Abstract:
A method for diagnosing Voice-over-Broadband circuitry including an Integrated Access Device. The method includes receiving a request to initiate diagnosis, pulsing source voltages of tip and ring amplifiers in the circuitry, aggregating signal line noise resulting from the pulsing, analyzing the aggregated noise for hallmark indicia, and reporting findings of the analysis.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The invention claims priority from U.S. Provisional Application Ser. No. 60/230,492, filed Sep. 6, 2000, and entitled “System and Method for Diagnosing a POTS Port and Circuitry”, the disclosure of which in herein incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to Voice-over-Broadband (VoB) communication systems, and particularly to diagnostic assessments of the integrity of VoB systems.  
           [0004]    2. Discussion of the Prior Art  
           [0005]    VoB systems are known in the prior art. VoB system service users are typically referred to as subscribers. FIG. 1 shows a prior art VoB system  100 , which commences at one end with traditional Plain Old Telephone Service (POTS) devices  110  that receive and transmit analog voice signals over subscriber lines  115 . An Integrated Access Device (IAD)  130  digitizes/packetizes these analog voice signals into a broadband format and integrates the resultant voice packets with additional digital data provided by other customer premise equipment such as personal computer  120 . IAD  130  prioritizes voice packets over data packets to preserve transmitted voice signal quality. The voice and data packets are carried over the local broadband access network to an access multiplexer known as a Digital Subscriber Line Access Multiplexer (DSLAM)  140 . DSLAM  140  aggregates the packets, transports voice packets to a voice gateway  150  and transports data packets to the Internet  160 . Voice gateway  150  depacketizes voice packets and converts them to standard analog POTS signals for delivery via a Class  5  switch  165  to the Public Switched Telephone Network (PSTN)  170 .  
           [0006]    [0006]FIG. 2 shows details of IAD  130 . A POTS device  110  connected to the subscriber&#39;s line  115  is in turn connected with a Subscriber Line Interface Circuit (SLIC)  210 . The SLIC  210  has inputs for a primary battery supply (VBAT1)  220  and an auxiliary battery supply (VBAT2)  230 , and has a battery switching circuit  373  (FIG. 5) for connecting to VBAT1  220  to present a high on-hook voltage, and then connecting to VBAT2  230  to present a low off-hook voltage in short-loop applications. VBAT1 and VBAT2 are connected in series by a diode  225 . The diode serves as a protection device to prevent the VBAT1 (−68V) supply from going more positive than the VBAT2 (−24V) supply. This would happen if the VBAT1 supply failed, since VBAT1 voltage (−68V) is obtained by adding a −44 voltage to the VBAT2 supply. SLIC  210  passes analog POTS signals to a coder/decoder (CODEC)  240  and receives analog signals from CODEC  240 . CODEC  240  converts analog voice signals into broadband digital format, and vice versa. IAD  130  can include a digital signal processor (DSP)  250  for removing noise from the digital signals. Finally, IAD  130  employs a microprocessor controller (MPC)  260  as a central software-driven controller. MPC  260  can manipulate digital signals as necessary per the instructions of an installed software application, can receive state information from the various IAD  130  components, and can send digital control signals to the other components of IAD  130 . In particular, MPC  260  sends digital control inputs  270  to SLIC  210 , which control internal SLIC states. FIG. 2, for clarity, shows only one POTS port and only the processing of voice data. In practice, an IAD  130  also processes incoming digital data and includes multiple ports (typically in RJ-11 format) for connecting multiple POTS devices  110 .  
           [0007]    Thus the IAD  130  is a critical component of a VoB system. As VoB systems gain market share in the communications industry, IAD equipment will proliferate and it will become more important that VoB service providers have the ability to efficiently and cost effectively maintain IADs. Additionally, as users of traditional POTS devices shift to VoB service, it will become imperative, for the sake of customer relations, that VoB service providers give useful customer support regarding the low technology POTS devices. POTS devices rely on a simple two-wire loop for all their power and signaling needs and do not provide any diagnostic signaling. Thus, there is a need in the art of VoB communications for diagnostic tests on IAD equipment and POTS devices that do not require additional hardware modifications and associated costs (i.e., abide by the constraints of existing hardware designs) and do not require physical site visits for the purpose of conducting the diagnostic tests.  
