Abstract:
Although the beam forming is quite a good scheme, if there exist particularly a plurality of users, the characteristic deterioration occurs in an associated communication line due to the tight radio resource on the reverse line and delay in the transmission time caused by the feedback of information exceeding the required information. The transmitter  1  in a radio communication system receives signals by the antennas  13 - 1  to  13 -M and the duplexers  14 - 1  to  14 -M, extracts user&#39;s profile information by the transmission signal controller  12 , determines in a unified manner a radio resource amount and its assignment as well as the application or non-application of the beam forming, generates by the transmission signal generator  11  transmission signals using user&#39;s transmission data according to the resource distribution and the application or non-application of the beam forming thus determined, and transmits the signals by use of the duplexers  14 - 1  to  14 -M and the antennas  13 - 1  to  13 -M.

Description:
TECHNICAL FIELD 
       [0001]    The present invention pertains to a radio communication system, and in particular, to a transmission apparatus including a plurality of antennas. 
       RELATED ART 
       [0002]    As described in non-patent document 1, in a Multi-Input Multi-Output (MIMO) system in which a transmitter-receiver uses a plurality of antennas, signal processing are executed employing channel information in a receiver and signal processing using the same channel information also in a transmitter, and hence considerable characteristic improvement is expected. Among these systems, a scheme in which the channel information between the transmitter-receivers is represented by a matrix and the transmitter conducts transmission beam forming by use of decomposition of the matrix is highest in the characteristic. This is because transmission parameters can be controlled, for a plurality of independent propagation paths formed by the signal processing in the transmitter-receiver, according to reception quality of each transmission path. In this situation, processing necessary for the receiver to form independent propagation paths is linear synthesis processing which uses a channel matrix and which is quite simple. 
         [0003]    On the other hand, if the transmitter does not adopt the channel information, signals sent from a plurality of transmission antennas interfere with each other when they are received by the receiver. In this operation, the characteristic remarkably depends on the reception scheme; in general, a more favorable characteristic is obtained by a receiver requires more complex processing. However, even in a case employing the maximum likelihood detection method for which the most favorable characteristic is expected, the characteristic is deteriorated when compared with the scheme in which the signal processing is carried out using the same channel information by the transmitter-receiver. 
       &lt;Article&gt; 
       [0004]    Non-patent document 1 Takeo OHGANE, Toshihiko NISHIMURA, and Yasutaka OGAWA “Applications of Space Division Multiplexing and Those Performance in a MIMO Channel”, IEICE, Proceedings in Japanese, Vol. J87-B, No. 9, pp. 1162-1173. 
       DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0005]    The first problem is that if the beam forming is applied to a plurality of users, the radio resources of reverse lines become tight. This is because it is necessary to feed back the channel information required for the beam forming via the reverse lines and the radio resource amount required for the feedback increases especially if there exist a plurality of users. 
         [0006]    The second problem is that the transmission characteristic of the user to whom the beam forming is applied deteriorates. This is because when a certain period of time passes from when the transmitter obtains the channel information to when the actual transmission is carried out, the channel information differs from an actual channel. 
         [0007]    A first object of the present invention is to provide a radio communication system and the like wherein in an environment where a plurality of users exist, an amount of radio resources to be allocated to each of N users (indicating there are N users. N is an integer equal to or more than two) and assignment thereof as well as application or non-application of beam forming are efficiently determined. 
         [0008]    A second object of the present invention is to provide a radio communication system and the like wherein assignment of radio resources is determined not to deteriorate the reception quality of the user to whom the beam forming is applied. 
         [0009]    A third object of the present invention is to provide a radio communication system and the like wherein application or non-application of the beam forming is determined by efficiently using resources of the reverse lines. 
       Means for Solving the Problem 
       [0010]    To solve the problems, in a first radio communication system provided by the present invention, signals are transmitted from a transmitter including an M antennas, transmission signal control means to determine an amount of radio resources to be allocated to each of N users and assignment thereof as well as application or non-application of beam forming, and transmission signal generator means for producing transmission signals using transmission data. As a result, the first to third objects can be achieved. 
         [0011]    In a second radio communication system provided by the present invention, the transmission signal control means included in the first radio communication system first determines the amount of radio resources to be allocated to each of the N users, the application or non-application of the beam forming is determined for all users to whom radio resources are allocated, and the assignment of radio resources are determined by use of the result of the determination. It is resultantly possible to achieve the first and second objects. 
         [0012]    In a third radio communication system provided by the present invention, the transmission signal control means included in the first radio communication system provisionally determines the application or non-application of the beam forming for all users, and the amount of radio resources to be allocated to each of N users and the assignment thereof as well as application or non-application of beam forming are determined by use of the result of the determination Resultantly, the first and second objects can be achieved. 
         [0013]    In a fourth radio communication system provided by the present invention, the transmission signal control means included in the first radio communication system primarily determines applicability of the beam forming according to particular information, and a request is issued only to the users for whom the primary determination is conducted, for information requiring the feedback. It is resultantly possible to achieve the first to third objects. 
       EFFECTS OF THE INVENTION 
       [0014]    A first advantage is that the application or non-application of the beam forming and the amount of radio resources to be distributed to each user and assignment thereof can be efficiently determined. This is because these items are determined in an integrated manner, in accordance with the present invention, on the basis of profile information of each user. 
         [0015]    A second advantage is mitigation of the characteristic deterioration for the user for whom the beam forming is applied. This is because the amount of radio resources and assignment thereof and the application or non-application of the beam forming are determined such that the transmission time of the user to whom the beam forming is applied is earlier than that of the user to whom the beam forming is not applied. 
         [0016]    A third advantage is that by efficiently using radio resources of reverse lines, the application or non-application of the beam forming and the amount of radio resources to be distributed to each user and assignment thereof can be determined. This is because the application or non-application of the beam forming is determined using known information and then the feedback is obtained for the users requiring information. 
       DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0017]    Next, referring to drawings, description will be given in detail of exemplary embodiments of a radio communication system and the like of the present invention.  FIG. 1  is a block diagram showing a configuration of a radio communication system. 
         [0018]    Referring to  FIG. 1 , the radio communication system in a first exemplary embodiment includes a transmitter  1  including M antennas  13 - 1  to  13 M (M is an integer equal to or more than two) and a receiver  2  including J antennas  13 - 1  to  13 -J (J is an integer equal to or more than one). 
         [0019]    The transmitter  1  includes duplexers  14 - 1  to  14 -M, transmission signal generator means  11 , transmission signal control means  12 , and a recording medium  15 . 
         [0020]      FIG. 2  is a flowchart showing operation of the radio communication system Processing shown in  FIG. 2  is realized when the transmitter  1  executes a program stored in the recording medium  15 . 
         [0021]    Referring to  FIGS. 1 and 2 , description will be given of the processing in the radio communication system. 
         [0022]    The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M receive signals (received signals are referred to as r( 1 ) to r(M); step S 11 ). The transmission signal control means  12  extracts profile information from the received signals r( 1 ) to r(M), determines the amount of radio resources to be allocated to each of the N users and assignment thereof and further determines whether the beam forming is applied thereto or not, and produces radio resource control signals R-ctrl( 1 ) to R-ctrl(N) and transmission mode control signals M-ctrl( 1 ) to M-ctrl(N) (step S 12 ). The transmission signal generator unit  11  creates transmission signals s( 1 ) to s(M) using as inputs thereto transmission data items din( 1 ) to din(N), radio resource control signals, and transmission mode control signals and then outputs the transmission signals therefrom (step S 13 ). The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M sends the transmission signals (step S 14 ). Resultantly, it is possible to efficiently determine the amount of radio resources to be allocated to each user and assignment thereof and the application or non-application of the beam forming thereto. 
         [0023]    Subsequently, referring to the drawings, description will be given in detail of a second exemplary embodiment of the radio communication system.  FIG. 3  is a block diagram showing structure of the radio communication system. 
         [0024]    The second embodiment is similar in structure to the radio communication system in the first exemplary embodiment of the present invention excepting that a transmitter  3  is disposed in place of the transmitter  1 . 
         [0025]    Referring to  FIG. 3 , the transmitter  3  in the second embodiment includes duplexers  14 - 1  to  14 -M, a transmission signal generator module  11 , a transmission signal control module  31 , and a recording medium  32 . The signal control module  31  includes a radio resource amount control unit  33 , a transmission mode control unit  34 , and a radio resource assignment control unit  35 . 
         [0026]      FIG. 4  is a flowchart showing operation of the radio communication system in the second embodiment. Processing shown in  FIG. 4  is realized when the transmitter  3  executes a program stored in the recording medium  32  shown in  FIG. 3 . 
         [0027]    Referring to  FIGS. 3 and 4 , description will be given of the radio communication system. 
         [0028]    The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M receive signals (step S 41 ). The radio resource amount control unit  33  extracts profile information to determine the radio resource amount to be allocated to each of the N users and produces radio resource amount control signals Ra-ctrl( 1 ) to Ra-ctrl(N) (step S 42 ). Next, the transmission mode control unit  34  determines the application or non-application of the beam forming for the user to whom the radio resources are allocated and then creates and outputs transmission mode control signals M-ctrl ( 1 ) to M-ctrl (N) (step S 43 ). Subsequently, the radio resource assignment control unit  35  determines the assignment of radio resources, by use of the transmission mode control signals and the radio resource amount control signals as inputs thereto, such that the signal transmission time of the user to whom the beam forming is applied is earlier than that of the user to whom the beam forming is not applied and then generates and outputs radio resource control signals R-ctrl( 1 ) to R-ctrl(N) (step S 44 ). Thereafter, on the basis of the radio resource control signal and the transmission mode control signal, the transmission signal generator  11  allocates radio resources to each of the N users and creates transmission signals (step S 45 ). The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M send the transmission signals (step S 46 ). 
         [0029]    By making the signal transmission time of the user to whom the beam forming is applied be earlier as above, occurrence of the difference between the channel information employed for the beam forming and the actual channel is suppressed, and it is hence possible to prevent deterioration in the transmission characteristic for the associated users. 
         [0030]    Incidentally, although the radio resource amount controller  33  and the transmission mode controller  34  extract profile information from the respective reception signals, a configuration in which a profile extraction unit is disposed to extract profile information such that the resource amount controller  33  and the mode controller  34  receive as inputs thereto the profile information from the profile extraction unit is also included in the present embodiment. 
         [0031]    Next, referring to the drawings, description will be given in detail of a third exemplary embodiment of the radio communication system of the present invention.  FIG. 5  is a block diagram showing structure of the third embodiment of the radio communication system. The third embodiment is similar in the configuration to the radio communication system in the first exemplary embodiment excepting that a transmitter  5  is arranged in place of the transmitter  1 . 
         [0032]    Referring to  FIG. 5 , the transmitter  5  in the third embodiment of the wireless communication system includes duplexers  14 - 1  to  14 -M, a transmission signal generator unit  11 , a transmission signal control unit  51 , and a recording medium  52 . The transmission signal controller  51  includes a provisional transmission mode control module  53  and a transmission signal control module  54 . 
         [0033]      FIG. 6  is a flowchart showing operation of the radio communication system in the third embodiment. Processing shown in  FIG. 6  is accomplished when the transmitter  5  executes a program stored in the recording medium  52  shown in  FIG. 5 . 
         [0034]    Referring to  FIGS. 5 and 6 , description will be given of the radio communication system in the third embodiment. 
