Abstract:
A telephone exchange apparatus includes a plurality of first interfaces each of which connects a first communication line for transmitting a voice packet and comprises an echo canceller that cancels an echo added to the voice packet, a second interface which connects a second communication line for transmitting an analog voice signal, and a controller which selectively connects between the first interfaces and between at least one of the first interfaces and the second interface, and controls the execution and stopping of the processing of the echo canceller according to a call setting request.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-372444, filed Oct. 31, 2003, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a telephone exchange apparatus to which an internet protocol (IP) network to transmit a voice packet can be connected and which has an echo canceller function of canceling an echo that is added to the voice packet. The invention also relates to a network telephone system to which a plurality of telephone exchange apparatuses are connected via the IP network.  
         [0004]     2. Description of the Related Art  
         [0005]     In recent years, the following system is proposed. A network telephone terminal (i.e., an internet Protocol (IP) telephone terminal) having a telephone call processing function and a media information processing function is connected to a local area network (LAN). The LAN is connected to an external communication network such as a public network via a main apparatus. The IP telephone terminal and the main apparatus carry out a protocol conversion and a data format conversion. With this arrangement, communications can be achieved between the IP telephone terminals and between the IP telephone terminal and the external communication network.  
         [0006]     In this type of system, an echo is added to a voice signal when the IP telephone terminal is connected to an office line in the main apparatus. To overcome this problem, a main apparatus that has an echo canceller function of canceling the echo added to the voice signal is investigated, as disclosed (see, for example, Document 1: U.S. Pat. No. 6,404,887, B1).  
         [0007]     The echo canceller function is incorporated in an IP interface unit that connects the IP telephone terminal. This function works effectively when the IP telephone terminal is connected with the office line. However, when the IP telephone terminals having small influence of the echo are connected to each other, the echo canceller function becomes unstable. Particularly, in the IP telephone system, a plurality of main apparatuses are connected via the IP network. In this case, the echo cancellers are in multiple connection, which makes the echo canceling operation unstable.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     It is an object of the present invention to provide a telephone exchange apparatus and a network telephone system capable of effectively canceling the echo added to the voice signal even when a plurality of mutually different communication lines are handled or when the echo cancellers are in multiple connection.  
         [0009]     According to an aspect of the present invention, there is provided a telephone exchange apparatus comprising: a plurality of first interfaces each of which connects a first communication line for transmitting a voice packet and comprises an echo canceller that cancels an echo added to the voice packet; a second interface which connects a second communication line for transmitting an analog voice signal; and a controller which selectively connects between the first interfaces and between at least one of the first interfaces and the second interface, and controls the execution and stopping of the processing of the echo canceller according to a call setting request.  
         [0010]     According to another aspect of the present invention, there is provided a network telephone system which comprises two or more telephone exchange apparatuses each of which connects between a first communication line for transmitting a plurality of voice packets and a second communication line for transmitting an analog voice signal, and connects between a plurality of the telephone exchanges with a third communication line for transmitting a voice packet, the network telephone system comprising: a first interface which connects the first communication line, and comprises an echo canceller which cancels an echo added to the voice packet, in each of the plurality of telephone exchange apparatuses; a second interface which connects the second communication line, in each of the plurality of telephone exchange apparatuses; a third interface which connects the third communication line, and comprises an echo canceller that cancels an echo added to the voice packets, in each of the plurality of telephone exchange apparatuses; a deciding circuit to decide a connection request origin and a connection request destination in a receiver-side telephone exchange, to generate a result of decision, when the connection request using the third communication line occurs; and a controller which controls execution and stopping of the echo canceller processing based on the result of decision.  
         [0011]     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0012]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
         [0013]      FIG. 1  is a diagram of an approximate configuration of an exchange system according to a first embodiment of the present invention.  
         [0014]      FIG. 2  is a diagram showing a relationship between number of echo cancellers in multiple connection and an echo convergence time.  
         [0015]      FIG. 3  is a flowchart of control procedure of the echo canceller according to the first embodiment.  
