Abstract:
A mobile communication terminal apparatus includes an antenna unit configured to select antenna radiation characteristics, and receives a first signal transmitted from transmitting station according to the selected antenna radiation characteristic, a transmitter which transmits a detection signal to other terminals, the designation signal generated from the first signal, for designating the antenna radiation characteristics, a first receiver which receives another designation signal from the other terminal apparatuses, a controller which controls the antenna unit to obtain the antenna radiation characteristics designated by the another designation signal, a second receiver which receives second signal that is transferred from the other terminal apparatuses and is obtained by the antenna radiation characteristics selected by the other terminal apparatuses, and a processor which processes the second signal and the detection signal in a diversity scheme.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2003-003289, filed Jan. 9, 2003, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a mobile communication terminal apparatus and mobile communication method capable of diversity reception in cooperation with the other terminal.  
           [0004]    2. Description of the Related Art  
           [0005]    A technique of allowing a plurality of mobile stations receiving a signal transmitted from a base station of a mobile communication system such as a cellular mobile communication system to cooperate with each other to perform diversity reception, has been known (see, for example, Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2001-189971).  
           [0006]    The technique of Document 1 allows the mobile stations to directly transfer signals which they receive from the base station, respectively, to each other via an ad hoc network. Each of the mobile stations performs diversity reception by synthesizing the signals received by the mobile stations.  
           [0007]    According to the technique of Document 1, a plurality of antennas can be greatly spaced from each other to obtain a signal used for the diversity reception, and generally a great diversity gain can be obtained.  
           [0008]    Incidentally, if the mobile station is capable of changing the antenna radiation characteristic, the antenna radiation characteristic is selected originally by each mobile station. For this reason, the diversity effect may not be sufficiently achieved in accordance with the state of the antenna radiation characteristic of each of a plurality of antennas used to obtain the signal utilized for the diversity reception.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The present invention has been accomplished in consideration of such a circumstance, and the object of the present invention is to effectively perform the diversity reception.  
           [0010]    According to an aspect of the present invention, there is provided a mobile communication terminal apparatus to communicate with a transmitting station together with other terminal apparatuses, comprising: an antenna unit configured to select at least one of a plurality of antenna radiation characteristics different from one another, and receive a signal transmitted from the transmitting station according to the selected one of the antenna radiation characteristics, to generate a first signal; a transmitter which transmits a detection signal to the other terminal apparatuses, the designation signal generated from the first signal, for designating the antenna radiation characteristics; a first receiver which receives another designation signal from the other terminal apparatuses; a controller which controls the antenna unit to obtain the antenna radiation characteristic designated by the another designation signal; a second receiver which receives a second signal that is transferred from one of the other terminal apparatuses and is obtained by the antenna radiation characteristics selected by the other terminal apparatuses; and  
           [0011]    a processor which processes the second signal and the detection signal in a diversity scheme.  
           [0012]    According to another aspect of the present invention, there is provided a mobile communication terminal apparatus to communicate with a transmitting station together with other terminal apparatuses, comprising: an antenna unit configured to select at least one of a plurality of antenna radiation characteristics different from one another, and receive a signal transmitted from the transmitting station according to the selected one of the antenna radiation characteristics, to generate a first signal; a wave detector which detects the first signal to output a detection signal; a receiver which receives a signal which is transmitted from the other terminal apparatuses and represents the detection signal, to generate a reference signal; an operator which operates a correlation value between the reference signal, and the detection signal of the selected antenna radiation characteristic at the time of selecting the antenna radiation characteristic; a determination device configured to determine first antenna radiation characteristics of the other terminal apparatuses and second antenna radiation characteristics to be set at the antenna unit, based on the correlation value; a first transmitter which transmits a designation signal for designating the first antenna radiation characteristics, to the other terminal apparatuses; a controller which controls the antenna unit to obtain the second antenna radiation characteristics; and a second transmitter which transmits the detection signal to the other terminal apparatuses, when the antenna unit has the second antenna radiation characteristics.  
           [0013]    According to another aspect of the present invention, there is provided a mobile communication method comprising: receiving a signal transmitted from a transmitting station by an antenna unit that selects at least one of a plurality of antenna radiation characteristics different from each other, to obtain a first signal; detecting the first signal to output a detection signal; transmitting the detection signal to other terminals as a designation signal to designate the antenna radiation characteristic at the time of selecting the antenna radiation characteristics; receiving another designation signal from the other terminal apparatuses; setting the antenna unit at the antenna radiation characteristics designated by the another designation signal; receiving a second signal that is transferred from the other terminal apparatuses and is obtained by the antenna radiation characteristics selected by the other terminal apparatuses; and processing the second signal and the detection signal in a diversity scheme.  