         [0035]    The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M receive signals (step S 61 ). The transmission mode control unit  53  receives a reception signal as an input thereto, extracts profile information from the reception signal, provisionally determines the application or non-application of the beam forming for all users, and then creates and outputs transmission mode control signals M-ctrl ( 1 ) to M-ctrl (N) (step S 62 ). Next, the transmission signal controller  54  receives the reception signals and the transmission mode control signals as inputs thereto, extracts profile information from the reception signal, determines the radio resource amount to be allocated to each of the N users and the assignment thereof and the application or non-application of the beam forming, and creates and outputs the radio resource control signals R-ctrl( 1 ) to R-ctrl(N) and the transmission mode control signals M-ctrl ( 1 ) to M-ctrl (N) (step S 63 ). Subsequently, on the basis of the radio resource control signals and the transmission mode control signals, the transmission signal generator  11  produces and outputs transmission signals using the transmission data (step S 64 ). The duplexers  14 - 1  to  14 -M and antennas  13 - 1  to  13 -M send the transmission signals (step S 65 ). 
         [0036]    As above, by determining, after the provisional determination of the application or non-application of the beam forming for all users, the radio resource amount to be allocated to each of the N users and the assignment thereof and the application or non-application of the beam forming are determined; it is therefore possible to preferentially allocate radio resources to the users to whom the beam forming is highly likely to be allocated, and hence the system can efficiently use the beam forming with a high transmission characteristic. 
         [0037]    Incidentally, although the provisional transmission mode control module  53  and the transmission signal control module  54  extract the profile information from the respective reception signals, a configuration in which a profile extraction module is arranged to extract profile information such that the mode controller  53  and the transmission signal controller  54  receive as inputs thereto the profile information from the profile extraction unit is also included in the present embodiment. 
         [0038]    Next, description will be given of concrete examples of the invention associated with the exemplary embodiments. 
       Example 1 
       [0039]      FIG. 7  is a block diagram showing a configuration of a transmitter of a first example of the present invention. 
         [0040]    It is assumed in this example that there exist five users and the transmitter includes two antennas to conduct a total of 100 Megabits per second (Mbps) transmission using 5 Mbps Binary Phase Shift Keying (BPSK) signals in Time Division Multiple Access (TDMA). It is also assumed that each user has a receiver  2  including two antennas. However, these are only premises for explanation and hence do not restrict any example of the present invention. 
         [0041]    Referring to  FIG. 7 , the transmitter  7  in the first example of the present invention includes two antennas  13 - 1  and  13 - 2 , two duplexers and  14 - 2  to conduct a changeover operation between transmission and reception, a transmission signal control unit  72 , a transmission signal generator unit  71 , and a recording medium  77 . 
         [0042]    The transmission signal controller  72  includes a profile information extractor module  73 , a radio resource amount control module  74 , a transmission mode control module  75 , and a radio resource assignment control module  76 . 
         [0043]    The antennas  13 - 1  and  13 - 2  and duplexers  14 - 1  and  14 - 2  receive signals from five users. The transmission signal controller  72  determines, by use of reception signals as inputs thereto, the radio resource amount to be allocated to each of the five users and the assignment thereof as well as the application or non-application of the beam forming for each of the five users, and produces the radio resource control signals R-ctrl( 1 ) to R-ctrl( 5 ) and the transmission mode control signals M-ctrl( 1 ) to M-ctrl( 5 ). The transmission signal generator  71  allocates radio resources to each user and produces transmission signals by use of transmission data items din( 1 ) to din( 5 ) of the five users, the resource control signals R-ctrl( 1 ) to R-ctrl( 5 ), and the mode control signals M-ctrl( 1 ) to M-ctrl( 5 ) as inputs thereto and then outputs transmission signals s( 1 ) and s( 2 ). 
         [0044]    Subsequently, the transmission signal controller  72  will be described in detail. 
         [0045]    The profile information extractor module  73  extracts profile information items p( 1 ) to p( 5 ) of the five users from the reception signals. Here, p(k) represents a profile information item of the k-th user and is information indicating the required rate and the channel variation speed of the user. Assume now that the profile information items p( 1 ) to p( 5 ) of the five users are p( 1 )=[60 Mbps,2 Hz], p( 2 )=[40 Mbps,10 Hz], p( 3 )=[30 Mbps,10 Hz], p( 4 ) [20 Mbps,3 z], and p( 5 )=[10 Mbps,5 Hz]. 
         [0046]    The radio resource assignment control module  76  allocates radio resources preferentially to users having a higher required rate. As a result, 50 Mbps is allocated to the first user, 40 Mbps is allocated to the second user, 0 Mbps is allocated to the third and fourth users, and 10 Mbps is allocated to the fifth user, and the radio resource amount control signals are produced as Ra-ctrl( 1 )=[50 Mbps], Ra-ctrl( 2 )=[40 Mbps], Ra-ctrl( 3 )=[0], Ra-ctrl( 4 )=[0], and Ra-ctrl( 5 )=[10 Mbps]. The transmission mode control module  75  determines the application or non-application of the beam forming to each user by use of the profile information items and the radio resource amount control signals as inputs thereto. The transmission mode controller  75  applies the beam forming to users whose channel variation speed is equal to or less than five herz and does not apply the beam forming to users whose channel variation speed exceeds five herz. Resultantly, the transmission mode control signals are M-ctrl( 1 )=[BF], M-ctrl( 2 )=[N-BF], M-ctrl( 3 )=[N-BF], M-ctrl( 4 )=[BF], and M-ctrl( 5 )=[BF] By use of the radio resource amount control signals and the transmission mode control signals as input thereto, the mode controller  75  determines the assignment of radio resources to create the radio resource control signals such that the transmission points time of the first and fifth users to which the beam forming is applied is earlier than the transmission point of time of the second user to which the beam forming is not applied and the transmission point of time of the fifth user having a higher channel variation in the users to which the beam forming is applied is earlier than that of the first user. As a result, the radio resource control signals are R-ctrl( 1 )=[50 Mbps,#2], R-ctrl( 2 )=[40 Mbps,#3], R-ctrl( 3 )=[0,0], R-ctrl( 4 )=[0,0], and R-ctrl( 5 )=[10 Mbps,#1]. Here, #k indicates an order of transmission time, and the transmission signal of the user of #1 is transmitted at the earliest point of time. 
