Abstract:
One of objects of a wireless communication apparatus according to the present invention is to realize stable communication regardless of received signal strength indication and information amount.  
     The wireless communication apparatus for communicating in an autonomous distributed wireless network, comprising: a detection unit which generates a detection signal by detecting a first wireless signal from a first wireless apparatus; a wireless circuit which receives a second wireless signal relating to said first wireless signal, transmitted from a second wireless apparatus which received said first wireless signal; a signal estimation unit which estimates said detection signal and the received second wireless signal; a signal selector which selects either said detection signal or the received second wireless signal, based on an estimation result of said signal estimation unit; and a demodulator which demodulates the signal selected by said signal selector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims benefit of priority under 35USC§119 to Japanese Patent Application No. 2002-128179, filed on Apr. 30, 2002, the entire contents of which are incorporated by reference herein.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a wireless communication apparatus having a plurality of antennas and a method of wireless communication.  
           [0004]    2. Related Art  
           [0005]    Conventional wireless apparatuses perform a diversity or have a smart antenna composed of an antenna on a single terminal or a mobile station, in order to reduce influence of fading seen as a problem of mobile communication. In this case, a plurality of antennas are necessary, and the antennas have to be disposed separate from each other by a prescribed distance, in order to obtain desirable properties which are omnidirectional and noncorrelated. Because of this, in most cases, it is impossible to realize the desirable properties in the terminal and the mobile station which have a limitation to body size.  
           [0006]    The size of the antenna may become large according to frequencies, in order to realize the antenna which ideally operates. If an antenna with small size is used, desirable properties of the antenna will not be obtained.  
           [0007]    As a method of solving these problems, techniques in which wireless terminals are connected to an autonomous distributed wireless network that does not need access points, and the diversity is performed by combining reception signals with each other is disclosed in Japanese patent Laid-open Pub. No. 2001-189971.  
           [0008]    In the conventional techniques, however, all the reception signals are transmitted between the terminals. Because of this, if information amount of the reception signals is large, huge load is added to the autonomous distributed wireless network. For example, when a data of moving images are received, communication has to be performed at a transmission speed of about several hundred kilometers in the autonomous distributed wireless network. When such signals are simultaneously transmitted between a plurality of terminals, congestion occurs, it becomes impossible to communicate between the terminals within a desirable time, and diversity reception originally intended may become impossible.  
         SUMMARY OF THE INVENTION  
         [0009]    An object of the present invention is to provide a wireless communication apparatus and a method of wireless communication capable of stably communicating, regardless of received signal strength indication and information amount.  
           [0010]    According to the present invention, a wireless communication apparatus for communicating in an autonomous distributed wireless network, comprising:  
           [0011]    a detection unit which generates a detection signal by detecting a first wireless signal from a first wireless apparatus;  
           [0012]    a wireless circuit which receives a second wireless signal relating to said first wireless signal, transmitted from a second wireless apparatus which received said first wireless signal;  
           [0013]    a signal estimation unit which estimates said detection signal and the received second wireless signal;  
           [0014]    a signal selector which selects either said detection signal or the received second wireless signal, based on an estimation result of said signal estimation unit; and  
           [0015]    a demodulator which demodulates the signal selected by said signal selector.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a diagram showing a first embodiment of a wireless communication apparatus according to the present invention.  
         [0017]    [0017]FIG. 2 is a conceptual figure showing the relationship among the wireless communication apparatus, a first terminal and a second terminal.  
         [0018]    [0018]FIG. 3 is a block diagram showing a detailed internal configuration of the wireless communication apparatus of FIG. 1.  
         [0019]    [0019]FIG. 4 is a flowchart showing processing operation of a first embodiment.  
         [0020]    [0020]FIG. 5 is a flowchart of a modified example of FIG. 4.  
         [0021]    [0021]FIG. 6 is a block diagram showing schematic configuration of an embodiment of a wireless communication apparatus having one antenna.  
         [0022]    [0022]FIG. 7 is a block diagram showing internal configuration of the antenna duplexer.  
         [0023]    [0023]FIG. 8 is a block diagram showing schematic configuration of a second embodiment of a wireless communication apparatus according to the present invention.  
         [0024]    [0024]FIG. 9 is a flowchart showing processing operation of a third embodiment of a wireless communication apparatus according to the present invention.  
