Abstract:
The packet communication system enables communication between a communication unit connected in a conventional telephone network and a communication unit in a packet communication network. A device for exclusively selecting the connection network is provided so that, at the time of transmission of a signal from one communication unit to another, the connection path is selected according to the kind of the network to which the other communication unit belongs. At the time of signal reception, the communication unit is connected to only one of the conventional telephone network and the packet communication network. The packet communication system includes a packet processor for converting an information signal, such as speech, inputted from an input unit (for example, a transmitter microphone of a handset) into the form of a packet

Description:
[0001]    This is a continuation application of U.S. Ser. No. 11/210,804, filed Aug. 25, 2005, which is a continuation application of U.S. Ser. No. 10/396,824, filed Mar. 26, 2003 (now U.S. Pat. No. 7,139,265); which is a continuation application of U.S. Ser. No. 09/238,160, filed Jan. 28, 1999 (now U.S. Pat. No. 6,563,815); which is a continuation application of U.S. Ser. No. 08/827,054, filed Mar. 26, 1997 (now abandoned); which is a continuation application of U.S. Ser. No. 08/436,183, filed May 9, 1995 (now U.S. Pat. No. 5,654,957). 
     
    
       [0002]    This application claims priority to JP 06-098508, filed May 12, 1994. 
       BACKGROUND OF THE INVENTION 
       [0003]    This invention relates to a packet communication system used for packet mode communication of a signal, such as, an audio signal or a video signal through a communication network, and more particularly to a packet communication system suitable for packet mode communication of a signal, such as, a speech signal between communication networks using signal types different from each other. 
         [0004]    With the recent progress of the architecture of a LAN (local area network), the network system connecting small size computers, such as, personal computers using the LAN is also increasing. Thus, an attempt is now being made for integration of communications by permitting voice communication on the LAN in addition to a conventional telephone network (including a PBX network that is a private branch exchange network). 
         [0005]    As an example of such an attempt, there is a “voice communication system” as shown in  FIG. 4 . This voice communication system is composed of telephones connected to a convention telephone network, packet communication units connected to a packeted speech signal communication network (referred to hereinafter as a packet communication network), and a communication gateway used to realize mutual connections between the telephones and the packet communication units. A network carrying such a speech packet on the LAN described above is an example of the packet communication network. 
         [0006]    Referring to  FIG. 4 , the reference numerals  21  and  22  designate telephones connected to a private branch exchange network (a PBX network)  13  and a public telephone network  20 ,  104  designates a subscriber line of the private branch exchange network  13 ,  105  designates a subscriber line of the public telephone network  20 , and they have the same interface. On the other hand, the reference numeral  101  designates a packeted speech signal transmission network in the form of, for example, a LAN based on the CSMA/CD (carrier sense multiple access with collision detection) scheme according to the standards defined in the IEEE 802.3. A plurality of packet communication units  14 ,  15  and  16  are connected to this LAN  101 . 
         [0007]    The packet communication units  14 ,  15  and  16  are in the form of small size computers, such as, personal computers provided with handsets  17 ,  18  and  19  respectively. These packet communication units  14 ,  15  and  16  have, on one hand, functions of packeting speech signal inputs from the handsets  17  to  19  and sending out the packeted speech signals onto the LAN  101  and, on the other hand, functions of converting the packeted speech signals received via the LAN  101  into ordinary voice streams again and reproducing the original speech by the handsets  17 ,  18  and  19 . 
         [0008]    The reference numeral  11  designates a mail box connected to the LAN  101  to store a filed voice mail. The packet communication units  14 ,  15  and  16  can store such filed voice mails in the mail box  11  through the LAN  101  and can also fetch such voice mails, transmitted from the other packet communication units and stored in the mail box  11 , so as to internally convert the stored voice mails into voice streams again and reproduce the original speech signals by the handsets  17 ,  18  and  19 . 
         [0009]    The reference numeral  12  designates a communication gateway which controls communication between the LAN  101  that is the packet communication network and the private branch exchange network  13  that is the conventional telephone network. In this case, a subscriber line accommodating an existing telephone is commonly used as a connection line  102  between the private branch exchange network  13  and the communication gateway  12 . However, this connection line  102  may be an interface between the telephones in the private branch exchange network. 
