Abstract:
A method and apparatus are provided for transmitting and receiving control information in a wireless communication system supporting multi-cell transmission. A method includes receiving a first pilot signal from a first cell and a second pilot signal from a second cell; generating first control information indicating channel quality for the first cell and second control information indicating channel quality for the second cell, based on the first pilot signal and the second pilot signal, respectively; separately encoding the first control information and the second control information; separately power controlling the encoded first control information and the encoded second control information; transmitting, on the first cell, the power controlled, encoded first control information on a first control channel; and transmitting, on the first cell, the power controlled, encoded second control information on a second control channel.

Description:
PRIORITY 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 13/130,716, which was filed in the U.S. Patent and Trademark Office on May 23, 2011, as National Stage Entry of PCT/KR2009/006946, filed on Nov. 24, 2009, and claims priority to Korean Application Serial No. 10-2008-0117215, which was filed in the Korean Intellectual Property Office on Nov. 25, 2008, the entire content of each of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to wireless communications and, more particularly, to a Channel Quality Indicator (CQI) transmission power control method for a wireless communication system supporting multi-cell High Speed Downlink Packet Data Access (HSDPA) in which multiple cells transmit packet data to a user equipment. 
         [0004]    2. Description of the Prior Art 
         [0005]    Universal Mobile Telecommunications System (UMTS), which is one of the third generation (3G) mobile telecommunication technologies based on the Wideband Code Division Multiple Access (WCDMA), has evolved from Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS) for providing mobile and computer users with packet-based multimedia services including text messaging and voice and video communication services in a consistent service environment. 
         [0006]    The UMTS system supports HSDPA service to enhance the packet data transfer speed and capacity in downlink. 
         [0007]    In order to secure high speed data transfer rate, HSDPA uses Adaptive Modulation and Coding (AMC) and Hybrid Automatic Repeat Request (HARQ). With the AMC, the Quadrature Phase-Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), and 64QAM modulation schemes are selectively used. The AMC technique selects the modulation scheme and coding format and coding rate on the basis of the channel condition and channel type between the Base station and the user equipment (UE) so as to improve the entire cell throughput. 
         [0008]    HARQ is implemented with fast retransmission and soft combining techniques. When an erroneous packet is detected, the retransmission is triggered between the base station and UE, and the recipient part combines the retransmitted packet with the previously received packets, thereby reducing the number of retransmission requests to improve overall efficiency. In order to support the HSDPA service, the base station and UE exchange control information such as Orthogonal Variable Spreading Factor (OVSF) codes and number of OVSF codes, Transport Block Sixe (TBS), Modulation and Coding Scheme (MCS), channel index information for HARQ, CQI for indicating the channel condition, and HARQ ACK/NACK. 
         [0009]      FIG. 1  is a sequence diagram illustrating operations of a cell and a UE in HSDPA system. 
         [0010]    Referring to  FIG. 1 , first the UE  102  transmits a Channel Quality Indicator (hereinafter called CQI) to a cell  101 . Since the UE  102  does not know when the data are transmitted in downlink, it transmits the CQI information periodically ( 103 ). When there are data to be sent, the Node B  101  performs scheduling based on the CQI. In the scheduling process, the Node B determines a number of code channels available for allocation and an MCS level. Such information is transmitted to the UE  102  through a High Speed Shared Control Channel (HS-SCCH) ( 105 ). The HS-SCCH is received by the UE  102  in a TTI, and the UE  102  receives data by demodulating the HS-PDSCH  106  with reference to the HS-SCCH. In order to make a status report for Hybrid Automatic Repeat Request (HARQ), the UE  102  performs Cyclic Redundancy Check (CRC) to determine Acknowledgement/Non-Acknowledgement (ACK/NACK) ( 103 ). If the data are received in error, the UE  102  transmits a NACK to Node B  101  to request retransmission of the data; and otherwise, an ACK to Node B  101  ( 107 ). The status reports of ACK/NACK and CQI are transmitted through a High Speed Dedicated Physical Control Channel (HS-DPCCH). 
         [0011]      FIG. 2  is a timing diagram illustrating transmissions of the physical channels of an HSDPA system. As shown in  FIG. 2 , the CQIs  205 ,  206 , and  207  are periodically transmitted via the HS-DPCCH. Node B transmits two slots of the HS-SCCH before it begins transmitting the HS-PDSCH in order for the UE to check the information on the demodulation of the HS-PDSCH. The ACK/NACK information  204  is transmitted 7.5 slots  203  after the transmission of the HS-PDSCH  202  in consideration of the demodulation and decoding of the data carried by the HS-PDSCH. 
         [0012]    The Dual-Cell HSDPA operation is described hereinafter with reference to  FIG. 3 . Unlike the conventional HSDPA in which the UE measures received signals strengths of the cells and connects to the most appropriate cell based on the measurements, the Dual-Cell HSDPA is characterized in that the UE  308  connects to two different cells  301  and  302  defined by two different carriers  303  and  304  of a Node B. The UE  308  receives the HSDPA signals from the second cell  302  in the first carrier f1  304  and from the first cell  301  in the second carrier f2  303 , simultaneously. In the WCDMA system, the transmission bandwidth of a cell is 5 MHz such that the UE must have a reception capability of 10 MHz for supporting Dual-Cell HSDPA. Since the HSDPA signals are received from two cells, the maximum transmission rate increases twice. In case of uplink, however, the Dual-Cell transmission function is not supported, whereby the uplink channel is transmitted to only one cell. Even in downlink transmission, common and dedicated channels that are not related to the HSDPA are received from a single cell. Typically, the cell which is in charge of controlling the uplink channel and common and dedicated downlink channels is called an “anchor cell” and the other cell is called a “supplementary cell”. 
         [0013]    Although the 3GPP standard specifies the Dual-Cell HSDPA service with two cells (including one anchor cell and one supplementary cell) as of year 2008, a multi-cell HSDPA can be implemented with the involvement of more than two cells (including one anchor cell and two or more supplementary cells). 
