Abstract:
An object of the present invention is to prevent congestion of networks and to effectively use a plurality of autonomous distributed wireless networks.  
     An autonomous distributed wireless network system in which a plurality of wireless terminals communicate with each other, comprising: a plurality of autonomous distributed wireless networks each having a different communication form, and being constituted of a plurality of wireless terminals, wherein each of said plurality of wireless terminals has a network selector which allocates said plurality of autonomous distributed wireless networks to communicate different categories of information with different autonomous distributed wireless networks.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims benefit of priority under 35USC §119 to Japanese Patent Application No. 2002-127282, filed on Apr. 26, 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 an autonomous distributed wireless network system, a method of autonomous distributed wireless network communication, and a wireless terminal having an autonomous distributed wireless network which communicates with a plurality of wireless terminals, without relaying a base station.  
           [0004]    2. Related Art  
           [0005]    A network constituted of only terminals (such as a PC, a PDA and a portable phone), which does not need access points, like a wireless LAN, is called an autonomous distributed wireless network or an ad-hoc network.  
           [0006]    Such an ad-hoc network has an advantage in which it is possible to temporarily constitute an LAN within a constant range without performing central control such as a cellular network, or to put it another way, without connecting to a central control network.  
           [0007]    In the near future, it is predicted that the amount of information transmitted and received between the wireless terminals increases, and the information with different communication properties such as communication quality and transmission speed will be transmitted on the ad-hoc network. In this case, with only a single ad-hoc network, the throughput of the entire system lowers, and congestion of the network may occur.  
           [0008]    Because of this, a network form that the wireless terminal belonging to a single ad-hoc network can also communicate with the central control network has been proposed.  
           [0009]    [0009]FIG. 18 is a diagram showing an example of such a communication system. The wireless terminals  1 - 5  of FIG. 18 are capable of connecting to a plurality of network systems. The wireless terminals  1 - 4  belong to only an ad-hoc network  10 , and the wireless terminal  5  belongs to both of the ad-hoc network and the central control network C.  
           [0010]    Although the wireless terminals  1 - 4  functionally can be connected to the multisystem, they belong to only the ad-hoc network  10 . Because of this, they cannot communicate with a plurality of wireless systems.  
           [0011]    Furthermore, there is a higher possibility in which information with different communication properties such as the amount of information, the communication quality and the transmission speed increases. Because of this, it may be impossible to normally receive all the information with only one wireless terminal.  
           [0012]    Moreover, the conventional wireless terminal performs a diversity by the antenna of a wireless terminal dedicated to reception or a mobile station, or tries to exactly receive larger amount of information by constituting a smart antenna. However, a plurality of antennas become necessary, and each antenna has to be disposed separate from a desirable distance to realize non-directivity and non-correlation. Because of this, it is difficult to realize non-directivity and non-correlation in the wireless terminal which advances downsizing.  
           [0013]    When various information of which properties such as the amount of information and the transmission speed are remarkably different is communicated by only a single ad-hoc network, communication quality lowers.  
           [0014]    On the other hand, if the wireless terminal which are capable of connecting the multisystem always belongs to a plurality of ad-hoc network, there is a problem in which power consumption increases.  
         SUMMARY OF THE INVENTION  
         [0015]    An object of the present invention is to provide an autonomous distributed wireless network system, a method of autonomous distributed wireless network communication and a wireless terminal apparatus capable which can use effectively a plurality of autonomous distributed wireless networks.  
           [0016]    In order to achieve the foregoing object, an autonomous distributed wireless network system in which a plurality of wireless terminals communicate with each other, comprising:  
           [0017]    a plurality of autonomous distributed wireless networks each having a different communication form, and being constituted of a plurality of wireless terminals,  
           [0018]    wherein each of said plurality of wireless terminals has a network selector which allocates said plurality of autonomous distributed wireless networks to communicate different categories of information with different autonomous distributed wireless networks. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a diagram showing a network form of a first embodiment of an ad-hoc network system according to the present invention.  
         [0020]    [0020]FIG. 2 is a diagram showing the other example of an ad-hoc network system which selectively uses for communication qualities.  
         [0021]    [0021]FIG. 3 is a block diagram showing internal configuration of a wireless terminal in a multisystem of FIGS. 1 and 2.  