           [0014]    According to yet another aspect of the present invention, there is provided a mobile communication method comprising: receiving a first signal transmitted from a transmitting station by an antenna unit that selects at least one of a plurality of antenna radiation characteristics different from one another; detecting the first signal to output a detection signal; receiving a reference signal which is transmitted from other terminals and represents the detection signal; operating a correlation value between the reference signal, and the detection signal of the selected antenna radiation characteristics at the time of changing the antenna radiation characteristic; determining first antenna radiation characteristics of the other terminal apparatuses and second antenna radiation characteristics to be set at the antenna unit, based on the correlation value; transmitting a designation signal to designate the first antenna radiation characteristics, to the other terminal apparatuses; controlling the antenna unit to obtain the second antenna radiation characteristics; and transmitting the detection signal to the other terminal apparatuses, when the antenna unit has the second antenna radiation characteristics.  
           [0015]    Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and *obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0016]    [0016]FIG. 1 is a block diagram showing a structure of a mobile communication system according to a embodiment of the present invention;  
         [0017]    [0017]FIG. 2 is a block diagram showing a structure of the controlled terminal of the first embodiment;  
         [0018]    [0018]FIG. 3 is a block diagram showing a structure of the receiver  3  of the selection scheme;  
         [0019]    [0019]FIG. 4 is a block diagram showing a structure of the receiver  3  of the synthesizing scheme;  
         [0020]    [0020]FIG. 5 is a block diagram showing a structure the controlling terminal according to the first embodiment;  
         [0021]    [0021]FIG. 6 is a flowchart showing a procedure of the controller  6  of the controlled terminal and the processing of the controller  13  of the controlling terminal, to select the antenna  1 ;  
         [0022]    [0022]FIG. 7 is a diagram showing a table of sharing of the correlation coefficient calculation;  
         [0023]    [0023]FIG. 8 is a diagram showing another table of sharing of the correlation coefficient calculation;  
         [0024]    [0024]FIG. 9 is a block diagram showing a structure of the controlled terminal according to the third embodiment;  
         [0025]    [0025]FIG. 10 is a block diagram showing a structure of a controlled terminal according to the fourth embodiment; and  
         [0026]    [0026]FIG. 11 is a block diagram showing a structure of a controlled terminal according to the fifth embodiment. 
     
    
       [0027]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    Embodiments of the present invention will be described below with reference to the drawings.  
         [0029]    [0029]FIG. 1 shows a summary of a mobile communication system to which the present invention is applied.  
         [0030]    In FIG. 1, a base station BS belongs to a certain mobile communication network. The base station BS forms a service area SA. The base station BS makes radio communication with mobile communication terminals MT 1 , MT 2  and MT 3  that are positioned in the range of the service area SA. Thus, the mobile communication terminals MT 1 , MT 2  and MT 3  can make communication through a network utilizing the base station BS. Each of the mobile communication terminals MT 1 , MT 2  and MT 3  has a function of making communication through the ad hoc network and they can make communication directly with each other without the base station BS.  
         [0031]    A wireless LAN in accordance with IEEE  802 . 11  or the like is, for example, expected as the network to which the base station BS belongs and Bluetooth (R) is, for example, expected as the radio communication scheme implementing the ad hoc network.  
         [0032]    (First Embodiment)  
         [0033]    A first embodiment will be described below.  
         [0034]    The first embodiment comprises two types of the mobile communication terminals MT 1 , MT 2  and MT 3 , i.e. a controlled type and a controlling type. In the following descriptions, the mobile communication terminal MT 1  of the controlled type is called a controlled terminal and the mobile communication terminal MT 2  of the controlling type is called a controlling terminal.  
         [0035]    [0035]FIG. 2 is a block diagram showing a structure of the controlled terminal of the first embodiment.  
         [0036]    The controlled terminal comprises a plurality of antennas  1 , a switch  2 , a receiver  3 , a transceiver  4 , an antenna  5  and a controller  6 .  