         [0016]      FIG. 4  is a diagram of an approximate configuration of an exchange system according to a second embodiment of the present invention.  
         [0017]      FIG. 5  is a flowchart of an incoming call processing operation of a main apparatus as a call origin according to the second embodiment.  
         [0018]      FIG. 6  is a flowchart of an echo canceller control procedure of a main apparatus as a call destination according to the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The embodiment of the present invention will be explained in detail with reference to the drawings.  
         [0000]     (First Embodiment)  FIG. 1  is a diagram of an approximate configuration of an exchange system according to a first embodiment of the present invention.  
         [0020]     As shown in  FIG. 1 , the exchange system includes a main apparatus  1 , and a plurality of IP telephone terminals  2  ( 2 - 1  to  2 - i ) and  3  ( 3 - 1  to  3 - j ) that are connected optionally to the main apparatus  1  via LANs  4  and  5  respectively.  
         [0021]     The main apparatus  1  has a control unit  11 , IP extension interface circuits  12  and  13  (hereinafter referred to as IP extension I/Fs  12  and  13 ), and an office line interface circuit  14  (hereinafter referred to as an office line I/F  14 ). The control unit  11 , the IP extension I/Fs  12  and  13 , and the office line I/F  14  are connected to each other via a bus  15 .  
         [0022]     The control unit  11  optionally exchanges and connects the IP extension I/Fs  12  and  13  and the office line I/F  14 .  
         [0023]     The IP telephone terminal  2  is connected to the IP extension I/F  12  when necessary. The IP extension I/F  12  carries out an extension interface operation concerning the connected IP telephone terminal  2 . The IP extension I/F  12  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  11  via the bus  15 .  
         [0024]     The IP telephone terminal  3  is connected to the IP extension I/F  13  when necessary. The IP extension I/F  13  carries out an extension interface operation concerning the connected IP telephone terminal  3 . The IP extension I/F  13  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  11  via the bus  15 .  
         [0025]     An office line L to be connected to a public network NW is connected to the office line I/F  14  when necessary. The office line I/F  14  carries out the interface operation concerning the connected office line L. The office line I/F  14  also gives and receives various kinds of control information concerning the interface operation with the control unit  11  via the bus  15 .  
         [0026]     The IP extension I/Fs  12  and  13  have echo cancellers  121  and  131  respectively that cancel an echo added to the voice signal. The control unit  11  controls to execute or stop a processing of the echo cancellers  121  and  131 .  
         [0027]     The operation of the exchange system having the above configuration will be explained next.  
         [0028]     When telephone calls are carried out between the IP telephone terminal  2 - 1  and the IP telephone terminal  3 - 1 , the echo cancellers  121  and  131  are in multiple connection. In general, when the echo cancellers  121  and  131  are in multiple connection, the convergence time of echo may become long, or the echo may not be converged in the worst case, as shown in  FIG. 2 .  
         [0029]     To cope with this situation, the control unit  11  controls to execute or stop the echo cancellers  121  and  131  according to the call setting request.  FIG. 3  is a flowchart of the processing operation of the control unit  11 .  
         [0030]     Assume that the IP telephone terminal  2 - 1  transmits a call to a subscriber telephone terminal of the pubic network NW, and that the incoming call arrives at the main apparatus  1  via the LAN  4  accordingly. Then, the IP extension I/F  12  detects the incoming call, and notifies the arrival of the incoming call to the control unit  11  via the bus  15 .  
         [0031]     The control unit  11  analyzes the dial number of a call destination based on the notified incoming call, and decides whether a call destination unit has a hybrid circuit based on the result of the analysis (step ST 3   a ). When the control unit  11  decides that the call destination is the public network NW (YES at step ST 3   a ), the control unit  11  operates the echo canceller  121  (step ST 3   b ).  
         [0032]     On the other hand, assume that the IP telephone terminal  2 - 1  transmits a call to the IP telephone terminal  3 - 2 , and that the incoming call arrives at the main apparatus  1  via the LAN  4  accordingly. When the control unit  11  decides that the call destination is the IP telephone terminal  3 - 2  (NO at step ST 3   a ), the control unit  11  stops the echo cancellers  121  and  131  (step ST 3   c ).  