         [0022]    [0022]FIG. 4 is a sequence diagram showing processing procedure performed by each of wireless terminals when the ad-hoc network is formed.  
         [0023]    [0023]FIG. 5 is a sequence diagram showing processing procedure in the case of selectively using a plurality of ad-hoc networks according to communication qualities.  
         [0024]    [0024]FIG. 6 is a diagram showing a network form of a second embodiment of an ad-hoc network system according to the present invention.  
         [0025]    [0025]FIG. 7 is a sequence diagram showing processing procedure of a second embodiment of an ad-hoc network system according to the present invention.  
         [0026]    [0026]FIG. 8 is a diagram showing a network form of a third embodiment of an ad-hoc network system according to the present invention.  
         [0027]    [0027]FIG. 9 is a sequence diagram showing processing procedure of an ad-hoc network system according to the present invention.  
         [0028]    [0028]FIG. 10 is a diagram showing a network form of a fourth embodiment of an ad-hoc network system according to the present invention.  
         [0029]    [0029]FIG. 11 is a diagram showing an example of receiving data from a base station while a plurality of wireless terminals cooperate.  
         [0030]    [0030]FIG. 12 is a diagram showing the other example in which a plurality of wireless terminals cooperate to receive data from a base station.  
         [0031]    [0031]FIG. 13 is a diagram showing internal configuration of a wireless terminal when a plurality of wireless terminals cooperatively receive data from a base station.  
         [0032]    [0032]FIG. 14 is a sequence diagram showing processing procedure in the case where fragments of information cooperatively received by wireless terminals are combined and distributed.  
         [0033]    [0033]FIG. 15 is a sequence diagram showing processing procedure in the case where a plurality of ad-hoc network are selectively used for interference tolerance.  
         [0034]    [0034]FIG. 16 is a diagram showing a network form of a fifth embodiment of an ad-hoc network system according to the present invention.  
         [0035]    [0035]FIG. 17 is a sequence diagram showing processing procedure of a fifth embodiment of an ad-hoc network system according to the present invention.  
         [0036]    [0036]FIG. 18 is a diagram showing one example of a system in which a wireless terminal belonging to an ad-hoc network communicates with a central control network. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Hereinafter, an autonomous distributed wireless network system, a method of autonomous distributed wireless network communication and a wireless terminal will be more specifically described with reference to drawings.  
         [0038]    (First Embodiment)  
         [0039]    One of features of a first embodiment lies in that a plurality of autonomous distributed wireless network (hereinafter, called an ad-hoc network) are selectively used for communication qualities.  
         [0040]    [0040]FIG. 1 is a diagram showing a network form of the first embodiment of an ad-hoc network system. The system of FIG. 1 has two ad-hoc network  101  and  102  with different communication speeds in which one is a short-distance wireless network using a frequency hopping system known as Bluetooth, and another is a wireless LAN using a direct spread system represented by IEEE802.11. The wireless terminals in the ad-hoc network  101  can communicate at higher speed than the wireless terminals in the ad-hoc network  102 . Since a plurality of systems with different speeds exist in the wireless LAN, one of wireless LANs with different speeds maybe the ad-hoc network  101 , and another maybe the ad-hoc network  102 .  
         [0041]    A plurality of wireless terminals  1 - 16  belong to the ad-hoc networks  101  and  102 . The wireless terminals  11 - 16  of FIG. 1 are capable of connecting to the multisystem, and can communicate with the ad-hoc networks  101  and  102 .  
         [0042]    For example, in the case of communicating with the wireless terminals  14 ,  15  and  16 , it is supposed that a distance between the terminals is short, the received signal strength indication is large (the influence of the fading is small), a state of a communication path is good, and a communication quality is good. Because of this, communication is performed by using the ad-hoc network with higher communication speed.  
         [0043]    On the other hand, in the case of communicating with the wireless terminals  13  and  14 , or the wireless terminals  11  and  12  of FIG. 1, it is supposed that the state of the communication path is not good, and the communication quality is not good. Because of this, communication is performed by using the ad-hoc network  102  at lower communication speed.  
         [0044]    The ad-hoc networks  101  and  102  may transmit and receive the same information or informations different from each other.  