         [0025]    [0025]FIG. 10 is a block diagram showing schematic configuration of a fourth embodiment of a wireless communication apparatus according to the present invention.  
         [0026]    [0026]FIG. 11 is a block diagram showing a detailed internal configuration of a wireless communication apparatus of FIG. 10.  
         [0027]    [0027]FIG. 12 is a flowchart showing processing operation of a fourth embodiment of a wireless communication apparatus according to the present invention.  
         [0028]    [0028]FIG. 13 is a block diagram showing schematic configuration of a fifth embodiment of a wireless communication apparatus according to the present invention.  
         [0029]    [0029]FIG. 14 is a block diagram showing schematic configuration of a sixth embodiment of a wireless communication apparatus according to the present invention.  
         [0030]    [0030]FIG. 15 is a block diagram in the case where a transmission system is added to FIG. 1.  
         [0031]    [0031]FIG. 16 is a block diagram showing a detailed internal configuration of FIG. 15.  
         [0032]    [0032]FIG. 17 is a block diagram in the case where a transmission circuit is added to the wireless communication apparatus of FIG. 10.  
         [0033]    [0033]FIG. 18 is a detailed block diagram of FIG. 17. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    Hereinafter, a wireless communication apparatus and a method of wireless communication will be more specifically described with reference to drawings.  
       First Embodiment  
       [0035]    [0035]FIG. 1 is a block diagram showing schematic configuration of a first embodiment of a wireless communication apparatus according to the present invention. The wireless communication apparatus of FIG. 1 shows one example of a wireless terminal capable of forming an autonomous distributed wireless network with other wireless terminals hereinafter, called as first and second terminals as shown in FIG. 2.  
         [0036]    [0036]FIG. 2 shows a relationship of the above mentioned wireless communication apparatus, first terminal and second terminals. The wireless communication apparatus denoted as reference number  801  and second terminal denoted as reference number  803  form first autonomous distributed wireless network  701 . The wireless communication apparatus  801  and second terminal  803  form second autonomous distributed wireless network  702  with first terminal denoted as reference number  802 . The wireless communication apparatus  801  and second terminal  803  belong to the central control network  703  such as cellular network, which is controlled by the base station  804 .  
         [0037]    Wireless communication apparatus  801  and second terminal  803  receive the same signal  602 , which is transmitted from first terminal  802  through second autonomous distributed wireless network  702 . Wireless communication apparatus  801  and second terminal  803  receive the same signal  601 , which is transmitted from base station  804  through the central control network  703 . Wireless communication apparatus  801  and second terminal  803  can transmit the control signal  604  or the received signal  603  from first terminal  802  and base station  804  through first autonomous distributed wireless network  701 .  
         [0038]    First terminal  802  can be replaced by base station  804 . The base station  804  can perform the same role as first terminal  802  if wireless communication apparatus  801  and second terminal  803  are in the network  703 .  
         [0039]    The autonomous distributed wireless network is a network such as a wireless LAN, and is composed of only terminals (such as a PC, a PDA and a cellular phone) capable of connecting each other by wireless signal. First autonomous distributed wireless network  701  can be wireless LAN. Second autonomous distributed wireless network  702  can be the Bluetooth network, and vice versa. The wireless communication apparatus of FIG. 1 has a first antenna  1 , a detection circuit  2 , a second antenna  3 , a wireless circuit for other terminal  4  for the autonomous distributed wireless network, an estimation circuit  5 , a signal selection circuit  6 , a demodulation circuit  7  and an output circuit  8 .  
         [0040]    The first antenna  1  can receive the signal from the base station of the central control network and the other terminal, which is forming the autonomous distributed wireless network. Here, the first antenna  1  receives the wireless signal from the first terminal. The detecting circuit  2  eliminates a carrier signal from a high frequency signal received by the first antenna  1  in order to convert into a modulation signal.  
         [0041]    The second antenna  3  can transmit and receive the wireless signal between the base station of the central control network and the other terminal, which is forming a part of the autonomous distributed wireless network. The second antenna  3  transmits and receives the wireless signal from/to the second terminal. The second terminal receives the wireless signal from the first terminal, and transmits the received wireless signal. The transmission signal from the second terminal is received by the second antenna  3 . The wireless circuit for other terminal  4  can receive the signal transmitted from the second terminal. The wireless circuit for other terminal  4  can transmit the signal detected by the detection circuit  2  to the second terminal. The second terminal is constituted in the same way as the wireless communication apparatus of FIG. 1. The estimation circuit  5  estimates the detection signal detected by the detection circuit  2  and the reception signal by the wireless circuit for other terminal  4 . For example, a received signal strength indication generally used for the cellular phone such as a CDMA system or a PDC system is used as an estimation function. The received signal strength indication is estimated based on an average value within a constant time period of an envelope curve amplitude of the detection signal and the reception by the wireless circuit for other terminal  4 .  