         [0014]    In order for the Dual-Cell HSDPA service to support the HARQ and AMC, the ACK/NACK and CQI should be transmitted to the respective cells, whereby the uplink channel permitted to the anchor cell must be configured to carry the ACK/NACKs and CQIs destined for the anchor and supplementary cells. In this case, the CQIs for the anchor and supplementary cells (each is 5-bit long) are concatenated into 10-bit control information and encoded with a (20, 10) block code. The block coded control information is transmitted through the HS-DPCCH specified for the CQI and ACK/NACK transmission. In case that the Dual-Cell HSDPA operation is not configured, the 5-bit CQI for the anchor cell is encoded with a (20, 5) block code and then transmitted through the HS-DPCCH specified for the CQI and ACK/NACK transmission. The Dual-Cell HSDPA operation is signaled by the base station to the UE. 
         [0015]    However, detailed uplink control information transmission method for the multi-cell HSDPA has not been discussed yet until now. 
       SUMMARY OF THE INVENTION 
       [0016]    Accordingly, the present invention is designed to address at least the problems and/or disadvantages described above and to provide at least the advantages described below. 
         [0017]    An aspect of the present invention is to provide a method for controlling transmission power of the physical control channel carrying the CQIs for multiple cells in a multi-cell HSDPA system that is capable of securing uniform CQI reception performance. 
         [0018]    Another aspect of the present invention is to provide a CQI transmission power control method for a wireless communication system providing multi-cell HSDPA service that secures uniform reception performance for multiple cells at the base station by controlling the transmission powers of the uplink physical control channels carrying the CQI information, resulting in improvement of CQI transmission efficiency and system performance. 
         [0019]    In accordance with an aspect of the present invention, a method is provided for transmitting control information by a user equipment in a wireless communication system supporting multi-cell transmission. The method includes receiving a first pilot signal from a first cell and a second pilot signal from a second cell; generating first control information indicating channel quality for the first cell and second control information indicating channel quality for the second cell, based on the first pilot signal and the second pilot signal, respectively; separately encoding the first control information and the second control information; separately power controlling the encoded first control information and the encoded second control information; transmitting the power controlled, encoded first control information on a first control channel; and transmitting the power controlled, encoded second control information on a second control channel. The first control channel and the second control channel are transmitted on the first cell. 
         [0020]    In accordance with another aspect of the present invention, a method is provided for receiving control information by a base station in a wireless communication system supporting multi-cell transmission. The method includes transmitting a first pilot signal via a first cell and a second pilot signal via a second cell to a user equipment (UE); receiving first control information indicating channel quality for the first cell based on the first pilot signal on a first control channel from the UE; and receiving second control information indicating channel quality for the second cell based on a second pilot signal on a second control channel from the UE. The first control information and the second control information are encoded and power controlled separately, and the first control channel and the second control channel are transmitted on the first cell. 
         [0021]    In accordance with another aspect of the present invention, a user equipment (UE) is provided for transmitting control information in a wireless communication system supporting multi-cell transmission. The UE includes a transceiver configured to receive a first pilot signal from a first cell and a second pilot signal from a second cell; and a controller configured to generate first control information indicating channel quality for the first cell and second control information indicating channel quality for the second cell, based on the first pilot signal and the second pilot signal, respectively, separately encode the first control information and the second control information, separately power control the encoded first control information and the encoded second control information, transmit the power controlled, encoded first control information on a first control channel, and transmit the power controlled, encoded second control information on a second control channel. The first control channel and the second control channel are transmitted on the first cell. 
         [0022]    In accordance with another aspect of the present invention, a base station is provided for receiving control information in a wireless communication system supporting multi-cell transmission. The base station includes a transceiver configured to transmit a first pilot signal via a first cell and a second pilot signal via a second cell a user equipment (UE), receive first control information indicating channel quality for the first cell, based on the first pilot signal on a first control channel from the UE, and receive second control information indicating channel quality for the second cell, based on a second pilot signal on a second control channel from the UE; and a controller configured to control the transceiver. The first control information and the second control information are encoded and power controlled separately, and the first control channel and the second control channel are transmitted on the first cell. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The above and other aspects, features, and advantages of certain embodiments of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
           [0024]      FIG. 1  is a sequence diagram illustrating operations of a cell and a UE in HSDPA system; 
           [0025]      FIG. 2  is a timing diagram illustrating transmissions of the physical channels of an HSDPA system; 
           [0026]      FIG. 3  is a conceptual diagram illustrating a Dual-Cell HSDPA service of a UMTS system; 
           [0027]      FIG. 4  is a conceptual diagram illustrating a principle of a CQI transmission power control method for a multi-cell HSDPA system according to an exemplary embodiment of the present invention; 
           [0028]      FIG. 5  is a flowchart illustrating a CQI transmission power control method for a multi-cell HSDPA system according to an exemplary embodiment of the present invention; 
           [0029]      FIG. 6  is a flowchart illustrating a CQI reception procedure of the CQI transmission power control method in the base station according to an exemplary embodiment of the present invention; 
