Patent Publication Number: US-11051281-B2

Title: Method and apparatus for transmitting and receiving uplink channel sounding reference signals in a wireless communication system

Description:
PRIORITY 
     This application is a Continuation Application of U.S. application Ser. No. 14/673,302, which was filed in the U.S. Patent and Trademark Office (USPTO) on Mar. 30, 2015, and issued as U.S. Pat. No. 9,986,538 on May 29, 2018, which is a Continuation Application of U.S. application Ser. No. 13/665,450, which was filed in the USPTO on Oct. 31, 2012, and issued as U.S. Pat. No. 8,995,563 on Mar. 31, 2015, which is a Continuation Application of U.S. application Ser. No. 12/110,828, which was filed in the USPTO on Apr. 28, 2008, and issued as U.S. Pat. No. 8,335,276, issued on Dec. 18, 2012, which claims priority under 35 U.S.C. § 119(a) to a Korean Patent Application Serial No. 10-2007-0041645, which was filed in the Korean Intellectual Property Office on Apr. 27, 2007, and a Korean Patent Application Serial No. 10-2007-0056836, which was filed in the Korean Intellectual Property Office on Jun. 11, 2007, the content of each of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a Frequency Division Multiple Access (FDMA)-based wireless communication system, and in particular, to a method and apparatus for transmitting and receiving Channel Sounding Reference Signals (CS RS). 
     2. Description of the Related Art 
     Recently, in mobile communication systems, intensive research has been conducted on Orthogonal Frequency Division Multiple Access (OFDMA) or Single Carrier-Frequency Division Multiple Access (SC-FDMA) as a scheme suitable for high-speed data transmission in wireless channels. 
     Presently, the OFDM and SC-FDMA technologies are applied in the downlink and uplink of the Evolved UMTS Terrestrial Radio Access (EUTRA) standard based on Universal Mobile Telecommunication Services (UMTS) defined by the 3 rd  Generation Partnership Project (3GPP). 
     SC-FDMA, a technology that is based on single-carrier transmission while guaranteeing orthogonality between multiple access users like OFDM, is advantageous in that a Peak-to-Average Power Ratio (PAPR) of transmission signals is very low. Therefore, SC-FDMA, when it is applied to the mobile communication system, can bring improvement of the cell coverage due to its low PAPR, compared to the OFDM technology. 
       FIG. 1  illustrates a structure of a general SC-FDMA transmitter and a slot structure, in which Fast Fourier Transform (FFT)  103  and Inverse Fast Fourier Transform (IFFT)  105  are used. 
     Referring to  FIG. 1 , a difference between OFDM and SC-FDMA will be considered in terms of the transmitter structure. Aside from IFFT  105  used for multi-carrier transmission in an OFDM transmitter, FFT  103  further exists in front of the IFFT  105  in an SC-FDMA transmitter. Here, M modulation symbols  100  constitute one block, and the block is input to the FFT  103  with a size M. Each of the blocks will be referred to herein as a ‘Long Block (LB)’, and 7 LBs constitute one 0.5-ms slot  102 . 
     Signals output from the FFT  103  are applied to the IFFT  105  as inputs having consecutive indexes (See  104 ), where the signals undergo inverse Fourier transform, and then are converted into an analog signal (See  106 ) before being transmitted. An input/output size N of the IFFT  105  is greater than an input/output size M of the FFT  103 . The SC-FDMA transmission signal has a lower PAPR than the OFDM signal because the signal processed by means of the FFT  103  and IFFT  105  has single-carrier characteristics. 
       FIG. 2  illustrates exemplary resource partitioning in the frequency-time domain in a EUTRA SC-FDMA system. 
     Referring to  FIG. 2 , a system bandwidth  201  is 10 MHz, and a total of 50 Resource Units (RUs)  202  exist in the system bandwidth  201 . Each RU  202  is composed of 12 subcarriers  203 , can have 14 LBs  204 , and is a basic scheduling unit for data transmission. The 14 LBs  204  constitute one 1-ms subframe  205 . 
