Abstract:
Before a party is admitted into a conference call, the party&#39;s communication connection to the conference bridge is tested for quality. If the quality is acceptable, the party is admitted into the conference. If the quality is not acceptable, an attempt is made to improve the quality. If the attempt fails, the party is given the choice of either hanging up and calling back or being admitted into the conference in a restricted mode that limits the adverse effects of the poor connection on the conference.

Description:
TECHNICAL FIELD 
     This invention relates to communications conferencing. 
     BACKGROUND OF THE INVENTION 
     The voice quality of a conference call depends on the quality of the conference bridge as well as the quality of the access lines and terminal equipment used by the participants. Often, the quality of the access lines and/or terminal equipment is the limiting factor. It is common that a poor-quality access line or terminal equipment of a single participant ruins the quality of a large multi-party call. For example, a participant calling in from a cell phone with high background noise due to a poor radio signal will inject noise into the whole conference. In another example, a participant calling in by using a speaker phone with low echo return loss can generate excessive echo for the whole conference and make it difficult for everyone else to listen or speak. 
     To maintain the quality of a conference call, various mechanisms have been put in place at conference bridges. Conference bridges usually include echo cancellers to cancel the echo returning from each individual port. Conference bridges often implement a volume-threshold which a participant&#39;s line volume-level must exceed before their signal is mixed into the conference&#39;s output audio stream. This mechanism is used to prevent the addition to the conference output stream of a large number of sources of background noise that would raise the conference&#39;s background noise level. Most conference bridges also implement some automatic gain control (AGC) mechanism to equalize the differences in levels between different participants. 
     These methods are usually applied to all ports of a conference call by static provisioning. Different processing parameters may also be administered for different port types or port groups, but once they are assigned, the processing parameters and strategies do not change with the particular conditions of individual legs of the conference call. While the processing algorithms are adaptive in nature (e.g., an echo canceller may adjust the cancellation-function&#39;s coefficient or an AGC may change the gain as the call progress), they do not exploit the full range of options of different strategies, such as, for example, choosing between linear echo-cancellation and half-duplex echo-suppression. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, before a party is admitted into a conference call, the party&#39;s connection (communication path to the conference bridge) is tested for quality. If the quality is acceptable, the party is admitted into the conference conventionally. If the quality is not acceptable, one or more attempts are made to improve the quality to an acceptable level. If the attempt succeeds, the party is admitted into the conference. If the attempt fails, the party is either not admitted into the conference (e.g., the party is asked to hang up and call again) or the party is admitted into the conference in a restricted mode that limits the adverse effect of the connection on the conference. 
     The goal and effect is to prevent one or more poorly-performing legs of the conference call from ruining the conference experience for all participants in the conference. 
     The invention may be implemented both as a method and an apparatus, as well as a computer-readable medium containing instructions which, when executed by a computer, cause the computer to perform the method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and other features and advantages of the invention will become more apparent from considering the following description of an illustrative embodiment of the invention together with the drawing, in which: 
         FIG. 1  is a block diagram of a communication conferencing system that includes an illustrative embodiment of the invention; and 
         FIG. 2  is a flowchart of operation of a connection-evaluation function of the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a communication conferencing system wherein a plurality of communication terminals  102 - 110  are connected by a communications network  112  to a conference bridge  116 . Terminals  102  comprise any desired voice-enabled user communication devices, such as wired or wireless telephones, personal digital assistants, softphones, etc. Network  112  is any desired communications network, such as a private or the public switched telephone network, a local area network, or a wide area network such as the Internet. Terminals  102 - 110  are usually connected to bridge  116  by a server  114  of network  112 . For example, if network  112  is the private or public switched telephone network, server  114  may comprise a telephone switch. If network  112  is a data network such as a Voice over Internet Protocol (VoIP) network, server  114  may comprise a communications manager, such as the Avaya Communications Manager, for example. Conference bridge  116  is illustratively a stored-program-controlled apparatus that comprises storage  120  for storing programs such as a conferencing program  122 , and a processor  128  for executing the programs. As described so far, the conferencing system of  FIG. 1  is conventional. 
     According to an aspect of the invention, conference bridge  116  implements a connection-evaluation function  200 . Function  200  is illustratively implemented by storing a connection-evaluation program  124  in storage  120  and executing program  124  by processor  128 . In alternative embodiments, connection-evaluation function  200  many be implemented either by server  114  or by an adjunct processor (not shown) that supplements and assists conference bridge  116 . Connection-evaluation function  200  tests each of the conference legs, i.e., the connections of each of terminals  102 - 110  (preferably including the terminals themselves) to conference bridge  116 , before admitting the corresponding terminal  102 - 110  into the conference. If it determines a deficiency in a conference leg, connection-evaluation function  200  preferably attempts to correct the deficiency. If it detects no deficiency or corrects the deficiency, connection-evaluation function  200  connects the corresponding terminal  102 - 110  into the conference in a normal manner, i.e., without restrictions. If it cannot correct a discovered deficiency, connection-evaluation function  200  either requests the user of the corresponding terminal  102 - 110  to hang up and call into the conference again, or connects the corresponding terminal  102 - 110  into the conference in a restricted mode that tries to minimize any adverse effect that the terminal&#39;s connection may have on the conference. 