           [0030]      FIG. 7  is a block diagram illustrating a configuration of a UE for supporting the multi-cell HSDPA according to an exemplary embodiment of the present invention; and 
           [0031]      FIG. 8  is a block diagram illustrating a configuration of a base station for supporting the multi-cell HSDPA according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, specific details such as detailed configuration and components are merely provided to assist the overall understanding of these embodiments of the present invention. Therefore, it should be apparent to those skilled in the art that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
         [0033]    In the following description, the CQI transmission power control method of the present invention is directed to the multi-cell HSDPA system in which multiple (N) cells are transmitting the HSDPA service data simultaneously, but the principle of the present invention can be applied to similar types of communication systems. 
         [0034]    In an exemplary embodiment of the present invention, the CQI transmission power control method of the present invention is described with an exemplary multi-cell HSDPA system in which N=3, and a UE transmits three 5-bit CQIs, i.e. a CQI(1) for an anchor cell, a CQI(2) for a first supplementary cell, a CQI(3) for a second supplementary cell, simultaneously while securing the uniform CQI reception performance. For this purpose, the UE generates a group of CQIs according to a predetermined rule and compensates the control information on the group to secure the reception performance at the base station. 
         [0035]    In more detail, the UE designates the CQI(1) as a first group and the CQI(2) and CQI(3) as a second group, and performs block coding on the CQI(1) with a first channel code. In an exemplary embodiment of the present invention, the first channel code is (20, 5) block code. Unless otherwise noted, the first channel code is (20, 5) block code in the following description. The UE encodes the CQI(1) with the (20, 5) block code and transmits the encoded control information through an HS-DPCCH1 which is the HS-DPCCH defined for carrying the CQI and ACK/NACK information. 
         [0036]    The UE also concatenates the CQI(2) and CQI(3) as the second group into 10-bit control information and encodes the second group control information with a second channel code. In an exemplary embodiment of the present invention, the second channel code is (20, 10) block code. Unless otherwise noted, the second channel code is (20, 10) block code in the following description. The UE encodes the CQI(2) and CQI(3) with the (20, 10) block code and transmits the encoded control information through a HS-DPCCH2. 
         [0037]    Which control information among the CQI(1), CQI(2), and CQI(3) is encoded with which of the (20, 5) and (20, 10) is determined according to a predetermined rule. The HS-DPCCH1 and HS-DPCCH2 are differentiated by orthogonal codes. 
         [0038]    The larger the minimum distance (d_min) as a metric of channel coding performance is or the lower the coding rate is, the superior the error correction performance. Accordingly, the (20, 5) block code is superior to the (20, 10) in error correction capability. In literatures, d_min is 9 in the (20, 5) block code and 6 in the (20, 10) block code. Thus, when the (20, 5) coded bits for the HS-DPCCH1 and the (20, 10) coded bits for the HS-DPCCH2 are transmitted without additional calibration, the reception performance of the CQI(1) transmitted on the HS-DPCCH1 is superior to that of the CQI(2) and CQI(3) transmitted on the HS-DPCCH2 at the base station. 
         [0039]    In an exemplary embodiment of the present invention, the UE sets the transmission power of the HS-DPCCH2 to be higher than that of the HS-DPCCH1 in order to secure the uniform CQI reception performance at the cells involved in the multi-cell HSDPA service. The transmission power offset can be preset or signaled from the base station to the UE. Detailed operations of the CQI transmission power control method is described with exemplary embodiments of the present invention. All the description is focused on the multi-cell HSDPA system in which three cells (N=3) are involved in the HSDPA service, the CQI transmission power control method of the present invention is applicable to the multi-cell HSDPA system operating with more than three cells. 
         [0040]    In the following description, a CQI transmission power control method for a multi-cell HSDPA system operating with three cells is described as an exemplary case. 
         [0041]      FIG. 4  is a conceptual diagram illustrating a principle of a CQI transmission power control method for a multi-cell HSDPA system according to an exemplary embodiment of the present invention. 
         [0042]    In the exemplary embodiment of  FIG. 4 , the UE transmits a 5-bit CQI(1) for the anchor cell, a 5-bit CQI(2) for a first supplementary cell, and a 5-bit CQI(3) for a second supplementary cell simultaneously. In this case, the UE encodes the CQI(1) with (20, 5) block code and transmits the 20 coded bits through the HS-DPCCH1 defined in the standard for transmission of CQI and HARQ ACK/NACK. At the same time, the UE concatenates the CQI(2) and CQI(3) into 10-bit control information, encodes the 10-bit control information with (20, 10) block code, and transmits the 20 coded bits through a newly introduced HS-DPCCH2. This means that the HS-DPCCH1 is coded with a channel code having a relatively high error correction capability and the HS-DPCCH2 is coded with a channel code having a relatively low error correction capability. The block code to be used for encoding each of the CQI(1), CQI(2), and CQI(3) is determined according to a predetermined rule. The HS-DPCCH1 and HS-DPCCH2 are distinguished by orthogonal codes. The CQI information is transmitted during a CQI feedback cycle  402  periodically. 
         [0043]    In an exemplary embodiment of the present invention, the transmission power of the HS-DPCCH2 is set with an offset as much as GP greater than that of the HS-DPCCH1 to secure the uniform CQI reception performance at the entire cells involve in the multi-cell HSDPA service with bias to a specific cell. That is, when the transmission power of the HS-DPCCH is P, the transmission power of the HS-DPCCH2 is set to P+GP. The transmission power offset can be preset or signaled from the system to the UE. 
         [0044]    The 3GPP standard TS25.212 specifies the (20, 5) block code and (20, 10) block code for HSDPA. The (20, 5) code for encoding CQI in HSDPA uses 5 basis sequences as shown in table 1. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 i 
                 M i, 0   
                 M i, 1   
                 M i, 2   
                 M i, 3   
                 M i, 4   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 
                 1 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 1 
                 0 
                 1 
                 0 
                 0 
                 1 
               
