Abstract:
An aspect of the invention provides a base station including: a communication unit configured to communicate with a wireless terminal; a determination unit that determines whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on a signal reception state of the wireless terminal; and a controller that controls the communication unit to communicate with the wireless terminal to alternately use one of first subcarriers when the wireless terminal is determined to be in the first communication area and that controls the communication unit to communicate with the wireless terminal to use a second subcarrier when the wireless terminal is determined to be outside of the cell edge which is a second communication area to be not overlapped with other communication area.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-157516, filed Jun. 6, 2006, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    This invention relates to a base station and a wireless communication method using a multicarrier wireless communication system. 
         [0004]    2. Related Art 
         [0005]    Conventionally, in a cellular system, whole service area is divided into cell units and a base station and a plurality of wireless terminals communicates with each other a each cell. In the cellular system, the adjacent cells are designed overlapping each other so that communications are also able to be conducted on the boundary between the cells. Thus, if the same frequency band is assigned to the cells, inter-cell interference may occur in the area where the adjacent cells overlap each other (which will be hereinafter referred to as a cell edge). 
         [0006]    JP-A 2001-231077 (KOKAI) discloses a system in which a frequency band is time-divided to be assigned to the cells with a time shift as a system in which inter-cell interference does not occur even when the same frequency band is assigned to the cells. 
         [0007]    In this system, frequency band A assigned to the system is time-divided into slots S 1 , S 2 , . . . and the slots S 1 , S 2 , . . . are assigned to cells C 1 , C 2 , . . . In each cell C 1 , C 2 , a base station and a plurality of wireless terminals occupy the frequency band A for communicating with each other within the time of the assigned slot S 1 , S 2 , . . . . Accordingly, the same frequency band is not used within the same time in each cell C 1 , C 2 , . . . , and inter-cell interference in the cell edge is not occurred. 
       SUMMARY 
       [0008]    In the system described in JP-A 2001-231077 (KOKAI), however, when the frequency band A is used in the cell C 1  during the Slot S 1 , the frequency band A is not used in other cells C 2 , C 3 , . . . during the time. Thus, if the number of cells belonging to the system increases, the whole throughput of the system may be lowered in proportion to the number of cells. 
         [0009]    The present invention has been made in view of above circumstances. Aspects of the invention provides a base station and a wireless communication method capable of suppressing interference with the adjacent cell while suppressing to lower the whole throughput of the system and ensuring the communication throughput in each cell. 
         [0010]    An aspect of the present invention provides a base station including: a communication unit configured to communicate with a wireless terminal; a determination unit that determines whether or not the wireless terminal is in a cell edge which is a first communication area to be overlapped with other communication area based on a signal reception state of the wireless terminal; and a controller that controls the communication unit to communicate with the wireless terminal to alternately use one of first subcarriers when the wireless terminal is determined to be in the first communication area and that controls the communication unit to communicate with the wireless terminal to use a second subcarrier when the wireless terminal is determined to be outside of the cell edge which is a second communication area to be not overlapped with other communication area. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a drawing to show a wireless communication system according to a first embodiment of the invention; 
           [0012]      FIGS. 2A and 2B  are drawings to show placement of subcarriers when a multicarrier wireless communication system, such as OFDM communication system is used according to the first embodiment; 
           [0013]      FIGS. 3A and 3B  are drawings to show a modified example 1 of subcarrier placement when the multicarrier wireless communication system, such as OFDM communication system is used; 
           [0014]      FIGS. 4A and 4B  are drawings to show a modified example 2 of subcarrier placement when the multicarrier wireless communication system, such as OFDM communication system is used; 
           [0015]      FIGS. 5A and 5B  are drawings to show a placement example of subcarriers when a frequency division multiplexing communication system is used; 
           [0016]      FIGS. 6A and 6B  are drawings to show a wireless frame format according to the first embodiment; 
           [0017]      FIG. 7  is a drawing to show the slot configuration of a wireless frame used by a first NodeB station according to the first embodiment; 
           [0018]      FIG. 8  is a drawing to show the slot configuration of a wireless frame used by a second NodeB according to the first embodiment; 
           [0019]      FIG. 9  is a drawing to show the slot configuration of wireless frames used by the first NodeB and second NodeB according to the first embodiment; 
           [0020]      FIGS. 10A to 10C  are drawings to show the configuration of each pilot symbol of cell edge subcarriers according to the first embodiment; 
           [0021]      FIG. 11  is a drawing to show a first modified example of the slot configuration of the cell edge subcarriers; 
           [0022]      FIG. 12  is a drawing to show a second modified example of the slot configuration of the cell edge subcarriers; 
           [0023]      FIG. 13  is a drawing to show a third modified example of the slot configuration of the cell edge subcarriers; 
           [0024]      FIG. 14  is a block diagram to show the first NodeB according to the first embodiment; 
           [0025]      FIG. 15  is a drawing to show a table of a UE management information storage according to the first embodiment; 
           [0026]      FIG. 16  is a drawing to show a table of a pattern storage according to the first embodiment; 
           [0027]      FIG. 17  is a block diagram to show a terminal according to the first embodiment; 
           [0028]      FIG. 18  is a chart to describe a sequence for the first NodeB to determine the reception state of the terminal according to the first embodiment; 
           [0029]      FIG. 19  is a chart to describe a sequence for the terminal to determine the reception state of the terminal according to the first embodiment; 
           [0030]      FIG. 20  is a flowchart to describe reception state determination processing according to the first embodiment; 
           [0031]      FIG. 21  is a flowchart to describe a modified example of the reception state determination processing according to the first embodiment; 
           [0032]      FIGS. 22A and 22B  are drawings to show a wireless frame format according to a second embodiment of the invention; 
           [0033]      FIGS. 23A and 23B  are drawings to show a modified example of the wireless frame format according to the second embodiment; and 
           [0034]      FIGS. 24A and 24B  are drawings to show a wireless frame format according to a third embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. 
       First Embodiment 
       [0036]    A wireless communication system according to a first embodiment of the invention will be discussed with  FIGS. 1 to 21 . 