         [0010]    Suppose now the case where voice communication is made among the packet communication units  14 ,  15  and  16  in the LAN  101  in the voice communication system having the structure described above. In the case of making voice communication between, for example, the packet communication units  14  and  16 , the speech packet is transferred through a communication path  121 . On the other hand, in the case of making communication between the packet communication unit  14  and the private branch exchange network  13  or the telephone  21  or  22  connected to the public telephone network  20 , the speech packet is transmitted through a communication path  122  in the LAN  101 . In this case, the packeted speech signal on the LAN  101  is converted by the communication gateway  12  into the corresponding voice stream before being transferred to the private branch exchange network  13  or the public telephone network  20 . In the case of a speech signal transmitted from the side of the private branch exchange network  13  or the public telephone network  20  toward the packet communication unit  14  in the LAN  101 , its voice stream is packeted by the communication gateway  12  to be sent out to the LAN  101 . 
         [0011]    In the case of integration of voice communication in a packet communication network in the form including a conventional telephone network, it is an undeniable fact that the number of users having their telephones connected to the conventional telephone network is actually predominantly large although the number of terminals connected to the packet communication network is increasing. Therefore, when the desired integration of the voice communication is considered, the amount of communication between the telephones connected to the conventional telephone network and the terminals connected to the packet communication network is expected to considerably increase. 
         [0012]    On the other hand, when the future of the packet communication network is reviewed, an undeniable situation will appear in which the users possessing their telephones already become new members of the packet communication network. For example, although specific users, such as, persons holding administrative positions in a company only possess the packet communication units in the LAN in the company at present, it is apparent that there will be an increasing tendency of introducing the packet communication units in future so that all the members of the company can possess the packet communication units. 
         [0013]    However, the prior art packet communication units connected in the packet communication network are basically considered to make communication in packet form. Thus, the desired integration of the voice communication in the form including the conventional telephone network will bring forth such a problem that the communication gateway tends to be overloaded due to concentration of loads, resulting in impossibility of connection or communication. 
         [0014]    Further, when the packet communication unit is newly provided for the user possessing his telephone already, the same user possesses both the telephone and the packet communication unit. As a result, the cost inevitably increases, and such a problem arises that the user cannot deal with simultaneous occurrence of a communication request from both the telephone and the packet communication unit. The same applies also to the case where the telephone is newly provided for the user who possesses the packet communication unit only. 
       SUMMARY OF THE INVENTION 
       [0015]    It is an object of the present invention to provide a packet communication system which can reliably and economically ensure communication between communication units connected in a conventional telephone network and those connected in a packet communication network. 
         [0016]    Another object of the present invention is to provide a packet communication system which is constructed to be accommodated in the prior art network by adding a function of connection to the conventional telephone network in addition to the function of connection to the packet communication network, so as to lighten loads imposed on a communication gateway, to decrease the amount of materials of an interface circuit or parts for connection to the conventional telephone network, and to reduce the cost of the system. 
         [0017]    Still another object of the present invention is to provide a packet communication system in which a user possessing his telephone already can transmit speech through his telephone subscriber line possessed already and which also makes it possible to make voice communication with another packet communication unit connected in the packet communication network. 
         [0018]    Yet another object of the present invention is to provide a packet communication system which, when an incoming call arrives at the user&#39;s packet communication unit from another while the user is talking, displays the arrival of the incoming call on a display, so that such a call can be dealt with while the other party does not know the fact. 
         [0019]    A further object of the present invention is to provide a packet communication system in which a speech or like signal arriving at the user&#39;s packet communication unit from the conventional telephone network is turned into mail form without the necessity for re-connection of the input to the communication gateway, so as to shorten the period of time required for turning the input into the mail form and also to lighten the load imposed on the communication gateway. 
         [0020]    A still further object of the present invention is to provide a packet communication system in which, even in the event of sudden power supply interruption, an output unit, such as, an externally located telephone is used for communication, so that, even when the exclusive user of the packet communication unit is absent, and the power supply is not turned on, another person can respond to the input. 
