Apparatus and method for enabling automatic measurement of performance in a telephony communication system

An apparatus and method are provided for obtaining, from an analog subscriber loop, test data that may be used to test the performance of a telephony communication system. The apparatus includes a digital-to-analog (D/A) converter, a first port, a second port, and an analog-to-digital (A/D) converter. The D/A converter receives digital data and converts the digital data into a first analog signal. The first port transmits the first analog signal across a first subscriber loop to a telephony communication network. The network, via A/D and D/A conversion, translates the first analog signal to a second analog signal and transmits the second analog signal to the second port via a second subscriber loop. The A/D converter receives the second analog signal from the second port and converts the second analog signal into the digital test data, which is then used to analyze the performance of the telephony communication system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to telephony performance measurement techniques and, in particular, to an apparatus and method for interfacing with an analog subscriber loop of a telephony communication system and for obtaining, from the subscriber loop, test data that may be used to test the performance of the telephony communication system.

2. Related Art

Initially, telephony networks provided an end-to-end analog communication connection for voice communication. During a telephone call, a user would speak into a telephone, which was coupled to an analog connection, referred to as a “subscriber loop.” The telephone would convert the user's voice into analog signals and transmit the analog signals across the subscriber loop to an analog network, such as the well known publicly switched telephone network (PSTN). The PSTN would then route the analog signals through various analog connections to another subscriber loop coupled to another telephone that receives the analog signals. The receiving telephone then converted the analog signals into sound so that a user at the receiving telephone could hear the conversation of the user at the transmitting telephone.

Each communication connection segment used to transmit the signals from the transmitting telephone to the receiving telephone was analog such that a single end-to-end analog communication connection was effectively provided that communicated the analog signals of the telephone call between the two telephones. Although there was a delay in transmitting from one telephone to the other telephone, each analog signal experienced approximately the same delay. Therefore, as long as the delay was small (e.g., on the order of about one second or less), users did not usually notice the delay.

Although most end-to-end analog communications were fairly reliable, problems sometimes developed that would cause excessive noise, cross-talk, or other similar performance degrading effects. To test the quality of the signals communicated by the analog network, an operator would usually place a call and listen to the sound produced by the analog signals transmitted through the network. If the operator detected significant performance degradation, such as significant noise, cross-talk, etc., the communication segments and devices used to transmit the signals would be further tested in an attempt to isolate and correct the problems causing the performance degradation.

Recently, many telephony networks have been redesigned to communicate digitally to improve the performance of the networks. However, due primarily to the expense of installing digital subscriber loops, many of the subscriber loops used to transmit voice signals have remained analog. Therefore, during a telephone call, a user typically speaks into a telephone that converts the user's voice into analog signals. These analog signals are then transmitted across an analog subscriber loop to a digital telephony network. At some point in the digital network, the analog signals are converted into digital signals and transmitted across digital connections. Prior to being communicated across the subscriber loop coupled to the receiving telephone, the digital signals are converted back into analog signals so that the signals are compatible with the subscriber loop. Therefore, the operation of the foregoing digital telephony network is similar to prior analog telephony networks, except that the signals communicated by the foregoing digital telephony network are converted into digital signals for transmission across at least a portion of the network.

Unfortunately, the conversion of the analog signals into digital signals can cause certain problems. For example, the digital portion of some networks utilizes packet switching techniques, in which the digital signals are transmitted as separate packets through the digital portion of the network. Although the packets are transmitted from the same beginning point and the same ending point within the digital portion of the network, the path for each packet may be different. Therefore, the delay experienced by each packet may be significantly different than the delay experienced by other packets. When the packets are received at the ending point, the packets are reassembled into the correct order before being converted back into analog signals so that the analog signals accurately represent the conversation being communicated. The aforementioned packet switching techniques introduce a delay, which is sometimes noticeable by the users associated with the telephone call.

