Abstract:
A method and apparatus accurately and reliably perform a dying gasp process for an external digital subscriber line communication terminal connected to a personal computer via the Ethernet. The state of an Ethernet port of the communication terminal connectable to the personal computer is sensed, and whether the Ethernet port is made inactive after the Ethernet port is made active is checked. The dying gasp process is performed upon sensing the occurrence of the inactive state of the Ethernet port after the Ethernet port is made active.

Description:
CLAIM OF PRIORITY  
         [0001]    This application claims priority to an application entitled “METHOD AND APPARATUS FOR PERFORMING DYING GASP PROCESS OF EXTERNAL DIGITAL SUBSCRIBER LINE COMMUNICATION TERMINAL”, filed in the Korean Industrial Property Office on Aug. 16,2001 and assigned Serial No. 2001-49232, the contents of which are hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates to a digital subscriber line communication terminal and, more particularly, to a method and apparatus for performing a dying gasp process for an external digital subscriber line communication terminal that is connected to a personal computer (PC) via the is Ethernet.  
           [0004]    2. Description of the Related Art  
           [0005]    A digital subscriber line, typically denoted by “xDSL”, relates to a high-speed modem technique that is being developed to meet the market demand for large-scale high-speed Internet access. The digital subscriber line also relates to a public network technique that supports a broad bandwidth at a limited distance using an existing copper telephone wire (twisted pair wire). This xDSL involves various kinds of techniques, such as an asymmetric digital subscriber line (ADSL), a high-bit-rate DSL (HDSL), a single-line DSL (SDSL), a single-pair high-speed SDSL (SHDSL), a very-high-data-rate DSL (VDSL), and so forth.  
           [0006]    In an ADSL network model of the xDSL, an ADSL transceiver unit-central (ATU-C) in a central office and an ADSL transceiver unit-remote (ATU-R) in a subscriber branch are interconnected via an ADSL using an existing telephone wire. Also, the ATU-C is connected to a network, and the ATU-R is connected to a PC via an Ethernet link. The Ethernet link is provided by local area network (LAN) interface logic in the ATU-R, a LAN card in the PC, and a LAN cable interconnecting them.  
           [0007]    A user of the PC can gain access to the network (for example, the Internet) via the ATU-R, the ADSL and the ATU-C. The ATU-R used for Internet access by the PC user in the ADSL network is so-called customer premise equipment (CPE) that is an external xDSL communication terminal.  
           [0008]    While maintaining the ADSL connection in the above manner, the CPE may perform a dying gasp process to terminate the ADSL connection due to, for example, the ending of Internet use by the user. The dying gasp signifies that the CPE sends a connection release message to a central system, as prescribed in ANSI T1.413, ITU-T 992.2 and ITU-T 992.1.  
           [0009]    A dying gasp processor of the CPE comprises a sensing circuit for generating an interrupt signal upon sensing a turned-off state of the CPE, and a CPE controller or central processing unit (CPU) for performing the dying gasp process in response to the interrupt signal from the sensing circuit. LAN interface logic is connected to the CPU and also, via the LAN cable, to the LAN card so as to provide the Ethernet link as stated previously. An input voltage is supplied to the CPE as an operating voltage to each component in the CPE through a capacitor, a diode and another capacitor. The sensing circuit includes an operational amplifier and resistors, and is connected between an input voltage source and the CPU. The operational amplifier has a non-inverting input terminal (+) connected to the input voltage source through the capacitor, an inverting input terminal (−) connected to ground through a first resistor, and an output terminal connected to the inverting input terminal (−) through a second resistor. When the input voltage falls below a predetermined level as the CPE is turned off, the operational amplifier generates an interrupt signal of logic “low”, and applies the generated interrupt signal to the CPU. Subsequently, in response to the interrupt signal from the operational amplifier, the CPU is interrupted so as to perform the dying gasp process. At this time, even though the CPE is turned off, the operating voltage continues to be supplied to the CPU due to charging voltages on the capacitors and, for a certain period of time, is required for the dying gasp process.  
           [0010]    As mentioned above, the dying gasp processor performs the dying gasp process by sensing, in a hardware manner, the moment when the CPE is turned off. That is, the processor has to sense the moment that the level of the input voltage drops, resulting in a reduction in accuracy of the dying gasp process. Further, the dying gasp process cannot be carried out when the user disconnects the xDSL connection under the condition that the CPE is not turned off. Furthermore, an additional hardware module, or sensing circuit, is required to sense the moment that the CPE is turned off.  