       FIG. 3  is a diagram illustrating resource allocation for transmission of a control channel and a data channel in the EUTRA uplink based on the resource partitioning structure of  FIG. 2 . 
     Referring to  FIG. 3 , control information, such as ACKnowledge (ACK)/Negative ACK (NACK) representative of response signals for a Hybrid Automatic Repeat reQuest (HARD) operation for downlink data and Channel Quality Indication (CQI) representative of channel state information for downlink data scheduling, is transmitted through the RUs located in both ends, i.e., RU # 1  and RU # 50  of the system band. Meanwhile, information such as data, Random Access CHannel (RACH) and other control channels, is transmitted through the RUs located in the middle  302  of the system band, i.e., all RUs except for RU # 1  and RU # 50 . 
     Control information transmitted in the first slot  308  of RU # 1  is repeatedly transmitted through RU # 50   311  in the next slot by frequency hopping, thereby obtaining frequency diversity gain. Similarly, control information transmitted using the first slot  309  of RU # 50  is repeatedly transmitted through RU # 1   310  in the next slot by frequency hopping. Meanwhile, several control channels are transmitted in one RU after undergoing Code Domain Multiplexing (CDM). 
       FIG. 4  illustrates the detailed CDM structure for control channels. 
     Referring to  FIG. 4 , ACK CHannel (ACKCH) # 1  and ACKCH # 2  allocated to different terminals transmit their associated ACK/NACK signals using the same Zadoff-Chu (ZC) sequence at every LB. Symbols of a ZC sequence  412  applied to ACKCH # 1  are transmitted in an order of s 1 , s 2 , . . . , s 12  at every LB, and symbols of a ZC sequence  414  applied to ACKCH # 2  are transmitted in an order of s 3 , s 4 , . . . , s 12 , s 1 , s 2 . That is, the ZC sequence applied to ACKCH # 2  is cyclic-shifted from the ZC sequence of ACKCH # 1  by 2 symbols (Δ (Delta)=2 symbols). ZC sequences having different cyclic shift values ‘0’  408  and Δ (Delta)  410  according to the ZC sequence characteristics having mutual orthogonality. By setting a difference between the cyclic shift values  408  and  410  to a value greater than the maximum transmission delay of a wireless transmission path, it is possible to maintain orthogonality between channels. 
     Corresponding ZC sequences of ACKCH # 1  and ACKCH # 2  are multiplied by ACK/NACK symbols b 1  and b 2  desired to be transmitted at every LB, respectively. Due to the orthogonality between the ZC sequences, even though ACKCH # 1  and ACKCH # 2  are transmitted at the same time in the same RU, a base station&#39;s receiver can detect the ACK/NACK symbols b 1  and b 2  of two channels without mutual interference. At LBs  405  and  406  located in the middle of a slot, Reference Signals (RSs) for channel estimation are transmitted during detection of the ACK/NACK symbols. Like the control information of ACKCH # 1  and ACKCH # 2 , the RS is also transmitted after undergoing CDM by means of its corresponding ZC sequence. In  FIG. 4 , b 1  and b 2  are repeated over several LBs, in order to enable even the terminal located in the cell boundary to transmit an ACK/NACK signal of sufficient power to the base station. 
     According to a similar principle, even the CQI channel transmits one modulation symbol at every LB, and different CQI channels can undergo CDM using ZC sequences having different cyclic shift values. 
       FIG. 5  illustrates a structure where five control channels  500 ˜ 504  are multiplexed in one RU for a 0.5-ms slot. 
     Referring to  FIG. 5 , there are shown two ACK Channels, ACKCH # 1   500  and ACKCH # 2   501 , employing coherent modulation; and three control channels of Non-Coherent Signaling Control CHannels (NCCCH) # 1   502 , # 2   503  and # 3   504  for transmitting 1-bit control information using a non-coherent modulation scheme. ACKCH # 1   500  and ACKCH # 2   502  transmit RS signals for channel estimation at the 2 nd  and 6 th  LBs (hereinafter, “RS LBs”)  511  and  512  ( 513  and  514 ), respectively, and transmit ACK/NACK symbols  515  at the remaining LBs (hereinafter, “control information LBs”). NCCCHs  502 ,  503  and  504  transmit only the control information at the 1 st , 3 rd , 4 th , 5 th , and 7 th  LBs. 