     An illustrative embodiment of connection-evaluation function  200  is shown in  FIG. 2 . Function  200  is invoked when a terminal  102 - 110  connects to conference bridge  116  (or to server  114  if server  114  implements function  200 ), at step  202 . In response, function  200  tests the connection, e.g., the quality of the terminal equipment and the access line, at step  204 , to determine any deficiencies of the connection that could adversely impact the conference. According to one aspect of the invention, function  200  provides both passive and active means for detecting and mitigating voice quality issues. Illustratively, function  200  tests for at least the following deficiencies of the connection: excessive background noise levels, insufficient echo return loss, and varying signal levels. Initial testing is preferably transparent to the parties (i.e., the users of terminals  102 - 110 ). For example, when a terminal  102 - 110  connects to bridge  116 , function  200  listens to the connection for a moment to determine the level of background noise on the connection. Illustratively, function  200  then plays (transmits) a welcome or entry sound on the connection and listens on the connection for the sound&#39;s echo. The sound preferably comprises tones of a plurality of different frequencies and is played at a plurality of different volumes (amplitudes) to determine if the connection is highly non-linear. Further illustratively, function  200  then plays an announcement (greeting) on the connection welcoming the party to the conference, and again listens on the connection, for the announcement&#39;s echo to determine the echo&#39;s level. The announcement may request the party to speak, e.g., their name. When the party speaks, function  200  measures the amplitude of the response, and the frequency-response and amplitude (level)-response characteristics of the line, to determine if the connection is too quiet or too loud and to determine if the connection has unacceptably-varying signal levels. It may also measure the speech signal-to-noise level of the connection to determine if it meets a threshold of acceptability. Other tests may be performed as desired in a particular environment.
         1. From the results, function  200  determines if the quality of the connection is good, i.e., if it passes specified thresholds, at step  206 . If it determines that connection quality is good, function  200  causes the connection to be bridged into the conference, at step  208 , thereby connecting the party at the corresponding terminal  102 - 110  into the conference. Function  200  then ends its operation, at step  210 . If it determines at step  206  that the connection quality is not good, function  200  checks its records to determine if the number of times or the time period that it has spent testing and attempting to repair deficiencies of the connection exceed a threshold, at step  212 . (On the first pass through step  208 , the threshold will not have been exceeded.) If the threshold is not exceeded, function  200  attempts to repair the connection, at step  214 . For example, if the noise level on the connection has been determined to be too high, function  200  adjusts the noise-gate threshold on the connection. Or, if the signal level on the connection has been determined to be too low or too high, function  200  may adjust the gain of the receiver of the connection at bridge  116 . The repair attempt may not be transparent to the party. For example, if it has been determined that the echo on the connection is too great, function  200  may give the echo canceler a longer time to calibrate itself, by playing another announcement on the connection. This announcement may prompt the party to speak something so that the echo in both directions of the connection can be adjusted. Or, function  200  may request the party to move closer to or further away from the microphone of terminal  102 - 110 , or to stop using a headset or a speakerphone of terminal  102 - 110  (if the party is doing so) and to use the handset instead. Other repair attempts may include measuring and mitigating total delay and/or packet loss, or setting jitter buffers for each individual call, or changing a packet loss concealment algorithm to improve quality. Function  200  then returns to step  204  to retest the connection,       

     Returning to step  212 , if function  200  determines there that the number of, or time spent in, testing and repair attempts has exceeded the threshold without the determined deficiencies having been adequately diminished, function  200  prompts the party to hang up and redial the conference, at step  218 , in order to establish a new connection that will hopefully not have the deficiencies. Other prompts may include system recommendations such as to use a cell phone over a VoIP system, to use a digital phone over VoIP, or to use a private system over a PSTN. At step  218 , function  200  further informs the party that instead of hanging up, the party may signal, e.g., by pressing a touch-tone button on terminal  102 - 110 , to enter the conference on the existing connection, in which case the party will be admitted to the conference in a restricted mode that minimizes the adverse effect that the deficiencies of the connection may have on the other participants of the conference. Such restricted mode may illustratively involve admitting the party into the conference in a listen-only mode, or connecting the party in a muted mode where signals from the party are admitted into the conference only when the party is speaking and the signal-to-noise ratio of the voice signals exceeds a threshold. Another example of the restricted mode is transmitting voice signals from the conference to the party at a low (quiet) level in order to limit the volume of the echo that the party&#39;s connection introduces into the conference. If the party hangs up, as determined at step  220 , the connection is torn down and operation of function  200  ends, at step  210 . If the party signals its intent to join the conference on its current connection, as determined at step  220 , function  200  plays an announcement to the party that informs the party of the type and/or limitations of the restricted mode of its connection to the conference, at step  222 . Alternatively, step  222  may be performed as a part of step  218 . Function  200  then causes the party to be admitted into the conference in the restricted mode, at step  224 . Operation of function  200  then ends, at step  210 . 
     Of course, various changes and modifications to the illustrative embodiment described above will be apparent to those skilled in the art. These changes and modifications can be made without departing from the spirit and the scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the following claims except insofar as limited by the prior art.