           [0011]    The following are considered to be generally pertinent to the present invention but are burdened by the disadvantages set forth above:  
           [0012]    U.S. Pat. No. 5,255,317 to Arai et al., which discloses a subscriber line interface circuit for serving ISDN subscribers using echo cancellers and POTS subscribers, issued Oct. 19, 1993;  
           [0013]    U.S. Pat. No. 5,408,260 to Amon, which discloses a customer premises ADSL signal distribution arrangement, issued Apr. 18, 1995;  
           [0014]    U.S. Pat. No. 5,410,343 to Coddington et al., which discloses a video-on-demand services using public switched telephone network, issued Apr. 25, 1995;  
           [0015]    U.S. Pat. No. 5,461,616 to Suzuki, which discloses an asymmetric digital subscriber line control system, issued Oct. 24, 1995;  
           [0016]    U.S. Pat. No. 5,519,731 to Cioffi, which discloses an ADSL compatible discrete multi-tone apparatus for mitigation of T1 noise;  
           [0017]    U.S. Pat. No. 5,771,279 to Cheston, III et al., which discloses an advanced intelligent network interacting with customer premises equipment, issued Jun. 23, 1998;  
           [0018]    U.S. Pat. No. 5,754,555 to Hurme et al, which discloses a subscriber network arrangement for connecting subscribers to a telephone network, issued May 19, 1998;  
           [0019]    U.S. Pat. No. 5,889,856 to O&#39;Toole et al., which discloses an ADSL integrated line card with digital splitter and POTS CODEC without bulky analog splitter, issued May 30, 1999;  
           [0020]    U.S. Pat. No. 6,263,016 to Bellenger et al., which discloses methods for interfacing a subscriber link to digital networks, issued Jul. 17, 2001;  
           [0021]    U.S. Pat. No.6,272,209 to Bridger et al., which discloses a lifeline telephony provision for voice over digital subscriber line; and  
           [0022]    U.S. Pat. No. 6,324,212 to Jenness, which discloses an apparatus using low spectrum selectively for proving both ADSL and POTS service, issued Nov. 27, 2001.  
         SUMMARY OF THE INVENTION  
         [0023]    Therefore, the present invention has been developed in view of the above problems, and it is an object of the present invention to provide a method and apparatus for performing a dying gasp process accurately and reliably.  
           [0024]    It is another object of the present invention to provide a method and apparatus for performing a dying gasp process without using additional hardware.  
           [0025]    In accordance with the present invention, the above and other objects can be accomplished by the provision of a method and apparatus for accurately and reliably performing a dying gasp process for an external digital subscriber line communication terminal that is connected to a personal computer via the Ethernet. The state of an Ethernet port of the communication terminal connectable to the personal computer is sensed, and whether the Ethernet port is made inactive is checked after the Ethernet port is made active. The dying gasp process is performed upon sensing the inactive state of the Ethernet port after the Ethernet port is made active. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference numerals indicate the same or similar components, and wherein:  
         [0027]    [0027]FIG. 1 is a schematic view of a typical ADSL network model;  
         [0028]    [0028]FIG. 2 is a circuit diagram of a dying gasp processor of a CPE;  
         [0029]    [0029]FIG. 3 is a block diagram showing the construction of a dying gasp processor of a CPE in accordance with the present invention; and  
         [0030]    [0030]FIG. 4 is a flowchart illustrating the operation of the dying gasp processor of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.  
         [0032]    [0032]FIG. 1 schematically shows the construction of an ADSL network model as an example of the xDSL. As shown in this drawing, an ATU-C  102  in a central office and an ATU-R  104  in a subscriber branch are interconnected via an ADSL  108  using an existing telephone wire. Also, the ATU-C  102  is connected to a network  100 , and the ATU-R  104  is connected to a PC  106  via an Ethernet link  110 . The Ethernet link  110  is provided by local area network (LAN) interface logic (not shown) in the ATU-R  104 , a LAN card (not shown) in the PC  106 , and a LAN cable interconnecting them.  
         [0033]    A user of the PC  106  can gain access to the network  100  (for example, the Internet) via the ATU-R  104 , the ADSL  108  and the ATU-C  102 . The ATU-R  104  used for Internet access by the use of PC  106  in the ADSL network is the so-called CPE, which is an external xDSL communication terminal.  
         [0034]    While maintaining the ADSL connection in the above manner, the CPE may perform a dying gasp process to terminate the ADSL connection due to, for example, the ending of the Internet use by the user. The dying gasp signifies that the CPE sends a connection release message to a central system, as prescribed in ANSI T1.413, ITU-T 992.2 and ITU-T 992.1.  