         [0042]    The signal selection circuit  6  selects either the detection signal detected by the detection circuit  2  or the reception signal by the wireless circuit for other terminal  4 . The demodulation circuit  7  generates the demodulation signal obtained by demodulating the signal selected by the signal selection circuit  6 , that is, an information signal such as sound and image. The information signal is outputted from the output circuit  8 .  
         [0043]    [0043]FIG. 3 is a block diagram showing detailed internal configurations of the wireless circuit for other terminal  4  and the signal selection circuit  6 . More specifically, FIG. 3 shows internal configurations of the wireless circuit for other terminal  4  and the signal selection circuit  6 .  
         [0044]    The wireless circuit for other terminal  4  has a reception circuit  11  and a transmission circuit  12  which are connected to the second antenna  3 , respectively. The transmission circuit  12  transmits the detection signal detected by the detection circuit  2  to the second terminal. The reason why the detection signal is transmitted to the second terminal is because it is possible to allow the information received by the first terminal to use for the second terminal. The transmission circuit  12  may transmit the information only when the second terminal has performed transmission request. The wireless signal transmitted from the second terminal is received by the reception circuit  11  in the wireless circuit for other terminal  4 . The reception circuit  11  detects the reception signal from the second terminal and supplies the detection signal to the estimation circuit  5  and the signal selection circuit  6 .  
         [0045]    The signal selection circuit  6  has a control circuit  13 , a comparison selection circuit  14  and a switch  15 . The control circuit  13  controls each part of the wireless communication apparatus of FIG. 1 as described below.  
         [0046]    The comparison selection circuit  14  selects either of the detection signal detected by the detection circuit  2  or the reception signal by the wireless circuit for other terminal  4 , based on the estimation result of the estimation circuit  5 , and notifies the control circuit  13  of the selection result. The comparison selection circuit  14  has a buffer or a memory not shown which accumulates the estimation result transmitted from the estimation circuit  5  at a certain time difference.  
         [0047]    The switch  15  selects either of the detection signal detected by the detection circuit  2  or the reception signal by the wireless circuit for other terminal  4  and supplies the selected signal to the demodulation circuit  7 . In FIG. 3, although the switch  15  is conceptually shown, the buffer or the memory may be practically provided. The reason why the buffer or the memory is provided is because the signal from the detection circuit  2  are transmitted at a certain timing different from the signal from the wireless circuit for other terminal  4 . The signal from the detection circuit  2  has to be stored in order to turn on/off the switch  15  one after another. When a plurality of terminals cooperatively receive the signal, the signal transmitted from these terminals has to be stored. Even in this case, the switch  15  has to have a function of the buffer or the memory. On the other hand, when the switch  15  is turned on/off by skipping instead of sequential comparison, the buffer or the memory becomes unnecessary.  
         [0048]    [0048]FIG. 4 is a flowchart showing processing operations of the first embodiment. Hereinafter, operations of the wireless communication apparatus of the present embodiment will be described with reference to this flowchart. Here, as a matter of convenience of explanation, an example of coordinating two terminals is described. However, the number of the terminals is not limited to two. Even if the number of the terminals increases, the basic operations are the same as those of FIG. 4.  
         [0049]    The wireless communication apparatus of FIG. 1 establishes the wireless communication network with the second terminal by using the wireless circuit for other terminal  4 . The wireless communication apparatus of FIG. 1 makes an agreement in which the second terminal receives the same wireless signal transmitted from the first terminal denoted as  802  in FIG. 2, and/or the base station  804 . This agreement is made through the established wireless communication network  701  shown in FIG. 2. It is decided that the signal received by each terminal in transmitted to the other terminal. The contents of the transmitted signal (such as the detection signal or the signal after demodulation) are decided to each other beforehand. After then, the wireless communication apparatus and second terminals begin communication with the base station and/or the other terminal such as first terminal.  
