Abstract:
There is a problem that if a transmitter apparatus having an adaptive modulation function is to be configured to divide data for transmission, the structure of the transmitter apparatus will be complicated and the cost thereof will be raised. In order to solve this problem, a transmitter apparatus comprises: a dividing means for dividing input data into a plurality of pieces of data; a plurality of transmitting means for transmitting the pieces of data as divided to respective transmission paths; and a modulation scheme deciding means for deciding, from among modulation schemes associated with the conditions of the transmission paths, a modulation scheme, which is to be used by the transmission means, such that the difference in transmission speed between the pieces of data transmitted by the plurality of transmitting means is within a predetermined range.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a transmitter apparatus and a transmission method which divide and transmits data, in particular a transmitter apparatus, a transmission method and a transmission system including an adaptive modulation function. 
       BACKGROUND ART 
       [0002]    A technology is known, in which data is transmitted in parallel by a plurality of transmitter apparatuses to enlarge a transmission capacity of a transmission section. For example, a technology exists, in which when data having a frame configuration, like a LAN (Local Area Network), data is divided for each frame and transmitted in parallel by the plurality of transmitter apparatuses. Patent document 1 and Patent document 2 disclose the technology that data is divided and transmitted. 
         [0003]    Patent document 1 discloses a configuration of a communication device which forms a plurality of logical links with an opposite communication device, and divides and transmits transmission data. The communication device described in Patent document 1 synthesizes the received data in order of a transmission number to restore the divided data into the original data. 
         [0004]    Patent document 2 describes a configuration of an edge device which generates divided frames by dividing a MAC frame, a length of which is longer than a predetermined length, which flows in the broad area Ethernet network (“Ethernet” is registered trademark). When transferring the divided frames from the network to the outside, the edge device described in Patent document 2 combines the divided frames. 
         [0005]    The communication device described in Patent documents 1 and 2 divides the transmission data and transmits them in parallel to enlarge the transmission capacity. 
         [0006]    As a method of optimizing the transmission capacity depending on a condition of a transmission path, Patent document 3 describes an adaptive modulation function. A transmitter apparatus with the adaptive modulation device decides a modulation scheme on the basis of the condition of the transmission path so that a transmission error is lower than an allowable amount. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0000]    
       
         [Patent Document 1] Tokukai 2006-279467 A (paragraphs [0059] to [0061]) 
         [Patent Document 2] Tokukai 2005-012831 A (paragraph [0039]) 
         [Patent Document 3] Tokukai-shou 57-159148 A (line  20  of upper right to line  8  of lower left in page 3) 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    In the transmitter apparatus with the adaptive modulation function described in Patent document 3, when the transmission data is divided and the pieces of data are transmitted by the plurality of the transmitter apparatuses, each transmitter apparatus which transmits the divided data may choose a different modulation scheme. In general, data is transmitted at different transmission speeds for different modulation schemes. Thus, if the divided data is transmitted with the different modulation scheme, the transmitter apparatus on the reception side may receive the data for each piece of the divided data at a different speed. 
         [0011]    Therefore, when the transmitter apparatus with the adaptive modulation function divides the data and transmits them in parallel, the transmitter apparatus on the reception side requires memory with a large capacity for storing the pieces of data while the original data before the division is restored from the received pieces of data. As a result, when the divided data are transmitted using the transmitter apparatus with the adaptive modulation function, a memory with large capacity should be installed so that the configuration of the transmitter is complicated and becomes costly. 
         [0012]    Patent documents 1 to 3 do not disclose any means for solving the problem which arises when the transmitter apparatus with the adaptive modulation function divides data and transmits them. 
         [0013]    An object of the present invention is to provide the means for solving the problem described above. 
       Solution to Problem 
       [0014]    The transmitter apparatus of the invention includes a dividing means for dividing input data into a plurality of pieces of data, a plurality of transmitting means for transmitting the pieces of data as divided to respective transmission paths, and a modulation scheme deciding means for deciding, from among modulation schemes associated with the conditions of the transmission paths, a modulation scheme, that is to be used by the transmission means, such that a difference in transmission speeds between the pieces of data transmitted by the plurality of transmitting means is within a predetermined range. 
         [0015]    The transmission method of the invention includes dividing input data into a plurality of pieces of data, transmitting the pieces of data as divided to respective transmission paths, and deciding, from among modulation schemes associated with the conditions of the transmission paths, a modulation scheme of the data, such that a difference in transmission speeds between the pieces of data that is transmitted is within a predetermined range. 
       Advantageous Effects of Invention 
       [0016]    The present invention includes the effect that when the transmitter apparatus with the adaptive modulation function divides data and transmits them, the transmitter apparatus does not get complicated and price increase thereof is suppressed. 
     
    
     
       BRIEF EXPLANATION OF DRAWINGS 
         [0017]      FIG. 1  is a diagram illustrating a configuration of a wireless transmission system of a first exemplary embodiment. 
           [0018]      FIG. 2  is a diagram illustrating division and integration of a MAC frame in the first exemplary embodiment. 
           [0019]      FIG. 3  is a diagram illustrating a processing procedure of the MAC frame which is performed when one of data outputted by a frame dividing unit is invalid data. 
           [0020]      FIG. 4  is a diagram illustrating a configuration of a frame integrating unit. 
           [0021]      FIG. 5  is a diagram explaining a bit width elongation procedure. 
           [0022]      FIG. 6  is a diagram illustrating a wireless transmission system of a second exemplary embodiment. 
           [0023]      FIG. 7  is a diagram illustrating a configuration of a transmitter apparatus of a third exemplary embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    First Exemplary Embodiment 
         [0025]    It is required that data is modulated using a modulation scheme in which modulation level is large as much as possible, in order to enlarge a transmission capacity of a wireless transmission system. However, as the modulation level of the modulation scheme becomes large, resistance of a wireless signal to variation of a transmission condition of a wireless transmission path is generally reduced. On the other hand, if the modulation level decreases, resistance of a wireless signal to variation of a transmission condition increases though a transmission capacity is reduced. 
         [0026]    A wireless transmission system with an adaptive modulation function optionally chooses a more suitable modulation scheme depending on a transmission path condition to reduce a transmission error and enlarge a transmission capacity. A procedure of the transmission system with the adaptive modulation function is well-known. Detailed descriptions on the adaptive modulation function are omitted. 
         [0027]      FIG. 1  is a diagram illustrating a configuration of a wireless transmission system of a first exemplary embodiment. 
         [0028]    A configuration of a radio transmitter apparatus  10  is described with reference to  FIG. 1 . In  FIG. 1 , a configuration and a function of a radio transmitter apparatus  30  is the same as that of the radio transmitter apparatus  10 . Descriptions on the configuration and the function of the radio transmitter apparatus  30  are omitted. A configuration of a radio transmitting/receiving unit  19  of the radio transmitter apparatus  10  is the same as that of a radio transmitting/receiving unit  15 . Detailed descriptions on the radio transmitter apparatus  30  and the radio transmitting/receiving unit  19  are, therefore, omitted. In  FIG. 1 , each part of the radio transmitting/receiving unit  19  corresponding to each part of the radio transmitting/receiving unit  15  is given a reference numeral of the radio transmitting/receiving unit  15  to which “A” is further added. 