         [0037]    The wireless communication system shown in  FIG. 1  includes a Radio Network Controller (RNC)  10 , base station apparatus (NodeB)  11  and  12  managed by the RNC  10 , and terminals (UE)  21 - 1 ,  21 - 2 , . . . ,  22 - 1 ,  22 - 2 , . . . receiving service from the NodeB  11  and NodeB  12 . In the description to follow, it is assumed that the UEs receiving service from the NodeB  11  and NodeB  12  are four of UE  21 - 1 , UE  21 - 2 , UE  22 - 1 , and UE  22 - 2 . The range in which the NodeB  11  can perform service of telephone call, data communications, etc., for each UE (which will be hereinafter referred to as communication area A 1 ) and the range in which the NodeB  12  can perform service for each UE (which will be hereinafter referred to as communication area A 2 ) overlap each other and hereinafter the overlap area will be referred to as a cell edge. 
         [0038]    It is assumed that the NodeB  11  performs service using a multicarrier wireless communication system for the UE  21 - 1 , UE  21 - 2 , and UE  22 - 2  existing in the communication area A 1 . On the other hand, it is assumed that the NodeB  12  performs service using a multicarrier wireless communication system for the UE  21 - 2 , UE  22 - 1 , and UE  22 - 2  existing in the communication area A 2 . That is, the UE  21 - 2  and UE  22 - 2  exist in the cell edge and may receive service from either of the NodeB  11  and NodeB  12 . In the description to follow, however, it is assumed that the UE  21 - 2  receives service from the NodeB  11  and the UE  22 - 2  receives service from the NodeB  12 . If the NodeB  11  and NodeB  12  conduct communications using the same frequency band at the same time for the UEs existing in any other area than the cell edge of the communication area A 1 , A 2  (which will be hereinafter referred to as cell center), such as the UE  21 - 1  and UE  22 - 1 , mutual communications do not interfere with each other. 
         [0039]    In  FIG. 1 , the number of NodeB managed by the RNC  10  is two, but more than two NodeB may be managed. In  FIG. 1 , the NodeB  11  and NodeB  12  existing at geographic distant positions from each other have the communication areas A 1  and A 2  respectively, but one NodeB may have a plurality of communication areas like sectors in a cell. 
         [0040]    Next, the configuration of subcarriers when the multicarrier wireless communication system is used will be discussed with  FIGS. 2A to 5B . Here, a configuration example of subcarriers used by the NodeB  11  will be discussed, but the configuration of subcarriers used by the NodeB  12  is similar to that used by the NodeB  11 . Subcarriers used for communications with the UE  21 - 1  existing in the cell center of the NodeB  11  are called cell center subcarriers and subcarriers used for communications with the UE  21 - 2  existing on the cell edge of the NodeB  11  are called cell edge subcarriers. 
         [0041]      FIGS. 2A and 2B  are drawings to show placement of subcarriers when a multicarrier wireless communication system, such as OFDM communication system is used. In  FIGS. 2A and 2B , the cell center subcarriers are indicated by solid lines and the cell edge subcarriers are indicated by dotted lines. 
         [0042]    The subcarriers shown in  FIGS. 2A and 2B  are made up of cell center subcarrier groups G 1  and G 2  each having M (in  FIGS. 2A and 2B , M=8) cell center subcarriers and a cell edge subcarrier group G 3  having F (in  FIGS. 2A and 2B , F=4) cell edge subcarriers, and the cell edge subcarrier group G 3  is placed between the cell center subcarrier groups G 1  and G 2 . 
         [0043]      FIG. 2A  shows an example of conducting communications using the cell edge subcarriers in addition to the cell center subcarriers. On the other hand,  FIG. 2B  shows an example of conducting communications using only the cell center subcarriers. The NodeB  11  communicates with the UE  21 - 1 , UE 21 - 2  using the subcarriers shown in  FIG. 2A  or  2 B. 
         [0044]    Downlink communications from the NodeB  11  to the UE  21 - 1 , UE  21 - 2  and uplink communications from the UE  21 - 1 , UE  21 - 2  to the NodeB  11  can be divided using time division duplex (TDD), frequency division duplex (FDD), etc. 
         [0045]    For the NodeB  11  to communicate with a plurality of UEs, time division multiplexing access, frequency division multiplexing access, orthogonal frequency division multiplexing access, code-division multiple access, etc., is used. 
       (Modified Example 1 of Subcarrier Placement) 
       [0046]      FIGS. 3A and 3B  are drawings to show modified example 1 of subcarrier placement when the multicarrier wireless communication system, such as OFDM communication system is used. 
         [0047]    In  FIGS. 2A and 2B , the cell edge subcarrier group G 3  is placed between the cell center subcarrier groups G 1  and G 2 . On the other hand, in the modified example shown in  FIGS. 3A and 3B , the cell center subcarrier groups G 1  and G 2  are placed adjacent to each other and cell edge subcarriers are placed at both sides, namely, at the low frequency side of the cell center subcarrier group G 1  and at the high frequency side of the cell center subcarrier group G 2 .  FIG. 3A  shows an example of conducting communications using the cell edge subcarriers in addition to the cell center subcarriers, and  FIG. 3B  shows an example of conducting communications using only the cell center subcarriers. 
       (Modified Example 2 of Subcarrier Placement) 
       [0048]    Subcarriers shown in  FIGS. 4A and 4B  have a configuration wherein three cell center subcarriers are placed between cell edge subcarriers. That is, in the subcarrier placement, one cell edge subcarrier is placed every four subcarriers. Here, the case where a cell edge subcarrier is placed every four subcarriers is shown, but unless the cell edge subcarriers are adjacent with each other, the cell edge subcarrier may be placed every given number of subcarriers or may be placed at any desired interval. 
       (Modified Example 3 of Subcarrier Placement) 
       [0049]    Unlike the subcarriers shown in  FIGS. 2A to 4B , the subcarriers shown in  FIGS. 5A and 5B  are independent from each other with respect to frequencies without overlapping each other.  FIG. 5A  shows an example of conducting communications using cell edge subcarriers in addition to cell center subcarriers, and  FIG. 5B  shows an example of conducting communications using cell center subcarriers. 
         [0050]    As shown in  FIG. 5A , a cell edge subcarrier group G 3  is placed on the low frequency side of a cell center subcarrier group G 1 . Downlink communications from the NodeB  11  to the UE  21 - 1 , UE  21 - 2  and uplink communications from the UE  21 - 1 , UE  21 - 2  to the NodeB  11  can be divided using time division duplex (TDD), frequency division duplex (FDD), etc. 