         [0050]    The processing operation of the wireless communication apparatus of the present embodiment will be described. It is determined whether or not the detection circuit  2  has notified the control circuit  13  of reception of the wireless signal (step S 1 ).  
         [0051]    The control circuit  13  instructs the detection circuit  2  to transmit a portion of the reception signal or the detection signal detected by the detection circuit  2  to the estimation circuit  5 , and instructs the detection circuit  2  to transmit the detection signal to the transmission circuit  12  in the wireless circuit for other terminal  4  and the switch  15  (step S 2 ).  
         [0052]    The control circuit  13  instructs the transmission circuit  12  in the wireless circuit for other terminal  4  to transmit the detection signal to the second terminal (step S 3 ).  
         [0053]    When the estimation result of the detection signal is obtained by the estimation circuit  5 , the control circuit  13  instructs the estimation circuit  5  to transmit the estimation result to the comparison selection circuit  14  (step S 4 ). The control circuit  13  instructs the comparison selection circuit  14  to hold the transmitted estimation result and to wait (step S 5 ).  
         [0054]    The control circuit  13  determines whether or not the reception circuit in the wireless circuit for other terminal  4  has received the wireless signal from the second terminal (step S 6 ). If the wireless signal has been received, the control circuit  13  instructs the reception circuit  11  to transmit the reception signal to the estimation circuit  5  and the switch  15  (step S 7 ).  
         [0055]    When the estimation result of the reception signal by the reception circuit  11  is obtained by the estimation circuit  5 , the control circuit  13  instructs the estimation circuit  5  to transmit the estimation result to the comparison selection circuit  14  (step S 8 ).  
         [0056]    The comparison selection circuit  14  selects, for example, the signal with stronger signal strength indication, among the detection signal detected by the detection circuit  2  and the reception signal by the reception circuit  11 . When the comparison selection circuit  14  performed signal selection, the control circuit  13  instructs the comparison selection circuit  14  to transmit the result of the signal selection to the control circuit  13  (step S 9 ).  
         [0057]    When the detection signal detected by the detection circuit  2  has been selected, the control circuit  13  instructs the switch  15  to transmit the detection signal detected by the detection circuit  2  to the demodulation circuit  7  (steps S 10  and S 11 ). When the reception signal by the reception circuit  11  in the wireless circuit for other terminal  4  has been selected, the control circuit  13  instructs the switch  15  to transmit the reception signal of the reception circuit  11  to the demodulation circuit  7  (steps S 10  and S 12 ).  
         [0058]    The demodulation signal demodulated by the demodulation circuit  7  is transmitted to the output circuit  8 , and the signal is displayed in a display apparatus not shown of the wireless communication apparatus of FIG. 1, or outputted by sound from a speaker not shown.  
         [0059]    Here, when transmission of the wireless signal from the second terminal is delayed, whether or not to wait the signal is automatically decided by the terminal based on the types of the reception signals (whether or not immediacy is required), or is decided according to will of users (users decide by notifying the delay to the users). The flowchart in this case is shown in FIG. 5.  
         [0060]    In the flowchart of FIG. 5, steps S 21  and S 22  are added to the flowchart of FIG. 4. It is determined whether or not the reception circuit  11  has received the signal from the second terminal within a prescribed time period (step S 21 ). When the signal is not received even if the prescribed time period has passed, it is determined whether or not to wait yet (step S 22 ). When it is determined not to wait, the processing of step S 11  is performed. In this processing, the detection circuit  2  is instructed to transmit the detection signal to the demodulation circuit  7 .  
         [0061]    According to the first embodiment, a so-called switching diversity is performed. In this switching diversity, the first and second terminals coordinate and the wireless signal of the terminal having better reception sensitivity is selectively demodulated. Because of this, as compared with the case of performing a combining diversity, it is possible to simplify internal configurations of the wireless communication apparatus, thereby downsizing the apparatus and reducing power consumption. The reason is because in phase combination required for the combining diversity becomes unnecessary. The wireless communication apparatus suitable for the portable terminal is obtained by using such a switching diversity.  
         [0062]    It is known that the switching diversity deteriorates a diversity gain a little bit, as compared with the combining diversity. However, since the amount of the deterioration is a little bit, performance does not change almost at all.  
         [0063]    In FIG. 1, although the example in which two antennas  1  and  3  are used has been described, it is possible to perform the same switching diversity as that of FIG. 1, even if there is only one antenna.  
