Abstract:
A radio communication system includes at least one mobile station and a base station, wherein one and the same two-dimensional table, in which resource block numbers are allocated to a plurality of resource blocks obtained by dividing a system bandwidth by a frequency domain, is stored in both the base station and the at least one mobile station, and allocation information representing allocation of the resource block numbers in the two-dimensional table is transmitted from the base station to one of the at least one mobile station.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-65427, filed on Mar. 14, 2008, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The present invention relates to a radio communication system having a base station and a mobile station, the base station, the mobile station, and a resource block allocation method. 
       BACKGROUND 
       [0003]    In 3GPP (3rd Generation Partnership Project), there has been proposed an LTE (Long Term Evolution)-based radio communication system between a base station and a mobile station. 
         [0004]    In LTE, a packet switching type access method is used so that radio resources are allocated based on frequency domain scheduling both in uplink and downlink communications (see 3GPP TS36.211 V8.0.0 (2007-09)). 
         [0005]    In downlink communications, a resource block is defined as a block having consecutive sub-carriers and consecutive OFDM (Orthogonal Frequency Division Multiplexing) symbols in a transmission band. The number of resource blocks takes a value of 6 to 110 in accordance with the transmission bandwidth. 
         [0006]    In a downlink shared data channel which is a channel used for transmission of traffic data, the transmission is performed by using resource blocks allocated by scheduling in a base station. A downlink control channel is a channel used for transmission of information (such as resource block allocation information) required for reception via the shared data channel. 
         [0007]    A theme under discussion in 3GPP is what data is used as the resource block allocation information of the shared data channel to be transmitted via the control channel. As an idea for the theme, resource blocks are divided into consecutive subsets so that the resource block allocation information to be transmitted via the control channel is defined by bitmap information indicating resource blocks in the subsets and bitmap information (header) indicating arbitrary ones of the subsets (see 3GPP, TSG-RAN WG1 #50bis R1-074221). 
         [0008]    Incidentally, in a system in which a base station transmits resource block allocation information to a mobile station, there has been proposed a method of transmitting the allocation information and information concerned with initial values of allocable resources and the required number of bits (e.g. see Japanese Laid-open Patent Publication No. 2007-282021). There has been further proposed a method of transmitting a resource block allocation table from an MS (mobile station) to a BTS (base transceiver station) to achieve improvement in efficiency of resource management (e.g. see Japanese Laid-open Patent Publication No. 2001-275153). 
         [0009]    As a method of dividing radio resources, there has been further proposed a method in which a base station composes radio resources in time, frequency and code in a three-dimensional space (e.g. see Japanese Laid-open Patent Publication No. 2005-117579). There has been further proposed a scheduling method in which radio resources in downlink communications are divided into resource blocks of the same size so that each allocated resource block is transmitted in a feed-forward manner (e.g. Japanese Laid-open Patent Publication No. 2006-515141). 
         [0010]    In the related-art method in which resource blocks are divided into consecutive subsets so that the resource block allocation information to be transmitted via the control channel is defined by bitmap information indicating resource blocks in the subsets and bitmap information (header) indicating arbitrary ones of the subsets, there is a problem that the number of bits in the resource block allocation information increases. This problem is not limited to the radio communication system of 3GPP, and may occur in other radio communication systems. 
       SUMMARY 
       [0011]    According to an aspect of some embodiments, a radio communication system includes at least one mobile station and a base station, wherein one and the same two-dimensional table, in which resource block numbers are allocated to a plurality of resource blocks obtained by dividing a system bandwidth by a frequency domain, is stored in both the base station and the at least one mobile station, and allocation information representing allocation of the resource block numbers in the two-dimensional table is transmitted from the base station to one of the at least one mobile station. 
         [0012]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the embodiments, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates a configuration view of an embodiment of a downlink resource block; 
           [0014]      FIG. 2  illustrates a block configuration diagram of an embodiment of a base station; 
           [0015]      FIG. 3  illustrates a block configuration diagram of an embodiment of a mobile station; 
           [0016]      FIG. 4  illustrates a configuration example of a first embodiment of a resource block table; 
           [0017]      FIG. 5  illustrates a view for explaining allocation of resource block numbers; 
           [0018]      FIG. 6  illustrates allocation information; 
           [0019]      FIG. 7  illustrates a view for explaining identification of allocated resource block numbers; 
           [0020]      FIG. 8  illustrates a state in which resource blocks are allocated to a plurality of mobile stations; 
           [0021]      FIG. 9  illustrates a configuration example of a second embodiment of the resource block table; 
           [0022]      FIG. 10  illustrates the configuration example of the second embodiment of the resource block table; 
           [0023]      FIGS. 11A and 11B  illustrate allocation information; 
           [0024]      FIG. 12  illustrates a configuration example of a fourth embodiment of the resource block table; 
           [0025]      FIGS. 13A and 13B  illustrate allocation information; 
           [0026]      FIG. 14  illustrates a state in which resource blocks are allocated to a plurality of mobile stations; 
           [0027]      FIGS. 15A and 15B  illustrate allocation information; and 
           [0028]      FIG. 16  illustrates a table for comparison between an embodiment of the invention and an example of the related art. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0029]      FIG. 1  illustrates a configuration view of an embodiment of a downlink resource block. One resource block is a domain having 7 OFDM symbols in a time direction and 12 sub-carriers in a frequency direction. 