         [0029]    The radio transmitter apparatus  10  is opposed to the radio transmitter apparatus  30 , and the apparatuses transmit a MAC frame to each other. The radio transmitter apparatus  10  divides an external LAN signal  100  inputted from a user network  40 , and transmits them to the radio transmitter apparatus  30  as a radio signal. The radio transmitter apparatus  30  restores data from the radio signal received from the radio transmitter apparatus  10 , and outputs it to a user network  50  as an external output LAN signal  501 . 
         [0030]    On the contrary, the radio transmitter apparatus  30  divides an external LAN signal  502  inputted from a user network  50 , and transmits them to the radio transmitter apparatus  10  as a radio signal. The radio transmitter apparatus  10  restores data from the radio signal received from the radio transmitter apparatus  30 , and outputs it to a user network  40  as an external output LAN signal  231 . 
         [0031]    The radio transmitter apparatus  10  includes a frame dividing unit  11 , generating units  12  and  13 , a transmission determining unit  14 , the radio transmitting/receiving units  15  and  19 , analyzing units  20  and  21 , a reception determining unit  22 , and a frame integrating unit  23 . 
         [0032]    Relation of connection between parts of the radio transmitter apparatus is mainly described below. Details of operations are explained in a section “explanation on operations of the exemplary embodiment”. 
         [0033]    The frame dividing unit  11  receives the external input LAN signal  100  from the user network  40  and a division control signal  141  from the transmission determining unit  14 . The external input LAN signal  141  is a MAC frame which is transmitted to the user network  50 . The frame dividing unit  11  divides the MAC frame of the external LAN signal  100  into two parts, and outputs them to the generating unit  12  and the generating unit  13  as a divided LAN signal  111  and a divided LAN signal  112 , respectively. 
         [0034]    The generating unit  12  receives the divided LAN signal  111  inputted from the frame dividing unit  11  and a multiple alarm signal  142  inputted from the transmission determining unit  14 . The generating unit  12  multiplexes the divided LAN signal  111  and the multiple alarm signal  142  and outputs it to a radio transmitting unit  16  in the radio transmitting/receiving unit  15  as a transmission signal  121 . 
         [0035]    The generating unit  13  receives the divided LAN signal  112  inputted from the frame dividing unit  11  and a multiple alarm signal  143  inputted from the transmission determining unit  14 . The generating unit  13  multiplexes the divided LAN signal  112  and the multiple alarm signal  143  and outputs it to a radio transmitting unit  16 A in the radio transmitting/receiving unit  19  as a transmission signal  131 . 
         [0036]    The radio transmitting/receiving units  15  and  19  are described below. 
         [0037]    The radio transmitting/receiving unit  15  includes the radio transmitting unit  16 , a radio receiving unit  17 , and an adaptive modulation deciding unit  18 . The radio transmitting/receiving unit  19  also includes the radio transmitting unit  16 A, a radio receiving unit  17 A, and an adaptive modulation deciding unit  18 A. A configuration and operations of the radio transmitting/receiving unit  19  are the same as those of the radio transmitting/receiving unit  15 . An explanation on each part of the radio transmitting/receiving unit  19  is therefore omitted. 
         [0038]    The radio transmitting unit  16  receives the transmission signal  121  from the generating unit  12 . The radio transmitting unit  16  modulates the transmission signal  121  on the basis of the modulation scheme designated by a modulation control signal  181 , and generates a radio signal  161 . The radio signal  161  is transmitted from an antenna  10 A to an opposite antenna  30 A connected with the radio transmitter apparatus  30  as a radio signal. 
         [0039]    An antenna  10 B connected with the radio receiving unit  17  receives a radio signal  301  which is generated by the radio transmitter apparatus  30  and is transmitted by an antenna  30 B via the antenna  10 B. The radio receiving unit  17  demodulates the inputted radio signal  301  and generates a reception signal  172 , and outputs the reception signal  172  to the analyzing unit  20 . The radio receiving unit  17  outputs a radio alarm signal  171  to the transmission determining unit  14  and to the reception determining unit  22 . The radio alarm signal  171  includes a reception power reduction alarm indicating that reception power of the radio receiving unit  17  is reduced. The radio receiving unit  17  further outputs a reception power monitoring signal  173  to the adaptive modulation deciding unit  18 . 
         [0040]    The adaptive modulation deciding unit  18  recognizes radio reception power of a signal received from the radio transmitter apparatus  30  which is radio-opposed, from the reception power monitoring signal  173 . The adaptive modulation deciding unit  18  chooses a modulation scheme on the basis of the magnitude relationship between the radio reception power and a predetermined threshold value. The adaptive modulation deciding unit  18  outputs the chosen modulation scheme to the radio transmitting unit  16  as the modulation control signal  181 . 
         [0041]    The adaptive modulation deciding unit  18  transmits and receives information on the modulation scheme to and from the adaptive modulation deciding unit  18 A of the radio transmitting/receiving unit  19  using a modulation scheme synchronization signal  182 . As a result, the adaptive modulation deciding unit  18  and the adaptive modulation deciding unit  18 A can recognize both of the modulation schemes which are chosen based on the transmission signal  121  and the transmission signal  131 . 
         [0042]    The radio transmitting unit  16 A of the radio transmitting/receiving unit  19 , the internal configuration of which is the same as that of the radio transmitting/receiving unit  15  performs an operation which is the same as that of the radio transmitting unit  16 . That is, the radio transmitting unit  16 A modulates and frequency converts the transmission signal  131  inputted from the generating unit  13 , and generates a radio signal  191 . The radio transmitting unit  16 A outputs the radio signal  191  to an antenna  10 C. 
         [0043]    The transmission determining unit  14  receives the radio alarm signal  171 , a radio alarm signal  192 , a reception alarm signal  202 , and a reception alarm signal  212 . The transmission determining unit  14  performs a predetermined determining procedure based on conditions of the alarm signals. The determining procedure is described in the section “explanation on operations of the exemplary embodiment”. The transmission determining unit  14  outputs the determination result to the frame dividing unit  11  as the division control signal  141 . The transmission determining unit  14  outputs the determination result to the generating unit  12  and  13  as the multiple alarm signal  142  and a multiple alarm signal  143 . 
         [0044]    The radio receiving unit  17  receives the radio signal  301  which is received from the radio transmitter apparatus  30  which is the radio-opposed station through the antennas  30 B and  10 B. The radio receiving unit  17  frequency-converts and demodulates the received radio signal  301 . The radio receiving unit  17  outputs the demodulated signal to the analyzing unit  20  as the reception signal  172 . The radio receiving unit  17  outputs the reception power reduction alarm indicating that reception power from the radio transmitter apparatus  30  is reduced, to the transmission determining unit  14  and the reception determining unit  22  as the radio alarm signal  171 . 