         [0064]    [0064]FIG. 6 is a block diagram showing schematic configurations of an embodiment of a wireless communication apparatus having only one antenna  41 . The wireless communication apparatus of FIG. 6 has only one antenna  41 , and an antenna duplexer  42  for distributing the reception electric wave received by the antenna  41 , instead of the first and second antennas  1  and  3 . The other configurations are the same as those of FIG. 1.  
         [0065]    The antenna  41  of FIG. 6 performs two frequency operations capable of matching with two frequencies. Various Prior Art documents propose the configuration of the antenna  41  which performs two frequency operations, and concrete forms of configurations will not be limited. More specifically, the antenna  41  receives the signal at a frequency band which can be detected by the detection circuit  2  (the signal transmitted from the first terminal) and the signal at a frequency band which can be received by the wireless circuit for other terminal  4  (the signal transmitted from the second terminal).  
         [0066]    The antenna duplexer  42  has two filters  43  and  44  passing through only the signals at frequency bands different from each other, as shown in a detail configuration of FIG. 7. The reception signal passing through the filter  43  is inputted to the detection circuit  2 , and the reception signal passing through the filter  44  is inputted to the wireless circuit for other terminal  4 . Therefore, even if the antenna is one, it is possible to select and demodulate the wireless signal from the terminal with better reception sensitivity by coordinating the first and second terminals.  
         [0067]    In the case of configurations of FIG. 6, since it is possible to decrease the number of antennas, as compared with FIG. 1. Because of this, it is possible to downsize the apparatus.  
       Second Embodiment  
       [0068]    One of features of a second embodiment is to perform a switching diversity by estimating a demodulation signal instead of a detection signal.  
         [0069]    [0069]FIG. 8 is a block diagram showing schematic configuration of a second embodiment of a wireless communication apparatus according to the present invention.  
         [0070]    The wireless communication apparatus of FIG. 8 disposes the demodulation circuit  7  adjacent to the detection circuit  2 . The estimation circuit  5  estimates an error rate based on the demodulation signal.  
         [0071]    When the reception electric field strength is estimated in the same way as the first embodiment, if there is an interference wave mixed in the same frequency or an adjacent frequency, it is impossible to correctly estimate the signal. On the other hand, when the error rate is estimated in the same way as the second embodiment, even if there is the interference wave mixed in the same frequency or the adjacent frequency, it is possible to correctly estimate the signal. Because of this, it is possible to appropriately select one of the terminal of its own and the other terminals, thereby improving diversity gain.  
         [0072]    Although operations of the second embodiment are similar to those of the first embodiment, the followings are different. The wireless communication apparatus of the second embodiment supplies the demodulation signal obtained by demodulating the detection signal to the wireless circuit for other terminal  4 , the estimation circuit  5  and the signal selection circuit  6 . The estimation circuit  5  estimates the reception signal based on the demodulation signal, and the signal selection circuit  6  selects either of the output of the demodulation circuit  7  or the reception signal of the wireless circuit for other terminal  4  to supply the selected signal to the output circuit  8 . The configurations except for the above-mentioned configurations are the same as those of FIG. 1.  
         [0073]    According to the second embodiment, because the reception signal is estimated based on the demodulation signal, it is possible to correctly select the signals without being influenced by the interference wave, thereby improving the diversity gain.  
       Third Embodiment  
       [0074]    One of features of a third embodiment requests transmission of the wireless signal from the wireless circuit for other terminal  4  to the second terminal, only when detection signal level estimated by the estimation circuit  5  is less than a prescribed threshold value.  
         [0075]    Although the wireless communication apparatus of the third embodiment has the same configuration as that of FIGS. 1 and 2, processing operations are different from the first embodiment.  
         [0076]    [0076]FIG. 9 is a flowchart showing processing operations of the third embodiment of the wireless communication apparatus according to the present invention. Hereinafter, processing operations different from the first embodiment will be mainly described.  
         [0077]    The first and second terminals transmit the received signals to the wireless communication apparatus only when the wireless communication apparatus of FIG. 1 requests transmission.  
         [0078]    It is determined whether or not the detection circuit  2  notified the control circuit  13  of the reception of the wireless signal (step S 31 ).  
         [0079]    The control circuit  13  instructs the detection circuit  2  to transmit a portion of the reception signal or the detection signal detected by the detection circuit  2  to the estimation circuit  5  (step S 32 ).  
