Abstract:
Apparatus and method for allocating a Channel Quality Information CHannel (CQICH) in a wireless communication system are provided. The method includes determining CQICH patterns required for users using information of one or more users to which CQICH resources are to be allocated, and selecting a CQICH pattern block, including all of the determined CQICH patterns, from among a plurality of pre-generated CQICH pattern blocks; and allocating CQICH sub-blocks corresponding to the users&#39; required CQICH patterns using resource layout information of the CQICH sub-blocks corresponding to the CQICH patterns of the selected CQICH pattern block, and transmitting CQICH allocation information to a Mobile Station (MS).

Description:
PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. § 119(a) to an application filed in the Korean Intellectual Property Office on Oct. 30, 2006 and assigned Serial No. 2006-105560, the contents of which are herein incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a wireless communication system, and in particular, to an apparatus and method for allocating Channel Quality Information CHannel (CQICH). 
         [0004]    2. Description of the Related Art 
         [0005]    Wireless access specifications based on a Orthogonal Frequency Division Multiple Access (OFDMA scheme), such as Institute of Electrical and Electronics Engineers (IEEE) 802.16e, IEEE 802.20, and IEEE 802.11n, which is recently under consideration, are taking into account Channel Quality Information (CQI) fed back from a terminal to determine a transmit mode and a transmit rate fit for a channel condition of a scheduled user. 
         [0006]    A CQI CHannel (CQICH) is an uplink channel for feeding back the CQI. If a plurality of users utilizes a fixed resource like a data channel, a Base Station (BS) informs the users of resource allocation information of the data channel. Likewise, the BS needs to transmit CQICH resource allocation information to the users. Similar to the resource allocation of the data channel, the CQICH resource allocation information should be transmitted such that every user in a cell can receive the information. To this end, it is important to reduce the amount of the information required for the CQICH allocation. 
         [0007]    A current IEEE 802.16e system informs each user of CQICH resource allocation information such as a user IDentification (CQICH_ID), a number of CQICH resources allocated to the corresponding user (CQICH_num), an allocation position (allocation index), an allocation period, and an allocation duration, using separate fields of messages used for the CQICH allocation. For doing so, the current system requires a great deal of downlink broadcast channel resources for the CQICH allocation because the CQICH allocation requires a great deal of information, and the system should inform every user of the information at every CQICH allocation period. As a result, overhead caused by the CQICH allocation is problematic. 
       SUMMARY OF THE INVENTION 
       [0008]    An aspect of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, an aspect of the present invention is to provide an apparatus and method for allocating a CQICH in a wireless communication system. 
         [0009]    Another aspect of the present invention is to provide an apparatus and method for reducing an amount of CQICH allocation information using a CQICH segmentation pattern in a wireless communication system. 
         [0010]    A further aspect of the present invention is to provide an apparatus and method for patterning CQICH resources in advance by reflecting a required CQICH pattern for each operation mode and transmitting a greater deal of information of the CQICH allocation with a single index to a terminal. 
         [0011]    The above aspects are achieved by providing a method for allocating a CQICH of a Base Station (BS) in a wireless communication system, which includes determining CQICH patterns required for users using information of one or more users to which CQICH resources are to be allocated, and selecting a CQICH pattern block including all of the determined CQICH patterns among a plurality of pre-generated CQICH pattern blocks; and allocating CQICH sub-blocks corresponding to the users&#39; required CQICH patterns using resource layout information of the CQICH sub-blocks corresponding to the CQICH patterns of the selected CQICH pattern block, and transmitting CQICH allocation information to a Mobile Station (MS). 
         [0012]    According to one embodiment of the present invention, a CQI feedback method of an MS in a wireless communication system includes receiving CQI CHannel (CQICH) allocation information from a BS; when a CQICH pattern block index of the CQICH allocation information is different from a previous CQICH pattern block index, reading CQICH pattern resource layout information corresponding to the received CQICH pattern block index from a CQICH pattern storage memory; and mapping a CQI message to an allocated CQICH according to the read information and the CQICH allocation information. 