         [0021]    The present invention which attains the above objects provides a packet communication system making communication between a communication unit connected in a conventional telephone network and that in a packet communication network, in which a function of connection to the conventional telephone network is added to a function of connection to the packet communication network, and means for exclusively selecting the connection network is provided so that, at the time of transmission of a signal from one of the communication units to the other, the connection path is selected according to the kind of network to which the other communication unit belongs, while, at the time of signal reception, the communication unit is connected to only one of the conventional telephone network and the packet communication network. That is, the packet communication system comprises packet processor means for converting a speech or like information signal inputted from an input unit (for example, a transmitter microphone of a handset) into the form of a packet to transmit the packet to the packet communication network and converting the packet transmitted from the packet communication network into the original speech or like information signal stream to reproduce the signal stream by an output unit (for example, a receiver of the handset), conventional telephone network interface control means for reproducing the speech or like information signal arrived from the conventional telephone network by the output unit, and exclusive selection means for exclusively selecting only one of the conventional telephone network and the packet communication network in response to the arrival of the input signal. 
         [0022]    Thus, in the case of communication between the communication unit connected in the packet communication network and the communication unit, such as, the telephone connected in the conventional telephone network, a connection path is formed between them by the function of connection to the conventional telephone network. On the other hand, in the case of communication between the communication units in the packet communication network, a communication path is formed between them by the function of connection to the packet communication network. Therefore, the communication gateway is utilized only for the communication between the communication unit (for example, the telephone) connected to the conventional telephone network only and the communication unit connected to the packet communication network only, and concentration of loads on the communication gateway is avoided. Thus, even when the number of the communication units connected in the conventional telephone network may be large, information, such as, audio information and/or video information can be reliably communicated between the communication units in the conventional telephone network and those in the packet communication network. 
         [0023]    Further, when the packet communication unit is newly provided for the user possessing his telephone already connected to the conventional telephone network, the sole requirement is to connect the subscriber telephone line to the packet communication system of the present invention, so that the telephone can be eliminated, and communication of information, such as, audio information and/or video information can be economically attained. When, in this case, information signals are simultaneously inputted from the communication unit connected in the packet communication network and that in the conventional telephone network, only one of the input signals is connected to the user&#39;s communication unit, and a busy tone is issued for the other input signal, so that the user does not feel any difficulty in dealing with such a situation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    These and other objects, and features of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention when read in conjunction with the drawings: 
           [0025]      FIG. 1  shows the system structure of an embodiment of the packet communication system using the packet communication unit according to the present invention. 
           [0026]      FIG. 2  is a block diagram showing in detail the structure of the packet communication unit used in the illustrated embodiment of the present invention. 
           [0027]      FIGS. 3A and 3B  show the structure of the packet communication unit provided with a connection switching circuit for switching over connection with an externally located telephone in the event of power supply interruption. 
           [0028]      FIG. 4  shows the structure of one form of a prior art packet communication system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Preferred embodiments of the present invention will now be described in detail by reference to the drawings. 
         [0030]      FIG. 1  shows the system structure of an embodiment of the packet communication system using the packet communication unit according to the present invention, and like reference numerals are used in  FIG. 1  to designate like parts appearing in  FIG. 4 . Referring to  FIG. 1 , the reference numeral  30  designates a packet communication unit having a function of connection both of a conventional telephone network and a LAN  101  that is a packet communication network. The packet communication unit  30  is provided with a connection path for connection to the LAN  101  and a connection interface line  103  for connection to a private branch exchange network  13  that is the conventional telephone network. The connection interface line  103  provides the same interface as that for subscriber lines connected to telephones  21  and  22 . The connection interface line  103  may be connected to a public telephone network  20  instead of the private branch exchange network  13 . However, for the convenience of description, it is supposed herein that the connection interface line  103  is connected to the private branch exchange network  12 . 
         [0031]      FIG. 2  shows in detail the structure of the packet communication unit  30 . The packet communication unit  30  is composed of a processor part  31  executing overall control, a display part  32  displaying various kinds of messages, for example, arrived messages, scenes, for example, address input scenes, etc., viewed by the user for the selection of the other party, a keyboard/mouse part  35  inputting information required for operation, a speech packet processor part  33  processing a speech input and a speech output to and from a handset  19  so as to transmit and receive a speech packet to and from the LAN  101 , a telephone interface control part  34  controlling the subscriber line interface of the conventional telephone network, and a switch part  36  switched over to select whether the speech stream to the handset  19  is to be supplied from the side of the LAN  101  or from the side of the private branch exchange network  13  therefor. These parts are interconnected with each other by a bus  301 . 