         [0045]    The radio transmitting unit  17 A of the radio transmitting/receiving unit  19 , the internal configuration of which is the same as that of the radio transmitting/receiving unit  15  performs an operation which is the same as that of the radio transmitting unit  17 . That is, the radio transmitting unit  17 A outputs a reception signal  193  to the analyzing unit  21  and outputs the radio alarm signal  192  to the transmission determining unit  14  and the reception determining unit  22 . 
         [0046]    The analyzing unit  20  receives the reception signal  172  and an integration control signal  221 . The analyzing unit  20  processes the reception signal  172  based on the integration control signal  221 , and outputs the process result to the frame integrating unit  23  as an integration LAN signal  201 . The analyzing unit  20  outputs an alarm which is detected from the radio alarm signal  171  to the transmission determining unit  14  and the reception determining unit  22  as the reception alarm signal  202 . 
         [0047]    The operation of the analyzing unit  21  is the same as that of the analyzing unit  20  except that an inputted signal is the reception signal  193  which is outputted from the radio transmitting/receiving unit  19 . The analyzing unit  21  receives the reception signal  193  which is outputted from the radio transmitting/receiving unit  19  and an integration control signal  222  which is outputted from the reception determining unit  22 . The analyzing unit  21  performs predetermined processing on the reception signal  193  based on the integration control signal  222  and outputs the process result to the frame integrating unit  23  as the integration LAN signal  211 . The analyzing unit  21  outputs the reception alarm signal  212  informing of an alarm detected from the reception signal  193  to the transmission determining unit  14  and the reception determining unit  22 . 
         [0048]    The frame integrating unit  23  receives the integration LAN signals  201  and  211  outputted by the analyzing units  20  and  21 , respectively. The frame integrating unit  23  integrates the inputted two signals and generates the MAC frame. The frame integrating unit  23  outputs the generated MAC frame to the user network  40  as the external output LAN signal  231 . 
         [0049]    The reception determining unit  22  receives the radio alarm signal  171  outputted by the radio receiving unit  17  and radio alarm signal  192  outputted by the radio transmitting/receiving unit  19 . The reception determining unit  22  performs the following determination based on the signals and outputs the determination result to the analyzing units  20  and  21  as the integration control signals  221  and  222 , respectively. 
       [Explanation on Operations of the Exemplary Embodiment] 
       [0050]    Operations of radio transmission system of the first exemplary embodiment are described in detail with reference to  FIG. 1  to  FIG. 5 . 
         [0051]    The frame dividing unit  11  of the radio transmitter apparatus  10  of  FIG. 1  receives the external input LAN signal  100  from the user network  40  and the division control signal  141  from the transmission determining unit  14 . 
         [0052]    The frame dividing unit  11  divides the MAC frame of the external LAN signal  100  into two parts on the basis of the division control signal  141 . The frame dividing unit  11  outputs one of the external LAN signals  100  divided into two parts to the radio transmitting/receiving unit  15  through the generating unit  12 . The frame dividing unit  11  outputs the other of the external LAN signals  100  divided into two parts to the radio transmitting unit  19  through the generating unit  13 . 
         [0053]    When a division scheme in a time of division of the MAC frame before transmission corresponds to that in a time of integration of the MAC frames after reception, the MAC frame may be divided based on an arbitrary procedure. For example, the MAC frame may be divided for each even byte or for each odd byte in the frame. The MAC frame may be divided into upper level bits and lower level bits for each one byte (eight bits) of data which composes the MAC frame. 
         [0054]      FIG. 2  is a diagram illustrating division and integration of the MAC frame in the first exemplary embodiment.  FIG. 2  illustrates, as an example, a form of the MAC frame which is taken when the MAC frame which is data with a unit of one byte (eight bits) (hereinafter referred to as “BYTE data”) is transmitted by dividing into upper level bits and lower level bits. 
         [0055]    S 1  to S 3  in  FIG. 2  shows procedures of dividing the MAC frame into two parts, upper level bits and lower level bits for one byte of data which composes the MAC frame. 
         [0056]    The upper level bits are the fifth bit to the eighth bit of data which is formed by dividing the external LAN signal  100  in a unit of byte, i.e. data indicated in  1 - 1 ,  2 - 1 ,  3 - 1 ,  4 - 1  . . . in  FIG. 2 . The lower bits are the first bit to the fourth bit of data which is formed by dividing the external LAN signal  100  in a unit of byte, i.e. data indicated in  1 - 2 ,  2 - 2 ,  3 - 2 ,  4 - 2  . . . in  FIG. 2 . The frame dividing unit  11  divides the external LAN signal  100  (S 1 ) into the divided LAN signal  111  (S 2 ) which is composed of data of the upper level bits and the divided LAN signal  112  (S 3 ). 
         [0057]    If the division control signal  141  instructs the frame dividing unit  11  to stop dividing, the frame dividing unit  11  stops dividing the MAC frame. When stop of dividing the MAC frame is instructed, the frame dividing unit  11  transmits invalid data in an instructed direction of the radio transmitting/receiving unit  15  or the radio transmitting/receiving unit  19 . The frame dividing unit  11  transmits the MAC frame without division in the direction to which the invalid data is not transmitted. 
         [0058]    Contents of the invalid data may be ones which can be recognized, at the time of reception, that the data is not a divided MAC frame. If all of the data are “0” or “1”, and all of the data which is read out at the time of reception are “0” or “1”, the data may be decided as the invalid data on the reception side. If the invalid data includes a specific pattern, the data including the specific pattern may be decided as the invalid data on the reception side when the specific pattern is detected on the reception side. 
         [0059]      FIG. 3  illustrates a procedure of the MAC frame which is performed when one of the data which is outputted by the frame dividing unit  11  is the invalid data. 
         [0060]    S 11  to S 13  of  FIG. 3  illustrates the MAC frames under a situation that the divided data is not transmitted on the system where the lower level bits are transmitted in  FIG. 2 , and the invalid data is transmitted in place of the divided data thereon. The frame dividing unit  11  alternately outputs data of the upper level bits and data of lower level bits in the external LAN signal  100  (S 1 ) as the divided LAN signal  111  (S 2 ). The frame dividing unit  11  outputs the invalid data as the divided LAN signal  112  (S 3 ). 
         [0061]    Operations of the generating units  12  and  13  are described. The generating units  12  and  13  in  FIG. 1  only differ in an output destination, i.e. the radio transmitting/receiving unit  15  or the radio transmitting/receiving unit  19  from each other. A configuration and operations of the generating unit  12  is the same as those of the generating unit  13 . The generating unit  12  is, therefore, described and the generating unit  13  is not described. 
         [0062]    The generating unit  12  multiplexes the divided LAN signal  111  received from the frame dividing unit  11  and the multiple alarm signal  142  received from the transmission determining unit  14 . The generating unit  12  inserts a synchronization pattern and an error detection code into the multiplexed signal at constant intervals. The generating unit  12  outputs the transmission signal  121  generated in this way, to the radio transmitting/receiving unit  15 . The synchronization pattern and the error detection code inserted into the transmission signal  121  at constant intervals are detected by the radio-opposed station  30  and used for estimation of transmission quality. 