         [0013]    According to another embodiment of the present invention, an apparatus for allocating a CHICH of a BS in a wireless communication system includes a CQICH pattern storage memory for storing resource layout information of CQICH patterns based on CQICH pattern blocks; and a controller for determining CQICH patterns required for users using information of one or more users to which a CQICH resources is to be allocated, selecting one CQICH pattern block including all of the determined CQICH patterns from a plurality of pre-generated CQICH pattern blocks, reading resource layout information of CQICH sub-blocks corresponding to CQICH patterns of the selected CQICH pattern block from the CQICH pattern storage memory, and allocating the CQICH sub-blocks corresponding to the CQICH patterns required for the users using the read information. 
         [0014]    According to yet another embodiment of the present invention, a CQI feedback apparatus of a Mobile Station (MS) in a wireless communication system includes a CQICH pattern storage memory for storing CQICH pattern resource layout information based on CQICH pattern blocks; a controller for receiving CQICH allocation information from a BS, when a CQICH pattern block index of the CQICH allocation information is different from a previous CQICH pattern block index, reading CQICH pattern resource layout information corresponding to the received CQICH pattern block index from the CQICH pattern storage memory, and outputting the read information and the CQICH allocation information; and a CQICH message generator for mapping a CQI message to an allocated CQICH according to the read information and the CQICH allocation information. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above and other objects, 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: 
           [0016]      FIG. 1  is a block diagram of a CQICH allocation apparatus of a Base Station (BS) in a wireless communication system according to the present invention; 
           [0017]      FIG. 2  is a block diagram of a CQI feedback apparatus of a Mobile Station (MS) in the wireless communication system according to the present invention; 
           [0018]      FIG. 3  is a flowchart of a CQICH allocation method of the BS in the wireless communication system according to the present invention; 
           [0019]      FIG. 4  is a flowchart of a CQI feedback method of the MS in the wireless communication system according to the present invention; and 
           [0020]      FIGS. 5A and 5B  are diagrams of a CQICH pattern block generation method in the wireless communication system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. 
         [0022]    The present invention provides an apparatus and method for allocating a Channel Quality Information CHannel (CQICH) in a wireless communication system. 
         [0023]    In the following explanation, an operation mode can be a channel coding type, a coding rate, a modulation scheme, a packet length, a Hybrid Automatic Repeat reQuest (H-ARQ) type, a Multiple Input Multiple Output (MIMO) scheme, etc. 
         [0024]      FIG. 1  is a block diagram of a CQICH allocation apparatus of a Base Station (BS) in a wireless communication system according to the present invention. The CQICH allocation apparatus includes a scheduler  101 , a controller  103 , a CQICH pattern storage memory  107 , a broadcast message sender  109 , and a CQICH resource allocation message generator  111 . 
         [0025]    The scheduler  101  of  FIG. 1  schedules to select users to be allocated CQICH and outputs the scheduling result. 
         [0026]    The controller  103  calculates a number of patterns required for the operation modes using information relating to the selected users, e.g., using operation mode information of the corresponding users according to the scheduling result input from the scheduler  101 , and selects one of pre-generated CQICH pattern blocks using the calculation result. Herein, the CQICH pattern block index according to the selection is fixed for a long term. Thus, the BS does not need to frequently transmit the CQICH pattern block index to Mobile Stations (MSs). When the CQICH pattern block index is output to the broadcast message sender  109 , if a change of the pattern block index is required or on a periodic basis, the determined CQICH pattern block can be sent to the MSs. The controller  103  reads resource layout information of sub-blocks constituting an active CQICH pattern of the CQICH pattern block index according to the selection, from the CQICH pattern storage memory  107 , allocates the sub-blocks of the CQICH pattern block to users using the read active CQICH pattern resource layout information, and outputs user CQICH allocation information to the CQICH resource allocation message generator  111 . 
         [0027]    The CQICH pattern storage memory  107  contains the resource layout information of the CQICH pattern constituting the corresponding CQICH pattern block for each CQICH pattern block index, and outputs active CQICH pattern resource layout information corresponding to a specific CQICH pattern block index to the controller  103  under the control of the controller  103 . The broadcast message sender  109  broadcasts the CQICH pattern block index fed from the controller  103  using a separate downlink broadcast channel. 
         [0028]    The CQICH resource allocation message generator  111  generates a CQICH resource allocation message using the CQICH allocation information of the selected user, which is input from the controller  103 , and transmits the generated CQICH resource allocation message to the MS. 