         SUMMARY  
         [0008]    The invention encompasses a method for diagnosing Voice-over-Broadband circuitry including an Integrated Access Device. The method includes receiving a request to initiate diagnosis, pulsing source voltages of tip and ring amplifiers in the circuitry, aggregating signal line noise resulting from the pulsing, analyzing the aggregated noise for hallmark indicia, and reporting findings of the analysis.  
           [0009]    A system in accordance with the invention remotely diagnoses Voice-over-Broadband circuitry by pulsing the source voltages of the tip and ring amplifiers in the circuitry and analyzing the resultant noise for hallmark indicia. The system comprises a broadband line and an Integrated Access Device connected to the broadband line. The Integrated Access Device includes a controller connected to the broadband line, a coder/decoder connected to the controller, a Subscriber Line Interface Circuit connected to the coder/decoder, primary and auxiliary power sources connected to the Subscriber Line Interface Circuit, a Plain Old Telephone System port connected to the Subscriber Line Interface Circuit, and a signal line which interconnects the broadband line, controller, coder/decoder, Subscriber Line Interface Circuit, and Plain Old Telephone System port. The Subscriber Line Interface Circuit has tip and ring amplifiers and a switching circuit for pulsing the source voltage of the tip and ring amplifiers. The controller executes software to control the switching circuit into pulsing the source voltages of the tip and ring amplifiers in accordance with the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a high-level view of a prior art voice-over-broadband architecture;  
         [0011]    [0011]FIG. 2 shows additional detail of a prior art IAD;  
         [0012]    [0012]FIG. 3 shows hardware aspects of the present invention;  
         [0013]    [0013]FIG. 4 shows detail of the SLIC of FIG. 3;  
         [0014]    [0014]FIG. 5 is a voltage versus time graph that traces the frequency sweep pulse characteristics of one embodiment of the invention;  
         [0015]    [0015]FIG. 6 is noise plot for a first embodiment of the invention when a POTS device is connected to the IAD;  
         [0016]    [0016]FIG. 7 is a noise plot for a first embodiment of the invention when no POTS device is connected to the IAD;  
         [0017]    [0017]FIG. 8 is a voltage versus time graph that traces the fixed period pulse characteristics of a third embodiment of the invention;  
         [0018]    [0018]FIG. 9 is a noise plot for a third embodiment of the invention when both power supplies are functional and a POTS device is connected to the IAD;  
         [0019]    [0019]FIG. 10 is a noise plot for a third embodiment of the invention when both supplies are functional and no POTS device is connected to the IAD;  
         [0020]    [0020]FIG. 11 is a noise plot for a third embodiment of the invention when the primary power supply is disabled and a POTS device is connected to the IAD; and  
         [0021]    [0021]FIG. 12 is a noise plot for a third embodiment of the invention when the primary power supply is disabled and no POTS device is connected to the IAD.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The invention provides a system and method for remotely conducting various diagnostic tests of an IAD&#39;s circuitry and connection integrity with a POTS device  110 . FIG. 3 shows an IAD  130  configuration including a SLIC  210 , a VBAT1 power supply  220 , a diode  225 , a VBAT2 power supply  230 , a CODEC  240 , an optional DSP  250 , an MPC  260 , and digital control inputs  270 . MPC  260  is connected to a broadband line  310 , a DSLAM  140 , an RS- 232  port  320 , and an external computer  330 . From a hardware perspective, the invention is similar to, and requires no additional hardware or design modifications over, the FIG. 2 prior art. Thus, the invention addresses the prior art need for efficient maintenance and support of IADs and associated POTS devices.  
         [0023]    External computer  330  is optional and is most likely to be used only to initiate the diagnostic tests. Execution of the diagnostic tests of the invention does not require external computer processing. The detailed diagnostic test instructions and the collection and analysis of test data can all be done by a computer software application installed within IAD  130 , preferably within MPC  260 . Thus, the invention can be practiced as a software-only upgrade to the prior art IAD hardware  130 .  
