Abstract:
A system and method for selectively muting a call of a wireless communication system. A first predetermined signal is received by the wireless communication system. The phone signal has a user signal associated with it. In response to the first predetermined signal, the wireless communication system pauses communication of the user signal to the end user while still maintaining the phone call between the wireless communication system and the conference bridge. In response to a second predetermined signal, the wireless communication system reiates communication of the user signal to the end user.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of telecommunications, and more particularly to muting transmissions from a cellular telephone. 
     2. Description of the Related Art 
     Conference bridging platforms allow multiple parties to be simultaneously connected to a telephone call in which the parties can hear and talk to each other even though they are geographically displaced at a variety of locations. The telephone call to which the parties are simultaneously connected is known as a conference call. Conference bridging platforms are typically operated by telecommunications carriers as part of a conferencing service. A party can participate in a conference call by calling the conferencing service and identifying the particular conference call to which the party wants to be connected. Before a party can participate in a conference call, arrangements ordinarily need to be made with the confddderencing service to set aside resources on the conference bridging platform to support the conference call as well as billing functions. 
     Problems can arise in using a typical conference bridging platform when one of the parties to a conference call is a cellular phone user. For example, problems arising in two different situations can have a detrimental effect on the other parties participating in the conference call. First, the cellular phone user is often in an environment with high ambient noise levels, such as taxicabs, airports, or restaurants. Consequently, the signal received at the bridging platform is likely to be very noisy. Second, the user may be operating from an area at the edge of a cell or other areas within the interior of a cell where the user&#39;s signal received at the base station is relatively noisy. In such situations, even if a party is not talking the signal received at the bridging platform may be very noisy because of the air link noise due to the poor link margin. These problems emanating from the operation of the cellular phone party can have a detrimental effect on the remaining parties participating in the conference call. 
     This detrimental effect arises because of the manner in which typical conference bridging platforms retransmit the signal received from one party to the remaining parties on the conference call. During the conference call, typically, a party can be heard by the other parties if the party&#39;s speech or sound level is the highest or the second (or maybe even the third) highest in comparison to the sound level of the other parties to the conference call. The party can be heard by the other parties because the conference bridging platform selects and rdddetransmits the signal which has the highest or second highest sound level to the remaining parties while the signals of the remaining parties are muted. This approach has the drawback of cellular phone conferees having loud or noisy connections, which often happens as described above, frequently dominating other conferees to the point where the latter are not heard by the noisy conferees. 
     This problem is pervasive and happens often whenever a cellular phone user is party to a conference call supported by a typical conference bridging platform. Foladare et al., U.S. Pat. No. 5,724,416, describes a conference bridging platform specifically designed to provide a solution to the dominating effect caused by conferees having loud or noisy connections. The invention of Foladare et al. resides in the conference bridging platform illustrated in FIG. 1 of U.S. Pat. No. 5,724,416. The platform includes a conventional conference bridging system, a plurality of noise adapters and a controller. 
     Subscribers access the conference bridge platform in a well-known manner by dialing a designated number. If the user of the cellular phone is in a high noise environment or an area of a cell with a poor link margin, such a user can avoid dominating the conference call by entering a predetermined touchtone or DTMF key, for example, the “#” key. The platform responds to entry of a touchtone “#” or other similar signal by muting the conference call branch in which the “#” was entered. 
     Alternatively, the platform responds to entry of a touchtone “#” or other similar signal by balancing the sound levels of the telephone calls participating in the conference call. Balancing is performed by the noise adapters and controller adjusting the threshold which a conferee&#39;s sound level must overcome in order for the conferee to participate the conference call. Balancing results in the threshold of less noisy conferees being lowered relative to the threshold of noisier conferees so that the less noisy conferees can participate in the conference call without having to raise their voices significantly. 