Due to the various problems that can be caused by utilizing a digital network in communicating voice signals, such as the delay introduced by packet switching, it is desirable to test the transmission quality of digital telephony networks more frequently as compared to traditional analog telephony networks. Therefore, various devices that enable automatic testing of voice signals in a digital telephony network have been developed. However, most of these devices are designed to interface with the digital portion of the telephony network and are designed to test the digital signals being communicated by the digital portion of the telephony network. The inventor of the present invention believes that a superior voice quality testing device can be implemented, if the testing device is interfaced at an analog end of the network and is configured to test the analog signals communicated at this analog end during a telephone call.

Thus, a heretofore unaddressed need exists in the industry for providing an improved apparatus and method for enabling automatic testing of voice signals at an analog end of a digital telephony network.

SUMMARY OF THE INVENTION

The present invention overcomes the inadequacies and deficiencies of the prior art as discussed hereinbefore. Generally, the present invention provides an apparatus and method for obtaining digital test data from an analog subscriber loop that may be used to test a telephony communication system.

In architecture, the present invention includes a digital-to-analog (D/A) converter, a first port, a second port, and an analog-to-digital (A/D) converter. The D/A converter receives digital data and converts the digital data into a first analog signal. The first port transmits the first analog signal across a first subscriber loop to a telephony communication network. The network, via A/D and D/A conversion, translates the first analog signal to a second analog signal and transmits the second analog signal to the second port via a second subscriber loop. The A/D converter receives the second analog signal from the second port and converts the second analog signal into digital test data, which is then used to analyze the performance of the telephony communication system.

In accordance with another feature of the present invention, a first digital signal processor is utilized to transmit the first analog signal via the first port, and a second digital processor is utilized to receive the second analog signal via the second port. As a result, signals may be simultaneously communicated via the first and second ports.

In accordance with another feature of the present invention, session control logic may be used to automatically control a hook status of the foregoing system and to establish a communication session via the first and second ports.

In accordance with another feature of the present invention, the system of the present invention may be implemented on a PCI card and interfaced with a personal computer that is configured to render data indicative of performance of the telephony communication system based on the information obtained by the system of the present invention.

In accordance with another feature of the present invention, additional ports may be included to enable communication via different types of signaling.

The present invention can also be viewed as providing a method for obtaining digital test data and for testing a telephony communication system based on said digital test data. The method can be broadly conceptualized by the following steps: transmitting a first analog signal from a subscriber loop interface to a telephony communication network via a first subscriber loop coupled to the subscriber loop interface; receiving a second analog signal at the subscriber loop interface, the second analog signal translated from the first analog signal by said telephony communication network and transmitted to the subscriber loop interface via a second subscriber loop coupled to the subscriber loop interface; analyzing information defined by the second analog signal; and determining, based on the analyzing step, a parameter indicative of performance of the telephony communication system.

Other features and advantages of the present invention will become apparent to one skilled in the art upon examination of the following detailed description, when read in conjunction with the accompanying drawings. It is intended that all such features and advantages be included herein within the scope of the present invention and protected by the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention generally provides an apparatus and method for obtaining test data to test the performance of analog and digital telephony communication systems. To illustrate the principles of the present invention, refer toFIG. 1, which depicts a conventional telephony communication system15that utilizes a digital network17.

As shown byFIG. 1, a communication device22, such as a telephone, for example, residing at a customer's premises25is coupled to a central office27of the telephony communication system15via a subscriber loop31, which is often a pair of copper wires configured to transmit analog signals. During a telephone call, voice signals are communicated between the telephone22at customer's premises25and another communication device33, such as another telephone, at another customer's premises35. Telephone33is usually coupled to another central office41via another subscriber loop44.

A user at premises25speaks into telephone22, which converts the user's voice into analog signals and transmits these analog signals to central office27via subscriber loop31. Devices at the central office27receive the analog signals and convert the analog signals into digital signals. These digital signals are then transmitted via digital network17to central office41. Although various types of digital networks may be used to communicate the digital signals, the digital network17shown byFIG. 1is often configured as a packet switching network, such as or similar to a network employing internet protocol (IP).