     ACKCH # 1   500  and ACKCH # 2   501  apply the same cyclic shift value A (shift of ZC)  510  to ZC sequences transmitted at each LB. Therefore, the same cyclic shift value A (shift of ZC)  510  is applied between the two channels  500  and  501  even at LBs  511 ˜ 514  for transmission of RS signals. 
     For orthogonal detection of ACK/NACK symbols b 1  and b 2  transmitted in the two channels  500  and  501 , the signals multiplexed to ZC sequences of ACKCH # 1   500  and ACKCH # 2   501  are multiplied by sequence symbols of N-bit orthogonal sequences S m,n    516  (where n denotes a sequence symbol index, for n=1, N) with different indexes m in units of LBs. For instance, a Fourier sequence defined as Equation (1) can be applied as the orthogonal sequence. 
     
       
         
           
             
               
                 
                   
                     
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     The Fourier sequence satisfies mutual orthogonality between sequences with different indexes m, and N=5 in the structure shown in  FIG. 5 . Aside from the Fourier sequence, other 5-bit sequences such as ZC and Generalized Chirp-Like (GCL) sequences can also be used as the orthogonal sequence. 
     In the example of  FIG. 5 , symbols of 5-bit sequences with indexes  1  and  2  are sequentially multiplied by signals of control information LBs of ACKCH # 1  and ACKCH # 2 , respectively. Specifically, at LB  520 , each symbol of a ZC sequence applied in common to ACKCH # 1  and ACKCH # 2  is multiplied by an ACK/NACK symbol b 1  of ACKCH # 1  and the first symbol S 1,1  of a Fourier sequence # 1 . Similarly, at LB  521 , each symbol of the ZC sequence is multiplied by an ACK/NACK symbol b 2  of ACKCH # 2  and the first symbol S 1,1  of a Fourier sequence # 2 . 
     Meanwhile, since two RS LBs  511 ˜ 514  exist in one slot, 2-bit Walsh sequences with different indexes are applied to ACKCH # 1   500  and ACKCH # 2   501  at RS LBs  511 ˜ 514 . When ZC sequences with the same cyclic shift value  510  are applied to ACKCH # 1   500  and ACKCH # 2   501  as described above, since a length of the orthogonal sequence S m,n  is 5, three more orthogonal sequences are available. However, as stated above, since only two LBs capable of transmitting the RS exist in one slot, there is a problem in that it is not possible to generate additional RS signals other than ACKCH # 1   500  and ACKCH # 2   501  when applying the same ZC sequences to the control information LBs. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is to provide a method and apparatus for transmitting CS RS in a wireless communication system, 
     Another aspect of the present invention is to provide a method and apparatus for multiplexing CS RS and other uplink control channels in an SC-FDMA-based wireless communication system. 
     Another aspect of the present invention is to provide a method and apparatus for maintaining the constant resource allocation bandwidth of CS RS regardless of the amount of resources for other uplink control channels thereby to fixedly allocate CS RS to each terminal in an SC-FDMA-based wireless communication system. 
     Another aspect of the present invention is to provide an ACK/NACK channel structure for multiplexing a CS RS channel and an ACK/NACK channel such that a slot where the CS RS is transmitted and a slot where the CS RS is not transmitted have the same ACK/NACK channel transmission capacity. 
     In accordance with an aspect of the present invention, a method is provided for transmitting uplink control information by a terminal in a wireless communication system. System information associated with an uplink transmission of a reference signal is received from a base station. Uplink control information to which a length-3 orthogonal sequence or a length-4 orthogonal sequence is applied is transmitted in a slot of a sub-frame. The reference signal is transmitted based on the received system information. 