     Unfortunately, there are many conference bridging platforms in use which do not incorporate manual muting, e.g., the invention described in Foladare et al. These platforms perform adequately until a conference call includes a cellular phone party whose signal is noisy. In such a situation, for all conferees to be heard, conferees who are dominated by the louder connection of a cellular phone party must typically raise the volume of their voices significantly. Otherwise, the conferees will hear only the noise emanating from the cellular phone party&#39;s dominating connection. Consequently, there is still a need for improved conference bridging platform support of conference calls which include a cellular phone party whose signal is noisy. This invention meets this need. 
     In the current state of the art there are two methods that are currently contemplated for muting the transmissions of a cellular telephone. First, the microphone input can be disengaged from the speech encoder input. In the case of advanced vocoders, this prohibits the vocoder from being able to track changes in the background noise. In addition, the transmitter still transmits packets indicative of the silence. These packets may be erroneously decoded that can result in very disturbing noise effects. In variable rate vocoders, a rate determination error can cause a very disturbing effect. 
     A second method of muting a cellular phone would be to cause its transmission to temporarily cease. However, in an analog phone this would result in the disastrous consequence of the base station tracking pure noise and providing it to the end user. In digital systems this would cause the call to drop based on a lost reverse link. Both of these solutions are unsatisfactory. Thus, there is a need for a method of muting the transmissions of a cellular telephone in an effective manner. 
     SUMMARY OF THE INVENTION 
     The system and method of the present invention provide a simple, but effective, technique for allowing a user of a wireless communication device to mute the transmission from his cellular telephone. One particularly advantageous application of the present invention is to prevent the user&#39;s domination of a conference call being supported by a conference bridge accessed using a wireless communication system. The user&#39;s domination of the conference call results in the other conferee&#39;s of the conference call not being heard by the user and/or other conferees. This invention does not require modification of the conference bridge. 
     In addition, the present invention applies to calls to a speaker phone where a cellular user calling into a meeting room can use the present invention to prevent noise associated with the user&#39;s noisy environment, or noise inserted in the over-the-air interface from generating loud, disruptive audio at the meeting room. 
     An additional benefit of the present invention is that the protocol enhancement allows the user to achieve privacy, even on regular phone conversations. The electronic microphones at cellular phones are so sensitive, that covering the microphone with a hand does not ensure that the audio is muted. Since this is implemented at the infrastructure, the feature is available to all users of cell phones, since it is proposed using regular DTMF digits to turn the audio on/off. 
     In case of the cellular user operating on an analog cellular system, such as AMPS, there is high chance of a constant noise being added to the user&#39;s audio. This is improved in digital systems, such as CDMA systems, they are more resistant to the over-the-air noise, but they are not completely immune to such noise, and if the noise becomes significant, it can generate audio signal with very high energy. The invention addresses both of these sources of noise. 
     In one embodiment, the wireless communication system is capable of receiving a signal from the wireless communication device at the instruction of the user. In response to the received signal, the wireless communication system mutes the user&#39;s signal preventing the noise associated with the wireless communication device from reaching the conference bridge. The noise associated with the wireless communication device can include ambient noise at the device or air link noise between the device and the wireless communication system. This noise often results in the user of a wireless communication device dominating a conference call in which the user is participating. 
     Thus, a user of a wireless communication device can prevent the user&#39;s domination of a conference call by muting the user&#39;s signal at the wireless system. By muting the user&#39;s signal at the wireless system, this invention allows the wireless communication device user to prevent the user&#39;s domination of conference calls even if the user is using a conference bridge that does not, itself, prevent domination of conference calls. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a wireless conference bridging system according to a presently preferred embodiment of the invention; 
     FIG. 2 is a diagram showing the operational flow of a wireless conference bridging system according to a presently preferred embodiment of the invention; and 
     FIG. 3 is a diagram showing the operation flow of a wireless conference bridging system according to a presently preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a system block diagram of a wireless communications system (CS or System)  200  according to the presently preferred embodiment of the invention. In the exemplary embodiment, the present invention will be illustrated in its application to a conference call. However, the present invention describes a method of muting the transmission of a cellular telephone after the transmission has propagated through the air interface. This method of muting of a cellular telephone can be applied to any condition in which it is desirable to effectively mute the transmissions. 