Therefore, devices at the central office27are designed to group the digital data produced from the analog signals received from subscriber loop31into separate packets of data. Each of the packets includes a header that identifies a device at central office41as the destination. Each packet is then transmitted via digital network17to the destination device at central office41. Although each packet should ultimately be received by the destination device at the central office41, the data packets may be transmitted via different paths and routers through the digital network17. As a result, it typically takes different time periods to transmit the different packets through the network17, and the packets are usually not received in the order that they were transmitted.

Devices at the central office41usually arrange the packets into the correct order (i.e., the order that the packets were transmitted from central office27) and then convert the digital data in the packets back into analog signals. The steps of transmitting signals digitally across digital network17and arranging the packets in the correct order generally increases the delay associated with transmitting signals from telephone22to telephone33.

Once the digital data received by the central office41has been converted back into analog signals, the central office41transmits the analog signals to telephone33via subscriber loop44. The telephone33then converts these analog signals into sound, which resembles the voice of the user at premises25when the user at premises25previously spoke into the telephone22.

The user at premises35may speak into telephone33, and the user's voice may be converted into analog signals by the telephone33. These analog signals may then be transmitted to telephone22via the telephony communication network15similar to how the analog signals produced at telephone22are transmitted to telephone33. Furthermore, the signals communicated between telephones25and33may be simultaneously transmitted by the system15in both directions such that the users can both hear and speak at the same time.

When a user speaks into a telephone22or33, it is common for the user to hear an echo. It is well known that a portion of each analog signal transmitted across a subscriber loop31or44is reflected back to the telephone22or33that originally transmitted the analog signal such that the user hears an echo of the original signal. The delay and volume of the echo varies depending on various characteristics (e.g., impedance, length, etc.) of the communication connections (e.g., subscriber loops31and44) used to transmit the signal.

The present invention, in general, provides a system and method for enabling automatic testing of performance of the telephony communication network15. As shown byFIG. 2, the present invention includes a voice quality testing (VQT) system50that interfaces with the analog subscriber loop31. In this regard, the testing system50preferably includes a standard RJ-11 or RJ-45 connector that enables the testing system50to be plugged directly into a standard RJ-11 or RJ-45 jack at the premises25of a user. However, it is possible to employ other techniques, such as wire splicing, for example, or other connectors to couple the testing system50to subscriber loop31, if desired. In addition, it is not necessary for the testing system50to be employed at the user's premises25, and it is possible for the testing system50to be interfaced with the system15at any point along the analog subscriber loop31.

The testing system50may be designed to establish a communication session with a transceiver at premises35(e.g., with the telephone33or another voice quality testing system60). Then, the testing system50is designed to transmit analog voice signals over subscriber loop31and to simultaneously detect the signals that are being transmitted over subscriber loop31. The testing system0then analyzes the detected signals to determine performance characteristics of the telephony communication system15. For example, the testing system50may transmit a recording of a person's speech as analog voice signals over the subscriber loop31. While the testing system50is transmitting the recording, the testing system50can simultaneously detect the echo29of the recording. Data defining the echo29can then be analyzed through conventional techniques to determine various characteristics, such as echo delay, echo signal strength, etc.

The analog voice signals transmitted by the testing system50pass through the telephony system15and are eventually transmitted over subscriber loop44. The analog signals are preferably converted into digital signals for transmission through a portion (i.e., digital network17) of the telephony system15.

The testing system60at premises35is configured to receive the analog voice signals and to test the analog voice signals through techniques known in the art. For example, the recorded speech that is being transmitted by the testing system50may be known to the testing system60. Therefore, the testing system60is aware of the original duration of the speech being transmitted by the testing system50, and it is possible to detect the delay introduced by the digital network17. In this regard, the delay of the digital network17is approximately the duration of the speech received by the testing system60minus the duration of the speech originally transmitted by testing system50. Note that the testing system60may be configured identical to the testing system50, which will be described in more detail hereinbelow.