         [0030]    The number of resource blocks varies according to a frequency band to be used. When the frequency bandwidth is 1.25 MHz, the number of resource blocks is 6. When the frequency bandwidth is 2.5 MHz, the number of resource blocks is 12. When the frequency bandwidth is 5 MHz, the number of resource blocks is 25. When the frequency bandwidth is 10 MHz, the number of resource blocks is 50. When the frequency bandwidth is 15 MHz, the number of resource blocks is 75. When the frequency bandwidth is 22 MHz, the number of resource blocks is 110. 
       Configuration of Base Station 
       [0031]      FIG. 2  illustrates a block configuration diagram of an embodiment of a base station. In  FIG. 2 , transmission data destined for mobile stations  1  to N are supplied to encoding portions  10 - 1  to  10 -N and encoded by the encoding portions  10 - 1  to  10 -N respectively. The encoded transmission data are supplied to modulation portions  11 - 1  to  11 -N, modulated by optimum modulation methods respectively and then supplied to a resource block mapping portion  12 . 
         [0032]    A scheduler  15  has a resource block table  16 , for example, stored in a non-volatile memory. The scheduler  15  controls the resource block mapping portion  12  to map respective transmission data of the mobile stations  1  to N on given resource blocks by referring to the resource block table  16 . In this manner, the resource block mapping portion  12  maps the respective transmission data of the mobile stations  1  to N on the given resource blocks and supplies the mapped data to a transmission portion  19  via a data channel. 
         [0033]    In addition, the scheduler  15  supplies mapping control information indicating respective mapping states of the mobile stations  1  to N, to an encoding portion  17 . The encoding portion  17  encodes the mapping control information. The encoded control information is modulated by a given modulation method in a modulation portion  18  and supplied to the transmission portion  19  via a control channel. The transmission portion  19  multiplexes the data channel and the control channel into a signal and transmits the signal from an antenna. 
       Configuration of Mobile Station 
       [0034]      FIG. 3  illustrates a block configuration diagram of an embodiment of a mobile station. In  FIG. 3 , a reception portion  21  separates a signal received by an antenna into a data channel and a control channel, and supplies the data channel to a resource block demapping portion  22  while supplying the control channel to a demodulation portion  23 . 
         [0035]    The demodulation portion  23  demodulates the control channel into a signal and supplies the demodulated signal to a decoding portion  24 . The decoding portion  24  decodes the demodulated signal to obtain mapping control information indicating respective mapping states of the mobile stations  1  to N, and supplies the mapping control information to a resource block mapping determination portion  25 . 
         [0036]    The resource block mapping determination portion  25  has a resource block table  26 , for example, stored in a non-volatile memory. The resource block table  26  has the same contents as those of the resource block table  16  in the base station. The resource block mapping determination portion  25  extracts mapping control information indicating only the mobile station&#39;s own mapping state from the mapping control information, obtains resource block information (e.g. resource block numbers) allocated to the mobile station itself by referring to the resource block table  26  with use of the extracted mapping control information, and supplies the resource block information to the resource block demapping portion  22 . 
         [0037]    In this manner, the resource block demapping portion  22  extracts information mapped on the resource blocks allocated to the mobile station in the data channel, and supplies the extracted information to a demodulation portion  27 . The demodulation portion  27  demodulates the information supplied from the resource block demapping portion  22  into a signal, and supplies the demodulated signal to a decoding portion  28 . The decoding portion  28  decodes the demodulated signal and outputs the decoded signal as transmission data for the mobile station. 
       First Embodiment 
       [0038]      FIG. 4  illustrates a configuration example of a first embodiment of the resource block table. This configuration example illustrates the case where the frequency band is 5 MHz (the number of resource blocks is 25). In the configuration, resource block numbers are allocated to respective elements of a 5×5 table region consecutively. The resource block table illustrated in  FIG. 4  is used as the resource block table  16 ,  26 . 