         [0035]    [0035]FIG. 2 is a circuit diagram of a dying gasp processor of the CPE. As shown in this drawing, the dying gasp processor comprises a sensing circuit  204  for generating an interrupt signal upon sensing a turned-off state of the CPE, and a CPE controller or central processing unit (CPU)  200  for performing a dying gasp process in response to the interrupt signal from the sensing circuit  204 . LAN interface logic  202  is connected to the CPU  200  and also, via a LAN cable, to the LAN card in the PC  106  of FIG. 1 so as to provide the Ethernet link as stated previously. An input voltage to the CPE is supplied as an operating voltage to each component in the CPE through a capacitor  212 , diode  214  and capacitor  216 . The sensing circuit  204  includes an operational amplifier  206  and resistors  208  and  210  connected between an input voltage source and the CPU  200 . The operational amplifier  206  has a non-inverting input terminal (+) connected to the input voltage source through the capacitor  212 , an inverting input terminal (−) connected to ground through the resistor  210 , and an output terminal connected to the inverting input terminal (−) through the resistor  208 . When the input voltage falls below a predetermined level as the CPE is turned off, the operational amplifier  206  generates an interrupt signal of logic “low”, and applies the generated interrupt signal to the CPU  200 . Subsequently, the CPU  200  is interrupted in response to the interrupt signal from the operational amplifier  206  so as to perform the dying gasp process. At this time, even though the CPE is turned off, the operating voltage continues to be supplied to the CPU  200 , owing to charging voltages on the capacitors  212  and  216 , for a certain period of time required for the dying gasp process.  
         [0036]    As mentioned above, the dying gasp processor performs the dying gasp process by sensing, in a hardware manner, the moment that the CPE is turned off. That is, the processor has to sense the moment that the level of the input voltage drops, resulting in a reduction in accuracy of the dying gasp process. Further, the dying gasp process cannot be carried out when the user disconnects the xDSL connection under the condition that the CPE is not turned off. Furthermore, an additional hardware module, or sensing circuit, is required to sense the moment that the CPE is turned off.  
         [0037]    [0037]FIG. 3 is a block diagram showing the construction of a dying gasp processor of a CPE in accordance with the present invention. With reference to FIG. 3, there is shown in block form the construction of a dying gasp processor of a CPE in accordance with the present invention. The CPU  200 , which is the CPE controller connected to the LAN interface logic  202  as described previously with reference to FIG. 2, includes an Ethernet link sensing module  302  and a dying gasp processing module  300 . The Ethernet link sensing module  302  and dying gasp processing module  300  are software modules executed by the CPU  200  in the typical CPE. Typically, the Ethernet link sensing module  302  functions to sense the state of an Ethernet port of the LAN interface logic  202 , and the dying gasp processing module  300  functions to perform a dying gasp process.  
         [0038]    If the user turns on the PC  106  as shown in FIG. 1 to use the xDSL, then the PC  106  is connected to the CPE via the Ethernet link  110 , thereby causing the Ethernet port to be made active. Thereafter, if the user ends the xDSL use and turns off the PC  106 , then the connection between the PC  106  and the CPE via the Ethernet link  110  is released, thus making the Ethernet port inactive. According to the present invention, the dying gasp processor performs the dying gasp process using the fact that the Ethernet port is made inactive as the PC  106  and the Ethernet of the CPE are electrically isolated from each other.  
         [0039]    A detailed description will hereinafter be given of the operation of the dying gasp processor with the above-stated construction in accordance with the present invention in conjunction with steps  400 - 404  in FIG. 4, which is a flowchart illustrating the operation of the dying gasp processor of FIG. 3. When the connection between the PC  106  and the CPE via the Ethernet link  110  is established in response to the turned-on state of the PC  106  and the Ethernet port is thus made active, then the Ethernet link sensing module  302  senses the active state of the Ethernet port at step  400 , and checks at step  402  whether the Ethernet port is made inactive. Thereafter, if the user ends the xDSL use and turns off the PC  106 , then the connection between the PC  106  and the CPE via the Ethernet link  110  is released, thus making the Ethernet port inactive. The Ethernet link sensing module  302  senses the inactive state of the Ethernet port at step  402 , and notifies the dying gasp processing module  300  of the sensed inactive state at step  404 . As a result, the dying gasp processing module  300  performs the dying gasp process in response to the inactive state of the Ethernet port.  
         [0040]    As is apparent from the above description, according to the present invention, the dying gasp processor can accurately perform the dying gasp process by sensing, on the basis of the inactivation of the Ethernet port, the moment that the PC  106  and the CPE are electrically isolated from each other. Further, the dying gasp process can be carried out even when the user disconnects the xDSL connection under the condition that the CPE is not turned off. Furthermore, the dying gasp process is performed by the sensing of the inactive state of the Ethernet port by the Ethernet link sensing module  300 , which is used in the typical CPE to sense the Ethernet port state. As a result, there is no need for additional hardware required to sense the moment that the CPE is turned off.  
         [0041]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the accompanying claims. For example, the PC  106  and the CPE may be interconnected via a universal serial bus (USB) although they have been disclosed herein as being interconnected via the Ethernet.