         [0047]    By use of the radio resource control signals, the transmission mode control signals, and the transmission data items as inputs thereto, the transmission signal generator  71  creates transmission signals of the first, second, and fifth users to whom radio resources are allocated. According to the transmission points of time, the processing is executed beginning at the fifth user. Since the radio resource allocated to the fifth user is 10 Mbps, it is only necessary to produce two 5 Mbps BPSK symbols. Here, the created BPSK symbols are represented as d 5 - 1  and d 5 - 2 . Subsequently, a singular value decomposition is carried out employing the channel matrix H( 5 ) generated using the channel information of the fifth user. This is written as H( 5 )=U( 5 )D( 5 )V H ( 5 ). Next, the beam forming is performed by use of the V( 5 ) matrix and time-series signals to produce transmission signals. Assume now that the V( 5 ) matrix is a two by two matrix and its elements are v 5 - 11 , v 5 - 12 , v 5 - 21 , and v 5 - 22 . In this situation, the time series of the transmission signals s( 1 ) and s( 2 ) are created through the beam forming as s( 1 )- 1 =v 5 - 11   d   5 - 1 +v 5 - 12   d   5 - 2  and s( 2 )- 1 =v 5 - 21   d   5 - 1 +v 5 - 22   d   5 - 2 . 
         [0048]    Next, the transmission signal for the first user is produced through the beam forming in the same way as for the fifth user. Since the radio resource allocated to the first user is 50 Mbps, it is only necessary to generate ten 5 Mbps BPSK symbols. The obtained symbols are d 1 - 1 , d 1 - 2 , d 1 - 3 , . . . , and d 1 - 10 . Subsequently, as in the case of the fifth user, by use of the V(i) matrix attained by conducting the singular value decomposition on the channel matrix H( 1 ) of the first user, the transmission signals s( 1 )- 2 , s( 2 )- 2  to s( 1 )- 6 , and s( 2 )- 6  are created as s( 1 )- 2 =v 1 - 11   d   1 - 1 +v 1 - 12   d   1 - 2 , s( 2 )- 2 =v 1 - 21 - d   11 -+v 1 - 22   d   1 - 2 , s( 1 )- 3  v 1 - 11   d   1 - 3 +v 1 - 13   d   1 - 4 , s( 2 )- 3 =v 1 - 21   d   1 - 3 +v 1 - 22   d   1 - 4 , . . . , s( 1 )- 6 =v 1 - 11   d   1 - 9 +v 1 - 12   d   1 - 10 , and s( 2 )- 6 =v 1 - 21   d   1 - 9 +v 1 - 22   d   1 - 10 . 
         [0049]    Next, since the beam forming is not applied to the second user, the transmission signals are generated without applying the beam forming. The radio resource allocated to the second user is 40 Mbps, and hence eight BPSK symbols d 2 - 1 , d 2 - 2 , . . . , d 2 - 8  are produced. By using these symbols, the transmission signals s( 1 )- 7 , s( 2 )- 7  to s( 1 )- 10 , and s( 2 )- 10  are created as s( 1 )- 7 =d 2 - 1 , s( 2 )- 7 =d 2 - 2 , s( 1 )- 8 =d 2 - 3 , s( 2 )- 8 =d 2 - 4 , . . . , s( 1 )- 10 =d 2 - 7 , and s( 2 )- 10 =d 2 - 8 . The transmission signal generator  71  outputs the transmission signals s( 1 )- 1  to s( 1 )- 10  and s( 2 )- 1  to s( 2 )- 10  respectively to the antennas  13 - 1  and  13 - 2 . 
         [0050]      FIG. 8  is a flowchart showing transmission processing of the transmitter  1  according to the first example of the present invention. Referring to  FIGS. 7 and 8 , description will be given of the transmission processing according to the first example of the present invention. Incidentally, the processing shown in  FIG. 8  is realized when the transmitter  7  executes a program in the recording medium  79  of  FIG. 7 . 
         [0051]    The two antennas  13 - 1  and  13 - 2  receive signals from a receiver (step s 81 ). The profile information extraction unit  73  extracts profile information items of five users and generates and outputs profile information items p( 1 ) to p( 5 ) (step S 82 ). The radio resource amount controller  74  preferentially selects users with a higher required rate and allocates 50 Mbps to the first user, 40 Mbps to the second user, and 10 Mbps to the fifth user such that the total transmission rate is equal to or less than 100 Mbps, and sets the radio resources allocated to the third and fourth users to zero to output the results as the radio resource amount control signals R-ctrl( 1 ) to R-ctrl( 5 ) (step S 83 ). The transmission mode controller  75  determines the application or non-application of the beam forming for each user and applies the beam forming to users whose channel variation speed is equal to or less than five herz, namely, the first, third, fourth, and fifth users. The mode controller  75  produces the results as transmission mode control signals (step S 84 ). The radio resource assignment controller  76  controls operation such that the transmission points of time of the first and fifth users to whom the beam forming is applied and who are selected from the first, second, and fifth users to whom the radio resources are allocated are earlier than that of the second user to whom the beam forming is not applied and the transmission point of time of users having a higher channel variation speed is earlier among the users to whom the beam forming is applied. As a result, the radio resource control signals are created to transmit signals in an order of the fifth, first, and second users (step S 85 ). By use of the radio resource control signals and the transmission mode control signals as inputs thereto, the transmission signal generator  71  creates and outputs transmission signals using the transmission data items of the first, second, and fifth users to whom radio resources are allocated, according to the radio resource control signals and the transmission mode control signals (step S 86 ). The duplexers  14 - 1  and  14 - 2  and the antennas  13 - 1  and  13 - 2  deliver the transmission signals (step S 87 ). 