         [0063]    The generating unit  12  and the generating unit  13  work by the same clock in the same apparatus. Therefore, the timing when the generating unit  12  inserts the synchronization pattern and the error detection code into the divided LAN signal  111  corresponds to the timing when the generating unit  13  inserts the synchronization pattern and the error detection code into the divided LAN signal  112 . 
         [0064]    The radio transmitting unit  16  receives the transmission signal  121  outputted by the generating unit  12 . The radio transmitting unit  16  frequency-converts and modulates the transmission signal  121 . The radio transmitting unit  16  modulates the transmission signal  121  based on the modulation scheme designated by the modulation control signal  181 . The radio transmitting unit  16  transmits the transmission signal  121  which is frequency-converted and modulated to the antenna  30 A of the radio transmitter apparatus  30  opposed thereto as the radio signal  161  through the antenna  10 A. 
         [0065]    The radio transmitting unit  16 A performs the same operation as that of the radio transmitting unit  16 . The radio transmitting unit  16 A modulates and frequency-converts the transmission signal  131 . The radio transmitting unit  16 A modulates the transmission signal  131  on the basis of the modulation scheme designated by the modulation control signal  181 A. The radio transmitting unit  16 A transmits the transmission signal, which is frequency-converted and modulated, to an antenna  30 C of the radio transmitter apparatus  30  through the antenna  10 C as the radio signal  161 . 
         [0066]    The adaptive modulation determining unit  18  transmits and receives information on the modulation scheme to and from the adaptive modulation determining unit  18 A of the radio transmitter apparatus  19  using the modulation scheme synchronization signal  182 . The adaptive modulation determining units  18  and  18 A choose the modulation scheme in accordance with a predetermined procedure so that transmission speeds on the transmission signals  121  and  131  accords with each other. As a result, the data transmitted by the radio transmitter apparatus  15  and the radio transmitter apparatus  19  are received by the radio transmitter apparatus opposed thereto, at the same speed. 
         [0067]    The adaptive modulation determining units  18  and  18 A can recognize both the modulation scheme designated by the modulation control signal  181  and the modulation scheme designated by the modulation control signal  181 A by the modulation scheme synchronization signal  182 . Therefore, if the modulation scheme, in which the transmission speed is the lowest, of the modulation scheme recognized by the adaptive modulation determining units  18  and  18 A in common is chosen, the adaptive modulation determining units  18  and  18 A can choose the same modulation scheme. 
         [0068]    The radio receiving unit  17  receives the radio signal  301  from the radio transmitter apparatus  30  which is the radio-opposed station through the antenna  30 B and  10 B. The radio receiving unit  17  frequency-converts and demodulates the radio signal  301  and outputs it to the analyzing unit  20  as the reception signal  172 . 
         [0069]    The radio receiving unit  17  transmits information on a reception alarm, which occurs due to a failure in the radio transmitter apparatus  15  and/or change of a transmission condition of a transmission path, to the transmission determining unit  14  and the reception determining unit  22  as the reception alarm signal  171 . The information on a reception alarm includes, for example, an alarm indicating that the reception power falls below a predetermined value. However, contents of the reception alarm may be an alarm related to the condition of the transmission path, the reception signal, or reception procedures, and are not limited to the above example. 
         [0070]    In the radio transmitting/receiving unit  19  the configuration of which is the same as the configuration of the radio transmitting/receiving unit  15 , the radio receiving unit  17 A frequency-converts and demodulates the radio signal  302  and outputs the reception signal  193  to the analyzing unit  21 . The radio receiving unit  17 A outputs the radio alarm signal  192  detected by the radio signal  302  to the transmission determining unit  14  and the reception determining unit  22 . 
         [0071]    The analyzing unit  20  receives the reception signal  172  outputted by the radio reception unit  17 . The analyzing unit  20  separates the reception signal  172  into the LAN signal and the alarm signal. The LAN signal is data to be transmitted to the user network  40 . The analyzing unit  20  outputs the separated LAN signal to the frame integrating unit  23  as the integration LAN signal  201 . 
         [0072]    The analyzing unit  20  detects an error of the reception signal  172  using the alarm signal separated from the reception signal  172  and the error detection code which is inserted at the generating unit of the radio-opposed station, and outputs it as the reception alarm signal  202 . If the error occurs and exceeds a predetermined reference value, the analyzing unit  20  generates the alarm information, adds the alarm information to the reception alarm signal  202 , and outputs the signal  202  with the information to the transmission determining  14 . 
         [0073]    The analyzing unit  21  outputs the LAN signal separated from the reception signal  193  to the frame integrating unit  23  as the integration LAN signal  211 , like the analyzing unit  20 . The analyzing unit  21  outputs the alarm signal separated from the reception signal  193  as the reception alarm signal  212 . The analyzing unit  21  adds the alarm information detected in the reception signal  193  to the reception alarm signal  212 , and outputs it to the transmission determining  14 . 
         [0074]    The frame integrating unit  23  receives the integration LAN signal  201  and the integration LAN signal  211 . If both the integration LAN signal  201  and the integration LAN signal  211  are not invalid, the frame integrating unit  23  integrates the two signals to generate the MAC frame. If one of the integration LAN signal  201  and the integration LAN signal  211  is invalid data, the frame integrating unit  23  generates the MAC frame using the other integration LAN signal. As a result, the frame integrating unit  23  restores the MAC frame before division at the time of transmission. The frame integrating unit  23  outputs the integrated MAC frame to the user network  40  as the external output LAN signal  231 . 
         [0075]    A frame integration procedure in the frame integrating unit  23  is described with reference to  FIG. 4 . 
         [0076]      FIG. 4  illustrates a configuration of the frame integrating unit  23 . In the frame integrating unit  23  shown in  FIG. 4 , the integration LAN signal  201  and the integration LAN signal  211  which are transmitted from the analyzing unit  20  and the analyzing unit  21  enter a delay correcting unit  23 _ 1  and a delay correcting unit  23 _ 3 , respectively. 
         [0077]    The delay correcting unit  23 _ 1  and the delay correcting unit  23 _ 3  detect a difference of propagation delay which occurs due to a difference of electrical length of the radio transmitting/receiving units  15  and  19 , wiring in and/or between devices, or the radio transmission path. The delay correcting unit  23 _ 1  and the delay correcting unit  23 _ 3 , specifically, detect the synchronization patterns which are inserted in the generating unit  12  and the generating unit  13 , and compare the detection timing with each other, respectively. As a result, the delay correcting unit  23 _ 1  and the delay correcting unit  23 _ 3  can detect the difference of the propagation delay between the integration LAN signal  201  and the integration LAN signal  211 . 
         [0078]    The delay correcting unit  23 _ 1  and the delay correcting unit  23 _ 3  shift the integration LAN signal  201  and the integration LAN signal  211  each other, respectively, and minimize the difference of the propagation delay between the integration LAN signal  201  and the integration LAN signal  211 . The minimum unit by which the integration LAN signal  201  or the integration LAN signal  211  is shifted is a unit of the clock generated from the signals. 