               
                   
                 2 
                 1 
                 1 
                 0 
                 0 
                 1 
               
               
                   
                 3 
                 0 
                 0 
                 1 
                 0 
                 1 
               
               
                   
                 4 
                 1 
                 0 
                 1 
                 0 
                 1 
               
               
                   
                 5 
                 0 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                 6 
                 1 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                 7 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                   
                 8 
                 1 
                 0 
                 0 
                 1 
                 1 
               
               
                   
                 9 
                 0 
                 1 
                 0 
                 1 
                 1 
               
               
                   
                 10 
                 1 
                 1 
                 0 
                 1 
                 1 
               
               
                   
                 11 
                 0 
                 0 
                 1 
                 1 
                 1 
               
               
                   
                 12 
                 1 
                 0 
                 1 
                 1 
                 1 
               
               
                   
                 13 
                 0 
                 1 
                 1 
                 1 
                 1 
               
               
                   
                 14 
                 1 
                 1 
                 1 
                 1 
                 1 
               
               
                   
                 15 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 16 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 17 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 18 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 19 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                   
               
             
          
         
       
     
         [0045]    The (20, 5) channel encoding is performed by linear combination of the 5 input information bits with the 5 basis sequences of length 20 as shown in table 1 using equation (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     b 
                     i 
                   
                   = 
                   
                     
                       ∑ 
                       
                         n 
                         = 
                         0 
                       
                       4 
                     
                      
                     
                         
                     
                      
                     
                       
                         ( 
                         
                           
                             a 
                             n 
                           
                           × 
                           
                             M 
                             
                               i 
                               , 
                               n 
                             
                           
                         
                         ) 
                       
                        
                       mod 
                        
                       
                           
                       
                        