     In one embodiment subscriber unit (SU)  212  includes a transmitter with muting signal generator  213 . System  200  may include multiple base stations (BS)  210 ,  220  (only two shown) each of which can communicate wirelessly with [a subscriber unit (SU)] SU  212  when SU  212  is within the geographic area covered by the base station. System  200  also includes a base station controller (BSC)  230  and a mobile switching center. (MSC)  240 . MSC  240  is connected to base stations  210 ,  220  through BSC  230 . MSC  240  is connected to the public switched telephone network (PSTN)  250  through a line  214  of the telephone network  250 . Lines  214  represent telephone connections within the telephone network  250  that are made to conference bridge  290 . Telephones  260 ,  270  are connected to the conference bridge  290  through a local exchange carrier  280  and lines  214 . 
     The general operation of SU  212 , BS  210  or  220 , BS  230 , MSC  240  and PSTN  250  in a cellular system is well known in the art and need not be described in great detail here. Moreover, the operation of a typical conference bridge is well known and need not be described herein. A subscriber using SU  212  typically accesses a conference bridge  290  by dialing a designated telephone number provided by the conference bridge&#39;s conferencing service by entering the digits of the number into a keypad (not shown) of SU  212 . Unlike a typical wired phone, the telephone number is keyed into the cellular phone “locally” before the request to initiate a call is made to the system  200 . In a current embodiment, when the user presses a “send” button to “originate” the call, the SU  212  sends the stored digits to BS  210 . BS  210  receives the digits and initiates a call set up process involving the BS  210 , BSC  230 , MSC  240  and PSTN  250 . The successful completion of the call set up process results in the establishment of a phone call between SU  212  and the conference bridge  290 . 
     The establishment of a phone call set up involves the allocation of resources in system  200  to permit the communication of signals from the user of. SU  212  to conference bridge  290  and from conference bridge  290  to the user of SU  212 . BS  210  sends the request to set up a call received from SU  212  to BSC  230 . BSC  230  contains a variety of subsystems (not shown) which manage communication between the various base stations in system  200  and communication between the MSC  240  and BS  210 . For example, BSC  230  handles communications between base stations that are trying to transfer control of a subscriber unit from one base station to another base station in system  200 . BSC  230  also handles communication between MSC  240  and BS  210 . BSC  230  sends the request for call setup received from BS  210  to the MSC  240 . 
     In response to the request for call set up, MSC  240 , using the digits entered by the subscriber at SU  212 , accesses the PSTN  250  in a well-known manner to set up the call. When the conference bridge responds, the voice connection is completed. To accommodate the data between SU  212  and BS  210 , the BSC  230  will allocate a wireless traffic channel for carrying data between the SU  212  and the BS  210 . The data being forwarded between SU  212  and BS  210  can be voice data or other types of data. Users of telephones  260 ,  270  access conference bridge  290  through their local exchange carrier (LEC) in a well-known manner. 
     IS System  200  can employ a variety of wireless communication schemes to effectuate provision of a telephone call by SU  212 . For example, in various embodiments of this invention communication can be provided using code division multiple access (CDMA), time division multiple access (TDMA), or frequency division multiple access (FDMA). System  200  can be a cellular telephone system such as provided by personal communications services (PCS), advanced mobile phone system (AMPS), or global system for mobile (GSM) communications. Alternatively, System  200  can be a local wireless loop in which SU  212  is stationary or moves infrequently or relatively slowly between cells of the local wireless loop. 
     FIG. 2 shows a flow diagram showing the operation of system  200 . At step  300 , subscribers desiring a conference call each dial a designated telephone number to access the conference call service. The bridge requests specific information from the respective subscribers in a well-known manner, such as a personal identification number (PIN) and other information for establishing the conference call. 