         [0033]     When the call origin is a subscriber telephone terminal of the public network NW, a similar processing operation is carried out.  
         [0034]     As explained above, according to the first embodiment, the control unit  11  has the control function of executing or stopping the processing of the echo cancellers  121  and  131 . Therefore, when the IP extension I/Fs  12  and  13  having small influence of echo are connected, the control unit  11  controls to stop the echo cancellers  121  and  131 . When the IP extension I/F  12  is connected to the office line I/F  14 , the control unit  11  controls to execute the echo canceller  121 . In this way, only an optimum echo canceller can be operated for each connected communication line.  
         [0000]     (Second Embodiment)  
         [0035]      FIG. 4  is a diagram of an approximate configuration of an exchange system according to a second embodiment of the present invention.  
         [0036]     As shown in  FIG. 4 , the exchange system has main apparatuses  6  and  7  that are connected to each other via a LAN  8 . The main apparatus  6  optionally connects each of a plurality of IP telephone terminals T 1  (T 11  to T 1   n ) via a LAN  9 - 1 . The main apparatus  7  optionally connects each of a plurality of IP telephone terminals T 2  (T 21  to T 2   m ) via a LAN  9 - 2 .  
         [0037]     The main apparatus  6  has a control unit  61 , an IP extension interface circuit  62  (hereinafter referred to as an IP extension I/F  62 ), an IP network interface circuit  63  (hereinafter referred to as a network I/F  63 ), and an office line interface circuit  64  (hereinafter referred to as an office line I/F  64 ). The control unit  61 , the IP extension I/F  62 , the network I/f  63 , and the office line I/F  64  are connected to each other via a bus  65 .  
         [0038]     The control unit  61  optionally exchanges and connects the IP extension I/F  62 , the network I/F  63 , and the office line I/F  64 .  
         [0039]     The IP telephone terminal T 1  is connected to the IP extension I/F  62  when necessary. The IP extension I/F  62  carries out an extension interface operation concerning the connected IP telephone terminal T 1 . The IP extension I/F  62  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  61  via the bus  65 .  
         [0040]     The LAN  8  is connected to the network I/F  63  when necessary. The network I/F  63  carries out the extension interface operation concerning the connected LAN  8 . The network I/F  63  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  61  via the bus  65 .  
         [0041]     The office line L to be connected to a public network NW- 1  is connected to the office line I/F  64  when necessary. The office line I/F  64  carries out the interface operation concerning the connected office line L. The office line I/F  64  also gives and receives various kinds of control information concerning the interface operation with the control unit  61  via the bus  65 .  
         [0042]     The IP extension I/F  62  and the network I/F  63  have echo cancellers  621  and  631  respectively that cancel the echo added to the voice signal. The control unit  61  controls to execute or stop the processing of the echo cancellers  621  and  631 .  
         [0043]     On the other hand, the main apparatus  7  has a control unit  71 , an IP extension interface circuit  72  (hereinafter referred to as an IP extension I/F  72 ), an IP network interface circuit  73  (hereinafter referred to as a network I/F  73 ), and an office line interface circuit  74  (hereinafter referred to as an office line I/F  74 ). The control unit  71 , the IP extension I/F  72 , the network I/F  73 , and the office line I/F  74  are connected to each other via a bus  75 .  
         [0044]     The control unit  71  optionally exchanges and connects the IP extension I/F  72 , the network I/F  73 , and the office line I/F  74 .  
         [0045]     The IP telephone terminal T 2  is connected to the IP extension I/F  72  when necessary. The IP extension I/F  72  carries out an extension interface operation concerning the connected IP telephone terminal T 2 . The IP extension I/F  72  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  71  via the bus  75 .  
         [0046]     The LAN  8  is connected to the network I/F  73  when necessary. The network I/F  73  carries out the extension interface operation concerning the connected LAN  8 . The network I/F  73  also gives and receives various kinds of control information concerning the extension interface operation with the control unit  71  via the bus  75 .  