         [0079]    In the present exemplary embodiment, after the MAC frame is divided by the frame dividing unit, the divided MAC frames are transmitted on the radio transmission paths and demodulated by the different radio receiving units. Therefore, it is highly likely that when the transmission speed of an extension signal  23 _ 21  is equal to that of an extension signal  23 _ 41 , phases of the signals do not accord with each other even if the delay correction of the clock unit is performed in the delay correcting unit  23 _ 1  and the delay correcting unit  23 _ 3 . Dynamic phase fluctuation may occur in transmission data because of fading due to change of the propagation condition of a radio wave. For the reason described above, a phase difference between the pieces of data of the two systems may temporally fluctuate. If the data of the two systems are processed by the clock which is synchronized with one of the data thereof, the other data may not be read out accurately since the phase of the other data deviates from the clock. 
         [0080]    In the first exemplary embodiment, the frame integrating unit  23  performs processing, i.e. bit width extension, with respect to the data in an extending unit  23 _ 2  and an extending unit  23 _ 4 . Procedures on the bit width extension are described below. 
         [0081]    The bit width extension means processing in which width of one bit of the data is extended without changing the data transmission speed by processing data to be processed in parallel. 
         [0082]      FIG. 5  is a diagram explaining the bit width extension processing. 
         [0083]    Suppose that two data lines (hereinafter referred to as “system  1  data”, “system  2  data”) which are synchronized with different clocks are read out at a falling edge of the clock generated from one data line thereof. When the phase difference between the system  1  data and the system  2  data exists, if timing when a clock which is synchronized with the system  1  data reads out the system  2  data accords with a changing point of the system, the data of the system which is not synchronized with the clock may not be correctly read out. 
         [0084]    In  FIG. 5 , (a) is a system  1  clock, (b) is the system  1  data, (c) is a system  2  clock, and (d) is the system  2  data. Since phase adjustment of the data is performed per a clock unit, if the phase difference between the system  1  data (b) and the system  2  data (d) is around half of a cycle of the clock as shown in  FIG. 5 , it is not possible to perform adjustment so that the phase difference between the system  1  data and the system  2  data becomes further small. 
         [0085]      FIGS. 5  (a) to (d) illustrate falling timing of the system  1  division clock (a) (K) and falling timing of the system  2  division clock (c) (L). If the system  1  data (b) and the system  2  data (d) are read out at the falling timing of the system  1  clock (a) which is synchronized with the system  1  data ((K) in  FIG. 5 ), the falling timing accords with the changing point of the system  2  data (d). In this case, the system  2  data (d) may not be read out correctly. 
         [0086]    If the system  1  data (b) and the system  2  data (d) are read out at the falling timing of the system  2  clock (c) ((L) in  FIG. 5 ), the falling timing accords with the changing point of the system  1  data (b). In this case, the system  1  data (b) may not be read out correctly. 
         [0087]    That is, if the phase difference between the system  1  data (b) and the system  2  data (d) is around half of a cycle of the clock, even though the clock of the system  1  or the system  2  is used, both the system  1  data (b) and the system  2  data (d) may not be read out correctly. 
         [0088]    In the bit width extension, n pieces of data (n is a integer equal to or greater than 2) are processed in parallel to increase a data width by n times. By performing the bit width extension processing, even if the phase relationship of the data is as shown by  FIG. 5  (a) to (d), the system  1  data and the system  2  data can be read out by using a clock which is generated from any one of the system  1  data and the system  2  data. 
         [0089]      FIGS. 5  (e) to (h) illustrate a clock and data which are shown when the bit width of the data is extended to be doubled through the bit width extension. 
         [0090]    In  FIG. 5 , a system  1  division clock (e) is a divide-by-2 clock of the system  1  clock, (f) is the system  1  data which is processed in parallel in two, (g) is a divide-by-2 clock of the system  2  clock, and (h) is the system  2  data which is processed in parallel in two.  FIGS. 5  (e) to (h) illustrate falling timing of the system  1  division clock (e) (M) and falling timing of the system  2  divide-by-2 clock (g) (N). 
         [0091]    As shown in  FIG. 5 , the system  1  data (f) and the system  2  data (h) are the data, a bit width of which is extended. In the system  1  data (f) and the system  2  data (h), parallelized data is read out and processed at the same time by a clock. A clock speed in each processing may be a half of the clock without bit width extension processing. The bit width extension operation corresponds to the transition from S 2  to S 4 , and the transition from S 3  to S 5 . 
         [0092]    The system  1  data (f) with the extended bit width and the system  2  data (h) with the extended bit width are parallelized in two, while synchronizing the system  1  data (b) and the system  2  data (d) with the clock (a) and the clock (c), respectively. The phase difference between the system  1  data (f) with the extended bit width and the system  2  data (h) with the extended bit width is equal to the phase difference between the system  1  data (b) and the system  2  data (d) (i.e. a half cycle of the clock (a) or the clock (c)). 
         [0093]    The phase difference between the system  1  data (f) with the extended bit width and the system  2  data (h) with the extended bit width is a half cycle of the clock (a) or the clock (c), and the length of the system  1  data (f) and the system  2  data (h) is doubled by parallelization. 
         [0094]    Here, falling of the system  1  division clock (e) and the system  2  division clock (g), and the data changing points of the system  1  data (f) and the system  2  data (h) are focused. The falling timing of the system  1  clock (e) and the system  2  clock (g) ((M), (N) in  FIG. 5 ) are located at positions which are different from the changing points of the data (f) and the data (h). Consequently, the data (f) and the data (h) can be read out correctly using any one of the system  1  clock (e) and the clock (g). 
         [0095]    In the bit width extension operation, the data is parallelized to extend the data width. By extending the data width, the timing of reading out the clocks of systems  1  and  2  ((M), (N) in  FIG. 5 ) can be located at the positions other than the changing points of the data. The signals with different phases can be read out using any clock of the systems  1  and  2 . In the first exemplary embodiment, the integration LAN signal  201  and the integration LAN signal  211  correspond to the system  1  data (or the system  2  data) and the system  2  data (or the system  1  data), respectively. 
         [0096]    In descriptions above, the parallel number of the data is two, and the clock is divided by two. If the parallel number of the data (i.e. division number of the clock) is equal to or greater than two, the similar effect is possible. 
         [0097]    In  FIG. 4 , the extending unit  23 _ 2  and the extending unit  23 _ 4  output the integration LAN signal  201  and the integration LAN signal  211 , bit width extension of which is performed, to a retiming unit  23 _ 5  as the extension signal  23 _ 21  and the extension signal  23 _ 41 , respectively. 
         [0098]    The retiming unit  23 _ 5  chooses a system which is not invalid data from one of the extension signal  23 _ 21  and the extension signal  23 _ 41 . The retiming unit  23 _ 5  compares a phase of a clock of the chosen signal with a phase of a retiming clock  23 _ 61  outputted by a PLL unit  23 _ 6 , and outputs a frequency controlling signal  23 _ 51  generated based on the comparison result to the PLL unit to control the PLL. As a result, the retiming unit  23 _ 5  can synchronize the retiming clock  23 _ 61  with the chosen clock. 