         [0024]    The external computer, if used, can be either: (a) located remotely and connected via the broadband line  310  to the IAD  130 ; or (b) located locally and connected via the RS-232 port  320 .  
         [0025]    The technique of the invention pulses the internal IAD DC power supplies (VBAT1  220  and VBAT2  230 ), collects resultant noise signals within the IAD  130  and analyzes the data to determine the status of IAD circuitry and the integrity of connections with POTS devices. It should be noted that in one commercial embodiment the noise signals are measured using an AC coupled measuring system originally intended to digitize voice signals on the telephone line and block the VBAT2 battery voltage, which is present in addition to the voice signal. In other words, the measurements in that embodiment are of the AC transients (or the first derivative) of the DC pulsing. However, other embodiments can rely on DC coupled measurements and the methods and systems detailed here remain completely applicable. The only impact caused by using DC coupled noise measurements, as opposed to AC coupled noise measurements, is to the magnitude of the diagnostic threshold values, which will be discussed below.  
         [0026]    [0026]FIG. 5 shows high level details of SLIC  210 . SLIC  210  communicates analog signals via transmit line  390  and receive line  392  to and from CODEC  240  and communicates via a combined tip  394  and ring  396  loop  115  with a POTS device  110 . The tip-ring loop  115  is formed by a POTS device  110  on one end connected via a tip line  394  and a ring line  396  to an appropriate apparatus such as IAD  130 . Tip line  394  is referenced against ring line  396  and hence tip-ring loop  115  is considered a two-wire loop. In contrast, transmit line  390  is referenced against a ground line and receive line  392  is also referenced against a ground line. Hence, a counterpart four-wire conceptual loop (not shown) is formed by the interconnection of: (a) the hybrid circuit  371 ; (b) one pair of wires that represent the transmit line  390  and the ground wire it is referenced to; (c) and another pair of wires that represent the receive line  392  and the ground wire it is referenced to; and (d) a device downstream of the communication path that connects with the four wires. Thus, the hybrid circuit  371  interfaces a 2-wire loop to a 4-wire loop. This 4-to-2 arrangement is backwardly compatible with conventional POTS network architectures, which use a 2-wire loop for local transmission (i.e., near the POTS device) and use a 4-wire arrangement (one 2-wire loop for transmitting and another 2-wire loop for receiving) for long-range transmissions. Long-range wire transmissions require signal amplification which is made possible by separation of the receive and transmit analog signals.  
         [0027]    The 4-wire to 2-wire interface has been accomplished in the prior art using a hybrid transformer. SLIC  210  includes the 4-wire to 2-wire interface in the form of hybrid circuit  371 , which includes Op amps  370 ,  372 , and  374 . The tip drive amplifier  370  and the ring amplifier  372  have significance to the invention because the supply voltage of these two Op amps is pulsed as discussed below.  
         [0028]    SLIC  210  interfaces via a relay  398  to the tip and ring lines  394  and  396 , respectively. The relay  398  disconnects analog voice signals from the POTS device when the POTS device is “on-hook,” and connects the analog signals when “off-hook.” When the POTS device is “on-hook” the tip-ring loop alternatively connects the POTS device ring detector (not shown) to the IAD  130 .  
         [0029]    SLIC  210  also receives digital MPC control inputs  270 , which control internal SLIC states. SLIC  210  includes a battery feed state control circuit  386 , which, per the MPC instructions, controls the switching circuit  373  that receives battery supply voltages VBAT1  220  and VBAT2  230  and feeds the appropriate voltage to the tip drive  370  and ring drive  372  amplifiers. Switching circuit  373  has at least three connection states: (a) VBAT1 connection  380 —when VBAT1 is fed to the amplifiers; (b) forward disconnection  382 —when the tip and ring amplifiers are turned off; and (c) VBAT2 connection  384 —when VBAT2 is fed to the amplifiers.  