         [0051]    For the NodeB  11  and a plurality of UEs to communicate with each other using cell center subcarriers or cell edge subscribers, time division multiplexing access, frequency division multiplexing access, code-division multiple access, etc., is used. 
         [0052]    Subsequently, a use example of the cell edge subcarriers will be discussed with  FIGS. 6A to 11 . 
         [0053]      FIG. 6A  shows the wireless frame format applied for the NodeB  11 , and  FIG. 6B  shows the wireless frame format applied for the NodeB  12 . The NodeB  11  and NodeB  12  perform service using the same frequency band.  FIGS. 6A and 6B  display the wireless frame formats of the same frequencies. 
         [0054]    The wireless frame format applied for the NodeB  11  shown in  FIG. 6A  displays the frequency axis in  FIG. 2A  on the vertical axis and the time on the horizontal axis, and a cell edge subcarrier group G 3  made up of F subcarriers is placed between cell center subcarrier groups G 1  and G 2  each made up of M subcarriers. On the time axis, each subcarrier is divided in slot. 
         [0055]    The wireless frame format applied for the NodeB  12  shown in  FIG. 6B  is the same as that in  FIG. 6A  and therefore will not be discussed again. For the formats shown in  FIGS. 6A and 6B , the subcarrier placement in  FIG. 2A  is used, but any of the subcarrier placements in  FIGS. 3A to 5B  may be used. 
         [0056]    Next, the slot configuration of a wireless frame will be discussed with  FIGS. 7 to 9 . 
         [0057]    In  FIGS. 7 to 9 , the number of subcarriers of each of the cell center subcarrier groups G 1  and G 2  is M=4 and the number of subcarriers of the cell edge subcarrier group G 3  is F=4. The cell edge subcarriers are called cell edge subcarrier  1 ,  2 ,  3 , and  4  in order from the subcarrier on the high frequency side. 
         [0058]      FIG. 7  is a drawing to show the slot configuration of a wireless frame applied for the NodeB  11 . One slot is made up of 10 symbols  1  to  10  and the top symbol  1  is a pilot symbol. To transmit a signal using cell center subcarriers, the NodeB  11  uses the subcarriers of the cell center subcarrier group G 1 , G 2  to transmit the signal. 
         [0059]    On the other hand, to transmit a signal using the cell edge subcarrier group G 3 , the NodeB  11  changes cell edge subcarriers  1  to  4  used for signal transmission in symbol units to make a transition. That is NodeB  11  alternately uses one of the cell edge subcarriers  1  to  4 . 
         [0060]    For example, in  FIG. 7 , the NodeB  11  first transmits a pilot symbol using the cell edge subcarriers  1  to  4  in the top symbol  1  of the slot, and transmits using the cell edge subcarrier  3  in the next symbol  2 . Further, the NodeB  11  transmits signal using the cell edge subcarrier  1  in the symbol  3 . 
         [0061]      FIG. 8  is a drawing to show the slot configuration of a wireless frame applied for the NodeB  12 . The slot configuration of the NodeB  12  is almost the same as the slot configuration in  FIG. 7  except for the transition pattern of the cell edge subcarriers. 
         [0062]    To transmit a signal using the cell edge subcarrier group G 3 , the NodeB  12  first transmits a pilot symbol using the cell edge subcarriers  1  to  4  in the top symbol  1  of the slot. The NodeB  12  transmits using the cell edge subcarrier  1  in the subsequent symbol  2  and transmits signal using the cell edge subcarrier  3  in the next symbol  3 . 
         [0063]      FIG. 9  is a drawing to show signals arriving at the UE  21 - 2  and UE  22 - 2  when the NodeB  11  transmits a signal according to the subcarrier transition pattern shown in  FIG. 7  and the NodeB  12  transmits a signal according to the subcarrier transition pattern shown in  FIG. 8  at the same time. The UE  21 - 2  and UE  22 - 2  can receive both signals transmitted from the NodeB  11  and NodeB  12  and therefore the signals transmitted from both of the NodeB  11  and NodeB  12  arrive at each of the UE  21 - 2  and UE  22 - 2 . However, the transition pattern of the cell edge subcarriers  1  to  4  of the NodeB  11  differs from that of the NodeB  12  and thus the transmission signals do not come into collision with each other. 
         [0064]    A control circuit  131  described later with reference to  FIG. 12  assigns the transition pattern of the cell edge subcarriers  1  to  4  in symbol units shown in  FIG. 7 ,  8  to each UE for transmitting a signal using the cell edge subcarrier group G 3 . Assignment of the transition pattern is described later in detail. 
         [0065]    Next, the configuration of each pilot symbol of the cell edge subcarrier group G 3  will be discussed with  FIGS. 10A to 10C . 
         [0066]    The pilot symbol is a very important symbol because the UE receiving a signal uses the pilot symbol as a reference symbol at the demodulating, for example. Therefore, preferably the pilot symbols transmitted from the NodeB  11  and NodeB  12  are orthogonal to each other so that the pilot symbols of the cell edge subcarrier group G 3  do not interfere with each other. 
         [0067]    Then,  FIGS. 10A to 10C  show configuration examples wherein the pilot symbols are orthogonal to each other. The pilot symbol transmitted from the NodeB  11  is shown on the left of each of  FIGS. 10A to 10C  and the pilot symbol transmitted from the NodeB  12  is shown on the right. 
         [0068]      FIG. 10A  is a drawing to show an example wherein the pilot symbols are made orthogonal to each other on the frequency axis. For example, the NodeB  11  transmits the pilot symbol using the cell edge subcarriers  2  and  4 , and the NodeB  12  transmits the pilot symbol using the cell edge subcarriers  1  and  3 . At this time, the NodeB  11  does not transmit a signal in the cell edge subcarriers  1  and  3 , and the NodeB  12  does not transmit a signal in the cell edge subcarriers  2  and  4 . 
         [0069]      FIG. 10B  is a drawing to show an example wherein the pilot symbols are made orthogonal to each other on the time axis. In this case, each pilot symbol is transmitted using not only the top symbol  1  of the slot, but also the symbol  2 . For example, the NodeB  11  transmits the pilot symbol using the cell edge subcarriers  1  to  4  in the symbol  1 , and the NodeB  12  transmits the pilot symbol using the cell edge subcarriers  1  to  4  in the symbol  2 . 