         [0045]    [0045]FIG. 2 is a diagram showing the other example of the ad-hoc network system which selectively uses a plurality of ad-hoc networks  101  and  102  according to communication qualities. The system of FIG. 2 has the ad-hoc network  101  used in the case of communicating with the wireless terminals in the same ad-hoc network and the ad-hoc network  102  capable of communicating with the base station  31  of a central control network such as a cellular network and the wireless terminals in the other ad-hoc network  201 .  
         [0046]    In the ad-hoc networks  101  and  102  of FIG. 2, specifications such as modulation systems, and multi-valued numbers and frequencies of the same modulation system are different from each other. The wireless terminals in the ad-hoc network  102  can communicate at higher speed than the wireless terminals in the ad-hoc network  101 .  
         [0047]    Wireless terminals  11 ,  13 ,  14 ,  16  and  17  which are capable of connecting to the multisystem and the wireless terminals  22  and  25  which are not capable of connecting to the multisystem exist in the ad-hoc network system of FIG. 2.  
         [0048]    The wireless terminal  13  uses the ad-hoc network  102  capable of communicating at high-speed when communicating with a base station  31  and the wireless terminals in the other ad-hoc network  201 . Furthermore, when the information obtained by communication with the base station  31  and the other ad-hoc network  201  has to be transmitted to the wireless terminals  22  and  25  which are not capable of connecting to the multisystem, the communication at lower speed is performed by using the ad-hoc network  101 .  
         [0049]    Thus, the wireless terminals  22  and  25  which are not capable of connecting to the multisystem can obtain the information from the base station  31  and the other ad-hoc network  201  through the wireless terminal  11  and so on in the multisystem.  
         [0050]    On the other hand, although it is possible to communicate with the wireless terminals in the same ad-hoc network at high speed, when the state of the communication path between the base station  31  and the other ad-hoc network  201  is not good, higher speed communication may be performed by using the ad-hoc network  101 , and lower speed communication may be performed by using the ad-hoc network  102 .  
         [0051]    [0051]FIG. 3 is a block diagram showing internal configuration of the wireless terminals in the multisystem of FIG. 1 and FIG. 2. The wireless terminal of FIG. 3 has a wireless unit  41  and an antenna  42  for connecting to the ad-hoc network  101 , a wireless unit  43  and an antenna  44  for connecting to the ad-hoc network  102 , a control unit for controlling the entire terminal, and a power supply for supplying power to each unit.  
         [0052]    The control unit instructs the wireless units  41  and  43  to measure the reception electric field strength. After receiving this instruction, the wireless units  41  and  43  measure the electric field strength of the reception signal received via the corresponding ad-hoc networks  101  and  102 , and transmit the measured result to the control unit  45 . The control unit  45  selects the wireless unit for communicating based on the electric field strength measured by the wireless units  41  and  43 .  
         [0053]    [0053]FIG. 4 is a sequence diagram performed by the wireless terminals at the time of forming the ad-hoc network. First of all, the wireless terminal (hereinafter, called a transmitting terminal) which wants to form the ad-hoc network transmits a control signal to a plurality of neighboring wireless terminals (step S 1 ). The plurality of neighboring wireless terminals determine whether or not the control signal has been received (step S 2 ). If the control signal is not received, an NACK signal is transmitted to the transmitting terminal. If the control signal is received, an ACK signal is transmitted to the transmitting terminal.  
         [0054]    Subsequently, the transmitting terminal detects the state of a plurality of wireless terminals based on the NACK signal and the ACK signal transmitted from a plurality of neighboring wireless terminals (step S 3 ). More specifically, it is determined that the transmitting terminal which returned the ACK signal within the prescribed time period can be participated in the ad-hoc network. The control information such as information relating to the other wireless terminals which participate in this network is transmitted to the wireless terminal that it has been determined to be able to participate in the ad-hoc network (step S 4 ). Therefore, the ad-hoc network is formed (step S 5 ).  
         [0055]    [0055]FIG. 4 shows processing procedure in the case of forming one ad-hoc network. The same processings as those of FIG. 4 are performed for each network in parallel or in order.  