     In accordance with another aspect of the present invention, a terminal is provided for transmitting uplink control information in a wireless communication system. The apparatus includes a transceiver and a controller coupled with the transceiver. The controller is configured to receive system information associated with an uplink transmission of a reference signal from a base station, and transmit uplink control information to which a length-3 orthogonal sequence or a length-4 orthogonal sequence is applied in a slot of a sub-frame. The reference is transmitted based on the received system information. 
     In accordance with an additional aspect of the present invention, a method is provided for receiving uplink control information by a base station in a wireless communication system. System information associated with an uplink transmission of a reference signal is transmitted. The uplink control information to which a length-3 orthogonal sequence or a length-4 orthogonal sequence is applied is received in a slot of a sub-frame from a terminal. The reference signal is received from the terminal receiving the system information. The reference signal is received based on the received system information. 
     In accordance with a further aspect of the present invention, a base station is provided for receiving uplink control information in a wireless communication system. The base station includes a transceiver and a controller coupled to the transceiver. The controller is configured to transmit system information associated with an uplink transmission of a reference signal, receive the uplink control information to which a length-3 orthogonal sequence or a length-4 orthogonal sequence is applied in a slot of a sub-frame from a terminal, and receive the reference signal from the terminal receiving the system information. The reference signal is received based on the received system information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates a structure of a general SC-FDMA transmitter and a slot structure; 
         FIG. 2  illustrates exemplary resource partitioning in the frequency-time domain in a EUTRA SC-FDMA system; 
         FIG. 3  is a diagram illustrating resource allocation for transmission of a control channel and a data channel in the EUTRA uplink based on the resource partitioning structure of  FIG. 2 ; 
         FIG. 4  illustrates the detailed CDM structure for control channels; 
         FIG. 5  illustrates a structure where five control channels are multiplexed in one RU for a 0.5-ms slot; 
         FIG. 6  illustrates typical multiplexing of a channel sounding channel and other channels; 
         FIG. 7  illustrates multiplexing of a CS RS channel and other channels according to a preferred embodiment of the present invention; 
         FIG. 8  illustrates an example where ACK/NACK channels using a ZC sequence, to which one same cyclic shift value is applied, are multiplexed in one LB according to an embodiment of the present invention; 
         FIG. 9  is a flowchart illustrating a transmission operation of a terminal according to an embodiment of the present invention; 
         FIG. 10  illustrates multiplexing of a CS RS channel and other channels according to another embodiment of the present invention; and 
         FIG. 11  is a diagram illustrating a wireless communication system, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Various embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, descriptions of known functions and configurations incorporated herein have been omitted for clarity and conciseness. Terms used herein are defined based on functions in the present invention and may vary according to users, operators&#39; intention, or usual practices. Therefore, the definition of the terms should be made based on contents throughout the specification. 
     Although a description of the present invention will be made herein with reference to an OFDM-based wireless communication system, especially to the 3GPP EUTRA standard, the present invention can be applied to other communication systems having a similar technical background and channel format with a slight modification without departing from the scope of the present invention. 
     Referring to  FIG. 11 , a diagram illustrates a wireless communication system, according to an embodiment of the present invention. A terminal  1102  is in communication with a base station  1104 . The terminal  1102  includes a transmitter  1106  for transmitting signals to the base station  1104 , a receiver  1108  for receiving signals from the base station  1104 , and a controller  1110  for controlling functions of the terminal  1102 . The base station  1104  includes a transmitter  1112  for transmitting signals to the terminal  1102 , a receiver  1114  for receiving signals from the terminal  1102 , and a controller  1116  for controlling functions of the base station  1104 . 
     An aspect of the present invention is to multiplex a Channel Sounding Reference Signal (CS RS) channel and an uplink control channel in a wireless communication system. A CS RS, which is a pilot signal that a base station receives from each terminal, is used by the base station in estimating a channel state from each terminal till the base station. Based on the estimation result, the base station determines a data channel of which terminal it will schedule, for every subframe. For a CS RS channel, each terminal can have a different transmission bandwidth and a different transmission period according to the terminal state. 
