH format. 
       FIG. 26  is a flowchart that describes operations of UE according to a sixth embodiment of the present invention. 
     Referring to  FIG. 26 , the UE obtains the setup information related to PUCCH transmission from eNB in operation  2601 . The setup information may contain control information, such as a condition as to whether UE is allowed to use a shortened PUCCH format, etc. 
     The UE is capable of obtaining control information regarding SRS transmission, from the eNB, such as a transmission period, resources for SRS transmission, etc., in operation  2602 . According to embodiments, the control information may be configured via higher-layer signaling. 
     The embodiment may also be modified in such a way that operation  2602  is performed earlier than operation  2601  or they are simultaneously performed. 
     The UE determines whether the transmission time points of SRS and PUCCH overlap with each other within the n th  subframe (subframe #n) in operation  2603 . The UE may determine the SRS transmission time point based on the SRS setup information obtained in operation  2602 . According to embodiments, when the eNB transmits downlink data to the UE at a time point of subframe #n-4 corresponding to subframe #n, the UE sends the subframe #n containing HARQ-ACK/NACK via PUCCH. 
     When the UE ascertains that the transmission time points of SRS and PUCCH do not overlap with each other within the subframe #n in operation  2603 , it is capable of transmitting PUCCH via the subframe #n in operation  2606 . In this case, the PUCCH is a general PUCCH which does not have a shortened PUCCH format. 
     On the other hand, when the UE ascertains that the transmission time points of SRS and PUCCH overlap with each other within the subframe #n in operation  2603 , it determines whether it is set to use a shortened PUCCH format according to the setup information of the eNB in operation  2604 . 
     When the UE ascertains that it is set by the eNB to use a shortened PUCCH format in operation  2604 , it is capable of transmitting SRS and PUCCH in the shortened PUCCH format, according to Method  1  or Method  2  of the sixth embodiment, in operation  2605 . That is, when the transmission interval of SRS is the last one symbol within a subframe, the UE is capable of receiving SRS and PUCCH via Method  1  of the sixth embodiment. When the transmission interval of SRS is the last two symbols or the second-to-last symbol in a special subframe, the UE is capable of receiving SRS and PUCCH via Method  2  of the sixth embodiment. Since the detailed description was explained in the previous embodiments, it is omitted below. 
     On the other hand, when the UE ascertains that it is not set by the eNB to use a shortened PUCCH format in operation  2604 , it is capable of transmitting PUCCH in operation  2606 . In this case, the PUCCH is a general PUCCH which does not have a shortened PUCCH format. 
       FIG. 27  is a block diagram showing a transmitting device of UE according to another embodiment of the present invention. 
     For the sake of the convenience, detailed descriptions of well-known functions and structures incorporated herein are omitted to avoid obscuring the subject matter of the invention. Referring to  FIG. 27 , UE is capable of including an FDD cell transmitter  2730 , a TDD cell transmitter  2750  and a controller  2710 . The FDD cell transmitter  2730  includes a PUCCH block  2731 , a multiplexer  2733 , and a transmitting RF block  2735 . The TDD cell transmitter  2750  includes an SRS block  2751 , a multiplexer  2753 , and a transmitting RF block  2755 . The controller  2710  is capable of controlling the components, included in the FDD cell transmitter  2730  and the TDD cell transmitter  2750 , to perform operations related to the PUCCH transmission and SRS transmission by the UE, using the method of the sixth embodiment described above, referring to control information received from the eNB. 
     The PUCCH block  2731  of the FDD cell transmitter  2730  creates PUCCH for UCI by performing processes, such as channel-encoding, modulation, etc. When the UE has uplink transmission signals to be transmitted to an FDD cell, the multiplexer  2733  multiplexes the uplink transmission signals with the created PUCCH. The transmitting RF block  2735  processes the multiplexed signals and transmits the processed signals to the eNB. 
     The SRS block  2751  of the TDD cell transmitter  2750  creates an SRS signal according to the settings of eNB. When the UE has uplink transmission signals to be transmitted to a TDD cell, the multiplexer  2753  multiplexes the uplink transmission signals with the created SRS signal. The transmitting RF block  2755  processes the multiplexed signals and transmits the processed signals to the eNB. 
     Although it is not shown, the FDD cell transmitter  2730  of the UE may further include a PUSCH block. In this case, the controller  2710  is capable of controlling the components, included in the FDD cell transmitter  2730  and the TDD cell transmitter  2750 , to perform operations related to the PUSCH transmission and SRS transmission by the UE, using the methods of the first to fifth embodiments described above, referring to control information received from the eNB. 
       FIG. 28  is a block diagram showing a receiving device of eNB according to another embodiment of the present invention. 
     Referring to  FIG. 28 , the eNB is capable of including an FDD cell receiver  2830 , a TDD cell receiver  2850  and a controller  2810 . The FDD cell receiver  2830  includes a PUCCH block  2831 , a de-multiplexer  2833 , and a receiving RF block  2835 . The TDD cell receiver  2850  includes an SRS block  2851 , a de-multiplexer  2853 , and a receiving RF block  2855 . The controller  2810  is capable of controlling the components, included in the FDD cell receiver  2830  and the TDD cell receiver  2850 , to perform operations of the eNB related to the reception of SRS and PUCCH transmitted from the UE, using the methods of the sixth embodiment described above. 
     The FDD cell receiver  2830 : processes signals received from the UE via the receiving RF block  2835 ; separates a PUCCH signal from the processed signals via the de-multiplexer  2833 ; and performs processes, such as demodulation, channel-decoding, etc., via the PUCCH block  2831 , thereby obtaining UCI. 
     The TDD cell receiver  2850 : processes signals received from the UE via the receiving RF block  2855 ; separates an SRS signal from the processed signal via the de-multiplexer  2853 ; and obtains uplink channel status information via the SRS block  2851 . 
     Although it is not shown, the FDD cell receiver  2830  of the eNB may further include a PUSCH block. In this case, the controller  2810  is capable of controlling the components, included in the FDD cell receiver  2830  and the TDD cell receiver  2850 , to perform operations of the eNB related to the reception of SRS and PUSCH transmitted from the UE, using the methods of the first to fifth embodiments described above. 
     The embodiments of the present invention described in the description and drawings are merely provided to assist in a comprehensive understanding of the invention and are not suggestive of limitation. It should be understood that the invention may include all modifications and/or equivalents and/or substitutions included in the idea and technical scope of the present disclosure. 
     Although embodiments of the invention have been described in detail above, it should be understood that many variations and modifications of the basic inventive concept herein described, which may be apparent to those skilled in the art, will still fall within the spirit and scope of the embodiments of the invention as defined in the appended claims.