         [0037]    The antennas  1  receive high-frequency signals transmitted from the base station BS, respectively. The switch  2  selects one of the high-frequency signals that the antennas  1  output respectively, and outputs the selected high-frequency signal to the receiver  3 . The antenna  1  selected by the switch  2  is instructed by the controller  6 .  
         [0038]    The receiver  3  detects the selected high-frequency signal. The receiver  3  has two modes, i.e. a memory mode and a transfer mode. The receiver  3  of the memory mode temporarily stores a detected signal (hereinafter called a detection signal) Sr 1  in a memory which is built in the receiver  3  and outputs the signal to the transceiver  4  under the control of the controller  6 . The receiver  3  of the transfer mode immediately outputs the detection signal Sr 1  to the transceiver  4 . The receiver  3  processes the detection signal Sr 1  and a transfer signal Sr 2  that is output from the transceiver  4 , in order to extract a speech signal or an image signal of the base band. The signal transmitted from the base station BS includes a speech signal, an image signal, an information signal such as text data and the like.  
         [0039]    The transceiver  4  makes communication with the other mobile communication terminals MT 2  and MT 3  (hereinafter called the other terminals) through the ad hoc network. The transceiver  4  outputs the detection signal Sr 1  to the ad hoc network to transmit the signal to the other terminals as a transfer signal. The signal from the ad hoc network received by the antenna  5  is input to the transceiver  4 . The transceiver  4  separates the transfer signal Sr 2  from the other terminals and a control signal Sc from the extracted signal. The transceiver  4  outputs the transfer signal Sr 2  to the receiver  3  and the control signal Sc to the controller  6 . The channel extracted by the transceiver  4  is instructed by the controller  6 .  
         [0040]    The controller  6  is formed by utilizing, for example, a microprocessor. The controller  6  performs various kinds of processings to totally control the controlled terminal. The controller  6  has a control function to be described later with reference to FIG. 6 and a function of controlling selecting the antenna  1  in response to the instruction from the controlling terminal, in addition to functions of well-known processings to implement various kinds of functions that the mobile communication terminal has.  
         [0041]    Incidentally, the structure of the receiver  3  is varied according to the selection scheme or the synthesizing scheme of the reception diversity.  
         [0042]    [0042]FIG. 3 is a block diagram showing a structure of the receiver  3  of the selection scheme.  
         [0043]    The receiver  3  comprises a wave detector  3   a,  an evaluation circuit  3   b,  a storing circuit  3   c,  a control circuit  3   d,  a processing circuit  3   e  and an outputting circuit  3   f.    
         [0044]    The wave detector  3   a  performs the above-described signal detection and outputs the detection signal Sr 1 .  
         [0045]    The detection signal Sr 1  and the transfer signal Sr 2  are input to the evaluation circuit  3   b  and the storing circuit  3   c,  respectively. The evaluation circuit  3   b  evaluates the quality of the detection signal Sr 1  and the quality of the transfer signal Sr 2 , and outputs evaluation information representing a result of the evaluation to the storing circuit  3   c.  For example, the evaluation circuit  3   b  handles a value obtained by adding values of received field intensity of the detection signal Sr 1  or the transfer signal Sr 2  for a certain period as the evaluation information of each of the signals.  
         [0046]    The storing circuit  3   c  stores the detection signal Sr 1  and the transfer signal Sr 2 , and also stores the evaluation information of the detection signal Sr 1  and the evaluation information of the transfer signal Sr 2 . If the evaluation information is newly output from the evaluation circuit  3   b,  the storing circuit  3   c  stores the new evaluation information and outputs a signal indicating a fact that the evaluation is newly completed to the control circuit  3   d.    
         [0047]    The control circuit  3   d  compares the evaluation results of the detection signal Sr 1  and the transfer signal Sr 2  stored in the storing circuit  3   c,  and selects the detection signal Sr 1  or the transfer signal Sr 2  having better quality. The control circuit  3   d  controls the storing circuit  3   c  to output the selected signal to the processing circuit  3   e.    
         [0048]    The processing circuit  3   e  converts the signal which is input from the storing circuit  3   c  into the initial information data. The outputting circuit  3   f  outputs the information data which is input from the processing circuit  3   e  as a speech signal or an image signal.  
         [0049]    [0049]FIG. 4 is a block diagram showing a structure of the receiver  3  of the synthesizing scheme.  