     The present invention provides a technology for transmitting a CS RS at the time completely separated from the transmission time of other uplink channels, including data and control channels, and matching a bandwidth of allocated resources to the entire uplink system bandwidth ( 300  in  FIG. 3 ), thereby preventing influence on the number of control channels transmittable in control channel resources  308 ,  309 ,  310  and  311  in the uplink. In addition, the present invention differently applies a length of an orthogonal sequence applied to a control channel, i.e., an ACK/NACK channel, in a slot where the CS RS is transmitted and a slot where the CS RS is not transmitted, thereby enabling transmission of the same number of ACK/NACK channels in the two slots regardless of whether the control channel and CS RS exist in the same slot. 
     A detailed description will now be made of a CS RS transmission technology provided by the present invention through the following embodiments. 
     An embodiment of the present invention does not overlap a CS RS in RUs for transmitting an uplink control channel, and according thereto, uses one of LBs that the control channel do not use, for the CS RS transmission. In this case, an orthogonal sequence is applied to an ACK/NACK channel according to the number of LBs for ACK/NACK bit transmission, remaining after being applied to the CS RS. 
       FIG. 6  illustrates typical multiplexing of a channel sounding channel and other channels. 
     Referring to  FIG. 6 , an uplink system band  601  is composed of N first RUs  602  and M second RUs  603 , all of which are used as control channel(s), and a central band between the first and second RUs  602  and  603 . In EUTRA, ACK/NACK symbols are transmitted using four LBs, and RS is transmitted using three LBs in control channel slots  608 ,  609 ,  610  and  611 . 
     As illustrated, a CS RS channel  600  can be multiplexed with other uplink channels. The CS RS channel  600  is disposed in the first LB interval of the central band to which a data channel  605  is mapped. CS RSs transmitted by several terminals undergo CDM using cyclic shifting of ZC sequences, or are multiplexed to different frequency resources. 
     Generally, the number of uplink RUs  602  and  603  used for control channel transmission can vary for every subframe according to the number of necessary control channels. In that case, in the CS RS multiplexing structure shown in  FIG. 6 , a transmission bandwidth of the CS RS channel  600  should change for every subframe according to the number of control channel RUs  602  and  603  in use so that a band of the CS RS channel  600  should not overlap with the band occupied by the control channels, which prevents interference from occurring between the CS RS channel  600  and the control channels. 
     For this reason, in order for the transmission bandwidth of the CS RS channel  600  to change, it is necessary that terminals transmitting CS RSs must continuously receive, from the base station, signaling information on a band of the CS RS channel to be applied in the corresponding subframe. In addition, it is necessary that CS RS channels of various bandwidths should be defined. In this case, multiplexing a CS RS from each terminal is complicated, causing a load of determining CS RS sequences of various lengths. Accordingly, there is a need to solve this problem. 
       FIG. 7  illustrates multiplexing of a CS RS channel and other channels according to a preferred embodiment of the present invention. 
     Referring to  FIG. 7 , an uplink system band  701  is composed of N first RUs  706  and M second RUs  707 , all of which are used as control channel(s), and a central band  705  between the first and second RUs  706  and  707 . A data channel is mapped to the central band  705 . ACK/NACK symbols for an ACK/NACK channel or CQI symbols for a CQI channel are transmitted in control channel slots  708  and  709  ( 710  and  711 ) of the control channel RUs  706  and  707 , respectively. 
     Here, in one subframe  703  composed of two slots  720  and  721 , a CS RS channel  700  is allocated resources over the entire system band  701  of the uplink during the first LB  713  regardless of the number of RUs  706  and  707  used for transmission of uplink control channels. Therefore, the transmission bandwidth of the CS RS channel  700  can be maintained constant in the subframe  703  regardless of the number of RUs  706  and  707  used for transmission of control channels. Accordingly, the system indicates the band and transmission period to be used as a CS RS channel for each terminal, and each terminal periodically transmits CS RS using the indicated resources without the need to receive additional signaling from the base station. 