         [0029]      FIG. 2  is a block diagram of a CQI feedback apparatus of an MS in the wireless communication system according to the present invention. The CQI feedback apparatus includes a controller  201 , a CQICH pattern storage memory  203 , and a CQI message generator  205 . 
         [0030]    Upon receiving the CQICH pattern block index over the downlink broadcast channel, the controller  201  of  FIG. 2  examines whether the received CQICH pattern block index matches a previously received CQICH pattern block index. When the two CQICH pattern block indexes do not match, the controller  201  reads active CQICH pattern resource layout information of the received CQICH pattern block index from the CQICH pattern storage memory  203 . When receiving the CQICH resource allocation message including the other CQICH allocation information, excluding the CQICH pattern block index, from the BS, the controller  201  outputs the current active CQICH pattern resource layout information and the CQICH allocation information of the received CQICH resource allocation message to the CQI message generator  205 . 
         [0031]    The CQICH pattern storage memory  203  contains resource layout information of the CQICH patterns based on the CQICH pattern block indexes, and outputs active CQICH pattern resource layout information corresponding to a specific CQICH pattern block index to the controller  201  under the control of the controller  201 . 
         [0032]    The CQI message generator  205  generate a CQI message including CQI information, and transmits the generated CQI message to the BS by mapping the generated CQI message to the allocated CQICH according to the active CQICH pattern resource layout information and the CQICH allocation information fed from the controller  201 . 
         [0033]      FIG. 3  is a flowchart of a CQICH allocation method of the BS in the wireless communication system according to the present invention. 
         [0034]    In  FIG. 3 , the BS selects users to be allocated CQICH resources through the scheduling in step  301 . In step  303 , the BS calculates a number of patterns required for each operation mode using information of the selected users, e.g., using operation mode information of the corresponding users, and selects one of pre-generated CQICH pattern blocks using the calculation result. In step  305 , the BS transmits the selected CQICH pattern block index to the users over the downlink broadcast channel when the CQICH pattern block index needs to change or on a periodic basis. Therefore, the inflexibility of the CQICH allocation can be addressed. The generation of the CQICH pattern block will be described in more detail by referring to  FIGS. 5A and 5B . 
         [0035]    In step  307 , the BS reads resource layout information of CQICH sub-blocks constituting the active CQICH pattern of the selected CQICH pattern block index, from the CQICH pattern storage memory  107 . Next, in step  309 , the BS allocates the sub-blocks of the CQICH pattern block to the selected users using the read active CQICH pattern resource layout information, generates a CQICH resource allocation message using a primary index which is mapped to the CQICH sub-blocks in relation to the user CQICH allocation information, i.e., using a CQICH index, and then transmits the generated message to the MS. 
         [0036]    The CQICH resource allocation message includes a user ID, a CQICH ID, a CQICH index for distinguishing the sub-block allocated to the corresponding user in the selected CQICH pattern block, a feedback type signifying the information to be transmit over the allocated CQICH, a CQICH type signifying the mapping scheme of the information to the allocated CQICH, and a transmission duration signifying how long the corresponding pattern is transmitted. Note that various bitwise options can be included. 
         [0037]    After step  309 , the BS finishes the CQICH allocation process. 
         [0038]      FIG. 4  is a flowchart of a CQI feedback method of the MS in the wireless communication system according to the present invention. 
         [0039]    In  FIG. 4 , the MS determines whether a CQICH pattern block index is received over the downlink broadcast channel in step  401 . Upon receiving the CQICH pattern block index, the MS examines whether the received CQICH pattern block index matches the previously received CQICH pattern block index in step  403 . When the two pattern block indexes do not match, the MS reads active CQICH pattern resource layout information corresponding to the received CQICH pattern block index from the CQICH pattern storage memory  203  in step  405 . In step  407 , the MS determines whether a CQICH resource allocation message including the other CQICH allocation information, excluding the CQICH pattern block index, is received from the BS. 
         [0040]    By contrast, when the CQICH pattern block index is not received in step  401  or when the two pattern block indexes are identical in step  403 , the MS determines whether a CQICH resource allocation message is received from the BS in step  407 . 