         [0050]    In the drawing, like portions as shown in FIG. 3 are denoted by like or similar reference numerals and their detailed explanations are omitted here.  
         [0051]    The receiver  3  comprises the wave detector  3   a,  the processing circuit  3   e,  the outputting circuit  3   f,  a storing circuit  3   g,  a control circuit  3   h,  and a synthesizer  3   i.    
         [0052]    The detection signal Sr 1  and the transfer signal Sr 2  are input to the storing circuit  3   g.  If the detection signal Sr 1  is newly transmitted from the receiver  3 , the storing circuit  3   g  notifies the control circuit  3   h  of this transmission and stores the detection signal Sr 1 . If the transfer signal Sr 2  is transmitted from the transceiver  4 , the storing circuit  3   g  notifies the control circuit  3   h  of this transmission and stores the transfer signal Sr 2 .  
         [0053]    The control circuit  3   h  controls storing circuit  3   g  and the synthesizer  3   i  to synthesize and add the detection signal Sr 1  and the transfer signal Sr 2 . As for the processing method of the synthesizer  3   i,  for example, a well-known diversity synthesizing method can be applied. An output signal of the synthesizer  3   i  is input to the processing circuit  3   e.  Even in this structure, a signal based on the initial information data can be obtained from the outputting circuit  3   f  similarly to FIG. 3.  
         [0054]    [0054]FIG. 5 is a block diagram showing a structure of the controlling terminal according to the second embodiment. In the drawing, like portions as shown in FIG. 2 are denoted by like or similar reference numerals and their detailed explanations are omitted here.  
         [0055]    The controlling terminal comprises a plurality of antennas  1 , the switch  2 , the receiver  3 , the antenna  5 , a transceiver  11 , a comparing circuit  12 , and a controller  13 . In other words, the controlling terminal comprises the transceiver  11  and the controller  13  instead of the transceiver  4  and the controller  6  of the controlled terminal, and further comprises the comparing circuit  12 .  
         [0056]    The transceiver  11  has substantially the same function as the transceiver  4 . However, the transceiver  11  also has a function of transmitting the control signal Sc that is output from the comparing circuit  12  to the other terminals. In addition, the transceiver  11  outputs a reference signal Sr 3  that the transceiver  11  receives to the comparing circuit  12 .  
         [0057]    The comparing circuit  12  generates control signals Sm and Sc on the basis of the detection -signal Sr 1  that is output from the receiver  3  and the reference signal Sr 3  that is output from the transceiver  11 . The comparing circuit  12  outputs the control signals Sm and Sc to the controller  13  and the transceiver  11 , respectively.  
         [0058]    The controller  13  is formed by utilizing, for example, a microprocessor. The controller  13  performs various kinds of processings to totally control the controlling terminal. The controller  13  has a function of controlling generating the control signals Sm and Sc by the comparing circuit  12  and a function of controlling selecting the antenna  1  in response to the control signal Sm, in addition to functions of performing well-known processings to implement various kinds of functions that the existing mobile communication terminal has.  
         [0059]    Next, operations of the mobile communication terminals MT 1 , MT 2 , and MT 3  according to the first embodiment will be explained.  
         [0060]    In the first embodiment, one controlled terminal and one controlling terminal, of the mobile communication terminals MT 1 , MT 2 , and MT 3 , are paired to make operations. The paired controlled terminal and controlling terminal cooperate with each other to perform the diversity reception by each terminal.  
         [0061]    [0061]FIG. 6 is a flow chart showing the processing of the controller  6  of the controlled terminal and the processing of the controller  13  of the controlling terminal, to select the antenna  1 .  
         [0062]    The controller  6  and the controller  13  simultaneously perform the processings shown in FIG. 6 by taking advantage of a period in which the signal transmitted from the base station BS is a preamble portion.  
         [0063]    In the controlled terminal, the controller  6  first sets the receiver  3  in the memory mode at step ST 11 . Then, the controller  6  controls the switch  2  to select the antenna  1  which has not been utilized for test reception in the current processing, at step ST 12 . The high-frequency signal which is output from the antenna  1  selected by the switch  2  is input to the receiver  3 . At the receiver  3 , the high-frequency signal is detected and the detection signal Sr 1  is obtained. At this time, the detection signal Sr 1  is stored in a memory built in the receiver  3  in order of time series since the receiver  3  is set in the memory mode as explained above.  