     If the user of subscriber unit  212  in FIG. 1 is in a high noise environment, such as a restaurant or an airport or is in an area of the cell such that the air link to the BS  210  is very noisy, the user is likely to dominate the conference call in which the user is participating. To avoid dominating the conference call inappropriately, the user at subscriber unit  212  presses a predetermined MUTE key (e.g., a dedicated MUTE key or DTMF key such as ‘#’) at step  310 . The MUTE key allows the selective muting of a call by stopping and restarting the forwarding of at least some portion of the subscriber unit&#39;s user signal being transmitted by SU  212 . The stopping and restarting of the forwarding of the user&#39;s signal can happen at BS  210 , BSC  230 , or MSC  240  in system  200 , as described below. The stopping and restarting of the forwarding of the user&#39;s signal is performed in a conventional manner using hardware and/or software well known in the art and which can be found in BS  210 , BSC  230  or MSC  240 . Additionally, the operation of the hardware and/or software which achieves muting is conventional and need not be described in great detail here. For ease of reference the hardware and/or software which achieves muting is referred to as the muting unit. In an embodiment of this invention, the stopping and restarting of the forwarding of the user signal can be performed on an audio portion of the user signal. However, in alternative embodiments of the invention the stopping and forwarding can happen to other portions of the user signal. 
     In a system  200  which is digital, the stopping of the audio portion of the user signal includes replacing the digital data that carry the audio signal with digital data that would generate no significant audio signal when converted into an analog signal at the MSC  240 . The restarting of the forwarding of the user signal stops the replacement of the digital data that carry the audio signal with digital data that generates no significant audio signal when converted into an analog signal at the MSC  240 . By stopping the replacement of the digital data that carry the audio signal, the audio signal travels through system  200  such that the signal produced at MSC  240  is substantially a reproduction of the user signal produced at SU  212 . 
     In one embodiment, the subscriber unit  212  is programmed to send a Mute message (or predetermined control signal) to the BS  210  in system (CS)  200  whenever the MUTE key is depressed. The present invention adds the Mute message to the message protocol associated with the communications scheme supported by system  200 . Enhancement of the standard protocol to include an additional command message is well-known in the art. 
     If the Mute message is received by BS  210 , BS  210  will maintain the phone call connection through MSC  240 , PSTN  250  to the conference bridge  290 . However, at step  340 , the muting unit of BS  210  will stop forwarding the decoded audio portion of the signal received from the SU  212  to BSC  230 . Upon receipt of the muting message, BS  210  ignores the received information data of the packet and sends a predetermined packet representative of silence to BSC  230 . 
     FIG. 3 shows a flow diagram showing the operation of system  200  when the MUTE key is depressed to restart forwarding of the audio portion of the signal received from the SU  212 . If the user of SU  212  no longer wishes his transmission to be muted, the user depresses the MUTE key at step  350 . As a result an un-Mute message is sent from the SU  212  to BS  210  of CS  200 . At step  380 , the muting unit of BS  210  will restart the forwarding of the audio portion of the signal received from the SU  212  to BSC  230 . At step  390 , the conference call continues with the audio received from SU  212  at system  200 . 
     The foregoing description of a specific application is provided only as an example. There are several alternative embodiments that are in accordance with this invention. Two alternative embodiments arise from the choice of location within system  200  at which the muting unit is placed so as to achieve the stopping and restarting of the forwarding of the audio signal. In one embodiment, the stopping and the restarting of the forwarding of the audio portion of the signal received by the system  200  occurs at the BSC  230  rather than the BS  210 . In such an embodiment, the muting unit of BSC  230 , at step  340 , on receipt of a Mute message forwarded by BS  210  will stop forwarding to MSC  240  the audio portion of the received signal. Additionally, in such an embodiment, the muting unit of BSC  230 , on receipt of an un-Mute message, will restart, at step  380 , the forwarding of the audio portion of the received signal to MSC  240 . 
     In yet another alternative embodiment of this invention, the stopping and the restarting of the forwarding of the audio portion of the signal received by the system  200  can occur at the MSC  240  rather than the BSC  230 . In such an embodiment, the muting unit of MSC  240 , at step  340 , on receipt of a Mute message forwarded by BSC  230  will stop forwarding to PSTN  250  the audio portion of the received signal. Additionally, in such an embodiment, the muting unit of MSC  240 , at step  380 , on receipt of an un-Mute message, will restart the forwarding of the audio portion of the received signal to PSTN  250 . 