         [0030]    The invention pulses the source voltage of the tip amplifier  370  and ring amplifier  372  as follows. To conduct the diagnostic methods of the invention, MPC  260  (FIG. 3) executes a software algorithm which sends the necessary control signals on lines  270  to battery feed state control circuit  386  which, based in part on MPC  260  inputs, makes the necessary power switching decisions for the switching circuit  373  to make the appropriate physical connection to feed the tip and drive amplifiers  370  and  372 .  
         [0031]    Pulsing the amplifier voltage source in various manners presents unique pulse characteristics that establish different aspects of the invention. FIG. 5 is a voltage versus time graph  500  of one such pulse characteristic that can be used to remotely determine whether a POTS device  110 , in an on-hook state, is connected to IAD  130  and whether VBAT2 is functional. Graph  500  Y-axis  520  corresponds to the voltage applied to the tip  370  and ring  372  amplifiers during diagnostic tests of the invention, and the graph  500  X-axis  510  corresponds to time. The graph  500  voltage cycles have fixed length pulses  550  and increasingly longer cycle periods  540 . The voltage applied to the tip  370  and ring  372  amplifiers pulses from a near zero value (obtained by placing SLIC  210  in a forward disconnect state  382 ) to a VBAT2 value  530 . The increasingly long cycle periods  540  represent a frequency sweep, which is central to this embodiment of the invention.  
         [0032]    In this embodiment, the noise caused by pulsing the amplifiers is aggregated at the CODEC  240  and, according to another aspect of the invention, analyzed by the MPC  260 . Sweeping through a range of frequencies in the AC loading of the ring detector and/or ringer circuit of a POTS device  110  presents a non-linear response at the CODEC  240 .  
         [0033]    [0033]FIGS. 6 and 7 provide contrasting examples of empirical data collected in experimental runs of this aspect of the invention. The FIG. 6 graph  600  has an x-axis  610 , a y-axis  620 , and a series of spikes  630   a  through  630   q  representing noise data where a POTS device  110  is connected to the IAD  130 . The FIG. 7 graph  700  has an x-axis  710 , a y-axis  720 , and a series of spikes  730   a  through  730   n  representing noise data where no POTS device is connected to the IAD  130 . In both graphs  600  and  700 , the x-axis correlates to time while the y-axis correlates to the magnitude of the noise measured by the CODEC  240 . This frequency sweep causes two indicia in the noise response, which the diagnostic algorithm looks for. First, as a comparison of FIG. 6 and FIG. 7 reveals, the connection of a POTS device  110  causes noise amplitude to increase as pulse frequency decreases. Second, the connection of a POTS device  110  causes FIG. 6 noise spikes  630   a  through  630   q  that have maximum amplitude below an apparent threshold of approximately 1000 linearized codec counts, while FIG. 7 noise spikes  730   a  through  730   n  all exceed that threshold by a factor of about  30 . Thus, if the appropriate amplitude indicia are present, the MPC  260  can report that a POTS device  110  is connected to the IAD  130 . Additionally, the MPC  260  can report that VBAT2  230  is also functional.  
         [0034]    Not shown in FIG. 6 and in FIG. 7 is empirical data dealing with a disabled VBAT2. However, if VBAT2 were not functioning, the peak-to-peak voltage swing would drop below a predetermined threshold value. Thus, a diagnostic algorithm would assess the failure of VBAT2 by noting a peak-to-peak noise measurement that is below a defined algorithm.  
         [0035]    A second embodiment of the present invention is similar to the first embodiment but the DSP  250 , if present, is instructed not to filter out noise. Then, with the POTS device  110  in an on-hook state, the same frequency sweep is remotely executed and the resultant noise is allowed to propagate all the way up to the gateway  150  or even beyond the class  5  switch. At the remote site, presence of the necessary noise indicia indicates that all hardware components up to the SLIC  210  (including VBAT2  230 ) are functional.  