     Therefore, the present invention can satisfy the single-carrier transmission characteristic required for SC-FDMA transmission even when a terminal should simultaneously transmit CS RS and a control channel in an arbitrary subframe. In addition, the present invention differently applies a length of an orthogonal sequence applied to an ACK/NACK channel in a slot where CS RS is transmitted and a slot where CS RS is not transmitted, thereby enabling transmission of the same number of ACK/NACK channels in the two slots regardless of multiplexing of CS RS. 
     Among the LBs constituting the first slot  720 , one LB is not used for a control channel as shown by reference numeral  712 , and since uplink control channels are transmitted while undergoing frequency hopping for a 1-ms subframe as described above, it is necessary that the same number of control channels can be transmitted in the control channel slots  709  and  710 . Similarly, even in the control channel slots  708  and  711 , the same number of control channels should be transmitted. An uplink ACK/NACK channel structure for satisfying such requirements will be described below. 
       FIG. 8  illustrates an example where ACK/NACK channels using a ZC sequence, to which one same cyclic shift value is applied, are multiplexed in one LB according to an embodiment of the present invention. 
     Referring to  FIG. 8 , S 3   i,j  denotes a j th  sample of a 3-bit orthogonal sequence having an i th  index, and S 4   i,j  denotes a j th  sample of a 4-bit orthogonal sequence having an i th  index. The orthogonal sequences S 3   i,j  and S 4   i,j  are used for transmission of ACKCH #i in the first slot  720  and the second slot  721 , respectively. 
     For the first slot  720 , since CS RS is transmitted at the first LB interval  806  as described in  FIG. 7 , a 3-bit orthogonal sequence S 3   i,j  is used in the first slot in order to maintain orthogonality between ACKCH # 1 ˜ 3 . For this purpose, a 3-bit Fourier sequence can be applied as the orthogonal sequence. 
     Meanwhile, a 3-bit sequence W i,j  is used as a CS RS for channel estimation of ACKCH #i. Since the LB where the sequence W i,j  is transmitted is not punctured by the CS RS, positions of the LB are equal in the first slot  720  and the second slot  721 . When the CS RS is transmitted at an arbitrary LB in a subframe as stated above, since the LB where the CS RS is transmitted cannot be used for control channel transmission, the number of LBs for ACK/NACK symbols and LBs for RS transmission, except the LB for transmission of the CS RS, which is set to be equal in both slots. 
     By proposing the ACK/NACK channel structure shown in  FIG. 8 , the number of ACK/NACK channels that can undergo coherent transmission can be maintained at three channels regardless of the transmission of the CS RS in the corresponding subframe. 
     Although an index of a sequence for ACKCH #i used in the first slot  720  and the second slot  721  does not change in this embodiment, when sequence hopping is applied between slots for inter-cell interference diversity, an index of a sequence used between the two slots can change for one ACK/NACK channel, and the index change is not limited in the present invention. 
     Although a description of an embodiment of the present invention has been made herein for a case where a CS RS is transmitted at the first LB of the first slot in a subframe, the present invention is not limited to the position of the CS RS channel. However, by providing that the LB of an ACK/NACK symbol is punctured in the slot where the CS RS is transmitted and the number of LBs where the CS RS is transmitted is equal between two slots, the number of transmittable ACK/NACK channels can be equal in the slot where the CS RS is transmitted and the slot where the CS RS is not transmitted. An example of this case will be described with reference to  FIG. 9 . 
       FIG. 9  is a flowchart illustrating a transmission operation of a terminal according to a preferred embodiment of the present invention. 
     Referring to  FIG. 9 , in step  900 , a terminal generates an ACK/NACK symbol according to a success or failure in decoding of data received over a data channel in the downlink. In step  901 , the terminal determines whether there are any LBs where a CS RS can be transmitted, in a subframe for transmitting the ACK/NACK symbol. The determination can be achieved from system configuration information or upper layer signaling information for uplink channels. 