         [0056]    When the ad-hoc network transmits and receives the signal to/from the base station, the base station may transmit the control information in step S 4  of FIG. 4, or if a representative wireless terminal exist in the ad-hoc network, the representative wireless terminal may transmit the control information.  
         [0057]    [0057]FIG. 5 is a sequence diagram showing processing procedure in the case where a plurality of ad-hoc networks  101  and  102  are selectively used for communication qualities. First of all, the transmitting terminal (or a wireless terminal which receives the signal from the other network or the base station, and distributes the signal) transmits the destination address and the control signal to peripheral wireless terminals (hereinafter, called a transmission destination terminal) (step S 11 ).  
         [0058]    The transmission destination terminals determine whether or not the destination address and the control signal have been received, and whether or not a current state is an idle state (step S 12 ). Here, the idle state shows the state in which the transmission destination terminals do not transmit and receive information by using the same ad-hoc network.  
         [0059]    If the destination address and the control signal are received, and the current state is the idle state, the ACK signal is transmitted to the transmission destination terminal.  
         [0060]    If the ACK signal is transmitted, the destination address and the control signal have not been received within a prescribed time period, or the current state is not the idle state, it is determined whether or not the other ad-hoc network exists (step S 13 ). If the other ad-hoc network does not exist, an END command is transmitted to the transmitting terminal. If the other ad-hoc network exists, changing to the other ad-hoc network is performed (step S 14 ), and the processings on and after step S 11  are performed.  
         [0061]    The transmitting terminal determines whether or not the number of the wireless terminals which returned the ACK signal is zero (step S 15 ). If zero, it is determined that communication is impossibility (step S 16 ).  
         [0062]    When determined that the number of the wireless terminals which returned the ACK signal is not zero, it is determined whether or not the number is “1” (step S 17 ). If “1”, the communication is begun by using the ad-hoc network which returned the ACK signal (step S 18 ).  
         [0063]    When determined that the number of the wireless terminals which returned the ACK signal is not “1”, a response of transmission path between the wireless terminals which returned the ACK signal is measured to detect the state S of the communication path (step S 19 ).  
         [0064]    Subsequently, it is determined for each wireless terminal whether or not the state S of the communication path is good (step S 20 ). If good, the high-speed ad-hoc network is selected (step S 21 ). If not good, the low-speed ad-hoc network is selected (step S 22 ). The communication is begun by using the selected ad-hoc network (step S 23 ).  
         [0065]    In the sequence diagram of FIG. 5, when a plurality of transmission destination terminals exist, the number of the ACK signals of all the transmission destination terminals maybe added, or the number of the ACK signals may be counted for each of transmission destination terminals. When the number of the ACK signals of all the transmission destination terminals is added, the processings of the transmitting terminal are simplified. If at least one of the transmission destination terminals does not return the ACK signal, it is determined that the communication is impossible. If the state of the communication path of at least one of the transmission destination terminals is bad, the low-speed ad-hoc network is used. On the other hand, when the number of the ACK signals is separately counted for each of the transmission destination terminals, although the processings of the transmission destination terminal become heavy, it is possible to perform the transmission suitable for the state of the transmission destination terminals.  
         [0066]    Thus, according to the first embodiment, the ad-hoc network is selected by judging the state of the communication path based on the information such as the reception signal strength from the wireless terminal or the base station of the communication destination. Because of this, it is possible to select the ad-hoc network in which the communication quality and the transmission speed are optimum.  
         [0067]    Furthermore, each of the wireless terminals belonging to the ad-hoc network may measure the reception signal strength of the other wireless terminal being the communication destination, or may detect the state of communication path by estimating the response of the transmission path.  
         [0068]    (Second Embodiment)  
         [0069]    One of features of a second embodiment lies in that a plurality of ad-hoc networks are selectively used for power consumption.  
         [0070]    [0070]FIG. 6 is a diagram showing a network form of a second embodiment of an ad-hoc network system. The system of FIG. 6 has two ad-hoc networks  101  and  102  with power consumption different from each other. It is assumed that the power consumption of the ad-hoc network  101  is larger than that of the ad-hoc network  102 . For example, the ad-hoc network  101  is a network with low power consumption using a frequency hopping system such as a Bluetooth network. The ad-hoc network  102  is a wireless LAN using a direct spread system represented by, for example, IEEE802.11. The terminals communicated with this network have the power consumption higher than the ad-hoc network  101 . The ad-hoc networks  101  and  102  are not limited to the Bluetooth system or the IEEE802.11, but may be the wireless LAN systems different from each other.  