         [0041]    Receiving the CQICH resource allocation message from the BS in step  407 , the MS maps a CQI message including CQI information to the allocated CQICH according to the CQICH allocation information of the CQICH resource allocation message and the active CQICH pattern resource layout information in step  409 . In step  411 , the MS transmits the CQI message to the BS. By contrast, when no CQICH resource allocation message is received from the BS in step  407 , the MS returns to step  401 . 
         [0042]    After step  411 , the MS finishes CQI feedback process. 
         [0043]      FIGS. 5A and 5B  are diagrams of a CQICH pattern block generation method in the wireless communication system according to the present invention. 
         [0044]    In  FIGS. 5A and 5B , the vertical axis indicates CQICH physical resources and the horizontal axis indicates frames. The CQICH pattern block is a two-dimensional block corresponding to the number of CQICHs per frame× the CQICH pattern period. The individual CQICH pattern block has a different combination of element patterns constituting the two-dimensional block. In  FIGS. 5A and 5B , the same colored portion is a whole CQICH sub-block. The CQICH sub-blocks are distinguished using their assigned resource indexes. 
         [0045]    For example, the patterns  1  and  2  in the CQICH pattern block  1 ( 5   a ) is a CQICH pattern allocated to the corresponding user to send the CQICH in every two frames. At one time, two CQICH resources are allocated for the large amount of feedback. At the other time, only one CQICH resource is allocated for the small amount of feedback. The pattern  7  in the CQICH pattern block  1 ( 5   a ) is allocated to the user to send the CQICH in every two frames, and allocates four CQICH resources at a time. The patterns  3 ,  10   14  and  16  of the CQICH pattern block  1  ( 5   a ) are the patterns for the operation mode which merely allocates one CQICH resource in every eight frames. The pattern block  2  ( 5   b ) is a combination of element patterns different from the pattern block  1  ( 5   a ). 
         [0046]    To generate the CQICH pattern block, the CQICH pattern is generated by taking into account the requirements for the required CQICH allocation period and the number of required CQICH resources for one allocation according to each operation mode. In other words, for each operation mode, the CQICH pattern is generated to signify the number of CQICH resource allocations required in every which frames in a certain frame. 
         [0047]    Next, a CQICH pattern sequence set is generated by considering the CQICH pattern required for each operation mode. The CQICH pattern sequence set includes a plurality of CQICH pattern groups that satisfy the different CQICH allocation pattern requirements. Each CQICH pattern group includes a plurality of element pattern sequences, and each CQICH pattern corresponds to one CQICH pattern group. 
         [0048]    For example, the CQICH pattern sequence set is generated in units of eight frames. To transmit the CQICH once every two frames to the corresponding user, the CQICH pattern first allocates two CQICH resources for a large amount of the feedback and then allocates only one CQICH resource for the small amount of remaining feedback. In this case, the CQICH pattern group can be expressed as Equation (1). 
         [0000]      P 11 =[20102010] 
         [0000]      P 12 =[02010201] 
         [0000]      P 13 =[10201020] 
         [0000]      P 4 =[01020102]  (1) 
         [0049]    When the pattern allocates only one CQICH resource per every eight frames, the CQICH pattern group can be expressed as Equation (2). 
         [0000]      P 21 =[10000000] 
         [0000]      P 22 =[01000000] 
         [0000]      P 23 =[00100000] 
         [0000]      P 24 =[000100000] 
         [0000]      P 24 =[00010000] 
         [0000]      P 25 =[00001000] 
         [0000]      P 26 =[00000100] 
         [0000]      P 27 =[00000010] 
         [0000]      P 28 =[00000001]  (2) 
         [0050]    When the pattern allocates only two CQICH resources per every two frames, the CQICH pattern group can be expressed as Equation (3). 
         [0000]      P 31 =[20202020] 
         [0000]      P 32 =[02020202]  (3) 
         [0051]    P ij  denotes a j-th element pattern sequence of an i-th CQICH pattern group. The element pattern sequences in the same CQICH pattern group have equal priority. 
         [0052]    The CQICH pattern group is determined by taking into account the CQICH allocation pattern required for each operation mode in a general condition as follows. The length of the element pattern sequence is equal to the CQICH allocation period, and a k-th item value of the element pattern sequence indicates the number of CQICHs allocated to the k-th frame. The first element pattern sequence of a specific CQICH pattern group is set to a random sequence, which meets the required CQICH allocation period and the required CQICH number of the corresponding operation mode. Every possible circular shifted sequence of the first element pattern sequence is generated and designated to the element pattern sequences of the corresponding CQICH pattern group. 