FIG. 3depicts another embodiment of the present invention. In the embodiment depicted byFIG. 3, the testing system50is coupled to another subscriber loop62. Instead of establishing a communication session with devices at a remote premises35, a communication session between multiple ports of the testing system50is established. Therefore, the analog voice signals transmitted to central office27via subscriber loop31are converted to digital data and pass through the digital network17, as described above, except that the digital data is routed to central office27instead of central office41. The central office27converts this digital data into analog signals and interfaces the analog signals with subscriber loop62. The testing system50receives the analog signals from subscriber loop62and then tests these signals via the same techniques used by testing system60to test the analog signals received via subscriber loop44in the previous embodiment.

FIG. 4depicts a more detailed view of the testing system50. As shown byFIG. 4, the testing system50includes a subscriber loop interface65and a computer system75. The computer system75preferably stores digital data defining speech that is to be transmitted over subscriber loop31by testing system50. When the digital speech data is to be transmitted over the subscriber loop31, the computer system75transmits the digital speech data to subscriber loop interface65, which converts the digital speech data into analog signals and interfaces these analog signals with the analog subscriber loop31.

While transmitting the analog signals over subscriber loop31, the subscriber loop interface65can be configured to simultaneously detect the signals being transmitted across the subscriber loop31. The subscriber loop interface65can then be designed to convert the detected signals into digital data and to transmit this digital data to computer system75. The computer system75is designed to analyze this digital data to determine various characteristics of the communication of the telephony communication system15, such as, but not limited to, characteristics of the echo received from subscriber loop31and/or the delay introduced by the digital network17.

FIG. 5depicts a more detailed view of the computer system75. As shown byFIG. 5, the computer system75includes a system manager82that controls the operation of the computer system75. The system manager82can be implemented in software, hardware, or a combination thereof. In the preferred embodiment, as illustrated by way of example inFIG. 5, the system manager82along with its associated methodology is implemented in software and stored in computer memory85of the computer system75.

The preferred embodiment of the computer system75ofFIG. 5comprises one or more conventional processing elements88, such as a digital signal processor (DSP), that communicate to and drive the other elements within the system75via a local interface91, which can include one or more buses. Furthermore, an input device93, for example, a keyboard or a mouse, can be used to input data from a user of the system75, and screen display95or a printer96can be used to output data to the user. A disk storage mechanism98can be connected to the local interface91to transfer data to and from a nonvolatile disk (e.g., magnetic, optical, etc.).

As shown byFIG. 5, digital speech data99, which defines the speech that is to be transmitted over subscriber loop31, is stored in memory85along with system manager82. As previously described, during a test of the system15, the speech data99is transmitted to subscriber loop interface65, which interfaces the speech data99with subscriber loop31.

FIG. 6depicts a more detailed view of the subscriber loop interface65. The subscriber loop interface65depicted byFIG. 5includes six ports111,113,115,116,117, and118, although a different number of ports may be utilized in other embodiments. Ports111and113are configured to interface signals between the testing system50and the subscriber loops31and/or62when FXO signaling is being used for communication. Ports115–118are configured to interface signals between the testing system50and the subscriber loops31and/or62when E&M signaling is being used for communication.

Port111is coupled to a digital signal processor (DSP)121via a digital-to-analog (D/A) converter123and an analog-to-digital (A/D) converter125. When port111is used for transmitting from the testing system50, digital speech data99is downloaded from the computer system75to the DSP121. The DSP121then transmits the speech data99to D/A converter123and provides the necessary control signals to D/A converter123, A/D converter125, and/or port111to enable the speech data99to be transmitted across subscriber loop31. In response, the D/A converter123converts the speech data99into analog signals and transmits the analog signals to port111. The port111then interfaces these analog signals with the subscriber loop31such that the analog signals are appropriately transmitted across the subscriber loop31.

When the port111is used for receiving data from the subscriber loop31, the DSP121provides control signals to port111, D/A converter123, and/or A/D converter125such that the analog signals received from subscriber loop31are transmitted to A/D converter125and converted into digital data by the A/D converter125. This digital data is then transmitted to DSP121, which stores the digital data. When desired, this digital data is uploaded to the computer system75, which then analyzes the digital data to determine the quality of the analog signals transmitted across the subscriber loop31and, in other words, to evaluate the performance of the telephony system15.