         [0070]      FIG. 10C  is a drawing to show an example wherein the pilot symbols are made orthogonal to each other using orthogonal code. For example, the pilot symbol transmitted from the NodeB  11  is a series of +1, +1, +1, +1, and the pilot symbol transmitted by the NodeB  12  is a series of +1, −1, −1, +1. 
         [0071]    Next, modified examples of the slot configuration of the cell edge subcarriers are shown with  FIGS. 11 to 13 . Here, the slot configuration of a wireless frame applied for the NodeB  11  is shown, but the slot configuration of a wireless frame applied for the NodeB  12  can also be modified in a similar manner. 
       (Modified Example 1 of Slot Configuration) 
       [0072]    In each of the slots shown in  FIGS. 7 to 9 , a signal is transmitted using one cell edge subcarrier in units of one symbol; in the slot shown in  FIG. 11 , a signal is transmitted using two cell edge subcarriers in units of one symbol. Thus, to change subcarriers to make a transition in symbol units, a plurality of cell edge subcarriers may be used for signal transmission. 
       (Modified Example 2 of Slot Configuration) 
       [0073]    In  FIGS. 7 to 9 , the cell edge subcarriers are changed to make a transition in symbol units; the cell edge subcarriers may be changed to make a transition in slot units as shown in  FIG. 12 . In this case, for example, the NodeB  11  first transmits a signal using the cell edge subcarrier  2  in slot  1 , changes the subcarrier to make a transition to the cell edge subcarrier  3  in the next slot  2 , and conducts communications using the cell edge subcarrier  3 . 
       (Modified Example 3 of Slot Configuration) 
       [0074]    In  FIG. 12 , a signal is transmitted using one cell edge subcarrier in units of one slot; in  FIG. 13 , a signal is transmitted using two cell edge subcarriers in units of one slot. Thus, to change subcarriers to make a transition in slot units, a plurality of cell edge subcarriers may be used for signal transmission. 
         [0075]    Although the wireless frame formats to transmit a signal from the base station (NodeB) to the terminal (UE) have been described with  FIGS. 7 to 13 , the wireless frame formats to transmit a signal from UE to NodeB are also similar to those described with  FIGS. 7 to 13 . 
         [0076]    Next, the configuration of the base station apparatus (NodeB) according to the embodiment will be discussed with  FIGS. 14 to 16 . Since the NodeB,  11  and NodeB  12  have the same configuration, the configuration of the NodeB  11  will be discussed. 
         [0077]      FIG. 14  is a block diagram to show the configuration of the NodeB  11 . 
         [0078]    The NodeB  11  includes a transmitter  110  having a transmission antenna  111 , a transmission wireless processing circuit  112 , a multicarrier modulation circuit  113 , a multiplexing circuit  114 , S/P circuits  115 - 1  to  115 - n , modulation circuits  116 - 1  to  116 - n , and coding circuits  117 - 1  to  117 - n , a receiver  120  having a reception antenna  121 , a reception wireless processing circuit  122 , and reception circuits  123 - 1  to  123 - n , and a controller  130  having a control circuit  131 , a UE management information storage  132 , and a pattern storage  133 . 
         [0079]    n of S/P circuits  115 - 1  to  115 - n , modulation circuits  116 - 1  to  116 - n , etc., means the number of UEs with which the NodeB  11  communicates at one time. 
         [0080]    Next, the components of the NodeB  11  will be discussed in detail. 
         [0081]    The transmitter  110  shown in  FIG. 14  has the coding circuits  117 - 1  to  117 - n  for coding the data input from an upper layer I/F and to be transmitted to each UE, the modulation circuits  116 - 1  to  116 - n  for modulating the data coded by the coding circuits  117 - 1  to  117 - n  to generate a modulated signal, the S/P circuits  115 - 1  to  115 - n  for performing S/P conversion for the modulated signals generated by the modulation circuits  116 - 1  to  116 - n , the multiplexing circuit  114  for inserting a pilot symbol into the signal input from each S/P circuit and further mapping the signals so as to transmit the signals with predetermined subcarriers, the multicarrier modulation circuit  113  for performing multicarrier modulation for the modulated signals input from the multiplexing circuit  114  to generate a multicarrier modulated signal, and the transmission wireless processing circuit  112  for performing wireless processing for the multicarrier modulated signal and transmitting the signal through the transmission antenna  111 . 
         [0082]    The receiver  120  has the reception wireless processing circuit  122  for performing wireless processing for the wireless signal received at the reception antenna  121  to generate a reception signal and the reception circuits  123 - 1  to  123 - n  for performing demodulation processing, etc., for the reception signal. 
         [0083]    Subsequently, the controller  130  has the control circuit  131  for referencing the UE management information storage  132  and the pattern storage  133  and determining the transition pattern of the cell edge subcarriers to be assigned to UE, etc. The UE management information storage  132  stores information of UE with which the NodeB  11  communicates. The pattern storage  133  stores the transition pattern of the cell edge subcarriers. 
         [0084]    The UE management information storage  132  will be discussed in detail with  FIG. 15 .  FIG. 15  is a drawing to show a table of the UE management information storage  132 . The UE management information storage  132  stores a UE identifier for uniquely identifying the UE with which the NodeB  11  communicates (in  FIG. 15 , 11-digit numeric value) and “pattern” indicating the transition pattern of the cell edge subcarriers when the UE uses the cell edge subcarriers. When the cell center subcarriers are used, the pattern becomes blank (in  FIG. 15 , “−” is entered); when the cell edge subcarriers are used, a symbol indicating the transition pattern is stored. The symbol indicating the transition pattern is described later. 
         [0085]    Next, the pattern storage  133  will be discussed in detail with  FIG. 16 .  FIG. 16  is a drawing to show a table of the pattern storage  133 . The pattern storage  133  stores the transition patterns of the cell edge subcarriers and unique symbols provided in a one-to-one correspondence with the transition patterns. 
         [0086]    In the table shown in  FIG. 16 , each transition pattern is stored as the numbers assigned to the cell edge subcarriers. For example, transition pattern “A” shown in the table is “3, 1, 2, . . . ” That is, the transition pattern “A” means that a signal is transmitted using the cell edge subcarrier  3  in the symbol  2  shown in  FIG. 7  and is transmitted using the cell edge subcarrier  1  in the next symbol  3  and is transmitted using the cell edge subcarrier  2  in the subsequent symbol  4 . 