         [0052]    As described for the example, a larger amount is allocated to a user requiring a higher transmission rate and the application or non-application of the beam forming and the transmission order are determined according to the channel variation, and hence efficient resource distribution and determination of the transmission mode are conducted for each user. 
         [0053]    Although the required transmission rate and the channel variation speed are adopted as the profile information in this example, this is only a premise for explanation and does not restrict the present invention. Additionally, although the beam forming and the space multiplexing using the singular value decomposition are employed as an example of the application or non-application of the beam forming, this is also a premise for explanation and does not restrict the present invention. 
       Example 2 
       [0054]      FIG. 9  is a block diagram showing a configuration of a transmitter according to a second example of the present invention. 
         [0055]    It is assumed in this example that there exist five users and the transmitter includes two antennas and employs Orthogonal Frequency Division Multiplex (OFDM) of subcarrier  50  in which one Mbps transmission is possible by one subcarrier. 
         [0056]    Referring to  FIG. 9 , the transmitter  9  in the second example of the present invention includes two antennas  13 - 1  and  13 - 2 , two duplexers  14 - 1  and  14 - 2  to conduct a change-over operation between transmission and reception, a transmission signal generator unit  71 , and a transmission signal control unit  92 . 
         [0057]    The transmission signal controller  92  includes a profile information extractor module  73 , a provisional transmission mode control module  93 , a radio resource control module  94 , and a transmission mode control module  95 . 
         [0058]    The second example of the present invention differs from the first example in the configuration and operation of the transmission signal controller  92  and the operation of the transmission signal generator  71 , and hence description will be given of the difference. 
         [0059]    Assume now that the profile information items are the required rate, the channel variation speed, and the radio resource amount of the reverse line required for the feedback of channel information of respective users and are p( 1 )=[50 Mbps,10 Hz,512 kbps], p( 2 )=[40 Mbps,30 Hz,512 kbps], p( 3 )=[30 Mbps, Hz,512 kbps], p( 4 )=[20 Mbps,4 Hz,256 kbps], and p( 5 )=[10 Mbps,22 Hz,256 kbps]. 
         [0060]    Using the profile information as an input thereto, the provisional transmission mode controller  93  provisionally determines the application or non-application of the beam forming on the basis of the channel variation speed. If the criterion to apply the beam forming is a channel variation equal to or less than 12 Hz, the beam forming is applied to the users other than the second user, and the provisional transmission mode control signals are Ma-ctrl( 1 )=[BF], Ma-ctrl( 2 )=[N-BF], Ma-ctrl( 3 )=[BF], Ma-ctrl( 4 )=[BF], and Ma-ctrl( 5 )=[BF]. 
         [0061]    The radio resource controller  94  determines, by use of the profile information and the provisional transmission mode controller  93 , the radio resource amounts to be assigned to the respective users and the assignment thereof. The resource controller  94  preferentially selects users to whom the beam forming is applicable, and particularly, the resource controller  94  preferentially allocates radio resources to users having a higher required rate. As a result, 50 Mbps is allocated to the first user, 30 Mbps is allocated to the third user, and 20 Mbps is allocated to the fourth user. Therefore, the radio resource control signals are R=ctrl( 1 )=[50 Mbps], R-ctrl( 2 )=[0], R-ctrl( 3 )=[30 Mbps], R-ctrl( 4 )=[20 Mbps], and R-ctrl( 5 )=[0]. Next, using the radio resource control signals and the profile information as inputs thereto, the mode controller  95  determines the application or non-application of the beam forming for each user. Assume now that the results of the application or non-application determined by the provisional transmission mode controller  93  are used without modification. Then, the beam forming is applied to the users other than the second user, and the transmission mode control signals are M-ctrl( 1 )=[BF], M-ctrl( 2 )=[N-BF], M-ctrl( 3 )=[BF], M-ctrl( 4 )=[BF], and M-ctrl( 5 )=[BF]. 
         [0062]    The transmission signal generator  71  produces transmission signals using the radio resource control signals and the transmission mode control signals as inputs thereto. The signal generator  71  prepares two OFDM symbols and allocates, for each of the symbols, 25 subcarriers to the first user, 15 subcarriers to the third user, and ten subcarriers to the fourth user. That is, for one of the OFDM signal, the allocation is conducted as f( 1 )=din( 1 )- 1 , f( 2 )=din( 1 )- 3 , . . . , f( 25 )=din( 1 )- 49 , f( 26 )=din( 3 )- 1 , f( 27 )=din( 3 )- 3 , . . . , f( 40 )=din( 3 )- 29 , f( 41 )=din( 4 )- 1 , f( 42 )=din( 4 )- 3 , . . . , f( 50 )=din( 4 )- 19 . For the other one of the OFDM signals, the allocation is conducted as g( 1 )=din( 1 )- 2 , g( 2 )=din( 1 )- 4 , . . . , g( 25 )=din( 1 )- 50 , g( 26 )=din( 3 )- 2 , g( 27 )=din( 3 )- 4 , . . . , g( 40 )=din( 3 )- 30 , g( 41 )=din( 4 )- 2 , g( 42 )=din( 4 )- 4 , . . . , g( 50 )=din( 4 )- 20 . Here, f(k) and g(k) represent the k-th subcarriers for the two OFDM signals. 