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where a n  is n th  information bit (a 0  is the Least Significant Bit (LSB), and a 4  is the Most Significant Bit (MSB)), and b i  is i th  output bit, i.e. i th  coded bit. Accordingly, the 5 information bits are encoded into 20 coded bits. 
         [0046]    The (20, 10) code 10 basis sequences as shown in table 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
             
               
                   
                 I 
                 M i,0   
                 M i,1   
                 M i,2   
                 M i,3   
                 M i,4   
                 M i,5   
               
               
                   
                   
               
               
                   
                  0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                  1 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                  2 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
               
               
                   
                  3 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
               
               
                   
                  4 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                  5 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                  6 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                  7 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                  8 
                 1 
                 0 
                 1 
                 0 
                 0 
                 0 
               
               
                   
                  9 
                 1 
                 1 
                 0 
                 1 
                 0 
                 0 
               
               
                   
                 10 
                 0 
                 1 
                 1 
                 0 
                 1 
                 0 
               
               
                   
                 11 
                 1 
                 0 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                 12 
                 1 
                 1 
                 0 
                 1 
                 1 
                 0 
               
               
                   
                 13 
                 1 
                 1 
                 1 
                 0 
                 1 
                 1 
               
               
                   
                 14 
                 0 
                 1 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                 15 
                 0 
                 0 
                 1 
                 1 
                 1 
                 0 
               
               
                   
                 16 
                 0 
                 0 
                 0 
                 1 
                 1 
                 1 
               
               
                   
                 17 
                 1 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                   
                 18 
                 0 
                 1 
                 0 
                 0 
                 0 
                 1 
               
               
                   
                 19 
                 1 
                 1 
                 1 
                 1 
                 1 
                 1 
               
               
                   
                   
               
               
                   
                   
                 I 
                 M i,6   
                 M i,7   
                 M i,8   
                 M i,9   
                 M i,10   
               
               
                   
                   
               
               
                   
                   
                  0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                  1 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                  2 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                  3 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                  4 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                  5 
                 0 
                 1 
                 0 
                 0 
                 0 
               
               
                   
                   
                  6 
                 0 
                 0 
                 1 
                 0 
                 1 
               
               
                   
                   
                  7 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                   
                   
                  8 
                 1 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                   
                  9 
                 0 
                 1 
                 1 
                 1 
                 1 
               
               
                   
                   
                 10 
                 0 
                 0 
                 1 
                 1 
                 1 
               
               
                   
                   
                 11 
                 0 
                 0 
                 0 
                 1 
                 0 
               
               
                   
                   
                 12 
                 1 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                 13 
                 0 
                 1 
                 0 
                 0 
                 0 
               
               
                   
                   
                 14 
                 1 
                 0 
                 1 
                 0 
                 1 
               
               
                   
                   
                 15 
                 1 
                 1 
                 0 
                 1 
                 0 
               
               
                   
                   
                 16 
                 0 
                 1 
                 1 
                 0 
                 1 
               
               
                   
                   
                 17 
                 1 
                 0 
                 1 
                 1 
                 1 
               
               
                   
                   
                 18 
                 1 
                 1 
                 0 
                 1 
                 0 
               
               
                   
                   
                 19 
                 1 
                 1 
                 1 
                 1 
                 1 
               
               
                   
                   
               
             
          
         
       
     
         [0047]    The (20, 10) channel encoding is performed by linear combination of the 10 input information bits with the 10 basis sequences of length 20 as shown in table 2 using equation (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     b 
                     i 
                   
                   = 
                   
                     
                       ∑ 
                       
                         n 
                         = 
                         0 
                       
                       9 
                     
                      
                     
                         
                     
                      
                     
                       
                         ( 
                         
                           
                             a 
                             n 
                           
                           × 
                           
                             M 
                             
                               i 
                               , 
                               n 
                             
                           
                         
                         ) 
                       
                        
                       mod 
                        
                       
                           
                       
                        