         [0064]    In this state, the controller  6  waits for a certain time T 1  to pass, at step ST 13 . In other words, the controller  6  makes the receiver  3  store the detection signal Sr 1  obtained by utilizing one of the antennas  1  during the time T 1 . When the time T 1  has passed, controller  6  verifies whether or not the test reception is performed with all the antennas  1 , at step ST 14 . If there are the antennas  1  that have not yet been utilized for the test reception, the controller  6  repeats the processings of steps ST 12  to ST 14 .  
         [0065]    If the controller  6  verifies that the test reception is ended with all the antennas  1  at step ST 14 , the controller  6  makes the transceiver  4  transmit the detection signal Sr 1  stored in the receiver  3  as a reference signal to the controlling terminal which is to be paired with the controlled terminal at step ST 15 .  
         [0066]    On the other hand, in the controlling terminal, the controller  13  first sets the receiver  3  in the memory mode at step ST 21 . Then, the controller  13  controls the switch  2  to select one of the antennas  1  in a predetermined order, at step ST 22 . The high-frequency signal which is output from the antenna  1  selected by the switch  2  is input to the receiver  3 . At the receiver  3 , the high-frequency signal is detected and the detection signal Sr 1  is obtained. At this time, the detection signal Sr 1  is stored in a memory built in the receiver  3  in order of time series since the receiver  3  is set in the memory mode as explained above.  
         [0067]    In this state, the controller  13  waits for a certain time T 2  to pass, at step ST 23 . In other words, the controller  6  makes the receiver  3  store the detection signal Sr 1  obtained by utilizing one of the antennas  1  during the time T 2 . When the time T 2  has passed, controller  6  verifies whether or not the test reception is performed with the last antenna  1  of the order, at step ST 24 . If the test reception has not been performed with the last antenna  1 , the controller  13  repeats the processings of steps ST 22  to ST 24 .  
         [0068]    If the controller  13  verifies that the test reception as explained above is ended with the last antenna  1  at step ST 24 , the controller  13  makes the comparing circuit  12  perform the comparing processing at step ST 25 . At this time, the controller  13  instructs the comparing circuit  12  to execute the comparing processing and also instructs the transceiver  11  to receive the reference signal transmitted from the controlled terminal as explained above. The controller  13  also instructs the receiver  3  to output the detection signal Sr 1  stored in the receiver  3  to the comparing circuit  12 . Thus, the reference signal Sr 3  obtained by performing the test reception in the controlled terminal and the detection signal Sr 1  obtained by performing the test reception in the controlling terminal are fed to the comparing circuit  12 . The comparing circuit  12  sequentially compares the reference signal Sr 3  and the detection signal Sr 1 . This comparison is performed by calculating a product of a time series signal of each of the signals and thereby calculating a correlation coefficient.  
         [0069]    It is preferable that the reference signal Sr 3  and the detection signal Sr 1  as compared should be obtained by receiving the same signals from the base station BS at the same time. For this reason, the sequence of the antennas  1  selected in the controlling terminal at the test reception is preliminarily determined by considering the number of the antennas  1  of the controlled terminal and those of the controlling terminal. If the paired terminals are changed, the number of antennas  1  needs to be notified between the controlled terminal and the controlling terminal through the ad hoc network and the sequence of selection of the antennas  1  needs to be determined to implement combination of all the antennas  1 .  
         [0070]    The comparing circuit  12  discriminates a signal combination having the lowest correlation coefficient, and determines that the antenna  1  corresponding to the reference signal Sr 3  in this signal combination should be utilized by the controlled terminal and that the antenna  1  corresponding to the detection signal Sr 1  in this signal combination should be utilized by the controlling terminal. The comparing circuit  12  generates the control signal Sc designating the antenna  1  which is determined to be utilized by the controlled terminal and outputs the signal to the transceiver  11 . The controller  13  controls the transceiver  11  to transmit the control signal Sc to the controlled terminal at step ST 26 .  
         [0071]    On the other hand, the comparing circuit  12  generates the control signal Sm designating the antenna  1  which is determined to be utilized by the controlling terminal and outputs the signal to the controller  13 . The controller  13  controls the switch  2  to select the antenna  1  designated by the control signal Sm at step ST 27 . Furthermore, the controller  13  sets the receiver  3  in the transfer mode at step ST  28  and terminates the current antenna selection.  