         [0071]    The wireless terminals  11 ,  13 ,  14 ,  32  and  35  of FIG. 6 can be connected to the multisystems. The wireless terminals  32  and  35  which do not now communicate set the power supply  46  for the ad-hoc network  101  to be off or to be in low power consumption mode. Therefore, it is possible to reduce useless power consumption.  
         [0072]    Although the wireless terminals  11 ,  13 ,  14 ,  32  and  35  of FIG. 6 have the same configuration as that of FIG. 3, the operations of the control unit  45  and the power supply  46  are different from those of the first embodiment. The power supply  46  of the present embodiment contains an ampere meter not shown. The control unit  45  instructs the wireless units  41  and  43  to transmit a signal with the same amount of information to the ad-hoc networks  101  and  102 . While the wireless units  41  and  43  is transmitting the signals to the ad-hoc networks  101  and  102 , the control unit  45  measures the current flowing through the ampere meter. The lower the current flowing through the ampere meter is, the lower the power consumption is. Because of this, the control unit  45  selects the wireless unit with lower power consumption, and performs subsequent communication.  
         [0073]    [0073]FIG. 7 is a sequence diagram showing processing procedure of a second embodiment of the ad-hoc network system.  
         [0074]    The steps S 31 -S 38  of FIG. 7 perform the same processings as steps S 11 -S 18  of FIG. 4. That is, if the number of the ACK signals transmitted from the transmission destination terminal is zero, it is determined that communication is impossible. If “1”, the ad-hoc network which returned the ACK signal is selected to communicate.  
         [0075]    On the other hand, the number of the ACK signals is two or more, it is determined whether it is necessary to communicate at low power consumption (step S 39 ). For example, the remaining battery capacity of the transmitting terminal or the transmission destination terminal is checked, and if the remaining battery capacity is low, the ad-hoc network  102  of low power consumption is selected (step S 40 ). If the remaining battery capacity is high, the ad-hoc network  101  of high power consumption is selected (step S 41 ).  
         [0076]    For example, it is assumed that the ad-hoc network  101  of FIG. 6 has been selected. Since the wireless terminals  32  and  35  turn off the power supply  46  for the network, it is impossible to transmit the information to the wireless terminals  32  and  35  through the network. In this case, the information is transmitted to the other wireless terminal  11  which can communicate with both of the ad-hoc networks  101  and  102 , and the information is transmitted from the wireless terminal  11  to the wireless terminals  32  and  35  through the ad-hoc network  102 .  
         [0077]    Thus, according to the second embodiment, a plurality of ad-hoc networks are selectively used for power consumption. Because of this, it is possible to reduce power consumption, and it is possible to transmit the information through the other ad-hoc network for the wireless terminal which turns off the power supply  46  for a certain ad-hoc network.  
         [0078]    For example, when the ad-hoc system  101  of high-speed and high power consumption and the ad-hoc system  102  of low-speed and low power consumption exist together, it is possible to distinguish the ad-hoc systems if necessary. For example, the ad-hoc system  101  is used for the information which has to communicate at high-speed, and the ad-hoc system  102  is used for the information which may be communicated at low speed.  
         [0079]    (Third Embodiment)  
         [0080]    One of features of a third embodiment lies in that a plurality of ad-hoc network are selectively used for security levels.  
         [0081]    [0081]FIG. 8 is a diagram showing a network form of the third embodiment of an ad-hoc network system. The system of FIG. 8 has two ad-hoc networks  101  and  102  with security levels different each other. It is assumed that the security level of the ad-hoc network  101  is higher than that of the ad-hoc network  102 .  
         [0082]    The ad-hoc network  101  is used when the wireless terminal belonging to the same network communicates only in the network, and the ad-hoc network  102  is used when communicating with the base station  31  or the other ad-hoc network  201 .  