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where a n  is n th  information bit (a 0  is the Least Significant Bit (LSB), and a 4  is the Most Significant Bit (MSB)), and b i  is ith output bit, i.e. ith coded bit. Accordingly, the 10 information bits are encoded into 20 coded bits. 
         [0048]      FIG. 5  is a flowchart illustrating a CQI transmission power control method for a multi-cell HSDPA system according to an exemplary embodiment of the present invention. 
         [0049]    Referring to  FIG. 5 , the UE first measures the Common Pilot Channels (CPICHs) of the anchor cell and the first and second supplementary cells to generate the CQI(1), CQI(2) and CQI(3) indicating channel statuses and MCS levels of the corresponding cells ( 502 ). At this time, the UE can classify the CQIs into a first CQI information group and a second CQI information group according to a predetermined rule. Next, the UE encodes one (the first CQI information group) of the three CQIs with (20, 5) block code and concatenates the rest two CQIs and then encodes the concatenated CQIs (the second CQI information group) with (20, 10) block code ( 504 ). The channel codes for encoding the CQIs are determined according to a predetermined rule. 
         [0050]    For instance, it is possible to assign a serial number (1, 2, and 3) to the respective cells and concatenate the CQIs of the cells assigned the first two serial numbers to be encoded with (20, 10) block code and then encode the CQI of the cell assigned the last serial number with (20, 5) block code. Also, it is possible to encode the CQI of the anchor cell with (20, 5) block code and concatenates and encodes the CQIs of the rest two supplementary cells with (20, 10) block code. 
         [0051]    In an exemplary embodiment of the present invention, the UE classifies the one of the CQIs into a first CQI group information and the rest two CQIs into a second CQI group information. 
         [0052]    Next, the UE checks the block code used for channel coding on the coded CQI information ( 505 ). If the CQI information is coded using (20, 5) block code, the UE spreads the coded bits over the HS-DPCCH1 as the first CQI dedicated physical control channel ( 506 ) and sets the transmission power of the HS-DPCCH1 to P ( 508 ). 
         [0053]    If the CQI information is coded using (20, 10) block code, the UE spreads the coded bits over the HS-DPCCH2 as the second CQI dedicated physical control channel ( 510 ) and sets the transmission power of the HS-DPCCH2 to P+ΔP ( 512 ). The HS-DPCCH1 and HS-DPCCH2 are distinguished by different orthogonal codes. Finally, the UE transmits the HS-DPCCH1 and HS-DPCCH2 ( 514 ). 
         [0054]    Table 3 shows the Transport Block Size (TBS), modulation scheme, and a number of HS-DPCCHs corresponding to each of CQI values specified for the current HSDPA system. For instance, the UE retrieves a CQI value corresponding to the measured channel quality of each channel from table 1 and transmits the selected CQI value to the base station through the above described procedure. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Transport 
                 Number of 
                   
               
               
                 CQI value 
                 Block Size 
                 HS-PDSCH 
                 Modulation 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 N/A 
                 Out of range 
               
             
          
           
               
                 1 
                 136 
                 1 
                 QPSK 
               
               
                 2 
                 176 
                 1 
                 QPSK 
               
               
                 3 
                 232 
                 1 
                 QPSK 
               
               
                 4 
                 320 
                 1 
                 QPSK 
               
               
                 5 
                 376 
                 1 
                 QPSK 
               
               
                 6 
                 464 
                 1 
                 QPSK 
               
               
                 7 
                 648 
                 2 
                 QPSK 
               
               
                 8 
                 792 
                 2 
                 QPSK 
               
               
                 9 
                 928 
                 2 
                 QPSK 
               
               
                 10 
                 1264 
                 3 
                 QPSK 
               
               
                 11 
                 1488 
                 3 
                 QPSK 
               
               
                 12 
                 1744 
                 3 
                 QPSK 
               
               
                 13 
                 2288 
                 4 
                 QPSK 
               
               
                 14 
                 2592 
                 4 
                 QPSK 
               
               
                 15 
                 3328 
                 5 
                 QPSK 
               
               
                 16 
                 3576 
                 5 
                 16-QAM 
               
               
                 17 
                 4200 
                 5 
                 16-QAM 
               
               
                 18 
                 4672 
                 5 
                 16-QAM 
               
               
                 19 
                 5296 
                 5 
                 16-QAM 
               
               
                 20 
                 5896 
                 5 
                 16-QAM 
               
               
                 21 
                 6568 
                 5 
                 16-QAM 
               
               
                 22 
                 7184 
                 5 
                 16-QAM 
               
               
                 23 
                 9736 
                 7 
                 16-QAM 
               
               
                 24 
                 11432 
                 8 
                 16-QAM 
               
               
                 25 
                 14424 
                 10 
                 16-QAM 
               
               
                 26 
                 15776 
                 10 
                 64-QAM 
               
               
                 27 
                 21768 
                 12 
                 64-QAM 
               
               
                 28 
                 26504 
                 13 
                 64-QAM 
               
               
                 29 
                 32264 
                 14 
                 64-QAM 
               
               
                 30 
                 32264 
                 14 
                 64-QAM 
               
               
                   
               
             
          
         
       
     
