Telephonic communications – Terminal – Having muting
Reexamination Certificate
2000-07-31
2004-06-22
Chiang, Jack (Department: 2642)
Telephonic communications
Terminal
Having muting
Reexamination Certificate
active
06754342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to telephony. In particular, the present invention relates to concealing the mute function in an IP-based telephony system.
2. The Prior Art
BACKGROUND.
The widespread acceptance and use of the Internet has generated much excitement, particularly among those who see the Internet as a possible substitute for the traditional telephone system. As the backbone of the Internet continues to be upgraded and expanded, the promise of a low-cost substitute to the traditional PBX system may now be realized.
One type of Internet-based telephony system that is gaining acceptance is IP telephony, which transfers voice information over the Internet Protocol (IP) of the TCP/IP protocol suite. While many standards exist, such as Voice over Packet (VOP) for Frame Relay and ATM networks, as used herein the term “IP telephony” will be used to designate voice over any packet-based network. In IP telephony, a user wishing to communicate uses an IP telephone, which is a device which transports voice over a network using data packets instead of the traditional switched circuits of a voice only network.
FIG. 1
shows an IP telephony system
100
of the prior art. System
100
includes a business system
102
configured to provide IP telephony in an enterprise environment. Business system
102
may include a network
104
, such as a corporate Ethernet LAN, to which a plurality of IP telephones
106
may be operatively coupled to network
104
using hardware and software standard in the art. To couple the business system
102
to the outside world, typically a gateway
108
standard in the art is provided and operatively coupled between network
104
and backbone network
110
.
Backbone network
110
may be any packet-based network standard in the art, such as IP, Frame Relay, or ATM. To provide voice communications to legacy POTS phones, typically a gateway
112
is provided, which may be a VoP gateway. Gateway
112
provides access to the Public Switched Telephone Network (PSTN)
114
. Through PSTN
114
, voice-only communications may be provided to legacy POTS phones
116
.
The system
100
of
FIG. 1
also includes an example of a broadband residential system
118
. To reach individual residences, typically local ISP providers provide a cable or DSL head end
120
standard in the art. An individual wishing to utilize the ISP's service may then employ a cable modem or DSL modem
122
coupled to the user's home LAN
124
. The user's home LAN may be provided by a home PC
126
configured to run software standard in the art such Microsoft Windows®. The user may then operatively couple an IP telephone
128
to the LAN
124
.
Thus, in the system
100
of
FIG. 1
, IP telephones
106
in business system
102
may communicate by voice with other similar business systems similarly configured with IP telephones. For a business enterprise, communication by IP telephony may be advantageous because the need for a traditional PBX system can be eliminated. Furthermore, an IP telephony system is scalable and may be upgraded along with the enterprise's network system.
Likewise, the residence of system
118
may communicate by voice to a POTS phone
116
using IP telephone
128
. From the view of the home user, the communication of
FIG. 1
is advantageous because the communication operates over the backbone network
110
without accessing traditional long-distance service providers.
FIG. 2
is conceptual block diagram of a prior art IP telephone system
200
including a TX unit
202
of a transmitting IP telephone standard in the art and a RX unit
204
of a receiving IP telephone standard in the art. TX unit
202
and RX unit
204
are shown operatively coupled to each other through a network cloud
216
. For the sake of clarity, elements of a typical IP telephone not essential to the explanation of the present invention are not shown in the disclosure.
TX unit
202
includes a microphone
206
coupled to a mute switch
207
. The mute switch is toggled by a mute user input
227
which may consist of a physical button or softkey on the IP telephone. Mute switch
207
couples the input audio stream to a Voice Activity Detector (VAD)
208
, a silence indication packet generator
212
and an encoder
214
. VAD
208
, encoder
214
, and silence indication packet source
212
are operatively coupled to each other to provide an output for transmission over network
216
.
In a typical operation, voice information is received on microphone
206
and presented to mute switch
207
. If the mute function of the IP telephone is not engaged through the mute user input
227
(i.e., the mute is off) the mute switch
207
will be closed, and the voice information will be presented to the VAD
208
, the encoder and the silence indication packet source
212
.
Using methods known in the art, the VAD
208
will determine whether there is voice activity present in the signal coming from microphone
206
. If there is voice activity in the signal, the switching logic will pass the output of the encoder (i.e., a packet stream) for transmission to network cloud
216
using methods standard in the art.
If the VAD
208
determines that there is no voice activity present on the signal coming from microphone
206
, then the switching logic
210
will send one or more silence indications packets to network cloud
116
. The silence indication packets contain at least a background noise level so that the comfort noise generator
218
on the receive side can generate noise similar in level and character to the actual background noise on the transmit side.
As is known by those skilled in the art, in some IP telephony systems, a user may disable the VAD of their IP telephone. In such a situation, only background noise can be sent, since silence indication packets can no longer be sent. As used herein, background noise will be used to designate either real background noise, or comfort noise, depending on how the IP telephone is configured.
Comfort noise is a prior art solution to save network bandwidth. The prior art methods determined that if there is no voice activity present, then no voice packets should be sent over the network. However, this results in a unnatural silence appearing on the receiving unit, since no packets are being sent. As a result, the prior art methods developed the concept of comfort noise, which presents the listener with generated noise designed to mimic the line noise of traditional legacy telephones when there is no voice activity present. The comfort noise reassures listeners that their connection is still active.
Referring still to
FIG. 2
, RX unit
204
includes a comfort noise generator
218
operatively coupled to a decoder
220
. The comfort noise generator
218
and decoder
220
are both operatively coupled to switching logic
224
. When the output of TX unit
202
has been transmitted over network
216
, it will be received by RX unit
204
, and presented to a decoder
220
and a comfort noise generator
218
using methods standard in the art.
If the switching logic receives an encoded voice packet it routes it to the decoder which then outputs the decoded audio signal tot the speaker
226
. If the switching logic receives a silence indication packet it routes it the comfort noise generator
218
which then generates comfort noise to the speaker
226
until further voice packets are received. Typically, the CF comprises white or pink noise.
While the systems of
FIGS. 1 and 2
perform well for there intended purpose, some disadvantages have been encountered when compared to legacy phone systems. For example, some users of IP telephones have reported inconveniences when using the mute function of an IP telephone.
Referring back to
FIG. 2
, when the mute function is engaged (i.e., the mute is turned on), mute switch
207
will be open. In prior art systems, the switching logic
210
will sense the opening of mute switch
207
, and cease to send voice packets or CF packets over the network. Thus, no information
Huart Pascal
Knappe Michael
Surazski Luke
Chiang Jack
Cisco Technology Inc.
Sierra Patent Group Ltd.
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