         [0083]    On the contrary, if it is assumed that only the terminals reliable to each other communicate, data communication with low security level may be performed by using the ad-hoc network  101  which is not connected to the other network. When communicating with the base station  31  or the other ad-hoc network  201 , data communication with high security level may be performed by using the ad-hoc network  102 .  
         [0084]    Furthermore, when communicating between the wireless terminals, when a circumstance for heightening the security level occurs, the ad-hoc network with high security level may be arbitrarily selected.  
         [0085]    As a method of heightening the security level, for example, a method of using data which excels in security performance or encryption data is supposed.  
         [0086]    The wireless terminals  11 - 15  belonging to the ad-hoc network  101  of FIG. 8 can be connected to the multisystem, and the internal configuration is the same as that of FIG. 3. Operation of the control unit  45  is different from those of the first and second embodiments.  
         [0087]    The control unit  45  in the wireless terminals  11 - 15  of the third embodiment instructs the wireless units  41  and  43  to check the security level of the ad-hoc networks  101  and  102 . The wireless units  41  and  43  check whether or not the other ad-hoc network  201  or the base station  31  is connected to the ad-hoc networks  101  and  102 . The control unit  45  determines that the security level of the ad-hoc network  101  to which nothing is connected is higher than that of the ad-hoc network  102  to which the other ad-hoc network  201  or the base station  31  is connected. When the information to be transmitted requires high security, the information is transmitted by using the ad-hoc network  101 . When the information does not require high security, the information is transmitted by using the ad-hoc network  102 .  
         [0088]    [0088]FIG. 9 is a sequence diagram showing processing procedure of the third embodiment of the ad-hoc network system.  
         [0089]    Steps S 51 -S 58  of FIG. 9 perform the same processings as step S 11 -S 18  of FIG. 5. That is, if the number of the ACK signals from the transmission destination terminal is zero, it is determined that communication is impossible. If “1”, the ad-hoc network which returned the ACK signal is selected to communicate.  
         [0090]    If the number of the ad-hoc network which returned the ACK signal is two or more, it is determined whether or not communication with high security level is necessary (step S 59 ). If such a communication is necessary, the ad-hoc network with high security level is selected (step S 60 ). If such a communication is unnecessary, the ad-hoc network with low security level is selected (step S 61 ).  
         [0091]    Thus, according to the third embodiment, since a plurality of ad-hoc networks are selectively used for the security levels, it is possible to prevent leakage of important data.  
         [0092]    (Fourth Embodiment)  
         [0093]    One of features of a fourth embodiment lies in that a plurality of ad-hoc networks are selectively used for interference tolerance properties.  
         [0094]    [0094]FIG. 10 is a diagram showing a network form of the fourth embodiment of the ad-hoc network system. The system of FIG. 10 has two ad-hoc networks  101  and  102  with modulation systems and frequencies different from each other, and the wireless terminal  14  receives the information from the base station  31  of a central control network such as a cellular network.  
         [0095]    Even if either of ad-hoc network  101  or  102  is used, when the wireless terminal  14  cannot normally receive the signal from the base station  31  due to fading, the wireless terminal  14  transmits the control signal which instructs the other wireless terminals  11 - 13  and  15  to cooperate to reception.  
         [0096]    Each of the wireless terminals  11 - 13  and  15  which has received the control signal receives a fragment of the signal including the large amount of information such as moving image and data from the base station  31  through the ad-hoc network  102  by cooperating to each other, as shown in FIG. 11, and transmits the received fragment to the wireless terminal  14 . The wireless terminal  14  combines the fragments of these information, and transmits the combined information to the respective wireless terminals which want transmission, through the ad-hoc network with better interference tolerance property at the time.  
         [0097]    Since the wireless terminals  11 - 13  and  15  receive the fragments of the information in units of a packet, the wireless terminal  14  combines the packets with reference to header information of the packets.  
         [0098]    As the other example, when the wireless terminal communicates with the base station and the other wireless terminal, the ad-hoc network with better interference tolerance at the time is selected to communicate. For example, when the ad-hoc network  101  is a Bluetooth network, and the ad-hoc network  102  is a wireless LAN using a direct spread system represented by IEEE802.11, if the wireless LAN is better in interference tolerance property of the wireless terminal than the Bluetooth network, the wireless LAN is used to communicate.  