         [0080]    If the estimation result by the estimation circuit is obtained, the control circuit  13  instructs the estimation circuit  5  to transmit the estimation result to the control circuit  13  (step S 33 ).  
         [0081]    The control circuit  13  determines whether or not the estimation result transmitted from the estimation circuit  5  is less than a prescribed threshold value (step S 34 ). If the estimation result is less than the threshold value, the control circuit  13  instructs the transmission circuit  12  in the wireless circuit for other terminal  4  to transmit the transmission request signal to the second terminal (step S 35 ).  
         [0082]    The same processing as steps S 6 -S 12  of FIG. 4 are performed in steps S 36 -S 42 .  
         [0083]    If determined that the estimation result is equal to or more than the threshold value in the above-mentioned step S 34 , the control circuit  13  performs the processing of step S 41 . That is, the control circuit  13  instructs the switch  15  to transmit the detection signal detected by the detection circuit  2  to the demodulation circuit  7 .  
         [0084]    On the other hand, the control circuit  13  determines whether or not the reception circuit  11  in the wireless circuit for other terminal  4  received transmission request by the second terminal (step S 43 ). If the control circuit  13  received the transmission request, the control circuit  13  instructs the detection circuit  2  to transmit the detection signal to the transmission circuit  12  in the wireless circuit for other terminal  4  (step S 44 ). Next, the control circuit  13  instructs the transmission circuit  12  in the wireless circuit for other terminal  4  to transmit the detection signal to the second terminal (step S 45 ).  
         [0085]    According to the third embodiment, only when the estimation result relating to the reception signal of the first antenna  1  by the estimation circuit  5  is less than the threshold value, the control circuit  13  requests the transmission of the signal for the second terminal. Because of this, it is possible to reduce the amount of communication with the second terminal. That is, if communication status between the first embodiment and the wireless communication apparatus is good, it is unnecessary to perform the diversity. In such a case, the diversity operation is stopped. Therefore, it is possible to reduce the amount of communication with the other terminals, thereby restricting congestion under communication with the terminals, and reducing power consumption of the wireless communication apparatus.  
       Fourth Embodiment  
       [0086]    One of features of a fourth embodiment is to transmit the estimation result of the estimation circuit  5  to the second terminal.  
         [0087]    [0087]FIG. 10 is a block diagram showing schematic configuration of a fourth embodiment of a wireless terminal according to the present invention. The wireless communication apparatus of FIG. 10 is different from the first embodiment in which the estimation result of the estimation circuit  5  is transmitted to the second terminal through the transmission circuit  12  in the wireless circuit for other terminal  4 .  
         [0088]    [0088]FIG. 11 is a block diagram showing detailed internal configurations of the wireless communication apparatus. As compared with FIG. 3, a signal path from the estimation circuit  5  through the transmission circuit  12  in the wireless circuit for other terminal  4  and a signal path from the reception circuit  11  through the comparison selection circuit  14  in the signal selection circuit  6  are added.  
         [0089]    [0089]FIG. 12 is a flowchart showing processing operations of the fourth embodiment of the wireless communication apparatus according to the present invention. Processing operations of the fourth embodiment will be described based on the flowchart. In the present embodiment, the estimation result of the wireless communication apparatus of FIG. 10 is transmitted to the second terminal, and then the detection signal detected by the detection circuit  2  is transmitted to the second terminal when there is the transmission request from the second terminal.  
         [0090]    It is determined whether or not the detection circuit  2  notified the control circuit  13  of the reception of the wireless signal (step S 51 ). The control circuit  13  instructs the detection circuit  2  to transmit a portion of the reception signal or the detection signal to the estimation circuit  5  and the switch  15  (step S 52 ).  
         [0091]    If the estimation result of the estimation circuit  5  is obtained, the control circuit  13  instructs the estimation circuit  5  to transmit the estimation result to the comparison selection circuit  14  and the transmission circuit  12  (step S 53 ).  
         [0092]    The control circuit  13  instructs the transmission circuit  12  to transmit the estimation result to the second terminal (step S 54 ). The control circuit  13  instructs the comparison selection circuit  14  to hold the transmitted estimation result and to wait (step S 55 ).  
         [0093]    It is determined whether or not the reception circuit  11  notified the control circuit  13  of the reception of the wireless signal from the second terminal (step S 56 ). If the reception was notified, the estimation result of the estimation circuit  5  is transmitted to the comparison selection circuit  14  (step S 57 ). If the selection result of the selection circuit  14  is obtained, the control circuit  13  instructs the comparison selection circuit  14  to transmit the selection result (step S 58 ).  