         [0036]    A second variation of the amplifier voltage source pulse characteristics provides a third embodiment of the invention. FIG. 8 shows a second pulse characteristic, which can be used to remotely assess some of the functionality in: the IAD batteries  220  and  260 , the SLIC  210  and associated switching circuits  373  and  386  and associated 4-wire to 2-wire hybrid circuit  371 , and the CODEC  240 .  
         [0037]    It should be noted that due to the protection diode between VBAT2 and VBAT1, VBAT1 can not be tested the same way VBAT2 is tested because even if VBAT1 fails, it will still have the VBAT2 voltage level due to the protection diode.  
         [0038]    [0038]FIG. 8 is a graph  800  with a y-axis  820  corresponding to the voltage applied to the tip  370  and ring  372  amplifiers during diagnostic testing and with an x-axis  810  corresponding to time. The graph  800  pulses have fixed duration cycle periods  840  and fixed duration pulses  850 . The voltage applied to the tip  370  and ring  372  amplifiers pulses from a VBAT2 value  830  (obtained by placing the SLIC  210  in a VBAT2 connection  384 ) to a VBAT1 value  835  (obtained by placing the SLIC  210  in a VBAT1 connection  380 ). The fixed cycle periods  840  are a central characteristic of this embodiment in contrast to the first and second embodiments where periodicity varies. In this third embodiment, as in the first and second embodiments, noise is aggregated at the CODEC  240  and analyzed by the MPC  260 .  
         [0039]    [0039]FIGS. 9 through 12 provide contrasting examples of empirical data collected in experimental runs of this fixed-frequency embodiment of the invention.  
         [0040]    [0040]FIG. 9 is a graph  900  having an x-axis  910  that correlates to time, a y-axis  920  that correlates to resultant noise magnitude, and a series of noise spikes  930   a  through  930   n . The empirical data of FIG. 9 has both VBAT1  220  and VBAT2  230  in a functional state and a POTS device  110  connected to IAD  130 .  
         [0041]    [0041]FIG. 10 is a graph  1000  having an x-axis  1010  that correlates to time, a y-axis  1020  that correlates to resultant noise magnitude, and a series of noise spikes  1030   a  through  1030   n . The empirical data of FIG. 10 has both VBAT1  220  and VBAT2  230  in a functional state but without a POTS device  110  connected to IAD  130 .  
         [0042]    [0042]FIG. 11 is a graph  1100  having an x-axis  1110  that correlates to time, a y-axis  1120  that correlates to resultant noise magnitude, and a series of noise spikes  1130   a  through  1130   z . The empirical data of FIG. 11 has VBAT1  220  in a disabled state and with a POTS device  110  connected to IAD  130 .  
         [0043]    Finally, FIG. 12 is a graph  1200  having an x-axis  1210  that correlates to time, a y-axis  1220  that correlates to resultant noise magnitude, and a series of noise spikes  1230   a  through  1230   q . The empirical data of FIG. 12 has VBAT1  220  in a disabled state but without a POTS device  110  connected to IAD  130 .  
         [0044]    A combined inspection of FIGS. 9 through 12 shows that a threshold indicia can be used to determine if the battery supplies  220  and  230  are functional, since the maximum amplitude of the noise spikes is overwhelmingly larger when both battery supplies  220  and  230  are functional versus when VBAT1  220  is disabled, irrespective of whether a POTS device  110  is connected to IAD  130 . Similar indicia can be used to assess the condition of other IAD  130  components. Thus, a third embodiment of the invention involves remotely initiating a pulsing of the tip  370  and ring  372  amplifiers in a fixed frequency mode. The resultant noise is aggregated at the CODEC  240  and analyzed by the MPC  260 . If the appropriate amplitude indicia are present, the MPC  260  can report on some of the functionality in: the IAD batteries  220  and  230 , the SLIC  210  and associated switching circuits  386  and  373  and the associated 4-wire to 2-wire hybrid circuit  371 , and the CODEC  240 .  
         [0045]    While the invention has been described herein with reference to three exemplary embodiments, they are for illustrative purposes only and not intended to be limiting. Therefore, those skilled in the art will recognize that other embodiments can be practiced without departing from the scope and spirit of the claims set forth below.