Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1997-10-29
2001-10-16
Vu, Huy D. (Department: 2663)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S352000, C370S401000
Reexamination Certificate
active
06304567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to network systems and methods which provide voice communications through a packet network, and more specifically, to network systems and methods for providing efficient voice communication through a packet network such as the Internet.
2. Description of the Related Art
A conventional telephone network
100
is illustrated in FIG.
1
and comprises, inter alia, a plurality of toll offices, such as toll offices (TS)
105
and
110
, that may be interconnected to one another to provide long distance voice and data communications for subscribers, such as the telephone users, associated with station sets S
1
and S
2
. The manner in which a telephone user, for example, the user associated with the station S
1
, establishes via network
100
a telephone connection to another such user, for example, the user associated with the station S
2
, is well known and will not be described in detail herein. However, it suffices to say that a telephone user, hereinafter also a subscriber, may establish such a connection by causing the station S
1
to go off hook and then dialing the telephone number associated with the station to which he wishes to connect, such as the station S
2
. Local central office
50
associated with station S
1
collects the telephone digits as they are dialed and establishes a connection
101
to a network toll office, for example, toll office
105
which may also be referred to hereinafter as a toll switch. Toll office, or switch
105
, in turn, and based on the dialed telephone number that it receives from the local central office
50
, establishes a connection
102
to a so-called destination toll switch, such as toll switch
110
. Destination toll switch
110
, in turn, extends the connection to central office
75
associated with the station S
2
and passes to that office the dialed telephone number. The latter central office responsive to receipt of the dialled digits then extends the connection
103
to station S
2
. The subscribers positioned respectively at stations S
1
and S
2
may then begin to speak to one another via the established connection.
Since the charges for long distance services, that is, for connections such as the link between toll switches
105
and
110
, typically amount to several dollars for every hour of connection time, lower-cost alternatives would be highly desirable. With the growth of the Internet and the increasing sophistication of Internet subscribers, the Internet could be employed to provide the long distance portion of such a telephone call. Since Internet access is often provided for a few tens of dollars per month, employing the Internet in this manner could save a frequent user hundreds of dollars per month. Even though the Internet is a relatively lossy medium due to the system overheads from uncontrolled access, telephone connections of acceptable quality are possible. Current Internet-based long distance services permit a user to dial a local access number which connects the user to an Internet Telephone Gateway (ITG). The ITG prompts the user for a destination telephone number, then routes the call over the Internet to a similar device at the local exchange of the destination and the destination ITG dials the end user, thereby completing the link. Although such services permit an Internet user to establish a telephone call, using the Internet for the long distance portion of the call, current approaches tend to employ protocols to establish and tear down a new Internet connection with each individual call and the conventional Internet protocols used to establish telephone calls are relatively inefficient, requiring excessive overhead, because the protocols were established to provide extensive feature sets for digital communications links, not for voice communications which, with analog telephones operating at either endpoint, do not require and cannot use the feature sets. Additionally, voice communications at relatively low data-rates are supported by emerging system components. That is, new coder/decoders (codecs) are emerging which can support near toll-quality voice communications at only 8 kilobits per second (kbps) and acceptable quality at 4 kbps. These low data rate codecs can significantly reduce the cost of providing ITG services.
Consequently, it would be highly desirable to provide long distance telephone services over a packet network, such as the Internet, and to increase the efficiency of the connections thereby established while supporting low data rate voice communications. Additionally, voice applications are important for other packet networks, such as the connection of private branch exchanges or the connection of voice access switches by a packet network. Improvements in efficiency are highly desirable for these applications as well.
SUMMARY OF THE INVENTION
The present invention is directed to systems and methods which substantially improve the efficiency of voice communications over a packetized communications system such as the Internet. The invention supports the use of variable-length packets and accommodates variable jitter and loss. The invention also achieves increased efficiency, in part, by multiplexing voice signals into the same transport level connection and/or packet which, for the sake of convenience, will be referred to hereinafter as the Internet although it will be recognized that other networks may be employed. The system uses the real time protocol (RTP) and employs internet telephone gateways (ITGs) to bind users to channel identifiers, to indicate payload type and length, to provide channel identification and time stamps, and to indicate cessation and resumption of voice traffic from a particular user through use of, for example, marker bits. Additionally, the low overhead operation of the new system enhances the ability to support low data-rate voice communications. Since new codecs are emerging which can support near toll-quality voice communications at only 8 kilobits per second (kbps) and acceptable quality at 4 kbps, and these low data rate codecs can significantly reduce the cost of providing ITG services, the present invention's support of low data rate codecs provides an additional cost advantage. The invention also supports the transmission of very low bit rate (1 kbps or less) information, to improve the quality of communications by reproducing background noise during periods of silence.
These and other features, aspects, and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings.
REFERENCES:
patent: 4771425 (1988-09-01), Baran et al.
patent: 5274635 (1993-12-01), Rahman et al.
patent: 5608786 (1997-03-01), Gordon
H. Schulzrinne, S. Casner, R Frederick, V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications”, Audio Visual Working Group Request for Comments RFC 1889, IETF, Jan. 1996.
H. Schulzrinne, “RTP Profile for Audio and Video Conferences with Minimal Control”, Audio Visual Working Group Request for Comments RFC 1890, IETF, Jan. 1996.
Lucent Technologies - Inc.
Priest & Goldstein PLLC
Vu Huy D.
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