         [0094]    The control circuit  13  instructs the switch  15  to select the signal from the detection circuit  2  when it is determined based on the transmitted selection result that the result of the signal detected by itself is good (steps S 59  and S 60 ).  
         [0095]    On the other hand, when the signal level from the second terminal is larger, the control circuit  13  instructs the transmission circuit  12  in the wireless circuit for other terminal  4  to transmit the transmission request to the second terminal (step S 61 ). After receiving the instruction, the transmission circuit  12  transmits the request signal to the second terminal for requesting the transmission of the wireless signal received from first terminal or the wireless signal received from the base station of the central control network.  
         [0096]    The control circuit  13  determines whether or not the reception circuit  11  in the wireless circuit for other terminal  4  notified the reception of the wireless signal from the second terminal (step S 62 ). The control circuit  13  which received the notification instructs the reception circuit  11  to transmit the reception signal to the switch  15  (step S 63 ), and allows the switch  15  to select the reception signal from the second terminal (step S 64 ).  
         [0097]    The signal selected by the switch  15  is demodulated by the demodulation circuit  7 , and is displayed in a display apparatus that the wireless communication apparatus holds, or is outputted from a speaker.  
         [0098]    If there is the transmission request from the second terminal, the control circuit  13  receives the transmission request, and then transmits the detection signal to the second terminal (step S 65 -S 67 ).  
         [0099]    According to the fourth embodiment, since the estimation result of the estimation circuit  5  is transmitted to the second terminal, the second terminal can determine whether or not to receive the signal from the wireless communication apparatus. Therefore, it is possible to reduce unnecessary communication.  
         [0100]    According to the fourth embodiment, only when performing the transmission request to second terminal, the wireless communication terminal  801  receives the signal from the second terminal. Because of this, it is possible to reduce the signal amount transmitted and received to/from the second terminal. The signal amount received by the wireless communication apparatus of FIG. 10 from the second terminal decreases, thereby restricting congestion and reducing power consumption.  
         [0101]    In the present invention, when there is a plurality of terminals in ad-hoc network (autonomous distributed wireless network), the estimation result is stored in the comparison selection circuit  14  and then compared with each other. By rating the reception level, even if communication becomes impossible in a terminal of a first candidate for any reason (such as under communication with the other terminals, or outside of network area), the transmission request for each terminal is performed in order such as a second candidate and a third candidate. Therefore, it is possible to stably perform the diversity.  
         [0102]    Since the second terminal is constituted in the same way as the wireless communication apparatus as described before, the second terminal also can transmit the estimation result estimated by its own to the wireless communication apparatus. If the estimation result transmitted from the second terminal is worse than the estimation result of its own, the transmission circuit  12  may begin transmitting the signal detected by the detection circuit  12 .  
         [0103]    As the other method, when there is a plurality of terminals in the autonomous distributed wireless network (the ad hoc network) the terminals transmit the estimation result of its own to the other terminals by multicast. The terminal having the highest estimation level transmits the signal from the base station of the central control network to the other terminal by multicast. Therefore, it is possible to reduce useless communication of the signal. As compared with the case where the terminals request the transmission of the signal for the other terminals, it is possible to prevent congestion in the case where one terminal is determined and performs transmission by multicast. Such a rule of the procedure may be chosen by the terminals in the network, after a network between the terminals is established.  
       Fifth Embodiment  
       [0104]    A fifth embodiment is a modified example of the second embodiment. One of features of a fifth embodiment is to transmit the demodulation signal demodulated by the demodulation circuit  7  to the second terminal.  
         [0105]    [0105]FIG. 13 is a block diagram showing schematic configuration of the fifth embodiment of a wireless communication apparatus according to the present invention. The wireless communication apparatus of FIG. 13 has almost the same configuration as that of FIG. 8, and is different from that of FIG. 8 in which a signal indicating the estimation result of the estimation circuit  5  is transmitted to the second terminal via the transmission circuit  12  in the wireless circuit for other terminal  4 .  
         [0106]    According to the fifth embodiment, it is possible to obtain advantageous effects which combine the effects of the second embodiment with the effects of the fourth embodiment. That is, it is possible to select the signal without being influenced by the interference wave signal, and to reduce the signal amount of transmitting and receiving to/from the other terminals.  