         [0032]    In response to the signal arrival information supplied from the speech packet processor part  33  or from the telephone interface control part  34 , the processor part  31  decides whether the communication unit of the other party is connected to the LAN  101  or to the private branch exchange network  13  and executes processing (for example, the exclusive control of the switch part  36 ) according to the result of decision. At the same time, according to the network to which the communication unit of the other party transmitting the signal is connected, the processor part  31  instructs the speech packet processor part  33  or the existing telephone interface control part  34  to originate a call. Also, the processor part  31  controls the switch part  36  to control the speech stream to be connected to the handset  19 . 
         [0033]    The packet communication unit  30  incorporated in this embodiment uses a communication path  121  when it communicates with, for example, a packet communication unit  14  located on the LAN  101 , while it uses another communication path  123  when it communicates with the telephones  21  and  22  connected to the conventional telephone network. Whether the communication unit of the other party is located on the LAN  101  or connected to the private branch exchange network  13  is decided on the basis of whether an identifier specifying the communication unit of the other party is a network address or a telephone number. Then, on the basis of the result of decision, the packet communication unit  30  selects the connection path. 
         [0034]    When, for example, the communication unit of the other party transmitting the call is the telephone  21 , the processor part  31  identifies according to the telephone number that the communication unit of the other party is connected in the private branch exchange network  13 , and the dial signal is generated from the telephone interface control part  34 . When, on the other hand, the communication unit of the other party transmitting the signal is the packet communication unit  14 , the processor part  31  identifies according to the network address that the communication unit of the other party is located on the LAN  101 , and the speech packet processor part  33  transmits the packet including the address of the other party. As this network address, the IP (internal protocol) address, the host name of the packet communication unit or the like is used. Whether the identifier used for specifying the unit transmitting the signal is the telephone number or the network address is decided on the basis of the rule for designating the identifier of the unit to which the signal is transmitted. Further, when it is so defined that the signal is transmitted through the communication gateway  12  when the identifier of the unit to which the signal is transmitted indicates the value in which the identifier allocated to the communication gateway  12  is added to the head of the telephone number, the packet communication unit  30  can communicate through the communication gateway  12  with the telephones  21  and  22  connected to the conventional telephone network. The network address or the telephone number of the communication unit transmitting the signal is inputted from the keyboard/mouse part  35  and displayed on the display part  32  of the packet communication unit  30 . 
         [0035]    The packet communication unit  14  in the prior art packet communication network must use the communication path  122  extending through the communication gateway  12  when it makes communication with the telephones  21  and  22  connected to the conventional telephone network only, as shown in  FIG. 4 . The practical mode in which the packet communication unit  30  is newly introduced to be provided for the user who possesses the existing telephone already will now be considered. In the case of the illustrated embodiment, a bypass route in the form of the connection interface line  103  directly connecting the packet communication unit  30  and the telephones  21  and  22  to the private branch exchange network  13  is provided as shown in  FIG. 1 , so that the load imposed on the communication gateway  12  can be greatly lightened. 
         [0036]    The manner of exclusive control for the communication path in the packet communication unit  30  will now be described. The processor part  31  in the packet communication unit  30  can recognize the state of both of the private branch exchange network  13  and the LAN  101  through the speech packet processor part  33  or the telephone interface control part  34 . Therefore, when a speech signal arrives while the packet communication unit  30  is making communication, that signal is dealt with as in the case of usual busy mode processing by the exclusive control function. 
         [0037]    More concretely, when the packet communication unit  30  starts to make communication with the telephone  21  connected to the private branch exchange network  13 , the processor part  31  changes over the switch part  36  to supply the speech input to the telephone interface control part  34  and cuts off the supply of the speech input from the speech packet processor part  33 . When another speech signal arrives from the other packet communication unit  14  under the above situation, the processor part  31  generates a packet indicating that the packet communication unit  30  is now busy, and this packet is transmitted from the speech packet processor part  33  to the signal transmitting packet communication unit  14  through the LAN  101 . 