         [0087]    The configuration of the UE according to the embodiment will be discussed with  FIG. 17 . Since the UE  21 - 1 , UE  21 - 2 , UE  22 - 1 , and UE  22 - 2  have the same configuration, only the configuration of the UE  21 - 1  will be discussed. 
         [0088]    The UE  21 - 1  shown in  FIG. 17  includes a transmitter  210  having a transmission antenna  211 , a transmission wireless processing circuit  212 , and a transmission circuit  213 , a receiver  220  having a reception antenna  221 , a reception wireless processing circuit  222 , a multicarrier demodulation circuit  223 , a selector  224 , a first P/S circuit  225 - 1 , a second P/S circuit  225 - 2 , a demodulation circuit  226 , a decoding circuit  227 , a first reception state measurement circuit  228 - 1 , and a second reception state measurement circuit  228 - 2 , and a controller  230  having a control circuit  231  and a pattern storage  233 . 
         [0089]    The components of the UE  21 - 1  will be discussed. 
         [0090]    The transmitter  210  includes the transmission circuit  213  for performing processing of coding, modulation, etc., for the data to be transmitted to generate a modulated signal, and the transmission wireless processing circuit  212  for performing wireless processing for the modulated signal and transmitting the signal through the transmission antenna  211 . 
         [0091]    Next, the receiver  220  has the reception wireless processing circuit  222  for performing wireless processing for the wireless signal received at the reception antenna  221  to generate a reception signal, the multicarrier demodulation circuit  223  for performing multicarrier demodulation for the reception signal, the selector  224  for selecting a signal to be input to the first P/S circuit  225 - 1  or the second P/S circuit  225 - 2 , the first P/S circuit  225 - 1  for performing P/S conversion for the signal input through the selector  225  and outputting the conversion result to the demodulation circuit  226  and the first reception state measurement circuit  228 - 1 , the second P/S circuit  225 - 2  for performing P/S conversion for the signal input through the selector  225  and outputting the conversion result to the second reception state measurement circuit  228 - 2 , the demodulation circuit  226  for performing demodulation for the signal input from the first P/S circuit  225 - 1 , the decoding circuit  227  for decoding the signal provided by the demodulation circuit  226  and outputting the result to the upper layer I/F, the first reception state measurement circuit  228 - 1  for measuring a signal-to-interference and noise power ratio (SINR), for example, of the signal input from the first P/S circuit  225 - 1  and sending the result to the controller  230 , and the second reception state measurement circuit  228 - 2  for measuring signal power and SINR, for example, of the signal input from the second P/S circuit  225 - 2  and sending the result to the controller  230 . 
         [0092]    The controller  230  has the control circuit  231  for determining whether to use the cell center subcarriers or to use the cell edge subcarriers for communications with the NodeB based on the reception state measurement results input from the first reception state measurement circuit  228 - 1  and the second reception state measurement circuit  228 - 2 , and the pattern storage  233  for previously storing the transition pattern of the cell edge subcarriers used when the cell edge subcarriers are used for communications with the NodeB. The pattern storage  233  has the same configuration as the pattern storage  133  of the NodeB  11  shown in  FIG. 16  and therefore will not be discussed. 
         [0093]    Next, the operation of the wireless communication system according to the first embodiment of the invention will be discussed with  FIGS. 14 to 21 . 
         [0094]    First, the operation of the NodeB  11  will be discussed with  FIG. 14 . The operation of the NodeB  12  is the same as the operation of the NodeB  11  and therefore will not be discussed. 
         [0095]    For the NodeB  11  to transmit a signal, data k to be transmitted to the UE  21 - k  (k=1, 2, . . . , n) is input from the upper layer I/F to the coding circuit  117 - k . The coding circuit  117 - k  performs error correction coding for the input data k according to a predetermined coding scheme and coding ratio and inputs the result to the corresponding modulation circuit  116 - k . The modulation circuit  116 - k  performs modulation for the input data k according to a predetermined modulation scheme and inputs a modulated signal k to the corresponding S/P circuit  115 - k . The S/P circuit  115 - k  performs S/P conversion for the input modulated signal k and inputs the result to the multiplexing circuit  114 . The multiplexing circuit  114  inserts a pilot symbol in the top symbol of the slot and maps the modulated signal k input from the S/P circuit  115 - k  so as to transmit the signal with a predetermined subcarrier in any other symbol than the top symbol. At this time, if there is UE using the cell edge subcarriers for communications, the multiplexing circuit  114  maps in accordance with the transition pattern corresponding to the UE. The controller  130  sends a notification of the subcarrier for mapping the modulated signal k, the presence or absence of UE using the cell edge subcarriers, the transition pattern of the cell edge subcarriers, etc. 
         [0096]    Subsequently, the multicarrier modulation circuit  113  performs multicarrier modulation for the signal input from the multiplexing circuit  114  to generate a multicarrier modulated signal, and inputs the multicarrier modulated signal to the transmission wireless processing circuit  112 . The transmission wireless processing circuit  112  performs predetermined wireless processing of D/A conversion, quadrature modulation, up conversion, band limiting, power amplification, etc., for the input multicarrier modulated signal to generate a wireless signal. The generated wireless signal is transmitted through the transmission antenna  111 . 
         [0097]    On the other hand, for the NodeB  11  to receive a signal, the wireless signal received at the reception antenna  121  is input to the reception wireless processing circuit  122 . The reception wireless processing circuit  122  performs predetermined wireless processing of band limiting, down conversion, quadrature demodulation, A/D conversion, etc., for the input wireless signal and inputs the signal to the reception circuits  123 - 1  to  123 - n  as the reception signal. The reception circuits  123 - 1  to  123 - n  demodulate the input reception signal according to the demodulation scheme corresponding to the predetermined modulation scheme and decodes based on a predetermined coding scheme and coding ratio and if the decoding result is control data of the reception state measurement result, etc., output the control data to the controller  130 ; if the decoding result is information data, output the information data to the upper layer I/F. 
         [0098]    Next, the operation of the controller  130  of the NodeB will be discussed. 
         [0099]    First, the control circuit  131  of the controller  130  uses the control data of the reception state measurement result, etc., input from the reception circuit  123 - 1 , . . . ,  123 - n  to determine whether to use the cell center subcarriers or to use the cell edge subcarriers for communications with UE. This determination is described later in detail. The controller  230  of the UE may also make the determination. The determination made by the UE is described later. 