     There are even further alternative embodiments that are in accordance with this invention. The alternative embodiments arise from the various forms that a request for stopping and restarting the communication of the audio portion of the signal from the SU  212  can take. In an alternative embodiment in accordance with this invention, the subscriber at subscriber unit  212  can press a first predetermined sequence of DTMF keys at step  310 . In response to the sequence of DTMF keys pressed by the subscriber, the SU  212  will either send the key sequence as a sequence of messages or as a sequence of tones. Sending the key sequence as a sequence of messages is preferable because of the error checking that is associated with the transmission of such messages. 
     For example, when a DTMF key is depressed in a typical CDMA system, a tone is not transmitted but rather a message according to the standard communication format is sent from the SU  212  to the system  200 . At the system  200 , receipt of the message caused by the depression of a DTMF key will cause the MSC  240  to generate a tone having the proper audio frequency components for transmission via the PSTN  250 . Additionally, receipt at the system  200  of a sequence of messages caused by the depression of a sequence of keys can be identified by either the BS  210 , BSC  230  or even the MSC  240  as an instruction to carry out a command. 
     Consequently, in an alternative embodiment in accordance with this invention, a sequence of messages caused by the depression, at step  310 , of a first predetermined sequence of DTMF keys (or a single DTMF key), results in the BS  210  stopping, at step  340 , the forwarding of the audio portion of the signal received from the SU  212 . Additionally, the depression at step  350  of a second predetermined sequence of DTMF keys (or a single key) causes the BS  210  to restart, at step  380 , the forwarding of the audio signal received from SU  212 . 
     Alternatively, if the depression of a first predetermined sequence of DTMF keys (or a single key) results in a first sequence of dual tones (or a single DTMF dual tone) rather than a sequence of messages being sent at step  320 , BS  210 , at step  340 , will stop audio forwarding. A depression by the user of SU  212  of a second predetermined sequence of DTMF keys (or single key) results in SU  212  sending a second sequence of tones (or a single DTMF dual tone) to BS  210 . BS  210  may send an acknowledgement to SU  212  at step  370 . At step  380 , BS  210  restarts the forwarding of the audio signal received from SU  212 . At step  390 , the conference call continues with the audio as received by system  200  from SU  212 . 
     The format of the messaging does not affect where in system  200  the stopping and restarting of the forwarding of the audio is performed. Regardless of whether the Mute and un-Mute messages are sent by the message protocol of system  200 , DTMF message or DTMF tones, the stopping and restarting of the forwarding of the audio can be done at the BS  210 , the BSC  230  or the MSC  240 . 
     There are numerous benefits to this invention that are not found in prior art such as Foladare et al. For example, this invention allows the user of a wireless phone to mute his or her signal to prevent domination of a conference call even though the conference call employs existing conference bridge platforms that do not themselves incorporate a muting function similar to that described by Foladare et al. Thus, the invention would allow the continued use of numerous existing conference bridges not employing the invention of the prior art, thereby extending their useful lifespan. 
     Other benefits arising from this invention result from transmitting the Mute request as a signaling message of the communication protocol of the wireless communication system rather than as one or more tones. First, messages are heavily protected by error checking so that, even in relatively noisy air link environments, the bits comprising the message can be reconstructed from the received, corrupted bits, allowing the message to be correctly identified. The conference bridge of the prior art, is not likely to respond as well to a mute signal when a subscriber unit sends the mute signal as a DTMF tone in an environment having relatively high ambient noise or a noisy air link. DTMF tones can be corrupted by ambient noise or the air link noise to such an extent as to be unrecognizable when received by the conference bridging platform. 
     Second, by employing a message to execute the Mute request, the invention takes advantage of acknowledgements which are part of the messaging protocol. An acknowledgement is sent to the subscriber unit when the message is received by the base station, base station controller, or the mobile switching center 
     Although the invention has been described in conjunction with particular embodiments, it will be appreciated that various modifications and alterations may be made by those skilled in the art without departing from the spirit and scope of the invention. The invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the amended claims.