To test the echo and other parameters associated with subscriber loop31, signals are simultaneously transmitted and received by port111. In this regard, the DSP121controls D/A converter123and A/D converter125such that both converters123and125are simultaneously active. The DSP121then transmits the digital data downloaded from computer system75to D/A converter123and stores the digital data received from A/D converter125. The data from A/D converter125being stored by the DSP121should define the echo of the speech defined by the digital data being transmitted to D/A converter123. Either during or after the interfacing of data between the port111and the subscriber loop31, the data from A/D converter125can be uploaded to computer system75for testing. Alternatively, the DSP121can be configured to test the echo data and to provide the results of the test to computer system75, which interfaces the results to a user of the computer system75.

Preferably, port113, DSP131, D/A converter133, and A/D converter135are configured identical to and operate the same as port111, DSP121, D/A converter123, and A/D converter125, respectively, except that port113is adapted for coupling to the other subscriber loop62. Therefore, port111may be used to transmit FXO signals from testing system50to subscriber loop31and/or to receive FXO signals from subscriber loop31, while port113is used to simultaneously transmit FXO signals from testing system50to subscriber loop62and/or to receive FXO signals from subscriber loop62.

Having another FXO port113enables a communication session to be established between port111and113when the system15is configured according toFIG. 3. When a communication session is established between ports111and113, any signals transmitted across subscriber loop31or62by one of the ports111or113passes through the digital network17and is received by the other port111or113. In other words, an end-to-end connection through the network17is established in which one of the ports111or113is coupled to or terminates one of the ends of the end-to-end connection and in which the other of the ports111or113is coupled to or terminates the other of the ends of the end-to-end connection.

As a result, the testing system50can control both ends of the end-to-end connection and, therefore, have more control over the test environment. In this regard, a number of events could occur to disrupt or degrade the test of the telephony system15in the configuration ofFIG. 1. For example, establishment of a communication session between premises25and35could be thwarted due to a busy signal. Also, a user at premises35could create an off-hook condition on the subscriber loop44with another communication device at premises35and attempt to place a call, thereby interrupting a previously established communication session. Furthermore, it is possible for the user at premises35to fail to couple the testing system60to the subscriber loop44, thereby preventing certain tests from being performed. There are numerous other events that could occur to prevent the testing or to degrade the quality of the testing performed by the testing system50, when one end of the end-to-end connection is located at a remote premises35. However, a user at premises25can prevent many of these events from occurring, when the configuration ofFIG. 3is used to perform a test of the system15. Furthermore, the configuration ofFIG. 3eliminates the need of a separate compatible testing system60.

As set forth hereinabove, ports115–118are configured to interface E&M signals between testing system50and subscriber loops31and/or62. As shown byFIG. 6, port115is coupled to a digital signal processor (DSP)141via a digital-to-analog (D/A) converter143and an analog-to-digital (A/D) converter145. When port115is used for transmitting from the testing system50, speech data99is downloaded from the computer system75to the DSP141. The DSP141then transmits the speech data99to D/A converter143and provides the necessary control signals to D/A converter143, A/D converter145, and/or port115to enable the speech data99to be transmitted across subscriber loop31. In response, the D/A converter143converts the speech data99into analog signals and transmits the analog signals to port115. The port115then interfaces these analog signals with the subscriber loop31such that the analog signals are appropriately transmitted across the subscriber loop31.

When the port115is used for receiving data from the subscriber loop31, the DSP141provides control signals to port115, D/A converter143, and/or A/D converter145such that the analog signals received from subscriber loop31are transmitted to A/D converter145and converted into digital data by the A/D converter145. This digital data is then transmitted to DSP141, which stores the digital data. When desired, this data is uploaded to the computer system75, which then analyzes the digital data to determine the quality of the analog signals transmitted across the subscriber loop31and, in other words, to evaluate the performance of the telephony system15.