         [0072]    When the receiver  3  of the controlling terminal is set in the transfer mode, the receiver  3  immediately outputs the detection signal Sr 1  to the transceiver  11 . The detection signal Sr 1  is transmitted to the controlled terminal via the antenna  5 , as a transfer signal, by the transceiver  11 . Therefore, the signal obtained by detecting the high-frequency signal received by the antenna  1  which is designated by the control signal Sm becomes being transmitted to the controlled terminal.  
         [0073]    If the control signal Sc is transmitted from the controlling terminal as explained above, the controller  6  of the controlled terminal receives the control signal Sc by the transceiver  4  at step ST 16 . The controller  6  controls the switch  2  to select the antenna  1  which is designated by the control signal Sc, at step ST 17 . Furthermore, the controller  6  sets the receiver  3  in the transfer mode at step ST  18  and terminates the current antenna selection.  
         [0074]    When the receiver  3  of the controlled terminal is set in the transfer mode, the receiver  3  immediately outputs the detection signal Sr 1  to the transceiver  4 . The detection signal Sr 1  is transmitted to the controlling terminal via the antenna  5 , as a transfer signal, by the transceiver  4 . Therefore, the signal obtained by detecting the high-frequency signal received by the antenna  1  which is designated by the control signal Sc becomes being transmitted to the controlling terminal.  
         [0075]    Thus, in the receiver  3  in any of the controlled terminal and the controlling terminal, the processing for the diversity reception is performed with the detection signal obtained by using two antennas determined by the comparing circuit  12 , i.e. two antennas having the smallest correlation coefficient. For this reason, communication can be made under better conditions while efficiently obtaining the diversity gain.  
         [0076]    (Second Embodiment)  
         [0077]    In the above-described first embodiment, one controlled terminal and one controlling terminal are paired. The antenna utilized in each of the mobile communication terminals MT 1 , MT 2 , and MT 3  can also be determined by discriminating the optimum pairing of antennas in the ad hoc network group in which three or more of mobile communication terminals MT 1 , MT 2 , and MT 3  exist.  
         [0078]    In this case, however, the number of pairings of the antennas increases according to the increase of the mobile communication terminals MT in the group, and the load of the controlling terminal to calculate the correlation coefficient is thereby increased.  
         [0079]    In the second embodiment, calculation of the correlation coefficient is dispersed by a plurality of controlling terminals while considering the above matter.  
         [0080]    The dispersing method is changed according to the number of the controlled terminals and controlling terminals existing in the ad hoc network group. In this embodiment, four mobile communication terminals MT, i.e. two controlled terminals and two controlling terminals exist in the ad hoc network group. Each of the terminals has two antennas  1 .  
         [0081]    First, a reference signal obtained by performing the test reception with each of four mobile communication terminals needs to be collected by each of two controlling terminals through the ad hoc network. This reference signal may be colleted by an arbitrary method, but two efficient methods are represented below.  
         [0082]    One of them is a method of multiplexing the transmission and reception of the reference signal.  
         [0083]    For example, in a case where there are comparatively many reference signals to be handled for the communication through the ad hoc network, much time is required for this communication and problems may thereby occur in the data processing. In this case, the reference signal can be multiplexed to make communication with different frequencies.  
         [0084]    If the reference signal can be multiplexed with different frequencies, for example, a controlling terminal # 2  can receive the reference signal from a controlled terminal # 4  by different frequency channels while a controlling terminal # 1  receives the reference signal from a controlled terminal # 3 . Next, the controlling terminal # 2  can receive the reference signal from the controlled terminal # 3  by different frequency channels while the controlling terminal # 1  receives the reference signal from the controlled terminal # 3 . Finally, the reference signal is transmitted or received between the controlling terminals # 1  and # 2 . Thus, the controlling terminals # 1  and # 2  can complete collection of the respective reference signals at three communication times.  
         [0085]    Another method uses a broadcast communication function.  
         [0086]    Some ad hoc networks have a broadcast communication function called multicast. If the reference signals are comparatively small and a communication time of the reference signals is short enough to cause no troubles in the data processing, all the reference signals can be transmitted or received among the terminals by using the broadcast communication function. For example, the reference signals can be multicast to the terminals # 1 , # 2 , # 3  and # 4  in order.  