         [0100]    If the subcarriers used by the UE are changed from the cell center subcarriers to the cell edge subcarriers as the result of the determination, the control circuit  131  references the UE management information storage  132 , selects an unused transition pattern, assigns the transition pattern to communications with the UE, updates the table of the UE management information storage  132 , and rewrites the pattern corresponding to the UE identifier of the UE to the symbol representing the selected transition pattern. 
         [0101]    In contrast, if the subcarriers used by the UE are changed from the cell edge subcarriers to the cell center subcarriers as the result of the determination, the control circuit  131  updates the table of the UE management information storage  132 , and erases the symbol representing the transition pattern stored in the pattern corresponding to the UE identifier of the UE. When transmitting a signal, the control circuit  131  references the UE management information storage  132  and the pattern storage  133 , and sends the transition pattern of the UE using the cell edge subcarriers to the multiplexing circuit  114  of the transmitter  110 , thereby controlling the subcarrier transition of the UE. 
         [0102]    Next, the operation of the UE  21 - 1  will be discussed with  FIG. 17 . It is assumed that the UE  21 - 1  uses the cell center subcarriers to communicate with the NodeB  11 . The operation of the UE  21 - 2 , UE  22 - 1 , UE  22 - 2  is the same as the operation of the UE  21 - 1  and therefore will not be discussed. 
         [0103]    For the UE  21 - 1  to transmit a signal, the transmission circuit  213  performs error correction coding for the control data input from the controller  230  and the information data input from the upper layer I/F according to a predetermined coding scheme and coding ratio and modulates the input data according to a predetermined modulation scheme and inputs a modulated signal to the transmission wireless processing circuit  212 . The transmission wireless processing circuit  212  performs predetermined wireless processing of D/A conversion, quadrature modulation, up conversion, band limiting, power amplification, etc., for the input modulated signal to generate a wireless signal. The generated wireless signal is transmitted through the transmission antenna  231 . 
         [0104]    On the other hand, for the UE  21 - 1  to receive a signal, the wireless signal received at the reception antenna  221  is input to the reception wireless processing circuit  222 . The reception wireless processing circuit  222  performs predetermined wireless processing of band limiting, down conversion, quadrature demodulation, A/D conversion, etc., for the input wireless signal and inputs the signal to the multicarrier demodulation circuit  223  as the reception signal. The multicarrier demodulation circuit  223  performs multicarrier demodulation for the input reception signal and inputs the result to the selector  224 . The selector  224  inputs the multicarrier modulation result corresponding to the subcarriers used for transmission to the UE  21 - 1  to the first P/S circuit  225 - 1  and inputs the pilot signal transmitted with cell edge subcarriers from the base station apparatus other than the NodeB  11  (here, NodeB  12 ) to the second P/S circuit  225 - 2 . The pilot signal transmitted with cell edge subcarriers from the NodeB  11  may also be input to the second P/S circuit  225 - 2 . 
         [0105]    Subsequently, the first P/S circuit  225 - 1  performs P/S conversion for the multicarrier demodulation result input from the selector  224  and inputs the result to the demodulation circuit  226  and also inputs the pilot symbol of the conversion result to the first reception state measurement circuit  228 - 1 . On the other hand, the second P/S circuit  225 - 2  performs P/S conversion for the pilot symbol input from the selector  224  and inputs the result to the second reception state measurement circuit  228 - 2 . 
         [0106]    The demodulation circuit  226  demodulates the P/S conversion result input from the first P/S circuit  225 - 1  according to the demodulation scheme corresponding to the predetermined modulation scheme and inputs the demodulation result to the decoding circuit  227  and if the demodulation result is control data such as a transition pattern of cell edge subcarriers, inputs the demodulation result to the controller  230 . The decoding circuit  227  decodes the demodulation result input from the demodulation circuit  226  based on the predetermined coding scheme and coding ratio and outputs the result to the upper layer I/F. 
         [0107]    The first reception state measurement circuit  228 - 1  uses the pilot symbol input from the first P/S circuit  225 - 1  to measure the wireless communication state with the NodeB  11 , for example, SINR and sends the result to the control circuit  231 . On the other hand, the second reception state measurement circuit  228 - 2  uses the pilot symbol input from the second P/S circuit  225 - 2  to measure the wireless communication state with the NodeB  12 , for example, reception power and sends the result to the control circuit  231 . The wireless communication state of communications with the NodeB  11  in the cell edge subcarriers, for example, the SINR of the pilot symbol transmitted from the NodeB  11  using the cell edge subcarriers may also be measured and the result may also be sent to the control circuit  231 . 
         [0108]    Next, the operation of the controller  230  is as follows: 
         [0109]    The control circuit  231  of the controller  230  inputs the reception state measurement results input from the reception state measurement circuits  228 - 1  and  228 - 2  to the transmission circuit  213  for transmission to the NodeB  11 . To determine whether to use the cell center subcarriers or to use the cell edge subcarriers, the control circuit  231  uses the reception state result to make the determination, and transmits the result to the NodeB  11 . When the UE  21 - 1  uses the cell edge subcarriers, the control circuit  231  references the pattern storage  233  and sends the subcarrier transition pattern assigned to the UE  21 - 1  to the selector  224  of the receiver  220 , thereby controlling the transition of the cell edge subcarriers of the UE  21 - 1 . 
         [0110]    Subsequently, a sequence of use subcarrier change in communications between the NodeB  11  and the UE  21 - 1  will be discussed with  FIGS. 18 and 19 . 
         [0111]      FIG. 18  is a sequence chart to describe the operation in the case of that the NodeB  11  determines the reception state of the UE  21 - 1 . It is assumed that the NodeB  11  and the UE  21 - 1  conduct communications using the cell center subcarriers until communications are established and the reception state of the UE  21 - 1  is determined. 
         [0112]    First, before starting wireless communications, the UE  21 - 1  sends the UE identifier to the NodeB  11  (step S 101 ) and communicates with the NodeB  11  using the cell center subcarriers (step S 102 ). Next, during communicating with the NodeB  11 , the UE  21 - 1  measures the reception state of the signal transmitted from the NodeB  11  and the reception state of the signal transmitted from the NodeB  12  not conducting communications after the expiration of a predetermined period (step S 103 ) and sends the measurement result to the NodeB  11  (step S 104 ). 