         [0099]    Although internal configuration of the wireless terminal  14  is the same as that of FIG. 3, the operation of the control unit  45  is different from the first to third embodiments.  
         [0100]    When the control unit  45  of the wireless terminal  14  determines that the wireless unit  41  cannot normally receive the signal, the control unit  45  transmits a signal which requests reception cooperation to the other wireless terminals. When the signal cooperatively received by the other wireless terminals is received by the wireless unit  43 , the processing for combining the reception signal with reference to header information of the packets is performed.  
         [0101]    [0101]FIG. 14 is a sequence diagram showing processing procedure in which the fragments of the information cooperatively received by the wireless terminals are combined and then distributed to the wireless base stations. First of all, the wireless terminal  14  which requests cooperation transmits cooperation request information to the other wireless terminals  11 - 13  and  15  in the network by including in the control information (step S 71 ).  
         [0102]    The wireless terminals  11 - 13  and  15  which received the control signal send back a response signal indicating whether or not to respond to the cooperation request and a signal indicating whether or not to desire distribution of information from the base station  31  received by the wireless terminal which requested cooperation (step S 72 ).  
         [0103]    Subsequently, the wireless terminal  14  which requested cooperation transmits a reception start signal (step S 73 ). Therefore, the wireless terminals  11 - 13  and  15  receive the fragments of the information from the base station  31 . FIG. 11 shows an example in which all the wireless terminals  11 - 13  and  15  in the ad-hoc network respond to cooperation request.  
         [0104]    The wireless terminals  11 - 13  and  15  which respond to the cooperation request transmit the fragments of the received information to the wireless terminal  14  which requested the cooperation, as shown in FIG. 11 (step S 74 ). The wireless terminal  14  which requested the cooperation combines the fragments of the information, and distributes the combined information to the wireless terminals  11 - 13  and  15  which desires the distribution, via the same or other ad-hoc network (step S 75 ).  
         [0105]    When the information is distributed, the ad-hoc network to be used is decided by taking into consideration the simultaneity of distribution and reception, and interference tolerance property of the networks during distribution period. For example, when distribution and reception of information are almost simultaneously performed, different ad-hoc networks are used between distribution and reception. When reception is performed after distribution of information, the ad-hoc network which excels in interference tolerance property is used.  
         [0106]    As shown in FIG. 12, the terminal used for the system of the present embodiment may be constituted of terminals capable of connecting to two ad-hoc networks  101  and  102  with modulation systems and frequencies different from each other, and a central control network such as a cellular network. FIG. 13 is a block diagram showing one example of such a terminal.  
         [0107]    In FIG. 13, reference number  41  is a wireless unit for connecting to the ad-hoc network  101 , reference number  42  is an antenna corresponding to the ad-hoc network  101 , reference number  43  is a wireless unit for connecting to the ad-hoc network  102 , reference number  44  is an antenna corresponding to the ad-hoc network  102 , and reference number  45  is a control unit. The wireless unit  3  is a wireless unit for connecting to the base station  31 , and reference number  48  is an antenna corresponding to the wireless unit  3 .  
         [0108]    The control unit  45  transmits the signal which requests reception cooperation to the other wireless terminals through the wireless units  41  and  43  when determined that the wireless terminal  47  cannot normally receive the signal. Since the data amount of the signal is small, communication may be performed by using the wireless unit  41  through the ad-hoc network  101  at low speed. The signal cooperatively received by the other wireless terminals may be transmitted and received through the ad-hoc network  102  at high speed. Therefore, it is possible to avoid data congestion. In FIG. 13, the wireless terminal  14  performs the processings which combine the signal from the other terminals which is received by the other wireless terminals, with reference to header information of the packet.  
         [0109]    [0109]FIG. 15 is a sequence diagram showing processing procedure in the case of selectively using a plurality of ad-hoc network according to interference tolerance properties.  
         [0110]    Steps S 81 -S 88  of FIG. 15 perform the same processings as steps S 11 -S 18  of FIG. 4. That is, if the number of the ACK signals from the transmission destination terminal is zero, it is determined that communication is impossible. If “1”, the ad-hoc network which returned the ACK signal is selected to communicate.  