         [0053]    Finally, a plurality of CQICH pattern blocks is generated by reflecting the different operation mode multiplexing ratios using the CQICH pattern group and the element pattern sequences. For doing so, conditions, which should be satisfied, are defined by considering the operation mode multiplexing ratios of the CQICH pattern blocks. For example, the condition of a certain CQICH pattern blocks requires the allocation of three or more P 1x  and four or more P 2x . Next, by taking into account the condition which should be satisfied for each CQICH pattern block, a pattern block satisfying Equation (4) is generated. 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
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         [0054]    The rightmost ‘1’ in Equation (4) denotes a vector having every element being ‘1’, and ρ ij  denotes the allocation number of the j-th element pattern sequence of the i-th CQICH pattern group. ρ ij  is zero or a positive number. n i  denotes a minimum allocation number of the i-th CQICH pattern group, N pattern  denotes the number of CQICH pattern groups, N CQICH  denotes the number of CQICHs per frame, and m i  denotes the number of element pattern sequences belonging to the i-th CQICH pattern group. The first line of Equation (4) signifies that the block of the number of CQICHs per frame× the CQICH pattern period in size is segmented into CQICH sub-blocks corresponding to the element pattern sequences without omission, and the second line signifies that there are at least n i -ary CQICH sub-blocks corresponding to the i-th pattern group in the segmented CQICH sub-blocks. 
         [0055]    In other words, the required CQICH patterns are generated for the different operation modes, and the CQICH pattern block corresponding to the CQICH number× the CQICH pattern period, which can allocate the patterns to the frames, is generated by combining the generated CQICH patterns. 
         [0056]    The primary resource indexes (e.g.,  1 - 18  of  FIG. 5A ,  1 - 20  of  FIG. 5B ) are assigned to the CQICH sub-blocks constituting the generated CQICH pattern block, and the CQICH pattern block indexes (e.g., the pattern  1  and the pattern  2  of  FIGS. 5A and 5B ) are assigned to the CQICH pattern blocks that meet the requirements of the different operation modes. The information relating to the generated CQICH pattern block is known to both of the BS and the MS. 
         [0057]    While the CQICH pattern block index is transmitted over the downlink broadcast channel and the CQICH resource allocation message including the other CQICH allocation information is separately transmitted according to the present invention, the transmitted CQICH resource allocation message can include the CQICH pattern block index information. 
         [0058]    When the CQICH resources are allocated using the CQICH pattern block according to the present invention, there is no need to send the information relating to the 4-bit CQICH resource number allocated to the corresponding user (CQICH_num), the 6-bit allocation position (allocation index), and the 3-bit allocation period of the CQICH allocation message information to the users in a conventional 802.16e system. While the CQICH resource allocation message including the CQICH type and feedback type information transmitted for each CQICH resource is sent in every frame, the information can be transmitted only once to reduce several bits. 
         [0059]    While the message is dedicated for the CQICH allocation, the information sent for the CQICH allocation can be transmitted together with the allocation message for the data channel at the same time. For example, if a resource allocation message for the data channel allocation is transmitted to the corresponding user, a message including the information for the CQICH allocation can be sent together with the resource allocation message for the data channel allocation. In this case, it is possible to reduce the overhead caused by CQICH_ID and Cyclic Redundancy Check (CRC) required for sending a message for a separate CQICH allocation. 
         [0060]    Alternatively, the information transmitted for the CQICH allocation can be piggybacked on the data. In this case, when the corresponding user has the data channel, a 1-bit indicator signifying whether the CQICH allocation is piggybacked is set and the CQICH allocation message is piggybacked. 
         [0061]    As set forth above, the CQICH resources are patterned in advance by reflecting the required CQICH patterns of the operation modes, and the great amount of information relating to the CQICH allocation is transmitted to the MS with the single index in the wireless communication system. Therefore, the resources required for the CQICH allocation can be reduced. 
         [0062]    While the invention has been shown and described with reference to certain preferred 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 invention as defined by the appended claims.