         [0099]    The extension signal  23 _ 21  and the extension signal  23 _ 41  have the bit width extension processing in the extending unit  23 _ 2  and the extending unit  23 _ 4 , respectively. Based on the operation described using  FIG. 5 , the retiming unit  23 _ 5  performs retiming of the data of both the extension signal  23 _ 21  and the extension signal  23 _ 41  using the retiming clock  23 _ 61  regenerated from one of the data. 
         [0100]    The retiming unit  23 _ 5  combines the extension signal  23 _ 21  and the extension signal  23 _ 41  on which retiming is performed so that BYTE data, in which the extension signal  23 _ 21  is arranged in an upper bit string and the extension signal  23 _ 41  is arranged in a lower bit string, is configured. This corresponds to the transition from S 4  to S 6  and the transition from S 5  to S 6 , in  FIG. 2 . 
         [0101]    The configured BYTE data is outputted to a shortening unit  23 _ 7  as a retiming signal  23 _ 52  (S 6  in  FIG. 2 ). 
         [0102]    In descriptions above, the BYTE data is configured using the extension signal  23 _ 21  and the extension signal  23 _ 41  if the both signals are normal data. If one of the extension signals is invalid data, the retiming unit  23 _ 5  configures the BYTE data only using the normal extension signal. This corresponds to the transition from S 14  to S 16 . 
         [0103]    The shortening unit  23 _ 7  receives the retiming signal  23 _ 52  outputted by the retiming unit  23 _ 5 . The shortening unit  23 _ 7  performs operations opposite to the bit width extension which is performed by the extending unit  23 _ 2  and the extending unit  23 _ 4  (transition from S 6  to S 7  in  FIG. 3 ) and changes the data width into the original width. The shortening unit  23 _ 7  outputs the data with the original bit width to the user network  40  in  FIG. 1  as the external output LAN signal  231 . 
         [0104]    The retiming unit  23 _ 5  chooses one of the extension signal  23 _ 21  and the extension signal  23 _ 41  as a clock source, and outputs it to the PLL unit  23 _ 6 . When the retiming unit  23 _ 5  uses by changing the clock source with a selector by itself without using a PLL circuit, instantaneous interruption of the clock or jump of a clock phase may occur. The instantaneous interruption of the clock or the jump of a clock phase causes occurrence of a signal error. In the first exemplary embodiment, therefore, the retiming unit  23 _ 5  works according to the clock outputted by the PLL unit  23 _ 6 . Thereby, probability, that the signal error occurs, in the retiming unit  23 _ 5 , due to the instantaneous interruption of the clock or the jump of a clock phase at the time of changing the clock source, may be reduced. 
         [0105]    The delay correction method and the retiming method in the frame integrating unit  23  which are described above are known as an uninterrupted switching method in a digital radio transmission field. Therefore, detailed descriptions are omitted. 
         [0106]    In the first exemplary embodiment, the transmission determining unit  14  in  FIG. 1  outputs an alarm state which the radio transmitter apparatus  10  holds to the generating unit  12  and the generating unit  13  as the multiple alarm signals  142  and  143 , respectively. An alarm included in the alarm state which is outputted from the transmission determining unit  14  includes a reception alarm due to a device failure of the radio transmitting/receiving units  15  and  19  and/or environment change in the radio transmission path, a signal error alarm on the reception signal, and a detection alarm on the invalid data. 
         [0107]    The reception alarm due to a device failure of the radio transmitting/receiving units and/or environment change in the radio transmission path is detected in the radio alarm signal  171  and the radio alarm signal  192 . The signal error alarm on the reception signal and the detection alarm on the invalid data are detected in the reception alarm signal  202  and the reception alarm signal  212 . 
         [0108]    When detecting the reception alarm detected by the radio transmitter apparatus  30  or the signal error alarm of the reception signal in the reception alarm signal  202  or the reception alarm signal  212 , the transmission determining unit  14  determines that a signal of the system in which these alarms are detected is invalid data. Determining that a signal of the system in which these alarms are detected is invalid data, the transmission determining unit  14  outputs the division control signal  141  instructing to determine that the signal of the system is the invalid data to the frame dividing unit  11 . 
         [0109]    The reception determining unit  22  receives the radio alarm signal  171  and the radio alarm signal  192 . The reception determining unit  22  detects a device failure alarm of the radio transmitting/receiving unit and/or a reception power reduction alarm due to the environment change on the radio transmission path in these radio alarm signals. Detecting the device failure alarm or the reception power reduction alarm, the reception determining unit  22  outputs a control signal determining the data of the system in which the alarm occurs is the invalid data as the integration control signals  221  and  222 . 
         [0110]    A first effect of the radio transmission system of the first exemplary embodiment described above is that it is possible to suppress complexity of configuration and price increase in the transmitter apparatus with the adaptive modulation function. In the radio transmission system of the first exemplary embodiment, the radio transmitter apparatus includes the adaptive modulation function. In the radio transmitter apparatus, the radio transmitting units of the two systems modulate data using the same modulation scheme. That is, in the radio transmission system of the first exemplary embodiment, the transmitting apparatus on the transmission side can choose a suitable modulation scheme depending on conditions of a plurality of the transmission paths and the transmitting apparatus on the reception side can receive divided data at the same modulation speed. Accordingly the transmitting apparatus on the reception side does not require memory for absorbing a difference of transmission speeds between the respective reception data and can suppress complexity of the configuration and price increase in the transmitter apparatus with the adaptive modulation function. 
         [0111]    A second effect of the radio transmission system of the first exemplary embodiment is that it is possible to easily increase a radio transmission capacity in the radio transmitting apparatus for transmitting the MAC frame of the LAN signal from the user network to a single opposed station wirelessly. 
         [0112]    Procedures obtaining the effects are as follows. The radio transmitter apparatus of the first exemplary embodiment divides the MAC frame into two parts in its own apparatus and inserts the synchronization pattern at a constant period. The radio transmitter apparatus of the first exemplary embodiment transmits the divided data from the radio transmitting/receiving units of the two systems arranged in its own apparatus to the radio-opposed stations. The opposed radio transmitter apparatus detects the propagation delay difference which occurs due to the electric length difference in the radio transmitting/receiving unit, the cable, the radio transmission path, and the like, by using the synchronization pattern in the reception signal. The opposed radio transmitter apparatus adjusts the phases of both of the MAC frames to absorb the propagation delay difference. After absorbing the propagation delay difference, the radio transmitter apparatus integrates the MAC frames which are divided in two parts into a single MAC frame. As a result, the radio transmission system of the first exemplary embodiment may include the transmission capacity which is twice as much as that of MAC frame transmission on the single radio transmission path. 
         [0113]    A third effect of the first exemplary embodiment is that even though it is impossible to transmit data because of a device failure of one of the radio transmitting/receiving units and/or degradation of a propagation condition of the radio transmission path, signal transmission may be performed using the other normal system. 