         [0113]    On the other hand, the NodeB  11  receiving the measurement result determines the reception state of the UE  21 - 1  in reception state determination processing described later and determines whether or not the use subcarriers are to be changed to the cell edge subcarriers (step S 105 ). If it is determined at step S 105  that the use subcarriers are to be changed to the cell edge subcarriers, the NodeB  11  sends a notification of change to the cell edge subcarriers and the transition pattern of the cell edge subcarriers to the UE  21 - 1  (step S 106 ). After the notification, the cell edge subcarriers are used for communications between the NodeB  11  and the UE  21 - 1  (step S 107 ). Whether or not the cell edge subcarriers are to be changed to the cell center subcarriers is also determined by determining the reception state of the UE  21 - 1  after the expiration of a predetermined period. 
         [0114]    Next, a sequence chart of the operation in the case of that the UE  21 - 1  determines the reception state of the UE  21 - 1  will be discussed with  FIG. 19 . It is assumed that the NodeB  11  and the UE  21 - 1  conduct communications using the cell center subcarriers until communications are established and the reception state of the UE  21 - 1  is determined. The sequence shown in  FIG. 19  is the same as the sequence shown in  FIG. 18  except that the UE  21 - 1  measures the reception state and requests the NodeB  11  to change the subcarriers from the cell center subcarriers to the cell edge subcarriers in response to the measurement result and therefore steps identical with those previously described with reference to  FIG. 18  are denoted by the same step numbers in  FIG. 19  and will not be discussed again. 
         [0115]    During communicating with the NodeB  11 , the UE  21 - 1  measures the reception state of the signal transmitted from the NodeB  11  and the reception state of the signal transmitted from the NodeB  12  not conducting communications after the expiration of a predetermined period (step S 103 ). The UE  21 - 1  determines the reception state in reception state determination processing described later and determines whether or not the use subcarriers are to be changed to the cell edge subcarriers (step S 204 ). If it is determined at step S 204  that the use subcarriers are to be changed to the cell edge subcarriers, the UE  21 - 1  requests the NodeB  11  to change the subcarriers to the cell edge subcarriers (step S 205 ). On the other hand, the NodeB  11  receiving the request sends a notification of change to the cell edge subcarriers and the transition pattern of the cell edge subcarriers to the UE  21 - 1  (step S 206 ). 
         [0116]    Next, the reception state determination processing performed by the control circuit  131  of the NodeB  11  will be discussed with  FIGS. 20 and 21 . The control circuit  231  of the UE  21 - 1  performs reception state determination processing similar to that of the control circuit  131  of the NodeB  11  and therefore will not be discussed. 
         [0117]      FIG. 20  is a flowchart to describe the reception state determination processing. 
         [0118]    The control circuit  131  of the NodeB  11  first determines whether or not a predetermined period has elapsed (step S 301 ). If the predetermined period has not yet elapsed, the reception state determination processing is terminated (NO at step S 301 ). If the predetermined period has elapsed, a comparison is made between the SINR of the pilot symbol transmitted from the NodeB  11  using the cell center subcarriers and a predetermined threshold value Th_S (step S 302 ). The UE  21 - 1  measures the SINR of the pilot symbol and sends the SINR to the NodeB  11  (see steps S 102  and S 103  in  FIG. 18 ). If the SINR of the NodeB  11  is the threshold value Th_S or greater as a result of the comparison, it is assumed that the signal from the NodeB  11  sufficiently arrives at the UE  21 - 1 , and the reception state determination processing is terminated without changing the used subcarriers (NO at step S 302 ). 
         [0119]    On the other hand, if the SINR of the NodeB  11  is less than the threshold value Th_S, a comparison is made between reception power of the signal transmitted from the NodeB  12  using the cell edge subcarriers and a threshold value Th_P (step S 303 ). The UE  21 - 1  measures the reception power and sends the reception power to the NodeB  11  (see steps S 102  and S 103  in  FIG. 18 ). If the reception power is the threshold value Th_P or less as a result of the comparison, it is assumed that the effect of the interference caused by the signal from the NodeB  12  is small, and the reception state determination processing is terminated without changing the used subcarriers (NO at step S 303 ). On the other hand, if the reception power is greater than the threshold value Th_P, it is assumed that the effect of the interference caused by the signal from the NodeB  12  is high, and the subcarriers used for communications with the UE  21 - 1  are changed from the cell center subcarriers to the cell edge subcarriers (step S 304 ). 
       (Modified Example of Reception State Determination Processing) 
       [0120]    Next, a modified example of the reception state determination processing performed by the control circuit  131  of the NodeB  11  will be discussed with  FIG. 21 . The flowchart of  FIG. 21  is the same as the flowchart of  FIG. 20  except that a comparison is made between the SINR of the signal transmitted from the NodeB  11  using the cell edge subcarriers and a threshold value Th_S 2  rather than a comparison is made between reception power of the signal transmitted from the NodeB  12  and the threshold value Th_P (see step S 303  in  FIG. 20 ) and therefore steps identical with those previously described with reference to  FIG. 20  are denoted by the same step numbers in  FIG. 21  and will not be discussed again. 
         [0121]    If the SINR of the NodeB  11  is less than the threshold value Th_S as a result of the comparison made at step S 302 , the control circuit  131  makes a comparison between the SINR of the signal transmitted from the NodeB  11  using the cell edge subcarriers and a threshold value Th_S 2  (step S 403 ), wherein the UE  21 - 1  measures the SINR and sends the SINR to the NodeB  11  (see steps S 102  and S 103  in  FIG. 18 ). 
         [0122]    If the SINR is the threshold value Th_S 2  or less as a result of the comparison, it is assumed that the effect of the interference caused by the signal from the NodeB  12  is small, and the reception state determination processing is terminated without changing the used subcarriers (NO at step S 403 ). On the other hand, if the SINR is greater than the threshold value Th_S 2 , it is assumed that the effect of the interference caused by the signal from the NodeB  12  is high, and the subcarriers used for communications with the UE  21 - 1  are changed from the cell center subcarriers to the cell edge subcarriers (step S 304 ). 