         [0039]    The size (the number of columns and the number of rows) of the table and the position of each resource block number may be determined freely while flexibility for allocating resource blocks is taken into consideration. Further, these values may be updated based on table information transmitted to each mobile station by the base station via a report channel, etc. 
         [0040]    Similarly, for each of the frequency bands other than the 5 MHz frequency band, a common resource block table having allocated resource block numbers is held in both the base station and each mobile station. The resource block tables for respective frequency bands may be switched from one to another based on frequency band information which is transmitted to each mobile station by the base station via a report channel, etc. 
         [0041]    Although the aforementioned embodiment has been described for the case where one table is defined for each frequency band, tables may be defined for each frequency band so that more flexible resource block allocation may be made when the tables are switched based on table selection information which is transmitted to each mobile station by the base station. 
         [0042]      FIG. 5  illustrates a view for explaining allocation of resource block numbers. In  FIG. 5 , allocation information has 5-bit column allocation information  31  and 5-bit row allocation information  32 . 
         [0043]    For example, in the column allocation information  31  and the row allocation information  32 , a bit of a value “1” represents “with allocation”. When both a bit in the column allocation information  31  and a bit in the row allocation information  32  represent “with allocation” in the resource block table  16  of the base station, a resource block number in an intersection position between a column indicated by the bit of the column allocation information  31  and a row indicated by the bit of the row allocation information  32  is allocated to the mobile station.  FIG. 5  illustrates the case where a resource block “ 7 ” and a resource block “ 8 ” are allocated to the mobile station. This allocation is performed in the scheduler  15  of the base station. 
         [0044]      FIG. 6  illustrates a state in which the column allocation information  31  and the row allocation information  32  illustrated in  FIG. 5  are combined into 10-bit allocation information  33 . The 10-bit allocation information  33  is transmitted to each mobile station by the base station via the control channel. 
         [0045]      FIG. 7  illustrates a view for explaining identification of allocated resource block numbers. Upon reception of the allocation information illustrated in  FIG. 6 , the mobile station identifies the allocated resource block numbers by using the same resource block table  26  as that of the base station. 
         [0046]    When both a bit in the column allocation information  31  and a bit in the row allocation information  32  represent “with allocation” in the resource block table  26  of the mobile station, a resource block number in an intersection position between a column indicated by the bit of the column allocation information  31  and a row indicated by the bit of the row allocation information  32  is identified as being allocated to the mobile station. 
         [0047]    When resource block allocation is made in this manner based on the column allocation information and the row allocation information transmitted/received, reduction in the data quantity of the control channel can be achieved. 
         [0048]      FIG. 8  illustrates a state in which resource blocks are allocated to a plurality of mobile stations in the first embodiment. In  FIG. 8 , a base station  40  creates allocation information  33   a  having column allocation information “111100” and row allocation information “11000” and transmits the allocation information  33   a  to a mobile station  41  via a control channel so that resource blocks of resource block numbers “ 1 - 3 ,  6 - 8 ” are allocated to the mobile station  41 . 
         [0049]    On the other hand, the base station  40  creates allocation information  33   b  having column allocation information “11111” and row allocation information “00110” and transmits the allocation information  33   b  to a mobile station  42  via a control channel so that resource blocks of resource block numbers “ 11 - 20 ” are allocated to the mobile station  42 . 
         [0050]    The mobile station  41  identifies that resource blocks of resource block numbers “ 1 - 3 ,  6 - 8 ” in intersection positions between columns and rows of “with allocation” (value “1”) in the column allocation information and the row allocation information are allocated to the mobile station  41  itself, by referring to a resource block table  26  with use of the column allocation information “11100” and the row allocation information “11000” of the allocation information  33   a.    
         [0051]    The mobile station  42  identifies that resource blocks of resource block numbers “ 11 - 20 ” in intersection positions between columns and rows of “with allocation” (value “1”) in the column allocation information and the row allocation information are allocated to the mobile station  42  itself, by referring to a resource block table  26  with use of the column allocation information “11111” and the row allocation information “00110” of the allocation information  33   b.    
       Second Embodiment 
       [0052]      FIGS. 9 and 10  illustrate configuration examples of a second embodiment of the resource block table. The configuration examples illustrate the case where the frequency band is 10 MHz (the number of resource blocks=50). In the configuration, resource block numbers are allocated to respective elements of an 8×7 table consecutively. This resource block table is used as a resource block table  16 ,  26 . 
         [0053]    Allocation information has 8-bit column allocation information  34  and 7-bit row allocation information  35 . For example, in the column allocation information  34  and the row allocation information  35 , a bit of a value “1” represents “with allocation”. 