         [0055]      FIG. 6  is a flowchart illustrating a CQI reception procedure of the CQI transmission power control method in the base station according to an exemplary embodiment of the present invention. Typically, the multi-cell HSDPA system is implemented with the anchor cell and the supplementary cells belonged to the same base station. 
         [0056]    Referring to  FIG. 6 , first the base station determines whether the CQI feedback cycle is started ( 602 ). If the CQI feedback cycle is not started yet, the base station waits for the start of the CQI feedback cycle while checking periodically. If the CQI feedback cycle is started, the base station despreads the HS-DPCCH1 and HS-DPCCH2 using the corresponding orthogonal codes ( 604 ). Next, the base station distinguishes the HS-DPCCH1 and the HS-DPCCH2 from each other (606). Once the HS-DPCCH1 and the HS-DPCCH2 are identified, the base station performs decoding on the HS-DPCCH1 with (20, 5) block code ( 608 ) and the HS-DPCCH2 with (20, 10) block code ( 610 ). As a consequence, the base station acquires the CQIs transmitted on the HS-DPCCH1 and the HS-DPCCH2 ( 612 ). 
         [0057]      FIG. 7  is a block diagram illustrating a configuration of a UE for supporting the multi-cell HSDPA according to an exemplary embodiment of the present invention. 
         [0058]    As shown in  FIG. 7 , the UE includes an anchor cell reception unit  712 , a first supplementary cell reception unit  724 , a second supplementary cell reception unit  740 , a first feedback unit  710 , a second feedback unit  700 , and a multi-cell HSDPA control unit  736 . 
         [0059]    The anchor cell reception unit  712  includes a CPICH receiver  714 , an HS-SCCH receiver  716 , an HS-PDSCH receiver  718 , a CQI measurer  720 , and a HS-SCCH control information extractor  722 . 
         [0060]    The first supplementary cell reception unit  724  includes a CPICH receiver  726 , an HS-SCCH receiver  728 , an HS-PDSCH receiver  730 , a CQI measurer  732 , and a HS-SCCH control information extractor  734 . 
         [0061]    The second supplementary cell reception unit  740  includes a CPICH receiver  746 , an HS-SCCH receiver  750 , an HS-PDSCH receiver  752 , a CQI measurer  742 , and a HS-SCCH control information extractor  748 . 
         [0062]    The first feedback unit  710  includes a feedback information generator  706  and an HS-DPCCH1 transmitter  708 . 
         [0063]    The second feedback unit  700  includes a feedback information generator  702  and an HS-DPCCH2 transmitter  704 . 
         [0064]    The multi-cell HSDPA control unit  736  includes an ACK/NACK controller  738  and a CQI controller  739 . 
         [0065]    The HS-SCCH receivers  716 ,  728 , and  750  despread, demodulate, and decode the HS-SCCHs received from the corresponding cells. 
         [0066]    The HS-SCCH control information extractors  722 ,  734 , and  748  extract information on the HS-PDSCHs (including TBS, channel code information and number, MCS, and HARQ information) from the decoding results output by the corresponding HS-SCCH receivers  716 ,  728 , and  750  and supports the HS-PDSCH reception operations of the HS-PDSCH receivers  718 ,  730 , and  752 . 
         [0067]    The HS-PDSCH receivers  718 ,  730 , and  752  despread, demodulate, and decode the packet data received from the corresponding cells and output the decoded packet data to the ACK/NACK controller  738  for CRC tests. 
         [0068]    The CPICH receivers  714 ,  726 , and  746  receive the CPICH signals transmitted by corresponding cells and output the received CPICH signals to the corresponding CQI measurers  720 ,  732 , and  742 . 
         [0069]    The CQI measurers  720 ,  732 , and  742  acquire the channel quality information of the corresponding cells from the CPICH signals and generate control information based on the channel quality information. For this purpose, the CQI measurers  720 ,  732 , and  742  measure the received signal qualities of the CPICH signals output by the CPICH receivers  714 ,  726 , and  746  and then provides the measured signal qualities to the CQI controller  739 . 
         [0070]    The ACK/NACK controller  738  of the multi-cell HSDPA control unit  736  performs CRC tests on the received packet data and determines transmission of ACK/NACK to the corresponding cells. 
         [0071]    The CQI controller  739  controls the first and second feedback units  710  and  700  to transmit the CQI(1), CQI(2), and CQI(3) for the anchor cell and the first and second cells simultaneously. The CQI controller  739  controls the first and second feedback units  710  and  700  to group the control information for the corresponding cells according to a predetermined rule and adjust the transmission power of the group control information to secure uniform reception performance at the base station. 