         [0063]    Next, the beam forming is carried out by use of the channel matrices of the first, third, and fourth users. Assume that the singular value decomposition of the channel matrix corresponding to the k-th subcarrier of the first user results in H( 1 ,k)=U( 1 ,k)D( 1 ,k)V H ( 1 ,k). Since the first user employs the first to 25th subcarriers, the beam forming is conducted using the two OFDM symbols as s( 1 , 1 )=v( 1 , 1 )- 11   f ( 1 )+v ( 1 , 1 )- 12   g ( 1 ), s( 2 , 1 )=v( 1 , 1 )- 21   f ( 1 )+v( 1 , 1 )- 22   g ( 1 ), s( 1 , 2 )=v( 1 , 2 )- 11   f ( 2 )+v( 1 , 2 )- 12   g ( 2 ), s( 2 , 2 )=v( 1 , 2 )- 21   f ( 2 )+v( 1 , 2 )- 21   g ( 2 ), . . . , s( 1 , 25 )=v( 1 , 25 )- 11   f ( 25 )+v( 1 , 25 )- 12   g ( 25 ), s( 2 , 25 )=v( 1 , 1 )- 21   f ( 25 )+v( 1 , 25 )- 21   g ( 25 ). Here, s( 1 ,k) and s( 2 ,k) represent the k-th subcarriers of the OFDM signals transmitted from the antennas  1  and  2 , and v( 1 ,k)-ij indicates an i-row and j-column element of v( 1 ,k). 
         [0064]    Subsequently, since the third user adopts the 26th to 40th subcarriers, the beam forming is conducted similarly as s( 1 , 26 )=v( 3 , 26 )- 11   f ( 26 )+v( 3 , 26 )- 12   g ( 26 ), s( 2 , 26 )=v( 3 , 26 )- 21   f ( 26 )+v( 3 , 26 )- 22   g ( 26 ), s( 1 , 27 )=v( 3 , 27 )- 11   f ( 27 )+v( 3 , 27 )- 12   g ( 27 ), s( 2 , 27 )=v( 3 , 27 )- 21   f ( 27 )+v( 3 , 27 )- 21   g ( 27 ), . . . , s( 1 , 40 )=v( 3 , 40 )- 11   f ( 40 )+v( 3 , 40 )- 12   g ( 40 ), s( 2 , 40 )=v( 3 , 40 )- 21   f ( 40 )+v( 3 , 40 )- 21   g ( 40 ). 
         [0065]    Finally, for the fourth user, the beam forming is similarly accomplished as s( 1 , 41 )=v( 4 , 41 )- 11   f ( 41 )+v( 4 , 41 )- 12   g ( 41 ), s( 2 , 41 )=v( 4 , 41 )- 21   f ( 41 )+v( 4 , 41 )- 22   g ( 41 ), s( 1 , 42 )=v( 4 , 42 )- 11   f ( 42 )+v( 4 , 42 )- 12   g ( 42 ), s( 2 , 42 )=v( 4 , 42 )- 21   f ( 42 )+v( 4 , 42 )- 21   g ( 42 ), . . . , s( 1 , 50 )=v( 4 , 50 )- 11   f ( 50 )+v( 4 , 50 )- 12   g ( 50 ), s( 2 , 50 )=v( 4 , 50 )- 21   f ( 50 )+v( 4 , 50 )- 21   g ( 50 ). After the resource allocation and the beam forming are applied for the two OFDM signals in this fashion, the signals are converted by a discrete Fourier transform into time signals to be outputted. 
         [0066]    As shown in the example, by provisionally determining the application or non-application of the beam forming for each user, it is possible to preferentially allocate radio resources to users to whom the beam forming with a high transmission characteristic is applicable, to thereby implement a highly efficient system. 
         [0067]    Incidentally, the transmission mode controller  96  of the example employs the results from the provisional transmission mode controller  93  without modification. However, it is possible to implement a more efficient system by using the profile information in the determination of the application or non-application of the beam forming. For example, in a case wherein the resources of the reserve lines required for the feedback of the channel information as the profile information are known as in the example, it is possible, particularly in a radio communication system sharing the pertinent line and its reverse line, to keep balance therebetween in consideration of the resources. 
         [0068]    Specifically, the amount of radio resources required for the reverse line is limited to 1.2 Mbps. In this situation, since the first, third, and fourth users respectively require 512 kbps, 512 kbps, and 256 kbps for the reverse lines, the beam forming is applied only to two users thereof. In this operation, the beam forming is applied to the first and third users having a higher required rate and is not applied to the fourth user. Resultantly, the transmission mode control signals are M-ctrl( 1 )=[BF], M-ctrl( 2 )=[N-BF], M-ctrl( 3 )=[BF], M-ctrl( 4 )=[N-BF], and M-ctrl( 5 )=[BF]. This makes it possible to suppress the radio resources on the reverse lines required for the feedback of the channel information. 
         [0069]    In this situation, the transmission signal generator  71  does not conduct the singular value decomposition of the channel matrix for the fourth user. Therefore, in the creation of the transmission signals, the 41st to 50th subcarriers are s( 1 , 41 )=f( 41 ), s( 2 , 41 )=g( 41 ), s( 1 , 42 )=f( 42 ), s( 2 , 42 )=g( 42 ), . . . , s( 1 , 50 )=f( 50 ), s( 2 , 50 )=g( 50 ). 
         [0070]    Also, the provisional transmission mode controller  93  of the example provisionally determines the application or non-application of the beam forming by use of the channel variation speed. However, the provisional determination may also be beforehand conducted by using more profile information items. For example, by determining a criterion for three profile information items as “the channel variation is equal to or less than ten herz” or “the required rate is equal to or more than 20 Mbps”, there remains possibility of the application of the beam forming for a larger number of users. Contrarily, by determining the criterion as “the channel variation is equal to or less than ten herz” and “the required rate is equal to or more than 20 Mbps”, it is possible to limit the application to users for whom the communication success probability is high when the beam forming is applied and the effect of the application is large. 
       Example 3 
       [0071]      FIG. 10  is a flowchart showing processing of the transmission signal control unit  72  in accordance with the third example of the present invention. 