         [0087]    In the case of the above-described data transmission, adoption of the multiplexing or the broadcast communication can be determined by comparing the magnitude of the reference signals and the bandwidth of the ad hoc network. Furthermore, the order of communication can be determined on the basis of the order of the terminals added to the network at the establishment of the ad hoc network, and the like.  
         [0088]    [0088]FIG. 7 shows a table of sharing of the correlation coefficient calculation. “# 1   a ” and the like represent the antennas  1  existing in the group. For example, “# 1   a ” represents one of the antennas of the terminal # 1 . Another antenna of the terminal # 1  is represented by “# 1   b ”. The terminal # 1  performs the calculation of the correlation coefficients relating to the pairing represented as ◯ and the terminal # 2  performs the calculation of the correlation coefficients relating to the pairing represented as Δ. “-” represents the pairing whose correlation coefficient does not need to be obtained.  
         [0089]    Thus, to compare the signals received by the antennas  1  of four mobile communication terminals MT, pairing of totally eight antennas, i.e. comparison of twenty-eight manners is required. In the above example, however, the pairings are shared by two control terminals # 1  and # 2  such that each of the control terminals calculates the correlation coefficients relating to the pairing of fourteen manners.  
         [0090]    By sharing the calculation of the correlation coefficients by two control terminals # 1  and # 2 , the processing can be completed for half of the processing time which is required for the processing centralized by a single control terminal.  
         [0091]    The correlation coefficients calculated by each of the controlling terminals # 1  and # 2  are colleted by a controlling terminal through the ad hoc network. This controlling terminal determines the antenna  1  to be utilized at each of the terminals and a terminal which should serve as a partner of each of the terminals, by considering all the correlation coefficients. The controlling terminal transmits control signals to determine the antenna  1  and the partner to each of the other terminals through the ad hoc network. Determination of the optimum pairing of the antennas can be performed by, for example, selecting the pairing by which the value obtained by summing up the correlation coefficients relating to various kinds of pairing of the antennas  1  is smallest. Otherwise, the optimum pairing may be determined such that the value of the diversity gain presumed from the values of the correlation coefficients is calculated and is made highest.  
         [0092]    The controlling terminal performing the processing to determine the antenna  1  which should be utilized at each of the terminals and the terminal which should serve as the partner of each terminal may be fixed to either of the controlling terminals. However, if the controlling terminals # 1  and # 2  alternately perform the determination, the power required for the data processing can be shared fairly by the controlling terminals. The sequence of this processing may be determined in advance through the ad hoc network.  
         [0093]    [0093]FIG. 8 shows another table of sharing of the correlation coefficient calculation.  
         [0094]    In FIG. 8, all of four existing mobile communication terminals MT are controlling terminals, and the calculation of the correlation coefficients is shared by the four controlling terminals.  
         [0095]    Thus, the processing time can be reduced to a quarter by sharing the calculation of the correlation coefficients.  
         [0096]    Even if the mobile communication terminals MT have a different number of antennas, the data processing time can be reduced by determining the sharing so that the processing amount of each terminal is as equal as possible, and the power required for the data processing can be further shared fairly.  
         [0097]    The sharing of the calculation of the correlation coefficients may arbitrarily be determined in accordance with predetermined rules and conditions of the mobile communication terminals MT existing in the ad hoc network.  
         [0098]    According to the second embodiment, as described above, calculation of the correlation coefficients can be performed during a short period. Therefore, the time required to determine the antennas which should be utilized at the respective terminals can be reduced. For this reason, the calculation can follow the rapid variation in propagation atmosphere.  
         [0099]    (Third Embodiment)  
         [0100]    In the first embodiment described above, the controlling terminal determines only one antenna  1  as the antenna which should be utilized.  
         [0101]    For example, however, if there are a plurality of antennas  1  that have correlation coefficients equal to or smaller than a predetermined threshold value, any of these antennas  1  may be determined as the antenna which should be utilized.  
         [0102]    In this case, it can be determined at each terminal which of the antennas  1  considered as the antennas which should be utilized is selected.  
         [0103]    [0103]FIG. 9 is a block diagram showing a structure of the controlled terminal according to the third embodiment. In the drawing, like portions as shown in FIG. 2 are denoted by like or similar reference numerals and their detailed explanations are omitted here.  
         [0104]    The controlled terminal of the third embodiment comprises a plurality of antennas  1 , the switch  2 , the receiver  3 , the transceiver  4 , the antenna  5 , and a controller  14  as shown in FIG. 9. In other words, the controlled terminal of the third embodiment comprises the controller  14  instead of the controller  6  in the controlled terminal of the first embodiment.  