         [0114]    That is because the generating unit of the radio transmitter apparatus inserts the signal error detecting code to perform the radio transmission. The radio transmitter apparatus detects abnormality on the radio transmission path based on the detection result of the reception power reduction alarm in the radio transmitting/receiving unit and the result of signal error detection in the analyzing unit. When detecting abnormality on the radio transmission path, the radio transmitter apparatus informs the radio-opposed station of the abnormal condition of the system on which abnormality is detected. In the radio transmitter apparatus, if the analyzing unit detects the information on the abnormal condition from the radio-opposed station, the frame dividing unit stops dividing the MAC frame. The radio transmitter apparatus transmits the invalid data to the system in which the abnormal condition occurs, and the MAC frame data only to the system which normally works. In the radio transmitter apparatus opposed thereto, the frame integrating unit integrates two divided signals to form the MAC frame if the integration LAN signal outputted by the analyzing unit is normal. If one of received divided data is the invalid data, the radio transmitter apparatus restores the MAC frame using only the data which is received from the normal system. As a result, in the radio transmission system of the first exemplary embodiment, even if abnormality occurs in one system, signal transmission may continue in the other normal system. 
         [0115]    A fourth effect of the first exemplary embodiment is that it is possible to avoid occurrence of order replacement of the MAC frame which occurs when the MAC frames having random length are delivered and transmitted to a plurality of the transmission paths. 
         [0116]    That is because in the first exemplary embodiment, the radio transmitter apparatus does not allocate the MAC frames to respective transmission path in a unit of the MAC frame, but divide inputted MAC frame into two parts and transmits them without replacing the order of the MAC frames. As a result, the radio transmitter apparatus opposed thereto integrates the data received from the radio transmission path in order of reception to restore the MAC frame of the LAN signal. The radio transmission system of the first exemplary embodiment can avoid occurrence of order replacement of the MAC frame. 
         [0117]    In the first exemplary embodiment, the adaptive modulation determining unit  18  chooses the modulation scheme on the basis of the magnitude relationship between the radio reception power in the opposed radio transmitter apparatus  30  and a predetermined threshold value. However, the adaptive modulation determining unit  18  may choose the modulation scheme based on other information. The opposed radio transmitter apparatus  30  may transmit, for example, CNR (Carrier to Noise Ratio, i.e. Carrier wave power to Noise power Ratio) of the signal received from the radio transmitter apparatus  10 , and/or an error rate of the reception signal to the radio transmitter apparatus  10 . The adaptive modulation determining unit  18  of the radio transmitter apparatus  10  may choose the modulation scheme of the radio transmitting unit  16  or the radio transmitting unit  16 A based on the CNR or the error rate received from the radio transmitter apparatus  30 . 
         [0118]    In the first exemplary embodiment, the adaptive modulation determining units  18  and  18 A of the radio transmitter apparatus  10  choose the modulation scheme so that the transmission speeds of the transmission signals  121  and  131  accord with each other. However, if a difference in the transmission speeds between the transmission signals  121  and  131  is small, the problem of complexity of the configuration of the radio transmitter apparatus  30  for receiving the transmission signals  121  and  131  and price increase thereof may not occur. For example, if the radio transmitter apparatus on the reception side does not require memory with a large amount of capacity even though the transmission signals  121  and  131  differ in the transmission speed from each other, the effect of the invention, in which it is possible to suppress complexity of the configuration of the radio transmitter apparatus and price increase thereof, is not lost, 
         [0119]    When the radio transmitter apparatus on the reception side allows some degree of difference of the transmission speeds, the adaptive modulation determining units  18  and  18 A may not necessarily decide the modulation scheme having the same transmission speed. 
         [0120]    For example, the adaptive modulation determining units  18  and  18 A may decide the modulation scheme so that the difference in the transmission speeds between the modulation schemes decided in the unit  18  and  18 A falls within a predetermined range. 
         [0121]    The adaptive modulation determining units  18  and  18 A may decide the range of the difference in the transmission speeds between the modulation schemes to be decided based on the allowable range of the transmission speed for the receiver apparatus. 
       Second Exemplary Embodiment 
       [0122]    In the first exemplary embodiment, the radio transmitter apparatus include the configuration in which the inputted MAC frame is divided into two parts and transmitted. The MAC frame is not necessarily divided into two parts. 
         [0123]      FIG. 6  is a diagram illustrating a radio transmitter apparatus of a second exemplary embodiment of the invention. A radio transmitter apparatus  10 _ 1  shown in  FIG. 6  includes a function for dividing the MAC frame into four parts and transmitting them to an opposed radio transmitter apparatus  30 _ 1 . In  FIG. 6 , an operation of each part in the radio transmitter apparatus  10 _ 1  is the same as that of the part with the same name in the radio transmitter apparatus  10 . In  FIG. 6 , therefore, description on detailed connection of respective parts and the inside of the radio transmitter apparatus is omitted. 
         [0124]    In  FIG. 6 , the radio transmitter apparatus  10 _ 1  faces the radio transmitter apparatus  30 _ 1  and the apparatuses transmit the MAC frame to each other. The radio transmitter apparatus  10 _ 1  divides the external LAN signal  100  which is inputted from the user network  40  and transmits them to the radio transmitter apparatus  30 _ 1  as a radio signal. The radio transmitter apparatus  30 _ 1  restores data from the radio signal received from the radio transmitter apparatus  10 _ 1  and outputs it to the user network  50  as the external output LAN signal  501 . 
         [0125]    The radio transmitter apparatus  30 _ 1  divides the external LAN signal  502  which is inputted from the user network  50  and transmits them to the radio transmitter apparatus  10 _ 1  as a radio signal. The radio transmitter apparatus  10 _ 1  restores data from the radio signal received from the radio transmitter apparatus  30 _ 1  and outputs it to the user network  40  as the external output LAN signal  231 . 
         [0126]    The radio transmission apparatus shown in  FIG. 6  divides the MAC frame into four parts in the frame dividing unit  11  and transmits them. For this, the apparatus includes four generating units  12 ,  13 ,  12 _ 1 , and  13 _ 1 , four analyzing units  20 ,  21 ,  20 _ 1 , and  21 _ 1 , and four radio transmitting/receiving units  15 ,  19 ,  15 _ 1 , and  19 _ 1 . Each radio transmitting/receiving unit includes the adaptive modulation function. The four radio transmitting/receiving units  15 ,  19 ,  15 _ 1 , and  19 _ 1  inform of information of the modulation scheme the radio transmitter apparatus each other, and operate so that all of the radio transmitting/receiving units use the modulation scheme with the same transmission speed. 
         [0127]    A configuration and operations of each part of the radio transmitter apparatus  10 A are similar to those of the radio transmitter apparatus  10  described in the first exemplary embodiment. Therefore, detailed descriptions on the parts are omitted. 
         [0128]    The radio transmitting/receiving unit  15  modulates the MAC frame which is outputted from the generating unit  12  and divided, and outputs them as the radio signal  161 . The radio signal  161  is transmitted to the radio transmitter apparatus  30 _ 1  through the antennas  10 A and  30 A. 
         [0129]    Similarly, the generating units  13 ,  12 _ 1  and  13 _ 1  output divided frame to the radio transmitting/receiving units  19 ,  15 _ 1  and  19 _ 1 , respectively. The radio transmitting/receiving units  19 ,  15 _ 1  and  19 _ 1  modulate inputted signals and output the radio signals  191 ,  101  and  102 , respectively. The radio signals  191 ,  101  and  102  are transmitted to the radio transmitter apparatus  30 _ 1  through the antennas  10 C,  10 E and  10 G, and the antennas  30 C,  30 E and  30 G, respectively. 