To test the echo and other parameters associated with subscriber loop31, signals are simultaneously transmitted and received by port115. In this regard, the DSP141controls D/A converter143and A/D converter145such that both converters143and145are simultaneously active. The DSP141then transmits the digital data downloaded from computer system75to D/A converter143and stores the digital data received from A/D converter145. The data from A/D converter145being stored by the DSP141should define the echo of the speech defined by the digital data being transmitted to D/A converter143. Either during or after the interfacing of data between port115and subscriber loop31, the data from A/D converter145can be uploaded to computer system75for testing. Alternatively, the DSP141can be configured to test the echo data and to provide the results of the test to computer system75, which interfaces the results to a user of the computer system75.

It is well known that E&M signaling sometimes occurs over a two pair connection instead of a single pair connection. In such an embodiment, the signals are transmitted from premises25to central office27via one of the pairs, and signals are transmitted from central office27to premises25via the other of the pairs. To enable simultaneous interfacing of data between the testing system50and both pairs of a two pair subscriber loop31, port115can be coupled to one of the pair of wires of the subscriber loop31, while port116is coupled to the other pair of wires of the subscriber loop31. In this regard, port116, DSP151, D/A converter153, and A/D converter155are preferably configured identical to and operate the same as port115, DSP141, D/A converter143, and A/D converter145, respectively. Therefore, assuming that port115is coupled to one of the wire pairs of a two pair subscriber loop31and that port116is coupled to the other wire pair of the two pair subscriber loop31, port115may be used to transmit and/or receive data via one of the pairs, while port116simultaneously transmits and/or receives data via the other pair of wires.

Port117, D/A converter163, A/D converter165, and DSP161are configured identical to and operate the same as port115, D/A converter143, A/D converter145, and DSP141, except that port117is configured to couple to the subscriber loop62ofFIG. 3. Furthermore, port118, D/A converter173, A/D converter175, and DSP171are configured identical to and operate the same as port116, D/A converter153, A/D converter155, and DSP151, except that port118is configured to couple to subscriber loop62ofFIG. 3. Therefore, E&M signals may be communicated over subscriber loop62via ports117and118in the same way that E&M signals are communicated over subscriber loop31via ports115and116. Since ports115and116are coupled to one subscriber loop31and ports117and118are coupled to another subscriber loop62, the testing system50can be coupled to both ends of an end-to-end connection. Therefore, the previously described benefits of controlling both ends of an end-to-end communication connection passing through network17can be realized for an E&M communication session.

As with ports111and113, it is desirable to provide each port115,116,117, and118with a separate DSP141,151,161, and171, respectively, in order to realize and/or maximize many of the advantages of the testing system50. Therefore, it is preferable for each of the ports115,116,117, and118to be coupled to and controlled by a dedicated DSP141,151,161, and171, as shown byFIG. 6. However, since ports111and113are not utilized during E&M signaling and since ports115–118are not utilized during FXO signaling, it is possible for the same DSP to be used for one of the ports111or113and for one of the ports115,116,117, or118. For example, when E&M signaling is being used for communication across subscriber loop31, DSP121may be coupled to and used to control port115instead of port111, thereby eliminating the need of a separate DSP141.

A controller185is configured to control the operation of the subscriber loop interface65. The controller185may be implemented in hardware, software, or a combination thereof. To this end, the controller185may include a DSP (not shown) and/or hardware logic (not shown) to implement the functionality of the controller185, which will be described in more detail below.

The controller185is configured to provide control signals to DSPs121,131,141,151,161, and171indicating whether each DSP121,131,141,151,161, and171should be in a transmit mode, a receive mode, or a non-active mode. Each DSP121,131,141,151,161, and171in a non-active mode is idle. Each DSP121,131,141,151,161, and171in a transmit mode receives digital data and causes its respective port111,113,115,116,117, or118to transmit the received data across subscriber loop31after the received data has been converted into analog signals. Each DSP121,131,141,151,161, and171in a receive mode causes its respective port111,113,115,116,117, or118to receive data from the subscriber loop31and to transmit the received data to the DSP111,113,115,116,117, or118via an A/D converter125,135,145,155,165, or175, which converts the received data into digital data. During an upload of this digital data to computer system75, the DSP121,131,141,151,161, or171transmits this digital data to controller185.