         [0072]    As aforementioned, the first feedback unit  710  includes the feedback information generator  706  and the HS-DPCCH1 transmitter  708 , and the second feedback unit  700  includes the feedback information generator  702  and the HS-DPCCH2 transmitter  704 . In an exemplary embodiment of the present invention, the HS-DPCCH1 transmitter  708  encodes the 5-bit CQI information for one cell using (20, 5) block code, and the HS-DPCCH2 transmitter  704  encodes the 10-bit CQI information for two cells using (20, 10) block code. The first and second feedback units  710  and  700  set the transmission powers of the HS-DPCCH1 transmitter and the HS-DPCCH2 transmitter to different values. For instance, the first feedback unit  710  sets the transmission power of the HS-DPCCH1 transmitter  708  to P, and the second feedback unit  700  sets the transmission power of the HS-DPCCH2 transmitter  704  to P+P. 
         [0073]      FIG. 8  is a block diagram illustrating a configuration of a base station for supporting the multi-cell HSDPA according to an exemplary embodiment of the present invention. In the exemplary embodiment of  FIG. 8 , a common buffer and a common scheduler for processing three cells are used to facilitate the multi-cell HSDPA service. 
         [0074]    As shown in  FIG. 8 , the base station includes an anchor cell transmission unit  812 , a first supplementary cell transmission unit  820 , a second supplementary cell transmission unit  840 , a first feedback reception unit  838 , a second feedback reception unit  836 , an HSDPA scheduler  828 , a buffer  834 , and a CQI determiner  810 . 
         [0075]    The anchor cell transmission unit  812  includes a HS-SCCH control information generator  814 , a HS-SCCH transmitter  816 , and a HS-PDCCH transmitter  818 . 
         [0076]    The first supplementary transmission unit  820  includes a HS-SCCH control information generator  822 , a HS-SCCH transmitter  824 , and a HS-PDCCH transmitter  826 . 
         [0077]    The second supplementary transmission unit  840  includes a HS-SCCH control information generator  842 , a HS-SCCH transmitter  844 , and a HS-PDCCH transmitter  846 . 
         [0078]    The first feedback reception unit  838  includes an HS-DPCCH1 receiver  806  and a feedback information extractor  808 . 
         [0079]    The second feedback reception unit  836  includes an HS-DPCCH2 receiver  802  and a feedback information extractor  804 . 
         [0080]    The first and second feedback reception unit  838  and  836  receive the feedback information including ACK/NACK and CQIs transmitted by the UE. The HS-DPCCH2 is transmitted with the transmission power greater than that of the HS-DPCCH1, and the HS-DPCCH1 carries the information coded with a channel code superior to that used for coding the HS-DPCCH2, thereby securing uniform CQI reception performance on the respective physical control channel. 
         [0081]    The HS-DPCCH1 receiver  806  and the HS-DPCCH2 receiver  802  despread, demodulate, and decode the respective HS-DPCCH1 and HS-DPCCH 2 and output the decoded information to the corresponding feedback information extractors  808  and  804 . 
         [0082]    The first and second feedback information extractors  808  and  804  extracts the ACK/NACK and CQI information for the respective cells from the decoded information output by the HS-DPCCH1 receiver  806  and the HS-DPCCH2 receiver  802  and outputs the ACK/NACK information to the HSDPA scheduler  802  and the CQI information to the CQI determiner  810 . The CQI determiner  810  calculates the CQI values for the respective cells base on the CQI information provided by the first and second feedback reception units  838  and  836  and outputs the CQI values to the HSDPA scheduler  828 . 
         [0083]    The HSDPA scheduler  820  determines the TBS, channel code of the HS-PDSCH and number of channel codes, MCS, and HARQ information based on the ACK/NACK and CQI information provided by the first and second feedback reception units  838  and  836  and the CQI determiner  810 . The HSDPA scheduler  828  generates the packet data into the buffer  834  to be supplied to the HS-PDCCH transmitters  818 ,  826 , and  846 . The HSDPA scheduler  828  also provides the information on the TBS, channel code of the HS-PDSCH and number of channel code, MCS, and HARQ information to the HS-DPSCH transmitters  818 ,  826 , and  846  such that the HS-PDSCH transmitters  818 ,  826 , and  846  transmit the packet data based on the information provided by the HSDPA scheduler  828 . 
         [0084]    The HSDPA scheduler  828  also sends the control information to the HS-SCCH control information generators  814 ,  822 , and  842  such that the control information is processed into appropriate format by the HS-SCCH control information generators  814 ,  822 , and  842  and then transmitted by means of the HS-SCCH transmitters  816 ,  824 , and  844 . The number of the HS-SCCH control information generators corresponds to the number of the cells involved in the multi-cell HSDPA service. 
         [0085]    As described above, the CQI transmission power control method for a wireless communication system providing multi-cell HSDPA service is capable of controlling the transmission powers of the uplink physical control channels carrying the CQI information so as to secure the uniform reception performance for multiple cells at the base station, resulting in improvement of CQI transmission efficiency and system performance. 
         [0086]    While the present invention has been particularly shown and described with reference to certain embodiments thereof, it will be understood by those of ordinary skill 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 following claims and their equivalents.