         [0072]    In the example, although the transmitter is the same as that of the first example, the operation of the transmission signal control unit  72  is different from that of the first example. Therefore, the difference will be described in detail. However, although the example conducts a total of 150 Mbps transmission, the operation in the transmission signal generator unit  71  is not substantially changed, and hence description thereof will be avoided. 
         [0073]    Referring to  FIG. 10 , the profile information extractor module  73  disposed in the signal controller  72  extracts profile information from the reception signals (step S 101 ). Here, it is assumed that the profile information items are the required rate, the channel variation speed, the radio resource amount required to feed back second profile information and are respectively p( 1 )-[45 Mbps,2 Hz,512 kbps], p( 2 )=[45 Mbps,5 Hz,256 kbps], p( 3 )=[30 Mbps,2 Hz,128 kbps], p( 4 )=[5 Mbps, 3 Hz, 128 kbps], and p( 5 )=[15 Mbps, 10 Hz, 128 kbps]. 
         [0074]    The radio resource amount controller  74  determines, using the profile information as an input thereto, the radio resource amount to be allocated to each user to generate radio resource amount control signals (step S 102 ). Since the sum of the required rates of the users is 150 Mbps for the overall radio resource amount of 150 Mbps, a radio resource amount equal to the required amount is allocated to each user to produce the radio resource amount control signals as Ra-ctrl( 1 )=[45 Mbps], Ra-ctrl( 2 ) [45 Mbps], Ra-ctrl( 3 )=[30 Mbps], Ra-ctrl( 4 )=[15 Mbps], and Ra-ctrl( 5 )=[15 Mbps]. 
         [0075]    The transmission mode controller  75  uses the profile information and the radio resource amount control signals as inputs thereto to determine the application or non-application of the beam forming for each user. In the operation, the mode controller  75  determines the users to whom the beam forming is applied through the primary determination and the secondary determination. Also, it is assumed that new profile information is not obtained until the first determination is completed. Therefore, the first profile information is a required rate, a channel variation speed, and a band required to feed back the second profile information. 
         [0076]    The mode controller  75  determines, as primary determination users, users whose channel variation speed is equal to or less than five herz and whose band attained to feed back the second profile information is equal to or less than 256 kbps (step S 103 ). As a result, the second, third, and fourth users are the primary determination users. Through the operation, the users are selected who do not consume a large amount of radio resources on the reverse line and to whom the beam forming is applicable. 
         [0077]    Next, a request is issued to the users for the second profile information, and only the second, third, and fourth users feed back respective channel information as the second profile information (step S 104 ). Using the channel information thus fed back, the mode controller  75  conducts the singular value decomposition for the channel information of each user to obtain the sum of the singular values. Assume now that each user has two singular values which are D( 2 ) [25,5], D( 3 )=[50,10], and D( 4 )=[20,0]. Therefore, assuming that the sum of two singular values of the k-th user is expressed as S(k), there are obtained S( 2 )=30, S( 3 )=60, and S( 4 )=20. Subsequently, a mean singular value available for the one Mbps transmission is obtained using the sum of singular values and the required rate. Assuming that this results in q, there are attained q( 2 )=0.667, q( 3 )=2, and q( 4 )=1.33 (step S 105 ). 
         [0078]    Next, the data items are sorted by assigning a priority level to users with a large value of q (step S 106 ). This is employed to possibly increase the transmission success probability when the beam forming is applied. According to the sorted results, the beam forming is allocated to two highest-level users (step S 107 ). Resultantly, there is obtained the secondary determination in which the beam forming is applied to the third and fourth users and the beam forming is not applied to the first, second, and fifth users. Therefore, the transmission mode control signals are M-ctrl( 1 )=[N-BF], M-ctrl( 2 )=[N-BF], M-ctrl( 3 )=[BF], M-ctrl( 4 )=[BF], and M-ctrl( 5 )=[BF]. Additionally, by use of the transmission mode control signals and the radio resource amount control signals as inputs thereto, the radio resource assignment controller  76  creates, as in the first example, the radio resource control signals such that the transmission time of the users to whom the beam forming is applied is earlier and the transmission time is earlier for the users having a higher channel variation speed (step S 108 ). This results in R-ctrl( 1 )=[45 Mbps,#3], R-ctrl( 2 )=[45 Mbps,#4], R-ctrl( 3 )=[30 Mbps,#2], R-ctrl( 4 )=[15 Mbps,#1], and R-ctrl( 5 )=[15 Mbps,#5]. 
         [0079]    As shown in the example, the application or non-application of the beam forming is determined through the primary determination and the secondary determination to issue a request of the feedback of information only to the primary determination users requiring the second profile information, it is hence possible to determine the application or non-application of the beam forming by efficiently using the radio resource on the reverse line. 
       Example 4 
       [0080]    Next, the fourth example will be described in detail. This example differs from the third example in the operation of the transmission mode controller  75 , and hence the difference will be described in detail. 
         [0081]      FIG. 11  is a flowchart for explaining operation of the transmission mode controller  75  in the fourth example of the present invention. It is here assumed that the profile information is channel information and a required rate of each user, i.e., p( 1 )=[H( 1 ),50 Mbps], p( 2 )=[H( 2 ),40 Mbps], p( 3 )=[H( 3 ),30 Mbps], p( 4 )=[H( 4 ),20 Mbps], and p( 5 )=[H( 5 ), 10 Mbps]. 
         [0082]    The mode controller  75  receives as inputs thereto the profile information and the radio resource control signals Ra-ctrl( 1 )=[50 Mbps], Ra-ctrl( 2 )=[40 Mbps], Ra-ctrl( 3 )=[30 Mbps], Ra-ctrl( 4 )=[20 Mbps], and Ra-ctrl( 5 )=[10 Mbps] (step S 111 ). 