         [0105]    The controller  14  is formed of, for example, a microprocessor. The controller  14  has substantially the same function as that of the controller  6 . However, when a plurality of antennas  1  are selected in accordance with the control signal Sc, the controller  14  selects one of the antennas  1  on the basis of an evaluation result of the evaluation circuit  3   b.    
         [0106]    Thus, in the third embodiment, the controller  14  selects the antenna  1  from which the highest quality can be obtained, of the antennas designated by the controlling terminal as explained above.  
         [0107]    As the reception is performed with the antenna  1  from which the highest quality can be obtained, of the antennas  1  having a small correlation coefficient, the communication can be further made under good conditions.  
         [0108]    The characteristic structure of the third embodiment can also be applied to the controlling terminal.  
         [0109]    (Fourth Embodiment)  
         [0110]    [0110]FIG. 10 is a block diagram showing a structure of a controlled terminal according to the fourth embodiment. In the drawing, like portions as shown in FIG. 2 are denoted by like or similar reference numerals and their detailed explanations are omitted here.  
         [0111]    The controlled terminal of the fourth embodiment comprises the receiver  3 , the transceiver  4 , the antenna  5 , a plurality of antenna devices  15 , a phase shifter  16 , and a controller  17  as shown in FIG. 10. In other words, the controlled terminal of the fourth embodiment comprises the antenna devices  15 , the phase shifter  16  and the controller  17  instead of the antennas  1 , the switch  2  and the controller  6  in the controlled terminal of the first embodiment.  
         [0112]    The plural antenna devices  15  are aligned two-dimensionally to form an array antenna. The phase shifter  16  varies a phase of the array antenna.  
         [0113]    The controller  17  is formed of, for example, a microprocessor. The controller  17  has substantially the same function as that of the controller  6 . However, the controller  17  changes an orienting direction of a beam of the array antenna by controlling the amount of phase shifting of the phase shifter  16 .  
         [0114]    In the fourth embodiment, the same advantage as that of the first embodiment can be obtained by preparing some beams in advance and selecting the beam in the same manner as the manner of selecting the antenna  1  in the first embodiment.  
         [0115]    (Fifth Embodiment)  
         [0116]    [0116]FIG. 11 is a block diagram showing a structure of a controlled terminal according to the fifth embodiment. In the drawing, like portions as shown in FIG. 2 are denoted by like or similar reference numerals and their detailed explanations are omitted here.  
         [0117]    The controlled terminal of the fifth embodiment comprises the single antenna  1 , the receiver  3 , the transceiver  4 , the antenna  5 , a passive element  18 , a variable terminal element  19 , and a controller  20  as shown in FIG. 11. In other words, the controlled terminal of the fifth embodiment comprises the passive element  18  and the variable terminal element  19  while limiting the antennas  1  in the controlled terminal of the first embodiment to the single antenna  1  and omitting the switch  2 . The controlled terminal also comprises the controller  20  instead of the controller  6 .  
         [0118]    The passive element  18  is arranged in the vicinity of the antenna  1 . The variable terminal element  19  is provided in a short circuit between the passive element  18  and a bottom board.  
         [0119]    The controller  20  is formed of, for example, a microprocessor. The controller  20  has substantially the same function as that of the controller  6 . However, the controller  20  varies the radiation characteristics (radiation pattern and the gain) of the antenna  1  by varying the value of the variable terminal element  19 .  
         [0120]    In the fifth embodiment, the same advantage as that of the first embodiment can be obtained by preparing in advance some values of the variable terminal element  19  and selecting the value of the variable terminal element  19  in the same manner as the manner of selecting the antenna  1  in the first embodiment. The value of the variable terminal element  19  is determined in advance by preliminarily confirming the variation in the radiation field of the antenna  1  such that, for example, the radiation field changes as much as possible.  
         [0121]    The present invention is not limited to the embodiments described above. For example, the receiver  3  may detect the signal transmitted from the transmission station other than the base station BS.  
         [0122]    The present invention can also be applied to a case of performing the processing for the diversity reception by using the transfer signal transmitted from the other plural terminals.  
         [0123]    The present invention can be modified in various manners without departing from the gist of the invention.  
         [0124]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.