         [0054]    In this case, there occur six empty regions (in the seventh row and the third to eighth columns). These empty regions are used for creation of resource block allocation patterns or allocation of redundant resource block numbers. 
         [0055]    In the configuration example of  FIG. 9 , for example, a region of the seventh row and the third column is used as a resource block allocation pattern which allocates resource block numbers “ 1 - 10 ” when the region is set as “with allocation” and, for example, a region of the seventh row and the fourth column is used as a resource block allocation pattern which allocates resource block numbers “ 11 - 21 ” when the region is set as “with allocation”. That is, the resource block allocation pattern performs resource block allocation without use of any resource block table. In this manner, specific consecutive resource block numbers can be allocated so that flexibility (degree of freedom) for resource block number allocation increases. 
         [0056]    In the configuration example of  FIG. 10 , resource block numbers “ 23 - 28 ” are allocated to regions of the seventh row and the third to eighth columns. Because the resource block numbers “ 23 - 28 ” are also allocated to regions of the third row and the seventh and eighth columns and regions of the fourth row and the first to fourth columns, this allocation is redundant. 
         [0057]    In the configuration example of  FIG. 9 , when column allocation information “11000011” and row allocation information “0011000” are intended to allocate resource numbers “ 23 - 26 ”, this allocation cannot be achieved because resource block numbers “ 17 ,  18 ,  31  and  32 ” are also allocated erroneously in addition to allocation of the resource block numbers “ 23 - 26 ”. In the configuration example of  FIG. 10 , resource block numbers “ 23 - 26 ” can be however allocated when column allocation information “00111100” and row allocation information “0000001” are used. 
         [0058]    Transmission of allocation information from the base station to one or more mobile stations in this embodiment is performed in the same manner as in  FIG. 8 . In this embodiment, more flexible resource block allocation can be performed without an increase in quantity of information to be transmitted/received. 
       Third Embodiment 
       [0059]    In the first or second embodiment, there is no situation that the values of all bits in the column allocation information  31 ,  34  are “0”, and there is no situation that the values of all bits in the row allocation information  32 ,  35  are “0”. It is therefore possible to give a special meaning to the case where the values of all bits in column allocation information or row allocation information are “0”. 
         [0060]    In  FIG. 11A ,  32  resource block allocation patterns may be designated by 5-bit row allocation information  32  when the values of all bits in column allocation information  31  are “0”. For example, odd resource block numbers “ 1 ,  3 , . . . ,  23 ,  25 ” may be allocated when the values of all bits in the column allocation information  31  are “0” and the row allocation information  32  is “01000”. 
         [0061]    In  FIG. 11B ,  31  resource block allocation patterns may be designated by 5-bit column allocation information  31  when the values of all bits in row allocation information  32  are “0”. For example, resource block numbers “ 1 - 6 ” may be allocated when the values of all bits in the row allocation information  32  are “0” and the column allocation information  31  is “00011”. 
         [0062]    This configuration may be applied not only to the first embodiment but also to the second embodiment. In this manner, more flexible resource block allocation can be made. 
       Fourth Embodiment 
       [0063]      FIG. 12  illustrates a configuration example of a fourth embodiment of the resource block table. This configuration example illustrates the case where the frequency band is 5 MHz (the number of resource blocks=25). In the configuration, resource block numbers are allocated to respective elements of a 6×6 table consecutively. This resource block table is used as a resource block table  16 ,  26 . 
         [0064]    Allocation information has 6-bit column allocation information  37  and 6-bit row allocation information  38 . For example, in the column allocation information  37  and the row allocation information  38 , a bit of a value “1” represents “with allocation”. 
         [0065]    In this case, there occur eleven empty regions (in the sixth row and the sixth column). These empty regions are used for creation of resource block allocation patterns or allocation of redundant resource block numbers. 
         [0066]    Transmission of allocation information from the base station to one or more mobile stations in this embodiment is performed in the same manner as in  FIG. 8 . In this embodiment, the quantity of information to be transmitted/received increases but more flexible resource block allocation may be performed. 
       Fifth Embodiment 
       [0067]    This embodiment is provided with a function of switching between a first mode for transmission/reception of resource block table allocation information and a second mode for transmission/reception of consecutive-number resource block allocation information. 
         [0068]      FIGS. 13A and 13B  illustrate the configuration of allocation information  51  in this embodiment. A leading bit of the allocation information  51  is set as a format information bit  52 . As illustrated in  FIG. 13A , when the value of the format information bit  52  is “0”, a bit string following the format information bit  52  is defined as a combination of column allocation information  53  and row allocation information  54  in the same manner as in the first embodiment. 