         [0123]    As described above, according to the first embodiment, the subcarriers used for communications of the NodeB  11  are divided into the two types of cell center subcarriers and cell edge subcarriers and the NodeB  11  uses either of the types of subcarrier depending on the location of the UE with which the NodeB  11  communicates, so that the NodeB  11  can communicate with the UE  21 - 1  existing in the cell center and the UE  21 - 2  existing in the cell edge at the same time and the throughput in the communication area A 1  can be ensured. The transition pattern of the cell edge subcarriers to be used is different between the NodeB  11  and the NodeB  12 , so that the probability that the NodeB  11  and the NodeB  12  may use the same carrier at the same time lessens and the interference between the adjacent communication areas A 1  and A 2  can be suppressed. Further, the NodeB  11 , NodeB  12  uses the cell edge subcarriers and the cell center subcarriers of the same frequency band at the same time to conduct communications, whereby the number of unused subcarriers can be reduced and lowering the whole throughput of the system can be minimized. 
       Second Embodiment 
       [0124]    Next, a wireless communication system according to a second embodiment of the invention will be discussed with  FIGS. 22A to 23B . The configuration and the operation of the wireless communication system according to the second embodiment are the same as those of the wireless communication system according to the first embodiment except the wireless frame format shown in  FIGS. 6A and 6B  and therefore parts identical with those previously described are denoted by the same reference numerals and will not be discussed again. 
         [0125]    In the embodiment, the whole subframe is used as a cell center subframe or a cell edge subframe rather than subframes are divided into the two types of cell center subcarriers and cell edge subcarriers.  FIG. 22A  shows the wireless frame format applied for NodeB  11 , and  FIG. 22B  shows the wireless frame format applied for NodeB  12 . The NodeB  11  and NodeB  12  perform service using the same frequency band.  FIGS. 22A and 22B  display the wireless frame formats of the same frequencies. 
         [0126]    In the wireless frame format shown in  FIGS. 6A and 6B , the NodeB  11  transmits a signal using both of the cell center subcarriers and the cell edge subcarriers at the same time; while, in the wireless frame format shown in  FIGS. 22A and 22B , a signal is transmitted using either of the cell center subcarriers and the cell edge subcarriers. In this case, all subcarriers are used as the cell center subcarriers or the cell edge subcarriers. 
         [0127]    In the example shown in  FIG. 22A , the NodeB  11  first transmits a signal using the cell center subcarriers in slots  1  and  2 . Next, the NodeB  11  transmits a signal using the cell edge subcarriers in slot  3 . That is, the NodeB  11  transmits a signal using the cell edge subcarriers every 3-slot period. 
         [0128]    On the other hand, the NodeB  12  also transmits a signal using the cell edge subcarriers every 3-slot period like the NodeB  11 , as shown in  FIG. 22B . Therefore, NodeB  11  and NodeB  12  transmit a signal using the cell center subcarriers or the cell edge subcarriers in the same slot. Here, the example wherein the NodeB  11 , NodeB  12  uses the cell edge subcarriers every 3-slot period is shown, but may use the cell edge subcarriers every L-slot period. 
         [0129]    Next, a modified example of the wireless frame format will be discussed with  FIGS. 23A and 23B .  FIG. 23A  shows the wireless frame format applied for NodeB  11 , and  FIG. 23B  shows the wireless frame format applied for NodeB  12 . 
         [0130]    In the wireless frame format shown in  FIGS. 23A and 23B , the NodeB  11 , NodeB  12  uses the cell edge subcarriers for transmission in any desired slot rather than uses the cell edge subcarriers for transmission every 3-slot period. The NodeB  11 , NodeB  12  uses the cell edge subcarriers or the cell center subcarriers at the same time and does not use the two types of subcarriers at the same time. 
         [0131]    As described above, according to the second embodiment, similar advantages to those of the first embodiment can be provided and in addition, the NodeB  11 , NodeB  12  can use all subcarriers that can be used for signal transmission as the cell center subcarriers or the cell edge subcarriers, so that the wireless communication performance can be improved by the frequency diversity effect. 
       Third Embodiment 
       [0132]    Next, a wireless communication system according to a third embodiment of the invention will be discussed with  FIGS. 24A and 24B . The configuration and the operation of the wireless communication system according to the third embodiment are the same as those of the wireless communication system according to the first embodiment except the wireless frame format shown in  FIGS. 6A and 6B  and therefore parts identical with those previously described are denoted by the same reference numerals and will not be discussed again. 
         [0133]      FIG. 24A  shows the wireless frame format applied for NodeB  11 , and  FIG. 24B  shows the wireless frame format applied for NodeB  12 . 
         [0134]    The NodeB  11  has slot S 1  in which all subcarriers are used as cell center subcarriers and slot S 2  wherein subcarriers are divided into cell center subcarrier groups G 1  and G 2  and a cell edge subcarrier group G 3  for use, as shown in  FIG. 24A . The configuration of the slot S 2  is the same as the slot configuration of the wireless frame shown in  FIGS. 7 to 9  and therefore will not be discussed again. 
         [0135]    The NodeB  11  transmits a signal in slot S 2  every 3-slot period and transmits a signal in slot S 1 . The wireless frame format applied for the NodeB  12  shown in  FIG. 24B  is the same as the wireless frame format shown in  FIG. 24A  and therefore will not be discussed again. Here, an example wherein the NodeB  11 , NodeB  12  uses the slot S 2  every 3-slot period is shown, but may use the slot S 2  every L-slot period, and slot S 2  may be inserted between consecutive slots S 1  as desired. 
         [0136]    As described above, according to the third embodiment, similar advantages to those of the first embodiment can be provided and in addition, each of the slots S 1  and S 2  has the cell center subcarriers and thus the NodeB  11 , NodeB  12  can use any slot to transmit a signal to UE existing in the cell center. Generally, the cell center area is wider than the cell edge area and the number of UEs existing in the cell center is larger than the number of UEs existing in the cell edge, so that the system throughput can be improved by transmitting a signal to UE existing in the cell center using any slot. 
         [0137]    It is to be understood that the invention is not limited to the specific embodiments described above and that the invention can be embodied with the components modified without departing from the spirit and scope of the invention. The invention can be embodied in various forms according to appropriate combinations of the components disclosed in the embodiments described above. For example, some components may be deleted from all components shown in the embodiment. Further, the components in different embodiments may be used appropriately in combination.