         [0038]    On the other hand, when the packet communication unit  30  starts to make communication with the other packet communication unit  14  connected to the LAN  101 , the processor part  31  changes over the switch part  36  to supply the speech input to the speech packet processor part  33  and cuts off the supply of the speech input from the telephone interface control part  34 . When another speech signal arrives from the telephone  21  connected to the private branch exchange network  13  under the above situation, the processor part  31  instructs the telephone interface control part  34  to generate a busy tone signal, and this signal is transmitted to the signal transmitting telephone  21  through the connection interface line  103  and the private branch exchange network  13 . 
         [0039]    The packet communication unit  30  operates to effect the above manner of exclusive control for a speech signal that arrives during communication, so that the user of the packet communication unit  30  is required to respond to the signal arriving from one of the networks only and is thus freed from such a situation in which he is embarrassed with simultaneous arrival of speech signals from both the networks. When a speech signal arrives during communication by the packet communication unit  30 , the processor part  31  displays the arrival of the signal on the display part  32 . In this case, the switch part  36  may be changed over by the user who viewed and confirmed the display on the display part  32 . 
         [0040]    The voice mail transfer function will now be described. When a speech signal transmitted from, for example, the telephone  21  to the packet communication unit  30  through the private branch exchange network  13  is processed to be received as a speech mail due to, for example, the absence of the user of the packet communication unit  30 , the speech signal received through the connection interface line  103  is turned into the speech file by the speech packet processor part  33  and is then transferred through the LAN  101  to a mail box  11  to be stored as the mail whose destination is the user&#39;s packet communication unit  30 . Thus, as in the case of an automatic answering telephone set, the speech signal arrived during the period of absence of the user of the packet communication unit  30  can be reproduced at any desired later time, so that the processing required for turning the speech signal into the speech mail via the communication gateway  12  is now unnecessary, and the period of time required for the processing can be shortened together with lightening of the load on the communication gateway  12 . 
         [0041]    How to bypass the speech signal to an externally located telephone in the event of interruption of the power supply to the packet communication unit  30  will now be described by reference to  FIGS. 3A and 3B . In  FIGS. 3A and 3B , the reference numeral  40  designates a packet communication unit exhibiting a bypass function in the event of power supply interruption or down,  45  designates a control part having a function similar to that of the packet communication unit  30  shown in  FIG. 2 ,  41  designates an externally located telephone, and  42  designates a handset of the telephone  41 . The externally located telephone  41  has a power supply different from that for the packet communication unit  40 . The reference numerals  43  and  44  designate relay contacts switched over under control of the processor part  31  shown in  FIG. 2 . More concretely, under the state in which the power supply for the packet communication unit  40  is not turned on, the relay contact  44  is switched over to the position where the connection interface line  103  is connected to the line terminal of the telephone  41  as shown in  FIG. 3A , while the relay contact  43  is switched over to the position where the handset  42  is connected to the handset terminal of the telephone  41 . 
         [0042]    On the other hand, under the state in which the power supply for the packet communication unit  40  is turned on, the relay contact  44  is switched over to the position where the connection interface line  103  is connected to the line terminal of the telephone interface control part  34  shown in  FIG. 2  and included in the control part  45  as shown in  FIG. 3B , while the relay contact  43  is switched over to the position where the handset  42  is connected to the handset terminal of the switch part  36  shown in  FIG. 2  and included in the control part  45 . 
         [0043]    By the above manner of bypass control, the externally located telephone  41  can be used to secure the speech even in the event of interruption of the power supply to the packet communication unit  40 . The function of the externally located telephone  41  can be built in the packet communication unit  40  when the circuit is designed to utilize the power fed from the telephone exchange equipment. 
         [0044]    The packet transmitted to and received from the LAN  101  in the embodiments described above may be any one of a packet having a variable length and that having a fixed length. 
         [0045]    Although the above embodiments have been described by reference to the case where a speech signal is transmitted and received, it is apparent that the present invention is also applicable to the case of transmission and reception of a video signal or an image signal. Thus, a video telephone or the like can be connected to the conventional telephone network. In the case of transmission and reception of a video signal or an image signal, the display part  32  functions as the output unit, while an image input unit, such as, a television camera connected in place of the transmitter microphone of the handset functions as the input unit.