         [0069]    As illustrated in  FIG. 13B , when the value of the format information bit  52  is “1”, the bit string following the format information bit  52  is defined as consecutive-number resource block allocation information. A 5-bit first half of the consecutive-number resource block allocation information is defined as start resource block number information  55 , and a 5-bit last-half of the consecutive-number resource block allocation information is defined as number-of-resource-blocks information  56 . 
         [0070]    In this embodiment, addition of only 1 bit makes it possible to allocate more flexibly an allocation pattern of consecutive-number resource blocks which cannot be allocated in the first embodiment. 
         [0071]      FIG. 14  illustrates a state in which resource blocks are allocated to a plurality of mobile stations in a fifth embodiment. In  FIG. 14 , a base station  60  creates allocation information  51   a  having a format information bit  52  of “0”, column allocation information  53  of “11100” and row allocation information  54  of “11000” and transmits the allocation information  51   a  to a mobile station  61  via a control channel so that resource blocks of resource block numbers “ 1 - 3 ,  6 - 8 ” are allocated to the mobile station  61 . 
         [0072]    On the other hand, the base station  60  creates allocation information  51   b  having a format information bit  52  of “1”, start resource block number information  55  of “01001” and number-of-resource-blocks information  56  of “01011” and transmits the allocation information  51   b  to a mobile station  62  via a control channel so that  11  resource blocks continued on the start resource block number “ 9 ” are allocated to the mobile station  62 . 
         [0073]    The mobile station  61  identifies that resource blocks of resource block numbers “ 1 - 3 ,  6 - 8 ” in intersection positions between columns and rows of “with allocation” (value “1”) in the column allocation information and the row allocation information are allocated to the mobile station  61  itself, by referring to a resource block table  26  with use of the column allocation information “11100” and the row allocation information “11000” of the allocation information  51   a.    
         [0074]    The mobile station  62  identifies that resource blocks of resource block numbers “ 9 - 19 ” are allocated to the mobile station  62  itself, based on the start resource block number information “01001” and the number-of-resource-blocks information “01011” of the allocation information  51   b.    
       Sixth Embodiment 
       [0075]    Description will be made on an embodiment for extending the second mode function for transmitting/receiving consecutive-number resource block allocation information. 
         [0076]    As illustrated in  FIG. 15A , when the format information bit  52  is “1” and the start resource block number information  55  is “11010-11111”, i.e. “26-31” in decimal notation, the start resource block number information  55  is invalid (because the total number of resource blocks is 25). Therefore,  32  resource block numbers or resource block allocation patterns indicating number-of-resource-blocks information  56  of “00000-11111” may be designated in each of the values “11010-11111” of the start resource block number information  55 . 
         [0077]    As illustrated in  FIG. 15B , when the format information bit  52  is “1” and the number-of-resource-blocks information  56  is “00000”, the number-of-resource-blocks information  56  is invalid (because the number of resource blocks is 0). Therefore,  32  resource block numbers or resource block allocation patterns indicating start resource block number information  55  of “00000-11111” may be designated when the number-of-resource-blocks information  56  is “00000”. In this manner, more flexible resource block allocation can be performed. 
         [0078]      FIG. 16  illustrates the total number of control bits required for resource block allocation in each of the aforementioned embodiment and the related-art example (Non-Patent Document 2). When the bandwidth is 5 MHz, the number of resource blocks is 25. According to the aforementioned embodiment, each of the column allocation information and the row allocation information is 5 bits and the format information bit is 1 bit, i.e. the total number of control bits is 11. On the other hand, according to the related art, the total number of control bits is 14. In short, according to the embodiment, the total number of control bits can be reduced by 3 bits. 
         [0079]    When the bandwidth is 22 MHz, the number of resource blocks is 110. According to the aforementioned embodiment, the column allocation information is 11 bits, the row allocation information is 10 bits and the format information bit is 1 bit, i.e. the number of control bits is 22. On the other hand, according to the related art, the total number of control bits is 32. In short, according to the aforementioned embodiment, the total number of control bits can be reduced by 10 bits. 
         [0080]    Incidentally, in the aforementioned embodiment, the encoding portion  17 , the modulation portion  18  and the transmission portion  19  are used as an example of the components in a transmission unit, and the demodulation portion  23 , the decoding portion  24  and the resource block mapping determination portion  25  are used as an example of the components in a resource block number acquisition unit. 
         [0081]    According to the radio communication system of certain aforementioned embodiments, the number of bits required for resource block allocation can be reduced. 
         [0082]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.