         [0083]    Next, the mode controller  75  estimates the first reception quality when the beam forming is not applied (step S 112 ). 
         [0084]    Since the channel information of each user has been acquired, the transmission mode controller  75  is capable of estimating the reception Signal-to-Noise Ratio (SNR). Assume in the transmitter  7  that the receiving method of each user is Zero Focusing (ZF) and the reception SNR of the first and second transmission signals of the k-th user are SNR(k)- 1  and SNR(k)- 2 . Then, there are obtained SNR(k)- 1 =((H H H) −1 ) H -11·Pt/s 2  and SNR(k)- 2 =((H H H) −1 ) H -22·Pt/s 2 . Here, H indicates the channel matrix of the k-th user and Pt represents the power of the transmission signal, and S 2  indicates the mean noise power. If it is assumed that Pt/s 2  is fixed, ((H H H) −1 ) H -11 or ((H H H) −1 ) H -22 may be regarded as the reception SNR. Assume now that SNR( 1 )- 1 =5, SNR( 1 )- 2 =5, SNR( 2 )- 1 =12, SNR( 2 )- 2 =8, SNR( 3 )- 1 =10, SNR( 3 )- 2 =20, SNR( 4 )- 1 =22, SNR( 4 )- 2 =18, SNR( 5 )- 1 =20, SNR( 5 )- 2 =30. Then, the sum of SNR is obtained as SNR( 1 )=10, SNR( 2 )=20, SNR( 3 )=30, SNR( 4 )=40, and SNR( 5 )=50. 
         [0085]    Next, SNR required for the one Mbps transmission is attained as the first reception quality. If the first reception quality of the k-th user is represented as u 1 ( k ), there are obtained u( 1 )=0.2, u( 2 )=0.5, u( 3 )=1, u( 4 )=2, and u( 5 )=5. If it is now assumed that SNR is required to be for the one Mbps transmission, it is known that the predetermined reception quality is attained without applying the beam forming to the fourth and fifth users. Therefore, it is determined that the beam forming is not applied to the fourth and fifth users (step S 113 ). 
         [0086]    Subsequently, for the first, second, and third users having not satisfied the predetermined first reception quality, the second reception quality u 2 ( k ) is acquired. It is here assumed that, as for the mean singular value available for the one Mbps transmission employed in the third example, the values for the second and third are the same as for the third example. If two eigen values of the first user is D( 1 )=[25,25], the second reception quality of each user is obtained as u 2 ( 1 )=1.11, u 2 ( 2 )=q( 2 )=0.667, and u 2 ( 3 )=q( 3 )=2 (step S 114 ). 
         [0087]    Next, the first reception quality is compared with the second reception quality for each user; if the first reception quality is better than the second reception quality, it is determined that the beam forming is applied; otherwise, it is determined that the beam forming is not applied (steps S 115  to S 117 ). Now, the second reception quality exceeds the first reception quality for all users, and hence it is determined that the beam forming is applied to the first to third users. Therefore, the transmission mode controller determines the transmission mode control signals as M-ctrl( 1 )=[BF], M-ctrl( 2 )=[BF], M-ctrl( 3 )=[BF], M-ctrl( 4 )=[N-BF], and M-ctrl( 5 )=[N-BF]. 
         [0088]    As shown in the example, the non-application of the beam forming is beforehand determined for the users who exceed the predetermined quality without applying the beam forming, and hence the beam forming can be efficiently allocated to the users for whom the characteristic is remarkably deteriorated when the beam forming is not applied. 
         [0089]    Incidentally, the embodiments described above are best embodiments to embody the present invention; however, it is to be understood that the present invention is not restricted by the embodiments. Consequently, the embodiments may be modified in various ways within a range in which the gist of the present invention is not changed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0090]    [ FIG. 1 ] is a block diagram for explaining a configuration of a radio communication system in a best embodying mode. 
           [0091]    [ FIG. 2 ] is a flowchart for explaining transmission processing by a transmitter of  FIG. 1 . 
           [0092]    [ FIG. 3 ] is a block diagram for explaining a configuration of a radio communication system in a second embodying mode. 
           [0093]    [ FIG. 4 ] is a flowchart for explaining transmission processing by a transmitter of  FIG. 3 . 
           [0094]    [ FIG. 5 ] is a block diagram for explaining a configuration of a radio communication system in a third embodying mode. 
           [0095]    [ FIG. 6 ] is a flowchart for explaining transmission processing by a transmitter of  FIG. 5 . 
           [0096]    [ FIG. 7 ] is a block diagram for explaining a configuration of a first embodiment of the present invention. 
           [0097]    [ FIG. 8 ] is a flowchart for explaining transmission processing by a transmitter of  FIG. 7 . 
           [0098]    [ FIG. 9 ] is a block diagram for explaining a configuration of a second embodiment of the present invention. 
           [0099]    [ FIG. 10 ] is a flowchart for explaining processing by a third embodiment of the present invention. 
           [0100]    [ FIG. 11 ] is a flowchart for explaining processing by a fourth embodiment of the present invention. 
       
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
       [0000]    
       
           1 ,  3 ,  5 ,  7 ,  9  Transmitter 
           2  Receiver 
           11 ,  71  Transmission signal generator unit 
           12 ,  31 ,  51 ,  54 ,  72 ,  92  Transmission signal control unit 
           13 - 1  to  13 -M,  13 -J Antenna 
           14 - 1  to  14 -M Duplexer 
           15 ,  32 ,  52 ,  77  Recording medium 
           33 ,  74  Radio resource amount control unit 
           34 ,  75  Transmission mode determining unit 
           35 ,  76  Radio resource assignment determining unit 
           53  Provisional transmission mode control unit 
           73  Profile information extracting unit 
           93  Provisional transmission mode control unit 
           94  Radio resource control unit 
           95  Transmission mode control unit