         [0111]    If the number of the ad-hoc networks which returned the ACK signal is two or more, the network with the best interference tolerance properties at that time is selected (step S 89 ).  
         [0112]    Thus, according to the fourth embodiment, when the information from the base station is received, a plurality of wireless terminals in the same ad-hoc network cooperate to each other to receive fragments of the information, and combine the information after receiving the information. Because of this, even if the information from the base station is a large amount of information, it is possible to receive the information at short time.  
         [0113]    Furthermore, when the combined information is distributed, the distributed ad-hoc network is determined by taking into consideration the simultaneity of reception and distribution of information, and the interference tolerance property of the ad-hoc network during distribution period. Because of this, it is possible to distribute the information to the transmission destinations without losing the information.  
         [0114]    (Fifth embodiment)  
         [0115]    One of features of a fifth embodiment lies in that a plurality of ad-hoc networks are selectively used for the transmitting and receiving information.  
         [0116]    [0116]FIG. 16 is a diagram showing a network form of an ad-hoc network system. The system of FIG. 16 has an ad-hoc network  101  for emphasizing immediacy such as phone call and an ad-hoc network  102  which does not emphasize immediacy such as data.  
         [0117]    Here, as the transmitting and receiving information, for example, it is assumed that there are the control signal, the phone call and data. Since the phone call and the control signal request immediacy, these are transmitted through the ad-hoc network  101 . Data such as character information and still image to which immediacy is not requested is transmitted through the ad-hoc network  102 . It is desirable that moving image is transmitted through the ad-hoc network  101  which requests immediacy.  
         [0118]    In the example of FIG. 16, the wireless terminal  11  transmits the control signal to the wireless terminals  12  and  13  through the ad-hoc network  101 , and the wireless terminals  14  and  15  perform phone call through the ad-hoc network  101  to each other. The wireless terminals  11  and  12  and the wireless terminals  13  and  14  perform data communication to each other through the ad-hoc network  102 .  
         [0119]    The wireless terminals  11 - 15  belonging to the ad-hoc network  101  of FIG. 16 can be connected to the multisystem, and the internal configuration thereof is the same as that of FIG. 3. The operation of the control unit  45  is different from the first to fourth embodiments.  
         [0120]    The control unit  45  in the wireless terminals  11 - 15  of the fifth embodiment determines whether or not the information to be transmitted requests the immediacy, and the wireless unit to transmit the information is determined according to the result of the determination.  
         [0121]    [0121]FIG. 17 is a sequence diagram showing processing procedure of a fifth embodiment of an ad-hoc network system.  
         [0122]    Steps S 101 -S 108  of FIG. 17 perform the same processings as step S 11 -S 18  of FIG. 5. That is, if the number of the ACK signals from the transmission destination terminal is zero, it is determined that communication is impossible, and if “1”, the ad-hoc network which returned the ACK signal is selected to communicate.  
         [0123]    If the number of the ad-hoc network which requested the ACK signals is two or more, it is determined whether or not the transmitting and receiving information require immediacy (step S 109 ). In the case of the information in which immediacy is required (for example, the case of transmitting the phone call and the control signal), the ad-hoc network  101  is selected (step S 110 ). In the case of the information in which immediacy is not required (for example, the case of transmitting data), the ad-hoc network  102  is selected (step S 111 ).  
         [0124]    In FIG. 17, the example in which the ad-hoc networks  101  and  102  are selectively used for whether or not the transmitting and receiving information requires immediacy has been shown. When the wireless LAN system capable of transmitting sound information at high sound quality and the other wireless LAN suitable for high speed data transmission exist together, one may be allocated to the ad-hoc network  101 , and another may be allocated to the ad-hoc network  102 .  
         [0125]    Thus, according to the fifth embodiment, a plurality of ad-hoc networks are selectively used for the types of the transmitting and receiving information. Because of this, it is possible to select the ad-hoc network most suitable for the kinds of the transmitting and receiving information, thereby effectively using resources.  
         [0126]    In the above first to fifth embodiments, an example in which two ad-hoc networks are provided has been described. Three or more ad-hoc networks may be provided. Furthermore, the present invention is applicable that a parent terminal and a child terminal distinguished to each other are included in a plurality of wireless terminals belonging to the ad-hoc networks.