         [0130]    The radio transmitting/receiving unit  15  receives the radio signal  301  which is transmitted by the radio transmitter apparatus  30 _ 1  through the antennas  30 B and  10 B. The radio transmitting/receiving unit  15  demodulates the radio signal  301  and outputs it to the analyzing unit  20 . The analyzing unit  20  separates the divided MAC frame  23  from the demodulated signal, and outputs them to the frame integrating unit  23 . The frame integrating unit  23  integrates the divided frames which are received from the analyzing units  20 ,  21 ,  20 _ 1  and  21 _ 1 , and outputs it to the user network  40  as the external output LAN signal  231 . 
         [0131]    Similarly, the radio transmitting/receiving units  19 ,  15 _ 1  and  19 _ 1  receive the radio signals  302 ,  303  and  304  which are transmitted by the radio transmitter apparatus  30 _ 1  through the antennas  30 D,  30 F and  30 H, and  10 D,  10 F and  10 H, respectively. The radio transmitting/receiving units  19 ,  15 _ 1  and  19 _ 1  demodulate these radio signals and output them to the analyzing units  21 ,  20 _ 1  and  21 _ 1 , respectively. Each analyzing unit separates the MAC frame which is divided from the demodulated signal, and outputs it to the frame integrating unit  23 . 
         [0132]    Transmitting the MAC frame after dividing it in four parts, the radio transmission system of the second exemplary embodiment can transmit the MAC frame at a high transmission speed, compared with the first exemplary embodiment, in addition to the effect of the first exemplary embodiment. 
         [0133]    In the first and second exemplary embodiment, the invention is explained with the case of its application to the radio transmission system with the radio transmitter apparatus. However, the invention is not limited to radio transmission. The invention is applicable to, for example, a wired transmitter apparatus with a coaxial cable or an optical fiber. 
         [0134]    The scheme of the radio transmission targeted by the invention is not limited a scheme using a radio wave. The invention is applicable to, for example, a transmitter apparatus using an optical space transmission scheme. 
       Third Exemplary Embodiment 
       [0135]      FIG. 7  is a diagram illustrating a configuration of a transmitter apparatus of a third exemplary embodiment of the invention. In  FIG. 7 , a transmitter apparatus  700  includes a dividing unit  701 , N pieces of transmitting units  702 _ 1  to  702 _N,N pieces of transmitting units  702 _ 1  to  702 _N, and a modulation scheme deciding unit  703 . 
         [0136]    The dividing unit  701  divides inputted data into a plurality of pierces. The transmitting units  702 _ 1  to  702 _N transmit divided data on transmission paths. The modulation scheme deciding unit  703  decides the modulation scheme, used by transmitting means, of schemes associated with conditions of the transmission paths so that the difference in the transmission speeds between a plurality of pieces of data transmitted by the plurality of transmitting means falls within a predetermined range. 
         [0137]    The transmitter apparatus of  FIG. 7  transmits data divided by the dividing unit  701  on the transmission paths using the plurality of transmitting units  702 _ 1  to  702 _N. The modulation schemes used by the transmitting units are associated with conditions of the transmission paths where the data is transmitted. The modulation scheme deciding unit  703  decides the modulation schemes by which the transmitting unit  702 _ 1  to  702 _N modulate the data from among these modulation schemes so that the difference in the transmission speeds between a plurality of pieces of data transmitted by the plurality of transmitting means falls within a predetermined range. 
         [0138]    When the modulation scheme deciding unit  703  decides the modulation schemes used by the transmitting units  702 _ 1  to  702 _N based on the modulation schemes associated with the transmitting units  702 _ 1  to  702 _N, complexity of a configuration of the transmitter apparatus on the reception side which is not shown, and price increase thereof are avoided. 
         [0139]    If the modulation scheme deciding unit  703  restricts the difference in the transmission speeds between the modulation schemes simultaneously used by the transmitting units  702 _ 1  to  702 _N, the range of the speeds of the modulation scheme to be processed at the same time and data are limited in the transmitter apparatus on the reception side. When the speeds of the modulation schemes falls within a predetermined range, the transmitter apparatus does not require memory with a large capacity for absorbing the difference in the transmission speeds between respective pieces of reception data. 
         [0140]    Consequently, the transmitter apparatus of the third exemplary embodiment enable to suppress complexity of the transmitter apparatus and price increase thereof, if the transmitter apparatus with the adaptive modulation function divides data and transmits them. 
         [0141]    While having described an invention of the present application referring to the embodiments 1 to 3, the invention of the present application is not limited to the above mentioned embodiments 1 to 3. It is to be understood that to the configurations and details of the invention of the present application, various changes can be made within the scope of the invention of the present application by those skilled in the art. 
         [0142]    This application is based upon and claims the benefit of priority from Japanese patent application No. 2010-058982 filed on Mar. 16, 2010, the disclosure of which is incorporated herein in its entirety by reference. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10 ,  10 _ 1 ,  30 ,  30 _ 1  Radio Transmitter Apparatus 
           40 ,  50  User Network 
           11  Frame Dividing Unit 
           12 ,  13 ,  12 _ 1 ,  13 _ 1  Generating Unit 
           20 ,  21 ,  20 _ 1 ,  21 _ 1  Analyzing Unit 
           14  Transmission Determining Unit 
           15 ,  15 _ 1 ,  19 ,  19 _ 1  Radio Transmitting/Receiving Unit 
           16 ,  16 A Radio Transmitting Unit 
           17 ,  17 A Radio Receiving Unit 
           18 ,  18 A Adaptive Modulation Deciding Unit 
           22  Reception Determining Unit 
           23  Frame Integrating Unit 
           23 _ 1 ,  23 _ 3  Delay Correcting Unit 
           23 _ 2 ,  23 _ 4  Extending Unit 
           23 _ 5  Retiming Unit 
           23 _ 6  PLL Unit 
           23 _ 7  Shortening Unit 
           10   a  to  10   h ,  30   a  to  30   h  Antenna 
           700  Transmitter Apparatus 
           701  Dividing Unit 
           702 _ 1  to  702 _N Transmitting Unit 
           703  Modulation Scheme Deciding Unit 
           100 ,  501  External LAN Signal 
           111 ,  112  Divided LAN Signal 
           121 ,  131  Transmission Signal 
           101 ,  102 ,  161 ,  191 ,  301  to  304  Radio Signal 
           181 ,  181 A Modulation Control Signal 
           141  Division Control Signal 
           142 ,  143  Multiple Alarm Signal 
           171 ,  192  Radio Alarm Signal
         172 ,  193  Reception Signal     201 ,  211  Integration LAN Signal     202 ,  212  Reception Alarm Signal     221 ,  222  Integration Control Signal   
     
           23 _ 21 ,  23 _ 41  Extension Signal 
           23 _ 51  Frequency Control Signal 
           23 _ 52  Retiming Signal 
           23 _ 61  Retiming Clock 
           231 ,  502  External Output LAN Signal