       Sixth Embodiment  
       [0107]    One of features of a sixth embodiment is to select either a switching diversity or a combining diversity.  
         [0108]    [0108]FIG. 14 is a block diagram showing schematic configurations of a sixth embodiment of a wireless communication apparatus according to the present invention. The wireless communication apparatus of FIG. 14 has a first antenna  1 , a detection circuit  2 , a second antenna  3 , a wireless circuit for other terminal  4 , an estimation circuit  5 , a signal selection circuit  6 , a demodulation circuit  7 , an output circuit  8 , a control circuit  13 , a combining circuit  23 , first and second switches  24  and  25 , and a signal amount estimation circuit  26 .  
         [0109]    The signal amount estimation circuit  26  estimates information amount communicated between the terminal and the base station and occurrence time frequency of communication, based on the demodulation signal. The control circuit  13  switches the first and second switches  24  and  25  based on the estimation result of the signal amount estimation circuit  26 .  
         [0110]    The combining circuit  23  combines the detection signal with the reception signal of the wireless circuit for other terminal  4 . The first switch  24  switches whether the detection signal detected by the detection circuit  2  is transmitted to the signal selection circuit  6  for the switching diversity or is transmitted to the combining circuit  23  for the combining diversity. The second switch  25  switches whether the reception signal by the reception circuit  11  in the wireless circuit for other terminal  4  is transmitted to the signal selection circuit  4  for the switching diversity or is transmitted to the combining circuit  23  for the combining diversity.  
         [0111]    The control circuit  13  performs the switching diversity by switching the switch  15  from the combining circuit  23  to the signal selection circuit  6 , when it is determined that it would be impossible to do signal processing on time if the combining diversity had been performed, such as the case where there is a large amount of the demodulation signal, or the case where the interval of the occurrence time frequency of the demodulation signal is short.  
         [0112]    When it is determined that the it would be impossible to do signal processing on time if the combining diversity had been performed, occurrence of delay may be notified to a user of the terminal via the output circuit  8 . If the user had allowed delay, the combining diversity would be continued. If the user had not allowed delay, the switch  15  would be switched from the combining circuit  23  to the signal selection circuit  6 .  
       Other Embodiment  
       [0113]    Even in the above-mentioned second to fifth embodiments, only one antenna may be provided in the same way as the FIG. 6, thereby downsizing the apparatus.  
         [0114]    In the above-mentioned embodiments, when communication with terminals (including the base station of the central control network) except for the first and second terminals is performed, an ad-hoc communication network is formed of wireless apparatuses provided in the terminals, and more stable communication becomes possible by communicating with the network.  
         [0115]    In the above-mentioned embodiment, an example in which the first antenna  1  is exclusively used for reception has been described. However, the first antenna  1  may transmit the wireless signal. In this case, the wireless communication apparatus of FIG. 1 is constituted as shown in FIG. 15.  
         [0116]    [0116]FIG. 15 has an input circuit  31 , a modulation circuit  32 , a frequency conversion &amp; amplification circuit  33  and a sharing circuit  34 , in addition to configurations of FIG. 1. The input circuit  31  supplies the input signal to be transmitted to the modulation circuit  32 . The modulation circuit  32  performs a prescribed modulation processing for the input signal. The modulation signal is converted into an intermediate frequency and amplified by the frequency conversion &amp; amplification circuit  33 . The sharing circuit  34  switches transmission/reception of the first antenna  1 .  
         [0117]    [0117]FIG. 16 is a block diagram showing a detailed internal configuration of FIG. 15. FIG. 16 adds the input circuit  31 , the modulation circuit  32 , the frequency conversion &amp; amplification circuit  33  and the sharing circuit  34 , in addition to configurations of FIG. 3. The input circuit  31  is constituted of an information input circuit  35  and a signal processing circuit  36 .  
         [0118]    [0118]FIG. 17 is a block diagram in the case where a transmission signal path is added to the wireless communication apparatus of FIG. 10. As compared with FIG. 10, the signal path which transmits the estimation result of the estimation circuit  5  to the wireless circuit for other terminal  4  is added. FIG. 18 is a detailed block diagram of FIG. 17. A signal path which transmits the estimation result of the estimation circuit  5  to the wireless circuit for other terminal  4  is added in FIG. 18, as compared with FIG. 11.