         [0047]     The office line L to be connected to a public network NW- 2  is connected to the office line I/F  74  when necessary. The office line I/F  74  carries out the interface operation concerning the connected office line L. The office line I/F  74  also gives and receives various kinds of control information concerning the interface operation with the control unit  71  via the bus  75 .  
         [0048]     The IP extension I/F  72  and the network I/F  73  have echo cancellers  721  and  731  respectively that cancel the echo added to the voice signal. The control unit  71  controls to execute or stop the processing of the echo cancellers  721  and  731 .  
         [0049]     The operation of the exchange system having the above configuration will be explained next.  
         [0050]      FIG. 5  is a flowchart of the processing operation of the control unit  61 .  
         [0051]     Assume that the IP telephone terminal T 11  transmits a call to a subscriber telephone terminal of the public network NW- 2 , and that an incoming call arrives at the main apparatus  6  via the LAN  9 - 1  accordingly (step ST 5   a ). Then, the IP extension I/F  62  detects the incoming call, and notifies the arrival of the incoming call to the control unit  61  via the bus  65 .  
         [0052]     The control unit  61  analyzes the dial number of a call destination based on the notified incoming call (step ST 5   b ), and decides whether a call destination is the main apparatus  7  based on the result of the analysis (step ST 5   c ). When the control unit  61  decides that the call destination is the main apparatus  7  (YES at step ST 5   c ), the control unit  61  transmits the incoming call to the main apparatus  7  via the LAN  8  (step ST 5   d ). In this case, the echo cancellers  621  and  631  are stopped.  
         [0053]     On the other hand, when the call destination is the main apparatus  6  (NO at step ST 5   c ), the control unit  61  controls the execution or stopping of the echo canceller  621  (step ST 5   e ).  
         [0054]      FIG. 6  is a flowchart of the processing operation of the control unit  71 .  
         [0055]     The control unit  71  always monitors the arrival of an incoming call (step ST 6   a ). When an incoming call arrives (YES at step ST 6   a ), the control unit  71  decides whether a call destination unit has a hybrid circuit (step ST 6   b ). When the control unit  71  decides that the call destination is the public network NW- 2  (YES at step ST 6   b ), the control unit  71  operates the echo canceller  731  (step ST 6   c ).  
         [0056]     On the other hand, assume that the IP telephone terminal Tll transmits a call to the IP telephone terminal T 21 , and that an incoming call arrives at the main apparatus  7  via the LAN  8  accordingly. When the control unit  71  decides that the call destination is the IP telephone terminal T 21  (NO at step ST 6   b ), the control unit  71  stops the echo cancellers  721  and  731  (step ST 6   d ).  
         [0057]     When the call origin is a subscriber telephone terminal of the public network NW- 1 , a similar processing operation is carried out.  
         [0058]     As explained above, according to the second embodiment, when the main apparatus  6  that receives the incoming call decides that the call destination is the public network NW- 2 , only the echo canceller  731  provided in the network I/F  73  within the main apparatus  7  is used.  
         [0059]     Therefore, it is possible to prevent a wasteful use of the echo cancellers  621  and  631 . Consequently, the effective utilization rate of the echo cancellers  621 ,  631 , and  731  can be increased, and the whole system can reduce power consumption.  
         [0000]     (Other Embodiments)  
         [0060]     The present invention is not limited to the above embodiments. For example, the call origin is explained as the IP telephone terminal in the above embodiments. However, when the call origin is an analog telephone terminal and the call destination is the IP telephone terminal, the execution and stopping of the echo cancellers can be controlled in a similar manner.  
         [0061]     While two main apparatuses are connected in the second embodiments, two or more main apparatuses can be also connected.  
         [0062]     Configurations and types of the system, configurations and types of the exchange such as the main apparatus, and control procedures of the echo cancellers can be modified within a range not deviating from the gist of the present invention.  
         [0063]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.