When the controller185receives digital data from one of the DSPs121,131,141,151,161, or171, the controller185is configured to transmit this data to the computer system75so that the computer system75can analyze the data. When the controller185receives the speech data99from the computer system75, the controller185is configured to transmit the speech data99to at least one of the DSPs121,131,141,151,161, or171in the transmit mode.

The controller185may also transmit any data received from one or more of the DSPs121,131,141,151,161, and171to a D/A converter191. The D/A converter191is configured to convert this data into analog signals and to transmit these analog signals to audio interface193. The audio interface193either produces sound based on the analog signals or interfaces the signals with a device (not shown) that is configured to produce sound based on the analog signals. Therefore, a user may hear the sounds defined by the analog signals received from subscriber loop31.

In addition, the controller185may be configured to transmit to the audio interface193the speech data99received from computer system75, thereby enabling the user to hear the sounds defined by the speech data99. The speech data99may be transmitted to the audio interface193alternatively to the data received from subscriber loop31or may be transmitted to the audio interface193in combination with the data received from subscriber loop31.

When the speech data99and the data received from subscriber loop31are both transmitted to the audio interface193, the user should be able to hear a simulation of the sounds defined by the data communicated across subscriber loop31. Therefore, a user should hear a sound defined by the speech data99as well as the echo produced in response to the data defining the sound. Assuming no significant delays between transmitting the speech data99to the audio interface193and transmitting the speech data99across subscriber loop31, the delay between the sound and the echo heard by the user via audio interface193should correspond to the delay of the echoes on subscriber loop31. As a result, the user may analyze the sufficiency of the echo delay across subscriber loop31by listening to the sounds produced via audio interface193.

In some embodiments, the telephone22may set up a telephone call to enable communication to occur over subscriber loop31. In this regard, the telephone22(after going off-hook) may dial the number identifying subscriber loop44or62, and through techniques known in the art, a communication session between the telephone22and another device, such as telephone33, testing system60, or testing system50, may occur.

However, in another embodiment, the testing system50may be designed to establish the communication session instead of the telephone22. In such an embodiment, the controller185is configured to transmit a call command to session control logic196. In response, the session control logic196is configured to create an off-hook condition on the subscriber loop31and then to dial or otherwise transmit the number identifying subscriber loop44or62. Once this occurs, a communication session is established between a communication device, such as telephone33or testing system60, at premises35and the testing system50, or a communication session between multiple ports of the testing system50is established, depending on which subscriber loop44or62is identified by the aforementioned number transmitted by testing system50.

Furthermore, the session control logic196may be configured to create an off-hook condition when the logic196detects a ringing signal on subscriber loop31. Therefore, a communication session between testing systems50and60or between multiple ports of testing system50can be established without the use of telephones22and/or33. In addition, when the communication session should be terminated, the controller185may transmit an end session command to session control logic196. In response, the session control logic196may create an on-hook condition or conditions to terminate the communication session. Therefore, if desired, the testing systems50and/or60may handle all or some of the functionality of establishing and/or terminating a communication session.

By equipping the controller185with a DSP, it is possible for the controller185to implement the functionality of analyzing the performance data obtained by the DSPs121,131,141,151,161, and/or171. This may be particularly advantageous when there is a large number of DSPs121,131,141,151,161, and171. In this regard, it is possible to form the system65on a PCI card and interface the controller185to the computer system75via a PC bus. Therefore, the configuration of the system65can be easily duplicated on multiple PCI cards, which are all interfaced with the computer system75to enable the testing system50to test a large number of subscriber loops or to test multiple channels of the same or multiple subscriber loops.

However, the computer system75could become overburdened with data when a large number of subscriber loops or channels are being tested. By analyzing the data obtained by the DSPs121,131,141,151,161, and171with a DSP of the controller185and providing the results of this analysis to the computer system75, the work load of the computer system75can be significantly reduced, thereby enabling the computer system75to manage a large number of interface systems65.

Operation

The preferred use and operation of the testing system50and associated methodology are described hereafter.