     If it is determined in step  901  that there is no LB where the CS RS can be transmitted in the subframe for transmitting the ACK/NACK symbol, the terminal maps in step  902  the ACK/NACK symbol or RS symbols to all LBs in the subframe according to a predefined pattern. In step  903 , the terminal applies an orthogonal sequence with a length predefined for each slot to the mapped ACK/NACK symbol or RS symbols, and then proceeds to step  906 . For example, when four ACK/NACK symbol LBs and three RS symbol LBs exist in one slot as in the second slot  721  of  FIG. 8 , a 4-bit orthogonal sequence S 4   i,j  can be applied to the four ACK/NACK symbol LBs and a 3-bit orthogonal sequence W i,j  can be applied to the three RS symbol LBs as shown in  FIG. 7 . In this case, for a high-speed terminal, a 2-bit orthogonal sequence can be applied twice to the four ACK/NACK symbol LBs. 
     However, if it is determined that there is an LB where the CS RS can be transmitted in the subframe for transmitting the ACK/NACK symbol, the terminal punctures, in step  904 , the ACK/NACK symbol allocated to the LB where the CS RS exists, does not map the ACK/NACK symbol allocated to the LB where the CS RS exists, and maps the ACK/NACK symbol or RS symbol to the remaining LBs in the subframe according to a predefined pattern. This process is as shown in the first slot  720  in  FIG. 7 . In step  905 , the terminal applies, to the slot, an orthogonal sequence having a length reduced by the number of punctured symbols for the ACK/NACK symbol punctured as in the first slot  720 , and applies an orthogonal sequence with a normal or a predefined length (sequence for ACK/NACK) to the ACK/NACK symbol or RS symbol of the unpunctured slot, and then proceeds to step  906 , i.e., the orthogonal sequence applied in step  905  is determined according to the number of LBs remaining after being applied to the CS RS. 
     In step  906 , the terminal applies a ZC sequence to the ACK/NACK symbol or RS symbol, as shown in  FIG. 4 , and then transmits the ACK/NACK symbol or RS symbol. 
       FIG. 10  illustrates multiplexing of a CS RS channel and other channels according to another preferred embodiment of the present invention. 
     Referring to  FIG. 10 , an uplink system band  1010  is composed of N first RUs  1001  and M second RUs  1002 , all of which are used as control channel(s), and a central band  1011  between the first and second RUs  1001  and  1002 . A data channel  1012  is mapped to the central band  1011 . ACK/NACK symbols for an ACK/NACK symbols or CQI symbols for a CQI channel are transmitted in the control channel RUs  1001  and  1002 . 
     A difference between the multiplexing structure shown in  FIG. 10  and the multiplexing structure shown in  FIG. 7  is in that a CS RS transmission band  1000  does not overlap with transmission bands  1001  and  1002  for an uplink control channel such as ACK/NACK channel and CQI channel. However, as in  FIG. 7 , in an LB  1005  where a CS RS is transmitted, the ACK/NACK symbol and the CQI symbol are not transmitted in the bands indicated by reference numerals  1003  and  1004 . By transmitting the CS RS only in the band of a data channel in this way, it is possible to prevent the power loss which may occur as the CS RS is transmitted even in the band of the uplink control channel, i.e., it is possible to improve estimation accuracy of channel state information for scheduling the uplink data channel. 
     As is apparent from the foregoing description, the present invention can satisfy the single-carrier transmission characteristic required for SC-FDMA transmission even when one terminal must simultaneously transmit a CS RS channel and a control channel in one subframe. That is, the present invention allows the CS RS channel and the control channel to be independently transmitted in the SC-FDMA system, so that each terminal can always transmit each channel whenever needed while satisfying the single-carrier transmission characteristic. The base station receives the CS RS channel and control channels from each terminal at a predetermined time, thereby scheduling a data channel to each terminal both in the uplink and downlink at the right time, i.e., at the corresponding timing, and thus contributing to an improvement of the system performance. 
     While the present invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.