Assume that a user would like to test the performance of telephony communication system15. To achieve this, the user may enter a command via input device93(FIG. 5) of computer system75. Preferably, the command indicates the type of signaling (e.g., FXO, E&M, or both) that is to be used during the test and the type of test that is to be performed (e.g., a test of the quality of the echo signal, a test of the delay of digital network17, etc.). In response, the system manager82of computer system75transmits initialization information and the speech data99to controller185. The initialization information is indicative of the type of test that is to be performed. Based on the initialization information, the controller185transmits control signals to DSPs121,131,141,151,161, and171to place each of the DSPs121,131,141,151,161, and171in the appropriate mode.

For example, assume that a test of the echo signal and of the delay of digital network17is to be performed with FXO signaling. Assume further that the configuration ofFIG. 3is utilized to perform the test. In this situation, the controller185transmits control signals to DSPs121,131,141,151,161, and171that place DSP121in a transmit mode and a receive mode, that place DSP131in a receive mode, and that place DSPs141,151,161, and171in a non-active mode. Then, the controller185transmits the speech data99to DSP121.

The controller185, in embodiments where the testing system50establishes a communication session, transmits a call command to session control logic196. In response to the call command, the session control logic196creates an off-hook condition at port111and dials or otherwise transmits a number identifying subscriber loop62. In response, the central office27transmits a ringing signal across subscriber loop62. In response to the ringing signal, the session control logic196creates an off-hook condition at port113, and a communication session between ports111and113of testing system50is thereby established.

Once the communication session is established, the DSP121then causes the speech data99to be transmitted over subscriber loop31. In particular, the DSP21transmits the speech data99to D/A converter123. This transmission may be serial or via the use of data words. The D/A converter123converts the digital speech data99into analog signals and transmits these analog signals to port111. The port111then interfaces the analog signals with subscriber loop31.

While the port111is interfacing the analog signals from D/A converter123with the subscriber loop31, the port111is receiving analog signals from subscriber loop31. The port111transmits these analog signals to A/D converter125, which converts these analog signals into digital data and transmits the digital data to DSP121. This transmission may be serial or via the use of data words. At some point, the DSP121transmits the digital data received from A/D converter125to controller185, which interfaces this data with computer system75. The computer system75then analyzes this data to determine various performance characteristics associated with the telephony system15, such as, but not limited to, the signal strength and delay of an echo signal. Data indicative of these performance characteristics may be displayed via display95(FIG. 5) or printer96, for example.

Note that the signals transmitted from port111to subscriber loop31pass through central office27, digital network17, and subscriber loop62and are received by the port113of testing system50. The port113transmits these analog signals to A/D converter135, which converts these analog signals into digital data and transmits the digital data to DSP131. This transmission may be serial or via the use of data words. At some point, the DSP131transmits the digital data received from A/D converter135to controller185, which interfaces this data with computer system75. The computer system75then analyzes this data to determine various characteristics of the system15, such as the delay introduced by digital network17. The testing system50may then display data indicative of these characteristics through conventional techniques.

Once the desired testing has been performed, the controller185preferably transmits an end session command to session control logic196. In response, the session control logic196creates an on-hook condition at ports111and113, and the communication session is, therefore, terminated.

Note that in other examples, the performance of the telephony system15can be tested via E&M signaling. In these examples, the DSPs121and131, based on control signals from controller185, are placed into a non-active state, while some or all of the DSPS141,151,161, and171are placed in either the transmit or receive state. For example, when the subscriber loop31includes only one pair of wires, DSP141can be placed in the transmit state and receive state, DSP151can be placed in the receive state, and DSPs161and171can be placed in the non-active state, assuming both DSPs141and151are coupled to the pair of wires. When the subscriber loop31includes two pair of wires, DSPs141and161can be placed in the transmit state and receive state, and DSPs151and171can be placed in the receive state, assuming DSPs141and151are coupled to one pair of wires in the subscriber loop31and DSPs161and171are coupled to the other pair of wires in the subscriber loop31. Note that in performing other types of tasks, any one of the DSPs121,131,141,151,161, and171may be placed in the non-active state, the transmit state, the receive state, or the transmit and receive state.